Objectively‐measured sleep and its association with adiposity and physical activity in a sample of Canadian children

Cross‐sectional associations between objectively‐measured sleep duration, sleep efficiency and sleep timing with adiposity and physical activity were examined in a cohort of 567 children from Ottawa, Canada. Five‐hundred and fifteen children (58.8% female; age: 10.0 ± 0.4 years) had valid sleep measurements and were included in the present analyses. Physical activity, sedentary time and sleep parameters were assessed over 7 days (actigraphy). Height, weight and waist circumference were measured according to standardized procedures. Percentage body fat was assessed using bioelectric impedance analysis. Light physical activity and sedentary time were greater in children with the shortest sleep durations (P < 0.0001), whereas children with the highest sleep efficiencies had lower light physical activity and more sedentary time across tertiles (P < 0.0001). In multivariable linear regression analyses, and after adjusting for a number of covariates, sleep efficiency was inversely related to all adiposity indices (P < 0.05). However, sleep duration and sleep timing were not associated with adiposity indices after controlling for covariates. Inverse associations were noted between sleep duration and light physical activity and sedentary time (P < 0.0001). Sleep efficiency (P < 0.0001), wake time and sleep timing midpoint (P < 0.05) were negatively associated with light physical activity, but positively associated with sedentary time. In conclusion, only sleep efficiency was independently correlated with adiposity in this sample of children. Participants with the shortest sleep durations or highest sleep efficiencies had greater sedentary time. More research is needed to develop better sleep recommendations in children that are based on objective measures of sleep duration, sleep efficiency and sleep timing alike.     

Computer‐Based Analysis of Dynamic QT Changes: Toward High Precision and Individual Rate Correction

Background: New strategies are needed to improve the results of automatic measurement of the various parts of the ECG signal and their dynamic changes. Methods: The EClysis software processes digitally‐recorded ECGs from up to 12 leads at 500 Hz, using strictly defined algorithms to detect the PQRSTU points and to measure ECG intervals and amplitudes. Calculations are made on the averaged curve of each sampling period (beat group) or as means ± SD for beat groups, after being analyzed at the individual beat level in each lead. Resulting data sets can be exported for further statistical analyses. Using QT and R‐R measured on beat level, an individual correction for the R‐R dependence can be performed. Results: EClysis assigns PQRSTU points and intervals in a sensitive and highly reproducible manner, with coefficients of variation in ECG intervals corresponding to ca. 2 ms in the simulated ECG. In the normal ECG, the CVs are 2% for QRS, 0.8% for QT, and almost 6% for PQ intervals. EClysis highlights the increase in QT intervals and the decrease of T‐wave amplitudes during almokalant infusion versus placebo. Using the observed linear or exponential relationships to adjust QT for R‐R dependence in healthy subjects, one can eliminate this dependence almost completely by individualized correction. Conclusions: The EClysis system provides a precise and reproducible method to analyze ECGs. A.N.E. 2002;7(4):289–301     

Effects of the Na+ antagonist cibenzoline on left ventricular function of postischemic hearts

Summary The negative inotropic effect of antiarrhythmic drugs is a major drawback in antiarrhythmic drug therapy, especially in patients with reduced contractile function of the left ventricle. The circulatory and myocardial effects of the new class I antiarrhythmic drug (a Na⁺ antagonist), cibenzoline (2 mg/kg i.v.), were investigated in 47 open-chest rats with normal and postischemic myocardium (3×4 minutes of global ischemia). Hemodynamic measurements in the intact circulation and isovolumic registrations (peak isovolumic left ventricular systolic pressure and peak isovolumic dP/dt_max) were compared to saline controls. In rats with postischemic myocardium, cibenzoline caused a significant (p<0.001) decrease in the cardiac output for 38%, in the dP/dt_max for 30%, and in the peak isovolumic dP/dt_max for 19% at the end of infusion (compared to the control). The heart rate was reduced by 22% (p<0.001), the mean aortic pressure by 22% (p<0.001), and the calculated systemic resistance by 20% (p<0.001). In contrast to the results with postischemic myocardium, no important changes in the hemodynamics were detectable after an identical dose in normal animals without left ventricular dysfunction. The results indicate that standard doses of the Na⁺ antagonist cibenzoline may induce significant cardiodepressant effects on postischemic left ventricles with reduced function.     

