To see the other types of publications on this topic, follow the link: Strained muscle.
Journal articles on the topic 'Strained muscle'
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 journal articles for your research on the topic 'Strained muscle.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse journal articles on a wide variety of disciplines and organise your bibliography correctly.
1
Lieber, R. L., and J. Friden. "Muscle damage is not a function of muscle force but active muscle strain." Journal of Applied Physiology 74, no. 2 (February 1, 1993): 520–26. http://dx.doi.org/10.1152/jappl.1993.74.2.520.
Full textAbstract:
Contractile properties of rabbit tibialis anterior muscles were measured after eccentric contraction to investigate the mechanism of muscle injury. In the first experiment, two groups of muscles were strained 25% of the muscle fiber length at identical rates. However, because the timing of the imposed length change relative to muscle activation was different, the groups experienced dramatically different muscle forces. Because muscle maximum tetanic tension and other contractile parameters measured after 30 min of cyclic activity with either strain timing pattern were identical (P > 0.4), we concluded that muscle damage was equivalent despite very different imposed forces. This result was supported by a second experiment in which the same protocol was performed at one-half the strain (12.5% muscle fiber length). Again, there was no difference in maximum tetanic tension after cyclic 12.5% strain with either strain timing. Data from both experiments were analyzed by two-way analysis of variance, which revealed a highly significant effect of strain magnitude (P < 0.001) but no significant effect of stretch timing (P > 0.7). We interpret these data to signify that it is not high force per se that causes muscle damage after eccentric contraction but the magnitude of the active strain (i.e., strain during active lengthening). This conclusion was supported by morphometric analysis showing equivalent area fractions of damaged muscle fibers that were observed throughout the muscle cross section. The active strain hypothesis is described in terms of the interaction between the myofibrillar cytoskeleton, the sarcomere, and the sarcolemma.
2
Sharma, Arpit, Priya Shah, Jyoti Dabholkar, and Neeti Kapre. "Thyroarytenoid Muscle Ablation for Treatment of Spasmodic Dysphonia." International Journal of Phonosurgery & Laryngology 1, no. 2 (2011): 91–92. http://dx.doi.org/10.5005/jp-journals-10023-1024.
Full textAbstract:
ABSTRACT Adductor spasmodic dysphonia is the most common form of laryngeal dystonia and comprises about 80% of all laryngeal dystonias. It is characterized by strained and strangled voice quality causing significant impairment to the patient. This article focuses on the surgical treatment of adductor spasmodic dysphonia by thyroarytenoid muscle ablation. It provides longlasting control of symptoms and patient satisfaction is very high.
3
Tidball, J. G., G. Salem, and R. Zernicke. "Site and mechanical conditions for failure of skeletal muscle in experimental strain injuries." Journal of Applied Physiology 74, no. 3 (March 1, 1993): 1280–86. http://dx.doi.org/10.1152/jappl.1993.74.3.1280.
Full textAbstract:
Failure in muscle strain injuries has been reported to occur within the muscle belly, at the myotendinous junction, or within muscle near the myotendinous junction. The goal of this investigation was to determine by electron-microscopic examination the site of lesion in whole muscle strained to failure. In addition, site and conditions for failure of stimulated and unstimulated muscle were compared. Frog semitendinosus myotendinous units with intact tendon-bone junctions were strained at physiological strain rates to failure. All failures occurred at or near the proximal myotendinous junction in both stimulated and unstimulated muscle. Stimulated muscle required approximately 30% more force and approximately 110% more energy to reach failure. Electron-microscopic examination of longitudinal sections of small bundles of fibers showed that unstimulated muscle failed within the muscle near the myotendinous junction. Failure occurred in a single transverse plane of each cell within Z disks. Other Z disks near the failure site displayed strains of several hundred percent. Stimulated muscle failed within the lamina lucida at the myotendinous junction in most fibers. No Z-disk strain was observed in those fibers. We conclude that the site of failure in muscle strain injuries varies with the state of activation of the cell at the time of injury. Furthermore, the data show that the breaking strength of the Z disk varied with muscle stimulation and indicate the existence of two load-bearing systems in parallel within Z disks.
4
Yucesoy, Can A., Guus C. Baan, Bart H. F. J. M. Koopman, Henk J. Grootenboer, and Peter A. Huijing. "Pre-Strained Epimuscular Connections Cause Muscular Myofascial Force Transmission to Affect Properties of Synergistic EHL and EDL Muscles of the Rat." Journal of Biomechanical Engineering 127, no. 5 (May 18, 2005): 819–28. http://dx.doi.org/10.1115/1.1992523.
Full textAbstract:
Background: Myofascial force transmission occurs between muscles (intermuscular myofascial force transmission) and from muscles to surrounding nonmuscular structures such as neurovascular tracts and bone (extramuscular myofascial force transmission). The purpose was to investigate the mechanical role of the epimuscular connections (the integral system of inter- and extramuscular connections) as well as the isolated role of extramuscular connections on myofascial force transmission and to test the hypothesis, if such connections are prestrained. Method of approach: Length-force characteristics of extensor hallucis longus (EHL) muscle of the rat were measured in two conditions: (I) with the neighboring EDL muscle and epimuscular connections of the muscles intact: EDL was kept at a constant muscle tendon complex length. (II) After removing EDL, leaving EHL with intact extramuscular connections exclusively. Results: (I) Epimuscular connections of the tested muscles proved to be prestrained significantly. (1) Passive EHL force was nonzero for all isometric EHL lengths including very low lengths, increasing with length to approximately 13% of optimum force at high length. (2) Significant proximodistal EDL force differences were found at all EHL lengths: Initially, proximal EDL force =1.18±0.11N, where as distal EDL force =1.50±0.08N (mean ± SE). EHL lengthening decreased the proximo-distal EDL force difference significantly (by 18.4%) but the dominance of EDL distal force remained. This shows that EHL lengthening reduces the prestrain on epimuscular connections via intermuscular connections; however; the prestrain on the extramuscular connections of EDL remains effective. (II) Removing EDL muscle affected EHL forces significantly. (1) Passive EHL forces decreased at all muscle lengths by approximately 17%. However, EHL passive force was still nonzero for the entire isometric EHL length range, indicating pre-strain of extramuscular connections of EHL. This indicates that a substantial part of the effects originates solely from the extramuscular connections of EHL. However, a role for intermuscular connections between EHL and EDL, when present, cannot be excluded. (2) Total EHL forces included significant shape changes in the length-force curve (e.g., optimal EHL force decreased significantly by 6%) showing that due to myofascial force transmission muscle length-force characteristics are not specific properties of individual muscles. Conclusions: The pre-strain in the epimuscular connections of EDL and EHL indicate that these myofascial pathways are sufficiently stiff to transmit force even after small changes in relative position of a muscle with respect to its neighboring muscular and nonmuscular tissues. This suggests the likelihood of such effects also in vivo.
5
Smith, P. G., T. Tokui, and M. Ikebe. "Mechanical strain increases contractile enzyme activity in cultured airway smooth muscle cells." American Journal of Physiology-Lung Cellular and Molecular Physiology 268, no. 6 (June 1, 1995): L999—L1005. http://dx.doi.org/10.1152/ajplung.1995.268.6.l999.
Full textAbstract:
Smooth muscle hypertrophy is often found in tissue subjected to abnormal physical stress. To determine if physical stress (strain) per se could increase the contractile potential of airway smooth muscle (ASM), we compared cultured ASM cells subjected to strain to control cells (no strain) for rates of 1) myosin light chain kinase (MLCK)-mediated myosin light chain (LC20) phosphorylation, 2) actin-activated myosin ATPase, and 3) myosin light chain phosphatase-mediated myosin dephosphorylation. Lysates from strained cells showed increases in both LC20 phosphorylation activity and actomyosin ATPase activity but decreased rates of phosphatase-dependent myosin dephosphorylation. The increased LC20 phosphorylation activity and ATPase activity of the strained cells were accompanied by increases in cellular content of MLCK and myosin, respectively, compared with control. Because the cultured ASM cells exposed to strain expressed higher MLCK activity and actomyosin ATPase activity but lower myosin light chain phosphatase activity, these data suggest that physical stress in part determines ASM potential for contractile state.
6
Somlyo, A. V., Y. E. Goldman, T. Fujimori, M. Bond, D. R. Trentham, and A. P. Somlyo. "Cross-bridge kinetics, cooperativity, and negatively strained cross-bridges in vertebrate smooth muscle. A laser-flash photolysis study." Journal of General Physiology 91, no. 2 (February 1, 1988): 165–92. http://dx.doi.org/10.1085/jgp.91.2.165.
Full textAbstract:
The effects of laser-flash photolytic release of ATP from caged ATP [P3-1(2-nitrophenyl)ethyladenosine-5'-triphosphate] on stiffness and tension transients were studied in permeabilized guinea pig protal vein smooth muscle. During rigor, induced by removing ATP from the relaxed or contracting muscles, stiffness was greater than in relaxed muscle, and electron microscopy showed cross-bridges attached to actin filaments at an approximately 45 degree angle. In the absence of Ca2+, liberation of ATP (0.1-1 mM) into muscles in rigor caused relaxation, with kinetics indicating cooperative reattachment of some cross-bridges. Inorganic phosphate (Pi; 20 mM) accelerated relaxation. A rapid phase of force development, accompanied by a decline in stiffness and unaffected by 20 mM Pi, was observed upon liberation of ATP in muscles that were released by 0.5-1.0% just before the laser pulse. This force increment observed upon detachment suggests that the cross-bridges can bear a negative tension. The second-order rate constant for detachment of rigor cross-bridges by ATP, in the absence of Ca2+, was estimated to be 0.1-2.5 X 10(5) M-1s-1, which indicates that this reaction is too fast to limit the rate of ATP hydrolysis during physiological contractions. In the presence of Ca2+, force development occurred at a rate (0.4 s-1) similar to that of intact, electrically stimulated tissue. The rate of force development was an order of magnitude faster in muscles that had been thiophosphorylated with ATP gamma S before the photochemical liberation of ATP, which indicates that under physiological conditions, in non-thiophosphorylated muscles, light-chain phosphorylation, rather than intrinsic properties of the actomyosin cross-bridges, limits the rate of force development. The release of micromolar ATP or CTP from caged ATP or caged CTP caused force development of up to 40% of maximal active tension in the absence of Ca2+, consistent with cooperative attachment of cross-bridges. Cooperative reattachment of dephosphorylated cross-bridges may contribute to force maintenance at low energy cost and low cross-bridge cycling rates in smooth muscle.
