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)

Hormonal regulation of mouse mammary tumor virus (MMTV) synthesis was studied in the CCL-51-SF cell subline derived from the Sykes' mammary tumor cell line CCL-51 and adapted to grow in semi-synthetic in vitro conditions. The virus was quantitated by measuring the supernatant reverse transcriptase activity in exogenous reaction using poly (rA)-oligo (dT) and poly (rC)-oligo (dG) as template/primers. The cells produced a low but significant amount of virus in the absence of any hormones and serum proteins. The synthetic glucocorticoid dexamethasone increased production considerably, up to 100-fold. Pretreatment of CCL-51-SF cells with serum or 5-bromodeoxyuridine, BrdUrd, partly reduced the stimulation by dexamethasone of MMTV production. Insulin and prolactin alone or in combination had no stimulating effect on spontaneous MMTV synthesis and cell growth. Prolactin, and more efficiently the prolactin-insulin combination, enhanced the MMTV production stumulated with dexamethasone. Insulin alone remained without effect. The polyamine spermidine, but not spermine, increased the MMTV production over the control by a factor of 2. Polyamines did not influence cell replication at the concentrations used.
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PMID:Mouse mammary tumor virus production stimulated by hormones and polyamines in cells grown in semi-synthetic in vitro conditions. 6 40

Insulin-like growth factor 1 and insulin, considered primarily as metabolic and growth modulatory hormones, were found to inhibit the replication of HIV-1 in cultured cord blood mononuclear cells and chronically HIV-infected U937 cells. The effect of IGF-1 was seen at physiological concentrations or lower (1.7 x 10(-10) M) while that of insulin was observed at supraphysiological concentrations (8 x 10(-7) M). The EC50 for IGF-1 was found to be in the physiological range (2.5-4.5 x 10(-9) M) while that for insulin was considerably higher (1.1-3.3 x 10(-6) M). Insulin-like growth factor 1 and insulin at the concentrations employed exhibited no toxicity on the cells used in these studies. Furthermore, neither IGF-1 nor insulin exhibited any inhibitory activity on purified reverse transcriptase in vitro. Epidermal growth factor from 1.6 x 10(-10) to 1.6 x 10(-8) M demonstrated no inhibition of HIV-1 replication, while IGF-1 inhibited p24 antigen production 49 and 42% at 1.3 x 10(-9) and 1.3 x 10(-8) M IGF-1, respectively. These results suggest that IGF-1 under certain conditions has significant inhibitory effects on HIV-1 replication at physiological concentrations. This may prove to be of therapeutic value in patients infected with HIV-1.
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PMID:Insulin-like growth factor 1 and insulin inhibit HIV type 1 replication in cultured cells. 757 11

Insulin-like growth factors I (IGF-I) and II (IGF-II) are anabolic for osteoblastic cells. Although expression of IGF-I and IGF-II mRNA has been demonstrated in rodent osteoblastic cells, little is known about IGF gene expression in human osteoblastic cell models. In this study we characterized IGF-I and -II mRNA expression in (1) normal human osteoblast-like (hOB) cells, (2) a simian virus 40 immortalized hOB (HOBIT) cell line, and (3) human osteosarcoma cell lines SaOS-2, TE-85, MG-63, and U-2. Since cross-hybridization of IGF cDNA probes with ribosomal RNA obscures detection of some of the multiple IGF transcripts in human cells, we replaced Northern analysis with the more specific ribonuclease protection assay (RPA). We also used the reverse transcriptase-polymerase chain reaction (RT-PCR) to assess whether mRNAs were present at trace levels. IGF-I mRNA expression was consistently observed in normal hOB cells only and by both RT-PCR and RPA. Among IGF-I transcript variants, Ea IGF-I mRNA was more abundant than the Eb mRNA in normal hOB cells. Trace levels of IGF-I mRNA were variably detected in SaOS-2 and U-2 osteosarcoma cells when RT-PCR was performed, but we found no IGF-I mRNA in HOBIT, TE-85, or MG-63 cells. IGF-II mRNA was expressed in normal hOB, HOBIT, TE-85, and U-2 cells as assessed by either method.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Normal human osteoblast-like cells consistently express genes for insulin-like growth factors I and II but transformed human osteoblast cell lines do not. 763 14

