Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 94.940
Filtrar
1.
Zhonghua Yi Xue Za Zhi ; 100(37): 2908-2912, 2020 Oct 13.
Artigo em Chinês | MEDLINE | ID: mdl-32993249

RESUMO

Objective: To investigate the characteristics of modified Oxford grading scale (MOS) and pelvic floor surface electromyography (sEMG) based on Glazer protocol in patients with stress urinary incontinence (SUI), and analyze the correlation between the two methods. Methods: This study was a cross-sectional survey. A total of 212 subjects in May 2019 were enrolled and divided into SUI group (n=61) and non-SUI group (n=151) based on the commonly used 3 incontinence questions (3IQ). MOS test and sEMG parameters were measured by the same rehabilitator. The sEMG parameters included the mean and variation coefficient in the prerest phase, the maximum and relaxation time of 5 rapid contractions, the mean and variability of EMG in 10 s tonic contraction phase, the mean and variability of EMG in 60 s endurance contraction phase, and the mean and variability of EMG in postrest phase. The differences of the above parameters between SUI group and non-SUI group were compared, the logistic regression and Spearman method were used to analyze the correlation between MOS and sEMG parameters. Results: The prevalence of SUI was 28.8%(61/212) in community, body mass index and delivery mode were the risk factors (all P<0.05). The MOS of the SUI group and the non-SUI group were 3 (2,3) and 3 (3,4), respectively, with significant difference (Z=-2.58, P=0.010). Among the sEMG parameters of SUI group and non-SUI group, the maximum values of phasic contractions were 23.12 (13.65, 37.89), 30.68 (20.28, 47.02) µV, the mean of tonic contractions were 14.32 (9.62, 21.49), 17.65 (12.05, 26.35) µV, and the mean of endurance contractions were 12.78(7.88, 18.76), 16.55(11.13, 22.40) µV, respectively, with statistical significance (Z=-2.34, -2.37, -3.20, all P<0.05). The multivariate logistic regression revealed that both the variation coefficient of tonic contractions (OR=157.86, 95%CI: 1.99-12 595.51, P<0.05) and the amplitude of endurance contractions(OR=1.11, 95%CI: 1.03-1.19, P<0.05) were correlated with SUI. The tonic contractions amplitude had the tendency to be related to SUI (OR=0.95, 95%CI: 0.09-1.00, P<0.05). In all subjects, MOS was correlated with the maximum value of rapid contractions, average value of tonic contractions and average value of endurance contractions (r=0.516, 0.503, 0.464, all P<0.05). In SUI group (r=0.510, 0.442, 0.385, all P<0.05), and non-SUI group (r=0.495, 0.524, 0.488, all P<0.05), MOS was correlated with the above parameters. Conclusions: MOS and sEMG based on Glazer protocol indicate that the contractility of pelvic floor muscle decreases in SUI patients. The results of sEMG and MOS are consistent, which can be used for quantitative evaluation of pelvic floor muscle function in SUI patients.


Assuntos
Diafragma da Pelve , Incontinência Urinária por Estresse , Estudos Transversais , Eletromiografia , Feminino , Humanos , Contração Muscular
2.
Proc Biol Sci ; 287(1935): 20201578, 2020 09 30.
Artigo em Inglês | MEDLINE | ID: mdl-32962547

RESUMO

The southern alligator lizard (Elgaria multicarinata) exhibits a courtship behaviour during which the male firmly grips the female's head in his jaws for many hours at a time. This extreme behaviour counters the conventional wisdom that reptilian muscle is incapable of powering high-endurance behaviours. We conducted in situ experiments in which the jaw-adductor muscles of lizards were stimulated directly while bite force was measured simultaneously. Fatigue tests were performed by stimulating the muscles with a series of tetanic trains. Our results show that a substantial sustained force gradually develops during the fatigue test. This sustained force persists after peak tetanic forces have declined to a fraction of their initial magnitude. The observed sustained force during in situ fatigue tests is consistent with the courtship behaviour of these lizards and probably reflects physiological specialization. The results of molecular analysis reveal that the jaw muscles contain masticatory and tonic myosin fibres. We propose that the presence of tonic fibres may explain the unusual sustained force properties during mate-holding behaviour. The characterization of muscle properties that facilitate extreme performance during specialized behaviours may reveal general mechanisms of muscle function, especially when done in light of convergently evolved systems exhibiting similar performance characteristics.


