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Biomedical subjects

F Crenner

Publications and source records attributed to F Crenner.

17 recordsLinked to original sources
PubMed1992

Interaction between permanent cardiac pacing and electrocautery: the significance of electrode position.

The danger in utilizing electrocautery during a surgical procedure on a pacemaker patient depends, to a great extent, on the position of the electrodes. We have studied this influence in an experimental model consisting of a plexiglass tank filled with a saline solution. Seven pacemakers were successively attached to an immersed and fixed frame and connected to a lead whose tip remains in the same location throughout the experiments. An ERBOTOM T 400 C generator (450 kHz) was used in an unmodulated unipolar mode at a maximum output (400 W). The high frequency current was delivered between a patch located successively at six preset positions in the tank and another electrode applied to 176 surface locations. For each position, we measured the currents in the lead with a separate measurement circuit connected in parallel on the same lead. Results were displayed on a map. Regardless of the patch position, currents were: (1) at a maximum when high frequency was delivered close to the pacemakers and around the tip of the lead; (2) negligible when applied to the path followed by the lead; and (3) a function of the distance between electrodes. These results may help to formulate recommendations to prevent accidents when using electrocautery in pacemaker patients.

Animals↗
PubMed1992

[Effects of electrocautery on the threshold values of permanent pacing. An experimental study].

One of the hazards of high frequency electrical interference (electrocautery) with cardiac pacing is thought to be related to an increase in the threshold values leading to loss of pacing. This hypothesis was examined in an experimental study performed on 5 dogs. A pacing catheter was introduced via the right jugular vein and positioned at the apex of the right ventricle and connected successively to several stimulators implanted in a latero-cervical subcutaneous pocket. A Bovie 400 CT generator was used to deliver a high frequency 1.75 MHz current between a probe applied near to the pacemaker pocket and an electrode placed under the right leg. One or two 5 second bursts were applied for each make of pacemaker, making a total of 3 to 6 applications per animal. A detecting circuit enabled the measurement of the currents in the catheter during the application. The thresholds of pacing were measured before and after each manipulation for several pacing impulse durations. At the maximal output of the generator, the highest recorded current was 117 mA (modulated) and 141 mA (unmodulated). The thresholds of stimulation did not change significantly and the pacing catheter impedance was also stable. This study suggests that high frequency current does not modify the threshold of stimulation in cardiac pacemaker patients. The loss of pacing sometimes observed after the use of electrocautery is probably related to pacemaker dysfunction.

Animals↗
PubMed1991

Autonomous telemetric capsule to explore the small bowel.

An intestinal telemetric capsule has been developed to study the small bowel in man. It consists of a cylinder (11 mm in diameter and 39 mm in length) containing a location detector, a radiotransmitter, a lithium battery and an interchangeable tip. After having been swallowed by the patient, the capsule passes through the whole gut and is recovered in the stools. During the transit through the small bowel, the information provided by the radiotransmitter allows continuous monitoring of the distance covered from the pylorus, the direction and the velocity of progression. Moreover, according to the type of interchangeable tip, it is possible, by remote control, to sample 0.5 ml of intraluminal fluid for subsequent analysis or to release 1 ml of any liquid substance in a precisely determined place for pharmacological studies. The main originality of the capsule is its ability to transmit its precise location inside the small bowel.

Gastrointestinal Motility↗
PubMed1990

Long-duration stress. Immediate and late effects on small and large bowel motility in rat.

No extensive information exists in literature concerning the late or residual effects of stress on motility of small bowel and colon. Moreover, the duration and magnitude of the intestinal motor response to stress are still ignored. Therefore, the aim of our work was to determine, in rat, the effect of long-duration stress induced by restraint on the motility of small bowel and colon. Observations were made during physical restraint and 60 h later. Bipolar electrodes were implanted on the gastrointestinal serosa from the pylorus to the sigmoid colon in male Wistar rats. Electromyographic (EMG) recordings were made during fasting state, and a control EMG recording session was performed during 12 hr, followed by a 12-hr recording during restraint stress. After a 60-hr resting period, another EMG recording session was performed during 3 hr. During stress in the pylorus and small bowel, the recurrence of migrating myoelectrical complexes (MMCs) was immediately interrupted and replaced by a continuous and irregular activity. The motility index (number of spike bursts/10 min) was augmented rapidly on the jejunum and ileum, but it increased only gradually on the pylorus. Only on the transverse colon were the number of spike bursts/hour and their relative duration increased after 7 hr of physical restraint. In contrast, the sigmoid colon displayed a gradual decrease in the relative duration of contractile activity during the first 6-7 hr of stress. At 60 hr after stress in the pylorus and small bowel, a normal control motor activity was restored (MMC, motility index) on the jejunum and on the ileum, but the motility index on the pylorus was decreased.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

