• Title, Summary, Keyword: Myogenic tone

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[$Ca^{2+}$ Sensitization Mechanism in Stretch-induced Myogenic Tone

  • Kim, Jung-Sup;Ryu, Sung-Kyung;Ahn, Duck-Sun;Kang, Bok-Soon;Lee, Young-Ho
    • The Korean Journal of Physiology and Pharmacology
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    • v.6 no.1
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    • pp.33-39
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    • 2002
  • It has been suggested that $Ca^{2+}$ sensitization mechanisms might contribute to myogenic tone, however, specific mechanisms have not yet been fully identified. Therefore, we investigated the role of protein kinase C (PKC)- or RhoA-induced $Ca^{2+}$ sensitization in myogenic tone of the rabbit basilar vessel. Myogenic tone was developed by stretch of rabbit basilar artery. Fura-2 $Ca^{2+}$ signals, contractile responses, PKC immunoblots, translocation of PKC and RhoA, and phosphorylation of myosin light chains were measured. Stretch of the resting vessel evoked a myogenic contraction and an increase in the intracellular $Ca^{2+}$ concentration $([Ca^{2+}]_i)$ only in the presence of extracellular $Ca^{2+}$. Stretch evoked greater contraction than high $K^+$ at a given $[Ca^{2+}]_i.$ The stretch-induced increase in $[Ca^{2+}]_i$ and contractile force were inhibited by treatment of the tissue with nifedipine, a blocker of voltage-dependent $Ca^{2+}$ channel, but not with gadolinium, a blocker of stretch-activated cation channels. The PKC inhibitors, H-7 and calphostin C, and a RhoA-activated protein kinase (ROK) inhibitor, Y-27632, inhibited the stretch-induced myogenic tone without changing $[Ca^{2+}]_i.$ Immunoblotting using isoform-specific antibodies showed the presence of $PKC_{\alpha}$ and $PKC_{\varepsilon}$ in the rabbit basilar artery. $PKC_{\alpha},$ but not $PKC_{\varepsilon},$ and RhoA were translocated from the cytosol to the cell membrane by stretch. Phosphorylation of the myosin light chains was increased by stretch and the increased phosphorylation was blocked by treatment of the tissue with H-7 and Y-27632, respectively. Our results are consistent with important roles for PKC and RhoA in the generation of myogenic tone. Furthermore, enhanced phosphorylation of the myosin light chains by activation of $PKC_{\alpha}$ and/or RhoA may be key mechanisms for the $Ca^{2+}$ sensitization associated with myogenic tone in basilar vessels.

The Hypertensive Vascular Tension-related Signal Transduction and the Relationship of Physical Therapy (고혈압 혈관조직의 장력-연관 신호전달과 물리치료의 상관성)

  • Kim, Jung-Hwan;Kim, Il-Hyun;Hwang, Byong-Yong
    • The Journal of Korean Physical Therapy
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    • v.20 no.4
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    • pp.35-42
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    • 2008
  • Purpose: Alterations in the structure and function of vascular smooth muscle cells (VSMCs) are important in cardiovascular disease and maintaining chronic hypertension. Chronic hypertension is associated with changes in vascular smooth muscle tone. The spontaneous or myogenic tone of a blood vessel reflects the ability to adapt smooth muscle tone to changes in transmural pressure. However, the intracellular signaling mechanisms involved in myogenic tone are not fully understood. Methods: Here, we investigated the relationship between mitogen-activated protein kinases (MAPKs) and phosphatidylinositol-3 kinase (PI3K) in isometric contraction and enzymatic activity using muscle strips from rats made hypertensive with aldosterone-analogue deoxycorticosterone acetate (DOCA) salts. Results: Changes in myogenic tone and intracellular $Ca^{2+}$ concentration ($[Ca^{2+}]_i$) were different after physiological salt solution (PSS) in normotensive and hypertensive rats. The myogenic tone and quiescent phosphorylation induced by the PSS treatment were inhibited by 10 ${\mu}$M PD098059, an extracellular-regulated protein kinase 1/2 (ERK1/2) inhibitor, and 10 ${\mu}$M wortmannin, an inhibitor of PI3K, in hypertensive rats. Conclusion: The development of DOCA-induced hypertension is associated with altered isometric contractions and $[Ca^{2+}]_i$ via changes in activation of ERK1/2 and PI3K after DOCA-salt treatment. Therefore, ERK1/2 and PI3K activity affect hypertension and may be suitable targets for physical therapy in cardiovascular disease.

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Enhanced Vasorelaxation Response to Cromakalim in Spontaneously Hypertensive Rats

  • Kim, Se-Hoon;Oh, Yeong-Seon;Kim, Hoe-Suk;Jeon, Byeong-Hwa;Chang, Seok-Jong
    • The Korean journal of physiology & pharmacology
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    • v.30 no.1
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    • pp.11-20
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    • 1996
  • To investigate the properties of cromakalim-opened $K^{+}\;channels$ in aorta of spontaneously hypertensive rats (SHR), the effect of cromakalim on tension was compared in endothelium-rubbed aortic rings from SHR and normotensive Wistar-Kyoto rats (WKY). 1. Cromakalim relaxed the aortic ring contracted by $10^{-7}$ M norepinephrine (NE) dose-dependently, and this relaxant response to cromakalim was blocked by $10^{-5}$ M glybenclamide. 2. Cromakalim also relaxed the contraction induced by high $K^{+}$-solution or 10 mM tetraethylammonium dose-dependently. However, the relaxant response to cromakalim was decreased by raising the $K^{+}$ concentration. 3. SHR aorta exhibited myogenic tone in resting state which was inhibited by cromakalim, verapamil or $Ca^{2+}-free\;PSS.$ Whereas, WKY aorta did not exhibit any myogenic tone in resting state. 4. When aortic rings from both strains were contracted by $20\;mM\;K^{+}\;or\;NE$, relaxant responses to low concentration of cromakalim $(below\;10^{-7}\;M)$ were not different between WKY and SHR, but maximum relaxant response to cromakalim $(above\;3{\times}10^{-7} \;M)$ was greater in SHR than in WKY. 5. When the relaxant response to cromakalim was expressed as percent of maximum relaxation induced by $Ca^{2+}-free\;PSS$, relaxant response to cromakalim in 20 mM $K^{+}-induced$ contraction was not different between WKY and SHR. From the above result, it is suggested that relaxant responses to cromakalim are greater in SHR than WKY, and this may be due to the myogenic tone of aortic rings from SHR.

