Search results for "Microsome"
showing 10 items of 262 documents
Effects of streptozotocin and dietary fructose on delta-6 desaturation in spontaneously hypertensive rat liver.
2004
We have investigated the effects of hypertension associated with diabetes mellitus on polyunsaturated fatty acid biosynthesis. For this purpose, two rat models for these pathologies have been established: a type 1 diabetic hypertensive model obtained by streptozotocin injection to spontaneously hypertensive rat (SHR), followed or not by insulin treatment (experiment 1); a type 2 diabetic hypertensive model by feeding SHR with a fructose enriched diet (experiment 2). Liver gene expression of delta-6 desaturase (D6D), microsomal D6D activities and fatty acid composition of total lipids were estimated. In experiment 1, an increase of linoleic acid (18:2 n-6) level was observed in the streptozo…
Influence of disulfiram on oxidative drug demethylation.
1970
In clinical antiepileptie therapy it has been observed that the simultaneous administration of diphenylhydantoin and various other drugs causes toxic reactions to diphenylhydantoin. I t was found that disulfiram (Olesen, 1966) as well as ehloramphenieol (Christensen and Skovsted, 1969) cause toxic effects in patients treated with diphenylhydantoin. They are attributed to an increased concentration of diphenylhydantoin in the plasma. Analogous observations show that chloramphenieol enhances the clinical effects of tolbutamide and dicoumarol (Christensen and Skovsted, 1969). Since diphenylhydantoin is metabolized chiefly by p-hydroxylation to 5-(p-hydroxyphenyl)-5-phenyl-hydantoin (Butler, 19…
Relationship between the target antigen of liver-kidney microsomal (LKM) autoantibodies and rat isoenzymes of cytochrome P-450
1988
Chronic active hepatitis (CAH) is a clinical syndrome of different etiologies. Liver-kidney microsomal (LKM) autoantibodies characterize a subgroup of HBsAg negative CAH, which is considered to be an autoimmune liver disease. By immunoblotting analysis (IB) LKM positive sera have been shown to react strongly with a poly-peptide band at 50 kD. Therefore we investigated various rat microsomal enzymes with a molecular weight around 50 kD as potential candidate target antigens. These included epoxide hydrolase, cytochrome P-450 reductase, and phenobarbital-inducible isoenzymes of cytochrome P-450 (PB1, PB2, PB3a, PB3b). By radioimmunoassay (RIA) and IB LKM positive sera were shown to react with…
Inducing properties of rifampicin and rifabutin for selected enzyme activities of the cytochrome P-450 and UDP-glucuronosyltransferase superfamilies …
1996
Important species differences have been reported concerning the induction properties of rifampicin towards enzymes of the P-450 superfamily. Mice, rabbits and humans are far more responsive than rats and guinea pigs. In the present study a strong induction of cytochrome P-450 3A-dependent enzyme activities was observed in female rat liver microsomes after high dose treatment (> or = 250 mg/kg/day for 9 days) with rifampicin, resulting in an up to 30-fold enhanced hydroxylation rate of testosterone in the 2 beta-, 6 beta- and 15 beta-position in vitro. Other cytochrome P-450 isozyme-selective reactions were not, or only marginally, affected. A steep increase in cytochrome P-450 3A activity o…
Distant downstream sequence determinants can control N-tail translocation during protein insertion into the endoplasmic reticulum membrane.
2000
We have studied the membrane insertion of ProW, an Escherichia coli inner membrane protein with seven transmembrane segments and a large periplasmic N-terminal tail, into endoplasmic reticulum (ER)-derived dog pancreas microsomes. Strikingly, significant levels of N-tail translocation is seen only when a minimum of four of the transmembrane segments are present; for constructs with fewer transmembrane segments, the N-tail remains mostly nontranslocated and the majority of the molecules adopt an 'inverted' topology where normally nontranslocated parts are translocated and vice versa. N-tail translocation can also be promoted by shortening of the N-tail and by the addition of positively charg…
Structure of Aspergillus niger epoxide hydrolase at 1.8 A resolution: implications for the structure and function of the mammalian microsomal class o…
2000
AbstractBackground: Epoxide hydrolases have important roles in the defense of cells against potentially harmful epoxides. Conversion of epoxides into less toxic and more easily excreted diols is a universally successful strategy. A number of microorganisms employ the same chemistry to process epoxides for use as carbon sources.Results: The X-ray structure of the epoxide hydrolase from Aspergillus niger was determined at 3.5 Å resolution using the multiwavelength anomalous dispersion (MAD) method, and then refined at 1.8 Å resolution. There is a dimer consisting of two 44 kDa subunits in the asymmetric unit. Each subunit consists of an α/β hydrolase fold, and a primarily helical lid over the…
Development of new Coumarin-based profluorescent substrates for human cytochrome P450 enzymes
2018
Cytochrome P450 (CYP) enzymes constitute an essential xenobiotic metabolizing system that regulates the elimination of lipophilic compounds from the body. Convenient and affordable assays for CYP enzymes are important for assessing these metabolic pathways.In this study, 10 novel profluorescent coumarin derivatives with various substitutions at carbons 3, 6 and 7 were developed. Molecular modeling indicated that 3-phenylcoumarin offers an excellent scaffold for the development of selective substrate compounds for various human CYP forms, as they could be metabolized to fluorescent 7-hydroxycoumarin derivatives. Oxidation of profluorescent coumarin derivatives to fluorescent metabolites by 1…
Characterization of monoclonal antibodies generated against bovine and porcine prostacyclin synthase and quantitation of bovine prostacyclin synthase
1994
AbstractMonoclonal antibodies were raised against prostacyclin synthases purified from bovine and porcine aortae, respectively. Two monoclonal antibodies, RS1 and RS2, were purified and characterized. As shown by enzyme activity precipitation and Western blot analysis, in solubilized bovine and porcine aortae microsomes the monoclonal antibodies reacted only with prostacyclin synthase. The monoclonal antibody RS1 cross-reacts with partially purified prostacyclin synthase from human umbilical veins in an ELISA-based assay. None of the antibodies inhibited the enzyme activity. By combination of the monoclonal antibody RS2 with a polyclonal antibody we established an enzyme-linked immunosorben…
Influence of cyclopropene fatty acids (Baobab seed oil) feeding on the in vitro Δ9 desaturation of stearic acid in rat liver microsomes
1993
Abstract Δ9 desaturation of [1−14C] stearic acid to oleic acid was studied in liver microsomes of rats fed either fresh Baobab seed oil, containing cyclopropene fatty acids (malvalic acid and sterculic acids), or heated Baobab oil, containing only minor amounts of these acids. This was compared with rats fed a control oil mixture or a fat-free diet. Up to 50 nmol of substrate, Δ9 desaturation rate was the same in rats fed the three fat diets. From 50 to 150 nmol, the desaturation rates were practically constant in rats fed fresh Baobab seed oil. It increased in heated oil-fed rats at the same rate as in the control group, but more slowly than in the fat-free diet group. Fatty acid compositi…