Spatial heterogeneity in the muscle functional MRI signal intensity time course: effect of exercise intensity

It has previously been observed that during isometric dorsiflexion exercise, the time course of T2-weighted signal intensity (SI) changes is spatially heterogeneous. The purpose of this study was to test the hypothesis that this spatial heterogeneity would increase at higher contraction intensities. Eight subjects performed 90-s isometric dorsiflexion contractions at 30% and 60% of maximum voluntary contraction (MVC) while T2-weighted (repetition time/echo time=4000/35 ms) images were acquired. SI was measured before, during and after the contractions in regions of interest (ROIs) in the extensor digitorum longus (EDL) muscle and the deep and superficial compartments of the tibialis anterior (D-TA and S-TA, respectively). For all ROIs at 30% MVC, SI changes were similar. The maximum postcontraction SI was greater than the SI during exercise. At 60% MVC, SI changes during contraction were greater in the S-TA than in the D-TA and EDL. For the EDL and D-TA, the maximum postcontraction SI was greater than those during exercise. For the S-TA, the maximum postcontraction change was greater than the changes at t=8, 20 and 56 s but not the end-exercise value. We conclude that spatial heterogeneity increases during more intense dorsiflexion contractions, possibly reflecting regional differences in perfusion or neural activation of the muscle.     

Control of static pressure by expiratory muscles during expiratory effort and phonation

Surface electromyography (EMG) impulse frequency was measured in six subjects at eight recording sites on the chest and abdomen during the maintenance of positive mouth pressures and the phonation of a long vowel ([a:] in the Finnish word aamu) at three intensity levels. The pattern of muscle activation was similar in these two behavioral tasks. In upright posture, at lung volumes from 20% vital capacity (VC) below to 30% above functional residual capacity (FRC), EMG frequency increased rather linearly with increasing mouth pressure within 0 and 20 cm H₂O. A qualitatively similar relationship was observed between EMG frequency and phonation intensity. The results suggest that the expiratory effort task can be used as a model for the control of subglottal pressure during phonation at static subglottal pressures     

Length-tension relationship of the feline thyroarytenoid muscle

Vocal fold tension during phonation is generated by coordinated contraction of the intrinsic laryngeal muscles. The thyroarytenoid muscle has been found to have increased stiffness at various levels of strain when compared with other intrinsic laryngeal muscles. The objective here is to test the hypothesis that the thyroarytenoid muscle exhibits high passive tension during maximal isometric tetanic force generation, and to test the hypothesis that the thyroarytenoid maintains the ability to generate contractile force at high levels of strain more effectively than other skeletal muscle. The thyroarytenoid muscles (n=9) and digastric muscle strips (n=7) were removed from adult random-bred cats. Maximal isometric tension and passive tension at optimum length were measured from each muscle in vitro. Active and passive length-tension curves were constructed for each muscle. The contractile properties of the thyroarytenoid group were compared with those of the digastric muscle group. The thyroarytenoid muscle group required on average 140 mN of passive tension to generate maximal isometric tetanic tension. This represented 39% of the average maximal isometric tetanic tension generated by the muscles. These results were significantly higher than the digastric muscle group, which required on average 28 mN of passive tension (9% of maximal isometric tetanic tension, p<0.05). At 110% of optimum length, the thyroarytenoid muscle maintained 89.8% of maximal isometric tetanic force, whereas the digastric muscle group maintained 67.7% of maximal isometric tetanic force (p<0.05). The thyroarytenoid muscle exhibits higher passive tension when generating maximal isometric tension than the digastric muscle control group. The thyroarytenoid muscle maintains higher levels of active tension at high strain than the digastric muscle control group. We conclude that these findings are related to the ability of the thyroarytenoid muscle to function as a fine tensor of the vocal fold in a high strain environment.     

Simultaneous registration of Ca2+ transients and volume changes in rat mesangial cells: Evaluation of the effects of protein kinase C down-regulation

The intracellular free Ca²⁺ concentration ([Ca²⁺]_i) could be correlated with the contractile response in rat mesangial cells using an apparatus which measured both biochemical processes simultaneously. Long-term pretreatment of mesangial cells with 12-O-tetradecanoly-phorbol 13-acetate (24 h, 500 nM) increased the (20 nM) angiotensin II-induced mobilization of Ca²⁺ and led to an enhanced and sustained contraction of the cells. The contractile response was delayed by approximately 3.5 s with respect to the intracellular increase in Ca²⁺ concentration. The simultaneous registration of Ca²⁺ transients and cell contractions confirms that [Ca²⁺]_i is the major determinant of the angiotensin II-mediated mesangial cell contraction.Dedicated to Professor Horst H. A. Linde on the occasion of his 60th birthday.     

