Farzad Ebrahimi | University of Illinois at Chicago (original) (raw)

Papers by Farzad Ebrahimi

Research paper thumbnail of Speckle- Tracking Echocardiography for the Staging of Diastolic Dysfunction: The Correlation Between Strain-Based Indices and the Severity of Left Ventricular Diastolic Dysfunction

Journal of Cardiothoracic and Vascular Anesthesia

Objectives: Left ventricular diastolic function can be assessed by various methods. Tissue Dopple... more Objectives: Left ventricular diastolic function can be assessed by various methods. Tissue Doppler imaging is among the most commonly used techniques. However, this imaging is angle-dependent, affected by loading conditions, and susceptible to myocardial tethering. Speckle-tracking echocardiography also can measure strain-based indices to assess diastolic function, and it has fewer limitations than tissue Doppler imaging. Using speckle-tracking echocardiography, the authors evaluated the correlation between the stage of diastolic dysfunction and strain-based indices in patients undergoing cardiac surgery to determine whether strain-based indices can be used intraoperatively to identify the extent of left ventricular diastolic dysfunction. Design: Retrospective clinical study. Setting: Single university hospital. Participants: Fifty-eight patients undergoing cardiac surgery (December 2017 to December 2019). Interventions: None. Measurement and Main Result: Preoperative echocardiographic reports and intraoperative echocardiographic images of the participants were studied. The correlation between the stage of left ventricular diastolic dysfunction and strain-based indices (including early diastolic peak longitudinal strain and tissue deceleration time) were evaluated. Early diastolic peak longitudinal strain rate significantly correlated with the stage of diastolic dysfunction (r = À0.7 and p < 0.0001). Tissue deceleration time significantly correlated with the stage of diastolic dysfunction in patients with diastolic abnormality (r = À0.4 and p = 0.02). When patients with normal diastolic function were included, this correlation was not significant (r= À0.25 and p = 0.05). Conclusions: Intraoperatively measured early diastolic peak longitudinal strain rate and tissue deceleration time correlated with the severity of diastolic dysfunction in patients undergoing cardiac surgery.

Research paper thumbnail of Creatine Revealed Anticonvulsant Properties on Chemically and Electrically Induced Seizures in Mice

Creatine exerts beneficial effects on a variety of pathologies in which energy metabolism and oxi... more Creatine exerts beneficial effects on a variety of pathologies in which energy metabolism and oxidative stress play an etiological role. Creatine supplements have shown beneficial effects on neurological disorders including Parkinson׳s disease, Huntington›s disease, amyotrophic lateral sclerosis, as well as Alzheimer›s disease and stroke. However, the potential benefits of creatine for patients with convulsive disorders remain poorly defined. While some authors did not suggest any anti- or pro-convulsant roles for creatine treatment, others suggest that creatine may be an anticonvulsant agent. In this study, we investigated the effects of creatine on seizures in mice. Three models were used to explore the role of creatine on seizures in mice including intravenous pentylenetetrazole (PTZ), intraperitoneal PTZ, and electroshock models. Acute creatine treatment (10, 20, 40 and 80 mg/Kg) significantly increased the clonic seizure threshold in the intravenous PTZ model. Sub-chronic admin...

Research paper thumbnail of Intraoperative assessment of left-ventricular diastolic function by two-dimensional speckle tracking echocardiography: relationship between pulmonary capillary wedge pressure and peak longitudinal strain rate during isovolumetric relaxation in patients undergoing coronary artery bypass graft surgery

Journal of cardiothoracic and vascular anesthesia, Jan 21, 2018

Two-dimensional speckle tracking echocardiography has advantages over tissue Doppler imaging duri... more Two-dimensional speckle tracking echocardiography has advantages over tissue Doppler imaging during isovolumetric relaxation for predicting left-ventricular end-diastolic pressure in non-surgical patients. Considering the direct and indirect effects of general anesthesia on hemodynamics, we examined correlations between strain-based indices during isovolumetric relaxation and pulmonary capillary wedge pressure in anesthetized patients. Moreover, we determined applicable cut-off values for strain-based indices to predict pulmonary capillary wedge pressure ≥15 mmHg intraoperatively. Retrospective clinical study. Single university hospital. Thirty adult patients with preserved ejection fraction undergoing coronary artery bypass grafting. None. Two-dimensional speckle tracking echocardiography was used to measure strain rate during isovolumetric relaxation (SR) and to calculate the mitral early diastolic inflow (E) to SR ratio (E/SR). Tissue Doppler imaging was used to calculate the E t...

Research paper thumbnail of Hypothyroidism improves random-pattern skin flap survival in rats

Journal of Surgical Research, 2012

Research paper thumbnail of Intestinal alkaline phosphatase has beneficial effects in mouse models of chronic colitis

Inflammatory Bowel Diseases, 2011

Research paper thumbnail of Investigating thermal effects on vibration behavior of temperature-dependent compositionally graded Euler beams with porosities

Research paper thumbnail of Steady-State Response Evaluation of Shape Memory Alloy Wire Under Resistive Heating Using a Newly Developed Element-Free Galerkin Meshless Method

Volume 2: Computer Technology, 2006

ABSTRACT

Research paper thumbnail of Application of the differential transformation method for nonlocal vibration analysis of functionally graded nanobeams

Journal of Mechanical Science and Technology, 2015

In this study, the applicability of differential transformation method (DTM) in investigations on... more In this study, the applicability of differential transformation method (DTM) in investigations on vibrational characteristics of functionally graded (FG) size-dependent nanobeams is examined. The material properties of FG nanobeam vary over the thickness based on the power law. The nonlocal Eringen theory, which takes into account the effect of small size, enables the present model to be effective in the analysis and design of nanosensors and nanoactuators. Governing equations are derived through Hamilton's principle. The obtained results exactly match the results of the presented Navier-based analytical solution as well as those available in literature. The DTM is also demonstrated to have high precision and computational efficiency in the vibration analysis of FG nanobeams. The detailed mathematical derivations are presented and numerical investigations performed with emphasis placed on investigating the effects of several parameters, such as small scale effects, volume fraction index, mode number, and thickness ratio on the normalized natural frequencies of the FG nanobeams. The study also shows explicitly that vibrations of FG nanobeams are significantly influenced by these effects. Numerical results are presented to serve as benchmarks for future analyses of FG nanobeams.

