Rees S, Clark M, Snowden M, Harding R
Department of Physiology, Monash University, Clayton, Victoria, Australia.
Int J Dev Neurosci. 1990;8(2):133-41. doi: 10.1016/0736-5748(90)90003-k.
A quantitative morphometric study of the development of myelinated fibres in the optic and trochlear nerves has been made in growth-retarded fetal sheep at 140 days gestation (term = 146 days). Intrauterine growth retardation was induced as a result of the reduction of placental mass, by prior removal of placentation sites in six ewes. In the optic nerve (central nervous system) the mean diameter of myelinated fibres was not significantly reduced but the thickness of the myelin sheath relative to axon diameter was disproportionately reduced. In the trochlear nerve (peripheral nervous system) there was a significant reduction of 23% (P less than 0.01) in the mean diameter of myelinated fibres; however the normal axon:myelin ratio was maintained. The total number of myelinated fibres in the trochlear nerve did not differ between the normal and growth-retarded group, indicating that there was not a greater than normal incidence of cell death during intrauterine growth retardation in the nucleus of the trochlear nerve. The differential effect of intrauterine growth retardation on myelination in the central and peripheral nervous systems suggests that chronic intrauterine deprivation affects oligodendrocyte activity but does not markedly affect the capacity of Schwann cells to produce myelin.
对妊娠140天（足月为146天）生长受限的胎羊视神经和滑车神经中髓鞘化纤维的发育进行了定量形态学研究。通过预先切除6只母羊的胎盘着床部位，减少胎盘质量，从而诱发子宫内生长受限。在视神经（中枢神经系统）中，有髓纤维的平均直径没有显著减小，但髓鞘厚度相对于轴突直径却不成比例地减小。在滑车神经（周围神经系统）中，有髓纤维的平均直径显著减小了23%（P<0.01）；然而，轴突与髓鞘的正常比例得以维持。正常组和生长受限组滑车神经中有髓纤维的总数没有差异，这表明在子宫内生长受限期间，滑车神经核内细胞死亡的发生率并未高于正常情况。子宫内生长受限对中枢神经系统和周围神经系统髓鞘形成的不同影响表明，慢性子宫内营养缺乏会影响少突胶质细胞的活性，但不会显著影响施万细胞产生髓鞘的能力。
