The emergence of the tracheophyte-based vascular system of land plants had major impacts on the evolution of terrestrial biology, in general, through its role in facilitating the development of plants with increased s...The emergence of the tracheophyte-based vascular system of land plants had major impacts on the evolution of terrestrial biology, in general, through its role in facilitating the development of plants with increased stature, photosynthetic output, and ability to colonize a greatly expanded range of environmental habitats. Recently, considerable progress has been made in terms of our understanding of the developmental and physiological programs involved in the formation and function of the plant vascular system. In this review, we first examine the evolutionary events that gave rise to the tracheophytes, followed by analysis of the genetic and hormonal networks that cooperate to orchestrate vascular development in the gymnosperms and angiosperms. The two essentialfunctions performed by the vascular system, namely the delivery of resources （water, essential mineral nutrients, sugars and amino acids） to the various plant organs and provision of mechanical support are next discussed. Here, we focus on critical questions relating to structural and physiological properties controlling the delivery of material through the xylem and phloem. Recent discoveries into the role of the vascular system as an effective long-distance communication system are next assessed in terms of the coordination of developmental, physiological and defense-related processes, at the whole-plant level. A concerted effort has been made to integrate all these new findings into a comprehensive picture of the state-of-the-art in the area of plant vascular biology. Finally, areas important for future research are highlighted in terms of their likely contribution both to basic knowledge and applications to primary industry.展开更多
Background Diabetes mellitus is associated with coronary dysfunction, contributing to a 2- to 4-fold increase in the risk of coronary heart diseases. The mechanisms by which diabetes induces vasculopathy involve endot...Background Diabetes mellitus is associated with coronary dysfunction, contributing to a 2- to 4-fold increase in the risk of coronary heart diseases. The mechanisms by which diabetes induces vasculopathy involve endothelial-dependent and -independent vascular dysfunction in both type 1 and type 2 diabetes mellitus. The purpose of this study is to determine the role of vascular large conductance Ca2＋-activated K＋ （BK） channel activities in coronary dysfunction in streptozotocin-induced diabetic rats. Methods Using videomicroscopy, immunoblotting, fluorescent assay and patch clamp techniques, we investigated the coronary BK channel activities and BK channel-mediated coronary vasoreactivity in streptozotocin-induced diabetic rats. Results BK currents （defined as the iberiotoxin-sensitive K＋ component） contribute （65＋4）% of the total K＋currents in freshly isolated coronary smooth muscle cells and 〉50% of the contraction of the inner diameter of coronary arteries from normal rats. However, BK current density is remarkably reduced in coronary smooth muscle cells of streptozotocin-induced diabetic rats, leading to an increase in coronary artery tension. BK channel activity in response to free Ca2＋ iS impaired in diabetic rats. Moreover, cytoplasmic application of DHS-1 （a specific BK channel i~ subunit activator） robustly enhanced the open probability of BK channels in coronary smooth muscle cells of normal rats. In diabetic rats, the DHS-1 effect was diminished in the presence of 200 nmol/L Ca2＋ and was significantly attenuated in the presence of high free calcium concentration, i.e., 1 μmol/L Ca2＋. Immunoblotting experiments confirmed that there was a 2-fold decrease in BK-β1 protein expression in diabetic vessels, without alterinq the BK channel a-subunit expression.Although the cytosolic Ca2＋ concentration of coronary arterial smooth muscle cells was increased from （103±23） nmol/L （n=5） of control rats to （193±22） nmol/L （n=6, P 〈0.05） of STZ-induced diabetic展开更多
The complex gut microbial flora harbored by individuals(microbiota) has long been proposed to contribute tointestinal health as well as disease. Pre-and probioticproducts aimed at improving health by modifyingmicrobio...The complex gut microbial flora harbored by individuals(microbiota) has long been proposed to contribute tointestinal health as well as disease. Pre-and probioticproducts aimed at improving health by modifyingmicrobiota composition have already become widelyavailable and acceptance of these products appearsto be on the rise. However, although required forthe development of effective microbiota basedinterventions, our basic understanding of microbiotavariation on a population level and its dynamics withinindividuals is still rudimentary. Powerful new parallelsequence technologies combined with other efficientmolecular microbiota analysis methods now allow forcomprehensive analysis of microbiota composition inlarge human populations. Recent fi ndings in the fi eldstrongly suggest that microbiota contributes to thedevelopment of obesity, atopic diseases, inflammatorybowel diseases and intestinal cancers. Through theongoing National Institutes of Health Roadmap 'HumanMicrobiome Project' and similar projects in other partsof the world, a large coordinated effort is currentlyunderway to study how microbiota can impact humanhealth. Translating findings from these studies intoeffective interventions that can improve health,possibly personalized based on an individuals existingmicrobiota, will be the task for the next decade(s).展开更多
In the East Asian monsoon region over eastern China,east of 100°E,summer rainfall controlled by the East Asian summer monsoon(EASM)is mainly concentrated during June–August.Summer rainfall accounts for more than...In the East Asian monsoon region over eastern China,east of 100°E,summer rainfall controlled by the East Asian summer monsoon(EASM)is mainly concentrated during June–August.Summer rainfall accounts for more than half of the annual total,or 52%,according to rainfall observations from 160 meteorological stations in China展开更多
Background & Aims: The natural history of nonalcoholic fatty liver disease (NAFLD) in the community remains unknown. We sought to determine survival and liver- related morbidity among community- based NAFLD patien...Background & Aims: The natural history of nonalcoholic fatty liver disease (NAFLD) in the community remains unknown. We sought to determine survival and liver- related morbidity among community- based NAFLD patients. Methods: Four hundred twenty patients diagnosed with NAFLD in Olmsted County, Minnesota, between 1980 and 2000 were identified using the resources of the Rochester Epidemiology Project. Medical records were reviewed to confirm diagnosis and determine outcomes up to 2003. Overall survival was compared with the general Minnesota population of the same age and sex. Results: Mean (SD) age at diagnosis was 49 (15) years; 231 (49% ) were male. Mean follow- up was 7.6 (4.0) years (range, 0.1- 23.5) culminating in 3192 person- years follow- up. Overall, 53 of 420 (12.6% ) patients died. Survival was lower than the expected survival for the general population (standardized mortality ratio, 1.34; 95% CI, 1.003- 1.76; P = .03). Higher mortality was associated with age (hazard ratio per decade, 2.2; 95% CI, 1.7- 2.7), impaired fasting glucose (hazard ratio, 2.6; 95% CI, 1.3- 5.2), and cirrhosis (hazard ratio, 3.1, 95% CI, 1.2- 7.8). Liver disease was the third leading cause of death (as compared with the thirteenth leading cause of death in the general Minnesota population), occurring in 7 (1.7% ) subjects. Twenty- one (5% ) patients were diagnosed with cirrhosis, and 13 (3.1% ) developed liver- related complications, including 1 requiring transplantation and 2 developing hepatocellular carcinoma. Conclusions: Mortality among community- diagnosed NA- FLD patients is higher than the general population and is associated with older age, impaired fasting glucose, and cirrhosis. Liver- related death is a leading cause of mortality, although the absolute risk is low.展开更多
