Continuous-flow optical pumping NMR in a closed circuit system.

In a typical continuous-flow optical pumping setup, the chemical shift of xenon in the adsorbed phase depends on the gas flow rate due to warming of the sample surface by the gas stream. Calibration of the system using the (207)Pb resonance of solid lead nitrate is necessary to determine the actual sample temperature. Optimum pulse repetition rates are strongly affected by gas flow and spin-lattice relaxation rates. The interplay of flow and pulse repetition rate alters signal intensity ratios and may lead to the complete suppression of signals.

Lack of association between 27-bp repeat polymorphism in intron 4 of the endothelial nitric oxide synthase gene and the risk of coronary artery disease.

The gene encoding endothelial nitric oxide synthase (ecNOS) is a candidate gene for the mediation of initial endothelial cell damage seen in arteriosclerosis. Although the association of ecNOS polymorphisms with hypertension has been studied extensively, there is little information regarding its association with coronary artery disease (CAD). We decided to study a 27 base-pair tandem repeat polymorphism in intron 4 of the ecNOS gene in 1043 individuals (413 controls, 630 patients with CAD) who consecutively underwent coronary angiography at our institution. The frequencies of the genotypes drawn from 1038 individuals were 0.69, 0.28 and 0.03 in the controls and 0.73, 0.25 and 0.02 in individulas with CAD for the ecNOS4b/b, ecNOS4b/a and ecNOS4a/a genotypes, respectively (p = n.s). There was no shift of the genotype frequencies from the expected distribution based on the Hardy-Weinberg equilibrium. Neither the rare ecNOS4a allele nor the ecNOS4a/a genotype conferred an independent risk factor for CAD in subgroups, e.g. smokers, diabetic individuals, hypertensive individuals and individuals with a low conventional risk for CAD. In five individuals we identified an additional 27-bp repeat in the ecNOS gene (ecNOS4c), which occurred heterozygous with the ecNOS4b allele (ecNOS4b/c genotype). In conclusion, the ecNOS4a allele as well as the ecNOS4a/a genotype did not show a general association with CAD in the studied European population. Even in high-risk subgroups the ecNOS4a/4a genotype did not represent an independent risk factor for CAD. In addition, the severity of CAD was not associated with the ecNOS4a allele/ecNOS4a/a genotype.