Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:2.7.7.49 (reverse transcriptase)
31,746 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Human chorionic gonadotropin (hCG)--a pregnancy-associated immunomodulating hormone--has been recently shown in vitro to suppress reverse transcriptase activity in chronically HIV-infected lymphocytes and monocytes and to block viral transmission resulting from cell-cell contact between virus-carrying lymphocytes and placental trophoblasts. In further pursuit of the query into the mechanism of action, purified alpha and beta subunits of hCG were tested for the inhibition of p24 gag protein synthesis in virus-producing ACH-2 lymphocytes and U1 monocytes. Unlike the alpha subunit, beta-hCG displayed a distinct U-shaped dose response, characteristic of the effect of dimer hCG. Maximum inhibition of viral expression has been achieved at 10-100 ng/ml, the concentration corresponding to blood levels of beta-hCG in pregnant women. The doses that were several logs higher of normal levels seemed to increase viral production in monocytes. The data presented supports our original observations regarding the effect of intact hCG on HIV replication. While the mechanism of action remains to be established, the results suggest that the virus-interfering activity of hCG is determined by hormone-specific beta chain but not by the alpha subunit--shared with the family of glycoprotein hormones from the pituitary--follicle-stimulating hormone, luteinizing hormone and thyrotropin.
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PMID:Anti-HIV effect of beta subunit of human chorionic gonadotropin (beta hCG) in vitro. 753 8

The ontogeny of the follicle-stimulating hormone (FSH) receptor (R) gene expression was studied in the rat testis and ovary between day 12.5 or 14.5 of fetal life (f), respectively, and adulthood. In Northern blots hydbridized with a cRNA probe corresponding to a part of the extracellular domain of the FSHR, specific hybridization to testicular RNA was detected from day f18.5, and to ovarian RNA from postnatal day 7 onwards. The main transcripts in the testis were at all ages 7.0 kb and 2.5 kb in size. In the ovary, the main transcript was always 2.5 kb in size. In order to increase the sensitivity of mRNA detection, the FSHR gene expression was also analyzed using the reverse transcriptase-polymerase chain reaction (RT-PCR) technique with primer pairs corresponding to the near full-length FSHR mRNA or to its extracellular domain. The specificity of the PCR products was verified by Southern hybridization using a nested 32P-labeled cDNA probe. The results indicated that the expression of the extracellular domain of the FSHR was first detected on day f14.5 in the testis and on day f20.5 in the ovary. The full-length mRNA appeared in both sexes 2 days later, which is in agreement with earlier measurements of appearance of FSHR binding in the rat testis (day f17.5) and ovary (day 3 post partum). In situ hybridization using an antisense cRNA probe for FSHR demonstrated that, as early in development as specific hybridization was detected, it was confined to the Sertoli cells in the testis and to granulosa cells in the ovary. When compared with the developmental onset of the LHR gene expression (our earlier data), a major difference was observed in the ovary; the message encoding the extracellular LHR domain appeared > 10 days earlier than that corresponding to the full-length LHR message. In the case of mRNAs for the testicular LHR, and for FSHR of both sexes, the difference between the developmental appearance of the truncated and full-length RNA forms was only 2 days.
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PMID:Ontogeny of follicle-stimulating hormone receptor gene expression in the rat testis and ovary. 776 31

An important question in the pathogenesis and regulation of human gonadotroph adenomas is whether heterogeneous gonadotropin responses to gonadotropin-releasing hormone (GnRH) are due to dysregulation of GnRH receptor biosynthesis and/or cell-signaling pathways. We investigated gonadotropin responsiveness to pulsatile GnRH in 13 gonadotroph adenomas. All tumors had evidence of follicle-stimulating hormone (FSH) beta and alpha subunit biosynthesis using reverse transcriptase/polymerase chain reaction (RTPCR) techniques. Four tumors significantly increased gonadotropin and/or free subunit secretion during pulsatile 10(-8) M GnRH administration. The GnRH antagonist Antide (10(-6) to 10(-8) M) blocked secretory increases in all GnRH-responsive tumors. Gonadotropin and/or free subunit secretion increased after 60 mM KCl, confirming that GnRH nonresponsiveness was not due to intracellular gonadotropin depletion. We hypothesized that GnRH nonresponsiveness in these tumors may be due to GnRH receptor (GnRH-Rc) biosynthetic defects. RTPCR analyses detected GnRH-Rc transcripts only in responsive tumors and normal human pituitary. This is the first demonstration of a cell-surface receptor biosynthetic defect in human pituitary tumors. We conclude (a) one third of gonadotroph tumors respond to pulsatile GnRH in vitro, (b) GnRH-Rc mRNA is detected in human gonadotroph adenomas and predicts GnRH responsiveness, and (c) GnRH-Rc biosynthetic defects may underlie GnRH nonresponsiveness in gonadotroph tumors.
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PMID:Gonadotropin-releasing hormone receptor mRNA expression by human pituitary tumors in vitro. 820 Sep 67