Relationship between radiographic measurements and knee adduction moment using 3D gait analysis

BackgroundRadiographic factors estimate the state of the static knee joint, and it is questionable how well these parameters reflect the dynamic knee condition. The external knee adduction moment (KAM) during gait is known to be a kinetic variable contributing to osteoarthritis progression. This study aims to investigate the effects of static radiographic parameters on the dynamic KAM during gait.MethodsOverall, 123 patients (mean age, 65.7 years; standard deviation, 8.1 years; 34 men and 89 women) were included. Seven radiographic parameters including the mechanical tibiofemoral angle (mTFA), Kellgren-Lawrence grade, and ankle joint line orientation (AJLO) were measured on radiographs, and the maximum KAM and KAM-time integral in the stance phase were obtained using three-dimensional gait analysis. The correlation and multiple regression analyses were performed for identifying significant radiographic measurements associated with the KAM.ResultsMost of the radiographic measurements correlated with the maximum KAM and KAM-time integral. As a result of multiple regression analysis, the mTFA (p < 0.001) and AJLO (p = 0.003) were identified as significant factors associated with the KAM-time integral (R² = 0.450); the mTFA (p < 0.001) and AJLO (p = 0.003) were identified as a significant factor associated with the maximum KAM (R² = 0.352) in multiple regression analysis. The discriminant validity of KAM was highest at varus 5.7 degree of the mTFA and 7.5 degree of the AJLO.SignificanceThe mTFA and AJLO were significantly associated with the KAM. However, to be used as a surgical indication for corrective osteotomy, a longitudinal study is needed to validate whether the mTFA and AJLO values directly cause osteoarthritis progression as we have suggested.Level of evidenceIII.     

新型组蛋白去乙酰化酶抑制剂对缺氧损伤心肌细胞的保护作用研究

目的：利用化学发光方法和细胞筛选模型,检测新型组蛋白去乙酰化酶抑制剂（ histone deacetylase inhibitor, HDACi）JZ005的抑制组蛋白去乙酰化酶（histone deacetylases,HDACs）的活性;建立氯化钴损伤的心肌细胞缺氧模型,初步探讨JZ005对缺氧损伤细胞的保护作用。方法采用脂质体转染法将含有p21启动子元件的荧光素酶报告基因真核表达载体pCI-p21-Luc转入到人胚肾细胞293中,用G418筛选获得稳定转染荧光素酶报告基因的单克隆细胞系;采用已报道的HDACi曲古抑菌素A（ trichostatina A,TSA）为阳性对照,检测细胞筛选模型的稳定性;用HDACi化学发光检测试剂盒及上述细胞筛选模型测定JZ005抑制HDACs的活性;用不同浓度的JZ005处理氯化钴缺氧损伤的大鼠胚胎心肌细胞（H9c2）,MTT法检测JZ005对缺氧损伤细胞的保护作用。免疫印迹法检测JZ005处理后正常及缺氧损伤心肌细胞组蛋白H3的乙酰化水平变化。流式细胞术检测JZ005对H9c2细胞缺氧损伤后凋亡的影响。结果建立含p21启动子元件荧光素酶报告基因的HDACi细胞筛选模型;JZ005能够显著抑制HDACs的活性,浓度50～400μmol／L,抑制率＞50％。对缺氧损伤的心肌细胞具有明显保护作用,与对照组相比,细胞存活率提高38．33％、56．00％和35．20％,同时能够上调缺氧损伤心肌细胞组蛋白H3的乙酰化水平,拮抗缺氧损伤心肌细胞的凋亡,细胞凋亡数目从对照组的12．89％分别下降到给药组（25,50和100μmol／L）的6．63％、10．56％和8．89％。结论成功建立了HDACi的细胞筛选模型;JZ005作为一种新型的HDACi ,具有明显的保护心肌细胞拮抗缺氧损伤的作用,提示JZ005有可能开发成一种治疗缺氧损伤的药物。