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Biomedical subjects

P Lafont

Publications and source records attributed to P Lafont.

At least 19 recordsLinked to original sources
PubMed1995

A specific immunoradiometric assay of cationic trypsin(ogen) that does not recognize trypsin-alpha-1-proteinase inhibitor complex.

An immunoradiometric assay using two monoclonal antibodies directed to human trypsin 1 was developed for measuring trypsin(ogen) in biological fluids. The assay is different from other assays in that it is specific for cationic trypsinogen and does not recognize the alpha-1-proteinase inhibitor-trypsin complex. It can be used as a complement to classical immunoassays to characterize trypsinogen activation in pathological cases. The evaluation and the specificity of the assay are presented.

Alpha-Globulins↗
PubMed1992

Monoclonal antibodies to human pancreatic trypsin 1 inhibit the activation of human trypsinogens 1 and 2.

Two monoclonal antibodies (Mab) raised against human pancreatic trypsin 1, Mab G6 and A8, were previously isolated and characterized. The two Mab which recognize trypsinogen 1 are found to inhibit the activation of trypsinogen 1 by enterokinase. The inhibition of activation by the two Mab is concentration-dependent, rapid and virtually complete with Mab G6. Activation of trypsinogen 2 is totally inhibited by Mab G6, while Mab A8 has no effect on the activation of trypsinogen 2. The two monoclonal antibodies have opposite effects on the proteolytic activity of trypsin 1; Mab G6 increases proteolytic activity while Mab A8 inhibits trypsin activity by as much as 40%. This inhibition is concentration dependent but cannot account for the complete inhibition of activation of trypsinogen 1. Neither monoclonal antibody significantly inhibits the esterolytic activity of either form of human trypsin. Western-blot analysis of the reactivity of the two monoclonal antibodies with trypsinogens of various species shows that only Mab G6 cross-reacts with dog trypsinogen.

Animals↗
PubMed1990

Production and characterization of two monoclonal antibodies to human pancreatic trypsin 1.

Two monoclonal antibodies (MAb) G6 and A8 directed against human trypsin 1 have been produced by hybridization of myeloma cells with spleen cells of OF1 immunized mice. Antibodies were screened by radioimmunoassay. Monoclonal antibodies were purified by affinity chromatography on Protein A-Sepharose, and we found that MAb G6 was of the IgG2b class and MAb A8 of the IgG2a class. Both MAbs had a high affinity for trypsin 1 with the respective affinity constants equal to 1.3 x 10(8) l/mol for G6 and 3.2 x 10(7) l/mol for A8. Epitope specificity was studied by western blotting, using human trypsinogens 1 and 2. Both MAbs gave a positive reaction with native trypsinogen 1 and no reaction with the same protein after reduction. Only MAb G6 reacted with trypsinogen 2 in the native form. Its affinity for trypsin 2 was found similar to that for trypsin 1 with a constant equal to 2.7 x 10(7) l/mol. Both antibodies appeared directed against conformational and not sequential epitopes.

Animals↗
PubMed1981

[Effect of mycotoxins on the rate of fermentation in Saccharomyces cerevisiae].

The rate of fermentation of Saccharomyces cerevisiae is partially inhibited by different mycotoxins. This effect is remarkable with T2-toxin and diacetoxyscirpenol, slight with aflatoxin-B1, penicillic acid and patulin. On the contrary, the butenolide appears as a stimulator of the alcoholic fermentation.

4-Butyrolactone↗
PubMed1981

[Modification of the koch bacillus by a material extracted from tuberculosis lesions].

Lymph node lesions of tuberculous cattle and swine gave, after disruption, centrifugation through 2.2 M sucrose, and ultrafiltration, a material that brings about, in vitro, modification of the tubercle bacilli or chromogenic mycobacteria into bacterial elements that are not acid fast, rapidly growing on nutritive agar supplemented with glycerol. The phenomenon is similar to that which the authors have previously described, using an inducing agent extracted from cultures of mycobacteria, called "endometallaxic conversion."

Animals↗
PubMed1980

[Photodensitometric determination of "PR-toxin", metabolite of Penicillium roqueforti (author's transl)].

