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D T Armstrong

Publications and source records attributed to D T Armstrong.

At least 181 records · Page 10Linked to original sources
PubMed1978

Prostaglandin I2 stimulation of granulosa cell cyclic AMP production.

The ability of prostaglandin I2 (PGI2) to stimulate cyclic AMP production by granulosa cells, isolated from intact immature rats, has been demonstrated in vitro. The minimal effective dose was 15 ng/ml, which was comparable to the minimal effective dose for PGE2. However, a concentration of 15 microgram/ml PGI2 was required to stimulate cyclic AMP production maximally, compared to a concentration of 1 microgram/ml PGE2, which produced the maximum response. It therefore appears that PGI2 is not more effective than PGE2 in stimulating cyclic AMP production in granulosa cells, and is possibly less effective. Submaximal concentrations of PGI2 appeared to be able to modify the stimulation of cyclic AMP production by follicle-stimulating hormone (FSH), but whether or not PGI2 plays any role in follicular function remains to be established.

Animals↗
PubMed1978

Effects of prolactin, progesterone, and 17beta-hydroxy-5alpha-androstan-3-one on squalene production by the preputial gland of the immature female rat.

To examine further the previously demonstrated synergism between prolactin and progesterone on preputial glands of hypophysectomized, ovariectomized, immature rats, their effects on squalene production were determined and compared with the ability of 17beta-hydroxy-5alpha-androstan-3-one (DHT) and prolactin to increase the amount of squalene in the preputial glands. Glands from progesterone-treated rats incubated in vitro with [14C]mevalonic acid incorporated radioactivity into squalene (identified by chromatographic mobility) more rapidly than glands from controls or prolactin-treated rats. Using the same in vitro system, glands from prolactin-treated rats incorporated more [14C]acetate into squalene than those from progesterone-treated animals. In addition, results showed that prolactin and DHT increased nonradioactive squalene (identified by mass spectral analysis) content in the gland while progesterone had no effect. It is proposed that prolactin increases preputial gland squalene content by enhancing synthesis of mevalonic acid, while progesterone increases incorporation of mevalonic acid into squalene.

Animals↗
PubMed1978

17 beta-Estradiol biosynthesis in cultured granulosa and thecal cells of human ovarian follicles: stimulation by follicle-stimulating hormone.

Cellular sites and gonadotropic control of human follicular estrogen secretion have been assessed by culturing the theca and granulosa components separately under different hormonal conditions. Granulosa cells from human follicles were grown in chemically defined media containing gonadotropins and/or testosterone (T) for 24 h. The production of 17 beta-estradiol (E2) by cells cultivated in T-free media with or without FSH was very low during the culture period. There was a highly significant increase (P less than 0.001) in E2 production when T alone was added and a more marked increase was consistently noted in the presence of FSH and T. In all cases, hCG failed to exert any significant effect on E2 production by granulosa cells in the presence or absence of T. No treatments examined altered the E2 production of thecal cells during a 24-h culture period and the amounts of E2 released into media were negligible when compared with levels produced by granulosa cells from the same follicles. It is concluded that granulosa cells but not thecal cells are the prime site of follicular estrogen production and that FSH regulates estrogen secretion by nonluteinized granulosa cells of the human follicle.

Adult↗
PubMed1978

Maturational changes in sheep ovarian follicles: gonadotrophic stimulation of cyclic AMP production by isolated theca and granulosa cells.

Theca and granulosa tissues isolated from sheep ovarian follicles of different sizes were incubated in the presence of human chorionic gonadotrophin (HCG; 5 IU/ml) or follicle stimulating hormone (FSH; 5 microgram NIH-FSH-S11/ml) for 40 min. Changes in the total amounts of cyclic 3',5'-adenosine monophosphate (cAMP) were used as an index of the responsiveness of these preparations to the hormones. Thecal tissue of both large (4-6 mm in diameter) and small (1-3 mm) follicles responded similarly to gonadotrophins. Granulosa cells from small follicles failed to respond to stimulation by HCG. FSH, however, consistently increased cAMP production in comparison with controls or cells treated with HCG. Granulosa cells of large follicles responded to both HCG and FSH.

Animals↗
PubMed1978

Serum estradiol-17 beta as determined by mass fragmentography and by radioimmunoassay.

We describe the preparation of [2,4,16,16-2H4]estradiol-17 beta. The method for quantitative determination of subpicomole amounts of estradiol-17 beta (trimethylsilyl ether derivatives) by gas-liquid chromatography-mass spectrometry with multiple ion detector and with [2H4]estradiol-17 beta as the carrier is presented and characterized. Values for serum samples, as measured by radioimmunoassay and by mass fragmentography, agreed well.

Estradiol↗
PubMed1977

The effect of human chorionic gonadotropin and estradiol-17beta on the maintenance of the human corpus luteum of early pregnancy.

The effect of exogenous human chorionic gonadotropin (HCG) and estradiol valerate (EV) on the maintenance of the corpus luteum of early pregnancy, assessed by serial estimations of serum progesterone and 17alpha-hydroxyprogesterone (17-OHP), was studied in 35 subjects following therapeutic termination of pregnancy by suction curettage before the tenth week of gestation. Continuous intravenous infusion of 50,000 International Units (I.U.) of HCG for 24 hours following termination of pregnancy delayed the decline of serum HCG levels, and 17-OHP levels were maintained at preoperative levels for the 24 hours of the infusion. Single intramuscular injections of 5,000 or 20,000 I.U. of HCG were ineffective. Administration of 25 mg. of EV intramuscularly immediately following therapeutic termination of pregnancy slightly retarded the decline of serum 17-OHP levels. The same treatment when administered in combination with the intravenous infusion of 50,000 I.U. of HCG completely prevented the ability of HCG to maintain serum levels of 17-OHP. These finding susggest an antagonism between estradiol and HCG in maintenance of the human corpus luteum during early pregnancy.

