Paclitaxel (Taxol) attenuates clinical disease in a spontaneously demyelinating transgenic mouse and induces remyelination.

Treatment with paclitaxel by four intraperitoneal injections (20 mg/kg) 1 week apart attenuated clinical signs in a spontaneously demyelinating model, if given with onset of clinical signs. If given at 2 months of age (1 month prior to clinical signs), disease was almost completely prevented The astrogliosis, prominent in our model, was reversed by paditaxel as determined by astrocyte counts and quantitation of GFAP. Electron microscopic examination of affected regions at 2.5 months demonstrated that the myelin was generally normal. By 4 months of age, demyelination was common in the superior cerebellar peduncle, maximal at 6 months, but continued to 8 months. In addition to myelin vacuolation and nude axons, the presence of many thin myelin sheaths suggested remyelination or partial demyelination. Although no evidence of oligodendrocyte loss was seen, nuclear changes were observed. To substantiate that remyelination was occurring, we measured MBP (18.5 kDa), MBP-exon II, Golli-MBP, TP8, Golli-MBP-J37, platelet-derived growth factor alpha (PDGFR alpha) and sonic hedgehog (SHH). Of these TP8, PDGFR alpha and SHH were up-regulated in the untreated transgenic. After paditaxel treatment, MBP-Exon II, TP8, PDGFR alpha and SHH were further up-regulated. We concluded that some of the effects of paditaxel were to stimulate proteins involved in early myelinating events possibly via a signal transduction mechanism.

Microarray analysis of gene expression in multiple sclerosis and EAE identifies 5-lipoxygenase as a component of inflammatory lesions.

Multiple sclerosis (MS) is a demyelinating disease of the central nervous system characterized by lesions that are areas of blood-brain barrier breakdown, inflammation and myelin damage. To identify genes that contribute to lesion pathology, we have compared gene expression in MS lesions and in brains of mice with experimental allergic encephalomyelitis (EAE) with that in normal white matter. Gene expression was analyzed by cDNA microarrays consisting of 2798 human genes. One of the genes found to be upregulated in both MS lesions and EAE brains was 5-lipoxygenase (5-LO), a key enzyme in the biosynthesis of the proinflammatory leukotrienes. The presence of 5-LO in MS lesions was confirmed by immunohistochemistry and indicated that 5-LO was primarily contained within macrophages. Although these findings are not specific for MS, they identify a potentially important component of pro-inflammatory activity in the demyelinating process in MS and suggest a possible target for anti-inflammatory therapy in MS.

Inhibition of experimental allergic encephalomyelitis in the Lewis rat by paclitaxel.

Experimental allergic encephalomyelitis (EAE), an animal model for multiple sclerosis (MS), is useful for preclinical testing for agents to be considered for treatment for this human demyelinating disease. Microtubules in lymphocytes play an important role in the cascade of human T cell activation, and paclitaxel (PTX), a microtubule stabilizer, can inhibit T cell function. A new formulation of micellar PTX, free of Cremophor and ethanol, was tested for its effect on the induction of EAE in Lewis rats. Adoptive EAE was induced with an encephalitogenic T cell line activated with guinea pig myelin basic protein (GP MBP) peptide 68-88. PTX (10 mg/kg) was administered 24 and 72 h after cell transfer. The clinical signs, fulminating in controls, were completely blocked by PTX, but mild CNS inflammation remained unaltered. A similar dose of PTX, given on days 6 and 8 to animals developing active EAE after immunization with GP MBP peptide 68-88 in complete Freund's adjuvant, greatly reduced the severity of paralysis and delayed the onset of disease by 8-9 days. Marked weight loss and severe toxicity were noted with higher and more prolonged administration. In vitro micellar PTX inhibited activation of encephalitogenic T cells by both specific antigen and mitogen. Lower doses and longer treatment programs may provide effective treatment with acceptable adverse effects with this agent in the treatment of inflammatory demyelinating disease.

The neuropathology of multiple sclerosis.

This article reviews the pathology of multiple sclerosis in an attempt to allow the reader to better understand the pathogenesis of the lesions. The elements comprising the lesions are discussed in light of their pathogenic implications. Current ideas of classification are discussed, and wherever possible, correlations with clinical and imaging studies are drawn.

Severe fetal asphyxia associated with neuropathology.

Studies of fetal monkeys and lambs have demonstrated the association between a single prolonged episode of severe fetal hypoxia and the occurrence of neurologic abnormality. This case represents a single episode of fetal hypoxia with severe metabolic acidosis at delivery accounting for neurologic abnormality on postmortem examination that closely parallels the results of experimental studies.

