大鼠大脑白质及白质内有髓神经纤维的性别与年龄差异

目的:研究正常年轻和中老年组雌雄性大鼠大脑白质及白质内有髓神经纤维之间的性别差异,并探讨大脑发育过程中性别差异随年龄增加的改变。方法:运用透射电子显微镜和体视学方法对6~8月龄的年轻Long-Evans大鼠及18月龄同种中老年大鼠大脑白质及其有髓神经纤维进行定量研究。结果:年轻组雄性大鼠大脑白质、有髓神经纤维及其髓鞘的总体积均显著大于雌性,而中老年组雌性大鼠大脑白质、有髓神经纤维体积密度、有髓神经纤维及其髓鞘的总体积均显著大于雄性。结论:年轻组及中老年组大鼠大脑白质、白质内有髓神经纤维及其髓鞘总体积均存在性别差异,随着年龄的增长,雄性大鼠大脑白质及白质内有髓神经纤维体积的减少较雌性更为明显。     

大脑白质有髓神经纤维髓鞘超微结构定量研究的体视学方法

目的:运用新的体视学方法研究大鼠白质有髓神经纤维髓鞘超微结构,以期为以后各种有关髓鞘超微结构的相关研究提供可靠的方法学依据.方法:6～8月龄雌性Long-Evans大鼠.运用电镜技术及相应的体视学方法计算白质内有髓神经纤维的总长度、有髓神经纤维髓鞘总体积、有髓神经纤维及轴突直径、髓鞘断面面积、髓鞘内外周长、髓鞘平均厚度.结果:获得了正常6～8月龄雌性Long-Evans大鼠有髓神经纤维总长度及髓鞘超微结构的各项数据,两种不同方法得到的髓鞘平均厚度并没有显著性差异.结论:把新的体视学方法和电子显微镜结合起来定量研究了大鼠大脑白质有髓神经纤维髓鞘超微结构,所描述的方法为以后进行髓鞘超微结构的定量研究提供了有用的工具.     

大鼠大脑白质及白质内有髓神经纤维老年性改变的体视学研究

目的 探讨老年大鼠大脑白质及白质内有髓神经纤维的改变.方法 运用透射电子显微镜和体视学方法分别对年轻组和老年组Long-Evans大鼠大脑白质及其内有髓神经纤维进行定量研究.结果 老年组大鼠大脑白质总体积,有髓神经纤维总长度分别下降了24.1%和41%;老年组大鼠有髓神经纤维体积密度、髓鞘体积密度和纤维直径分别增加了30%、23.9%和31%,具有统计学意义.但是有髓神经纤维长度密度、有髓神经纤维总体积和髓鞘的总体积没有显著老年性改变.结论 正常老年大脑的萎缩主要是由白质体积的下降引起的.正常老年大脑白质的有髓神经纤维总长度显著性降低,并且主要是由于白质内细小直径的有髓神经纤维丢失所造成的.     

短期丰富生存环境对老年雌性大鼠海马及海马内有髓神经纤维的影响

目的:探讨短期丰富生存环境的干预对老年雌性大鼠海马及海马内有髓神经纤维的影响.方法:将雌性SD大鼠随机分为丰富生存环境组和对照组,采用Morris水迷宫对大鼠的空间学习能力进行测试;透射电子显微镜和新的体视学方法分别对各组大鼠大脑海马及其有髓神经纤维进行定量研究.结果:短期丰富生存环境组老年雌性大鼠与空白对照组相比,其空间学习能力无显著差异;大脑海马总体积、海马内有髓神经纤维总长度、海马内有髓神经纤维总体积和海马内有髓神经纤维直径均无显著改变.结论:4个月短期丰富生存环境的干预对于28月龄雌性大鼠空间学习能力、海马内有髓神经纤维均没有产生显著性影响.     

雄性大鼠大脑半球白质及其内有髓神经纤维老年改变的侧别差异

目的 探讨雄性大鼠左右大脑半球白质及其内有髓神经纤维是否存在显著性差异,以及每侧大脑半球白质及其内有髓神经纤维的老年性改变是否一致.方法运用透射电子显微镜和体视学方法分别对5只年轻(6～8月龄)和4只老年(18月龄)雄性Long-Evans大鼠左侧、右侧大脑半球白质体积及白质内有髓神经纤维体积、长度和直径进行定量研究.结果年轻组大鼠和老年组大鼠左右大脑半球白质体积及白质内有髓神经纤维体积、长度和直径均不存在显著性差异.每侧大脑半球白质及其内有髓神经纤维总长度和总体积均随年龄增加而降低,右侧半球白质体积、右侧半球白质内有髓神经纤维总体积和左侧半球白质内有髓神经纤维总长度随年龄增长分别显著性降低32.9%、28.6%和49.3%.结论正常年轻和老年雄性Tong-Evans大鼠两侧大脑半球的白质及其内有髓神经纤维均不存在显著性侧别差异.老年雄性Long-Evans大鼠右侧大脑半球白质体积、右侧大脑半球白质内有髓神经纤维的总体积和左侧大脑半球白质内有髓神经纤维总长度存在显著老年性改变.     

