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At least 19 recordsLinked to original sources
PubMed2002

[The mammary gland, an endocrine gland].

Features of acromegaly had developed in a 6-year-old crossbred Belgian shepherd dog (dog A) following treatment with medroxyprogesterone and an 8-year-old beagle dog (dog B) during the luteal phase of the oestrus cycle. Discontinuation of progesterone administration in dog A and ovariohysterectomy in both dogs was followed by a regression of the soft tissue changes and a normalisation of the initially high plasma growth hormone concentrations. These cases illustrate that the mammary gland is not just a gland which delivers milk in response to certain stimuli, but that it also transmits humoral signals, i.e., the mammary gland is an endocrine gland. Progestin-induced growth hormone is produced in areas of hyperplastic mammary epithelium and in mammary tumours. This suggests that locally-produced growth hormone is involved in the proliferation of unaffected and tumorous mammary tissue in an autocrine or paracrine manner. Now that the expression of the growth hormone gene has also been demonstrated in the human mammary gland, further studies are needed to answer questions such as (a) does mammary growth hormone also reach the systemic circulation in women?, (b) what is the role of local growth-hormone production in tumourigenesis?, and (c) does this phenomenon provide possibilities for therapeutic intervention in women with breast cancer?

Acromegaly↗
PubMed1985

[Intermediate lobe of the amphibian pituitary gland: an endocrine gland with multiple secretions and under multi-hormonal control].

The cells of the frog pars intermedia synthesize a 36 000 (36K) protein called proopiomelanocortin (POMC). After [3H]glucosamine incorporation, separation of newly synthesized products by SDS-polyacrylamide gel electrophoresis showed that this 36K protein was glycosylated. Tryptic mapping revealed only one site of glycosylation and showed that the carbohydrate side-chain was located in the N-terminal region of POMC. The 36K protein was not released by the melanotrophs, but it generated, through specific intracellular proteolytic cleavage, a number of smaller peptides which were subsequently released. These peptides were identified by various methods including selective amino-acid incorporation, HPLC purification, acid-urea gel electrophoresis, tryptic and chymotryptic mapping, assay of melanotropic activity, radioimmunoassays and immunoprecipitations. Some of the newly synthesized N-terminal (18K) fragment of the POMC was secreted intact while a portion of it was further processed, via an intermediate peptide, to give mature gamma-MSH. All three of these peptides were glycosylated. In addition, the mature peptide (gamma-MSH) exhibited a low but significant melanotropic activity. The C-terminal portion of the prohormone was very rapidly processed to give des N alpha-acetyl alpha-MSH, corticotropin-like-intermediate lobe peptide (CLIP) and beta-endorphin. Authentic alpha-MSH was always absent in cellular extracts: acetylation to give rise to alpha-MSH was a late enzymatic process strictly linked to hormonal release. Since acetylation of alpha-MSH is required for full biological activity of this peptide, it is possible to conceive that this later step could be under neuroendocrine control. Using the perifusion technique we have been able to show the complexity of the control mechanisms regulating amphibian melanotrophs. It is generally accepted that the aminergic innervation of the intermediate lobe of the pituitary is involved in the hypothalamic control of melanotropin release. We have demonstrated that, in amphibians, dopamine inhibits alpha-MSH secretion through D2-type dopaminergic receptors whereas norepinephrine and (or) epinephrine stimulate alpha-MSH secretion via beta-adrenergic receptors. The existence of peptidergic fibers within parenchymal cells of the pars intermedia has been demonstrated. Evidence for TRH-containing fibers has been obtained by immunohistochemistry. Using a specific radioimmunoassay for TRH, we have confirmed the presence of TRH in the neurointermediate lobe of the frog. We have shown that TRH is a powerful MSH-releasing factor in these animals.(ABSTRACT TRUNCATED AT 400 WORDS)

Amphibians↗