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Biomedical subjects

D K Wilson

Publications and source records attributed to D K Wilson.

At least 19 recordsLinked to original sources
PubMed2005

How many days of pedometer monitoring predict weekly physical activity in adults?

BACKGROUND: The study purpose was to establish the number (and type) of days needed to estimate mean pedometer-determined steps/day in a field setting. METHODS: Seven days of data were collected from 90 participants (33 males, age = 49.1 +/- 16.2 years, BMI = 27.2 +/- 4.1 kg/m(2); 57 females, age = 44.8 +/- 16.9 years, BMI = 27.0 +/- 5.9 kg/m(2)). Mean steps/day were computed for all 7 days (the criterion), each single day, and combinations of days. Analyses included repeated measures ANOVA, intra-class correlations (ICC), and regression. RESULTS: There was a significant difference (P < 0.001) between days. The difference was limited to Sunday and accounted for 5% of the variance. ICC analyses indicated a minimum of 3 days is necessary to achieve a reliability of 0.80. The adjusted R(2) was 0.79 for a single day (specifically Wednesday), 0.89 for 2 days (Wednesday, Thursday), and 0.94 for 3 days (Wednesday, Thursday, Friday). Sunday was the last day to enter the model. CONCLUSIONS: Although there is a statistical difference between days, there is little practical difference, and the primary distinction appears limited to Sunday. Although a single day of collection is not acceptable, any 3 days can provide a sufficient estimate.

Adult↗
PubMed2003

Performance bounds for passive sensor arrays operating in a turbulent medium: plane-wave analysis.

The performance bounds of a passive acoustic array operating in a turbulent medium with fluctuations described by a von Kármán spectrum are investigated. This treatment considers a single, monochromatic, plane-wave source at near-normal incidence. A line-of-sight propagation path is assumed. The primary interests are in calculating the Cramer-Rao lower bounds of the azimuthal and elevational angles of arrival and in observing how these bounds change with the introduction of additional unknowns, such as the propagation distance, turbulence parameters, and signal-to-noise ratio. In both two and three dimensions, it is found that for large values of the index-of-refraction variance, the Cramer-Rao lower bounds of the angles of arrival increase significantly at large values of the normalized propagation distance. For small values of the index-of-refraction variance and normalized propagation distance, the signal-to-noise ratio is found to be the limiting factor. In the two-dimensional treatment, it is found that the estimate of the angle of arrival will decouple from the estimates of the other parameters with the appropriate choice of array geometry. In three dimensions, again with an appropriate choice of array geometry, the estimates of the azimuth and elevation will decouple from the estimates of the other parameters, but due to the constraints of the model, will remain coupled to one another.

Journal Article↗
PubMed2001

The crystal structure of the GCY1 protein from S. cerevisiae suggests a divergent aldo-keto reductase catalytic mechanism.

The crystal structure of the GCY1 gene product from Saccharomyces cerevisiae has been determined to 2.5 A and is being refined. The model includes two protein molecules, one apo and one holo, per asymmetric unit. Examination of the model reveals that the active site surface is somewhat flat when compared with the other aldo-keto reductase structures, possibly accommodating larger substrates. The K(m) for NADPH (28.5 microM) is higher than that seen for other family members. This can be explained structurally by the lack of the 'safety belt' of residues seen in other aldo-keto reductases with higher affinity for NADPH. Catalysis also differs from the other aldo-keto reductases. The tyrosine that acts as an acid in the reduction reaction is flipped out of the catalytic pocket. This implies that the protein must either undergo a conformational change before catalysis can take place or that there is an alternate acid moiety.

Alcohol Oxidoreductases↗
PubMed2001

Sound propagation in a turbulent atmosphere near the ground: a parabolic equation approach.