AIM To evaluate the possibility of usingcultured human hepatocytes as a bridge betweenbioartificial liver and liver transplantation.METHODS In this experiment,the efficacy ofextracorporeal bioartificial liver support ...AIM To evaluate the possibility of usingcultured human hepatocytes as a bridge betweenbioartificial liver and liver transplantation.METHODS In this experiment,the efficacy ofextracorporeal bioartificial liver support system(EBLSS)consisting of spheriodal human livercells and cultured hepatocytes supernatant wasassessed in vivo using galactosamine inducedrabbit model of fulminant hepatic failure.RESULTS There was no difference of survivalbetween the two groups of rabbits,but in thesupported rabbits serum alanineaminotransferase,total bilirubin and creatininewere significantly lower and hepatocyte necrosiswas markedly milder than those in controlanimals.In addition,a good viability of humanliver cells was noted after the experiment.CONCLUSION EBLSS plays a biologic role inmaintaining and compensating the function ofthe liver.展开更多
Background Off-label application of drug-eluting stents （DES） during percutaneous coronary intervention （PCI） was not uncommon in daily practice, however DES in treating Chinese patients with complex lesion subset...Background Off-label application of drug-eluting stents （DES） during percutaneous coronary intervention （PCI） was not uncommon in daily practice, however DES in treating Chinese patients with complex lesion subset was under-investigated. The primary objective of the FIREMAN registry was to evaluate the long term efficacy and safety of the Firebird sirolimus-eluting stent （SES） in treating patients with complex coronary lesions. Here we report the mid-term of one-year clinical outcomes and eight-month angiographic follow-up results of FIREMAN registry.Methods The FIREMAN registry was a prospective multi-center registry, which included 1029 consecutive patients undergoing PCI with Firebird SES implantation between September 2006 and July 2007 in 45 centers in China. The clinical follow-up was designed to be performed at 1, 6, 12, 18, 24, 30 and 36 months post index procedure, and non-mandatory angiographic follow-up at 8 months was planned. One hundred percent site monitoring was conducted.Results Long lesions （59.2%）, multi-vessel disease （50.4%）, and small vessel disease （31.6%） were mostly found in angiography. Major adverse cardiac events （MACE） occurred in 51 （5.1%） patients at 1 year clinical follow-up,including cardiac mortality in 6 （0.6%）, non-fatal myocardial infarction in 11 （1.1%）, and target lesion revascularization in 36 （3.5%） of the patients. Definite and probable stent thrombosis （ST） by Academic Research Consortium （ARC） definition occurred in 12 （1.36%） patients at one-year clinical follow-up. The 8-month binary restenosis rate was 5.7% in-segment and 4.3% in-stent, respectively. Late lumen loss was （0.21±0.40） mm in-segment and （0.23±0.36） mm in-stent, respectively. Furthermore, Cox regression analysis revealed that diabetes, small vessel diameter, and chronic total occlusion were independent predictors of ST.Conclusions The results showed that the Firebird SES was effective and safe in treating Chinese patients with complex coron展开更多
Background: The prevalence of heart failure with preserved ejection fraction may be changing as a result of changes in population demographics and in the prevalence and treatment of risk factors for heart failure. Cha...Background: The prevalence of heart failure with preserved ejection fraction may be changing as a result of changes in population demographics and in the prevalence and treatment of risk factors for heart failure. Changes in the prevalence of heart failure with preserved ejection fraction may contribute to changes in the natural history of heart failure. We performed a study to define secular trends in the prevalence of heart failure with preserved ejection fraction among patients at a single institution over a 15-year period. Methods: We studied all consecutive patients hospitalized with decompensated heart failure at Mayo Clinic Hospitals in Olmsted County, Minnesota, from 1987 through 2001. We classified patients as having either preserved or reduced ejection fraction. The patients were also classified as community patients(Olmsted County residents) or referral patients. Secular trends in the type of heart failure, associated cardiovascular disease, and survival were defined. Results: A total of 6076 patients with heart failure were discharged over the 15-year period; data on ejection fraction were available for 4596 of these patients(76 percent). Of these, 53 percent had a reduced ejection fraction and 47 percent had a preserved ejection fraction. The proportion of patients with the diagnosis of heart failure with preserved ejection fraction increased over time and was significantly higher among community patients than among referral patients(55 percent vs. 45 percent). The prevalence rates of hypertension, atrial fibrillation, and diabetes among patients with heart failure increased significantly over time. Survival was slightly better among patients with preserved ejection fraction(adjusted hazard ratio for death, 0.96; P=0.01). Survival improved over time for those with reduced ejection fraction but not for those with preserved ejection fraction. Conclusions: The prevalence of heart failure with preserved ejection fraction increased over a 15-year period, while the rate of death from this disorder remained展开更多
In the last half century,a significant warming trend occurred in summer over eastern China in the East Asian monsoon region.However,there were no consistent trends with respect to the intensity of the East Asian summe...In the last half century,a significant warming trend occurred in summer over eastern China in the East Asian monsoon region.However,there were no consistent trends with respect to the intensity of the East Asian summer monsoon(EASM) or the amount of summer rainfall averaged over eastern China.Both of the EASM and summer rainfall exhibited clear decadal variations.Obvious decadal shifts of EASM occurred around the mid- and late 1970 s,the late 1980 s and the early 1990 s,and the late 1990 s and early 2000 s,respectively.Summer rainfall over eastern China exhibited a change in spatial distribution in the decadal timescale,in response to the decadal shifts of EASM.From the mid- and late 1970 s to the late 1980 s and the early 1990 s,there was a meridional tri-polar rainfall distribution anomaly with more rainfall over the Yangtze River valley and less rainfall in North and South China; but in the period from the early 1990 s to the late 1990 s and the early 2000 s the tri-polar distribution changed to a dipolar one,with more rainfall appearing over southern China south to the Yangtze River valley and less rainfall in North China.However,from the early 2000 s to the late 2000 s,the Yangtze River valley received less rainfall.The decadal changes in EASM and summer rainfall over eastern China in the last half century are closely related to natural internal forcing factors such as Eurasian snow cover,Arctic sea ice,sea surface temperatures in tropical Pacific and Indian Ocean,oceaneatmospheric coupled systems of the Pacific Decadal Oscillation(PDO) and AsianePacific Oscillation(APO),and uneven thermal forcing over the Asian continent.Up to now,the roles of anthropogenic factors,such as greenhouse gases,aerosols,and land usage/cover changes,on existing decadal variations of EASM and summer rainfall in this region remain uncertain.展开更多
