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PubMed1986

Effect of cyclosporin A, silica quartz dust, and protease inhibitors on virus-induced demyelination.

Treatment with cyclosporin A, from the time of virus infection, suppressed inflammation and demyelination in the spinal cord of SJL/J or ASW(H-2s) mice persistently infected with Theiler's murine encephalomyelitis virus. Demyelination was not decreased if treatment was given after inflammation was established. The decrease was independent of serum titers of immunoglobulin G to purified viral antigen but did correlate with decreased proliferation of T lymphocytes to virus and myelin antigens. Silica quartz dust, a direct toxin of macrophages, suppressed demyelination and inflammation if begun at time of virus infection. No therapeutic effect was seen with inhibitors of plasminogen activators or other neutral proteases found primarily in macrophages.

Animals↗
PubMed1987

Antibody responses in chronic relapsing experimental allergic encephalomyelitis: correlation of serum demyelinating activity with antibody titre to the myelin/oligodendrocyte glycoprotein (MOG).

Antibody responses to the myelin/oligodendrocyte glycoprotein (MOG) and myelin basic protein (MBP) were determined in the sera of Hartley guinea pigs with chronic relapsing experimental allergic encephalomyelitis (CREAE) using an enzyme-linked immunoassay. The sera were also tested for in vivo demyelinating activity by infusion into the subarachnoid space of normal rats. In contrast to the MBP titres, the anti-MOG antibody titres showed good correlation with the in vivo demyelinating activity of the sera (r = 0.91, P less than 0.001). This result suggests that antibodies directed against MOG may be involved in the pathogenesis of demyelination in CREAE.

Animals↗
PubMed1987

Effects of regional spinal X-irradiation on demyelinating disease caused by Theiler's virus, mouse hepatitis virus or experimental allergic encephalomyelitis.

The effects of X-irradiation on the course of chronic demyelinating disease were examined in mice with experimental allergic encephalitis (EAE), mouse hepatitis virus (MHV) or Theiler's virus (DAV) infection. One month after the induction of EAE or 2-16 months after inoculation of DAV, exposure of the cervical spinal cord to 20 Gy X-rays caused local exacerbation of disease activity but spinal irradiation did not affect MHV-induced demyelination. In EAE, there was a significant increase in the number of inflammatory cells in the irradiated part of the cord. Mice infected with DAV showed locally increased demyelination and axonal degeneration but no change in the titer of infectious virus within the cord. Thus in DAV infection, as in EAE, the exacerbation of disease seemed to be due to vascular or immunological factors rather than viral reactivation.

Animals↗
PubMed1992

The role of macrophages in demyelination.

Experimental allergic encephalomyelitis (EAE) is an autoimmune inflammatory disease of the central nervous system (CNS). In particular in the CsA-induced chronic relapsing form (CREAE), pronounced demyelination occurs, in temporal association with relapses. It is still a matter of discussion which cell type ultimately is responsible for the actual process of demyelination. Macrophages, cytotoxic T lymphocytes and also astrocytes are possible candidates. In this short overview, the role of macrophages in the pathogenesis of EAE is discussed. It is shown that in particular, newly recruited macrophages play a crucial role in the generation of clinical signs. Possible mechanisms by which macrophages are involved in the pathogenesis of demyelinating diseases are presented.

Animals↗
PubMed1992

Myelin gene expression during demyelination and remyelination in aggregating brain cell cultures.

Remyelination can be studied in aggregating rat brain cell cultures after limited demyelination. Demyelination was induced using a monoclonal antibody against myelin/oligodendrocyte glycoprotein (MOG mAb), in the presence of complement. De- and remyelination were assessed by measuring myelin basic protein (MBP). Two days after removing the MOG mAb, MBP levels reached 50% of controls and after 7 days 93%. During this period, cell proliferation determined by [14C]thymidine incorporation was similar in remyelinating and control cultures. Hormones and growth factors were tested for possible stimulatory effect on remyelinating cultures. Bovine growth hormone (bGH), triiodothyronine (T3), basic fibroblast growth factor (bFGF) and platelet-derived growth factor (PDGF) did not improve remyelination. Only epidermal growth factor (EGF) increased the level of remyelination. PDGF increased the rate of cell proliferation in both control and remyelinating cultures. A significant proportion of oligodendrocytes entered the cell division cycle and were not available for remyelination. The results obtained with PDGF and FGF (inhibition) support the idea that a pool of progenitor cells was still present and able to proliferate and differentiate into myelinating oligodendrocytes. The levels of myelin protein mRNAs were investigated during de- and remyelination. During demyelination, myelin protein mRNA levels decreased to approximately 50% of control cultures and returned to normal during remyelination. These preliminary results indicate that normal levels of gene transcription are sufficient to meet the increased need for newly synthesized myelin proteins during remyelination.

