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61.
Mechanotransduction of bone cells<Emphasis Type="Italic">in vitro</Emphasis>: Mechanobiology of bone tissue 总被引:11,自引:0,他引:11
Mullender M El Haj AJ Yang Y van Duin MA Burger EH Klein-Nulend J 《Medical & biological engineering & computing》2004,42(1):14-21
Mechanical force plays an important role in the regulation of bone remodelling in intact bone and bone repair. In vitro, bone
cells demonstrate a high responsiveness to mechanical stimuli. Much debate exists regarding the critical components in the
load profile and whether different components, such as fluid shear, tension or compression, can influence cells in differing
ways. During dynamic loading of intact bone, fluid is pressed through the osteocyte canaliculi, and it has been demonstrated
that fluid shear stress stimulates osteocytes to produce signalling molecules. It is less clear how mechanical loads act on
mature osteoblasts present on the surface of cancellous or trabecular bone. Although tissue strain and fluid shear stress
both cause cell deformation, these stimuli could excite different signalling pathways. This is confirmed by our experimental
findings, in human bone cells, that strain applied through the substrate and fluid flow stimulate the release of signalling
molecules to varying extents. Nitric oxide and prostaglandin E2 values increased by between two- and nine-fold after treatment with pulsating fluid flow (0.6±0.3 Pa). Cyclic strain (1000
μstrain) stimulated the release of nitric oxide two-fold, but had no effect on prostaglandin E2. Furthermore, substrate strains enhanced the bone matrix protein collagen I two-fold, whereas fluid shear caused a 50% reduction
in collagen I. The relevance of these variations is discussed in relation to bone growth and remodelling. In applications
such as tissue engineering, both stimuli offer possibilities for enhancing bone cell growth in vitro. 相似文献
62.
我们利用FitzHugh-Nagumo(FHN)类型方程,对二维心肌可激媒质系统螺旋波(Spiral wave,SW)的形成、演化和控制进行了数值模拟,主要有以下研究结果:(1)改变系统的可激性,不会影响SW的激发区宽度,却改变SW的自转周期和旋波核的大小;当可激性达到某一极限值时,SW的自转周期与旋波核的半径趋于无穷大,系统不再出现SW。(2)对SW的均匀近共振小电流驱动,可以引导旋波头(Spiral wave tip,SWT)的漂移运动;当驱动频率接近SW的自转频率时,SWT会沿着圆周漂移,当驱动频率达到共振频率时,SWT会沿着直线漂移。 相似文献
63.
Shear stress induced membrane currents and calcium transients in human vascular endothelial cells 总被引:3,自引:0,他引:3
Gero Schwarz Guy Droogmans Bernd Nilius 《Pflügers Archiv : European journal of physiology》1992,421(4):394-396
We have measured membrane currents induced by shear stress together with intracellular calcium signals in endothelial cells from human umbilical cord veins. In the presence of extracellular calcium (Ca2+]o), shear stress induced an inward current at a holding potential of 0 mV which is accompanied by a rise in intracellular Ca2+ ([Ca2+]i). In the absence of extracellular calcium shear stress was unable to evoke a calcium signal but still induced a membrane current. The voltage dependence of the shear stress induced current was obtained from difference currents evoked by linear voltage ramps before and during application of shear stress. Its reversal potential Erev shifted from –2.3±0.8 mV (n=4) in a nominally Ca2+ free solution to +1.5±1.6 mV at 1.5 mM [Ca2+]o (n=4) and to +21.9±4.4 mV (n=7) at 10 mM [Ca2+]o. From our data we conclude that shear stress opens an ion channel that is 12.5±2.9 (n=7) times more permeable for calcium than for sodium or cesium. 相似文献
64.
Alberto Utrero-Rico Javier Ruiz-Hornillos Cecilia González-Cuadrado Claudia Geraldine Rita Berta Almoguera Pablo Minguez Antonio Herrero-González Mario Fernández-Ruiz Octavio Carretero Juan Carlos Taracido-Fernández Rosario López-Rodriguez Marta Corton José María Aguado Luisa María Villar Carmen Ayuso-García Estela Paz-Artal Rocio Laguna-Goya 《The Journal of allergy and clinical immunology》2021,147(5):1652-1661.e1
65.