The interference of the direct wave from the point source to the receiver and the wave reflected from the impedance ground in a turbulent atmosphere is studied. A parabolic equation approach for calculating the sound pressure p at the receiver is formulated. Then, the parabolic equation is solved by the Rytov method yielding expressions for the complex phases of direct and ground-reflected waves. Using these expressions, a formula for the mean squared sound pressure [absolute value(p)2] is derived for the case of anisotropic spectra of temperature and wind velocity fluctuations. This formula contains the "coherence factor," which characterizes the coherence between direct and ground-reflected waves. It is shown that the coherence factor is equal to the normalized coherence function of a spherical sound wave for line-of-sight propagation. For the case of isotropic turbulence, this result allows one to obtain analytical formulas for [absolute value(p)2] for the Kolmogorov, Gaussian, and von Karman spectra of temperature and wind velocity fluctuations. Using these formulas, the effects of temperature and wind velocity fluctuations, and the effects of different spectra of these fluctuations on the mean squared sound pressure, are numerically studied. Also the effect of turbulent anisotropy on the interference of direct and ground reflected waves is numerically studied. Finally, it is shown that the mean squared sound pressure [absolute value(p)2] calculated for the von Karman spectrum of temperature fluctuations agrees well with experimental data obtained in a laboratory experiment.

Journal Article↗
PubMed2001

Statistical moments of the sound field propagating in a random, refractive medium near an impedance boundary.

Propagation of a monochromatic sound field in a refractive and turbulent medium near an impedance boundary is considered. Starting from the parabolic equation for a moving medium and using the Markov approximation, a closed equation for the statistical moments of arbitrary order of the sound-pressure field is derived. Numerical methods for directly solving the first- and second-moment versions of this equation are formulated. The first-moment formulation is very similar to parabolic equations (PEs) that are now widely used to calculate sound fields for particular realizations of a random medium. The second-moment formulation involves a large, fringed tridiagonal matrix, which is solved using iterative refinement and Cholesky factorization. The solution is computationally intensive and currently restricted to low frequencies. As an example, the first and second moments are directly calculated for upwind and downwind propagation of a sound wave through a turbulent atmosphere. For these cases, predictions from the second-moment PE were statistically indistinguishable from the result of 40 random trials calculated with a standard Crank-Nicholson PE, although the second-moment PE yielded smoother results due to its ensemble-average nature.

Journal Article↗
PubMed2001

Atmospheric scattering for varying degrees of saturation and turbulent intermittency.

Atmospheric turbulence is inherently inhomogeneous and intermittent. Short periods of high activity are embedded in longer periods of relative calm. Local spatial and temporal changes in sound speed associated with this intermittency increase the likelihood of measuring large values of scattered acoustic signals. Previous work successfully predicted the probability density functions (pdf's) of fully saturated, scattered signals measured within an acoustic shadow zone [Wilson et al., J. Acoust. Soc. Am. 99, 3393-3400 (1996)]. The more general case of incompletely saturated scattering is considered in this paper; using the Rice-Nagakami distribution a theory is developed. The predicted intensity pdf has two free parameters: one to describe the degree of intermittency and a second for the degree of saturation. For validation purposes, outdoor propagation measurements were made over a flat, hard ground at ranges of 146-283 m and at frequencies of 50-540 Hz. The saturation parameter was determined from the acoustic data and also estimated from the turbulence conditions. The degree of saturation increased with frequency, and measured intensity pdf's were found to be in excellent agreement with the theory.

Journal Article↗
PubMed2001

The role of gender and family support on dietary compliance in an African American adolescent hypertension prevention study.

Social support experiences vary markedly across gender groups, and little is known about the role of social support in promoting healthy dietary compliance in African American adolescents who are at increased risk for developing hypertension. This study examined the relation between gender, dietary social support, and compliance to a low sodium diet. Casual blood pressures were also examined in relation to dietary compliance and gender One hundred eighty-four healthy African American adolescents (83 boys, 101 girls) participated in an intensive 5-day low sodium diet (50 mEq/24 hr) as part of a hypertension prevention program. Emotional dietary social support from family members and friends was measured at baseline. Compliance was defined as urinary sodium excretion of < or = 50 mEq/24 hr at postsodium restriction. The results indicated a significant Gender x Compliance effect for positive family support (p < .05). Girls who were compliant reported higher levels of dietary support from family members (19.2 +/- 7.8) than boys who were compliant (16.9 +/- 7.0). In contrast, boys who were compliant reported lower levels of dietary support from family members (16.9 +/- 7.0) than boys who were not compliant (20.2 +/- 7.5). Systolic blood pressure showed a trend toward decreasing in compliant participants (104.4 +/- 8.4 vs. 101.7 +/- 8.0, mm Hg, p < .06), but the effect diminished when Quetelet Index (kg/m2) was controlled for in the analyses (p < .12). These results suggest that higher levels of emotional dietary support from family members are associated with better adherence to short-term sodium restriction for African American girls as compared to boys. Further research is needed to determine the long-term impact of social support on sodium restriction in adolescent populations.

