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)

Although accumulating data show that placenta is able to synthesize 1,25-dihydroxyvitamin D3, the presence of cytochrome P(450) enzyme capable of converting 25-hydroxyvitamin D3 (250HD(3)) to the biologically active form of vitamin D in this tissue, has not been yet clearly established. In this study, we have investigated the presence of 25-hydroxyvitamin D3 1alpha-hydroxylase (1alpha-(OH)ase) gene expression products in cultured human syncytiotrophoblast. Total RNA was isolated from cultured placental cells and subjected to Northern blots or RT-PCR by using 1alpha-(OH)ase-specific primers. The amplified complementary DNA fragments were analyzed by gel electrophoresis and nucleotide sequencing. Total RNA from kidney HEK 293 cells was subjected to reverse transcriptase reaction, and a 298-bp complementary DNA 1alpha-(OH)ase probe was generated by PCR. Primary cultures of human syncytiotrophoblasts exhibited 1alpha-(OH)ase activity, and a transcript for this gene could be demonstrated in these cells. Northern blot analysis revealed the presence of a 2.5-kb product, similar in size to that previously reported in kidney. RT-PCR analysis demonstrated the presence of a single transcript with nucleotide sequence identical to that previously reported for human 1alpha-(OH)ase complementary DNA clones. In addition, data are presented which suggest that differentiation of cytotrophoblast to the syncytial state was not necessary for this gene to be expressed, which may indicate a role of this enzyme all through pregnancy. The overall results of this study provide evidence for the presence of 1alpha-(OH)ase in the human placenta, suggesting that conversion of 25OHD(3) to 1,25-dihydroxyvitamin D3 in the trophoblast is most probably attributed to an enzymatic 1alpha-hydroxylation reaction.
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PMID:Identification of a 25-hydroxyvitamin D3 1alpha-hydroxylase gene transcription product in cultures of human syncytiotrophoblast cells. 1090 6

Human colorectal cancer cells not only express the nuclear vitamin D receptor (VDR) but are also endowed with 25-hydroxy-vitamin D(3)-1alpha-hydroxylase activity and therefore are able to produce the specific ligand for the VDR, the hormonally active steroid 1alpha,25-dihydroxyvitamin D(3) (1alpha,25(OH)(2)D(3)). In the present study we show by semiquantitative reverse transcriptase polymerase chain reaction (RT-PCR) as well as by Western blotting and immunohistochemical methods, that in human large intestinal carcinomas expression of the genes encoding the 25-(OH)D(3)-1alpha-hydroxylase as well as the VDR increases in parallel with ongoing dedifferentiation in the early phase of cancerogenesis, whereas in poorly differentiated late stage carcinomas only low levels of the respective mRNAs can be detected. This indicates that, through up-regulation of this intrinsic 1alpha,25(OH)(2)D(3)/VDR system which mediates the anti-mitotic effects of the steroid hormone, colorectal cancer cells are apparently able to increase their potential for an autocrine counter-regulatory response to neoplastic cell growth, particularly in the early stages of malignancy.
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PMID:25-Hydroxyvitamin D(3)-1alpha-hydroxylase and vitamin D receptor gene expression in human colonic mucosa is elevated during early cancerogenesis. 1117 36

