scholarly journals FURTHER OBSERVATIONS ON THE STRUCTURE OF MYELIN SHEATHS IN THE CENTRAL NERVOUS SYSTEM

1964 ◽  
Vol 20 (2) ◽  
pp. 281-296 ◽  
Author(s):  
A. Peters
Keyword(s):  
Central Nervous System ◽  
Nervous System ◽  
Direct Evidence ◽  
Radial Component ◽  
Adult Rats ◽  
Direction Parallel ◽  
Myelin Sheaths ◽  
Adult Mice ◽  
Central Myelin ◽  
The Central Nervous System

Direct evidence has been presented to confirm the existence of a spiral in the myelin sheaths of the central nervous system. An account of some of the variations in structure of central myelin sheaths has been given and it has been shown that the radial component of myelin sheaths has the form of a series of rod-like thickenings of the intraperiod line. These thickenings extend along the intraperiod line in a direction parallel to the length of the axon. The relative position of the internal mesaxon and external tongue of cytoplasm has been determined in a number of transverse sections of sheaths from the optic nerves of adult mice, adult rats, and young rats. In about 75 per cent of the mature sheaths examined, these two structures were found within the same quadrant of the sheath, so that the cytoplasm of the external tongue process tends to lie directly outside that associated with the internal mesaxon. The frequency with which the internal mesaxon and external tongue lie within the same quadrant of the sheath increases both with the age of the animal and with the number of lamellae present within a sheath. The possible significance of these findings is discussed.

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.

Hippocampal glutamine synthetase: insensitivity to glucocorticoids and stress

1990 ◽  
Vol 258 (5) ◽  
pp. E894-E897 ◽  
Author(s):  
G. C. Tombaugh ◽  
R. M. Sapolsky
Keyword(s):  
Skeletal Muscle ◽  
Central Nervous System ◽  
Nervous System ◽  
Glutamine Synthetase ◽  
Glutamate Metabolism ◽  
Glutamatergic Synapses ◽  
Adult Rats ◽  
Glucocorticoid Induction ◽  
The Central Nervous System ◽  
The Brain

Glucocorticoids enhance the neurotoxic potential of several insults to the rat hippocampus that involve overactivation of glutamatergic synapses. These hormones also stimulate the synthesis of glutamine synthetase (GS) in peripheral tissue. Because this enzyme helps regulate glutamate metabolism in the central nervous system, glucocorticoid induction of GS in the brain may underlie the observed synergy. We have measured GS activity in the hippocampus and skeletal muscle (plantaris) of adult rats after bilateral adrenalectomy (ADX), corticosterone (Cort) replacement, or stress. No significant changes in GS were observed in hippocampal tissue, whereas muscle GS was significantly elevated after Cort treatment or stress and was reduced after ADX. These results suggest that Cort-induced shifts in GS activity probably do not explain Cort neurotoxicity, although the stress-induced rise in muscle GS may be relevant to certain types of myopathy.

scholarly journals Distribution of Transglutaminase 6 in the Central Nervous System of Adult Mice

2013 ◽  
Vol 296 (10) ◽  
pp. 1576-1587 ◽  
Author(s):  
Yu-Tao Liu ◽  
Bei-Sha Tang ◽  
Wei Lan ◽  
Ning-Ning Song ◽  
Ying Huang ◽  
...  
Keyword(s):  
Central Nervous System ◽  
Nervous System ◽  
Adult Mice ◽  
The Central Nervous System

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

scholarly journals Preoperative Management and Postoperative Delirium in Older People

2021 ◽  
Vol 1 (2) ◽  
pp. 38-40
Author(s):  
Victor Pulpa Seda
Keyword(s):  
Central Nervous System ◽  
Nervous System ◽  
Neutralizing Antibodies ◽  
Memory Impairment ◽  
Postoperative Delirium ◽  
High Morbidity ◽  
Preoperative Management ◽  
Adult Rats ◽  
Memory Decline ◽  
The Central Nervous System

Inflammation of the central nervous system cause postoperative delirium (POD),it is due to systematic inflammation induced by surgery. This can be known afterexperiments with animals. Memory impairment and neutralizing antibodies maybe caused by the high-morbidity cluster box protein. This may decreasepostoperative memory decline in experiments on adult rats. Recently, it is knownthat POD can increase the incidence of morbidity and mortality in postoperativepatients. Prehabilitation is highly recommended for POD. However, the use of VRcan be an option for elderly patients, patients with cognitive impairment andstroke. VR is also a hope for the population. This study is also very important totest VR Neuroprehabilitation for the prevention of POD in certain populations.

Magneto- and electrophosphene thresholds in the retina: a dosimetry modeling study

2021 ◽  
Author(s):  
Janita Nissi ◽  
Ilkka Laakso
Keyword(s):  
Central Nervous System ◽  
Nervous System ◽  
Electric Fields ◽  
Current Density ◽  
Computational Models ◽  
Threshold Current ◽  
Radial Component ◽  
Threshold Current Density ◽  
Exposure Limits ◽  
The Central Nervous System

Abstract Objective: Sensations of flickering light produced by time-varying magnetic fields or electric currents are called magneto- or electrophosphenes. Phosphene thresholds have been used in international guidelines and standards as an estimate of the thresholds of exposure that produce effects in the central nervous system. However, the estimated threshold values have a large range of uncertainty. Approach: Phosphene thresholds were approximated by simulating five phosphene threshold experiments. Retinal electric fields and currents induced by electric and magnetic stimulation were calculated using the finite element method and 14 anatomically realistic computational models of human heads. Main results: The radial component of retinal current density was determined to be in the range of 6.0~--~20.6~mA/m$^2$. This study produces more accurate estimates for threshold current density in the retina using detailed anatomical models and the estimates had a reduced range of uncertainty compared to earlier studies. Significance: The results are useful for studying the mechanisms of retinal phosphenes and for the development of exposure limits for the central nervous system.

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.

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