Impedance, gas mixing, and bimodal ventilation in constricted lungs

2003 ◽  
Vol 94 (3) ◽  
pp. 1003-1011 ◽  
Author(s):  
Ron C. Anafi ◽  
Kenneth C. Beck ◽  
Theodore A. Wilson
Keyword(s):  
Smooth Muscle ◽  
Muscle Activation ◽  
High Resistance State ◽  
Phase Iii ◽  
Extended Model ◽  
Stable States ◽  
Control Value ◽  
Model Predictions ◽  
Resistance State ◽  
Expired Gas

To evaluate the effect of increasing smooth muscle activation on the distribution of ventilation, lung impedance and expired gas concentrations were measured during a 16-breath He-washin maneuver in five nonasthmatic subjects at baseline and after each of three doses of aerosolized methacholine. Values of dynamic lung elastance (El,dyn), the curvature of washin plots, and the normalized slope of phase III ( S N) were obtained. At the highest dose, El,dyn was 2.6 times the control value and S N for the 16th breath was 0.65 liter−1. A previously described model of a constricted terminal airway was extended to include variable muscle activation, and the extended model was tested against these data. The model predicts that the constricted airway has two stable states. The impedances of the two stable states are independent of smooth muscle activation, but driving pressure and the number of airways in the high-resistance state increase with increasing muscle activation. Model predictions and experimental data agree well. We conclude that, as a result of the bistability of the terminal airways, the ventilation distribution in the constricted lung is bimodal.

Increased myofibrillar protein phosphatase-1 activity impairs rat aortic smooth muscle activation after hypoxia

2003 ◽  
Vol 284 (4) ◽  
pp. H1182-H1189 ◽  
Author(s):  
Hwee Teoh ◽  
Mary Zacour ◽  
Avraham D. Wener ◽  
Lakshman Gunaratnam ◽  
Michael E. Ward
Keyword(s):  
Smooth Muscle ◽  
Light Chain ◽  
Protein Phosphatase ◽  
Myosin Light Chain ◽  
Muscle Activation ◽  
Smooth Muscle Contraction ◽  
Control Group ◽  
Aortic Smooth Muscle ◽  
Control Value ◽  
Normoxic Control

We hypothesized that increased myofibrillar type 1 protein phosphatase (PP1) catalytic activity contributes to impaired aortic smooth muscle contraction after hypoxia. Our results show that inhibition of PP1 activity with microcystin-LR (50 nmol/l) or okadaic acid (100 nmol/l) increased phenylephrine- and KCl-induced contraction to a greater extent in aortic rings from rats exposed to hypoxia (10% O2) for 48 h than in rings from normoxic animals. PP1 inhibition also restored the level of phosphorylation of the 20-kDa myosin light chain (LC20) during maximal phenylephrine-induced contraction to that observed in the normoxic control group. Myofibrillar PP1 activity was greater in aortas from rats exposed to hypoxia than in normoxic rats ( P < 0.05). Levels of the protein myosin phosphatase-targeting subunit 1 (MYPT1) that mediates myofibrillar localization of PP1 activity were increased in aortas from hypoxic rats (193 ± 28% of the normoxic control value, P < 0.05) and in human aortic smooth muscle cells after hypoxic (1% O2) incubation (182 ± 18% of the normoxic control value, P < 0.05). Aortic levels of myosin light chain kinase were similar in normoxic and hypoxic groups. In conclusion, after hypoxia, increased MYPT1 protein and myofibrillar PP1 activity impair aortic vasoreactivity through enhanced dephosphorylation of LC20.

Functional Gradient Transparent Conducting Oxide Nanowire Arrays as Monophasic Schottky-Barrier Free Memristors for Bipolar Linear Switching

2020 ◽  
Author(s):  
Thomas Herzog ◽  
Naomi Weitzel ◽  
Sebastian Polarz
Keyword(s):  
Schottky Barrier ◽  
Data Storage ◽  
Tin Oxide ◽  
Transparent Conducting Oxide ◽  
Electrical Potential ◽  
High Resistance State ◽  
Nanowire Arrays ◽  
Metal Metal ◽  
Resistance State ◽  
Barrier Free