Two methods are proposed for the determination of PR-toxin. One allows a direct quantitative estimation of the mycotoxin, the other utilizes an imine formation after reaction with ammonium hydroxide. In both cases a fluorodensitometric assay on thin-layer chromatographic plates is carried out after spraying with p-dimethylaminobenzaldehyde reagent. The two procedures can be applied to estimate the toxin in foodstuffs at levels as low as 10 and 1 microgram/kg, respectively.

Chromatography, Thin Layer↗
PubMed1980

[Contamination of cow's milk during ingestion of small quantities of aflatoxin].

Sixteen cows, some in the early and the rest in the late lactation period, were given daily, during a eight day period a ration of peanut meal naturally contaminated by aflatoxin. The analysis for aflatoxin M1 of the milk obtained from these cows indicates the following points: --the level of aflatoxin M1 is not influenced by the volume of the daily milk secretion; --the quantity of this hydroxy-derivative expressed as a percentage of the parent toxin varies from 0.14 to 0.34 in the animals in the late lactation period, and from 0.66 to 0.95 in the cows producing some twenty litres of milk per day; --in order to achieve a tolerance limit of 20 ng/kg of aflatoxin M1, in the milk, the daily ingestion of the mycotoxin by cows should not exceed 90--100 micrograms per animal.

Aflatoxin B1↗
PubMed1980

[Formation of nitrosamines in cheese products].

Several strains of micromycetes used as fermentation agents in the cheese industry or having led to accidents during cheese making are able to favor the formation of nitrosamines in 60% of the cases. The concentrations observed are similar to those found by other authors with other microorganisms. The results obtained in a semi-synthetic medium are checked during the ripening of experimental camembert type cheese made from milk containing nitrates and cultured with a strain of Penicillium camemberti, which favors very much the synthesis of nitrosamines. The amount of nitrosodimethylamine formed in this cheese increases from 5 to 20 ppb during ripening. A tentative explanation of the mechanism of formation is outlined.

Cheese↗
PubMed1979

[Effect of sterigmatocystin on the toxinogenesis of the Aspergillus flavus group].

The aflatoxinogenesis of Aspergillus parasiticus is significantly enhanced by the presence, in the medium, of sterigmatocystin at a high level (35--50 microgram/ml); low concentrations, in the order of 175 microgram/ml, have no effect on the production of aflatoxins. During the period where the aflatoxinogenesis of the culture is high, no variation of the sterigmatocystin level is noted, Experiments with 14C-sterigmatocystin indicate that the mold does not utilize the metabolite itself as a precursor of aflatoxins.

Aflatoxins↗
PubMed1979

Production of mycophenolic acid by Penicillium roqueforti strains.

Sixteen strains of Penicillium roqueforti Thom, isolated from blue-molded cheeses, were studied. In vitro, all of these strains produced mycophenolic acid, some on the order of 0.8 to 4 mg/g od dry culture. The greatest yields were obtained after 10 days of incubation of cultures at 15 degrees C. However, under some experimental conditions, mycophenolic acid was not alone responsible for the toxicity of culture extracts to chicken embryos.

Animals↗
PubMed1979

[Transmissible modification induced in Mycobacterium tuberculosis and Mycobacterium bovis in vitro].

A biologically active material (fraction "S") is isolated from cultures of scotochromogenic mycobacteria. Mycobacterium tuberculosis, or Mycobacterium bovis by disrupting the cells, sedimentation through 2.2 M sucrose, and ultrafiltration. The fraction "S" induces the modification of tubercle bacilli into non acid-fast bacteria forming smooth colonies on nutritive glycerol agar within 24-36 h of incubation. Three new phenotypes are thus obtained; two proved to be stable upon subculturing. Frequently the phenomenon occurs with a very large part of the Koch's bacillus population exposed to the inducing agent effect. It can be reproduced with crude preparations of DNA obtained from the fraction "S." It is inhibited by concanavalin A. The observed modification does not correspond to a transfer of characteristics of the inducing agent from the donor mycobacteria; furthermore it can be manifested even in the strain used for the preparation of the fraction "S."

Agar↗