Research paper thumbnail of Pentoxifylline improves reoxygenation-induced contractile recovery through a nitric oxide-dependent mechanism in rat papillary muscles

Journal of cardiovascular pharmacology, 2006

In this study, the protective effect of pentoxifylline against hypoxia-reoxygenation injury and t... more In this study, the protective effect of pentoxifylline against hypoxia-reoxygenation injury and the possible involvement of nitric oxide (NO)-mediated pathways in this protection were investigated in isolated rat papillary muscles. Papillary muscles were excised and isolated in Krebs-Henseleit solution aerated with 95% O2 and 5% CO2. Hypoxia was simulated by substituting O2 with argon. Three sets of experiments, testing 30, 60, and 90 min of hypoxia, were performed. The effects of different pentoxifylline concentrations on papillary muscle contractile parameters and responsiveness to isoproterenol were assessed. To investigate the role of NO, N(omega)-nitro-L-arginine methyl ester was added before pentoxifylline treatment. Pentoxifylline did not show any inotropic effect on papillary muscles. Hypoxia caused a profound depression of contractile parameters, which was not affected by pentoxifylline treatment. Reoxygenation resulted in significant partial recovery of contractile paramet...

Research paper thumbnail of Vibration and buckling analysis of two-layered functionally graded cylindrical shell, considering the effects of transverse shear and rotary inertia

Materials & Design, 2010

This research investigates the free vibration and buckling of a two-layered cylindrical shell mad... more This research investigates the free vibration and buckling of a two-layered cylindrical shell made of inner functionally graded (FG) and outer isotropic elastic layer, subjected to combined static and periodic axial forces. Material properties of functionally graded cylindrical shell are considered as temperature dependent and graded in the thickness direction according to a power-law distribution in terms of the volume fractions of the constituents. Theoretical formulations are presented based on two different methods of first-order shear deformation theory (FSDT) considering the transverse shear strains and the rotary inertias and the classical shell theory (CST). The results obtained show that the transverse shear and rotary inertias have considerable effect on the fundamental frequency of the FG cylindrical shell. The results for nondimensional natural frequency are in a close agreement with those in literature. It is inferred from the results that the geometry parameters and material composition of the shell have significant effect on the critical axial force, so that the minimum critical load is obtained for fully metal shell. Good agreement between theoretical and finite element results validates the approach. It is concluded that the presence of an additional elastic layer significantly increases the nondimensional natural frequency, the buckling resistance and hence the elastic stability in axial compression with respect to a FG hollow cylinder.

Research paper thumbnail of An analytical study on the free vibration of smart circular thin FGM plate based on classical plate theory

Thin-Walled Structures, 2008

Analytical investigation of the free vibration behavior of thin circular functionally graded (FG)... more Analytical investigation of the free vibration behavior of thin circular functionally graded (FG) plates integrated with two uniformly distributed actuator layers made of piezoelectric (PZT4) material based on the classical plate theory (CPT) is presented in this paper. The material ...

Research paper thumbnail of ATP-sensitive potassium channels contribute to the time-dependent alteration in the pentylenetetrazole-induced seizure threshold in diabetic mice

Seizure, 2010

ATP-sensitive K + (K ATP ) channels exist in many excitable cells, including cardiac myocytes, pa... more ATP-sensitive K + (K ATP ) channels exist in many excitable cells, including cardiac myocytes, pancreatic b cells, muscle cells, and neurons 1,2 and are involved in several physiological functions. 3,4 KATP channels are expressed pre-and post-synaptically in many brain regions. They open and close in response to changes in intracellular ATP/ADP ratios. Low ATP levels open these channels, allowing K + efflux and cell hyperpolarization. 5 Therefore, the activity of K ATP channels is regulated by cell metabolism and provides a means of linking the electrical activity of a cell to its metabolic state. Pharmacological studies have also demonstrated that K ATP channels play an important role in the control of seizure threshold in several in vitro and in vivo models. 3,7-12 Moreover, it has been shown that mice lacking a subunit of K ATP channels (Kir 6.2 À/À mice) are vulnerable to hypoxia, exhibiting a reduced threshold for generalized seizure. 9 Transgenic mice, overexpressing the sulfonylurea receptor (SUR1) gene in the forebrain, show a significant increase in the threshold for kainite-induced seizures. 13 Thus, physiopathologic conditions altering the K ATP activation could possibly affect the seizure threshold.

