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1.
Nat Commun ; 11(1): 6248, 2020 12 07.
Artigo em Inglês | MEDLINE | ID: mdl-33288763

RESUMO

Optogenetics allows light-driven, non-contact control of neural systems, but light delivery remains challenging, in particular when fine spatial control of light is required to achieve local specificity. Here, we employ organic light-emitting diodes (OLEDs) that are micropatterned into linear arrays to obtain precise optogenetic control in Drosophila melanogaster larvae expressing the light-gated activator CsChrimson and the inhibitor GtACR2 within their peripheral sensory system. Our method allows confinement of light stimuli to within individual abdominal segments, which facilitates the study of larval behaviour in response to local sensory input. We show controlled triggering of specific crawling modes and find that targeted neurostimulation in abdominal segments switches the direction of crawling. More broadly, our work demonstrates how OLEDs can provide tailored patterns of light for photo-stimulation of neuronal networks, with future implications ranging from mapping neuronal connectivity in cultures to targeted photo-stimulation with pixelated OLED implants in vivo.


Assuntos
Drosophila melanogaster/fisiologia , Rede Nervosa/fisiologia , Optogenética/métodos , Células Receptoras Sensoriais/fisiologia , Animais , Larva/fisiologia , Locomoção/fisiologia , Contração Muscular/fisiologia , Estimulação Luminosa/métodos
2.
PLoS One ; 15(11): e0241441, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-33175860

RESUMO

OBJECTIVE: The gastrointestinal environment in which drug products need to disintegrate before the drug can dissolve and be absorbed has not been studied in detail due to limitations, especially invasiveness of existing techniques. Minimal in vivo data is available on undisturbed gastrointestinal motility to improve relevance of predictive dissolution models and in silico tools such as physiologically-based pharmacokinetic models. Recent advances in magnetic resonance imaging methods could provide novel data and insights that can be used as a reference to validate and, if necessary, optimize these models. The conventional method for measuring gastrointestinal motility is via a manometric technique involving intubation. Nevertheless, it is feasible to measure gastrointestinal motility with magnetic resonance imaging. The aim of this study was is to develop and validate a magnetic resonance imaging method using the most recent semi-automated analysis method against concomitant perfused manometry method. MATERIAL AND METHODS: Eighteen healthy fasted participants were recruited for this study. The participants were intubated with a water-perfused manometry catheter. Subsequently, stomach motility was assessed by cine-MRI acquired at intervals, of 3.5min sets, at coronal oblique planes through the abdomen and by simultaneous water perfused manometry, before and after administration of a standard bioavailability / bioequivalence 8 ounces (~240mL) drink of water. The magnetic resonance imaging motility images were analysed using Spatio-Temporal Motility analysis STMM techniques. The area under the curve of the gastric motility contractions was calculated for each set and compared between techniques. The study visit was then repeated one week later. RESULTS: Data from 15 participants was analysed. There was a good correlation between the MRI antral motility plots area under the curve and corresponding perfused manometry motility area under the curve (r = 0.860) during both antral contractions and quiescence. CONCLUSION: Non-invasive dynamic magnetic resonance imaging of gastric antral motility coupled with recently developed, semi-automated magnetic resonance imaging data processing techniques correlated well with simultaneous, 'gold standard' water perfused manometry. This will be particularly helpful for research purposes related to oral absorption where the absorption of a drug is highly depending on the underlying gastrointestinal processes such as gastric emptying, gastrointestinal motility and availability of residual fluid volumes. CLINICAL TRIAL: This trial was registered at ClinicalTrials.gov as NCT03191045.


Assuntos
Jejum/fisiologia , Motilidade Gastrointestinal/fisiologia , Voluntários Saudáveis , Imagem por Ressonância Magnética , Manometria , Antro Pilórico/diagnóstico por imagem , Antro Pilórico/fisiologia , Água/farmacologia , Adulto , Área Sob a Curva , Disponibilidade Biológica , Feminino , Motilidade Gastrointestinal/efeitos dos fármacos , Humanos , Masculino , Pessoa de Meia-Idade , Contração Muscular/fisiologia , Antro Pilórico/efeitos dos fármacos , Equivalência Terapêutica , Fatores de Tempo , Adulto Jovem
3.
BMC Med Genet ; 21(Suppl 1): 197, 2020 10 22.
Artigo em Inglês | MEDLINE | ID: mdl-33092578

RESUMO

BACKGROUND: Myotonia congenita is a rare neuromuscular disease, which is characterized by a delay in muscle relaxation after evoked or voluntary contraction. Myotonia congenita can be inherited in a dominant (Thomsen disease) and recessive form (Becker disease) and both are caused by pathogenic variants in the CLCN1 gene. Noncanonical splice site variants are often classified as variants of uncertain significance, due to insufficient accuracy of splice-predicting tools. Functional analysis using minigene plasmids is widely used in such cases. Moreover, functional analysis is very useful in investigation of the disease pathogenesis, which is necessary for development of future therapeutic approaches. To our knowledge only one noncanonical splice site variant in the CLCN1 gene was functionally characterized to date. We further contribute to this field by evaluation the molecular mechanism of splicing alteration caused by the c.1582 + 5G > A in a homozygous state. CASE PRESENTATION: We report a clinical case of an affected 6-y.o boy with athletic appearance due to muscle hypertrophy, calf muscle stiffness, cramping and various myotonic signs in a consanguineous family with no history of neuromuscular disorders. The neurological examination showed percussion-activated myotonia in the hands and legs. Plasma creatine kinase enzyme and transaminases levels were normal. Electromyography at the time of examination shows myotonic runs in the upper and lower extremities. CONCLUSIONS: Functional analysis of the variant in a minigene system showed alteration of splicing leading to loss of function, thereby confirming that the variant is pathogenic.


