bluuebunny/crossref_metadata_2025_split huggingface dataset:
A comparison of the responses of cultured myoblasts and chondrocytes to fibroblast and epidermal growth factors
Authors: Gospodarowicz Denis , Mescher Anthony L. 
Published: February 2005

AbstractThe effects of fibroblast and epidermal growth factors on proliferation and differentiation of cultured myoblasts and chondrocytes have been compared. FGF stimulated myoblast proliferation, as determined by monitoring levels of DNA synthesis during seven days growth in vitro and by the morphology of the cultures after myotube formation. EGF has relatively little effect on myoblast proliferation. With chondrocytes, both FGF and EGF are mitogenic and FGF's, but not EGF's effect is potentiated by dexamethasone. One implication of these results is that in the course of differentiation cell types which develop from the same embryonic origin as fibroblasts are controlled by different sets of mitogenic factors. Myoblasts become primarily dependent on mitogenic agents such as FGF while chondrocytes can respond to both FGF and EGF.
The mechanism of killing of mouse fibroblasts by the amino acid analogue 5‐fluorotryptophan
Authors: Taub Mary 
Published: February 2005

AbstractThe mechanism of killing of A9 fibroblasts by 5‐fluorotryptophan has been studied. L‐tryptophan competitively relieves the growth inhibition caused by 5FT. After incubation with 5FT, 3H‐5FT was incorporated into protein, replacing tryptophan residues. During the initial hours of incubation with 5FT, a specific inhibition was observed of the incorporation of L‐tryptophan into protein; later this inhibition was followed by a general inhibition of protein synthesis and cell division. However, nuclear division continued after cell division had ceased. While 5FT was observed to be incorporated into protein after a 1 hour period in MEM + 0.40 mM 5FT in A9, no 3H‐5FT was incorporated into protein in a mutant isolated by its resistance to killing by 5FT. These results support the hypothesis that cell death occurs due to malfunctioning proteins which contain 5FT residues.
The inhibition by 6‐diazo‐5‐oxo‐L‐norleucine of glutamine catabolism of the cultured human lymphoblast
Authors: Willis Randall C. , Edwin Seegmiller J. 
Published: February 2005

AbstractThe rapid catabolism of glutamine by the cultured human lymphoblast line WI‐L2 can be inhibited greater than 95% by incubation of cell suspensions with 6‐diazo‐5‐oxo‐L‐norleucine (DON). The inhibition persists for at least four hours after removal of DON from the cell suspension. The exposure of cells to DON inhibits over 95% of the glutaminase activity measured in lysates in the presence of either phosphate or maleate. Similarly, γ‐glutamyl transpeptidase, assayed with γ‐glutamyl‐p‐nitroanilide as substrate and glycylglycine as acceptor, is inhibited over 90%. DON‐treated and control cells accumulated radioactive material from suspensions containing [14C]‐L‐glutamine at similar initial rates; the radioactive material accumulated by the DON‐treated cells is all recoverable as glutamine while the radioactive material accumulated by untreated cells is principally recovered as glutamate.
The effect of histamine on the growth of cultured fibroblasts isolated from normal and keloid tissue
Authors: Russell James D. , Russell Shirley B. , Trupin Kathryn M. 
Published: February 2005

AbstractCultured fibroblasts derived from human keloid tissue are presented as a possible model system for studying the genetic regulation of cell growth. Histamine is shown to have a marked effect on the growth of cultured fibroblasts. A small increase in growth rate is seen during the log phase of the culture cycle and a 50% increase in cell number is observed during the plateau phase. Differences in the extent of growth stimulation are observed between strains isolated from different individuals. While most strains showed approximately 50% stimulation, a few were not stimulated and some strains gave a 100% or greater increase in cell number due to histamine. This phenotypic difference in extent of growth stimulation in response to histamine cannot be attributed to the gene or genes for keloid formation. However, elevated levels of histamine in vivo may be a contributing factor to the abnormal cell growth observed in this disorder. The extent of growth stimulation due to histamine decreases with repeated subculturing.
Effects of ph and type of sugar in the medium on tyrosinase activity in cultured melanoma cells
Authors: Saeki Hisaaki , Oikawa Atsushi 
Published: February 2005

