C P Ludwig | PubMed Health

PubMed1997

Substance P receptor expression and cellular responses to substance P in prenatal rat spinal cord cells.

Substance P receptors (SPRs) are expressed by prenatal rat spinal cord neurons and glial cells early in their differentiation, and SPRs may mediate developmental influences in the developing spinal cord. In order to understand better early SPR expression, we quantified SPR mRNA in the rat spinal cord during prenatal development using a cDNA probe for the rat SPR in nuclease protection assays. SPR mRNA was present in the rat spinal cord at E14, the earliest stage examined, and the presence of specific binding sites for radiolabeled SP suggested that SPRs were expressed at the protein level as well. Comparisons of samples from rats at different prenatal ages showed that the relative abundance of SPR mRNA declined by about 75% from E14 through the remainder of prenatal development. Assays of the hydrolysis of phosphatidyl inositol performed on prenatal spinal cord cells in culture revealed that SP caused a small but significant stimulation. These results show that expression of SPRs is an early molecular event in the development of the rat spinal cord in vivo and that SPRs on young spinal cord cells can mediate functional responses at early developmental stages.

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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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