190 CELLULAR METABOLISM 



nuclear constituents. The same is true for mustard gas, ethylenimines, 

 and numerous other compounds (3, 110, 114). The extent of the inter- 

 ference due to ionizing radiation depends partly on the dose and partly 

 on the density of ionization temporarily produced in the tissue. Inter- 

 ference with cell division may result, followed by mutation and cell 

 degeneration. 



The formation of desoxyribonucleoprotein molecules involves the par- 

 ticipation of histone or other proteins, of desoxy pentose, of purine, of 

 pyrimidine, and of phosphate groups. It is easiest to assume that the 

 assembly and possibly even the synthesis of some of the constituents 

 involved in the synthesis take place at an interphase. The synthetic 

 process requires energy expenditure, the energy most likely being 

 supplied through carbohydrate metabolism. Thus, in addition to syn- 

 thesis of desoxyribonucleoproteins, the above-mentioned constituents 

 require the presence of sugar (glycogen), oxygen, and an intact enzyme 

 system. 



Energy Supply and Mitotic Division 



Bullough (4) in the study of diurnal mitotic rhythm of the female 

 mouse has shown that mitosis could not occur unless there was an ade- 

 quate concentration of sugar or glycogen in the tissue. He suggested 

 that the function of this carbohydrate is to supply the energy for cell 

 division and showed that in the vagina of the mouse the glycogen dis- 

 appears as mitosis proceeds. Sugar lack, however, depresses mitosis. 

 In conditions of sudden acute hypoglycemia induced by insulin, all those 

 divisions which had already reached the prophase were found to be nor- 

 mally completed. From these observations it follows that the depressing 

 effect of sugar lack is felt only during the transition of a resting cell 

 to the prophase. Bullough defines the precise time at which the glucose 

 and oxygen exert their effect. It is a matter of minutes before the pro- 

 phase becomes recognizable, in a stage of division which may be called 

 the antiphase. Any division which has proceeded beyond the antiphase 

 can pass to completion in the absence of both glucose and oxygen. Also, 

 almost all the mitoses present at the time of death due to hypoglycemia 

 continue without interruption and not even at a significantly delayed 

 rate (5). That cells which have passed through the critical phase com- 

 plete mitosis was observed by Koller (122). 



In conditions of sugar lack few cells enter prophase but those which 

 do so complete their division at about normal speed. Conversely, it 

 has also been shown by Bullough that with an abundance of sugar a 

 greater number of resting cells were stimulated to divide, although here 

 too the time for a mitotic division remained normal. Hence, it may be 



