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D. S. FALCONER, R. G. EDWARDS, R. E. FOWLER and R. C. ROBERTS

Summary.

The variation in the number of eggs shed by the two ovaries of mice has been examined by statistical analyses of 697 egg counts and 390 corpora lutea counts, made on mice from a variety of outbred strains, both after natural oestrus and after oestrus induced in adults by pregnant mares' serum (pms) and human chorionic gonadotrophin (HCG). The numbers of eggs or corpora lutea were distributed between sides approximately at random, the variation conforming fairly closely to a binomial distribution. This was true even after superovulation. There was, however, a slight but significant excess of variation between sides over the random amount in the egg counts, particularly after natural ovulation. Corpora lutea counts differed from egg counts in showing a slight but significant reduction of the variation below the random amount. Several possible reasons for these small deviations from a random distribution are discussed.

The correlation between the numbers of eggs shed by the two ovaries was negative after natural ovulation but positive after superovulation. This difference can be fully accounted for by the random distribution between sides together with the differences of mean and variance between natural ovulation and superovulation. The variation of total egg number was proportional to the mean egg number after natural ovulation. The variation after superovulation was much higher than after natural ovulation, even when the difference of mean was taken into account, and the greater variation of total egg number caused the correlation between sides to be positive after superovulation.

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Ruth E. Fowler, N. L. Fox, R. G. Edwards and P. C. Steptoe

Summary. Granulosa cells were aspirated 3–4 h before the expected time of ovulation from 10 follicles of 4 patients treated with gonadotrophins: 4 of the follicles were immediately preovulatory. The granulosa cells were cultured for 10 h with 17α-hydroxypregnenolone or dehydroepiandrosterone and samples of medium removed at 3 and 10 h were assayed for 6 steroids.

Granulosa cells were unable to synthesize androgens from endogenous substrate or undertake conversions via the Δ5 pathway, but cells from all follicles were capable of aromatizing exogenous androgens to oestrogens although this capability was reduced in cells from follicles beginning to luteinize. Granulosa cells from preovulatory follicles synthesized more progesterone from endogenous substrate than cells from follicles which had not begun to luteinize. The results provide further support for the two-cell theory of oestrogen biosynthesis whereby granulosa cells aromatize androgens which are synthesized by the thecal cells in vivo.

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R. G. Edwards, R. E. Fowler, R. E. Gore-Langton, R. G. Gosden, E. C. Jones, C. Readhead and P. C. Steptoe

We wish to present an analysis of the data gained by a group of workers studying various aspects of ovarian activity. Our work has been concerned primarily with two aspects of the development of follicles: the initiation and control of follicular growth, and differentiation and steroidogenesis in follicles approaching ovulation. The scope of our contributions spans the lifetime of the female from the early stages of growth in the fetal ovary to the final stages of follicular development in ageing females and includes both animal and clinical studies. The results are given in two main sections: follicular growth, and normal and abnormal differentiation and steroidogenesis in follicles approaching ovulation. Several aspects of follicular growth are considered in the discussion.