Showing papers in "General and Comparative Endocrinology in 1991"

TL;DR: In this article, male tree lizards (Urosaurus ornatus) were subjected to two forms of stress: acute stress and chronic stress and the response to the acute stress was much greater for both hormones than to the chronic stress, although in both cases testosterone levels changed less in response to stress than corticosterone levels.

TL;DR: The coincident increases in cortisol and thyroid hormones support previous results of a synergistic action of both hormones during metamorphosis in the flounder, and the significance of the "selective" clearance of the three hormones from eggs remains unclear.

TL;DR: The acute stress of handling followed by confinement for a period of 1 or 24 hr caused a typical stress response in rainbow trout (elevation of plasma ACTH and cortisol) and a significant reduction in the concentration of circulating growth hormone.

TL;DR: The effects of two fully characterized, structurally distinct gonadotropins (GtH I and GtH II) on the uptake of vitellogenin (VTG) into oocytes of the rainbow trout, Oncorhynchus mykiss, were investigated both in vivo and in vitro as mentioned in this paper.

TL;DR: Results indicate that plasma glucose levels are maintained in salmon during fasting and that fasting-induced hyperlipidemia is mediated by lipolytic enzyme activity.

TL;DR: It is suggested that a major role of growth hormone during starvation is to aid in the mobilisation of fatty acids and glycerol from adipose stores, and a strong negative correlation was observed between the plasma growth hormone level and the coefficient of condition of the fish.

TL;DR: It is suggested that excess JH may affect adult development of imaginal structures if present at the onset of postembryonic cell proliferation of the imaginal discs or histoblasts, and commitment for adult differentiation must occur early during this proliferative phase.

TL;DR: These studies suggest either that exogenous estrogen is capable of coordinating cortical/medullary development in the gonad so that intersexes are prevented or that estrogen acts "upstream" of the developmental processes responsible for coordinating gonadal development.

TL;DR: The affinities of GR were consistently lower in all tissues from chronically stressed fish than in tissues from controls; however, numbers of GR increased in whole leukocytes and decreased in gill, suggesting heterogeneity of response to stress.

TL;DR: It is suggested that 11KT plays a key role in instigating natural sex and color change, but that once sex change is complete, 11KT is not necessary for spermatogenesis or spawning behavior.

TL;DR: Cortisol was administered to brook charr (Salvelinus fontinalis) in the form of slow-release intraperitoneal implants to investigate the effect of chronic cortisol stimulation (up to 60 days) on various aspects of intermediary metabolism, and to determine whether such cortisol-induced changes were comparable to those seen in chronically fasted charr as mentioned in this paper.

TL;DR: The results demonstrate that the release of GnRH from goldfish P-AH slices and pituitary fragments in vitro in response to various secretagogues and monoamines can be studied using a static incubation system.

TL;DR: It is demonstrated that 5- HT has a stimulatory effect on gonadotropin secretion, probably through a 5-HT2 receptor type, and an inhibitory effect on growth hormone through an unidentified receptor type.

TL;DR: Pelissero et al. as mentioned in this paper examined estrogenic effects of dietary soya bean meal and of commercial trout diet on vitellogenesis in sturgeon and found that the SC diet had a very pronounced effect on the plasma viteLLogenin level, which reached 6 mg vitllogenin/ml.

TL;DR: A neuropeptide which stimulates the motility of the cockroach hindgut has been isolated from an extract of 9000 brain-corpora cardiaca-Corpora allata-subesophageal ganglion complexes of Locusta migratoria and synthesized and shown to have chromatographic and biological properties identical to those of the native material.

TL;DR: The present work outlines the presence of specific binding for chinook salmon growth hormone (sGH) in different tissue preparations of rainbow trout, which was saturable, of high affinity, and very specific, properties which are in agreement with the characteristics of hormonal receptors.

TL;DR: The results suggest that the developmental changes in the muscular tissue of metamorphosing flounder are regulated by thyroid hormone.

TL;DR: It is concluded that oGH significantly enhances whole-body growth rates as a result of the stimulatory effect on protein synthesis rates with little effect onprotein degradation.

TL;DR: This study describes the development of a highly specific and very sensitive radioimmunoassay for salmonid growth hormone, which was able to inhibit growth when injected into rainbow trout (Oncorhynchus mykiss) and observed a strong inhibiting effect of SRIF and a stimulatory effect of hGRF.

TL;DR: Results indicate a function of 17 alpha, 20 beta-P in male reproductive function, probably spermiation, and a relationship of Leydig cell development and high levels of 11-KT production to the terminal male phenotype, perhaps reproductive or aggressive behavior, rather than to male gametogenesis per se.

TL;DR: The appearance in these ancient bony fish of a mammalian-like form of GnRH, which has not been found in the jawless or cartilaginous fish studied to date, suggests that mGnRH arose in a common phylogenetic ancestor of the bonyFish and tetrapods.

TL;DR: Results indicate that melatonin secretion from the superfused goldfish pineal gland is directly photosensitive and that the goldfish Pineal gland harbors a circadian oscillator which generatesmelatonin secretion rhythms.

TL;DR: This study provides the first characterization of pituitary PRL mRNA and its comparison with plasma and pituitARY PRL levels during the avian reproductive cycle and appears to be related to the changes in PRL-releasing activity observed at each of the reproductive stages.

TL;DR: The ability of cortisol to increase gill Na+,K(+)-ATPase activity was examined in several salmonid species during development and found it had a limited but significant effect in chinook salmon fry, and had no effect in coho and Atlantic salmon fry.

TL;DR: Juvenile coho salmon adapted to fresh water or seawater were either acutely handled or continuously stressed by severe confinement, showing a rapid, more transient increase in plasma cortisol titer with no apparent effect on prolactin.

TL;DR: Hemolymph ecdysteroid (Ecd) titers were measured using radioimmunoassay (RIA) during the molt cycle of the American lobster, Homarus americanus.

TL;DR: It is concluded that chronic physiologic cortisol treatment enhances plasma T3 clearance without change in hepatic T4 to T3 conversion, resulting in a decline in T3 concentration in both plasma and tissue (muscle) compartments.

TL;DR: An effect of prolactin on chloride cell size is demonstrated and a morphological correlate for decreased secretory activity of chloride cells following prolactIn injections is provided.

TL;DR: The results suggest that the elevated growth hormone concentration in mature male trout was a consequence not of reproduction per se, but of the loss of condition that accompanied spawning, and this hypothesis was supported by the results from the females.

TL;DR: The effects of the neuropeptide Y (NPY), alone or in combination with a gonadotropin-releasing hormone analogue, D-Ala6-desGly10-Pro9-Net LHRH (LHRHa), have been studied on the in vivo secretion of the maturational gonadotropic hormone analogue in the rainbow trout Oncorhynchus mykiss and the common carp Cyprinus carpio.