Parasite immunity and the major histocompatibility complex

Parasite infestations offer fertile ground for investigation of the relationship between immunity, disease and the major histocompatibility complex (MHC). However, due to the complexities of parasite life cycles and the success of parasites in evading the immune response, immune reactions against the parasite often do not parallel protective immunity, and immunity does not imply lack of disease. — An additional level of complexity is introduced in some forms of parasite immunity by accessory effector cells, e. g., macrophages and eosinophils, that need to be activated for maximal effectiveness, and the activated form of these cells may partly compensate for a deficiency in specific immune responses. — It is not surprising, therefore, that polygenic effects operate in parasite immunity and reports linking non-MHC genes with parasite immunity far out number those linking MHC genes with it. From the reports that do link MHC genes with parasite immunity, two areas emerge that are interesting. First, the increased incidence of certainHLA genes in people with schistosomiasis who develop hepatosplenic disease may pinpoint individuals at risk of morbidity and direct early treatment to them. Second, mechanisms that intimately involve MHC products but are not linked to a particular MHC haplotype, may indicate newer areas in the investigation of parasite immunity.     

The effects of different horticultural practices on the chemical flavour composition of some cabbage cultivars

Variations in the chemical flavour composition of three cultivars of cabbage were determined for plants of different horticultural histories. In some i     

Dimethyl sulphoxide reduction by micro-organisms.

Dimethyl sulphoxide (DMSO) was reduced to dimethyl sulphide by a wide variety of micro-organism, including prokaryotes and eukaryotes, aerobes and anaerobes. Dimethyl sulphone was not reduced by any of the organisms tested. Cell-free extracts of Escherichia coli reduced DMSO using reduced pyridine nucleotides as electron donors. Activity was greater in anaerobically grown cells than in those grown aerobically. Two other sulphoxides, methionine sulphoxide and tetramethylene sulphoxide, substantially inhibited DMSO reduction by extracts. Mutants of E. coli, which were unable to reduce biotin sulphoxide to biotin, were tested for their ability to reduce DMSO in whole cells and extracts. These mutants were in four different gene loci, bisA to bisD. DMSO reductase activity of the mutants was generally less than that of the wild-type strain, and activity depended upon the gene locus involved, the growth medium and the growth conditions. Only the bisA mutant had very low activity under all conditions. All of the bis mutants were able to grow using methionine sulphoxide as a sulphur source, indicating that biotin sulphoxide and methionine sulphoxide are reduced by different enzyme systems. DMSO may be reduced by both of these enzyme systems.     

On the massive legs of a Moa (Pachyornis elephantopus, Dinornithes)

Pachyornis , which is extinct, was a huge bird with massively thick leg bones. These have been measured, to assess their strength. A mathematical model is used to calculate the forces that must have acted on them, when Pachyornis ran. Hence it is shown that the stresses likely to have acted on them are similar in magnitude to the stresses experienced (in stenuous activities) by bones of modem birds and mammals. The femur and tarsometatanus, however, seem disproportionately strong in comparison with the tibiotanus.