RÉSUMÉ
Objective To study the hemodynamic effects of enhanced external counter pulsation(EECP)on typical coronary artery disease and microcirculation angina.Methods A physiological model of the right dominant coronary artery,including the coronary conduit arteries and coronary microcirculation,was established using lumped parameter models.Pathological conditions,such as one-vessel lesions,three-vessel lesions,and microcirculation angina,were simulated.EECP intervention models were established,and the hemodynamic effects of EECP on pathological models was simulated.Results The simulation results of the coronary physiological model,pathological models,and EECP intervention model established in this study were consistent with experimental data in related literature.EECP improved coronary blood flow in all three pathological conditions.For one-vessel lesions,EECP could not recover the blood flow of left main coronary artery to a normal level after the stenosis rate reached 80%-85%.For three-vessel lesions,EECP treatment could not be used if the stenosis rate in one of the three vessels exceeded 90%.For microcirculation angina,EECP was effective when critical condition myocardial blood flow was>1.03 mL/min·g and coronary flow reserve was>1.64.Conclusions The model of coronary disease under EECP interference established in this study meets expectations,and the obtained simulation data have certain reference values for the clinical application of EECP.
RÉSUMÉ
ObjectiveTo analyze the characteristics of plantar pressure of diabetic patients during gait cycle, and to design a offloading insole with variable stiffness. MethodsThe plantar pressure experiment was carried out and a database including 157 subjects was established. The differences of plantar pressure distribution were analyzed among diabetic patients with and without peripheral neuropathy, and healthy people. The insole pressure area was divided, and porous units were filled in different insole areas according to the pressure gradient. The fed-calf-insole finite element model of diabetic patients was constructed. The simulation analysis of different insole schemes was carried out under the conditions of push-off, footheel-strike and dynamic neutrality posture, and to explore the most reasonable insole stiffness design. ResultsCompared with the healthy group, the percentage of peak pressure and high pressure in the left and right heel areas of diabetic neuropathy patients showed a decreasing trend, in which the left peak pressure was significantly reduced by 11% (P = 0.026) and the percentage of high pressure was significantly reduced by 9.8% (P = 0.02). When the porous elements of 2.5 MPa and 1.9 MPa were used in the high pressure area of the insole metatarsal and high pressure area of the heel, the peak plantar pressure of footheel-strike, dynamic neutral and push-off was reduced by 42.4%, 27.4% and 26.4%, and the peak stress of the soft tissue was reduced by 49.8%, 43.6% and 25.1%, respectively. ConclusionThere is a higher risk of ulcer in the metatarsal region than in the heel region for diabetic patients. The variable stiffness insoles based on the optimization of plantar pressure and internal stress under multi-posture can effectively reduce the peak pressure of plantar and peak stress of soft tissue during walking, which provides a reference for the design of variable stiffness insoles.
RÉSUMÉ
Traumatic brain injury ( TBI ) has caused serious economic and social burdens, but due to its heterogeneity, there is no effective treatment. In TBI with different severity, diffuse axonal injury (DAI) incidenceis high. The investigation on DAI will contribute to the diagnosis and treatment of TBI. In this study, the classification of TBI and the research status of DAI were summarized. The method to judge the severity of TBI and DAI, and animal experimental models and related injury criteria and thresholds were reviewed. The result show that DAI is mainly generated by rotational acceleration and it is related to angular acceleration, angular velocity and duration. Several TBI animal models can induce the pathology of DAI, and inertial rotation models which can produce only rotational acceleration have been developed. However, these models are instantaneous rotation models, and the rotation duration is uncontrollable, thus a longer duration is impossible, and DAI severity under long rotational motion cannot be studied. The study proposes that a new rotation animal model which can control rotation duration should be developed. The development of the animal model and investigation on pathomechanism of the model will contribute to the prevention and treatment of DAI.
