bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effects of inhibition of RNA or protein synthesis on CHO cell cycle progression
Authors: Traganos Frank , Kimmel Marek , Bueti Connie , Darzynkiewicz Zbigniew 
Published: February 2005

AbstractChinese hamster ovary (CHO) cells, synchronized by selective detachment at mitosis, were treated with various concentrations of actinomycin D (AMD) or cycloheximide (CHX) either immediately, or 1, 2, or 3 hr after mitosis. Since the minimum duration of G1 phase in these cultures was 3.4 hr, the addition of RNA or protein synthesis inhibitors took place at the beginning, first third, second third, or end (G1–S boundary) of G1 phase. The kinetics of exit from G1 phase, the rate and extent of traverse of S phase, and the reaccumulation of RNA were estimated under each set of growth conditions by flow cytometry of acridine orange‐stained cells. A mathematical model was constructed to describe the trajectories of the cell populations with respect to their increase in RNA and DNA content in the absence or presence of the inhibitor. The chronologic synchrony imposed on the CHO cell population began to decay within 3 hr, resulting in stochastic entrance of cells into S phase in the absence of inhibitor. Addition of AMD or CHX at 0, 1, 2, or 3 hr after mitosis, regardless of the inhibitor concentration, did not provide evidence of a critical restriction point in G1 beyond which cells were committed to enter S phase and were no longer sensitive to moderate suppression of RNA or protein synthesis. The observed kinetics of cell entrance into and traverse of S phase were consistent with an inherently heterogenous response to serum stimulation occurring at or just after cell division.
Megakaryocyte colony growth‐supporting activities in human plasma: Modification by platelets and platelet membranes
Authors: Yamasaki Kazuo , Jamal Nazir , Mann Kenneth G. , Messner Hans A. 
Published: February 2005

AbstractHuman megakaryocyte colonies are grown in methylcellulose with platelet‐poor plasma and medium conditioned by phytohemagglutinin‐stimulated leukocytes (PHA‐LCM) as a source of megakaryocyte colony stimulating factor (MEG‐CSF). The megakaryocyte colony growth‐supporting activity in human plasma can be absorbed by intact platelets or degranulated platelet membranes. It was possible to recover the activity by solubilized platelet membrane with cholic acid. Filtration of the solubilized platelet membrane preparations through a Sephadex G‐100 column yielded at least two activity peaks. The molecular weight of these two activities differs from that of the growth‐promoting activity in PHA‐LCM.
Effect of 5′‐difluoromethylthioadenosine, an inhibitor of methylthioadenosine phosphorylase, on proliferation of cultured cells
Authors: Nishikawa Seiji , Ueno Akemichi , Inoue Hideo , Takeda Yoshiro 
Published: February 2005

Abstract5′‐Methylthioadenosine (MTA) is formed from decarboxylated S‐adenosylme‐thionine during biosynthesis of polyamines. This nucleoside is cleaved by methylthioadenosine phosphorylase (MTA Pase) to adenine and 5‐methyl‐thioribose‐l‐phosphate in mammalian cells. 5′‐Difluoromethylthioadenosine (DFMTA), a synthetic analog of MTA, was not a substrate for MTA Pase, but was a strong competitive inhibitor of the enzyme (Ki = 0.48 μM). DFMTA caused marked accumulation of labeled MTA formed from [35S]methionine in Raji cells, which contain MTA Pase, but not in CCRF‐CEM cells, which do not contain this enzyme, suggesting that it also inhibits the enzyme in intact cells. DFMTA inhibited the growth of a variety of cultured cells and its cytostatic effect was roughly proportional to the MTA Pase activity of the cells. MTA also depressed the growth of cultured cells but, in contrast with DFMTA, its inhibitory effect was greater in MTA Pase‐deficient cells (CCRF‐CEM) than MTA Pase‐containing cells (Raji). Inhibition of growth of Raji cells by DFMTA was partially reversed by exogenous adenine, a reaction product of MTA Pase. These results suggest that the utilization of adenine formed from MTA was important for proliferation of cells containing MTA Pase under the culture conditions employed, and that DFMTA inhibited cell growth by inhibiting MTA Pase activity.
Cell cycle and growth factor‐dependent phosphoprotein of 78kD differently regulated in normal and transformed mouse fibroblasts
Authors: Yang Henry C. , Pardee Arthur B. 
Published: February 2005

