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Biomedical subjects

W C Hymer

Publications and source records attributed to W C Hymer.

At least 73 records · Page 4Linked to original sources
PubMed1981

Pituitary cell transplants to the cerebral ventricle suppress the pituitary of the recipient host.

Implantation of 1 x 10(6) acutely dispersed rat pituitary cells into the lateral ventricles of sexually immature and mature female rats of both the Sprague-Dawley and Fisher strains significantly suppressed the weight and protein content of the in situ pituitary 12 days postimplantation. Body weight gains in the young animals were also significantly lower. Changes in the in situ pituitary of the cell implanted groups were demonstrated by repeatable reductions (approximately 50%) in total pituitary GH and PRL content. Total pituitary TSH, FSH and LH were usually unaffected. Although the mechanism of cell-mediated suppression of the host pituitary is unknown, the approach should be of use in future studies of feedback regulation on pituitary gland function.

Animals↗
PubMed1978

Culture of human pituitary prolactin and growth hormone cells.

Fragments of pituitary tissue obtained from a total of 37 patients with either breast cancer, diabetic retinopathy, galactorrhea, or acromegaly were dissociated into single cell suspensions prior to cell culture. Release of human growth hormone (hGH) and human prolactin (hPRL) into the culture medium was measured by radioimmunoassay. During a 3-week culture period, prolactin cells released 9--13 times the intracellular levels of hPRL at the time of seeding, whereas hGH release from growth hormone cells was only 1--2 times that of their initial intracellular level during this same time. Both growth hormone and prolactin cells retained distinctive ultrastructural features during culture. The prolactin cells responded to TRH stimulation by elevated release of PRL into the medium. No evidence for mitotic division of prolactin cells in vitro was found.

Breast Neoplasms↗
PubMed1978

Thyroid hormone effects on protein and RNA metabolism in the rat anterior pituitary.

Thyroidectomy reduced the incorporation of [3H]amino acids into total rat pituitary proteins as well as into electrophoretic fractions corresponding to growth hormone (GH) and prolactin. A single injection of thyroxine (200 microgram/kg) reversed the effects of thyroidectomy on the GH (12 h) and prolactin (36 h) fractions. Evidence for a general increase in the rate of pituitary protein synthesis following this treatment was less conclusive, but two injections of the hormone had a definite stimulatory effect. [3H]Uridine uptake by the pituitary and its incorporation into RNA were elevated for 2 weeks after thyroidectomy. Thyroxine failed to suppress these changes for at least 36 h after injection. Actinomycin C (400 microgram/kg) inhibited pituitary RNA synthesis and blocked the stimulatory effect of thyroxine on amino acid incorporation into the GH fraction. These results indicate that thyroid hormones: (1) promote pituitary protein synthesis, probably as a consequence of their effects on somatotrophs and lactotrophs; (2) exert a stimulatory effect on GH synthesis by affecting transcription.

Amino Acids↗
PubMed1977

Functional heterogeneity in somatotrophs isolated from the rat anterior pituitary.

Somatotrophs in suspensions of anterior pituitary cells from adult male rats can be separated into 2 fractions by density gradient centrifugation. In addition to their different densities, somatotrophs in these 2 fractions can be distinguished morphologically by their staining characteristics and ultrastructure. Somatotrophs of lesser density (type I; approximately 1.068 g/cm3) have fewer secretory granules and a more extensive Golgi apparatus than the somatotrophs of greater density (type II; approximately 1.073 g/cm3). Responsiveness of type I and type II cells to secretory agents (i.e., dibutyryl cyclic adenosine monophosphate, somatostatin, thyroxine, and hydrocortisone) was evaluated by GH radioimmunoassay. Type I cells were consistently more responsive (% GH release) than type II cells. During 7 days in culture, type I cells produced more (approximately 200%) GH than they initially contained, whereas type II cells did not show evidence of increased GH production. Hydrocortisone significantly stimulated GH production in type I, but not type II cells. These results support the hypothesis that at least 2 functionally distinct populations of somatotrophs are present in the anterior pituitary gland of the adult male rat.