A significant contribution of the forestomachs in net calcium (Ca2+) absorption from the gastrointestinal tract has been postulated from in vivo and in vitro studies in different ruminant species. However, the potential role of vitamin D3 and its metabolites in controlling these mechanisms is still under discussion. It was therefore the aim of the present study to investigate the effectiveness of treatment with vitamin D3 in stimulating active Ca2+ absorption from sheep rumen. Four mature, non-lactating, non-pregnant sheep that had been treated 7 and 4 days before the Ca2+ flux rate measurements with intramuscular injections of 300000 IU of vitamin D3 each in aqueous solution were used. Two female and three male placebo-treated sheep served as controls. To characterize the effects of vitamin D3 application on plasma parameters the time courses of total calcium, inorganic phosphate, calcitriol and intact parathyroid hormone (iPTH) were recorded. In vitro studies of unidirectional Ca2+ flux rates across isolated, intact rumen wall epithelia were carried out by applying the Ussing-chamber technique. Western blot analysis and reverse transcriptase-polymerase chain reaction analysis (RT-PCR) were applied to identify vitamin D receptors (VDR) in ruminal and jejunal tissues. In addition, Western blot analysis for qualitative examination of epithelial calbindin D9k levels was carried out in these tissues. Total calcium and phosphate levels in plasma were not significantly affected treatment with vitamin whereas calcitriol concentrations significantly increased by about 130 and 63% after the first and second application, respectively. In contrast, iPTH tended to decrease by about 60% indicating regulatory effects of calcitriol on systemic Ca homeostasis. The Ca2+ flux rate measurements in Ussing-chambers revealed significant net Ca2+ absorption indicating the contribution of active mechanisms for Ca2+ transport in rumen epithelia. This, however, was not significantly affected by increased calcitriol concentrations in plasma. Western blot analysis on the basis of a human recombinant VDR protein and RT-PCR clearly indicated the presence of VDR in ruminal and jejunal epithelia, but, in contrast to jejunum, this was not reflected by respective amounts of calbindin-D9k in ruminal tissues. The results suggest the absence of classical calbindin-D9k-mediated mechanisms for active Ca2+ transport in sheep rumen.
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PMID:No effect of vitamin D3 treatment on active calcium absorption across ruminal epithelium of sheep. 1155 93

The epithelial Ca2+ channel, ECaC1, is primarily expressed in the apical membrane of vitamin D-responsive tissues. This study characterizes for the first time the presence of this novel channel in pancreatic tissue by reverse transcriptase-polymerase chain reaction and immunohistochemistry. In addition, the expression of ECaC1 was investigated in an animal model for Type 2 diabetes mellitus, the Zucker diabetic fatty (ZDF) rat. Identical staining patterns for ECaC1 and insulin were observed, whereas no co-localization of ECaC1 with glucagon was found. ECaC1, insulin, and prohormone convertase 1 (a neuroendocrine endoprotease expressed in secretory granules) showed a similar punctate staining. ECaC1 co-localized with the Ca2+ binding protein calbindin-D(28K) in the beta-cells. Furthermore, in contrast to wild-type rats, in ZDF rats aging led to a progressive decrease in both insulin and ECaC1 staining. Plasma 1,25-dihydroxyvitamin D3 levels were similar in both control and ZDF rats and decreased with aging. Taken together, our findings indicate that this novel Ca2+ channel may play a role in the regulation of endocrine Ca2+ homeostasis.
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PMID:Expression of the novel epithelial Ca2+ channel ECaC1 in rat pancreatic islets. 1201 95

In addition to its classical calciotropic effects, the active form of vitamin D, 1,25-dihydroxyvitamin D(3) (1,25(OH)(2)D(3)) is a potent anti-proliferative/immunomodulatory secosteroid. The enzyme that catalyzes the synthesis of 1,25(OH)(2)D(3), 1alpha-hydroxylase (1alpha-OHase), is expressed in many human tissues, highlighting its possible role as an autocrine/paracrine activator of vitamin D. Immunohistochemical and RNA analyses were used to characterize the ontogeny of 1alpha-OHase expression in human placenta and decidua. Protein for 1alpha-OHase was detectable in trophoblast and decidua; the latter being stronger in decidualized stromal cells than macrophages, with no staining of lymphocytes. Quantitative reverse transcriptase-polymerase chain reaction was used to assess changes in mRNA expression for 1alpha-OHase at different gestations: first (mean, 9.1 +/- 1.5 weeks); second (mean, 14 +/- 1.8 weeks), and third trimester (mean, 39.3 +/- 2.5 weeks). 1alpha-OHase expression in decidua was approximately 1000-fold higher in first (95% confidence limits, 611 to 1376) and second (95% confidence limits, 633 to 1623) trimester biopsies when compared with the third trimester (95% confidence limits, 0.36 to 2.81) (both P < 0.001). In placenta, 1alpha-OHase expression was 80-fold higher in the first (range, 42 to 137) and second (range, 30 to 199) trimester when compared with third trimester biopsies (0.6 to 1.6) (both P < 0.001). Similar results were obtained by semiquantitative IHC. Parallel analysis of the receptor for 1,25(OH)(2)D(3) (vitamin D receptor) indicated that, as with 1alpha-OHase, highest levels of expression occurred in first trimester decidua. However, changes in vitamin D receptor mRNA expression across gestation were less pronounced than 1alpha-OHase. These spatiotemporal data emphasize the potential importance of 1alpha-OHase during early fetoplacental life and, in particular, suggest an autocrine/paracrine immunomodulatory function for the enzyme.
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PMID:The ontogeny of 25-hydroxyvitamin D(3) 1alpha-hydroxylase expression in human placenta and decidua. 1210 95