<div><div><div><p>One of the fascinating properties of metal-semiconductor Schottky-barriers, which has been observed for some material combinations, is memristive behavior. Memristors are smart, since they can reversibly switch between a low resistance state and a high resistance state. The devices offer a great potential for advanced computing and data storage, including neuromorphic networks and resistive random-access memory. However, as for many other cases, the presence of a real interface (metal - metal oxide) has numerous disadvantages. The realization of interface-free, respectively Schottky-barrier free memristors is highly desirable. The aim of the current paper is the generation of nanowire arrays with each nanorod possessing the same crystal phase (Rutile) and segments only differing in composition. The electric conductivity is realized by segments made of highly-doped antimony tin oxide (ATO) transitioning into pure tin oxide (TO). Complex nanoarchitectures are presented, which include ATO-TO, ATO-TO-ATO nanowires either with a stepwise distribution of antimony or as a graded functional material. The electrical characterization of the materials reveals that the introduction of memristive properties in such structures is possible. The special features observed in voltage-current (IV) curves are correlated to the behavior of mobile oxygen vacancies (VO..) at different values of applied electrical potential.</p></div></div></div>

scholarly journals Gradually Modified Conductance in the Self-Compliance Region of an Atomic-Layer-Deposited Pt/TiO2/HfAlOx/TiN RRAM Device

Metals ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 1199
Author(s):  
Hojeong Ryu ◽  
Sungjun Kim
Keyword(s):  
Photoelectron Spectroscopy ◽  
Depth Profiling ◽  
Atomic Layer ◽  
High Resistance State ◽  
Long Term Potentiation ◽  
Memory Device ◽  
Bipolar Resistive Switching ◽  
Term Potentiation ◽  
Resistance State ◽  
Neuromorphic System

This study presents conductance modulation in a Pt/TiO2/HfAlOx/TiN resistive memory device in the compliance region for neuromorphic system applications. First, the chemical and material characteristics of the atomic-layer-deposited films were verified by X-ray photoelectron spectroscopy depth profiling. The low-resistance state was effectively controlled by the compliance current, and the high-resistance state was adjusted by the reset stop voltage. Stable endurance and retention in bipolar resistive switching were achieved. When a compliance current of 1 mA was imposed, only gradual switching was observed in the reset process. Self-compliance was used after an abrupt set transition to achieve a gradual set process. Finally, 10 cycles of long-term potentiation and depression were obtained in the compliance current region for neuromorphic system applications.

Analysis on Resistance Change Mechanism of NiO-ReRAM Using Visualization Technique of Data Storage Area With Secondary Electron Image

2010 ◽  
Vol 1250 ◽  
Author(s):  
Kentaro Kinoshita ◽  
Tatsuya Makino ◽  
Yoda Takatoshi ◽  
Dobashi Kazufumi ◽  
Kishida Satoru
Keyword(s):  
Data Storage ◽  
Secondary Electron ◽  
High Resistance State ◽  
Secondary Electron Image ◽  
Resistance Change ◽  
Force Microscopy ◽  
Electron Image ◽  
Storage Area ◽  
Resistance State ◽  
Pt Films

AbstractBoth a low resistance state and a high resistance state which were written by the voltage application in a local region of NiO/Pt films by using conducting atomic force microscopy (C-AFM) were observed by using scanning electron microscope (SEM) and electron probe micro analysis (EPMA). The writing regions are distinguishable as dark areas in a secondary electron image and thus can be specified without using complicated sample fabrication process to narrow down the writing regions such as the photolithography technique. In addition, the writing regions were analyzed by using energy dispersive X-ray spectroscopy (EDS) mapping. No difference between the inside and outside of the writing regions is observed for all the mapped elements including C and Rh. Here, C and Rh are the most probable candidates for contamination which affect the secondary electron image. Therefore, our results suggested that the observed change in the contrast of the second electron image is related to the intrinsic change in the electronic state of the NiO film and a secondary electron yield is correlated to the physical properties of the film.

Resistive Switching Characteristics in TiO2 ReRAM with Top Electrode of Co Selectively Formed on SAMs Printed Patterns

2007 ◽  
Vol 124-126 ◽  
pp. 603-606
Author(s):  
Sang Hee Won ◽  
Seung Hee Go ◽  
Jae Gab Lee
Keyword(s):  
Resistive Switching ◽  
Random Access ◽  
Atomic Layer ◽  
High Resistance State ◽  
Resistive Random Access Memory ◽  
Tio2 Thin Films ◽  
Selective Deposition ◽  
Precise Control ◽  
Resistance State ◽  
Switching Characteristics

Simple process for the fabrication of Co/TiO2/Pt resistive random access memory, called ReRAM, has been developed by selective deposition of Co on micro-contact printed (μ-CP) self assembled monolayers (SAMs) patterns. Atomic Layer Deposition (ALD) was used to deposit TiO2 thin films, showing its ability of precise control over the thickness of TiO2, which is crucial to obtain proper resistive switching properties of TiO2 ReRAM. The fabrication process for Co/TiO2/Pt ReRAM involves the ALD of TiO2 on sputter-deposited Pt bottom electrode, followed by μ-CP with SAMs and then selective deposition of Co. This results in the Co/TiO2/Pt structure ReRAM. For comparison, Pt/TiO2/Pt ReRAM was produced and revealing the similar switching characteristics as that of Co/TiO2/Pt, thus indicating the feasibility of Co replacement with Pt top electrode. The ratios between the high-resistance state (Off state) and the low-resistance state (On state) were larger than 102. Consequently, the selective deposition of Co with μ-CP, newly developed in this study, can simplify the process and thus implemented into the fabrication of ReRAM.