Adolescent↗
PubMed2000

Crystallization and aldo-keto reductase activity of Gcy1p from Saccharomyces cerevisiae.

Crystallization and preliminary X-ray diffraction studies of Gcy1p, an aldo-keto reductase from Saccharomyces cerevisiae, have been performed. Both the wild type and a double-mutant form of Gcy1p were crystallized using the hanging-drop method at 298 K; however, only the double-mutant form has so far yielded crystals suitable for X-ray diffraction analysis. These crystals belonged to the primitive monoclinic space group P2(1), with unit-cell parameters a = 50.94, b = 65.64, c = 86.23 A, beta = 92.64 degrees. Diffraction data were collected to 2.5 A. Assuming two 35 kDa subunits in the asymmetric unit yielded a V(m) of 2.06 A(3) Da(-1). Additionally, a kinetic study performed by measuring the rate of oxidation of NADPH in the presence of several substrates indicates that both wild-type and double-mutant proteins are enzymes possessing NADPH-dependent reductase activity.

Alcohol Oxidoreductases↗
PubMed2000

Socioeconomic status and blood pressure reactivity in healthy black adolescents.

Adolescents in low-socioeconomic-status environments are more susceptible to illnesses, such as hypertension and cardiovascular diseases. This study examined the influence of both neighborhood- and family-level socioeconomic status (SES) on blood pressure (BP) reactivity in a healthy sample of 76 black adolescents. It was hypothesized that a higher level of parental education and/or income would reduce the elevated BP reactivity associated with living in poorer neighborhoods. Census-derived data were obtained using each participant's address. Neighborhood level of SES was based on percentage of households below the poverty line, female-headed households, owner-occupied housing, percentage vacant housing, and average number of persons per household. Family level of SES was based on self-reported level of parental education and annual family income. Adolescents participated in a competitive video game to establish their BP reactivity scores. As predicted, adolescents who lived in poorer neighborhoods had lower diastolic BPs if their parents were more (versus less) educated (P<0.05; 7+/-8 versus 13+/-6 mm Hg). Adolescents who lived in poorer neighborhoods also had significantly lower diastolic BP reactivity (P<0.05) if their family had a higher (versus lower) annual income (7+/-7 versus 12+/-8 mm Hg). These data are the first to demonstrate the buffering effect of family SES on the negative health consequences of living in low-SES neighborhoods in healthy black adolescents.

Adolescent↗
PubMed1999

The influence of gender and emotional versus instrumental support on cardiovascular reactivity in African-American adolescents.

Research suggests that females seek out, prefer, and are more receptive to emotional support (encouragement), and that males seek out, prefer, and are more receptive to instrumental support (problem-solving). Thus, we hypothesized that boys would show lower blood pressure (BP) reactivity in response to instrumental than emotional or no support, and that girls would show lower BP reactivity in response to emotional than instrumental or no support. Forty-eight healthy African-American adolescents (50% males) participated in a role play conflict task and were randomized to receive either emotional, instrumental, or no support (presence only) from a confederate. Boys showed lower systolic blood pressure (SBP) reactivity in the instrumental than in the emotional or no support conditions and lower recovery SBP as compared to boys in the emotional or no support conditions. A similar pattern of results was demonstrated for diastolic blood pressure (DBP) reactivity. Girls, however, did not demonstrate lower BP reactivity in response to emotional as compared to instrumental support. These findings suggest that instrumental and emotional support differentially influence cardiovascular (CV) reactivity in African-American boys versus girls.

Adolescent↗
PubMed1999

Ambulatory blood pressure nondipping status in salt-sensitive and salt-resistant black adolescents.

