Delaney A J, Samorajski T, Fuller G N, Wiggins R C
J Nutr. 1981 Apr;111(4):746-54. doi: 10.1093/jn/111.4.746.
Developing Long-Evans rats were undernourished to produce a body-weight deficit of 39% at the age of weaning. Well-nourished litter mates were used as controls. Morphometric analyses were made of pyramidal tracts and posterior tibial nerves of each animal. In measuring pyramidal tract, we observed that axonal circumferences of myelinated fibers were smaller in the undernourished rats and that the number of myelin lamellae per axon appeared reduced by a small amount. The most striking observation in the undernourished rats compared to the controls was that the proportion of myelinated fibers was decreased by 40% at 20 days of age. Axon circumferences of nonmyelinated axons were not measured. Similar decreases were observed in myelinated axon circumference and myelin lamellae of posterior tibial nerves of undernourished rats. Because of sampling problems, we did not attempt to compare the proportion of myelinated and nonmyelinated fibers in posterior tibial nerves of undernourished and well-nourished rats. These morphometric data, particularly the reduction of myelinated fibers, are consistent with biochemical studies of brain hypomyelination in undernourished rats. The data indicate that the mechanism of hypomyelination in nutritionally deprived rats involves a failure of the "trigger" by which myelin-forming cells begin to sheath axons in myelin.
对发育期的Long-Evans大鼠进行营养缺乏处理，使其在断奶时体重比正常水平低39%。营养良好的同窝幼鼠作为对照。对每只动物的锥体束和胫后神经进行形态计量学分析。在测量锥体束时，我们观察到，营养不良大鼠有髓纤维的轴突周长较小，并且每个轴突的髓鞘板层数似乎略有减少。与对照组相比，营养不良大鼠最显著的观察结果是，在20日龄时，有髓纤维的比例下降了40%。未测量无髓轴突的轴突周长。在营养不良大鼠的胫后神经有髓轴突周长和髓鞘板层中也观察到了类似的减少。由于取样问题，我们没有尝试比较营养不良和营养良好大鼠胫后神经中有髓和无髓纤维的比例。这些形态计量学数据，特别是有髓纤维的减少，与营养不良大鼠脑髓鞘形成不足的生化研究结果一致。数据表明，营养缺乏大鼠髓鞘形成不足的机制涉及髓鞘形成细胞开始用髓鞘包裹轴突的“触发”过程失败。
