Characterization of water of hydration fractions in rabbit skeletal muscle with age and time of post-mortem by centrifugal dehydration force and rehydration methods

Centrifugal dehydration force (CDF) and rehydration isotherm (RHI) methods were used to measure and characterize hydration fractions in rabbit psoas skeletal muscle. The CDF method assessed fluid flow rate from rabbit muscle and hydration capacity of the fractions. Bulk and multiple non-bulk water fractions were identified. The non-bulk water was divisible into the following fractions: two outer non-bulk fractions, a main chain proteins backbone or double water bridge fraction, and a single water bridge fraction. The total non-bulk water amounts to about 85% of the total water in the muscle. The sizes of the water fractions (in g water/g dry mass) agree with a recently proposed molecular stoichiometric hydration model (SHM) applicable to all proteins in and out of cells (Fullerton GD, Cameron IL. Water compartments in cells. Methods Enzymol, 2007; Cameron IL, Fullerton GD. Interfacial water compartments on tendon/collagen and in cells. In: Pollack GH, Chin WC, editors. Phase transitions in cells. Dordrecht, The Netherlands: Springer, 2008). Age of the rabbit significantly slowed the flow rate of the outer non-bulk water fraction by about 50%. Also, muscle of the older rabbit (26 weeks vs. 12 weeks old) had less bulk water and less outer non-bulk water but the same amount of main chain backbone water compared to muscle of the younger rabbit. Increase in time post-mortem from 30min to 4h resulted in rigor mortis and a significantly slower flow rate of water from the outer non-bulk water fraction, which is attributed to muscle contraction, increased packing of contractile elements and increased obstructions to flow of fluid from the muscle fibers.     

Heterogeneity of muscle activation in relation to force direction: A multi-channel surface electromyography study on the triceps surae muscle

Several skeletal muscles can be divided into sub-modules, called neuromuscular compartments (NMCs), which are thought to be controlled independently and to have distinct biomechanical functions. We looked for distinct muscle activation patterns in the triceps surae muscle (TS) using surface electromyography (EMG) during voluntary contraction. Nine subjects performed isometric and isotonic plantar flexions combined with forces along pre-defined directions. Besides the forces under the ball of the foot, multi-channel surface EMG was measured with electrodes homogeneously distributed over the entire TS. Using principal component analysis, common (global) components were omitted from the EMG signals, thereby estimating muscle activity sufficiently accurate to track fine fluctuations of force during an isotonic contraction (r = 0.80 ± 0.09). A subsequent cluster analysis showed a topographical organization of co-activated parts of the muscle that was different between subjects. Low and negative correlations between the EMG activity within clusters were found, indicating a substantial heterogeneity of TS activation. The correlations between cluster time series and forces at the foot in specific directions differed substantially between clusters, showing that the differentially activated parts of the TS had specific biomechanical functions.     

A practicable and accurate method to differentiate between intra- and extracellular water of microbial cells

A thermographimetric method which allows for a quick and accurate estimation of intra- and extracellular water of microbial cells is reviewed and improved. Knowledge of these fractions is important for physiological as well as for toxicological investigations. Results of the study indicate that besides the species, nutrient availability and growth conditions affect the intracellular water content. Intra- and extracellular water, dry matter, volume and density of a single cell of Arthrobacter sp. are calculated. There are indications that intracellular compartments of eukaryotes could also be investigated with this method.     

A simple and novel method for recovering adenovirus 41 in small volumes of source water

Aim: A new procedure was developed to recover adenovirus 41 in small volumes (1 l) of water samples based on adsorption, elution and evaporation. Methods and Results: One litre of source water seeded with adenovirus 41 was adjusted to pH 3·5 and filtered using a large pore size (8·0 μm) negatively charged membrane filter (SCWP, 47 mm diameter, made of mixed‐cellulose esters). Then, the filter was eluted using 4 ml of 1·5% beef extract plus 0·75% glycerol (pH 9·0). The eluate was reconcentrated to 0·1 ml or less volumes through evaporation assisted with air flow and heating at 55°C. Recovery of adenovirus 41 reached 55% under tested conditions and reduced filtration time by 85% in contrast to the widely used small pore size filter (0·45 μm pore size, 47 mm diameter). Reconcentration by evaporation achieved approx. 86·8% recovery from source water in approx. 1 h at no cost. Conclusion: The virus concentration method developed in this study is simple and cost‐effective and can be used to efficiently recover adenovirus 41 from turbid water samples. Significance and Impact of the Study: The procedure developed can be applied to detect adenovirus 41 in source water within hours of sampling. In addition, this is the first application of evaporation to concentrate viruses in water samples.     

