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Biomedical subjects

A M Clark

Publications and source records attributed to A M Clark.

At least 163 records · Page 9Linked to original sources
PubMed1976

Naturally occuring mutagens.

Naturally occurring mutagens have usually been discovered as a result of outbreaks of disease in agricultural livestock, or as a result of epidemiological studies of cancer of the liver in man. Subsequent work has then shown that the toxic agents responsible often have mutagenic properties. Examples are the pyrrolizidine alkaloids, cyasin, a range of mycotoxins produced by various fungi, and at least two unidentified toxic agents in bracken. Commonly the toxic agent itself does not show high biological activity, but after ingestion it is converted by metabolic processes into the active mutagen or carcinogen. Some of these toxic substances have been responsible for considerable losses of agricultural livestock and therefore are of economic significance. From the view-point of genetic hazards to man, the most significant compounds are probably the mycotoxins, e.g. aflatoxin, because of the common risk of fungal contamination of food, especially in tropical regions. No information is yet available on the effects of these mutagens on natural populations of animals. Plants containing the pyrrolizidine alkaloids are found in areas of Africa and the Middle East where plagues of the migratory locust occur. Although it is known that some of the alkaloids can induce chromosomal damage in grasshoppers, whether such damage ever becomes a significant factor under ecological conditions is not known. In some cases, insects have not only evolved resistance towards mutagenic alkaloids but have become dependent on them for certain purposes. The males of certain Danaid butterflies feed on plants containing pyrrolizidine alkaloids. After ingestion, the alkaloids are metabolised to dihydropyrrolizine derivatives, which are then secreted on special organs (hair pencils) and, following dissemination into the atmosphere, act as pheromones for the stimulation of mating behaviour.

Aflatoxins↗
PubMed1972

Evidence for post-cleavage fertilization among mosaics in Habrobracon juglandis.

Habrobracon females homozygous for the mutant ebony produce about 5% mosaic progeny among fertilized eggs. The present experiment demonstrates by means of a test-cross method that in the production of these mosaics only one pronucleus is involved, and that this nucleus cleaves before union of one of its daughter nuclei with the sperm nucleus.

Animals↗