To address the question whether fish brain can produce insulin, pink salmon (Oncorhynchus gorbusha) brains were extracted and processed according to the procedure developed for purification of pancreatic insulin (Rusakov and Bondareva, 1979). Biological and immunological activity of the resulting material was evaluated respectively by a cartilage sulfation assay and by radioimmunoassay homologous for salmon insulin. Preparations from salmon brain stimulated the [35S]sulfate uptake into salmon branchial cartilage with a potency comparable to pure mammalian or salmon insulins but lower than that of mammalian insulin-like growth factor (IGF-I). In contrast, only trace amounts of radioimmunoreactive insulin could be detected by homologous radioimmunoassay. To determine whether insulin mRNA was present in salmon brain, primers specific for salmon proinsulin and salmon prepro-IGF-I were designed to amplify corresponding cDNA regions by reverse transcriptase-PCR. Insulin mRNA was found only in the endocrine pancreas (Brockmann body) while IGF-I mRNA was detected in the brain, liver, and the Brockmann body. Our results suggest that in fish pancreatic-type insulin is most likely produced only in the endocrine pancreas and then transported to the brain through blood/cerebrospinal fluid system. However, it does not exclude a possibility that some yet unknown insulin-like substances may be expressed in the neural system of ectotherm vertebrates.
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PMID:Does salmon brain produce insulin? 840 93

Insulin-like growth factor 1 (IGF-1) is involved in the regulation of brain development and has been suggested as an autocrine stimulator of brain tumor cell proliferation. This study demonstrates the expression of IGF-1 in tumor tissue from human gliomas and one esthesioneuroblastoma. Using immunohistochemistry, expression of an IGF-1-like peptide was localized in tumor cells of 6 of the 9 gliomas examined as well as the esthesioneuroblastoma. From one anaplastic oligodendroglioma (which showed strong IGF-1 immunostaining) the IGF-1 transcripts were characterized after isolation of mRNA followed by amplification using the reverse transcriptase-polymerase chain reaction. Two IGF-1 complementary DNAs resulting from alternative splicing of the IGF-1 primary transcript were identified. These transcripts encode two different precursor proteins which correspond to Ea IGF-1 and Eb IGF-1. The significance of IGF-1 alternative mRNA splicing pathways remains to be determined.
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PMID:Characterization of insulin-like growth factor 1 in human primary brain tumors. 849 8

Insulin and insulin-like growth factors (IGF-I and -II) are members of a family of growth factors which are known to be developmentally regulated during preimplantation mouse embryogenesis. The physiological actions of the insulin family of growth factors are mediated by interactions with specific cell surface receptors that are detectable on the cells of preimplantation mouse embryos. Mouse embryonic stem (ES) cells are totipotent cells derived directly from the inner cell mass of the blastocyst. ES cells have the ability to differentiate into all three germ layers and have unlimited growth potential under certain culture conditions. The great advantage of ES cells is the ability to obtain large amounts of tissue for biochemical studies as compared with preimplantation embryos. To examine in greater detail the biological actions of the insulin family of growth factors, the expression of their cognate receptors on ES cells was examined. ES cells were cultured in DMEM medium supplemented with leukemia inhibitory factor (LIF) to maintain the undifferentiated state. Receptor expression was evaluated at the mRNA level using the reverse transcription polymerase chain reaction (RT-PCR), and at the protein level by radioactive labeled ligand-receptor binding assay. Using RT-PCR, mRNAs of all three growth factor receptors were detected in ES cells. Messenger RNA from ES cells was reverse transcribed into cDNA by AMV reverse transcriptase at 42 degrees C for 1 hr. The reverse transcription reaction was amplified with Taq polymerase and specific primers for insulin, IGF-I, or IGF-II receptors by PCR. RT-PCR and the control plasmid cDNA PCR products were resolved electrophoretically on 3% agarose gels. Each amplified PCR product showed the predicted correct size.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Mouse embryonic stem cells express receptors of the insulin family of growth factors. 856 62

