Bovine embryos produced by in vitro maturation, feretilization and development was examined for presevation and transfer. The fertilization medium used BO medium with 5 mM/ caffeine and 10/ heparin and adjusted to a pH of 7.2 to 7.4. The final concentration of spermatozoa was adjusted to 1 cells/ motile sperm during fertilization in vitro. At 8~10 hrs after insemination, the oocytes were transferred into CR1aa medium and cultured for 7 days. Embryos were preserved by vitrification method for transfer. When the embryos of early, blastocyst and expanded blastocyst stages were frozen-thawed, the proportions of embryos with normal morphology 83.6, 88.1 and 85.2%. (중략)

The purpose of this is to investigate the effects of vitrification in open pulled straws (OPS) on in vitro survival of porcine embryos. Blastocysts were produced by in vitro fertilization of slaughterhouse-derived, in vitro matured oocytes with frozen-thawed boar semen, and subsequent culture on granulosa cell monolayer. After frozen-thawing, embryos were culture in NCSU-23 medium with 5 mM hypotaurine, 4 mg/ BSA and 10 ng/ for 48 hrs to survival tests. When blastocysts were frozen-thawed by OPS methods, the embryos with normal morphology were 32.1, 34.5 and 38.9 % in early blastocyst, blastocyst and expanded blastocyat stages. The rates of partial damaged embryos were significantly (P<0.05) higher in early biastocysts than expanded blastocysts. In another experiment, the embryos frozen by OPS methods were cultured for 48 hrs for survival and developmental rates in vitro. The proportions of embryos hatched were 11.8, 20.2 and 33.3% in embryos frozen-thawed at stages of early blastocyst, blastocyst and expanded embryos. On the other hand, The proportions of embryo with normal morphology after culture were 23.5, 25.0 and 33.3% in embryos frozen-thawed at stages of early blastocyst, blastocyst and expanded embryos. These finding indicate the possible broader application for OPS methods that this procedure described is relatively harmless, that it can be used for blastocysts of different developmental stages.

DNA methylation is involved in epigenetic processes such as X-chromosome inactivation, imprinting and silencing of transposons. DNA methylation is a highly plastic and critical component of mammalian development The DNA methyltransferases (Dnmts) are responsible for the generation of genomic methylation patterns, which lead to transcriptional silencing. The maintenance DNA methyltransferase enzyme, Dnmt 1, and the de novo methyltransferase, Dnmt3a and Dnmt3b, are indispensable for development because mice homozygous for the targeted disruption of any of these genes are not viable. The occurrence of DNA methylation is not random, and it can result in gene silencing The mechanisms underlying these processes are poorly understood. It is well established that DNA methylation and histone deacetylation operate along a common mechanistic pathway to repress transcription through the action of methyl-binding domain proteins (MBDs), which are components of, or recruit, histone deacetylase (HDAC) complexes to methylated DNA. As a basis for future studies on the role of the DNA-methyl-transferase in porcine development, we have isolated and characterized a partial cDNA coding for the porcine Dnmt1. Total RNA of testis, lung and ovary was isolated with TRlzol according to the manufacture's specifications. 5 ug of total RNA was reverse transcribed with Super Script II in the presence of porcine Dnmt 1 specific primers. Standard PCRs were performed in a total volume of 50 ul with cDNA as template. Two DNA fragmenets in different position were produced about 700bp, 1500bp and were cloned into pCR II-TOPO according to the manufacture's specification. Assembly of all sequences resulted in a cDNA from 158bp of 5'to 4861bp of 3'compare with the known human maintenance methyltransferase. Now, we are cloning the unknown Dnmt 1 region by 5'-RACE method and expression of Dnmt 1 in tissues from adult porcine animals.