Assuntos
Canais de Cloreto/genética , Contração Muscular/fisiologia , Miotonia Congênita/genética , Miotonia Congênita/patologia , Criança , Eletromiografia , Predisposição Genética para Doença/genética , Humanos , Masculino , Contração Muscular/genética , Músculo Esquelético/patologia , Miotonia Congênita/diagnóstico , Isoformas de Proteínas/genética
4.
Sci Rep ; 10(1): 16372, 2020 10 02.
Artigo em Inglês | MEDLINE | ID: mdl-33009449

RESUMO

Muscles perform a wide range of motile functions in animals. Among various types are skeletal and cardiac muscles, which exhibit a steady auto-oscillation of force and length when they are activated at an intermediate level of contraction. This phenomenon, termed spontaneous oscillatory contraction or SPOC, occurs devoid of cell membranes and at fixed concentrations of chemical substances, and is thus the property of the contractile system per se. We have previously developed a theoretical model of SPOC and proposed that the oscillation emerges from a dynamic force balance along both the longitudinal and lateral axes of sarcomeres, the contractile units of the striated muscle. Here, we experimentally tested this hypothesis by developing an imaging-based analysis that facilitates detection of the structural changes of single sarcomeres at unprecedented spatial resolution. We found that the sarcomere width oscillates anti-phase with the sarcomere length in SPOC. We also found that the oscillatory dynamics can be altered by osmotic compression of the myofilament lattice structure of sarcomeres, but they are unchanged by a proteolytic digestion of titin/connectin-the spring-like protein that provides passive elasticity to sarcomeres. Our data thus reveal the three-dimensional mechanical dynamics of oscillating sarcomeres and suggest a structural requirement of steady auto-oscillation.


Assuntos
Contração Muscular/fisiologia , Músculo Estriado/metabolismo , Músculo Estriado/fisiologia , Sarcômeros/metabolismo , Sarcômeros/fisiologia , Animais , Conectina/metabolismo , Elasticidade/fisiologia , Masculino , Modelos Biológicos , Músculo Esquelético/metabolismo , Músculo Esquelético/fisiologia , Miocárdio/metabolismo , Miofibrilas/metabolismo , Coelhos
5.
Proc Natl Acad Sci U S A ; 117(45): 28485-28495, 2020 11 10.
Artigo em Inglês | MEDLINE | ID: mdl-33097666

RESUMO

The recent discovery of sensory (tastant and odorant) G protein-coupled receptors on the smooth muscle of human bronchi suggests unappreciated therapeutic targets in the management of obstructive lung diseases. Here we have characterized the effects of a wide range of volatile odorants on the contractile state of airway smooth muscle (ASM) and uncovered a complex mechanism of odorant-evoked signaling properties that regulate excitation-contraction (E-C) coupling in human ASM cells. Initial studies established multiple odorous molecules capable of increasing intracellular calcium ([Ca2+]i) in ASM cells, some of which were (paradoxically) associated with ASM relaxation. Subsequent studies showed a terpenoid molecule (nerol)-stimulated OR2W3 caused increases in [Ca2+]i and relaxation of ASM cells. Of note, OR2W3-evoked [Ca2+]i mobilization and ASM relaxation required Ca2+ flux through the store-operated calcium entry (SOCE) pathway and accompanied plasma membrane depolarization. This chemosensory odorant receptor response was not mediated by adenylyl cyclase (AC)/cyclic nucleotide-gated (CNG) channels or by protein kinase A (PKA) activity. Instead, ASM olfactory responses to the monoterpene nerol were predominated by the activity of Ca2+-activated chloride channels (TMEM16A), including the cystic fibrosis transmembrane conductance regulator (CFTR) expressed on endo(sarco)plasmic reticulum. These findings demonstrate compartmentalization of Ca2+ signals dictates the odorant receptor OR2W3-induced ASM relaxation and identify a previously unrecognized E-C coupling mechanism that could be exploited in the development of therapeutics to treat obstructive lung diseases.