7
Hamilton, Bruce. "Medical management of hamstring muscle injury: strained evidence for platelet rich plasma." British Journal of Sports Medicine 48, no. 18 (July 18, 2014): 1336. http://dx.doi.org/10.1136/bjsports-2014-094009.
Full text
8
Ciematnieks, Uģis, and Evita Tomanoviča. "EFFECT OF FOAM ROLLER AND STATIC STRETCHING ON BIOMECHANICAL PARAMETERS OF MUSCLE." SOCIETY. INTEGRATION. EDUCATION. Proceedings of the International Scientific Conference 6 (May 20, 2020): 150. http://dx.doi.org/10.17770/sie2020vol6.5082.
Full textAbstract:
After training, it is needed to perform flexibility exercises for muscle stretching, but many choose to use the foam roller. With a foam roller, you can both exercise and perform a myofascial release that affects the deep tissues of extremities. Myofascial release improves blood circulation in muscle, develops elasticity, flexibility and minimizes the risk of an unwanted injury (Myers & Frederick, 2012). Many studies are being carried out to determine the effects of the various types of stretching on balance, speed and reaction (Apostolopoulos, Metisos, Flouris & Koutedakis, 2015). Training programs are designed so that after applying different workloads at the end there is cool-down through stretching exercises, but these training plans rarely recommends foam rollers as stretching means, even though they are popular every day. Aim of study: Find out the most effective method for reducing muscle tension in lower extremities. The study identifies changes in the biomechanical parameters of the hamstring muscle group after general stretching exercises and foam roller, after GRIP fitness concept class, using the Myoton PRO biomechanical parameters measurement. The study do not show any significant differences that may be in favour of one or the other method. Literature sources indicate that foam rollers exercises helps to relieve and restore the strained muscles more quickly, increases flexibility (Barrett, 2017). Our study did not confirm any of such findings. Foam roller exercises for myophascial release is as effective as static stretching exercises.
9
Connolly, Sarah C., Paul G. Smith, Nigel J. Fairbank, Carolyn A. Lall, Darren J. Cole, James D. MacKinnon, and Geoffrey N. Maksym. "Chronic oscillatory strain induces MLCK associated rapid recovery from acute stretch in airway smooth muscle cells." Journal of Applied Physiology 111, no. 4 (October 2011): 955–63. http://dx.doi.org/10.1152/japplphysiol.00812.2009.
Full textAbstract:
A deep inspiration (DI) temporarily relaxes agonist-constricted airways in normal subjects, but in asthma airways are refractory and may rapidly renarrow, possibly due to changes in the structure and function of airway smooth muscle (ASM). Chronic largely uniaxial cyclic strain of ASM cells in culture causes several structural and functional changes in ASM similar to that in asthma, including increases in contractility, MLCK content, shortening velocity, and shortening capacity. However, changes in recovery from acute stretch similar to a DI have not been measured. We have therefore measured the response and recovery to large stretches of cells modified by chronic stretching and investigated the role of MLCK. Chronic, 10% uniaxial cyclic stretch, with or without a strain gradient, was administered for up to 11 days to cultured cells grown on Silastic membranes. Single cells were then removed from the membrane and subjected to 1 Hz oscillatory stretches up to 10% of the in situ cell length. These oscillations reduced stiffness by 66% in all groups ( P < 0.05). Chronically strained cells recovered stiffness three times more rapidly than unstrained cells, while the strain gradient had no effect. The stiffness recovery in unstrained cells was completely inhibited by the MLCK inhibitor ML-7, but recovery in strained cells exhibiting increased MLCK was slightly inhibited. These data suggest that chronic strain leads to enhanced recovery from acute stretch, which may be attributable to the strain-induced increases in MLCK. This may also explain in part the more rapid renarrowing of activated airways following DI in asthma.
10
Hasaneen, Nadia A., Stanley Zucker, Richard Z. Lin, Gayle G. Vaday, Reynold A. Panettieri, and Hussein D. Foda. "Angiogenesis is induced by airway smooth muscle strain." American Journal of Physiology-Lung Cellular and Molecular Physiology 293, no. 4 (October 2007): L1059—L1068. http://dx.doi.org/10.1152/ajplung.00480.2006.
Full textAbstract:
Angiogenesis is an important feature of airway remodeling in both chronic asthma and chronic obstructive pulmonary disease (COPD). Airways in those conditions are exposed to excessive mechanical strain during periods of acute exacerbations. We recently reported that mechanical strain of human airway smooth muscle (HASM) led to an increase in their proliferation and migration. Sustained growth in airway smooth muscle in vivo requires an increase in the nutritional supply to these muscles, hence angiogenesis. In this study, we examined the hypothesis that cyclic mechanical strain of HASM produces factors promoting angiogenic events in the surrounding vascular endothelial cells. Our results show: 1) a significant increase in human lung microvascular endothelial cell (HMVEC-L) proliferation, migration, and tube formation following incubation in conditioned media (CM) from HASM cells exposed to mechanical strain; 2) mechanical strain of HASM cells induced VEGF expression and release; 3) VEGF neutralizing antibodies inhibited the proliferation, migration, and tube formations of HMVEC-L induced by the strained airway smooth muscle CM; 4) mechanical strain of HASM induced a significant increase in hypoxia-inducible factor-1α (HIF-1α) mRNA and protein, a transcription factor required for VEGF gene transcription; and 5) mechanical strain of HASM induced HIF-1α/VEGF through dual phosphatidylinositol 3-kinase (PI3K)/Akt/mammalian target of rapamycin (mTOR) and ERK pathways. In conclusion, exposing HASM cells to mechanical strain induces signal transduction pathway through PI3K/Akt/mTOR and ERK pathways that lead to an increase in HIF-1α, a transcription factor required for VEGF expression. VEGF release by mechanical strain of HASM may contribute to the angiogenesis seen with repeated exacerbation of asthma and COPD.
11
Wang, Da-an, Qing-zheng Li, and Dong-ming Jia. "Low-Frequency Electrical Stimulation Promotes Satellite Cell Activities to Facilitate Muscle Regeneration at an Early Phase in a Rat Model of Muscle Strain." BioMed Research International 2021 (February 6, 2021): 1–8. http://dx.doi.org/10.1155/2021/4218086.
Full textAbstract:
The capability of regeneration for skeletal muscle after injury depends on the differentiation and proliferation ability of the resident stem cells called satellite cells. It has been reported that electrical stimulation was widely used in clinical conditions to facilitate muscle regeneration after injury, but the characterization of satellite cell responses to the context of low-frequency electrical stimulation in early-phase muscle strain conditions has not been fully clarified. In this study, we aim to investigate the effects of low-frequency electrical stimulation (frequency: 20 Hz; duration: 30 minutes, twice daily) on satellite cell activities in a rat model for the early phase of muscle strain. Firstly, we adopted our previously developed rat model to mimic the early phase of muscle strain in human. After then, we examined the effects of low-frequency electrical stimulation on histopathological changes of the muscle fiber by hematoxylin and eosin (H&E) staining. Finally, we investigated the effects of low-frequency electrical stimulation on satellite cell proliferation and differentiation by quantification of the expression level of the specific proteins using western blot analyses. The muscle strain in biceps femoris muscles of rats can be induced by high-speed rotation from knee flexion 50° to full knee extension at 960°·s-1 angular velocity during its tetany by activating the sciatic nerve, as evidenced by a widening of the interstitial space between fibers, and more edema or necrosis fibers were detected in the model rats without treatment than in control rats. After treatment with low-frequency electrical stimulation (frequency: 20 Hz; duration: 30 minutes, twice daily), the acute strained biceps femoris muscles of rats showed obvious improvement of histomorphology as indicated by more mature muscle fibers with well-ordered formation with clear boundaries. Consistently, the expression levels of the MyoD and myogenin were marked higher than those in the rats in the animal model group, indicating increased satellite cell proliferating and differentiating activities by low-frequency electrical stimulation. This study shows that low-frequency electrical stimulation provides an effective stimulus to upregulate the protein expression of MyoD/myogenin and accelerate the restoration of structure during the early phase of muscle strain. This may have significance for clinical practice. Optimization of low-frequency electrical stimulation parameters may enhance the therapeutic outcome in patients.
12
Meiss, Richard A., and Ramana M. Pidaparti. "Mechanical state of airway smooth muscle at very short lengths." Journal of Applied Physiology 96, no. 2 (February 2004): 655–67. http://dx.doi.org/10.1152/japplphysiol.00388.2003.
Full textAbstract:
Although the shortening of smooth muscle at physiological lengths is dominated by an interaction between external forces (loads) and internal forces, at very short lengths, internal forces appear to dominate the mechanical behavior of the active tissue. We tested the hypothesis that, under conditions of extreme shortening and low external force, the mechanical behavior of isolated canine tracheal smooth muscle tissue can be understood as a structure in which the force borne and exerted by the cross bridge and myofilament array is opposed by radially disposed connective tissue in the presence of an incompressible fluid matrix (cellular and extracellular). Strips of electrically stimulated tracheal muscle were allowed to shorten maximally under very low afterload, and large longitudinal sinusoidal vibrations (34 Hz, 1 s in duration, and up to 50% of the muscle length before vibration) were applied to highly shortened (active) tissue strips to produce reversible cross-bridge detachment. During the vibration, peak muscle force fell exponentially with successive forced elongations. After the episode, the muscle either extended itself or exerted a force against the tension transducer, depending on external conditions. The magnitude of this effect was proportional to the prior muscle stiffness and the amplitude of the vibration, indicating a recoil of strained connective tissue elements no longer opposed by cross-bridge forces. This behavior suggests that mechanical behavior at short lengths is dominated by tissue forces within a tensegrity-like structure made up of connective tissue, other extracellular matrix components, and active contractile elements.
