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H de F Webster

Publications and source records attributed to H de F Webster.

9 recordsLinked to original sources
PubMed1995

Astrocytes upregulate glial fibrillary acidic protein (GFAP), but not insulin-like growth factor-I (IGF-I) during experimental autoimmune neuritis (EAN).

T cell-mediated autoimmune neuritis produces rapid activation of spinal cord microglia. To determine whether this microglial response upregulates astrocytic expression of IGF-related proteins, we induced EAN and used in situ hybridization and immunocytochemistry to examine the mRNAs and peptides for glial fibrillary acidic protein (GFAP), insulin-like growth factor-I (IGF-I), IGF-I receptor (IGFR-I) and IGF binding protein-2 (IGFBP-2). Relative levels of GFAP mRNA and peptide were highest in the lumbar spinal cord 4-10 d following T cell transfer and significant GFAP elevations were still present after three weeks. The astrocytes expressing GFAP mRNA and peptide were localized around motoneurons which were related topographically to axons in peripheral nerve inflammatory lesions. In the nucleus gracilis, where terminals of dorsal root ganglion neurons are located, astrocytic levels of GFAP mRNA and peptide rose later and did not reach their highest levels until 21 d after T cell transfer. Even though microglia were activated in both locations 2-4 d after transfer, astrocytic levels of IGF-I, IGFR-I and IGFBP-2 mRNA and peptide did not differ significantly from those observed in controls. The dissociation of GFAP and IGF-I expression in EAN suggests that these astrocytic responses may be independently regulated. We also suggest that the type and severity of remote neuronal injury are probably more important inducers and regulators of these astrocytic responses than microglial cell activation.

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PubMed1972

Cell elongation in the cultured embryonic chick lens epithelium with and without protein synthesis. Involvement of microtubules.

Previous studies have shown that cells in the 6-day old embryonic chick lens epithelium elongate in tissue culture. In the present study, the time course of elongation during the 1st day of cultivation has been examined histologically. Cultured epithelia were also treated with cycloheximide or colchicine in order to determine if cell elongation depends on new protein synthesis and on the utilization of microtubules, respectively. In the first 5 hr of culture, the mean cell length increased from 11 micro to 21 micro. Subsequently, elongation was slower; the mean cell length was 28 micro after 24 hr in culture. Continuous exposure to cycloheximide did not inhibit the initial doubling of cell length, but did prevent further elongation. By contrast, colchicine inhibited elongation almost immediately. When added after the cell length had doubled, cycloheximide and colchicine each inhibited further elongation; the treated cells remained columnar. Radioautographic and electrophoretic tests showed that protein synthesis was not appreciably affected by colchicine, but was suppressed by cycloheximide. Electron microscopic examination revealed that microtubules oriented along surface membranes were present in epithelia cultured with serum alone and with cycloheximide, but not in those incubated with colchicine. These results indicate that the early stages of cell elongation in the cultured lens epithelium require an initial assembly and organization of preexisting microtubular elements and that continued elongation depends, in addition, on the de novo synthesis of protein, possibly microtubule protein.

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