scholarly journals ELECTRON MICROSCOPE STUDIES OF THE FORMATION OF NODES OF RANVIER IN MOUSE SCIATIC NERVES

1957 ◽  
Vol 3 (4) ◽  
pp. 589-598 ◽  
Author(s):  
Betty Geren Uzman ◽  
Genevieve Nogueira-Graf
Keyword(s):  
Electron Microscope ◽  
Schwann Cell ◽  
Cell Surface ◽  
Myelin Sheath ◽  
Three Dimensions ◽  
Nodes Of Ranvier ◽  
Internodal Length ◽  
Intimate Contact ◽  
General Picture ◽  
Sciatic Nerves

Observations with the electron microscope of longitudinal sections of the sciatic nerves of infant mice during the period of early myelin formation are described. These observations are interpreted in relation to previous studies of transverse sections, and a general picture of the formation of an internodal length of the myelin sheath in three dimensions is formulated. In general, an internodal length of myelin sheath is attained by the spiral wrapping of the infolded Schwann cell surface; the increase in length of the internode during maturation is at least partially explained by the increased length of axon covered by the overlapping of successive layers during the wrapping of the infolded Schwann cell surface; and the nodes of Ranvier refer to the structure complex at the junctions of adjacent non-syncytial Schwann cells. The fact that the mode of formation of myelin brings each of its layers into intimate contact with the axon surface at the nodes is emphasized because of the possible functional significance of this arrangement. The manner of origin of Schmidt-Lantermann clefts remains obscure. Certain isolated observations provide evidence for the possibility that occasional internodes of myelin may form from several small segments of myelin within a single Schwann cell.

scholarly journals THE ULTRASTRUCTURE OF ADULT VERTEBRATE PERIPHERAL MYELINATED NERVE FIBERS IN RELATION TO MYELINOGENESIS

1955 ◽  
Vol 1 (4) ◽  
pp. 271-278 ◽  
Author(s):  
J. David Robertson
Keyword(s):  
Electron Microscope ◽  
Schwann Cell ◽  
Cell Surface ◽  
Peripheral Nerve ◽  
Myelin Sheath ◽  
Nerve Fibers ◽  
Myelinated Nerve ◽  
Thin Sections ◽  
Double Membrane ◽  
Myelinated Nerve Fibers

Adult chameleon myelinated peripheral nerve fibers have been studied with the electron microscope in thin sections. The outer lamella of the myelin sheath has been found to be connected as a double membrane to the surface of the Schwann cell. The inner lamella is connected as a similar double membrane with the double axon-Schwann membrane. The relations of these double connecting membranes suggest that the layered myelin structure is composed of a double membrane which is closely wound about the axon as a helix. These findings support the new theory of myelinogenesis proposed recently by Geren. The possible significance of these results with respect to cell surface membranes and cytoplasmic double membranes is discussed.

scholarly journals The Ultrastructure of Schmidt-Lanterman Clefts and Related Shearing Defects of the Myelin Sheath

1958 ◽  
Vol 4 (1) ◽  
pp. 39-46 ◽  
Author(s):  
J. David Robertson
Keyword(s):  
Electron Microscopy ◽  
Endoplasmic Reticulum ◽  
Schwann Cell ◽  
Outer Layer ◽  
Dynamic Process ◽  
Myelin Sheath ◽  
The Other ◽  
Cross Sectional ◽  
Thin Sections ◽  
Sciatic Nerves

Schmidt-Lanterman clefts in frog sciatic nerves have been studied in thin sections by electron microscopy utilizing permanganate fixation and araldite embedding. It is shown that they are shearing defects in myelin in which the lamellae are separated widely at the major dense lines. Each lamella consisting of two apposed Schwann cell unit membranes ∼ 75 A across traverses the cleft intact. The unit membranes composing each lamella sometimes are slightly (∼ 50 to 100 A) separated in the clefts. The layers between the lamellae contain membranous structures which may be components of the endoplasmic reticulum. These layers are continuous with the outer layer of Schwann cytoplasm and the thin and inconstant cytoplasmic layer next to the axon (Mauthner's sheath). Each of these layers in perfect clefts constitutes a long helical pathway through the myelin from the axon. One of these is connected with Schwann cytoplasm and the other directly with the outside. A type of cross-sectional shearing defect, not hitherto recognized, is described and shown to be a kind of Schmidt-Lanterman cleft. Incomplete clefts are seen and interpreted as representing stages in a dynamic process whereby the myelin lamellae may be constantly separating and coming together again in life.

scholarly journals Myelination of peripheral nerves is controlled by PI4KB through regulation of Schwann cell Golgi function

