Observations on the Chemical Composition of Myelin and the Smallest Size of Myelinated Nerve-Fibres in the Central Nervous System

1948 ◽  
Vol s3-89 (5) ◽  
pp. 89-102
Author(s):  
A. BRODAL ◽  
R. G. HARRISON
Keyword(s):  
Central Nervous System ◽  
Nervous System ◽  
Chemical Composition ◽  
Nile Blue ◽  
Nerve Fibres ◽  
Myelinated Nerve ◽  
Myelin Sheaths ◽  
The Central Nervous System

Baker's (1946) acid haematein and pyridine-extraction control tests, claimed to be specific for phospholipines (Baker, 1947), have been applied to various parts of the central nervous system of rats and man. The sudan black method for the detection of lipoids and the nile blue method for the staining of acidic lipoids have also been used. The findings are in agreement with older statements in the literature that myelin contains a considerable amount of phospholipines. It was impossible to determine whether galactolipines or neutral lipoids are also present. In the acid haematein-stained sections finer fibres were seen than when other stains for myelin sheaths are employed. Fibres with a diameter of 0.5 µ or even somewhat less were stained in various parts of the central nervous system of rats. It is regarded as probable from these findings that fibres down to 0.5 µ or even smaller possess a lipoid investment. These observations lend support to the now commonly accepted view that the distinction between myelinated and so-called unmyelinated fibres is arbitrary. Some observations are made, however, which indicate that the presence of truly unmyelinated fibres cannot be excluded.

On the relation between fibre diameter and conduction velocity in myelinated nerve fibres

1982 ◽  
Vol 217 (1206) ◽  
pp. 29-35 ◽  
Keyword(s):  
Central Nervous System ◽  
Nervous System ◽  
Conduction Velocity ◽  
Fibre Diameter ◽  
Nerve Fibres ◽  
Myelinated Nerve ◽  
Fibre Size ◽  
Central Nervous Systems ◽  
The Central Nervous System ◽  
Myelinated Fibres

Myelinated fibres less than 1 μm in diameter are rare in the peripheral nervous system; but fibres down to 0.2 μm in diameter exist in the central nervous system. These observations are consistent with Rushton’s theory on the effects of fibre size on conduction in myelinated nerve when the different processes of myelination in the peripheral and central nervous systems are taken into account.

scholarly journals Biology of the repair of central nervous system demyelinated lesions: an appraisal

1996 ◽  
Vol 54 (2) ◽  
pp. 331-334 ◽  
Author(s):  
L. A. V Peireira ◽  
M. A. Cruz-Höfling ◽  
M. S. J. Dertkigil ◽  
D. L. Graça
Keyword(s):  
Central Nervous System ◽  
Nervous System ◽  
Schwann Cells ◽  
Demyelinating Disease ◽  
Experimental Models ◽  
Primitive Cell ◽  
Marked Influence ◽  
Myelin Sheaths ◽  
Human Material ◽  
The Central Nervous System

The integrity of myelin sheaths is maintained by oligodendrocytes and Schwann cells respectively in the central nervous system (CNS) and in the peripheral nervous system. The process of demyelination consisting of the withdrawal of myelin sheaths from their axons is a characteristic feature of multiple sclerosis, the most common human demyelinating disease. Many experimental models have been designed to study the biology of demyelination and remyelination (repair of the lost myelin) in the CNS, due to the difficulties in studying human material. In the ethidium bromide (an intercalating gliotoxic drug) model of demyelination, CNS remyelination may be carried out by surviving oligodendrocytes and/or by cells differentiated from the primitive cell lines or either by Schwann cells that invade the CNS. However, some factors such as the age of the experimental animals, intensity and time of exposure to the intercalating chemical and the topography of the lesions have marked influence on the repair of the tissue.

scholarly journals A STRUCTURAL ANALYSIS OF THE MYELIN SHEATH IN THE CENTRAL NERVOUS SYSTEM

1967 ◽  
Vol 34 (2) ◽  
pp. 555-567 ◽  
Author(s):  
Asao Hirano ◽  
Herbert M. Dembitzer
Keyword(s):  
Central Nervous System ◽  
Nervous System ◽  
Electron Microscope ◽  
Myelin Sheath ◽  
Cerebral White Matter ◽  
Experimental Conditions ◽  
Myelin Sheaths ◽  
Basic Theme ◽  
Cell Processes ◽  
The Central Nervous System