2',3'-Cyclic-Nucleotide Phosphodiesterases↗
PubMed1993

Effect of immunization with Theiler's virus on the course of demyelinating disease.

Intracerebral (i.c.) inoculation of susceptible mice with Theiler's murine encephalomyelitis virus (TMEV) results in a demyelinating disease similar to human multiple sclerosis (MS). Mice develop a strong immune response to TMEV and the disease is believed to be immune-mediated. In order to investigate the effects of the immune response to TMEV on the course of demyelination, we immunized host mice with UV-inactivated TMEV at various time periods in relation to intracerebral inoculation with live TMEV. Here, we show that subcutaneous immunization of mice with TMEV prior to infection with virus is able to protect susceptible, SJL/J mice from demyelinating disease. This protective effect appears to be long-lasting; immunization greater than 90 days prior to i.c. inoculation of the virus protects mice from subsequent infection. However, immunization of mice after i.c. infection with TMEV does not confer protection, but rather exacerbates the disease symptoms. Thus, this system offers a model for studying viral capsid proteins and/or epitopes which are involved in either protection from disease or immune-mediated pathogenesis leading to myelin destruction in susceptible mice.

Animals↗
PubMedDate not supplied

The electroretinogram in multiple sclerosis and demyelinating optic neuritis.

The electroretinogram (ERG) to flashes of white light presented under photopic conditions and the pattern reversal visual evoked potentials (PR-VEPs) from both eyes were recorded from 14 patients with multiple sclerosis (MS) with monocular demyelinating optic neuritis (DON) and from 11 patients soon after presenting with monocular demyelinating optic neuritis alone. Fifteen and 10 normal subjects, matched for age and sex, were used as controls for each group of patients respectively. In the DON group of patients and controls the flicker following ERG (FF-ERG) to white flashes of light at 40 Hz was also recorded. Skin electrodes and averaging procedures were used for all the recordings. The PR-VEP elicited with stimulation of the affected eye was absent or abnormally delayed, and the amplitude of the 'b' wave of ERG of the affected eye was diminished in all patients. The 'b' wave latency, however, was similar in both affected and non-affected eyes and the controls. There was no difference in 'a' wave amplitude and latency between eyes of patients and normal subjects. The FF-ERG in 8 out of 10 patients with satisfactory recordings was diminished in the affected eye. These results provide neurophysiological evidence that retinal damage is not due to loss of myelin but is an early feature of demyelinating optic neuritis. This damage preferentially affects the retinal elements associated with the generation of the 'b' wave of the ERG, probably the glial cells of Müller.

Demyelinating Diseases↗
PubMed1994

Quantitative analysis of the compound muscle action potential in early acute inflammatory demyelinating polyneuropathy.

