Role of the α- and β-adrenergic systems in the regulation of heat production by shivering in cats

Experiments on cats in which adrenergic drugs (phenylephrine, phentolamine, isoproterenol, and propranolol) were injected into the lateral ventricle showed that -adrenergic receptors are included in the system activating cold shivering and -adrenergic receptors in the system inhibiting it.Laboratory of Neurophysiology of Thermoreception and Heat Exchange, O. V. Kuusinen University, Petrozavodsk. (Presented by Academician of the Academy of Medical Sciences of the USSR P. N. Veselkin.) Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 84, No. 8, pp. 133–135, August, 1977.     

Control of shivering and heart rate in incubating bantam hens upon sudden exposure to cold eggs

To distinguish shivering released by cooling of the brood patch from shivering released by low core temperature, incubating bantam hens were exposed to water perfused eggs. Responses to a period of egg cooling were compared to the recovery period after egg temperature had been returned to 40 ^oC, but cloacal temperature (T_b) still was low. At an ambient temperature (T_a) of 23 ^oC and exposure of the hens to between two and eight eggs cooled to 10–35 ^oC (series 1), electromyographic (EMG) activity of musculus iliotibialis increased rapidly with an occasional overshoot, and was higher during egg cooling than during recovery. This hysteresis in EMG activity and T_b was weakly correlated to egg temperature and clutch size. Heart rate (HR) showed an almost parallel increased to shivering except that a maximum HR was reached at high shivering intensities. These responses were also present at a T_a of 37 ^oC when the hens were slightly hyperthermic before exposure to eight eggs at 20 ^oC (Series 2). At the highest starting T_bs EMG activity increased linearly after a drop in T_b. Shivering in m. pectoralis showed a lower threshold T_b and lower activity than m. iliotibialis during egg cooling, and immediately ceased at the end of egg cooling. Total body thermosensitivity estimated from the recovery periods at low and high T_a was –9.7 and –6.4 W kg^-1oC^-1, respectively. It is concluded that shivering in incubating birds warming cold eggs probably is stimulated both by peripheral and central thermoreceptors. The peripheral component shows phasic properties typical for skin receptors.     

基于伺服电机的上肢康复机器人力矩 交互控制系统

目的为了实现上肢康复机器人主动训练中力矩控制的精确性,设计一种基于伺服电机的上肢康复机器人力矩交互控制系统。方法首先利用三自由度中央驱动式上肢康复机器人实验平台建立由运动意图采集模块和伺服力矩控制模块组成的力矩交互系统;再通过建立上肢动力学模型提出上肢助力训练算法;最后通过力矩响应实验、运动意图检测实验。结果依据在一定电流输入范围内,输出力矩能够保持稳定,验证了基于直流伺服电机实现助力训练方法的可行性。采用伺服力矩控制模块在目标力矩设定后,输出力矩在1 ms时间内能够达到设定的目标值并能够保持稳定,目标力矩响应的实时性良好,由此可以得出力矩交互控制方法达到了人机力矩交互稳定的结果。结论采用上肢康复机器人力矩交互控制方法可以在主动训练中实现较为精确的力矩控制。     

Disinhibition of upper limb motor area by voluntary contraction of the lower limb muscle

