scholarly journals A LIGHT AND ELECTRON HISTOCHEMICAL APPROACH TO THE NODE OF RANVIER AND MYELIN OF PERIPHERAL NERVE FIBERS

1967 ◽  
Vol 15 (12) ◽  
pp. 722-731 ◽  
Author(s):  
O. K. LANGLEY ◽  
D. N. LANDON
Keyword(s):  
Osmium Tetroxide ◽  
Node Of Ranvier ◽  
Nerve Fibers ◽  
Blue Pigment ◽  
Staining Reaction ◽  
Myelinated Nerve ◽  
Structural Localization ◽  
Axon Membrane ◽  
Specific Localization ◽  
Exchange Properties

The Hale staining reaction has been used to study the nature and distribution of acid mucopolysaccharides associated with mammalian peripheral myelinated nerve fibers. Histochemical blocking reactions were employed to determine the specificity of the method. Electron micrographs of parallel preparations were examined to discover the fine structural localization of the optically visible Prussian blue pigment. The observations reported suggest that there is a specific localization of a sulfated mucopolysaccharide in the region immediately surrounding the axolemma at the node of Ranvier. Other parts of the fiber, in particular the myelin sheath, show a preponderance of carboxyl groups. Attention is drawn to the variation in the form and distribution of the Hale stain product after differing fixation procedures. The effect of osmium tetroxide on ferrocyanide-treated material is examined and discussed. Attention is directed to possible physiologic implications of the presence of material with the known ion exchange properties of a sulfated mucopolysaccharide in the immediate environment of the ionically active nodal axon membrane.

scholarly journals The Inner Quaternary Ammonium Ion Receptor in Potassium Channels of the Node of Ranvier

1972 ◽  
Vol 59 (4) ◽  
pp. 388-400 ◽  
Author(s):  
Clay M. Armstrong ◽  
Bertil Hille
Keyword(s):  
Potassium Channels ◽  
Quaternary Ammonium ◽  
Node Of Ranvier ◽  
Nerve Fibers ◽  
Ammonium Ion ◽  
Ammonium Ions ◽  
Myelinated Nerve ◽  
Quaternary Ammonium Ions ◽  
Activation Gate ◽  
Almost All

Quaternary ammonium ions were applied to the inside of single myelinated nerve fibers by diffusion from a cut end. The resulting block of potassium channels in the node of Ranvier was studied under voltage-clamp conditions. The results agree in almost all respects with similar studies by Armstrong of squid giant axons. With tetraethylammonium ion (TEA), pentyltriethylammonium ion (C5), or nonyltriethylammonium ion (C9) inside the node, potassium current during a depolarization begins to rise at the normal rate, reaches a peak, and then falls again. This unusual inactivation is more complete with C9 than with TEA. Larger depolarizations give more block. Thus the block of potassium channels grows with time and voltage during a depolarization. The block reverses with repolarization, but for C9 full reversal takes seconds at -75 mv. The reversal is faster in 120 mM KCl Ringer's and slower during a hyperpolarization to -125 mv. All of these effects contrast with the time and voltage-independent block of potassium, channels seen with external quaternary ammonium ions on the node of Ranvier. External TEA, C5, and C9 block without inactivation. The external quaternary ammonium ion receptor appears to be distinct from the inner one. Apparently the inner quaternary ammonium ion receptor can be reached only when the activation gate for potassium channels is open. We suggest that the inner receptor lies within the channel and that the channel is a pore with its activation gate near the axoplasmic end.

Peroxidases in Tobacco Abscission Zone Tissue

1973 ◽  
Vol 13 (2) ◽  
pp. 591-601 ◽  
Author(s):  
E. W. HENRY ◽  
T. E. JENSEN
Keyword(s):  
Cell Walls ◽  
Osmium Tetroxide ◽  
Specific Inhibitor ◽  
Potassium Cyanide ◽  
Staining Reaction ◽  
Intercellular Spaces ◽  
Structural Investigations ◽  
Structural Localization ◽  
Nicotiana Tabacum L ◽  
Peripheral Areas

