Effects of salinity on pre- and post-fertilization developmental events in the mangrove oyster Crassostrea rhizophorae (GUILDING, 1828).

The mangrove oyster Crassostrea rhizophorae is identified as a potentially valuable species for tropical aquaculture, however, information on the physiological mechanisms of reproduction under laboratory conditions for this species is limited. This study investigated the effects of salinity at different concentrations (15, 20, 25, 30, 35, and 40 g/L) on the induction of germinal vesicle breakdown (GVBD) of oocytes obtained through stripping, the release of polar bodies (PB1 and PB2), and the larval development of the mangrove oyster. The results revealed a relationship between salinity and the percentage of GVBD, with the most effective range being 30-40 g/L within the hydration time frame between 70 and 120 min. The release of 50 % of PB1 was detected within this salinity range, while for the release of 50 % of PB2, the saline treatments of 35 and 40 g/L showed the best results. Overall, the salinity range of 30-40 g/L is suggested as the most suitable of polyploidy induction methodologies through the retention of PB1 or PB2. Regarding larval hatching, while salinities between 25 and 40 g/L presented similar percentages, at 15 g/L no hatching was observed. This study demonstrated that salinity is a key factor in early pre- and post-fertilization stages for the successful reproduction of mangrove oyster in hatcheries and that the percentages of oocyte maturation and artificial fertilization can be optimized by adjusting salinity.

Effects of salinity on pre- and post-fertilization developmental events in the clam Anomalocardia flexuosa (Linnaeus, 1767).

The knowledge about the effect of salinity on the physiological mechanism of bivalve reproduction is fundamental to improve production strategies in hatcheries. The present work evaluated the influence of different salinity concentrations (15, 20, 25, 30, 35 and 40 g⋅L-1) on pre- and post-fertilization development processes in the clam, Anomalocardia flexuosa, oocytes obtained by stripping. Salinity directly interfered with the germinal vesicle breakdown (GVBD) rate and in the cellular stability of unfertilized oocytes. Salinity concentrations between 30 and 35 g⋅L-1 provided better percentages of stable GVBD within 120 min, and incubation of oocytes in the salinity range of 30-35 g⋅L-1 for a time interval of 80-120 min provided > 80% GVBD. In the post-fertilization analysis, salinity affected the rate of the extrusion of the first and second polar bodies (PB1 and PB2). The release of 50% of the PBs was faster at a salinity of 35 g⋅L-1, with an estimated time of 10 min for PB1 and 30 min for PB2. Thus, chromosome manipulation methodologies aiming triploids should be applied at 35 g⋅L-1 salinity, with application of post-fertilization shock before 10 min for PB1 retention or before 30 min for PB2 retention.

Effects of salinity on pre- and post-fertilization developmental events in the clam Anomalocardia flexuosa (Linnaeus, 1767)

The knowledge about the effect of salinity on the physiological mechanism of bivalve reproduction is fundamental to improve production strategies in hatcheries. The present work evaluated the influence of different salinity concentrations (15, 20, 25, 30, 35 and 40 g⋅L−1) on pre- and post-fertilization development processes in the clam, Anomalocardia flexuosa, oocytes obtained by stripping. Salinity directly interfered with the germinal vesicle breakdown (GVBD) rate and in the cellular stability of unfertilized oocytes. Salinity concentrations between 30 and 35 g⋅L−1 provided better percentages of stable GVBD within 120 min, and incubation of oocytes in the salinity range of 30-35 g⋅L−1 for a time interval of 80-120 min provided > 80% GVBD. In the post-fertilization analysis, salinity affected the rate of the extrusion of the first and second polar bodies (PB1 and PB2). The release of 50% of the PBs was faster at a salinity of 35 g⋅L−1, with an estimated time of 10 min for PB1 and 30 min for PB2. Thus, chromosome manipulation methodologies aiming triploids should be applied at 35 g⋅L−1 salinity, with application of post-fertilization shock before 10 min for PB1 retention or before 30 min for PB2 retention.(AU)

State of the art of nuclear transfer technologies for assisting mammalian reproduction.

