THE ROLE OF DNA SYNTHESIS IN THE DETERMINATION OF AXIAL POLARITY OF REGENERATING PLANARIANS

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Abstract
1. Levels of chloramphenicol which can produce bipolar heads in regenerating planarians were found to inhibit severely the synthesis of both DNA and RNA. A shorter period of exposure to chloramphenicol, which did not affect the polarity of the regenerating worms, produced only a slight inhibition of DNA synthesis. 2. Incubation of blastemata and adjacent areas of regenerating planarians with labeled CO2 for periods of 2, 4, 6 and 24 hours revealed a maximal stimulation of DNA at 4-7 hours and of RNA at 6-9 hours after the worms were cut. It is at this time that the blastemata destined to form heads attain a higher level of DNA and RNA synthesis than the blastemata which will form tails. The maximal stimulation of protein synthesis occurred 24-27 hours after cutting the worms. 3. The necessity of obtaining a severe inhibition of DNA synthesis with chloramphenicol in order to produce bipolar heads in regenerating worms, as well as the sequential nature of DNA, RNA and protein synthesis in the regeneration blastemata, suggests that the stimulation of DNA synthesis is involved in the establishment of polarity of regenerating worms. These patterns of DNA synthesis may reflect the incidence of cell division during this period.