Biomedical subjects
M Weisbart
Publications and source records attributed to M Weisbart.
Seasonal changes in osmoregulation, cortisol, and cortisol receptor activity in the gills of parr/smolt of steelhead trout and steelhead-rainbow trout hybrids, Oncorhynchus mykiss.
Steelhead and hybrid trout (rainbow trout male, steelhead female) presmolts and smolts, Oncorhynchus mykiss, exposed to 30/1000 seawater (SW) for 24 hr manifested progressively lower plasma sodium values from December to May. The increase in plasma sodium after 24 hr in SW diminished significantly after March, with the hybrids (which were heavier in weight than the steelheads) reaching their peak osmoregulatory ability in the middle of April, and the steelheads in late May. In fresh water there was little difference in plasma osmotic concentration but steelhead plasma chloride fell significantly from March 30 levels to May 23 levels, whereas hybrid plasma chloride levels did not change during this time. In steelheads but not hybrids, plasma cortisol correlated negatively with plasma sodium of fish exposed 24 hr in SW. However, in both steelheads and hybrids, plasma sodium values 24 hr after SW exposure had an inverse correlation with cytosol cortisol from the gills. Again, in both steelheads and hybrids, plasma values of fish exposed 24 hr in SW correlated positively with cytosol receptor activity. In hybrids, the nuclear extract receptor activity, Nmax, increased significantly until late March and then dropped significantly thereafter. In steelheads, there were no significant differences but Nmax followed the same trends as occurred in hybrids. Thus seasonal changes in cortisol and cortisol receptors in steelhead occur during smoltification and preparation for marine life and suggest an important role for cortisol. In hybrids there appears to be a reduction in seasonality.
Simplified high throughput protocol for northern hybridization.
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Dynamics of cortisol receptor activity in the gills of the brook trout, Salvelinus fontinalis, during seawater adaptation.
Injection of cortisol into freshwater-adapted brook trout caused a rapid increase in plasma cortisol and a significant drop in plasma osmolality, thyroxine (T4), and chloride concentrations, but a nonsignificant drop in plasma triiodothyronine (T3). Concomitantly, cortisol cytosolic receptor activity decreased and cortisol nuclear extract receptor activity increased significantly. Transfer of brook trout into 30% seawater evoked a significant rise in plasma cortisol, osmotic, and chloride concentrations and a significant drop in plasma T4 and T3. Cortisol cytosol receptor activity rapidly dropped following entry into seawater, and cortisol nuclear extract receptor activity rose significantly in a manner similar to the effects of the injection of cortisol. Although there was a lack of correlation between the cytosol cortisol concentration and the cytosol receptor concentration, a significant and positive correlation occurred between the nuclear extract cortisol concentration and the nuclear extract cortisol receptor activity. This positive correlation may reflect an important role for the putative nuclear receptor. These results support the hypothesis that cortisol has an important role in the adaptation of brook trout to the marine environment.
The presence of corticosteroid receptor activity in the gills of the brook trout, Salvelinus fontinalis.
Gill tissue from brook trout was examined for the presence of cortisol receptors. Both cytosolic and nuclear preparations from the gills manifested high equilibrium association constants (Ka) and low maximum binding capacities (Nmax) indicative of high-affinity and low-capacity receptor activity (cytosol: Ka = 0.31 +/- 0.02 X 10(9)/M, Nmax = 223.9 +/- 22.8 fmol/mg protein; nuclear extract: Ka = 0.02 +/- 0.003 X 10(9)/M, Nmax = 424.6 +/- 96.3 fmol/mg protein). Gel permeation (Sephacryl S-300) column chromatography gave two incompletely separated peaks at 326,000 and 189,000 Da and Stokes radii of 5.96 and 4.81 nm using [3H]triamcinolone acetonide and only one peak at 219,000 Da and 5.4 nm using [3H]cortisol. The binding of the synthetic compounds, triamcinolone acetonide and dexamethasone, appears to be different from that of the natural steroid, cortisol. The receptor activity appears to be highly specific for cortisol since cortisone and 11 beta,17 alpha,21-trihydroxy-4-pregnen-3,20-dione-21-phosphate bind with much lower affinity. The gill tissue cytosol fractions had the highest cortisol-binding activity, followed by liver, intestine, and muscle. The association constants for the liver, intestine, and muscle were the same order of magnitude as that for the gill. These results are consistent with the concept of nonmembrane steroid receptors of target organs.
Cortisol dynamics during seawater adaptation of Atlantic salmon Salmo salar.
We examined plasma cortisol concentration (PCC), cortisol metabolism, and cortisol protein binding (CPB) in chronically cannulated Atlantic salmon (Salmo salar) during seawater (SW) adaptation. PCC rose significantly 2 h after freshwater (FW) to SW changeover but tended to be lower for 6 days thereafter. Plasma chloride concentrations began to stabilize 24-48 h after entry to SW. Cortisol metabolic clearance rate (MCR) was significantly higher 24 h after SW transfer than in FW; CPB and plasma protein concentration were significantly lower, but cortisol production rate was unchanged. The change in plasma chloride after 24 h in SW was negatively correlated with the change in plasma protein (r = -0.915, n = 9, P less than 0.001). The changes in CPB and plasma protein were correlated with the change in MCR (r = -0.643, n = 14, P less than 0.02; r = -0.850, n = 9, P less than 0.005). We hypothesize that these changes in protein concentration reflect an ion-induced expansion of extracellular volume and lead to increased MCR.
