Search Results
Search for other papers by B. E. ELEFTHERIOU in
Google Scholar
PubMed
Search for other papers by R. L. CHURCH in
Google Scholar
PubMed
Aggression, in animals, can be produced by a variety of methods ranging from simple isolation-frustration to more complex behavioural manipulations. For the past 5 yr. aggression and defeat have been studied in this laboratory utilizing the training method of Scott (1946). Thus, we have studied specifically the effects of combative behaviour for measured periods of time, on aggressive mice and on defeated mice and the mode of endocrine adaptation.
This investigation was conducted to determine the levels of the hypothalamic luteinizing hormone-releasing factor (LH-RF) in C57BL/6J mice that were trained to be aggressive and in mice defeated repeatedly by the aggressive mice. The experimental design and treatment were identical to those described previously (Eleftheriou & Church, 1967). Groups of 30 male mice each were killed at each of the following periods: 0 (control), 1, 2, 4, 8 and 16 days after daily exposure for two 5 min. periods to trained
Search for other papers by C. H. G. IRVINE in
Google Scholar
PubMed
SUMMARY
Studies on the rate of thyroxine secretion (t.s.r.) in the horse, as measured from degradation of labelled thyroxine, are reported. In the resting horse, the mean t.s.r. was 0·49 mg./453·6 kg. (1000 lb.), with a mean value of PBI of 1·80 μ./100 ml., volume distribution of 60 1., and a half-life of 2·31 days. Partly and fully trained horses showed increases of 38% and 65% in t.s.r. associated with lower values for PBI and a greatly decreased half-life. During adaptation to cold, there was an increase of 66% in t.s.r. In horses adapted to cold, t.s.r. was increased by 17%. In pregnancy, the mean increase in t.s.r. of 18% was not statistically significant.
Search for other papers by A. D. CARE in
Google Scholar
PubMed
Search for other papers by L. L. ANDERSON in
Google Scholar
PubMed
Search for other papers by C. W. COOPER in
Google Scholar
PubMed
Search for other papers by S. L. OXENREIDER in
Google Scholar
PubMed
Search for other papers by M. PHILLIPPO in
Google Scholar
PubMed
The surgically isolated thyroid gland in the pig has been shown to secrete thyrocalcitonin (TC) when perfused with an artificial medium, hypercalcaemic with respect to ionized calcium concentration (Care & Gitelman, 1968). Therefore, hypophysial hormones must not be essential for the release of at least some TC stimulated by hypercalcaemia. The present work was designed to evaluate quantitatively the effect of previous hypophysectomy on the rate of secretion of TC in response to a given degree of hypercalcaemia.
In preliminary experiments, a pair of litter-mate male piglets, 19 days old, was selected and one was hypophysectomized by an adaptation of the method of Liggins, Kennedy & Holm (1967). At autopsy, hypophysectomy was confirmed by visual examination of the sella turcica. Nine days after operation, the thyroid was isolated in situ and perfused with hypercalcaemic blood (6·7 m-equiv.Ca/1.) for 2 hr. according to the method of Care (1965). The thyroid of
Search for other papers by W. N. HOLMES in
Google Scholar
PubMed
Search for other papers by D. G. BUTLER in
Google Scholar
PubMed
SUMMARY
The effects were studied of cortisol, corticosterone and aldosterone on the concentrations of sodium and potassium in muscle and blood plasma and on water content of muscle in the fresh-water rainbow trout (Salmo gairdneri).
These steroids appeared to cause a loss in plasma sodium throughout the 96 hr. experimental period. An initial rise in muscle sodium was observed during the first 24 hr. after commencement of the treatments. The subsequent decline in muscle sodium was interrupted by a transient rise followed by a continuing decline.
The effect of these hormones on the potassium concentrations in plasma was variable, although there was a significant rise in the potassium concentration in muscle during the period of decline in sodium concentration.
The significance of these results in relation to the possible enhanced adrenocortical activity of the trout during adaptation to a marine environment is discussed.
