Base de dados : MEDLINE
Pesquisa : G01.374.618 [Categoria DeCS]
Referências encontradas : 3262 [refinar]
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  1 / 3262 MEDLINE  
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PMID:28268401
Autor:Younbaek Lee; Byungjung Choi; Jongwon Lee; Minhyung Lee; Se-Gon Roh; Jeonghun Kim; Hyundo Choi; Yong-Jae Kim
Título:Flexible sliding frame for gait enhancing mechatronic system (GEMS).
Fonte:Conf Proc IEEE Eng Med Biol Soc; 2016:598-602, 2016 Aug.
ISSN:1557-170X
País de publicação:United States
Idioma:eng
Resumo:This paper presents a novel flexible sliding thigh frame for a gait enhancing mechatronic system. With its two-layered unique structure, the frame is flexible in certain locations and directions, and stiff at certain other locations, so that it can fît well to the wearer's thigh and transmit the assisting torque without joint loading. The paper describes the basic mechanics of this 3D flexible frame and its stiffness characteristics. We implemented the 3D flexible frame on a gait enhancing mechatronic system and conducted experiments. The performance of the proposed mechanism is verified by simulation and experiments.
Tipo de publicação: JOURNAL ARTICLE


  2 / 3262 MEDLINE  
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PMID:28648660
Autor:Simunovic M; Manneville JB; Renard HF; Evergren E; Raghunathan K; Bhatia D; Kenworthy AK; Voth GA; Prost J; McMahon HT; Johannes L; Bassereau P; Callan-Jones A
Endereço:Laboratoire Physico Chimie Curie, Institut Curie, PSL Research University, CNRS UMR168, 75005 Paris, France; Sorbonne Universités, UPMC University Paris 06, 75005 Paris, France; Department of Chemistry, Institute for Biophysical Dynamics, James Franck Institute, The University of Chicago, 5735 S. El
Título:Friction Mediates Scission of Tubular Membranes Scaffolded by BAR Proteins.
Fonte:Cell; 170(1):172-184.e11, 2017 Jun 29.
ISSN:1097-4172
País de publicação:United States
Idioma:eng
Resumo:Membrane scission is essential for intracellular trafficking. While BAR domain proteins such as endophilin have been reported in dynamin-independent scission of tubular membrane necks, the cutting mechanism has yet to be deciphered. Here, we combine a theoretical model, in vitro, and in vivo experiments revealing how protein scaffolds may cut tubular membranes. We demonstrate that the protein scaffold bound to the underlying tube creates a frictional barrier for lipid diffusion; tube elongation thus builds local membrane tension until the membrane undergoes scission through lysis. We call this mechanism friction-driven scission (FDS). In cells, motors pull tubes, particularly during endocytosis. Through reconstitution, we show that motors not only can pull out and extend protein-scaffolded tubes but also can cut them by FDS. FDS is generic, operating even in the absence of amphipathic helices in the BAR domain, and could in principle apply to any high-friction protein and membrane assembly.
Tipo de publicação: JOURNAL ARTICLE
Nome de substância:0 (Membrane Proteins); 0 (centaurin beta2, human); EC 2.3.- (Acyltransferases); EC 2.3.1.52 (2-acylglycerophosphate acyltransferase)


  3 / 3262 MEDLINE  
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PMID:28528195
Autor:Pawlak Z; Yusuf KQ; Pai R; Urbaniak W
Endereço:Tribochemistry Consulting, Salt Lake City, UT 84117, USA; University of Economy, Biotribology Laboratory, Garbary 2, 85-229 Bydgoszcz, Poland; Kujawy University, Plac Wolnosci 1, 87-800 Wloclawek, Poland. Electronic address: zpawlak@xmission.com.
Título:Repulsive surfaces and lamellar lubrication of synovial joints.
Fonte:Arch Biochem Biophys; 623-624:42-48, 2017 Jun 01.
ISSN:1096-0384
País de publicação:United States
Idioma:eng
Resumo:Surface-active phospholipid (SAPL) secreted in the synovial joint plays an important role in cartilage integrity. In healthy joints, phospholipid multibilayers coat the cartilage surface, providing boundary lamellar-repulsive hydration lubrication. Current mechanism for lubrication of synovial joints, as well as the physical and chemical nature of the cartilage surface is discussed. Friction between phospholipid (PL) bilayers attached to cartilage surfaces is considered including a discussion on the recent observation of an extreme friction reduction as a consequence of a less charged hydrophilic cartilage surface. It is proposed that the highly efficient lubrication occurring in natural joints arises from the presence of negatively charged cartilage surfaces. The lamellar-repulsive mechanisms for the reduction of friction is supported by phospholipid lamellar phases and charged macromolecules residing between contacting cartilage surfaces at pH ∼7.4.
Tipo de publicação: JOURNAL ARTICLE
Nome de substância:0 (Phosphates); 0 (Phospholipids)


