Effects of a single dose of isosorbide-5-mononitrate on the left ventricular diastolic function in systemic hypertension

The effect of a single dose of isosorbide-5-mononitrate on left ventricular (LV) diastolic function was assessed by radionuclide ventriculography in 18 hypertensive patients. The effect of the mononitrate on atrial filling also was assessed. As expected, there was a significant decrease in mean blood pressure (120 +/- 17 to 102 +/- 18 mm Hg, p less than 0.005). Global LV ejection fraction did not show a significant change, increasing slightly from 64 +/- 9 to 68 +/- 8% (difference not significant). The mononitrate prolonged the time to peak filling rate from 176 +/- 36 to 195 +/- 29 ms (p less than 0.0001). The percentage of time to peak filling rate from diastole also increased, from 46 to 53% (p less than 0.05), whereas the normalized peak filling rate did not change (2.36 +/- 0.6 to 2.31 +/- 0.6 end-diastolic volumes/s, difference not significant). This effect on LV diastolic function was closely related to a certain reduction in preload, as suggested by the reduction in mean left atrial filling (45 +/- 12 to 40 +/- 13 counts/s, p less than 0.005) and LV diastolic counts, suggesting that the "impairment" of diastolic function induced by nitrates is secondary to the reduction in venous return to the left atrium. The mononitrate did not affect the mean right atrial filling rate (50 +/- 12 to 52 +/- 13 counts/s) and the right ventricular end-diastolic counts, suggesting a primary vasodilatory effect of nitrates on the pulmonary vascular bed.

Distribution of gene frequency as a test of the theory of the selective neutrality of polymorphisms

The variation in gene frequency among populations or between generations within a population is a result of breeding structure and selection. But breeding structure should affect all loci and alleles in the same way. If there is significant heterogeneity between loci in their apparent inbreeding coefficients F=s(p) (2)/p(1-p), this heterogeneity may be taken as evidence for selection. We have given the statistical properties of F and shown how tests of heterogeneity can be made. Using data from human populations we have shown highly significant heterogeneity in F values for human polymorphic genes over the world, thus demonstrating that a significant fraction of human polymorphisms owe their current gene frequencies to the action of natural selection. We have also applied the method to temporal variation within a population for data on Dacus oleae and have found no significant evidence of selection.