bluuebunny/crossref_metadata_2025_split huggingface dataset:
Exercise stress, intestinal permeability and gastric ulceration in racing Alaskan sled dogs
Authors: Royer Christopher M , Willard Michael , Williamson Katherine , Steiner Jörg M , Williams David A , David Michael 
Published: May 2005

AbstractSustained strenuous exercise has been shown to produce gastrointestinal disease in athletic species, but the causative factors remain unknown. Since exercise results in oxidative stress and hypercortisolaemia, we tested the hypothesis that oxidative and physiological stress cause gastrointestinal disease in racing Alaskan sled dogs. Dogs from three racing teams were examined before (pre) and immediately after (post) completing a 1770-km sled dog race in approximately 11 days. Serum cortisol and isoprostane concentrations were compared with markers of gastrointestinal barrier integrity and endoscopic evidence of gastric ulceration. Gastric barrier integrity was assessed by measuring the urinary recovery of sucrose and intestinal barrier integrity was assessed using the urinary recovery ratio of lactulose to rhamnose (L/R), administered together by orogastric gavage. Exercise produced a significant increase in median serum cortisol (pre: 1040, 717–2946 pg ml−1(range); post: 8072, 2228–29 571 pg ml−1;P<0.0001) and L/R recovery ratio (pre: 0.110, 0.060–0.270; post: 0.165, 0.080–0.240;P=0.009) but not isoprostane (pre: 1007, 656–2305 pg ml−1; post: 1164, 23–4710 pg ml−1;P=0.194) concentration. The increased serum cortisol concentration was not correlated with a change in L/R recovery ratio or urine sucrose concentration. Dogs with abnormal gastric endoscopy results (61% of finishers) had higher serum cortisol concentrations than dogs with normal endoscopy results (P=0.0007). We have demonstrated concurrent hypercortisolaemia and gastrointestinal barrier dysfunction with no correlation of the two. Thus, our data do not provide support for the hypothesis that increased serum cortisol concentration causes exercise-induced gastrointestinal disease.
Relationships between exercise capacity and front hoof longitudinal balance in horses
Authors: Tacchio G , Davies HMS , Morgante M , Bernardini D 
Published: May 2005

AbstractTo the authors' knowledge, the effect of hoof balance alteration on exercise capacity or performance has not been investigated. With the aim of evaluating the relationships between longitudinal front hoof balance and exercise capacity (lactate vs. speed relationship, run time and stride characteristics), two experiments were undertaken. In the first test the horses, left unshod, performed an incremental speed test in which parameters chosen to evaluate exercise capacity were related to hoof longitudinal balance. In the second part of the study the same group of horses had the length of the toe altered (decreased and increased) with the application of shoes, while the angle of the foot and the height of the foot from the ground remained the same. The relative change in exercise capacity due to the alteration of longitudinal balance was observed. In the unshod experiment, lactate level at the speed of 10 ms-1(5.0±2.0 mmoll-1) was significantly associated with the angles DC° (angle described by the dorsal cortex with respect to the ground; 50.0±3.2°) and PC° (angle described by the palmar cortex with respect to the ground; 29.6 ± 2.9°), while run time (14.07 ± 1.44 min) was associated with breakover indices (Breakover index1 0.33±0.03; Breakover index2 0.30 ± 0.04 – all values mean ± standard deviation (SD)) (breakover indices were created to express the distance between the point of the toe and the point of the third phalanx relative to the length of the palmar cortex or relative to the distance between the point of the third phalanx and the centre of rotation of the distal interphalangeal joint). These associations have to be judged cautiously because the influence of hoof balance on exercise capacity could be biased by other physiological factors and because hoof balance parameters themselves could reflect the conformation of other anatomical structures far from the phalanges. The selective alteration of front hoof balance in the second part of the study produced a significant difference in blood lactate level only at 6 ms-1(mean ± SD: La6?m?s-10.32 ± 0.39 mmoll-1), with this benefit in terms of lactate level being associated with an increase in stride length (mean ± SD: ΔSL6ms-10.01 ± 0.05 m; ΔSL10ms-10.112 ± 0.218 m). In conclusion, while higher exercise capacity seemed to be associated with lower DC°, PC° and breakover indices, decreasing the toe length without altering the foot angle was beneficial only in terms of lactate level at the speed of 6 ms-1for horses with DC° greater than 45°; this benefit was accompanied by a slight lengthening of the stride at both 6 and 10 ms-1.
Hoof landing velocity is related to track surface properties in trotting horses
Authors: Burn Jeremy F , Usmar Steven J 
Published: May 2005