We quantitated the size and configuration of compound muscle action potentials (CMAPs) in 266 nerves (66 median, 67 ulnar, 71 tibial and 62 peroneal) of 72 patients with acute inflammatory demyelinating polyneuropathy (AIDP) initially studied within 19 days of symptom onset. Results were compared with criteria for CMAP abnormalities, including criteria for abnormal negative peak duration and desynchronisation, derived from a control population of 50 median, ulnar, tibial and peroneal nerves. Other motor conduction abnormalities including minimal F response latency were also examined. We also analysed patterns of CMAP abnormality, peak disability and outcome for AIDP patients who had at least 3 motor nerves evaluated at first electrophysiologic study. Amongst AIDP nerves, low amplitude of the distal CMAP, usually with prolonged distal latency, was much more common than an abnormal fall in CMAP amplitude between stimulus sites. Using our CMAP criteria more than half of these low amplitude distal responses showed prolonged negative peak duration of desynchronisation or both, consistent with demyelination. Of the 47 AIDP patients who had 3 or more nerves initially studied, 37 (78.7%) had at least 1 motor nerve with a distal CMAP showing evidence of temporal dispersion. In addition, those with at least 75% of motor nerves showing a pattern of low amplitude of the distal CMAP without a further significant fall in amplitude between stimulus sites had greater peak disability and a poorer outcome. Assessment of temporal dispersion of the distal CMAP should be included in electrophysiologic criteria for acute demyelination. In addition, for some patients with AIDP patterns of CMAP amplitude abnormality amongst motor nerves are present early in the illness and may provide prognostic information.

Action Potentials↗
PubMed1984

Structural specializations in cat of chronically demyelinated spinal cord axons as seen in freeze-fracture replicas.

Axons in chronically demyelinated spinal cord lesions, induced by ethidium bromide injection, display patches of intramembranous particles and indentations resembling nodal and paranodal axolemmal specializations respectively. Both occur in the marginal region of the lesions where the demyelinated axons are intimately associated with astrocytic and oligodendrocytic processes, and probably correspond to the aberrant node-like and paranodal junctional complexes seen in thin sections of this region. Demyelinated axons in the center of the lesion, which are not in contact with glial processes, do not display these membrane specializations.

Animals↗
PubMed1985

Demyelination-induced plasticity in the axon membrane: an ultrastructural cytochemical study of lead neuropathy in the rat.

We examined the distribution of ferric ion-ferrocyanide stain (a marker for excitable regions of myelinated fibers) in the lead-induced demyelinating neuropathy of the rat. By electron microscopy, we found that paranodal degeneration resulted in spreading of the reaction product from nodal to internodal axolemma. During repair, nodal-like stained areas formed at the contact zones between preremyelinating Schwann cells. These data suggest that the location and extent of excitable axonal regions are influenced by axoglial relationships. Additionally, some fibers displayed staining at paranodal axolemma adjacent to demyelinated segments, suggesting it might be an alternative site for impulse generation in demyelinated fibers.

Animals↗
PubMed1996

Segmental demyelination induced by cerebrospinal fluid of progressive spastic paraparesis: correlation with altered proteolytic parameters.

Progressive spastic paraparesis (PSP) is a demyelinating disease of the central nervous system. We studied the ability of the cerebrospinal fluid (CSF) of patients to induce alterations in rat peroneal nerves, and to modify the proteolytic activity of trypsin in vitro. Subperineurial injection of native or heated CSF of patients induced segmental demyelination and other cytological alterations 5-7 days later, in the infiltrated zone, while proximal and distal regions were normal. The CSF of normal subjects did not induce demyelination, but upon heating, it did so. Trypsin was strongly inhibited by the normal CSF but upon heating, its inhibitory activity was replaced by a strong potentiation. In contrast, native and heated CSF of patients potentiated trypsin. Our findings indicate that (1) the normal CSF contains a thermostable factor that potentiates trypsin whose function is overruled by thermolabile protease inhibitors; (2) the CSF of PSP patients has a reduced inhibitory activity and a conserved ability to potentiate trypsin; and (3) the CSF is endowed with a pathogenic power that correlates with an unchecked potentiating activity. We propose that the imbalance of a protease system may play a role in the pathogenesis of PSP lesions.

Animals↗
PubMed1993

Synergistic action of estradiol and myelin basic protein on mast cell secretion and brain myelin changes resembling early stages of demyelination.

