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| Author(s): |
Fabiane Gilli Zaffalon
Total Authors: 1
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| Document type: | Doctoral Thesis |
| Press: | Pirassununga. |
| Institution: | Universidade de São Paulo (USP). Faculdade de Zootecnica e Engenharia de Alimentos (FZE/BT) |
| Defense date: | 2014-07-31 |
| Examining board members: |
Cláudia Lima Verde Leal;
André Furugen Cesar de Andrade;
Luciano Andrade Silva;
Yeda Fumie Watanabe
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| Advisor: | Cláudia Lima Verde Leal |
| Abstract | |
In vitro maturation of oocytes is a limiting factor in the in vitro production of bovine embryos. In vivo, this maturation is a highly orchestrated process in which meiosis resumption by the gonadotropin surge that precedes ovulation induces the decrease in cAMP levels in the oocyte. However, when oocytes are removed from follicles, they spontaneously resume maturation compromising the competence for its development. cAMP is synthesized by adenylyl cyclase (AC) and degraded by phosphodiesterases (PDE), and there are some PDEs related to degradation of cAMP and/or cGMP. Thus, the purpose of this work was to investigate the contribution of different isoforms of phosphodiesterases in the resumption of meiosis and levels of cAMP and, also, to determine differences in signaling pathways when maintaining high levels of cAMP and its influence on oocyte competence. For this purpose, cumulus-oocyte complexes (COC) were matured in vitro in the presence, absence or combination of inhibitors of cAMP- and cGMP-specific PDEs and FSH. Samples be were evaluated in relation to: 1) maturation rate, 2) intracellular levels of cAMP and cGMP in COCs, 3) rate of blastocyst development and 4) activation of MAPK in oocytes and cumulus cells. The results of the first experiment showed that the PDE3 inhibitor is more effective (p <0.05) in delaying meiosis resumption, at nine hours of maturation, but was not capable of altering cAMP levels (p> 0.05) either alone or in combination with the PDE8 inhibitor. In experiment two, the PDE5 inhibitor alone did not affect the meiosis resumption (p> 0.05), however, when associated with PDE3 and PDE8 inhibitors it delayed their resumption (p <0.05) and also altered cGMP and cAMP levels of (p <0.05) in the early hours of maturation. The third experiments showed the influence of FSHr during IVM, which stimulated the resumption of meiosis, but in combination with PDE5 and PDE8 inhibitors meiosis was delayed (p <0.05). Furthermore, FSHr causes increased levels of cAMP and its association with PDE5 and PDE8 inhibitors caused an additional increase (p <0.05). Culture conditions studied in experiment four showed that induced maturation (pre-IVM for two hours with agents to elevate cAMP followed by 22 hours IVM with FSH associated with PDE inhibitors) delayed the resumption of meiotic maturation at nine hours, but has no effect on meiosis progression at 24, 28 and 30 hours. The treatments, however, did not improve oocyte competence after in vitro fertilization and caused minor variations in the activation of MAPK in oocytes and cumulus cells. (AU) | |
| FAPESP's process: | 10/20188-6 - Influence of different phosphodiesterase isoform in the control of bovine oocyte maturation |
| Grantee: | Fabiane Gilli Zaffalon |
| Support Opportunities: | Scholarships in Brazil - Doctorate |