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)

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

In mammals, one of the major actions of insulin-like growth factor I (IGF-I) is to increase skeletal growth by stimulating new cartilage formation. IGF-I stimulates chondrocytes in vitro to synthesize new cartilage matrix, measured by enhanced uptake of 35S-sulfate, but the addition of insulin does not produce a similar effect except when added at high concentrations. However, recent studies have shown that, in teleosts, both insulin and IGF-I are potent activators of 35S-sulfate uptake in gill cartilage. To further characterize the growth-promoting activities of these hormones in fish, we have used reverse transcriptase-linked PCR to analyze the expression of insulin receptor family genes in salmon gill cartilage. Partial cDNA sequences encoding the tyrosine kinase domains from six distinct members of the IR gene family were obtained, and sequence comparisons revealed that four of the cDNAs encoded amino acid sequences that were highly homologous to human IR whereas the encoded sequences from two of the cDNAs were more similar to the human type I IGF receptor (IGF-R). Furthermore, a comparative reverse transcriptase-linked PCR assay revealed that the four putative IR mRNAs expressed in toto in gill cartilage were 56% of that found in liver whereas the expressed amount of the two IGF-R mRNAs was 9-fold higher compared with liver. These results suggest that the chondrogenic actions of insulin and IGF-I in fish are mediated by the ligands binding to their cognate receptors. However, further studies will be required to characterize the binding properties and relative contribution of the individual IR and IGF-R genes.
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PMID:Expression of multiple insulin and insulin-like growth factor receptor genes in salmon gill cartilage. 935 69

Insulin-like growth factors (IGF-I and IGF-II) are believed to mediate and modulate steroid hormone actions in the endometrium. In this study we determined the effects of an intrauterine system (IUS), releasing 20 microg levonorgestrel (LNG) daily, on endometrial expression of mRNAs encoding IGFs and insulin-like growth factor binding protein (IGFBP)-1. In Northern blotting, IGF-I mRNA was undetectable in all endometrial specimens from women with an LNG-IUS (n = 11) and in pregnancy decidua, whereas several transcripts of 0.6-7.6 kb were detected in proliferative and secretory phase endometria. In contrast, mRNAs encoding IGF-II and IGFBP-1 were strongly expressed in pregnancy and in all endometrial samples from women with an LNG-IUS, but were undetectable in proliferative or early to mid-secretory phase endometria. Using the more sensitive reverse transcriptase-polymerase chain reaction (RT-PCR) method, IGF-I and IGF-II mRNAs were detectable in all cycling endometria, in early pregnancy decidua and in LNG-exposed endometrium. IGFBP-1 mRNA was constantly expressed in LNG-exposed endometrium, in early pregnancy decidua and in premenstrual endometrium, but was undetectable in all specimens from proliferative or early to mid-secretory endometrium. Our data demonstrate that progestin treatment can affect the gene expression of endometrial growth factors in vivo. The consistent expression of mRNAs encoding IGF-II and IGFBP-1, with suppression of IGF-I mRNA in endometria exposed to LNG, suggests that this mode of hormone treatment can inhibit IGF-I action in the endometrium. If IGF-I mediates and modulates oestrogen action, suppression of IGF-I mRNA may be one of the molecular mechanisms which accounts for the antiproliferative effects of progestogens on oestrogen-primed endometrium and the atrophy of endometrial epithelium resulting from use of an LNG-IUS.
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PMID:mRNA expression of insulin-like growth factor-I (IGF-I) is suppressed and those of IGF-II and IGF-binding protein-1 are constantly expressed in the endometrium during use of an intrauterine levonorgestrel system. 935 99

The cytokine interleukin-1beta (IL-1beta) has been shown to inhibit insulin secretion and destroy pancreatic islets by a mechanism that involves the expression of inducible nitric oxide synthase (iNOS), and the production of nitric oxide (NO). Insulin containing beta-cells, selectively destroyed during the development of autoimmune diabetes, appear to be the islet cellular source of iNOS following treatment with IL-1beta. In this study we have evaluated the presence of type I IL-1 signaling receptors on purified pancreatic beta-cells. We show that the interleukin-1 receptor antagonist protein (IRAP) prevents IL-1beta-induced nitrite formation and IL-1beta-induced inhibition of insulin secretion by isolated islets and primary beta-cells purified by fluorescence-activated cell sorting (FACS). The protective effects of IRAP correlate with an inhibition of IL-1beta-induced iNOS expression by islets and FACS purified beta-cells. To provide direct evidence to support beta-cell expression of IL-1 type I signaling receptors, we show that antiserum specific for the type I IL-1 receptor neutralizes IL-1beta-induced nitrite formation by RINm5F cells, and that RINm5F cells express the type I IL-1 receptor at the protein level. Using reverse transcriptase-polymerase chain reaction (RT-PCR), the expression of type I IL-1 signaling receptors by FACS purified beta-cells and not alpha-cells is demonstrated. These results provide direct support for the expression of type I IL-1 receptors by primary pancreatic beta-cells, the cell type selectively destroyed during the development of autoimmune diabetes.
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PMID:Evidence for the presence of type I IL-1 receptors on beta-cells of islets of Langerhans. 937 6