Role of Cl− currents in rat aortic smooth muscle activation by prostaglandin F2α

2003 ◽  
Vol 481 (2-3) ◽  
pp. 133-140 ◽  
Author(s):  
Jihua Jiang ◽  
Peter H Backx ◽  
Hwee Teoh ◽  
Michael E Ward
Keyword(s):  
Smooth Muscle ◽  
Muscle Activation ◽  
Prostaglandin F2α ◽  
Aortic Smooth Muscle

Isotonic relaxation of control and sensitized airway smooth muscle

2005 ◽  
Vol 83 (10) ◽  
pp. 941-951 ◽  
Author(s):  
N L Stephens ◽  
A Fust ◽  
H Jiang ◽  
W Li ◽  
X Ma
Keyword(s):  
Smooth Muscle ◽  
Intracellular Calcium ◽  
Airway Smooth Muscle ◽  
Light Chain ◽  
Myosin Light Chain ◽  
Phase Iii ◽  
Contractile Element ◽  
Second Phase ◽  
Half Time ◽  
Phase Phase

Smooth muscle relaxation has most often been studied in isometric mode. However, this only tells us about the stiffness properties of the bronchial wall and thus only about wall capacitative properties. It tells us little about airflow. To study the latter, which of course is the meaningful parameter in regulation of ventilation and in asthma, we studied isotonic shortening of bronchial smooth muscle (BSM) strips. Failure of BSM to relax could be another important factor in maintaining high airway resistance. To analyze relaxation curves, we developed an index of isotonic relaxation, t1/2(P, lCE), which is the half-time for relaxation that is independent of muscle load (P) and of initial contractile element length (lCE). This index was measured in curves of relaxation initiated at 2 s (normally cycling crossbridges) and at 10 s (latch-bridges). At 10 s no difference was seen for adjusted t1/2(P, lCE) between curves obtained from control and sensitized BSM, (8.38 ± 0.92 s vs. 7.78 ± 0.93 s, respectively). At 2 s the half-time was almost doubled in the sensitized BSM (6.98 ± 0.01 s (control) vs. 12.74 ± 2.5 s (sensitized)). Thus, changes in isotonic relaxation are only seen during early contraction. Using zero load clamps, we monitored the time course of velocity during relaxation and noted that it varied according to 3 phases. The first phase (phase i) immediately followed cessation of electrical field stimulation (EFS) at 10 s and showed almost the same velocity as during the latter 1/3 of shortening; the second phase (phase ii) was linear in shape and is associated with zero load velocity, we speculate it could stem from elastic recoil of the cells' internal resistor; and the third phase (phase iii) was convex downwards. The zero load velocities in phase iii showed a surprising spontaneous increase suggesting reactivation of the muscle. Measurements of intracellular calcium (Fura-2 study) and of phosphorylation of the 20 kDa myosin light chain showed simultaneous increments, indicating phase iii represented an active process. Studies are under way to determine what changes occur in these 3 phases in a sensitized muscle. And of course, in the context of this conference, just what role the plastic properties of the muscle play in relaxation requires serious consideration.Key words: airway smooth muscle, sensitized smooth muscle, isotonic relaxation, intracellular calcium transients, myosin light chain (20 kDa) phosphorylation.

scholarly journals Effect of pharmacologically induced smooth muscle activation on permeability in murine colitis

2003 ◽  
Vol 12 (1) ◽  
pp. 21-27 ◽  
Author(s):  
Freek J. Zijlstra ◽  
Marieke E. van Meeteren ◽  
Ingrid M. Garrelds ◽  
Maarten A.C. Meijssen
Keyword(s):  
Smooth Muscle ◽  
Intestinal Permeability ◽  
Muscle Activation ◽  
Tap Water ◽  
Water Solution ◽  
Smooth Muscles ◽  
Distal Colon ◽  
Mucosal Inflammation ◽  
Smooth Muscle Relaxation ◽  
Organ Bath