Insulin-like growth factors IGF-I and IGF-II are potent inducers of oligodendrocyte development. Because IGF-I is produced, in some cases, by the same cells that respond to it (autocrine/paracrine action), we examined the possibility that IGF-I is expressed by developing oligodendroglial cells. We employed a sensitive method, reverse transcriptase-polymerase chain reaction (RT-PCR), to detect IGF-I mRNA in purified populations of oligodendroglial cells isolated from rat brain during the period of oligodendrocyte development. Cells were purified by fluorescence activated cell sorting (FACS), using antibodies to the cell surface antigenic markers O4 and galactocerebroside (GC). RNA was isolated from the sorted cells, reverse-transcribed, and PCR-amplified, using a strategy that recognizes IGF-I mRNA but not DNA. The amplified band was identified as IGF-I by size, hybridization to an IGF-I-specific antisense probe, and restriction analysis. IGF-I mRNA was detected in O4-positive/GC-negative oligodendrocyte precursors and, more weakly, in GC-positive oligodendrocytes. IGF-I mRNA could be detected reproducibly in RNA extracted from 100-cell samples of O4-positive cells, making it unlikely that the mRNA was derived from contaminants in the FACS-sorted cell populations. We conclude that IGF-I is expressed by developing oligodendroglia. Autocrine expression of IGF-I by developing oligodendroglial cells suggests that oligodendrocyte development is, in part, autoregulatory.
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PMID:Developing oligodendroglia express mRNA for insulin-like growth factor-I, a regulator of oligodendrocyte development. 856 38

Reduction of GLUT2 is associated with loss of glucose-induced insulin secretion in genetic and chemical diabetes and in transplanted islets exposed to chronic hyperglycemia. To examine the mechanisms for this loss of GLUT2 in normal islets exposed to hyperglycemia, we performed studies on Sprague Dawley rats 4 weeks after a 90% partial pancreatectomy (Px), a well-characterized model of hyperglycemia. GLUT2 immunofluorescence in the beta-cell of Px rats was greatly reduced. Western blot analysis of homogenates of isolated Px islets also showed a reduction in GLUT2 protein; densitometry measurements were 36 +/- 3% of values from islets of sham-operated controls. Insulin protein levels were decreased to a similar extent. Islet GLUT2 and insulin mRNA were measured with quantitative reverse transcriptase-polymerase chain reaction. The level of GLUT2 mRNA from Px islets was 24 +/- 4% of that of islets from sham-operated controls; similar results were obtained for insulin. Because both these beta-cell-specific messages were reduced, we analyzed the Px islets for the pancreas-duodenum-specific transcription factor IDX-1(IPF-1, STF-1, PDX-1) protein. It was markedly reduced (approximately 80%) in islets from the Px rats. These data suggest that 1) the loss of GLUT2 protein associated with hyperglycemia is at least partially explained by reduced levels of the GLUT2 gene transcripts; 2) the reduction of beta-cell insulin content during chronic hyperglycemia may not be completely due to degranulation (reduced levels of gene transcripts may play a role); and 3) the reduction in the transcription factor IDX-1 raises the possibility that dysregulation of transcription factors may contribute to the abnormal beta-cell function found in states of chronic hyperglycemia.
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PMID:Reduced insulin, GLUT2, and IDX-1 in beta-cells after partial pancreatectomy. 900 Jul 3

