The alcohol dehydrogenase genes of the yeast, Saccharomyces cerevisiae: isolation, structure, and regulation.
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Alcohol Oxidoreductases↗
Biomedical subjects
J Osterman
Publications and source records attributed to J Osterman.
Estradiol receptors of two distinct populations of Leydig cells.
UNLABELLED: The optimal concentrations of molybdate (Mo) to prevent thermal inactivation of estrogen receptor (ER) were found to be 5-20 mM. Using metrizamide density centrifugation, interstitial cells of adult Sprague-Dawley rat testes (2-3 months of age) can be separated into 5 distinct bands. Band 2 (B2) and 3 (B3) cells represented functionally different Leydig cells. For measurement of cytosolic ER, purified Leydig cells (B2 and B3 cells) were homogenized in 10 mM Tris-EDTA buffer with 5 mM of Mo (pH 7.4) and centrifuged at 105,000xg for 60 min. Cytosols were used immediately for ER determination. ER of B2 cells was 24.0 +/- 3.1 fmol/mg protein (mean +/- SE, n = 7), which was significantly higher than that of B3 cells, 18.6 +/- 3.2 fmol/mg protein (n = 7), p less than 0.005. The association constants of these two populations of Leydig cells for E2 receptor were comparable, 5.1 X 10(10)M-1 for B2 cells and 4.2 x 10(10)M-1 for B3 cells. In response to hCG 100 IU s.c., ER of B2 cells was reduced to 2.0 +/- 0.38 fmol/mg protein (n = 5), which was 8.4% of the control B2 cells. ER of B3 cells was almost completely depleted by the same dose of hCG, to 0.70 +/- 0.38 fmol/mg protein, 3.7% of the control B3 cells. IN CONCLUSION: B2 cells contained higher amounts of ER under basal conditions than B3 cells, and hCG-induced desensitization caused depletion of ER of both B2 and B3 cells.
Animals↗
Protein kinase activity of purified Leydig cells: low protein kinase activity causes impaired steroidogenesis by band two cells.
Using a 0-32% continuous metrizamide density gradient, interstitial cells could be separated into five distinct bands. Cells localized in bands 1 (B1), 2 (B2), and 3 (B3) were isolated and incubated for 1h with or without human chorionic gonadotropin (hCG). Both B2 and B3 cells responded to hCG with increased cyclic AMP formation, but only B3 cells produced significantly more testosterone. Protein kinase activity of B2 cells was found to be extremely low compared with B1 and B3 cells. Additional treatment of B3 cells with collagenase did not cause any change in protein kinase activity. These results indicate that decreased protein kinase activity may be responsible for impaired testosterone synthesis in B2 cells.
Animals↗
The aging Leydig cell V. Diurnal rhythms in aged men.
Basal circulating levels of progesterone, 17 alpha-OH-progesterone, dehydroepiandrosterone, androstenedione, testosterone and oestradiol-17 beta were measured in 'young' (median age 34 years) and 'old' (median age 73 years) normal males between 08.30 and 17.00 h. Diurnal rhythms for 17 alpha-OH-progesterone, dehydroepiandrosterone, androstenedione and testosterone were observed in both young and old men. No rhythms were discernible for progesterone or oestradiol-17 beta in both age groups.
Adult↗
The aging Leydig cell: VI. Response of testosterone precursors to gonadotrophin in men.
The effects of a single im injection of human chorionic gonadotrophin (hCG) on circulating testosterone precursor levels at 0, 1-6, 24, 48 and 72 h were examined in normal young adult (mean age 34 years) and normal aged men (mean age 74 years) Basal 08.30- 09.00 h concentrations of androstenedione and dehydroepiandrosterone were lower in aged men while progesterone levels were not significantly different from young men. A significant biphasic increase of circulating progesterone was observed in young men, characterized by an early peak at 2 h (33% above basal) and a secondary peak at 24 h (49% above basal). In old men there were no increases in circulating progesterone levels following hCG treatment during the early (1-6 h) or late (24-72 h) periods. There were not discernable increases in circulating dehydroepiandrosterone levels following hCG administration in both groups of men. Androstenedione levels in young men. Androstenedione levels in young men did not change during the first 6 h following hCG but increased significantly at 48 and 72 h, while in old men there was a small peak at 4 h (which was not statistically significant) and a secondary significant rise at 48 and 72 h. However, early and late stimulated absolute levels for androstenedione were lower in the aged population. Thus, there are differences in precursor concentrations in the basal state and in response to hCG in aged men.
