猫视神经年龄相关的形态学变化

对4只青年猫(1-3龄)和4只老年猫(10-13龄)视神经进行形态计量比较研究。取两个年龄组的颅内相应部分视神经进行横向连续切片,H.E染色于光镜下观察其基本结构;相邻切片进行结晶紫染色显示胶质细胞;神经丝蛋白(NF)免疫染色显示视神经纤维,胶质纤维酸性蛋白(GFAP)免疫染色显示星形胶质细胞(AS),对实验结果进行统计学分析并绘制纤维直径谱。与青年猫相比,老年猫视神经外膜厚度、直径、面积均显著增加,视神经纤维的密度和数量显著下降,且以视神经中央部纤维密度下降最显著;纤维直径谱分析结果显示,青、老年猫纤维直径分布范围相似,但老年猫的峰直径及纤维平均直径比青年猫的显著减小;另外,老年猫视神经束中的星形胶质细胞明显膨大,胶质细胞密度以及星形胶质细胞占胶质细胞总数的百分比均显著增加。结果表明:在衰老过程中视神经纤维出现明显的丢失现象,纤维平均直径显著减小使其对视觉信息的传导速度减慢,这可能是导致老年个体视觉分析速度下降的重要原因;老年个体视神经束内胶质细胞活动增强可能对维持视神经纤维形态、功能或延缓视神经进一步衰老起保护作用

Age-related morphological changes in the optic nerve of the cat

A morphometric study was carried out on the optic nerve of 4 young adult cats (1-3 years old) and 4 old cats (12 years old). The intracranial portion of the optic nerves was comparatively studied. Consecutive cross-sections from two age groups were stained with hematoxylin-eosin to observe the intra-structure of the optic nerve. Adjacent sections were stained with crystal violet for demonstration of glial cells. Neurofilament (NF) immunoreaction was used for locating and characterizing optic nerve axons and glial fibrillary acidic protein (GFAP) labeling for visualization of astrocytes. All results were subjected to statistical analysis, and diameter spectrum of nerver fibers was quantitatively described. The myelin sheath's thickness, diameter and area of optic nerves in old cats were significantly increased compared with those of young adults. Whereas in terms of density and number of optic nerve fibres were considerably decreased in old cats in comparison with young cats, especially in the center of optic nerve, which can be illustrated in comparison on the diameter spectrum of optic nerve fibres between young and old cats. Their dynamic range was quite similar, but the old animals showed a significant decrease both in the peak diameter and the average diameter. Astrocytes in old cats showed considerably hypertrophic and occupied a larger proportion among total glial cells when compared with that in young adult ones. Our results suggested that a significant loss of optic nerve fibres especially thicker fibres and a declined diameter of nerve fibers in senile individuals, which might lead to a degradation of visual processing during senescence. An age-related activity enhancement of glial cells in the optic nerve of old cats may provide protective effects on nerve fibers during aging