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Biomedical subjects

A Steinberger

Publications and source records attributed to A Steinberger.

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

Computed tomographic demonstration of giant aneurysms of the vertebrobasilar system: report of eight cases.

Giant aneurysms of the vertebrobasilar system can easily mimic other mass lesions in the posterior fossa and 3rd ventricle. Recently, we treated eight cases of giant aneurysm in the vertebrobasilar circulation that were demonstrated by computed tomography with angiographic correlation. We describe the salient radiological features that help to distinguish giant aneurysms from neoplasms and discuss their clinical manifestations and surgical management.

Adolescent↗
PubMed1979

Hormone interactions in the Sertoli cells.

The effects of follicle-stimulating hormone (FSH) and testosterone in rat Sertoli cells were investigated in vitro by means of isolated cell populations. The Sertoli cells selectively bind FSH, and respond to FSH stimulation with increased accumulation of endogenous cyclic AMP and secretion of androgen-binding protein (ABP). FSH binding and cyclic AMP response in the Sertoli cells change dramatically during sexual maturation. Cyclic AMP response decreases despite an increase in FSH-binding receptors per cell. Evidence has been provided for the existence of cytoplasmic and nuclear androgen receptors and chromatin acceptor-sites that specifically bind the androgen-receptor complex in the Sertoli cells. A model has been proposed for the hormonal interactions in the seminiferous tubule and the possible role of Sertoli cells in mediating the hormonal effects on spermatogenesis.

Animals↗
PubMed1979

In vitro metabolism of testosterone by cultured Sertoli cells and the effect of FSH.

Cultures of Sertoli cells isolated from testes of 18-and 36-day-old Long Evans rats were used to investigate their capacity to metabolize testosterone and the effect of FSH on such metabolism. Three different approaches were used: 1) investigation of the metabolism of radiolabeled testosterone under saturating substrate conditions; 2) study of the metabolism of radiolabeled testosterone utilizing trace amounts of high specific activity substrates; 3) the utilization of radioimmunoassay for measurement of estradiol-17 beta. The following steroids were isolated and identified by recrystallization to constant specific acitvity from the control and FSH-treated cultures; testosterone (unconverted substrate), androstenedione, dihydrotestosterone, 3 alpha-hydroxy-5 alpha-androstan-17-one and 5 alpha-androstane-3 alpha, 17 beta-diol. Radioimmunoassay data suggests that the Sertoli cells produce an estradiol-17 beta-like compound from unlabeled testosterone and that this production is stimulated by FSH. However, the radioactive metabolite from all our studies that behaved chromatographically like estradiol--17 beta failed to crystallize to constant specific activity, while in each experiment, authentic radiolabeled estradiol-17 beta added as recovery tracer did. The data demonstrate that : 1) cultures of Sertoli cells from immature rats have 5 alpha-reductase, 3 alpha- and 17 beta-hydroxysteroid oxidoreductase activities; 2) these enzymes may be affected by FSH; 3) based on radiolabeled metabolic techniques, Sertoli cells were unable to biotransform testosterone to estradiol-17 beta even in the presence of FSH.

3-Oxo-5-alpha-Steroid 4-Dehydrogenase↗
PubMed1979

Effect of ionic strength on the interaction of androgens with Sertoli cell nuclei.

Only 35-50% of the label accumulated after incubation of cultured Sertoli cells with 3H-testosterone was readily extractable with 0.4 M KCl during a 1 h exposure. The degree of extractability was relatively constant over the pH range 7.0-8.5 but could be increased by prolonged (15 h) exposure. While 0.1 M KCl extracted a measurable amount of label, 0.4 M KCl was significantly more efficient. Furthermore, a higher proportion of the material extracted with 0.4 M KCl was associated with macromolecular species. After a 45 min exposure to 3H-testosterone, the nuclear fraction contained primarily labeled testosterone and its 5 alpha-reduced metabolites. The relative distribution of these metabolites between salt-resistant and readily extractable forms varied between experiments. In contrast, 3H-R1881 (17 beta-hydroxy-17-methylestra-4,9,11-trien-3-one) remained essentially intact in the nuclear fraction but also was only 35% extractable with 0.4 M KCl. In conclusion, although the quantitative aspects of salt extractability appear to depend to some extent upon the extraction conditions, it is apparent that the Sertoli cell nuclear fraction accumulates a significant amount of androgen in a form which is relatively resistant to removal with 0.4 M KCl. The biological significance of this phenomenon remains to be established.

