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1.
Ylva Gårdinger Anna Dieden Joanna Hlebowicz Ola Björgell Magnus Dencker 《Cardiovascular ultrasound》2017,15(1):10
Background
Myocardial performance index (MPI) has been investigated in a variety of populations, but the effect of food intake has not been evaluated. We assessed whether myocardial performance index is affected by food intake in healthy subjects.Methods
Twenty-three healthy subjects aged 25.6?±?4.5 years were investigated. MPI was measured before, 30 min after, and 110 min after a standardized meal.Results
MPI decreased significantly (P?<?0.05) from fasting values 30 min after the meal, and had almost returned to baseline after 110 min. MPI decreased from 0.28?±?0.06 (fasting) to 0.20?±?0.07 30 min after eating. At 110 min after eating the index value was almost back to the baseline value 0.26?±?0.06. (P?=?0.15).Conclusions
This study shows that myocardial performance index is affected by food intake in healthy subjects.2.
Alfred Nimmerichter Johann Holdhaus Lars Mehnen Claudia Vidotto Markus Loidl Alan R. Barker 《International journal of biometeorology》2014,58(7):1503-1512
Limited research has suggested that acute exposure to negatively charged ions may enhance cardio-respiratory function, aerobic metabolism and recovery following exercise. To test the physiological effects of negatively charged air ions, 14 trained males (age: 32?±?7 years; \( \overset{\cdotp }{V}{\mathrm{O}}_{2 \max } \) : 57?±?7 mL min?1 kg?1) were exposed for 20 min to either a high-concentration of air ions (ION: 220?±?30?×?103 ions cm?3) or normal room conditions (PLA: 0.1?±?0.06?×?103 ions cm?3) in an ionization chamber in a double-blinded, randomized order, prior to performing: (1) a bout of severe-intensity cycling exercise for determining the time constant of the phase II \( \overset{\cdotp }{V}{\mathrm{O}}_2 \) response (τ) and the magnitude of the \( \overset{\cdotp }{V}{\mathrm{O}}_2 \) slow component (SC); and (2) a 30-s Wingate test that was preceded by three 30-s Wingate tests to measure plasma [adrenaline] (ADR), [nor-adrenaline] (N-ADR) and blood [lactate] (BLac) over 20 min during recovery in the ionization chamber. There was no difference between ION and PLA for the phase II \( \overset{\cdotp }{V}{\mathrm{O}}_2 \) τ (32?±?14 s vs. 32?±?14 s; P?=?0.7) or \( \overset{\cdotp }{V}{\mathrm{O}}_2 \) SC (404?±?214 mL vs 482?±?217 mL; P?=?0.17). No differences between ION and PLA were observed at any time-point for ADR, N-ADR and BLac as well as on peak and mean power output during the Wingate tests (all P?>?0.05). A high-concentration of negatively charged air ions had no effect on aerobic metabolism during severe-intensity exercise or on performance or the recovery of the adrenergic and metabolic responses after repeated-sprint exercise in trained athletes. 相似文献
3.
M. Remmelink K. D. Sjauw Z. Y. Yong J. D. E. Haeck M. M. Vis K. T. Koch J. G. P. Tijssen R. J. de Winter J. P. S. Henriques J. J. Piek J. Baan Jr. 《Netherlands heart journal》2013,21(5):238-244
Background
Coronary microvascular resistance is increased after primary percutaneous coronary intervention (PCI) for ST-elevation myocardial infarction (STEMI), which may be related in part to changed left ventricular (LV) dynamics. Therefore we studied the coronary microcirculation in relation to systolic and diastolic LV function after STEMI.Methods
The study cohort consisted of 12 consecutive patients, all treated with primary PCI for a first anterior wall STEMI. At 4 months, we assessed pressure-volume loops. Subsequently, we measured intracoronary pressure and flow velocity and calculated coronary microvascular resistance. Infarct size and LV mass were assessed using magnetic resonance imaging.Results
Patients with an impaired systolic LV function due to a larger myocardial infarction showed a higher baseline average peak flow velocity (APV) than the other patients (26?±?7 versus 17?±?5 cm/s, p?=?0.003, respectively), and showed an impaired variable microvascular resistance index (2.1?±?1.0 versus 4.1?±?1.3 mmHg?cm?1?s?1, p?=?0.003, respectively). Impaired diastolic relaxation time was inversely correlated with hyperaemic APV (r?=??0.56, p?=?0.003) and positively correlated with hyperaemic microvascular resistance (r?=?0.48, p?=?0.01). LV dilatation was associated with a reduced variable microvascular resistance index (r?=?0.78, p?=?0.006).Conclusion
A larger anterior myocardial infarction results in impaired LV performance associated with reduced coronary microvascular resistance variability, in particular due to higher coronary blood flow at baseline in these compromised left ventricles. 相似文献4.
