scholarly journals Adhesion and detachment characteristics of Chinese hamster cell membrane mutants.

1978 ◽  
Vol 76 (1) ◽  
pp. 43-49 ◽  
Author(s):  
R L Juliano
Keyword(s):  
Initial Phase ◽  
Chinese Hamster ◽  
Chinese Hamster Cell ◽  
Galactose Oxidase ◽  
Wild Type ◽  
Chinese Hamster Cells ◽  
Altered Cell ◽  
Morphological Differences ◽  
Glass Surfaces ◽  
Surface Glycoproteins

We have investigated the adhesion and detachment properties of wild-type Chinese hamster cells and of variant lines, which possess altered cell surface glycoproteins as detected by galactose oxidase-[3H]borohydride labeling. The wild-type and variant lines tested all adhered to protein-coated glass surfaces at the same rate; however, the variant cells differed from wild type and from each other in terms of the ease with which they were detached by trypsinization. Morphological differences between the various lines were also apparent. Our results suggest that the carbohydrate moieties of the terminal region of surface glycoproteins are not directly involved in the initial phase of cell-to-substratum attachment, but that they may modulate the proteolytic susceptibility of surface components which are involved in cell detachment.

scholarly journals 8-AZAGUANINE RESISTANCE IN MAMMALIAN CELLS I. HYPOXANTHINE-GUANINE PHOSPHORIBOSYLTRANSFERASE

Genetics ◽  
1972 ◽  
Vol 72 (2) ◽  
pp. 239-252 ◽  
Author(s):  
F D Gillin ◽  
D J Roufa ◽  
A L Beaudet ◽  
C T Caskey
Keyword(s):  
Nucleic Acid ◽  
Mammalian Cells ◽  
Chinese Hamster ◽  
Acid Synthesis ◽  
Ethyl Methanesulfonate ◽  
Nucleic Acid Synthesis ◽  
Wild Type ◽  
Chinese Hamster Cells ◽  
Hypoxanthine Guanine Phosphoribosyltransferase

ABSTRACT Chinese hamster cells were treated with ethyl methanesulfonate or N-methyl-N'-nitro-N-nitrosoguanidine, and mutants resistant to 8-azaguanine were selected and characterized. Hypoxanthine-guanine phosphoribosyltransferase activity of sixteen mutants is extremely negative, making them suitable for reversion to HGPRTase+. Ten of the extremely negative mutants revert at a frequency higher than 10-7 suggesting their point mutational character. The remaining mutants have demonstrable HGPRTase activity and are not useful for reversion analysis. Five of these mutants have < 2% HGPRTase and are presumably also HGPRTase point mutants. The remaining 14 mutants utilize exogenous hypoxanthine for nucleic acid synthesis poorly, and possess 20-150% of wild-type HGPRTase activity in in vitro. Their mechanism of 8-azaguanine resistance is not yet defined.

Coordinate amplification of metallothionein I and II genes in cadmium-resistant Chinese hamster cells: implications for mechanisms regulating metallothionein gene expression

1985 ◽  
Vol 5 (2) ◽  
pp. 320-329
Author(s):  
B D Crawford ◽  
M D Enger ◽  
B B Griffith ◽  
J K Griffith ◽  
J L Hanners ◽  
...  
Keyword(s):  
Gel Electrophoresis ◽  
Polyacrylamide Gel Electrophoresis ◽  
Chinese Hamster ◽  
Chinese Hamster Cell ◽  
Chinese Hamster Cells ◽  
Future Studies ◽  
Noncoding Regions ◽  
Genes Encoding ◽  
Chinese Hamster Cell Line

We describe here the derivation, characterization, and use of clonal cadmium-resistant (Cdr) strains of the Chinese hamster cell line CHO which differ in their metallothionein (MT) induction capacity. By nondenaturing polyacrylamide gel electrophoresis, we showed that the stable Cdr phenotype is correlated with the augmented expression of both isometallothioneins (MTI and MTII). In cells resistant to concentrations of CdCl2 exceeding 20 microM, coordinate amplification of genes encoding both isometallothioneins was demonstrated by using cDNA MT-coding sequence probes and probes specific for 3'-noncoding regions of Chinese hamster MTI and MTII genes. Molecular and in situ hybridization analyses supported close linkage of Chinese hamster MTI and MTII genes, which we have mapped previously to Chinese hamster chromosome 3. This suggests the existence of a functionally related MT gene cluster in this species. Amplified Cdr variants expressing abundant MT and their corresponding Cds parental CHO cells should be useful for future studies directed toward elucidating the mechanisms that regulate expression of the isometallothioneins.

