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PubMed1997

Alterations in gene expression associated with primary demyelination and remyelination in the peripheral nervous system.

Primary demyelination is an important component of a number of human diseases and toxic neuropathies. Animal models of primary demyelination are useful for isolating processes involved in myelin breakdown and remyelination because the complicating events associated with axonal degeneration and regeneration are not present. The tellurium neuropathy model has proven especially useful in this respect. Tellurium specifically blocks synthesis of cholesterol, a major component of PNS myelin. The resulting cholesterol deficit in myelin-producing Schwann cells rapidly leads to sychronous primary demyelination of the sciatic nerve, which is followed by rapid synchronous remyelination when tellurium exposure is discontinued. Known alterations in gene expression for myelin proteins and for other proteins involved in the sequence of events associated with demyelination and subsequent remyelination in the PNS are reviewed, and new data regarding gene expression changes during tellurium neuropathy are presented and discussed.

Animals↗
PubMed2003

Axonal and demyelinating forms of the MPZ Thr124Met mutation.

OBJECTIVE: We report on a Japanese family with Charcot Marie Tooth disease (CMT) with the Thr124Met mutation in the peripheral myelin protein zero (MPZ) gene. MATERIAL AND METHODS: Based on the clinical study, we investigated MPZ gene by direct sequence analysis and polymerase chain reaction restriction fragment length polymorphism analysis. RESULTS: Genotyping of four symptomatic family members showed that one family member with severe disease symptoms was homozygous, while the other three were heterozygous. The heterozygous cases were clinicopathologically determined to be the axonal type, which is characterized by late-onset and slow progression associated with Adie's pupil and deafness. The homozygous case was the demyelinating type, which showed earlier onset, rapid progression, sural nerve demyelination, and cranial nerve demyelination at autopsy. CONCLUSIONS: We suggest that axonal and demyelinating forms of CMT are not two distinct classes, but rather parts of a spectrum of genotypically related conditions, particularly with some MPZ mutations.

Adult↗
PubMed1980

Effects of 4-aminopyridine on normal and demyelinated mammalian nerve fibres.

We have previously demonstrated that a drug which prolongs action potentials can, like a reduction in temperature, overcome conduction failure in demyelinated nerve fibres. Although the particular substance then used, a scorpion venom, was not a suitable therapeutic agent, we suggested that other drugs, with similar but milder effects on the action potential, might be effective in the symptomatic treatment of multiple sclerosis. We now report some encouraging results obtained with 4-amino-pyridine (4AP), a substance which blocks the voltage-dependent potassium current in squid giant axons. The use of a potassium-blocking agent to prolong action potentials may seem surprising because we previously found tetraethylammonium chloride (TEA), another potassium blocker, ineffective on normal rat myelinated fibres, and two recent voltage-clamp studies have confirmed that mammalian nodes have few, if any, potassium channels. On the other hand, 4AP strongly potentiates transmitter release from the unmyelinated terminals of rat motor nerves, and the possibility arose that demyelinated axon membrane, which can conduct impulses continuously like an unmyelinated fibre, might further resemble its unmyelinated terminals by responding to 4AP. In testing this hypothesis, we have found that both TEA and 4AP prolong action potentials of demyelinated and unmyelinated fibres, and both facilitate conduction in fibres blocked by demyelination. 4AP is effective at lower concentrations, and is the more promising for clinical use, as it has already been used with beneficial effects in the treatment of Eaton-Lambert syndrome and myasthenia gravis.

Action Potentials↗
PubMed1997

Primary demyelination in transgenic mice expressing interferon-gamma.

Ever since the use of interferon-gamma to treat patients with multiple sclerosis resulted in enhanced disease, the role of IFN-gamma in demyelination has been under question. To address this issue directly, transgenic mice were generated that expressed the cDNA of murine IFN-gamma in the central nervous system by using an oligodendrocyte-specific promoter. Expression of the transgene occurred after 8 weeks of age, at which time the murine immune and central nervous systems are both fully developed. Directly associated with transgene expression, primary demyelination occurred and was accompanied by clinical abnormalities consistent with CNS disorders. Additionally, multiple hallmarks of immune-mediated CNS disease were observed including upregulation of MHC molecules, gliosis and lymphocytic infiltration. These results demonstrate a direct role for IFN-gamma as an inducer of CNS demyelination leading to disease and provide new opportunities for dissecting the mechanism of demyelination.

