模拟失重对大鼠血液电阻抗谱影响的实验研究

利用RC等效电路模型解析模拟失重引起大鼠血液变化的电生理机制。采用大鼠尾部悬吊方法建立模拟失重动物模型,使用Aligent 4294A阻抗分析仪测量对照组与模拟失重大鼠血液电阻抗谱,通过血液等效电路模型的数值计算和曲线拟合,比较、分析对照组与模拟失重组血液电学参数（电阻和电容）。结果表明,模拟失重60 d后,与对照组比较,失重大鼠血液的红细胞比容（Hct）降低,细胞膜电阻率减少,细胞外和细胞内电阻率分别减少16.44%和1.54%,细胞膜和细胞内电容分别减少4.66%和0.83%,细胞外电容不变。模拟失重使大鼠血液的红细胞比容（Hct）明显降低,红细胞膜电阻率显著降低,导致细胞外液和全血电阻抗降低,导电性增加,电阻抗谱向低阻方向移动。     

球扩式介入主动脉瓣膜支架的抗迁移力学行为

目的 研究球扩式主动脉瓣膜支架植入后的抗迁移力学行为。 方法 建立球扩式瓣膜支架介入主动脉瓣膜后的抗迁移力学模型,采用数值模拟方法研究不同瓣环椭圆率、摩擦因数、瓣膜支架材料及自体瓣叶钙化情况对瓣膜支架抗迁移力的影响规律。 结果 当主动脉瓣环椭圆率为 0. 2、0. 3、0. 4、0. 5 时,对应的最大抗迁移力分别为12. 37、10. 94、8. 50、4. 75 N;当摩擦因数为 0. 1、0. 2、0. 3 时,瓣膜支架的最大抗迁移力分别为 8. 98、11. 00、13. 10 N;L605 钴铬合金制成的瓣膜支架的锚定性要优于 316L 不锈钢制成瓣膜支架的锚定性,其对应的最大抗迁移力分别为 13. 10、9. 82 N;当自体瓣叶发生钙化时,最大抗迁移力为 13. 1 N,而未钙化时最大抗迁移力仅为 5. 51 N,相比而言降低了 57. 9% 。 结论 随着主动脉瓣瓣环椭圆率不断增大,瓣膜支架的锚定性逐渐降低;随着瓣膜支架与组织间的摩擦因数不断增大,最大抗迁移力也不断增大;L605 钴铬合金制成的瓣膜支架比 316L 不锈钢制成瓣膜支架的锚定性能优异;瓣膜发生钙化情况下瓣膜支架的锚定性要优于未发生钙化时的锚定性。 研究结果为抗迁移瓣膜支架的结构设计和临床选择提供重要的科学依据。     

口腔修复陶瓷材料的磨损性能北大核心

背景:陶瓷材料因具有优良的机械性能、与口腔组织良好的生物相容性及高度美观性广泛应用于口腔修复领域,良好的磨损性能对修复体临床应用有重要意义。目的:综述口腔修复陶瓷材料磨损性能机制及临床研究,以期为临床选择适宜的陶瓷材料提供思路。方法:应用计算机在PubMed和Web of Science数据库检索在2016年1月至2021年4月期间涉及口腔修复陶瓷材料磨损性能的相关研究。英文检索词为“dental ceramic material,wear property”,最终共纳入36篇文献进行分析。结果与结论:①全瓷材料自身耐磨性均高于树脂陶瓷复合材料,全瓷材料中氧化锆陶瓷磨损性能最佳,美学性能较弱。②玻璃陶瓷中氧化锆加强型硅酸锂玻璃陶瓷磨损性能较好,但应用时间较短,长期疗效还有待更多的研究证实。③树脂陶瓷复合材料中树脂纳米陶瓷材料磨损性能优于聚合物渗透陶瓷。④在后牙区全冠修复可选择氧化锆陶瓷,前牙区全冠修复可以根据患者的美学需求选择高透性氧化锆陶瓷或玻璃陶瓷。⑤贴面、嵌体和高嵌体修复可选择长石瓷、玻璃陶瓷和树脂陶瓷复合材料,但树脂陶瓷复合材料耐磨性差,需避免用于高应力承载区。⑥对牙本质暴露、氟斑牙和牙齿酸蚀症患者可考虑树脂纳米陶瓷材料,但这类患者适宜的陶瓷材料相关研究较少。⑦表面粗糙度对陶瓷材料的磨损性能有显著影响,临床口腔修复应用中采用良好的抛光表面可提高陶瓷材料磨损性能,而且对修复体进行定期复查也至关重要。     

IL-32与肿瘤生物学行为

肿瘤是威胁人类健康的重大疾病,其进程与肿瘤微环境密切相关。炎性介质是肿瘤微环境的重要组分, IL?32是一种炎性因子,主要由免疫细胞及上皮细胞表达,目前共发现IL?32α、β、γ、δ、ε、η、s、θ、ζ9种亚型。 IL?32可诱导IL?6、 IL?8、 IL1β等介质的表达,参与炎性疾病的进程,还可以通过NF?κB （核因子κB）、 MMP?2（基质蛋白酶2）等信号通路影响乳腺癌、宫颈癌、胃癌、肝癌等肿瘤的侵袭转移、增殖和凋亡。文章介绍了IL?32的发现、生物结构、分泌及其受体, IL?32在肿瘤微环境中的表达特点及其对肿瘤的生物学效应,旨在为IL?32的研究及肿瘤分子靶向治疗提供思路。     

