1,721,110 research outputs found
Locus Coeruleus Noradrenergic Neurons and Astroglia in Health and Disease
No full textThe diffuse canvas of neuronal projections, arising from the brainstem locus coeruleus (LC) nucleus, is the primary sourc of noradrenaline (NA) in the central nervous system (CNS). During development the network of LC neurons develop in parallel with the neocortex, while projections of these neurons innervate virtually all areas in the CNS. The dense vascularization of the LC, and its proximity to the ventricles indicates high metabolic activity and vulnerability of these clls, which, in pathologic conditions can lead to the LC cll death, an early event in Parkinson's and Alzheimer's diseases. Reduced availability of NA affects astrocytes, the key homeostasis-providing clls in the CNS. Thus maintenanc in the LC nucleus and/or enhancment of mechanisms that mimic the action of NA, delays the onset of clinical signs in neurodegeneration, a new strategy to mitigate neurodegeneration.</p
Transient and permanent fusion of vesicles in Zea mays coleoptile protoplasts measured in the cell-attached configuration
No full textExocytosis in protoplasts from Zea mays L. coleoptiles was studied using patch-clamp techniques. Fusion of individual vesicles with the plasma membrane was monitored as a step increase of the membrane capacitance (C-m). Vesicle fusion was observed as (i) An irreversible step increase in C-m. (ii) Occasionally, irreversible C-m steps were preceded by transient changes in C-m, suggesting that the electrical connection between the vesicle with the plasma membrane opens and closes reversibly before full connection is achieved. (iii) Most frequently, however, stepwise transient changes in C-m did not lead to an irreversible C-m step. Within one patch of membrane capacitance steps due to transient and irreversible fusions were of similar amplitude. This suggests that the exocytosis events do not result from the fusion of vesicles with different sizes but are due to kinetically different states in a fusion process of the same vesicle type. The dwell time histogram of the transient fusion events peaked at about 100 msec. Fusion can be described with a circular three-state model for the fusion process of two fused states and one nonfused state. It predicts that energy input is required to drive the system into a prevailing direction
The Concept of Neuroglia
No full textNeuroglia represent a diverse population of non-neuronal cells in the nervous systems, be that peripheral, central, enteric or autonomic nervous system. Arguably, these cells represent about half of the volume of the human brain. This volumetric ratio, and by extension glia to neurone ratio, not only widely differ depending on the size of the animal species brain and its positioning on the phylogenetic tree, but also vary between the regions of an individual brain. Neuroglia derived from a dual origin (ectoderm and mesodermal) and in an assorted morphology, yet their functional traits can be mainly classified into being keepers of homeostasis (water, ions, neurotransmitters, metabolites, fuels, etc.) and defenders (e.g., against microbial organisms, etc.) of the nervous system. As these capabilities go awry, neuroglia ultimately define their fundamental role in most, if not, all neuropathologies. This concept presented in this chapter serves as a general introduction into the world of neuroglia and subsequent topics covered by this book.</p
Physiology of Astroglia
No full textAstrocytes are principal cells responsible for maintaining the brain homeostasis. Additionally, these glial cells are also involved in homocellular (astrocyte-astrocyte) and heterocellular (astrocyte-other cell types) signalling and metabolism. These astroglial functions require an expression of the assortment of molecules, be that transporters or pumps, to maintain ion concentration gradients across the plasmalemma and the membrane of the endoplasmic reticulum. Astrocytes sense and balance their neurochemical environment via variety of transmitter receptors and transporters. As they are electrically non-excitable, astrocytes display intracellular calcium and sodium fluctuations, which are not only used for operative signalling but can also affect metabolism. In this chapter we discuss the molecules that achieve ionic gradients and underlie astrocyte signalling.</p
The anatomy of astrocytic vesicles containing gliotransmitters
No full textSlovenian Research Agency [P3 0310, J3 3632, J3 4146, J3 7605
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