Cellular Behavior

Biodegradable Injectable Systems for Bone Tissue Engineering 

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Morphogens are form-generating substances, whose configuration within a tissue prefigures the pattern (Meinhardt, 1983). These substances set up an extracellular concentration gradient, which in turns orchestrates a coherent set of cellular behaviors that will eventually result in the proportionate growth of an or-... 

The three-component method is applicable to the synthesis of various C(6)- or C(7)-functionalized PGs. Scheme 11 illustrates the tandem conjugate addition-aldol reaction that affords 7-hydroxy-PGE derivatives (18). Both saturated and unsaturated C7 aldehydes can be used as a side-chain units. The aldol adducts can be transformed to naturally occurring PGs (5a, 19) and, more importantly, to a variety of analogues such as tumor-suppressing A7-PGA, (20) or 7-fluoro-PGI2, a stabilized prostacyclin (21). The unique cellular behavior displayed by A7-PGA methyl ester is well correlated to its chemical reaction with thiols (20). 

A common mechanism for modulating the function of regulatory pathways is controlled expression of one or more of the pathway components. This could be especially useful for the RGS-RhoGEFs where such expression could determine the coordinated regulation of RhoA by G12/13 versus regulation of other downstream pathways by the G proteins. As noted previously and in the next section, potential selective functions of specific RhoGEFs may determine differential cellular behavior. 

Many cells and subcellular organelles maintain an electrostatic potential difference across their membranes. This potential typically is important to the operation of the cell or organelle. For example, in nerve cells and other cells with excitable membranes such as muscle cells, the electrostatic potential is an important signal that governs cellular behavior. In these cells, some form of electrochemical signal that is sent to the cell can elicit an action potential - a transient change in the membrane potential that can trigger intracellular events, such as contraction of a muscle cell. 

Capsular and extracellular polysaccharides are involved in several aspects of cellular behavior that are tied to bacterial survival and virulence [321]. The capsule layer provides a physical barrier that prevents the bacteria from drying out, aiding in survival outside a host. CPS are also involved in colonization and biofilm formation. In some bacteria CPS promote adherence to surfaces, aiding colonization and biofilm formation, while CPS in other bacteria inhibit adhesion and biofilm formation [344]. 

Figure 35.1 Cellular behavior originating from the external stimuli surrounding the cell.

Figure 35.2 A number of external factors affecting cellular behavior simultaneously.

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