3,334 research outputs found
Superposition of Substrate Deformation Fields Induced by Molecular Clutches Explains Cell Spatial Sensing of Ligands
No full textCells can sense the physical properties of the extracellular matrices (ECMs), such as stiffness and ligand density, through cell adhesions to actively regulate their behaviors. Recent studies have shown that varying ligand spacing of ECMs can influence adhesion size, cell spreading, and even stem cell differentiation, indicating that cells have the spatial sensing ability of ECM ligands. However, the mechanism of the cells' spatial sensing remains unclear. In this study, we have developed a lattice-spring motor-clutch model by integrating cell membrane deformation, the talin unfolding mechanism, and the lattice spring for substrate ligand distribution to explore how the spatial distribution of integrin ligands and substrate stiffness influence cell spreading and adhesion dynamics. By applying the Gillespie algorithm, we found that large ligand spacing reduces the superposition effect of the substrate's displacement fields generated by pulling force from motor-clutch units, increasing the effective stiffness probed by the force-sensitive receptors; this finding explains a series of previous experiments. Furthermore, using the mean-field theory, we obtain the effective stiffness sensed by bound clutches analytically; our analysis shows that the bound clutch number and ligand spacing are the two key factors that affect the superposition effects of deformation fields and, hence, the effective stiffness. Overall, our study reveals the mechanism of cells' spatial sensing, i.e., ligand spacing changes the effective stiffness sensed by cells due to the superposition effect of deformation fields, which provides a physical clue for designing and developing biological materials that effectively control cell behavior and function
A chemo-mechanical model for growth and mechanosensing of focal adhesion
No full textFocal adhesion (FA), the complex molecular assembly across the lipid membrane, serves as a hub for physical and chemical information exchange between cells and their microenvironment. Interestingly, studies have shown that FAs can grow along the direction of contractile forces generated by actomyosin stress fibers and achieve larger sizes on stiffer substrates. In addition, the cellular traction transmitted to the substrate was observed to reach the maximum near the FA center. However, the biomechanical mechanisms behind these intriguing findings remain unclear. To answer this important question, here we first developed a one-dimensional (1D) chemo-mechanical model of FA where key features like adhesion plaque deformation, active contraction by stress fibers, force-dependent association/dissociation of integrin bonds connecting two surfaces, and substrate compliance have all been considered. Within this formulation, we showed that the rigidity-sensing capability of FAs originates from the deformability of stress fibers while the force-dependent breakage of integrin bonds leads to the appearance of the traction peak at the FA center. Furthermore, by extending the model into three-dimensional as well as incorporating assembly/dis-assembly kinetics of adhesion proteins, we also demonstrated how anisotropic stress/strain field within the adhesion plaque will be induced by the presence of contractile forces which leads to the directional growth of the FA
Ca2+ transmembrane transport enhances oscillatory growth of cancer cell invadopodia
No full textAbstract Invadopodia, dynamic cancer cell protrusions, deform and degrade extracellular matrix (ECM) to facilitate invasion. Intracellular calcium ions (Ca2+) are critical second messengers involved in cancer cells migration, proliferation, and apoptosis, but their role in invadopodia dynamics remains unclear. Here, we propose a chemo-mechanical model integrating Ca2+ transmembrane transport, myosin contractility, adhesion dynamics, actin polymerization, and membrane type 1 matrix metalloproteinase (MT1-MMP) hydrolysis. We find that increased invadopodia length elevates membrane tension, activating mechanosensitive channels and raising intracellular Ca2+ levels, aligning with experimental observations. Our model reveals that invadopodia oscillatory and monotonic dynamics are governed by actin polymerization and myosin recruitment, with Ca2+ transport enhancing dynamics via myosin recruitment and reciprocal effects on Ca2+ transport. Furthermore, by incorporating MT1-MMP-mediated ECM degradation in our model, we find that ECM degradation promotes invadopodia extension and elevates Ca2+ levels, which shifts the invadopodia dynamics from monotonic to oscillatory. Overall, our model offers a comprehensive theoretical framework for understanding Ca2+ transport and invadopodia dynamics in cancer cells
