scholarly journals Modification of Synaptic Plasma Membrane Ca 2+ -ATPase in Ischemic Injury in an Animal Model of Global Ischemia

Stroke ◽  
2001 ◽  
Vol 32 (suppl_1) ◽  
pp. 354-354
Author(s):  
Asma Zaidi ◽  
Angela M Cross ◽  
Jennifer L Bean ◽  
Mary L Michaelis
Keyword(s):  
Molecular Weight ◽  
Animal Model ◽  
Plasma Membrane ◽  
High Molecular Weight ◽  
Critical Role ◽  
Ischemic Injury ◽  
Global Ischemia ◽  
Synaptic Membranes ◽  
Synaptic Plasma Membrane ◽  
Reducing Conditions

P83 Regulation of [Ca 2+ ] i is altered in neurons during ischemic injury in stroke, but the precise mechanism(s) underlying the Ca 2+ dysregulation are not known. The plasma membrane Ca 2+ -ATPase (PMCA) is one of the two main Ca 2+ extrusion systems that play a critical role in maintaining neuronal Ca 2+ homeostasis. We have substantial evidence showing that this enzyme is very sensitive to oxidative stress. When exposed to very low concentrations of physiologically relevant oxidants, the PMCA has been shown to form high molecular weight aggregates and this is accompanied by the decline in its enzymatic activity. Because stroke-induced hypoxia is associated with the overproduction of reactive oxygen species (ROS) and a loss of Ca 2+ homeostasis, we carried out studies to determine if the PMCA is modified in an in vivo animal model of stroke. Global ischemia was induced in Sprague Dawley rats by occlusion of the common carotid arteries for defined time periods. The V max of PMCA activity in brain homogenates as well as in purified synaptic plasma membranes was significantly reduced following occlusion of the vessels, and the reduction was proportional to the time of ischemia. The loss in PMCA activity could not be reversed by addition of exogenous ATP, suggesting an alteration in the protein itself. Immunoblots of the synaptic membranes run under non-reducing conditions showed crosslinking of PMCA molecules to form high molecular weight adducts, and this too increased with increasing periods of ischemia. The PMCA aggregates were partially reversed under reducing conditions, indicating the involvement of sulphydryl group oxidation. These observations support the hypothesis that increased formation of ROS under ischemic conditions can oxidatively modify specific proteins critical for the regulation of free [Ca 2+ ] i levels. Such oxidative damage is likely to contribute to the loss of neuronal Ca 2+ regulation and neuronal viability in stroke. (Supported by AHA 9960343Z, AG 12993, and the Higuchi Biosciences Center, University of Kansas)

Derivation of the material models for ultra-high molecular-weight polyethylene fiber-reinforced armor-grade composites with different architectures

2016 ◽  
Vol 33 (3) ◽  
Author(s):  
Mica Grujicic ◽  
Jennifer Snipes ◽  
S. Ramaswami ◽  
Vasudeva Avuthu ◽  
Chian-Fong Yen ◽  
...  
Keyword(s):  
Molecular Weight ◽  
High Molecular Weight ◽  
Design Methodology ◽  
Critical Role ◽  
Fiber Reinforcement ◽  
Mechanical Tests ◽  
Transverse Impact ◽  
Material Models ◽  
Polyethylene Fiber ◽  
Ultra High Molecular Weight

Purpose To overcome the problem of inferior through-the-thickness mechanical properties displayed by armor-grade composites based on 2-D reinforcement architectures, armor-grade composites based on 3D fiber-reinforcement architectures have recently been investigated experimentally. Design/methodology/approach The subject of the present work is armor-grade composite materials reinforced using ultra-high-molecular-weight polyethylene fibers and having four (two 2D and two 3D) prototypical architectures, as well as the derivation of the corresponding material models. The effect of the reinforcement architecture is accounted for by constructing the appropriate unit cells (within which the constituent materials and their morphologies are represented explicitly) and subjecting them to a series of virtual mechanical tests. The results obtained are used within a post-processing analysis to derive and parameterize the corresponding homogenized-material models. One of these models (specifically, the one for 0°/90° cross-collimated fiber architecture) was directly validated by comparing its predictions with the experimental counterparts. The other models are validated by examining their physical soundness and details of their predictions. Lastly, the models are integrated as user-material subroutines, and linked with a commercial finite-element package, in order to carry out a transient non-linear dynamics analysis of ballistic transverse impact of armor-grade composite-material panels with different reinforcement architectures. Findings It is found that the reinforcement architecture plays a critical role in the overall ballistic limit of the armor panel, as well as in its structural and damage/failure response. Originality/value To the authors’ knowledge, the present work is the first reported attempt to assess, computationally, the utility and effectiveness of 3D fiber-reinforcement architectures for ballistic impact applications.