Objective
Closure of atrial septal defects (ASD) prevents pulmonary hypertension, right heart failure and thromboembolic stroke. The exact timing for ASD closure is controversial.Methods
In a prospective study to address the question whether unapparent pulmonary hypertension can be revealed prior to right ventricular (RV) remodelling, patients were investigated before and 6, 12, and 24 months after ASD closure using exercise stress echocardiography (ESE) and ergospirometry (n?=?24).Results
At rest, RV systolic pressure (RVSP) was normal in 58.8 %, slightly elevated in 26.5 %, and moderately elevated in 11.8 %. One patient showed severe pulmonary hypertension. During ESE, all patients with normal RVSP at rest exhibited an increase (25.7?±?1.2 mmHg vs. 45.3?±?2.3 mmHg, p?<?0.001). After closure the RVSP was lower, both at rest and ESE. RV diameters decreased too. Tricuspid annulus plane systolic excursion (TAPSE) at rest remained lower after closure (24.0?±?0.9 vs. 22.0?±?0.9 mm, p?<?0.05). TAPSE in ESE was elevated, and stayed stable after closure (30.1?±?1.8 mm vs. 29.3?±?1.6 mm). Before closure, RV systolic tissue velocities (sa) at rest were normal and decreased after closure (14.0?±?1.0 cm/s vs. 11.5?±?0.7 (6 month) vs. 10.6?±?0.5 cm/s (12 month), p?<?0.05). During ESE, sa velocity was similar before and after closure (23.0?±?1.3 cm/s vs. 23.3?±?1.9 cm/s). Maximal oxygen uptake (VO2/kg) did not differ between baseline and follow-ups.Conclusion
Latent pulmonary hypertension may become apparent in ESE. ASD closure leads to a significant reduction in this stress-induced pulmonary hypertension and to a decrease in the right heart diameters indicating reverse RV remodelling. RV functional parameters at rest did not improve. The VO2/kg did not change after ASD closure. 相似文献5.
Patrizia Aruta Denisa Muraru Andrada Camelia Guta Sorina Mihaila Niccolò Ruozi Chiara Palermo Basma Elnagar Sabino Iliceto Luigi P. Badano 《Cardiovascular ultrasound》2018,16(1):27
Background
Transcatheter mitral valve replacement (TMVR) is a new therapeutic option for high surgical risk patients with mitral regurgitation (MR). Mitral valve (MV) geometry quantification is of paramount importance for success of the procedure and transthoracic 3D echocardiography represents a useful screening tool. Accordingly, we sought to asses MV geometry in patients with functional MR (FMR) that would potentially benefit of TMVR, focusing on the comparison of mitral annulus (MA) geometry between patients with ischemic (IMR) and non ischemic mitral regurgitation (nIMR).Methods
We retrospectively selected 94 patients with severe FMR: 41 (43,6%) with IMR and 53 (56,4%) with nIMR. 3D MA analysis was performed on dedicated transthoracic 3D data sets using a new, commercially-available software package in two moments of the cardiac cycle (early-diastole and mid-systole). We measured MA dimension and geometry parameters, left atrial and left ventricular volumes.Results
Maximum (MA area 10.7?±?2.5 cm2 vs 11.6?±?2.7 cm2, p?>?0.05) and the best fit plane MA area (9.9?±?2.3 cm2 vs 10.7?±?2.5 cm2, p?>?0.05, respectively) were similar between IMR and nIMR. nIMR patients showed larger mid-systolic 3D area (9.8?±?2.3 cm2 vs 10.8?±?2.7 cm2, p?<?0.05) and perimeter (11.2?±?1.3 cm vs 11.8?±?1.5 cm, p?<?0.05) with longer and larger leaflets, and wider aorto-mitral angle (135?±?10° vs 141?±?11°, p?<?0.05). Conversely, the area of MA at the best fit plane did not differ between IMR and nIMR patients (9?±?1.1 cm2 vs 9.9?±?1.5 cm2, p?>?0.05).Conclusions
Patients with ischemic and non-ischemic etiology of FMR have similar maximum dimension, yet systolic differences between the two groups should be taken into account to tailor prosthesis’s selection.Trial registration
N.A.6.
