The technique of multiple simultaneous recordings from a large number of extracellular electrodes (> 100) is currently used in the study of normal and abnormal electrical conduction in the heart and the genesis of cardiac arrhythmias. To investigate whether such a system could also be applied in gastrointestinal electrophysiology, several studies were performed with this technique on segments of isolated rabbit duodenum. A multiple-electrode assembly consisting of 240 silver wires was positioned on the serosal surface of the duodenum, and the recorded signals were, after suitable processing, stored. Thereafter, analysis of all simultaneously recorded slow waves during a selected period of time was performed to reconstruct the pattern of conduction in the duodenum. The first results show that there is a considerable variation in conduction pattern, which is determined by the site of the natural pacemaker. Several experiments were performed to rule out possible deleterious effects of positioning the multiple-electrode assembly on the duodenum. Furthermore, prolonged periods of recording did not influence propagation speed and pattern provided that the positioning of the multiple electrode assembly was performed with care. Entrainment of the natural pacemaker was possible by applying electrical stimuli through 2 of the 240 extracellular electrodes during simultaneous recordings. In conclusion, multisite extracellular mapping of gastrointestinal smooth muscle is possible and can be used to study origin and spread of slow-wave activity.
Structural, dielectric, ferroelectric and piezoelectric properties of lead magnesium niobate–lead titanate, PMN–PT (66:34), prepared at different sintering temperatures (1150–1250°C) are discussed for actuator applications. System sintered at 1200 and 1250°C showed better perovskite phase stabilization and higher values of dielectric constant (ε
r). Remnant polarization (P
r) was found to be higher (45 µC/cm2) for the system sintered at 1250°C. The piezoelectric coefficients, d
33, d
31, d
h and strain induced in the system by a large electric field were found to be sintering temperature dependent. Hysteresis free strain behavior of the system sintered at 1200°C showed the suitability of this material for actuator applications.
The practice of laparoscopic appendectomy as an ambulatory surgery is uncommon even in apex institutes, more so in developing countries, despite proven feasibility. To promote this practice in the developing countries like ours, we attempted to find the safety and cost effectiveness in such institutions which have limited resources. Thirty cases of symptomatic appendicitis were tried for same day discharge after laparoscopic appendectomies. The results were encouraging with 87% patients discharged on the same day and 13% on the next day in the early morning. Among the next day discharged cases, only 03% stayed for medical reasons (nausea, vomiting, and pain) while 10% stayed as their attendants declined to leave (social reasons), even though they were medically eligible for discharge from the hospital. There were no significant postoperative complications except tolerable pain in all patients and mild to moderate nausea/vomiting in 80%. There was no readmission. The mean length of hospital stay was 11.20 hrs. At the time of discharge all patients were highly satisfied. We concluded that routine same day discharge is safe and feasible after appendectomies in developing countries, with social decline as the main hurdle which can be improved by proper communication.
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