RÉSUMÉ
Objective To study the mechanical effects of cyclic strain on neural differentiation of rat bone marrow mesenchymal stem cells (rBMSCs). Methods The rBMSCs were subjected to cyclic strain for 24 hours andthen cultured for 5 days. The expression of neural markers and the phosphorylation of relative signaling pathway proteins were evaluated. The stress distribution on cell surface was analyzed by finite element method. The differentially expressed genes induced by strain were identified by RNA sequencing analysis. Results The 0. 5 Hz strain with 5% magnitude could significantly induce higher expression of neural markers and elevated phosphorylation level of extracellular-signal-regulated kinase (ERK), protein kinase B (AKT) and mammalian target of rapamycin ( mTOR). KEGG pathway analysis showed that the focal adhesion and ECM-receptor interaction were significantly enriched under cyclic strain. Conclusions Cyclic strain could change the interaction of cells with the extracellular matrix ( ECM) and enhance the AKT/ mTOR and ERK pathway, finally promote rBMSC neural differentiation. Knowledge about the impact of mechanical stimulation on BMSC neural differentiation is expected to improve the efficiency of stem cell differentiation, shed light on device design for tissue engineering, and promote clinical application of mesenchymal stem cells in neural issue repair and regeneration.
RÉSUMÉ
Carotid is in a high risk of atherosclerosis due to its special geometric features and complex flow characteristics. Various biomechanical parameters are practical tools for carotid risk assessment. It has beenwidely accepted that oscillatory low shear environment promotes plaque formation. Based on this, more and more biomechanical indexes have been proposed, such as time-average wall shear stress, oscillatory shear index, relative residence time and so on. In this paper, multiple biomechanical parameters were introduced from the perspectives of shear stress and its temporal and spatial variation, turbulence, platelet transport and activation, stress concentration in vascular wall, etc. The development trend of biomechanical parameters related to carotid artery risk assessment was also analyzed, so as to provide the theoretical basis for more comprehensive and rapid carotid risk assessment
RÉSUMÉ
Cardiovascular disease is the leading cause of death worldwide, accounting for 48.0% of all deaths in Europe and 34.3% in the United States. Studies have shown that arterial stiffness takes precedence over vascular structural changes and is therefore considered to be an independent predictor of many cardiovascular diseases. At the same time, the characteristics of Korotkoff signal is related to vascular compliance. The purpose of this study is to explore the feasibility of detecting vascular stiffness based on the characteristics of Korotkoff signal. First, the Korotkoff signals of normal and stiff vessels were collected and preprocessed. Then the scattering features of Korotkoff signal were extracted by wavelet scattering network. Next, the long short-term memory (LSTM) network was established as a classification model to classify the normal and stiff vessels according to the scattering features. Finally, the performance of the classification model was evaluated by some parameters, such as accuracy, sensitivity, and specificity. In this study, 97 cases of Korotkoff signal were collected, including 47 cases from normal vessels and 50 cases from stiff vessels, which were divided into training set and test set according to the ratio of 8 : 2. The accuracy, sensitivity and specificity of the final classification model was 86.4%, 92.3% and 77.8%, respectively. At present, non-invasive screening method for vascular stiffness is very limited. The results of this study show that the characteristics of Korotkoff signal are affected by vascular compliance, and it is feasible to use the characteristics of Korotkoff signal to detect vascular stiffness. This study might be providing a new idea for non-invasive detection of vascular stiffness.
