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Biological Rhythms (biological + rhythm)
Selected AbstractsImportance and Relevance of Melatonin to Human Biological RhythmsJOURNAL OF NEUROENDOCRINOLOGY, Issue 4 2003J. Arendt Abstract The pineal hormone melatonin is a remarkable molecule, with a conserved time-keeping function across species. It is extensively used as a self-administered remedy for sleep disturbance in countries where it is freely available, and to some extent when it is available on prescription, as in the UK. In some circumstances, notably free-running sleep disorder of the blind, it is the treatment of choice. It is also the marker rhythm of choice for the determination of circadian phase and period. This review outlines the current state of knowledge within a physiological perspective with emphasis on human biological rhythms. [source] The role of cell-specific circadian clocks in metabolism and diseaseOBESITY REVIEWS, Issue 2009M. S. Bray Summary Biological rhythms are an integral component of essentially all aspects of life. These rhythms are controlled in part by circadian clocks, transcriptionally based mechanisms that synchronize the organism to its changing environment. The central circadian clock is located within the suprachiasmatic nucleus of the brain, while peripheral clocks are located within virtually all cells outside of the suprachiasmatic nucleus. Although our understanding of central clock structure and function is well advanced, the role of peripheral clocks in whole body energy metabolism is just beginning to be elucidated. Both central and peripheral circadian clocks likely regulate many physiological functions, including insulin sensitivity, endocrine regulation, energy homeostasis, satiety signalling, cellular proliferation and cardiovascular function. Widely varying phenotypes have been reported following global genetic disruption of the clock mechanism in mice, with phenotype dependent on both the clock component targeted and genetic background. The inconsistency in phenotypes associated with clock disruption may be due, in part, to cell-specific effects of the circadian clocks. To address this question, many laboratories have begun generating animal models of cell type-specific clock disruption. In this review, we summarize the existing literature on tissue-specific models of circadian clock disruption and provide a focus for future research in this area. [source] Preliminary evaluation of electroencephalographic entrainment using thalamocortical modellingEXPERT SYSTEMS, Issue 4 2009Dean Cvetkovic Abstract: The concept of linked oscillators in biological control systems has long been established. Frequency entrainment is a predominant explanation behind many biological rhythms. In this paper a preliminary examination of electroencephalographic entrainment is made to survey the possibility and methods of achieving signal entrainment at the highest level of neurological organization and function. A model of the thalamocortical system is employed to generate simulated electroencephalographic signals and is tested in various configurations in the search for entrainment under very simple conditions. Additionally, an analysis of the coupled Van der Pol model of the circadian rhythm controller is performed to identify the possibility of affecting that system with a drastically different coupling input signal. We were able to conclude that overall signal shape can have a significant impact on the entrainment characteristics of the system. Due to the nature of the underlying mathematical structure of the model, by examining the circadian rhythm controller, we found that it is unsuitable for entrainment to an incident entraining signal of much higher frequency. [source] Importance and Relevance of Melatonin to Human Biological RhythmsJOURNAL OF NEUROENDOCRINOLOGY, Issue 4 2003J. Arendt Abstract The pineal hormone melatonin is a remarkable molecule, with a conserved time-keeping function across species. It is extensively used as a self-administered remedy for sleep disturbance in countries where it is freely available, and to some extent when it is available on prescription, as in the UK. In some circumstances, notably free-running sleep disorder of the blind, it is the treatment of choice. It is also the marker rhythm of choice for the determination of circadian phase and period. This review outlines the current state of knowledge within a physiological perspective with emphasis on human biological rhythms. [source] Mind, Brain, Education, and Biological TimingMIND, BRAIN, AND EDUCATION, Issue 1 2008Diego A. Golombek ABSTRACT, Circadian rhythms, in particular the sleep,wake cycle, modulate most, if not all, aspects of physiology and behavior. Their impact on education has recently begun to be understood, including a clear positive relationship between sleep and learning. In fact, sleep deprivation, common to adolescents throughout the world, has a deep effect on academic performance, and this fact is often increased by inadequate school schedules. This special issue of Mind, Brain, and Education deals with the relation between biological rhythms and learning, as discussed in an International Mind, Brain, and Education Society meeting that took place in Erice, Italy in May 2007. The articles (with contributors from Brazil, Croatia, Sweden, Spain, United Kingdom, United States, and Argentina) cover several aspects of this fundamental link between timing and education and suggest strategies to optimize school and sleep schedules