cyanine-dye-3 and Alzheimer-Disease

To compare the fluorescence intensity and duration of qdots streptavidin conjugate (QDs-SA) with Cy3 as the molecular probe of β-amyloid precursor protein (APP), and to provide evidence for early molecular imaging and diagnosis of Alzheimer's disease (AD).. With the help of laser scanning confocal microscope and flow cytometry, the flurescence probe based on the QDs-SA was used to detect APP in HEK293 cells stably transfected pcDNA3.1/APP, and to compare with conventional fluroimmunoassay Cy3.. The immunofluorescence staining detection indicated APP expression was mainly located in the plasma membrane. The mean fluorescence intensity of QDs-SA (34.2336±4.2455) was greater than that of Cy3 (21.6023±3.0102)under the confocal fluorescence microscope (P<0.05). After persistent exciting for 12 min, the fluorescence intensity of APP stained by QDs-SA decreased by 27.87%. The other stained by Cy3 decreased by 79.60%. The positive rate of APP staining had no significant difference between the QDs-SA(54.4700±3.4433)% and Cy3 (54.3800±8.5229)% by flow cytometry, but the mean fluorescence intensity had statistical significance(P<0.05). The QDs-SA (1 045.4167±47.3623) was significantly higher than the mean fluorescence intensity of Cy3 (658.5467±55.0591).. QDs-SA fluorescence probes can effectively recognize APP and are sensitive and exceptionally photostable, suggesting that QDs-SA fluorescence probes could be a potential method in APP detection and offer a novel way for the diagnosis of Alzheimer's disease.

Topics: Alzheimer Disease; Amyloid beta-Protein Precursor; Carbocyanines; Fluorescent Dyes; Gene Transfer Techniques; HEK293 Cells; Humans; Molecular Imaging; Quantum Dots

Human recombinant tau can bind to the end of isolated human paired helical filaments (PHF). The sequential binding of tau protein to PHF could result in an elongation of the previously polymerized PHF. However, we have observed that the elongation takes place in a different way on different types of PHF. We have found that there are at least three populations of PHF. For one population, tau protein is able to bind to the ends of the filament and to elongate that filament. In the second PHF population, tau protein binds but does not elongates the filament. In the third, neither tau binding nor elongation was observed.

Topics: Alzheimer Disease; Binding Sites; Carbocyanines; Fluorescent Antibody Technique; Fluorescent Dyes; Humans; Intermediate Filament Proteins; Microscopy, Electron; Microtubules; Molecular Conformation; tau Proteins; Tubulin Modulators

Excitotoxic lesions in the magnocellular nucleus basalis (MBN) lead to a significant damage of cholinergic neurons concomitant with increased amyloid precursor protein (APP) expression in the cerebral cortex. However, the sensitivity of non-cholinergic neurons to excitotoxicity, and changes of APP expression in the damaged MBN are still elusive. Hence, we performed multiple-labeling immunocytochemistry for choline-acetyltransferase (ChAT), neuron-specific nuclear protein (NeuN) and APP 4, 24, and 48 h after NMDA infusion in the MBN. Whereas all cholinergic neurons were immunoreactive for NeuN, this neuronal marker also labeled a population of ChAT-immunonegative non-cholinergic neurons. Both neuron populations exhibited a similar degree of sensitivity to NMDA excitotoxicity that became evident as early as 4 h post-lesion. Cholinergic MBN neurons showed abundant APP immunoreactivity (approximately 90%), while only a fraction (approximately 20-30%) of non-cholinergic neurons expressed the protein. Remarkably, cholinergic but not non-cholinergic neurons retained their APP immunoreactivity after NMDA infusion. In conclusion, cholinergic MBN neurons are not preferentially sensitive to short-term excitotoxicity, but are one of the major sources of APP in the basal forebrain.

Topics: Acetylcholine; Alzheimer Disease; Amyloid beta-Protein Precursor; Animals; Basal Nucleus of Meynert; Biomarkers; Carbocyanines; Cell Count; Choline O-Acetyltransferase; Cholinergic Fibers; Down-Regulation; Fluorescent Dyes; Immunoglobulin G; Immunohistochemistry; Male; N-Methylaspartate; Neurons; Neurotoxins; Nuclear Proteins; Rats; Rats, Wistar; Receptor, Nerve Growth Factor

Class A scavenger receptors (SR-A) mediate microglial interaction with fibrillar beta-amyloid (fAbeta). We report here that neonatal microglia from SR-A knockout mice (SR-A-/-) adhere to surface-bound fAbeta, and produce reactive oxygen species (ROS) as efficiently as wildtype microglia; that both wildtype and SR-A-/- microglia express SR-BI; that antibodies against SR-BI do not affect adhesion or ROS production by wildtype microglia, but inhibit adhesion and ROS production of SR-A-/- microglia to immobilized fAbeta by approximately 40%. Adhesion to fAbeta-coated surfaces, and uptake of fAbeta by both wildtype and SR-A-/- microglia was almost completely inhibited by incubation with fucoidan. Thus SR-BI and SR-A mediate similar effector functions in neonatal microglia, which suggests that SR-BI plays as important a role as SR-A, and can maintain the wildtype phenotype in SR-A-/- microglia.

Topics: Alzheimer Disease; Amyloid beta-Peptides; Animals; Animals, Newborn; Antineoplastic Agents; Brain; Carbocyanines; CD36 Antigens; Cell Adhesion; Cells, Cultured; Fluorescent Dyes; Gene Expression; Liver; Membrane Proteins; Mice; Mice, Inbred BALB C; Mice, Knockout; Microglia; Peptide Fragments; Polysaccharides; Reactive Oxygen Species; Receptors, Immunologic; Receptors, Lipoprotein; Receptors, Scavenger; Scavenger Receptors, Class A; Scavenger Receptors, Class B