BACKGROUND: Intravenous hypnotics are used in pregnancy, labor and delivery. The aim of the present study was to investigate and compare the relaxant effects of propofol, thiopental, ketamine, and etomidate on isolated rat uterine smooth muscles. METHODS: Uterine smooth muscle preparations were obtained from non-pregnant female rats. The uterus of the rat was dissected and cut into 10 mm strips. The muscle strips were bathed in Krebs solution. After spontaneous uterine contractile activity had been accomplished, propofol, ketamine, thiopental, and etomidate in various concentrations were added cumulatively to the baths and resting tension, active tension, and frequency of contration were recorded at each concentration of agents. EC(5), EC(25), EC(50), EC(75), and EC(95) of each drug on active tension and frequency of contraction were calculated using a probit model. RESULTS: Propofol, thiopental, and etomidate reduced uterine contractions in a concentration-dependent manner. Ketamine concentrations of 10(-7) to 10(-5) M augmented uterine contractions but ketamine concentrations of 10(-4) to 10(-3) M attenuated uterine contractions. The EC(50)'s of propofol, thiopental, ketamine, and etomidate on active tension were 1.56 x 10(-5) M, 4.97 x 10(-5) M, 3.52 x 10(-4) M, and 2.73 x 10(-5) M, respectively. CONCLUSIONS: All four intravenous hypnotics relaxed the uterine smooth muscle of rats except for ketamine in low concentrations (10(-7) to 10(-5) M). Propofol had the greatest relaxant effects on isolated rat uterine smooth muscle among these hypnotics. It seems that ketamine is a suitable obstetric hypnotic agent for hypovolemic parturients and propofol is a useful hypnotic agent for uterine relaxation during pregnancy.
Animals ; Baths ; Contracts ; Etomidate ; Female ; Humans ; Hypnotics and Sedatives ; Hypovolemia ; Isotonic Solutions ; Ketamine ; Muscle, Smooth ; Muscles ; Pregnancy ; Propofol ; Rats ; Relaxation ; Thiopental ; Uterine Contraction ; Uterus

Myometrial relaxation of mouse via expression of two-pore domain acid sensitive (TASK) channels was studied. In our previous report, we suggested that two-pore domain acid-sensing K⁺ channels (TASK-2) might be one of the candidates for the regulation of uterine circular smooth muscles in mice. In this study, we tried to show the mechanisms of relaxation via TASK-2 channels in marine myometrium. Isometric contraction measurements and patch clamp technique were used to verify TASK conductance in murine myometrium. Western blot and immunehistochemical study under confocal microscopy were used to investigate molecular identity of TASK channel. In this study, we showed that TEA and 4-AP insensitive non-inactivating outward K⁺ current (NIOK) may be responsible for the quiescence of murine pregnant longitudinal myometrium. The characteristics of NIOK coincided with two-pore domain acid-sensing K⁺ channels (TASK-2). NIOK in the presence of K⁺ channel blockers was inhibited further by TASK inhibitors such as quinidine, bupivacaine, lidocaine, and extracellular acidosis. Furthermore, oxytocin and estrogen inhibited NIOK in pregnant myometrium. When compared to non-pregnant myometrium, pregnant myometrium showed stronger inhibition of NIOK by quinidine and increased immunohistochemical expression of TASK-2. Finally, TASK-2 inhibitors induced strong myometrial contraction even in the presence of L-methionine, a known inhibitor of stretch-activated channels in the longitudinal myometrium of mouse. Activation of TASK-2 channels seems to play an essential role for relaxing uterus during pregnancy and it might be one of the alternatives for preventing preterm delivery.
Acidosis ; Animals ; Blotting, Western ; Bupivacaine ; Estrogens ; Female ; Isometric Contraction ; Lidocaine ; Methionine ; Mice* ; Microscopy, Confocal ; Muscle, Smooth ; Myometrium ; Oxytocin ; Pregnancy ; Quinidine ; Relaxation* ; Tea ; Uterine Contraction ; Uterus

BACKGROUND: It has been reported that etomidate has the relaxant effects on vascular, tracheal, and non-pregnant uterine smooth muscle in vitro. The purpose of this study was to investigate the relaxant effects of etomidate on the contraction of the pregnant rat uterine smooth muscle. METHODS: Uterine muscle tissues were obtained from pregnant rats (n = 15). The uterine segments were mounted in organ baths filled with Krebs solution. After oxytocin-induced contractile activity had been established, etomidate in incremental concentrations (10(-7) to 10(-3) M) was added cumulatively to the bath, each administered 20 min apart, and resultant changes in contractile activity were continuously recorded. EC5 (effective concentration of 5% reduction), EC25, EC50, EC75, and EC95 on active tension were calculated using a probit model. RESULTS: Etomidate (10(-7) to 10(-3) M) induced dose-dependent decreases in amplitude and frequency of uterine contraction. The EC50 of etomidate on active tension were 5.91 x 10(-5) M. CONCLUSIONS: These results demonstrate that etomidate had inhibitory effects on pregnant rat uterine muscle at supraclinical concentration (5.91 x 10(-5) M).
Animals ; Baths ; Contracts ; Etomidate ; Female ; Isotonic Solutions ; Mice ; Muscle, Smooth ; Myometrium ; Oxytocin ; Rats ; Uterine Contraction