P> 短期丰富生存环境增加中老年雄性大鼠海马结构内有髓神经纤维的总长度/P>

目的 探讨短期丰富生存环境干预对正常中老年雄性大鼠海马结构及海马内有髓神经纤维的影响。 方法 将20只14月龄的雄性SD大鼠随机分为丰富生存环境组与空白对照组,前者在丰富生存环境条件下饲养4个月,后者在普通环境中饲养4个月后,采用Morris水迷宫测试两组大鼠的空间学习能力;运用透射电子显微镜和体视学方法对两组大鼠海马结构及海马内有髓神经纤维进行定量研究。 结果 丰富生存环境组大鼠空间学习能力与空白对照组之间不存在显著性差异;丰富生存环境组与空白对照组相比较,海马结构总体积两组间无显著性差异。丰富生存环境组海马结构内有髓神经纤维的总体积、有髓神经纤维总长度、有髓神经纤维平均直径显著增加。 结论 短期丰富生存环境干预对14月龄雄性大鼠海马有髓神经纤维具有显著性影响。这一研究结果为将来寻找延缓大脑衰老进程的行为学手段提供了重要的理论依据。     

大鼠大脑白质无髓神经纤维老年改变的机制探讨

目的 运用体视学方法研究大鼠大脑白质无髓神经纤维的老年性改变,探讨导致老年白质有髓神经纤维总长度降低的确切原因,并探讨性别因素在老年大脑改变中所起的作用.方法 6～8月龄Long-Evans大鼠9只和18月龄同种大鼠8只.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和总长度.结果 雄性和雌性大鼠大脑白质无髓神经纤维总长度均无显著的老年性降低.白质内无髓神经纤维总体积在雌性组存在显著的老年性降低,从年轻组的平均32.79mm3下降到了老年组的平均18.60mm3.雄性大鼠无髓神经纤维总体积老年性降低虽无显著性,但也从年轻组的平均34.79mm3下降到老年组的平均24.02mm3.降低高达31%.年轻组与老年组的各项指标中雄性与雌性动物间均不存在显著的性差别. 结论老年大鼠大脑白质存在大直径无髓神经纤维的显著件丢失,同时存在的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老年白质内小直径无髓神经纤维的丢失.     

短期丰富生存环境增加中老年雄性大鼠海马结构内有髓神经纤维的总长度

目的探讨短期丰富生存环境干预对正常中老年雄性大鼠海马结构及海马内有髓神经纤维的影响。方法将20只14月龄的雄性SD大鼠随机分为丰富生存环境组与空白对照组,前者在丰富生存环境条件下饲养4个月,后者在普通环境中饲养4个月后,采用Morris水迷宫测试两组大鼠的空间学习能力;运用透射电子显微镜和体视学方法对两组大鼠海马结构及海马内有髓神经纤维进行定量研究。结果丰富生存环境组大鼠空间学习能力与空白对照组之间不存在显著性差异;丰富生存环境组与空白对照组相比较,海马结构总体积两组间无显著性差异。丰富生存环境组海马结构内有髓神经纤维的总体积、有髓神经纤维总长度、有髓神经纤维平均直径显著增加。结论短期丰富生存环境干预对14月龄雄性大鼠海马有髓神经纤维具有显著性影响。这一研究结果为将来寻找延缓大脑衰老进程的行为学手段提供了重要的理论依据。     

短期丰富生存环境对中老年雌性大鼠海马结构及其内有髓神经纤维的影响

目的 探讨短期丰富生存环境干预对中老年雌性大鼠海马结构及其内有髓神经纤维的影响。 方法 将20只14月龄的雌性SD大鼠随机分为丰富生存环境组和标准环境组,每组各10只,对丰富生存环境组的动物给予4个月丰富生存环境干预, 标准环境组于普通标准环境下饲养4个月;然后每组各随机选取5只,采用Morris水迷宫对大鼠的空间学习能力进行测试,然后运用透射电子显微镜和体视学方法分别对大鼠大脑海马结构及其内有髓神经纤维进行定量研究。 结果 短期丰富生存环境组中老年雌性大鼠与标准环境组相比,其空间学习能力明显增强;丰富生存环境组海马结构内有髓神经纤维总长度和总体积分别显著增加了43.4%和47.4%,且有髓神经纤维总长度的增加主要是由于细小直径的有髓神经纤维长度增加所致。海马结构总体积和海马结构内有髓神经纤维直径未见改变。 结论 4个月丰富生存环境干预对于14月龄雌性大鼠空间学习能力、海马内有髓神经纤维均有显著性影响。     

