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)

Expression of mRNA for hSSTR1-5 was determined in secretory (GH, PRL, TSH, ACTH) and nonsecretory pituitary tumors, as well as normal human fetal and adult pituitary by reverse transcriptase (RT) PCR followed by Southern blots. All 5 hSSTR subtype mRNAs were expressed in fetal pituitary, while adult pituitary was positive for 4 subtypes, lacking hSSTR4 mRNA. All 15 tumors analyzed were positive for SSTR mRNA, 14 expressing more than one subtype. SSTR2 mRNA in all tissues was expressed as the 2A variant, there being no detectable transcript for SSTR2B. Amongst the 5 SSTRs, mRNA for SSTR2A was the most frequently expressed (87% of tumors) followed by SSTR1 (73%), SSTR3 (53%), SSTR5 (47%), and SSTR4 (40%). The frequency and pattern of expression of the SSTR mRNAs was virtually identical in the different tumor subclasses and did not correlate with tumor size. Since pituitary tumors are monoclonal in origin, multiple SSTR genes are expressed in individual cells. Most tumors are rich in SSTR1 and SSTR2A mRNA compared to the other subtypes. This implies that SST analogs like SMS 201-995, known to interact with SSTR2A, but not with SSTR1, act on pituitary tumors mainly via the SSTR2 subtype.
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PMID:Expression of mRNA for all five human somatostatin receptors (hSSTR1-5) in pituitary tumors. 753 Jul 98

The thyroid gland is a highly vascular tissue, and its blood flow changes dramatically in various pathological conditions. Although the mechanisms regulating these changes in vascularity and blood flow are not well understood, candidate mediators include endothelin-1 (ET-1) and nitric oxide (NO). In the present study, we used a reverse transcriptase-polymerase chain reaction assay to determine which components of these vasoregulatory pathways are present in the thyroid and to analyze changes in gene expression in an experimental model of goiter formation and involution. Expression of messenger RNAs (mRNAs) encoding ET-1, ET receptors (ETA and ETB), ET-converting enzyme, and the three nitric oxide synthase (NOS) isoforms (NOS I, NOS II, and NOS III) was readily detected in the rat thyroid. After goiter formation was induced by thiouracil and a low iodine diet, there was increased expression of the genes encoding ET-related proteins (ET-1, 3.2-fold; ETA, 2.9-fold; ETB, 3.5-fold) as well as two of the three NOS isoforms (NOS I, 2.7-fold; NOS III, 4.9-fold). During iodide-induced involution, the ET-related mRNA levels remained elevated, whereas those of the two NOS isoforms returned to basal values. ET-converting enzyme, NOS II, and thyroglobulin mRNAs were minimally affected in this model, providing evidence for selective regulation of these genes. To assess whether NO plays a role in vascular changes during goiter formation, animals were treated with a NOS inhibitor, N-nitro-L-arginine methyl ester (NAME). NOS activity in the thyroid was inhibited by more than 75% after treatment with NAME. Thyroid hormone and TSH levels were unchanged. Although NAME had little effect on overall thyroid size, vascular expansion during goiter formation was decreased by 36%. We conclude that the thyroid gland expresses a complex network of vasoactive genes whose expression is regulated dynamically during thyroid goiter formation and involution. NO production and probably other locally produced vasoactive substances are involved in changes in thyroid vascularization.
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PMID:Expression of nitric oxide synthase isoforms in the thyroid gland: evidence for a role of nitric oxide in vascular control during goiter formation. 758 72

We studied the effects of thyroid hormone (T3) on GH, TSH, and T3 receptor (TR) gene expression as well as deiodinase activities during rat pituitary development. By reverse transcriptase-polymerase chain reaction, GH and TSH beta transcripts were detectable on fetal day 15. Although with certain differences, the expression of both GH and TSH beta genes was under T3 control during fetal and neonatal life. Differences in plasma, but not pituitary, TSH concentrations were observed between control and hypothyroid animals throughout the period studied. Both TR alpha and TR beta genes were expressed in the fetal pituitary. TR alpha 1, TR beta 2, and c-erbA alpha 2 transcripts displayed a developmental profile different from that of TR beta 1. Thyroid hormone repressed TR alpha 1, TR beta 2, and c-erbA alpha 2 and stimulated TR beta 1. Type I and type II deiodinase activities (5'DI and 5'DII, respectively) had different ontogenic patterns; 5'D-II was the predominant activity in fetuses, with levels similar to those in adults, whereas the level of 5'D-I was low and increased with age. T3 stimulated 5'D-I and decreases 5'D-II. These results demonstrate that in somatotroph and thyrotroph cells, the mechanisms responsible for T3 action are mature and active very early in development and suggest an involvement of this hormone in the establishment and/or maintenance of the somatotroph and thyrotroph phenotype.
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PMID:Effect of perinatal hypothyroidism on the developmental regulation of rat pituitary growth hormone and thyrotropin genes. 766 53

