High resolution (SE-I) scanning electron microscopy features of primate cerebellar cortex.

This paper provides an exploration into the outer and inner surfaces of primate cerebellar neurons using secondary electron-I (SE-I) topographic contrast. SE-I enriched, chromium coated, cryofractured cerebellum staged within the condenser/objective lens stage of SEMs, equipped with high brightness LaB6 and field emission emitter, generated quality images of intact and fractured nerve cells studied at intermediate and high magnifications. Granule and Golgi cell surfaces revealed smooth, accurately delineated profiles of the true cell surface features, which lacked the SE-III dominated brilliance of conventional gold or gold-palladium decorated images. Fractured non synaptic segments of parallel fibers in the molecular layer showed interconnected anastomotic networks of ER tubules, vesicles and cisterns, whereas cross fractured presynaptic "en passant" endings of these fibers exhibited spheroidal synaptic vesicles and SE-I edge brightness contrast delineated their limiting plasma membranes. Parallel fiber fractured synaptic endings showed a homogeneous extravesicular material surrounding the synaptic vesicles. The neuroglial cytoplasm ensheathing nerve processes exhibited a smooth discontinuous surface. The high mass density surface of the myelin sheath showed a mixed population of globular structures, 10-30 nm, corresponding to protein and phospholipid microdomains.