The Global Stratotype Section and Point （GSSP） for the base of the Silurian System was defined in 1985. Since that time, a number of researchers have suggested that this section has serious deficiencies for use as a...The Global Stratotype Section and Point （GSSP） for the base of the Silurian System was defined in 1985. Since that time, a number of researchers have suggested that this section has serious deficiencies for use as a GSSP. As a result, in 2000, the Subcommission on Silurian Stratigraphy （SSS） proposed undertaking a formal restu@ of this GSSP, which was subsequently approved by the International Commission of Stratigraphy （ICS）. The result of this restudy was the formal proposal that the current GSSP, at 1.6 m above the base of the Birkhill Shale, at Dob＇s Linn, Scotland, should be maintained as the same locality and stratigraphic level, but the bios- tratigraphical definition of the boundary should be revised. The previously defined, basal Silurian grapto- lite zone, the Parakidograptus acuminatus Zone, should be subdivided into a lower Akidograptus ascensus Zone and a higher E acuminatus Zone. The base of the A. ascensus Zone, marked by the first appearance of A. ascensus, should be regarded as the biostratigraphic mark for the base of the Silurian. This proposal has now been formally approved by the SSS and ICS, and ratified by International Union of Geological Sciences. This is the first GSSP to undergo formal restudy and redefini- tion, and the proposal also included a recommended procedure for restudy of GSSPs.展开更多
QUANTIZED radiation fields exhibiting nonclassical properties have been of great theoretical andexperimental interest in the last two decades. It is shown that various nonclassical states suchas squeezed state and Sch...QUANTIZED radiation fields exhibiting nonclassical properties have been of great theoretical andexperimental interest in the last two decades. It is shown that various nonclassical states suchas squeezed state and Schrodinger cat state can be generated out of coherent state in thenonlinear process of the interaction of atom and field although the radiation field in a展开更多
BACKGROUND: Contrast-enhanced ultrasonography (CEUS) is increasingly accepted in clinical settings for diagnostic imaging of focal liver lesions (FLLs). This study aimed to assess the efficacy of CEUS in the character...BACKGROUND: Contrast-enhanced ultrasonography (CEUS) is increasingly accepted in clinical settings for diagnostic imaging of focal liver lesions (FLLs). This study aimed to assess the efficacy of CEUS in the characterization of FLLs in comparison with final diagnosis based on gold standard assessment. METHODS: The study was approved by the local ethics committee and participating patients provided written informed consent. A total of 148 patients with 164 FLLs were studied. Unenhanced ultrasonography (US) and CEUS were performed using fundamental and harmonic imaging, respectively. Contrast enhancement was assessed during the arterial, portal and late vascular phases after intravenous administration of contrast (SonoVue (R), Bracco, Italy). Sensitivity, specificity and diagnostic accuracy of US and CEUS were compared in identifying the lesion as benign, malignant or indeterminate and its actual tumor type. Final diagnosis was established by biopsy (129/164), MR imaging (11/164) or medical history (24/164). RESULTS: When compared to the gold standard, the number of indeterminate diagnoses was reduced from 56.7% (93/164) as assessed by fundamental imaging to 6.1% (10/164) after SonoVue (R) enhanced US examination. Sensitivity and specificity improved from 49% and 25% at baseline US to 93% and 75% with CEUS, respectively (P<0.01). Diagnostic accuracy of CEUS was 88% in contrast to 41% of baseline US. CONCLUSION: SonoVue (R) enhanced US improves the characterization of FLLs and may limit the need for further investigations.展开更多
A tectonic facies investigation carried out in the West Kunlun, China allows us to have worked out a tectonic model of orogen. The tectonic facies, from the north to the south, are composed of the following: 1. Southe...A tectonic facies investigation carried out in the West Kunlun, China allows us to have worked out a tectonic model of orogen. The tectonic facies, from the north to the south, are composed of the following: 1. Southern Tarim tectonic realm; 2. North Kudi magmatic arc; 3. Kudi melange; 4. Kudi micro-continent; 5. main shear zone; 6. Xianan Bridge calc alkaline complex; 7. Mazar-Kangxiwar melange-accretion complex; and 8. Tianshuihai foreland fold-thrust belt. The tectonic facies 1->5 recorded the history of the northward subduction of the Prototethys and southward accretion of Eurasia in the Late Proterozoic-Early Paleozoic time, while the tectonic facies 6->8 recorded the history of the northward subduction of the Paleotethys and southward accretion of Eurasia in the Late Paleozoic-Early Mesozoic time, that of the tectonic evolution of the passive margin of the Qiangtang block, and that of the docking and the final amalgamation of the Qiangtang block to the Eurasian continent. The tectonic facies investigation has indicated that a complicated archipelago-accretion orogenesis took place in the West Kunlun orogen, which was the important character of southward growth of the Eurasian continent.展开更多
Background & Aims: Although diabetes occurs frequently in pancreatic cancer, the value of new-onset diabetes as a marker of underlying pancreatic cancer is unknown. Methods: We assembled a population-based cohort ...Background & Aims: Although diabetes occurs frequently in pancreatic cancer, the value of new-onset diabetes as a marker of underlying pancreatic cancer is unknown. Methods: We assembled a population-based cohort of 2122 Rochester, Minnesota, residents age ≥ 50 years who first met standardized criteria for diabetes between January 1, 1950, and December 31, 1994, and identified those who developed pancreatic cancer within 3 years of meeting criteria for diabetes. We compared observed rates of pancreatic cancer with expected rates based on the Iowa Surveillance Epidemiology and End Results registry. In a nested case control study, we compared body mass index (BMI) and smoking status in diabetes subjects with and without pancreatic cancer. Results: Of 2122 diabetic subjects, 18 (0.85% ) were diagnosed with pancreatic cancer within 3 years of meeting criteria for diabetes; 10 of 18 (56% ) were diagnosed < 6 months after first meeting criteria for diabetes, and 3 were resected. The observed-to-expected ratio of pancreatic cancer in the cohort was 7.94 (95% CI, 4.70- 12.55). Compared with subjects without pancreatic cancer, diabetic subjects with pancreatic cancer were more likely to have met diabetes criteria after age 69 (OR = 4.52, 95% CI, 1.61- 12.74) years but did not differ significantly with respect to BMI values (29.2 ± 6.8 vs 26.5 ± 5.0, respectively). A larger proportion of those who developed pancreatic cancer were ever smokers (92% vs 69% , respectively), but this did not reach statistical significance. Conclusions: Approximately 1% of diabetes subjects aged < 50 yearswill be diagnosed with pancreatic cancer within 3 years of first meeting criteria for diabetes. The usefulness of new-onset diabetes as marker of early pancreatic cancer needs further evaluation.展开更多
