AIM: To investigate the effect of the heat shock response on the reperfusion arrhythmias(RAs) and the possible mechanism involved. METHODS: Fifty-five Sprague Dawley rats were randomly divided into 2 groups: the heat shock group (group H, n=29 ) and the control group (group C, n=26 ). The rats in group H were preconditioned with heat shock 24 hours before, and that in group C were not. The hearts of 16 rats in group H and 16 in group C were exercised and mounted on a non-circulating Langendorff perfusion apparatus and perfused retrogradely with modified K-H buffer and mimic ischemia/reperfusion was applied. Additionally, conventional intracellular microelectrode techniques were used for recording such electrophysiological parameters as resting potential(RP), action potential amplitude(APA), over shot(OS), maximum depolarization velocity(Vmax) of the hearts of other 13 rats in group H and 10 in group C. RESULTS: ①Prior heat stress significantly decreased reperfusion arrhythmia. ②The amount of CK release in the effluent in group H was much less than that in group C. ③Myocardial HSP70 content was elevated significantly in group H. ④Heat stress significantly increased myocardial anti-oxydases activity and decreased lipid peroxydative products. Additionally, heat stress significantly reduced the Vmax of action potential. It indicated that rapid Na + channel of papillary muscles may be inhibited by heat shock. The degree of change of Vmax after ischemia in H group was significantly less than that in group C. And the time of reperfusoin with Tyrode's solution till the action potential appeared as large as that before perfusion with mimic ischemic solution is shorter in group H than in group C. CONCLUSION: Heat shock pretreatment markedly reduces ischemia/reperfusion-induced injury of heart and ventricular arrhythmias in rats and this effect may be associated with the inhibition of rapid Na + channel of papillary muscles by heat shock and the increase in myocardial HSP70 and anti-oxydase activity.

OBJECTIVE: To investigate the correlation of mental workload and prevalence of work-related musculoskeletal disorders musculoskeletal disorders( WMSDs) in railway vehicle manufacturing workers.METHODS: A total of 362 male workers in assembling and welding workshop from a railway vehicle manufacturing enterprise were selected as study subjects by cluster sampling method.The level of mental workload and prevalence of WMSDs were investigated using a revised Subjective Workload Assessment Technique and China Musculoskeletal Questionnaire.RESULTS: The median score of mental workload was 67 and the prevalence rate of WMSDs was 56.9%.The multivariate logistic regression analysis results indicated that the higher the mental workload of railway vehicle manufacturers,the higher their risk for WMSDs after excluding the influence of confounding factors( P < 0.05).Workers in welding work showed a higher risk than those in assembling work( P < 0.01).Workers with fast work rhythm showed higher risk of WMSDs than those with regular working rhythm( P < 0.01).Workers with comfortable working environment and temperature showed lower risk of WMSDs than those with uncomfortable working environment and temperature( P < 0.01).CONCLUSION: The mental workload can increase the risk of WMSDs,with a dose-effect relationship in railway vehicle manufacturing workers.The type of work,work frequency and the temperature in working environment are also influencing factors of WMSDs.

OBJECTIVE: To analyze the prevalence and influencing factors of multisite work-related musculoskeletal disorders(WMSDs) of workers in a railway vehicle manufacturing enterprise. METHODS: A total of 366 male workers in the assembly and riveting workshop of a railway vehicle manufacturing enterprise were selected as the research subjects using the cluster sampling method. The Chinese Musculoskeletal Questionnaire was used to investigate the prevalence of multiple sites of WMSDs. Multiple logistic regression analysis was used to analyze the influencing factors. RESULTS: The total prevalence of WMSDs was 56.3%(206/366). The prevalence of WMSDs in all parts from high to low was as follows: lower back(35.5%), hand and wrist(27.6%), neck(23.2%), shoulder(21.0%), knee(19.9%), upper back(18.6%), hip and leg(18.0%), ankle/foot(15.8%) and elbow(12.3%)(P<0.01). The total prevalence of multisite WMSDs was 38.0%(139/366). The prevalence of WMSDs in different numbers of parts from high to low was as follows: 6 or more parts(12.0%), 2 parts(10.7%), 3 parts(6.6%), 5 parts(5.5%) and 4 parts(3.3%)(P<0.01). Multiple logistic regression analysis results showed that the overweight and obese workers had higher risk of multi site WMSDs than those with normal body mass index(P<0.05).Those with long-term low heads, frequent bending, long bending of the elbows, and higher frequency of work requirements, and less frequently communicated with the leader had higher risk of multi site WMSDs(P<0.05). CONCLUSION: The prevalence of multisite WMSDs in railway vehicle manufacturing enterprise is relatively high. The influencing factors include individual factors, adverse ergonomic factors and psychosocial factors.