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M F Bartholdi

Publications and source records attributed to M F Bartholdi.

27 records · Page 2Linked to original sources
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↗
PubMed1986

Preneoplastic phenotype and chromosome changes of cultured human Bloom syndrome fibroblasts (strain GM 1492).

The Bloom syndrome fibroblast strain, GM 1492, was examined for phenotypic properties generally associated with neoplastic cells. A serial clonogenicity assay indicated that these cells can proliferate in culture, achieving approximately twice the number of population doublings as compared to normal human skin fibroblasts. Strain GM 1492 appeared to be partially transformed in that these cells showed a slight degree of anchorage independence when grown in methylcellulose, and also appeared to have relaxed growth requirements compared to normal fibroblasts. GM 1492 cells are heteroploid, with 20 to 80 chromosomes/cell and a modal chromosome number of 44. Cytogenetic analysis of G-banded metaphase chromosomes indicated that most cells contained at least one copy of each normal human chromosome, and many cells exhibited only aneuploidies with no detectable chromosomal rearrangements. Minute chromosomes were seen in a few of the metaphase cells examined. GM 1492 cells did not form tumors in athymic nude mice. Since many of the characteristics of GM 1492 cells are similar to those seen only in tumor cells, but the strain is nontumorigenic, we suggest that GM 1492 cells are preneoplastic and thus represent an ideal system for the in vitro study of human neoplastic progression.

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

Counterstaining human chromosomes for flow karyology.

Isolated human metaphase chromosomes stained with the fluorochromes 4'-6-diamidino-2-phenylindole (DAPI) and chromomycin A3(CA3), and counterstained with nonfluorescent netropsin (NTR), have been analyzed by dual-laser flow cytometry. Counterstaining with NTR reduces DAPI fluorescence except at regions on chromosomes 1,9,15,16, and Y, corresponding to C-band heterochromatin. Bivariate flow karyology of human chromosomes treated with this triple-stain combination resolves chromosomes 1,9, and Y distinctly from the remaining chromosomes and resolves variations between chromosome homologues not detected by staining with propidium iodide (PI) or with the double stain combination Hoechst 33258(HO) and CA3.

Cells, Cultured↗
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↗
PubMed1983

Chromosome analysis by high illumination flow cytometry.

Fluorescence measurements from metaphase chromosomes of the Chinese hamster, stained with propidium iodide excited at high illumination irradiance, completely resolve each chromosome type. The measurements are performed in a specially designed flow cytometer that achieves high irradiance (4 MW/cm2) by using high power laser output (2 W at 488 nm) focused to small spot size (1% irradiance variation over 2 microns). The coefficient of variation of each chromosome peak is near 1.5%. Saturation of the fluorescence transition and photobleaching, two consequences of high irradiance, are shown to occur. Even with a nonlinear dependence of fluorescence upon illumination irradiance, fluorescence retains a proportional response to chromosome type; each chromosome peak maintains a consistent ratio to the others at every irradiance. No perturbation of fluorescence by the optical or geometrical properties of the chromosomes is evident. The advantages of high irradiance illumination are an increase in fluorescence sufficient to reduce the statistical error in photoelectron number to a low level and reduced influence of laser power fluctuations and variable chromosome flow trajectories on the precision. These benefits improve the resolution of chromosome analysis by flow cytometry, particularly the resolution of smaller chromosomes.

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↗