The expression of vitamin D-receptor (VDR) and retinoid X-receptor alpha (RXR-alpha) has been analysed immunohistochemically in benign (n = 62 and n = 5 respectively) and malignant (n = 228 and n = 15 respectively) breast tissue samples using a monoclonal antibody 9A7gamma against VDR and a polyclonal antibody against RXR-alpha. A recently developed immunoreactive scoring method (IRS) was employed. The expression of VDR was detected at the RNA-level using the reverse transcriptase-polymerase chain reaction. A statistically significant higher expression of VDR at the protein level was seen in breast cancer compared with benign breast tissue, whereas at the mRNA level no visible differences in the expression of VDR were found. A higher expression of RXR-alpha was seen in breast cancer compared with benign breast tissue. Our findings indicate that breast tissue may be a new target organ for therapeutically applied vitamin D and retinoid analogues. VDR and RXR-alpha are upregulated at the protein level in breast carcinomas as compared to normal breast tissue, indicating a possibly increased sensitivity to therapeutically applied vitamin D analogues. New vitamin D analogues exerting less calcemic side effects may be promising new drugs for the treatment or chemoprevention of breast carcinomas as well as of precancerous breast lesions. Combination therapies of vitamin D and retinoid analogues with fewer side effects seen promising for the treatment of breast cancer.
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PMID:Analysis of vitamin D-receptor (VDR) and retinoid X-receptor alpha in breast cancer. 1236 98