The fine-structural localization of peroxidases during ethylene-induced abscission of flower pedicels of Nicotiana tabacum L. cv. ‘Little Turkish’ has been investigated. Peroxidase activity has been localized in both the cell walls and intercellular spaces of ethylene-treated flower pedicels which were fixed in glutaraldehyde, incubated in diaminobenzidine (DAB) medium with postfixation in 2% osmium tetroxide. Peroxidase staining is present in the cell walls and intercellular spaces of control tissue but is not as intense as in ethylene-treated tissue. Increased peroxidase staining is evident in the intercellular spaces and cell walls after 2 h of exposure to ethylene and increases in intensity between 2 and 5 h. At 5 h, ethylene-induced abscission occurs. Fine-structural investigations revealed prominent staining in the middle-lamellar and peripheral areas of the cell walls in ethylene-treated tissue. The peroxidase staining appears to be due to peroxidase as prior incubation with potassium cyanide gives a marked reduction in the staining reaction. Incubation of the ethylene-exposed tissue in aminotriazole, a specific inhibitor of catalase, does not reduce peroxidase staining, except in the microbodies, which reportedly contain catalase.

scholarly journals CHOLINESTERASE ACTIVITY OF NODAL AND INTERNODAL REGIONS OF MYELINATED NERVE FIBERS OF FROG

1967 ◽  
Vol 32 (3) ◽  
pp. 577-583 ◽  
Author(s):  
Miro Brzin ◽  
Wolf-D. Dettbarn
Keyword(s):  
Enzyme Activity ◽  
Esterase Activity ◽  
Cholinesterase Activity ◽  
Node Of Ranvier ◽  
Nerve Fibers ◽  
Selective Inhibitors ◽  
Myelinated Nerve ◽  
Myelinated Nerve Fibers ◽  
Significant Difference ◽  
Saltatory Conduction

The distribution of cholinesterase (Ch-esterase) in isolated myelinated fibers of the frog has been investigated. Quantitative microgasometric measurements have confirmed the previous histochemical observations. Both approaches indicate that in frog nerve fibers acetylcholinesterase (ACh-esterase) is the only or the predominant enzyme when selective inhibitors and different substrates are used: acetylcholine (ACh), butyrylcholine, and acetyl-B-methylcholine (Mecholyl). By means of the microgasometric technique, a significant difference in ACh-esterase activity between axons isolated from ventral (37.2 ± 1.7 µmole x 10-5 ACh/mm2/hr) and dorsal roots (2.0 ± 0.9 µmole x 10-5 ACh/mm2/hr) was found. In the region of the node of Ranvier the enzyme activity (50.4 ± 4.4 µmole x 10-5 ACh/mm2/hr) appears to be considerably higher than in the internodal area (36.6 ± 2.1 µmole x 10-5 ACh/mm2/hr). The findings are discussed in relation to the theory of saltatory conduction and the ACh system.

scholarly journals The mechanosensitive ion channel TRAAK is localized to the mammalian node of Ranvier

2019 ◽  
Author(s):  
Stephen G. Brohawn ◽  
Weiwei Wang ◽  
Jürgen R. Schwarz ◽  
Annie Handler ◽  
Ernest B. Campbell ◽  
...  
Keyword(s):  
Action Potential ◽  
Action Potentials ◽  
Polyclonal Antibodies ◽  
Node Of Ranvier ◽  
Nerve Fibers ◽  
Resting Membrane Potential ◽  
Myelinated Nerve ◽  
Myelinated Nerve Fibers ◽  
Behavioral Studies ◽  
Mechanosensitive Ion Channel

ABSTRACTTRAAK is a membrane tension-activated K+ channel that has been associated through behavioral studies to mechanical nociception. We used specific monoclonal antibodies in mice to show that TRAAK is localized exclusively to nodes of Ranvier, the action potential propagating elements of myelinated nerve fibers. Approximately 80 percent of myelinated nerve fibers throughout the central and peripheral nervous system contain TRAAK in an all-nodes or no-nodes per axon fashion. TRAAK is not observed at the axon initial segment where action potentials are first generated. We used polyclonal antibodies, the TRAAK inhibitor RU2 and node clamp amplifiers to demonstrate the presence and functional properties of TRAAK in rat nerve fibers. TRAAK contributes to the ‘leak’ K+ current in mammalian nerve fiber conduction by hyperpolarizing the resting membrane potential, thereby increasing Na+ channel availability for action potential propagation. Mechanical gating in TRAAK might serve a neuroprotective role by counteracting mechanically-induced ectopic action potentials. Alternatively, TRAAK may open in response to mechanical forces in the nodal membrane associated with depolarization during saltatory conduction and thereby contribute to repolarization of the node for subsequent spikes.

scholarly journals Damage and repair of the peripheral myelin sheath and node of Ranvier after treatment with trypsin.