Search for other papers by D. M. ENSOR in
Google Scholar
PubMed
Search for other papers by J. G. PHILLIPS in
Google Scholar
PubMed
SUMMARY
The pituitary prolactin levels were measured in the domestic duck (Anas platyrhynchos) and in juvenile gulls from a mixed population of herring and lesser black-backed gulls. In the domestic duck the pituitary prolactin levels increased on the 2nd and 3rd days of maintenance on 0·3 m-NaCl, but by the 5th day they had fallen appreciably below the control levels. Maintenance of gulls with 0·3 m-NaCl produced no change in pituitary prolactin levels after 5 days, but a marked fall in prolaction levels when the birds were maintained on 0·7 m-NaCl for 5 days. This difference in response between the two species may be related to their degree of adaptation to a marine environment.
Search for other papers by RJ Arends in
Google Scholar
PubMed
Search for other papers by J Rotllant in
Google Scholar
PubMed
Search for other papers by Metz JR in
Google Scholar
PubMed
Search for other papers by JM Mancera in
Google Scholar
PubMed
Search for other papers by SE Wendelaar Bonga in
Google Scholar
PubMed
Search for other papers by G Flik in
Google Scholar
PubMed
MSH is a pituitary hormone derived by post-translational processing from POMC and involved in stress and background adaptation. N-terminal acetylation of MSH to monoacetyl alpha-MSH or diacetyl alpha-MSH increases the bioactivity of the peptide. The aim of this study was to characterize alpha-MSH acetylation in the sea bream (Sparus aurata L.) pituitary gland in response to the stressors air exposure and confinement, as well as in fish adapted for 15 days to a white, gray or black background. Pituitary homogenates were purified by reversed-phase HPLC (RP-HPLC). The alpha-MSH content of fractions was measured by RIA. Immunoreactive RP-HPLC fractions were further analyzed by electrospray mass spectrometry and the peptide sequence determined as SYSMEHFRWGKPV-NH2. In the pituitary gland of sea bream, des-, mono- and diacetyl alpha-MSH were identified. Then plasma alpha-MSH levels were measured in sea bream adapted to different backgrounds. Surprisingly, we found the highest plasma alpha-MSH levels in white-adapted as compared with black-adapted sea bream with intermediate values for gray-adapted fish. This observation is in contrast with results that have been obtained in eel, trout or terrestrial vertebrates. Next, des-, mono- and diacetyl alpha-MSH forms were measured in homogenates of the pituitary gland and in plasma of sea bream exposed to air, to confinement, or to different backgrounds. Monoacetyl alpha-MSH was the predominant form in all control and experimental groups. The lowest content of monoacetyl alpha-MSH relative to des- and diacetyl alpha-MSH was found in white-adapted fish. Levels of des- and diacetyl alpha-MSH forms were similar under all conditions. We observed that monoacetyl alpha-MSH is the most abundant isoform in the pituitary gland after background adaptation, confinement and air exposure, in sea bream. These data indicate that the physiologically most potent isoform of alpha-MSH may vary from species to species.
Search for other papers by F Rivero in
Google Scholar
PubMed
Search for other papers by L Goya in
Google Scholar
PubMed
Search for other papers by C Aláez in
Google Scholar
PubMed
Search for other papers by A M Pascual-Leone in
Google Scholar
PubMed
Abstract
The purpose of the present study was to investigate the influence of nutrients and insulin on IGFs and their binding proteins (IGFBPs) during the fetal and neonatal periods of three rat populations: (a) rats undernourished by a 35% reduction in the diet from day 16 of gestation, (b) streptozotocin-induced diabetic rats from the same day, or 4 days after birth, and (c) control rats. Fetuses from the diabetic population showed a decrease in insulinemia at 19 and 21 days, along with an increase in glycemia at all stages. Neither glycemia nor insulinemia changed in the fetuses of undernourished mothers, but body weight was decreased at birth. Serum IGF-II decreased at 18 and 19 days of gestation in fetuses from undernourished mothers, and increased at 18, 19 and 21 days in fetuses from diabetic mothers. Serum IGFBPs of low molecular weight (IGFBP-1 and IGFBP-2) increased in the three fetal populations studied, although no changes in serum IGFBPs were found from the effect of undernutrition or diabetes, but fetal liver IGFBP-1 mRNA expression was found to be decreased in undernourished and diabetic animals as compared with controls. In neonatal rats, body weight, insulinemia and serum GH decreased in both undernourished and diabetic rats vs controls, while glycemia decreased in the undernourished and increased in the diabetic group. Serum IGF-II decreased only in diabetic rats and serum IGF-I decreased in both groups. The neonatal serum 30 kDa complex (IGFBP-1 and -2) also increased in undernutrition and diabetes parallel to the expression of mRNA. But, taken together, the changes in IGFBP peptide levels and liver mRNA expression strongly suggest that the 30 kDa complex seems to be composed mostly of IGFBP-1 in the diabetic group and of both IGFBP-1 and -2 in the undernourished animals. The studies of liver mRNA expression of IGFs and IGFBPs confirm the different metabolic control mechanism for the availability of IGFs by the IGFBPs, depending on the animal's maturity. The different adaptation shown by the diabetic neonatal population was confirmed by correlation studies between body weight, glycemia, insulinemia, IGF-I and IGFBPs. The different mechanism of adaptation in diabetic vs undernourished rats seems to be probably due to the decisive role played by hyperglycemia in the diabetic population, and also shows the crucial influence of nutritional status on IGFs and IGFBPs.
