Application of cryofracture and SEM to the study of human cerebellar cortex.

The SEM and cryofracture methods were used to study neuronal architecture and some synaptic connections of human cerebellum. Samples were processed according to the technique of Humphreys et al. (1975) with minor modifications. The granule cells, arranged in groups or randomly distributed, appeared as spheroidal, rough surfaced microneurons with unbranched filiform axons and coniform dendritic processes. The mossy fibers were observed as thick axons showing the rosette expansions covered by numerous granule cell dendritic processes at the glomerular regions. The mossy glomeruli were seen as round or ovoid clews or balls of yarn separating the granule cell groups. The uncovered mossy rosettes, devoid of the postsynaptic granule cell dendritic digits, unattached by the cryofracture technique appear as solid club-like structures. the climbing fibers were characterized by their thick collaterals. Some fractographs exhibited isolated Golgi cells showing the entire ascending and horizontal dendrites and their beaded shape axonal plexus. At the Purkinje layer, the surface fracture was produced at the level of Bergmann glial cells, which are selectively removed, thus allowing us to visualize the rough surface of purkinje cell soma and the supra and infraganglionic plexuses of basket cell axons. At the molecular layer the stellate neurons were characterized with their horizontal short axons and the Bergmann fiber ends were seen attached to the surface of the folia forming the external glial limiting membrane.