Inhibition of NP propagation in vitro by levamisole. A: Kidney stone derived-NPs were cultured in flasks in DMEM/10% FBS for 21 days. Baseline (day 1) turbidity (NTU) of NP-seeded medium was slightly above that of unseeded blanks. After 21 days, turbidity increased significantly in seeded flasks. Turbidity was significantly reduced in the presence of 1 mM levamisole, an ALP inhibitor. Mean ± SEM, n = 5. Significant difference (P < 0.05) from corresponding: *, blank; †, untreated seeded sample. B: Inhibition of ALP reduces NP mineralization in vitro. Transmission electron micrographs of NPs derived from a calcified human aortic aneurysm taken after propagation in DMEM/10% FBS for 3 weeks in the absence (control, left) or presence (right) of 1 mM levamisole. The deposition of crystals seen in control NPs, shown by previous work to be hydroxyapatite [9], was reduced by levamisole, thus resulting in smaller sized NPs.