276 research outputs found
Water calcium concentration modifies whole-body calcium uptake in sea bream larvae during short-term adaptation to altered salinities
Whole-body calcium uptake was studied in gilthead sea bream larvae (9–83·mg) in response to changing environmental salinity and [Ca2+]. Calcium uptake increased with increased fish size and salinity. Fish
exposed to calcium-enriched, diluted seawater showed increased calcium uptake compared with fish in diluted seawater alone. Calcium uptake was unchanged in Na+-
enriched, diluted seawater. Overall, [Ca2+], and not salinity/osmolarity per se, appears to be the main factor contributing to calcium uptake. By contrast, drinking was
reduced by a decrease in salinity/osmolarity but was little affected by external [Ca2+]. Calculations of the maximum contribution from drinking-associated calcium uptake
showed that it became almost insignificant (less than 10%) through a strong decrease in drinking rate at low salinities (0–8‰). Diluted seawater enriched in calcium to the
concentration present in full-strength seawater (i.e. constant calcium, decreasing salinity) restored intestinal calcium uptake to normal. Extra-intestinal calcium uptake
also benefited from calcium addition but to a lesser extent
К разработке технологии возведения геокомпозитных охранных систем горных выработок
У статті розглянуто відмінності використання особливо тонко дисперсних в’яжучих
(ОТДВ) у підземних умовах для створення елементів геокомпозитних конструкцій.In article the differences of the use especially thinly of dispersible astringent are considered in
underground terms for creation elements of geocomposit constructions
Effects of salinity challenge on the endocrine control of osmoregulation and calcium homeostasis in the sea bream
The gilthead sea bream (Sparus auratu) is a marine species often found in coastal lagoons, experimenting episodic exposures to both brackish and hypersaline environments.
However, little is known about the underlying endocrine mechanisms controlling osmoregulation in this and in most marine species. This study aimed at characterising some of the endocrine basis of sea bream osmoregulation, with emphasis on calcium homeostasis. Juvenile fish were exposed to different salinities, either by direct transfer or continuous adaptation over
a short period of time. Salinities ranged from 0 to 55 p.p.t. and sampling was carried out 4, 24, 96 and 192 h after transfer. Six
fish per group and per time point were sacrificed and plasma and tissue samples were collected. Osmolarity, osmolites and
cortisol were measured in plasma. Prolactin, growth hormone, stanniocalcin, and calcitonin mRNA expressions were determined by PCR and northern blot. Mortality occurred after 4 hours in FW. Sea bream fry (2 month old, 20-60 may) were exposed to hypersaline and dilute seawater loaded with Ca and
calcium fluxes were determined. Exposure of fry to lowered external salinity (50 and 25% SW) resulted in no mortality within 24 h and significantly decreased whole body calcium
influx. Results will be discussed in relation to gene expression.PMG is in receipt of a PRAXIS XXI grant
BD/9207/96T. his study was funded by EC grant FAIR CT-96 1742
Transport and Boundary Scattering in Confined Geometries: Analytical Results
We utilize a geometric argument to determine the effects of boundary
scattering on the carrier mean-free path in samples of various cross sections.
Analytic expressions for samples with rectangular and circular cross sections
are obtained. We also outline a method for incorporating these results into
calculations of the thermal conductivity.Comment: 35 pages, Late
Het effect van verhoogde ammonia concentratie in het water op fysiologie, groei en voeropname van Afrikaanse meerval (Clarias gariepinus)
IMARES onderzocht het effect van de ammoniaconcentratie in het kweekwater op groei, voeropname en fysiologie van Afrikaanse meerval (Clarias gariepinus). Het doel van dit onderzoek was het vaststellen van de maximale ammoniaconcentratie (grenswaarde) waarbij geen negatieve effecten op welzijn van de vis en de productie waar te nemen zijn
Calcium fluxes in Hoplosternum littorale (tamoatá) exposed to different types of Amazonian waters
Early life glucocorticoid exposure modulates immune function in zebrafish (Danio rerio) larvae
