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Journal of Neurochemistry Apr 1983An axolemma-enriched fraction prepared from a purified myelinated axon fraction isolated from rat CNS was found to contain phospholipase D at a specific activity similar...
An axolemma-enriched fraction prepared from a purified myelinated axon fraction isolated from rat CNS was found to contain phospholipase D at a specific activity similar to that of a microsomal fraction isolated from whole brain. There was a concomitant threefold enrichment in the specific activity of phospholipase D and acetylcholinesterase in the axolemma-enriched fraction compared with the specific activities of these enzymes in the starting white matter whole homogenate. This axonal phospholipase D may be involved in remodeling of phospholipid, which in turn may affect axonal functions such as ion translocation.
Topics: Acetylcholinesterase; Animals; Axons; Brain; Cell Fractionation; Cell Membrane; Electron Transport Complex IV; NADH Dehydrogenase; Phospholipase D; Phospholipases; Rats; Subcellular Fractions
PubMed: 6300326
DOI: 10.1111/j.1471-4159.1983.tb08114.x -
Neurochemical Research Mar 1993Axolemma-enriched fractions were isolated from bovine spinal accessory nerves, bovine intradural dorsal roots, and rabbit sciatic nerve by differential centrifugation... (Comparative Study)
Comparative Study
Axolemma-enriched fractions were isolated from bovine spinal accessory nerves, bovine intradural dorsal roots, and rabbit sciatic nerve by differential centrifugation and separation on a linear 10-40% sucrose (w/w) gradient. The fractions were enriched 4 to 10 fold in acetylcholinesterase, a biochemical marker for axolemma. Axolemma-enriched fractions isolated from uniformly well-myelinated fibers (bovine spinal accessory nerve) contained lower CNPase activity and higher acetylcholinesterase activity than comparable fractions isolated from variably myelinated fibers (rabbit sciatic nerve and bovine intradural roots). Separation by polyacrylamide electrophoresis showed that the molecular weight distribution of all peripheral nerve axolemma-enriched fractions was similar and ranged from 20 to over 150 kilodaltons. All axolemma-enriched fractions appeared to contain a small but variable amount of myelin-specific proteins. Based on biochemical properties, peripheral nerves containing uniformly well-myelinated fibers yield an axolemma-enriched fraction which is least contaminated with myelin-related membranes.
Topics: 2',3'-Cyclic-Nucleotide Phosphodiesterases; 5'-Nucleotidase; Acetylcholinesterase; Animals; Axons; Cattle; Cell Fractionation; Centrifugation, Density Gradient; Electrophoresis, Polyacrylamide Gel; Intracellular Membranes; Nerve Fibers, Myelinated; Peptides; Peripheral Nerves; Rabbits
PubMed: 8386812
DOI: 10.1007/BF00969086 -
Journal of Neurocytology Aug 1981Freeze-fracture observations have been made on unfixed cryoprotected, and glutaraldehyde-perfused and cryoprotected rat sciatic nerve. In the juxtaparanodal region of...
Freeze-fracture observations have been made on unfixed cryoprotected, and glutaraldehyde-perfused and cryoprotected rat sciatic nerve. In the juxtaparanodal region of the internode, numerous particle clusters were observed on the axolemmal E face and rings of particles of uniform size on the P face of the adaxonal Schwann cell membrane. Both of these particle aggregates were concentrated in the internodal region immediately adjacent to the paranode (juxtaparanodal). The findings provide evidence for a close association between the two particle formations, suggesting a unitary structure forming links between the axolemma and Schwann cell membrane. Figures are given for the density distribution of these particles at the juxtaparanodal region. They were rarely observed on membrane fracture faces of the general internodal regions. It is possible that these particle formations may represent potassium channels or that they could provide channels for other metabolic communication between the Schwann cell and the axon.
Topics: Animals; Cell Membrane; Female; Freeze Fracturing; Male; Microscopy, Electron; Ranvier's Nodes; Rats; Rats, Inbred Lew; Schwann Cells; Sciatic Nerve
PubMed: 6975804
DOI: 10.1007/BF01262597 -
Journal of Biochemical and Biophysical... Apr 2007Quantum mechanical calculations of transmission coefficients for some permeant molecules across the human red cell and resting axolemma squid axon membranes are carried...
