Seasonal effects of pimozide and des Gly10 [D-Ala6] LH-RH ethylamide on gonadotrophin secretion in goldfish

The seasonal changes in the gonadotrophin-release-inhibitory activity of dopamine and responsiveness to gonadotrophin-releasing hormone were investigated by determining the effects of injection of pimozide, a dopamine receptor antagonist, des-Gly10 [D-Ala6] LH-RH ethylamide (LRH-A), or the combination of pimozide plus LRH-A on serum gonadotrophin (GtH) levels of goldfish, held at 12 or 20 degrees C, at different stages of gonadal development. As in previous studies, pimozide greatly potentiated the GtH-release response to LRH-A. The highest concentrations of serum GtH induced by injection of pimozide or LRH-A alone, or the combination of pimozide plus LRH-A were in females in late stages of ovarian recrudescence; fish that were sexually regressed (males and females combined) were the least responsive, and fish that were in early stages of gonadal recrudescence, and mature females ( = prespawning, completed ovarian recrudescence) were intermediate. Fish held at 20 degrees C had a more rapid onset of GtH release and had higher serum GtH levels initially compared to fish at 12 degrees C at similar sexual stages; however, the fish held at 12 degrees C generally had a more prolonged increase in serum GtH levels, indicating that temperature influence the time course of the GtH-release response. The results indicate that there is a seasonal variation in responsiveness to injection of pimozide, LRH-A and the combination of pimozide plus LRH-A. These seasonal changes may be due to differences in the pituitary content of GtH, the ability of the pituitary to synthesize GtH, or changes in GtH cell receptors for GnRH and dopamine, or a combination of these and other unknown factors.

A peptide in gastric secretion with inhibin-like properties

The presence of inhibin like peptide which is biologically active in reducing FSH secretion in castrated rats and suppressing hCG-induced increase in ovarian weights of immature mice, is reported for the first time in gastric aspirates of normal men. Immunological characteristics of this peptide were similar to inhibin extracted from human seminal plasma. The concentration of inhibin-like peptide measured by RIA developed for seminal inhibin is more than thirty-fold higher in gastric aspirates compared with serum.

Localization of hypophysiotropic neurohormones by assay of sections from various brain areas

The results of studies of the localization of the hypothalamic hypophysiotropic factors based on their direct determination in sections or nuclear punches are described. Luteinizing hormone-releasing hormone was found in high concentrations in the median eminence-arcuate nucleus complex, in lower concentrations in the mediobasal zone of the preoptic area. In addition to these hypothalamic sites, it is present in all four periventricular organs, especially in the organum vasculosum laminae terminalis. Thyrotropin releasing hormone has a widespread distribution. High concentrations are in the median eminence, arcuate nucleus, dorsomedial nucleus, and anterior part of the ventromedial nucleus. Lower concentrations are in several other structures of the hypothalamus, preoptic area and septum, and low but measurable quantities are found in most of the structures of the brain. Somatostatin is also present in most structures of the central nervous system, with highest concentrations in the median eminence, arcuate nucleus, ventromedial nucleus and periventricular nucleus. There are indications that the ventromedial nucleus or its immediate vicinity contains growth hormone releasing factor. Prolactin releasing activity was present in the median eminence and mediobasal parts of the anterior hypothalamus, whereas prolactin inhibitory activity was in the dorsolateral parts of the anterior hypothalamus and/or preoptic area.

Secretion of an FSH-inhibiting factor by cultured Sertoli cells

Levels of LH and FSH released in vitro by rat anterior pituitary cells which were either co-cultured with isolated rat Sertoli cells or were grown with spent media recovered from the cultured Sertoli cells were measured by radioimmunoassay. The amounts of FSH released by pituitary cells grown for three days with Sertoli cells isolated from 31-36 day old rats or spent media from the cultured Sertoli cells, were significantly (P less than 0.01) lower compared to control pituitary cultures grown with fresh chemically defined medium. In contrast, the levels of LH were similar to the controls. The selective inhibition of FSH release was not observed when pituitary cells were co-cultured with rat spleen or kidney cells or with ruptured Sertoli cells. The FSH-inhibiting Sertoli-cell factor (SCF) was found to be a heat-labile macromolecule. It is suggested that the SCF may be secreted by the Sertoli cells in vivo, and regulate FSH secretion via negative feedback mechanism at the pituitary level.

The amenorrhoea-galactorrhea syndrome: present diagnostic and therapeutic perspectives

Recent progress in the field of radioimmunology, especially as regards prolactin (PRL) assay, as well as the use of new drugs have opened new perspectives for a better understanding of the "amenorrhoea-galactorrhea syndrome" both from the diagnostic and therapeutic points of view. This syndrome which formerly was considered infrequent, is now observed more and more often, perhaps as a result of the more widespread use of drugs such as phenothiazines, reserpine derivatives, alpha-methyldopa and tricyclic antidepressants, as well as owing to the large-scale use of estrogens and above all of estrogen-progestogen contraceptives. The problems of etiopathogenesis and management of the amenorrhea-galactorrhea syndrome are complicated by the fact that a variety of factors are responsible, as is shown also by the classical nosographic classification with the Forbes-Albright syndrome in the presence of a pituitary tumour, the Chiari-Frommel syndrome of amenorrhea-galactorrhea following pregnancy, and the Argonz-del Castillo-Ahumada syndrome in the absence of lither pregnancy or tumor.