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Biomedical subjects

D W Watson

Publications and source records attributed to D W Watson.

At least 55 records · Page 3Linked to original sources
PubMed1978

Nonspecific and specific immunological mitogenicity by group A streptococcal pyrogenic exotoxins.

Group A streptococcal pyrogenic exotoxin (SPE) types A, B, and C induced lymphocyte proliferation both specifically and nonspecifically, and the responses showed characteristics associated with both types of stimulation. Guinea pig lymphocytes from animals presensitized to SPE A displayed immunologically specific proliferation in response to SPE A; control lymphocytes showed little activity in the presence of SPE A. Lymphocytes from guinea pigs not presensitized to SPE responded nonspecifically to SPE types B and C. Guinea pig lymphocytes from SPE A-presensitized animals showed enhanced proliferation over controls when treated with SPE B, suggesting that a degree of cross-reactivity between SPE types may exist, though they are serologically distinct. Mouse splenic lymphocytes exhibited low-level responsiveness to all SPE types, as would be expected for an antigen-specific proliferative response. Unlike mouse splenic lymphocytes, rabbit spleen cells and human cord blood, lymphocytes responded nonspecifically to all SPE types. Although rabbit spleen cells and human cord blood lymphocytes responded nonspecifically, the maximum response occurred at day 4 or 5, comparable to an antigen-specific system rather than a day 2 or 3 such as that with the nonspecific thymus-derived cell mitogen, concanavalin A.

Animals↗
PubMed1977

Purification and characterization of group A streptococcal pyrogenic exotoxin type C.

Group A streptococcal pyrogenic exotoxin (SPE) type C was partially purified by differential solubility in ethanol and acetate-buffered saline. Toxin prepared in this way consisted of protein and hyaluronic acid. After removal of hyaluronic acid, the toxin remained pyrogenic, enhanced susceptibility of rabbits to letahl endotoxin shock, was stable when treated with acid, base, or pepsin, but was inactivated by heat. Toxin further purified by thin-layer isoelectric focusing was pyrogenic and enhanced the susceptibility of rabbits to lethal endotoxin shock. Purified type C toxin appeared homogeneous when tested by Ouchterlony immunodiffusion and migrated as a single protein band in isoelectric focusing polyacrylamide gels (isoelectric point, 6.7) and sodium dodecyl sulfate-polyacrylamide gels (molecular weight, 13,200). The purified toxin was antigenically distinct from A and B SPE, and antisera raised against the purified toxin neutralized pyrogenic activity. The amino acid composition was determined.

Amino Acids↗
PubMed1976

Further purification of group A streptococcal pyrogenic exotoxin and characterization of the purified toxin.

Streptococcal pyrogenic exotoxin (SPE) isolated from culture filtrates of strain NY-5 (type 10), and separated from other extracellular by differential solubility in ethanol and acetate-buffered saline, has previously been shown to exhibit a wide range of biological activities including erythrogenic activity, pyrogenicity, enhancement of susceptibility to endotoxin shock, blockage of the reticuloendothelial system immmunosuppression, and lymphocyte mitogenicity. Toxin prepared in this way was found to consist of hyaluronic acid and several proteins which could be distinguished by thin-layer polyacrylamide isoelectric focusing (IEF), SPE has been further purified by ion exchange chromatography on QAE-Sephadex columns. One of the fractions isolated from QAE-Sephadex, and shown to be a homogenous protein by thin-layer IEF and Ouchterlony with hyperimmune serum, was highly active erythrogenically, pyrogenically, and in enhancing susceptibility to endotoxin. This fraction was identified as exotoxin A. A second, less active fraction identified as SPE B showed similar activities, but differed from the other fraction antigenically and in net charge and molecular weight. These findings indicate that a single highly purified protein can mediate at least three of the biological activities attributed to SPE and NY-5 produces pyrogenic exotoxins A and B in vitro as well as in vivo.

Bacterial Proteins↗
PubMed1975

Decrease in ribosomal density of Proteus mirabilis exposed to subinhibitory concentrations of ampicillin or cephalothin.

The finding of reduced ribosomal densities at lower concentrations than those required to stop growth or cause visible defects in the cell wall is in contrast to the current view that the initial lesion produced by penicillins or cephalosporins is a defect in murein synthesis (11). This reduction in ribosomal density could be a primary or secondary effect and might be due to a decreased rate of growth, which has been shown to be associated with a lower ribosome frequency (12, 13) or to less stable ribosomes which disintegrated either spontaneously or as a result of the fixation procedures. The possibility that the decrease in ribosomal frequency was due to dilution (influx of liquid through a defective cell wall and/or cytoplasmic membrane, or efflux of ribosomes) remains, but no gross defect in cell wall was seen in more than 50 sections of cells showing reductions in ribosomal frequency. These findings suggest that an effect on ribosomes may antecede an effect on the cell wall.

Ampicillin↗
PubMed1974

Pyrogenic specificity of streptococcal exotoxins, staphylococcal enterotoxin, and gram-negative endotoxin.

Streptococcal exotoxin and staphylococcal enterotoxin share several biological properties, including pyrogenicity, lymphocyte mitogenicity, and enhancement of gram-negative endotoxin lethality. These analogies of the toxins prompted comparative pyrogenic studies. When American Dutch rabbits were immunized by repeated intravenous injections of small amounts of staphylococcal enterotoxin, they exhibited a decreased febrile response upon challenge when compared with control animals not previously injected. The same animals responded similarly to control groups when challenged with streptococcal exotoxin A, B, or C. No cross-reactivity was observed in reciprocal cross-tests, using animals immune to the streptococcal toxins and challenging with staphylococcal enterotoxin. No cross-reactivity between either the streptococcal or staphylococcal toxins and bacterial endotoxin was observed.

Animals↗
PubMed1973

Enhanced immune response after immunosuppression by Streptococcal pyrogenic exotoxin.

Streptococcal pyrogenic exotoxin (SPE) was shown previously to be a potent immunosuppressant. This paper presents data documenting that immunosuppression frequently was followed by elevated antibody and plaque-forming cell levels as noted in our earlier report. The data are interpreted as a differential effect of SPE upon suppressor T cells and secreting B cells.

Antibody Formation↗
PubMed1973

Pyrogenicity and immunogenicity of lipid A complexed with bovine serum albumin or human serum albumin.

The lipid A component of bacterial lipopolysaccharides (endotoxins), when complexed to bovine serum albumin (BSA) or human serum albumin (HSA), was shown to be a potent pyrogen. Furthermore, rabbits could be protected against endotoxin fever by immunization with both lipid A.BSA and lipid A.HSA complexes. The results presented in this paper show that lipid A is responsible for the pyrogenic activity of endotoxins and their ability to induce pyrogenic immunity.

Animals↗