Biomaterial Database

Ultraviolet-induced alterations of the sodium inactivation in myelinated nerve fibres. 1977

W Schwarz, and J M Fox

Ultraviolet radiation irreversibly reduces the sodium permeability in nerve membranes and, in addition, induces a change of the potential dependence of the kinetic parameters of sodium inactivation in the node of Ranvier. This second ultraviolet effect shifts the kinetic parameters of sodium inactivation h infinity (V), alpha h (V), and beta h (V) to more negative potentials (no changes of the slopes of the curves). The amount of the displacement delta V along the potential axis is equal for the three parameters and depends on the ultraviolet dose. It is about delta V = --10 mV after an irradiation dose of 0.7 Ws/cm2 at 280 nm. Both ultraviolet-induced effects depend on membrane potential and on the wavelength of the applied radiation. But while the potential shift is enhanced at more negative holding potentials, the ultraviolet blocking is diminished and vice versa. Further, the ultraviolet-induced potential shift is greater at 260 nm than at 280 nm, whereas a maximum sensitivity of ultraviolet blocking is found at 280 nm. Therefore, the two radiation effects are the result of two separate photoreactions. For explanation of the radiation-induced potential shift it is assumed that ultraviolet radiation decreases the density of negative charges at the inner surface of the nodal membrane. From this hypothesis a value for the inner surface potential psii was derived. --19 mV less than or equal to psii less than or equal to --14 mV.

UI	MeSH Term	Description	Entries
D008564	Membrane Potentials	The voltage differences across a membrane. For cellular membranes they are computed by subtracting the voltage measured outside the membrane from the voltage measured inside the membrane. They result from differences of inside versus outside concentration of potassium, sodium, chloride, and other ions across cells' or ORGANELLES membranes. For excitable cells, the resting membrane potentials range between -30 and -100 millivolts. Physical, chemical, or electrical stimuli can make a membrane potential more negative (hyperpolarization), or less negative (depolarization).	Resting Potentials,Transmembrane Potentials,Delta Psi,Resting Membrane Potential,Transmembrane Electrical Potential Difference,Transmembrane Potential Difference,Difference, Transmembrane Potential,Differences, Transmembrane Potential,Membrane Potential,Membrane Potential, Resting,Membrane Potentials, Resting,Potential Difference, Transmembrane,Potential Differences, Transmembrane,Potential, Membrane,Potential, Resting,Potential, Transmembrane,Potentials, Membrane,Potentials, Resting,Potentials, Transmembrane,Resting Membrane Potentials,Resting Potential,Transmembrane Potential,Transmembrane Potential Differences
D011893	Rana esculenta	An edible species of the family Ranidae, occurring in Europe and used extensively in biomedical research. Commonly referred to as "edible frog".	Pelophylax esculentus
D011901	Ranvier's Nodes	Regularly spaced gaps in the myelin sheaths of peripheral axons. Ranvier's nodes allow saltatory conduction, that is, jumping of impulses from node to node, which is faster and more energetically favorable than continuous conduction.	Nodes of Ranvier,Nodes, Ranvier's,Ranvier Nodes,Ranviers Nodes
D002462	Cell Membrane	The lipid- and protein-containing, selectively permeable membrane that surrounds the cytoplasm in prokaryotic and eukaryotic cells.	Plasma Membrane,Cytoplasmic Membrane,Cell Membranes,Cytoplasmic Membranes,Membrane, Cell,Membrane, Cytoplasmic,Membrane, Plasma,Membranes, Cell,Membranes, Cytoplasmic,Membranes, Plasma,Plasma Membranes
D002463	Cell Membrane Permeability	A quality of cell membranes which permits the passage of solvents and solutes into and out of cells.	Permeability, Cell Membrane
D000818	Animals	Unicellular or multicellular, heterotrophic organisms, that have sensation and the power of voluntary movement. Under the older five kingdom paradigm, Animalia was one of the kingdoms. Under the modern three domain model, Animalia represents one of the many groups in the domain EUKARYOTA.	Animal,Metazoa,Animalia
D001001	Anura	An order of the class Amphibia, which includes several families of frogs and toads. They are characterized by well developed hind limbs adapted for jumping, fused head and trunk and webbed toes. The term "toad" is ambiguous and is properly applied only to the family Bufonidae.	Bombina,Frogs and Toads,Salientia,Toad, Fire-Bellied,Toads and Frogs,Anuras,Fire-Bellied Toad,Fire-Bellied Toads,Salientias,Toad, Fire Bellied,Toads, Fire-Bellied
D012584	Sciatic Nerve	A nerve which originates in the lumbar and sacral spinal cord (L4 to S3) and supplies motor and sensory innervation to the lower extremity. The sciatic nerve, which is the main continuation of the sacral plexus, is the largest nerve in the body. It has two major branches, the TIBIAL NERVE and the PERONEAL NERVE.	Nerve, Sciatic,Nerves, Sciatic,Sciatic Nerves
D012964	Sodium	A member of the alkali group of metals. It has the atomic symbol Na, atomic number 11, and atomic weight 23.	Sodium Ion Level,Sodium-23,Ion Level, Sodium,Level, Sodium Ion,Sodium 23
D013696	Temperature	The property of objects that determines the direction of heat flow when they are placed in direct thermal contact. The temperature is the energy of microscopic motions (vibrational and translational) of the particles of atoms.	Temperatures