The freeze-fracture appearance of fenestrations of sinusoidal endothelial cells has been reassessed in perfusion-fixed rat liver. Fenestrations, limited to the attenuated portions of the endothelial cell cytoplasm are usually round or oval in shape, with diameters ranging from 40-600 nm. Within a given fenestrated region, they are disposed in clusters forming sieve plates. In addition, the presence of wide, irregularly shape openings suggest that adjacent fenestrations may coalesce and result in the larger openings. Our data thus confirm the existence of both small and large fenestrae in the endothelial wall, in contradistinction to previous studies showing only regular, medium sized (100 nm) openings.

No abstract

The supcrior cervical sympathetic ganglion of thc rat kept in vitro in a bicarbonate-buffered Krebs' solution retains its capacity for synaptic transmission and axonal conduction during morc than 36 hr. Aftcr glucose withdrawal, synaptic transmission is lost in 21~ hr and this loss is irrcvcrsible; on thc othcr hand, axonal conduction can still be measured on the postganglionic nervc for more than 24 hr aftcr glucose deprivation. Electrophysiological measuremcnts as well as electron microscopc studics rcvealcd specific changes at the Icvel of thc presynaptic tcrminal proccsses, while thc ganglion cells and the satcllite cells remained relatively unaltcrcd. The prcsynaptic lesion due to lack of glucosc can bc prevented by keeping the preparation in vitro at 6°C. This strongly suggcsts that this lesion results from a major disturbance of the metabolism of thc presynaptic fibcrs.

No abstract

No abstract