The myoelectrical activity of the gastroduodenal area in ulcer formation due to serotonin

The effects of prolonged subcutaneous administration of serotonin on the myoelectric activity of the gastroduodenal junction were investigated in conscious rabbits. Serotonin produced the duodenogastric discoordination by increasing duodenal activity and decreasing the activity of stomach and pylorus. This discoordination resulted in gastric ulceration. Atropine prevented both duodenogastric discoordination and ulceration. These results indicate that serotonin ulceration is related to duodenogastric discoordination.     

Effects of propranolol on the gastroduodenal myoelectrical activity]

The effects of propranolol on the myoelectrical activity of the stomach, pylorus and duodenum were investigated in chronic experiments on rabbits. During the first phase of propranolol action a positive gastro-chronotropic effect was accompanied by a negative cardio-chronotropic effect. The gastro-chronotropic effect was 3 times higher than cardio-chronotropic one. The second phase of the propranolol effect manifested with periodical fluctuation of the gastroduodenal myoelectrical activity during stable bradycardia. Marked reactivity of the gastro-duodenum and periodical fluctuation of its activity are evidence of vital importance of the autoregulation mechanisms for gastroduodenal myoelectric activity.     

The mechanism of the duodenal motility strengthening under psychogenic stress in rabbits

In experiments on unanaesthetized rabbits, myoelectric activity (contractile activity index) of two sites of duodenum and of antral and pyloric parts of the stomach was studied under stress induced by fastening a rabbit to a table in supine position. In both sites of duodenum, the stress impact induced a short-time inhibition of contractile activity which was followed by its strengthening that exceeded the initial level. Meanwhile in antrum and pylorus, the whole period of stress impact was characterized by suppression of contractile activity, the latter being more pronounced in the antrum. The strengthening of the duodenal contractile activity was preserved after muscarinic ornicotinic cholinoceptor blockade. It was concluded that the contractile response of duodenum seemed to be of humoral origin.     

Neuromedin-N inhibits migrating myoelectric complex and induces irregular spiking in the small intestine of rats; comparison with neurotensin.

The effects of neuromedin-N on migrating myoelectric complexes in the small intestine of rats were studied. As neuromedin-N and neurotensin are structurally related peptides a comparison with neurotensin was made. Myoelectric activity was recorded by means of three bipolar electrodes implanted into the wall of the small intestine at 5, 15 and 25 cm distal to the pylorus. The peptides were administered as intravenous infusions to fasted conscious rats. Neuromedin-N at doses of 100-800 pmol kg-1 min-1 caused a dose-dependent disruption of the migrating myoelectric complexes and induced irregular spiking activity (n = 7, P less than 0.05). Neurotensin induced a similar response, but at doses of 1.0-8.0 pmol kg-1 min-1 (n = 5, P less than 0.05). Thus, on a molar basis, neuromedin-N appeared to be about 100-times less potent than neurotensin. Hexamethonium (20 mg kg-1 i.v.) inhibited the migrating motor complexes and induced quiescence, but did not block the effect of neuromedin-N at a dose of 800 pmol kg-1 min-1. Atropine (1 mg kg-1 i.v.) and mepyramine (2 mg kg-1 i.v.) did not affect the migrating motor complexes, nor did they block the effect of neuromedin-N. Simultaneous infusion of neuromedin-N and neurotensin in a 1:1 molar ratio at doses of 2 pmol kg-1 min-1 showed inhibition of the response to neurotensin in eight out of ten experiments. In conclusion, neuromedin-N changes the myoelectric activity in the small intestine from a fasting to a fed pattern.(ABSTRACT TRUNCATED AT 250 WORDS)     

On the mechanism of gastroduodenal motility inhibition under psychogenic stress in rabbits

In experiments on unanaesthetized rabbits, myoelectric activity (contractile activity index) in antral and pyloric parts of the stomach and in two sites of proximal duodenum was studied under stress induced by fastening rabbit to a table in supine position. The stressor impact induced inhibition of contractile activity in antrum and pylorus. The duodenal contractile activity after initial complete suppression overshot its initial level. Blockade of beta1/beta2-adrenoceptor with propranolol and blockade of alpha2-adrenoceptor with yohimbine did not influence qualitatively the pattern of the stressor responses of antrum and pylorus, and of the postpyloric part of duodenum. In conditions of unselective blockade of alpha-adrenoceptor with dihydroergotoxin there was no initial complete inhibition of duodenal contractile activity, and its strengthening was more expressed than in the control experiments. The received data indicate that the stressor inhibition of antral and pyloric contractile activity possibly results from activation of non-adrenergic inhibitory neurons of the enteric nervous system. The initial short-term suppression of duodenal motility resulted from its "adrenergic" inhibition which can also be a factor limiting the manifestation of stimulating effect of the humoral agent on the duodenal motility. In the period after release of the animal, index of antral and pyloric contractile activity did not significantly differ from its initial level; after beta1/beta2-adrenoceptor blockade in antral and after alpha2-adrenoceptor blockade or nonselective alpha-blockade in antral and pyloric parts of the stomach, there was decrease of contractile activity compared with its initial level; after alpha2- or beta1/beta2-adrenoceptor blockade there was no poststressor exceeding of the initial level of the duodenal contractile activity, observed in the control experiments.     

