Increase In Myoelectrical Activity Research Articles

The patterns of myoelectrical activity and reaction for teat stimulation recorded in highly productive dairy cows’ udders

The aim of the study was to evaluate electrical properties of the mammary gland of dairy cow during manual and mechanical milking and to adapt the electrographic method for analysis of udder physiology. Udder myoelectrical activity was measured on 10 healthy highly productive dairy cows of Slovak Pied cattle breed. The electrical activity of four quarters of the udder was recorded simultaneously using four bipolar electrodes. The udder was stimulated by delicate two-finger massage, manual milking and mechanical milking. During the experiment the duration of the reaction for stimulation and the amplitude of spike dischargers were listed. The udder stimulation through palpational massage of the teat end, manual and mechanical milking caused immediate reaction. The udder responded to stimulation with an increase in myoelectrical activity: increase in discharge frequency to 2.33 ± 0.6 per min and an increase in discharge amplitude with the average of 457 ± 147 µV. The average count of spike discharges was 3.86 ± 0.97, the average duration of the action potential was 8.12 ± 1.68 s and the average myoelectrical index was 31 ± 4%. Manual milking caused the highest increase in the udder myoelectrical activity. Evaluation of the mammary gland myoelectrical activity may provide an alternative method to study milk ejection disorders and to diagnose mastitis.

Influence of Hip External Rotation on Hip Adductor and Rectus Femoris Myoelectric Activity During a Dynamic Parallel Squat

This study sought to compare the myoelectric activity of the hip adductors (HAs) and rectus femoris (RF) when the hip was in a neutral position or externally rotated by 30° or 50° (H0, H30, and H50, respectively) during a parallel squat. Ten healthy subjects performed 10 repetitions of squats in each of the 3 hip positions and the myoelectric activities of the HAs and RF were recorded. The signal was then divided into categories representing concentric (C) and eccentric (E) contractions in the following ranges of motion: 0-30° (C1 and E1), 30-60° (C2 and E2), and 60-90° (C3 and E3) of knee flexion. From those signals, an root mean square (RMS) value for each range of motion in each hip position was obtained. All values were normalized to those obtained during maximum voluntary isometric contraction. We found that HAs showed a significant increase in myoelectric activity during C3 and E3 in the H30 and H50 positions, as compared with H0. Meanwhile, RF activity did not significantly differ between hip positions. Both muscles showed higher activation during 60-90° (C3 and E3) of knee flexion, as compared with 0-30° (C1 and E1) and 30-60° (C2 and E2). The results suggest that if the aim is to increase HA activity despite the low percentage of muscle activation, squats should be performed with 30° of external rotation and at least 90° of knee flexion.

Effect of 4-(5-Chloro-2-hydroxyphenyl)-3-(2-hydroxyethyl)-6-(trifluoromethyl)-quinolin-2(1H)-one (BMS-223131), a Novel Opener of Large Conductance Ca2+-Activated K+(Maxi-K) Channels on Normal and Stress-Aggravated Colonic Motility and Visceral Nociception

We evaluated the effects of 4-(5-chloro-2-hydroxyphenyl)-3-(2-hydroxyethyl)-6-(trifluoromethyl)-quinolin-2(1H)-one (BMS-223131), an opener of large conductance Ca(2+)-activated potassium (maxi-K) channels, on normal and stress-exacerbated colonic motility and visceral nociception in the rat. Fecal output was employed as an index of motility. Visceral nociception, in response to intracolonic balloon distension (10-90 mm Hg; 30 s duration), was evaluated using one of three indices: change in blood pressure, abdominal withdrawal, or myoelectrical activity. BMS-223131 (2, 6, or 20 mg/kg i.p.) produced a small but dose-dependent and significant reduction in cumulative 24-h fecal output. Fecal output in response to stress (1-h restraint plus bursts of air to the face) was markedly inhibited by BMS-223131, and moisture content was significantly reduced. With regard to visceral pain, the transient and distention-dependent reduction in arterial pressure in anesthetized animals was inhibited by BMS-223131 in a dose-dependent manner. Distension-induced abdominal withdrawal in conscious rats was also dose-dependently attenuated by BMS-223131. BMS-223131 at a dose of 20 mg/kg markedly attenuated the increase in myoelectrical activity evoked by balloon distention in conscious animals. BMS-223131 was also evaluated in viscerally hypersensitive rats (sensitized as neonates by intracolonic mustard oil) where it produced a robust dose-dependent attenuation of the abdominal withdrawal response. Compared with naive animals, BMS-223131 was more potent in the sensitized animals. Thus, BMS-223131 effectively reduced stress-induced colonic motility and visceral nociception supporting the potential utility of maxi-K channel openers for the treatment of bowel disorders involving dysfunctional motility and visceral sensitivity.