The Value of Laryngeal Electromyography in the Evaluation of Laryngeal Motion Abnormalities

SUMMARY: Laryngeal electromyography (EMG) functions routinely as a prognostic tool in the evaluation of vocal fold paralysis, as a guide for therapeutic injections into the laryngeal muscles, and more recently as an assessment tool in the evaluation of vocal fold paresis. This study investigates the clinical utility of laryngeal EMG as a diagnostic aid in the evaluation of movement disorders of the larynx in patients complaining of dysphonia. A retrospective chart review of all laryngeal EMGs performed at a tertiary laryngology referral center over a 13-month period was performed. All laryngeal EMGs were performed to evaluate laryngeal motion abnormalities in dysphonic patients. Thirty-seven laryngeal EMGs were completed during this study period. Analysis of the data revealed that the medical treatment plan changed as a result of findings on laryngeal EMG in 10/37 patients (27.0%); laryngeal EMG guided and/or confirmed the course of treatment in 12/37 patients (32.4%) and did not change the treatment plan in 15/37 patients (40.5%). Laryngeal EMG is a useful diagnostic tool that, in this study, contributed significantly to and helped guide the evaluation and management of motion disorders in the larynx of dysphonic patients.     

基于变分模态分解-传递熵的脑肌电信号耦合分析

皮层肌肉功能耦合是大脑皮层和肌肉组织间的相互作用, 脑肌电信号的多尺度耦合特征可以体现皮层-肌肉间多时空的功能联系. 本文引入变分模态分解并与传递熵结合, 构建变分模态分解-传递熵模型应用于脑肌间耦合研究. 首先基于变分模态分解将同步采集的脑电(EEG) 和肌电(EMG) 信号分别进行时频尺度化, 然后计算不同时频尺度间的传递熵值, 获取不同耦合方向(EEG→EMG 及EMG→EEG) 上不同尺度间的非线性耦合特征. 结果表明, 在静态握力输出条件下, 皮层与肌肉beta (15—35 Hz) 频段间的耦合强度最为显著; EEG→EMG 方向上脑电与肌电高gamma (50—72 Hz) 频段的耦合强度总体上高于EMG→EEG 方向.研究结果揭示皮层-肌肉功能耦合具有双向性, 且脑肌间不同耦合方向上、不同频段间的耦合强度有所差异.因此可利用变分模态分解-传递熵方法定量刻画大脑皮层与肌肉各时频段之间的非线性同步特征及功能联系.     

Contraction-induced cluster formation in cardiac cell culture

The evolution of the spatial arrangement of cells in a primary culture of cardiac tissue derived from newborn rats was studied experimentally over an extended period. It was found that cells attract each other spontaneously to form a clustered structure over the timescale of several days. These clusters exhibit spontaneous rhythmic contraction and have been confirmed to consist of cardiac muscle cells. The addition of a contraction inhibitor (2,3-butanedione-2-monoxime) to the culture medium resulted in the inhibition of both the spontaneous contractions exhibited by the cells as well as the formation of clusters. Furthermore, the formation of clusters is suppressed when high concentrations of collagen are used for coating the substratum to which the cells adhere. From these experimental observations, it was deduced that the cells are mechanically stressed by the tension associated with repeated contractions and that this results in the cells becoming compact and attracting each other, finally resulting in the formation of clusters. This process can be interpreted as modulation of a cellular network by the activity associated with contraction, which could be employed to control cellular networks by modifying the dynamics associated with the contractions in cardiac tissue culture.     

