Effects of N-benzyl-1α,25-(OH)2D3-26,23-lactam analogues and N-phenetyl-1α,25-(OH)2D3-26,23-lactam analogues on OCL formation by human MVNP-transduced CFU-GM cells (A) and mouse bone marrow cells (B) treated with 1α,25-(OH)2D3. The experimental procedures for OCL formation from human MVNP-transduced CFU-GM cells and mouse bone marrow cells were carried out as described in Materials and Methods. Multinucleated cells that cross-reacted with the 23C6 antibody in human MVNP-transduced CFU-GM cells and TRAP-positive in mouse bone marrow cells and had three or more nuclei were scored an OCL. Data are expressed as the mean ± S.D. of quadruplicate determinations. ap<0.001, compared with cells treated with media alone. *p<0.05, **p<0.01 and ***p<0.001, compared with cells treated with 10−9M 1α,25-(OH)2D3 or 10−8M 1α,25-(OH)2D3, respectively. Similar results were seen in two independent experiments.