bluuebunny/crossref_metadata_2025_split huggingface dataset:
Moderate exercise, postprandial lipaemia and triacylglycerol clearance
Authors: Gill J. M. R. , Mees G. P. , Frayn K. N. , Hardman A. E. 
Published: March 2003

Moderate intensity exercise reduces postprandial triacylglycerol (TG) concentrations. We tested whether this reflects increased TG clearance.Eight normotriglyceridaemic men, aged 48·3 ± 7·3 years (mean ± SD), performed two oral fat tolerance tests (blood samples taken in the fasted state and for six hours after a high‐fat meal containing 1·00 g fat, 0·97 g carbohydrate, 58 kJ energy kg−1 fat‐free body mass) and two intravenous fat tolerance tests (blood samples in the fasted state and after a bolus injection of Intralipid, 0·1 g fat kg−1 body mass). The afternoon before one oral and one intravenous test, subjects walked briskly for 90 min; no exercise was performed before the control tests.Prior exercise reduced fasting TG concentration similarly in the oral (16 ± 7 %) (mean ± SEM) and intravenous (18 ± 7 %) tests, and reduced postprandial TG concentrations in the oral test by 18 ± 6 % (all P < 0·05). However, prior exercise did not increase Intralipid clearance (disappearance curve slopes: control, 4·69 ± 0·49 % min−1; exercise, 4·85 ± 0·40 % min−1).These data suggest that mechanisms other than increased TG clearance mediate the lower postprandial TG concentrations seen after moderate exercise.
Extrasystolic beats affect transmural electrical dispersion during programmed electrical stimulation
Authors: Wolk R. , Stec S. , Kulakowski P. 
Published: March 2003

Background Experimental studies suggest that the electrocardiographic Tpeak–Tend (TpTe) interval reflects transmural dispersion of repolarization (TDR). The genesis and role of the TpTe interval in a clinical setting have not been established. This study aimed to assess the clinical usefulness of the TpTe interval as an index of TDR and a pro‐arrhythmic marker.Materials and methods Endocardial monophasic action potential (MAP) duration and electrocardiographic QTp, QTe and TpTe intervals were assessed in 13 patients undergoing an electrophysiological study. Surface electrocardiograms were recorded during right ventricular pacing (Basic Cycle Length = 600 ms) before and after single extrastimuli.Results Ventricular arrhythmia was induced in six patients. During ventricular pacing, MAP duration and QTp intervals shortened in response to extrastimuli applied at progressively shorter coupling intervals. In contrast, QTe intervals increased in response to premature stimulation and QTe dispersion increased at short coupling intervals. During sinus rhythm, the TpTe interval was greater in the inducible group in leads V3‐V4. Premature stimulation increased the duration of TpTe intervals, suggesting an increase in TDR. The maximum TpTe interval was greater in the inducible than in the noninducible group, both during baseline ventricular drive pacing (163 ± 22 vs. 130 ± 27 ms, respectively, P < 0·03) and after application of shortly coupled extrastimuli (263 ± 66 vs. 200 ± 47 ms, respectively, P < 0·05).Conclusions The TpTe interval of surface ECG is likely to represent TDR. TDR is increased by premature ventricular stimulation and the magnitude of the maximum TpTe interval (i.e. maximum TDR) during ventricular pacing is greater in patients with inducible arrhythmias.
Effect of homocysteine on arachidonic acid release in human platelets
Authors: Signorello M. G. , Pascale R. , Leoncini G. 
Published: March 2003

AbstractBackgroundIt has been suggested that homocysteine is implicated in the risk of atherosclerosis and thrombosis. The pathogenic mechanism has not been clarified, but oxygen‐free species produced by the homocysteine metabolism and auto‐oxidation could have a role.DesignWe have studied the effect of homocysteine on arachidonic acid release in human platelets. Two important products of arachidonic acid metabolism – thromboxane B2(TXB2) and reactive oxygen species (ROS) – have been assayed.ResultsResults indicate that homocysteine induces arachidonic acid release that is partially inhibited by 5,8,11,14‐eicosatetraynoic acid (ETYA). Platelet incubation with homocysteine significantly increases basal levels of TXB2and ROS. The effect is time‐ and dose‐dependent. The TXB2formation is strictly correlated with the arachidonic acid release. Moreover, ROS accumulation is largely inhibited by ETYA and partially reduced by diphenyleneiodonium (DPI), suggesting the involvement both of enzymes metabolising arachidonic acid (cyclooxygenase, lipooxygenase, cytochrome P450 monooxygenase) and of NAD(P)H oxidase.ConclusionHomocysteine induces oxidative stress in human plateletsin vitro. The unbalance in platelet redox‐state and the increased TXB2formation may generate hyperactivation, contributing to a thrombogenic state leading to cardiovascular diseases.
Role of calcitonin in the rapid minute‐to‐minute regulation of plasma Ca2+ homeostasis in the rat
Authors: Wang W. , Lewin E. , Olgaard K. 
Published: March 2003

