The morphology and growth pattern of human ovarian follicles has been studied between birth and 9 years of age. Follicles have been classified according to their morphology, diameter, the diameter of the oocyte and the number of granulosa cells in the widest cross-section. Nine major classes offollicle were recognized. The smallest, Class B follicles, contained a non-growing oocyte and were surrounded by a single layer of flattened granulosa cells. The largest, Class F follicles, which were up to 6 mm in diameter, contained an oocyte which had completed growth (80 \g=m\m) and a large fluid-filled antrum. The range of follicles and the pattern of oocyte growth in relation to follicle growth found in the ovary was independent of age during childhood.Follicular growth and atresia are discussed in the light of current concepts of gonadal and pituitary function during infancy and childhood.

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RNA synthesis in the oocyte and granulosa cell nuclei of growing follicles has been studied in the mouse ovary . The RNA precursor [ 3 H]uridine was administered intraperitoneally to adult mice and the amount of label incorporated into ovarian RNA was quantitated autoradiographically using grain-counting procedures . Uridine incorporation into the nucleus is low in oocytes of small, resting follicles but increases during follicle growth and reaches a peak prior to the beginning of antrum formation . Thereafter uptake rapidly declines and is very low in the oocytes of maturing follicles . Uridine incorporation into granulosa cell nuclei, in contrast to that found in the oocyte, increases gradually during most of the period of follicle growth .Qualitative studies of the activity of endogenous, DNA-dependent RNA polymerases have also been made in fixed oocytes isolated from follicles at different stages of growth .Polymerase activity is demonstrable in the nucleolus and nucleoplasm of oocytes from growing follicles, but is absent from maturing oocytes of large follicles .

The growth of the first hair coat in male mice was studied during administration of epidermal growth factor (EGF). Injections of 1 or 4 micrograms EGF/g body weight for 14 consecutive days from birth resulted in the development of curved overhairs (monotrichs), caused a retardation in rate of growth in length of hair and a reduction in hair diameter and length of follicle bulb. Growth rate partially recovered after cessation of EGF treatment. However, some of the effects produced by injections of EGF during the formation of the first coat were detected in the second and third generations of hair. Since EGF also retarded rate of body growth, we compared the effect of EGF on hair growth with that of restricting food intake in neonatal mice during the development of the first coat. Hair growth was slowed in underfed animals but the effects were less marked than those found in EGF-treated mice of similar body weights.

Transcriptionof the oocyte genome has been measured during follicle growth in the mouse.

Twenty-four adult Merino wethers were given mouse epidermal growth factor (mEGF) subcutaneously at doses ranging from 0.02 to 0.12 mg/kg body weight or intravenously in the dose range 0.10 to 0.14 mg/kg body weight for periods ranging from 3 to 48 h. Plasma concentrations of mEGF were measured by radioimmunoassay and effects of treatment on food consumption and wool growth were observed. Plasma concentrations of the protein sustained for 15-24 h at about 20 ng mEGF/ml (or exceeding this) almost invariably caused feed rejection and casting of the fleeces. This last result clearly indicated disruption of proliferative activity among the replicating cells in wool follicles which regulate wool growth. The inhibitory effects on appetite and wool growth of smaller doses of the protein and of plasma concentrations equal to those above which were sustained for shorter periods have also been examined. Approximately 10% of the dose of mEGF appeared in the urine of three sheep 1 to 3 days after the start of s.c. infusions of 5 mg for 7 h.

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