bluuebunny/crossref_metadata_2025 huggingface dataset:
Different intracellular polyamine concentrations underlie the difference in the inward rectifier K+ currents in atria and ventricles of the guinea‐pig heart
Authors: Yan Ding‐Hong , Nishimura Kazuhiro , Yoshida Kaori , Nakahira Kei , Ehara Tsuguhisa , Igarashi Kazuei , Ishihara Keiko
Published: January 2005

The outward component of the strong inward rectifier potassium current, IK1, is significantly larger in ventricles than in atria of the heart, resulting in faster repolarization at the final phase of the action potential in ventricles. However, the underlying mechanism of the difference in IK1 remains poorly understood. IK1 channels are composed of subunits from the Kir2 subfamily, and IK1 amplitude is determined by the voltage‐dependent blockade of the channel by the intracellular polyamines spermine and spermidine, and by Mg2+. Using a perforated patch‐clamp method, which minimizes changes in the intracellular polyamine and Mg2+ concentrations, we detected repolarization‐induced outward IK1 transients, which are caused by competition between Mg2+ and spermine to block the channel, in ventricular but not in atrial myocytes from guinea‐pig heart. The contribution of the Kir2.3 subunit to the IK1 channel was found to be minor in the guinea‐pig heart, because the activation time course of the Kir2.3 currents was ∼10‐fold slower than those of IK1, and the marked external pH sensitivity of the Kir2.3 currents was not found in IK1. Both the Kir2.1 and Kir2.2 currents recorded from inside‐out patches exhibited outward transients similar to those of ventricular IK1 in the presence of 5–10 μm spermine and 0.6–1.1 mm Mg2+, and their amplitudes were diminished by increasing the spermine or spermidine concentrations. The total and free polyamine concentrations in guinea‐pig cardiac tissues were higher in atria than ventricles. These results strongly suggest that different intracellular polyamine concentrations are responsible for the difference in atrial and ventricular IK1 of the guinea‐pig heart.
Influence of nontrophic interactions between benthic invertebrates on river sediment processes: a microcosm study
Authors: Mermillod-Blondin Florian , Gérino Magali , Sauvage Sabine , Châtelliers Michel Creuzé des
Published: January 2005

The main objective of this study was to measure the impact of benthic invertebrate diversity on river sediment processes. We quantified the effects of interactions between three taxa (asellids, chironomid larvae, and tubificid worms). The impacts of different taxa richness treatments were measured on sediment reworking, O2 concentrations, bacterial abundances, and numbers of active bacteria in slow filtration sandgravel columns. The coefficients of sediment reworking measured in multitaxa treatments were lower than those predicted from one-taxon treatments. The interactions among invertebrates also significantly reduced O2 concentrations in sediments. These results were probably due to interactions between the different sediment structures produced by each taxon (tubes, macropores, and fecal pellets) that modified water flow and associated microbial activities in the interstitial habitat. The stimulation of aerobic microbial processes with two- and three-taxa treatments, whereas one-taxon treatments could increase or decrease O2 consumption in columns, indicates that interactions among invertebrates limited the variability of the system functioning. We suggest that, beyond a small number of detritivorous taxa, a threshold effect on bioturbation process and microbial activities was produced by animals in the experimental system. Finally, the interactions between taxa played a significant role in microbial processes in the system studied.
Acoustic characteristics of forage fish species in the Gulf of Alaska and Bering Sea based on Kirchhoff-approximation models
Authors: Gauthier Stéphane , Horne John K
Published: January 2005

Acoustic surveys are routinely used to assess fish abundance. To ensure accurate population estimates, the characteristics of echoes from constituent species must be quantified. Kirchhoff-ray mode (KRM) backscatter models were used to quantify acoustic characteristics of Bering Sea and Gulf of Alaska pelagic fish species: capelin (Mallotus villosus), Pacific herring (Clupea pallasii), walleye pollock (Theragra chalcogramma), Atka mackerel (Pleurogrammus monopterygius), and eulachon (Thaleichthys pacificus). Atka mackerel and eulachon do not have swimbladders. Acoustic backscatter was estimated as a function of insonifying frequency, fish length, and body orientation relative to the incident wave front. Backscatter intensity and variance estimates were compared to examine the potential to discriminate among species. Based on relative intensity differences, species could be separated in two major groups: fish with gas-filled swimbladders and fish without swimbladders. The effects of length and tilt angle on echo intensity depended on frequency. Variability in target strength (TS) resulting from morphometric differences was high for species without swimbladders. Based on our model predictions, a series of TS to length equations were developed for each species at the common frequencies used by fisheries acousticians.
Discharge-dependent covariation patterns in the population dynamics of brown trout (Salmo trutta) within a Cantabrian river drainage
Authors: Lobón-Cerviá Javier
Published: January 2005

Patterns of spatial covariation in the population dynamics of brown trout (Salmo trutta) across Rio Esva (northwestern Spain) were explored by using the residuals from stockrecruitment relationships as indices of survival rates of spawner-to-recruit (STR), spawner-to-cohort size (STC), and spawner-to-spawner (STS). Positive correlations in pairwise comparisons among survival rates together with highly significant spatiotemporal variation in STC (74.3%) and STS (51.5%) explained by variation in STR provided evidence for persistent spatial covariation across the river drainage during the whole lifetime. Split-line regressions fitted to the survival rates versus river discharge in March (when trout emerge) highlighted the importance of discharge during, or just after, trout emergence as a major determinant of recruitment whose effects are reflected in the population over the lifetime and emphasized the synchrony between environmental processes and brown trout dynamics. Synchrony in recruitment is caused by hydrological synchrony that, in turn, is determined by climatic synchrony (rainfall) operating at the regional scale. The importance of discharge for recruitment is consistent with studies on native and introduced populations, suggesting its broad effect on the dynamics of stream brown trout across geographical regions.
Interpopulation variation in early growth of threespine sticklebacks (Gasterosteus aculeatus) under laboratory conditions
Authors: Wright Hazel A , Wootton Robert J , Barber Iain
Published: January 2005

