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Objective@#To explore correlations between physical activity (PA), sedentary behavior (SB) and physical posture disorders in primary school students, and to provide reference for the prevention and correction of adverse body posture in this group.@*Methods@#From September to December 2020, 206 children from 4 primary schools in Chaoyang District of Beijing were selected by multistage stratified cluster random sampling method. Body posture and PA were assessed using a body posture tester and a triaxial accelerometer. Children s Leisure Activity Questionnaire was used to investigate SB.@*Results@#The detection rate of abnormal body posture in primary school students was 76.70%. PA showed positive assocation with high and low shoulder, X/O leg, pelvis forward, spine curvature and comprehensive evaluation ( β =0.17, 0.21, 0.19, 0.24, 0.19, P <0.05). SB had significant negative linear correlation with high and low shoulder, X/O leg,pelvis forward, spine curvature and comprehensive evaluation ( β = -0.24 , -0.22, -0.36, -0.24, -0.27, P <0.05). In the combination analysis, children with high PA plus low SB ( OR=2.12, 95%CI= 1.46-3.37, P <0.05) and children with low PA plus high SB had the highest and lowest advantages of qualified rate of body posture assessment,respectively. Compare with low SB and low PA( OR=1.71, 95%CI=1.41-2.74, P <0.05), high PA and high SB ( OR=1.85, 95%CI=1.38-2.86, P <0.05) had higher qualified rate of body posture assessment.@*Conclusion@#Physical activity shows positive effects on physical posture while sedentary behavior shows negative effects on physical posture. The combination of PA and SB has a counteracting or synergistic interaction effect.
RESUMO
<p><b>OBJECTIVE</b>To compare the nature of the metabolites formed from the phase I metabolism (hydroxylation and oxidation) and phase II metabolism (glutathionyl conjugation) of PCBs that have different chlorine substitution patterns. To discuss the structure-activity relationships and metabolic mechanisms of PCBs.</p><p><b>METHODS</b>4-Cl-biphenyl (PCB3), 4,4'-Cl-biphenyl (PCB15), 3,4,3',4'-Cl-biphenyl (PCB77) were used for in vitro metabolic study. LC/MS and UV-Vis studies were performed for metabolites identification.</p><p><b>RESULTS</b>The cytochrome P-450 catalyzed hydroxylation rate decreased as the number of chlorine substitutions increased. In this reaction, PCB3 was fully metabolized, approximately half of the PCB15 was metabolized and PCB77 was not metabolized at all. The oxidation rate of PCB15-HQ was higher than that of PCB3-HQ under various oxidation conditions. The LC/MS and UV-Vis data suggest that in the conjugation reaction of PCB15-Q and GSH, the Michael addition reaction occurs preferentially over the displacement reaction.</p><p><b>CONCLUSION</b>The metabolic profiles of polychlorinated biphenyls (PCBs) are dramatically affected by chlorine substitution patterns. It is suggested that the metabolic profiles of PCBs are related to their chlorine substitution patterns, which may have implications for the toxicity of PCB exposure.</p>