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)

Sucrose density gradient analysis of purified pancreatic homogenates from glycaemic C57BL/Ks diabetes (db/db) mice and their normoglycaemic controls have revealed the presence in the diabetics of increased Mg++-dependent RNA-directed DNA polymerase activity sedimenting with a density of approximately 1.21 g/cm3. Electron microscopy revealed that this fraction contained typical intracisternal A-particles. Purified cultures of pancreatic islet cells 4--7 day old postnatal "misty diabetic" mice and normal siblings were established and then maintained in Eagle's minimal essential medium without serum. Under these conditions, the presence of intracisternal A-particles in beta cells of both mutant and control genotypes was very rare. No change in numbers of intracisternal A-particles was seen after 2--4 days of incubation in Dulbecco's-modified minimal essential medium containing 5.5 mmol/l glucose. However, when the glucose concentration of Dulbecco's medium was elevated to 16.5 mmol/l, ultrastructural changes specific to the beta cell population occurred that were reminiscent of those alterations observed in situ. Intracisternal A-particles were commonly seen in cultured beta cells showing hypersecretion-stress morphology. Since equal numbers of intracisternal A-particles were present in cultured beta cells from normal and mutant mice, it was concluded that the db gene itself was not required for intracisternal A-particle expression. The cell culture results suggest that elevated intracisternal A-particle activity observed in vivo may be produced directly or indirectly by the ambient high blood glucose levels characteristic of this mutant.
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PMID:Intracisternal A-particles in genetically diabetic mice: identification in pancreas and induction in cultured beta cells. 22 51

We have used a reverse transcriptase-polymerase chain reaction (RT-PCR) protocol to examine the expression of cytokines in the pancreases and islets of patients with type I diabetes. We detect a significant increase in the level of expression of interferon (IFN)-alpha in the pancreases of the diabetic patients as compared with the control pancreases. In contrast, IFN-beta was detected at comparable levels in both groups, while IFN-gamma was detected in three of four control pancreases and one of four pancreases from the diabetic individuals. The IFN-alpha cDNAs generated by the RT-PCR were cloned and sequenced to determine which alpha-subtypes were being expressed. We found that the repertoire of subtypes was quite limited in any one individual (diabetic or not), although each individual was different with respect to the pattern of subtypes expressed. We also examined these pancreases for the expression of tumor necrosis factor (TNF)-alpha, interleukin (IL)-1 beta, IL-2, IL-4, and IL-6. We found no detectable expression of TNF-alpha or IL-2 in any pancreases, and the expression of the other cytokines was variable, with no pattern emerging from the comparison of the diabetic and nondiabetic individuals. We conclude that, of the cytokines examined, only IFN-alpha was significantly increased in the diabetic patients, a result that is consistent with the possibility that this cytokine is directly involved in the development of type I diabetes.
Diabetes 1995 Jun
PMID:Interferon expression in the pancreases of patients with type I diabetes. 754 May 71

An inducible nitric oxide (NO) synthase isoform (iNOS) is specifically induced in the beta-cells of interleukin (IL)-1 beta-exposed rat islets, suggesting a role for NO in the pathogenesis of type I diabetes. The aim of this study was to clone and characterize iNOS cDNA from cytokine-exposed islets. Neither NO production nor iNOS transcription could be detected in rat islets or in rat insulinoma RIN-5AH beta-cells cultured in the absence of cytokines. Addition of IL-1 beta alone or in combination with tumor necrosis factor-alpha induced a concentration- and time-dependent expression of the iNOS gene and associated NO production (measured as nitrite) from both islets and RIN cells. iNOS transcripts were cloned by reverse transcriptase-polymerase chain reaction from the cytokine-exposed rat islets and RIN cells, and DNA sequence analysis revealed a near 100% identity to the recently published iNOS cDNA cloned from cytokine-exposed rat hepatocytes and smooth muscle cells. Recombinant rat islet iNOS was transiently and stably expressed in human kidney 293 fibroblasts, and the high enzymatic activity was inhibited by addition of the L-arginine analogs, N omega-nitro-L-arginine methyl ester and aminoguanidine. Two-dimensional gel electrophoresis revealed the recombinant iNOS as a series of spots with the expected molecular mass of 131 kDa and pI values in the range of 6.8 to 7.0. In conclusion, the IL-1 beta-induced iNOS cloned and expressed from rat islets and RIN cells is encoded by the same transcript as the iNOS induced in other cell types.
Diabetes 1995 Jul
PMID:Cloning and expression of cytokine-inducible nitric oxide synthase cDNA from rat islets of Langerhans. 754 May 73