Effect of pulsed transcranial ultrasound stimulation at different number of tone-burst on cortico-muscular coupling

Background

Pulsed transcranial ultrasound stimulation (pTUS) can modulate the neuronal activity of motor cortex and elicit muscle contractions. Cortico-muscular coupling (CMC) can serve as a tool to identify interaction between the oscillatory activity of the motor cortex and effector muscle. This research aims to explore the neuromodulatory effect of low-intensity, pTUS with different number of tone burst to neural circuit of motor-control system by analyzing the coupling relationship between motor cortex and tail muscle in mouse. The motor cortex of mice was stimulated by pulsed transcranial ultrasound with different number of tone bursts (NTB?=?100 150 200 250 300). The local field potentials (LFPs) in tail motor cortex and electromyography (EMG) in tail muscles were recorded simultaneously during pTUS. The change of integral coupling strength between cortex and muscle was evaluated by mutual information (MI). The directional information interaction between them were analyzed by transfer entropy (TE).

Results

Almost all of the MI and TE values were significantly increased by pTUS. The results of MI showed that the CMC was significantly enhanced with the increase of NTB. The TE results showed the coupling strength of CMC in descending direction (from LFPs to EMG) was significantly higher than that in ascending direction (from EMG to LFPs) after stimulation. Furthermore, compared to NTB?=?100, the CMC in ascending direction were significantly enhanced when NTB?=?250, 300, and CMC in descending direction were significantly enhanced when NTB?=?200, 250, 300.

Conclusion

These results confirm that the CMC between motor cortex and the tail muscles in mouse could be altered by pTUS. And by increasing the NTB (i.e. sonication duration), the coupling strength within the cortico-muscular circuit could be increased, which might further influence the motor function of mice. It demonstrates that, using MI and TE method, the CMC could be used for quantitatively evaluating the effect of pTUS with different NTBs, which might provide a new insight into the effect of pTUS neuromodulation in motor cortex.

     

Relationships between Changes in Oxygenation during Exercise and Recovery in Trained Athletes

The purpose of this study was to investigate the relationships of rate of deoxygenation determined using near-infrared spectroscopy (NIRS) during isometric contraction exercise (Rate_deoxy) with maximal muscle strength, muscle thickness and muscle oxidative capacity of knee extensors in eight well-trained male athletes. The subjects performed sustained isometric extension at 30% and 50% of the maximal voluntary contraction (MVC) load for 10s and 30 repetitive maximal isokinetic knee extensions. Rate_deoxy in the final 5s of 30% MVC was negatively correlated with maximal muscle strength, muscle thickness of knee extensors and the half-time of deoxygenation recovery (T1/2) determined by NIRS after 30 repetitive maximal isokinetic contractions, defined as muscle oxidative capacity. The results suggest that Rate_deoxy during submaximai isometric contraction reflects muscle aerobic capacity.     

Comparison of MRI with EMG to study muscle activity associated with dynamic plantar flexion

This study compared magnetic resonance imaging (MRI) and surface electromyography (EMG) to evaluate the effect of knee angle upon plantar flexion activity in the triceps surae muscles [medial & lateral gastrocnemius (MG, LG) and the soleus (SOL)]. Two weight & height matched groups performed identical protocols, twelve (6M, 6F) in the MRI group, twelve (8M, 4F) in the EMG group. Subjects plantar flexed dynamically for 2 min at 25% of 1-repetition maximum voluntary contraction (1-RM). Exercise was performed with the knee extended (0 degrees flexion), flexed (90 degrees ), and partially flexed (45 degrees ). In the MRI group spin-echo images were acquired before and immediately following each exercise session. T(2) times, calculated at rest and after exercise by fitting the echoes to a monoexponential decay pattern with a least-squares algorithm, were compared with EMG data. In the EMG group a bipolar electrode was used to collect samples were from the MG, LG, SOL, and anterior tibialis (TA) during exercise at each knee angle, MRI also examined the peroneus (PER). At 0 degrees flexion MRI demonstrated a significant post-exercise T(2) increase in the MG (p < or = 0.001), LG (p < or = 0.001), and PER (p < or = 0.01), with no T(2) change in the SOL or TA. At 90 degrees flexion there was a significant T(2) increase in the SOL (p < or = 0.001) with no significant T(2) change in the MG, LG, PER, or TA. At 45 degrees T(2) increased significantly in the SOL (p < or = 0.001) and LG (p < or = 0.05), but not the MG, PER, or TA. EMG produced similar results with the exception that there was significant activity in the TA during the relaxation cycle of the 90 degrees protocol. We conclude that: 1) Soleus activity is measurable by MRI; and 2) MRI and EMG produce similar results from different physiological sources, and are therefore complementary tools for evaluating muscle activity.     

