Provisional model for propagation of electrical activity in upper urinary tract.

A theory on the function of the renal pelvis as a pacemaker for ureteral peristalsis is given. The bioengineering "black box" approach is used to describe peristaltic behavior monitored at the ureter and thr renal pelvis, by both peristaltic pressure and electromyographic methods. The model provides a stimulus to further thought on the nature and significance of electrical activity in the upper urinary tract.

The electrogastrogram and its analysis.

In recent years interest in the electrogastrogram, the EGG, has manifested itself in an increasing number of articles. In this review a brief exposition of the EGG phenomenon is made and the more prominent methods of signal analysis relevant to the EGG are presented and discussed.

Electrical activity of canine gallbladder.

Our aims were to describe the myoelectrical activity in the single very thin layer of muscle of the canine gallbladder. The study was performed on 22 freshly removed canine gallbladders. Electrical activity was studied by the single sucrose-gap method and contractility of the tissue was measured simultaneously using a force transducer. The strips (15 x 1 mm) from different regions of gallbladder (fundus, corpus, neck) were cut in longitudinal, circular and oblique axes. The sucrose-gap apparatus together with connecting tubes, solutions and electrodes were kept at 37 degrees C and the initial tension applied to the tissue was set to 1 g. In 82.7% of recordings, spontaneous myoelectrical activity consisted of regular rhythmic changes in membrane potential similar to slow waves recorded in intestinal tissue. The overall mean frequency was 11.4 +/- 5.2 (mean +/- SD) cycles per min: 11.1 +/- 4.4 cycles per min in fundus, 11.9 +/- 6.2 cycles per min in corpus and 10.8 +/- 3.8 cycles per min in the neck of the gallbladder. In 84.2% of cases electrical activity correlated with mechanical activity and preceded it. No significant differences were seen between the electrical patterns in strips with different orientations or from the different regions of the gallbladder.

Simultaneous measurement of electrical activity from two colonic smooth muscle layers using a dual sucrose gap apparatus.

An apparatus using the sucrose gap technique is presented. With this apparatus simultaneous measurements of contractile and intracellular electrical activity from the two smooth muscle layers of the colon are made. An "L-shaped" muscle preparation consisting of a leg from the circular muscle layer and a leg from the longitudinal muscle layer is used. A theoretical discussion of the device's operation is presented. Finally, experimental results that validate the theory are included.

An active feedback system for isotonic studies of smooth muscle.

A feedback system used to perform isotonic studies of smooth muscle is presented. This system is capable of applying a constant force to muscle samples regardless of their contractile activities. The force applied to the tissue is controlled using a proportional integral control system that drives a linear motor. The device is integrated into a sucrose gap tissue bath apparatus where measurements of displacement and electrical activity are also possible. The frequency of canine colonic smooth-muscle electrical oscillations is positively related to applied force.

Intracellular electrical activity in circular muscle of canine colon.

In vivo and extracellular in vitro studies of colon muscle have led to a great deal of disagreement on the characteristics of slow wave activity. As intracellular recordings of electrical activity in single cells give clear records which are easier to analyse, we used this method to study the slow wave activity of the circular muscle of three different parts of the canine colon. Mucosa was removed from segments of proximal, mid and distal canine colon and specimens from each segment were mounted in an organ bath perfused with oxygenated Krebs' solution. Membrane potential, amplitude and frequency of slow waves were measured using intracellular electrodes. Slow wave activity was present at a single, continuous frequency of 4-6 cpm in the circular muscle at all the sites studied in canine colon. There was no significant frequency gradient along the colon: the membrane potential and amplitude of slow waves did not differ significantly in the three parts of the colon.

Electrical and mechanical activity in the ex vivo perfused total canine colon.

Electrical and mechanical activity were studied in the ex vivo total canine colon, supported in a perfusion chamber by a supporting dog. Regular electrical activity could be recognized visually in 50--70% of the records. The frequency of this activity was in the range of 7--10/min. Fourier analysis also revealed dominant frequencies in this range. Two types of mechanical activity were observed. The first consisted of small amplitude repetitive contractions, which appeared both during quiescent periods and during vigorous contractions. The frequency of this rippling, when periodic, usually approximated that of the electrical activity. The second type consisted of large amplitude prolonged (30--135 sec) contractions. Without stimulation, the large amplitude contractions were asynchronous and not propagated. Following neostigmine, however, the large amplitude contractions were always propagated aborally and were usually associated with evacuation of the colon. The rippling contractions had a frequency similar to the regular electrical activity and are probably under their control. The large amplitude, prolonged duration contractions are unlikely, however, to be solely under myogenic control.

Electrical and mechanical interactions between the muscle layers of canine proximal colon.

Electrical and mechanical interactions between the two smooth muscle layers of canine colon have been studied using a dual sucrose gap apparatus. Muscle samples were dissected into an L-shape, with one leg cut in the circular direction and the other cut in the longitudinal direction. Longitudinal muscle was removed from the circular leg and circular muscle was removed from the longitudinal leg. The bend of the L contained both layers. The activity of the two layers was studied simultaneously under basal conditions, after stimulation by neostigmine and carbachol, and in the presence of tetrodotoxin. Interactions were more common after stimulation and were marked by modification of one layer's mechanical and electrical activity during increased activity in the other layer. Two patterns were commonly observed. First, during a burst of membrane potential oscillations and spike potentials in the longitudinal layer, slow waves in the circular layer developed spike potentials and some slow waves were also prolonged. Second, during a slow-wave cycle in the circular layer, the amplitude of membrane potential oscillations in the longitudinal layer was increased with an associated increase in the incidence of spike potentials. These interactions were associated with contractions of increased strength, which were similar in both layers. All interactions continued after nerve-conduction blockade by tetrodotoxin.

