脑组织压缩力学性能和本构模型

目的 研究脑组织在不同应变率下的压缩力学性能和本构模型。方法 使用电子万能试验机对猪脑组织白质和灰质开展准静态压缩和中速压缩试验,获得脑组织不同应变率下的应力-应变曲线。采用Ogden本构模型对试验曲线进行拟合,确定本构模型参数,并在有限元软件中进行仿真验证。结果 脑组织应力-应变曲线呈现非线性特征,具有较强的应变率相关性和敏感性。压缩至0.6应变时,在5×10-4~5×10-2 s-1应变率下,白质和灰质的应力分别增加102%和129%,在1~1.5 s-1应变率下则分别增加50.7%和54.6%;1.5 s-1应变率下白质、灰质应力比5×10-4 s-1应变率下分别增加347%、413%。Ogden模型拟合下的R2>0.99,仿真结果与试验结果误差在15%以内,验证了模型的有效性。结论 研究结果有助于实现对脑组织变形的预测,为建立更加科学合理的人体模拟靶标以及在设计和改进颅脑防护装备上提供准确的理论依据。     

基于可行方向法的脂肪组织本构模型参数反求优化

目的研究脂肪组织在中等应变率下本构模型及其参数反求。方法基于脂肪组织力学性能实验,通过有限元方法重构脂肪组织压缩实验,并对常见表征脂肪组织的本构模型进行参数筛选。结合最优化方法中的可行方向法(method of feasible direction,MFD),进行中应变率下脂肪组织本构模型相关参数的反求。结果中应变率(260 s~(-1))下黏弹性本构模型相比Ogden本构模型更适合表征脂肪组织的力学响应,并反求得到适用于仿真的本构模型参数。结论中等应变率下黏弹性本构模型更适合表征脂肪组织力学响应。研究结果为汽车碰撞有限元仿真中探究人体脂肪组织对人体损伤的影响提供参考。     

实验小鼠脂肪组织石蜡切片制作方法的改进

<正>脂肪组织是机体重要的能量仓库,广泛分布于全身的皮下及内脏各处[1],薄层疏松的结缔组织将其分割成许多小叶结构[2],小叶内有大量的脂肪细胞。近年来,人们越来越重视对脂肪组织的研究[3-5],而这些研究都离不开形态学方面(如HE、免疫组化染色)的观察。因此,制作优质的脂肪组织切片标本至关重要。由于脂肪组织结构特殊,含有大量的油脂成分,如果组织固定、脱水脱脂不完全,切片时往往出现组织碎渣,有空洞、触摸较软、放置后蜡块表面有凹陷、不易保存等各     

血红细胞在渗透实验中的变形分析

目的数值模拟血红细胞在渗透实验中的变形具体全过程并寻找渗透压临界值。方法建立细胞的壳体模型,采用Neo-Hookean应变能形式的超弹性本构关系,采用文献提供的细胞膜剪切模量实测数据,使用有限元软件ABAQUS进行计算。结果得到了在血红细胞渗透实验中细胞膜受渗透压作用而逐渐变形的全过程,发现当渗透压增加到50～60 mPa时,细胞膜由双凹形迅速变成椭球形。该渗透压临界值落在文献给出的计算结果范围内。同时得到了在该临界值两侧细胞膜的Mises应力分布图。结论血红细胞由双凹形变成椭球形的临界渗透压为50～60 mPa。采用壳体模型以及Neo-Hookean形式的超弹性材料本构关系进行血红细胞渗透实验的数值模拟,可以较好地展示血红细胞在渗透实验中的变形全过程。     