Sujet(s)
Humains , Rigidité vasculaire , 29935 , Maladies cardiovasculaires/diagnostic , Sensibilité et spécificitéRÉSUMÉ
Objective:To explore the clinical effects of intramuscular injection of oryzanol for 5 and 10 days in the treatment of menopausal syndrome.Methods:This study adopts a case-control study method.Twenty patients with menopausal syndrome admitted to Peking Union Medical College Hospital from July 2021 to March 2022 were selected and randomly divided into a control group and an observation group using a random number table method, with 10 patients in each group. The control group was given intramuscular injection of oryzanol once a day for 5 consecutive days on the basis of routine health education; On the basis of routine health education, the observation group was given intramuscular injection of oryzanol once a day for 10 consecutive days. Two groups of patients completed a total of 6 visits before treatment and on days 5, 10, 30, 60, and 90 of treatment. Baseline survey was conducted to record the basic information of patients, including demography data, menstruation, past history, surgical history, drug allergy and the main symptoms of climacteric syndrome, and the baseline hormone level of patients was detected. Compare the menopausal symptoms by modified K-score, Pittsburgh sleep quality index (PSQI) score, menopausal specific quality of life (MENQOL) score, post treatment injection site pain by visual analog score (VAS), and observe adverse reactions during treatment between the two groups of patients at each visit time point.The measurement data conforming to the normal distribution is expressed in xˉ± s. The comparison between the two groups is performed by t test, and the change trend of the two groups at each time point is compared by repeated measurement analysis of variance; The measurement data that do not conform to the normal distribution are represented by M( Q1, Q3), and the Kruskal Wallis test is used for comparison between groups; Counting data is represented by examples(%), Fisher's exact probability method is used for inter group comparison, and Wilcoxon rank sum test is used for rank data comparison. Results:The body mass of the control group was higher than that of the observation group [(62.50±11.88) kg vs (52.90±4.28) kg, t=2.40, P=0.027]. There was no statistical difference between the two groups in other demography data and previous history, sex hormone levels, menopausal symptoms, and menstrual conditions (all P>0.05). Compared with the baseline, the modified K-score, PSQI score, and MENQOL vascular dilation and contraction, psychological state, physiological state, and sexual life scores of the two groups of patients on the 5th, 10th, 30th, 60th, and 90th day of treatment were significantly reduced, and showed a gradually decreasing trend with the extension of observation time (the values in Group F were 36.37, 12.40, 18.69, 24.73, 40.77, and 18.39, respectively, P<0.001), but there was no statistically significant difference between the groups (all P>0.05). After treatment, the VAS score of the control group was 1 point in 2 cases, 2 points in 4 cases, and 3 points in 4 cases; The VAS score of the observation group was 1 in 4 cases, 2 in 3 cases, and 3, 5, and 6 in 1 case each. There was no statistically significant difference in VAS scores between the two groups ( Z=0.43, P=0.664), and no adverse events or serious adverse events were observed during the treatment period. Conclusions:Intramuscular injection of oryzanol injection for 5 and 10 days can improve menopausal symptoms, improve sleep quality and overall quality of life in patients with menopausal syndrome, and the overall effect is similar.
RÉSUMÉ
Stem cells have been regarded with promising application potential in tissue engineering and regenerative medicine due to their self-renewal and multidirectional differentiation abilities. However, their fate is relied on their local microenvironment, or niche. Recent studied have demonstrated that biophysical factors, defined as physical microenvironment in which stem cells located play a vital role in regulating stem cell committed differentiation. In vitro, synthetic physical microenvironments can be used to precisely control a variety of biophysical properties. On this basis, the effect of biophysical properties such as matrix stiffness, matrix topography and mechanical force on the committed differentiation of stem cells was further investigated. This paper summarizes the approach of mechanical models of artificial physical microenvironment and reviews the effects of different biophysical characteristics on stem cell differentiation, in order to provide reference for future research and development in related fields.
Sujet(s)
Signaux , Cellules souches , Différenciation cellulaire , Médecine régénérative , Ingénierie tissulaireRÉSUMÉ
Objective To explore the spatial distribution of microstructural parameters and mechanical properties for trabecular bone in the femoral head with osteonecrosis. Methods Microstructural parameters and mechanical properties of trabecular bone in different regions were analyzed by combined use of imaging measurements and numerical simulation method, and the spatial distribution of biomechanical properties for trabecular bone along coronal, sagittal and vertical directions was investigated. Results Microstructural characteristics and mechanical properties of trabecular bone were Y-shaped distributed along coronal and sagittal directions, and mechanical properties of trabecular bone in Y-shaped region were higher than those in the other regions. Such distribution characteristics was consistent with the location of principle compressive group in the femoral head. Conclusions Necrotic lesions in Y-shaped region had a greater influence on stress distribution of the femoral head and might cause the deterioration of osteonecrosis. The spacial correlation between necrotic lesions and Y-shaped region should be fully considered during clinical diagnosis.
