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Biomedical subjects

S LESKOWITZ

Publications and source records attributed to S LESKOWITZ.

At least 19 recordsLinked to original sources
PubMed1963

Immunochemical study of antigenic specificity in delayed hypersensitivity. II. Delayed hypersensitivity to polytyrosine-azobenzenearsonate and its suppression by haptens.

Delayed hypersensitivity in guinea pigs was produced by immunization. with a conjugate prepared by coupling diazotized arsanilic acid to polytyrosine. The resulting sensitivity could be demonstrated by skin test with conjugates prepared from a wide variety of tyrosine-containing proteins. Definite but smaller degrees of sensitivity could be induced with conjugates of proteins containing little or no tyrosine. The apparent absence of carrier-specificity is considered to be due to the narrowed range of immunologic response produced by immunization with polytyrosine-azobenzenearsonate. Injections of the hapten N-acetyltyrosine-azobenzenearsonate was found to suppress completely the delayed reaction attributable to the tyrosine-azobenzenearsonate group. The same hapten was only slightly effective in suppressing reactions in guinea pigs immunized with guinea pig serum albumin-azobenzenearsonate, suggesting that a broader range of specificities is involved with such antigens. Confirmation of such increased range of specificity attributable to antigenic determinants contributed by the carrier protein was obtained by desensitization studies with N-acetyltyrosine-azobenzenearsonate and guinea pig serum albumin-azobenzoate. While separately these materials produced only a slight decrease in skin reactivity to guinea pig serum albumin-azobenzenearsonate, the combination was found to give almost complete suppression.

Animals↗
PubMed1952

The isolation and identification of para-aminobenzoic acid produced by staphylococci resistant to sulfonamide.

Previous studies have shown that when Staphylococcus aureus becomes resistant to sulfonamides, an antisulfonamide substance is produced in the growth medium. Although these studies suggested that the substance was p-aminobenzoic acid (PABA), isolation and positive identification were not achieved. Because of the importance of these observations, unequivocal identification of the product was attempted. A strain of Stapkylococcus aureus resistant to sulfonamides was cultivated on a simplified medium, the organisms separated in a Sharples centrifuge and the diazotisable amine absorbed on amberlite IR-120 previously acidified. Elution was accomplished with pyridine and the amine recovered by ether extraction at pH 3.7. Paper chromatography revealed one amine resembling PABA and another contaminating diazotizable amine present in very small amounts. The PABA-like amine was further separated by chromatography; its R(f) value and its spectrum in the ultraviolet then equalled those obtained with PABA. A 2,4-dlnltrophenyl derivative of the amine was prepared and the m.p. was similar to that of the derivative made from PABA. On the basis of the physical and chemical properties described, it would appear unequivocal that this bacterial amine is PABA.

4-Aminobenzoic Acid↗