Outer cell membrane

An outer cell membrane separates the intracellular solution or cytoplasm from the extracellular solution. These two solutions differ in their compositions. The extracellular fluid contains primarily Na and CH ions (0.1 to 0.5 M) as well as minor amounts of K+, Ca, and Mg ions, while the cytoplasm has a high concentration of K+ ions (0.1 to 0.5M) and low concentrations of Na and CH ions. Principal anions in the cytoplasm are the relatively large anions of different organic acids, incfuding pofyanions. As an example we report the major inorganic ions contained in the extra- and intracellular solutions of frog muscle (inniM) ... 

More recently, screening efforts at Novartis have identified a hydroxamic acid containing a benzothiazinone ring system (32) [108]. This inhibitor is very potent versus S. aureus Ni -PDF (<5nM) and displays good selectivity versus matrix metalloprotease-2 (MMP-2) and MMP-13. Unfortunately (32), and all other analogues prepared, such as carbon isosteres (33), sulfones (34), N-substituted analogues (35) and N-formyl-N-hydroxylamines (36), lacked appreciable antibacterial activity in spite of their potent enzyme inhibitory activity. Further studies performed by Novartis suggest that these molecules are unable to penetrate the outer cell membrane of E. coli, and may bind to the cell membrane of S. aureus [108]. 

FIGURE 7.2 Diagram to show G-protein a, p, and y subunits attached to the outer cell membrane. (Adapted from Clapham, D. E., Nature, 379, 297, 1996. With permission.)... 

ESR spectra indicated that ultrasound enhanced the penetration of 16-DS into the structurally stronger sites of the inner and outer cell membranes. The effect of ultrasound on the cell membranes was transient in that the initial membrane permeability was restored upon termination of the ultrasound treatment. These results suggested that the resistance of gram-negative bacteria to the action of hydrophobic antibiotics was caused by a low permeability of the outer cell membranes and that this resistance may be reduced by the simultaneous application of antibiotic and ultrasound. 

In the unstimulated state electrostatic forces prevent the melting of the vesicle membranes with the outer cell membrane. If the outer cell membrane is depolarized by either an action potential or acetylcholine (in the adrenal medulla) the electrostatic repulsion is neutralized by positively charged... 

Cromoglycate and nedocromil are known to stabilize the outer cell membrane of mast cells and thereby inhibiting the release of histamine and leukotrienes. Their antiallergic effect might be due to more than one mechanism, for example by additionally reducing the sensitivity of inflammatory cells towards histamine. 

The thin (8 nm) outer cell membrane or "plasma-lemma" (Fig. 1-7) controls the flow of materials into and out of cells, conducts impulses in nerve cells and along muscle fibrils, and participates in chemical communication with other cells. Deep infoldings of the outer membrane sometimes nm into the cytoplasm. An example, is the "T system" of tubules which functions in excitation of muscle contraction (Figs. 19-7, 19-21). Surfaces of cells designated to secrete materials or to absorb substances from the surrounding fluid, such as the cells lining kidney tubules and pancreatic secretory cells, are often covered with very fine projections or microvilli which greatly increase the surface area. 

These secretion granules move to the surface and are released from the cell. In this process of exocytosis the membranes surrounding the granules fuse with the outer cell membrane. The rough ER appears to contribute membrane material to the smooth ER and Golgi apparatus, while material from Golgi membranes can become incorporated into the outer cell membrane and into lysosomes. Outer mitochondrial membranes and membranes around vacuoles in plant cells may also be derived directly from the ER. Outer membrane materials are probably "recycled" by endocytosis. 

TERS experiments were performed to study the bacterial cell surface. Biju et al. combined silver island films on glass coverslips with an AFM to investigate the effect of electron-acceptor limitation on the outer cell membrane of Shewanella one.ide.nsis [103]. 

Although many applications of flow cytometry involve the staining of cells for proteins expressed on the outer membrane, cells also have many proteins that are not displayed on their surface. With appropriate procedures, flow cytometry can provide a means to analyze these intracellular proteins. The outer cell membrane is impermeable to large molcules like antibodies however, if we intentionally fix cells to stabilize proteins and then disrupt the outer membrane, the cells can be stained with fluorochrome-conjugated monoclonal antibodies against intracellular proteins. After time to allow the antibodies to pass through the now-permeabilized membrane, the cells are washed to remove loosely bound antibodies and then are run through the flow cytometer to measure their fluorescence intensity. 

ROS into more vital regions of the bacterial cells (note that S. aureus has no outer cell membrane). In recent research, it was demonstrated by Wilson that the photosensitizer methylene blue is more active on gold particles and kills even MRSA (with 2 log reductions after 10 min irradiation with green light) without degrading a polysiloxane or a polyurethane matrix and with only 10% photobleaching after 6 months [128]. 

The a-dispersion is presently the least clarified. Intracellular structures, such as the tubular apparatus in muscle cells, which connect with the outer cell membranes, could be responsible in all such tissues which contain such cell structures. Relaxation of counterions about the charged cellular surface is another mechanism suggested by us. Last, but not least, relaxational behavior of membranes per se, such as reported recently for the giant squid axon membrane, can account for it (2). The relative contribution of the various mechanisms varies, no doubt, from one case to another and needs further elaboration. 

Cholesterol is exported to the peripheral tissues in LDL and VLDL (see Chapter 1). About 70 percent of the cholesterol molecules in LDL are esterified with a fatty acid (for example, palmitate) on the OH group (at Carbon 3 see Figure 2-5). Cells take up cholesterol from the LDL by means of LDL receptors in the outer cell membrane. 

HOOK AND THE MOTOR IMBEDDED IN THE INNER AND OUTER CELL MEMBRANES AND THE CELL WALL (BOTTOM) ONE PROPOSED MODEL FOR THE FUNCTIONING OF THE ACID-DRIVEN, ROTARY MOTOR. THE DRAWING SHOWS THE INTERNAL COMPLEXITY OF THE MOTOR, WHICH IS NOT DISCUSSED IN THE TEXT. 

Decreased permeability to drug Decreased penetration of the antibiotic through the outer cell membrane prevents the drug from reaching the target penicillin-binding proteins (PBPs). 

Calcium homeostasis is also affected by an overload in peroxides. In some instances, this may be due to activation of so-called calcium channels. In the presence of extracellular calcium, exposure of smooth muscle cells to 0.3 mM H2O2 was shown to induce a rapid increase in intracellular calcium concentration, followed by a decrease to a new constant level approximately twice higher than the initial one [140]. Subsequent treatment of the cells with Ca2+-channel blockers, with disulfide-reducing agents or with antioxidants such as trolox, prevented the stabilization of intracellular calcium at the high steady-state concentration. These results suggest that an increased disulfide/thiol ratio activates voltage-dependent calcium channels of the outer cell membrane. 

Immunofluroescence requires that the target organisms be cultivated so that antibodies can be produced against the cells to be enumerated. The antibodies responsible for the ceU-staining reaction are those that interact with components of the outer cell membrane, and the reaction can be very specific (Ward and Carlucci, 1985). This is both a strength and a disadvantage of the method. It allows... 

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