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L WEINSTEIN

Publications and source records attributed to L WEINSTEIN.

At least 19 recordsLinked to original sources
PubMed1964

STAPHYLOCOCCAL ALPHA-HEMOLYSIN: DETECTION ON THE ERYTHROCYTE MEMBRANE BY IMMUNOFLUORESCENCE.

Purified staphylococcal alpha-hemolysin (but not the toxoid) was demonstrated on the surface of rabbit and human erythrocytes by immunofluorescence. This occurred during the period of maximal hemolysis and was a transient event. These findings have been analyzed in relation to previous data on the kinetics of leakage of both small and complex molecular constituents of the erythrocyte.

Animals↗
PubMed1964

INHIBITION OF SYNTHESIS OF THE CELL WALL OF STAPHYLOCOCCUS AUREUS BY CEPHALOTHIN.

Cephalothin, 7-(thiophene-2-acetamido)-cephalosporanic acid, suppresses synthesis of the cell of Staphylococcus aureus. Exposure to this agent led to a reduction in the degree of incorporation of carbon-14-lysine into the mucopeptide of the cell wall material and to an accumulation of N-acetyl glucosamine in the cell. The intensity of the lesions was comparable to that produced by penicillin.

Anti-Bacterial Agents↗
PubMed1964

HEMOLYSIS OF RABBIT ERYTHROCYTES BY PURIFIED STAPHYLOCOCCAL ALPHA-TOXIN. I. KINETICS OF THE LYTIC REACTION.

Cooper, Louis Z. (New England Center Hospital, Boston, Mass.), Morton A. Madoff, and Louis Weinstein. Hemolysis of rabbit erythrocytes by purified staphylococcal alpha-toxin: I. Kinetics of the lytic reaction. J. Bacteriol. 87:127-135. 1964.-The hemolytic activity of purified staphylococcal alpha-lysin was found to be directly proportional to toxin concentration and inversely related to the log concentration of rabbit erythrocytes. Activity was directly proportional to the duration of lysin-red cell incubation until inactivating effects of heat and dilution became significant; this linear relationship was prolonged by incubation at a lower temperature and addition of bovine serum albumin. Study of the time course of hemolysis at different alpha-lysin concentrations revealed a family of sigmoid curves characterized by a prelytic lag phase and a period of rapid linear release of hemoglobin. The duration of prelytic lag varied inversely with the quantity of toxin, but the rate of hemolysis was directly proportional to toxin and red-cell concentrations. The presence of bovine serum albumin decreased the prelytic lag, prolonged the linear phase of the reaction, and increased total hemolysis. In the range of 25 to 46 C, the prelytic lag period became shorter with increase in temperature; at 48 to 52 C, it was markedly prolonged and hemolysis was strikingly diminished. As the incubation temperature was increased from 25 to 52 C, there was a decrease in the degree of maximal hemolysis, presumably due to thermal inactivation of alphalysin. The rate of hemolysis, when measured to 50% hemolysis, was optimal between 34 and 42 C but, when determined to the 10% level, was greatest between 40 and 46 C. The features of the hemolytic reaction suggest that staphylococcal alpha-toxin has the characteristics of an enzyme.

Animals↗
PubMed1964

HEMOLYSIS OF RABBIT ERYTHROCYTES BY PURIFIED STAPHYLOCOCCAL ALPHA-TOXIN. II. EFFECTS OF INHIBITORS ON THE HEMOLYTIC SEQUENCE.

Cooper, Louis Z. (New England Center Hospital, Boston, Mass.), Morton A. Madoff, and Louis Weinstein. Hemolysis of rabbit erythrocytes by purified staphylococcal alpha-toxin. II. Effect of inhibitors on the hemolytic sequence. J. Bacteriol. 87:136-144. 1964.-Study of the time course of hemolysis of rabbit erythrocytes by purified staphylococcal alpha-lysin revealed that the specific toxin-red cell reaction occurs during the prelytic period. This reaction could be prevented or decreased by alpha-lysin antitoxin added early, but not by antitoxin added at the end of the prelytic phase or at any time thereafter. In contrast, hemolysis is suppressed temporarily by sucrose and permanently by polyethylene glycol, even when these are added during the period of rapid release of hemoglobin. When sucrose is present together with alpha-lysin and red cells only during the prelytic period, and when the cells are then washed and resuspended in phosphate-buffered saline, their subsequent hemolysis is not altered by the presence of the sugar. This is not so when antitoxin is employed. When erythrocytes are laked by a measured excess of alpha-lysin, only a portion of the original hemolytic activity can be recovered. Repeated exposure of lysin to red cells produces a loss of activity represented by a linear function when logs of residual activity are plotted sequentially. Once alpha-lysin has reacted with red cells, it does not appear to be available for attachment to other erythrocytes.

