Knaapen M W, Vrolijk B C, Wenink A C
Department of Anatomy and Embryology, Leiden, Netherlands.
Anat Rec. 1996 Jan;244(1):118-25. doi: 10.1002/(SICI)1097-0185(199601)244:1<118::AID-AR12>3.0.CO;2-S.
In the embryonic heart, the individual cardiac segments show different growth rates. For the analysis of changing form in relation with changing function, data on number and shape of cardiomyocytes are necessary. Such data will give insight into the process of hypertrophy and/or hyperplasia as they may take place in the myocardium in the embryonic period.
We have measured the volumes of the nuclei and myocytes as well as the surface areas of the nuclear envelope and cellular membrane using stereological tools in rat embryos from 11 days postcoitum to 17 days postcoitum. From the data of the cellular volume of the myocytes and the myocardial volume of the individual segments, we have calculated the total number of myocytes during the developmental period.
It is shown that the sinus venosus, sinu-atrial junction, and atrium increase their cellular volume during development, whereas the other cardiac segments show no difference in cellular volume. Similarly, the surface area of the cell membrane of the sinus venosus and sinu-atrial junction had increased during development. The nuclear volume and the surface area of the nuclear envelope did not differ during the period studied. The total number of myocytes showed a conspicuously smaller increase in the atrio-ventricular canal and distal outlet segment than in the other segments.
The increase of the cellular volume in the segments sinus venosus and sinu-atrial junction seems to be due to a late differentiation process. In general, however, the increase of the myocardial volume in the individual cardiac segments is caused by hyperplasia of the cardiomyocytes in these segments and not by hypertrophy. The surface area of cells has a fixed relationship with cell volume, indicating that no important changes take place in the developmental period studied.
在胚胎心脏中，各个心脏节段显示出不同的生长速率。为了分析形态变化与功能变化的关系，心肌细胞数量和形状的数据是必要的。这些数据将有助于深入了解胚胎期心肌中可能发生的肥大和/或增生过程。
我们使用体视学工具测量了从受孕后11天到受孕后17天的大鼠胚胎中细胞核和心肌细胞的体积以及核膜和细胞膜的表面积。根据心肌细胞的细胞体积数据和各个节段的心肌体积，我们计算了发育期间心肌细胞的总数。
结果表明，静脉窦、窦房交界和心房在发育过程中细胞体积增加，而其他心脏节段的细胞体积没有差异。同样，静脉窦和窦房交界的细胞膜表面积在发育过程中有所增加。在所研究的时期内，核体积和核膜表面积没有差异。房室管和远端出口节段中心肌细胞的总数增加明显少于其他节段。
静脉窦和窦房交界节段细胞体积的增加似乎是由于后期分化过程。然而，一般来说，各个心脏节段中心肌体积的增加是由这些节段中心肌细胞的增生引起的，而不是肥大。细胞表面积与细胞体积有固定的关系，表明在所研究的发育时期没有发生重要变化。
