The Phosphodiesterase Inhibitor, Isobutyl-1-Methylxanthine Prevents the Sudden Drop in Cyclic Adenosine Monophosphate Concentration and Modulates Glucose Metabolism of Equine Cumulus-Oocyte Complexes Matured in Vitro

Spontaneous nuclear maturation of mammalian oocytes can occur when physically removed from the ovarian follicle during in vitro oocyte maturation (IVM), largely because of a decrease in cyclic adenosine monophosphate (cAMP) concentration. Modulation of oocyte cAMP during IVM by using phosphodiesterase inhibitors has been shown to maintain elevated oocyte cAMP concentrations and control meiotic resumption of bovine and ovine oocytes. This study determined the effect of inclusion of isobutyl-1-methylxanthine (IBMX) during collection and the first 12 hours of incubation of equine oocytes on cAMP concentration and glucose metabolism of cumulus-oocyte complexes (COCs). Abattoir-derived COCs were collected in aspiration medium with (Asp-IBMX) or without (Asp) IBMX. Cumulus-oocyte complexes were then incubated for 12 hours in IVM medium with (Mat-IBMX) or without (Mat) IBMX, followed by additional 24 hours in Mat medium. The cAMP concentration, glucose consumption, lactate production, and metaphase II rates of the COCs were assessed. Cumulus-oocyte complexes aspirated into Asp-IBMX (62.2 ± 2.6 fmol per COC) medium had higher cAMP concentration than Asp (31.8 ± 2.8 fmol per COC) control group (P < .05). Likewise, at 12 hours of IVM, Mat-IBMX group (33.2 ± 2.1 fmol per COC) had higher cAMP concentration than the Mat group (7.68 ± 0.5 fmol per COC; P < .05). Glucose consumption and lactate production were lower during the first 12 hours of incubation in COCs cultured in Mat-IBMX (P < .05). Isobutyl-1-methylxanthine prevented the rapid drop in cAMP concentration and altered metabolism of glucose by the COC. Preventing the sudden drop in cAMP prevents the premature nuclear maturation of in vitro-matured oocytes causing poor developmental competence.

190 Effect of TCM-199 and synthetic oviductal fluid medium supplemented with varying hormone concentrations on invitro maturation of canine oocytes

Invitro oocyte maturation (IVM) in the domestic canine is yet to be optimized, with low rates of cumulus-oocyte complexes (COCs) reaching MII. This limits the progression of assisted reproductive technologies, which could benefit breeding programs for assistance dogs and endangered Canidae. Canine oocyte maturation differs from that in other mammals, with the ovulation of a COC in the germinal vesicle stage and nuclear maturation occurring in the oviduct. Because of this, the environment in which a canine COC matures is unlike that of other mammals, meaning that IVM protocols cannot be readily adapted. The aim of the current work was to determine (1) the effects of varying concentrations of FSH, human chorionic gonadotrophin (hCG), and oestradiol (E2) during IVM on meiotic resumption and nuclear maturation of canine COCs; and (2) the optimal medium base, either synthetic oviductal fluid (SOF) or tissue culture medium-199 (TCM). Reproductive tracts of bitches (6 months to 7 years of age) were collected from veterinary clinics within 2h of routine spaying. Ovaries were sliced using a scalpel blade, releasing the COCs into aspiration medium. The COCs were randomly allocated to a maturation medium consisting of one of the hormones at two concentrations (FSH: 5 or 10µgmL−1; hCG: 5 or 10IUmL−1; E2: 1 or 5µgmL−1) and for both SOF and TCM base. Each hormone was tested individually for a replicate of eight animals per hormone (total of 12 experimental groups; 24 animals). The COCs were cultured for 72h in their allocated medium and then denuded and stained with Hoechst 33258. Fluorescence microscopy was used to determine nuclear maturation stage. Nuclear maturation rates to MII were analysed using a general linear model with pairwise comparison (SPSS version 25; SPSS Inc./IBM Corp.) with each individual animal acting as a replicate. Canine COCs matured in a SOF-based media had higher rates of meiotic resumption (MI and MII) (SOF: 38.68%, n=515; TCM: 25.78%, n=542; P&lt;0.05) and number reaching MII (SOF: 7.54%; TCM: 4.39%; P&lt;0.05) compared with TCM-based medium. Resumption of meiosis and nuclear maturation to MII did not differ between media with differing E2 or hCG concentrations. The use of FSH at 10µgmL−1 in SOF medium decreased resumption of meiosis (8.57%) and MII rates (0%) compared with 5µgmL−1 FSH in SOF (29.41% and 3.92%, respectively; P&lt;0.05). In summary, our data indicated that higher concentrations of FSH during IVM have a negative effect on meiotic resumption and maturation to MII, whereas canine COCs resume meiosis and mature to MII in higher rates in a SOF-based medium compared with a TCM base. An IVM medium that replicates the invivo environment in which canine COCs mature is beneficial. However, rates of IVM canine oocytes reaching maturity are low, signifying that future research must investigate a greater range of hormone concentrations and combinations to better mimic invivo conditions to assess the possible benefits for canine IVM.

