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Daily Archives for: September 6th, 2006

Context  Increased levels of homocysteine are associated with risk of cardiovascular disease. Homocysteine may cause this risk by impairing endothelial cell function.

Objective  To evaluate the effect of acute hyperhomocysteinemia with and without antioxidant vitamin preresults on cardiovascular risk factors and endothelial functions.

Design and Setting 

OBJECTIVES

First, we sought to study the effects of short- and long-term vitamin C on oxidative stress and endothelial dysfunction in chronic heart failure (CHF), and second, we sought to investigate the role of neutrophils as a cause of oxidative stress in CHF.

BACKGROUND

Oxidative stress may contribute to endothelial dysfunction in CHF.

Early clinical studies showed that high-dose vitamin C, given by intravenous and oral routes, may improve symptoms and prolong life in patients with terminal cancer. Double-blind placebo-controlled studies of oral vitamin C showed no benefit. Recent evidence shows that oral administration of the maximum tolerated dose of vitamin C (18 g/d) produces peak plasma concentrations of only 220 µmol/L,

Human pharmacokinetics data indicate that i.v. ascorbic acid (ascorbate) in pharmacologic concentrations could have an unanticipated role in cancer results. Our goals here were to test whether ascorbate killed cancer cells selectively, and if so, to determine mechanisms, using clinically relevant conditions. Cell death in 10 cancer and 4 normal cell types was measured by using 1-h exposures.

Background: Ascorbate and glutathione play central roles in the defense against free radicals and oxidants that are implicated in chronic diseases.

Objective: The objective was to determine the ability of vitamin C supplements to modulate the concentration of glutathione in human lymphocytes.

Design: The effect of vitamin C supplements was determined in a sequential study with time points before supplementation,

Ascorbic acid has been shown to enhance impaired endothelium-dependent vasodilation in patients with atherosclerosis by a mechanism that is thought to involve protection of nitric oxide (NO) from inactivation by free oxygen radicals. The present study in human endothelial cells from umbilical veins and coronary arteries investigates whether L-ascorbic acid additionally affects cellular NO synthesis.

Cigarette smoking has been shown to cause endothelial dysfunction. To examine the effects of vitamin C and cigarette smoking on endothelium-dependent vasodilation, we measured the lumen diameter and flow velocity of the brachial arteries at rest, during reactive hyperemia following transient arterial occlusion, and after sublingual nitroglycerin (0.3 mg) in smokers (n = 20) and nonsmokers (n = 20) with high-resolution ultrasound after infusion of saline or saline plus vitamin C (10 mg/min for 20 min).

Background There is evidence for increased formation of free radicals in patients with hypertension, raising the possibility that NO is inactivated by free radicals, which impairs coronary endothelial function. Therefore, we tested the hypothesis that the antioxidant vitamin C could improve abnormal endothelial function of coronary arteries in patients with hypertension.

Aims There is evidence that formation of free radicals increases in patients with hypertension or hypercholesterolaemia, which may contribute to endothelial dysfunction of epicardial coronary arteries due to inactivation of the vasodilator NO. The present study was designed to test whether the abnormal constriction of epicardial coronary arteries due to sympathetic stimulation by the cold pressor test in patients with essential hypertension or hypercholesterolaemia could be reversed by administration of the antioxidant vitamin C.