Thomas P K, Fraher J P, O'Leary D, Moran M A, Cole M, King R H
Department of Neurological Science, Royal Free Hospital School of Medicine, London, Great Britian.
Acta Neuropathol. 1990;79(4):375-86. doi: 10.1007/BF00308713.
The relative changes in the growth and maturation of axon size and myelin thickness were studied in the medial plantar division of the tibial nerve in the lower leg and in the motor branches of the tibial nerve to the calf muscles in rats in which diabetes mellitus had been induced with streptozotocin at the time of weaning. Observations were made at 6 weeks and 3, 6, 9 and 12 months of diabetes for comparison with age-matched controls. Similar changes were observed in both nerves. Growth in body weight and skeletal growth was severely retarded from the time of induction of diabetes but at the 6-week stage axon size was not reduced, suggesting that neural growth may initially be relatively protected. At later stages axon size was consistently reduced in the diabetic animals as compared with the controls and showed an absolute reduction at 12 months, as compared with 9 months, that was greater than in the controls. Myelin thickness became reduced earlier and was more severely affected than axon size so that the fibers were relatively hypomyelinated. The myelin changes were greater in larger than in smaller fibers. The index of circularity of axons was reduced in the diabetic nerves. These results show that induction of diabetes in prepubertal rats produces effects on peripheral nerve fibers which differ from those resulting from diabetes induced in adult animals. The effects also differ between large and small nerve fibres. These observations may explain some of the disparate findings obtained in previous studies on experimental diabetes in rats.
在断奶时用链脲佐菌素诱导糖尿病的大鼠中，研究了小腿胫神经内侧足底分支以及胫神经至小腿肌肉的运动分支中轴突大小和髓鞘厚度的生长及成熟的相对变化。在糖尿病发病6周以及3、6、9和12个月时进行观察，并与年龄匹配的对照组进行比较。在两条神经中均观察到类似变化。自糖尿病诱导之时起，体重增长和骨骼生长严重受阻，但在6周龄阶段轴突大小并未减小，这表明神经生长最初可能相对受到保护。在后期阶段，与对照组相比，糖尿病动物的轴突大小持续减小，并且与9个月时相比，12个月时出现了绝对减小，且这种减小幅度大于对照组。髓鞘厚度比轴突大小更早减小且受影响更严重，因此纤维相对髓鞘形成不足。较大纤维的髓鞘变化比较小纤维更大。糖尿病神经中轴突的圆度指数降低。这些结果表明，青春期前大鼠诱导糖尿病对外周神经纤维产生的影响不同于成年动物诱导糖尿病所产生的影响。大小神经纤维的影响也有所不同。这些观察结果可能解释了先前关于大鼠实验性糖尿病研究中一些不同的发现。