We have generated transgenic mice that express the simian virus 40 (SV40) large T antigen under the control of a 1109 bp 5'-flanking sequence of the human thyrotropin beta-subunit (TSH beta) gene. The hybrid gene, termed TTP-1, was microinjected into fertilized mouse eggs and 11 transgenic mice were obtained. One of the transgenic mice, a female, a phenotypical dwarf, developed a pituitary tumor and wasted away from 7 to 9 weeks after birth. To establish the transgenic mouse line, her ovaries were transferred to a normal female, whose ovaries were removed beforehand. To examine the tissue specificity of transgene expression, mRNA of SV40 large T antigen was monitored in various tissues from the transgenic mice by the reverse transcriptase-polymerase chain reaction analysis, and was detected only in the pituitary. Histological and immunohistochemical analyses showed that the pituitary tumors of the transgenic mice were composed of poorly differentiated pituitary cells expressing SV40 large T antigen. These results indicated that the 1109 bp sequence of the human TSH beta 5'-flanking region is essential for pituitary-specific expression of SV40 large T antigen in transgenic mice, which exhibited a dwarf phenotype and developed pituitary tumors. The tumors were composed of undifferentiated cells and did not produce thyrotropin. These transgenic mice should provide a valuable animal model for studying the pathogenesis of anterior pituitary tumors.
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PMID:Targeted pituitary tumorigenesis using the human thyrotropin beta-subunit chain promoter in transgenic mice. 785 21

Although thyrotropin is known to regulate thyroid cell differentiation and proliferation, human thyroid carcinoma cells are relatively insensitive or resistant to TSH stimulation. The expression levels of TSH receptor are significantly lower in carcinoma tissues than in normal tissues. Furthermore, in vitro human thyroid cell growth is not regulated by TSH itself. We, therefore, isolated neomycin-resistant stable human thyroid carcinoma cell (WRO cell) transfectants overexpressing intact human TSH receptor to evaluate the functional role of TSH receptor on carcinoma cells. Southern blot analysis confirmed incorporation and amplification of human TSH receptor complementary DNA sequences into genomic DNA. Northern gel analysis and reverse transcriptase-polymerase chain reaction analysis revealed the presence of specific TSH receptor messenger RNA (4.0 kilobases), and the specific binding and the affinity of [125I]TSH on stably transfected WRO cells were demonstrated compared to wild type. Nevertheless, impaired cAMP production to transfectants by TSH was observed. cAMP production was confirmed after stimulation of both wild type and transfectants by forskolin, cholera toxin, and isoproterenol. In contrast, TSH could affect the cytoplasmic calcium mobilization immediately after the addition of TSH to WRO transfectants. These results suggest that the impairment of TSH action on human thyroid carcinoma cells is not due to a major structural abnormality of the TSH receptor, reduction in the receptor number, or receptor affinity, but much more likely due to a TSH receptor-guanyl nucleotide-binding protein coupling defect.
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PMID:Overexpression of the intact thyrotropin receptor in a human thyroid carcinoma cell line. 838 Oct 75

