Experiments and finite element modelling for the study of prolapse in the pelvic floor system

Pelvic prolapse affects one woman in three of all ages combined and is quite common for more than 60% of patients over 60 years of age. The treatment of this pathological problem is one of the biggest challenges to the gynaecologist today. The rate of surgical intervention failure is quite significant. The recurrence of prolapse could be related to inadequate surgical technique or the pathology or/and biomechanical deficiency of the soft tissues. The modelling and simulation of the behaviour of the pelvic cavity could be a major tool for specific evaluation of pelvic status. A first stage of this model is being developed and reported. The computer-aided design model of the organs of the pelvic floor is created using magnetic resonance image data and the ligament boundary conditions are defined. A multi-organ geometric model is thus created and studied.     

Active response of skeletal muscle: In vivo experimental results and model formulation

The contractile properties of the tibial anterior (TA) of Wistar rats were measured by means of a multipurpose testing machine. The muscle was isolated from the connective tissues, preserving the proximal insertion. The distal tendon was transected and fixed to the machine actuator. The leg was inmobilised using a pin drilled through the femoral condyle. In this way the force response was studied in vivo at different constant lengths for some voltages and frequencies. Mathematical functions are proposed for adjusting the force-length, force-frequency and force-time relations. The model includes a novel formulation for the depression response during muscle tetanisation.     

Linking hyperelastic theoretical models and experimental data of vaginal tissue through histological data

Mechanical characterization of living tissues and computer-based simulations related to medical issues, has become increasingly important to improve diagnostic processes and treatments evaluation. This work proposes a link between the mechanical testing and the material model predictions through histological data of vaginal tissue. Histological data was used to link tensile testing experiments with material-dependent parameters; the approach was adequate to capture the nonlinear response of ovine vaginal tissue over a large strain range.The experimental data obtained on a previous study, has two main components: tensile testing and histological analysis of the ovine vaginal tissue. Uniaxial tensile test data and histological data were collected from three sheep groups: virgins, pregnant and parous. The distal part of vaginal wall was selected since it is prone to tears induced by vaginal delivery.The HGO (Holzapfel-Gasser-Ogden) model parameters were fitted using a stochastic approach, namely the Simple Genetic Algorithm (SGA). The SGA was able to fit the experimental data successfully (R² > 0.986). The dimensionless coefficient ξ, was highly correlated with histological data. The ratio was seen to increase linearly with increasing collagen content.Coefficient ξ brings a new way of interpreting and understanding experimental data; it connects the nonlinear mechanical behaviour (tensile test) with tissue’s morphology (histology). It can be used as an ‘inverse’ (approximate) method to estimate the mechanical properties without direct experimental measurements, through basic histology.In this context, the proposed methodology appears very promising in estimating the response of the tissue via histological information.     

盆底超声参数与经阴道分娩初产妇产后盆底功能的关系及对早期发生盆腔脏器脱垂的预测研究

摘要 目的：探讨盆底超声参数与经阴道分娩初产妇产后盆底功能的关系及对早期发生盆腔脏器脱垂的预测价值。方法：选择2021年9月至2022年9月来我院行规律产检的阴道分娩产妇80例作为研究对象。本研究对80例产妇在产后6~8周进行盆底超声检查,记录检查时的Valsalva、缩肛动作下的肛提肌裂孔面积、前后径、膀胱尿道后角信息。对比两组静息、缩肛状态下及Valsalva动作的肛提肌裂孔面积、前后径、膀胱尿道后角水平,分析两组盆底肌功能指标,分析病例组盆底肌功能指标与静息、缩肛、Valsalva动作时盆底超声参数指标的相关性,盆底超声参数预测早期发生盆腔脏器脱垂的ROC曲线分析。结果：病例组的静息、缩肛状态下及Valsalva动作的肛提肌裂孔面积、前后径、膀胱尿道后角水平较对照组高（P<0.05）。病例组的盆底Ⅰ类肌肌力、盆底Ⅱ类肌肌力、阴道指诊盆底肌力明显较对照组低（P<0.05）。盆底Ⅰ类肌肌力、盆底Ⅱ类肌肌力、阴道指诊盆底肌力与静息、缩肛、Valsalva动作时的肛提肌裂孔面积、前后径、膀胱尿道后角水平均呈负相关（P均<0.05）。静息、缩肛、Valsalva动作时的盆底超声参数指标对盆腔脏器脱垂的AUC均超过0.5,P均<0.05。结论：盆底超声参数与经阴道分娩初产妇产后盆底功能呈负相关,可用于早期发生盆腔脏器脱垂的预测,值得临床上推广应用。     