13
Hakim, Chady H., Robert W. Grange, and Dongsheng Duan. "The passive mechanical properties of the extensor digitorum longus muscle are compromised in 2- to 20-mo-old mdx mice." Journal of Applied Physiology 110, no. 6 (June 2011): 1656–63. http://dx.doi.org/10.1152/japplphysiol.01425.2010.
Full textAbstract:
Muscle rigidity and myotendinous junction (MTJ) deficiency contribute to immobilization in Duchenne muscular dystrophy (DMD), a lethal disease caused by the absence of dystrophin. However, little is known about the muscle passive properties and MTJ strength in a diseased muscle. Here, we hypothesize that dystrophin-deficient muscle pathology renders skeletal muscle stiffer and MTJ weaker. To test our hypothesis, we examined the passive properties of an intact noncontracting muscle-tendon unit in mdx mice, a mouse model for DMD. The extensor digitorum longus (EDL) muscle-tendon preparations of 2-, 6-, 14-, and 20-mo-old mdx and normal control mice were strained stepwisely from 110% to 160% of the muscle optimal length. The stress-strain response and failure position were analyzed. In support of our hypothesis, the mdx EDL preparation consistently developed higher stress before muscle failure. Postfailure stresses decreased dramatically in mdx but not normal preparations. Further, mdx showed a significantly faster stress relaxation rate. Consistent with stress-strain assay results, we observed significantly higher fibrosis in mdx muscle. In 2- and 6-mo-old mdx and 20-mo-old BL10 mice failure occurred within the muscle (2- to 14-mo-old BL10 preparations did not fail). Interestingly, in ≥14-mo-old mdx mice the failure site shifted toward the MTJ. Electron microscopy revealed substantial MTJ degeneration in aged but not young mdx mice. In summary, our results suggest that the passive properties of the EDL muscle and the strength of MTJ are compromised in mdx in an age-dependent manner. These findings offer new insights in studying DMD pathogenesis and developing novel therapies.
14
Smith, Paul G., Linhong Deng, Jeffrey J. Fredberg, and Geoffrey N. Maksym. "Mechanical strain increases cell stiffness through cytoskeletal filament reorganization." American Journal of Physiology-Lung Cellular and Molecular Physiology 285, no. 2 (August 2003): L456—L463. http://dx.doi.org/10.1152/ajplung.00329.2002.
Full textAbstract:
We tested the hypothesis that cytoskeletal reorganization induced by cyclic strain increases cytoskeletal stiffness (G′). G′ was measured by optical magnetic twisting cytometry in control cells and cells that had received mechanical strain for 10–12 days. G′ was measured before and after both contractile and relaxant agonists, and in the strained cells both parallel (Para) and perpendicular (Perp) to the aligned cytoskeleton. Before activation, G′ Para was 24 ± 5% (± SE) greater compared with Perp ( P < 0.05), and 35% ± 6 greater compared with control (Cont, P < 0.01). The difference between strained and control cells was enhanced by KCl, increasing G′ 171 ± 7% Para compared with 125 ± 6% Perp and 129 ± 8% Cont ( P < 10-5 both cases). The decrease in G′ from baseline due to relaxant agonists isoproterenol and dibutyryl cAMP was similar in all groups. Long-term oscillatory loading of airway smooth muscle (ASM) cells caused stiffness to increase and become anisotropic. These findings are consistent with the hypothesis that cytoskeletal reorganization can enhance ASM stiffness and contractility. They imply, furthermore, that oscillatory loading of ASM may contribute to airway narrowing and failure of airway dilation in asthma.
15
Newhard, Christopher S., Sam Walcott, and Douglas M. Swank. "The load dependence of muscle’s force-velocity curve is modulated by alternative myosin converter domains." American Journal of Physiology-Cell Physiology 316, no. 6 (June 1, 2019): C844—C861. http://dx.doi.org/10.1152/ajpcell.00494.2018.
Full textAbstract:
The hyperbolic shape of the muscle force-velocity relationship (FVR) is characteristic of all muscle fiber types. The degree of curvature of the hyperbola varies between muscle fiber types and is thought to be set by force-dependent properties of different myosin isoforms. However, the structural elements in myosin and the mechanism that determines force dependence are unresolved. We tested our hypothesis that the myosin converter domain plays a critical role in the force-velocity relationship (FVR) mechanism. Drosophila contains a single myosin heavy chain gene with five converters encoded by alternative exons. We measured FVR properties of Drosophila jump muscle fibers from five transgenic lines each expressing a single converter. Consistent with our hypothesis, we observed up to 2.4-fold alterations in FVR curvature. Maximum shortening velocity ( v0) and optimal velocity for maximum power generation were also altered, but isometric tension and maximum power generation were unaltered. Converter 11a, normally found in the indirect flight muscle (IFM), imparted the highest FVR curvature and v0, whereas converter 11d, found in larval body wall muscle, imparted the most linear FVR and slowest v0. Jump distance strongly correlated with increasing FVR curvature and v0, meaning flies expressing the converter from the IFM jumped farther than flies expressing the native jump muscle converter. Fitting our data with Huxley’s two-state model and a biophysically based four-state model suggest a testable hypothesis that the converter sets muscle type FVR curvature by influencing the detachment rate of negatively strained myosin via changes in the force dependence of product release.
16
Henderson, Keith, Jess Pantinople, Kyle McCabe, Hazel L. Richards, and Nick Milne. "Forelimb bone curvature in terrestrial and arboreal mammals." PeerJ 5 (April 26, 2017): e3229. http://dx.doi.org/10.7717/peerj.3229.
Full textAbstract:
It has recently been proposed that the caudal curvature (concave caudal side) observed in the radioulna of terrestrial quadrupeds is an adaptation to the habitual action of the triceps muscle which causes cranial bending strains (compression on cranial side). The caudal curvature is proposed to be adaptive because longitudinal loading induces caudal bending strains (increased compression on the caudal side), and these opposing bending strains counteract each other leaving the radioulna less strained. If this is true for terrestrial quadrupeds, where triceps is required for habitual elbow extension, then we might expect that in arboreal species, where brachialis is habitually required to maintain elbow flexion, the radioulna should instead be cranially curved. This study measures sagittal curvature of the ulna in a range of terrestrial and arboreal primates and marsupials, and finds that their ulnae are curved in opposite directions in these two locomotor categories. This study also examines sagittal curvature in the humerus in the same species, and finds differences that can be attributed to similar adaptations: the bone is curved to counter the habitual muscle action required by the animal’s lifestyle, the difference being mainly in the distal part of the humerus, where arboreal animals tend have a cranial concavity, thought to be in response the carpal and digital muscles that pull cranially on the distal humerus.
17
Hirano, Minoru, Shigejiro Kurita, and Hidetaka Matsuoka. "Vocal Function following Hemilaryngectomy." Annals of Otology, Rhinology & Laryngology 96, no. 5 (September 1987): 586–89. http://dx.doi.org/10.1177/000348948709600521.
Full textAbstract:
Vocal function following hemilaryngectomy was investigated in 54 cases in which a superiorly based sternohyoid muscle flap was used for glottic reconstruction. Four types of material were employed for covering the muscle flap: Hypopharyngeal mucosa, lip mucosa, thyroid perichondrium, and island cervical skin flap. The vocal function varied greatly from individual to individual; however, the following tendencies were observed in many cases: 1) the glottis did not close completely; 2) supraglottic structures (false fold, arytenoid region, and epiglottis) were hyperfunctional and vibrated instead of or together with the unaffected vocal fold; 3) vibrations of the laryngeal structures were irregular; 4) maximum phonation time was short; 5) mean airflow rate was high; 6) fundamental frequency and intensity ranges of phonation were limited; 7) the voice was rough, breathy, and/or strained; and 8) cases with poor vocal function were most frequent in the skin flap group and least frequent in the lip mucosa group.
18
Smith, Paul G., Chaity Roy, Steven Fisher, Qi-Quan Huang, and Frank Brozovich. "Selected Contribution: Mechanical strain increases force production and calcium sensitivity in cultured airway smooth muscle cells." Journal of Applied Physiology 89, no. 5 (November 1, 2000): 2092–98. http://dx.doi.org/10.1152/jappl.2000.89.5.2092.
Full textAbstract:
Cultured airway smooth muscle cells subjected to cyclic deformational strain have increased cell content of myosin light chain kinase (MLCK) and myosin and increased formation of actin filaments. To determine how these changes may increase cell contractility, we measured isometric force production with changes in cytosolic calcium in individual permeabilized cells. The pCa for 50% maximal force production was 6.6 ± 0.4 in the strain cells compared with 5.9 ± 0.3 in control cells, signifying increased calcium sensitivity in strain cells. Maximal force production was also greater in strain cells (8.6 ± 2.9 vs. 5.7 ± 3.1 μN). The increased maximal force production in strain cells persisted after irreversible thiophosphorylation of myosin light chain, signifying that increased force could not be explained by differences in myosin light chain phosphorylation. Cells strained for brief periods sufficient to increase cytoskeletal organization but insufficient to increase contractile protein content also produced more force, suggesting that strain-induced cytoskeletal reorganization also increases force production.
19
Colombini, Barbara, Marta Nocella, Giulia Benelli, Giovanni Cecchi, and M. Angela Bagni. "Effect of temperature on cross-bridge properties in intact frog muscle fibers." American Journal of Physiology-Cell Physiology 294, no. 4 (April 2008): C1113—C1117. http://dx.doi.org/10.1152/ajpcell.00063.2008.
Full textAbstract:
It is well known that the force developed by skeletal muscles increases with temperature. Despite the work done on this subject, the mechanism of force potentiation is still debated. Most of the published papers suggest that force enhancement is due to the increase of the individual cross-bridge force. However, reports on skinned fibers and single-molecule experiments suggest that cross-bridge force is temperature independent. The effects of temperature on cross-bridge properties in intact frog fibers were investigated in this study by applying fast stretches at various tension levels ( P) on the tetanus rise at 5°C and 14°C to induce cross-bridge detachment. Cross-bridge number was measured from the force (critical force, Pc) needed to detach the cross-bridge ensemble, and the average cross-bridge strain was calculated from the sarcomere elongation needed to reach Pc (critical length, Lc). Our results show that P c increased linearly with the force developed at both temperatures, but the P c /P ratio was considerably smaller at 14°C. This means that the average force per cross bridge is greater at high temperature. This mechanism accounts for all the tetanic force enhancement. The critical length L c was independent of the tension developed at both temperatures but was significantly lower at high temperature suggesting that cross bridges at 14°C are more strained. The increased cross-bridge strain accounts for the greater average force developed.