Transforming growth factor-beta (TGF beta) is a member of a family of growth factors that regulates differentiation and cellular proliferation in a wide variety of tissues, including the anterior pituitary gland. TGF beta regulates the expression of various proteins, including p27Kipl (p27), a cell cycle inhibitory protein. The cell types in normal rat anterior pituitary producing TGF beta1, one of the principal isoforms of TGF beta, and p27 were examined by in situ methods. The regulation of p27 messenger RNA (mRNA) and protein by TGF beta1 was also examined in cultured anterior pituitary cells. In situ hybridization, in situ reverse transcriptase PCR, and immunocytochemical staining for pituitary hormones showed that PRL, TSH, and gonadotroph cells all had a higher percentage of cells expressing TGF beta1 mRNA and p27 protein than did GH and ACTH cells. After treatment with 10(-9) M TGF beta1 in vitro for 3 days, there were significant decreases in p27 mRNA and protein levels (P < 0.05) in normal pituitary cells. The GH3 and GHRH-CL1 cell lines, which secrete PRL and GH, had undetectable p27 protein by immunocytochemical staining and immunoblotting, although the GH3 cell line had p27 mRNA detected by reverse transcriptase PCR. Analysis of [3H]thymidine uptake in cultured dissociated pituitary cells by double staining for hormones showed that only PRL cells had significant proliferative activity during a 3-day cell culture period. There was a biphasic effect of TGF beta1 on PRL cell proliferation, with marked inhibition by 10(-9) M and a slight stimulation by 10(-13) M. These results indicate that there is a differential distribution of both TGF beta1 and p27 in various anterior pituitary cell types and that TGF beta1 directly down-regulates p27 in cultured anterior pituitary cells.
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PMID:Transforming growth factor-beta and p27 expression in pituitary cells. 877 Sep 31

In this study, we provide the first report on the production of granulocyte-macrophage colony-stimulating factor (GM-CSF) by human thyroid epithelial cells. Primary cultures of highly purified thyrocytes and thyroid-derived fibroblasts (n = 3) and three thyroid anaplastic and one largely papillary carcinoma cell lines were exposed to different potent GM-CSF stimulators, employing interleukin 1 alpha (Il-1 alpha) and tumour necrosis factor-alpha (TNF-alpha). Cytokine mRNA levels were monitored by semi-quantitative reverse transcriptase-PCR including an internal heterologous competitor fragment after 3, 6 and 18 h of culture. Culture supernatants were assayed for GM-CSF using a highly sensitive ELISA (detection limit < or = 0.5 pg/ml) after 24 h. Basal GM-CSF mRNA expression was higher in fibroblasts and SW 1736 cells compared with thyrocytes, C 634, 8505 C and HTh 74 cells. GM-CSF was spontaneously secreted by fibroblasts (means +/- S.E.M.; 43 +/- 15 pg/ml), SW 1736 (59 +/- 4 pg/ml), HTh 74 (34 +/- 4 pg/ml) and C 643 cells (12 +/- 1 pg/ml) but not by thyrocytes and 8505 C cells. Treatment with Il-1 alpha (10 U/ml) resulted in a marked increase of GM-CSF mRNA within 3 h and an increase or induction of protein expression in thyrocyte (2350 +/- 214 pg/ml), fibroblast (5242 +/- 1400 pg/ml), SW 1736 (20016 +/- 280 pg/ml) and C 643 cultures (1285 +/- 79 pg/ml). Stimulation with TNF-alpha (10 U/ml) yielded divergent results. No significant increase of GM-CSF mRNA or protein expression was found in thyrocytes although TNF-alpha receptor expression in these cells is well documented. Stimulation with TNF-alpha resulted in an increased GM-CSF production in fibroblasts (361 +/- 14 pg/ml), HTh 74 (148 +/- 51 pg/ml) and SW 1736 cultures (235 +/- 43 pg/ml). TSH (10 mU/ ml) did not stimulate GM-CSF secretion in thyrocytes and HTh 74 cells, both expressing the TSH receptor. Phorbol 12-myristate 13-acetate (10 ng/ml) enhanced GM-CSF mRNA and protein levels in all cell types investigated. Our data suggest that both thyrocytes and fibroblasts synthesize GM-CSF in response to Il-1 alpha, but only fibroblasts respond to TNF-alpha with a significant increase in GM-CSF. Anaplastic thyroid carcinomas are potential GM-CSF producers.
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PMID:Differential regulation of granulocyte-macrophage colony-stimulating factor mRNA and protein expression in human thyrocytes and thyroid-derived fibroblasts by interleukin-1 alpha and tumor necrosis factor-alpha. 895 88

