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  • 1995-1999  (226)
  • 1985-1989
  • 1945-1949
  • 1940-1944
  • 1935-1939
  • 1999  (226)
  • Life and Medical Sciences  (96)
  • nitrogen  (75)
  • pharmacokinetics
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  • 1995-1999  (226)
  • 1985-1989
  • 1945-1949
  • 1940-1944
  • 1935-1939
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  • 1
    Electronic Resource
    Electronic Resource
    Human Interindividual Variability in Parameters Related to Health Risks (1999)
    Springer
    Risk analysis 19 (1999), S. 711-726 
    Details
    ISSN: 1539-6924
    Keywords: variability ; exposure ; susceptibility ; risk assessment ; pharmacokinetics ; pharmacodynamics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract This paper reviews existing data on the variability in parameters relevant for health risk analyses. We cover both exposure-related parameters and parameters related to individual susceptibility to toxicity. The toxicity/susceptibility data base under construction is part of a longer term research effort to lay the groundwork for quantitative distributional analyses of non-cancer toxic risks. These data are broken down into a variety of parameter types that encompass different portions of the pathway from external exposure to the production of biological responses. The discrete steps in this pathway, as we now conceive them, are: •Contact Rate (Breathing rates per body weight; fish consumption per body weight) •Uptake or Absorption as a Fraction of Intake or Contact Rate •General Systemic Availability Net of First Pass Elimination and Dilution via Distribution Volume (e.g., initial blood concentration per mg/kg of uptake) •Systemic Elimination (half life or clearance) •Active Site Concentration per Systemic Blood or Plasma Concentration •Physiological Parameter Change per Active Site Concentration (expressed as the dose required to make a given percentage change in different people, or the dose required to achieve some proportion of an individual's maximum response to the drug or toxicant) •Functional Reserve Capacity–Change in Baseline Physiological Parameter Needed to Produce a Biological Response or Pass a Criterion of Abnormal Function Comparison of the amounts of variability observed for the different parameter types suggests that appreciable variability is associated with the final step in the process–differences among people in “functional reserve capacity.” This has the implication that relevant information for estimating effective toxic susceptibility distributions may be gleaned by direct studies of the population distributions of key physiological parameters in people that are not exposed to the environmental and occupational toxicants that are thought to perturb those parameters. This is illustrated with some recent observations of the population distributions of Low Density Lipoprotein Cholesterol from the second and third National Health and Nutrition Examination Surveys.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1007045922532
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  • 2
    Electronic Resource
    Electronic Resource
    Evaluation of the Uncertainty in an Oral Reference Dose for Methylmercury Due to Interindividual Variability in Pharmacokinetics (1999)
    Springer
    Risk analysis 19 (1999), S. 547-558 
    Details
    ISSN: 1539-6924
    Keywords: MeHg ; pharmacokinetics ; PBPK model ; variability ; risk assessment
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract An analysis of the uncertainty in guidelines for the ingestion of methylmercury (MeHg) due to human pharmacokinetic variability was conducted using a physiologically based pharmacokinetic (PBPK) model that describes MeHg kinetics in the pregnant human and fetus. Two alternative derivations of an ingestion guideline for MeHg were considered: the U.S. Environmental Protection Agency reference dose (RfD) of 0.1 μg/kg/day derived from studies of an Iraqi grain poisoning episode, and the Agency for Toxic Substances and Disease Registry chronic oral minimal risk level (MRL) of 0.5 μg/kg/day based on studies of a fish-eating population in the Seychelles Islands. Calculation of an ingestion guideline for MeHg from either of these epidemiological studies requires calculation of a dose conversion factor (DCF) relating a hair mercury concentration to a chronic MeHg ingestion rate. To evaluate the uncertainty in this DCF across the population of U.S. women of child-bearing age, Monte Carlo analyses were performed in which distributions for each of the parameters in the PBPK model were randomly sampled 1000 times. The 1st and 5th percentiles of the resulting distribution of DCFs were a factor of 1.8 and 1.5 below the median, respectively. This estimate of variability is consistent with, but somewhat less than, previous analyses performed with empirical, one-compartment pharmacokinetic models. The use of a consistent factor in both guidelines of 1.5 for pharmacokinetic variability in the DCF, and keeping all other aspects of the derivations unchanged, would result in an RfD of 0.2 μg/kg/day and an MRL of 0.3 μg/kg/day.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1007017116171
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  • 3
    Electronic Resource
    Electronic Resource
    Compensatory responses of Samea multiplicalis larvae when fed leaves of different fertilization levels of the aquatic weed Pistia stratiotes (1999)
    Springer
    Entomologia experimentalis et applicata 92 (1999), S. 205-216 
    Details
    ISSN: 1570-7458
    Keywords: Samea multiplicalis ; Spodoptera pectinicornis ; Pistia stratiotes ; waterlettuce ; nitrogen utilization efficiency ; compensatory feeding ; nitrogen ; biological control of weeds
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Compensatory responses of caterpillars fed low quality food include increased consumption and utilization of essential nutrients. Information about an insect's responses to nutritional challenges from their host plants could benefit weed biological control efforts in the selection and establishment of new agents. The target weed, Pistia stratiotes L. (Araceae) is a floating aquatic plant that has relatively low nitrogen levels which are further diluted with high water content. Efforts to establish the insect Spodoptera pectinicornis (Hampson) (Lepidoptera: Noctuidae) for biological control of P. stratiotes could benefit by examining the nutritional responses of a similar widely established lepidopteran species, Samea multiplicalis (Guenèe) (Lepidoptera: Pyralidae). Larvae of this species were fed leaves of P. stratiotes plants that had been fertilized (NPK) at high and low rates. The leaves of the fertilized plants had a 4.3-fold increase in nitrogen (dry weight) and a 1.6-fold increase in water content. The results suggest that no compensatory increases occurred in larvae fed leaves from the low fertilized plants as no changes were found in fresh mass consumption or nitrogen utilization efficiency. Consequently, development time from second-third instars to pupation was delayed about 3 days compared with larvae fed the high nitrogen leaves. Furthermore, consumption of nitrogen was only 30% and its accumulation into larval tissues was only 60% compared with the larvae fed the high fertilized leaves. The resulting larvae had both a final biomass and a growth rate that were reduced by 40%. Regardless of plant fertilizer level, the larvae fed at a rate 5–10 times greater than that of similar lepidopteran species consuming either low or high quality diets, suggesting that the S. multiplicalis larvae may be functioning at their biological limit for ingesting food.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1003771512722
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  • 4
    Electronic Resource
    Electronic Resource
    Plant quality or quantity? Host exploitation strategies in three Chrysomelidae species associated with Asteraceae host plants (1999)
    Springer
    Entomologia experimentalis et applicata 92 (1999), S. 165-177 
    Details
    ISSN: 1570-7458
    Keywords: Chrysomelidae ; herbivory ; Asteraceae ; life history ; nitrogen ; plant quality ; season
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Phytophagous insects which feed on the leaves of herbaceous host plants have to adapt their life histories to the fact that protein nitrogen is usually highest in growing tissues in spring. We monitored field populations of larvae and adults of three chrysomelid species (Galeruca tanaceti (L.) (main host Achillea millefolium (L.) Yarrow), Cassida rubiginosa (Mueller) (main host Cirsium arvense (L.) Scop.) and Oreina luctuosa (Suffrian) (host Centaurea scabiosa (L.)) together with the amount of protein nitrogen of their food resources and host plant biomass. As expected, the development of host quality, measured as concentration of protein nitrogen, and host plant biomass showed inverse trends during the season. The euryphagous G. tanaceti attacks Achillea early and profits from high nitrogen concentrations in the leaves. Occasional overexploitations of local populations of Achillea are compensated by the capacity to move to other host species. In C. rubiginosa, a species with a host range restricted to the Cardueae, the main larval feeding activity is postponed to a period when the nitrogen content of the host leaves had dropped to 50% of its initial value, but when host plant biomass had increased by 30%. In the monophagous O. luctuosa the larval development is synchronized with a still later phase of host phenology, at which the nitrogen content is below 50% but plant biomass has reached its maximum. There seem to be selection factors, which oppose the use of high quality food in spring and which force the latter two species to postpone their larval development to a later time in the year. This could be caused by numerous factors like, for example, mean daytime temperature. Later in the season the larvae have to cope with the low quality of their host plants. They have, however, the advantage of large quantities of food available. A laboratory study with adults and mature larvae of O. luctuosa shows that this species can overcome low levels of protein nitrogen either by selecting younger leaves with higher nitrogen concentrations or by increasing the daily food consumption rate (RCR) on leaves with a low level of nitrogen and by a prolongation of the feeding period. In this way the larvae compensate the effect of lower daily growth rates (RGR) and a lower food conversion index (ECI) on poor food quality: Regardless of the level of protein nitrogen there was no statistically significant difference in total gain of weight during the third-instar feeding period and in the weight at the end of the third larval stage. The three investigated chrysomelids show that there exists a broad spectrum of adaptations to overcome the dilemma of variable food quality.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1003709622409
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  • 5
    Electronic Resource
    Electronic Resource
    Pharmacokinetic schedule finding study of the combination of gemcitabine and cisplatin in patients with solid tumors (1999)
    Springer
    Annals of oncology 10 (1999), S. 441-448 
    Details
    ISSN: 1569-8041
    Keywords: cisplatin ; dFdCTP accumulation ; gemcitabine ; pharmacodynamics ; pharmacokinetics ; phase I study ; Pt-DNA adducts
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Purpose: To determine possible schedule dependent pharmacokinetic and pharmacodynamic interactions between gemcitabine (2′,2′-difluorodeoxycytidine, dFdC) and cisplatin (cis-diamminedichloroplatinum, CDDP) in patients with advanced stage solid tumors in a phase I trial. Patients and methods: A total of 33 patients with advanced stage solid tumors were treated with gemcitabine (30-min infusion, 800 mg/m2) and cisplatin (one-hour infusion, 50 mg/m2). Sixteen patients had a four-hour interval between gemcitabine (days 1, 8, 15) and cisplatin (days 1 and 8), followed by the reverse schedule and seventeen patients had a 24-hour interval between gemcitabine (days 1, 8, 15) and cisplatin (days 2 and 9), followed by the reverse schedule. Gemcitabine and cisplatin pharmacokinetics were measured in plasma and white blood cells (WBC), isolated from blood samples taken at several time points after the start of treatment. Results: A four-hour time interval between both agents did not reveal major differences in plasma pharmacokinetics of gemcitabine, dFdU (deaminated gemcitabine) and platinum (Pt), and of gemcitabine–triphosphate (dFdCTP) accumulation and Pt-DNA adduct formation in WBC between the two different sequences of gemcitabine and cisplatin. In the patients treated with the 24-hour interval, cisplatin before gemcitabine did not significantly change peak gemcitabine levels and the AUC of plasma dFdU, but tended to increase dFdCTP AUC in WBC 1.5-fold (P 〈 0.06). Gemcitabine before cisplatin decreased the plasma AUC of Pt 2.1-fold (P = 0.03). No significant differences in Pt-DNA adduct levels in WBC were found, although gemcitabine before cisplatin tended to increase the 24-hour retention of Pt-DNA adducts. Creatinine clearance on day 28 was related to the peak plasma levels of total Pt (linear regression coefficient (r) = 0.47, P = 0.02, n = 26). Furthermore, the increase in the Pt-GG to Pt-AG ratio 24 hours after cisplatin treatment was related to the overall response of patients (r = 0.89, P 〈 0.01, n = 8). Conclusions: Of all schedules the treatment of patients with cisplatin 24 hours before gemcitabine led to the highest dFdCTP accumulation in WBC and total Pt levels in plasma. These characteristics formed the basis for further investigation of this schedule in a phase II clinical study.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008301522349
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  • 6
    Electronic Resource
    Electronic Resource
    FTIR spectroscopic evidence of formation of geminal dinitrogen species during the low-temperature N2 adsorption on NaY zeolites (1999)
    Springer
    Catalysis letters 58 (1999), S. 21-26 
    Details
    ISSN: 1572-879X
    Keywords: adsorption ; adsorption isotherms ; dinitrogen ; FTIR spectroscopy ; geminal species ; NaY ; nitrogen ; zeolites
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Adsorption of N2 on NaY zeolites at 85 K and equilibrium pressures higher than 1 kPa results in the formation of geminal dinitrogen complexes characterized by an IR band at 2333.5 cm−1 (2255.4 cm−1 after adsorption of 15N2). With decreasing equilibrium pressure the complexes tend to loose one N2 ligand, thus forming linear species characterized by an IR band at 2336.8 cm−1 (2258.7 cm−1 after adsorption of 15N2). All species disappear completely after evacuation. Co-adsorption of N2 and CO revealed that the dinitrogen complexes are formed on Na+ cations. The changes in the concentrations of the linear and geminal N2 species with the changes in the equilibrium pressure are excellently described by equations of adsorption isotherms proposed earlier for mono- and di-carbonyls.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1019040825491
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  • 7
    Electronic Resource
    Electronic Resource
    Pure and Binary Gas Adsorption Equilibria and Kinetics of Methane and Nitrogen on 4A Zeolite by Isotope Exchange Technique (1999)
    Springer
    Adsorption 5 (1999), S. 145-158 
    Details
    ISSN: 1572-8757
    Keywords: kinetics ; isotope-exchange ; nitrogen ; adsorption ; methane ; zeolite ; equilibria
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract The Isotope Exchange Technique (IET) was used to simultaneously measure pure and binary gas adsorption equilibria and kinetics (self-diffusivities) of CH4 and N2 on pelletized 4A zeolite. The experiment was carried out isothermally without disturbing the adsorbed phase. CH4 was selectively adsorbed over N2 by the zeolite because of its higher polarizability. The multi-site Langmuir model described the pure gas and binary adsorption equilibria fairly well at three different temperatures. The selectivity of adsorption of CH4 over N2 increased with increasing pressure at constant gas phase composition and temperature. This curious behavior was caused by the differences in the sizes of the adsorbates. The diffusion of CH4 and N2 into the zeolite was an activated process and the Fickian diffusion model described the uptake of both pure gases and their mixtures. The self-diffusivity of N2 was an order of magnitude larger than that for CH4. The pure gas self-diffusivities for both components were constants over a large range of surface coverages (0 〈 θ 〈 0.5). The self-diffusivities of CH4 and N2 from their binary mixtures were not affected by the presence of each other, compared to their pure gas self-diffusivities at identical surface coverages.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008917308002
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  • 8
    Electronic Resource
    Electronic Resource
    Sequential administration of temozolomide and fotemustine: Depletion of O6-alkyl guanine-DNA transferase in blood lymphocytes and in tumours (1999)
    Springer
    Annals of oncology 10 (1999), S. 831-838 
    Details
    ISSN: 1569-8041
    Keywords: melanoma ; pharmacodynamics ; pharmacokinetics ; temozolomide
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Background: The DNA repair protein O6-alkylguanine-DNA alkyl transferase (AT) mediates resistance to chloroethylnitrosoureas. Agents depleting AT such as DTIC and its new analogue temozolomide (TMZ) can reverse resistance to chloroethylnitrosoureas. We report the results of a dose finding study of TMZ in association with fotemustine. Patients and methods: Twenty-four patients with metastatic melanoma or recurrent glioma were treated with escalating dose of oral or intravenous TMZ ranging from 300 to 700 mg/m2, divided over two days. Fotemustine 100 mg/m2 was given intravenously on day 2, 4 hours after TMZ. AT depletion was measured in peripheral blood mononuclear cells (PBMCs) and in selected cases in melanoma metastases and was compared to TMZ pharmacokinetics. Results: The maximum tolerated dose (MTD) of TMZ was 400 mg/m2 (200 mg/m2/d) when associated with fotemustine the 2nd day with myelosuppression as dose limiting toxicity. The decrease of AT level in PBMCs was progressive and reached 34% of pretreatment values on day 2. There was however wide interindividual variability. AT reduction was neither dose nor route dependent and did not appear to be related to TMZ systemic exposure (AUC). In the same patients, AT depletion in tumour did not correlate with the decrease of AT observed in PBMCs. Conclusions: PBMCs may not be used as a surrogate of tumour for AT depletion. Further study should concentrate on the pharmacokinetic pharmacodynamic relationship in tumour to provide the basis for individually tailored therapy.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008304032421
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  • 9
    Electronic Resource
    Electronic Resource
    Effect of split applications of cattle slurry and mineral fertilizer–N on the yield of silage maize in a slurry-based cropping system (1999)
    Springer
    Nutrient cycling in agroecosystems 53 (1999), S. 209-218 
    Details
    ISSN: 1573-0867
    Keywords: cattle slurry ; fertilizer splitting ; nitrogen ; recovery ; residual nitrogen ; Zea mays L
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The recovery of soil mineral nitrogen (N) by crops, and its subsequent utilisation for dry matter (DM) production may be increased when the application of N is postponed until after crop emergence. The significance of this strategy for silage maize was studied in nine field experiments on Dutch sandy soils from 1983 to 1988. In five experiments the effect of slurry applied before planting at a rate of circa 66 m3 ha-1, was compared to the effect of a similar rate of which half was applied before planting and half at the 4–6 leaf stage. In the 4-6 leaf stage slurry was either injected or banded. In four other experiments the effect of mineral fertilizer-N splitting was studied. In these experiments, 30 m3 ha-1 cattle slurry, applied before planting, was supplemented with mineral fertilizer-N at rates ranging from 40 to 160 kg ha-1, either fully applied before crop emergence or split. When split, 40 kg ha-1 of the mineral fertilizer-N rate was banded at the 4–6 leaf stage. According to balance sheet calculations, substantial losses of slurry N and mineral fertilizer-N occurred during the growing season. Losses were compensated for, however, by apparent mineralization, ranging from 0.34 to 0.77 kg N ha-1 day-1. Split applications of cattle slurry had a significant positive effect on the DM yield in two out of five experiments compared to the conventional non-split application, but only when the post-emergence slurry application was banded which is no longer in accordance with present legislation. Split applications of mineral fertilizer-N had a significant positive effect in one experiment where rainfall was excessive but not in the others. The results provide insufficient evidence to recommend farmers to split applications. Soil mineral N sampling at the 4–6 leaf stage should hence be considered a control on the appropriateness of early N applications after exceptional weather conditions rather than a routine observation on which the post-emergence N dressing is to be based in a deliberate splitting strategy. Our data suggest that the financial return of a 40 kg ha-1 supplementation with mineral fertilizer-N, was questionable when more than 175 kg N ha-1 were found in the upper 0.6 m soil layer at the 4–6 leaf stage.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009796021850
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  • 10
    Electronic Resource
    Electronic Resource
    Using nitrogen budgets to indicate nitrogen use efficiency and losses from whole farm systems: a comparison of three methodological approaches (1999)
    Springer
    Nutrient cycling in agroecosystems 53 (1999), S. 259-267 
    Details
    ISSN: 1573-0867
    Keywords: farming systems ; nitrogen ; nitrogen budgets ; sustainability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Three approaches to nitrogen budgeting were developed and their ability to quantitatively describe nitrogen cycling in a fertilizer based and a grass–clover based beef system tested. Budgets ranged in complexity from the Economic Input:Output (EIO) budget, which accounted simply for purchases and sales of nitrogen over the farmgate, through the Biological Input:Output (BIO) budget, which included estimates of biological nitrogen fixation and attempted to partition losses into leaching and gaseous forms, to the Transfer:Recycle:Input:Output (TRIO) budget, which also accounted for key soil processes. Nitrogen unaccounted for in the fertilized system decreased with increasing budget complexity (285, 212 and 188 kg ha-1 yr-1 unaccounted for by the EIO, BIO and TRIO budgets, respectively). In the legume based grass–clover system, the EIO budget did not accurately describe total nitrogen inputs as it did not include 146 kg ha-1 yr-1 from symbiotic nitrogen fixation. In the grass–clover system, nitrogen unaccounted for was again greater using the BIO than the TRIO budget (103 and 79 kg ha-1 yr-1, respectively). In conclusion, the most complex budgeting approach (TRIO) was able to account for the fate of a greater proportion of nitrogen inputs than the simpler approaches. However, the perceived success of the different approaches was strongly dependent on the precise objective.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009793120577
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  • 11
    Electronic Resource
    Electronic Resource
    Nitrogen uptake and chlorophyll meter measurements in Spring Wheat (1999)
    Springer
    Nutrient cycling in agroecosystems 55 (1999), S. 1-6 
    Details
    ISSN: 1573-0867
    Keywords: chlorophyll meter ; irrigation ; LAI ; nitrogen ; Spring Wheat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract A Spring Wheat crop was grown using three irrigation levels and nitrogen rate applications to evaluate chlorophyll meter measurements as a possible nitrogen nutrition index for modelling. These measurements yielded the most reliable indications at Zadoks GS45. The lower limit indicating severe nitrogen deficiency in the leaves was approximately 35 SPAD units while the upper limit of 45 SPAD units, indicated an excess consumption.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009843813004
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  • 12
    Electronic Resource
    Electronic Resource
    The fate of algal nitrogen in a flooded soil system (1999)
    Springer
    Nutrient cycling in agroecosystems 55 (1999), S. 89-94 
    Details
    ISSN: 1573-0867
    Keywords: algae ; flooded soils ; N cycling ; nitrogen ; 15N ; rice
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Algal N labelled with 15N added to a flooded soil in laboratory columns without plants was studied to determine the changes over time in the fate of N assimilated by algae and to study how its fate is affected by (a) exclusion of light simulating complete closure of the rice canopy, and (b) addition of fertilizer-NH4 *. In the light but with no added fertilizer-N there was little net mineralization of the added algal N during the first 4 weeks, but after 8 weeks 42% had been mineralized, of which 95% was denitrified. Exclusion of light caused net mineralization to proceed more rapidly in the first 4 weeks due to the death of algal cells and lowered reassimilation. After 8 weeks 51% had been mineralized, of which 54% was denitrified, 16% volatilized and 30% was present as KCl exchangeable NH4 +-N. Application of fertilizer-NH4 + apparently caused mineralization of 25% of the algal N within one week but the results were probably affected by pool substitution in which labelled N mineralized to NH4 +-N was diluted with fertilizer – NH+ 4 and then immobilized leaving more labelled NH4–N in the mineral pool. After 8 weeks, 42% of algal N had been mineralized, of which 69% was estimated to have been denitrified, 19% lost through NH3 volatilization and 12% remained as extracted NH4 ++NO- 3. Uptake of N by a rice crop would reduce the gaseous losses. Algal N was mineralized quickly enough to be available during the growing season of a rice crop and, depending on field conditions, algae may have a role in assimilating N and protecting it from loss as well as being a major driving force for NH3 volatilization through diurnal increases in pH.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009850915579
