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PubMed1979

Recurrent demyelination in chronic central nervous system infection produced by Theiler's murine encephalomyelitis virus.

A morphologic study of demyelination produced by Theiler's encephalomyelitis virus (TMEV) infection in C3H/He mice was performed. Demyelination in this strain of mouse was less intense and had a milder gliomesodermal response than that observed in SJL mice. As early as 80 days after infection numerous remyelinated axons were present in C3H/He mice, and later, extensive remyelination was observed and was mainly by Schwann cells. About one-third of remyelinated plaques showed recurrent demyelinating activity at 200 days. The best evidence of recurrent demyelination was the loss of myelin by abons which had been previously remyelinated by Schwann cells. In addition, acute areas of demyelination were also seen in spinal cords which contained chronic or quiescent plaques. The demonstration of recurrent demyelination in TMEV infection is important for it increases the relevance of this model to multiple sclerosis (MS). In addition TMEV infection of C3H/He mice appears to be an excellent model for further studies of Schwann cell remyelination and recurrent demyelination in the central nervous system (CNS).

Animals↗
PubMedDate not supplied

Histology and ultrastructure of alterations in neuropathy.

Histologic findings are described in nerves from men exposed to lead, from patients with discrete clinical signs of peripheral neuropathy, and from controls. Every nerve from control subjects showed an abnormality (paranodal remyelination, segmental remyelination, or regeneration) in teased fibers. The only histologic alteration in eight lead-exposed males without signs or symptoms of neuropathy was a slightly increased incidence of paranodal remyelination. Sixteen patients with discrete neurologic symptoms and signs had a loss of large myelinated fibers and an increased incidence of regenerated fibers among teased fibers. Electron microscopy of unmyelinated fibers showed an increased occurrence of Schwann-cell processes, of fibers undergoing degeneration, and of Schwann-cell subunits with many profiles as the earliest signs of abnormality. Clinically mild neuropathies may exhibit advanced regeneration in the case of unmyelinated fibers. The earliest sign of degeneration in myelinated fibers was a diminution in the number of axonal organelles.

Adult↗
PubMed1979

Demyelinating encephalomyelitis induced by a long-term corona virus infection in rats. A preliminary report.

About 30% of weanling rats inoculated with JHM virus developed a subacute demyelinating encephalomyelitis (SDE) 3 weeks after inoculation (a.i.). From the remaining animals, 5% displayed overt neurological signs 3, 6, and 8 months a.i. Animals with and without clinical signs 6-8 months a.i. were morphologically examined. Fresh demyelinating lesions could be demonstrated in paralyzed animals. Viral antigen was demonstrated and infectious JHM virus could be recovered from one animal which developed clinical signs at 3 months a.i. In one animal with clinical onset of 8 months a.i. completely remyelinated areas as well as recent demyelinating lesions were observed, suggesting a recurrence of the disease process. Remyelinated areas were also found in 40% of clinically silent animals. The morphology of the late onset of the demyelination was similar to that occurring in SDE. Remyelination consisted of both CNS and PNS-type. This animal model offers the possibility to investigate the virus-host relationship which is responsible for the induction of a demyelinating process after a long incubation period.

Animals↗
PubMed1978

Lesions in the cat spinal cord following local injections of 6-aminonicotinamide.

Lesions were made in the spinal cord of cats by means of local injections of 6-aminonicotinamide. The concentration needed to induce primary demyelination also caused extensive axonal death. In the early stages following injection there was evidence of astrocyte and oligodendrocyte destruction and with longer survival times most of the surviving demyelinated axons were remyelinated by Schwann cells. This experimental system indicates that Schwann cell remyelination of central axons follows astrocyte destruction, but it was not considered a suitable model system for the study of cellular relationships in remyelination because of the extensive concomitant axonal damage.

6-Aminonicotinamide↗
PubMed1978

Chronic relapsing experimental allergic encephalomyelitis: CNS plaque development in unsuppressed and suppressed animals.

