AIM:To study recent experience and safety of ergonovine stress echocardiography in our centre.METHODS:In this study we collected the clinical variables of patients referred since 2002 for ergonovine stress echocardiog...AIM:To study recent experience and safety of ergonovine stress echocardiography in our centre.METHODS:In this study we collected the clinical variables of patients referred since 2002 for ergonovine stress echocardiography,in addition to indications,the results of this test,complications,blood pressure and heart rate values during the test and the number and results of tests requested before this technique.RESULTS:We performed 40 tests in 38 patients,2 tests were carried out to verify therapy efficacy.The prevalence of classic cardiovascular risk factors was low and the most frequent indication was chest pain (57.5%).Coronary angiography was performed in 32 patients,and showed normal coronary arteries in 27 patients and non-significant stenosis in 5 cases.In 16 patients,coronary angiography was carried out after a positive or inconclusive ischemia test.Another 6 patients had a normal stress test(5 exercise electrocardiography tests and 1 nuclear imaging test).Of the 40 ergonovine stress echocardiography tests,6 were positive(4 in the right coronary artery territory and 2 in the circumflex coronary artery territory),all of them by echocardiographic criteria,and by electrocardiographic criteria in only 3(50%).The presence of non-significant coronary artery stenosis was more frequent in patients with positive ergonovine stress echocardiography(50%vs 6%,P =0.038),and were related to ischemic territory.During the maximum stress stage,there was a higher systolic(130.26±19.17 mmHg vs 136.58±27.27 mmHg,95%CI:-12.77 to 0.14 mmHg,P=0.055)and diastolic blood pressure(77.89±13.49 mmHg vs 83.95± 15.73 mmHg,95%CI:-10.41 to-1.69 mmHg,P=0.008) than at the baseline stage,and the same was registered with heart rate(73±10.96 beats/minvs 79.79± 11.72 beats/min,95%CI:-9.46 to-4.11 beats/min,P <0.01).Nevertheless,there were only 2 hypertensive reactions during the last stage,which did not force a premature end to the test,without sustained tachy or bradyarrhythmias,and the technique was well tolerated in 58%of cases.A unique complication(2.5%)of this test was a prolonged vasospasm with a slight increase in necrosis biomarkers,however,this was without repercussion.CONCLUSION:Ergonovine stress echocardiography can be performed with safety,is well tolerated in the majority of cases,and is useful for determining the ischemia mechanism in selected cases.展开更多
Background: Dobutamine stress echocardiography (DSE) is a well-established method for detecting myocardial ischemia. The classic echocardiographic findings of ischemia are new or worsening abnormalities of radial wall...Background: Dobutamine stress echocardiography (DSE) is a well-established method for detecting myocardial ischemia. The classic echocardiographic findings of ischemia are new or worsening abnormalities of radial wall thickening. However, interpretation of these findings is subjective and dependent on experience. Speckle tracking strain imaging (STI) has been introduced as a novel method to overcome these limitations. Objective: The aim of the study is to evaluate the value of speckle tracking imaging (STI) by estimating the mean global longitudinal systolic (GLS) and the mean global circumferential systolic (GCS) strain imaging at recovery period of dobutamine stress echocardiography for prediction of significant coronary artery disease (CAD) in patients with chest discomfort. Methods: Fifty three patients presented for evaluation of chest discomfort underwent dobutamine stress echocardiography and coronary angiography at Cardiology Department,Menoufia University Hospital. The mean global left ventricular longitudinal systolic strain (GLS) at apical views—3 chambers, 4 chambers & 2 chambers apical views and global left ventricular circumferential systolic strain (GCS) at short axis view at level of papillary muscle were measured at rest and during recovery period of dobutamine stress echocardiography using automated functional imaging (AFI). Coronary angiography was done for all patients. Significant coronary artery lesion was defined as having a ≥ 70% diameter stenosis on coronary angiography. Patients were divided into two groups based on the presence or absence of significant coronary artery lesion into CAD positive (+ve) group vs. CAD negative (-ve) group. Results: In both groups,there were no statistically significant differences in the clinical characteristics and baseline conventional transthoracic echocardiography. GLS and GSC at recovery were lower in the CAD (+ve) group than in the CAD (-ve) group (-16.69% ± 1.10% vs -19.05% ± 1.41% p ). GLS and GCS during recovery period of DSE were valuable for prediction of CAD when cutoff at recovery is less than -17.95% (sensitivity of 84% & specificity of 84%) for GLS and less than -20.2% (sensitivity of 76% & specificity of 84%) for GCS. Also, we observed that the GLS and GCS percentile decreased from baseline to recovery period of DSE by about -9.95% ± 4.82% and -7.72% ± 3.90% respectively. Conclusion: Speckle tracking Imaging GLS and GCS at recovery period of Dobutamine Stress Echocardiography is feasible and offers an objective technique for prediction of significant coronary artery disease with increasing the accuracy of DSE in patient with chest discomfort.展开更多
BACKGROUND Left atrial(LA)enlargement is a marker of increased risk in the general population undergoing stress echocardiography.African American(AA)patients with hypertension are known to have less atrial remodeling ...BACKGROUND Left atrial(LA)enlargement is a marker of increased risk in the general population undergoing stress echocardiography.African American(AA)patients with hypertension are known to have less atrial remodeling than whites with hypertension.The prognostic impact of LA enlargement in AA with hypertension undergoing stress echocardiography is uncertain.AIM To investigate the prognostic value of LA size in hypertensive AA patients undergoing stress echocardiography.METHODS This retrospective outcomes study enrolled 583 consecutive hypertensive AA patients who underwent stress echocardiography over a 2.5-year period.Clinical characteristics including cardiovascular risk factors,stress and echocardiographic data were collected from the electronic health record of a large community hospital.Treadmill exercise and Dobutamine protocols were conducted based on standard practices.Patients were followed for all-cause mortality.The optimal cutoff value of antero-posterior LA diameter for mortality was assessed by receiver operating characteristic analysis.Cox regression was used to determine variables associated with outcome.RESULTS The mean age was 57±12 years.LA dilatation was present in 9%(54)of patients(LA anteroposterior≥2.4 cm/m^(2)).There were 85 deaths(15%)during 4.5±1.7 years of follow-up.LA diameter indexed for body surface area had an area under the curve of 0.72±0.03(optimal cut-point of 2.05 cm/m^(2)).Variables independently associated with mortality included age[P=0.004,hazard ratio(HR)1.34(1.10-1.64)],tobacco use[P=0.001,HR 2.59(1.51-4.44)],left ventricular hypertrophy[P=0.001,HR 2.14(1.35-3.39)],Dobutamine stress[P=0.003,HR 2.12(1.29-3.47)],heart failure history[P=0.031,HR 1.76(1.05-2.94)],LA diameter≥2.05 cm/m^(2)[P=0.027,HR 1.73(1.06-2.82)],and an abnormal stress echocardiogram[P=0.033,HR 1.67(1.04-2.68)].LA diameter as a continuous variable was also independently associated with mortality but LA size≥2.40 cm/m^(2) was not.CONCLUSION LA enlargement is infrequent in hypertensive AA patients when traditional reference values are used.LA enlargement is independently associated with mortality when a lower than“normal”threshold(≥2.05 cm/m^(2))is used.展开更多
Background: The predictive value of Dobutamine Stress Echocardiography (DSE) in the obese African American patient population is not well known. Methods: We conducted a retrospective study of 555 African American pati...Background: The predictive value of Dobutamine Stress Echocardiography (DSE) in the obese African American patient population is not well known. Methods: We conducted a retrospective study of 555 African American patients between 1/1/2001-12/31/2001. DSE responses were classified into normal, ischemia, scar, or scar +/? ischemia. End-points utilized were all cause death (ACD) and major adverse cardiac events (MACE). Results: There were a total of 409 obese patients and 146 non-obese patients. By multi-variate analysis only the scar group in the obese population predicted ACD (p = 0.003) and combined MACE (p = 0.014). Kaplan Meir analysis demonstrated that only the scar group was associated with decrease in freedom from all cause death (p < 0.001) and combined MACE (p < 0.001). Conclusion: DSE retains its prognostic power in the obese African American population and scar has important impli-cations for MACE.展开更多
Exercise stress echocardiography(ESE)is a widely used diagnostic test in cardiology departments.ESE is mainly used to study patients with coronary artery disease;however,it has increasingly been used in other clinical...Exercise stress echocardiography(ESE)is a widely used diagnostic test in cardiology departments.ESE is mainly used to study patients with coronary artery disease;however,it has increasingly been used in other clinical scenarios including valve pathology,congenital heart disease,hypertrophic and dilated cardiomyopathies,athlete evaluations,diastolic function evaluation,and pulmonary circulation study.In our laboratories,we use an established methodology in which cardiac function is evaluated while exercising on a treadmill.After completing the exercise regimen,patients remain in a standing position or lie down on the left lateral decubitus,depending on the clinical questions to be answered for further evaluation.This method increases the quality and quantity of information obtained.Here,we present the various methods of exercise stress echocardiography and our experience in many clinical arenas in detail.We also present alternatives to ESE that may be used and their advantages and disadvantages.We review recent advances in ESE and future directions for this established method in the study of cardiac patients and underline the advantage of using a diagnostic tool that is radiation-free.展开更多