基于线性调频信号的高帧率超声成像系统 总被引:5,自引:0,他引:5
基于有限衍射波束的高帧率超声成像系统能实现快速成像,但由于仅通过一次发射事件成像,信噪比较低,本研究针对该问题提出一种改进方案。它采用合成孔径雷达中所使用的线性调频信号作为激励信号,在接收端则利用线性调频信号的脉冲压缩比等于信号的时间带宽积的特征,将接收信号通过匹配滤波器处理。结果表明该方案不仅能显著提高成像系统的信噪比,改善重构图像的质量,增加成像深度,而且不损失分辨率。 相似文献
66.
血流切应力调控内皮型一氧化氮合酶的分子机制 总被引:2,自引:0,他引:2
血流切应力(flowshear stress,rss)是生理或病理条件下调节血管内皮细胞产生一氧化氮的最重要的刺激因素。FSS对内皮型一氧化氮合酶(endothelial nitric oxide synthase,eNOS)的调控包括基因转录的调节、转录后的调节和翻译后的调节。eNOS基因转录以及转录后mRNA的稳定性能被FSS诱导加强。FSS通过游离钙离子浓度、磷酸化、eNOS相关蛋白以及细胞内易位等途径调节eNOS的催化活性。此外,FSS还能调控eNOS催化反应的辅助因子。 相似文献
67.
根据Wiederhielm的阻抗平衡压力检测原理,设计了一个改进的伺服零微血管测压系统。利用该系统检测了蟾蜍及蛙肠系膜内微小动脉的压力、获得了各管径级的压力和脉压的参数,并观察了药物的作用,探讨了微动脉内压力的波动特性以及应激情况下压力的骤变式与脉动式的交替,为微循环研究提供一些有价值的现象。 相似文献
68.
Septal unit activity and hippocampal EEG during the sleep-wakefulness cycle of the rat 总被引:1,自引:0,他引:1
The functional relationship between septal unit activity and hippocampal EEG was studied during the sleep-wakefulness cycle in chronically implanted unrestrained rats. Results were statistically analyzed in order to obtain the time interval and auto and crosscorrelation histograms. During REM sleep and restless wakefulness the hippocampal EEG showed a theta rhythm of 4–8 cps and the septal unit activity was characterized by the presence of rhythmic bursts with a frequency in every single instance similar to that of the hippocampus. The septal units showed a bimodal time interval histogram. Their autocorrelation histogram exhibited a sinusoidal pattern of decreasing amplitude. The crosscorrelation histogram of septal units and the hippocampal EEG also showed a sinusoidal pattern suggestive of the functional relationship between both neural structures. During slow wave sleep and quiet wakefulness there was a disappearance of the hippocampal theta rhythm and rhythmic septal unit bursts. The second mode was missing in the time interval histogram and the auto and crosscorrelation histograms showed an irregular pattern. It is concluded that medial septal nucleus and hippocampal temporal patterns of activity are similar during REM sleep and restless wakefulness. 相似文献
69.
Long time-constant EEG recording during paired stimuli has led to the discovery of the contingent negative variation or expectancy wave (Walter, 1964). This effect is produced when a conditional stimulus signals that an imperative stimulus demanding action, decision, or attention will follow at a short, constant time interval. Symbolic and meaningful stimuli were presented to subjects tachistoscopically, and the evoked responses in the brain were electronically averaged. The cerebral evoked responses to such psychological stimuli are more complex than to flashes. A slow negative DC potential shift (CNV) was seen during the interval between an auditory ready signal and the visual exposure if recognition of the stimulus was required, or if it was interesting. Following the visual exposure, a slow positive DC shift occurred. The method has been developed to study the brain responses to psychological stimuli. The amplitude of the responses relates to the information content and subjective factors rather than to the physical strength of the stimulus. 相似文献
70.