Socioeconomic variation and prostate specific antigen testing in the community: a United Kingdom based population study.

PURPOSE: We examined the association of prostate specific antigen testing with prostate cancer incidence, tumor differentiation and mortality according to socioeconomic status. MATERIALS AND METHODS: Participants were 96,484 men between 40 and 99 years old without preexisting prostate cancer who were registered with a general practitioner in the Tayside region of Scotland, United Kingdom, between January 1, 2003 and December 31, 2008. We performed a retrospective cohort analysis using anonymized health data, including biochemistry data on prostate specific antigen tests, Scottish Index of Multiple Deprivation, cancer registry data set and General Register Office for Scotland death records. Main outcome measures were prostate specific antigen testing, prostate cancer incidence and death. RESULTS: Men in the most affluent Scottish Index of Multiple Deprivation quintile had a greater chance of undergoing a prostate specific antigen test (OR 1.48, 95% CI 1.40-1.57, p <0.001) and having prostate cancer (OR 1.48, 95% CI 1.15-1.91, p = 0.002) than men in the most deprived quintile, adjusting for age. There was no association between deprivation index quintile and prostate cancer death. CONCLUSIONS: Increased affluence was associated with a higher likelihood of a prostate specific antigen test and a higher incidence of prostate cancer. However, there were no observed differences by social class of the likelihood of a positive prostate specific antigen test or prostate cancer related death.

Effects of elevated plasma tryptophan on brain activation associated with the Stroop task.

RATIONALE: Central fatigue, such as that found in chronic fatigue syndrome, is a state in which cognition and action require increasing effort and performance is impaired without evidence for reduced peripheral motor responsiveness. Previous studies identified functional changes in subcortical regions in patients who experience central fatigue but did not address neural correlates of the subjective experience of fatigue. OBJECTIVES: This study investigated responses to acute tryptophan feeding (after administration of 30 mg/kg body mass) using functional magnetic resonance imaging to investigate neural correlates of central fatigue during a cognitively demanding exercise, the counting Stroop task. MATERIALS AND METHODS: In a double-blind, cross-over study, eight subjects ingested L: -tryptophan (Trp) or placebo (Plac) on two separate test days. Neutral (N) and interference (I) Stroop tasks were carried out. RESULTS: Plasma-free tryptophan (p[FT]) increased tenfold after L: -Trp administration (P < 0.01). Although reaction times were longer after Trp (mean+/-SD, Plac-Neut 669 +/- 163 ms, I 715 +/- 174 ms, P < 0.01; Trp-Neut 712 +/- 193 ms, I 761 +/- 198 ms, P < 0.05), the Stroop effect was not significantly different between Plac and Trp. L: -Trp administration was associated with relatively decreased activation in regions, including the left postcentral, angular, inferior frontal, and the lateral orbital gyri and the inferior frontal sulcus relative to Plac. Relatively increased activation was found after Trp in the left precuneus and in the posterior cingulate gyrus. CONCLUSIONS: Thus, Trp administration before the Stroop task caused distributed functional changes in primary sensory and in multimodal neocortex, including changes in a brain region, the activity of which has been shown previously to vary with conscious awareness (precuneus). Previous reports suggest that primary mechanisms of central fatigue may be predominantly subcortical. The present results demonstrate that neocortical activity changes are also found. Whether this activity contributes to the primary mechanisms underlying central fatigue or not, the neocortical activity changes may provide an index of the conscious experience.

Manipulation of systemic oxygen flux by acute exercise and normobaric hypoxia: implications for reactive oxygen species generation.

Maximal exercise in normoxia results in oxidative stress due to an increase in free radical production. However, the effect of a single bout of moderate aerobic exercise performed in either relative or absolute normobaric hypoxia on free radical production and lipid peroxidation remains unknown. To examine this, we randomly matched {according to their normobaric normoxic VO2peak [peak VO2 (oxygen uptake)]} and assigned 30 male subjects to a normoxia (n = 10), a hypoxia relative (n = 10) or a hypoxia absolute (n = 10) group. Each group was required to exercise on a cycle ergometer at 55% of VO2peak for 2 h double-blinded to either a normoxic or hypoxic condition [FiO2 (inspired fraction of O2) = 0.21 and 0.16 respectively]. ESR (electron spin resonance) spectroscopy in conjunction with ex vivo spin trapping was utilized for the direct detection of free radical species. The main findings show that moderate intensity exercise increased plasma-volume-corrected free radical and lipid hydroperoxide concentration (pooled rest compared with exercise data, P < 0.05); however, there were no selective differences between groups (statexgroup interaction, P > 0.05). The delta change in free radical concentration was moderately correlated with systemic VO2 (r2 = 0.48, P < 0.05). The hyperfine coupling constants recorded from the ESR spectra [aN = 13.8 Gauss, and a(H)beta = 1.9 Gauss; where 1 Gauss = 10(-4) T (telsa)] are suggestive of oxygen-centred free radical species formed via the decomposition of lipid hydroperoxides. Peripheral leucocyte and neutrophil cells and total CK (creatine kinase) activity all increased following sustained exercise (pooled rest compared with exercise data, P < 0.05), but no selective differences were observed between groups (state x group interaction, P > 0.05). We conclude that a single bout of moderate aerobic exercise increases secondary free radical species. There is also evidence of exercise-induced muscle damage, possibly caused by the increase in free radical generation.