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R L Knobler

Publications and source records attributed to R L Knobler.

88 records · Page 5Linked to original sources
PubMed1983

Peripheral neuropathy in the Twitcher mutant. A new experimental model of endoneurial edema.

The Twitcher mouse (Twi/Twi) is a recently identified mutant experimental model for human globoid leukodystrophy. Affected mice develop neurologic abnormalities with demyelination of white matter and peripheral nerve due to an inherited enzyme deficiency. The neuropathy has unusual pathologic features:severe interstitial edema and infiltration by eosinophils. To investigate its pathogenesis and to identify the mechanism of demyelination, we studied vascular permeability and measured endoneurial fluid pressure. Significantly increased endoneurial fluid pressure was detected in clinically affected animals (average, 6.4 cm H2O) versus controls (1.7 cm H2O), and these data are the first measurements of EFP to be reported in mice. Increased vascular permeability to horseradish peroxidase was visualized by electron microscopy with leakage of horseradish peroxidase between endothelial cells and flooding of the endoneurial interstitium. Numerous eosinophils were present in the interstitium, as well as some polymorphonuclear cells, occasional erythrocytes, and degranulating mast cells. Abnormalities of nerve fibers included swelling of Schwann cells with intracytoplasmic inclusions, demyelination, and remyelination. As well as being a model for globoid leukodystrophy, the Twitcher is the first spontaneously occurring experimental model for endoneurial edema and increased endoneurial fluid pressure.

Animals↗
PubMed1982

Virus persistence and recurring demyelination produced by a temperature-sensitive mutant of MHV-4.

Mouse hepatitis virus type 4 (MHV-4, the JHM strain), a positive-strand RNA virus of the coronavirus family, is well documented as an inducer of acute and chronic demyelination in mice, as well as subacute demyelination in rats, due to a cytolytic infection of oligodendrocytes. However, experiments to explore the role of virus and host factors in the production of chronic or recurrent demyelinating disease have been limited because MHV-4 usually produces demyelination in conditions that frequently induce a fatal necrotizing encephalomyelitis. To circumvent this problem, we had made and selected mutant viruses that caused both a high incidence of demyelination and a low incidence of encephalitis-induced mortality. One such mutant, designated ts8, consistently caused acute demyelinating disease in over 90% of intracerebrally or intranasally (natural route of infection) inoculated, 4-5 week-old mice from several susceptible strains within 6-10 days. In addition, ts8 typically did not cause fatal necrotizing encephalitis, showing a low mortality (less than 5%). This reflected a unique tropism of ts8 for oligodendrocytes, but a limited one for neuronal cells. We now report that ts8 is also useful for inducing persistent infection of the mouse central nervous system (CNS). The histopathological correlate of this infection is chronic recurrent demyelination, and virus can be demonstrated ultrastructurally in intact oligodendrocytes, in the vicinity of demyelinated areas.

Animals↗
PubMed1982

In vivo and in vitro models of demyelinating diseases. V. Comparison of the assembly of mouse hepatitis virus, strain JHM, in two murine cell lines.

The developmental sequence of a neurotropic strain (JHM) of mouse hepatitis virus was examined by transmission electron microscopy and immunocytology. The nucleoprotein core of this coronavirus, which contains RNA of positive polarity and is helical in configuration, becomes incorporated into enveloped particles in the same manner as the nucleocapsids of the orthomyxo- and paramyxoviruses. However, JHM virus is assembled intracellularly by budding at surfaces of smooth membranous vacuoles. A comparison of JHM virus replication in L2 and 17Cl-1 cell lines revealed that L2 cells undergo more rapid cytopathology and cease virus production much sooner than 17Cl-l cells. In L2 cells the accumulation of core material appears to continue after the abrupt cessation of virus assembly. This is evident by the massive cytoplasmic accumulation of structure resembling nucleocapsids, which react with hybridoma antibody to the nucleocapsid antigen as demonstrated by the immunoperoxidase procedure. The current findings are consistent with our previously published demonstration, using cells of neural and other deviation, of the fundamental role of the host cell type in regulating the replication and expression of coronaviruses.

Animals↗
PubMed1982

Selected mutants of mouse hepatitis virus type 4 (JHM strain) induce different CNS diseases. Pathobiology of disease induced by wild type and mutants ts8 and ts15 in BALB/c and SJL/J mice.

