BACKGROUND:Acute myocardial infarction can cause cardiac remodeling and heart failure,as well as skeletal myopathy,affecting patients'quality of life.Exercise therapy is an important rehabilitation method for patients with heart failure;however,the optimal exercise prescription has not been clarified. OBJECTIVE:To compare the effects of different exercise modes(aerobic exercise,resistance exercise)on skeletal muscle remodeling in rats with acute myocardial infarction induced heart failure and to explore the possible mechanism,so as to provide a basis for optimizing the exercise rehabilitation program. METHODS:Forty-eight Sprague-Dawley rats were randomly divided into sham operation group,myocardial infarction group,aerobic exercise group and resistance exercise group.Coronary artery ligation was used to create model of heart failure.After 3 months,animals in the aerobic exercise group and resistance exercise group underwent 12 weeks of corresponding exercise mode interventions,while those in the sham operation group and myocardial infarction group were kept quietly in mouse cages.After the experiment,maximal running speed and maximal weight-bearing load were measured by graded treadmill exercise test and ladder-climbing test respectively,and heart structure and function were evaluated by echocardiography.The heart was isolated,and hematoxylin-eosin staining and Sirius red staining were performed to detect cardiac remodeling.For the gstrocnemius muscle,ATPase staining was performed to observe changes in muscle fiber type and cell cross-sectional area,dihydroethidium method was used to evaluate reactive oxygen species levels,enzyme-linked immunosorbent method was used to determine malondialdehyde content and antioxidant enzyme activity,western blot was used to determine the expression of ubiquitin-proteasome system proteins,and the number of activated satellite cells(Pax7+/MyoD+)were detected by double immunofluorescence staining. RESULTS AND CONCLUSION:(1)Exercise performance:Compared with the sham operation group,maximal running speed and maximal weight-bearing load in the myocardial infarction group decreased(P<0.05);compared with the myocardial infarction group,the maximal running speed of the aerobic exercise group and the maximal weight-bearing load of the resistance exercise group increased(P<0.05).(2)Cardiac remodeling:Compared with the sham operation group,infarction area,myocardial cell cross-sectional area,and collagen content in the myocardial infarction group increased(P<0.05),while leftventricular ejection fraction and shortening fraction decreased(P<0.05);compared with the myocardial infarction group,there was no statistical difference in the above parameters in both aerobic exercise resistance exercise groups(P>0.05).(3)Skeletal muscle remodeling:Compared with the sham operation group,gastrocnemius muscle mass,gastrocnemius muscle mass index,cell cross-sectional area,superoxide dismutase activity,glutathione peroxidase activity,and the number of activated satellite cells decreased in myocardial infarction group(P<0.05),while reactive oxygen species content,malondialdehyde content,and the protein expression of ubiquitin,MuRF1 and MAFbx increased(P<0.05);compared with the myocardial infarction group,gastrocnemius muscle mass index,superoxide dismutase activity,the number of activated satellite cells increased in both aerobic exercise and resistance exercise groups(P<0.05),while reactive oxygen species content and the protein expression of ubiquitin,MuRF1,and MAFbx decreased(P<0.05);compared with the aerobic exercise group,gastrocnemius muscle mass,gastrocnemius muscle mass index,cell cross-sectional area,reactive oxygen species content,malondialdehyde content,the number of activated satellite cells increased in resistance exercise group(P<0.05),while superoxide dismutase activity,glutathione peroxidase activity down-regulated(P<0.05).To conclude,aerobic exercise and resistance exercise can both improve exercise performance of rats with heart failure,and the mechanism is related to reducing oxidative stress,inhibiting ubiquitin-proteasome system activity and activating satellite cells to improve skeletal muscle remodeling.Aerobic exercise has a better effect on improving skeletal muscle oxidative stress,while resistance exercise has a more significant effect on promoting skeletal muscle regeneration.

