Effects of atorvastatin on vascular function, inflammation, and androgens in women with polycystic ovary syndrome: a double-blind, randomized, placebo-controlled trial.

To determine the effects of statins on vascular function, inflammation, and androgen levels in women with polycystic ovary syndrome (PCOS), we randomized 20 women with PCOS who had low-density lipoprotein cholesterol levels >100 mg/dL to atorvastatin (40 mg/day) or placebo for 6 weeks and found that atorvastatin reduced androgen levels, biomarkers of inflammation, and blood pressure; increased insulin levels and brachial artery conductance during reactive hyperemia; and failed to improve brachial artery flow-mediated dilation. We conclude that until additional studies demonstrate a clear risk-to-benefit ratio favoring statin therapy in PCOS, statins should only be used in women with PCOS who meet current indications for statin treatment.

Brachial artery conductance during reactive hyperemia is increased in women with polycystic ovary syndrome.

Objective: To examine changes in brachial artery conductance (BAC) during reactive hyperemia in women with polycystic ovary syndrome (PCOS) compared to controls.

Study Design: This is a pilot case-control study performed at a single academic medical center. Changes in BAC during reactive hyperemia were evaluated in 31 women with PCOS and 11 healthy control women.

Hypoxia-induced vasodilation and effects of regional phentolamine in awake patients with sleep apnea.

Obstructive sleep apnea (OSA) is associated with increased sympathetic nerve activity, endothelial dysfunction, and premature cardiovascular disease. To determine whether hypoxia is associated with impaired skeletal muscle vasodilation, we compared femoral artery blood flow (ultrasound) and muscle sympathetic nerve activity (peroneal microneurography) during exposure to acute systemic hypoxia (fraction of inspired oxygen 0.1) in awake patients with OSA (n=10) and controls (n=8).

A real-time device for converting Doppler ultrasound audio signals into fluid flow velocity.

A Doppler signal converter has been developed to facilitate cardiovascular and exercise physiology research. This device directly converts audio signals from a clinical Doppler ultrasound imaging system into a real-time analog signal that accurately represents blood flow velocity and is easily recorded by any standard data acquisition system. This real-time flow velocity signal, when simultaneously recorded with other physiological signals of interest, permits the observation of transient flow response to experimental interventions in a manner not possible when using standard Doppler imaging devices.

Vasoconstrictor responses in the upper and lower limbs to increases in transmural pressure.

The purpose of this study was to examine upper and lower limb vasoconstrictor responses to changes in transmural pressure in humans. Brachial and femoral blood mean blood velocity (MBV) and vessel diameter (Doppler ultrasound) were measured in 20 supine healthy subjects (10 men and 10 women; 27 +/- 1 yr; mean +/- SE) during four levels of limb suction at -25, -50, -75, and -100 mmHg, respectively. Limb suction led to an initial rise in MBV followed by a rapid fall in flow velocity to a level below MBV baseline, indicating a vasoconstriction effect.

Metabolic forearm vasodilation is enhanced following Bier block with phentolamine.

The extent to which sympathetic nerve activity restrains metabolic vasodilation in skeletal muscle remains unclear. We determined forearm blood flow (FBF; ultrasound/Doppler) and vascular conductance (FVC) responses to 10 min of ischemia [reactive hyperemic blood flow (RHBF)] and 10 min of systemic hypoxia (inspired O(2) fraction = 0.1) before and after regional sympathetic blockade with the alpha-receptor antagonist phentolamine via Bier block in healthy humans.

The role of the cyclooxygenase products in evoking sympathetic activation in exercise.

Animal studies suggest that prostaglandins in skeletal muscles stimulate afferents and contribute to the exercise pressor reflex. However, human data regarding a role for prostaglandins in this reflex are varied, in part because of systemic effects of pharmacological agents used to block prostaglandin synthesis. We hypothesized that local blockade of prostaglandin synthesis in exercising muscles could attenuate muscle sympathetic nerve activity (MSNA) responses to fatiguing exercise.

Short-term intermittent hypoxia enhances sympathetic responses to continuous hypoxia in humans.

Short-term intermittent hypoxia leads to sustained sympathetic activation and a small increase in blood pressure in healthy humans. Because obstructive sleep apnea, a condition associated with intermittent hypoxia, is accompanied by elevated sympathetic activity and enhanced sympathetic chemoreflex responses to acute hypoxia, we sought to determine whether intermittent hypoxia also enhances chemoreflex activity in healthy humans. To this end, we measured the responses of muscle sympathetic nerve activity (MSNA, peroneal microneurography) to arterial chemoreflex stimulation and deactivation before and following exposure to a paradigm of repetitive hypoxic apnea (20 s/min for 30 min; O(2) saturation nadir 81.

