Cell substratum interactions

Fibronectin is an extracellular matrix protein that mediates a variety of cellular effects. It is important in cell-cell and cell-substratum interactions ( 3.9), mediates reticuloendothelial cell activity and binds both to Clq (the first component of complement) and to bacteria. It also increases the tu-mouricidal activity of macrophages and activates complement receptors, by regulating the binding of C3b-coated particles to neutrophils. It may mediate attachment of Staphylococcus aureus to neutrophils and may also play a role as an adhesion factor, promoting the adhesion of neutrophils to surfaces. Fibronectin mRNA (8.7-8.8 kb) is detected only at low levels in... 

Rabito CA, Tchao R, Valentich J Leighton J (1980) Effect of cell substratum interaction of hemicyst formation by MDCK cells. In Vitro 16 461-468. 

TGF-P also regulates cell-substratum interactions by a selectively increasing expression of integrins, a major class of cell-adhesion receptors. Integrins bind fibronectin, collagens, and other ECM proteins28-29 and thus modulate the adhesion cascade, which modulates cell migration. 

Gangliosides play two major roles in membrane-mediated physiological processes (1) control of transmembrane signaling and (2) mediation of cell-cell or cell-substratum interaction. 

Mediation of Cell-Cell or Cell-Substratum Interaction... 

Biological systems are complex by nature, and accordingly so, too, are their interactions with superhydrophobic materials. The dynamic nature of both the cells themselves and the wetting processes that occur on complex interfaces can lead to a range of observed effects that vary with time and conditions, and it cannot therefore be explicitly stated that superhydrophobic surfaces are beneficial or detrimental to cells in general. Rather, superhydrophobic surfaces are potentially usefiol in any application in which mediation of cell-substratum interactions is required with proper and careful control of the conditions, superhydrophobic surfaces can both prevent and enhance cellular adhesion, and these surfaces may be able to exert an effect on the metabolism of the attaching organism. 

Fig. 2 Cell attachment on surface through ceU-ECM interactions. (A) Cell attachment and spreading mechanism. (B) Cellcell and ceU-substratum interactions in two-dimensional and three-dimensional environments. (View this art in color at WWW. dekker. com.)...

In the last ten years or so there have been major advances in understanding many of the adhesive interactions described above and in identifying the cell adhesion molecules involved. Much of this progress has been due to the production of specific antibodies able to perturb cell-cell or cell-substratum contacts in functional adhesion assays. The antibodies, prepared against membrane fractions conventionally or by hybridoma technologies, proved to be invaluable reagents for the isolation of functional adhesion... 

The Ig-superfamily contains many proteins involved in immune recognition such as products of the MHC complex and accessory molecules [53]. In addition there are ten or more members associated mainly with nervous tissues in mature animals and several others in non-nervous tissue that are important factors in cell-cell and cell-substratum adhesion in non-immune cells. See [54] and [55] for detailed discussion of other aspects of Ig-superfamily glycoproteins. All of the cell adhesion glycoproteins in the family contain a variable number of Ig-like domains of about one hundred amino-acid residues, usually but not always defined within a pair of disulfide-bonded cysteine residues, and of the C2 type fold. In many cases the molecules contain variable numbers of another type of modular sequence known as the fibronectin type III repeat, sinee it was discovered in fibroneetin. In the following discussion, some principles of the structure and functions of this large family of cell adhesion molecules will be considered with particular emphasis on the interplay between different members in adhesion and modulation of adhesive interactions by carbohydrates. 

Several biological activities have been proposed for HFN. These activities include the ability to mediate cell-substratum and cell-cell interaction, to promote wound healing and to function as an opsonin. The study of in vivo roles for HFN under normal and pathological conditions requires rapid, simple and reproducible methods for obtaining HFN levels in plasma and other biological fluids. 

Microbial cells transported with the stream of fluid above the surface interact with conditioning films. Immediately after attachment, microorganisms initiate production of slimy adhesive substances, predominantly exopolysaccharides (EPS) that assist the formation of microcolonies and microbial films. EPS create bridges for microbial cells to the substratum and permit negatively charged bacteria to adhere to both negatively and positively charged surfaces. EPS may also control interfacial chemistry at the mineral/biofilm interface. 

Attachment of bacteria. At low ionic strength of the medium — as in many freshwaters — bacteria-surface interactions are controlled by the effects of van der Waals attraction and electrostatic repulsion. At high ionic strength — as in seawater — steric interactions between the outer cell surface macromolecules and the substratum gain in importance (van Loosdrecht et al., 1989 Rijnaarts etal., 1999). Additionally, flagellar and twitching motility of bacteria was found to be essential in the process of attachment by bacteria onto surfaces (Pratt and Kolter, 1998 O Toole and Kolter, 1998). It seems that extracellular polysaccharides of bacteria are not involved in the adhesion process itself. However, bacterial extracellular polysaccharides are necessary for the development of a biofilm and for the formation of microcolonies (Allison and Sutherland, 1987 Hoyle et al., 1993). 

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