Assuntos
Anoctamina-1/metabolismo , Regulador de Condutância Transmembrana em Fibrose Cística/metabolismo , Músculo Liso/metabolismo , Proteínas de Neoplasias/metabolismo , Receptores Odorantes/metabolismo , Adenilil Ciclases/metabolismo , Brônquios/metabolismo , Cálcio/metabolismo , Células Cultivadas , Humanos , Pulmão/metabolismo , Contração Muscular/fisiologia , Relaxamento Muscular , Miócitos de Músculo Liso/metabolismo , Receptores Odorantes/genética
6.
PLoS One ; 15(10): e0240135, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-33007044

RESUMO

AIMS: The main aim of the present review was to update the available evidence on the value interest of post-competition recovery strategies in male professional or semi-professional soccer players to determine its effect on post-game performance outcomes, physiological markers, and wellness indicators. METHODS: A structured search was carried out following the PRISMA guidelines using six online databases: Pubmed, Scopus, SPORTDiscus, Web of Science, CINAHL and Cochrane Central Register of Controlled Trials. The risk of bias was completed following the Cochrane Collaboration Guidelines. Meta-analyses of randomized controlled trials were conducted to determine the between and within-group effects of different recovery strategies on performance, physiological markers and wellness data. Final meta-analyses were performed using the random-effects model and pooled standardized mean differences (SMD). RESULTS: Five randomized controlled trials that used Compression Garments (n = 3), Cold Water Immersion (n = 1), and acute Sleep Hygiene Strategy (n = 1) were included. Greater CMJ values at 48h for the intervention group (SMD = 0.70; 95% CI 0.14 to 1.25; p = 0.001; I2 = 10.4%) were found. For the 20-m sprint and MVC, the results showed no difference either at 24h or 48h. For physiological markers (CK and CRP) and wellness data (DOMS), small to large SMD were present in favor of the intervention group both at 24h (-0.12 to -1.86) and 48h (-0.21 to -0.85). No heterogeneity was present, except for MVC at 24h (I2 = 90.4%; p = 0.0012) and CALF DOMS at 48h (I2 = 93.7%; p = 0.013). CONCLUSION: The use of recovery strategies offers significant positive effects only in jumping performance (CMJ), with no effects on the 20-m sprint or MVC. Also, the use of recovery strategies offers greater positive effects on muscle damage (physiological markers and wellness data), highlighting the importance of post-match recovery strategies in soccer.


Assuntos
Desempenho Atlético/fisiologia , Futebol/fisiologia , Estudos de Casos e Controles , Humanos , Masculino , Contração Muscular/fisiologia , Viés de Publicação , Ensaios Clínicos Controlados Aleatórios como Assunto , Risco , Fatores de Tempo
7.
Proc Biol Sci ; 287(1937): 20202133, 2020 10 28.
Artigo em Inglês | MEDLINE | ID: mdl-33109011

RESUMO

The force-length relation is one of the most defining features of muscle contraction, and yet a topic of debate in the literature. The sliding filament theory predicts that the force produced by muscle fibres is proportional to the degree of overlap between myosin and actin filaments, producing a linear descending limb of the active force-length relation. However, several studies have shown forces that are larger than predicted, especially at long sarcomere lengths (SLs). Studies have been conducted with muscle fibres, preparations containing thousands of sarcomeres that make measurements of individual SL challenging. The aim of this study was to evaluate force production and sarcomere dynamics in isolated myofibrils and single sarcomeres from the rabbit psoas muscle to enhance our understanding of the theoretically predicted force-length relation. Contractions at varying SLs along the plateau (SL = 2.25-2.39 µm) and the descending limb (SL > 2.39 µm) of the force-length relation were induced in sarcomeres and myofibrils, and different modes of force measurements were used. Our results show that when forces are measured in single sarcomeres, the experimental force-length relation follows theoretical predictions. When forces are measured in myofibrils with large SL dispersions, there is an extension of the plateau and forces elevated above the predicted levels along the descending limb. We also found an increase in SL non-uniformity and slowed rates of force production at long lengths in myofibrils but not in single sarcomere preparations. We conclude that the deviation of the descending limb of the force-length relation is correlated with the degree of SL non-uniformity and slowed force development.


Assuntos
Contração Muscular/fisiologia , Miofibrilas/fisiologia , Coelhos/fisiologia , Sarcômeros/fisiologia , Citoesqueleto de Actina , Animais , Fenômenos Biomecânicos , Citoesqueleto , Extremidades , Fibras Musculares Esqueléticas , Músculos Psoas
8.
Am J Physiol Cell Physiol ; 319(6): C1029-C1044, 2020 12 01.
Artigo em Inglês | MEDLINE | ID: mdl-32936700

RESUMO

The contraction of myotubes using electrical pulse stimulation is a research tool used to mimic muscle contractile activity and exercise in rodents and humans. Most protocols employed in previous work used low-frequency twitch contractions. However, high-frequency tetanus contractions that are more physiologically relevant to muscle contractions in vivo are poorly characterized. In this report, the similarities and differences in acute responses and chronic adaptations with different contractile modes using twitches (2 Hz, continuous, 3 h) and tetanus (66 Hz, on: 5 s/off: 5 s, 3 h) were investigated. RNA sequencing-based transcriptome analysis and subsequent bioinformatics analysis suggest that tetanus may promote bioenergetic remodeling rather than twitch. Based on in silico analyses, metabolic remodeling after three contractile sessions of twitch and tetanus were investigated. Although twitch and tetanus had no significant effect on glycolysis, both types of contraction upregulated glucose oxidation capacity. Both twitch and tetanus qualitatively caused mitochondrial adaptations (increased content, respiratory chain enzyme activity, and respiratory function). The magnitude of adaptation was much greater under tetanus conditions. Our findings indicate that the contraction of myotubes by tetanus may be a useful experimental model, especially in the study of metabolic adaptations in C2C12 myotubes.


