Cerebellar foliation in rats. 3. Mid-line distortion of the primary fissure in normal foetal rats.
Indentation of the surface during the formation of cerebellar fissures in the rat is preceded by a local thickening of the external granular layer (EGL) and an indentation of the Purkinje cell layer (Conradi 1985). The local thickening of the EGL is due to an increase in premigratory granule cells. In the present study, two types of mid-line distortion of the primary fissure are described. These distortions were seen in the cerebella of most foetuses examined, whereas other fissures were distorted very rarely. The indentation of the surface was delayed or it lay asymmetrically in relation to the thickening of the EGL and indentation of the Purkinje cell layer. The distortions were accompanied by a local increase in the proliferative zone of the EGL, which in the case of delayed indentation of the surface replaced the deeper portion of the fissure. The findings show that foliation may proceed independently of fissuration and have implications for the understanding of pathological foliation in the brain. Angio-architectonic studies on distorted regions suggest that the increase of vessels in fissuric regions (Conradi et al. 1980) begins prior to the indentation of the surface.
D000818:Animals; D002531:Cerebellum / Q000098:blood supply / Q000166:cytology / Q000196:embryology*; D005260:Female; D005333:Fetus; D051381:Rats; D011919:Rats, Inbred Strains