  4 / 3262 MEDLINE  
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PMID:28380319
Autor:Kleiner A; Galli M; Franceschini M; De Pandis MF; Stocchi F; Albertini G; de Barros RM
Título:The coefficient of friction in Parkinson's disease gait.
Fonte:Funct Neurol; 32(1):17-22, 2017 Jan/Mar.
ISSN:1971-3274
País de publicação:Italy
Idioma:eng
Resumo:This study aimed to characterize the coefficient of friction (COF) curves of patients with Parkinson's disease (PD) during barefoot gait and to evaluate the relationships between this variable and functional scales. Twenty-two subjects with PD (ON phase of levodopa) and 22 healthy subjects participated in this study. The participants walked barefoot along a pathway that went over two force plates embedded in the floor of the data collection room. The instantaneous COF was calculated as the ratio between the horizontal and vertical components of the ground reaction forces. Two-sample t-tests applied to every 1% of the support phase of the COF curve were used to compare the groups and to identify the phases in which the two groups were different. Specifically, three COF areas were computed: Area 1 (for the loading response phase), Area 2 (for the midstance phase) and Area 3 (for the terminal stance phase). Pearson's tests were applied to assess the associations between the COF curve areas and the clinical scales. The subjects with PD exhibited lower COF values during the loading response and terminal stance phases and higher COF values during the mid-stance phase compared with the control group. A strong positive correlation was observed between Area 1 and the Timed Up and Go Test (90.3%). In conclusion, the patients' COFs exhibited patterns that were different from those of the control group. Moreover, during the loading response phase, these differences were well-correlated with the Timed Up and Go Test scale data; Timed Up and Go Test data can be used to identify the risk of falls among PD patients.
Tipo de publicação: JOURNAL ARTICLE
Nome de substância:0 (Antiparkinson Agents); 46627O600J (Levodopa)


  5 / 3262 MEDLINE  
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PMID:28095766
Autor:Zamani AR; Oyadiji SO
Endereço:1 Fecad Ltd, Manchester, UK.
Título:Clamping of fine Kirschner wires in external fixators.
Fonte:Proc Inst Mech Eng H; 230(11):1036-1042, 2016 Nov.
ISSN:2041-3033
País de publicação:England
Idioma:eng
Resumo:In Ilizarov circular (ring) external fixators, fine Kirschner wires are used to fix the bone to the fixator. Clamping of the wires to the rings with different bolt torques has been studied. However, the relation between the bolt torque and the fixation load applied to the wire was not investigated. In this work, finite element method is used to address this problem. Here, a fully three-dimensional model of the wire fixation assembly was built, with geometric details like threads on the bolt to produce a realistic simulation of the clamping of the wire. Both cannulated and slotted bolt types were studied and values of 0.2, 0.25, 0.3 and 0.45 were used for coefficient of friction. A torque was applied to the nut while the ring section and bolt kept in place. The results for bolt load, nut rotation as well as axial and radial wire deformations were obtained. The results demonstrated a linear relation between the bolt load and the bolt torque. The coefficient of this relationship was shown to be inversely proportional to the coefficient of friction. For all results, the bolt load (N) was approximately 124 times the bolt torque (N m) divided by the friction coefficient. The results highlighted the difference between the cannulated and the slotted bolts in terms of their grip on the wire.
Tipo de publicação: JOURNAL ARTICLE


