Studies On Histological Characteristics Of Follicle And Corpus Luteum In Yaks During Pregnancy

Forty-five female yaks during defferent pregnancy were used to study the histoiogical structure of follicular and luteum corpus in their ovaries by light and electron microscopes. The results were as follows:1 There were cortical granules (CGs)in the oocyte of Yaks as other manmmals . Cortical granules and zone pellucida (ZP) appeared when oocytos were surrounded hy 2-4 cuhoidal follicles. A few short microvilli began to emerge on the oolemma of oocytes when they were surrounded hy simple cuhoidal follicles. With the development of oocyte, microvilli became long and the zone pellucida became thicker. Oocyte and follicular cells were linked by zone pellucida and microvilli. The number of mitochondria (Mi) , smooth endoplasmic reticulum, (SER) , cortical granules all increased and all organelles moved to the cortical region with development of the oocytes. The CGs developed and arranged in cluster. In maturing oocytes, CGs began to arrange themselves beneath the oolemma, and mitochondria dispersed toward the central region of cytoplasm. The phenomenon of the partial coalescence of mitochondria and endoplasmic reticulum existed in cytoplasm.During the pregnancy of 20-70 days, luteal cells were small and there were no prominent morphological changes in cytoplasm. In this time luteum corpus provided a rich source of microvascular and there were no or only few intravasular cellular debris. During the pregnancy of 70~180 days luteal cells increased significantly, with development of luteum corpus many capillaries contained cellular debris and thick walled vessels became numerous. From pregnancy of 20~180 days there were spaces between oolemma and cytoplasm in luteum cells, it was early regressional change. Following the development of regressional changes the granulose luteal cells enlarged, had round, ovum or polyhedral morphology character; cytoplasm eosinnophilia and nuclear chromation aggregated. To observe the ultrastructure of luteal corpus during pregnancy of yaks the characteristic changes occurred in lipid droplets and smooth endoplasmic ret iculum. From 20 days to 70 days of pregnancy there were numerous lipid droplets,from 70 days to 180 days they decreased regularly hut smooth endoplasmic reticulum increased from 20 to 180 days with typical morphology of annulate lamellae. There were continuous capillary and fenestratcd capillary in luteum corpus of yaks. Granulose luteal cells were linked hy gap-junction and tight junction. The ulstastructure of regressional granulose luteal cell followed as: nucl ear decondensed, nuclear membrane wrinkled, all organelles denaturated, LI) accumulated, SER decreased or disappeared, RKR increased and Mi regressed, Golgi complex swelled and lysosome increased and its membrane disappeared.