On the contraction of the W(001)-(1 × 1) surface using LEED intensity analysis

Three recent independent attempts at deducing the W(001)-(1 × 1) surface structure by LEED beam intensity analysis have yielded contractions of the topmost layer spacing of 6 ± 6%, 11 ± 2%, 4.4 ± 3% normal to the surface plane. We investigate possible reasons for the discrepancies by comparing published experimental and theoretical profiles of these workers as well as our own. Our main conclusions are that the direct comparison of experimental data of different investigators shows deviations which are comparable to the changes in the calculated profiles for various surface contractions. Also the deviations between calculated intensity profiles using different (but still realistic) assumed scatteting potentials are comparable to the changes in the calculated profiles for various surface contractions. The main uncertainty in the scattering potential is the choice between the Slater free electron exchange-correlation term (coefficient α = 1) or the Kohn-Sham version ($\text{α =}\text{2}\text{3}$) or a value in between. For tungsten the corrections due to relativistic atomic scattering must also be considered. These uncertainties in the calculated and experimental profiles lead to the conclusion that the surface layer contraction of W(001)-(1 × 1) is not known at the present time. To assess the potential of LEED in deducing surface structures of this type further comprehensive analyses are required where the uncertainties in the theoretical scattering potential are also examined.     

Kevlar纤维表面接枝改性及其稳定化

文章试图通过化学处理方法在Kevlar纤维表面引入活性基团,从而达到对Kevlar纤维进行表面接枝改性的目的。采用红外光谱分析甲苯-2,4-二异氰酸酯(TDI)接枝kevlar纤维的表面组成,用己内酰胺及聚乙二醇PEG(400)对接枝物进行封端稳定化处理;分析了不同n_TDI∶n_PEG值对其产物表面组成的影响。实验结果表明,当n_TDI∶n_PEG=1∶3时, 接枝后红外谱图在3 300 cm-1处的吸收峰强度有所减弱,而在1 700～1 720 cm-1处得到加强;当n_TDI∶n_PEG=1∶1和1∶2时,接枝后红外谱图在3 300及1 700～1 720 cm-1处的吸收峰强度基本相同。n_TDI∶n_PEG=1∶3时稳定化效果最佳。     

High-resolution strain analysis of the human heart with fast-DENSE.

Single breath-hold displacement data from the human heart were acquired with fast-DENSE (fast displacement encoding with stimulated echoes) during systolic contraction at 2.5 x 2.5 mm in-plane resolution. Encoding strengths of 0.86-1.60 mm/pi were utilized in order to extend the dynamic range of the phase measurements and minimize effects of physiologic and instrument noise. The noise level in strain measurements for both contraction and dilation corresponded to a strain value of 2.8%. In the human heart, strain analysis has sufficient resolution to reveal transmural variation across the left ventricular wall. Data processing required minimal user intervention and provided a rapid quantitative feedback. The intrinsic temporal integration of fast-DENSE achieves high accuracy at the expense of temporal resolution.     

The role of simulations in the study of thermoluminescence (TL)

The traffic of charge carriers in a luminescent material during its excitation by irradiation and during readout either in the measurement of thermoluminescence (TL) or optically stimulated luminescence (OSL) is governed by sets of coupled nonlinear differential equations. The analytical solution of these sets is usually not possible, and one can resort to one of two options. Some researchers preferred to make simplifying assumptions and thus got approximate solutions whereas others performed simulations by solving the simultaneous equations numerically. Each of these routes has its pitfalls. The simplifying assumptions, mainly the quasi-equilibrium assertion or the assumption that certain relations between the relevant parameters and functions hold, may be valid in certain ranges of the TL or OSL curve, and may cease to be valid, say at the high-temperature range in TL. Performing simulations using the numerical solution of the relevant set of equations may yield results which are accurate, but cannot be considered as being general because they depend on the specific choice of the parameters. Repeating the simulations with several sets of the physically plausible parameters would add credibility to the conclusions drawn. The combination of the two approaches is highly recommended, i.e, if similar results are found by approximations and simulations, the validity of the conclusions is strengthened. Evidently, the comparison of these theoretical results to experimental effects is essential. In the present work we consider the occurrence of unusually high and unusually low values of the activation energy and the effective frequency factor. In particular, we can simulate a recently discovered behavior of TL in LiF:Mg, Cu, P at the ultra-high dose range and get qualitatively the main elements of the experimentally found results.     

