Biomedical subjects

K S Nelson

Publications and source records attributed to K S Nelson.

27 records · Page 2Linked to original sources

PubMed2001

Measurement of the branching ratio and asymmetry of the decay Xi degrees -->Sigma degrees gamma.

We have studied the rare weak radiative hyperon decay Xi degrees -->Sigma degrees gamma in the KTeV experiment at Fermilab. We have identified 4045 signal events over a background of 804 events. The dominant Xi degrees -->Lambdapi degrees decay, which was used for normalization, is the only important background source. An analysis of the acceptance of both modes yields a branching ratio of B(Xi degrees -->Sigma degrees gamma)/B(Xi degrees -->Lambdapi degrees ) = (3.34+/-0.05+/-0.09)x10(-3). By analyzing the final state decay distributions, we have also determined that the Sigma degrees emission asymmetry parameter for this decay is alpha(XiSigma) = -0.63+/-0.09.

Journal Article↗

PubMed2001

Study of the K(0)(L) --> pi(+)pi(-)gamma Direct Emission Vertex.

We have performed studies of the K(0)(L)-->pi(+)pi(-)gamma direct emission ( DE) and inner Bremsstrahlung ( IB) vertices, based on data collected by KTeV during the 1996 Fermilab fixed target run. We find a(1)/a(2) = -0.737+/-0.034 GeV2 for the DE form-factor parameter in the rho-propagator parametrization, and report on fits of the form factor to linear and quadratic functions as well. We concurrently measure gamma(K(0)(L)-->pi(+)pi(-)gamma,E(*)(gamma)>20 MeV)/gamma(K(0)(L)-->pi(+)pi(-)) = (20.8+/-0.3)x10(-3), and a K(0)(L)-->pi(+)pi(-)gamma DE/(DE+IB) branching ratio of 0.683+/-0.011.

Journal Article↗

PubMed2001

Search for the decay KL --> pi(0)e+e-.

We report on a search for the decay KL-->pi(0)e+e- carried out by the KTeV/E799 experiment at Fermilab. This decay is expected to have a significant CP violating contribution and the measurement of its branching ratio could support the Cabibbo-Kobayashi-Maskawa mechanism for CP violation or could point to new physics. Two events were observed in the 1997 data with an expected background of 1.06+/-0.41 events, and we set an upper limit B(KL-->pi(0)e+e-)<5.1 x 10(-10) at the 90% confidence level.

Journal Article↗

PubMed1994

Ethnic differences in circadian hemodynamic profile.

Since the introduction of 24-h ambulatory blood pressure monitoring (ABPM), some studies, although not all, have suggested the presence of a blunted nocturnal blood pressure decline in black versus white subjects, a difference that may help explain the higher incidence of target organ damage in blacks. To better define ethnic differences in diurnal hemodynamic profiles, we studied ABPM recordings from 275 black (55.6% women) and 246 white (43.1% women) previously untreated subjects, with a similar age distribution (from 20 to 79 years) and a wide range of systolic (100-230 mm Hg) and diastolic (50-130 mm Hg) blood pressures. Average clinic systolic (diastolic) blood pressures were higher in black v white men by 10.2 (7.3) mm Hg; P = .04 (P = .004), with a similar trend in women (P = NS). On ABPM, blacks had higher average values, a difference that was greater during sleep (9.4 mm Hg for systolic blood pressure) than while awake (4.7 mm Hg; P = .003). Average diurnal change in systolic blood pressure (awake minus sleep values) was 13.1 +/- 0.7 v 18.0 +/- 0.6 mm Hg for blacks v whites (P < .001). There was a strong negative correlation between baseline (ie, sleep) blood pressure and the diurnal change (r = -0.58; P < .001), but at each given level, blacks had a lower daytime increment/nocturnal fall (P = .02). Results for diastolic blood pressure and heart rate were similar. The data suggest that the smaller diurnal change in blacks may be related in part to their higher blood pressure levels, but that there is an additional, independent effect of race. This results in a greater 24-h blood pressure load in blacks than whites for each given clinic (daytime) value, and may help explain differences in target organ damage. Future studies investigating the effects of blood pressure on target organs in different populations should consider diurnal profiles in addition to clinic blood pressure.

Adult↗

PubMed1991

Diurnal blood pressure variation: differences among disparate ethnic groups.

We examined the possibility that excess cardiovascular morbidity in American blacks compared with whites might be partly the result of differences in diurnal blood pressure variation. Urban American blacks have higher night-time blood pressures and show a smaller increase in blood pressure during the waking day than whites. This difference is associated with a higher cardiac mass in the blacks and occurs despite similar duration and quality of sleep in blacks and whites. Both groups show similar levels of sympatho-adrenal activity at night, but the diurnal increase is smaller in blacks, paralleling the smaller increase in blood pressure. In Africa blacks show a diurnal pressure pattern similar to American whites. Disparities in cation consumption do not explain the differences in blood pressure variation between these groups.

Black People↗

PubMed1990

Renal and hemodynamic effects of intravenous fenoldopam versus nitroprusside in severe hypertension.