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  • 13
    Electronic Resource
    Electronic Resource
    Influence of Canopy Height and Fertilization Levels on the Resistance of Lycopersicon Hirsutum to Aculops Lycopersici (Acari: Eriophyidae) (1999)
    Springer
    Experimental and applied acarology 23 (1999), S. 633-642 
    Details
    ISSN: 1572-9702
    Keywords: tomato plants ; susceptibility ; mite ; tridecan-2-one ; nitrogen ; potasium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The objective of this work was to study the effect of NK fertilization levels and canopy height on the resistance of Lycopersicon hirsutum and Lycopersicon esculentum to Aculops lycopersici (Acari: Eriophydae). The effects of NK fertilization levels and canopy height in the leaf size and density of trichomes and their effects on tridecan-2-one (2-TD) and undecan-2-one (2-UD) limiting the attack of A. lycopersici on tomato plants were assessed. Different NK fertilization levels had no effect on the resistance of L. hirsutum to A. lycopersici. No significant differences were found in attack rates of this mite on leaves of the top and median parts of L. hirsutum canopy. The type and density of trichomes were the main determining factor of A. lycopersici attack on tomato plants. High trichome densities and type VI glandular trichomes which produce tridecan-2-one are important resistance factors on tomato plants. L. hirsutum showed a high resistance level to A. lycopersici due to high densities of type VI glandular trichomes and consequently higher levels of tridecan-2-one in its leaves.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006201915292
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  • 14
    Electronic Resource
    Electronic Resource
    Pharmacokinetically guided dose escalation of carboplatin in epithelial ovarian cancer: Effect on drug-plasma AUC and peripheral blood drug-DNA adduct levels (1999)
    Springer
    Annals of oncology 10 (1999), S. 329-334 
    Details
    ISSN: 1569-8041
    Keywords: carboplatin ; drug-target interaction ; ovarian cancer ; pharmacokinetically based dosing ; pharmacokinetics ; platinum-DNA adducts
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Background: Platinum based drugs are active agents in epithelial ovarian cancer and increased platinum drug dose intensity is thought to lead to improved survival, because of the largely untested assumption that increased dose intensity results in an increased interaction of the platinum drug with its target, DNA. In a previously reported phase I trial (Lind et al., J Clin Oncol 1996; 14: 800–5), carboplatin dose intensity was increased by the use of G-CSF to support the bone marrow and using pharmacokinetically-guided carboplatin dosing. The objectives of this study were to validate the carboplatin dosing formula during high dose intensity therapy and evaluate the relationship between systemic carboplatin exposure and Pt-DNA adduct levels in peripheral blood leucocytes. Patients and methods: A total of 17 patients were studied over four levels of dose intensification. The carboplatin dose was calculated using the ‘Calvert formula’. Levels of drug-target interaction in peripheral blood leukocytes were measured using an immunoassay based on a monoclonal antibody that recognises DNA-platinum adducts. Pharmacokinetic measurements were carried out using a previously validated single sample method. Results: The area under the curve of concentration of unbound carboplatin in plasma versus time (AUC) for target AUC values of 5, 7 and 9 mg/ml·min were: 5.6 ± 1.0, 7.3 ± 0.7 and 9.8 ± 0.5 mg/ml·min (mean ± S.D.). There was a good correlation between target and achieved dose intensities (r2 = 0.899) and the slope of the linear regression line was 0.95 (± 0.09 SD) not significantly different to 1.0 (P 〉 0.6). The levels of immunoreactive DNA adducts were not detectable at a target AUC of 5 mg/ml·min but increased progressively at the higher AUC levels. Accumulation of adducts between courses was not detected. Conclusions: Pharmacokinetically-based carboplatin dosing during high intensity therapy accurately predicted the dose required to achieve a target AUC and resulted in consistent patient exposure to active drug. During the dose escalation study, peripheral blood leucocyte DNA platinum-DNA adduct levels were positively related to drug dose and drug AUC.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008355506863
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  • 15
    Electronic Resource
    Electronic Resource
    Pharmacokinetics of interleukin-2 in two anephric patients with metastatic renal cell cancer (1999)
    Springer
    Annals of oncology 10 (1999), S. 1381-1383 
    Details
    ISSN: 1569-8041
    Keywords: (adeno)carcinoma ; interleukin-2 ; kidney neoplasms ; nephrectomy ; pharmacokinetics ; renal cell
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Background: Most patients with metastatic renal cell carcinoma (RCC) have undergone unilateral- and some bilateral nephrectomy. Because interleukin-2 (IL-2) is thought to be mainly cleared via the kidneys, we investigated whether IL-2 treatment is safe in anephric patients. Patients and methods: The pharmacokinetics of i.v. bolus, i.v. infusion and s.c. recombinant IL-2 were investigated in two anephric patients with progressive metastatic RCC. Results: Following i.v. bolus administration of IL-2, plasma half-lives of 126 and 84 minutes respectively, and plasma clearances of 151 ml/min and 273 ml/min respectively, were measured in the two patients. In one patient plasma clearance of IL-2 was enhanced to 760 ml/min after continuous i.v. infusion of 4 and 6 million IU IL-2/24 hours, as compared to a clearance of 310 ml/min at a dose of 2 million IU IL-2/24 hours. In the other patient, during IL-2 infusion of 2, 4 or 6 × 106 IU/24 hours, each over the course of 3 days, plasma clearance of IL-2 increased from 311 to 761, and to 687 ml/min, respectively. IL-2 could not be detected in haemo- or peritoneal dialysates. Conclusions: IL-2 plasma half-life is only moderately prolonged in anephric patients as compared to patients with normal renal function. Based on our findings, intravenous or subcutaneous treatment of anephric patients with IL-2 seems feasible.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008362620308
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  • 16
    Electronic Resource
    Electronic Resource
    Pharmacokinetic interactions of paclitaxel, docetaxel and their vehicles with doxorubicin (1999)
    Springer
    Annals of oncology 10 (1999), S. 391-395 
    Details
    ISSN: 1569-8041
    Keywords: docetaxel ; doxorubicin ; interaction ; mice ; paclitaxel ; pharmacokinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Background: The combination of doxorubicin (Dx) with paclitaxel or docetaxel is clinically effective but there are concerns regarding the higher incidence of cardiotoxicity of the combination compared with Dx alone. The mechanism of the increased toxicity is still unclear. Purpose: To assess whether there is a pharmacokinetic interaction between paclitaxel, docetaxel or their vehicles and Dx in mice. Materials and methods: CDF1 male mice were treated with Dx either alone (10 mg/kg i.v.) or in combination with paclitaxel (25 mg/kg) or docetaxel (25 mg/kg) or their vehicles, i.e., cremophor-ethanol-glucose (cremophor) or polysorbate80-ethanol-glucose (polysorbate). Four mice were killed 4, 8 or 24 hours after Dx in each experimental group and Dx was assayed in serum and in heart, liver, kidney and spleen by HPLC. Results: Four hours after treatment the concentrations of Dx in heart, liver and kidney were much higher in mice concomitantly treated with paclitaxel, docetaxel (dissolved in either cremophor or polysorbate) and cremophor. At subsequent times the differences were modest and only reached statistical significance in a few cases. Dx metabolites were modified by concomitant treatment with taxanes or their vehicles. In particular, the levels of Dx aglycone in liver and kidney were significantly lower in mice treated with the combination than in mice given Dx alone. Conclusions: paclitaxel, docetaxel and cremophor when given together with Dx modify its distribution and metabolism, increasing Dx levels in many tissues including the heart. This might have some bearing on the toxicity of regimens in which Dx is combined with taxanes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008309916974
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  • 17
    Electronic Resource
    Electronic Resource
    Nitrogen Addition to an O-1 Tool Steel (1999)
    Springer
    Journal of materials synthesis and processing 7 (1999), S. 311-319 
    Details
    ISSN: 1573-4870
    Keywords: Iron ; carbon ; nitrogen ; microstructure ; characterization ; HIP-drip
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract A new processing technique makes nitrogen alloying possible by adding nitrogen under elevated nitrogen pressure to prealloyed Fe-C ingots during continuous casting, producing a whole new class of precipitation-free, iron–carbon–nitrogen alloys. When both carbon and nitrogen bulk concentration levels exceeded 0.5 wt%, a duplex fcc-/(bcc-bct-) Fe microstructure resulted that is iron carbide- and nitride-free. With increasing carbon and nitrogen concentrations, there was an increase in the retained fcc-Fe phase. In cooling rate studies, increasing carbon and nitrogen concentrations shifted the knee of the fcc-Fe-to-bcc-Fe phase time–temperature–transformation (T–T–T) curve to longer times. Hardness, compression strength, and wear resistance increased with increasing carbon and nitrogen concentrations and were superior to iron–carbon alloys without the nitrogen addition.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1021877121902
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  • 18
    Electronic Resource
    Electronic Resource
    The Metabolism of Atypical Antipsychotic Drugs: An Update (1999)
    Springer
    Annals of clinical psychiatry 11 (1999), S. 145-158 
    Details
    ISSN: 1573-3238
    Keywords: clozapine ; olanzapine ; quetiapine ; risperidone ; sertindole ; ziprasidone ; metabolism ; pharmacokinetics ; flavin-containing monooxygenases ; glucuronidation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract This paper reviews the current literature describing the metabolism of both multi-receptor clozapine analogue atypical antipsychotic drugs (clozapine, olanzapine, and quetiapine) and serotonin-dopamine antagonist atypical antipsychotic drugs (risperidone, sertindole and ziprasidone), to highlight the significance of those data in the context of clinical practice. The former group of atypical antipsychotic drugs shares a similar tricyclic structural nucleus and are metabolized through three major categorical metabolic pathways—N +-oxidation, N-glucuronidation, and phases 1 and 2 biotransformation with final glucuronidation before renal excretion. Differing in clozapine and olanzapine, quetiapine has incomplete data describing its metabolism. The latter group of atypical antipsychotic drugs has diversified chemical structures and absence of data on N +-oxidation and N-glucuronidation in the literature. But their metabolic routes in phase 1 biotransformation are versatile although current data are far from completion. No apparent significant drug interactions in clinical practice are reported, although QT prolongation is implicated in all those three drugs. None of all six atypical antipsychotic drugs are identified as significant inhibitors or inducers to any co-administered medication. The author suggests the need for more research to address some pertinent clinical issues in the metabolism of those drugs.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1022312111429
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  • 19
    Electronic Resource
    Electronic Resource
    Improving the field performance of micro-and minitubers (1999)
    Springer
    Potato research 42 (1999), S. 559-568 
    Details
    ISSN: 1871-4528
    Keywords: plastic mulch ; transplanting ; nitrogen ; planting depth ; seed tuber weight ; physiological age ; radiation conversion efficiency ; harvest index
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary In many seed potato producing areas, micro- and minitubers are too small for direct planting as seed tubers in the field. Such use of these propagules can, however, be feasible if the crop's growth and development can be advanced. Increasing light interception, harvest index and yield of useable progeny tubers has been proved possible with plastic mulch and pre-planting of small tubers in a greenhouse. High amounts of nitrogen (up to 180 kg ha−1) or deep planting (up to 9 cm) were less effective. Using older or pre-sprouted micro- or minitubers may be beneficial, because this might increase the number of sprouts per mother tuber (and thus stems per plant) or advance the growth of sprouts or stems. However, this would require even more careful management, due to the weakness of these sprouts and stems. Micro- and minitubers should be as large as feasible when used for direct planting in the field.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02358172
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  • 20
    Electronic Resource
    Electronic Resource
    Retention of nutrients in river basins (1999)
    Springer
    Aquatic ecology 33 (1999), S. 29-40 
    Details
    ISSN: 1573-5125
    Keywords: denitrification ; nature restoration ; nitrogen ; phosphorus ; riparian areas ; sedimentation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In Denmark, as in many other European countries, the diffuse losses of nitrogen (N) and phosphorus (P) from the rural landscape are the major causes of surface water eutrophication and groundwater pollution. The export of total N and total P from the Gjern river basin amounted to 18.2 kg ha−1 and 0.63 kg P ha−1 during June 1994 to May 1995. Diffuse losses of N and P from agricultural areas were the main nutrient source in the river basin contributing 76% and 51%, respectively, of the total export. Investigations of nutrient cycling in the Gjern river basin have revealed the importance of permanent nutrient sinks (denitrification and overbank sedimentation) and temporary nutrient storage in watercourses. Temporary retention of N and P in the watercourses thus amounted to 7.2–16.1 g N m−2 yr−1 and 3.7–8.3 g P m−2 yr−1 during low-flow periods. Deposition of P on temporarily flooded riparian areas amounted from 0.16 to 6.50 g P m−2 during single irrigation and overbank flood events, whereas denitrification of nitrate amounted on average to 7.96 kg N yr−1 per running metre watercourse in a minerotrophic fen and 1.53 kg N yr−1 per linear metre watercourse in a wet meadow. On average, annual retention of N and P in 18 Danish shallow lakes amounted to 32.5 g N m−2 yr−1 and 0.30 g P m−2 yr−1, respectively, during the period 1989–1995. The results indicate that permanent nutrient sinks and temporary nutrient storage in river systems represent an important component of river basin nutrient budgets. Model estimates of the natural retention potential of the Gjern river basin revealed an increase from 38.8 to 81.4 tonnes yr−1 and that P-retention increased from −0.80 to 0.90 tonnes yr−1 following restoration of the water courses, riparian areas and a shallow lake. Catchment management measures such as nature restoration at the river basin scale can thus help to combat diffuse nutrient pollution.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009947907811
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  • 21
    Electronic Resource
    Electronic Resource
    Variation in nutrient availability and plant species diversity across forb and graminoid zones of a Northern New England high salt marsh (1999)
    Springer
    Plant ecology 143 (1999), S. 219-228 
    Details
    ISSN: 1573-5052
    Keywords: mineralization ; nitrogen ; phosphorus ; salinity ; stress
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Plant zonation patterns across New England salt marshes have been investigated for years, but how nutrient availability differs between zones has received little attention. We investigated how N availability, P availability, and plant N status varied across Juncus gerardii, Spartina patens, and mixed forb zones of a Northern New England high salt marsh. We also investigated relationships between several edaphic factors and community production and diversity across the high marsh. P availability, soil salinity, and soil moisture were higher in the mixed forb zone than in the two graminoid zones. NH+ 4-N availability was highest in the J. gerardii zone, but NO− 3-N availability and mid season net N mineralization rates did not vary among zones. Plant tissue N concentrations were highest in the mixed forb zone and lowest in the S. patens zone, reflecting plant physiologies more so than soil N availability. Community production was highest in the J. gerardii zone and was positively correlated with N availability and negatively correlated with soil moisture. Plant species diversity was highest in the mixed forb zone and was positively correlated with P availability and soil salinity. Thus, nutrient availability, plant N status, and plant species diversity varied across zones of this high marsh. Further investigation is needed to ascertain if soil nutrient availability influences or is a result of the production and diversity differences that exist between vegetation zones of New England high salt marshes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009887727465
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  • 22
    Electronic Resource
    Electronic Resource
    Denitrification in coastal ecosystems: methods, environmental controls, and ecosystem level controls, a review (1999)
    Springer
    Aquatic ecology 33 (1999), S. 41-54 
    Details
    ISSN: 1573-5125
    Keywords: denitrification ; eutrophication ; estuary ; nitrogen ; sediment-water exchange
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In this review of sediment denitrification in estuaries and coastal ecosystems, we examine current denitrification measurement methodologies and the dominant biogeochemical controls on denitrification rates in coastal sediments. Integrated estimates of denitrification in coastal ecosystems are confounded by methodological difficulties, a lack of systematic understanding of the effects of changing environmental conditions, and inadequate attention to spatial and temporal variability to provide both seasonal and annual rates. Recent improvements in measurement techniques involving 15 N techniques and direct N2 concentration changes appear to provide realistic rates of sediment denitrification. Controlling factors in coastal systems include concentrations of water column NO 3 − , overall rates of sediment carbon metabolism, overlying water oxygen concentrations, the depth of oxygen penetration, and the presence/absence of aquatic vegetation and macrofauna. In systems experiencing environmental change, either degradation or improvement, the importance of denitrification can change. With the eutrophication of the Chesapeake Bay, the overall rates of denitrification relative to N loading terms have decreased, with factors such as loss of benthic habitat via anoxia and loss of submerged aquatic vegetation driving such effects.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009921414151
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  • 23
    Electronic Resource
    Electronic Resource
    A human capecitabine excretion balance and pharmacokinetic study after administration of a single oral dose of 14C-labelled drug (1999)
    Springer
    Investigational new drugs 17 (1999), S. 49-56 
    Details
    ISSN: 1573-0646
    Keywords: pharmacokinetics ; capecitabine ; 5-fluorouracil ; phase I trials
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Abstract An excretion balance and pharmacokinetic study was conducted in cancer patients with solid tumors who received a single oral dose of capecitabine of 2000 mg including 50 μ Ci of 14C-radiolabelled capecitabine. Blood, urine and fecal samples were collected until radioactive counts had fallen to below 50 dpm/mL in urine, and levels of intact drug and its metabolites were measured in plasma and urine by LC/MS-MS (mass spectrometry) and 19F-NMR (nuclear magnetic resonance) respectively. Based on the results of the 6 eligible patients enrolled, the dose was almost completely recovered in the urine (mean 95.5%, range 86–104% based on radioactivity measurements) over a period of 7 days after drug administration. Of this, 84% (range 71–95) was recovered in the first 12 hours. Over this time period, 2.64% (0.69–7.0) was collected in the feces. Over a collection period of 24–48h, a total of 84.2% (range 80–95) was recovered in the urine as the sum of the parent drug and measured metabolites (5′-DFCR, 5′-DFUR, 5-FU, FUH2, FUPA, FBAL). Based on the radioactivity measurements of drug-related material, absorption is rapid (tmax 0.25–1.5 hours) followed by a rapid biphasic decline. The parent drug is rapidly converted to 5-FU, which is present in low levels due to the rapid metabolism to FBAL, which has the longest half-life. There is a good correlation between the levels of radioactivity in the plasma and the levels of intact drug and the metabolites, suggesting that these represent the most abundant metabolites of capecitabine. The absorption of capecitabine is rapid and almost complete. The excretion of the intact drug and its metabolites is rapid and almost exclusively in the urine.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006263400888
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  • 24
    Electronic Resource
    Electronic Resource
    A Sensitive Docetaxel Assay in Plasma by Solid-Phase Extraction and High Performance Liquid Chromatography – UV Detection: Validation and Suitability in Phase I Clinical Trial Pharmacokinetics (1999)
    Springer
    Investigational new drugs 17 (1999), S. 325-333 
    Details
    ISSN: 1573-0646
    Keywords: docetaxel ; plasma assay ; clinical trials ; pharmacokinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Abstract We have developed a specific and sensitive method aiming atdocetaxel (Taxotere®) determination in plasma of treatedpatients. This involved solid-phase extraction of 1 ml of plasmaonto carboxylic acid (CBA) grafted silica cartridges followed byreversed-phase liquid chromatography with UV detection. The bestselectivity was obtained through the use of C18 Uptisphere® asstationary phase. The low limit of quantitation obtained (LOQ:5 ng/ml) allowed measurements of docetaxel up to 24 hours afterone-hour infusions with low dosages of drug (60 mg/m2). Themethod was applied successfully to monitor docetaxel plasma levelswithin two protocols associating fixed dosages of either methotrexate or gemcitabine with escalating doses of Taxotere®.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006327302041
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  • 25
    Electronic Resource
    Electronic Resource
    Effect of meteorology and nutrient load on oxygen depletion in a Danish micro-tidal estuary (1999)
    Springer
    Aquatic ecology 33 (1999), S. 55-64 
    Details
    ISSN: 1573-5125
    Keywords: estuaries ; nitrogen ; oxygen depletion ; phosphorus ; regression model ; vertical mixing
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In a detailed analysis of oxygen saturation in a shallow Danish estuary it was possible to separate the effect of meteorological forcings (i.e. wind and solar radiation) and nutrient loads on oxygen depletion in bottom water. Regression analysis showed that oxygen saturation tied to nitrogen load rather than to phosphorus load. During summer periods of stratification the oxygen saturation could be attributed to the time elapsed after the onset of stratification and the accumulated nitrogen loading 10 month prior to measurement. Using a 10-year meteorological database and an empirical model it was calculated that a 25% reduction in nitrogen loading would reduce the number of days with severe oxygen depletion (i.e. 〈15% of saturation) by more than 50%.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009956210537
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  • 26
    Electronic Resource
    Electronic Resource
    ACNU, MTX And 5-FU Penetration of Rat Brain Tissue and Tumors (1999)
    Springer
    Journal of neuro-oncology 45 (1999), S. 9-17 
    Details
    ISSN: 1573-7373
    Keywords: ACNU ; MTX ; 5-FU ; pharmacokinetics ; leptomeningeal tumor
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The distribution of radio-labeled ACNU, MTX and 5-FU in brain and tumor tissue was studied in female Wistar rats by macroautoradiography after intrathecal administration. In normal rats, ACNU and 5-FU, administered intracisternally, distributed rapidly in the subarachnoid space, ventricular system and cerebrospinal fluid (CSF). 5-FU and MTX penetrated the brain deeply; the diffusional transport of ACNU was limited to a depth of 1 or 2 mm from the CSF surface of the brain. MTX and 5-FU clearance into the blood circulation was rather slow while ACNU cleared relatively quickly. The half time of ACNU, 5-FU and MTX radioactivity at the ventricular surface was 10, 21, and 110 min, respectively, at their maximal concentration after intracisternal administration. In rats with leptomeningeal tumor induced by intracisternal inoculation of Walker 256 cells, the distribution patterns of ACNU, 5-FU, and MTX were essentially the same as in normal rats despite 10–20 cell layers of tumor growing in the subarachnoid space. 5-FU and MTX were able to penetrate tumor masses in the subarachnoid space; MTX penetration was slower than that of 5-FU and ACNU failed to penetrate to more than a depth of 1 or 2 mm from the tumor surface.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006377312403
