Spring constants and adhesive properties of native bacterial biofilm cells measured by atomic force microscopy.

Bacterial biofilms were imaged by atomic force microscopy (AFM), and their elasticity and adhesion to the AFM tip were determined from a series of tip extension and retraction cycles. Though the five bacterial strains studied included both Gram-negative and -positive bacteria and both environmental and laboratory strains, all formed simple biofilms on glass surfaces. Cellular spring constants, determined from the extension portion of the force cycle, varied between 0.16+/-0.01 and 0.41+/-0.01 N/m, where larger spring constants were measured for Gram-positive cells than for Gram-negative cells. The nonlinear regime in the extension curve depended upon the biomolecules on the cell surface: the extension curves for the smooth Gram-negative bacterial strains with the longest lipopolysaccharides on their surface had a larger nonlinear region than the rough bacterial strain with shorter lipopolysaccharides on the surface. Adhesive forces between the retracting silicon nitride tip and the cells varied between cell types in terms of the force components, the distance components, and the number of adhesion events. The Gram-negative cells' adhesion to the tip showed the longest distance components, sometimes more than 1 microm, whereas the shortest distance adhesion events were measured between the two Gram-positive cell types and the tip. Fixation of free-swimming planktonic cells by NHS and EDC perturbed both the elasticity and the adhesive properties of the cells. Here we consider the biochemical meaning of the measured physical properties of simple biofilms and implications to the colonization of surfaces in the first stages of biofilm formation.

Neuropsychological performance of adults with attention deficit hyperactivity disorder (ADHD): diagnostic classification estimates for measures of frontal lobe/executive functioning.

ADHD adults (N = 26) were compared to normal controls (N = 26) on 6 neuropsychological measures believed sensitive to frontal lobe-executive functioning. MANOVA analyses and subsequent univariate tests indicated that most of the neuropsychological measures discriminated between the two groups. To address clinical significance diagnostic classification rates were also generated for each measure individually, and for the battery as a whole. Levels of positive predictive power (PPP) for each of the 6 measures (83-100%) indicated that abnormal scores on these tests were good predictors of ADHD. However, estimates of negative predictive power (NPP) suggested that normal scores poorly predicted the absence of ADHD. When classification rates were calculated for the overall battery classification accuracy improved substantially. Thus, neuropsychological tests can differentiate adults suffering from ADHD from adults without ADHD, while also providing good classification accuracy. Finally, the pattern of neurobehavioral impairments exemplified through the Summary Index scores was interpreted as consistent with conceptualizations of ADHD depicting mild neurologic dysfunction in networks associated with the frontal lobes.

Developing a simulated disaster.

Disaster drills are often accomplished through paper exercises and questionable preparation of staff. A successful simulated disaster involves creativity, planning, the players, disaster day and debriefing.

Senile dementia and parietal lobe dysfunction.

Two samples of patients suffering from senile dementia were administered the Kew tests for parietal lobe function and aphasia. No evidence emerged of any clinical heterogeneity; parietal lobe test performance was found to be more a function of degree of impairment rather than of age.