Fragments of neural tissue from normal newborn mouse were stained with Hoechst 33342 dye before transplantation into the newborn shiverer mouse brain. Combination of this technique with immunohistochemistry demonstrated that, after transplantation, these cells are able to survive as long as unstained cells and to myelinate in the shiverer mouse host brain. Stained cells express the normal sequence of differentiation in terms of chronology of differentiation marker expression [04, galactocerebroside (GalC), myelin basic protein (MBP)], as normal cell do in situ. It has thus been possible by this technique to show the migration pathways of transplanted cells and to correlate them with the expression of specific markers: long distance migration along white matter axonal pathways occurs when cells are o4-positive, GalC-negative. By contrast, only GalC-positive cells are able to migrate across the grey matter in the absence of radial glia. Finally, it has been possible to propose a migration and differentiation sequence of these cells, suggesting that MBP-positive oligodendrocytes divide after migration in the target zone.

No abstract

The use of intermediate host snails of Schistosoma spp. which are insusceptible to infection has been proposed as a possible method of controlling schistosomiasis. The objective of this approach is to change the susceptibility of natural snail populations from being predominantly susceptible to a non-susceptible state, through the release of refractory snails into natural habitats. In an attempt to determine whether or not such refractory Bulinus africanus populations occur in eastern South Africa, F1 generation snails of populations from 8 different areas were exposed to miracidia hatched from eggs excreted in the urine of schoolchildren infected with Schistosoma haematobium in the Nelspruit district. The proportion of snails successfully infected ranged from 27 to 100%, which revealed considerable genetic heterogeneity amongst populations of the same snail species. One population from Natal could be regarded as partially refractory, while a laboratory population from Durban proved to be 100% susceptible. A completely refractory strain of B. africanus has not yet been identified.

No abstract