Assuntos
Arcada Osseodentária/anatomia & histologia , Lagartos/fisiologia , Músculos da Mastigação/anatomia & histologia , Comportamento Sexual Animal , Animais , Força de Mordida , Corte , Feminino , Masculino , Contração Muscular , Músculo Esquelético
3.
PLoS One ; 15(8): e0236731, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32866151

RESUMO

Ankle proprioception is crucial for balance and relies upon accurate input from calf muscle spindles. Spindle input, in turn, depends upon the physiological and mechanical properties of surrounding muscle tissue. Altering these properties could affect ankle proprioception, with potential consequences for balance. Here we determine the effects of prior muscle cooling, stretch and contraction upon performance of a contralateral ankle joint matching task. Participants stood passively leaning against a board oriented 22° rearward from vertical. Their right ankle was rotated to a randomised position between ± 6° plantar/dorsiflexion. The task was to align the left ankle to the same position, without vision. In the first experiment, immediately prior to each testing session, participants either produced a strong calf muscle contraction in a fully plantarflexed (tiptoe) posture or underwent 15° dorsiflexion stretch. Contraction had no effect on task performance, whereas stretch produced a significant bias in ankle placement of 0.89 ± 0.6°, indicating that participants perceived their foot to be more plantarflexed compared to a control condition. In the second experiment, the right lower leg was cooled in iced water (≤ 5°C) for 10 minutes. Cooling increased joint matching error by ~0.4°, through a combination of increased bias and variability. These results confirm that conditioning the triceps surae muscles can alter perception of ankle joint position. Since body movement during quiet stance is in the order of 1°, the magnitude of these changes are relevant for balance.


Assuntos
Tornozelo/fisiologia , Músculo Esquelético/fisiologia , Propriocepção , Adulto , Retroalimentação Fisiológica , Feminino , Humanos , Masculino , Contração Muscular , Temperatura Cutânea , Adulto Jovem
4.
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
5.
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
6.
PLoS Genet ; 16(8): e1008644, 2020 08.
Artigo em Inglês | MEDLINE | ID: mdl-32776941

RESUMO

Correct regulation of cell contractility is critical for the function of many biological systems. The reproductive system of the hermaphroditic nematode C. elegans contains a contractile tube of myoepithelial cells known as the spermatheca, which stores sperm and is the site of oocyte fertilization. Regulated contraction of the spermatheca pushes the embryo into the uterus. Cell contractility in the spermatheca is dependent on actin and myosin and is regulated, in part, by Ca2+ signaling through the phospholipase PLC-1, which mediates Ca2+ release from the endoplasmic reticulum. Here, we describe a novel role for GSA-1/Gαs, and protein kinase A, composed of the catalytic subunit KIN-1/PKA-C and the regulatory subunit KIN-2/PKA-R, in the regulation of Ca2+ release and contractility in the C. elegans spermatheca. Without GSA-1/Gαs or KIN-1/PKA-C, Ca2+ is not released, and oocytes become trapped in the spermatheca. Conversely, when PKA is activated through either a gain of function allele in GSA-1 (GSA-1(GF)) or by depletion of KIN-2/PKA-R, the transit times and total numbers, although not frequencies, of Ca2+ pulses are increased, and Ca2+ propagates across the spermatheca even in the absence of oocyte entry. In the spermathecal-uterine valve, loss of GSA-1/Gαs or KIN-1/PKA-C results in sustained, high levels of Ca2+ and a loss of coordination between the spermathecal bag and sp-ut valve. Additionally, we show that depleting phosphodiesterase PDE-6 levels alters contractility and Ca2+ dynamics in the spermatheca, and that the GPB-1 and GPB-2 Gß subunits play a central role in regulating spermathecal contractility and Ca2+ signaling. This work identifies a signaling network in which Ca2+ and cAMP pathways work together to coordinate spermathecal contractions for successful ovulations.