AbstractBackground  Plasma ionized calcium (Ca2+) is maintained at a very stable concentration in mammals. The hormones or factors involved in the very rapid regulation of calcium homeostasis are still debated. Thus, previous results from our laboratory have clearly shown that parathyroid hormone (PTH) and 1,25(OH)2D3 are not responsible for the rapid up‐regulation of plasma Ca2+ after a brief induction of hypocalcaemia. The present investigation therefore examined in vivo the possible role of calcitonin (CT) in the very rapid, minute‐to‐minute regulation of plasma Ca2+ in rats.Study design  The rapid calcaemic response to acute thyroparathyroidectomy (TPTX) and to acute selective thyroidectomy (TX) (n = 10), as well as the possible effect of CT on the very rapid recovery of plasma Ca2+ after termination of a brief induction of hypocalcaemia were studied. Hypocalcaemia was induced by a 30‐min EGTA infusion in rats in three different protocols: 1 h after TPTX (n = 9) compared with control TPTX rats not given EGTA (n = 13); 1 h after TX (n = 7); and 1 h after TPTX, but during supplementation with exogenous CT (n = 8) and compared with the response in TPTX rats infused with vehicle (n = 8).Results  An immediate and significant increase of plasma Ca2+ was found after TPTX (P < 0·01) as well as after selective TX (P < 0·01) in the nonfasting rats. Significant hypercalcaemia (P < 0·05) was still present in rats fasting for 2 days before these procedures, but the increase in plasma Ca2+ was considerably less (P < 0·01). After induction of a brief period of hypocalcaemia by infusion of EGTA a significant (P < 0·01) and rapid recovery of plasma Ca2+ took place within 10 min and a further increase within the next 60 min (P < 0·01), whether or not the rats were normal, TPTX, TX or were supplemented by CT during the experiments. The plasma Ca2+ recovery curves after termination of a brief induction of hypocalcaemia all had similar appearances, indicating that presence or absence of CT had no influence on this very rapid Ca2+ recovery after induction of hypocalcaemia.Conclusions  Acute removal of the tonus of CT results in an acute increase in plasma Ca2+ for up to 3 h. This effect of CT is probably mainly related to the postprandial maintenance of normocalcaemia, but is also seen in fasting rats, although to a lesser degree. The very rapid calcaemic recovery after discontinuation of a brief induction of hypocalcaemia is, however, not a result of suppressed plasma calcitonin levels.
Molecular cloning of the cDNAs encoding the feline B‐lymphocyte activation antigen B7–1 (CD80) and B7–2 (CD86) homologues which interact with human CTLA4‐Ig
Authors: Nishimura Y. , Shimojima M. , Miyazawa T. , Sato E. , Nakamura K. , Izumiya Y. , Ikeda Y. , Mikami T. , Takahashi E. 
Published: March 2003

AbstractWe cloned the cDNAs encoding the feline homologues of B‐lymphocyte activation antigens B7–1 (CD80) and B7–2 (CD86). We expressed recombinant feline CD80 and CD86 molecules by the baculovirus expression system, and demonstrated their binding ability to human CTLA4‐murine immunoglobulin fusion protein.
Cloning and analysis of the gene encoding the human neonatal Fc receptor
Authors: Mikulska J. E. , Pablo L. , Canel J. , Simister N. E. 
Published: March 2003

