bluuebunny/crossref_metadata_2025_split huggingface dataset:
Electrophoretic distribution and dissociation into subunits of lactate dehydrogenase derived from human myeloid leukemia cells before and after induction of differentiation
Authors: Pavelić Krešimir , Pekić Bosa 
Published: February 2005

AbstractThe electrophoretic distribution of lactate dehydrogenase (LDH) isoenzymes, Michaelis constant, reaction with substrate, and dissociation into subunits with guanidine hydrochloride was examined in undifferentiated and differentiated human myeloid leukemia cells. Differentiation was induced with 1/ μg/ml tunicamycin. Undifferentiated cells did not display phagocytic ability, and less than 5% of these cells had Fc receptors. After exposure to tunicamycin for 40 hr, 40% of these differentiated cells had Fc receptors, and 35% showed phagocytic activity after 160 hr. The majority of the LDH activity in the undifferentiated cells was found in fraction 3, and following differentiation almost a 50% reduction in LDH activity was observed in this fraction. In addition, LDH 3 isoenzyme levels were found to be greater in patients containing a high percentage of undifferentiated cells than in patients containing a high percentage of differentiated cells. Differentiated cells displayed LDH isoenzyme fraction pattern, Michaelis constant, and reaction with substrate similar to those found in the normal granulocytes. Differences in the dissociation of LDH into subunits with guanidine hydrochloride were found between undifferentiated and differentiated acute myeloid leukemia (AML) cells. Treatment with 0.75 M guanidine hydrochloride caused complete inactivation of LDH derived from normal differentiated cells, whereas similar treatment caused complete inactivation of LDH derived from AML or normal granulocytes. LDH isoenzymes derived from normal granulocytes and differentiated AML cells were also more sensitive to guanidine hydrochloride depression of fluorescence intensity. The sedimentation constant for single peak LDH at 5.5 M guanidine hydrochloride was calculated as 1.65 sec for differentiated and 1.70 sec for undifferentiated cells. The molecular weight of the polypeptide subunits for undifferentiated cells was 30,000 and for differentiated cells was 39,000. The apparent parallel between leukemic cells after induction of differentiation and normal granulocytes indicates that the leukemic cells retain their maturation potential when exposed to an inducer of differentiation.
Glutamine is responsible for stimulating glycolysis by L929 cells
Authors: Lanks Karl W. 
Published: February 2005

AbstractL929 cells synthesize relatively little lactate when using glucose as their primary energy source, and neither glucose oxidation nor lactate production is highly sensitive to stimulation by insulin. Addition of glutamine to the system containing glucose and insulin markedly stimulates lactate production from glucose without inhibiting glucose oxidation. A mechanism in which reducing equivalents derived from glutamine oxidation are used to drive lactate production is discussed.
Posttranscriptional regulation of ornithine decarboxylase activity
Authors: Dircks Lori , Grens Ann , Slezynger Thelma C. , Scheffler Immo E. 
Published: February 2005

AbstractWe have used a Chinese hamster ovary cell line (DF3) that overproduces ornithine decarboxylase (ODC) to examine various parameters in the cell cycle‐dependent regulation of this enzyme. Under a variety of conditions, alterations in the activity of ODC were accompanied by parallel changes in the levels of the protein, as measured by immunologically cross‐reactive material (CRM). While putrescine has been known to suppress the induction of ODC, we have found that in DF3 cells 10−4M ornithine completely suppresses ODC activity. We also show that the levels of ODC mRNA are not modulated when the levels of ODC activity and CRM change drastically. The data can be interpreted in terms of models involving either an effect of putrescine on the translation of ODC mRNA, or on the activity of a relatively specific protease with ODC as its target.
The modulation of transcobalamin II (TC‐II) production by cyclic adenosine 3′,5′‐monophosphate in the murine macrophage cell line J774: Relationship to growth behavior
Authors: Melmed R. N. , Rachmilewitz B. , Schneider Aviva , Rachmilewitz M. 
Published: February 2005