Logistical difficulties associated with accurately measuring juvenile stages have contributed to a lack of detailed information on population-level variation in the early growth of fish. In this study, we used computerised image analysis to determine the trajectories of early growth, from hatching to 126 days posthatch, of replicated, laboratory-bred, full-sibling groups of threespine stickleback (Gasterosteus aculeatus) from five resident freshwater populations. Sibling groups were held under controlled "common garden" conditions and fed ad libitum, to excess, and standard lengths (SL) of all individuals in each sibling group were recorded at regular intervals over four separate time periods (06, 638, 3870, and 70126 days). Although there was no significant population-level variation in SL at hatching, we detected significant population-level differences in growth trajectory after 38 days and population differences in mean SL of up to 6.8 mm (16.6%) by 126 days. Our results suggest that population-level variation in the intrinsic growth rates of juvenile sticklebacks has a strong genetic component.
Reconstructing the salinity and environment of the Limfjord and Vejlerne Nature Reserve, Denmark, using a diatom model for brackish lakes and fjords
Authors: Ryves David B , Clarke Annemarie L , Appleby Peter G , Amsinck Susanne L , Jeppesen Erik , Landkildehus Frank , Anderson N John
Published: January 2005

Diatoms in surface sediments from a data set of 27 brackish lakes and nine fjords in Jutland, Denmark (range 0.2  31 g·L1 total dissolved solids (TDS)), were analysed using multivariate methods to determine response to measured parameters (depth, total phosphorus (TP), total nitrogen (TN), TN/TP, salinity, water body type). Water body type, salinity, depth and TP together explained 25.3% of the variation in the diatom data and were all independently significant predictors. A diatomsalinity model (r2jack = 0.887, root mean square error of prediction = 0.246 log salinity, g·L1) was developed from the 36 sample training set and applied to fossil diatom assemblages in three sediment cores from the east Vejlerne wetland, Denmark, a nature reserve created after the damming of an embayment of the polyhaline Limfjord (~26 g·L1 TDS) in the late 19th century. The diatominferred salinity reconstructions reflect the known salinity history of the Limfjord and the freshwatersubsaline Vejlerne lakes, and appear sensitive to documented North Sea storms in the 16th and 17th centuries, which had major impacts on the brackish Limfjord herring fishery. Diatomsalinity models may be useful tools in long-term studies of coastal and estuarine areas to test hypotheses concerning aquatic resources and ecological, hydrographic, and cultural change.
Deriving condition indices from standard fisheries databases and evaluating their sensitivity to variation in stored energy reserves
Authors: Marshall C Tara , Needle Coby L , Yaragina Nathalia A , Ajiad Adnan M , Gusev Evgeny
Published: January 2005

To evaluate interstock differences in condition, it would be advantageous to develop stock-level condition indices from standardized databases on weight and length. This study describes a method for estimating stock-level condition when individual-level observations on length and weight are not easily accessible. For each year in a 56-year time series (19462001) for Northeast Arctic cod (Gadus morhua), pseudo-observations of weight and length were generated by pairing the Norwegian and Russian values for weight-at-age provided annually to the assessment working group with estimates of length-at-age derived from the same databases. A weightlength relationship fit to each year was then used to predict weight-at-length, i.e., girth, for a range of standard lengths (30120 cm). This index was uncorrelated with both the liver condition index and the abundance of Barents Sea capelin (Mallotus villosus), suggesting that at the stock level, the girth of cod is not necessarily indicative of the magnitude of stored energy reserves. Partitioning body size into length-at-age and girth revealed long-term trends in body size. In particular, large/old cod showed substantially higher values of both length-at-age and girth that could be the result of long-term increases in fishing mortality.
Movement of Atlantic bluefin tuna (Thunnus thynnus) as determined by satellite tagging experiments initiated off New England
Authors: Stokesbury Michael JW , Teo Steven LH , Seitz Andrew , O'Dor Ronald K , Block Barbara A
Published: January 2005

Pop-up satellite archival tags were attached to 35 Atlantic bluefin tuna (Thunnus thynnus) off the New England coast of the United States of America in 1998, 2000, and 2001. The tags provided information on the horizontal and vertical movements and environmental preferences of bluefin tuna. Fish showed movement patterns that can be categorized by age and season. Mature individuals were linked to the Gulf of Mexico breeding grounds based on light level longitude and sea surface temperature latitude estimates of geolocation and a radiosatellite endpoint position. A track based on geolocation indicated that a single individual moved from the tagging release location to the Gulf of Mexico and back to New England waters. Tag-generated water column profiles of depth versus temperature were consistent with fish movement along the shelf and into the Gulf of Mexico. Adolescent fish moved from the New England offshore feeding locations to winter aggregations in the coastal shelf and slope waters of North and South Carolina. Bluefin tuna showed a preference for ambient temperatures that ranged from 14 to 26 °C in autumn and from 18 to 24 °C in winter.
Optimum sampling levels in discard sampling programs
Authors: Borges Lisa , Zuur Alain F , Rogan Emer , Officer Rick
Published: January 2005