The cerebral white matter of rats subjected to a variety of noxious experimental conditions was examined in the electron microscope. Several unusual configurations of the myelin sheath are identified in addition to the usual configuration. These variations include the presence of (a) formed organelles within the inner and outer loops, (b) isolated islands of cytoplasm in unfused portions of the major dense lines, (c) apparently unconnected cell processes between the sheath and the axon, and (d) concentric, double myelin sheaths. A generalized model of the myelin sheath based on a hypothetical unrolling of the sheath is described. It consists of a shovel-shaped myelin sheet surrounded by a continuous thickened rim of cytoplasm. Most of the unusual myelin configurations are explained as simple variations on this basic theme. With the help of this model, an explanation of the formation of the myelin sheath is offered. This explanation involves the concept that myelin formation can occur at all cytoplasmic areas adjacent to the myelin proper and that adjacent myelin lamellae can move in relation to each other.

Preferential localization of prostamide/prostaglandin F synthase in myelin sheaths of the central nervous system

2011 ◽  
Vol 1367 ◽  
pp. 22-32 ◽  
Author(s):  
Keisuke Yoshikawa ◽  
Shiro Takei ◽  
Sanae Hasegawa-Ishii ◽  
Yoichi Chiba ◽  
Ayako Furukawa ◽  
...  
Keyword(s):  
Central Nervous System ◽  
Nervous System ◽  
Myelin Sheaths ◽  
Preferential Localization ◽  
Prostaglandin F ◽  
The Central Nervous System

The Effects of Curare in the Cockroach

1970 ◽  
Vol 52 (3) ◽  
pp. 583-592
Author(s):  
K. J. FRIEDMAN ◽  
A. D. CARLSON
Keyword(s):  
Central Nervous System ◽  
Nervous System ◽  
Motor Nerve ◽  
Nerve Fibres ◽  
Affected Area ◽  
Metathoracic Ganglion ◽  
The Central Nervous System ◽  
Mechanical Studies

1. The nature of insect curarization has been investigated in the cockroach, P. americana. Mechanical studies of leg contraction revealed that dTC, whether injected into the abdomen, injected into a leg or applied to the metathoracic ganglion, produces failure of contraction. 2. The contraction failure caused by injecting dTC into a leg or by applying dTC to the metathoracic ganglion could be reversed by washing the drug out of the affected area. 3. The central nervous system does not appear to be essential for curare-induced contraction failure. The contraction of metathoracic legs deprived of their metathoracic ganglion is abolished in the presence of curare. 4. Since curare produces contraction failure when applied to the metathorax and when injected into a leg, the site of curare action must be present in both these locations. The motor nerve fibres are present in both these locations and it is proposed that contraction failure is due to the action of curare on these fibres.

scholarly journals THE FORMATION AND STRUCTURE OF MYELIN SHEATHS IN THE CENTRAL NERVOUS SYSTEM

1960 ◽  
Vol 8 (2) ◽  
pp. 431-446 ◽  
Author(s):  
A. Peters
Keyword(s):  
Central Nervous System ◽  
Nervous System ◽  
Electron Microscope ◽  
Xenopus Laevis ◽  
Peripheral Nervous System ◽  
Nerve Fibre ◽  
Potassium Permanganate ◽  
Myelin Sheaths ◽  
A Cell ◽  
The Central Nervous System

The development and structure of myelin sheaths have been studied in the optic nerves of rats and of Xenopus laevis tadpoles. Both potassium permanganate- and osmium-fixed material was examined with the electron microscope. In the first stage of myelinogenesis the nerve fibre is surrounded by a cell process which envelops it and forms a mesaxon. The mesaxon then elongates into a loose spiral from which the cytoplasm is later excluded, so that compact myelin is formed. This process is similar to myelinogenesis in the peripheral nervous system, although in central fibres the cytoplasm on the outside of the myelin is confined in a tongue-like process to a fraction of the circumference, leaving the remainder of the sheath uncovered, so that contacts are possible between adjacent myelin sheaths. The structure of nodes in the central nervous system has been described and it is suggested that the oligodendrocytes may be the myelin-forming cells.

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