敲除PAMM基因对小鼠白色和棕色脂肪组织基因表达的影响

目的：巨噬细胞集落刺激因子诱导单核细胞活化的类过氧化物酶2(peroxiredoxin-like 2 activated in M-CSF stimulated monocytes, PAMM)是一种具有抗炎、抗氧化功能的蛋白,在脂肪组织中高表达,本文拟利用基因敲除小鼠,探究PAMM对白色和棕色脂肪组织形态及基因表达等的影响,以期为其功能研究提供新思路。方法：利用CRISPR-Cas9等技术构建PAMM基因敲除（knockout, KO）小鼠,用野生型（wild-type, WT）小鼠作为对照。收集腹股沟皮下白色脂肪组织（inguinal adipose tissue, IAT）和背部棕色脂肪组织（brown adipose tissue, BAT）,通过HE染色观察组织形态,利用RNA-seq和RT-qPCR检测相关基因的表达。结果：通过基因组PCR及测序,证明基因敲除小鼠构建正确。敲除PAMM后IAT和BAT形态无明显变化,但E2F靶点、未折叠蛋白反应等基因集在IAT或BAT中富集。比较WT和KO小鼠组织,发现33个基因的变化趋势在IAT和BAT中保持一致;而仅在IAT中出现变化的...     

脑组织本构模型及其生物力学特性分析

在交通事故中,颅脑损伤因其高发率和高致命率成为最严重的损伤。颅脑有限元模型成为开展头部损伤研究的重要工具。模型中脑组织所应用的本构模型及材料属性是决定颅脑损伤预测结果的关键因素。本文旨在针对应用于模拟脑组织的本构模型和材料属性进行综述,从而深入理解脑组织生物力学特性,为颅脑损伤的有限元研究提供参考。     

用三维重建和有限元方法对人体心脏进行力学分析

目的　建立人体心脏的三维几何模型和有限元网格模型，进行有限元仿真计算。方法　利用可视化人体心脏数据集，通过3D-DOCTOR软件和SOLIDWORKS软件重建心脏外形和内腔的三维结构数据，以STEP格式导入ABAQUS有限元软件形成网格模型。在有限元网格模型的基础上进行心脏自振频率、内腔血压等载荷情况下的力学性能分析。结果　建立了一个数字化心脏可视模型。能够反映心脏三维形状和内腔结构；得到了心脏内腔的大致容积；反映了心脏心肌不同区域的不同性质；得到了心脏3个方向的自振频率和振型，以及内腔血压下的应力分布。结论　建立了可视化三维心脏的几何和网格模型，反映了心脏的外形和内腔。利用有限元分析方法，能够为心脏的生物力学分析提供可视化的数值仿真平台。     

不同材料赋值下股骨静力学有限元模型的力学仿真分析

文题释义： 材料赋值：由于人体骨骼结构复杂,由骨膜、皮质骨和松质骨构成,并且不同骨质的材料属性差异很大,因此在很多生物力学分析过程中为了简化模型,提高分析效率,很多学者在进行生物力学仿真研究中对骨骼模型采用了不同的赋值方法。 股骨模型材料赋值：给股骨分配不同的材料属性成为建立个性化有限元模型的基本步骤,而且材料属性分配将对分析结果产生很大的影响。但是目前有关不同赋值方法对人体骨科生物力学仿真分析研究的影响还很少有全面系统的研究。 背景：不同骨质的材料属性差异很大,因此在很多生物力学分析过程中为了简化模型,提高分析效率,很多学者在进行生物力学仿真研究中对骨骼模型采用了不同的赋值方法,而材料属性分配将对生物力学分析结果产生很大的影响。 目的：采用不同的材料属性赋值方法建立3种股骨有限元模型并进行有限元仿真分析,探究不同材料赋值方法对股骨有限元生物力学仿真分析的影响。 方法：采集志愿者股骨CT扫描数据,以DICOM格式文件导入Mimics医学影像处理软件重建股骨模型,对模型分别赋予3种不同的材料属性,即均一材料赋值、皮-松质骨赋值和灰度赋值,并将模型导入有限元分析软件Abaqus 6.14中,设置相同的载荷和边界条件进行应力及位移分析。 结果与结论：①3种股骨模型的应力输出结果相差不大,且均在合理范围内;②但是均一材料赋值股骨模型与皮-松质骨赋值股骨模型的最大应力主要分布于股骨干部位,而灰度赋值股骨模型的最大应力分布在股骨颈处,这也与现实状态下股骨骨折部位主要出现于股骨颈部位所吻合;③皮-松质骨赋值模型和灰度赋值模型输出的位移值基本一致;而均一材料赋值的股骨模型位移值最小,并且与其他2种模型位移量相差40%左右;④提示灰度赋值的方法能够较好地反映人体股骨的生物力学特性,从而可以更准确地模拟真实股骨的生物力学特征,这也为骨科生物力学进行有限元仿真建模提供了重要理论依据。 ORCID: 0000-0001-5075-7333(颜继英) 中国组织工程研究杂志出版内容重点：人工关节;骨植入物;脊柱;骨折;内固定;数字化骨科;组织工程     

