Exercise stress echocardiography:Where are we now?

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.

Grain Yield,Biomass Accumulation,and Leaf Photosynthetic Characteristics of Rice under Combined Salinity-Drought Stress

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.

Ergonovine stress echocardiography: Recent experience and safety in our centre

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.

The Value of Speckle Tracking Strain Imaging at Recovery Period of Dobutamine Stress Echocardiography

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.

Prognostic value of left atrial size in hypertensive African Americans undergoing stress echocardiography

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.

Prognostic Utility of Dobutamine Stress Echocardiography in the Obese African American Population

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.

Heat stress induced hepatocyte apoptosis in largemouth bass Micropterus salmoides via IRE1α/TRAF2/ASK1/JNK pathway

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.

Assessment of mitral valve reserve capacity before and after percutaneous balloon valvuloplasty with isoproterenol stress echocardiography

Objective: To explore whether successful valvuloplasty increases mitral valve reserve capacity in patients with mitral stenosis. Methods: Thirty-eight patients with pure rheumatic mitral stenosis underwent isoproterenol stress echocardiography before and after successful percutaneous balloon valvuloplasty. The 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 infusion to achieve heart rate of different stages. Results:Between the measurements before and after valvuloplasty, significant differences were observed in the mitral valve area (0. 91±0. 28 vs 1. 87±0. 23 cm2, P<0. 01), mean transmitral pressure gradient (12. 5±6. 3 vs 3. 9±1. 9 mmHg, P<0. 01) and cardiac output (3. 93±1. 44 vs 4. 73±1. 01 L/min, P<0. 05) at rest. Before valvuloplasty, the mean transmitral pressure gradient increased significantly (P<0. 01) as heart rate increased, but there were no significant differences in the measurements of mitral valve area and cardiac output (both P>0. 05). In contrast, there was a significant increase after valvuloplasty in the mean transmitral pressure gradient (P<0. 01), but both mitral valve area and cardiac output further increased (both P< 0. 01) as heart rate increased. Moreover, valvuloplasty decreased the mean transmitral pressure gradient at peak heart rate from 23. 0±4. 5 to 7. 75±2. 30 mmHg (F<0. 01) under submaximal stress. Conclusion: Successful percutaneous balloon valvuloplasty soon causes a significant increase of mitral valve reserve capacity in patients with mitral stenosis, which is conspicuously manifested under condition of hemodynamic stress. Stress echocardiography provides a safe, feasible and non-invasive means of assessing the reserve capacity.

Disturbance failure mechanism of highly stressed rock in deep excavation:Current status and prospects

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.

Brain region-specific roles of brain-derived neurotrophic factor in social stress-induced depressive-like behavior

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.

Isoproterenol Stress Echocardiography in Assessing Mitral Valve Area Reserve before and after Percutaneous Balloon Valvuloplasty

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.

Overexpression of the transcription factor MdWRKY115 improves drought and osmotic stress tolerance by directly binding to the MdRD22 promoter in apple

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.

Effects of sevoflurane on left ventricular function by speckletracking echocardiography in coronary bypass patients: A randomized trial

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.

Upregulation of the glycine-rich protein-encoding gene GhGRPL enhances plant tolerance to abiotic and biotic stressors by promoting secondary cell wall development

Abiotic and biotic stressors adversely affect plant survival,biomass generation,and crop yields.As the global availability of arable land declines and the impacts of global warming intensify,such stressors may have increasingly pronounced effects on agricultural productivity.Currently,researchers face the overarching challenge of comprehensively enhancing plant resilience to abiotic and biotic stressors.The secondary cell wall plays a crucial role in bolstering the stress resistance of plants.To increase plant resistance to stress through genetic manipulation of the secondary cell wall,we cloned a cell wall protein designated glycine-rich protein-like(GhGRPL)from cotton fibers,and found that it is specifically expressed during the period of secondary cell wall biosynthesis.Notably,this protein differs from its Arabidopsis homolog,AtGRP,since its glycine-rich domain is deficient in glycine residues.GhGRPL is involved in secondary cell wall deposition.Upregulation of GhGRPL enhances lignin accumulation and,consequently,the thickness of the secondary cell walls,thereby increasing the plant’s resistance to abiotic stressors,such as drought and salinity,and biotic threats,including Verticillium dahliae infection.Conversely,interference with GhGRPL expression in cotton reduces lignin accumulation and compromises that resistance.Taken together,our findings elucidate the role of GhGRPL in regulating secondary cell wall development through its influence on lignin deposition,which,in turn,reinforces cell wall robustness and impermeability.These findings highlight the promising near-future prospect of adopting GhGRPL as a viable,effective approach for enhancing plant resilience to abiotic and biotic stress factors.