Central nervous system (CNS) lesion morphology has been studied in inbred Strain 13 guinea pigs sensitized for chronic relapsing EAE in which the disease was either left to develop (unsuppressed) or was suppressed with injections containing myelin basic protein (MBP). Pathologic changes correlated well with clinical activity. In unsuppressed chronic EAE animals, active clinical disease was invariably matched by acute inflammation in the CNS. In more chronic states, the CNS displayed fibrosis and remyelination while relapses showed the CNS to contain recent changes superimposed upon old lesions. In animals in which the disease was suppressed by injections of MBP, clinical signs did not develop. However, some early subclinical changes were seen morphologically. These lesions were able to remyelinate early on and there was no progression in lesion formation. Apparently, therefore, MBP had a beneficial effect upon the course of the disease and had promoted structural repair. It thus appears that MBP therapy might be one effective approach for the prevention of chronic relapsing EAE. The findings should prove relevant to future MBP trials in multiple sclerosis.

Animals↗
PubMed1977

Attempts to induce chronic experimental allergic neuritis in strain 13 and Hartley guinea pigs.

An attempt has been made to develop a model of chronic experimental allergic neuritis (EAN) using juvenile and adult inbred (Strain 13) and Hartley guinea pigs sensitized with peripheral nerve in complete Freund's adjuvant. Animals were followed clinically for periods ranging from 2 to 44 weeks postinoculation and then sacrificed for light and electron microscopy. Out of a total of 39 animals, 16 showed either clinical signs or had histopathologic changes. The remaining 23 guinea pigs were free of any disease. The animals' age at inoculation and strain did not seem to affect either the clinical course or ultimate histopathologic changes. The 7 animals that had clinical EAN displayed signs ranging from weight loss and soiling to quadriparesis (one animal). The histologic changes consisted of meningeal and perivascular inflammation as well as peripheral nervous system (PNS) and central nervous system demyelination and remyelination. An interesting abnormality seen the nerve roots of several animals was the proliferation of Schwann cells around remyelinated PNS fibers reminiscent of the "onion-bulb" formations seen in human hypertrophic neuropathies. Because of the lack of ongoing demyelination, onion-bulb formation appeared in this case to be a secondary proliferation of Schwann cells after a single primary episode of demyelination. It is concluded from the present study that despite some interesting histopathologic changes, the animals studied were largely resistant both to acute as well as chronic EAN.

Age Factors↗
PubMed1977

Regeneration of oligodendroglia during recovery from demyelinating disease.

Infection of mice with the JHM strain of mouse hepatitis virus causes demyelination as a result of a cytolytic infection of oligodendroglia. In recovery, animals show remyelination, which could result either from surviving oligodendrocytes extending their territory or by generation of new oligodendroglia. Electron microscopic autoradiographic studies with 3H-labeled thymidine demonstrate that the cells associated with remyelination are newly generated oligodendroglia.

Animals↗
PubMed1977

The role of Schwann cells in paradoxical regeneration in the axolotl.

The experiments described here examine further the conditions under which paradoxical regeneration occurs and provide support for the hypothesis that a proximal migration of Schwann cells is responsible for the phenomenon. When only the hand is shielded from irradiation and the limb is denervated, amputation through the forearm or upper arm sometimes results in regeneration. The effects of variation in the time interval between denervation and amputation, the level of amputation and the method and number of denervations on the incidence of regeneration were investigated. The presence or absecce of viable Schwann cells at the amputation plane was deduced from the remyelination of nerves under conditions which do or do not permit paradoxical regeneration. The nerves of totally irradiated and denervated limbs remain unmyelinated following regrowth of axons and such limbs do not regenerate after amputation. When only the hand was shielded from irradiation before the limbs were denervated, the new axons became completely remyelinated and some of these limbs regenerated when amputated. It is suggested that under these conditions Schwann cells can migrate proximally and can then proliferate further to form a blastema, since they would be the only unirradiated tissue present at the amputation plane.

Ambystoma↗
PubMed1977

Lead neuropathy. 1) Morphometry, nerve conduction, and choline acetyltransferase transport: new finding of endoneurial edema associated with segmental demyelination.