20
Dejonckere, PH, and C. Manfredi. "Long-term Follow-up of Patients with Spasmodic Dysphonia Repeatedly Treated with Botulinum Toxin Injections." International Journal of Phonosurgery & Laryngology 1, no. 2 (2011): 57–60. http://dx.doi.org/10.5005/jp-journals-10023-1014.
Full textAbstract:
ABSTRACT Adductor spasmodic dysphonia (SD) is a focal laryngeal dystonia mainly resulting in a strained voice quality with spastic voice breaks and frequency shifts, perturbing fluency and intelligibility. SD-patients report unusually high impairment of their quality of life. The standard treatment is botulinum toxin injection in the thyroarytenoid muscles, in order to interfere with the perturbed sensory feedback loop of kinetic muscle tension regulation. The globally favorable effects are temporary, but the botulinum injections can be repeated. There is a lack of information about long-term effects. This is the first study investigating effects over several years, and comparing self-evaluation of patients with objective multimodal acoustic analysis. Results show that 72% of the individual injections are successful. The effects of botulinum are not reduced after repeated injections. In contrary, the self-perceived improvement increases in average over time. When self-evaluations preinjection are considered, patients tend to evaluate their voice and their handicap as worsening over time. This contrasts with the results of multimodal acoustic analysis. Objective data reveal a relative stability over time for as well pre- as postinjection. This seems to indicate that there is no shift over time in the objective severity of deviance in voice quality.
21
Lacerda, Carla M. R., John Kisiday, Brennan Johnson, and E. Christopher Orton. "Local serotonin mediates cyclic strain-induced phenotype transformation, matrix degradation, and glycosaminoglycan synthesis in cultured sheep mitral valves." American Journal of Physiology-Heart and Circulatory Physiology 302, no. 10 (May 15, 2012): H1983—H1990. http://dx.doi.org/10.1152/ajpheart.00987.2011.
Full textAbstract:
This study addressed the following questions: 1) Does cyclic tensile strain induce protein expression patterns consistent with myxomatous degeneration in mitral valves? 2) Does cyclic strain induce local serotonin synthesis in mitral valves? 3) Are cyclic strain-induced myxomatous protein expression patterns in mitral valves dependent on local serotonin? Cultured sheep mitral valve leaflets were subjected to 0, 10, 20, and 30% cyclic strain for 24 and 72 h. Protein levels of activated myofibroblast phenotype markers, α-smooth muscle actin (α-SMA) and nonmuscle embryonic myosin (SMemb); matrix catabolic enzymes, matrix metalloprotease (MMP) 1 and 13, and cathepsin K; and sulfated glycosaminoglycan (GAG) content in mitral valves increased with increased cyclic strain. Serotonin was present in the serum-free media of cultured mitral valves and concentrations increased with cyclic strain. Expression of the serotonin synthetic enzyme tryptophan hydroxylase 1 (TPH1) increased in strained mitral valves. Pharmacologic inhibition of the serotonin 2B/2C receptor or TPH1 diminished expression of phenotype markers (α-SMA and SMemb) and matrix catabolic enzyme (MMP1, MMP13, and cathepsin K) expression in 10- and 30%-strained mitral valves. These results provide first evidence that mitral valves synthesize serotonin locally. The results further demonstrate that tensile loading modulates local serotonin synthesis, expression of effector proteins associated with mitral valve degeneration, and GAG synthesis. Inhibition of serotonin diminishes strain-mediated protein expression patterns. These findings implicate serotonin and tensile loading in mitral degeneration, functionally link the pathogeneses of serotoninergic (carcinoid, drug-induced) and degenerative mitral valve disease, and have therapeutic implications.
22
Opar, David A., Morgan D. Williams, Ryan G. Timmins, Nuala M. Dear, and Anthony J. Shield. "Rate of Torque and Electromyographic Development During Anticipated Eccentric Contraction Is Lower in Previously Strained Hamstrings." American Journal of Sports Medicine 41, no. 1 (October 29, 2012): 116–25. http://dx.doi.org/10.1177/0363546512462809.
Full textAbstract:
Background: The effect of prior strain injury on myoelectrical activity of the hamstrings during tasks requiring high rates of torque development has received little attention. Purpose: To determine if recreational athletes with a history of unilateral hamstring strain injury will exhibit lower levels of myoelectrical activity during eccentric contraction, rate of torque development (RTD), and impulse (IMP) at 30, 50, and 100 milliseconds after the onset of myoelectrical activity or torque development in the previously injured limb compared with the uninjured limb. Study Design: Case control study; Level of evidence, 3. Methods: Twenty-six recreational athletes were recruited. Of these, 13 athletes had a history of unilateral hamstring strain injury (all confined to biceps femoris long head), and 13 had no history of hamstring strain injury. Following familiarization, all athletes undertook isokinetic dynamometry testing and surface electromyography (integrated EMG; iEMG) assessment of the biceps femoris long head and medial hamstrings during eccentric contractions at −60 and −180 deg·s−1. Results: In the injured limb of the injured group, compared with the contralateral uninjured limb, RTD and IMP was lower during −60 deg·s−1 eccentric contractions at 50 milliseconds (RTD: injured limb, 312.27 ± 191.78 N·m·s−1 vs uninjured limb, 518.54 ± 172.81 N·m·s−1, P = .008; IMP: injured limb, 0.73 ± 0.30 N·m·s vs uninjured limb, 0.97 ± 0.23 N·m·s, P = .005) and 100 milliseconds (RTD: injured limb, 280.03 ± 131.42 N·m·s−1 vs uninjured limb, 460.54 ± 152.94 N·m·s−1, P = .001; IMP: injured limb, 2.15 ± 0.89 N·m·s vs uninjured limb, 3.07 ± 0.63 N·m·s, P < .001) after the onset of contraction. Biceps femoris long head muscle activation was lower at 100 milliseconds at both contraction speeds (–60 deg·s−1, normalized iEMG activity [×1000]: injured limb, 26.25 ± 10.11 vs uninjured limb, 33.57 ± 8.29, P = .009; –180 deg·s−1, normalized iEMG activity [×1000]: injured limb, 31.16 ± 10.01 vs uninjured limb, 39.64 ± 8.36, P = .009). Medial hamstring activation did not differ between limbs in the injured group. Comparisons in the uninjured group showed no significant between limbs difference for any variables. Conclusion: Previously injured hamstrings displayed lower RTD and IMP during slow maximal eccentric contraction compared with the contralateral uninjured limb. Lower myoelectrical activity was confined to the biceps femoris long head. Regardless of whether these deficits are the cause of or the result of injury, these findings could have important implications for hamstring strain injury and reinjury. Particularly, given the importance of high levels of muscle activity to bring about specific muscular adaptations, lower levels of myoelectrical activity may limit the adaptive response to rehabilitation interventions and suggest that greater attention be given to neural function of the knee flexors after hamstring strain injury.
23
Honkanen, Anne M., Heidi Leskinen, Vesa Toivonen, Nest McKain, R. John Wallace, and Kevin J. Shingfield. "Metabolism ofα-linolenic acid during incubations with strained bovine rumen contents: products and mechanisms." British Journal of Nutrition 115, no. 12 (April 18, 2016): 2093–105. http://dx.doi.org/10.1017/s0007114516001446.
Full textAbstract:
AbstractDescription ofα-linolenic acid (cis-9,cis-12,cis-15-18 : 3, ALA) metabolism in the rumen is incomplete. Ruminal digesta samples were incubated with ALA and buffer containing water or deuterium oxide to investigate the products and mechanisms of ALA biohydrogenation. Geometric Δ9,11,15-18 : 3 isomers were the main intermediates formed from ALA. An increase in then+1 isotopomers of Δ9,11,15-18 : 3 was due to2H labelling at C-13. Isomers of Δ9,11,13-18 : 3,cis-7,cis-12,cis-15-18 : 3 andcis-8,cis-12,cis-15-18 : 3 were also formed. No increase inn+1 isotopomers of Δ7,12,15-18 : 3 or Δ8,12,15-18 : 3 was detected. Enrichment inn+2 isotopomers of 18 : 2 products indicated that ALA metabolism continued via the reduction of 18 : 3 intermediates. Isomers of Δ9,11,15-18 : 3 were reduced to Δ11,15-18 : 2 labelled at C-9 and C-13. ALA resulted in the formation of Δ11,13-18 : 2 and Δ12,14-18 : 2 containing multiple2H labels. Enrichment of then+3 isotopomer of Δ12,15-18 : 2 was also detected. Metabolism of ALA during incubations with rumen contents occurs by one of three distinct pathways. Formation of Δ9,11,15-18 : 3 appears to be initiated by H abstraction on C-13. Octadecatrienoic intermediates containingcis-12 andcis-15 double bonds are formed without an apparent H exchange with water. Labelling of Δ9,11,13-18 : 3 was inconclusive, suggesting formation by an alternative mechanism. These findings explain the appearance of several bioactive fatty acids in muscle and milk that influence the nutritional value of ruminant-derived foods.
24
Cavagna, G. A., M. Mazzanti, N. C. Heglund, and G. Citterio. "Storage and release of mechanical energy by active muscle: a non-elastic mechanism?" Journal of Experimental Biology 115, no. 1 (March 1, 1985): 79–87. http://dx.doi.org/10.1242/jeb.115.1.79.
Full textAbstract:
In frog muscle fibres, tetanically stimulated at a sarcomere length of about 2 micron, stretched at a velocity of 1 lengths-1 and released against a force equal to the maximum isometric, P0, a phase of rapid isotonic shortening takes place after release. As the amplitude of the stretch is increased from 1.5 to 9% of the initial length: (1) the amount of rapid isotonic shortening increases up to 9–10 nm per half sarcomere and (2) the stiffness of the fibre (an indication of the number of bridges attached) decreases to a value about equal to that measured during an isometric contraction. If a 5–10 ms delay is left between the end of stretch and release, the amount of rapid isotonic shortening increases to about 12 nm hs-1. A 300–500 ms delay, however, results in a decrease in rapid isotonic shortening to about 5 nm hs-1 and also results in a velocity transients against P0 that are similar to those described during release from a state of isometric contraction. It is concluded that the force attained after large, fast stretches is due to a greater force developed by each bridge and not to a greater number of bridges. After the elastic recoil (when the force is suddenly reduced to P0), these strained bridges are able to shorten by about 12 nm hs-1, suggesting that, during and immediately after stretching, they are charged to levels of potential energy greater than those attained in an isometric contraction.
