Differences between NMRI and DBA/2J mice in the development of somites and susceptibility to methylnitrosourea-induced skeleton anomalies

ABSTRACT The development of DBA/2J mouse strain embryos is nearly 12 h - or 6 somite pairs - delayed as compared to the outbred NMRI mouse embryos of the same age on gestation days (GD) 8-12. To evaluate inter-strain differences in susceptibility to teratogens, dams were treated with methylnitrosourea (MNU, 5 mg/kg body weight i.p.) on defined gestation days (NMRI: GD 9, 91/2 or 10; DBA/2J: GD 10 or 101/2). Skeletal anomalies produced by MNU on both mouse strains varied with the GD of treatment. The pattern of anomalies produced by MNU on a given GD markedly differed between the two mouse strains, yet they were similar -with a few exceptions- when exposures at equivalent embryonic stages are compared. Findings from this study indicated that strain-dependent differences in the developmental stage of mouse embryos of the same gestational age occur, a possibility that has been often neglected when inter-strain differences in susceptibility to developmental toxicants are interpreted.

Evaluación de la embriotoxicidad de misoprostol utilizando el ensayo cultivo de embriones postimplantación / Evaluation of embryotoxicity of misoprostol using the whole embryo culture assay

Background: Approximately 15 percent of misoprostol-induced-abortions may not be successful, leading to in utero exposure to the drug and to the induction of a series of defects including central nervous system, limb and visceral defects. A commonproposal is that the drug causes disruption of the fetal vasculature leading to embryonic or fetal hypoxia. Aim: To evaluate the teratogenicity of misoprostol using the rat post-implantation embryo culture. Material and Methods: Rat embryos were collected at the beginning of organogenesis and cultured in rat serum containing misoprostol at concentrations of 200, 2,000 or 20,000 pg/ml. Functionality, morphology and morphometry parameters were evaluated. Results: Misoprostol induced a dose-dependent embryotoxic effect causing a decrease in embryo viability and function (poor vascular development and survival) and morphometry (alterations in branchial arches, heart and cephalic portions of the neural tube, among others). Conclusions: All the manifestations observed are indicative of the ability of misoprostol to directly induce developmental retardation and alterations.

Avances en la patogénesis de la embriopatía diabética / Recent advances in the pathogenesis of diabetic embryopathy

The congenital malformations in the off spring of diabetic mothers are the result of a multifactorial process. Susceptibility to the effects of maternal diabetes in the pathogenesis of these anomalies is influenced by the genetic background, indicating that there are polymorphic genes that modify the cellular response to hyperglycemia. The modifier genes for the teratogenic effect of maternal diabetes are yet unknown. An excessive glucose supply to embryonic tissues leads to a state of oxidative stress, which affects the expression of genes encoding scavenging enzymes such as super oxide dismutase (SOD) and catastases and activates development genes such as PAX3, involved in neural tube defects. Cell proliferation and cell death are important mechanisms underlying malformations in infants born to diabetic mothers. There is an increase of apoptotic Bax and caspase-3 proteins and a low expression of Bcl-Z ant apoptotic protein in embryos exposed to a diabetic environment. Hyperglycemia decreases intracellular levels of reduced GSH, prostaglandin EZ (PGEZ) and DNA synthesis in embryo's tissues. Understanding the molecular pathogenesis of diabetic embryopathy will allow the use of effective therapies for the prevention of teratogenic effects in diabetic mothers.

Effect of vitrification on viability and chromosome abnormalities in 8-cell mouse embryos at various storage durations

This study was desµgned to investµgate the effect of vitrification and post-thaw survival and chromosomal aberrations caused by vitrification of vitrified 8-cell mouse embryos in comparison with a controligroup. To this purpose the survival rate and the frequency of chromosomal aberrations were assessed in frozen-thawed 8-cell mouse embryos after various storage durations in the presence of ethyleneiglycol as cryoprotectant. eight-cell mouse embryos were obtained from NMRI mice 3 days after mating. Retrieved embryos were transferred to vitrification solution containing ethyleneiglycol as cryoprotectant, then transferred into a vitrification straw using standard technique, and vitrified in liquid nitrogen. Sixigroups of embryos according to storage duration (24 hours, 1 and 2 weeks, 1-6 months) were frozen. After appropriate storage periods embryos were thawed and studied for their viability 4-6 hours after thawing and intact embryos were transferred to fresh medium containing colcemid. After 48 hours, the embryos were fixed and studied for their chromosome abnormalities using Tarkowsky's drying technique. Results indicate that freezing affects the viability and chromosome structure of embryos when compared with the controligroup. Furthermore increasing the storage duration reduces the viability and increases the chromosome aberrations of embryos (such as aneuploidy and polyploidy). This result mµght indicate that the effects of vitrification on the cytoskeleton or other cellular organelle mµght produce chromosomal alterations leading to cell death.