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  • 1
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Responses of stomatal conductance (gs) to increasing vapour pressure deficit (D) generally follow an exponential decrease described equally well by several empirical functions. However, the magnitude of the decrease – the stomatal sensitivity – varies considerably both within and between species. Here we analysed data from a variety of sources employing both porometric and sap flux estimates of gs to evaluate the hypothesis that stomatal sensitivity is proportional to the magnitude of gs at low D (≤ 1 kPa). To test this relationship we used the function gs=gsref–m· lnD where m is the stomatal sensitivity and gsref=gs at D= 1 kPa. Regardless of species or methodology, m was highly correlated with gsref (average r2= 0·75) with a slope of approximately 0·6. We demonstrate that this empirical slope is consistent with the theoretical slope derived from a simple hydraulic model that assumes stomatal regulation of leaf water potential. The theoretical slope is robust to deviations from underlying assumptions and variation in model parameters. The relationships within and among species are close to theoretical predictions, regardless of whether the analysis is based on porometric measurements of gs in relation to leaf-surface D (Ds), or on sap flux-based stomatal conductance of whole trees (GSi), or stand-level stomatal conductance (GS) in relation to D. Thus, individuals, species, and stands with high stomatal conductance at low D show a greater sensitivity to D, as required by the role of stomata in regulating leaf water potential.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Ultrastructural features of spermatozoa and spermatogenesis are described for the first time in a monoplacophoran and compared with data for other conchiferan molluses. Spermatozoa of Laevipilina antarctica Warén and Hain, 1992, are of the structurally simple, aquasperm type, featuring a conical acrosome, a compact nucleus with lacunae, a short midpiece and a single flagellum. The acrosomal vesicle shows an electron-dense inner zone, and a basal invagination (subacrosomal space) contains granular material but no axial rod. The nucleus exhibits a shallow indentation apically which contains subacrosomal material, and five (sometimes four) indentations posteriorly which partially accommodate the five (rarely four) midpiece mitochondria. Two centrioles are present, the distal connected to the annulus by satellite fibres and acting as a basal body for the flagellum (axoneme probably 9+2 structure). Spermatogonia, characterized by an oblong nucleus and one or two nucleoli, line the basal membrane of the testis wall; spermatids of varying stages of maturity occupy the remainder of the testis. Acrosome and flagellum production is already well advanced in spermatids and probably commences at the spermatocyte stage. Cytoplasmic bridges occur in all developmental stages, most visibly in spermatids. The spermatid chromatin condenses in large tracts, leaving electron-lucent lacunae. Mitochondria collect posteriorly and form, presumably by fusion, the five (or four) larger, spherical mitochondria which gather around the centrioles.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1432-0827
    Keywords: Key words: Apolipoprotein E — Genetic — Bone fracture — Hemodialysis — Vitamin K.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Abstract. This investigation of 219 hemodialysis patients relates the history and prospective risk of bone fractures to apolipoprotein E (apoE) genotype. A greater percentage of the 41 patients with the E3/4 and E4/4 genotypes than of the 38 patients with the E2/3 and E2/2 genotypes had a history of bone fractures at the time of recruitment (44% versus 16%, P 〈 0.005). During the 4 years following recruitment, more of the patients with apoE genotypes E3/4 and E4/4 than with apoE genotypes E2/3 and E2/2 suffered bone fractures, but this difference was not statistically significant (17.1 versus 5.3%, P 〈 0.1). ApoE genotype appears to be an important genetic risk factor for bone fracture, possibly due to its previously reported influence on vitamin K concentrations in blood.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1432-1106
