bluuebunny/crossref_metadata_2025_split huggingface dataset:
Cell cycle‐related variations in UV damage and repair capacity in chinese hamster (CHO‐K1) cells
Authors: Collins A. R. S. , Downes C. S. , Johnson R. T. 
Published: February 2005

AbstractUV damage to CHO cell DNA, measured by formation of thymine‐containing dimers, increases from mitosis to early S phase. Computer simulation of UV absorption by the DNA of an idealized CHO cell at different stages in the cell cycle resembles the cycle dependence of UV damage.Incision at UV damage sites, measured by the accumulation of breaks in preexisting DNA during 30 minutes' post‐irradiation incubation with the DNA synthesis inhibitors 1‐β‐D arabinofuranosylcytosine and hydroxyurea, increases from mitosis to interphase. Analysis of the dose dependence of DNA break accumulation indicates that both the affinity of the endonuclease for dimer sites and the maximum enzyme activity at saturating levels of dimers are significantly lower in mitosis than in interphase.The killing of CHO cells by UV is enhanced if repair is temporarily inhibited by ara C. The DNA gyrase inhibitor novobiocin prevents UV‐induced incision.
Differential expression of lectin receptors during hemopoietic differntiation: Enrichment for granulocyte‐macrophage progenitor cells
Authors: Nicola Nicos A. , Burgess Antony W. , Staber Fritz G. , Johnson Gregory R. , Metcalf Donald , Battye Francis L. 
Published: February 2005

AbstractMolecular changes occur at the surface of hemopoietic cells during differentiation from progenitor cells to mature granulocytes and macrophages. The differential expression of surface carbohydrate residues has been probed using lectins and the results used to purify normal mouse granulocyte‐macrophage progenitor cells. Ten different lectins were screened for selective interaction with mouse hemopoietic colony‐forming cells (CFCs), using agglutination or a quantitative analysis of the number of fluoresceinated lectin molecules bound per cell using a fluorescence activated cell sorter (FACS). Pokeweed mitogen (PWM), Helix pomatia agglutinin (HPA), soybean agglutinin (SBA), and peanut agglutinin (PNA) preferentially bound to CFCs so that it was possible to enrich 4 to 10‐fold for these progenitor cells by sorting for the highly fluorescent cells. Further analysis of the low and high angle light scattering characteristics of the CFCs indicated that these cells were polydisperse, but could be enriched ten‐fold by selecting for cells with high intensity low angle (90°) scatter and low intensity high angle (90°) scatter. PWM gave the best enrichment (10 to 15‐fold) for adult bone marrow CFCs, for CFCs from fetal sources (fetal liver, fetal blood), and for CFCs from the spleens of mice injected previously with outer membrane lipoprotein from E. coli. Three parameter sorting for CFC using the FACS (low angle scatter, high angle scatter, and PWM‐fluorescence) resulted in large enrichment factors (16 to 50‐fold) for CFCs from all the above sources. Over 7% of the cells sorted from bone marrow, 10% of the cells sorted from post‐lipoprotein spleen, and 28% of the cells sorted from fetal peripheral blood were hemopoietic CFCs. Ninety percent of the cells in these fractions had the morphology of blast cells or myelocytes. Thus, it was possible to identify the morphological characteristics of the hemopoietic progenitor cells. Screening of other developmental systems using quantitation of fluorescence with lectins should prove of general value for the purification of selected differentiation states.
The apparent discrepancy of ouabain inhibition of cation transport and of lymphocyte proliferation is explained by time‐dependency of ouabain binding
Authors: Segel George B. , Lichtman Marshall A. 
Published: February 2005

AbstractMitogenesis of human blood lymphocytes in culture is inhibited by concentrations of ouabain that are approximately one order of magnitude lower than those that block Na and K transport. For example, the 50% inhibition (ID50) of Na‐K transport, 280 nM, is seven‐fold greater than the ID50 for RNA synthesis, DNA synthesis, or blastogenesis, ˜40 nM. Yet, inhibition of transport and consequent reduction in cell K is considered responsible for the effects of ouabain on mitogenesis. Since synthetic processes are assessed at least 24 hours after lymphocyte stimulation, this discrepancy could be explained by either 1) a progressive increase in K leak, or 2) a progressive inhibition of Na‐K transport by ouabain during 24 hours of PHA treatment. We found that the lymphocyte membrane leak rate of K increased immediately after PHA treatment but did not increase further from 4 to 24 hours. In contrast, the ouabain sensitivity of 42K uptake was markedly increased with time: ID50 for 42K uptake of 35 nM at 24 hours as compared to 280 nM at 30 minutes. Measurement of ouabain binding revealed a seven‐fold increase in the lymphocyte‐associated ouabain after 24 hours compared to binding at 1 hour. These data indicate that the dose response of ouabain inhibition of active K transport and lymphocyte proliferation are closely correlated if one considers the slow membrane binding of ouabain at low concentrations.
Murine sarcoma growth factors affect the growth and morphology of cultured mouse epithelial cells
Authors: Keski‐Oja Jorma , De Larco Joseph E. , Rapp Ulf R. , Todaro George J. 
Published: February 2005

