Transport processes indirect effects

The inhibition of amino-acid transport has been regarded as the main toxic effect of mercury compounds [82], The biochemical mechanism underlying the inhibition is unclear. In unfertilized sea-urchin eggs an interaction with the amino-acid carrier was found, whereas in fertilized eggs inhibition of amino-acid transport was indirect and might result from an elevation of the Na + content of the egg caused by the inhibition of the Na+ pump [83]. The action on the diffusional process could be mediated by an effect on membrane phospholipids or on membrane proteins, or by interaction with Ca2+ which stabilizes membrane structure. Mercuric chloride in skate liver cells inhibited amino acid transport, decreased Na + /K + -ATPase (adenosinetriphosphatase) activity, impaired volume regulatory mechanisms and increased the permeability of the plasma membrane to potassium [84]. It has been suggested that... 

The uptake and accumulation of various amino acids in Lactobacillus arabinosus have been described. Deficiencies of vitamin B6, biotin, and pantothenic acid markedly alter the operation of these transport systems. Accumulation capacity is decreased most severely by a vitamin B6 deficiency. This effect appears to arise indirectly from the synthesis of abnormal cell wall which renders the transport systems unusually sensitive to osmotic factors. Kinetic and osmotic experiments also exclude biotin and pantothenate from direct catalytic involvement in the transport process. Like vitamin B6, they affect uptake indirectly, probably through the metabolism of a structural cell component. The evidence presented supports a concept of pool formation in which free amino acids accumulate in the cell through the intervention of membrane-localized transport catalysts. 

Arguments in favour of a role of the anion-sensitive ATPase in transport are mainly based on an observed parallelism between the effect of certain inhibitors on the enzyme activity and the transport process. However, in nearly all cases the inhibitor used is the lipophilic anion thiocyanate, which might inhibit the transport process by other means. Moreover, inhibition of the mitochondrial ATPase activity led to a reduction in the amount of ATP available for other transport processes (e.g. (Na -I-K )-ATPase) causing indirect inhibition of anion transport. 

Although decay of because of its long half-life of 4.5 billion yr, plays almost no role in U plume attenuation, soil transport of U is affected by most of the processes that control transport of other radionuclides (sorption, indirect effects of biologic activity, etc.) hence consideration of U plumes is a useful starting place. After an overview describing U plume sources, a general review of U chemistry and transport is presented, which is itself followed by a description of plume case studies. The sequence of source identification, fate and transport, and plume description will be the path followed for subsequent treatment of Sr, Cs (half-life = 30.1 yr), Pu, and tritium. 

There is reason to beheve that cardiac glycosides, like other inotropic substances, act on the contractibility of the heart by affecting the process of calcium ion transfer through the membrane of myocardiocytes. The effect of cellular membranes in electric conductivity is mediated by transport of sodium, calcium, and potassium ions, which is a result of indirect inhibitor action on the (Na+-K+) ATPase of cell membranes. 

Such a complicated interactivity of processes can both directly and indirectly affect formation of the atmospheric greenhouse effect. Derwent et al. (2001) described a global 3-D Lagrangian chemistry transport model (STOCHEM) which reproduces chemical processes including MGC transport and can be used to reproduce interrelated fields of TO and methane concentration (Johnson et al., 2002) under conditions of emission to the atmosphere of short-lived TO precursors such as CH4, CO, NOx, and hydrogen. At the same time, the radiative forcing (RF) of NOx emissions depends on the location of emissions near the surface or in the upper troposphere, in the Northern or Southern Hemisphere. For each short-lived MGC/... 

A probable tolerance mechanism behind this would be transporting TGFp by means of either in vitro or in vivo indirect contact of suppressive cell and regulatory cell. The reason for that is assumed to be a new CD4 lymphocyte clone which does not produce IL 2 (Thorstenson and Khoruts, 2001). The observed effect is suppression of Thl lymphocytes which release mainly INFy and lymphotoxin. Thus it has been concluded that TGFP is the most involved cytokine in the food tolerance process, which is confirmed by Nakamura (Nakamura et al., 2001). 

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