Recent development of tuberculosis in Japan tends to converge on a specific high risk group. The proportion of tuberculosis developing particularly from the compromised hosts in the high risk group is especially high. At this symposium, therefore, we took up diabetes mellitus, gastrectomy, dialysis, AIDS and the elderly for discussion. Many new findings and useful reports for practical medical treatment are submitted; why these compromised hosts are predisposed to tuberculosis, tuberculosis diagnostic and remedial notes of those compromised hosts etc. It is an important question for the future to study how to prevent tuberculosis from these compromised hosts. 1. Tuberculosis in diabetes mellitus: aggravation and its immunological mechanism: Kazuyoshi KAWAKAMI (Department of Internal Medicine, Division of Infectious Diseases, Graduate School and Faculty of Medicine, University of the Ryukyus). It has been well documented that diabetes mellitus (DM) is a major aggravating factor in tuberculosis. The onset of this disease is more frequent in DM patients than in individuals with any underlying diseases. However, the precise mechanism of this finding remains to be fully understood. Earlier studies reported that the migration, phagocytosis and bactericidal activity of neutrophils are all impaired in DM patients, which is related to their reduced host defense to infection with extracellular bacteria, such as S. aureus and E. colli. Host defense to mycobacterial infection is largely mediated by cellular immunity, and Th1-related cytokines, such as IFN-gamma and IL-12, play a central role in this response. It is reported that serum level of these cytokines and their production by peripheral blood mononuclear cells (PBMC) are reduced in tuberculosis patients with DM, and this is supposed to be involved in the high incidence of tuberculosis in DM. Our study observed similar findings and furthermore indicated that IFN-gamma and IL-12 production by BCG-stimulated PBMC was lower in poorly-controlled DM patients than that in well-controlled DM patients and healthy subjects. Thus, these clinical data suggest that the high incidence of tuberculosis in DM patients is due to the impaired production of Th1-related cytokines. However, direct evidences to prove this possibility remain to be obtained. In 1980, Saiki and co-workers reported that host defense and delayed-type hypersensitivity response to M. tuberculosis was hampered in a mouse DM model established by injecting streptozotocin (Infect Immun. 1980; 28: 127-131). We followed their investigation with the similar observations. Interestingly, levels of IFN-gamma and IL-12 in serum, lung, liver and spleen after infection were significantly reduced in DM mice when compared with those in control mice. Considered collectively, these results strongly suggest that the reduced production of Th1-related cytokines leads to the susceptibility of DM to mycobacterial infection. However, it remains to be understood how DM hampers the synthesis of Th1-related cytokines. In our preliminary study, the production of these cytokines by PBMC from DM patients and healthy subjects was not affected under a high glucose condition. Thus, it is not likely that the increased level of glucose directly suppresses the cell-mediated immune responses. Further investigations are needed to make these points clear. 2. A study of gastrectomy cases in pulmonary tuberculosis patients: Takenori YAGI (Division of Thoracic Disease, National Chiba-Higashi Hospital). Patients who have undergone gastric resection are considered at increased risk of developing pulmonary tuberculosis. I have investigated the role played by gastrectomy in giving rise to pulmonary tuberculosis. Of 654 pulmonary tuberculosis patients admitted to National Chiba-Higashi Hospital from January 1999 to December 2001, 55 patients (31-84 years old, mean 63.5 +/- 12.5 years, 48 males and 7 females) had the history of gastric resection. The incidence of gastrectomy among patients with pulmonary tuberculosis was 8.4 percent. The mean age of gastric resection was 50.2 +/- 16.6 years, and the mean interval from gastrectomy to pulmonary tuberculosis was 13.6 +/- 11.0 years. On admission to our hospital, 34 out of 55 cases were smear positive by sputum examination for acid-fast bacilli and 39 cases had cavitary lesions on chest X-ray. Gastrectomy was done due to carcinoma of the stomach in 31 cases, gastric and/or duodenal ulcer in 21 cases, adenomatous polyp in two cases, and accidental injury in one case. 52 patients improved, but three cases died due to pulmonary tuberculosis. No one had recurrence of carcinoma of the stomach. Body weight, Body Mass Index, Prognostic Nutritional Index (PNI; 10x serum albumin concentration +0.005 x peripheral lymphocyte count) which was proposed by Onodera, serum albumin level and serum total cholesterol level were lower in the gastrectomy group than in the non-gastrectomy group. I calculated the odds of tuberculosis among gastrectomy patients to be 3.8 times that of appropriate controls. This study confirms that gastrectomy is one of the risk factor(s) of tuberculosis. However, whether gastrectomy in itself is a risk factor or whether it is secondarily associated with another risk factor such as underweight status and/or inadequate nutrition following surgery remains unclear. 3. Immunodefficiency and tuberculosis in dialysis patients: Hajime INAMOTO (Division of Dialysis, Keio University School of Medicine). The patients who have renal insufficiency is fatal, but they can live much longer by dialysis. The number of lymphocytes of the patients whose serum creatinine was 10 mg/dl or more has decreased to about 50% of the people who have normal kidney. When the lymphocyte was cultured after it was stimulated with PHA, the DNA synthesis of the patients' lymphocyte was much lower than that of the modest people's. In the dialysis food, the nutrient such as vitamins, minerals, etc. were lacked. The density of the serum albumin of the dialysis patient has decreased. Many of them were thin when their BMI was examined. The size of the patients' erythema by the tuberculin test has become small. There were many patients receiving dialysis with erythema but no induration. It means that the delayed skin reaction specific to Mycobacterium tuberculosis has decreased among the dialysis patients. The morbidity rate, the mortality rate and the prevalence of tuberculosis was much higher than the general population. The anamnesis of tuberculosis was also high. Most of those tuberculosis patients appear the disease from the period immediately before the beginning of dialysis to one year after that. That is also the period that patients' number of peripheral blood lymphocyte decreased and the tuberculin reaction positivity rate fell sharply. During the dialysis patients, pulmonary tuberculosis with cavities was minority and extrapulmonary tuberculosis and miliary tuberculosis were remarkably many. People with large reaction against the tuberculin test were better prognosis than those with smaller reaction. It was thought that anorexia, weakening, and a weight decrease were seen when the immunity decreased. At the end stage of renal failure, kidney shrink, vitamin D activation becomes difficult, and the low calcium blood syndrome appears. The calcification of tuberculoma is absorbed, soft tuberculoma becomes baring, the caseation abscess melts, and the endogenous infection occurs. The cell immunity has decreased, and tuberculosis attacks. It might be such circumstances that tuberculosis happen frequently at the dialysis introduction period. There are a lot of cases that the caseation necrosis is a little, and the formation of tuberculoma is bad in the pathology opinion. Due to the decrease in the cell immunity, cavities are not formed easily. It is easy to stay in the leaching lesion so that anti-tuberculosis drugs are much effective, and the patients recover easily. However, if the treatment is delayed, it is fatally because hematogenous metastasis are easy to occur and become miliary tuberculosis. 4. AIDS and tuberculosis: Hideaki NAGAI (Department of Respiratory Diseases, National Tokyo Hospital). With AIDS patients with tuberculosis, there are the following problems on the treatment. (1) The adverse reactions by antituberculosis drugs tend to occur in AIDS patients. Eleven of 33 AIDS patients with tuberculosis had the adverse reactions (skin rash, fever, liver dysfunction) considered to be due to antituberculosis drugs. It is a very large burden for the HIV infected persons to take simultaneously antituberculosis drugs, medicines for opportunistic infections, and anti-HIV medicines. Since many medicines are taken, it is difficult to determine which drug is the cause once an adverse reaction occurs and all medicines should be often stopped. (2) The combined use with rifampicin (RFP) is difficult for the protease inhibitors and nonnuclear acid reverse transcriptase inhibitors. RFP induces cytochrome P-450 in liver, accelerates the metabolism of some concomitant drug agents, and reduces blood concentration them remarkably. When starting the two above-mentioned medicines during tuberculosis treatment, RFP should be changed to rifabutin (RFB) which has less induction of P-450 than RFP. However, some procedures are required for acquisition of RFB and it is a little complicated in Japan. CDC mentioned the combined use with RFP and efavirenz (EFV) is possible. So, the treatment with EFV and RFP is recently chosen. However, the monitor of the blood concentration of EFV is required, and the dose of EFV should be increased if it is a low value. (3) When a highly active antiretroviral therapy (HAART) is given to AIDS patients with tuberculosis, transient worsening of tuberculosis may develop after about two weeks. (ABSTRACT TRUNCATED)
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PMID:[Tuberculosis in compromised hosts]. 1467 50