Assuntos
Proteínas de Caenorhabditis elegans/metabolismo , Sinalização do Cálcio , Subunidades Catalíticas da Proteína Quinase Dependente de AMP Cíclico/metabolismo , Contração Muscular , 3',5'-AMP Cíclico Fosfodiesterases/metabolismo , Animais , Caenorhabditis elegans , Proteínas de Caenorhabditis elegans/genética , Subunidades Catalíticas da Proteína Quinase Dependente de AMP Cíclico/genética , Células Epiteliais/metabolismo , Células Epiteliais/fisiologia , Subunidades beta da Proteína de Ligação ao GTP/metabolismo , Mutação com Ganho de Função , Células Musculares/metabolismo , Células Musculares/fisiologia , Oócitos/fisiologia
7.
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
8.
Life Sci ; 258: 118179, 2020 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-32758626

RESUMO

OBJECTIVE: To evaluate whether approved gastroprokinetic agent, acotiamide exerts a direct excitatory effect on bladder to help explain the reported meaningful reduction of post-void residual urine volume (PVR) in detrusor underactivity (DU) patients after thrice daily oral intake of acotiamide 100 mg for 2 weeks. METHODS: Effect of acotiamide [1-16 µM] was assessed on nerve-mediated contractions evoked by electrical field stimulation (EFS) for 5 s with 5 ms pulse trains of 10 V in longitudinal, mucosa intact rat and human bladder strips to construct frequency response curve (1-32 Hz) and repeat 10 Hz stimulation at 60s interval. Effect of acotiamide 2 µM on spontaneous and carbachol evoked contractions was also assessed. RESULTS: Acotiamide 2 µM significantly enhanced the Atropine and Tetrodotoxin (TTX)-sensitive EFS evoked contractions of rat and human bladder at 8-32 Hz (Two-way ANOVA followed Sidak's multiple comparison; *p < 0.01) and on repeat 10 Hz stimulation (Paired Student's t-test; *p < 0.05), while producing a modest effect on the spontaneous contractions and a negligible effect on the carbachol evoked contractions. CONCLUSIONS: Enhancement of TTX-sensitive evoked contractions of rat and human bladder by acotiamide is consistent with the enhancement of excitatory neuro-effector transmission mainly through prejunctional mechanisms. Findings highlight immense therapeutic potential of antimuscarinics with low M3 receptor affinity like acotiamide in Underactive bladder (UAB)/DU treatment.


Assuntos
Benzamidas/uso terapêutico , Tiazóis/uso terapêutico , Bexiga Inativa/tratamento farmacológico , Bexiga Urinária/patologia , Animais , Benzamidas/química , Benzamidas/farmacologia , Carbacol/farmacologia , Estimulação Elétrica , Humanos , Masculino , Contração Muscular/efeitos dos fármacos , Ratos Sprague-Dawley , Tiazóis/química , Tiazóis/farmacologia , Bexiga Urinária/efeitos dos fármacos , Bexiga Urinária/inervação
9.
PLoS One ; 15(8): e0237133, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32760097

RESUMO

BACKGROUND: Accessory nerve shoulder dysfunction is common after neck dissection in oral cancer survivors. This study aimed to investigate the short-term effects of scapular muscle strengthening exercises with motor-control techniques on neck dissection-related shoulder dysfunction in oral cancer survivors before the initiation of radiotherapy. METHODS: Thirty-eight participants were randomly allocated into the motor-control and regular-exercise groups. Each group received conventional physical therapy and specific scapular muscle strengthening exercises for 1 month immediately after neck dissection. Motor control techniques were integrated with scapular strengthening exercises for the motor-control group. Shoulder pain, active range of motion (AROM) of shoulder abduction, and scapular muscle activities including upper trapezius (UT), middle trapezius (MT), lower trapezius (LT), and serratus anterior (SA) when performing maximal voluntary isometric contraction (MVIC) and scapular muscle exercises were evaluated at baseline and after 1 month of training. RESULTS: Both groups reduced shoulder pain and increased muscle activity of maximum voluntary isometric contraction (MVIC) of each muscle after the intervention. Increased AROM of shoulder abduction was only observed in the motor-control group (95% CI 3.80 to 20.51, p = 0.004). Relative to baseline evaluation, muscle activities of UT decreased in the motor-control group when performing shoulder shrug with 1-kg weight (95% CI -33.06 to -1.29, p = 0.034). Moreover, the SA activity decreased in the motor-control group (95% CI -29.73 to -27.68, p<0.001) but increased in the regular-exercise group (95% CI 28.16 to 30.05, p<0.001) when performing shoulder horizontal adduction and flexion. CONCLUSION: Early strengthening exercise with motor control techniques has greater benefits for improving AROM of shoulder abduction, muscle economy, and reducing compensatory scapular muscle activities in patients with neck dissection-related shoulder dysfunction before the initiation of radiotherapy.


