PubMed Health⌕ Search

Biomedical subjects

F A Ray

Publications and source records attributed to F A Ray.

28 records · Page 2Linked to original sources
PubMed1986

Spontaneous in vitro neoplastic evolution: recurrent chromosome changes of newly immortalized Chinese hamster cells.

Spontaneous neoplastic progression in cultured Chinese hamster cells was studied at the earliest stage possible. Eighteen independent newly immortalized cell populations (from six individual Chinese hamsters) were characterized for karyotype instability. Colonies were selected from initial sparse platings of adult or fetal cells and were expanded for study. The chromosomes from these newly established cell lines were studied using a combination of G-banding and flow karyotype analysis. At a slightly later passage, the 18 cell lines were tested for tumorigenicity in nude mice. Frequent recurring chromosome changes were observed in the karyotypes. The most frequent changes were either total or partial trisomy of chromosome #3 (83%) and trisomy of chromosome #5 (61%). Only 4 of 18 clones (22%) were tumorigenic at the time of testing, and these had long latent periods. The presence of recurrent chromosome changes did not obligate these cell lines to become tumorigenic, but the karyotype instability appeared to be an indicator of the ongoing process of neoplasia.

Animals↗
PubMed1986

Spontaneous immortalization rate of cultured Chinese hamster cells.

Chinese hamster cell cultures derived from either fetal cell suspensions or adult ear clippings invariably became permanent cell lines during conventional subcultivation. The immortal cell cultures arose from rare spontaneous cellular events during the in vitro cultivation of cells with limited proliferative capacity. Immortality was not related to rare, precommitted cells from the animals. The expansion of clones of cells with limited life-span to form permanent cell lines was routinely successful only when the initial, unsubdivided culture achieved a total number in excess of 10(6) cells. On the basis of this observation, a serial clonogenicity assay was developed for determining the life-span of the cells with limited proliferative capacity and for determining whether a cell population is immortal. In addition, the technique of clonal expansion was used for a fluctuation analysis to determine the rate of immortalization. This analysis yielded a rate of 1.9 X 10(6) per cell per generation.

Animals↗
PubMed1984

Flow karyology of serially cultured Chinese hamster cell lineages.

Flow karyology of serially cultured Chinese hamster cell lineages has been observed to be influenced by the degree of cellular heterogeneity in culture. The minimum coefficient of variation (CV) and debris fraction obtainable vary as a cell lineage evolves from a primary cell culture to an established cell line. The cell lineages pass through a stage of decreased cellular heterogeneity from which flow karyotypes can be obtained with lower CV and debris fraction. The influence of cellular heterogeneity on flow karyology is observed with constant preparative protocol and constant instrument performance, and can be an additional source of variability.

Animals↗
PubMed1984

Chromosome polymorphism involving heterochromatic blocks in Chinese hamster chromosome 9.

A chromosome polymorphism was detected between two early passage euploid Chinese hamster cell strains when a fluorescence shift of the small metacentric No. 9 chromosome was resolved by flow cytometry. The characteristics of the polymorphism were studied using cultures established from ear clippings taken from 16 additional hamsters from our breeding colony. Additional variants of chromosome 9 were detected using flow cytometry, and a subset of these variants were analyzed by G- and C-banding. An increase of fluorescence recorded by flow cytometry correlated with an increase of centromeric heterochromatin. Autosomal normalization of the flow karyotype from 18 different animals indicated three distinct peak positions for chromosome 9. The results indicate that a discrete block of constitutive heterochromatin may be present in one or two extra copies within the small inbred colony of hamsters studied. To determine the inheritance patterns, hamsters with known polymorphic No. 9 chromosomes were bred. The flow karyotypes derived from the offspring of these matings provide strong evidence that chromosomal polymorphisms are inherited in Mendelian fashion.

Animals↗
PubMed1984

Transferrin receptor function in hereditary hemochromatosis.

