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alpha-Synuclein: A synuclein that is a major component of LEWY BODIES that plays a role in neurodegeneration and neuroprotection.Synucleins: A family of homologous proteins of low MOLECULAR WEIGHT that are predominately expressed in the BRAIN and that have been implicated in a variety of human diseases. They were originally isolated from CHOLINERGIC FIBERS of TORPEDO.Lewy Bodies: Intracytoplasmic, eosinophilic, round to elongated inclusions found in vacuoles of injured or fragmented neurons. The presence of Lewy bodies is the histological marker of the degenerative changes in LEWY BODY DISEASE and PARKINSON DISEASE but they may be seen in other neurological conditions. They are typically found in the substantia nigra and locus coeruleus but they are also seen in the basal forebrain, hypothalamic nuclei, and neocortex.beta-Synuclein: A synuclein that is closely related to ALPHA-SYNUCLEIN. It may play a neuroprotective role against some of the toxic effects of aggregated ALPHA-SYNUCLEIN.Parkinson Disease: A progressive, degenerative neurologic disease characterized by a TREMOR that is maximal at rest, retropulsion (i.e. a tendency to fall backwards), rigidity, stooped posture, slowness of voluntary movements, and a masklike facial expression. Pathologic features include loss of melanin containing neurons in the substantia nigra and other pigmented nuclei of the brainstem. LEWY BODIES are present in the substantia nigra and locus coeruleus but may also be found in a related condition (LEWY BODY DISEASE, DIFFUSE) characterized by dementia in combination with varying degrees of parkinsonism. (Adams et al., Principles of Neurology, 6th ed, p1059, pp1067-75)Lewy Body Disease: A neurodegenerative disease characterized by dementia, mild parkinsonism, and fluctuations in attention and alertness. The neuropsychiatric manifestations tend to precede the onset of bradykinesia, MUSCLE RIGIDITY, and other extrapyramidal signs. DELUSIONS and visual HALLUCINATIONS are relatively frequent in this condition. Histologic examination reveals LEWY BODIES in the CEREBRAL CORTEX and BRAIN STEM. SENILE PLAQUES and other pathologic features characteristic of ALZHEIMER DISEASE may also be present. (From Neurology 1997;48:376-380; Neurology 1996;47:1113-1124)gamma-Synuclein: A homolog of ALPHA-SYNUCLEIN that plays a role in neurofilament network integrity. It is overexpressed in a variety of human NEOPLASMS and may be involved in modulating AXON architecture during EMBRYONIC DEVELOPMENT and in the adult. Gamma-Synuclein may also activate SIGNAL TRANSDUCTION PATHWAYS associated with ETS-DOMAIN PROTEIN ELK-1.Nerve Tissue ProteinsInclusion Bodies: A generic term for any circumscribed mass of foreign (e.g., lead or viruses) or metabolically inactive materials (e.g., ceroid or MALLORY BODIES), within the cytoplasm or nucleus of a cell. Inclusion bodies are in cells infected with certain filtrable viruses, observed especially in nerve, epithelial, or endothelial cells. (Stedman, 25th ed)Multiple System Atrophy: A syndrome complex composed of three conditions which represent clinical variants of the same disease process: STRIATONIGRAL DEGENERATION; SHY-DRAGER SYNDROME; and the sporadic form of OLIVOPONTOCEREBELLAR ATROPHIES. Clinical features include autonomic, cerebellar, and basal ganglia dysfunction. Pathologic examination reveals atrophy of the basal ganglia, cerebellum, pons, and medulla, with prominent loss of autonomic neurons in the brain stem and spinal cord. (From Adams et al., Principles of Neurology, 6th ed, p1076; Baillieres Clin Neurol 1997 Apr;6(1):187-204; Med Clin North Am 1999 Mar;83(2):381-92)Neurodegenerative Diseases: Hereditary and sporadic conditions which are characterized by progressive nervous system dysfunction. These disorders are often associated with atrophy of the affected central or peripheral nervous system structures.Substantia Nigra: The black substance in the ventral midbrain or the nucleus of cells containing the black substance. These cells produce DOPAMINE, an important neurotransmitter in regulation of the sensorimotor system and mood. The dark colored MELANIN is a by-product of dopamine synthesis.Amyloid: A fibrous protein complex that consists of proteins folded into a specific cross beta-pleated sheet