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Vestibular Evoked Myogenic Potential (전정유발근육전위)

  • Kim, Sung Hun;Nam, Eui Cheol
    • Annals of Clinical Neurophysiology
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    • v.7 no.1
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    • pp.1-6
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    • 2005
  • Loud click or tone burst sound can activate vestibular receptor and evoke reflex changes in tonic electromyographic activity within the stenocleidomastoid muscles. This reflex is assumed to originate in the saccule, the afferent pathways being the inferior vestibular nerve, and the efferent pathways the vestibulospinal tract. Averaging these muscular responses allows vestibular evoked myogenic potentials (VEMP) to be obtained. The earliest response ipsilateral to a loud click, p13n23, is dependent upon vestibular activation, specifically saccular afferents. These new techniques are beginning to be applied clinically in the patient of vestibular neuritis, Meniere's disease, acoustic neuromas, Tullio phenomenon, etc. VEMP recording will provide both a straightforward non-invasive exploration of each vestibule independently and an attractive method by which to explore otolithic receptors and vestibulospinal pathways.

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The Effect of Differences in Age and Sex on Vestibular Evoked Myogenic Potentials (연령과 성별의 차이가 전정 유발근전위에 미치는 영향)

  • Moon, Sung-Sik;Kim, Kyoung-Mi;Kim, Young-Ji;Kim, Young-Hwal
    • Korean Journal of Clinical Laboratory Science
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    • v.39 no.2
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    • pp.136-140
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    • 2007
  • The aim of this study was to examine the effect of differences in age and sex on vestibular evoked myogenic potentials (VEMP), particularly in normal participants. Briefly, the VEMP is a response elicited by loud clicks or tone bursts recorded from the tonically contracted sternocleidomastoid muscle. A total of 72 participants were divided into 6 groups according to their age and sex (20~30/F, 20~30/M, 40~50/F, 40~50/M, ${\geq}60/F$, ${\geq}60/M$). We got the data of latency, amplitude, and asymmetry index of the amplitude(ASI) from them. As a result of this study, there are variations in VEMP amplitudes and ASI depending on the muscle tension and the intensity of stimuli. In contrast, the latency of the response is usually less varied and does not differ significantly.

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EXPERIMENTAL ESOPHAGITIS AND SIGNAL TRANSDUCTION TO SMOOTH MUSCLE MOTILITY

  • Sohn, Uy-Dong
    • Proceedings of the Korean Society of Applied Pharmacology
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    • pp.41-46
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    • 1997
  • Lower esophageal sphincter (LES) is characterized by the ability to maintain a sustained pressure, and to relax allowing the passage of a bolus, whereas the esophagus is normally relaxed and contracts only briefly when required to produce peristalsis (fig. 1). The neuromuscular mechanisms that participate in the physiological regulation of these functions are not well understood, but it is thought that LES tone is spontaneous and regulated mostly through myogenic mechanisms, whereas LES relaxation and esophageal contraction are induced by neural mechanisms. Gastroesophageal reflux represents the effortless movement of gastric contents from stomach to esophagus. Because this phenomenon occurs in virtually everyone multiple times every day and in the majority of people without clinical consequences, the reflux per se is not disease. However in some cases, it can be pathologic, producing symptoms and signs called gastroesophageal reflux disease (GERD), which mechanism is not well known. It may result in heart burn, chronic esophagitis, aspiration pneumonia, esophageal strictures, and Barrett's esophagus.

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CARE OF TRISMUS AND OROCUTANEOUS FISTULA BY ODONTOGENIC INFECTION IN A DISABLED PATIENT (장애환자에서 치성감염에 의한 아관긴급과 구강피부누공의 관리)

  • Oh, Ji-Hyeon;Son, Jeong-Seog;Yoo, Jae-Ha;Kim, Jong-Bae
    • The Journal of Korea Assosiation for Disability and Oral Health
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    • v.9 no.2
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    • pp.111-117
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    • 2013
  • Some odontogenic infections erode into fascial spaces directly and spread toward lymphatic tissues and blood streams. The principal maxillary primary spaces are the canine, buccal, and infratemporal space, the next secondary spaces are the masseteric, temporal and pharygeal space. As a result of the infection, trismus and orocutaneous fistula may be occurred. Trismus is owing to conditions not associated with temporomandibular joint itself and may be of myogenic, neurogenic, or psychogenic nature. Muscular trismus is due to infection adjacent to the elevator muscles of the jaw. The four principles of treatment of infection are as follows: (1) removal of the cause, (2) establishment of drainage, (3) institution of antibiotic therapy, and (4) provision of supportive care, including rest, nutrition and physiotherapy. Jaw physiotherapy is necessary to increase the amount of mouth opening and regain normal muscle tone. If proper care of odontogenic infection could be attained, the orocutaneous fistula will heal and close spontaneously by wound contraction mechanism of natural homeostatic response. This is a case report of the care of trismus and orocutaneous fistula due to fascial space abscess by advanced odontogenic infection in a physically disabled patient.