Research paper thumbnail of NMDA receptor/nitrergic system blockage augments antidepressant-like effects of paroxetine in the mouse forced swimming test

Psychopharmacology, 2009

In this study, we evaluated the involvement of N-methyl-D-aspartate receptor (NMDAR)/nitric oxide... more In this study, we evaluated the involvement of N-methyl-D-aspartate receptor (NMDAR)/nitric oxide (NO) system on the antidepressant-like effects of paroxetine in the mouse forced swimming test. Swim sessions were conducted by placing mice in individual glass cylinders filled with water for 6 min. The duration of behavioral immobility during the last 4 min of the test was evaluated. Paroxetine (8 and 16 mg/kg, intraperitoneal [i.p.]) significantly reduced the immobility times of mice, whereas lower doses (2 and 4 mg/kg) had no effect. NMDA antagonists MK-801 (0.1 and 0.25 mg/kg, i.p.) and ifenprodil (1 and 3 mg/kg, i.p.) and the NO synthase inhibitor NG-L-arginine methyl ester (L-NAME; 30 and 100 mg/kg, i.p.) significantly decreased the immobility time. Lower doses of MK-801 (0.01 and 0.05 mg/kg), ifenprodil (0.1 and 0.5 mg/kg), and L-NAME (10 mg/kg) had no effect. Combined treatment of subeffective doses of paroxetine (4 mg/kg) and MK-801 (0.05 mg/kg), ifenprodil (0.5 mg/kg), and L-NAME (10 mg/kg) robustly exerted an antidepressant-like effect. The noneffective dose of a NO precursor L: -arginine (750 mg/kg, i.p.) prevented the antidepressant-like effect of paroxetine (30 mg/kg). We suggested, for the first time, a possible role for NMDAR/NO signaling in the antidepressant-like effects of paroxetine, providing a new approach for the treatment of depression.

Research paper thumbnail of Effect of lithium on endothelium-dependent and neurogenic relaxation of rat corpus cavernosum: Role of nitric oxide pathway

Nitric Oxide, 2007

Some studies have reported erectile dysfunction in patients receiving lithium through a mechanism... more Some studies have reported erectile dysfunction in patients receiving lithium through a mechanism that has not yet been defined. The aim of the present study was to verify the effect of acute lithium administration on the nonadrenergic noncholinergic (NANC)- and endothelium-mediated relaxation of rat isolated corpus cavernosum. The isolated rat corporeal strips were precontracted with phenylephrine hydrochloride (7.5 microM) and electrical field stimulation (EFS) was applied at different frequencies (2, 5, 10, and 15 Hz) to obtain NANC-mediated relaxation or relaxed by adding cumulative doses of acetylcholine (10nM-1mM) to obtain endothelium-dependent relaxation in the presence or absence of lithium (0.3, 0.5, 1, and 5mM). Also, effects of combining lithium (0.3mM) with 30 nM and 0.1 nM L-NAME (an NO synthase inhibitor) on NANC- and acetylcholine-mediated relaxation was investigated, respectively. Moreover, effects of combining lithium (1mM) with 0.1mM and 10 microM L-arginine (a precursor of NO) on NANC- and endothelium-mediated relaxation was assessed, respectively. Also, the effect of lithium (1mM) on relaxation to sodium nitroprusside (SNP; 1nM-1mM), an NO donor, was investigated. The NANC-mediated relaxation was significantly (P&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt;0.001) reduced by 1 and 5mM, but not by 0.3 and 0.5mM lithium. Lithium significantly (P&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt;0.001) attenuated the maximum response to acetylcholine in a concentration-dependent manner. Combination of lithium (0.3mM) with 30 and 0.1 nM L-NAME, which separately had a minimum effect on NANC- and endothelium-mediated relaxation, significantly (P&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt;0.001) reduced the NANC- and endothelium-mediated relaxation, respectively. Although L-arginine at 10 microM and 0.1mM did not alter the relaxant responses to acetylcholine and EFS, it improved the inhibition by lithium (1mM) of relaxant responses to acetylcholine and EFS, respectively. Also, SNP produced similar concentration-dependent relaxations from both groups. Our experiments indicated that lithium likely by interfering with NO pathway in both endothelium and nitrergic nerve can result in impairment of both the endothelium- and NANC-mediated relaxation of rat corpus cavernosum.

Research paper thumbnail of Nonlinear Thermomechanical Post-Buckling Analysis of Thin Functionally Graded Annular Plates Based on Von-Karman's Plate Theory

Mechanics of Advanced Materials and Structures, 2011

In this article, a nonlinear bending and axisymmetric thermal buckling analysis of thin functiona... more In this article, a nonlinear bending and axisymmetric thermal buckling analysis of thin functionally graded (FG) annular plates is presented based on classical nonlinear Von-Karman's plate theory. Using a shooting method the nonlinear ordinary differential equations are solved numerically. The presented solution is validated by comparing the obtained results with those of an isotropic plate. The emphasis is placed on

Research paper thumbnail of An Investigation on the Influence of Transverse Shear and Rotary Inertia on Vibration and Buckling of Functionally Graded Cylindrical Shells

Mechanics of Advanced Materials and Structures, 2010

Mechanics of Advanced Materials and Structures, 17:176–182, 2010 Copyright © Taylor & Francis... more Mechanics of Advanced Materials and Structures, 17:176–182, 2010 Copyright © Taylor & Francis Group, LLC ISSN: 1537-6494 print / 1537-6532 online DOI: 10.1080/15376490903243845 ... An Investigation on the Influence of Transverse Shear and ... Rotary Inertia on Vibration ...

