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Biomedical subjects

W C Ma

Publications and source records attributed to W C Ma.

27 records · Page 2Linked to original sources
PubMed1988

Toxicity and bioaccumulation of chlorophenols in earthworms, in relation to bioavailability in soil.

The acute toxicity of five chlorophenols for two earthworm species was determined in two sandy soils differing in organic matter content and the results were compared with adsorption data. Adsorption increased with increasing organic matter content of the soils, but for tetra- and pentachlorophenol was also influenced by soil pH. Earthworm toxicity was significantly higher in the soil with a low level of organic matter. This difference disappeared when LC50 values were recalculated to concentrations in soil solution using adsorption data. Eisenia fetida andrei showed LC50 values lower than those of Lumbricus rubellus although bioaccumulation was generally higher in the latter species. Toxicity and bioaccumulation based on soil solution concentrations increased with increasing lipophilicity of the chlorophenols. The present results indicate that the toxicity and bioaccumulation and therefore the bioavailability of chlorophenols in soil to earthworms are dependent on the concentration in soil solution and can be predicted on the basis of adsorption data. Both the toxicity of and bioaccumulation data on chlorophenols in earthworms demonstrated surprisingly good agreement with those on chlorophenols in fish.

Adsorption↗
PubMed1975

Structural modulations in the tsetse fly milk gland during a pregnancy cycle.

Gross ultrastructural and histochemical details of the integumental milk glands of the tsetse fly Glossina morsitans have been examined during the pregnancy cycle. Structural evidence for protein secretion is found between Days 3-8 of the nine-day cycle: termination of activity is completed on the day of parturition. Onset of lactation is synchronized with the eclosion of the first instar larva. The changes in cell volume (notably in the extracellular reservoir) occurring throughout the pregnancy cycle are illustrated in electron micrographs, and a one hundred-fold volume increase in the reservoir volume between the inactive phase and the active period is illustrated and discussed in terms of membrane modulation of the limiting membrane of the reservoir. Intracellular membrane changes during the cycle, particularly the development of extensive ER arrays in the actively secreting cell, are illustrated and discussed. It is suggested that cytoplasmic microtubules play a part in maintaining the form of the distended secretory cell, at the height of secretory release and storage. Histochemical observations on the milk secretion, and the contents of the larval gut are presented.

Animals↗
PubMedDate not supplied

Effect of soil pollution with metallic lead pellets on lead bioaccumulation and organ/body weight alterations in small mammals.

Using small mammals as bioindicators, the bioavailable status and ecotoxicity of lead was investigated in an acidic sandy soil environment polluted with metallic lead pellets from shotgun ammunition. Average concentrations of lead in kidney, liver and bone tissue of wood mice (Apodemus sylvaticus), bank voles (Clethrionomys glareolus), and shrews (Sorex araneus) were strongly elevated, compared to tissue levels of conspecifics collected from an adjacent unpolluted area. All shrews and some bank voles collected from the shooting range exceeded the critical renal Pb concentration of 25 micrograms/g dry weight, considered diagnostic of lead intoxication in mammals. The geometric mean renal Pb concentration in shrews was 270 micrograms/g dry weight, with an upper range of more than 1,000 micrograms/g. The population of shrews and bank voles from the shooting range also showed a significantly increased average relative kidney weight (kidney-to-body weight ratio), which is indicative of lead poisoning. The results suggest that metallic lead pellets deposited in an acidic sandy soil are transformed to a chemical form of lead, probably Pb2+, which is toxic to organisms and which can readily enter the terrestrial food chain.

Analysis of Variance↗