Assuntos
Contração Muscular/fisiologia , Fibras Musculares Esqueléticas/fisiologia , Músculo Esquelético/metabolismo , Animais , Linhagem Celular , Estimulação Elétrica , Perfilação da Expressão Gênica , Glucose/metabolismo , Glicogênio/metabolismo , Glicólise/fisiologia , Ácido Láctico/metabolismo , Camundongos , Camundongos Endogâmicos C57BL , Mitocôndrias/metabolismo , Fibras Musculares Esqueléticas/metabolismo , Oxirredução , Condicionamento Físico Animal/fisiologia , Período Refratário Eletrofisiológico/fisiologia , Transcriptoma/genética
9.
Am J Physiol Cell Physiol ; 319(6): C1158-C1162, 2020 12 01.
Artigo em Inglês | MEDLINE | ID: mdl-32997515

RESUMO

The myosin super-relaxed state (SRX) in skeletal muscle is hypothesized to play an important role in regulating muscle contractility and thermogenesis in humans but has only been examined in model organisms. Here we report the first human skeletal muscle SRX measurements, using quantitative epifluorescence microscopy of fluorescent 2'/3'-O-(N-methylanthraniloyl) ATP (mantATP) single-nucleotide turnover. Myosin heavy chain (MHC) isoform expression was determined using gel electrophoresis for each permeabilized vastus lateralis fiber, to allow for novel comparisons of SRX between fiber types. We find that the fraction of myosin in SRX is less in MHC IIA fibers than in MHC I and IIAX fibers (P = 0.008). ATP turnover of SRX is faster in MHC IIAX fibers compared with MHC I and IIA fibers (P = 0.001). We conclude that SRX biochemistry is measurable in human skeletal muscle, and our data indicate that SRX depends on fiber type as classified by MHC isoform. Extension from this preliminary work would provide further understanding regarding the role of SRX in human muscle physiology.


Assuntos
Contração Muscular/fisiologia , Fibras Musculares Esqueléticas/metabolismo , Cadeias Pesadas de Miosina/metabolismo , Termogênese/fisiologia , Adulto , Humanos , Isoformas de Proteínas/metabolismo , Músculo Quadríceps/citologia , Músculo Quadríceps/metabolismo , Adulto Jovem
10.
PLoS One ; 15(9): e0239471, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32946493

RESUMO

Humans can innately track a moving target by anticipating its future position from a brief history of observations. While ballistic trajectories can be readily extrapolated, many natural and artificial systems are governed by more general nonlinear dynamics and, therefore, can produce highly irregular motion. Yet, relatively little is known regarding the behavioral and physiological underpinnings of prediction and tracking in the presence of chaos. Here, we investigated in lab settings whether participants could manually follow the orbit of a paradigmatic chaotic system, the Rössler equations, on the (x,y) plane under different settings of a control parameter, which determined the prominence of transients in the target position. Tracking accuracy was negatively related to the level of unpredictability and folding. Nevertheless, while participants initially reacted to the transients, they gradually learned to anticipate it. This was accompanied by a decrease in muscular co-contraction, alongside enhanced activity in the theta and beta EEG bands for the highest levels of chaoticity. Furthermore, greater phase synchronization of breathing was observed. Taken together, these findings point to the possible ability of the nervous system to implicitly learn topological regularities even in the context of highly irregular motion, reflecting in multiple observables at the physiological level.


Assuntos
Dinâmica não Linear , Análise e Desempenho de Tarefas , Adulto , Sistema Nervoso Autônomo/fisiologia , Fenômenos Biomecânicos/fisiologia , Eletroencefalografia , Eletromiografia , Força da Mão/fisiologia , Humanos , Cinética , Aprendizagem/fisiologia , Movimento (Física) , Contração Muscular/fisiologia , Adulto Jovem
11.
Sci Rep ; 10(1): 15099, 2020 09 15.
Artigo em Inglês | MEDLINE | ID: mdl-32934308

RESUMO

The small intestine is covered by a network of coupled oscillators, the interstitial cells of Cajal (ICC). These oscillators synchronize to generate rhythmic phase waves of contraction. At points of low coupling, oscillations desynchronise, frequency steps occur and every few waves terminates as a dislocation. The amplitude of contractions is modulated at frequency steps. The phase difference between contractions at a frequency step and a proximal reference point increased slowly at first and then, just at the dislocation, increased rapidly. Simultaneous frequency and amplitude modulation (AM/FM) results in a Fourier frequency spectrum with a lower sideband, a so called Lashinsky spectrum, and this was also seen in the small intestine. A model of the small intestine consisting of a chain of coupled Van der Pol oscillators, also demonstrated simultaneous AM/FM at frequency steps along with a Lashinsky spectrum. Simultaneous AM/FM, together with a Lashinsky spectrum, are predicted to occur when periodically-forced or mutually-coupled oscillators desynchronise via a supercritical Andronov-Hopf bifurcation and have been observed before in other physical systems of forced or coupled oscillators in plasma physics and electrical engineering. Thus motility patterns in the intestine can be understood from the viewpoint of very general dynamical principles.