M. Voskuil W. L. Verloop P. J. Blankestijn P. Agostoni P. R. Stella P. A. Doevendans 《Netherlands heart journal》2011,19(7-8):319-323
Background
In a subpopulation of patients with essential hypertension, therapeutic targets are not met, despite the use of multiple types of medication. In this paper we describe our first experience with a novel percutaneous treatment modality using renal artery radiofrequency (RF) ablation.Methods
Patients who were resistant to at least three types of antihypertensive medical therapy (office systolic blood pressure?≥?160 mmHg; n?=?9) or who did not tolerate medication (n?=?2) were selected. Between July and November 2010, a total of 11 patients received percutaneous RF treatment. Patients were followed up for 1 month after treatment. Urine and blood samples were taken to evaluate the effects on renal function and neurohumeral factors.Results
No periprocedural complications or adverse events during follow-up were noted. A reduction of mean office blood pressure was seen from 203/109?±?32/19 mmHg at baseline to 178/97?±?28/21 mmHg at 1 month follow-up (mean difference 25?±?12 mmHg, p?<?0.01). Also, we noted a significant decrease in aldosterone level (391?±?210 pmol/L versus 250?±?142 pmol/L; p?=?0.03), while there was no decrease in plasma renin activity (190?±?134 fmol/L/s versus 195?±?163 fmol/L/s; p?=?0.43). No change in renal function was noted.Conclusion
Catheter-based renal denervation seems an attractive novel minimally invasive treatment option in patients with resistant hypertension, with a low risk of serious adverse events. 相似文献7.
Comparing soil carbon sequestration in coastal freshwater wetlands with various geomorphic features and plant communities in Veracruz,Mexico 总被引:1,自引:0,他引:1
José Luis Marín-Muñiz María E. Hernández Patricia Moreno-Casasola 《Plant and Soil》2014,378(1-2):189-203
Background and aims
Wetlands are important carbon sinks across the planet. However, soil carbon sequestration in tropical freshwater wetlands has been studied less than its counterpart in temperate wetlands. We compared carbon stocks and carbon sequestration in freshwater wetlands with various geomorphic features (estuarine, perilacustrine and depressional) and various plant communities (marshes and swamps) on the tropical coastal plain of the Gulf of Mexico in the state of Veracruz, Mexico. These swamps are dominated by Ficus insipida, Pachira aquatic and Annona glabra and the marshes by Typha domingensis, Thalia geniculata, Cyperus giganteus, and Pontederia sagittata.Methods
The soil carbon concentration and bulk density were measured every 2 cm along 80 cm soil profiles in five swamps and five marshes. Short-term sediment accretion rates were measured during a year using horizontal makers in three of the five swamps and marshes, the carbon sequestration was calculated using the accretion rates, and the bulk density and the percentage of organic carbon in the surficial layer was measured.Results
The average carbon concentration ranged from 50 to 150 gC kg?1 in the marshes and 50 to 225 gC kg?1 in the swamps. When the wetlands were grouped according to their geomorphic features, no significant differences in the carbon stock (P?=?0.095) were found (estuarine (25.50?±?2.26 kgC m?2), perilacustrine (28.33?±?2.74 kgC m?2) and depressional wetlands (34.93?±?4.56 kgC m?2)). However, the carbon stock was significantly higher (P?=?0.030) in the swamps (34.96?±?1.3 kgC m?2) than in the marshes (25.85?±?1.19 kgC m?2). The average sediment accretion rates were 1.55?±?0.09 cm yr?1 in the swamps and 0.84?±?0.02 cm yr?1 in the marshes with significant differences (P?=?0.040). The rate of carbon sequestration was higher (P?=?0.001) in swamp soils (0.92?±?0.12 kgC m?2 yr?1) than marsh soils (0.31?±?0.08 kgC m?2 yr?1). Differences in the rates of carbon sequestration associated with geomorphic features were found between the swamp ecosystems (P?<?0.05); i.e., higher values were found in the swamps than in the marshes in perilacustrine and estuarine wetlands (P?<?0.05). However, no significant differences (P?=?0.324) in carbon sequestration rates were found between the marsh and swamp areas of the depressional site.Conclusions
Swamp soils are more important contributors to the carbon stock and sequestration than are marsh soils, resulting in a reduction in global warming, which suggests that the plant community is an important factor that needs to be considered in global carbon budgets and projects of restoration and conservation of wetlands. 相似文献8.