for a better quality of life and improved academic performance of students. [source] Circadian biology and sleep: missing links in obesity and metabolism?OBESITY REVIEWS, Issue 2009J. M. Gimble Summary This supplement highlights key talks presented at the Pennington Symposium. The collected papers provide a state of the art review of circadian biology at the basic and clinical levels in the context of nutrition, obesity and sleep medicine. Investigators from multiple disciplines attempted to translate new information concerning molecular mechanisms into practical clinical applications, as well as foster new research hypotheses and directions to this exciting field of science and medicine. Furthermore, we hope to spark the interest and attention of the next generation of scientists who will tackle the questions presented by the changing interface between technology, lifestyle and biological rhythms. [source] Circadian rhythms and the evolution of photoperiodic timing in insectsPHYSIOLOGICAL ENTOMOLOGY, Issue 4 2009DAVID S. SAUNDERS Abstract. This review discusses possible evolutionary trends in insect photoperiodism, mainly from a chronobiological perspective. A crucial step was the forging of a link between the hormones regulating diapause and the systems of biological rhythms, circadian or circannual, which have independently evolved in eukaryotes to synchronize physiology and behaviour to the daily cycles of light and darkness. In many of these responses a central feature is that the circadian system resets to a constant phase at the beginning of the subjective night, and then ,measures' the duration of the next scotophase. In ,external coincidence', one version of such a clock, light now has a dual role. First, it serves to entrain the circadian system to the stream of pulses making up the light/dark cycle and, second, it regulates the nondiapause/diapause switch in development by illuminating/not illuminating a specific light sensitive phase falling at the end of the critical night length. Important work by A. D. Lees on the aphid Megoura viciae using so-called ,night interruption experiments' demonstrates that pulses falling early in the night lead to long-day effects that are reversible by a subsequent dark period longer than the critical night length and also show maximal sensitivity in the blue,green range of the spectrum. Pulses falling in the latter half of the night, however, produce long-day effects that are irreversible by a subsequent long-night and show a spectral sensitivity extending into the red. With movement to higher latitudes, insects develop genetic clines in various parameters, including critical night length, the number of long-night cycles needed for diapause induction, the strength of the response, and the ,depth' or intensity of the diapause thus induced. Evidence for these and other types of photoperiodic response suggests that they provided strong selective advantages for insect survival. [source] OsEF3, a homologous gene of Arabidopsis ELF3, has pleiotropic effects in ricePLANT BIOLOGY, Issue 5 2009C. Fu Abstract Heading date is an important agronomic trait in rice. A rice mutant with a late heading date and no photoperiodic sensitivity in long or short day conditions was obtained from rice T-DNA insertion mutants in Zhonghua11 (ZH11). Through isolation and analysis of the flanking sequence of the T-NDA insertion site, the target sequence of insertion was obtained and found to locate in AP003296, the sequence accession number of rice chromosome 1 of RGP (http://rgp.dna.affrc.go.jp). The putative amino acid sequences of this target gene are homologous to the Arabidopsis protein ELF3 encoded by an early flowering gene. The rice target gene orthologous to Arabidopsis ELF3 is named OsEF3; this encodes a putative nematode responsive protein-like protein. OsEF3 has pleiotropic effects in rice that differ from the effects of Arabidopsis ELF3, which only affects biological rhythms. OsEF3 regulates heading date by influencing the BVG stage and does not affect photoperiodic sensitivity, which suggests that the OsEF3 gene may be involved in an autonomous pathway in rice. OsEF3 may affect root development and kilo-grain weight by delaying cell division or cell elongation. [source] Sleep and depression: an intimate relationshipPROGRESS IN NEUROLOGY AND PSYCHIATRY, Issue 2 2008Mark Greener Sleeping problems are among the most common and debilitating symptoms of depression and recent studies show the intimate relationship between depression and biological rhythms,which may influence treatment choice,explains Mark Greener. Copyright © 2008 Wiley Interface Ltd [source] The Biochemistry of Drug Metabolism , An IntroductionCHEMISTRY & BIODIVERSITY, Issue 10 2009Abstract This review on intra-individual factors affecting drug metabolism completes our series on the biochemistry of drug metabolism. The article presents the molecular mechanisms causing intra-individual differences in enzyme expression and activity. They include enzyme induction by transcriptional activation and enzyme inhibition on the protein level. The influencing factors are of physiological, pathological, or external origin. Tissue characteristics and developmental age strongly influence enzyme-expression patterns. Further influencing factors are pregnancy, disease, or biological rhythms. Xenobiotics, drugs, constituents of herbal remedies, food constituents, ethanol, and tobacco can all influence enzyme expression or activity and, hence, affect drug metabolism. [source] | |||||||||||||