Acute fulminant symmetrical vasculitic polyneuropathy: need for early biopsy.

We report 2 patients with acute symmetrical axonal motor and sensory polyneuropathy associated with vasculitis. The clinical presentation in each case was not that of a mononeuritis multiplex. Serial electrophysiological studies in 1 of the patients documented the development of confluent axonal degeneration involving several motor and sensory territories over the same period of time. In both patients the diagnosis of necrotizing vasculitis was established by peripheral nerve biopsy and recovery followed treatment with prednisone and cyclophosphamide. Biopsy of an involved nerve should be routinely sought in unexplained acute axonal polyneuropathies.

Myelination by mature ovine oligodendrocytes in vivo and in vitro: evidence that different steps in the myelination process are independently controlled.

The ability of isolated mature post-myelination ovine oligodendrocytes to myelinate was investigated in tissue culture and in vivo. In culture, although the cells adhered preferentially to rat dorsal root ganglia (DRG) axons, sent out processes that encircled and wrapped them, proliferated, and synthesised myelin proteins (MBP), no myelination was found. This failure to find myelination occurred despite the fact that the oligodendrocytes both in the present experiments and in previous studies elaborated membranous structures that have been shown chemically and structurally to be similar to normal central nervous system myelin. These findings contrasted with those seen when neonatal rodent glial cells were added to similar DRG neuron cultures, in which myelination readily occurred. When the same adult ovine oligodendrocytes were transplanted into the brains of Shiverer mice, normal compact myelin was formed, proving that the cells were capable of myelination and suggesting that cross-species incompatibility was probably not a major factor in the lack of myelination in vitro. It is possible that the failure of ovine oligodendrocytes to myelinate DRG axons is due either to the relatively low number of supporting glial cells, such as astrocytes or microglia which may be necessary for satisfactory myelination, or that some other factor in the microenvironment is lacking; in any event, these results point to the complexity of oligodendrocyte-axon interactions. It is clear that each of the events, from adherence to proliferation to wrapping and the myelin compaction may be under the control of a different signal and may operate through a distinct mechanism, even though each process is dependent on the other. The results also point to the potential usefulness of this model system for deciphering such signals and mechanisms.

A syndrome of acute severe muscle necrosis in intensive care unit patients.

Four septic patients and one asthmatic patient are described who developed a severe paralytic disorder in an intensive care unit (ICU), associated with a rise in serum creatine kinase and a severe necrotizing myopathy. All cases had received non-depolarizing muscle blocking agents and large intravenous doses of glucocorticoids. Three patients developed myoglobinuria. No improvement or very little improvement in muscle function was noted in the four fatal cases. The single survivor recovered his strength after 6 months. This syndrome ("necrotizing myopathy of intensive care") provides one of the differential diagnoses for ICU-acquired weakness. The myopathy appears to have several interdependent causes and it is proposed that these should be classified as myonecrosis "priming" factors (glucocorticoids, myotropic infections, sepsis) and "triggering" factors (non-depolarizing muscle blocking agents).

Delayed wallerian degeneration in the central nervous system of Ola mice: an ultrastructural study.

The ultrastructural features of wallerian degeneration in the optic nerves of the mutant mouse, C57BL/Ola, was compared with that occurring in age matched control mice, to determine whether the previously described defect in the peripheral nervous system was present in the central nervous system as well. On ultrastructural examination, marked delay in the rate of degeneration was seen in the Ola mice nerves seen most clearly at all stages up to 4 weeks post-enucleation, following which differences progressively became undetectable. Once degeneration began, however, the pattern and mechanisms were similar to those seen in control animals, with macrophages, oligodendrocytes, and astrocytes apparently behaving similarly. In both the experimental animals and the controls, the rate of degeneration was slower than that seen in the peripheral nervous system. This study confirms a previous electrophysiological study that the defect in this mutant affects axons in both the peripheral and the central nervous systems.

Oligodendrocytes from optic nerves subjected to long term Wallerian degeneration retain the capacity to myelinate.

