Jong-Taek Yoon

Effects of Electric Stimulation on Bovine Oocyte Activation and Embryo Development in Intracytoplasmic Sperm Injection Procedure

AbstractPurpose: This study was carried out to investigate the efficacyof electric stimulation before and/or after intracytoplasmicsperm injection (ICSI) on bovine oocyte activation andembryo development. Methods: The oocytes were treated with electric shock before(B), before and after (B&A), and after (A) sperm injection.In each group, sham ICSI (ICSI-s) was performed to excludethe effect of parthenogenesis (B ICSI-s, B&A ICSI-s, and AICSI-s). An electric pulse was applied with a single directcurrent (DC) pulse (0.8 kV/cm, 70 μsec). Results: One pronucleus (PN) formation in the B&A ICSI-sgroup was slightly higher than that found in B and B&AICSI group; however, the difference was not significant. TwoPN formation in B&A ICSI group was higher than that foundin sham ICSI groups (P < 0.05). There were no differencesamong treatment groups in the cleavage rate; however, morulaeand blastocyst formation in the B&A embryos wassignificantly higher than that of other groups (P < 0.05)and got pregnant. Conclusions: Electric stimulation before and after injectionwas an effective method in inducing bovine oocyte activationand in sustaining embryo development to the morulae andblastocyst stage.

Delayed parturition in cloned calves associated with persistently elevated placentomal TGF-β1 expression

The objective of this study was to investigate hormonal and TGF-beta(1) characterizations of delayed parturition in the SCNT recipients (Korean native beef cattle: Hanwoo). The SCNT blastocysts produced by Hanwoo fetal fibroblast cells were transferred into the synchronized Hanwoo recipients. The artificially inseminated Hanwoo recipients (AI-R) were used as control. All AI-R were labored by natural delivery. The SCNT recipients (SCNT-R) with no signs of delivery were operated by Caesarean section. The blood and placentomes were collected during parturition. The weight of placentomes in SCNT-R (n=12, 301+/-41.22 g) was significantly higher than that of AI-R (n=10, 204.8+/-24.89 g) (p<0.05). There were significantly lower E2 (p<0.05) or higher P4 (p<0.01) and TGF-beta(1) (p<0.01) levels in the SCNT-R compared to that of AI-R, respectively. The SCNT-R showed a higher placentomal TGF-beta(1) protein level compared to that of AI-R (p<0.01). Interestingly, the TGF-beta(1) protein level in SCNT-R with normal delivery was dramatically decreased as same as AI-R, but it was highly maintained in C-sec at days 250 of pregnancy in AI-R. These results suggest that delayed parturition in clone calving may be associated with persistence of elevated TGF-beta-1 expression in late pregnancy.

Effects of Hormones on the Expression of Matrix Metalloproteinases and Their Inhibitors in Bovine Spermatozoa

Proteases and protease inhibitors play key roles in most physiological processes, including cell migration, cell signaling, and cell surface and tissue remodeling. Among these, the matrix metalloproteinase (MMPs) pathway is one of the most efficient biosynthetic pathways for controlling the activation of enzymes responsible for protein degradation. This also indicates the association of MMPs with the maturation of spermatozoa. In an attempt to investigate the effect of MMP activation and inhibitors in cultures with various hormones during sperm capacitation, we examined and monitored the localization and expression of MMPs (MMP-2 and MMP-9), tissue inhibitors of metalloproteinases (TIMP-2 and TIMP-3), as well as their expression profiles. Matured spermatozoa were collected from cultures with follicle-stimulating hormone (FSH), luteinizing hormone (LH), and Lutalyse at 1 h, 6 h, 18 h, and 24 h. ELISA detected the expression of MMP-2, MMP-9, TIMP-2, and TIMP-3 in all culture media, regardless of medium type (FSH-supplemented fertilization Brackett-Oliphant medium (FFBO), LH-supplemented FBO (LFBO), or Lutalyse-supplemented FBO (LuFBO)). TIMP-2 and TIMP-3 expression patterns decreased in LFBO and LuFBO. MMP-2 and MMP-9 activity in FBO and FFBO progressively increased from 1 h to 24 h but was not detected in LFBO and LuFBO. The localization and expression of TIMP-2 and TIMP-3 in sperm heads was also measured by immunofluorescence analysis. However, MMPs were not detected in the sperm heads. MMP and TIMP expression patterns differed according to the effect of various hormones. These findings suggest that MMPs have a role in sperm viability during capacitation. In conjunction with hormones, MMPs play a role in maintaining capacitation and fertilization by controlling extracellular matrix inhibitors of sperm.

Rams genetically superior for IGF-I do not exhibit improved male reproductive traits

Insulin-like growth factors (IGFs) play an important role in regulating normal physiology, and may be involved in the control of reproduction. The aim of this study was to define the relationship between IGF-I concentrations and reproductive performance over the breeding and non-breeding seasons in lines of New Zealand Romney rams that had been selected for low and high blood serum IGF-I concentration. Yearling rams from two selection lines (13 from the high line and 19 from the low line) were examined in July (winter), September (autumn) and November (summer) 2006 and March (spring) 2007. Scrotal circumference including the inguinal skin was recorded. Semen was collected by electroejaculation on 4 occasions over a 12-month period. Semen was evaluated according to standard procedures (volume, motility, density and morphology). Samples were collected from four animals from each group for measurements of mRNA for IGF-I and the IGF type 1 receptor (IGF 1R) in the testis, and IGF-I, IGF 1R and the insulin receptor (IR) in the liver. Blood samples were collected via jugular venipuncture for the measurement of IGF-I, insulin and testosterone. The incidences of morphologically abnormal sperm cells, the scrotal circumference and sperm motility were higher in the breeding than in non-breeding season. Seasonal changes were found in the percentage of abnormal sperm, scrotal circumference, sperm motility and sperm density, but there were no differences between lines in any reproductive parameters. IGF-I mRNA levels were higher in the high than the low line in the liver but not in the testis, whereas the opposite was found for levels of IGF 1R mRNA. mRNA levels for the insulin receptor in the liver were higher in the high line. Plasma testosterone concentrations did not differ between lines, whereas the concentrations of IGF-I and insulin were higher in the high line. The results suggest that IGF-I may be locally produced in the liver and the testis, and that selection for high IGF-I may not be associated with improved reproductive performance in rams.