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Long Intervals (long + interval)
Selected AbstractsMechanisms by which atrial fibrillation-associated mutations in the S1 domain of KCNQ1 slow deactivation of IKs channelsTHE JOURNAL OF PHYSIOLOGY, Issue 17 2008Lioara Restier The slow delayed rectifier K+ current (IKs) is a major determinant of action potential repolarization in the heart. IKs channels are formed by coassembly of pore-forming KCNQ1 ,-subunits and ancillary KCNE1 ,-subunits. Two gain of function mutations in KCNQ1 subunits (S140G and V141M) have been associated with atrial fibrillation (AF). Previous heterologous expression studies found that both mutations caused IKs to be instantaneously activated, presumably by preventing channel closure. The purpose of this study was to refine our understanding of the channel gating defects caused by these two mutations located in the S1 domain of KCNQ1. Site-directed mutagenesis was used to replace S140 or V141 with several other natural amino acids. Wild-type and mutant channels were heterologously expressed in Xenopus oocytes and channel function was assessed with the two-microelectrode voltage clamp technique. Long intervals between voltage clamp pulses revealed that S140G and V141M KCNQ1-KCNE1 channels are not constitutively active as previously reported, but instead exhibit extremely slow deactivation. The slow component of IKs deactivation was decreased 62-fold by S140G and 140-fold by the V141M mutation. In addition, the half-point for activation of these mutant IKs channels was ,50 mV more negative than wild-type channels. Other substitutions of S140 or V141 in KCNQ1 caused variable shifts in the voltage dependence of activation, but slowed IKs deactivation to a much lesser extent than the AF-associated mutations. Based on a published structural model of KCNQ1, S140 and V141 are located near E160 in S2 and R237 in S4, two charged residues that could form a salt bridge when the channel is in the open state. In support of this model, mutational exchange of E160 and R237 residues produced a constitutively open channel. Together our findings suggest that altered charge-pair interactions within the voltage sensor module of KCNQ1 subunits may account for slowed IKs deactivation induced by S140 or V141. [source] Increased Incidence of Colorectal Malignancies in Renal Transplant Recipients: A Case Control StudyAMERICAN JOURNAL OF TRANSPLANTATION, Issue 9 2010J. M. Park This study was to evaluate the frequency of colorectal neoplasia in renal transplant recipients and to investigate the association with Epstein-Barr virus (EBV) and cytomegalovirus (CMV) infection. We compared the frequency of colorectal neoplasia among renal transplant recipients with that of the healthy subjects. Specimens of colorectal neoplasia were examined for EBV and CMV using in situ hybridization and immunohistochemistry, respectively. Of 796 renal transplantation cohorts, 315 were enrolled. The frequency of colorectal neoplasia among the patients was 22.9%. Compared with the healthy subjects, the odds ratio (OR) for advanced adenoma was 3.32 (95% CI, 1.81,6.10). The frequency of cancer among the patients was 1.9% (OR, 12.0; 95% CI, 1.45,99.7). A long interval between transplantation and colonoscopy was a significant factor in the development of advanced colorectal neoplasia. EBV positivity was detected in 30.6% of colorectal neoplasia specimens from renal transplant recipients, which was higher than that for the controls (p = 0.002). CMV was not detected in any lesions of patients or controls. In conclusion, renal transplant recipients have a significantly increased risk of advanced colorectal neoplasia. EBV was more frequently found in specimens of advanced colorectal neoplasm obtained from the renal transplant recipients. [source] Theoretical and conceptual issues in time,place discriminationEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 9 2009Jonathon D. Crystal Abstract The need to discover resources that are available under specific environmental constraints represents a fundamental environmental pressure on the evolution of behavior. Time,place discrimination refers to the ability to secure resources when they are available under specific temporal and spatial contingencies. This article reviews a number of examples of time,place discrimination. The review highlights theoretical and conceptual issues that are needed to behaviorally identify the mechanisms responsible for time,place performance. Next, limitations on time,place performance that may be imposed by a circadian system are described. Finally, a number of lines of research that broaden these limitations are discussed. These lines of research include studies that suggest that (i) a broad range of long intervals (outside the limited range of circadian entrainment) are timed, (ii) at least some long intervals (16,21 h) are timed with an endogenous self-sustaining