Many gastrointestinal complaints and motility disorders are described in patients suffering from different eating disorders. These have a negative impact on refeeding. This report evaluated–on admission-gastric empty...Many gastrointestinal complaints and motility disorders are described in patients suffering from different eating disorders. These have a negative impact on refeeding. This report evaluated–on admission-gastric emptying of a standardized solid meal with 13C octanoic acid breath test in anorexic adolescents. The results were compared with age and gender matched controls. Gastric emptying data were related to a subjective symptom score. 21 Anorexic girls and 3 boys (mean age: 15.6 y ± 1.3 y), body mass index (mean 15.6 kg/m2 ± 1.6 kg/m2), weight loss (mean: 22.2% ± 10.7%) were studied. T? of the gastric emptying time exceeded the P95 in 14/24 (58%) patients, classified as having delayed gastric emptying (DGE). One patient (4%) had a T? exceeding P75 and was classified as slow (SGE), whereas 9/24 (38%) patients had normal gastric emptying (NGE). In comparison to NGE, subjects with DGE had significantly higher symptom scores (p = 0.01) and more weight loss. The DGE and SGE patients lost 25.29% and 21.38% of weight respectively, whereas a weight loss of 17.64% was found in anorexics with NGE. In conclusion, gastric emptying is delayed in patients with anorexia. This is associated with more significant gastrointestinal symptoms and higher weight loss.展开更多
Understanding the physiological adaptations of non-treeline trees to environmental stress is important to understand future shifts in species composition and distribution of current treeline ecotone.The aim of the pre...Understanding the physiological adaptations of non-treeline trees to environmental stress is important to understand future shifts in species composition and distribution of current treeline ecotone.The aim of the present study was to elucidate the mechanisms of the formation of the upper elevation limit of non-treeline tree species,Picea jezoensis,and the carbon allocation strategies of the species on Changbai Mountain.We employed the^(13)C in situ pulse labeling technique to trace the distribution of photosynthetically assimilated carbon in Picea jezoensis at different elevational positions(tree species at its upper elevation limit(TSAUE,1,700 m a.s.l.)under treeline ecotone;tree species at a lower elevation position(TSALE,1,400 m a.s.l.).We analyzed^(13)C and the non-structural carbohydrate(NSC)concentrations in various tissues following labeling.Our findings revealed a significant shift in carbon allocation in TSAUE compared to TSALE.There was a pronounced increase inδ^(13)C allocation to belowground components(roots,soil,soil respiration)in TSAUE compared to TSALE.Furthermore,the C flow rate within the plant-soil-atmosphere system was faster,and the C residence time in the plant was shorter in TSAUE.The trends indicate enhanced C sink activity in belowground tissues in TSAUE,with newly assimilated C being preferentially directed there,suggesting a more conservative C allocation strategy by P.jezoensis at higher elevations under harsher environments.Such a strategy,prioritizing C storage in roots,likely aids in withstanding winter cold stress at the expense of aboveground growth during the growing season,leading to reduced growth of TSAUE compared to TSALE.The results of the present study shed light on the adaptive mechanisms governing the upper elevation limits of non-treeline trees,and enhances our understanding of how non-treeline species might respond to ongoing climate change.展开更多
Fast pyrolysis of biomass will produce various furan derivatives, among which 5-hydroxymethyl furfural（5-HMF） and furfural（FF） are usually the two most important compounds derived from holocellulose. In this study...Fast pyrolysis of biomass will produce various furan derivatives, among which 5-hydroxymethyl furfural（5-HMF） and furfural（FF） are usually the two most important compounds derived from holocellulose. In this study, density functional theory（DFT） calculations are utilized to reveal the formation mechanisms and pathways of 5-HMF and FF from two hexose units of holocellulose, i.e., glucose and mannose. In addition, fast pyrolysis experiments of glucose and mannose are conducted to substantiate the computational results, and the orientation of 5-HMF and FF is determined by 13C-labeled glucoses. Experimental results indicate that C1 provides the aldehyde group in both 5-HMF and FF, and FF is mainly derived from C1 to C5 segment. According to the computational results, glucose and mannose have similar reaction pathways to form 5-HMF and FF with d-fructose（DF） and 3-deoxy-glucosone（3-DG） as the key intermediates. 5-HMF and FF are formed via competing pathways. The formation of 5-HMF is more competitive than that of FF, leading to higher yield of 5-HMF than FF from both hexoses. In addition, compared with glucose,mannose can form 5-HMF and FF via extra pathways because of the epimerization at C2 position. Therefore, mannose pyrolysis results in higher yields of 5-HMF and FF than glucose pyrolysis.展开更多
The priming effect is well acknowledged in soil systems but the effect of nitrogen(N)fertilization remains elusive.To explore how N modifies the priming effect in soil organic matter(SOM),one in situ experiment with 1...The priming effect is well acknowledged in soil systems but the effect of nitrogen(N)fertilization remains elusive.To explore how N modifies the priming effect in soil organic matter(SOM),one in situ experiment with 13C labeled glucose addition(0.4 mg C g^–1 soil,3.4 atom %^13C)was conducted on soil plots fertilized with three gradients of urea(0,4 and 16 g N m^–2 yr^–1).After glucose addition,the soil CO2 concentration and phospholipid fatty acid(PLFA)were measured on day 3,7,21 and 35.The study found that N fertilization decreased soil CO2,PLFA and the fungi to bacteria ratio.Glucose triggered the strongest positive priming in soil at 0 g N m^–2 yr^–2,meanwhile N fertilization decreased SOM-derived CO2.Soil at 4 g N m^–2 yr^–2 released the largest amount of glucose-derived carbon(C),likely due to favorable nutrient stoichiometry between C and N.Stable microbial community biomass and composition during early sampling suggests"apparent priming"in this grassland.This study concludes that N fertilization inhibited soil priming in semi-arid grassland,and shifted microbial utilization of C substrate from SOM to added labile C.Diverse microbial functions might be playing a crucial role in soil priming and requires attention in future N fertilization studies.展开更多