Strength training is one of the most common exercises practiced in the field of physical therapy or sports training. However, limited methodology is available to evaluate its effect on the target muscle. This study aimed to test the hypothesis that surface electromyographic (EMG) data from both isometric and isotonic exercise can express changes within the muscle during a 12-week strength training program. Ten healthy male volunteer students (5 for training, 5 for controls) from Yonsei University were recruited for evaluation in this study. DeLorme's axiom was practiced for 12 weeks in the dominant elbow flexors and knee extensors of the training group. Tension for 1 repetition maximum and maximal voluntary isometric contraction, and surface EMG information such as the integrated EMG and three variables from the regression line of median frequency (MDF) data were measured at weeks 0, 3, 6, 9, and 12. The limb circumference was measured at weeks 0 and 12. During the strength training, which was enough for the increment of muscle strength and limb circumference, the rectified-integrated EMG and initial MDF increased with a significant linear pattern in both types of contraction. The two surface EMG variables were able to monitor the physiologic muscle changes during the training. Based on these results, we propose that these two surface EMG variables can be used for monitoring electrophysiological changes in the specific muscle that is undergoing the training program, under conditions where the contraction mode for EMG data collection is either static or dynamic.
Quadriceps Muscle/anatomy & histology/physiology ; Muscle, Skeletal/anatomy & histology/physiology ; Male ; Isotonic Contraction/physiology ; Isometric Contraction/physiology ; Humans ; Fourier Analysis ; Exercise Therapy/*methods ; Electromyography/*methods ; Body Weights and Measures ; Adult

OBJECTIVE: To investigate the association of the muscle contraction with gating of the sensory input at central and peripheral levels according to the intensity of muscle contraction and location of the muscles, somatosensory evoked potentials (SSEPs) studies were evaluated at different levels of isometric contraction in the different muscles. METHOD: Median nerve SSEPs were recorded at Erb's point and scalp in the ten healthy adult subjects with isometric contraction of ipsilateral abductor pollicis brevis (APB), ipsilateral abductor digiti minimi (ADM) and contralateral APB. Median nerve SSEPs were recorded in each of these conditions during precontraction, weak contraction, strong contraction and 4 minutes after contraction. RESULTS: 1) N9 amplitudes of median SSEPs recorded at Erb's point were augumented during weak contraction and these amplitude augumentations were statistically significant in the ipsilateral APB contraction (p<0.05). 2) N20 amplitudes recorded at scalp were inhibited during strong isometric contraction and these amplitude inhibitions were statistically significant in the ipsilateral APB contraction (p<0.05). 3) The latencies of N9 and N20 potentials were not significantly changed during isometric contraction. CONCLUSION: Therefore peripheral nervous system as well as central nervous system is responsible for gating, so the subject should be asked for the best relaxation possible for higher reliability of SSEPs.
Adult ; Central Nervous System ; Evoked Potentials, Somatosensory* ; Humans ; Isometric Contraction ; Median Nerve ; Muscle Contraction* ; Muscles ; Peripheral Nervous System ; Relaxation ; Scalp

BACKGROUND/AIMS: High-resolution methods have advanced esophageal and anorectal manometry interpretation but are incompletely established for intestinal manometry. We characterized normal fasting duodeno-jejunal manometry parameters not measurable by standard techniques using clustered closely-spaced recordings. METHODS: Ten fasting recordings were performed in 8 healthy controls using catheters with 3–4 gastrointestinal manometry clusters with 1–2 cm channel spacing. Migrating motor complex phase III characteristics were quantified. Spatial-temporal contour plots measured propagation direction and velocity of individual contractions. Coupling was defined by pressure peak continuity within clusters. RESULTS: Twenty-three phase III complexes (11 antral, 12 intestinal origin) with 157 (95% CI, 104–211) minute periodicities, 6.99 (6.25–7.74) minute durations, 10.92 (10.68–11.16) cycle/minute frequencies, 73.6 (67.7–79.5) mmHg maximal amplitudes, and 4.20 (3.18–5.22) cm/minute propagation velocities were recorded. Coupling of individual contractions was 39.1% (32.1–46.1); 63.0% (54.4–71.6) of contractions were antegrade and 32.8% (24.1–41.5) were retrograde. Individual phase III contractions propagated > 35 fold faster (2.48 cm/sec; 95% CI, 2.25–2.71) than complexes themselves. Phase III complexes beyond the proximal jejunum were longer in duration (P = 0.025) and had poorer contractile coupling (P = 0.025) than proximal complexes. Coupling was greater with 1 cm channel spacing vs 2 cm (P < 0.001). CONCLUSIONS: Intestinal manometry using clustered closely-spaced pressure ports characterizes novel antegrade and retrograde propagation and coupling properties which degrade in more distal jejunal segments. Coupling is greater with more closely-spaced recordings. Applying similar methods to dysmotility syndromes will define the relevance of these methods.
Catheters ; Fasting ; Intestines ; Jejunum ; Manometry ; Muscle Contraction ; Myoelectric Complex, Migrating ; Periodicity

