In Vivo Kinematics of Functional Ankle Instability Patients and Lateral Ankle Sprain Copers During Stair Descent

Patients with mechanic ankle instability experience increased tibiotalar and subtalar joint laxity. However, in vivo joint kinematics in functional ankle instability (FAI) patients and lateral ankle sprain (LAS) copers, especially during dynamic activities, are poorly understood. Ten FAI patients, 10 LAS copers, and 10 healthy controls were included in this study. A dual fluoroscopic imaging system was used to analyze the tibiotalar and subtalar joint kinematics during stair descent. Five key poses of stair descent were analyzed. Kinematic data from six degrees of freedom were calculated utilizing a solid modeling software. The range of motion and joint positions in each degree of freedom were compared among the three groups. The tibiotalar joints of FAI patients and LAS copers were significantly more inverted than those of healthy controls during the foot strike (p = 0.016, = 0.264). The subtalar joints of FAI patients were significantly more anteriorly translated (pose 2, p = 0.003, = 0.352; pose 3, p < 0.001, = 0.454; pose 4, p = 0.004, = 0.334), inverted (pose 4, p = 0.027, = 0.234; pose 5,p = 0.034, = 0.221), and externally rotated (pose 4, p = 0.037, = 0.217; pose 5; p = 0.004, = 0.331) than those of healthy controls during the mid‐stance and the heel off. The FAI patients showed excessive tibiotalar inversion and subtalar joint hypermobility during stair descent. Meanwhile, the LAS copers maintained subtalar joint stability, and only showed excessive tibiotalar inversion in foot strike. These data provide insight into the mechanisms behind the development of FAI after initial LAS. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 37:1860–1867, 2019     

Characterization and prediction of gradient acoustic noise in MR imagers

Gradient acoustic noise has been measured and characterized for an epoxy-potted, shielded gradient assembly in a 1.5 T MRI system. Noise levels vary by 10 dB or more as a function of longitudinal position in the scanner and reflect the pattern of forces applied to the gradient assembly. The noise level increases slightly (1–3 dB) with a patient in the scanner. The spectrum of the noise is similar (but not identical) to the spectrum of the input signal. A gradient-pulse-to-acoustic-noise transfer function was obtained by using a white noise voltage input to the gradient system. The transfer function enabled us to accurately predict acoustic noise output for a pulse sequence consisting of a series of trapezoidal pulses on a single axis and for a clinical fast spin echo sequence with gradients present on all three axes.     

差商最速下降法及其收敛性

证明了精确线搜索下的差商最速下降法的整体收敛性,提出了非精确线搜索下的有关算法并证明了收敛性。     

Peripheral nerve stimulation during MRI: Effects of high gradient amplitudes and switching rates

The application of high gradient amplitudes and switching rates for MRI and spectroscopy, resulting in short rise times for the gradient field and high changes of the magnetic flux density in the patient, is known to possibly evoke peripheral nerve stimulation (PNS) in patients. These effects have been studied on 20 volunteers under different experimental circumstances. The results of these measurements are partially in line with earlier findings reported in the literature. New information is found for the dependence of the PNS threshold level as a function of the rise time of the gradient waveform. The PNS threshold level, expressed in terms of dB/dt, is found to be proportional with t^?05, where t is the switch time for the gradients. Indications are found that |B|, the modulus of the gradient vector field, is more closely related to the PNS threshold level than B_z, the imaging component of the gradient field. From the experiments, it is furthermore concluded that only for the imaging protocols characterized by the application of long bipolar repetitive gradient pulse trains, such as echo-planar imaging, PNS is expected at the reported threshold levels. For the protocols based on spin echo, turbo spin echo, inversion recovery, fast field echo, etc., characterized by shorter gradient pulse trains, the threshold levels are expected to be much higher.     

低场强MRI对主动脉夹层的诊断价值

目的 评价低场强磁共振成像对主动脉夹层的诊断价值。方法 对16例主动脉夹层在低场强MRI自旋回波（SE）序列和梯度回波（GRE）表现进行回顾性分析总结，其中，6例经手术病理证实。结果 16例均能清晰显示病变的范围、夹层起始部位、内膜片、真假腔，6例假腔内显示血栓。结论 低场强MRI作为一种无创性检查能对主动脉夹层作出准确及时的诊断。     

The acceleration of the extraneuronal efflux of 3H-(±)-isoprenaline induced by high extracellular potassium

