• Molecular & Cellular Toxicology
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• v.4 no.1
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• pp.72-77
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• 2008

The present study was undertaken to determine whether pioglitazone treatment influences on the agonist-induced vascular smooth muscle contraction and, if so, to investigate the related mechanism. The measurement of isometric contractions using a computerized data acquisition system was combined with molecular experiments. Pioglitazone decreased Rho-kinase activating agonist-induced contraction but not phorbol ester-induced contraction suggesting the least involvement of $Ca^{2+}$-independent thin filament regulation of contractility. Furthermore, pioglitazone decreased thromboxane $A_2$ mimeticinduced phosphorylation of MYPT1 at Thr855, the newly-highlighted site, instead of Thr696. In conclusion, this study provides the evidence and possible related mechanism concerning the vasorelaxing effect of pioglitazone as an antihypertensive on the agonist-induced contraction in rat aortic rings regardless of endothelial function.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 1994.04a
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• pp.394-398
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• 1994

The aim of the present study was to determine the influence of vibration frequency and muscle contraction level at constant vibration displacement amplitudes on a commonly observed motor response elicited by local vibratory stimulation, i.e., the Tonic Vibration Reflex (TVR). Vibration was applied to the distal tendons of the hand flexor muscles. Changes in activity of the hand flexor and extensor muscles were analyzed as a function of the vibration frequency (40-200 Hz), displacement amplitude(200.mu.m and 300.mu.m peak-to-peak), and the initial contraction level of the flexor muscles (0%, 10%, and 20% of the maximal voluntary contraction: MVC). The main results indicate that the TVR increases with vibration frequency up to 100-150 Hz and decreases beyond, and the TVR attains its maximum at 10% MVC. It appears that high frequency vibration tends to induce less muscle/tendon stress. Such a result is of particular importance for the design of handheld vibrating tools.

• Physical Therapy Korea
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• v.23 no.2
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• pp.75-83
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• 2016

Background: Several studies have discussed diverse exercise methods considered to be useful for the selective contraction of the vastus medialis oblique (VMO) muscle for the treatment of patellofemoral pain syndrome. Some studies have reported that exercise methods, including hip adduction, in closed kinetic chain exercises are more effective in terms of the muscle activation of the VMO and the timing of the muscle's initial contraction. We focused on isometric contraction during a closed kinetic chain exercise with hip adduction. Objects: The purpose of this study was to examine muscle activation in the VMO and the vastus lateralis (VL) and the onset time difference between their initial contractions via closed kinetic chain isometric quadriceps femoris exercises including hip adduction. Methods: In total, 36 healthy subjects adopted two hip positions during isometric contraction of the quadriceps femoris in a closed kinetic chain exercise (hip neutral and hip adduction position). Statistical analyses were conducted using a paired t-test (${\alpha}=.05$). Results: Isometric contraction of the quadriceps femoris in a closed kinetic chain exercise caused a greater increase in VMO muscle activity in the hip adduction position [$52.68{\pm}22.21$ percentage of maximal voluntary isometric contraction (%MVIC)]than the hip neutral position ($43.43{\pm}19.85%MVIC$). The onset time difference (VL-VMO) decreased more in the hip adduction position ($-82.14{\pm}34.2ms$) than the hip neutral position ($73.94{\pm}2.94ms$). Conclusion: We recommend this exercise as a clinically useful therapeutic method for patients with patellofemoral pain syndrome due to weakening of the VMO muscle and lateral inclination of the patella.

