Geology topics

J. M. Mancera

Publications and source records attributed to J. M. Mancera.

5 recordsLinked to original sources

USGS2007

Role of prolactin, growth hormone, insulin-like growth factor I and cortisol in Teleost Osmoregulation

This chapter focuses on the endocrine mechanisms that control the overall capacity of the ion regulatory mechanisms in teleost fish, focusing on the osmoregulatory actions of prolactin (PRL), the growth hormone (GH)/insulin-like growth factor I (IGF-I) axis and cortisol. PRL has been shown to regulate several aspects of the ion regulatory mechanisms that are characteristic of freshwater (FW) fish. In FW, teleosts must counteract the passive loss of ions and gain of water by actively taking up ions, and removing excess water by excreting a dilute urine. Cortisol is the major corticosteroid produced by the interrenal tissue of teleost fish. This hormone has several established physiological roles related to osmoregulation, intermediary metabolism, growth, stress and immune function. In addition to the independent osmoregulatory actions of PRL, GH/IGF-I axis and cortisol, there is substantial evidence indicating the existence of synergy and antagonism of these hormones with one another.

Book chapter↗

USGS2000

Rapid activation of gill Na+, K+-ATPase the euryhaline teleost Fundulus heteroclitus

The rapid activation of gill Na + ,K + -ATPase was analyzed in the mummichog ( Fundulus heteroclitus ) and Atlantic salmon ( Salmo salar ) transferred from low salinity (0.1 ppt) to high salinity (25–35 ppt). In parr and presmolt, Salmo salar gill Na + ,K + -ATPase activity started to increase 3 days after transfer. Exposure of Fundulus heteroclitus to 35 ppt seawater (SW) induced a rise in gill Na + ,K + -ATPase activity 3 hr after transfer. After 12 hr, the values dropped to initial levels but showed a second significant increase 3 days after transfer. The absence of detergent in the enzyme assay resulted in lower values of gill Na + ,K + -ATPase, and the rapid increase after transfer to SW was not observed. Na + ,K + -ATPase activity of gill filaments in vitro for 3 hr increased proportionally to the osmolality of the culture medium (600 mosm/kg > 500 mosm/kg > 300 mosm/kg). Osmolality of 800 mosm/kg resulted in lower gill Na + ,K + -ATPase activity relative to 600 mosm/kg. Increasing medium osmolality to 600 mosm/kg with mannitol also increased gill Na + ,K + -ATPase. Cycloheximide inhibited the increase in gill Na + ,K + -ATPase activity observed in hyperosmotic medium in a dose-dependent manner (10 –4 M > 10 –5 M > 10 –6 M). Actinomycin D or bumetanide in the culture (doses of 10 –4 M, 10 –5 M, and 10 –6 M) did not affect gill Na + ,K + -ATPase. Injection of fish with actinomycin D prior to gill organ culture, however, prevented the increase in gill Na + ,K + -ATPase activity in hyperosmotic media. The results show a very rapid and transitory increase in gill Na + ,K + -ATPase activity in the first hours after the transfer of Fundulus heteroclitus to SW that is dependent on translational and transcriptional processes.

Journal of Experimental Zoology↗

USGS1999

Influence of cortisol, growth hormone, insulin-like growth factor I and 3,3′,5-triiodo-l-thyronine on hypoosmoregulatory ability in the euryhaline teleost Fundulus heteroclitus

The capacity of cortisol, ovine growth hormone (oGH), recombinant bovine insulin-like growth factor I (rbIGF-I) and 3,3′,5-triiodo-l-thyronine (T 3 ) to increase hypoosmoregulatory capacity in the euryhaline teleost Fundulus heteroclitus was examined. Fish acclimated to brackish water (BW, 10 ppt salinity) were injected with a single dose of hormone suspended in oil and transferred to seawater (SW, 35 ppt salinity) 10 days post-injection. Fish were sampled 24 h after transfer and plasma osmolality and gill Na + , K + -ATPase activity were examined. Transfer from BW to SW induced significantly increased plasma osmolality but not gill Na + , K + -ATPase activity. Cortisol (50 μg g −1 body weight) improved the ability to maintain plasma osmolality and to increase gill Na + , K + -ATPase activity. oGH (5 μg g −1 body weight) also increased hypoosmoregulatory ability and gill Na + , K + -ATPase activity. A cooperation between oGH and cortisol was observed in increasing hypoosmoregulatory ability but not in increasing gill Na + , K + -ATPase activity. rbIGF-I (0.5 μg g −1 body weight) alone was without effect in increasing salinity tolerance or gill Na + , K + -ATPase activity. rbIGF-I and oGH showed a positive interaction in increasing salinity tolerance, but not gill Na + , K + -ATPase activity. Treatment with T 3 (5 μg g −1 body weight) alone did not increase salinity tolerance or gill Na + , K + -ATPase activity, and there was no consistent significant interaction between cortisol and T 3 or between GH and T 3 . The results confirm the classical role of cortisol as a seawater-adapting hormone and indicate an interaction between cortisol and the GH/IGF-I axis during seawater acclimation of Fundulus heteroclitus.

