DOUGLAS MARSLAND 119 



and determines when and where its essential gel structures shall be formed. 

 Apparently the metabolic energy which the cell diverts into the building of 

 its gel structures finally appears in the form of mechanical work during 

 the contraction phase of the sol-gel cycle. 



The importance of adenosine triphosphate (ATP) as an energy source 

 in many tissues naturally suggested that this important metabolite might 

 contribute energy to the sol-gel cycle in cells generally. Indeed, con- 

 siderable evidence in this regard has begun to come from several direc- 

 tions. Runnstrom (29) showed that egg cells immersed in ATP solution 

 became more resistant to hypotonic cytolysis, which seemed to be related 

 to a gelling effect upon the cytoplasm. Kriszat (8, 9) found that ATP 

 distinctly modifies the movements of Amoeba proteus (Chaos chaos). 

 Loewy (16) extracted an actomyosin type of protein from the amoeboid 

 slime mold, Pelomyxa, and showed that this preparation displayed con- 

 siderable changes in its gelational structure in the presence of ATP and 

 related compounds. H. H. Weber demonstrated that glycerol extracted 

 fibroblasts underwent a quick and forceful contraction of their elongate 

 pseudopodia when treated with ATP solutions and that this remarkable 

 contraction could be stopped quickly and reversibly when the cells 

 were treated with mersalyl acid (salyrgan), a compound that inhibits the 

 hydrolytic splitting of the high energy bonds of ATP (32). And finally, 

 Hoffman-Berling (6) found that fibroblasts killed and glycerol-extracted 

 just at the beginning of telophase, when shallow cleavage furrows first 

 appeared, showed a remarkable deepening of the furrows — virtually to 

 the point of complete cleavage — when appropriate concentrations of ATP 

 were added to the immersion medium. Accordingly, adenosine triphosphate 

 was chosen as the first metabolite to be investigated in relation to the 

 temperature-pressure parameters of the plasmagel system; and mersalyl 

 acid (salyrgan) was used as an inhibitor of the ATP system. 



ATP Effects on Furrowing Strength. Both Arbacia and Chaetopterus 

 eggs displayed a distinct increase in the strength of the furrowing reaction 

 as a result of adding ATP (0.0005 molal ) to the sea water, starting approxi- 

 mately 25 minutes prior to the onset of first cleavage. This may be seen 

 in figures 7 and 8 which show that the minimum pressures required to block 

 the furrows are distinctly higher at each of the different temperatures. 

 At atmospheric pressure also, the additional ATP enabled the eggs to 

 complete their furrowing at temperatures which ordinarily are too low 

 to allow for successful cleavage. Specifically for Arbacia, more than 90% 

 of the ATP-treated eggs achieve successful furrowing at 9°C (compared 

 to 10% for the untreated specimens) ; and for Chaetopterus at 17°C, 

 89% of the treated eggs went through (compared to 4% in the untreated 

 specimens). In fact, to achieve an equivalent low temperature inhibition 