This paper presents optimum sampling levels in discard sampling programs considering cost and precision objectives simultaneously and explores their dependence on both variables. The analysis is based on the Irish discard program: an onboard-observer voluntary sampling scheme aimed at estimating discard rates in trawl fisheries. Multistage analysis was performed to establish the precision levels achieved in the past, and a cost function was determined to estimate the financial cost of the program. Gear, fishing ground, targeted species, and International Council for the Exploration of the Sea (ICES) divisions were the main factors affecting discarding, together with random effects of the three nested groups considered: haul, trip, and vessel. Reductions in the present budget will imply only marginal decreases in precision, although changes in cost variables can have an impact on sampling levels. On the other hand, increasing the target precision by one-half will imply a considerable increase in sampling and associated cost, which will be difficult if not impossible to achieve. Finally, the analysis by fleet components suggests a marked increase in sampling levels, which emphasizes the importance of clearly stated discard sampling objectives.
Seasonal changes in the lipids of Mysis mixta (Mysidacea) from the hyperbenthos of a cold-ocean environment (Conception Bay, Newfoundland)
Authors: Richoux Nicole B , Deibel Don , Thompson Raymond J , Parrish Christopher C
Published: January 2005

Total lipid (TL) and lipid class composition of Mysis mixta Lilljeborg from 240-m depth in a cold-water marine bay were studied throughout 1999 and 2000. The objective was to relate the seasonal lipid dynamics in an abundant and lipid-rich hyperbenthic species to its life cycle and to the annual phytoplankton bloom. Mysis mixta accumulated high levels of lipid reserves similar to those reached by other cold-water zooplankton. Greatest accumulation occurred in maturing females and males upon initiation of the spring bloom and continued for 6 months. The lowest TL level was ~5% dry mass (DM) in small juveniles, post-spawned males, and spent females, and the highest level was 32% DM in females approaching full maturity (overall content range 0.316 mg·mysid1). Most females accumulated lipid for 2 years before spawning, although a few females spawned 7 months early with a very low TL content. Seasonal variation in TL resulted primarily from net changes in triacylglycerol, the predominant neutral lipid. Seasonal and interannual variation in TL quantities in individuals and in areal concentrations of lipid in the hyperbenthic population indicates a strong trophic link between M. mixta and the pelagic production cycle.
Coupling of methyl and total mercury in a minerotrophic peat bog in southeastern Sweden
Authors: Regnell O , Hammar T
Published: January 2005

During most of an annual cycle, we studied the temporal variation of total mercury (HgT) and methyl mercury (MeHg) in unfiltered and filtered (0.45 µ) peat water from a minerotrophic peat bog in southeastern Sweden. MeHg in bulk water ([MeHgT]) and total Hg in filtered water in discharge water from the peat bog ([HgD]) were an order of magnitude higher than in upland runoff water entering the peat bog. At the discharge end, peat-water [HgD] and [MeHgD] ranged from 8 to 54 pmol·L1 and from 1 to 32 pmol·L1, respectively. Whereas the variation of [MeHgT] was explained by changes in [MeHgD], the variation of inorganic HgT [IHgT] = [HgT]  [MeHgT] was explained by changes in particle-bound IHg [IHgP] = [IHgT]  [IHgD]. Filterable organic matter and sulfide in the water both correlated poorly with [HgD]. Neither did the amount of HgT in precipitation and upland runoff water correlate well with the estimated discharge of HgD from the peat bog. However, there was a strong correlation between [HgD] and [MeHgT] in the peat water (r = 0.96). Furthermore, a significant fraction of HgD was MeHg (mean 28%; range 860%). These results suggest that methylation increased the mobility of Hg.
Slow initial decomposition and fungal colonization of pine branches in a nutrient-rich lowland stream
Authors: Spänhoff Bernd , Gessner Mark O
Published: January 2005

Mass loss, fungal colonization, and chemical changes of submerged pine (Pinus sylvestris) branches were monitored in a nutrient-rich lowland stream. Branches retrieved from the stream were analyzed for water-soluble substances to assess mass loss by leaching. Concentrations of substances soluble in hot 1% NaOH were determined in order to detect changes in wood-tissue structure indicating microbial degradative activity, and fungal colonization was estimated as ergosterol concentration. Decomposition of the pine branches was slow, with a mean mass loss of 8.3% within 13 months and an overall decay coefficient, k, of 0.074·year1. Concentrations of water-soluble substances in wood decreased from 2.8% to 1.7% after 5 weeks and in bark from 5.6% to 3.8% within 2 weeks. No further losses were noted, nor were significant changes observed in concentrations of substances soluble in hot dilute NaOH. Fungal biomass in bark increased within the first 5 weeks (1469 µg ergosterol·g1dry mass) but was invariably low in wood. These results indicate that decomposition of intact fully corticated pine branchwood in streams proceeds very slowly, with little fungal colonization and no notable changes in wood structure occurring after more than a year even when dissolved nutrients in stream water are readily available.
Past and future chemistry changes in acidified Nova Scotian Atlantic salmon (Salmo salar) rivers: a dynamic modeling approach
Authors: Clair Thomas A , Dennis Ian F , Amiro Peter G , Cosby B J
Published: January 2005

