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  • 1
    Electronic Resource
    Electronic Resource
    Terahertz radiation from delta-doped GaAs (1994)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 65 (1994), S. 79-81 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Terahertz pulse emission from four different delta-doped molecular beam epitaxially grown GaAs samples is studied. We observe a decrease of the emitted THz pulse amplitude as the distance of the delta-doped layer from the surface is increased, and a change in polarity of the THz pulses as compared to bulk n-type doped GaAs reference samples. The electric fields in the region of the doping layer are investigated by photoreflectance spectroscopy. A careful analysis of Franz–Keldysh oscillations observed in the photoreflectance spectra provides information about the built-in fields on both sides of the delta-doped layer.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.113080
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  • 2
    Electronic Resource
    Electronic Resource
    Fasting modulates metabolic responses to cortisol, GH and IGF-I in Arctic charr hepatocytes (2005)
    Oxford, UK; Malden, USA : Blackwell Publishing Ltd/Inc.
    Journal of fish biology 67 (2005), S. 0 
    Details
    ISSN: 1095-8649
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Hepatocytes in primary culture from fed and 2 month fasted Arctic charr Salvelinus alpinus were exposed to physiological doses of either cortisol, salmon growth hormone (GH), salmon insulin-like growth factor-I (IGF-I) or a combination of salmon GH and salmon IGF-I. Fasting significantly lowered medium glucose levels compared to the fed fish, but had no significant effects on hepatocyte glycogen content or on the activities of enzymes involved in the intermediary metabolism. Cortisol treatment had no effect on hepatocyte glycogen content or on the enzyme activities investigated, but resulted in a significant increase in medium glucose concentration in hepatocytes isolated from fasted, but not fed fish. GH and IGF-I treatments, both singly and in combination, significantly increased the glycogen content of hepatocytes isolated from fed fish, with less pronounced effects on hepatocytes isolated from fasted fish. The combination of GH and IGF-I significantly increased lactate dehydrogenase activity regardless of the feeding state and significantly reduced the phosphenolpyruvate carboxykinase activity and medium glucose concentration in hepatocytes isolated from fed fish. Further, GH and IGF-I significantly increased the activities of alanine aminotransferase and aspartate aminotransferase in hepatocytes isolated from fasted fish, but not fed fish. There were no effects of GH, IGF-I, or their combination, on glucose 6-phosphate dehydrogenase or 3-hydroxyacyl-CoA dehydrogenase activities. The results demonstrated that nutritional status of the animal modulates hepatocyte responsiveness to metabolic hormones, and suggested a role for GH and IGF-I in hepatic glycogen conservation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1095-8649.2005.00870.x
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  • 3
    Electronic Resource
    Electronic Resource
    High-affinity uptake of an ammonium analogue by two marine microflagellates from the oligotrophic Pacific (1983)
    Springer
    Marine biology 74 (1983), S. 161-168 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Two marine microflagellates, isolated from the North Pacific Central Gyre, and tentatively identified as Platymonas sp. and Mantoniella sp., were examined for uptake of 14C-methylamine, a non-metabolizable analogue of ammonium. Half-saturation constants (K m) for ammonium transport, estimated from competitive inhibition of methylamine transport by ammonium, were 50 nM for Platymonas sp. and 2.9 nM for Mantoniella sp. These values are the lowest so far reported, indicating that the transport systems are well adapted to extremely low ammonium environments. The ratio of the K m for methylamine to the K m for ammonium was 17 for Platymonas sp. and 41 for Mantoniella sp. The observed ratios fell within the relatively narrow range reported for various organisms, including bacteria, fungi and phytoplankton (25.0±15.5, $$\bar x$$ ± SD, n=9), although the reported K mvalues for both ammonium and methylamine vary over a thousand-fold range. The use of 14C-methylamine may therefore be a promising technique for studying the kinetics of ammonium transport by marine microorganisms, particularly those in oligotrophic environments.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00413919
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  • 4
    Electronic Resource
    Electronic Resource
    Microbial uptake of dissolved organic matter in Mcmurdo Sound, Antarctica (1981)
    Springer