AbstractA novel 78kD phosphoprotein (pp78) of BALB/c 3T3 mouse fibroblasts is reported. Its properties of appearance in late G1 phase, dependence on specific growth factors, and altered constitutive kinetics in benzo(a)pyrene‐transformed (BPA31) cells suggest its role in growth and transformation. Pp78 phosphorylation is in a dynamic state and is stabilized by inhibitors of protein and mRNA synthesis, possibly because of inhibition of a labile phosphatase or protease. Its disappearance in S phase and its low level in exponential cells also indicate a dynamic control that is dependent on growth conditions. Enhancement by phorbol myristate acetate indicates that phosphorylation of pp78 is a consequence of protein kinase C activation, but it appears much later than does an 80kD phosphoprotein (pp80), which is a recognized substrate of kinase C. No simple relation between the appearance of pp78 and mitogenesis was found. Two other phosphoproteins varied with growth conditions. One is the pp80 kinase C substrate which was found in the untransformed (A31) 3T3 cells early after stimulation but was absent in BPA31 cells. The other is an 18kD phosphoprotein that appeared shortly after quiescent 3T3 cells were stimulated.
Regulation of thyroidal inducibility of Na,K‐ATPase and binding of epidermal growth factor in wild‐type and cold‐sensitive E1a mutant type 5 adenovirus‐transformed CREF cells
Authors: Guernsey Duane L. , Duigou Gregory J. , Babiss Lee E. , Fisher Paul B. 
Published: February 2005

AbstractWe have analyzed the relationship between expression of the transformed phenotype and thyroid hormone (triiodothyronine, T3) inducibility of Na,K‐ATPase and binding of 125I‐epidermal growth factor (EGF) to cell membrane receptors in wild‐type (wt) and mutant type 5 adenovirus (Ad5)‐transformed CREF cells displaying a cold‐sensitive (cs) expression of the transformed phenotype. CREF cells respond to thyroid hormone treatment with increased Na,K‐ATPase activity and bind similar levels of 125I‐EGF at 32°C, 37°C and 39.5°C. In contrast, CREF cells transformed by wt Ad5 or the E1A plus E1b‐transforming genes of wt Ad5 are refractile to T3 treatment and bind lower levels of 125I‐EGF than CREF cells at all three temperatures. By employing a series of cloned CREF cell lines transformed by a host‐range cold‐sensitive mutant virus, H5hr1 or H5dl101, or the E1a or E1a plus E1b genes from these viruses, we have investigated expression of the transformed state and its relationship with hormone inducibility and EGF binding. When cs virus‐, cs E1a‐ or cs E1a plus E1b‐transformed CREF clones were grown at 32°C, a nonpermissive transforming temperature in which cs‐transformed cells exhibit properties similar to untransformed CREF cells, T3 induced Na,K‐ATPase activity and these cells bound similar levels of 125I‐EGF as CREF cells. However, when cs virus‐and cs Ela plus Elb‐transformed CREF clones were incubated at 37°C or 39.5°C, temperatures at which cs‐transformed cells exhibit properties similar to wt Ad5‐transformed CREF cells, they did not respond to T3 and bound lower levels of 125I‐EGF than CREF cells. In the case of cs E1a‐transformed CREF clones, thyroid hormone responsiveness was observed at both 32°C and 37°C, but not at 39.5°C. By performing temperature shift experiments‐i.e. 32°C to 37°C, 32°C to 39.5°C, 37°C to 32°C, and 39.5°C to 32°C, it was demonstrated that after a shift from lower to higher temperature a 24‐hr lag period was required for cs‐transformed CREF cells to lose T3 inducibility and exhibit reduced EGF binding, whereas 96 hr after a shift from higher to lower temperature a 96‐hr lag period was required for cs‐transformed cells to regain T3 inducibility and increased 125I‐EGF binding. Flow cytometric analysis indicated that the ability of T3 to induce Na,K‐ATPase in CREF cells was not a consequence of alterations in cell‐cycle distribution. These results indicate that the loss of thyroid hormone inducibility of Na,K‐ATPase and a decreased binding of 125I‐EGF are properties which correlate with expression of the transformed phenotype in Ad5‐transformed CREF cells.
Recombinant human interleukin‐1 inhibits the induction by dexamethasone of alkaline phosphatase activity in murine capillary endothelial cells
Authors: Mulkins Mary A. , Allison Anthony C. 
Published: February 2005

