Early origin and recent expansion of Plasmodium falciparum

The emergence of virulent Plasmodium falciparum in Africa within the past 6000 years as a result of a cascade of changes in human behavior and mosquito transmission has recently been hypothesized. Here, we provide genetic evidence for a sudden increase in the African malaria parasite population about 10,000 years ago, followed by migration to other regions on the basis of variation in 100 worldwide mitochondrial DNA sequences. However, both the world and some regional populations appear to be older (50,000 to 100,000 years old), suggesting an earlier wave of migration out of Africa, perhaps during the Pleistocene migration of human beings.     

Identification of Mycoplasma gallisepticum and M. synoviae by flow cytometry

Immunofluorescence and flow cytometric methods were examined to detect and distinguish Mycoplasma gallisepticum and M. synoviae. The procedure employed 24-hr broth cultures of each organism, direct immunofluorescence staining with either homologous or heterologous antiserum, and analyses by flow cytometry. The organisms were distinguishable on the basis of fluorescent profiles when stained with the appropriate antiserum.     

A systems analysis of the guyanese livestock industry

This paper attempts to contribute to the capability for livestock sub-sector analysis. A model structure which offers potential for evaluation of changes of policy, available production technology, or factor and product market conditions is described. The structure integrates a multi-year biological cattle simulator with a price endogenous model of the cattle sub-sector to yield a model designed to simulate aggregate behaviour of profit maximising cattle producers interacting through competitive factor and product markets. The general model structure is specified to reflect conditions in Guyana, South America. The model, specified for Guyanese conditions, is used to evaluate the probable impact of a number of technical and economic changes in the system.