RÉSUMÉ
Objective To investigate the influence of internal and external sphincter loss synergy on stress distributions and urine flow rates of lower urinary tract organs and tissues. Methods Based on collodion slice, the geometric model of the lower urinary tract was reconstructed, and finite element model of the lower urinary tract with muscle active force was established. Through fluid structure coupling simulation, the changes of tissue stress and urine flow rate were simulated under four conditions: normal contraction of internal and external sphincter, total loss of muscle active force and single loss of muscle active force for internal and external sphincters at the end of urination. Results The urethral stress changes in normal contraction of internal and external sphincter muscles were the same as the clinically measured urethral pressure changes. Compared with normal contraction, when the internal sphincter lost its muscle active force alone, stress of the internal sphincter and the urethra of the prostate was reduced by 33.6% and 13.8%, and flow rate of urine in this position was also reduced. When the external sphincter lost its muscle active force alone, the urethral stress of the external sphincter and external urethra was reduced by 59.5% and 24.03%, respectively. When the internal and external sphincter lost muscle active force, stress of the internal sphincter, the prostate, the external sphincter and the external urethra were reduced by 38.77%, 18.6%, 63.58%, 29.74%, respectively, and flow velocity in the corresponding position was also reduced. Conclusions Internal and external sphincter loss synergy resulted in the difference of tissue stress and urine flow rate. The results can provide the theoretical basis for surgical treatment of urinary incontinence caused by sphincter.
RÉSUMÉ
Neovascularization plays an important role in many physiological and pathological processes, but its mechanism is still unclear. Since vascular cells are subjected to a variety of biochemical and biomechanical stimulations in vivo and live in a complex microenvironment, it is necessary to construct the vascular model in vitro and simulate the in vivo microenvironment to explore the mechanism of neovascularization. Recently, owing to the advance of micromachining and microfluidic technology, various in vitro microvascular models have emerged. Variables such as shear stress, interstitial flow and biochemical gradient of angiogenic factors have been controlled in these models, which greatly promotes the research of neovascularization. The construction, development and biomechanical design of various microvascular models are reviewed in this paper.
RÉSUMÉ
Objective:To determine the effects of menopausal stage, age and other associated risk factors on symptoms of anxiety and depression among women in a community in Beijing.Methods:This study was a community-based prospective cohort. Participants who had transitioned through natural menopause, completed two or more depressive and anxiety symptoms evaluations, aged 35 to 64 years, and did not use hormone therapy were selected from the Peking Union Medical College Hospital aging longitudinal cohort of women in midlife to this analysis. The primary outcome variables were depressive and anxiety symptoms, assessed by hospital anxiety and depression scale (HADS). The generalized estimation equation was used in the statistical analysis.Results:Followed up from 2006 to 2014, 430 women and 2 533 HADS assessments were retained in the cohort. Depressive symptoms were more common than anxiety symptoms during all menopausal stages. The incidences of depressive and anxiety symptoms were 14.5% (19/191) and 3.1% (4/191) in the premenopausal -3 stage, respectively. The incidence increased in both menopausal transition and postmenopausal stage, with the highest incidence in the +1c stage [20.6% (155/751) and 8.8% (66/751), respectively]. However, these differences were not statistically significant (all P>0.05). Depressive symptoms were highest in the ≥60-<65 age group [20.8% (74/355)], and anxiety symptoms were highest in the ≥50-<55 age group [8.2% (62/754)]; but there were no statistical significances between different age groups and depressive and anxiety symptoms (all P>0.05). Multivariable analysis showed that high body mass index, low education status, and poor health status were independently associated with depressive symptoms (all P<0.05), and that poor health status, trouble falling asleep, and early awakening were independently associated with anxiety symptoms (all P<0.01). Conclusions:Depressive and anxiety symptoms are more common during menopausal transition and postmenopausal stage compared with reproductive stage. Depressive symptoms are more common than anxiety symptoms. To screen and assess depressive and anxiety symptoms in perimenopausal women is essential, especially for women with high risk factors.