Animals↗
PubMed2001

Episodic demyelination and subsequent remyelination within the murine central nervous system: changes in axonal calibre.

Exposure of young adult C57BL/6 mice to cuprizone in the diet initiated profound and synchronous demyelination of the corpus callosum, which was virtually complete by 4 weeks of exposure. Interestingly, even in the face of a continued exposure to cuprizone, there was spontaneous remyelination 2 weeks later. This remyelination preferentially involved smaller calibre axons. There was a suggestion of yet another cycle of demyelination (at 10 weeks) and remyelination (at 12 weeks), but by 16 weeks of exposure, the regenerative capacity was exhausted and the animals were near death. The relapsing-remitting pattern suggests this may be a useful model for certain human demyelinating disorders. In contrast to the above chronic model, the corpus callosum from mice exposed to cuprizone for only 6 weeks continued to remyelinate, with 67% of the axons being myelinated or remyelinated at 10 weeks. Interestingly, a significant reduction in the mean value for axonal diameter was observed during acute demyelination. Upon remyelination, however, the axonal calibre distribution returned to near-normal. In contrast, when mice were maintained on a cuprizone diet for 16 weeks, the mean value for axonal diameter was reduced to 60% of normal. These results provide further evidence that the interactions between oligodendrocytes and axons alter axonal calibre.

Amidines↗
PubMed2002

Demyelinating pseudotumor.

Demyelinating disease presenting as a solitary contrast-enhancing mass poses a diagnostic challenge for both radiologists and surgical pathologists. We report the cases of two female patients, aged 23 and 37 years, who exhibited the clinical and radiologic features of a space-occupying mass strongly suggestive of neoplasia. In both patients, magnetic resonance imaging showed a ring-enhancing parietal lesion. Intraoperative frozen sections in both patients displayed histologic features strongly suggestive of a glial neoplasm, including marked hypercellularity, a prominent astrocytic component, and easily identifiable mitotic figures. However, permanent sections showed additional and helpful histologic findings that included Creutzfeldt astrocytes and granular mitoses. Subsequent immunostaining showed that the hypercellularity was principally caused by macrophage infiltration (HAM-56 and CD68) and an associated reactive astrocytosis (glial fibrillary acidic protein). Additional confirmatory tests included special stains for myelin (Luxol-fast-blue), which demonstrated focal, sharply marginated loss of myelin, and for axons (silver stain for axons and neurofilament protein immunohistochemistry), which showed relative preservation of axons in areas of myelin loss. Together, the special stains confirmed the demyelinating nature of the lesions. The keys to avoiding misdiagnosing a demyelinating pseudotumor as a diffuse glioma include a general awareness of this potential pitfall, including the radiologic appearance of demyelinating pseudotumors as contrast-enhancing solitary masses that mimic tumor; knowledge of the characteristic histologic features, including Creutzfeldt astrocytes and granular mitoses; and a high index of suspicion for macrophage infiltration combined with a willingness to use appropriate confirmatory immunohistochemical studies in suspicious or uncertain cases. This approach will minimize the chance of misdiagnosis and subsequent use of inappropriate and deleterious therapies.

Adult↗
PubMed1998

Guillain-Barré syndrome and chronic inflammatory demyelinating polyneuropathy.

Acute and chronic inflammatory demyelinating polyneuropathies represent an important group of disorders. Although the acute form is more common, all clinical neurologists will eventually encounter patients with these disorders. Acute inflammatory demyelinating polyneuropathy, or Guillain-Barré syndrome, is the most common cause of acute generalized weakness. Chronic inflammatory demyelinating polyneuropathy, characterized by progressive or relapsing weakness, is important to recognize because it represents a significant number of all initially undiagnosed acquired neuropathies. There are a variety of reasonable therapies available for both of these acquired demyelinating neuropathies. Recently much has been learned about pathogenesis and treatment. This review describes the clinical presentations, laboratory studies, diagnostic criteria, treatment, and prognosis for each disorder.

