120 research outputs found
Specific isomyosin proportions in hyperexcitable and physiologically denervated mouse muscle
No full textAgbulut O, Noirez P, Butler-Browne G, Jockusch H. Specific isomyosin proportions in hyperexcitable and physiologically denervated mouse muscle. FEBS LETTERS. 2004;561(1-3):191-194.We show here, by high resolution sodium dodecyl sulfate gel electrophoresis, that the proportions of myosin heavy chain (MyHC) isoforms of mouse muscles are specifically shifted by hereditary neuromuscular diseases. In wild-type and dystrophic MDX anterior tibial muscle (TA) about 60% of the MyHC is IIB, 30% IIX, at most 10% IIA and < 2% type I (slow). In myotonic fast muscles, hyperexcitability leads to a drastic reduction of MyHC IIB which is compensated by IIA. Slow muscles, like soleus and diaphragm, were only marginally changed by myotonia. The MyHC pattern of TA of spinal muscular atrophy (SMA) 'wobbler' mice is shifted to a faster phenotype, with nearly 90% IIB. In the SMA mutant 'muscle deficient', all four adult isomyosins are expressed in the TA. These findings may be relevant for the future diagnosis of neurological disorders both in mouse disease models and in human patients. (C) 2004 Published by Elsevier B.V. on behalf of the Federation of European Biochemical Societies
Serum Metabolome Adaptations Following 12 Weeks of High-Intensity Interval Training or Moderate-Intensity Continuous Training in Obese Older Adults
No full text: Physical activity can be effective in preventing some of the adverse effects of aging on health. High-intensity interval training (HIIT) and moderate-intensity continuous training (MICT) are beneficial interventions for the quality of life of obese older individuals. The understanding of all possible metabolic mechanisms underlying these beneficial changes has not yet been established. The aim of this study was to analyze changes in the serum metabolome after 12 weeks of HIIT and MICT in obese older adults. Thirty-eight participants performed either HIIT (n = 26) or MICT (n = 12) three times per week for 12 weeks. Serum metabolites as well as clinical and biological parameters were assessed before and after the 12-week intervention. Among the 364 metabolites and ratio of metabolites identified, 51 metabolites changed significantly following the 12-week intervention. Out of them, 21 significantly changed following HIIT intervention and 18 significantly changed following MICT. Associations with clinical and biological adaptations revealed that changes in acyl-alkyl-phosphatidylcholine (PCae) (22:1) correlated positively with changes in handgrip strength in the HIIT group (r = 0.52, p < 0.01). A negative correlation was also observed between 2-oxoglutaric acid and HOMA-IR (r = -0.44, p < 0.01) when considering both groups together (HIIT and MICT). This metabolite also correlated positively with quantitative insulin-sensitivity check index (QUICKI) in both groups together (r = 0.46, p < 0.01) and the HIIT group (r = 0.51, p < 0.01). Additionally, in the MICT group, fumaric acid was positively correlated with triglyceride levels (r = 0.73, p < 0.01) and acetylcarnitine correlated positively with low-density lipoprotein (LDL) cholesterol (r = 0.81, p < 0.01). These four metabolites might represent potential metabolites of interest concerning muscle strength, glycemic parameters, as well as lipid profile parameters, and hence, for a potential healthy aging. Future studies are needed to confirm the association between these metabolites and a healthy aging
Reply to the “Commentary by D. Collin & P. Martinoty”
No full textWe would like to thank the authors of the commentary [1] for their efforts
to reproduce in the range of the narrow gap geometry (10–40 μm), our experiments [2]
using the same polymer (PBuA – poly(n-butyl acrylate) – for the ordinary
polymer) and a cyano-biphenyl substituted polyacrylate for the liquid
crystal polymer sample. The comparison of their results with ours is very
instructive
Identification of thermal shear bands in a low molecular weight polymer melt under oscillatory strain field
No full textInternational audienceWe present real-time micro-thermal measurements of the response of viscous fluids (low molecular weight unentangled and entangled polymer melts) submitted to an oscillatory mechanical shear strain (in conditions of conventional viscoelastic measurements). We show that thermal changes occur at the early steps of the applied deformation. A succession of thermodynamic states is identified showing the formation of non-uniform temperature shear bands along the strain direction. These thermal shear bands indicate the coexistence of cold and warm zones appearing in phase with the deformation. The synchronism of the temperature variation with the mechanical strain reveals a reversible process of elastic type indicating that viscous liquids might exhibit thermoelastic behaviors
Revealing the solid-like nature of glycerol at ambient temperature
No full textInternational audienceWe report on new dynamic measurements indicating a low frequency solid-like behaviour far above the glass transition and above the melting point in glycerol. Several tens micron thicknesses of pure (anhydrous) glycerol are deposited on highly wetting substrates. The response of the material to a mechanical stress is probed at room temperature as a function of the time and the frequency. The first type of experiment consists in measuring the linear dynamic response in a frequency range from 0.1 up to 10 rad/s. The second type of experiment consists in measuring the stress relaxation under a weak constant shear stress. In both cases, these independent experiments reveal that the glycerol exhibits a non-vanishing shear elasticity indicating a macroscopic solid-like character above its melting point. These results are compared with recent important observations reported, in particular, in the liquid state of glycerol by dielectric relaxation and in its supercooled states using low stress rheology