数字滤波方法在TDLAS逃逸氨检测中的选用

介绍了可调谐半导体激光吸收光谱技术(TDLAS)原理和实验系统,并对系统噪声进行了分析;以体积比浓度为90×10-6和30×10-6的NH₃为例,利用TDLAS系统采集了该浓度气体的二次谐波原始光谱。为改善光谱信号,分别用五种数字滤波方法对原始光谱进行了滤波处理比较,做了NH₃的浓度梯度实验并对浓度为20×10-6 NH₃进行了长时间监测实验。实验结果表明,算术平均-小波变换滤波相比其他方法更有效地对原始光谱信号进行了改善,提高了系统信噪比和信号平滑度,使系统浓度检测限由原来的10×10-6降低到1.25×10-6,信噪比提高了约14倍,为逃逸氨极低浓度检测提供了一种较为有效的数据预处理方法。     

Estimation and visualization of longitudinal muscle motion using ultrasonography: A feasibility study

Ultrasonography is a convenient and widely used technique to look into the longitudinal muscle motion as it is radiation-free and real-time. The motion of localized parts of the muscle, disclosed by ultrasonography, spatially reflects contraction activities of the corresponding muscles. However, little attention was paid to the estimation of longitudinal muscle motion, especially towards estimation of dense deformation field at different depths under the skin. Yet fewer studies on the visualization of such muscle motion or further clinical applications were reported in the literature. A primal–dual algorithm was used to estimate the motion of gastrocnemius muscle (GM) in longitudinal direction in this study. To provide insights into the rules of longitudinal muscle motion, we proposed a novel framework including motion estimation, visualization and quantitative analysis to interpret synchronous activities of collaborating muscles with spatial details. The proposed methods were evaluated on ultrasound image sequences, captured at a rate of 25 frames per second from eight healthy subjects. In order to estimate and visualize the GM motion in longitudinal direction, each subject was asked to perform isometric plantar flexion twice. Preliminary results show that the proposed visualization methods provide both spatial and temporal details and they are helpful to study muscle contractions. One of the proposed quantitative measures was also tested on a patient with unilateral limb dysfunction caused by cerebral infarction. The measure revealed distinct patterns between the normal and the dysfunctional lower limb. The proposed framework and its associated quantitative measures could potentially be used to complement electromyography (EMG) and torque signals in functional assessment of skeletal muscles.     

The anxiolytic effects of midazolam during anticipation to pain revealed using fMRI

BACKGROUND AND PURPOSE: Functional neuroimaging can distinguish components of the pain experience associated with anticipation to pain from those associated with the experience of pain itself. Anticipation to pain is thought to increase the suffering of chronic pain patients. Inappropriate anxiety, of which anticipation is a component, is also a cause of disability. We present a pharmacological functional magnetic resonance imaging (fMRI) study in which we investigate the selective modulation by midazolam of brain activity associated with anticipation to pain compared to pain itself. METHODS: Eight right-handed male volunteers underwent fMRI combined with a thermal pain conditioning paradigm and midazolam (30 mug/kg) or saline administration on different occasions, with order randomized across volunteers. Volunteers learned to associate a colored light with either painful, hot stimulation or nonpainful, warm stimulation to the back of the left hand. RESULTS: Comparison of the period during thermal stimulation (pain-warm) revealed a network of brain activity commonly associated with noxious stimulation, including activities in the anterior cingulate cortex (ACC), the bilateral insular cortices (anterior and posterior), the thalamus, S1, the motor cortex, the brainstem, the prefrontal cortex and the cerebellum. Comparison of the periods preceding thermal stimulation (anticipation to pain-anticipation to warm) revealed activity principally in the ACC, the contralateral anterior insular cortex and the ipsilateral S2/posterior insula. Detected by a region-of-interest analysis, midazolam reduced the activity associated specifically with anticipation to pain while controlling for anticipation to warm. This was most significant in the contralateral anterior insula (P<.05). There were no significant drug effects on the activity associated with pain itself. CONCLUSION: In identifying a pharmacological effect on activity preceding but not during pain, we have successfully demonstrated an fMRI assay that can be used to study the action of anxiolytic agents in a relatively small cohort of humans.     

