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Biomedical subjects

J G MICHAEL

Publications and source records attributed to J G MICHAEL.

At least 19 recordsLinked to original sources
PubMed1963

ASSOCIATION OF "NATURAL" ANTIBODIES TO GRAM-NEGATIVE BACTERIA WITH THE GAMMA-1-MACROGLOBULINS.

"Natural" antibodies to representative species of Enterobacteriaceae were found to be principally associated with the gamma(1)-macroglobulin prepared from Cohn fraction III-I of pooled human plasma. The amount of antibodies present was estimated by measuring the bactericidal, hemagglutinating, mouse-protective, and opsonophagocytic activities of this fraction. Comparison with the antibody activity of gamma(2)-globulin of Cohn fraction II showed that up to 100 times more antibody activity on a weight basis was present in the macroglobulin fraction. These findings suggest that differences between natural and immune antibody result from the physicochemical properties of 2 different classes of immune globulin.

Animals↗
PubMed1963

EFFECT OF SUBLETHAL CONCENTRATIONS OF PENICILLIN ON THE VIRULENCE AND ANTIGENIC COMPOSITION OF GROUP A STREPTOCOCCI.

Michael, J. Gabriel (House of the Good Samaritan, Children's Hospital Medical Center, Boston, Mass.), Benedict F. Massell, and Robert E. Perkins. Effect of sublethal concentrations of penicillin on the virulence and antigenic composition of group A streptococci. J. Bacteriol. 85:1280-1287. 1963.-Virulent strains of group A streptococci were grown in sublethal concentrations of penicillin and tested for possible changes in colonial morphology, virulence, and antigenic composition. After overnight growth in broth containing penicillin, there was a marked reduction in precipitable group A and M protein content of the bacteria. Upon transfer to broth without antibiotic, the streptococci regained their ability to produce these substances. After multiple transfers in broth containing non-bactericidal levels of penicillin, variants developed which lacked group and type substances and which were also relatively resistant to penicillin. These variants were avirulent for mice and susceptible to the bactericidal action of normal human blood. Two of three strains tested, when grown on blood agar, failed to produce beta hemolysis. The mutants produced by multiple transfers in broth containing small amounts of penicillin, when passed through mice, regained all of their original properties.

Animals↗
PubMed1962

Factors involved in the induction of non-specific resistance to streptococcal infection in mice by endotoxin.

Endotoxins derived from several species of Gram-negative bacteria, while inducing non-specific resistance to typhoid bacilli in mice, failed to increase the resistance of these animals to infection with virulent strains of Group A streptococci. However, if administration of endotoxin was followed by injection of minute amounts of type-specific antiserum, a substantial degree of protection against the streptococcal pathogen was obtained. The same amount of type-specific antiserum given to the animals by itself did not have any effect on the outcome of the streptococcal infection. Fresh rabbit blood, obtained from animals pretreated with endotoxin, together with anti-M protein immune serum, was found strongly bactericidal for streptococci. These observations suggest that, at least with regard to streptococcal infection, both humoral and cellular factors are required for induction of non-specific resistance.

Animals↗
PubMed1962

Studies on natural antibodies to gram-negative bacteria.

A study was made of the origin, occurrence, and properties of natural antibodies to Gram-negative bacteria in the normal serum of several species. Antibody was measured by a procedure based on the bactericidal reaction carried out under conditions in which activity was a function of the amount of antibody contributed by the test serum. Antibody to seven genera of the family Enterobacteriaceae were demonstrated in normal human serum. The specificity of these antibodies was affirmed by absorption with homologous bacteria and by inhibition of bactericidal activity with purified homologous somatic antigen. Absorption with graded amounts of bacterial suspensions showed that a large excess of bacteria led to non-specific removal of antibodies. Analogous findings were also made with immune antibody. As determined by quantitative absorption tests no difference could be found in the avidity of natural and immune antibody. Natural antibody in the serum of various species differed considerably as regards their lability to heat, but in parallel tests immune antibody of each species was significantly more heat-stable. The time and appearance of the antibodies varied in young animals, of different species. Mice developed these antibodies at the earliest age, with guinea pigs, rats, and rabbits following in that order. Serum from germ-free rats and chickens had no demonstrable antibodies to E. coli or S. typhosa whereas these antibodies were present in the serum of litter mates reared under conventional conditions. On the other hand germ-free and conventional mice did not differ appreciably as regards the levels of these same antibodies.

Animals↗
PubMed1962

Bactericidal method for the measurement in normal serum of antibody to gramnegative bacteria.

Landy, Maurice (National Cancer Institute, Bethesda, Md.), J. Gabriel Michael, and James L. Whitby. Bactericidal method for the measurement in normal serum of antibody to gram-negative bacteria. J. Bacteriol. 83:631-640. 1962.-The bactericidal effect of normal serum on gram-negative bacteria was investigated with the objective of determining whether this antibody-complement reaction could be used for the measurement of antibody. The major variables affecting the outcome of this complement-dependent reaction were explored systematically to establish the test conditions in which specific antibody was the limiting factor. Among these were the use of an excess of absorbed human serum as a complement source, inoculum, reaction conditions, and precise enumeration of surviving bacteria. It was demonstrated that the test conditions could be controlled so as to provide a sensitive and objective assay for antibody to representative strains of various gram-negative genera.

Anti-Bacterial Agents↗
PubMed1961

Effect of exposure of bacteria to endotoxin on their susceptibility to the lethal action of normal serum.

Michael, J. Gabriel (National Cancer Institute, Bethesda, Md.), and Maurice Landy. Effect of exposure of bacteria to endotoxin on their susceptibility to the lethal action of normal serum. J. Bacteriol. 82:257-264. 1961.-The uptake of typhoid endotoxin by Escherichia coli and Shigella dysenteriae was investigated with respect to its effect on the susceptibility of these strains to the bactericidal action of serum. The attachment of endotoxin to the organisms was found to be dependent on time, temperature, concentration, and the physiological state of the bacteria. Short exposure leading to the adsorption or incorporation of small amounts of endotoxin enhanced the lethal effect of serum, whereas long periods of exposure leading to the uptake of larger amounts rendered the bacteria relatively resistant.

Antitoxins↗