Mutations in ClC-5 cause Dent's disease, a disorder associated with low molecular weight proteinuria, hyperphosphaturia, and kidney stones. ClC-5 is a Cl(-)/H(+)-exchanger predominantly expressed in the kidney, where it facilitates the acidification of proximal tubular endosomes. The reduction in proximal tubular endocytosis resulting from a lack of ClC-5 raises the luminal concentration of filtered proteins and peptides like parathyroid hormone (PTH). The increase in PTH may explain the hyperphosphaturia observed in Dent's disease. Expression profiling, quantitative reverse transcriptase-polymerase chain reaction (qRT-PCR), and hormone measurements were used to investigate whether the disruption of ClC-5 affects other signalling pathways. Although the upregulation of 25(OH)(2)-vitamin D(3) 1alpha-hydroxylase and downregulation of vitamin D(3) 24-hydroxylase suggested an increased formation of 1,25(OH)(2)-vitamin D(3), the concentration of this active metabolite was reduced in the serum of ClC-5 knockout (KO) mice. However, target genes of 1,25(OH)(2)-vitamin D(3) were upregulated in KO kidneys. Expression analysis of intestine and bone revealed that the upregulation of 1,25(OH)(2)-vitamin D(3) target genes was kidney intrinsic and not systemic. In spite of reduced serum levels of 1,25(OH)(2)-vitamin D(3) in ClC-5 KO mice, 1,25(OH)(2)-vitamin D(3) is increased in later nephron segments as a consequence of impaired proximal tubular endocytosis. This leads to a kidney-specific stimulation of 1,25(OH)(2)-vitamin D(3) target genes that may contribute to the pathogenesis of Dent's disease. The activation of genes in distal nephron segments by hormones that are normally endocytosed in the proximal tubule may extend to other pathways like those activated by retinoic acid.
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PMID:Kidney-specific upregulation of vitamin D3 target genes in ClC-5 KO mice. 1667 9