Tachykinin-stimulated small bowel myoelectric pattern: sensitization by NO inhibition, reversal by neurokinin receptor blockade

Tachykinins stimulate motility whereas NO inhibits motility in the gastrointestinal tract. AIM: To investigate if inhibition of NO production sensitizes myoelectric activity to subthreshold doses of tachykinins in the small intestine of awake rats. METHODS: Rats were supplied with a venous catheter and bipolar electrodes at 5, 15 and 25 cm distal to pylorus for electromyography of small intestine. The motor responses were evaluated using pattern recognition. Substance P and neurokinin A dose-dependently stimulated gut motility, with neurokinin A being more potent than substance P. Therefore, neurokinin A was chosen and administered under baseline conditions and 45-60 min after N(omega)-nitro-L-arginine (L-NNA) 1 mg kg(-1), with or without pretreatment with L-arginine 300 mg kg(-1). In addition, myoelectric activity effects of neurokinin A in conjunction with L-NNA were studied before and after administration of the tachykinin receptor antagonists, SR140333 (NK1), SR48968 (NK2) and SR142801 (NK3), each at 2.5 mg kg(-1). RESULTS: Dose-finding studies verified 10 pmol kg(-1) min(-1) to be the threshold dose at which NKA caused phase II-like activity in a low percentage of experiments (12%, n=41). This dose was therefore used in combination with L-NNA for sensitization experiments of gut myoelectric activity. In experiments where NKA-induced no response, pretreatment with L-NNA led to phase II-like activity in 9 of 18 (50%, p<0.05) experiments. Co-administration of SR140333 and SR48968 abolished this effect. CONCLUSION: NO counteracts the stimulatory effect of tachykinins on small bowel myoelectric activity in the rat. Inhibition of the L-arginine/NO pathway sensitizes the gut to tachykinin-stimulated motor activity.     

NO在胆道加压引起的反射活动中的作用

向胆道加压至 4kPa ,可同时引起血压降低和Oddi括约肌 (SO)肌电活动减弱或消失 ,这总称为胆道加压反射 ,其中前者称为胆道 血压反射 ,后者称为胆道 SO反射。本实验应用 3 2只家兔观察一氧化氮 (NO)对胆道加压反射活动的影响。在静脉滴注去甲肾上腺素 4 μg/(kg·min)引起血压升高和SO肌电振幅增大的基础上 ,再行胆道加压至 4kPa ,仍同时引起血压降低和Oddi括约肌 (SO)肌电活动减弱 ;而在静脉注射NO合酶抑制剂NG 硝基 L 精氨酸 (L NNA) 10mg/kg引起血压升高和SO肌电振幅增大的基础上 ,再行胆道加压至 4kPa,全部动物胆道 血压反射受到完全抑制 ,即未出现血压降低反应 ;少数 ( 3 /8)动物胆道 SO反射受到完全抑制 ,多数 ( 5 /8)动物该反射受到明显抑制 (P <0 0 1)。向SO局部灌注L NNA ,只引起SO肌电振幅增大而不影响血压 ,在此基础上行胆道加压 ,对胆道 SO反射的影响与全身用药相似 ,对胆道 血压反射却无影响。这提示 ,这两种反射活动是相对独立的 ,是经不同传出途径和效应器实现的 ;且这两种反射都主要是通过NO介导的     

Myoelectric response of the small intestine to the orad presence of the tapeworm Hymenolepis diminuta.