Simultaneous stresses of salinity and drought often coincide during rice-growing seasons in saline lands,primarily due to insufficient water resources and inadequate irrigation facilities.Consequently,combined salinit...Simultaneous stresses of salinity and drought often coincide during rice-growing seasons in saline lands,primarily due to insufficient water resources and inadequate irrigation facilities.Consequently,combined salinity-drought stress poses a major threat to rice production.In this study,two salinity levels(NS,non-salinity;HS,high salinity)along with three drought treatments(CC,control condition;DJ,drought stress imposed at jointing;DH,drought stress imposed at heading)were performed to investigate their combined influences on leaf photosynthetic characteristics,biomass accumulation,and rice yield formation.Salinity,drought,and their combination led to a shortened growth period from heading to maturity,resulting in a reduced overall growth duration.Grain yield was reduced under both salinity and drought stress,with a more substantial reduction under the combined salinity-drought stress.The combined stress imposed at heading caused greater yield losses in rice compared with the stress imposed at jointing.Additionally,the combined salinity-drought stress induced greater decreases in shoot biomass accumulation from heading to maturity,as well as in shoot biomass and nonstructural carbohydrate(NSC)content in the stem at heading and maturity.However,it increased the harvest index and NSC remobilization reserve.Salinity and drought reduced the leaf area index and SPAD value of flag leaves and weakened the leaf photosynthetic characteristics as indicated by lower photosynthetic rates,transpiration rates,and stomatal conductance.These reductions were more pronounced under the combined stress.Salinity,drought,and especially their combination,decreased the activities of ascorbate peroxidase,catalase,and superoxide dismutase,while increasing the contents of malondialdehyde,hydrogen peroxide,and superoxide radical.Our results indicated a more significant yield loss in rice when subjected to combined salinity-drought stress.The individual and combined stresses of salinity and drought diminished antioxidant enzyme activities,inhibited leaf photosynthetic functions,accelerated leaf senescence,and subsequently lowered assimilate accumulation and grain yield.展开更多
Heat stress(HS)has been shown to adversely affect fish livers and can lead to extensive apoptosis.To investigate the relationship between endoplasmic reticulum(ER)stress and HS-induced apoptosis in fish livers,we isol...Heat stress(HS)has been shown to adversely affect fish livers and can lead to extensive apoptosis.To investigate the relationship between endoplasmic reticulum(ER)stress and HS-induced apoptosis in fish livers,we isolated and cultured primary hepatocytes of largemouth bass,Micropterus salmoides by trypsin method,then established an in-vitro model of liver cells under HS(35℃).The contents of lactic dehydrogenase(LDH)and hydrogen peroxide(H2O2)were determined to evaluate the effects of HS on hepatocyte injury and oxidative stress.RT-qPCR was performed to discover the key genes in unfolded protein response(UPR)pathways involved at different HS duration.ERS inhibitor 4-PBA and IRE1αinhibitor 4μ8C were used to further investigate the effects of HS on IRE1αapoptosis pathway in hepatocytes.Results show that HS led to significant increases in the release of LDH,the content of H2O2,and the expressions of oxidative protein folding genes(ero1αand pdi)under HS,suggesting severe hepatocyte injury and oxidative stress happened in heat-stressed largemouth bass hepatocytes.The continuous activation of IRE1αpathway genes(grp78,grp94,atf6,perk,eif2a,atf4,chop,ire1α,traf2,ask1,jnk1,and jnk2)indicated that HS led significantly to ER stress.In particular,the mRNA expression levels of ER stress-related genes(grp78,grp94,atf6,perk,ire1α,chop,jnk1,and jnk2)in the high temperature(HT)+4-PBA group and the HT+4μ8C group were significantly down-regulated under HS.After 4μ8C treatment,the expression levels of apoptosis-related genes(caspase-2,caspase-3,caspase-6,caspase-7,caspase-8,caspase-9,and caspase-10)and LDH content were significantly decreased,whereas the cell survival rate was significantly increased when given 4-PBA or 4μ8C treatment.These findings demonstrate that HS could induce liver apoptosis of largemouth bass through the IRE1αpathway,which may act as a key switch mediating liver apoptosis of largemouth bass under HS.展开更多
The hydraulic testing of pre-existing fractures(HTPF)is one of the most promising in situ stress measurement methods,particularly for three-dimensional stress tensor determination.However,the stress tensor determinati...The hydraulic testing of pre-existing fractures(HTPF)is one of the most promising in situ stress measurement methods,particularly for three-dimensional stress tensor determination.However,the stress tensor determination based on the HTPF method requires at least six tests or a minimum of 14-15 tests(under different conditions)for reliable results.In this study,we modified the HTPF method by considering the shear stress on each pre-existing fracture,which increased the number of equations for the stress tensor determination and decreased the number of tests required.Different shear stresses were attributed to different fractures by random sampling;therefore,the stress tensors were obtained by searching for the optimal solution using the least squares criterion based on the Monte Carlo method.Thereafter,we constrained the stress tensor based on the tensile strength criterion,compressive strength criterion,and vertical stress constraints.The inverted stress tensors were presented and analyzed based on the tensorial nature of the stress using the Euclidean mean stress tensor.Two stress-measurement campaigns in Weifang(Shandong Province,China)and Mercantour road tunnel(France)were implemented to highlight the validity and efficiency of the modified HTPF(M-HTPF)method.The results showed that the M-HTPF method can be applied for stress tensor inversion using only three to four tests on pre-existing fractures,neglecting the stress gradient.The inversion results were confined to relatively small distribution dispersions and were significantly reliable and stable due to the shear stresses on the fractures and the stress constraints employed.The M-HTPF method is highly feasible and efficient for complete stress tensor determination in a single borehole.展开更多
In deep hard rock excavation, stress plays a pivotal role in inducing stress-controlled failure. While the impact of excavation-induced stress disturbance on rock failure and tunnel stability has undergone comprehensi...In deep hard rock excavation, stress plays a pivotal role in inducing stress-controlled failure. While the impact of excavation-induced stress disturbance on rock failure and tunnel stability has undergone comprehensive examination through laboratory tests and numerical simulations, its validation through insitu stress tests remains unexplored. This study analyzes the three-dimensional stress changes in the surrounding rock at various depths, monitored during the excavation of B2 Lab in China Jinping Underground Laboratory Phase Ⅱ(CJPL-Ⅱ). The investigation delves into the three-dimensional stress variation characteristics in deep hard rock, encompassing stress components and principal stress. The results indicate changes in both the magnitude and direction of the principal stress during tunnel excavation. To quantitatively describe the degree of stress disturbance, a series of stress evaluation indexes are established based on the distances between stress tensors, including the stress disturbance index(SDI), the principal stress magnitude disturbance index(SDIm), and the principal stress direction disturbance index(SDId). The SDI indicates the greatest stress disturbance in the surrounding rock is 4.5 m from the tunnel wall in B2 Lab. SDIm shows that the principal stress magnitude disturbance peaks at2.5 m from the tunnel wall. SDId reveals that the largest change in principal stress direction does not necessarily occur near the tunnel wall but at a specific depth from it. The established relationship between SDI and the depth of the excavation damaged zone(EDZ) can serve as a criterion for determining the depth of the EDZ in deep hard rock engineering. Additionally, it provides a reference for future construction and support considerations.展开更多
This article reviews the current status on the dynamic behavior of highly stressed rocks under disturbances.Firstly,the experimental apparatus,methods,and theories related to the disturbance dynamics of deep,high-stre...This article reviews the current status on the dynamic behavior of highly stressed rocks under disturbances.Firstly,the experimental apparatus,methods,and theories related to the disturbance dynamics of deep,high-stress rock are reviewed,followed by the introduction of scholars’research on deep rock deformation and failure from an energy perspective.Subsequently,with a backdrop of highstress phenomena in deep hard rock,such as rock bursts and core disking,we delve into the current state of research on rock microstructure analysis and residual stresses from the perspective of studying the energy storage mechanisms in rocks.Thereafter,the current state of research on the mechanical response and the energy dissipation of highly stressed rock formations is briefly retrospected.Finally,the insufficient aspects in the current research on the disturbance and failure mechanisms in deep,highly stressed rock formations are summarized,and prospects for future research are provided.This work provides new avenues for the research on the mechanical response and damage-fracture mechanisms of rocks under high-stress conditions.展开更多