Quantum mechanical calculations of transmission coefficients for some permeant molecules across the human red cell and resting axolemma squid axon membranes are carried out. The calculations depend on (i) the molecular weight of the molecule and (ii) the depth and width of the potential well of the membrane. In most cases good agreement between calculated and experimental values is found.
Topics: Animals; Axons; Cell Membrane Permeability; Decapodiformes; Erythrocyte Membrane; Humans; In Vitro Techniques; Membrane Potentials; Models, Biological; Quantum Theory
PubMed: 17011039
DOI: 10.1016/j.jbbm.2006.08.004 -
Journal of Neuroscience Research Sep 1999Bovine splenic nerve was used as a source of axolemma-enriched fractions derived from mammalian unmyelinated axons. By electron microscopy, splenic nerve consisted...
Bovine splenic nerve was used as a source of axolemma-enriched fractions derived from mammalian unmyelinated axons. By electron microscopy, splenic nerve consisted entirely of fascicles of unmyelinated axons and associated Schwann cells. The epineurium and blood vessels were stripped from the dissected nerve, which was then homogenized followed by preparation of a microsomal fraction by differential centrifugation. The microsomes were fractionated on a 10% to 40% continuous sucrose gradient. The individual fractions were combined into six fractions based on sucrose concentration and each fraction was analyzed for membrane markers. The 20% to 23% region of the sucrose gradient was enriched approximately sevenfold in acetylcholinesterase activity and twofold enrichment in saxitoxin binding activity was noted in the same fraction. Relative to other microsomal fractions, this same fraction was less enriched in a microsomal marker (cytochrome c reductase) and only moderately enriched in the activity of a myelin membrane marker (2',3' cyclic nucleotide 3' phosphohydrolase, CNPase). Polyacrylamide electrophoresis of the axolemma-enriched fraction revealed five prominent peptides ranging in molecular weight from 40 kDa to 130 kDa. Lipids, comprising 59.4% of the dry weight, were enriched in cholesterol and sphingomyelin, consistent with the origin from a peripheral nervous system (PNS) plasma membrane. On a molar basis, the major gangliosides were G(T1b), G(D1a), and G(M1). As a whole, these molecular characteristics are consistent with the origin of the axolemma-enriched fraction in the unmyelinated splenic nerve axons. This membrane preparation should prove useful in future studies of the myelinogenic potential of mammalian unmyelinated axolemma.
Topics: Acetylcholinesterase; Amphibian Proteins; Animals; Axons; Carrier Proteins; Cattle; Cell Fractionation; Cell Membrane; Centrifugation, Zonal; Cytochrome c Group; Membrane Lipids; Microsomes; Peptides; Sodium Channels; Spleen; Sympathetic Nervous System
PubMed: 10462691
DOI: No ID Found -
The Journal of Cell Biology Feb 1980Using freeze-fracture techniques, we have analyzed the glial-axonal junction (GAJ) between Schwann cells and axons in the peripheral nervous system, and between... (Comparative Study)
Comparative Study
Rows of dimeric-particles within the axolemma and juxtaposed particles within glia, incorporated into a new model for the paranodal glial-axonal junction at the node of Ranvier.
Using freeze-fracture techniques, we have analyzed the glial-axonal junction (GAJ) between Schwann cells and axons in the peripheral nervous system, and between oligodendrocytes and axons in the central nervous system of the rat. We have identified a new set of dimeric-particles arranged in circumferential rows within the protoplasmic fracture faces (P-faces) of the paranodal axolemma in the region of glial-axonal juxtaposition. These particles, 260 A in length, composed of two 115-A subunits, are observed in both aldehyde-fixed and nonfixed preparations. The rows of dimeric-particles within the axonal P-face are associated with complementary rows of pits within the external fracture face (E-face) of the paranodal axolemma. These axonal particles are positioned between rows of 160-A particles that occur in both fracture faces of the glial loops in the same region. We observed, in addition to these previously described 160-A particles, a new set of 75-A glial particles within the glial P-faces of the GAJ. These 75-A particles form rows that are centered between the rows of 160-A particles and are therefore superimposed over the rows of dimeric-particles within the paranodal axolemma. Our new findings are interpreted with respect to methods of specimen preparation as well as to a potential role for the paranodal organ in saltatory conduction. We conclude that this particle-rich junction between axon and glia could potentially provide an intricate mechanism for ion exchange between these two cell types.
