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

1)在观察杆细胞数量增加的组织学基础上，研究了硬骨鱼成熟视网膜中增殖细胞核抗原（PCNA）免疫反应细胞的分布。在洄游数千公里的鳗鲡（Anguilla japonica）成年视网膜的外核层和内核层中都发现了大量的pcna免疫反应细胞，在适应底栖动物栖息地和夜间觅食的左眼比目鱼（parichthys olivaceus）幼鱼视网膜的外核层中也发现了大量的pcna免疫反应细胞。这些结果表明，视网膜杆状细胞在其一生中都在增殖，随着杆状细胞前体从鳗鱼内核层的祖细胞群和比目鱼外核层的基底区迁移到顶端区。2)在缺少褪黑激素合成生物钟的2岁虹鳟鱼的松果体器官中，与视蛋白免疫反应性光感受器外节段一起，在囊泡末端和茎部发现了大量的pcna免疫反应细胞。虽然有时发现视蛋白阳性光感受器外段与PCNA免疫反应细胞接近，但PCNA与视蛋白没有或很少共存。这些发现表明，成年虹鳟鱼的松果体光感受器细胞也在增殖，从而保持了活性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.