Insulin-like growth factor (IGF)-binding protein-3 (IGFBP-3) is a polypeptide that forms a ternary complex with IGFs and an acid-labile subunit. The hormonal regulation of the components of this complex is highly controversial, and both IGF-I and GH have been shown to mediate the expression/synthesis of IGFBP-3. This study investigates the regulation of IGFBP-3 protein, measured by RIA and Western ligand blot, and messenger RNA (mRNA) expression, measured by Northern analysis and reverse transcriptase-PCR, in SKHEP-1 human hepatocarcinoma cells. SKHEP-1 cells significantly increased the IGFBP-3 concentrations in conditioned medium (CM) when treated with GH (0.1-10 ng/ml), IGF-I (1-100 ng/ml), or Des(1-3)-IGF-I (1-100 ng/ml) in a dose-dependent manner (>3-fold). The increase in IGFBP-3 protein concentrations in CM was accompanied by a corresponding increase in IGFBP-3 mRNA levels. Interestingly, time-course studies showed that the GH-induced increase in IGFBP-3 mRNA preceded the IGF-I-induced increase (6 h for GH-induced IGFBP-3 mRNA; 12 h for IGF-I-induced IGFBP-3 mRNA). The half-life of IGFBP-3 mRNA was evaluated after transcriptional arrest by treatment with a RNA polymerase II inhibitor (5,6-dichloro-1beta-D-ribofuranosylbenzimidazole), and was found to be 14-18 h and unaltered by GH or IGF-I treatment. The induction of IGFBP-3 by GH was not due to the indirect action of locally synthesized IGF-I, because 1) no immunoreactive IGF-I was detected in the CM of control or GH-treated cells; 2) Northern blots revealed no IGF-I mRNA expression in SKHEP-1 cells; 3) reverse transcriptase-PCR did not detect any expression of the IGF-I gene; and 4) time-course studies showed an earlier increase in IGFBP-3 mRNA after GH treatment than after IGF-I treatment. Thus, the results obtained in this study are consistent with an IGF-I-independent regulation of IGFBP-3 gene expression by GH.
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PMID:Evidence for insulin-like growth factor (IGF)-independent transcriptional regulation of IGF binding protein-3 by growth hormone in SKHEP-1 human hepatocarcinoma cells. 907 3

Insulin-like growth factor (IGF)-I has profound effects on tissue repair. IGF-II is felt to exert its influence predominately during fetal development. The purpose of this study was to localize and quantify the expression of IGF-I and IGF-II mRNA and protein during early wound healing in diabetic and nondiabetic mice. The hypothesis is that IGF-I and IGF-II are up-regulated in the healing wound, but their expression is inhibited in diabetics. Full-thickness cutaneous wounds were made on genetically diabetic (C57BL/ KsJ-db/db) mice and their nondiabetic littermates. At various times after wounding, one-half of each wound was fixed and paraffin embedded for immunohistochemistry and in situ hybridization. The other half was flash-frozen for quantification of IGF mRNA by competitive reverse transcriptase polymerase chain reaction and protein by radioimmunoassay. IGF-I mRNA rose sharply in nondiabetics at day 3. Expression in diabetic wounds was significantly delayed until 14 days after wounding. Even then, diabetic IGF-I mRNA levels were 50% less than those in the nondiabetics at their peak. Although not usually considered active in adult life, IGF-II mRNA expression was augmented after wounding, peaking at 3 days in nondiabetics. As with IGF-I, diabetic wounds exhibited a delay in IGF-II mRNA expression, with maximal levels at 10 days after wounding. Interestingly, peak concentrations of IGF-II mRNA were four times greater in diabetics versus nondiabetics. Trends in IGF-I protein expression followed the patterns of mRNA expression. IGF-I levels in nondiabetics were initially double those in diabetics and peaked at 5 days. Diabetic wound concentrations of IGF-I did not peak until 21 days after wounding, at which time they rose to nondiabetic levels. IGF-I and IGF-II proteins were localized to the advancing epithelial edge, to the epithelial cells of adjacent hair follicles, and to the granulation tissue of the wounds. IGF-I and IGF-II mRNA expression was noted in the epithelial edge and in the hair follicles adjacent to the wound, paralleling protein expression. Both IGF-I and IGF-II are up-regulated in the healing wound. A delay in IGF-I and -II presence is noted in the diabetic wound. The impairment in tissue repair in diabetic animals is at least partially due to a deficiency in the production of the IGFs.
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PMID:Differential expression and localization of insulin-like growth factors I and II in cutaneous wounds of diabetic and nondiabetic mice. 928 20


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