During its 24-hr migratory cycle in the small intestine, Hymenolepis diminuta is located in the orad part of the small intestine during the early morning hours and then in the caudad part of the small intestine during the late afternoon and early evening. During the later period, tapeworm-induced alterations of interdigestive myoelectric activity, a correlate of smooth muscle contraction or intestinal motility, are most intense in the ileal region. The hypothesis tested was that the tapeworm-induced changes in intestinal motility are local responses of the intestine responding to the close proximity of the lumenally positioned tapeworm and to the nutritional state of the host. The small intestine was monitored before and for 20 days after infection using electrodes implanted on the serosa of the small intestine. Myoelectric recordings were analyzed for the frequency of the normal patterns of interdigestive myoelectric spiking patterns and the altered myoelectric spiking related to tapeworm infection. During the morning hours, when the tapeworms are situated in the orad small intestine, no changes were observed during the normal myoelectric pattern of the digestive phase in any region of the intestine. When examined after the conversion of the digestive to interdigestive phase of motility, only on day 10 postinfection was the interdigestive phase significantly altered. It was concluded that the presence of the tapeworm in the orad small intestine during the satiety stage of the rat causes no changes in the electric events of the small intestine, with the exception of day 10 postinfection. Because tapeworms in the orad small intestine do not induce the tapeworm-altered myoelectric activity observed in the afternoon and evening with caudally positioned tapeworms, tapeworm-altered motility is not simply a response of the small intestine to the local presence of the tapeworm.     

Myeloelectric complex of the small intestine and variations in the intestinal motility in sheep]

The motor pattern of the small intestine of the sheep fed ad libitum is characterized by the regular occurrence of myoelectric complexes comprising a phase of regular and irregular spiking activities. Each complex is propagated along the ovine small intestine at a mean velocity of 17 cm/min and originated on the duodenal bulb at 70-100 mn intervals. Reduction and increase in duration of the phase of irregular spiking activity of the complex occurred during fasting and overfeeding respectively. Reduction in spiking activity is paralleled by an increased velocity of propagation whilst a lower migration and a reduced number of the complexes are characteristic of overfeeding. It is concluded that duration, number and velocity of propagation of the myoelectric complexes are adaptative factors in changes of the intestinal flow rate.     

Hormonal component of the postprandial motility response of the proximal stomach in dogs

The motility of a proximal gastric pouch, that has been extinsically denervated by autotransplantation, has been studied in 4 dogs. In the same time, the electrical activity of the duodenum was recorded with AgAgCl electrodes. Recordings were made in the fasting state and after oral administration of 250 ml NaCl 154 mM solutions containing 15 kcal/kg of either glucose, peptides or lipids, or 3 X 5 kcal/kg of a mixture of these three nutrients. The results showed, in the fasting state, that a cyclic activity took place in the denervated gastric pouch corresponding to the myoelectric complex observed at the same time in the duodenum. After feeding the dogs with any nutrient solution, we observed: 1) a decrease in pouch pressure; 2) an interruption of the cyclic activity in both the pouch and duodenum. A fasting motility resumed simultaneously in both the pouch and duodenum. These results indicate that hormonal agents are involved in the motility of the proximal stomach as well as in the postprandial interruption of the myoelectric complex.     

十二指肠内胆盐对胃肌电和运动的影响及其神经...

Changes of gastric myoelectric fast wave, slow wave and gastric motility were studied after intraduodenal infusion of sodium taurocholate (ST) in an attempt to search the concerned neuromechanism. Frequency and total amplitude of the fast wave and slow wave of gastric myoelectric activity and of gastric contractile wave were recorded every five minutes before and after intraduodenal infusion of ST under the background action of various drugs. The frequency and amplitude were expressed in percentage change of the respective premedication value. After intraduodenal infusion of ST (n = 10) the frequency and the amplitude of fast wave and gastric contractile wave were suppressed. Blocking anesthesia of celiac plexus, reserpinization and intravenous infusion of carbachol could eliminate the inhibition induced by ST, which could be partly eliminated by intravenous infusion of propranolol but not affected by phentolamine at all. The results demonstrate that intraduodenal infusion of bile salt suppresses the fast wave of gastric myoelectric activity and gastric motility, most probably controlled by efferent sympathetic adrenergic fibres through beta-receptor.     

Task-specific recruitment of motor units for vibration damping

Vibrations occur within the soft tissues of the lower extremities due to the heel-strike impact during walking. Increases in muscle activity in the lower extremities result in increased damping to reduce this vibration. The myoelectric intensity spectra were compared using principal component analysis from the tibialis anterior and lateral gastrocnemius of 40 subjects walking with different shoe conditions. The soft insert condition resulted in a significant, simultaneous increase in muscle activity with a shift to higher myoelectric frequencies in the period 0-60 ms after heel-strike which is the period when the greater vibration damping occurred. These increases in myoelectric frequency match the spectral patterns which indicate increases in recruitment of faster motor units. It is concluded that fast motor units are recruited during the task of damping the soft-tissue resonance that occurs following heel-strike.     