Hidden solidlike properties in the isotropic phase of the 8CB liquid crystal
No full textInternational audienceNovel dynamic experiments have enabled the identification of a macroscopic solidlike response in the isotropic phase of a low molecular weight liquid crystal, 4,4'-n-octylcyanobiphenyl (8CB). This unknown property indicates that the low frequency shear elasticity identified in the isotropic phase of liquid crystal polymers is not reminiscent from the glass transition but reveals likely a generic property of the liquid state. The comparison to high molecular weight liquid crystals indicates, however, that the shear modulus is much enhanced when the liquid crystal moieties are attached to a polymer chain. The macroscopic length scales probed (0.050–0.100 mm) exclude wall-induced effects. DOI: 10.1103/PhysRevE.88.050501 PACS number(s): 61.30.Hn, 68.08.−p, 87.15.hg, 83.85.Vb The knowledge of the timescales involved in liquid crystalline systems is of outmost importance to understand, control, and improve their characteristics. The submillimeter scales properties attract a tremendous research interest [1–4]. However, few studies concern the isotropic phase away from pretransitional effects. Assimilated to ordinary viscous liquids, the isotropic phase is not supposed to exhibit solidlike properties, or at very high frequency only (mega-or gigahertz) as ordinary liquids. For this reason, the low frequency behavior of the isotropic phase remains mistakenly unexplored. Experimentally, the viscous or solidlike nature of a material is deduced from its response to a low frequency mechanical solicitation. A couple of years ago, careful dynamic experiments carried out in the isotropic phase of high molecular weight liquid crystals [side-chain liquid crystalline polymers (SCLCPs)] have revealed an as-yet unknown property: the isotropic melt does not flow but exhibits a finite shear elasticity of about several thousand Pascals at low frequency (0.1–10 Hz) [5–9]. The identification of low frequency shear elasticity in the isotropic phase of SCLCPs away from the isotropic-nematic transition opens numerous questions on the origin of this new property. It neither seems to result from the contribution of the liquid crystal moieties nor from surface anchoring effects, but likely from a generic property of the liquid state. Measurable in SCLCPs at macroscopic length scales as far as 100 • away from the glass transition temperature [5,7,9], the shear elasticity of SCLCPs still raises the debated question of reminiscent glass transition effects. In this Rapid Communication, we probe the dynamic properties of the low molecular counterpart: the 4,4'-n-octylcyanobiphenyl (8CB). The widely studied molecule can be considered as a representative liquid crystal molecule. 8CB exhibits a crystalline phase at low temperatures that enables one to rule on the question of pretransitional glass transition effects. We reveal a low frequency, solidlike response at several tens of micrometers sample thickness in the isotropic phase of 8CB, meaning that long range correlations are preserved when the orientational order is lost. This shear elasticity is detectable if special attention is paid to boundary conditions between the substrate and the sample. Under these conditions, the shear stress is optimally transmitted between the sampl
What about your muscles when pou are getting older [Le muscle, les années et la sarcopénie]
No full textNational audienceMuscle aging is characterized by sarcopenia, characterized by reduction of muscle mass and strength. Muscle strength reduction can be explained, in part, by a decrease in muscle mass. Consequently, alternative hypothesis have been propose d based on neuromuscular alterations and their implicated mechanisms in these alterations. As the level of activity diminishes with age, it is important to distinguish changes specific to reduced activity (low muscular activity, bed rest, immobilization,...) from those due to aging. Thus, it seems that sarcopenia could be in part explained by a decreased neuromuscular activity and that physiological muscle stimulation by exercise could be a good way to delay the effects of muscular aging as well the effects of aging in general. © La Revue De Geratrie
Harmonic strain-optical response revealed in the isotropic (liquid) phase of liquid crystals
No full textInternational audienceA strong optical birefringence is observed when applying a small amplitude oscillatory strain to theliquid phase of a liquid crystal. This unpredicted birefringence is found to oscillate at the samefrequency as the driving frequency, with frequencies down to 0.01 Hz. This birefringence is visibleup to 15 C above the liquid crystal transition. This opto-dynamic property is interpreted as a resultof a coupling of the orientational pretransitional fluctuations existing in the isotropic phase andlong range elastic interactions recently identified in liquids. The conversion of the mechanicalwave in an optical response is shapeable. Two examples of synchronized periodic signals areshown: the sine and the square waves. The optimization of the signal is analyzed using aHeaviside-step shear test. This optical property is immediately exploitable to design low energyon/off switching material
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