Hildebrand C
Department of Cell Biology, Faculty of Health Sciences, University of Linköping, Sweden.
J Neurocytol. 1989 Jun;18(3):285-94. doi: 10.1007/BF01190831.
In order to elicit de- and remyelination adult rat sciatic nerves were injected with diphtheria toxin dissolved in phosphate buffered saline (PBS). Control nerves were injected with PBS alone. After survival times of 1-10 weeks, the animals were perfused with glutaraldehyde. Specimens from the injected nerves were processed for light microscopic (LM) examination of teased fibres or for electron microscopic (EM) examination of longitudinal thin sections. LM examination of teased fibres after survival times of 6-10 weeks, showed that most remyelinated internodes are 150-300 microns long. In addition, some exceptionally short Schwann cell sheaths, with lengths of 15-150 microns, occur intercalated between conventional remyelinated internodes. EM analysis of thin sections showed that axonal evaginations penetrate in between the terminating myelin lamellae in fibres with nodal widening and/or paranodal demyelination, at early stages of demyelination. Such alterations are not present in relation to myelin sheaths formed during remyelination, which commences about 3 weeks after injection. In addition, some scattered contracted Schwann cell sheaths, which may be as short as 5-10 microns, occur at all stages. These are more frequent shortly after onset of remyelination than at later stages, and they are either composed of a cytoplasmic investment bordered by heminodes, or a more or less distorted myelin sheath bordered by nodes of Ranvier. This picture is very similar to the myelin sheath remodelling observed in regenerated rat sciatic nerves, and in some developing nerves with a mismatch between nerve growth and internodal elongation. It is concluded that a myelin sheath remodelling occurs in de- and remyelinated rat sciatic nerve, presumably as a result of the lack of longitudinal growth.
为了引发脱髓鞘和再髓鞘形成，将溶解于磷酸盐缓冲盐水（PBS）中的白喉毒素注射到成年大鼠坐骨神经中。对照神经仅注射PBS。在存活1至10周后，用戊二醛灌注动物。对注射神经的标本进行处理，用于对 teased 纤维进行光镜（LM）检查或对纵向薄片进行电镜（EM）检查。在存活6至10周后对 teased 纤维进行LM检查，结果显示大多数再髓鞘化的节间长度为150至300微米。此外，在常规再髓鞘化节间之间夹有一些异常短的施万细胞鞘，长度为15至150微米。对薄片的EM分析表明，在脱髓鞘早期，轴突外翻会穿透具有结加宽和/或结旁脱髓鞘的纤维中终末髓鞘板之间。在注射后约3周开始的再髓鞘化过程中形成的髓鞘中不存在这种改变。此外，在所有阶段都出现一些散在的收缩施万细胞鞘，其长度可能短至5至10微米。这些在再髓鞘化开始后不久比后期更频繁，它们要么由以半结为边界的细胞质包裹组成，要么由以郎飞结为边界的或多或少扭曲的髓鞘组成。这一情况与在再生大鼠坐骨神经以及一些神经生长与节间伸长不匹配的发育中的神经中观察到的髓鞘重塑非常相似。得出结论认为，在脱髓鞘和再髓鞘化的大鼠坐骨神经中发生了髓鞘重塑，推测是由于缺乏纵向生长所致。