Summary After loading of the extraneuronal tissues of the perfused rat heart with ³H-isoprenaline the elevation of extracellular K⁺ concentration (from 2.7 to 15 mmol/1) in the perfusion solution about doubled the rate constant for efflux of the ³H-amine. As this increase was not seen in the presence of 100 mol/13-O-methyl-isoprenaline (OMI, a potent inhibitor of the uptake₂-carrier), it is concluded that the change in the concentration of K⁺ modulates OMI-sensitive outward transport of ³H-isoprenaline by uptake₂, not the diffusional efflux of the amine.Abbreviations MAO monoamine oxidase - COMT catechol-O-methyltransferase - OMI 3-O-methyl-isoprenaline - U-0521A 3,4-dihydroxy-2-methyl propiophenone     

海藻酸钙微胶珠的载药性能优化

利用高压静电法制备了海藻酸钙微胶珠，以牛血红蛋白作为模型药物，考察了牛血红蛋白（Hb）的稳定性、制备条件对微胶珠载药的影响。结果表明：Hb在10℃下能稳定存在，1．8％（w／v）Na-Alg与4．5％（w／v）CaCl2制备的微胶珠载药量较大，真空干燥的微胶殊彼此粘连破坏严重，冷冻干燥则表面出现明显的内陷，乙醇梯度洗脱-真空干燥球形度较好。水凝胶态的微胶珠载药后球形度完好，是理想的载药方式，24h时载药量达28．4％，为干燥后的2～3倍。     

梯度降温、深低温保存同种骨组织生物力学特性研究

目的　研究梯度降温、深低温保存同种骨组织的生物力学特性 ,为临床应用理想的同种骨移植材料修复各种原因引起的骨缺损提供理论依据。方法　将新鲜尸体的股骨经过预处理后 ,梯度降温 (- 2℃ /min)至 - 6 0℃ ,投入 - 80℃深低温冰箱中保存。一月后取出 ,进行生物力学实验。结果　实验得出的数据与以往研究新鲜骨的数据十分接近。结论　梯度降温、深低温保存的同种骨保持与新鲜骨最为接近的生物力学特性 ,实验得出的数据也将为以后的进一步研究提供依据     

Neutrophil Migration in Opposing Chemoattractant Gradients Using Microfluidic Chemotaxis Devices

Neutrophils migrating in tissue respond to complex overlapping signals generated by a variety of chemotactic factors (CFs). Previous studies suggested a hierarchy between bacteria-derived CFs and host-derived CFs but could not differentiate neutrophil response to potentially equal host-derived CFs (IL-8 and LTB₄). This paper reports neutrophil migration in conflicting gradients of IL-8 and LTB₄ using a microfluidic chemotaxis device that can generate stable and well-defined gradients. We quantitatively characterized the movement of cells from time-lapse images. Neutrophils migrate more efficiently toward single IL-8 gradients than single LTB₄ gradients as measured by the effective chemotactic index (ECI). In opposing gradients of IL-8 and LTB₄, neutrophils show obvious chemotaxis toward a distant gradient, consistent with previous reports. When an opposing gradient of LTB₄ is present, neutrophils show less effective chemotaxis toward IL-8 than when they are in a gradient of IL-8 alone. In contrast, the chemotactic response of neutrophils to LTB₄ is not reduced in opposing gradients as compared to that in a single LTB₄ gradient. These results indicate that the presence of one host-derived CF modifies the response of neutrophils to a second CF suggesting a subtle hierarchy between them.This revised version was published online in May 2005 with corrected author affiliations     

具有梯度的流体切应力促进血管内皮细胞增殖

目的探讨流体切应力(shear stress,SS)对血管内支架边缘内皮细胞(endothelial cells,ECs)增殖的影响。方法应用具有切应力梯度的平行平板流动腔(梯度切应力组)和普通矩形平行平板流动腔(恒定切应力组),分别对ECs施加0.566￣1.438Pa和1.137Pa的切应力,加载时间6h,以未施加切应力的ECs为静止对照组。流式细胞仪检测各组ECs细胞周期的变化。结果梯度切应力组ECs在受力6h后进入S期与G2+M期细胞明显多于静止对照组与稳定切应力组(P<0.05);恒定切应力组的ECs受力后进入S期与G2+M期细胞明显少于其他两组(P<0.05)。结论梯度切应力促进ECs进入分裂增殖期,而稳定的层流切应力则产生对ECs细胞周期的抑制作用。提示血管内支架植入后,继发的血流切应力改变诱导细胞进入分裂、增殖期,这可能是引起支架内再狭窄过程中血管内膜增生的原因之一。