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 .

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

The injection of gonadotrophin (PMSG) into mice between the ages of 3 and 6 days did not alter the number of follicles that started growth, suggesting that it did not provide the stimulus to small follicles to start their development. The injection of PMSG had no influence on small oocyte atresia.