It is well known that monosynaptic spinal reflexes and motor evoked potentials following transcranial magnetic stimulation (TMS) are reinforced during phasic and intensive voluntary contraction in the remote segment (remote effect). However, the remote effect on the cortical silent period (CSP) is less known. The purpose of the present study is to determine to what extent the CSP in the intrinsic hand muscle following TMS is modified by voluntary ankle dorsiflexion and to elucidate the origin of the modulation of CSP by the remote effect. CSP was recorded in the right first dorsal interosseous while subjects performed phasic dorsiflexion in the ipsilateral side under self-paced and reaction-time conditions. Modulation of the peripherally-induced silent period (PSP) induced by electrical stimulation of the ulnar nerve was also investigated under the same conditions. In addition, modulation of the CSP was investigated during ischemic nerve block of the lower limb and during application of vibration to the tibialis anterior tendon. The duration of CSP was significantly shortened by phasic dorsiflexion, and the extent of shortening was proportional to dorsiflexion force. Shortening of the CSP duration was also observed during tonic dorsiflexion. In contrast, the PSP duration following ulnar nerve stimulation was not altered during phasic dorsiflexion. Furthermore, the remote effect on the CSP duration was seen during ischemic nerve block of the lower limb and the pre-movement period in the reaction-time paradigm, but shortening of the CSP was not observed during tendon vibration. These findings suggest that phasic muscle contraction in the remote segment results in a decrease in intracortical inhibitory pathways to the corticospinal tract innervating the muscle involved in reflex testing and that the remote effect on the CSP is predominantly cortical in origin.     

Changes in muscle function in response to 10 days of lower limb unloading in humans

Force-generating capacity and electromyographic (EMG) activity of the knee extensor muscles were studied before and after short-term (10 d) unilateral lower limb unloading and during 4 days of recovery. Ten healthy males used crutches to prevent one of their lower limbs from weight-bearing while maintaining joint mobility as well as daily ambulatory activities. Knee extensor torque and quadriceps rectified EMG during maximal voluntary isometric contraction (MVC) was measured repeatedly before and after the intervention. Also, EMG at a fixed submaximal level (100 Nm; 30–45% MVC) and maximal angular velocity (AV_max), during unresisted knee extension, were assessed. Maximum torque decreased (P<0.05) by 13±8% in response to unloading while maximum EMG activity did not change after unloading or during recovery (P=0.35). Submaximum EMG increased (P<0.05) by 25±16% after unloading. Maximum and submaximum torque/EMG ratios decreased (P<0.05) after unloading. AV_max decreased (P<0.05) by 9±8% after unloading. The post value, however, was not different from that of the weight-bearing limb. Torque, EMG and AV_max were recovered (P>0.05) after 4 days of resumed weight-bearing. The pronounced decrease and the rapid recovery in maximum torque appears not to be attributed to a change in muscle mass alone. Because the findings of unchanged maximum EMG and increased EMG at a submaximal force level suggest no change in neural drive, we propose that unspecific tissue factors in part impair muscle function in response to short-term loss of weight-bearing activity. Results also indicate that recovery in muscle function after short-term unloading seems to be completed in a time span shorter than the period of preceding inactivity.     

Experimental muscle pain changes motor control strategies in dynamic contractions

This study investigated the effect of muscle pain on muscle activation strategies during dynamic exercises. Ten healthy volunteers performed cyclic elbow flexion/extension movements at maximum speed for 2 min after injection of (1) hypertonic (painful) saline in the biceps brachii, (2) hypertonic saline in both biceps brachii and triceps brachii, and (3) isotonic (nonpainful) saline in the biceps brachii muscle. Surface electromyographic (EMG) signals were collected from the upper trapezius, biceps brachii, triceps brachii, and brachioradialis muscles (to estimate EMG amplitude) and with an electrode arrays from biceps brachii (to estimate muscle fiber conduction velocity [CV]). In all conditions, the acceleration of the movement decreased throughout the exercise, and kinematic parameters were not altered by pain. With respect to the control condition, pain induced a decrease of the biceps brachii (mean ± SE, –23±4%) and brachioradialis (–10±0.4%) integrated EMG (IEMG) in the beginning of the exercise, and an increase (45±3.5%) of the upper trapezius IEMG at all time points during the exercise. The biceps brachii IEMG decreased over time during the nonpainful exercises (–11±0.6%) while it remained constant in the painful condition. Biceps brachii CV decreased during painful conditions (–12.8±2.2%) while it remained constant during the nonpainful condition. In conclusion, muscle pain changes the motor control strategy to sustain the required dynamic task both in the relative contribution between synergistic muscles and in the motor unit activation within the painful muscle. Such a changed motor strategy may be highly relevant in models of occupational musculoskeletal pain conditions.     

