bluuebunny/crossref_metadata_2025_split huggingface dataset:
Cyclic AMP does not modulate hexose uptake of serum‐deprived BHK‐21 fibroblasts
Authors: Lavis Victor R. , Davenport Roxann , Pontier Paul , Thompson W. Joseph , Strada Samuel J. 
Published: February 2005

AbstractWe have studied the uptakes of the glucose analogs, 2‐deoxyglucose (2DG), and 3‐O‐methylglucose (3OMG) in serum‐deprived BHK‐21 fibroblasts. Incubation for 4 hours with 0.25 mM 1‐methyl‐3‐isobutylxanthine (MIX) increased cellular cyclic AMP 3 to 15 fold, without affecting the initial rates of uptake of these sugars. Incubation with 100 nM insulin, doubled hexose uptake without affecting cyclic AMP. Insulin did not modify the cyclic AMP response to MIX; nor did MIX alter the hexose uptake response to insulin. There was no effect of 0.1 mM L‐isoproterenol (ISO) or 0.1 mM prostaglandin E1 (PGE1) on cyclic AMP. PGE1 slightly stimulated uptake of 2DG but not 3OMG; ISO did not affect hexose uptake. We conclude that cyclic AMP does not directly regulate hexose uptake in these cells.
Reversible inhibition by human serum lipoproteins of cell proliferation
Authors: Ito Fumiaki , Takii Yuko , Suzuki Jiro , Masamune Yukito 
Published: February 2005

AbstractNormal human serum or plasma was studied for the presence of inhibitors of cell proliferation by assaying inhibition of incorporation of labeled thymidine into acid‐insoluble fraction using human FL cells. Lipoprotein fraction obtained by gel filtration through Sepharose 4B and by KBr density gradient centrifugation was found to play a major part of the inhibitory activity of the serum. It was also shown that the inhibitory activity resides in low‐density lipoprotein (LDL). The addition of the lipoprotein fraction to growing FL cells caused an early decrease in the transport of uridine and thymidine across the membrane. This change in the permeability of membrane was followed by the preferential inhibition of DNA synthesis and a reduction in the percentage of mitotic cells in the cell population. The inhibition of the growth was reversible and was observed in various types of cells irrespective of species.
Species specific differences in the toxicity of mithramycin, chromomycin A3, and olivomycin towards cultured mammalian cells
Authors: Gupta Radhey S. 
Published: February 2005

AbstractThree structurally related anticancer drugs, mithramycin, chromomycin A3, and olivomycin, showed large unexpected differences (up to more than 1000 fold) in their toxicity towards cultured cells from various species (human, Chinese hamster, Syrian hamster, and mouse). Among the cell types examined, human cells (both a diploid fibroblast cell strain and HeLa cells) were maximally sensitive to all these drugs, followed by the Syrian hamster kidney cells (BHK 21). The mouse (LMTK− cells) and Chinese hamster (CHO) cells, which were more resistant, showed interesting differences in their sensitivity towards these drugs. For example, whereas the mouse cells were more resistant to mithramycin than CHO cells, the sensitivity pattern was reversed for both chromomycin A3 and olivomycin. In cell extracts derived from human, mouse, and Chinese hamster cells RNA synthesis, which is the cellular target of these drugs, showed identical sensitivity to both mithramycin and chromomycin A3, indicating that the species specific differences in the toxicity to these drugs are at the level of cellular entry of these compounds. Based on the structures of these glycosidic antibiotics and their patterns of toxicity, it is suggested that the intracellular transport of these drugs involves specific interactions between the sugar residues on these compounds and some type of cell surface receptor(s), which differ among different cell types. Some implications of these results for toxicity studies are discussed.
The amount of a specific cellular protein (p53) is a correlate of differentiation in embryonal carcinoma cells
Authors: Chandrasekaran Krish , Mora Peter T. , Nagarajan Lalitha , Anderson Wayne B. 
Published: February 2005

