EXPERIMENTAL ANALYSIS 



has been interfered with'. That reversible migration of potassium 

 across the cell membrane may occur during cell division is shown by the 

 observations of Oddo and Esposito.^"^^ 



It is desirable to see whether this parallel can be extended further. 

 Davson and Danielli^"" showed that a number of haemolytic agents 

 in concentrations below the lytic threshold induce an abnormally 

 high permeability of the erythrocyte to potassium, but their effects 

 on mitosis in tissue culture have not yet been investigated. It would 

 also be desirable to examine whether substances which exert an 

 action at other points in the mitotic cycle have any effect on the 

 ionic equilibria of the red cells. Where there is normally a difference in 

 concentration of potassium on either side of the erythrocyte membrane, 



Figure 65 Number of mitoses in the fragments 

 of the ears of mice severed at 13.00 hours, 

 and maintained in physiological salt 

 solutions. From Bullough^"* {By courtesy, 

 Proc. roy. Soc. B). 



100 n.OO 15.00 - 16.00 

 Time of day 



77.00 



18.00 



it is beheved to be maintained by a metabolic process such as glycolysis 

 which absorbs energy, although the 'pre-haemolytic state' (Davson 

 and Danielli^""), is not necessarily related to this. The efTect of 

 fluoride on permeability to potassium is probably an indirect one; 

 Davson^"^ has suggested that intermediate products of glycolysis, 

 accumulating at the cell membrane, may be responsible for the in- 

 crease in permeability. The effects of iodoacetate and fluoride in 

 preventing the entry of cells into prophase may not be due to the 

 inhibition of glycolysis alone; other agents which exert this efTect on 

 the tissue culture are not known to affect carbohydrate metabolism. 



In a series of papers, Bullough^"^"^^^ has produced evidence that the 

 entry into mitosis of epithelial cells of the ear of the mouse is dependent 

 on the amount of carbohydrate within the tissues. Once a cell in the 

 epithelium is in prophase, it can continue division even when the ear 

 is severed from the animal and kept in physiological salt solution. If the 

 medium contains glucose, fresh cells can enter mitosis under these 

 conditions (Bullough^"^) (Figure 65). Bullough suggests that cells 



187 