The renal and hemodynamic effects of intravenously administered fenoldopam mesylate, a novel dopamine-1 receptor agonist, were compared with those of sodium nitroprusside in 28 patients (18 male; 26 black, two white; average age, 49 +/- 3 years) with an average blood pressure of 219/137 mm Hg, most of whom presented with acute target organ damage. Fenoldopam and nitroprusside lowered blood pressure safely to an average pressure of 176/105 mm Hg; highly significant dose-response relations were found for the 13 patients receiving fenoldopam and the 15 receiving nitroprusside. Volume and sodium, potassium, and creatinine concentrations were measured in freely voided urine specimens both before and during intravenous therapy. In the fenoldopam-treated patients, there were significant increases in urinary flow (92 +/- 21 to 168 +/- 37 ml/hr, p less than 0.003), sodium excretion (227 +/- 73 to 335 +/- 90 mu eq/min, p less than 0.001), and creatinine clearance (70 +/- 11 to 93 +/- 13 ml/hr, p less than 0.003). In the nitroprusside-treated group, however, all these parameters decreased, but not significantly. For direct comparison of the two agents, the increments in urinary flow rate (+76 +/- 20 vs. -16 +/- 15 ml/hr, fenoldopam vs. nitroprusside), sodium excretion (+109 +/- 28 vs. -39 +/- 28 mu eq/min), and creatinine clearance (+23 +/- 6 vs. -11 +/- 7 ml/min) were significantly greater (p less than 0.001 for each) in the fenoldopam-treated group. Significant differences were also obtained when these parameters were calculated as percentage increase over baseline. Fenoldopam and nitroprusside are effective therapies for severe, accelerated, or malignant hypertension, but fenoldopam had additional salutary renal effects in these patients.

2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-ben↗

PubMed1988

Cross-validation of six short forms of the WAIS-R in a healthy geriatric sample.

A number of methods have been developed in recent years to estimate full-scale IQ scores from abbreviated versions of the revised Wechsler Adult Intelligence Scale (WAIS-R), including Silverstein's (1982) two- and four-subtest short forms, Reynolds, Willson, and Clark's (1983) four-subtest short form, and Brooker and Cyr's (1986) two-, three- and four-subtest short forms. Short forms are of particular interest to the clinician and researcher who need a brief screening scale of cognitive abilities for the elderly, but their effectiveness with a normal aging sample has not been established. The present study examines the accuracy of six methods of estimating full-scale IQs from abbreviated versions of the WAIS-R in a middle-aged to elderly nonpsychiatric sample of 28 healthy males. Although all six methods were found to yield scores that were correlated highly with full scale scores, the method of Reynolds et al. (1983) resulted in short-form IQ estimates that were significantly different statistically from full-scale IQ scores. Although most of the six short-form methods appear to be useful screening measures for cognitive functioning and longitudinal changes in intellectual functions in the elderly, their use for classification purposes is not supported in the present study.

Achievement↗

PubMed1988

Effects of selective dopamine-1 receptor activation on intraocular pressure in man.

The lack of specific agonists and antagonists has, until recently, precluded investigation of a role for dopamine receptors in the control of intraocular pressure. In the present study, we have examined the effects of fenoldopam, a novel selective dopamine1 (DA1) receptor agonist, on intraocular pressure, in eight healthy human volunteers. Fenoldopam, infused intravenously at 0.5 micrograms kg-1 min-1, increased intraocular pressure from 14.6 +/- 0.9 to 17.6 +/- 1.4 mmHg (P less than 0.05) while a control saline infusion had no effect. Pupil diameter and blood pressure did not change. In the same subjects, i.v. norepinephrine or angiotensin II both increased intraocular pressure--from 13.8 +/- 1.4- to 17.6 +/- 1.4 mmHg and from 13.4 +/- 1.3- to 17.5 +/- 1.7 mmHg respectively (P less than 0.05), and mean arterial pressure by about 20 mmHg. These data suggest that: (1) DA1 receptor activation can modulate intraocular pressure; (2) the intraocular pressure effects of the DA1 receptor agonist, fenoldopam, are independent of changes in systemic blood pressure, in contrast to those of norepinephrine or angiotensin II where intraocular and systemic blood pressures increase in parallel; (3) the ability of a DA1 receptor antagonist to lower intraocular pressure merits investigation.

Adolescent↗

PubMed1988

Evaluation of the Suntech Accutracker. A novel noninvasive ambulatory blood pressure monitor.

The "Accutracker," a novel ambulatory blood pressure monitor based on auscultation triggered by the electrocardiographic R wave, was evaluated by comparing its blood pressure readings with those obtained by direct auscultation. Simultaneous measurements were made (in 24 volunteers, by 4 trained observers) using a Y connector so that the Accutracker and a mercury sphygmomanometer were in parallel. Average blood pressure by direct auscultation (215 readings) was 129.1 +/- 12.0/77.8 +/- 14.4, and by Accutracker was 130.9 +/- 13.0/75.9 +/- 14.5 mm Hg (P less than 0.01). The Accutracker overestimated systolic blood pressure by 1.7 +/- 5.8 and underestimated diastolic blood pressure by 1.9 +/- 7.6 mm Hg. The average difference between pairs of readings was 5.0 mm Hg for systolic and 5.5 mm Hg for diastolic pressure. These data indicate that the concordance of blood pressure readings recorded by Accutracker and direct auscultation is sufficient to justify its use in noninvasive ambulatory blood pressure monitoring.

Auscultation↗