Atlantic salmon (Salmo salar) populations have been extirpated from a number of rivers in Nova Scotia, Canada, as a result of acid rain. We applied the model of acidification of groundwater in catchments (MAGIC) to 35 regional rivers to estimate pre-industrial water chemistry conditions and the potential future changes in water chemistry under three acid deposition scenarios for the region. Our model results indicate that water chemistry in the study streams remained relatively unchanged until the 1950s and reached their maximum effects on pH in the mid-1970s. The main effects of acid deposition have been a decrease in pH and an increase in base cations to surface waters, as the ion-exchange processes in soils release soil cations into surface waters. We forecast future water chemistry in the rivers using three deposition scenarios: no change in sulfate deposition from year 2000 and 10% and 20% sulfate reductions per decade. We show that the more rapid the reduction in acid deposition, the faster the recovery. We also show that although stream water acidity will recover within a few decades, in most streams, base cations will not recover to pre-industrial levels within the next 100 years.
Short-term effects of seasonal prescribed burning on the ectomycorrhizal fungal community and fine root biomass in ponderosa pine stands in the Blue Mountains of Oregon
Authors: Smith J E , McKay D , Niwa C G , Thies W G , Brenner G , Spatafora J W
Published: January 2005

The effects of seasonal prescribed fire on the belowground ectomycorrhizal community and live fine root biomass were investigated before, 1 year after, and 2 years after prescribed underburning. Ectomycorrhizas were sampled from four replications of three treatments (fall underburning, spring underburning, and a nonburned control) in a randomized complete block design. Samples were separated in two subsamples representing the upper 5 cm and lower 5 cm of a soil core. Molecular tools were used to distinguish 140 restriction fragment length polymorphism (RFLP) species of fungi directly from the ectomycorrhizas. Prior to underburning, the number of RFLP species and amount of live root biomass were similar among treatment units and between upper and lower core samples. Fall underburning largely removed live root biomass to a depth of 10 cm and significantly reduced ectomycorrhizal species richness compared with spring underburning and the nonburned control for at least 2 years. RFLP species richness and live root biomass following spring underburning were generally similar to the nonburned treatment. The successful reintroduction of fire to the ecosystem to retain high species diversity of ectomycorrhizal fungi and achieve the desired future condition of large-tree ponderosa pine retention with low fuel loads may require more than underburning in a single season.
Imputing missing height measures using a mixed-effects modeling strategy
Authors: Robinson Andrew P , Wykoff William R
Published: January 2005

This paper proposes a method whereby heightdiameter regression from an inventory can be incorporated into a height imputation algorithm. Point-level subsampling is often employed in forest inventory for efficiency. Some trees will be measured for diameter and species, while others will be measured for height and 10-year increment. Predictions of these missing measures would be useful for estimating volume and growth, respectively, so they are often imputed. We present and compare three imputation strategies: using a published model, using a localized version of a published model, and using best linear unbiased predictions from a mixed-effects model. The bases of our comparison are four-fold: minimum fitted root mean squared error and minimum predicted root mean squared error under a 2000-fold cross-validation for tree-level height and volume imputations. In each case the mixed-effects model proved superior. This result implies that substantial environmental variation existed in the heightdiameter relationship for our data and that its representation in the model by means of random effects was profitable.
Effects of shading and humus fertility on growth, competition, and ectomycorrhizal colonization of boreal forest tree seedlings
Authors: Dehlin Helena , Nilsson Marie-Charlotte , Wardle David A , Shevtsova Anna
Published: January 2005

We performed a pot experiment to study the effects of varying levels of vegetation shade and humus fertility, simulating natural conditions of the boreal forest, on growth, interspecific competition, and ectomycorrhizal colonization of seedlings of three coexisting tree species: Pinus sylvestris L., Picea abies (L.) Karst., and Betula pendula Roth. In contrast to late-successional Picea abies, early-successional species Pinus sylvestris and particularly B. pendula responded to shade with an increase in stem height and with some changes in biomass, especially in the high-fertility humus. Humus fertility had greater effects on biomass of seedlings than did shade treatments. Interspecific competition among pairwise combinations of the three species was greatest in the high-fertility humus, but was not affected by shade. Betula pendula was the strongest competitor among species; it was not affected by the presence of coexisting species and strongly suppressed coniferous seedlings, especially in the high-fertility humus. Generally, ectomycorrhizal colonization was not affected by shade treatments, but was highest in the low-fertility humus. These results show that effects of light, humus fertility, and presence of neighbours are species specific, and these differences are important for the competitive and recruitment abilities of seedlings of coexisting tree species and ultimately for the species composition of developing forests.
EQUILIBRIUM CURRENTS IN A QUANTUM DOUBLE RING SYSTEM: A NON-TRIVIAL ROLE OF SYSTEM-RESERVOIR COUPLING
Authors: BENJAMIN COLIN , JAYANNAVAR A. M.
Published: January 2005

Amperes law states that the magnetic moment of a ring is given by current times the area enclosed. Also from equilibrium statistical mechanics, it is known that magnetic moment is the derivative of free energy with respect to magnetic field. In this work, we analyze a quantum double ring system interacting with a reservoir. A simple S-Matrix model is used for system-reservoir coupling. We see complete agreement between the aforesaid two definitions when coupling between system and reservoir is weak, increasing the strength of coupling parameter, however, leads to disagreement between the two, thereby signifying the important role played by the coupling parameter in mesoscopic systems.
FROM SEAS TO SURGERIES, FROM BABBLING BROOKS TO BABY SCANS: THE ACOUSTICS OF GAS BUBBLES IN LIQUIDS
Authors: LEIGHTON T. G.
Published: January 2005