    Marine biology 61 (1981), S. 89-94 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The distribution and activity of bacterioplankton, and the turnover of dissolved organic matter (DOM) were examined in McMurdo Sound, Antarctica. On the eastern side of the Sound, bacteria averaged 6.5×108 l-1, and turnover rates of dissolved adenosine triphosphate, D-glucose and l-leucine averaged 16, 116 and 124 h, respecitvely. These molecules as well as thymidine were taken up maximally from 0° to 5°C and near-maximally from -1.5° to 0°C, indicating bacterial adaptation to rapid turnover of dissolved organic matter at the ambient temperature. On the west side of the Sound, bacteria averaged only 0.65×108 l-1, and turnover times for adenosine triphosphate, D-glucose and lleucine averaged 59, 20454, and 3070 h, respectively. Total microbial adenosine triphosphate (an indicator of total microbial biomass) and chlorophyll a were also much lower at the western than at the eastern side stations. Moreover, no primary production could be detected at one western side station (New Harbor). Thus, in McMurdo Sound, the western side is highly oligotrophic, but the eastern side has an abundant active bacterioplankton, comparable to that of temperate coastal waters.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00386648
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  • 5
    Electronic Resource
    Electronic Resource
    Renal plasma clearance: A valuable marker in myelomatosis (1982)
    Springer
    Annals of hematology 45 (1982), S. 1-11 
    Details
    ISSN: 1432-0584
    Keywords: Bence Jones proteinuria ; Glomerular filtration rate ; Myelomatosis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Forty-two consecutive patients with untreated myelomatosis (MM) formed the basis of settling the validity of measuring the renal plasma clearance (RPC), either indirectly using the serum creatinine or directly using the glomerular filtration rate (GFR) when studying anaemia, calcium metabolism, proteins in serum and urine, and prognosis. Patients without light chain excretion in the urine had a higher GFR (P〈0.01) than patients with light chain excretion. The haemoglobin concentration (Hb) was strongly correlated (P〈0.001) to both, serum creatinine and GFR. Patients with normal serum concentrations of the physiological immunoglobulins had higher Hb (P〈0.01) than patients with reduced serum immunoglobulins. Patients with serum calcium 〉3.00 mmol/l had additional reduced GFR compared with the other myeloma patients. The serum parathyroid hormone was decreased (P〈0.01) and inversely correlated to the GFR. Patients with increased serum creatinine, reduced GFR or with osteolytic bone lesions had a decreased survival rate. The study shows that the major factor in prediction of Hb and prognosis in patients with MM is the RPC expressed either as the serum creatinine or the GFR. In addition, the significant correlations between the GFR and the other variables in MM assessed the RPC to be a useful and valuable marker in studies of anaemia, protein and calcium metabolism and prognosis in MM.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00320493
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  • 6
    Electronic Resource
    Electronic Resource
    A nationwide cross-sectional study of retinopathy and microalbuminuria in young Norwegian Type 1 (insulin-dependent) diabetic patients (1992)
    Springer
    Diabetologia 35 (1992), S. 1049-1054 
    Details
    ISSN: 1432-0428
    Keywords: Type 1 (insulin-dependent) diabetes mellitus ; retinopathy ; microalbuminuria ; risk factors ; adolescents ; blood pressure ; puberty
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary A nationwide cohort of Type 1 (insulin-dependent) diabetic patients was studied to determine the prevalence of retinopathy and microalbuminuria and to evaluate the association to various risk factors. Of 600 subjects with mean age of 19.8 years (range 8.0–30.3) and a mean duration of diabetes of 10.5 years (range 6.2–17.3),371 (60 %) volunteered for a clinical examination which included fundus photography, timed overnight urine samples for albumin excretion rate, measurement of arterial blood pressure and determination of HbA1c, Retinopathy was found in 122 of 371 patients (32.8 %), in 3 of 41(7.3 %) patients aged less than 13 years. The youngest subject with retinopathy was 9.6 years old. Microalbuminuria was found in 44 of 351 patients (12.5 %), in 1 of 41(2.4 %) patients aged less than 13 years. The youngest subject with microalbuminuria was 11.5 years old. Mean HbA1c was 8.6 % (normal range 4.5–6.1 %). Patients with retinopathy had significantly higher mean age (p = 0.0001), longer mean duration of diabetes (p = 0.0001), higher mean HbA1c (p = 0.009), and higher mean arterial blood pressure (p = 0.0001) compared to patients without retinopathy. In microalbuminuric patients HbA1c (p =0.0001) and mean arterial blood pressure (p = 0.01) were significantly higher compared to non-microal-buminuric patients, but there was no difference in age or diabetes duration. Ina multiple logistic regression model, age, HbA, duration of diabetes and mean arterial blood pressure were found to be significantly associated with retinopathy, while HbA1c mean arterial blood pressure and onset before 13.0 years of age were found to be associated with microalbuminuria. The prevalence of retinopathy and microalbuminuria was relatively low. Both retinopathy and microalbuminuria were strongly associated with blood glucose control and developed at prepubertal age in some patients. The findings indicate that more intense optimization of blood glucose control in children and adolescents with Type 1 diabetes is warranted.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02221680