Nitrous oxide emissions and nitrate leaching from a rain-fed wheat-maize rotation in the Sichuan Basin, China 总被引:3,自引:0,他引:3
Minghua Zhou Bo Zhu Klaus Butterbach-Bahl Xunhua Zheng Tao Wang Yanqiang Wang 《Plant and Soil》2013,362(1-2):149-159
Aims
A 3-year field experiment (October 2004–October 2007) was conducted to quantify N2O fluxes and determine the regulating factors from rain-fed, N fertilized wheat-maize rotation in the Sichuan Basin, China.Methods
Static chamber-GC techniques were used to measure soil N2O fluxes in three treatments (three replicates per treatment): CK (no fertilizer); N150 (300 kg N fertilizer ha?1 yr?1 or 150 kg N?ha?1 per crop); N250 (500 kg N fertilizer ha?1 yr?1 kg or 250 kg N?ha?1 per crop). Nitrate (NO 3 ? ) leaching losses were measured at nearby sites using free-drained lysimeters.Results
The annual N2O fluxes from the N fertilized treatments were in the range of 1.9 to 6.7 kg N?ha?1 yr?1 corresponding to an N2O emission factor ranging from 0.12 % to 1.06 % (mean value: 0.61 %). The relationship between monthly soil N2O fluxes and NO 3 - leaching losses can be described by a significant exponential decaying function.Conclusions
The N2O emission factor obtained in our study was somewhat lower than the current IPCC default emission factor (1 %). Nitrate leaching, through removal of topsoil NO 3 ? , is an underrated regulating factor of soil N2O fluxes from cropland, especially in the regions where high NO 3 - leaching losses occur. 相似文献9.
Background and aims
Rhizosphere effect is controlled by spatial distribution of rhizodeposits, which may be influenced by soil aggregation and soil moisture regime in relation to water uptake by roots. The objectives of this study were to measure soil organic carbon (SOC) concentration and its δ13C abundance by aggregate size in the rooted bulk soil and by distance in the root-free soil vertically and horizontally away from roots, and to measure DOC concentration and its δ13C abundance in pore water in the rooted bulk soil after a seasonal pulse labelings of 13CO2 to maize (Zea mays L.).Methods
Pulse labeling was conducted in the field once a week for 11 weeks. Soil cells (50 mm in diameter and 100 mm long) mimicking root-free soils were imbedded vertically and horizontally 25–50 mm away from the main root of a maize crop. The rooted bulk soils were sampled to extract soil pore water at different suctions and to fractionate aggregates by wet sieving. The root-free soil cells were sliced by 1 mm intervals from the root end to 20 mm away. All the sampling was 12 days after the last labeling after the crop was harvested.Results and discussion
The δ13C abundance before and after the continuous labeling was ?24.20?±?0.05?‰ and ?23.80?±?0.05?‰ in the rooted bulk soil. The labeling caused increases in δ13C abundance in all the aggregates in the rooted bulk soil and down to 14 mm away from the roots in both the root-free cells. The δ13C abundance was enriched in the >2 mm and 1–2 mm aggregates (?23.17?±?0.12?‰ and ?23.26?±?0.05?‰) though the SOC concentration was not different among the >0.25 mm aggregates, indicating that rhizodeposits or their metabolites were protected and distributed widely in whole soil through soil aggregation. The δ13C abundance in pore water (?24.0?±?0.01?‰) was much lower than those soil aggregates and greatest from the >2 μm soil pores though the DOC concentration was greater from the <20 μm soil pores. The δ13C abundance was in general greater in the horizontal cell than in the vertical cell. The δ13C abundance decreased with the increasing distance to the roots in the vertical cell and peaked at the 5 and 6 mm distance to the roots in the horizontal cell (?23.66?±?0.11?‰ and ?23.5?±?0.10?‰), possibly due to the drier condition unfavorable to microbial decomposition in the horizontal cell. The higher δ13C abundance in the horizontal cell than in the vertical cell was accompanied by a lower SOC concentration and a lower C: N ratio within 3 mm away from the roots, suggesting a stronger priming effect due to the longer residence time of rhizodeposits in the horizontal cell than in the vertical cell.Conclusions
Rhizodeposits or their metabolites were protected during soil aggregation and distributed to 14 mm beyond the rhizosphere in the natural soil-plant system. This extension is of significance in regulating the formation of soil structure and the priming of soil organic matter during the whole life cycle of plants, which needs further study. 相似文献10.
