Journal of Smooth Muscle Research
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Volume 45 , Issue 5
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Original
  • Takayuki Matsumoto, Yuta Ozawa, Kumiko Taguchi, Tsuneo Kobayashi, Kats ...
    Type: Original
    Volume 45 (2009) Issue 5 Pages 197-208
    Released: November 11, 2009
    JOURNALS FREE ACCESS
    We previously reported that isolated perfused hearts from streptozotocin (STZ)-induced diabetic rats exhibited increases in the sensitivity of the coronary vasoconstriction induced by acetylcholine (ACh) infusion (versus age-matched controls) (Kamata et al., 2008). Here, we examined the ACh-induced coronary vasoconstriction in perfused hearts taken from Otsuka Long-Evans Tokushima Fatty (OLETF) rats, a type 2 diabetes model, at the chronic stage of diabetes (38-40 weeks old). The ACh-induced vasoconstriction was greatly enhanced in such rats [versus age-matched control Long-Evans Tokushima Otsuka (LETO) rats]. This enhancement was improved by the chronic administration of the angiotensin II type I receptor (AT1-receptor) antagonist losartan (25 mg kg-1, p.o., for 4 weeks). Further, the enhancement of the ACh-induced vasoconstriction seen in the OLETF group was suppressed by tempol, a superoxide dismutase mimetic. These results suggest that the coronary artery contractile response to ACh is enhanced in type 2 diabetic OLETF rats, and that this enhancement may be attributable to increased AT1 receptor-mediating signaling and/or to increased oxidative stress.
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  • Shinji Homma, Ichiro Mashima, Yoshiyuki Muramatsu, Fumitake Gejyo
    Type: Original
    Volume 45 (2009) Issue 5 Pages 209-216
    Released: November 11, 2009
    JOURNALS FREE ACCESS
    The respiratory rate, LF, HF, and the LF/HF ratio from heart rate variability (HRV) were compared between outpatients (n=25) and controls (n=58) during rest and while performing a mirror drawing test (MDT). Anxiety and depression scores were obtained before the test. In addition, the power content of the electrogastrograms (EGGs) recorded during MDT were compared to those recorded during rest (c-MDT/r). The anxiety scores, depression scores, resting heart rate, resting respiratory rate and the 3 cpm resting frequency of the epigastric EGG were significantly higher in outpatients than in controls. Both the heart rate and the 3 cpm frequency in the infraumbilical EGG during the stress of the MDT were significantly higher in outpatients than in controls. Instability factors (IF, standard deviation/mean frequency) of the 3 cpm frequency in the epigastric EGG were higher in controls than in outpatients, though the spectral frequencies were similar and insignificantly different between the two groups. Interestingly, the slope of the significant linear correlation was positive in controls but was negative in outpatients between both the resting LF/HF and the power content ratio of the 3 cpm frequency in the infraumbilical EGG, c-MDT/r, which corresponds to the colonic responses to MDT stress.
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  • Thomas J. Eddinger
    Type: Original
    Volume 45 (2009) Issue 5 Pages 217-230
    Released: November 11, 2009
    JOURNALS FREE ACCESS
    This study was designed to test the hypothesis that there is heterogeneous expression of contractile and structural proteins between the smooth muscle cells (SMCs) in the inner and outer circular muscle (ICM and OCM) layers of the ileum. Immunohistochemical staining and quantitation of fresh frozen sections of the dog ileum was performed using protein specific antibodies. Smooth muscle (SM) SMA myosin heavy chain (MHC), α- and γ-SM actin, and vinculin all show greater expression in the ICM relative to the OCM. SMB MHC and fibronectin show the opposite pattern, with greater expression in the OCM relative to the ICM. Differences in expression of these proteins are consistent with proposed differences in function of these muscle layers. Hypotheses regarding muscle tone and the coordination and regulation of peristalsis via these different muscle layers based on this data can now be made and tested.
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  • Ismail M. Mahomed, John A. O. Ojewole
    Type: Original
    Volume 45 (2009) Issue 5 Pages 231-239
    Released: November 11, 2009
    JOURNALS FREE ACCESS
    Some traditional health practitioners of South Africa have claimed that Harpagophytum procumbens DC (family: Pedaliaceae) secondary root is a useful obstetric remedy for induction or acceleration of labour, as well as for expelling retained placentas in pregnant women. In the present study, therefore, we investigated the effect of H. procumbens secondary root aqueous extract (HPE) on longitudinal, tubular uterine horn muscle strips taken from non-pregnant and pregnant, young adult, female rats. HPE (10-800 μg/ml) induced concentration-related and significant (P<0.05) increases in the baseline tone, and caused powerful rhythmic, myogenic contractions of, oestrogen-dominated rat longitudinal uterine horn muscle strips taken from stilboesterol-pretreated, non-pregnant female rats. Relatively low to high concentrations of HPE (10-800 μg/ml) also provoked concentration-dependent and significant (P<0.05-0.001) increases in the baseline tone of, and contracted, longitudinal, tubular uterine horn muscle strips taken from female rats in the early, middle and late stages of pregnancy. Moderate to high concentrations of HPE (200-1,000 μg/ml) always provoked powerful contractions of isolated longitudinal, tubular uterine horn muscle preparations of non-pregnant and pregnant rats. The results of this in vitro study indicate that H. procumbens secondary root aqueous extract possesses spasmogenic, uterotonic action on mammalian uterine muscles. These findings lend pharmacological credence to the suggested folkloric obstetric uses of the plant's secondary root for induction and/or acceleration of labour, as well as for expelling retained placentas in pregnant women.
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  • John A. O. Ojewole, Gbola Olayiwola, Agatha Nyinawumuntu
    Type: Original
    Volume 45 (2009) Issue 5 Pages 241-248
    Released: November 11, 2009
    JOURNALS FREE ACCESS
    This study was undertaken to investigate the bronchorelaxant effect of Hypoxis hemerocallidea corm (`African potato') aqueous extract (APE) on spasmogen-provoked contractions of guinea-pig isolated tracheal smooth muscle preparations. APE (25-400 mg/ml) relaxed spasmogen (histamine-, carbachol- and potassium-)-induced contractions of the isolated tracheal muscle preparations in a concentration-dependent manner. The relaxant effects of APE on spasmogen-evoked contractions of the tracheal muscle preparations were not altered by bath-applied propranolol (0.1-5.0 μg/ml), which markedly inhibited or completely abolished the relaxant effects of isoprenaline (0.1-5.0 μg/ml). Although the precise mechanism of the bronchorelaxant effect of APE could not be established in the present study, it is unlikely that the herb's aqueous extract stimulates the β2-adrenoceptors present on the bronchial smooth muscles to produce its bronchodilatation. The finding that APE significantly relaxed (P<0.05) histamine-, carbachol- and high potassium ion concentration (K+, 80 mM)-induced contractions of guinea-pig isolated bronchial muscle preparations appears to suggest that the bronchospasmolytic effect of the plant's extract is probably not mediated through a specific receptor, but rather, probably mediated via a non-specific bronchospasmolytic mechanism.
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