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

---

Query: EC:2.7.7.49 (reverse transcriptase)
31,746 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

In vitro studies on mouse oocytes have shown that two closely related sterols, subsequently named meiosis-activating sterols (MAS), can overcome the inhibitory effect of hypoxanthine on the resumption of meiosis. These sterols are synthesized by cytochrome P(450) lanosterol 14alpha-demethylase (LDM), a key enzyme in cholesterol biosynthesis. We have used specific inhibitors of LDM, azalanstat (RS-21607) and RS-21745, to test whether MAS is an obligatory mediator in the resumption of meiosis in the rat. Addition of azalanstat and RS-21745 (1-200 microM) to culture medium of rat isolated cumulus-enclosed oocyte and preovulatory follicle-enclosed oocyte stimulated by LH/hCG did not allow separation between their inhibition of the resumption of meiosis and the degeneration of oocytes. In both models, doses of the drug that inhibited oocyte maturation also increased oocyte degeneration. The inhibitors only partially suppressed follicular progesterone production. We have examined by reverse transcriptase-polymerase chain reaction, Western blotting, and immunocytochemistry the ovarian expression of LDM mRNA and protein during the preovulatory period. We did not find evidence for the stimulation of this enzyme by LH/hCG. The strongest staining by LDM antiserum was obtained in primordial and primary oocytes, and the staining was reduced with oocyte growth. In addition, strong LDM staining could be observed in some of the granulosa cells, especially of the corona radiata localized in close proximity to the oocyte. In conclusion, our results with specific inhibitors and molecular approaches do not reveal evidence to support the hypothesis that MAS is an obligatory step in the stimulation of the resumption of meiosis. Specific inhibitors of MAS synthesis did not prevent spontaneous or LH-stimulated meiosis at doses that have previously been shown to effectively suppress LDM activity. Much higher concentrations of the inhibitors, which affected meiosis, were detrimental to oocytes, leading to their degeneration. The timing of LDM expression in the ovary was incompatible with a role for MAS in meiosis. Finally, the preferential localization of LDM protein to the oocytes suggests MAS production in oocytes rather than its transport from the somatic compartment as implied by the proposed role of MAS as a cumulus-oocyte signal molecule.
...
PMID:Role of meiosis-activating sterols in rat oocyte maturation: effects of specific inhibitors and changes in the expression of lanosterol 14alpha-demethylase during the preovulatory period. 1113 87

Increasing evidence suggests that altered gene expression is associated with the induction and maintenance of malignancy in various organs including mouse lung adenocarcinomas. A competitive cDNA library screening (CCLS) was used to examine gene expression in 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone-induced lung adenocarcinomas from (C3H/HeJ x A/J])F1 mice. Comparisons of RNA expression in lung adenocarcinomas to those of normal surrounding lung tissue revealed altered expression in 220 clones from more than 50,000 clones screened. Fifty clones were selected for quantitative reverse transcriptase-polymerase chain reaction (PCR) analysis to verify altered expression. PCR primers were designed based on partial sequence analysis of the clones. Twenty-two clones were found to be differentially expressed in lung adenocarcinomas compared with normal lungs. GenBank database analysis showed that 14 of the 22 clones were homologous with known genes, whereas 8 clones contained novel sequences. Thirteen clones were down regulated in tumors compared to normal lung tissues, and 9 were overexpressed. The clones underexpressed or absent include adipocyte p27, carbonic anhydrase III, carbonyl reductase, cytochrome CYP2E1, skelemin, myosin, major urinary protein, and contrapsin. Overexpressed clones include Bruton's tyrosine kinase, cyclin D3, poly(A)-binding protein, alpha-fetoprotein, transferrin, and mouse B2 family repetitive sequence. Further examination of biologic implications of the differentially expressed genes in lung adenocarcinomas is necessary to understand their role(s) in mouse lung carcinogenesis.
...
PMID:Detection of differentially expressed genes in mouse lung adenocarcinomas. 1129 25