RÉSUMÉ
Bone defects have always been an important cause of threat to human health, and artificial biomimetic bone repair replacement materials are currently one of the most effective and feasible solution approaches to treat bone damage. To develop artificial bone biomimetic materials, an in vitro biomimetic mineralization system must be constructed first to study in vitro biomimetic mineralization mechanism of natural bone matrix. Collagen is a template for mineralization, and its properties such as crosslinking degree, diameter, osmotic pressure, and surface charge can all directly affect mineralization progress. The biochemical and mechanical environments in which mineralization occurs are also quite distinct in their effects on mineralization process, particularly noncollagenous proteins and fluid shear stress (FSS). FSS is considered to be the main mechanical stimulation of bone tissues in micro-environment, which is of great significance to bone growth, repair and health maintenance. FSS at different levels and loading regimes has significant effects on transformation of amorphous calcium phosphate to bone apatite, self-assembly and directional alignment of collagen fibrils, and formation of hierarchical intrafibrillar mineralization. In this paper, the factors affecting collagen mineralization and their mechanism were summarized, with focus on regulation of FSS on collagen mineralization, and development direction in future was also prospected.
RÉSUMÉ
Objective To make classification and segment measurement for the cases with tibiofibular and ankle fractures in parachuting landing, and investigate main classification types of parachuting fractures and fracture segments of high risk.Methods A total of 56 fracture cases in parachuting landing were collected, and the tibiofibula and ankle fractures were classified according to AO-OTA or Lauge-Hansen classification standards respectively based on their digital X-ray images. The medium plane between talus and tibia joint planes in ankle joint was defined as the reference plane. The highest and lowest injury points of tibia and fibula were marked respectively, and the fracture segment was defined between the highest and lowest point for statistical analysis.Results For tibiofibular and ankle fracture cases in parachuting landing, fracture at both tibia and fibula accounted for 80.4%. The major classification of tibiofibula fracture was 42-D/5.2 (45.8%) and 42-D/5.1 (16.7%). The major classification for ankle fracture was pronation-external rotation (PER, 59.4%) and supination-external rotation (SER, 37.5%). When tibiofibular and ankle fracture cases in parachuting landing occurred, the fracture segment of the tibia was mainly from 57 to 143 mm above the reference plane and from 6 mm below the reference plane to 24 mm above the reference plane, while the fracture segment of the fibula was 4-45 mm and 74-83 mm above the reference plane. Injury risks of all above segments were higher than 50%.Conclusions For protection of lower limbs in parachuting landing, the fracture at both tibia and fibula should be highly noticed. The ankle motion of PER and SER should be especially restricted in parachuting ankle protection.
RÉSUMÉ
Objective Based on hemodynamic analysis, to investigate the cause of distal re-entry tear in Stanford type B aortic dissection after thoracic endovascular aortic repair (TEVAR).Methods A patient with type B aortic dissection was reexamined regularly with computed tomography angiography (CTA) at 1st month, 6th month, 12th month and 24th month after TEVAR. Based on the CTA images in each period, three-dimensional (3D) aorta models were reconstructed to perform morphological analysis and hemodynamic simulation.Results Compared with the diameter at 1st month after TEVAR, the diameter of true lumen at 12 months after TEVAR increased by 1.8 times and the global distortion of aorta increased by 16.67%. At postoperative 1st, 6th and 12th month, the maximum blood velocities at the new entry tear in systole were 69.6%, 33.7% and 92.1% higher than the average ones at distal landing zone, and the maximum wall shear stresses (WSSs) were 2.52, 2.32 and 3.52 times of the average WSSs respectively. In addition, the maximum time-averaged WSS (TAWSS) at 1st, 6th and 12th month after TEVAR were 1.88, 2.53 and 3.62 times of the mean TAWSS respectively.ConclusionsThe morphology of the aorta remodeled after TEVAR, and a sudden change in the diameter of true lumen occurred at distal anchoring zone and continued to increase. As a result, the blood flow velocity in this area accelerated, and the intima was continuously exposed to high WSS, leading to the redissection.
