An Ultrastructural Study of the Membranes of Keratinizing Wool Follicle Cells

Abstract

Measurements of the widths of apposed plasma membranes and of the spaces between them were made at different stages of differentiation of keratinizing and hardening cells of the wool follicle. In contrast to findings in the hair follicle, no changes were detected for apposed cortex, cortex/fibre cuticle and fibre cuticle/fibre cuticle cells until keratinization had taken place. The trilaminar appearance of the plasma membranes was then lost and the intercellular material decreased in width. However, the inner root sheath cells developed a ‘membrane complex’ in enlarged intercellular spaces prior to hardening. Desmosomes are apparently retained in the hardened ‘membrane complexes’. A band of cytoplasmic material was also formed adjacent to the inner lamellae of the plasma membranes immediately before hardening of the cells. The presence of gap and tight junctions in differentiating cell lines of the wool follicle was noted.