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At least 343 records · Page 19Linked to original sources
PubMed1989

Physiology of the male reproductive system: endocrine, paracrine and autocrine regulation.

This presentation reviews the male reproductive system, concentrating on newer advances in our knowledge of its physiology, biochemistry, and regulation, and introduces the topic of male reproductive toxicology. GnRH is the hypothalamic peptide responsible for the stimulation of LH and FSH release from the pituitary. It is synthesized as a pro-hormone, processed in the hypothalamus and released into the portal system in a pulsatile fashion. The timing of these pulses is critical to the release of LH and FSH into the general circulation. While LH and FSH are the main trophic hormones for the testis, we now realize the importance of not only endocrine control, but also of paracrine and autocrine regulation. Specifically, the local control of Leydig cells, Sertoli cells, and germ cells appears to be modulated by numerous growth factors and local regulators arising from within the testis. This point is emphasized both during a discussion of the interaction of the various cell types in the testis and during a discussion of spermatogenesis, where techniques which show stage-specific secretions are highlighted. Newest advances in the mechanism of action of steroidal and peptide hormones are also emphasized with special reference to the possible interaction between toxicants and endocrine control of the reproductive system. This update of the reproductive system "sets the stage" for an in-depth examination of the site and mechanism of action of reproductive toxicants.

Animals↗
PubMedDate not supplied

[Evaluation of the reproductive endocrine system in a population of hemodialyzed adult males].

There is a high incidence of sexual disorders of multifactorial origin in hemodialysed patients. The endocrine reproduction system was evaluated in 19 male adult hemodialysed patients. Slightly enhanced levels of prolactin and gonadotropins were found together with normal levels of total and free testosterone. Androgen biosynthesis intermediates were substantially normal. Hypophyseal stimulation tests using TRH and GnRH revealed a prolactin and gonadotropins response which was reduced, slow and protracted compared to normal. Hypophyseal stimulation did not cause any variation in testosterone levels. Prolactin and gonadotropins were not pulsatile. Data obtained appear to indicate that the hormonal component in sexual disorders in uremic patients is related to dynamic alterations of the system rather than basic hormonal changes.

Adult↗
PubMed1991

Immunoreactivities for chromogranin A and B, and secretogranin II in the guinea pig entero-endocrine system: cellular distributions and intercellular heterogeneities.

The family of the chromogranin/secretogranin proteins consists of three major subtypes: chromogranin A (CgA), chromogranin B (CgB) and secretogranin II (SgII). These proteins are present in various endocrine cells and organs. Using immunohistochemistry on serial semithin sections, we have investigated ten endocrine cell types of the guinea pig gastro-intestinal tract for their content of chromogranin/secretogranin proteins. The gastrin cell was the only cell type containing immunoreactivities for all three chromogranin subtypes. The majority of entero-endocrine cells showed immunoreactivities for CgA and SgII. Somatostatin cells lacked immunoreactivities for any of the chromogranins. Moreover, the densities of the corresponding immunoreactivities varied among the different endocrine cell types or even among endocrine cells of a given population. Aminergic endocrine cells (e.g., enterochromaffin and enterochromaffin-like cells) regularly exhibited strong immunoreactivities for CgA but failed to react for SgII. In peptidergic endocrine cells, the immunoreactivities for both CgA and SgII ranged from dense to faint. This was also true for CgB in gastrin cells. Hence, only CgA and SgII can be considered as regular constituents of entero-endocrine cells. The intercellular differences in immunoreactivities for all three chromogranin subtypes indicate that every endocrine cell has its own composition of chromogranin/secretogranin proteins. This may be due to differences in the regulation of biosynthesis or processing of the chromogranins in individual endocrine cells; this in turn might be related to the functional states of endocrine cells.

Animals↗