Morphological and structural study of Landolt's club in the chick retina.

Light and electron microscopy were used to study Landolt's club of the bipolar cells in the newborn chick retina as well as in early embryonic stages. In the embryo, the bipolar cells were connected to the outer limiting membrane by Landolt's club. Some of the bipolar cells disconnect from this membrane, by complete retraction of Landolt's club, giving rise to bipolar cells without this process. The newly hatched chick, was used for analysis of the ultrastructure of Landolt's club. Zones of apposition between Muller cells and Landolt's club are associated with cytoplasmic vesicles in both cells. Muller cells appear to transmit vesicular material, possibly nutrients, to bipolar cells through Landolt's club. Thus, Landolt's club provides substrates to bipolar cells in the poorly vascularized region of the chick retina.