We investigated changes in peripheral concentrations of inhibin A, total inhibin, steroids, and gonadotropins throughout the intact estrous cycle of the sow in relation to ovarian changes determined by daily transrectal ultrasonography. All visible follicles of 3 mm or more in diameter were classified as small (R3 and !6 mm) or large (R6 mm). Follicular recruitment was identified in two periods of the cycle: one from the late luteal to the follicular phase, characterized by an increase in the number of small follicles followed by the appearance of large follicles; and another during the early luteal phase, consisting only of increased numbers of small follicles. Plasma concentrations of inhibin A increased (P!0.05), coinciding with the two periods of follicle emergence. Estradiol (E 2 ) levels increased (P!0.05) during the follicular phase, but not during the early luteal phase. An inverse relationship (P!0.01) between the patterns of inhibin and FSH concentrations was noted around the two periods of follicle emergence, but there was no relationship (PR0.1) between the patterns of plasma E 2 and FSH during the early luteal phase. In conclusion, measurement of plasma inhibin A levels combined with ultrasonographic examination of the ovaries revealed two periods of synchronous follicular growth during the sow's estrous cycle. The results strongly suggest that inhibin A functions as a negative feedback regulator of FSH secretion throughout the estrous cycle, whereas E 2 appears to influence FSH secretion only during the follicular phase.Reproduction (2010) 139 153-161

Abstract. The aims of this study were to determine whether a single treatment of estradiol dipropionate (EDP) could induce pseudopregnancy in gilts and to determine the effectiveness of PGF2α treatment on estrus synchronization in EDP-induced pseudopregnant gilts. In experiment 1, gilts were treated with 20 mg of EDP (n=11) or vehicle (n=5) on Day 12 (Day 0=onset of estrus). Establishment of pseudopregnancy was defined as a lack of estrus and maintenance of the plasma progesterone concentration above 1 ng/ml between Days 12 and 36. Nine of 11 gilts (82%) treated with EDP became pseudopregnant. The plasma estradiol-17β level was significantly higher in the EDP-treated gilts than in the control gilts until Day 29. In experiment 2, PGF2α was administered twice with a 24-h interval from Day 36 in pseudopregnant gilts (n=6) or Day 10 in cyclic gilts (control; n=5). Estrus after PGF2α treatment was observed in 83% of the pseudopregnant gilts. The interval from the day of the first PGF2α treatment to the onset of estrus and the peak of the LH surge was significantly shorter in the pseudopregnant gilts than in the control gilts. In experiment 3, six pseudopregnant gilts were bred by artificial insemination at the estrus after PGF2α treatment. The farrowing rate and average litter size did not differ between the PGF2α-treated pseudopregnant and cyclic gilts. These results indicate that a single treatment of EDP on Day 12 of the estrous cycle can induce pseudopregnancy in pigs and that a convenient protocol for administering PGF2α to EDP-induced pseudopregnant pigs is available for estrus synchronization programs in cyclic pigs. Key words: Estradiol dipropionate, Estrus control, Pig, Pseudopregnancy (J. Reprod. Dev. 56: [421][422][423][424][425][426][427] 2010) t is desirable to have female pigs in estrus at certain times to provide maximum use of intensive pork production facilities. Application of estrus synchronization programs enhances economic performance in the swine industry by reducing the labor required to detect estrus, facilitating the use of artificial insemination (AI) and assisting in batch farrowing. Therefore, being able to control the time of estrus in a breeding herd results in decreased reproductive efforts and costs.Artificially shortening or extending the luteal phase is important for control of the interestrous interval in cyclic animals. The corpus luteum (CL) of the cycling pig generally exhibits resistance to prostaglandin F2α (PGF2α)-induced luteolysis prior to Day 12 of the estrous cycle [1][2][3]. Consequently, multiple administrations of PGF2α in the early luteal phase are required to induce luteolysis of the functional CL and shorten the estrous cycle [2,3]. In contrast to the CL before Day 12 of the estrous cycle, the CL of the pregnant pig easily reacts to exogenous administration of PGF2α [4,5], and prompt estrus can be induced between 4 and 7 days after PGF2α treatment; however, exogenous administration of PGF2α is associated with abortion in pregnant pigs [4,6].In pigs, two phases of ...

