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Biomedical subjects

A Carr

Publications and source records attributed to A Carr.

At least 199 records · Page 11Linked to original sources
PubMed1983

Expression of the large T protein of polyoma virus promotes the establishment in culture of "normal" rodent fibroblast cell lines.

Transfer into mouse and rat embryo fibroblasts in primary culture of cloned polyoma virus genes encoding only the large T protein led to the establishment of flat colonies in sparse subcultures at a frequency equal to that of transformation by wild-type virus. Cell lines could be derived from such colonies and maintained in culture for large numbers of generations without entering crisis. They exhibited a normal phenotype, by the criteria of growth on plastic to a low saturation density and of anchorage dependency. However, they required a lower serum concentration for growth than spontaneously established 3T3 cells. Similar results were obtained after transfer of recombinant DNA molecules encoding only the amino-terminal 40% of the large T protein, suggesting that this "immortalization" function corresponds to the activity of an amino-terminal domain of the protein. Immunoprecipitation analysis of T antigens in cell lines established after transfer of the full-size and of the truncated large T genes demonstrated the expression of the full-size large T protein and of a Mr 40,000 antigen expressed from the amino-terminal part of the gene, respectively. After transfer of a "large T only" plasmid that carries a tsa mutation, cell lines were established at 33 degrees C with the same efficiency as with the wild-type large T gene, but their growth was arrested after a shift to 40 degrees C, with a progressive loss in cell viability. This result indicates a continuous requirement for a large T function in the maintenance of "immortality."

Animals↗
PubMed1983

Association between alpha-1-antitrypsin types and the common cold.

Associations have been found between self-reported cold symptoms and Pi type in 84 pairs of identical twins. The risk of cold symptoms relative to MM phenotypes was 1.2 times greater in MS and 2.5 times greater in MZ individuals. Up to 9% of variance in cold symptoms could be attributed to Pi type, representing at least 20% of the total genetical variance.

Common Cold↗
PubMed1982

The roles of individual polyoma virus early proteins in oncogenic transformation.

The expression in normal rat cells of modified polyoma virus genomes, separately encoding large T, middle T or small T antigens, has allowed the investigation of the roles of these proteins in oncogenic transformation. Middle T is sufficient to transform cells of established lines but the transformants are serum dependent. Large T lacks intrinsic oncogenic potential but can relieve the serum dependence of normal and transformed cells. Middle T alone cannot transform primary rat embryo fibroblasts.

Animals↗
PubMed1982

Pathways of differentiation in chick embryo neuroretinal cultures.

Markers of neuronal cell differentiation (GABA accumulation, choline acetyltransferase activity) are shown to increase initially and then decline sharply in monolayer cultures of 9 day embryo neuroretinal (NR) cells. A glial marker (glutamine synthetase, GSase) is precociously inducible by hydrocortisone (HC) in dens "monolayer' NR cultures (containing aggregates of neuronal cells overlying the glian sheet) as well as in chick embryo retinal explants. The induced level of GSase activity is not maintained in the continued presence of HC, but rather declines by 20 days in vitro. Choline acetyltransferase (CAT) activity is higher in HC-treated cultures than in controls only during the period when induced GSase activity is detectable. Furthermore, the subsequent transdifferentiation of lens cells (monitored as delta crystalline content) in these cultures is delayed by 10 days and much reduced in extent when HC is present throughout the culture period. We suggest a simple model to account for these results, on the basis of recent evidence that lens cells are derived mainly from the retinal epithelial cells (immature Müller glia) of 9-day embryonic NR, and that transdifferentiation results from a change in cell determination during the early stages of "monolayers' culture. In outline, our model proposes that early determination of the retinal glia is associated with a decline of neuronal cell markers (dedifferentiation) followed eventually by loss of the neuronal cells. Hydrocortisone, by inducing transient glial cell differentiation (GSase activity), both prolongs the expression of a neuronal marker (CAT) and also reduces later transdifferentiation into lens.

Animals↗