Brain-derived neurotrophic factor is a key factor in stress adaptation and avoidance of a social stress behavioral response.Recent studies have shown that brain-derived neurotrophic factor expression in stressed mice ...Brain-derived neurotrophic factor is a key factor in stress adaptation and avoidance of a social stress behavioral response.Recent studies have shown that brain-derived neurotrophic factor expression in stressed mice is brain region–specific,particularly involving the corticolimbic system,including the ventral tegmental area,nucleus accumbens,prefrontal cortex,amygdala,and hippocampus.Determining how brain-derived neurotrophic factor participates in stress processing in different brain regions will deepen our understanding of social stress psychopathology.In this review,we discuss the expression and regulation of brain-derived neurotrophic factor in stress-sensitive brain regions closely related to the pathophysiology of depression.We focused on associated molecular pathways and neural circuits,with special attention to the brain-derived neurotrophic factor–tropomyosin receptor kinase B signaling pathway and the ventral tegmental area–nucleus accumbens dopamine circuit.We determined that stress-induced alterations in brain-derived neurotrophic factor levels are likely related to the nature,severity,and duration of stress,especially in the above-mentioned brain regions of the corticolimbic system.Therefore,BDNF might be a biological indicator regulating stress-related processes in various brain regions.展开更多
Objective: Bicuspid Aortic Valve (BAV) is normally asymptomatic for a long time in both the general population and regularlytrained athletes. The study aimed to evaluate the role of physical stress echocardiography in...Objective: Bicuspid Aortic Valve (BAV) is normally asymptomatic for a long time in both the general population and regularlytrained athletes. The study aimed to evaluate the role of physical stress echocardiography in early identification of any possible dissimilarities in the Left Ventricle (LV) performance and the valve functioning of asymptomatic BAV athletes as compared to the Tricuspid Aortic Valve (TAV) athletes. Design: Data were collected for BAV and TAV athletes from echocardographic examinations to evaluate any possible differences between them. Setting: Sport Medicine Center University of FlorenceItaly. Participants: 66 male BAV athletes and 45 TAV athletes Assessment of risk factors: decrease in LV performance and aortic valve dysfunction during stress test. Main outcome measures: Measure of the standard echocardiographic parameters. Comparison of LV Ejection Fraction (EF) and Aortic Peak Flow Velocity (APFV) data in the two groups at rest and after stress. Results: At rest, values were normal in both groups, although LV systolic diameters tended to be higher in BAV. After physical effort, APFV and EF showed a significant increase in both groups, and for the former the values were at the upper limits in BAV (2.55 m/s BAV 2.12 m/s TAV). Conclusions: The data confirm normal LV performance in asymptomatic BAV athletes. Considering the tendency of this group to show slight enhancement of both APFV and LV dimensions in this group periodical evaluation with physical stress echography might be proposed as a followup procedure for early detection of any additional effect of physical exercise.展开更多
Objective To determinewhether successful valvuloplasty causes an increase of mitral valve area reserve in patients with mitral stenosis, isoproterenol stress echocardiography was used to compare mitral valve area and ...Objective To determinewhether successful valvuloplasty causes an increase of mitral valve area reserve in patients with mitral stenosis, isoproterenol stress echocardiography was used to compare mitral valve area and hemodynamic changes between pre - and post - valvuloplasty under conditions of increased cardiac work. Methods Thirty-eight patients with pure rheumatic mitral stenosis who had received successful percutaneous balloon valvuloplasty underwent isoproterenol stress echocardiography pre- and post - valvuloplasty. Mitral valve area (by direct planimetry of two - dimensional echocardiography), mean transmitral pressure gradient (by continuous-wave Doppler echocardiography), and cardiac output (by M-mode echocardiography) were measured at rest and under isoproterenol stress to achieve heart rate of different stages. Results Mitral valve area (0.91±0.28 to 1.87±0.23 cm2, P<0. 01), mean transmitral pressure gradient (12. 5±6. 3 to 3. 9± 1. 9 mmHg, P < 0. 01) and cardiac output (3. 93± 1. 44 to 4. 73±1. 01 L/min, P < 0. 05) at rest between pre - and post - valvuloplasty were significantly different. Pre - valvuloplasty, as heart rate increased under stress, mean transmitral pressure gradient increased significantly ( P < 0. 01), but there were no significant differences in the measurements of mitral valve area and cardiac output (both P>0. 05) . In contrast, as heart rate increased post-valvuloplasty, there was a significant increase in mean transmitral pressure gradient (P<0.01), but both mitral valve area and cardiac output further increased significantly (bothP<0. 01) . Moreover, valvuloplasty decreased mean transmitral pressure gradient at peak heart rate from 23. 0±4. 5 to 7. 75 ± 2. 30 mmHg ( P < 0. 01) under submaximal stress. Conclusions Successful percutaneous balloon valvuloplasty soon causes a significant increase of mitral valve area reserve in patients with mitral stenosis, which is markedly manifested under conditions of hemodynamic stress. Stress echocardiog-raphy provides a safe, feasible and non-invasive means of assessing this reserve capacity.展开更多
The present study aimed to dynamically observe the segmental and global myocardial movements of the left ventricle during coronary artery bypass grafting by transesophageal speckle-tracking echocardiography,and to ass...The present study aimed to dynamically observe the segmental and global myocardial movements of the left ventricle during coronary artery bypass grafting by transesophageal speckle-tracking echocardiography,and to assess the effect of sevoflurane on cardiac function.Sixty-four patients scheduled for the off-pump coronary artery bypass grafting were randomly divided into a sevoflurane-based anesthesia(AS)group and a propofolbased total intravenous anesthesia(AA)group.The AS group demonstrated a higher absolute value of left ventricular global longitudinal strain than that of the AA group at both T1(after harvesting all grafts and before coronary anastomosis)and T_(2)(30 min after completing all coronary anastomoses)(P<0.05).Moreover,strain improvement in the segment with the highest preoperative strain was significantly reduced in the AS group,compared with the AA group at both T1 and T_(2)(P<0.01).The flow of the left internal mammary artery-left anterior descending artery graft was superior,and the postoperative concentration of troponin T decreased rapidly in the AS group,compared with the AA group(P<0.05).Compared with total intravenous anesthesia,sevoflurane resulted in a significantly higher global longitudinal strain,stroke volume,and cardiac output.Sevoflurane also led to an amelioration in the condition of the arterial graft.Furthermore,sevoflurane significantly reduced strain improvement in the segmental myocardium with a high preoperative strain value.The findings need to be replicated in larger studies.展开更多
Abiotic stresses, such as drought, salt, extreme temperatures, and heavy metal pollution, are the main environmental factors that limit crop growth and yield. Sorghum, a C4 grass plant with high photosynthetic efficie...Abiotic stresses, such as drought, salt, extreme temperatures, and heavy metal pollution, are the main environmental factors that limit crop growth and yield. Sorghum, a C4 grass plant with high photosynthetic efficiency, can grow in adverse environmental conditions due to its excellent stress resistance characteristics. Therefore, unraveling the stress-resistance mechanism of sorghum could provide a theoretical basis for developing and cultivating various stress-resistant crops. This understanding could also help to create a conducive environment for using marginal soil in agriculture and ensuring food security. In this review, we discuss the adaptation mechanisms of sorghum under drought, salinity, temperature, and soil heavy metal stresses, the specific response to stress, the screening of sorghum-resistant germplasm, and the identification and functional analysis of the relevant genes and quantitative trait loci(QTL). In addition, we discuss the application potential of different stress-tolerant sorghum germplasms reported to date and emphasize the feasibility and potential use in developing and promoting highly stress-tolerant sorghum in marginal soil.展开更多
To gain insight into the flow mechanisms and stress sensitivity for fractured-vuggy reservoirs,several core models with different structural characteristics were designed and fabricated to investigate the impact of ef...To gain insight into the flow mechanisms and stress sensitivity for fractured-vuggy reservoirs,several core models with different structural characteristics were designed and fabricated to investigate the impact of effective stress on permeability for carbonate fractured-vuggy rocks(CFVR).It shows that the permeability performance curves under different pore and confining pressures(i.e.altered stress conditions)for the fractured core models and the vuggy core models have similar change patterns.The ranges of permeability variation are significantly wider at high pore pressures,indicating that permeability reduction is the most significant during the early stage of development for fractured-vuggy reservoirs.Since each obtained effective stress coefficient for permeability(ESCP)varies with the changes in confining pressure and pore pressure,the effective stresses for permeability of four representative CFVR show obvious nonlinear characteristics,and the variation ranges of ESCP are all between 0 and 1.Meanwhile,a comprehensive ESCP mathematical model considering triple media,including matrix pores,fractures,and dissolved vugs,was proposed.It is proved theoretically that the ESCP of CFVR generally varies between 0 and 1.Additionally,the regression results showed that the power model ranked highest among the four empirical models mainly applied in stress sensitivity characterization,followed by the logarithmic model,exponential model,and binomial model.The concept of“permeability decline rate”was introduced to better evaluate the stress sensitivity performance for CFVR,in which the one-fracture rock is the strongest,followed by the fracture-vug rock and two-horizontalfracture rock;the through-hole rock is the weakest.In general,this study provides a theoretical basis to guide the design of development and adjustment programs for carbonate fractured-vuggy reservoirs.展开更多