Comparison of shivering in man exposed to cold in water and in air

Summary Metabolic rate (M), mean skin temperature ( ) and rectal temperature (Tre) were studied during 2 h exposure to cold in the air (Ta=15–25°C) and in water . From the results, it was possible to draw tentative equations of the metabolic response in transient and steady state as functions of body temperatures: M_air=41,3–57.77 dTsk/dt-5.01 and M_water=M_air+984.15–23.79 Tre. These equations show an important difference between the two groups of experiments: in water, both and Tre are required, whereas suffices in air. This leads to discuss the usage of mean weighted skin temperature and rectal temperature to describe peripheral and central input respectively, specially on man in cold air, in the range of these experiments.     

Central and peripheral thermoreceptors. Comparative analysis of the effects of prolonged adaptation to cold and noradrenaline

This report presents results obtained from many years of study of the effects of prolonged adaptation to cold and noradrenaline on the spike activity of central hypothalamic and peripheral skin thermoreceptors. The involvement of the sympathetic nervous system in forming adaptive changes in the regulatory characteristics of temperature homeostasis and the significance of the various components of thermoreceptor activity to the formation of effector responses are discussed. The roles of different groups of thermoreceptors in forming temperature sensations are analyzed. __________ Translated from Rossiiskii Fiziologicheskii Zhurnal imeni I. M. Sechenova, Vol. 91, No. 12, pp. 1492–1503, December, 2005.     

Effects of blood pressure manipulations on shivering thermogenesis in the pigeon

The effects of blood pressure (BP) manipulations on shivering thennogenesis were studied in conscious pigeons. A rise in BP induced by noradrenaline (NA) or equipotent doses of angiotensin II (Ang 11) effectively suppressed shivering at +12°C and partly abolished the cold-induced vasoconstriction in the feet. The inhibition commenced when the rise in BP reached +40 nunHg, and a fall in body temperature followed these responses. Comparison of the trajectories in the BP-shivering plane revealed that the inhibition of shivering by Ang II could be completely explained by changes in BP, whereas NA had also another, more prolonged inhibitory action independent of baroreceptor activity. A similar dose-dependence for effects on BP and shivering could be established with both drugs. An acute reduction of BP by sodium nitroprusside had also a very potent inhibitory effect on shivering. In hypotensive pigeons elevation of BP with NA initially enhanced shivering, but when BP was raised beyond normal levels shivering was again suppressed. We conclude that both a ripe and a fall in BP can inhibit shivering in the pigeon, and that normal levels of BP facilitate shivering. NA inhibits shivering by more than one mechanism, but the initial effect is mediated through a baroreflexive action. The interactions of thermoregulatory and cardiovascular mechanisms suggest an integrated control of body temperature and circulation, which should be considered in experimental approaches to these homeostatic systems.     