Assuntos
Terapia por Exercício/métodos , Neoplasias Bucais/cirurgia , Força Muscular , Esvaziamento Cervical/efeitos adversos , Complicações Pós-Operatórias/terapia , Adulto , Idoso , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Neoplasias Bucais/radioterapia , Contração Muscular , Amplitude de Movimento Articular , Ombro/fisiopatologia , Músculos Superficiais do Dorso/fisiopatologia
10.
Georgian Med News ; (303): 55-58, 2020 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-32841181

RESUMO

Type of breathing (nasal, oral, oronasal) can turn out to be a causative factor for (or result of) orthodontic anomalies alongside the respiratory-metabolic disorders. Consequently, assessment of functional characteristics of the masticatory apparatus, which differ in oral and nasal breathing modes, could be of interest for the evaluation of the degree of orthodontic dysfunction and formation of an effective individualized treatment plan. Aim of the study was to assess electrophysiologic characteristics of the masticatory muscles bilaterally in nasal and oral breathing modes. The study was conducted on the group of 22 women-volunteers aged 18-30 years. All subjects enrolled in the study had permanent dentition with all second molars present; minimum 28 natural teeth in total. None of them had clinical manifestations of somatic, neurological or endocrine disorders or those of nasal cavity, paranasal sinus or tonsillar disorders.Written informed consent was obtained from all subjects. To narrow the selection of patients eligible for the study, we applied a protocol of normalized electromyographic recording during maximal voluntary contraction of clenching on a cotton roll. Indicators of the degree of mean muscle contractility recorded as a result of standardized maximal voluntary contraction show that in nasal breathing muscle activity is homogenous and symmetric in the right and left masseter and temporalis muscles. Conversely, the indicators are dissociated in oral breathing. Electrophysiological activity and, consequently, contractility of the muscles are reduced, which must be caused by recruitment of decreasing number of less excitable motor units. The results yielded by the study suggest that the data on the state of neuromuscular balance of the masticatory apparatus could be utilized for the assessment of the degree of orthodontic dysfunction and for development of individualized treatment plan.


Assuntos
Músculos da Mastigação , Músculo Temporal , Adolescente , Adulto , Eletromiografia , Feminino , Humanos , Músculo Masseter , Contração Muscular , Adulto Jovem
11.
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
12.
PLoS One ; 15(7): e0235156, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32667945

RESUMO

BACKGROUND: Single repetition, contraction-phase specific and total time-under-tension (TUT) are crucial mechano-biological descriptors associated with distinct morphological, molecular and metabolic muscular adaptations in response to exercise, rehabilitation and/or fighting sarcopenia. However, to date, no simple, reliable and valid method has been developed to measure these descriptors. OBJECTIVE: In this study we aimed to test whether accelerometer data obtained from a standard smartphone placed on the weight stack can be used to extract single repetition, contraction-phase specific and total TUT. METHODS: Twenty-two participants performed two sets of ten repetitions of their 60% one repetition maximum with a self-paced velocity on nine commonly used resistance exercise machines. Two identical smartphones were attached on the resistance exercise weight stacks and recorded all user-exerted accelerations. An algorithm extracted the number of repetitions, single repetition, contraction-phase specific and total TUT. All exercises were video-recorded. The TUT determined from the algorithmically-derived mechano-biological descriptors was compared with the video recordings that served as the gold standard. The agreement between the methods was examined using Limits of Agreement (LoA). The association was calculated using the Pearson correlation coefficients and interrater reliability was determined using the intraclass correlation coefficient (ICC 2.1). RESULTS: The error rate of the algorithmic detection of single repetitions derived from two smartphones accelerometers was 0.16%. Comparing algorithmically-derived, contraction-phase specific TUT against video, showed a high degree of correlation (r>0.93) for all exercise machines. Agreement between the two methods was high on all exercise machines as follows: LoA ranged from -0.3 to 0.3 seconds for single repetition TUT (0.1% of mean TUT), from -0.6 to 0.3 seconds for concentric contraction TUT (7.1% of mean TUT), from -0.3 to 0.5 seconds for eccentric contraction TUT (4.1% of mean TUT) and from -1.9 to 1.1 seconds for total TUT (0.5% of mean TUT). Interrater reliability for single repetition, contraction-phase specific TUT was high (ICC > 0.99). CONCLUSION: Data from smartphone accelerometer derived resistance exercise can be used to validly and reliably extract crucial mechano-biological descriptors. Moreover, the presented multi-analytical algorithmic approach enables researchers and clinicians to reliably and validly report missing mechano-biological descriptors.


