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https://www.readbyqxmd.com/read/28729509/experimentally-realized-mechanochemistry-distinct-from-force-accelerated-scission-of-loaded-bonds
#1
Sergey Akbulatov, Yancong Tian, Zhen Huang, Timothy J Kucharski, Qing-Zheng Yang, Roman Boulatov
Stretching polymer chains accelerates dissociation of a variety of internal covalent bonds, to an extent that correlates well with the force experienced by the scissile bond. Recent theory has also predicted scenarios in which applied force accelerates dissociation of unloaded bonds and kinetically strengthens strained bonds. We report here unambiguous experimental validation of this hypothesis: Detailed kinetic measurements demonstrate that stretching phosphotriesters accelerates dissociation of the unloaded phosphorus-oxygen bond orthogonal to the pulling axis, whereas stretching organosiloxanes inhibits dissociation of the aligned loaded silicon-oxygen bonds...
July 21, 2017: Science
https://www.readbyqxmd.com/read/28729390/walking-economy-is-predictably-determined-by-speed-grade-and-gravitational-load
#2
Lindsay W Ludlow, Peter G Weyand
The metabolic energy human walking requires can vary by more than 10-fold depending on the speed, surface gradient and load carried. Although the mechanical factors determining economy are generally considered to be numerous and complex, we tested a minimum-mechanics hypothesis that only three variables are needed for broad, accurate prediction: speed, surface grade, and total gravitational load. We first measured steady-state rates of oxygen uptake in 20 healthy adult subjects during unloaded treadmill trials from 0...
July 20, 2017: Journal of Applied Physiology
https://www.readbyqxmd.com/read/28726961/functional-single-walled-carbon-nanotubes-car-for-targeting-dopamine-delivery-into-the-brain-of-parkinsonian-mice
#3
Qing Guo, Huihui You, Xu Yang, Bencheng Lin, Zhihong Zhu, Zhisong Lu, Xiaoxiao Li, Yun Zhao, Lin Mao, Shiping Shen, Haoyan Cheng, Jiting Zhang, Lingfu Deng, Jianhua Fan, Zhuge Xi, Rui Li, Chang Ming Li
Current treatments for Parkinson's disease (PD) are limited, partly due to the difficulties posed by the blood brain barrier (BBB) when delivering drugs to the brain. Herein, we explore the feasibility and efficacy of functional single-walled carbon nanotubes 'CAR' (SWCNT-PEGs-Lf) which carry and target-deliver dopamine (DA) to the brain in PD mice for treatment. SWCNTs can penetrate the cell-membrane remarkably, with the characteristics including high drug-loading and pH-dependent therapeutic unloading capacities...
July 20, 2017: Nanoscale
https://www.readbyqxmd.com/read/28726563/mechanically-strong-and-ph-responsive-carboxymethyl-chitosan-graphene-oxide-polyacrylamide-nanocomposite-hydrogels-with-fast-recoverability
#4
Yang Chen, Hongqiu Wang, Junrong Yu, Yan Wang, Jing Zhu, Zuming Hu
The biocompatible, quickly recoverable, mechanically strong and tough polymer hydrogels has great potential for biomedical applications. A novel carboxymethyl chitosan (CMCTs)/graphene oxide (GO)/polyacrylamide (PAM) nanocomposite (NC) hydrogel with excellent mechanical performance was synthesized through a facile, one-pot free radical polymerization, using GO nanosheets as the crosslink centers instead of toxic organic molecules. The content of GO nanosheets and CMCTs has great influence on the mechanical properties of CMCTs/GO/PAM NC hydrogels...
July 20, 2017: Journal of Biomaterials Science. Polymer Edition
https://www.readbyqxmd.com/read/28726101/eukaryotic-elongation-factor-2-kinase-activation-in-m-soleus-under-14-day-hindlimb-unloading-of-rats
#5
Y N Lomonosova, S P Belova, T M Mirzoev, I B Kozlovskaya, B S Shenkman
Functional unloading of m. soleus of male Wistar rats was found to cause a reduction in protein synthesis. The level of phosphorylation of the translation elongation factor 2 (eEF2) and the eEF2 kinase (eEF2k) activity in m. soleus after 14 days of unloading were assessed. Rats were divided into the control group (C) and the group with hindlimb unloading for 14 days (HU14). The level of eEF2 phosphorylation in group HU14 was 80%, whereas in the control is was 40%. The indices of eEF2k expression and protein content in group HU14 increased compared to group C...