Objective To establish a liquid chromatography method for the simultaneous determination of 13 aromatic amine compounds (AAs) in workplace air. Methods A total of 13 AAs in both vapor and aerosol phases were collected in workplace air using a new GDH-6 sampling tube. Samples were desorbed and eluted with methanol, separated using a Symmetry Shield™ RP₁₈ reversed-phase liquid chromatography column, and detected with a diode array detector. Quantification was performed using an external standard method. Results The linear range of the 13 AAs measured by this method was 0.02-373.60 μg/L with the correlation coefficients greater than 0.999 0. The minimum detection concentration was 0.09-14.37 μg/m³, and the minimum quantitative concentration was 0.31-47.90 μg/m³ (both calculated based on sampling 15.0 L of air and 3.0 mL of elution volume). The average desorption and elution efficiency ranged from 97.46% to 101.23%. The within-run relative standard deviation (RSD) was 0.10%-5.99%, and the between-run RSD was 0.17%-2.71%. Samples could be stably stored in sealed conditions at 2-8 ℃ for more than seven days. Conclusion This method is suitable for the simultaneous determination of 13 AAs in workplace air, including both vapor and aerosol phases.

Objective To establish a method for simultaneous determination of four high-molecular-weight thiol derivatives (TDs) in workplace air by gas chromatography. Methods The four kinds of vapor-phase macromolecular TDs (1-pentanethiol, 1-hexanethiol, 1-benzyl mercaptan, and n-octanethiol) in the workplace air were collected using the GDH-1 air sampling tubes, desorbed with anhydrous ethanol, separated on a DB-FFAP capillary column, and determined by flame ionization detector. Results The quantitation range of the four TDs was 0.30-207.37 mg/L, with the correlation coefficients greater than 0.999 00. The minimum detection mass concentrations and minimum quantitation mass concentrations were 0.18-0.32 and 0.60-1.05 mg/m³, respectively (both calculated based on the 1.5 L sample and 3.0 mL desorption solvent). The mean desorption efficiencies ranged from 87.07% to 103.59%. The within-run and between-run relative standard deviations were 1.92%-8.22% and 1.89%-8.45%, respectively. The samples can be stored at room temperature or 4 ℃ for three days and up to 7 days at -18 ℃. Conclusion This method is suitable for the simultaneous determination of four vapor-phase TDs in workplace air.

Objective To improve the national standardized method for determining biphenyl in workplace air, which was based on activated carbon tube sampling, carbon disulfide desorption, and gas chromatography, by developing a method using GDX-502 tubes for sampling, toluene for desorption, and gas chromatography. Methods Workplace air samples were collected using GDX-502 sampling tubes and desorbed with toluene, followed by determination with gas chromatography. Results The improved method demonstrated good linearity for biphenyl concentrations ranging from 0.33 to 330.00 mg/L, with a correlation coefficient of 0.999 9. The detection limit and lower limit of quantification were 0.06 and 0.21 mg/L, and the minimum detection concentration and minimum quantification concentration were 0.04 and 0.14 mg/m³ (based on 1.5 L air sample volume), respectively. The average desorption efficiency ranged from 96.6% to 101.1%. The within-run and between-run relative standard deviations were 0.6%-1.4% and 1.4%-3.3%, respectively, with 100.0% sampling efficiency. Samples remained stable for at least 14 days at room temperature. Conclusion The improved method for biphenyl detection demonstrates rapid and accurate performance, with the advantages of low detection limits and high sampling and desorption efficiency.

