Control mechanisms compensatory

In addition to excess sodium intake, abnormal renal sodium retention may be the primary event in the development of hypertension, and it includes abnormalities in the pressure-natriuresis mechanism. In hypertensive individuals, this theory proposes a shift in the control mechanism preventing the normalization of blood pressure. The mechanisms behind the resetting of the pressure-natriuresis curve may include afferent arteriolar vasoconstriction, decreased glomerular ultrafiltration, or an increase in tubular sodium reabsorption.4 Other theories supporting abnormal renal sodium retention suggest a congenital reduction in the number of nephrons, enhanced renin secretion from nephrons that are ischemic, or an acquired compensatory mechanism for renal sodium retention.9... 

Because the control mechanisms that attempt to maintain blood pressure constant are intact in patients with pheochromocytoma (they are reset in patients with ordinary hypertension), a number of compensatory changes are observed in pheochromocytoma patients tsee Figure 6 ). These include reduced renin, angiotensin, and aldosterone levels in the blood. With the reduced aldosterone effect on the kidney, more salt and water is excreted, reducing blood volume. Since the red cell mass is not affected, hematocrit is often increased. If the tumor releases only norepinephrine, a compensatory bradycardia may also be present, but most patients release enough epinephrine to maintain heart rate at a normal or even increased level. 

Maintain an open ainway and assist ventilation if necessary (see pp 1-7). Warning Ensure adequate ventilation to prevent respiratory acidosis, and do not allow controlled mechanical ventilation to interfere with the patienf s need for compensatory efforts to maintain the semm pH. Administer supplemental oxygen. Obtain serial arterial blood gases and chest x-rays to obsenre for pulmonary edema (more common with chronic or severe intoxication). 

The spreader most commonly found in the rubber industry has a working width across the application roller/blade of 1.5 metres. Wider spreaders (up to 4 metres) exist for very wide cloth coating but they require special control of the bending of the doctor blade and have compensatory mechanisms to overcome this problem. 

Abstract For more than a half century, tobacco manufacturers have conducted sophisticated internal research to evaluate nicotine delivery, and modified their products to ensure availability of nicotine to smokers and to optimize its effects. Tobacco has proven to be a particularly effective vehicle for nicotine, enabling manipulation of smoke chemistry and of mechanisms of delivery, and providing sensory cues that critically inform patterns of smoking behavior as well as reinforce the impact of nicotine. A range of physical and chemical product design changes provide precise control over the quantity, form, and perception of nicotine dose, and support compensatory behavior, which is driven by the smoker s addiction to nicotine. Cigarette... 

Signal transduction pathways and protein regulatory networks are not linear (26) but contain branches, negative feedback loops, and common points of connection between seemingly parallel pathways known as nodes. Furthermore, these pathways and networks are tightly controlled within cells so that disruption of any point has a rippling effect often activating compensatory mechanisms... 

The a-blocker phentolamine (83-3) was used fairly extensively as an antihypertensive agent prior to the availability of more effective and far better tolerated drugs. Some of the most important side effects from use of this drug, such as fluid retention and tachycardia, were at that time attributed to compensatory mechanisms, casting a cloud on all a-blockers. The use of this class of agents for controlling elevated blood... 

Mezzanotte WS, Tangel DJ, White DP (1992) Waking genioglossal electromyogram in sleep apnea patients versus normal controls (a neuromuscular compensatory mechanism). J Clin Invest 89 1571-1579... 

The relatively mild phenotype of these mice suggests a minor role of ASP in TAG storage and mobilization control or the existence of compensatory mechanisms rescuing part of the physiological function of ASP. 

One remaining problem with tissue-specific null mutants that exploit the Cre/ lox-P system is that early excision at the time of birth of sensory neurons may allow developmental compensatory mechanisms to occur, again complicating phenotypic analysis, particularly in terms of behaviour. It would thus be ideal to be able to delete genes in adult animals, whose behaviour under control conditions has already been assessed. Recent advances in gene dehvery suggest that this approach may be feasible. 

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