May 2017: Doklady. Biochemistry and Biophysics
https://www.readbyqxmd.com/read/28723812/effects-of-12-weeks-resistance-training-on-sprint-and-jump-performance-in-competitive-adolescent-rugby-union-players
#6
Simon K Harries, David R Lubans, Anthony Buxton, Thomas H J MacDougall, Robin Callister
Sprint performance is an important characteristic for success in many sports, including rugby union. Resistance training is used to increase muscular fitness (i.e. strength, endurance and power) and may also be effective for improving sprint and jump performances. The aims of this study were to examine the effects of resistance training using two different periodized programs (linear and daily undulating) on sprint and jump performance and explore relationships between performance measures. Sixteen male (16...
July 17, 2017: Journal of Strength and Conditioning Research
https://www.readbyqxmd.com/read/28720522/patients-with-non-ambulatory-cerebral-palsy-have-higher-sclerostin-levels-and-lower-bone-mineral-density-than-patients-with-ambulatory-cerebral-palsy
#7
Yoon-Kyum Shin, Young Kwon Yoon, Kyung Bae Chung, Yumie Rhee, Sung-Rae Cho
Bone loss is a serious clinical issue in patients with cerebral palsy (CP). Sclerostin has garnered interest as a key mechanosensor in osteocytes, leading to considerations of the therapeutic utilization of anti-sclerostin medications. This study was undertaken to determine associations among mechanical unloading, sclerostin levels, and bone imbalance in patients with CP. A total of 28 patients with CP participated in this cross-sectional study. The following measurements were taken: anthropometrics, clinical diagnosis of CP subtype and ambulatory status, bone mineral density (BMD) z-scores at the lumbar spine and hip, and blood biochemical markers, including sclerostin, parathyroid hormone (PTH), osteocalcin, C-terminal telopeptide, 25-hydroxyvitamin D, 1,25-dihydroxyvitamin D, creatinine, calcium, and phosphorus...
July 15, 2017: Bone
https://www.readbyqxmd.com/read/28720182/ground-reaction-forces-during-reduced-gravity-running-in-parabolic-flight
#8
Peter Cavanagh, Andrea Rice, Molly Glauberman, Amanda Sudduth, Arien Cherones, Shane Davis, Michael Lewis, Andrea Hanson, Grier Wilt
BACKGROUND: Treadmills have been employed as both a form of exercise and a countermeasure to prevent changes in the musculoskeletal system on almost all NASA missions and many Russian missions since the early Space Shuttle flights. It is possible that treadmills may also be part of exercise programs on future Mars missions and that they may be a component of exercise facilities in lunar or Martian habitats. METHODS: In order to determine if the ambient gravity on these destinations will provide osteogenic effects while performing exercise on a treadmill, ground reactions forces (GRFs) were measured on eight subjects (six women and two men) running at 6 mph during parabolic flight in Martian and lunar gravity conditions...
August 1, 2017: Aerospace Medicine and Human Performance
https://www.readbyqxmd.com/read/28717991/prolonged-bed-rest-impairs-rapid-cpi-17-phosphorylation-and-contraction-in-rat-mesenteric-resistance-arteries-to-cause-orthostatic-hypotension
#9
Toshio Kitazawa, Kazuyo Kitazawa
Prolonged bed rest (PBR) causes orthostatic hypotension (OH). Rapid constriction of splanchnic resistance arteries in response to a sudden increase in sympathetic tone contributes to the recovery of orthostatic arterial pressure upon standing. However, the molecular mechanism of PBR-induced dysfunction in arterial constriction is not fully understood. Previously, we showed that CPI-17, a regulatory protein for myosin phosphatase, mediates α1A-adrenergic receptor-induced rapid contraction of small mesenteric arteries...
July 17, 2017: Pflügers Archiv: European Journal of Physiology
https://www.readbyqxmd.com/read/28715542/simultaneous-analysis-of-elastic-and-non-specific-adhesive-properties-of-thin-sample-and-biological-cell-considering-bottom-substrate-effect
#10
Viswanath Managuli, Sitikantha Roy
A new asymptotically correct contact model has been developed for conical tip based AFM nanoindentation. This new model provides both elastic and non-specific adhesion properties of cells and soft gels by taking sample thickness at the point of indentation and its depth of indentation into consideration. The bottom substrate effect is the most common source of error in the study of "AFM force maps" of the cellular sample. The present model incorporates an asymptotically correct correction term as a function of depth of indentation to eliminate the substrate effect in the analysis...
