Lower vertebrates can detect UV light with the pineal complex independently of eyes. Electrophysiological studies, together with chromophore extraction analysis, have suggested that the underlying pigment in the lamprey pineal exhibits a bistable nature, that is, reversible photoreaction by UV and visible light, which is never achieved by known UV pigments. Here we addressed the molecular identification of the pineal UV receptor. Our results showed that the long-hypothesized pigment is a lamprey homologue of parapinopsin, which exhibits an absorption maximum at 370 nm, in the UV region. UV light causes cis-trans isomerization of its retinal 2 chromophore, forming a stable photoproduct having an absorption maximum at 515 nm, in the green region. The photoproduct reverts to the original pigment upon visible light absorption, showing photoregeneration of the pigment. In situ hybridization showed that parapinopsin is selectively expressed in the cells located in the dorsal region of the pineal organ. We successfully obtained the hyperpolarizing responses with a maximum sensitivity of Ϸ380 nm from the photoreceptor cells at the dorsal region, in which the outer segment was clearly stained with anti-parapinopsin antibody. These results demonstrated that parapinopsin is the pineal UV pigment having photointerconvertible two stable states. The bistable nature of the parapinopsin can account for the photorecovery of the pineal UV sensitivity by background green light in the lamprey. Furthermore, we isolated the parapinopsin homologues from fish and frog pineal complexes that exhibit UV sensitivity, suggesting that parapinopsin is a common molecular basis for pineal UV reception in the vertebrate.

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The electrochemical formation of Nd-Ni alloys was investigated in a molten LiF-CaF 2-NdF 3 (0.30 mol%) system at 1123 K. Cyclic voltammetry and open-circuit potentiometry indicated the formation of several phases of Nd-Ni alloys. The whole electrode became almost NdNi 2 phase by potentiostatic electrolysis of a 0.2 mm-thick Ni plate at 0.15 V vs. Li + /Li for 75 minutes. The formed NdNi 2 electrodes were transformed to other phases such as NdNi 3 and NdNi 5. The existences of NdNi 2 , NdNi 3 and NdNi 5 were confirmed by powder XRD analysis. By summarizing the results, the formation potential for each alloy phase has been determined.