Changes in the proportion of free and bound ribosomes in the syncytiotrophoblast of normal human placenta during pregnancy.
Samples of normal human placental tissue from the first and second trimester and the end of pregnancy were processed for electron microscopy. The ratio of free to bound ribosomes in the syncytiotrophoblast was determined by the point-counting method in photographs giving a 45,000-fold final magnification. The ratio of free to bound ribosomes was found to be significantly higher at 9-11 weeks than at 6-8 weeks and to be significantly lower at 12-14 weeks than at 9-11 weeks. No significant differences were found between the 12th to 14th week and the 20th to 25th week. These data were compared with the ratio of free to bound ribosomes in different regions of the placenta at the end of pregnancy.
Department of Embryology, Faculty of Medicine, Charles University, Prague.
M
M
Jirkovská
D005260:Female; D006801:Humans; D011247:Pregnancy; D012270:Ribosomes / Q000648:ultrastructure*; D014327:Trophoblasts / Q000648:ultrastructure*