Age Factors↗
Direct inhibition of rat leydig cell function by tamoxifen.
The effects of tamoxifen on rat testicular steroidogenesis were studied using dispersed interstitial cells. Tamoxifen significantly inhibited LH-, and 8-bromo-adenosine 3',5'-monophosphate (8-bromo-cyclic AMP)-stimulated testosterone synthesis in a dose-dependent manner. Tamoxifen (10(-5)M) also reduced LH-stimulated cyclic AMP formation. The addition of equimolar concentrations of 17 beta-estradiol or tamoxifen separately to interstitial cells resulted in similar inhibition of LH-stimulated testosterone synthesis. When equimolar concentrations of 17 beta-estradiol and tamoxifen were added concomitantly to interstitial cells, the inhibition was additive. Present studies demonstrate that tamoxifen has direct inhibitory effects on testicular steroidogenesis: both at the plasma membrane resulting in decreased cyclic AMP formation and also at steps subsequent to cyclic AMP.
Animals↗
The aging Leydig cell: 2. Two distinct populations of Leydig cells and the possible site of defective steroidogenesis.
Using metrizamide gradient centrifugation two populations of Leydig cells were found in both 60-90 day-old and 24 month-old rats. Cells from both Band 2 (B2) and Band 3 (B3) responded to LH stimulation with increased cyclic AMP formation; however, only B3 cells produced significant amounts of testosterone. Cells from both B2 and B3 of the old rats synthesized less cyclic AMP and testosterone than cells from their younger counterparts. In response to LH stimulation, 0.01 - 1.0 mIU/ml, no appreciable difference of cyclic AMP formation could be detected between young and old Leydig cells. Maximal testosterone production occurred when 1 mIU/ml LH was used. Only when LH concentration was increased to 10 and 100 mIU/ml, did young Leydig cells produce significantly more cyclic AMP than old Leydig cells. After addition of 5X10(-7)M of pregnenolone or progesterone to the incubation medium, both young and old Leydig cells produced comparable amounts of testosterone. These results demonstrate no impairment of old rat Leydig cells to synthesize testosterone from pregnenolone and progesterone.
Aging↗
The aging Leydig cell: VII. Cytoplasmic estradiol receptors.
Plasma estradiol and cytosolic estradiol receptor levels of testes were determined in a group of young (2-3 months) and old (24 months) Sprague-Dawley rats. Estradiol binding sites for the young rats averaged 5.6 +/- 0.3 fmol/mg protein (x +/- SE, n=12), which was comparable to that of the old rats, 5.7 +/- 0.3 fmol/mg protein (n=12). Using Scatchard analyses, the association constants at equilibrium of estradiol receptor binding of the old and young rats were the same, 6.1 x 10 10 M-1. Plasma estradiol levels were also similar in both groups-19.6 +/- 2.8 pg/ml (n=14) for the young and 19.2 +/- 2.6 pg/ml (n=10) for the old rats. Our results suggest that impaired testosterone biosynthesis in old rats was not due to elevated plasma estradiol levels or to differences in testicular estradiol receptor content.
Aging↗
Regulation of cyclic guanosine 3',5'-monophosphate in interstitial cells of the rat testis.
The present studies were performed to evaluate the role of luteinizing hormone (LH) and calcium on cyclic guanosine 3',5'-monophosphate (cyclic GMP) formation in rat testicular interstitial cells. Dose related increases were observed in both intra-and extra-cellular cyclic GMP when various concentrations of LH (1, 10, 100 mlU/ml) were added to the purified Leydig cells. Cyclic GMP was also increased significantly with calcium ionophore A23187 at concentrations of 0.1, 1 and 10 microgram/ml. Adding LH concomitantly with A23187 resulted in a synergistic response and greatly enhanced cyclic GMP formation. When interstitial cells were incubated in calcium-free medium with 1 mM EGTA, the effects of LH and 123187 on cyclic GMP formation were abolished. These data suggest that LH and A23187 can increase cyclic GMP formation in interstitial cells and this response requires extracellular calcium.
Animals↗
Gossypol inhibits testicular steroidogenesis.
