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Biomedical subjects

J R Warren

Publications and source records attributed to J R Warren.

At least 73 records · Page 4Linked to original sources
PubMed1978

Damage of proliferating lymphoid cell deoxyribonucleic acid by methyl methanesulfonate and N-acetoxy-2-acetylaminofluorene.

Replicative synthesis of deoxyribonucleic acid by splenic lymphoid cells cultured from C57BL/6J strain mice and stimulated to proliferate with concanavalin A (Con A) was strongly suppressed by short exposure (10-60 min) of the cells to the direct-acting carcinogens methyl methanesulfonate or N-acetoxy-2-acetylaminofluorene. Carcinogen-treated lymphoid cells failed to recover stimulated levels of replicative synthesis after incubation for several hours in fresh medium without carcinogen. In contrast, spleen cells treated with hydroxyurea (a metabolic inhibitor of deoxyribonucleic acid replication) fully recovered stimulated rates of replicative synthesis upon incubation in medium without hydroxyurea. Furthermore, the inhibition of replicative synthesis by the carcinogens was accompanied by marked stimulation of deoxyribonucleic acid repair synthesis. Concomitant measurement of replicative and repair synthesis appears to be an effective approach for the in vitro study of carcinogen-induced damage in the deoxyribonucleic acid of proliferating lymphoid cells.

Acetoxyacetylaminofluorene↗
PubMed1977

Effect of alkali-treated lipopolysaccharide on the intracellular cations of human erythrocytes.

The adsorption to human erythrocytes of Escherichia coli lipopolysaccharide treated by mild alkaline hydrolysis (h-LPS) stimulated an increase in the intracellular Na+ concentration and a decrease in the intracellular K+ concentration of the erythrocytes. Erythrocytes treated by h-LPS remained responsive to the membrane adenosine triphosphatase inhibitors ouabain and ethacrynic acid, indicating that hLPS did not alter erythrocyte cations be depleting energy intermediates or uncoupling energy metabolism from active cation transport. The h-LPS-treated erythrocytes became non-agglutinable by the lectin concanavalin A prior to the development of changes in intracellular cations. In addition, h-LPS-treated erythrocytes demonstrated a three-fold greater cation response to ethacrynic acid than the untreated erythrocytes; this greater response was probably due to local membrane effects by h-LPS on the ethacrynic acid-sensitive adenosine triphosphatase. It is suggested that the h-LPS-induced alteration of erythrocyte cation content was secondary to an increase in ion permeability localized to the concanavalin A receptor regions of the erythrocyte membrane, possibly combined with indirect effects of membrane-bound h-LPS on ethacrynic acid-sensitive adenosine triphosphatase.

Agglutination↗
PubMed1976

beta Structure of aqueous staphylococcal enterotoxin B by spectropolarimetry and sequence-based conformational predictions.

Conformations of the globular protein staphylococcal enterotoxin B have been examined experimentally by ultraviolet circular dichroism (CD) and visible optical rotatory dispersion (ORD). Chen-Yang-Chau analysis (Chen, Y.-H., Yang, J.T., and Chau, K. H. (1974), Biochemistry 13, 3350) of the far-ultraviolet CD spectrum of native enterotoxin B revealed (assuming an average helix length of 11 residues) 9% alpha helix, 38% beta structure, and 53% random coil. A fourfold increase in alpha-helix was observed for enterotoxin exposed to 0.2% sodium dodecyl sulfate, behavior typical for globular proteins of low helical content. Values of -40 to -50 for the Moffitt-Yang parameter b0 calculated from visible ORD suggested 6-13% alpha helix in native enterotoxin. Application of a new predictive model (Chou, P. Y., and Fasman, G. D. (1974), Biochemistry 13,222) to the amino acid sequence of enterotoxin B indicated 11% alpha helix, 34% beta structure, and 55% coil in native enterotoxin. The excellent agreement for the amount of alpha and beta conformation utilizing different optical and predictive methods indicates beta structure as the dominant secondary structure in native enterotoxin B. Most of the beta structure is predicted by Chou-Fasman analysis to reside in two large regions of antiparallel beta sheet involving residues 81-148 and residues 184-217. Such highly cooperative regions of anti-parallel beta sheet account for the slow unfolding of enterotoxin B in concentrated guanidine hydrochloride and rapid folding of guanidine hydrochloride denatured enterotoxin B to native conformation(s) (Warren, J.R., Spero, L., and Metzger, J. F. (1974), Biochemistry 13, 1678). A more than twofold increase in alpha-helix content with a small diminution in beta structure was detected by CD and ORD upon acidification of aqueous enterotoxin to pH 2.5. Thus, the beta structure of enterotoxin B appears to resist isothermal denaturation and constitutes a stable interior core of structure in the enterotoxin molecule.

