江豚和白鱀豚视网膜神经节细胞的研究

江豚和白暨豚视网膜神经节细胞根据其形态结构可分为1、2两型。其密度分布在大多数江豚和1头白(既鱼)豚呈两个高密度区。第一高密度区位于视网膜鼻侧偏腹方,第二高密度区位于颞侧偏背方。第一和第二高密度区的细胞的最高密度在江豚大多数分别为每平方毫米250和210左右,在一例白暨豚约180和140以上。其组成、密度分布及细胞总数在采自长江和黄海沿岸的江豚之间差异不显著。在白(既鱼)豚由于大神经节细胞相对增多,细胞平均直径比江豚的大;细胞数在40微米左右处形成特有的第二个峰;2型的细胞极少,且没有发现典型的星形神经节细胞。 几种豚类的视网膜神经节细胞的比较表明,在适应弱光环境的过程中,视网膜神经节细胞的组成发生了一些改变:2型的神经节细胞逐渐减少甚至消失;大神经节细胞相对增多;神经节细胞密度减小。视觉敏度提高,锐度下降。

ON THE RETINAL GANGLION CELLS OF NEOPHOCAENA AND LIPOTES

The retinal ganglion cells can be classified into type 1 and type 2 in both Neophocaena and Lipotes. Both types all show two areas of high cell density in most of the 14 retinas from Neophocaena and the one retina from Lipotes. The first high-density area is located slightly ventrally at the rostral side, the second one slightly dorsally at the temporal side. The maximum densities at the two areas mostly amount to about 250/mm2 and 210/mm2 respectively in Neophocaena, and exceed 180/mm2 and 140/mm2 in Lipotes. No significant differences are found between the Yellow sea coastal specimens and the Yangtze specimens of Neo-phocaena in composition, density distribution and the total number of the retinal ganglion cells. In Lipotes, the mean diameter of the ganglion cells is relatively larger with a unique numerical second peak at about 40 micra. Only a few polygonal cells of type 2 are found, with no typical star-shaped cells.The comparisons between the retinal ganglion cells of Delphinus, Tursiops, Neophocaena. Lipous and Plaianina have revealed that the changes resulting from adaptation to dim light environment are 1) number of ganglion cells of type 2 gradually decreased or even disappeared. 2) number of larger ganglion cells relatively increased. 3) density of ganglion cells decreased. Thus, the sensitivity of the eye increases with decreasing resolving power.