Showing papers in "General and Comparative Endocrinology in 1996"

TL;DR: A number of hypotheses are suggested that could explain the modification in the phenotype of the juvenile male living in Lake Apopka, which includes a smaller penis size, lower plasma androgen concentrations, and lack of responsiveness of the penis to the plasma androgens present.

TL;DR: Although IGF-I and cortisol implants had no significant effect after 7 days, in combination they significantly increased gill Na+, K(+)-ATPase activity of Atlantic salmon and together act in synergy.

TL;DR: It is concluded that analyses of fecal progestins can provide an effective, noninvasive means of characterizing ovarian activity in free-ranging African elephants.

TL;DR: The discovery and localization of two mRNAs encoding distinct GnRH forms in an advanced mammal suggest that other mammals may also have a second GnRH gene with expression localized in the midbrain, and suggests an important, conserved nongonadotropic role.

TL;DR: Kasten et al. as discussed by the authors reported the cDNA sequences and expression patterns for two distinct genes encoding the hypotha- lamic and mesencephalic GnRH forms in the brain of a placental mammal, the tree shrew (Tupaia glis belangeri).

TL;DR: It is suggested that gonadal steroids are involved in the regulation of both baseline and stress-induced activity of the pituitary-interrenal axis in salmonid fish.

TL;DR: The presence of Prog and estradiol in these cultures suggest that Preg and DHEA can potentially serve as substrates for the ultimate formation of active sex steroids in the songbird telencephalon.

TL;DR: Results show that the three types of steroids are released into the water by three different routes: free steroids, gills; sulfated steroids, urine; and glucuronidated steroids, bile.

TL;DR: Acute increases in glucocorticoids lower thyroidal T4 secretion in both pre- and posthatch chickens but have clearly different effects on peripheral thyroid hormone deiodination and hence on circulating T3 at both developmental stages.

TL;DR: Although cloacal temperatures were significantly higher in summer samples, corticosterone concentrations of large turtles captured during summer did not differ between seasons until 1 hr after capture, and it is possible that the lower cortic testosterone response of large Turtles captured duringSummer may be associated with reproductive condition.

TL;DR: Although reproductive development appears to be resistant to naturally relevant temperature extremes in both sexes, low environmental temperature impaired preparations for migration in females but not males.

TL;DR: Results suggest that expression of P450arom mRNA occurring in the genetic female gonad around Day 6 is associated, at least in a part, with sexual differentiation toward femaleness by increasing E2 production which may promote cellular proliferation of the left gonad.

TL;DR: Results suggest that melatonin can influence GtH II secretion by acting at the level of POAH and also directly at the pituitary to stimulate GTH II release.

TL;DR: The proposed hypothesis is that the stability in primary structure in bony vertebrates is due to selective pressure, and in Chondrichthyes the occurrence of an urea-based osmoregulation has relieved the hormones from the control of ionic homeostasis.

TL;DR: It is demonstrated that two forms of GnRH precursor (sGnRH and cGn RH-II) mRNA are expressed in goldfish brain tissue and that the sGnrh transcript and a low level of cGNRH-II transcript are also expressed in the goldfish ovary.

TL;DR: Results suggest that expression of P450(arom) mRNA and estrogen plays an important role in sex differentiation of the female gonad of the chicken.

TL;DR: Tropical, aseasonal, opportunistic breeding frogs appeared to have lower androgen levels, generally, than confamilial temperate, seasonal breeders, consistent with the hypothesis that maintenance of high plasma testosterone levels is energetically expensive.

TL;DR: Examples are provided to support the hypothesis that some neuropeptid and polypeptide precursors and some high molecular weight polyPEptide hormones can be used as data sets for resolving deep divergences among vertebrate taxa.

TL;DR: The importance of AA and PGE2 in the regulation of ovarian steroidogenesis in the goldfish is underscored as both transcription and translation are involved.

TL;DR: Full-length cDNA sequences encoding the β-subunits of the gonadotropins GtHI and GtHII were isolated, cloned, and sequenced from a single gilthead seabream pituitary using RACE PCR.

TL;DR: Given that the brain-pituitary-gonadal axis seems to be intact during the process of sexual differentiation and the fluctuations of steroid levels during this process, sex steroids may play the driving role for sexual differentiation of rainbow trout.

TL;DR: It is suggested that GH, via its own receptor, promotes more satellite cells to proliferate by inhibiting their differentiation, leading to the addition of more nuclei to the growing muscle.

TL;DR: The results suggest that the relationship between steroid hormones and spawning behavior in male salmonids is likely more complex than suggested by experiments conducted solely on laboratory-held rainbow trout.

TL;DR: It is found that specific growth rates (SGR) were positively and significantly related to feeding levels and the involvement of T3 in tilapia growth and probably in the differential growth between males and females.

TL;DR: Both testosterone and estradiol may act on the synthesis and release of GnRH, with testosterone having a greater influence on the control of gonadotropin secretion, especially at the end of the cycle.

TL;DR: The proposed TSH-mediated effect of CRF on thyroid function was further confirmed in two in vitro experiments in which oCRF did not directly influence the thyroidal T4 secretion but, when applied to pituitaries, clearly increased the alpha-subunit release.

TL;DR: It is concluded that GH acts directly on the liver to potentiate E2 induction of eel hepatic Vg synthesis, and appears to be time- and dose-dependent and modulated as a function of hormonal status (E2 priming) of the eel.

TL;DR: It is suggested that photoperiodic modulation of PRL secretion in the turkey is influenced by hypothalamic VIP neuronal system.

TL;DR: To design a homologous bioassay for the molt-inhibiting hormone and the crustacean hyperglycemic hormone of the shrimp Penaeus vannamei, the effect of sinus gland homogenate (SGh), in vitro, on ecdysteroid production by Y-organs (YOs), and the effect

TL;DR: It is demonstrated that an IGFBP of low molecular weight is increased with growth inhibition in the fasting striped bass, suggesting that a teleost fish counterpart to mammalian IGFBP-1 may exist.