Effect Of Mercaptan Research Articles

The effects of mercaptans on the acetaminophen induced cytotoxicity in freshly isolated rat hepatocytes

The effects of mercaptans on the acetaminophen induced cytotoxicity in freshly isolated rat hepatocytes

The methionine analog S-methylthiocysteine stimulates neutral amino acid transport by isolated brain microvessels

Abstract As an extension of the hypothesis suggesting that the role of hyperammonemia and of plasma amino acid imbalance in the pathogenesis of hepatic encephalopathy is mediated by glutamine formation at the level of the blood-brain barrier, the possible effects of mercaptans on neutral amino acid transport by isolated brain microvessels were investigated. In this experimental system, methanethiol as such had no effect on any of the neutral amino acid transport systems. If the isolated brain microvessels were preloaded in the presence of both methanethiol and cystine (or cysteine), there was a marked stimulation of the L-system-mediated uptake of hydrophobic (branched or aromatic) neutral amino acids, this enhancement being similar to that caused by glutamine preloading. Cystine or cysteine alone were ineffective, nor could they be replaced by other non-sulfur-containing amino acids. The stimulation of the L-system could be attributed to the formation of S -methylthiocysteine, a mixed disulfide whose chemical structure is similar to that of methionine. S -methylthiocysteine was found to be formed spontaneously, upon preincubation with methanethiol plus cystine or cysteine, within the endothelial cells of isolated brain microvessels. Methanethiol, via S -methylthiocysteine formation, appears therefore to deserve a place, synergistically with the ammonia-glutamine system, among the precipitating causes of hepatic encephalopathy.

Mercaptans Decrease Selenium-Dependent Glutathione Peroxidase Activity in the Chick

A variety of mercaptans, especially the β-mercaptocarboxylic acids, inhibited the selenium (Se)-dependent glutathione peroxidase (SeGSHpx) activity of chick liver postmitochondrial supernatant or cytosol and of purified bovine erythrocyte SeGSHpx. The effects of mercaptans and a glutathione analogue on Se utilization were determined by subcutaneous injection of test compounds into vitamin E–deficient chicks fed diets containing 0.1 ppm Se (as Na2SeO3) at times when > 50% of vitamin E– and Se-deficient chicks showed the vitamin E–, Se-deficiency disease exudative diathesis (ED). D-(-)-Penicillamine hydrochloride (the positive control model compound), sodium β-mercaptopyruvate, t-butyl mercaptan and S-methylglutathione (nonmercaptan glutathione analogue) decreased SeGSHpx activity in chick liver postmitchondrial supernatants within 24 h of injection and increased the incidence of ED within 4 d. Other mercaptans tested did not increase ED incidence or affect liver, kidney or plasma SeGSHpx activities. Although mercaptosuccinic acid, N-(2-mercaptopropionyl)glycine and sodium thioglycolate each strongly inhibited SeGSHpx in vitro, each also significantly increased chick mortality in the dosage range tested; therefore, their effects on SeGSHpx in vivo could not be evaluated. It appears that the β-mercaptocarboxylic acids, mercaptans with a high degree of steric hinderance in close proximity to the thiol group and a close structural analogue of glutathione are capable of altering selenium status in chicks.

Effects of mercaptans upon dihydropyridine binding sites on transverse tubules isolated from triads of rabbit skeletal muscle

The binding of nitrendipine to transverse (T) tubules isolated from skeletal muscle triads is inhibited by dithiothreitol (KI approximately 0.05 mM) and glutathione (KI approximately 3 mM). The t 1/2's of inhibition (18.3 and 11.5 min, respectively) suggest that these hydrophylic reagents act upon the exposed surface of the vesicles. Dithiothreitol shifts the apparent KD for nitrendipine from 8.5 nM to 30 nM without altering the Bmax extrapolated by Scatchard analysis. That T-tubules isolated by disruption of triad junctions are constrained to have the protoplasmic (P) face uniformly exposed was experimentally confirmed. These studies show that a sulfhydryl residue on the P-face of the T-tubule influences the affinity of the receptor for dihydropyridines.

Immunology of DNA. VI. The effect of mercaptans on IgG and IgM anti-dsDNA

Reduction of IgM antibodies to DNA with mercaptans such as dithioerythrol or 2-mercaptoethanol completely destroys DNA binding in the Farr assay and in the immunofluorescence technique by Crithidia luciliae. In contrast reduction of IgG antibodies to DNA results in a six-fold increase of DNA binding in the Farr assay while no effect on titres in the immunofluorescence technique can be observed. Our results lead to the following conclusions: 1) The Farr assay is selective for high avidity interactions; only a minor part of IgG antibodies to DNA is measured; 2) 7S IgM antibodies to DNA cannot be demonstrated in the Farr assay or the immunofluorescence technique; obviously only multivalent interactions, as obtained with the intact 19S IgM molecule are stable in these assays; 3) reduction of IgG leads to a greater flexibility of this molecule; this facilitates monogamous bivalent binding to DNA; 4) the presentation of DNA in the kinetoplast of Crithidia luciliae favours a monogamous bivalent binding of antibodies to DNA with high avidity; this accounts for occasionally observed discrepancies between anti-DNA activity in the Farr assay and in the immunofluorescence technique.

Effect of mercaptans on extreme-pressure properties of fuels for gas turbine engines

Effect of mercaptans on extreme-pressure properties of fuels for gas turbine engines

The photoreduction of benzophenone by an ether. Effect of mercaptan

The photoreduction of benzophenone by an ether. Effect of mercaptan

The catalytic effect of mercaptans on the conversion of borontrialkyls by means of ammonia, amines and alcohols

1. In the presence of catalytic amounts of mercaptans borontrialkyls react with ammonia, amines and alcohols at 20–100° with formation of the dialkyl (amino) borons, the N-substituted compounds or the ester dialkyl borinic acids respectively. 2. With substituted amines dialkyl (amino) borons undergo a transamination reaction.

Effect of mercaptan on the rate of chain termination for methyl methacrylate

Effect of mercaptan on the rate of chain termination for methyl methacrylate