July 17, 2017: Journal of Biomechanical Engineering
https://www.readbyqxmd.com/read/28712025/side-to-side-asymmetries-in-landing-mechanics-from-a-drop-vertical-jump-test-are-not-related-to-asymmetries-in-knee-joint-laxity-following-anterior-cruciate-ligament-reconstruction
#11
Christophe A G Meyer, Paul Gette, Caroline Mouton, Romain Seil, Daniel Theisen
PURPOSE: Asymmetries in knee joint biomechanics and increased knee joint laxity in patients following anterior cruciate ligament reconstruction (ACLR) are considered risk factors for re-tear or early onset of osteoarthritis. Nevertheless, the relationship between these factors has not been established. The aim of the study was to compare knee mechanics during landing from a bilateral drop vertical jump in patients following ACLR and control participants and to study the relationship between side-to-side asymmetries in landing mechanics and knee joint laxity...
July 15, 2017: Knee Surgery, Sports Traumatology, Arthroscopy: Official Journal of the ESSKA
https://www.readbyqxmd.com/read/28711612/exemestane-loaded-alginate-nanoparticles-for-cancer-treatment-formulation-and-in-vitro-evaluation
#12
Jayapal John Joseph, Dhanaraj Sangeetha
Alginate, a biopolymer is most useful for anticancer drug delivery, because of it is biocompatible, nontoxic, biodegradable and exploiting ligand-receptor interaction. Breast cancer is spreading very fast due to the changing food habits and environmental causes. Exemestane (EXE) an oral chemotherapeutic drug was used to treat breast cancer, while loading EXE in alginate nanoparticles, the side effects which was faced during administration are expected to be reduced and control the release of exemestane. Thus, in the present study, an anticancer drug EXE was loaded into the Alginate nanoparticles (ALG-NPs) through simple controlled gelation method and evaluated in vitro to study the performance of ALG-NPs in delivering the anticancer drug EXE...
July 12, 2017: International Journal of Biological Macromolecules
https://www.readbyqxmd.com/read/28708775/continuous-cardiac-autonomic-and-hemodynamic-responses-to-isometric-exercise
#13
Katrina A Taylor, Jonathan D Wiles, Damian D Coleman, Rajan Sharma, Jamie M Oʼdriscoll
PURPOSE: Elevated arterial blood pressure (BP) is associated with autonomic dysfunction and impaired hemodynamic control mechanisms. Isometric exercise (IE) training has been demonstrated effective at reducing BP; however, the continuous cardiovascular responses during IE are underinvestigated. We hypothesized that reflex autonomic cardiovascular control is an important mediator in reducing BP. To test our hypothesis, we investigated continuous cardiac autonomic modulation and baroreceptor reflex sensitivity (BRS) in response to IE...
August 2017: Medicine and Science in Sports and Exercise
https://www.readbyqxmd.com/read/28707188/hemodynamic-benefits-of-counterpulsation-implantable-percutaneous-and-intraaortic-rotary-blood-pumps-an-in-silico-and-in-vitro-study
#14
Yu Wang, Steven C Koenig, Michael A Sobieski, Mark S Slaughter, Guruprasad A Giridharan
Mechanical circulatory support (MCS) devices have become a standard therapy for heart failure (HF) patients. MCS device designs may differ by level of support, inflow and/or outflow cannulation sites, and mechanism(s) of cardiac unloading and blood flow delivery. Investigation and direct comparison of hemodynamic parameters that help characterize performance of MCS devices has been limited. We quantified cardiac and vascular hemodynamic responses for different types of MCS devices. Continuous flow (CF) left ventricular (LV) assist devices (LVAD) with LV or left atrial (LA) inlet, counterpulsation devices, percutaneous CF LVAD, and intra-aortic rotary blood pumps (IARBP) were quantified using established computer simulation and mock flow loop models...
July 13, 2017: Cardiovascular Engineering and Technology
https://www.readbyqxmd.com/read/28705996/different-gene-response-to-mechanical-loading-during-early-and-late-phases-of-rat-achilles-tendon-healing
#15
Malin Hammerman, Parmis Blomgran, Arie Dansac, Pernilla Eliasson, Per Aspenberg
Mechanical loading stimulates tendon healing both when applied in the inflammatory phase and in the early remodeling phase of the process, although not necessarily via the same mechanisms. We investigated the gene response to mechanical loading in these two phases of tendon healing. The right Achilles tendon in rats was transected and the hind limbs were unloaded by tail suspension. The rats were exposed to 5 minutes of treadmill running 3 or 14 days after tendon transection. Thereafter, they were re-suspended for 15 minutes or 3 hours until euthanasia...
