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Biomedical subjects

C Denef

Publications and source records attributed to C Denef.

At least 109 records · Page 6Linked to original sources
PubMed1980

Dopaminergic stimulation of prolactin release.

Prolactin (PRL) secretion from anterior pituitary is believed to be under tonic inhibitory control of dopamine (DA) released from the tubero-infundibular dopaminergic neurones into the hypophysial portal blood. Inhibition of PRL release by DA seems to be mediated by sereospecific DA receptors located in PRL cells. Apomorphine and various ergot alkaloids such as bromocryptine mimic the inhibitory effect of DA both in vivo and in vitro, presumably by a direct agonist action on these 'inhibitory' receptors. We now report that PRL secretion in primary cultures of rat pituitary cells can be stimulated by DA when concentrations a thousand times lower than those required for inhibition are used. Secretion rates above basal release can also be induced by apomorphine and bromocryptine when the 'inhibitory' receptors are blocked with certain DA receptor antagonists.

Animals↗
PubMed1978

Pituitary basophils from immature male and female rats: distribution of gonadotrophs and thyrotrophs as studied by unit gravity sedimentation.

Isolated pituitary cells from 14-day-old female, 14-day-old male, and adult male rats were separated into several fractions by unit gravity sedimentation. With preparations from 14-day-old animals, the percentage of basophils increased from top to bottom of the gradient. The bottom fractions contained large basophils with a purity attaining almost 90% in the female and 75% in the male preparation. The same fraction prepared from adult male rats was composed of over 80% of large acidophils. As identified by immunostaining, the majority of the female large basophils were gonadotrophs, whereas in 14-day-old males about 1/3 of these basophils were thyrotrophs. The relative proportion of medium and small sized gonadotrophs and of thyrotrophs was also higher in the 14-day-old rats than in the adults. An estimate of the distribution of FSH and LH among the gonadotrophs was made by comparing the number of cells reacting with anti-FSH, with anti-LH, and with a mixture of both antisera. The data suggested that irrespective of cell size, the majority of the gonadotrophs in 14-day-old rats contained both FSH and LH. In most fractions, the occurrence of cells with only one hormone was more apparent in the males than in the females. In adult rats, cells with only FSH were most abundant in the fraction with large gonadotrophs. The distribution of hormone content, as measured by RIA, was highly characteristic for each animal group. In 14-day-old females, more than 70% of the recovered hormones was in the large gonadotrophs. In 14-day-old and adult males, substantial amounts of hormone were also recovered from medium sized gonadotrophs. The present findings suggest a relationship between developmental changes in pituitary hormone secretion and changes in pituitary cell type distribution.

Aging↗
PubMed1978

Monolayer cultures of gonadotrophs separated by velocity sedimentation: heterogeneity in response to luteinizing hormone-releasing hormone.

Isolated pituitary cells from 14-day-old male and female and adult male rats were separated into enriched populations of gonadotrophs by velocity sedimentation at unit gravity. The cells, collected from five gradient fractions, were established in monolayer culture. Hormone content and hormonal secretion in response to LHRH were measured after 3 days in culture. Stored FSH and LH declined during culture, but the relative differences between fractions and between animal groups were maintained. In all fractions, LHRH stimulated the release of both FSH and LH in a dose-response fashion. The secretory potential per gonadotroph changed with fraction and the pattern was highly characteristic for each animal group. In 14-day-old females, both FSH and LH secretion increased 20 times from the fraction with the smallest to the fraction with the largest gonadotrophs. In preparations from 14-day-old males, only the release of FSH consistently rose with gonadotroph cell size. With cells from adult males, FSH as well as LH release increased with cell size, but the pattern was different for each hormone. Secretion did not always correlate with the cellular content of hormone before stimulation. The present findings suggest that gonadotrophs isolated from animals in a different physiological or developmental status may retain in short term culture certain of their previous functional characteristics. There is evidence that the gonadotroph cell population is heterogeneous not only in terms of the magnitude of the response to LHRH but also in terms of the relative proportion of FSH and LH secreted. Changes in the relative proportion of certain variants of gonadotrophs may be a cellular basis for differential regulation of FSH and LH secretion by a single releasing hormone.

Aging↗
PubMed1976

A specific population of gonadotrophs purified from immature female rat pituitary.

When dispersed pituitary cells from 14-day-old female rats were sedimented in a bovine serum albumin gradient, a fraction was isolated which consisted of almost 90 percent of large cells that stained purple in the periodic acid-Schiff (PAS) reaction. Immunostaining indicated that over 85 percent of these PAS-purple cells were gonadotrophs containing both follicle stimulating and luteinizing hormone. Reproducible cell cultures could be obtained on poly-L-lysine coated dishes. As early as the second day in culture, the secretion of both follicle stimulating and luteinizing hormone was highly stimulated by luteinizing hormone-releasing hormone. The effect of FSH was as marked as that on LH. The data suggest that the isolated gonadotrophs are a specific functional subtype.

Age Factors↗