This study examined the relationship between salt sensitivity and ambulatory blood pressure in 53 healthy black adolescents. Salt sensitivity was defined as an increase in mean blood pressure greater than or exceeding 5 mm Hg from a 5-day low-salt diet (50 mmol/24 h) to a 10-day high-salt diet (150 mmol/24 h NaCl supplement). Sixteen subjects were salt sensitive and 37 subjects were salt resistant (showed < 5 mm Hg increase in mean blood pressure). Subjects were classified as dippers (> or =10% decrease in blood pressure from awake to asleep) based on their 24-h ambulatory blood pressure values. Nondippers showed higher systolic, diastolic, and mean asleep blood pressures than dippers (P < .05 for all). Salt-sensitive subjects showed greater daytime diastolic and mean blood pressures than salt-resistant subjects (P < .05 for both). A significantly greater percentage of nondippers were salt sensitive, compared with salt resistant for diastolic blood pressure (P < .001) and mean blood pressure (P < .05). For both of these blood pressure measures, 50% of the salt-sensitive subjects had a nondipping status, compared with only 5.4% of the salt-resistant subjects for diastolic blood pressure, and 18.9% of the salt-resistant subjects for mean blood pressure. These results are the first to indicate that salt sensitivity is associated with nondipper blood pressure status in a black normotensive adolescent population.

Adolescent↗
PubMed1999

Effects of potassium on blood pressure in salt-sensitive and salt-resistant black adolescents.

This study examined the effects of increasing dietary potassium on ambulatory blood pressure nondipping status (<10% decrease in blood pressure from awake to asleep) and cardiovascular reactivity in salt-sensitive and salt-resistant black adolescents. A sample of 58 normotensive (blood pressure, 101/57+/-9/4 mm Hg) black adolescents (aged 13 to 16 years) participated in a 5-day low sodium diet (50 mmol/24 h) followed by a 10-day high sodium diet (150 mmol/24 h NaCl supplement) to determine salt-sensitivity status. Participants showed a significant increase in urinary sodium excretion (24+/-19 to 224+/-65 mmol/24 h) and were identified as salt-sensitive if their mean blood pressure increase was >/=5 mm Hg from the low to high sodium diet. Sixteen salt-sensitive and 42 salt-resistant subjects were then randomly assigned to either a 3-week high potassium diet (80 mmol/24 h) or usual diet control group. Urinary potassium excretion significantly increased in the treatment group (35+/-7 to 57+/-21 mmol/24 h). At baseline, a significantly greater percentage of salt-sensitive (44%) compared with salt-resistant (7%) subjects were nondippers on the basis of diastolic blood pressure classifications (P<0.04). After the dietary intervention, all of the salt-sensitive subjects in the high potassium group achieved dipper status as a result of a drop in nocturnal diastolic blood pressure (daytime, 69 versus 67 mm Hg; nighttime, 69 versus 57 mm Hg). No significant group differences in cardiovascular reactivity were observed. These results suggest that a positive relationship between dietary potassium intake and blood pressure modulation can still exist even when daytime blood pressure is unchanged by a high potassium diet.

Adolescent↗
PubMed1999

The prevalence of salt sensitivity in an African-American adolescent population.

This study examined the prevalence of salt-sensitivity (SS) in 140 healthy African-American adolescents. SS was defined as an increase in mean blood pressure > or =5 mm Hg from a 5-day low salt (Na+) diet (50 mmol/24 hr) to a 10-day high Na+ diet (150 mmol/24 hr NaCl supplement); remaining subjects were classified as salt-resistant (SR). Dietary compliance was defined as Na+ excretion < or =50 mmol/24 hr for the low Na+ diet and > or =165 mmol/24 hr for the high NaCl supplement diet. 31 (22%) subjects were classified as SS and 109 (78%) as SR. There were no significant differences between SS and SR subjects on baseline characteristics, family history of hypertension, or on resting blood pressure or heart rate measures. As expected, SS subjects showed a greater increase in mean, systolic, and diastolic blood pressures (P<.001 for all) than SR subjects in response to the high NaCl supplement. There was a greater increase in weight (P<.01) and Quetelet Index (P<.05) for SS than SR subjects in response to Na+ loading. These results are the first to show that SS is prevalent in a subgroup of healthy African-American adolescents.

Adolescent↗
PubMed1998

Structural features of the aldose reductase and aldehyde reductase inhibitor-binding sites.

The three-dimensional structures of aldose reductase and aldehyde reductase, members of the aldo-keto reductase superfamily, are composed of similar alpha/beta TIM-barrels. However, examination of the structures reveals that the inhibitor-binding site of aldose reductase differs from that of aldehyde reductase due to the participation of non-conserved residues in its formation. This information will be useful in the design of inhibitors to prevent or delay diabetic retinopathy. A review of the structures of the inhibitor-binding sites is presented.

Aldehyde Reductase↗
PubMed1998

Gynecologic cancers metastatic to the breast.

