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Biomedical subjects

M Roberfroid

Publications and source records attributed to M Roberfroid.

At least 19 recordsLinked to original sources
PubMed1979

Determination of Kováts retention indices with a capillary column and electron-capture detection: application to the assay of the enzymatic conversion of 3,4-epoxy-1-butene into diepoxybutane.

A method is described that allows for alternate operation of a "pin and cup"-type electron-capture detector (ECD) in the normal ECD mode and in the metastable argon ionization mode. By such means, marker n-alkanes can be run without a change of the gas or temperature parameters, and measurements can be made of the Kováts retention indices of unknown compounds that are detectable in trace amounts by ECD only. As an application, tests are reported which support the probable enzymatic conversion of 3,4-epoxy-1-butene into diepoxybutane during incubation of the former with rat liver microsomes.

Animals↗
PubMed1979

Microsomal vinyl oxide synthetase: modification of its kinetic parameters by chemical carcinogens.

The kinetic parameters of liver microsomal vinyl oxide synthetase as well as their modifications under the influence of various pretreatments have been evaluated, using 1,1,2-trichlorethylene (TCE) as a substrate. The results were correlated with those obtained using aldrin oxide synthetase and benzpyrene hydroxylase as typical cytochrome P-450 dependent enzymatic activity. The treatments of animals with chemical carcinogens selectively increase the affinity of those enzymes for their substrates.

Aldrin↗
PubMed1979

Liver extract mediated mutagenicity of acrylonitrile.

The mutagenic activity of acrylonitrile vapours towards Salmonella typhimurium strains strictly depends upon the presence of a liver postmitochondrial fraction. The reversion rate varies according to the animal species from which the S9 fraction is obtained as well as to the pretreatment of the animals. The comparatively weak activating effect of the microsomal fraction and the inability of both SKF525A and carbon monoxide to inhibit the S9 mediated mutagenicity of acrylonitrile (ACN) suggest that the cytochrome P-450-dependent monooxygenases do not play a major role in the metabolic activation of ACN into a mutagenic intermediate (s).

Acrylonitrile↗
PubMed1978

Sensitive gas chromatographic methods for the determination of vinyl epoxide synthetase activity using trichloroethylene as a model substrate.

Two specific and very sensitive methods for the determination of vinyl epoxide synthetase activity in liver microsomes are described. Trichloroethylene, which is used as a substrate, is converted into trichloroethylene oxide by a hepatic epoxide synthetase. Chloral hydrate, the final rearrangement product of trichloroethylene oxide, is determined by electron-capture gas chromatography, either after derivatization with pentafluorophenylhydrazine or after its conversion into chloroform under alkaline conditions. The kinetic parameters of the epoxidation reaction were determined on rat hepatic microsomal suspensions.

Animals↗
PubMed1978

A very sensitive gas chromatographic method for the evaluation of styrene oxidase and styrene oxide hydratase activities.

Styrene is a compound widely used in the manufacture of polystyrenic plastics and it has recently been shown to exert mutagenic effects after metabolic activation into styrene oxide by the microsomal mixed function oxidases; this oxide is further converted into inactive styrene glycol. In order to investigate the relative importance of activation and desactivation processes of styrene, we developed a gas chromatographic method which enables us to simultaneously measure styrene oxide and styrene glycol formed after incubation of styrene with microsomal preparations from different tissues. After selective extraction of the two compounds from the incubation mixture, they are derivatized with pentafluorobenzoyl chloride and measured by gas chromatography using an electron capture detector. The high sensitivity of the method, which allows 0.01 ng of both compounds to be measured, as well as its selectiveity, has permitted us to adequately evaluate the kinetic parameters of styrene oxidase and styrene oxide hydratase activities, as well as their modifications under the influence of various pretreatments of the animals.

Animals↗
PubMed1978

A gas chromatographic method for the evaluation of the vinyl epoxidase activity.

Two alternative specific and very sensitive methods for determination of vinyl epoxide synthetase activity in liver microsomes are described. Trichloroethylene, which is used as a substrate, is converted into trichloroethylene oxide by a hepatic epoxide synthetase. Chloral hydrate, the final rearrangement product of trichloroethylene oxide, is evaluated by electron capture gas chromatography, either after derivatization with pentafluorophenyl-hydrazine or after its conversion into chloroform under alcaline conditions. The kinetic parameters of the epoxidative reaction have been determined on rat hepatic microsomal suspensions.

Animals↗
PubMed1978

Mutagenicity tests with styrene oxide in mammals.

The capability of styrene oxide to induce chromosome damage in vivo has been tested in the male mouse by examination of bone-marrow cells, by scoring micronuclei in polychromatic erythrocytes, by observation of meiotic chromosomes from treated males and by the dominant-lethality test. Furthermore, studies have been performed on short-term cultures of human lymphocytes in vitro. Whereas an increase in the yield of chromatid and chromosomal aberrations was observed after exposure in vitro, only negative results were obtained in the tests in vivo. One has, therefore, to conclude that styrene oxide is potentially capable of breaking mammalian chromosomes but that an exposure to an acute dose in vivo does not produce visible damage in somatic cells or in male germ cells.

Animals↗
PubMed1978

Mutagenicity of acrylonitrile.

Incubation of Salmonella typhimurium strains in an atmosphere of 0.2% gaseous acrylonitrile increased the numbers of his+ revertants/plate only in the presence of a fortified S9 liver fraction. The mutagenic effect was particularly pronounced with strains TA1530, TA1535 and TA1950 and much weaker with strains TA100, TA98 and TA1978. The results of bacterial fluctuation tests confirmed the necessity of the presence of S9 mix and showed the particular sensitivity of TA1530. The reversion rate varied with the S9 mix composition, the animal species utilized and the type of pretreatments applied to the animals. The mutagenicity of acrylonitrile in S. typhimurium is therefore microsome-mediated and is particularly discernable with strains sensitive to base-substitution mutagens.

Acrylonitrile↗
PubMed1978

Specific modification of the properties of the N-hydroxylase. Relationship with carcinogenesis by aromatic amides.

N-hydroxylation represents the first and limiting step in the metabolic pathway leading to the carcinogenic activity of aromatic amines and amides. Using a method recently developed by the same authors (Analytical Biochemistry, in press), the effects of pretreatment of male adult rats with N-2-acetylaminofluorene (2AAF), N-4-acetylaminofluorene (4AAF), N-4-acetyl-aminobiphenyl, (4-AABP), and phenobarbital (PB), on the kinetic parameters of the N-hydroxylase activity have been evaluated and compared. Our resutls clearly demonstrate that both hepatocarcinogenic amides, 2-AAF and 4-AABP very significantly increase the affinity of the activating enzyme towards both substrates; on the other hand, 4-AAF and PB, which are non-carcinogenic compounds slightly decrease the affinity of the enzyme. In conclusion, the carcinogenic aromatic amides seem to specifically modify the catalytic properties of the enzyme responsible for their own metabolic activation.

2-Acetylaminofluorene↗