• The Korean Journal of Physiology
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• v.21 no.1
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• pp.35-46
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• 1987

It has been well known that estrogens stimulate the uterine contractility and progestins inhibit it. Then, one may expect that the uterine contractility and sensitivities to oxytocin (OT) and prostaglandin $F_{2{\alpha}}\;(PGF_{2{\alpha}})$ would be different among the estrus cycle. These hypotheses were tested using the mature female rat. Spontaneous isometric contractions of isolated uterine strips $(1{\times}0.3\;cm)$ from cyclic rats in various stages of the estrus cycle, bilateral ovarectomized rats and hypophysectomized rats were recorded in absence or presence with $estradiol-17{\beta}\;(E_2)$, progesterone $(P_4)$, OT and $PGF_{2{\alpha}}$. The results were summarized as follows: 1) The spontaneous uterine contractile force was the highest in the estrus rat and the lowest in the ovarectomized or the hypophysectomized rat. In the proestrus rat, the contractile frequency was the lowest (2.7 beats/10 min) and the contractile duration was the longest (70 sec). In the other groups, there were no any differencies in frequency (9 beats/10 min) and in duration (30 sec). 2) OT and $PGF_{2{\alpha}}$ stimulated the uterine contractility in all groups tested except in the hypophysectomized rat in which OT failed to stimulate the uterine contraction. $PGF_{2{\alpha}}$ was more effective in stimulating the uterine contraction than OT in all groups tested except in the estrus rat. OT-induced contraction was the highest in the estrus rat and $PGF_{2{\alpha}}-induced$ contraction was the lowest in the hypophysectomized rat. 3) Uterine contractilities were not changed by the in vitro treatments of $E_2$ or $P_4$ under the influence of endogenous steroids, however, $E_2$ and $P_4$ stimulated the uterine contraction in the ovarectomized rat in which endogenous steroids were almost abolished. 4) Increased uterine contraction by the treatment of OT was suppressed by in vitro $E_2$ or $P_4$ in the estrus rat, while it was potentiated by the $P_4$ in the proestrus rat. In other groups, exogenous $E_2$ or $P_4$ did not affect the OT-induced uterine contraction. 5) $PGF_{2{\alpha}}-induced$ uterine contraction was suppressed in the ovarectomized rat by $E_2$ and $P_4$, in the diestrus and proestrus rats by $P_4$ and in the hypophysectomized rat by $E_2$. In other groups, exogenous $E_2$ or $P_4$ was ineffective in altering the $PGF_{2{\alpha}}-induced$ uterine contraction. According to the above results, it may conclude that the mechanisms of the different uterine contractility and the different uterine sensitivity to OT or $PGF_{2{\alpha}}$ according to the estrus cycle are not explicable with only the serum concentrations of steroids, OT and $PGF_{2{\alpha}}$ but also other unknown factors.

• Steel and Composite Structures
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• v.9 no.3
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• pp.191-208
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• 2009

Observations from experiments and real fire indicate that restrained steel beams have better fire-resistant capability than isolated beams. Due to the effects of restraints, a steel beam in fire condition can undergo very large deflections and the run away damage may be avoided. However disgusting damages may occur in the beam-to-column connections, which is considered to be mainly caused by the enormous axial tensile forces in steel beams resulted from temperature decreasing after fire dies out. Over the past ten years, the behaviour of restrained steel beams subjected to fire during heating has been experimentally and theoretically investigated in detail, and some simplified analytical approaches have been proposed. While the performance of restrained steel beams during cooling has not been so deeply studied. For the safety evaluation and repair of steel structures against fire, more detailed investigation on the behaviour of restrained steel beams subjected to fire during cooling is necessary. When the temperature decreases, the elastic modulus and yield strength of steel recover, and the contraction force in restrained steel beams will be produced. In this paper, an incremental method is proposed for analyzing the behaviour of restrained steel beams subjected to cooling. In each temperature decrement, the development of deformation and internal forces of a restrained beam is divided into four steps, in order to consider the effect of the recovery of the elastic modulus and strength of steel and the contraction force generated by temperature decrease in the beam respectively. At last, the proposed approach is validated by FE method.

