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Biomedical subjects

M Steyn

Publications and source records attributed to M Steyn.

72 records · Page 4Linked to original sources
PubMed1977

New species of Aspergillus producing sterigmatocystin.

A number of species belonging to the genus Aspergillus were evaluated for their toxicity to ducklings and the ability to produce sterigmatocystin. Three new species capable of producing sterigmatocystin were found, namely, Aspergillus aurantio-brunneus, Aspergillus quadrilineatus, and Aspergillus ustus. All three were toxic to ducklings. The production of sterigmatocystin by Aspergillus rugulosus was confirmed, and the toxicity of Aspergillus stellatus and Aspergillus multicolor is described.

Aflatoxins↗
PubMed1976

Production of sterigmatocystin by Aspergillus versicolor and Bipolaris sorokiniana on semisynthetic liquid and solid media.

Higher yields of sterigmatocystin were obtained with Aspergillus versicolor than with Bipolaris sorokiniana both in liquid and on solid media. The optimum temperature for sterigmatocystin production by A. versicolor was 27 to 29 degrees C and 23 degrees C for B. sorokiniana. In liquid shake cultures, production of sterigmatocystin by B. sorokiniana was negligible, whereas maximal production by A. versicolor was 210 mg/liter. On solid substrates, the highest yields (8 g/kg) were obtained with A. versicolor on still cultures of whole corn supplemented with Soytone.

Aspergillus↗
PubMed1975

Production of sterigmatocystin.

A procedure for the isolation of pure sterigmatocystin is described. It involves cultivation of an appropriate fungus on sterile maize, and extraction and column chromatographic purification of the crude extract. With this method sterigmatocystin may be obtained at a fraction of its commercial cost. Aspergillus versicolor seemed to be the best producer (5-12 g/kg) in 250 ml Erlenmeyer flasks. The yield dropped markedly with increasing flask size.

Aspergillus↗
PubMed1971

A comparative study on aflatoxin B 1 metabolism in mice and rats.

In vivo metabolic studies on rats and mice revealed a marked difference in the fluorescent compounds produced after ingestion of aflatoxin B(1). The mouse converted aflatoxin B(1) to three unknown fluorescent compounds, designated x(1), x(2) and x(3) and the known aflatoxin M(1), while the rat was only capable of producing aflatoxin M(1). The results suggested that metabolites x(1), x(2), x(3) and aflatoxin M(1) were not part of a major metabolic pathway, but produced independently. These unknown yellowish-green fluorescent compounds did not seem to be conjugated with sulphate or glucuronic acid.In vitro incubations of various mouse liver cell fractions with aflatoxin B(1) showed that metabolites x(1), x(2), x(3) and aflatoxin M(1), could only be produced by the microsomal fraction and that NADPH was needed as a co-factor. The differences in aflatoxin metabolism by mice and rats are discussed in relation to the apparent resistance of the mouse to the carcinogenic effects of this toxin.

Absorption↗
PubMedDate not supplied

The combating of tuberculosis: health perceptions, intentions and vaccination of children.

This study was part of a comprehensive research project undertaken at the request of the SANTA Health Education Committee to evaluate the tuberculosis guidance programme. The aim of the research was to examine factors influencing black people's health perceptions and intentions concerning the combating of tuberculosis as well as vaccination of their children. Data were collected by means of a questionnaire based on the Health Belief Model. The research was conducted in selected areas of the OFS, the Transvaal and Natal (N = 1,198). It was found that factors indicating a greater degree of development of the individual (e.g. literacy) were positively associated with positive health perceptions such as that medical treatment can cure TB completely. Some positive associations were also found between perceptions/modifying factors and intentions/vaccination. Indications were also found of an inability on the part of health personnel to influence the public positively.

Adolescent↗