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M. F. O’Dea

Publications and source records attributed to M. F. O’Dea.

4 recordsLinked to original sources
USGS2008

Are we missing a mineralocorticoid in teleost fish? Effects of cortisol, deoxycorticosterone and aldosterone on osmoregulation, gill Na + ,K + -ATPase activity and isoform mRNA levels in Atlantic salmon

It has long been held that cortisol, acting through a single receptor, carries out both glucocorticoid and mineralocorticoid actions in teleost fish. The recent finding that fish express a gene with high sequence similarity to the mammalian mineralocorticoid receptor (MR) suggests the possibility that a hormone other than cortisol carries out some mineralocorticoid functions in fish. To test for this possibility, we examined the effect of in vivo cortisol, 11-deoxycorticosterone (DOC) and aldosterone on salinity tolerance, gill Na + ,K + -ATPase (NKA) activity and mRNA levels of NKA α1a and α1b in Atlantic salmon. Cortisol treatment for 6–14 days resulted in increased, physiological levels of cortisol, increased gill NKA activity and improved salinity tolerance (lower plasma chloride after a 24 h seawater challenge), whereas DOC and aldosterone had no effect on either NKA activity or salinity tolerance. NKA α1a and α1b mRNA levels, which increase in response to fresh water and seawater acclimation, respectively, were both upregulated by cortisol, whereas DOC and aldosterone were without effect. Cortisol, DOC and aldosterone had no effect on gill glucocorticoid receptor GR1, GR2 and MR mRNA levels, although there was some indication of possible upregulation of GR1 by cortisol (p = 0.07). The putative GR blocker RU486 inhibited cortisol-induced increases in salinity tolerance, NKA activity and NKA α1a and α1b transcription, whereas the putative MR blocker spironolactone had no effect. The results provide support that cortisol, and not DOC or aldosterone, is involved in regulating the mineralocorticoid functions of ion uptake and salt secretion in teleost fish.

General and Comparative Endocrinology↗
USGS2003

Endocrine and physiological changes in Atlantic salmon smolts following hatchery release

Physiological and endocrine changes during smolt development were examined in Atlantic salmon (Salmo salar) reared and released as part of a restoration program on the Connecticut River and its tributaries. Fish were reared in a cold water hatchery in Pittsford, VT and released into the Farmington River, CT (a major tributary of the Connecticut River) or into 'imprint ponds' fed by the Farmington River. Smelts were recaptured 10-20 days after their release at a smolt bypass facility 16 km downstream of their release site. Fish sampled at the hatchery from January to May had only moderate smolt development based on salinity tolerance, gill Na+,K+-ATPase activity and hormone profiles. In contrast, smolts released into the river or imprint ponds had higher salinity tolerance, gill Na+,K+-ATPase activity, plasma growth hormone, insulin-like growth factor I (IGF-I) and thyroxine than smolts that remained in the hatchery. These physiological and endocrine changes were nearly identical to those of smolts that had been released into the river 2 years earlier as fry and were captured as active migrants at the same bypass facility (stream-reared smolts). The stomach contents as a percent of body weight (primarily aquatic insects) varied greatly among individuals and were greater in hatchery-reared fish than stream-reared smolts. Results from the rearing of hatchery fish at temperatures similar to that of the Farmington River indicate that some of the physiological changes may be due to increased temperature after release, though other factors may also be involved. The results indicate that substantial physiological smolt development can occur after hatchery release, coincident with downstream migration. ?? 2003 Published by Elsevier Science B.V.

Aquaculture↗
USGS1998

Repeated acute stress reduces growth rate of Atlantic salmon parr and alters plasma levels of growth hormone, insulin-like growth factor I and cortisol

Atlantic salmon ( Salmo salar ) parr were subjected to acute handling stresses and growth-monitored for at least 30 days. In fish stressed twice daily, growth rate in weight was 61% lower than controls after 11 days (1.00 vs. 2.57% day −1 ) and over a 30 day period it was 50% lower than controls (1.53 vs. 3.07% day −1 ). In fish stressed once daily, growth rate was 18% lower than controls after 10 days (2.17 vs. 2.63% day −1 ) and over a 30-day period it was 34% lower than controls (1.71 vs. 2.59% day −1 ). In fish stressed once daily, food consumption was reduced by 62% and 37% after 17 and 37 days, respectively. At the end of 40 days of acute stress once daily, control and stressed fish were sampled 1 h prior to, 3 and 7 h after a stress event. Plasma growth hormone levels were significantly higher in the stressed group than in the controls prior to and 7 h after stress. Plasma insulin-like growth factor I (IGF-I) levels were higher in the stressed group only 3 and 7 h after stress. Plasma cortisol levels were lower in the stressed group prior to and 3 h after stress. The results indicate that acute stressors decrease growth of Atlantic salmon parr, with increasing frequency of stress having a more rapid and greater effect.

Aquaculture↗