Index Of Electrical Activity Research Articles

МОТОРНО-ЭВАКУАТОРНАЯ ФУНКЦИЯ ЖЕЛУДКА И ДВЕНАДЦАТИПЕРСТНОЙ КИШКИ У БОЛЬНЫХ ЯЗВЕННОЙ БОЛЕЗНЬЮ С СОПУТСТВУЮЩЕЙ ДУОДЕНАЛЬНОЙ НЕДОСТАТОЧНОСТЬЮ

The purpose: to study the peculiarities of motor and evacuation functions of the stomach and duodenum in patients with peptic ulcer with associated chronic duodenal insufficiency (СDI). Materials and methods. The complex examination was carried out by 160 patients with ulcer disease (UD) with concomitant CDI (group 1) and 104 patients with no concomitant CDI (2nd group). The verification of UD was carried out by clinical and fibrogastroduodenoscopy studies. In the definition of CDI contrast duodenography and fibrogastroduodenoscopy were used. The evaluation of the motor-evacuation function (MEF) of the stomach and duodenum was carried out with the help of the peripheral electrogastroenterograph. Results of the study. In patients with UD with associated HDI before meals were identified bradygastria (75%) and hypertension (67%) of the stomach, and after eating the parameters of the electrical activity of the stomach in frequency and amplitude were decreased. We revealed hypokinesia (74%) and hypertension (52%) of duodenum on an empty stomach, postprandial frequency of it decreases compared with a thorough examination. The duodenogastric reflux is revealed in the fasting phase of the study. A segmenting and peristaltic contractions of the duodenum are slowed down, which is manifested in a decrease in the evacuation function of stomach and duodenum. Before meals in patients with UD without accompanying HDI were identified hypertension of the stomach (15%) and duodenum (68,95%), after a meal the indices of electrical activity of the stomach and duodenum were increased. In patients with duodenum ulcer of 1 group the electrical activity of duodenum before meals was corresponded to hyperkinetic (98.2%) and hypertensive (62.3%) type of the curve. The eating in patients of this group increases the peristaltic contractions of the longitudinal muscle layer of the duodenum, thereby accelerating the evacuation of the chyme without mixing it and disrupting the digestion process. In patients with duodenal ulcer without accompanying HDI before meals were identified the hypertension of the stomach (15%) and duodenum (68.95%), coordinated work of stomach and duodenum, as well as evacuation of food chyme were preserved. The conclusion. In patients with ulcer disease of stomach and duodenum with accompanying duodenal insufficiency, there was a violation of motor and evacuation activity of the stomach and duodenum both on an empty stomach and after eating, which adversely affects the course of ulcer disease.

Absence of glucose transporter 4 diminishes electrical activity of mouse hearts during hypoxia

Insulin resistance, which characterizes type 2 diabetes, is associated with reduced translocation of glucose transporter 4 (GLUT4) to the plasma membrane following insulin stimulation, and diabetic patients with insulin resistance show a higher incidence of ischaemia, arrhythmias and sudden cardiac death. The aim of this study was to examine whether GLUT4 deficiency leads to more severe alterations in cardiac electrical activity during cardiac stress due to hypoxia. To fulfil this aim, we compared cardiac electrical activity from cardiac-selective GLUT4-ablated (G4H-/-) mouse hearts and corresponding control (CTL) littermates. A custom-made cylindrical 'cage' electrode array measured potentials (Ves) from the epicardium of isolated, perfused mouse hearts. The normalized average of the maximal downstroke of Ves ( (|d Ves/dt(min)|na), which we previously introduced as an index of electrical activity in normal, ischaemic and hypoxic hearts, was used to assess the effects of GLUT4 deficiency on electrical activity. The |d Ves/dt(min)|na of G4H −/− and CTL hearts decreased by 75 and 47%, respectively (P < 0.05), 30 min after the onset of hypoxia. Administration of insulin attenuated decreases in values of |d Ves/dt(min)|na in G4H −/− hearts as well as in CTL hearts, during hypoxia. In general, however, G4H −/− hearts showed a severe alteration of the propagation sequence and a prolonged total activation time. Results of this study demonstrate that reduced glucose availability associated with insulin resistance and a reduction in GLUT4-mediated glucose transport impairs electrical activity during hypoxia, and may contribute to cardiac vulnerability to arrhythmias in diabetic patients.

The Maximal Downstroke of Epicardial Potentials as an Index of Electrical Activity in Mouse Hearts

The maximal upstroke of transmembrane voltage (dV(m)/dt(max)) has been used as an indirect measure of sodium current I(Na) upon activation in cardiac myocytes. However, sodium influx generates not only the upstroke of V(m), but also the downstroke of the extracellular potentials V(e) including epicardial surface potentials V(es). The purpose of this study was to evaluate the magnitude of the maximal downstroke of V(es) (|dV(es)/dt (min)|) as a global index of electrical activation, based on the relationship of dV(m)/dt(max) to I(Na). To fulfill this purpose, we examined |dV(es)/dt(min)| experimentally using isolated perfused mouse hearts and computationally using a 3-D cardiac tissue bidomain model. In experimental studies, a custom-made cylindrical "cage" array with 64 electrodes was slipped over mouse hearts to measure V(es) during hyperkalemia, ischemia, and hypoxia, which are conditions that decrease I(Na). Values of |dV(es)/dt(min)| from each electrode were normalized (|dV(es)/dt (min)|(n)) and averaged (|dV(es)/dt(min)|(na)). Results showed that |dV(es)/dt(min)|(na) decreased during hyperkalemia by 28, 59, and 79% at 8, 10, and 12 mM [K(+)](o), respectively. |dV(es)/dt(min)| also decreased by 54 and 84% 20 min after the onset of ischemia and hypoxia, respectively. In computational studies, |dV(es)/dt(min)| was compared to dV(m)/dt(max) at different levels of the maximum sodium conductance G(Na), extracellular potassium ion concentration [K(+)](o), and intracellular sodium ion concentration [Na(+)](i), which all influence levels of I(Na). Changes in |dV(es)/dt(min)|(n) were similar to dV(m)/dt (max) during alterations of G(Na), [K(+)](o), and [Na(+)](i). Our results demonstrate that |dV(es)/dt(min)|(na) is a robust global index of electrical activation for use in mouse hearts and, similar to dV(m)/dt(max), can be used to probe electrophysiological alterations reliably. The index can be readily measured and evaluated, which makes it attractive for characterization of, for instance, genetically modified mouse hearts and drug effects on cardiac tissue.

Combined intracerebral microdialysis and electrophysiological recording: methodology and applications

A microdialysis probe is described that can simultaneously monitor indices of electrical activity, ionic homeostasis and changes in the composition of the extracellular fluid at the same brain site in anaesthetised laboratory animals. The probe is no larger than its conventional counterpart and avoids tissue injury problems due to implantation of separate recording electrodes. Examples are given of its application to the study of changes following probe implantation, cerebral ischaemia and local high K +-induced depolarisation.

Studies of the electrical activity of thunderstorms with lightning flash-counters

The results of thunderstorm observations made with local lightning flash counters at Poona during 1967–1969 are presented. A positive correlation between the average total count when the count exceeds 20 per hour on a 5V/m counter, and the number of days per month when thunder is heard has been established. The diurnal and seasonal variations in thunderstorm activity are described. It is seen that although a single isolated storm can vitiate the normal pattern of thunderstorm activity in a month or season, a long term statistical average can be taken with a greater degree of confidence as a better index of electrical activity than the current aural method of observation of thunderstorms.