Aims Non-structural carbohydrates(NSCs)are plant storage compounds used for metabolism,transport,osmoregulation and regrowth following the loss of plant tissue.Even in conditions suitable for optimal growth,plants con...Aims Non-structural carbohydrates(NSCs)are plant storage compounds used for metabolism,transport,osmoregulation and regrowth following the loss of plant tissue.Even in conditions suitable for optimal growth,plants continue to store NSCs.This storage may be due to passive accumulation from sink-inhibited growth or active reserves that come at the expense of growth.The former pathway implies that NSCs may be a by-product of sink limitation,while the latter suggests a functional role of NSCs for use during poor conditions.Methods Using 13C pulse labelling,we traced the source of soluble sugars in stem and root organs during drought and everwet conditions for seedlings of two tropical tree species that differ in drought tolerance to estimate the relative allocation of NSCs stored prior to drought versus NSCs assimilated during drought.We monitored growth,stomatal conductance,stem water potential and NSC storage to assess a broad carbon response to drought.Important Findings We found that the drought-sensitive species had reduced growth,conserved NSC concentrations in leaf,stem and root organs and had a larger proportion of soluble sugars in stem and root organs that originated from pre-drought storage relative to seedlings in control conditions.In contrast,the drought-tolerant species maintained growth and stem and root NSC concentrations but had reduced leaf NSCs concentrations with a larger proportion of stem and root soluble sugars originated from freshly assimilated photosynthates relative to control seedlings.These results suggest the drought-sensitive species passively accumulated NSCs during water deficit due to growth inhibition,while the drought-tolerant species actively responded to water deficit by allocating NSCs to stem and root organs.These strategies seem correlated with baseline maximum growth rates,which supports previous research suggesting a trade-off between growth and drought tolerance while providing new evidence for the importance of plasticity in NSC allocation during drought.展开更多
Aims The ground level of boreal pine forests consists of a dense layer of eri-caceous shrubs,herbs,grasses,mosses and lichens.The primary prod-uctivity of this forest floor vegetation is notable but the role the most ...Aims The ground level of boreal pine forests consists of a dense layer of eri-caceous shrubs,herbs,grasses,mosses and lichens.The primary prod-uctivity of this forest floor vegetation is notable but the role the most common ericoid dwarf shrub plant species,Calluna vulgaris,Vaccinium myrtillus and Vaccinium vitis-idaea,play in carbon(C)cycling in these ecosystems is poorly understood.Here,we studied their C dynamics in detail using plants of similar size(age 14-19 months)in a microcosm study.Methods We determined the full C balances of these dwarf shrubs for the first time and compared them to those of Pinus sylvestris by using long-term biomass accumulation,^(13)C pulse labelling and CO_(2) ex-change measurements in a controlled laboratory experiment.Important Findings Pinus sylvestris had significantly higher biomass-based C fluxes than dwarf shrubs,both aboveground and belowground,but the dwarf shrubs did not differ in the biomass-based fluxes.We showed that root respiration of the evergreen ericoid dwarf shrubs was sensitive to the aboveground light conditions as belowground respiration was 50-70%higher under light compared with dark conditions.Such light-related dif-ferences were not observed for Scots pine.The observed differences in C dynamics are important in estimating the origin of belowground CO_(2) fluxes and in evaluating their biological relevance.Our results improve current understanding of CO_(2) sources and sinks in boreal ecosystems.展开更多
文摘Many gastrointestinal complaints and motility disorders are described in patients suffering from different eating disorders. These have a negative impact on refeeding. This report evaluated–on admission-gastric emptying of a standardized solid meal with 13C octanoic acid breath test in anorexic adolescents. The results were compared with age and gender matched controls. Gastric emptying data were related to a subjective symptom score. 21 Anorexic girls and 3 boys (mean age: 15.6 y ± 1.3 y), body mass index (mean 15.6 kg/m2 ± 1.6 kg/m2), weight loss (mean: 22.2% ± 10.7%) were studied. T? of the gastric emptying time exceeded the P95 in 14/24 (58%) patients, classified as having delayed gastric emptying (DGE). One patient (4%) had a T? exceeding P75 and was classified as slow (SGE), whereas 9/24 (38%) patients had normal gastric emptying (NGE). In comparison to NGE, subjects with DGE had significantly higher symptom scores (p = 0.01) and more weight loss. The DGE and SGE patients lost 25.29% and 21.38% of weight respectively, whereas a weight loss of 17.64% was found in anorexics with NGE. In conclusion, gastric emptying is delayed in patients with anorexia. This is associated with more significant gastrointestinal symptoms and higher weight loss.
