This article originated in the study of one Northern Ghanaian group, the Frafras, as migrants to the urban areas of Southern Ghana. It describes the economic activities of the low-income section of the labour force in Accra, the urban sub-proletariat into which the unskilled and illiterate majority of Frafra migrants are drawn.Price inflation, inadequate wages, and an increasing surplus to the requirements of the urban labour market have led to a high degree of informality in the income-generating activities of the sub-proletariat. Consequently income and expenditure patterns are more complex than is normally allowed for in the economic analysis of poor countries. Government planning and the effective application of economic theory in this sphere has been impeded by the unthinking transfer of western categories to the economic and social structures of African cities. The question to be answered is this: Does the ‘reserve army of urban unemployed and underemployed’ really constitute a passive, exploited majority in cities like Accra, or do their informal economic activities possess some autonomous capacity for generating growth in the incomes of the urban (and rural) poor?

Three variations to the structure of the nicotinamide adenine dinucleotide (NAD)-dependent L-lactate dehydrogenase from Bacillus stearothermophilus were made to try to change the substrate specificity from lactate to malate: Asp197----Asn, Thr246----Gly, and Gln102----Arg). Each modification shifts the specificity from lactate to malate, although only the last (Gln102----Arg) provides an effective and highly specific catalyst for the new substrate. This synthetic enzyme has a ratio of catalytic rate (kcat) to Michaelis constant (Km) for oxaloacetate of 4.2 x 10(6)M-1 s-1, equal to that of native lactate dehydrogenase for its natural substrate, pyruvate, and a maximum velocity (250 s-1), which is double that reported for a natural malate dehydrogenase from B. stearothermophilus.

The immunodominant CD4 T cell epitope region, Th2R, of the circumsporozoite protein of Plasmodium falciparum is highly polymorphic. Such variation might be utilized by the parasite to escape from or interfere with CD4 T cell effector functions. Here, we show that costimulation with naturally occurring altered peptide ligands (APL) can induce a rapid change from IFNgamma production to the immunosuppressive mediator interleukin 10 (IL-10). This mechanism may contribute to the low levels of T cell responses observed to this pathogen in malaria-endemic areas.

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