Sympathetic chemoreflex responses in obstructive sleep apnea and effects of continuous positive airway pressure therapy.

Background: Sympathetic nerve activity is increased in awake and regularly breathing patients with obstructive sleep apnea (OSA). Over time, repetitive hypoxic stress could alter sympathetic chemoreflex function in OSA.

Methods: We determined the responses to acute hypoxia (fraction of inspired oxygen of 0.

Effects of an oral glucose tolerance test on the myogenic response in healthy individuals.

The myogenic response, the inherent ability of blood vessels to rapidly respond to changes in transmural pressure, is involved in local blood flow autoregulation. Animal studies suggest that both acute hyperglycemia and hyperinsulinemia may impair myogenic vasoconstriction. The purpose of this study was to examine the effects of an oral glucose load on brachial mean blood velocity (MBV) during increases in forearm transmural pressure in humans.

Effects of intermittent hypoxia on sympathetic activity and blood pressure in humans.

Sympathetic nerve activity and arterial pressure are frequently elevated in patients with obstructive sleep apnea (OSA). The mechanisms responsible for chronic sympathetic activation and hypertension in OSA are unknown. To determine whether repetitive apneas raise sympathetic nerve activity and/or arterial pressure, awake and healthy young subjects performed voluntary end-expiratory apneas for 20 s per min for 30 min (room air apneas).

Heterogeneous vasodilator responses of human limbs: influence of age and habitual endurance training.

Forearm endothelium-dependent vasodilation is impaired with age in sedentary, but not endurance-trained, men. The purpose of this investigation was to determine whether these age- and physical activity-related differences in endothelium-dependent vasodilation also occur in the leg. Brachial and common femoral arterial blood flow were measured with Doppler ultrasound during increasing doses of acetylcholine (1, 4, and 16 microg.

Different vasodilator responses of human arms and legs.

Forearm vascular responses to intra-arterial infusions of endothelium-dependent and -independent vasodilators have been thoroughly characterized in humans. While the forearm is a well-established experimental model for studying human vascular function, it is of limited consequence to systemic cardiovascular control owing to its small muscle mass and blood flow requirements. In the present study we determined whether these responses could be generalized to the leg.

Sympathetic responses to Valsalva's manoeuvre following bed rest.

The purpose of this study was to examine whether 14 days of head-down tilt bed rest (HDBR) alters autonomic regulation during Valsalva's manoeuvre (VM) and if this would predict blood pressure control during a 60 degrees head-up tilt (HUT) test. To examine autonomic control of blood pressure, we measured the changes in systolic (delta SBP) and diastolic (delta DBP) blood pressure between baseline and the early straining (Phase IIE) period of VM (20 sec straining to 40 mmHg; N = 7) in conjunction with changes in muscle sympathetic nerve activity (MSNA; microneurography) burst frequency (B/min) and total activity (% delta) from baseline over the 20-sec straining period. MSNA data were successfully recorded from 6 of the 7 individuals.

Autonomic and vascular responses to reduced limb perfusion.

The purpose of this study was to examine hemodynamic responses to graded muscle reflex engagement in human subjects. We studied seven healthy human volunteers [24 +/- 2 (SE) yr old; 4 men, 3 women] performing rhythmic handgrip exercise [40% maximal voluntary contraction (MVC)] during ambient and positive pressure exercise (+10 to +50 mmHg in 10-mmHg increments every minute). Muscle sympathetic nerve activity (MSNA), mean arterial blood pressure (MAP), and mean blood velocity were recorded.

Aging and the exercise pressor reflex in humans.

Background: Blood flow limitation to exercising muscles engages the muscle reflex during exercise, evoking an increase in heart rate (HR), blood pressure (BP), and muscle sympathetic nerve activity (MSNA).

Methods And Results: In the current study, we examined forearm flow and autonomic responses to ischemic handgrip in young and older subjects. We studied 6 younger subjects (mean age 23.

Venous plasma potassium is not associated with maintenance of the exercise pressor reflex in humans.

Increases in the concentration of interstitial potassium concentration during exercise may play a role in the modulation of the cardiovascular response to exercise. However, it is not known if changes in potassium correlate with indexes of muscle reflex engagement. Eight healthy subjects performed dynamic [rhythmic handgrip (RHG)] and static handgrip (SHG) exercise at 40% of maximal voluntary contraction.

Attenuated sympathetic nerve responses after 24 hours of bed rest.

Bed rest reduces orthostatic tolerance. Despite decades of study, the cause of this phenomenon remains unclear. In this report we examined hemodynamic and sympathetic nerve responses to graded lower body negative pressure (LBNP) before and after 24 h of bed rest.