Fish Physiology and Biochemistry↗

USGS1998

Evidence for growth hormone/insulin-like growth factor I axis regulation of seawater acclimation in the euryhaline teleost Fundulus heteroclitus

The ability of ovine growth hormone (oGH), recombinant bovine insulin-like growth factor I (rbIGF-I), recombinant human insulin-like growth factor II (rhIGF-II), and bovine insulin to increase hypoosmoregulatory capacity in the euryhaline teleost Fundulus heteroclitus was examined. Fish acclimated to brackish water (BW, 10 ppt salinity, 320 mOsm/kg H 2 O) were injected with a single dose of hormone and transferred to seawater (SW, 35 ppt salinity, 1120 mOsm/kg H 2 O) 2 days later. Fish were sampled 24 h after transfer and plasma osmolality, plasma glucose, and gill Na + ,K + -ATPase activity were examined. Transfer from BW to SW increased plasma osmolality and gill Na + ,K + -ATPase activity. Transfer from BW to BW had no effect on these parameters. rbIGF-I (0.05, 0.1, and 0.2 μg/g) improved the ability to maintain plasma osmolality and to increase gill Na + , K + -ATPase activity in a dose-dependent manner. oGH (0.5, 1, and 2 μg/g) also increased hypoosmoregulatory ability but only the higher doses (2 μg/g) significantly increased gill Na + ,K + -ATPase activity. oGH (1 μg/g) and rbIGF-I (0.1 μg/g) had a significantly greater effect on plasma osmolality and gill Na + ,K + -ATPase activity than either hormone alone. rhIGF-II (0.05, 0.1, and 0.2 μg/g) and bovine insulin (0.01 and 0.05 μg/g) were without effect. The results suggest a role of GH and insulin-like growth factor I (IGF-I) in seawater acclimation of F. heteroclitus. Based on these findings and previous studies, it is concluded that the capacity of the GH/IGF-I axis to increase hypoosmoregulatory ability may be a common feature of euryhalinity in teleosts.

Connecticut↗

USGS1998

Osmoregulatory actions of the GH/IGF axis in non-salmonid teleosts

Salmonid fishes provided the first findings on the influence of the growth hormone (GH)/insulin-like growth factor I (IGF-I) axis on osmoregulation in teleost fishes. Recent studies on non-salmonid species, however, indicate that this physiological action of the GH/IGF-I axis is not restricted to salmonids or anadromous fishes. GH-producing cells in the pituitary of fish acclimated to different salinities show different degrees of activation depending on the species studied. Plasma GH levels either increase or do not change after transfer of fish from freshwater to seawater. Treatment with GH or IGF-I increases salinity tolerance and/or increases gill Na + ,K + -ATPase activity of killifish ( Fundulus heteroclitus ), tilapia ( Oreochromis mossambicus and Oreochromis niloticus ) and striped bass ( Morone saxatilis ). As in salmonids, a positive interaction between GH and cortisol for improving hypoosmoregulatory capacity has been described in tilapia ( O . mossambicus ). Research on the osmoregulatory role of the GH/IGF-I axis is derived from a small number of teleost species. The study of more species with different osmoregulary patterns will be necessary to fully clarify the osmoregulatory role of GH/IGF-I axis in fish. The available data does suggest, however, that the influence of the GH/IGF-I axis on osmoregulation may be a common feature of euryhalinity in teleosts.

Comparative Biochemistry and Physiology, Part B: B↗