Nervous system

About: Nervous system is a research topic. Over the lifetime, 16729 publications have been published within this topic receiving 847181 citations.

Emerging Role of Neuronal Exosomes in the Central Nervous System

Abstract: Exosomes are small extracellular vesicles, which stem from endosomes fusing with the plasma membrane, and can be recaptured by receiving cells. They contain lipids, proteins and RNAs able to modify the physiology of receiving cells. Functioning of the brain relies on intercellular communication between neural cells. These communications can modulate the strength of responses at sparse groups of specific synapses, to modulate circuits underlying associations and memory. Expression of new genes must then follow to stabilize the long-term modifications of the synaptic response. Local changes of the physiology of synapses from one neuron driven by another, have so far been explained by classical signal transduction to modulate transcription, translation and post-translational modifications. In vitro evidence now demonstrate that exosomes are released by neurons in a way depending on synaptic activity; these exosomes can be retaken by other neurons suggesting a novel way for interneuronal communication. The efficacy of inter-neuronal transfer of biochemical information allowed by exosomes would be far superior to that of direct cell to-cell contacts or secreted soluble factors. Indeed, lipids, proteins and RNAs contained in exosomes secreted by emitting neurons could directly modify signal transduction and protein expression in receiving cells. Exosomes could thus represent an ideal mechanism for inter-neuronal transfer of information allowing anterograde and retrograde signalling across synapses necessary for plasticity. They might also allow pathological proteins to spread across the nervous system.

Lesioned corticospinal tract axons regenerate in myelin-free rat spinal cord.

Abstract: In the adult central nervous system (CNS) of higher vertebrates lesioned axons seemed unable to regenerate and reach their former target regions due to influences of the CNS microenvironment. Evidence from in vitro and biochemical experiments has demonstrated the presence of inhibitory substrate components in CNS tissue, in particular in white matter. These CNS components, which strongly inhibit neurite growth, were identified as minor membrane proteins of defined molecular mass (35 and 250 kDa) in oligodendrocyte membranes and CNS myelin. Oligodendrocyte development and myelin formation can be prevented by x-irradiation of newborn rats. Here we show that in myelin-free spinal cords cortico-spinal tract fibers transected at 2 weeks of age show reelongation of many millimeters within 2-3 weeks after the lesion. In normally myelinated controls, regenerative sprouts grew less than 1.7 mm caudal to the lesion.

Protein metabolism of the nervous system.

Abstract: Publisher Summary The chapter discusses cerebral protein metabolism, general problems of protein metabolism in other organs and organisms, and some of the recent reviews discussing the areas of importance in cerebral protein metabolism. In the brain, more than in any other organ, the functional metabolism seems to involve changes in the proteins of the organ. The controlling factors of cerebral protein metabolism are of interest, particularly because there is very little regeneration in the central nervous system. Some diseases of the nervous system are apparently caused by the lack of some enzyme proteins normally present. In other diseased states, the presence of abnormal proteins, and structural changes in normal proteins, are found. Also of interest are the reported effects of a number of drugs on cerebral protein metabolism. The control of protein metabolism in all its aspects is the most important problem. It is related to processes of growth, differentiation, degeneration, as well as maintenance of the cells and their protein complement. The growth factor discussed affects one or more of these processes. This factor is specific for a part of the nervous system, but controlling factors of decisive influence may be operative that are specific for other parts of the nervous system, or specific for a cell type in other organs. The knowledge of the mechanism of action of such factors sheds light on the control mechanisms of cellular metabolism.