AbstractWe undertook a study to define the role of cyclic AMP [cAMP] in modulating the secretion of transcobalamin II (TC‐II) in the mouse macrophage like cell line J774. J774 was observed to secrete large amounts of TC‐II, particularly in the presence of 8‐bromo cAMP or cholera toxin or when grown in medium supplemented with low concentrations of horse serum (1% or 5%) or in serum‐free medium. Variant cell lines derived from J774 and deficient either in adenylate cyclase (ac ‐ ) or cAMP‐dependent protein kinase (pk ‐ ) activity showed very low and intermediate levels of basal secretory activity of TC‐II, respectively, compared to J774. Maximum secretory activity of TC‐II was observed in J774 under conditions in which growth was poorest (in the presence of 8‐bromo‐cAMP or 1% or 5% horse serum‐supplemented medium or in serum‐free medium). Cells grown in serum‐free medium were found to have elevated basal adenylate cyclase activity and cAMP levels compared to those grown in medium supplemented with 20% horse serum. The data from this study demonstrate a negative correlation between growth activity and TC‐II secretion in the J774 cell line. The stimulatory effect of exogenous cAMP on TC‐II secretion by J774, the reduced secretory activity of the variant lines ac ‐ and pk ‐ and the observed increase in cell cAMP levels under conditions of serum starvation in which TC‐II secretion is considerably enhanced, suggest that cell cAMP is an important modulator of TC‐II secretion and growth behavior in the J774 cell line.
Evidence for a pool of non‐recycling transferrin receptors in peripheral sheep reticulocytes
Authors: Adam M. , Wu C. , Turbide C. , Larrick J. , Johnstone R. M. 
Published: February 2005

AbstractSheep reticulocytes from phlebotomized animals have a total transferrin binding potential that may exceed by an order of magnitude the surface binding capacity. Steady state uptake of transferrin at 37°C is generally less than 50% of the total transferrin binding capacity. During long‐term incubation of the reticulocytes, all transferrin binding ability is lost, the ability to internalize being lost most rapidly. The loss in ability to bind transferrin during long‐term incubation is independent of the number of surface transferrin binding sites, since removal of surface receptors with pronase does not affect the rate of loss of the internal pool of receptors during long‐term incubation. Moreover, after removing surface receptors with pronase, only a fraction of the original number of receptors is restored to the surface, despite the presence of a large pool of internal receptors. These data suggest that only a fraction of the internal pool of receptors is capable of recycling to the cell surface in sheep reticulocytes.
Alteration in cyclic adenosine 3′:5′‐monophosphate binding proteins during the phenotypic change of mouse macrophages transformed by a temperature‐sensitive mutant (tsA640) of SV40
Authors: Takayama Hisao , Tanigawa Takahiko , Tanaka Yoshinori , Onodera Kazukiyo 
Published: February 2005

AbstractBy using a photoaffinity ligand, cell extracts from transformed macrophages that were established by infection with temperature‐sensitive mutants (tsA640) of simian virus 40 (SV40) were examined for cyclic adenosine 3′:5′‐monophosphate (cAMP)‐binding proteins. At the nonpermissive temperature for SV40 large T antigen, 39.0°C, no significant cAMP‐binding proteins could be detected, such as primary mouse macrophages. At the permissive temperature of 33.0°C, cAMP‐binding proteins appeared later than SV40 T antigen expression and cellular DNA synthesis. The profile of cAMP‐binding proteins was similar to that of resting, but not proliferating, mouse clonal fibroblasts (BALB/c 3T3). These and previous results suggest that SV40 T antigen influences the expression of cAMP‐binding proteins in tsA640‐transformed macrophages; the large/small T antigen converts the profile of cAMP‐binding proteins from macrophage to fibroblastic cells.
Nuclear endogenous Ca2+‐dependent endodeoxyribonuclease in differentiating chick embryonic lens fibers
Authors: Muel Anne S. , Chaudun Elisabeth , Courtois Yves , Modak Sohan P. , Counis Marie F. 
Published: February 2005

AbstractDuring terminal differentiation of lens epithelial cells into fiber cells, nuclei become pycnotic and DNA degradation occurs. We investigated the putative role in this process of an endogenous DNAase. After incubation of isolated nuclei of both cell types at 37°C, DNAase activity was revealed by DNA size analysis on 0.3–1% neutral and alkaline agarose, one‐ and two‐dimensional gels. This DNAase activity is more prominent in lens fiber nuclei than in epithelial nuclei at all the embryonic stages probably because of a preexisting higher concentration of divalent cations in the former. This activity is calcium or magnesium dependent in both types of nuclei.
Cellular basis for the species differences in sensitivity to cardiac glycosides (digitalis)
Authors: Gupta Radhey S. , Chopra Arvind , Stetsko Dawn K. 
Published: February 2005