AbstractA mouse embryo epithelial cell line, MMC‐E, was used to study the effects of purified murine sarcoma growth factors (SGFs) on the growth of epithelial cells. Murine SGF was a partially purified preparation from the serum‐free culture media of mouse fibroblasts transformed by Moloney murine sarcoma virus. SGFs stimulated DNA‐synthesis in resting cells and induced them to grow to higher densities than control cells. With continued exposure to SGFs, MMC‐E cells lost their postconfluency inhibition of division and formed small expanding foci. When the SGFs were removed and the cells were subcultured, they regained their normal phenotype, showing that the effects of SGFs are reversible on these epithelial cells. SGFs could also stimulate the MMC‐E epithelial cells to grow in soft agar, like the syngeneic fibroblasts (MMC‐F) from the same mouse embryo, but slower than the control fibroblastic clone. Microgram quantitites of SGFs were needed to stimulate soft ager growth of MMC‐E cells. The results indicate that SGF can bring about a phenotypic change in the growth pattern of epithelial cells as well as fibroblastic cells.
The effects of 5‐bromodeoxyuridine on the growth and morphology of transformed rat liver cells
Authors: Avdalovic Nebojsa , Weibel Josef , Diamond Leila 
Published: February 2005

AbstractThe effects of bromodeoxyuridine (BrdUrd) on the growth, morphology, and tumorigenicity of the spontaneously transformed rat liver cell line R72/3 were studied. These cells grow either in suspension or in a monolayer and are tumorigenic. In monolayer cultures, cells treated with low concentrations (2.5 μg/ml) of BrdUrd were larger, more spread out, and more firmly attached to the substratum than were untreated controls. Treated cells failed to grow in suspension or on confluent monolayers of 3T3 cells and did not form colonies in soft agar. Scanning electron microscopy revealed extensive flattening of treated cells and a dramatic reduction in the number of microvilli on the cell surface. Transmission electron microscopy showed an increase in polyribosomes and rough endoplasmic reticulum, as well as an enlargement of endoplasmic reticulum cisternae and a complete absence of the bundles of intermediate size filaments that were conspicuous in untreated cells. The persistence of these changes required the continuous presence of BrdUrd in the medium. The effects of BrdUrd were readily reversed by withdrawal of BrdUrd and were not expressed in the presence of excess thymidine.
Lack of correlation between effects of tumor promoter TPA on plasminogen activator production, phosphatidyl choline synthesis, and hexose transport in mammalian cell culture systems
Authors: Plagemann Peter G. W. , Estensen Richard D. 
Published: February 2005

AbstractWe have investigated the effects of the tumor promoter 12‐0‐tetradecanoyl‐phorbol‐13‐acetate (TPA) on plasminogen activator production, hexose transport and metabolism, and the incorporation of choline into the acid soluble pool and into phosphatidylcholine in suspension cultures of mouse L, mouse P388 leukemia, human HeLa, and Chinese hamster ovary cells, and in monolayer cultures of baby hamster kidney (BHK), mouse 3T3, mouse 3T6, and mouse P388D1 macrophage‐like cells. BHK, 3T3, P388D1, and P388 cells produced plasminogen activator constitutively, but no significant production was observed in the other cell lines. Plasminogen activator production was induced or stimulated by TPA only in P388 cells (10‐ to 20‐fold by 100 ng TPA/ml). On the other hand, phosphatidylcholine synthesis was stimulated by TPA only in HeLa cells, and hexose transport, as measured with 3‐0‐methyl‐D‐glucose, only in 3T3 and P388D1 cells, as well as in human lymphocytes. The stimulation of hexose transport occurred more rapidly than the induction of plasminogen activator production and seemed to be part of the mitogenic response of cells to TPA treatment. A stimulation of deoxyglucose uptake was similarly limited to 3T3 and P388D1 cells. A significant decarboxylation of carbon 1 of deoxyglucose occurred in P388 and P388D1 cells, but not in Novikoff cells, and any decarboxylation that occurred was not stimulated by TPA. The results indicate that the various investigated responses of cells to TPA are unrelated and occur independent of each other. The time courses of the biochemical responses also differ significantly.
Detection of lymphoid leukemia colony‐forming cells in abelson virus infected mice: Differences in inbred strains
Authors: Earl Christopher D. , Scher Charles D. 
Published: February 2005

