Journal of Smooth Muscle Research
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Volume 46 , Issue 5
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Original
  • Hiroyasu Sakai, Yusuke Kurihara, Yuki Hashimoto, Yoshihiko Chiba, Miwa ...
    Type: Original
    Volume 46 (2010) Issue 5 Pages 225-233
    Released: December 23, 2010
    JOURNALS FREE ACCESS
    In airway smooth muscle, protein kinase C (PKC) has been implicated in a number of functional responses including the regulation of contractility. However, the exact role of PKC on bronchial smooth muscle (BSM) contraction is still unclear. In the present study, to determine the role of PKC activation in the BSM contraction, the effects of phorbol 12,13-dibutyrate (PDBu, a direct PKC activator) on BSM tone were examined in the absence and presence of K+-induced depolarization stimulation. The force development was not evoked by treatment with 1 μM PDBu alone. However, a strong contraction was induced by PDBu during high K+ contraction. The contraction induced by PDBu during high K+ stimulation was significantly abolished by pretreatment with nicardipine, an L-type voltage dependent Ca2+ channel blocker. In RT-PCR analysis, mRNAs of PKCα, β, γ, δ, ε, η and θ isoforms were detected in mouse BSM. Gö6976 (an inhibitor of PKCs α and β) and rottlerin (an inhibitor of PKCδ) significantly but partially inhibited the PDBu-induced BSM contraction during K+ stimulation. GF109203X (an inhibitor of PKCs α, β, γ, and ε) completely inhibited the PDBu-induced contraction during K+ stimulation. In conclusion, it is suggested that the PDBu-induced BSM contraction is dependent on an increase in cytosolic Ca2+. Furthermore, it is possible that both cPKC and nPKC(s) participate in the PDBu-induced contraction of mouse BSM during K+ stimulation.
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  • Shinji Homma, Yasuo Kobayashi, Shinichi Kosugi, Manabu Ohashi, Tatsuo ...
    Type: Original
    Volume 46 (2010) Issue 5 Pages 235-248
    Released: December 23, 2010
    JOURNALS FREE ACCESS
    The electrogastrographic indices of spectral frequency, instability factor (IF), power amplitude, and power content (%) were compared between control subjects (C), and subjects following either total gastrectomy (TG), total colectomy (TC), distal gastrectomy (DG) or colonic replacement surgery (CR). In the fasting state, both the spectral frequency and IF of the epigastric 3-cycle per minute (cpm) group of the TC subjects were significantly lower than those indices in C, TG, DG, and CR subjects. In contrast, the power amplitude and power content of the epigastric 3-cpm group of both TG and DG subjects were significantly lower than those of C and TC subjects. The original epigastric waves of TG had remarkably high amplitudes. Furthermore, the absolute power of the epigastric 3-cpm of the TC subjects was 10 times higher than that in either the C or TG subjects. These results may be partially explained by the assumption that the recorded epigastric electrogastrography (EGG) is mainly contributed to by the 3-cpm myoelectric activity of the stomach and colon, while the infraumbilical EGG is mainly contributed to by the 3-cpm myoelectric activity of the colon. Topographic EGG maps visually supported these assumptions.
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  • Hiroaki Kusunoki, Ken Haruma, Mutsuhiro Hara, Jiro Hata, Motonori Sato ...
    Type: Original
    Volume 46 (2010) Issue 5 Pages 249-258
    Released: December 23, 2010
    JOURNALS FREE ACCESS
    Background: Impaired gastric accommodation of the proximal stomach is one of the major pathophysiological mechanisms in functional dyspepsia (FD). However, no useful method exists for the clinical evaluation of this phenomenon. Aim: The aim of the present study was to establish a simple and non-invasive method for evaluating the accommodation reflex of the proximal stomach. Methods: Nine healthy subjects received up to 1,700 mL water (stepwise administration in 100-mL increments) using a nasogastric tube while they were in a supine position. To assess the meal-induced gastric accommodation reflex, we measured the cross-sectional area of the proximal stomach via ultrasonography (US) at 3-min intervals after administration of water. We also measured the pressure of the water column using the same tube. Then, we administrated up to 400 mL of water in 100-mL increments and measured the area of the proximal stomach in 44 FD patients with early satiation (the measurements were performed at intervals of 3-min), and we compared the results with those for 44 healthy subjects. Results: The incremental changes in the area of the proximal stomach corresponded well with the amount of water administered. The area of the proximal stomach increased, but the antral area and the intragastric pressure remained relatively stable. After administration of more than 100 ml water, the area of the proximal stomach in healthy subjects was significantly greater than that in FD patients. Conclusion: US can be used to assess the isotonic expansion of the proximal stomach. We were able to distinguish FD patients with impaired accommodation reflex from healthy individuals by using this simple and easy method.
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  • Hiroyasu Sakai, Yusuke Kurihara, Yuki Hashimoto, Yoshihiko Chiba, Miwa ...
    Type: Original
    Volume 46 (2010) Issue 5 Pages 259-266
    Released: December 23, 2010
    JOURNALS FREE ACCESS
    To explore the role of protein kinase C (PKC) in the augmented bronchial smooth muscle (BSM) contraction observed in the antigen-induced airway hyperresponsive (AHR) mice, the effects of a PKC activator, phorbol 12,13-dibutylate (PDBu), on BSM contraction were compared between the AHR and control mice. Actively sensitized mice were repeatedly challenged by antigen inhalation. Twenty-four hours after the final antigen challenge the isometrical contractions of the BSMs were measured. The BSM contraction induced by acetylcholine, but not high K+ depolarization, was significantly augmented in the AHR mice. In BSMs of control mice, PDBu caused a significant increase in tension when the tissues were precontracted with high K+, although PDBu itself had no effect on basal tone. The PDBu-mediated contraction was markedly augmented in BSMs of the AHR mice. These findings suggest that an increase in the PKC-mediated signaling is involved in the augmented contraction of BSMs in the antigen-induced AHR mice.
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