scholarly journals Effects of electrical stimulation on isolated rodent gastric smooth muscle cells evaluated via a joint computational simulation and experimental approach

2009 ◽  
Vol 297 (4) ◽  
pp. G672-G680 ◽  
Author(s):  
P. Du ◽  
S. Li ◽  
G. O'Grady ◽  
L. K. Cheng ◽  
A. J. Pullan ◽  
...  
Keyword(s):  
Smooth Muscle ◽  
Electrical Stimulation ◽  
Pulse Train ◽  
Pulse Width ◽  
Computational Simulation ◽  
Minimum Energy ◽  
Experimental Studies ◽  
Single Pulse ◽  
Plateau Phase ◽  
Wide Range

Gastric electrical stimulation (GES) involves the delivery of electrical impulses to the stomach for therapeutic purposes. New GES protocols are needed that are optimized for improved motility outcomes and energy efficiency. In this study, a biophysically based smooth muscle cell (SMC) model was modified on the basis of experimental data and employed in conjunction with experimental studies to define the effects of a large range of GES protocols on individual SMCs. For the validation studies, rat gastric SMCs were isolated and subjected to patch-clamp analysis during stimulation. Experimental results were in satisfactory agreement with simulation results. The results define the effects of a wide range of GES parameters (pulse width, amplitude, and pulse-train frequency) on isolated SMCs. The minimum pulse width required to invoke a supramechanical threshold response from SMCs (defined at −30 mV) was 65 ms (at 250-pA amplitude). The minimum amplitude required to invoke this threshold was 75 pA (at 1,000-ms pulse width). The amplitude of the invoked response beyond this threshold was proportional to the stimulation amplitude. A high-frequency train of stimuli (40 Hz; 10 ms, 150 pA) could invoke and maintain the SMC plateau phase while requiring 60% less power and accruing ∼30% less intracellular Ca2+ concentration during the plateau phase than a comparable single-pulse protocol could in a demonstrated example. Validated computational simulations are an effective strategy for efficiently identifying effective minimum-energy GES protocols, and pulse-train protocols may also help to reduce the power consumption of future GES devices.

Cellular effects of gastric electrical stimulation on antral smooth muscle cells in rats

2010 ◽  
Vol 298 (6) ◽  
pp. R1580-R1587 ◽  
Author(s):  
Shiying Li ◽  
Jiande D. Z. Chen
Keyword(s):  
Smooth Muscle ◽  
Electrical Stimulation ◽  
Cell Membrane ◽  
Smooth Muscle Cells ◽  
Action Potentials ◽  
Pulse Train ◽  
Pulse Width ◽  
Pulse Frequency ◽  
Membrane Potentials ◽  
Cellular Effects

The cellular effects of gastric electrical stimulation (GES), which has recently been introduced as a potential therapy for the treatment of gastroparesis and obesity, were investigated in rat antrum smooth muscle cells (SMCs). Effects on cell membrane potentials of single electrical current pulses (pulse width from 0.1 ms to 200 ms) and 2-s pulse train stimuli with different pulse widths (0.1–4 ms), different frequencies (20–200 Hz), and different intensities were studied: 1) the stimulus amplitude had an exponential relationship to the pulse width from 2 ms to 200 ms, along with a rapidly rising strength-duration curve at pulse widths less than 5 ms, and a relatively flat curve at pulse widths greater than 50 ms; 2) when the pulse frequency was at 80 Hz or above, pulse train electrical stimulation, with a pulse width of 2 ms or above but not ≤1 ms, was able to depolarize cell membrane potentials to above −30 mV and/or generate action potentials. Electrical stimulation with a single long pulse and a width of 50 ms or greater is effective in depolarizing cell membrane potentials of SMCs with low amplitude. Pulse train electrical stimulation with a pulse width of ≤1 ms fails to generate action potentials in SMCs, whereas pulse train electrical stimulation with a pulse width of 2–4 ms and a sufficiently high pulse frequency is able to generate action potentials. These cellular findings may be useful in optimizing stimulation parameters of GES.

scholarly journals Venular endothelium-derived NO can affect paired arteriole: a computational model

2006 ◽  
Vol 290 (2) ◽  
pp. H716-H723 ◽  
Author(s):  
Mahendra Kavdia ◽  
Aleksander S. Popel
Keyword(s):  
Smooth Muscle ◽  
Computational Model ◽  
Reaction Rate ◽  
Soluble Guanylate Cyclase ◽  
Experimental Studies ◽  
Vascular Wall ◽  
No Production ◽  
Wide Range ◽  
Venular Endothelium