Large strain behaviour of brain tissue in shear: some experimental data and differential constitutive model.

In this paper, some experimental measurements of the behaviour of bovine brain tissue under large shear strains in vitro are reported, and a constitutive model which is consistent with the data is developed. It was determined that brain tissue is not strain-time separable, showing slower relaxation at higher strains, and that the stresses in shear are not linear with increasing shear strain. The new constitutive model is a differential model, including both an "elastic" term, of the Mooney type and a nonlinear viscoelastic term. The latter allows for the change in relaxation behaviour with strain, by modifying an upper convected multimode Maxwell model with a damping function. The model shows good agreement with the experimental shear results and could be used to describe other types of data.     

Mechanical responses of the periodontal ligament based on an exponential hyperelastic model: a combined experimental and finite element method

The V–W exponential hyperelastic model is adopted to describe the instantaneous elastic response of the periodontal ligament (PDL). The general theoretical framework of constitutive modeling is described based on nonlinear continuum mechanics, and the elasticity tensor used to develop UMAT subroutine is formulated. Nanoindentation experiment is performed to characterize mechanical properties of an adult pig PDL specimen. Then the experiment is simulated by using the finite element (FE) analysis. Meanwhile, the optimized material parameters are identified by the inverse FE method. The good agreement between the simulated results and experimental data demonstrates that the V–W model is capable of describing the mechanical behavior of the PDL. Therefore, the model and its implementation into FE code are validated. By using the model, we simulate the tooth movement under orthodontic loading to predict the mechanical responses of the PDL. The results show that local concentrations of stress and strain in the PDL are found.     

组织器官通讯对骨骼肌发育的作用及调控机制研究进展

骨骼肌是动物机体最重要的器官之一,研究骨骼肌发育调控机制对于肌肉相关疾病的诊断以及家畜肉质的改善都有着重要意义。骨骼肌发育调控是一个复杂的过程,受到大量肌肉分泌因子和信号通路的调节。此外,为了维持体内代谢稳态并最大限度地利用能量,机体协调多个组织器官形成了复杂而又精密的代谢调控网络,对于调控骨骼肌发育也发挥着重要的作用。随着组学技术的发展,人们对于组织器官通讯的潜在机制进行了深入研究。本文综述了脂肪组织、神经组织、肠道等组织器官通讯对于骨骼肌发育的影响,以期为靶向调控骨骼肌发育提供理论基础。     

Reirradiation at long time intervals in mouse kidney: a comparison between experimental results and the predictions of the F-type tissue model

The tolerance of a late-responding tissue to reirradiation after long time intervals has been analysed using the F-type tissue model. In this model the tissue is composed of identical cells, each of which is capable of extensive proliferation and of tissue-specific function. The model was adapted to calculate the response to two fractions of radiation given in a variable overall time. For two equal doses of radiation the repair of tissue damage after the first fraction could be detected theoretically by a change in the rate of cell depletion after retreatment and by an increase in the minimum cell number attained. For an 'experimental set-up', in which a constant first dose was followed by a range of retreatment doses in a variable overall time, the repair of tissue damage theoretically could be detected most sensitively by a shift of the dose-response curves to higher retreatment doses as the time interval between the two doses was increased. A prerequisite for a proper comparison of these dose-response curves was that the responses were evaluated at times after the first dose determined by the minimal latency times after high retreatment doses. From a comparison of these theoretical results with experimental findings for mouse kidneys it was concluded that no recovery of tissue function took place over a 6-month period. Instead it appeared that the kidneys had become more sensitive to irradiation over this period.     