大鼠大脑皮质有髓神经纤维老年性改变的定量研究

目的:探讨中枢神经系统是否普遍存在老年性轴突变性和髓鞘破坏。方法:运用透射电子显微镜和体视学方法分别对青年组(6～8月龄)和老年组(18月龄以上)Long-Evans大鼠大脑皮质及皮质内有髓神经纤维进行定量研究。结果:老年大鼠的皮质体积,皮质内有髓神经纤维的总长度和总体积以及直径较年青大鼠有所下降,但这些降低均无统计学意义。结论:老年大鼠大脑皮质不存在显著性有髓神经纤维退行性改变。     

Enriched Environment Increases the Myelinated Nerve Fibers of Aged Rat Corpus Callosum

In this study, the effect of enriched environment (EE) on the spatial learning of aged rats was examined, and then the effects of EE on the aged corpus callosum (CC) were investigated by means of the modern stereological methods. We found that EE significantly improved the spatial learning of aged rats. The CC volume, the total volume of the myelinated fibers and total volume of the myelin sheaths in the CC, the total length of the myelinated fibers in the CC of enriched rats were significantly increased when compared to standard rats. The increase of the myelinated fibers in enriched rat CC might provide one of the structural bases for the enrichment‐related improvement of the spatial learning. This study provided, to the best of our knowledge, the first evidence of environmental enrichment‐induced increases of the CC and the myelinated fibers in the CC of aged rats. Anat Rec, , 2012. © 2012 Wiley Periodicals Inc.     

Stereological Methods for Estimating the Myelin Sheaths of the Myelinated Fibers in White Matter

In the present study, efficient and unbiased stereological techniques to investigate the myelin sheaths of the myelinated fibers in rat white matter were established. In the present design, four tissue blocks were obtained from the entire white matter of rat brain in a uniform, random fashion. Isotropic, uniform random (IUR) sections were ensured by the use of the isector technique. One section with the thickness of 60 nm was cut from the center of each epon block. Eight to 10 fields of vision were randomly photographed under a transmission electron microscope. The total length of the myelinated fibers and the total volume of the myelin sheaths in the white matter were the products of the length density, volume density, and the volume of the white matter obtained with the Cavalieri principle. The mean areas of the myelinated fibers profiles and myelin sheaths were estimated with the point counting technique. The inner and outer perimeters of the myelin sheaths were estimated by the use of a line grid, and the thickness of the myelin sheaths was estimated by direct orthogonal measurements in uniform, random locations. The described methods will provide very useful tools for future quantitative studies of changes in the myelin sheaths of white matter in various experimental conditions and in various neurodegenerative diseases. Anat Rec, 2009. © 2009 Wiley‐Liss, Inc.     

Side differences of the age-related changes in the white matter and the myelinated nerve fibers in the white matter of female rats

The present study tested if there were side differences of the white matter and the myelinated fibers in the white matter of female rats, and if there were side differences in the age-related changes of the white matter and the myelinated fibers in the white matter of female rats. Five young, five middle-aged and five aged female Long-Evans rats were quantitatively investigated using electron microscopic technique and stereological methods. We found no side differences of the white matter volume, the total volume, total length and mean diameter of the myelinated fibers in the white matter of young, middle-aged, and aged female rats. When compared to middle-aged female rats, the total length of the myelinated fibers in the white matter of the left hemisphere in aged female rats was decreased significantly, but the total length of the myelinated fibers in the white matter of the right hemisphere in aged female rats was non-significantly decreased. Our data indicated that there were no significant side differences in the white matter and the myelinated fibers in the white matter in young, middle-aged, and aged female rats. However, we demonstrated that the aged-related changes of the myelinated fibers in the white matter of the left hemisphere and right hemisphere were different. The results obtained in the present study will provide biological basis for the understanding of the asymmetry of cerebral functions.     

The effects of short-term enriched environment on capillaries of the middle-aged rat cortex

There has been no study investigating the effects of enriched environment on the capillaries of cortex with new stereological methods. In the present study, both 14 month female and male Sprague-Dawley rats were randomly divided into enriched environment (EE) rats and standard environment (SE) rats. EE rats were reared in enriched environment and SE rats were reared in standard environment for 4 months. The effects of short-term enriched environment on the cortex volume and on the total volume, total length, total surface area and mean diameter of the capillaries in the cortex of mid-aged Sprague-Dawley rats were quantitatively investigated with immunohistochemistry technique and unbiased stereological methods. There were no significant differences in the cortex volume, the total length and total surface area of the capillaries in the cortex between EE rats and SE rats. The total volume of the capillaries in the cortex of female EE rats and male EE rats was significantly increased when compared to female SE rats and male SE rats. The mean diameter of the capillaries in the cortex of female EE rats was significantly decreased when compared to that in female SE rats, but there was no significant difference in the mean diameter of the capillaries in the cortex between male EE rats and male SE rats. The present results indicate that enriched environment had a positive effect on the capillaries in the cortex of middle-aged rats. The present study might provide an important morphological basis for searching the ethology strategy to delay the progress of brain aging in the future.