  6 / 3262 MEDLINE  
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PMID:28002747
Autor:Gonzalez-Rodriguez D; Guillou L; Cornat F; Lafaurie-Janvore J; Babataheri A; de Langre E; Barakat AI; Husson J
Endereço:Laboratoire de Chimie et Physique - Approche Multi-échelles des Milieux Complexes, Université de Lorraine, Metz, France.
Título:Mechanical Criterion for the Rupture of a Cell Membrane under Compression.
Fonte:Biophys J; 111(12):2711-2721, 2016 Dec 20.
ISSN:1542-0086
País de publicação:United States
Idioma:eng
Resumo:We investigate the mechanical conditions leading to the rupture of the plasma membrane of an endothelial cell subjected to a local, compressive force. Membrane rupture is induced by tilted microindentation, a technique used to perform mechanical measurements on adherent cells. In this technique, the applied force can be deduced from the measured horizontal displacement of a microindenter's tip, as imaged with an inverted microscope and without the need for optical sensors to measure the microindenter's deflection. We show that plasma membrane rupture of endothelial cells occurs at a well-defined value of the applied compressive stress. As a point of reference, we use numerical simulations to estimate the magnitude of the compressive stresses exerted on endothelial cells during the deployment of a stent.
Tipo de publicação: JOURNAL ARTICLE


  7 / 3262 MEDLINE  
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PMID:28141804
Autor:Wheeler RJ
Endereço:Sir William Dunn School of Pathology, University of Oxford, Oxford, United Kingdom.
Título:Use of chiral cell shape to ensure highly directional swimming in trypanosomes.
Fonte:PLoS Comput Biol; 13(1):e1005353, 2017 Jan.
ISSN:1553-7358
País de publicação:United States
Idioma:eng
Resumo:Swimming cells typically move along a helical path or undergo longitudinal rotation as they swim, arising from chiral asymmetry in hydrodynamic drag or propulsion bending the swimming path into a helix. Helical paths are beneficial for some forms of chemotaxis, but why asymmetric shape is so prevalent when a symmetric shape would also allow highly directional swimming is unclear. Here, I analyse the swimming of the insect life cycle stages of two human parasites; Trypanosoma brucei and Leishmania mexicana. This showed quantitatively how chirality in T. brucei cell shape confers highly directional swimming. High speed videomicrographs showed that T. brucei, L. mexicana and a T. brucei RNAi morphology mutant have a range of shape asymmetries, from wild-type T. brucei (highly chiral) to L. mexicana (near-axial symmetry). The chiral cells underwent longitudinal rotation while swimming, with more rapid longitudinal rotation correlating with swimming path directionality. Simulation indicated hydrodynamic drag on the chiral cell shape caused rotation, and the predicted geometry of the resulting swimming path matched the directionality of the observed swimming paths. This simulation of swimming path geometry showed that highly chiral cell shape is a robust mechanism through which microscale swimmers can achieve highly directional swimming at low Reynolds number. It is insensitive to random variation in shape or propulsion (biological noise). Highly symmetric cell shape can give highly directional swimming but is at risk of giving futile circular swimming paths in the presence of biological noise. This suggests the chiral T. brucei cell shape (associated with the lateral attachment of the flagellum) may be an adaptation associated with the bloodstream-inhabiting lifestyle of this parasite for robust highly directional swimming. It also provides a plausible general explanation for why swimming cells tend to have strong asymmetries in cell shape or propulsion.
Tipo de publicação: JOURNAL ARTICLE


