Guy J, Ellis E A, Kelley K, Hope G M
Department of Ophthalmology, University of Florida College of Medicine, Gainesville 32610.
J Comp Neurol. 1989 Sep 22;287(4):446-54. doi: 10.1002/cne.902870404.
The spectra of fiber and axon diameter, myelin sheath thickness, fiber density, and g ratio of the optic nerve were analyzed for the strain-13 guinea pig, an animal extensively utilized in the investigation of experimental disorders of demyelination. Our detailed analytical study of the normal guinea pig optic nerve provides the basis for comparison to disease states and the morphology of other species. As in the rat, mouse, and chipmunk, fiber diameters in the guinea pig were unimodal, but dissimilar to the trimodal fiber spectra of the cat and primate. The predominance of medium-sized fibers (0.80-2.00 microns), common to most species, contributed to the larger mean fiber diameter (1.45 microns) of the guinea pig optic nerve, in which small fibers (0.50 microns or less) were infrequent and fibers larger than 5.00 microns in diameter, seen in the cat and primate, were absent. While myelin sheath thickness increased with axon diameter in the guinea pig, as in other species, a g ratio of 0.81 in the guinea pig was greater than in most mammals. Since conduction velocity is dependent on axon size, as well as myelin properties, the relatively larger mean axon diameter of the guinea pig optic nerve (1.18 microns) may compensate for the decrease in its myelination.
对13号品系豚鼠的视神经纤维和轴突直径、髓鞘厚度、纤维密度及g值进行了分析，该动物在脱髓鞘实验性疾病研究中被广泛应用。我们对正常豚鼠视神经进行的详细分析研究为与疾病状态及其他物种的形态学进行比较提供了基础。与大鼠、小鼠和花栗鼠一样，豚鼠的纤维直径呈单峰分布，但与猫和灵长类动物的三峰纤维光谱不同。大多数物种中常见的中等大小纤维（0.80 - 2.00微米）占主导地位，这使得豚鼠视神经的平均纤维直径（1.45微米）更大，其中小纤维（0.50微米或更小）很少见，而在猫和灵长类动物中可见的直径大于5.00微米的纤维则不存在。与其他物种一样，豚鼠的髓鞘厚度随轴突直径增加，但豚鼠的g值为0.81，高于大多数哺乳动物。由于传导速度取决于轴突大小以及髓鞘特性，豚鼠视神经相对较大的平均轴突直径（1.18微米）可能弥补了其髓鞘形成的减少。