oscillator, (iii) short intervals (in the range of 1,3 min) are timed with an endogenous self-sustaining oscillator, and (iv) memory for specific unique events (including when and where they occurred) is based on a circadian representation of time. It is concluded that a unified theory of timing that can retain the times of occurrence of individual events is needed. The time of occurrence of an event may be encoded not only with respect to a circadian oscillator but also with respect to other oscillators in the long-interval and short-interval ranges. [source] History of marine biodiversityGEOLOGICAL JOURNAL, Issue 3-4 2001Peter M. Sheehan Abstract During the Phanerozoic, three steps of increasing diversity each had a unique Evolutionary Fauna (EF). During each EF, there were geologically long intervals of community stasis referred to as Ecological Evolutionary Units (EEUs). These intervals were characterized by communities composed of incumbent faunas that dominated particular habitats. Niches that were already occupied by incumbents were seldom invaded by new taxa, and the resilience of the incumbents to new competitors resulted in the long interval stasis. Most EEUs were terminated by extinction events that were caused by severe disruptions of the physical environment such as glaciations and extraterrestrial impacts. During mass extinctions many niches were vacated when incumbents were eliminated. Mass extinctions were followed by recovery intervals lasting on the order of 5 million years during which many surviving clades evolved adaptations which allowed them to move into vacated niches. New incumbents were established during these recovery intervals, and the next EEU began. In many ways, the recovery intervals resemble times when organisms invaded previously unoccupied ecospace, such as the emergence of life on land or the progressive filling of previously unoccupied habitats such as deep-burrowing and high epifaunal tiers that were colonized during the Palaeozoic. The recognition of long intervals of ecological stasis and the importance of physical disruptions in clearing incumbents is forcing revision of the traditional evolutionary viewpoint. The idea that most evolutionary change was accomplished very gradually by competition between organisms and by becoming better adapted to a relatively stable environment is being replaced by a recognition that major morphological and synecological changes tend to occur very rapidly and at times when there are few established competitors. Copyright © 2001 John Wiley & Sons, Ltd. [source] Measurement of atmospheric water vapour on the ground's surface by radio wavesHYDROLOGICAL PROCESSES, Issue 11 2001Tokuo Kishii Abstract Water vapour in the atmosphere and various meteorological phenomena are essential to the understanding of the mechanism of the water cycle. However, it is very difficult to observe water vapour in the atmosphere because the quantities are usually observed at a single point not over long intervals or in a specific plane or volume. Accordingly, the use of radio waves is considered to be necessary to observe water vapour. Radio waves can be transmitted over long intervals and across large areas, and generally speaking, the characteristics of radio waves change due to material in the atmosphere, especially water vapour. Usually absorption is used to observe the quantity of water vapour. But the relationship between absorption and the quantity of water vapour is not linear, so we try to utilize the phase difference between two radio waves as an alternative method. First, the relationship between the phase delay and the water vapour was induced by a physical equation and the resulting phase delay was found to be proportional to the quantity of water vapour. Furthermore, the phase difference between two separate points was observed by use of two radio waves in the field, specifically 84 GHz and 245 GHz. For reference and comparison, water vapour density in the atmosphere was simultaneously observed by meteorological observation. As a result, the density of the water vapour was found to be proportional to the phase difference between the two radio waves. The result also shows that this method is able to measure the diurnal changes in water vapour density in each season. Copyright © 2001 John Wiley & Sons, Ltd. [source] Does the foraging strategy of adult Short-tailed Shearwaters cause obesity in their chicks?JOURNAL OF AVIAN BIOLOGY, Issue 3 2000Mark A. Schultz The chick provisioning behaviour of Short-tailed Shearwaters Puffinus tenuirostris breeding at the northern edge of their distribution on Montague Island, New South Wales, was examined in February and March 1997. The duration of individual foraging trips of parents, weight changes of adults and chicks, and meal sizes delivered to chicks were determined. It was found that individual parents mixed a long foraging trip to Antarctic waters (14.4±2.0 days) with one to three