AbstractA specific cellular protein of molecular weight of 53–55,000 (p53) has been shown to be induced in all SV40 transformed cells. A similar protein has also been shown to be present in embryonal carcinoma cells and in midgestation murine embryo primary cells, which are not infected by SV40. In embryo cell primaries the amount of the protein was shown to decrease with the increase in the stage of embryo development. As differentiation or decrease in cell growth rate can account for this, and since the growth rate of embryo primary cells cannot be measured, we chose to investigate various embryonal carcinoma cells. We report that the p53 is present in a pluripotent embryonal carcinoma cell OTT6050, and in its differentiated parietal endoderm derivative, PYS‐2 cells. The amount of p53 is higher in the undifferentiated EC stem cells than in the differentiated PYS‐2 (parietal endoderm) cells. The amount of the protein decreases in F9 embryonal carcinoma cells induced to differentiate to a parietal endoderm cell type by treatment with retinoic acid, as it does following spontaneous differentiation of OTT6050 EC cells. To determine if a change in growth rate, rather than differentiation, might acount for the diminished levels of this protein, the amount ofp53 was measured in growing and in growth arrested cell populations. When the growth rate of F9 cells was reduced by treatment with 8‐bromocyclic AMP there was no change in the amount of p53. The half life of the p53 was compared in the undifferentiated and the differentiated cell types to determine if a change in stability might account, in part, for the altered levels of this protein. The p53 is found to be most stable in the SV40 transformed established clonal cells. It is less stable in the fibroblast clonal cells which were not transformed by SV40. The results of these experiments indicate that a decrease in the amount of p53 primarily correlates with differentiation in the embryonal carcinoma cell lines studied and not with cell growth rate. Furthermore, the decrease appears to be related (in part) to the decreased stability of the p53.
Self‐renewal and commitment to differentiation of human leukemic promyelocytic cells (HL‐60)
Authors: Fibach Eitan , Peled Tony , Rachmilewitz Eliezer A. 
Published: February 2005

AbstractMore than 80% of cells from a human promyelocytic leukemic cell line (HL‐60) possess the capacity for self‐renewal as evidenced by their ability to form large primary colonies in semisolid medium and the presence within these colonies of cells capable of subsequent colony formation. Colony development is independent of the normal regulator‐the myeloid colony stimulating factor. The observed autostimulation suggests the production of specific growth promoters by the cells. Differentiation either to mature granulocytes or macrophages, induced by various agents, was associated with reduced cloning potential. Nevertheless, colonies containing differentiated cells could be developed either by cloning cells in the presence of suboptimal concentrations of inducer or by adding inducers over colonies developed in its absence. Upon differentiation, there was a morphological change from compact to diffused colony morphology due to cell mobility in the semisolid medium. Even at suboptimal concentrations of inducer more than 95% of the colonies became diffused, indicating clonaI homogeneity of the population with respect to differentiation capacity. The loss of self‐renewal was found to be one of the early properties which changed following the initiation of differentiation. The loss preceded not only the overt expression of maturation‐specific functions but also cellular commitment to terminal differentiation; shorter contact with the inducer was required to cause loss of self‐renewal than to induce an irreversible transition to differentiation. This resulted in cells that lost their self‐renewal potential without being able to complete their program of differentiation.
Effect of exogenous gangliosides on human neural cell division
Authors: Icard‐Liepkalns Christine , Liepkalns Vis A. , Yates Allan J. , Rodriguez Zoe R. , Stephens Ralph E. 
Published: February 2005

AbstractHuman neural cells in exponential growth phase were transferred to a serum‐free medium and maintained for 72 hr without any detectable loss in viability. The two normal fetal cell lines (CHI and CHII) showed a serum‐dependent cell proliferation, but the glioblastoma multiforme cells (12–18) were able to continue proliferating in this totally synthetic medium. The incorporation of [3H] thymidine into the acid‐precipitable fraction of both normal and neoplastic human neural cells was assayed in the presence and the absence of exogenous gangliosides by a convenient new method. In serum‐free medium, gangliosides (50 μM) inhibited the thymidine incorporation into the normal fetal cells within 24 hr and, in serum containing medium, reduced their proliferation within 48 hr. No such effects were detectable in the glioma cells. The inhibition of thymidine incorporation in the normal cells was reversible upon removal of the gangliosides. These results indicate a role of gangliosides in the postmitotic phase of normal human neural cells resulting in the regulation of cell proliferation.
Control of cytolysis of BALB/c‐3T3 cells by platelet‐derived growth factor: A model system for analyzing cell death
Authors: Scher Charles D. , Young Shelley A. , Locatell Kathryn L. 
Published: February 2005