AbstractThe neonatal Fc receptor, FcRn, is expressed in human placental syncytiotrophoblast, capillary endothelium, intestinal epithelium, and other tissues. By analogy with its role in the mouse, human FcRn is expected to transport maternal IgG to the foetus, and protect circulating IgG from catabolism. The larger subunit of FcRn is homologous to the α chains of the major histocompatibility complex (MHC) class I proteins, but is encoded outside the MHC on chromosome 19. We report the isolation of clones encoding the α chain of human FcRn from chromosome 19‐specific libraries. The sequence revealed a similar organization to classical and non‐classical MHC, and MHC‐related genes. Compared with classical MHC class I genes, the human FcRn α chain gene has expanded by acquiring many repetitive sequences in its introns, including multiple Alu elements in the fourth intron. Primer extension analysis showed that there are two transcription initiation sites in the upstream flanking sequence.
Immobilization of cadmium and zinc in soil by Al‐montmorillonite and gravel sludge
Authors: Lothenbach B. , Krebs R. , Furrer G. , Gupta S. K. , Schulin R. 
Published: March 2003

SummaryWe investigated the potential of montmorillonite, Al‐montmorillonite and gravel sludge to immobilize polluting heavy metals in agricultural soil. Batch experiments showed that both Al‐montmorillonite and montmorillonite immobilized zinc and cadmium. Zinc was bound specifically on Al‐montmorillonite and became increasingly incorporated into the interlayer hydroxy‐Al polymer, whereas there was no specific sorption on montmorillonite. Cadmium was bound on montmorillonite and Al‐montmorillonite unspecifically by cation exchange, but there was no incorporation into the lattice.In pot experiments montmorillonite, Al‐montmorillonite, or gravel sludge were added to a soil contaminated with zinc and cadmium. Increasing doses of these agents decreased the concentrations of NaNO3‐extractable zinc and cadmium. Aluminium‐montmorillonite and gravel sludge were more efficient than montmorillonite in immobilizing both zinc and cadmium. Remobilization tests at pH between 4 and 5.5 showed that cadmium and zinc desorbed more easily from montmorillonite than from Al‐montmorillonite. Gravel sludge application increased the buffer capacity of the contaminated soil substantially. The binding agents decreased zinc concentrations in red clover (Trifolium pratense), and gravel sludge also reduced the cadmium concentrations.
Chemical nature of soil organic matter under grassland and recently established forest
Authors: CONDRON L. M. , NEWMAN R. H. 
Published: March 2003

SummaryCarbon‐13 (C‐13) solid‐state NMR spectroscopy was used to investigate the chemical nature of organic C in mineral topsoil sampled under grassland and adjacent recently established (10–17 years old) coniferous forest (Douglas fir, Pseudotsuga menziesii; Ponderosa pine, Pinus ponderosa; Corsican pine, Pinus nigra) at two sites (Craigieburn, Cave Stream) in the South Island of New Zealand. This involved using a Cross‐Polarized/Magic‐Angle Spinning (CP/MAS) technique to identify different chemical forms of soil organic C, whilst Proton Spin Relaxation Editing (PSRE) was used to determine different ‘pools’ of soil organic C. Results obtained from the Craigieburn soils (0–5 cm) were more promising than those obtained from the Cave Stream soils (0–10 cm) because the total Fe content was smaller, and indicated a shift towards more recalcitrant forms of organic C in soil under trees compared with grassland, which might reflect reduced inputs of fresh organic matter to the soil under trees.
An improved method for determining the specific surface areas of topsoils with varied organic matter content, texture and clay mineral composition
Authors: Theng B. K. G. , Ristori G. G. , Santi C. A. , Percival H. J. 
Published: March 2003

SummaryMeasuring the specific surface area (SSA) of soils that contain much organic matter (OM) is problematic. The adsorption of p‐nitrophenol (pNP) from xylene at room temperature yielded realistic values for the SSA of a wide range of clays, oxides and subsoils. Here we have extended the same measurement to some topsoils with varied OM content, texture and clay mineral composition. Specifically, we have compared the surface areas measured by adsorption of N2, and, applying the BET equation, with the values obtained by adsorption of pNP, before and after treatment of the samples with hydrogen peroxide. In all instances, the removal by H2O2 of organic matter – albeit in part only – led to a marked increase in the SSAs measured by nitrogen because of the exposure of micropores previously blocked or covered by OM. The surface areas measured by pNP were appreciably larger than those obtained by the standard BET equation, and showed little change after removal of organic matter. However, the surface area of two smectite‐rich samples measured by pNP increased substantially after peroxidation, presumably because smectite crystals decomposed during treatment with H2O2.The results suggest that, under the experimental conditions used, pNP could diffuse without hindrance into and through organic matter, enabling it to adsorb on to micropore surfaces within clay aggregates (domains). In keeping with this suggestion, the relation between the surface areas measured by pNP and the corresponding values calculated from the clay and OM contents, and clay mineral composition, of the soils was close to 1:1. An even stronger relation was observed between the measured and calculated values for cation exchange capacity.
Modelling long‐term phosphorus leaching and changes in phosphorus fertility in excessively fertilized acid sandy soils
Authors: Del Campillo M. C. , Van Der Zee S. E. A. T. M. , Torrent J. 
Published: March 2003