structure. This fibrillar structure has been found as an alternative folding pattern for a variety of functional proteins. Deposits of amyloid in the form of AMYLOID PLAQUES are associated with a variety of degenerative diseases. The amyloid structure has also been found in a number of functional proteins that are unrelated to disease.Parkinsonian Disorders: A group of disorders which feature impaired motor control characterized by bradykinesia, MUSCLE RIGIDITY; TREMOR; and postural instability. Parkinsonian diseases are generally divided into primary parkinsonism (see PARKINSON DISEASE), secondary parkinsonism (see PARKINSON DISEASE, SECONDARY) and inherited forms. These conditions are associated with dysfunction of dopaminergic or closely related motor integration neuronal pathways in the BASAL GANGLIA.Dopamine: One of the catecholamine NEUROTRANSMITTERS in the brain. It is derived from TYROSINE and is the precursor to NOREPINEPHRINE and EPINEPHRINE. Dopamine is a major transmitter in the extrapyramidal system of the brain, and important in regulating movement. A family of receptors (RECEPTORS, DOPAMINE) mediate its action.Neurons: The basic cellular units of nervous tissue. Each neuron consists of a body, an axon, and dendrites. Their purpose is to receive, conduct, and transmit impulses in the NERVOUS SYSTEM.Dopaminergic Neurons: Neurons whose primary neurotransmitter is DOPAMINE.Brain: The part of CENTRAL NERVOUS SYSTEM that is contained within the skull (CRANIUM). Arising from the NEURAL TUBE, the embryonic brain is comprised of three major parts including PROSENCEPHALON (the forebrain); MESENCEPHALON (the midbrain); and RHOMBENCEPHALON (the hindbrain). The developed brain consists of CEREBRUM; CEREBELLUM; and other structures in the BRAIN STEM.Nerve Degeneration: Loss of functional activity and trophic degeneration of nerve axons and their terminal arborizations following the destruction of their cells of origin or interruption of their continuity with these cells. The pathology is characteristic of neurodegenerative diseases. Often the process of nerve degeneration is studied in research on neuroanatomical localization and correlation of the neurophysiology of neural pathways.Tyrosine 3-Monooxygenase: An enzyme that catalyzes the conversion of L-tyrosine, tetrahydrobiopterin, and oxygen to 3,4-dihydroxy-L-phenylalanine, dihydrobiopterin, and water. EC 1.14.16.2.Mice, Transgenic: Laboratory mice that have been produced from a genetically manipulated EGG or EMBRYO, MAMMALIAN.Ubiquitin: A highly conserved 76-amino acid peptide universally found in eukaryotic cells that functions as a marker for intracellular PROTEIN TRANSPORT and degradation. Ubiquitin becomes activated through a series of complicated steps and forms an isopeptide bond to lysine residues of specific proteins within the cell. These "ubiquitinated" proteins can be recognized and degraded by proteosomes or be transported to specific compartments within the cell.tau Proteins: Microtubule-associated proteins that are mainly expressed in neurons. Tau proteins constitute several isoforms and play an important role in the assembly of tubulin monomers into microtubules and in maintaining the cytoskeleton and axonal transport. Aggregation of specific sets of tau proteins in filamentous inclusions is the common feature of intraneuronal and glial fibrillar lesions (NEUROFIBRILLARY TANGLES; NEUROPIL THREADS) in numerous neurodegenerative disorders (ALZHEIMER DISEASE; TAUOPATHIES).Lysosomal-Associated Membrane Protein 2: An abundant lysosomal-associated membrane protein that has been found to shuttle between LYSOSOMES; ENDOSOMES; and the PLASMA MEMBRANE. Loss of expression of lysosomal-associated membrane protein 2 is associated with GLYCOGEN STORAGE DISEASE TYPE IIB.Proteasome Endopeptidase Complex: A large multisubunit complex that plays an important role in the degradation of most of the cytosolic and nuclear proteins in eukaryotic cells. It contains a 700-kDa catalytic sub-complex and two 700-kDa regulatory sub-complexes. The complex digests ubiquitinated proteins and protein activated via ornithine decarboxylase antizyme.Protein Binding: The process in which substances, either endogenous or exogenous, bind to proteins, peptides, enzymes, protein precursors, or allied compounds. Specific protein-binding