脑瘫尖足患儿站立和行走中下肢肌肉的表面肌电图

文题释义：表面肌电图(surface lectromyography,SEMG)：是分析相关肌肉功能状况的一种无创性检查手段,可以客观评定静止或运动时肌肉的活动情况。在控制良好的情况下,肌电信号活动的变化在很大程度上能够定量反映肌肉功能状态、肌张力、肌力水平、多肌群协调性等肌肉的变化,对肌肉功能状况提供客观指标,对于肌肉相关疾病的康复设计、康复治疗,特别是疗效评定有着不可替代的重要作用。 平均振幅：是用来描述一段时间内肌电幅值的平均变化特征。一般认为与运动单位募集程度和兴奋节律的同步化有关,它间接反映肌肉收缩力大小。一定范围内,平均振幅与肌肉收缩过程中参与工作运动单位数量呈正比,反映了肌肉收缩强度的变化。 背景：在控制良好的情况下,肌电信号活动的变化在很大程度上能够定量反映肌肉功能状态、肌张力、肌力水平、多肌群协调性等肌肉的变化,对肌肉功能状况提供客观指标。 目的：探讨脑瘫尖足患儿站立和行走中下肢肌肉的表面肌电图变化。 方法：应用美国NORAXON公司生产的 TELEMYO 2400R G2表面肌电图遥测仪对20例脑瘫单侧尖足患儿在静止站立、常态行走下进行双下肢胫前肌、腓肠肌内侧的表面肌电测试。比较受试者尖足侧与对侧肌肉的肌电活动。研究方案经过了上海瑞金医院伦理委员会批准,所有受试者及监护人均签署了“知情同意书”。 结果与结论：①受试者静止站立和常态行走时,其尖足侧腓肠肌内侧的平均肌电振幅、平均肌电积分均低于对侧(P < 0.05);②受试者静止站立和常态行走时,其尖足侧胫前肌和腓肠肌内侧的平均频率、中位频率均高于对侧(P < 0.05);③结果说明,脑瘫患儿尖足侧胫前肌、腓肠肌内侧存在表面肌电图信号异常,脑瘫单侧尖足患儿下肢肌肉活动不均衡,提示表面肌电图对脑瘫患儿神经肌肉系统功能状态的评价具有实用价值。 ORCID: 0000-0001-8732-8452(许萍);0000-0001-9909-3355(梁雷超) 中国组织工程研究杂志出版内容重点：组织构建;骨细胞;软骨细胞;细胞培养;成纤维细胞;血管内皮细胞;骨质疏松;组织工程     

Changes in the probability of firing of motor units following electrical stimulation in human limb muscles

Changes in the probability of motor unit firing was studied in ten different muscles (six muscles in the upper extremity and four muscles in the lower extremity) of eleven healthy human subjects. The responses were elicited by the electrical stimulation of cutaneous or mixed nerves during weak voluntary contraction of the muscle studied, and were recorded by averaging the rectified surface electromyogram. In eight of the ten muscles, well-detectable, short and long latency excitatory phases were observed. The most constant and well-identified excitatory responses were observed in the first interosseus dorsalis muscle in the hand, and in the extensor digitorum brevis muscle in the foot. These two distal muscles seem to be the most useful muscles for routine determination of the short and long latency responses to cutaneous stimulation.     

The control of rapid limb movement in the cat II. Scaling of isometric force adjustments

Summary In the previous study it was shown that cats were capable of making rapid and accurate adjustments in the force they applied to a lever in accord with information provided by a compensatory display. In the present study, isometric responses were examined in greater detail to determine 1. if a general control policy (or model) governing responses of different magnitudes could be inferred from the relations among output parameters and 2. if the earliest output measures were scaled to the preceding sensory events.The force adjustments elicited by the sudden motion of the display showed a linear relation between the peak force and the peak of its first derivative, dF/dt. Similarly, the peak d²F/dt² was a linear function of dF/dt. By contrast, the times required to achieve the peak force and the peak dF/dt were largely independent of their magnitudes. These adjustments were produced by a burst of EMG activity in agonist muscles which coincided with the rising phase of dF/dt. The observations suggest that such motor outputs are determined by a pulse-step control policy. The amplitude of the pulse would control the rate of rise of dF/dt (and therefore also the peak force since the rising phase of dF/dt was of constant duration), and the step would control the level of the terminal steady state force.Both the peak force and the preceding peak dF/dt were highly correlated with the amplitude of the perturbation. Changes in display gain, which altered the required relation between input and output magnitudes, resulted in a gradual readjustment of the output parameters. It was concluded that the motor outputs were scaled from their inception to requirements dictated by the initial sensory information. The selection by the cat of the appropriate scaling function was contingent upon its previous experience with the device.     