AbstractThe resistance of a track surface to deformation is known to be positively related to the magnitude of foot impact experienced during locomotion. Although passive mechanics suggests that this might be entirely due to the action of the track surface material decelerating the foot, it is also possible that the dynamics of locomotion are altered in a way that changes the landing velocity of the foot. The observed relationship between track properties and foot impact would then be due to a combination of the direct effect of the surface material and altered foot kinematics at impact. In this study we measured hoof landing velocity, stance time and limb landing angle in horses trotting over surfaces that differed significantly in their deformability. In comparison with a surface that underwent negligible deformation during stance phase, a surface that deformed 25 mm led to significantly increased stance time, significantly greater leg landing angle and significantly greater hoof landing velocity. Although the increased hoof landing velocity would act to counteract the increased shock absorption on the softer surface, we suggest that this effect is relatively small.
HU‐α binds to the putative double‐stranded DNA mimic HI1450 from Haemophilus influenzae
Authors: Parsons Lisa M. , Liu Fang , Orban John 
Published: May 2005

AbstractRecently, the solution structure of the hypothetical protein HI1450 from Haemophilus influenzae was solved as part of a structure‐based effort to understand function. The distribution of its many negatively charged residues and weak structure and sequence homology to uracil DNA glycosylase inhibitor (Ugi) suggested that HI1450 may act as a double‐stranded DNA (dsDNA) mimic. We present supporting evidence here and show that HI1450 interacts with the dsDNA‐binding protein HU‐α. The interaction between HI1450 and HU‐α from H. influenzae is characterized using calorimetry and NMR spectroscopy. HU‐α binds to HI1450 with a Kd of 3.0 ± 0.2 μM, which is similar in affinity to its interaction with dsDNA. Chemical shift perturbation data indicate that the β1‐strand of HI1450 and neighboring regions are most directly involved in interactions with HU‐α. These results show that HI1450 and its structural homolog, Ugi, use similar parts of their structures to recognize DNA‐binding proteins.
Calcium‐ and magnesium‐dependent interactions between calcium‐ and integrin‐binding protein and the integrin αIIb cytoplasmic domain
Authors: Yamniuk Aaron P. , Vogel Hans J. 
Published: May 2005

AbstractCalcium‐ and integrin‐binding protein (CIB) is a small EF‐hand calcium‐binding protein that is involved in hemostasis through its interaction with the αIIb cytoplasmic domain of integrinαIIbβ3. We have previously demonstrated that CIB lacks structural stability in the absence of divalent metal ions but that it acquires a well‐folded conformation upon addition of Ca2+ or Mg2+. Here, we have used fluorescence spectroscopy, NMR spectroscopy, and isothermal titration calorimetry to demonstrate that both Ca2+‐bound CIB (Ca2+‐CIB) and the Mg2+‐bound protein (Mg2+‐CIB) bind with high affinity and through a similar mechanism to αIIb cytoplasmic domain peptides, but that metal‐free CIB (apo‐CIB) binds in a different manner. The interactions are thermodynamically distinct for Ca2+‐CIB and Mg2+‐CIB, but involve hydrophobic interactions in each case. Since the Mg2+ concentration inside the cell is sufficient to saturate CIB at all times, our results imply that CIB would be capable of binding to the αIIb cytoplasmic domain independent of an intracellular Ca2+ stimulus in vivo. This raises the question of whether CIB can act as a Ca2+ sensor in αIIbβ3 signaling or if other regulatory mechanisms such as fibrinogen‐induced conformational changes in αIIbβ3, post‐translational modifications, or the binding of other accessory proteins mediate the interactions between CIB and αIIbβ3. Differences in NMR spectra do suggest, however, that Ca2+‐binding to the Mg2+‐ CIB‐αIIb complex induces subtle structural changes that could further modulate the activity of αIIbβ3.
Capsid structure and dynamics of a human rhinovirus probed by hydrogen exchange mass spectrometry
Authors: Wang Lintao , Smith David L. 
Published: May 2005

