Ill 



CELL GROWTH AND MULTIPLICATION 



l6l 



Na-iodoacetate leads to disturbance of mitosis (pyknosis) (O'Connor, 1950a, b). 

 Nowinski (1955) investigated the connection between cell metabolism and 

 multiplication by comparing homologous cell populations which grow rapidly 

 or slowly (leg and wing of the embiyonic chicken). According to expectation, there 

 is an absolute increase of O2 consumption and CO2 production with the increase 

 in mass but Qq^ (calculated on the basis of 100 [xg DNA) remains constant, and 

 there is no significant difference between leg and wing. In contrast, anaerobic 

 glycolysis shows a continuous decrease and a significant drop between the fifth 

 and sixth day. A significant difference between wing and leg is found on the 

 sixth and seventh day. It is concluded from the parallelism between high growth 

 rate and anaerobic glycolysis that the latter is connected with multiplicative 

 (exponential) growth. 



(d) Mathematical theory of cell growth 



It is a basic question why i. a cell does not surpass a certain limiting size in spite 

 of its continuous assimilation (principle of constant cell size) and 2. which factors 

 lead to division when this limiting size is reached. According to Linzbach (1955), 

 the cause "why cells during growth do not surpass a certain size, as well as the 

 causes which lead to mitosis, are unknown". Even though no explanation in detail 

 is possible at present, some model conceptions can be advanced in this respect. 



Some answer to the first qviestion can be given on the basis of the consideration 

 that the cell is an open system maintaining itself in continuous degradation and 

 synthesis of building materials. The growth of micro-organisms presents arguments 

 for the thesis that growth is regulated by a surface-volume ratio. There is a basic 

 difference in the growth curve of rodlike and spherical microorganisms (Schmal- 

 hausen and Bordzilowskaja, 1930; Bayne-Jones and Adolph, 1932; Bertalanffy, 



150 160 170 10 20 30 40 50 

 Time after inoculation in min 



170 190 210 230 250 270 290 

 Time after inoculation in min 



Fig. 5. Growth of micro-organisms, a Growth of individual cells of Bac. megatherium. 

 h Growth of yeast cells. Rod-like bacteria (a) show simple exponential growth (Type II); 

 in spheroid micro-organisms {b) (yeast, micrococci) growth is determined by the surface- 

 volume ratio (Type I). From the micro-cinematographic measurements of Bayne-Jones 

 and Adolph (1932) calculated by Bertalanffy, 1951a. 



Literature p. 253 



