人体神经定量电流感觉检测系统的研制

电流感觉阈值测试是人体神经感觉功能的定量感觉测试方法的一种．它采用特定频率的正弦恒电流刺激人体神经末梢感受器，检测人体对电流刺激的最小感受量，用于定量评估神经功能。本文回顾了国际上电流感觉阈值测试技术的发展与现状，介绍了我们开发的人体神经定量电流感觉检测系统。该系统采用生理心理统计算法过滤人体主观感受的影响，具有双盲全自动测量功能，测量结果具有很好的重复性。     

Ia Afferent input alters the recruitment thresholds and firing rates of single human motor units

Vibration of the patellar tendon recruits motor units in the knee extensors via excitation of muscle spindles and subsequent Ia afferent input to the α-motoneuron pool. Our first purpose was to determine if the recruitment threshold and firing rate of the same motor unit differed when recruited involuntarily via reflex or voluntarily via descending spinal pathways. Although Ia input is excitatory to the α-motoneuron pool, it has also been shown paradoxically to inhibit itself. Our second purpose was to determine if vibration of the patellar tendon during a voluntary knee extension causes a change in the firing rate of already recruited motor units. In the first protocol, 10 subjects voluntarily reproduced the same isometric force profile of the knee extensors that was elicited by vibration of the patellar tendon. Single motor unit recordings from the vastus lateralis (VL) were obtained with tungsten microelectrodes and unitary behaviour was examined during both reflex and voluntary knee extensions. Recordings from 135 single motor units showed that both recruitment thresholds and firing rates were lower during reflex contractions. In the second protocol, 7 subjects maintained a voluntary knee extension at 30 N for approximately 40–45 s. Three bursts of patellar tendon vibration were superimposed at regular intervals throughout the contraction and changes in the firing rate of already recruited motor units were examined. A total of 35 motor units were recorded and each burst of superimposed vibration caused a momentary reduction in the firing rates and recruitment of additional units. Our data provide evidence that Ia input modulates the recruitment thresholds and firing rates of motor units providing more flexibility within the neuromuscular system to grade force at low levels of force production. Electronic Publication     

Effects of aerobic exercise conditioning at intensities corresponding to lactate threshold in the elderly

Summary In this study we attempted to determine the effects of exercise training at the intensity corresponding to lactate threshold (Th_la ^–) on various health-related variables in sedentary but apparently healthy elderly subjects. Six men and five women volunteers [mean age 68.9 (SD 3.4) years] performed supervised endurance-type training on stationary cycle ergometers for 30 min and recreational activities for 30 min, 3 days a week for 12 weeks. Four men and four women served as the control group [68.8 (SD 4.4) years]. As a result of the training programme, statistically significant increases in maximal oxygen consumption (10%), oxygen consumption at Th_la ^–(18%), distance covered in 12-min walk, side step, and leg extensor power were found in the training group, while no changes occurred in the control group. The changes in serum cholesterol and triglyceride concentrations from the pre- to post-training period were statistically significant. High-density lipoprotein cholesterol remained unchanged, and low-density lipoprotein cholesterol tended to decrease following the training programme. These data would indicate that exercise training at the intensity corresponding to Th_la ^–may have favourable effects on overall physical fitness and some serum lipid variables in older individuals.     

The Reliability of Arousal Threshold During Sleep

Thirty-five subjects from two independent studies were awakened at EEG-defined periods during the night with 1000 Hz ascending tone series. Awakenings were made five to eight times per night during stage 2, stage 4, or REM sleep over a series of nights in good and poor sleepers. Reliability was assessed within stage, within night, between stages, and between nights. Good and poor sleepers did not differ in either depth of sleep or reliability of arousal threshold and were thus pooled in the analyses. From night to night, the most consistency was seen in stage 4 (r=.74), although REM reliability (r?₁= .49) and stage 2 reliability (r?₁= .50 and r?₁= .69 in the two respective studies) estimates were also greater than zero. Early sleep onset and morning arousals were more variable. Reliability estimates on arousal thresholds taken within the same night for stage 2 were r= .64 and r?₁= .77 for the two studies and r= .96 for REM. The depth of sleep was not correlated with awake auditory threshold. It was concluded that five or six carefully placed arousals could give a good estimate of an individual's usual arousal threshold.     