Abiotic stress reduces plant yield and quality.WRKY transcription factors play key roles in abiotic stress responses in plants,but the molecular mechanisms by which WRKY transcription factors mediate responses to drou...Abiotic stress reduces plant yield and quality.WRKY transcription factors play key roles in abiotic stress responses in plants,but the molecular mechanisms by which WRKY transcription factors mediate responses to drought and osmotic stresses in apple(Malus×domestica Borkh.)remain unclear.Here,we functionally characterized the apple GroupⅢWRKY gene MdWRKY115.qRT-PCR analysis showed that MdWRKY115 expression was up-regulated by drought and osmotic stresses.GUS activity analysis revealed that the promoter activity of MdWRKY115 was enhanced under osmotic stress.Subcellular localization and transactivation assays indicated that MdWRKY115 was localized to the nucleus and had a transcriptional activity domain at the N-terminal region.Transgenic analysis revealed that the overexpression of MdWRKY115 in Arabidopsis plants and in apple callus markedly enhanced their tolerance to drought and osmotic stresses.DNA affinity purification sequencing showed that MdWRKY115 binds to the promoter of the stress-related gene MdRD22.This binding was further verified by an electrophoretic mobility shift assay.Collectively,these findings suggest that MdWRKY115 is an important regulator of osmotic and drought stress tolerance in apple.展开更多
Background This study investigated the effects of inorganic and organic minerals on physiological responses,oxidative stress reduction,and rumen microbiota in Holstein bull calves(123.81±9.76 kg;5 months old)duri...Background This study investigated the effects of inorganic and organic minerals on physiological responses,oxidative stress reduction,and rumen microbiota in Holstein bull calves(123.81±9.76 kg;5 months old)during short-term heat stress(HS)and recovery periods.Eight Holstein calves were randomly assigned to four treatment groups:no mineral supplementation(Con),inorganic minerals(IM),organic minerals(OM),and high-concentration organic minerals(HOM)and two thermal environments(HS and recovery)using 4×2 factorial arrangement in a crossover design of four periods of 35 d.Calves were maintained in a temperature-controlled barn.The experimental period consisted of 14 d of HS,14 d of recovery condititon,and a 7-d washing period.Results Body temperature and respiration rate were higher in HS than in the recovery conditions(P<0.05).Selenium concentration in serum was high in the HOM-supplemented calves in both HS(90.38μg/dL)and recovery periods(102.00μg/dL)(P<0.05).During the HS period,the serum cortisol was 20.26 ng/mL in the HOM group,which was 5.60 ng/mL lower than in the control group(P<0.05).The total antioxidant status was the highest in the OM group(2.71 mmol Trolox equivalent/L),followed by the HOM group during HS,whereas it was highest in the HOM group(2.58 mmol Trolox equivalent/L)during the recovery period(P<0.05).Plasma malondialdehyde and HSP70 levels were decreased by HOM supplementation during the HS and recovery periods,whereas SOD and GPX levels were not significantly affected(P>0.05).The principal coordinate analysis represented that the overall rumen microbiota was not influenced by mineral supplementation;however,temperature-induced microbial structure shifts were indicated(PERMANOVA:P<0.05).At the phylum level,Firmicutes and Actinobacteria decreased,whereas Fibrobacteres,Spirochaetes,and Tenericutes increased(P<0.05),under HS conditions.The genus Treponema increased under HS conditions,while Christensenella was higher in recovery conditions(P<0.05).Conclusion HOM supplementation during HS reduced cortisol concentrations and increased total antioxidant status in Holstein bull calves,suggesting that high organic mineral supplementation may alleviate the adverse effects of HS.展开更多
Probiotics could effectively eliminate excess reactive oxygen species(ROS)generated during aging or lipid metabolism disorders,but their mechanism is unclear.The major purpose of this study was to investigate the mech...Probiotics could effectively eliminate excess reactive oxygen species(ROS)generated during aging or lipid metabolism disorders,but their mechanism is unclear.The major purpose of this study was to investigate the mechanism of Lactiplantibacillus plantarun AR113 alleviating oxidative stress injury in the D-galactose induced aging mice.The result showed that pretreatment with L.plantarun AR113 significantly relieving H_(2)O_(2)induced cytotoxicity in HepG2 cells by maintain cell membrane integrity and increasing antioxidant enzyme activities.In D-galactose induced aging mice,L.plantarun AR113 could significantly attenuate liver damage and inflammatory infiltration by promoting endogenous glutathione(GSH)synthesis and activating the Nrf2/Keap1 signaling pathway in mice,and increasing the expression of regulated phaseⅡdetoxification enzymes and antioxidant enzymes.Further analysis shown that gavage of L.plantarun AR113 could significantly reduce the expression of G protein-coupled receptor 78(GPR78)and C/EBP homologous protein(CHOP)proteins,and promote the restoration of endoplasmic reticulum(ER)homeostasis,thereby activating cell anti-apoptotic pathways.These results were also confirmed in H_(2)O_(2)-treated HepG2 experiments.It indicated that L.plantarun AR113 could inhibit D-galactose-induced liver injury through dual inhibition of ER stress and oxidative stress.L.plantarun AR113 have good application potential in anti-aging and alleviating metabolic disorders.展开更多
Stress waves affect the stress field at the crack tip and dominate the dynamic crack propagation.Therefore,evaluating the influence of blasting stress waves on the crack propagation behavior and the mechanical charact...Stress waves affect the stress field at the crack tip and dominate the dynamic crack propagation.Therefore,evaluating the influence of blasting stress waves on the crack propagation behavior and the mechanical characteristics of crack propagation is of great significance for engineering blasting.In this study,ANSYS/LS-DYNA was used for blasting numerical simulation,in which the propagation characteristics of blasting stress waves and stress field distribution at the crack tip were closely observed.Moreover,ABAQUS was applied for simulating the crack propagation path and calculating dynamic stress intensity factors(DSIFs).The universal function was calculated by the fractalmethod.The results show that:the compressive wave causes the crack to close and the reflected tensile wave drives the crack to initiate and propagate,and failure mode is mainly tensile failure.The crack propagation velocity varies with time,which increases at first and then decreases,and the crack arrest occurs due to the attenuation of stress waves and dissipation of the blasting energy.In addition,crack arrest toughness is smaller than the crack initiation toughness,applied pressure waveforms(such as the peak pressure,duration,waveforms,wavelengths and loading rates)have a great influence on DSIFs.It is conducive to our deep understanding or the study of blasting stress waves dominated fracture,suggesting a broad reference for the further development of rock blasting in engineering practice.展开更多
文摘AIM:To study recent experience and safety of ergonovine stress echocardiography in our centre.METHODS:In this study we collected the clinical variables of patients referred since 2002 for ergonovine stress echocardiography,in addition to indications,the results of this test,complications,blood pressure and heart rate values during the test and the number and results of tests requested before this technique.RESULTS:We performed 40 tests in 38 patients,2 tests were carried out to verify therapy efficacy.The prevalence of classic cardiovascular risk factors was low and the most frequent indication was chest pain (57.5%).Coronary angiography was performed in 32 patients,and showed normal coronary arteries in 27 patients and non-significant stenosis in 5 cases.In 16 patients,coronary angiography was carried out after a positive or inconclusive ischemia test.Another 6 patients had a normal stress test(5 exercise electrocardiography tests and 1 nuclear imaging test).Of the 40 ergonovine stress echocardiography tests,6 were positive(4 in the right coronary artery territory and 2 in the circumflex coronary artery territory),all of them by echocardiographic criteria,and by electrocardiographic criteria in only 3(50%).The presence of non-significant coronary artery stenosis was more frequent in patients with positive ergonovine stress echocardiography(50%vs 6%,P =0.038),and were related to ischemic territory.During the maximum stress stage,there was a higher systolic(130.26±19.17 mmHg vs 136.58±27.27 mmHg,95%CI:-12.77 to 0.14 mmHg,P=0.055)and diastolic blood pressure(77.89±13.49 mmHg vs 83.95± 15.73 mmHg,95%CI:-10.41 to-1.69 mmHg,P=0.008) than at the baseline stage,and the same was registered with heart rate(73±10.96 beats/minvs 79.79± 11.72 beats/min,95%CI:-9.46 to-4.11 beats/min,P <0.01).Nevertheless,there were only 2 hypertensive reactions during the last stage,which did not force a premature end to the test,without sustained tachy or bradyarrhythmias,and the technique was well tolerated in 58%of cases.A unique complication(2.5%)of this test was a prolonged vasospasm with a slight increase in necrosis biomarkers,however,this was without repercussion.CONCLUSION:Ergonovine stress echocardiography can be performed with safety,is well tolerated in the majority of cases,and is useful for determining the ischemia mechanism in selected cases.
