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.      

Morphological variations and climatic differences

As it has been shown long ago by physicists, the volume/surface ratio influences the cooling of bodies. Unfortunately, the volume of living things in most cases is difficult to assess. Therefore it can be reasonably replaced by body-weight, as it is usual in biological work. A second ratio, total limbs length/body weight, also plays an obvious role in body-heat regulation.Both ratios were studied experimentally on more than 100 men, in a hot room or on a tread-mill. On the other hand they were studied statistically on many different populations belonging to all the major divisions of the human species. These ratios are not the cornerstone of body-heat regulation, but both influence it. As a general tendency, body-weight/body-surface ratio decreases in warm climates, whereas limbs-length/body weight ratio increases. These geographical differences may be considered as ecological gradients related to body-heat regulation.These gradients do not exactly follow latitudes, because other factors, such as altitude, must be also taken into account. Perhaps there are several similar gradients, represented by different figures in different branches of human species. Some small gradient irrégularities can probably be explained by sampling errors: adaptation is a statistical phenomenon and small samples may sometimes distort a gradient's orderliness. Finally, body-weight/body-surface ratio is to some extent related to age. As we have shown it elsewhere, some numerical “inconsistencies” disappear if the age influence is statistically eliminated. Unfortunately, this correction is often impossible because in many populations the exact age of adult subjects is unknown.     

High expression of cloned genes in E. coli and its consequences

Using recombinant DNA technology it is relatively easy to construct strains of bacteria which over-produce foreign proteins such as those from human, animal or viral sources. In the near future the same methodology will be used to increase the production of natural products of microorganism by manipulating metabolic pathways, e.g. those involved in antibiotic or amino acid syntheses. This article reviews the factors which lead to over-expression of proteins in E. coli and the possible consequences when large scale culture is undertaken.