AbstractThe relative toxicity of numerous cardiotonic steroids (viz. ouabain, digitoxin, digoxin, convallatoxin, SC4453, bufalin, gitaloxin, digoxigenin, actodigin, oleandrin, digitoxigenin, gitoxin, strophanthidin, gitoxigenin, lanatosides A, B and C, α‐ and β‐acetyl digoxin, α‐ and β‐methyl digoxin) and related compounds towards a number of independent cell lines established from human, monkey, mouse, Syrian hamster, and Chinese hamster have been determined. All cardiac glycosides and their genins, as well as the cardiotonic alkaloid cassaine, exhibited > 100‐fold higher toxicity towards cultured human and monkey cells in comparison to the cell lines of mouse, Syrian hamster, and Chinese hamster origins. These differences are species‐related as all cell lines (both normal as well as transformed) from any one species, as well as cells from the closely related species (e.g., man and monkey or mouse, Chinese hamster, and Syrian hamster), showed similar sensitivity towards these drugs. The failure to see any significant differences in cellular toxicity for a larger number of other compounds which either bear limited structural resemblance to cardiac glycosides (viz. estradiol 17‐β‐acetate, testosterone propionate, 21‐acetoxy pregnenolone, β‐estradiol, digitonin, tigogenin, and tomatine) or interact with the Na+/K+ ATPase in a different manner (viz. veratridine, sanguinarine nitrate, penicillic acid, vanadium pentoxide, harmaline‐HCI, 5,5′‐diphenyl hydantoin, quindonium bromide, and methyl quinolizinum bromide) provides strong evidence that the observed species‐related differences are highly specific for cardiotonic steroids. Studies on the binding of [3H]ouabain show that, in comparison to human and monkey cell lines, no significant binding of the drug is observed in cells derived from the resistant species (i.e., mouse and Chinese hamster). The Na+/K+ ATPase from cells of the resistant species is inhibited at much higher concentrations of ouabain and digitoxin in comparison to the enzyme from human cells, and a good correlation is observed between these concentrations and those reported for inhibition of the enzyme from isolated heart muscles of the same species. These results provide strong evidence that the species‐related differences in sensitivity to digitalis have a cellular basis and that the cultured cells from various mammalian species provide a useful model system for investigating the mechanism of action of cardiac glycosides.
Superoxide anion release by human endothelial cells: Synergism between a phorbol ester and a calcium ionophore
Authors: Matsubara Tsukasa , Ziff Morris 
Published: February 2005

AbstractIn order to study the signal transduction mechanism of human endothelial cells (EC), the regulation of superoxide anion (O2−) release in EC has been investigated using the calcium ionophore A23187 and phorbol myristate acetate (PMA), a potential activator of the Ca2+ activated, phospholipid‐dependent protein kinase, designated “protein kinase C.” PMA enhanced O2− release from EC, and this enhancement occurred regardless of the presence or absence of extracellular Ca2+. A similar increase was produced by A23187; omission of extracellular Ca2+ prevented this increase. Simultaneous stimulation with PMA and A23187 produced a large increase in O2− release at submaximal concentrations of these agents, which, when added separately, caused minimal effects. These findings indicate that the activation of protein kinase C and mobilization of Ca2+ evoked by PMA and A23187 respectively are synergistically effective for eliciting a full physiological response of EC in the generation and release of O2−.
Forskolin, phosphodiesterase inhibitors, and cyclic AMP analogs inhibit proliferation of cultured bovine aortic endothelial cells
Authors: Leitman Dale C. , Fiscus Ronald R. , Murad Ferid 
Published: February 2005

