神經系統是動物的協調中樞，其中負責絕緣、傳導及修復受損軸突的髓鞘是非常重要的結構。若周邊神經產生病變會降低偵測危險的能力，甚至導致死亡，例如糖尿病引起的慢性併發症及局部脫髓鞘化。因此了解具髓鞘神經纖維徑向機械性質可能有助於預防永久性神經損害。本研究以微針梳整正常(控制組)與糖尿病(實驗組) SD 大鼠坐骨神經束，取得單一具髓鞘神經纖維，在原子力顯微鏡的自選力-集壓痕模式下，得到其形貌並準確測量神經纖維的彈性力學特性，由接觸力量－壓深曲線，配合 Bilodeau 模型估測視楊氏模數 ， 發現控制組為27.57±11.08 kPa，實驗組為 45.02±33.96 kPa 。 此外， 利用穿透式電子顯微鏡的橫截面影像，建立二維有限元素模型，以彈性與超彈性材料描述具髓鞘神經纖維的非線性彈性響應，並分別估測軸突及髓鞘的材料性質。逆向有限元素分析結果顯示實驗組的髓鞘切楊氏模數大於控制組，且髓鞘是徑向負載下主要承受應力的結構。

The coordination center of animals is the nerve system, in which the myelin is an important structure to provide isolation, saltatory signal transmission and repairing injured nerve. Peripheral neuropathies, such as diabetic polyneuropathy (DPN), are believed to be related to bnormal
mechanical behavior of myelin and myelinated axon, which may even lead to death due to the decreased ability to detect danger. Understanding the transverse mechanical properties of myelinated nerve fiber may aid preventing permanent nerve injuries in this kind of patients. A micro-needle was employed to tease normal and diabetic Sprague -Dawley rat sciatic nerves into isolated nerve fibers. An AFM with flexible multi-indentation tests was used to obtain the topography and elastic properties of the isolated nerve fibers. With a maximum indentation depth of 9% of height, the force-indentation curve was fitted with Bilodeau model to estimate apparent Young’s modulus, which is 27.57±11.08 kPa in normal group and 45.02±33.96 kPa in diabetic group. A two-dimensional finite element model was built based on the transmission electron microscopy(TEM)images of rehydrated myelinated nerve fiber. The stress -strain relationships of axon and myelin were postulated as a linear elastic model and a hyperelastic model, respectively. The inverse finite element analysis was used to estimate
the material parameters. The results showed that tangential Young’s modulus of diabetic myelin was higher, and myelin is the main structure to bear radial stress.

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