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J Torreilles

Publications and source records attributed to J Torreilles.

48 records · Page 3Linked to original sources
PubMed1979

Specific sulfonation of tyrosine, tryptophan and hydroxy-amino acids in peptides.

1. ClSO3H in trifluoroacetic acid rapidly converts serine and threonine into O-sulfate ester derivatives while tyrosine and tryptophan are converted into arylsulfonic acids. 2. H2SO4 in trifluoroacetic acid reacts more slowly with serine, threonine and tyrosine while is not able to modify tryptophan. 3. All other amino acids are perfectly stable under the above reaction conditions. 4. Peptides containing susceptible amino acid residues are specifically converted into the corresponding sulfonated derivatives in high or quantitative yield.

Amino Acids↗
PubMedDate not supplied

Murexide bleaching: a new direct assay method for characterizing reactive oxygen species.

The murexide (5,5'-nitrilodibarbituric acid, monoammonium salt) is an efficient scavenger for superoxide and hydroxyl radicals. When exposed to oxygen radicals, murexide is converted to a colorless alloxan derivative and its absorbance at 520 nm decreases in proportion to the radicals produced. It is used to detect these reactive oxygen species in biochemical systems such as acetaldehyde oxidation by xanthine oxidase and the respiratory burst of polymorphonuclear leukocytes induced by phorbol 12-myristate, 13-acetate. The method was sensitive enough to allow direct monitoring of the production of superoxides from 10(6) phorbol 12-myristate, 13-acetate polymorphonuclear leukocyte-stimulated cells. Moreover, murexide bleaching is inhibited in the presence of radical scavengers, allowing a comparison of their scavenging activities.

Barbiturates↗
PubMedDate not supplied

Peroxidase-release associated with phagocytosis in Mytilus galloprovincialis haemocytes.

Fluorescence spectra of the supernatant of adherent haemocyte monolayers from Mytilus galloprovincialis, supplemented with homovanillic acid or with a tyrosyl peptide glycylglycyltyrosine (GGY), were recorded before and after stimulation by zymosan. The formation of fluorescent derivatives was observed to have spectral characteristics similar to those of fluorescent compounds generated by the exposure of homovanillic acid or GGY to a horseradish peroxidase/hydrogen peroxide system in vitro. Lucigenine-enhanced chemiluminescence (CLluc) of M. galloprovincialis haemocytes stimulated by zymosan or by phorbol ester (PMA) was measured in the presence and absence of sodium azide, a peroxidase inhibitor. Sodium azide inhibited the CLluc of haemocytes stimulated by zymosan, an effective stimulus for myeloperoxidase secretion in human polymorphonuclear leukocytes, but not the CLluc of haemocytes stimulated by PMA, indicating the presence of peroxidases with some properties of myeloperoxidase, in adherent haemocytes from M. galloprovincialis.

Animals↗
PubMedDate not supplied

Casein-derived peptides can modulate the production of 5-hydroxyeicosatetraenoic acid in human neutrophils.

The effects of peptides derived from bovine casein hydrolysates were evaluated on oxygen-free radical release, 5-hydroxyeicosatetraenoic acid (5-HETE), and leukotriene B4 (LTB4) production by human polymorphonuclear leukocytes (PMNs). PMNs were activated by N-formyl-methionyl-leucyl-phenylalanine, phorbol myristate acetate, calcium ionophore (A23187), or opsonized zymosan. Tyrosyl-prolyl-phenylalanyl-proline (fragment 60-63 from bovine beta-casein) inhibited oxygen-free radical production and 5-HETE production but had no effect on the production of LTB4 and LTB4 isomers. Arginyl-tyrosyl-leucyl-glycyl-tyrosyl-leucine (fragment 90-95 from bovine alpha-casein) enhanced the production of oxygen-free radical and 5-HETE but had no effect on the production of LTB4 and isomers. Both peptides unsignificantly enhanced the release of arachidonic acid by A23187-stimulated PMNs previously supplemented with [14C]arachidonic acid. Casein-derived peptides then seemed to act on the enzymatic activities of endogenous peroxidases that reduced hydroperoxyeicosatetraenoic acid to 5-HETE. 5-HETE is recognized as an ubiquitous cell function mediator and modulation of PMN 5-HETE production by casein-derived peptides could be implicated in the manifestation of some adverse effects to cow's milk.

Animals↗
PubMedDate not supplied

[Evaluation of lipid peroxidation by measuring thiobarbituric acid reactive substances].

Malondialdehyde assay is the most generally used test in the appreciation of the role of oxidative stress in disease. Malondialdehyde is one of several products formed during the radical induced decomposition of polyunsaturated fatty acids. Most often, malondialdehyde assay used its reactivity at high temperature and low pH, towards thiobarbituric acid. This reaction is very sensitive but its specificity, even with improvement of pre-analytical (sampling, preservatives), and analytical stages (fluorescence, HPLC) is still a matter of debate. At present, the concept of "thiobarbituric acid reactive substances" (TBARS) have merged and progressively replaced the initial malondialdehyde assay. In this review, we presented the main results concerning the assays of TBARS and malondialdehyde in blood and different biological medium. In the future, oxidative stress appreciation will need the precise analytical determination of different molecules triggered by free radicals. The TBARS assay should be considered as a global test, allowing a global approach of lipoperoxidation whereas specific determination of malondialdehyde can only appreciate one of the end-product formed during oxidative stress.

Animals↗