Changes in aquatic vegetation and fish communities following 5 years of sustained low water levels in coastal marshes of eastern Georgian Bay,Lake Huron

Aquatic vegetation in the relatively pristine coastal wetlands of eastern Georgian Bay provides critical habitat for a diverse fish community. Declining water levels in Lake Huron over the past decade, however, have altered the wetland plant assemblages in favour of terrestrial (emergent and meadow) taxa and have thus reduced or eliminated this important ecosystem service. In this study, we compared IKONOS satellite images for two regions of eastern Georgian Bay (acquired in 2002 and 2008) to determine significant changes in cover of four distinct wetland vegetation groups [meadow (M), emergent (E), high‐density floating (HD) and low‐density floating (LD)] over the 6 years. While LD decreased significantly (mean ?2995.4 m²), M and HD increased significantly (mean +2020.9 m² and +2312.6 m², respectively) between 2002 and 2008. Small patches of LD had been replaced by larger patches of HD. These results show that sustained low water levels have led to an increasingly homogeneous habitat and an overall net loss of fish habitat. A comparison of the fish communities sampled between 2003 and 2005 with those sampled in 2009 revealed that there was a significant decline in species richness. The remaining fish communities were also more homogeneous. We suggest that the observed changes in the wetland plant community due to prolonged low water levels may have resulted in significant changes in the fish communities of coastal wetlands in eastern Georgian Bay.     

Temperature‐induced water stress in high‐latitude forests in response to natural and anthropogenic warming

The Arctic is particularly sensitive to climate change, but the independent effects of increasing atmospheric CO₂ concentration (pCO₂) and temperature on high‐latitude forests are poorly understood. Here, we present a new, annually resolved record of stable carbon isotope (δ¹³C) data determined from Larix cajanderi tree cores collected from far northeastern Siberia in order to investigate the physiological response of these trees to regional warming. The tree‐ring record, which extends from 1912 through 1961 (50 years), targets early twentieth‐century warming (ETCW), a natural warming event in the 1920s to 1940s that was limited to Northern hemisphere high latitudes. Our data show that net carbon isotope fractionation (Δ¹³C), decreased by 1.7‰ across the ETCW, which is consistent with increased water stress in response to climate warming and dryer soils. To investigate whether this signal is present across the northern boreal forest, we compiled published carbon isotope data from 14 high‐latitude sites within Europe, Asia, and North America. The resulting dataset covered the entire twentieth century and spanned both natural ETCW and anthropogenic Late Twentieth‐Century Warming (~0.7 °C per decade). After correcting for a ~1‰ increase in Δ¹³C in response to twentieth century pCO₂ rise, a significant negative relationship (r = ?0.53, P < 0.0001) between the average, annual Δ¹³C values and regional annual temperature anomalies is observed, suggesting a strong control of temperature on the Δ¹³C value of trees growing at high latitudes. We calculate a 17% increase in intrinsic water‐use efficiency within these forests across the twentieth century, of which approximately half is attributed to a decrease in stomatal conductance in order to conserve water in response to drying conditions, with the other half being attributed to increasing pCO₂. We conclude that annual tree‐ring records from northern high‐latitude forests record the effects of climate warming and pCO₂ rise across the twentieth century.     

A century of fish growth in relation to climate change,population dynamics and exploitation

Marine ecosystems, particularly in high‐latitude regions such as the Arctic, have been significantly affected by human activities and contributions to climate change. Evaluating how fish populations responded to past changes in their environment is helpful for evaluating their future patterns, but is often hindered by the lack of long‐term biological data available. Using otolith increments of Northeast Arctic cod (Gadus morhua) as a proxy for individual growth, we developed a century‐scale biochronology (1924–2014) based on the measurements of 3,894 fish, which revealed significant variations in cod growth over the last 91 years. We combined mixed‐effect modeling and path analysis to relate these growth variations to selected climate, population and fishing‐related factors. Cod growth was negatively related to cod population size and positively related to capelin population size, one of the most important prey items. This suggests that density‐dependent effects are the main source of growth variability due to competition for resources and cannibalism. Growth was also positively correlated with warming sea temperatures but negatively correlated with the Atlantic Multidecadal Oscillation, suggesting contrasting effects of climate warming at different spatial scales. Fishing pressure had a significant but weak negative direct impact on growth. Additionally, path analysis revealed that the selected growth factors were interrelated. Capelin biomass was positively related to sea temperature and negatively influenced by herring biomass, while cod biomass was mainly driven by fishing mortality. Together, these results give a better understanding of how multiple interacting factors have shaped cod growth throughout a century, both directly and indirectly.     

A simple method to estimate the contribution of biological floc and reactor-solution to mass transfer of oxygen in activated sludge processes

In this study, the mass transfer coefficient of biological floc (K(L)a(bf)) was estimated from the mass transfer coefficient of the mixed-liquor (K(L)a(f)) and the reactor-solution (K(L)a(e)). The biological floc resistance (BFR) and reactor-solution resistance (SR) were defined as the reciprocal of K(L)a(bf) and K(L)a(e), respectively, by applying the concept of serial-resistance originally presented in two-film theory (Lewis and Whitman (1924) Ind Eng Chem 16:1215-1220). The specific biological floc resistance (SBFR) was defined as biological floc resistance per unit biomass concentration. The data indicated that an activated sludge process yielding low BFR/MLR and BFR/SR tended to produce higher oxygen transfer efficiency. Surprisingly, the reactor-solution posed the same level of resistance as clean water in all experiments, except in a 5-day SRT, non-nitrifying, completely mixed activated sludge (CMAS) process run. Furthermore, SBFR successfully represented biological floc and showed a positive correlation to sludge volume index (SVI). In addition, SBFR/SR and oxygen transfer efficiency (OTE(f)) followed an exponential relationship for the complete data set. The method of separating the mixed-liquor into biological floc and reactor-solution improved the understanding of oxygen transfer under process conditions, without resorting to intrusive techniques or direct handling of fragile biological floc.     