[In vitro study of the effects of high frequency electrical current on cardiac pacemakers].

The authors studied the possible consequences of the use of high frequency electrical currents of cardiac pacemaker function. Twenty-five unipolar pacemakers (22 single and 3 double chamber) were tested. They were connected to a pacing catheter, emerged in a saline bath and submitted to a modulated and then unmodulated current of 348 KHz in as many pacing modes as possible for each unit. Three dangerous deprogrammations were observed which could nevertheless be easily corrected. Five pacemakers immediately adopted the reversion mode specified by their manufacturer. The other changes observed only lasted as long as the electric current was applied. The commonest abnormality was a drop in the output voltage proportional to the energy delivered which sometimes led to true inhibition of the pacemaker. Two abnormal rate increases were observed reaching frequencies higher than 250/mn. No particular pacing mode seemed to protect the pacemakers from the effects of high frequency currents.

Cardiac Pacing, Artificial↗
PubMed1989

Ag/AgCl electrode assembly for thin smooth muscle electromyography.

An electrode assembly for in vivo recording of the electrical activities of thin muscular layers is described. It comprises an active electrode surrounded by a ring, which avoids the recording of interfering signals. An improved technique for chlorinating the silver electrodes is presented: a partial electrolytic removal of an initial thick deposit is performed. This decreases the impedance, and lowers the ageing degradation of the electrodes in vivo. Recordings of extremely low frequency signals are allowed, whereas standard Ag/AgCl electrodes are inefficient when recording signals in the frequency domain under 0.1 Hz. The technical features which are described can be adapted to any Ag/AgCl electrode developed for in vivo measurements.

Animals↗
PubMed1988

Adaptive changes in postprandial motility after intestinal resection and bypass. Electromyographic study in rats.

An electromyographic technique was used to study the changes in postprandial motility induced by jejunal and ileal resection and jejunal bypass (50% reduction of total length of small bowel). Electrodes were implanted in rats throughout the intestine. Compared to control animals, the duration of postprandial interruption of the myoelectric complex (DIMC) was rapidly increased after jejunal resection, more gradually augmented after jejunal bypass, and remained constant after ileal resection. The frequency of occurrence of spike bursts during the postprandial period was significantly decreased in the short remaining proximal segment after jejunal resection and was not changed in the ileum. The jejunal bypass induced no change in the frequency throughout the remaining bowel. Ileal resection was followed by a decrease on the jejunum. The percentage of slow waves superimposed by a spike burst remained constant after jejunal resection and bypass but was significantly decreased after ileal resection on the whole remaining intestine. These results show important modifications in postprandial motor activity of the small bowel, which appear rapidly after jejunal resection, more gradually after jejunal bypass, and which are less pronounced after ileal resection. This electromyographic study emphasizes the role of intestinal motility in the development of adaptation after small bowel resection or bypass.

Adaptation, Physiological↗
PubMed1986

Cyclic motor activity and trophicity after jejunal resection and bypass in rats.