AbstractThe tyrosinase (EC 1.14.18.1) activity of cultured mouse melanoma cells B16 in the stationary phase of growth, depends greatly on the pH of the medium and the kind of sugar present.The enzyme activity of a homogenate of cells grown at pH 7.2 in Eagles's MEM supplemented with 10% new born calf serum and containing galactose in place of glucose, was about ten times that of a homogenate of cells cultured at pH 6.3 in the same medium. The tyrosinase activity changed reversibily on changing the pH of the culture medium.When cultured at a constant pH of 7.2, cells grown with 1 mM galactose had about five times higher tyrosinase activity than cells grown with 1 mM glucose. Only a small amount of lactate accumulated in cultures with glucose and it had little effect on the enzyme activity.These two findings explain the very low tyrosinase activity of cells cultured in medium with 5 mM glucose: the low activity is due to the presence of glucose and to the low pH resulting from conversion of glucose to lactic acid.
Regulation of protein synthesis in human diploid fibroblasts: Reduced initiation efficiency in resting cultures
Authors: Meedel Thomas H. , Levine Elliot M. 
Published: February 2005

AbstractThe level of poly A+ RNA in growing cultures of human diploid fibroblasts is 1.8‐fold times greater than in resting cultures. The level of functional ribosomes in growing cultures is 2.8 times that in resting cultures. Since transit times are similar in both types of cells, it can be concluded that the rate of protein synthesis in growing cultures is 2.8 times that in resting cultures. A reduced efficiency of mRNA translation at the level of initiation in resting cultures is proposed as a probable explanation for the fact that the decrease in protein synthesis rates is greater than the decrease in mRNA levels. This hypothesis is supported by the observations that: (a) poly A+ RNA is associated with smaller polysomes in resting than in growing cells, and (b) cycloheximide treatment of resting cells results in recruitment of nonpolysomal poly A+ RNA into polysomes and a shift of polysomal poly A+ RNA into larger polysomes.
Changes in membrane dynamics associated with myogenic cell fusion
Authors: Herman B. A. , Fernandez S. M. 
Published: February 2005

AbstractChanges in membrane dynamic properties associated with membrane fusion are studied employing in vitro myoblast fusion as a model system. We utilize a microscopic fluorescence relaxation approach which makes feasible the study of local variations in membrane dynamics within surface subdomains of single intact cells. Studies of the average rotational mobility of the fluorescent probe‐1‐anilino‐naphthalene‐8‐sulfonate by this technique indicate that myoblast fusion activity is preceded by a generalized increased in membrane fluidity and that areas of cell contact between fusing cells exhibit higher fluidity and polarity, locally, than non‐fusion regions.
Density‐dependent effects of oxygen on the growth of mammalian fibroblasts in culture
Authors: Taylor William G. , Camalier Richard F. , Sanford Katherine K. 
Published: February 2005

AbstractVarious concentrations of oxygen were used to determine the optimum culture medium P for survival and proliferation of attached human and mouse fibroblasts grown from different inoculum sizes. When T−15 flasks were seeded with ⪕ 2 × 104 cells (⪕ 1.3 × 103 cells/cm2), the highest plating efficiencies and cell yields were obtained with a culture medium P of 40—60 mm Hg. At higher inoculum sizes (105 cells per T‐15) used routinely for mass cultures, no difference in cell yield or glycolytic activity was observed between cultures gassed with atmospheric, i.e., 18% O2 (growth medium P ≅ 125—135 mm Hg) and those gassed with 1% O2 (growth medium P ≅ 40—60 mm Hg). The enhanced clonal growth observed at the latter P results from an increased proliferation rate rather than more efficient attachment and survival of inoculated cells. Glucose uptake and lactic acid accumulation were increased in sparse cultures sparged with 1% O2. A slight extension of lifespan was observed in WI−38 cells serially subcultured with a gas phase of 1% O2.
The transport of L‐alanine by the hamster kidney cell line BHK21‐C13
Authors: Scott D. M. , Pateman J. A. 
Published: February 2005

AbstractThe uptake of L‐alanine into BHK21‐C13 cells in culture has been studied. This amino acid appears to be transported essentially via a relatively low affinity, high capacity, sodium ion dependent transport system. Inhibition studies using other amino acids or their analogues provided information about the specificity of this system. This alanine transport system was shown to exhibit a broad substrate specificity and appeared to be capable of transporting most naturally occurring neutral α‐amino acidsKinetic studies of the inhibition of L‐alanine uptake also indicated the presence of a second neutral amino acid transport system capable of transporting this amino acid. However, it is unlikely that this second uptake system contributes greatly to L‐alanine uptake. Inhibition of the uptake of L‐leucine indicated that this transport system has a similar specificity to the "L"‐system initially described for Ehrlich ascites carcinoma cells.
Malignant mouse melanoma cells do not form tumors when mixed with cells of a non‐malignant subclone: Relationships between plasminogen activator expression by the tumor cells and the host's immune response
Authors: Newcomb Elizabeth W. , Silverstein Samuel C. , Silagi Selma 
Published: February 2005