Research paper thumbnail of Cholestasis induces apoptosis in mice cardiac cells: the possible role of nitric oxide and oxidative stress

Liver International, 2010

Acute cholestasis is associated with cardiovascular complications. The purpose of the present stu... more Acute cholestasis is associated with cardiovascular complications. The purpose of the present study was to investigate the effect of cholestasis on heart apoptosis and the involvement of nitric oxide (NO) and oxidative stress in the possible altered apoptosis of cholestatic hearts. Cholestasis was induced by bile duct-ligation, and sham-operated mice served as controls. Three days after the surgery, heart tissues were evaluated for apoptosis and the level of malondialdehyde (MDA), and the activities of catalase (CAT), glutathione peroxidase (GSHPx) and superoxide dismutase (SOD) have been studied in cardiac tissues. The role of treatment with l-NAME, a non-selective inhibitor of NO synthase, or with d-NAME, an inactive isomer of l-NAME, on cholestatic and sham cardiac apoptosis, level of MDA and CAT, SOD and GSHPx activities was also investigated. The content of NO in cardiac tissue was also determined. Cholestatic hearts showed structural abnormalities and increased apoptosis compared with sham hearts. Treatment with l-NAME, but not d-NAME, improved both structural abnormalities and enhanced apoptosis of cholestatic hearts. Cholestatic hearts also had an increased level of MDA and decreased activities of CAT and GSHPx, which were not modified by d-NAME treatment. By l-NAME treatment, the level of MDA decreased and activities of CAT, GSHPx and SOD increased in BDL mice. The content of NO was higher in cholestatic cardiac tissue, which was decreased by l-NAME treatment. In conclusion, apoptosis in cholestatic heart might have occurred because of NO overproduction, which could induce oxidative stress in the heart of cholestatic mice.

Research paper thumbnail of Chronic Lithium Impairs Skin Tolerance to Ischemia in Random-Pattern Skin Flap of Rats

Journal of Surgical Research, 2011

Despite its apparent anti-apoptotic effect, lithium impairs endothelium-dependent vasorelaxation ... more Despite its apparent anti-apoptotic effect, lithium impairs endothelium-dependent vasorelaxation in various tissues. In this study, we assessed the effect of lithium treatment on ischemic skin flap survival and its interaction with nitric oxide pathway. Seventy-six male Sprague-Dawley rats were randomly assigned into 13 groups. For skin flap surgery, dorsal skin flap measuring 8 × 2 cm was elevated on the midline. After local injections (if needed), the cranial pedicle was cut and flap was sutured back. Flap survival was assessed after 7 d. Animals in the chronic lithium group received lithium chloride in tap water for 4 wk preoperatively and 7 d postoperatively. Acute lithium groups received 3 nmol, 10 nmol and 3 μmol/flap lithium locally. In another experiment, interaction with nitric oxide synthase inhibitor L-NAME as well as nitric oxide precursor L-arginine was studied, and the effect of ischemic preconditioning on skin flap survival in lithium treated rats was investigated. Chronic lithium group had mean flap survival value of 32.6% ± 5.2% (mean ± SD), which was significantly lower than normal subjects (52.7% ± 6.1%, P &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; 0.001), while acute local lithium treatment had no effect. In chronic lithium group, systemic L-NAME (10 mg/kg, 30 min before flap elevation) failed to significantly decrease the survival, while sub-effective systemic L-arginine (100 mg/kg) and ischemic preconditioning significantly increased flap survival (P &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; 0.001 and P &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; 0.01, respectively). We conclude that long-term lithium treatment impairs the skin tolerance to ischemia in rats, which seems to be nitric oxide mediated. This effect is prevented by ischemic preconditioning or L-arginine treatment. The results suggest that skin-involving interventions should be applied more cautiously in patients who are on lithium treatment.

Research paper thumbnail of Schauder fixed point theorem based existence of periodic solution for the response of Duffing’s oscillator

Journal of Mechanical Science and Technology, 2009

An initial-boundary value problem that is Duffing's oscillator with time varying coefficients wil... more An initial-boundary value problem that is Duffing's oscillator with time varying coefficients will be studied. Using Banach's fixed-point theorem, the existence of periodic solution of the equation will be predicted. The method applied in this paper is the Schauder second fixed point theorem, which includes the response of structures under vibratory force systems. As an example, the dynamics of nonlinear simply supported rectangular thin plate under influence of a relatively moving mass is studied. By expansion of the solution as a series of mode functions, the governing equations of motion are reduced to an ordinary differential equation for time development vibration amplitude, which is Duffing's oscillator. Finally, a parametric study is developed, after that some numerical examples are solved, and the validity of the present analysis is clearly shown.

Research paper thumbnail of Geometrically nonlinear vibration analysis of piezoelectrically actuated FGM plate with an initial large deformation

Journal of Mechanical Science and Technology, 2009

A theoretical model for geometrically nonlinear vibration analysis of piezoelectrically actuated ... more A theoretical model for geometrically nonlinear vibration analysis of piezoelectrically actuated circular plates made of functionally grade material (FGM) is presented based on Kirchhoff's-Love hypothesis with von-Karman type geometrical large nonlinear deformations. To determine the initial stress state and pre-vibration deformations of the smart plate a nonlinear static problem is solved followed by adding an incremental dynamic state to the pre-vibration state. The derived governing equations of the structure are solved by exact series expansion method combined with perturbation approach. The material properties of the FGM core plate are assumed to be graded in the thickness direction according to the power-law distribution in terms of the volume fractions of the constituents. Control of the FGM plate's nonlinear deflections and natural frequencies using high control voltages is studied and their nonlinear effects are evaluated. Numerical results for FG plates with various mixture of ceramic and metal are presented in dimensionless forms. In a parametric study the emphasis is placed on investigating the effect of varying the applied actuator voltage as well as gradient index of FGM plate on vibration characteristics of the smart structure.