Insulin-like growth factors (IGF)-I and IGF-II are produced by osteoblasts and are important paracrine/autocrine regulators of osteoblast proliferation and differentiation. Estrogen has been reported to increase gene expression of IGF-I in rodent osteoblasts. However, because species differences have been demonstrated in expression of various aspects of the IGF system in bone cells, it is not known whether this action also occurs in human osteoblasts. Thus, we assessed the effects of estrogen treatment on IGF-I and IGF-II gene expression in vitro in a recently developed human fetal osteoblast cell line that has high levels of estrogen receptors. As assessed by a quantitative reverse transcriptase-polymerase chain reaction method, treatment of hFOB/ER9 cells with 17beta-estradiol (E2) increased steady state levels of IGF-I mRNA in a time- and dose- dependent fashion with a maximal increase of 319% +/- 33% (P < 0.01) of control occurring after treatment with 10(-7) M E2 for 48 hours. In contrast, E2 did not alter steady state levels of IGF-II mRNA. The pure (type 2) antiestrogens ICI 182,780 (10(-7) M) and ICI 164,384 (10(-6) M) blocked the E2- induced increase in IGF-I mRNA levels. Interestingly, 4-hydroxytamoxifen (10(-7) M), a documented pure antiestrogen in reproductive tissues, also increased IGF-I mRNA to levels similar to those observed in E2-treated cells. Since E2 was shown to mediate its effects on some target genes through a cAMP-dependent pathway, we studied the interaction between E2 and agents that are known to increase intracellular cAMP. Forskolin (10(-8) M) and dibutyryl cAMP (10(-3) M) increased IGF-I mRNA levels sixfold, and cotreatment with E2 did not affect these changes, consistent with a possible mediation of the estrogen effect on IGF-I gene expression by cAMP. We conclude that in human osteoblastic cells, the IGF-I gene is a target for estrogen action, suggesting that IGF-I may mediate part of the effects of estrogen in human bone.
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PMID:Estrogen effects on insulin-like growth factor gene expression in a human osteoblastic cell line with high levels of estrogen receptor. 940 35

The hormone regulation of viruses has been of great interest since the discovery of glucocorticoid stimulation of mouse mammary tumor virus via a hormone response element in the viral long terminal repeat (LTR) promoter region. This report describes the investigation of the hormone responsiveness of bovine leukemia virus (BLV), an oncogenic retrovirus that infects dairy and beef cattle worldwide. It is a member of the human T cell leukemia (HTLV)/BLV group of retroviruses, which encode a protein, Tax, that is essential for regulating transcription of their own proviruses and for transforming host cells. We investigated the responsiveness of BLV to the hormones 17 beta-estradiol, progesterone, prolactin, insulin, and dexamethasone, a potent glucocorticoid. Only dexamethasone, in combination with insulin or insulin/prolactin, consistently stimulated BLV expression, as measured by reverse transcriptase activity, RNA blot hybridization (Northern blots), and CAT (chloramphenicol acetyltransferase) reporter assays of cell lines transiently or stably transfected with the BLV LTR. This effect required the presence of glucocorticoid receptors and Tax. This is the first report of hormone responsiveness in a virus of the HTLV/BLV group.
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PMID:Hormone regulation of bovine leukemia virus via the long terminal repeat. 943 16

The acid-labile subunit (ALS) of the ternary insulin-like growth factor-binding protein complex has a central role in controlling the bioavailability of circulating insulin-like growth factors. We have shown that gene expression of ALS is regulated by a number of factors, particularly growth hormone. Our aim was to characterize the ALS gene in order to define the mechanism of its regulation. Southern analysis suggests a single copy of the ALS gene in the rat genome. The protein-coding and 3'-untranslated regions span approximately 3.5 kilobases of rat genome and are divided into two exons. The 5' flanking region of the gene lacks a consensus TATA-box or Inr sequence, and primer extension and reverse transcriptase PCR experiments locate multiple transcriptional initiation sites between -505 and -385 nucleotides relative to the translational initiation codon. This putative promoter region, when inserted upstream of the luciferase reporter gene, directs luciferase expression when transfected into H4-II-E cells. Our data demonstrate the uncomplicated structure of the rat ALS gene, and the promoter function and presence of potential regulatory elements in the region upstream of the protein-coding sequence.
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PMID:Cloning and characterization of the rat gene for the acid-labile subunit of the insulin-like growth factor binding protein complex. 946 Jun 48