The binding of 125I-diferric transferrin to cultured skin fibroblasts and phytohemagglutinin-stimulated lymphocytes was studied in cells derived from individuals homozygous for hereditary hemochromatosis and from normal individuals. Receptors with a high affinity for diferric transferrin were present on all cells. Transferrin receptor number decreased by more than 50% when fibroblasts from both normal and hemochromatotic subjects were maintained in iron-supplemented medium. The number of transferrin receptors expressed by normal and hemochromatotic lymphocytes after mitogen stimulation in iron-supplemented media was less than 50% that of lymphocytes which were mitogen stimulated in standard medium. No change in the affinity of the receptors for diferric transferrin was seen in cells maintained in iron-supplemented medium. Competition experiments in the presence of deferoxamine suggested that the transferrin receptors of fibroblasts and mitogen-stimulated lymphocytes have a 70- to 100-fold higher affinity for diferric transferrin than for apotransferrin. No differences in the properties of transferrin receptors were found between patients with hereditary hemochromatosis and normal individuals. Although transferrin binding decreases when cells are exposed to high levels of iron in the medium, the failure to totally abolish transferrin binding to the receptor suggests that the concentration of diferric transferrin to which cells are exposed may be a major determinant of cellular iron loading in hereditary hemochromatosis.

Cells, Cultured↗
PubMed1983

Spontaneous neoplastic evolution of Chinese hamster cells in culture: multistep progression of phenotype.

Chinese hamster cell strains, each initiated from a separate fetus, were carried in culture and tested for tumorigenicity and in vitro indicators of neoplasia at various passage levels. In the absence of any treatment, all 20 such lineages yielded permanent cell lines and showed other indications of neoplastic progression. A preimplanted gelatin sponge assay method was used to monitor tumorigenicity in nude mice. The process of spontaneous neoplastic progression in vitro could be divided into four stages. The rate of progression through these stages, as measured by passage level, was extremely variable between independent lineages. Detailed studies of one lineage showed that transformation indicators, in general, correlated with tumorigenicity but did not indicate whether or not a preneoplastic, permanent lineage would rapidly progress.

Animals↗
PubMed1983

Spontaneous neoplastic evolution of Chinese hamster cells in culture: multistep progression of karyotype.

Chromosomes from successive passages of a Chinese hamster cell strain (WCHE/5) that spontaneously progressed from a euploid primary cell culture to a heteroploid tumorigenic cell line were isolated and analyzed by Giemsa banding and high-resolution flow karyotype analysis. The frequency and identification of aneuploid and marker chromosomes were determined at both pre- and postcrisis culture stages and pre- and posttumorigenic stages. The combination of Giemsa banding and flow karyotypes provided detailed analysis of karyotype instability at each stage of cell culture progression. Aneuploidy (trisomy of chromosome 5) preceded the appearance of tumorigenicity in nude mice as well as in vitro indicators of neoplasia. The four stages of neoplastic progression defined in the previous paper correlated with a steady progression in karyotypic instability, including, in sequence: trisomy of chromosome 5; an 8q marker chromosome; a 3q+ insertion; and trisomy of chromosome 8. Additional changes continued to appear as the cells acquired classical properties of in vitro transformation.

Animals↗
PubMed1981

Recognition of nucleophile-treated alpha 2-macroglobulin by the alveolar macrophage alpha-macroglobulin . protease complex receptor.

Rabbit alveolar macrophages exhibit high affinity surface receptors which recognize alpha 2-macroglobulin . protease complexes but not native alpha 2- macroglobulin. Binding of alpha 2-macroglobulin . protease complexes to surface receptors is independent of the protease used to form the complex. In this communication, we demonstrate that treatment of human alpha 2-macroglobulin with nucleophilic agents (methyl amine, ammonium salts) converts native alpha 2-macroglobulin into a form recognized by the surface receptor for alpha 2-macroglobulin protease complexes. Analysis of the concentration dependency of ligand binding revealed that the surface receptor did not distinguish between nucleophile-treated alpha 2-macroglobulin and alpha 2-macroglobulin . protease complexes. These results are consistent with the hypothesis that proteases or nucleophilic agents effect the hydrolysis of an internal thiol-ester bond (Tack, B. F., Harrison, R. A., Janatova, J., Thomas, M. L., and Prahl, J. W. (1980) Proc. Natl. Acad. Sci. U. S. A. 77, 5764-5768), leading to an alteration in alpha 2-macroglobulin conformation. The altered conformation results in recognition of the alpha 2-macroglobulin by surface receptors.

Ammonium Chloride↗