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  • 27
    Electronic Resource
    Electronic Resource
    Application of a Combined “Effect Compartment/Indirect Response Model” to the Central Nervous System Effects of Tiagabine in the Rat (1999)
    Springer
    Journal of pharmacokinetics and pharmacodynamics 27 (1999), S. 301-323 
    Details
    ISSN: 1573-8744
    Keywords: pharmacokinetics ; pharmacodynamics ; effect compartment model ; indirect response ; sigmoid E max ; tiagabine ; GABA uptake inhibitor
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Pharmacological inhibition of GABA uptake transporters provides a mechanism for increasing GABAergic transmission, which may be useful in the treatment of various neurological disorders. The purpose of our investigations was to develop an integrated pharmacokinetic–pharmacodynamic (PK/PD) model for the characterization of the pharmacological effect of tiagabine, R-N-(4,4-di-(3-methylthien-2-yl)but-3-enyl)nipecotic acid, in individual rats in vivo. The tiagabine-induced increase in the amplitude of the EEG 11.5–30 Hz frequency band (β), was used as pharmacodynamic endpoint. Chronically instrumented male Wistar rats were randomly allocated to four groups which received an infusion of 3, 10, or 30 mg kg −1 $$(\bar x \pm SE,{\text{ }}n = 23)$$ $$96 \pm 9$$ ml min -1 kg−1, 1.5ŷ0.1 L kg−1 and 20ŷ0.2 min.A time delay was observed between the occurrence of maximum plasma drug concentrations and maximal response. A physiological PK/PD model has been used to account for this time delay, in which a biophase was postulated to account for tiagabine available to the GABA uptake carriers in the synaptic cleft and the increase in EEG effect was considered an indirect response due to inhibition of GABA uptake carriers. The population values for the pharmacodynamic parameters characterizing the delay in pharmacological response relative to plasma concentrations were keo=0.030 min −1 and kout=81 min−1, respectively. Because of the large difference in these values the PK/PD model was simplified to the effect compartment model. Population estimates $$(\bar x \pm SE)$$ were E0=155 ŷ 6 μV, Emax=100 ŷ 5 μV, EC50=287 ŷ 7 ng ml−1, Hill factor=1.8 ŷ 0.2 and keo=0.030 ŷ 0.002 min −1. The results of this analysis show that for tiagabine the combined “effect compartment-indirect response” model can be simplified to the classical “effect compartment” model.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1020999114109
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  • 28
    Electronic Resource
    Electronic Resource
    Assuming Peripheral Elimination: Its Impact on the Estimation of Pharmacokinetic Parameters of Muscle Relaxants (1999)
    Springer
    Journal of pharmacokinetics and pharmacodynamics 27 (1999), S. 491-512 
    Details
    ISSN: 1573-8744
    Keywords: muscle relaxants ; peripheral elimination ; pharmacokinetics ; peripheral concentrations ; volume of distribution ; pharmacokinetic model
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract For anesthetic drugs undergoing nonorgan-based elimination, there is a definite trend towards using pharmacokinetic (PK) models in which elimination can occur from both central (k10 ) and peripheral compartments(k20 ). As the latter cannot be assessed directly, assumptions have to be made regarding its value. The primary purpose of this paper is to evaluate the impact of assuming various degrees of peripheral elimination on the estimation of PK parameters. For doing so, an explanatory model is presented where previously published data from our laboratory on three muscle relaxants, i.e., atracurium, doxacurium, and mivacurium, are used for simulations. The mathematical aspects for this explanatory model as well as for two specific applications are detailed. Our simulations show that muscle relaxants having a short elimination half-life are more affected by the presence of peripheral elimination as their distribution phase occupies the major proportion of their total area under the curve. Changes in the exit site dependent PK parameters (Vdss ) are also mostly significant when k20 is smaller than k10 . Although the physiological processes that determine drug distribution and those affecting peripheral elimination are independent, the two are mathematically tied together in the two-compartment model with both central and peripheral elimination. It follows that, as greater importance is given to k20 , the rate of transfer from the central compartment (k12 ) increases. However, as a result of a proportional increase in the volume of the peripheral compartment, peripheral concentrations remain unchanged whether or not peripheral elimination is assumed. These findings point out the limitations of compartmental analysis when peripheral elimination cannot be measured directly.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1023286329945
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  • 29
    Electronic Resource
    Electronic Resource
    Pharmacokinetics and Dosage Regimen of Enrofloxacin in Buffalo Bulls after Intramuscular Administration (1999)
    Springer
    Veterinary research communications 23 (1999), S. 501-505 
    Details
    ISSN: 1573-7446
    Keywords: antibiotics ; buffalo ; disposition ; dosage ; enrofloxacin ; pharmacokinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The disposition kinetics and dosage regimen of enrofloxacin were investigated in breeding buffalo bulls following a single intramuscular administration of 5 mg/kg. The absorption half-life, half-life of the terminal phase, apparent volume of distribution and total body clearance were 0.262±0.099 h, 1.97±0.23 h, 0.61±0.13 L/kg and 210.2±18.6 ml/(kg.h), respectively. Therapeutic plasma levels (≥1 μg/ml) were maintained for up to 6 h. A satisfactory intramuscular dosage regimen for enrofloxacin in buffalo bulls would be 8.5 mg/kg followed by 8.0 mg/kg at 8 h intervals.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006366507016
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  • 30
    Electronic Resource
    Electronic Resource
    Pharmacokinetics of Amoxicillin Trihydrate in Desert Sheep and Nubian Goats (1999)
    Springer
    Veterinary research communications 23 (1999), S. 507-514 
    Details
    ISSN: 1573-7446
    Keywords: amoxicillin ; bioavailability ; breed ; goats ; pharmacokinetics ; sheep
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The pharmacokinetics of amoxicillin were studied in five Desert sheep and five Nubian goats after intravenous (i.v.) or intramuscular (i.m.) administration of a single dose of 10 mg/kg body weight. Following i.v. injection, the plasma concentration-versus-time data were best described by a two-compartment open model. The kinetic variables were similar in both species except for the volume of the central compartment (Vc), which was larger in sheep (p〈0.05). Following i.m. injection, except for the longer half-life time of absorption in goats (p〈0.05), there were no significant differences in other pharmacokinetic parameters between sheep and goats. The route of amoxicillin administration had no significant effect on the terminal elimination half-life in either species. The bioavailability of the drug (F) after i.m. administration was high (〉0.90) in both species. These results indicate that the pharmacokinetics of amoxicillin did not differ between sheep and goats; furthermore, because of the high availability and short half-life of absorption, the i.m. route gives similar results to the i.v. route. Therefore, identical intramuscular and intravenous dose regimens should be applicable to both species.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006318623854
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  • 31
    Electronic Resource
    Electronic Resource
    Comparative Anthelmintic Activity of Strategic Sustained Low-level Administration of Albendazole in Feed Pellets Compared to Single Doses of Closantel and Tetramisole against Natural Ovine Parasitic Gastroenteritis (1999)
    Springer
    Tropical animal health and production 31 (1999), S. 193-204 
    Details
    ISSN: 1573-7438
    Keywords: albendazole ; anthelmintic ; closantel ; control ; delivery ; dosage ; Haemonchus contortus ; in-feed ; pharmacokinetics ; sheep ; tetramisole
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The strategic use of single therapeutic doses of closantel, tetramisole or sustained low-level administration of albendazole in feed pellets in controlling naturally acquired parasitic gastroenteritis in sheep was investigated on a farm in semi-arid Rajasthan, India. A total of 303 5- to 6-month-old sheep were divided into three groups. Two groups were dosed with single therapeutic doses of closantel and tetramisole and the third group was given a low-level medication with albendazole through feed pellets for 30 days. Faecal egg counts revealed significantly lower counts (p〈0.001) in the group treated with closantel compared to the other two groups. The faecal egg counts in the group receiving sustained low-level albendazole rose after withdrawal of the medication but remained significantly lower than those in the group treated with tetramisole up to 7 weeks after treatment (p〈0.05). On the other hand, in the group treated with tetramisole, the mean faecal egg count rose from 3 weeks after treatment and remained continuously higher than those in any other group up to 12 weeks after treatment. The closantel-treated group gained more body weight but the first six-monthly greasy fleece yield was greater in the group treated with medicated pellets. During the first 3 months of the experiment, three animals in the group treated with tetramisole died of parasitic gastroenteritis. Following sustained low-level administration of albendazole in feed pellets, the plasma disposition curve of both the sulphoxide and sulphone metabolites reached its plateau level by day 5 and remained almost constant thereafter. The comparative cost-effectiveness of the three treatment regimes during the first 3 months of treatment was best for the group treated with closantel followed by the group treated with medicated feed pellets.
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    URL: http://dx.doi.org/10.1023/A:1005223025851
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  • 32
    Electronic Resource
    Electronic Resource
    Some Pharmacokinetic Parameters of Eprinomectin in Goats following Pour-on Administration (1999)
    Springer
    Veterinary research communications 23 (1999), S. 449-455 
    Details
    ISSN: 1573-7446
    Keywords: eprinomectin ; goat ; pharmacokinetics ; topical application
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Some pharmacokinetic parameters of eprinomectin were determined in goats following topical application at a dose rate of 0.5 mg/kg. The plasma concentration versus time data for the drug were analysed using a one-compartment model. The maximum plasma concentration of 5.60±1.01 ng/ml occurred 2.55 days after administration. The area under the concentration–time curve (AUC) was 72.31±11.15 ng day/ml and the mean residence time (MRT) was 9.42±0.43 days. Thus, the systemic availability of eprinomectin to goats was significantly lower than that for cows. The low concentration of eprinomectin in the plasma of goats suggests that the pour-on dose of 0.5 mg/kg would be less effective in this species than in cows. Further relevant information about the optimal dosage and residues in the milk of dairy goats is needed before eprinomectin should be used in this species.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006373609314
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  • 33
    Electronic Resource
    Electronic Resource
    Lack of Sex-influence on the In Vitro Metabolism of Ivermectin by Hepatic Microsomal Preparations from Cattle (1999)
    Springer
    Veterinary research communications 23 (1999), S. 223-227 
    Details
    ISSN: 1573-7446
    Keywords: cattle ; gender ; ivermectin ; metabolism ; pharmacokinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006249009553
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  • 34
    Electronic Resource
    Electronic Resource
    Influence of Diet Type and Pretreatment Fasting on the Disposition Kinetics of Albendazole in Sheep (1999)
    Springer
    Veterinary research communications 23 (1999), S. 229-240 
    Details
    ISSN: 1573-7446
    Keywords: albendazole ; diet ; fasting ; green fodder ; pharmacokinetics ; sheep
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The influence of the quality and quantity of diets on the disposition kinetics of albendazole were studied in sheep in two different experiments. The plasma concentration profiles of albendazole sulphoxide and albendazole sulphone were measured following intraruminal administration of albendazole at 5.0 mg/kg body weight in weaner sheep offered three different diets: 100% green Sorghum spp., 100% dry mature Cenchrus ciliaris hay and a 50:50 mix of these two diets. The peak plasma concentrations and the availability of the albendazole metabolites, as measured by the area under the concentration–time curve, were significantly higher (p〈0.01) in the animals offered exclusively dry fodder compared to other diets. Changing the diet from dry to green fodder resulted in a significantly lower systemic availability of the drug metabolites. It is suggested that a decreased transit time of the digesta in the bowel on the green diet, with its high water content, limited the systemic availability of the drug by reducing the time available for gastrointestinal absorption. An experiment on the influence of different levels of pretreatment fasting on the pharmacokinetics of albendazole revealed significantly higher (p〈0.05) plasma concentrations of the anthelmintically active sulphoxide metabolite from 12 h onwards following administration of the drug in animals subjected to 24 h of pretreatment fasting compared to other groups with pretreatment fasting of 8, 12 or 18 h. The area under the concentration–time curve and the minimum residence time of the drug metabolites were significantly greater (p〈0.05) in animals that had been fasted for 24 h. It is suggested that fasting induces a decrease in the flow of digesta through the gastrointestinal tract of ruminants and prolongs the duration of dissolution of the drug, resulting in enhancement of the absorption of albendazole and of the systemic availability of its metabolites.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006201226391
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  • 35
    Electronic Resource
    Electronic Resource
    Effects of Potato-cyst Nematodes (Globodera pallida) and Soil pH on Root Growth, Nutrient Uptake and Crop Growth of Potato (1999)
    Springer
    European journal of plant pathology 105 (1999), S. 61-76 
    Details
    ISSN: 1573-8469
    Keywords: core sampling ; foliar nutrient concentrations ; minirhizotrons ; nitrogen ; phosphorus ; potassium ; Rhizolab
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Potato-cyst nematodes (Globodera pallida) cause severe yield losses in potato. Plants infected with potato-cyst nematodes generally have reduced concentrations of nitrogen, phosphorus and potassium in the foliage. This study investigated whether reduced growth of nematode-infected potato is caused by nutrient limitation. Experiments in the field and in containers showed that phosphorus concentration correlated best with total crop biomass at early stages of growth. The role of phosphorus in nematode damage was further investigated in the field and in the Wageningen Rhizolab. The experimental field was infested with potato-cyst nematodes and two levels of nematode density were established by fumigation with a nematicide. Prior applications of calcium carbonate resulted in pHKCl levels of 4.8 and 6.1. Two levels of phosphorus fertiliser were applied: either 0 or 225 kg P ha−1. In the Wageningen Rhizolab, soil of both pH levels from the field was used after treatment with 1 MRad gamma irradiation to kill the nematodes. Subsequently, half of the soil was inoculated with cysts to give a nematode density of 30 viable juveniles per gram of soil. In the field, nine weeks after planting, the total crop biomass ranged from 107 g m−2 for the treatment with nematodes at pHKCl 6.1 without phosphorus fertiliser to 289 g m−2 for the fumigated treatment at pHKCl 4.8 with phosphorus fertiliser. The differences in total biomass for the various treatments were explained by differences in foliar phosphorus concentration. Nematodes induced or aggravated P deficiency and reduced total biomass. This was not the only damage mechanism as at high, non-limiting levels of foliar phosphorus concentration, nematodes still reduced total biomass. In the Wageningen Rhizolab, directly after planting, the number of roots visible against minirhizotrons was reduced by nematodes. However, the increase of root number in the nematode treatment continued longer than in the control, until root number was higher than that of the control. The compensary root growth of the nematode treatment was restricted to the top 30 cm and nematodes reduced rooting depth. High soil pH reduced growth, mainly by reducing the availability of phosphate. Both nematodes and high soil pH reduced nutrient uptake per unit root length. Our results lead us to suggest an interaction between nematodes and soil pH, with nematode damage being higher at pHKCl 6.1 than at pHKCl 4.8.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008641511688
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  • 36
    Electronic Resource
    Electronic Resource
    Deposition Rates of Terrestrial and Marine Organic Carbon in the Osaka Bay, Seto Inland Sea, Japan, Determined Using Carbon and Nitrogen Stable Isotope Ratios in the Sediment (1999)
    Springer
    Journal of oceanography 55 (1999), S. 1-11 
    Details
    ISSN: 1573-868X
    Keywords: Osaka Bay ; sediment ; carbon ; nitrogen ; organic matter ; stable isotope ratio ; terrestrial organic matter ; TOC ; POC
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract Carbon and nitrogen stable isotope ratios (δ13C and δ15N) of surface sediments were measured within Osaka Bay, in the Seto Inland Sea in Japan, in order to better understand the sedimentation processes operating on both terrestrial and marine organic matter in the Bay. The δ13C and δ15N of surface sediments in the estuary of the Yodo River were less than −23‰ and 5‰ respectively, but increased in the area up to about 10 km from the river mouth. At greater distances they became constant (giving δ13C of about −20‰ and δ15N about 6‰). It can be concluded that large amounts of terrestrial organic matter exist near the mouth of the Yodo River. Stable isotope ratios in the estuary of the Yodo River within 10 km of the river mouth were useful indicators allowing study of the movement of terrestrial organic matter. Deposition rates for total organic carbon (TOC) and total nitrogen (TN) over the whole of the Bay were estimated to be 63,100 ton C/year and 7,590 ton N/year, respectively. The deposition rate of terrestrial organic carbon was estimated to be 13,200 (range 2,000–21,500) ton C/year for the whole of Osaka Bay, and terrestrial organic carbon was estimated to be about 21% (range 3–34) of the TOC deposition rate. The ratio of the deposition rate of terrestrial organic carbon to the rate inflow of riverine TOC and particulate organic carbon (POC) were estimated to be 19% (range 3–31) and 76% (range 12–100), respectively.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1007850003262
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  • 37
    Electronic Resource
    Electronic Resource
    Rapid Attainment of Steady-State Plasma Drug Concentrations Within Precise Limits in Multicompartment Mammillary Systems (1999)
    Springer
    Journal of pharmacokinetics and pharmacodynamics 27 (1999), S. 325-328 
    Details
    ISSN: 1573-8744
    Keywords: anesthetic techniques ; continuous infusion ; pharmacokinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract We have previously described a method of rapidly obtaining a specified steady-state plasma concentration of an intravenous drug within precise limits. However the method is limited to drugs whose disposition may be characterized by an open two-compartment system. In this paper, we illustrate how the method can be extended to drugs whose disposition may be characterized by a mammillary model with any number of compartments. Refinements of our previous technique are also described.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1020951230947
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  • 38
    Electronic Resource
    Electronic Resource
    Population Pharmacokinetics and Pharmacodynamics of the Anti-CD11a Antibody hu1124 in Human Subjects with Psoriasis (1999)
    Springer
    Journal of pharmacokinetics and pharmacodynamics 27 (1999), S. 397-420 
    Details
    ISSN: 1573-8744
    Keywords: psoriasis ; hu1124 ; CD11a ; CD3-positive lymphocytes ; pharmacokinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The pharmacokinetics of hu1124, a human anti-CD11a antibody, were investigated in human subjects with psoriasis. CD11a is a subunit of LFA-1, a cell surface molecule involved in T cell mediated immune responses. Subjects received a single dose of 0.03, 0.1, 0.3, 0.6, 1, 2, 3, or 10 mg/kg of hu1124 intravenously over 1–3 hr. Blood samples were collected at selected times from 60 min to 72 days after administration. Plasma samples were assayed for hu1124 by ELISA, and pharmacokinetic analyses were performed on the drug plasma concentrations. As the dose of hu1124 was increased, the clearance decreased from 322 ml/day per kg at 0.1 mg/kg to 6.6 ml/day per kg at 10 mg/kg of hu1124. The plasma hu1124 concentration–time profile suggested that the clearance of hu1124 was saturable above 10 μg/ml. In addition, treatment with hu1124 caused a rapid reduction in the level of CD11a expression on CD3-positive lymphocytes (T cells) to about 25% of pretreatment levels. Regardless of the hu1124 dose administered, cell surface CD11a remained at this reduced level as long as hu1124 was detectable (〉0.025 μg/ml) in the plasma. When hu1124 levels fell below 3 μg/ml, the drug was rapidly cleared from the circulation and expression of CD11a returned to normal within 7–10 days thereafter. In vitro, half-maximal binding of hu1124 to lymphocytes was achieved at about 0.1 μg/ml and saturation required more than 10 μg/ml. One of the receptor-mediated pharmacokinetic/pharmacodynamic models which was developed describes the dynamic interaction of hu1124 binding to CD11a, resulting in the removal of hu1124 from the circulation and reduction of cell surface CD11a. The model accounts for the continually changing number of CD11a molecules available for removing hu1124 from the circulation based on prior exposure of cells expressing CD11a to hu1124. In addition, the model also accounts for saturation of CD11a molecules by hu1124 at drug concentrations of approximately 10 μg/ml, thereby reducing the clearance rate of hu1124 with increasing dose.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1020917122093
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  • 39
    Electronic Resource
    Electronic Resource
    Drug–Drug Pharmacodynamic Interaction Detection by a Nonparametric Population Approach. Influence of Design and of Interindividual Variability (1999)
    Springer
    Journal of pharmacokinetics and pharmacodynamics 27 (1999), S. 531-554 
    Details
    ISSN: 1573-8744
    Keywords: drug–drug interactions ; NPML ; experimental design ; pharmacodynamic variability ; pharmacokinetics ; entropy ; covariate ; second stage model ; controlled trial
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Population approaches are appealing methods for detecting then assessing drug–drug interactions mainly because they can cope with sparse data and quantify the interindividual pharmacokinetic (PK) and pharmacodynamic (PD) variability. Unfortunately these methods sometime fail to detect interactions expected on biochemical and/or pharmacological basis and the reasons of these false negatives are somewhat unclear. The aim of this paper is firstly to propose a strategy to detect and assess PD drug–drug interactions when performing the analysis with a nonparametric population approach, then to evaluate the influence of some design variates (i.e., number of subjects, individual measurements) and of the PD interindividual variability level on the performances of the suggested strategy. Two interacting drugs A and B are considered, the drug B being supposed to exhibit by itself a pharmacological action of no interest in this work but increasing the A effect. Concentrations of A and B after concomitant administration are simulated as well as the effect under various combinations of design variates and PD variability levels in the context of a controlled trial. Replications of simulated data are then analyzed by the NPML method, the concentration of the drug B being included as a covariate. In a first step, no model relating the latter to each PD parameter is specified and the NPML results are then proceeded graphically, and also by examining the expected reductions of variance and entropy of the estimated PD parameter distribution provided by the covariate. In a further step, a simple second stage model suggested by the graphic approach is introduced, the fixed effect and its associated variance are estimated and a statistical test is then performed to compare this fixed effect to a given value. The performances of our strategy are also compared to those of a non-population-based approach method commonly used for detecting interactions. Our results illustrate the relevance of our strategy in a case where the concentration of one of the two drugs can be included as a covariate and show that an existing interaction can be detected more often than with a usual approach. The prominent role of the interindividual PD variability level and of the two controlled factors is also shown.
