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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.

As a preliminary to establishing a frozen valve bank for replacement surgery, the possible effects of the proposed freezing and thawing procedure on tissue structure were assessed in 16 human pulmonary valves removed from cadavers at necropsy and nine dog valves obtained fresh. The valves were frozen and stored in liquid nitrogen for intervals ranging from 23 to 380 days. Blocks of tissue cut from the central area of one leaflet, and including some adjacent arterial wall and ventricular myocardium, were obtained both before freezing and after thawing and examined by a large specimen resin embedding technique for light and electron microscopy, with histochemical staining for matrix material. Control and thawed tissue from all valves appeared similar, indicating good preservation irrespective of storage time. Fine structural alterations in the cellular elements correlated with the total interval of autolysis (from death to freezing) rather than the cause of death or other variables and were not uniform in any of the specimens. A further nine valves, both pulmonary and aortic, were obtained fresh from dogs used for short term experimental cardiac surgery and were frozen within two to three hours of collection.The freezing technique was based on that used routinely in the department of cardiac surgery of the Prince Charles Hospital, Chermside, Queensland, Australia. Each valve was sealed into an individual plastic bag containing 20 ml of 10% dimethyl sulphoxide in TC 199 medium, and the bag was insulated in such a manner as to produce a cooling rate of about 1.5°C a minute after it had been placed in a liquid nitrogen freezer. Valves were stored in a vapour phase of liquid nitrogen (boiling point -196°C) and thawed rapidly by immersion of the bag in water at 40°C for two minutes, with subsequent rinsing in Hanks' s solution.In this study both human and dog valves were stored for periods ranging from 23 to 380 days before being thawed.Both before freezing and after thawing a block 778 on 7 May 2018 by guest. Protected by copyright.

The presence and distribution of coated vesicles in the cells of the lower third of the Romney wool follicle are described, with special reference to cortical cells. Coated vesicles were typically found free in the cytoplasm and associated with plasma membranes and Golgi complexes. They were most prevalent in the bulb and in the elongation and lower keratogenous zones of the cortex. However, the numbers of coated vesicles decreased markedly in the remainder of the keratogenous zone, especially of those associated with plasma membranes. A similar decrease in the numbers and sizes of Golgi complexes in this zone was also noted. The possible role of coated vesicles in the lower wool follicle is discussed.