BackgroundUtilization of estrus synchronization program in livestock industry would provide greater options for reproductive management in herd. To develop a convenient method for estrus synchronization in pigs, we determined the effective protocol using estradiol dipropionate (EDP) for the establishment of pseudopregnancy and investigated follicular development during the estrus synchronization with prostaglandin F2alpha (PGF2alpha) in association with reproductive hormone profiles in pseudopregnant sows.MethodsIn Experiment 1, the effective dose (0, 10, 20, or 30 mg) and timing (5, 8, 11 or 13 days after ovulation) of a single administration of EDP in cyclic pigs for the induction of pseudopregnancy were investigated. In Experiment 2, four pseudopregnant sows were treated with PGF2alpha twice at a 24-h interval between 24 and 28 days after EDP treatment. The changes in plasma concentrations of reproductive hormones were analyzed by time-resolved fluoroimmunoassay. Follicular development and ovulation following PGF2alpha administration were monitored by transrectal ultrasonography.ResultsHigh efficiency (greater than 80%) of pseudopregnancy was achieved with a single treatment with 20 mg of EDP at 8 and 11 days after ovulation (equivalent to 9-13 days after the onset of estrus). Plasma estradiol-17beta concentrations in pseudopregnant sows were significantly higher between 12 h and 7 days than before EDP treatment. Total inhibin concentrations significantly decreased following EDP treatment and remained low for 14 days. The number of small follicles was increased from 6.3 +/- 2.6 at PGF2alpha treatment to 22.8 +/- 4.8 at 3 days later; this was associated with increased plasma concentrations of inhibin. Onset of estrus was detectable in all sows on 5.3 +/- 0.3 days after PGF2alpha treatment and the number of ovulated follicles was 15.5 +/- 1.4 detected at 7.6 +/- 0.2 days after the treatment.ConclusionsThis study has defined the effective dose and timing of EDP treatment for inducing pseudopregnancy in cyclic pigs. Our results also indicated that EDP caused a lowering of inhibin concentrations during pseudopregnancy and small numbers of follicles from 20 to 28 days after EDP. In contrast, EDP-induced pseudopregnancy appears to have no adverse effect on follicular development and subsequent ovulation following PGF2alpha administration.

Abstract.To induce meiotic resumption of porcine oocytes, it is thought to be necessary to expose the cumulus-oocyte complexes (COCs) to gonadotropins during in-vitro maturation (IVM). However, the detailed mechanism of meiotic resumption by gonadotropins is still unknown, and successful piglet production has not been reported by using oocytes matured in gonadotropin-free media and fertilized in vitro. The present study was undertaken to examine the combinational effects of epidermal growth factor (EGF)-family members and dibutyryl cyclic AMP (cAMP) in a chemically defined medium on IVM of porcine oocytes and the developmental competence following in vitro fertilization (IVF). The basic IVM medium was a chemically defined medium, modified porcine oocyte medium (mPOM). Supplementation of the IVM medium with 10 or 1000 ng/ml EGF, amphiregulin and betacellulin during the whole IVM period, except for 10 ng/ml amphiregulin, increased the percentage of oocytes maturing to the metaphase-II stage. When COCs were exposed to both dibutyryl cAMP and EGF-family members during the first 20-h of IVM and then culture was continued in the absence of EGF-family members and dibutyryl cAMP, the incidence of metaphase-II oocytes was significantly increased and was not different from that of oocytes cultured in a standard IVM system with gonadotropins. The developmental competence of the oocytes to the blastocyst stage following IVF was no different from that of control oocytes matured with gonadotropins. When these blastocysts were transferred into the uterine horn of three recipients, all of gilts became pregnant and delivered a total of 11 piglets. These observations indicate that supplementation of a chemically defined maturation medium with EGF-family members and dibutyryl cAMP during the first 20 h of IVM can support well the meiotic progress and developmental