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    URL: http://dx.doi.org/10.1023/A:1023290530853
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  • 40
    Electronic Resource
    Electronic Resource
    Wastewater Irrigation-Economic Concerns Regarding Beneficiary and Hazardous Effects of Nutrients (1999)
    Springer
    Water resources management 13 (1999), S. 303-314 
    Details
    ISSN: 1573-1650
    Keywords: economics ; irrigation ; nitrogen ; nutrients ; wastewater
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Notes: Abstract The optimal wastewater treatment level is affected by costs, hazards and benefits. Lowering the wastewater treatment level decreases fertilization costs because of the increased levels of available nutrients left in the water, and irrigation costs decrease if water prices reflect the lower treatment costs. Agricultural yields and/or prices may decrease according to differences between levels of nutrients needed by crops and those available in wastewater. The present article focuses on determination of monthly optimal treatment levels and of the mix of crops calculated to maximize agricultural incomes, according to farmers' point of view. It does not reflect the national point-view focusing on maximization of net national benefits considering also environmental hazards. The methodology appears in Haruvy (1994) and application will be presented in another article (Haruvy et al., 1999).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008114225469
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  • 41
    Electronic Resource
    Electronic Resource
    Pharmacokinetics and Hemostatic Effects of Saruplase in Patients with Acute Myocardial Infarction: Comparison of Infusion, Single-Bolus, and Split-Bolus Administration (1999)
    Springer
    Journal of thrombosis and thrombolysis 8 (1999), S. 213-221 
    Details
    ISSN: 1573-742X
    Keywords: saruplase ; pharmacokinetics ; bolus administration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Saruplase, or unglycosylated, single-chain urokinase-type plasminogen activator (scu-PA) selectively activates fibrin-bound plasminogen, and is subsequently converted to its two-chain derivative tcu-PA (urokinase) by plasmin. The efficacy of a 20 mg IV bolus followed by an infusion of 60 mg over 1 hour (standard regimen) has been demonstrated in acute myocardial infarction (AMI). The Bolus Administration of Saruplase in Europe (BASE) study compared the efficacy of standard therapy, single bolus (80 mg), and split bolus (2 × 40 mg at 30-minute intervals) in AMI. In a substudy of BASE, the pharmacokinetics of total u-PA activity (amidolytic activity after plasmin treatment), high molecular weight (HMW) u-PA antigen, and tcu-PA activity were compared in patients receiving standard therapy (n = 4), single bolus (n = 4), or split bolus (n = 5). Total u-PA activity and HMW u-PA antigen were similar. The maximum concentration (Cmax,, mean ± SD) of total u-PA activity was 2.2 ± 0.3 µg/mL after standard therapy, 16.3 ± 3.9 µg/mL after single bolus, and 8.2 ± 1.6 ug/mL after split bolus. The area under the concentration versus time curve (AUC) values of total u-PA activity were 1.7 ± 0.1 µg/mL*h (standard therapy), 4.0 ± 0.9 µg/mL*h (bolus), and 3.0 ± 0.7 µg/mL*h (split bolus). The dominant initial half-lives (t1/2 α) were 7.1 ± 1.1 minutes (standard), 8.8 ± 0.8 minutes (bolus), and 5.1 ± 2.1 minutes (split bolus). Maximum plasma concentrations of of tcu-PA activity were observed at 5.2 ± 7 minutes (standard), 21 ± 10 minutes (bolus), and 42 ± 2 minutes (split bolus). Cmax was lowest after standard therapy (0.6 ± 0.3 µg/mL), highest after bolus (4.2 ± 2.2 µg/mL), and approximately twice as high as standard therapy after split bolus (1.3 ± 0.8 µg/mL). After standard therapy the mean fibrinogen concentration decreased gradually from approximately 300 mg/dL to 70 mg/dL at 90 and 120 minutes. After a single bolus the fibrinogen concentration decreased below the limit of quantification within 30 minutes and remained there for at least 120 minutes. Directly after the second 40 mg dose of the split bolus, the fibrinogen levels had an accelerated and more pronounced decrease to approximately 65 mg/dL at 90 and 120 minutes. A single bolus results in very high early total u-PA activity, which accelerates the appearance of tcu-PA activity and fibrinogen consumption. The pharmacokinetics and hemostatic effects of the split-bolus regimen are more comparable with those of standard therapy.
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    URL: http://dx.doi.org/10.1023/A:1008914321384
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  • 42
    Electronic Resource
    Electronic Resource
    Do top-down and bottom-up controls interact to exclude nitrogen-fixing cyanobacteria from the plankton of estuaries? An exploration with a simulation model (1999)
    Springer
    Biogeochemistry 46 (1999), S. 203-231 
    Details
    ISSN: 1573-515X
    Keywords: Baltic Sea ; cyanobacteria ; estuaries ; grazing ; iron ; lakes ; molybdenum ; nitrogen ; nitrogen fixation ; nitrogen limitation ; Zooplankton
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Explaining the nearly ubiquitous absence of nitrogen fixation by planktonic organisms in strongly nitrogen-limited estuaries presents a major challenge to aquatic ecologists. In freshwater lakes of moderate productivity, nitrogen limitation is seldom maintained for long since heterocystic, nitrogen-fixing cyanobacteria bloom, fix nitrogen, and alleviate the nitrogen limitation. In marked contrast to lakes, this behavior occurs in only a few estuaries worldwide. Primary production is limited by nitrogen in most temperate estuaries, yet no measurable planktonic nitrogen fixation occurs. In this paper, we present the hypothesis that the absence of planktonic nitrogen fixers from most estuaries is due to an interaction of bottom-up and top-down controls. The availability of Mo, a trace metal required for nitrogen fixation, is lower in estuaries than in freshwater lakes. This is not an absolute physiological constraint against the occurrence of nitrogen-fixing organisms, but the lower Mo availability may slow the growth rate of these organisms. The slower growth rate makes nitrogen-fixing cyanobacteria in estuaries more sensitive to mortality from grazing by Zooplankton and benthic organisms. We use a simple, mechanistically based simulation model to explore this hypothesis. The model correctly predicts the timing of the formation of heterocystic, cyanobacterial blooms in freshwater lakes and the magnitude of the rate of nitrogen fixation. The model also correctly predicts that high Zooplankton biomasses in freshwaters can partially suppress blooms of nitrogen-fixing cyanobacteria, even in strongly nitrogen-limited lakes. Further, the model indicates that a relatively small and environmentally realistic decrease in Mo availability, such as that which may occur in seawater compared to freshwaters due to sulfate inhibition of Mo assimilation, can suppress blooms of heterocystic cyanobacteria and prevent planktonic nitrogen fixation. For example, the model predicts that at a Zooplankton biomass of 0.2 mg l−1, cyanobacteria will bloom and fix nitrogen in lakes but not in estuaries of full-strength seawater salinity because of the lower Mo availability. Thus, the model provides strong support for our hypothesis that bottom-up and top-down controls may interact to cause the absence of planktonic nitrogen fixation in most estuaries. The model also provides a basis for further exploration of this hypothesis in individual estuarine systems and correctly predicts that planktonic nitrogen fixation can occur in low salinity estuaries, such as the Baltic Sea, where Mo availability is greater than in higher salinity estuaries.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01007580
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  • 43
    Electronic Resource
    Electronic Resource
    Nitrogen stable isotopic composition of leaves and soil: Tropical versus temperate forests (1999)
    Springer
    Biogeochemistry 46 (1999), S. 45-65 
    Details
    ISSN: 1573-515X
    Keywords: N15 ; nitrogen ; nutrient cycling ; plants ; stable isotopes ; soil ; temperate forest ; tropical forest
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Several lines of evidence suggest that nitrogen in most tropical forests is relatively more available than N in most temperate forests, and even that it may function as an excess nutrient in many tropical forests. If this is correct, tropical forests should have more open N cycles than temperate forests, with both inputs and outputs of N large relative to N cycling within systems. Consequent differences in both the magnitude and the pathways of N loss imply that tropical forests should in general be more 15N enriched than are most temperate forests. In order to test this hypothesis, we compared the nitrogen stable isotopic composition of tree leaves and soils from a variety of tropical and temperate forests. Foliar δ15N values from tropical forests averaged 6.5‰ higher than from temperate forests. Within the tropics, ecosystems with relatively low N availability (montane forests, forests on sandy soils) were significantly more depleted in 15N than other tropical forests. The average δ15N values for tropical forest soils, either for surface or for depth samples, were almost 8‰ higher than temperate forest soils. These results provide another line of evidence that N is relatively abundant in many tropical forest ecosystems.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006100128782
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  • 44
    Electronic Resource
    Electronic Resource
    The impact of accelerating land-use change on the N-Cycle of tropical aquatic ecosystems: Current conditions and projected changes (1999)
    Springer
    Biogeochemistry 46 (1999), S. 109-148 
    Details
    ISSN: 1573-515X
    Keywords: estuaries ; lakes ; marine ; nitrogen ; phosphorus ; rivers ; streams ; temperate ; tropics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Published data and analyses from temperate and tropical aquatic systems are used to summarize knowledge about the potential impact of land-use alteration on the nitrogen biogeochemistry of tropical aquatic ecosystems, identify important patterns and recommend key needs for research. The tropical N-cycle is traced from pre-disturbance conditions through the phases of disturbance, highlighting major differences between tropical and temperate systems that might influence development strategies in the tropics. Analyses suggest that tropical freshwaters are more frequently N-limited than temperate zones, while tropical marine systems may show more frequent P limitation. These analyses indicate that disturbances to pristine tropical lands will lead to greatly increased primary production in freshwaters and large changes in tropical freshwater communities. Increased freshwater nutrient flux will also lead to an expansion of the high production, N- and light-limited zones around river deltas, a switch from P- to N-limitation in calcareous marine systems, with large changes in the community composition of fragile mangrove and reef systems. Key information gaps are highlighted, including data on mechanisms of nutrient transport and atmospheric deposition in the tropics, nutrient and material retention capacities of tropical impoundments, and N/P coupling and stoichiometric impacts of nutrient supplies on tropical aquatic communities. The current base of biogeochemical data suggests that alterations in the N-cycle will have greater impacts on tropical aquatic ecosystems than those already observed in the temperate zone.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006156213761
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  • 45
    Electronic Resource
    Electronic Resource
    Do top-down and bottom-up controls interact to exclude nitrogen-fixing cyanobacteria from the plankton of estuaries? An exploration with a simulation model (1999)
    Springer
    Biogeochemistry 46 (1999), S. 203-231 
    Details
    ISSN: 1573-515X
    Keywords: Baltic Sea ; cyanobacteria ; estuaries ; grazing ; iron ; lakes ; molybdenum ; nitrogen ; nitrogen fixation ; nitrogen limitation ; zooplankton
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Explaining the nearly ubiquitous absence of nitrogen fixation by planktonic organisms in strongly nitrogen-limited estuaries presents a major challenge to aquatic ecologists. In freshwater lakes of moderate productivity, nitrogen limitation is seldom maintained for long since heterocystic, nitrogen-fixing cyanobacteria bloom, fix nitrogen, and alleviate the nitrogen limitation. In marked contrast to lakes, this behavior occurs in only a few estuaries worldwide. Primary production is limited by nitrogen in most temperate estuaries, yet no measurable planktonic nitrogen fixation occurs. In this paper, we present the hypothesis that the absence of planktonic nitrogen fixers from most estuaries is due to an interaction of bottom-up and top-down controls. The availability of Mo, a trace metal required for nitrogen fixation, is lower in estuaries than in freshwater lakes. This is not an absolute physiological constraint against the occurrence of nitrogen-fixing organisms, but the lower Mo availability may slow the growth rate of these organisms. The slower growth rate makes nitrogen-fixing cyanobacteria in estuaries more sensitive to mortality from grazing by zooplankton and benthic organisms. We use a simple, mechanistically based simulation model to explore this hypothesis. The model correctly predicts the timing of the formation of heterocystic, cyanobacterial blooms in freshwater lakes and the magnitude of the rate of nitrogen fixation. The model also correctly predicts that high zooplankton biomasses in freshwaters can partially suppress blooms of nitrogen-fixing cyanobacteria, even in strongly nitrogen-limited lakes. Further, the model indicates that a relatively small and environmentally realistic decrease in Mo availability, such as that which may occur in seawater compared to freshwaters due to sulfate inhibition of Mo assimilation, can suppress blooms of heterocystic cyanobacteria and prevent planktonic nitrogen fixation. For example, the model predicts that at a zooplankton biomass of 0.2 mg l−1, cyanobacteria will bloom and fix nitrogen in lakes but not in estuaries of full-strength seawater salinity because of the lower Mo availability. Thus, the model provides strong support for our hypothesis that bottom-up and top-down controls may interact to cause the absence of planktonic nitrogen fixation in most estuaries. The model also provides a basis for further exploration of this hypothesis in individual estuarine systems and correctly predicts that planktonic nitrogen fixation can occur in low salinity estuaries, such as the Baltic Sea, where Mo availability is greater than in higher salinity estuaries.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006189121030
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  • 46
    Electronic Resource
    Electronic Resource
    A Compartmental Analysis of the Pharmacokinetics of Propofol in Sheep (1999)
    Springer
    Journal of pharmacokinetics and pharmacodynamics 27 (1999), S. 329-338 
    Details
    ISSN: 1573-8744
    Keywords: propofol ; anaesthesia ; pharmacokinetics ; compartment models ; effect compartment models
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Conventional compartmental pharmacokinetic analysis may provide inaccurate prediction of drug concentrations after rapid iv administration. To examine this, compartment and effect compartment analysis was applied to measured arterial and brain concentrations of propofol in sheep after iv administration at a range of doses and dose rates. Although arterial and brain concentrations were reasonably well fitted to compartmental and effect compartment models for individual doses and dose rates, the structure and parameters of all models differed with changes in both dose and rate of administration. There were large discrepancies between predicted and measured arterial and brain concentrations when these models were used to predict drug concentrations across doses and dose rates. These data support the limitations of this type of modeling in the setting of rapid propofol administration.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1020903315017
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  • 47
    Electronic Resource
    Electronic Resource
    Indirect-Response Modeling of Desmopressin at Different Levels of Hydration (1999)
    Springer
    Journal of pharmacokinetics and pharmacodynamics 27 (1999), S. 513-529 
    Details
    ISSN: 1573-8744
    Keywords: desmopressin ; indirect-response modeling ; overhydration ; pharmacokinetics ; pharmacodynamics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The objective of the present study was to investigate the pharmacokinetics (PK) and pharmacodynamics (PD) of desmopressin in healthy male subjects at different levels of overhydration. Also, we examined if an indirect-response model could be related to renal physiology and the pharmacological action of desmopressin. Eight healthy male subjects participated in this open, randomized crossover study with three periods. Each subject was orally water loaded (0 to 20ml·kg −1 body weight) on 3 study days in order to achieve three different levels of hydration. After the initial water load, urine was voided every 15 min and the volumes were measured. To ensure continuous overhydration the subjects replaced their fluid loss with drinking-water. When a steady-state diuresis was achieved after approximately 2 hr, 0.396 μg of desmopressin was administered intravenously as a bolus injection. Blood was sampled and urine was collected at intervals throughout the study day (10 hr). An indirect-response model, where desmopressin was assumed to inhibit the elimination of response, was fit to the urine osmolarity data. There were no statistically significant effects of different levels of hydration, as expressed by urine flow rate at baseline, on the estimates of the PK and PD model parameters. The calculated terminal half-lives of elimination (t1/2 β) ranged between 2.76 and 8.37 hr with an overall mean of 4.36 hr. The overall means of plasma clearance and the volumes of distribution of the central compartment (Vc ) and at steady state (Vss ) were estimated to be 1.34 (SD 0.35) ml·min −1 ·kg −1 , 151 (SD28) ml·kg −1 , and 386 (SD 63) ml·kg −1 , respectively. High urine flow rate, indicating overhydration, produced a diluted urine and thus a low osmolarity at baseline (R0 ). The effect of the urine flow rate on the urine osmolarity at baseline was highly significant (p〈0.0001). The mean values for IC50 and the sigmoidicity factor (γ) were 3.7 (SD 1.2) pg·ml −1 and 13.0 (SD 3.5), respectively. In most cases when there was a high urine flow rate at baseline, the model and the estimated PD parameters could be related to the pharmacological action of desmopressin and renal physiology. Thus, the indirect-response model used in this study offers a mechanistic approach of modeling the effect of desmopressin in overhydrated subjects.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1023238514015
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  • 48
    Electronic Resource
    Electronic Resource
    Constructing a Prediction Interval for Time to Reach a Threshold Concentration Based on a Population Pharmacokinetic Analysis: An Application to Basiliximab in Renal Transplantation (1999)
    Springer
    Journal of pharmacokinetics and pharmacodynamics 27 (1999), S. 213-230 
    Details
    ISSN: 1573-8744
    Keywords: prediction interval ; pharmacokinetics ; population analysis ; NONMEM ; inverse regression ; immunosuppressives
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Basiliximab is an immunosuppressant chimeric monoclonal antibody directed to the human interleukin-2 receptor α-chain used for prevention of acute rejection episodes in organ transplantation. The minimally effective serum concentration necessary to saturate receptor epitopes in kidney transplant patients is 0.2 μg/ml. To guide dose selection for Phase 3 efficacy trials, a population pharmacostatistical model was fitted to intensively sampled Phase 2 pharmacokinetic data. This served as a basis from which to examine candidate dose regimens with respect to the duration over which receptor-saturating concentrations would be achieved posttransplant. Three prediction methods were assessed: one based on simulations, and two others based on first-order approximation using either inverse regression or inversion of confidence intervals. An 80% prediction interval was generated by each method to evaluate its predictive performance against prospectively collected Phase 3 data in 39 renal transplant patients who received two injections of 20mg basiliximab, one prior to surgery and one on Day 4 posttransplant. All methods provided correct prediction of the duration of receptor-saturating concentration. As anticipated, the best performance was obtained from the simulation method which predicted 30 values in the 80% prediction interval, 19.7–52.7 days. The actually observed 80% interval from the Phase 3 data was 23.7–58.3 days.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1020658023774