Assuntos
Acelerometria/instrumentação , Contração Muscular/fisiologia , Músculo Esquelético/fisiologia , Treinamento de Resistência , Smartphone , Adulto , Idoso , Feminino , Voluntários Saudáveis , Humanos , Masculino , Pessoa de Meia-Idade , Reprodutibilidade dos Testes , Levantamento de Peso/fisiologia , Adulto Jovem
13.
Zhejiang Da Xue Xue Bao Yi Xue Ban ; 40(7): 958-964, 2020 May 25.
Artigo em Chinês | MEDLINE | ID: mdl-32701234

RESUMO

OBJECTIVE: To investigate the protective effect of melatonin against myocardial ischemia reperfusion (IR) injury in isolated rat hearts and explore the underlying mechanisms. METHODS: The isolated hearts from 40 male SD rats were randomly divided into 4 groups (n=10): the control group, where the hearts were perfused with KH solution for 175 min; IR group, where the hearts were subjected to global ischemia for 45 min followed by reperfusion for 120 min; IR+melatonin (Mel+IR) group, where melatonin (5 µmol/L) was administered to the hearts 1 min before ischemia and during the first 5 min of reperfusion, followed by 115 min of reperfusion; and IR+2, 3-butanedione monoxime (IR+BDM) group, where the hearts were treated with BDM (20 mmol/L) in the same manner as melatonin treatment. Myocardial injury in the isolated hearts was assessed based on myocardial injury area, caspase-3 activity, and expressions of cytochrome C and cleaved caspase-3 proteins. Cardiac contracture was assessed using HE staining and by detecting lactate dehydrogenase (LDH) activity and the content of cardiac troponin I (cTnI) in the coronary outflow, measurement of left ventricular end-diastolic pressure (LVEDP) and electron microscopy. The content of ATP in the cardiac tissue was also determined. RESULTS: Compared with those in the control group, the isolated hearts in IR group showed significantly larger myocardial injury area and higher caspase-3 activity and the protein expressions of cytochrome C and cleaved caspase-3 with significantly increased LDH activity and cTnI content in the coronary outflow and elevated LVEDP at the end of reperfusion; HE staining showed obvious fractures of the myocardial fibers and the content of ATP was significantly decreased in the cardiac tissue; electron microscopy revealed the development of contraction bands. In the isolated hearts with IR, treatment with Mel or BDM significantly reduced the myocardial injury area, caspase-3 activity, and protein expressions of cytochrome C and cleaved caspase-3, obviously inhibited LDH activity, lowered the content of cTnI and LVEDP, reduced myocardial fiber fracture, and increased ATP content in the cardiac tissue. Both Mel and BDM inhibited the formation of contraction bands in the isolated hearts with IR injury. CONCLUSIONS: Mel can alleviate myocardial IR injury in isolated rat hearts by inhibiting cardiac contracture, the mechanism of which may involve the upregulation of ATP in the cardiac myocytes to lessen the tear of membrane and reduce cell content leakage.


Assuntos
Coração , Melatonina , Contração Muscular , Traumatismo por Reperfusão Miocárdica , Animais , Coração/efeitos dos fármacos , Masculino , Melatonina/farmacologia , Melatonina/uso terapêutico , Contração Muscular/efeitos dos fármacos , Traumatismo por Reperfusão Miocárdica/tratamento farmacológico , Miócitos Cardíacos/efeitos dos fármacos , Ratos , Ratos Sprague-Dawley
14.
PLoS One ; 15(7): e0233988, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32615583

