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Guang-Kui Xu, Bo Li, Xi-Qiao Feng, Huajian Gao
Deciphering the mechanisms underlying the high sensitivity of cells to mechanical microenvironments is crucial for understanding many physiological and pathological processes, e.g., stem cell differentiation and cancer cell metastasis. Here, a cytoskeletal tensegrity model is proposed to study the reorientation of polarized cells on a substrate under biaxial cyclic deformation. The model consists of four bars, representing the longitudinal stress fibers and lateral actin network, and eight strings, denoting the microfilaments...
October 4, 2016: Biophysical Journal
Natalie Reznikov, Hila Chase, Yehonatan Ben Zvi, Victoria Tarle, Matthew Singer, Vlad Brumfeld, Ron Shahar, Steve Weiner
UNLABELLED: Trabecular bone is an intricate 3D network of struts and plates. Although the structure-function relations in trabecular bone have been studied since the time of Julius Wolff, controversy still exists regarding the architectural parameters responsible for its stability and resilience. We present a parameter that measures the angle between two connected trabeculae - the Inter-Trabecular Angle (ITA). We studied the ITA values derived from μCT scans of different regions of the proximal femora of 5 individuals of different age and sex...
October 15, 2016: Acta Biomaterialia
Li-Fan Zhang, Shu Zhang
It has been shown that the minimum gravity exposure requirements vary greatly among different physiological systems. A preliminary comparison between two extremes, vessels vs. bones, shows that not only the mechanostat at the tissue level differs greatly, but also the bone loss during weightlessness may also involve calcium deposition-resorption changes. It seems that the surprising efficacy of intermittent artificial gravity (IAG) is due to the vascular tissues possessing a strong resilience or "memory" function toward restoring their original pre-stress and tensegrity state at the 1 G environment...
August 25, 2016: Sheng Li Xue Bao: [Acta Physiologica Sinica]
John N Maina
Among the extant air-breathing vertebrates, the avian respiratory system is structurally the most complex and functionally the most efficient gas exchanger. Having been investigated for over four centuries, some aspects of its biology have been extremely challenging and highly contentious and others still remain unresolved. Here, while assessing the most recent findings, four notable aspects of the structure and function of the avian respiratory system are examined critically to highlight the questions, speculations, controversies and debates that have arisen from past research...
July 28, 2016: Biological Reviews of the Cambridge Philosophical Society
Haruka Sudo, Kazunori Nakajima
The microtubule associated-protein tau has been identified as an effective positive prognostic indicator in breast cancer. To explore the physiological function of tau in early carcinogenesis, endogenous tau was knocked down in primary cultured human mammary epithelial cells. This resulted in chromosome-bridging during anaphase followed by micronucleation, both of which were suppressed by a further katanin-like1 knockdown. We also detected that the exogenously expressed katanin-like1 induction of cellular transformation is prevented by exogenous tau in rat fibroblasts...
July 20, 2016: Oncotarget
Fanlong Meng, Eugene M Terentjev
We develop a continuum theory for equilibrium elasticity of a network of crosslinked semiflexible filaments, spanning the full range between flexible entropy-driven chains to stiff athermal rods. We choose the 3-chain constitutive model of network elasticity over several plausible candidates, and derive analytical expressions for the elastic energy at arbitrary strain, with the corresponding stress-strain relationship. The theory fits well to a wide range of experimental data on simple shear in different filament networks, quantitatively matching the differential shear modulus variation with stress, with only two adjustable parameters (which represent the filament stiffness and the pre-tension in the network, respectively)...
August 10, 2016: Soft Matter
Diana Cholakova, Nikolai Denkov, Slavka Tcholakova, Ivan Lesov, Stoyan K Smoukov
The general mechanisms of structure and form generation are the keys to understanding the fundamental processes of morphogenesis in living and non-living systems. In our recent study (Denkov et al., Nature 528 (2015) 392) we showed that micrometer sized n-alkane drops, dispersed in aqueous surfactant solutions, can break symmetry upon cooling and "self-shape" into a series of geometric shapes with complex internal structure. This phenomenon is important in two contexts, as it provides: (a) new, highly efficient bottom-up approach for producing particles with complex shapes, and (b) remarkably simple system, from the viewpoint of its chemical composition, which exhibits the basic processes of structure and shape transformations, reminiscent of morphogenesis events in living organisms...