文摘Background: Dobutamine stress echocardiography (DSE) is a well-established method for detecting myocardial ischemia. The classic echocardiographic findings of ischemia are new or worsening abnormalities of radial wall thickening. However, interpretation of these findings is subjective and dependent on experience. Speckle tracking strain imaging (STI) has been introduced as a novel method to overcome these limitations. Objective: The aim of the study is to evaluate the value of speckle tracking imaging (STI) by estimating the mean global longitudinal systolic (GLS) and the mean global circumferential systolic (GCS) strain imaging at recovery period of dobutamine stress echocardiography for prediction of significant coronary artery disease (CAD) in patients with chest discomfort. Methods: Fifty three patients presented for evaluation of chest discomfort underwent dobutamine stress echocardiography and coronary angiography at Cardiology Department,Menoufia University Hospital. The mean global left ventricular longitudinal systolic strain (GLS) at apical views—3 chambers, 4 chambers & 2 chambers apical views and global left ventricular circumferential systolic strain (GCS) at short axis view at level of papillary muscle were measured at rest and during recovery period of dobutamine stress echocardiography using automated functional imaging (AFI). Coronary angiography was done for all patients. Significant coronary artery lesion was defined as having a ≥ 70% diameter stenosis on coronary angiography. Patients were divided into two groups based on the presence or absence of significant coronary artery lesion into CAD positive (+ve) group vs. CAD negative (-ve) group. Results: In both groups,there were no statistically significant differences in the clinical characteristics and baseline conventional transthoracic echocardiography. GLS and GSC at recovery were lower in the CAD (+ve) group than in the CAD (-ve) group (-16.69% ± 1.10% vs -19.05% ± 1.41% p ). GLS and GCS during recovery period of DSE were valuable for prediction of CAD when cutoff at recovery is less than -17.95% (sensitivity of 84% & specificity of 84%) for GLS and less than -20.2% (sensitivity of 76% & specificity of 84%) for GCS. Also, we observed that the GLS and GCS percentile decreased from baseline to recovery period of DSE by about -9.95% ± 4.82% and -7.72% ± 3.90% respectively. Conclusion: Speckle tracking Imaging GLS and GCS at recovery period of Dobutamine Stress Echocardiography is feasible and offers an objective technique for prediction of significant coronary artery disease with increasing the accuracy of DSE in patient with chest discomfort.
文摘BACKGROUND Left atrial(LA)enlargement is a marker of increased risk in the general population undergoing stress echocardiography.African American(AA)patients with hypertension are known to have less atrial remodeling than whites with hypertension.The prognostic impact of LA enlargement in AA with hypertension undergoing stress echocardiography is uncertain.AIM To investigate the prognostic value of LA size in hypertensive AA patients undergoing stress echocardiography.METHODS This retrospective outcomes study enrolled 583 consecutive hypertensive AA patients who underwent stress echocardiography over a 2.5-year period.Clinical characteristics including cardiovascular risk factors,stress and echocardiographic data were collected from the electronic health record of a large community hospital.Treadmill exercise and Dobutamine protocols were conducted based on standard practices.Patients were followed for all-cause mortality.The optimal cutoff value of antero-posterior LA diameter for mortality was assessed by receiver operating characteristic analysis.Cox regression was used to determine variables associated with outcome.RESULTS The mean age was 57±12 years.LA dilatation was present in 9%(54)of patients(LA anteroposterior≥2.4 cm/m^(2)).There were 85 deaths(15%)during 4.5±1.7 years of follow-up.LA diameter indexed for body surface area had an area under the curve of 0.72±0.03(optimal cut-point of 2.05 cm/m^(2)).Variables independently associated with mortality included age[P=0.004,hazard ratio(HR)1.34(1.10-1.64)],tobacco use[P=0.001,HR 2.59(1.51-4.44)],left ventricular hypertrophy[P=0.001,HR 2.14(1.35-3.39)],Dobutamine stress[P=0.003,HR 2.12(1.29-3.47)],heart failure history[P=0.031,HR 1.76(1.05-2.94)],LA diameter≥2.05 cm/m^(2)[P=0.027,HR 1.73(1.06-2.82)],and an abnormal stress echocardiogram[P=0.033,HR 1.67(1.04-2.68)].LA diameter as a continuous variable was also independently associated with mortality but LA size≥2.40 cm/m^(2) was not.CONCLUSION LA enlargement is infrequent in hypertensive AA patients when traditional reference values are used.LA enlargement is independently associated with mortality when a lower than“normal”threshold(≥2.05 cm/m^(2))is used.
文摘Background: The predictive value of Dobutamine Stress Echocardiography (DSE) in the obese African American patient population is not well known. Methods: We conducted a retrospective study of 555 African American patients between 1/1/2001-12/31/2001. DSE responses were classified into normal, ischemia, scar, or scar +/? ischemia. End-points utilized were all cause death (ACD) and major adverse cardiac events (MACE). Results: There were a total of 409 obese patients and 146 non-obese patients. By multi-variate analysis only the scar group in the obese population predicted ACD (p = 0.003) and combined MACE (p = 0.014). Kaplan Meir analysis demonstrated that only the scar group was associated with decrease in freedom from all cause death (p < 0.001) and combined MACE (p < 0.001). Conclusion: DSE retains its prognostic power in the obese African American population and scar has important impli-cations for MACE.
文摘Exercise stress echocardiography(ESE)is a widely used diagnostic test in cardiology departments.ESE is mainly used to study patients with coronary artery disease;however,it has increasingly been used in other clinical scenarios including valve pathology,congenital heart disease,hypertrophic and dilated cardiomyopathies,athlete evaluations,diastolic function evaluation,and pulmonary circulation study.In our laboratories,we use an established methodology in which cardiac function is evaluated while exercising on a treadmill.After completing the exercise regimen,patients remain in a standing position or lie down on the left lateral decubitus,depending on the clinical questions to be answered for further evaluation.This method increases the quality and quantity of information obtained.Here,we present the various methods of exercise stress echocardiography and our experience in many clinical arenas in detail.We also present alternatives to ESE that may be used and their advantages and disadvantages.We review recent advances in ESE and future directions for this established method in the study of cardiac patients and underline the advantage of using a diagnostic tool that is radiation-free.