Demyelinating Diseases↗
PubMed1994

Chronic immune demyelinating neuropathies.

The classification of immune-mediated demyelinating polyneuropathies has become more complex in recent years. Initial definitions of chronic inflammatory demyelinating polyneuropathy (CIDP) were often broad enough to include almost any acquired polyneuropathy with demyelinating features. However, subdivision of acquired demyelinating polyneuropathies into different categories seems justified because 1) several distinct clinical syndromes have been identified, 2) characteristic and distinctive patterns of serum antibody binding are associated with each specific clinical syndrome and, 3) the syndromes respond differently to immune modulating treatments (Table 1). Larger series and controlled trials will be necessary to determine the therapeutic regimens that optimize the benefit:risk considerations for patients with these syndromes.

Autoantibodies↗
PubMed1985

Anti-peripheral myelin antibody in patients with demyelinating neuropathy: quantitative and kinetic determination of serum antibody by complement component 1 fixation.

The role of anti-peripheral nerve myelin antibody (anti-PNM Ab) in the pathogenesis of acquired demyelination of peripheral nerve is unclear, in part, due to the poor correlation between antibody and disease activity. Previous studies show that only 27-50% of patients with acute demyelinating neuropathy or Guillain-Barré syndrome (GBS) had serum Abs to peripheral nerve or PNM as demonstrated by consumption of hemolytic activity of serum complement 1 (C1) fixation and transfer assay, quantitative determinations of anti-PNM Ab showed significantly high titers in the serum of patients with GBS, chronic and recurrent polyneuritis, and paraproteinemia associated with peripheral neuropathy. All 11 patients with acute-phase GBS had Ab titers 6-56 times higher than controls. In 6 GBS patients, serial Ab determinations showed that titers were highest on admission, fell rapidly the first week, and became undetectable or barely detectable by the third week. Declining Ab titers coincided with cessation of clinical progression. In 3 GBS patients, depletion of serum IgM lowered anti-PNM Ab titers significantly, whereas IgG depletion failed to produce a similar effect. This study shows that the C1 fixation and transfer assay is a sensitive method to detect anti-PNM Ab in the serum of patients with a variety of demyelinating neuropathies and provides good correlation between Ab level and the clinical course of GBS patients. It may provide important information about the pathogenesis of the demyelinating neuropathies.

Antibodies↗
PubMed1992

Insulin-like growth factor I gene expression is induced in astrocytes during experimental demyelination.

To investigate insulin-like growth factor I (IGF-I) and IGF-I receptor gene expression during experimental demyelination and myelin regeneration, young mice were fed cuprizone (( bis(cyclohexanone) oxaldihydrazone )). This copper-chelating agent produces demyelination in the corpus callosum and superior cerebellar peduncles, and when treatment is stopped, there is rapid remyelination. At intervals during cuprizone treatment and recovery, brain sections were hybridized with specific probes and immunostained with antibodies to determine the localization and relative amounts of IGF-I and IGF-I receptor mRNAs and peptides. In untreated littermates, IGF-I and IGF-I receptor mRNAs and peptides were not detected in white matter. In cuprizone-treated mice, high levels of both IGF-I mRNA and peptide were expressed by astrocytes in areas of myelin breakdown. Astrocyte IGF-I expression decreased rapidly during recovery and oligodendroglial expression of myelin-related genes increased. In severely demyelinated areas, immature oligodendroglia exhibited a transient increase in IGF-I receptor mRNA and peptide immunoreactivity during early recovery. This highly specific pattern of IGF-I induction in astrocytes during demyelination and the expression of the IGF-I receptor in regenerating oligodendrocytes during recovery suggest that IGF-I functions in the regulation of oligodendrocyte and myelin metabolism in vivo.