Animals↗
PubMed1976

Characterization of mammotrophs separated from the human pituitary gland.

Human pituitary tissues from 27 patients and 7 persons post mortem were dissociated into single cell suspensions. On the average, 23% of the cells were mammotrophs. The concentration of prolactin in these suspensions averaged 3.8 ng/1,000 cells. After cell separation by velocity sedimentation at unit gravity, mammotrophs and other cell types were enriched twofold to threefold. The separated mammotrophs retained structural integrity at light and electron microscopic levels. In eight separation experiments, cells recovered from different gradient regions were assayed for intracellular prolactin levels. In cells from "normal" subjects, 8.5% of the prolactin recovered from the gradient was associated with large mammotrophs, whereas in patients with breast cancer, 28% of the hormone was associated with large mammotrophs. The number of mammotrophs recovered from this gradient region (beyond fraction 6) was doubled in breast cancer (2 expts). These mammotrophs showed areas of hypertrophied Golgi and endoplasmic reticulum. Culture of the separated cells from 1 patients with diabetes and 2 patients with breast cancer for 21 days showed that mammotrophs in the upper gradient fractions (diabetic) secreted seven times more hormone than those in the lower regions, whereas those mammotrophs from patients with breast cancer that fell to the lower gradient regions secreted 15 times more prolactin than did those in the upper regions. These data suggest that pituitaries of patients with breast cancer contain a small pool (10-20%) of hypertrophied mammotrophs that have the potential for significant secretory activity in vitro.

Adult↗
PubMed1976

Maintenance of separated rat pituitary mammotrophs in cell culture.

Dispersed female rat anterior pituitary cells were cultured in Medium 199 containing 20% fetal calf serum for 30 days. Prolactin levels in the culture medium remained relatively constant during this time, ranging from 30-40 ng/10,000 cells seeded/day. The total quantity of prolactin released into the medium was 10-15 times that originally contained in the cells. Morphological integrity of the mammotrophs was maintained. Using velocity sedimentation at unit gravity, cells from untreated, overiectomized or estrogen-primed animals were separted into several fractions, and subsequently cultured for 14 days. Not all mammotrophs secreted the same quantity of hormone during this time. The data suggest that the pituitary of the female rat is composed of a heterogeneous population of mammotrophs, and that their capacity to secrete prolactin in vitro may, in part, be reflected by the previous physiological status of the animal.

Animals↗
PubMed1975

A short method for the isolation of somatotrophs from the rat pituitary gland.

Application of a density gradient centrifugation procedure for the isolation of somatotrophs from dispersed rat anterior pituitary cells is described. Two sequential discontinuous gradients of bovine serum albumin are used to enrich the somatotroph population from a frequency of 38% in the initial cell suspension to a final purity of 85%. The isolated somatotrophs retain both histochemical and ultrastructural integrity throughout the isolation procedure. The isolated somatotrophs also release immunoassayable growth hormone when incubated with 6 mM dibutyryl 3',5'-cyclic AMP. The method offers the advantages of being both simple and short.

Animals↗
PubMed1975

Effects of hypothalamic extract and dibutyryl cyclic adenosine monophosphate on follicle-stimulating hormone production in the rat adenohypophysis in vitro.

An assay system, using the characteristic migration of follicle-stimulating hormone (FSH) on polyacrylamide gels, was developed to evaluate the effects of hypothalamic factors on amino acid incorporation into FSH in the rat adenohypophysis incubated in vitro. Follicle-stimulating hormone extracted from rat pituitary secretory granules was found to migrate on 7-5% polyacrylamide gels, pH 9-5, as a protein with an Rf of 0-614. The characteristic Rf was used to measure [14C]amino acid incorpotation into FSH in rat adenohypophyses in vitro. Follicle-stimulating hormone synthesis increased after addition of crude hypothalamic extract to the incubation medium. Hormone synthesis was also increased three times after the addition of dibutyryl cyclic AMP.

Amino Acids↗