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Two techniques for the preparation of boar spermatozoa for in vitro fertilization were studied: a simple washing procedure and centrifugation on a discontinuous Percoll gradient. Their respective effects on motility of spermatozoa were analysed by computer-assisted sperm analysis. The Percoll density gradient technique selected spermatozoa with significantly (P < 0.0001) enhanced motility and movement characteristics. In vitro matured oocytes inseminated with spermatozoa prepared by Percoll gradient centrifugation had significantly (P < 0.0001) greater cleavage rates than did oocytes inseminated with washed spermatozoa. This increased penetration ability was not due to an increased proportion of acrosome-reacted spermatozoa. Transmission electron microscopy revealed no unique ultrastructural differences between the spermatozoa from either preparation. Spermatozoa prepared by Percoll gradient centrifugation are recommended for insemination and studies of porcine in vitro fertilization.
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Summary. Ovaries were collected from naturally cycling gilts during the preovulatory period and the stage relative to the LH surge estimated by measurement of oestradiol and progesterone concentrations in follicular fluid. Many of the follicles recovered had become flaccid with an associated increase in follicular fluid viscosity. Marked infolding of both the granulosa and theca tissue in some follicles suggested early luteinization. However, these morphological changes did not necessarily occur simultaneously in the same follicle, or in all follicles within an ovary. Moreover, they were not consistently related to characteristic differences in the concentration of follicular fluid steroids, suggesting either that the morphological and biochemical aspects of the luteinization of follicles may be independently controlled, or may respond at different rates to the same signal.
Keywords: pig; follicle; histology; heterogeneity
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Summary. Ovaries were recovered from groups of naturally cyclic pigs (N = 5) on each of Days 16, 18, 20 and 21 of the oestrous cycle. Follicular diameter, follicular fluid volume and concentrations of oestradiol, testosterone and progesterone, and granulosa cell number were determined in all follicles ⩾2 mm in diameter (n = 511). In alternate follicles either granulosa cell aromatase activity and theca testosterone content or 125I-labelled hCG binding to granulosa and theca were determined. The mean total number of follicles recovered per animal decreased as the follicular phase progressed and a strong positive relationship (P < 0·001) existed between follicular diameter and volume on all days. The number of granulosa cells recovered per follicle was variable, and not related to oestrogenic activity of the follicles. Mean follicular fluid oestradiol, testosterone and 125I-labelled hCG binding all increased until Day 20 and decreased on Day 21, whereas mean theca testosterone content, 125I-labelled hCG binding to theca tissue and aromatase were all maximal on Day 21. On Days 20 and 21 a subset of 14–16 large follicles was readily distinguishable from the remaining smaller, less oestrogenically active population in each animal. Yet, consistently within these subsets there was a difference in follicular diameter of ∼ 2·0 mm and also a considerable range of biochemical development even among follicles of equal size. These results indicate asynchrony at the time of recruitment and selection among follicles destined to ovulate and suggest that heterogeneity continues into the immediate preovulatory period.
Keywords: follicle; development; pig; heterogeneity