Influence of human skin surface lipids on protection time of topical mosquito repellent

Skin surface lipids were extracted from volunteers who had been ranked according to the duration of protection from mosquitoes by diethyltoluamide. These lipids were analyzed by GLC-mass spectrometry for their fatty acid contents. Correlations were found between total skin lipid content and protection time of diethyltoluamide and between certain fatty acid concentrations in the skin lipids and the protection time of diethyltoluamide.

Modification by calcium ions of adenine nucleotide translocation in rat liver mitochondria

1. Added Ca(2+) stimulates the translocation of ATP by isolated rat liver mitochondria. 2. The apparent K(m) for added Ca(2+) in stimulating the translocation of 200mum-ATP is approx. 160mum (75mum ;free' Ca(2+)). 3. The greatest stimulation of ATP translocation by Ca(2+) occurs at the lower concentrations of ATP. 4. Sr(2+) (and to a lesser extent Ba(2+)) can replace Ca(2+) whereas Mg(2+) and Mn(2+) have only little ability to stimulate ATP translocation. 5. Translocation of dATP is also stimulated by Ca(2+) whereas that of ADP is stimulated to only a relatively small degree. 6. Studies with metabolic inhibitors and uncouplers provide evidence that stimulation by Ca(2+) and by uncouplers is additive and that the mechanism of Ca(2+) stimulation does not seem to involve the high-energy intermediate of oxidative phosphorylation. 7. In the presence of Ca(2+), ATP is able to effectively compete with ADP for translocation. 8. Added K(+) further enhances the ability of Ca(2+) to stimulate ATP translocation. 9. These findings are discussed in relation to the potential involvement of Ca(2+) in modifying enzymic reactions involved in the regulation of cell metabolism.