• The Korean Journal of Physiology and Pharmacology
• /
• 제4권3호
• /
• pp.211-217
• /
• 2000

Paxillin is a regulatory component of the complex of cytoskeletal proteins that link the actin cytoskeleton to the plasma membrane. However, the role of paxillin during smooth muscle contraction is unclear. We investigated a possible role for the membrane-associated dense plaque protein paxillin in the regulation of contraction in rat aortic vascular smooth muscle. The tyrosine phosphorylation of paxillin, which was increased by norepinephrine, reached a peak level after 1 min stimulation and then decreased with time. However, norepinephrine induced a sustained contraction that reached a steady state 30 min after application. Pretreatment with tyrphostin, an inhibitor of tyrosine kinase, inhibited the tyrosine phosphorylation of paxillin and also the contraction stimulated by norepinephrine. Both inhibitions were concentration-dependent, and the degree of correlation between them was high. These results show that, in rat aortic smooth muscle, tyrosine kinase(s) activated by norepinephrine may phosphorylate the tyrosine residues of paxillin, thereby providing a source of regulation during vascular smooth muscle contraction.

• The Korean Journal of Physiology
• /
• 제24권2호
• /
• pp.353-362
• /
• 1990

Fluoride (F-), a known stimulator of G-protein, induced strong contraction in rabbit trachealis muscle. $AlCl_3\;(5{\sim}20\;{\mu}M)$, which is required for G-protein stimulation by $F^-$, potentiated the contractile response to $F^-$. $Ca^{2+}-removal$ and verapamil, a calcium channel blocker, inhibited the fluoroaluminate-induced contraction. Fluoroaluminate increased $^{45}Ca$ influx in the absence and presence of verapamil. In heparin-loaded muscle high $K^+-induced$ contraction was not affected, but acetylcholine and fluoroaluminate-induced contractions were inhibited. The fluoroaluminate-induced contraction was partially relaxed by isoproterenol, a stimulator of adenylate cyclase. Pertussis toxin partially inhibited fluoroaluminate-induced contraction and potentiated isoproterenol-induced relaxation in the presence of fluoroaluminate, but had no effect on acetylcholine-induced contraction and the isoproterenol-induced relaxation in the presence of acetylcholine. These results suggest that fluoroaluminate has the ability to stimulate at least two putative G-proteins in rabbit trachealis muscle; One causes $Ca^{2+}$ influx through the potential-operated $Ca^{2+}$ channel and the other induces intracellular $Ca^{2+}$ release by the increase of inositol-1, 4, 5-triphosphate.

• 한국전산유체공학회:학술대회논문집
• /
• 한국전산유체공학회 2010년 춘계학술대회논문집
• /
• pp.136-141
• /
• 2010

This study describes effects of width contraction in vaneless diffuser on the performance of centrifugal compressors using commercial CFD code. Numerical analysis for three different diffusers such as Parallel, half contraction, and full contraction was performed. The results show that the performance of the centrifugal compressor is improved through the use of the diffusers with width parallel in high flow rate. The width contraction of diffusers is influenced static pressure rises. Comparison with the experimental data shows agreement.

• 한국임상수의학회지
• /
• 제20권3호
• /
• pp.341-344
• /
• 2003

This study was carried out to investigate the effects of the wound contraction of chitosan, aloe vera, fucidin natrium, and premycin ointment on defected wound from full-thickness skin defects(1 cm $\times$ 1 cm). Twelve dogs were designed in 5 different positions on the dorsal thoracolumbar. We examined the effects of wound contraction every four other day 16 for days. Percentage of wound contraction based on epitherial overall area of defected wound which calculated by image analyzer and computer. Four to 8 days after wound contraction in wound defected dogs, the epithelial overall rate were the most high presented by 48.1 % in the chitosan group and were the lowest by 26.8% in the premycin group. In 16 days, chitosan group were the most heigh presented by 94.4% and premycin group were the lowest by 76.5% compare to saline group of 85.9%. Thus, we conclude that the chitosan is a possible role for improvement of wound contraction by wound defected dogs.