The androgen-binding protein (ABP) gene P1 promoter directs cell-specific gene regulation of ABP secreted by Sertoli cells. A recent study using the mouse Sertoli cell line (MSC-1) with a luciferase reporter system demonstrated Sertoli cell-specific gene expression with 619 bp of P1 DNA. Furthermore, based on studies of the rat and human genes, several controversies developed over the promoter characteristics, including the promoter type, the transcription start site, and whether the gene is regulated directly by androgens. In this study, the answers to several of these controversies were deciphered using the MSC-1 cell model. The results of mutagenesis experiments were consistent with the presence of the major transcription start site at 36 bp upstream of the initiating Met residue. Modification of the initiator sequence at the start site reduced activity in MSC-1 and NIH3T3 fibroblast cells. Mutation of a putative modified TATA sequence or conversion to the consensus TATA sequence had no effect on activity. Modification of a consensus RNA splice sequence at the start site also had no effect on activity. Furthermore, a minor start site was localized 179 bp upstream of the major site using reverse transcriptase-polymerase chain reaction with various P1 primers (primer walking), primer extension, and cDNA cloning. RNA transcripts from the minor site contain an untranslated 5' exon but apparently encode the same protein as the major transcript. The effect of androgens on P1 expression was also investigated. Cotransfection experiments with pCMVAR, which encodes the androgen receptor, demonstrated that dihydrotestosterone had no effect on the activity in MSC-1 cells. Taken together, these experiments and previous studies indicate that the rat ABP promoter P1 is regulated at the major start site by an initiator element without a TATA sequence, and the gene appears not to be directly regulated by follicle-stimulating hormone or androgens.
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PMID:Analysis of promoter and androgen regulatory sequences required for optimal transcription of the rat androgen-binding protein gene. 953 95

The genes encoding the cynomolgus monkey gonadotropin subunits, alpha, follicle-stimulating hormone (FSH) beta and luteinizing hormone (LH) beta, were cloned by reverse transcriptase polymerase chain reaction (RT-PCR) using pituitary RNA. The predicted amino acid sequences displayed 82, 96 and 87% identity to human subunit sequences, respectively. Northern blot hybridization of monkey tissues revealed pituitary specific transcripts of 1.0 and 0.6 kb for the alpha and LHbeta subunit, respectively, and two bands of 1.8 and 0.65 kb for the FSHbeta. Upon sequencing LHbeta cDNAs from different monkeys, two polymorphic sites were detected, resulting in the amino acid transitions Ser32Thr and His60Arg. Restriction analysis revealed different homo- and heterozygous combinations of the polymorphic sites indicating linkage dysequilibrium. Transient co-expression of the alpha subunit together with the FSHbeta or LHbeta subunit in COS7 and CHO cells resulted in secretion of in vitro bioactive hormones. This work represents a further step towards production of recombinant monkey LH and FSH which can be used in a homologous experimental setting in the cynomolgus monkey.
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PMID:Cloning and expression of cynomolgus monkey (Macaca fascicularis) gonadotropins luteinizing hormone and follicle-stimulating hormone and identification of two polymorphic sites in the luteinizing hormone beta subunit. 1061 25

