Ascorbate as an induction inhibitor of beta-lactamase in a strain of Enterobacter cloacae.

The effect of ascorbate and anaerobiosis of beta-lactamase content (constitutive and inducible) in relation to the susceptibility of a standard strain of Enterobacter cloacae to ampicillin was studied. Enterobacter cloacae ATCC 13047 showed increasing susceptibility to ampicillin when incubated anaerobically in the presence of increasing concentrations of ascorbic acid. The inducible beta-lactamase activity in the cell-free extracts of Ent. cloacae decreased when the bacterium was grown aerobically in the presence of ascorbic acid. Under anaerobic growth conditions, however, ascorbic acid abrogated the induction of the enzyme completely. On the other hand, the constitutive enzymatic activity was markedly decreased as the bacterium was grown anaerobically. Thus under these growth conditions ascorbate-anaerobiosis, the total beta-lactamase level in the presence of ampicillin as inducer fell below the basal constitutive activity observed in the absence of ampicillin.

Evidence for superoxide radical production by a simple flavoprotein: glucose oxidase.

Nitroblue tetrazolium was reduced to blue formazan during the oxidation of glucose by glucose oxidase. The rate of blue color formation was dependent on the concentrations of glucose, nitroblue tetrazolium and glucose oxidase. The rate of the reaction was negligible below pH 8.4, but sharply increased with increasing pH. The reduction of nitroblue tetrazolium was inhibited by superoxide dismutase, consistent with the participation of superoxide anion radical in the reaction.

Role of oxygen and metal ions in the instability of streptolysin O.

Thiol-containing preparations of streptolysin O (SLO) and pure cysteine generate superoxide radicals in alkaline buffer on autoxidation of the thiol groups. Autoxidation is stimulated by cupric ions. Reconstituted SLO preparations accumulate hydrogen peroxide with a concomitant loss of activity on storage at room temperature. Short-term protection of hemolytic activity was achieved by inclusion of catalase in the preparation; no apparent protection was observed by superoxide dismutase, whereas 1,10-O-phenanthroline offered long-term protection of the hemolysin.

A nitrate reductase-based colorimetric assay for the study of bacterial adherence.

Washed intact cells of Escherichia coli and Staphylococcus aureus, grown under partial anaerobic conditions in nitrate media, reduced nitrate quantitatively when formate was used as a reducing substrate. Nitrate reductase was applied as an index for bacterial adherence to different target surfaces including uroepithelial cells, HeLa cells and fibrin clots. Nitrate reduction by adhered as well as control cells was determined by quantitative diazotization reaction for nitrite. Variations in the conditions which affect adherence gave rise to corresponding variations in the nitrate reduction index from which bacterial adherence can be conveniently determined under these conditions. This method is simple, reproducible and easy to perform in a short time.

Antimicrobial activity of artemisinin and its derivatives against anaerobic bacteria.

Artemisinin and nine of its semisynthetic derivatives were tested for antibacterial activity against anaerobic, facultative anaerobic, microaerophilic and aerobic bacteria. Only anaerobic bacteria and gonococci showed sensitivity to artemisinin derivatives. Artemisinin and its deoxy derivatives had no activity at 100 micrograms/ml concentration. The newly synthesized methyl diperoxy derivative had the highest activity against all tested anaerobes with a MIC of 9.4 micrograms/ml.

Antioxidant enzymes in Trichomonas vaginalis.

The activities of artificial donor peroxidase, catalase, and superoxide dismutase in clinical isolates of T. vaginalis were studied. None of the tested strains exhibited activity of the three enzymes. Inclusion of catalase in Diamond-TYM solid medium did not support growth under aerobic conditions. The correlation between the absence of these enzymes and the growth conditions of the organism is discussed.

Influence of new quinolones on normal immune capabilities.

Ciprofloxacin, pefloxacin, norfloxacin, and ofloxacin were investigated for immunomodulatory activity on humoral and cell-mediated immune responses. Ciprofloxacin and pefloxacin altered the humoral immune responses of mice to sheep red blood cells. This effect was not exhibited by norfloxacin or ofloxacin. All four quinolones did not alter cell-mediated responses. When these antimicrobial agents were tested for their interaction with human polymorphonuclear phagocytic activity, all agents suppressed this activity. In addition, all except norfloxacin showed anti-inflammatory activity.

The patients' view of life in a psychiatric hospital. A questionnaire study and associated methodological considerations.

In any assessment of hospital life, the patients' view is indispensable, but there is no generally accepted way of seeking it. In this study, the views of 258 patients in four 'traditional' English psychiatric hospitals were obtained by a questionnaire of 45 items supplemented by freehand comments. Their experience of fellow patients, the staff and the material and institutional aspects of hospital care were explored. Some of the benefits and problems of questionnaire use in this realm are discussed.

