The Experts below are selected from a list of 189 Experts worldwide ranked by ideXlab platform
Denis A. Magoffin - One of the best experts on this subject based on the ideXlab platform.
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stem cell factor and insulin like growth factor i stimulate luteinizing hormone independent differentiation of rat ovarian theca cells
Biology of Reproduction, 2001Co-Authors: Chris T F Huang, Stacy R Weitsman, Barbara N Dykes, Denis A. MagoffinAbstract:The signal initiating ovarian theca cell (TC) differentiation is gonadotropin independent because theca precursor cells do not contain LH receptors. Previously we demonstrated that preantral follicles produce paracrine TC differentiating factors that promote androgen production by an LH-independent mechanism. This study tested the effects of two granulosa cell-produced peptides, insulin-like growth factor-I (IGF-I) and stem cell factor (SCF), on TC differentiation and androgen production. Neutralizing antibodies to either IGF-I or SCF blocked the stimulatory effects of follicle-conditioned medium on TC precursor differentiation more than 90%. The TC isolated from the ovaries of hypophysectomized immature rats by percoll gradient centrifugation were cultured (48 h) with and without SCF (0-100 ng/ml) and IGF-I (0-100 ng/ml) to test their effects on TC differentiation. Androsterone in the medium was measured by RIA. Luteinizing hormone receptor, steroidogenesis acute regulatory protein (StAR), CYP11A, CYP17, and 3beta-hydroxysteroid dehydrogenase (3beta-HSD) mRNAs were measured by specific reverse transcriptase polymerase chain reaction assays. Stem cell factor or IGF-I alone did not stimulate Androsterone production but in combination caused a concentration-dependent increase in Androsterone levels. Maximum Androsterone levels were less than those stimulated by LH (0.1 ng/ml) alone. Although IGF-I synergistically augmented LH stimulation of Androsterone production, SCF did not alter LH-stimulated Androsterone production in the presence or absence of IGF-I. Stem cell factor alone had no effect on LH receptor, StAR, CYP11A, and 3beta-HSD mRNA expression but decreased CYP17 mRNA levels. Insulin-like growth factor-I alone had no effect on StAR or CYP17 mRNA expression but increased LH receptor, CYP11A, and 3beta-HSD mRNA levels. In combination, SCF plus IGF-I increased the expression of all five mRNAs. These data support the conclusion that IGF-I and SCF are important regulators of TC differentiation.
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granulosa cell modulation of luteinizing hormone dependent androgen production by ovarian theca interstitial cells a temporal switch from suppression to augmentation stimulated by follicle stimulating hormone in vitro
Biology of Reproduction, 1995Co-Authors: Rob J Zachow, Denis A. MagoffinAbstract:The production of estradiol-170 (E2) by granulosa cells (GC) of the dominant follicle is dependent upon LH-stimulated synthesis of androgens by ovarian theca-interstitial cells (TIC). Recent evidence has pointed toward an intrafollicular paracrine system, regulated by FSH and involving GC, that may modulate the LH-dependent production of androgens by TIC. In the present study, the role of GC and FSH in modulating LH-dependent TIC Androsterone production was examined. In cultures of dispersed whole ovarian cells (containing populations of both GC and TIC) from intact immature rats, LH stimulated a 10-fold increase in Androsterone production (maximum Androsterone = 21.0 ± 1.1 ng/ml). By comparison, Androsterone production was increased 50-fold in LH-stimulated cultures of dispersed whole ovarian cells from hypophysectomized immature rats (108 18 ng Androsterone/ml). The EC5 for LH (0.02 0.001 ng/ml) was identical in the two cell preparations. We hypothesized that the lesser androgen production by whole ovarian cell cultures from intact rats was due to suppression by the GC. To investigate the role of GC in modulating TIC androgen production, highly purified TIC from immature hypophysectomized rats were cultured in the presence of GC obtained from intact immature rats. Increasing numbers of GC (2.5-100 x 103 GC per well) caused a progressive decrease in LH-dependent Androsterone production by TIC. Additionally, LH-dependent Androsterone production was suppressed by the conditioned medium from recombinant human FSH (rFSH)-stimulated GC (54% of the value for LHstimulated TIC controls), indicating the involvement of a GC-secreted paracrine factor or factors. E 2 concentrations in the medium were approximately 30-fold below those previously shown to impair TIC androgen production in this model. Up to 48 h in culture, rFSH potentiated the suppressive effect of GC on TIC Androsterone production in cocultures; however, rFSH stimulated LH-dependent Androsterone production at 96 h. These results indicate that GC suppress LH-dependent TIC Androsterone production by a paracrine mechanism. Importantly, the initial inhibitory effect was potentiated by FSH; but with continued FSH treatment, a stimulatory effect was detected. Hence, FSH may induce GC to change from production of one or more inhibitory paracrine factors to production of stimulatory paracrine factors that can modulate LH-dependent androgen production by TIC. This may be a mechanism to ensure the viability and promote selection of the dominant follicle.