• Archives of Plastic Surgery
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• v.50 no.1
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• pp.106-115
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• 2023

Background Primary contraction of full-thickness graft has been traditionally quoted to be 40%. There are lacunae in literature to elaborate on the factors influencing it ever since. Methods About 75 subjects who underwent full-thickness grafting procedures to resurface small defects were included in the study. The initial and final graft dimensions after primary contraction were traced on X-ray templates and the percentage of contraction was evaluated using the graphical method. This was further correlated with age, collagen, elastic matrix metalloproteinases-1 (MMP-1) and -2 content along with dermal thickness of the skin specimen sent from the graft. Results The primary contraction of the graft had a very significant correlation only with the initial size of graft harvested with a linear regression of 33.3% and a Spearman's correlation of 0.587 significant at a p-value of 0.001. Conclusion This study though preliminary tries to highlight an important factor that primary contraction of grafts is a physical phenomenon independent of its contents like collagen, elastin, or MMP-1 and -2 or age and dependent on its initial size of harvest instead.

• International Journal of Highway Engineering
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• v.14 no.4
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• pp.63-72
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• 2012

PURPOSES : Hot-mix asphalt(HMA) concretes show a trend of strength increase at low temperature due to binder stiffness increase, but strength decrease below a ceratin low temperature. This is due to the differential thermal contraction(DTC) which is induced by a significant difference in coefficients of thermal contraction between aggregate and asphalt which is coated around the aggregate. This DTC damage is well known to occur in HMA concrete, but is not yet investigated in warm-mix asphalt(WMA) concretes. METHODS : To evaluate DTC damage on WMA in this study, the flexural strength($S_f$) of WMA concretes, which were produced at $30{\sim}40^{\circ}C$ lower temperature, was evaluated in comparison with that of HMA at -5, -15 and $-25^{\circ}C$. RESULTS : Most of WMA and HMA mixtures showed flexural strength increase down to $-15^{\circ}C$ and decrease below $-15^{\circ}C$. this type of strength reduction below $-15^{\circ}C$ can e explained as the effect of differential thermal contraction that is a consequence of the large difference in coefficients of thermal contraction between aggregate and asphalt. the property reduction of WMA is similar the result of previous works dealt with HMA mixtures. CONCLUSIONS : Even though there is some differences by materials used, the WMA concretes showed a significantly lower DTC damage than HMA concrete at low temperature at ${\alpha}$=0.05 level.

• The Korean Journal of Physiology and Pharmacology
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• v.3 no.4
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• pp.439-445
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• 1999

This study is to investigate the mechanism of inhibitory effect of imipramine on the calcium utilization in single cells isolated from canine detrusor. 2 mm thick smooth muscle chops were incubated in 0.12% collagenase solution at $36^{circ}C,$ and aerated with 95% $O_2/5%\;CO_2,$ and then cell suspension was examined. Acetylcholine (ACh) evoked a concentration-dependent contraction of the isolated detrusor cells in normal physiologic salt solution (PSS), and the ACh-induced contraction was significantly inhibited by imipramine. In $Ca^{2+}-free$ PSS, ACh-induced contraction was less than those in normal PSS and it was not affected by the pretreatment with imipramine. $Ca^{2+}-induced$ contraction in $Ca^{2+}-free$ PSS was supressed by imipramine, but addition of A 23187, a calcium ionophore, overcomed the inhibitory effect of imipramine. High potassium-depolarization (40 mM KCl) evoked cell contraction, which was inhibited by imipramine. Caffeine, a releasing agent of the stored $Ca^{2+}$ from sarcoplasmic reticulum, evoked a contraction of the cells that was not blocked by the pretreatment with imipramine. These results suggest that imipramine inhibits the influx of calcium in the detrusor cells through both the receptor-operated- and voltage-gated-calcium channels, but does not affect the release of calcium from intracellular storage site.