Animals↗
PubMed1964

HEMOLYSIS OF RABBIT ERYTHROCYTES BY PURIFIED STAPHYLOCOCCAL ALPHA-TOXIN. III. POTASSIUM RELEASE.

Madoff, Morton A. (New England Center Hospital, Boston, Mass.), Louis Z. Cooper, and Louis Weinstein. Hemolysis of rabbit erythrocytes by purified staphylococcal alpha-toxin. III. Potassium release. J. Bacteriol. 87:145-149. 1964.-The reaction between staphylococcal alpha-toxin and erythrocytes was characterized by rapid release of K(+) from the cells, early in the prelytic period; 50 to 75% of this loss occurred before leakage of hemoglobin was detectable. The addition of specific antitoxin early enough in the reaction to inhibit gross hemolysis also inhibited cation release. The presence of sucrose or polyethylene glycol prevented hemoglobin release, but was without effect on K(+) leak. These observations suggest that K(+) loss is a more specific indication of the progress of the reaction between alpha-toxin and erythrocytes than is the release of hemoglobin.

Animals↗
PubMed1964

MORPHOLOGICAL CHANGES IN GRAM-NEGATIVE BACILLI EXPOSED TO CEPHALOTHIN.

Chang, Te-Wen (Tufts University School of Medicine, Boston, Mass.), and Louis Weinstein. Morphological changes in gram-negative bacilli exposed to cephalothin. J. Bacteriol. 88:1790-1797. 1964.-Exposure of gram-negative bacteria to cephalothin (7-[thiophene-2-acetamido]-cephalosporanic acid) revealed the formation of long filaments and large bodies, which were capable of reverting to normal cells when removed from contact with the drug. The degree of morphological change was found to be related to the concentration of antibiotic in which the organisms were suspended. The large bodies were altered by contact with solutions of varying osmolarity. Different species showed variation in the ability to develop large bodies. A relationship between antibiotic sensitivity and the capacity to resist morphological alteration was observed. Though most sensitive gram-negative bacilli were strikingly changed by exposure to cephalothin, naturally resistant ones were unaffected. Organisms made drug-resistant in vitro underwent changes in cellular form which were qualitatively the same but less intense than those which developed in parent strains originally sensitive to cephalothin.

Anti-Bacterial Agents↗
PubMed1963

IN VITRO BIOLOGICAL ACTIVITY OF CEPHALOTHIN.

Chang, Te-Wen (Tufts University School of Medicine, Boston, Mass.) and Louis Weinstein. In vitro biological activity of cephalothin. J. Bacteriol. 85:1022-1027. 1963.-Cephalothin is a "broad-spectrum" antibiotic active, in low concentrations, against Diplococcus pneumoniae, Streptococcus pyogenes, and Staphylococcus aureus. Shigella, Salmonella, and Proteus mirabilis were the most sensitive of the gram-negative organisms. Escherichia coli and Aerobacter aerogenes were suppressed to a lesser degree, whereas Pseudomonas aeruginosa and Herellea were highly resistant. Penicillin-sensitive and -resistant strains of S. aureus were equally susceptible to cephalothin. Exposure to increasing concentrations of the drug very frequently led to the development of resistance in gram-negative organisms; this was observed less often with S. aureus. Cephalothin stimulated the production of penicillinase by staphylococci, which remained sensitive to the cephalosporanic acid derivatives despite repeated subculture in increasing concentrations of the agent. Cephalothin was not inhibited by penicillinase. This antibiotic was more toxic to cultures of human amnion and mouse embryo cells than benzyl penicillin G but was less injurious than oxytetracycline, chlortetracycline, and demethylchlortetracycline; tetracylcine produced about the same degree of cellular damage as cephalothin.

Acinetobacter↗