基金supported by the National Natural Science Foundation of China(Grant numbers 4237105242271100+3 种基金4197112442371095)the Natural Science Foundation of Jilin Province,China(Nos.YDZJ202201ZYTS483YDZJ202201ZYTS470)。
文摘Understanding the physiological adaptations of non-treeline trees to environmental stress is important to understand future shifts in species composition and distribution of current treeline ecotone.The aim of the present study was to elucidate the mechanisms of the formation of the upper elevation limit of non-treeline tree species,Picea jezoensis,and the carbon allocation strategies of the species on Changbai Mountain.We employed the^(13)C in situ pulse labeling technique to trace the distribution of photosynthetically assimilated carbon in Picea jezoensis at different elevational positions(tree species at its upper elevation limit(TSAUE,1,700 m a.s.l.)under treeline ecotone;tree species at a lower elevation position(TSALE,1,400 m a.s.l.).We analyzed^(13)C and the non-structural carbohydrate(NSC)concentrations in various tissues following labeling.Our findings revealed a significant shift in carbon allocation in TSAUE compared to TSALE.There was a pronounced increase inδ^(13)C allocation to belowground components(roots,soil,soil respiration)in TSAUE compared to TSALE.Furthermore,the C flow rate within the plant-soil-atmosphere system was faster,and the C residence time in the plant was shorter in TSAUE.The trends indicate enhanced C sink activity in belowground tissues in TSAUE,with newly assimilated C being preferentially directed there,suggesting a more conservative C allocation strategy by P.jezoensis at higher elevations under harsher environments.Such a strategy,prioritizing C storage in roots,likely aids in withstanding winter cold stress at the expense of aboveground growth during the growing season,leading to reduced growth of TSAUE compared to TSALE.The results of the present study shed light on the adaptive mechanisms governing the upper elevation limits of non-treeline trees,and enhances our understanding of how non-treeline species might respond to ongoing climate change.
基金financial support from the National Natural Science Foundation of China (51576064, 51676193)Beijing Nova Program (Z171100001117064)+2 种基金Beijing Natural Science Foundation (3172030)the Foundation of Stake Key Laboratory of Coal Combustion (FSKLCCA1706)the Fundamental Research Funds for the Central Universities (2017MS071, 2016YQ05)
文摘Fast pyrolysis of biomass will produce various furan derivatives, among which 5-hydroxymethyl furfural（5-HMF） and furfural（FF） are usually the two most important compounds derived from holocellulose. In this study, density functional theory（DFT） calculations are utilized to reveal the formation mechanisms and pathways of 5-HMF and FF from two hexose units of holocellulose, i.e., glucose and mannose. In addition, fast pyrolysis experiments of glucose and mannose are conducted to substantiate the computational results, and the orientation of 5-HMF and FF is determined by 13C-labeled glucoses. Experimental results indicate that C1 provides the aldehyde group in both 5-HMF and FF, and FF is mainly derived from C1 to C5 segment. According to the computational results, glucose and mannose have similar reaction pathways to form 5-HMF and FF with d-fructose（DF） and 3-deoxy-glucosone（3-DG） as the key intermediates. 5-HMF and FF are formed via competing pathways. The formation of 5-HMF is more competitive than that of FF, leading to higher yield of 5-HMF than FF from both hexoses. In addition, compared with glucose,mannose can form 5-HMF and FF via extra pathways because of the epimerization at C2 position. Therefore, mannose pyrolysis results in higher yields of 5-HMF and FF than glucose pyrolysis.
