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Biomedical subjects

J M Wal

Publications and source records attributed to J M Wal.

68 records · Page 4Linked to original sources
PubMed1980

High performance liquid chromatographic determination of chloramphenicol in milk.

A rapid and sensitive high performance liquid chromatographic method for the determination of trace amounts of chloramphenicol (CP) in milk has been developed. The antibiotic can be quantitated at a 10 ppb level with a limit of detectability estimated at 5 ppb. Recoveries ranged from 72 to 99.5%. Milking studies have been carried out on goats that received CP either by intramuscular injection or by intramammary administration. CP was measured in milk samples collected 1, 2, 3, 4, 5, 6, 7, 8, 24, 32 h after treatments. No residue could be detected 32 h after treatment. No interfering peaks appeared on control milk chromatograms.

Animals↗
PubMed1979

Electron-capture detection of chloramphenicol using a heptafluorobutyrate derivative. Application to residues in milk.

A gas-liquid chromatographic method is described for the quantitation of the halogenated heptafluorobutyrate derivative of chloramphenicol, using electron-capture detection. Treatment of the chromatographic support with heptafluorobutyric anhydride permits a linear recovery even at very low concentrations. After extraction using acetonitrile followed by a convenient cleaning procedure, this method can be applied to the determination of trace amounts of chloramphenicol in milk. Interfering peaks have been observed on the chromatograms of some control milk samples. These determine the detection limit of 50 ppb.

Animals↗
PubMed1979

[Immunochemical method for study and identification of unicellular organisms (yeasts and bacteria) incorporated into food products as a protein source].

The expected increase and diversification of single cell proteins production already requires the development of convenient methods for the identification of producing strains from the processed S.C.P., i.e. killed and dried cells. A simple immunological method based on double immunodiffusion analysis is proposed, that enables the identification of Toprinal L (Candida tropicalis), Toprina G (Candida lipolytica) and Pruteen (Pseudomonas methylotropha), all S.C.P. having received an approval from different european countries. Sensitivity and specificity are high enough to enable the identification of these products mixed to feeds in concentrations as low as 5 p. cent (1 p. cent with Pruteen).

Bacterial Proteins↗
PubMed1979

[Evolution of the concept of residues in the products of animals raised with the use of antibiotics].

The concept of residues of antibiotics used as feed additives or veterinary drugs in food producing animals is analysed, and implications on human public health are discussed. The examples of Tylosin and Penicillin are developed to illustrate the both notions of "high risk residue" and "toxicodisponibility" of residues. The "high risk residue" may be an active metabolite different by its chemical structure and by its pharmacological properties from the original drug administered. Slight modifications of the molecule, as the rupture of the beta lactam ring of the Penicillin, occuring in vivo, lead to a metabolite, e.g. penicilloyl group, that has lost all antibiotic activity but possesses allergenic potential. Toxicity of the residue, compared with that of the original drug, can then be modified or increased. On the other hand, such an active metabolite having a definite chemical structure, even if different from the original compound, can be present in the organism, either free or bound to serum or tissues proteins. Moreover, it is shown here, that in the case of a covalent binding of the drug or its metabolite (e.g. penicilloyl group) to serum albumin, the residues are mostly masked inside the tertiary structure of the albumin molecule, and are not accessible to antibodies. These different forms have then an effect upon the biodisponibility, the "toxicodisponibility", of the residues for the human consumer of animal products where they are present. These forms are only accessible with more and more specific and sensitive analytical methods which relates also the qualitative and quantitative notions of residue to the technological degree used for investigation, determination and identification. As to cooking techniques, they can lead to a thermodegradation of the residue or, on the opposite, to an unmasking of the residue present as a protein conjugate, e.g. penicilloyl-protein conjugate in milk.

Animal Feed↗
PubMed1975

[Preparation of an iodinated penicillin derivative for radioimmunologic use].

A 125I-BSA Penicilloyl conjugate was prepared by coupling Penicillin G to Bovine Serum Albumine previously labeled with Iodine-125. The reaction of fixation by covalent binding was made in alkaline solution without the use of carbodiimide. Immunoreactivity and specific activity of this labeled conjugate enable radioimmunoassay of penicilloyl groups.

Chemical Phenomena↗
PubMedDate not supplied

Molecular basis of IgE cross-reactivity between human beta-casein and bovine beta-casein, a major allergen of milk.

Twenty patients allergic to cow's milk proteins and with high levels of specific IgE directed against bovine whole casein were selected to evaluate reactivity of their IgE antibodies with human beta-casein. Highly purified human and bovine beta-caseins were prepared by selective precipitations and FPLC separation. Their identity and purity were assessed by HPLC, analysis of amino acid composition, sequencing of the five N-terminal amino acid residues and immunochemical tests. Direct and indirect ELISAs were performed using human and bovine beta-casein coated into microtiter plates and monoclonal anti-human IgE antibody AChE labelled for revelation. Seven sera contained specific IgE directed against human beta-casein. Inhibition studies using native human and bovine beta-caseins as well as bovine beta-casein-derived peptides demonstrated that, depending on the sera, one or several common epitopes located in different parts of the molecule were shared by the two homologous proteins.

Adolescent↗
PubMedDate not supplied

New aspects of metabolic conjugation of chloramphenicol.

New and major chloramphenicol (CP) metabolites have been isolated from the urine of goats administered [3H]CP. The CP-3-sulfoconjugate has been identified formally from its chromatographic behaviour and mass spectrometric analysis, as well as from incubations of CP with liver cytosol, using synthetic CP-conjugate as reference. Only a strong assumption is made of the identity of the CP-3-phosphoconjugate.

Animals↗
PubMedDate not supplied

Simple and ion-pair high performance liquid chromatography as an improved analytical tool for chloramphenicol metabolic profiling.

Simple and ion-pair reverse phase high performance chromatographic separations combined with selective extraction were developed in order to achieve a qualitative and quantitative analysis of [3H]chloramphenicol (CP) metabolites in rat urine. Complete separation followed by unequivocal identification of all the metabolites was obtained, especially of the toxicologically significant CP-arylamine. Metabolic profiles were established from human and goat urine which confirmed data already available, but was used to identify new acidic metabolites in the latter species. This methodology appears to be a useful research tool in comparative metabolic studies.

Animals↗