Michio Matsui - One of the best experts on this subject based on the ideXlab platform.
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Large deletion of Androsterone UDP-glucuronosyltransferase gene in the inherited deficient strain of Wistar rats.
Biochimica et biophysica acta, 1992Co-Authors: Hiroshima Homma, Hiroyuki Kawai, Miho Kubota, Michio MatsuiAbstract:Abstract LA Wistar rats have a deficiency of Androsterone UDP-glucuronosyltransferase (UDPGT) and are present in Wistar rat colonies around the world. In order to clarify the molecular mechanism of the deficiency, Androsterone UDPGT cDNA clone, pGT2 was isolated from rat liver cDNA library and was digested with restriction enzymes to afford three probes for Northern and Southern blot analyses in HA (normal), heterozygous LA and LA Wistar rats. In Northern blot analysis, Androsterone UDPGT mRNA was totally absent in LA Wistar rat liver. Southern blot analysis suggested a large deletion of Androsterone UDPGT gene in the rats. Genomic DNA amplifications with synthetic primers which have nucleotide sequences corresponding to the 5′-region of Androsterone UDPGT cDNA, suggested that Androsterone UDPGT gene has exon 1 with a length of some 700 bp and that this exon is deleted in LA Wistar rats. Based on these lines of evidence, it is concluded that the large portion of Androsterone UDPGT gene is deleted in LA Wistar rats, which results in the absence of Androsterone UDPGT mRNA and consequently the corresponding enzyme protein.
P A Elder - One of the best experts on this subject based on the ideXlab platform.
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plasma Androsterone epiAndrosterone sulfates as markers of 5α reductase activity effect of finasteride in normal men
Steroids, 1997Co-Authors: J G Lewis, P M George, P A ElderAbstract:Abstract Plasma Androsterone/epiAndrosterone sulfates, dehydroepiAndrosterone sulfate, dihydrotestosterone, testosterone, androstenedione, and cortisol were measured in three normal adult men before and following finasteride administration (5 mg/day). Plasma Androsterone/epiAndrosterone sulfates and dihydrotestosterone declined in parallel to 50% of basal levels with little change in either dehydroepiAndrosterone sulfate, cortisol, or androstenedione. The results suggest that the direct measurement of plasma Androsterone/epiAndrosterone sulfates by enzyme-linked immunosorbent assay provide similar information to plasma dihydrotestosterone and therefore provide a simple alternative for the assessment of 5α-reductase activity.
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Plasma Androsterone/epiAndrosterone sulfates as markers of 5α-reductase activity: Effect of finasteride in normal men
Steroids, 1997Co-Authors: J G Lewis, P M George, P A ElderAbstract:Abstract Plasma Androsterone/epiAndrosterone sulfates, dehydroepiAndrosterone sulfate, dihydrotestosterone, testosterone, androstenedione, and cortisol were measured in three normal adult men before and following finasteride administration (5 mg/day). Plasma Androsterone/epiAndrosterone sulfates and dihydrotestosterone declined in parallel to 50% of basal levels with little change in either dehydroepiAndrosterone sulfate, cortisol, or androstenedione. The results suggest that the direct measurement of plasma Androsterone/epiAndrosterone sulfates by enzyme-linked immunosorbent assay provide similar information to plasma dihydrotestosterone and therefore provide a simple alternative for the assessment of 5α-reductase activity.
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Plasma Androsterone/epiAndrosterone sulfates as markers of 5 alpha-reductase activity: effect of finasteride in normal men.
Steroids, 1997Co-Authors: J G Lewis, P M George, P A ElderAbstract:Plasma Androsterone/epiAndrosterone sulfates, dehydroepiAndrosterone sulfate, dihydrotestosterone, testosterone, androstenedione, and cortisol were measured in three normal adult men before and following finasteride administration (5 mg/day). Plasma Androsterone/epiAndrosterone sulfates and dihydrotestosterone declined in parallel to 50% of basal levels with little change in either dehydroepiAndrosterone sulfate, cortisol, or androstenedione. The results suggest that the direct measurement of plasma Androsterone/epiAndrosterone sulfates by enzyme-linked immunosorbent assay provide similar information to plasma dihydrotestosterone and therefore provide a simple alternative for the assessment of 5 alpha-reductase activity.