RESUMO

Light touch with an earth-fixed reference point improves balance during quite standing. In our current study, we implemented a paradigm to assess the effects of disrupting the right posterior parietal cortex on dynamic stabilization of body sway with and without Light Touch after a graded, unpredictable mechanical perturbation. We hypothesized that the benefit of Light Touch would be amplified in the more dynamic context of an external perturbation, reducing body sway and muscle activations before, at and after a perturbation. Furthermore, we expected sway stabilization would be impaired following disruption of the right Posterior Parietal Cortex as a result of increased postural stiffness. Thirteen young adults stood blindfolded in Tandem-Romberg stance on a force plate and were required either to keep light fingertip contact to an earth-fixed reference point or to stand without fingertip contact. During every trial, a robotic arm pushed a participant's right shoulder in medio-lateral direction. The testing consisted of 4 blocks before TMS stimulation and 8 blocks after, which alternated between Light Touch and No Touch conditions. In summary, we found a strong effect of Light Touch, which resulted in improved stability following a perturbation. Light Touch decreased the immediate sway response, steady state sway following re-stabilization, as well as muscle activity of the Tibialis Anterior. Furthermore, we saw gradual decrease of muscle activity over time, which indicates an adaptive process following exposure to repetitive trials of perturbations. We were not able to confirm our hypothesis that disruption of the rPPC leads to increased postural stiffness. However, after disruption of the rPPC, muscle activity of the Tibialis Anterior is decreased more compared to sham. We conclude that rPPC disruption enhanced the intra-session adaptation to the disturbing effects of the perturbation.


Assuntos
Lobo Parietal/fisiologia , Equilíbrio Postural/fisiologia , Tato/fisiologia , Adulto , Mapeamento Encefálico , Retroalimentação Sensorial , Feminino , Humanos , Masculino , Contração Muscular , Neuronavegação , Pressão , Estresse Mecânico , Estimulação Magnética Transcraniana , Adulto Jovem
15.
Nat Commun ; 11(1): 3711, 2020 07 24.
Artigo em Inglês | MEDLINE | ID: mdl-32709891

RESUMO

The skeletal muscle T-tubule is a specialized membrane domain essential for coordinated muscle contraction. However, in the absence of genetically tractable systems the mechanisms involved in T-tubule formation are unknown. Here, we use the optically transparent and genetically tractable zebrafish system to probe T-tubule development in vivo. By combining live imaging of transgenic markers with three-dimensional electron microscopy, we derive a four-dimensional quantitative model for T-tubule formation. To elucidate the mechanisms involved in T-tubule formation in vivo, we develop a quantitative screen for proteins that associate with and modulate early T-tubule formation, including an overexpression screen of the entire zebrafish Rab protein family. We propose an endocytic capture model involving firstly, formation of dynamic endocytic tubules at transient nucleation sites on the sarcolemma, secondly, stabilization by myofibrils/sarcoplasmic reticulum and finally, delivery of membrane from the recycling endosome and Golgi complex.


Assuntos
Contração Muscular/fisiologia , Proteínas Musculares/metabolismo , Músculo Esquelético/metabolismo , Músculo Esquelético/ultraestrutura , Sarcolema/fisiologia , Sarcolema/ultraestrutura , Animais , Canais de Cálcio/metabolismo , Canais de Cálcio/ultraestrutura , Canais de Cálcio Tipo L/metabolismo , Proteínas de Transporte/metabolismo , Biologia do Desenvolvimento , Complexo de Golgi/metabolismo , Masculino , Microscopia Eletrônica , Proteínas Musculares/química , Músculo Esquelético/química , Miofibrilas/metabolismo , Sarcolema/química , Retículo Sarcoplasmático/metabolismo , Peixe-Zebra
16.
Nat Commun ; 11(1): 3722, 2020 07 24.
Artigo em Inglês | MEDLINE | ID: mdl-32709902

RESUMO

Human movement occurs through contraction of the basic unit of the muscle cell, the sarcomere. Sarcomeres have long been considered to be arranged end-to-end in series along the length of the muscle into tube-like myofibrils with many individual, parallel myofibrils comprising the bulk of the muscle cell volume. Here, we demonstrate that striated muscle cells form a continuous myofibrillar matrix linked together by frequently branching sarcomeres. We find that all muscle cells contain highly connected myofibrillar networks though the frequency of sarcomere branching goes down from early to late postnatal development and is higher in slow-twitch than fast-twitch mature muscles. Moreover, we show that the myofibrillar matrix is united across the entire width of the muscle cell both at birth and in mature muscle. We propose that striated muscle force is generated by a singular, mesh-like myofibrillar network rather than many individual, parallel myofibrils.


