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Biomedical subjects

S Wolfe

Publications and source records attributed to S Wolfe.

At least 91 records · Page 5Linked to original sources
PubMed1982

High performance liquid chromatographic assay of cyclization activity in cell-free systems from Streptomyces clavuligerus.

A thirteen-fold excess of dithiothreitol maintains delta-(L-alpha-aminoadipyl)-L-cysteinyl-D-valine (ACV) in its monomeric form under the conditions normally encountered in an ACV cyclization assay system, using Streptomyces clavuligerus. A reversed phase high performance liquid chromatographic (HPLC) system which separates ACV monomer from isopenicillin N, penicillin N and from other cyclization assay components has been developed as follows; mobile phase: 5% methanol-95% KH2PO4 (0.05 M adjusted to pH 4.0 with concentrated H3PO4; stationary phase: muBondapak-C18; flow rate: 2 ml/minute for 5 minutes, 3 ml/minute for the remainder; detection: 220 nm). Under these conditions, authentic samples of isopenicillin N and penicillin N elute with a retention time of 5.25 minutes, which coincides with a peak of newly-formed material observed in cyclization reaction mixtures. The combined concentration of isopenicillin N and penicillin N[(iso)penicillin N] in cyclization reaction mixtures corresponds closely to the concomitant decrease in the ACV monomer. Cyclization reaction mixtures, in which crude cell-free extract from S. clavuligerus NRRL 3585 is the enzyme source, contain (iso)penicillin N at a concentration of 43.3 micrograms/ml after a 1-hour incubation period. Cyclization reaction mixtures, in which salt-precipitated cell-free extract from S. clavuligerus is the enzyme source, contain 39.0 micrograms/ml (iso)penicillin N.

Anti-Bacterial Agents↗
PubMed1982

Cephalosporin formation by cell-free extracts from Streptomyces clavuligerus.

Cell-free extracts of Streptomyces clavuligerus convert delta-L-(alpha-aminoadipyl)-L-cysteinyl-D-valine (ACV) into an antibiotic product which is 30 approximately 50% penicillinase-insensitive. Thin-layer chromatography resolves this antibiotic product into one major penicillinase-sensitive component and one major and one minor penicillinase-resistant component. The major and minor penicillinase-resistant antibiotics co-chromatograph with deacetoxycephalosporin C and deacetylcephalosporin C, respectively. Ring expansion of a penicillin intermediate, as evidenced by the production of penicillinase-resistant antibiotic, shows an absolute requirement for alpha-ketoglutarate, while ATP, K+ and Mg2+ have lesser effects. Ring expansion activity is not sedimented by high speed centrifugation and is unaffected by membrane-disrupting treatments. Penicillin N and ACV (presumably via penicillin N) are the only substrates so far accepted by the ring expanding enzyme. New syntheses of penicillin N and isopenicillin N are described.

Cephalosporins↗
PubMed1982

Cyclization of delta-(L-alpha-aminoadipyl)-L-cysteinyl-D-valine to penicillins by cell-free extracts of Streptomyces clavuligerus.

Cell-free extracts prepared by sonication of Streptomyces clavuligerus cyclized delta-(L-alpha-aminoadipyl)-L-cysteinyl-D-valine (ACV) into a penicillin-type antibiotic. The antibacterial spectrum of this antibiotic suggested it was a mixture of isopenicillin N and penicillin N indicating that both cyclization and racemase activities were present. Cyclization activity was optimal in extracts prepared from 48 hours cultures. Extracts incubated at 20 degrees C produced antibiotic for 2 hours before activity ceased. Cyclization activity showed an absolute requirement for dithiothreitol (DTT) and O2 and was stimulated by ascorbic acid and FeSO4. No requirement for ATP was observed.

Cell-Free System↗
PubMed1976

Unmet needs as sociomedical indicators.

This paper discusses the Meharry Medical College Study of Unmet Needs designed to measure the effectiveness of alternative health care delivery systems: (a) comprehensive care with broad outreach, (b) comprehensive care with limited outreach, and (c) traditional care. Unmet needs are defined as the differences between services judged necessary to deal appropriately with health problems and services actually received. The central hypothesis is that comprehensive health programs will be more effective than traditional care in reducing unmet needs. Unmet needs are viewed as measures of program outcome and are one of several types of sociomedical indicators which use factors other than biomedical or biological states as measures of outcome. The distinction is made between unmet needs are discussed and the relatively limited focus of these is contrasted with the more comprehensive Meharry approach. Household interviews and clinical examinations provide the data base for deriving professional judgements of unmet needs in the medical, dental, nursing, and social services areas. The Meharry work suggests several areas in which further work on unmet needs would be useful.

Comprehensive Health Care↗