基金National Natural Science Foundation of China(31770519)National Key Research and Development Program of China(2017YFC0503805)
文摘The priming effect is well acknowledged in soil systems but the effect of nitrogen(N)fertilization remains elusive.To explore how N modifies the priming effect in soil organic matter(SOM),one in situ experiment with 13C labeled glucose addition(0.4 mg C g^–1 soil,3.4 atom %^13C)was conducted on soil plots fertilized with three gradients of urea(0,4 and 16 g N m^–2 yr^–1).After glucose addition,the soil CO2 concentration and phospholipid fatty acid(PLFA)were measured on day 3,7,21 and 35.The study found that N fertilization decreased soil CO2,PLFA and the fungi to bacteria ratio.Glucose triggered the strongest positive priming in soil at 0 g N m^–2 yr^–2,meanwhile N fertilization decreased SOM-derived CO2.Soil at 4 g N m^–2 yr^–2 released the largest amount of glucose-derived carbon(C),likely due to favorable nutrient stoichiometry between C and N.Stable microbial community biomass and composition during early sampling suggests"apparent priming"in this grassland.This study concludes that N fertilization inhibited soil priming in semi-arid grassland,and shifted microbial utilization of C substrate from SOM to added labile C.Diverse microbial functions might be playing a crucial role in soil priming and requires attention in future N fertilization studies.
基金supported by the Universität Zürich MSc Ecology Program with additional support by the Universität Zürich Research Priority Program on Global Change and Biodiversity(URPP-GCB).M.O.B.was supported by the Atracción de Talento Investigador Modalidad I Fellowship from the Comunidad de Madrid(grant number 2018-T1/AMB-11095)during the preparation of the manuscript.
文摘Aims Non-structural carbohydrates(NSCs)are plant storage compounds used for metabolism,transport,osmoregulation and regrowth following the loss of plant tissue.Even in conditions suitable for optimal growth,plants continue to store NSCs.This storage may be due to passive accumulation from sink-inhibited growth or active reserves that come at the expense of growth.The former pathway implies that NSCs may be a by-product of sink limitation,while the latter suggests a functional role of NSCs for use during poor conditions.Methods Using 13C pulse labelling,we traced the source of soluble sugars in stem and root organs during drought and everwet conditions for seedlings of two tropical tree species that differ in drought tolerance to estimate the relative allocation of NSCs stored prior to drought versus NSCs assimilated during drought.We monitored growth,stomatal conductance,stem water potential and NSC storage to assess a broad carbon response to drought.Important Findings We found that the drought-sensitive species had reduced growth,conserved NSC concentrations in leaf,stem and root organs and had a larger proportion of soluble sugars in stem and root organs that originated from pre-drought storage relative to seedlings in control conditions.In contrast,the drought-tolerant species maintained growth and stem and root NSC concentrations but had reduced leaf NSCs concentrations with a larger proportion of stem and root soluble sugars originated from freshly assimilated photosynthates relative to control seedlings.These results suggest the drought-sensitive species passively accumulated NSCs during water deficit due to growth inhibition,while the drought-tolerant species actively responded to water deficit by allocating NSCs to stem and root organs.These strategies seem correlated with baseline maximum growth rates,which supports previous research suggesting a trade-off between growth and drought tolerance while providing new evidence for the importance of plasticity in NSC allocation during drought.
基金This work was supported by Academy of Finland(grant numbers 277623,263858,292699)by the Academy of Finland Centre of Excellence Program(grant number 272041).
文摘Aims The ground level of boreal pine forests consists of a dense layer of eri-caceous shrubs,herbs,grasses,mosses and lichens.The primary prod-uctivity of this forest floor vegetation is notable but the role the most common ericoid dwarf shrub plant species,Calluna vulgaris,Vaccinium myrtillus and Vaccinium vitis-idaea,play in carbon(C)cycling in these ecosystems is poorly understood.Here,we studied their C dynamics in detail using plants of similar size(age 14-19 months)in a microcosm study.Methods We determined the full C balances of these dwarf shrubs for the first time and compared them to those of Pinus sylvestris by using long-term biomass accumulation,^(13)C pulse labelling and CO_(2) ex-change measurements in a controlled laboratory experiment.Important Findings Pinus sylvestris had significantly higher biomass-based C fluxes than dwarf shrubs,both aboveground and belowground,but the dwarf shrubs did not differ in the biomass-based fluxes.We showed that root respiration of the evergreen ericoid dwarf shrubs was sensitive to the aboveground light conditions as belowground respiration was 50-70%higher under light compared with dark conditions.Such light-related dif-ferences were not observed for Scots pine.The observed differences in C dynamics are important in estimating the origin of belowground CO_(2) fluxes and in evaluating their biological relevance.Our results improve current understanding of CO_(2) sources and sinks in boreal ecosystems.