Gossypol, a compound isolated from cottonseed, has been used in the People's Republic of China as an antifertility agent in men. It was reported that gossypol is highly effective in reducing sperm count. Our study suggests that gossypol inhibits luteinizing hormone, 8-bromo-adenosine 3',5'-monophosphate-induced testosterone formation, and the conversion of pregnenolone to testosterone in isolated rat interstitial cells. Serum testosterone levels were also significantly reduced in rats after 1 week of treatment with gossypol. Oligospermia and azoospermia in men caused by gossypol may be secondary to decreased testosterone biosynthesis.
Animals↗
Full recovery from severe orthostatic hypotension after vacor rodenticide ingestion.
A patient who had severe orthostatic hypotension secondary to ingesting Vacor, a rodenticide containing N-3 pyridilmethyl-N'-nitrophenyl urea (PNU), fully recovered from this initially disabling condition 11 months after poisoning. Initial treatments with elastic stockings, fludrocortisone acetate, and dihydroergotamine mesylate resulted in no obvious improvement of his orthostasis. Findings from a hemodynamic study performed with the patient was severely orthostatic suggested functional impairment of vascular adrenergic nerve terminals as a major lesion. A similar study after recovery from orthostasis showed that the baroreceptor reflex mechanism returned to normal. This report shows that initially severe and disabling orthostatic hypotension may not be a hopelessly permanent sequela of PNU intoxication and that a gradual, spontaneous full recovery from orthostasis is possible.
Adult↗
The effects of cytochalasin B on testosterone synthesis by interstitial cells of rat testis.
The present study examined the effects of cytochalasin B on various steps in the luteinizing hormone (LH)-stimulated increase in testosterone synthesis by collagenase-dispersed interstitial cells of adult rat testis. Cytochalasin B at a concentration range of 0.1--50 microM inhibited the LH-stimulated increase in testosterone synthesis in a dose-dependent manner. Both intracellular and medium (released) testosterone levels were reduced, thus indicating that the decrease was not due to the accumulation of testosterone inside the cell as a result of cytochalasin B treatment. Cytochalasin B also inhibited the 8-bromocyclic AMP and pregnenolone-stimulated testosterone synthesis in a similar dose-dependent manner. Cytochalasin B at the two higher doses (10 and 50 microM) also inhibited the LH-stimulated generation of cyclic AMP by interstitial cells. However, this drug had no effect on basal testosterone synthesis except at the highest concentration added. Previous studies on adrenocorticotropic hormone (ACTH)- and LH-stimulated increase in glucocorticoid and testosterone synthesis in adrenal and Leydig cells, respectively, demonstrated that cytochalasin B or anti-actin inhibited the transport of cholesterol into mitochondria. The present studies suggest that cytochalasin B inhibits at least two additional steps in the LH-stimulated increase in testosterone synthesis: (1) the generation of cyclic AMP at the level of the plasma membrane, and (2) the conversion of pregnenolone to testosterone at the level of the smooth endoplasmic reticulum. It remains to be established whether these are direct effects of cytochalasin B, or whether they are mediated by disruption of microfilaments by cytochalasin B.
8-Bromo Cyclic Adenosine Monophosphate↗
The effects of calcium ionophore A23187 on interstitial cell steroidogenesis.
The present study was performed to evaluate the effects of calcium ionophore A23187 on adenosine 3',5'-monophosphate (cyclic AMP) and testosterone production in rat interstitial cells. Interstitial cells were incubated in Krebs-Ringer solution with varying amounts of luteinizing hormone, pregnenolone, or A23187. Cyclic AMP and testosterone were measured in the incubation medium after 4 h incubation. A23187 (0.01--10 microgram/ml) caused progressive increases of cyclic AMP formation (from 0.18 +/- 0.02 (S.E.) pmol/10(6) cells for the control of 0.42 +/- 0.02 pmol/10(6) cells, P less than 0.025), while testosterone production remained unaltered. When varying amounts of A23187 were added concomitantly with luteinizing hormone (5 IU/l), A23187 inhibited luteinizing hormone-induced steroidogenesis in a dose-dependent manner, but it had no effect on luteinizing hormone-induced cyclic AMP formation. When pregnenolone (10(-6) M) was added to the cells, testosterone formation increased from 1.50 +/- 0.22 to 8.46 +/- 1.65 ng/10(6) cells. A23187 (1 microgram/ml) had no discernable effect on the conversion of pregnenolone to testosterone. The main effect of increased cytosol calcium on steroidogenesis seems to be at the steps beyond adenylate cyclase-cyclic AMP. These results suggest that calcium is important for the conversion of cholesterol to pregnenolone, while the steps beyond pregnenolone are relatively independent of Ca2+.