Stallion Sperm Integrity After Centrifugation to Reduce Seminal Plasma Concentration and Cool Storage for 4 days

The objective of the study was to investigate if reducing the seminal plasma of stallion extended semen by centrifugation once will suffice to maintain acceptable semen quality for insemination after 4 days of cool storage. Collected semen was extended to 25 × 10⁶ sperm/mL and subjected to one of the following treatments: noncentrifuged (control), centrifuged for 10 minutes at 900 × g and 1800 × g. The supernatant was partially removed, and the sperm pellet, reconstituted and re-extended. It was then placed in a passive cooling device overnight and then transferred to a refrigerator for the remainder of the cooling period. At day 0, 2, and 4, total motility (TM), progressive motility (PM), and plasma (PLM) and acrosomal membrane integrity were assessed. Centrifuged groups had higher TM and PM at day 4 than the control group (P < .05). Likewise, centrifuged groups had higher intact PLM in day 4 (P < .05). A single centrifugation cycle to reduce seminal plasma concentration will suffice to preserve sperm integrity acceptable for an artificial insemination dose up to 4 days of cool storage.

59 EFFECT OF STORAGE DURATION ON POST-THAW PARAMETERS OF BULL SEMEN

It has been proposed that once good-quality sperm are collected, extended, and cryopreserved that the post-thaw quality will remain high regardless of the duration of storage. A previous study has suggested that there is no effect on post-thaw sperm motility of bovine semen stored in liquid nitrogen up to 13 years. However, no studies have reported the effect of extended storage of bovine semen in LN2. In this study, cryopreserved semen from Angus bulls (n = 25) was utilized. Time frames were assigned to each bull based on the year of collection and cryopreservation: time frame 1 (1960–1975), time frame 2 (1976–1991), and time frame 3 (1992–2006). Due to differences in packaging methods across time periods (glass ampules and plastic straws), thawing methods utilized were different and based on the packaging type. Semen packaged in glass ampules (n = 7) were thawed in a 37°C water bath for 80 s, while those in plastic straws (n = 18) were thawed in a 37°C water bath for 30 s. Once thawed all packages were wiped dry and either scribed (glass ampule) or the end cut (plastic straw) and the semen expelled into a 1.5-mL microcentrifuge tube and maintained at 37°C for evaluation. For sperm motility, a 20-µL sample was placed onto a prewarmed microscope slide for analysis. Sperm motility parameters (total motility and progressive motility) were evaluated by 2 experienced technicians and averaged. A hemocytometer was used to determine sperm concentration in a final dilution of 1 : 100. An eosin/nigrosin stain was used to determine sperm morphology. Parameters were analyzed using one-way ANOVA. There was no difference in sperm concentration between time frames 1 and 2 (53 × 106 mL–1 and 59 × 106 mL–1, respectively) or time frames 1 and 3 (53 × 106 mL–1 and 37 × 106 mL–1, respectively). However, time frame 2 exhibited a higher (P < 0.05) sperm concentration compared with time frame 3 (59 × 106 mL–1 v. 37 × 106 mL–1, respectively). There were no differences among time frames 1, 2, or 3 for total (42, 51, and 55%, respectively) and progressive sperm motility (29, 38, and 41%, respectively). Similarly, there were no differences among time frames 1, 2, and 3 for percent normal sperm (80 ± 3.6, 76 ± 5.0, and 71 ± 4.0%, respectively) and abnormal sperm (19 ± 3.6, 23 ± 5.0, and 28 ± 4.0%, respectively). Furthermore, time frames 1, 2, and 3 did not exhibit a difference in primary (9 ± 2.5, 7 ± 2.6, and 6 ± 1.0%, respectively), secondary (2 ± 0.8, 5 ± 1.4, 6 ± 2.0%, respectively), or tertiary abnormalities (7 ± 2.4, 10 ± 2.7, and 16 ± 2.7%, respectively). These data suggest that once good-quality bovine sperm is cryopreserved, the duration of storage (up to 43 years) has no effect on Angus bull post-thaw semen parameters.

Effect of resveratrol on intimal hyperplasia after endothelial denudation in an experimental rabbit model

The ability of resveratrol to inhibit vascular intimal thickening was tested in an experimental model in which endothelial denudation was performed in the normal rabbit iliac artery. Resveratrol (2 approximately 4mg/ kg/d) was administered intragastrically for 5 weeks beginning 1 week before denudation. At the higher concentration of resveratrol, the intimal hyperplasia of injured vascular wall was effectively inhibited; the intimal proliferation index also was significantly less than that in the untreated control group (0.28 +/- 0.07 vs 0.41 +/- 0.13, respectively, p<0.01); the relative luminal area increased from 0.38 +/- 0.06 in the untreated control group to 0.53 +/- 0.10 in the resveratrol treatment group (p < 0.001); and the count of smooth muscle cells in the thickened intima was statistically significantly reduced in the high dose resveratrol treatment group than that in the untreated group (1,115 +/- 510 vs 1,796 +/- 963, respectively, p < 0.05). Resveratrol added to the culture media of cultured rabbit vascular smooth muscle cells inhibited DNA synthesis in a dose-dependent manner. These results showing that resveratrol is capable of inhibiting intimal hyperplasia of injured artery raise the possibility that this polyphenol might have clinical potential in prevention and treatment of restenosis after angioplasty.