AbstractA mutual antagonism exists between interleukin‐1s (IL‐1s) as pro‐inflammatory and glucocorticoids as anti‐inflammatory mediators. This report examines the effects of IL‐1 on the induction by dexamethasone of alkaline phosphatase in LEII murine endothelial cells. Dexamethasone increases the specific activity of alkaline phosphatase in a time‐ and dose‐dependent fashion (maximum 14‐fold induction at 10−6 M, IC50 = 10−8 M), and this induction can be completely inhibited by simultaneous incubation with picomolar concentrations of recombinant human IL‐1α or IL‐1β. This IL‐1‐mediated antagonism of dexamethasone activity is not due to a down‐regulation of glucocorticoid receptors in the cell line used, because the number of receptors and their affinity for dexamethasone is unchanged in IL‐1‐treated cells. However, induction of alkaline phosphatase by dexamethasone in LEII cells is receptor‐mediated, since it can also be inhibited by glucocorticoid‐receptor antagonists.
The cell cycle associated change of the Ki‐67 reactive nuclear antigen expression
Authors: Sasaki Kohsuke , Murakami Tomoyuki , Kawasaki Masahiro , Takahashi Manabu 
Published: February 2005

AbstractThe change of human nuclear antigen expression in proliferating cells recognized by a monoclonal antibody, Ki‐67, during the cell cycle was investigated in HeLa S3 cells using a bivariate‐flow‐cytometric analysis. The antigen was immunocytochemically stained with FITC, and DNA was stained with propidium iodide (PI). The expression of the antigen increased with cell‐cycle progression, especially in the latter half of S‐phase and reached a maximum at G2M‐phase, although its content varied greatly from cell to cell. The cells in which DNA synthesis was inhibited by treatment with hydroxyurea increased markedly in the antigen expression (as compared to untreated cells). Treatment with adriamycin also elevated the antigen content. After digestion with DNase I, but not after RNase treatment, FITC fluorescence from the antigen disappeared. These results suggest that the Ki‐67 antigen is bound to DNA and its expression does not depend on DNA replication. Although the biological implications of the antigen remain unresolved, the antigen may be considered to be essential for maintaining the proliferating state of cells.
Isolation of Thy‐1 caps and analysis of their phospholipid composition in mouse T‐lymphoma cells
Authors: Suchard Suzanne J. , Lo Hilda K. , Bourguignon Lilly Y. W. 
Published: February 2005

AbstractIn this study we have used a density perturbation method to isolate anti‐Thy‐1 antibody‐induced Thy‐1 caps from mouse T‐lymphoma cells in the absence of detergents, and then compared the phospholipid composit on of these capped membranes with that of uncapped membranes. Initial phospholipid analysis by two‐dimensional thin layer chromatography (2‐D TLC) reveals a significant increase in the amount of 32P‐labeled phosphatidylcholine in the Thy‐1 capped membrane. In contrast, no significant changes are observed in the labeling of phosphatidylserine, phosphatidylethanolamine, or the sphingomyelins. Therefore, it is suggested that phosphatidylcholine may be involved in the organization and/or regulation of Thy‐1 antigen redistribution. The composition of phosphoinositide in uncapped and capped membranes was analysed separately using one‐dimensional thin layer chromatography (1‐D TLC) to resolve phosphatidylinositol (PI), phosphatidylinositol 4‐phosphate (PIP), and phosphatidylinositol 4, 5‐bisphosphate (PIP2) from all other phospholipids. This analysis reveals a significant reduction in levels of PIP and PIP2, but not PI, in Thy‐1 caps. Through the use of ion exchange column chromatography, we have found an increased production of all three species of inositol phosphates during anti‐Thy‐1 antibody‐induced capping. Inositol 1, 4, 5 ‐triphosphate (IP3) shows the most significant increase, compared to the much smaller increases in inositol 4, 5‐bisphosphate (IP2) and inositol monophosphate (IP). These results suggest that the binding of anti‐Thy‐1 antibody to Thy‐1 antigen activates phospholipase C which, in turn, initiates polyphosphoinositide turnover and IP3 production. It is proposed that these observed effects are the result of early signal transducing events which are prerequisite steps in Thy‐1 receptor cap formation.
Synergistic antiproliferative effects of glucocorticoids and interferon‐α on some lymphoid cell lines
Authors: Elliott Keith R. F. , Princler Gerald L. , Urba Walter J. , Faltynek Connie R. 
Published: February 2005