AbstractIn culture medium supplemented with 10% clotted blood serum, the saturation density of BALB/c‐3T3 cells is determined jointly by cell replication and cell loss. By prelabelling cellular DNA with 3H‐thymidine and also by time lapse photography, we studied cell loss independently of replication. Cell loss was accelerated when BALB/c‐3T3 cells were transferred from serum‐supplemented medium, which contains the platelet derived growth factor (PDGF), to medium supplemented with platelet‐poor plasma which lacks it. Loss occurred via the disintegration of cell attached to the surface of the tissue culture dish. Cytolysis of individual cells occurred rapidly; less than 15 minutes transpired between the first indication of a perturbance (by phase contrast microscopy) and fragmentation of the cell cytoplasm. Kinetic analysis was consistent with random cell death rather than a fixed lifetime.The percentage of cells undergoing cytolysis was governed by the cell density; at high densities, such as are present in confluent cultures, a higher percentage of cell loss was noted than at low density. Cell death was antagonized by partially purified or electrophoretically homogenous preparations of‐PDGF. Pure PDGF stimulated cell survivial at ng/ml in a concentration dependent fashion. The process of cell replication was not necessary for survival because PDGF prevented cytolysis in the presence of methotrexate, an inhibitor of DNA synthesis. A brief (4 hour) treatment with PDGF prevented cell death; such PDGF treated cells displayed increased survival after being taken up with trypsin and planted onto a fresh surface in plasma supplemented medium. Pituitary fibroblast growth factor, a functional analogue of PDGF for induc of DNA synthesis in BALB/c‐3T3 cells, also functioned as an anticytolytic agent. By contrast, epidermal growth factor and insulin did not. Cytolysis of SV40‐transformed cells occurred at a constitutively low rate and was insensitive to PDGF.
The characteristics of an anchorage‐independent clonal agar assay for primary explanted bovine granulosa cells
Authors: Bertoncello I. , Bradley T. R. , Chamley W. A. , Hodgson G. S. 
Published: February 2005

AbstractNormal, primary explanted, bovine granulosa cells grow reproducibly in agar culture as anchorage‐independent clones. Epidermal growth factor (EGF) and rat erythrocytes are effective stimulators of colony formation, and when both are added to the culture medium at optimal concentrations, there is an enhancement of colony numbers and colony size, indicative of an independent, and operationally additive, mode of action for the two factors. The ability of cells propagated from agar clones to secrete progesterone, and to augment progesterone secretion 4‐fold in the presence of 1 mM dbcAMP is proof that colonies originate from and are composed of functional granulosa cells.Maximal colony numbers are present at day 10 of incubation, and colony forming cells undergo self‐renewal as assessed by the ability of cells from primary colonies to redone in agar. Absolute cloning efficiency, however, is dependent on a number of factors. Inherent variability exists in cloning efficiency of granulosa cells from individual follicles. Quantitative and qualitative clonal growth was improved at an osmolality of less than 300 mOsm when compared with higher osmolalities. Cl‐1 medium and the alpha modification of Eagle's medium were equally effective in supporting agar clonogenic growth, whereas both Ham's F12 and NCTC 135 media exhibited poor clonogenic growth supporting properties. The substitution of agarose for agar did not affect colony numbers but colonies grown in the presence of agarose tended to be smaller and more uniform in size.
Human mutant cell lines with altered RNA polymerase II
Authors: Shander Monica T. M. , Croce Carlo , Weinmann Roberto 
Published: February 2005