    Keywords: Key words Neurotrophic factor ; Growth factor ; GDNF ; Neurite outgrowth ; Postnatal development ; Enteric nervous system ; Myenteric plexus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  Glial cell-line-derived neurotrophic factor (GDNF), a member of the transforming growth-factor- (TGF-) β-family, is an essential factor for the development of the enteric nervous system (ENS) during embryogenesis. In the present study, the effects of GDNF on postnatal ENS development were investigated using cultures of myenteric plexus from the small intestine of newborn albino rats of different developmental phases (P1, P7, P14). Myenteric plexus was dissociated and cultivated as mixed cultures of enteric neurons and glial cells. After seeding, the cultures were kept for 24 h or 7 days in serum-free medium containing various doses (1, 10, 100 ng/ml) of GDNF. The effect of the neurotrophic factor was evaluated using parameters such as cell size, neuronal survival, or neurite elongation. While neither glial-cell nor neuronal size was influenced by GDNF, there was an observable effect upon neuronal survival and neurite elongation. The cultures treated with GDNF displayed increased neurite outgrowth. The promoting effect was dose- and age-dependent, decreasing clearly during the early postnatal period. Already after 24 h, neuronal survival was increased in P1 and P7, but not in P14 cultures. In long-term cultures, a marked tendency to form cell aggregates and dense fiber networks was observed when treated with GDNF. These observations suggest that GDNF plays an important role not only in pre-, but also in postnatal development of the enteric nervous system.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1432-2013
    Keywords: Stimulus transduction ; Bursting ; Temperature dependence ; Calcium entry blockers ; Siluriformes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Spontaneous afferent activity was recorded from 26 single ampullary electroreceptive organs of freshwater catfish (Ictalurus nebulosus LeS) at various temperatures. Regular grouping of action potentials was apparent in this secondary sensory system at 35°C and occasionally at 30°C. Impulse groups consisted of up to seven impulses. The precise timing of impulse generation and the temporal sequence of impulses indicated that oscillating processes are involved. Expectation density functions were calculated for records of afferent activity obtained at various temperatures below 35°C. In the majority of records the function was periodic. Impulse grouping and expectation density functions became more distinct in units exhibiting extremely high thresholds (i.e. being insensitive) to electrical stimuli. The results suggest that the oscillations originate from the postsynaptic membrane. The temporal pattern of impulse generation within impulse groups of ampullary electroreceptor organs and of specific warm and cold receptors was compared and found to be similar. Application of cadmium and menthol, which both reduce calcium entry, suppressed spontaneous activity in normal and insensitive electroreceptor systems, attenuated the sensitivity of normal receptors and modified the periodic pattern. This indicates that calcium is implicated in sensory transduction and in postsynaptic mechanisms. The data suggest that an oscillating process is one component of signal transmission in ampullary electroreceptor organs of teleost fish.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Applied physics 61 (1995), S. 249-251 
    ISSN: 1432-0649
    Keywords: 42.68 ; 42.30
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The combination of remote sensing methods like Doppler lidar and FTIR offers the possibility to determine mass fluxes of gases remotely. Doppler lidar measures the three-dimensional wind vector in the vicinity of diffuse sources or the velocity of air in a chimney plume if an industrial complex is monitored. FTIR is a multi-component remote sensing method for gas concentrations. The Fourier transformation of an interferogram of a Michelson interferometer within a FTIR system converts the recorded intensity (function of optical path length) to a spectral signal (function of wavenumber). Both information, velocity and concentration, give the mass fluxes of the tracer (gas). A first test was performed at Munich-North power station with FTIR and cw-Doppler lidar. Fluxes of CO2, CO, NO, and HC1 were determined. The results are in good agreement with the fluxes measured by in-situ instruments of the power station. The method can be used to control industrial complexes from an outside observation site.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Applied physics 68 (1999), S. 321-324 
    ISSN: 1432-0630
    Keywords: PACS: 42.70; 66.30
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: 3 by diffusion doping is investigated by means of secondary neutral mass spectrometry and secondary ion mass spectrometry. The diffusion of praseodymium in LiNbO3 can be described by Fick’s laws of diffusion with a concentration-independent diffusion coefficient and a limited solubility of praseodymium in LiNbO3 increasing exponentially with rising temperature. The diffusion depends on the Li2O content of the LiNbO3 crystal. For LiNbO3 crystals with a nominal slight difference in the congruent composition, the diffusion constants and activation energies for Z-cut LiNbO3 are 3.28×10-5 cm2/s and 2.27 eV, and 1.39×10-5 cm2/s and 2.24 eV, respectively. Titanium-doped waveguides are formed in Pr:LiNbO3 and characterised in relation to waveguide loss and absorption in the visible and near infrared.