Mast cells are known for their participation in immediate and, more recently, delayed hypersensitivity reactions. They have been found in the meninges and certain brain areas where they are strictly perivascular, in close apposition to neurons, and they are activated by direct nerve stimulation or by neuropeptides. Intracranial mast cells contain many vasoactive substances which can increase the permeability of the blood-brain barrier, proteolytic enzymes which can degrade myelin in vitro, as well as chemotactic molecules which can attract inflammatory molecules in vivo. Connective tissue mast cells, with which intracranial mast cells share many characteristics, contain cytokines which can cause inflammation directly. Multiple sclerosis is a human demyelinating disease of unknown etiology, with a high prevalence in women which results in penetration of blood-borne immune cells within the brain parenchyma and subsequent destruction of myelin. Here, we report that 17 beta-estradiol and myelin basic protein, a major suspected immunogen in multiple sclerosis, had a synergistic action on inducing mast cell secretion. This effect was more pronounced in Lewis rats, which are susceptible to the development of experimental allergic encephalomyelitis, an animal model for multiple sclerosis, than in Sprague-Dawley rats, which are fairly resistant. Moreover, 18 h incubation of purified peritoneal mast cells with homogeneic slices of brain white matter in the presence of 17 beta-estradiol and myelin basic protein resulted in myelin changes resembling early stages of brain demyelination, which were also more evident in Lewis rats than in Sprague-Dawley rats. These results support the notion that mast cells could participate in the pathophysiology of demyelinating diseases.

Animals↗
PubMed1995

Melanin, melatonin, melanocyte-stimulating hormone, and the susceptibility to autoimmune demyelination: a rationale for light therapy in multiple sclerosis.

Multiple sclerosis is a central nervous system demyelinating disease. Significant evidence, including similarities with its animal model, experimental autoimmune encephalomyelitis, supports an autoimmune mechanism, activated by putative environmental factors in genetically predisposed individuals. Genetic factors strongly influence the susceptibility to demyelinating diseases in humans and rodents. Understanding the mechanisms governing susceptibility versus resistance may help to identify individuals at risk or design therapeutic strategies. The hypothesis formulated here is based on the observation that resistance to multiple sclerosis and experimental autoimmune encephalomyelitis is associated with dark skin pigmentation. While this may signify a protective role for melanin against environmental factors producing oxidative damage, the mechanism postulated here is that susceptibility to autoimmune demyelination is influenced by hormonal factors, i.e. the neurohormones melatonin and melanocyte stimulating hormone, which have opposing effects on immune functions and, the same time, are important determinants of the individual's production of melanin.

Animals↗
PubMed1987

Late onset, symptomatic, demyelinating encephalomyelitis in mice infected with MHV-JHM in the presence of maternal antibody.

The presence of maternal antibodies protected suckling C57BL/6 mice from the clinical manifestations of the acute encephalomyelitis caused by mouse hepatitis virus, strain JHM (MHV-JHM), a coronavirus, even though histological evidence of encephalomyelitis was found at early times after inoculation. 100% of infected suckling mice developed a fatal disease in the absence of maternal antibody. By 14 days after inoculation, the brains of all antibody-protected mice examined were nearly normal on histological examination. At 3-8 weeks post-inoculation, approximately 40% of the antibody-protected mice developed a neurological disease characterized by hindlimb paralysis and wasting. Evidence of inflammation and demyelination was apparent in the spinal cord and brainstem. The mice that remained asymptomatic at this time showed few signs of inflammation and none developed clinical disease over the following 9 months. Viral antigen could be detected in most of the mice examined at all times after inoculation, whether symptomatic or not, and was particularly evident in the animals with hindlimb paralysis. MHV-JHM could be consistently cultured from the mice with hindlimb paralysis. These results show that maternal immune factors can completely protect susceptible mice from the acute, fatal, clinical encephalomyelitis caused by MHV-JHM, but cannot prevent the establishment of a latent state and subsequent development of virus-induced, clinically evident, demyelinating disease. This model will be useful for studying the virus and host factors important for the development of MHV-JHM latency and subsequent virus-induced demyelination.

Animals↗
PubMed1994

Tonic "seizures" in a patient with brainstem demyelination: MRI study of brain and spinal cord.

