Fine structural localisation of acid phosphatase in neural tumours induced by N-ethyl-N-nitrosourea in rats

Neuronal changes in experimental gliomas

Gliomas were induced transplancentally by the administration of ethylnitrosourea to pregnant rats on the 15th day of gestation. The fine structure of neurones involved in these tumours was studied in order to assess the changes caused by neoplasia. The severity of the neuronal damage depended on their location, Those within the tumours being more affected than those in the neighbouring brain. The histological type and grade of malignancy also influenced the changes: periventricular pleomorphic gliomas and ependymomas of high-grade malignancy caused the most severe alterations. Neurones displayed a spectrum of appearances from apparent normality to complete necrosis. Both nucleus and cytoplasm were affected: of the cytoplasmic organelles the rough-surfaced endoplasmic reticulum and mitochondria showed the most striking changes. There were many lipofuscin granules and autophagic vacuoles. Axons underwent advanced degeneration: swollen mitochondria, disrupted vesicles and vacuoles, disintegrated microtubules, irregular filaments and unidentified debris were sometimes seen. Disintegration of myelin sheaths frequently occurred with consequent engulfing of their debris by macrophages and reacting astrocytes. The neuronal satellites--mainly oligodendrocytes--were often replaced by neoplastic glial cells. Hydrolytic 'marker' enzymes were demonstrated in neurones at various stages of degeneration. In all cases neurones displayed low acid phosphatase activity, while thiamine pyrophosphatase activity decreased with increasing neuronal degeneration.

The histochemical behaviour of zinc-activated tartrate-resistant phosphatase (ZnTP) in early stages of experimental tumors in the rat trigeminal nerve

The activity of the ZnTP (Felicetti und Rath 1975; Rath and Felicetti 1975) was investigated histo- and biochemically in neurinomas of trigeminal nerves of rats. The tumors were induced by a single transplacental pulse of 30 mg ENU/kg on the 17th day of gestation. The rats were killed at the age of 40 to 160 days. The activity of the ZnTP is demonstrated histochemically by a coupling azo dye technique with 1-naphthylphosphate after Rath and Felicetti (1975) as well as a lead nitrate method with 4-nitrophenyl phosphate at the age of 40 to 140 days. Biochemical investigations of the trigeminal nerves are performed at the age of 140 and 160 days only. The separation of ZnTP is carried out by isoelectrofocusing in polyacrylamide gels after Felicetti and Rath (1975). Together 14 neurinomas are found in the trigeminal nerves of 53 rats. All neurinomas show a high activity of the ZnTP. The ZnTP activity is absent in normal Schwann cells. Three trigeminal nerves of rats subjects to the transplacental pulse of ENU harbour small foci of ZnTP activity without detectable neoplastic cell proliferation. Similar spots of enhanced ZnTP activity have never been found in control rats. This rises suspicion that the neoplastic proliferation of cells is preceded by the activation of ZnTP.

Acid hydrolase and cytochrome oxidase activities in nitrosourea induced tumors of the nervous system

Nitrosourea induced tumors of the nervous system in rats have proven useful for biochemical studies combined with morphological approaches. The pattern of enzyme activities for acid hydrolases and cytochrome oxidase resemble those previously observed in spontaneous nervous system tumors of man. The activities of 4 acid hydrolases were generally high in the gliomas. This could not be attributed solely to zones of regression or necrosis but was a general characteristic of the neoplasms. The activities were predominantly particulate and most likely lysosomal in localization. In schwannomas a similar increase in hydrolases was found in comparison with normal neural tissues but aryl-sulfatase was not increased. Cytochrome oxidase activities were markedly reduced in all tumors studied. The proportionate reduction with respect to normal brain was comparable to that noted in man. No differences were found with respect to fairly well differentiated gliomas.

Macrophages in brain tumours induced transplacentally by N-ethyl-N-nitrosourea in rats: an electron-microscope study

The fine structure of macrophages has been studied in experimental brain tumours induced transplacentally in BD-IX rats by a single intravenous injection of 30 mg of N-ethyl-N-nitrosourea per kg of body weight on the 15th day of gestation. The tumours, depending on their localisation and size, caused various lesions in the brain, namely axonal degeneration, loss of myelin, oedema, haemorrhage and cell necrosis. The tumours and the resulting alterations elicited a strong reaction by macrophages: activation of microglial cells in situ and infiltration of the brain by leucocytes, chiefly by monocytes. Since both microglial cells and monocytes underwent morphological changes, it was difficult, or impossible, to establish the origin of these reacting cells. In a few cases, however, microglial cells and monocytes could be distinguished; this indicated that microglial cells were still being activated and leucocytes were still entering the brain. Various stages of activity of macrophages have been described: the number of lysosomes and cytoplasmic inclusions were thought to indicate activation, phagocytosis and repletion. Activation is characterised by an increase of lysosomes and frequent cell divisions. Phagocytic activity is accompanied by the appearance of inclusions which varied in different lesions: protein-like material in oedema, remnants of erythrocytes in haemorrhages and myelin-lamellae with lipid droplets in demyelination. These various inclusions were frequently present in the same cell, since the different lesions not uncommonly occurred at the same time. In the stage of repletion macrophages contained mainly lipid droplets and unidentifiable debris in their abundant cytoplasm and thus corresponded to the compound granular corpuscles.