Background:Both intestinal permeability and contractility are altered in inflammatory bowel disease. Little is known about their mutual relation. Therefore, anin vitroorgan bath technique was developed to investigate the simultaneous effects of inflammation on permeability and smooth muscle contractility in different segments of the colon.Methods and materials:BALB/c mice were exposed to a 10% dextran sulphate sodium drinking water solution for 7 days to induce a mild colitis, while control mice received normal tap water. Intestinal segments were placed in an oxygenated organ bath containing Krebs buffer. Permeability was measured by the transport of the marker molecules3H-mannitol and14C-polyethyleneglycol 4000. Contractility was measured through a pressure sensor. Smooth muscle relaxation was obtained by salbutamol and l-phenylephrine, whereas contraction was achieved by carbachol and 1-(3-chlorophenyl)-biguanide.Results:The intensity of mucosal inflammation increased throughout the colon. Also, regional differences were observed in intestinal permeability. In both normal and inflamed distal colon segments, permeability was diminished compared with proximal colon segments and the non-inflamed ileum. Permeability in inflamed distal colon segments was significantly decreased compared with normal distal segments. Pharmacologically induced relaxation of smooth muscles did not affect this diminished permeability, although an increased motility positively affected permeability in inflamed and non-inflamed distal colon.Conclusions:Inflammation and permeability is inversely related. The use of pro-kinetics could counteract this disturbed permeability and, in turn, could regulate the disturbed production of inflammatory mediators.

U46619, a thromboxane A2 agonist, inhibits KCa channel activity from pig coronary artery

1992 ◽  
Vol 262 (3) ◽  
pp. C708-C713 ◽  
Author(s):  
F. S. Scornik ◽  
L. Toro
Keyword(s):  
Smooth Muscle ◽  
Coronary Artery ◽  
Lipid Bilayers ◽  
Thromboxane A2 ◽  
Inhibitory Effect ◽  
Channel Activity ◽  
Open Probability ◽  
Control Value ◽  
Kca Channels ◽  
Internal Side

Thromboxane A2 (TxA2) is a potent vasoconstrictor derived from the metabolism of arachidonic acid. Because potassium channels are involved in the contraction of vascular smooth muscle, their blockade could contribute to the TxA2-induced contraction. To test this possibility, we studied the effect of the TxA2 stable analogue U46619 on calcium-activated potassium (KCa) channels from coronary artery reconstituted into lipid bilayers. Addition of U46619 (50-150 nM) to the external but not to the internal side of the channel decreased the channel open probability (Po) between 15 and 80% of the control value. The inhibitory effect of U46619 affected both the open and closed states of the channel and could be reversed by internal calcium. Thromboxane B2, the inactive hydrolysis derivative of TxA2, did not affect channel activity. SQ 29548, a TxA2 receptor antagonist, was able to prevent the inhibition by U46619. Furthermore, SQ 29548 added after U46619 could restore channel activity to near control values. These results suggest that TxA2 could be a regulatory factor of KCa channels from coronary smooth muscle and that this regulation could be related to its action as a vasoconstrictor.

Interleukin-1 beta alters actin expression and inhibits contraction of rat thoracic aorta

1992 ◽  
Vol 262 (4) ◽  
pp. C828-C833 ◽  
Author(s):  
L. A. Trinkle ◽  
D. Beasley ◽  
R. S. Moreland
Keyword(s):  
Smooth Muscle ◽  
Vascular Smooth Muscle ◽  
Protein Content ◽  
Muscle Activation ◽  
Smooth Muscle Actin ◽  
Interleukin 1 ◽  
Contractile Protein ◽  
Interleukin 1 Beta ◽  
Alpha Smooth Muscle Actin ◽  
Mlc Phosphorylation

Previous studies have indicated that interleukin-1 beta (IL-1) inhibits contraction of rat aortas by activating nitric oxide production in vascular smooth muscle cells, with subsequent increases in guanosine 3',5'-cyclic monophosphate (cGMP). This study determined if the effect of IL-1 involves the primary regulatory event in smooth muscle activation, myosin light chain (MLC) phosphorylation. This study also examined whether IL-1 affects contractile protein content. IL-1 (20 ng/ml) significantly decreased stress in response to 0.1 microM phenylephrine with a concomitant decrease in MLC phosphorylation. Incubation with IL-1 for 3 h or longer decreased alpha-smooth muscle actin and increased gamma-actin isoform, with no change in beta-nonmuscle actin or myosin isozyme content. These results suggest that IL-1 inhibition of a vascular smooth muscle contraction may be due to a decrease in activator calcium, which may account for the resultant decrease in MLC phosphorylation. These results also indicate that IL-1 significantly affects contractile protein content, enhancing gamma-actin isoforms and decreasing the vascular smooth muscle specific alpha-isoactin.

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