بررسي فراساختار جنينهاي حاصل از تخمكهاي موش مسن و جوان در محيط كشت

Ultra Structural Study of Mice Embryos Obtained from Young and Old Oocytes

Purpose: The aim of this study was to compare ultra structure of embryos obtained from young and old mouse oocytes. Materials and Methods: Metaphase II oocytes were retrieved from old NMRI mouse (7-9 months old) and young NMRI (10-12 weeks old) after ovarian stimulation. NMRI mouse sperms (10-12 weeks old) were added to T6 medium containing retrieved oocytes. After PN formation, embryos were transferred to culture medium (comtaining 15mg/ml BSA). Developmenting of embryos was recorded every 24 hours. 2 cell embryos after were fined in 2.5% glutardehid phosphate. Then samples were dehydrated and embedded. Blokes were sliced after timming. Seim thin (500 nm) and ultra thin (70 nm) sections had been (collected on copper grids) stained. Samples were studied by election microscopy. Results: At the (LM) level, embryos driven from young and old oocytes were surrounded by zona pellocida polar bodies and cellular fragmentation were seen in perivitelline space which was morefrequent in older embryos. In embryos driven from old oocytes, perivittelline space was more expanded and microvillies were arragned reqularly. Nuclei of blastocytes were enchromatin in both embroyos. In old embryos, intramuscular anulatellae lamllae was ween which was secndary to folding of nucleous inhere membra. Mithochondies and intermediate filaments were seen in both embryos in cytoplasmo which were similar in morphology and ultra structure. But their arrangement and distribution were different. In embryos driven from oocytes most of mitochonderies were central and around the nuclei. While in young embryos, they were distributed in cytoplasm. SER collection was higher in young embryos while residual bodies and lipid were more frequent in old embryos. Conclusion: This study revels that embryos driven from old oocytes had several ultra structure changes in comparison with young embryos. This may be one of the reasons that implantation and birth rate are lower in old subjects.