Research paper thumbnail of Speckle- Tracking Echocardiography for the Staging of Diastolic Dysfunction: The Correlation Between Strain-Based Indices and the Severity of Left Ventricular Diastolic Dysfunction

Journal of Cardiothoracic and Vascular Anesthesia

Objectives: Left ventricular diastolic function can be assessed by various methods. Tissue Dopple... more Objectives: Left ventricular diastolic function can be assessed by various methods. Tissue Doppler imaging is among the most commonly used techniques. However, this imaging is angle-dependent, affected by loading conditions, and susceptible to myocardial tethering. Speckle-tracking echocardiography also can measure strain-based indices to assess diastolic function, and it has fewer limitations than tissue Doppler imaging. Using speckle-tracking echocardiography, the authors evaluated the correlation between the stage of diastolic dysfunction and strain-based indices in patients undergoing cardiac surgery to determine whether strain-based indices can be used intraoperatively to identify the extent of left ventricular diastolic dysfunction. Design: Retrospective clinical study. Setting: Single university hospital. Participants: Fifty-eight patients undergoing cardiac surgery (December 2017 to December 2019). Interventions: None. Measurement and Main Result: Preoperative echocardiographic reports and intraoperative echocardiographic images of the participants were studied. The correlation between the stage of left ventricular diastolic dysfunction and strain-based indices (including early diastolic peak longitudinal strain and tissue deceleration time) were evaluated. Early diastolic peak longitudinal strain rate significantly correlated with the stage of diastolic dysfunction (r = À0.7 and p < 0.0001). Tissue deceleration time significantly correlated with the stage of diastolic dysfunction in patients with diastolic abnormality (r = À0.4 and p = 0.02). When patients with normal diastolic function were included, this correlation was not significant (r= À0.25 and p = 0.05). Conclusions: Intraoperatively measured early diastolic peak longitudinal strain rate and tissue deceleration time correlated with the severity of diastolic dysfunction in patients undergoing cardiac surgery.

Research paper thumbnail of Creatine Revealed Anticonvulsant Properties on Chemically and Electrically Induced Seizures in Mice

Creatine exerts beneficial effects on a variety of pathologies in which energy metabolism and oxi... more Creatine exerts beneficial effects on a variety of pathologies in which energy metabolism and oxidative stress play an etiological role. Creatine supplements have shown beneficial effects on neurological disorders including Parkinson׳s disease, Huntington›s disease, amyotrophic lateral sclerosis, as well as Alzheimer›s disease and stroke. However, the potential benefits of creatine for patients with convulsive disorders remain poorly defined. While some authors did not suggest any anti- or pro-convulsant roles for creatine treatment, others suggest that creatine may be an anticonvulsant agent. In this study, we investigated the effects of creatine on seizures in mice. Three models were used to explore the role of creatine on seizures in mice including intravenous pentylenetetrazole (PTZ), intraperitoneal PTZ, and electroshock models. Acute creatine treatment (10, 20, 40 and 80 mg/Kg) significantly increased the clonic seizure threshold in the intravenous PTZ model. Sub-chronic admin...

Research paper thumbnail of Intraoperative assessment of left-ventricular diastolic function by two-dimensional speckle tracking echocardiography: relationship between pulmonary capillary wedge pressure and peak longitudinal strain rate during isovolumetric relaxation in patients undergoing coronary artery bypass graft surgery

Journal of cardiothoracic and vascular anesthesia, Jan 21, 2018

Two-dimensional speckle tracking echocardiography has advantages over tissue Doppler imaging duri... more Two-dimensional speckle tracking echocardiography has advantages over tissue Doppler imaging during isovolumetric relaxation for predicting left-ventricular end-diastolic pressure in non-surgical patients. Considering the direct and indirect effects of general anesthesia on hemodynamics, we examined correlations between strain-based indices during isovolumetric relaxation and pulmonary capillary wedge pressure in anesthetized patients. Moreover, we determined applicable cut-off values for strain-based indices to predict pulmonary capillary wedge pressure ≥15 mmHg intraoperatively. Retrospective clinical study. Single university hospital. Thirty adult patients with preserved ejection fraction undergoing coronary artery bypass grafting. None. Two-dimensional speckle tracking echocardiography was used to measure strain rate during isovolumetric relaxation (SR) and to calculate the mitral early diastolic inflow (E) to SR ratio (E/SR). Tissue Doppler imaging was used to calculate the E t...

Research paper thumbnail of Hypothyroidism improves random-pattern skin flap survival in rats

Journal of Surgical Research, 2012

Research paper thumbnail of Intestinal alkaline phosphatase has beneficial effects in mouse models of chronic colitis

Inflammatory Bowel Diseases, 2011

Research paper thumbnail of Investigating thermal effects on vibration behavior of temperature-dependent compositionally graded Euler beams with porosities

Research paper thumbnail of Steady-State Response Evaluation of Shape Memory Alloy Wire Under Resistive Heating Using a Newly Developed Element-Free Galerkin Meshless Method

Volume 2: Computer Technology, 2006

ABSTRACT

Research paper thumbnail of Application of the differential transformation method for nonlocal vibration analysis of functionally graded nanobeams

Journal of Mechanical Science and Technology, 2015

In this study, the applicability of differential transformation method (DTM) in investigations on... more In this study, the applicability of differential transformation method (DTM) in investigations on vibrational characteristics of functionally graded (FG) size-dependent nanobeams is examined. The material properties of FG nanobeam vary over the thickness based on the power law. The nonlocal Eringen theory, which takes into account the effect of small size, enables the present model to be effective in the analysis and design of nanosensors and nanoactuators. Governing equations are derived through Hamilton's principle. The obtained results exactly match the results of the presented Navier-based analytical solution as well as those available in literature. The DTM is also demonstrated to have high precision and computational efficiency in the vibration analysis of FG nanobeams. The detailed mathematical derivations are presented and numerical investigations performed with emphasis placed on investigating the effects of several parameters, such as small scale effects, volume fraction index, mode number, and thickness ratio on the normalized natural frequencies of the FG nanobeams. The study also shows explicitly that vibrations of FG nanobeams are significantly influenced by these effects. Numerical results are presented to serve as benchmarks for future analyses of FG nanobeams.