ObjectiveTo understand the monitoring result of occupational hazard in the workplace of key industries in Guangdong Province from 2020 to 2023. Methods The data of occupational hazards in the workplace of 20 key industries in Guangdong Province from 2020 to 2023 were collected from the “Workplace Occupational Hazard Monitoring System” of the Chinese Disease Prevention and Control System subsystem. The monitoring result of occupational hazard factors, occupational health training, occupational health examination, occupational protection, detection of occupational hazardous agents such as dust, chemical substances and noise were analyzed. Results A total of 13 058 enterprises from key industries were recruited as the monitoring subjects in Guangdong Province. There were 290 large-, 1 342 medium-, 7 635 small-, and 3 791 micro-enterprises, with small and micro-enterprises accounting for 58.5% and 29.0% of the total, respectively. A total of 7 542 enterprises exceeded the national standard in the detection of occupational hazards, with a rate of 57.8%. A total of 1 942 517 workers from 13 058 enterprises were recruited, with 835 567 workers were exposed to occupational hazards, with a rate of 43.0%. The rate of occupational health training for enterprise leaders, occupational health management personnel, and workers was 71.9%, 73.8%, and 86.5%, respectively. The abnormal rate of occupational health examinations for workers exposed to noise, dust, and chemical agents was 2.0%, 0.6%, and 1.0%, respectively. The distribution rate of dust masks, anti-poisoning masks or face masks, and noise prevention earplugs or earmuffs was 83.3%, 71.3%, and 77.8%, respectively. The rate of installation of dust prevention facilities, anti-poisoning facilities, and noise prevention facilities was 85.6%, 81.2%, and 50.1%, respectively. The rate of exceeded the national standard of dust, noise in the worksites/types and workplaces showed a decreasing trend year by year (all P<0.01), while the rate of exceeded the national standard of chemical agents in worksites/types and workplaces showed an increasing trend year by year in various occupational hazards (all P<0.01). Conclusion Occupational hazards in the workplace of key industries in Guangdong Province are relatively common. The proportion of workers exposed to occupational hazards is relatively high. It is necessary to further improve the use of noise prevention facilities and protective equipment, strengthen occupational health training for enterprises throughout the province and regularly monitor occupational hazards to reduce the risk of occupational diseases.

ObjectiveTo establish a method for the determination of 1,1,1,2-tetrachloroethane (TeCA) and 1,1,2,2-TeCA in human urine using liquid-liquid extraction-gas chromatography. Methods The 5.0 mL urine sample was mixed with 2.0 g anhydrous sodium sulfate and 5.0 mL ethyl acetate, then vortexed mixing. The 1.0 mL extraction was separated by 100% dimethylpolysiloxane capillary gas chromatography column, detected by flame ionization detector, and quantified by an external standard method. Results The linear ranges of 1,1,1,2-TeCA and 1,1,2,2-TeCA were 0.250-50.750 mg/L, with both correlation coefficients of >0.999 9. The detection limit of 1,1,1,2-TeCA in urine was 0.020 mg/L, and the lower limit of quantification was 0.060 mg/L. The average recovery was 88.02%-101.32%, and the within-run and between-run relative standard deviations (RSDs) were 0.11%-0.47% and 0.39%-1.09%, respectively. The detection limit of 1,1,2,2-TeCA in urine was 0.050 mg/L, and the lower limit of quantification was 0.150 mg/L. The average recovery was 93.42%-101.32%, and the within-run and between-run RSDs were 0.28%-1.04% and 0.50%-1.03%, respectively. Both the 1,1,1,2-TeCA and 1,1,2,2-TeCA cannot be stored at room temperature. The 1,1,2,2-TeCA can be stored at 4 ℃ for at least three days. At -20 ℃, the 1,1,1,2-TeCA can only be stored for one day, while 1,1,2,2-TeCA can be stored for at least five days. Conclusion This method has high sensitivity, good specificity, simple sample pretreatment, and more intuitive and reliable results. It can be used to determine the level of 1,1,1,2-TeCA and 1,1,2,2-TeCA in urine of occupational population.