P物质尾核微量注射抑制小鼠胃肌电活动和胃运动

本文观察了小鼠尾核微量注射Ｐ物质或乙酰胆碱对胃肌电和胃运动的ｍ影响;并初步探讨了两者作用的关系。用双极康铜导线引导胃窦部肌电;用水囊连接压力换能器记录胃窦部运动。上述信息经生物电放大器和载波放大器放大后,由四道记录仪描记曲线,同时输入微机进行采集、贮存和处理。计算出注药前后每分钟胃肌电快波、慢波和胃运动波的频率和总幅度的变化百分数。结果如下：尾核注射ＳＰ或ＡＣｈ胃电快波和胃运动呈明显的抑制效应。用     

The pancreatic polypeptide family and the migrating motor complex of the rat: differential effects in the duodenum and jejunum

AIM: To investigate the effects of members of the pancreatic polypeptide family on migrating myoelectric complexes in rats in vivo. METHODS: Rats were supplied with bipolar electrodes at 5 (duodenum), 15 and 25 cm (jejunum) distal to pylorus for electromyography. The natural ligands neuropeptide Y, pancreatic polypeptide, peptide YY1-36 and peptide YY3-36 were infused IV at doses of 0.5-400 pmol kg(-1) min(-1). The mechanisms of action were studied after pre-treatment with N(omega)-nitro-L-arginine (L-NNA) 1 mg kg(-1), guanethidine 3 mg kg(-1) and in bilaterally vagotomized animals. RESULTS: PP inhibited myoelectrical activity dose-dependently in both the duodenum (ED50 5.8 pmol kg(-1) min(-1)) and jejunum (2.6 pmol kg(-1) min(-1)). PYY1-36 and PYY3-36 also had inhibitory effect in the jejunum (4.4 and 130 pmol kg(-1) min(-1), respectively). PYY1-36 had no significant effect in the duodenum, whereas PYY3-36 stimulated myoelectrical activity at the highest doses. NPY was without effect. In the jejunum neither L-NNA, guanethidine or vagotomy had any significant influence on the inhibitory effects of PP, PYY1-36 and PYY3-36. In the duodenum, the effect of PP was inhibited by guanethidine, but not L-NNA or vagotomy. The stimulatory effect of PYY3-36 in the duodenum was blocked by L-NNA and vagotomy, whereas guanethidine was without effect. CONCLUSION: Peptides of the PP family modulate small bowel motility differentially. Whereas their general effect is inhibitory in the jejunum, the mixing duodenal compartment is stimulated by PYY3-36, suggested to reflect receptor distribution distinction in the gut. This implicates distribution of distinct receptors in the gut being activated by either peptide.     

Myoelectric signal processing for control of powered limb prostheses

Progress in myoelectric control technology has over the years been incremental, due in part to the alternating focus of the R&D between control methodology and device hardware. The technology has over the past 50 years or so moved from single muscle control of a single prosthesis function to muscle group activity control of multifunction prostheses. Central to these changes have been developments in the means of extracting information from the myoelectric signal. This paper gives an overview of the myoelectric signal processing challenge, a brief look at the challenge from an historical perspective, the state-of-the-art in myoelectric signal processing for prosthesis control, and an indication of where this field is heading. The paper demonstrates that considerable progress has been made in providing clients with useful and reliable myoelectric communication channels, and that exciting work and developments are on the horizon.     

胎儿胃肌间神经节胆碱能神经元的研究

本文采用胆碱乙酰转移酶（ＣｈＡＴ）和乙酰胆碱酯酶（ＡＣｈＥ）酶组织化学方法和显微图像分析技术对３２周～４０周胎儿胃底部、胃体部、胃窦部及胃幽门管部的肌间神经节内胆碱能神经元进行光镜定位定量观察。结果表明：胆碱能神经元的分布,细胞大小及酶活性在胃各部有所不同,胆碱能神经元数量由胃底至幽门管部逐渐递增;胃痛和胃体部以中小型神经元为主,胃窦和胃幽门管部以大中型神经元为主;胃各区酶活性强度不一,胃底部和胃体部酶活性显著高于胃幽门部,胃体部酶活性最强。提示胃各部的运动功能和代谢功能有所不同。     

The role of migrating myoelectric complexes in the regulation of digesta transport in the preruminant calf.

