An empirical attempt at evaluating stress: a failure discovered through cross-validation

Stress remains popular as a psychological construct. Different aspects of stress are emphasized depending upon the environmental issue, target population, and measure used. Existing measures are often confounded between causes of stress and effects of stress and also may emphasize a particular perspective on stress. Here we evaluate the empirical method of item selection as an alternative for developing a stress scale, using salivary cortisol levels as the empirical criterion. Items were adapted from measures of perceived stress, daily hassles, and life events as used in two studies of stress that measured salivary cortisol. Correlations with cortisol levels led to the retention of 75 items of the pool of 535, which were administered to a third sample of 28 medical students. The 75-item scale did not correlate with cortisol levels. Of 15 individual items that did, six correlated in the opposite direction to that predicted. Results illustrate the dangers of empirical item selection methods

A dedicated haem lyase is required for the maturation of a novel bacterial cytochrome c with unconventional covalent haem binding

In bacterial c-type cytochromes, the haem cofactor is covalently attached via two cysteine residues organized in a haem c-binding motif. Here, a novel octa-haem c protein, MccA, is described that contains only seven conventional haem c-binding motifs (CXXCH), in addition to several single cysteine residues and a conserved CH signature. Mass spectrometric analysis of purified MccA from Wolinella succinogenes suggests that two of the single cysteine residues are actually part of an unprecedented CX15CH sequence involved in haem c binding. Spectroscopic characterization of MccA identified an unusual high-potential haem c with a red-shifted absorption maximum, not unlike that of certain eukaryotic cytochromes c that exceptionally bind haem via only one thioether bridge. A haem lyase gene was found to be specifically required for the maturation of MccA in W. succinogenes. Equivalent haem lyase-encoding genes belonging to either the bacterial cytochrome c biogenesis system I or II are present in the vicinity of every known mccA gene suggesting a dedicated cytochrome c maturation pathway. The results necessitate reconsideration of computer-based prediction of putative haem c-binding motifs in bacterial proteomes

Factors Associated with Revision Surgery after Internal Fixation of Hip Fractures

Background: Femoral neck fractures are associated with high rates of revision surgery after management with internal fixation. Using data from the Fixation using Alternative Implants for the Treatment of Hip fractures (FAITH) trial evaluating methods of internal fixation in patients with femoral neck fractures, we investigated associations between baseline and surgical factors and the need for revision surgery to promote healing, relieve pain, treat infection or improve function over 24 months postsurgery. Additionally, we investigated factors associated with (1) hardware removal and (2) implant exchange from cancellous screws (CS) or sliding hip screw (SHS) to total hip arthroplasty, hemiarthroplasty, or another internal fixation device. Methods: We identified 15 potential factors a priori that may be associated with revision surgery, 7 with hardware removal, and 14 with implant exchange. We used multivariable Cox proportional hazards analyses in our investigation. Results: Factors associated with increased risk of revision surgery included: female sex, [hazard ratio (HR) 1.79, 95% confidence interval (CI) 1.25-2.50; P = 0.001], higher body mass index (fo

An empirical attempt at evaluating stress: A failure discovered through cross-validation

Stress remains popular as a psychological construct. Different aspects of stress are emphasized depending upon the environmental issue, target population, and measure used. Existing measures are often confounded between causes of stress and effects of stress and also may emphasize a particular perspective on stress. Here we evaluate the empirical method of item selection as an alternative for developing a stress scale, using salivary cortisol levels as the empirical criterion. Items were adapted from measures of perceived stress, daily hassles, and life events as used in two studies of stress that measured salivary cortisol. Correlations with cortisol levels led to the retention of 75 items of the pool of 535, which were administered to a third sample of 28 medical students. The 75-item scale did not correlate with cortisol levels. Of 15 individual items that did, six correlated in the opposite direction to that predicted. Results illustrate the dangers of empirical item selection methods