Preimplantation diagnosis.

Preimplantation embryonic biopsy and analysis offer couples at increased risk of having offspring affected with a genetic disorder the possibility of an early prenatal diagnosis. For many couples, this approach would avoid the issue of the selective termination of affected fetuses. Substantial advances have been made in the area of preimplantation diagnosis, but the possible difficulties with this approach cannot be ignored.     

Preimplantation genetic diagnosis

Preimplantation genetic diagnosis (PGD) is an evolving technique that provides a practical alternative to prenatal diagnosis and termination of pregnancy for couples who are at substantial risk of transmitting a serious genetic disorder to their offspring. Samples for genetic testing are obtained from oocytes or cleaving embryos after in vitro fertilization. Only embryos that are shown to be free of the genetic disorders are made available for replacement in the uterus, in the hope of establishing a pregnancy. PGD has provided unique insights into aspects of reproductive genetics and early human development, but has also raised important new ethical issues about assisted human reproduction.     

Responsible animal-based research: three flags to consider

Flagging experiments is one way to reduce the amount of nonhuman animal-based research. Experiments flagged for the following 3 characteristics are highly questionable: few or no citations received in the years following publication, thus having little or no influence on subsequent research; large numbers of animals used; and invasive procedures, such as injections or anesthesia and surgery, used on animals who were then allowed to recover enough to be tested in some way. Selecting and analyzing a sample of articles describing such experiments (such as those by authors at Canadian universities) determines which journals, author-affiliated universities, and acknowledged funding sources have the most flags. One could also assess the work of individual scientists. Using recommendations supplied, efforts to reduce the suffering of animals and the waste of tax dollars can then focus especially on these entities.     

Preimplantation Stress and Development

The developmental origins of health and disease hypothesis holds that inappropriate environmental cues in utero, a period marked by tremendous developmental sensitivity, facilitate cellular reprogramming to ultimately predispose disease in adulthood. In this review, we analyze if stress during early stages of development can affect future health. This has wide clinical importance, given that 5 million children have been conceived with assisted reproductive technologies (ART). Because the primary outcome of assisted reproduction procedures is delivery at term of a live, healthy baby, the postnatal effects occurring outside ofthe neonatal period are often overlooked. To this end, the long‐term outcome of ART is appropriately the most relevant concern of the field today. Evidence of adverse consequences is controversial. The majority of studies have concluded no obvious problems in IVF‐conceived children, although a number of isolated cases of imprinted diseases, cancers, or malformations have been reported. Given that animal studies suggest alteration of metabolic pathways following preimplantation stress, it will be of great importance to follow‐up ART individuals as they enter later stages of adult life. Birth Defects Research (Part C) 96:299–314, 2012. © 2013 Wiley Periodicals, Inc.     

Factors to consider in the verification of urinary biomarkers

正Dear Editor,Because urine is not under homeostatic control, changes occur earlier in urine than in blood; therefore, urine is a better source of early and sensitive biomarkers. The composition of urine is affected by a variety of factors, and urine is susceptible to complex changes. To exclude the impact of multiple factors, an appropriate animal model can be used in which control over all experimental factors is possible and each factor can be separately observed. Additionally, some common confounding factors should be considered when choosing disease candidate biomarkers for clinical verification.     

Preimplantation genetic diagnosis--an overview.

Since the early 1990s, preimplantation genetic diagnosis (PGD) has been expanding in scope and applications. Selection of female embryos to avoid X-linked disease was carried out first by polymerase chain reaction, then by fluorescence in situ hybridization (FISH), and an ever-increasing number of tests for monogenic diseases have been developed. Couples with chromosome rearrangements such as Robertsonian and reciprocal translocations form a large referral group for most PGD centers and present a special challenge, due to the large number of genetically unbalanced embryos generated by meiotic segregation. Early protocols used blastomeres biopsied from cleavage-stage embryos; testing of first and second polar bodies is now a routine alternative, and blastocyst biopsy can also be used. More recently, the technology has been harnessed to provide PGD-AS, or aneuploidy screening. FISH probes specific for chromosomes commonly found to be aneuploid in early pregnancy loss are used to test blastomeres for aneuploidy, with the aim of replacing euploid embryos and increasing pregnancy rates in groups of women who have poor IVF success rates. More recent application of PGD to areas such as HLA typing and social sex selection have stoked public controversy and concern, while provoking interesting ethical debates and keeping PGD firmly in the public eye.