Peroxidase-mediated oxidation of isoniazid.

Oxidation of isonicotinic acid hydrazide (isoniazid) by horseradish peroxidase at the expense of H2O2 yielded reactive species which were able to reduce nitroblue tetrazolium and bleach p-nitrosodimethylaniline. Nicotinic acid hydrazide oxidation did not cause these effects. At slightly alkaline pH, oxidation of isonicotinic acid hydrazide by horseradish peroxidase proceeded at the expense of molecular O2, and the reaction was oxygen consuming. The addition of H2O2 abolished O2 consumption. Bovine liver catalase enhanced the rate of nitroblue tetrazolium reduction and decreased the maximal velocity of the reaction proportionately to catalase concentration. During oxidation of isonicotinic acid hydrazide by horseradish peroxidase-H2O2, splitting of the heme group of horseradish peroxidase took place as shown by the disappearance of the Soret and minor bands in the visible region of the spectrum.

Evidence for the generation of active oxygen by isoniazid treatment of extracts of Mycobacterium tuberculosis H37Ra.

Crude extracts of Mycobacterium tuberculosis H37Ra, an isonicotinic acid hydrazide (isoniazid) (INH)-susceptible strain which has peroxidase activity, catalyzed the production of catechol from phenol in the presence of INH and H2O2 as shown by the development of the 444-nm absorption peak of oxidized catechol product. Extracts of the INH-resistant strain of M. tuberculosis H37Ra, which has no peroxidase, did not catalyze the reaction. The rate of development of the 444-nm peak increased proportionately with increased superoxide dismutase concentrations. The hydroxyl radical (. OH) scavengers dimethylsulfoxide and mannitol inhibited the reaction. Isonicotinamide, isonicotinic acid, and nicotinic acid could not replace INH.

Enzymatic and nonenzymatic superoxide-generating reactions of isoniazid.

During the course of horseradish peroxidase-mediated oxidation of either o-dianisidine or 2-2'-azino-di(3-ethyl-benzthiazoline-6-sulfonic acid) (ABTS), no O2 consumption took place. When isonicotinic acid hydrazide (isoniazid) (INH) was included in the reaction mixture, O2 was consumed in amounts linearly related to the INH concentration. Nicotinic acid hydrazide at equimolar concentrations induced lower rates of O2 consumption. Superoxide dismutase activated O2 consumption. At equimolar concentrations, INH, nicotinic acid hydrazide, and phenylhydrazine induced bleaching of p-nitrosodimethylaniline in the horseradish peroxidase mediation of ABTS oxidation. Bleaching was not inhibited by hydroxyl radical (. OH) scavengers. After a short lag period, INH reacted with NADH at alkaline pH to produce superoxide radical (O2-), as detected by superoxide dismutase-inhibitable Nitro Blue Tetrazolium reduction. Nicotinic acid hydrazide with NADH caused a lower rate of O2- production after a longer lag period than INH.

Effect of oxygen radical scavengers on K-cell cytolysis.

We have shown that the hydroxyl radical scavengers sodium benzoate, phenol, dimethyl sulfoxide, sodium formate, and mannitol protect chicken erythrocyte (Ec) target cells from lysis by K-cells in plaque assays. The protection afforded by benzoate, phenol, mannitol, and dimethyl sulfoxide was abrogated if the target cells were pretreated with sodium chromate. Neither superoxide dismutase nor catalase protected Ec target cells, indicating that superoxide and H2O2 are not involved in lysis. The lysis obtained on chromium-treated Ec target cells in the presence of benzoate, phenol, and mannitol is likely due to singlet oxygen, because 1,4-diazabicyclo[2.2.2]octane and bilirubin, singlet oxygen scavengers, protected chromium-treated Ec target cells in the presence of phenol. Ec target cells not treated with chromium were not protected by either of the singlet oxygen scavengers.

Synthesis and biological activity evaluation of some quinolines.

Synthesis of some quinolines having the thiosemicarbazide and nitrostyryl moieties is described. 8-nitroquinoline-4-acraldehyde undergoes Vilsmeier reaction with dimethylacetamide to afford the respective pentadiene amide. Screening of the synthesized quinolines for bactericidal and mollusicidal activities is reported.

Synthesis and biological activity of some quinoline acrylamides.

Synthesis of some quinoline acrylamides is described. The NMR spectra of some representatives are discussed. Screening of the synthesized compounds for molluscicidal and bactericidal activity is commented.