Tensile Tests of Collagen Fibers Obtained from the Rabbit Patellar Tendon

Tensile properties of collagen fibers of approximately 1 m in diameter were determined using a newly developed micro tensile test system for cells and fine fibrous biological tissues. The test system consists of a thermostatic test chamber, an inverted microscope, micromanipulators, a direct drive linear actuator, a cantilever-type load cell, and a video dimension analyzer (VDA). The fibers were isolated with a mechanical method from collagen fascicles (approximately 300 m in diameter) cut out from the rabbit patellar tendon. The ends of each fiber were attached to the tips of a pair of glass microtubes (15 to 20 m in outer diameter) using a cyanoacrylate adhesive. One of the microtubes was attached to the load cell; the other one was connected to the linear actuator which was utilized to stretch the fiber. Load applied to the fiber was measured with the load cell, while its elongation was determined with the VDA using the images of the edges of the adhesive as markers. Tangent modulus, tensile strength, and strain at failure of the tested fibers were 54.3± 25.1 MPa, 8.5± 2.6 MPa, and 21.6± 3.0%, respectively. These values were much different from those of collagen fascicles (300 m in diameter) cut out from the rabbit patellar tendon and also from those of the bulk patellar tendon (Trans. ASME, J. Biomech. Eng. 121, 124–294, 1999); for example, tensile strength and strain at failure of the fibers were approximately 50 and 200% of those of the fascicles, respectively. These results suggest that the mechanical interactions between fibers and between fibers and ground substances contribute much to the mechanical properties of collagen fascicles and bulk tendons.     

The atomic force microscope: a new tool for artificial organ research

The atomic force microscope (AFM) was developed by modifying the scanning tunneling microscope (STM). It has high resolution on the subnanometer scale (10⁻¹⁰ m), does not require troublesome preprocessing of the sample, and permits observation of living samples. With these attractive features, the AFM is expected to be a new research tool in the field of artificial organs in the near future. This review describes the history and mechanism of the AFM and some of our observations of biological samples.     

血液的交流电导特性研究

对血液的交流电特性做了较全面的研究。针对血液这一特殊对象,在测试方法及测量系统设计中做了较深入的工作。在１ＨＺ－１０ＨＭＺ频率范围内测定了正常成人全血的电频谱特性。实验发现,正常成人血液电导随测量信号频率增加在１００ＨＺ－１０ＫＨＺ范围内有显著的增加,但相位基本不变,考虑到血液的这一电特性,将对以前电导法测红血球压积,血液粘度等工作做一定的补充和修正,并帮助我们建立更合理的血液等效电模型。     

纤维蛋白原活性测定在血液流变学检测中的作用及意义

目的：研究血浆中纤维蛋白原活性对血液流变性的影响。方法：对临床３７９例患者进行血浆和血清粘度的测定,应用其结果计算出纤维蛋白原的活性,按照公式：纤维蛋白原活性（ｇ／Ｌ）＝纤维蛋白原量（ｇ／Ｌ）／［血浆粘度（ｍＰａ·ｓ）－血清粘度（ｍＰａ·ｓ）］。结果：结果显示,只有在纤维蛋白原活性增强时,血浆粘度才有所提高,从而使全血粘度升高,故此纤维蛋白原活性与其含量的增粘作用不成比例。结论：临床测定纤维蛋白原活性能提高血液流变学检查的特异性及敏感性。     

CT图象小波变换系数的统计特征

本文研究了ＣＴ图象小波变换系数的统计特征,用ｘ２检验方法得到了小波变换系数的统计分布。实验表明,各高频子图象系数近似服从ｒ＝０．４的广义高斯分布。同时计算了均值、方差、相关系数等统计量,从中得到一些可以指导医学图象编码的结论。     

Biophysical and histological determinants underlying natural firing behaviors of splanchnic sympathetic preganglionic neurons in neonatal rats

Isolated thoracic spinal cords of neonatal rats spontaneously generate splanchnic sympathetic nerve discharge (SND) with a quasiperiodic rhythm 1-Hz. Using in vitro nerve-cord preparations that retained T6–T12 spinal segments, we investigated whether the natural firing behavior of sympathetic preganglionic neurons (SPNs) encoded the SND rhythm and what were the main biophysical and histological determinants of SPN firing. Under extracellular recording conditions, electrical stimulation of splanchnic nerves elicited antidromic responses in 212 SPNs. Among them, 92 SPNs were quiescent; 120 active SPNs had an average firing rate of 0.72±0.04 Hz, which was close to the quasiperiodic rhythm of SND. SPNs with rhythmic burst firing were rare. Probability plots of interspike intervals were constructed to extract mathematical features underlying SPN firing. Most active SPNs (88%) had a firing well described by unimodal Gaussian, suggesting a predominantly tonic pattern with normal variations. Biophysical properties of 112 SPNs were measured under whole-cell recording conditions. The charging time constant, τ, is positively correlated with the average firing rate. Histological properties were examined in 45 SPNs with intracellular diffusion of Lucifer Yellow or biocytin. SPNs with pyramidal somata and multipolar dendrites tend to be spontaneously active. In contrast, those with bipolar somata and fewer dendritic branches were quiescent in firing. These observations suggest that activity levels of SPNs are correlated with their capacity for temporal and spatial summation of synaptic inputs. How the seemingly tonic firing of individual SPNs is integrated into whole-nerve SND with quasiperiodic rhythms is discussed.