To assess the alteration of apolipoprotein (apo) B mRNA editing in non-insulin-dependent diabetes mellitus (NIDDM), we measured plasma apoB-100 and apoB-48 levels and apoB mRNA editing efficiency in the liver and intestine from GK (Goto-Kakizaki) rats, a genetically NIDDM animal. Male GK rats and control littermates, aged 25 weeks, were used in this study. Ventromedial hypothalamus (VMH)-lesioned control rats were used as hyperinsulinemic models. VMH-lesioned GK rats (GK+VMH) were treated as an insulin-exhausted NIDDM model. Plasma cholesterol and triglyceride levels were increased in GK rats. Very low density lipoprotein (VLDL)-triglyceride and low density lipoprotein (LDL)-cholesterol concentrations were significantly higher in GK rats than in controls. The increase of VLDL-triglyceride was most marked in GK+VMH rats. Plasma apoB-48 levels, quantified by immunoblot, were increased in GK rats. However, apoB-100 levels were minimally elevated in GK rats. Therefore, the apoB-48/apoB-100 ratio was remarkably increased in GK rats. ApoB mRNA editing was analyzed by reverse transcriptase-polymerase chain reaction coupled with dideoxynucleotide chain termination assay. The ratio of apoB-48-type cDNA to apoB-100-type cDNA was significantly increased in the liver from GK rats compared with controls. Although the development of the VMH lesion increased plasma apoB-48 levels, it had no effect on the proportion of apoB-48-type to apoB-100-type cDNA in the liver from both GK and control littermates. ApoB mRNA in the intestine was almost totally edited (approximately 95%). Intestinal apoB-48/apoB-100 cDNA ratio showed no significant difference among the four groups. In conclusion, an enhanced apoB mRNA editing was indicated in the non-insulin-dependent diabetic rats, which might contribute to the increase of plasma apoB-48 levels.
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PMID:Increased proportion of plasma apoB-48 to apoB-100 in non-insulin-dependent diabetic rats: contribution of enhanced apoB mRNA editing in the liver. 759 89

Recent studies have shown that two different voltage-dependent Ca2+ channels are expressed in pancreatic islets, the beta-cell/neuroendocrine-brain and the cardiac subtypes. The effects of chronic hyperglycemia on the levels in pancreatic islets of the mRNAs encoding the alpha 1-subunits of the beta-cell and cardiac subtype Ca2+ channels were studied in rats made hyperglycemic by infusion of glucose for 48 h. A competitive reverse transcriptase-polymerase chain reaction procedure was used to obtain quantitative data on the levels of these two transcripts in islets obtained from individual rats. The quantitative polymerase chain reaction data indicate that the levels of mRNA encoding the alpha 1-subunit of the beta-cell Ca2+ channel are 2.5-fold greater than those for the cardiac subtype. The levels of beta-cell Ca2+ channel mRNA were 72.9% lower in the glucose-infused animals when compared with the saline-infused animals (P < 0.005) and those of the cardiac channel were 72.1% lower in the animals infused with glucose (P < 0.02). In contrast, glucose infusion resulted in a twofold increase in insulin mRNA levels and did not significantly alter levels of beta-actin mRNA. In situ hybridization studies revealed that the mRNAs for these two Ca2+ channels are expressed at higher levels in normal rat islets than in the surrounding acinar tissue, which suggests that the observed changes in mRNA levels occur within cells of the pancreatic islet. To assess the possible functional consequences of this reduction in expression of mRNA for the Ca2+ channels, the insulin secretory responses of perfused pancreases to the Ca2+ channel agonist Bay K8644 were studied.(ABSTRACT TRUNCATED AT 250 WORDS)
Diabetes 1993 Jul
PMID:Expression of calcium channel mRNAs in rat pancreatic islets and downregulation after glucose infusion. 768 20

The inducible NO synthase (iNOS) was found to be expressed in pancreatic lesions of adult diabetes-prone BB rats. Pancreatic iNOS mRNA was detected by reverse transcriptase PCR in pancreatic RNA of adult diabetes-prone BB rats but not in normal Wistar rats, young diabetes-prone BB rats without insulitis or in diabetes-resistant BB rats. Immunohistochemistry of pancreatic sections using an iNOS-specific antiserum labeled the pancreas of adult diabetes-prone BB rats but not Wistar rats. Parallel staining for ED1-positive macrophages showed restriction of iNOS expression to areas of islet infiltration by macrophages. In conclusion, the data provide direct evidence for enhanced expression of inducible NO synthase in tissue lesions during the development of autoimmune diabetes.
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PMID:Transcription and translation of inducible nitric oxide synthase in the pancreas of prediabetic BB rats. 768 27

