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D J McComb

Publications and source records attributed to D J McComb.

31 records · Page 2Linked to original sources
PubMed1982

Bromocriptine suppression of dispersed pituitary lactotrophs from estrogen-pretreated rats: a quantitative electron microscopic study.

Dispersed rat lactotrophs were treated with bromocriptine (10(-10) M) for either 30 min or 3 h to investigate its effect on cell morphology using light and electron microscopy and ultrastructural morphometry. After 30 min, lactotrophs treated with bromocriptine exhibited an increase in storage granule size (p less than 0.05). Crinophagy was also evident and a significant increase in lysosome volume density was observed (p less than 0.001). However, no significant change in prolactin content in the media was detected until 3 h of incubation in bromocriptine (p less than 0.05). At this time a nonsignificant decrease in Golgi region volume density was also observed.

Animals↗
PubMed1982

Some functional and morphological characteristics of an acutely dispersed purified cell suspension of rat lactotrophs prepared with Percoll.

A cell suspension containing more than 90% lactotrophs can be prepared from enzymically dispersed adenohypophyses obtained from male rats pretreated with estradiol. The lactotrophs are separated from the mixed cell population by centrifugation on a discontinuous density gradient prepared from a commercial preparation of colloidal silica (Percoll, Pharmacia). The method allows isopycnic separation of these delicate cells under very mild conditions; normal ionic strength and normal pH were maintained throughout the gradient, centrifugal acceleration did not exceed 1600 X g, and all procedures were done at room temperature. Histological verification that at least 90% of the cells were lactotrophs was done using specific immunoperoxidase staining. The functional capability of the lactotrophs was established by measuring the dose--response to the dopamine agonist bromocriptine and to thyrotropin-releasing hormone (TRH). Bromocriptine decreased spontaneous release in a dose-related way over the concentration range of 10(-10) to 10(-8) M. TRH, which causes an in vivo release of prolactin (PRL) in estrogen-primed rats, produced a dose-related increase in the release of PRL over the concentration range of 3 X 10(-10) to 3 X 10(-8) M after the high spontaneous release had been previously reduced by bromocriptine (3 X 10(-8) M).

Adrenocorticotropic Hormone↗
PubMed1982

Ultrastructural differentiation in the nude mouse of transformed cells isolated from the human fetal pituitary gland.

Spontaneously transformed human fetal pituitary cells were isolated from first-passage cultures after 3 to 6 months of long-term maintenance in growth medium containing 15% fetal calf serum. The cells, when injected into nude mice, developed into large tumors in 1 to 2 weeks. Attempts to detect growth hormone, prolactin, follicle-stimulating hormone, luteinizing hormone, or thyroid-stimulating hormone from nude mouse plasma and tumor homogenate by radioimmunoassay were unsuccessful. These hormones could not be demonstrated in tumor cell cytoplasm by immunocytochemistry. Two human fetal pituitary (HFP) cell strains (HFP-T2, HFP-F4) from tissue culture examined at the electron microscopic level were undifferentiated by ultrastructural criteria. However, tumor cells in the nude mice showed signs of fine structural differentiation with well-developed rough endoplasmic reticulum profiles, secretory granules, and intercellular junctions. The tumor cells lost the features of morphological differentiation when returned to tissue culture. These changes could be repeated by alternate passage in nude mouse and tissue culture.

Animals↗
PubMed1981

Five different adenomas derived from the rat adenohypophysis: immunocytochemical and ultrastructural study.

With the use of electron microscopic morphology and immunochemistry, 5 tumors were studied: a spontaneous prolactin-producing adenoma (LEP rats); an estrogen-induced intrasellar tumor (R-Amsterdam rats); and 3 transplanted tumors, MtT.W10 and MtT.W5 (WF rats) and MtT.F4 (F344 rats). All tumors were derived from rat adenohypophysis and are known to secrete prolactin, growth hormone, or adrenocorticotropic hormone. The spontaneous tumor consisted of a uniform population of cells containing only immunoreactive prolactin. In the estrogen-induced tumor, prolactin and growth hormone were localized in separate cell types with the use of the immunoperoxidase technique. In the MtT.W10 tumor, both immunoreactive prolactin and growth hormone were observed in the same cell and in separate cell types. In the MtT.F4 and MtT.W5 tumors, one cell type was identified that was characterized by lack of morphologic differentiation, reduced secretory granule number, and inconclusive immunopositivity.

Adenoma↗
PubMed1981

Enhanced responsiveness of lactotrophs in ectopic pituitaries to bromocryptine and estrone acetate.

