Dedifferentiation

Morphologically, the lens is arranged so that dedifferentiated or disorientated lens fibres are not eliminated but are pushed to the core (Spector, 1984,). Damage to the cell-fibre membranes or to the proteins they contain is irreversible. The lens is therefore dependent on the peripheral cells of the epithelial layer for protection against insult. 

Solute uptake can also be evaluated in isolated cell suspensions, cell mono-layers, and enterocyte membrane vesicles. In these preparations, uptake is normalized by enzyme activity and/or protein concentration. While the isolation of cells in suspension preparations is an experimentally easy procedure, disruption of cell monolayers causes dedifferentiation and mucosal-to-serosal polarity is lost. While cell monolayers from culture have become a popular drug absorption screening tool, differences in drug metabolism and carrier-mediated absorption [70], export, and paracellular transport may be cell-type- and condition-depen-dent. 

A. Collagen substrate, 0% FCS (fetal calf serum) B. Spider silk-ELP substrate, 0% FCS C. No substrate, 0% FCS D No substrate, 10% FCS. In A and C, the cells have an elongated, fibroblastoid morphology, which characterizes dedifferentiation. The spider silk-elastin substrate (B) or the presence of 10% FCS in dishes without a substrate (D) produce a more favorable morphology. 

Honorati MC, Cattini L, Facchini A IL-17, IL-lbeta and TNF-alpha shmulate VEGF production by dedifferentiated chondrocytes. Osteoarthritis Cartilage 2004 12 683-691. 

Even with the appropriate reactive positive controls, a negative result still does not absolutely rule out a particular differentiation state. Some tumors may lose their ability to express some antigens (dedifferentiation), although they can still be recognized to be of a particular differentiation by other methods (morphology, electron microscopy, and so forth). Because of this reason, negative results can never be as meaningful as positive results. 

H. Bernstein, H. Holubec, J. A. Warneke, H. Garewal, D. L. Earnest, C. M. Payne, D. J. Roe, H. Cui, E. L. Jacobson and C. Bernstein, Patchy field defects of apoptosis resistance and dedifferentiation in flat mucosa of colon resections from colon cancer patients, Ann. Surg. Oncol., 2002, 9(5), 505. 

Leaf organ cultures of C. roseus have also been described 118). A typical 2.5-g fresh weight inoculum produced 29 g fresh weight of leaf material after 35 days dedifferentiated tissue was absent. The alkaloids found included ajmalicine (39), sitsirikine (48), tetrahydroalstonine (39), serpentine (40), and vindoline (3). 

Malda, J., van Blitterswijk, C. A., van Geffen, M., Martens, D. E., Tramper, J., and Riesle, J. (2004). Low oxygen tension stimulates the redifferentiation of dedifferentiated adult human nasal chondrocytes. Osteoarthritis Cartilage 12, 306-313. 

This leads to one key issue in treating the comeal eye bums with the necessity of taking measures that prevent the cornea from additional damage, to prevent damage of the differentiated cells, and more to keep stem cells ahve and dedifferentiated. Therefore, any measure in treatment of comeal eye bums must prevent additional damage from cells. 

Vamvakas, S., Richter, H. Bittner, D. (1996) Induction of dedifferentiated clones of LLC-PKi cells upon long-term exposure to dichlorovinylcysteine. Toxicology, 106,65-74... 

Cloning. Asexual propagation (cloning) of plants ordinarily occurs by virture of the ability of embryonic meristematic tissue to differentiate into roots and shoots. If isolated phloem cells or other more differentiated cells are cultured, the result is often the formation of a callus, a dedifferentiated mass of cells somewhat reminiscent of embryonic cells. Under proper conditions, e.g., in a coconut milk culture and in the presence of the correct auxin-to-cytokinin ratio, some carrot root phloem cells revert to embyronic cells and develop into intact plants.99 This experiment provided proof that the differentiated carrot phloem cells... 

These pioneering studies demonstrating nuclear differentiation and dedifferentiation are supported by a broad range of genetic and biochemical findings that indicate that chromosomal structural differences often can be correlated with changes in the potential for gene expression. 

Jermendy G, Nadas J, Sapi Z. Lipoblastoma-like lipoa-trophy induced by human insulin morphological evidence for local dedifferentiation of adipocytes Diabetologia 2000 43(7) 955-6. 

Philips J-C, Petite C, Willi J-P, Buchegger F, Meier CA. Effect of peroxisome proliferator-activated receptor 8 agonist rosiglitazone on dedifferentiated thyroid cancers. Nucl Med Comm 2004 25 1183-6. 

Figure 1.12 Schema of EGF stimulation of astrocyte proliferation and dedifferentiation into neuroblasts. Prolonged exposure to EGF causes astrocytes (taken as representative of neuroglial cells) to proliferate rapidly. It also causes them to lose their neuroglial characteristics, as shown by the decline in the activity of their specific marker enzymes simultaneously, they will also reduce growth rate to control levels. They will eventually acquire precursor cell characteristics to become neuroblasts and neurons. Some of the proliferating astrocytic cells will maintain their characteristics, migrate to their usual location, and fulfill their usual functions.4748 (From Timiras, PS. et al., Mech. Ageing Dev., 126, 3, 2005. With permission.)...

---