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On page 510, a paper by Sun et al., "Cytoplasmic Impact on Cross-Genus Cloned Fish Derived from Transgenic Common Carp (Cyprinus carpio) Nuclei and Goldfish (Carassius auratus) Enucleated Eggs," reports an effect of the recipient cytoplasm on a phenotypic characteristic of offspring produced by interspecific cloning in fish. In this remarkable study, nuclei from common carp embryos were transplanted in the cytoplasm of a distantly related goldfish egg, which had been enucleated. The offspring mostly resembled the carp species that provided the nuclei. Surprisingly, however, the number of vertebrae in the clones was that of the species providing the recipient egg. Thus the egg cytoplasm, and not the genetic code of the transplanted nucleus, affected this skeletal characteristic in the offspring. Although the mechanism remains to be resolved, it is possible that factors affecting the timing of early development is determined by maternal factors and that this timing, a so-called "segmentation clock," is somehow responsible for determining the number of somites and, therefore, the vertebral number.
A Model for Implantation: Co-Culture of Blastocysts and Uterine Endometrium in Mice. Yi Tan, Dongmei Tan, Mingzhong He, Meili Gu, Zhibiao Wang, Guoqing Zeng, and Enkui Duan. Biol Reprod 2005; 72:556–561. published online 10 November 2004; 10.1095/biolreprod.104.032821
On page 556, a paper by Tan et al., "A Model for Implantation: Co-Culture of Blastocysts and Uterine Endometrium in Mice," addresses the important issue of limitations in embryo implantation research due to the lack of an available in vitro model that replicates embryo-uterine interactions. This study used intact mouse uterine endometrium from Day 4 of pregnancy and blastocysts in direct contact for co-culture experiments. The authors demonstrated that embryos attached to the uterine endometrium and displayed partial invasion into the endometrial stroma, but the model had the limitation of not supporting trophoblast outgrowth. Nonetheless, this model can be applied to advance experimental analysis of implantation in mammals. It offers great promise for future adaptation to support attachment, adhesion, and invasion of endometrium by blastocysts. Together, these represent the major phases of conceptus-endometrial interactions during the peri-implantation period of pregnancy.
Reduced Utero-Placental Perfusion Alters Uterine Arcuate Artery Function in the Pregnant Sprague-Dawley Rat. Cindy M. Anderson, Faye Lopez, Hai-Ying Zhang, Kristin Pavlish, and Joseph N. Benoit. Biol Reprod 2005; 72:762–766. published online 24 November 2004; 10.1095/biolreprod.104.036715
On page 762, a paper by Anderson et al., "Reduced Utero-Placental Perfusion Alters Uterine Arcuate Artery Function in the Pregnant Sprague-Dawley Rat," contributes significant new information indicating that reduced utero-placental perfusion has a major role in the etiology of preeclampsia and events leading to hypertension. This study focused on responsiveness of uterine arcuate arteries, which exhibited maximal tension in response to phenylephrine, potassium chloride, and angiotensin II and reduced responsiveness to endothelium-dependent relaxation in response to acetylcholine and the calcium ionophore A23187. Using this rat model, it was found that fetal growth restriction resulted from endothelium-dependent impaired relaxation in uterine arcuate arteries; this led to reduced placental perfusion.
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