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The relative rate of turnover of individual membrane proteins and glycoproteins in exponentially growing and contact-inhibited MK2 cells was investigated. Plasma membranes were isolated from cells that had been sequentially labelled with 14C and 3H isotopes of leucine and glucosamine. The membranes were then solubilized in sodium dodecylsulfate and their polypeptides separated by acrylamide gel electrophoresis. The 3H/14C ratios of the individual polypeptides reflected their relative rates of turnover. The proteins and glycoproteins of the exponentially growing cells exhibited markedly heterogeneous rates of turnover. In contrast, polypeptides in membranes of contact-inhibited cells exhibited a lesser degree of heterogeneity of turnover. In both exponential and contacted cell membranes a glycoprotein with a high apparent molecular weight exhibited the fastest rate of turnover.

Moskowitz, Merwin (Purdue University, Lafayette, Ind.). Separation and properties of a red cell sensitizing substance from streptococci. J. Bacteriol. 91: 2200–2204. 1966.—An antigen that binds onto red cells and causes them to be agglutinated by antiserum was separated from streptococci. Various procedures to extract the antigen from streptococci were investigated, and the greatest amount of antigen was obtained by extraction of cells with a phenol-water mixture. The reaction of the antigen with red cells was shown to be reversible by use of the Ashby mixed agglutination technique. The antigen also combines with a number of different tissues, and it was demonstrated that the antigen could be transferred from red cells to tissues and vice versa. An hypothesis is presented on the basis of these findings which suggests a possible role for this antigen in the etiology of rheumatic fever.

The toxicity of Clostridium perfringens was determined in mice utilizing three different routes of inoculation. There was marked variation in the minimum lethal dose with the different routes; the largest amount was required for the intracutaneous route, less for the intravenous route, and least with the intraperitoneal route. The relationship of toxicity to the lecithinase content of different toxin preparations was assayed. It was found that the toxicity of toxin preparations in different states of purification was not correlated with their lecithinase content.

The inhibition of Clostridium perfringens α-toxin by ethylenediaminetetraacetate (EDTA) and diethylenetriaminepentacetate (DTPA) was studied utilizing three different in vitro assay procedures: diffusion on egg yolk-agar, disintegration of muscle sections, and manometric assay with partially purified lecithin as substrate. DTPA was 10 to 20 times more efficient as an inhibitor than EDTA in systems containing relatively large amounts of calcium ; these observations were similar to those observed in previous in vivo protection studies. A number of other chelating agents were tested for their ability to inhibit α-toxin in vitro and protect mice against it; the chelating agents which were the most efficient in vitro inhibitors had the greatest in vivo protective ability.

The relative ability of the calcium chelates of calcium disodium ethylenediaminetetraacetate (EDTA) and calcium trisodium ethylenetriaminepentaacetate (DTPA) to protect mice against lethal doses of Clostridium perfringens α-toxin was investigated. Their protective ability was assayed by the increase in survival time of mice which had been given large doses of toxin, and by determining the median protective dose of chelate that would protect mice against toxin at a minimum lethal dose of two. In both assay procedures, intraperitoneal, intravenous, and intracutaneous injections of toxin were utilized, and with each toxin injection route the protective ability of the chelate was determined with the three routes of injection. DTPA was 10 to 20 times more effective than EDTA with both types of assay procedure and with all injection routes. DTPA may be superior to EDTA as a protective agent not only because it binds zinc to a greater extent, but also because of its greater retention in the body and its ability to gain entrance into cells. It appears that DTPA may be of value as a therapeutic agent in gas-gangrene.

Jackson, Robert W. (Purdue University, Lafayette, Ind.), and Merwin Moskowitz . Nature of a red cell sensitizing substance from streptococci. J. Bacteriol. 91: 2205–2209. 1966.—A method for purifying a streptococcal antigen which sensitizes red cells to agglutination by antiserum is described. The antigen, when purified by this method, is almost exclusively composed of glycerophosphate and d -alanine. The ratio of alanine to glycerophosphate varies from 1:5 to 1:3. The glycerophosphate is polymerized and is thus a teichoic acid. The polyglycerophosphate appears to be the antigenic determinant for agglutination. d -Alanine is readily removed by mild base and appears to be necessary for the attachment of the teichoic acid to red cells. Quantitative removal of alanine does not affect the ability of the polymer to absorb antibody from serum.

Cultured mammalian cells killed by streptomycin were essentially unaffected by an identical concentration of dihydrostreptomycin.

IN the course of a study on factors that may be involved in the in vivo destruction of stored red cells, an experiment was performed which suggests that the antigenicity of red cells is altered when blood is kept for a long period of time under standard storage conditions, and individuals may be sensitized with such stored red cells.

IT was reported previously that ethylenediamine tetraacetic acid was capable of protecting mice against the toxin of Clostridium perfringens 1. The protection thus afforded was shown to be probably due to the removal of a metallic ion or ions necessary for the activity of the toxin from the area where the toxin was acting. Inasmuch as the metallic ion or ions necessary for the action of the toxin apparently were higher in the preferential chelation series than calcium, the calcium chelate was shown to be able to protect when given systemically2. In this report, studies on the duration of the protection afforded by calcium ethylenediamine tetraacetic acid are presented and their implications are discussed.

IN the course of a study of the effects of formalin on red cells it was noted that formalin was capable of completely inhibiting the agglutinability of red cells by antisera without destroying the antigens of the cells.