Algal biomass dynamics during colonization of artificial islands: experimental results and a model

Algal biomass during colonization of polyurethane foam islands (5.1 cm × 7.6 cm × 7.6 cm) was approximated by measuring chlorophyll a levels on islands after exposure periods of 1, 2, 3, 4, and 6 weeks at six locations in a small lake in central Tennessee, USA. Chlorophyll, ash-free dry weight, and concurrent environmental data were collected for two colonization periods: one in late winter and spring (Set 1), a second in summer (Set 2).During Set 1 algal biomass levels, as indicated by chlorophyll a, showed a sharp rise initially, but Set 2 islands exhibited a lag period of 7 to 12 days before a rapid increase in algal biomass was noted. Equilibrium chlorophyll a values were similar for both sets. High levels of phaeopigments were found at Stations 2, 3, and 4 during Set 2 resulting in large corrections in chlorophyll a readings. Ash-free dry weight values increased steadily through each colonization period.A model of biomass accumulation during colonization was constructed postulating three major processes — photosynthesis, respiration, and passive accumulation — which were modulated by three environmental factors — light, temperature, and plankton chlorophyll a levels. For simulations parameter values were taken from the literature where possible. Additional parameter values were set and literature values adjusted when the model was tuned to Set 2 data. A simulation with the tuned model using Set 1 environmental input resulted in a good prediction of equilibrium values, but a misinterpretation of initial values. The discrepancy between model predictions and data was alleviated when the passive accumulation rate was increased demonstrating the dependence of biomass values early in colonization on passive accumulation from the plankton.     

A convenient screening test system and a model for thermal germination responses of wild plant seeds: behaviour of model and real seeds in the system

Abstract A convenient test system for screening the thermal germination behaviour of seeds was developed for both basic and applied research in seed germination ecophysiology. Only two temperature-controlled facilities, a test period of about a month and a relatively small number of sample seeds arc needed to obtain information on the thermal-germination parameters of individual seed populations, such as lower or higher limit temperatures, and thermal times required for germination. In the test system, the germination performances of sample seed populations were compared under two temperature regimes: a gradually increasing temperature regime and a gradually decreasing temperature regime, in which the seeds were subjected to gradually changing temperatures in the range of 4 36°C. In order to assess the effects of various values for thermal-germination parameters on the patterns of germination performance in the system, the behaviour of model seeds characterized by a definite set of thermal germination parameters were investigated. Referring to the results of the simulations, the actual germination patterns of some wild-seed populations in the test system were interpreted in terms of thermal-germination parameters.     

Optical incoherent technique for noninvasive assessment of blood flow in tissues: Theoretical model and experimental study

Laser noninvasive methods for assessment of a tissue blood flow (BF), for example, the Laser Doppler Flowmetry (LDF), are well-known today. However, in such methods, low-frequency fluctuations (LFFs) in the registered optical signal caused by blood volume changes inside a tissue have not been studied in details until now. The aim of this study is to investigate the LFFs formation and to justify the LFFs-based diagnostic technique for cutaneous BF assessment. LFFs are theoretically described and experimentally shown in the input LDF signal inside the frequency range 0 to 10 Hz. They are substantiated as the basis of the new diagnostic method, in which BF is defined as the magnitude of blood volume changes in a tissue per unit time. The hand-made prototype of the promising diagnostic tool with light emitted diodes is used to validate the technique in experiments in vivo on 16 healthy volunteers in comparison with the LDF method. Experimental results show a good similarity of the recorded BF for both coherent and incoherent method. The proposed technique makes it possible the creation of inexpensive diagnostic equipment for assessment of cutaneous BF without using lasers and coherent light, completely and functionally comparable to LDF devices.     