2',3'-Cyclic-Nucleotide Phosphodiesterases↗
PubMed1995

Spontaneous inflammatory demyelinating disease in transgenic mice showing central nervous system-specific expression of tumor necrosis factor alpha.

Cytokines are now recognized to play important roles in the physiology of the central nervous system (CNS) during health and disease. Tumor necrosis factor alpha (TNF-alpha) has been implicated in the pathogenesis of several human CNS disorders including multiple sclerosis, AIDS dementia, and cerebral malaria. We have generated transgenic mice that constitutively express a murine TNF-alpha transgene, under the control of its own promoter, specifically in their CNS and that spontaneously develop a chronic inflammatory demyelinating disease with 100% penetrance from around 3-8 weeks of age. High-level expression of the transgene was seen in neurons distributed throughout the brain. Disease is manifested by ataxia, seizures, and paresis and leads to early death. Histopathological analysis revealed infiltration of the meninges and CNS parenchyma by CD4+ and CD8+ T lymphocytes, widespread reactive astrocytosis and microgliosis, and focal demyelination. The direct action of TNF-alpha in the pathogenesis of this disease was confirmed by peripheral administration of a neutralizing anti-murine TNF-alpha antibody. This treatment completely prevented the development of neurological symptoms, T-cell infiltration into the CNS parenchyma, astrocytosis, and demyelination, and greatly reduced the severity of reactive microgliosis. These results demonstrate that overexpression of TNF-alpha in the CNS can cause abnormalities in nervous system structure and function. The disease induced in TNF-alpha transgenic mice shows clinical and histopathological features characteristic of inflammatory demyelinating CNS disorders in humans, and these mice represent a relevant in vivo model for their further study.

Animals↗
PubMed2006

Assesment criteria for experimental demyelination induced in frog peripheral nerve.

In ideal conditions the area under compound action potential may be used as an index for the number of activated fibers in a nerve trunk whereas peak amplitude, maximum time derivative, and duration may be used as an indicator for the rate of contribution to compound action potential and the degree of velocity dispersion. In this study, the time domain effect of demyelination on compound action potential has been investigated in experimentally demyelinated frog sciatic nerve. The results were analyzed in order to suggest criteria for demyelination. The results suggest that the changes in peak amplitude and maximum time derivative of compound action potential that is made up by the contribution of the active fibers may be more useful in the assessment of early phase of demyelination. Therefore, it may be concluded that these two parameters, intrinsically, carry augmented information on the velocity dispersion originated from larger-diameter fibers.

Action Potentials↗
PubMed2001

CD8-deficient SJL mice display enhanced susceptibility to Theiler's virus infection and increased demyelinating pathology.

Theiler's murine encephalomyelitis virus (TMEV) infection of the central nervous system (CNS) induces a chronic, progressive demyelinating disease in susceptible mouse strains characterized by inflammatory mononuclear infiltrates and spastic hind limb paralysis. Our lab has previously demonstrated a critical role for TMEV- and myelin-specific CD4(+) T cells in initiating and perpetuating this pathology. It has however, also been shown that the MHC class I loci are associated with susceptibility/resistance to TMEV infection and persistence. For this reason, we investigated the contribution of CD8(+) T cells to the TMEV-induced demyelinating pathology in the highly susceptible SJL/J mouse strain. Here we show that beta2M-deficient SJL mice have similar disease incidence rates to wild-type controls, however beta2M-deficient mice demonstrated earlier onset of clinical disease, elevated in vitro responses to TMEV and myelin proteolipid (PLP) epitopes, and significantly higher levels of CNS demyelination and macrophage infiltration at 50 days post-infection. beta2M-deficient mice also displayed a significant elevation in persisting viral titers, as well as an increase in macrophage-derived pro-inflammatory cytokine mRNA expression in the spinal cord at this same time point. Taken together, these results indicate that CD8(+) T cells are not required for clinical or histologic disease initiation or progression in TMEV-infected SJL mice. Rather, these data stress the critical role of CD4(+) T cells in this capacity and further emphasize the potential for CD8(+) T cells to contribute to protection from TMEV-induced demyelination.

