Development of explanted rat embryos in circulating medium

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Abstract
A method is described for growing post-implantation rat embryos, explanted with their embryonic membranes, in circulating medium. Embryos cultured by this method grow to about five times the maximum weight attainable in static medium in watch-glasses. Homologous serum, equilibrated with 95 % O2/5 % CO2, has proved to be a satisfactory culture medium, and it makes no difference whether the serum is from pregnant or non-pregnant animals. Good development is obtained in 2–3 ml serum per embryo, and little or no improvement is gained by using more than this. About 50 % of embryos explanted at 7–15 somites develop to 30-to 35-somite stages and synthesize O·3–O·5mg protein during the period in culture. Further development of these embryos appears to be prevented by the abnormal formation of a large blood vessel bypassing the allantoic placenta. About 50 % of embryos explanted at 22–28 somites develop to 40–46 somite stages and synthesize about 1–1·5 mg protein. Embryos explanted at more than 45 somites do not develop. The rate of flow of the circulating medium is critical. Embryos explanted at 7–15 somites develop much better in serum flowing at 1 ml/min (= 2 cm/min through the embryo chamber) than at 10 ml/min. Embryos explanted at 22–28 somites develop much better in serum flowing at > 10 ml/min than at 1 ml/min.