2020 ◽  
Vol 117 (45) ◽  
pp. 28102-28113 ◽  
Author(s):  
Takashi Baba ◽  
Alejandro Alvarez-Prats ◽  
Yeun Ju Kim ◽  
Daniel Abebe ◽  
Steve Wilson ◽  
...  
Keyword(s):  
Schwann Cell ◽  
Peripheral Nerves ◽  
Large Diameter ◽  
Small Diameter ◽  
Nerve Fibers ◽  
Protein Glycosylation ◽  
Mutant Mice ◽  
Nodes Of Ranvier ◽  
Golgi Compartment ◽  
Sciatic Nerves

Better understanding myelination of peripheral nerves would benefit patients affected by peripheral neuropathies, including Charcot–Marie–Tooth disease. Little is known about the role the Golgi compartment plays in Schwann cell (SC) functions. Here, we studied the role of Golgi in myelination of peripheral nerves in mice through SC-specific genetic inactivation of phosphatidylinositol 4-kinase beta (PI4KB), a Golgi-associated lipid kinase. Sciatic nerves of such mice showed thinner myelin of large diameter axons and gross aberrations in myelin organization affecting the nodes of Ranvier, the Schmidt–Lanterman incisures, and Cajal bands. Nonmyelinating SCs showed a striking inability to engulf small diameter nerve fibers. SCs of mutant mice showed a distorted Golgi morphology and disappearance of OSBP at the cis-Golgi compartment, together with a complete loss of GOLPH3 from the entire Golgi. Accordingly, the cholesterol and sphingomyelin contents of sciatic nerves were greatly reduced and so was the number of caveolae observed in SCs. Although the conduction velocity of sciatic nerves of mutant mice showed an 80% decrease, the mice displayed only subtle impairment in their motor functions. Our analysis revealed that Golgi functions supported by PI4KB are critically important for proper myelination through control of lipid metabolism, protein glycosylation, and organization of microvilli in the nodes of Ranvier of peripheral nerves.

scholarly journals THE GEOMETRY OF PERIPHERAL MYELIN SHEATHS DURING THEIR FORMATION AND GROWTH IN RAT SCIATIC NERVES

1971 ◽  
Vol 48 (2) ◽  
pp. 348-367 ◽  
Author(s):  
Henry deF. Webster
Keyword(s):  
Growth Rate ◽  
Schwann Cell ◽  
Cell Surface ◽  
Transverse Plane ◽  
Electron Micrograph ◽  
Myelin Sheaths ◽  
Sciatic Nerves ◽  
Length And Area ◽  
Different Levels ◽  
Small Bundle

In rat sciatic nerves, a small bundle of fibers was identified in which myelin sheaths were absent at birth, appeared within 3 days, and grew rapidly for 2 wk. During this interval, nerves were removed from littermates and were sectioned serially in the transverse plane. Alternating sets of thin and thick sections were used to prepare electron micrograph montages in which single myelinating axons could be identified and traced distally. During the formation of the first spiral turn, the mesaxon's length and configuration varied when it was studied at different levels in the same Schwann cell. The position of the mesaxon's termination shifted while its origin, at the Schwann cell surface, remained relatively constant. Along myelin internodes composed of two to six spiral turns, there were many variations in the number of lamellae and their contour. Near the mesaxon's origin, longitudinal strips of cytoplasm separated the myelin layers. Thicker sheaths were larger in circumference, more circular in transverse sections, and more uniform at different levels. Irregularities were confined to the paranodal region, and separation of lamellae by cytoplasm occurred at Schmidt-Lantermann clefts. Approximate dimensions of the bundle, its largest fibers, and their myelin sheaths were measured and calculated. The myelin membrane's transverse length and area increased exponentially with time; the growth rate increased rapidly during the formation of the first four to six spiral layers and remained relatively constant during the subsequent enlargement of the compact sheath.

Incorporation of Cholesterol into Peripheral Nerve Myelin

1972 ◽  
Vol 30 ◽  
pp. 334-335
Author(s):  
Frank A. Rawlins
Keyword(s):  
Electron Microscope ◽  
Sciatic Nerve ◽  
Electron Microscope Autoradiography ◽  
Myelin Sheaths ◽  
Microscope Autoradiography ◽  
Grain Distribution ◽  
Sciatic Nerves ◽  
Autoradiographic Analysis ◽  
Old Mice ◽  
Short Times

Several speculations exist as to the site of incorporation of preformed molecules into myelin. The possibility that an autoradiographic analysis of cholesterol-1,2-H3 incorporation at very short times after injection might shed some light in the solution of that problem led to the present experiment.Cholesterol-1,2-H3 was injected intraperitoneally into 24 tenday old mice. The animals were then sacrificed at 10,20,30,40,60,90,120 and 180 min after the injection and the sciatic nerves were processed for electron microscope autoradiography. To analyze the grain distribution in the autoradiograms of cross and longitudinal sections from each sciatic nerve myelin sheaths were subdivided into three compartments named: outer 1/3, middle 1/3 and inner 1/3 compartments.It was found that twenty min. after the injection of cholesterol -1.2-H3 (Figs. 1 and 2), 55% of the total number of grains (t.n.g) found in myelin were within the outer 1/3 compartment, 9% were within the middle 1/3 and 36% within the inner 1/3 compartment

