Daniel E E, Wang Y F
Department of Biomedical Sciences, Health Sciences, McMaster University, 1200 Main St. W., Hamilton L8N 3Z5, ON, Canada.
Neurogastroenterol Motil. 1999 Oct;11(5):375-92. doi: 10.1046/j.1365-2982.1999.00159.x.
Networks of interstitial cells of Cajal (ICC) in the myenteric plexus (Myp) or circular muscle (CM) function as pacemakers for gastrointestinal slow waves. ICC in contact with muscle and closely associated with nerves in the CM may mediate inhibitory neurotransmission. We wondered if ICC in Myp and CM and their connections are immature at birth and mature first in the proximal gut in association with nerves. Tissues from lower esophageal sphincter (LES), pylorus (PYL), small intestine (SI) and colon (CO) of 18 term fetal dogs taken from six females were fixed and prepared for ultrastructural examination and studied. Ganglia were present where expected in the Myp and submucous plexus (SMP). ICC cells were present in the Myp of PYL, SI and CO and appeared to have normal relationships to the outer border of CM as in adults. ICC in CM were found associated with nerves in the LES and in PYL, but not in SI or CO. However, axons in CM were everywhere usually free of glial covering, indicating ongoing migration or development. No organized deep muscular plexus (DMP) in SI or submuscular plexus (SP) in colon was present. Visible gap junctions were absent everywhere except for very rare ones between circular muscle cells. We conclude that at birth the neural and ICC networks of CM are more immature in intestine and colon than in oesophagus and stomach. Development of nerve and ICC of CM in oesophagus and stomach apparently precedes that in the remaining gut. However networks in these regions have not achieved adult organization and ICC and smooth muscle cells are anatomically poorly coupled. These findings suggest the reasons that gut motility at birth will not be adult in pattern are because ICC, nerve and muscle control systems are not fully differentiated. Further developmental delays in ICC and nerve maturation could have serious consequences for feeding of infant animals.
肌间神经丛（Myp）或环行肌（CM）中的 Cajal 间质细胞（ICC）网络作为胃肠慢波的起搏器发挥作用。与肌肉接触并与 CM 中的神经紧密相关的 ICC 可能介导抑制性神经传递。我们想知道 Myp 和 CM 中的 ICC 及其连接在出生时是否不成熟，以及是否首先在近端肠道与神经相关联的情况下成熟。从六只雌性孕犬中取出 18 只足月胎儿犬的食管下括约肌（LES）、幽门（PYL）、小肠（SI）和结肠（CO）组织进行固定，准备用于超微结构检查并进行研究。在 Myp 和黏膜下神经丛（SMP）中预期的位置存在神经节。ICC 细胞存在于 PYL、SI 和 CO 的 Myp 中，并且与成年动物一样，与 CM 的外边界似乎具有正常关系。在 LES 和 PYL 的 CM 中发现 ICC 与神经相关联，但在 SI 或 CO 中未发现。然而，CM 中的轴突通常到处都没有神经胶质覆盖，表明正在进行迁移或发育。SI 中没有有组织的深层肌神经丛（DMP），结肠中也没有肌下神经丛（SP）。除了环行肌细胞之间非常罕见的连接外，到处都没有可见的缝隙连接。我们得出结论，出生时，肠道和结肠中 CM 的神经和 ICC 网络比食管和胃中的更不成熟。食管和胃中 CM 的神经和 ICC 的发育显然先于其余肠道。然而，这些区域的网络尚未达到成年期的组织结构，并且 ICC 和平滑肌细胞在解剖学上耦合不良。这些发现表明出生时肠道运动模式与成年动物不同的原因是 ICC、神经和肌肉控制系统没有完全分化。ICC 和神经成熟的进一步发育延迟可能会对幼龄动物的喂养产生严重后果。