Previous work has indicated that, during the process of gametogenesis in salmon, follicle-stimulating hormone (FSH) and luteinizing hormone (LH) are differentially synthesized and released. Although substantial information is available on the regulation of LH in many fish species, relatively little is known about the regulation of FSH biosynthesis and secretion or the regulation of two types of alpha subunit in salmon. In this study, the effects of salmon gonadotropin-releasing hormone (sGnRH) on in vitro secretion of FSH, and alpha1, alpha2, LH beta, and FSH beta subunit gene expression were investigated in coho salmon (Oncorhynchus kisutch) using primary pituitary cell cultures. To quantify FSH beta, LH beta, alpha1, and alpha2 subunit transcript levels, a multiplex RNase protection assay (RPA) was developed. Probes for the beta subunits of coho salmon FSH and LH were available from previous studies. To generate probes for the alpha subunit RPAs, alpha1 and alpha2 subunit cDNAs were cloned using reverse transcriptase PCR. Release of FSH and LH into cell culture medium was quantified by radioimmunoassays. The effects of sGnRH on gonadotropin release and gene expression were tested at two points during the spring (April and May) prior to spawning in the autumn; a period when plasma and pituitary FSH levels are increasing and females are in early stages of secondary oocyte growth. In both experiments, sGnRH increased steady-state mRNA levels of FSH beta, alpha1, and alpha2, whereas LH beta mRNA levels were not detectable. Secretion of FSH was stimulated by sGnRH in a concentration-dependent manner. Medium LH was not detectable in the first experiment (April) and was measurable only after sGnRH treatment in the second experiment (May). Control levels of medium FSH and transcripts for FSH beta and alpha1 subunits increased approximately fourfold between April and May, whereas alpha2 transcript levels remained relatively constant, suggesting that the seasonal increase in FSH release may involve increased production of alpha1. Therefore, sGnRH has direct stimulatory effects on both secretion of FSH and FSH subunit biosynthesis, most likely due to increased transcription. However, alterations in rates of transcript degradation cannot be ruled out.
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PMID:Effects of salmon gonadotropin-releasing hormone on follicle stimulating hormone secretion and subunit gene expression in coho salmon (Oncorhynchus kisutch). 1084 95

The aim of the present study is to investigate the effect of insulin-like growth factor (IGF-I) on the development of cultured rat pre-antral follicles. Pre-antral follicles with a diameter between 140 and 160 microm are mechanically isolated from ovaries of 10-day-old rats and cultured in groups for 6 days in FSH and insulin-containing serum-free medium in the absence or presence of IGF-I at concentrations of 1, 10, and 100 ng/ml, respectively. DNA content of the follicles before and after culture is measured to evaluate whether a possible growth is due to proliferation of follicular cells and the ultrastructure of the cultured follicles is studied with transmission electron microscopy to evaluate the quality of follicles cultured under different conditions. Furthermore, reverse transcriptase polymerase chain reaction (RT-PCR) is used to assess the gene expression of IGF-I and type I IGF receptor in pre-antral follicles. When follicles were cultured in medium containing IGF-I at a concentration of 1 and 10 ng/ml, the increase in follicle diameter after a 6-day culture differs significantly from that in the absence of IGF-I. The ultrastructure of follicles cultured in IGF-I-containing medium is better sustained when compared to that of follicles cultured in the absence of IGF-I. Especially, theca cells, which are undergoing degeneration under controlled culture condition, demonstrate normal cellular ultrastructure with some characteristics of steroid-secreting cells in the presence of IGF-I. Moreover, in oocytes of follicles cultured in the presence of IGF-I, cortical granules are observed distributed along the ooplasma membrane whereas cortical granules are hardly present in follicles cultured without IGF-I. With RT-PCR, the presence of the mRNA of IGF-I and type I IGF receptor is demonstrated in both the somatic follicular cells and the oocytes. Taken together, these results suggest that IGF-I, in the presence of follicle-stimulating hormone (FSH), enhances rat pre-antral follicle development in vitro and supports the morphology of cultured pre-antral follicles. The stimulatory effect of exogenous IGF-I on the development of pre-antral follicle together with the gene expression of both IGF-I and type I IGF receptor in pre-antral follicles suggests the involvement of IGF-I in early folliculogenesis and its actions are likely mediated by the putative type I IGF receptor, via both endocrine and paracrine/autocrine pathways.
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PMID:Insulin-like growth factor-I (IGF-I) stimulates the development of cultured rat pre-antral follicles. 1117 Feb 70

