The
14C incorporation into purine bases of fetal brains was investigated when DL-serine-3-
14C, L-histidine-2-
14C, or formate-
14C was injected intraperitoneally to dams with or without pre-treatment with aminopterin. The radioactivity of
14C in fetal brain tissues was estimated on the 18th day of gestation. On the 11th day of gestation, DL-serine-3-
14C, L-histidine-2-
14C, or formate-
14C was injected to dams intraperitoneally. In the case of aminopterin treatment, aminopterin, 0.076mg/kg, was injected intraperitoneally to dams on the 10th day of gestation.
The results in these experimental conditions showed that the
14C incorporation from formate-
14C into adenine of fetal brains and that from DL-serine-3-
14C into guanine of fetal brains were impaired significantly by aminopterin injection to dams prior to injections of the labeled materials.
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