Venular endothelial cells can release nitric oxide (NO) in response to intraluminal flow both in isolated venules and in vivo. Experimental studies suggest that venular endothelium-released NO causes dilation of the adjacent paired arteriole. In the vascular wall, NO stimulates its target hemoprotein, soluble guanylate cyclase (sGC), which relaxes smooth muscle cells. In this study, a computational model of NO transport for an arteriole and venule pair was developed to determine the importance of the venular endothelium-released NO and its transport to the adjacent arteriole in the tissue. The model predicts that the tissue NO levels are affected within a wide range of parameters, including NO-red blood cell reaction rate and NO production rate in the arteriole and venule. The results predict that changes in the venular NO production affected not only venular endothelial and smooth muscle NO concentration but also endothelial and smooth muscle NO concentration in the adjacent arteriole. This suggests that the anatomy of microvascular tissue can permit the transport of NO from arteriolar to venular side, and vice versa, and may provide a mechanism for dilation of proximal arterioles by venules. These results will have significant implications for our understanding of tissue NO levels in both physiological and pathophysiological conditions.

Single Pulse and Pulse Train Modulation of Cutaneous Electrical Stimulation: A Comparison of Methods

2009 ◽  
Vol 26 (1) ◽  
pp. 54-60 ◽  
Author(s):  
Esther M. van der Heide ◽  
Jan R. Buitenweg ◽  
Enrico Marani ◽  
Wim L. C. Rutten
Keyword(s):  
Electrical Stimulation ◽  
Pulse Train ◽  
Single Pulse ◽  
Comparison Of Methods

scholarly journals Single-pulse electrical stimulation methodology in freely moving rat

2021 ◽  
Vol 353 ◽  
pp. 109092
Author(s):  
Eloïse Gronlier ◽  
Estelle Vendramini ◽  
Julien Volle ◽  
Agata Wozniak-Kwasniewska ◽  
Noelia Antón Santos ◽  
...  
Keyword(s):  
Electrical Stimulation ◽  
Single Pulse ◽  
Freely Moving

scholarly journals Image Statistics Preserving Encrypt-then-Compress Scheme Dedicated for JPEG Compression Standard

Entropy ◽  
2021 ◽  
Vol 23 (4) ◽  
pp. 421
Author(s):  
Dariusz Puchala ◽  
Kamil Stokfiszewski ◽  
Mykhaylo Yatsymirskyy
Keyword(s):  
Statistical Analysis ◽  
Image Encryption ◽  
Experimental Studies ◽  
Quality Measures ◽  
Input Image ◽  
Jpeg Compression ◽  
Image Statistics ◽  
Compression Stage ◽  
Wide Range ◽  
The Impact

In this paper, the authors analyze in more details an image encryption scheme, proposed by the authors in their earlier work, which preserves input image statistics and can be used in connection with the JPEG compression standard. The image encryption process takes advantage of fast linear transforms parametrized with private keys and is carried out prior to the compression stage in a way that does not alter those statistical characteristics of the input image that are crucial from the point of view of the subsequent compression. This feature makes the encryption process transparent to the compression stage and enables the JPEG algorithm to maintain its full compression capabilities even though it operates on the encrypted image data. The main advantage of the considered approach is the fact that the JPEG algorithm can be used without any modifications as a part of the encrypt-then-compress image processing framework. The paper includes a detailed mathematical model of the examined scheme allowing for theoretical analysis of the impact of the image encryption step on the effectiveness of the compression process. The combinatorial and statistical analysis of the encryption process is also included and it allows to evaluate its cryptographic strength. In addition, the paper considers several practical use-case scenarios with different characteristics of the compression and encryption stages. The final part of the paper contains the additional results of the experimental studies regarding general effectiveness of the presented scheme. The results show that for a wide range of compression ratios the considered scheme performs comparably to the JPEG algorithm alone, that is, without the encryption stage, in terms of the quality measures of reconstructed images. Moreover, the results of statistical analysis as well as those obtained with generally approved quality measures of image cryptographic systems, prove high strength and efficiency of the scheme’s encryption stage.

scholarly journals Influence of Tool Geometry and Process Parameters on the Properties of Friction Stir Spot Welded Multiple (AA 5754 H111) Aluminium Sheets