• Archives of Plastic Surgery
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• v.39 no.5
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• pp.457-462
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• 2012

Background The elasticity of the back skin of the rat reduced the tension around wounds during the wound healing process in that region, and thus activates wound contraction. The authors proposed two skin fixation methods using readily available materials to decrease the influence of wound contraction on wound healing and designed an experiment to determine their effects. Methods The authors made 36 skin wounds on the backs of 18 rats, and they divided them into three groups. Each group was treated with three different kinds of dressing materials, each with different skin fixing characteristics. Group A was a control group. Group B and group C were dressed by the first and the second skin fixation method. We measured the areas of the wounds post-surgically and calculated the wound area reduction rates. Results The two skin fixation methods both reduced the effect of wound contraction compared to the control group. Each of the two methods had different outcomes in reducing wound contraction. Conclusions The experiment demonstrated significant differences among the wound areas and the wound area reduction rates of the three groups as a result of differences in the degree of wound contraction. To obtain accurate results from wound healing experiments, appropriate skin fixation methods must be adopted.

• The Journal of Internal Korean Medicine
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• v.19 no.1
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• pp.385-408
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• 1998

Pyeongpaesan (平肺散) has been used in Korea for many centuries as a treatment for respiratory disease. The effect of Pyeongpaesan (平肺散) on tracheal smooth muscle is not known. The purpose of the present study is to determine the effect of Pyeongpaesan (平肺散) 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 Pyeongpaesan (平肺散). In guinea pig tracheal smooth muscle, the mean percent inhibition of acetylcholine induced contraction was 13.5% (p<0.05) after $10{\mu}l/ml$ Pyeongpaesan (平肺散), $64.6\(p<0.01)\;after\;30{\mu}l/ml$ Pyeongpaesan (平肺散), and $92.8\(p<0.01)\;after\;100{\mu}l/ml$ Pyeongpaesan (平肺散). In rat tracheal smooth muscle, the mean percent inhibition of acetylcholine induced contraction was $60.9\(p<0.01)\;after\;30{\mu}l/ml$ Pyeongpaesan (平肺散), and $91.2\(p<0.01)\;after\;100{\mu}l/ml$ Pyeongpaesan (平肺散). Also, in guinea pig tracheal smooth muscle, the mean percent inhibition of histamine induced contraction was $104.8\(p<0.01)\;after\;30{\mu}l/ml$ Pyeongpaesan (平肺散) and $142.3\(p<0.01)\;after\;100{\mu}l/ml$ Pyeongpaesan (平肺散). In rat tracheal smooth muscle, the mean percent inhibition of histamine induced contraction was $63.7\(p<0.01)\;after\;30{\mu}l/ml$ Pyeongpaesan (平肺散), and $107.5\(p<0.01)\;after\;100{\mu}l/ml$ Pyeongpaesan (平肺散). Propranolol $(10^{-7}M)$ slightly but significantly attenuated the inhibitory effects of Pyeongpaesan (平肺散). Following treatment with propranolol, the mean percent inhibition caused by $100{\mu}l/ml$ Pyeongpaesan (平肺散) fell to 15.7% (p<0.05) in guinea pig induced by acetylcholine contraction and the mean percent inhibition caused by $100{\mu}l/ml$ Pyeongpaesan (平肺散) fell to 22.3% (p<0.05) in guinea pig induced by histamine contraction and by $100{\mu}l/ml$ Pyeongpaesan (平肺散) fell to 28.7% (p<0.01) in rat induced by histamine contraction. Indomethacin and methylene blue $(10^{-7}\;M)$ did not significantly alter the inhibitory effect of Pyeongpaesan (平肺散). Also, I could find the effects of Pyeongpaesan (平肺散) and Pyeongpaesanga (平肺散加) morphine on the tracheal smooth muscle in guinea pig and rat did not change significantly. These results indicate that Pyeongpaesan. (平肺散) can relax histamine and acetylcholine-induced contraction of guinea pig and rat tracheal smooth muscle, and that this inhibition involves sympathetic effects and the release of cyclooxygenase products.