• Korean Journal of Acupuncture
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• v.17 no.1
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• pp.75-80
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• 2000

Fructus Aristolochiae has been used in Korea for many centuries as a treatment for various disease.The purpose of the present study is to determine the effect of Fructus Aristolochiae on norepinephrine(NE) induced blood vessel contraction in rabbits. Rabbit(2 kg, male) were killed by $CO_2$ exposure and a segment (8-10mm) of each rabbit was cut into equal segments and mounted in a tissue bath. Contractile force was measured with force displacement transducers under 2-3 g loading tension. The dose of norepinephrine(NE) which evoked 50% of maximal response ($ED_{50}$) was obtained from cumulative dose response curves for NE ($10^{-6}{\sim}10^{-3}M$). Contractions evoked by NE ($ED_{50}$) were inhibited significantly by Fructus Aristolochiae in abdominal aorta and femoral artery. Fructus Aristolochiae inhibited the relaxation pretreated propranolol and L-NNA in femoral artery. But Fructus Aristolochiae did not effect the relaxation pretreated ODQ in femoral artery and abdominal aorta. These results indicate that Fructus Aristolochiae can relax NE induced contraction of rabbit blood vessel selectively, and that this relaxation relates to nitric oxide synthesis and sympathetic action.

• Korean Journal of Applied Biomechanics
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• v.27 no.2
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• pp.83-90
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• 2017

Objective: To investigate the effect of short-term vibration frequencies on muscle force generation capabilities. Method: Six healthy participants were recruited for this study and only their dominant leg was tested. The subjects were tested under five conditions of vibration frequencies with constant amplitude: 0 Hz (no vibration), 30 Hz, 60 Hz, and 90 Hz, and the vibration amplitude was 10 mm for all frequency conditions. The vibration was applied to the rectus femoris (RF). The subjects were then instructed to maintain a steady-state isometric knee joint torque (100 Nm) for the first 6 s. After the steady-state torque production, the subjects were required to produce isometric knee joint torque by leg extension as hard as possible with a start signal within the next 3 s. The vibration was applied for ~4 s starting from 1 s before initiation of the change in the steady-state knee joint torque. Results: The results showed that the maximum voluntary torque (MVT) of the knee joint increased with the vibration frequencies. On average, the MVTs were 756.47 Nm for 0 Hz (no vibration) and 809.61 Nm for 90 Hz. There was a significant positive correlation (r = 0.71) between the MVTs and integrated electromyograms (iEMGs). Further, the co-contraction indices (CCIs) were computed, which represent the ratio of the iEMGs of the antagonist muscle to the iEMGs of all involved muscles. There was a significant negative correlation (r = 0.62) between the CCIs and MVTs, which was accompanied by a significant positive correlation (r = 0.69) between the iEMGs of the vibrated muscle (RF). There was no significant correlation between the MVTs and iEMGs of the antagonist muscle. Conclusion: The results of this study suggest that the short-term vibration on the muscle increases the level of muscle activation possibly owing to the increased Ia afferent activities, which enhances the muscle force generation capability.

• Journal of Sensor Science and Technology
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• v.30 no.2
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• pp.109-113
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• 2021

In this study, an automated culture media replacement system was developed to analyze changes in the contraction characteristics of cardiomyocytes according to the state of the culture media. For the long-term storage of culture media, a Peltier refrigerator with a temperature of 5 to 8℃ was provided and a pH of 7.4 was maintained. The cell culture media of the cardiomyocytes was continuously replaced using interlocking pumps at a flow rate of 0.83 μl/h. The cardiomyocytes in which the culture media was replaced automatically demonstrated lower heartbeats per minute compared to samples in which there was no replacement. However, these cardiomyocytes moved more uniformly and produced greater displacement in one heartbeat cycle. It was observed that the sarcomere length of the cardiomyocytes increased due to the automated culture media replacement system. These cardiomyocytes were found to demonstrate better maturation compared to the control group. The maturation of cardiomyocytes was verified through staining images. The proposed automated culture media replacement system generates a uniform heart rate and improvements in contraction force. Based on the study, patient-specific drug toxicity assessments can be conducted using differentiated cardiomyocytes in induced pluripotent stem cells.

