Administration of 6-methoxybenzoxazolinone (MBOA) does not augment ovulatory responses in St. Croix White ewes superovulated with PMSG

Comparison of Five Protocols of Estrous Synchronization on Reproductive Performance of Hu Sheep

The purpose of this study is to compare five protocols of estrous synchronization for Hu ewes to obtain the most effective and economical protocol, to apply the advantageous scheme in large-scale sheep farming. Healthy multiparous Hu ewes (n = 150) were randomly divided into five groups, and all ewes were administered fluorogestone acetate (FGA, 45 mg) vaginal sponge. The sponges of the first three groups (Groups I, II, and III) were removed on the 11th day, and 0.1 mg of PGF_2α was injected intramuscularly on the ninth day. Group I received 6 μg of gonadotropin-releasing hormone (GnRH) by intramuscular injection at 36th h after withdrawal of the sponge. Group II was injected 330 IU of pregnant mare serum gonadotropin (PMSG) on the ninth day. The combination of 6 μg of GnRH and 330 IU of PMSG was treated in Group III at the same time as Group I and Group II. The sponges of the latter two groups (Groups IV and V) were removed on the 13th day, and 330 IU of PMSG was injected intramuscularly simultaneously. PGF_2α (0.1 mg) was administered on the 12th day in Group IV. All ewes were detected for estrus at 24, 36, 48, 60, and 72 h after the sponge removal. The loss of sponge and vaginitis was recorded when the sponge was withdrawn. Cervical artificial insemination (AI) was performed with fresh semen of Dorper rams diluted with skimmed milk. After 30 days of insemination, the conception was detected with a veterinary B-ultrasound scanner. The lambing status of all ewes and the cost of drugs for estrous synchronization in each group were recorded. The results showed the following: (1) on the whole, the average percentage of estrous ewes in the period of 24–36 h and 36–48 h after removal was significantly higher than other three periods and that of the period of 60–72 h was significantly lower than the first three periods after removal; (2) there was no significant difference in percentages of estrous ewes in any of the five time periods, sponge loss rate, vaginitis rate, total percentage of estrous ewes, conception rate, single lambing rate, twinning rate, and multiple lambing rate of ewes among five protocols; (3) total percentage of estrous ewes and conception rate were more than or equal to 80% in the Groups II and III, and the twinning lamb rate of the Group II protocol was 70%; (4) there was no difference in lambing rate of ewes among Groups II, III, IV, and V; (5) the Group III had the highest drug cost of 22.5 CNY. In conclusion, considering the lambing rate, twinning lamb rate, and drug cost for estrous synchronization, Group II was the most advisable for application and promotion in large-scale sheep farms among these five protocols of estrus synchronization.

Effect of photoperiod and 6-methoxybenzoxazolinone (6-MBOA) on the reproduction of male Brandt's voles (Lasiopodomys brandtii)

Plant secondary metabolite 6-methoxybenzoxazolinone (6-MBOA) has been suggested to stimulate animal reproduction. 6-MBOA is detected in Leymus chinensis, a main diet of Brandt's vole (Lasiopodomys brandtii). We have previously reported a stimulatory effect of 6-MBOA on reproduction of male Brandt's voles under a short-day photoperiod. The goal of this study was to investigate the effect of 6-MBOA on reproductive physiology of male Brandt's voles under a long-day photoperiod and examine if 6-MBOA under this photoperiodic regime altered the reproductive status of male Brandt's voles differently than the short-day photoperiod. Under the long-day photoperiod, a high dose of 6-MBOA decreased KiSS-1 mRNA in the arcuate nucleus (ARC), and we also saw a decrease in circulating levels of luteinizing hormone (LH), follicle-stimulating hormone (FSH), and testosterone (T). Steroidogenic acute regulatory protein (StAR) and cytochrome P450_11a1 (CYP11a1) in the testes, and relative testis weight also decreased with 6-MBOA administration. Compared to the short-day photoperiod, animals under the long-day photoperiod exhibited increased body weight as well as all other reproductive parameters. Our results showed that 6-MBOA inhibited the reproduction of male Brandt's vole under a long-day photoperiod, a stark contrast from its stimulatory effects under a short-day photoperiod. The paradoxical effects of 6-MBOA suggest it may act as a partial agonist of melatonin. These results provide insight into the complex interactions between environmental factors such as photoperiod and diet in the control of Brandt's vole reproduction.

Reproductive responses of male Brandt's voles (Lasiopodomys brandtii) to 6-methoxybenzoxazolinone (6-MBOA) under short photoperiod

The plant secondary metabolite 6-methoxybenzoxazolinone (6-MBOA) can stimulate and enhance animal reproduction. This compound has been successfully detected in Leymus chinensis, which is the main diet of Brandt's voles. The aim of this study was to investigate the effect of different 6-MBOA doses on the reproductive physiology of male Brandt's voles under a short photoperiod. The results showed that 6-MBOA administration increased relative testis weight, regardless of the dose, but it had little effect on the body mass. Low and middle doses of 6-MBOA increased the concentrations of luteinizing hormone and testosterone in the serum and the mRNA levels of StAR and CYP11a1 in the testes. However, 6-MBOA did not cause any significant increase in the mRNA levels of KiSS-1, GPR54, and GnRH compared to those in the control group. The mRNA level of KiSS-1 in the arcuate nucleus (ARC) was higher than that in the anteroventral periventricular nucleus (AVPV). Collectively, our results demonstrated that the number of KiSS-1-expressing neurons located in the ARC was the highest, and that 6-MBOA, which might modulate the reproductive activity along the hypothalamic-pituitary-gonadal axis, had a dose-dependent stimulatory effect on the reproductive activity of Brandt's voles under a short photoperiod. Our study provided insights into the mechanism of 6-MBOA action and the factors influencing the onset of reproduction in Brandt's voles.