Assuntos
Fenômenos Mecânicos , Músculo Esquelético/fisiologia , Miofibrilas/fisiologia , Sarcômeros/fisiologia , Animais , Feminino , Humanos , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Microscopia Eletrônica , Contração Muscular/fisiologia , Desenvolvimento Muscular , Músculo Esquelético/citologia , Miofibrilas/patologia , Sarcômeros/patologia
17.
PLoS One ; 15(7): e0235985, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32678865

RESUMO

Chronic constipation (CC) is one of the most common gastrointestinal disorders worldwide. Its pathogenesis, however, remains largely unclear. The purpose of the present work was to gain an insight into the role of contractility and microbiota in the etiology of CC. To this end, we studied spontaneous and evoked contractile activity of descending colon segments from patients that have undergone surgery for refractory forms of CC. The juxta-mucosal microbiota of these colon samples were characterized with culture-based and 16S rRNA sequencing techniques. In patients with CC the spontaneous colonic motility remained unchanged compared to the control group without dysfunction of intestinal motility. Moreover, contractions induced by potassium chloride and carbachol were increased in both circular and longitudinal colonic muscle strips, thus indicating preservation of contractile apparatus and increased sensitivity to cholinergic nerve stimulation in the constipated intestine. In the test group, the gut microbiota composition was assessed as being typically human, with four dominant bacterial phyla, namely Firmicutes, Bacteroidetes, Proteobacteria, and Actinobacteria, as well as usual representation of the most prevalent gut bacterial genera. Yet, significant inter-individual differences were revealed. The phylogenetic diversity of gut microbiota was not affected by age, sex, or colonic anatomy (dolichocolon, megacolon). The abundance of butyrate-producing genera Roseburia, Coprococcus, and Faecalibacterium was low, whereas conventional probiotic genera Lactobacillus and Bifidobacteria were not decreased in the gut microbiomes of the constipated patients. As evidenced by our study, specific microbial biomarkers for constipation state are absent. The results point to a probable role played by the overall gut microbiota at the functional level. To our knowledge, this is the first comprehensive characterization of CC pathogenesis, finding lack of disruption of motor activity of colonic smooth muscle cells and insufficiency of particular members of gut microbiota usually implicated in CC.


Assuntos
Colo/microbiologia , Colo/fisiopatologia , Constipação Intestinal/microbiologia , Constipação Intestinal/fisiopatologia , Microbioma Gastrointestinal , Contração Muscular , Adulto , Idoso , Doença Crônica , Classificação , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Adulto Jovem
18.
Am J Physiol Renal Physiol ; 319(2): F257-F283, 2020 08 01.
Artigo em Inglês | MEDLINE | ID: mdl-32628539

RESUMO

Urinary bladder smooth muscle (UBSM), also known as detrusor smooth muscle, forms the bladder wall and ultimately determines the two main attributes of the organ: urine storage and voiding. The two functions are facilitated by UBSM relaxation and contraction, respectively, which depend on UBSM excitability shaped by multiple ion channels. In this review, we summarize the current understanding of key ion channels establishing and regulating UBSM excitability and contractility. They include excitation-enhancing voltage-gated Ca2+ (Cav) and transient receptor potential channels, excitation-reducing K+ channels, and still poorly understood Cl- channels. Dynamic interplay among UBSM ion channels determines the overall level of Cav channel activity. The net Ca2+ influx via Cav channels increases global intracellular Ca2+ concentration, which subsequently triggers UBSM contractility. Here, for each ion channel type, we describe UBSM tissue/cell expression (mRNA and protein) profiles and their role in regulating excitability and contractility of UBSM in various animal species, including the mouse, rat, and guinea pig, and, most importantly, humans. The currently available data reveal certain interspecies differences, which complicate the translational value of published animal research results to humans. This review highlights recent developments, findings on genetic knockout models, pharmacological data, reports on UBSM ion channel dysfunction in animal bladder disease models, and the very limited human studies currently available. Among all gaps in present-day knowledge, the unknowns on expression and functional roles for ion channels determined directly in human UBSM tissues and cells under both normal and disease conditions remain key hurdles in the field.


Assuntos
Canais Iônicos/metabolismo , Músculo Liso/metabolismo , Miócitos de Músculo Liso/metabolismo , Bexiga Urinária/metabolismo , Animais , Humanos , Canais de Potássio Ativados por Cálcio de Condutância Alta/metabolismo , Contração Muscular/fisiologia
19.
Am J Physiol Regul Integr Comp Physiol ; 319(3): R296-R314, 2020 09 01.
Artigo em Inglês | MEDLINE | ID: mdl-32697655