  8 / 3262 MEDLINE  
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PMID:28063775
Autor:Ramoutar DN; Crosnier EA; Shivji F; Miles AW; Gill HS
Endereço:Nottingham University Hospitals NHS Trust, Nottingham, United Kingdom.
Título:Assessment of Head Displacement and Disassembly Force With Increasing Assembly Load at the Head/Trunnion Junction of a Total Hip Arthroplasty Prosthesis.
Fonte:J Arthroplasty; 32(5):1675-1678, 2017 May.
ISSN:1532-8406
País de publicação:United States
Idioma:eng
Resumo:BACKGROUND: Most femoral components used now for total hip arthroplasty are modular, requiring a strong connection at assembly. The aim of this study was to assess the effect of assembly force on the strength of head-trunnion interface and to measure the initial displacement of the head on the trunnion with different assembly forces. METHODS: Three assembly load levels were assessed (A: 2 kN, B: 4 kN, C: 6 kN) with 4 implants in each group. The stems were mounted in a custom rig and the respective assembly loads were applied to the head at a constant rate of 0.05 kN/s (ISO7260-10:2003). Load levels were recorded during assembly. Head displacement was measured with a laser sensor. The disassembly force was determined by a standard pull-off test. RESULTS: The maximum head displacement on the trunnion was significantly different between the 2 kN group and the other 2 groups (4 kN, 6 kN, P = .029), but not between the 4 kN and 6 kN groups (P = .89). The disassembly forces between the 3 groups were significantly different (mean ± standard deviation, A: 1316 ± 223 kN; B: 2224 ± 151 kN; C: 3965 ± 344 kN; P = .007), with increasing assembly load leading to a higher pull-off force. For the 4 kN and 6 kN groups, a first peak of approximately 2.5 kN was observed on the load recordings during assembly before the required assembly load was eventually reached corresponding to sudden increase in head displacement to approximately 150 µm. CONCLUSION: An assembly force of 2 kN may be too low to overcome the frictional forces needed to engage the head and achieve maximum displacement on the trunnion and thus an assembly load of greater than 2.5 kN is recommended.
Tipo de publicação: JOURNAL ARTICLE


  9 / 3262 MEDLINE  
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PMID:28346437
Autor:Smutny M; Ákos Z; Grigolon S; Shamipour S; Ruprecht V; Capek D; Behrndt M; Papusheva E; Tada M; Hof B; Vicsek T; Salbreux G; Heisenberg CP
Endereço:Institute of Science and Technology Austria, Am Campus 1, A-3400 Klosterneuburg, Austria.
Título:Friction forces position the neural anlage.
Fonte:Nat Cell Biol; 19(4):306-317, 2017 Apr.
ISSN:1476-4679
País de publicação:England
Idioma:eng
Resumo:During embryonic development, mechanical forces are essential for cellular rearrangements driving tissue morphogenesis. Here, we show that in the early zebrafish embryo, friction forces are generated at the interface between anterior axial mesoderm (prechordal plate, ppl) progenitors migrating towards the animal pole and neurectoderm progenitors moving in the opposite direction towards the vegetal pole of the embryo. These friction forces lead to global rearrangement of cells within the neurectoderm and determine the position of the neural anlage. Using a combination of experiments and simulations, we show that this process depends on hydrodynamic coupling between neurectoderm and ppl as a result of E-cadherin-mediated adhesion between those tissues. Our data thus establish the emergence of friction forces at the interface between moving tissues as a critical force-generating process shaping the embryo.
Tipo de publicação: JOURNAL ARTICLE
Nome de substância:0 (Cadherins); 0 (Zebrafish Proteins)


  10 / 3262 MEDLINE  
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PMID:28269415
Autor:Anzhu Gao; Murphy RJ; Hao Liu; Iordachita I; Armand M
Título:Evaluating the deflection of dexterous continuum manipulators with unevenly distributed compliant joints.
Fonte:Conf Proc IEEE Eng Med Biol Soc; 2016:5099-5102, 2016 Aug.
ISSN:1557-170X
País de publicação:United States
Idioma:eng
Resumo:Dexterous continuum manipulators (DCMs) offer great potential for increasing instrument reach in minimally-invasive surgical procedures. We previously designed and fabricated a tendon driven DCM with a large instrument channel and evenly distributed compliant joints for minimally-invasive skull base surgery and the treatment of osteolysis during hip revision surgery. The evenly distributed compliant joints, in some cases, may limit the reach of the DCM during lesion removal. In this paper, we propose a finite element analysis (FEA) method for optimizing the distribution of the compliant joints based on treatment space requirements determined preoperatively. After performing experiments to validate the FEA results, we investigated the effects of height and cross distance of unevenly distributed compliant joints on tip trajectories and deflection shapes of DCMs. A boundary exploration for skull base surgery was performed to investigate the improvement in the percent of boundary explored by the optimized DCMs with the unevenly distributed compliant joints. Results show the advantage of using DCMs with unevenly distributed joints in reaching the boundary of the lesion. For a typical lesion in the petrous apex during skull base surgery, simulation results indicates that the design of unevenly distributed compliant joints can increase the reach of the DCM accomplishing 71% lesion removal compared with 59% from the DCM with evenly distributed compliant joints.
Tipo de publicação: EVALUATION STUDIES; JOURNAL ARTICLE



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