[Age-related changes in interneuronal synapses in human cerebral cortex]. 1983

A S Iontov, and V F Shefer

In 5 persons that did not suffer from any psychical or neurological illnesses, at the age of 75-83 years, ultrastructure of dendrites, axons and axonal terminals was studied in the 40th field of the cerebral cortex, layer after layer. Various forms of changes in the dendrites were revealed demonstrating certain degenerative alterations in them and their loss of synaptic contacts with the axonal terminals. Two types of the axonal changes were followed. One of them, the most spread, has features of functional alterations (a tight arrangement of a great number of coarse neurotubules, while the axoplasm is remained). The state of such fibers is considered by the authors as a reversible one. Changes of the other type of axons (they are deprived of normal organells of axoplasm) are considered by the authors as irreversible. Degeneration of the axonal terminals, noted in all cortical layers, is realized mainly according to the "dark" type and seldom--according to the "light" one. In most cases these contacts are performed by unchanged dendrites. A gradual degeneration and death of neurocytes should be considered as a main course of the disturbances in the interneuronal connections of the cortex.

UI MeSH Term Description Entries
D008854 Microscopy, Electron Microscopy using an electron beam, instead of light, to visualize the sample, thereby allowing much greater magnification. The interactions of ELECTRONS with specimens are used to provide information about the fine structure of that specimen. In TRANSMISSION ELECTRON MICROSCOPY the reactions of the electrons that are transmitted through the specimen are imaged. In SCANNING ELECTRON MICROSCOPY an electron beam falls at a non-normal angle on the specimen and the image is derived from the reactions occurring above the plane of the specimen. Electron Microscopy
D009413 Nerve Fibers, Myelinated A class of nerve fibers as defined by their structure, specifically the nerve sheath arrangement. The AXONS of the myelinated nerve fibers are completely encased in a MYELIN SHEATH. They are fibers of relatively large and varied diameters. Their NEURAL CONDUCTION rates are faster than those of the unmyelinated nerve fibers (NERVE FIBERS, UNMYELINATED). Myelinated nerve fibers are present in somatic and autonomic nerves. A Fibers,B Fibers,Fiber, Myelinated Nerve,Fibers, Myelinated Nerve,Myelinated Nerve Fiber,Myelinated Nerve Fibers,Nerve Fiber, Myelinated
D009435 Synaptic Transmission The communication from a NEURON to a target (neuron, muscle, or secretory cell) across a SYNAPSE. In chemical synaptic transmission, the presynaptic neuron releases a NEUROTRANSMITTER that diffuses across the synaptic cleft and binds to specific synaptic receptors, activating them. The activated receptors modulate specific ion channels and/or second-messenger systems in the postsynaptic cell. In electrical synaptic transmission, electrical signals are communicated as an ionic current flow across ELECTRICAL SYNAPSES. Neural Transmission,Neurotransmission,Transmission, Neural,Transmission, Synaptic
D002540 Cerebral Cortex The thin layer of GRAY MATTER on the surface of the CEREBRAL HEMISPHERES that develops from the TELENCEPHALON and folds into gyri and sulci. It reaches its highest development in humans and is responsible for intellectual faculties and higher mental functions. Allocortex,Archipallium,Cortex Cerebri,Cortical Plate,Paleocortex,Periallocortex,Allocortices,Archipalliums,Cerebral Cortices,Cortex Cerebrus,Cortex, Cerebral,Cortical Plates,Paleocortices,Periallocortices,Plate, Cortical
D003712 Dendrites Extensions of the nerve cell body. They are short and branched and receive stimuli from other NEURONS. Dendrite
D006801 Humans Members of the species Homo sapiens. Homo sapiens,Man (Taxonomy),Human,Man, Modern,Modern Man
D000368 Aged A person 65 years of age or older. For a person older than 79 years, AGED, 80 AND OVER is available. Elderly
D000375 Aging The gradual irreversible changes in structure and function of an organism that occur as a result of the passage of time. Senescence,Aging, Biological,Biological Aging
D001369 Axons Nerve fibers that are capable of rapidly conducting impulses away from the neuron cell body. Axon
D013569 Synapses Specialized junctions at which a neuron communicates with a target cell. At classical synapses, a neuron's presynaptic terminal releases a chemical transmitter stored in synaptic vesicles which diffuses across a narrow synaptic cleft and activates receptors on the postsynaptic membrane of the target cell. The target may be a dendrite, cell body, or axon of another neuron, or a specialized region of a muscle or secretory cell. Neurons may also communicate via direct electrical coupling with ELECTRICAL SYNAPSES. Several other non-synaptic chemical or electric signal transmitting processes occur via extracellular mediated interactions. Synapse

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