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)

Breast tumor cell lines have been shown to secrete at least five distinct insulin-like growth factor (IGF) binding proteins (IGFBP), the secretion being related to the estrogen receptor (ER) content. In this study we investigated IGFBP mRNA expression and IGFBP content in relation to ER content in human breast tumors. Tissue specimens from 47 breast cancers were studied. In five cases the adjacent histologically normal tissue was also analyzed. IGFBP content in tissue homogenates was studied by Western ligand blot analysis, using [125I] IGF-I as a label, and IGFBP mRNA expression by reverse transcriptase polymerase chain reaction. The results show that human breast tumors express mRNAs encoding IGFBP-1, IGFBP-2, IGFBP-3, IGFBP-4 and IGFBP-5. The pattern of IGFBPs in different tumors varies. No correlation exists between ER content and IGFBPs with molecular weights 24,000 Mr, 28,000 Mr, 34,000 Mr or 43,000 Mr, whereas the 49,000 Mr IGFBP was more abundant in ER negative tumors (P less than 0.05). The IGFBP content was significantly (P less than 0.05) higher in five tumors than in their adjacent normal tissues suggesting that increased content of IGFBPs is a feature typically associated with the malignant transformation of breast tissue.
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PMID:Insulin-like growth factor binding proteins in human breast cancer tissue. 138 38

The insulin-like growth factor (IGF)-II/mannose-6-phosphate (M6P) receptor, which targets acid hydrolases to lysosomes, is a multifunctional protein with separate binding sites for IGF-II and M6P. The purpose of this study was to determine if alveolar macrophages (AM) and their precursor cells, blood monocytes, expressed this receptor. AM expressed IGF-II/M6P receptors as detected by [125]IGF-II surface binding that was not reduced by recombinant IGF-I or IGF-I receptor monoclonal antibody (alpha IR3). Surface binding was also detected on blood monocytes and could be upregulated approximately 4-fold by incubation with lipopolysaccharide. There were no differences in surface binding by AM lavaged from individuals with asbestos exposure or from normal volunteers. Using the polymerase chain reaction and reverse transcriptase to reverse-transcribe mRNA from mononuclear phagocytes, specific IGF-II/M6P receptor cDNA was amplified and detected by agarose gel electrophoresis from both AM and blood monocytes. The IGF-II/M6P receptor has an intracellular transport role in many cells cycling from the cell surface to the cytoplasm, or binding to phosphorylated acid hydrolases in the Golgi and transporting them to an acidic prelysosomal site where they dissociate and fuse to the lysosomes and IGF-II/M6P recycles to the trans-Golgi. These functions may be particularly important in asbestosis and other interstitial lung diseases where AM are activated, intracellular lysosomes are a prominent morphologic feature, and acid hydrolases are found in recovered lavage fluid.
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PMID:Human mononuclear phagocytes express the insulin-like growth factor-II/mannose-6-phosphate receptor. 164 80

The insulin-like growth factor (IGF) system is thought to function as a mediator of steroid hormone actions in the endometrium. IGFs (IGF-I and IGF-II) are also potent mitogens in endometrial cancer. The biological actions of IGFs are modulated by specific binding proteins (IGFBP)--6 cloned and sequenced so far--which may either inhibit or enhance the effects of IGF at the cellular level. In the endometrium, IGFBP-1 gene expression is stimulated by progesterone and inhibited by insulin, while IGFBP-1 inhibits the mitogenic action of IGF-I. In this study, we used a quantitative reverse transcriptase polymerase chain reaction (RT-PCR) to investigate IGFBP-1, IGFBP-2, IGFBP-4, IGFBP-5 and IGFBP-6 gene expression in endometrial cancer tissues. Endometrial cancer tissue samples were collected from 20 women (aged 54-79 yrs) with stage I to II well-differentiated endometrial adenocarcinoma. Samples of normal endometrium (n = 14) obtained from women undergoing tubal ligation in various phases of the menstrual cycle, and normal early-pregnancy endometrium (decidua) were studied for comparison. In endometrial cancer tissues, the IGFBP-1 mRNA was undetectable or minimally expressed when studied by RT-PCR. The mean (+ SD) levels of IGFBP-2 and IGFBP-4 and IGFBP-5 mRNAs in endometrial cancer tissues did not differ from those in normal endometrium, in which no cyclic variation was observed, suggesting that the genes encoding IGFBP-2, IGFBP-4 and IGFBP-5 are not hormonally regulated in the endometrium. The IGFBP-6 mRNA expression showed a significant cyclic variation in normal endometrium, with low levels in late-proliferative and early- to mid-secretory phases and high expression in late-secretory and early-proliferative phases. In endometrial cancer tissues, the mean IGFBP-6 mRNA level was similar to that in cycling endometrium during the peri-ovulatory period. In summary, a continuous stimulation of the endometrial epithelial cells by IGFs with suppressed IGFBP-1 expression may lead to an imbalance in the IGF system of the endometrium and trigger an uncontrolled cell proliferation, ultimately resulting in malignant transformation.
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PMID:Suppressed expression of insulin-like growth factor binding protein-1 mRNA in the endometrium: a molecular mechanism associating endometrial cancer with its risk factors. 752 16