A decade of boreal rich fen greenhouse gas fluxes in response to natural and experimental water table variability

Rich fens are common boreal ecosystems with distinct hydrology, biogeochemistry and ecology that influence their carbon (C) balance. We present growing season soil chamber methane emission (F_CH4), ecosystem respiration (ER), net ecosystem exchange (NEE) and gross primary production (GPP) fluxes from a 9‐years water table manipulation experiment in an Alaskan rich fen. The study included major flood and drought years, where wetting and drying treatments further modified the severity of droughts. Results support previous findings from peatlands that drought causes reduced magnitude of growing season F_CH4, GPP and NEE, thus reducing or reversing their C sink function. Experimentally exacerbated droughts further reduced the capacity for the fen to act as a C sink by causing shifts in vegetation and thus reducing magnitude of maximum growing season GPP in subsequent flood years by ~15% compared to control plots. Conversely, water table position had only a weak influence on ER, but dominant contribution to ER switched from autotrophic respiration in wet years to heterotrophic in dry years. Droughts did not cause inter‐annual lag effects on ER in this rich fen, as has been observed in several nutrient‐poor peatlands. While ER was dependent on soil temperatures at 2 cm depth, F_CH4 was linked to soil temperatures at 25 cm. Inter‐annual variability of deep soil temperatures was in turn dependent on wetness rather than air temperature, and higher F_CH4 in flooded years was thus equally due to increased methane production at depth and decreased methane oxidation near the surface. Short‐term fluctuations in wetness caused significant lag effects on F_CH4, but droughts caused no inter‐annual lag effects on F_CH4. Our results show that frequency and severity of droughts and floods can have characteristic effects on the exchange of greenhouse gases, and emphasize the need to project future hydrological regimes in rich fens.     

A new water-soluble N-protecting group, 2-(phenyl(methyl)sulfonio)ethyloxycarbonyl tetrafluoroborate, and its application to solid phase peptide synthesis in water.

A new water-soluble N-protecting group, 2-[phenyl(methyl)sulfoniolethyloxycarbonyl tetrafluoroborate, has been prepared and its application to solid phase peptide synthesis in water has been studied. Leu-enkephalin amide was successfully synthesized in water by the solid phase method using this protecting group.     

Tidal downwelling and implications for the carbon biogeochemistry of cold‐water corals in relation to future ocean acidification and warming

Cold‐water coral (CWC) reefs are recognized as ecologically and biologically significant areas that generate habitats and diversity. The interaction between hydrodynamics and CWCs has been well studied at the Mingulay Reef Complex, a relatively shallow area of reefs found on the continental shelf off Scotland, UK. Within ‘Mingulay Area 01’ a rapid tidal downwelling of surface waters, brought about as an internal wave, is known to supply warmer, phytoplankton‐rich waters to corals growing on the northern flank of an east‐west trending seabed ridge. This study shows that this tidal downwelling also causes short‐term perturbations in the inorganic carbon (C_T) and nutrient dynamics through the water column and immediately above the reef. Over a 14 h period, corresponding to one semi‐diurnal tidal cycle, seawater pH overlying the reef varied by ca. 0.1 pH unit, while pCO₂ shifted by >60 μatm, a shift equivalent to a ca. 25 year jump into the future, with respect to atmospheric pCO₂. During the summer stratified period, these downwelling events result in the reef being washed over with surface water that has higher pH, is warmer, nutrient depleted, but rich in phytoplankton‐derived particles compared to the deeper waters in which the corals sit. Empirical observations, together with outputs from the European Regional Shelf Sea Ecosystem Model, demonstrate that the variability that the CWC reefs experience changes through the seasons and into the future. Hence, as ocean acidification and warming increase into the future, the downwelling event specific to this site could provide short‐term amelioration of corrosive conditions at certain times of the year; however, it could additionally result in enhanced detrimental impacts of warming on CWCs. Natural variability in the C_T and nutrient conditions, as well as local hydrodynamic regimes, must be accounted for in any future predictions concerning the responses of marine ecosystems to climate change.     

Water in protein cavities: A procedure to identify internal water and exchange pathways and application to fatty acid-binding protein

A computational approach based on Delaunay triangulation is presented to identify internal water molecules in proteins and to capture pathways of exchange with the bulk. The implemented procedure is computationally efficient and can easily be applied to long molecular dynamics trajectories of protein simulations. In an application to fatty acid-binding protein in apo-form and with bound palmitate, several protein orifices known from crystal structures have been confirmed to be major portals of solvent exchange. Differences between the two forms of the protein are observed and discussed.