competence of porcine oocytes. Key words: Cyclic AMP (cAMP), Epidermal growth factor (EGF), In vitro maturation, Oocyte, Pig (J. Reprod. Dev. 55: [446][447][448][449][450][451][452][453] 2009) uccessful in-vitro production of porcine embryos has the potential to provide an effective system for mass production of embryos for better understanding of the physiology of embryonic development and animal reproductive technologies, including production of transgenic and/or cloned animals [1,2]. Relatively efficient systems for in-vitro production of porcine embryos have already been developed, but they contain materials derived from organisms, such as porcine follicular fluid and bovine serum albumin, in the culture media [3,4]. Chemically defined media, which only known chemicals, but none derived from animals, yeast or plants, should be useful in clarifying the mechanism of interactive communication between the oocyte and the surrounding cumulus cells during meiosis, the oocyte reaction following sperm penetration and early development. Furthermore, application of a defined system for in-vitro embryo production would be good for a quality control against the risk of viral c...

Aim: Experimental studies of human atherogenesis require an appropriate animal model that mimics human physiology and pathology. Because swine physiology is similar to human physiology, we developed a hyperlipidemia-induced atherosclerosis model using the recently developed world's smallest Microminipig TM . Methods: These animals weigh only 5 kg at 3 months of age, much smaller than any other miniature pig. We found that the administration of a high-fat/high-cholesterol diet containing at least 0.2% cholesterol without cholic acid for as little as eight weeks induces hypercholesterolemia and subsequent atherosclerosis in these animals. Results: The serum levels of low-density lipoprotein cholesterol (LDL-C) and the percent distribution of cholesterol in the LDL fractions were markedly increased. The hepatic expression of LDL receptor and hydroxymethylglutaryl-CoA reductase was coordinately decreased. The cholesteryl ester transfer protein activity, which plays a role in reverse cholesterol transport, was detected in the serum of the Microminipigs. Niemann-Pick C1-like 1 protein was expressed in both the liver and small intestine; however, hepatic apoB mRNA editing enzyme was not expressed. As in humans, and in contrast to that observed in mice, most of the hepatic lipase activity was localized in the liver. These results suggest that the hyperlipidemia-induced gene expression profile linked to cholesterol homeostasis and atherogenesis is similar in Microminipigs and humans. Conclusion: We conclude that the characteristics of the Microminipig, including its easy handling size, make it an appropriate model for studies of atherosclerosis and related conditions. IntroductionAtherosclerosis is a predominant risk factor for cardiovascular and cerebrovascular events and is closely related to serious morbidity and mortality in developed nations. The recent westernization of lifestyle in Japan, especially the increased caloric intake from a fatty diet, may account for the increasing inciHiroaki Kawaguchi and Tomonobu Yamada contributed equally to this work. 187Atherosclerosis in the World's Smallest Microminipig Japan) has recently been established as an experimental animal 13) . The MMPig is the world's smallest pig, with a body weight of only 5 kg at 3 months of age that remains at less than 10 kg at 7 months of age. Our preliminary study demonstrated that hyperlipidemia-induced atherosclerosis develops in MMPigs fed HcD containing sodium cholate (SC) 14) . Dietary SC is required to accelerate the progression of hyperlipidemia and atherosclerosis, presumably by inhibiting cholesterol excretion into bile; however, it is also known to cause hepatotoxicity 15) . AimThe specific aims of the present study were to further expand upon our previous research and detect evidence of close similarities between MMPigs and humans with respect to lipid metabolism and atherogenesis. We specifically investigated whether HcD alone (with no SC) induces atherosclerosis in the MMPigs and determined the minimum cholesterol content requi...