AbstractA human fibrosarcoma cell line, HT‐1080‐6TG‐9AM, resistant to α‐amanitin at concentrations up to 10 μg/ml, was isolated after ethylmethanesulfonate mutagenesis and stepwise selection. The mutation is stable and dominant. RNA polymerase II purified from the mutant cells showed an altered affinity for labeled α‐amanitin and the sensitivity of the enzyme to the fungal toxin was decreased 50‐to 100‐fold. This functional test demonstrated that the biochemical basis for the resistance of the cells to α‐amanitin is due to an alteration of RNA polymerase II.
Rapid induction of foci escaping density‐dependent inhibition in baby mouse skin cultures
Authors: Cooper Peter D. , Marshall Susan A. , Masinello Gillian R. 
Published: February 2005

AbstractMesenchymal cells from primary BMS (baby mouse skin) cultures formed secondary monolayers subject to density–dependent inhibition. The monolayers remained quiescent but in good condition for 6–8 weeks if given weekly medium changes. Exposure of the primary cultures to fluorescent light and/or oxygen produced “altered” cells that gave rise in the secondary cultures to foci of up to 10 4 cells after 15 days. These foci overgrew the background BMS cells. The rate of growth, morphology, and arrangement of the altered cells varied greatly between foci but much less within a focus, which usually showed one or more characters of neoplastic cells. The initiation of foci was apparently not transmissible by an infectious agent.
Properties of cell lines derived from altered‐cell foci in baby mouse skin cultures
Authors: Cooper Peter D. , Marshall Susan A. , Masinello Gillian R. 
Published: February 2005

AbstractLong‐term cell lines were readily developed from a proportion of either baby mouse skin (BMS) cultures passing through colchicine‐induced crisis or altered‐cell foci selected from BMS cultures exposed to light and/or oxygen followed by colchicine. The developing cell lines behaved as though they passed through a continuing, profound genetic reshuffling process, which was usually lethal but which in some cases eventually yielded a gene set that favored long‐term survival. Some cell lines have passed 120 cell doublings, and none has shown a second crisis or signs of senescence. As soon after isolation as measurement was possible (19–50 days) the cell lines were predominantly or entirely tetraploid or subtetraploid. Although BMS cells and all of the cell lines were density inhibited, the BMS, C14, C21 and C23 cells overgrew (formed colonies on) monolayers of the same cells in most combinations. The cell lines retained a variety of neoplastic morphological characters, although their morphology was more normal than in the original focus. No cell line, however, showed anchorage‐independent growth or formed tumors in syngeneic hosts. The cell lines may all, therefore, be regarded as preneoplastic.
Growth and death of hela cells in the presence of caffeine
Authors: Beetham Karen L. , Tolmach L. J. 
Published: February 2005

AbstractProliferation and death were measured in synchronously growing cultures of HeLa S3 cells during treatment with up to 30 mM caffeine. Changes in the number of colony‐forming cells were determined by single‐cell plating, while changes in the total number of cells were measured both by electronic counting and by monitoring cell division and physiological death cinemicrographically. At concentrations between 2 and 5 mM, cell killing occurs over several days during which the cells traverse the generation cycle once or a few times before losing colony‐forming ability, with consequent proliferation of non‐colony‐forming cells. This indicates that lethal damage is accumulated with time. Death occurs more rapidly at higher concentrations, without proliferation, the kinetics of inactivation being strongly dependent on the phase of the cycle (cell age) at which treatment is initiated. G1 cells are killed more slowly in 10 mM caffeine than are S cells, but G1 cells respond rapidly to 20 mM caffeine, suggesting the inception of an additional mode of killing. The incidence of sister‐cell fusion increases with increasing caffeine concentration above 1 mM. On addition of 10 mM caffeine to a culture prepared from collected mitotic cells, the cells undergo a transient rounding and then respread after several hours; with 20 mM, they never respread. The generation cycle is prolonged in a concentration‐dependent fashion, as is the duration of G1; the generation time is doubled in 5–6 mM caffeine. G2 and M are also prolonged at concentrations above 3 mM, but S is not prolonged even by 10 mM caffeine.
The effects of temperature and ouabain on steady‐state Na and K exchanges in human lymphocytes
Authors: Negendank William , Shaller Calvin 
Published: February 2005