AbstractBALB/c or DBA/2 mice were infected with Abelson murine leukemia virus (A‐MuLV), pseudotype Molony murine leukemia virus (M‐MuLV). Infection of these mice with 104 focus‐forming units of A‐MuLV (M‐MuLV) induced overt leukemia, detectable grossly or microscopically in 90% of the mice at 20–38 days. However, these methods did not detect leukemia at 17 days or before. Bone marrow cells from A‐MuLV‐infected leukemic or preleukemic mice were placed in tissue culture in a soft agarose gel. Cells from leukemic or preleukemic BALB/c mice grew to form colonies of 103 cells or more, composed of lymphoblasts, whereas marrow cells from normal uninfected mice did not. Cells from these colonies grew to form ascitic tumors after intraperitoneal inoculation into pristane‐primed BALB/c recipient. Colony‐forming leukemia cells could be detected in the marrow of A‐MuLV‐infected mice as early as 8 days after virus incoluation. The number of colony‐forming leukemia cells increased as a function of time after virus inoculation.Colony‐forming leukemia cells require other cells in order to replicate in tissue culture. Normal bone marrow cells, untreated or after treatment with mitomycin‐C, provide this “helper” function. Only in the presence of untreated or mitomycin‐C treated helper cells was the number of colonies approximately proportional to the number of leukemia cells plated.Marrow cells from leukemic BALB/c mice form more colonies than those from leukemic DBA/2 mice. The number of colonies formed per 103 microscopically identifiable leukemia cells plated was determined to be 2–3 for leukemic BALB/c mice and 0.3 for DBA/2 mice. Cocultivation of leukemic DBA/2 marrow cells with mitomycin‐C treated normal BALB/c cells did not increase the number of colonies formed by the DBA/2 leukemic cells. Thus, the decreased ability of DBA/2 leukemia cells to form colonies appears to be a property of the leukemia cell population.
Augmentation of erythroid burst formation by the addition of thymocytes and other myelo‐lymphoid cells
Authors: Kanamaru Akihisa , Durban Elisa , Gallagher Michael T. , Miller Sandra C. , Trentin John J. 
Published: February 2005

AbstractBone marrow from barrier‐sustained specific pathogen‐free (SPF) CBA and C57BL/6 mice gave relatively low numbers of BFU‐E colonies in methylcellulose culture, as compared to conventional mice. Addition of thymocytes to the marrow cultures increased the yield of BFU‐E colonies more than fourfold in SPF mice but only 1.5‐fold in conventional mice. Colony size was also increased.Increased yield of BFU‐E colonies was also obtained by co‐culture of bone marrow with lymph node cells or with bone marrow or spleen cells from 900R whole‐body‐irradiated mice. The effect appeared to be cellular rather than humoral. It was not reproduced by conditioned medium from thymus or pokeweed mitogen stimulated spleen cells. The helper effect of thymus cells was eliminated or reduced by freezing and thawing, or by 48 hours of incubation after irradiation. Treatment of bone marrow cells in vitro with anti‐theta serum and complement did not decrease the number of BFU‐E colonies. The putative helper cells appear not to be T cells, were non‐adherent to the plastic culture dish, and were cortisone resistant and radioresistant. The low BFU‐E colony yield from SPF mouse marrow is presumed to be largely the result of deficiency of these non‐T helper cells in SPF bone marrow, rather than of BFU‐E progenitor cells.
Insertion of muntjac gene segment into hamster cells by cell fusion
Authors: Tsukamoto Kyozo , Klein Richard , Hatanaka Masakazu 
Published: February 2005