scholarly journals PROTEINS OF THE POSTSYNAPTIC DENSITY

1974 ◽  
Vol 63 (2) ◽  
pp. 456-465 ◽  
Author(s):  
G. Banker ◽  
L. Churchill ◽  
C. W. Cotman
Keyword(s):  
Molecular Weight ◽  
Plasma Membrane ◽  
Polyacrylamide Gel Electrophoresis ◽  
Sodium Dodecyl ◽  
Protein Composition ◽  
Synaptic Plasma Membrane ◽  
Brain Protein ◽  
Single Polypeptide ◽  
Structural Matrix ◽  
Polypeptide Band

An analysis was made of the protein composition of a fraction of postsynaptic densities (PSDs) prepared from rat brain. Protein makes up 90% of the material in the PSD fraction. Two major polypeptide fractions are present, based on sodium dodecyl sulfate polyacrylamide gel electrophoresis. The major polypeptide fraction has a molecular weight of 53,000, makes up about 45% of the PSD protein, and comigrates on gels with a major polypeptide of the synaptic plasma membrane. The other polypeptide band has a molecular weight of 97,000, accounts for 17% of the PSD protein, and is not a prominent constituent of other fractions. Six other polypeptides of higher molecular weight (100,000–180,000) are consistently present in small amounts (3–9% each). The PSD fraction contains slightly greater amounts of polar amino acids and proline than the synaptic plasma membrane fraction, but no amino acid is usually prominent. The PSD apparently consists of a structural matrix formed primarily by a single polypeptide or class of polypeptides of 53,000 molecular weight. Small amounts of other specialized proteins are contained within this matrix.

High-Molecular-Weight, High-Unsaturation Copolymers of Isobutylene and Conjugated Dienes. I. Synthesis

1976 ◽  
Vol 49 (4) ◽  
pp. 960-966 ◽  
Author(s):  
W. A. Thaler ◽  
D. J. Buckley
Keyword(s):  
Molecular Weight ◽  
High Molecular Weight ◽  
Cationic Polymerization ◽  
Critical Role ◽  
Conjugated Dienes ◽  
Solution Properties ◽  
Insight Into

Abstract This investigation has provided insight into the critical role of solution properties on the course of cationic polymerization and has led to a technique for reconciling the opposing demands for synthesis of isoolefin-diene copolymers both free from gel and high in molecular weight. By this technique, the synthesis of a broad range of intermediate-unsaturation elastomers of quality has been realized.

scholarly journals Single particle characterization of biomass burning organic aerosol (BBOA): evidence for non-uniform mixing of high molecular weight organics and potassium

2015 ◽  
Vol 15 (22) ◽  
pp. 32157-32183 ◽  
Author(s):  
A. K. Y. Lee ◽  
M. D. Willis ◽  
R. M. Healy ◽  
J. M. Wang ◽  
C.-H. Jeong ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Black Carbon ◽  
High Molecular Weight ◽  
Biomass Burning ◽  
Single Particle ◽  
Critical Role ◽  
Organic Aerosol ◽  
Mixing State ◽  
Particle Measurements ◽  
Near Ultraviolet

Abstract. Biomass burning is a major source of black carbon (BC) and primary organic aerosol globally. In particular, biomass burning organic aerosol (BBOA) is strongly associated with atmospheric brown carbon (BrC) that absorbs near ultraviolet and visible light, resulting in significant impacts on regional visibility degradation and radiative forcing. The mixing state of BBOA can play a critical role in the prediction of aerosol optical properties. In this work, single particle measurements from a soot-particle aerosol mass spectrometer coupled with a light scattering module (LS-SP-AMS) were performed to examine the mixing state of BBOA, refractory black carbon (rBC) and potassium (K+, a tracer for biomass burning aerosol) in an air mass influenced by aged biomass burning. Cluster analysis of single particle measurements identified five BBOA-related particle types. rBC accounted for 3–14 w.t. % of these particle types on average. Only one particle type exhibited a strong ion signal for K+, with mass spectra characterized by low molecular weight organic species. The remaining four particle types were classified based on the apparent molecular weight of the BBOA constituents. Two particle types were associated with low potassium content and significant amounts of high molecular weight (HMW) organic compounds. Our observations indicate non-uniform mixing of particles within a biomass burning plume in terms of molecular weight and illustrate that HMW BBOA can be a key contributor to low-volatility BrC observed in BBOA particles.

scholarly journals High molecular weight amyloid β 1‐42 oligomers induce neurotoxicity via plasma membrane damage

2019 ◽  
Vol 33 (8) ◽  
pp. 9220-9234 ◽  
Author(s):  
Taro Yasumoto ◽  
Yusaku Takamura ◽  
Mayumi Tsuji ◽  
Takahiro Watanabe‐Nakayama ◽  
Keiko Imamura ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Plasma Membrane ◽  
High Molecular Weight ◽  
Membrane Damage ◽  
Amyloid Β ◽  
Plasma Membrane Damage
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