• Physical Therapy Korea
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• v.13 no.4
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• pp.10-15
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• 2006

This study examined the ability of human subjects to match a force in their quadriceps muscle during fatigue. Twenty subjects (mean age: 23.4 yrs, mean height: 167.8 cm, mean weight, 62.6 kg) were enrolled in the experiment. In the force-matching task, the quadriceps muscle generated 50% of the MVIC (maximum voluntary isometric contraction) torque under visual control and then without visual feedback. After inducing fatigue in the quadriceps muscle, the subjects were required to match 50% of the MVIC torque without visual feedback. The perceived magnitude of the force and force-matching errors were measured. 50% of the MVIC torque was perceived from 39.96 Nm in the pre-fatigue condition to 44.95 Nm in the post-fatigue condition. 50% of the MVIC torque-matching errors increased significantly from .55% in the pre-fatigue condition to 9.6% in the post-fatigue condition (p<.001). in addition, there were significantly more force-matching errors in women than in men (p<.01). In conclusion muscle fatigue can interfere with a subject's ability to match a force. This suggests that muscle fatigue may contributes to the sensitization of the proprioception.

• Physical Therapy Korea
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• v.27 no.2
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• pp.126-132
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• 2020

Background: Augmented somatosensory feedback stimulates the mechanoreceptor to deliver information on bodily position, improving the postural control. The various types of such feedback include ankle-foot orthoses (AFOs) and vibration. The optimal feedback to mitigate postural sway remains unclear, as does the effect of augmented somatosensory feedback on muscle co-contraction. Objects: We compared postural sway and ankle muscle co-contraction without feedback (control) and with either of two forms of somatosensory feedback (AFOs and vibration). Methods: We recruited 15 healthy subjects and tested them under three feedback conditions (control, AFOs, vibration) with two sensory conditions (eyes open, or eyes closed and the head tilted back), in random order. Postural sway was measured using a force platform; the mean sway area of the 95% confidence ellipse (AREA) and the mean velocity of the center-of-pressure displacement (VEL) were assessed. Co-contraction of the tibialis anterior and gastrocnemius muscles was measured using electromyography and converted into a co-contraction index (CI). Results: We found significant main effects of the three feedback states on postural sway (AREA, VEL) and the CI. The two sensory conditions exerted significant main effects on postural sway (AREA and VEL). AFOs reduced postural sway to a level significantly lower than that of the control (p = 0.014, p < 0.001) or that afforded by vibration (p = 0.024, p < 0.001). In terms of CI amelioration, the AFOs condition was significantly better than the control (p = 0.004). Vibration did not significantly improve either postural sway or the CI compared to the control condition. There was no significant interaction effect between the three feedback conditions and the two sensory conditions. Conclusion: Lower-extremity devices such as AFOs enhance somatosensory perception, improving postural control and decreasing the CI during static standing.

• The Journal of Internal Korean Medicine
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• v.19 no.1
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• pp.409-427
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• 1998