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  • 49
    Electronic Resource
    Electronic Resource
    Modeling Interactions between Adrenal Suppression and T-Helper Lymphocyte Trafficking during Multiple Dosing of Methylprednisolone (1999)
    Springer
    Journal of pharmacokinetics and pharmacodynamics 27 (1999), S. 559-575 
    Details
    ISSN: 1573-8744
    Keywords: T-helper cells ; trafficking ; rebound ; corticosteroids ; circadian rhythm ; methylprednisolone ; drug interactions ; pharmacokinetics ; pharmacodynamics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A physiologic pharmacodynamic model was developed to jointly characterize the effects of corticosteroid treatment on adrenal suppression and T-helper cell trafficking during single and multiple dosing in asthmatic patients. Methylprednisolone (MP), cortisol, and T-helper cell concentrations obtained from a previously published study during single day and 6 days of multiple dosing MP treatment were examined. The formation and disposition kinetics of MP were described with a compartmental model. The biorhythmic profile of basal cortisol secretion rate was analyzed using a recent Fourier approach based on circadian harmonics. A three-compartment loop model was proposed to represent three major T-helper cell pools: blood, extravascular site, and lymph nodes. T-helper cell synthesis and degradation rate constants were obtained from the literature. The suppressive effects of cortisol and MP on T-helper cell concentrations were described with a joint additive inhibition function altering the cell migration rate from lymph nodes to blood. The model adequately described both plasma cortisol profiles and T-helper cells in blood after single and multiple doses of MP. The potency of MP for suppression of cortisol secretion was estimated as IC50 = 0.8 ng/ml. The biorhythmic nature of the basal T-helper cells in blood was well described as under the influence of basal circadian cortisol concentrations with IC50 = 79 ng/ml. The model fitted potency of MP for suppression of T-helper cells was IC50 = 4.6 ng/ml. The observed rebound of T-helper cells in blood can also be described by the proposed model. The rhythm and suppression of plasma cortisol and T-helper cells before and during single and multiple dose MP treatment were adequately described by these extended indirect response models.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1020974408657
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  • 50
    Electronic Resource
    Electronic Resource
    Relationship Between Etomidate Plasma Concentration and EEG Effect in the Rat (1999)
    Springer
    Pharmaceutical research 16 (1999), S. 924-929 
    Details
    ISSN: 1573-904X
    Keywords: etomidate ; pharmacokinetics ; pharmacodynamics ; rat ; electroencephalogram
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Purpose. The effect-plasma concentration relationship of etomidate was studied in the rat using electroencephalographic changes as a pharmacodynamic parameter. Methods. Etomidate was infused (50 mg/kg/h) in chronically instrumented rats (n = 6) until isoelectric periods of 5 s or longer were observed in the electroencephalogram (EEG). The EEG was continuously recorded during the experiment and frequent arterial blood samples were taken for determination of etomidate plasma concentrations. The changes observed in the raw EEG signal were quantified using aperiodic analysis in the 2.5−7.5 Hz frequency band. The return of the righting reflex was used as another parameter of anesthesia. Results. A mean dose of 8.58 ± 0.41 mg/kg needed to be infused to reach the end point of 5 s isoelectric EEG. The plasma concentration time profiles were most adequately fitted using a three-exponential model. Systemic clearance, volume of distribution at steady-state and elimination half-life averaged 93 ± 6 ml/min/kg, 4.03 ± 0.24 l/kg and 59.4 ± 10.7 min respectively. The EEG effect-plasma concentration relationship was biphasic exhibiting profound hysteresis. Semi-parametric minimization of this hysteresis revealed an equilibration half-life of 2.65 ± 0.15 min, and the biphasic effect-concentration relationship was characterized nonparametrically by descriptors. The effect-site concentration at the return of the righting reflex was 0.44 ± 0.03 μg/ml. Conclusions. The results of the present study show that the concentration-effect relationship of etomidate can be characterized in individual rats using aperiodic analysis in the 2.5−7.5 Hz frequency band of the EEG. This characterization can be very useful for studying the influence of diseases on the pharmacodynamics of etomidate in vivo.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1018894523734
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  • 51
    Electronic Resource
    Electronic Resource
    Prediction of Pharmacokinetic Parameters and the Assessment of Their Variability in Bioequivalence Studies by Artificial Neural Networks (1999)
    Springer
    Pharmaceutical research 16 (1999), S. 944-948 
    Details
    ISSN: 1573-904X
    Keywords: bioequivalence ; neural networks ; prediction ; pharmacokinetics ; verapamil
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Purpose. The methodology of predicting the pharmacokinetic parameters (AUC, cmax, tmax) and the assessment of their variability in bioequivalence studies has been developed with the use of artificial neural networks. Methods. The data sets included results of 3 distinct bioequivalence studies of oral verapamil products, involving a total of 98 subjects and 312 drug applications. The modeling process involved building feedforward/backpropagation neural networks. Models for pharmacokinetic parameter prediction were also used for the assessment of their variability and for detecting the most influential variables for selected pharmacokinetic parameters. Variables of input neurons based on logistic parameters of the bioequivalence study, clinical-biochemical parameters, and the physical examination of individuals. Results. The average absolute prediction errors of the neural networks for AUC, cmax, and tmax prediction were: 30.54%, 39.56% and 30.74%, respectively. A sensitivity analysis demonstrated that for verapamil the three most influential variables assigned to input neurons were: total protein concentration, aspartate aminotransferase (AST) levels, and heart-rate for AUC, AST levels, total proteins and alanine aminotransferase (ALT) levels, for cmax, and the presence of food, blood pressure, and body-frame for tmax. Conclusions. The developed methodology could supply inclusion or exclusion criteria for subjects to be included in bioequivalence studies.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1018857108713
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  • 52
    Electronic Resource
    Electronic Resource
    A Physiological Pharmacokinetic Model for Solute Disposition in Tissues Below a Topical Application Site (1999)
    Springer
    Pharmaceutical research 16 (1999), S. 1392-1398 
    Details
    ISSN: 1573-904X
    Keywords: topical application ; dermal absorption ; cutaneous perfusion ; pharmacokinetics ; binding ; half life
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Purpose. Many compounds are applied to the skin with the aim of targeting deeper underlying tissues. This work sought to define the pharmacokinetics of solutes in tissues below a topical application site in terms of perfusate binding, tissue binding and perfusate flow rate. Methods. The disposition kinetics of diclofenac in a single pass perfused limb preparation after dermal application disposition was studied using dextran and bovine serum albumin (BSA) containing perfusates. A pharmacokinetic model was then developed to relate the tissue retention half lives for diclofenac, diazepam, water, lignocaine and salicylate to their fraction unbound in the tissues, their fraction unbound in the perfusate and the perfusate flow rate. Results. Diclofenac had estimated tissue retention half lives of 18.1 hr and 3.5 hr for the dextran and BSA containing perfusates, respectively. The fraction of diclofenac and other solutes unbound in the tissues correlated with their corresponding fraction unbound in the perfusate. The tissue retention half lives for diclofenac and other solutes could be described in terms of the fraction of solute unbound in the tissues and perfusate, together with the flow rate. Conclusions. The tissue pharmacokinetics of solutes below a topical application are a function of their binding in the tissues, binding in perfusate and local blood flow.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1018998908655
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  • 53
    Electronic Resource
    Electronic Resource
    Venous Irritation, Pharmacokinetics, and Tissue Distribution of Tirilazad in Rats Following Intravenous Administration of a Novel Supersaturated Submicron Lipid Emulsion (1999)
    Springer
    Pharmaceutical research 16 (1999), S. 930-938 
    Details
    ISSN: 1573-904X
    Keywords: submicron lipid emulsion ; supersaturation ; tirilazad ; venous irritation ; pharmacokinetics ; tissue distribution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Purpose. To compare the venous irritation, pharmacokinetics, and tissue distribution of tirilazad in rats after intravenous administration of a submicron lipid emulsion with that of an aqueous solution. Methods. Venous irritation was determined by microscopic evaluation of injury to the lateral tail veins of rats. Pharmacokinetic parameters were determined by following plasma concentrations of drug. Tissue distribution of [14C]-tirilazad was determined by quantitative whole body autoradiography. Results. Single dose injections of tirilazad as an emulsion at doses ranging from 1.52 mg to 13.5 mg were non-irritating whereas the solution was irritating at a dose of 1.3 mg. The pharmacokinetic parameters were not statistically different between the emulsion and the solution (p 〉 0.2) at doses of 6 mg/kg/day and 20 mg/kg/day. However, at 65 mg/kg/day dose, a higher AUC(0,6) (4-fold) and lower Vss (18-fold) and CL(5-fold) were observed for the lipid emulsion as compared to the solution (p 〈 0.05). Tissue distribution showed higher initial concentrations (two fold or more) in most tissues for the solution. These values, however, equilibrated by 4 h and AUC(0,4) differences were less than two fold in most tissues. Conclusions. Formulating tirilazad in the lipid emulsion significantly reduces the venous irritation without changing the pharmacokinetics and tissue distribution at low doses.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1018846607804
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  • 54
    Electronic Resource
    Electronic Resource
    Distribution and Binding Kinetics of Ciprofloxacin and Ofloxacin in the Hindlimb of the Rat (1999)
    Springer
    Pharmaceutical research 16 (1999), S. 587-591 
    Details
    ISSN: 1573-904X
    Keywords: quinolones ; pharmacokinetics ; permeability ; tissue binding ; hindlimb
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1011939616948
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  • 55
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    Electronic Resource
    Pharmacokinetics of Methotrexate in the Extracellular Fluid of Brain C6-Glioma After Intravenous Infusion in Rats (1999)
    Springer
    Pharmaceutical research 16 (1999), S. 1219-1225 
    Details
    ISSN: 1573-904X
    Keywords: C6-glioma ; methotrexate ; microdialysis ; pharmacokinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Purpose. Establishment of the pharmacokinetic profile of methotrexate (MTX) in the extracellular fluid (ECF) of a brain C6-glioma in rats. Methods. Serial collection of plasma samples and ECF dialysates after i.v. infusion of MTX (50 or 100 mg/kg) for 4 h. HPLC assay. Results. Histological studies revealed the presence of inflammation, edema, necrosis, and hemorrhage in most animals. In vivo recovery (reverse dialysis) was 10.8 ± 5.3%. MTX concentrations in tumor ECF represented about 1−2% of the plasma concentrations. Rapid equilibration between MTX levels in brain tumor ECF and plasma. ECF concentrations almost reached steady-state by the end of the infusion (4 h), then decayed in parallel with those in plasma. Doubling of the dose did not modify MTX pharmacokinetic parameters (t1/2α, t1/2β, MRT, fb, Vd, and CLT), except for a 1.7-fold increase of AUCPlasma and a 3.8-fold increase in AUCECF which resulted in a 2.3-fold increase in penetration (AUCECF/AUCPlasma). In spite of an important interindividual variability, a relationship between MTX concentrations in plasma and tumor ECF could be established from mean pharmacokinetic parameters. Conclusions. High plasma concentrations promote the penetration of MTX into brain tissue. However, free MTX concentrations in tumor ECF remain difficult to predict consistently.
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    URL: http://dx.doi.org/10.1023/A:1018945529611
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  • 56
    Electronic Resource
    Electronic Resource
    Evaluation of the Pharmacokinetic Features and Tissue Distribution of the Potent Nonnucleoside Inhibitor of HIV-1 Reverse Transcriptase, N-[2-(2-fluorophenethyl)]-N′-[2-(5-bromopyridyl)]-thiourea (HI-240) with an Analytical HPLC Method (1999)
    Springer
    Pharmaceutical research 16 (1999), S. 1226-1232 
    Details
    ISSN: 1573-904X
    Keywords: HI-240 ; nonnucleoside inhibitor ; pharmacokinetics ; HPLC
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Purpose. The purpose of the present study was to examine the pharmacokinetic features and tissue distribution of N-[2-(2-fluorophenethyl)]-N′-[2-(5-bromopyridyl)]-thiourea (HI-240), a novel non-nucleoside inhibitor of HIV reverse transcriptase with potent anti-viral activity against AZT-sensitive as well as multidrug-resistant HIV-1 strains. Methods. A sensitive and accurate high performance liquid chromatography (HPLC)-based quantitative detection method was established to measure concentrations of HI-240 in pharmacokinetic studies. The plasma concentration-time data were modeled by using the WinNonlin program to estimate the pharmacokinetic parameter values. Results. HI-240 had an elimination half-life of 78.3 ± 2.0 min after i.v. administration and 196.8 ± 3.1 min after i.p. administration. The systemic clearance of HI-240 was 2194 ± 61 ml/h/kg after i.v. administration and 9339 ± 1160 ml/h/kg after i.p. administration. Following i.v. injection, HI-240 rapidly distributed to and accumulated in multiple tissues with particularly high accumulation in adipose tissue, adrenal gland, and uterus+ovary. The concentration of HI-240 in brain tissue was comparable to that in the plasma, indicating that HI-240 easily crosses the blood-brain-barrier. Following i.p. injection, HI-240 was rapidly absorbed with a t1/2ka and a tmax values of less than 10 min. Following oral administration, HI-240 was absorbed with a t1/2ka of 4.2 ±1.1 min and a tmax of 95.1 ± 25.1 min. The intraperitoneal bioavailability was estimated at 23.5%, while the oral bioavailability was only 1%. Conclusions. The HPLC-based accurate and precise analytical detection method and pilot pharmacokinetic studies described herein provide the basis for advanced preclinical pharmacodynamic studies of HI-240. The ability of HI-240 to distribute rapidly and extensively into extravascular compartments and easily cross the blood-brain barrier represent significant pharmacokinetic advantages over AZT.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1014814313681
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  • 57
    Electronic Resource
    Electronic Resource
    Pharmacokinetic Features and Metabolism of Calphostin C, A Naturally Occurring Perylenequinone with Antileukemic Activity (1999)
    Springer
    Pharmaceutical research 16 (1999), S. 1003-1009 
    Details
    ISSN: 1573-904X
    Keywords: pharmacokinetics ; Calphostin C ; HPLC ; perylenequinone
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Purpose. To examine the pharmacokinetic features and metabolism of calphostin C, a naturally occurring perylenequinone with potent antileukemic activity. Methods. HPLC-based quantitative detection methods were used to measure calphostin C levels in lysates of leukemic cells and in plasma of mice treated with calphostin C. The plasma concentration-time data were analyzed using the WinNonlin program. In vitro esterases and a microsome P450 preparation in conjunction with a LC-MS(API-EI) system were used to study the metabolism of calphostin C. Results. An intracellular exposure level (AUC0−6h) of 257 μM·h was achieved after in vitro treatment of NALM-6 cells with calphostin C at a 5 μM final concentration in culture medium. After intraperitoneal (i.p.) injection of a 40 mg/kg nontoxic bolus dose of calphostin C, the estimated Cmax was 2.9 μM, which is higher than the effective in vitro concentration of calphostin C against leukemic cells. Drug absorption after i.p. administration was rapid with an absorption half-life of 24.2 min and the estimated tmax was 63.0 min. Calphostin C was cleared with an elimination half-life of 91.3 min. An inactive and smaller metabolite (calphostin B) was detected in plasma of calphostin C-treated mice with a tmax of 41.3 min. Esterase (but not P450) treatment of calphostin C in vitro yielded an inactive metabolite (calphostin B) of the same size and elution profile. Conclusions. Target plasma calphostin C concentrations of potent antileukemic activity can be reached in mice at nontoxic dose levels. This pilot pharmacokinetic study of calphostin C combined with the availability of the described quantitative HPLC method for its detection in cells and plasma provide the basis for future preclinical evaluation of calphostin C and its potential as an anti-leukemic drug.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1018923430094
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  • 58
    Electronic Resource
    Electronic Resource
    Improved Lipid Lowering Activity of Bezafibrate Following Continuous Gastrointestinal Administration: Pharmacodynamic Rationale for Sustained Release Preparation of the Drug (1999)
    Springer
    Pharmaceutical research 16 (1999), S. 1093-1097 
    Details
    ISSN: 1573-904X
    Keywords: bezafibrate ; hyperlipidemia ; pharmacodynamics ; pharmacokinetics ; sustained release
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Purpose. To evaluate the role of different routes and modes of administration of bezafibrate (BZF) on its hypolipidemic activity. We hypothesize that the major sites of BZF action are located presystemically as in other 'gastrointestinal (GI) drugs.' Thus, continuous administration of the drug to the GI tract is expected to augment its efficacy and provides a rationale for an oral sustained release preparation of the drug. Methods. The hypothesis was investigated in three experimentally induced-hyperlipidemia rat models. Models A and B were based on cholesterol-enriched diets and Model C on induced acute hyperlipidemia by triton 225 mg/kg. The pharmacokinetics and the pharmacodynamics of the drug following various modes of administration were examined. Results. In all cases, continuous administration of the drug into the duodenum (IGI) at a dose of 30 mg/kg/day for 3 days (Models A and B) or over 18 hr (Model C) reduced significantly both total cholesterol and triglycerides levels and elevated HDL cholesterol levels in comparison to bolus oral administration of the same dose, as well as in comparison to equivalent intravenous infusion (Model C). Infusion of the drug directly into the portal vein produced an equivalent activity to IGI administration. The pharmacokinetic study showed 100% oral bioavailability, good colonic absorption properties and an indication for an enterohepatic cycle. Conclusions. The results confirm that BZF has a first pass hepatic pharmacodynamic effect. Administration of BZF in a slow release matrix tablet to the rats produced the same magnitude of effect as IGI administration, thus proving the pharmacodynamic rationale for this mode of administration for GI drugs.
