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Biomedical subjects

P S Steyn

Publications and source records attributed to P S Steyn.

At least 19 recordsLinked to original sources
PubMed1995

Mycotoxins, general view, chemistry and structure.

Mycotoxins induce diverse and powerful biological effects in test systems; some are carcinogenic, mutagenic, teratogenic, estrogenic, hemorrhagic, immunotoxic, nephrotoxic, hepatotoxic, dermotoxic, and neurotoxic. Mycotoxins have been unambiguously linked to the etiology of several diseases in animals. The discovery of aflatoxins in the early 1960s led to the resurgence of interest in human mycotoxicoses; mycotoxins are now recognized as causal factors of primary liver cancer, ergotism and alimentary toxic aleukia. The fumonisins and ochratoxins are suspected of playing a role in the etiology of esophageal cancer and Balkan endemic nephrotoxicity, respectively.

Aflatoxins↗
PubMed1994

Conservative management of severe chronic hypertension in pregnancy.

Severe chronic hypertension in pregnancy is a condition frequently associated with poor maternal and fetal outcome. Meticulous antenatal care can lead to a reduction in morbidity and mortality. The case described is that of a primigravida who presented with severe chronic hypertension in the midtrimester of pregnancy. She was treated with four antihypertensive drugs and aspirin, and a favourable pregnancy outcome was achieved.

Adult↗
PubMed1989

Influence of ochratoxin B on the ochratoxin A inhibition of phenylalanyl-tRNA formation in vitro and protein synthesis in hepatoma tissue culture cells.

Ochratoxin B (OTB), the dechloro-analogue of ochratoxin A (OTA), was studied separately and in combination with OTA on the aminoacylation of phenylalanine tRNA (tRNAPhe) catalysed by mice liver phenylalanyl-tRNA synthetase. OTB was neither a significant inhibitor of the reaction nor an antagonist of OTA. OTB was also assayed for its possible antagonistic effect on the in vivo protein synthesis inhibition caused by OTA in hepatoma tissue culture cells. No prevention of OTA inhibition could be found for OTB. It rather showed a slight additional inhibitory activity when mixed (100-180 microM) with low concentrations of OTA (40-60 microM). In conclusion, these results are not in favor of an antagonistic effect of OTB with respect to OTA action, at least on the level of cellular protein synthesis.

Animals↗
PubMed1987

Smodingium dermatitis.

Smodingium argutum is the plant most commonly responsible for causing acute allergic contact dermatitis in South Africa. When an outbreak of Smodingium dermatitis occurred in a local school the allergenic principle present in this plant was chemically isolated and identified, and its allergenic property proved in the clinic by patch testing. The value of using an extract of fresh Smodingium leaves in lieu of fresh leaves themselves was confirmed, but freeze-dried material was found to be unsuitable for patch-test purposes.

Acute Disease↗
PubMed1984

Toxicity of rhizonin A, isolated from Rhizopus microsporus, in laboratory animals.

Maize culture material of 25 isolates of the genera Rhizopus and Mucor caused deaths in day-old unsexed Pekin ducklings when fed as a 50% (w/w) mixture with duckling feed. Nine of these isolates were tested for toxicity in young inbred male BD IX rats, which were fed a mixture of 50% (w/w) culture material and rat feed. Only one isolate of Rhizopus microsporus was clearly toxic, causing 100% mortality in rats within 10 days. Growth in rats was reduced by adding culture material of this isolate to the feed in concentrations of 2.5, 5, 10 or 20% (w/w). The same isolate of R. microsporus was used to produce the mycotoxin rhizonin A. Pure rhizonin A was dissolved in dimethylsulphoxide and given to young male partially inbred albino rats by gavage in single doses of 70, 96, 131 or 180 mg/kg. The lowest dose exceeded the LD100. Evaluated by light microscopy, lesions in livers and kidneys were similar in rats fed culture material and in those intubated with rhizonin A. Hepatocytes showed changes ranging from degeneration to necrosis, the liver-tissue architecture was changed by disassociation of liver cell cords and there was periportal bile-duct proliferation. Renal tubular epithelium showed changes ranging from degeneration to necrosis.

Animals↗
PubMed1983

Comparative study of the effect of ochratoxin A analogues on yeast aminoacyl-tRNA synthetases and on the growth and protein synthesis of hepatoma cells.

Ochratoxin A (OTA), a naturally occurring mycotoxin of Aspergillus and Penicillium species, consists of a 5' chlorinated dihydromethyl isocoumarin linked to L,beta-phenylalanine by an alpha-amide bond. 8 analogues of OTA were prepared in which the phenylalanine was always substituted by another amino acid. The effects of these analogues on yeast tRNA amino acylation reaction and on growth and protein synthesis of hepatoma culture cells were compared with those of OTA. In addition, Ochratoxin B (OTB) and ochratoxin alpha (OT alpha) were examined. All the analogues of OTA had inhibitory effects in the 3 test systems, although to a lesser degree than OTA. The degree of inhibition depended on the kind of substituted amino acid, the tyrosine, valine, serine and alanine analogues being most effective, in contrast to the proline analogue. OTB and OT alpha were ineffective.

Amino Acyl-tRNA Synthetases↗
PubMed1979

Screening methods for the detection of thirteen common mycotoxins.

A study of screening methods for thirteen mycotoxins showed that they can be separated as neutral and acidic metabolites. RF values were determined in several solvent systems. The reactions of the mycotoxins with well known spray reagents were investigated, and their detection limits were established. A general procedure for the extraction of mycotoxins from contaminated samples is described.

Chromatography, Thin Layer↗
PubMed1977

Some newly discovered mycotoxins.

The discovery of the aflatoxins in 1960 has taken place in the present era of the intense awareness of the importance of environmental contaminants. It has dramatically influenced subsequent fungal research with the resulting rapid increase in the number of publications describing mycological, chemical, toxicological and epidemiological aspects of mycotoxins. In this contribution results will be discussed which were published only subsequent to 1970. In this period the importance of several new classes of mycotoxins was realized, e.g. the toxic cytochalasins and the tremorgens. The potential role of highly oxygenated metabolites in mycotoxicosis was emphasized by the establishment of secalonic acids A and D. emodin, moniliformin, altenuisiol alternariol and austdiol as toxins. The structure of viridicatumtoxin, C30H31NO11, a metabolite produced by Penicillium viridicatum will be described. It is a novel compound, structurally related to the tetracyclines. The characterization of several mycotoxins from other toxigenic fungi will be reported.

Cytochalasins↗