Gas bubbles are the most potent naturally-occurring entities that influence the acoustic environment in liquids. Upon entrainment under breaking waves, waterfalls, or rainfall over water, each bubble undergoes small amplitude decaying pulsations with a natural frequency that varies approximately inversely with the bubble radius, giving rise to the "plink" of a dripping tap or the roar of a cataract. When they occur in their millions per cubic metre in the top few metres of the ocean, bubbles can dominate the underwater sound field. Similarly, when driven by an incident sound field, bubbles exhibit a strong pulsation resonance. Acoustic scatter by bubbles can confound sonar in the shallow waters which typify many modern maritime military operations. If they are driven by sound fields of sufficient amplitude, the bubble pulsations can become highly nonlinear. These nonlinearities might be exploited to enhance sonar, or to monitor the bubble population. Such oceanic monitoring is important, for example, because of the significant contribution made by bubbles to the greenhouse gas budget. In industry, bubble monitoring is required for sparging, electrochemical processes, the production of paints, pharamaceuticals and foodstuffs. At yet higher amplitudes of pulsation, gas compression within the collapsing bubble can generate temperatures of several thousand Kelvin whilst, in the liquid, shock waves and shear can produce erosion and bioeffects. Not only can these effects be exploited in industrial cleaning and manufacturing, and research into novel chemical processes, but we need to understand (and if possible control) their occurrence when biomedical ultrasound is passed through the body. This is because the potential of such bubble-related physical and chemical processes to damage tissue will be desireable in some circumstances (e.g. ultrasonic kidney stone therapy), and undesireable in others (e.g. foetal scanning). This paper describes this range of behaviour. Further information on these topics, including sound and video files, can be found at .
DOUBLE-TIME GREEN'S FUNCTION APPROACH TO THE SPIN 1/2 SPATIALLY ANISOTROPIC ANTIFERROMAGNETIC HEISENBERG MODEL
Authors: WANG ZHAO-MING , CHEN YUAN
Published: January 2005

By use of the double-time Green's function method in the cubic-lattice S=1/2 anisotropic antiferromagnetic two-sublattice Heisenberg model, in the Tyablikov approximation, the staggered magnetization m, the correlation function and the static susceptibility are investigated. And the effects of spatial anisotropy are explored. The magnetic properties of this model are found to be dependent of anisotropy.
SELF-SIMILAR CORRECTIONS TO THE ERGODIC THEOREM FOR THE PASCAL-ADIC TRANSFORMATION
Authors: JANVRESSE É. , DE LA RUE T. , VELENIK Y.
Published: January 2005

Let T be the Pascal-adic transformation. For any measurable function g, we consider the corrections to the ergodic theorem [Formula: see text] When seen as graphs of functions defined on {0,…,ℓ - 1}, we show for a suitable class of functions g that these quantities, once properly renormalized, converge to (part of) the graph of a self-affine function. The latter only depends on the ergodic component of x, and is a deformation of the so-called Blancmange function. We also briefly describe the links with a series of works on Conway recursive $10,000 sequence.
THE STOCHASTIC WAVE EQUATION DRIVEN BY FRACTIONAL BROWNIAN NOISE AND TEMPORALLY CORRELATED SMOOTH NOISE
Authors: CAITHAMER PETER
Published: January 2005

The stochastic wave equation in one spatial dimension driven by a class of fractional noises or, alternately, by a class of smooth noises with arbitrary temporal covariance is studied. In either case, the wave equation is explicitly solved and the upper and lower bounds on both the large and small deviations of several sup norms associated with the solution are given. Finally the energy of a system governed by such an equation is calculated and its expected value is found.
ASYMPTOTICS FOR RETURN TIMES OF RANK-ONE SYSTEMS
Authors: CHAUMOÎTRE VINCENT , KUPSA MICHAL
Published: January 2005

We give a condition for nonperiodic rank-one systems to have non-exponential asymptotic distribution (equal to 1[1,∞[) of return times along subsequences of cylinders. Applying this result to the staircase transformation, we derive mixing dynamical systems with non-exponential asymptotics. Moreover, we show for two columns rank-one systems unique asymptotic along full sequences of cylinders.
ON PREDICTABILITY OF PARTICLE CLUSTERS IN A STOCHASTIC FLOW
Authors: PITERBARG LEONID I.
Published: January 2005

In many physical applications it is important to predict particle trajectories in a turbulent flow using a numerical model of the flow. One of the major reasons for a poor prediction is the limited resolution in space. We discuss the problem of predictability limits in the framework of a stochastic flow modeling inertial particles in turbulence.