measures are often used as assays in diagnostic assessments.Protein Folding: Processes involved in the formation of TERTIARY PROTEIN STRUCTURE.Disease Models, Animal: Naturally occurring or experimentally induced animal diseases with pathological processes sufficiently similar to those of human diseases. They are used as study models for human diseases.Rotenone: A botanical insecticide that is an inhibitor of mitochondrial electron transport.Mutation: Any detectable and heritable change in the genetic material that causes a change in the GENOTYPE and which is transmitted to daughter cells and to succeeding generations.Protein Structure, Secondary: The level of protein structure in which regular hydrogen-bond interactions within contiguous stretches of polypeptide chain give rise to alpha helices, beta strands (which align to form beta sheets) or other types of coils. This is the first folding level of protein conformation.Protein Multimerization: The assembly of the QUATERNARY PROTEIN STRUCTURE of multimeric proteins (MULTIPROTEIN COMPLEXES) from their composite PROTEIN SUBUNITS.Microscopy, Atomic Force: A type of scanning probe microscopy in which a probe systematically rides across the surface of a sample being scanned in a raster pattern. The vertical position is recorded as a spring attached to the probe rises and falls in response to peaks and valleys on the surface. These deflections produce a topographic map of the sample.Circular Dichroism: A change from planar to elliptic polarization when an initially plane-polarized light wave traverses an optically active medium. (McGraw-Hill Dictionary of Scientific and Technical Terms, 4th ed)Microscopy, Electron, Transmission: Electron microscopy in which the ELECTRONS or their reaction products that pass down through the specimen are imaged below the plane of the specimen.Autophagy: The segregation and degradation of damaged or unwanted cytoplasmic constituents by autophagic vacuoles (cytolysosomes) composed of LYSOSOMES containing cellular components in the process of digestion; it plays an important role in BIOLOGICAL METAMORPHOSIS of amphibians, in the removal of bone by osteoclasts, and in the degradation of normal cell components in nutritional deficiency states.Lysosomes: A class of morphologically heterogeneous cytoplasmic particles in animal and plant tissues characterized by their content of hydrolytic enzymes and the structure-linked latency of these enzymes. The intracellular functions of lysosomes depend on their lytic potential. The single unit membrane of the lysosome acts as a barrier between the enzymes enclosed in the lysosome and the external substrate. The activity of the enzymes contained in lysosomes is limited or nil unless the vesicle in which they are enclosed is ruptured. Such rupture is supposed to be under metabolic (hormonal) control. (From Rieger et al., Glossary of Genetics: Classical and Molecular, 5th ed)Endopeptidase K: An enzyme that catalyzes the hydrolysis of keratin, and of other proteins with subtilisin-like specificity. It hydrolyses peptide amides. Endopeptidase K is from the mold Tritirachium album Limber. (Enzyme Nomenclature, 1992) EC 3.4.21.64.1-Methyl-4-phenylpyridinium: An active neurotoxic metabolite of 1-METHYL-4-PHENYL-1,2,3,6-TETRAHYDROPYRIDINE. The compound reduces dopamine levels, inhibits the biosynthesis of catecholamines, depletes cardiac norepinephrine and inactivates tyrosine hydroxylase. These and other toxic effects lead to cessation of oxidative phosphorylation, ATP depletion, and cell death. The compound, which is related to PARAQUAT, has also been used as an herbicide.PC12 Cells: A CELL LINE derived from a PHEOCHROMOCYTOMA of the rat ADRENAL MEDULLA. PC12 cells stop dividing and undergo terminal differentiation when treated with NERVE GROWTH FACTOR, making the line a useful model system for NERVE CELL differentiation.Paraquat: A poisonous dipyridilium compound used as contact herbicide. Contact with concentrated solutions causes irritation of the skin, cracking and shedding of the nails, and delayed healing of cuts and wounds.Cell Death: The termination of the cell's ability to carry out vital functions such as metabolism, growth, reproduction, responsiveness, and adaptability.Recombinant Proteins: Proteins prepared by recombinant DNA technology.