Abstract
Study of chick embryos in early stages of development has shown that the rate of cell multiplication slows as organ differentiation begins. We calculated the rate of doubling of cells in the endoderm/mesoderm layer from Hamburger-Hamilton stage 5 to stage 12+ (head-process to 17-somite stages, 24-47 hours of incubation). Equally-sized tritiated-thymidine-labeled transplants were excised from the endoderm/mesoderm layers of donor embryos, and placed in homologous positions in 12 pairs of recipient embryos. One recipient of each pair (the control embryo) was fixed as soon as the transplant had healed, and the other was reincubated for 4-23 hours before fixing. All embryos were embedded in paraffin, serially sectioned and mounted. The slides were radioautographed with exposure times of 5-42 days, and the labeled cells in each embryo were counted. In each pair of embryos, the number of labeled cells in the control embryo was compared to the number of labeled cells in the embryo reincubated for a longer period. The resulting ratios were plotted on a graph against the number of hours of reincubation; the ratios were grouped at 4, 15-16, 18-18.5 and 21.5-23 hours. The resulting growth curve indicated that the number of endoderm/mesoderm cells had doubled at five hours of reincubation (approximately the one-somite stage) and again 12 hours later. These multiplication rates are within the range of rates calculated by previous investigators from mitotic or radioactive indices.
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Rosenquist, G. 1216 MULTIPLICATION RATES OF ENDODERM/MESODERM IN HEAD PROCESS-TO 17-SOMITE-STAGE CHICK EMBRYOS. Pediatr Res 15 (Suppl 4), 645 (1981). https://doi.org/10.1203/00006450-198104001-01242
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DOI: https://doi.org/10.1203/00006450-198104001-01242