AbstractViral capsids are dynamic protein assemblies surrounding viral genomes. Despite the high‐resolution structures determined by X‐ray crystallography and cryo‐electron microscopy, their in‐solution structure and dynamics can be probed by hydrogen exchange. We report here using hydrogen exchange combined with protein enzymatic fragmentation and mass spectrometry to determine the capsid structure and dynamics of a human rhinovirus, HRV14. Capsid proteins (VP1–4) were labeled with deuterium by incubating intact virus in D2O buffer at neutral pH. The labeled proteins were digested by immobilized pepsin to give peptides analyzed by capillary reverse‐phase HPLC coupled with nano‐electrospray mass spectrometry. Deuterium levels incorporated at amide linkages in peptic fragments were measured for different exchange times from 12 sec to 30 h to assess the amide hydrogen exchange rates along each of the four protein backbones. Exchange results generally agree with the crystal structure of VP1–4,with extended, flexible terminal and surface‐loop regions in fast exchange and folded helical and sheet structures in slow exchange. In addition, three α‐helices, one from each of VP1–3, exhibited very slow exchange, indicating high stability of the protomeric interface. The β‐strands at VP3 N terminus also had very slow exchange, suggesting stable pentamer contacts. It was noted, however, that the interface around the fivefold axis had fast and intermediate exchange, indicating relatively more flexibility. Even faster exchange rates were found in the N terminus of VP1 and most segments of VP4, suggesting high flexibilities, which may correspond to their potential roles in virus uncoating.
Cellular automata and ecology
Authors: Rohde Klaus 
Published: May 2005

A fascinating and potentially very fertile new approach for solving various scientific problems in mathematics, physics, cosmology, chemistry, biology, psychology and economics, to mention only the most important ones, is that pioneered by Stephan Wolfram. In the following, I give a brief outline of his “NKS” (new kind of science”) with emphasis on cellular automata; some of his conclusions concerning evolutionary biology; a comparison with other approaches; and an application of the method to some problems of ecology.The principles of NKS (“new kind of science”) developed by Stephen Wolfram are discussed, with emphasis on cellular automata. Wolfram's conclusions concerning optimisation and the evolution of complexity in biological systems are outlined and compared with those from some other recent approaches. NKS is applied to some central problems of ecology, i.e. the possibility of establishing general ecological laws, the existence of vacant niches, the importance of interspecific competition and the causes of latitudinal gradients in species diversity.
Electrostrictive Coefficients of 0.9Pb(Mg1/3Nb2/3)O3‐0.1PbTiO3 Relaxor Ferroelectric Ceramics in the Ferroelectricity‐Dominated Temperature Range
Authors: Park Jae‐Hwan , Kim Byung‐Kook , Park Soon Ja 
Published: May 2005

Polarization and strain induced by unipolar electric fields (Puni, Suni) as well as those induced by bipolar electric fields (Pbi, Sbi) were measured in 0.9Pb(Mgl/3Nb2/3)O3‐0.1PbTiO3 relaxor ferroelectric ceramics in the temperature range of −50°‐90°C to observe the phase transition in this region and calculate the electrostrictive coefficients from the purely electric‐field‐induced polarization and strain. By considering both the electrostrictive component (Funi, Suni) and the piezoelectric component (Pr, Sr), it is shown quantitatively how the transition occurs from pure electrostrictive to partially piezoelectric properties across the phase transition range. Puni represents unmixed electric‐field‐induced polarization.while Fbi represents the summation of Puni and Pr. Similarly, Suni represents unmixed electric‐field‐induced strain, while Sbi represents the summation of Suni and Sr. The effective electrostrictive coefficient (Qeff) is calculated even in the ferroelectric region far below the phase transition temperature using Suni and Puni which are purely electric field induced. Qeff significantly increases as the temperature decreases below the phase transition temperature, which was attributed to the decreased rattling space of B‐site atoms.
Increased leaf area dominates carbon flux response to elevated CO2in stands ofPopulus deltoides(Bartr.)
Authors: Murthy Ramesh , Barron‐Gafford Greg , Dougherty Phillip M. , Engel Victor C. , Grieve Katie , Handley Linda , Klimas Christie , Potosnak Mark J. , Zarnoch Stanley J. , Zhang Jianwei 
Published: May 2005

