[Necroses in the granular cell layer of the cerebellum due to methylchloride intoxication in guinea pigs (author's transl)].

QUESTION

Neurotoxic action of methylchloride was reported by various authors. As this solvent is widely used in chemical industry the morphological changes in the CNS of guinea pigs due to methylchloride intoxication were comparatively studied by light- and electron-microscopy.

MATERIAL AND METHODS

19 guinea pigs of both sexes (body weight 300-600 g) were individually exposed to inhalation of methylchloride mixed to normal breathed air in a 2 Vol.-% amount in a pressurised vessel of 20,000 cm3 volume (details on the experimental arrangement see VOLK 1973) for each 10 min 6 times a week. 3 control animals were fed like the experimental animals and exposed to normal breathing air for the same time in the pressurised vessel. The experimental period varied between 7 and 70 days, the number of inhalations was between 6 and 61. At the end of the experiment the animals were sacrificed by perfusion with 3% buffered glutaraldehyde under Thiogenal anesthesia. For light microscopy paraffin sections were prepared from tissue samples of the cerebrum, cerebellum, brain stem, mesencephalon, spinal medulla and spinal ganglia (stainings: HE; Turnbull's blue; Nissl; Klüver-Barrera; Mallory; Bodian and Kossa). For electron microscopy tissue blocks of the cortex, corpus callosum, striatum, mesencephalon and cerebellum as well as of spinal medulla and spinal ganglia were postfixed in 1% OsO4 and embedded in Araldit in the common way.

RESULTS

Clinical observations--9 animals showed normal behaviour after 32 inhalations in 37 days.--6 animals displayed staggering, atactic moving of the head, retardation in spontaneous reactions and mobility. Ataxia and paresis of the hind legs occurred earliest after 17 inhalations. 4 animals showed all these symptoms only after 25 days. Morphological findings: Macroscopy: Occurrence of necroses in the cerebellar cortex was mainly observed in the lower part of the vermis; pressings of tissue in the occipital foramen, tissue swellings around the aqueduct and consecutive enlargement of the lateral ventricles occurred. Light microscopy: Changes in the Stratum granulosum in the lower part of the vermis as pyknosis of the cell nuclei and hydropic swelling of the cytoplasm (fig. 1a) were seen after 10 days. Focal necroses of the granular layer as well as "Status spongiosus" and edema occurred after 21 days (fig. 1b). In later phases these alterations were also present in other regions of the vermis and of the cerebellum, too. Furthermore, edema of the Lamina dissecans, hydropic swelling of the Bergmann's glia and marked edematous transformation of the molecular layer were observed. In this phase the hitherto intact Purkinje cells responded to the intoxication by homogenization of the cytoplasm and cell necroses. Electron microscopy: Initially an increase in density of the nuclear chromatin of the granular cells was observed associated with formation of homogeneous electron dense chromatin fragments which were finally released to the perikaryon (figs. 2a, 2b)...