September 2016: Advances in Colloid and Interface Science
Hatem O Abdallah, Yoel P Ohayon, Arun Richard Chandrasekaran, Ruojie Sha, Keith R Fox, Tom Brown, David A Rusling, Chengde Mao, Nadrian C Seeman
The tensegrity triangle is a robust DNA motif that can self-assemble to generate macroscopic three-dimensional crystals. However, the stability of these crystals is dependent on the high ionic conditions used for crystal growth. Here we demonstrate that a triplex-forming oligonucleotide can be used to direct the specific intercalation, and subsequent photo-cross-linking, of 4,5',8-trimethylpsoralen to single or multiple loci within or between the tiles of the crystal. Cross-linking between the tiles of the crystal improves their thermal stability...
June 28, 2016: Chemical Communications: Chem Comm
Natalie K Gordon, Richard Gordon
The cell state splitter is a membraneless organelle at the apical end of each epithelial cell in a developing embryo. It consists of a microfilament ring and an intermediate filament ring subtending a microtubule mat. The microtubules and microfilament ring are in mechanical opposition as in a tensegrity structure. The cell state splitter is bistable, perturbations causing it to contract or expand radially. The intermediate filament ring provides metastability against small perturbations. Once this snap-through organelle is triggered, it initiates signal transduction to the nucleus, which changes gene expression in one of two readied manners, causing its cell to undergo a step of determination and subsequent differentiation...
2016: Theoretical Biology & Medical Modelling
Linda Brochhausen, Jan Maisch, Peter Nick
Nuclear migration and positioning are crucial for the morphogenesis of plant cells. We addressed the potential role of nuclear positioning for polarity induction using an experimental system based on regenerating protoplasts, where the induction of a cell axis de novo can be followed by quantification of specific regeneration stages. Using overexpression of fluorescently tagged extranuclear (perinuclear actin basket, kinesins with a calponin homology domain (KCH)) as well as intranuclear (histone H2B) factors of nuclear positioning and time-lapse series of the early stages of regeneration, we found that nuclear position is no prerequisite for polarity formation...
September 2016: Journal of Integrative Plant Biology
Armando Aranda-Anzaldo
Each mammalian chromosome is constituted by a DNA fiber of macroscopic length that needs to be fitted in a microscopic nucleus. The DNA fiber is subjected at physiological temperature to random thermal bending and looping that must be constrained so as achieve structural stability thus avoiding spontaneous rupturing of the fiber. Standard textbooks assume that chromatin proteins are primarily responsible for the packaging of DNA and so of its protection against spontaneous breakage. Yet the dynamic nature of the interactions between chromatin proteins and DNA is unlikely to provide the necessary long-term structural stability for the chromosomal DNA...
March 21, 2016: Journal of Theoretical Biology
Jeroen Burms, Ken Caluwaerts, Joni Dambre
In embodied computation (or morphological computation), part of the complexity of motor control is offloaded to the body dynamics. We demonstrate that a simple Hebbian-like learning rule can be used to train systems with (partial) embodiment, and can be extended outside of the scope of traditional neural networks. To this end, we apply the learning rule to optimize the connection weights of recurrent neural networks with different topologies and for various tasks. We then apply this learning rule to a simulated compliant tensegrity robot by optimizing static feedback controllers that directly exploit the dynamics of the robot body...
2015: Frontiers in Neurorobotics
Eric Boucher, Craig A Mandato
Wounding leads not only to plasma membrane disruption, but also to compromised cytoskeleton structures. This results not only in unwarranted exchanges between the cytosol and extracellular milieu, but also in loss of tensegrity, which may further endanger the cell. Tensegrity can be described as the interplay between the tensile forces generated by the apparent membrane tension, actomyosin contraction, and the cytoskeletal structures resisting those changes (e.g., microtubules). It is responsible for the structural integrity of the cell and for its ability to sense mechanical signals...
