Biomedical subjects

N A Flaris

Publications and source records attributed to N A Flaris.

4 recordsLinked to original sources

PubMed1995

Developmentally-regulated lectin binding in the embryonic mouse telencephalon.

Cell-surface carbohydrate epitopes are important determinants in cell-cell and cell-matrix interactions, and oligosaccharide groups are structural components of many growth factor receptors and cell adhesion molecules. These epitopes may participate in the regulation of stem cell proliferation and differentiation during central nervous system development. To further understand these cellular phenomena, it is important to define the changes in neuroepithelial cell-surface carbohydrate expression during development. We used a panel of fluorescein-conjugated lectins to label live, freshly dissociated cells from the embryonic day 11 to 18 (E11 to E18) mouse telencephalon. The intensity and heterogeneity of lectin labeling was assessed by flow cytometry. The lectins that we examined exhibited widely varying levels of labeling intensity. Lectins with the highest degree of binding included cholera toxin B subunit (CTB), which binds primarily to the gangliosides GM1 and GD1b, phaseolus vulgaris erythroagglutinating lectin (PHA-E), which binds to a variety of cell adhesion molecules, and wheat germ agglutinin (WGA). Many lectins showed increasing labeling intensity and cellular heterogeneity as development progressed. To determine if the observed cellular heterogeneity in lectin binding reflected biological differences in neuroepithelial cell subpopulations, cells from the E14 telencephalon were separated into two populations based on their intensity of CTB labeling using a fluorescence activated cell sorter. The population of weakly CTB labeled cells contained more than four times as many cells in S-phase of the cell cycle than the population of intensely CTB labeled cells. These observations suggest that lectin cytochemistry and flow cytometry can be useful in identifying specific cell subpopulations of neuroepithelial precursor cells during development, allowing their isolation and characterization in vitro.

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PubMed1994

Neurotrophin-4 selectively promotes survival of striatal neurons in organotypic slice culture.

The neurotrophins (NGF, BDNF, NT-3, and NT-4) provide trophic support to subpopulations of neurons in the central and peripheral nervous systems. We examined organotypic slices of neonatal mouse striatum maintained in medium supplemented with neurotrophins or with CNTF to determine which of these factors influence the survivability of striatal neurons. Neuron counts at the end of the culture period revealed that NT-4 was the only factor that had a significant effect on neuronal survival, suggesting that NT-4 is a trophic factor for striatal neurons in organotypic slices.

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PubMed1993

Characterization of microglia and macrophages in the central nervous system of rats: definition of the differential expression of molecules using standard and novel monoclonal antibodies in normal CNS and in four models of parenchymal reaction.

This report describes the development of a new panel of monoclonal antibodies produced following immunization of mice with cultured rat microglial cells. Using these new reagents and previously defined antibodies that bind to microglia or macrophages, the responses of parenchymal microglia, perivascular "microglial" cells, and infiltrating macrophage/monocytes were examined in 4 divergent models of central nervous system reaction. These were brain abscess, experimental allergic encephalomyelitis, Wallerian degeneration, and stab wound. No single new antibody was specific only for microglia; all antibodies positively staining microglial cells also labeled various subsets of macrophage/monocytic cells in normal tissues of the immune system. Moreover, the results indicate that microglia are capable of different levels and a variety of types of response, as defined by the molecules they elaborate. These findings suggest that these CNS resident cells belong to the extended monocyte/macrophage/dendritic cell family and that they do not respond in a stereotypic manner to all forms of CNS insult.

Animals↗

PubMed1992

Development and characterization of an experimental model of brain abscess in the rat.

Brain abscesses were produced in the rat by direct intracerebral injection of agarose beads laden with Staphylococcus aureus. The method proved to be easy, reproducible, effective and was associated with a low mortality rate. The histopathologic features of the experimental abscess are similar to other animal models and to human abscesses. The encapsulation of the lesion, macrophage/microglial response, astrocytic activation, and changes in the surrounding brain parenchyma were studied by immunohistochemistry. Edema, diffuse microglial activation and diffuse astrocytosis characterized the early reaction of the injected cerebral hemisphere. After day 10, edema subsided, and the microglial and astrocytic responses became restricted to the area around the lesion. Fibronectin deposition in the capsule preceded the appearance of myofibroblasts, which was concurrent with the beginning of collagen deposition on day 9. Hypervascularity of the capsule appeared as early as day 6 and persisted through day 28. This study suggests that brain abscess formation can be separated into three components: an initial period of edema and glial activation; an intermediate phase of neovascularization and fibronectin deposition; and a final phase of collagen deposition and progressive fibrosis. This new model offers an excellent paradigm for the analysis of neural tissue reaction and de novo fibrous tissue deposition.

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