Importance of changing CO2, temperature, precipitation, and ozone on carbon and water cycles of an upland-oak forest: incorporating experimental results into model simulations

Observed responses of upland‐oak vegetation of the eastern deciduous hardwood forest to changing CO₂, temperature, precipitation and tropospheric ozone (O₃) were derived from field studies and interpreted with a stand‐level model for an 11‐year range of environmental variation upon which scenarios of future environmental change were imposed. Scenarios for the year 2100 included elevated [CO₂] and [O₃] (+385 ppm and +20 ppb, respectively), warming (+4°C), and increased winter precipitation (+20% November–March). Simulations were run with and without adjustments for experimentally observed physiological and biomass adjustments. Initial simplistic model runs for single‐factor changes in CO₂ and temperature predicted substantial increases (+191% or 508 g C m^?2 yr^?1) or decreases (?206% or ?549 g C m^?2 yr^?1), respectively, in mean annual net ecosystem carbon exchange (NEE_a≈266±23 g C m^?2 yr^?1 from 1993 to 2003). Conversely, single‐factor changes in precipitation or O₃ had comparatively small effects on NEE_a (0% and ?35%, respectively). The combined influence of all four environmental changes yielded a 29% reduction in mean annual NEE_a. These results suggested that future CO₂‐induced enhancements of gross photosynthesis would be largely offset by temperature‐induced increases in respiration, exacerbation of water deficits, and O₃‐induced reductions in photosynthesis. However, when experimentally observed physiological adjustments were included in the simulations (e.g. acclimation of leaf respiration to warming), the combined influence of the year 2100 scenario resulted in a 20% increase in NEE_a not a decrease. Consistent with the annual model's predictions, simulations with a forest succession model run for gradually changing conditions from 2000 to 2100 indicated an 11% increase in stand wood biomass in the future compared with current conditions. These model‐based analyses identify critical areas of uncertainty for multivariate predictions of future ecosystem response, and underscore the importance of long term field experiments for the evaluation of acclimation and growth under complex environmental scenarios.     

Impact of apolipoprotein A1- or lecithin:cholesterol acyltransferase-deficiency on white adipose tissue metabolic activity and glucose homeostasis in mice

High density lipoprotein (HDL) has attracted the attention of biomedical community due to its well-documented role in atheroprotection. HDL has also been recently implicated in the regulation of islets of Langerhans secretory function and in the etiology of peripheral insulin sensitivity. Indeed, data from numerous studies strongly indicate that the functions of pancreatic β-cells, skeletal muscles and adipose tissue could benefit from improved HDL functionality. To better understand how changes in HDL structure may affect diet-induced obesity and type 2 diabetes we aimed at investigating the impact of Apoa1 or Lcat deficiency, two key proteins of peripheral HDL metabolic pathway, on these pathological conditions in mouse models. We report that universal deletion of apoa1 or lcat expression in mice fed western-type diet results in increased sensitivity to body-weight gain compared to control C57BL/6 group. These changes in mouse genome correlate with discrete effects on white adipose tissue (WAT) metabolic activation and plasma glucose homeostasis. Apoa1-deficiency results in reduced WAT mitochondrial non-shivering thermogenesis. Lcat-deficiency causes a concerted reduction in both WAT oxidative phosphorylation and non-shivering thermogenesis, rendering lcat^?/? mice the most sensitive to weight gain out of the three strains tested, followed by apoa1^?/? mice. Nevertheless, only apoa1^?/? mice show disturbed plasma glucose homeostasis due to dysfunctional glucose-stimulated insulin secretion in pancreatic β-islets and insulin resistant skeletal muscles. Our analyses show that both apoa1^?/? and lcat^?/? mice fed high-fat diet have no measurable Apoa1 levels in their plasma, suggesting no direct involvement of Apoa1 in the observed phenotypic differences among groups.