Animals↗
PubMed1979

Pneumocephalus after ventriculoatrial shunt.

Pneumocephalus developing after a ventriculoatrial shunting procedure is described. This was found to be caused by a defect in the posterior wall of the frontal sinus, possibly secondary to chronically increased intracranial pressure. A review of the pertinent literature revealed only two other similar cases.

Adult↗
PubMed1979

Inhibin production by Sertoli cells in culture.

Studies on the secretion of inhibin and its mode of action were carried out in vitro, utilizing cell cultures. Isolated rat Sertoli cells secreted an inhibin-like heat-labile, non-dialysable substance, Sertoli Cell Factor (SCF), which could selectively suppress FSH secretion by rat anterior pituitary cells. SCF selectively suppressed the basal and GnRH-stimulated FSH release as well as the de-novo synthesis of FSH by acting directly on the pituitary cells. In 1 out of 5 experiments, SCF also suppressed the synthesis of LH, possibly by affecting the overall protein synthesis. Under similar culture conditions, Sertoli cells isolated from animals between 18 and 90 days of age secreted comparable amounts of SCF. In contrast, anterior pituitary cells from adult rats (60-90 days old) were considerably more sensitive to SCF than pituitary cells obtained from younger (18-33 days old) animals, suggesting that decline in circulating FSH level, occurring at approximately 35 days of age, may result from increased pituitary sensitivity to inhibin. Besides identifying the Sertoli cells as the site of inhibin production in the testis, these studies demonstrated direct action of inhibin at the pituitary cell level, resulting in suppression of FSH synthesis and release.

Animals↗
PubMed1978

Effects of estrogen on human seminiferous tubules: light and electron microscopic analysis.

Morphological features of testes from four subjects after long-term treatment with ethinyl-estradiol (1--2 mg daily) and from five non-treated patients with prostatic carcinoma were studied by means of light and electron microscopy. The non-treated seminiferous tubules contained spermatagonia, spermatocytes, spermatids, spermatozoa, and Sertoli cells and showed no apparent morphologic abnormalities. On the other hand, the estrogen-treated testicular tissue contained only Sertoli cells and very few spermatogonia within the seminiferous tubules. The nuclei of Sertoli cells occasionally contained two nucleoli. The nucleolar complex was composed of a fine granular spherical body surrounded by a large granular, reticular network. The cytoplasm of the Sertoli cell contained osmiophilic lipid-like bodies. These lipid-like bodies appeared more pronounced in patients treated with higher doses of estrogen, suggesting a diminution of secretion of Sertoli cell hormone. Blebbing from the outer nuclear membrane appeared to have formed numerous vesicles in the cytoplasm. These vesicles usually contained several membrane-bound granular bodies. In the estrogen-treated testes, there was a marked increase in thickness and infolding of the basement membrane. Two unusual patterns of the basement membrane were observed: one appeared to be a reticular anastomosis, the other, an electron-dense trilayer. The morphological picture of seminiferous tubules from the estrogen-treated subjects appeared to correlate well with the suppressed plasma and testicular levels of testesterone, the undetectable circulating gonadotrophins, and the elevated plasma and testicular levels of estradiol-17 beta reported by Rodriguez-Rigau et al. ('77).

Adult↗
PubMed1978

Inhibition of de novo synthesis of FSH by the Sertoli cell factor (SCF).

The effects of SCF, a substance produced by isolated rat Sertoli cells in culture, on the synthesis of FSH and LH were studied in vitro. Anterior pituitaries from adult male rats were organ-cultured 24-48h in the presence and absence of SCF in the culture medium. The incorporation of 3H-leucine into FSH and LH was determined following 6h incubation with this labelled precursor and immunoprecipitation with specific FSH or LH antibodies. Total FSH and LH were measured by radioimmunoassay. The results indicate that SCF can selectively reduce the incorporation of 3H-leucine into immunoprecipitable FSH without decreasing the incorporation into LH.

Animals↗
PubMed1978

Progesterone metabolism by cultured Sertoli cells.