BACKGROUND: We report a series of gynecologic cancers metastatic to the breast, illustrating the diagnostic and prognostic implications of this rare event. STUDY DESIGN: By reviewing the gynecologic oncology data base, we identified 10 women with gynecologic cancer metastatic to the breast who were treated at Indiana University School of Medicine between August 1978 and February 1995. Medical records were reviewed for pertinent data concerning the presentation, evaluation, and treatment of the primary gynecologic malignancy and the metastatic breast tumor. RESULTS: The mean patient age was 56.8 years (range, 30-80 years). The most common gynecologic malignancy was ovarian cancer (five patients), followed by cervical cancer (two patients) and cancers of the vagina, endometrium, or peritoneum (one patient each). A palpable solitary breast mass was found in 8 of 10 patients (80%), and the upper outer quadrant of the breast was the most common site of tumor involvement. One woman presented with examination findings resembling inflammatory breast cancer, and one patient presented with multiple firm subcutaneous nodules. Despite further treatment, which in all cases consisted of systemic chemotherapy, 83% of the patients died with a breast metastasis within 1 year of presentation. CONCLUSIONS: Secondary breast malignancy should be suspected in any patient with a breast tumor and a known history of gynecologic cancer. A breast metastasis implies widespread tumor dissemination and a poor prognosis. Radical breast surgery should be avoided.

Adult↗
PubMed1998

Symptomatic age-related macular degeneration in Asian patients.

PURPOSE: To characterize retinal and fluorescein angiographic findings of Asian patients with symptoms secondary to age-related macular degeneration (ARMD). METHODS: We retrospectively reviewed 453 consecutive medical records corresponding to fluorescein angiograms performed between November 1992 and November 1995 to identify Asian patients with symptomatic ARMD. Presenting visual symptoms, best-corrected Snellen visual acuities, and retinal examination findings were determined from the medical records. Fundus photos and fluorescein angiograms were reviewed. RESULTS: There were 26 symptomatic eyes in 19 Asian patients with a median age of 73 years. Presenting visual symptoms included decreased visual acuity (19 eyes), metamorphopsia (5 eyes), or scotoma (2 eyes). Retinal findings included occult choroidal neovascularization (CNV) in 5 (19%) eyes, serous pigment epithelial detachment (PED) in 8 (31%) eyes, PED with CNV in 5 (19%) eyes, drusen in 5 (19%) eyes, retinal pigment epithelial atrophy in 1 (4%) eye, vitreous hemorrhage in 1 (4%) eye, and a disciform scar in 1 (4%) eye. CONCLUSION: In this cohort of Asian patients with ARMD, the majority of symptomatic eyes had either CNV (46%) or serous PED (31%).

Aged↗
PubMed1997

The role of divalent cations in structure and function of murine adenosine deaminase.

For murine adenosine deaminase, we have determined that a single zinc or cobalt cofactor bound in a high affinity site is required for catalytic function while metal ions bound at an additional site(s) inhibit the enzyme. A catalytically inactive apoenzyme of murine adenosine deaminase was produced by dialysis in the presence of specific zinc chelators in an acidic buffer. This represents the first production of the apoenzyme and demonstrates a rigorous method for removing the occult cofactor. Restoration to the holoenzyme is achieved with stoichiometric amounts of either Zn2+ or Co2+ yielding at least 95% of initial activity. Far UV CD and fluorescence spectra are the same for both the apo- and holoenzyme, providing evidence that removal of the cofactor does not alter secondary or tertiary structure. The substrate binding site remains functional as determined by similar quenching measured by tryptophan fluorescence of apo- or holoenzyme upon mixing with the transition state analog, deoxycoformycin. Excess levels of adenosine or N6- methyladenosine incubated with the apoenzyme prior to the addition of metal prevent restoration, suggesting that the cofactor adds through the substrate binding cleft. The cations Ca2+, Cd2+, Cr2+, Cu+, Cu2+, Mn2+, Fe2+, Fe3+, Pb2+, or Mg2+ did not restore adenosine deaminase activity to the apoenzyme. Mn2+, Cu2+, and Zn2+ were found to be competitive inhibitors of the holoenzyme with respect to substrate and Cd2+ and Co2+ were noncompetitive inhibitors. Weak inhibition (Ki > or = 1000 microM) was noted for Ca2+, Fe2+, and Fe3+.

Adenosine Deaminase↗