John R. G. Challis
University of Toronto
392 Papers
5.8K Citations
John R. G. Challis is an academic researcher from University of Toronto. The author has contributed to research in topics: Fetus & Placenta. The author has an hindex of 70, co-authored 392 publications. Previous affiliations of John R. G. Challis include McMaster University & Canadian Institutes of Health Research.
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Papers
Activation of the hypothalamic-pituitary-adrenal axis with repetitive umbilical cord occlusion in the preterm ovine fetus.
Lucy R. Green,Lucy R. Green,Y. Kawagoe,Y. Kawagoe,Mhoyra Fraser,Mhoyra Fraser,John R. G. Challis,John R. G. Challis,B. S. Richardson,B. S. Richardson +9 more
TL;DR: Repetitive umbilical cord occlusion in the preterm ovine fetus resulted in the activation of the HPA axis, with increased adrenocortical responsiveness over time, and involved differential regulation of POMC mRNA expression in the pars distalis and pars intermedia of the pituitary, but with no change in GR.
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Administration of extra-amniotic arachidonic acid and the suppression of uterine prostaglandin synthesis during pregnancy in the rhesus monkey
Jeffrey S. Robinson,R. L. K. Chapman,John R. G. Challis,Murray D. Mitchell,Geoffrey D. Thorburn +4 more
TL;DR: After extra-amniotic treatment of pregnant rhesus monkeys premature parturition was induced, it is suggested that the availability of substrate, arachidonic acid, is not a major factor governing the control of PG synthesis but that the latter is suppressed during pregnancy.
Increased uteroplacental production of prostaglandin-e2 during ethanol infusion
A. D. Bocking,K. R. Sinervo,Graeme N. Smith,Lesley Carmichael,John R. G. Challis,D. M. Olson,James Brien +6 more
TL;DR: The hypothesis that the placenta is the major source of the elevated fetal and maternal plasma PGE2 concentrations produced in pregnant sheep by maternal ethanol administration is supported.
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Steroid modulation of pregnenolone to progesterone conversion by human placental cells in vitro
TL;DR: It is concluded that this system is a useful model for studying progesterone production by human placental tissue, and that placental progestersone production may be significantly influenced by the presence of other steroid hormones.
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