Abdominal pain is a major clinical problem in patients with chronic pancreatitis. The cause of pain is usually multifactorial with a complex interplay of factors contributing to a varying degree to the pain in an indi...Abdominal pain is a major clinical problem in patients with chronic pancreatitis. The cause of pain is usually multifactorial with a complex interplay of factors contributing to a varying degree to the pain in an individual patient and, therefore, a rigid standardized approach for pain control tends to lead to suboptimal results. Pain management usually proceeds in a stepwise approach beginning with general lifestyle recommendations. Low fat diet, alcohol and smoking cessation are encouraged. Analgesics alone are needed in almost all patients. Maneuvers aimed at suppression of pancreatic secretion are routinely tried. Patients with ongoing symptoms may be candidates for more invasive options such as endoscopic therapy, and resective or drainage surgery. The role of pain modifying agents (antidepressants, gabapentin, peregabalin), celiac plexus block, antioxidants, octreotide and total pancreatectomy with islet cell auto transplantation remains to be determined.展开更多
Adventitious rooting(AR)is critical to the propagation,breeding,and genetic engineering of trees.The capacity for plants to undergo this process is highly heritable and of a polygenic nature;however,the basis of its g...Adventitious rooting(AR)is critical to the propagation,breeding,and genetic engineering of trees.The capacity for plants to undergo this process is highly heritable and of a polygenic nature;however,the basis of its genetic variation is largely uncharacterized.To identify genetic regulators of AR,we performed a genome-wide association study(GWAS)using 1148 genotypes of Populus trichocarpa.GWASs are often limited by the abilities of researchers to collect precise phenotype data on a high-throughput scale;to help overcome this limitation,we developed a computer vision system to measure an array of traits related to adventitious root development in poplar,including temporal measures of lateral and basal root length and area.GWAS was performed using multiple methods and significance thresholds to handle non-normal phenotype statistics and to gain statistical power.These analyses yielded a total of 277 unique associations,suggesting that genes that control rooting include regulators of hormone signaling,cell division and structure,reactive oxygen species signaling,and other processes with known roles in root development.Numerous genes with uncharacterized functions and/or cryptic roles were also identified.These candidates provide targets for functional analysis,including physiological and epistatic analyses,to better characterize the complex polygenic regulation of AR.展开更多
Management and conservation efforts that support the recovery and protection of large rivers are daunting,reflecting the complexity of the challenge and extent of effort(in terms of policy,economic investment,and spat...Management and conservation efforts that support the recovery and protection of large rivers are daunting,reflecting the complexity of the challenge and extent of effort(in terms of policy,economic investment,and spatial extent)needed to afford measurable change.These large systems have generally experienced intensive development and regulation,compromising their capacity to respond to disturbances such as climate change orwildfire.Functionally,large river and basin management require insights gained from social,ecological,geophysical,and hydrological sciences.This multidisciplinary perspective can unveil the integrated relationship between a river network's biotic community and seasonally variableenvironmental conditions that are ofteninfluencedbyhumanactivities.Large rivers andtheir basins are constantly changing due to anthropogenic influences and as climate modifies patterns of temperature and precipitation.Because of these factors,the state of knowledge must advance to address changing conditions.The Willamette River,in western Oregon,USA,is a prime example of a basin that has experienced significant degradation and investment in rehabilitation in recent decades.Innovative science has facilitated development of fine-scale,spatially extensive datasets and models that can generate targeted conservation and rehabilitation actions that are prioritized across the entire river network.This prioritization allows investment decisions to be driven by site-specific conditions while simultaneously considering potentials for ecological improvement.Here,we review hydrologic,geomorphic,ecologic,and social conditions in the Willamette River basin through time—including pre-settlement,river development,andcontemporary periods—andoffer a futurevisionfor consideration.Currently,detailed informationaboutfish populations and habitat,hydrologic conditions,geomorphology,water quality,and land use can be leveraged to make informed decisions about protection,rehabilitation,and development.The time is ripe for strategic manageme展开更多
Patients with infl ammatory bowel disease (IBD) are at increased risk for colorectal cancer (CRC). Risk factors for the development of CRC in the setting of IBD include disease duration, anatomic extent of disease, ag...Patients with infl ammatory bowel disease (IBD) are at increased risk for colorectal cancer (CRC). Risk factors for the development of CRC in the setting of IBD include disease duration, anatomic extent of disease, age at time of diagnosis, severity of inflammation, family history of colon cancer, and concomitant primary sclerosing cholangitis. The current surveillance strategy of surveillance colonoscopy with multiple random biopsies most likely reduces morbidity and mortality associated with IBD-related CRC. Unfortunately, surveillance colonoscopy also has severe limitations including high cost, sampling error at time of biopsy, and interobserver disagreement in histologically grading dysplasia. Furthermore, once dysplasia is detected there is disagreement about its management. Advances in endoscopic imaging techniques are already underway, and may potentially aid in dysplasia detection and improve overall surveillance outcomes. Management of dysplasia depends predominantly on the degree and focality of dysplasia, with the mainstay of management involving either proctocolectomy or continued colonoscopic surveillance. Lastly, continued research into additional chemopreventive agents may increase our arsenal in attempting to reduce the incidence of IBD-associated CRC.展开更多