RESUMO

The present study aimed to simultaneously examine the age-related, muscle-specific, sex-specific, and contractile mode-specific changes in isolated mouse skeletal muscle function and morphology across multiple ages. Measurements of mammalian muscle morphology, isometric force and stress (force/cross-sectional area), absolute and normalized (power/muscle mass) work-loop power across a range of contractile velocities, fatigue resistance, and myosin heavy chain (MHC) isoform concentration were measured in 232 isolated mouse (CD-1) soleus, extensor digitorum longus (EDL), and diaphragm from male and female animals aged 3, 10, 30, 52, and 78 wk. Aging resulted in increased body mass and increased soleus and EDL muscle mass, with atrophy only present for female EDL by 78 wk despite no change in MHC isoform concentration. Absolute force and power output increased up to 52 wk and to a higher level for males. A 23-36% loss of isometric stress exceeded the 14-27% loss of power normalized to muscle mass between 10 wk and 52 wk, although the loss of normalized power between 52 and 78 wk continued without further changes in stress (P > 0.23). Males had lower power normalized to muscle mass than females by 78 wk, with the greatest decline observed for male soleus. Aging did not cause a shift toward slower contractile characteristics, with reduced fatigue resistance observed in male EDL and female diaphragm. Our findings show that the loss of muscle quality precedes the loss of absolute performance as CD-1 mice age, with the greatest effect seen in male soleus, and in most instances without muscle atrophy or an alteration in MHC isoforms.


Assuntos
Envelhecimento/fisiologia , Contração Muscular/fisiologia , Músculo Esquelético/fisiologia , Atrofia Muscular/fisiopatologia , Animais , Diafragma/fisiopatologia , Camundongos , Fadiga Muscular/fisiologia , Doenças Musculares/fisiopatologia
20.
Am J Physiol Regul Integr Comp Physiol ; 319(3): R358-R365, 2020 09 01.
Artigo em Inglês | MEDLINE | ID: mdl-32726156

RESUMO

Studies have shown that early-stage type 1 diabetes mellitus (T1DM) leads to an exaggerated reflex pressor response to both static muscle contraction and tendon stretch. However, whether similar responses are present during dynamic exercise (i.e., intermittent contraction) is not known. Therefore, the purpose of this study was to determine whether T1DM leads to an exaggerated reflex pressor response to intermittent muscle contraction. We measured the exercise pressor reflex in unanesthetized, decerebrated T1DM (50 mg/kg streptozotocin; STZ) and healthy control (CTL) Sprague-Dawley rats by intermittently contracting the hindlimb muscles for 30 s while measuring mean arterial pressure (MAP), renal sympathetic nerve activity (RSNA), and heart rate (HR). Intermittently contracting the hindlimb muscles evoked exaggerated mean RSNA (STZ: Δ109 ± 21%, n = 4 rats; CTL: Δ61 ± 8%, n = 5 rats, P < 0.05), peak MAP (STZ: Δ32 ± 2 mmHg, n = 9 rats; CTL: Δ12 ± 2 mmHg, n = 6 rats, P < 0.05), blood pressure index (STZ: Δ625 ± 60 mmHg/s, n = 9 rats; CTL: Δ241 ± 46 mmHg/s, n = 6 rats, P < 0.05), and HR (STZ: Δ24 ± 3 beats/min, n = 9 rats; CTL: Δ9 ± 3 beats/min, n = 6 rats, P < 0.05) responses to similar developed tensions (P > 0.05) in T1DM compared with CTL rats. T1DM rats also exhibited exaggerated early-onset sympathetic (onset: 1 s) and pressor (onset: 5 s) responses. These data show that early-stage T1DM leads to an exaggerated pressor reflex evoked by intermittent muscle contraction. The early onset and greater blood pressure index suggest that cardiovascular strain during dynamic exercise may be significantly higher in individuals with T1DM.NEW & NOTEWORTHY This is the first study to provide evidence that early-stage type 1 diabetes mellitus (T1DM) leads to an exaggerated exercise pressor reflex evoked by intermittent muscle contraction, resulting in substantially higher cardiovascular strain. These findings are significant as they indicate that interventions targeting the exercise pressor reflex may work to alleviate the increased cardiovascular strain and overall burden during exercise in T1DM.


Assuntos
Fenômenos Fisiológicos Cardiovasculares , Diabetes Mellitus Tipo 1/fisiopatologia , Contração Muscular/fisiologia , Músculo Esquelético/fisiologia , Condicionamento Físico Animal/fisiologia , Animais , Sistema Cardiovascular , Ratos Sprague-Dawley , Reflexo/fisiologia , Sistema Nervoso Simpático/fisiopatologia
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA