Photoreceptor proliferation in the mature retina and pineal organ of the teleost fish.

1)在组织学观察视杆细胞数量增加的同时，观察了增殖细胞核抗原免疫反应细胞在硬骨鱼成熟视网膜中的分布。在迁徙数千公里在海洋中繁殖的鳗鱼成体视网膜的外、内核层均有大量的增殖细胞核抗原免疫反应细胞，而在适应底栖环境和夜间摄食的牙鲆幼鳗视网膜的外核层均有大量的增殖细胞核抗原免疫反应细胞。这些结果表明，随着视杆前体细胞从鳗鱼内核层的祖细胞簇向外核层的顶端区域迁移，视网膜视杆细胞在其整个生命周期中都在增殖。2)在缺乏褪黑素合成生物钟的2岁虹鱼松果体器官的终囊和柄中，连同视蛋白免疫反应阳性的光感受器外节，大量的增殖细胞核抗原免疫反应阳性细胞被显示在松果体器官的末端囊泡和柄中。尽管有时可见视蛋白阳性的感光细胞外段与增殖细胞核抗原免疫反应细胞接近，但未见或仅有少量的视蛋白与视蛋白共存。这些发现表明，松果体光感受器细胞也在成年虹鱼体内增殖，从而保持了活跃的褪黑素合成的高度敏感的信号转导机制。

1)In parallel with histological observation on the increase in number of the rod cells, the distribution of proliferating cell nuclear antigen (PCNA)-immunoreactive cells was investigated in the mature retina of the teleost fish. A great number of PCNA-immunoreactive cells were demonstrated in both the outer and inner nuclear layers in the adult retina of the river eel Anguilla japonica migrating thousands of kilometers to breed in the ocean, and throughout the outer nuclear layer in the juvenile retina of the lefteye flounder Paralichthys olivaceus adapted to the benthic habitat and nocturnal feeding. These results suggest that the retinal rod cells proliferate throughout their life, following migration of the rod precursors from the progenitor clusters in the inner nuclear layer in the eel and from the basal to the apical region in the outer nuclear layer in the flounder.2)Together with opsin-immunoreactive photoreceptor outer segments, a tremendous number of PCNA-immunoreactive cells were demonstrated throughout the end-vesicle and stalk in the pineal organ of the 2 years-old rainbow trout Oncorhynchus mykiss lacking a circadian clock of melatonin synthesis. No or little coexistence of PCNA and opsin was demonstrated, although the close approaches of opsin-positive photoreceptor outer segments and PCNA-immunoreactive cells were found sometimes. These findings suggested that the pineal photoreceptor cells also proliferate in the adult rainbow trout, thus keeping highly sensitive signal-transduction mechanisms for active melatonin synthesis.