RÉSUMÉ
Objective To study the wear condition of rotating hinge knee prosthesis (RHKP) during horizontal walking gait, and provide technical references for wear prediction and clinical application of this kind of prosthesis. Methods A finite element wear model of RHKP was established based on the standard ISO 14243, and the simulation results including the wear distribution and mass wear rate of tibiofemoral joint surface were compared with the results from in vitro experiments on the same type of prosthesis. Results The mass wear rate of the polyethylene insert was 26.01 mg/MC (million cycle)from finite element analysis (FEA) and (30.06±1.21) mg/MC from in vitro experiments, and the mass wear rate of the upper surface of polyethene insert from FEA was about 3.3 times that of the lower surface. The wear area obtained by FEA was basically consistent with that obtained by in vitro wear measurement. The main wear area was symmetrically distributed in the middle and back of the upper surface. Conclusions The mass wear rate of RHKP, as a semi-restrictive prosthesis, is obviously higher than that of primary total knee joint prosthesis. More attention should be paid to wear test and evaluation of RHKP.
RÉSUMÉ
Objective To investigate the hemodynamic effects of morphological parameters on renal artery stenosis （RAS）, so as to provide theoretical references for clinical practice. Methods The idealized models of RAS were established, then the hemodynamic effects from morphological parameters of stenosis including its area, symmetry, length and shape on renal artery was explored using computational fluid dynamics （CFD） method. Results The renal perfusion, pressure drop and wall shear stress (WSS) distributions in renal artery were significantly correlated with area stenosis (AS). When the stenosis area increased from 50% to 70%, all hemodynamic parameters changed significantly. In addition, an asymmetrical stenosis resulted in a significant increase of abnormally high WSS and length of recirculation flow in renal artery, but the change of stenosis length or shape only led to marginal changes in hemodynamics. Conclusions Although AS is still the most significant factor to influence hemodynamics in RAS, other morphological parameters, especially asymmetric stenosis, cannot be neglected. Therefore, it is suggested that clinical treatment plans should be a comprehensive evaluation based on these morphological parameters.
RÉSUMÉ
Objective To measure mechanical properties of calcified tissues from human aortic valve by nanoindentation test. Methods Leaflets from 5 patients with aortic stenosis were collected. Elastic modulus and hardness of the calcified leaflets were obtained by nanoindentationtest. Results The elastic modulus and hardness of the calcified leaflets were (15.69±3.89) GPa and (0.59±0.15) GPa, respectively. Conclusions The elastic modulus and hardness of the calcified valve tissues can be obtained by nanoindentationtest, which provides experimental data for biomechanical research of the valve.
RÉSUMÉ
Objective Aiming at the problem that mechanical properties for the continuum of muscle tissues cannot be considered in active and passive behaviors of different structurally coupled muscles, a method of passive and active coupling in the same constitutive equation was proposed to construct ahyperelastic active and passive constitutive model of skeletal muscle continuum. Methods In order to calibrate parameters of the passive constitutive model, the uniaxial tensile experiment method and conditions were given, and through theoretical derivation, the specific method of using experimental data to solve the passive model parameters was introduced. In order to verify effectiveness of the active model, the model was verified with an example. Results The curves predicted by the model were in good agreement with the experimental output stress-stretch ratio curves. At the same strain, the maximum error of passive stress and total stress were only 20 kPa and 40 kPa. Conclusions The continuum hyperelastic constitutive model can better simulate active and passive behavior of skeletal muscles, which is beneficial for modeling and simulation of human muscles in further study.
RÉSUMÉ
Mechanical ventilation is an importmant life-sustaining treatment for patients with acute respiratory distress syndrome. Its clinical outcomes depend on patients' characteristics of lung recruitment. Estimation of lung recruitment characteristics is valuable for the determination of ventilatory maneurvers and ventilator parameters. There is no easily-used, bedside method to assess lung recruitment characteristics. The present paper proposed a method to estimate lung recruitment characteristics from the static pressure-volume curve of lungs. The method was evaluated by comparing with published experimental data. Results of lung recruitment derived from the presented method were in high agreement with the published data, suggesting that the proposed method is capable to estimate lung recruitment characteristics. Since some advanced ventilators are capable to measure the static pressure-volume curve automatedly, the presented method is potential to be used at bedside, and it is helpful for clinicians to individualize ventilatory manuevers and the correpsonding ventilator parameters.