The aim of the study was to examine the changes in intestinal motility induced by an extensive jejunal resection and bypass in rats using an electromyographic technique. The relationship, if any, between the development of motility and adaptive modifications of intestinal trophicity was also studied. A massive jejunal resection, preserving a 7-cm segment distal to the ligament of Treitz, was performed in one group of animals. In a second group, the jejunum was bypassed as a self-emptying blind loop. Two sham-operated groups underwent transection and reanastomosis on the proximal jejunum or ileum. Electromyographic activity was studied at the 10th and 30th postoperative days by means of electrodes implanted throughout the remaining or bypassed bowel and was expressed by means of the pattern of recurrence of the migrating myoelectric complex (MMC). After a month, the animals were sacrificed. Mucosal and muscular wet weight and protein content (mg/cm) of the intestine were then determined. The results showed that 10 days after the jejunal resection in the fasting state, MMC cycle duration is different in the remaining jejunum and in the ileum. However, the distribution of MMC phases in the jejunum was modified and was similar to the one in the ileum. Thirty days after resection, MMC cycle duration, as well as phase distribution in the remaining jejunum, resemble the MMC patterns in the ileum. These changes were not observed after bypass. After the return of MMCs after postprandial inhibition produced by a meal, MMC duration in the ileum was greatly decreased until a month after jejunal resection. In contrast, the jejunal bypass did not produce this modification.

Action Potentials↗
PubMed1986

Electromyographic characteristics of small bowel motility in the rat.

Rats are widely used in intestinal motility studies, but no precise observation has yet been carried out on the organization of motility throughout the whole small bowel of the rat. The aim of this work was to investigate the characteristics of small intestinal motility of the rat using an electromyographic technique. The variables describing the pattern of occurrence of the migrating myoelectric complex (MMC) were studied as well as the relative distribution of the 3 phases within the MMC cycles. The mean duration of the MMC was 20 min on the jejunum, and it increased up to twofold along the ileum. The propagation of the MMCs was regular in the jejunum, but about half the MMCs disappeared along the ileum and did not reach the caecum. The electromyographic characteristics of the jejunum are greatly different from those of the ileum, and the motility of a segment is not representative of the whole small bowel motility. Considering these particularities of intestinal motility, rats differ in many details from other species.

Animals↗
PubMed1985

Changes in motility after jejunal and ileal resection: electromyographic study in rats.

The aim of this work was to compare the effects of massive jejunal and ileal resections on intestinal motility using an electromyographic technique. Male Wistar rats were used: in the first group a massive jejunal resection was performed, conserving a 7-cm segment after the ligament of Treitz; the rats of the second group underwent an ileal resection, preserving 7 cm of the terminal ileum. Motility was studied at the 10th and 30th postoperative days by means of electrodes implanted throughout the remaining bowel and was expressed by the pattern of recurrence of the migrating myoelectric complex (MMC). In a fasting state, in both transected and resected animals at the 10th postoperative day, the gradient in the duration of MMC along the intestine still existed. However, on the 30th postoperative day, in animals with jejunal resection only, there was an adaptive process: the duration of MMC in the remaining jejunum was significantly increased to the duration in the ileum. After the end of the postprandial inhibition of the appearance of the MMC, on the 10th postoperative day there was a significant decrease in the duration of MMC in the ileum in both types of resection, compared to the controls. However, on the 30th postoperative day, the duration of MMC returned to its control value. In conclusion, jejunal resection seems to induce more important adaptive processes in intestinal motility than does ileal resection. The different results are discussed.

Animals↗
PubMed1984

[Intestinal motility following jejunal resection: electromyography study in the rat].

The influences of massive resections on motility of the small intestine remain poorly known. The aim of our study was to determine the effects of jejunal resection on the pattern of occurrence of the migrating myoelectric complex and its postprandial inhibition. The experiments were performed over a period of 1 month after surgery. Transections were done on the jejunum or on the ileum in sham-operated animals. Ten days after resection, the motility of the anastomosed jejunal and ileal segments was dissociated. After one month, a functional continuity appeared through the anastomosis: the whole intestine worked synchronously at the same rhythm as the ileum. Food intake induced an increase in the frequency of the migrating myoelectric complexes measured 10 days after surgery. An adaptative phenomenon appeared after 30 days, the postprandial motor activity returning to its control level.

Animals↗
PubMed1981

Inhibition of canine duodenal interdigestive myoelectric complex by nutrient perfusion of jejunal and ileal Thirty-Vella loops.