AbstractThe temperature‐dependence of steady‐state exchanges of K and Na were determined under conditions in which cell viability, ATP, water, Ca, and Mg were not confounding variables. Steady‐state ion contents are near‐normal between 37° and 10° C, Below 10° C K is replaced by Na in a mole‐for‐mole fashion with significant net K retention and Na exclusion occurring even below 3°C. The rates of steady‐state Kand Na exchanges have markedly different temperature‐dependences; between 37° and 10° C, for example, that of K decreases markedly while that of Na remains near‐normal, and there is no consistent correlation between the steady‐state exchanges and the ionic contents. Ouabain increases steady‐state Na flux at 37° C and induces a more marked temperature‐dependence over the entire temperature range. This effect is not due simply to inhibition of some processes and unmasking others; it mirrors a pronounced effect of ouabain on the intrinsic properties of Na self‐exchange. These results are compatible with a model based on two simple concepts: (1) partial ionic exclusion from cellular water that is ordered by interaction with proteins; and (2) ionic accumulation mediated by adsorption onto and desorption from fixed macromolecular anionic sites, the majority of which interact with one another in a cooperative fashion. In this view, the sharp temperature transition in the net replacement of K by Na below 10° C is due to a critical transition in the selectivity of the cooperatively interacting adsorption sites. The rates of steady‐state self‐exchanges of K and Na are determined by parameters of ion‐site interaction, and the major set of ion‐adsorbing sites that interact cooperatively have a steep thermal activation energy of ionic self‐exchange. When they are in the K‐preferring state above 10° C, exchange of K has a steep temperature‐dependence. When they are in the Na‐preferring state below 10° C, exchange of Na has a steep temperature‐dependence. When these sites are forced into a Na‐preferring state at all temperatures by treatment with ouabain, exchange of Na acquires a steep temperature‐dependence over the entire temperature range 37° to 0° C.
Cell heterogeneity during the cell cycle
Authors: Darzynkiewicz Z. , Crissman H. , Traganos F. , Steinkamp J. 
Published: February 2005

AbstractUsing flow cytometry, populations of Chinese hamster ovary cells, asynchronous and synchronized in the cycle, were measured with respect to cellular RNA‐ and protein‐content, as well as cell light scatter properties. Heterogeneities of cell populations were expressed as coefficients of variation (c.v.) in percent of the respective mean values. Populations of cells immediately after mitosis have about 15% higher c.v. than mitotic cell populations, regardless of whether RNA, proteins, or light scatter are measured. These data indicate that cytoplasmic constituents are unequally distributed into the daughter cells during cytokinesis and that unequal cytokinesis generates intercellular metabolic variability during the cycle. An additional increase in heterogeneity, although of smaller degree, occurs during G2 phase. Populations of S‐phase cells measured in the selective window equivalent to 15–60 min progression through the cycle, i.e., comparable with the mitotic and postmitotic populations, are the most uniform, having 20–30% lower c.v. than the postmitotic cells. Cell progression through S does not involve any significant increase in intercellular variability with respect to RNA or protein content. In unperturbed exponentially growing cultures a critical RNA content is required for G1 cells prior to their entrance into S. Thus, the cells equalize in G1 with respect to RNA and protein and, during the transition from the period (compartment) of equalization (G1A) to the prereplicative compartment (G1B), they exhibit minimal heterogeneity. The cell residence times in the equalization compartments are exponentially distributed, which may reflect the randomness generated by the uneven division of metabolic constituents to daughter cells during cytokinesis. The cell heterogeneities were presently estimated at two metabolic levels, transcription (RNA content) and translation (proteins). The most uniform were populations stained for RNA and the highest variability was observed after staining of proteins. This suggests that the regulatory mechanisms equalizing cells in the cell cycle may operate primarily at the level of DNA transcription.