الفهرس 
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Abstract
In study (A) Assessment of autophagy and apoptosis in CL regression; The expression levels of autophagy-stimulating genes (MAP1LC3α, MAP1LC3α, Atg3 and Atg7) were elevated during CL regression, while the autophagy inhibitor (mTOR) expression was decreased. Protein distribution of LC3 protein was higher in late CL than mid especially the active form LC3-II. This in addition to higher apoptotic-related factors; higher caspase 3 activity and mRNA abundance, higher expression of cathepsins genes especially cathepsin B and increase of average lysosomal size in late CL than mid. Therefore, it was clear that autophagy and apoptosis level increases molecularly during CL regression. In study (B) Assessment of autophagy and apoptosis in oocytes and embryos development: Inhibition of autophagy during IVM or IVC aggravates maturation rate, oocytes and embryos developmental competence. Autophagy is critical for normal embryo development as autophagy related genes expressions were higher in the normal developed than abnormal developed embryos. Autophagy-CTSB relation is an inverse relation as autophagy inhibition during oocyte maturation increases the CTSB activity and gene expression and vice versa. Using autophagy inducer and CTSB inhibitor during IVM or IVC significantly improved the subsequent developmental competence better than autophagy inducer alone or CTSB inhibitor alone. Therefore, autophagy and CTSB can regulate oocyte and embryo development. In study (C) Assessment of anti-apoptotic role of vitamin B6 and its involvement in oocytes and embryos development: Addition of Vitamin B6 (Pyridoxine) to the IVM medium inhibits the CTSB activity and mRNA expression in IVM COCs and oocytes; moreover, it improves the subsequent developmental competence. In addition, using pyridoxine during maturation improves the quality of the resultant embryos by decreasing the TUNEL positive cells, decreasing CTSB mRNA abundance, and increasing trophectoderm and total cell number. Therefore, pyridoxine can be a promising tool to enhance the developmental competence of bovine oocytes and the quality of their embryos