Adult Atlantic tomcod, Microgadus tomcod, from the Hudson River, New York State, USA, exhibit reduced inducibility of hepatic cytochrome P4501A1 (CYP1A1) mRNA compared with adult tomcod from the cleaner Miramichi River, New Brunswick, Canada, when treated with coplanar polychlorinated biphenyl (PCB) congeners or 2,3,7,8-tetrachlorodibenzo-p-dioxin. In contrast, little difference in CYP1A1 inducibility is observed between tomcod from these two rivers when treated with polycyclic aromatic hydrocarbons (PAHs). We sought to determine if impaired hepatic CYP1A1 inducibility in Hudson River tomcod results from a multigenerational, genetic adaptation or a single generational, physiological acclimation. Embryos and larvae from controlled experimental crosses of Hudson River and Miramichi River parents were exposed for 24 h to water-borne PCB congener 77 (10 ppm), benzo[a]pyrene (BaP; 10 ppm), or dimethysulfoxide, and CYP1A1 expression was assessed in individual larva using competitive reverse transcriptase polymerase chain reaction (RT-PCR) analysis. The CYP1A1 mRNA was significantly induced in larvae from both populations by BaP (47- and 52-fold) and PCB 77 (9- and 22-fold), although levels of expression were higher in offspring of Miramichi matings. Most important, CYP1A1 mRNA was significantly induced by PCB 77 in larvae from Hudson River parents. Concentrations of dioxin, furan, and PCB congeners were measured in livers and eggs of female tomcod from these two locales to quantify the extent of maternal transfer of contaminants. For both rivers, wet-weight contaminant concentrations were significantly higher (4-7 times) in livers than in eggs of the same females, suggesting that a threshold level of contaminants may have to be reached before CYP1A1 transcription is impaired. We conclude that reduced inducibility of hepatic CYP1A1 mRNA in adult tomcod from the Hudson River is most consistent with single-generational acclimation.
...
PMID:An evaluation of the etiology of reduced CYP1A1 messenger RNA expression in the Atlantic tomcod from the Hudson River, New York, USA, using reverse transcriptase polymerase chain reaction analysis. 1133 64

This report investigates the pathomechanism of acute renal failure caused by toxic acute tubular necrosis after treatment with the antiretroviral agent adefovir. A 38-year-old white homosexual man with human immunodeficiency virus infection and no history of opportunistic infections was maintained on highly active antiretroviral therapy (HAART), including hydroxyurea, stavudine, indinavir, ritonavir, and adefovir dipivoxil. Histologic examination of the renal biopsy showed severe acute tubular degenerative changes primarily affecting the proximal tubules. On ultrastructural examination, proximal tubular mitochondria were extremely enlarged and dysmorphic with loss and disorientation of their cristae. Functional histochemical stains for mitochondrial enzymes revealed focal tubular deficiency of cytochrome C oxidase (COX), a respiratory chain enzyme partially encoded by mitochondrial DNA (mtDNA), with preservation of succinate dehydrogenase, a respiratory chain enzyme entirely encoded by nuclear DNA (nDNA). Immunoreactivity for COX subunit I (encoded by mtDNA) was weak to undetectable in most tubular epithelial cells, although immunoreactivities for COX subunit IV and iron sulfur subunit of respiratory complex III (both encoded by nDNA) were well preserved in all renal tubular cells. Single-renal tubule polymerase chain reaction revealed marked reduction of mtDNA in COX-immunodeficient renal tubules. We conclude that adefovir-induced nephrotoxicity is mediated by depletion of mtDNA from proximal tubular cells through inhibition of mtDNA replication. This novel form of nephrotoxicity may serve as a prototype for other forms of renal toxicity caused by reverse transcriptase inhibitors.
...
PMID:Adefovir nephrotoxicity: possible role of mitochondrial DNA depletion. 1209 87

Erythrocytes contain a plasma membrane redox system that can reduce extracellular ascorbate radicals by using intracellular ascorbate as an electron donor. In this study, the hypothesis was tested that cytochrome b561 was a component of this system. Spectroscopic analysis of erythrocyte membrane preparations revealed the presence of cytochrome b5 and hemoglobin but also of a cytochrome with properties similar to cytochrome b561, reducible by ascorbate and insensitive to CO. The presence of cytochrome b561 was studied further by reverse transcriptase-PCR analysis of erythrocyte progenitor cells, reticulocytes. However, no cytochrome b561 mRNA could be found. These results were corroborated by Western blot analysis with an anti-cytochrome b561 serum. No cytochrome b561 protein could be detected in extracts of erythrocyte membranes. It is therefore concluded that erythrocytes do not contain cytochrome b561 in their membranes. The possible involvement of other b-cytochromes in ascorbate-ascorbate free radical oxidoreductase activity is discussed.
...
PMID:The ascorbate: ascorbate free radical oxidoreductase from the erythrocyte membrane is not cytochrome b561. 1173 44

