This paper studies the active force characteristics of the neck muscles under the condition of rapid braking, which can provide theoretical support for reducing the neck injury of pilots when carrier-based aircraft blocks the landing. We carried out static loading and real vehicle braking experiments under rapid braking conditions, collected the active contraction force and electromyography (EMG) signals of neck muscles, and analyzed the response characteristics of neck muscle active force response. The results showed that the head and neck forward tilt time was delayed and the amplitude decreased during neck muscle pre-tightening. The duration of the neck in the extreme position decreased, and the recovery towards the seat direction was faster. The EMG signals of trapezius muscle was higher than sternocleidomastoid muscle. This suggests that pilots can reduce neck injury by pre-tightening the neck muscles during actual braking flight. In addition, we can consider the design of relevant fittings for pre-tightening the neck muscles.
The contractile force of hepatic stellate cells plays a very important role in liver damage, hepatitis and fibrosis. In this paper, a method based on polydimethylsiloxane (PDMS) thin micropillar arrays is proposed to measure the contractile force of human hepatic stellate cell line LX-2, which enables dynamic measurement of the subcellular distribution of force magnitude and direction. First, thin micropillar arrays on glass bottom dish were fabricated using two-step casting process in order to meet the working distance requirement of 100× objective lens. After hydrophilic treatment and protein imprint, cells were seeded on the micropillar arrays. LX-2 cells, which were quiesced by growth in serum-free medium, were activated by adding fetal bovine serum (FBS). The deflections of the micropillars were achieved by image processing technique, and then the contractile force of cells exerted on the micropillars was calculated according to mechanical simulation results, and was analyzed under both quiescent and activated conditions. The experimental results show that the average traction force of quiescent cells is about 20 nN, while the contractile force of activated cells increased to 110 nN upon adding FBS. This method can quantify the contractile force of LX-2 cell on subcellular scale in both quiescent and activated states, which may benefit pathology study and drug screen for chronic liver diseases resulted from liver fibrosis.
Objective To study the short and medium term effect of myocardial contractile force by implantation of endothelial progenitor cells （EPCs） in the myocardial infarction model. Methods Hundred and twenty SD rats were equally and randomly divided into experimental group and control group （60 rats in each group）. Acute myocardial infarction model was created by ligation of LAD. Autologous EPCs were purified from peripheral blood then implanted into the acute myocardial infarct site via topical injection. IMDM were used in control group. Specimens and muscle strip were harvested at 3, 6 weeks, 6, 8 and 12 months after EPCs implantation for contractile force study and to detect the expression of vascular endothelial growth factor（VEGF）, basic fibroblast growth factor （bFGF） and Ⅷ factor by immunohistology and video image digital analysis system. Results The expression of VEGF, bFGF and the microvessel counts in experimental group were much higher than those of control group（P〈 0.01） at 3, 6 weeks and 6 months after transplantation. The contractile force in experimental group was better than that in control group（P〈0.01） at the same time. But from 8 months after implantation, the contractile force and so on were not up in the experimental group. Conclusion EPCs, after being implanted into infarct myocardium, shows the ability of improvement of the contractile performance in infarcted myocardium by means of angiogenesis and vasculogenesis and the medium term results are persistent.
ObjectiveTo analyze the recovery rule of atrial contractility (AC) function after Maze Ⅳ procedure of valvular atrial fibrillation (AF).MethodsIn our hospital from March 2016 to April 2018, 103 patients who underwent cryoablation Maze Ⅳ procedure due to mitral valve lesions associated with persistent or long-term persistent AF were enrolled. There were 42 males and 61 females, with an average age of 58.5±9.1 years. Electrocardiogram and echocardiography were followed up at discharge and 1, 3, 6, 12 months after procedure. A multivariate Cox analysis of predictive factors for AC recovery was applied.ResultsAll the 103 patients were followed up for 1 year. The recovery rate of AC increased gradually after operation. It was not until 3 months after procedure that most of the right atrial contractility (RAC) was accompanied by synchronous recovery of the corresponding left atrial contractility (LAC, Kappa coefficient≥0.40, P<0.05). However, the coexistence of sinus rhythm (SR) and bilateral AC was not consistent well until 1 year after operation (Kappa coefficient≥0.40, P<0.05). One year after procedure, the recovery rates of SR and bilateral AC were 86.4% (89/103) and 66.0% (68/103) respectively. By Cox multivariate regression analysis, longer preoperative AF duration (P=0.040), larger preoperative left atrial diameter (LAD, P=0.003), and AC deletion 3 months after surgery (P=0.037) were predictive factors for AF recurrence in the middle and advanced stages (>3 months) after Maze surgery. At the same time, longer preoperative AF duration and larger preoperative LAD were also negative predictors of middle and late recovery of LAC and bilateral AC (All P<0.05). Receiver operating characteristic curve analysis showed that the best critical value of preoperative AF time and preoperative LAD for prediction of AC recovery was 37 months (sensitivity 99.6%, specificity 76.3%) and 60.5 mm (sensitivity 98.5%, specificity 78.9%), respectively.ConclusionThe recovery of AC after Maze procedure is a dynamic improvement process. Early recovery of AC is beneficial to the stable maintenance of SR in the future. Prolonged duration of AF and enlarged LAD have adverse effects on the outcome of Maze Ⅳ procedure.