基金financed by the National Key Research and Development Program,China(Grant Nos.2022YFE0113400 and 2022YFD1500402)National Natural Science Foundation of China(Grant No.32001466)+3 种基金Scientific and Technological Innovation Fund of Carbon Emissions Peak and Neutrality of Jiangsu Provincial Department of Science and Technology,China(Grant Nos.BE2022304 and BE2022305)Joints Funds of the National Natural Science Foundation of China(Grant No.U20A2022)Postdoctoral Research Foundation of China(Grant No.2020M671628)the Priority Academic Program Development of Jiangsu Higher Education Institutions,China.
文摘Simultaneous stresses of salinity and drought often coincide during rice-growing seasons in saline lands,primarily due to insufficient water resources and inadequate irrigation facilities.Consequently,combined salinity-drought stress poses a major threat to rice production.In this study,two salinity levels(NS,non-salinity;HS,high salinity)along with three drought treatments(CC,control condition;DJ,drought stress imposed at jointing;DH,drought stress imposed at heading)were performed to investigate their combined influences on leaf photosynthetic characteristics,biomass accumulation,and rice yield formation.Salinity,drought,and their combination led to a shortened growth period from heading to maturity,resulting in a reduced overall growth duration.Grain yield was reduced under both salinity and drought stress,with a more substantial reduction under the combined salinity-drought stress.The combined stress imposed at heading caused greater yield losses in rice compared with the stress imposed at jointing.Additionally,the combined salinity-drought stress induced greater decreases in shoot biomass accumulation from heading to maturity,as well as in shoot biomass and nonstructural carbohydrate(NSC)content in the stem at heading and maturity.However,it increased the harvest index and NSC remobilization reserve.Salinity and drought reduced the leaf area index and SPAD value of flag leaves and weakened the leaf photosynthetic characteristics as indicated by lower photosynthetic rates,transpiration rates,and stomatal conductance.These reductions were more pronounced under the combined stress.Salinity,drought,and especially their combination,decreased the activities of ascorbate peroxidase,catalase,and superoxide dismutase,while increasing the contents of malondialdehyde,hydrogen peroxide,and superoxide radical.Our results indicated a more significant yield loss in rice when subjected to combined salinity-drought stress.The individual and combined stresses of salinity and drought diminished antioxidant enzyme activities,inhibited leaf photosynthetic functions,accelerated leaf senescence,and subsequently lowered assimilate accumulation and grain yield.
基金Supported by the Scientific Fund of Jiangsu Province(No.BY2015039-10)the Aquatic Three Project of Jiangsu Province(No.Y2017-37)+2 种基金the Priority Academic Program Development of Jiangsu Higher Education Institutions(PAPD)the Top-notch Academic Programs Project of Jiangsu Higher Education Institutions(TAPP)the Jiangsu Funding Program for Excellent Postdoctoral Talent。
文摘Heat stress(HS)has been shown to adversely affect fish livers and can lead to extensive apoptosis.To investigate the relationship between endoplasmic reticulum(ER)stress and HS-induced apoptosis in fish livers,we isolated and cultured primary hepatocytes of largemouth bass,Micropterus salmoides by trypsin method,then established an in-vitro model of liver cells under HS(35℃).The contents of lactic dehydrogenase(LDH)and hydrogen peroxide(H2O2)were determined to evaluate the effects of HS on hepatocyte injury and oxidative stress.RT-qPCR was performed to discover the key genes in unfolded protein response(UPR)pathways involved at different HS duration.ERS inhibitor 4-PBA and IRE1αinhibitor 4μ8C were used to further investigate the effects of HS on IRE1αapoptosis pathway in hepatocytes.Results show that HS led to significant increases in the release of LDH,the content of H2O2,and the expressions of oxidative protein folding genes(ero1αand pdi)under HS,suggesting severe hepatocyte injury and oxidative stress happened in heat-stressed largemouth bass hepatocytes.The continuous activation of IRE1αpathway genes(grp78,grp94,atf6,perk,eif2a,atf4,chop,ire1α,traf2,ask1,jnk1,and jnk2)indicated that HS led significantly to ER stress.In particular,the mRNA expression levels of ER stress-related genes(grp78,grp94,atf6,perk,ire1α,chop,jnk1,and jnk2)in the high temperature(HT)+4-PBA group and the HT+4μ8C group were significantly down-regulated under HS.After 4μ8C treatment,the expression levels of apoptosis-related genes(caspase-2,caspase-3,caspase-6,caspase-7,caspase-8,caspase-9,and caspase-10)and LDH content were significantly decreased,whereas the cell survival rate was significantly increased when given 4-PBA or 4μ8C treatment.These findings demonstrate that HS could induce liver apoptosis of largemouth bass through the IRE1αpathway,which may act as a key switch mediating liver apoptosis of largemouth bass under HS.
基金supported by the National Natural Science Foundation of China(Grant No.42174118)a research grant(Grant No.ZDJ 2020-7)from the National Institute of Natural Hazards,Ministry of Emergency Management of China.
文摘The hydraulic testing of pre-existing fractures(HTPF)is one of the most promising in situ stress measurement methods,particularly for three-dimensional stress tensor determination.However,the stress tensor determination based on the HTPF method requires at least six tests or a minimum of 14-15 tests(under different conditions)for reliable results.In this study,we modified the HTPF method by considering the shear stress on each pre-existing fracture,which increased the number of equations for the stress tensor determination and decreased the number of tests required.Different shear stresses were attributed to different fractures by random sampling;therefore,the stress tensors were obtained by searching for the optimal solution using the least squares criterion based on the Monte Carlo method.Thereafter,we constrained the stress tensor based on the tensile strength criterion,compressive strength criterion,and vertical stress constraints.The inverted stress tensors were presented and analyzed based on the tensorial nature of the stress using the Euclidean mean stress tensor.Two stress-measurement campaigns in Weifang(Shandong Province,China)and Mercantour road tunnel(France)were implemented to highlight the validity and efficiency of the modified HTPF(M-HTPF)method.The results showed that the M-HTPF method can be applied for stress tensor inversion using only three to four tests on pre-existing fractures,neglecting the stress gradient.The inversion results were confined to relatively small distribution dispersions and were significantly reliable and stable due to the shear stresses on the fractures and the stress constraints employed.The M-HTPF method is highly feasible and efficient for complete stress tensor determination in a single borehole.
基金financial support for this work from the National Natural Science Foundation of China(Nos.42202320 and 42102266)the Open Project of Engineering Research Center of Phosphorus Resources Development and Utilization of Ministry of Education(No.LKF201901).
文摘In deep hard rock excavation, stress plays a pivotal role in inducing stress-controlled failure. While the impact of excavation-induced stress disturbance on rock failure and tunnel stability has undergone comprehensive examination through laboratory tests and numerical simulations, its validation through insitu stress tests remains unexplored. This study analyzes the three-dimensional stress changes in the surrounding rock at various depths, monitored during the excavation of B2 Lab in China Jinping Underground Laboratory Phase Ⅱ(CJPL-Ⅱ). The investigation delves into the three-dimensional stress variation characteristics in deep hard rock, encompassing stress components and principal stress. The results indicate changes in both the magnitude and direction of the principal stress during tunnel excavation. To quantitatively describe the degree of stress disturbance, a series of stress evaluation indexes are established based on the distances between stress tensors, including the stress disturbance index(SDI), the principal stress magnitude disturbance index(SDIm), and the principal stress direction disturbance index(SDId). The SDI indicates the greatest stress disturbance in the surrounding rock is 4.5 m from the tunnel wall in B2 Lab. SDIm shows that the principal stress magnitude disturbance peaks at2.5 m from the tunnel wall. SDId reveals that the largest change in principal stress direction does not necessarily occur near the tunnel wall but at a specific depth from it. The established relationship between SDI and the depth of the excavation damaged zone(EDZ) can serve as a criterion for determining the depth of the EDZ in deep hard rock engineering. Additionally, it provides a reference for future construction and support considerations.
基金supported by the National Natural Science Foundation of China(Nos.52004015,51874014,and 52311530070)the fellowship of China National Postdoctoral Program for Innovative Talents(No.BX2021033)+1 种基金the fellowship of China Postdoctoral Science Foundation(Nos.2021M700389 and 2023T0025)the Fundamental Research Funds for the Central Universities of China(No.FRF-IDRY-20-003,Interdisciplinary Research Project for Young Teachers of USTB).
