THE COMPUTER IN BIOLOGICAL RESEARCH 



311 



where a is activity in per cent of initial value, and k the specific rate of loss 

 or iron, in hours -1 . Values of A; for different subjects are given in Table 11-1. 



(a) 



iron exchanging 

 with plasma but 

 not with iron of 

 spent red blood 

 cells, 

 (storage phase) 



iron exchanging 

 with plasma and 

 aiding the break- 

 down of spent 

 red blood cells 

 (reticulo endo- 

 thelial phase) 



m 



all of the iron 

 n the pla sma 



(b) 



iron i n red 

 blood cell 

 precursor 

 system 

 (bone marrow) 



Figure 11-6. Schematic Flow Sheet for Production of Red Blood Cells, Showing Two 

 Models or Theories, (a) and (b), of the Metabolism of Iron. The k's are specific rate con- 

 stants, assumed to be for first-order reactions. 



If this law were obeyed rigorously, the story would now be complete. 

 However, this law is seen to be badly broken if measurements are continued 

 for a few days instead of a few hours: the rate constant diminishes as the 



TABLE 11-1. Values of the Turnover Rate Constant* for Iron in Blood Plasma. 



Subjects 



k(hr-') 



Normal subjects 

 Polycythemia vera 

 Aplastic anemia 

 Normal subjects taken to 



1 5,000 ft above sea level 

 Normal subjects living at 



15,000 ft above sea level 



0.18to0.21 



0.9 to 1 . 1 (very fast turnover) 

 ~0.05 (very slow turnover) 



0.3 to 0.4 



0.25 to 0.30 



*For the first few hours onlv. 