Amino Acid Sequence↗
PubMed1976

The nature of alkylurea and urea denaturation of alpha-chymotrypsinogen.

The optical rotatory dispersion of alpha-chymotrypsinogen in aqueous solution became less levorotatory upon the addition of ethyl-, propyl-, or butylurea; less negative values for the Moffitt-Yang parameter, alphao, were also obatined. This change in optical rotation of alpha-chymotrypsinogen induced by the alkylureas was similar in direction and magnitude to that observed for alcohols but was opposite to that caused by unsubstituted urea. It appears, therefore, that the alkylureas share with the alcohols an ability to rearrange alpha-chymotrypsinogen into a non-native yet regularly ordered conformation. The effectiveness of the alkylureas and alcohols as denaturants for this protein increased in the order ethyl less than propyl less than butyl derivatives. An identical rank-order was observed for the ability of the alkylureas and alcohols to diminish attractive forces between aliphatic groups, as measured by a model system based upon the extent of aggregation of glass beads coated with methyl groups. These findings indicate that the denaturing action of alkylureas for alpha-chymotrypsinogen is a function of the substituted aliphatic group and is predominantly hydrophobic in character. Non-hydrophobic interactions of unsubstituted urea with alpha-chymotrypsinogen appear to be critical for unfolding of the protein to a random-coil configuration.

1-Propanol↗
PubMed1975

Biological activity and complementation of the two peptides of staphylococcal enterotoxin B formed by limited tryptic hydrolysis.

Tryptic hydrolysis after reduction and carboxamidomethylation of staphylococcal enterotoxin B cleaved the single susceptible bond located between the 2 half-cystines of the molecule, Lys-Thr at positions 97 and 98 (Spero, L., Warren, J. R., and Metzger, J. F. (1973) J. Biol. Chem. 248, 7289-7294). The product remained as a single particle but was separated into the two constituent peptides by denaturants, and purification of the two fragments was accomplished by chromatography on CM-cellulose in 8 M urea. Antigenic activity was exhibited by the separated peptides after dialysis of urea solutions against dilute buffer, but was very labile. No emetic activity in rhesus monkeys was found for either separated peptide. The derivative behaved as two random coil peptides in 6 M guanidine hydrochloride but upon removal of guanidine refolded to a single molecular entity. Viscosity and unfolding kinetics in 1.5 M guanidine indicated physical identity of the recombined peptides with the derivative prior to treatment with guanidine. Three biological measures (serological, mitogenic, and emetic activity) were also essentially unaltered for the recombined material. Since these biological activities are dependent upon different aspects of enterotoxin structure, it is concluded that the recombined derivative was restored to its original conformation.

Animals↗
PubMed1975

Immunogenicity of formaldehyde-inactivated enterotoxins A and C1 of Staphylococcus aureus.

Quantitative precipitation of antisera specific for native enterotoxin revealed that 70% and 60%, respectively, of the antigenic determinants of enterotoxins A and C1 of Staphylococcus aureus were inactivated by formaldehyde at pH 5.0 or 7.5 contained large polymers (excluded by Sepharose 2B) and induced strong humoral immune responses in rhesus monkeys. Enterotoxin A inactivated at pH 5.0 or 7.5 was composed mostly of small polymers (excluded by Sephadex G-100 but included by Sepharose 2B); it provoked a poor immune response in monkeys (about equivalent to the response obtained with weakly reactive toxin inactivated at alkaline pH). It was concluded that potent enterotoxoids were formed by extensive cross-linking of enterotoxin C1 into large polymers in acidic or neutral formaldehyde solution.

Animals↗
PubMed1975

Evidence for cell-receptor activity in lymphocyte stimulation by staphylococcal enterotoxin.

A wide dose-response curve and the inhibitory effect on mitogenicity of specific antitoxin suggest that polyclonal lymphocyte activation by staphylococcal enterotoxin requires direct interaction of toxin with lymphocyte receptors of low avidity for the protein. Staphylococcal enterotoxins A, B, and C1 demonstrated equivalent mitogenic activity. Lymphocyte receptors involved in enterotoxin activation thus appear to be specific for nonantigenic regions of the toxin molecule. Monosaccharide (hapten) inhibiton data indicate that lymphocyte receptors for staphylococcal enterotoxin lack alpha-mannoside, galactose, acetylgalactosamine, acetylglucosamine, and fucose (or closely related saccharides) as determinant sugars and thus differ significantly in structure from lectin cell receptors.

Acetylgalactosamine↗