Temperature and freeze-thaw events are two key factors controlling litter decomposition in cold biomes.Predicted global warming and changes in freeze-thaw cycles therefore may directly or indirectly impact litter deco...Temperature and freeze-thaw events are two key factors controlling litter decomposition in cold biomes.Predicted global warming and changes in freeze-thaw cycles therefore may directly or indirectly impact litter decomposition in those ecosystems. Here, we conducted a2-year-long litter decomposition experiment along an elevational gradient from 3000 to 3600 m to determine the potential effects of litter quality, climate warming and freeze-thaw on the mass losses of three litter types [dragon spruce（Picea asperata Mast.）, red birch（Betula albosinensis Burk.）, and minjiang fir（Abies faxoniana Rehd. et Wild）]. Marked differences in mass loss were observed among the litter types and sampling dates. Decay constant（k） values of red birch were significantly higher than those of the needle litters. However, mass losses between elevations did not differ significantly for any litter type.During the winter, lost mass contributed 18.3-28.8 % of the net loss rates of the first year. Statistical analysis showed that the relationships between mass loss and litter chemistry or their ratios varied with decomposition periods. Our results indicated that short-term field incubations could overestimate the k value of litter decomposition.Considerable mass was lost from subalpine forest litters during the wintertime. Potential future warming may not affect the litter decomposition in the subalpine forest ecosystems of eastern Tibetan Plateau.展开更多
基金supported in part by the National Science Foundation (grants IOS-0752997 and IOS-0918433 to WJL grants IOS#0749731, IOS#051909 to PK)+8 种基金the Department of Energy, Division of Energy Biosciences (grantsDE-FG02-94ER20134 to WJL)the US Department of Agriculture, Agricultural Research Service (under Agreement number58-6250-0-008 to MAG)the Spanish Ministry of Science andInnovation (MICINN) (grants AGL2007-61948 and AGL2009-09018 to AFLM)the Ministry of Education, Science, Sportsand Culture of Japan (grant 19060009 to HF)the JapanSociety for the Promotion of Science (JSPS grant 23227001to HF)the NC-CARP project (to HF)the NationalKey Basic Research Program of China (grant 2012CB114500to XH)the National Natural Science Foundation of China (grant31070156 to XH)the NSFC-JSPS cooperation project(grant 31011140070 to HF and XH)
文摘The emergence of the tracheophyte-based vascular system of land plants had major impacts on the evolution of terrestrial biology, in general, through its role in facilitating the development of plants with increased stature, photosynthetic output, and ability to colonize a greatly expanded range of environmental habitats. Recently, considerable progress has been made in terms of our understanding of the developmental and physiological programs involved in the formation and function of the plant vascular system. In this review, we first examine the evolutionary events that gave rise to the tracheophytes, followed by analysis of the genetic and hormonal networks that cooperate to orchestrate vascular development in the gymnosperms and angiosperms. The two essentialfunctions performed by the vascular system, namely the delivery of resources （water, essential mineral nutrients, sugars and amino acids） to the various plant organs and provision of mechanical support are next discussed. Here, we focus on critical questions relating to structural and physiological properties controlling the delivery of material through the xylem and phloem. Recent discoveries into the role of the vascular system as an effective long-distance communication system are next assessed in terms of the coordination of developmental, physiological and defense-related processes, at the whole-plant level. A concerted effort has been made to integrate all these new findings into a comprehensive picture of the state-of-the-art in the area of plant vascular biology. Finally, areas important for future research are highlighted in terms of their likely contribution both to basic knowledge and applications to primary industry.
基金the National Natural Science Foundation of China，Natural Science Foundation of Jiangsu Province，Medical Key Personnel of Jiangsu Province，Top Qualified Personnel in Six Fields of Jiangsu Province (006) to WANG Ru-xing and the American Diabetes Association Junior Faculty Awards
文摘Background Diabetes mellitus is associated with coronary dysfunction, contributing to a 2- to 4-fold increase in the risk of coronary heart diseases. The mechanisms by which diabetes induces vasculopathy involve endothelial-dependent and -independent vascular dysfunction in both type 1 and type 2 diabetes mellitus. The purpose of this study is to determine the role of vascular large conductance Ca2＋-activated K＋ （BK） channel activities in coronary dysfunction in streptozotocin-induced diabetic rats. Methods Using videomicroscopy, immunoblotting, fluorescent assay and patch clamp techniques, we investigated the coronary BK channel activities and BK channel-mediated coronary vasoreactivity in streptozotocin-induced diabetic rats. Results BK currents （defined as the iberiotoxin-sensitive K＋ component） contribute （65＋4）% of the total K＋currents in freshly isolated coronary smooth muscle cells and 〉50% of the contraction of the inner diameter of coronary arteries from normal rats. However, BK current density is remarkably reduced in coronary smooth muscle cells of streptozotocin-induced diabetic rats, leading to an increase in coronary artery tension. BK channel activity in response to free Ca2＋ iS impaired in diabetic rats. Moreover, cytoplasmic application of DHS-1 （a specific BK channel i~ subunit activator） robustly enhanced the open probability of BK channels in coronary smooth muscle cells of normal rats. In diabetic rats, the DHS-1 effect was diminished in the presence of 200 nmol/L Ca2＋ and was significantly attenuated in the presence of high free calcium concentration, i.e., 1 μmol/L Ca2＋. Immunoblotting experiments confirmed that there was a 2-fold decrease in BK-β1 protein expression in diabetic vessels, without alterinq the BK channel a-subunit expression.Although the cytosolic Ca2＋ concentration of coronary arterial smooth muscle cells was increased from （103±23） nmol/L （n=5） of control rats to （193±22） nmol/L （n=6, P 〈0.05） of STZ-induced diabetic
文摘The complex gut microbial flora harbored by individuals(microbiota) has long been proposed to contribute tointestinal health as well as disease. Pre-and probioticproducts aimed at improving health by modifyingmicrobiota composition have already become widelyavailable and acceptance of these products appearsto be on the rise. However, although required forthe development of effective microbiota basedinterventions, our basic understanding of microbiotavariation on a population level and its dynamics withinindividuals is still rudimentary. Powerful new parallelsequence technologies combined with other efficientmolecular microbiota analysis methods now allow forcomprehensive analysis of microbiota composition inlarge human populations. Recent fi ndings in the fi eldstrongly suggest that microbiota contributes to thedevelopment of obesity, atopic diseases, inflammatorybowel diseases and intestinal cancers. Through theongoing National Institutes of Health Roadmap 'HumanMicrobiome Project' and similar projects in other partsof the world, a large coordinated effort is currentlyunderway to study how microbiota can impact humanhealth. Translating findings from these studies intoeffective interventions that can improve health,possibly personalized based on an individuals existingmicrobiota, will be the task for the next decade(s).
