Biomedical subjects

Kenneth B Davis

Publications and source records attributed to Kenneth B Davis.

3 recordsLinked to original sources

PubMed2006

The effect of temperature, stress, and cortisol on plasma IGF-I and IGFBPs in sunshine bass.

The mechanisms through which stress and cortisol regulate insulin like growth factor-I (IGF-I) and insulin like growth factor binding proteins (IGFBPs) were studied in sunshine bass, by measuring plasma IGF-I and IGFBPs in fish maintained at 5, 10, 15, 20, 25, or 30 degrees C, fish subjected to an acute 15 min confinement stress at 25 and 30 degrees C, and fish fed 100 mg cortisol/kg feed. Plasma IGF-I concentrations were higher at 25 and 30 degrees C than at 20 degrees C and below. A 15 min confinement stress resulted in a decrease in IGF-I 2h post-confinement. Plasma concentrations of IGFBP with molecular weights of 24, 28, and 33 kDa were similar for fish acclimated to different temperatures, except for 5 degrees C where a 33-kDa IGFBP was significantly reduced. After a 15 min low-water stress at 25 degrees C, a 33-kDa IGFBP was reduced and IGFBPs with molecular weights of 24 and 28 kDa were increased at 2 and 6h, respectively. A 15 min low-water stress at 30 degrees C, resulted in no change in levels of a 33-kDa IGFBP over the 6-h recovery period. However, levels of a 24- and 28-kDa IGFBP were significantly increased at 2 and 6h, respectively. A single feeding with 100 mg cortisol/kg feed increased plasma cortisol but did affect plasma concentrations of IGF-I or any of the three IGFBPs. Acute stress appears to result in a decrease in IGF-I, but the mechanism of the decrease does not appear to be caused by cortisol released during the stress.

Acclimatization↗

PubMed2006

Rates of cortisol increase and decrease in channel catfish and sunshine bass exposed to an acute confinement stressor.

Channel catfish and sunshine bass were exposed to a low-water stress event and allowed to recover in fresh water or a solution of metomidate (dl-1-(1-phenylethyl)-5-(metoxycarbonyl) imidazole hydrochloride), which inhibits the synthesis of cortisol. Change in time of plasma cortisol was used as an index of cortisol secretion and clearance. Plasma cortisol and glucose increased during the exposure to low-water stress in both fish, but the changes of both plasma components were more dramatic in sunshine bass. Exposure to metomidate during recovery resulted in a short-term increase in plasma glucose but differences between controls and metomidate-exposed fish were relatively minor thereafter. Cortisol began to decrease in catfish immediately after the removal of the stress but continued to increase for 15 min in sunshine bass recovering in fresh water and for 5 min in bass recovering in metomidate. Catfish recovering in fresh water had a cortisol elimination rate of -1.28 ng/mL/min compared with -2.45 ng/mL/min for fish recovering in metomidate (P>0.05) while sunshine bass recovering in fresh water had an elimination rate of -6.96 ng/mL/min compared with -4.50 ng/mL/min for fish recovering in metomidate (P>0.05). These data indicate that the rapid decrease of plasma cortisol after removal of the stressor is due to an almost immediate decrease of secretion, tissue uptake and a rapid renal loss due to the absence of a plasma binding protein.

Animals↗

PubMed2004

Temperature affects physiological stress responses to acute confinement in sunshine bass (Morone chrysops x Morone saxatilis).

Sunshine bass (Morone chrysopsxMorone saxatilis) were subjected to a 15-min low-water confinement stressor at temperatures ranging from 5 to 30 degrees C. Physiological responses were evaluated by measuring hematocrit, and plasma chloride, glucose and cortisol. Fish acclimated to 30 degrees C had initial glucose concentrations of 3.13 mM (564 mg/L) which were significantly lower than in fish acclimated to 5 and 10 degrees C (4.32 and 4.82 mM or 779 and 868 mg/l, respectively). Fish survived the conditions imposed at every temperature except 30 degrees C, where 15 out of 42 fish died during the stress and recovery protocol. The general pattern was an initial increase in hematocrit, followed by a delayed decrease in hematocrit and chloride, and an increase in plasma glucose and cortisol. In general, fish stressed at temperatures below 20 degrees C had lower and more delayed changes in plasma glucose and cortisol than fish tested at 20, 25 and 30 degrees C. Initial cortisol concentrations were 65 ng/ml and increased to above 200 ng/ml in fish held at 20 degrees C and above. At the higher temperatures, glucose concentrations were twice the initial concentration after stress and cortisol changes were four to five times the initial concentration after the stress. Quantitative responses for glucose and cortisol were moderate and recovery rapid in fish stressed at 10 and 15 degrees C; therefore, this range of water temperature is recommended when handling sunshine bass.

Animals↗