Ledda M, De Palo S, Pannese E
Institute of Histology, Embryology and Neurocytology, University of Milan, Milan, Italy.
Tissue Cell. 2004 Feb;36(1):55-62. doi: 10.1016/j.tice.2003.09.001.
We studied the ratios between number of neuroglial (=satellite) cells and number and volume of neurons with which they are associated in the spinal ganglia of two species of reptiles (lizard and gecko) and three species of mammals (mouse, rat, and rabbit). In all five species, we found that the number of satellite cells associated with a nerve cell body increased with increasing volume of the latter. This result shows that there is a quantitative balance between neuroglia and nerve tissue in spinal ganglia. This balance seems to be maintained by a tight regulation of the number of satellite cells. We also found that the mean volume of nerve cell body corresponding to a satellite cell was lower for small neurons than for large ones. Since satellite cells metabolically support spinal ganglion neurons, the metabolic needs of small neurons are better satisfied than those of large ones. For a nerve cell body of a given size, the number of associated satellite cells did not differ between the lizard and gecko, nor between the mouse, rat, and rabbit. However, this number was significantly smaller in the reptiles than in the mammals. This result could be explained by the lower metabolic rate in the nervous system of poikilotherms than mammals, or could have a phylogenetic significance. These two interpretations are not mutually exclusive.
我们研究了两种爬行动物（蜥蜴和壁虎）以及三种哺乳动物（小鼠、大鼠和兔子）脊髓神经节中神经胶质细胞（=卫星细胞）数量与它们所关联的神经元数量及体积之间的比例关系。在所有这五个物种中，我们发现与神经细胞体相关联的卫星细胞数量会随着后者体积的增加而增多。这一结果表明脊髓神经节中的神经胶质和神经组织之间存在着数量上的平衡。这种平衡似乎是通过对卫星细胞数量的严格调控来维持的。我们还发现，对于小神经元而言，与一个卫星细胞相对应的神经细胞体平均体积要小于大神经元。由于卫星细胞在代谢上支持脊髓神经节神经元，所以小神经元的代谢需求比大神经元能得到更好的满足。对于给定大小的神经细胞体，蜥蜴和壁虎之间以及小鼠、大鼠和兔子之间与之相关联的卫星细胞数量并无差异。然而，爬行动物的这一数量明显少于哺乳动物。这一结果可能是由于变温动物神经系统的代谢率低于哺乳动物，或者可能具有系统发育学上的意义。这两种解释并非相互排斥。