The inducibility of cytochrome P4501A1 gene (CYP1A1) expression was examined in human lung samples from 27 subjects, using an explant culture system and semi-quantitative reverse transcriptase-polymerase chain reaction (RT-PCR) analysis. CYP1A1 transcripts were present in all of the lung specimens and were induced by the prototypic inducers 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and benzo[a]pyrene (B[a]P), and by the atypical inducers pyridine, nicotine, and omeprazole. 2-Hydroxypyridine was a better inducer than pyridine, implicating metabolites in CYP1A1 induction by the parent compound. The prototypical inducers were the most effective inducers in many samples but were ineffective in some samples in which the atypical compounds were effective inducers. Cytochrome P4501A2 (CYP1A2) transcripts were also detected in most of the lung specimens and were inducible in some specimens. The results show the suitability of the explant culture system for examining the inducibility of human pulmonary CYP1A1 and CYP1A2, indicate the heterogeneity in individual sensitivity to the induction, and underscore the need to include atypical inducers in studies of CYP1A inducibility in humans.
...
PMID:Induction of CYP1A1 and CYP1A2 expressions by prototypic and atypical inducers in the human lung. 1184 38

Cytochrome P450arom, a key enzyme in the hormonal steroidogenic pathway, mediates the conversion of androgens to estrogens. This work describes the molecular cloning of the cDNA encoding the European sea bass (Dicentrarchus labrax L.) cytochrome P450arom by means of reverse transcriptase and polymerase chain reaction (RT-PCR) and 5' and 3'-rapid amplification of cDNA ends (RACE) analyses. The cDNA is 1822bp in length and encodes a putative protein of 517 amino acids. Northern blot analysis revealed that the ovary expressed a transcript of about 2.2kb in size. Analysis of the deduced amino acid sequence indicated 62-86% identity with ovarian P450arom of other teleost fish, the highest identity being found with the Japanese flounder, Paralichthys olivaceous. Identity was lower (56-65%) with the P450arom forms first reported in teleost brain. Only 52% identity was observed with the corresponding fragment of the cartilaginous fish, Dasyatis sabina. RT-PCR revealed that the sea bass P450arom mRNA was also expressed, at low levels, in testis and brain. Between the 5' and 3'-untranslated terminal regions (UTR), the sea bass CYP19 gene contains eight introns. All introns conform to the GT/AG rule for RNA splicing and are inserted in exactly the same positions as those found in Oryzias latipes and the human CYP19 gene.
...
PMID:European sea bass (Dicentrarchus labrax L.) cytochrome P450arom: cDNA cloning, expression and genomic organization. 1186 61

In fish, the embryos and larvae are the life-stages most sensitive to damage from environmentally borne dioxin-like compounds and polycyclic aromatic hydrocarbons (PAHs). Methods are not routinely available to measure the body burdens of contaminants in embryos and larvae, thus precluding the investigation of links between exposure and biological effects. Quantification of expression of cytochrome P4501A1 (CYP1A1) provides an index of relative exposure of natural populations to bioavailable aromatic hydrocarbons (AH) and an initial evaluation of their biological effects. We developed a quantitative approach to standardize total RNA loading and then used competitive reverse transcriptase-polymerase chain reaction (RT-PCR) to quantify the CYP1A1 mRNA expression in environmentally exposed Atlantic tomcod (Microgadus tomcod) post yolk-sac larvae (postlarvae) from the Hudson River, New York, and in chemically treated postlarval offspring of controlled laboratory crosses of Hudson River parents. Significant induction of CYP1A1 expression was observed in tomcod postlarvae exposed to waterborne 3,3',4,4'-tetrachlorobiphenyl (PCB 77) (four-fold) and benzo[a]-pyrene (eight-fold) compared with vehicle-exposed controls. In contrast, CYP1A1 was not induced in Hudson River-exposed postlarvae compared with vehicle-exposed controls. This study demonstrates the feasibility of using competitive RT-PCR for the measurement of gene expression in environmentally exposed larvae of sentinel species, and is consistent with the hypothesis that postlarvae exposed to the Hudson River environment have not bioaccumulated sufficient levels of AHs to induce CYP1A1 expression. The high levels of hepatic CYP1A1 mRNA expression previously reported in 5-8 month old juvenile tomcod from the Hudson River coincides with their descent to the benthic habitat and the onset of independent feeding on AH-contaminated benthic prey.
...
PMID:Cytochrome P4501A1 is induced by PCB 77 and benzo[a]pyrene treatment but not by exposure to the Hudson River environment in Atlantic tomcod (Microgadus tomcod) post-yolk sac larvae. 1210 35

