FIG. 7.

Comparison of the cell blot densities of a susceptible N2a line grown in high-glucose DMEM or MEM. Cultures were inoculated with ScN2a cell homogenate. The amount inoculated is expressed as an estimate of the mouse ID₅₀ titer, based on previous studies of ScN2a cells (4). Cell blotting was performed 25 days after inoculation. Density measurements were made using NIH Image software on scanned images of cell blots. Measurements were normalized by determining the ratio of the density of the blot to the mean density of blots of uninoculated cells on the same membrane. Each data point represents the average measurements of four separate cell blots and is expressed as a mean percent above background density [(normalized density − 1) × 100]. Error bars show the total relative standard deviation for the normalized density calculation. For cells grown in DMEM (solid squares), Student's t-test gives P values of 0.01 or lower for comparisons between any of the three inoculation titers and mean. However, for cells grown in MEM (open diamonds), P values are less than 0.05 only for the group receiving the highest inoculum titer. Thus, cell blot sensitivity is 1 to 2 log ID₅₀ units greater for cells grown in DMEM than for cells grown in MEM.