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Biochemistry, Biophysics, and Structural Biology Commons™
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Full-Text Articles in Biochemistry, Biophysics, and Structural Biology
Effects Of Sham Air And Cigarette Smoke On A549 Lung Cells: Implications For Iron-Mediated Oxidative Damage, Jonathan J. Mayo, Pete Kohlhepp, Dianzheng Zhang, Joy J. Winzerling
Effects Of Sham Air And Cigarette Smoke On A549 Lung Cells: Implications For Iron-Mediated Oxidative Damage, Jonathan J. Mayo, Pete Kohlhepp, Dianzheng Zhang, Joy J. Winzerling
PCOM Scholarly Papers
Inhalation of airborne pollution particles that contain iron can result in a variety of detrimental changes to lung cells and tissues. The lung iron burden can be substantially increased by exposure to cigarette smoke, and cigarette smoke contains iron particulates, as well as several environmental toxins, that could influence intracellular iron status. We are interested in the effects of environmental contaminants on intracellular iron metabolism. We initiated our studies using lung A549 type II epithelial cells as a model, and we evaluated the effects of iron dose and smoke treatment on several parameters of intracellular iron metabolism. We show that …
Activation Kinetics Of Skinned Cardiac Muscle By Laser Photolysis Of Nitrophenyl-Egta, Hunter Martin, Marcus G. Bell, Graham C. Ellis-Davis, Robert J. Barsotti
Activation Kinetics Of Skinned Cardiac Muscle By Laser Photolysis Of Nitrophenyl-Egta, Hunter Martin, Marcus G. Bell, Graham C. Ellis-Davis, Robert J. Barsotti
PCOM Scholarly Papers
The kinetics of Ca2+-induced contractions of chemically skinned guinea pig trabeculae was studied using laser photolysis of NP-EGTA. The amount of free Ca2+ released was altered by varying the output from a frequency-doubled ruby laser focused on the trabeculae, while maintaining constant total [NP-EGTA] and [Ca2+]. The time courses of the rise in stiffness and tension were biexponential at 23°C, Ph 7.1, and 200 Mm ionic strength. At full activation (pCa < 5.0), the rates of the rapid phase of the stiffness and tension rise were 56 ± 7 s-1 (n = 7) and 48 ± 6 s-1 (n = 11) while the amplitudes were 21 ± 2 and 23 ± 3%, respectively. These rates had similar dependencies on final [Ca2+] achieved by photolysis: 43 and 50 s-1 per Pca unit, respectively, over a range of [Ca2+] producing from 15% to 90% of maximal isometric tension. At all [Ca2+], the rise in stiffness initially was faster than that of tension. The maximal rates for the slower components of the rise in stiffness and tension were 4.1 ± 0.8 and 6.2 ± 1.0 s-1. The rate of this slower phase exhibited significantly less Ca2+ sensitivity, 1 and 4 s-1 per Pca unit for stiffness and tension, respectively. These data, along with previous studies indicating that the force-generating step in the cross-bridge cycle of cardiac muscle is marginally sensitive to [Ca2+], suggest a mechanism of regulation in which Ca2+ controls the attachment step in the cross-bridge cycle via a rapid equilibrium with the thin filament activation state. Myosin kinetics sets the time course for the rise in stiffness and force generation with the biexponential nature of the mechanical responses to steps in [Ca2+] arising from a shift to slower cross-bridge kinetics as the number of strongly bound cross-bridges increases.