Shikonin, a natural flavonoid found in the roots of Lithospermum erythrorhizon, has been shown to possess many biological functions. The present study was undertaken to investigate the influence of shikonin on vascular smooth muscle contractility and to determine the mechanism involved. Denuded aortic rings from male rats were used and isometric contractions were recorded and combined with molecular experiments. Shikonin significantly relaxed fluoride-, thromboxane A2- or phorbol ester-induced vascular contraction suggesting as a possible anti-hypertensive on the agonist-induced vascular contraction regardless of endothelial nitric oxide synthesis. Furthermore, shikonin significantly inhibited fluoride-induced increases in pMYPT1 levels and phorbol ester-induced increases in pERK1/2 levels suggesting the mechanism involving the inhibition of Rho-kinase activity and the subsequent phosphorylation of MYPT1 and the inhibition of MEK activity and the subsequent phosphorylation of ERK1/2. This study provides evidence regarding the mechanism underlying the relaxation effect of shikonin on agonist-induced vascular contraction regardless of endothelial function.
Animals ; Fluorides ; Humans ; Isometric Contraction ; Lithospermum ; Male ; Muscle, Smooth, Vascular ; Nitric Oxide ; Phosphorylation ; Rats ; Relaxation ; rho-Associated Kinases

Fisetin, a natural flavonoid found in a variety of vegetables and fruits, has been shown to possess many biological functions. The present study was undertaken to investigate the influence of fisetin on vascular smooth muscle contractility and to determine the mechanism involved. Denuded aortic rings from male rats were used and isometric contractions were recorded and combined with molecular experiments. Fisetin significantly relaxed fluoride-, thromboxane A2- or phorbol ester-induced vascular contraction suggesting as a possible anti-hypertensive on the agonist-induced vascular contraction regardless of endothelial nitric oxide synthesis. Furthermore, fisetin significantly inhibited fluoride-induced increases in pMYPT1 levels and phorbol ester-induced increases in pERK1/2 levels suggesting the mechanism involving the inhibition of Rho-kinase activity and the subsequent phosphorylation of MYPT1 and MEK activity and the subsequent phosphorylation of ERK1/2. This study provides evidence regarding the mechanism underlying the relaxation effect of fisetin on agonist-induced vascular contraction regardless of endothelial function.
Animals ; Fluorides ; Fruit ; Humans ; Isometric Contraction ; Male ; Muscle, Smooth, Vascular ; Nitric Oxide ; Phosphorylation ; Rats ; Relaxation ; rho-Associated Kinases ; Vegetables

The present study was undertaken to investigate the influence of hypothermia on endothelium-independent vascular smooth muscle contractility and to determine the mechanism underlying the relaxation. Denuded aortic rings from male rats were used and isometric contractions were recorded and combined with molecular experiments. Hypothermia significantly inhibited fluoride-, thromboxane A2-, phenylephrine-, and phorbol ester-induced vascular contractions regardless of endothelial nitric oxide synthesis, suggesting that another pathway had a direct effect on vascular smooth muscle. Hypothermia significantly inhibited the fluoride-induced increase in pMYPT1 level and phorbol ester-induced increase in pERK1/2 level, suggesting inhibition of Rho-kinase and MEK activity and subsequent phosphorylation of MYPT1 and ERK1/2. These results suggest that the relaxing effect of moderate hypothermia on agonist-induced vascular contraction regardless of endothelial function involves inhibition of Rho-kinase and MEK activities.
Animals ; Fluorides ; Humans ; Hypothermia* ; Isometric Contraction ; Male ; Muscle, Smooth, Vascular ; Nitric Oxide ; Phosphorylation ; Rats ; Relaxation ; rho-Associated Kinases*

OBJECTIVE: The purpose of this study is to determine the proper hand position during driving by measuring of the wheel rotation strength according to the wheel angle and hand position to the wheel. METHOD: BTE Work Simulator was used to measure the clockwise and counter clockwise static wheel rotation force of twenty healthy men in three different hand position (2~10 spot, 3~9 spot, and 4~8 spot) and two different wheel angle (45 degrees and 60 degrees), average and peak force were measured during maximal isometric contraction. RESULTS: The average and peak force was significantly different by the wheel angle, and hand position (p<0.01), but the direction of rotation didn't an effect on the rotation force. The hand position was the most significant factor, especially wheel rotation force at 2~10 spot hand position was significantly lower than that of 3~9 spot and 4~8 spot (p<0.05). The rotation force by the wheel angle was influenced by hand position, and lower in 60 degrees wheel angle in the 2~10 spot (p<0.05). CONCLUSION: The rotation force of wheel was influenced by the hand position. Therefore proper hand position is recommended during driving to reduce muscle fatigue.
Hand* ; Humans ; Isometric Contraction ; Male ; Muscle Fatigue