Nicoline Jochmann Franziska Schröter Fabian Knebel Robert Hättasch Christine Gericke Karl Stangl Gert Baumann Verena Stangl 《Cardiovascular ultrasound》2014,12(1):1-6
Background
Experimental data suggests that exclusive heart rate reduction with ivabradine is associated with the amelioration of the endothelial function. Since it is presently unknown whether this also applies to humans, the aim of this pilot study was to investigate whether heart rate reduction with ivabradine modulates the endothelial function in humans with an established coronary heart disease.Methods
Using high-sensitivity ultrasound, we analysed the flow-mediated (FMD) and nitro-mediated dilation (NMD) of the brachial artery in 25 patients (62.9?±?8.4 years) with a stable coronary heart disease and a resting heart rate of ≥70 beats per minute (bpm). To assess acute effects, measurements were performed before and 4 hours after the first intake of ivabradine 7.5 mg. Sustained effects of an ivabradine therapy (5 mg to 7.5 mg twice daily) were investigated after 4 weeks.Results
We found a significant decrease in heart rate, both 4 hours after the intake of 7.5 mg of ivabradine (median -8 [interquartile range (IQR) -14 to -4] bpm) and after 4 weeks of twice daily intake (median -10 [IQR-17 to -5] bpm) (p?<?0.05). However, the FMD did not change significantly: neither after first dose of ivabradine nor after sustained therapy (baseline FMD: median 5.0 [IQR 2.4 to 7.9]%; FMD 4 hours after 7.5 mg of ivabradine: median 4.9 [IQR 2.7 to 9.8]%; FMD after 4 weeks of ivabradine therapy: median 6.1 [IQR 4.3 to 8.2]%). No significant changes of the NMD were observed. In regression analysis, the heart rate and FMD did not correlated, irrespective of the ivabradine intake (r2?=?0.086).Conclusion
In conclusion, in our study heart rate reduction through ivabradine does not improve the endothelial function in patients with a stable coronary heart disease. Moreover, we found no correlation between the heart rate and the endothelial function. 相似文献11.
Background and aims
Dominance of C4 grasses has been proposed as a means of increasing soil organic carbon (SOC) sequestration in restored tallgrass prairies. However, this hypothesis has not been tested on long time scales and under realistic (e.g. N-limited) environmental conditions. We sampled a restoration in southern Illinois 33 years after establishment to determine the effects of varying plant communities on SOC sequestration in the top 50 cm of soil.Methods
SOC, total nitrogen (TN), and the stable isotopic composition of SOC (δ13C) were used to calculate SOC sequestration rates, N storage, and the relative contributions of C3 vs. C4 plant communities as a function of soil depth.Results
While both a forb-dominated and a mixed forb-grass plant community showed positive sequestration rates (0.56?±?0.13 and 0.27?±?0.10 Mg C ha?1 yr?1, respectively), a C4 grass-dominated community showed SOC losses after 33 years of restoration (?0.31?±?0.08 Mg C ha?1 yr?1). Soil δ13C values were significantly more negative for forb-dominated plant communities, increasing the confidence that plant communities were stable over time and an important contributor to differences in SOC stocks among transects.Conclusion
These results suggest that functional diversity may be necessary to sustain sequestration rates on the scale of decades, and that dominance of C4 grasses, favored by frequent burning, may lead to SOC losses over time. 相似文献12.
Aims
This study aimed to measure the effect of plant diversity on N uptake in grasslands and to assess the mechanisms contributing to diversity effects.Methods
Annual N uptake into above- and belowground organs and soil nitrate pools were measured in the Jena experiment on a floodplain soil with mixtures of 2–16 species and 1–4 functional groups, and monocultures. In mixtures, the deviation of measured data from data expected from monoculture performance was calculated to assess the contribution of complementarity/facilitation and selection.Results
N uptake varied from <1 to 45 g?N m?2 yr?1, and was higher in grasslands with than without legumes. On average, N uptake was higher in mixtures (21?±?1 g?N m?2 yr?1) than monocultures (13?±?1 g?N m?2 yr?1), and increased with species richness in mixtures. However, compared to N uptake expected from biomass proportions of species in mixtures, N uptake of mixtures was only slightly higher and a significant surplus N uptake was confined to mixtures containing legumes and non-legumes.Conclusions
In our study, high N uptake of species rich mixtures was mainly due to dominance of productive species and facilitation by legumes whereas complementarity among non-legumes was of minor relevance. 相似文献13.