Assuntos
Relógios Biológicos/fisiologia , Intestino Delgado/fisiologia , Contração Muscular/fisiologia , Animais , Feminino , Células Intersticiais de Cajal/fisiologia , Camundongos , Músculo Liso/fisiologia
12.
Am J Physiol Gastrointest Liver Physiol ; 319(4): G519-G528, 2020 10 01.
Artigo em Inglês | MEDLINE | ID: mdl-32877218

RESUMO

The first contractile waves in the developing embryonic gut are purely myogenic; they only involve smooth muscle. Here, we provide evidence for a transition from smooth muscle to interstitial cell of Cajal (ICC)-driven contractile waves in the developing chicken gut. In situ hybridization staining for anoctamin-1 (ANO1), a known ICC marker, shows that ICCs are already present throughout the gut, as from embryonic day (E)7. We devised a protocol to reveal ICC oscillatory and propagative calcium activity in embryonic gut whole mount and found that the first steady calcium oscillations in ICCs occur on (E14). We show that the activation of ICCs leads to an increase in contractile wave frequency, regularity, directionality, and velocity between E12 and E14. We finally demonstrate that application of the c-KIT antagonist imatinib mesylate in organ culture specifically depletes the ICC network and inhibits the transition to a regular rhythmic wave pattern. We compare our findings to existing results in the mouse and predict that a similar transition should take place in the human fetus between 12 and 14 wk of development. Together, our results point to an abrupt physiological transition from smooth muscle mesenchyme self-initiating waves to ICC-driven motility in the fetus and clarify the contribution of ICCs to the contractile wave pattern.NEW & NOTEWORTHY We reveal a sharp transition from smooth muscle to interstitial cell of Cajal (ICC)-driven motility in the chicken embryo, leading to higher-frequency, more rhythmic contractile waves. We predict the transition to happen between 12 and 14 embryonic wk in humans. We image for the first time the onset of ICC activity in an embryonic gut by calcium imaging. We show the first KIT and anoctamin-1 (ANO1) in situ hybridization micrographs in the embryonic chicken gut.


Assuntos
Motilidade Gastrointestinal/fisiologia , Células Intersticiais de Cajal/fisiologia , Intestinos/embriologia , Animais , Anoctamina-1/análise , Cálcio/metabolismo , Embrião de Galinha , Trato Gastrointestinal/embriologia , Trato Gastrointestinal/fisiologia , Humanos , Células Intersticiais de Cajal/química , Intestinos/fisiologia , Camundongos , Contração Muscular/fisiologia , Músculo Liso/embriologia , Músculo Liso/fisiologia , Fatores de Tempo
13.
Medicine (Baltimore) ; 99(34): e21889, 2020 Aug 21.
Artigo em Inglês | MEDLINE | ID: mdl-32846850

RESUMO

Electromyographic biofeedback (EMG-BF) therapy provides information on the state of contraction of the targeted muscles and relaxation of their antagonists, which can facilitate early active range of motion (RoM) after elbow surgery. Our aim in this study was to calculate the minimum detectable change (MDC) during EMG-BF therapy, initiated in the early postoperative period after elbow surgery.This study is an observational case series. EMG-BF of muscle contraction and relaxation was provided during active elbow flexion and extension exercises. Patients completed 3 sets of 10 trials each of flexion and extension over 4 weeks. The total range of flexion-extension motion and scores on the Japanese Society for Surgery of the Hand version of the disability of the arm, shoulder, and hand questionnaire and the Japanese version of the Patient-Rated Elbow Evaluation were obtained at baseline and weekly during the 4-week intervention period. A prediction formula was developed from the time-series data obtained during the intervention period, using the least-squares method. The estimated value was calculated by removing the slope from the prediction formula and adding the initial scores to residuals between the measured scores and predicted scores individually. Systematic error, MDC at the 95th percentile cutoff (MDC95), repeatability of the measures, and the change from the baseline to each time-point of intervention were assessed.The MDC95 was obtained for all 3 outcome measures and the range of values was as follows: RoM, 8.3° to 22.5°; Japanese version of the Patient-Rated Elbow Evaluation score, 17.6 to 30.6 points; and disability of the arm, shoulder, and hand questionnaire subscale: disability and symptoms score, 14.2 to 22.9 points.The efficacy of EMG-BF after elbow surgery was reflected in earlier initiation of elbow RoM after surgery and improvement in patient-reported upper limb function scores. The calculated MDC95 cut-offs could be used as reference values to assess the therapeutic effects of EMG-BF in individuals.