肾脏钝性撞击损伤影响因素的有限元方法研究

目的 采用有限元方法研究肾脏钝性撞击损伤的影响因素。方法 基于肾脏CT图像构建不同年龄人群肾脏有限元模型,重构肾脏钝性撞击实验,分析肾脏材料本构参数、肾脏组织结构、肾脏大小、撞击位置和撞击速度等参数对肾脏损伤的影响。结果 相同撞击工况下,肾皮质应力随肾脏质量的增加有所减少,随撞锤撞击速度的增加而增加;肾包膜具有一定的吸能效果,从而降低肾脏的应力;肾脏受到撞击时,侧面撞击的肾皮质应力明显高于正面撞击。结论 相比黏弹性本构模型,Mooney Rivlin材料本构模型更适合用于肾脏损伤的有限元评价;肾脏损伤随肾脏质量的增加有所减少;撞锤撞击速度的增加会加剧肾脏损伤;肾包膜会一定程度上减轻肾脏损伤,故在进行肾脏有限元建模时,必须考虑肾包膜结构的存在;相比正面和背面撞击,肾脏侧面受到撞击时损伤相对更严重。     

胸腰段椎体压缩性骨折三维有限元模型的建立及其意义

目的:建立胸腰段骨质疏松性椎体压缩性骨折的三维有限元模型.方法:螺旋CT扫描骨质疏松性椎体压缩性骨折患者的胸11椎体上缘-腰1椎体下缘,所得数据经Photoshop处理后转入Pro/Engineer软件,采用实体建模的方法重建出三维立体几何图像,再利用自由造型模型系统对图像进行修改,通过铺面形成椎体三维图形,转入有限元软件进行网格划分,建成三维有限元分析模型.结果:所建模型外观逼真,几何相似性好.结论:为脊柱胸腰段三维有限元模型的建立提供了一种简便,精确的方法,为分析和研究该模型在各种受力情况下的生物力学表现创造了条件.     

脂肪组织工程研究进展

组织工程为临床疑难问题的解决提供了新的思路 ,而工程化脂肪组织具有组织重建与填充作用 ,广泛应用于外科领域。本文就脂肪组织工程涉及的前脂肪细胞生长分化、分子调控、聚合物支架及细胞外基质、微环境等方面进行综述     

Ⅱ型固有淋巴细胞在白色脂肪棕色化中的作用

正Ⅱ型固有淋巴细胞(typeⅡinnate lymphoid cells,ILC2s)于2001年被发现,由共同淋巴样祖细胞发育而来,广泛分布在血液、肠道、气管、肺脏、脾脏、肝脏、动物脂肪和皮肤等部位,经白细胞介素(interleukin,IL)-25或IL-33刺激后可产生IL-5和IL-13等2型辅助性T(type 2 helper T,Th2)细胞因子,在Th2     

Multiaxial mechanical properties and constitutive modeling of human adipose tissue: A basis for preoperative simulations in plastic and reconstructive surgery