Journal of Endocrinology (1995) 145, 427–440
Search for other papers by T Okabe in
Google Scholar
PubMed
Search for other papers by R Takayanagi in
Google Scholar
PubMed
Search for other papers by M Adachi in
Google Scholar
PubMed
Search for other papers by K Imasaki in
Google Scholar
PubMed
Search for other papers by H Nawata in
Google Scholar
PubMed
Nur77 is a member of the steroid receptor superfamily and is known to be expressed in animals under stress. We studied the role of nur77 in the regulation of the hypothalamic-pituitary-adrenal (HPA) axis during the stress response using a murine pituitary corticotrope cell line, AtT-20. Corticotropin-releasing hormone (CRH), a stress mediator in the HPA axis, induced the expression of nur77 transiently in AtT-20 cells. Gel shift assay showed that nur77 bound to negative glucocorticoid responsive element (nGRE) in the promoter of the human proopiomelanocortin (POMC) gene and the formation of the nur77-nGRE complex increased after treatment of the cells with CRH. Negative GRE is known to be necessary for the negative regulation by glucocorticoid of the POMC gene expression. In stable transformants of AtT-20 cells expressing a human homolog of nur77, NAK-1, at a high level, glucocorticoid-mediated inhibition of both POMC mRNA induction and ACTH secretion was significantly lower than that in the NAK-1-non-expressing cells (P < 0.001). These results strongly suggest that nur77 antagonizes the negative feedback effect of glucocorticoid on the synthesis and secretion of ACTH in pituitary corticotropes. This suggests that nur77 plays an important role in the pituitary gland in the biological adaptation to overcome stress.
Search for other papers by M. M. Vijayan in
Google Scholar
PubMed
Search for other papers by J. F. Leatherland in
Google Scholar
PubMed
ABSTRACT
Preparations of head kidney tissue (containing the interrenal cells) from brook charr (Salvelinusfontinalis) which had been held at a high stocking density (120 kg/m3) showed a higher spontaneous secretion rate of cortisol than those from brook charr held at a low stocking density (30 kg/m3). Challenges with ACTH at 5 and 500 mU/ml stimulated the secretion of cortisol in interrenal preparations taken from fish stocked at low density but the high ACTH challenge resulted in a lower cortisol secretion rate. The ACTH-stimulated cortisol secretion by the interrenal cells of brook charr stocked at high density was lower than that of the low density group.
There was no difference in the metabolic clearance rate of cortisol in brook charr held at the two stocking densities. The clearance rate of [3H]cortisol from the tissues suggested that in fish held at high stocking density cortisol is rapidly taken up by the liver and subsequently catabolized. Cortisol uptake by the liver in fish held at high stocking density may be an adaptation, which results in altered hepatic metabolic activity.
Journal of Endocrinology (1990) 124, 311–318
Search for other papers by D. J. Nichols in
Google Scholar
PubMed
Search for other papers by M. Weisbart in
Google Scholar
PubMed
Search for other papers by J. Quinn in
Google Scholar
PubMed
ABSTRACT
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 ∼ 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.
J. Endocr. (1985) 107, 57–69