Inheritance pattern of wood traits viz. specific gravity, fibre dimensions and fibre-derived biometrical indices and their interactions among themselves and with that of growth are reported in Hevea brasiliensis. Girth (h2 =???0.02?±?0.44 to h2 =?0.35?±?0.24) showed moderate genetic control. Among wood traits, specific gravity (h2?=?0.15?±?0.31 to h2 =?0.33?±?0.28) was found to be under moderate genetic control. Fibre traits viz., fibre length (h2 =???0.26?±?0.30 to h2 =?0.50?±?0.34), fibre diameter (h2 =?0.19?±?0.49 to h2 =?0.70?±?0.11), fibre lumen diameter (h2 =???0.18?±?0.35 to h2 =?0.56?±?0.47) and fibre wall thickness (h2 =???5.17?±?5.26 to h2 =?0.50?±?0.50) were under moderate to strong genetic control. Among fibre-derived indices, flexibility coefficient (h2 =?0.48?±?0.21 to h2 =?0.89?±?0.29) showed moderate to very strong genetic control. The Runkel ratio (h2 =???0.40?±?0.27 to h2 =?0.42?±?0.29) and slenderness ratio (h2 =???0.36?±?0.29 to h2 =?0.43?±?0.28) showed moderate genetic control. Girth showed very strong positive genetic correlation with fibre wall thickness and strong positive correlation with fibre width indicating scope of indirect selection potential for these traits. Wood specific gravity was not correlated with either girth or fibre traits. Hence, it would be possible to concomitantly improve growth and fibre traits without adversely affecting wood specific gravity. Moderate to very high estimates of heritability for fibre traits, girth and specific gravity indicated that considerable genetic gain can be realised for these traits. Implications of the above findings in genetic improvement of wood in Hevea are discussed. 相似文献
14.
Background and aims
The roots of tussock-forming plants contribute to the formation of microtopographic features in many ecosystems, but the dynamics of such roots are poorly understood. We examined the spatial heterogeneity of tussock fine root dynamics to investigate allocation patterns and the role of root productivity in the persistence of tussock structures.Methods
We compared the spatial variability of fine root (<1 mm, 1–2 mm) density, biomass, % live, allocation, turnover rate (using bomb 14C), and productivity of four Carex stricta Lam.-dominated tussock meadows in the upper Midwest, USA (3 reference, 1 restored site).Results
Relative to underlying microsites, tussocks were warm, dry, and high in root density, productivity, % live biomass, and turnover. Root productivity averaged 649 g?m?2 yr?1 (±208) in reference sites, comprised 57 % (±10) of total net production, and was concentrated in tussocks (70 %?±?4). Root turnover rate averaged 0.63 yr?1 (±0.08), but tussocks had ~50 % faster root turnover than the underlying soil, and <1 mm roots turned over ~40 % faster than 1–2 mm roots.Conclusions
Our detailed analysis of the spatial heterogeneity of tussock root dynamics suggests that high allocation and elevated turnover of tussock roots facilitates organic matter accumulation and tussock persistence over time. 相似文献15.
Plant and soil responses of an alpine steppe on the Tibetan Plateau to multi-level nitrogen addition 总被引:2,自引:0,他引:2
Yongwen Liu Xu-Ri Xingliang Xu Da Wei Yinghong Wang Yuesi Wang 《Plant and Soil》2013,369(1-2):515-529
Background
Although plant growth in alpine steppes on the Tibetan Plateau has been suggested to be sensitive to nitrogen (N) addition, the N limitation conditions of alpine steppes remain uncertain.Methods
After 2 years of fertilization with NH4NO3 at six rates (0, 10, 20, 40, 80 and 160 kg N ha?1 yr?1), the responses of plant and soil parameters as well as N2O fluxes were measured.Results
At the vegetation level, N addition resulted in an increase in the aboveground N pool from 0.5?±?0.1 g m?2 in the control plots to 1.9?±?0.2 g m?2 in the plots at the highest N input rate. The aboveground C pool, biomass N concentration, foliar δ15N, soil NO3 ?-N and N2O flux were also increased by N addition. However, as the N fertilization rate increased from 10 kg N ha?1 yr?1 to 160 kg N ha?1 yr?1, the N-use efficiency decreased from 12.3?±?4.6 kg C kg N?1 to 1.6?±?0.2 kg C kg N?1, and the N-uptake efficiency decreased from 43.2?±?9.7 % to 9.1?±?1.1 %. Biomass N:P ratios increased from 14.4?±?2.6 in the control plots to 20.5?±?0.8 in the plots with the highest N input rate. Biomass N:P ratios, N-uptake efficiency and N-use efficiency flattened out at 40 kg N ha?1 yr?1. Above this level, soil NO3 ?-N began to accumulate. The seasonal average N2O flux of growing season nonlinearly increased with increased N fertilization rate and linearly increased with the weighted average foliar δ15N. At the species level, N uptake responses to relative N availability were species-specific. Biomass N concentration of seven out of the eight non-legume species increased significantly with N fertilization rates, while Kobresia macrantha and the one legume species (Oxytropics glacialis) remained stable. Both the non-legume and the legume species showed significant 15N enrichment with increasing N fertilization rate. All non-legume species showed significant increased N:P ratios with increased N fertilization rate, but not the legume species.Conclusions
Our findings suggest that the Tibetan alpine steppes might be N-saturated above a critical N load of 40 kg N ha?1 yr?1. For the entire Tibetan Plateau (ca. 2.57 million km2), a low N deposition rate (10 kg N ha?1 yr?1) could enhance plant growth, and stimulate aboveground N and C storage by at least 1.1?±?0.3 Tg N yr?1 and 31.5?±?11.8 Tg C yr?1, respectively. The non-legume species was N-limited, but the legume species was not limited by N. 相似文献16.