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    URL: http://dx.doi.org/10.1023/A:1018900219616
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  • 59
    Electronic Resource
    Electronic Resource
    Dopamine release in the prefrontal cortex in response to memantine following sub-chronic NMDA receptor blockade with memantine: a microdialysis study in rats (1999)
    Springer
    Journal of neural transmission 106 (1999), S. 803-818 
    Details
    ISSN: 1435-1463
    Keywords: Keywords: Dopamine ; memantine ; microdialysis ; pharmacokinetics ; pre-frontal cortex.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary. Memantine is an uncompetitive N-methyl-D-aspartate receptor antagonist which blocks the NMDA receptor with moderate-affinity in a use- and voltage dependent manner. In clinical practice it is used chronically in the treatment of dementia and does not induce psychotomimetic effects as, high affinity, uncompetitive antagonists. Thus, it was of interest to determine dopamine (DA) and metabolite (DOPAC – dihydroxyphenylacetic acid and HVA – homovanillic acid) concentrations in the prefrontal cortex (PFC) in response to 14 days administration of memantine (20 mg/kg/day). It was previously determined that in rats this treatment induces sensitization to the locomotor effect and tolerance to the learning impairing properties of high doses of memantine. Acute administration of memantine (20 mg/kg, ip) did not affect dopamine levels in the PFC. It did however increase DA metabolite (DOPAC and HVA) concentrations. Administration of memantine (20 mg/kg/day) for 14 days before the acute challenge only slightly changed memantine's effect on PFC neurochemistry even though pharmacokinetic tolerance was observed. When memantine was administered to the sham group, which had been repeatedly treated with Hypnorm (including neuroleptic), an increase in PFC dopamine and metabolite content was seen. In accordance with the fact that memantine does not possess psychotomimetic activity at therapeutically relevant doses, these experiments showed that it does not affect the prefrontal cortex dopamine levels.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s007020050201
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  • 60
    Electronic Resource
    Electronic Resource
    The effect of regeneration burns on the growth, nutrient acquisition and mycorrhizae of Eucalyptus regnans F. Muell. (mountain ash) seedlings (1999)
    Springer
    Plant and soil 210 (1999), S. 273-283 
    Details
    ISSN: 1573-5036
    Keywords: ectomycorrhizae ; Eucalyptus regnans ; forest burns ; nitrogen ; phosphorus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract This study was conducted to compare the effects on the growth of Eucalyptus regnans seedlings of unheated soil and soil heated to different extents (as indicated by soil colour–bright red or black) in burnt logging coupes, and to separate the effects of heating of the soil on direct nutrient availability and on morphotypes and effectiveness of ectomycorrhizae. Burnt soils were collected from three logging coupes burnt 2, 14 and 25 months previously and unbumt soil from adjacent regrowth forests. Compared to unburnt soil, the early seedling growth was stimulated in black burnt soil from all coupes (burnt 2, 14 and 25 months previously). Seedling growth was generally poor in red burnt soil, especially in soil collected 2 months after burning. However, the concentration of extractable P was extremely high in red burnt soil, especially in soil collected 2 months after burning. In black burnt soil, extractable P was increased in soil 2 months after burning, but not in the soils collected 14 or 25 months after burning. However, both total P content and concentration in seedlings were increased in all collections of black burnt soil. Frequency of ectomycorrhizae was high in seedlings grown in all black burnt soils, but the mycorrhizal mantles were poorly developed in seedlings in black burnt soil collected 2 months after burning. Seedlings were also ectomycorrhizal in red burnt soil, except in soil collected 2 months after burning. Fine root inocula from seedlings grown in black burnt soils collected 14 and 25 months after burning significantly stimulated both seedling growth and P uptake compared with the uninoculated control, whereas the fine root inocula from the seedlings grown in all the other soils did not. These results suggest that, in black burnt soil, both direct nutritional changes and changes in the ectomycorrhizae may contribute to seedling growth promotion after regeneration burns. The generally poor seedling growth in red burnt soils is likely to have been due to N deficiency as the seedlings in these soils were yellow-green and the tissue concentrations of N were significantly lower than in other treatments.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1004609912315
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    A comparison of direct and indirect 15N isotope techniques for estimating crop N uptake from organic residues (1999)
    Springer
    Plant and soil 208 (1999), S. 259-270 
    Details
    ISSN: 1573-5036
    Keywords: crop residues ; isotope dilution ; 15N ; nitrogen ; organic matter ; pool substitution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Experiments were carried out to compare the direct approach for estimating crop N uptake from 15N labelled organic inputs, to two indirect approaches, 15N isotope dilution and A value. In the first experiment soils received 25, 50, 75, or 100 mg N kg soil−1 in the form of Casuarina equisitifolia residues in addition to ammonium sulphate fertiliser, to give a total of 100 mg N kg soil−1 added. This was a cross labelling design, thus two matching sets of treatments, were set up, identical in all but the position of the 15N label. Maize (Zea mays L.) plants were grown in the soils amended with residues for 11 weeks and N derived from residues (Ndfr) estimated using the A-value or the direct approach. The A-value approach appeared to significantly overestimate %Ndfr compared to the direct method. In the second experiment contrasting residues were added to soil, fababean (Vicia faba L. var. minor), alfalfa (Medicago sativa L.), soyabean fixing, (Glycine max (L.) Merrill), soyabean non-fixing, barley (Hordeum vulgare L.) and maize. This was also cross-labelling design, labelled and unlabelled residues were used. Maize plants were grown in these soils for 11 weeks and %Ndfr in the maize plants estimated using 15 N isotope dilution and the direct approach. The 15 N isotope dilution approach also overestimated %Ndfr compared to the direct method in this experiment. Pool substitution appeared to be responsible for the discrepancy between the direct and indirect techniques. It was concluded that 15N isotope dilution and A-value approaches as used in these experiments (i.e where residues and 15N label are added simultaneously) were not appropriate techniques for estimating N derived from organic residues in soils.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1004529711231
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  • 62
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    Timing of nitrogen uptake affects winter storage and spring remobilisation of nitrogen in nectarine (Prunus persica var. nectarina) trees (1999)
    Springer
    Plant and soil 211 (1999), S. 149-153 
    Details
    ISSN: 1573-5036
    Keywords: nitrogen ; Prunus ; remobilisation ; storage ; uptake
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Two-year old nectarine trees (Prunus persica, Batsch, var. nectarina, cv. Starkredgold on GF305 rootstock) planted in pots each received five applications of 1.0 g 15N labelled urea either from mid May to mid July (early uptake) or from mid August to the beginning of October (late uptake). All trees were supplied with a corresponding amount of unlabelled urea when they did not receive the labelled N. In autumn, all abscised leaves were collected and during winter randomly selected trees were harvested and divided into main organs. The remaining trees were transplanted into similar pots filled with sand; they received no N fertiliser and were harvested in May to evaluate the remobilisation of N. Total N and 15N abundance were determined in each organ. Nectarine trees took up similar amounts of N in the 'early' and in the 'late' period; however, more labelled nitrogen was recovered in the perennial organs during the winter when trees received the labelled N in the 'late' than in the 'early' period. Some 73–80% of the N present in the dormant trees was stored in the roots, which contained almost twice the amount of labelled N taken up 'late' than that absorbed 'early'. Nitrogen for spring growth was remobilised predominantly from the roots and accounted for some 43–49% of the labelled N recovered in the tree during winter. Results suggest that the nitrogen taken up 'late' in the season is preferentially stored in roots and used by peach trees to sustain new growth the following spring.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1004698422522
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  • 63
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    Effects of sulphur nutrition on growth and nitrogen fixation of pea (Pisum sativum L.) (1999)
    Springer
    Plant and soil 212 (1999), S. 207-217 
    Details
    ISSN: 1573-5036
    Keywords: legume ; nitrogen ; N2-fixation ; pea ; sulphur
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract A S-deficient soil was used in pot experiments to investigate the effects of S addition on growth and N2-fixation in pea (Pisum sativum L.). Addition of 100 mg S pot−1 increased seed yield by more than 2-fold. Numbers of pods formed were the most sensitive yield component affected by S deficiency. Sulphur addition also increased the concentration of N in leaves and stems, and the total content of N in the shoots. The amounts of N fixed by pea were determined at four growth stages from stem elongation to maturity, using the 15N dilution technique. Sulphur addition doubled the amount of N fixed at all growth stages. In contrast, leaf chlorophyll content and shoot dry weight were increased significantly by S addition only after the flowering and pod fill stage, respectively. Pea roots were found to have high concentrations of S, reaching approximately 10 mg g−1 dry weight and being 2.6–4.4 times the S concentration in the shoots under S-sufficient conditions. These results suggest that roots/nodules of pea have a high demand for S, and that N2-fixation is very sensitive to S deficiency. The effects of S deficiency on pea growth were likely to be caused by the shortage of N, due to decreased N2-fixation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1004618303445
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  • 64
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    Electronic Resource
    Persistence of tree related patterns in soil nutrients following slash-and-burn disturbance in the tropics (1999)
    Springer
    Plant and soil 209 (1999), S. 137-157 
    Details
    ISSN: 1573-5036
    Keywords: fire ; nitrogen ; phosphorus ; soil nutrient heterogeneity ; tree effects ; tropical dry forest
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Individual trees are known to influence soil chemical properties, creating spatial patterns that vary with distance from the stem. The influence of trees on soil chemical properties is commonly viewed as the agronomic basis for low-input agroforestry and shifting cultivation practices, and as an important source of spatial heterogeneity in forest soils. Few studies, however, have examined the persistence of the effects of trees on soil after the pathways responsible for the effects are removed. Here, we present evidence from a Mexican dry forest indicating that stem-related patterns of soil nutrients do persist following slash-and-burn removal of trees and two years of cropping. Pre-disturbance concentrations of resin extractable phosphorus (P), bicarbonate extractable P, NaOH extractable P, total P, total nitrogen (N) and carbon (C), KCl extractable nitrate (NO3 -), and net N mineralization and nitrification rates were higher in stem than dripline soils under two canopy dominant species of large-stemmed trees with contrasting morphologies and phenologies (Caesalpinia eriostachys Benth. and Forchhammeria pallida Liebm.). These stem effects persisted through slash burning and a first growing season for labile inorganic and organic P, NaOH inorganic P, and plant-available P, and through a second growing season for labile organic P, NaOH organic P, and plant-available P. While stem effects for extractable NO3 -, net nitrification rates, total N and C disappeared after felling and slash burning, these stem effects returned after the first growing season. These results support the view that tree-influenced patterns of soil nutrients do persist after tree death, and that trees contribute to the long-term spatial heterogeneity of forest soils.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1004503023973
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  • 65
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    Nitrogen and phosphorus requirement of the microbiota in soils of the Bornhöved Lake district (1999)
    Springer
    Plant and soil 212 (1999), S. 173-181 
    Details
    ISSN: 1573-5036
    Keywords: nitrogen ; phosphatase activity ; phosphorus ; protease activity ; soil microbial biomass ; substrate-induced respiration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Estimating in situ N and P status of the soil microbiota is complicated because microbiological features reflect potentials rather than field conditions. Complementary microbiological assays were, therefore, combined to evaluate the N and P requirement of the microbiota in seven agricultural, grassland and forest topsoils of the Bornhöved Lake district as follows: (i) the sensitivity of the substrate-induced respiration (SIR) to supplemental addition of N and P was monitored during microbial growth and (ii) soil protease and phosphatase activities were analysed and related to soil mass and microbial biomass content. Nitrogen addition increased the maximal SIR rate in all except one soil indicating that the growth of organisms is restricted by this element when easily degradable C source is present. Supplemental N (and in some cases also P) retarded the respiratory response within the first 24 h which suggests microbial sensitivity and/or greater anabolic efficiency. With additional N the maximal SIR rate was most strongly enhanced in topsoils of the beech forest and the dystric alder forest. Thus, the microbial growth in these soils that were below litter horizons seems to be mostly restricted by N. Supplemental P positively affected respiratory response of soils under monoculture, wet grassland and dystric alder forest. In the dystric alder forest soil, high rates of alkaline and unbuffered phosphatase activity were observed when activity was related to either soil mass or microbial biomass content. The data of proteolytic and phospholytic enzymes are discussed with reference to nutrient deficiency and microbial strategy for N and P adsorption.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1004677427165
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  • 66
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    Contributions to nitrogen leaching and pasture uptake by autumn-applied dairy effluent and ammonium fertilizer labeled with 15N isotope (1999)
    Springer
    Plant and soil 210 (1999), S. 189-198 
    Details
    ISSN: 1573-5036
    Keywords: effluent ; leaching ; 15N isotope ; nitrogen ; pasture ; uptake
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The objective of this study was to compare the N leaching loss and pasture N uptake from autumn-applied dairy shed effluent and ammonium fertilizer (NH4Cl) labeled with 15N, using intact soil lysimeters (80 cm diameter, 120 cm depth). The soil used was a sandy loam, and the pasture was a mixture of perennial ryegrass (Lolium perenne) and white clover (Trifolium repens). The DSE and NH4Cl were applied twice annually in autumn (May) and late spring (November), each at 200 kg N ha-1. The N applied in May 1996 was labeled with 15N. The lysimeters were either spray or flood irrigated during the summer. The autumn-applied DSE resulted in lower N leaching losses compared with NH4Cl. However, the N applied in the autumn had a higher potential for leaching than N applied in late spring. Between 4.5–8.1% of the 15N-labeled mineral N in the DSE and 15.1–18.8% of the 15N-labeled NH4Cl applied in the autumn were leached within a year of application. Of the annual N leaching losses in the DSE treatments (16.0–26.9 kg N ha-1), a fifth (20.3–22.9%) was from the mineral N fraction of the DSE applied in the autumn, with the remaining larger proportion from the organic fraction of the DSE, soil N and N applied in spring. In the NH4Cl treatments, more than half (53.8–64.8%) of the annual N leaching loss (55.9–57.6 kg N ha-1) was derived from the autumn-applied NH4Cl. DSE was as effective as NH4Cl in stimulating pasture production. Since only 4.4–4.5% of the annual herbage N uptake in the DSE treatment and 12.3–13.3% in the NH4Cl treatment were derived from the autumn-applied mineral N, large proportions of the annual herbage N uptake must have been derived from the N applied in spring, the organic N fraction in the DSE, soil N and N fixed by clover. The recoveries of 15N in the herbage were similar between the DSE and the NH4Cl treatments, but those in the leachate were over 50% less from the DSE than from the NH4Cl treatment. The lower leaching loss of 15N in the DSE treatment was attributed to the stimulated microbial activities and increased immobilization following the application of DSE.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1004677902049
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    Relationships between eutrophication variables: from nutrient loading to transparency (1999)
    Springer
    Hydrobiologia 408-409 (1999), S. 375-387 
    Details
    ISSN: 1573-5117
    Keywords: eutrophication ; multi-lake studies ; phosphorus ; nitrogen ; chlorophyll-a ; transparency ; zooplankton ; macrophytes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Monitoring data obtained from 231 freshwater lakes and ponds in the Netherlands, covering the period 1980–1996, were used to analyse the relationships between (a) transparency and chlorophyll-a, and the effect of system characteristics on this relationship, (b) chlorophyll-aand nutrient concentrations, and the effect of biological variables and (c) nutrient concentrations and nutrient loading. (a) Chlorophyll-aimposes a maximum on water transparency, but deviations from this maximum can be large. Reducing chlorophyll-a, therefore, does not guarantee a sufficient improvement of transparency. Soil type and the average depth of a lake were shown to influence the relationship between chlorophyll-aand transparency. (b) The maximum ratios of both chlorophyll-a: total-P and chlorophyll-a: total-N were higher in systems dominated by filamentous cyanobacteria than in systems dominated by other algae, indicating the efficiency of the former group with respect to nutrients. In systems with an areal coverage with submersed macrophytes above 5%, concentrations of chlorophyll-aand nutrients were lower than in systems with lower coverages. The ratios between chlorophyll-aand nutrients were lower at coverages larger than 10%. This indicates both bottom-up and top-down control of algae by macrophytes. Grazing pressure by zooplankton was also found to lower the chlorophyll-a: nutrient ratios. (c) System specific linear relationships were found between the average concentrations of total-P and total-N in the incoming water and the summer mean concentration in the lake. This allows the assessment of admissible loads for individual lakes, with narrower confidence limits compared to traditional relationships based on combined data from many lakes. From the analysis, it is concluded that the chain of relationships from nutrient loading to transparency is complex, and depends on biological variables as well as system characteristics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1017090931476
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  • 68
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    A simulation model of organic matter and nutrient accumulation in mangrove wetland soils (1999)
    Springer
    Biogeochemistry 44 (1999), S. 93-118 
    Details
    ISSN: 1573-515X
    Keywords: Everglades National Park ; mangrove soils ; organic matter ; nitrogen ; phosphorus ; sedimentation ; simulation model
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract The distribution and accumulation of organic matter, nitrogen (N) and phosphorus (P) in mangrove soils at four sites along the Shark River estuary of south Florida were investigated with empirical measures and a process-based model. The mangrove nutrient model (NUMAN) was developed from the SEMIDEC marsh organic matter model and parameterized with data from mangrove wetlands. The soil characteristics in the four mangrove sites varied greatly in both concentrations and profiles of soil carbon, N and P. Organic matter decreased from 82% in the upstream locations to 30% in the marine sites. Comparisons of simulated and observed results demonstrated that landscape gradients of soil characteristics along the estuary can be adequately modeled by accounting for plant production, litter decomposition and export, and allochthonous input of mineral sediments. Model sensitivity analyses suggest that root production has a more significant effect on soil composition than litter fall. Model simulations showed that the greatest change in organic matter, N, and P occurred from the soil surface to 5 cm depth. The rapid decomposition of labile organic matter was responsible for this decrease in organic matter. Simulated N mineralization rates decreased quickly with depth, which corresponded with the decrease of labile organic matter. The increase in organic matter content and decrease in soil bulk density from mangrove sites at downstream locations compared to those at upstream locations was controlled mainly by variation in allochthonous inputs of mineral matter at the mouth of the estuary, along with gradients in mangrove root production. Research on allochthonouns sediment input and in situ root production of mangroves is limited compared to their significance to understanding nutrient biogeochemistry of these wetlands. More accurate simulations of temporal patterns of nutrient characteristics with depth will depend on including the effects of disturbance such as hurricanes on sediment redistribution and biomass production.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00993000
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  • 69
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    Nutrient budgets and biogeochemistry in an experimental agricultural watershed in Southeastern China (1999)
    Springer
    Biogeochemistry 45 (1999), S. 1-19 
    Details
    ISSN: 1573-515X
    Keywords: Chaohu Lake ; chemical fertilizer ; cycling ; denitrification ; multipond system ; nitrogen ; nutrient budget ; phosphorus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract During a two-year field study, an annual nutrient budget and cycles were developed for a small agricultural watershed. The study emphasized the integrated unit of the watershed in understanding the biogeochemistry. It was found that the total nutrient input was 39.1× 104 kg nitrogen and 3.91×104 kg phosphorus in the year 1995, of which the greatest input of nutrients to the watershed was chemical fertilizer application, reaching 34.7×104 kg (676 kg/ha) nitrogen and 3.88×104 kg (76 kg/ha) phosphorus. The total nutrient output from the watershed was 13.55×104 kg nitrogen and 0.40×104 kg phosphorus, while the largest output of nitrogen was denitrification, accounting for 44.1% of N output; the largest output of phosphorus was sale of crops, accounting for 99.4% of P output. The results show that the nutrient input is larger than output, demonstrating that there is nutrient surplus within the watershed, a surplus which may become a potential source of nonpoint pollution to area waters. The research showed that both denitrification and volatilization of nitrogen are key ways of nitrogen loss from the watershed. This suggests that careful management of fertilizer application will be important for the sustainable development of agriculture. The research demonstrated that a multipond system within the watershed had high retention rate for both water and nutrients, benefiting the water, nutrient and sediment recycling in the terrestrial ecosystem and helping to reduce agricultural nonpoint pollution at its source. Therefore, this unique watershed system should be recommended due to its great potential relevance for sustainable agricultural development.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00992870
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  • 70
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    Nutrient losses in runoff from grassland and shrubland habitats in Southern New Mexico: I. rainfall simulation experiments (1999)
    Springer
    Biogeochemistry 45 (1999), S. 21-34 
    Details
    ISSN: 1573-515X
    Keywords: Chihuahuan desert ; desert ; desertification ; grassland ; nitrogen ; nutrient budgets ; phosphorus ; runoff
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Rainfall simulation experiments were performed in areas of semiarid grassland (Bouteloua eriopoda) and arid shrubland (Larrea tridentata) in the Chihuahuan desert of New Mexico. The objective was to compare the runoff of nitrogen (N) and phosphorus (P) from these habitats to assess whether losses of soil nutrients are associated with the invasion of grasslands by shrubs. Runoff losses from grass- and shrub-dominated plots were similar, and much less than from bare plots located in the shrubland. Weighted average concentrations of total dissolved N compounds in runoff were greatest in the grassland (1.72 mg/1) and lowest in bare plots in the shrubland (0.55 mg/1). More than half of the N transported in runoff was carried in dissolved organic compounds. In grassland and shrub plots, the total N loss was highly correlated to the total volume of discharge. We estimate that the total annual loss of N in runoff is 0.25 kg/ha/yr in grasslands and 0.43 kg/ha/yr in shrublands — consistent with the depletion of soil N during desertification of these habitats. Losses of P from both habitats were very small.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00992871
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  • 71
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    Pore water N and P concentration in a floodplain marsh of the Lower Paraná River* (1999)
    Springer
    Hydrobiologia 392 (1999), S. 65-71 
    Details
    ISSN: 1573-5117
    Keywords: nitrogen ; phosphorus ; pore water ; macrophyte ; floodplain ; Paraná River
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Inorganic nitrogen and soluble reactive phosphate (o-P) concentrations were measured in the water of a marsh and in its interstitial water at two sites, and in the river water of a floodplain marsh of the Lower Paraná River. These values were compared with the N and P concentration in sediments and macrophyte biomass in order to assess nutrient availability, fate and storage capacity. High variability was found in the interstitital water using a 1 cm resolution device. Nitrate was never detected in the pore water. Depth averaged NH4 + concentrations in the upper 30 cm layer often ranged from N = 1.5 to 1.8 mg l-1, but showed a pronounced minimum (0.5–0.7 mg l-1), close to (March 95), or relatively soon after (May 94) the end of the macrophyte growing season. Soluble phosphate showed a large variation between P = 0.1–1.1 mg l-1 without any discernible seasonal pattern. NH4 + depletion in the pore water concentration and low N/P ratios (3.7 by weight) within the macrophyte biomass at the end of the growing period suggest that available N limits plant growth. NH4 + and o-P concentrations were 35 and 7 times higher, respectively, in the pore water than in the overlying marsh, suggesting a permanent flux of nutrients from the sediments. o-P accumulate in the marsh leading to higher concentrations than in the incoming river. NH4 + did not accumulate in the marsh, and no significant differences were observed between the river and the marsh water, while the NO3 - contributed by the river water was depleted within the marsh, caused probably by coupled nitrification-denitrification at the sediment–water interface. Although an order of magnitude smaller, the pore water pool can supply enough nutrients to build up the macrophyte biomass pool, but only if a fast turnover is attained. The Paraná floodplain marsh retains a large amount of nutrients being stored mainly in the sediment compartment.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1003505424569
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  • 72
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    The N and P budget of the shallow, flushed lake Müggelsee: retention, external and internal load (1999)
    Springer
    Hydrobiologia 408-409 (1999), S. 159-166 
    Details
    ISSN: 1573-5117
    Keywords: shallow lake ; nutrient loading ; retention ; nitrogen ; phosphorus ; release
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The shallow (mean depth 4.9 m), polymictic and eutrophic lake Müggelsee was highly loaded with phosphorus (6 gP m-2a-1) and nitrogen (170 gN m-2a-1) by the river Spree up to the end of the 1980s. Annual load declined by 40–50% during the last years (1991–97). Phosphorus retention fluctuated strongly during the seasonal cycle between −200 and +100 kgP d-1and from year to year between −44% and + 26% of the P import. At the end of the eighties, the P retention capacity of the sediment was exceeded and Müggelsee became a source of phosphorus. The lake regained its ability to retain P in the sediments after external load reduction in the 1990s. However, the internal load of P reached the level of the external one. The release of P during summer was strongly related to the import of nitrate. On long-term average (1979–1997), less than 1% of the P input was retained in Müggelsee. About 24% of the nitrogen load were removed in the lake on annual mean. This rate decreased during the last years.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1017023717324
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  • 73
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    Electronic Resource
    Legislative challenges for lake eutrophication control in Europe (1999)
    Springer
    Hydrobiologia 395-396 (1999), S. 389-401 
    Details
    ISSN: 1573-5117
    Keywords: legislation ; eutrophication ; phosphorus ; nitrogen ; wildlife conservation ; SSSI