文摘This article reviews the current status on the dynamic behavior of highly stressed rocks under disturbances.Firstly,the experimental apparatus,methods,and theories related to the disturbance dynamics of deep,high-stress rock are reviewed,followed by the introduction of scholars’research on deep rock deformation and failure from an energy perspective.Subsequently,with a backdrop of highstress phenomena in deep hard rock,such as rock bursts and core disking,we delve into the current state of research on rock microstructure analysis and residual stresses from the perspective of studying the energy storage mechanisms in rocks.Thereafter,the current state of research on the mechanical response and the energy dissipation of highly stressed rock formations is briefly retrospected.Finally,the insufficient aspects in the current research on the disturbance and failure mechanisms in deep,highly stressed rock formations are summarized,and prospects for future research are provided.This work provides new avenues for the research on the mechanical response and damage-fracture mechanisms of rocks under high-stress conditions.
基金supported financially by the National Natural Science Foundation of China,No.82071272(to YZ).
文摘Brain-derived neurotrophic factor is a key factor in stress adaptation and avoidance of a social stress behavioral response.Recent studies have shown that brain-derived neurotrophic factor expression in stressed mice is brain region–specific,particularly involving the corticolimbic system,including the ventral tegmental area,nucleus accumbens,prefrontal cortex,amygdala,and hippocampus.Determining how brain-derived neurotrophic factor participates in stress processing in different brain regions will deepen our understanding of social stress psychopathology.In this review,we discuss the expression and regulation of brain-derived neurotrophic factor in stress-sensitive brain regions closely related to the pathophysiology of depression.We focused on associated molecular pathways and neural circuits,with special attention to the brain-derived neurotrophic factor–tropomyosin receptor kinase B signaling pathway and the ventral tegmental area–nucleus accumbens dopamine circuit.We determined that stress-induced alterations in brain-derived neurotrophic factor levels are likely related to the nature,severity,and duration of stress,especially in the above-mentioned brain regions of the corticolimbic system.Therefore,BDNF might be a biological indicator regulating stress-related processes in various brain regions.
文摘Objective: Bicuspid Aortic Valve (BAV) is normally asymptomatic for a long time in both the general population and regularlytrained athletes. The study aimed to evaluate the role of physical stress echocardiography in early identification of any possible dissimilarities in the Left Ventricle (LV) performance and the valve functioning of asymptomatic BAV athletes as compared to the Tricuspid Aortic Valve (TAV) athletes. Design: Data were collected for BAV and TAV athletes from echocardographic examinations to evaluate any possible differences between them. Setting: Sport Medicine Center University of FlorenceItaly. Participants: 66 male BAV athletes and 45 TAV athletes Assessment of risk factors: decrease in LV performance and aortic valve dysfunction during stress test. Main outcome measures: Measure of the standard echocardiographic parameters. Comparison of LV Ejection Fraction (EF) and Aortic Peak Flow Velocity (APFV) data in the two groups at rest and after stress. Results: At rest, values were normal in both groups, although LV systolic diameters tended to be higher in BAV. After physical effort, APFV and EF showed a significant increase in both groups, and for the former the values were at the upper limits in BAV (2.55 m/s BAV 2.12 m/s TAV). Conclusions: The data confirm normal LV performance in asymptomatic BAV athletes. Considering the tendency of this group to show slight enhancement of both APFV and LV dimensions in this group periodical evaluation with physical stress echography might be proposed as a followup procedure for early detection of any additional effect of physical exercise.
文摘Objective To determinewhether successful valvuloplasty causes an increase of mitral valve area reserve in patients with mitral stenosis, isoproterenol stress echocardiography was used to compare mitral valve area and hemodynamic changes between pre - and post - valvuloplasty under conditions of increased cardiac work. Methods Thirty-eight patients with pure rheumatic mitral stenosis who had received successful percutaneous balloon valvuloplasty underwent isoproterenol stress echocardiography pre- and post - valvuloplasty. Mitral valve area (by direct planimetry of two - dimensional echocardiography), mean transmitral pressure gradient (by continuous-wave Doppler echocardiography), and cardiac output (by M-mode echocardiography) were measured at rest and under isoproterenol stress to achieve heart rate of different stages. Results Mitral valve area (0.91±0.28 to 1.87±0.23 cm2, P<0. 01), mean transmitral pressure gradient (12. 5±6. 3 to 3. 9± 1. 9 mmHg, P < 0. 01) and cardiac output (3. 93± 1. 44 to 4. 73±1. 01 L/min, P < 0. 05) at rest between pre - and post - valvuloplasty were significantly different. Pre - valvuloplasty, as heart rate increased under stress, mean transmitral pressure gradient increased significantly ( P < 0. 01), but there were no significant differences in the measurements of mitral valve area and cardiac output (both P>0. 05) . In contrast, as heart rate increased post-valvuloplasty, there was a significant increase in mean transmitral pressure gradient (P<0.01), but both mitral valve area and cardiac output further increased significantly (bothP<0. 01) . Moreover, valvuloplasty decreased mean transmitral pressure gradient at peak heart rate from 23. 0±4. 5 to 7. 75 ± 2. 30 mmHg ( P < 0. 01) under submaximal stress. Conclusions Successful percutaneous balloon valvuloplasty soon causes a significant increase of mitral valve area reserve in patients with mitral stenosis, which is markedly manifested under conditions of hemodynamic stress. Stress echocardiog-raphy provides a safe, feasible and non-invasive means of assessing this reserve capacity.
基金supported by Jiangsu Province Hospital(the First Affiliated Hospital of Nanjing Medical University)Clinical Capacity Enhancement and was awarded to the first author,Chanjuan Gong(Grant No.JSPH-MC-2022-4).
文摘The present study aimed to dynamically observe the segmental and global myocardial movements of the left ventricle during coronary artery bypass grafting by transesophageal speckle-tracking echocardiography,and to assess the effect of sevoflurane on cardiac function.Sixty-four patients scheduled for the off-pump coronary artery bypass grafting were randomly divided into a sevoflurane-based anesthesia(AS)group and a propofolbased total intravenous anesthesia(AA)group.The AS group demonstrated a higher absolute value of left ventricular global longitudinal strain than that of the AA group at both T1(after harvesting all grafts and before coronary anastomosis)and T_(2)(30 min after completing all coronary anastomoses)(P<0.05).Moreover,strain improvement in the segment with the highest preoperative strain was significantly reduced in the AS group,compared with the AA group at both T1 and T_(2)(P<0.01).The flow of the left internal mammary artery-left anterior descending artery graft was superior,and the postoperative concentration of troponin T decreased rapidly in the AS group,compared with the AA group(P<0.05).Compared with total intravenous anesthesia,sevoflurane resulted in a significantly higher global longitudinal strain,stroke volume,and cardiac output.Sevoflurane also led to an amelioration in the condition of the arterial graft.Furthermore,sevoflurane significantly reduced strain improvement in the segmental myocardium with a high preoperative strain value.The findings need to be replicated in larger studies.
基金financial support from the National Key R&D Program of China(2022YFD1201702)the National Natural Science Foundation of China(32272040)the Agricultural Fine Seed Project of Shandong Province,China(2021LZGC006)。
文摘Abiotic stresses, such as drought, salt, extreme temperatures, and heavy metal pollution, are the main environmental factors that limit crop growth and yield. Sorghum, a C4 grass plant with high photosynthetic efficiency, can grow in adverse environmental conditions due to its excellent stress resistance characteristics. Therefore, unraveling the stress-resistance mechanism of sorghum could provide a theoretical basis for developing and cultivating various stress-resistant crops. This understanding could also help to create a conducive environment for using marginal soil in agriculture and ensuring food security. In this review, we discuss the adaptation mechanisms of sorghum under drought, salinity, temperature, and soil heavy metal stresses, the specific response to stress, the screening of sorghum-resistant germplasm, and the identification and functional analysis of the relevant genes and quantitative trait loci(QTL). In addition, we discuss the application potential of different stress-tolerant sorghum germplasms reported to date and emphasize the feasibility and potential use in developing and promoting highly stress-tolerant sorghum in marginal soil.
基金This work was supported by the Joint Fund of NSFC for Enterprise Innovation and Development(Grant No.U19B6003-02-06)the National Natural Science Foundation of China(Grant No.51974331)+1 种基金the Natural Science Foundation of Jiangsu Province(Grant No.BK20200525)The authors would like to sincerely acknowledge these funding programs for their financial support.Particularly,the support provided by the China Scholarship Council(CSC)during a visit of Ke Sun(File No.202106440065)to the University of Alberta is also sincerely acknowledged.