The ability of Sertoli cells to metabolize progesterone to testosterone (T) and 5alpha-dihydrotestosterone (DHT) was investigated in vitro. Cultures of Sertoli cells isolated from testes of 80-day-old rats were incubated with [7(n)-3H]progesterone (10 muCi/3.0 nmol) for 0.5, 1, 2, and 3 h. The amount of progesterone converted to T, androstenedione (A), DHT, 17alpha-hydroxyprogesterone, and 20alpha-dihydroprogesterone was calculated on the basis of crystallization data. The amount of substrate converted to the various steroids increased between 0.5-3 h of incubation. During this period, T increased 6-fold; A, 2-fold; DHT, 4-fold; 17alpha-hydroxyprogesterone, 3-fold; and 20alpha-dihydroprogesterone, 12-fold. The amount of substrate converted to C-19 steroids (T, A, and DHT) increased linearly with time; 19.4 ng androgen/1 x 10(6) cells were formed within 3 h, the largest amount (11.83 ng) being DHT. Although the amount of 3H-labeled C-19 steroids formed from [3H]-progesterone by Sertoli cells is relatively small (1.8% conversion) compared to T formation by whole testicular tissue or by isolated interstitial cells, the ability of Sertoli cells to form T and DHT from progesterone may be physiologically important in the local regulation of Sertoli cell function and spermatogenesis.

Animals↗
PubMed1978

Effects of an LH-RH analogue in male rats pretreated with oestradiol benzoate.

Treatment of adult male rats with oestradiol benzoate (OB) for 21 days significantly decreased the body, testicular and accessory sex organ weights but increased anterior pituitary weight. OB treatment also significantly suppressed circulating FSH and LH levels as well as plasma and testicular concentrations of testosterone. The seminiferous tubules and interstitial cells were partly atrophied, and there was some effect on spermatogenesis, with step 14 to 19 spermatids being fewer than normal. Rats treated with OB for 21 days were then treated daily with LH-RH analogue ((D-Leu6, des-Gly-NH2(10))-LH-RH-ethylamide), to see if testicular function could be recovered. Circulating gonadotrophins were significantly elevated, testicular histology was normal and testicular and plasma testosterone concentrations and the accessory sex organ weights remained suppressed. These results suggest possible extra-pituitary effects of the LH-RH analogue, including a direct action on the testes and/or accessory sex organs.

Animals↗
PubMed1978

Unusual anti-reproductive properties of the analog [d-Leu6,des-Gly-NH2(10)]-luteinizing hormone-releasing hormone ethylamide in male rats.

Nanogram quantities of a luteinizing hormone-releasing hormone (LHRH) agonist, [D-Leu6,des-Gly-NH2(10)]-LHRH ethylamide, were injected into immature male rats twice daily for 40 days. Treatment with the analog significantly increased serum luteinizing hormone and follicle-stimulating hormone levels, but suppressed accessory sex organ weights. Plasma and testicular concentrations of testosterone were also significantly decreased. The agonist did not alter body, pituitary, or testis weights. Spermatogenesis and the morphology or density of the Leydig cells also appeared not to be affected. A possible direct effect of the analog on the testes is discussed.

Animals↗
PubMed1977

Direct measurement of androgen receptors in cultured Sertoli cells.

Cytoplasmic and nuclear forms of macromolecules with the properties of androgen receptors have been demonstrated by direct labeling techniques in cultured Sertoli cells. The cytoplasmic form was excluded from Sephadex G-200 and could be distinguished from androgen binding protein (ABP) on the basis of size, heat stability, relative electrophoretic mobility, and binding complex dissociation rate. When cultured Sertoli cells were incubated with 3H-testosterone, a time- and temperature-dependent accumulation of label into the nuclear fraction was observed, 46% of which crystallized as authentic testosterone. Specific binding was saturable with an apparent association constant of 0.4nM-1. Approximately 30% of the nuclear bound hormone was extracted within 1 h by 0.4M KCl and 34% of this was associated with macromolecular species as measured by gel filtration. Unlabeled androgens and to some degree progestogens competed with 3H-testosterone for binding sites. These data constitute direct evidence that Sertoli cells contain androgen receptors.

Animals↗