AbstractMouse melanoma clones B559 and B78 are highly tumorigenic when injected into C57BL/6J mice. Tumor formation by these cells is suppressed when they are mixed with nonmalignant bromodeoxyuridine‐grown clone C3471 before injection. C3471 cells suppress tumor formation only in immunocompetent hosts; mixtures of B559 and C3471 cells or C3471 cells alone form tumors in antithymocyte serum (ATS)‐treated mice. Explants of C3471 tumors grown in ATS‐treated mice form tumors in immunocompetent mice, most of which regress. Inability of C3471 or mixtures of C3471 with malignant cells to grow in normal mice, as contrasted with ability to grow in immunosuppressed mice, indicates that host response is involved. Both tumorigenic clones have high plasminogen activator activity, whereas nontumorigenic clone C3471 has none. Mixture of either tumorigenic clone with C3471 cells decreases plasminogen activator in vitro. C3471 tumor explants from ATS‐treated mice initially express plasminogen activator, but lose the capacity to express this activity upon prolonged cultivation in vitro. Explants from B559 tumors retain plasminogen activator in long term culture. Close physical contact between C3471 and B559 cells appears essential both for inhibition of plasminogen activator expression by B559 cells in vitro, and for tumor suppression in vivo. These findings suggest that production of plasminogen activators by tumor cells may play an important role in suppressing the host's immune response locally to an inoculum of syngeneic tumor cells.
2‐Amino‐isobutyric acid and 3‐0‐methyl‐D‐glucose transport in 3T3, SV40‐transformed 3T3 and revertant cell lines
Authors: Dubrow Robert , Pardee Arthur B. , Pollack Robert 
Published: February 2005

AbstractIn order to further investigate the connection between transport and growth control, 3T3 cells, SV40 transformed 3T3 cells (SV101), and three revertant cell lines derived from SV101 which have regained certain manifestations of growth control were used. Transport rates of 2‐aminoisobutyric acid and 3‐0‐methyl‐D‐glucose were measured in sparse, confluent, serum‐starved, and serum‐stimulated cultures.As shown before, cessation of 3T3 cell growth in G0 under conditions of confluence or serum deprivation was associated with reduced rates of transport for both compounds, whereas the density and serum dependence of growth and transport was largely eliminated in SV101. The density revertant F1SV101, which has regained density regulation of growth similar to 3T3 cells, has also regained density regulation of transport. Neither growth nor transport were serum dependent. The serum revertants AγSV7 and LsSV6 have regained both density and serum regulation of growth, but not according to the original mechanism of 3T3 cells of entry into a G0 state. Transport was high under conditions of confluence or serum deprivation. Thus for these cells rates of transport were not reduced simply as a consequence of slower cell growth nor were low transport rates responsible for growth arrest. The data are consistent with the possibility that growth arrest specifically in the G0 state could shut off a number of cellular activities, including transport.
Further observations on metabolic responses in hamster cells: Changes in udpg dehydrogenase activity
Authors: Ullrey Donna B. , Kalckar Herman M. , Christopher C. William 
Published: February 2005

AbstractAdministration of radioactively labeled galactose to cultured mammalian cells brings about an accumulation of metabolic products the pattern of which seems to be governed by a variety of vectors in the intracellular milieu. By manipulation of culture conditions some of these vectors appear to be a function of glycolysis. In the non‐glycolytic culture, label from a galactose probe appears as Galactose‐1‐phosphate (Gal‐1‐P) and UDPglucuronic acid (UDPGlcUA). Conversely, glycolytic culture conditions seem not to permit the formation to UDPGlcUA since the only labeled accumulation product formed was UDPHex. A suggestion is made that the difference in metabolic activity of glucose‐fed and glucose‐starved cultures may be related to the effect of NADH on the in situ activity of UDPG dehydrogenase (UDPglucose:NAD oxidoreductase, E.C. 1.1.1.22) (abbreviation, UDPG‐DH). This prompted an investigation of the effects of NAD and NADH on the activity of partially purified UDPG‐DH. The results of these experiments strongly suggest that the activity of UDPG‐DH (in situ) is negatively controlled by increased levels of NADH; the latter condition is known to exist in glycolytically active cells (Schwartz and Johnson, 1976). Added to this is a second control mechanism which is characterized by a transient inhibition of uridylyltransferase (UDP glucose:α‐D‐galactose‐1‐phosphate uridylyltransferase, E.C. 2.7.7.12). Since it is known that there is little, if any, effect on galactokinase (ATP:D‐galactose‐1‐phosphotransferase, E.C. 2.7.1.6) activity as a result of sugar starvation (Christopher et al., 1976), the low in vivo activity of uridylyltransferase contributes not only to the increased accumulation of Gal‐1‐P but also to a drastic decrease of labeled UDPhexoses, although the pre‐existing pool of UDPhexose was found to decrease only moderately under the condition of glucose starvation (30% still persisted). The benefit of this type of control is not clear.
Lack of a correlation between polyamine synthesis and DNA synthesis by cultured rat liver cells and fibroblasts
Authors: Rupniak H. T. , Paul D. 
Published: February 2005