1975 ◽  
Vol 64 (1) ◽  
pp. 1-14 ◽  
Author(s):  
R C Yu ◽  
R P Bunge
Keyword(s):  
Schwann Cell ◽  
Light And Electron Microscopy ◽  
Node Of Ranvier ◽  
Nerve Fibers ◽  
Myelinated Nerve ◽  
Nodal Region ◽  
Fetal Rat ◽  
The Matrix ◽  
Cell Processes

Cultures of whole fetal rat sensory ganglia which had matured and myelinated in culture were treated for 1-3 h with a pulse of 0.2% trypsin. The tissue was observed during the period of treatment and during subsequent weeks using both light and electron microscopy. Within minutes after trypsin addition the matrix of the culture was altered and the nerve fascicles loosened. Progressive changes included the retraction of Schwann cell processes from the nodal region the detachment of the myelin-related paranodal Schwann cell loops from the axon, and lengthening of the nodal region as the axon was bared. The retraction of myelin from nodal stabilized several hours after trypsin withdrawal. Breakdown of the altered myelin segments was rare. There were no discernable changes in neurons or their processes after this exposure to trypsin. The partial repair which occured over a period of several weeks included the reattachment of paranodal Schwann cell loops to the axolemma and the insertion of new myelin segments where a substantial length of axolemma had been bared. The significance of these observations to the characterization of the Schwann cell-axolemmal junctions on myelinated nerve fibers is discussed. The dramatic degree of myelin change that can occur without concomitant myelin breakdown is particularly noted, as is the observation that these altered myelin segments are, in part, repaired.

Conduction blockade in myelinated fibers by gaseous and volatile substances

1991 ◽  
Vol 260 (3) ◽  
pp. R540-R545
Author(s):  
F. G. Carpenter
Keyword(s):  
Partial Pressure ◽  
Large Diameter ◽  
Small Diameter ◽  
Aqueous Solubility ◽  
Nerve Fibers ◽  
Myelinated Nerve ◽  
Molal Volume ◽  
Axon Membrane ◽  
Anesthetic Action ◽  
Solubility Ratio

The minimum ambient partial pressure required to reversibly disrupt conducted responses in myelinated nerve fibers (Pblock) was determined for 11 gases and chloroform. For all but one substance, Pblock was inversely proportional to their nonaqueous solubility; large-diameter fibers were less vulnerable than fibers of small diameter. No "anesthetic" effect was displayed by SF6. At the Pblock for three of the agents, the time for completion of their anesthetic action (tb) was proportional to their lipid-to-aqueous solubility ratio. When the ratio was large, tb was longer than when the ratio was small; blockade became complete after the partial pressure of the agent in the lipid or nonaqueous phase of the axon membrane became equal to Pblock. The access of these substances to an nonaqueous site was neither pH nor frequency dependent, but in the case of SF6 access did appear to be limited by its molal volume.

scholarly journals The mechanosensitive ion channel TRAAK is localized to the mammalian node of Ranvier

eLife ◽  
2019 ◽  
Vol 8 ◽  
Author(s):  
Stephen G Brohawn ◽  
Weiwei Wang ◽  
Annie Handler ◽  
Ernest B Campbell ◽  
Jürgen R Schwarz ◽  
...  
Keyword(s):  
Action Potential ◽  
Polyclonal Antibodies ◽  
Node Of Ranvier ◽  
Nerve Fibers ◽  
K Channel ◽  
Resting Membrane Potential ◽  
Na Channel ◽  
Nodes Of Ranvier ◽  
Myelinated Nerve ◽  
Myelinated Nerve Fibers

