Biomedical subjects

William Yu

Publications and source records attributed to William Yu.

3 recordsLinked to original sources

PubMed2006

The utility of extended longitudinal profiles in predicting future health care expenditures.

BACKGROUND: Health care spending is highly concentrated. Prediction models that accurately identify the characteristics of individuals most likely to incur high levels of health expenditures in a subsequent year are important analytical and statistical tools. OBJECTIVES: This study examined the capacity of alternative models to predict the likelihood of incurring high levels of medical expenditures in a subsequent year. This effort also evaluated the utility of an additional year of longitudinal information. SUBJECTS: A nationally representative sample from the Medical Expenditure Panel Survey (MEPS). METHODS: The MEPS longitudinal data are used to examine the persistence of high expenditures during a 2-year period. With the unique linkage of the MEPS to the National Health Interview Survey, the utility of an additional year of data also was examined. Resultant models were evaluated in terms of sensitivity, specificity, and predictive capacity. RESULTS: Only modest marginal gains in discrimination capacity were realized from the use of extended longitudinal profiles from the National Health Interview Survey, relative to information on prior year characteristics. CONCLUSIONS: Our results highlight the continuing concentration of health care expenditures during the period 1996 to 2002 and reveal some attenuation in magnitude in the tail of this distribution over time. Further, our results provide evidence of the utility of probabilistic models as prediction tools to identify individuals likely to incur high levels of expenditures in future years. Predictive capacity does not suffer when restricted to a single year of prior information.

Adolescent↗

PubMed2004

Racial differences in potassium disposal.

BACKGROUND: African Americans appear relatively potassium (K(+))-deficient compared with Caucasian Americans whether on unregulated diets or on diets controlled for K(+) content. METHODS: To determine whether extrarenal K(+) disposal was affected by race, KCl (0.5 mEq/kg in 0.9% saline) was infused over 48 minutes to 12 African American and 12 Caucasian American normotensive, healthy subjects. Identical infusions were administered before and after 10 days of fixed electrolyte intake. In addition to serum K(+), glucose, insulin, renin, and aldosterone were measured in blood, and K(+) and sodium (Na(+)) in urine voided spontaneously during the infusions. Data were analyzed using a two-factor analysis of variance (ANOVA) with repeated measures. RESULTS: Basal serum K(+) did not differ between races (African American 3.97 +/- 0.06 mEq/L and Caucasian American 3.98 +/- 0.05, P= NS). The rise in serum K(+) during the infusion and the area under the curve of serum K(+) over the 3.5 hours of observation were both greater in African American (African American +0.82 +/- 0.07 mEq/L and Caucasian American +0.61 +/- 0.06, P= 0.001; and African American 6.9 +/- 0.5 units and Caucasian American 5.1 +/- 0.6, P= 0.0012). The 10-day period of controlled intake did not abolish these differences. Aldosterone at baseline was lower and insulin was higher in African Americans at the end of the infusion. Urinary K(+), plasma glucose, and renin levels did not differ between African Americans and Caucasian Americans. CONCLUSION: Disposal of an intravenous (iv) K(+) load is decreased in African Americans compared with Caucasian Americans, which may reflect decreased Na(+),K(+)-ATPase activity in African Americans in vivo.

Adolescent↗

PubMed2003

Myocardin is a critical serum response factor cofactor in the transcriptional program regulating smooth muscle cell differentiation.

The SAP family transcription factor myocardin functionally synergizes with serum response factor (SRF) and plays an important role in cardiac development. To determine the function of myocardin in the smooth muscle cell (SMC) lineage, we mapped the pattern of myocardin gene expression and examined the molecular mechanisms underlying transcriptional activity of myocardin in SMCs and embryonic stem (ES) cells. The human and murine myocardin genes were expressed in vascular and visceral SMCs at levels equivalent to or exceeding those observed in the heart. During embryonic development, the myocardin gene was expressed abundantly in a precise, developmentally regulated pattern in SMCs. Forced expression of myocardin transactivated multiple SMC-specific transcriptional regulatory elements in non-SMCs. By contrast, myocardin-induced transactivation was not observed in SRF(-/-) ES cells but could be rescued by forced expression of SRF or the SRF DNA-binding domain. Furthermore, expression of a dominant-negative myocardin mutant protein or small-interfering-RNA-induced myocardin knockdown significantly reduced SM22 alpha promoter activity in SMCs. Most importantly, forced expression of myocardin activated expression of the SM22 alpha, smooth muscle alpha-actin, and calponin-h1 genes in undifferentiated mouse ES cells. Taken together, these data demonstrate that myocardin plays an important role in the SRF-dependent transcriptional program that regulates SMC development and differentiation.

Amino Acid Sequence↗