Hiroshima Homma - One of the best experts on this subject based on the ideXlab platform.
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Large deletion of Androsterone UDP-glucuronosyltransferase gene in the inherited deficient strain of Wistar rats.
Biochimica et biophysica acta, 1992Co-Authors: Hiroshima Homma, Hiroyuki Kawai, Miho Kubota, Michio MatsuiAbstract:Abstract LA Wistar rats have a deficiency of Androsterone UDP-glucuronosyltransferase (UDPGT) and are present in Wistar rat colonies around the world. In order to clarify the molecular mechanism of the deficiency, Androsterone UDPGT cDNA clone, pGT2 was isolated from rat liver cDNA library and was digested with restriction enzymes to afford three probes for Northern and Southern blot analyses in HA (normal), heterozygous LA and LA Wistar rats. In Northern blot analysis, Androsterone UDPGT mRNA was totally absent in LA Wistar rat liver. Southern blot analysis suggested a large deletion of Androsterone UDPGT gene in the rats. Genomic DNA amplifications with synthetic primers which have nucleotide sequences corresponding to the 5′-region of Androsterone UDPGT cDNA, suggested that Androsterone UDPGT gene has exon 1 with a length of some 700 bp and that this exon is deleted in LA Wistar rats. Based on these lines of evidence, it is concluded that the large portion of Androsterone UDPGT gene is deleted in LA Wistar rats, which results in the absence of Androsterone UDPGT mRNA and consequently the corresponding enzyme protein.
Virendra B Mahesh - One of the best experts on this subject based on the ideXlab platform.
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an autoregulatory process for androgen production in rat thecal interstitial cells
Biology of Reproduction, 1993Co-Authors: Deborah A. Simone, Virendra B MaheshAbstract:The regulation of androgen production by thecal-interstitial cells (TIC) of the mammalian ovary is a complex process. Although androgen production is primarily controlled by LH, a variety of factors have been demonstrated to alter LH-stimulated androgen production. It is uncertain, however, if an androgen-mediated autoregulatory process for androgen production exists in TIC. To determine the existence of this phenomenon, TIC obtained from ovaries of immature hypophysectomized rats were enriched by Percoll density gradient centrifugation. When TIC (20,000 viable cells/0.2 ml/well) were cultured for 48 h in the presence of a maximal concentration of hCG (0.2 ng/ml), Androsterone production was increased 26-fold versus control levels. Treatment with increasing concentrations (5-1000 nM) of the synthetic androgen 17 beta-hydroxy-7 alpha,17 alpha-dimethyl-4-estren-3-one (mibolerone) inhibited hCG-stimulated Androsterone production by an average of 32% at every dose tested. Mibolerone (100 nM) alone was without effect on basal levels of androgens. The addition of insulin (100 ng/ml) or insulin-like growth factor I (100 ng/ml) to TIC cultures did not alter the basal accumulation of Androsterone but significantly augmented hCG-induced androgen production by 2- and 3-fold, respectively, versus controls. Concomitant treatment with mibolerone (100 nM) decreased the synergistic action of insulin or IGF-I on hCG-stimulated Androsterone synthesis by 46% and 40%, respectively. To elucidate the mechanism(s) of action of mibolerone, we investigated the effects on 8-bromo-cAMP-stimulated androgen production. At a dose of 0.1 mM 8-bromo-cAMP, Androsterone production was maximally stimulated to levels observed with 0.2 ng/ml hCG. In the presence of mibolerone (100 nM), cAMP-induced Androsterone synthesis was inhibited by 41%. This result suggested that mibolerone was acting at a site distal to cAMP formation. Additional evidence revealed that through the use of the combination of cAMP analogs, N6-monobutyryl-cAMP (50 microM) and 8-bromo-cAMP (75 microM)--which are known activators of the cAMP-dependent protein kinase isoenzymes PKA I and II--Androsterone synthesis was increased by 130-fold over basal levels. Treatment with mibolerone (100 nM), however, reduced this cAMP-stimulated androgen synthesis by 51%. Therefore, the results demonstrate the existence of an autoregulatory process for androgen production in TIC, which may be important in limiting the overproduction of androgens.