CONTACT-SPACING AMONG ASTROCYTES IS INDEPENDENT OF NEIGHBORING STRUCTURES - INVIVO AND INVITRO EVIDENCE

We have examined the morphology of astrocytes and the arrays they form in two situations, in retinas from which ganglion cells and blood ves sels have been caused to degenerate, and in vitro. These observations were made to test whether the regularity of the spacing of astrocytes within normal central nervous tissue results from interaction among as trocytes, or from interaction between astrocytes and other elements of that tissue. Both in the partially degenerated cat retina, and in cul tures of astrocytes from neonatal rat cortex, astrocytes make and main tain contact with neighbouring astrocytes, yet space their somas apart , giving regularity to the arrays. These results support the hypothesi s that the regularity observed in arrays of astrocytes in intact tissu e results from an interaction among astrocytes, independent of neighbo uring structures, and lead us to suggest that the cell-cell interactio ns involved in contact spacing serve to distribute astrocytes through the central nervous system, and may, in other tissues, underlie the fo rmation of epithelia.