AbstractGrowth stimulation of either fetal rat liver cells or rat embryo fibroblasts in culture results in considerable increases in intracellular polyamine levels as cells proceed through the cell cycle. Treatment of such cell cultures with appropriate levels of two inhibitors of polyamine synthesis, namely α‐hydrazino ornithine and methylglyoxal bis(guanylhydrazone), can essentially completely block these increases in cellular polyamine content. Under such conditions, where the elevation in intracellular polyamine content is prevented, cell cultures are nevertheless able to initiate DNA synthesis and subsequently synthesize DNA at rates comparable to untreated control cultures that have been growth‐stimulated. These two cell types therefore contain sufficient polyamines when in a resting state (G1) to enable them to enter from G1 into S phase and traverse S phase at normal rates in the absence of further polyamine synthesis. The recruitment of cells into the first cell cycle, through serum stimulation of growth, therefore appears not to be mediated or regulated by the increases in intracellular levels of polyamines that occurs under these conditions. Conversely, the arrest of growth of these cell types resulting from serum deprivation is not mediated by a limitation of intracellular polyamine content.
Membrane bound and cellular cationic changes associated with insulin stimulation of cultured cells
Authors: Sanui Hisashi , Rubin A. Harry 
Published: February 2005

AbstractInsulin was employed as a stimulant in our continuing investigations of the molecular mechanisms involved in the coordinate control of cellular metabolism and growth. Incubation of chicken embryo fibroblasts for 16 hours in media containing 0–0.1 U insulin/ml resulted in a 17‐fold increase in the rate of 3H‐thymidine incorporation into DNA. Concomitantly, there were graded increases in intracellular K+ (14%) and Mg2+ (22%) and no significant change in Ca2+. These changes in cation content occurred within 10 to 30 minutes and preceded the changes in 3H‐thymidine incorporation. Insulin produced a consistent graded decrease in externally bound Mg2+ and Ca2+ and a concomitant increase in bound Na+ and K+ with no significant change in the rates of K+ and Mg2+ efflux. The results are consistent with the concept of Mg2+ as a second messenger for insulin action, as well as with the more general hypothesis that Mg2+ is the central agent in the coordinate control of metabolism and growth in animal cells.
Erythrocyte membrane antigen expression during friend cell differentiation: Analysis of two non‐inducible variants
Authors: MacDonald Marcy E. , Letarte Michelle , Bernstein Alan 
Published: February 2005

