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Biomedical subjects

E Küster

Publications and source records attributed to E Küster.

26 records · Page 2Linked to original sources
PubMed1971

Resistance of Bacillus subtilis spores to inactivation by gamma irradiation and heating in the presence of a bactericide. 3. Factors affecting rates of inactivation by phenylmercuric nitrate.

Aqueous suspensions of Bacillus subtilis NCTC 8236 spores, surviving gamma irradiation from a cesium-137 source, exhibited an enhanced rate of inactivation compared to nonirradiated spores when heated with 0.04% phenylmercuric nitrate. The enhanced rate of inactivation, observable from survival curves, was noted when spores were irradiated with 150,000 rad under air in either the presence or absence of the bactericide. The magnitude of the enhanced inactivation rate increased as the irradiation dose under air increased from 150,000 to 300,000 rad. The inactivation rates of spores surviving irradiation with 150,000 rad under either oxic or anoxic conditions did not exhibit a simple quantitative relationship. The enhancement effect was observed when the severity of the heat treatment was increased by either reducing the pH from 8 to 6 or raising the temperature from 70 to 90 C.

Air↗
PubMed1970

Resistance of Bacillus subtilis spores to inactivation by gamma irradiation and heating in the presence of a bactericide. I. Suitability of viable count procedures.

A statistical evaluation of viable count procedures utilized for obtaining treatment survival curve data for Bacillus subtilis NCTC 8236 spores is described. Within the various recovery conditions tested, incubation on nutrient agar containing 1% dextrose for 48 hr at 37 C was found to promote the highest count of viable spores surviving a variety of bactericidal treatments involving gamma irradiation, heat, and chlorocresol. The count of viable spores on the medium was not significantly altered when the dextrose was added to the nutrient agar either before autoclaving or aseptically at 50 to 55 C from a solution sterilized by filtration. The volume of medium which promoted the highest count of viable spores was 20 ml per 85 mm of diameter in disposable plastic plates. Counts of viable spores were reproducible on successive batches of media. The carry-over of variable concentrations of chlorocresol into the medium from serial dilutions affected the count of viable spores. Spores in the aqueous stock suspension used for all experiments were uniformly distributed after shaking and did not diminish significantly in viability after 16 months of storage at 5 C. Grouping of indexes of dispersion, calculated from quintuplicate plate colony counts, indicated that the suitability of the viable count procedures, employed for the enumeration of spores surviving the various bactericidal treatments, tended to diminish as the level of spore inactivation exceeded 95%.

Agar↗
PubMed1970

Resistance of Bacillus subtilis spores to inactivation by gamma irradiation and heating in the presence of a bactericide. II. Factors affecting rates of inactivation by phenolic bactericides.

Aqueous suspensions of Bacillus subtilis NCTC 8236 spores, surviving 150,000 or 300,000 rad of gamma irradiation under air from a cesium-137 source, exhibited an enhanced rate of inactivation, compared to nonirradiated spores, when heated with different phenolic bactericides. The apparent magnitude of the enhanced inactivation rate, observed from survival curves, increased progressively with the irradiation dose applied and diminished progressively as the severity of heat treatment with 0.2% chlorocresol was increased either by raising the temperature from 70 to 90 C or reducing the pH from 8 to 6. The enhanced inactivation rate was unaffected when the concentration of sodium chloride added to 0.2% chlorocresol was altered from 0.4 to 0.8%. The enhancement effect was also observed when the heat treatment was carried out with 0.5% phenol and 0.3% m-cresol.

Bacillus subtilis↗
PubMedDate not supplied

Comparison of cholin- and carboxylesterase enzyme inhibition and visible effects in the zebra fish embryo bioassay under short-term paraoxon-methyl exposure.

The acute zebra fish embryo test (Danio rerio Hamilton-Buchanan, 1822) is an accepted bioassay to assess the toxicity of waste water that may be used for the replacement of testing with adult fish. It is also suggested for chemical hazard characterization and assessment, although only a few groups of substances have yet been studied. Specifically acting substances such as neurotoxic insecticides pose a potentially hazard for non-target fish. To establish whether the proposed zebra fish embryo test protocol and the inhibition of cholinesterases (acetylcholinesterase EC 3.1.1.7, propionylcholinesterase EC 3.1.1.8) and carboxylesterase (EC 3.1.1.1) enzymes can be used in a similar fashion for hazard characterization and risk assessment of chemicals and environmental samples, two types of experiments were conducted. Visual effects of exposure to the organophosphate metabolite paraoxon-methyl after 24 and 48 h in the zebra fish embryo test system were analysed with the use of an inverse microscope (rate of mortality, developmental disturbances, heart rate and others). The inhibition to cholinesterases and carboxylesterase was also measured. Enzyme inhibition as a biomarker of exposure was about 70 times more sensitive than the effects in the zebra fish embryo test with an IC50 below 1.2 micromol compared with an EC50 of 91 micromol. The dose-response relationships showed different curve characteristics with a linear increase of enzyme inhibition compared with a sigmoidal curve for the overt effects. Significant overt effects could only be seen at concentrations at which already 80% of the activities of the different esterases were inhibited.

Animals↗