It has previously been shown in the adult rat optic nerve that cells with many features of oligodendrocytes are capable of surviving for extended periods of time in the absence of axons. This is in contrast to the situation in the developing nervous system, where removal of axons leads to the failure of differentiation and to the death of oligodendrocytes. In the adult, these surviving oligodendrocytes were not typical in their appearance, and could only be identified with certainty using cell specific markers. In the present experiments, the functional capacity of these long-term quiescent cells to regenerate and myelinate was tested using the Shiverer mouse, a mutant lacking the gene for myelin basic protein (MBP), as a host animal. Fragments of optic nerve from adult rats which had been enucleated up to 2 years previously, were implanted into neonatal Shiverer mice. Four weeks later, the brains were removed and the formation of myelin investigated with antibodies to MBP, to ensure that this was of donor origin. Axons were demonstrated to have grown into the implants, and may have provided the stimulus for the production of MBP by the oligodendrocytes, which were stained positively within the implant. Myelin was demonstrated both within and adjacent to the implant. This study indicates that in the adult central nervous system, cells can survive for extended periods of time in the absence of axons, albeit in an inactive state, and are then capable of functional regeneration when placed in contact with unmyelinated axons. The origin of these cells, either from surviving oligodendrocytes which had previously myelinated the axons, or from progenitors lying within the adult nerve is unclear. The implications of these results are of importance in the further investigation of the potential for central nervous system regeneration.

Phagocytosis in the rat optic nerve following Wallerian degeneration.

Unilateral enucleation of the eye in adult male rats was performed in an attempt to resolve the longstanding controversy as to the nature of the phagocytic cells during Wallerian degeneration in the central nervous system. Previously both resident microglia and circulating monocytes, as well as oligodendrocytes, have all been considered to be the phagocytic cells. In these present experiments macrophages and microglia were studied using lectin histochemistry for Griffonia simplicifolia agglutinin and the monoclonal antibody ED1 at light microscopic level. Oligodendrocytes were demonstrated ultrastructurally using immunohistochemistry with monoclonal antibodies against myelin oligodendrocyte glycoprotein (MOG). Ultrastructural examination of the degeneration optic nerves confirmed longstanding reports of the slow nature of breakdown in the adult central nervous system. During the early periods of breakdown, starting at 1 week and continuing to 1 or 2 months, it was difficult to type, on ultrastructural examination alone, the nature of all the cells undergoing phagocytosis, but many of them resembled microglia/macrophages. Myelin debris cleared very slowly and could still be recognised prominently in the nerve up to 22 months post-enucleation. Lectin and immunochemical examination showed that the early major phagocytic component of phagocytosis was carried out by macrophages, probably both circulating and resident. In addition, however, myelin and axonal debris was taken up or retracted into oligodendrocyte processes, which were stained with antibodies to MOG. This oligodendrocyte component appeared to be small in relationship to the overall degree of debris.(ABSTRACT TRUNCATED AT 250 WORDS)

Oligodendrocyte survival in Wallerian degeneration.

The long-term survival of oligodendrocytes in the absence of axons in adult animals was studied following Wallerian degeneration of the optic nerves of adult rats for periods up to 22 months. In contrast to the findings in development and in young animals, large numbers of oligodendrocytes survived during this time period even when deprived of axonal stimuli. The morphological phenotype of many of these cells differed from those of normal oligodendrocytes, and their oligodendrocytic nature was confirmed at a light microscopic level using antibodies to carbonic anhydrase, and at an electron microscopic level by using antibodies to myelin oligodendrocyte glycoprotein. Although there did appear to be some loss of oligodendrocytes over time, a large proportion appeared to remain intact. Many of the remaining cells and processes appeared to resemble resting or quiescent cells. The survival of these cells demonstrates the differential susceptibility of mature and developing oligodendrocytes to loss of axonal stimulus and also indicates a possible reserve capacity for repair following central nervous system injury.

Spontaneous recovery from the encephalomyelitis in mice caused by street rabies virus.

Recovery from rabies was studied in an experimental model. Young adult mice were inoculated in a hindlimb footpad with street rabies virus (fox salivary gland isolate). In a group of 62 mice, 97% developed clinical rabies with paresis of the extremities and spasticity, and 37% recovered with neurological sequelae. There was an acute inflammatory reaction in the brainstem and grey matter of the spinal cord, and degeneration of myelinated axons in the white matter of the cord and in the dorsal roots. Rabies virus antigen was found in the central nervous system of all mice examined between day 5 and 13, and also in trigeminal and dorsal root ganglia. Surviving mice had neutralizing antibodies in serum and brain tissue, and 90% survived an intracerebral challenge with the CVS strain of fixed rabies virus. Spontaneous recovery from rabies encephalomyelitis was demonstrated with evidence of viral replication and pathological changes in the central nervous system.