AbstractThe Daudi B lymphoblastoid cell line was previously demonstrated to be highly sensitive to the antiproliferative effect of recombinant interferon‐αA (rlFN‐α). In the present study, glucocorticoid hormones were shown to act synergistically with rlFN‐α to further increase the sensitivity of Daudi cells to rlFN‐α.At 106M, dexamethasone, prednisolone, or hydrocortisone alone had little effect on Daudi cell growth, but they greatly potentiated the antiproliferative activity of rlFN‐α. The synergy between rlFN‐α and glucocorti‐coids on Daudi cells was not related to the inhibitory effects of glucocorticoids on prostaglandin or leukotriene synthesis, since no synergy was observed between rlFN‐α and indomethacin or nordihydroguaiaretic acid. Glucocorticoids and rlFN‐α also had appreciable synergistic antiproliferative effects on two out of five other IFN‐sensitive lymphoid cell lines. When Raji B lymphoblastoid cells, which were quite resistant to the antiproliferative effect of rlFN‐α, were treated with the combination of glucocorticoids and rlFN‐α, no significant synergistic effects were observed. The synergistic antiproliferative effects of glucocorticoids and rlFN‐α observed with some IFN‐sensitive lymphoid cell lines in this in vitro study may have clinical relevance in the treatment of certain lymphoid malignancies that are sensitive to rlFN‐α therapy.
Inhibition of growth and induction of enzyme activities in a clonal human hepatoma cell line (Li‐7A): Comparison of the effects of epidermal growth factor and an anti‐epidermal growth factor receptor antibody
Authors: Knowles Aileen F. 
Published: February 2005

AbstractA cloned human hepatoma cell line (Li‐7A), possessing epidermal growth factor (EGF) receptors numbering in the range of 10‐20 pmol/106 cells, was inhibited in its growth by EGF as well as an antagonist monoclonal antibody (MoAb) to the EGF receptor. The mode of action of the two ligands of EGF receptors appeared to be different as indicated by the following results: (1) EGF induced marked alteration in cell morphology, whereas the antibody did not; (2) cellular protein accumulated in the EGF‐treated cells but not in the antibody treated cells; and (3) ectoATPase activities were greatly enhanced in Li‐7A cells treated with EGF and cholera toxin but were unaffected in cells treated with antibody and cholera toxin. The last result also suggests that expression of ectoATPase activities is under the regulation of both EGF and cholera toxin. Li‐7A cells provide an additional valuable experimental system for the study of EGF action, as well as the interactive effects of EGF and cholera toxin. The enrichment of the ATPase activities in the EGF‐cholera toxin‐treated cells can be exploited for the detailed study and isolation of these enzymes and elucidation of their physiological functions.
Interferon and phorbol esters down‐regulate slgM expression by independent pathways
Authors: Schaffer Frederick M. , Benedict Stephen H. , Petsche Dieter , Lau Alan , Williams Bryan R. G. , Mills Gordon B. , Gelfand Erwin W. 
Published: February 2005

AbstractWe studied the effects of recombinant, interferon, 12‐O‐tetradecanoylphorbol13‐acetate (TPA), and phorbol 12,13 dibutyrate (PDB) on surface immunoglobulin expression by Daudi cells. Incubation of cells with recombinant alpha2interferon (IFN‐α2) caused a 2.5‐fold (60%) decrease in slgM expression as measured by relative fluorescence index (RFI) using a flow cytometer. This decrease in slgM expression was independent of inhibitory effects on proliferation and cell cycle progression. TPA or PDB also caused a threefold (67%) decrease in slgM expression, while enhancing proliferation and cell cycle progression. Coincubation of cells with IFN‐α2 or TPA decreased slgM expression by more than fourfold (>75%), which was greater than the decrease induced by the optimal concentration of either agent alone. Molecular studies demonstrated that the treatment of cells with IFN‐α2 or TPA decreased the steady‐state levels of mRNA for the heavy chain of IgM (cμ), suggesting that down‐regulation of slgM occurred at a pretranslational level. Activation of the cell membrane sodium/proton antiport did not play an integral role in the IFN‐α2 or phorbol‐ester‐induced pathway of slgM down‐regulation. Whereas IFN‐α2 induced an increase in the activity of 2′,5′‐oligoadenylate (2–5A) synthetase, the addition of TPA to IFN‐α2 caused a significant decrease in the activity of this enzyme. Although IFN‐α2 and TPA exhibited additive effects on slgM expression, they had opposing effects on cell proliferation, cell cycle progression, and induction of 2–5A synthetase activity, suggesting that these agents down‐regulate slgM expression through independent pathways.
Evidence of intracellular and trans‐acting differentiation‐inducing activity in human promyelocytic leukemia HL‐60 cells: Its possible involvement in process of cell differentiation from a commitment step to a phenotype‐expression step
Authors: Okazaki Toshiro , Kato Yoshiki , Tashima Masaro , Sawada Hiroyoshi , Uchino Haruto 
Published: February 2005

