Universidad de Buenos Aires Facultad de Ciencias...
Among Eutherian mammals, L. maximus shows many unusual reproductive traits such as a high ovulation rate and a process of selective embryo resorption that occurs during the first\nhalf of gestation. Despite the high ovulatory rate, a few 8 to 12 oocytes are fertilized and implanted, and just the emb...
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| Formato: | Tesis doctoral acceptedVersion |
| Lenguaje: | Español |
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Universidad de Buenos Aires. Facultad de Ciencias Veterinarias
2018
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| Acceso en línea: | http://repositoriouba.sisbi.uba.ar/gsdl/cgi-bin/library.cgi?a=d&c=avaposgra&cl=CL1&d=HWA_5659 https://repositoriouba.sisbi.uba.ar/gsdl/collect/avaposgra/index/assoc/HWA_5659.dir/5659.PDF |
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| Sumario: | Among Eutherian mammals, L. maximus shows many unusual reproductive traits such as a high ovulation rate and a process of selective embryo resorption that occurs during the first\nhalf of gestation. Despite the high ovulatory rate, a few 8 to 12 oocytes are fertilized and implanted, and just the embryos nearest to the cervix develop normally to term; the remaining embryos are resorbed. A balance between immunological Th1/Th2 processes\nbiased in favor of Th2 activity is needed for a successful gestation; prevalence of Th1\nprocesses is associated with fetal miscarriage. In domestic animals, 80% of embryo loss occurs at the peri-implantation period. Insufficient levels of uterine progesterone (P4) may\ninduce a considerable embryo loss. The aim of this investigation was to analyze the possible causes and mechanisms involved in the unusual embryo resorption process shown in L.\nmaximus and its relationship with immune response. In L. maximus decidualization and embryo resorption are found as two processes that occur in a diferred and reversed way along the uterine horn. The uterine area nearest the cervix showed the higher P4\nconcentration. The only embryo that is gestated to term showed the highest levels of P4 and\nestradiol (E2). This presence of high hormonal levels has its origin in the ascending trajectory of the uterine artery, a branch of iliac artery. During pregnancy, low levels of IL-10 were\nfound with a marked presence of IFN-? indicating an active Th1 immune response. Embryo\nresorption would be originated through apoptosis followed by necrosis, P4 levels being insufficient to trigger the immunoprotection of the embryo. The decrease of P4 during gestation would be responsible of embryo-harmful Th1 cytokine release. When pseudo\novulation takes place at mid-gestation, the formation of secondary CL induces a new rise of P4 which helps to rescue the only surviving foetus from resorption. In L. maximus, hormonal\nalterations during pregnancy induce changes in the immune system that generate the\nselective embryo resorption. Finally, the finding of penile spikes in males led to establish L. maximus as an ovulatory-induced species |
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