Intrasellar and transplanted pituitaries removed from the same rats were studied using light microscopy, immunocytology, electron microscopy and ultrastructural morphometry following treatment with bromocryptine and/or estrone acetate. Ectopic lactotrophs of rats treated with bromocryptine showed an increase in storage granule size and number, which was not observed in the lactotrophs of corresponding intrasellar pituitaries. In lactotrophs of intrasellar and ectopic pituitaries, treatment with estrone acetate caused a decrease of storage granule size, while rough endoplasmic reticulum (RER) and Golgi region volume density increased. When rats were treated with a combination of bromocryptine and estrone acetate, intrasellar lactotrophs exhibited increased volume density and diameter size in forming granules as well as increased RER volume density. In ectopic lactotrophs, combined treatment led to a decrease in RER, volume densities of Golgi region and forming granules, as well as increased storage granule size. It can be concluded that ectopic lactotrophs were more sensitive to the inhibiting effects of bromocryptine treatment than intrasellar lactotrophs. Intrasellar lactotrophs were more susceptible to estrone acetate than bromocryptine treatment. As a result, the increased responsiveness of ectopic lactotrophs to estrone acetate was less conspicuous.

Animals↗
PubMed1981

Response to thyrotropin-releasing hormone (TRH) of rat lactotrophs and somatotrophs deprived of hypothalamic control.

Intrasellar and ectopic lactotrophs and somatotrophs of intact and hypophysectomized rats were studied by histology, immunohistochemistry, electron microscopy and ultrastructural morphometry after 2 weeks of TRH treatment. Both ectopic lactotrophs and somatotrophs of hypophysectomized rats showed subcellular changes indicative of stimulation following TRH treatment. Ultrastructural morphometry revealed that in these ectopic lactotrophs, nuclear volume density decreased, while that of Golgi region and forming granules increased. Similar but less striking morphometric findings were noted in somatotrophs of this group and the intrasellar lactotrophs of treated nongrafted rats. Intrasellar somatotrophs showed increased nuclear volume density and reduced Golgi region volume density, following TRH administration. Ectopic lactotrophs and somatotrophs of intact animals were least responsive to treatment. These results indicate that both ectopic lactotrophs and somatotrophs of hypophysectomized rats are more sensitive to the stimulatory effects of TRH than those of intact animals.

Animals↗
PubMed1981

Adrenocortical hemorrhagic necrosis: the role of catecholamines and retrograde medullary-cell embolism.

We investigated the pathogenesis of adrenal necrosis using animal models of the disease (induced by administration of acrylonitrile, cysteamine, or pyrazole) and human cases. Results of electron-microscopic and histochemical time-response studies with rat models revealed an early, retrograde embolization of medullary cells and cell fragments in the cortical capillaries that showed prominent endothelial injury. The experimental adrenal lesions were prevented by surgical removal of the medulla one month before administration of adrenocorticolytic chemicals, or by the administration of the alpha-adrenergic antagonist phenoxybenzamine hydrochloride. Histochemical staining for medullary (argyrophil) granules in human cases of adrenal necrosis demonstrated tissue fragments that stained positively for silver in vascular cortical spaces in nine of ten autopsy specimens and in all four surgical cases we reviewed. Thus, catecholamines released from the adrenal medulla and from the retrograde medullary emboli in the cortex may have a role in the pathogenesis of adrenocortical necrosis.

Acrylonitrile↗
PubMed1980

Correlative ultrastructural morphometry of human prolactin-producing adenomas.

Ultrastructural morphometry was applied to 24 surgically removed human sparsely granulated prolactin cell adenomas in an attempt to correlate the measurements with blood prolactin levels, size of tumour, and age and sex of patient. No correlation was apparent. However, further evaluation revealed that correlation existed between size of tumour and blood prolactin levels, indicating that tumour mass, and not subcellular morphology, was related to the amount of prolactin released.

Adenoma↗
PubMed1980

Pituitary prolactin cell hyperplasia.

In female Long-Evans rats, development of prolactin cell adenomas is preceded by hyperplasia of prolactin cells, suggesting that factors affecting the endocrine function of prolactin cells might have an important role in the genesis of prolactin-producing pituitary tumors.

Adenoma↗
PubMed1979

An immunohistochemical and ultrastructural comparison of the effects of 2-bromo-alpha-ergocryptine on intrasellar and transplanted rat pituitaries.

Following 2 weeks of administration of 2-bromo-alpha-ergocryptine, a marked decrease was observed in prolactin immunoreactivity of the grafted pituitaries, whereas no reduction was noted in the intrasellar pituitaries. No evidence of crinophagy was revealed by electron microscopy in prolactin cells of 2-bromo-alpha-ergocryptine-treated rats.

Animals↗
PubMed1978

Ultrastructural morphometry of sparsely granulated prolactin cell adenomas of the human pituitary.

Fifteen sparsely granulated prolactin-producing adenomas and 10 nontumourous adenohypophyses, removed by surgical hypophysectomy, have been studied using morphometry at the electron microscopic level. Compared to non-tumourous prolactin cells, sparsely granulated adenomatous prolactin cells showed a significant decrease in diameter and volume density of secretory granules and an increased volume density of rough-surfaced endoplasmic reticulum and Golgi apparatus. The volume density of mitochondria remained unchanged. These results indicate that the cells of the adenoma are in a highly active functional state. It appears that the equilibrium between hormone synthesis, storage and release is altered in adenomatous prolactin cells.

Adenoma↗