AbstractThe role of cyclic AMP on endothelial cell proliferation was investigated, since these cells can be exposed to high concentrations of physiological and pharmacological agents that alter cyclic AMP metabolism. Cloned bovine aortic endothelial cells were plated at 25,000 cells/35mm dish and grown for 5 days in the presence of phosphodiesterase (PDE) inhibitors, forskolin, or cyclic AMP analogs. The PDE inhibitors dipyridamole, ZK 62 711, isobutylmethylxanthine (IBMX) and theophylline inhibited cell growth in a concentration‐dependent manner. Dipyridamole produced a 30% and a 50% inhibition at 5μM and 12.5μM, while higher concentrations were cytotoxic. At its therapeutic plasma concentration range (50‐100μM) theophylline inhibited cell proliferation by 15–25%, while IBMX and the highly specific cyclic AMP phosphodiesterase inhibitor, ZK 62 711 inhibited growth by 60–80% and 40–50%, respectively. Forskolin (5μM) increased cyclic AMP levels and cyclic AMP‐kinase activity ratios by 2.5‐fold and 2‐fold. In the absence of PDE inhibitors forskolin produced a 20% growth inhibition at 0.5μM and a 60% inhibition at 10μM. The forskolin dose‐response curve was not altered by theophylline, but was shifted to the left by approximately 10‐fold with dipyridamole and ZK 62 711 and 5‐fold with IBMX. Forskolin (5μM), by itself produced a 1.8‐fold increase in cyclic AMP. In the presence of 5μM theophylline, dipyridamole, IBMX, and ZK 62 711, cyclic AMP was increased by forskolin 2.0, 2.6, 3.5, and 6.6‐fold, respectively. 8‐Bromo cyclic AMP and dibutyryl cyclic AMP produced a 55% and 60% growth inhibition at 100μM. The cyclic GMP analogs were less effective inhibitors of growth (15–30%). Our results demonstrate that cyclic AMP analogs and pharmacological agents that elevate intracellular cyclic AMP levels inhibit cell growth and suggest that cyclic AMP may be an important endogenous regulator of endothelial cell proliferation.
Expression of phenotypic traits following modulation of colchicine resistance in J774.2 cells
Authors: Lothstein Leonard , Horwitz Susan Band 
Published: February 2005

AbstractDevelopment of resistance to colchicine in the mouse macrophage‐like cell line J774.2 coincides with the expression of a variety of phenotypic traits. A cloned subline (J7/CLC‐20), maintained in 20 μM colchicine, exhibits reduced steady‐state association with drug, increased presence of a 140,000–145,000 dalton (140–145 kD) phosphoglycoprotein associated with the plasma membrane, double minute chromosomes and cross‐resistance to other drugs. While similar phenotypic traits are observed in J774.2 cells resistant to taxol and vinblastine, differences in the electrophoretic mobilities of the resistance‐specific glycoproteins in each of the three sublines suggest that multi‐drug resistant sublines exhibit specificity for individual drugs. In an attempt to elucidate the relationships between the phenotypic traits associated with colchicine resistance, the degree of colchicine resistance in J7/CLC‐20 cells was modulated and the levels of expression of the phenotypic traits were quantitated. In the absence of colchicine in the growth medium, J7/CLC‐20 cells reverted to drug sensitivity within 35 days. A decrease in the level of resistance coincided with coordinate changes in both the quantity of the resistance‐specific glycoprotein and the average number of double minute chromosomes. We propose that the emergence and disappearance of the resistance‐specific glycoprotein and double minute chromosomes may be closely linked. However, J7/CLC‐20 cells which had regained their drug sensitivity after growth in drug‐free medium maintained a reduced level of steady‐state drug association. The persistence of reduced drug association in cells that have reverted to a drug‐sensitive state suggests that this phenomenon, although related to colchicine resistance, need not be the primary or only mechanism of drug resistance.
Accumulation of cells with 4N DNA content at nonpermissive temperature in rat embryo diploid cells transformed by tsA mutant of simian virus 40
Authors: Okuda Atsuyuki , Tamura Hideaki , Shimura Hideo , Kimura Genki 
Published: February 2005

AbstractPrimary rat embryo cells were transformed by a tsA mutant (tsA640) of simian virus 40 (SV40). Proliferation of all four independent diploid transformants was suppressed at a nonpermissive temperature (40.3°C), being accompanied by a marked increase in the fraction of cells with a 4N DNA content (a 4N peak in the flow cytofluorogram). However, in this case, the fraction of cells with a 2N DNA content (a 2N peak in the flow cytofluorogram) was preserved. Both effects (suppression of proliferation and increase in the 4N peak) diminished when transformed cells were superinfected with wild‐type SV40. The increased 4N peak was preserved, albeit not completely, for at least 24 hours, when cells were further incubated in the presence of hydroxyurea at the nonpermissive temperature. On the other hand, the preserved 2N peak all but disappeared within 24 hours, when cells were further incubated in the presence of colcemid at the nonpermissive temperature. These results suggest that the thermolabile large T antigen of SV40 directly or indirectly induces an accumulation of cells with a 4N DNA content, at the nonpermissive temperature, by prolonging the G2 (and/or late S) period.
Characterization of water in unfertilized and fertilized sea urchin eggs
Authors: Merta Philip J. , Fullerton Gary D. , Cameron Ivan L. 
Published: February 2005

