Abstract-There is indirect evidence for a gender difference in nitric oxide (NO) synthesis from vascular endothelium. The aim of the present study was to determine NO production more directly in healthy women and men by the measurement of 15 N nitrate excreted in urine after the intravenous administration of L-[ 15 N] 2 -guanidino arginine. Twenty-four healthy volunteers (13 men aged 22 to 40 years and 11 women aged 23 to 42 years) participated in this study. No subjects were receiving any medication. Women were studied between the 7th and 14th days of their menstrual cycles. Arterial blood pressure was measured oscillometrically, and 1.13 mol L-[ 15 N] 2 arginine was administered intravenously after an overnight fast. Urine was collected for the next 36 hours in separate 12-hour periods. Urinary 15 N/ 14 N nitrate ratio was assessed by dry combustion in an isotope ratio mass spectrometer. Mean 36-hour urinary 15 N nitrate excretion was greater in women than in men (2111Ϯ139 versus 1682Ϯ87 mol; PϽ0.05). Furthermore, total urinary 15 N nitrate excretion was associated inversely with the mean arterial blood pressure in the whole group of subjects (coefficient of correlation, 0.47; Pϭ0.022). The present data show that whole-body production of NO is greater in healthy premenopausal women than in men under ambulatory conditions. The cellular origin of NO measured in this study is unknown, but differences in endothelial production could underlie differences in vascular function between men and women. (Hypertension. 1998;32:730-734.) Key Words: endothelium-derived relaxing factor Ⅲ arginine Ⅲ nitrates Ⅲ gender Ⅲ adults P remenopausal women have less atheromatous arterial disease, including stroke or coronary artery disease, than men of similar age.1 Synthesis of nitric oxide (NO) by the endothelium regulates vascular tone in the arterial bed and modulates interactions between the endothelium and circulating blood cells, including platelets and leukocytes.2 Previous studies have suggested that a gender difference in the production of NO due to ovarian hormones (ie, estrogens) could contribute to this low risk of cardiovascular events in women of reproductive age. However, the role of NO is controversial because increased 3,4 or diminished 5,6 production in women compared with men has been reported. It is possible that the indirect nature and relative specificity of the methods used for the measurement of NO in those studies might account for these discrepancies. Measurement of urinary or serum nitrate is highly affected by diet.7 Cyclic GMP is also the second messenger of atrial natriuretic peptide, 8 and exhaled NO reflects local biosynthesis in the lung and/or upper airways rather than in the whole body. We have developed a sensitive and specific method to measure more directly the conversion of L-arginine to NO. 9 The method is based on the measurement of 15 N nitrate (stable oxidation product of NO) excretion in urine after intravenous single administration of the stable isotope L-[ 15 N] 2 -guanidino arginine. Us...

Unlike conventional methods, the interrupter method for measuring airway resistance is non-invasive and requires minimal patient co-operation. It can therefore be applied in critically ill patients, acute asthmatics, neonates, pre-school children, geriatric patients and unconscious patients. The method is based on transient interruption of airflow at the mouth for a brief period during which alveolar pressure equilibrates with mouth pressure. Measurement of mouth pressure is used to estimate alveolar pressure prior to interruption and the ratio of this to flow prior to interruption gives airway resistance. Using the interrupter method we have developed a portable device for measuring airway resistance which is simple to use and gives a direct instantaneous reading. Measurements of airway resistance obtained using the new device were compared with those obtained using conventional body plethysmograph methods in 43 adult patients. A close correlation was seen (r = 0.86). The two methods appear equally sensitive in detecting changes in airway resistance following bronchodilator therapy. The device has been used successfully in pre-school children unable to co-operate with conventional methods.

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radiological features, suggesting extensive pulmonary disease and clinical evidence of activity. (3) Serial SACE measurement is a useful monitor of active sarcoidosis and its response to steroids.

Methods: We recruited 54 healthy volunteers and performed a complete echocardiographic exam. We included in the analysis a short axis view of the aortic arch, after the emergence of the brachiocephalic artery. The 2D-ST methodology was used to off-line calculate aortic arch mechanics (EchoPAQ, GE Healthcareâ). The analysis was performed for circumferential aortic strain (CAS) and for early circumferential aortic strain rate (eCASR). We assessed the aortic pulse wave velocity (PVW) with the Compliorâ. Kolmogorov-Smirnov test was used for normality assessment. Results: We included 50 controls with a gender balance and a mean age of 33AE9 years. Of the total 300 aortic wall segments, 278 had adequate waveforms for analysis. Global CAS had a normal distribution (pZ0.20); the mean and median CAS were 11.3AE3.2% and 11.5% (8.4 -13.7) respectively. Global eCASR also had a normal distribution (pZ0.10); the mean and median eCASR were 1. 5AE0.4 s-1 and 1.6 s-1 (1.3 -1.7), respectively. There was a significant negative correlation between CAS, age (rZ-0.46, p<0.01), pulse pressure (rZ-0.40, p<0.01), PWV (rZ-0.52, pZ0.03) and the vascular augmentation index (rZ-0.60, pZ0.01). A similar association was identified for eCARS. Conclusion: 2D-ST is a feasible methodology for the analysis of the aortic arch mechanics; in this study, we obtained reference values and normal distributions.