Two stochastic flows called the "model" and "true" are considered. The "model" flow is the "true" flow smoothed in space. The principal measure of discrepancy of the flows is the distance between the centers of mass of two initially identical particle clusters driven by the "true" and "model" flows respectively. The predictability limit is defined as a moment when this distance exceeds the space correlation scale of the true flow. The main result is a simple formula relating the predictability limit with the smoothing scale. This relation is well supported by stochastic simulations and could be a helpful tool in planning experiments in numerical models of turbulent flows. Also the difference between particle scattering in the "true" and "model" flows is studied.
RANDOM SHUFFLING OF SWITCHING PARAMETERS IN A MODEL OF GENE EXPRESSION REGULATORY NETWORK
Authors: VOLCHENKOV D. , LIMA R.
Published: January 2005

A discrete time model of large gene expression regulatory networks is considered. Transcriptional degrees of regulations and activation thresholds are shuffled randomly that helps to study the highly reproducible dynamical patterns of regulatory processes in a lack of empirical data concerning genetic switches. The multistationarity and multiperiodicity of oscillations exhibited by the system relay upon the feedback circuits. Statistics of their appearance depends upon the relative number of negative regulations between the genes of network, the number of cycles in the maximal graph, and their lengths.

The model defined on the scalable graphs demonstrates the high persistence in oscillations and the high error tolerance.
EARTHQUAKE TRIGGERING BY STATIC, DYNAMIC, AND POSTSEISMIC STRESS TRANSFER
Authors: Freed Andrew M.
Published: January 2005

▪ Abstract  Earthquake triggering is the process by which stress changes associated with an earthquake can induce or retard seismic activity in the surrounding region or trigger other earthquakes at great distances. Calculations of static Coulomb stress changes associated with earthquake slip have proven to be a powerful tool in explaining many seismic observations, including aftershock distributions, earthquake sequences, and the quiescence of broad, normally active regions following large earthquakes. Delayed earthquake triggering, which can range from seconds to decades, can be explained by a variety of time-dependent stress transfer mechanisms, such as viscous relaxation, poroelastic rebound, or afterslip, or by reductions in fault friction, such as predicted by rate and state constitutive relations. Rapid remote triggering of earthquakes at great distances (from several fault lengths to 1000s of km) is best explained by the passage of transient (dynamic) seismic waves, which either immediately induce Coulomb-type failure or initiate a secondary mechanism that induces delayed triggering. The passage of seismic waves may also play a significant role in the triggering of near-field earthquakes.
THE DIFFUSION-MULTIPLE APPROACH TO DESIGNING ALLOYS
Authors: Zhao Ji-Cheng (J.-C.)
Published: January 2005

▪ Abstract  The diffusion-multiple approach—the creation of composition gradients and intermetallic phases by long-term annealing of junctions of three or more phases/alloys—enables the generation of a large number of phases and compositions for efficient mapping of phase diagrams, phase properties, and kinetics. With an efficiency much higher than that of a conventional approach, many critical materials data, which otherwise would be too time-consuming and expensive to acquire, can be obtained and employed to accelerate alloy design. The critical data for structural materials design include phase diagrams, diffusion coefficients, precipitation kinetics, solution-strengthening effects, and precipitation-strengthening effects. All these data can be obtained from diffusion multiples. The combination of the diffusion-multiple approach with the CALPHAD approach can impact computational design of structural materials. The diffusion-multiple approach can also be applied to combinatorial screening of functional materials having unique physical, chemical, or other properties when micro-scale measurement techniques are available for these properties. Examples are shown to illustrate the progress made to date on applying the diffusion-multiple approach to accelerated design/discovery of materials.
PPAR-α activation required for decreased glucose uptake and increased susceptibility to injury during ischemia
Authors: Panagia Marcello , Gibbons Geoffrey F. , Radda George K. , Clarke Kieran
Published: January 2005

The transcription of key metabolic regulatory enzymes in the heart is altered in the diabetic state, yet little is known of the underlying mechanisms. The aim of this study was to investigate the role of peroxisome proliferator-activated receptor-α (PPAR-α) in modulating cardiac insulin-sensitive glucose transporter (GLUT-4) protein levels in altered metabolic states and to determine the functional consequences by assessing cardiac ischemic tolerance. Wild-type and PPAR-α-null mouse hearts were isolated and perfused 6 wk after streptozotocin administration or after 14 mo on a high-fat diet or after a 24-h fast. Myocardial d-[2-3H]glucose uptake was measured during low-flow ischemia, and differences in GLUT-4 protein levels were quantified using Western blotting. In wild-type mice in all three metabolic states, elevated plasma free fatty acids were associated with lower total cardiac GLUT-4 protein levels and decreased glucose uptake during ischemia, resulting in poor postischemic functional recovery. Although PPAR-α-null mice also had elevated plasma free fatty acids, they had neither decreased cardiac GLUT-4 levels nor decreased glucose uptake during ischemia and, consequently, did not have poor recovery during reperfusion. We conclude that elevated plasma free fatty acids are associated with increased injury during ischemia due to decreased cardiac glucose uptake resulting from lower cardiac GLUT-4 protein levels, the levels of GLUT-4 being regulated, probably indirectly, through PPAR-α activation.
Sympathetic innervation promotes vascular smooth muscle differentiation
Authors: Damon Deborah H.
Published: January 2005

