Figure 1. Culture of NB from serum and formation of NLP.

(A) Culture of NB from FBS (top panel) and HS (bottom panel). Serum was inoculated into DMEM to the indicated concentrations. After incubating for 1 month at 37°C, NB were detected by visual inspection and A₆₅₀ (insets). For FBS, the amount of NB was maximal at 0.3%, decreasing thereafter with higher FBS concentrations, while for HS, NB were only visually noticeable at HS concentrations exceeding 3%. (B) Formation of NLP in DMEM. NLP were prepared by successively adding solutions of 0.25 M CaCl₂, Na₂CO₃, and NaH₂PO₄ (pH 7.4) into DMEM as indicated and incubated at 37°C overnight, which resulted in dose-dependent formation of NLP (top row). The same experiment was repeated in the presence of 1% FBS, which showed inhibition of NLP formation (bottom row). This serum inhibition was overcome by increased concentrations of precipitating reagents, at 3 mM and above.