Flynn M E, Pikalow A S, Kimmelman R S, Searls R L
Department of Biology, Temple University, Philadelphia, PA 19122.
Anat Embryol (Berl). 1991;184(4):411-20. doi: 10.1007/BF00957902.
Chick embryos, during stages 14 to 25, undergo an arching of the hindbrain and cervical neural tube that is termed cervical flexure. We have found that if the truncus arteriosus is severed during stage 12-13, the embryos survive for more than 24 h and do not show cervical flexure. The embryos have a beating heart, the expected number of somites, and often have discernible wing and leg buds. Light and electron micrographs reveal no histological abnormalities. The percentage of cells that become labeled with tritiated thymidine is close to normal, indicating that most of the cells are healthy. These results suggest that cervical flexure is related to normal morphogenesis of the heart. At stage 10, the heart is almost straight, with the prospective ventricle cranial to the prospective sinus venosus. The heart tube loops between stage 10 and stage 23, first to the right and then caudad, so that the ventricle becomes caudal to the sinus venosus. The heart undergoes these morphogenetic movements autonomously. The truncus arteriosus does not increase in length during caudal movement of the ventricle, so the cervical region is pulled into an arch. Bending of the cervical region into an arch can be prevented in intact embryos by injecting agar into the foregut, so that the foregut cannot bend. However, after about 24 h of further growth, if the axis cannot bend, the truncus begins to leak blood and the embryo dies. We conclude that cervical flexure is a response of the embryonic axis to the morphogenesis of the heart.
在第14至25阶段的鸡胚，后脑和颈神经管会发生一种称为颈曲的弓形变化。我们发现，如果在第12 - 13阶段切断动脉干，胚胎能存活超过24小时且不会出现颈曲。这些胚胎有跳动的心脏、预期数量的体节，并且常常有可辨认的翅芽和腿芽。光学和电子显微镜照片显示没有组织学异常。用氚标记的胸腺嘧啶核苷标记的细胞百分比接近正常，表明大多数细胞是健康的。这些结果表明颈曲与心脏的正常形态发生有关。在第10阶段，心脏几乎是直的，预期的心室位于预期的静脉窦的头侧。心脏管在第10阶段和第23阶段之间发生环化，首先向右然后向尾侧，这样心室就位于静脉窦的尾侧。心脏自主地经历这些形态发生运动。在心室向尾侧移动期间，动脉干长度不增加，因此颈部区域被拉成弓形。通过向前肠注射琼脂以使前肠不能弯曲，在完整胚胎中可以防止颈部区域弯曲成弓形。然而，在进一步生长约24小时后，如果轴不能弯曲，动脉干开始出血，胚胎死亡。我们得出结论，颈曲是胚胎轴对心脏形态发生的一种反应。
