Fig. 2. Regulation of LR Ca_i²⁺ levels along the node. Fura-2-loaded embryos were treated with the indicated pharmacological agent or left untreated. The upper panels show a representative Fura-2 image; lower images are the line-scan quantitation of fluorescent intensity versus right-left axis for that embryo, at the position indicated by the yellow line in the upper panel. Images are ventral views with anterior at the top; right (R) and left (L) are as indicated in A; asterisks indicate Hensen's node. (A,B) Untreated embryos at HH5 (A) and HH6 (B). (C) HH6 embryo treated with the intracellular Ca_i²⁺ chelator Bapta-AM. (D) HH6 embryo treated with EGTA. (E) HH6 embryo treated with the IP₃ antagonist xestospongin C. (F) HH6 embryo treated with the phospholipase C antagonist U73122. (G) HH6 embryo treated with the RyR antagonist 9,21-dehydroryanodine. (H) HH6 embryo treated with the calmodulin antagonist calmidizolium. Some treatments had inconsistent, minor effects on morphology but did not affect the Fura-2 measurements.