Oxygen influx

The migration of gas becomes an important consideration in certain geoenvironmental engineering applications when the gas content in a porous medium is sufficiently high such that the gas phase is continuous. Examples of such apphcations include the removal of VOCs and SVOCs from the imsaturated or vadose zone above the water table in the subsurface via the gas phase and the minimization of oxygen influx or radon efflux from engineered covers for tailings disposal applications. In the former case, removal efficiency is improved as gas permeability increases, whereas in the latter case, the objective is to minimize the gas permeability and therefore minimize the gas flow. 

Decreased cerebral blood flow, resulting from acute arterial occlusion, reduces oxygen and glucose delivery to brain tissue with subsequent lactic acid production, blood-brain barrier breakdown, inflammation, sodium and calcium pump dysfunction, glutamate release, intracellular calcium influx, free-radical generation, and finally membrane and nucleic acid breakdown and cell death. The degree of cerebral blood flow reduction following arterial occlusion is not uniform. Tissue at the... 

As a rule, oxygen radical overproduction in mitochondria is accompanied by peroxidation of mitochondrial lipids, glutathione depletion, and an increase in other parameters of oxidative stress. Thus, the enhancement of superoxide production in bovine heart submitochondrial particles by antimycin resulted in a decrease in the activity of cytochrome c oxidase through the peroxidation of cardiolipin [45]. Iron overload also induced lipid peroxidation and a decrease in mitochondrial membrane potential in rat liver mitochondria [46]. Sensi et al. [47] demonstrated that zinc influx induced mitochondrial superoxide production in postsynaptic neurons. 

Figure 16. Conceptual model for biological redox cycling in a hot spring environment. Influx of external aqueous Fe(II) [Aeap-Ext] may reflect hydrothermal fluids or other sources of Fe(II),q. Oxidation of Fe(II),qis envisioned to occur by Fe(II)-oxidizing phototrophs in anaerobic conditions, but could also occur through interaction of Fe(II), with an oxygen-rich atmosphere. Oxidation of Fe(II) produces a flux of ferric oxide/hydroxide precipitates [Aeanjppt] that settle to the lower, anaerobic sections of the pool. These ferric precipitates are in turn partially reduced by DIR bacteria, returning a flux of Fe(II), to the pool [Aem-Bio] ...

The enhanced catalatic activity could arise from more facile exhaust of products just as easily as from enhanced substrate accessibility. The effect of inhibitors is a largely static process that is complete once the inhibitor has become bound in the active site. The catalatic process, on the other hand, requires a constant influx of substrate peroxide and efflux of product oxygen and water. As a result, the inlet channels for inhibitors and substrate may be different. 

Decreasing intracellular Ca2+ Calcium channel blockers predictably cause vasodilation because they reduce intracellular Ca2+, a major modulator of the activation of myosin light chain kinase (Figure 12-1). (3 blockers and calcium channel blockers reduce Ca2+ influx in cardiac muscle, thereby reducing rate, contractility, and oxygen requirement under most circumstances.)... 

Cardiac muscle is highly dependent on calcium influx for normal function. Impulse generation in the sinoatrial node and conduction in the atrioventricular node—so-called slow-response, or calcium-dependent, action potentials—may be reduced or blocked by all of the calcium channel blockers. Excitation-contraction coupling in all cardiac cells requires calcium influx, so these drugs reduce cardiac contractility in a dose-dependent fashion. In some cases, cardiac output may also decrease. This reduction in cardiac mechanical function is another mechanism by which the calcium channel blockers can reduce the oxygen requirement in patients with angina. 

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