Three-dimensional stress variation characteristics in deep hard rock of CJPL-Ⅱ project based on in-situ monitoring

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.

Lactobacillus plantarum AR113 attenuates liver injury in D-galactose-induced aging mice via the inhibition of oxidative stress and endoplasmic reticulum stress

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.

Effect of organic mineral supplementation in reducing oxidative stress in Holstein calves during short‑term heat stress and recovery conditions

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.

Effect of Blasting Stress Wave on Dynamic Crack Propagation

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.

Support design method for deep soft-rock tunnels in non-hydrostatic high in-situ stress field

Due to the long-term plate tectonic movements in southwestern China,the in-situ stress field in deep formations is complex.When passing through deep soft-rock mass under non-hydrostatic high in-situ stress field,tunnels will suffer serious asymmetric deformation.There is no available support design method for tunnels under such a situation in existing studies to clarify the support time and support stiffness.This study first analyzed the mechanical behavior of tunnels in non-hydrostatic in-situ stress field and derived the theoretical equations of the ground squeezing curve(GSC)and ground loosening curve(GLC).Then,based on the convergence confinement theory,the support design method of deep soft-rock tunnels under non-hydrostatic high in-situ stress field was established considering both squeezing and loosening pressures.In addition,this method can provide the clear support time and support stiffness of the second layer of initial support.The proposed design method was applied to the Wanhe tunnel of the China-Laos railway in China.Monitoring data indicated that the optimal support scheme had a good effect on controlling the tunnel deformation in non-hydrostatic high in-situ stress field.Field applications showed that the secondary lining could be constructed properly.

Analytical investigations of in situ stress inversion from borehole breakout geometries

This study aims to investigate the feasibility of deriving in situ horizontal stresses from the breakout width and depth using the analytical method.Twenty-three breakout data with different borehole sizes were collected and three failure criteria were studied.Based on the Kirsch equations,relatively accurate major horizontal stress(sH)estimations from known minor horizontal stress(sh)were achieved with percentage errors ranging from 0.33%to 44.08%using the breakout width.The Mogi-Coulomb failure criterion(average error:13.1%)outperformed modified Wiebols-Cook(average error:19.09%)and modified Lade(average error:18.09%)failure criteria.However,none of the tested constitutive models could yield reasonable sh predictions from known sH using the same approach due to the analytical expression of the redistributed stress and the nature of the constitutive models.In consideration of this issue,the horizontal stress ratio(sH/sh)is suggested as an alternative input,which could estimate both sH and sh with the same level of accuracy.Moreover,the estimation accuracies for both large-scale and laboratory-scale breakouts are comparable,suggesting the applicability of this approach across different breakout sizes.For breakout depth,conformal mapping and complex variable method were used to calculate the stress concentration around the breakout tip,allowing the expression of redistributed stresses using binomials composed of sH and sh.Nevertheless,analysis of the breakout depth stabilisation mechanism indicates that additional parameters are required to utilise normalised breakout depth for stress estimation compared to breakout width.These parameters are challenging to obtain,especially under field conditions,meaning utilising normalised breakout depth analytically in practical applications faces significant challenges and remains infeasible at this stage.Nonetheless,the normalised breakout depth should still be considered a critical input for any empirical and statistical stress estimation method given its significant correlation with horizontal stresses.The outcome of this paper is expected to contribute valuable insights into the breakout stabilisation mechanisms and estimation of in situ stress magnitudes based on borehole breakout geometries.