Janice L. Bolaffi

Thyrotropin-releasing hormone (TRH): Immunohistochemical distribution in tadpole and frog brain ☆

The anatomical localization of immunoreactive TRH (IR-TRH) was demonstrated by the peroxidase-antiperoxidase technique in the brain and pituitary gland of larval and adult Rana catesbeiana. In the adult frog main sites of IR-TRH are perikarya and neuronal fibers in the preoptic and infundibular nuclei of the hypothalamus and in the amygdala and diagonal band of Broca of the telencephalon. In addition, TRH-positive neuronal fibers and endings were found in the septum, pallium, and brain stem as well as in the preoptico-hypophyseal tract, the external zone of the median eminence (which matures during late larval stages), and the pars nervosa; fibers were less extensive in the pars intermedia, and were absent from the pars distalis. In early larval stages, the magnocellular nucleus of the posterior preoptic area is the main site of immunoreactive perikarya. During late stages the extensive adult pattern of distribution of IR-TRH becomes established. The study represents the first immunohistochemical demonstration of IR-TRH in larval anurans, and serves as a basis for clarification of the neuroendocrine regulation of metamorphosis.

Presence of immunoreactive β-endorphin and enkephalin-like material in the retina and other tissues of the frog, Rana pipiens

Abstract Substantial quantities of immunoreactive (IR)-β-endorphin have been demonstrated in the retina of Rana pipiens in amounts not affected by exposure to constant light or constant darkness. IR-β-endorphin has also been measured in blood, pituitary, hypothalamus, and extrahypothalamic brain of this species, while lower concentrations of IR-Met-enkephalin and IR-Leu-enkephalin have also been found in these tissues. The significance of the widespread distribution of opioid peptide-like material in amphibian tissues remains to be determined.

Induced metamorphosis in Ambystoma mexicanum: Lack of effect of triiodothyronine on tissue or blood levels of thyrotropin-releasing hormone (TRH)

Abstract In order to test the hypothesis that thyroid hormone affects thyrotropin-releasing hormone (TRH) during metamorphosis, the latter was induced in the facultative neotenic amphibian, Ambystoma mexicanum , by injection of triiodothyronine (T 3 ). Plasma levels of T 3 were readily detectable up to 2 weeks after injection. Immunoreactive TRH was found in large quantities in the hypothalamus and brain, in much smaller amounts in the pituitary, pineal, and skin, and was only occasionally detectable in blood. No changes in tissue or blood levels of TRH were found during metamorphosis after treatment with T 3 , suggesting that any hypothalamic action of thyroid hormone during metamorphosis does not involve TRH in this species.

Immunohistochemical localization of thyrotropin-releasing hormone (TRH) in skin of Rana pipiens

SummaryUsing immunofluorescent techniques thyrotropin releasing hormone (TRH) is demonstrated in skin of Rana pipiens and R. catesbeiana. The immunofluorescent-TRH is localized in all cell layers of the epidermis and in the epithelium lining the various cutaneous glands, but not in the dermal layer.

TRH Stimulation of in vivo GH Release in the Domestic Fowl

Thyrotropin-releasing hormone (TRH) stimulated in vivo growth hormone (GH) release in conscious and anesthetized young domestic fowl. The administration of the presumed metabolites of TRH, deamido-TRH (TRH-OH) and histidyl-proline diketopiperazine (HPD), was followed by small but significant (p less than 0.05) increases in the plasma concentrations of GH in both conscious and anesthetized chicks. However, the ability of TRH-OH or HPD to stimulate GH secretion was less than that observed with a 100-fold lower dose of TRH. The administration of either TRH-OH or HPD with TRH increased the GH response over that observed with TRH alone. The ability of chicken plasma to degrade exogenous TRH in vitro was determined by measuring immunoreactive TRH (IR-TRH) content and by assessing the ability of the incubated samples to increase the plasma concentration of GH when administered to young fowl. The in vitro half-life of TRH was estimated to be 9.8 (by immunoassay) and 9.6 (by a biological index) min for plasma from adult male chickens and 23.9 (by immunoassay) and 20.2 (by biological index) min for plasma from 6-week-old chicks. This difference in degradation may account, at least in part, for the observed age-related decrease in the plasma concentration of GH in birds and for the diminished GH responsiveness of adult birds to exogenous TRH.

Identification of 11-ketotestosterone, 11β-hydroxytestosterone, and testosterone in plasma of Necturus maculosus (Rafinesque)

Abstract Both 11β-hydroxytestosterone and 11-ketotestosterone are present in significant amounts in the plasma of male Necturus maculosus and are not detectable in female plasma. Both ovine FSH and LH decrease male plasma levels of these 11-oxygenated androgens.

Changes in thyrotropin-releasing hormone levels in alligator stomach during fasting ☆

Stomach tissue of the American alligator, Alligator mississippiensis, contains substantial levels of thyrotropin-releasing hormone (TRH) which behaves identically to the synthetic hormone on radioimmunoassay (RIA) and high performance liquid chromatography (HPLC). Fasting induces a marked increase in gastric tissue levels of this hypophysiotropic hormone, but is without effect on hypothalamic content, suggesting a physiological role for TRH in gastric function of this vertebrate.