Impact of Lipid Peroxidation on the Response of Cell Membranes to High-Speed Equibiaxial Stretching: A Computational Study

2021 ◽  
Vol 125 (38) ◽  
pp. 10736-10747
Author(s):  
Lingzhi Gu ◽  
Tong Wei ◽  
Mi Zhou ◽  
Hong Yang ◽  
Yang Zhou
Keyword(s):  
Lipid Peroxidation ◽  
High Speed ◽  
Cell Membranes ◽  
Computational Study

scholarly journals Stimulation of 5-lipoxygenase activity under conditions which promote lipid peroxidation

1989 ◽  
Vol 263 (2) ◽  
pp. 565-572 ◽  
Author(s):  
D Riendeau ◽  
D Denis ◽  
L Y Choo ◽  
D J Nathaniel
Keyword(s):  
Lipid Peroxidation ◽  
High Speed ◽  
Chemical Reduction ◽  
Gel Filtration ◽  
Maximal Activity ◽  
Lipoxygenase Activity ◽  
Supernatant Fraction ◽  
Acid Oxidation ◽  
Thiol Compounds ◽  
Stimulation Of

The characteristics of hydroperoxide activation of 5-lipoxygenase were examined in the high speed supernatant fraction prepared from rat polymorphonuclear leukocytes. Stimulation of 5-lipoxygenase activity by the 5-hydroperoxyeicosatetraenoic acid (5-HPETE) reaction product was strongly dependent on the presence of thiol compounds. Various reducing agents such as mercaptoethanol and glutathione (0.5-2 mM) inhibited the reaction and increased the concentrations of 5-HPETE (1-10 microM) necessary to achieve maximal arachidonic acid oxidation. The requirement for 5-HPETE was not specific and could be replaced by H2O2 (10 microM) but not by the 5-hydroxyeicosatetraenoic acid (5-HETE) analogue. Furthermore, gel filtration chromatography of the soluble extract from leukocytes resolved different fractions which can increase the hydroperoxide dependence or fully replace the stimulation by 5-HPETE. Maximal activity of the 5-HPETE-stimulated reaction required Ca2+ ions (0.2-1 mM) and ATP with the elimination of the HPETE requirement at high ATP concentrations (2-4 mM). In addition, NADPH (1-2 mM), FAD (1 mM), Fe2+ ions (20-100 microM) and chelated Fe3+ (0.1 mM-EDTA/0.1 mM-FeCl3) all markedly increased product formation by 5-lipoxygenase whereas NADH (1 mM) was inhibitory and Fe3+ (20-100 microM) alone had no effect on the reaction. The stimulation by Fe2+ ions and NADPH was also observed under various conditions which increase the hydroperoxide dependence such as pretreatment of the enzyme preparation with glutathione peroxidase or chemical reduction with 0.015% NaBH4. These results provide evidence for an hydroperoxide activation of 5-lipoxygenase which is not product-specific and is modulated by thiol levels and several soluble components of the leukocytes. They also indicate that stimulation of 5-lipoxygenase activity can contribute to increase lipid peroxidation in iron and nucleotide-promoted reactions.

scholarly journals THE MECHANISM OF THE NEPHRIDIAL APPARATUS OF PARAMECIUM MUL TIMICRONUCLEATUM

1968 ◽  
Vol 37 (1) ◽  
pp. 139-146 ◽  
Author(s):  
Alan E. Organ ◽  
Eugene C. Bovee ◽  
Theodore L. Jahn ◽  
Duncan Wigg ◽  
James R. Fonseca
Keyword(s):  
Electron Microscopy ◽  
Excretory Pore ◽  
High Speed ◽  
Cell Membranes ◽  
Recent Analysis ◽  
Opposite Wall ◽  
Active Contraction ◽  
High Speed Cinematography ◽  
Excretory Canal

Recent analysis of the mechanism of the nephridial apparatus of Paramecium multimicronucleatum by high-speed cinematography (300 fps at x 250) confirms the observations by electron microscopy (Schneider, 1960) that once the pore is opened, the vesicle is invaginated by adjacent cytoplasm and is emptied by collapsing under pressure from that cytoplasm, aided perhaps by pressure of the fibrils which anchor the ampullae to the excretory canal. There is no indication of active contraction of the vesicle or its membrane. There is no permanent pore to the vesicle. The vesicle is closed by a sealing of the ruptured membrane where it is in contact with the pellicular excretory canal. At onset of expulsion of vesicular fluid the membrane across the basal opening of the excretory canal is ripped along one semicircular portion of the excretory pore and is driven up against the opposite wall as a flap while the water rushes out. A constriction of the vesicular and cell membranes at the base of the excretory canal reseals the opening.