Morphometric and pathologic studies along the length of the peripheral nervous system were obtained in groups of rats fed 4% lead carbonate for 3 and 6 months and in match-fed controls. The number and diameter histograms of L6 cytons of spinal ganglia and of myelinated fibers of proximal and distal portions of peroneal and sural nerve were not significantly different from the control groups. On the other hand, segmental demyelination occurred approximately as frequently in proximal as in distal parts of nerves. At 3 months approximately 1/3 of teased myelinated fibers showed changes of segmental demyelination (Condition C), or of remyelination after segmental demyelination (Condition F) or of both segmental demyelination and of remyelination (Condition D), while at 6 months more than 4/5ths of fibers showed these changes. As expected, regression lines of axonal area on number of lamellae of myelin, were less steep in nerves of rats fed on lead for 6 months as compared to controls. Axonal transport of choline acetyltransferase in lead neuropathy did not differ from that in control rats. As expected from the studies of others, conduction velocity of myelinated fibers of caudal nerve were low. A new finding was the often quite striking increase of transverse fascicular area of peripheral nerves. This was due to edema which appeared to develop at about the time of onset os segmental demyelination. Although the edema may be an epiphenomenon, it could be an important observation bearing on the development of lead neuropathy. It would be important to know next whether or not the blood nerve barrier is altered in lead neuropathy.

Animals↗
PubMed1975

Mouse hepatitis virus-induced recurrent demyelination. A preliminary report.

Four-week-old BALB/c mice inoculated intracerebrally with the JHM strain of mouse hepatitis virus developed an acute demyelinating disease followed by apparent recovery with remyelination. When surviving mice were examined 16 months later, small areas of active demyelination were still present. This is the first reported example, to our knowledge, of an experimental viral infection in which acute demyelination with recovery is followed by persisting or recurring demyelination.

Animals↗
PubMed1975

Axonal degeneration in sodium cyanate-induced neuropathy.

Two patients with sickle cell disease who had been maintained on sodium cyanante therapy for periods of 440 and 600 days on dosages up to 44 and 41 mg/kg per day developed a motor and sensory neuropathy. In both, definite abnormalities of myelinated and unmyelinated fibers were found. In one, the predominant abnormality of myelinated fibers was segmental demyelination and remyelination; in the other, there were histological features typical of axonal degeneration. It seems unlikely that the brunt of the metabolic derangement was on Schwann cells in the first case and on the nerve cell in the second. Probably, in both cases, the primary effect was on the nerve, with Schwann cell changes being concomitant or secondary. The clustered distribution of the segmental demyelination favors the latter.

Adult↗
PubMed1976

Axonal degeneration in beriberi neuropathy.

Ultrastructural and teased-fiber studies were carried out on the sural nerves of nine patients with beriberi neuropathy Axonal degeneration was the most prominent feature, and large myelinated fibers were more affected than unmyelinated ones. An unusual change with accumulation of flattened sacs or tubuli was recognized in the axoplasm of myelinated fibers of untreated patients. Active regeneration was extensive in patients receiving vitamin B. Segmental demyelination, remyelination, and early onion bulbs were scarece in patients with a long and relapsing course before treatment.

Adolescent↗
PubMed1977

Conduction in myelinated, unmyelinated, and demyelinated fibers.

Conduction in demyelinated axons is characterized by decreased conduction velocity, temporal dispersion of impulses, and conduction failure. It is not possible to infer the electrical properties of the bared internodal axon membrane in demyelinated fibers from observations of decreased conduction velocity or conduction failure. Cytochemical evidence indicates that there are, in fact, distinct structural differences between nodal and internodal regions of the normal axon membrane. This conclusion is confirmed by freeze-fracture and pharmacological studies. A number of approaches to the development of effective symptomatic therapy in the demyelinating diseases are suggested by recent experimental findings: determination of the membrane properties necessary for conduction across focally demyelinated regions and the identification of agents that would encourage the development of these properties; alterations in the external milieu of demyelinated fibers; and the development of agents that might promote remyelination.

Animals↗
PubMed1975

Mechanisms of functional loss and recovery in spinal cord damage.

Two main classes of morphological change follow trauma to central nerve fibres: (1) axonal disruption leads to total disintegration of the fibre distal (with respect to the cell body) to the lesion; (2) less severe trauma produces focal demyelination with preservation of axonal continuity. Large experimental demyelinating lesions produce complete conduction block. The histologically normal portions of the fibres, proximal and distal to the lesion, retain the ability to transmit impulses. Smaller lesions allow conduction to continue, but at a reduced velocity, and the ability of the fibres to carry long trains of impulses faithfully is impaired. All three defects of conduction contribute to functional loss. After acute transient compression of the spinal cord of the cat, demyelination increases during the first week. Evidence of remyelination appears in the third week. Inappropriately thin myelin is seen surrounding histologically normal axons. By one month, 90% of the fibres in the lesion have acquired new sheaths. Studies on single fibres have shown that the myelin is organized into segments bounded by nodes. The segments are abnormally thin and short. The myelin increases in thickness with time but thin segments are still present at 18 months. Electron microscopy shows that many of the known ultrastructural prerequisites for conduction are present in the new segments. It is not yet known, however, whether the chains of very short internodes which occur on some fibres allow conduction to be restored.

