Updating embryonic ontogenesis in Araucaria angustifolia: from Burlingame (1915) to the present.

This study addresses gaps in our understanding of pre-fertilization and archegonia development and reinterprets embryonic ontogenesis from Burlingame (Bot Gaz 59:1-39, 1915) to the present based on timescale and structural features allowing us to determine functionally and developmentally accurate terminology for all these stages in A. angustifolia. Different from previous reports, only after pollination, pre-fertilization tissue development occurs (0-13 months after pollination (MAP)) and gives rise to a mature megagametophyte. During all this period, pollen is in a dormant state at the microphyla, and pollen tube germination in nucellus tissue is only observed at the stage of archegonia formation (13 MAP) and not at the free nuclei stage as reported before. For the first time, 14 months after pollination, a fertilization window was indicated, and at 15 MAP, the polyzygotic polyembryony from different archegonia was also seen. After that, subordinated proembryo regression occurs and at least three embryonic developmental stages of dominant embryo were characterized: proembryogenic, early embryogenic, and late embryogenic (15-23 MAP). Along these stages, histochemical and ultrastructural analyses suggest the occurrence of cell death in suspensor and in cap cells of dominant embryo that was not previously reported. The differentiation of meristems, procambium, pith, and cortex tissues in late embryogenic stage was detailed. The morphohistological characterization of pre-fertilization and embryonic stages, together with the timescale of megastrobili development, warranted a referential map of female reproductive structure in this species.

Comparación entre el clivaje temprano y el estadio pronuclear como parámetros de referencia para inducir el embarazo en pacientes ovoreceptoras en Cali (Colombia) / Comparing early cleavage and pronuclear state as reference parameters for inducing pregnancy in embryo implantation patients in Cali, Colombia

Introducción: algunos autores han propuesto métodos no invasivos que se centran en el clivaje temprano del estadio de dos células a las 25 y 27 horas luego de ocurrida la inseminación, los cuales son aplicables a los programas de fertilización in vitro que aumentan la probabilidad de implantación y embarazo. Objetivo: comparar la tasa de embarazo en pacientes ovoreceptoras con embriones provenientes de clivaje temprano con respecto a la del estadio pronuclear. Metodología: se realizó un estudio de cohorte retrospectivo, en el cual se incluyeron a las pacientes ovoreceptoras que asistieron entre abril de 2004 y diciembre de 2007 al Centro de Biomedicina -FECUNDAR en Cali (Colombia) por presentar baja respuesta al ciclo de estimulación ovárica controlada, factor edad, falla ovárica o por ser pacientes subrogadas o gestacionales. El tamaño de la muestra se dividió de la siguiente manera: el porcentaje de embarazo esperado para el grupo de clivaje temprano-singamia (grupo 1) fue 79% (36 pacientes) mientras que el porcentaje de embarazo para el grupo pronuclear (grupo 2) llegó a ser 21% (9 pacientes). A partir de la obtención de estos datos, se determinaron las tasas de implantación y de embarazo y se compararon los dos grupos por medio de la prueba Chi-cuadrado (X2). Resultados: de un total de 289 cigotos, se incluyeron 183 que cumplieron los parámetros propuestos, entre embriones provenientes de clivaje temprano (CT), singamia (S) y estadio pronuclear (PN) a las 25 y 27 horas posinseminación. De este total, 79% provenían del estadio clivaje temprano-singamia y 21% del estadio pronuclear. El promedio de embriones transferidos a las pacientes ovoreceptoras fue tres embriones, la edad promedio fue 38 años, la tasa de embarazo obtenida al transferir los embriones provenientes de clivaje temprano fue 44% en comparación con 41% para la transferencia de los embriones no clivados a las 25 horas posinseminación. Finalmente, no se encontraron diferencias significativas en la obtención del embarazo. Conclusión: bajo las condiciones del estudio, el resultado muestra que no hay diferencias en la tasa de éxitos para ambos procedimientos.

Introduction: some authors have proposed that non-invasive embryo implantation methods (based on early cleavage or pronuclear stage for two cells 25 and 27 hours post-insemination) are applicable to in vitro fertilisation programmes, thereby increasing the probability of implantation and pregnancy. Objective: comparing pregnancy rates in patients implanted with embryos originating from early cleavage to those from the pronuclear stage. Methodology: a retrospective cohort study was carried out. Embryo implantation patients were included who had been attending the FECUNDAR -Biomedicine Centre in Cali, Colombia, from April 2004 to December 2007 who presented a poor response to the controlled ovarian stimulation cycle, age factor and/or ovarian failure and pregnancy substitute patients. The sample consisted of 45 patients; 36 patients (79%) were expected to become pregnant in the early-syngamy and cleavage group (group 1) and 9 patients (21%) in the pronuclear group (group 2). Implantation and pregnancy rates were determined and the Chi-square (X2) test was used for comparing both groups. Results: 183 of the 289 zygotes complied with the proposed parameters (i.e. embryos from early cleavage, syngamy and pronuclear stage 25 and 27 hours post-insemination); 79% of these 183 came from the early cleavage and syngamy stage and 21% from the pronuclear stage. Three embryos on average were transferred to embryo implantation patient; average age was 38, the pregnancy rate obtained when transferring early cleavage embryos was 44% compared to 41% for non-cleaved embryo transfer 25 hours post-insemination. No statistically significant differences were found regarding how pregnancy was induced. Conclusion: equal success rates were obtained for both procedures in the given study conditions.