Alternative splicing of the 36-base pair exon 11 of the human insulin receptor (IR) gene and of the corresponding domain of the rat IR gene results in the synthesis of two IR isoforms with distinct functional characteristics. Altered expression of these IR isoforms has been previously demonstrated in the skeletal muscle of patients with non-insulin-dependent diabetes mellitus (NIDDM); however, this observation was not confirmed by other studies and is still a matter of debate. To assess whether the reported altered isoform expression is due to the secondary metabolic derangement of diabetes, we examined alternative splicing of IR mRNAs (IR36+ and IR36-, corresponding to human Ex11+ and Ex11-) in the skeletal muscle and liver of 6-hour fasting 90% pancreatectomized insulin-resistant diabetic and control Sprague-Dawley rats, using the reverse transcriptase-polymerase chain reaction (PCR) technique. Both diabetic and control rats showed the same pattern of IR mRNA expression: the liver exclusively expressed IR36+ mRNA, whereas only IR36- mRNA was detected in muscle. In conclusion, diabetes mellitus per se does not alter the expression of IR isoforms in the liver and skeletal muscle, and therefore, at least in this animal model of NIDDM, impaired insulin action develops independently from a relative increase in IR36+ mRNA expression in skeletal muscle.
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PMID:Expression of the two insulin receptor isoforms is not altered in the skeletal muscle and liver of diabetic rats. 947 57

A 17.5 kDa protein was isolated from porcine whey by reverse phase HPLC and identified as a putative whey acidic protein (WAP) homologue by sequencing 35 and 40 amino acid residues of the amino- and carboxy-terminus respectively. Degenerate oligonucleotides to both of these amino acid sequences were designed and used in reverse transcriptase PCR with RNA from lactating porcine mammary gland as a template. A 162 bp PCR fragment was detected and sequenced. Compilation of the deduced and determined amino acid sequence revealed a protein of 111 amino acids, which had approximately 75, 50, 40 and 35% similarity at amino acid level to camel, rabbit, rat and mouse WAP respectively. It also included the four-disulphide core characteristic of all WAP proteins and most Kunitz-type protease inhibitors. This provides the first unequivocal evidence for WAP secretion in the pig. SDS PAGE analysis of the whey fraction showed that WAP is secreted as a major protein in sow's milk from farrowing to weaning. The molecular mass of WAP in SDS PAGE was significantly greater than the 11.7 kDa determined from amino acid sequence, indicating that porcine WAP is possibly glycosylated. Northern analysis detected a single mRNA transcript of approximately 600 bp in porcine RNA from the mammary gland of lactating sows. To examine the hormone-regulated expression of the WAP gene the mammary glands of sows at day 90 of pregnancy were biopsied and explants cultured for 3 days in the presence of various combinations of porcine insulin (I), cortisol (F) and porcine prolactin (P). Northern analysis of RNA extracted from the tissue indicated that WAP gene expression was barely detectable in the mammary gland prior to culture and there was no increment in explants cultured in the presence of I and F. However, a significant increase in the accumulation of WAP mRNA was observed in explants cultured in I, F and P. A similar result was observed for beta-casein and alpha-lactalbumin gene expression.
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PMID:Molecular characterisation and hormone-dependent expression of the porcine whey acidic protein gene. 951 79

Previously we demonstrated that bradykinin infusion could increase glucose uptake into dog peripheral tissues, and that bradykinin could potentiate insulin-induced glucose uptake through glucose transporter 4 (GLUT4) translocation in dog adipocytes. However, skeletal muscle is the predominant tissue for insulin-mediated glucose disposal. The aim of this study was to determine how bradykinin affected insulin-stimulated glucose uptake in dog skeletal muscle and myotubes transformed from rat L6 myoblasts. The bradykinin receptor binding studies revealed that dog skeletal muscle and rat L6 myoblasts possessed significant numbers of bradykinin receptors (Kd = 88 and 76 pmol/l, Bmax = 82.5 and 20 fmol/mg protein respectively). An RT-PCR (reverse transcriptase-polymerase chain reaction) amplification showed mRNA specific for bradykinin B2 receptor in both cells. Bradykinin significantly increased 2-deoxyglucose uptake in isolated muscle and L6 myoblasts in the presence of insulin (10(-7) mol/l) in a dose-dependent manner, but not in the absence of insulin. Bradykinin also enhanced insulin-stimulated GLUT4 translocation, and insulin-induced phosphorylation of insulin receptor beta subunit and insulin receptor substrate-1 (IRS-1) without affecting the binding affinities or numbers of cell surface insulin receptors in both cells. It is concluded that bradykinin could potentiate the insulin-induced glucose uptake through GLUT4 translocation in dog skeletal muscle and rat L6 myoblasts. This effect could be explained by the potency of bradykinin to upregulate the insulin receptor tyrosine kinase activity which stimulates phosphorylation of IRS-1, followed by an increase in GLUT4 translocation.
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PMID:Bradykinin potentiates insulin-stimulated glucose uptake and enhances insulin signal through the bradykinin B2 receptor in dog skeletal muscle and rat L6 myoblasts. 953 11


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