Comparative ultrastructural analysis of diestrous and anestrous canine Grade 1 cumulus-oocyte complexes.
The objective of the present study was to characterize, by means of transmission electron microscopy, immature Grade 1 cumulus-oocyte complexes (COCs) obtained from ovaries collected from bitches at diestrus and anestrus, after routine ovariohysterectomy. Cumulus-oocyte complexes were recovered after slicing the ovarian cortex and Grade 1 COCs were selected and prepared for transmission electron microscopy. All oocytes were at germinal vesicle stage in two different configurations. In 29 out of 37 COCs, oocytes presented a central or eccentric located nucleus (GVc), frequently containing a reticulated nucleolus, with a predominance of profound follicular cell processes (FCP), abundant endoplasmic reticulum (ER) and a moderated number of lipid droplets. In eight out of 37 COCs, oocytes had a peripheral located nucleus (GVp) containing small compact nucleolus, a thin perivitelline space, both superficial and profound FCP, moderate ER content and abundant lipid droplets. A higher (p<0.05) proportion of GVp was found in oocytes collected in diestrus (36.8% - 7 out of 19) than in anestrus (5.6% - 1 out of 18). In addition, distinct ultrastructure characteristics among GVc associated with estrous phase were noted. Furthermore, a number of structures, some of which had not been reported before, were present in canine prophase I oocytes at variable frequencies. The evident variation in the presence, quantity and distribution of cell organelles in canine immature Grade 1 oocytes is discussed in relation to the biological phase of the oocyte and the reproductive stage of the donor bitch.
Department of Veterinary Clinics, ICBAS - Abel Salazar Biomedical Institute, University of Porto, Rua Padre Amando Quintas, 4485-661 Vairão, Portugal. gracalopes@mail.icav.up.pt
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Lopes
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Rocha
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Sousa
D000780:Anestrus; D000818:Animals; D002466:Cell Nucleolus / Q000648:ultrastructure; D002467:Cell Nucleus / Q000648:ultrastructure; D054885:Cumulus Cells / Q000648:ultrastructure*; D003593:Cytoplasm / Q000648:ultrastructure; D004031:Diestrus; D004285:Dogs / Q000033:anatomy & histology*; D004721:Endoplasmic Reticulum / Q000648:ultrastructure; D005260:Female; D046529:Microscopy, Electron, Transmission; D009865:Oocytes / Q000648:ultrastructure*