October 2015: Biochimica et Biophysica Acta
Krzysztof Kassolik, Waldemar Andrzejewski, Iwona Wilk, Marcin Brzozowski, Kamila Voyce, Ewa Jaworska-Krawiecka, Barbara Nowak, Donata Kurpas
PURPOSE OF THE RESEARCH: The purpose of the study was to compare the effectiveness of massage based on the tensegrity principle and classical abdominal massage performed on patients with constipation. MATERIALS AND METHODS: The study group consisted of 29 subjects with a pre-existing diagnosis of constipation based on the Rome III criteria. The patients were divided into two groups: the first group was made up of 15 patients who underwent tensegrity massage (average age: 59...
September 2015: Archives of Gerontology and Geriatrics
Atil Iscen, Ken Caluwaerts, Jonathan Bruce, Adrian Agogino, Vytas SunSpiral, Kagan Tumer
Soft robots offer many advantages over traditional rigid robots. However, soft robots can be difficult to control with standard control methods. Fortunately, evolutionary algorithms can offer an elegant solution to this problem. Instead of creating controls to handle the intricate dynamics of these robots, we can simply evolve the controls using a simulation to provide an evaluation function. In this article, we show how such a control paradigm can be applied to an emerging field within soft robotics: robots based on tensegrity structures...
2015: Artificial Life
Keyao Pan, Do-Nyun Kim, Fei Zhang, Matthew R Adendorff, Hao Yan, Mark Bathe
DNA can be programmed to self-assemble into high molecular weight 3D assemblies with precise nanometer-scale structural features. Although numerous sequence design strategies exist to realize these assemblies in solution, there is currently no computational framework to predict their 3D structures on the basis of programmed underlying multi-way junction topologies constrained by DNA duplexes. Here, we introduce such an approach and apply it to assemblies designed using the canonical immobile four-way junction...
2014: Nature Communications
Hamed Pardehshenas, Nader Maroufi, Mohammad Ali Sanjari, Mohamad Parnianpour, Stephen M Levin
PURPOSE: According to the conventional arch model of the pelvis, stability of the sacroiliac joints may require a predominance of form and force closure mechanisms: the greater the vertical shear force at the sacroiliac joints, the greater the reliance on self-bracing by horizontally or obliquely oriented muscles (such as the internal oblique). But what happens to the arch model when a person stands on one leg? In such cases, the pelvis no longer has imposts, leaving both the arch, and the arch model theory, without support...
October 2014: Journal of Bodywork and Movement Therapies
Špela Zemljič Jokhadar, Jure Derganc
Cellular structural integrity is provided primarily by the cytoskeleton, which comprises microtubules, actin filaments, and intermediate filaments. The plasma membrane has been also recognized as a mediator of physical forces, yet its contribution to the structural integrity of the cell as a whole is less clear. In order to investigate the relationship between the plasma membrane and the cytoskeleton, we selectively disrupted the plasma membrane and each of the cytoskeletal elements in Chinese hamster ovary cells and assessed subsequent changes in cellular structural integrity...
April 2015: Cell Biochemistry and Biophysics
Yi Chung Lim, Michael T Cooling, David S Long
In endothelial cells (ECs), the mechanotransduction of fluid shear stress is partially dependent on the transmission of force from the fluid into the cell (mechanotransmission). The role of the primary cilium in EC mechanotransmission is not yet known. To motivate a framework towards quantifying cilia contribution to EC mechanotransmission, we have reviewed mechanical models of both (1) the primary cilium (three-dimensional and lower-dimensional) and (2) whole ECs (finite element, non-finite element, and tensegrity)...
June 2015: Biomechanics and Modeling in Mechanobiology
Maria Evelina Mognaschi, Paolo Di Barba, Giovanni Magenes, Andrea Lenzi, Fabio Naro, Lorenzo Fassina
We have implemented field models and performed a detailed numerical dosimetry inside our extremely-low-frequency electromagnetic bioreactor which has been successfully used in in vitro Biotechnology and Tissue Engineering researches. The numerical dosimetry permitted to map the magnetic induction field (maximum module equal to about 3.3 mT) and to discuss its biological effects in terms of induced electric currents and induced mechanical forces (compression and traction). So, in the frame of the tensegrity-mechanotransduction theory of Ingber, the study of these electromagnetically induced mechanical forces could be, in our opinion, a powerful tool to understand some effects of the electromagnetic stimulation whose mechanisms remain still elusive...
2014: SpringerPlus
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