AbstractWe examined the effects of atmospheric vapor pressure deficit (VPD) and soil moisture stress (SMS) on leaf‐ and stand‐level CO2exchange in model 3‐year‐old coppiced cottonwood (Populus deltoidesBartr.) plantations using the large‐scale, controlled environments of the Biosphere 2 Laboratory. A short‐term experiment was imposed on top of continuing, long‐term CO2treatments (43 and 120 Pa), at the end of the growing season. For the experiment, the plantations were exposed for 6–14 days to low and high VPD (0.6 and 2.5 kPa) at low and high volumetric soil moisture contents (25–39%). When system gross CO2assimilation was corrected for leaf area, system net CO2exchange (SNCE), integrated daily SNCE, and system respiration increased in response to elevated CO2. The increases were mainly as a result of the larger leaf area developed during growth at high CO2, before the short‐term experiment; the observed decline in responses to SMS and high VPD treatments was partly because of leaf area reduction. Elevated CO2ameliorated the gas exchange consequences of water stress at the stand level, in all treatments. The initial slope of light response curves of stand photosynthesis (efficiency of light use by the stand) increased in response to elevated CO2under all treatments. Leaf‐level net CO2assimilation rate and apparent quantum efficiency were consistently higher, and stomatal conductance and transpiration were significantly lower, under high CO2in all soil moisture and VPD combinations (except for conductance and transpiration in high soil moisture, low VPD). Comparisons of leaf‐ and stand‐level gross CO2exchange indicated that the limitation of assimilation because of canopy light environment (in well‐irrigated stands; ratio of leaf : stand=3.2–3.5) switched to a predominantly individual leaf limitation (because of stomatal closure) in response to water stress (leaf : stand=0.8–1.3). These observations enabled a good prediction of whole stand assimilation from leaf‐level data under water‐stressed conditions; the predictive ability was less under well‐watered conditions. The data also demonstrated the need for a better understanding of the relationship between leaf water potential, leaf abscission, and stand LAI.
Influence of drought‐induced acidification on the mobility of dissolved organic carbon in peat soils
Authors: Clark Joanna M. , Chapman Pippa J. , Adamson John K. , Lane Stuart N. 
Published: May 2005

AbstractA strong relationship between dissolved organic carbon (DOC) and sulphate (SO42−) dynamics under drought conditions has been revealed from analysis of a 10‐year time series (1993–2002). Soil solution from a blanket peat at 10 cm depth and stream water were collected at biweekly and weekly intervals, respectively, by the Environmental Change Network at Moor House‐Upper Teesdale National Nature Reserve in the North Pennine uplands of Britain. DOC concentrations in soil solution and stream water were closely coupled, displaying a strong seasonal cycle with lowest concentrations in early spring and highest in late summer/early autumn. Soil solution DOC correlated strongly with seasonal variations in soil temperature at the same depth 4‐weeks prior to sampling. Deviation from this relationship was seen, however, in years with significant water table drawdown (>−25 cm), such that DOC concentrations were up to 60% lower than expected. Periods of drought also resulted in the release of SO42−, because of the oxidation of inorganic/organic sulphur stored in the peat, which was accompanied by a decrease in pH and increase in ionic strength. As both pH and ionic strength are known to control the solubility of DOC, inclusion of a function to account for DOC suppression because of drought‐induced acidification accounted for more of the variability of DOC in soil solution (R2=0.81) than temperature alone (R2=0.58). This statistical model of peat soil solution DOC at 10 cm depth was extended to reproduce 74% of the variation in stream DOC over this period. Analysis of annual budgets showed that the soil was the main source of SO42−during droughts, while atmospheric deposition was the main source in other years. Mass balance calculations also showed that most of the DOC originated from the peat. The DOC flux was also lower in the drought years of 1994 and 1995, reflecting low DOC concentrations in soil and stream water. The analysis presented in this paper suggests that lower concentrations of DOC in both soil and stream waters during drought years can be explained in terms of drought‐induced acidification. As future climate change scenarios suggest an increase in the magnitude and frequency of drought events, these results imply potential for a related increase in DOC suppression by episodic acidification.
Productivity of high‐latitude lakes: climate effect inferred from altitude gradient
Authors: Karlsson Jan , Jonsson Anders , Jansson Mats 
Published: May 2005