Electrophysiological studies of muscles in the human upper limb: The biceps brachii

The biceps brachii (BB) belongs to elbow flexors. However, because the BB acts not only as the flexor, but also as a forearm supinator in humans, its activities are much different from those of the other flexors (the brachialis and brachioradialis: BR and BRR, respectively). The present paper describes unique characteristics of the BB that emerged from recent studies using electrophysiological techniques (i.e. electromyography (EMG), electrical neuromuscular stimulation (ENS), Hoffmann (H)-reflex and post-stimulus time-histogram (PSTH)) in normal human subjects. The EMG studies have shown reciprocal contractions between the BB and the other flexors during forearm pronation/supination movements. Comparisons of EMG activities of the flexors between the pronated and supinated positions of the forearm have indicated clear differences of contraction properties between the BB and the other flexors. The ENS studies have shown that reciprocal activation between the BB and BRR following stimulation can produce a motion of supination with maintenance of flexion. This finding supports the theory that the reciprocal contractions should occur to keep constant force in flexion for supporting weight below the elbow. Studies using H-reflex and PSTH techniques have shown neural connections, which are spinal reflex arcs modulating motoneuron excitabilities with excitatory and inhibitory inputs from low-threshold muscle afferent fibers, among muscles in the human upper limb. These studies have demonstrated inhibitory neural connections between the BB and BRR. Moreover it has been shown that the connections concerning the BB differ from those concerning the BRR. Several reports have shown differences in connections between humans and animals. Therefore, the BB in humans has been compared with that in animals.     

Effect of side dominance on myoelectric manifestations of muscle fatigue in the human upper trapezius muscle

The purpose of this study was to investigate whether differences in the peripheral and control properties of the neuromuscular system due to long-term preferential use, related to side dominance, affect postural muscles, such as the upper trapezius. Therefore, fatigability properties of the upper trapezius muscles of the dominant and non-dominant side were assessed. Surface EMG signals were detected from the upper trapezius muscles of both sides of nine right- and five left-handed subjects with adhesive linear electrode arrays consisting of eight contact points. Static constant force contractions with the arms 90° abducted were performed by the subjects while holding hand loads of 0 kg, 0.5 kg, and 1 kg. Surface EMG spectral and amplitude variables were computed from the recorded signals. EMG spectral variable rate of change (indicating fatigue) showed a statistically significant difference between the two sides, with the dominant side less fatigable than the non-dominant one. The observed differences held for both the right- and left-handed subject group. A possible explanation for the results is that long preferential use of one side with respect to the other leads to changes in muscle fiber membrane and control properties, in agreement with previous results on limb muscles.     

训练轨迹对上肢肌肉协同的影响

目的通过分析康复机器人辅助训练过程中沿不同轨迹运动的上肢肌肉协同特性,探究运动轨迹对上肢肌肉骨骼特性的影响,为康复机器人训练轨迹优化设计提供基础实验数据与指导。方法首先在末端牵引式康复机器人系统中设计3种上肢运动训练轨迹(L1为直线,L2为弧线,L3为半圆),然后采集12名健康志愿者在沿3种训练轨迹上肢运动过程中的表面肌电信号,并使用非负矩阵分解算法进行肌肉协同特性的获取,对不同轨迹组间肌肉协同结构的相似系数、屈肌占比以及募集模式积分系数进行对比分析,探讨康复机器人不同训练轨迹对上肢肌肉骨骼特性的影响。结果同一训练轨迹中各志愿者的肌肉协同结构具有较高相似性(平均SI>0.81)。各轨迹组的肌肉协同结构中的屈肌占比随运动进程逐渐增加。各轨迹组的肌肉协同募集模式均具有时序特性,前期伸肌起主要作用,后期屈肌起主要作用,中期屈肌占比随轨迹曲率增加而增加。轨迹L1与L2、L2与L3协同结构非常相似(SI>0.90),而L1与L3协同结构较为相似(SI>0.75)。结论康复机器人辅助上肢的训练轨迹对上肢肌肉特性有一定影响,不同训练轨迹带来的肌肉协同结构较为相似,但是运动过程中屈肌群占比及协同贡献度会为了协调动作而发生变化。由此可推测不同训练轨迹对不同肌群的训练强度可能会有所不同。康复机器人训练轨迹设计需根据康复需求进行优化设计。     

