Cells, living Permeability

The first method employs the ballistic gun (2,3), where cells are exposed to ballistic bombardment by microparticles coated with the molecules of choice (e g., DNA). The second method is based on exposing the cells to ultrasound leading to an increased transmembrane transport (4). The third approach is based on an electrically driven process (electroporation), where cells are exposed to high-electric fields for short durations of micro- to milliseconds (5). This exposure leads to induction of short-lived permeability changes in the membrane ( pores ) enabling the diffusion of molecules across the membrane along their electrochemical gradients. 

The mydriatic effect of topically applied corticosteroids was investigated in living monkey eyes. Instillation of dexamethasone 0.1% (Decadron) produced pupillary dilation and ptosis as well as elevation of lOP. When the steroids were tested without their vehicles but in saline solntion, the effects on lOP, pupil size, and upper eyelid did not occnr.Thns it has been snggested that an excipient in the vehicle mixture causes the effects, possibly by altering cell membrane permeability to the steroid. 

This assay is used to measure cell viability. It is a two-color fluorescence assay that simultaneously determines live (viable) and dead (nonviable) cells Live cells have intracellular esterases that convert nonfluorescent, cell-permeable fluorescein di-O-acetate to the intensely fluorescent fluorescein (green). Cleaved fluorescein is retained within cells. Dead cells have damaged membranes propidium iodide enters damaged cells and is fluorescent when bound to nucleic acids. It produces a bright red fluorescence in damaged or dead cells. 

Wu HY, Tomizawa K, Matsushita M, Lu YF, Li ST, Matsui H. Poly-arginine-fused calpastatin peptide, a living cell membrane-permeable and specific inhibitor for calpain. NeurosciRes2J003 4T. 131 135. 

The significance of a is bettei understood when we study the osmotic behavloui of living cells. Living cells have selectively permeable membranes which are very permeable to water and some low molecular weight solutes, but much less permeable to other substances. This leads to the inflow of some solute molecules along with the solvent while others are retained. Under these cohdltlons, the solution exhibits only that fraction of its total osmotic pressure that is due to the solutes which are retained. This fraction of the total osmotic pressure of a solution is termed as its tonicity. If the cells are placed in a medium whose osmotic pressure matches that of the cell contents inside, there is no unidirectional flow of solvent and the cell size remains the... 

A dual isotope labeling technique [85] has been used to measure membrane permeability in plant cells, based on the selective permeabiHty of the membranes of living cells to tritiated water and carbon-14 labeled mannitol. Kieran [29] showed that the results of the dual isotope labeling and Evan s Blue staining methods correlated well as indicators of cell viability however, the latter was preferable in terms of reagent cost and ease of analysis. 

Chang MCY, Pralle A, Isacoff EY et al (2004) A selective, cell-permeable optical probe for hydrogen peroxide in living cells. J Am Chem Soc 126 15392-15393... 

Living cells visualization of membranes, lipids, proteins, DNA, RNA, surface antigens, surface glycoconjugates membrane dynamics membrane permeability membrane potential intracellular pH cytoplasmic calcium, sodium, chloride, proton concentration redox state enzyme activities cell-cell and cell-virus interactions membrane fusion endocytosis viability, cell cycle cytotoxic activity... 

PET-11 (Zinpyr-1), containing fluorescein as a fluorophore, and bis(2-pyridylmethyl)amine as a chelating moiety, has been designed for probing Zn11 in living cells. This compound is indeed cell-permeable and it has essentially no... 

The question of the criteria of autopoiesis is formalized at length, but not always clearly, in the primary literature on autopoiesis. Varela, in his latest book (2000), has simplified these criteria into three basic ones, which can he expressed as follows Verify (1) whether the system has a semi-permeable boundary that (2) is produced from within the system and (3) that encompasses reactions that regenerate the components of the system. Thus, a virus is not an autopoietic system, as it does not produce the protein coat of its boundary or the nucleic acids (the host cell does this, and it is living). A computer virus is also not autopoietic, as it needs a computer system that is not produced hy the virus itself. A growing crystal is not autopoietic, as the components are not generated from an internalized network of reactions. 

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