When people are completely isolated from environmental time cues, their circadian rhythms free run with a nearly 24-h cycle, generated by an internal body clock. Free-running temperature, cortisol, and melatonin rhythms have also been described in totally blind people, even though they were living in normal society and had access to abundant time cues; thus an intact visual system may be essential for synchronization of the circadian system. However, because of the small numbers of subjects studied, the incidence and clinical significance of circadian rhythm abnormalities among the blind has remained uncertain. In this study, plasma melatonin (n = 20), cortisol (n = 4), and sleep propensity (n = 1) were measured in serial samples taken from totally blind subjects for 24 h. Most totally blind subjects had circadian rhythm abnormalities. In about half of the subjects, the rhythms were free-running. Some blind subjects suffered recurrent insomnia and daytime sleepiness that were maximal when the internal rhythms were out of phase with the preferred sleep times. The high incidence of abnormal circadian rhythms in blind people underscores the importance of the light-dark cycle as an important environmental synchronizer for the human circadian system.

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SummaryThe biochemical and cell cycle-dependent properties of proliferating cell nuclear antigen (OsPCNA) and ap endonuclease-1 (OsFEN-1) were characterized from rice (Oryza sativa). OsPCNA was physically associated with OsFEN-1 and increased the¯ap-endonuclease activity of OsFEN-1 by 2.5-fold. Northern and Western blotting analysis revealed that OsPCNA and OsFEN-1 were present in meristematic tissues such as cultured cells, shoot apical meristem and root apical meristem. No expression was detected in the mature leaves, although they were exposed to UV. Both of these proteins were localized in the nuclei of the interphase cells including G1, S and G 2 , and in the nuclear region at telophase. The distribution patterns of plant PCNA and FEN-1 in meiotic cell progression were investigated using microsporocytes of lily (Lilium longi¯orum cv. Hinomoto). During the leptotene to pachytene stages, PCNA and FEN-1 were localized in the nuclear region. The¯orescence gradually disappeared from diplotene to metaphase I. Interestingly, signals for PCNA formed 10±20 intense spots at leptotene. The number of spots decreased to 1±5 at zygotene and ®nally to 1 at pachytene. The roles of OsPCNA and OsFEN-1 in mitotic and meiotic cell cycles are discussed.