• The Korean Journal of Physiology
• /
• 제24권1호
• /
• pp.161-170
• /
• 1990

The effects of $H^{+}$ on the arterial contraction and their mechanisms were investigated in the renal artery of a rabbit. The helical strips of isolated renal artery were immersed in the HEPES-buffered or $CO_{2}/HCO_{3}^{-}$-buffered Tyrode's solution. The contractions induced by agonists (norepinephrine, histamine, serotonin and angiotensin II) or high $K^{+}$ were observed with change of extracellular or intracellular $H^{+}$ concentration. The contractions induced by norepinephrine, histamine, serotonin, angiotensin II or high $K^{+}$ in HEPES-buffered Tyrode's solution were inhibited by increase in extracellular $H^{+}$ concentration and potentiated by decrease in extracellular $H^{+}$ concentration. The degrees of these effects were most evident in the contraction induced by serotonin and angiotensin II, moderate in those by histamine and high $K^{+}$, and least in those by norepinephrine. Maximal contraction by norepinephrine, histamine and high $K^{+}$ were not influenced by change in extracellular $H^{+}$ concentration, but influenced in those contration by serotonin and angiotensin II. The attenuated contractions by an acidic pH were not returned to the level of contraction at normal pH (7.4) by elevation of extracellular $Ca{2+}$ concentration. The agonists (norepinephrine, histamine and serotonin)-induced contractions in $Ca{2+}$-free Tyrode's solution were also attenuated by increase in extracellular $H^{+}$ concentration and potentiated by decrease in extracellular $H^{+}$ concentration. Elevation of $Pco_{2}$ in the $CO_{2}/HCO_{3}^{-}$-buffered Tyrode's solution, which increase the intracellular $H^{+}$ concentration, at constant extracellular pH (7.4), increased the contraction by 30 mM $K^{+}$. From the above results, it is suggested that the decrease in contractions by increase in extracellular $H^{+}$ concentration may be resulted from that $H^{+}$ make the receptors less sensitive to agonists and cell membrane hyperpolarize and then inhibit the $Ca{2+}$ influx as well as $Ca{2+}$ release from intracellular $Ca{2+}$ storage site.

• 한국조명전기설비학회지:조명전기설비
• /
• 제6권3호
• /
• pp.33-42
• /
• 1992

This paper presented time dependent high-pressure arc discharge model considering the axial convection and verified the pertinence with application to the high pressure mercury lamp. Using this model, this paper xmaminse the effect of the axial convection and arc contraction of lower electrode region. This model consisted with the results of experiments in few [%] error, and showed the arc contraction of lower electrode region.

• 약학회지
• /
• 제55권2호
• /
• pp.138-144
• /
• 2011

The aim of present study was to investigate the possible influence and related mechanism of resveratrol on U-46619 (high concentration)-induced vasoconstriction. Agonist-induced vascular smooth muscle contractions involve the activation of thick or thin filament pathway. However, there are no reports addressing the question whether this pathway is involved in resveratrol-induced relaxation in rat aortae contracted with high U-46619. We hypothesized that MEK or Rho-kinase inhibition plays a role in vascular relaxation evoked by resveratrol in rat aortae. Endothelium-denuded arterial rings from male Sprague-Dawley rats were used and isometric contractions were recorded using a computerized data acquisition system. Resveratrol fully inhibited U-46619 in low concentration-induced contraction regardless of endothelial function. However, resveratrol partially decreased U-46619 in high concentration-induced contraction regardless of endothelial function. Interestingly, only in U-46619 (high concentration)-induced contraction, no significant decrease was observed in phospho-ERK1/2 levels and slight decrease in phospho-MYPT1 levels suggesting that additional pathways different from them or endothelial nitric oxide synthesis might be involved in the vasorelaxation. In conclusion, in high U-46619-contracted rat aortae, resveratrol showed relaxation response regardless of endothelial function significantly but slightly decreasing MYPT1 phosphorylation rather than ERK1/2 phosphorylation.