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract There is no single piece of legislation which comprehensively addresses the problem of eutrophication of freshwater lakes. An examination is made of the extent to which national and EU laws applicable in England and Wales may be used to reduce phosphorus inputs to eutrophicated lakes. This case study is then used to outline the shortcomings of existing legislation and the future challenges for lake eutrophication control. Applicable legislation may be divided into that relating to nature conservation, to water quality and to agricultural extensification. Nature conservation laws are applicable, in that lakes designated as Sites of Special Scientific Interest (SSSIs), are theoretically safeguarded from degradation. The main limitation of the SSSI system lies in the boundary definition process under which, as a rule, no other category of legally protected land may be designated. Thus, the use of surrounding buffer land to protect water quality at the catchment level is generally precluded. The introduction of consultation areas around SSSIs of international importance under the EU Directive on Habitats is unlikely to alleviate the problem, since the area involved remains minimal compared to the extent of the majority of catchments. Intensive agricultural practices are responsible for significant nutrient enrichment of rivers and lakes, so that legislation aimed at extensification is also relevant. Examples of agricultural extensification include the Environrnentally Sensitive Areas programme and various options available for Set-Aside land. However, the prime purpose of such initiatives is the alleviation of surplus and budgetary problems and, as such, they fall short of a fully integrated approach to the ecological management of farmland. Nutrient enrichment is, essentially, a water quality issue, but policy and legislation in this area are not yet sufficiently developed to address the problem comprehensively. The current regulatory process for water quality carries the potential to work comparatively well for point sources under the system of consents to discharge. This potential is limited, however, by the paucity of information available on ecologically acceptable concentrations of phosphorus in discharges. In addition, the consents system is not constructed to deal effectively with diffuse agricultural losses of phosphorus, since, unlike point sources, these tend to arise from the cumulative effect of many activities. The main legislative challenge for lake eutrophication control lies in the area of diffuse agricultural losses of phosphorus. In this respect, experience in the U.S.A. reveals that the use of comprehensive and catchment-wide ‘Best Management Practices’ is capable of producing significant water quality improvements, providing that some degree of mandatory compliance is incorporated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1017007315753
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  • 74
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    Electronic Resource
    Lake and catchment management in Denmark (1999)
    Springer
    Hydrobiologia 395-396 (1999), S. 419-432 
    Details
    ISSN: 1573-5117
    Keywords: Integrated lake management ; biomanipulation ; lake recovery ; phosphorus ; nitrogen ; eutrophication ; restoration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The majority of Danish lakes are highly eutrophic due to high nutrient input from domestic sources and agricultural activities. Reduced nutrient retention, and more rapid removal, in catchments as a result of agricultural drainage of wetlands and lakes and channelisation or culverting of streams also play a role. Attempts have recently been made to reduce nutrient loading on lakes by intervening at the source level and by improving the retention capacity of catchment areas. The former measures include phosphorus stripping and nitrogen removal at sewage works, increased use of phosphate-free detergents, and regulations concerning animal fertiliser storage capacity, fertiliser application practices, fertilisation plans and green cover in winter. In order to improve nutrient retention capacity of catchments, wetlands and lakes have been re-established and channelised streams have been remeandered. In addition, cultivation-free buffer strips have been established alongside natural streams and there has been a switch to manual weed control. These measures have resulted in a 73% reduction of the mean total phosphorus concentration of point-source polluted streams since 1978; in contrast, there has been no significant change in the total nitrogen concentration. Despite the major reduction in stream phosphorus concentrations, lake water quality has often not improved. This may reflect a too high external or internal phosphorus loading or biological resistance. Various physico-chemical restoration measures have been used, including dredging and oxidation of the hypolimnion with nitrate and oxygen. Biological restoration measures have been employed in 17 Danish lakes. The methods include reducing the abundance of cyprinids, stocking with 0+ pike ( Esox lucius) to control 0+ cyprinids, and promoting macrophyte recolonization by protecting germinal submerged macrophyte beds against grazing waterfowl and transplanting out macrophyte shoots. In several lakes, marked and long-lasting improvements have been obtained. The findings to date indicate that fish manipulation has a long-term effect in shallow lakes, providing nutrient loading is reduced to a level so low as to ensure an equilibrium lake water phosphorus concentration of less than 0.05–0.1 mg phosphorus l−1. If nitrogen loading is very low, however, positive results may be obtained at higher phosphorus concentrations. Macrophyte refuges and transplantation seem to be the most successful as restoration measures in the same nutrient-phosphorus regime as fish manipulation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1017071602549
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  • 75
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    Electronic Resource
    A simulation model of organic matter and nutrient accumulation in mangrove wetland soils (1999)
    Springer
    Biogeochemistry 44 (1999), S. 93-118 
    Details
    ISSN: 1573-515X
    Keywords: Everglades National Park ; mangrove soils ; organic matter ; nitrogen ; phosphorus ; sedimentation ; simulation model
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract The distribution and accumulation of organic matter, nitrogen (N) and phosphorus (P) in mangrove soils at four sites along the Shark River estuary of south Florida were investigated with empirical measures and a process-based model. The mangrove nutrient model (NUMAN) was developed from the SEMIDEC marsh organic matter model and parameterized with data from mangrove wetlands. The soil characteristics in the four mangrove sites varied greatly in both concentrations and profiles of soil carbon, N and P. Organic matter decreased from 82% in the upstream locations to 30% in the marine sites. Comparisons of simulated and observed results demonstrated that landscape gradients of soil characteristics along the estuary can be adequately modeled by accounting for plant production, litter decomposition and export, and allochthonous input of mineral sediments. Model sensitivity analyses suggest that root production has a more significant effect on soil composition than litter fall. Model simulations showed that the greatest change in organic matter, N, and P occurred from the soil surface to 5 cm depth. The rapid decomposition of labile organic matter was responsible for this decrease in organic matter. Simulated N mineralization rates decreased quickly with depth, which corresponded with the decrease of labile organic matter. The increase in organic matter content and decrease in soil bulk density from mangrove sites at downstream locations compared to those at upstream locations was controlled mainly by variation in allochthonous inputs of mineral matter at the mouth of the estuary, along with gradients in mangrove root production. Research on allochthonouns sediment input and in situ root production of mangroves is limited compared to their significance to understanding nutrient biogeochemistry of these wetlands. More accurate simulations of temporal patterns of nutrient characteristics with depth will depend on including the effects of disturbance such as hurricanes on sediment redistribution and biomass production.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006076405557
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  • 76
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    Electronic Resource
    Nutrient budgets and biogeochemistry in an experimental agricultural watershed in Southeastern China (1999)
    Springer
    Biogeochemistry 45 (1999), S. 1-19 
    Details
    ISSN: 1573-515X
    Keywords: Chaohu Lake ; chemical fertilizer ; cycling ; denitrification ; multipond system ; nitrogen ; nutrient budget ; phosphorus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract During a two-year field study, an annual nutrient budget and cycles were developed for a small agricultural watershed. The study emphasized the integrated unit of the watershed in understanding the biogeochemistry. It was found that the total nutrient input was 39.1 × 104 kg nitrogen and 3.91 × 104 kg phosphorus in the year 1995, of which the greatest input of nutrients to the watershed was chemical fertilizer application, reaching 34.7 × 104 kg (676 kg/ha) nitrogen and 3.88 × 104 kg (76 kg/ha) phosphorus. The total nutrient output from the watershed was 13.55 × 104 kg nitrogen and 0.40 × 104 kg phosphorus, while the largest output of nitrogen was denitrification, accounting for 44.1% of N output; the largest output of phosphorus was sale of crops, accounting for 99.4% of P output. The results show that the nutrient input is larger than output, demonstrating that there is nutrient surplus within the watershed, a surplus which may become a potential source of nonpoint pollution to area waters. The research showed that both denitrification and volatilization of nitrogen are key ways of nitrogen loss from the watershed. This suggests that careful management of fertilizer application will be important for the sustainable development of agriculture. The research demonstrated that a multipond system within the watershed had high retention rate for both water and nutrients, benefiting the water, nutrient and sediment recycling in the terrestrial ecosystem and helping to reduce agricultural nonpoint pollution at its source. Therefore, this unique watershed system should be recommended due to its great potential relevance for sustainable agricultural development.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006073408623
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  • 77
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    The fate of NH4NO3 added toSphagnum magettanicum carpets at five European mire sites (1999)
    Springer
    Biogeochemistry 45 (1999), S. 73-93 
    Details
    ISSN: 1573-515X
    Keywords: atmospheric deposition ; moss ; bog ; nitrogen ; phosphorus ; water table
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Nitrogen additions as NH4NO3 corresponding to 0 (N0), 1 (N1), 3 (N3) and 10 (N10) g N m−2 yr−1 were made toSphagnum magellanicurn cores at two-week intervalsin situ at four sites across Europe, i.e. Lakkasuo (Finland). Männikjärve (Estonia), Moidach More (UK) and Côte de Braveix (France). The same treatments were applied in a glasshouse experiment in Neuchâtel (Switzerland) in which the water table depth was artificially maintained at 7, 17 and 37 cm below the moss surface. In the field, N assimilation in excess of values in wet deposition occurred in the absence of growth, but varied widely between sites, being absent in Lakkasuo (moss N∶P ratio 68) and greatest in Moidach More (N∶P 21). In the glasshouse, growth was reduced by lowering the water table without any apparent effect on N assimilation. Total N content of the moss in field sites increased as the mean depth of water table increased indicating growth limitation leading to increased N concentrations which could reduce the capacity for N retention. Greater contents of NH4 + in the underlying peat at 30 cm depth, both in response to NH4NO3 addition and in the unamended cores confirmed poor retention of inorganic N by the moss at Lakkasuo. Nitrate contents in the profiles at Lakkasuo, Moidach More, and Côte de Braveix were extremely low, even in the N10 treatment, but in Männikjärve, where the mean depth of water table was greatest and retention absent, appreciable amounts of NO3 − were detected in all cores. It is concluded that peatland drainage would reduce the capture of inorganic N in atmospheric deposition bySphagnum mosses.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00992874
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  • 78
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    Electronic Resource
    Nitrogen stable isotopic composition of leaves and soil: Tropical versus temperate forests (1999)
    Springer
    Biogeochemistry 46 (1999), S. 45-65 
    Details
    ISSN: 1573-515X
    Keywords: N15 ; nitrogen ; nutrient cycling ; plants ; stable isotopes ; soil ; temperate forest ; tropical forest
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Several lines of evidence suggest that nitrogen in most tropical forests is relatively more available than N in most temperate forests, and even that it may function as an excess nutrient in many tropical forests. If this is correct, tropical forests should have more open N cycles than temperate forests, with both inputs and outputs of N large relative to N cycling within systems. Consequent differences in both the magnitude and the pathways of N loss imply that tropical forests should in general be more15N enriched than are most temperate forests. In order to test this hypothesis, we compared the nitrogen stable isotopic composition of tree leaves and soils from a variety of tropical and temperate forests. Foliar δ15N values from tropical forests averaged 6.5‰ higher than from temperate forests. Within the tropics, ecosystems with relatively low N availability (montane forests, forests on sandy soils) were significantly more depleted in15N than other tropical forests. The average δ15N values for tropical forest soils, either for surface or for depth samples, were almost 8‰ higher than temperate forest soils. These results provide another line of evidence that N is relatively abundant in many tropical forest ecosystems.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01007573
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  • 79
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    Electronic Resource
    The impact of accelerating land-use change on the N-Cycle of tropical aquatic ecosystems: Current conditions and projected changes (1999)
    Springer
    Biogeochemistry 46 (1999), S. 109-148 
    Details
    ISSN: 1573-515X
    Keywords: estuaries ; lakes ; marine ; nitrogen ; phosphorus ; rivers ; streams ; temperate ; tropics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Published data and analyses from temperate and tropical aquatic systems are used to summarize knowledge about the potential impact of land-use alteration on the nitrogen biogeochemistry of tropical aquatic ecosystems, identify important patterns and recommend key needs for research. The tropical N-cycle is traced from pre-disturbance conditions through the phases of disturbance, highlighting major differences between tropical and temperate systems that might influence development strategies in the tropics. Analyses suggest that tropical freshwaters are more frequently N-limited than temperate zones, while tropical marine systems may show more frequent P limitation. These analyses indicate that disturbances to pristine tropical lands will lead to greatly increased primary production in freshwaters and large changes in tropical freshwater communities. Increased freshwater nutrient flux will also lead to an expansion of the high production, N- and light-limited zones around river deltas, a switch from P- to N-limitation in calcareous marine systems, with large changes in the community composition of fragile mangrove and reef systems. Key information gaps are highlighted, including data on mechanisms of nutrient transport and atmospheric deposition in the tropics, nutrient and material retention capacities of tropical impoundments, and N/P coupling and stoichiometric impacts of nutrient supplies on tropical aquatic communities. The current base of biogeochemical data suggests that alterations in the N-cycle will have greater impacts on tropical aquatic ecosystems than those already observed in the temperate zone.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01007576
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  • 80
    Electronic Resource
    Electronic Resource
    ATP levels of chinook salmon (Oncorhynchus tshawytscha) sperm following in vitro exposure to various oxygen tensions (1999)
    Springer
    Fish physiology and biochemistry 20 (1999), S. 389-397 
    Details
    ISSN: 1573-5168
    Keywords: adenosine triphosphate ; fertility ; nitrogen ; salmonid ; semen ; spermatocrit ; viability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Adenosine triphosphate (ATP) levels in sperm from chinook salmon (Oncorhynchus tshawytscha) were found to be 12.1±1.9 pmol ATP per 106 sperm cells (mean±SEM, n=18). Sperm were stored at 0–2 °C for up to 72 h under 100, 21, and 0% O2. Changes in sperm ATP content of samples maintained under 100 and 21% O2 were indistinguishable, decreasing to 50% of initial values after 72 h. ATP levels of sperm stored under 0% O2 decreased to 10% of initial values within 8 h and remained unchanged throughout the following 64 h. The initial percent of living sperm (sperm viability) was 94.7±1.7% (mean±SEM, n=12) and was unaltered at 24 h under all O2 tensions. At 72 h, sperm viability remained unchanged under 21% O2 and had decreased by 20% under 100% O2 and by 30% under 0% O2. Therefore, reductions in sperm ATP levels could not be attributed to cell lysis, as viability decreased only modestly over these durations. Fertilizing ability correlated positively with sperm ATP levels. Spermatocrit values increased by 20% for the samples maintained under 100 and 21% O2 after 72 h. However, a 20% increase in spermatocrit occurred within 24 h in samples maintained under 0% O2, rising 70% after 72 h under 0% O2. These data indicate that chinook sperm ATP (1) can be altered and manipulated without significant loss of viability, (2) is positively associated with fertilization, and (3) probably plays a role in sperm packing and cell flexibility.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1007749703803
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  • 81
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    Electronic Resource
    Effect of soil characteristics on sequential reduction and methane production in sixteen rice paddy soils from China, the Philippines, and Italy (1999)
    Springer
    Biogeochemistry 47 (1999), S. 267-293 
    Details
    ISSN: 1573-515X
    Keywords: acetate ; carbon dioxide ; hydrogen ; methanogenesis ; iron ; organic carbon ; nitrogen ; redox balance ; rice paddy soil ; sulfate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract The potentials for sequential reduction of inorganic electron acceptors and production of methane have been examined in sixteen rice soils obtained from China, the Philippines, and Italy. Methane, CO2, Fe(II), NO 3 - , SO 4 2 , pH, Eh, H2 and acetate were monitored during anaerobic incubation at 30 °C for 120 days. Based on the accumulation patterns of CO2 and CH4, the reduction process was divided into three distinct phases: (1) an initial reduction phase during which most of the inorganic electron acceptors were depleted and CO2 production was at its maximum, (2) a methanogenic phase during which CH4 production was initiated and reached its highest rate, and (3) a steady state phase with constant production rates of CH4 and CO2. The reduction phases lasted for 19 to 75 days with maximum CO2 production of 2.3 to 10.9 μmol d-1 g-1 dry soil. Methane production started after 2 to 87 days and became constant after about 38--68 days (one soil 〉120 days). The maximum CH4 production rates ranged between 0.01 and 3.08 μmol d-1 g-1. During steady state the constant CH4 and CO2 production rates varied from 0.07 to 0.30 μmol d-1 g-1 and 0.02 and 0.28 μmol d-1 g-1, respectively. Within the 120 d of anaerobic incubation only 6--17% of the total soil organic carbon was released into the gas phase. The gaseous carbon released consisted of 61--100% CO2, 〈0.1--35% CH4, and 〈5% nonmethane hydrocarbons. Associated with the reduction of available Fe(III) most of the CO2 was produced during the reduction phase. The electron transfer was balanced between total CO2 produced and both CH4 formed and Fe(III), sulfate and nitrate reduced. Maximum CH4 production rate (r = 0.891) and total CH4 produced (r = 0.775) correlated best with the ratio of soil nitrogen to electron acceptors. Total nitrogen content was a better indicator for “available” organic substrates than the total organic carbon content. The redox potential was not a good predictor of potential CH4 production. These observations indicate that the availability of degradable organic substrates mainly controls the CH4 production in the absence of inorganic electron acceptors.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006186420644
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  • 82
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    Electronic Resource
    Effect of soil characteristics on sequential reduction and methane production in sixteen rice paddy soils from China, the Philippines, and Italy (1999)
    Springer
    Biogeochemistry 47 (1999), S. 269-295 
    Details
    ISSN: 1573-515X
    Keywords: acetate ; carbon dioxide ; hydrogen ; methanogenesis ; iron ; organic carbon ; nitrogen ; redox balance ; rice paddy soil ; sulfate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract The potentials for sequential reduction of inorganic electron acceptors and production of methane have been examined in sixteen rice soils obtained from China, the Philippines, and Italy. Methane, CO2, Fe(II), NO 3 − , SO 4 2− , pH, Eh, H2 and acetate were monitored during anaerobic incubation at 30 °C for 120 days. Based on the accumulation patterns of CO2 and CH4, the reduction process was divided into three distinct phases: (1) an initial reduction phase during which most of the inorganic electron acceptors were depleted and CO2 production was at its maximum, (2) a methanogenic phase during which CH4 production was initiated and reached its highest rate, and (3) a steady state phase with constant production rates of CH4. and CO2. The reduction phases lasted for 19 to 75 days with maximum CO2 production of 2.3 to 10.9μmol d−1 g−1 dry soil. Methane production started after 2 to 87 days and became constant after about 38–68 days (one soil 〉120 days). The maximum CH4 production rates ranged between 0.01 and 3.08μmol d−1 g−1. During steady state the constant CH4 and CO2 production rates varied from 0.07 to 0.30μmol d−1 g−1 and 0.02 and 0.28μmol d−1 g−1, respectively. Within the 120 d of anaerobic incubation only 6–17% of the total soil organic carbon was released into the gas phase. The gaseous carbon released consisted of 61–100% CO2, 〈0.1–35% CH4, and 〈5% nonmethane hydrocarbons. Associated with the reduction of available Fe(III) most of the CO2 was produced during the reduction phase. The electron transfer was balanced between total CO2 produced and both CH4 formed and Fe(III), sulfate and nitrate reduced. Maximum CH4 production rate (r=0.891) and total CH4 produced (r =0.775) correlated best with the ratio of soil nitrogen to electron acceptors. Total nitrogen content was a better indicator for “available” organic substrates than the total organic carbon content. The redox potential was not a good predictor of potential CH4 production. These observations indicate that the availability of degradable organic substrates mainly controls the CH4 production in the absence of inorganic electron acceptors.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00992910
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  • 83
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    Electronic Resource
    Pharmacokinetics of sterically stabilized hexadecylphosphocholine liposomes versus conventional liposomes and free hexadecylphosphocholine in tumor-free and human breast carcinoma bearing mice (1999)
    Springer
    Breast cancer research and treatment 58 (1999), S. 71-80 
    Details
    ISSN: 1573-7217
    Keywords: hexadecylphosphocholine ; human breast carcinoma ; pharmacokinetics ; sterically stabilized liposomes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The pharmacokinetics of free and different liposomal formulations of hexadecylphosphocholine (HPC) was investigated in tumor-bearing (human mammary tumor MaTu) and tumor-free mice after intravenous and intraperitoneal administration. The levels of HPC were evaluated at different times in serum, normal tissues, and tumor. The purpose was to test the hypothesis that the enhanced therapeutic efficacy of sterically stabilized HPC liposomes in comparison to conventional vesicles and free HPC is due to its pharmacokinetics. Conventional non-compartmental pharmacokinetic analysis and an elaborate three- and four-compartmental model were used for explaining the experimental data. The serum levels of HPC obtained with sterically stabilized liposomes were only consistently higher in comparison to conventional vesicles and free HPC in the first 4 h. In the xenografted MaTu carcinoma, the differences of the HPC content between the different groups are unexpectedly low and do not reflect the high therapeutic activity [5] of sterically stabilized HPC liposomes. Detailed analysis shows that the liposomally encapsulated drug displays a modified pharmacokinetic behavior, which may also involve lymphatic absorption of the liposomal drug.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006224611505
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  • 84
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    Electronic Resource
    Aging effects on drug disposition and effect (1999)
    Springer
    Geriatric nephrology and urology 9 (1999), S. 15-19 
    Details
    ISSN: 1573-7306
    Keywords: aging ; creatinine clearance ; drug deposition ; pharmacodynamics ; pharmacokinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008333511884
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  • 85
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    Estimation of the Importance of Spatially Variable Nitrogen Application and Soil Moisture Holding Capacity to Wheat Production (1999)
    Springer
    Precision agriculture 1 (1999), S. 27-38 
    Details
    ISSN: 1573-1618
    Keywords: CERES ; wheat ; soil moisture ; nitrogen ; variability ; precision agriculture ; spatial
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Crop growth modelling techniques were used to investigate the performance of a wheat crop over a range of weather conditions, nitrogen application rates and soil types. The data were used to predict long term benefits of using spatially variable fertilizer application strategies where fertilizer application rate was matched to the soil type, against a strategy of uniform fertilizer application. The model was also run with modified soil properties to determine the importance of soil moisture holding capacity in the variability of crop yield. It was found that the benefits of spatially variable nitrogen management when fertilizer was applied at the beginning of the season were modest on average. The range of results for different weather conditions was much greater than the average benefit. A large proportion of the variability of crop performance between soil types could be explained by differing soil moisture holding capacity. Devising techniques for managing this variability was concluded to be important for precision farming of cereals.
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    URL: http://dx.doi.org/10.1023/A:1009973802295
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  • 86
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    Electronic Resource
    Nitrogen utilization from diluted and undiluted nitric acid treated cattle slurry following surface application to grassland (1999)
    Springer
    Nutrient cycling in agroecosystems 53 (1999), S. 269-280 
    Details
    ISSN: 1573-0867
    Keywords: acidification ; ANE ; ANR ; calcium ammonium nitrate ; cattle slurry ; dilution ; grassland ; nitric acid ; nitrogen ; residual effect
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Acidification of cattle slurry with nitric acid to pH 4.5 was studied on experimental dairy farms in the Netherlands as a measure to reduce ammonia losses. This paper presents the results of two field experiments, carried out to assess the utilization of nitrogen (N) from nitric acid treated cattle slurry following surface application to grassland. Three aspects were studied: (i) the utilization of N from nitric acid treated cattle slurry following a single surface application to grassland; (ii) the effects of multiple applications of nitric acid treated cattle slurry on N utilization, residual inorganic N in the soil and sward quality; and (iii) the residual effects of nitric acid treated slurry on DM and N yield. In these experiments undiluted acidified slurry (UAS) and diluted acidified slurry (DAS) were compared with calcium ammonium nitrate (CAN). Apparent N recoveries (ANR) and apparent N efficiencies (ANE) were calculated on the basis of inorganic N in applied fertilizer and slurries. Following single applications of UAS and CAN on the sward on the clay soil, the average ANR values of UAS and CAN were 0.74 and 0.75 kg kg-1, respectively. The average ANE values of UAS and CAN were 30.3 and 29.5 kg DM per kg N, respectively. Single applications of DAS and CAN on the sandy soil resulted in average ANR values of 0.65 and 0.84 kg kg-1 and average ANE values of 24.1 and 29.2 kg DM per kg N for DAS and CAN, respectively. On average, the direct ANR values after four successive applications of CAN, UAS or DAS were 0.82, 0.82 and 0.74 kg kg-1, respectively and the direct ANE values were 28.4, 27.8 and 27.0 kg DM per kg N. On the sandy soil, the amount of residual inorganic N in the soil after the 4th cut increased with increasing rates of inorganic N application, with a slightly higher amount on plots treated with acidified slurry than on plots fertilized with CAN. On the clay soil, the amount of residual inorganic N was not affected by N application rate nor N source. On average, the residual ANR values, in the unfertilized 5th and 6th cuts, of CAN, UAS or DAS were 0.08, 0.10 and 0.09 kg kg-1, respectively and the residual ANE values were 2.7, 3.3 and 3.0 kg DM per kg N. It was concluded that nitric acid treated cattle slurry is an effective N fertilizer on grassland and that the residual effect of nitric acid treated cattle slurry is only marginally higher than that of CAN. Repeated applications of nitric acid treated cattle slurry did not affect sward composition.