A preoperative simulation of soft tissue deformations during plastic and reconstructive surgery is desirable to support the surgeon’s planning and to improve surgical outcomes. The current development of constitutive adipose tissue models, for the implementation in multilayer computational frameworks for the simulation of human soft tissue deformations, has proved difficult because knowledge of the required mechanical parameters of fat tissue is limited. Therefore, for the first time, human abdominal adipose tissues were mechanically investigated by biaxial tensile and triaxial shear tests. The results of this study suggest that human abdominal adipose tissues under quasi-static and dynamic multiaxial loadings can be characterized as a nonlinear, anisotropic and viscoelastic soft biological material. The nonlinear and anisotropic features are consequences of the material’s collagenous microstructure. The aligned collagenous septa observed in histological investigations causes the anisotropy of the tissue. A hyperelastic model used in this study was appropriate to represent the quasi-static multiaxial mechanical behavior of fat tissue. The constitutive parameters are intended to serve as a basis for soft tissue simulations using the finite element method, which is an apparent method for obtaining promising results in the field of plastic and reconstructive surgery.     

Effect of the β-adrenoblocker propranolol on adrenalin lipolysis in adipose tissue of rats with spontaneous genetic hypertension

The action of the -adrenoblocker propranolol on adrenalin lipolysis was studied in adipose tissue of rats with spontaneous hypertension and of control rats. The degree of lipolysis was judged from the accumulation of glycerol in the incubation mediumin vitro. The maximal response of adipose tissue to adrenalin was found to be the same in rats with hypertension and control animals. The adrenalin concentration evoking half the maximal response (K_A) in rats with hypertension was found to be half that observed in control rats. In the presence of propranolol this parameter increased more in SHR rats than in the controls. The results indicate increased sensitivity of the adipose tissue of SHR rats to propranolol, possibly in connection with changes in the properties of the -adrenoreceptor in this form of hypertension.Central Research Laboratory, Fourth Main Board, Ministry of Health of the USSR. Department of Pathomorphology, Moscow. (Presented by Academician of the Academy of Sciences of the USSR E. I. Chazov.) Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 88, No. 11, pp. 553–555, November, 1979.     

Effect of ventromedial hypothalamic stimulation on blood flow of brown adipose tissue in rats

The changes in regional blood flows to the rat's interscapular brown adipose tissue and several other tissues during electrical stimulation of the ventromedial hypothalamus (VMH) were studied using radioactively labelled microspheres. Measurement of blood flow was carried out, along with monitoring heart rate, under anesthesia and at thermoneutrality. During VMH stimulation the heart rate was clearly augmented and cardiac output increased about 45%. Regional blood flows were significantly increased in response to VMH stimulation in interscapular brown adipose tissue, adrenal glands, diaphragm and gastrocnemius muscles. The response of interscapular brown adipose tissue was the most prominent (approx. fiftyfold increase). Blood flows tended to decrease in spleen, lungs and kidneys during VMH stimulation, but did not change in liver or in other visceral organs. These observations suggest that the VMH is concerned with the regulation of regional blood flow to brown adipose tissue and contributes to thermogenesis in this tissue.     

Comparison of DNA synthesis in white and brown adipose tissue in rats with ventromedial hypothalamic lesions

Ventromedial hypothalamic (VMH) lesions cause excessive fat accumulation in white adipose tissue (WAT), and brown adipose tissue (BAT); however, little information is available on whether or not cell proliferation occurs in WAT and BAT after VMH lesioning. In this study, we determined the DNA content and thymidine incorporation in unilateral parametrial WAT and interscapular BAT 0, 1, 3, and 7 days after VMH lesioning, and examined the mechanism of increased DNA content in WAT. In rats with VMH lesions, the weight of WAT and BAT had increased significantly at 7 days, and the DNA content and thymidine incorporation of WAT had increased significantly at 3 days and continued to increase for up to 7 days, while those of BAT did not increase for as long as 7 days after VMH lesioning. Restricted food intake according to the pair-feeding method partially inhibited the increased DNA content in WAT. The increased DNA content in WAT was mostly restored but not completely by the administration of anti-insulin antibody, and by administration of propranolol, a -adrenergic blocker. The results demonstrated that VMH lesions induced DNA synthesis in WAT early after VMH lesioning, but did not induce DNA synthesis in BAT, and suggested that either hyperinsulinemia or a -adrenergic receptor mechanism or both may be responsible for the increased DNA content in WAT.     