Active and passive characteristics of the canine cricothyroid muscles

Active and passive characteristics of the canine cricothyroid muscle were investigated through a series of experiments conducted in vitro and compared with their counterparts in the thyroarytenoid muscle. Samples from separate portions of canine cricothyroid muscle, namely, the pars recta and pars obliqua, were dissected from dog larynges excised a few minutes before death and kept in Krebs-Ringer solution at a temperature of 37°C ± 1° C and a pH of 7.4 ± 0.05. Active tetanic stress was obtained in isometric and isotonic conditions by applying field stimulation to the muscle samples through a pair of parallel-plate platinum electrodes and using a train of square pulses of 0.1-ms duration and 85-V amplitude. Force and elongation of the samples were obtained electronically with a dual-servo system (ergometer). The results indicate that the dynamic response of the canine cricothyroid muscle is almost twice as slow as that of the thyroarytenoid muscle. The average 50% tetanic contraction times for pars recta and pars obliqua were 84 ms and 109 ms, respectively, in comparison to 50 ms for thyroarytenoid. The examination of force-velocity response of this muscle indicates a maximum shortening velocity of 2 to 3 times its length per second, which is about half of the thyroarytenoid shortening speed. The passive properties of the pars recta and pars obliqua portions are similar to those of thyroarytenoid muscle.     

The Progress of the Gait Impairment and Brain Activation in a Patient with Post-stroke Hemidystonia

Objective: We explore the effects of body weight-supported (BWS) treadmill training, including the change of cortical activation, on a patient with post-stroke hemidystonia. Patient: The patient was a 71-year-old man with left thalamus hemorrhage. His motor symptoms indicated slight impairment. There was no overactive muscle contraction in the supine, sitting, or standing positions. During his gait, the right initial contact was the forefoot, and his right knee showed an extension thrust pattern. These symptoms suggested that he had post-stroke hemidystonia. Methods: The patient performed BWS treadmill training 14 times over 3 weeks. The effects of the BWS training were assessed by a step-length analysis, electromyography and functional magnetic resonance imaging (fMRI). Results: The patient''s nonparetic step length was extended significantly in the Inter-BWS (p<0.001) and Post-BWS (p=0.025) periods compared to the Pre-BWS session. The excessive muscle activity of the right gastrocnemius medialis in the swing phase was decreased at the Inter-BWS, Post-BWS, and follow-up compared to the Pre-BWS session. The peak timing difference of the bilateral tibialis anterior muscle became significant (p<0.05) on the first day of the intervention. The fMRI revealed that the cortical areas activated by the motor task converged through the intervention (p<0.05, family-wise error corrected). Conclusion: These results suggest that there was improvement of the patient''s symptoms of post-stroke hemidystonia due to changes in the brain activity during voluntary movement after BWS intervention. Body weight-supported treadmill training may thus be an effective treatment for patients with poststroke hemidystonia.     

基于多尺度传递熵的脑肌电信号耦合分析

神经运动控制中脑肌电同步特征可以反映皮层与肌肉之间的功能联系. 为定量研究脑电和肌电信号在不同时间尺度上的同步耦合特征, 提出多尺度传递熵方法实现静态握力输出下的脑肌电耦合分析: 对同步采集的头皮脑电信号(EEG) 和表面肌电信号(EMG)进行多尺度化, 计算不同尺度因子下EEG与EMG间的传递熵值, 获取不同耦合方向(EEG→EMG及EMG→EEG)上的非线性脑肌电耦合特征; 进一步计算功能频段下的显著性面积指标, 定量分析不同尺度下皮层肌肉功能耦合强度的差异. 分析结果显示, 静态握力输出时beta频段(15–35 Hz)皮层肌肉功能耦合特征显著, 且beta2频段(25–35 Hz)在不同尺度上EEG→EMG方向的耦合强度大于EMG→EEG方向, 耦合强度最大值和方向间耦合强度差异显著值均出现于较高时间尺度. 研究结果揭示: 皮层肌肉功能耦合具有双向性, 且耦合强度在不同时间尺度和不同功能频段上有所差异, 可利用多尺度传递熵定量刻画大脑皮层与肌肉之间的非线性同步特征及功能联系.