25
Gazzola, Morgan, Fatemeh Khadangi, Marine Clisson, Jonathan Beaudoin, Marie-Annick Clavel, and Ynuk Bossé. "Airway smooth muscle adapting in dynamic conditions is refractory to the bronchodilator effect of a deep inspiration." American Journal of Physiology-Lung Cellular and Molecular Physiology 318, no. 2 (February 1, 2020): L452—L458. http://dx.doi.org/10.1152/ajplung.00270.2019.
Full textAbstract:
Airway smooth muscle (ASM) is continuously strained during breathing at tidal volume. Whether this tidal strain influences the magnitude of the bronchodilator response to a deep inspiration (DI) is not clearly defined. The present in vitro study examines the effect of tidal strain on the bronchodilator effect of DIs. ASM strips from sheep tracheas were mounted in organ baths and then subjected to stretches (30% strain), simulating DIs at varying time intervals. In between simulated DIs, the strips were either held at a fixed length (isometric) or oscillated continuously by 6% (length oscillations) to simulate tidal strain. The contractile state of the strips was also controlled by adding either methacholine or isoproterenol to activate or relax ASM, respectively. Although the time-dependent gain in force caused by methacholine was attenuated by length oscillations, part of the acquired force in the oscillating condition was preserved postsimulated DIs, which was not the case in the isometric condition. Consequently, the bronchodilator effect of simulated DIs (i.e., the decline in force postsimulated versus presimulated DIs) was attenuated in oscillating versus isometric conditions. These findings suggest that an ASM operating in a dynamic environment acquired adaptations that make it refractory to the decline in contractility inflicted by a larger strain simulating a DI.
26
Friedman, Michael, Vytenis T. Grybauskas, Dean M. Toriumi, and Edward L. Applebaum. "Implantation of a Recurrent Laryngeal Nerve Stimulator for the Treatment of Spastic Dysphonia." Annals of Otology, Rhinology & Laryngology 98, no. 2 (February 1989): 130–34. http://dx.doi.org/10.1177/000348948909800209.
Full textAbstract:
Spastic dysphonia, a rare speech disorder, is characterized by strained phonation with excessively adducted vocal cords. Recurrent laryngeal nerve section, botulinum toxin injection into the vocalis-thyroarytenoid muscle complex, and other techniques have been used to treat this disorder. We have used percutaneous electrical stimulation of the recurrent laryngeal nerve with good results. Previous dog studies demonstrated the relative safety of an implantable recurrent laryngeal nerve stimulator. In this study, we directly stimulated the recurrent laryngeal nerve and vagus nerve in a dog without change in cardiorespiratory status. A Medtronic peripheral nerve stimulator was implanted in a patient with abductor spastic dysphonia. The cuff electrode was positioned around the recurrent laryngeal nerve and stimulation resulted in improvement in her voice. Extensive cardiopulmonary monitoring did not reveal any adverse response to stimulation and there was no discomfort to the patient. On the basis of the good results of this preliminary study, further study with long-term follow-up is under way.
27
Gordon, A. M., and E. B. Ridgway. "Stretch of active muscle during the declining phase of the calcium transient produces biphasic changes in calcium binding to the activating sites." Journal of General Physiology 96, no. 5 (November 1, 1990): 1013–35. http://dx.doi.org/10.1085/jgp.96.5.1013.
Full textAbstract:
In voltage-clamped barnacle single muscle fibers, muscle shortening during the declining phase of the calcium transient increases myoplasmic calcium. This extra calcium is probably released from the activating sites by a change in affinity when cross-bridges break (Gordon, A. M., and E. B. Ridgway, 1987. J. Gen. Physiol. 90:321-340). Stretching the muscle at similar times causes a more complex response, a rapid increase in intracellular calcium followed by a transient decrease. The amplitudes of both phases increase with the rate and amplitude of stretch. The rapid increase, however, appears only when the muscle is stretched more than approximately 0.4%. This is above the length change that produces the breakpoint in the force record during a ramp stretch. This positive phase in response to large stretches is similar to that seen on equivalent shortening at the same point in the contraction. For stretches at different times during the calcium transient, the peak amplitude of the positive phase has a time course that is delayed relative to the calcium transient, while the peak decrease during the negative phase has an earlier time course that is more similar to the calcium transient. The amplitudes of both phases increase with increasing strength of stimulation and consequent force. When the initial muscle the active force. A large decrease in length (which drops the active force to zero) decreases the extra calcium seen on a subsequent restretch. After such a shortening step, the extra calcium on stretch recovers (50 ms half time) toward the control level with the same time course as the redeveloped force. Conversely, stretching an active fiber decreases the extra calcium on a subsequent shortening step that is imposed shortly afterward. Enhanced calcium binding due to increased length alone cannot explain our data. We hypothesize that the calcium affinity of the activating sites increases with cross-bridge attachment and further with cross-bridge strain. This accounts for the biphasic response to stretch as follows: cross-bridges detached by stretch first decrease calcium affinity, then upon reattachment increase calcium affinity due to the strained configuration brought on by the stretch. The experiments suggest that cross-bridge attachment and strain can modify calcium binding to the activating sites in intact muscle.
28
Tsivitse, Susan K., Eleni Mylona, Jennifer M. Peterson, William T. Gunning, and Francis X. Pizza. "Mechanical loading and injury induce human myotubes to release neutrophil chemoattractants." American Journal of Physiology-Cell Physiology 288, no. 3 (March 2005): C721—C729. http://dx.doi.org/10.1152/ajpcell.00237.2004.
Full textAbstract:
The purpose of this study was to 1) test the hypothesis that skeletal muscle cells (myotubes) after mechanical loading and/or injury are a source of soluble factors that promote neutrophil chemotaxis and superoxide anion (O2−·) production and 2) determine whether mechanical loading and/or injury causes myotubes to release cytokines that are known to influence neutrophil responses [tumor necrosis factor-α (TNF-α), IL-8, and transforming growth factor-β1 (TGF-β1)]. Human myotubes were grown in culture and exposed to either a cyclic strain (0, 5, 10, 20, or 30% strain) or a scrape injury protocol. Protocols of 5, 10, and 20% strain did not cause injury, whereas 30% strain and scrape injury caused a modest and a high degree of injury, respectively. Conditioned media from strained myotubes promoted chemotaxis of human blood neutrophils and primed them for O2−· production in a manner that was dependent on a threshold of strain and independent from injury. Neutrophil chemotaxis, but not priming, progressively increased with higher magnitudes of strain. Conditioned media only from scrape-injured myotubes increased O2−· production from neutrophils. Concentrations of IL-8 and total TGF-β1 in conditioned media were reduced by mechanical loading, whereas TNF-α and active TGF-β1 concentrations were unaffected. In conclusion, skeletal muscle cells after mechanical loading and injury are an important source of soluble factors that differentially influence neutrophil chemotaxis and the stages of neutrophil-derived reactive oxygen species production. Neutrophil responses elicited by mechanical loading, however, did not parallel changes in the release of IL-8, TGF-β1, or TNF-α from skeletal muscle cells.
29
Pascoe, Chris D., Chun Y. Seow, Peter D. Paré, and Ynuk Bossé. "Decrease of airway smooth muscle contractility induced by simulated breathing maneuvers is not simply proportional to strain." Journal of Applied Physiology 114, no. 3 (February 1, 2013): 335–43. http://dx.doi.org/10.1152/japplphysiol.00870.2012.
Full textAbstract:
The lung is a dynamic organ and the oscillating stress applied to the airway wall during breathing maneuvers can decrease airway smooth muscle (ASM) contractility. However, it is unclear whether it is the stress or the attendant strain that is responsible for the decline of ASM force associated with breathing maneuvers, and whether tone can prevent the decline of force by attenuating the strain. To investigate these questions, ovine tracheal strips were subjected to oscillating stress that simulates breathing maneuvers, and the resulting strain and decline of force were measured in the absence or presence of different levels of tone elicited by acetylcholine. In relaxed ASM, high stress simulating 20 cm H2O-transpulmonary pressure excursions strained ASM strips by 20.7% and decreased force by 17.1%. When stress oscillations were initiated during measurement of ACh concentration-response curves, tone almost abrogated strain at an ACh concentration of 10−6 M (1.1%) but the decline of force was not affected (18.9%). When stress oscillations were initiated after ACh-induced contraction had reached its maximal force, strain was almost abrogated at an ACh concentration of 10−6 M (0.9%) and the decline of force was attenuated (10.1%). However, even at the highest ACh concentration (10−4 M), substantial decline of force (6.1%) was still observed despite very small strain (0.7%). As expected, the results indicate that tone attenuated the strain experienced by ASM during breathing maneuver simulations. More surprisingly, the reduction of strain induced by tone was not proportional to its effect on the decline of force induced by simulated breathing maneuvers.
30
Reda, Sherif M., and Murali Chandra. "Cardiomyopathy mutation (F88L) in troponin T abolishes length dependency of myofilament Ca2+ sensitivity." Journal of General Physiology 150, no. 6 (May 18, 2018): 809–19. http://dx.doi.org/10.1085/jgp.201711974.
Full textAbstract:
Recent clinical studies have revealed a new hypertrophic cardiomyopathy–associated mutation (F87L) in the central region of human cardiac troponin T (TnT). However, despite its implication in several incidences of sudden cardiac death in young and old adults, whether F87L is associated with cardiac contractile dysfunction is unknown. Because the central region of TnT is important for modulating the muscle length–mediated recruitment of new force-bearing cross-bridges (XBs), we hypothesize that the F87L mutation causes molecular changes that are linked to the length-dependent activation of cardiac myofilaments. Length-dependent activation is important because it contributes significantly to the Frank–Starling mechanism, which enables the heart to vary stroke volume as a function of changes in venous return. We measured steady-state and dynamic contractile parameters in detergent-skinned guinea pig cardiac muscle fibers reconstituted with recombinant guinea pig wild-type TnT (TnTWT) or the guinea pig analogue (TnTF88L) of the human mutation at two different sarcomere lengths (SLs): short (1.9 µm) and long (2.3 µm). TnTF88L increases pCa50 (−log [Ca2+]free required for half-maximal activation) to a greater extent at short SL than at long SL; for example, pCa50 increases by 0.25 pCa units at short SL and 0.17 pCa units at long SL. The greater increase in pCa50 at short SL leads to the abolishment of the SL-dependent increase in myofilament Ca2+ sensitivity (ΔpCa50) in TnTF88L fibers, ΔpCa50 being 0.10 units in TnTWT fibers but only 0.02 units in TnTF88L fibers. Furthermore, at short SL, TnTF88L attenuates the negative impact of strained XBs on force-bearing XBs and augments the magnitude of muscle length–mediated recruitment of new force-bearing XBs. Our findings suggest that the TnTF88L-mediated effects on cardiac thin filaments may lead to a negative impact on the Frank–Starling mechanism.
31
Prodanovic, Momcilo, Thomas C. Irving, and Srboljub M. Mijailovich. "X-ray diffraction from nonuniformly stretched helical molecules." Journal of Applied Crystallography 49, no. 3 (April 18, 2016): 784–97. http://dx.doi.org/10.1107/s1600576716003757.
Full textAbstract:
The fibrous proteins in living cells are exposed to mechanical forces interacting with other subcellular structures. X-ray fiber diffraction is often used to assess deformation and movement of these proteins, but the analysis has been limited to the theory for fibrous molecular systems that exhibit helical symmetry. However, this approach cannot adequately interpret X-ray data from fibrous protein assemblies where the local strain varies along the fiber length owing to interactions of its molecular constituents with their binding partners. To resolve this problem a theoretical formulism has been developed for predicting the diffraction from individual helical molecular structures nonuniformly strained along their lengths. This represents a critical first step towards modeling complex dynamical systems consisting of multiple helical structures using spatially explicit, multi-scale Monte Carlo simulations where predictions are compared with experimental data in a `forward' process to iteratively generate ever more realistic models. Here the effects of nonuniform strains and the helix length on the resulting magnitude and phase of diffraction patterns are quantitatively assessed. Examples of the predicted diffraction patterns of nonuniformly deformed double-stranded DNA and actin filaments in contracting muscle are presented to demonstrate the feasibly of this theoretical approach.
32
Kim, Hyoung Bok, Jae Chul Yoo, and Jeung Yeol Jeong. "Evaluation of Muscular Atrophy and Fatty Infiltration Using Time-zero Magnetic Resonance Imaging as Baseline Data, After Rotator Cuff Repair." Clinics in Shoulder and Elbow 22, no. 2 (June 1, 2019): 70–78. http://dx.doi.org/10.5397/cise.2019.22.2.70.
Full textAbstract:
Background: This study evaluated postoperative changes in the supraspinatus from time-zero to 6 months, using magnetic resonance imaging (MRI). We hypothesized that restoration of the musculotendinous unit of the rotator cuff by tendon repair immediately improves the rotator cuff muscle status, and maintains it months after surgery.Methods: Totally, 76 patients (29 men, 47 women) with rotator cuff tears involving the supraspinatus tendon who underwent arthroscopic rotator cuff repairs were examined. MRI evaluation showed complete repair with intact integrity of the torn tendon at both time-zero and at 6 months follow-up. All patients underwent standardized MRI at our institution preoperatively, at 1 or 2 days postoperative, and at 6 months after surgery. Supraspinatus muscular (SSP) atrophy (Thomazeau grade) and fatty infiltrations (Goutallier stage) were evaluated by MRI. The cross-sectional area of SSP in the fossa was also measured.Results: As determined by MRI, the cross-sectional area of SSP significantly decreased 11.41% from time-zero (immediate repair) to 6 months post-surgery, whereas the Goutallier stage and Thomazeau grade showed no significant changes (<i>p</i><0.01). Furthermore, compared to the preoperative MRI, the postoperative MRI at 6 months showed a no statistically significant increase of 8.03% in the crosssectional area. In addition, morphological improvements were observed in patients with high grade Goutallier and Thomazeau at timezero, whereas morphology of patients with low grade factors were almost similar to before surgery.Conclusions: Our results indicate that cross-sectional area of the initial repair appears to decrease after a few months postoperatively, possibly due to medial retraction or strained muscle.
33
Goering, Edward K., and Lisa Qiu. "Counterstrain as a Diagnostic and Treatment Tool for Rectus Femoris Origin Injuries: A Case Report." AAO Journal 29, no. 2 (June 1, 2019): 19–23. http://dx.doi.org/10.53702/2375-5717-29.2.19.
Full textAbstract:
Abstract Counterstrain (CS) is an osteopathic manipulative technique that utilizes indirect and passive positions of strained tissues to address musculoskeletal dysfunctions. As such, CS has potential as a treatment option for muscle strain injuries, such as rectus femoris origin (RFO) injuries. This case highlights an instance where the CS technique was used as an effective and inexpensive diagnostic tool to confirm the involvement of the reflected head of the rectus femoris muscle (RHRF) in an RFO injury. The presentation of symptoms in this case, like many other hip pain cases, was nonspecific, making it difficult to diagnose without the use of advanced imaging techniques, which are often time consuming and costly for patients. The use of CS was able to support a diagnosis of a reflected head of the RFO injury. After an osteopathic structural examination, it was noted that the patient had multiple bilateral tender points of the anterior thoracic region and hip: anterior thoracic-10 (AT10), proximal psoas (PP, formerly abdominal lumbar 2), iliacus, and reflected head of the rectus femoris (RHRF).1 In his 1981 text, Jones referred to an anterior medial trochanter tender point that is similar to the RHRF point; however, the location was described to be more lateral, rather than inferior, to the anterior inferior iliac spine than the RHRF point.2 Once all tender points were identified, treatment using the CS technique was administered weekly over the period of a month, and the patient noted markedly reduced tenderness of the tender points treated and was able to reincorporate soccer and other athletic activities back into his life.
34
Stavig, Ward. "Continuing the Bleeding of These Pueblos Will Shortly Make Them Cadavers: The Potosi Mita, Cultural Identity, and Communal Survival in Colonial Peru." Americas 56, no. 4 (April 2000): 529–62. http://dx.doi.org/10.1017/s0003161500029837.
Full textAbstract:
The exploitation of Andean villagers under the forced labor regime for the mines of Potosi is almost as infamous as the silver they extracted from the cerro rico is famous. Established by Viceroy Toledo in the 1570s, the mita, as the system of forced labor was known, remained in place until the smoke and shot of Latin American independence struggles were in the air. For over two centuries, Spain forced thousands upon thousands of naturales (a common colonial term for indigenous people) from communities throughout the southern Andean highlands to lend their muscle and sweat, and all too often their blood and their lives, to keep Potosi's veins open and flowing. Through this work the mitayos and their communities not only drove the colonial economy, but also were a major force in sustaining the Spanish empire and in helping forge the modern world's dominant economic system. Conversely, mita exploitation threatened the very survival of the communities subject to it. The mita was so onerous that virtually all indigenous peoples subject to the labor draft, regardless of ethnicity or class, raised an almost continuous voice of protest from their communities against the mita and its abuses. Tensions created by the mita also severely strained the bonds that linked community, curaca, and the state, which were primary ingredients in the social glue that kept colonial Andean society from coming apart. To avoid descending into the mines, and to escape such horrors as laboring over mercury vapors, many people permanently fled their communities, giving up the status of originarios (community members with rights such as access to land and subject to state obligations) to become forasteros (indigenous person not living in community of origin, or descendant of the same, without communal rights but exempt from many state obligations). In this way the mita, one of the few forces that had potential for uniting Andean peoples in opposition to the state also fractured them. Communal solidarity was severely strained and neither the shared experience of the mita nor the commonality of experience in Potosi created sufficient cohesion to overcome the ethnic and regional differences that divided them.
35
Girton, T. S., V. H. Barocas, and R. T. Tranquillo. "Confined Compression of a Tissue-Equivalent: Collagen Fibril and Cell Alignment in Response to Anisotropic Strain." Journal of Biomechanical Engineering 124, no. 5 (September 30, 2002): 568–75. http://dx.doi.org/10.1115/1.1504099.
Full textAbstract:
A method to impose and measure a one dimensional strain field via confined compression of a tissue-equivalent and measure the resulting cell and collagen fibril alignment was developed. Strain was determined locally by the displacement of polystyrene beads dispersed and entrapped within the network of collagen fibrils along with the cells, and it was correlated to the spatial variation of collagen network birefringence and concentration. Alignment of fibroblasts and smooth muscle cells was determined based on the long axis of elongated cells. Cell and collagen network alignment were observed normal to the direction of compression after a step strain and increased monotonically up to 50% strain. These results were independent of time after straining over 24 hr despite continued cell motility after responding instantly to the step strain with a change in alignment by deforming/convecting with the strained network. Since the time course of cell alignment followed that of strain and not stress which, due to the viscoelastic fluid-like nature of the network relaxes completely within the observation period, these results imply cell alignment in a compacting tissue-equivalent is due to fibril alignment associated with anisotropic network strain. Estimation of a contact guidance sensitivity parameter indicates that both cell types align to a greater extent than the surrounding fibrils.
36
Taniguchi, Tsuyoshi, Sota Yamamoto, Atsushi Hayakawa, Eiichi Tanaka, Hideyuki Kimpara, and Kazuo Miki. "OS07W0228 Strain-rate and muscle-tonus dependence of mechanical properties of rabbit tibialis anterior muscle." Abstracts of ATEM : International Conference on Advanced Technology in Experimental Mechanics : Asian Conference on Experimental Mechanics 2003.2 (2003): _OS07W0228. http://dx.doi.org/10.1299/jsmeatem.2003.2._os07w0228.
Full text
37
Kisku, Deepak Kumar, Sudhir Kumar Panigrahi, Amaresh Mishra, Abinash Kanungo, and Niranjan Moharana. "Conservative management of an iliopsoas hematoma causing walking difficulty in an elderly patient on anticoagulation therapy: a case report." International Surgery Journal 7, no. 1 (December 26, 2019): 313. http://dx.doi.org/10.18203/2349-2902.isj20195994.
Full textAbstract:
Spontaneous iliopsoas hematoma is a rare complication in patients suffering from bleeding disorders like hemophilia, Von Willebrand’s disease or those taking blood thinners like aspirin and clopidogrel or anticoagulant medications like warfarin for atrial fibrillation or post-thrombotic status. It can present as severe pain, muscle dysfunction, difficult walking or neurological dysfunction due to compression on femoral nerve or lumbar plexus. A high index of suspicion with early blood and radiological investigations like contrast enhanced computed tomography (CECT) or magnetic resonance imaging (MRI) of the part is immensely helpful in diagnosis and prompt management of such patients. A low hemoglobin or hematocrit level and a high INR is supportive while CECT or MRI of the abdomen and pelvis is confirmatory. Management in a hemodynamically and neurologically stable patient include immediate withdrawl of the anticoagulant, bed rest, infusion of I.V. fluids, vitamin K, fresh frozen plasma and packed red cell transfusion, which ensures complete recovery in most of the cases. However angio-embolization to control ongoing arterial bleeding is lifesaving when feasible or emergent open decompression and bleeding control surgery can save the life or prevent permanent neurological damage to the limb. Decompression of the hematoma by ultrasound or computed tomography guided catheter drainage is helpful alternative in few selected cases. We report an elderly patient on warfarin, who suddenly developed difficulty in walking within hours of a strained defecation, diagnosed to suffer from left iliopsoas hematoma and responded to conservative management with complete resolution of symptoms by 3 weeks.
38
Gollapudi, Sampath K., Jil C. Tardiff, and Murali Chandra. "The functional effect of dilated cardiomyopathy mutation (R144W) in mouse cardiac troponin T is differently affected by α- and β-myosin heavy chain isoforms." American Journal of Physiology-Heart and Circulatory Physiology 308, no. 8 (April 15, 2015): H884—H893. http://dx.doi.org/10.1152/ajpheart.00528.2014.
Full textAbstract:
Given the differential impact of α- and β-myosin heavy chain (MHC) isoforms on how troponin T (TnT) modulates contractile dynamics, we hypothesized that the effects of dilated cardiomyopathy (DCM) mutations in TnT would be altered differently by α- and β-MHC. We characterized dynamic contractile features of normal (α-MHC) and transgenic (β-MHC) mouse cardiac muscle fibers reconstituted with a mouse TnT analog (TnTR144W) of the human DCM R141W mutation. TnTR144W did not alter maximal tension but attenuated myofilament Ca2+ sensitivity ( pCa50) to a similar extent in α- and β-MHC fibers. TnTR144W attenuated the speed of cross-bridge (XB) distortion dynamics ( c) by 24% and the speed of XB recruitment dynamics ( b) by 17% in α-MHC fibers; however, both b and c remained unaltered in β-MHC fibers. Likewise, TnTR144W attenuated the rates of XB detachment ( g) and tension redevelopment ( ktr) only in α-MHC fibers. TnTR144W also decreased the impact of strained XBs on the recruitment of new XBs (γ) by 30% only in α-MHC fibers. Because c, b, g, ktr, and γ are strongly influenced by thin filament-based cooperative mechanisms, we conclude that the TnTR144W- and β-MHC-mediated changes in the thin filament interact to produce a less severe functional phenotype, compared with that brought about by TnTR144W and α-MHC. These observations provide a basis for lower mortality rates of humans (β-MHC) harboring the TnTR141W mutant compared with transgenic mouse studies. Our findings strongly suggest that some caution is necessary when extrapolating data from transgenic mouse studies to human hearts.
39
Chandra, Vikram, Sampath K. Gollapudi, and Murali Chandra. "Rat cardiac troponin T mutation (F72L)-mediated impact on thin filament cooperativity is divergently modulated by α- and β-myosin heavy chain isoforms." American Journal of Physiology-Heart and Circulatory Physiology 309, no. 8 (October 2015): H1260—H1270. http://dx.doi.org/10.1152/ajpheart.00519.2015.
Full textAbstract:
The primary causal link between disparate effects of human hypertrophic cardiomyopathy (HCM)-related mutations in troponin T (TnT) and α- and β-myosin heavy chain (MHC) isoforms on cardiac contractile phenotype remains poorly understood. Given the divergent impact of α- and β-MHC on the NH2-terminal extension (44–73 residues) of TnT, we tested if the effects of the HCM-linked mutation (TnTF70L) were differentially altered by α- and β-MHC. We hypothesized that the emergence of divergent thin filament cooperativity would lead to contrasting effects of TnTF70L on contractile function in the presence of α- and β-MHC. The rat TnT analog of the human F70L mutation (TnTF72L) or the wild-type rat TnT (TnTWT) was reconstituted into demembranated muscle fibers from normal (α-MHC) and propylthiouracil-treated (β-MHC) rat hearts to measure steady-state and dynamic contractile function. TnTF72L-mediated effects on tension, myofilament Ca2+ sensitivity, myofilament cooperativity, rate constants of cross-bridge (XB) recruitment dynamics, and force redevelopment were divergently modulated by α- and β-MHC. TnTF72L increased the rate of XB distortion dynamics by 49% in α-MHC fibers but had no effect in β-MHC fibers; these observations suggest that TnTF72L augmented XB detachment kinetics in α-MHC, but not β-MHC, fibers. TnTF72L increased the negative impact of strained XBs on the force-bearing XBs by 39% in α-MHC fibers but had no effect in β-MHC fibers. Therefore, TnTF72L leads to contractile changes that are linked to dilated cardiomyopathy in the presence of α-MHC. On the other hand, TnTF72L leads to contractile changes that are linked to HCM in the presence of β-MHC.
40
Sichting, Freddy. "Pelvic Belt Effects on Sacroiliac Joint Ligaments: A Computational Approach to Understand Therapeutic Effects of Pelvic Belts." Pain Physician 17;1, no. 1;17 (January 14, 2014): 43–51. http://dx.doi.org/10.36076/ppj.2014/17/43.
Full textAbstract:
Background: The sacroiliac joint is a widely described source of low back pain. Therapeutic approaches to relieve pain include the application of pelvic belts. However, the effects of pelvic belts on sacroiliac joint ligaments as potential pain generators are mostly unknown. Objectives: The aim of our study was to analyze the influence of pelvic belts on ligament load by means of a computer model. Study Design: Experimental computer study using a finite element method. Methods: A computer model of the human pelvis was created, comprising bones, ligaments, and cartilage. Detailed geometries, material properties of ligaments, and in-vivo pressure distribution patterns of a pelvic belt were implemented. The effects of pelvic belts on ligament strain were computed in the double-leg stance. Results: Pelvic belts increase sacroiliac joint motion around the sagittal axis but decrease motion around the transverse axis. With pelvic belt application, most of the strained sacroiliac joint ligaments were relieved, especially the sacrospinous, sacrotuberous, and the interosseous sacroiliac ligaments. Sacroiliac joint motion and ligament strains were minute. These results agree with validation data from other studies. Limitations: Assigning homogenous and linear material properties and excluding muscle forces are clear simplifications of the complex reality. Conclusions: Pelvic belts alter sacroiliac joint motion and provide partial relief of ligament strain that is subjectively marked, although minimal in absolute terms. These findings confirm theories that besides being mechanical stabilizers, the sacroiliac joint ligaments are likely involved in neuromuscular feedback mechanisms. The results from our computer model help with unraveling the therapeutic mechanisms of pelvic belts. Key words: Finite element computer study, low back pain, neuromuscular feedback, pelvic biomechanics, pelvic belt intervention, sacroiliac joint ligaments, sacroiliac joint motion
41
Howard, A. B., R. W. Alexander, R. M. Nerem, K. K. Griendling, and W. R. Taylor. "Cyclic strain induces an oxidative stress in endothelial cells." American Journal of Physiology-Cell Physiology 272, no. 2 (February 1, 1997): C421—C427. http://dx.doi.org/10.1152/ajpcell.1997.272.2.c421.
Full textAbstract:
Hypertension imposes an oxidant stress on the aorta and also causes mechanical deformation of the aortic wall. To assess whether deformation causes an oxidative stress, isolated porcine aortic endothelial cells (PAEC) were subjected to cyclic strain, and the cumulative amount of thiobarbituric acid reactive substances (TBARS, an index of lipid peroxidation) and H2O2 (a reactive oxygen species) was measured in the eluent at 2, 6, and 24 h. TBARS were increased by 40.5 +/- 9.2% after 24 h in cells exposed to cyclic strain vs. static controls (P < 0.05). No difference was seen at 2 and 6 h. H2O2 release was increased after 6 and 24 h of cyclic strain by 22.0 +/- 8.0 and 57.6 +/- 11.1 nmol H2O2/mg, respectively (P < 0.005), but was not increased after 2 h of strain. In vascular smooth muscle cells, TBARS were not observed and H2O2 release was not increased by cyclic strain. To investigate a potential source of H2O2 induced by strain, the activity of NADH/NADPH oxidase, a superoxide-generating enzyme, was measured by chemiluminescence. After 2 h, cells exposed to cyclic strain had greater activity than static controls (531.0 +/- 68.4 vs. 448.3 +/- 54.2 pmol O2- x mg(-1) x s(-1), respectively, when incubated with NADH, P < 0.005; 85.8 +/- 8.9 vs. 71.6 +/- 3.8 pmol O2- x mg(-1) x s(-1) when incubated with NADPH, P < 0.05). No effect on NADH/NADPH oxidase activity was seen after 6 or 24 h. The following conclusions were made: 1) cyclic strain induces an oxidant stress in PAEC monolayers as measured by TBARS formation and H2O2 release, 2) NADH/NADPH oxidase is a potential source of H2O2 release in cyclically strained cells, and 3) mechanical deformation of endothelial cells may play a critical role in the generation of oxidative stress within the vessel wall.
42
Voronkov, L. G., К. V. Voitsekhovska, S. V. Fedkiv, V. I. Koval, and P. M. Babich. "Clinical prognosis for 12 months and its predictors in patients with chronic heart failure and a reduced left ventricular ejection fraction." Ukrainian Journal of Cardiology 26, no. 6 (February 2, 2020): 53–64. http://dx.doi.org/10.31928/1608-635x-2019.6.5364.
Full textAbstract:
The aim – to establish and determine the limiting values of clinical and instrumental parameters associated with the development of adverse cardiovascular events (death or hospitalization) in patients with chronic heart failure (CHF) and left ventricular ejection fraction (LVEF) ≤ 35 % at 12-month follow-up.Materials and methods. 120 hemodynamically stable patients, 18–75 years of age, with CHF, II–IV NYHA functional class, LVEF ≤ 35 % were examined. Patients were included in the study in the phase of clinical compensation. The endpoint was combined and defined as the time until the first hospitalization in connection with decompensation of CHF or death. The observation period was 12 months, the mean time before the onset of the combined critical point (CCP) was 8.67 months. The search for the limit values of the predictors was carried out using cluster analysis with two variables. Results and discussion. According to the results of the cluster analysis, the informative predictors of achieving a combined endpoint in patients with CHF within 12 months are the number of kilograms lost over the previous 6 months > 4.5 kg or body weight loss > 6.03 %, shoulder circumference of an unstrained arm ≤ 32.5 cm, strained arm ≤ 35 cm, hips ≤ 50 cm, cutaneous fat fold thickness above triceps ≤ 24 mm and in the inguinal region ≤ 8.5 mm, percentage of cutaneous fat mass ≤ 16.7 %, limb muscle mass index ≤ 8.96 kg/m2, BMI ≤ 31.2 kg/m2, C-reactive protein > 4.52 mg/ml, blood cholesterol ≤ 4.5 mmol/l, flow-dependent vasodilation result ≤ 9.09 %, TAPSE ≤ 11mm and the relation of TAPSE to pulmonary artery systolic pressure (PASP) ≤ 0.27, the total score for the Minnesota questionnaire > 61 points, according to the DEFS scale > 22 points, according to Duke University questionnaire ≤ 8.575 points, test with 6-minute walk ≤ 255m and test with extension of the lower limb ≤ 22. Conclusions. The results of measuring anthropometric indicators reflecting the nutritional status of patients with CHF have an advantage over the results of densitometric determination of tissue components of the body in stratification of their long-term clinical risk.
43
SLAMET, Samuel Susanto, Naoki TAKANO, and Tomohisa NAGASAO. "209105 Biomechanics Analysis of Pressure Ulcers Focusing on the Interface Strain between Bone and Muscle in the Buttock Model." Proceedings of Conference of Kanto Branch 2011.17 (2011): 291–92. http://dx.doi.org/10.1299/jsmekanto.2011.17.291.
Full text
44
Kawashima, Osamu, Tamio Kamei, Yuji Shimizu, Takao Shizuka, and Morito Nakayama. "Malignant mesenchymoma of the larynx." Journal of Laryngology & Otology 104, no. 5 (May 1990): 440–44. http://dx.doi.org/10.1017/s0022215100158694.
Full textAbstract:
AbstractA Case report of a laryngeal malignant mesenchymoma, a very rare head and neck and even rarer laryngeal leison, is reported.In this case, an 85-years-old man, who had undergone several panendoscopies and biopsies that were non-diagnostic, subsequently succumbed to pulmonary metastases and died from respiratory failure. At autospy, tumour cells were demonstrated to constiute both bone and straited muscle cell types. As the tumour cells differentiated into two types of specialized cells from one type of embryonal tissue, the diagnosis of maligant mesenchymoma was established.
45
Ryan, Keith P. "Instructions for Safe Use of Microscopes." Microscopy Today 6, no. 2 (March 1998): 10–11. http://dx.doi.org/10.1017/s1551929500059551.
Full textAbstract:
Looking through a microscope for extended periods is not what we were designed for - it requires holding our bodies in an unnaturally rigid position. This can cause cramped muscles and strained tendons and ligaments in the head, neck, back, shoulders, arms and wrists, Also, repetitive movements associated with microscope work can cause strain injuries. There are specific health and safety regulations for computer use. Yet, you are tied much more to a microscope than to a computer, because of the eye-piece requirements.Main problem - microscopists know how to align their microscope but few align themselves! Many users are “slumpers”, and need training to avoid problems later.
46
McCabe, Kyle, Keith Henderson, Jess Pantinople, Hazel L. Richards, and Nick Milne. "Curvature reduces bending strains in the quokka femur." PeerJ 5 (March 22, 2017): e3100. http://dx.doi.org/10.7717/peerj.3100.
Full textAbstract:
This study explores how curvature in the quokka femur may help to reduce bending strain during locomotion. The quokka is a small wallaby, but the curvature of the femur and the muscles active during stance phase are similar to most quadrupedal mammals. Our hypothesis is that the action of hip extensor and ankle plantarflexor muscles during stance phase place cranial bending strains that act to reduce the caudal curvature of the femur. Knee extensors and biarticular muscles that span the femur longitudinally create caudal bending strains in the caudally curved (concave caudal side) bone. These opposing strains can balance each other and result in less strain on the bone. We test this idea by comparing the performance of a normally curved finite element model of the quokka femur to a digitally straightened version of the same bone. The normally curved model is indeed less strained than the straightened version. To further examine the relationship between curvature and the strains in the femoral models, we also tested an extra-curved and a reverse-curved version with the same loads. There appears to be a linear relationship between the curvature and the strains experienced by the models. These results demonstrate that longitudinal curvature in bones may be a manipulable mechanism whereby bone can induce a strain gradient to oppose strains induced by habitual loading.
47
Karemaker, J., F. A. Mooi, E. L. de Beer, and P. Schiereck. "High-speed transient-recording microprocessor system for the analysis of asymmetrical diffraction spectra from straited muscle." Journal of Biochemical and Biophysical Methods 12, no. 1-2 (January 1986): 89–99. http://dx.doi.org/10.1016/0165-022x(86)90054-0.
Full text
48
Ananthakumar, Anandita, Yiling Liu, Cristina E. Fernandez, George A. Truskey, and Deepak Voora. "Modeling statin myopathy in a human skeletal muscle microphysiological system." PLOS ONE 15, no. 11 (November 25, 2020): e0242422. http://dx.doi.org/10.1371/journal.pone.0242422.
Full textAbstract:
Statins are used to lower cholesterol and prevent cardiovascular disease. Musculoskeletal side effects known as statin associated musculoskeletal symptoms (SAMS), are reported in up to 10% of statin users, necessitating statin therapy interruption and increasing cardiovascular disease risk. We tested the hypothesis that, when exposed to statins ex vivo, engineered human skeletal myobundles derived from individuals with (n = 10) or without (n = 14) SAMS and elevated creatine-kinase levels exhibit statin-dependent muscle defects. Myoblasts were derived from muscle biopsies of individuals (median age range of 62–64) with hyperlipidemia with (n = 10) or without (n = 14) SAMS. Myobundles formed from myoblasts were cultured with growth media for 4 days, low amino acid differentiation media for 4 days, then dosed with 0 and 5μM of statins for 5 days. Tetanus forces were subsequently measured. To model the change of tetanus forces among clinical covariates, a mixed effect model with fixed effects being donor type, statin concentration, statin type and their two way interactions (donor type*statin concentration and donor type* statin type) and the random effect being subject ID was applied. The results indicate that statin exposure significantly contributed to decrease in force (P<0.001) and the variability in data (R2C [R square conditional] = 0.62). We found no significant differences in force between myobundles from patients with/without SAMS, many of whom had chronic diseases. Immunofluorescence quantification revealed a positive correlation between the number of straited muscle fibers and tetanus force (R2 = 0.81,P = 0.015) and negative correlation between number of fragmented muscle fibers and tetanus force (R2 = 0.482,P = 0.051) with no differences between donors with or without SAMS. There is also a correlation between statin exposure and presence of striated fibers (R2 = 0.833, P = 0.047). In patient-derived myobundles, statin exposure results in myotoxicity disrupting SAA organization and reducing force. We were unable to identify differences in ex vivo statin myotoxicity in this system. The results suggest that it is unlikely that there is inherent susceptibility to or persistent effects of statin myopathy using patient-derived myobundles.
49
Hruban, V., V. Horak, K. Fortyn, J. Hradecky, J. Klaudy, D. M Smith, H. Reisnerova, and I. Majzlik. "Inheritance of malignant melanoma in the melim strain of miniature pigs." Veterinární Medicína 49, No. 12 (March 29, 2012): 453–59. http://dx.doi.org/10.17221/5739-vetmed.
Full textAbstract:
Selective breeding of miniature pigs bearing cutaneous tumours resulted in the establishment of the MeLiM strain with hereditary malignant melanoma. The inheritance of melanoma was tested in a two-generation kindred comprising 456 progeny from 78 litters. Melanomas were recognisable visually as black-pigmented lesions on the skin. Their size, shape, number, progression and metastatic spreading varied widely. All possible melanoma forms known in human melanoma, i.e. pigmented naevi, dysplastic naevi, superficial spreading melanoma and nodular malignant melanoma, were found in the MeLiM pigs. Because the occurrence of nodular malignant melanoma segregated in all recorded litters we have included only this form in the genetic analysis. The tumours were nodular with exophytic growth over the skin surface. All showed similar histopathological features, vertical growth to muscle fascia and high metastatic activity. We hypothesize, on the basis of segregation ratios obtained from various mating types, that the mode of inheritance of nodular melanoma in the MeLiM strain is probably controlled by three genes.
50
Kern, Mark, Patrick Sanvanson, Ling Mei, Francis O. Edeani, Dilpesh Agrawal, Krupa Patel, Elliot S. Yu, and Reza Shaker. "Su191 EFFECTS OF SWALLOWING AGAINST LARYNGEAL RESISTANCE (SALR) ON BOLUS DYNAMICS OF THE ESOPHAGEAL STRAITED MUSCLE AND PHARYNGOESOPHAGEAL JUNCTION." Gastroenterology 160, no. 6 (May 2021): S—642. http://dx.doi.org/10.1016/s0016-5085(21)02246-0.
Full text