SummaryThe sound management of agricultural soils that are heavily loaded with phosphorus (P) involves minimizing the losses of P responsible for eutrophication of surface waters, while ensuring enough P for crops. This paper describes a simple model to examine the compatibility of these two objectives in acid sandy soils in a temperate humid climate. The model is based on several assumptions regarding reversible and irreversible P sorption by P‐reactive soil compounds (mainly poorly crystalline Fe and Al oxides) and release of P to water (water‐P test). Model inputs are amount of P leached, P uptake by crops, and contents of poorly crystalline Fe and Al oxides in soil. The model predicts that reducing the amount of leached P to what is environmentally acceptable (e.g. 0.44 kg P ha–1 year–1, equivalent to 1 kg P2O5 ha–1 year–1) results in the long run in available soil P test values below target concentrations for optimum crop growth. When the amount of leached P is set to a fixed value the model predicts that soils with large contents of Fe and Al oxides can maintain the initial soil P test values for longer periods than other soils. The content in available P decreases if fertilizer P is applied to the soil at a rate equal to P uptake by crops. These results stress the difficulties involved in trying to make agricultural and environmental needs compatible in acid sandy soils.
Nitrogen fertilizer leaching from cropped and irrigated sandy soil in Central Turkey
Authors: Ünlü K. , Özeni˙rler G. , Yurteri˙ C. 
Published: March 2003

SummaryPollution of ground water caused by excessive and uncontrolled use of nitrogen fertilizer is worrying. A recent example of such pollution has been observed in an agricultural basin in the province of Nevsehir, Turkey, where up to 900 kg ha−1 nitrogen fertilizer is used for growing potatoes in sandy soils under irrigation. Using nitrogen fertilizer in amounts that guarantee large yields without polluting ground water is essential. We present results of field experiments and numerical simulations involving 15N‐labelled nitrogen fertilizer leaching. In the field, we monitored the movement of water and the distributions of nitrogen species within the soil–water–plant continuum. The detailed dynamics of the nitrogen cycle within the system were simulated. Simulations included calibration and validation of the nitrogen version of the LEACHM model (LEACHN, version 3) and long‐term applications of the model. The model’s predictions of nitrogen fluxes under long‐term use of fertilizer and irrigation were analysed. Nearly half of the applied ammonium‐N was converted to nitrate‐N during the growing season. With increasing additions of N the rate of plant uptake declined, while leaching increased significantly, and the fraction of nitrogen remaining in the soil profile increased only moderately. In long‐term applications, a significant fraction of the applied fertilizer tended to accumulate after the first year in soil as the residual nitrogen not taken up by the crop. Accumulated residual nitrogen is converted to nitrate‐N and leached rapidly from the soil profile during the wet season following the harvest. To reduce leaching of the residual nitrate, the rates, frequencies and timings of fertilizer application and irrigation must be scheduled in accordance with the plant growth periods and the hydraulic regime of the soil.
A comparison of some robust estimators of the variogram for use in soil survey
Authors: Lark R. M. 
Published: March 2003

SummaryThe standard estimator of the variogram is sensitive to outlying data, a few of which can cause overestimation of the variogram. This will result in incorrect variances when estimating the value of a soil property by kriging or when designing a sampling grid to map the property to a required precision. Several robust estimators of the variogram, based on location and scale estimation, have been proposed as improvements. They seem to be suitable for analysis of soil data in circumstances where the standard estimator is likely to be affected by outliers. Robust estimators are based on assumptions about the distribution of the data which will not always hold and which need not be made in kriging or in estimating the variogram by the standard estimator.The estimators are reviewed. Simulation studies show that the robust estimators vary in their susceptibility to moderate skew in the underlying distribution, but that the effects of outliers are generally greater. The estimators are applied to some soil data, and the resulting variograms used for ordinary kriging at sites in a separate validation data set. In most cases the variograms derived from the standard estimator gave kriging variances which appeared to overestimate the mean squared error of prediction (MSEP). Kriging with variograms based on robust estimators sometimes gave kriging variances which underestimated the MSEP or did not differ significantly from it. Estimates of kriging variance and the MSEP derived from the validation data were generally close to estimates from cross‐validation on the prediction set used to derive the variograms. This indicates that variogram models derived from different estimators could be compared by cross‐validation.
Temperature dependence of thermal conductivity of soil over a wide range of temperature (5–75°C)
Authors: Hiraiwa Y. , Kasubuchi T. 
Published: March 2003