AbstractErythrocyte membrane antigens have been detected on induced Friend erythroleukemic cells with a rabbit antiserum raised against mouse erythrocyte membranes. The antibody specificities of this antiserum have been quantitatively analyzed using a cellular radioimmunoassay. After absorption with thymocytes, the rabbit anti‐erythrocyte membrane serum bound to dimethylsulfoxide (DMSO)‐induced Friend erythroleukemic cells and to mouse erythrocytes but not to uninduced Friend cells or thymocytes. Reciprocal inhibition studies demonstrated that, following complete thymocyte absorption, the antiserum detected similar antigenic specificities, termed erythrocyte membrane antigens (EMA), on both mature erythrocytes and induced Friend cells.The expression of these erythrocyte membrane antigens was also induced on Friend cells by other agents, such as ouabain and dimethylacetamide (DMA). In contrast, exogenous hematin, which did not induce hemoglobin synthesis in the Friend cell clones used in this study, also did not induce erythrocyte membrane antigen expression.Two independently derived variant clones which do not produce hemoglobin in reponse to DMSO were analyzed for their ability to produce erythrocyte membrane antigens in response to various inducers of Friend cell differentiation. Clone TG‐13 is not inducible by DMSO or hematin but is weakly induced by DMA for both hemoglobin production and erythrocyte membrane antigen expression. Another variant clone, M18, was also analyzed. This clone does not synthesize detectable hemoglobin when grown in either DMSO or hematin alone, but undergoes extensive hemoglobin synthesis when grown in medium containing both DMSO and hematin. M18 does, however, express erythrocyte membrane antigens when grown in DMSO alone: the presence of hematin and DMSO together in the growth medium does not enhance expression of these antigens. Thus M18 appears to be defective for hemoglobin inducibility, and this defect can be overcome by exogenous hematin; however, the expression of erythrocyte membrane antigens is not affected by this block in hemoglobin synthesis. The results with the variant clones are discussed in terms of a program for Friend cell differentiation in which the induction of hemoglobin synthesis and erythrocyte membrane antigen expression are under both co‐ordinate and separate controls.
Genetic characterization of hydroxyurea‐resistance in chinese hamster ovary cells
Authors: Lewis William H. , Wright Jim A. 
Published: February 2005

AbstractHydroxyurea is an excellent selective agent for obtaining drug‐resistant mutants. At a frequency of approximately 1 × 10−5 it was possible to select, in a single step, colonies that exhibited significant resistance to the cytotoxic effects of the drug. These hydroxyurea‐resistant cell lines maintained their resistant phenotype after extensive cultivation in the absence of the drug. Reconstruction experiments indicated that the expression of hydroxyurea‐resistance and the frequency of drug‐resistant colonies was independent of cell densities up to 5 × 105 cells per 100‐mm selection plate. Luria‐Delbrück fluctuation analyses indicated that the appearance of hydroxyurea‐resistant cells in wild type populations occurred spontaneously and at a rate of 4.8 × 10−6 per cell per generation in the presence of 0.33 mM drug. Studies with the mutagen, ethyl methane sulfonate indicated that it was capable of increasing the frequency of hydroxyurea‐resistant cells by a factor of approximately 10. Also, cell‐cell hybridization experiments showed that hydroxyurea‐resistance behaves as a dominant or codominant trait and that hydroxyurea‐resistance was a useful new genetic marker for selection of somatic cell hybrids. Furthermore, similar to many other drug‐resistant cell lines hydroxyurea‐resistant cells were found to exhibit an altered sensitivity to a number of non‐selective agents (guanazole, N‐carbamoyloxyurea, formamidoxime, and hydroxyurethane). Except for guanazole these compounds are structurally very similar to hydroxyurea and may be expected to have similar modes of action. The results presented in this paper support the view that hydroxyurea‐resistance is expressed as a normal genetic trait and is a useful genetic marker for somatic cell genetic studies.
Cell cycle dependence of the reactivation of chick erythrocyte nuclei after transplantation into mouse L929 cell cytoplasts
Authors: Lipsich Leah Ann , Lucas Joseph J. , Kates Joseph R. 
Published: February 2005

AbstractMonolayer cultures of cytoplasts were formed from synchronized mouse L929 cells in the G1, S and G2 phases of the cell cycle by cytochalasin‐induced enucleation. Chick embryo erythrocytes were then fused to the cytoplasts using Sendai virus. Extensive reactivation of the dormant erythrocyte nuclei‐determined by nuclear swelling, nucleoli formation and incorporation of 3H‐uridine into RNA‐was observed upon fusion to the three types of cytoplasts. By all of these criteria, reactivation was greatest when nuclei were introduced into G1 cytoplasts.Similar experiments in which DNA synthesis was measured showed that both G1 and G2 cytoplasts almost completely lacked the ability to induce DNA synthesis in the chick nuclei. But at least 26% of the erythrocyte nuclei within S cytoplasts exhibited significant levels of DNA synthesis. Cytoplasts prepared from cells three hours after entry into the S phase, which is six to seven hours in length in L929 cells, possessed the maximum capacity to induce DNA replication in chick nuclei. As many as 60% of the nuclei introduced into 3‐hour S phase cytoplasts synthesized significant quantities of DNA.The effect of cycloheximide, an inhibitor of protein synthesis, on erythrocyte nuclear reactivation within G1 phase cytoplasts was also investigated. Protein synthesis was necessary to maximize the reactivation of erythrocyte nuclei. However, it appeared that protein synthesis occurring prior to enucleation was more important in the reactivation process than synthesis occurring following enucleation.