Research paper thumbnail of Pentoxifylline improves reoxygenation-induced contractile recovery through a nitric oxide-dependent mechanism in rat papillary muscles

Journal of cardiovascular pharmacology, 2006

In this study, the protective effect of pentoxifylline against hypoxia-reoxygenation injury and t... more In this study, the protective effect of pentoxifylline against hypoxia-reoxygenation injury and the possible involvement of nitric oxide (NO)-mediated pathways in this protection were investigated in isolated rat papillary muscles. Papillary muscles were excised and isolated in Krebs-Henseleit solution aerated with 95% O2 and 5% CO2. Hypoxia was simulated by substituting O2 with argon. Three sets of experiments, testing 30, 60, and 90 min of hypoxia, were performed. The effects of different pentoxifylline concentrations on papillary muscle contractile parameters and responsiveness to isoproterenol were assessed. To investigate the role of NO, N(omega)-nitro-L-arginine methyl ester was added before pentoxifylline treatment. Pentoxifylline did not show any inotropic effect on papillary muscles. Hypoxia caused a profound depression of contractile parameters, which was not affected by pentoxifylline treatment. Reoxygenation resulted in significant partial recovery of contractile paramet...

Research paper thumbnail of Vibration and buckling analysis of two-layered functionally graded cylindrical shell, considering the effects of transverse shear and rotary inertia

Materials & Design, 2010

This research investigates the free vibration and buckling of a two-layered cylindrical shell mad... more This research investigates the free vibration and buckling of a two-layered cylindrical shell made of inner functionally graded (FG) and outer isotropic elastic layer, subjected to combined static and periodic axial forces. Material properties of functionally graded cylindrical shell are considered as temperature dependent and graded in the thickness direction according to a power-law distribution in terms of the volume fractions of the constituents. Theoretical formulations are presented based on two different methods of first-order shear deformation theory (FSDT) considering the transverse shear strains and the rotary inertias and the classical shell theory (CST). The results obtained show that the transverse shear and rotary inertias have considerable effect on the fundamental frequency of the FG cylindrical shell. The results for nondimensional natural frequency are in a close agreement with those in literature. It is inferred from the results that the geometry parameters and material composition of the shell have significant effect on the critical axial force, so that the minimum critical load is obtained for fully metal shell. Good agreement between theoretical and finite element results validates the approach. It is concluded that the presence of an additional elastic layer significantly increases the nondimensional natural frequency, the buckling resistance and hence the elastic stability in axial compression with respect to a FG hollow cylinder.

Research paper thumbnail of An analytical study on the free vibration of smart circular thin FGM plate based on classical plate theory

Thin-Walled Structures, 2008

Analytical investigation of the free vibration behavior of thin circular functionally graded (FG)... more Analytical investigation of the free vibration behavior of thin circular functionally graded (FG) plates integrated with two uniformly distributed actuator layers made of piezoelectric (PZT4) material based on the classical plate theory (CPT) is presented in this paper. The material ...

Research paper thumbnail of ATP-sensitive potassium channels contribute to the time-dependent alteration in the pentylenetetrazole-induced seizure threshold in diabetic mice

Seizure, 2010

ATP-sensitive K + (K ATP ) channels exist in many excitable cells, including cardiac myocytes, pa... more ATP-sensitive K + (K ATP ) channels exist in many excitable cells, including cardiac myocytes, pancreatic b cells, muscle cells, and neurons 1,2 and are involved in several physiological functions. 3,4 KATP channels are expressed pre-and post-synaptically in many brain regions. They open and close in response to changes in intracellular ATP/ADP ratios. Low ATP levels open these channels, allowing K + efflux and cell hyperpolarization. 5 Therefore, the activity of K ATP channels is regulated by cell metabolism and provides a means of linking the electrical activity of a cell to its metabolic state. Pharmacological studies have also demonstrated that K ATP channels play an important role in the control of seizure threshold in several in vitro and in vivo models. 3,7-12 Moreover, it has been shown that mice lacking a subunit of K ATP channels (Kir 6.2 À/À mice) are vulnerable to hypoxia, exhibiting a reduced threshold for generalized seizure. 9 Transgenic mice, overexpressing the sulfonylurea receptor (SUR1) gene in the forebrain, show a significant increase in the threshold for kainite-induced seizures. 13 Thus, physiopathologic conditions altering the K ATP activation could possibly affect the seizure threshold.