BACKGROUND:The renin-angiotensin system plays a key role in the occurrence and development of hypertension,in which angiotensin(1-7)has antihypertensive effect and reversely regulates the adverse effects of angiotensin Ⅱ.Exercise rehabilitation therapy is an important non-pharmaceutical means to prevent and treat hypertension;however,whether angiotensin(1-7)and exercise have a synergistic effect is not yet clear. OBJECTIVE:To explore the effect of angiotensin(1-7)supplementation combined with exercise therapy on cardiac remodeling in rats with renal hypertension and to investigate the possible mechanism of angiotensin(1-7)and its receptor signal axis. METHODS:Sixty male Sprague-Dawley rats were selected,of which 12 rats were randomly selected as normotensive group and the remaining 48 rats were used to make animal models of renal hypertension using two-kidney one-clip method and were then randomly divided into hypertension control group,hypertension exercise group,angiotensin(1-7)group and combined treatment group.One week after successful modeling,different interventions were given(for a period of 6 weeks)as follows:the hypertension exercise group was subjected to a running training on an electric treadmill,the angiotensin(1-7)group was perfused with angiotensin(1-7)by implanting Alzet microosmotic pump subcutaneously on the back of the rats,and the combined treatment group was perfused with angiotensin(1-7)after running training,while the normotensive group and hypertension control group were caged quietly.At 48 hours after the last training session,the tail artery blood pressure was measured with a non-invasive sphygmomanometer;the heart structure and function were detected by echocardiography;the left ventricular myocardium was taken for histopathological observation by hematoxylin-eosin and Masson staining,and the cardiomyocyte cross-sectional area and collagen volume fraction were obtained by image analysis software as markers of myocardial hypertrophy and fibrosis,respectively;the content of angiotensin(1-7)in the heart was detected by high performance liquid chromatography;the mRNA expression of cardiac embryonic genes,atrial natriuretic peptide and β-myosin heavy chain,was detected by real-time fluorescence quantitative PCR;and the protein expression of cardiac Mas receptor,angiotensin Ⅱ type 2 receptor and endothelial nitric oxide synthase was measured by western blot assay. RESULTS AND CONCLUSION:Compared with the normotensive group,blood pressure increased(P<0.05),cardiac function had no significant changes(P>0.05),cardiomyocyte cross-sectional area and collagen volume fraction increased(P<0.05),mRNA expression of atrial natriuretic peptide and β-myosin heavy chain was upregulated(P<0.05),angiotensin(1-7)content and protein expression of Mas receptor,angiotensin Ⅱ type 2 receptor and endothelial nitric oxide synthase was downregulated(P<0.05)in the hypertension control group.Compared with the hypertension control group,blood pressure decreased(P<0.05),cardiac function improved(P<0.05),collagen volume fraction decreased(P<0.05),cardiomyocyte cross-sectional area and angiotensin(1-7)content showed no significant changes(P>0.05),mRNA expression of atrial natriuretic peptide and β-myosin heavy chain was downregulated(P<0.05),and the protein expression of Mas receptor,angiotensin Ⅱ type 2 receptor and endothelial nitric oxide synthase was upregulated(P<0.05)in the hypertension exercise group;except for an increase in myocardial angiotensin(1-7)content(P<0.05),other parameters had no statistical significance(P>0.05)in the hypertension angiotensin(1-7)group.Compared with the hypertension exercise group,blood pressure decreased(P<0.05),cardiomyocyte cross-sectional area and cardiac function had no significant changes(P>0.05),collagen volume fraction decreased(P<0.05),angiotensin(1-7)content increased(P<0.05),mRNA expression of atrial natriuretic peptide and β-myosin heavy chain was downregulated(P<0.05),and the protein expression of Mas receptor,angiotensin Ⅱ type 2 receptor and endothelial nitric oxide synthase was upregulated(P<0.05)in the combined treatment group.To conclude,supplementation of angiotensin(1-7)alone cannot improve cardiac remodeling in rats with renal hypertension,but it can enhance the efficacy of exercise.The mechanism is related to the improvement of angiotensin(1-7)receptor deficiency and restoration of its signaling pathway function.