Demyelinating Diseases↗
PubMed1977

Polyradiculoneuropathy accompanying procainamide-induced lupus erythematosus: evidence for drug-induced enhanced sensitization to peripheral nerve myelin.

Factors involved in the development of an insidious polyradiculoneuropathy in association with a procainamide-induced, lupuslike syndrome were explored. A 73-year-old man with this clinical syndrome had sural nerve changes consisting of loss of large myelinated fibers with evidence of remyelination and Schwann cell proliferation. The patient's lymphocytes showed marked incorporation of tritiated thymidine when cultured with either procainamide or extracts of human peripheral nerve myelin, and there was an enhanced response with the combination. We also found that procainamide-treated rats showed acceleration of lymphocyte sensitization to peripheral nerve myelin as judged by the early development of inhibition of macrophage migration and positive skin tests to extracts of peripheral nerve myelin. These studies suggest that procainamide can enhance lymphocyte sensitization to peripheral nerve myelin and may have predisposed this individual to development of a polyradiculoneuropathy.

Aged↗
PubMed1977

Giant axonal neuropathy: a childhood disorder of microfilaments.

A sural nerve biopsy was performed on an 8-year-old boy with a chronic, slowly progressive polyneuropathy. Light and electron microscopy as well as teased nerve-fiber preparations demonstrated numerous giant axons filled with closely packed neurofilaments. Both myelinated and unmyelinated fibers were involved. Segmental demyelination, remyelination, and onion-bulb formation by multiple Schwann cell processes were observed, suggesting recurrent Schwann cell dysfunction. Abundant aggregates of cytoplasmic microfilaments occurred in Schwann cells, endothelial cells, perineurial cells, endoneurial fibroblasts, and endomysial fibroblasts. These findings support the proposal that giant axonal neuropathy is a generalized disorder of cytoplasmic microfilaments and that segmental demyelination occurs concomitantly with axonal and Schwann cell disease. The pathogenesis of this rare disorder is discussed with reference to experimental toxic neuropathies.

Axons↗
PubMed1976

Regeneration of retinal axons into the goldfish optic tectum.

The growth of regenerating retinal axons into the central portion of the optic tectum of adult goldfish was examined with the light and electron microscopes. Optic tracts were cut and, two days to five months later, the animals were perfused and the tecta prepared for microscopy. Regenerating axons first reached central regions of the tectum seven to ten days postoperatively. Regenerating axons appear in very large numbers and travel in fascicles in the stratum opticum (SO) and in the adjacent neuropil, the stratum fibrosum et griseum superficiale (SFGS). In the SO, the fascicles are bordered by glial cells and degenerating debris. Within the SFGS, however, the fascicles do not seem to be similarly associated with glial cells and degenerating debris. The youngest regenerating axons are very slender processes, containing microtubules but few or no neurofilaments or dense granular material. By 10 to 14 days postoperatively, neurofilaments can be seen and, in addition, large numbers of vesicles with dense cores appear. The vesicles with dense cores increase in numbers until about 28 days postoperatively and then become quite rare. That vesicles with dense cores were seen in regenerating axons in both SO and SFGS during the period of growth into the tectum but were not seen in axon terminals at any time, suggests that they may be concerned with axon elongation. During the period one month to five months postoperatively, the regenerating axons gradually increase in diameter but do not reach preoperative sizes, suggesting that the regenerative changes may still be occurring. Remyelination is delayed and proceeds slowly. Many axons remain unmyelinated for as long as five months postoperatively.

Animals↗
PubMedDate not supplied

Early recognition of nerve disorders by near-nerve recording of sensory action potentials.

Evaluated herein are the advantages and limitations of recording sensory action potentials with a gross electrode placed near the nerve. This technique has proved to be a sensitive measure of early nerve damage for two reasons: first, electrodes can be positioned in such a way that maximal velocity is determined only along the abnormal stretch of the nerve; and second, small late components originating from demyelinated, remyelinated, or regenerating fibers can be detected.

Demyelinating Diseases↗