The kidney is not only a primary vitamin D target organ but also is a key site of vitamin D metabolism. Recent studies have shown that vitamin D has important physiologic effects on proliferation and differentiation in a variety of benign and malignant cells. Our preliminary immunohistochemical study showed that vitamin D receptor (VDR) was highly expressed in renal distal tubules and collecting ducts, whereas the renal proximal tubules and glomeruli did not express VDR. These observations led us to study the expression of VDR in various kidney tumors to determine the possible diagnostic utility of VDR. Paraffin tissue microarray (TMA) blocks were constructed containing core cylinders from clear cell (52), papillary (35), chromophobe (20), sarcomatoid (20), and metastatic (59) renal cell carcinomas (RCCs). Oncocytomas (20), normal adult kidneys (12), and normal adult adrenals (6) were also included. In addition, 30 clear cell RCCs and 3 collecting duct carcinomas were also studied using conventional sections. Furthermore, VDR messenger RNA and protein expression was also quantified using real-time reverse transcriptase-polymerase chain reaction and Western blot analysis. Vitamin D receptor was strongly positive in collecting duct carcinomas (100% [3/3], cytoplasmic), papillary RCCs (94% [33/35], cytoplasmic), chromophobe RCCs (85% [17/20], membranous), and oncocytomas (90% [18/20], cytoplasmic with perinuclear accentuation). In contrast, VDR expression was focal/weak and present only in the peripheral regions of clear cell RCCs. Vitamin D receptor was weakly positive in sarcomatoid variant RCCs (88% [14/16]) regardless of the type of associated original RCC. Overall, VDR is a discriminative marker for renal cell tumors. The preferential expression of VDR in chromophobe RCCs, oncocytomas, and collecting duct carcinomas is in agreement with the concept that these tumors differentiate toward epithelium lining the distal convoluted tubules and collecting ducts. Considering the different VDR expression patterns, VDR is a useful ancillary tool in distinguishing chromophobe RCCs from oncocytomas. In addition, the focal and much weaker VDR expression in clear cell RCCs makes VDR valuable in distinguishing clear cell RCC from other types of RCCs.
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PMID:Expression of vitamin D3 receptor in kidney tumors. 1694 27

Evidence is accruing that environmental exposures during critical periods of early development induce persisting changes in skeletal growth, and alter fracture risk in later life. We have previously demonstrated that placental calcium transport, partly determined by maternal 25-(OH) vitamin D status, may underlie this phenomenon. However, the precise relationship between expression of calcium transport proteins in the human placenta, and neonatal bone mineral accrual in the offspring, remains unknown. Tissue samples from 70 human placentae were fast frozen in liquid nitrogen and stored at -70 degrees C. A quantitative real time reverse transcriptase polymerase chain reaction was used to measure the mRNA expression of PMCA isoforms 1-4, using beta-actin as a control gene. Neonatal whole body bone area, mineral content and areal density (BA, BMC, BMD) were measured within 2 weeks of birth using DXA. PMCA3 mRNA expression predicted BA (r=0.28, p=0.02), BMC (r=0.25, p=0.04), placental weight (r=0.26, p=0.04) and birth weight (r=0.33, p=0.006) of the neonate. In a multivariate model, the relationship between placental PMCA3 expression and neonatal BMC was independent of maternal height, pre-pregnant fat stores, parity, physical activity, smoking, and calcium intake (p<0.05). Expression of the placental calcium transporter PMCA3 mRNA predicts neonatal whole body bone mineral content. This association may explain, in part, the mechanism whereby a mother's 25(OH)-vitamin D stores influence her offspring's bone mass.
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PMID:Placental calcium transporter (PMCA3) gene expression predicts intrauterine bone mineral accrual. 1733 74


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