Effect of progesterone on canine colonic smooth muscle.

This study was undertaken to ascertain the effect and mode of action of progesterone on canine colonic smooth muscle in vitro. Circularly orientated strips of smooth muscle exhibited low-amplitude contractions at the slow wave frequency. Longitudinally orientated strips exhibited larger-amplitude contractions that were associated, electrically, with a series of "spikes" superimposed on a high-frequency oscillation in membrane potential. Progesterone reduced the contractile force of both the circularly and longitudinally orientated strips and the contractile frequency of the longitudinally orientated strips in a dose-dependent manner; this inhibitory effect was observed in the presence of tetrodotoxin but not atropine. The stimulatory effects of a high-potassium superfusate were antagonized by progesterone and verapamil, the effect of progesterone being reversed by increasing the calcium concentration of the superfusate. We conclude that progesterone exerts an inhibitory effect on colonic smooth muscle and this may be mediated by changes in the cytoplasmic calcium concentration.

Accuracy of cutaneous recordings of gastric electrical activity.

BACKGROUND: This study was undertaken to determine the accuracy of cutaneous electrogastrography (EGG). METHODS: The ability of EGG to assess gastric contractions and electrical frequency, phase lag, and waveform was studied in 4 healthy volunteers with cutaneous electrodes before and after eating, 4 healthy fasting volunteers with intraluminal pressure recording tubes and cutaneous electrodes, 1 patient with surgically implanted gastric serosal electrodes, and 4 anesthetized dogs with serosal force transducers and implanted and cutaneous electrodes. In 2 of the dogs, an intragastric distending balloon was introduced. RESULTS: The use of long-distance serosal electrodes allowed direct comparison of internal and cutaneous signals. Cutaneous electrodes recognized 80%-85% of changes in frequency with spectral analysis. Only 30%-40% of increases in EGG amplitudes were associated with gastric contractions. Gradual distention of the canine stomach after blocking contractions with atropine and glucagon increased the EGG amplitudes. No appreciable phase lag could be discerned with EGG. The descending portion of the EGG waveform was predominant. CONCLUSIONS: Frequency dynamics is currently the only reliable cutaneous EGG parameter.

In vitro electrical activity in canine colon.

In vitro slow wave activity was studied in strips of right and left canine colon with silver/silver chloride electrodes. Using visual and computer analysis, slow wave frequency and coupling was assessed between different recording sites and the effect of a cholinergic agonist on coupling and frequency was determined. A regular slow wave was always found to be present. Frequency in the left colon was slightly higher than in the right with a slight decline noted with time. Spike activity was rarely seen in unstimulated specimens. Administration of a cholinergic agonist produced a decrease in frequency with no improvement in coupling. Coupling was usually better in a circular than in a longitudinal direction. It was concluded that if electrical activity is important in the control of colon contractions, it is more likely to be involved in the control of segmentation than in propagated contractions.

Colonic and anorectal motility in young women with severe idiopathic constipation.

Forty-four severely constipated women and 16 (8 female, 8 male) asymptomatic volunteers underwent assessment of colon function by (a) clinical examination, (b) rectosigmoid intraluminal pressure recording, (c) colonic transit utilizing radiopaque markers, (d) anorectal manometry, and (e) rectosigmoid electrical activity. Constipated patients were characterized by (a) a greater volume and pressure of rectal distention required for both sensation and sphincter relaxation, (b) diminished basal and postmorphine motility indices only in the distal rectum, (c) delayed transit, and (d) an empty rectum when severely constipated. A neural abnormality affecting afferent nerves may be present in the rectum of female patients with severe idiopathic constipation. Delivery of stool to the rectum is impaired in these patients.

Inductive displacement gauge.

Strain gauges are often used for the measurement of contractile activity of muscle tissue. In these cases the strain gauge is used as a force measuring device. Because of its stiffness, the strain-gauge-type transducer resists changes in length produced by contraction, and this could cause secondary effects. This paper describes an alternative method to evaluate contractions. Displacement rather than force is measured. The device offers very little resistance to motion and thus does not constrain the tissue. The sensitivity of the transducer is very high. An additional feature is the low cost of the transducer compared to strain-gauge devices.

Optimal placement of impedance epigastrography electrodes.

Impedance electrogastrography (IE) is a noninvasive method to assess gastric contractile activity. This indirect method uses a four-terminal impedance measuring method to determine impedance variations of the gastric region of the torso. These variations can be related to changes in the stomach shape and, therefore, to gastric contractions. Because the impedance variations are very small, the placement of the measuring electrodes on the skin is critical. In this study, a three-dimensional resistor model consisting of 4,466 resistors was used to simulate the human torso. The model was implemented on a personal computer, and the experimentally obtained optimal electrode locations were found to be superior to the commonly used ones. Measurements of volunteers confirmed these findings.