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  • 7
    Electronic Resource
    Electronic Resource
    Blood glucose control and microvascular complications — what do we do now? (1994)
    Springer
    Diabetologia 37 (1994), S. 1172-1177 
    Details
    ISSN: 1432-0428
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00399789
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  • 8
    Electronic Resource
    Electronic Resource
    Blood glucose control and microvascular complications – what do we do now? (1994)
    Springer
    Diabetologia 37 (1994), S. 1172-1177 
    Details
    ISSN: 1432-0428
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00399789
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  • 9
    Electronic Resource
    Electronic Resource
    Nitrogen assimilation by phytoplankton in the Scotia Sea (1983)
    Springer
    Polar biology 2 (1983), S. 137-147 
    Details
    ISSN: 1432-2056
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary This study of nitrogen metabolism of phytoplankton was one component of a large multidisciplinary program designed to examine the biological productivity of the eastern Scotia Sea, Antarctica, with regard to the importance of the zone of mixing of the northern outflow of the Weddell Sea with Drake Passage waters. The total integrated N-uptake for the euphotic zone in the southwest part of the Scotia Sea was estimated to be in the range of 9.7–14.1 mmol N·m-2·d-1, while for the eastern part of the Scotia Sea it was less than half of this, being 2.1 to 4.7 mmol N·m-2·d-1. The rate of primary production could not be correlated with the front between the two major water masses. Assimilation rates of 15N-enriched substrates indicate that phytoplankton production in the Scotia Sea during austral summer subsists predominantly on ammonia (85%), with lower incorporation rates for nitrate (14%) and nitrite (1%). Nitrate assimilation was much more light-dependent than the uptake of ammonia. These data indicate that there is a rapid and extensive mineralization of organic matter in the surface waters, resulting in a recycling of nitrogen approximately eight times before it is lost from the euphotic zone. This has important implications with regard to the dynamics of the microbial food web in antarctic waters.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00448963
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  • 10
    Electronic Resource
    Electronic Resource
    Submerged macrophyte seed bank in a Mediterranean temporary marsh: abundance and relationship with established vegetation (1993)
    Springer
    Oecologia 94 (1993), S. 1-6 
    Details
    ISSN: 1432-1939
    Keywords: Submerged macrophytes ; Annuals ; Seed size ; Seed bank ; Temporary Mediterranean marsh
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The abundance and composition of the submerged macrophyte seed bank in the Doñana marsh (southwestern Spain) was evaluated to assess its relationship with the overlying vegetation. The results obtained demonstrate the existence of a dense seed-bank, both in terms of the number of seeds and their biomass, which represented about 10% (5% for angiosperms and 〉20% for Charophyta) of the total plant biomass, which ensures the maintenance of the annual submerged macrophyte populations of the seasonally inundated Donñana marsh. Seed bank and established vegetation were coupled, as reflected in the existence of significant correlations between their structure and abundance. This coupling was lacking for Charophyta, whose oospores are widespread and abundant across the marsh, even at locations where they are absent, or rare, in the established vegetation. These differences between the seed bank of annual angiosperms and Charophyta appear to reflect, in part, structural differences between angiosperm seeds and Charophyta oospores, with important ecological consequences. An important aspect of these differences is the allocation of Charophyta reproductive effort to many small propagules lacking embryo storage, compared to those of angiosperms, which ensures their efficient dispersal and numerical abundance in the seed bank.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00317293
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