The energy charge in wild-type and respiration-deficient chinese hamster cell mutants

1980 ◽  
Vol 103 (1) ◽  
pp. 169-172 ◽  
Author(s):  
K. Soderberg ◽  
E. Nissinen ◽  
B. Bakay ◽  
I. E. Scheffler
Keyword(s):  
Energy Charge ◽  
Chinese Hamster ◽  
Chinese Hamster Cell ◽  
Wild Type

CHINESE HAMSTER CELL LINES RESISTANT TO THE CYTOTOXIC ACTION OF FLUORIDE

1978 ◽  
Vol 20 (1) ◽  
pp. 71-84 ◽  
Author(s):  
Ralph Mankovitz ◽  
R. Kisilevsky ◽  
Marie Florian
Keyword(s):  
Molecular Basis ◽  
Culture Medium ◽  
Chinese Hamster ◽  
Chinese Hamster Cell ◽  
Ovary Cell ◽  
Cytotoxic Action ◽  
Wild Type ◽  
Resistant Lines ◽  
Ovary Cell Line ◽  
Resistant Cells

The proliferation and efficiency of colony formation of a Chinese hamster ovary cell line, CHO, was found to be inhibited by concentrations of fluoride ≥ 10−3 M. From mutagenized populations of CHO cells, clones were isolated that were from 1.6 to 13 times more resistant than the wild-type to the cytotoxic action of fluoride. The resistant clones were found to be stable in the absence of selection. The fluoride sensitivity of wild-type and fluoride resistant clones was not altered by changes in the pyruvate concentration in the culture medium, indicating that the cytotoxic effect of fluoride is not due to the action of fluoride on the glycolytic pathway. On the other hand, both the incorporation of 3H-leucine into acid precipitable material and the distribution of polyribosomes were sensitive only to fluoride concentrations that were cytotoxic, suggesting that the molecular basis of fluoride induced cytotoxicity in both wild-type and fluoride resistant cells is the sensitivity of protein synthesis to fluoride. At concentrations of fluoride at which the wild-type cells are inhibited but fluoride resistant cells are not, the intracellular concentration of fluoride in the fluoride resistant cells was found to be 1/5 to 1/10 that of the wild-type, suggesting that fluoride exclusion is the basis for resistance in the resistant lines.

scholarly journals DERIVATION OF TK- CLONES FROM REVERTANT TK+ MAMMALIAN CELLS

Genetics ◽  
1973 ◽  
Vol 75 (3) ◽  
pp. 515-530
Author(s):  
D J Roufa ◽  
B N Sadow ◽  
C T Caskey
Keyword(s):  
Cell Lines ◽  
Mammalian Cells ◽  
Chinese Hamster ◽  
Chinese Hamster Cell ◽  
Single Step ◽  
Wild Type ◽  
Cell Clones ◽  
Selection Experiments ◽  
Step Selection ◽  
Selection Of

ABSTRACT In order to obtain a large collection of Chinese hamster cell clones defective in thymidine kinase (TK-), BrdUr selection experiments have been performed on wild-type and revertant TK+ cell lines. No clones (< 10-9) were obtained from the wild-type TK+ cell line by single-step selection. In contrast, revertant TK+ clones readily gave rise to stable TK- derivatives (1 - 2 × 10-4). Both wild-type and revertant TK+ clones spontaneously yielded 8-AGr colonies with the same frequency (1 - 5 × 10-6), suggesting that the differences between wild-type and revertant cell lines specifically affected selection of the TK- phenotype. The increased frequency of TK- clones reflects perhaps the number (ploidy) or character of the autosomal TK loci in TK+ revertants, or perhaps the mechanisms which regulate expression of the TK genes. Several mutagens, EMS, MNNG and UV, stimulated the TK+ revertants' frequency of TK- subclones only slightly (< 3-fold). Biochemical and genetic data indicated that the TK- clones derived from one revertant are phenotypically different. The phenotypes displayed by these cell lines are stable and do not depend upon the continued presence of the selective agent.

Biochemical evidence for multiple independent emetine resistance genes in Chinese hamster cells

1983 ◽  
Vol 3 (2) ◽  
pp. 198-202
Author(s):  
K Nielsen-Smith ◽  
S McGill ◽  
M Frahm ◽  
D J Roufa
Keyword(s):  
Molecular Basis ◽  
Ribosomal Proteins ◽  
Chinese Hamster ◽  
Chinese Hamster Cell ◽  
Ovary Cell ◽  
Chinese Hamster Cells ◽  
Molecular Product ◽  
Translation Apparatus ◽  
Hybrid Clones

Hybridization-complementation studies indicated that mutations in multiple genes can render Chinese hamster cells resistant to the alkaloid translation inhibitor emetine. Two of the genes, emtA and emtB, recognized in Chinese hamster lung and ovary cell lines, respectively, are known to affect the ribosomes of the cells directly. Although mutations in a third gene, emtC, affect the translation apparatus of Chinese hamster peritoneal cells in vitro (Wasmuth et al., Mol. Cell. Biol. 1:58-65, 1981), the molecular product of the emtC locus remains to be determined. To study the molecular basis for genetic complementation among emetine-resistant Chinese hamster cell mutants, we analyzed ribosomal proteins elaborated by complementing, emetine-sensitive hybrid clones (EmtB X EmtA and EmtB X EmtC) and by emetine-resistant clones that segregated from the hybrids. The electrophoretic forms of ribosomal protein S14 (the emtB gene product) elaborated by these clones indicated that the EmtA and EmtC phenotypes are independent of the emtB locus and that the emtA and emtC loci are not chromosomally linked to emtB.

scholarly journals Coordinate amplification of metallothionein I and II genes in cadmium-resistant Chinese hamster cells: implications for mechanisms regulating metallothionein gene expression.

