Effect of secretin on electrical activity of small intestine.

The effect of intravenously administered secretin (0.5, 2.0, 6.0 U/kg-h) and intraduodenal acidification (13.2 meq/h HCl) on the electrical activity of the small bowel of three conscious dogs with gastric and duodenal cannulas was observed. Electrical activity was recorded in fasted as well as fed conditions through silver wire electrodes implanted along the entire length of the small bowel. Intravenous infusion of secretin in all dosages and in all dogs delayed the onset of the interdigestive myoelectric complex and reduced the total percentage of slow waves with superimposed spike potentials. Intraduodenal acidification also inhibited the interdigestive myoelectric complex, which developed incompletely with fewer action potentials on slow waves. Secretin did not produce any alteration in the fed pattern of activity, slow-wave frequency, or the caudal migration of the interdigestive myoelectric complex. The present study indicates that the nuerohumoral mechanisms responsible for initiation of the interdigestive myoelectric complex may be different from those responsible for its caudal migration.     

核素显像评价电刺激对健康青年人小肠运动功能影响的试验研究

目的利用放射性核素显像研究十二指肠电刺激对人小肠通过时间的影响。方法12例健康青年志愿者,男女各6例,年龄21～25岁,中位年龄23岁。在胃镜引导下留置导管至十二指肠水平部,并安置电极,将99mTc-DTPA(二乙撑三胺五乙酸)和乳果糖混合液注入导管,用单光子发射式计算机断层仪(SPECT)进行连续小肠显像。择日对受试者进行电刺激,刺激条件:频率13Hz、波宽300ms、刺激强度5mA的方波,采用上述方法进行显像。使用感兴趣区分析法,生成小肠时间-放射性曲线,计算出小肠半排时间(T50),比较刺激前后小肠半排时间的变化。结果电刺激前后小肠平均半排时间分别为(49.5±15.8)min和(29.6±10.9)min,刺激前后T50变化有统计学意义(P<0.01)。结论放射性核素显像能很好地反映小肠运动变化,十二指肠电刺激能明显加快小肠运动。     

A mathematical model of the slow-wave electrical activity of the human small intestine

Based on available data of the slow-wave electrical activity in the small intestine of humans and dogs, a mathematical model has been developed. The model comprises an interconnected chain of 100 Van der Pol relaxation oscillators with the method of coupling and its magnitude chosen so that known phenomena in the small intestine are reproduced by the mathematical model. Results from digital simulations on an ICL 1907 computer are presented which show how the model matches the data from the small intestine. Further phenomena such as a travelling area of reduced frequency along the oscillator chain have also been found, and it is shown that this effect is related to the phase relationships along the chain.     

Effect of muscular exertion on invertase activity of the small intestine

Invertase activity of the proximal, middle, and distal parts of the small intestine after muscular exertion lasting 2, 4, and 10 h (forced swimming in water at 35±1°C) was studied in acute experiments on male albino rats. After swimming for 2 h the invertase activity in the first two parts of the intestine was sharply reduced and it returned to its initial level after 48–72 h. This decrease was much less marked in the distal portion. Swimming for both 4 and 10 h led to a slight increase in enzyme activity in all three parts of the intestine 24 h after the beginning of the experiments, followed by a decrease in the first two parts and a marked increase in the distal portion 48 h after the beginning of the experiment. It is suggested that these changes are brought about through the hypothalamic-pituitary-adrenal system in accordance with the principle of the general nonspecific adaptation syndrome.Laboratory of the Physiology of Digestion and Laboratory of General Physiology, Institute of Physiology, Academy of Sciences of the Uzbek SSR, Tashkent. (Presented by Academician of the Academy of Medical Sciences of the USSR N. A. Yudaev.) Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 82, No. 11, pp. 1335–1337, November, 1976.     