基金supported by the National Natural Science Foundation of China(41221064)
文摘In the East Asian monsoon region over eastern China,east of 100°E,summer rainfall controlled by the East Asian summer monsoon(EASM)is mainly concentrated during June–August.Summer rainfall accounts for more than half of the annual total,or 52%,according to rainfall observations from 160 meteorological stations in China
文摘Background & Aims: The natural history of nonalcoholic fatty liver disease (NAFLD) in the community remains unknown. We sought to determine survival and liver- related morbidity among community- based NAFLD patients. Methods: Four hundred twenty patients diagnosed with NAFLD in Olmsted County, Minnesota, between 1980 and 2000 were identified using the resources of the Rochester Epidemiology Project. Medical records were reviewed to confirm diagnosis and determine outcomes up to 2003. Overall survival was compared with the general Minnesota population of the same age and sex. Results: Mean (SD) age at diagnosis was 49 (15) years; 231 (49% ) were male. Mean follow- up was 7.6 (4.0) years (range, 0.1- 23.5) culminating in 3192 person- years follow- up. Overall, 53 of 420 (12.6% ) patients died. Survival was lower than the expected survival for the general population (standardized mortality ratio, 1.34; 95% CI, 1.003- 1.76; P = .03). Higher mortality was associated with age (hazard ratio per decade, 2.2; 95% CI, 1.7- 2.7), impaired fasting glucose (hazard ratio, 2.6; 95% CI, 1.3- 5.2), and cirrhosis (hazard ratio, 3.1, 95% CI, 1.2- 7.8). Liver disease was the third leading cause of death (as compared with the thirteenth leading cause of death in the general Minnesota population), occurring in 7 (1.7% ) subjects. Twenty- one (5% ) patients were diagnosed with cirrhosis, and 13 (3.1% ) developed liver- related complications, including 1 requiring transplantation and 2 developing hepatocellular carcinoma. Conclusions: Mortality among community- diagnosed NA- FLD patients is higher than the general population and is associated with older age, impaired fasting glucose, and cirrhosis. Liver- related death is a leading cause of mortality, although the absolute risk is low.
基金the national key project fund of the"9th Five Year Plan",No.96-920-12-02
文摘AIM To evaluate the possibility of usingcultured human hepatocytes as a bridge betweenbioartificial liver and liver transplantation.METHODS In this experiment,the efficacy ofextracorporeal bioartificial liver support system(EBLSS)consisting of spheriodal human livercells and cultured hepatocytes supernatant wasassessed in vivo using galactosamine inducedrabbit model of fulminant hepatic failure.RESULTS There was no difference of survivalbetween the two groups of rabbits,but in thesupported rabbits serum alanineaminotransferase,total bilirubin and creatininewere significantly lower and hepatocyte necrosiswas markedly milder than those in controlanimals.In addition,a good viability of humanliver cells was noted after the experiment.CONCLUSION EBLSS plays a biologic role inmaintaining and compensating the function ofthe liver.
基金National Natural Science Foundation of China，Beijing Natural Science Foundation，Specilized Research Fund for the Doctoral Program of High Education of China
文摘Background Off-label application of drug-eluting stents （DES） during percutaneous coronary intervention （PCI） was not uncommon in daily practice, however DES in treating Chinese patients with complex lesion subset was under-investigated. The primary objective of the FIREMAN registry was to evaluate the long term efficacy and safety of the Firebird sirolimus-eluting stent （SES） in treating patients with complex coronary lesions. Here we report the mid-term of one-year clinical outcomes and eight-month angiographic follow-up results of FIREMAN registry.Methods The FIREMAN registry was a prospective multi-center registry, which included 1029 consecutive patients undergoing PCI with Firebird SES implantation between September 2006 and July 2007 in 45 centers in China. The clinical follow-up was designed to be performed at 1, 6, 12, 18, 24, 30 and 36 months post index procedure, and non-mandatory angiographic follow-up at 8 months was planned. One hundred percent site monitoring was conducted.Results Long lesions （59.2%）, multi-vessel disease （50.4%）, and small vessel disease （31.6%） were mostly found in angiography. Major adverse cardiac events （MACE） occurred in 51 （5.1%） patients at 1 year clinical follow-up,including cardiac mortality in 6 （0.6%）, non-fatal myocardial infarction in 11 （1.1%）, and target lesion revascularization in 36 （3.5%） of the patients. Definite and probable stent thrombosis （ST） by Academic Research Consortium （ARC） definition occurred in 12 （1.36%） patients at one-year clinical follow-up. The 8-month binary restenosis rate was 5.7% in-segment and 4.3% in-stent, respectively. Late lumen loss was （0.21±0.40） mm in-segment and （0.23±0.36） mm in-stent, respectively. Furthermore, Cox regression analysis revealed that diabetes, small vessel diameter, and chronic total occlusion were independent predictors of ST.Conclusions The results showed that the Firebird SES was effective and safe in treating Chinese patients with complex coron
文摘Background: The prevalence of heart failure with preserved ejection fraction may be changing as a result of changes in population demographics and in the prevalence and treatment of risk factors for heart failure. Changes in the prevalence of heart failure with preserved ejection fraction may contribute to changes in the natural history of heart failure. We performed a study to define secular trends in the prevalence of heart failure with preserved ejection fraction among patients at a single institution over a 15-year period. Methods: We studied all consecutive patients hospitalized with decompensated heart failure at Mayo Clinic Hospitals in Olmsted County, Minnesota, from 1987 through 2001. We classified patients as having either preserved or reduced ejection fraction. The patients were also classified as community patients(Olmsted County residents) or referral patients. Secular trends in the type of heart failure, associated cardiovascular disease, and survival were defined. Results: A total of 6076 patients with heart failure were discharged over the 15-year period; data on ejection fraction were available for 4596 of these patients(76 percent). Of these, 53 percent had a reduced ejection fraction and 47 percent had a preserved ejection fraction. The proportion of patients with the diagnosis of heart failure with preserved ejection fraction increased over time and was significantly higher among community patients than among referral patients(55 percent vs. 45 percent). The prevalence rates of hypertension, atrial fibrillation, and diabetes among patients with heart failure increased significantly over time. Survival was slightly better among patients with preserved ejection fraction(adjusted hazard ratio for death, 0.96; P=0.01). Survival improved over time for those with reduced ejection fraction but not for those with preserved ejection fraction. Conclusions: The prevalence of heart failure with preserved ejection fraction increased over a 15-year period, while the rate of death from this disorder remained
基金supported by the National Natural Science Foundation of China (41221064)
文摘In the last half century,a significant warming trend occurred in summer over eastern China in the East Asian monsoon region.However,there were no consistent trends with respect to the intensity of the East Asian summer monsoon(EASM) or the amount of summer rainfall averaged over eastern China.Both of the EASM and summer rainfall exhibited clear decadal variations.Obvious decadal shifts of EASM occurred around the mid- and late 1970 s,the late 1980 s and the early 1990 s,and the late 1990 s and early 2000 s,respectively.Summer rainfall over eastern China exhibited a change in spatial distribution in the decadal timescale,in response to the decadal shifts of EASM.From the mid- and late 1970 s to the late 1980 s and the early 1990 s,there was a meridional tri-polar rainfall distribution anomaly with more rainfall over the Yangtze River valley and less rainfall in North and South China; but in the period from the early 1990 s to the late 1990 s and the early 2000 s the tri-polar distribution changed to a dipolar one,with more rainfall appearing over southern China south to the Yangtze River valley and less rainfall in North China.However,from the early 2000 s to the late 2000 s,the Yangtze River valley received less rainfall.The decadal changes in EASM and summer rainfall over eastern China in the last half century are closely related to natural internal forcing factors such as Eurasian snow cover,Arctic sea ice,sea surface temperatures in tropical Pacific and Indian Ocean,oceaneatmospheric coupled systems of the Pacific Decadal Oscillation(PDO) and AsianePacific Oscillation(APO),and uneven thermal forcing over the Asian continent.Up to now,the roles of anthropogenic factors,such as greenhouse gases,aerosols,and land usage/cover changes,on existing decadal variations of EASM and summer rainfall in this region remain uncertain.