Insamjungchuntang has been used in Korea for many centuries as a treatment for respiratory disease. The effect of Insamjungchuntang on tracheal smooth muscle is not known. The purpose of the present study is to determine the effect of Insamjungchuntang on histamine and acetylcholine induced tracheal smooth muscle contraction in rats and guinea pigs. Guinea pig (500 g, male) and Sprague Dawley rats (200 g, male) were killed by $CO_2$ exposure and a segment (8-10 mm) of the thoracic trachea from each rat and guinea pig was cut into equal segments and mounted 'in pairs' in a tissue bath. Contractile force was measured with force displacement transducers under 0.5 g loading tension. The dose of histamine (His) and acetylcholine (Ach) which evoked 50% of maximal response $(ED_{50})$ was obtained from cumulative dose response curves for histamine and acetylcholine$(10^{-7}{\sim}10^{-4}\;M)$. Contractions evoked by His ($ED_{50}$) and Ach $(ED_{50})$ were inhibited significantly by Insamjungchuntang. In guinea pig tracheal smooth muscle, the mean percent inhibition of acetylcholine induced contraction was $38.58\(p<0.05)\;after\;10{\mu}l/ml$ Insamjungchuntang, $90.75\(p<0.01)\;after\;30{\mu}l/ml$. Insamjungchuntang and $133.17\(p<0.01)\;after\;100{\mu}l/ml$ Insamjungchuntang. In rat tracheal smooth muscle, the mean percent inhibition of acetylcholine induced contraction was $10.0\(p<0.05)\;after\;10{\mu}l/ml$ Insamjungchuntang, $80.71\(p<0.01)\;after\;30{\mu}/ml$ Insamjungchuntang and $118.29\(p<0.01)\;after\;100{\mu}l/ml$ Insamjungchuntang. Also, in guinea pig tracheal smooth muscle, the mean percent inhibition of histamine induced contraction was $45.5\(p<0.01)\;after\;10{\mu}l/ml$ lnsamjungchuntang, and $93.17\(p<0.01)\;after\;30{\mu}l/ml$. lnsamjungchuntang $134.50\(p<0.01)\;after\;100{\mu}l/ml$ Insamjungchuntang. In rat tracheal smooth muscle, the mean percent inhibition of histamine induced contraction was $37.83\(p<0.01)\;after\;10{\mu}l/ml$ lnsamjungchuntang, $90.5\(p<0.01)\;after\;30{\mu}l/ml$ Insamjungchuntang and $135.17\(p<0.01)\;after\;100{\mu}l/ml$ Insamjungchuntang. Propranolol $(10^{-7}\;M)$ slightly but significantly attenuated the inhibitory effects of Insamjungchuntang. Following treatment with propranolol, the mean percent inhibition caused by $100{\mu}l/ml$. Insamjungchuntang fell to 46.42% in guinea pig induced by acetylcholine contraction and by $100{\mu}l/ml$ Insamjungchuntang fell to 5.43% (p<0.05) in rat induced by acetylcholine contraction and the mean percent inhibition caused by $100{\mu}l/ml$ Insamjungchuntang fell to 49.0% in guinea pig induced by histamine contraction and by $100{\mu}l/ml$ Insamjungchuntang fell to 48.6% (p<0.05) in rat induced by histamine contraction. Indomethacin and methylene blue $(10^{-7}\;M)$ did not significantly alter the inhibitory effect of lnsamjungchuntang. Also, I could find the effects of lnsamjungchuntang and Insamjungchuntanggamorphine on the tracheal smooth muscle in guinea pig and rat did not change significantly. These results indicate that Insamjungchuntang can relax histamine and acetylcholine-induced contraction of guinea pig and rat tracheal smooth muscle, and that this inhibition involves sympathetic effects.

• Journal of Oral Medicine and Pain
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• v.10 no.1
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• pp.63-71
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• 1985

A kinematical study of bite force during voluntary isometric contraction was investigated in 20 Korean men with TMJ dysfunction and 30 Korean men as normal subject, ranging from 20 to 27 years old. The author observed maximum bite force, slope of bite force graph, curve index and duration of maximum bite force with the use of the foil strain gauge (MPM-3000) and RS Dymograph (Beckman). The obtained results were as follows : 1. Maximum bite forces were 29kg and 29kg for left and right side of normal subject (p>0.05) and 19kg and 29kg for affected and non-affected side of TMJ dysfunction patient. 2. The slopes of bite force graph were $68^{\circ}$ and $68^{\circ}$ for left and right side of normal subject (p>0.05) and $59^{\circ}$ and $71^{\circ}$ for affected and non-affected side of TMJ dysfunction patient. (p<0.01) 3. The curve indices were 0.93 and 0.90 for left and right side of normal subject and 1.10 and 0.90 for affected and non-affected side of TMJ dysfunction patient. (p>0.05) 4. The durations of maximum bite force were 424 msec and 413 msec for left and right side of normal subject and 337 msec and 334 msec for affected and non-affected side of TMJ dysfunction patient. (p>0.05)

• Journal of Oral Medicine and Pain
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• v.9 no.1
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• pp.139-145
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• 1984

A Kinematical study of bite force during voluntary isometric contraction was investigated in 20 Korean women with TMJ dysfunction and 50 Korean women a normal subject, ranging from 19 to 29 years old. The author observed maximal bite force, slope of bite force graph, curve index and duration of maximal bite force by way of the foil strain guage(MPM-3000) and Dymograph(Beckman). The obtained results were as follows : 1. Maximal bite forces were 26.48kg and 21.38kg for left and right side of normal subject and 12.85kg and 20.70kg for affected and mon-affected side of TMJ dysfunction patients. 2. The slope of bite force graph were 64.69。and 63.83。 for left and right side of normal subject and 53.14。and 69.57。for affected and non-affected side. 3. The curve indexes were 0.54 and 0.80 for left and right side of normal subject and 2.30 and 0.60 for affected and non-affected side. 4. The duration of maximal bite force were 383.12 msec and 393.60 msec for left and right side of normal subject and 345.30 msec and 312.25 msec for affected and non-affected side.