Electrical stimulation of the gastrocnemius muscle in the spontaneously hypertensive rat increases the pain threshold: role of different serotonergic receptors

In a previous study, prolonged low-frequency muscle stimulation in the hind leg of the fully conscious spontaneously hypertensive rat (SHR) was shown to induce a long-lasting reduction of blood pressure. It was also shown that opioid and serotonergic (5-HT) systems were involved. More recently, we have shown that the 5-HT₁ receptors are involved in the post-stimulatory decrease in blood pressure. In the present study, the influence of this type of muscle stimulation on the pain threshold was investigated. Pain perception was measured as the squeak threshold to noxious electric pulses. After cessation of the stimulation, an analgesic response was elicited within 60 min and peak analgesia developed after 120 min, being 139 ±10% (P < 0.01) of the prestimulatory control value. The increased pain threshold lasted for another 2 h. One group of SHR was pretreated with PCPA, a serotonin synthesis blocker, which completely abolished the post-stimulatory analgesia. To analyse further the involvement of different serotonin systems, drugs with selective affinity for 5-HT receptors were used. In one group a prestimulatory dose of metitepine maleate (a 5-HT_1&2 receptor antagonist) abolished the post-stimulatory elevation of the pain threshold. The prolonged analgesic response was still present after prestimulatory treatment with ritanserin or ICS 205–930 (5-HT₂ and 5-HT₃ blocking agents respectively). In another group of experiments, the serotonin receptor antagonists were administered post-stimulation to animals with fully elicited analgesia. None of the antagonists used could reverse the elevation of pain threshold towards prestimulatory levels. Thus, intact 5-HT systems were necessary to elicit the analgesia to muscle stimulation and the response was mediated by the 5-HT₁ receptor. However, the results indicate that serotonin is not required to maintain the analgesia once it has been elicited.     

Active and inactive renin after exercise

Summary The effects of graded exercise on plasma concentrations of active and inactive renin were studied in seven healthy men. Exercise was performed on a cycle ergometer at four different exercise intensities (corresponding to 30%, 50%, 80% and 87% of ) for 10 min each. Concentrations of active renin and total renin after activation by trypsin were measured by direct immunoradiometric assay. Non-trypsin-activated renin concentration (inactive) was obtained by subtraction. Active renin concentrations at 30%, 50%, 80% and 87% of were 1.2, 1.9, 3.1 and 4.6 times higher than the control concentration, respectively. Similar increases in plasma renin concentration, determined by conventional enzymatic assay, were observed at every stage. In contrast, changes in inactive renin concentration were not significant at any stage. Significant increases in noradrenaline concentration were found at every exercise stage, but adrenaline, aldosterone and lactate concentrations were significantly elevated only after exercise at 50%, 80% and 87% of . The similarity between the changes in concentration of active renin and noradrenaline would suggest that sympathetic nerve activity may have been responsible either for the release of active renin or for the conversion of inactive renin to its active form in the kidney.     

脑室注射促甲状腺素释放激素对电针镇痛及脑内亮氨酸脑啡肽含量的影响

实验用大鼠76只,用辐射热-甩尾法测痛,以电针后痛阈变化的百分率评价镇痛效应;用放射免疫分析法测定脑内L-Enk含量。发现脑室注入三肽-促甲状腺素释放激素(TRH)后,能显著降低电针镇痛效果;提高丘脑内L-Enk含量,但痛阈与脑内L-Enk含量的变化无相关关系。本文证明,TRH在电针镇痛过程中是对抗作用。已知针刺镇痛与脑内多种神经质和肽类有关,在不利于针刺镇痛的因素中,TRH是新添的“一员”。     

蠕变局部损伤开裂的有限元模型

建立了蠕变局部损伤法模型,并给出单元进入损伤态的判据和失效的临界拉伸应变条件,局部蠕变损伤理论的实质就是试样是多种不同蠕变性能材料的统一,并由蠕变应力再分布得到证实,应用有限元对双缺口圆试样作了蠕变局部损伤分析,启裂时间和断裂蠕变应变值均与实验结果相吻合。