Ovulation rate, serum hormone concentrations, follicular fluid (FFL) concentrations of steroids and IGF, IGF binding protein (IGFBP) activity in FFL, and follicular IGF-I and -II mRNA were compared during the follicular phase among five genotypes of ewes: Finn (F), Composite III (C), 1/2 Booroola Merino (B) x 1/2 F (B x F), 1/2 F x 1/2 C (F x C), 1/2 B x 1/2 C (B x C). Composite III ewes were a Columbia x Suffolk x Hampshire crossbred. Ovulation rates for F (n = 7), C (n = 5), B x F (n = 6), F x C (n = 3), and B x C (n = 8) ewes were 3.1, 1.6, 3.8, 2.9, and 2.9 (Pooled SEM = .5), respectively. Concentrations of IGF-I in FFL were 53% greater (P < .05) in large (> or = 4.1 mm) than in small (< 4.1 mm) follicles but did not differ (P > .10) among genotypes. In contrast, FFL IGF-II concentrations were greater (P < .05) in B x C and B x F ewes than in C or F x C ewes but did not differ between small and large follicles. Ligand blotting revealed that IGFBP activity of three species (34, 27 to 29, and 24 kDa) were lower (P < .05) in FFL of large than in FFL of small follicles but did not differ (P < .10) among genotypes. Follicular wall IGF-I mRNA and IGF-II mRNA was detected in 5 and 32% of the samples from preovulatory follicles, respectively, using reverse transcriptase-PCR and ethidiumbromide staining. Ovarian IGF-I mRNA levels, assessed by Northern analysis, in B x F and B x C ewes were greater (P < .05) than those in C ewes; ovarian IGF-I mRNA levels in F and F x C ewes were intermediate and did not differ (P > .10) from those in C ewes. Small follicles from B x C and B x F ewes had severalfold greater (P < .05) estradiol concentrations than those from F or C ewes, whereas large follicles from B x F ewes had twice (P < .05) the estradiol concentrations of follicles from F or C ewes. Progesterone in FFL did not differ among genotypes. Serum LH, FSH, inhibin, IGF-I, and progesterone did not differ (P > .10) among genotypes.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Serum hormones, follicular fluid steroids, insulin-like growth factors and their binding proteins, and ovarian IGF mRNA in sheep with different ovulation rates. 754 85

The human neuroblastoma line, SK-N-SH, has been subcloned into SH-SY5Y, a neuroblast N cell line, and SH-EP, an epithelial Schwann S cell line. We have previously shown that SH-SY5Y neuroblastoma cells produce insulin-like growth factor II (IGF-II), which acts by an autocrine mechanism to stimulate cell growth. In the current study, we examined the effect of IGF-II on SH-EP neuroblastoma cells. Northern blot and reverse transcriptase-polymerase chain reaction analyses indicate that SH-EP cells do not produce IGF-I or IGF-II but express the type I and type II IGF receptors (IGF-IR and IGF-IIR). Cell surface expression of IGF-IR, assessed by fluorescence-activated sorting, was lower in SH-EP cells than in SH-SY5Y cells. Immunoprecipitation of IGF-IR, followed by anti-phosphotyrosine or anti-IGF-IR immunoblotting, demonstrated functional expression of these receptors in both cell types and confirmed the lower level of IGF-IR expression in SH-EP cells. IGF-II promoted SH-EP cell growth in the presence of low concentrations of calf serum (0.1-0.3%) or 10 ng/ml epidermal growth factor (EGF). IGF-II stimulation of SH-EP growth was eliminated by the IGF-IR blocking antibody (alpha IR-3) but not by an IGF-IIR blocking antibody. Stimulation of cell growth via this receptor was also indicated by the ligand specificity for IGF analogs and insulin (IGF-II approximately IGF-I approximately des(1-3)IGF-I >> insulin). These results indicate that in the presence of a permissive factor such as calf serum or EGF, IGF-II stimulates SH-EP cell growth via the IGF-IR. Collectively, these data suggest that within primary neuroblastomas, IGF-II may act as a paracrine factor to contribute to the promotion of S cell growth.
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PMID:Insulin-like growth factor-II as a paracrine growth factor in human neuroblastoma cells. 758 43

