Figure 1. Slow formation of NB-like particles by serum inoculated into DMEM.

(A) Formation of NB-like particles by FBS. FBS was inoculated into DMEM to the indicated % by volume. Visual inspection and A₆₅₀ turbidity reading (insets) were performed within 1 hour following inoculation (top panel, “Day 1”) as well as after incubation at 37°C in cell culture conditions for “1 Month” (middle panel) or “2 Months” (bottom panel). Notice the gradual increase in turbidity observed with time as well as the bell-shaped increase in turbidity as a function of the amount of serum inoculated, with maximum turbidity reached at 0.3% FBS, while higher concentrations of FBS resulted in increasingly lower turbidities. (B) Formation of NB-like particles by HS, performed as described in (A), except that higher serum concentrations varying from 1 to 10% were used. Notice the bell-shaped increase in turbidity, with peak reached at 1-to-3% HS at “1 Month” and 3% at “2 Months.”