Isthmic and ampullary oviductal epithelia sampled from Merino ewes at days -1, 1, 3, and 10 of the estrous cycle (estrus = day 0) were studied by scanning and transmission electron microscopy after fixation by vascular perfusion. Secretory cells, ciliated cells, and lymphocytelike basal cells were observed in both isthmic and ampullary epithelium at all stages of the estrous cycle studied and their ultrastructural features were analyzed. Synthesis of lamellated secretory granules occurred in the ampullary secretory cells during the follicular and early luteal phases, and their contents were released by exocytosis into the oviductal lumen during the luteal phase. Granule release was associated with nucleated apical protrusion of these cells into the oviductal lumen. No such secretory activity was displayed by isthmic secretory cells even though a few cells contained nonlamellated granules. Apocrine release of apical vesicles and accompanying cytoplasmic material from apical protrusions of ciliated cells occurred in the isthmus around estrus but not in the ampulla. This unexpected feature has not previously been reported in any other mammal. Dendritic basal cells were distinguished in the lower part of the epithelium by their heterochromatic nuclei, electron-lucent cytoplasm, and lack of attachment zones. No migration of basal cells was observed, and their ultrastructural features were similar in the ampulla and isthmus and at all stages of the estrous cycle examined. The function of these lymphocytelike cells in the epithelium is uncertain, but the presence of phagocytic bodies and lysosomes in 20% of them may indicate a phagocytic role.

The hairs and follicles from mice carrying the naked (N) gene have been examined using both scanning and transmission electron microscopy in addition to light microscopy. Fibre cuticle cells and occasionally cortical cells were absent from the follicles of N/ + mice when the base of the hair was growing. In N/N follicles there was a frequent lack of both cuticle and cortical cells throughout the growth phase of the follicles. Abnormalities were also observed in the manner in which the synthesized keratin was deposited in the fibres. The possible mode of action of the N gene is discussed in the light of these results.

Intramuscular injection of 50 mg dexamethasone trimethylacetate produced variable effects on the fleeces of Merino sheep, ranging from an obvious discontinuity in the fleece, due to inhibition of growth of the majority of fibres, to no macros copically observable effect. In the most affected animals, the mitotic activity and size of the follicle bulbs decreased during thefirst five days. Subsequently, fibre and inner roots heath cells with drew from around the dermal papillae and were replaced by cells from the outer roots heaths. Autophagic vacuoles developed in these replacement cells. Regression of follicles proceeded until brush-ends formed on the fibres after 9–15 days. The amount of glycogen decreased in the outer roots heath cells, which exhibited various responses at different levels in the follicles. The proportion of regressed follicles and to some extent the rate of regression were highest in the sheep with the most obvious discontinuity in the fleece. Regeneration of follicles was well advancedin all sheep 29 days after the injection.