Physico-chemical and functional characteristics of a subfraction of low-density lipoproteins isolated by ion-exchange column chromatography

Fractionation of human blood plasma low density lipoproteins (LDL) was performed by ion-exchange chromatography, using a linear NaCl gradient. It was shown that the binding of LDL subfractions eluted with a low ionic strength buffer (i.e., containing the particles with a lower negative charge) to B, E-receptors of fibroblasts was more effective than that of subfractions eluted with a high ionic strength buffer (i.e., containing the particles with a higher negative charge). The LDL particles with a lower negative charge had lower values of flotation coefficients (according to analytical ultracentrifugation data), smaller dimensions (according to gradient gel electrophoresis data) and a lower phospholipid/protein ratio (w/w). The experimental results suggest that LDL subfractions having different electrical parameters of the particle surface also differ in other physicochemical properties and seem to play a different role in atherogenesis.     

Size and mortality rates of Glossina pallidipes in the semi-arid zone of southwestern Kenya

Seasonal changes in the mean size of tsetse, Glossina pallidipes Austen, as indicated by wing vein length, were monitored during 1983-86 at Nguruman, southwestern Kenya. Changes in size of nulliparous females and wing fray category 1 males were shown to be correlated with the relative humidity 2 months before they were captured. Soil temperature when flies were in the pupal stage had much less effect. Size dependent mortality was demonstrated, with the mean size of flies emerging from pupae significantly less than that of field-caught flies. This mortality must occur at emergence, since there was no evidence of size-dependent mortality once the flies became available to the trap. Size was correlated with density-independent mortality acting on the parent population 2 months previously. It might therefore be possible to use size as an index of the intensity of such mortality. This could be useful when assessing the level of additional mortality required to suppress tsetse populations.     

Nuclear DNA sequences from late Pleistocene megafauna

We report the retrieval and characterization of multi- and single-copy nuclear DNA sequences from Alaskan and Siberian mammoths (Mammuthus primigenius). In addition, a nuclear copy of a mitochondrial gene was recovered. Furthermore, a 13,000-year-old ground sloth and a 33,000- year-old cave bear yielded multicopy nuclear DNA sequences. Thus, multicopy and single-copy genes can be analyzed from Pleistocene faunal remains. The results also show that under some circumstances, nucleotide sequence differences between alleles found within one individual can be distinguished from DNA sequence variation caused by postmortem DNA damage. The nuclear sequences retrieved from the mammoths suggest that mammoths were more similar to Asian elephants than to African elephants.