Nuclear size and density were determined in brain regions with different glial--neurone composition in rats up to 35 weeks after porto-caval anastomosis. In the white matter, i.e. corpus callosum, both the total cell count and the percentage of astrocytes and oligodendrocytes were unchanged. In the corpus striatum, where the glial/neurone ratio is about 1, the number of nuclei registered as astrocytes increased, and after 35 weeks astrocytes comprised 29% of glial cells (compared with 15% in controls). However, the number of oligodendrogial nuclei decreased simultaneously, leaving the total glial number unchanged. In the animals with longest experimental period there was a 15% loss of neurones. In a region with higher glial/neurone ratio, i.e. the Purkinje cell layer, the neurones showed a similar reduction, whereas the number of Bergmann astrocyte nuclei increased less than striatal astrocytes. A small group of animals with pronounced signs of encephalopathy had a higher loss of neurones and, furthermore, the glial number in corpus striatum and callosum was reduced, due to loss of oligodendrocytes. Despite the use of perfusion fixation, the size of astrocyte nuclei increased, this was reversible, as only slight changes were seen after 35 weeks. A possible explanation of the increase in astrocyte nuclear count and decrease in oligodendroglial count could be that nuclei normally considered to be oligodendroglial are transformed into nuclei with morphological characteristics of astrocytes.
281 histologically verified brain tumours in children were revised and reclassified according to degree of histological malignancy. Survival graphs based on 100 per cent follow-up after 15-40 years show that, of those who survived for more than 1 month after diagnosis and possible operation, 40 per cent were still alive more than 15 years later. There was a clear correlation between survival and degree of malignancy. Sixty-five per cent of those with tumours of malignancy grade I and only 3 per cent of those with malignancy grade IV were alive after 15 years.
Following injections of iodophendylate (Pantopaque) in adult rats, the contrast medium was shown to be refrained in the dilated cerebral ventricles for at least 180 days. Histological examination revealed macrophages containing phagocytosed lipid on the ependymal lining of the ventricles, but there was no leukocytic reaction to retained or encysted contrast material. The macrophages were considered to be involved in the removal of iodophendylate. The irritative reaction in the normal central nervous system was limited, as opposed to the severe reactions previously reported in animals with inflammation of the brain and meninges.
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