应用新体视学方法研究大鼠白质无髓神经纤维老年性改变

目的阐述如何应用新体视学方法研究大鼠白质无髓神经纤维的老年性改变,以便弄清楚导致老年白质有髓神经纤维总长度缩短的确切原因。方法本实验用10只6~8月龄Long-Ev-ans大鼠和8只18月龄以上同种大鼠。应用电镜技术及相应的体视学方法计算白质内无髓神经纤维的体积密度、长度密度和白质内无髓神经纤维的总体积、总长度。结果本研究发现雄性和雌性大鼠大脑白质无髓神经纤维总长度均无显著性老年性缩短;白质内无髓神经纤维总体积其雌性组和综合性别组均存在显著性的老年性降低;雄性大鼠无髓神经纤维总体积老年性降低虽然没有显著性,但是降低高达31%。结论老年大脑白质存在着大直径无髓神经纤维的显著性丢失,同时存在细小直径的有髓神经纤维脱髓鞘改变,在一定程度上掩盖了小直径无髓神经纤维的丢失。本研究在国际上首次把新的体视学方法和电子显微镜结合起来定量研究大鼠大脑白质无髓神经纤维的老年性改变。研究结果除进一步推动对老年大脑白质神经纤维改变的认识以外,还为在正常状态下大鼠白质无髓神经纤维长度和体积提供了基本数据,为以后应用这种动物模型作进一步的研究提供了参考资料。

Application of the new stereological methods to investigate the age-related changes of the unmyelinated fibers in rat white matter

Objective Application of the new stereological techniques to investigate the age-related changes of the unmyelinated nerve fibers in rat white matter was described in order to figure out the exact reason for a decline of the myelinated nerve fibers in aged white matter.Methods In the present study,10 adult Long-Evans rats(6~8 months) and aged LongEvans rats(older than 18 months) were used.The volume density,length density, total volume and total length of the unmyelinated fibers in white matter were estimated with the stereological techniques and transmission electron microscope technique.Results(Both in) the male and female rats,there was no significant decrease of the total length of the unmyelinated fibes in white matter between young rats and aged rats.However,there was significant decrease of the total volume of the unmyelinated fibers in white matter,between young female rats and aged female rats,between young male and female rats together and aged male and female rats together.The total volume of the unmyelinated fibers in white matter of aged male rats was decreased by 31% when compared to that of young male rats even though the difference was not statistically significant.Conclusion In aged rat white matter,there was significant decrease of the unmyelinated fibers with large diameters.However,the myelinolysis of the myelinated fibers with small diameters made the decrease of the unmyelinated fibers with small diameters unnoticeable.The present study for the first time in the world combined the new stereological techniques and transmission electron microscope technique to quantitatively study the age-related changes of the unmyelinated fibers in rat white matter.The results of the present study will not only help the further understanding of age-related changes of nerve fibers in white matter but also provide the normal data of the volume and length of the unmyelinated fibers in the rat white matter that will provide the baseline value to compare with future studies on this animal model.