Healthy humans have CD4+ T cells specific for self-components. Since autoreactive T cells in autoimmune patients may use a limited number of TCR V-region genes, we investigated here whether this also occurs for the potentially autoreactive CD4+ cells present in healthy persons. We studied CD4+ cells specific for human TSH receptor (TSHr) sequences, that are present with high frequency in healthy subjects and, as expected, in Graves' disease (GD) patients. We used short-term CD4+ cell lines propagated from four GD patients and five healthy subjects by cycles of stimulation with a pool of overlapping synthetic peptides corresponding to the putative extracellular parts of the TSHr sequence. The lines recognized the pool of TSHr peptides specifically and vigorously. Their epitope repertoire had been characterized previously: each line recognized one or a few TSHr peptides, different for each subject. We determined their TCR Vbeta usage by a semi-quantitative reverse transcriptase PCR assay, using primers specific for each known human Vbeta region family, in conjunction with a constant region primer. Six lines preferentially used one Vbeta family (42-94%), different for each line. In all lines, three or less Vbeta families accounted for approximately 60% or more of the Vbeta usage. Different Vbeta regions were used by each subject. There was no obvious difference between the Vbeta usage of the lines from GD patients and healthy controls. These results suggest that a limited pool of potentially autoreactive T cells survives clonal deletion. The pathogenic CD4+ cells involved in autoimmune diseases are likely recruited from that pool, since they have similar characteristics of epitope and TCR repertoire as the CD4+ cells specific for the same autoantigen in healthy subjects.
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PMID:TCR vbeta usage of TSH receptor-specific CD4+ T cells in Graves' disease patients and healthy humans. 937 76

Thyrotropin (TSH)-secreting pituitary adenomas cause hyperthyroxinemia in the presence of "inappropriately" elevated concentrations of TSH. TSH production under these circumstances escapes the normal negative feedback effect of thyroid hormone. We propose that this defective negative feedback is mediated by an abnormality of thyroid hormone receptor (TR) expression. Two TSH-secreting pituitary adenomas were analyzed by immunocytochemistry for TR isoform protein expression and by semiquantitative reverse transcriptase polymerase chain reaction (RT-PCR) for TR isoform mRNA expression. The results obtained from these tumors were compared with the findings from six normal human pituitaries. Neither tumor examined expressed detectable levels of nuclear TRalpha or TRbeta proteins, in contrast to the normal pituitaries studied, which expressed all TR isoforms. Application of RT-PCR, however, revealed mRNAs encoding each TR isoform in all tumorous and normal tissues examined. Semiquantitative RT-PCR revealed similar levels of expression of TRalpha and TRbeta isoform mRNAs in tumors and normal tissue, in contrast to the observed difference in TR proteins. Absent TRalpha and TRbeta protein expression, in association with normal mRNA levels, implies a post-transcriptional defect in TR mRNA processing in TSH-secreting adenomas. Reduced TR expression in these tumors may explain defective negative feedback of thyroid hormone on TSH production, and may also contribute to uncontrolled tumor growth.
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PMID:An abnormality of thyroid hormone receptor expression may explain abnormal thyrotropin production in thyrotropin-secreting pituitary tumors. 949 47

In healthy infants, the levels of TSH are known to peak at 50-100 times adult values during the first days of life. In studies of isolated human infant adipocytes, we have earlier shown that bovine TSH (bTSH) has a strong lipolytic effect, accompanied by a blunted response of adipocytes to catecholamines. In this study, we used human recombinant TSH (hTSH), and incubation of adipocytes with hTSH induced a lipolytic response similar to that obtained with the beta-adrenergic receptor agonist isoprenaline in adipocytes isolated from three infants. The lipolytic effect of hTSH was completely blocked by inhibitory TSH receptor (TSHR) antibodies. The TSHR mediates the effects of TSH in the thyroid, and it has been detected in some extrathyroid tissues, but not in isolated human adipocytes or childhood adipose tissue. In this study, we found TSHR RNA in infant and adult adipose tissues and isolated adipocytes with reverse transcriptase-PCR. The sequence of the amplified PCR product agreed with the published sequence. Northern blot hybridization on RNA prepared from infant adipose tissue showed a transcript of the expected size, and the expression of TSHR seemed higher in infant than in adult adipose tissue. In conclusion, this study indicates that TSH plays an active role in the metabolic adaptation after birth.
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PMID:Presence of thyrotropin receptor in infant adipocytes. 954 14


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