short foraging trips (1.36±0.7 days, mode=1 day). Adults gained body mass on long trips and lost weight on short trips. The size of meals fed to the chicks was significantly greater after a long trip (161±21 g) than after a short trip (135±28 g), although short trips increased the overall chick feeding frequency. The variable number of short trips made by adult Short-tailed Shearwaters and the relationship between short trips and adult body condition were consistent with current life-history theory: adults do not sacrifice their own body condition to increase food delivered to their chicks. Modelling revealed that this dual foraging strategy inevitable leads to chicks enduring long intervals between meals. These long intervals may have led to the evolution of an over-feeding strategy by parents and the nestling obesity reported in this shearwater. The durations of the long trips from Montague Island were significantly greater than those for Short-tailed Shearwaters breeding at the centre of their distribution in Tasmania, although there was no significant difference in the length of short trips. A commitment to feed regularly in Antarctic waters may explain why the breeding distribution of this species does not extend much further north. [source] From simple rules to cycling in community assemblyOIKOS, Issue 2 2004Sebastian J. Schreiber Simulation studies of community assembly have frequently observed two related phenomena: (1) the humpty dumpty effect in which communities can not be reconstructed by "sequential" invasions (i.e. single species invasions separated by long intervals of time) and (2) cycling between sub-communities. To better understand the mechanisms underlying these phenomena, we analyze a system consisting of two predators and two prey competing for a shared resource. We show how simple dominance rules (i.e. R* and P* rules) lead to cycling between sub-communities consisting of predator,prey pairs; predator and prey invasions alternatively lead to prey displacement via apparent competition and predator displacement via exploitative competition. We also show that these cycles are often dynamically unstable in the population phase space. More specifically, while for too slow invasion rates (i.e. "sequential" invasions) the system cycles indefinitely, faster invasion rates lead to coexistence of all species. In the later case, the assembly dynamics exhibit transient cycling between predator-prey subcommunities and the length of these transients decreases with the invasion rate and increases with habitat productivity. [source] Does adaptive training work?APPLIED COGNITIVE PSYCHOLOGY, Issue 2 2009Claudia Metzler-Baddeley People intuitively alter the allocation of study time between items of varying difficulty, and such adaptive learning methods are widely used in education and in commercially available memory training programs. We investigated the effectiveness of a computer-based adaptive learning system that utilises spacing and repetition effects by presenting difficult items with short gaps to establish fast learning, and easy items with long intervals to optimise long-term retention. The immediate and delayed effects of adaptive training on cued recall were investigated relative to a control condition of non-adaptive, random spacing. Adaptive training produced significantly higher immediate and delayed recall rates than random spacing. These results encourage the use of adaptive training in education and rehabilitation. Copyright © 2008 John Wiley & Sons, Ltd. [source] Self-harm and depression in women with urinary incontinence: a record-linkage studyBJU INTERNATIONAL, Issue 3 2007Michael J. Goldacre OBJECTIVE To investigate the association between self-harm and urinary incontinence (UI), and between depression and UI, in women. PATIENTS AND METHODS The incidence of self-harm in women with UI is not well documented. We analysed a statistical database that includes hospital contact data for UI and for self-harm and depression. We calculated rate ratios for self-harm and depression in a cohort of women admitted for UI, and rate ratios for UI in cohorts of women admitted with self-harm or depression, compared with a control cohort. RESULTS After admission for UI, self-harm was significantly high in young women (aged <45 years: rate ratio 1.73, 95% confidence intervals 1.37,2.14) but not in older women. Depression was associated with UI in all age groups, e.g. after admission for depression the rate ratio for UI within 5 years was 1.46 (1.33,1.75); and for UI at ,,5 years after admission for depression, it was 1.20 (1.05,1.35). CONCLUSIONS Young women with UI are at risk of self-harm. For all age groups studied, depression was more common in women with UI than in others. Depression might be a consequence of UI, but the increase in risk at long intervals before admission with UI suggests that they might share underlying causal mechanisms. [source] | |||||||||||||