AbstractIndian muntjac diploid cells that have only three pairs of easily discernible large chromosomes were fused with hamster cells deficient in hypoxanthine guanine phosphoribosyltransferase (HGPRT) using polyethylene glycol. Cells that survived in hypoxanthine‐aminopterine‐thymidine (HAT)‐oubaine medium were analyzed.Hybrid cells containing both muntjac and hamster chromosomes in a given cell were not found. Instead, the cells had the same chromosomal sets as those of either parental muntjac or hamster cells.A clonal isolate that had the same chromosomal sets as those of parental hamster cells was analyzed in detail and showed the following characteristics: (1) portions of the survival curve in various concentrations of HAT medium were intermediate between those of parental cells; (2) expressions of both muntjac and hamster antigen(s) were detected by immunofluorescence staining; (3) the mobility of the enzyme HGPRT in gel electrophoresis differed from that of parental hamster or muntjac cells. These results indicate that the clonal isolate (AD202h) is a somatic cell hybrid of hamster and muntjac that contains chromosomal sets of hamster with an inserted segment of the muntjac genome, including HGPRT.The formation of such an unusal hybrid and a possible explanation of transfer of some gene segments in the hybrid cell in this system are discussed.
Expression of SV40 tumor antigen in SV40 transformed teratocarcinoma‐derived cell lines
Authors: Axelrod Helena R. , Levine Arnold J. 
Published: February 2005

AbstractThe relative importance of viral tumor antigen expression and the cellular background in the maintenance of a transformation phenotype was examined in five SV40‐transformed teratocarcinoma‐derived cell lines. These cell lines show qualitative differences in growth characteristics associated with transformation, and vary in their state of differentiation. Viral T antigen expression was evaluated by two criteria: 1) the amount of immunoprecipitated antigen in growing cells, and 2) the amount and rate of antigen synthesis in density‐inhibited cells. There was no direct correlation found between retention, or rate of synthesis, of the viral T antigen and the degree of transformation. These findings imply that the cellular environment has a more important influence on the growth properties of a stably transformed cell than the quantitative levels of viral T antigen expression.
Selective high metabolic lability of uridine triphosphate in response to glucosamine feeding of untransformed and polyoma virus‐transformed hamster fibroblasts
Authors: Rapaport Eliezer , Christopher C. William , Ullrey Donna , Kalckar Herman M. 
Published: February 2005

AbstractDerepression of hexose transport in a line of Syrian hamster fibroblasts (Nil) and polyoma‐transformed (PyNil) hamster fibroblasts is obtained when cells are either starved for glucose or fed with fructose as the only hexose source. D‐glucosamine feeding of these cells does not alter the repressed state with regard to hexose transport. High, derepressed rates of galactose transport were changed to low, repressed rates, within 18 hours of refeeding glucose‐starved cells with D‐glucosamine as the only hexose source. Nil and PyNil cells, when cultured in the presence of D‐glucosamine, undergo rapid reductions in total cellular uridine 5′‐triphosphate (UTP) pool sizes. By contrast, the total cellular pools of adenosine 5′‐triphosphate, guanosine 5′‐triphosphate, and cytosine 5′‐triphosphate (ATP, GTP, and CTP) were only moderately affected by the treatment of the cells with glucosamine. The metabolic drain of the UTP pools in PyNil cells was much more pronounced than in the untransformed cells. The larger and more rapid metabolic lability of UTP pools in the transformed cells may be the primary reason for the selective toxicity of glucosamine on tumor cells. A comparison of the effects of glucosamine on hexose‐starved Nil and PyNil cells demonstrated that only the untransformed cells were able to utilize glucosamine to increase the hexose starvation‐depleted pools of all nucleoside triphosphates. Accumulation of UDP‐glucosamine and UDP‐N‐acetylglucosamine followed the reduction in the UTP pools. Inhibition of protein synthesis by cycloheximide during glucosamine feeding led to higher levels of UDP‐glucosamine and UDP‐N‐acetylglucosamine accumulation. It is suggested that the drain of UTP pools during glucosamine treatment proceeds through the formation of the UDP‐aminosugars which turn over due to the action of intracellular UDP‐aminosugar pyrophosphatase activities.
Cation transport in different volume populations of genetically low K+ lamb red cells
Authors: Lauf P. K. , Valet G. 
Published: February 2005

