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Non-enzymatic glycation of paired helical filament tau and the amyloid beta-protein in Alzheimer disease causes the formation of advanced glycation end products that permit intracellular production of reactive oxygen intermediates (ROIs). ROIs induce cellular oxidant stress, leading to increased neuronal dysfunction and ultimately, death.

Lewy bodies are inclusion bodies common in cases of Parkinson's disease, and in this disorder are found predominantly in the part of the brain called the substantia nigra. Inclusion bodies are small abnormal structures present inside cells and visible upon microscopic examination of tissue. Lewy bodies are not limited to Parkinson's disease, however. It is clear that some cases of dementia are associated with the presence of Lewy bodies in many parts of the brain. This condition has been termed diffuse Lewy body disease (DLBD). In this disease, the Lewy bodies are most prevalent in the parahippocampal gyrus, the cingulate gyrus, the insular cortex, and the amygdala. However, Lewy bodies are also found in many areas in all lobes of the cerebral cortex. The pathological observation of Lewy bodies is now aided by the availability of highly specific antibodies. While the Lewy bodies might be discernable using conventional stains for tissue specimens, using antibodies and immunocytochemical techniques, the Lewy bodies stand out well against the background. The most sensitive antibody for this purpose recognizes the important cell protein ubiquitin. The entire brain is much too large to be examined thoroughly on a routine basis: using antibodies to ubiquitin, researchers have found that the relatively small hippocampus provides the necessary information for distinguishing DLBD from other dementing disorders such as Alzheimer's disease. After investigating hippocampal specimens from 104 brains, including 45 brains from DLBD patients, some tiny nerve fibers called neurites that reacted with the ubiquitin could be found in every DLBD specimen and in none of the specimens from control subjects or subjects with Alzheimer's disease or Parkinson's disease. These neurites were located in the portion of the hippocampus classified by anatomists as CA2 to CA3. The hippocampus is an area of the brain significantly affected in Alzheimer's disease, and is often examined by pathologists. The present study shows that the immunocytochemical staining of this same region using ubiquitin antibodies appears to be a useful means of readily detecting diffuse Lewy body disease. (Consumer Summary produced by Reliance Medical Information, Inc.)

The relative roles of radiative and nonradiative processes and the polarization field on the light emission from blue (∼425 nm) InGaN light emitting diodes (LEDs) have been studied. Single and multiple double heterostructure (DH) designs have been investigated with multiple DH structures showing improved efficiencies. Experimental results supported by numerical simulations of injection dependent electron and hole wavefunction overlap and the corresponding radiative recombination coefficients suggest that increasing the effective active region thickness by employing multiple InGaN DH structures separated by thin and low barriers is promising for LEDs with high efficiency retention at high injection. The use of thin and low barriers is crucial to enhance carrier transport across the active region. Although increasing the single DH thickness from 3 to 6 nm improves the peak external quantum efficiency (EQE) by nearly 3.6 times due to increased density of states and increased emitting volume, the internal quantum efficiency (IQE) suffers a loss of nearly 30%. A further increase in the DH thickness to 9 and 11 nm results in a significantly slower rate of increase of EQE with current injection and lower peak EQE values presumably due to degradation of the InGaN material quality and reduced electron-hole spatial overlap. Increasing the number of 3 nm DH active regions separated by thin (3 nm) In0.06Ga0.94N barriers improves EQE, while maintaining high IQE (above 95% at a carrier concentration of 1018 cm-3) and showing negligible EQE degradation up to 550 A/cm2 in 400 × 400 μm2 devices due to increased emitting volume and high radiative recombination coefficients and high IQE. Time-resolved photoluminescence measurements revealed higher radiative recombination rates with increasing excitation due to screening of the internal field and enhanced electron and hole overlap at higher injection levels. To shed light on the experimental observations, the effect of free-carrier screening on the polarization field at different injection levels and the resulting impact on the quantum efficiency were investigated by numerical simulations. [ABSTRACT FROM AUTHOR]