Centrality dependence of pi(+/-), K(+/-), p, and (-)p production from sqrt[s(NN)] = 130 GeV Au + Au collisions at RHIC

Identified pi(+/-), K(+/-), p, and (-)p transverse momentum spectra at midrapidity in sqrt[s(NN)] = 130 GeV Au+Au collisions were measured by the PHENIX experiment at RHIC as a function of collision centrality. Average transverse momenta increase with the number of participating nucleons in a similar way for all particle species. Within errors, all midrapidity particle yields per participant are found to be increasing with the number of participating nucleons. There is an indication that K(+/-), p, and (-)p yields per participant increase faster than the pi(+/-) yields. In central collisions at high transverse momenta (p(T) > or =2 GeV/c), (-)p and p yields are comparable to the pi(+/-) yields.

Transverse-mass dependence of two-pion correlations in Au+Au collisions at square root[s(NN)] = 130 GeV

Two-pion correlations in square root[s(NN)] = 130 GeV Au+Au collisions at RHIC have been measured over a broad range of pair transverse momentum k(T) by the PHENIX experiment at RHIC. The k(T) dependent transverse radii are similar to results from heavy-ion collisions at square root[s(NN)] = 4.1, 4.9, and 17.3 GeV, whereas the longitudinal radius increases monotonically with beam energy. The ratio of the outwards to sidewards transverse radii (R(out)/R(side)) is consistent with unity and independent of k(T).

Measurement of single electrons and implications for charm production in Au+Au collisions at square root[s(NN)] = 130 GeV

Transverse momentum spectra of electrons from Au+Au collisions at square root[s(NN)] = 130 GeV have been measured at midrapidity by the PHENIX experiment at the Relativistic Heavy Ion Collider. The spectra show an excess above the background from photon conversions and light hadron decays. The electron signal is consistent with that expected from semileptonic decays of charm. The yield of the electron signal dN(e)/dy for p(T) > 0.8 GeV/c is 0.025+/-0.004(stat)+/-0.010(syst) in central collisions, and the corresponding charm cross section is 380+/-60(stat)+/-200(syst) microb per binary nucleon-nucleon collision.

Lambda spectra in 11.6A GeV/c Au-Au collisions

E896 has measured Lambda production in 11.6A GeV/c Au-Au collisions over virtually the whole rapidity phase space. The midrapidity p(t) distributions have been measured for the first time at this energy and appear to indicate that the Lambda hyperons have different freeze-out conditions than protons. A comparison with the relativistic quantum molecular dynamics model shows that while there is good shape agreement at high rapidity the model predicts significantly different slopes of the m(t) spectra at midrapidity. The data, where overlap occurs, are consistent with previously reported measurements.

Patient satisfaction with store-and-forward teledermatology

We assessed patient satisfaction with a nurse-led store-and-forward teledermatology service in Manchester. A teledermatology nurse obtained the patient's history, took digital photographs of the patient's skin lesion and then sent the information to a hospital dermatologist, who responded with management advice the following week. Of 141 patients who attended their teledermatology appointment, 123 (50 male, 73 female) completed the study questionnaire (87%). The average age of respondents was 42 years (SD 17, range 18-90 years). Ninety-three per cent reported that they were happy with the teleconsultation while 86% reported that it was more convenient than going to the outpatient clinic. Forty per cent agreed that they would feel more comfortable seeing the dermatologist in person while only 58% were comfortable with not speaking to the dermatologist about their skin condition. The absence of interaction with the dermatologist and the delay in receiving management advice may have contributed to the somewhat low satisfaction rates.