The sympathetic nervous system (SNS) is an important modulator of vascular smooth muscle (VSM) growth and function. Several lines of evidence suggest that the SNS also promotes VSM differentiation. The present study tests this hypothesis. Expression of smooth muscle myosin (SM2) and α-actin were assessed by Western analysis as indexes of VSM differentiation. SM2 expression (normalized to α-actin) in adult innervated rat femoral and tail arteries was 479 ± 115% of that in noninnervated carotid arteries. Expression of α-actin (normalized to GAPDH or total protein) in 30-day-innervated rat femoral arteries was greater than in corresponding noninnervated femoral arteries from guanethidine-sympathectomized rats. SM2 expression (normalized to α-actin) in neonatal femoral arteries grown in vitro for 7 days in the presence of sympathetic ganglia was greater than SM2 expression in corresponding arteries grown in the absence of sympathetic ganglia. In VSM-endothelial cell cultures grown in the presence of dissociated sympathetic neurons, α-actin (normalized to GAPDH) was 300 ± 66% of that in corresponding cultures grown in the absence of neurons. This effect was inhibited by an antibody that neutralized the activity of transforming growth factor-β2. All of these data indicate that sympathetic innervation increased VSM contractile protein expression and thereby suggest that the SNS promotes and/or maintains VSM differentiation.
Effect of pravastatin on development of left ventricular hypertrophy in spontaneously hypertensive rats
Authors: Lee Tsung-Ming , Lin Mei-Shu , Chou Tsai-Fwu , Tsai Chang-Her , Chang Nen-Chung
Published: January 2005

Endothelin (ET)-1 has been implicated in the development of cardiac hypertrophy. We investigated the effect of pravastatin on development of ventricular hypertrophy in spontaneously hypertensive rats (SHR) and whether the attenuated hypertrophic effect was via reduced ET-1 expression. Normolipidemic SHR were treated with one of the following therapies for 8 wk: vehicle, the nonselective ET receptor antagonists bosentan, pravastatin, mevalonate, hydralazine, or combination of pravastatin + mevalonate from the age of 8 wk at the very early stage of cardiac hypertrophy. Treatment with bosentan and pravastatin significantly decreased left ventricular mass index for body weight and cardiomyocyte sizes isolated by enzymatic dissociation. The myocardial ET-1 levels and preproET-1 mRNA assessed using real-time quantitative RT-PCR were significantly higher (both P < 0.001) in the SHR compared with Wistar-Kyoto rats. The increased tissue ET-1 levels can be inhibited after pravastatin administration. Immunohistochemical analysis confirmed the changes of ET-1. Left ventricular mass index for body weight correlated positively with tissue ET-1 levels ( P = 0.0004). A dissociation between the effects of blood pressure and cardiac structure was noted, because pravastatin and hydralazine reduced arterial pressure similarly. Pravastatin-induced effects were reversed by the addition of mevalonate. In conclusion, these results suggest a crucial role of cardiac endothelin system in the early development of ventricular hypertrophy in the SHR. Pravastatin is endowed with cardiac antihypertropic properties that are independent of its hemodynamic and hypolipidemic effects and appear to be related to their capacity to decrease cardiac ET-1 levels, which is linked to mevalonate metabolism.
Reduced voltage dependence of inactivation in the SCN5A sodium channel mutation delF1617
Authors: Chen Tiehua , Inoue Masashi , Sheets Michael F.
Published: January 2005

Deletion of a phenylalanine at position 1617 (delF1617) in the extracellular linker between segments S3 and S4 in domain IV of the human heart Na+ channel (hH1a) has been tentatively associated with long QT syndrome type 3 (LQT3). In a mammalian cell expression system, we compared whole cell, gating, and single-channel currents of delF1617 with those of wild-type hH1a. The half points of the peak activation-voltage curve for the two channels were similar, as were the deactivation time constants at hyperpolarized test potentials. However, delF1617 demonstrated a significant negative shift of −7 mV in the half point of the voltage-dependent Na+ channel availability curve compared with wild type. In addition, both the time course of decay of Na+ current ( INa) and two-pulse development of inactivation of delF1617 were faster at negative test potentials, whereas they tended to be slower at positive potentials compared with wild type. Mean channel open times for delF1617 were shorter at potentials <0 mV, whereas they were longer at potentials >0 mV compared with wild type. Using anthopleurin-A, a site-3 toxin that inhibits movement of segment S4 in domain IV (S4-DIV), we found that gating charge contributed by the S4-DIV in delF1617 was reduced 37% compared with wild type. We conclude that deletion of a single amino acid in the S3-S4 linker of domain IV alters the voltage dependence of fast inactivation via a reduction in the gating charge contributed by S4-DIV and can cause either a gain or loss of INa, depending on membrane potential.
Preconditioning of salvaged myocardium in conscious rabbits with postinfarction dysfunction
Authors: Aouam Karim , Tissier Renaud , Bruneval Patrick , Mandet Chantal , Berdeaux Alain , Ghaleh Bijan
Published: January 2005

Protection against postinfarction myocardial dysfunction is modest with classic preconditioning (PC). We investigated whether multiple cycles of PC could improve this protection and whether postinfarction dysfunction only depends on the amount of viable tissue. Eighteen rabbits were chronically instrumented with coronary occluders and ultrasonic crystals (segment shortening, SH) in the ischemic zone. A control group underwent 30-min coronary artery occlusion (CAO) with 72-h reperfusion (CAR). In two other groups, PC was induced by six 4-min CAO/4-min CAR cycles (PC×6) or one 5-min CAO/10-min CAR cycle (PC×1). After 72-h CAR, depression in SH was reduced in PC×1 (−68 ± 7% from baseline) and to a greater extent in PC×6 (−18 ± 10%) vs. control (−99 ± 7%; all P < 0.05). Infarct sizes were reduced in PC×1 (15 ± 2%) and to a greater extent in PC×6 (3 ± 1%) vs. control (46 ± 5%; P < 0.05). Contractility of salvaged myocardium was evaluated by calculating the ratio between SH at 72-h CAR and the amount of viable tissue. This index was enhanced in PC×1 (0.39 ± 0.07, P < 0.05) and to a greater extent in PC×6 (0.82 ± 0.09) vs. control (0.0 ± 0.10). This differential effect of PC was not related to changes in apoptosis, endothelial nitric oxide synthase (NOS) expression, or macrophages infiltration but, rather, to blunted inducible NOS expression in PC×6 vs. control and PC×1. Thus multiple cycles of PC induced an almost complete protection against postinfarction dysfunction, potentially involving beneficial effects on salvaged myocardium.
Estimating oxygen consumption rates of arteriolar walls under physiological conditions in rat skeletal muscle
Authors: Shibata Masahiro , Ichioka Shigeru , Kamiya Akira
Published: January 2005