文摘The Global Stratotype Section and Point （GSSP） for the base of the Silurian System was defined in 1985. Since that time, a number of researchers have suggested that this section has serious deficiencies for use as a GSSP. As a result, in 2000, the Subcommission on Silurian Stratigraphy （SSS） proposed undertaking a formal restu@ of this GSSP, which was subsequently approved by the International Commission of Stratigraphy （ICS）. The result of this restudy was the formal proposal that the current GSSP, at 1.6 m above the base of the Birkhill Shale, at Dob＇s Linn, Scotland, should be maintained as the same locality and stratigraphic level, but the bios- tratigraphical definition of the boundary should be revised. The previously defined, basal Silurian grapto- lite zone, the Parakidograptus acuminatus Zone, should be subdivided into a lower Akidograptus ascensus Zone and a higher E acuminatus Zone. The base of the A. ascensus Zone, marked by the first appearance of A. ascensus, should be regarded as the biostratigraphic mark for the base of the Silurian. This proposal has now been formally approved by the SSS and ICS, and ratified by International Union of Geological Sciences. This is the first GSSP to undergo formal restudy and redefini- tion, and the proposal also included a recommended procedure for restudy of GSSPs.
文摘QUANTIZED radiation fields exhibiting nonclassical properties have been of great theoretical andexperimental interest in the last two decades. It is shown that various nonclassical states suchas squeezed state and Schrodinger cat state can be generated out of coherent state in thenonlinear process of the interaction of atom and field although the radiation field in a
文摘BACKGROUND: Contrast-enhanced ultrasonography (CEUS) is increasingly accepted in clinical settings for diagnostic imaging of focal liver lesions (FLLs). This study aimed to assess the efficacy of CEUS in the characterization of FLLs in comparison with final diagnosis based on gold standard assessment. METHODS: The study was approved by the local ethics committee and participating patients provided written informed consent. A total of 148 patients with 164 FLLs were studied. Unenhanced ultrasonography (US) and CEUS were performed using fundamental and harmonic imaging, respectively. Contrast enhancement was assessed during the arterial, portal and late vascular phases after intravenous administration of contrast (SonoVue (R), Bracco, Italy). Sensitivity, specificity and diagnostic accuracy of US and CEUS were compared in identifying the lesion as benign, malignant or indeterminate and its actual tumor type. Final diagnosis was established by biopsy (129/164), MR imaging (11/164) or medical history (24/164). RESULTS: When compared to the gold standard, the number of indeterminate diagnoses was reduced from 56.7% (93/164) as assessed by fundamental imaging to 6.1% (10/164) after SonoVue (R) enhanced US examination. Sensitivity and specificity improved from 49% and 25% at baseline US to 93% and 75% with CEUS, respectively (P<0.01). Diagnostic accuracy of CEUS was 88% in contrast to 41% of baseline US. CONCLUSION: SonoVue (R) enhanced US improves the characterization of FLLs and may limit the need for further investigations.
文摘A tectonic facies investigation carried out in the West Kunlun, China allows us to have worked out a tectonic model of orogen. The tectonic facies, from the north to the south, are composed of the following: 1. Southern Tarim tectonic realm; 2. North Kudi magmatic arc; 3. Kudi melange; 4. Kudi micro-continent; 5. main shear zone; 6. Xianan Bridge calc alkaline complex; 7. Mazar-Kangxiwar melange-accretion complex; and 8. Tianshuihai foreland fold-thrust belt. The tectonic facies 1->5 recorded the history of the northward subduction of the Prototethys and southward accretion of Eurasia in the Late Proterozoic-Early Paleozoic time, while the tectonic facies 6->8 recorded the history of the northward subduction of the Paleotethys and southward accretion of Eurasia in the Late Paleozoic-Early Mesozoic time, that of the tectonic evolution of the passive margin of the Qiangtang block, and that of the docking and the final amalgamation of the Qiangtang block to the Eurasian continent. The tectonic facies investigation has indicated that a complicated archipelago-accretion orogenesis took place in the West Kunlun orogen, which was the important character of southward growth of the Eurasian continent.
文摘Background & Aims: Although diabetes occurs frequently in pancreatic cancer, the value of new-onset diabetes as a marker of underlying pancreatic cancer is unknown. Methods: We assembled a population-based cohort of 2122 Rochester, Minnesota, residents age ≥ 50 years who first met standardized criteria for diabetes between January 1, 1950, and December 31, 1994, and identified those who developed pancreatic cancer within 3 years of meeting criteria for diabetes. We compared observed rates of pancreatic cancer with expected rates based on the Iowa Surveillance Epidemiology and End Results registry. In a nested case control study, we compared body mass index (BMI) and smoking status in diabetes subjects with and without pancreatic cancer. Results: Of 2122 diabetic subjects, 18 (0.85% ) were diagnosed with pancreatic cancer within 3 years of meeting criteria for diabetes; 10 of 18 (56% ) were diagnosed < 6 months after first meeting criteria for diabetes, and 3 were resected. The observed-to-expected ratio of pancreatic cancer in the cohort was 7.94 (95% CI, 4.70- 12.55). Compared with subjects without pancreatic cancer, diabetic subjects with pancreatic cancer were more likely to have met diabetes criteria after age 69 (OR = 4.52, 95% CI, 1.61- 12.74) years but did not differ significantly with respect to BMI values (29.2 ± 6.8 vs 26.5 ± 5.0, respectively). A larger proportion of those who developed pancreatic cancer were ever smokers (92% vs 69% , respectively), but this did not reach statistical significance. Conclusions: Approximately 1% of diabetes subjects aged < 50 yearswill be diagnosed with pancreatic cancer within 3 years of first meeting criteria for diabetes. The usefulness of new-onset diabetes as marker of early pancreatic cancer needs further evaluation.
