Factors influencing cell growth

Each neurotrophic factor influences the growth and development of a specific group of neuronal types, with some cells being sensitive to several such factors. Many sustain specific neuronal populations whose death underlines various neurodegenerative diseases. This raises the possibility that these regulatory molecules may be of benefit in treating such diseases. Results from early clinical trials have been at best mixed, but many remain optimistic that neurotrophic factors may provide future effective treatments for some currently incurable neurodegenerative conditions. 

It is suggested that PPARa activation may lead to DNA replication, cell growth, and inhibition of apoptosis via tumor necrosis factor a (TNF-a). Alternatively or additionally, the oxidative stress could activate the MAP kinase pathway, which will also influence cell growth (Fig. 7.11), but this might be independent of PPARa activation. However, the role of these events is still unclear. 

Other extrinsic factors have also been considered (R7). The overall hormonal milieu influences cell growth and can apparently exert a selective influence on the proliferation of transplanted mammary carcinoma cells with specific ERP properties. This suggests that hormonal manipulation could affect ERP properties of... 

In summary, transcription of the Cdc25-type phosphatase encoded by string limits the progression of many embryonic cell cycles, which are rapid (1—3 h) and require little cell growth. The massive ofi-regulatory region of string acts as a sophisticated pattern sensor that is influenced by a wide variety of cell type-specific transcription factors (Fig. 2A). 

Raff I am not aware of any example where a limit to cell growth has been demonstrated in vivo. Generally, if you increase the amount of cell growth factor available, cells will get bigger. Thus the levels of extracellular signals can influence cell size in an animal. 

At the moment, the role of p53 and its related genes in the regulation of cell growth signaling by carotenoids is not well understood and the results appear controversial. It is possible that several factors may influence the modulatory effects of P-carotene and other carotenoids on p53 levels, including the concomitant presence of smoke, the type and the concentration of the carotenoid, the association with other antioxidants as well as the biological cellular environment. 

The differentiation, growth and division of eukaryotic cells is modulated by various influences, of which growth factors are amongst the most important for many cell types. A wide range of polypeptide growth factors have been identified (Table 10.1) and more, undoubtedly, remain to be characterized. Factors that inhibit cell growth also exist. For example, interferons and TNF inhibit proliferation of various cell types. 

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