Annular structures in erythrocyte membranes of various animal species as revealed by electron microscopy.

Electron microscopic examination of negatively stained erythrocyte membranes revealed the presence of annular structures having an overall diameter of 33 nm and a ring-thickness of 9 nm. Each annular structure appeared to be composed of eleven globular subunits. The structures were most conspicuous in human erythrocyte membranes which showed, on the average, 160 per membrane. Appreciably smaller numbers of what appeared to be the same structures were seen in erythrocyte membranes derived from rhesus monkey, cat, guinea pig, rabbit, horse, dog and chicken. None at all could be found in erythrocyte membranes from sheep, deer, goat and ox. The size and shape of these structures readily distinguishes them from ring-like entities whose formation is induced by treatment of membranes with a variety of haemolytic agents.