AbstractDuring the first three months after birth lambs produce sequentially three erthryocyte populations of different mean volume as demonstrated by electric sizing methods (Valet, Franz, and Lauf, J. Cell. Physiol. 94 (1978) 215). We separated by centrifugal elutriation the small volume population (type II) red cells of a genotypically low K+ (LK) lamb from the population containing the larger volume type I and III cells, an admixture of fetal (I) and adult (III) erythrocytes. The cells were separated at various time intervals after birth and analyzed with respect to their volumes, cation contents, and cation flux properties by means of 86Rb uptake. The effect of anti‐L on K+ pump and leak fluxes was ascertained in unseparated and separated red cells. It was found that the small red cells of population II, transiently present for several weeks, were fully developed LK cells with K+ pumps responding characteristically to the stimulatory action of anti‐L. In constrast, the larger cells of population I and III were of high K+ (HK) nature at early time points, the K+ pump activities approximately ten times higher than adult LK cells. These cells constitute an admixture of type I fetal HK cells, and type III reticulocytes which are precursors for the final type III adult LK cells, since anti‐L had a small stimulatory effect. At later times, however, only adult type III LK cells predominated. The data directly support our earlier finding that the HK‐LK transition in genotypically LK lambs is primarily governed by cellular replacement.
Lymphocyte capping induced by polycationized ferritin
Authors: Butman Bryan T. , Bourguignon Gerard J. , Bourguignon Lilly Y. W. 
Published: February 2005

AbstractIn order to better understand the mechanism of lymphocyte surface receptor redistribution induced by externally added ligands, polycationized ferritin (PCF), a nonconventional ligand, was tested using both fluorescence and electron microscopy for its ability to cause patching and capping of anionic molecules on the surface of both transformed and normal mouse lymphocytes. Binding of PCF at 0°C for 1 hour induces the appearance of patches; subsequent incubation at 37° for 30–60 minutes causes the formation of a cap structure with the lymphoid cells tested (T‐lymphoma cells and splenic lymphocytes). Using various experimental treatments (e.g., sodium azide, cytochalasin B and D, colchicine, prefixation, and cold temperatures), PCF‐induced capping has been found to be temperature sensitive, and to require metabolic energy and an intact cytoskeletal system. In addition, using double immunofluorescence techniques which involve rhodamine‐labeled PCF and fluorescein‐conjugated heavy meromyosin, it has been observed that the formation of the PCF‐induced cap coincides with an accumulation of intracellular actin directly beneath the cap structure. Furthermore, agents such as dibutyryl cyclic AMP and theophylline, which cause an increase in intracellular cyclic AMP, have been shown to stimulate PCF‐associated capping. This study suggests that increasing levels of intracellular cyclic AMP may activate, directly or indirectly, membrane‐associated contractile elements required for the aggregation of membrane proteins into patches and caps.
Cell density and amino acid transport in 3T3, SV3T3, and SV3T3 revertant cells
Authors: Borghetti Angelo F. , Piedimonte Giuseppe , Tramacere Mariarosaria , Severini Alberto , Ghiringhelli Paolo , Guidotti Guido G. 
Published: February 2005

AbstractThe transport of selected neutral and cationic amino acids has been studied in Balb/c 3T3, SV3T3, and SV3T3 revertant cell lines. After properly timed preincubations to control the size of internal amino acid pools, the activity of systems A, ASC, L, and Ly+ has been discriminated by measurements of amino acid uptake (initial entry rate) in the presence and absence of sodium and of transportspecific model substrates. L‐Proline, 2‐aminoisobutyric acid, and glycine were primarily taken up by system A; L‐alanine and L‐serine by system ASC; L‐phenylalanine by system L; and L‐lysine by system Ly+ in SV3T3 cells. L‐Proline and L‐serine were also preferential substrates of systems A and ASC, respectively, in 3T3 and SV3T3 revertant cells. Transport activity of the Na+‐dependent systems A and ASC decreased markedly with the increase of cell density, whereas the activity of the Na+‐independent systems L and Ly+remained substantially unchanged. The density‐dependent change in activity of system A occurred through a mechanism affecting transport maximum (Vmax) rather than substrate concentration for half‐maximal velocity (Km). Transport activity of systems A and ASC was severalfold higher in transformed SV3T3 cells than in 3T3 parental cells at all the culture densities that could be compared. In SV3T3 revertant cells, transport activity by these systems remained substantially similar to that observed in transformed SV3T3 cells. The results presented here add cell density as a regulatory factor of the activity of systems A and ASC, and show that this control mechanism of amino acid transport is maintained in SV40 virus‐transformed 3T3 cells that have lost density‐dependent inhibition of growth, as well as in SV3T3 revertant cells that have resumed it.