Browsing by Author "Guo, Xiaomei"

Now showing 1 - 2 of 2
  • Thumbnail Image
    Item
    Distension-Induced Gastric Contraction is Attenuated in an Experimental Model of Gastric Restraint
    (Springer Verlag, 2010-08-13) Lu, Xiao; Guo, Xiaomei; Mattar, Samer G.; Navia, Jose A.; Kassab, Ghassan S.; Biomedical Engineering, School of Engineering and Technology
    Background Gastric distension has important implications for motility and satiety. The hypothesis of this study was that distension affects the amplitude and duration of gastric contraction and that these parameters are largely mediated by efferent vagus stimulation. Methods A novel isovolumic myograph was introduced to test these hypotheses. The isovolumic myograph isolates the stomach and records the pressure generated by the gastric contraction under isovolumic conditions. Accordingly, the phasic changes of gastric contractility can be documented. A group of 12 rats were used under in vivo conditions and isolated ex vivo conditions and with two different gastric restraints (small and large) to determine the effect of degree of restraint. Results The comparison of the in vivo and ex vivo contractility provided information on the efferent vagus mediation of gastric contraction, i.e., the in vivo amplitude and duration reached maximum of 12.6±2.7 mmHg and 19.8±5.6 s in contrast to maximum of 5.7±0.9 mmHg and 7.3±1.3 s in ex vivo amplitude and duration, respectively. The comparison of gastric restraint and control groups highlights the role of distension on in vivo gastric contractility. The limitation of gastric distension by restraint drastically reduced the maximal amplitude to below 2.9±0.2 mmHg. Conclusions The results show that distension-induced gastric contractility is regulated by both central nervous system and local mechanisms with the former being more substantial. Furthermore, the gastric restraint significantly attenuates gastric contractility (decreased amplitude and shortened duration of contraction) which is mediated by the efferent vagus activation. These findings have important implications for gastric motility and physiology and may improve our understanding of satiety.
  • Thumbnail Image
    Item
    Rosiglitazone reverses endothelial dysfunction but not remodeling of femoral artery in Zucker diabetic fatty rats
    (BMC, 2010-05-19) Lu, Xiao; Guo, Xiaomei; Karathanasis, Sotirios K.; Zimmerman, Karen M.; Onyia, Jude E .; Peterson, Richard G.; Kassab, Ghassan S.; Biomedical Engineering, School of Engineering and Technology
    Objectives Endothelial dysfunction precedes atherogenesis and clinical complications in type 2 diabetes. The vascular dysfunction in Zucker diabetic fatty (ZDF) rats was evaluated at different ages along with the effect of treatment with rosiglitazone (Rosi) on endothelial function and mechanical remodeling. Methods The Rosi treatment was given to ZDF rats for 3 weeks. The endothelium-dependent vasodilation and α-adrenoceptor-dependent vasoconstriction of femoral arteries were studied using an ex-vivo isovolumic myograph. The biomechanical passive property of the arteries was studied in Ca2+-free condition. The expressions of endothelial nitric oxide synthase (eNOS), α-adrenoceptor, matrix metalloproteinase 9 (MMP9), and elastase were evaluated. Results Endothelium-dependent vasorelaxation of the femoral artery was blunted at low doses in ZDF rats at 11 weeks of age and attenuated at all doses in ZDF rats at 19 weeks of age. The expression of eNOS was consistent with the endothelium-dependent vasorelaxation. The α-adrenoceptor was activated and the mechanical elastic modulus was increased in ZDF rats at 19 weeks of age. The expressions of α-adrenoceptor, MMP9, and elastase were up regulated in ZDF rats at 19 weeks of age. Rosi treatment for 3 weeks restored endothelium-dependent vasorelaxation and the expression of eNOS and the adrenoceptor activation at the doses below 10-6 mole/L in ZDF rats at 19 weeks of age. Rosi treatment for 3 weeks did not, however, improve the mechanical properties of blood vessel, the expressions of α-adrenoceptor, MMP9, and elastase in ZDF rats. Conclusion The endothelial dysfunction and mechanical remodeling are observed as early as 19 weeks of age in ZDF rat. Rosi treatment for 3 weeks improves endothelial function but not mechanical properties.