The estrogen-injected female mouse: new insight into the etiology of PCOS

<p>Abstract</p> <p>Background</p> <p>Female mice and rats injected with estrogen perinatally become anovulatory and develop follicular cysts. The current consensus is that this adverse response to estrogen involves the hypothalamus and occurs because of an estrogen-induced alteration in the GnRH delivery system. Whether or not this is true has yet to be firmly established. The present study examined an alternate possibility in which anovulation and cyst development occurs through an estrogen-induced disruption in the immune system, achieved through the intermediation of the thymus gland.</p> <p>Methods, Results and Conclusion</p> <p>A putative role for the thymus in estrogen-induced anovulation and follicular cyst formation (a model of PCOS) was examined in female mice by removing the gland prior to estrogen injection. Whereas all intact, female mice injected with 20 ug estrogen at 5–7 days of age had ovaries with follicular cysts, no cysts were observed in animals in which thymectomy at 3 days of age preceded estrogen injection. In fact, after restoring immune function by thymocyte replacement, the majority of thymectomized, estrogen-injected mice had ovaries with corpora lutea. Thus, when estrogen is unable to act on the thymus, ovulation occurs and follicular cysts do not develop. This implicates the thymus in the cysts' genesis and discounts the role of the hypothalamus. Subsequent research established that the disease is transferable by lymphocyte infusion. Transfer took place between 100-day-old estrogen-injected and 15-day-old naïve mice only when recipients were thymectomized at 3 days of age. Thus, a prerequisite for cyst formation is the absence of regulatory T cells. Their absence in donor mice was judged to be the result of an estrogen-induced increase in the thymus' vascular permeability, causing de facto circumvention of the final stages of regulatory T cell development. The human thymus has a similar vulnerability to steroid action during the fetal stage. We propose that in utero exposure to excessive levels of steroids such as estrogen has a long-term effect on the ability of the thymus to produce regulatory T cells. In female offspring this can lead to PCOS.</p

Comparison of post-cervical and cervical porcine artificial insemination in nulliparous and multiparous

The post-cervical artificial insemination (PCAI) in sows increases semen performance compared to cervical artificial insemination (CAI). In Argentina the use of the PCAI is restricted to multiparous while it is not applied to nulliparous. The aim of this study was to compare porcine CAI and PCAI in nulliparous and multiparous. Pregnancy rates and number of live pups with CAI and PCAI in nulliparous and multiparous, assessing advantages and disadvantages of each method were compared. This is a small-scale work (4 CAI and 7 PCAI in nulliparous, 3 CAI and 3 PCAI in multiparous) in a small field productive site in the Province of Buenos Aires. Here the boar was omitted for heat detection and to stimulate the sow during AI. Pregnancy rates and the number of pups born alive per pregnant sow were similar with the two techniques and two categories. The PCAI is a good practice in nulliparous and multiparous because this technique increases semen performance compared to CAI and it is omitted the presence of the boar