Schooling mediates brain reserve in Alzheimer's disease: findings of fluoro-deoxy-glucose-positron emission tomography.

BACKGROUND: Functional imaging studies report that higher education is associated with more severe pathology in patients with Alzheimer's disease, controlling for disease severity. Therefore, schooling seems to provide brain reserve against neurodegeneration. OBJECTIVE: To provide further evidence for brain reserve in a large sample, using a sensitive technique for the indirect assessment of brain abnormality (18F-fluoro-deoxy-glucose-positron emission tomography (FDG-PET)), a comprehensive measure of global cognitive impairment to control for disease severity (total score of the Consortium to Establish a Registry for Alzheimer's Disease Neuropsychological Battery) and an approach unbiased by predefined regions of interest for the statistical analysis (statistical parametric mapping (SPM)). METHODS: 93 patients with mild Alzheimer's disease and 16 healthy controls underwent 18F-FDG-PET imaging of the brain. A linear regression analysis with education as independent and glucose utilisation as dependent variables, adjusted for global cognitive status and demographic variables, was conducted in SPM2. RESULTS: The regression analysis showed a marked inverse association between years of schooling and glucose metabolism in the posterior temporo-occipital association cortex and the precuneus in the left hemisphere. CONCLUSIONS: In line with previous reports, the findings suggest that education is associated with brain reserve and that people with higher education can cope with brain damage for a longer time.

UV-B absorbance and UV-B absorbing compounds (para-coumaric acid) in pollen and sporopollenin: the perspective to track historic UV-B levels.

UV-B absorbance and UV-B absorbing compounds (UACs) of the pollen of Vicia faba, Betula pendula, Helleborus foetidus and Pinus sylvestris were studied. Sequential extraction demonstrated considerable UV-B absorbance both in the soluble (acid methanol) and insoluble sporopollenin (acetolysis resistant residue) fractions of UACs, while the wall-bound fraction of UACs was small. The UV-B absorbance of the soluble and sporopollenin fraction of pollen of Vicia faba plants exposed to enhanced UV-B (10 kJ m(-2) day(-1) UV-B(BE)) was higher than that of plants that received 0 kJ m(-2) day(-1) UV-B(BB). Pyrolysis gas chromatography-mass spectrometry (py-GC-MS) analysis of pollen demonstrated that p-coumaric acid and ferulic acid formed part of the sporopollenin fraction of the pollen. The amount of these aromatic monomers in the sporopollenin of Vicia faba appeared to increase in response to enhanced UV-B (10 kJ m(-2) day(-1) UV-B(BE)). The detection limit of pyGC-MS was sufficiently low to quantify these phenolic acids in ten pollen grains of Betula and Pinus. The experimental data presented provide evidence for the possibility that polyphenolic compounds in pollen of plants are indicators of solar UV-B and may be applied as a new proxy for the reconstruction of historic variation in solar UV-B levels.

A scanning electron microscopy analysis of a spontaneous hemodialysis catheter fracture.

Central venous catheters have become increasingly important in hemodialysis treatment. With their increased use, catheter-related problems will be seen more frequently, and more rare complications may be observed. We describe the first case of asymptomatic spontaneous breakdown of a tunneled cuffed silicone catheter used for long-term hemodialysis treatment. This was discovered on removal of the catheter, leaving behind a catheter fragment in the left lower pulmonary lobe. An extensive scanning electron microscopy study showed accumulation of lumps of nonsilicone material at the place of the fracture, leading to severe disruption of the original cross-linked elastomer structure. Using energy-dispersive X-ray spectral analysis, which shows all elements with an atomic number of 11 or greater in a material, we found the lumps were aggregates of barium sulfate particles used to visualize the catheter on fluoroscopy. We suggest that the use of too small or too many barium sulfate particles led to high viscosity of the raw silicone before polymerization, causing improper mixing of barium sulfate particles in the silicone matrix. This resulted in insufficient removal of admixed air bubbles and unequal dispersion of barium sulfate, with the potential for weak spots after extrusion of the silicone into its definitive shape. With the increasing use of hemodialysis catheters for prolonged periods, catheter-related complications related to materials or manufacturing errors can be expected to occur more often.