Effect of acute gastric dilatation on gastric myoelectic and motor activity in dogs.

OBJECTIVE: To investigate the effects of experimentally induced acute gastric dilatation on electrical and mechanical activities of the stomach in dogs. ANIMALS: 7 healthy dogs. PROCEDURE: Electrodes and strain-gauge force transducers were implanted on the serosal surface of the antrum and pylorus. Eight days later, baseline gastric electrical and contractile activities were recorded. The dogs were anesthetized and mechanically ventilated to maintain normocapnia while the stomach was distended (intragastric pressure, 30 mm Hg) for 180 minutes, using a thin compliant bag. Gastric electrical and contractile activities were recorded again on days 1 and 10 after dilatation. Recordings were analyzed to determine gastric slow-wave frequency, slow-wave dysrhythmia, propagation velocity of slow-waves, coupling of contractions to slow waves, motility index on the basis of relative contractile amplitudes, and onset of contractions after a standardized meal. RESULTS: Electrical or contractile activities were not significantly different 18 hours after acute gastric dilatation (day 1). Arrhythmias were evident before and after gastric dilatation in dogs from which food was withheld and in dogs after consumption of a meal. CONCLUSIONS: Variables for assessing gastric electrical and contractile activities were unaffected 18 hours after acute gastric dilatation. CLINICAL RELEVANCE: Analysis of results of this study indicated that altered electrical and contractile activities in dogs with short-term gastric dilatation are not likely to be secondary to the process of acute gastric dilatation.

Effect of circumcostal gastropexy on gastric myoelectric and motor activity in dogs.

Gastric electrical and contractile activities were assessed in healthy adult dogs on the eighth day after circumcostal gastropexy surgery, using serosal electrodes and strain gauge force transducers. Recordings were analysed to determine gastric slow wave frequency, presence of gastric slow wave dysrhythmias, gastric slow wave propagation velocity, coupling of gastric contractions to slow waves, a gastric motility index based on relative contractile amplitudes, and onset of gastric contractions after a standardised meal. Overall, gastric electrical and contractile activities were relatively unaffected by circumcostal gastropexy.

Effect of metoclopramide on fed-state gastric myoelectric and motor activity in dogs.

OBJECTIVE: To investigate the effects of metoclopramide, a putative gastroprokinetic agent, on dogs that had recovered from gastric dilatation-volvulus (GDV), a disorder characterized by delayed gastric emptying. ANIMALS: 6 healthy dogs and 5 dogs after treatment and recovery from GDV. PROCEDURE: Baseline recordings of gastric electrical and contractile activities were made 8 or 10 days after circumcostal gastropexy and implantation of serosal electrodes and strain-gauge force transducers. Gastric activities were recorded again the next day after treatment with the clinically recommended oral metoclopramide dose (0.3 mg/kg of body weight) administered a half hour before feeding. Recordings were analyzed to determine gastric slow-wave frequency, presence of slow-wave dysrhythmia, slow-wave propagation velocity, coupling of contractions to slow waves, a motility index based on relative contractile amplitudes, and onset of contractions after a standardized meal. RESULTS: Significant differences in gastric electrical or contractile activities were not detected after metoclopramide treatment in dogs with GDV. Compared with control dogs after metoclopramide treatment, gastric slow-wave propagation velocity was significantly (P = 0.03) faster for the dogs with GDV at postprandial minute 90. CONCLUSION: At a clinically recommended dosage, metoclopramide treatment did not change gastric myoelectric and motor activities in a way that would promote increased gastric emptying in dogs with GDV. CLINICAL RELEVANCE: Metoclopramide treatment may not benefit dogs with GDV and delayed gastric emptying.

Gastric myoelectric and motor activity in dogs after isoflurane anesthesia.