Assuntos
Biorretroalimentação Psicológica/métodos , Cotovelo/cirurgia , Amplitude de Movimento Articular/fisiologia , Reabilitação/métodos , Adulto , Idoso , Avaliação da Deficiência , Cotovelo/patologia , Eletromiografia , Terapia por Exercício/métodos , Feminino , Humanos , Japão/epidemiologia , Masculino , Pessoa de Meia-Idade , Contração Muscular/fisiologia , Relaxamento Muscular/fisiologia , Medidas de Resultados Relatados pelo Paciente , Período Pós-Operatório , Reabilitação/tendências , Reprodutibilidade dos Testes , Inquéritos e Questionários , Resultado do Tratamento
14.
Am J Physiol Regul Integr Comp Physiol ; 319(3): R323-R328, 2020 09 01.
Artigo em Inglês | MEDLINE | ID: mdl-32783690

RESUMO

Black men have attenuated increases in forearm vascular conductance (FVC) and forearm blood flow (FBF) during moderate- and high-intensity rhythmic handgrip exercise compared with White men, but the underlying mechanisms are unclear. Here, we tested for the first time the hypothesis that functional sympatholysis (i.e., attenuation of sympathetic vasoconstriction in the exercising muscles) is impaired in Black men compared with White men. Thirteen White and 14 Black healthy young men were studied. FBF (duplex Doppler ultrasound) and mean arterial pressure (MAP; Finometer) were measured at rest and during rhythmic handgrip exercise at 30% maximal voluntary contraction. FVC was calculated as FBF/MAP. Sympathetic activation was induced via lower body negative pressure (LBNP) at -20 Torr for 2 min at rest and from the 3rd to the 5th min of handgrip. Sympathetic vasoconstriction was assessed as percent reductions in FVC during LBNP. The groups presented similar resting FVC, FBF, and MAP. During LBNP at rest, reductions in FVC were not different between White (-35 ± 10%) and Black men (-32 ± 14%, P = 0.616), indicating similar reflex-induced sympathetic vasoconstriction. During handgrip exercise, there were minimal reductions in FVC with LBNP in either group (White: -1 ± 7%; Black: +1 ± 8%; P = 0.523), indicating functional sympatholysis in both groups. Thus, contrary to our hypothesis, our findings indicate a preserved functional sympatholysis in healthy young Black men compared with White men, suggesting that this mechanism does not appear to contribute to reduced exercise hyperemia during moderate-intensity rhythmic handgrip in this population.


Assuntos
Exercício Físico/fisiologia , Força da Mão/fisiologia , Consumo de Oxigênio/fisiologia , Vasoconstrição/fisiologia , Adulto , Humanos , Masculino , Contração Muscular/fisiologia , Músculo Esquelético/fisiologia , Fluxo Sanguíneo Regional/fisiologia , Sistema Nervoso Simpático/fisiopatologia
15.
Proc Biol Sci ; 287(1933): 20200431, 2020 08 26.
Artigo em Inglês | MEDLINE | ID: mdl-32811308

RESUMO

Ground contact duration and stride frequency each affect muscle metabolism and help scientists link walking and running biomechanics to metabolic energy expenditure. While these parameters are often used independently, the product of ground contact duration and stride frequency (i.e. duty factor) may affect muscle contractile mechanics. Here, we sought to separate the metabolic influence of the duration of active force production, cycle frequency and duty factor. Human participants produced cyclic contractions using their soleus (which has a relatively homogeneous fibre type composition) at prescribed cycle-average ankle moments on a fixed dynamometer. Participants produced these ankle moments over short, medium and long durations while maintaining a constant cycle frequency. Overall, decreased duty factor did not affect cycle-average fascicle force (p ≥ 0.252) but did increase net metabolic power (p ≤ 0.022). Mechanistically, smaller duty factors increased maximum muscle-tendon force (p < 0.001), further stretching in-series tendons and shifting soleus fascicles to shorter lengths and faster velocities, thereby increasing soleus total active muscle volume (p < 0.001). Participant soleus total active muscle volume well-explained net metabolic power (r = 0.845; p < 0.001). Therefore, cyclically producing the same cycle-average muscle-tendon force using a decreased duty factor increases metabolic energy expenditure by eliciting less economical muscle contractile mechanics.


Assuntos
Metabolismo Energético/fisiologia , Músculo Esquelético/fisiologia , Tendões/fisiologia , Adulto , Tornozelo/fisiologia , Feminino , Marcha/fisiologia , Humanos , Masculino , Contração Muscular/fisiologia , Corrida/fisiologia , Caminhada/fisiologia
16.
Ideggyogy Sz ; 73(7-08): 249-252, 2020 Jul 30.
Artigo em Húngaro | MEDLINE | ID: mdl-32750241

