Gap junctions in ciliary epithelium under conditions of oxygenation (upper) and anoxia (lower), in tissue prepared by ultrarapid freezing using liquid helium. Under oxygenated conditions, the connexo...

Freeze fracture images of synaptic junctions in the retina of Macaca mulatta. The electron micrograph in the top panel shows two invaginating synapses between cone and horizontal cells in the outer p...