Summary Recently, we reported the anti-angiogenic action along with anti-tumour activity of TNP-470 (AGM-1470). In this study, the effect of TNP-470 on the growth of human umbilical vein endothelial (HUVE) cells was examined. TNP-470 inhibited the growth of HUVE cells in a biphasic manner. The inhibition was cytostatic in the first phase (complete inhibition at 300 pg ml' to 3 fig ml-' with an IC50 of 15 pg ml-') and cytotoxic in the second phase ( > 30 ,ug ml-'). The cytostatic inhibition of HUVE cell growth by TNP-470 was durable after washing out TNP-470 in culture. Incorporation of thymidine but not uridine and leucine by HUVE cells was inhibited in the first phase, while that of all three compounds was inhibited in the second phase. Human and rat endothelial cells among various types of cells were the most sensitive to the cytostatic inhibition, while differences in the cytotoxic inhibition were minimal. These results suggest that TNP-470 exerts its specific anti-angiogenic action by inhibiting cytostatically growth of endothelial cells in a relatively specific manner.

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ABSTRACT. Cultures of mesenchymal cells dissociated from the hind limb buds of 3.5 day quail embryos (stages 22-23) were used to study the effect of the cellular microenvironment on chondrogenesis. The degree of chondrogenesis in cultures was estimated by two methods : the number of cartilage nodules (characteristic structures formed by chondrocytes) was counted under a phasecontrast microscope, and the amount of toluidine blue absorbed into the extracellular matrix of chondrocytes was measured by spectrophotometry. A culture technique with cellophane films was devised to establish a suitable microenvironment for culture. When mesenchymal cells were cultured by this technique, chondrogenesis was much greater than in usual cultures without cellophane films. Examinations of differences between cultures with and without films indicated that cellophane films promoted differentiation of mesenchymal cells, by the accumulation of some effective factor(s) in culture medium.