RESUMO

Objective - Conflicting theoretical models exist regarding the mechanism related to the ability of the Jendrassik maneuver to reinforce reflex parameters. Our objective was to investigate if vigorous handgrip would induce changes in recurrent inhibition of soleus motoneurons. Method - Soleus H reflex was evoked by stimulating the tibial nerve at rest and during bilateral vigorous handgrip, alternating single (H1) and paired stimulation (H2). At paired stimulation we used interstimulus intervals of 10, 15, 20 and 25 ms and supramaximal test stimulus. H1- and H2-wave amplitudes were expressed as percentage of maximal M-wave amplitude. Conditioned H2 wave maximal (H2max) and minimal (H2) amplitudes evoked at rest and expressed as a percentage of the unconditioned H1max amplitude were compared with the corresponding values obtained during handgrip by means of paired Student test and Bonferroni correction. Subjects - At the study participated 28 healthy volunteers. Results - The H1max/Mmax × 100 values obtained during handgrip (37.5±10.1) were significantly higher than those obtained at rest (27.1±7.4). The H2max/H1max × 100-va-lues obtained at paired stimulation were significantly higher during handgrip than at rest, while no significant diffe-rence was found between the H2/H1max × 100-values obtained during handgrip and at rest respectively. Discussion - The H2max/H1max is determined by both the excitability of the motoneurons and the recurrent inhibition elicited by the conditioning stimulus, while H2/H1max indicates only the level of recurrent inhibition. According to our results the Renshaw cells retain their inhibitory effect on the soleus alpha motoneurons during remote muscle contraction. Conclusion - Soleus H reflex enhancement during Jendrassik maneuver is not due to decrease of recurrent inhibition.


Assuntos
Antebraço/fisiologia , Reflexo H , Força da Mão , Contração Muscular/fisiologia , Músculo Esquelético/fisiologia , Eletromiografia , Reflexo H/fisiologia , Humanos , Músculos/inervação , Nervo Tibial/fisiologia
17.
Am J Physiol Gastrointest Liver Physiol ; 319(4): G454-G461, 2020 10 01.
Artigo em Inglês | MEDLINE | ID: mdl-32755311

RESUMO

High-resolution esophageal manometry (HRM) in its current form assesses only the contraction phase of peristalsis. Degree of esophageal distension ahead of contraction is a surrogate of relaxation and can be measured from intraluminal esophageal impedance measurements. The characteristics of esophageal contractions, i.e., their amplitude, duration, velocity, and modulating factors, have been well studied. We studied the effect of bolus volume and viscosity and posture on swallow-induced distension and contraction and the temporal relationship between the two. HRM impedance recordings of 50 healthy subjects with no esophageal symptoms were analyzed. Eight to ten swallows of 5 and 10 mL of 0.5 N saline and a viscous bolus were recorded in the supine and Trendelenburg positions. Custom-built computer software generated the distension-contraction plots and numerical data of the amplitudes of distension (cross-sectional area) and contraction, and the temporal relationship between distension and peak contraction. The hallmarks of distension waveforms are that 1) distension peak, similarly to contraction, travels the esophagus in a peristaltic fashion, and the amplitude of distension increases from the proximal-to-distal direction; 2) the amplitude of distension is greater with 10 mL than with 5 mL and greater in Trendelenburg than in supine posture; and 3) bolus viscosity increases the amplitude of distension and alters the temporal relationship between distension and contraction waveforms. We describe the characteristics of esophageal distension during peristalsis and the relationship between distension and contraction in a relatively large cohort of normal subjects. These data can be used to compare differences between normal subjects and patients with various esophageal motility disorders in future studies.NEW & NOTEWORTHY We studied esophageal distension (surrogate of inhibition) ahead of contraction during peristalsis from intraluminal esophageal impedance measurements. Esophageal distension, similarly to contraction, travels the esophagus in a sequential manner, and the amplitude of esophageal distension increases from proximal to distal direction in the esophagus. Bolus volume, viscosity and posture have significant effects on the amplitude of distension and its temporal relationship with contraction.


Assuntos
Esôfago/fisiologia , Peristaltismo/fisiologia , Postura/fisiologia , Adulto , Idoso , Fenômenos Biomecânicos , Deglutição/fisiologia , Impedância Elétrica , Transtornos da Motilidade Esofágica , Feminino , Decúbito Inclinado com Rebaixamento da Cabeça , Voluntários Saudáveis , Humanos , Masculino , Manometria , Pessoa de Meia-Idade , Contração Muscular/fisiologia , Decúbito Dorsal , Viscosidade
18.
J Neurosci ; 40(31): 6035-6048, 2020 07 29.
Artigo em Inglês | MEDLINE | ID: mdl-32611708

RESUMO

Control of the body requires inhibiting complex actions, involving contracting and relaxing muscles. However, little is known of how voluntary commands to relax a muscle are cancelled. Action inhibition causes both suppression of muscle activity and the transient excitation of antagonist muscles, the latter being termed active breaking. We hypothesized that active breaking is present when stopping muscle relaxations. Stop signal experiments were used to compare the mechanisms of active breaking for muscle relaxations and contractions in male and female human participants. In experiments 1 and 2, go signals were presented that required participants to contract or relax their biceps or triceps muscle. Infrequent Stop signals occurred after fixed delays (0-500 ms), requiring that participants cancelled go commands. In experiment 3, participants increased (contract) or decreased (relax) an existing isometric finger abduction depending on the go signal, and cancelled these force changes whenever Stop signals occurred (dynamically adjusted delay). We found that muscle relaxations were stopped rapidly, met predictions of existing race models, and had Stop signal reaction times that correlated with those observed during the stopping of muscle contractions, suggesting shared control mechanisms. However, stopped relaxations were preceded by transient increases in electromyography (EMG), while stopped contractions were preceded by decreases in EMG, suggesting a later divergence of control. Muscle state-specific active breaking occurred simultaneously across muscles, consistent with a central origin. Our results indicate that the later stages of action inhibition involve separate excitatory and inhibitory pathways, which act automatically to cancel complex body movements.SIGNIFICANCE STATEMENT The mechanisms of how muscle relaxations are cancelled are poorly understood. We showed in three experiments involving multiple effectors that stopping muscle relaxations involves transient bursts of EMG activity, which resemble cocontraction and have onsets that correlate with Stop signal reaction time. Comparison with the stopping of matched muscle contractions showed that active breaking was muscle state specific, being positive for relaxations and negative for contractions. The two processes were also observed to co-occur in agonist-antagonist pairs, suggesting separate pathways. The rapid, automatic activation of both pathways may explain how complex actions can be stopped at any stage of their execution.


