Ultrastructural investigation on the cell membranes of the vomeronasal organ in the rat: a freeze-etching study.
The free surfaces and cell contacts in the epithelia of the vomeronasal organ of the rat were investigated by freeze-etching. The microvilli of receptor cells show a lower density of intramembranous particles (IMP) than the microvilli in the receptor-free epithelium. The ratio between the IMP on P- and E-face is approximately 11 : 1 in the receptor terminals, and 3.5 : 1 in the cilia and microvilli of the receptor-free epithelium. Although atypical in length and only poorly equipped with rootlet fibers, the cilia of the receptor-free epithelium are furnished with typical ciliary necklace structures of up to 10 rows of membrane particles. Differences in the density of IMP on the P-faces of different cilia are probably due to continual ciliogenesis and also due to the different age of cilia in the receptor-free epithelium. Zonulae occludentes show different configurations in the neuroepithelium and in the receptor-free epithelium. In the former, they show a tendency to cross-link and form facet-like patterns, reflecting a constant morphology and relative stability for this apical region. In the receptor-free epithelium the junctional rows of zonulae occludentes display only loosely interconnected networks and a tendency to orient parallel to each other and to the free surface. In addition to zonulae occludentes, typical square aggregations of IMP are observed in the receptor-free epithelium. They are not exclusively restricted to the zone of intensive cell contacts by means of fine interdigitating cell processes, and their function has yet to be identified experimentally.
D000818:Animals; D002462:Cell Membrane / Q000648:ultrastructure*; D002923:Cilia / Q000648:ultrastructure; D004848:Epithelium / Q000648:ultrastructure; D005613:Freeze Etching; D008297:Male; D008871:Microvilli / Q000648:ultrastructure; D009300:Nasal Septum / Q000294:innervation / Q000648:ultrastructure*; D051381:Rats