Adaptation of cultured human lymphoblasts to growth in citrulline |
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Authors: | L B Jacoby |
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Institution: | Department of Zoology, University of California, Berkeley, Calif. 94720, USA |
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Abstract: | DNA synthesis is initiated in unfertilized sea urchin eggs (Strongylocentrotus purpuratus and Lytechinus pictus) by exposing them to NH4OH-sea water (ordinary sea water titrated to pH 9–9.1 with NH4OH). The eggs are considered to be unfertilized eggs by visual and electro-biological criteria and because they can later be fertilized and then do give visible and electrobiological fertilization reactions. The incorporation of 3H-thymidine proceeds in rounds, the magnitude increasing in successive rounds. It is also reported that the treatment with NH4OH activates the uptake of thymidine by the eggs, although the internal thymidine builds up more slowly in unfertilized eggs treated with NH4OH than it does in fertilized eggs. The magnitude of the incorporation of exogenously supplied labelled thymidine into DNA is lower in the NH4OH-treated unfertilized eggs than in normal fertilized eggs. This difference is not attributed to differences in the amount of DNA synthesized and the explanation is sought in thymidine uptake and nucleotide pathways. |
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