• Korean Journal of Veterinary Research
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• v.37 no.1
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• pp.119-128
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• 1997

The relaxation of gastric fundus smooth muscles is the primary physiological event which induces the receptive relaxation of monogastric animals. L-arginine/Nitric oxide(L-arg/NO) system is known to mediate the inhibitory non-adrenergic non-cholinergic(NANC) neurotransmission in various tissues including gastrointestinal smooth muscles. The longitudinal smooth muscles of porcine gastric fundus showed fast relaxation during electrical field stimulation(EFS) and rebound contraction after EFS in NANC condition. So, the purpose of present study was elucidation of the neurotrasmitters related to the NANC relaxation and explanation of the relation between NANC relaxation and L-arg/NO system. The longitdinal smooth muscles of porcine gastric fundus were hung in the organ bath and under the presence of guanethidine($5{\times}10^{-5}M$), precontraction was induced by carbachol($1{\times}10^{-6}M$). The muscle responses to EFS and drugs were isomerically recorded. The rusults were summarized as follows. 1. The longtudinal muscles of porcine gastric fundus showed frequency-dependent relaxation and rebound contraction to electrical field stimulaton(1ms, 8V, 1~16Hz, 20sec, EFS). These responses were blocked by tetrodotoxin($1{\times}10^{-6}M$). 2. The relaxation and rebound contraction of the longitudinal muscles of porcine gastric fundus to EFS were inhibited by L-NAME($2{\times}10^{-5}M$). The inhibitory effect of L-NAME was antagonized by L-arginine($1{\times}10^{-3}M$), but not by D-arginine($1{\times}10^{-3}M$). 3. Exogenous NO($NaNO_2$, $1{\times}10^{-5}{\sim}1{\times}10^{-4}M$, pH=2.0) caused concentration-dependent relaxation as EFS did. 4. Methylene Blue($2{\times}10^{-5}M$), a soluble guanylate cyclase inhibitor, inhibited the relaxation and rebound contraction of the longitudinal muscles of porcine gastric fundus induced by EFS, but N-ethlmaleimide, a adenylate cyclase inhibitor, did not. 5. 8-Br-cGMP($1{\times}10^{-6}{\sim}3{\times}10^{-6}M$), permeable cGMP analogue, induced dose-dependent relaxation. but 8-Br-cAMP($1{\times}10^{-6}{\sim}3{\times}10^{-6}M$), permeable cAMP analogue, did not. Both did not evoked rebound contraction. 6. ${\alpha}$-chymotrypsin did not affect the relaxation of the longitudinal muscles of porcine gastric fundus. 7. Reactive blue 2($1{\times}10^{-4}M$, 40min) siginificantly inhibited the rebound contraction induced by EFS and inhibited contraction caused by exogenous ATP($1{\times}10^{-4}{\sim}1{\times}10^{-3}M$). These results suggests that NANC relaxation of the longitudinal muscles of porcine gastric fundus mainly mediated by NO and the rebound contraction is related to NO and other neurotransmitters.

• The Korean Journal of Pharmacology
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• v.24 no.2
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• pp.189-195
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• 1988

This study aimed to investigate the autonomic innervations of human vas deferens and the effect of diazepam, a benzodiazepine sedative antianxiety drug, on the smooth muscle contractility of vas deferens. The specimens were obtained from healthy volunteers undergoing elective vasectomy with local anesthesia. The muscle preparation did not show any spontaneous contraction, but showed a good contraction induced by norepinephrine exerting the strongest response at $33^{\circ}C$. Phentolamine inhibited the norepinephrine-induced contraction concentration-dependently. Isoproterenol, a beta-adrenergic agonist evoked a considerable extent of contraction, and this contractile activity was antagonized by propranolol, a beta-adrenergic blocking agent. Acetylcholine induced a dashing contraction of the human vas deferens, and atropine, a muscarinic receptor blocking agent abolished the acetylcholine-induced contraction. Diazepam inhibited the norepinephrine-induced contraction in a concentration dependent manner. These results suggest that the smooth muscle of human vas deferens has cholinergic muscarinic and beta adrenergic receptors as well as the predominant alpha adrepergic receptor. Diazepam inhibits the motility, especially norepinephrine-induced contraction of human vas deferens.