The mechanisms by which the intestinal interdigestive myoelectric complex (IDMEC), recurring at about 90 minute intervals in the fasted dog, is disrupted by feeding remain unknown. We investigated whether the IDMEC could be disrupted in the duodenum by perfusing a Thiry-Vella loop with glucose in the dog. An intestinal Thiry-Vella loop, measuring one half (80 to 160 cm) of the total length of the small bowel was constructed in four dogs from the jejunum, and in four other dogs from the ileum. Extracellular nichrome electrodes were sewn on the duodenum for recording the electrical activity of the intestine. After three weeks' recovery, electrical recordings were performed in the fasted dogs in order to observe whether the IDMEC persisted in the duodenum when the Thiry-Vella loops were perfused, at different days, for four hours with solutions made of either (1) NaCl 154 mM, (2) NaCl 308 mM, (3) glucose 300 mM, or (4) glucose 600 mM, at a rate of 8 ml/min. NaCl 308 mM and glucose 600 mM were also delivered at a rate of 4 ml/min. Glucose output from the Thiry-Vella loops was measured throughout the experiments over consecutive five minute intervals. Each experiment was performed three times in each dog. The results showed that perfusing the Thiry-Vella loops with NaCl 154 mM or NaCl 308 mM did not suppress the IDMEC in the duodenum whether the flow rate was 4 or 8 ml/min. On the contrary, perfusing the jejunal loops with glucose 300 mM disrupted the IDMEC in 54% of the experiments; perfusing glucose 600 mM disrupted the IDMEC in 83% of the experiments. In the ileal Thiry-Vella loop experiments, the IDMEC was disrupted in 33% of the cases with glucose 300 mM and in 66% of the cases with 600 mM. No significant difference was observed with glucose 300 mM delivered at a rate of 8 ml/min and glucose 600 mM delivered at a rate of 4 ml/min. Finally, the inhibitory effect of perfusing the Thiry-Vella loops with glucose increased as the amount of absorbed glucose increased. These results indicate that interruption of the IDMEC by feeding probably involves extraintestinal factors. These factors do not seem to be specific for any one part of the small intestine, but they seem to be activated by intestinal absorption.

Action Potentials↗
PubMed1980

[Changes in intestinal motility after intravenous injection of alcohol].

It has been well established that the electrical activity of the small intestine consists, in the fasting state, in a cyclic phenomenon - the myoelectric complex - that recurs at about 90 minutes intervals in the dog. The myoelectric complex is disrupted by oral feeding whereas intravenous feeding does not change the cyclically recurring myoelectric activity. The aim of our work was to investigate whether intravenous ethanol was followed by changes in the myoelectric complex. 5 dogs were prepared with Ag AgCl electrodes sewn in the jejunum. After 15 days recovery, the electrical activity was recorded in the dogs fasted for 24 hours, after injection of 100% ethanol at doses of 2, 5 and 10 ml, the total volume of the solution being adjusted to 20 ml with saline. Controls were made with saline 154 mM. Each experiment was repeated twice. The effects of alcohol were studied on the 3 interdigestive cycles following injections of alcohol. The results showed that neither saline nor ethanol at dose of 2 ml did change the myoelectric complex with cycle was meanly of 90 +/- 3 minutes +/- SEM. On the contrary injection of ethanol at doses of 5 and 10 ml was followed by a disruption of the myoelectric complex during respectively 195 +/- 9 and 200 +/- 8 minutes. These results indicate that intravenous ethanol significantly interrupts the myoelectric complex. Therefore, ethanol cannot be considered as a usual nutriment as far as its effect on the electrical activity of the intestine is concerned.

Animals↗
PubMedDate not supplied

[Intestinal motility and continuous enteral nutrition: electromyographic study in dogs].

In fasting dogs, intestinal motility is characterized by the recurrence of a cyclic pattern, named the myoelectric complex; when inhibited by meals, the myoelectric complex is replaced by typical postprandial activity. Numerous studies have been performed concerning small intestinal motility but they all concerned acute food intakes. On the contrary, the aim of our work was to investigate the influence of continuous enteral nutrition in dogs for different caloric loads. The results showed that after a temporary inhibition caused by the onset of continuous enteral nutrition, the myoelectric complexes reappeared, first with long and irregular intervals of recurrence, later and finally with the same characteristics observed during the fasting state. We conclude that small intestinal motility can present the typical features of the fasting state, in spite of the presence of nutrients in the digestive tract. The factors inducing postprandial inhibition of myoelectric complexes loose their effectiveness after a period of time which depends on the caloric load in continuous enteral nutrition.

Animals↗