Topics: Animals; Axons; Cell Membrane; Fixatives; Freeze Etching; Freeze Fracturing; Glycerol; Models, Neurological; Neuroglia; Ranvier's Nodes; Rats
PubMed: 7380883
DOI: 10.1083/jcb.84.2.261 -
Neuroscience Research Oct 1987The present report reviews the physiological and morphological specializations of Pacinian corpuscles and other mechanoreceptors that are present in the skin and... (Review)
Review
The present report reviews the physiological and morphological specializations of Pacinian corpuscles and other mechanoreceptors that are present in the skin and connective tissues of the body as well as the cochlea. The remarkable sensitivity of Pacinian corpuscles is such that the only form of mechanical energy that could be perceived by a Pacinian corpuscle is a sound wave. In fact the human finger as demonstrated by Munger and Ide (1987) can perceive sound waves when water is the coupling agent. The structural specializations are equally remarkable with extensive membrane specializations of both the inner core and inner portion of the outer core. The halves of the inner core are each coupled with gap junctions and the inner portion of the outer core joined with numerous tight junctions. The cleft regions have specializations involving the axolemma that consist of numerous axonal spines containing bundles of filaments projecting into the cleft of the inner core. These structural specializations are thought to represent specializations for mechano-electric transduction analogous in many respects to the hair cells of the cochlea. A hypothesis for mechano-electric transduction is presented that may account in part for the extreme sensitivity of Pacinian corpuscles and other mechanoreceptors.
Topics: Animals; Cochlea; Connective Tissue; Electric Conductivity; Mechanoreceptors; Skin
PubMed: 3323953
DOI: 10.1016/0168-0102(87)90019-8 -
Journal of Neuroscience Research Feb 1993The axolemma membrane forms a stable and reproducible monomolecular layer at the air-aqueous interface. The major lipids and proteins are present in this monolayer in...
The axolemma membrane forms a stable and reproducible monomolecular layer at the air-aqueous interface. The major lipids and proteins are present in this monolayer in molar ratios similar to the original membrane. Acetylcholinesterase and Na-K-ATPase activities are preserved in the monolayer to levels of 64% and 25%, respectively. The total lipid fraction forms a homogeneously mixed phase. The presence of proteins in the monolayer introduces surface inhomogeneties. Among other features, this is revealed by the presence of two values of lateral pressure at which the monolayer shows partial or total collapse: a broad partial collapse at surface pressures between 13 to 30 mN/m and a sharp collapse point at 46 mN/m. The average molecular areas, the broad collapse point, and the variation of the surface potential per molecule suggest the relocation of protein components at surface pressures between 13 to 30 mN/m. The behavior is consistent with the extrusion and exposure of proteins toward the aqueous medium that depends on the lateral pressure. Schwann cells grown on coverslips coated with axolemma monolayers at 13 mN/m (beginning of the broad collapse) and 34 mN/m (above the broad collapse) recognize the difference in the surface organization of axolemma caused by the lateral pressure which affects their proliferation, morphology, and spatial pattern of organization. Our results show for the first time that response of Schwann cells depends on the intermolecular organization of the axolemma surface with which they interact. These results suggest that the local expression of putative surface molecules of axolemma that may mediate membrane recognition and the signalling of morphological and proliferative changes can be modulated by long range supramolecular properties.
Topics: Animals; Axons; Cattle; Cell Membrane; Cells, Cultured; Chemical Phenomena; Chemistry, Physical; Lipids; Nerve Tissue Proteins; Rats; Schwann Cells; Surface Properties; Thymidine
PubMed: 8450564
DOI: 10.1002/jnr.490340208 -
The Journal of Cell Biology Dec 1988Recycling of synaptophysin (p38), a synaptic vesicle integral membrane protein, was studied by the use of antisera raised against the protein purified from frog brain....
