• 作者： 劉克明
• 作者服務機構： 高雄醫學院解剖學科
• 中文摘要： 利用電子顯微鏡術研究剛出生（一天）之小白鼠，其第四頸椎高度之脊髓背索中，神經髓鞘開始形成時的微細構造情
  形。方出生時，背索中之大部份神經纖維都還沒有神經髓鞘，祇有少數纖維具有薄薄的初期神經髓鞘。於神經髓鞘開始
  形成時，一小段的寡樹突膠質細胞的突起，緊靠?神經軸突的外方。不久，此小段突起之兩唇繞?神經軸突延伸，將神
  經軸突完全包圍，且互相接觸，形成了第一個接觸點。隨之，以此接觸點為支持點，突起的兩唇更加延長且互相擁抱摺
  疊，構成了未來神經髓鞘之內舌與外舌。而旦，?近的舌狀突起之相對細胞膜，其兩外表層於約略相等距離處互相接觸
  ，產生了更多的接觸點。然後，內、外兩舌狀突起，更進一步彼此相對的反相環繞形成了同心圓環狀排列；於此種環狀
  構造的寡樹突膠質細胞突起的?近層之間，亦互相接觸而形成了很多的接觸點。同時，?近的接觸點間的空間消失，兩
  相對之細胞膜外表層緊靠在一起，開始形成神經髓鞘之週間?。於神經髓鞘開始形成時，往往可觀察到單一條神經軸突
  被兩個分開的寡樹突膠質細胞突起構成之神經髓鞘成同心圓環繞?，以及好幾條神經軸突被單一寡樹突膠質細胞的突起
  所環繞。形態測量學所得資料顯示：未被神經髓鞘環繞之神經軸突，其橫切面之面積為0.01-0.2μm2，中央值為0.07
  μm2；而開始有神經髓鞘環繞之神經軸突，其橫切而之面積為0.09-1.4μm2，中央值為0.61μm2。這些結果指出神
  經軸突之面積大小為神經髓鞘開始形成之重要臨界因素。出
• 英文摘要： The early myelination of the dorsal funiculus at the level of the 4th cervical spinal cord was ultra-structurally studied in the one-day-old mouse. It was found that the fibers were mainly unmyelinated.However, some early myelinated fibers were scattered among unmyelinated fibers. In the initial stage ofthe myelination, the axon was partially contacted by a piece of cytoplasmic process of the oligodendroglialcell. The two lips of the oligodendroglial process then extended and converged, enwrapping the axoncompletely and forming the first contact point. With the anchorage of that contact point, the two lips ofthe process became elongated and enfolded by each other, and produced the internal and external tonguesof the future myelin sheath. More contact points were formed at a regular interval by the regional fusion ofthe two external surface layers of the opposed cytoplasmic membranes of adjacent tongue processes. Withthe advanced bidirectional spiralization of the two tongue processes, many contact points were foundbetween the adjacent lamellae of the concentrically arranged oligodendroglial process; simultaneously, thecleft between the neighboring contact points disappeared and formed the initial sites of the intraperiod line.During the early myelination, one single axon ensheathed concentrically by two different oligodendroglialprocesses as well as several axons enwrapped by a continuous spiral myelin sheath of one oligodendroglialcell were frequently observed. The cross-sectional areas of unmyelinated axons varied from 0.01 to 0.2μm2, with a median of 0.07 μm2; whereas, that of promyelinated axons ranged from 0.09 to 1.4 μm2,with a median at 0.61 μm2. These data support the suggestion that the axon calibre is a critical factor forthe initiation of central myelination.
• 中文關鍵字： oligodendrogila process; myelination; funiculus; cervical dorsal spinal cord; mouse; new-born
• 英文關鍵字： --