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 1569-8041
    Keywords: neuroblastoma ; prognosis ; telomerase activity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Background: Treatment of neuroblastoma has remained a major challenge in pediatric oncology because the assessment of the individual prognosis, particularly in disseminated disease is still obscure. Previous studies have correlated clinical outcome with activity levels of telomerase, a cellular reverse transcriptase which has been detected in the majority of human malignant tumors. Patients and methods: In this blind-trial study, a non-radioactive telomeric repeat amplification protocol (TRAP) with an internal telomerase-assay standard was used on an automated laser fluorescence sequencer for the detection and semiquantitative analysis of telomerase activity (TA) in 67 neuroblastomas of all clinical stages from the German Neuroblastoma Trial and 2 ganglioneuromas. TA levels were correlated with event-free and overall survival rates and established prognostic markers such as MYCN. Results: TA was present in 14 of 69 (20%) samples, including 3 of 22 stage IVS, 8 of 14 stage IV, 1 of 10 stage III, 1 of 7 stage II and 1 of 14 stage I neuroblastomas and 0 of 2 ganglioneuromas. We found a strong statistical correlation between the presence of TA and poor clinical prognosis with regard to all tumor stages. Multivariate analysis revealed TA as an independent prognostic marker. In particular, the analysis of TA in IVS neuroblastomas distinguished two different prognostic groups. Conclusions: Our data suggest that TA is an independent prognostic marker in neuroblastoma which, in combination with other markers such as MYCN, may proof useful in assessing the individual patient's prognosis.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Chromatographia 40 (1995), S. 550-556 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Open tubular columns ; Short chain fatty acids ; Intestinal fluids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A capillary gas-liquid chromatography method for the analysis of free short chain fatty acids in intestinal samples was developed. Analytical results obtained with intestinal samples are influenced not only by high molecular mass matrix constituents but also by matrix components with a molecular weight smaller than 5000 daltons. To achieve a faithful transfer of SCFA into the chromatographic system it was important to avoid accumulation of involatile deposits on the surface of the inlet liner. Cleaning of the inlet linear lead to a significant weakening of matrix effects. The method described, using an Innowax column, is more effective, particularly with respect to precision and sensitivity, and is clearly superior to packed columns. The capillary is the column of choice for the separation of short fatty acids in samples from the small intestine and stomach.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Langenbeck's archives of surgery 382 (1997), S. 380-392 
    ISSN: 1435-2451
    Keywords: Key words Drainage ; Abdomen ; Effects ; Schlüsselwörter Abdominaldrainagen ; Verhalten ; Auswirkungen
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Zusammenfassung In einer prospektiven randomisierten Studie an 30 Mischrassekaninchen wurden nach 2 standardisierten Dickdarmresektionen bei je 10 Tieren Penrose-, Gummirohr- und Silikonkautschukrohrdrainagen in den Unterbauch eingesetzt und als geschlossenes Drainagesystem subkutan abgeleitet. Eine der Darmanastomosen wurde ebenfalls drainiert. Auswertung und Befunderhebung erfolgten am 7. postoperativen Tag. An mechanischen Auswirkungen wurde nur 1mal ein Druckulkus durch Anstemmen einer Silikonrohrdrainage im Unterbauch beobachtet. „Wetz“-Spuren waren sonst nur lokale unspezifische Entzündungsreaktionen gegen den Fremdkörper Drain, die in gleichem Maß bei allen Draintypen auftraten. Eine vom Drain ausgehende, aufsteigende Infektion wurde nicht beobachtet. Infektionen hatten ihren Ursprung immer von Komplikationen im Operationsgebiet. Entgegen bisheriger Vorstellungen waren die Drainagen im Unterbauch frei von Verwachsungen und Verklebungen zu den Organen der Bauchhöhle. Lediglich die Durchtrittsstelle an der Bauchdecke und der Baumwolldocht der Penrose-Drainage zeigten regelmäßig Verwachsungen. Die ausgedehnten Verwachsungen der Anastomosendrainagen waren auf Auswirkungen der Darmanastomosen und deren Komplikationen zurückzuführen. Gummirohr und Latexgummi zeigten materialbedingt großflächige Fibrinauflagerungen. Durch Verstopfung des Drainrohrs und des Baumwolldochts mit Fibrinkoageln waren nach 7 Tagen nur noch ca. 20% der Drainagen durchgängig. Prinzipiell bestand kein Unterschied im Verhalten der 3 verschiedenen Drainagetypen bei Materialvorteilen des Silikonkautschuks.
    Notes: Abstract In a prospective randomised study 30 mongrel rabbits recieved two standard colon-resections. Three types of drains were testet: (latex-rubber-) Penrose-drains, rubbertube- and silikontube-drains, which were placed in the lower abdomen. As a closed drainage-system the extraperitoneal tip of the drain was placed in a closed subcutis-pocket. One of the two colon-anastomoses also was drained. The findings were recorded on the 7th postoperative day. A single mechanic alteration was found, an ulcer caused by a silicon-drain, that pushed against the abdominal wall. The other signs of mechanic irritation were microscopically unspecified inflammatory reactions to the foreign body drain. There was no ascending infection caused by the drain. All infections came from complications of the colon resections. In contrast to common opinions the drains in the lower abdomen showed no adhäsions to the abdominal wall or organs. Only the entrance of the drain into the peritoneum and the cotton-gaze of Penrose-drains showed in nearly all cases adhesions. The large amount of adhesions to the anastomosis-drains came from complications of the colon-anastomoses. As a cause of material, rubber- and latex-rubber-drains showed large fibrin-clotts on their surfaces. 7 days after the operation only about 20% of the drains had sufficient function. The rest was occluded by fibrin-clotts in the lumen of the drain or the cotton-gaze. Over all there is no difference in changes and effects of the three different types of drains, but silicon as material showed advantages.
    Type of Medium: Electronic Resource
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