Electron Microscopic Studies of Capillary Permeability in Normal and Ames Waltzer Deaf Mice

Abstract

At no stage after birth do Ames waltzer mice show evidence of auditory function. Fluid spaces of the organ of Corti fail to develop normally. Later, hair cells and spiral ganglion cells degenerate and disappear. These deaf mice exhibit no other morphological defects. The saccule is normal. Circulation and innervation are anatomically normal during maturation. The tracer substance, horseradish peroxidase, escapes from capillaries by passing between endothelial cells in the peripheral circulation. Tight junctions of brain capillaries prevent penetration of this substance. In the stria vascularis, horseradish peroxidase passes out of capillaries into the fluid spaces of the epithelium, but it is stopped at marginal cell tight junctions. This is added evidence that the effective barrier between high-potassium endolymph and high-sodium extracellular fluid is the marginal cell tight junction. Histamine increases peripheral capillary permeability to horseradish peroxidase in moderate dosage. It does not facilitate brain capillary or stria vascularis penetration by this tracer. Ames waltzer mice showed no significant permeability abnormalities.