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Day/night Cycles (night + cycle)
Selected AbstractsRFI2, a RING-domain zinc finger protein, negatively regulates CONSTANS expression and photoperiodic floweringTHE PLANT JOURNAL, Issue 5 2006Mingjie Chen Summary The red and far-red light-absorbing phytochromes interact with the circadian clock, a central oscillator that sustains a 24-h period, to measure accurately seasonal changes in day-length and regulate the expression of several key flowering genes. The interactions and subsequent signalling steps upstream of the flowering genes such as CONSTANS (CO) and FLOWERING LOCUS T (FT) remain largely unknown. We report here that a photomorphogenic mutant, red and far-red insensitive 2-1 ( rfi2-1), flowered early particularly under long days. The rfi2-1 mutation also enhanced the expression of CO and FT under day/night cycles or constant light. Both co-2 and gigantea-2 (gi-2) were epistatic to rfi2-1 in their flowering responses. The gi-2 mutation was also epistatic to the rfi2-1 mutation in the expression of CO and hypocotyl elongation. However, the rfi2-1 mutation did not affect the expression of GI, a gene that mediates between the circadian clock and the expression of CO. Like many other flowering genes, the expression of RFI2 oscillated under day/night cycles and was rhythmic under constant light. The amplitude of the rhythmic expression of RFI2 was significantly reduced in phyB-9 or lhy-20 plants, and was also affected by the gi-2 mutation. As previously reported, the gi-2 mutation affects the period length and amplitude of CCA1 and LHY expression, and GI may act through a feedback loop to maintain a proper circadian function. We propose a regulatory step in which RFI2 represses the expression of CO, whereas GI may maintain the proper expression of RFI2 through its positive action on the circadian clock. The regulatory step serves to tune the circadian outputs that control the expression of CO and photoperiodic flowering. [source] Synchronization of the Fungal and the Plant Circadian Clock by LightCHEMBIOCHEM, Issue 16 2008László Kozma-Bognár Abstract Circadian clocks are endogenous time keeping devices that provide temporal control of physiology in accordance with predicted daily changes in the environment. Photoentrainment is the process that synchronizes circadian clocks-and thereby clock-controlled gene expression and physiology-to the environmental day/night cycles. Light is primarily detected by specialized photoreceptors that are coupled,directly or through other signaling components,to the rhythm-generating oscillator. As a consequence, the expression, the activity or the stability of oscillator components are altered, resulting in a change of phase and/or pace of the oscillator. In this review our present knowledge about light absorption/transduction and light-induced modifications of oscillator components in Neurospora crassa and Arabidopsis thaliana is summarized. These systems provide a basis for understanding the molecular mechanisms of entrainment in the fungal and plant circadian systems. [source] Rhythmic diel movements of pandalid shrimps in the western Mediterranean continental shelf and upper slopeJOURNAL OF ZOOLOGY, Issue 4 2007J. Aguzzi Abstract In marine ecosystems, information on diel rhythmic movements of species is of importance to characterize temporal changes in the community structure. In this sense, patterns of bottom trawl catches of the pandalid caridean shrimps Chlorotocus crassicornis, Plesionika gigliolii and Plesionika martia were analysed, as a proxy of the timing and duration of their presence on the seabed, close to the autumn equinox (October) and the summer solstice (June) on the continental shelf (100 m) and the upper slope (400 m). The size structure of catches was also studied for each species to assess the possible occurrence of a modulation of rhythmic movements during ontogeny. Data showed marked diel patterns of catchability on the bottom in association with light intensity cycles in both sampling seasons and depths. Chlorotocus crassicornis on the shelf showed nocturnal peaks in catches. On the slope, Pl. gigliolii showed mainly a higher catchability at dusk and dawn, whereas the catchability of Pl. martia was mainly higher during the day time. Juveniles and adults of Pl. gigliolii and Pl. martia showed ontogenetic differences in their occurrence patterns. This phenomenon is discussed by comparing the reported catchability patterns with those of some prey species that also show rhythmic behaviour in association with the day,night cycle. [source] Finnegan neonatal abstinence scoring system: normal values for first 3 days and weeks 5,6 in non-addicted infantsADDICTION, Issue 3 2010Urs Zimmermann-Baer ABSTRACT Objective The neonatal abstinence scoring system proposed by Finnegan is used widely in neonatal units to initiate and to guide therapy in babies of opiate-dependent mothers. The purpose of this study was to assess the variability of the scores in newborns and infants not exposed to opiates during the first 3 days of life and during 3 consecutive days in weeks 5 or 6. Patients and methods Healthy neonates born after 34 completed weeks of gestation, whose parents denied opiate consumption and gave informed consent, were included in this observational study. Infants with signs or symptoms of disease or with feeding problems were excluded. A modified scoring system was used every 8 hours during 72 hours by trained nurses; 102 neonates were observed for the first 3 days of life and 26 neonates in weeks 5,6. A meconium sample and a urine sample at weeks 5,6 were stored from all infants to be analysed for drugs when the baby scored high. Given a non-Gaussian distribution the scores were represented as percentiles. Results During the first 3 days of life median scores remained stable at 2 but the variability increased, with the 95th percentile rising from 5.5 on day 1 to 7 on day 2. At weeks 5,6 median values were higher during daytime (50th percentile = 5, 95th percentile = 8) than night-time (50th percentile = 2, 95th percentile = 6, P = 0.02). Conclusion Scores increase from days 1,3 to weeks 5,6 and show day,night cycles with 5,6 weeks. Values above 8 can be considered pathological. This data may help to raise suspicion of narcotic withdrawal and to guide therapy. [source] | ||||||||||