It has been reported that the level of Tap-1 (transporter associated with antigen processing) mRNA and the expression of class I on splenocytes are low in NOD mice. Class I expression at 37 degrees C depends on an adequate supply of peptides, so a decrease in Tap could lead to lower class I levels. Since hypoexpression of class I correlated uniformly with the development of diabetes, it has also been suggested that Tap-1nod is diabetogenic. However, others report normal Tap-1 and class I levels in NOD mice. We examined Tap-1 and Tap-2 mRNA levels in NOD/Smrf mice using a reverse transcriptase-polymerase chain reaction method that detects > or = 25% changes in mRNA. We also assessed class I expression with three monoclonal antibodies. No difference in Tap-1 or Tap-2 mRNA levels for females of different ages or between diabetic and nondiabetic animals was observed. Tap-1 mRNA levels were identical between NOD/Smrf and BALB/cJ mice. Kd expression was significantly lower on NOD lymphocytes than in BALB/cJ cells, but the difference was due to the smaller size of the NOD splenic lymphocyte. When cells of the same size were analyzed, no difference in class I levels was observed. Class I levels were also identical in diabetic and age-matched nondiabetic NOD and BALB/c females. Both NOD Tap-1 mRNA and class I were increased by interferon-gamma. We find no evidence for impaired NOD Tap gene activity or class I expression, as previously reported for this strain.
Diabetes 1995 May
PMID:Levels of Tap-1 and Tap-2 mRNA and expression of Kd and Db on splenic lymphocytes are normal in NOD mice. 772 18

Islet-1 (Isl-1) is a unique transcription factor that binds to the enhancer region of the insulin gene. To evaluate this gene in non-insulin-dependent diabetes mellitus (NIDDM), a full-length human Isl-1 cDNA was isolated and the genomic structure was characterized. The cDNA [2,395 bp plus additional poly(A) residues] contained an open reading frame from an initiator methionine at nucleotide 240 to an opal stop codon at nucleotide 1,286 (GenBank accession number UO7559), encoding a predicted protein of 349 amino acids (39 kDa). From their ends, 23 additional clones were sequenced, revealing 15 incomplete cDNAs and 8 intron-containing partially processed precursors. As determined by Northern blotting and reverse transcriptase-polymerase chain reaction analysis, Isl-1 was most abundantly expressed as a 2.4-kb mRNA in human islets, with a restricted pattern of expression in other adult human tissues. Analysis of genomic clones revealed that Isl-1 is encoded by six exons, varying in size from 168 bp (exon 5) to 1,230 bp (exon 6). Exons 2 and 3 each encode a LIM domain, while the homeodomain is completely contained within exon 4.(ABSTRACT TRUNCATED AT 250 WORDS)
Diabetes 1995 Jun
PMID:Characterization of the LIM/homeodomain gene islet-1 and single nucleotide screening in NIDDM. 778 34

The injection of complete Freund's adjuvant into diabetic nonobese diabetic (NOD) mice at the time of syngeneic islet transplantation prevents monocytic/lymphocytic cell infiltration into the islet graft, Beta-cell destruction, and autoimmune diabetes recurrence. We have used semiquantitative reverse transcriptase-polymerase chain reaction analysis to examine and compare cytokine mRNA expression profiles in islet grafts from complete Freund's adjuvant-injected and control NOD mice. Interleukin 10 mRNA expression was significantly increased whereas interleukin 2 and interferon gamma mRNA levels were significantly decreased in islet grafts from complete Freund's adjuvant-injected mice compared to control mice. Levels of mRNA for interleukin 1 beta, interleukin 4, and tumour necrosis factor alpha were not significantly different in islet grafts from complete Freund's adjuvant-injected and control mice. These findings suggest that a Th1 subset of lymphocytes and their cytokine products, interleukin 2 and interferon gamma, may be involved in the rejection of syngeneic islet grafts and diabetes recurrence in NOD mice, and that the protective effect of complete Freund's adjuvant may result from the induction of interleukin 10 production and consequent down-regulation of Th1 cells and cytokines in the islet graft.
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PMID:Analysis of cytokine mRNA expression in syngeneic islet grafts of NOD mice: interleukin 2 and interferon gamma mRNA expression correlate with graft rejection and interleukin 10 with graft survival. 798 86

Basement membrane thickening is the most prominent and characteristic feature of early diabetic microangiopathy. Unknown is not only the causative process but also whether the thickening reflects increased synthesis of specific components. Because collagen type IV is uniquely present in basement membranes and represents their predominant structural element, we studied its expression in retinas obtained postmortem from five patients with 8 +/- 3 yr of diabetes and six nondiabetic controls. The collagen IV transcript proved to be rare in adult human retina and undetectable by Northern analysis. We thus identified a set of primers and conditions to detect the transcript by the reverse transcriptase polymerase chain reaction and to measure its level relative to an endogenous internal standard (beta-actin mRNA). In the diabetic patients the levels of collagen IV mRNA were increased twofold over levels in controls, whereas the actin mRNA levels were similar in the two groups. Hence, the collagen IV/actin ratio was 0.53 +/- 0.15 in diabetic samples and 0.24 +/- 0.09 in control samples (P = 0.004). These results indicate that diabetes induces a twofold increase in the expression of collagen IV by the cells that synthesize basement membranes in the adult retina (vascular cells). Insofar as high ambient glucose in vitro elicits the same effect, it may be proposed that basement membrane thickening in diabetes results from enhanced synthesis of specialized component molecules sustained by hyperglycemia.
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PMID:Increased expression of basement membrane collagen in human diabetic retinopathy. 828 17


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