In vitro grown sheep preantral follicles yield oocytes with normal nuclear-epigenetic maturation

Background

Assisted reproductive technologies allow to utilize a limited number of fully grown oocytes despite the presence in the ovary of a large pool of meiotically incompetent gametes potentially able to produce live births. In vitro folliculogenesis could be useful to recruit these oocytes by promoting their growth and differentiation.

Methodology/Principal Findings

In vitro folliculogenesis was performed starting from sheep preantral (PA) follicles to evaluate oocyte nuclear/epigenetic maturation. Chromatin configuration, quantification of global DNA methylation, and epigenetic remodelling enzymes were evaluated with immunocytochemistry, telomere elongation was assessed with the Q-FISH technique, while the DNA methylation status at the DMRs of maternally IGF2R and BEGAIN, and paternally H19 methylated imprinted genes was determined by bisulfite sequencing and COBRA. Specifically, 70% of PA underwent early antrum (EA) differentiation and supported in culture oocyte global DNA methylation, telomere elongation, TERT and Dnmt3a redistribution thus mimicking the physiological events that involve the oocyte during the transition from secondary to tertiary follicle. Dnmt1 anticipated cytoplasmic translocation in in vitro grown oocytes did not impair global and single gene DNA methylation. Indeed, the in vitro grown oocytes acquired a methylation profile of IGF2R and BEGAIN compatible with the follicle/oocyte stage reached, and maintained an unmethylated status of H19. In addition, the percentage of oocytes displaying a condensed chromatin configuration resulted lower in in vitro grown oocytes, however, their ability to undergo meiosis and early embryo development after IVF and parthenogenetic activation was similar to that recorded in EA follicle in vivo grown oocytes.

Conclusions/Significance

In conclusion, the in vitro folliculogenesis was able to support the intracellular/nuclear mechanisms leading the oocytes to acquire a meiotic and developmental competence. Thus, the in vitro culture may increase the availability of fertilizable oocytes in sheep, and become an in vitro translational model to investigate the mechanisms governing nuclear/epigenetic oocyte maturation.

6-MBOA affects testis size, but not delayed-type hypersensitivity, in white-footed mice (Peromyscus leucopus)

Many rodents use day length to time reproduction to occur when resources are abundant, but some species also use supplementary environmental cues. One supplementary cue is the plant-derived compound, 6-methoxy-2-benzoxazolinone (6-MBOA). Most rodents grow their gonads in response to 6-MBOA in their diets, but it is presently unknown whether they also use 6-MBOA to adjust other aspects of physiology, specifically their immune systems. 6-MBOA is structurally similar to melatonin, and seasonal changes in rodent immune activities are often mediated by melatonin. We therefore predicted that white-footed mice (Peromyscus leucopus), which breed seasonally and are reproductively sensitive to melatonin, would adjust their immune systems when fed 6-MBOA. 6-MBOA treated mice in long day lengths regressed their testes to a greater extent than mice fed a standard diet, or mice kept in short day lengths and fed 6-MBOA or a standard diet. One type of immune activity (delayed-type hypersensitivity) was not affected by 6-MBOA, however, although responses were greater in short versus long day mice. In sum, P. leucopus responded reproductively to 6-MBOA, although differently than other species; immune activity was unaffected. Other aspects of the immune system, especially in herbivorous rodents, may be affected by 6-MBOA and thus warrant further study.

Modifications in chromatin morphology and organization during sheep oogenesis

This research has been designed to study the major events of nuclear remodeling that characterize sheep oocytes during the early stage of folliculogenesis (transition from preantral to antral stage). In particular, the modifications in large-scale chromatin configuration, the global DNA methylation, and the process of telomere elongation have been investigated as crucial events of oocyte nuclear maturity. In addition, the spatio-temporal distribution of the major enzymes involved in DNA methylation, the DNA methyltransferase 1 (Dnmt1), and in telomere elongation, telomerase catalytic subunit (TERT), have been described. To these aims, the nuclei of isolated oocytes were investigated using immunocytochemistry and Q-FISH analyses. In absence of preliminary information, these nuclear determinants were compared with those of fully competent germ cells obtained from medium and preovulatory antral follicles. The nuclei of sheep oocytes acquired a condensed chromatin configuration, stable high levels of global DNA methylation, and a definitive telomere length already in the majority of late growing stage oocytes (110 microm) derived from early antral follicles. In addition, while the process of methylation resulted strictly related to oocyte diameter, the telomeric program appeared to be highly chromatin configuration-dependent. The translocation of Dnmt1 and TERT from the nucleus to the cytoplasm in the oocytes derived from early antral follicles seems to confirm the definitive chromatin asset of these germ cells. In conclusion, changes in large-scale chromatin structure, epigenesis, and telomere size in the sheep are established prior to oocyte acquires the ability to resume meiosis.