The transfer of nuclear genomic DNA from a cell to a previously enucleated oocyte or zygote constitutes one of the main tools for studying epigenetic reprogramming, nucleus-cytoplasm compatibility, pluripotency state, and for genetic preservation or edition in animals. More than 50 years ago, the first experiences in nuclear transfer began to reveal that factors stored in the cytoplasm of oocytes could reprogram the nucleus of another cell and support the development of an embryo with new genetic information. Furthermore, when the nuclear donor cell is an oocyte, egg, or a zygote, the implementation of these technologies acquires clinical relevance for patients with repeated failures in ART associated with poor oocyte quality or mitochondrial dysfunctions. This review describes the current state, scope, and future perspectives of nuclear transfer techniques currently available for assisting mammal reproduction.

Live births after polar body biopsy and frozen-thawed cleavage stage embryo transfer: case report.

Pre-implantation genetic diagnosis (PGD) or screening (PGS) technology, has emerged and developed in the past few years, benefiting couples as it allows the selection and transfer of healthy embryos during IVF treatments. These techniques can be performed in oocytes (polar-body biopsy) or embryos (blastomere or trophectoderm biopsy). In this case report, we describe the first two live births to be published in Brazil after a polar-body (PB) biopsy. In case 1, a 42-year-old was submitted to PB biopsy with PGS due to advanced maternal age and poor ovarian reserve. Five MII oocytes underwent first and second polar body biopsy and four cleavage embryos were cryopreserved. The PGS analysis resulted in two euploid embryos (next generation sequence). A frozen-thawed embryo transfer (FET) was performed after endometrial priming and a healthy baby was delivered after a cesarean section (37 weeks, female, 3390g, 47.5 cm). In case 2, a 40-year old patient with balanced translocation and poor ovarian response was submitted to PB biopsy. Two MII oocytes underwent first and second polar body biopsy and two embryos were cryopreserved in cleavage stage. The analysis resulted in one euploid embryo that was transferred after endometrial priming. A preterm healthy baby (34 weeks, female, 2100g, 40 cm) was delivered via cesarean section. In conclusion, although the blastocyst biopsy is the norm when performing PGS/PGD during IVF treatments, other alternatives (as PB biopsy) should be considered in some specific situations.

Técnicas emergentes en medicina reproductiva: diagnóstico cromosómico del primer corpúsculo polar del ovocito / Emerging techniques in reproductive medicine: chromosomal diagnosis of the oocyte first polar body

El Diagnóstico Genético Preimplantacional (PGD) se ha convertido en una herramienta de rutina para la detección de anormalidades cromosómicas o genéticas, en muchos países del mundo. Se han reportado más de 20.000 ciclosde PGD, desde su desarrollo hace más de 20 años, habiendo nacido más de 4.000 niños hasta el año 2007. En Chile, esta técnica es realizada por la Unidad de Medicina Reproductiva de Clínica Las Condes, y se realiza sólo en la variante previa a la fecundación, en donde se biopsia el primer corpúsculo polar y sólo se insemina a los ovocitos encontrados cromosómicamente sanos. Las indicaciones más comunes para este tratamiento son: 1) evitar el aborto en pacientes con aborto recurrente sin explicación anatómica ni clínica; 2) mejorar las tasas de implantación en mujeres mayores de 37 años con antecedentesde procedimientos anteriores en los que se transfirieron embriones de buena calidad; 3) evitar el nacimiento deniños con enfermedades de origen cromosómico en mujeres mayores de 39 años.

Pre-implantational Genetic Diagnosis has become a common tool in most countries of the world. In almost 20 years since its development, it has been reported more than 20,000 cycles of PGD and till 2007, more than 4,000 children have been born. In Chile, this technique is done by the Unit of Reproductive Medicine of Clínica Las Condes. It is done only in the mode previous to fertilization. In where we study polar bodies and only chromosomically healthy oocytes are inseminated. The most common indications for this treatment are: 1) to avoid abortions in patients with recurrent abortion without anatomical nor clinical explanation; 2) to improve implantation rates in women older than 37 years of age, with previous procedures in which good quality embryos were transferred; 3) to avoid birth of children with diseases of chromosomal origin in women over 39 year of age.