• The Korean Journal of Physiology and Pharmacology
• /
• 제13권6호
• /
• pp.503-510
• /
• 2009

To elucidate the mechanism of cyclic nucleotides, such as adenosine 3',5'-cyclic monophosphate (cAMP) and guanosine 3',5'-cyclic monophosphate (cGMP), in the regulation of human gastric motility, we examined the effects of forskolin (FSK), isoproterenol (ISO) and sodium nitroprusside (SNP) on the spontaneous, high $K^+$ and acetylcholine (ACh)-induced contractions of corporal circular smooth muscle in human stomach. Gastric circular smooth muscle showed regular spontaneous contraction, and FSK, ISO and SNP inhibited its phasic contraction and basal tone in a concentration-dependent manner. High $K^+$ (50 mM) produced sustained tonic contraction, and ACh $(10\;{\mu}M)$ produced initial transient contraction followed by later sustained tonic contraction with superimposed phasic contractions. FSK, ISO and SNP inhibited high $K^+$-induced tonic contraction and also ACh-induced phasic and tonic contraction in a reversible manner. Nifedipine $(1\;{\mu}M)$, inhibitor of voltage-dependent L-type calcium current $(VDCC_L)$, almost abolished ACh-induced phasic contractions. These findings suggest that FSK, ISO and SNP, which are known cyclic nucleotide stimulators, inhibit smooth muscle contraction in human stomach partly via inhibition of $VDCC_L$.

• 대한수의학회지
• /
• 제60권2호
• /
• pp.55-59
• /
• 2020

This study was purposed to make the referenced range of stomach antral contraction strain in 50 dogs using 2-dimensional speckle tracking. In addition, the strain results were compared among body condition scores to reveal the correlations of obesity among the subjects of the study. Finally, the medetomidine group that was comprised of 10 dogs was compared with the normal group to identify the medetomidine pharmacologic effect in the stomach antral contraction. Clinically healthy 50 dogs were recruited for the study. In an ultrasonographic examination, the stomach antrum region was scanned, and at least one cycle of antral contraction was recorded. The peak strain of antral contraction in healthy dogs was 58.2 ± 20.47% (mean ± SD). The obesity group showed a high strain result and there were significant correlations between the body condition score (BCS) 2, BCS 3 groups and BCS 8 group. The medetomidine group revealed a low strain result and was significantly correlated with normal group. Two-dimensional speckle tracking was useful to the evaluation of stomach motility disorders.

• 한국전문물리치료학회지
• /
• 제9권2호
• /
• pp.115-131
• /
• 2002

Functional electrical stimulation (FES) training of the knee extensors is a useful way to rehabilitate the ability to stand and walk. However, training using FES has not been able to solve the problem of fatigue; clinical application of FES quickly produces muscle fatigue, due to the continuous activation of the muscles of the lower extremity. Therefore, reduction of muscle fatigue is an important factor in increasing the effectiveness of FES training in paraplegia. Intermittent high frequency alternating stimulation is a method that combines the advantages of high frequency (leading to strong muscle contractions) and alternating stimulation (reducing muscle fatigue), thereby continuously strengthening muscles. It is not known whether low frequency simultaneous stimulation results in stronger muscle contraction than high frequency alternating stimulation. This study compared the effectiveness of high frequency alternating stimulation with low frequency synchronized stimulation. Muscle power using FES on the quadriceps of 20 normal subjects were compared. Intermittent high frequency alternating stimulation did not produce more powerful muscle contraction than intermittent low frequency synchronized stimulation, because the muscle characteristics differed individually. Significant individual variation according to muscle characteristics was founded when applying FES. Accordingly, when physical therapists use FES to treat patients, they must be aware of individual variation in muscle characteristics.