July 13, 2017: Journal of Applied Physiology
https://www.readbyqxmd.com/read/28705992/beyond-just-hemoglobin-red-blood-cell-potentiation-of-hemoglobin-oxygen-unloading-in-fish
#16
Colin J Brauner, Till S Harter
Teleosts comprise 95% of fish species, and almost half of all vertebrate species, and represent one of the most successful adaptive radiation events among vertebrates. This is thought to be in part due to their unique oxygen (O2) transport system. In salmonids, recent in vitro and in vivo studies indicate that hemoglobin-oxygen (Hb-O2) unloading to tissues may be doubled or even tripled under some conditions without changes in perfusion. This is accomplished through the short-circuiting of red blood cell (RBC) pH regulation resulting in a large arterial-venous pH difference within the RBC and induced reduction in Hb-O2 affinity...
July 13, 2017: Journal of Applied Physiology
https://www.readbyqxmd.com/read/28705316/cell-specific-pathways-supporting-persistent-fibrosis-in-heart-failure
#17
Stephen D Farris, Creighton Don, Deri Helterline, Christopher Costa, Tabitha Plummer, Susanne Steffes, Claudius Mahr, Nahush A Mokadam, April Stempien-Otero
BACKGROUND: Only limited data exist describing the histologic and noncardiomyocyte function of human myocardium in end-stage heart failure (HF). OBJECTIVES: The authors sought to determine changes in noncardiomyocyte cellular activity in patients with end-stage HF after left ventricular assist device (LVAD)-induced remodeling to identify mechanisms impeding recovery. METHODS: Myocardium was obtained from subjects undergoing LVAD placement and/or heart transplantation...
July 18, 2017: Journal of the American College of Cardiology
https://www.readbyqxmd.com/read/28704681/cytokine-il1%C3%AE-and-lactate-as-markers-for-tissue-damage-in-spineboard-immobilisation-a-prospective-randomised-open-label-crossover-trial
#18
Baukje Hemmes, Luuk A de Wert, Peter R G Brink, Cees W J Oomens, Dan L Bader, Martijn Poeze
BACKGROUND: Spinal immobilisation using a rigid long spineboard is a well-established procedure in trauma care. During immobilisation, the body is exposed to high tissue-interface pressures. This may lead to a localised inflammatory response of the skin, which may be used to monitor the body's response to different types of immobilisation device. AIM: In this study we compared the standard rigid spineboard with a new soft-layered spineboard regarding tissue-interface pressures, skin redness as an indicator of reactive hyperaemia and cutaneous IL1α and lactate release...
June 23, 2017: Journal of the Mechanical Behavior of Biomedical Materials
https://www.readbyqxmd.com/read/28702807/effect-of-rest-pause-vs-traditional-bench-press-training-on-muscle-strength-electromyography-and-lifting-volume-in-randomized-trial-protocols
#19
J Adam Korak, Max R Paquette, Justin Brooks, Dana K Fuller, John M Coons
PURPOSE: Rest-pause (4-s unloaded rest between repetitions) training effects on one repetition maximum (1 RM), lifting volume, and neural activation via electromyography (EMG) are currently vague in the literature and can benefit strength and conditioning professionals for resistance training programme design. Therefore, this study compared 1 RM, neural activation via (EMG), and volume differences between rest-pause vs. traditional resistance training. METHODS: Trained males (N = 20) were randomly assigned to either a rest-pause or a traditional training group...
July 12, 2017: European Journal of Applied Physiology
https://www.readbyqxmd.com/read/28698113/patient-specific-biomechanical-model-of-hypoplastic-left-heart-to-predict-post-operative-cardio-circulatory-behaviour
#20
Elena Cutrì, Alessio Meoli, Gabriele Dubini, Francesco Migliavacca, Tain-Yen Hsia, Giancarlo Pennati
Hypoplastic left heart syndrome is a complex congenital heart disease characterised by the underdevelopment of the left ventricle normally treated with a three-stage surgical repair. In this study, a multiscale closed-loop cardio-circulatory model is created to reproduce the pre-operative condition of a patient suffering from such pathology and virtual surgery is performed. Firstly, cardio-circulatory parameters are estimated using a fully closed-loop cardio-circulatory lumped parameter model. Secondly, a 3D standalone FEA model is build up to obtain active and passive ventricular characteristics and unloaded reference state...
July 8, 2017: Medical Engineering & Physics
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