The effect of rate of cooling,time of day and light regime on the shivering response in rabbits

In man hypothermia exists when core temperature (T_e) falls below 35 °C. The onset of hypothermia is often insidious in that it can occur without any particular symptoms of serious discomfort. There is evidence that this decrease in thermosensitivity is most likely to occur when the rate of body cooling is slow. In addition there is some evidence that the susceptibility to become hypothermic varies with the circadian rhythm of T_e, particularly in animals maintained under constant light conditions. A systematic investigation has been carried out to determine whether the thermoregulatory response to body core cooling is affected by the rate of change of body temperature, the time of day at which the cooling takes place and/or by the light regime under which the animals are maintained. The investigation was made in rabbits maintained either under a 12-h light/dark (LD) cycle or under conditions of continuous light (LL). Thermosensitivity (relationship between falling T_e and the induced increase in metabolic heat production) was determined at two different rates of body cooling (1 °C decrease in core temperature in either 30 or 160 min.) and at different times of the day. A chronically implanted intravascular heat exchanger was used to extract heat from the animals. The results indicate that neither the rate of body cooling nor the time of day at which the cooling took place had any clear effect on the shivering response. Likewise there was no clear difference in the shivering response of the animals maintained under (LD) conditions as compared to those maintained under (LL) conditions.     

Effect of quadriceps contraction on upper limb position sense errors in humans

Short-length muscle contraction (hold-short conditioning) causes limb position sense errors after the muscle returns to its intermediate length; this is due to intrafusal muscle thixotropy, which raises the muscle spindle sensitivity. In humans, contraction of muscles in the upper body (referred to as the Jendrassik manoeuvre) reinforces tendon reflexes in the lower limbs. However, it is unclear whether such a reinforcement manoeuvre enhances thixotropic position sense errors. We studied the effect of quadriceps contraction on upper limb position sense errors induced by hold-short conditioning of the biceps in 12 healthy men. Quadriceps contraction increased the tonic vibration reflex of the biceps, suggesting that quadriceps contraction has a reinforcing effect similar to that of the Jendrassik manoeuvre. After hold-short conditioning of the right biceps, subjects perceived that the conditioned forearm was placed in a more extended position than it actually was. Such position sense errors were enhanced during quadriceps contraction and the degree of error was increased with the intensity of the quadriceps contraction. These results suggest that limb position sense is affected by remote muscle contraction.     

Muscle metaboreflex control of the circulation during exercise

This review covers the control of blood pressure, cardiac output and muscle blood flow by the muscle metaboreflex which involves chemically sensitive nerves located in muscle parenchyma activated by metabolites accumulating in the muscle during contraction. The efferent response to metaboreflex activation is an increase in sympathetic nerve activity that constricts the systemic vasculature and also evokes parallel inotropic and chronotropic effects on the heart to increase cardiac output. The metaboreflex elicits a significant blood pressure elevating response during exercise and functions to redistribute blood flow and blood volume. Regional specificity in the efferent response to the metaboreflex activated from either the leg or the arm is seen in the balance between signals for vasoconstriction to curtail blood flow and signals to increase cardiac output. The metaboreflex has dual functions. It can both elevate and decrease muscle blood flow depending on (1) the intensity and mode of contraction, (2) the limb in which the reflex is evoked, (3) the strength of the signal defined by the muscle mass, (4) the extent to which blood flow is redistributed from inactive vascular beds to increase central blood volume and (5) the extent to which cardiac output can be increased.