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The concentration or threshold of 25-hydroxyvitamin D [25(OH)D] needed to maximally suppress intact serum parathyroid hormone (iPTH) has been suggested as a measure of optimal vitamin D status. Depending upon the definition of maximal suppression of iPTH and the 2-phase regression approach used, 2 distinct clusters for a single 25(OH)D threshold have been reported: 16-20 ng/mL (40-50 nmol/L) and 30-32 ng/mL (75-80 nmol/L). To rationalize the apparently disparate published results, we compared thresholds from several regression models including a 3-phase one to estimate simultaneously 2 thresholds before and after adjusting for possible confounding for age, BMI, glomerular filtration rate, dietary calcium, and season (April-September vs. October-March) within a single data set, i.e. data from the Tufts University Sites Testing Osteoporosis Prevention/Intervention Treatment study, consisting of 181 men and 206 women (total n = 387) ages 65-87 y. Plasma 25(OH)D and serum iPTH concentrations were (mean [+ or -] SD) 22.1 [+ or -] 7.44 ng/mL (55.25 [+ or -] 18.6 nmol/L) and 36.6 [+ or -] 16.03 pg/mL (3.88 [+ or -] 1.7 pmol/L), respectively. The 3-phase model identified 2 thresholds of 12 ng/mL (30 nmol/L) and 28 ng/mL (70 nmol/L); similar results were found from the 2-phase models evaluated, i.e. 13-20 and 27-30 ng/mL (32.5-50 and 67.5-75 nmol/L) and with previous results. Adjusting for confounding did not change the results substantially. Accordingly, the 3-phase model appears to be superior to the 2-phase approach, because it simultaneously estimates the 2 threshold clusters found from the 2-phase approaches along with estimating confidence limits. If replicated, it may be of both clinical and public health importance. doi: 10.3945/jn.109.116681.

Objectives. This study evaluated the effect of comorbidity at diagnosis on racial differences in survival among men with prostate cancer. Methods. Clinical and demographic data were abstracted from records of 864 patients diagnosed at 4 Chicago area hospitals between 1986 and 1990. Comorbidity was scored on the basis of clinical information in the Charlson index. Cause-specific relative mortality adjusted for age, stage, differentiation, and treatment was compared across Charlson scores with Cox proportional hazards functions. Results. Blacks had significantly greater mortality from prostate cancer and other causes (vs Whites, relative risk [95% confidence interval] = 1.84 [1.22, 2.79] and 1.69 [1.33, 2.29], respectively; P Conclusions. Absence of a significant preexisting medical diagnosis is associated with a higher risk for excess mortality among Black men diagnosed with prostate cancer. (Am J Public Health. 2004;94:803-808)

Reactive oxygen species (ROS) are increasingly believed to be important intracellular signaling molecules in mitogenic pathways involved in the pathogenesis of glomerulonephritis (GN). We explored the effects of the antioxidants [alpha]-lipoic acid and N-acetyl-L-cysteine on ERK activation in cultured mesangial cells and the role of ERK activation in the severity of glomerular injury in a rat model of anti-Thy 1 GN. In cultured mesangial cells, growth factors stimulated ERK phosphorylation by 150-450%. Antioxidants reduced this increase by 50-60%. Induction of anti-Thy 1 nephritis in rats led to a 210% increase in glomerular ERK phosphorylation. This increase in phosphorylated ERK was reduced by 50% in animals treated with [alpha]-lipoic acid. Treatment with [alpha]-lipoic acid resulted in significant improvement of glomerular injury. Cellular proliferation was reduced by 100%, and the number of proliferating cell nuclear antigenpositive cells was reduced by 64%. The increased expression of glomerular transforming growth factor-[[beta].sub.1] protein and mRNA in rats with anti-Thy 1 nephritis was significantly attenuated and mesangial cell transformation into myofibroblasts was completely prevented by treatment with [alpha]-lipoic acid. The effects of [alpha]-lipoic acid were at least partially due to inhibition of oxidative stress. In rats with anti-Thy 1 nephritis, ROS production was increased 400-500%, and this increase was inhibited by 55% by treatment with [alpha]-lipoic acid. We suggest that ROS may mediate glomerular injury by inducing ERK phosphorylation. [alpha]-Lipoic acid should be considered a potential therapeutic agent in certain types of human GN. [alpha]-lipoic acid; anti-Thy 1 nephritis; extracellular signal-regulated kinase; [alpha]-smooth muscle actin; transforming growth factor-[[beta].sub.1]

Objectives. We compared patterns of mortality among men with prostate cancer at 2 Department of Veterans Affairs (VA) and 2 private-sector hospitals in the Chicago area. Methods. Mortality rates for 864 cases diagnosed between 1986 and 1990 were estimated using Cox proportional hazards models that incorporated age; income; cancer stage, differentiation, and treatments; and baseline comorbidity. Results. Race tended to associate with all-cause mortality irrespective of health care setting (Blacks vs Whites: hazard rate ratio [HRR]=1.68 [95% confidence interval (CI)=1.06, 2.67]; P Conclusions. Determinants of all-cause mortality in men with prostate cancer vary according to health care setting.