Objective To establish a rapid qualitative analysis method for volatile organic components in chemicals. Methods Headspace gas chromatography-mass spectrometry was used to qualitatively determine 19 volatile organic components, including benzene, 1,2-dichloroethane, and n-hexane, in chemicals. Different sample amounts, heating temperatures, heating times, and sample volumes were analyzed to assess their effects on detection results and optimize sampling conditions. Results Based on the set chromatography, the optimal sampling process of this method was as follows： 5.0 g sample in a 20.0 mL headspace bottle, incubated at 40 ℃ for 30 minutes in a constant-temperature drying incubator, and a 1.00 mL headspace gas injection. The within-run and between-run relative standard deviations of all components ranged from 0.00% to 21.05% and 0.00% to 33.33%, respectively. The samples stored in sealed glass containers were stable at room temperature for at least 60 days. Conclusion This method offers simplicity, good reproducibility, and stability, making it suitable for rapid qualitative analysis of volatile organic components in chemicals.

Objective To establish a high performance liquid chromatography (HPLC) method for simultaneous determination of six aniline compounds (ADs) in workplace air. Methods GDH-1 air sampling tube was used to collect six co-existing ADs such as aniline, o-toluidine, N-methylaniline, m-methylaniline, p-methylaniline and N,N-dimethylaniline in the vapor and aerosol of workplace air. The samples were desorbed and eluted using a methanol solution containing 1.00% ammonia water, followed by separation on a C₁₈ chromatographic column and detection using a diode array detector. Results The quantification range of the method was 0.19 -253.50 mg/L, with the correlation coefficient of 0.999 9 for all six ADs. The minimum detection range was 0.02-0.06 mg/m³, and the minimum quantitation range was 0.04-0.19 mg/m³ [both calculated for a 15.0 L sample with a desorption (elution) solution volume of 3.00 mL]. The average desorption and elution efficiencies were 92.15%-104.41% (silica gel) and 94.29%-104.29% (filter membrane). The intra-assay relative standard deviation (RSD) ranged from 0.90%-9.72% (silica gel) and 0.57%-6.96% (filter membrane). The inter-assay RSD ranged from 2.03%-9.78% (silica gel) and 2.50%-8.62% (filter membrane). The samples were stable at room temperature for seven days. Conclusion This method can be used for the simultaneous determination of six ADs in workplace air.

Objective To analyze the overall situation of regular monitoring of occupational hazards in enterprises in Guangdong Province in 2022. Methods Analysis and quality sampling from enterprises were conducted on the occupational hazard regular monitoring reports submitted by various occupational health institutions through the Guangdong Province Occupational Health Quality Control Platform for the year 2022. Results In 2022, a total of 40 129 enterprises in Guangdong Province conducted regular monitoring of occupational hazards, accounting for 5.9%. More than 4.85 million workers were enrolled, of which more than 1.99 million workers were exposed to occupational hazards, with an incidence of 41.1%. The incidence of exposure to chemicals, dust, and noise were 18.2%, 11.9%, and 23.5%, respectively. The incidence of exceeding national standard for chemical substances, dust and noise in enterprises were 2.7%, 3.3%, and 42.7%, respectively. The incidence of exceeding national standard for all occupational hazards increased with the scale of enterprises from micro, small, medium to large enterprises (29.1% vs 46.7% vs 61.3% vs 65.4%, all P<0.05). The top three key industries, with more enterprises exceeding national standard, were metal furniture manufacturing, wooden furniture manufacturing, and other metal daily necessities manufacturing. The concentration of 97 chemical hazardous agents such as silica dust and benzene in work site exceeded the national standard, but less than 1.0% chemical hazardous agents exceeded national standard in most of the chemical-exposed work site. The incidence of noise exceeding national standard was 45.4%, while the incidence of silica dust exceeding national standard was 17.3%. Conclusion The percentage of regular monitoring of occupational hazards in enterprises in Guangdong Province is relatively low. The main occupational hazard that exceeds the national standard was noise, indicating the need for special attention on noise protection in workplace.