Matsuda Seiji, Kobayashi Naoto, Terashita Takehiro, Shimokawa Tetsuya, Shigemoto Kazuhiro, Mominoki Katsumi, Wakisaka Hiroyuki, Saito Shouichiro, Miyawaki Kyoujy, Saito Kyoko, Kushihata Fumiki, Chen Jie, Gao Shuang-Yan, Li Chun-Yu, Wang Min, Fujiwara Takashi
Department of Anatomy and Embryology, Ehime University School of Medicine, Toon, Ehime 791-0295, Japan.
J Comp Neurol. 2005 Oct 24;491(3):234-45. doi: 10.1002/cne.20713.
Cajal's initial glomeruli (IG) and Dogiel's pericellular nests (PCNs) were first described from methylene blue preparations of healthy animal tissues around the beginning of the last century. Since that time, although many reports have been published concerning these structures, few have focused on their development and phylogeny in healthy animals. The aim of this study was to examine the phylogenetic development of the sensory neurons in Cajal's IG (also called axonal glomeruli) and Dogiel's PCNs in the dorsal root ganglion (DRG) of the healthy adult frog, chick, rat, and rabbit. The three-dimensional architecture of the neurons was observed in ganglia by scanning electron microscopy after removal of the connective tissue. The neurons in the DRG of fish are known to be bipolar, but DRG neurons in the species examined here were found to be pseudounipolar, with single stem processes. The proportion of neurons having IG or PCNs increased with increasing phylogenetic complexity in the species examined here. Cajal's initial glomeruli, the convolution of the stem process near the parent cell body: In frogs, the ganglia were small and the neuronal stem processes were very short and straight. In chicks, the stem processes were longer; sometimes very long, tortuous processes were observed. However, no neurons with typical IG were observed in either species. Typical IG were observed in rats and rabbits; their occurrence was much more frequent in rabbits. Pseudounipolarization, i.e., the transition from bipolar to pseudounipolar neurons, is thought to save space, limit the length of neuronal processes, and reduce conduction time. However, an explanation of the evolutionary advantage of the IG, which is formed by the excessive prolongation of the stem process, remains elusive. The cytological and electrophysiological importance of IG has been discussed. Dogiel's pericellular nests (PCNs), which resemble balls of yarn made of thin unmyelinated nerve fibers around DRG neurons, have been observed in the DRG of rats and rabbits, but not in frogs or chicks. This interesting structure shows not only ontogenetic development in healthy animals but also phylogenetic development among species. The nerve fibers in the PCNs were less than 1.2 mum in diameter and had some varicosities. An immunohistochemical study using anti-tyrosine hydroxylase (TH) antibody revealed that some PCNs contain TH-positive nerve fibers and varicosities. Such TH-positive PCNs disappear after sympathectomy. These results suggest that the PCNs are made up of autonomic nerve fibers.
卡哈尔氏初级神经球（IG）和多吉尔氏细胞周巢（PCN）最早是在大约上世纪初从健康动物组织的亚甲蓝制剂中描述出来的。从那时起，尽管已经发表了许多关于这些结构的报告，但很少有研究关注它们在健康动物中的发育和系统发育。本研究的目的是研究健康成年青蛙、鸡、大鼠和兔子背根神经节（DRG）中卡哈尔氏IG（也称为轴突神经球）和多吉尔氏PCN中感觉神经元的系统发育。去除结缔组织后，通过扫描电子显微镜观察神经节中神经元的三维结构。已知鱼类DRG中的神经元是双极的，但在此处检查的物种中，DRG神经元被发现是假单极的，具有单个干突。在此处检查的物种中，具有IG或PCN的神经元比例随着系统发育复杂性的增加而增加。卡哈尔氏初级神经球，即靠近母细胞体的干突卷曲：在青蛙中，神经节小，神经元干突非常短且直。在鸡中，干突较长；有时观察到非常长且曲折的干突。然而，在这两个物种中均未观察到具有典型IG的神经元。在大鼠和兔子中观察到典型的IG；它们在兔子中的出现频率更高。假单极化，即从双极神经元向假单极神经元的转变，被认为可以节省空间、限制神经元突起的长度并减少传导时间。然而，对于由干突过度延长形成的IG的进化优势的解释仍然难以捉摸。已经讨论了IG的细胞学和电生理重要性。多吉尔氏细胞周巢（PCN）类似于由围绕DRG神经元的细无髓神经纤维制成的线球，已在大鼠和兔子的DRG中观察到，但在青蛙或鸡中未观察到。这种有趣的结构不仅显示了健康动物中的个体发育，还显示了物种间的系统发育。PCN中的神经纤维直径小于1.2微米，并有一些膨体。使用抗酪氨酸羟化酶（TH）抗体的免疫组织化学研究表明，一些PCN含有TH阳性神经纤维和膨体。这种TH阳性PCN在交感神经切除术后消失。这些结果表明PCN由自主神经纤维组成。