1985 ◽  
Vol 5 (2) ◽  
pp. 320-329 ◽  
Author(s):  
B D Crawford ◽  
M D Enger ◽  
B B Griffith ◽  
J K Griffith ◽  
J L Hanners ◽  
...  
Keyword(s):  
Gel Electrophoresis ◽  
Polyacrylamide Gel Electrophoresis ◽  
Chinese Hamster ◽  
Chinese Hamster Cell ◽  
Chinese Hamster Cells ◽  
Future Studies ◽  
Noncoding Regions ◽  
Genes Encoding ◽  
Chinese Hamster Cell Line

We describe here the derivation, characterization, and use of clonal cadmium-resistant (Cdr) strains of the Chinese hamster cell line CHO which differ in their metallothionein (MT) induction capacity. By nondenaturing polyacrylamide gel electrophoresis, we showed that the stable Cdr phenotype is correlated with the augmented expression of both isometallothioneins (MTI and MTII). In cells resistant to concentrations of CdCl2 exceeding 20 microM, coordinate amplification of genes encoding both isometallothioneins was demonstrated by using cDNA MT-coding sequence probes and probes specific for 3'-noncoding regions of Chinese hamster MTI and MTII genes. Molecular and in situ hybridization analyses supported close linkage of Chinese hamster MTI and MTII genes, which we have mapped previously to Chinese hamster chromosome 3. This suggests the existence of a functionally related MT gene cluster in this species. Amplified Cdr variants expressing abundant MT and their corresponding Cds parental CHO cells should be useful for future studies directed toward elucidating the mechanisms that regulate expression of the isometallothioneins.

Selection of temperature-resistant mutants of Chinese hamster cells for growth on D-galactose

1982 ◽  
Vol 28 (3) ◽  
pp. 356-359
Author(s):  
Jean-Paul Thirion ◽  
E. J. Aw
Keyword(s):  
Gene Regulation ◽  
Mammalian Cells ◽  
Selection Pressure ◽  
Chinese Hamster ◽  
Wild Type ◽  
Chinese Hamster Cells ◽  
Growth Properties ◽  
Regulation Of Carbohydrate Metabolism ◽  
Resistant Mutants ◽  
Selection Of

Somatic cell variants of Chinese hamster V79 were selected for rapid growth on D-galactose at high temperatures. Their phenotypes are stable after many generations in the absence of selection pressure. They clone in D-galactose at temperatures at which the wild type cannot, while in D-glucose, the variants and the wild type appear to have the same growth properties. The use of such variants should be very important for the study of gene regulation of carbohydrate metabolism in mammalian cells.

Transcription of mouse rDNA and associated formation of the nucleolus organizer region after gene transfer and amplification in Chinese hamster cells

1985 ◽  
Vol 5 (11) ◽  
pp. 2943-2950
Author(s):  
V N Dhar ◽  
D A Miller ◽  
O J Miller
Keyword(s):  
Silver Staining ◽  
Transcription Initiation ◽  
Large Fraction ◽  
Organizer Region ◽  
Nucleolus Organizer Region ◽  
Chinese Hamster ◽  
Initiation Site ◽  
Chinese Hamster Cell ◽  
Nucleolus Organizer ◽  
Chinese Hamster Cells

Mouse rDNA can initiate transcription by using only Chinese hamster cell components, and this is associated with nucleolus organizer activity. To demonstrate this, we transferred a 3.2-kilobase segment of mouse rDNA containing the promoter, the transcription initiation site, and part of the external transcribed spacer to dihydrofolate reductase-deficient Chinese hamster cells by cotransformation with an abbreviated mouse dhfr gene. Stepwise selection for methotrexate resistance produced sublines in which the mouse rDNA was usually coamplified with the donor dhfr DNA and occupied the same site or sites in the hamster genome, as shown by in situ hybridization. Transcription from mouse rDNA was demonstrated in two such lines, and S1 protection mapping indicated faithful initiation of the transcript. In some cells from both lines, the chromosome segments containing amplified mouse rDNA showed multiple silver-staining regions (i.e., active nucleolus organizers). Although the transferred mouse rDNA was able to use the rDNA transcriptional machinery of the Chinese hamster, the level of transcription was much lower than expected from the rDNA copy number, and a large fraction of each amplified region showed no silver staining. Since the absence of silver staining is generally correlated with the absence of transcription, many copies of the amplified mouse rDNA may have been in a chromatin conformation in which they could not be transcribed. This was not associated with the extensive methylation seen in other amplified, inactive rDNA sequences.

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