The expression of insulin-like growth factors and their binding proteins in normal human peripheral lymphocytes was studied using the reverse transcriptase polymerase chain reaction method and Western ligand blotting. A quantitation of RT-PCR products was used to study the differences between normal and PHA stimulated lymphocytes. Normal freshly collected lymphocytes expressed mRNAs for both IGF-I receptor and IGF-II receptor but no expression of the corresponding growth factors was detectable. After stimulation with phytohemagglutinin the lymphocytes, however, expressed both IGF-I and IGF-II. Of the five IGFBPs examined, unstimulated lymphocytes expressed only IGFBP-2 and -3. Stimulated lymphocytes expressed IGFBP-4 and -5, in addition to IGFBP-2 and -3, whereas IGFBP-1 mRNA remained undetectable. The ligand blotting of lymphocyte conditioned media revealed production of 34K, 43K and 49K IGFBPs. The addition of estrogen, progesterone, IGF-I or growth hormone did not affect secretion of IGFBPs by lymphocytes.
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PMID:The expression of insulin-like growth factors and their binding proteins in normal human lymphocytes. 768 Aug 35

Goat IGF-I (gIGF-I) cDNA was cloned using the reverse transcriptase-polymerase chain reaction (RT-PCR). The cDNA, which was homologous to rat class 1 IGF-I cDNA, was 969 bp long. From the open reading frame found in it, we predicted a 154 amino acid protein consisting of a 49 amino acid signal peptide, a 70 amino acid mature IGF-I peptide, and a 35 amino acid E domain (the COOH-terminal peptide). From the gIGF-I gene, we isolated and sequenced some segments containing four exons that encompassed the entire gIGF-I cDNA sequence. Goat liver RNA was analyzed by RT-PCR, and the nucleotides of the RT-PCR products were sequenced and checked with the nucleotide sequences of the segments from the gIGF-I gene. The gene had three leader exons (1W, 1, and 2, from upstream to downstream) and was transcribed into three kinds of mRNAs (classes 1W, 1, and 2). Another RNA species was detected by RT-PCR analysis of exon 1W. We sequenced it and found that in this transcript, the 3'-portion of exon 1 was inserted between exons 1W and 3, resulting in class 1W-1 del. mRNA. That is to say, the gIGF-I gene had three leader exons and four kinds of mature mRNA.
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PMID:Dynamic aspects in the expression of the goat insulin-like growth factor-I (IGF-I) gene: diversity in transcription and post-transcription. 776 81

Recent studies have indicated that growth factors such as insulin-like growth factors (IGFs) increase the growth rate of cultured preimplantation embryos. We therefore hypothesized that the fallopian tube may produce IGFs which in turn participate in the regulation of preimplantation embryo development in vivo. In the present study we examined the expression of IGF-I in the fallopian tube. We demonstrated that IGF-I transcripts (7.0, 1.7, and 1.2-0.8 kilobases) were abundant in the fallopian tube. Immunoreactive IGF-I was most abundant in the epithelial cells in the fallopian tube, and IGF-I messenger RNA (mRNA) was detected in the luminal region of the fallopian tube. A solution hybridization assay was used to examine the regulation of IGF-I mRNA. The abundance of IGF-I transcripts changed markedly during the 4-day estrous cycle with the highest levels on the day of proestrus. The increase in IGF-I mRNA between the day of diestrus II and the day of proestrus was 4-fold (P < 0.01). The pattern of IGF-I mRNA expression in the fallopian tube resembled the pattern of ovarian estrogen production during the estrous cycle. The level of IGF-I mRNA decreased after hypophysectomy. The expression of IGF-I mRNA in the fallopian tube was dose-dependently regulated by estradiol, and a single sc injection of estradiol [5 micrograms/100 g body wt (BW)] increased the IGF-I mRNA in a time-dependent manner with a significant increase after 3 h (P < 0.01). The lowest estradiol dose tested (0.1 microgram/100 g BW) increased the expression after 6 h, whereas progesterone (5 micrograms/100 g BW) was ineffective. The presence of embryos in the fallopian tube did not statistically significantly influence the abundance of IGF-I transcripts as measured with a solution hybridization assay on RNA extracted from whole fallopian tubes. In order to determine possible targets for fallopian tube-derived IGF-I we examined the expression of IGF-I receptor mRNA. Northern blot analysis revealed that an 11-kilobase IGF-I receptor transcript was expressed in the fallopian tube. Using a reverse transcriptase-polymerase chain reaction, IGF-I receptor mRNA was also detected in the eight-cell but not two-cell preimplantation embryo. The present study demonstrates that IGF-I is produced in the fallopian tube and its expression is regulated by estradiol. Both the fallopian tube and the eight-cell preimplantation embryo express IGF-I receptors and are therefore potential target tissues.
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PMID:Expression of insulin-like growth factor-I (IGF-I) in the rat fallopian tube: possible autocrine and paracrine action of fallopian tube-derived IGF-I on the fallopian tube and on the preimplantation embryo. 840 50

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 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


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