To characterize the effects of isoflurane on gastric motility, gastric electrical and contractile activities were assessed in six healthy adult dogs before and after recovery from anesthesia. Baseline recordings (fasting and fed state) were obtained in unanesthestized dogs 8 days after implantation of serosal electrodes and strain-gauge force transducers. After an overnight fast, dogs were anesthetized with 1.3 minimum alveolar concentration (MAC) isoflurane for 4.5 hours (approximately 6 MAC hours). No other anesthetic or sedative drugs were administered. During anesthesia, ventilation was mechanically controlled to maintain arterial carbon dioxide tension at 36 +/- 4 mm Hg. Gastric electrical and contractile activities (fasting and fed state) were recorded again 18 hours after recovery from isoflurane anesthesia. Recordings were analyzed to determine gastric slow-wave frequency, presence of slow-wave dysrhythmias, slow-wave propagation velocity, coupling of contractions to slow waves, a motility index based on relative contractile amplitudes, and onset and duration of contractions after a standardized meal. The only variable that was significantly decreased 18 hours after 6 MAC hours of isoflurane anesthesia was the gastric motility index during fasting-state phase III. This decrease was not apparent in the fed-state test periods. Our results suggest that, with the exception of gastric motility index during fasting-state phase III, variables for gastric electrical and contractile activities in dogs are unaffected by isoflurane 18 hours after anesthesia.

Gastric myoelectric and motor activity in dogs with gastric dilatation-volvulus.

Electrical and contractile properties of the stomach were assessed in six adult dogs after recovery from surgical treatment for gastric dilatation-volvulus (GDV), a disorder characterized by delayed gastric emptying of the solid phase. Electrodes and strain-gauge force transducers were sutured to the serosa of the antrum and pylorus at the time of surgical intervention for GDV. Ten days after implantation, electrical and mechanical activities were recorded before and after a standardized meal. The analog FM tape recordings of the electrical and mechanical signals were converted to digital time series for analysis by computer. Recordings from dogs after GDV showed increased slow wave propagation velocity in both the fasting and the fed states compared with controls. In addition, the GDV dogs had atypical fasting state phase III activity fronts. We found no difference in gastric slow wave frequency, dysrhythmia, or electromechanical coupling between the two groups. These results indicate that delayed gastric emptying in this syndrome is associated with increased gastric slow wave propagation velocity.

A programmable stimulator for electrophysiological studies.

We report on the design and construction of a programmable stimulator for use by neuroscientists. The stimulator is small, lightweight, and low powered. It generates positive, negative, or positive and negative pulses with widths and periods programmed by the user. The stimulator has ten parallel outputs to enable it to drive ten preparations at one time. It operates from 50-60 Hz, 115 v AC or 230 v AC and had a nominal peak-to-peak output of 30 volts. A liquid crystal display was used for the user interface and the timing was software-generated by a mincrocontroller.

An analog data acquisition board for the Macintosh II.

The Macintosh II has the hardware to make a good scientific data acquisition and data processing machine. The data acquisition boards currently available do not sample multiple channels simultaneously. They are also relatively slow. We have designed a fast Analog-to-Digital Board for the Macintosh II that samples eight channels at once. This board acquires data with sampling periods from 1 microsecond to 1.6777215 seconds in increments of 100 nanoseconds. Any jitter is due to the stability of the clock which is about one part per billion. The actual analog-to-digital conversion time is 500 nanoseconds with another 500 nanoseconds taken up by the track-and-hold amplifier acquisition time and the multiplexer setting time. The board samples as many as eight channels, giving 12-bit resolution for signals between plus and minus 2.5 volts. For eight channels the maximum Nyquist frequency is 62.5 KHz. The board will acquire single-channel data that has frequencies up to 500 KHz. Simultaneous comparisons of two channels can be made for signals that have a highest frequency component of 250 KHz. Thirty-eight integrated circuits were used on a single-slot board that connects to the Macintosh II's 32-bit NuBus.

Ketamine-acepromazine as an anaesthetic agent for chinchillas (Chinchilla laniger).

Intramuscular injections of ketamine-acepromazine provided satisfactory surgical levels of anaesthesia. Induction was smooth. There was a wide margin of safety with no significant side effects, and there were no deaths attributable to anaesthesia. Induction time was 4-6 min, duration of surgical anaesthesia was 40-60 min, with complete recovery in 2-5 h. 80 chinchillas were used for this study.

Analysis of nonexponential fluorescence decay data by a method of moments.

A method of moments is presented for the analysis of convoluted fluorescence decay data when the impulse response function is given by f(t) = alpha exp (-At - Bt1/2). Examples of this method are given using both simulated and measured fluorescence decays. It is also shown that this method, used with moment index displacements, will correct for light-scatter leakage, zero-point time shifts, and slow lamp drift.