Tonic seizures are a poorly understood manifestation of demyelinating disease, first reported in 4 patients with multiple sclerosis. We describe a patient with tonic extension of the left limbs caused by a right-sided brainstem lesion as the first manifestation of demyelinating disease. A 19-year-old man was referred with a 4-month history of spontaneous attacks of mild paresthesias of the left arm and leg, followed by 15-45 s of rigid extension of the left limbs, occurring up to 25 times per day. Two months after onset, an MRI scan revealed areas of T2 abnormality in the lateral right cerebral peduncle and deep frontal white matter. The EEG was normal, including during hyperventilation which induced a typical episode. All attacks were successfully suppressed by carbamazepine, phenytoin, and valproate monotherapy. Serologic testing for toxoplasmosis, cytomegalovirus, Epstein-Barr virus, Lyme disease, and HIV was negative. Cerebrospinal fluid oligoclonal bands were absent but cerebrospinal fluid immunoglobulin G was mildly elevated (4.2 mg/dl). Over the next 30 months, serial MRIs revealed a normal spinal cord and persistence of the midbrain lesion, with resolution of some of the white matter lesions but reappearance of others. At 46 months, the midbrain lesion resolved on MRI, and the spasms no longer occurred spontaneously, nor could they be elicited by hyperventilation. While two previous reports have shown internal capsule lesions to underlie the tonic spasms in demyelinating disease, this is the first report in which a brainstem lesion has been causative.

Adult↗
PubMed1988

Immunological and cytological studies of autoimmune demyelination and multiple sclerosis.

The early history of experimental allergic encephalomyelitis is reviewed from the point of view of the characterization and recognition of myelin basic protein and the active agent in acid-fast bacilli, namely muramyl dipeptide. Protocols effective in inducing demyelination are pinpointed. Special attention is paid to the protocol which depends on pretreating guinea pigs with muramyl dipeptide and foreign protein followed by a second injection of foreign protein and then the animals are injected with myelin basic protein and Freund's complete adjuvant. Variations in the timing and amounts of muramyl dipeptide are described as are their effects on the demyelination. The myelin breakdown has been studied with a monoclonal antibody reactive to P2. Similar pretreatment enhances the demyelination in Semliki Forest virus infection in mice. The changes in the blood brain barrier are found at 7 days after the myelin basic protein is injected and show grossly increased uptake by the cerebral vascular endothelium of IgG and perivascular uptake of IgG. The changes in the cerebrospinal fluid (CSF) proteins are described (IgG and albumin). Studies of P2 protein in the CSF by means of a new ELISA technique have been performed on human CSF in multiple sclerosis.

Animals↗
PubMed2006

Photophobia associated with a demyelinating lesion of the retrochiasmal visual pathway.

PURPOSE: To present two patients in whom photophobia was a predominant presenting symptom of retrochiasmal demyelination. DESIGN: Observational case report. METHODS: Two women who experienced an acute onset of photophobia underwent neuroophthalmic examination and investigations at a single institution. RESULTS: Examination revealed a homonymous visual field defect in both patients. Magnetic resonance imaging (MRI) demonstrated a hyperintense lesion in the area of the right posterior thalamus in one patient and enhancing lesions in the deep white matter of the temporal lobes bilaterally with contrast enhancement of the right optic tract in the second patient. Additional investigations, including lesion biopsy in the first patient, revealed demyelination as the most likely etiology. Improvement of photophobia, visual field defect, and radiographic abnormalities was documented over the next three to four months without accompanying treatment in both patients. CONCLUSIONS: Central pathology, including demyelination of the retrochiasmal visual pathway, should be considered in patients who experience acute photophobia.

Adult↗
PubMed2005

Thyroid hormone and remyelination in adult central nervous system: a lesson from an inflammatory-demyelinating disease.

Re-myelination in the adult CNS has been demonstrated in different experimental models of demyelinating diseases. However, there is no clear evidence that re-myelination is effective in multiple sclerosis (MS), the most diffuse demyelinating disease. Moreover, chronic disabilities in MS are believed to be due to remyelination failure and consequent neuron damage and degeneration. Due to the presence of numerous oligodendrocyte precursors inside demyelination plaques, reasons for remyelination failure are unknown. In this paper, we reviewed data from embryonic development and in vitro studies supporting the primary role of thyroid hormone in oligodendrocyte maturation. We also reviewed personal data on the possibility of promoting myelination in chronic experimental allergic encephalomyelitis (EAE), a widely used experimental model of MS, by recruiting progenitors and channeling them into oligodendroglial lineage through the administration of thyroid hormone.

Animals↗