Research paper thumbnail of NMDA receptor/nitrergic system blockage augments antidepressant-like effects of paroxetine in the mouse forced swimming test

Psychopharmacology, 2009

In this study, we evaluated the involvement of N-methyl-D-aspartate receptor (NMDAR)/nitric oxide... more In this study, we evaluated the involvement of N-methyl-D-aspartate receptor (NMDAR)/nitric oxide (NO) system on the antidepressant-like effects of paroxetine in the mouse forced swimming test. Swim sessions were conducted by placing mice in individual glass cylinders filled with water for 6 min. The duration of behavioral immobility during the last 4 min of the test was evaluated. Paroxetine (8 and 16 mg/kg, intraperitoneal [i.p.]) significantly reduced the immobility times of mice, whereas lower doses (2 and 4 mg/kg) had no effect. NMDA antagonists MK-801 (0.1 and 0.25 mg/kg, i.p.) and ifenprodil (1 and 3 mg/kg, i.p.) and the NO synthase inhibitor NG-L-arginine methyl ester (L-NAME; 30 and 100 mg/kg, i.p.) significantly decreased the immobility time. Lower doses of MK-801 (0.01 and 0.05 mg/kg), ifenprodil (0.1 and 0.5 mg/kg), and L-NAME (10 mg/kg) had no effect. Combined treatment of subeffective doses of paroxetine (4 mg/kg) and MK-801 (0.05 mg/kg), ifenprodil (0.5 mg/kg), and L-NAME (10 mg/kg) robustly exerted an antidepressant-like effect. The noneffective dose of a NO precursor L: -arginine (750 mg/kg, i.p.) prevented the antidepressant-like effect of paroxetine (30 mg/kg). We suggested, for the first time, a possible role for NMDAR/NO signaling in the antidepressant-like effects of paroxetine, providing a new approach for the treatment of depression.

Research paper thumbnail of Effect of lithium on endothelium-dependent and neurogenic relaxation of rat corpus cavernosum: Role of nitric oxide pathway

Nitric Oxide, 2007

Some studies have reported erectile dysfunction in patients receiving lithium through a mechanism... more Some studies have reported erectile dysfunction in patients receiving lithium through a mechanism that has not yet been defined. The aim of the present study was to verify the effect of acute lithium administration on the nonadrenergic noncholinergic (NANC)- and endothelium-mediated relaxation of rat isolated corpus cavernosum. The isolated rat corporeal strips were precontracted with phenylephrine hydrochloride (7.5 microM) and electrical field stimulation (EFS) was applied at different frequencies (2, 5, 10, and 15 Hz) to obtain NANC-mediated relaxation or relaxed by adding cumulative doses of acetylcholine (10nM-1mM) to obtain endothelium-dependent relaxation in the presence or absence of lithium (0.3, 0.5, 1, and 5mM). Also, effects of combining lithium (0.3mM) with 30 nM and 0.1 nM L-NAME (an NO synthase inhibitor) on NANC- and acetylcholine-mediated relaxation was investigated, respectively. Moreover, effects of combining lithium (1mM) with 0.1mM and 10 microM L-arginine (a precursor of NO) on NANC- and endothelium-mediated relaxation was assessed, respectively. Also, the effect of lithium (1mM) on relaxation to sodium nitroprusside (SNP; 1nM-1mM), an NO donor, was investigated. The NANC-mediated relaxation was significantly (P&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt;0.001) reduced by 1 and 5mM, but not by 0.3 and 0.5mM lithium. Lithium significantly (P&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt;0.001) attenuated the maximum response to acetylcholine in a concentration-dependent manner. Combination of lithium (0.3mM) with 30 and 0.1 nM L-NAME, which separately had a minimum effect on NANC- and endothelium-mediated relaxation, significantly (P&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt;0.001) reduced the NANC- and endothelium-mediated relaxation, respectively. Although L-arginine at 10 microM and 0.1mM did not alter the relaxant responses to acetylcholine and EFS, it improved the inhibition by lithium (1mM) of relaxant responses to acetylcholine and EFS, respectively. Also, SNP produced similar concentration-dependent relaxations from both groups. Our experiments indicated that lithium likely by interfering with NO pathway in both endothelium and nitrergic nerve can result in impairment of both the endothelium- and NANC-mediated relaxation of rat corpus cavernosum.

Research paper thumbnail of Nonlinear Thermomechanical Post-Buckling Analysis of Thin Functionally Graded Annular Plates Based on Von-Karman's Plate Theory

Mechanics of Advanced Materials and Structures, 2011

In this article, a nonlinear bending and axisymmetric thermal buckling analysis of thin functiona... more In this article, a nonlinear bending and axisymmetric thermal buckling analysis of thin functionally graded (FG) annular plates is presented based on classical nonlinear Von-Karman's plate theory. Using a shooting method the nonlinear ordinary differential equations are solved numerically. The presented solution is validated by comparing the obtained results with those of an isotropic plate. The emphasis is placed on

Research paper thumbnail of An Investigation on the Influence of Transverse Shear and Rotary Inertia on Vibration and Buckling of Functionally Graded Cylindrical Shells

Mechanics of Advanced Materials and Structures, 2010

Mechanics of Advanced Materials and Structures, 17:176–182, 2010 Copyright © Taylor & Francis... more Mechanics of Advanced Materials and Structures, 17:176–182, 2010 Copyright © Taylor & Francis Group, LLC ISSN: 1537-6494 print / 1537-6532 online DOI: 10.1080/15376490903243845 ... An Investigation on the Influence of Transverse Shear and ... Rotary Inertia on Vibration ...

