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Chronic Increase (chronic + increase)
Selected AbstractsReactive Oxygen Species Are Necessary for High Flow (Shear Stress)-induced Diameter Enlargement of Rat Resistance ArteriesMICROCIRCULATION, Issue 5 2009ERIC J. BELIN DE CHANTEMÈLE ABSTRACT Objectives: Chronic increases in blood flow induce remodeling associated with increases in diameter and endothelium-mediated dilation. Remodeling requires cell growth and migration, which may involve reactive oxygen species (ROS). Nevertheless, the role of ROS in flow-mediated remodeling in resistance arteries is not known. Materials and Methods: Rat mesenteric resistance arteries (MRAs) were exposed to high flow (HF) by sequentially ligating second-order MRAs in vivo. After three weeks, arteries were collected for structural, pharmacological, and biochemical analysis. Results: In HF arteries, luminal diameter (431±12 to 553±14 ,m; n=10), endothelium (acetylcholine)-mediated vasodilatation (61±6 to 77±6% relaxation) and NAD(P)H subunit (gp91phox and p67phox) expression levels, and ROS (dihydroethydine microphotography) and peroxynitrite (3-nitro-tyrosine) production were higher than in normal flow arteries. Acute ROS scavenging with tempol improved acetylcholine-dependent relaxation (92±4% relaxation), confirming that ROS are produced in HF arteries. Chronic treatment with tempol prevented the increase in diameter, reduced ROS and peroxynitrite production, and improved endothelium-mediated relaxation in HF arteries. Thus, ROS and NO were involved in HF-induced diameter enlargement, possibly through the formation of peroxynitrite, while ROS reduced the increase in endothelium-dependent relaxation. Conclusions: ROS production is necessary for flow-mediated diameter enlargement of resistance arteries. However, ROS counteract, in part, the associated improvement in endothelium-mediated relaxation. [source] Urodynamic evaluation of the human bladder response tgo an increase in outlet resistanceNEUROUROLOGY AND URODYNAMICS, Issue 6 2002Jason D. Engel Abstract Aim. We prospectively evaluated the response of the human bladder to a chronic increase in urethral resistance according to the indices of pressure, volume flow rate, total (external) bladder work, and maximum and average detrusor power. Methods. Six men with incontinence after radical prostatectomy were evaluated urodynamically before and 3,6 months after undergoing a bulbourethral sling procedure. Results. None of the men suffered from significant obstructive or irritative voiding symptoms preoperatively. Urodynamic evaluation showed postoperative increases in both average detrusor pressure and pressure at maximum flow, but there were no significant changes in voided volume, void time, or postvoid residual urine volume. Maximum detrusor power, average detrusor power, and total (external) bladder work were all significantly increased. Conclusion. These data confirm that the human bladder possesses a functional reserve, which is elicited by an increase in urethral resistance. Neurourol. Urodynam. 21:524,528, 2002. © 2002 Wiley-Liss, Inc. [source] Aldosterone synthase gene variation and adrenocortical response to sodium status, angiotensin II and ACTH in normal male subjectsCLINICAL ENDOCRINOLOGY, Issue 2 2004Brian Kennon Summary objective, Aldosterone synthase, a key enzyme in the terminal steps of aldosterone synthesis, is encoded by the CYP11B2 gene. A polymorphism in the 5, coding region of this gene (,344 C/T) is associated with hypertension, particularly with elevation of the aldosterone to renin ratio. A second polymorphism (a conversion in intron 2 to resemble that of the neighbouring 11,-hydroxylase (CYP11B1) gene) is found in close linkage dysequilibrium with the variant at ,344 C/T. The mechanism by which these variants predispose to cardiovascular disease and the precise intermediate phenotype associated with them remains speculative. design, We performed a focused physiological study in normal volunteers stratified by CYP11B2 genotype. patients, Twenty-three subjects homozygous for the T allele and 21 homozygous for the C allele of the ,344 C/T polymorphism of CYP11B2 were studied. measurements, Basal and angiotensin II stimulated plasma and 24-h urinary steroid excretion during low (60 mmol/day) and high (160 mmol/day) sodium intake and plasma steroids after ACTH stimulation were measured. results, No influence of polymorphic variation on basal or stimulated plasma cortisol or aldosterone or other plasma steroid concentrations during either dietary phase was seen. However, excretion of tetrahydro-11-deoxycortisol (the urinary metabolite of 11-deoxycortisol), which is the precursor of cortisol) was increased in TT subjects during sodium restriction, consistent with impairment of zona fasciculata 11,-hydroxylation. conclusions, We conclude that this polymorphism has no major influence on normal zona glomerulosa function but is associated with a change in 11,-hydroxylation in the zona fasciculata. The mechanism remains uncertain, but alteration of 11-deoxycortisol levels without change in cortisol suggests altered efficiency of 11,-hydroxylation. In the long term, this may lead to a minor but chronic increase in ACTH drive to the gland, which may have consequences for steroid synthesis and predispose to the risk of cardiovascular disease. [source] Chest pain is inversely associated with blood pressure during exercise among individuals being assessed for coronary heart diseasePSYCHOPHYSIOLOGY, Issue 2 2007Blaine Ditto Abstract Acute and chronic increases in blood pressure have been related to decreases in pain perception. This phenomenon has been studied primarily using acute experimental pain stimuli. To extend the literature to naturalistic pain and in particular the problem of silent cardiac ischemia, this study examined the relationship between blood pressure and chest pain during exercise stress testing. Nine hundred seven (425 men, 482 women) individuals undergoing exercise stress testing for diagnosis of possible myocardial ischemia completed the McGill Pain Questionnaire (MPQ) immediately afterward and other questionnaires before and after testing. Blood pressure was measured before, during, and after exercise. Systolic blood pressure at the end of exercise was inversely related to a number of measures of pain such as total score on the MPQ. The relationship could not be explained by individual differences in exercise duration, medication use, sex, or other measured variable. In sum, the inverse relationship between blood pressure and sensitivity to pain that has been observed in other populations in experimental and naturalistic conditions was observed for chest pain during exercise. Blood pressure may contribute to episodes of silent ischemia. [source] | ||||||||||