AbstractThe water in unfertilized and fertilized sea urchin eggs was characterized with a proton nuclear magnetic resonance (NMR) titration method assuming fast proton diffusion (FPD) between water compartments. This method involves stepwise dehydration with sequential T1 relaxation time and water content determinations. The results analyzed by the FPD model give evidence of intracellular water compartments with three different correlation times: 6 × 10−12 sec (bulk water), 1 × 10−10 sec (structured water) and about 2 × 10−9 sec (bound water). Fertilization is accompanied by a substantial increase in bulk water (from 111 to 414 g H2O per 100 g dry mass) and by a decrease in the water of hydration (from 128 g to 56 g per 100 g dry mass). This study shows that 54% of the water in the unfertilized sea urchin egg has motional properties different from bulk water and that this percentage decreases dramatically shortly after fertilization. Most of the change in T1 relaxation rate observed at fertilization can be accounted for by uptake of bulk water associated with elevation of the fertilization membrane.
Temporal order of replication of genes responsible for hypoxanthine phosphoribosyl transferase and Na+/K+ ATPase in chemically transformed human fibroblasts
Authors: Tsutsui Takeki , Suzuki Nobuko , Elmore Eugene , Maizumi Heiji 
Published: February 2005

AbstractThe cytotoxic and mutagenic effects of a direct perturbation of DNA during various portions of the DNA synthetic period (S phase) of a chemically induced, transformed line (Hut‐11A cells) derived from diploid human skin fibroblasts were examined. The cells were synchronized by a period of growth in low serum with a subsequent blockage of the cells at the G1/S boundary by hydroxyurea. This method resulted in over 90% synchrony, although approximately 20% of the cells were noncycling. Synchronized cells were treated for each of four 2‐h periods during the S phase with 5‐bromodeoxyuridine (BrdU) followed by irradiation with near‐ultraviolet (UV). The BrdU‐plus‐irradiation treatment was cytotoxic and mutagenic, while treatment with BrdU alone or irradiation alone was neither cytotoxic nor mutagenic. The cytotoxicity was dependent upon the periods of S phase during which treatment was administered. The highest lethality was observed for treatment in early to middle S phase, particularly in the first 2 h of S phase, whereas scare lethality was observed in late S phase. The BrdU‐plus‐irradiation treatment induced ouabain‐ and 6‐thioguanine‐resistant mutants, while BrdU alone or irradiation alone was not mutagenic. Ouabain‐resistant mutants were induced during early S phase by the BrdU‐plus‐irradiation treatment. 6‐Thioguanine‐resistant mutants, however, were induced during middle to late S phase. These results suggest that a certain region or regions in the DNA of Hut‐11A cells, as designated by their specific temporal relationship in the S phase, may be more sensitive to the DNA perturbation by BrdU treatment plus near‐UV irradiation for cell survival and that gene(s) responsible for Na+/K+ ATPase is replicated during early S phase and gene(s) for hypoxanthine phosphoribosyl transferase is replicated during middle to late S phase.
Regulation of cell attachment and cell number by fibronectin and laminin
Authors: Terranova Victor P. , Aumailley Monique , Sultan Leslie H. , Martin George R. , Kleinman Hynda K. 
Published: February 2005

AbstractWe have examined the effect of laminin and fibronectin on the attachment and growth on type IV collagen of a line of mouse epithelial cells and a strain of adult human fibroblasts. Laminin stimulated attachment of the epidermal cells and fibronectin stimulated fibroblast attachment. At high concentrations (100 μg/ml), the attachment proteins altered the growth of cells in culture. The epidermal cells grew better in media containing fibronectin‐free serum supplemented with laminin. Fibroblasts, on the other hand, grew best in media containing serum supplemented with fibronectin. These data suggest that laminin promotes epithelial cell growth whereas fibronectin promotes fibroblast growth. This observation was confirmed when these cells were cocultured in the presence of the attachment proteins or of their respective antibodies. The mouse epidermal cells grew best when laminin was added to cocultures of fibroblasts and epithelial cells. Fibroblasts grew best in the presence of antibody to laminin and poorly in the presence of antibody to fibronectin. Thus, fibronectin and laminin may participate in the regulation of cell populations in vivo and may be involved in epithelial‐mesenchymal interactions.