AbstractClimate change is predicted to be dramatic at high latitudes. Still, climate impact on high latitude lake ecosystems is poorly understood. We studied 15 subarctic lakes located in a climate gradient comprising an air temperature difference of about 6°C. We show that lake water productivity varied by one order of magnitude along the temperature gradient. This variation was mainly caused by variations in the length of the ice‐free period and, more importantly, in the supply of organic carbon and inorganic nutrients, which followed differences in terrestrial vegetation cover along the gradient. The results imply that warming will have rapid effects on the productivity of high latitude lakes, by prolongation of ice‐free periods. However, a more pronounced consequence will be a delayed stimulation of the productivity following upon changes of the lakes terrestrial surroundings and subsequent increasing input of elements that stimulate the production of lake biota.
Effects of simulated long‐term climatic change on the bryophytes of a limestone grassland community
Authors: Bates Jeffrey W. , Thompson Ken , Grime J. Philip 
Published: May 2005

AbstractThe bryophyte vegetation of upland limestone grassland at Buxton in the southern Pennine Hills (UK) was studied following seven years' continuous simulated climate change treatments. The experimental design involved two temperature regimes (ambient, winter warming by 3°C) in factorial combination with three moisture regimes (normal, summer drought, supplemented summer rainfall) and with five replicate blocks. Percentage cover of the bryophytes was estimated visually using 15 randomly positioned quadrats (30 cm × 30 cm) within each of the 30 3 m × 3 m plots. Significant treatment effects were found but these were relatively modest. Total bryophyte cover and cover of Calliergonella cuspidata and Rhytidiadelphus squarrosus responded negatively to drought, whereas Fissidens dubius increased in the droughted plots. Campyliadelphus chrysophyllus increased with winter warming, while R. squarrosus, Lophocolea bidentata and species richness all decreased. The effects on the total bryophyte flora were further studied by canonical correspondence analysis, which yielded a first axis reflecting the combined effects of the moisture and temperature treatments. However, this analysis and a detrended correspondence analysis of the plot data also revealed that natural factors were more important causes of variation in the grassland community than the simulated climate treatments. It was concluded that dewfall may be an important source of moisture for grassland bryophytes and that this factor may have reduced the impact of the moisture treatments. The absence of some thermophilous species such as Homalothecium lutescens in the plots initially may also have reduced their scope for major vegetational change.
Species enrichment in an agriculturally improved grassland and its effects on botanical composition, yield and forage quality
Authors: Hofmann M. , Isselstein J. 
Published: May 2005

AbstractIn a field experiment, the effects of different management treatments on the botanical development and productivity of a previously species‐poor, intensively managed, lowland permanent grass sward were investigated over a 4‐year period. Fertilizer inputs were stopped and nine main treatments, based on three pre‐sowing and three post‐sowing cutting regimes, were applied. Half of each treatment plot was oversown with a mixture of forb (wildflower) species and half left unsown. The aims were: (1) to investigate the effect of cutting regimes on the establishment of introduced forb species, (2) to assess the development and dry‐matter (DM) yield potential of these introduced species, and (3) to compare the DM yield and forage quality of swards with and without introduced species. Seedling establishment was recorded until the end of the second year. From the third year onwards, a common twice‐yearly cutting regime was imposed on all treatments, and the development of the introduced species was recorded. The DM yield of the nine oversown sub‐treatments was compared with the sub‐treatments not oversown. Frequent cutting after oversowing resulted in the greatest number of established plants and three times greater harvested DM yield of introduced species, compared with infrequent cutting. Plantago lanceolata and Trifolium pratense were the best performing introduced species. By years 3 and 4, there was proportionately 0·15 and 0·23, respectively, additional herbage DM yield harvested from the oversown treatments compared with unsown treatments, and up to 0·60 more in some treatments. The introduction of forbs increased the crude protein concentration, but decreased the digestibility of the forage.