Many studies have demonstrated that cyclophosphamide (CPA) can affect hepatic cytochrome p450 (CYP) isoenzyme activity in animals. We have investigated the effect of CPA on gene expression of various CYP enzymes as well as beta-actin in the human acute promyelocytic leukemia cell line (HL-60S) and its multidrug-resistant (MDR) phenotype HL-60R. Cells were incubated at different concentrations of CPA ranging between 50 micro g/ml and 5 mg/ml. In determination of cytotoxicity and resistance factor (RF: IC(50) HL-60R/IC(50) HL-60S), concentrations of 100 and 500 micro g/ml CPA were selected to treat HL-60S and HL-60R up to 72 h. CYP gene expression in the cells prior to and after treatment with CPA was determined using semiquantitative reverse transcriptase-polymerase chain reaction (RT-PCR) and real-time PCR. Unexposed cell lines did not contain measurable levels of mRNA for CYP2B6, CYP3A4, CYP2C9 and CYP2C19 and no induction was observed after exposure. However, CYP1B1-specific mRNA, which is predominantly expressed in HL-60 cell line, was suppressed after exposure to CPA in a concentration-dependent manner. Beta-actin gene expression was also decreased. The HL-60 RF to CPA was calculated to 0.71, indicating that the multidrug-resistant (MDR) phenotype is not involved in the mechanism of resistance to CPA. No CYPs were induced by CPA in vitro, which probably indicates that the CYP inducibility in blood cells is poor. Our study suggests that suppression of beta-actin gene expression contributes or is involved in the CPA cytotoxicity.
...
PMID:Effect of cyclophosphamide on gene expression of cytochromes p450 and beta-actin in the HL-60 cell line. 1216 60

Solid organ transplantations have been performed successfully in selected HIV-positive patients with highly active antiretrovirus therapy (HAART). However, some of the medications in the HAART regimen require metabolism via the cytochrome P4503A, the same enzyme complex responsible for clearance of the calcineurin inhibitors cyclosporine and tacrolimus. Several case reports have described significant interactions between the agents used in HAART and immunosuppressive drugs. The goal of this report is to examine the extent of potential drug interactions between antiretroviral agents and tacrolimus after liver and kidney transplantation. Seven liver transplant (LTx) patients (M = 6, F = 1) and four kidney transplant (KTx) patients (M = 4) infected with HIV underwent surgery between September 1997 and January 2001. Initial immunosuppression consisted of tacrolimus and steroids for LTx patients or tacrolimus, steroids, and mycophenolate mofetil for KTx recipients. Their current baseline immunosuppression and HAART regimen were examined retrospectively. Of the seven liver recipients, one (case 4) died 2 weeks after LTx and never received HAART therapy posttransplantation. The remaining six patients were placed on a regimen consisting of two nucleoside reverse transcriptase inhibitors (NRTI) and one protease inhibitor (PI) (nelfinavir in 5, indinavir in 1) based on known viral sensitivities or history of a previous clinical response. Kidney recipients received NRTI and nonnucleoside reverse transcriptase inhibitors (NNRTI). The mean dose of tacrolimus in liver recipients was 0.6 mg/d, with mean trough concentration of 9.7 mg/mL. Compared with historic controls (liver transplant patients not on HAART), the average tacrolimus dose was 16-fold lower in patients on HAART. In contrast to liver recipients, HIV-positive kidney recipients not on PI therapy required a mean tacrolimus dose of 9.5 mg/d to maintain a mean trough concentration of 9.6 ng/mL. Of the two protease inhibitors used, nelfinavir seems to have a more profound effect than indinavir. When patients on nelfinavir alone (n = 5) were compared with a control group not on antiretroviral therapy, the need for a tacrolimus dose was 38 times lower (mean dose, 0.26 mg/d). Profound drug interactions between PI and tacrolimus have been observed requiring up to 50-fold reductions in dosage. This effect seems to be most pronounced with the use of nelfinavir as opposed to indinavir, although further experience is required to confirm this observation. In contrast, HAART using NRTI and NNRTI without the use of PI, as shown in kidney recipients, produces less significant effects on tacrolimus metabolism. Great caution and frequent drug level monitoring are necessary when HAART is introduced or withdrawn in HIV-positive recipients of organ transplants.
...
PMID:The interaction between antiretroviral agents and tacrolimus in liver and kidney transplant patients. 1220 Jul 88


<< Previous 1 2 3 4 5 6 7 8 Next >>

---