SummaryThe coupled heat and mass transfer in soil can be analysed by examining the temperature dependence of thermal conductivity. We have measured the thermal conductivity of two kinds of soil (Ando soil and Red Yellow soil) as a function of both temperature (5–75°C) and water content by the twin heat probe method. From our results we concluded that the thermal conductivity resulting from the latent heat transfer can be separated from the apparent thermal conductivity by subtracting the thermal conductivity at a temperature near 0°C from that at a higher temperature. The relation between the phenomenological enhancement factor (β) and the volumetric air‐filled porosity was divided into two parts: β increases linearly as the volumetric air‐filled porosity increases from zero (that is, water saturation), to the point at which soil water potential corresponds to −320 J kg−1; from that point to oven‐dry condition, β decreased logistically with the volumetric air‐filled porosity. From these results, we could generalize the behaviour of β.
Estimating variograms of soil properties by the method‐of‐moments and maximum likelihood
Authors: Lark R. M. 
Published: March 2003

SummaryVariograms of soil properties are usually obtained by estimating the variogram for distinct lag classes by the method‐of‐moments and fitting an appropriate model to the estimates. An alternative is to fit a model by maximum likelihood to data on the assumption that they are a realization of a multivariate Gaussian process. This paper compares the two using both simulation and real data.The method‐of‐moments and maximum likelihood were used to estimate the variograms of data simulated from stationary Gaussian processes. In one example, where the simulated field was sampled at different intensities, maximum likelihood estimation was consistently more efficient than the method‐of‐moments, but this result was not general and the relative performance of the methods depends on the form of the variogram. Where the nugget variance was relatively small and the correlation range of the data was large the method‐of‐moments was at an advantage and likewise in the presence of data from a contaminating distribution. When fields were simulated with positive skew this affected the results of both the method‐of‐moments and maximum likelihood.The two methods were used to estimate variograms from actual metal concentrations in topsoil in the Swiss Jura, and the variograms were used for kriging. Both estimators were susceptible to sampling problems which resulted in over‐ or underestimation of the variance of three of the metals by kriging. For four other metals the results for kriging using the variogram obtained by maximum likelihood were consistently closer to the theoretical expectation than the results for kriging with the variogram obtained by the method‐of‐moments, although the differences between the results using the two approaches were not significantly different from each other or from expectation. Soil scientists should use both procedures in their analysis and compare the results.
Effects of rock fragment cover on soil infiltration, interrill runoff and erosion
Authors: Cerdà A. 
Published: March 2003

SummaryConsiderable attention has been paid recently to the influence of surface rock fragments on hydrological and erosional processes, although much of this research has been done on disturbed soils under laboratory conditions. I have studied the effects of rock fragments on soil infiltration, runoff and erosion under field conditions using simulated rainfall on bare areas of natural soils within typical Mediterranean scrubland characterized by patchily distributed vegetation. Sample areas were chosen where rock fragments cover more than half the surface within unvegetated patches. Twenty experiments were carried out by applying rain at an intensity of 55 mm h−1 for 60 minutes. This approach shows that rock fragments (i) retard ponding and surface runoff, and (ii) give greater steady‐state infiltration rates and smaller interrill runoff discharges, sediment concentrations and interrill erosion rates. A second set of six experiments was carried out by applying rainfall at an intensity of 55 mm h−1 for two runs of 60 minutes. The second run was initiated 10 minutes after the first. During this interval, surface rock fragments were removed in order to measure their effects on infiltration, interrill runoff and erosion rates. In this way, I showed that water and soil losses are reduced by the rock fragments. After the removal of rock fragments the steady‐state infiltration rate diminished from 44.5 to 27.5 mm h−1 and the runoff coefficient, sediment concentration and erosion rates were, respectively, 3, 33 and 39 times greater than they were before the rock fragments were removed.