大鼠白色和棕色脂肪来源的间充质干细胞成脂分化特性的比较

目的探讨白色脂肪组织(WAT)和棕色脂肪组织(BAT)来源的间充质干细胞成脂分化特性的差异。方法雄性SD大鼠15只,3只用于细胞分离培养,12只用于细胞移植。体外分离培养WAT和BAT两种来源的脂肪干细胞,用油红O染色检测两种干细胞的成脂分化率,用免疫荧光技术检测成脂诱导、分化后的细胞是棕色脂肪细胞还是白色脂肪细胞。4’6-二脒基-2-苯基吲哚(DAPI)标记两种来源的干细胞后移植至腹股沟区,分别在第1、2、3周取材,免疫荧光技术检测植入细胞的分化趋向。结果 WAT来源的干细胞增殖速度明显快于BAT来源的干细胞,前者成脂分化率为0.205±0.069,后者为0.165±0.053,两种干细胞的成脂诱导率差异无统计学意义(P0.05)。两种干细胞分别植入体内后,在第1、2、3周发现,两种干细胞均表达棕色脂肪特异性蛋白解耦联蛋白1(UCP1)。结论 WAT和BAT来源的干细胞在体外及体内诱导成脂后均分化为棕色脂肪细胞。     

A decade of progress in adipose tissue macrophage biology

One decade has passed since seminal publications described macrophage infiltration into adipose tissue (AT) as a key contributor to inflammation and obesity-related insulin resistance. Currently, a PubMed search for ‘adipose tissue inflammation’ reveals over 3500 entries since these original reports. We now know that resident macrophages in lean AT are alternatively activated, M2-like, and play a role in AT homeostasis. In contrast, the macrophages in obese AT are dramatically increased in number and are predominantly classically activated, M1-like, and promote inflammation and insulin resistance. Mediators of AT macrophage (ATM) phenotype include adipokines and fatty acids secreted from adipocytes as well as cytokines secreted from other immune cells in AT. There are several mechanisms that could explain the large increase in ATMs in obesity. These include recruitment-dependent mechanisms such as adipocyte death, chemokine release, and lipolysis of fatty acids. Newer evidence also points to recruitment-independent mechanisms such as impaired apoptosis, increased proliferation, and decreased egress. Although less is known about the homeostatic function of M2-like resident ATMs, recent evidence suggests roles in AT expansion, thermoregulation, antigen presentation, and iron homeostasis. The field of immunometabolism has come a long way in the past decade, and many exciting new discoveries are bound to be made in the coming years that will expand our understanding of how AT stands at the junction of immune and metabolic co-regulation.     

Effect of reflex stimuli on vascular resistance and glycerol release in in vivo dog subcutaneous adipose tissue

Summary Although direct autonomic nerve stimulation and infusion of catecholamine has been shown to result in substantial amounts of lipolysis in dog subcutaneous adipose tissue, there is no evidence to indicate that reflex autonomic stimulation will result in qualitatively and quantitatively similar changes. The present studies were, performed to evaluate the effects of reflex autonomic stimulation on vascular resistance and glycerol release in isolated, innervated and blood-perfused subcutaneous fat pad. Autonomic nerve stimulation at physiological frequencies was performed and resulted in release of glycerol that was compatible with previously reported data. Reflex stimulation by moderate and severe hypoxemia did not result in a significant glycerol release, but a maximal reflex stimulus (ventricular fibrillation) did. Since the majority of these reflex stimuli resulted in large changes in vascular resistance, it would appear that reflex hemodynamic changes can occur in these preparations without concommitant changes in glycerol release. Alpha blockade of the vasoconstriction resulted in the appearance of rising glycerol output suggesting that vasoconstriction prevents lipolysis.Supported by: American Heart Association Grant 72-615 and NIH, Medical Cardiology Training Grant HL05635 (Drs. Croke and Longo) and by USPHS Career Developement Award I KOY HF46346 (Dr. Skinner).