The model system of central nervous system (CNS) disease induced by mouse hepatitis virus type 4 (MHV-4) is explored by comparison of wild type (wt) MHV-4 and two temperature-sensitive (ts) mutants, designated ts8 and ts15, in BALB/c and SJL/J mice. In BALB/c mice, 3 plaque-forming units (PFU) of wt MHV-4 given intracerebrally caused fatal encephalomyelitis in all mice by 7 days after infection, with spread of virus outside the CNS, especially to liver. In SJL/J mice, 3 PFU of wt virus was cleared within 2-3 days, with little spread, and up tp 100 PFU failed to cause fatal encephalomyelitis. However, larger amounts of virus, like 1000 PFU, caused fatal encephalomyelitis in SJL/J mice. In contrast, 10(4) PFU of MHV-4 ts8 did not cause death in either BALB/c or SJL/J mice, and persisted in the CNS of both strains while retaining its ts phenotype. There was significatnly less spread of virus outside the CNS. BALB/c mice usually showed demyelination, remyelination, and recurrent demyelination with ts8, while SJL/J mice only rarely had lesions. Intracerebral inoculation with 10(4) PFU of MHV-4 ts15 was associated with a persistent infection in CNS and liver of BALB/c mice; however, only occasional demyelination and hepatic lesions occurred. TS15 did not cause death in either BALB/c or SJL/J mice and did not cause histopathologic injury in SJL/J mice.

Animals↗
PubMed1981

Mouse hepatitis virus type 4 (JHM strains). induced fatal central nervous system disease. I. genetic control and murine neuron as the susceptible site of disease.

Mouse hepatitis virus (JHM strain) type 4 induces acute encephalitis followed by death in many strains of laboratory mice. Immunohistochemical study in vivo and analysis of mouse neuronal cells in vitro both indicate that the target cells in this infection is the neuron. Further, examination of several inbred mouse strains and neuronal cells from them shows that disease expression is controlled by a single autosomal gene action at the level of the neuronal cell. Susceptibility is dominant but not H-2 linked. However, cultured neuronal cells and macrophages from SJL/J mice, which are resistant to this infection, fail to make significant amounts of infectious virus after an appropriate viral inoculation. Apparently the defect is not at the level of the virus-cell receptor, because these cells, in part, express viral antigens.

Animals↗
PubMed1981

Inverse ocular bobbing.

A new form of abnormal spontaneous eye movement termed inverse ocular bobbing is described. It consists of a slow downward eye movement followed by delayed quick return upward to midposition. It is contrasted with other types of abnormal vertical eye movements.

Adult↗
PubMed1981

Selective localization of wild type and mutant mouse hepatitis virus (JHM strain) antigens in CNS tissue by fluorescence, light and electron microscopy.

Demyelination may be induced by several different pathogenetic mechanisms. We have been utilizing mouse hepatitis virus (MHV) to study virus-induced demyelination in the central nervous system (CNS). To learn whether the different disease phenotypes in 4-week-old mice, caused by wild type (a model for fatal encephalomyelitis) or mutant ts8 (a model for primary demyelination), is due to an altered cellular tropism, we have developed an immunolabeling technique to evaluate critically the localization of MHV antigens in the unique cells of the CNS. Using mouse derived L-cells and primary neuronal cells in vitro, we determined an appropriate fixative (4% paraformaldehyde and 0.5% glutaraldehyde) that both preserved MHV antigenicity and cell structure. These studies in vitro showed the presence of MHV antigens on the surface of cells. Utilizing immunoperoxidase labeling as developed, we studied the localization of MHV antigens in vivo. MHV antigens associated with wild type (wt) virus were localized in neuronal cells as well as oligodendrocytes, which might account for the encephalomyelitis and primary demyelination, respectively. In contrast, MHV antigens associated with ts8 were localized rarely in neurons but commonly in oligodendrocytes. This might account for the uncommon occurrence of fatal encephalomyelitis, but the frequent presence of primary demyelination. Of interest was the finding of viral antigens during MHV infection in the cytoplasmic processes of oligodendrocytes surrounding intact myelin sheaths. We conclude that the different disease phenotypes caused by wt and mutant ts8 reflect differences in the cellular tropism of the two viruses for cells in the CNS.

Animals↗
PubMedDate not supplied

Acute and persistent viral infections of differentiated nerve cells.

Within the nervous system the highly specialized structure and function of nerve cells renders the pathogenesis of viral infections amazingly complex. In vivo and in vitro studies reveal that viruses may display tropism for distinct types of cells such as neurons, myelin-forming cells, or astrocytes. In neurons, RNA viruses mature in the cell body and in dendrites close to synapses, from which they can spread to synaptic endings. Undefined host factors and stage of differentiation may favor defective viral assembly, which, in turn, results in persistent infections of neurons. In myelin-forming cells, lytic infection results is persistent infections of neurons. In myelin-forming cells, lytic infection results in degeneration of myelin and, consequently, in altered conduction in those axons that are ensheathed by a myelin-forming cell. In addition, breakdown of myelin may induce an autoimmune response, which then leads to further demyelination. Autoimmune demyelination may also occur when glial cells other than myelin-forming cells are infected. Astrocytes are prone to persistent infection or viral transformation.

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