文摘To gain insight into the flow mechanisms and stress sensitivity for fractured-vuggy reservoirs,several core models with different structural characteristics were designed and fabricated to investigate the impact of effective stress on permeability for carbonate fractured-vuggy rocks(CFVR).It shows that the permeability performance curves under different pore and confining pressures(i.e.altered stress conditions)for the fractured core models and the vuggy core models have similar change patterns.The ranges of permeability variation are significantly wider at high pore pressures,indicating that permeability reduction is the most significant during the early stage of development for fractured-vuggy reservoirs.Since each obtained effective stress coefficient for permeability(ESCP)varies with the changes in confining pressure and pore pressure,the effective stresses for permeability of four representative CFVR show obvious nonlinear characteristics,and the variation ranges of ESCP are all between 0 and 1.Meanwhile,a comprehensive ESCP mathematical model considering triple media,including matrix pores,fractures,and dissolved vugs,was proposed.It is proved theoretically that the ESCP of CFVR generally varies between 0 and 1.Additionally,the regression results showed that the power model ranked highest among the four empirical models mainly applied in stress sensitivity characterization,followed by the logarithmic model,exponential model,and binomial model.The concept of“permeability decline rate”was introduced to better evaluate the stress sensitivity performance for CFVR,in which the one-fracture rock is the strongest,followed by the fracture-vug rock and two-horizontalfracture rock;the through-hole rock is the weakest.In general,this study provides a theoretical basis to guide the design of development and adjustment programs for carbonate fractured-vuggy reservoirs.
基金supported by grants from the Natural Science Foundation of Hebei Province(Grant No.C2022204086)the Hebei Apple Innovation Team of Modern Agricultural Industry Technology System(Grant No.HBCT2021100211)the National Natural Science Foundation of China(Grant No.32072524).
文摘Abiotic stress reduces plant yield and quality.WRKY transcription factors play key roles in abiotic stress responses in plants,but the molecular mechanisms by which WRKY transcription factors mediate responses to drought and osmotic stresses in apple(Malus×domestica Borkh.)remain unclear.Here,we functionally characterized the apple GroupⅢWRKY gene MdWRKY115.qRT-PCR analysis showed that MdWRKY115 expression was up-regulated by drought and osmotic stresses.GUS activity analysis revealed that the promoter activity of MdWRKY115 was enhanced under osmotic stress.Subcellular localization and transactivation assays indicated that MdWRKY115 was localized to the nucleus and had a transcriptional activity domain at the N-terminal region.Transgenic analysis revealed that the overexpression of MdWRKY115 in Arabidopsis plants and in apple callus markedly enhanced their tolerance to drought and osmotic stresses.DNA affinity purification sequencing showed that MdWRKY115 binds to the promoter of the stress-related gene MdRD22.This binding was further verified by an electrophoretic mobility shift assay.Collectively,these findings suggest that MdWRKY115 is an important regulator of osmotic and drought stress tolerance in apple.
基金supported by the Cooperative Research Program for Agriculture Science and Technology Development(Project No.PJ015039032023)Rural Development Administration,Republic of Korea.
文摘Background This study investigated the effects of inorganic and organic minerals on physiological responses,oxidative stress reduction,and rumen microbiota in Holstein bull calves(123.81±9.76 kg;5 months old)during short-term heat stress(HS)and recovery periods.Eight Holstein calves were randomly assigned to four treatment groups:no mineral supplementation(Con),inorganic minerals(IM),organic minerals(OM),and high-concentration organic minerals(HOM)and two thermal environments(HS and recovery)using 4×2 factorial arrangement in a crossover design of four periods of 35 d.Calves were maintained in a temperature-controlled barn.The experimental period consisted of 14 d of HS,14 d of recovery condititon,and a 7-d washing period.Results Body temperature and respiration rate were higher in HS than in the recovery conditions(P<0.05).Selenium concentration in serum was high in the HOM-supplemented calves in both HS(90.38μg/dL)and recovery periods(102.00μg/dL)(P<0.05).During the HS period,the serum cortisol was 20.26 ng/mL in the HOM group,which was 5.60 ng/mL lower than in the control group(P<0.05).The total antioxidant status was the highest in the OM group(2.71 mmol Trolox equivalent/L),followed by the HOM group during HS,whereas it was highest in the HOM group(2.58 mmol Trolox equivalent/L)during the recovery period(P<0.05).Plasma malondialdehyde and HSP70 levels were decreased by HOM supplementation during the HS and recovery periods,whereas SOD and GPX levels were not significantly affected(P>0.05).The principal coordinate analysis represented that the overall rumen microbiota was not influenced by mineral supplementation;however,temperature-induced microbial structure shifts were indicated(PERMANOVA:P<0.05).At the phylum level,Firmicutes and Actinobacteria decreased,whereas Fibrobacteres,Spirochaetes,and Tenericutes increased(P<0.05),under HS conditions.The genus Treponema increased under HS conditions,while Christensenella was higher in recovery conditions(P<0.05).Conclusion HOM supplementation during HS reduced cortisol concentrations and increased total antioxidant status in Holstein bull calves,suggesting that high organic mineral supplementation may alleviate the adverse effects of HS.
基金supported by the National Science Fund for Distinguished Young Scholars(32025029)the Shanghai Education Committee Scientific Research Innovation Projects(2101070007800120)+1 种基金the Yili Health Science Foundation of Chinese Institute of Food Science and Technology(2021-Y06)the Shanghai Engineering Research Center of food microbiology program(19DZ2281100)。
文摘Probiotics could effectively eliminate excess reactive oxygen species(ROS)generated during aging or lipid metabolism disorders,but their mechanism is unclear.The major purpose of this study was to investigate the mechanism of Lactiplantibacillus plantarun AR113 alleviating oxidative stress injury in the D-galactose induced aging mice.The result showed that pretreatment with L.plantarun AR113 significantly relieving H_(2)O_(2)induced cytotoxicity in HepG2 cells by maintain cell membrane integrity and increasing antioxidant enzyme activities.In D-galactose induced aging mice,L.plantarun AR113 could significantly attenuate liver damage and inflammatory infiltration by promoting endogenous glutathione(GSH)synthesis and activating the Nrf2/Keap1 signaling pathway in mice,and increasing the expression of regulated phaseⅡdetoxification enzymes and antioxidant enzymes.Further analysis shown that gavage of L.plantarun AR113 could significantly reduce the expression of G protein-coupled receptor 78(GPR78)and C/EBP homologous protein(CHOP)proteins,and promote the restoration of endoplasmic reticulum(ER)homeostasis,thereby activating cell anti-apoptotic pathways.These results were also confirmed in H_(2)O_(2)-treated HepG2 experiments.It indicated that L.plantarun AR113 could inhibit D-galactose-induced liver injury through dual inhibition of ER stress and oxidative stress.L.plantarun AR113 have good application potential in anti-aging and alleviating metabolic disorders.
基金This researchwas supported by the National Natural Science Foundation of China(No.52227805)the Fundamental Research Funds for Central Universities(No.2022JCCXLJ01).Awards were granted to the author Liyun Yang.
文摘Stress waves affect the stress field at the crack tip and dominate the dynamic crack propagation.Therefore,evaluating the influence of blasting stress waves on the crack propagation behavior and the mechanical characteristics of crack propagation is of great significance for engineering blasting.In this study,ANSYS/LS-DYNA was used for blasting numerical simulation,in which the propagation characteristics of blasting stress waves and stress field distribution at the crack tip were closely observed.Moreover,ABAQUS was applied for simulating the crack propagation path and calculating dynamic stress intensity factors(DSIFs).The universal function was calculated by the fractalmethod.The results show that:the compressive wave causes the crack to close and the reflected tensile wave drives the crack to initiate and propagate,and failure mode is mainly tensile failure.The crack propagation velocity varies with time,which increases at first and then decreases,and the crack arrest occurs due to the attenuation of stress waves and dissipation of the blasting energy.In addition,crack arrest toughness is smaller than the crack initiation toughness,applied pressure waveforms(such as the peak pressure,duration,waveforms,wavelengths and loading rates)have a great influence on DSIFs.It is conducive to our deep understanding or the study of blasting stress waves dominated fracture,suggesting a broad reference for the further development of rock blasting in engineering practice.