Cellular events, regulation

Although blood pressure control follows Ohm s law and seems to be simple, it underlies a complex circuit of interrelated systems. Hence, numerous physiologic systems that have pleiotropic effects and interact in complex fashion have been found to modulate blood pressure. Because of their number and complexity it is beyond the scope of the current account to cover all mechanisms and feedback circuits involved in blood pressure control. Rather, an overview of the clinically most relevant ones is presented. These systems include the heart, the blood vessels, the extracellular volume, the kidneys, the nervous system, a variety of humoral factors, and molecular events at the cellular level. They are intertwined to maintain adequate tissue perfusion and nutrition. Normal blood pressure control can be related to cardiac output and the total peripheral resistance. The stroke volume and the heart rate determine cardiac output. Each cycle of cardiac contraction propels a bolus of about 70 ml blood into the systemic arterial system. As one example of the interaction of these multiple systems, the stroke volume is dependent in part on intravascular volume regulated by the kidneys as well as on myocardial contractility. The latter is, in turn, a complex function involving sympathetic and parasympathetic control of heart rate intrinsic activity of the cardiac conduction system complex membrane transport and cellular events requiring influx of calcium, which lead to myocardial fibre shortening and relaxation and affects the humoral substances (e.g., catecholamines) in stimulation heart rate and myocardial fibre tension. 

Additional cellular events linked to the activity of blood pressure regulating substances involve membrane sodium transport mechanisms Na+/K.+ ATPase Na+fLi countertransport Na+ -H exchange Na+-Ca2+ exchange Na+-K+ 2C1 transport passive Na+ transport potassium channels cell volume and intracellular pH changes and calcium channels. 

Brain development occurs in a complex series of events regulated by cellular and environmental interactions (Levitt, 1998). Most abused substances readily cross the placenta. Many are concentrated in the amniotic fluid and metabolized less efficiently by the fetus, exacerbating the teratogenic consequences of exposure. The effects of prenatal exposure to drugs of abuse... 

Investigate the cellular events involved in the regulation of the mouse AhR in vivo... 

Dendritic cells, depending on their degree of maturation, may or may not secrete the contents of the MVE. Rather than being released in the extracellular medium, intralumenal vesicles contained in MIIC compartment can fuse back with the limiting membrane of the multivesicular structure (Kleijmeer et al. 2001). The tetraspanins CD9 and CD81, which have been shown to be involved in cell fusion regulation (Rubinstein etal. 2006), could participate in this cellular event. Moreover, this process of back fusion is related to activation and maturation of dendritic cells. As a consequence, the intracellular exosomal pool of MHC class II molecules (>50% of the total pool in immature DC) rapidly redistributes to the plasma membrane (Kleijmeer et al. 2001). Thus in both cases, dendritic cells and red cells use exosomes to remodel their surface as a function of their differentiation requirements. 

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