Sedmera D, Pexieder T, Hu N, Clark E B
Institute of Histology and Embryology, University of Lausanne, Switzerland david.sedmera @ibcm.unil.ch
Eur J Morphol. 1998 Apr;36(2):105-19. doi: 10.1076/ejom.36.2.105.4775.
During the early developmental period, ventricular myoarchitecture undergoes a transition from a smooth-walled cardiac tube, to left and right ventricular chambers filled with a sponge-like network of trabecular struts. We measured the quantitative changes of ventricular myocardium properties in normal stage 21-29 chick embryos and after chronic verapamil suffusion, which is known to decrease work load and decelerate ventricular growth. The morphologic parameters (compact layer thickness, ventricular wall composition, porosity of different layers and trabecular orientation) were determined from scanning electron micrographs of transversely dissected perfusion-fixed hearts. A vascular bed of stage 21 chick embryos was suffused with 1 ng of verapamil at 1 microliter per hour up to stages 24, 27 and 29 via a miniosmotic pump. From stage 24, the thickness of the compact myocardium in the left ventricle was greater than that of the right. The increase in thickness was minimal between stages 24 and 27, while the predominantly radially arranged trabeculae comprised up to 75% to total myocardial mass. The ratio of intertrabecular spaces to trabeculae (local porosity) decreased form the ventricular center (70%) towards the compact myocardium (0%). In verapamil-treated embryos, the hearts were smaller and showed delayed development. The compact myocardium was thinner than normal, and the proportion of trabeculae was higher than in controls. The local porosity values were similar in control and experimental groups. Decreased load resulted in delayed growth and morphogenesis, expressed as persistence of trabeculae and a thinner compact myocardium. Embryonic heart pumping function is largely based on extensively developed trabeculation with regionally different properties.
在发育早期，心室肌结构经历从光滑壁的心脏管到充满海绵状小梁支柱网络的左、右心室腔的转变。我们测量了正常21-29期鸡胚以及慢性维拉帕米灌注后心室心肌特性的定量变化，已知维拉帕米可降低工作负荷并减缓心室生长。形态学参数（致密层厚度、心室壁组成、不同层的孔隙率和小梁方向）由横向解剖的灌注固定心脏的扫描电子显微镜图像确定。通过微量渗透泵，在21期鸡胚的血管床中以每小时1微升的速度灌注1纳克维拉帕米，直至24、27和29期。从24期开始，左心室致密心肌的厚度大于右心室。在24期和27期之间，厚度增加最小，而主要呈放射状排列的小梁占心肌总质量的75%。小梁间隙与小梁的比例（局部孔隙率）从心室中心（70%）向致密心肌（0%）降低。在维拉帕米处理的胚胎中，心脏较小且发育延迟。致密心肌比正常的薄，小梁的比例高于对照组。对照组和实验组的局部孔隙率值相似。负荷降低导致生长和形态发生延迟，表现为小梁持续存在和致密心肌变薄。胚胎心脏的泵血功能很大程度上基于广泛发育的具有区域不同特性的小梁结构。