Dong gong xuan mi jue yao lan /
No full textTitle on cover: Dong gong xuan ze mi jue.Mode of access: Internet
Real Exchange Rate, Foreign Trade and Employment: Evidence from China
No full textCoordination of macro-economic development and employment is an essential issue for China's social development, which largely depends on economic expansion, as well as integration into the global market to create jobs. Through the literature review and empirical test, this paper analyses the relationship between macro-economic policy and employment, and discusses the impact of real exchange rate and foreign trade on employment. The research indicates that a stable and competitive exchange rate policy plays an indispensable role in employment promotion, more effective than monetary and fiscal policies, while the export growth also plays a positive role in employment promotion.China, employment, foreign trade, real exchange rate
Three new species of genus Mecopoda Serville, 1831 from China (Orthoptera: Tettigoniidae: Mecopodinae)
No full textLiu, Yun-Fei, Shen, Chu-Ze, Gong, Pu, Zhang, Ling, He, Zhu-Qing (2019): Three new species of genus Mecopoda Serville, 1831 from China (Orthoptera: Tettigoniidae: Mecopodinae). Zootaxa 4585 (3): 561-572, DOI: 10.11646/zootaxa.4585.3.1
Falun Gong
No full textFalun Gong, founded by Li Hongzhi in 1992, attracted international attention in 1999 after staging a demonstration outside government offices in Beijing. It was subsequently banned. Followers then created a number of media outlets outside China focused on protesting the PRC's attack on the 'human rights' of practitioners. This volume focuses on Falun Gong and violence. Though the author notes accusations of how Chinese authorities have abused and tortured practitioners, the volume will focus on Li Hongzhi's teachings about 'spiritual warfare', and how these teachings have motivated practitioners to deliberately seek brutalization and martyrdom.</jats:p
Mecopoda mamorata Liu & Shen & Gong & Zhang & He 2019, sp. nov.
No full text2.5 <i>M</i>. <i>mamorata</i> He sp. nov. <p> <b>Holotype:</b> female, CHINA, Yunnan, Menglun 25-iv-2017, coll. He Zhu-Qing.</p> <p> <b>Description.</b> This species is very similar to <i>M</i>. <i>elongata elongata</i>, but the new species has longer forewing and has longest ovipositor among other species (Fig. 2J).</p> <p> <b>Male.</b> Not known.</p> <p> <b>Coloration.</b> Nearly brown. Forewing yellow with brown wave pattern, and three big black spots on the base.</p> <p> <b>Etymology.</b> The species is named after the wave pattern on the forewing.</p> <p> <b>Measurements (in mm).</b> Female: SZ 87.2, PR 11.48, FW 76.33, HW 80.27, HF 59.41, OV 35.65.</p> <p> <b>Distribution.</b> China (Yunnan).</p> <p> <b>Note.</b> We found one male near the female (holotype), the color patter of forewing was similar. Unfortunately, we failed to collect it.</p>Published as part of <i>Liu, Yun-Fei, Shen, Chu-Ze, Gong, Pu, Zhang, Ling & He, Zhu-Qing, 2019, Three new species of genus Mecopoda Serville, 1831 from China (Orthoptera: Tettigoniidae: Mecopodinae), pp. 561-572 in Zootaxa 4585 (3)</i> on page 571, DOI: 10.11646/zootaxa.4585.3.10, <a href="http://zenodo.org/record/2640098">http://zenodo.org/record/2640098</a>
Trends. Immaterial Materialism: The Communist Party Confronts Falun Gong and Qi Gong in the People\u27s Republic of China
No full textThe author discusses the April 1999 demonstration by members of the Falun Gong sect outside the Zhongnanhai compound in Beijing
The Psychology of Qi Gong: A Qualitative Study
No full text This article presents an in-depth, qualitative study, analyzing responses to focus-group interviews regarding individuals’ self-reported experiences and attitudes during Qi Gong practice. Semistructured interviews were conducted with three Qi Gong groups in order to collect research data. These data were transcribed verbatim and subjected to content and thematic analysis across and within groups. The analysis indicates extraordinary experiences of Qi Gong practitioners on various levels of bio-psycho-spiritual/energetic functioning. The results indicate how Qi Gong influences the complexity and multidimensionality of individuals’ health. In the discussion, the author compares and contrasts his results with other recently performed research. </jats:p
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