scholarly journals Experimental and Computational Study of Trapped Vortex Combustor Sector Rig with High-Speed Diffuser Flow

2001 ◽  
Vol 7 (6) ◽  
pp. 375-385 ◽  
Author(s):  
R. C. Hendricks ◽  
D. T. Shouse ◽  
W. M. Roquemore ◽  
D. L. Burrus ◽  
B. S. Duncan ◽  
...  
Keyword(s):  
Gas Turbine ◽  
High Speed ◽  
Fuel Injection ◽  
Computational Study ◽  
Combustion Efficiency ◽  
Flame Stabilization ◽  
Performance Data ◽  
Pollutant Emissions ◽  
Choked Flow ◽  
Trapped Vortex

The Trapped Vortex Combustor (TVC) potentially offers numerous operational advantages over current production gas turbine engine combustors. These include lower weight, lower pollutant emissions, effective flame stabilization, high combustion efficiency, excellent high altitude relight capability, and operation in the lean burn or RQL modes of combustion. The present work describes the operational principles of the TVC, and extends diffuser velocities toward choked flow and provides system performance data. Performance data include EINOx results for various fuel-air ratios and combustor residence times, combustion efficiency as a function of combustor residence time, and combustor lean blow-out (LBO) performance. Computational fluid dynamics (CFD) simulations using liquid spray droplet evaporation and combustion modeling are performed and related to flow structures observed in photographs of the combustor. The CFD results are used to understand the aerodynamics and combustion features under different fueling conditions. Performance data acquired to date are favorable compared to conventional gas turbine combustors. Further testing over a wider range of fuel-air ratios, fuel flow splits, and pressure ratios is in progress to explore the TVC performance. In addition, alternate configurations for the upstream pressure feed, including bi-pass diffusion schemes, as well as variations on the fuel injection patterns, are currently in test and evaluation phases.

An Experimental and Analytical Study of the Dynamic Response of a Linkage Fabricated from a Unidirectional Fiber-Reinforced Composite Laminate

1983 ◽  
Vol 105 (3) ◽  
pp. 526-533 ◽  
Author(s):  
B. S. Thompson ◽  
D. Zuccaro ◽  
D. Gamache ◽  
M. V. Gandhi
Keyword(s):  
High Speed ◽  
Computational Study ◽  
Continuum Theory ◽  
Elastic Solid ◽  
Fiber Reinforced ◽  
Element Analysis ◽  
High Productivity ◽  
Orthotropic Properties ◽  
Fiber Reinforced Material ◽  
Four Bar Linkage

A large class of industrial machinery and commercial equipment is operated at high speed to satisfy the demands for high productivity. In order to further improve performance, it is proposed herein that the designer should consider fabricating the mechanism components in one of the commercially available composite materials because they offer many desirable characteristics with the promise of even higher speeds of operation. This paper presents an experimental and computational study of a flexible planar four-bar linkage fabricated from one of these composites. This fiber-reinforced material is modeled as an elastic solid by using a continuum theory which accommodates laminae with orthotropic properties, and differing densities, thicknesses, and elastic moduli. The theory is embodied in a variational theorem which serves as the basis for a finite element analysis of the mechanism.

Lability of red blood cell membranes to lipid peroxidation: Application to humans fed polyunsaturated lipids

Lipids ◽  
1990 ◽  
Vol 25 (2) ◽  
pp. 111-114 ◽  
Author(s):  
Cesar G. Fraga ◽  
A. L. Tappel ◽  
Brian E. Leibovitz ◽  
Franz Kuypers ◽  
Daniel Chiu ◽  
...  
Keyword(s):  
Lipid Peroxidation ◽  
Blood Cell ◽  
Red Blood Cell ◽  
Cell Membranes ◽  
Red Blood Cell Membranes ◽  
Polyunsaturated Lipids
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