Materials ◽  
2021 ◽  
Vol 14 (5) ◽  
pp. 1157
Author(s):  
Danka Labus Zlatanovic ◽  
Sebastian Balos ◽  
Jean Pierre Bergmann ◽  
Stefan Rasche ◽  
Milan Pecanac ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Process Parameters ◽  
Spot Welding ◽  
Minimum Energy ◽  
Tool Geometry ◽  
Friction Stir ◽  
Minimum Energy Consumption ◽  
Punch Test ◽  
Wide Range ◽  
Lap Welding

Friction stir spot welding is an emerging spot-welding technology that offers opportunities for joining a wide range of materials with minimum energy consumption. To increase productivity, the present work addresses production challenges and aims to find solutions for the lap-welding of multiple ultrathin sheets with maximum productivity. Two convex tools with different edge radii were used to weld four ultrathin sheets of AA5754-H111 alloy each with 0.3 mm thickness. To understand the influence of tool geometries and process parameters, coefficient of friction (CoF), microstructure and mechanical properties obtained with the Vickers microhardness test and the small punch test were analysed. A scanning acoustic microscope was used to assess weld quality. It was found that the increase of tool radius from 15 to 22.5 mm reduced the dwell time by a factor of three. Samples welded with a specific tool were seen to have no delamination and improved mechanical properties due to longer stirring time. The rotational speed was found to be the most influential parameter in governing the weld shape, CoF, microstructure, microhardness and weld efficiency. Low rotational speeds caused a 14.4% and 12.8% improvement in joint efficiency compared to high rotational speeds for both tools used in this investigation.

Elevated levels of activin A in clinical and experimental pulmonary hypertension

2009 ◽  
Vol 106 (4) ◽  
pp. 1356-1364 ◽  
Author(s):  
Arne Yndestad ◽  
Karl-Otto Larsen ◽  
Erik Øie ◽  
Thor Ueland ◽  
Camilla Smith ◽  
...  
Keyword(s):  
Pulmonary Hypertension ◽  
Smooth Muscle ◽  
Smooth Muscle Cells ◽  
Transforming Growth Factor ◽  
Experimental Studies ◽  
Plasminogen Activator Inhibitor ◽  
Muscle Cells ◽  
Activin A ◽  
Plasminogen Activator Inhibitor 1 ◽  
And Control

Activin A, a member of the transforming growth factor (TGF)-β superfamily, is involved in regulation of tissue remodeling and inflammation. Herein, we wanted to explore a role for activin A in pulmonary hypertension (PH). Circulating levels of activin A and its binding protein follistatin were measured in patients with PH ( n = 47) and control subjects ( n = 14). To investigate synthesis and localization of pulmonary activin A, we utilized an experimental model of hypoxia-induced PH. In mouse lungs, we also explored signaling pathways that can be activated by activin A, such as phosphorylation of Smads, which are mediators of TGF-β signaling. Possible pathophysiological mechanisms initiated by activin A were explored by exposing pulmonary arterial smooth muscle cells in culture to this cytokine. Elevated levels of activin A and follistatin were found in patients with PH, and activin A levels were significantly related to mortality. Immunohistochemistry of lung autopsies from PH patients and lungs with experimental PH localized activin A primarily to alveolar macrophages and bronchial epithelial cells. Mice with PH exhibited increased pulmonary levels of mRNA for activin A and follistatin in the lungs, and also elevated pulmonary levels of phosphorylated Smad2. Finally, we found that activin A increased proliferation and induced gene expression of endothelin-1 and plasminogen activator inhibitor-1 in pulmonary artery smooth muscle cells, mediators that could contribute to vascular remodeling. Our findings in both clinical and experimental studies suggest a role for activin A in the development of various types of PH.