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    URL: http://dx.doi.org/10.1023/A:1009745204647
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  • 87
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    Growth dynamics of reed canarygrass ( Phalaris arundinacea L.) and its allocation of biomass and nitrogen below ground in a field receiving daily irrigation and fertilisation (1999)
    Springer
    Nutrient cycling in agroecosystems 54 (1999), S. 21-29 
    Details
    ISSN: 1573-0867
    Keywords: carbon balance ; daily irrigation and fertilisation ; minirhizotrons ; nitrogen ; Phalaris arundinacea ; roots
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Biomass and nitrogen in the roots, rhizomes, stem bases and litter of reed canarygrass (Phalaris arundinacea L.) were repeatedly estimated by soil coring, and root growth dynamics of this potential energy crop was studied for two years using minirhizotrons. Results are discussed in relation to above-ground biomass and nitrogen fertilisation. Five treatments were used: C0, unfertilised control; C1, fertilised with solid N fertiliser in spring; I1, irrigated daily, fertilised as in C1; IF1 , irrigated as I1 and fertilised daily through a drip-tube system; IF2, as in IF1 but with higher N fertiliser rates. Biomass of below-ground plant parts of reed canarygrass increased between the first and second years. Up to 50% of total plant biomass and nitrogen were recovered below-ground. The highest proportions were found in C0. The calculated annual input via root turnover ranged between 80 and 235 g m-2. In absolute terms, up to 1 kg and 10 g m-2 of biomass and nitrogen, respectively, were found in below-ground plant fractions. High inputs of stubble and accumulated below-ground biomass will occur when the ley is ploughed, which will result in a highly positive soil carbon balance for this crop in comparison with that of conventional crops such as cereals.
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    URL: http://dx.doi.org/10.1023/A:1009701422394
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  • 88
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    Effect of Rhizobium inoculation and nitrogen fertilization on yield and protein content of six chickpea (Cicer arietinum L.) cultivars in marginal soils under irrigation (1999)
    Springer
    Nutrient cycling in agroecosystems 54 (1999), S. 57-63 
    Details
    ISSN: 1573-0867
    Keywords: chickpea ; marginal soils ; nitrogen ; protein content ; Rhizobium ; yield
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract A field experiment was carried out for two consecutive seasons 1994/95 and 1995/96 at ElRwakeeb (a sandy clay loam) to study the effect of Rhizobium sp. (Cicer) inoculation and N fertilization on six chickpea cultivars (Baladi, Gabel marra, NEC 25–27, NEC 2010, ILC 1919, and Flip 85–108). Plants were either inoculated with three Rhizobium sp. (Cicer) strains (TAL 480, TAL 620 and TAL 1148) separately, or N fertilized (50 kg N ha-1). The results of the two seasons indicated the absence of infective strains for chickpea in the soil. Rhizobium inoculation or N fertilization significantly increased the total nodule number per plant, 100 seed weight, yield and protein content of seeds. The results indicated that the three Rhizobium strains are infective and effective in nitrogen fixation. Inoculation with Rhizobium strain TAL 1148 resulted in a significant increment in most of the parameters studied, compared to other strains and untreated control. Cultivar ILC 1919 was the best yielding cultivar, whereas, cultivar NEC 2010 contained the highest protein content, however cultivar Gabel marra showed the highest amount of protein due to inoculation or N fertilization, in the two seasons. Inoculation with Rhizobium strain TAL 1148 increased yield by 72 and 70%, whereas, 50 kg N ha-1 increased it by 70 and 69% in the first and second seasons, respectively. The amounts of protein accumulated (kg ha-1) due to N or Rhizobium inoculation were determined for all cultivars. The results obtained from the inoculation were comparable to those of 50 kg N ha-1.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009778727102
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  • 89
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    Electronic Resource
    Nutrient cycling and growth in forest ecosystems of south western Australia: Relevance to agricultural landscapes (1999)
    Springer
    Agroforestry systems 45 (1999), S. 215-244 
    Details
    ISSN: 1572-9680
    Keywords: biodiversity ; disturbance ; nitrogen ; phosphorus ; resilience ; resistance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Nutrient and hydrologic cycles in harvested native forests in southern Australia are largely balanced. For example, we have little or no evidence of any decline in nutrient capital or availability in harvested forests. Short-term and small-scale reductions in evapotranspiration due to loss of leaf area after harvesting are adequately balanced at the landscape scale by large areas of regenerating or older-age forest. In contrast, agricultural systems on similar soils are a) dependent on large inputs of fertilisers to maintain growth and b) frequently subject to increasing salinity and waterlogging or other forms of degradation. The large-scale replacement of long-lived communities of perennial and often deep- rooting native species with annual crops or other communities of shallow-rooting species might be better managed within the framework of knowledge developed from studies of native plant communities. However, application of such a mimic concept to systems of low natural productivity is limited when agricultural systems require continued high productivity. Nonetheless, the mimic concept may help in developing sustainable management of agriculture on marginal lands, and contribute to the nutritional resilience of agroecosystems. Relevant characteristics for mimic agroecosystems in south western Australia include: high species diversity, diversity of rooting attributes, utilisation of different forms of nutrients (especially of N and P) in space and time, and the promotion of practices which increase soil organic matter content.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006267604313
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  • 90
    Electronic Resource
    Electronic Resource
    Effect of nitrogen and phosphorus addition on phenanthrene biodegradation in four soils (1999)
    Springer
    Biodegradation 10 (1999), S. 43-50 
    Details
    ISSN: 1572-9729
    Keywords: biodegradation ; nitrogen ; nutrients ; phenanthrene ; phosphorus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Energy, Environment Protection, Nuclear Power Engineering , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Phenanthrene mineralization rates were found to vary widely among four soils; differences in soil nutrient levels was one hypothesis to explain this variation. To test this hypothesis, phenanthrene mineralization rates were measured in these soils with, and without, added nitrogen and phosphorus. Mineralization rates either remained unchanged or were depressed by the addition of nitrogen and phosphorus. Phenanthrene degradation rates remained unchanged in the soil which had the highest indigenous levels of nitrogen and phosphorus and which showed the largest increase in phosphorus levels after nutrients were added. The soils in which degradation rates were depressed had lower initial phosphorus concentrations and showed much smaller or no measurable increase in phosphorus levels after nutrients were added to the soils. To understand the response of phenanthrene degradation rates to added nitrogen and phosphorus, it may be necessary to consider the bioavailability of added nutrients and nutrient induced changes in microbial metabolism and ecology.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008359606545
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  • 91
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    Electronic Resource
    Vibrational Spectra of Nitrogen in Simple Mixtures at High Pressures (1999)
    Springer
    International journal of thermophysics 20 (1999), S. 867-876 
    Details
    ISSN: 1572-9567
    Keywords: dilute mixtures ; high pressure ; high-resolution Raman spectroscopy ; line width ; nitrogen
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Previous investigations have revealed a considerable difference between the spectral behavior of a molecule in a pure substance and that in a mixture. To gain more insight into the influence of the intermolecular interaction and of the mass of the molecules, we performed high-resolution measurements of the linewidths and peak positions of the vibrational Raman spectrum of pure nitrogen, nitrogen in argon, and nitrogen in helium. The research was carried out at room temperature and at pressures up to the melting line. It turns out that, in contrast with expectation, the linewidth as well as the frequency shift is essentially the same for pure nitrogen as for nitrogen diluted in argon, although both the mass and the potential well depth are quite different. The experimental results show the same tendency as recent computer simulations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1022635203155
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  • 92
    Electronic Resource
    Electronic Resource
    Soil community composition and ecosystem processes: Comparing agricultural ecosystems with natural ecosystems (1999)
    Springer
    Agroforestry systems 45 (1999), S. 159-185 
    Details
    ISSN: 1572-9680
    Keywords: decomposition ; environmental monitoring ; fertiliser ; mineralisation ; nitrogen ; pesticides
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Soil organisms play principal roles in several ecosystem functions, i.e. promoting plant productivity, enhancing water relations, regulating nutrient mineralisation, permitting decomposition, and acting as an environmental buffer. Agricultural soils would more closely resemble soils of natural ecosystems if management practices would reduce or eliminate cultivation, heavy machinery, and general biocides; incorporate perennial crops and organic material; and synchronise nutrient release and water availability with plant demand. In order to achieve these goals, research must be completed to develop methods for successful application of organic materials and associated micro-organisms, synchronisation of management practices with crop and soil biota phenology, and improve our knowledge of the mechanisms linking species to ecosystem processes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006299100678
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  • 93
    Electronic Resource
    Electronic Resource
    Wildfire effects on carbon and nitrogen in inland coniferous forests (1999)
    Springer
    Plant and soil 209 (1999), S. 233-243 
    Details
    ISSN: 1573-5036
    Keywords: bioassay ; carbon ; erosion ; forest soil ; nitrogen ; wildfire
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract A ponderosa pine/Douglas-fir forest (Pinus ponderosa Dougl., Pseudotsuga menziesii (Mirb.) Franco; PP/DF) and a lodgepole pine/Engelmann spruce forest (Pinus contorta Loud., Picea engelmannii Parry ex Engelm.; LP/ES) located on the eastern slopes of the Cascade Mountains in Washington state, USA, were examined following severe wildfire to compare total soil carbon and nitrogen capitals with unburned (control) forests. One year after fire, the average C content (60 cm depth) of PP/DF and LP/ES soil was 30% (25 Mg ha-1) and 10% (7 Mg ha-1) lower than control soil. Average N content on the burned PP/DF and LP/ES plots was 46% (3.0 Mg ha-1) and 13% (0.4 Mg ha-1) lower than control soil. The reduction in C and N in the PP/DF soil was largely the result of lower nutrient capitals in the burned Bw horizons (12–60 cm depth) relative to control plots. It is unlikely that the 1994 fire substantially affected nutrient capitals in the Bw horizons; however, natural variability or past fire history could be responsible for the varied nutrient capitals observed in the subsurface soils. Surface erosion (sheet plus rill) removed between 15 and 18 Mg ha-1 of soil from the burned plots. Nutrient losses through surface erosion were 280 kg C ha-1 and 14 kg N ha-1 in the PP/DF, whereas LP/ES losses were 640 and 22 kg ha-1 for C and N, respectively. In both forests, surface erosion of C and N was ∼1% to 2% of the A-horizon capital of these elements in unburned soil. A bioassay (with lettuce as an indicator plant) was used to compare soils from low-, moderate- and high-severity burn areas relative to control soil. In both forests, low-severity fire increased lettuce yield by 70–100% of controls. With more severe fire, yield decreased in the LP/ES relative to the low-intensity burn soil; however, only in the high-severity treatment was yield reduced (14%) from the control. Moderate- and high-severity burn areas in the PP/DF were fertilized with ∼56 kg ha-1 of N four months prior to soil sampling. In these soils, yield was 70–80% greater than the control. These results suggest that short-term site productivity can be stimulated by low-severity fire, but unaffected or reduced by more severe fire in the types of forests studied. Post-fire fertilization with N could increase soil productivity where other environmental factors do not limit growth.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1004602408717
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  • 94
    Electronic Resource
    Electronic Resource
    Vertical and horizontal development of the root system of carrots following green manure (1999)
    Springer
    Plant and soil 212 (1999), S. 143-151 
    Details
    ISSN: 1573-5036
    Keywords: carrot ; green manure ; nitrogen ; organic production ; rooting depth ; root distribution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Cover crops grown as green manure or for other purposes will affect nitrogen (N) distribution in the soil, and may thereby alter root growth of a succeeding crop. During two years, experiments were performed to study effects of nitrogen supply by green manure on root development of carrots (Daucus carota L). Total root intensity (roots cm−2 on minirhizotrons) was significantly affected by the green manures, and was highest in the control plots where no green manure had been grown. Spread of the root system into the interrow soil was also affected by green manure treatments, as the spread was reduced where spring topsoil Nmin was high. Although N supply and distribution in the soil profile differed strongly among the treatments, no effect was observed on the rooting depth of the carrot crops. Across all treatments the rooting front penetrated at a rate of 0.82 and 0.68 mm day−1 °C−1 beneath the crop rows and in the interrow soil, respectively. The minirhizotrons only allowed measurements down to 1 m, and the roots reached this depth before harvest. Extrapolating the linear relationship between temperature sum and rooting depth until harvest would lead to rooting depths of 1.59 and 1.18 m under the crop rows and in the interrow soil respectively. Soil analysis showed that the carrot crop was able to reduce Nmin to very low levels even in the 0.75 to 1.0 m soil layer, which is in accordance with the root measurements. Still, where well supplied, the carrots left up 90 kg N ha−1 in the soil at harvest. This seemed to be related to a limited N uptake capacity of the carrots rather than to insufficient root growth in the top metre of the soil.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1004646522369
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  • 95
    Electronic Resource
    Electronic Resource
    Retention of nutrients in river systems: dependence on specific runoff and hydraulic load (1999)
    Springer
    Hydrobiologia 410 (1999), S. 111-122 
    Details
    ISSN: 1573-5117
    Keywords: phosphorus ; nitrogen ; retention ; river systems ; specific runoff ; hydraulic load
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The total nutrient inputs (emissions) from point and diffuse sources into 100 different river basins in Europe are compared with the measured load (transport). The catchment areas range between 121 and 194 000 km2. Other characteristic parameters of the basins, including specific runoff, surface water area and the nutrient concentration show large differences. Independent of the different methods applied for estimating nutrient emissions, these are in general higher than the actual transport. The ratio of the transport to the emission was used to exclude the effects of basin size and to facilitate comparisons between river basins. A statistical model of the retention, including net sedimentation and denitrification, is derived for the description of the discrepancy between the measured transport and the estimated total emission of nutrients, which is assumed to reflect retention of nutrients in a river system. It was found that the load-weighted retention of phosphorus is controlled practically only by the specific runoff of the basin. The load- weighted retention of nitrogen is further dependent on the proportion of the basin area occupied by surface water, the basin size itself and the mean annual nitrogen concentration at a specific monitoring station. Application of the statistical model reduces the mean deviation between the calculated emissions and the values given by different authors from about 40% to 20%.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1003735225869
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  • 96
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    Electronic Resource
    The fate of NH4NO3 added to Sphagnum magellanicum carpets at five European mire sites (1999)
    Springer
    Biogeochemistry 45 (1999), S. 73-93 
    Details
    ISSN: 1573-515X
    Keywords: atmospheric deposition ; moss ; bog ; nitrogen ; phosphorus ; water table
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Nitrogen additions as NH4NO3 corresponding to 0 (N0), 1 (N1), 3 (N3) and 10 (N10) g N m-2 yr-1 were made to Sphagnum magellanicum cores at two-week intervals in situ at four sites across Europe, i.e. Lakkasuo (Finland), Männikjärve (Estonia), Moidach More (UK) and Côte de Braveix (France). The same treatments were applied in a glasshouse experiment in Neuchâtel (Switzerland) in which the water table depth was artificially maintained at 7, 17 and 37 cm below the moss surface. In the field, N assimilation in excess of values in wet deposition occurred in the absence of growth, but varied widely between sites, being absent in Lakkasuo (moss N:P ratio 68) and greatest in Moidach More (N:P 21). In the glasshouse, growth was reduced by lowering the water table without any apparent effect on N assimilation. Total N content of the moss in field sites increased as the mean depth of water table increased indicating growth limitation leading to increased N concentrations which could reduce the capacity for N retention. Greater contents of NH4+ in the underlying peat at 30 cm depth, both in response to NH4NO3 addition and in the unamended cores confirmed poor retention of inorganic N by the moss at Lakkasuo. Nitrate contents in the profiles at Lakkasuo, Moidach More, and Côte de Braveix were extremely low, even in the N10 treatment, but in Männikjärve, where the mean depth of water table was greatest and retention absent, appreciable amounts of NO3- were detected in all cores. It is concluded that peatland drainage would reduce the capture of inorganic N in atmospheric deposition by Sphagnum mosses.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006133828518
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  • 97
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    Electronic Resource
    Cytochrome P450 Enzymes and Drug Metabolism—Basic Concepts and Methods of Assessment (1999)
    Springer
    Cellular and molecular neurobiology 19 (1999), S. 309-323 
    Details
    ISSN: 1573-6830
    Keywords: cytochrome P450 ; enzyme inhibition ; enzyme induction ; pharmacokinetics ; drug interaction ; in vitro assessment ; clinical assessment
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract 1. The cytochrome P450 enzyme family is one of the major drug metabolizing systems in man. 2. Factors such as age, gender, race, environment, and drug treatment may have considerable influence on the activity of these enzymes. 3. There are now well-established in vitro techniques for assessing the role of specific cytochrome P450 enzymes in the metabolism of drugs, as well as the inhibitory or inducing effects of drugs on enzyme activity. In vitro data have been utilized to predict clinical outcomes (i.e., pharmacokinetic interactions), with close correlations between in vitro and in vivo data. 4. This information can be of considerable practical assistance to clinicians, to help with rational prescribing or to prevent or minimize the potential for drug interactions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006993631057
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  • 98
    Electronic Resource
    Electronic Resource
    Chirality and Drugs Used in Psychiatry: Nice to Know or Need to Know? (1999)
    Springer
    Cellular and molecular neurobiology 19 (1999), S. 355-372 
    Details
    ISSN: 1573-6830
    Keywords: enantiomers ; racemic ; chiral ; stereoselective ; pharmacokinetics ; cytochrome P450 ; geometric isomers
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract 1. Many drugs used to treat psychiatric disorders contain a chiral center or a center of unsaturation and are marketed as a mixture of the resultant enantiomers or geometric isomers, respectively. These enantiomers or geometric isomers may differ markedly with regard to their pharmacodynamic and/or pharmacokinetic properties. 2. Examples of the effects of chiral centers or geometric centers on such properties are given for drugs from the following classes: antidepressants (tricyclics, selective serotonin reuptake inhibitors, monoamine oxidase inhibitors, viloxazine, bupropion, trazodone, mianserin, venlaflaxine); benzodiazepines, zoplicone, and antipsychotics. 3. As described in this review, there are several notable examples of psychiatric drugs currently available where the individual enantiomers or geometric isomers differ considerably with regard to factors such as effects on amine transport systems, interactions with receptors and metabolizing enzymes, and clearance rates from the body. Indeed, relatively recent developments in analytical and preparative resolution of racemic and geometric drug mixtures and increased interest in developing new drugs which interact with specific targets, which have been described in detail at the molecular level, have resulted in increased emphasis on stereochemistry in drug development.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006997731966
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  • 99
    Electronic Resource
    Electronic Resource
    Metabolism and Pharmacokinetics of Selective Serotonin Reuptake Inhibitors (1999)
    Springer
    Cellular and molecular neurobiology 19 (1999), S. 443-466 
    Details
    ISSN: 1573-6830
    Keywords: selective serotonin reuptake inhibitors ; metabolism ; pharmacokinetics ; fluoxetine ; fluvoxamine ; paroxetine ; sertraline ; citalopram ; cytochrome P450
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract 1. Five drugs with the predominant pharmacologic effect of inhibiting the neuronal reuptake of serotonin are available worldwide for clinical use. This class of psychoactive drugs, known as selective serotonin reuptake inhibitors (SSRIs), is comprised of fluoxetine, sertraline, paroxetine, fluvoxamine, and citalopram. 2. The SSRIs appear to share similar pharmacodynamic properties which translate to efficacy in the treatment of depression and anxiety syndromes. The drugs are differentiated by their pharmacokinetic properties with regard to stereochemistry, metabolism, inhibition of cytochrome enzymes, and participation in drug–drug interactions. Studies focusing on the relationship of plasma drug concentration to therapeutic and adverse effects have not confirmed the value of plasma concentration monitoring. 3. This review summarizes the metabolism and relevant pharmacokinetic properties of the SSRIs.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006934807375
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  • 100
    Electronic Resource
    Electronic Resource
    Modelling regional and large-scale response of Baltic Sea ecosystems to nutrient load reductions (1999)
    Springer
    Hydrobiologia 393 (1999), S. 35-43 
    Details
    ISSN: 1573-5117
    Keywords: eutrophication ; modelling ; biogeochemical cycles ; nitrogen ; phosphorus ; load reduction ; Baltic Sea ; Gulf of Finland
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The entire Baltic Sea, as well as many of its different sub-regions, are subject to eutrophication due to high nutrient inputs. To plan expensive water management measures one needs a tool to quantify effects of different water management policy decisions. The tools implemented here are simulation models based on similar descriptions of biochemical interactions in the water and sediments but coupled to different hydrodynamical models. For the Baltic Proper a 1D physical model with high vertical resolution but horizontally integrated was used. Simulations for 20 years made with 50% load reduction each 5 year show that for this domain and at these scales the recovery would take decades. The most effective is reduction of phosphorus, while reduction of only nitrogen leads to a dramatic increase in cyanobacteria blooms. For the Gulf of Finland a high-resolution 3D hydrodynamic model was coupled to a more crude 3D-box biogeochemical model describing concrete conditions during August and November 1991. In the Eastern Gulf of Finland the effects of a 50% load reduction from the St. Petersburg region are pronounced even after two weeks. Here, nitrogen reduction would be more beneficial than that of phosphorus, both locally and at a larger scale. The conclusion from these simulations is that the difference in effects of nitrogen versus phosphorus reduction is dependent on scales and locations of management.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1003529531198
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