Normalized cell maturation variable

Rubinow defined a normalized cell maturation variable, p. such that a cell will divide when / = 1. Now /x is related to the biochemical events occurring during the cell cycle in some undetermined fashion. It is, therefore, a semiempirical variable and is operationally defined in terms of measured cell cycle times. This implies that all cells divide after the cell cycle time of t hours. It is observed, however, that cell division times are scattered about a mean value. This randomness must be accounted for suitably. Most models account for this with an explicit operation in the mathematical solution by averaging cell division times over the entire population. This scheme leads to the solution of a rather difficult integral equation (see, e.g., Trucco (4)). Recently Subramarian et al. (8) have considered weighted-residual methods for more easily solving these problems. 

Patients with homozygous sickle cell disease (SS) had a mean serum folate of 5.8 JLg/liter compared with 7.2 p.g/liter in patients with sickle cell trait and 7.9 p.g/liter in healthy controls. However, there was no correlation between the serum folate and the hematocrit or reticulocyte count. Since reticulocytes may have a higher folate concentration than mature erythrocytes, Liu found that the erythrocyte folate, measured before and after removal of the reticulocytes, was a reliable indicator of the folate status in patients with sickle cell disease despite the variable degree of re-ticulocytosis. Using this technique only one of nine patients was found to have a low erythrocyte concentration of the vitamin. Treatment with fohc acid resulted in higher hematocrits in three of four patients with low serum and erythrocyte folate concentrations, but only one of 12 patients with a normal folate concentration showed any improvement when treated with folate. 

These tumors have prominent cells that resemble oligodendroglia and NF-positive neurons (or synaptophysin-positive neurons, or both) that often appear to float within Alcian blue-positive acid mucopolysaccharide. These are called floating neurons (see Fig. 20.35B). Other large neurons lack their normal spacing (see Fig. 20.35C). GFAP-positive astrocytes are variably present within the tumor and often surround it. This tumor s low MIBl LI, mature histotopographic appearance, and... 

---