TRAAK is a membrane tension-activated K+ channel that has been associated through behavioral studies to mechanical nociception. We used specific monoclonal antibodies in mice to show that TRAAK is localized exclusively to nodes of Ranvier, the action potential propagating elements of myelinated nerve fibers. Approximately 80 percent of myelinated nerve fibers throughout the central and peripheral nervous system contain TRAAK in what is likely an all-nodes or no-nodes per axon fashion. TRAAK is not observed at the axon initial segment where action potentials are first generated. We used polyclonal antibodies, the TRAAK inhibitor RU2 and node clamp amplifiers to demonstrate the presence and functional properties of TRAAK in rat nerve fibers. TRAAK contributes to the ‘leak’ K+ current in mammalian nerve fiber conduction by hyperpolarizing the resting membrane potential, thereby increasing Na+ channel availability for action potential propagation. We speculate on why nodes of Ranvier contain a mechanosensitive K+ channel.

scholarly journals The pH-dependent rate of action of local anesthetics on the node of Ranvier.

1977 ◽  
Vol 69 (4) ◽  
pp. 475-496 ◽  
Author(s):  
B Hille
Keyword(s):  
Membrane Permeability ◽  
Local Anesthetics ◽  
Time Course ◽  
Node Of Ranvier ◽  
Nerve Fibers ◽  
Lipid Solubility ◽  
Myelinated Nerve ◽  
Degree Of Ionization ◽  
Hydrophobic Barrier ◽  
High Lipid Solubility

Local anesthetic solutions were applied suddenly to the outside of single myelinated nerve fibers to measure the time course of development of block of sodium channels. Sodium currents were measured under voltage clamp with test pulses applied several times per second during the solution change. The rate of block was studied by using drugs of different lipid solubility and of different charge type, and the external pH was varied from pH 8.3 to pH 6 to change the degree of ionization of the amine compounds. At pH 8.3 the half-time of action of amine anesthetics such as lidocaine, procaine, tetracaine, and others was always less than 2 s and usually less than 1 s. Lowering the pH to 6.0 decreased the apparent potency and slowed the rate of action of these drugs. The rate of action of neutral benzocaine was fast (1 s) and pH independent. The rate of action of cationic quaternary QX-572 was slow (greater than 200 s) and also pH independent. Other quaternary anesthetic derivatives showed no action when applied outside. The result is that neutral drug forms act much more rapidly than charged ones, suggesting that externally applied local anesthetics must cross a hydrophobic barrier to reach their receptor. A model representing diffusion of drug into the nerve fiber gives reasonable time courses of action and reasonable membrane permeability coefficients on the assumption that the hydrophobic barrier is the nodal membrane. Arguments are given that there may be a need for reinterpretation of many published experiments on the location of the anesthetic receptor and on which charge form of the drug is active to take into account the effects of unstirred layers, high membrane permeability, and high lipid solubility.

Fine Structure of Planarian Neuroglial Cell

1976 ◽  
Vol 34 ◽  
pp. 188-189 ◽  
Author(s):  
Michio Morita ◽  
Jay Boyd Best
Keyword(s):  
Endoplasmic Reticulum ◽  
Ventral Nerve Cord ◽  
Osmium Tetroxide ◽  
Golgi Body ◽  
Nerve Fibers ◽  
Neuroglial Cell ◽  
Glutaraldehyde Solution ◽  
Deep Indentation ◽  
Cytoplasmic Processes ◽  
Longitudinal Nerve

The species of the planarian Dugesia dorotocephala was used as the experimental animal to study a neuroglial cell in the ventral nerve cord. Animals were fixed with 3% buffered glutaraldehyde solution and postfixed with 1% buffered osmium tetroxide.The neuroglial cell is multipolar, expanding into three or four cytoplasmic processes with many daughter branches. Some neuroglial processes are found to extend perpendicular to the longitudinal nerve fibers, whereas others are seen to be parallel to them. The nucleus of the neuroglial cell is irregular in shape and frequently has a deep indentation. Convex portions of the nucleus seem to be related to the areas from which cytoplasmic processes are extended. Granular endoplasmic reticulum (Fig. 4), Golgi body (Fig. 2), mitochondria (Figs. 1 and 2), microtubules (Fig. 4), and many glycogen granules are observable in the electron dense neuroglial cytoplasm. Neuroglial cells are also observed to contain various sizes of phagosomes and lipids (Fig. 2).

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