Mechanotransduction of bone cells<Emphasis Type="Italic">in vitro</Emphasis>: Mechanobiology of bone tissue

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.     

Dynamic Mechanical Conditioning of Collagen-Gel Blood Vessel Constructs Induces Remodeling In Vitro

Dynamic mechanical conditioning is investigated as a means of improving the mechanical properties of tissue-engineered blood vessel constructs composed of living cells embedded in a collagen-gel scaffold. This approach attempts to elicit a unique response from the embedded cells so as to reorganize their surrounding matrix, thus improving the overall mechanical stability of the constructs. Mechanical conditioning, in the form of cyclic strain, was applied to the tubular constructs at a frequency of 1 Hz for 4 and 8 days. The response to conditioning thus evinced involved increased contraction and mechanical strength, as compared to statically cultured controls. Significant increases in ultimate stress and material modulus were seen over an 8 day culture period. Accompanying morphological changes showed increased circumferential orientation in response to the cyclic stimulus. We conclude that dynamic mechanical conditioning during tissue culture leads to an improvement in the properties of tissue-engineered blood vessel constructs in terms of mechanical strength and histological organization. This concept, in conjunction with a proper biochemical environment, could present a better model for engineering vascular constructs. © 2000 Biomedical Engineering Society. PAC00: 8719Rr, 8714Ee, 8718-h, 8768+z     

Zika virus diagnosis: challenges and solutions

Background

Since its sudden appearance and link to microcephaly in 2015, the number of PubMed references for Zika virus (ZIKV) has risen from 181 to 5163, at time of writing, with a vast proportion focused on the consequences of ZIKV infection during pregnancy. This level of attention underlies increased demand for sensitive and specific diagnostic tools able to assess risk to an unborn child, as well as to understand the dynamics and consequences of viral persistence.

Ras homolog gene family H (RhoH) deficiency induces psoriasis-like chronic dermatitis by promoting TH17 cell polarization

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Immunosuppressive Effect of Cyclosporin A in Two Lymphocyte Transfer Models in Rats: Comparison of in Vivo and in Vitro Treatment

The immunosuppressive effect of CS-A was first studied in the assay for local GvHR. 3 x 10⁶ viable spleen cells from LEW rats were injected into one foot pad of LEW x BN hybrids and both PLN were weighed 7 days later. Treatment of the recipients with 3 doses of 50 mg/kg/day of CS-A suppressed this local GvHR. The effect was more pronounced when treatment started at the time of cell transfer rather than a few days before peak response. In-vitro incubation of the cellular inoculum with CS-A also prevented local GvHR. Histology of the PLN confirmed the quantitative results expressed by the PLN index. CS-A was further investigated in the EAE model in LEW rats. It protected rats sensitised with spinal cord emulsified in complete Freund's adjuvant for as long as they were treated with CS-A. Treatment delayed until after the appearance of EAE also markedly improved their condition. Oral treatment of recipients with 50 mg/kg/day CS-A prevented the development of adoptive EAE following the transfer of lymphoid cells conditioned in vitro. The presence of 0.1-1.0 μg CS-A in the medium of the sensitised lymphoid cells also inhibited the adoptive transfer of EAE. Finally, if the cells for the adoptive transfer were derived from CS-A-treated sensitised donors, they failed to induce EAE. Histological examination supported the symptomatic findings     

Does Low FEV1 in Addition to Fixed Ratio and/or Lower Limit of Normal of FEV1/FVC Improve Prediction of Mortality in COPD? The NHANES-III-linked-mortality Cohort

Purpose

There is presently an ongoing debate on the relative merits of suggested criteria for spirometric airway obstruction. This study tests the null hypothesis that no superiority exists with the use of fixed ratio (FR) of forced expiratory volume in the first second (FEV1)/forced vital capacity (FVC) < 0.7 versus less than lower limit predicted (LLN) criteria with or without FEV1 <80% predicted in regards to future mortality.

重组卡介苗及猪苓多糖对荷瘤小鼠巨噬细胞NO释放量的影响

目的 观察重组卡介苗（rBCG)和中药猪苓多糖（PPS），对荷瘤小鼠空巨噬细胞释放NO的影响。方法 将黑色素瘤细胞株B16接种于小鼠左大腿外侧皮下，建立荷瘤小鼠模型，分别用rBCG－IL-2,rBCG-IL-2 PPSPPS进行局部治疗。于给药后第1，2，3和5wk处死小鼠，用NO酶法测定小鼠腹腔巨噬细胞释放NO的水平，并观察不同实验组瘤体的变化。结果 rBCG－IL－2组小鼠腹腔巨噬细胞释放NO的水平最高。与对照组相比较，PPS组小鼠腹腔巨噬细胞释放NO的水平在第1wk与第2wk增高，第3wk起与对照组释放的NO水平没有差异。rBCG－IL－2组小鼠随给药时间的延长，皮下瘤体逐渐缩小。PPS组小鼠瘤体在给药后第1wk和第2wk生长缓慢，第3wk起瘤体生长速度明显增加。结论 rBCG－IL－2与PPS能提高小鼠腹腔巨噬细胞释放NO的水平，rBCG－IL－2能明显抑制肿瘤生长。     

Mild atopic dermatitis lacks systemic inflammation and shows reduced nonlesional skin abnormalities

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微机控制的韧带动态力学特性测试系统

本系统是为自动测试人体韧带或类似组织的动态力学特性试验而研制的。在试验时,受控的加载过程和数据采集过程同时进行。系统向韧带试件提供一个快速的匀速可控的拉伸载荷,模拟人体剧烈运动的实况,同时实时采集力和变形的数据。系统还提供对所采集数据的分析手段,从而得到力、变形、应力、应变、弹性模量和变形能等参数之间的关系,并可以图形和文字形式输出。系统亦可将各数据文件转换为其它应用软件包可接受的形式,以便利用标准商品软件包的数据和图象处理能力。系统采用菜单提示的人机对话方式进行监控。     

流行性乙型脑炎病毒活疫苗株SA14-14-2基因稳定性研究

目的 通过研究流行性乙型脑炎活疫苗减毒株基因稳定性，从分子水平证实流行性乙型脑炎活疫苗的遗传稳定性。方法分析流行性乙型脑炎活疫苗主种子、工作种子及其相应的疫苗病毒E蛋白基因核苷酸和氨基酸序列，并与其强毒株和基因库中乙脑病毒减毒株(AF15119)比较。结果乙脑活疫苗主种子、工作种子及其相应的疫苗病毒的E蛋白基因核苷酸序列完全相同。这些病毒E蛋白的氨基酸序列与基因库中乙脑病毒弱毒株(AF315119)比较显示第E447位点氨基酸有差异。结论乙脑病毒活疫苗减毒株遗传学特性稳定。