Amino Acid Sequence↗
PubMed2002

Differential induction of apoptosis in demyelinating and nondemyelinating infection by mouse hepatitis virus.

The role of apoptosis in mouse hepatitis virus (MHV) infection is still controversial. To better assess the role of apoptosis in MHV infection, we used three different biologic phenotypes of MHV to examine their differential effect on the induction of apoptosis. MHV-A59 produces acute hepatitis, meningoencephalitis, and chronic demyelination. MHV-2 causes only acute hepatitis and meningitis, whereas Penn98-1 produces acute hepatitis and meningoencephalitis without demyelination. We detected TdT-mediated dUTP nick-end labeling (TUNEL) staining in the livers and meninges of MHV-A59-, MHV-2-, and Penn98-1-infected mice. TUNEL staining in brain parenchyma was only detected in MHV-A59- and Penn98-1-infected mice. We detected apoptosis by electronmicroscopy in olfactory neurons during acute infection with MHV-A59. The kinetics and distribution of TUNEL staining correlated with the pathologic damage and colocalized with viral antigen in some cells. At 1 month, TUNEL staining was found exclusively in areas of demyelination in the spinal cord of MHV-A59-infected mice; however, it was not found in nondemyelinated mice infected with MHV-2 or Penn98-1, or in mock-infected mice. TUNEL-positive cells were identified as macrophage/microglial cells, some astrocytes, and some oligodendrocytes, by colabeling with cell-specific markers. The presence of TUNEL staining in oligodendrocytes suggests that apoptosis may play an important role in MHV-induced demyelination.

Animals↗
PubMed1989

In vivo analysis of glial cell phenotypes during a viral demyelinating disease in mice.

C57 BL/6N mice injected intracranially with the A59 strain of mouse hepatitis virus exhibit extensive viral replication in glial cells of the spinal cord and develop demyelinating lesions followed by virus clearing and remyelination. To study how different glial cell types are affected by the disease process, we combine three-color immunofluorescence labeling with tritiated thymidine autoradiography on 1-micron frozen sections of spinal cord. We use three different glial cell specific antibodies (a) to 2',3' cyclic-nucleotide 3' phosphohydrolase (CNP) expressed by oligodendrocytes, (b) to glial fibrillary acidic protein (GFAP) expressed by astrocytes, and (c) the O4 antibody which binds to O-2A progenitor cells in the rat. These progenitor cells, which give rise to oligodendrocytes and type 2 astrocytes and react with the O4 antibody in the adult central nervous system, were present but rare in the spinal cord of uninfected mice. In contrast, cells with the O-2A progenitor phenotype (O4 + only) were increased in number at one week post viral inoculation (1 WPI) and were the only immunostained cells labeled at that time by a 2-h in vivo pulse of tritiated thymidine. Both GFAP+ only and GFAP+, O4+ astrocytes were also increased in the spinal cord at 1 WPI. Between two and four WPI, the infected spinal cord was characterized by the loss of (CNP+, O4+) oligodendrocytes within demyelinating lesions and the presence of O-2A progenitor cells and O4+, GFAP+ astrocytes, both of which could be labeled with thymidine. As remyelination proceeded, CNP immunostaining returned to near normal and tritiated thymidine injected previously during the demyelinating phase now appeared in CNP+ oligodendrocytes. Thus O4 positive O-2A progenitor cells proliferate early in the course of the demyelinating disease, while CNP positive oligodendrocytes do not. The timing of events suggests that the O-2A progenitors may give rise to new oligodendrocytes and to type 2 astrocytes, both of which are likely to be instrumental in the remyelination process.

2',3'-Cyclic-Nucleotide Phosphodiesterases↗
PubMed2004

Combined demyelination plus Schwann cell transplantation therapy increases spread of cells and axonal regeneration following contusion injury.