AbstractWe previously reported that human promyelocytic leukemia HL‐60 cells, when treated with various inducers in magnesium‐deficient medium, became committed to differentiate but did not express the differentiation‐related phenotypes (Okazaki et al., J. Cell. Physiol., 131:50–57, 1987). In the present study we demonstrated the existence of an intracellular differentiation‐inducing activity (int‐DIA) in differentiation‐committed phenotype‐nonexpressing HL‐60 cells by using cybrid formation between untreated HL‐60 cells and cytoplasts from HL‐60 cells treated in magnesium‐deficient medium with 100 nM 1α,25‐dihydroxyvitamin D3 (1,25(OH)2D3). Cell extracts from similarly treated HL‐60 cells also showed int‐DIA, which when added (10 mg total protein/ml) to culture of untreated HL‐60 cells, could increase the percentages of nitroblue tetrazolium (NBT)‐ and nonspecific esterase (NSE)‐positive cells from 1% to 53%, and from 0 to 32%, respectively. They also induced differentiation of human monoblastic leukemia U‐937 cells and of human myeloblastic leukemia KG‐1 cells but not of erythroleukemia K‐562 cells. These results suggested that the int‐DIA had a common effect on differentiation induction in several human myeloid cell lines and may be involved in inducing cells to proceed from a commitment to a phenotype‐expression step during human myeloid cell differentiation.
Combinative ligand‐receptor interactions: Epinephrine depresses RAW264 macrophage antibody‐dependent phagocytosis in the absence and presence of met‐enkephalin
Authors: Petty Howard R. , Berg Kelly A. 
Published: February 2005

AbstractMacrophages have been shown to possess cell surface receptors for opiates and catecholamines. The abilities of these ligands to affect RAW264 macrophage antibody‐dependent effector activity directed against sheep red blood cells were tested. Phagocytosis was measured by the uptake of 51Cr labeled erythrocytes and optical microscopy. Cytolysis was measured by 51Cr‐release assays. Met‐enkephalin increased specific antibody‐dependent phagocytosis in a dose‐dependent fashion; the optimal dose was found to be 10−8 M. Epinephrine diminished phagocytosis in a dose‐dependent manner exhibiting a maximal inhibition at 10−4–10−5 M. This inhibition can be blocked by propranolol. The combined effects of simultaneous treatment with met‐enkephalin and epinephrine were measured. At the several doses tested, the combined effects of these two ligands on the amount of phagocytosis were equivalent to or more inhibitory than epinephrine alone. Thioglycolate‐elicited murine peritoneal macrophages demonstrated similar responses to epinephrine, met‐enkephalin, and their combination. Therefore, in vitro models more closely approximating in vivo neuroregulation of macrophage function demonstrate phagocytic inhibition.
Characterization of the rebinding of 125I‐epidermal growth factor released from BALB/c‐3T3 cells following accumulation in the presence of chloroquine
Authors: Cooper Janet L. , Wakshull Eric , Wharton Walker 
Published: February 2005

AbstractLysosomotropic amines, such as chloroquine and methylamine, increase the intracellular accumulation of 125I‐EGF by inhibiting lysosomal degradation. It has been shown previously that BALB/c‐3T3 cells, prelabeled at 4°C with 125I‐EGF for 3 h and subsequently chased at 37°C in the presence of chloroquine, internalized the surface bound 125I‐EGF which was subsequently released into the extracellular medium in a high molecular weight form which co‐migrated with native 125I‐EGF. The secreted 125I‐EGF rebound to the cells from which it was released more efficiently than does peptide in the extracellular media. We now show that when the BALB/c‐3T3 cells were prelabeled at 37°C for 2 h in the presence of chloroquine, the internalized 125I‐EGF released into the medium was in a high molecular weight form which co‐migrated with native 125I‐EGF and did not rebind anymore efficiently than did peptide in the extracellular media. This lack of rebinding was not due to an alteration in the 125I‐EGF molecule since it was still capable of rebinding to naive A431 cells, nor was it due to the exhaustion of EGF receptors on the BALB/c‐3T3 cells. The inhibition of rebinding was observed only when the cells were treated with EGF in the presence of chloroquine, and was not due to a general down‐regulation of membrane receptors. The differences between the rebinding of 125I‐EGF at 4°C and 37°C suggest that EGF may be processed via different pathways in the cell.