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Biomedical subjects

S Razin

Publications and source records attributed to S Razin.

At least 127 records · Page 7Linked to original sources
PubMed1970

Immunogenicity of Mycoplasma pneumoniae glycolipids: a novel approach to the production of antisera to membrane lipids.

The glycolipid haptens of Mycoplasma pneumoniae were bound to membrane proteins of acholeplasma laidlawii (formerly Mycoplasma laidlawii) by reaggregation. This process consisted of the solubilization of lipid-depleted A. laidlawii membranes and M. pneumoniae glycolipids in 20 mM sodium dodecyl sulfate, and dialysis of the mixed solutions against 20 mM Mg(2+). The hybrid reaggregate, collected by centrifugation, was highly immunogenic in rabbits, eliciting the production of a high titer of antibodies that fixed complement with the purified glycolipids and inhibited the metabolism of M. pneumoniae cells. The free glycolipids, or their mixture with A. laidlawii proteins, were much less effective in stimulating these antibodies. The antibodies to the hybrid reaggregate agglutinated M. pneumoniae cells and inhibited their ability to absorb erythrocytes, which indicates that at least some of the serologically-active glycolipids are exposed at the outer membrane surface. The ability to bind selected membrane lipids to membrane proteins of a serologically unrelated species provides a new tool for producing antibodies to lipid haptens.

Acholeplasma laidlawii↗
PubMed1970

Role of Glycolipids and Phosphatidylglycerol in the Serological Activity of Mycoplasma pneumoniae.

Mycoplasma pneumoniae lipids were fractionated by combined silicic acid and diethylaminoethyl-cellulose chromatography. The lipid fractions were tested for complement-fixing activity and for blocking of metabolism-inhibiting antibodies in human and rabbit antisera to M. pneumoniae. Thin-layer chromatography and carbohydrate analysis of hydrolysates of the lipid fractions indicated that glycolipids were responsible for the specific serological activities of the lipid extracts of the organism. Phosphatidylglycerol, which accompanied the glycolipids, was serologically inactive when isolated free from glycolipids. Phosphatidylglycerol considerably enhanced the serological activity of the glycolipids, serving as an auxiliary lipid. Because of this auxiliary effect, minute quantities of contaminating glycolipids sufficed to render serological activity to "purified" phosphatidylgylcerol preparations, providing an explanation to the previous identification of the active lipid as a phospholipid.

Journal Article↗
PubMed1970

Cholesterol requirement of mycoplasmas.

Cholesterol requirement for growth of mycoplasmas was tested in a serum-free medium supplemented with albumin, l-arginine, palmitic acid, and various concentrations of cholesterol dissolved in Tween 80. In cases in which Tween 80 was shown to inhibit growth, the test medium was supplemented with cholesterol dissolved in ethanol. Of the 31 species examined, all but Mycoplasma laidlawii, M. granularum, and Mycoplasma species strain S-743 exhibited a growth response to cholesterol. No requirement for cholesterol could be shown with the stable L-phase variants of Streptobacillus moniliformis and Proteus species. The results provide experimental support for the view that the large majority of the established Mycoplasma species require cholesterol for growth.

Arginine↗
PubMed1970

Acholeplasma axanthum, sp. n.: a new sterol-nonrequiring member of the Mycoplasmatales.

Mycoplasmas recovered from tissue cultures and previously shown to belong to the sterol-nonrequiring group of mycoplasmas have been further characterized. The biological and serological properties of these strains show them to be clearly distinct from Acholeplasma laidlawii and A. granularum, two species of sterol-nonrequiring mycoplasmas recently reclassified. It is proposed that the newly described mycoplasmas be designated Acholeplasma axanthum, sp. n.

Animals↗
PubMed1969

Immunological analysis of Mycoplasma membranes.

The antigens responsible for the production of antibodies to Mycoplasma laidlawii and M. gallisepticum causing growth and metabolic inhibition of these organisms were localized in the cell membrane. Various membrane fractions were tested for serological activity. Membrane lipids were completely or almost completely inactive, whereas several preparations of defatted membrane proteins retained some serological activity, shown by their ability to stimulate metabolic inhibition antibody in rabbits and to adsorb metabolic inhibition antibody and form precipitation lines with an antiserum to the membrane. When the membranes were heated to 65 C for 1 hr, they virtually lost their ability to adsorb metabolic inhibition antibody, which suggests that the antigenic determinants are proteins. Serological activity was retained in reaggregated membranes obtained by dialysis against Mg(2+) of membranes solubilized in sodium dodecyl sulfate. The amount of solubilized membrane protein and lipid incorporated into the reaggregated membranes could be regulated by varying the Mg(2+) concentration. As the serological tests indicated that the various membrane antigens were selectively incorporated into the different reaggregated membranes, the use of controlled reaggregation of solubilized membranes is suggested as a new tool for the fractionation and antigenic analysis of membrane proteins.

Adsorption↗
PubMed1969

Sugar transport in Mycoplasma gallisepticum.

Mycoplasma gallisepticum cells were found to contain two different sugar transport systems, one for d-glucose and alpha-methyl-d-glucoside (alpha-MG) and the other for d-mannose and d-fructose. Both systems were noninducible, stereospecific, dependent on temperature and pH, and sensitive to sulfhydryl-blocking reagents. The rate of sugar uptake depended on its external concentration, obeying Michaelis-Menten kinetics. The sugar accumulated in the cells against a concentration gradient, and an energy requirement for accumulation was demonstrated with alpha-MG. Both transport systems thus meet the criteria of active transport. The exit of alpha-MG from the cells, like its entry, depended on temperature and was accelerated by energy supplied by the oxidizable d-mannose. d-Glucose accelerated alpha-MG exit, apparently by an exchange reaction. A method for measuring the intercellular space and intracellular free-water volume of Mycoplasma was devised, and several of its applications are described.

Biological Transport, Active↗
PubMed1969

Characteristics of a new sterol-nonrequiring Mycoplasma.

Two Mycoplasma strains recovered from tissue culture environments were found to grow in complex media devoid of serum or serum fractions containing cholesterol and in a cholesterol-free synthetic medium. Neither strain was capable of synthesizing pigmented carotenoids, although these compounds are present in, and characteristic of, other sterol-nonrequiring mycoplasmas. Serological tests and an analysis of their cell protein patterns obtained by gel electrophoresis indicated that the isolates were similar to each other but distinct from other sterol-nonrequiring serotypes, Mycoplasma laidlawii and M. granularum, as well as from sterol-requiring species. The existence of Mycoplasma other than M. laidlawii and M. granularum without sterol requirements suggested the need for some taxonomic changes in this group of organisms.

Acetates↗