Search results for "Microsome"
showing 10 items of 262 documents
Sub-cellular proteomic analysis of a Medicago truncatula root microsomal fraction
2004
Since the last decade, Medicago truncatula has emerged as one of the model plants particularly investigated in the field of plant-microbe interactions. Several genetic and molecular approaches including proteomics have been developed to increase knowledge about this plant species. To complement the proteomic data, which have mainly focused on the total root proteins from M. truncatula, we carried out a sub-cellular approach to gain access to the total membrane-associated proteins. Following the setting up of the purification process, microsomal proteins were separated on 2-DE. Ninety-six out of the 440 well-resolved proteins were identified by MALDI-TOF peptide mass fingerprinting. A high p…
A microplate version of the SOS/umu-test for rapid detection of genotoxins and genotoxic potentials of environmental samples
1991
Abstract The umu-microtest is a miniaturized automated short-term test version proposed for screening of umuC-dependent mutagenic potentials of chemicals relevant to environmental pollution, river water and industrial waste water. The test is based on the SOS/umu-test and has been modified in order to allow extensive testing of environmental samples. Genetically engineered Salmonella typhimurium (TA1535/pSK1002) are incubated on a microplate rotor in a sloping position for 2 h with the test samples, followed by addition of fresh culture medium to reach a 10-fold dilution of the incubation medium. 2 h later, the activity of the β-galactosidase, which reflects umuC induction, is determined co…
Epoxides metabolically produced from some known carcinogens and from some clinically used drugs. I. Differences in mutagenicity.
1975
The epoxide metabolites of two clinically used drugs and an experimental psychotropic agent, carbamazepine 10,11-oxide, cyproheptadine 10,11-oxide and cyclobenzaprine 10,11-oxide, were fully devoid of any mutagenic activity under conditions where K-region-epoxide metabolites of some known carcinogens, such as benzo (a)pyrene, proved to be potent frameshift mutational agents for Salmonella typhimurium TA 1537 and TA 1538. All epoxides tested were non-mutagenic for TA 1535, designed to detect substitution mutations. The 10,11-epoxides of the three drugs, carbamazepine, cyproheptadine and cyclobenzaprine, were not cytotoxic to any of the bacterial tester strains used, precluding that mutagenic…
Prevention of benzo(a)pyrene-induced mutagenicity by homogeneous epoxide hydratase
1976
Benzo(a)pyrene and benz(a)anthrancene which, in contrast to the K-region epoxides benzo(a)pyrene 4,5-oxide and benz(a)anthracene 5,6-oxide, are not mutagenic to Salmonella typhimurium TA 1537 in the absence of mammalian enzyme preparations, were activated by liver microsomes from C3H mice, which had not received any pretreatment, to mutagens reverting this tester strain to histidine prototrophy. Addition of epoxide hydratase inhibitors greatly increased this mutagenicity and addition of pure epoxide hydratase reduced it by more than 95% down to the range of spontaneous mutations as observed in absence of any added mutagen. This demonstrates that the metabolic pathway responsible for the mut…
The influence of automobile exhausts on mutagenicity of soils: contamination with, fractionation, separation, and preliminary identification of mutag…
2000
To test the assumption that automobile exhausts contribute to soil mutagenicity, two soils with low levels of mutagenic activities were exposed to traffic exhausts at a heavily charged junction of German motorways (Autobahnen) for 3, 7, 10, 13, 17, 21, and 26 weeks. Indeed, in the presence of a metabolic activation system from rat liver (S9), an average increase of 8 and 9 (4 and 12) revertants per gram per week was found in Salmonella typhimurium TA 98 (TA 100). In the absence of S9, meaningful measurements were impossible on account of a concurrent dose dependent increase of toxicity. No correlation between the increase of mutagenicity and the contents of polycyclic aromatic hydrocarbons …
Genotoxicity of six pesticides by Salmonella mutagenicity test and SOS chromotest.
1997
Abstract Two in vitro tests (Ames test and SOS chromotest), one for bacterial mutagenicity and one for primary DNA damage, were assayed to determine the genotoxic activity of 6 pesticides (atrazine, captafol, captan, chlorpyrifosmethyl, molinate and tetrachlorvinphos). Assays were carried out both in the absence and presence of S9 fractions of liver homogenate from rat (Sprague–Dawley) pretreated with Aroclor 1254. Captan and captafol were genotoxic on both the Ames test and the SOS chromotest. Comparisons with mutagenesis data in Salmonella indicated that the SOS assay detected as genotoxic the pesticides that were mutagenic on the Salmonella test. Non-genotoxic effects were not detected i…
Metabolites of diethylstilboestrol induce sister chromatid exchange in human cultured fibroblasts
1979
Diethylstilboesterol (DES) is one of the few substances for which a clear association with carcinogenicity has been established in man. Nevertheless, it is still widely used, mainly as a cheap oestrogen to increase the slaughter weight of beef, but in spite of this it is not known if residues in the meat or metabolites excreted by the cattle are hazardous to man. It is also unknown whether there is a threshold dose below which DES is harmless. A threshold might be expected if a hormonal mechanism of carcinogensis rather than metabolic activation to an electrophically reactive species operats. This possibility was supported by the observations that DES, in contrast to most other carcinogens,…
Dual role of epoxide hydratase in both activation and inactivation of benzo(a)pyrene.
1977
The effect of epoxide hydratase upon the mutagenicity of benzo(a)pyrene was investigated using two Salmonella typhimurium strains (TA 1537 and TA 98). These two bacterial strains were found to differ characteristically in their susceptibility to different mutagens biologically produced from benzo(a)pyrene providing a diagnostic tool to investigate which types of mutagenic metabolites were produced in various metabolic situations. The results showed that the pattern of mutagenic metabolites produced by microsomes from methylcholanthrene-treated mice was very different from that produced by microsomes from phenobarbital-treated or untreated mice. However in all cases at least two mutagenic me…
Differential Effects of Fluvoxamine and Other Antidepressants on the Biotransformation of Melatonin
2001
Melatonin, the predominant product of the pineal gland, is involved in the maintenance of diurnal rhythms. Nocturnal blood concentrations of melatonin have been shown to be enhanced by fluvoxamine, but not by other serotonin reuptake inhibitors. Because fluvoxamine is an inhibitor of several cytochrome P450 (CYP) enzymes, the authors studied the biotransformation of melatonin and the effects of fluvoxamine on the metabolism of melatonin in vitro using human liver microsomes and recombinant human CYP isoenzymes. Melatonin was found to be almost exclusively metabolized by CYP1A2 to 6-hydroxymelatonin and N-acetylserotonin with a minimal contribution of CYP2C19. Both reactions were potently in…
The microsomal epoxide hydrolase has a single membrane signal anchor sequence which is dispensable for the catalytic activity of this protein
1994
The microsomal epoxide hydrolase (mEH) catalyses the hydrolysis of reactive epoxides which are formed by the action of cytochromes P-450 from xenobiotics. In addition it has been suggested that mEH might mediate the transport of bile acids. For the mEH it has been shown that it is co-translationally inserted into the endoplasmic reticulum. Here we demonstrate that the N-terminal 20 amino acid residues of this protein serve as its single membrane anchor signal sequence and that the function of this sequence can also be supplied by a cytochrome P-450 (CYP2B1) anchor signal sequence. The evidence supporting this conclusion is as follows: (i) the rat mEH and a CYP2B1-mEH fusion protein, in whic…