F. Pax C. Blamey J. Bernhard Wehr Peng Wang Neal W. Menzies Peter M. Kopittke 《Plant and Soil》2014,379(1-2):301-314
Background and aims
Close regulation of cellular Ca in roots is required in the face of marked changes in soil solution Ca over time and space. This study’s aims were to quantify and gain insights into the ways in which roots respond to changes in solution Ca.Methods
Root elongation rate (RER) of cowpea (Vigna unguiculata (L.) Walp.) seedlings was determined at 0.05 to 15 mM Ca for up to 24 h both without and with added K, Mg, or Na. Root tip concentrations of Ca, K, Mg, and Na were determined and binding of cations by root tips estimated by subsequent Cu sorption.Results
Transfer from higher to lower Ca solutions (and with added K at high Ca) resulted in RER?≥?2 mm h?1 within minutes. This was attributed to greater cell wall relaxation through lower Ca binding aided by a decrease to pH?≤?5.1 in solution. Transfer to higher Ca solutions, which remained at ~pH 5.6, led to an equally rapid decrease in RER to ~0.5 mm h?1, an effect ascribed to greater cell wall binding of Ca. Thereafter, a gradual increase in RER to ~1.8 mm h?1 occurred over 24 h, an effect likely due to reduced cell wall Ca binding as shown by decreasing Cu sorption at a rate of 0.027 mmol Cu kg?1 FM h?1 over 24 h.Conclusion
The kinetics of changes in RER and cations in root tips suggest that roots respond to changes in solution Ca through effects on cell wall relaxation of the rhizodermis and outer cortex in the elongation zone. 相似文献17.
Annual nitrous oxide emissions from open-air and greenhouse vegetable cropping systems in China 总被引:5,自引:0,他引:5
Aims
A field experiment was conducted to quantify annual nitrous oxide (N2O) fluxes from control and fertilized plots under open-air and greenhouse vegetable cropping systems in southeast China. We compiled the reported global field annual N2O flux measurements to estimate the emission factor of N fertilizer for N2O and its background emissions from vegetable fields.Methods
Fluxes of N2O were measured using static chamber-GC techniques over the 2010–2011 annual cycle with multiple cropping seasons.Results
The mean annual N2O fluxes from the controls were 46.1?±?2.3 μg N2O-N m?2 hr?1 and 68.3?±?4.1 μg N2O-N m?2 hr?1 in the open-air and greenhouse vegetable systems, respectively. For the plots receiving 900 kg?N?ha?1, annual N2O emissions averaged 90.6?±?8.9 μg N2O-N m?2 hr?1 and 106.4?±?6.6 μg N2O-N?m?2 hr?1 in the open-air and greenhouse vegetable systems, respectively. By pooling published field N2O flux measurements taken over or close to a full year, the N2O emission factor for N fertilizer averaged 0.63?±?0.09 %, with a background emission of 2.67?±?0.80 kg N2O-N ha?1 in Chinese vegetable fields. Annual N2O emissions from Chinese vegetable systems were estimated to be 84.7 Gg N2O-N yr?1, consisting of 72.5 Gg N2O-N yr?1 and 12.2 Gg N2O-N yr?1 in the open-air and greenhouse vegetable systems, respectively.Conclusions
While N2O emissions from the greenhouse vegetable cropping system tended to be slightly higher compared to the open-air system in our experiment, the synthesis of literature data suggests that N2O emissions would be greater at low N-rates but smaller at high N-rates in greenhouse systems than in open-air vegetable cropping systems. The estimates of this study suggest that vegetable cropping systems covering 11.4 % in national total cropping area, contributed 21–25 % to the total N2O emission from Chinese croplands. 相似文献18.
