Bioelectric phenomena related to protein-fixed charge in a crab nerve fiber

The bioelectrical characteristics of a crab nerve fiber subjected to solutions containing the impermeant anions ferrocyanide, glutamate, or ethanolsulfate substituted for chloride include prolonged slow depolarizations that elicit prolonged trains of impulses sulperimposed on the plateau portion. Propionate and nitrate depress repetitive firing while thiocyancite has only a slighit effect. Nerves treated with ferrocyanide lose potassium and gain sodium, which fact may account for their depolarization. On the other hand, studies with interference microscopy reveal shift by ferrocyanide in the interference fringe pattern of the sheath material; this suggests a reorientation of fixed charges in the protein layers by direct action of the anion on these layers. This may also account for the electrical manifestations observed.     

Pathogenicity of a Hong Kong-origin H5N1 highly pathogenic avian influenza virus for emus, geese, ducks, and pigeons

The H5N1 type A influenza viruses that emerged in Hong Kong in 1997 are a unique lineage of type A influenza viruses with the capacity to transmit directly from chickens to humans and produce significant disease and mortality in both of these hosts. The objective of this study was to ascertain the susceptibility of emus (Dramaius novaehollandiae), domestic geese (Anser anser domesticus), domestic ducks (Anas platyrhynchos), and pigeons (Columba livia) to intranasal (i.n.) inoculation with the A/chicken/Hong Kong/220/97 (H5N1) highly pathogenic avian influenza virus. No mortality occurred within 10 days postinoculation (DPI) in the four species investigated, and clinical disease, evident as neurologic dysfunction, was observed exclusively in emus and geese. Grossly, pancreatic mottling and splenomegaly were identified in these two species. In addition, the geese had cerebral malacia and thymic and bursal atrophy. Histologically, both the emus and geese developed pancreatitis, meningoencephalitis, and mild myocarditis. Influenza viral antigen was demonstrated in areas with histologic lesions up to 10 DPI in the geese. Virus was reisolated from oropharyngeal and cloacal swabs and from the lung, brain, and kidney of the emus and geese. Moderate splenomegaly was observed grossly in the ducks. Viral infection of the ducks was pneumotropic, as evidenced by mild inflammatory lesions in the respiratory tract and virus reisolation from oropharyngeal swabs and from a lung. Pigeons were resistant to HK/220 infection, lacking gross and histologic lesions, viral antigen, and reisolation of virus. These results imply that emus and geese are susceptible to i.n. inoculation with the HK/220 virus, whereas ducks and pigeons are more resistant. These latter two species probably played a minimal epidemiologic role in the perpetuation of the H5N1 Hong Kong-origin influenza viruses.     

Spreading deserts or spatially confined environmental impacts? land degradation and cattle ranching in the kalahari desert of botswana

The Kalahari Desert of Botswana is being increasingly used for livestock production, particularly through the establishment of ranches dependent on borehole water supplies. Reports of the environmental impacts of land use practices in such drylands are conflicting, with livestock systems supplied by boreholes and wells being regarded in some studies as centres for the spread of desertification and in others as having environmental impacts that are overridden by the effects of natural climatic variability. the results of an environmental study focused on a block of borehole ranches established in the eastern Kalahari as part of Botswana's Tribal Grazing Lands Policy dating from the 1970s are reported. the investigations concentrated on ecological, soil chemistry and soil erosion impacts on the study ranches. Although important changes in the ecology and soil nutrient status of the ranches are identified, their contribution to environmental degradation must be viewed in terms of stocking levels, The radial nature of range usage, giving rise to marked spatial variations in impact, and natural climatic variability. Changes are not solely detrimental, but long-term monitoring, especially in relation to climatic fluctuations, needs to be undertaken to fully establish the dynamic interactions of variables.