Scarring, the end result of the wound healing process in adult mammals, is a problem of significant clinical importance. We observed that athymic nude-nu mice, similar to mammalian fetuses, are able to restore the structure and integrity of injured skin through a process resembling regeneration, where scar formation is absent. Among the postinjured skin tissues collected from athymic nude-nu, wild-type controls (C57BL/6J), severe-combined immunodeficient, Rag (lack of B and T cells), athymic (thymectomized neonates and adult C57BL/6J), and mice treated with an immunosuppressant (cyclosporin A), only athymic nude-nu mice showed: a lack of scar by histological examination (hematoxylin & eosin and Masson's trichrome staining), low levels of collagen (as determined by hydroxyproline content), high levels of hyaluronic acid, a statistically significant increase in elastic modulus for injured samples over unwounded (biomechanical testing) and low levels of the pro-scarring cytokines platelet-derived growth factor-B and transforming growth factor beta1. Additionally, immunohistochemical and Western blot analyses of postinjured tissues as well as flow cytometry analysis of blood samples showed the presence of CD8-positive cells in all studied animals except nude-nu mice. We conclude that scarless skin healing in athymic nude-nu mice provides a new model to study the influence of the immune system on tissue regeneration.

Abstract. The objective of the present study was to investigate the influence of prostaglandin F2α (PGF2α) and nitric oxide (NO) on production of steroids and PGs by culturing bovine luteal cells obtained from ovaries on days 8-12 of the estrous cycle with a nitric oxide (NO) donor (Spermine NONOate), and a NO synthase inhibitor (N G -nitro-L-arginine methyl ester dihydrochloride: L-NAME). When the cells were exposed for 24 h to PGF2α (10 -7 -10 -5 M), production of progesterone (P4) increased significantly at all doses used (P<0.05). Moreover, PGF2α stimulated PGF2α production (P<0.01), depressed testosterone (T) production (P<0.05), but did not affect synthesis of prostaglandin E2 (PGE2). Spermine NONOate decreased P4 production to 66%, 47% and 34% of the control concentration after treatment with 10 -5 M, 10 -4 M and 10 -3 M, respectively, but did not affect T production, and increased PGF2α synthesis (P<0.05) and PGE2 (P<0.01) at all doses used. L-NAME increased production of P4 (P<0.01) but did not affect (P>0.05) secretion of T, PGF2α and PGE2. Estradiol-17β (E2) was detectable on the level of sensitivity of assay and was not significantly altered by any treatments. The overall results suggest that PGF2α and NO produced locally in bovine CL play roles in the regulation of the secretory function of the bovine CL as auto/paracrine factors. Key words: Prostaglandins, Progesterone, Nitric oxide, Corpus luteum, Cow (J. Reprod. Dev. 50: [411][412][413][414][415][416][417] 2004) he function of the bovine corpus luteum (CL) is responds to many intra-and extraluteal factors [1,2]. It has been well documented that injections of prostaglandin F 2 α , (PGF 2 α ) analogues in ruminants decrease progesterone (P 4 ) production, consequently shortening the estrous cycle [2]. However, a number of in vitro studies indicate that PGF 2α does not have a direct, luteolytic influence on the bovine steroidogenic luteal cells [3,4]. It has been suggested that some substances produced locally in the bovine CL by steroidogenic as well as non-steroidogenic cells mediate the luteolytic action of PGF 2α . We found that nitric oxide (NO) is locally produced in the bovine CL during the estrous cycle with higher levels during the late luteal phase [5]. Moreover, the effects of PGF 2α were inhibited by an inhibitor of NO synthase (NOS), suggesting that NO is a potent mediator of the luteolytic action of PGF 2α in vivo [5][6][7].Recent studies have demonstrated that NO also regulates P4 and PG production in the bovine CL

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Abstract.Recently, significant progress has been achieved in improving the yield of good quality embryos in vitro. However, efforts are still required to recognize the factors and understand the mechanisms of oocyte maturation, which are essential for subsequent embryo development. The aims of the present study were to determine the frequency of apoptosis in oocytes recovered from slaughterhouse ovaries and to investigate whether insulin-like growth factor (IGF)-I action during oocyte maturation in vitro may withhold apoptosis and improve oocyte quality. Only oocytes of proper morphology with homogenous ooplasm and compact cumulus cells were selected for this study. All oocytes recovered from the slaughterhouse ovaries were divided into two groups. One group of oocytes, chosen for apoptosis detection, was examined immediately after recovery. The other group of oocytes was maturated in vitro. Oocytes were maturated with IGF-I supplementation (100 ng/ml). Oocytes without supplementation were used as a control. Apoptosis in oocytes was determined by positive results of TUNEL assay and active caspase labeling. The percentage of apoptotic oocytes detected by TUNEL fell to zero when the maturation medium was supplemented with IGF-I in comparison to the control matured oocytes (0 vs. 9.87%; P<0.05). However, active caspase labeling was only slightly decreased in the IGF-I matured oocytes compared with the control matured oocytes (1.13 vs. 2.08%; P<0.05). The results indicate that IGF-I may serve as an antiapoptotic factor during oocyte maturation. We suggest that IGF-I may inhibit apoptosis in oocytes at the stage of caspase activation and may prevent further advancement of oocyte apoptosis.

The effect of progesterone on oxytocin-induced secretion of prostaglandin (PG) F(2alpha) from bovine endometrial tissue explants was examined. Endometrial tissue from the late luteal phase were preincubated for 20 h in control medium. Explants were then treated for 6 h with control medium, oxytocin (10(-7) M), progesterone (10(-5) M), or both hormones. Oxytocin increased the medium concentration of 13,14-dihydro-15-keto-PGF(2alpha), whereas progesterone completely suppressed the stimulatory effect of oxytocin. In experiment 2, isolated endometrial epithelial cells were incubated with progesterone (10(-5) M), oxytocin (10(-7) M), and combinations of these hormones with or without actinomycin D (1 ng/ml). Only oxytocin stimulated secretion of PGF(2alpha), and this response was suppressed by progesterone. Oxytocin induced a rapid increase in intracellular concentrations of Ca(2+) detected within 1 min of exposure of epithelial cells from the same cows. Progesterone pretreatment diminished this response. In experiment 3, direct effects of progesterone (2 nM-20 microM) on binding of (3)H-oxytocin to the membrane preparation from epithelial cells were determined by saturation analysis. Oxytocin binding was suppressed by progesterone at every dosage tested. Progesterone is capable of suppressing the ability of oxytocin to induce endometrial secretion of PGF(2alpha). This effect appears to be mediated through a direct interference in the interaction of oxytocin with its own receptor.

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