Animals↗
Direct inhibition of testosterone synthesis in rat testis interstitial cells by ethanol: possible sites of action.
The present in vitro studies using interstitial cells of adult rat testes demonstrated that ethanol inhibits LH- and 8-bromo-cyclic AMP-stimulated testosterone synthesis, pregnenolone- and progesterone-stimulated testosterone synthesis, and basal testosterone synthesis. However, the patterns of inhibition following exposure to 0.22 to 880 or 1100 mM ethanol were different. In general, the inhibition curves for LH-, 8-bromo-cyclic AMP-, pregnenolone- and progesterone-stimulated testosterone synthesis were biphasic, with a gradual slope from 0.22 to 220 mM ethanol, and a sharper slope with concentrations of ethanol greater than 220 mM. Basal testosterone synthesis was reduced only to 74% of control with ethanol concentrations up to 44 mM, and higher concentrations of ethanol reduced testosterone synthesis no further. The effect of ethanol on Lh-stimulated cyclic AMP accumulation showed an even different pattern: some of the lower concentrations of ethanol inhibited cyclic AMP accumulation, while higher levels of ethanol progressively increased cyclic AMP accumulation. These studies demonstrate that isolated interstitial cells are highly sensitive to the direct effects of ethanol; they also suggest that the principle site of ethanol inhibition may be at the level of the smooth endoplasmic reticulum where progesterone is converted to testosterone.
8-Bromo Cyclic Adenosine Monophosphate↗
The aging Leydig cell: 1. Testosterone and adenosine 3',5'-monophosphate responses to gonadotropin stimulation in rats.
Plasma testosterone levels before and after a single injection of hCG were significantly lower in 24-month old rats than 60--90 day old animals (p less than 0.001). Even with repeated hCG administration for three weeks, plasma testosterone levels of old rats could not be restored to levels present in unstimulated young rats. In response to in vitro LH and 8-bromo-cyclic AMP stimulation, purified young Leydig cells produced significantly higher amounts of testosterone than Leydig cells from old rats. Maximal testosterone formation of the young Leydig cells in response to LH was 42.0 +/- 6.88 ng/10(6) cells, while cells from old rats produced only 16.8 +/- 3.69 ng/10(6) cells (p less than 0.01). However, the dose of LH at which one half maximal response (ED50) occurred was 0.1 mIU/ml for young Leydig cells and 0.05 mIU/ml for old Leydig cells. Basal and 1.0 mIU LH-stimulated cyclic AMP formation were comparable in both groups, but cyclic AMP formation in response to 10 mIU of LH was significantly less in the old rats (p less than 0.05). Present results demonstrate impaired steroidogenic capacity of old rats both in vivo and in vitro. Decreased testosterone response in old rats most likely is the consequence of understimulation of Leydig cells by gonadotropin; however, there appear to be additional intrinsic defects in old Leydig cells.
Animals↗
Testosterone and 17 OH-progesterone responses in men to 3 h LH infusions.
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Adult↗
Morning and evening human Leydig cell responses to hCG.
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Adult↗
A comparative trial of transsphenoidal hypophysectomy and estrogen suppression with aminoglutethimide in advanced breast cancer.
We compared two treatment regimens, transsphenoidal hypophysectomy and estrogen suppression with aminoglutethimide in women with metastatic breast carcinoma. Three of fourteen patients experienced partial objective tumor regression with a median duration of 4.6 months following hypophysectomy, whereas 10 of 21 women receiving aminoglutethimide responded (2 complete, 8 partial) with a median duration of 11.5 months. Side effects in the medical group were minimal while surgical complications included 2 cases of CSF rhinorrhea, one leading to meningitis and death. In patients receiving aminoglutethimide, urinary free cortisol and plasma dehydroepiandrosterone sulfate fell significantly as did plasma estrone and estradiol. In the hypophysectomy group, anterior-pituitary function testing postoperatively revealed adequate suppression of gonadotropin and prolactin secretion but incomplete inhibition of the ACTH-cortisol axis in 4 of 7 surgical patients studied. Five patients initially treated with hypophysectomy experienced a further reduction of plasma (and urinary) estrone and estradiol levels when given aminoglutethimide. We conclude that estrogen suppression therapy with aminoglutethimide is a feasible alternative to surgical hypophysectomy in providing endocrine suppression and palliation in advanced breast carcinoma.
Adult↗