Cell attachment

The adherence and proliferation of human umbilical vein endothelial cells (HUVECs) were evaluated on the fabricated PCLA scaffold. Results showed that the HUVECs were adhered and proliferated well on the small-diameter-fiber fabrics (0.3 and 1.2 mm in diameter), whereas markedly reduced cell adhesion, restricted cell spreading, and no signs of proliferation were observed on the large-diameter-fiber fabric (7 mm in diameter). That may be due to the high-surface-density fibers provide an extremely high surface/volume ratio, which favors cell attachment and proliferation. 

Cell attachment-recognition site Various proteins involved in cell-cell (eg, sperm-oocyte), virus-cell, bacterium-cell, and hormone-cell interactions... 

Influenza virus hemagglutinin Responsible for host-cell attachment and membrane fusion... 

Using the cell-attached patch clamp technique on frog muscle fibers (79), one can observe only two conditions the open, conducting state of the receptor and a nonconducting state of unknown identity. The transitions behave according to stochastic principles the lifetimes of any particular condition are distributed exponentially. The open state has a mean duration that is the inverse of the rate of channel closing. Because channel open time depends only upon a conformational shift, agonist concentration does not influence the parameter. It is, however, influenced... 

The increase in the open probability of the ICOR channel induced by hormones in cell attached patches is moderate at best. 

In respiratory epithelial (RE) cells the Cl -conductance was attributed to the ICOR channel. In fact, it was reported by Frizzell et al. and Welsh s laboratories that catecholamines increased the incidence of ICOR channels in cell attached patches of normal RE cells but failed to do so in CF cells [110,111], Later both laboratories presented data on excised membrane patches of RE cells in which the protein kinase A which was added to the cytosolic side produced ICOR channel activity in the normal cells but not in the CF tissues [19,20]. This finding was reproduced by Guggino and coworkers [22] for RE cells and by others for lymphocytes [46]. Protein kinase C at physiological Ca -activities had a comparable effect in normal cells but also failed to function in CF cells [22,112]. 

Our own laboratory obtained different results. Not only were we unable to see a clear cut correlation between the incidence of ICOR channels in cell attached patches and the degree of hormonal stimulation [57], we were also unable to reproduce the activation studies in excised patches. In our hands, the activation of ICOR channels occurred simply by the excision, and this was equally true for the normal as for the CF cells [57]. We did note, however, that the other laboratories worked at room temperature whereas we always work at 37°C. Welsh s laboratory has shown meanwhile that excision activation of ICOR Cl -channels is a temperature-dependent process [113]. At low temperature, excision activation is largely delayed [113] but it is immediate in our experiments at 37°C [57]. We concluded that the activation of the ICOR channels has probably little to do with phosphorylation but is rather due to the fact that the excised patch faces a new environment on the cytosolic side [57,72],... 

The study of flotation kinetics relates to a number of mass transfer processes and these are listed in Table 2.8. The term, entrainment which figures in the mass transfer process statements made in Table 2.8 may be elaborated. It is the process by which particles enter the base of a flotation froth and are transferred up and out of the flotation cell suspended in the water between bubbles. Entrainment should be distinguished from true flotation, whereby particles come out of the cell attached to bubble surfaces. True flotation is chemically selective, while the entrainment process recovers both gangue and valuable minerals alike. Entrainment harms the product grade since recovery of the more abundant gangue mineral reduces the quality of the concentrate. This is especially true in the processing of fine ores. Much flotation research has dealt with reducing entrainment in order to improve... 

The sole purpose of the filter support and any applied extracellular matrix is simply to provide a surface for cell attachment and thus to provide mechanical support to the monolayer. However, the filter and matrix also can act as serial barriers to solute movement after diffusion through the cell monolayer. The important variables are the chemical composition of the filter, porosity, pore size, and overall thickness. In some cases, pore tortuosity also can be important. It is desired that the filter, with or without an added matrix, provide a favorable surface to which the cells can attach. However, in some cases these properties can also result in an attractive surface for nonspecific adsorption of the transported solute. In these instances, the appearance of the solute in the receiver compartment of the diffusion cell will not be a true reflection of its movement across the mono-layer. Such problems must be examined on a case-by-case basis. 

Figure 1 Schematic diagrams illustrating the patch-clamp technique. (A) Overall setup for isolating single ionic channels in an intact patch of cell membrane. P = patch pipet R = reference microelectrode I = intracellular microelectrode Vp = applied patch potential Em = membrane potential Vm = Em — Vp = potential across the patch A = patch-clamp amplifier. (From Ref. 90.) (B) Five different recording configurations, and procedures used to establish them, (i) Cell attached or intact patch (ii) open cell attached patch (iii) whole cell recording (iv) excised outside-out patch (v) excised inside-out patch. Key i = inside of the cell o = outside of the cell. (Adapted from Ref. 283.)...

When the bacteria to be detected are less than 1% of the total population in a sample, IFAs cannot be used because of interference from unrelated particles that are concentrated when large volumes of sample are filtered. To overcome this problem, the organism of interest may be concentrated by immunomagnetic separation.10,51 62 For this procedure magnetic beads coated with monoclonal or polyclonal antibodies are mixed with the sample. The beads are collected with a magnet, and the cells attached to the beads then are removed, enumerated, and identified by IFAs. 

Cell-to-cell attachment the glycocalyx of one cell may attach to the glycocalyx of another cell, which causes the cells to become attached. 

Fig. 21.4. Vesicle formation and patch-clamp techniques used to record levamisole receptor channel currents from Ascaris muscle. (A) Muscle membrane vesicles bud-off from the bag membrane following a 10 min collagenase treatment and incubation for 1 h at 37°C in Ascaris saline. (B) Levamisole is applied to the outside surface of the membrane to activate receptor channels cell-attached patches are usually used but it is also possible to make inside-out and outside-out patch recordings.

Fig. 21.5. Levamisole-activated single-channel currents activated by 30 pM levamisole in a cell-attached patch and current voltage relationship. The rectangular current pulses were recorded at different patch potentials to determine the relationship between channel current and potential. The slope was linear with a conductance of 34 pS.

Fig. 21.15. GABA and piperazine single-channel currents recorded from cell-attached patches of Ascaris bag muscle membrane. Trans-patch potential, -75 mV GABA channel mean open-time, 32 ms piperazine channel open-time, 18 ms GABA 3 pM in the pipette piperazine 500 pM in the pipette.

Some cell lines, such as HEK293, may detach during the permeabilization step due to a strong Ca2+ dependence for attachment. While it is critical that cells are permeabilized as a monolayer, detachment does not seem to hinder cytosolic ribosome release, as they tend to detach as a (partial) monolayer. Following the permeabilization step, cells can simply be separated from the soluble cytosol phase by centrifugation at 750-1000 Xg for 5 min. Transfer the supernatant (cytosol) to a new tube. Remove any remaining cells attached to the flask via the wash buffer, combine with the cell pellet, and recover by centrifugation. Proceed with the membrane solubilization step. 

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