Assuntos
Contração Muscular/fisiologia , Relaxamento Muscular/fisiologia , Músculo Esquelético/fisiologia , Adulto , Eletromiografia , Feminino , Dedos/fisiologia , Músculos Isquiossurais/fisiologia , Humanos , Contração Isométrica , Masculino , Movimento/fisiologia , Tempo de Reação
19.
Sci Rep ; 10(1): 10625, 2020 06 30.
Artigo em Inglês | MEDLINE | ID: mdl-32606297

RESUMO

The sensorimotor integration during unconstrained reaching movements in the presence of variable environmental forces remains poorly understood. The objective of this study was to quantify how much the primary afferent activity of muscle spindles can contribute to shaping muscle coactivation patterns during reaching movements with complex dynamics. To achieve this objective, we designed a virtual reality task that guided healthy human participants through a set of planar reaching movements with controlled kinematic and dynamic conditions that were accompanied by variable muscle co-contraction. Next, we approximated the Ia afferent activity using a phenomenological model of the muscle spindle and muscle lengths derived from a musculoskeletal model. The parameters of the spindle model were altered systematically to evaluate the effect of fusimotor drive on the shape of the temporal profile of afferent activity during movement. The experimental and simulated data were analyzed with hierarchical clustering. We found that the pattern of co-activation of agonistic and antagonistic muscles changed based on whether passive forces in each movement played assistive or resistive roles in limb dynamics. The reaching task with assistive limb dynamics was associated with the most muscle co-contraction. In contrast, the simulated Ia afferent profiles were not changing between tasks and they were largely reciprocal with homonymous muscle activity. Simulated physiological changes to the fusimotor drive were not sufficient to reproduce muscle co-contraction. These results largely rule out the static set and α-γ coactivation as the main types of fusimotor drive that transform the monosynaptic Ia afferent feedback into task-dependent co-contraction of antagonistic muscles. We speculate that another type of nonlinear transformation of Ia afferent signals that is independent of signals modulating the activity of α motoneurons is required for Ia afferent-based co-contraction. This transformation could either be applied through a complex nonlinear profile of fusimotor drive that is not yet experimentally observed or through presynaptic inhibition.


Assuntos
Modelos Biológicos , Neurônios Motores/fisiologia , Movimento/fisiologia , Contração Muscular/fisiologia , Músculo Esquelético/fisiologia , Adulto , Fenômenos Biomecânicos/fisiologia , Feminino , Humanos , Masculino , Fusos Musculares/fisiologia , Adulto Jovem
20.
Artigo em Inglês | MEDLINE | ID: mdl-32645967

RESUMO

Myostatin A55T genotype is one of the candidates showing inter-individual variation in skeletal muscle phenotypes. The aim of this study was to investigate the effect of the myostatin A55T genotype on markers of muscle damage after eccentric exercise. Forty-eight young, healthy male college students (age = 24.8 ± 2.2 years, height = 176.7 ± 5.3 cm, weight = 73.7 ± 8.3 kg) were enrolled in this study, and muscle damage was induced through 50 reps of maximal eccentric muscle contraction. As markers of muscle damage, maximal isometric strength (MIS), muscle soreness, creatine kinase (CK), and aspartate transaminase (AST) were measured. Myostatin A55T genotypes were classified into homozygous myostatin A55T allele (AA, n = 34, 72%), heterozygous myostatin A55T allele (AT, n = 13, 26%), and homozygous mutant carriers (TT, n = 1, 2%). After eccentric exercise, the subjects with heterozygous for AT showed markedly quicker MIS recovery compared to the AA group (p = 0.042). However, there were no significant variations in muscle soreness (p = 0.379), CK (p = 0.955), and AST (p = 0.706) among the groups. These results suggest that AT in myostatin A55T genotype may be associated with quicker strength recovery following exercise-induced muscle damage.


Assuntos
Grupo com Ancestrais do Continente Asiático/genética , Exercício Físico/fisiologia , Força Muscular/fisiologia , Mialgia/etiologia , Miostatina/genética , Genótipo , Humanos , Masculino , Contração Muscular/genética , Contração Muscular/fisiologia , Força Muscular/genética , Músculo Esquelético/fisiologia , Polimorfismo de Nucleotídeo Único , Recuperação de Função Fisiológica , Treinamento de Resistência
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