Effect of changes in myocardial epinephrine stores on plasma norepinephrine gradient across the dog heart

1994 ◽  
Vol 266 (6) ◽  
pp. H2404-H2409 ◽  
Author(s):  
F. Peronnet ◽  
G. Boudreau ◽  
J. de Champlain ◽  
R. Nadeau
Keyword(s):  
Electrical Stimulation ◽  
Adrenal Medulla ◽  
Pulse Width ◽  
Stellate Ganglion ◽  
Plasma Norepinephrine ◽  
Direct Support ◽  
Left Stellate Ganglion ◽  
Ici 118,551 ◽  
Beta 2 ◽  
Stimulation Of

Plasma norepinephrine (NE) concentration ([NE]) gradient across the heart was measured under electrical stimulation of the left stellate ganglion (LSG; 4 Hz, 4 V, 2 ms pulse width, 1 min) in control (Ctrl) and in adrenalectomized (Adrx) dogs, without and with a 10-min epinephrine (Epi) infusion (92 ng.kg-1.min-1), which partly restored myocardial Epi stores in Adrx dogs (2.9 +/- 0.7 ng/g vs. 6.4 +/- 0.7 ng/g in Ctrl dogs) and slightly increased tissue Epi stores in Ctrl dogs (10.5 +/- 1.3 pg/g). Compared with Ctrl dogs (1,069 +/- 172 pg/ml), the [NE] gradient across the heart under stimulation of the LSG was not modified 1 wk after bilateral adrenalectomy (1,190 +/- 122 pg/ml) or after Epi infusion in Ctrl (1,134 +/- 276 pg/ml) and Adrx (1,259 +/- 279 pg/ml) dogs. The beta 2-antagonist ICI-118,551 significantly reduced the stimulation-induced [NE] gradient across the heart in Ctrl dogs (621 +/- 190 and 603 +/- 86 pg/ml without and with a 10-min Epi infusion, respectively) but not in Adrx dogs deprived of tissue Epi (1,345 +/- 345 pg/ml). Partial repletion of myocardial Epi stores in Adrx dogs restored the effect of ICI-118,551 on the stimulation-induced [NE] gradient (776 +/- 121 pg/ml). These results provide direct support of the hypothesis that tissue Epi, which originates from the adrenal medulla and which is released locally along with NE, is the endogenous agonist for presynaptic beta 2-receptors and potentiates NE release.

Discussion on the Polarity Effect of EDM

2010 ◽  
Vol 154-155 ◽  
pp. 429-432 ◽  
Author(s):  
Wei Zhao
Keyword(s):  
Electric Discharge ◽  
Pulse Width ◽  
Single Pulse ◽  
Electric Discharge Machining ◽  
Polarity Effect ◽  
Large Pulse ◽  
Positive Ion

the problem of polarity effect in EDM is researched in this paper. In order to find out the deterioration of the anode and the cathode, the experiment with single pulse is taken in kerosene oil. We find the deterioration of the anode is larger than that of the cathode even in the condition of large pulse width. But this result is contradictory with that gotten in electric discharge machining with continue pulses. Through analyzing the movement of the electron and positive ion in plasma canal, we explain the phenomenon above rationally.

scholarly journals Probability-Based Prediction of Activity in Multiple Arm Muscles: Implications for Functional Electrical Stimulation

2008 ◽  
Vol 100 (1) ◽  
pp. 482-494 ◽  
Author(s):  
Chad V. Anderson ◽  
Andrew J. Fuglevand
Keyword(s):  
Electrical Stimulation ◽  
Functional Electrical Stimulation ◽  
Muscle Activity ◽  
Probability Distributions ◽  
Probabilistic Methods ◽  
Muscle Stimulation ◽  
Implanted Electrodes ◽  
Motor Behaviors ◽  
Wide Range ◽  
Arm Muscles

Functional electrical stimulation (FES) involves artificial activation of muscles with implanted electrodes to restore motor function in paralyzed individuals. The range of motor behaviors that can be generated by FES, however, is limited to a small set of preprogrammed movements such as hand grasp and release. A broader range of movements has not been implemented because of the substantial difficulty associated with identifying the patterns of muscle stimulation needed to elicit specified movements. To overcome this limitation in controlling FES systems, we used probabilistic methods to estimate the levels of muscle activity in the human arm during a wide range of free movements based on kinematic information of the upper limb. Conditional probability distributions were generated based on hand kinematics and associated surface electromyographic (EMG) signals from 12 arm muscles recorded during a training task involving random movements of the arm in one subject. These distributions were then used to predict in four other subjects the patterns of muscle activity associated with eight different movement tasks. On average, about 40% of the variance in the actual EMG signals could be accounted for in the predicted EMG signals. These results suggest that probabilistic methods ultimately might be used to predict the patterns of muscle stimulation needed to produce a wide array of desired movements in paralyzed individuals with FES.

Sign in / Sign up

Export Citation Format

Share Document