文摘Abdominal pain is a major clinical problem in patients with chronic pancreatitis. The cause of pain is usually multifactorial with a complex interplay of factors contributing to a varying degree to the pain in an individual patient and, therefore, a rigid standardized approach for pain control tends to lead to suboptimal results. Pain management usually proceeds in a stepwise approach beginning with general lifestyle recommendations. Low fat diet, alcohol and smoking cessation are encouraged. Analgesics alone are needed in almost all patients. Maneuvers aimed at suppression of pancreatic secretion are routinely tried. Patients with ongoing symptoms may be candidates for more invasive options such as endoscopic therapy, and resective or drainage surgery. The role of pain modifying agents (antidepressants, gabapentin, peregabalin), celiac plexus block, antioxidants, octreotide and total pancreatectomy with islet cell auto transplantation remains to be determined.
文摘Adventitious rooting(AR)is critical to the propagation,breeding,and genetic engineering of trees.The capacity for plants to undergo this process is highly heritable and of a polygenic nature;however,the basis of its genetic variation is largely uncharacterized.To identify genetic regulators of AR,we performed a genome-wide association study(GWAS)using 1148 genotypes of Populus trichocarpa.GWASs are often limited by the abilities of researchers to collect precise phenotype data on a high-throughput scale;to help overcome this limitation,we developed a computer vision system to measure an array of traits related to adventitious root development in poplar,including temporal measures of lateral and basal root length and area.GWAS was performed using multiple methods and significance thresholds to handle non-normal phenotype statistics and to gain statistical power.These analyses yielded a total of 277 unique associations,suggesting that genes that control rooting include regulators of hormone signaling,cell division and structure,reactive oxygen species signaling,and other processes with known roles in root development.Numerous genes with uncharacterized functions and/or cryptic roles were also identified.These candidates provide targets for functional analysis,including physiological and epistatic analyses,to better characterize the complex polygenic regulation of AR.
文摘Management and conservation efforts that support the recovery and protection of large rivers are daunting,reflecting the complexity of the challenge and extent of effort(in terms of policy,economic investment,and spatial extent)needed to afford measurable change.These large systems have generally experienced intensive development and regulation,compromising their capacity to respond to disturbances such as climate change orwildfire.Functionally,large river and basin management require insights gained from social,ecological,geophysical,and hydrological sciences.This multidisciplinary perspective can unveil the integrated relationship between a river network's biotic community and seasonally variableenvironmental conditions that are ofteninfluencedbyhumanactivities.Large rivers andtheir basins are constantly changing due to anthropogenic influences and as climate modifies patterns of temperature and precipitation.Because of these factors,the state of knowledge must advance to address changing conditions.The Willamette River,in western Oregon,USA,is a prime example of a basin that has experienced significant degradation and investment in rehabilitation in recent decades.Innovative science has facilitated development of fine-scale,spatially extensive datasets and models that can generate targeted conservation and rehabilitation actions that are prioritized across the entire river network.This prioritization allows investment decisions to be driven by site-specific conditions while simultaneously considering potentials for ecological improvement.Here,we review hydrologic,geomorphic,ecologic,and social conditions in the Willamette River basin through time—including pre-settlement,river development,andcontemporary periods—andoffer a futurevisionfor consideration.Currently,detailed informationaboutfish populations and habitat,hydrologic conditions,geomorphology,water quality,and land use can be leveraged to make informed decisions about protection,rehabilitation,and development.The time is ripe for strategic manageme
文摘Patients with infl ammatory bowel disease (IBD) are at increased risk for colorectal cancer (CRC). Risk factors for the development of CRC in the setting of IBD include disease duration, anatomic extent of disease, age at time of diagnosis, severity of inflammation, family history of colon cancer, and concomitant primary sclerosing cholangitis. The current surveillance strategy of surveillance colonoscopy with multiple random biopsies most likely reduces morbidity and mortality associated with IBD-related CRC. Unfortunately, surveillance colonoscopy also has severe limitations including high cost, sampling error at time of biopsy, and interobserver disagreement in histologically grading dysplasia. Furthermore, once dysplasia is detected there is disagreement about its management. Advances in endoscopic imaging techniques are already underway, and may potentially aid in dysplasia detection and improve overall surveillance outcomes. Management of dysplasia depends predominantly on the degree and focality of dysplasia, with the mainstay of management involving either proctocolectomy or continued colonoscopic surveillance. Lastly, continued research into additional chemopreventive agents may increase our arsenal in attempting to reduce the incidence of IBD-associated CRC.
基金supported by the National Natural Science Foundation of China(3157044531570601+2 种基金31500509 and31570605)Postdoctoral Science Foundation of China(2013M540714 and 2014T70880)Collaborative Innovation Center of Ecological Security in the Upper Reaches of Yangze River
文摘Temperature and freeze-thaw events are two key factors controlling litter decomposition in cold biomes.Predicted global warming and changes in freeze-thaw cycles therefore may directly or indirectly impact litter decomposition in those ecosystems. Here, we conducted a2-year-long litter decomposition experiment along an elevational gradient from 3000 to 3600 m to determine the potential effects of litter quality, climate warming and freeze-thaw on the mass losses of three litter types [dragon spruce（Picea asperata Mast.）, red birch（Betula albosinensis Burk.）, and minjiang fir（Abies faxoniana Rehd. et Wild）]. Marked differences in mass loss were observed among the litter types and sampling dates. Decay constant（k） values of red birch were significantly higher than those of the needle litters. However, mass losses between elevations did not differ significantly for any litter type.During the winter, lost mass contributed 18.3-28.8 % of the net loss rates of the first year. Statistical analysis showed that the relationships between mass loss and litter chemistry or their ratios varied with decomposition periods. Our results indicated that short-term field incubations could overestimate the k value of litter decomposition.Considerable mass was lost from subalpine forest litters during the wintertime. Potential future warming may not affect the litter decomposition in the subalpine forest ecosystems of eastern Tibetan Plateau.
