Dominant role in regulating

Chapter 24, Integration of Metabolism and Hormone Action, explains the organization strategies used to integrate metabolic processes in a multicellular organism. Like the first chapter in part 4, the content of chapter 24 relates to all of the chapters on metabolism (chapters 11-24). This chapter emphasizes the fact that hormones and closely related growth factors play a dominant role in regulating metabolic activities in different tissues. 

Similarly, apolipoprotein E expression increases in neurotoxicity mediated by KA (Table 6.3) (Boschert et al., 1999). Apolipoprotein E is a major lipoprotein in the brain. It is involved in the transport, distribution, and other aspects of cholesterol homeostasis. Apolipoprotein E also plays a dominant role in the mobilization and redistribution of brain lipids in repair, growth, and maintenance of nerve cells (Mahley, 1988). The secretion of apolipoproteins E and D may be differentially regulated in cultured astrocytes. In cell culture systems this depends upon the extracellular lipid milieu (Patel et al., 1995). During neurotoxicity mediated by KA, apolipoprotein E levels increase moderately in astrocytes and apolipoprotein E mRNA increases very strongly in clusters of CA1 and CA3 pyramidal neurons. Based on hybridization in situ and immunohistochemical studies, expression of apolipoprotein E in neurons may be a part of a rescue program to counteract neurodegeneration mediated by KA (Boschert et al., 1999). 

Calcium is a unique cation in living systems because of it dominant role in intracellular signaling. Therefore bone cells which must handle massive amounts of this mineral take special care in its regulation. Sustained elevation of intracellular calcium leads to cell death that is not effectively opposed by the usual regulators of apoptosis. We have undertaken to present what is known about how bone cells deal with calcium. However much remains to be learned and the acquisition of this knowledge will inform our treatment of many important medical conditions. 

ATP has a ubiquitous and dominant role in cellular metabolism. This role can be appreciated more fully if cognizance is extended to the energy requirements of cells, to the regulation of cellular activity and metabolism imposed by ATP, and to what interference with ATP production means to the growth of a chloro-phyllous plant. Plants store oxidative and photochemical energy in the terminal phosphate bonds of ATP. The terminal bond energy is used subsequently to perform the chemical, mechanical, and osmotic work of the cell. 

We have seen how interactions between DNA-binding proteins such as CAP and RNA polymerase can activate transcription in prokaryotic cells (Section 31.1.6). Such protein-protein interactions play a dominant role in eukaryotic gene regulation. In contrast with those of prokaryotic transcription, few eukaryotic transcription factors have any effect on transcription on their own. Instead, each factor recruits other proteins to build up large complexes that interact with the transcriptional machinery to activate or repress Panscription. 

Collectively, these studies suggest that COX-2 plays a dominate role in the regulation of salt and water excretion in prostaglandin dependent patient, while the role of COX-1 seems to involve the regulation of renal hemodynamics, including GFR. The Swan et al. [127] study suggests that COX-2 may also play a role in regulating GFR however, the combination of elderly patients who are salt depleted may have provided a more severe hemodynamic stress than was present in the other three studies. 

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