Leptin receptor (leptin-R) is a polypeptide consisting of a single transmembrane-spanning component. Recent studies performed by reverse transcriptase polymerase chain reaction (RT-PCR) have shown the production of leptin-R in various tissues including the pituitary, hypothalamus and reproductive organs. The localization of leptin-R protein in the pituitary gland, however, has not been extensively studied. This study deals with the expression of leptin-R in the normal rat pituitary gland, which was disclosed primarily in the plasma membrane fraction by immunoblotting and immunohistochemical staining methods. Double immunohistochemical staining revealed that the colocalization of leptin-R and anterior pituitary hormone expression was seen mainly in growth hormone (GH)-secreting cells (97.4 +/- 1.3%; GH-positive cells/leptin-R-positive cells), but in less than 1% of prolactin (PRL)-, adrenocorticotropic hormone (ACTH)-, thyroid-stimulating hormone-beta (TSH beta)- and follicle-stimulating hormone-beta (FSH beta)/luteinizing hormone-beta (LH beta)-positive cells. In contrast, leptin was localized most frequently in FSH beta/LH beta- and less frequently in TSH beta-positive cells. The above findings suggest that, in the rat anterior pituitary gland, there are paracrine relationships between leptin-producing cells and cells with leptin-R, which may regulate the function of GH cells.
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PMID:Expression and localization of leptin receptor in the normal rat pituitary gland. 1157 88

Kidney and liver are the major organs of erythropoietin (Epo) synthesis. However, Epo messenger RNA (mRNA) has been detected in several organs, such as brain, lung, and testis. Furthermore, functional Epo receptors have been demonstrated on different cell types, including rat Leydig cells. The aim of the study was to identify testicular cells expressing Epo mRNA and to quantitate its levels by competitive reverse transcriptase-polymerase chain reaction (RT-PCR). Besides whole testis, Epo transcripts were found in Sertoli and peritubular myoid cells, while no signal was detected in Leydig cells. Exposure of Sertoli cells to CoCl(2) led to an increase of Epo mRNA level. Semiquantitative competitive RT-PCR presented an increase in the level of Epo mRNA in Sertoli cells stimulated by follicle-stimulating hormone, while exposure of peritubular myoid cells cultures to testosterone reduced Epo mRNA expression. Due to the blood-testis barrier, basal expression of Epo suggests a not yet defined function of this hormone in testis.
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PMID:Erythropoietin expression in primary rat Sertoli and peritubular myoid cells. 1167 66

Vascular endothelial growth factor (VEGF) is a heparin-binding, dimeric polypeptide with potent mitogenic effects on endothelial cells. VEGF expression has also been reported in ovarian epithelial tumors (OETs), which may be associated with gonadotropin stimulatioin. We recently reported that most OETs, including OET cell lines, express gonadotropin receptors. Here we studied VEGF mRNA expression in 141 OET and 35 benign ovarian samples using reverse transcriptase polymerase chain reaction and in situ hybridization (ISH). We also studied VEGF production by OET cell lines under stimulation of gonadotropins. AO (serous carcinoma), low malignant potential (LMP; SV40-transformed borderline tumor) and ML-5 (SV40-transformed cystadenoma) cells were examined for VEGF protein production under the regulation of gonadotropins in vitro. The biologic function of VEGF was confirmed by using bovine endothelial growth assay. Whereas VEGF was not detected in benign ovarian surface epithelium or in ovarian epithelial inclusions, it was detected in both epithelial and stromal compartments of OETs. For VEGF epithelial expression, only 5% of ovarian cystadenomas and 30% of borderline tumors were positive for VEGF detection by ISH, whereas VEGF mRNA signal was detected in 80% of ovarian carcinoma cases. This increment of VEGF expression in ovarian carcinomas was statistically significant compared with benign and borderline tumors. Within ovarian carcinomas, the percentage of VEGF-positive cells was significantly associated with the grade of cancer but not with cancer cell types or cancer stages. Both follicle-stimulating hormone (FSH) and luteinizing hormone (LH) stimulated the expression of VEFG(165) in AO cells in a dose-dependent manner. Maximal induction was obtained for FSH at dose of 40 mIU/ml and for LH at 50 mIU/ml after 48 hr of culture. Compared with the nonstimulated cells, VEGF level was significantly elevated in both LMP and AO cells after stimulation of gonadotropins. Furthermore, the induction of VEGF expression was significantly stronger in carcinoma cells than in borderline OET cells. These observations suggest that VEGF may play a role in the development of ovarian cancer and that the elevated gonadotropins, as found in menopause and in most ovarian cancer patients after surgery, could accelerate tumor growth and tumor recurrence by inducing VEGF expression in OETs.
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PMID:VEGF expression and enhanced production by gonadotropins in ovarian epithelial tumors. 1177 59


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