Several cell populations have been shown to provide a permissive environment for axonal extension following transplantation to injury sites. The limited spread of transplanted cells from implantation sites in the mature CNS, and the superior substrate and trophic environment that they provide, likely contribute to the fact that few transplantation-based therapies have elicited axonal extension beyond the transplant. The aim of this study was to determine whether (1) regions of demyelination cranial and caudal to a spinal cord injury site would improve the spread of Schwann cells transplanted into the site of injury, and (2) whether this combination therapy was associated with improved anatomical regeneration. Three days following contusion injury, anti-galactocerebroside antibodies plus complement proteins were injected into the dorsal column cranial and caudal to the injury site, resulting in complete and well defined regions of demyelination that extended 8 mm either side of the injury site. One day later, naïve Schwann cells in suspension were injected into the contusion site. Transplanted Schwann cells homogeneously redistributed throughout the contusion site and the adjacent regions of demyelination cranial and caudal to the contusion site, providing a long-distance prospective path for repair that was free of myelin and contained transplanted cells. Animals that received demyelination plus transplantation therapy, but not untreated or single-treatment groups, exhibited robust axonal regeneration beyond the contusion site within the treated dorsal column. Axonal regeneration in these animals was not associated with an improvement in locomotor ability. These findings suggest that this combination therapy may overcome a central limitation of transplant strategies in which the permissive environment provided remains at the implantation site.

Animals↗
PubMed1992

Effects of dorsal column demyelination on evoked potentials in nucleus gracilis.

Intraspinal injections of lysolecithin were used to produce unilateral demyelination in the dorsal columns of the rat spinal cord. The purpose of this study was to evaluate the effects of demyelination on the conductive properties of axons belonging to a spinal pathway of known origin and site of termination. At 5 and 50 day intervals following injections, animals were prepared for acute experiments during which recordings of tibial nerve evoked potentials were made from the surface of the lumbar spinal cord (L5-L6) and nucleus gracilis (0.5-1.0 mm caudal to obex). Latency, duration, and strength of potentials were evaluated in control (uninjected) and lysolecithin-injected animals. The analysis of these potentials showed increases in latency and decreases in duration and strength of responses recorded 5 days after lysolecithin injections. Animals examined 50 days postinjection showed a decreased latency and increased duration and strength of responses compared to those recorded 5 days postinjection. Ultrastructural examination of lysolecithin injection sites showed these improvements to parallel the remyelination of axons by oligodendrocytes and Schwann cells. The improvement in physiologic characteristics of evoked potentials coupled with the remyelination of dorsal column axons supports the conclusion that remyelination of chemically demyelinated axons is an important factor in reestablishing the functional connectivity of demyelinated axons.

Animals↗
PubMed1997

The application of multifactorial cluster analysis in the staging of plaques in early multiple sclerosis. Identification and characterization of the primary demyelinating lesion.

Tissues from 13 exceptionally early cases of multiple sclerosis were studied to identify and characterize the primary demyelinating lesion, using a variety of histological and immunocytochemical methods. Multifactorial cluster analysis identified five significantly distinct lesion groups, which showed histological progression from simple microglial lesions, predominating in tissues from the earliest cases, to complex hypercellular fully demyelinated plaques, chiefly associated with cases of intermediate duration. Quiescent lesions showing evidence of remyelination were found at all stages of the disease studied, but hypocellular inactive plaques, were associated with older cases. Evidence is presented that initial demyelination is effected by activated resident microglia. Undegraded myelin is initially enveloped by membranes bearing fixed complexes of immunoglobulin and complement. In contrast with perivenous encephalomyelitis, in which demyelination was dominated by T-cell infiltration, multiple sclerosis lesions of comparable duration and maturity exhibited humoral immune reactions. Parenchymal CD4+ T-cell infiltration developed in association with subsequent plaque maturation. These results emphasize the need for lesion staging when multiple sclerosis tissues are being used in the investigation of pathogenic mechanisms, and suggest that further analysis of the oligoclonal B-cell response may be productive in the search for primary provoking antigens.

Adult↗