Membranes, accumulation

Ribosomes are spherical cell structures enriched with ribonucleoprotein and with a diameter of 15-20 nm. Each ribosome is formed by two subunits of different sizes, only visible through high resolution electron microscopy. Ribosomes connected to the rough endoplasmic reticulum are involved in the biosynthesis of proteins that are temporarily stored or transported to the cell s outer environment. Proteins synthesized by ribosomes connected to membranes accumulate in the cisternae before passage to the plasma membrane for secretion. 

Balaz and Lukacova (1999) attempted to model the partitioning of 36 non-ionizable compounds in 7 tissues. Amphiphilic compounds, or those possessing extreme log Kow values, tended to show complex distribution kinetics because of their slow membrane transport. However for the non-amphiphilic, non-ionizable compounds with non-extreme log Kow values studied it should be possible to characterize their distribution characteristics based on tissue blood PCs. Distribution is dependent on membrane accumulation, protein binding, and distribution in the aqueous phase. As these features are global rather than dependent on specific 3D structure, distribution is not expected to be structure-specific. In this study, tissue compositions in terms of their protein, lipid, and water content were taken from published data. This information was used to generate models indicating that partitioning was a non-linear function of the compound s lipophilicity and the specific tissue composition. 

Concentration polarization This occurs when solutes or particles rejected by the membrane accumulate on or near the membrane surface. As a direct consequence of this condition, there is an increase in the resistance to solvent transport resulting in a flux decrease and possibly changes in the retention characteristics. 

The termination of signaling by Gq-generated second messengers is achieved by dephosphorylation of IPS and deacylation of DAG. Removal of Ca from the cytoplasm is achieved by Ca -binding proteins and Ca " pumps. Ca pumps in the plasma membrane remove Ca from the cell whereas pumps in organellar membranes accumulate Ca to replenish intracellular Ca stores. 

Oxidizing substances, such as ozone, can cause peroxidation of cellular membranes, leading to membrane damage and increased permeability. The edematous fluid permeates through such membranes, accumulating and blocking the airway. This results in edema. Many other toxicants may produce cellular damage and edema, however. 

Concentration polarisation Accumulation of solutes within the boundary layer above the membrane surface. Solutes that do not pass through the membrane accumulate on the membrane surface causing either an increased resistance to solvent transport or an increase in local osmotic pressure (either of which may decrease flux), and possibly a change in the separation characteristics of the membrane. See also Gel Layer and Polarisation Modulus. 

The effects of ionic strength, ion valence and pH value on the streaming potential of the fiber membrane were investigated. It was demonstrated that the PVB membrane accumulates a weak negative charge due to the specific adsorption of ions. 

GO Monkey renal cells 10-300 mg mL" 24 h Cell membrane accumulation and dose-dependent oxidative stress 142... 

General reaction mechanism of the PPIs with the H,K ATPase in the membrane of the parietal cell canaliculus, showing passive diffusion across the canalicular membrane, accumulation of the protonated form, conversion to the sulfenamide, and reaction with one or more cysteines in the catalytic subunit of the H,K ATPase. The outline of the pump structure illustrates the vestibule of the pump on its outside surface where binding of the PPIs results in inhibition of acid secretion correlated with inhibition of ATPase activity. 

As solution passes through a membrane, accumulation of solute at the membrane surface occurs as a result of one or more possible mechanisms, i.e., partial or total size exclusion of solute molecules from pores, electrostatic repulsion of solute molecules by a membrane, chemical reaction, adsorption of solute molecules, etc. The configuration of the eoncentrated solute region contiguous to the solution-— membrane interfaces makes it amenable to analysis by the film-theory model [132]. 

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