In this study we have assessed the effects of increased cortisol levels during early embryonic development on immune function in zebrafish (Danio rerio) larvae. Fertilized eggs were exposed to either a cortisol-containing, a dexamethasone-containing (to stimulate the glucocorticoid receptor selectively) or a control medium for 6 h post-fertilization (0-6 hpf). First, we measured baseline expression of a number of immune-related genes (socs3a, mpeg1.1, mpeg1.2, andirg1l) 5 days post-fertilization (dpf) in larvae of the AB and TL strain to assess the effectiveness of our exposure procedure and potential strain differences. Cortisol and dexamethasone strongly up-regulated baseline expression of these genes independent of strain. The next series of experiments were therefore carried out in larvae of the AB strain only. We measured neutrophil/macrophage recruitment following tail fin amputation (performed at 3 dpf) and phenotypical changes as well as survival following LPS-induced sepsis (150 mu g/ml; 4-5 dpf). Dexamethasone, but not cortisol, exposure at 0-6 hpf enhanced neutrophil recruitment 4 h post tail fin amputation. Cortisol and dexamethasone exposure at 0-6 hpf led to a milder phenotype (e.g., less tail fin damage) and enhanced survival following LPS challenge compared to control exposure. Gene-expression analysis showed accompanying differences in transcript abundance oftlr4bb, cxcr4a, myd88, il1 beta, and il10. These data show that early-life exposure to cortisol, which may be considered to be a model or proxy of maternal stress, induces an adaptive response to immune challenges, which seems mediated via the glucocorticoid receptor.Animal science
Current-induced highly dissipative domains in high Tc thin films
We have investigated the resistive response of high Tc thin films submitted
to a high density of current. For this purpose, current pulses were applied
into bridges made of Nd(1.15)Ba(1.85)Cu3O7 and Bi2Sr2CaCu2O8. By recording the
time dependent voltage, we observe that at a certain critical current j*, a
highly dissipative domain develops somewhere along the bridge. The successive
formation of these domains produces stepped I-V characteristics. We present
evidences that these domains are not regions with a temperature above Tc, as
for hot spots. In fact this phenomenon appears to be analog to the nucleation
of phase-slip centers observed in conventional superconductors near Tc, but
here in contrast they appear in a wide temperature range. Under some
conditions, these domains will propagate and destroy the superconductivity
within the whole sample. We have measured the temperature dependence of j* and
found a similar behavior in the two investigated compounds. This temperature
dependence is just the one expected for the depairing current, but the
amplitude is about 100 times smaller.Comment: 9 pages, 9 figures, Revtex, to appear in Phys. Rev.
Regenerating zebrafish scales express a subset of evolutionary conserved genes involved in human skeletal disease
BACKGROUND: Scales are mineralised exoskeletal structures that are part of the dermal skeleton. Scales have been mostly lost during evolution of terrestrial vertebrates whilst bony fish have retained a mineralised dermal skeleton in the form of fin rays and scales. Each scale is a mineralised collagen plate that is decorated with both matrix-building and resorbing cells. When removed, an ontogenetic scale is quickly replaced following differentiation of the scale pocket-lining cells that regenerate a scale. Processes promoting de novo matrix formation and mineralisation initiated during scale regeneration are poorly understood. Therefore, we performed transcriptomic analysis to determine gene networks and their pathways involved in dermal scale regeneration. RESULTS: We defined the transcriptomic profiles of ontogenetic and regenerating scales of zebrafish and identified 604 differentially expressed genes (DEGs). These were enriched for extracellular matrix, ossification, and cell adhesion pathways, but not in enamel or dentin formation processes indicating that scales are reminiscent to bone. Hypergeometric tests involving monogenetic skeletal disorders showed that DEGs were strongly enriched for human orthologues that are mutated in low bone mass and abnormal bone mineralisation diseases (P< 2× 10(−3)). The DEGs were also enriched for human orthologues associated with polygenetic skeletal traits, including height (P< 6× 10(−4)), and estimated bone mineral density (eBMD, P< 2× 10(−5)). Zebrafish mutants of two human orthologues that were robustly associated with height (COL11A2, P=6× 10(−24)) or eBMD (SPP1, P=6× 10(−20)) showed both exo- and endo- skeletal abnormalities as predicted by our genetic association analyses; col11a2(Y228X/Y228X) mutants showed exoskeletal and endoskeletal features consistent with abnormal growth, whereas spp1(P160X/P160X) mutants predominantly showed mineralisation defects. CONCLUSION: We show that scales have a strong osteogenic expression profile comparable to other elements of the dermal skeleton, enriched in genes that favour collagen matrix growth. Despite the many differences between scale and endoskeletal developmental processes, we also show that zebrafish scales express an evolutionarily conserved sub-population of genes that are relevant to human skeletal disease. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s12915-021-01209-8
Patient to patient hepatitis B transmission during heart biopsy procedures. A report of a European Working Party on Viral Hepatitis in Heart Transplant Recipients.
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