Mehri Jamilian Shahrzad Zadeh Modarres Mehrnush Amiri Siavashani Maryam Karimi Alireza Mafi Vahidreza Ostadmohammadi Zatollah Asemi 《Biological trace element research》2018,185(1):48-55
This study was carried out to investigate the effects of chromium intake on glycemic control, markers of cardio-metabolic risk, and oxidative stress in infertile polycystic ovary syndrome (PCOS) women candidate for in vitro fertilization (IVF). This randomized double-blind, placebo-controlled trial was done among 40 subjects with infertile PCOS candidate for IVF, aged 18–40 years old. Individuals were randomly allocated into two groups to take either 200 μg/day of chromium (n?=?20) or placebo (n?=?20) for 8 weeks. Biochemical parameters were assessed at baseline and at end-of-trial. Compared with the placebo, taking chromium supplements led to significant reductions in fasting plasma glucose (??2.3?±?5.7 vs. +?0.9?±?3.1 mg/dL, P?=?0.03), insulin levels (??1.4?±?2.1 vs. +?0.4?±?1.7 μIU/mL, P?=?0.004), homeostatic model of assessment for insulin resistance (??0.3?±?0.5 vs. +?0.1?±?0.4, P?=?0.005), and a significant increase in quantitative insulin sensitivity check index (+?0.004?±?0.008 vs. ??0.001?±?0.008, P?=?0.03). In addition, chromium supplementation significantly decreased serum triglycerides (??19.2?±?33.8 vs. +?8.3?±?21.7 mg/dL, P?=?0.004), VLDL- (??3.8?±?6.8 vs. +?1.7?±?4.3 mg/dL, P?=?0.004) and total cholesterol concentrations (??15.3?±?26.2 vs. ??0.6?±?15.9 mg/dL, P?=?0.03) compared with the placebo. Additionally, taking chromium supplements was associated with a significant increase in plasma total antioxidant capacity (+?153.9?±?46.1 vs. ??7.8?±?43.9 mmol/L, P?<?0.001) and a significant reduction in malondialdehyde values (?0.3?±?0.3 vs. +?0.1?±?0.2 μmol/L, P?=?0.001) compared with the placebo. Overall, our study supported that chromium administration for 8 weeks to infertile PCOS women candidate for IVF had beneficial impacts on glycemic control, few variables of cardio-metabolic risk, and oxidative stress. 相似文献
19.
Xinyi Gao Meera Gujjar Patel Pooja Bakshi Dipali Sharma Ajay K. Banga 《AAPS PharmSciTech》2018,19(8):3501-3511
Honokiol is a natural phenolic anti-cancer compound isolated from an extract of seed cones from Magnolia grandiflora. This study investigated the transdermal delivery of honokiol using various enhancement methods and to explore the potential of honokiol to treat breast cancer directly via delivery through mammary papilla. Poration of dermatomed human skin with microneedles significantly increased the delivery of honokiol by nearly 3-fold (97.81?±?18.96 μg/cm2) compared with passive delivery (32.56?±?5.67 μg/cm2). Oleic acid was found to be the best chemical penetration enhancer, increasing the delivery almost 27-fold (868.06?±?100.91 μg/cm2). Addition of oleic acid also resulted in better retention of drug in the porcine mammary papilla (965.41?±?80.26 μg/cm2) compared with breast skin (294.16?±?8.49 μg/cm2). Anti-cancer effect of honokiol was demonstrated with the decrease in the release of cytokine IL-6 and further suppression of Ki-67 proliferative protein. In addition, the topical honokiol formulation investigated was found to be safe and non-irritant. In summary, both microneedles and chemical enhancers can improve the absorption of honokiol through skin. Directly applying honokiol on mammary papilla is a potential administration route which can increase localized delivery into breast tissue. 相似文献
20.
Saoirse R. Tracy Colin R. Black Jeremy A. Roberts Ann McNeill Rob Davidson Mark Tester Marko Samec Dean Koro?ak Craig Sturrock Sacha J. Mooney 《Plant and Soil》2012,353(1-2):195-208