Chorionic Gonadotropin↗
PubMed1977

Radioimmunoassays for androsterone, 5alpha-androstane-3alpha, 17beta-diol and 5alpha-androstane-3beta, 17beta-diol.

Androsterone (3alpha-hydroxy-5alpha-androstan-17-one), 5alpha-androstane-3alpha, 17beta-diol and 5alpha-androstane-3beta, 17beta-diol were conjugated at C-16 through sulfur to bovine and human serum albumin. Rabbits injected with these conjugates produced antibodies suitable for radioimmunoassays of these hormone metabolites. Samples were purified on Sephadex LH-20 columns. Levels of these steroids were measured in a rat blood serum pool and in ovarian tissue extract pools.

Androstane-3,17-diol↗
PubMed1977

Androgen production by theca and granulosa isolated from proestrous rat follicles.

Theca and granulosa isolated from proestrous rat ovarian follicles were cultured for 72 h in the presence or absence of highly purified luteinizing hormone (LH, 0.1 microng/ml) and/or follicle-stimulating hormone (FSH, 0.1 microng/ml). Medium was collected and replaced at 3, 6, 12, 24, 48, and 72 h of culture and measured for testosterone by radioimmunoassay. Pieces of isolated theca secreted androgen; androgen production was greatest during the first 12 h of culture. Addition of highly purified LH to the culture medium produced a significant increase (P less than 0.001) in the thecal androgen secretion, while addition of highly purified FSH had no significant effect. Addition of LH + FSH to culture medium produced the same effect as addition of LH alone. The response of the theca to LH was dose-dependent with doses of 0.01 microng/ml or greater eliciting a maximum response. The addition of eoxgenous progesterone (5 x 10(-7)M) to culture medium had no effect on thecal androgen production. Thecal androgen secretion was the same in the presence or absence of fetal calf serum. Since the testosterone antibody used was not entirely specific for testosterone, testosterone and the cross-reacting androgen, 17beta-hydroxy-5alpha-androstan-3-one (DHT), were chromatographically isolated from samples and assayed separately. The androgen measured in culture medium was found to consist primarily of testosterone; DHT was present in much lower concentrations. Granulosa cells isolated from the same follicles as the theca and grown in monolayer culture produced negligible amounts of androgen. It is concluded that the theca is the site of follicular androgen production and that LH regulates androgen secretion by rat ovarian follicles. The results suggest that the theca provides the androgen precursor needed for follicular estradiol-17beta synthesis.

Animals↗
PubMed1977

Estrogen biosynthesis in the ovaries and testes.

This review has presented some of our recent data on estrogen biosynthesis and has drawn upon these, as well as numerous observations, to design the two-cell type, two-gonadotropin model, applicable to both sexes, for the biosynthesis of gonadal estrogens and its regulation. Some of the data upon which this model, depicted in Figure 15, are based are quite preliminary and in many cases have been derived from experiments with tissues from animals over a rather narrow age span. Consequently, in future years this model may appear too simplistic to explain gonadal estrogen synthesis at all stages of development. However, whatever the fate of the model, whether it be broken and rebuilt on firmer foundations or furnished more lavishly, it is hoped that it will result in some of the corners being "rounded." There has been an emphasis on some of the similarities between the two sexes with respect to enzyme capacities, hormone receptors, and control mechanisms for the various cell types in the ovaries as compared to the testes. In particular, the striking similarities both structurally and functionally between Sertoli cells and granulosa cells are now recognized. Vive la difference.

Animals↗
PubMed1976

Induction of vaginal mucification in rats with testosterone and 17beta-hydroxy-5alpha-androstan-3-one.

Based on histological criteria, Kingsley and Bogdanove (3) reported that the benzoate ester of 17beta-hydroxy-5alpha-androstan-3-one (5alpha-DHT), unlike testosterone propionate, is unable to induce vaginal mucification when given subcutaneously to rats. In contrats, Kennedy (4) found in estrogen-pretreated rats that both 5alpha-DHT and testosterone induced vaginal mucification as indicated by increased vaginal sialic acid concentration. To determine if esterification of these androgens altered their ability to induce vaginal mucification, ovariectomized rats, pretreated for 3 days with 0.25 mug estradiol-17beta, were treated for 8 days with either sesame oil or 7 mumoles of testosterone, 5alpha-DHT and their respective propionate and benzoate esters. All treatments except 5-alpha-DHT benzoate increased vaginal weight and vaginal mucification, as assessed histochemically and biochemically. 5alpha-DHT propionate was less effective than 5alpha-DHT while testosterone benzoate, but not propionate was less effective than testosterone. To determine if estrogens are necessary for the vaginal effects of androgens, ovariectomized and ovariectomized-adrenalectomized rats were treated with testosterone or 5alpha-DHT. Adrenalectomy did not significantly affect the vaginal response to either androgen. It is therefore concluded that androgens are capable of inducing vaginal mucification in the absence of estrogens.

Adrenalectomy↗