Effect of cisapride on myoelectrical activity of the gastrointestinal tract in the conscious miniature pig.

In conscious miniature pigs with electrodes implanted in the wall of the antrum pylori, duodenum, jejunum, ileum and caecum, the influence of intravenous injection of cisapride, 0.5 and 1 mg/kg, on gastrointestinal myoelectrical activity, was examined. Cisapride, 1 mg/kg, induced a delayed and sustained increase in antral myoelectrical activity. The studied intestinal segments were rather insensitive to the stimulating effect of the benzamide, since only the jejunum and the caecum revealed an increase in myoelectrical activity with the higher dose studied.

Effects of octreotide on gallbladder pressure and myoelectric activity of Oddi sphincter in rabbits.

AIM:To observe the effect of octreotide (OT) and somatostatin (SS) on gallbladder pressure and myoelectric activity of SO in rabbits.METHODS:Male rabbits fasted for 15h-18h and anesthetized with urethane. The mean gallbladder pressure (GP) and myoelectric activity of SO were simutaneously measured with a frog bladder connected to a transducer and a pair of copper electrodes.RESULTS:After injection of OT (10&mgr;g/kg, iv), the GP decreased in 2min and reached the lowest value in about 60min (P < 0.01, n = 19), and completely or partially returned to the normal level in 120min. The frequency of myoelectric activty of SO was reduced, even disappeared in 2min (P < 0.01, n = 19) and returned to normal in about 20min. Injection of SS (10&mgr;g/kg, iv) also decreased GP and myoelectric activity of SO (P < 0.01, n = 7); Before and after injection of OT or SS, injection of CCK-8 (100ng or 200ng) caused similar increase in myoelectric activity of SO and GP (P >0.05). Before and after injection of OT, there were no significant differences in increases of myoelectric activity of SO and GP caused by electric stimulation of dorsal motor nucleus of vagus (P >0.05).CONCLUSION:OT and SS decreased GP and myoelectric activity of SO, demonstrating that effects of OT were similar to those of SS. Intravenous injection of OT did not affect the increase of myoelectric activity of SO and GP caused by CCK-8 or electric stimulation of dorsal motor nucleus of vagus.

Intradiskal pressure, intra-abdominal pressure and myoelectric back muscle activity related to posture and loading.

Intradiskal pressures, intra-abdominal pressures and myoelectric activities of posterior back muscles have been measured simultaneously in vivo in 4 subjects. Five different angles of forward flexion were studied while externally loading the trunk with 200N. At 30 degrees of forward flexion studies were made when the load was increased from 0 to 300N. Asymmetric loading was studied with the trunk erect, in lateral flexion and in rotation. The measurement parameter values all increased when the angle of flexion increased and when the external load was increased at a fixed angle of flexion. Linear relationships were established. During asymmetric loading pressure values and the myoelectric activity increased. The increase in myoelectric activity was comparatively greater on the contralateral side of the lumbar region and on the ipsilateral side of the thoracic region. The disk pressure, the intra-abdominal pressure, and the FRA-values were higher throughout when the trunk was loaded in rotation, than in lateral flexion.

The Sitting Posture: An Electromyographic and Discometric Study

The disc pressure of the third lumbar disc and the myoelectric activity of several muscles of the back were measured. Three standing and nine unsupported sitting positions were studied as well as eight support parameters and six sedentary tasks. 1. Myoelectric activity is about the same in standing and in relaxed unsupported sitting. In the unsupported sitting positions the highest level of activity is found in anterior sitting and the lowest in posterior sitting. In the muscles of the cervical and lumbar regions the activity is always lower than in the muscles of the thoracic region. The disc pressure is considerably higher in unsupported sitting than in standing. In the unsupported sitting positions the highest disc pressure is found in anterior sitting and the lowest in sitting straight. 2. Both the myoelectric activity and the disc pressure decrease when the back is supported. Of the support parameters, the backrest inclination is the most important, myoelectric activity and disc pressure both decreasing with an increase in inclination. The disc pressure is considerably reduced also when the lumbar support is increased and when armrests are used. 3. Myoelectric activity and disc pressure are both comparatively low in writing, higher in typing, and still higher in lifting. In the car driver's seat the disc pressure increases both when the gear is shifted and when the clutch pedal is depressed. When the gear is shifted, there is also an increase in myoelectric activity.