Four calves were equipped with an electromagnetic flow probe inside the transverse duodenum and with electrodes at intervals of 2 cm on either side of the probe. Amounts of 0.5, 2.0, 3.5, and 5.0 kg of whole milk were given according to a latin square design. Recordings of digesta flow and myoelectric activity were made during a 5.6-h period after feeding to quantify the influence of migrating myoelectric complexes on digesta flow through the transverse duodenum of preruminant calf under different levels of milk intake. Immediately after feeding, a phase of irregular spiking activity appeared; its length increasing linearly (p = 0.002) with the amount of milk fed. Increasing milk intake led to linear increases in duration (p = 0.001) and total electrical activity (p = 0.002) of the irregular activity phases, quadratic shortening of the quiescent phases (p = 0.021), and linear decrease (p = 0.006) in the numbers of migrating myoelectric complexes. Intermittent flows of digesta, each of them corresponding to a strong spike burst, appeared during irregular spiking activity phases. Augmentation of the milk ingested did not affect the volume of each gush of digesta but caused a cubic increase in the number of gushes (p = 0.023) and in the total volume of digesta (p = 0.009). These cubic effects implied that with increased intake of milk, the duodenum endeavoured to accelerate the flow of digesta in an attempt to return to an "empty state" in about the same time for all levels of milk consumed. This was achieved mainly through adjustments in the duration and activity of the irregular spiking activity phase.     

The effect of foot orthotics on myoelectric fatigue in the vastus lateralis during a simulated skier’s squat

Fatigue in the legs is a problem experienced by skiers. It has been suggested that optimal orthotics may reduce muscle fatigue for a given movement task by minimising muscle activity (Med. Sci. Sports Exerc. 31 (1999) S421). The aims were to determine whether EMG would provide an independent method of analysing myoelectric fatigue in the vastus lateralis (VL) during a skier’s squat and whether orthotics could affect this fatigue response. Six skiers performed skier’s squats for as long as possible with no orthotic, low volume orthotics and high volume orthotics in their ski boots. Bipolar, active surface electrodes recorded EMG activity in the VL throughout each squat. Results for the EMG median frequency showed a significant shift in the power density spectrum towards the lower frequencies (P<0.05) at the end of the contraction, suggesting that myoelectric fatigue was occurring and was measurable using EMG. All conditions displayed a significant decrease in median frequency at the end of the contraction (P=0.001). The high volume orthotic showed a significant reduction in myoelectric fatigue, however, there was no difference in the duration of squats across the three conditions (P>0.05). Subjective and objective findings support the use of the high volume foot orthotic for skiers.     

Partial characterization of a tapeworm-secreted signal factor inducing sustained spike potentials in the smooth muscle of the rat small intestine

The rat tapeworm Hymenolepis diminuta alters the myoelectric activity of the small intestine. To determine if secreted factors from the tapeworm are responsible for these alterations of intestinal smooth muscle activity, tapeworm-conditioned medium (TCM) obtained from in vitro culture was infused via an indwelling cannula into the duodenum of an uninfected rat. Myoelectric recordings were analyzed for sustained spike potentials (SSP) and repetitive bursts of action potentials (RBAP), the previously characterized tapeworm modifications of the normal interdigestive myoelectric pattern. Results indicated that TCM initiated SSP, but not RBAP in the intestine of the uninfected rat. The SSP-inducing signal factor activity, present in TCM, was retained after boiling, prolonged freezing, proteinase treatment, and passage through a 10-kDa exclusion filter. The signal factor was soluble in the aqueous phase on lipid extraction. It was concluded that the SSP-inducing signal factor is a nonproteinaceous, heat-resistant, low-molecular weight, water soluble molecule.     

Quadriceps and hamstrings prelanding myoelectric activity during landing from different heights among male and female athletes

ACL tear is a major concern among athletes, coaches and sports scientists. More than taking the athlete away from training and competition, ACL tear is a risk factor for early-onset of knee osteoarthritis, and, therefore addressing strategies to avoid such injury is pertinent not only for competitive athletes, but for all physically active subjects. Imbalances in the prelanding myoelectric activity of the hamstrings and quadriceps muscles have been linked to ACL injuries. We investigated the effect of landing from different heights on prelanding myoelectric activity of the hamstrings and quadriceps muscles in recreational athletes. Thirty recreational athletes (15 male and 15 female) performed three bilateral drop jumps from two different heights; 20 cm and 40 cm while myoelectric activity of the vastus medialis, rectus femoris, biceps femoris and medial hamstrings were collected. When increasing the height of drop landing tasks prelanding normalized myoelectric activity of the quadriceps was increased by 15–20% but no significant changes were found for the hamstrings. Female athletes exhibited higher activity of the medial hamstrings compared to their male counterparts. We concluded that increasing the height of drop landing tasks is associated with increased myoelectric activity of the quadriceps but not the hamstrings in recreational athletes. These differences in muscle activity may be related to increased risk for ACL injury when the height is increased. Female athletes demonstrated higher recruitment of the medial hamstrings.