. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. URETHAN INHIBITION OF CLEAVAGE 395 alone. Ribonuclease ("Worthington 3X," crystals) had no effect on the urethan- treated eggs. In no case, however, was there more than a temporary recover}-. The eggs divided a few times to produce grape-like clusters of cells but did not develop into larvae. 100 H 80- UJ > LU _1 O 60- 40- 20- X control O • O 1% urethan + trypsin, .1 mg/ml + chymotrypsin, " + lipase,. HOURS AFTER INSEMINATION FIGURE 4. Attempt to overcome urethan inhibition of division by trypsin, chymotryp
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. URETHAN INHIBITION OF CLEAVAGE 395 alone. Ribonuclease ("Worthington 3X," crystals) had no effect on the urethan- treated eggs. In no case, however, was there more than a temporary recover}-. The eggs divided a few times to produce grape-like clusters of cells but did not develop into larvae. 100 H 80- UJ > LU _1 O 60- 40- 20- X control O • O 1% urethan + trypsin, .1 mg/ml + chymotrypsin, " + lipase,. HOURS AFTER INSEMINATION FIGURE 4. Attempt to overcome urethan inhibition of division by trypsin, chymotrypsin, and lipase. Eggs were exposed to urethan-containing solutions 5 minutes after insemination. DISCUSSION Several workers have attempted to explain the action of urethan as a mitotic poison in terms of an inhibition of energy metabolism (McElroy, 1947; Fisher and Henry, 1944; Warburg. 1956). Bullough (1952) suggested that the cell accumulates an energy reservoir during interphase by means of respiration and glycolysis, sufficient to maintain itself during the entire division process. Until this storage is completed the division does not begin, but once begun a division is completed at normal speed in almost any circumstance short of the death of the cell itself. Bullough's hypothesis is based, in part, on observations that the ap- plication of many physical and chemical inhibitors to cells during mitosis or cytokinesis is without effect on that division but blocks subsequent Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Marine Biological Laboratory (Woods Hole, Mass. ); Marine Biological Laboratory (Woods Hole, Mass. ). Annual report 1907/08-1952; Lillie, Frank Rattray, 1870-1947; Moore, Carl Richard, 1892-; Redfield, Alfred Clarence, 1890-1983. Woods Hole, Mass. : Marine Biological Laborat
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