The localization of sodium and calcium to Schwann cell paranodal loops at nodes of Ranvier and of calcium to compact myelin

1980 ◽  
Vol 9 (2) ◽  
pp. 185-205 ◽  
Author(s):  
Mark H. Ellisman ◽  
Peter L. Friedman ◽  
W. J. Hamilton
Keyword(s):  
Schwann Cell ◽  
Nodes Of Ranvier

scholarly journals Stimulation of corneal differentiation by interaction between cell surface and extracellular matrix. I. Morphometric analysis of transfilter "induction".

1975 ◽  
Vol 66 (2) ◽  
pp. 275-291 ◽  
Author(s):  
L Meier ◽  
E D Hay
Keyword(s):  
Extracellular Matrix ◽  
Electron Microscope ◽  
Cell Surface ◽  
Pore Size ◽  
Collagen Synthesis ◽  
Lens Capsule ◽  
Physical Contact ◽  
Corneal Epithelial ◽  
Cell Processes

The present study was undertaken to determine whether or not physical contact with the substratum is essential for the stimulatory effect of extracellular matrix (ECM) on corneal epithelial collagen synthesis. Previous studies showed that collagenous substrata stimulate isolated epithelia to produce three times as much collagen as they produce on noncollagenous substrate; killed collagenous substrata (e.g., lens capsule) are just as effective as living substrata (e.g., living lens) in promoting the production of new corneal stroma in vitro. In the experiments to be reported here, corneal epithelia were placed on one side of Nucleopore filters of different pore sizes and killed lens capsule on the other, with the expectation that contact of the reacting cells with the lens ECM should be limited by the number and size of the cell processes that can tranverse the pores. Transfilter cultures were grown for 24 h in [3H]proline-containing median and incorporation of isotope into hot trichloroacetic acid-soluble protein was used to measure corneal epithelial collagen production. Epithelial collagen synthesis increases directly as the size of the pores in the interposed filter increases and decreases as the thickness of the filter layer increases. Cell processes within Nucleopore filters were identified with the transmission electron microscope with difficulty; with the scanning electron microscope, however, the processes could easily be seen emerging from the undersurface of even 0.1-mum pore size filters. Morphometric techniques were used to show that cell surface area thus exposed to the underlying ECM is linearly correlated with enhancement of collagen synthesis. Epithelial cell processes did not pass through ultrathin (25-mum thick) 0.45-mum pore size Millipore filters nor did "induction" occur across them. The results are discussed in relation to current theories of embryonic tissue interaction.

Schwann Cell Vulnerability to Demyelination is Associated with Internodal Length in Tellurium Neuropathy

1988 ◽  
Vol 47 (1) ◽  
pp. 41-47 ◽  
Author(s):  
Thomas W. Bouldin ◽  
Gregory Samsa ◽  
Todd S. Earnhardt ◽  
Martin R. Krigman
Keyword(s):  
Schwann Cell ◽  
Internodal Length

scholarly journals Polarization of myelinating Schwann cell surface membranes: role of microtubules and the trans-Golgi network

1995 ◽  
Vol 15 (3) ◽  
pp. 1797-1807 ◽  
Author(s):  
BD Trapp ◽  
GJ Kidd ◽  
P Hauer ◽  
E Mulrenin ◽  
CA Haney ◽  
...  
Keyword(s):  
Schwann Cell ◽  
Cell Surface ◽  
Trans Golgi Network ◽  
Myelinating Schwann Cell ◽  
Golgi Network

LIPID–PROTEIN COMPLEXES IN MEMBRANES OF NERVOUS TISSUE

1962 ◽  
Vol 40 (1) ◽  
pp. 1261-1271
Author(s):  
L. S. Wolfe
Keyword(s):  
Nervous System ◽  
Sialic Acid ◽  
Schwann Cell ◽  
Myelin Sheath ◽  
Nervous Tissue ◽  
Chemical Structure ◽  
Grey Matter ◽  
Protein Complexes ◽  
Functional Importance ◽  
Acetylneuraminic Acid

Recent investigations have demonstrated that cellular and intracellular membranes within the nervous system contain complex associations of lipids, proteins, and carbohydrates. The myelin sheath contains such complexes derived from the Schwann cell or satellite cell membranes. Similar complexes are found in membranes from grey matter together with less familiar associations between lipids and carbohydrates. Gangliosides are a group of acidic glycolipids which contain among other sugars the sialic acid, N-acetylneuraminic acid. The present state of knowledge on the chemical structure, metabolism, and functional importance of these complex macromolecules is discussed.

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