To examine the effects of vascular tone reduction on O2consumption of the vascular wall, we determined the O2consumption rates of arteriolar walls under normal conditions and during vasodilation induced by topical application of papaverine. A phosphorescence quenching technique was used to quantify intra- and perivascular Po2in rat cremaster arterioles with different branching orders. Then, the measured radial Po2gradients and a theoretical model were used to estimate the O2consumption rates of the arteriolar walls. The vascular O2consumption rates of functional arterioles were >100 times greater than those observed in in vitro experiments. The vascular O2consumption rate was highest in first-order (1A) arterioles, which are located upstream, and sequentially decreased downstream in 2A and 3A arterioles under normal conditions. During papaverine-induced vasodilation, on the other hand, the O2consumption rates of the vascular walls decreased to similar levels, suggesting that the high O2consumption rates of 1A arterioles under normal conditions depend in part on the workload of the vascular smooth muscle. These results strongly support the hypothesis that arteriolar walls consume a significant amount of O2compared with the surrounding tissue. Furthermore, the reduction of vascular tone of arteriolar walls may facilitate an efficient supply of O2to the surrounding tissue.
Protective effect of prenatal water restriction on offspring cardiovascular homeostasis in response to hemorrhage
Authors: Desai Mina , Guerra Catalina , Wang Shengbiao , Ross Michael G.
Published: January 2005

We determined the cardiovascular and AVP responses of prenatally dehydrated (PreDehy) neonates to intravascular hemorrhage. Ewes with singleton fetuses were subjected to water restriction from 110 days of gestation to full term to achieve hypernatremia of 8–10 meq/l. Water and food were provided ad libitum to control ewes. After delivery, water and food were provided ad libitum to ewes from both groups, and newborns were allowed to nurse ad libitum. At 15 ± 2 days of age, PreDehy and control lambs were prepared with bladder and femoral catheters and studied at 25 ± 2 days of age. After a 2-h basal period, lambs were hemorrhaged to 30% of blood volume over 1 h (0.5% of blood volume/min) and monitored 1 h after hemorrhage. Neonatal arterial blood pressure was measured, and blood samples were collected. Basal plasma sodium levels, plasma osmolality, hematocrit, and mean arterial pressure were increased in PreDehy lambs compared with controls. Both groups had similar basal AVP levels and heart rate. In response to hemorrhage, all parameters remained significantly elevated in PreDehy lambs. Blood pressure decreased less in PreDehy lambs than in controls. The hemorrhage-AVP threshold (percent blood volume withdrawal at which plasma AVP values significantly increased) was markedly elevated (20 vs. 15%) and peak hemorrhage-induced AVP plasma levels were lower (5.6 ± 1.5 vs. 10.1 ± 1.5 pg/ml, P < 0.01) in PreDehy lambs than in controls. Thus offspring of dehydrated ewes demonstrate enhanced AVP secretory responses to hypotension. Despite potential long-term adverse effects of systemic hypertension, these results suggest a protective effect of prenatal water restriction on offspring cardiovascular homeostasis during blood volume reduction.
Activation of Rho-associated kinase during augmented contraction of the basilar artery to serotonin after subarachnoid hemorrhage
Authors: Watanabe Yoshimasa , Faraci Frank M. , Heistad Donald D.
Published: January 2005

Delayed cerebral vasospasm after subarachnoid hemorrhage (SAH) may be due, in part, to altered regulation of arterial smooth muscle contraction. Contraction of cerebral arteries to serotonin is augmented after experimental SAH. We hypothesized that activation of Rho-associated kinase (Rho kinase) contributes to augmented contraction of cerebral arteries to serotonin after SAH. Autologous arterial blood (SAH) or artificial cerebrospinal fluid (control) was injected into the cisterna magna of anesthetized rabbits. At 2 days after injection, the basilar artery was excised and isometric contraction of arterial rings was recorded. Maximum contraction of the basilar artery to serotonin was augmented about fourfold in SAH compared with control rabbits ( P < 0.01). Contraction to histamine was similar in the two groups. Fasudil hydrochloride (3 μmol/l), an inhibitor of Rho kinase, markedly attenuated serotonin-induced contraction. Fasudil had little effect on contractions induced by histamine or phorbol 12,13-dibutyrate. In addition, phosphorylation of myosin phosphatase, a major target of Rho kinase in regulation of smooth muscle contraction, in the basilar artery was examined by Western blotting. In basilar arteries of SAH, but not control, rabbits, serotonin increased phosphorylation of myosin phosphatase about twofold at Thr853 of the myosin-targeting subunit. These results suggest that enhanced activation of Rho kinase contributes to augmented contraction of the basilar artery to serotonin after SAH.