Comparison of two in vitro angiogenesis assays for evaluating the effects of netrin-1 on tube formation

Netrin-1 is a neural guidance cue that also regulates vascu- lar development. Controversial results, however, have been obtained concerning the roles of netrin-1 in vascular devel- opment both in vivo and in vitro. In the present study, two in vitro angiogenesis assays were compared to evaluate the effects of netrin-1 secreted by retrovirally transduced mel- anoma cells （Mel2a-netrinl） on tube formation. The results showed that there was no obvious difference in tube forma- tion induced by conditioned media （CM） from the control, Mel2a-netrinl and Mel2a cells in a matrigel assay. The results of another in vitro assay, in which endothelial cells were co-cultured with human fibroblasts, however, showed that Mel2a-netrinl CM inhibited the tube formation, sup- posedly through blocking the elongation and coalescence of human umbilical vein endothelial cells （HUVECs）. These results confirmed that the matrigel assay is not able to demonstrate the anti-angiogenic roles of netrin-1.     

The formation of the right and left heart ventricles from the ventricular part of the cardiac tube during embryogenesis

It has been generally assumed that the initial rudiment of the heart ventricle is divided by the longitudinal interventricular septum into the right and left ventricles. This paper presents evidence for the hypothesis that the right and the left ventricles are produced during normal development from different sequentially located segments of the cardiac tube. These segments yielding rudiments of the right and left ventricles could be detected even during early embryogenesis. This hypothesis requires a new explanation for the process of the formation of two separate outlets from the heart ventricles.