A synopsis is presented of hormonal profiles (peripheral plasma values of LH, FSH, progesterone; urinary oestrogens) during the oestrous cycle of cattle. After ovulation (day one) progesterone levels begin to increase from about day 4, reach a plateau around day 10, and decrease to basal concentrations starting on days 17 to 18. Corresponding with the progesterone decrease, urinary oestrogens show a main increase reaching its maximum one day before ovulation. LH levels are fairly constant from ovulation until day 5, small but significant peaks can be observed between days 6 and 10 in some cows (6 out of 21) and levels then decrease from day 11 to 13. A gradual additional increase begins on day 17, resulting in the preovulatory LH peak 25.7 ± 6.9 h (n = 75) before ovulation. This peak has a duration of 7.4 ± 2.6 h (n = 89) and occurs any time of the day but preferentially around 8 a. m. and 8 p. m. respectively. Likewise related are the two main periods for ovulation. During oestrus, (average duration of 16.9 ± 4.9 h (n = 28) the electrical resistance of the vaginal mucus decreases and the lowest values always correspond with the LHpeak. FSH levels show a wavelike pattern with peaks around days 4, 8, 12–13, 17, 18 and also coinciding with the pre-ovulatory LH peak. The sharp decrease in FSH between the two peaks on days 17 and 18 correlates with the decrease of progesterone during luteolysis. Obviously there is a parallelism between FSH elevations and follicular growth (determined by means of pelviscopic observations).
The growth of the pituitary and of the reproductive tract of Suffolk rams from birth to 168 days of age has been studied. Pituitary icsh and fsh concentrations were determined by bio-assay. The pattern of testicular androgen production has been examined using chemical and histological techniques and the relationship to spermatogenesis studied. Pituitary gonadotrophin content increased sharply from 42 days of age but was only weakly correlated with other parameters measured.The androstenedione : testosterone ratio was at its narrowest at birth; however, testosterone was the predominant androgen from birth onwards. Androgen concentration fluctuated but the total content increased with increase in testicular weight. Fructose was present in the seminal vesicles from birth and citric acid from 14 days; citric acid concentration was about one-tenth that of fructose. There was a significant correlation between testicular androgen content and the fructose and citric acid concentration and content of the seminal vesicles.Seminiferous tubule diameter was significantly correlated with most of the parameters measured. Testicular weight increased sharply from 42 days of age. Androgen production was present at birth and preceded spermatogenesis which began when testis weight exceeded 10 g, which was after 56 days of age. Spermatozoa were present in the seminiferous tubules at 112 days of age. J. D. Skinner et al. development of the seminal vesicles, prostate and bulbo-urethral gland, which in the late-term foetus resemble those in the castrated adult.The object of the present study was to examine the sexual development of the Suffolk ram from birth to 168 days of age.
MATERIALS AND METHODSMaterial was provided by fifty-four Suffolk lambs allocated at random into six groups for slaughter at intervals of 14 days, from birth to 168 days. To obtain sufficient material for assay the numbers in the groups were as follows: ten at birth, eight at 14 days, six at 28 days, four from 42 to 70 days, two from 84 to 154 days, and six at 168 days. Histological observations on the testes of a 103-day-old ram foetus and a 105-day-old ram have also been included.The lambs were weighed before slaughter, after which the head was im¬ mediately removed, the pituitary gland removed, weighed, sealed in tin foil and frozen over solid C02 within 3 min of slaughter.The testes were then removed, weighed and slices taken for histology, the testes were then stored over solid C02. The amount of testosterone and androstenedione in the testes was estimated later. The remainder of the tract was dissected out, the accessory glands weighed individually, slices taken for histology and the seminal vesicles then stored over solid C02. The amount Sexual development in the ram 465 were evaporated to dryness and preliminarily chromatographed using thin-layer chromatography, medium Silica-gel GF 254 and solvent system CHCl3:EtoAc (2:1). This step finally removed contaminating substances which would otherwise have interfered with the resolution of the paper chromatograp...
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