Research paper thumbnail of Cholestasis induces apoptosis in mice cardiac cells: the possible role of nitric oxide and oxidative stress

Liver International, 2010

Acute cholestasis is associated with cardiovascular complications. The purpose of the present stu... more Acute cholestasis is associated with cardiovascular complications. The purpose of the present study was to investigate the effect of cholestasis on heart apoptosis and the involvement of nitric oxide (NO) and oxidative stress in the possible altered apoptosis of cholestatic hearts. Cholestasis was induced by bile duct-ligation, and sham-operated mice served as controls. Three days after the surgery, heart tissues were evaluated for apoptosis and the level of malondialdehyde (MDA), and the activities of catalase (CAT), glutathione peroxidase (GSHPx) and superoxide dismutase (SOD) have been studied in cardiac tissues. The role of treatment with l-NAME, a non-selective inhibitor of NO synthase, or with d-NAME, an inactive isomer of l-NAME, on cholestatic and sham cardiac apoptosis, level of MDA and CAT, SOD and GSHPx activities was also investigated. The content of NO in cardiac tissue was also determined. Cholestatic hearts showed structural abnormalities and increased apoptosis compared with sham hearts. Treatment with l-NAME, but not d-NAME, improved both structural abnormalities and enhanced apoptosis of cholestatic hearts. Cholestatic hearts also had an increased level of MDA and decreased activities of CAT and GSHPx, which were not modified by d-NAME treatment. By l-NAME treatment, the level of MDA decreased and activities of CAT, GSHPx and SOD increased in BDL mice. The content of NO was higher in cholestatic cardiac tissue, which was decreased by l-NAME treatment. In conclusion, apoptosis in cholestatic heart might have occurred because of NO overproduction, which could induce oxidative stress in the heart of cholestatic mice.

Research paper thumbnail of Chronic Lithium Impairs Skin Tolerance to Ischemia in Random-Pattern Skin Flap of Rats

Journal of Surgical Research, 2011

Despite its apparent anti-apoptotic effect, lithium impairs endothelium-dependent vasorelaxation ... more Despite its apparent anti-apoptotic effect, lithium impairs endothelium-dependent vasorelaxation in various tissues. In this study, we assessed the effect of lithium treatment on ischemic skin flap survival and its interaction with nitric oxide pathway. Seventy-six male Sprague-Dawley rats were randomly assigned into 13 groups. For skin flap surgery, dorsal skin flap measuring 8 × 2 cm was elevated on the midline. After local injections (if needed), the cranial pedicle was cut and flap was sutured back. Flap survival was assessed after 7 d. Animals in the chronic lithium group received lithium chloride in tap water for 4 wk preoperatively and 7 d postoperatively. Acute lithium groups received 3 nmol, 10 nmol and 3 μmol/flap lithium locally. In another experiment, interaction with nitric oxide synthase inhibitor L-NAME as well as nitric oxide precursor L-arginine was studied, and the effect of ischemic preconditioning on skin flap survival in lithium treated rats was investigated. Chronic lithium group had mean flap survival value of 32.6% ± 5.2% (mean ± SD), which was significantly lower than normal subjects (52.7% ± 6.1%, P &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; 0.001), while acute local lithium treatment had no effect. In chronic lithium group, systemic L-NAME (10 mg/kg, 30 min before flap elevation) failed to significantly decrease the survival, while sub-effective systemic L-arginine (100 mg/kg) and ischemic preconditioning significantly increased flap survival (P &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; 0.001 and P &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; 0.01, respectively). We conclude that long-term lithium treatment impairs the skin tolerance to ischemia in rats, which seems to be nitric oxide mediated. This effect is prevented by ischemic preconditioning or L-arginine treatment. The results suggest that skin-involving interventions should be applied more cautiously in patients who are on lithium treatment.

Research paper thumbnail of Schauder fixed point theorem based existence of periodic solution for the response of Duffing’s oscillator

Journal of Mechanical Science and Technology, 2009

An initial-boundary value problem that is Duffing's oscillator with time varying coefficients wil... more An initial-boundary value problem that is Duffing's oscillator with time varying coefficients will be studied. Using Banach's fixed-point theorem, the existence of periodic solution of the equation will be predicted. The method applied in this paper is the Schauder second fixed point theorem, which includes the response of structures under vibratory force systems. As an example, the dynamics of nonlinear simply supported rectangular thin plate under influence of a relatively moving mass is studied. By expansion of the solution as a series of mode functions, the governing equations of motion are reduced to an ordinary differential equation for time development vibration amplitude, which is Duffing's oscillator. Finally, a parametric study is developed, after that some numerical examples are solved, and the validity of the present analysis is clearly shown.

Research paper thumbnail of Geometrically nonlinear vibration analysis of piezoelectrically actuated FGM plate with an initial large deformation

Journal of Mechanical Science and Technology, 2009

A theoretical model for geometrically nonlinear vibration analysis of piezoelectrically actuated ... more A theoretical model for geometrically nonlinear vibration analysis of piezoelectrically actuated circular plates made of functionally grade material (FGM) is presented based on Kirchhoff's-Love hypothesis with von-Karman type geometrical large nonlinear deformations. To determine the initial stress state and pre-vibration deformations of the smart plate a nonlinear static problem is solved followed by adding an incremental dynamic state to the pre-vibration state. The derived governing equations of the structure are solved by exact series expansion method combined with perturbation approach. The material properties of the FGM core plate are assumed to be graded in the thickness direction according to the power-law distribution in terms of the volume fractions of the constituents. Control of the FGM plate's nonlinear deflections and natural frequencies using high control voltages is studied and their nonlinear effects are evaluated. Numerical results for FG plates with various mixture of ceramic and metal are presented in dimensionless forms. In a parametric study the emphasis is placed on investigating the effect of varying the applied actuator voltage as well as gradient index of FGM plate on vibration characteristics of the smart structure.