Intracellular study of electrical activity of Auerbach's plexus in guinea-pig small intestine

Intracellular recording revealed two general categories of ganglion cells in Auerbach's plexus. The characteristics of one category were relatively low resting potentials, high input resistance, discharge of spikes throughout a depolarizing current pulse, stimulus-evoked synaptic potentials and spontaneous electrical activity. Characteristics of the second category were high resting potentials, low input resistance, spikes only at the onset of a depolarizing current pulse and long duration hyperpolarizing after-potentials. Responses to extracellular electrical stimulation of the ganglia and interganglionic fiber tracts consisted of electrotonic spread of spikes from the processes to the cell soma, somal action potentials and depolarizing and hyperpolarizing responses that were probably EPSPs and IPSPs. Some of the neurons which received excitatory synaptic input responded with a prolonged train of spikes that outlasted by many seconds the duration of the stimulus to the fiber tract. Spontaneous electrical activity consisted of single EPSPs, patterned bursts of spikes that originated in the cell processes and spread electrotonically to, the recording site, IPSPs and action potentials. The burst-type activity showed periodic conversions from a burst pattern to a trainlike pattern of continuous discharge. Spontaneous discharge of single action potentials was superimposed upon a background of continuous synaptic input to the cell. Spontaneously occurring hyperpolarizing potentials were converted to depolarizing potentials when the membrane was hyperpolarized by current injected through the recording electrode. This work was supported by BMVg In San and National Institutes of Health AM 16813     

A linked oscillator model of electrical activity of human small intestine.

The electrical slow-wave activity of the human small intestine has been simulated by a chain of 64 coupled electronic relaxation oscillators. The model simulates the frequency gradient of recorded patoentials in the human small intestine and when transected, behaves in a similar way to the transected canine small intestine. The model exhibits a spontaneous effect whereby several adjacent oscillators periodically are in the same state. This effect travels down the model in the time of 20-30 min.     

Intraluminal pressure of the small intestine of the unanesthetized dog

Summary Intraluminal pressure recordings have been performed in 14 unanesthetized dogs via a Mann-Bollman fistula by means of an air-filled balloon catheter system and a water-filled catheter system. The dynamic response is adequate for studying intraluminal pressures of the small intestine.Resting pressures in the proximal, middle and distal jejunum averaged approximately 6 mm Hg above atmosphere and no appreciable differences were noted between the different areas. The contraction time of simple, monophasic waves was fairly constant (approximately 1.0 s in duration) and usually unrelated to amplitude of the wave. Propulsion of intraluminal contents occurred in the absence of complex (type III) waves. A pressure wave in a proximal segment of jejunum was temporally related to a wave occurring 5 cm distally. The mean intervals between the proximal and distal contractions were: 0.42 s in the proximal jejunum; 0.74 s in the middle jejunum; 1.56 s in the distal jejunum; 2.79 s in the ileum. These time lags have a log normal distribution. The length of the physiologic segment in the jejunum of the dog varied from 1.0–8.0 cm and was usually 2–4 cm.     

Effect of toxigenic Escherichia coli on myoelectric activity of small intestine.

When exposed to cholera toxin (CT), distal ileal loops of the rabbit small intestine showed an alteration in myoelectric activity. This alteration was defined as the migrating action potential complex (MAPC). The purpose of this study was to determine, using myoelectric recording techniques, the effects of live toxigenic Escherichia coli (TEC) on motility. Live TEC, live nontoxigenic E. coli (NTEC), and culture filtrates of these organisms were studied. Live TEC and its filtrate induced MAPC activity similar to that of CT. Live TEC induced a mean of 3.8 MAPCs/h, significantly greater than induced by live NTEC. TEC filtrate induced a mean of 14.2 MAPCs/h, significantly greater than NTEC filtrate. Heating the TEC filtrate to 100 degrees C before use resulted in a significant decrease of MAPC activity. This experiment demonstrated that live TEC and its culture filtrate altered ileal myoelectric activity. The effect may have been mediated by a heat-labile enterotoxin. This study suggests that alterations in small intestinal motility may be important in the pathogenesis of TEC diarrhea.     

Effect of high temperature on enzyme activity of the small intestine in thyroidectomized rats

Changes in the activity of certain intestinal enzymes (invertase, monoglyceride lipase, dipeptidase, and alkaline phosphatase) were compared in thyroidectomized rats and rats undergoing a mock operation, when both were kept at a high ambient temperature for 2 h (40°C; relative humidity 30–40%). Exposure to heat led to changes in the spectrum of enzyme activity of the mucous membrane of the small intestine in both groups of rats. However, the severity and direction of the changes depended on the presence of the thyroid gland.Laboratory of Physiology of Digestion, Department of Physiology, Academy of Sciences of the Uzbek SSR, Tashkent. (Presented by Academician V. N. Chernigovskii.) Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 80, No. 9, pp. 31–33, September, 1975.