Recycling of synaptophysin (p38), a synaptic vesicle integral membrane protein, was studied by the use of antisera raised against the protein purified from frog brain. When frog cutaneous pectoris muscles were fixed at rest, a bright, specific immunofluorescent signal was observed in nerve-terminal regions only if their plasma membranes had been previously permeabilized. When muscles were fixed after they had been treated for 1 h with a low dose of alpha-latrotoxin in Ca2+-free medium, an equally intense fluorescence could be observed without previous permeabilization. Under this condition, alpha-latrotoxin depletes nerve terminals of their quantal store of acetylcholine and of synaptic vesicles. These results indicate that fusion of synaptic vesicles leads to the exposure of intravesicular antigenic determinants of synaptophysin on the outer surface of the axolemma, and provide direct support for the vesicle hypothesis of neurotransmitter release. After 1 h treatment with the same dose of alpha-latrotoxin in the presence of 1.8 mM extracellular Ca2+, immunofluorescent images were obtained only after permeabilization with detergents. Under this condition, the vesicle population was maintained by an active process of recycling and more than two times the initial store of quanta were secreted. Thus, despite the active turnover of synaptic vesicles and of quanta of neurotransmitter, no extensive intermixing occurs between components of the vesicle and presynaptic plasma membrane.
Topics: Animals; Autoradiography; Axons; Electrophoresis, Polyacrylamide Gel; Exocytosis; Fluorescent Antibody Technique; Immunoblotting; Membrane Proteins; Molecular Weight; Nerve Tissue Proteins; Neuromuscular Junction; Ranidae; Spider Venoms; Synaptic Vesicles; Synaptophysin
PubMed: 3144557
DOI: 10.1083/jcb.107.6.2717 -
Journal of Neurotrauma Apr 1999Recent work in animal models of human diffuse axonal injury has generated the hypothesis that, rather than there being physical disruption of the axolemma at the time of...
Freeze-fracture and cytochemical evidence for structural and functional alteration in the axolemma and myelin sheath of adult guinea pig optic nerve fibers after stretch injury.
Recent work in animal models of human diffuse axonal injury has generated the hypothesis that, rather than there being physical disruption of the axolemma at the time of injury, a pertubation of the membrane occurs, which leads, over time, to a dysfunction of the physiology of the axolemmal. This dysfunction is posited to lead to a disruption of ionic homeostasis within the injured axon, leading to secondary axotomy some hours after the initial insult. We decided to test the hypothesis that membrane pump/ion channel activity or function is compromised and this would be reflected in structural changes within the axolemma and myelin sheath. We used freeze fracture and cytochemical techniques to provide evidence for change in membrane structure and the activity of membrane pumps after nondisruptive axonal injury in the adult guinea pig optic nerve. Within 10 min of injury, structural changes occurred in the distribution and number of intramembranous particles (IMPs) in the internodal axolemma. By 4 h, there was novel labeling for Ca-ATPase membrane pump activity at the same site. There was loss of IMPs from the nodal axolemma extending over several hours after injury. There was loss of both membrane pump Ca-ATPase and p-nitro-phenylphosphatase (p-NPPase) activity of the node. There was loss of ecto-Ca-ATPase activity but increased labeling for p-NPPase activity at sites of dissociation of compacted myelin. Quantitative freeze-fracture demonstrated statistically significant changes in membrane structure. We provide support for the hypothesis that structural and functional changes occur in the axolemma and myelin sheath at nondisruptive axonal injury.
Topics: 4-Nitrophenylphosphatase; Animals; Axons; Brain Injuries; Calcium-Transporting ATPases; Cell Membrane; Disease Models, Animal; Disease Progression; Freeze Fracturing; Guinea Pigs; Homeostasis; Male; Microscopy, Electron; Myelin Sheath; Optic Nerve; Optic Nerve Injuries; Ranvier's Nodes; Stress, Mechanical; Time Factors
PubMed: 10225214
DOI: 10.1089/neu.1999.16.273