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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Acta neuropathologica 69 (1986), S. 288-294 
    ISSN: 1432-0533
    Keywords: Experimental glioma ; Vascular permeability ; Dexamethasone ; Mannitol
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The vessels of experimental gliomas show an abnormally high permeability to small polar molecules, such as mannitol. To establish whether this change in vessel permeability is modified by treatment with the corticosteroid dexamethasone, the kinetics of [14C]mannitol transfer into rat astrocytomas were estimated in both steroid- and saline-treated, tumourbearing animals. This was achieved by injecting [14C]mannitol i.v., using a specially devised technique, so as to maintain a constant concentration of tracer in the blood plasma. In separate experiments steady levels of the tracer were maintained in the circulation from 1 to 30 min. Mean plasma and tumour radioactivity were measured, and the apparent transfer constant of mannitol across the vascular endothelium and the size of the extravascular extracellular mannitol space in the tumours were calculated. Despite a significant clinical improvement in the treated animals and adequate circulating levels of dexamethasone at the time of the permeability studies, no difference in either the apparent transfer constant for the movement of mannitol into the tumours or the fractional extracellular mannitol space was detected between these animals and the controls. With steroid treatment both tumour-bearing and non-tumour bearing animals lost weight, and in the latter there was no consistent change in routine biochemical or haematological parameters. It was concluded that under these conditions it is unlikely that clinical improvement with dexamethasone therapy was due to a non-specific reduction in tumour vessel permeability to polar substances.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A captive population of Australian red-claw crayfish, Cherax quadricarinatus, of known age was used for the study. Lipofuscin concentration in the left olfactory lobe cell mass of the brain was measured using image analysis of fluorescence micrographs. Age predictions based on lipofuscin concentration were more accurate and had narrower 95% confidence limits than those derived from the more conventional body size and weight predictors for all age groups tested (180, 300, 420, 780 d). Overall, use of lipofuscin concentration produced a significantly lower (p0.001) mean age-prediction error (16.65%) than use of carapace length or body weight (32.45 and 32.3%, respectively). Carapace length was of little value for prediction of the age of older individuals. Mathematical models defining the relationships between temperature, age and lipofuscin accumulation were derived from laboratory-reared individuals. These models did not describe adequately the course of lipofuscin accumulation in crayfish from the field over the whole lifespan. Field data from three “known” year-classes were used to generate simulated size-frequency and lipofuscin concentration-frequency histograms. Year-classes in the lipofuscin concentration frequency-histogram were much more easily distinguished than in the size-frequency histogram. Under field conditions, lipofuscin concentration was a better predictor of chronological age than conventional morphometric measures.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Nitrogen excretion rates of demersal macrozooplankton were measured together with nitrogen concentrations in the water column and sediments in lagoons of Heron Reef and One Tree Reef, Great Barrier Reef, Australia, during August and November 1991. Excretion rates increased with body weight, and weight-specific excretion rates of the demersal macrozooplankton were comparable to those of pelagic zooplankton and meiofauna in the Great Barrier Reef. Values of demersal macrozooplankton abundance from previous studies and excretion rates from this study were combined to estimate fluxes of ammonium from demersal macrozooplankton in coral reef lagoons. The estimated fluxes in the water column and sediments were 12 μM NH4 m-2 d-1 and 34 μM NH4 m-2d-1, respectively. These fluxes were compared with reported fluxes of ammonium in coral reef lagoons in the Great Barrier Reef, Australia. The estimated flux from the demersal macrozooplankton in the water column was 29 and 9% of those reported for microheterotroph regeneration and phytoplankton utilization, respectively. It was 10% of the reported advective flux during periods of low advection and 13% of the maximum efflux from sediments computed from diffusion models. The estimated flux from the demersal macrozooplankton in the sediments exceeded those reported for meiofauna, and was 5 to 32% and 2 to 13% of those reported for ammonification and utilization in sediments, respectively. The potential importance of demersal macrozooplankton in mediating sediment-water column exchanges in the absence of diffusive effluxes and when they swarm is discussed.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A total of 34 zooplanktonic taxa were common in emergence trap, reentry trap, and net-tow samples taken in the lagoon of Heron Reef, Great Barrier Reef, between 27 February and 22 March and between 11 June and 4 July 1985. Twenty-nine of these taxa were classified as demersal (17 taxa), meroplanktonic and larval (10 taxa), or incidental (2 taxa). The remaining five multispecific groups yielded variable results. Differences were observed between two locations separated by 200 m, with emergence 2 to 62 times greater for 22 taxa at a deeper site with larger coral formations. Most zooplankters were more common (2 to 122 times) in samples from 1 m2 areas around 0.25 to 0.5 m2 patches of branching coral. However, two species of copepods, Pseudodiaptomus colefaxi and Metis holothuriae, were taken in greater numbers (3 to 12 times) from open sand. Seasonal increases (2 to 322 times) were observed for 13 adult taxa and 8 classes of larvae or juveniles in the summer and for 10 adult taxa and one larval group in the winter. Fourteen of the 17 demersal taxa and 4 groups of large larvae or juveniles emerged in numbers 2 to 323 times greater during lunar quarters or new moons. In contrast, 6 larval taxa and 4 groups of small or transparent adults displayed significant emergence during full moons. Five diurnal emergence patterns were shown by 27 taxa, with patterns varying primarily among lunar periods. The variety of taxon-specific patterns observed in this study highlight a need for caution when generalizing about demersal zooplankton.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Industrial relations journal 3 (1972), S. 0 
    ISSN: 1468-2338
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Economics
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Biochemical and Biophysical Research Communications 77 (1977), S. 1317-1325 
    ISSN: 0006-291X
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology , Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Sensors and Actuators A: Physical 37-38 (1993), S. 82-85 
    ISSN: 0924-4247
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Electrical Engineering, Measurement and Control Technology
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Journal of Development Economics 26 (1987), S. 129-143 
    ISSN: 0304-3878
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Political Science , Economics
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Biochemical and Biophysical Research Communications 77 (1977), S. 1317-1325 
    ISSN: 0006-291X
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology , Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
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  • 10
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: The genes coding for the binding-protein-dependent lactose transport system and β-galactosidase in Agrobacterium radiobacter strain AR50 were cloned and partially sequenced. A novel lac operon was identified which contains genes coding for a lactose-binding protein (lacE), two integral membrane proteins (lacF and lacG), an ATP-binding protein (lacK) and β-galactosidase (lacZ). The operon is transcribed in the order lacEFGZK, The operon is controlled by an upstream regulatory region containing putative -35 and -10 promoter sites, an operator site, a CRP-binding site probably mediating catabolite repression by glucose and galactose, and a regulatory gene (lacl) encoding a repressor protein which mediates induction by lactose and other galactosides in wild-type A. radiobacter (but not in strain AR50, thus allowing constitutive expression of the lac operon). The derived amino acid sequences of the gene products indicate marked similarities with other binding-protein-dependent transport systems in bacteria.
    Type of Medium: Electronic Resource
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