Schlaepfer W W, Bunge R P
J Cell Biol. 1973 Nov;59(2 Pt 1):456-70. doi: 10.1083/jcb.59.2.456.
Light and electron microscope studies were conducted on the nature of the degenerative changes in amputated nerve fibers of cultured rat sensory ganglia and on the effects of media with differing calcium concentrations upon these changes. With glucose-enriched Eagle's media (MEM) containing 1.6 mM calcium, the amputated myelinated and unmyelinated axons undergo a progressive granular disintegration of their axoplasm with collapse and fragmentation of myelin sheaths between 6 and 24 h after transection. With MEM containing only 25-50 microM calcium, the granular axoplasmic degeneration does not occur in transected fibers and they retain their longitudinal continuity and segmental myelin ensheathment for at least 48 h. Addition of 6 mM EGTA to MEM (reducing the estimated Ca(++) below 0.3 microM) results in the structural preservation of both microtubules and neurofilaments within transected axons. A transient focal swelling of amputated axons occurs, however, in cultures with normal and reduced calcium. These observations suggest that an alteration in the permeability of the axolemma is a crucial initiating event leading to axonal degenerative changes distal to nerve transection. The loss of microtubules and neurofilaments and the associated granular alterations of the axoplasm in transected fibers appears to result from the influx of calcium into the axoplasm.
对培养的大鼠感觉神经节中切断的神经纤维退变变化的性质以及不同钙浓度培养基对这些变化的影响进行了光镜和电镜研究。在含有1.6 mM钙的富含葡萄糖的伊格尔培养基（MEM）中，切断的有髓和无髓轴突在横断后6至24小时内，其轴浆会逐渐发生颗粒状崩解，同时髓鞘塌陷和断裂。在仅含有25 - 50 microM钙的MEM中，切断的纤维不会发生颗粒状轴浆退变，并且它们至少在48小时内保持其纵向连续性和节段性髓鞘包裹。向MEM中添加6 mM EGTA（将估计的Ca(++)降低至0.3 microM以下）可导致切断轴突内的微管和神经丝结构得以保存。然而，在正常钙浓度和低钙浓度的培养物中，切断的轴突会出现短暂的局灶性肿胀。这些观察结果表明，轴膜通透性的改变是导致神经横断远端轴突退变变化的关键起始事件。切断纤维中微管和神经丝的丢失以及轴浆相关的颗粒状改变似乎是由于钙流入轴浆所致。