Cortisol kinetics and fluid distribution in brook trout (Salvelinus fontinalis).
Cortisol kinetics were examined in brook trout (Salvelinus fontinalis) to assess possible relationships with body fluid distribution during acclimation to sea water (SW). The disappearance curve of [3H]cortisol in plasma, after a bolus injection, was analysed by compartmental analysis using a three-pool mammillary model. The results indicated that only approximately 10% of the total exchangeable cortisol was located in the plasma pool. Over 75% of the total cortisol was associated with a large slowly exchanging pool and the remaining cortisol was located in a second extravascular tissue pool which was in rapid exchange with the plasma pool. Two days after transfer of trout from fresh water to SW, when plasma chloride concentration was at a new steady state, body weight, intracellular fluid volume, haematocrit and inulin clearance rate were lowered but plasma, blood and extracellular volumes were unaltered. Cortisol plasma clearance rate was unaltered but plasma cortisol concentration, cortisol secretion rate, total cortisol pool size and interpool transport rates were increased. These results are consistent with an acute role for cortisol in SW adaptation of brook trout. The fraction of the total cortisol cleared was smaller and the average time that cortisol spent in the tissue pools was slightly longer in trout after transfer to SW, possibly reflecting altered fluid dynamics. The fractional disappearance rate was larger at higher plasma cortisol concentrations in the SW trout. This relationship is compatible with the hypothesis that cortisol protein binding protects cortisol from metabolism.
Radioimmunoassay of cortisone in the adult Atlantic salmon, Salmo salar L.
A radioimmunoassay (RIA) was developed to measure cortisone in Atlantic salmon plasma. Diatomaceous earth microcolumn chromatography was used to separate the cortisone from other steroids. The RIA method following chromatography was validated by analyzing each of six samples of blood by double isotope derivative assay (DIDA) and RIA. The RIA gave significantly lower plasma cortisone concentrations (P less than 0.05) than the DIDA: the correlation coefficient was 0.84. Accuracy of the RIA was also demonstrated by addition of radioinert cortisone and measurement of increasing volumes of plasma. Specificity of the antisera was very good. Sensitivity of the RIA was 11 pg/RIA tube or 0.025 micrograms cortisone/dl plasma corrected for recovery and fraction assayed. Plasma cortisone concentrations in adult Atlantic salmon ranged from 2 to 26 micrograms/dl. The mean plasma cortisone concentration of salmon in fresh water was not significantly different from that in sea water. The mean cortisone/cortisol ratio in both adult and juvenile Atlantic salmon was between 1.40 and 1.92 indicating that cortisone and not cortisol may be the principal corticosteroid in Atlantic salmon.
Plasma cortisol concentrations in Atlantic salmon, Salmo salar: episodic variations, diurnal change, and short term response to adrenocorticotrophic hormone.
Short term episodic peaks 1-2 hr in duration in plasma cortisol levels were observed in adult Atlantic salmon. These results support the concept that episodic secretion of corticosteroids may be a characteristic feature of the vertebrate adrenal/interrenal regulatory system and provide an explanation for the variability frequently observed in plasma cortisol concentrations in salmonids. Plasma cortisol levels also varied throughout the light-dark cycle and mean concentrations were higher during the night. High frequency variations in plasma cortisol levels (with a time scale of minutes rather than hours) were not observed. Porcine adrenocorticotrophic hormone (ACTH) and ACTH1-24 but not alpha-melanocyte-stimulating hormone (alpha-MSH) increased plasma cortisol levels 10 min after injection. The change in plasma cortisol levels after injection of 1 mU/kg porcine ACTH was of similar magnitude and duration as endogenous episodic variations. Plasma cortisol levels during episodic peaks, circadian changes, or after ACTH injection were less than the binding capacity of the "high" affinity protein binding system for cortisol. Hence, the unbound cortisol concentration is a linear function of the total cortisol concentration. Whereas episodic release of cortisol is indicated here, the physiological importance of this mode of hormone secretion is unclear. Plasma glucose levels were unaffected up to 2 hr after injection of ACTH and did not show close temporal correlation with endogenous episodic peaks in plasma cortisol.
Radioimmunoassay of cortisol in the adult Atlantic salmon, Salmo salar L.
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The presence of steroids in the sera of the Pacific hagfish, Eptatretus stouti, and the sea lamprey, Petromyzon marinus.
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Biochemical, histochemical, and ultrastructural analyses of presumed steroid-producing tissues in the sexually mature sea lamprey, Petromyzon marinus L.
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In vivo formation of steroids from [1,2,6,7-3H]-progesterone by the sea lamprey, Petromyzon marinus L.
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Steroid formation in the larval and parasitic adult sea lamprey, Petromyzon marinus L.
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Sublethal effect of DDT on osmotic and ionic regulation by the goldfish Carassius auratus.
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The distribution and tissue retention of mercury-203 in the goldfish (Carassius auratus).
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Identification and quantification of corticosteroids in the Atlantic halibut, Hippoglossus hippoglossus L.
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Steroids of a chondrostean: corticosteroids and testosterone in the plasma of the American Atlantic sturgeon, Acipenser oxyrhynchus Mitchill.
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