Patient satisfaction with store-and-forward teledermatology

We assessed patient satisfaction with a nurse-led store-and-forward teledermatology service in Manchester. A teledermatology nurse obtained the patient's history, took digital photographs of the patient's skin lesion and then sent the information to a hospital dermatologist, who responded with management advice the following week. Of 141 patients who attended their teledermatology appointment, 123 (50 male, 73 female) completed the study questionnaire (87%). The average age of respondents was 42 years (SD 17, range 18-90 years). Ninety-three per cent reported that they were happy with the teleconsultation while 86% reported that it was more convenient than going to the outpatient clinic. Forty per cent agreed that they would feel more comfortable seeing the dermatologist in person while only 58% were comfortable with not speaking to the dermatologist about their skin condition. The absence of interaction with the dermatologist and the delay in receiving management advice may have contributed to the somewhat low satisfaction rates.

Suppression of hadrons with large transverse momentum in central Au+Au collisions at root square[s(NN)] = 130 GeV

Transverse momentum spectra for charged hadrons and for neutral pions in the range 1 GeV/c<p(T)<5 GeV/c have been measured by the PHENIX experiment at RHIC in Au+Au collisions at root square[s(NN)] = 130 GeV. At high p(T) the spectra from peripheral nuclear collisions are consistent with scaling the spectra from p+p collisions by the average number of binary nucleon-nucleon collisions. The spectra from central collisions are significantly suppressed when compared to the binary-scaled p+p expectation, and also when compared to similarly binary-scaled peripheral collisions, indicating a novel nuclear-medium effect in central nuclear collisions at RHIC energies.

Interventions for preventing obesity in children

BACKGROUND

The prevalence of obesity and overweight is increasing in both adult and child populations throughout the world. Obesity in children impacts on their health in both the short and longer term, and obesity prevention is an international public health priority. However, the efficacy of prevention strategies is poorly understood.

OBJECTIVES

To assess the effectiveness of educational, health promotion and/or psychological/family/behavioural therapy/counselling/management interventions that focussed on diet, physical activity and/or lifestyle and social support, and were designed to prevent obesity in childhood.

SEARCH STRATEGY

The following databases were searched: MEDLINE, Psyclit, EMBASE, Science Citation Index, Social Science Citation Index, CINAHL, Cochrane Controlled Trials Register (CCTR) and the Cochrane Heart Group's specialised register from 1985 to July 2001. Non English language papers were included. Experts were contacted to seek additional references or unpublished studies.

SELECTION CRITERIA

RCTs and non-randomised trials with concurrent control group that observed participants for a minimum of three months were included

DATA COLLECTION AND ANALYSIS

Two reviewers independently extracted data and assessed study quality.

MAIN RESULTS

Ten studies were included; seven were long-term (children observed for at least one year), three were shorter term (at least 3 months). Eight were school/nursery-based interventions, one was a community-based intervention targeting low-income African-American families, and one was a family-based intervention that targeted non-obese children of obese parents. The studies included were diverse in terms of study design and quality, target population, theoretical underpinning of intervention approach, and outcome measures, so it was not possible to combine study findings using statistical methods. Three of the four long-term studies that combined dietary education and physical activity interventions resulted in no difference in overweight, whereas one study reported an improvement in favour of the intervention group. In two studies of dietary education alone, a multimedia action strategy appeared to be effective but other strategies did not. The one long term study that only focussed on physical activity resulted in a slightly greater reduction in overweight in favour of the intervention group, as did two short term studies of physical activity.

REVIEWER'S CONCLUSIONS

There is limited high quality data on the effectiveness of obesity prevention programs and no generalisable conclusions can be drawn. However, concentration on strategies that encourage reduction in sedentary behaviours and increase in physical activity may be fruitful. The need for well-designed studies that examine a range of interventions remains a priority, although a number of important studies are underway.

Which common clinical conditions should medical students be able to manage by graduation? A perspective from Australian interns

The objectives of the study were to report the development of a core curriculum that details the clinical conditions medical students should be able to manage upon graduation; and to canvass the opinion of interns (first-year postgraduate doctors) regarding their perceptions of the level of skill required to manage each condition. Literature relating to core curriculum development and training of junior medical officers was reviewed and stakeholders in the education and training of medical students and junior doctors in the state of New South Wales, Australia (intern supervisors, academics, registrars, nurses and interns) were consulted. The final curriculum spanned 106 conditions, 77 'differentiated' and 29 'undifferentiated'. Four levels of skill at which conditions should potentially be managed were also identified: 'Theoretical knowledge only'; 'Recognize symptoms and signs without supervision'; Initiate preliminary investigations, management and/or treatment without supervision'; and 'Total investigation, management and/or treatment without supervision'. The list of conditions in the curriculum was converted to a survey format and a one-in-two random sample of interns (n = 193) practising in New South Wales who graduated from the state's three medical schools were surveyed regarding the level of skill required for managing each clinical condition at graduation. A total of 51.3% of interns responded to the survey. Interns felt they should be able to initiate preliminary investigation, management and/or treatment for most conditions in the curriculum, with more than half acknowledging this level of management for 53 of the differentiated and 28 of the undifferentiated conditions. It is concluded that developing core curricula in medical education can involve multiple stakeholders, including junior doctors as the consumers of educational experiences. The data gathered may be useful to medical schools revising their curricula.

Patient satisfaction with teledermatology is related to perceived quality of life

BACKGROUND

There is a lack of good data about patient satisfaction with teledermatology and about its potential interaction with quality-of-life factors.

OBJECTIVES

To assess the association between perceived skin-related quality of life and patient satisfaction with a nurse-led teledermatology service.

METHODS

In a mobile nurse-led teledermatology clinic located in four inner city general practices in Manchester, the teledermatology service used digital cameras to capture and store images of skin conditions for remote diagnosis by dermatologists. One hundred and twenty-three adult patients, non-urgent dermatology referrals from primary care, completed the Dermatology Life Quality Index (DLQI) and a 15-item patient satisfaction questionnaire.

RESULTS

In common with other studies of patient satisfaction, subjects reported highly favourable views of 'hotel' aspects of the service (93%) and found it 'convenient' (86%). However, 40% of patients would have preferred to have had a conventional face-to-face consultation with a dermatologist, and 17% felt unable to speak freely about their condition. Patient satisfaction with the service was related to quality of life. Patients reporting lower quality of life as measured by the DLQI were more likely to prefer a face-to-face encounter with a dermatologist (r = 0.216, P < 0.05), and to evince anxiety about being photographed (r = 0.223, P < 0.05).

CONCLUSIONS

Patient acceptance and satisfaction with telemedicine services is complicated by patients' subjective health status. Telehealthcare providers need to recognize that patients with poor quality of life may want and benefit from face-to-face interaction with expert clinicians.

Selective cannabinoid CB1 receptor activation inhibits spinal nociceptive transmission in vivo

Cannabinoid1 (CB1) receptors are located at CNS sites, including the spinal cord, involved in somatosensory processing. Analgesia is one of the tetrad of behaviors associated with cannabinoid agonists. Here, effects of a potent cannabinoid CB1 receptor agonist arachidonyl-2-chloroethylamide (ACEA) on evoked responses of dorsal horn neurons in anesthetized rats were investigated. Extracellular recordings of convergent dorsal horn neurons were made in halothane anesthetized Sprague-Dawley rats (n = 16). Effects of spinal application of ACEA on electrically evoked responses of dorsal horn neurons were studied. Mean maximal effects of 0.5, 5, 50, and 500 ng/50 microl ACEA on the C-fiber-mediated postdischarge response were 79 +/- 6, 62 +/- 10, and 54 +/- 7% (P < 0.01), 45 +/- 6% (P < 0.01), of control, respectively. ACEA (500 ng/50 microl) also reduced the C-fiber-evoked nonpotentiated responses of neurons (59 +/- 9% of control, P < 0.05) and Adelta-fiber-evoked responses of neurons (68 +/- 10% of control, P < 0.01). Minor effects of ACEA on Abeta-fiber-evoked responses were observed. Spinal pre-administration of the selective CB1 receptor antagonist SR141716A (0.01 microg/50 microl) significantly reduced effects of ACEA (500 ng/50 microl) on postdischarge responses of dorsal horn neurons. This study demonstrates that spinal CB1 receptors modulate the transmission of C- and Adelta-fiber-evoked responses in anesthetized rats; this may reflect pre- and/or postsynaptic effects of cannabinoids on nociceptive transmission. CB1 receptors inhibit synaptic release of glutamate in rat dorsolateral striatum, a similar mechanism of action may underlie the effects of ACEA on noxious evoked responses of spinal neurons reported here.

Nonselective versus selective beta-adrenergic receptor blockade in congestive heart failure: differential effects on sympathetic activity

BACKGROUND

Activation of the sympathetic nervous system has important prognostic implications in chronic heart failure. Nonselective versus selective beta-adrenergic receptor antagonists may have differential effects on norepinephrine release from nerve terminals mediated by prejunctional beta(2)-adrenergic receptors.

METHODS AND RESULTS

Thirty-six patients with chronic heart failure were randomized to the nonselective beta-blocker carvedilol or the selective beta-blocker metoprolol (double-blind). Measurements of hemodynamics and cardiac and systemic norepinephrine spillover as well as microneurographic recordings of muscle sympathetic nerve traffic were made before and after 4 months of therapy. In the carvedilol group (n=17), there were significant reductions in both total body (-1.7+/-0.5 nmol/min, P<0.01) and cardiac norepinephrine spillover (-87+/-29 pmol/min, P<0.01). By contrast, in the metoprolol group (n=14), there were no significant changes in total body or cardiac norepinephrine spillover. Responses in the carvedilol group were significantly different from those observed in the metoprolol group (P<0.05). Both agents caused a reduction in heart rate and increases in pulse pressure, although mean arterial pressure did not change. Importantly, microneurographic measures of sympathetic nerve traffic to skeletal muscle did not change in either group.

CONCLUSIONS

Therapy with carvedilol caused significant decreases in systemic and cardiac norepinephrine spillover, an indirect measure of norepinephrine release. Such changes were not observed in patients treated with metoprolol. There was no effect of either agent on sympathetic efferent neuronal discharge to skeletal muscle. These findings suggest that carvedilol, a nonselective beta-blocker, caused its sympathoinhibitory effect by blocking peripheral, prejunctional beta-adrenergic receptors.

A systematic review of the staging performance of endoscopic ultrasound in gastro-oesophageal carcinoma

BACKGROUND

Endoscopic ultrasound (EUS) may be used for preoperative staging of gastro-oesophageal carcinoma but performance values given in the literature differ.

AIMS

To identify and synthesise findings from all articles on the performance of EUS in tumour, node, metastasis (TNM) staging of gastro-oesophageal carcinoma.

SOURCE

Published and unpublished English language literature, 1981-1996.

METHODS

Data on the staging performance of EUS were retrieved and evaluated. Summary receiver operator characteristic methodology was used for synthesis, and a summary estimate of performance, Q*, obtained. Multiple regression analysis was used to assess study validity and investigate reasons for differences in performance.

RESULTS

Twenty seven primary articles were assessed in detail. Thirteen supplied results for staging oesophageal cancer, 13 for gastric cancer, and four for cancers at the gastro-oesophageal junction. For gastric T staging, Q*=0.93 (95% confidence interval (CI) 0.91-0.95) and for oesophageal T staging, Q*=0.89 (95% CI 0.88-0.92). For gastro-oesophageal T staging, including cancers at the gastro-oesophageal junction, Q*=0.91 (95% CI 0.89-0.93). Inclusion of cases with non-traversable stenosis was found to slightly reduce staging performance. For N staging, Q*=0.79 (95% CI 0.75-0.83). In articles that compared EUS directly with incremental computed tomography, EUS performed better. None of the variables assessed in the regression analysis was significant using a Bonferroni correction. Three variables (anatomical location, traversability, and blinding) showed strong relationships for future research and validation.

CONCLUSIONS

EUS is highly effective for discrimination of stages T1 and T2 from stages T3 and T4 for primary gastro-oesophageal carcinomas. The failure rate of EUS from non-traversability of a stenotic cancer may be a limitation in some patient groups.

Evidence supporting abnormalities in nitric oxide synthase function induced by nitroglycerin in humans

OBJECTIVES

We studied the effects of nitroglycerin (GTN) therapy on the response to endothelium-dependent and independent vasoactive agents in the forearm circulation of healthy subjects.

BACKGROUND

Recent evidence suggests that therapy with GTN may induce specific changes in endothelial cell function, including increased superoxide anion production and sensitivity to vasoconstrictors. Additionally, continuous GTN therapy worsens endothelial function in the coronary circulation of patients with ischemic heart disease.

METHODS

Forearm blood flow was measured with venous occlusion, mercury-in-silastic strain gauge plethysmography.

RESULTS

Sixteen male volunteers (26 +/- 6 years) were randomized to no therapy (control) or GTN, 0.6 mg/h/24 h, for six days in an investigator-blind, parallel-design study. The flow responses to brachial artery infusions of acetylcholine ([Ach] 7.5, 15.0, 30.0 microg/min), N-monomethyl-L-arginine (L-NMMA) (1, 2, 4 micromol/min) and sodium nitroprusside (SNP) (0.8, 1.6, 3.2 microg/min) were recorded. The vasodilator responses to Ach were blunted in the GTN group as compared with the control group (p < 0.05). The vasoconstrictor responses to L-NMMA were also blunted in the GTN group (p < 0.001). In the GTN group, paradoxical vasodilation was observed in response to the lowest infused concentration of L-NMMA. The vasodilator responses to SNP did not differ between groups.

CONCLUSIONS

The response to Ach confirms the hypothesis that continuous GTN causes endothelial dysfunction. The responses to L-NMMA suggest that GTN therapy causes abnormalities in nitric oxide synthase (NOS) function; the vasodilation observed at the lowest infused concentration of L-NMMA in the GTN group also suggests that continuous GTN therapy is associated with a NOS-mediated production of a vasoconstrictor.

Barriers to research implementation by community nurses

This article presents the community findings from a study of nurses in community and acute settings using Funk et al's Barriers to Research Utilization Scale (Barriers) (Funk et al, 1991a), which aimed to identify the main barriers to implementing research in practice. The Barriers questionnaire was sent to all nurses working in three community trusts in Yorkshire (n=2327), and practice nurses in one Yorkshire health authority (n=190). A 51.5% response rate gave a sample of 1297 nurses. The top two barriers were reported to be lack of time and resources. There were significant differences between sub-samples, e.g. older women perceived more barriers than younger colleagues, and practice nurses had particular problems with the cooperation of GPs. Factor analysis generated four new factors different from those found by Funk et al (1991a) (shown in brackets): benefits (nurse characteristics); quality (research characteristics); accessibility (presentation of the research characteristics) and resources (setting characteristics). Recommendations include developing nurses' critical appraisal skills so that, given more time and adequate resources, research findings might be judiciously implemented in practice.

Relation between quality of recovery in hospital and quality of life at 3 months after cardiac surgery

BACKGROUND

Improved quality of life (QoL) is a desirable outcome of cardiac surgery. The aim of the current study was to measure the association between quality of recovery 3 days after surgery and QoL measured 3 months later.

METHODS

After obtaining ethics committee approval and consent, 120 adult cardiac surgical patients were studied. A 40-item quality of recovery score (QoR-40) was used to measure postoperative health status on days 1-3 and 1 month after surgery. QoL was measured using the short-form health survey (SF-36) at 1 and 3 months after surgery. The effect size (delta mean/SD) was used to define responsiveness, a clinically important difference in health. Associations were measured using correlation and reliability coefficients.

RESULTS

There was a significant change in the mean QoR-40 for up to 1 month after surgery (P < 0.0005). QoL was improved at 3 months (P < 0.0005) but not 1 month (P = 0.29) after surgery. There was a moderate correlation between day-3 QoR-40 and 3-month SF-36 (r = 0.39; P < 0.0005). A poor-quality recovery in hospital predicted a poor QoL at 3 months (adjusted odds ratio, 4.20; 95% confidence interval, 1.41-12.5; P = 0.01).

CONCLUSIONS

The QoR-40 is a valid measure of quality of recovery after surgery and anesthesia. When compared with the SF-36, it is a better measure of early postoperative recovery. A poor-quality recovery on the days after surgery can predict a poor QoL at 3 months after surgery. This may allow earlier and more effective support strategies while patients are still in the hospital (counseling, home assistance, local doctor notification, cardiac rehabilitation).

The sinister significance of dysphagia

BACKGROUND

The majority of patients presenting with oesophageal cancer have symptoms for more than three months and advanced disease at presentation. Most appear unaware of the significance of dysphagia as a symptom. Cancer awareness programmes focus on symptoms such as lumps and bleeding.

AIM

To sample the level of public awareness of the potentially sinister significance of the symptom of dysphagia.

METHODS

A community survey was conducted using a questionnaire to evaluate the subjects' impression of the significance of dysphagia, and compare it with their perception of the significance of breast lump. Patients were stratified to male and female, under and over 45 years.

RESULTS

There were 164 subjects interviewed. Seventy-five per cent stated that they would visit their doctor within one week of developing dysphagia compared with 87 per cent questioned about a breast lump (96 per cent females, 80 per cent males). Only 17 per cent felt that cancer was a probable explanation for dysphagia compared with 80 per cent who would consider cancer a likely cause of breast lump.

CONCLUSION

There is evident need of an awareness programme of the potential significance of dysphagia if prognosis for oesophageal cancer is to be improved.

Minimal ischaemic neuronal damage and HSP70 expression in MF1 strain mice following bilateral common carotid artery occlusion

Investigation into the influence of specific genes and gene products upon the pathophysiology of cerebral ischaemia has been greatly enhanced by the use of genetically modified mice. A simple model of global cerebral ischaemia in mouse is bilateral common carotid artery occlusion (BCCAo) and the neuropathological impact of BCCAo has been investigated in several mouse strains. Bilateral carotid occlusion produces extensive neuronal damage in C57Bl/6J strain mice and this damage is linked to posterior communicating artery (PcomA) hypoplasticity in the circle of Willis. In the present study, we investigated the effect of BCCAo in MF1 strain mice and compared them with C57Bl/6J mice. The neuropathological consequences of BCCAo were assessed using standard histochemical staining and heat shock protein 70 (HSP70) immunohistochemical staining (to demarcate cells that had been ischaemically stressed). The effect of BCCAo on mean arterial blood pressure (MABP) was also measured. The plasticity of the circle of Willis was recorded using carbon black perfusion. MF1 mice displayed significantly less ischaemic neuronal damage and HSP70 immunoreactivity compared to C57Bl/6J mice following 10-20 min BCCAo. Moreover, ischaemic neuronal damage and HSP70 immunoreactivity in MF1 mice subjected to extended BCCAo (25-45 min) was never as extensive or widespread as that observed in C57Bl/6J mice after 20 min BCCAo. MABP in MF1 mice (102+/-5 mmHg) was significantly higher than in C57Bl/6J mice (87+/-5) during 20 min BCCAo. MABP in MF1 mice during 20 and 40 min (103+/-12 mmHg) BCCAo remained above pre-occlusion values for the entire occlusion period. MF1 mice had significantly greater circle of Willis plasticity (more PcomAs) than C57Bl/6J mice did. These data indicate that MF1 mice are less susceptible to BCCAo than C57Bl/6J mice and that this could be due to maintained increases in MABP during BCCAo and the lower prevalence of abnormalities of the circle of Willis in MF1 mice.

Risk factors for chronic rejection after pediatric liver transplantation

BACKGROUND

Chronic rejection is a major cause of graft failure and a frequent reason for retransplantation after pediatric liver transplantation. Identification of risk factors for chronic rejection in pediatric transplant recipients is vital to understanding the pathogenesis of chronic rejection and may help prevent further graft loss.

METHODS

The study population consisted of 285 children with 385 liver transplants performed at University of Chicago between 1991 and 1999. Logistic regression analysis was used to evaluate risk factors for chronic rejection, including age, sex, race, type of graft (living related vs. cadaveric), native liver disease, acute rejection episodes, cytomegalovirus (CMV) infection, and posttransplant lymphoproliferative disease (PTLD).

RESULTS

The chronic rejection rate was significantly lower in recipients of living-related grafts than in recipients of cadaveric grafts (4% vs. 16%, P=0.001). African-American recipients had a significantly higher rate of chronic rejection than did Caucasian recipients (26% vs. 8%, P<0.001). Numbers of acute rejection episodes, transplantation for autoimmune disease, occurrence of PTLD, and CMV infection were also significant risk factors for chronic rejection. However, recipient age, gender, donor-recipient gender mismatch, and donor-recipient ethnicity mismatch were not associated with higher incidence of chronic rejection

CONCLUSION

We have identified a number of risk factors for chronic rejection in a large group of pediatric liver allograft recipients. We believe that donor-recipient matching for gender or race is not likely to reduce the incidence of chronic rejection. The elucidation of the mechanisms by which living-related liver transplantation affords protection against chronic rejection may provide insight into the immunogenetics of chronic rejection and help prevent further graft loss.

Folic acid prevents nitroglycerin-induced nitric oxide synthase dysfunction and nitrate tolerance: a human in vivo study

BACKGROUND

In healthy humans, continuous treatment with nitroglycerin (GTN) causes nitric oxide synthase dysfunction, probably through the reduced bioavailability of tetrahydrobiopterin. Recent studies proposed that folic acid is involved in the regeneration of tetrahydrobiopterin in different disease states. Therefore, we investigated whether folic acid administration would prevent this phenomenon. We also sought to determine if folic acid supplementation could prevent the development of tolerance to GTN.

METHODS AND RESULTS

On the first visit, 18 healthy male volunteers (aged 19 to 32 years) were randomized to receive either oral folic acid (10 mg once a day) or placebo for 1 week in a double-blind designed study. All subjects also received continuous transdermal GTN (0.6 mg/h). On the second visit, forearm blood flow was measured with venous occlusion strain gauge plethysmography in response to incremental infusions of acetylcholine (7.5, 15, and 30 microgram/min), N-monomethyl-L-arginine (1, 2, and 4 micromol/min), and GTN (11 and 22 nmol/min). Folic acid prevented GTN-induced endothelial dysfunction, as assessed by responses to intraarterial acetylcholine and N-monomethyl-L-arginine (P<0.01). Moreover, in the subjects treated with folic acid plus transdermal GTN, responses to intraarterial GTN were significantly greater than those observed after transdermal GTN plus placebo (P<0.05).

CONCLUSION

Our data demonstrate that supplemental folic acid prevents both nitric oxide synthase dysfunction induced by continuous GTN and nitrate tolerance in the arterial circulation of healthy volunteers. We hypothesize that the reduced bioavailability of tetrahydrobiopterin is involved in the pathogenesis of both phenomena. Our results confirm the view that oxidative stress contributes to nitrate tolerance.