Microenvironment factors influencing

Aghi M, Cohen KS, Klein RJ, Scadden DT, Chiocca EA (2006) Tumor stromal-derived factor-1 recruits vascular progenitors to mitotic neovasculature, where microenvironment influences their differentiated phenotypes. Cancer Res 66 9054-9064... 

As outhned earUer every single step of hematopoiesis is regulated and controlled in vivo by the cell s microenvironment. This not only includes the composition and concentration of growth factors, but also the local oxygen concentration, the pH, the osmolaHty, the supply of nutrients and the cellular and molecular surrounding of the cells (cell-cell contact, adhesion molecules and extracellular matrix). All these parameters affect the fate of the cell and, to estabUsh a cell culture process to cultivate or generate a specific subpopulation, the influence of all these factors has to be considered in the experimental set-up. In the following sections these parameters will be discussed in brief. 

The microenvironment in solid tumors may significantly influence the interstitial transport of drags and genes through various environmental factors. These factors... 

The emission properties of lumophores change when included within the microenvironment of a supramolecule bucket. Nonradiative decay processes are generally curtailed within the confines of the bucket interior and luminescence intensity is therefore increased [138,208,209], Because CDs present a more protected microenvironment than calixarenes, the binary complexes of the former supramolecule have been examined most extensively. Spurred by Cramer s pioneering observation that the spectral properties of a lumophore are perturbed by complexation within a CD [210], a large body of work has sought to define the influence of CDs on the photophysics of bound lumophores. Different factors contribute to the enhanced luminescence of 1 1 CDilumophore complexes. These include the following. 

Only two amino acids, tyrosine and histidine, form stable derivatives as the result of peroxidase-catalyzed iodination. All the tyrosine and histidine residues in a protein are not identical with respect to their reactivity or their geographic position. The residue which will be iodinated by lactoperoxidase must have the proper geometric position, while other methods of halogenation are influenced only by reactivity. The reactivity depends upon the microenvironment of the residue. There is an inverse relationship between the extent of tyrosine iodination and the dielectric constant of the environment of the tyrosine. Tyrosine iodination increases with decreasing dielectric constant. Steric factors also influence iodination since the relatively large iodine atom may be blocked in either the production of monoiodotyrosine or the formation of diiodotyrosine. 

Stem cell renewal and differentiation occur within the bone marrow under the influence of the marrow microenvironment. Stromal endothelial cells, fibroblasts, and fat cells (adipocytes) are necessary to support stem cell proliferation and division by providing anchorage for adhesion and secreting various hematopoietic growth factors necessary for differentiation. It is the characteristics of the local microenvironment (cellular matrix and growth factor concentrations) that influence the differentiation of a particular hematopoietic lineage, favoring it over another. 

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