bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effects of epidermal growth factor, estrogen, and progestin on DNA synthesis in mammary cells in vivo are determined by the developmental state of the gland
Authors: Haslam Sandra Z. , Counterman Laura J. , Nummy Katherine A. 
Published: February 2005

AbstractEstrogen (E), progesterone (P), and epidermal growth factor (EGF) are involved in the growth and development of the normal mammary gland. While studies have been carried out to investigate the in vivo effects of EGF in the immature mammary gland, nothing is known about the growth effects of EGF or its potential interactions with E and/or P in the adult mammary gland. The present studies were undertaken to investigate the effects of EGF, E, and P on mammary cell proliferation in immature, peripubertal vs. adult, sexually mature mice. We have found that EGF promotes epithelial and stromal cell proliferation in both the immature and adult mammary glands. In the immature gland, the end bud epithelium is most responsive to the proliferative effects of EGF and there is no apparent interaction between EGF, E, and/or P. In contrast, in the mature gland EGF adds to the proliferative effects of E+P in the ductal epithelium resulting in more extensive ductal sidebranching. Thus these results demonstrate that the developmental state of the mammary gland determines the nature and extent of the interactions between EGF, E, and P in growth and development. © 1993 Wiley‐Liss, Inc.
Cell density, negative proliferation control, and phosphorylation of retinoblastoma protein
Authors: Böhmer Ralph M. 
Published: February 2005

AbstractCell density negative control (CDNC) of normal human fibroblast proliferation occurs after stimulation by mitogens with different signal transduction mechanism. Delayed exposure to agents that interfere with CDNC, such as doublestranded RNA and vanadate, reveals the existence of a biochemical event, involved in CDNC, that occurs 5–8 hr after the beginning of mitogenic stimulation. This is earlier than the point of “mitogenic commitment,” defined by the duration of mitogen exposure required for cell cycle entry (8–18 hr). Phosphorylation of the retinoblastoma gene product (pRB) begins 8–10 hr after mitogen stimulation and is nearly complete at 18 hr, just as the first cells enter S‐phase. CDNC prevents pRB phosphorylation. Interferon β delays pRB phosphorylation by up to 20 hr but has little effect on the timing of mitogenic commitment. Thus mitogenic commitment is located in time between CDNC and pRB phosphorylation. When agents that cause a release from CDNC are applied to dense, negatively controlled cultures after 18 hr of EGF stimulation, pRB phosporylation occurs 6–8 hr after release. This suggests that the negatively controlled cells process the mitogenic signal but accumulate at a restriction point. The relatively early timing of CDNC‐related events in the prereplicative phase raises the possibility that pRB phosphorylation is a consequence rather than a prerequisite for release from cell density negative control. © 1993 Wiley‐Liss, Inc.
Dissociation of early and late markers of murine myeloid differentiation by interferon‐gamma and interleukin‐6
Authors: Ruhl Stefan , Pluznik Dov H. 
Published: February 2005

AbstractMurine myeloid leukemia M1 cells undergo terminal differentiation to mature macrophages after stimulation with interleukin‐6 (IL‐6). This process can be monitored by measuring the expression of early markers such as the high affinity receptor for monomeric IgG2a (FcγRI) and la antigen followed by late markers such as lysozyme production and finally morphological changes from blast cells to mature macrophages. The same early markers that are expressed on M1 cells after induction with IL‐6 are also expressed on monocytic cells after activation with interferon‐γ (IFNγ). We used IL‐6 and IFNγ to investigate whether the early stages of M1 cell differentiation could be accomplished without commitment of the cells to terminal differentiation. Cytofluorometry shows that the expression of the same early differentiation markers (FcγRI and la antigen) that are inducible by IL‐6 on M1 cells can be induced by IFNγ as well. However, stimulation with IFNγ, in contrast to IL‐6, does not induce the late differentiation markers such as lysozyme production, phagocytic activity, and morphological changes. Northern analysis supports these findings in that expression of FcγRI mRNA is induced by either cytokine, whereas expression of mRNA for lysozyme is inducible by IL‐6 only. Nuclear run‐on analysis reveals that the changes in steady state mRNA levels of both FcγRI and lysozyme are regulated by a transcriptional mechanism. These data suggest that early stages in the process of myeloid differentiation can be separately induced by IFNγ and thus are independent from the later events induced by IL‐6. © 1993 Wiley‐Liss, Inc.
Epidermal growth factor receptors lose ligand binding ability as WI‐38 cells progress from short‐term to long‐term quiescence
Authors: Donigan Anne M. , Cavalli R. Christopher , Pena Angel A. , Savage C. Richard , Soprano Dianne Robert , Soprano Kenneth J. 
Published: February 2005

AbstractWI‐38 cells, density arrested for short periods of time, can be stimulated to re‐enter the cell cycle by epidermal growth factor (EGF) alone. However, cells density arrested for longer periods have a prolonged prereplicative phase when serum stimulated and cannot be stimulated by EGF alone. Radio‐ligand binding studies performed on WI‐38 cells showed that actively growing cells bind [125I]EGF at relatively low levels that increase to a maximum as the cells become contact inhibited. As the cells enter a state of deeper quiescence, EGF binding falls to one‐third to one‐fifth the short‐term growth arrested levels, remaining constant thereafter. The EGF‐receptor complexes internalize more slowly in long‐term growth arrested cells, and the rate of ligand association to the receptor is lower than short‐term growth arrested cells. The amount of EGF receptor protein in lysates of equal numbers of both short‐ and long‐term quiescent cells remains the same. These results suggest that the failure of long‐term growth arrested cells to respond to EGF is not due to dramatic changes in the amount of receptor protein during prolonged quiescence but more likely to an alteration in the ability of these receptors to bind ligand and/or activate the EGF signal transduction pathway. © 1993 Wiley‐Liss, Inc.
Regulation of malic enzyme gene expression by nutrients, hormones, and growth factors in fetal hepatocyte primary cultures
Authors: Molero Cristina , Benito Manuel , Lorenzo Margarita 
Published: February 2005

AbstractThe culture of fetal hepatocytes for 64 h in medium supplemented with 5 mM glucose, T3, insulin, and dexamethasone resulted in the coordinate precocious expression of malic enzyme mRNA, protein, and specific activity. T3 was the main inducer; meanwhile, insulin exerted a small synergistic effect when added with T3. Dexamethasone had a potentiation effect on the T3 response of malic enzyme mRNA expression regardless of the presence of insulin. This effect of dexamethasone on T3 response of malic enzyme mRNA expression was time (64 h) and glucose dependent. Glucagon, and to a greater degree dibutyryl‐cAMP, repressed malic enzyme mRNA as well as protein expression by T3 and dexamethasone, in the absence of insulin. Glucose and other carbon sources such as lactate‐pyruvate or dihydroxyacetone induced the abundance of malic enzyme mRNA in the absence of hormones. Insulin and T3 produced a high accumulation of malic enzyme mRNA in lactate‐pyruvate medium, this effect being decreased by dexamethasone. EGF supressed the induction produced by T3 and dexamethasone on malic enzyme mRNA, while the expression of β‐actin mRNA remained essentially unmodified. © 1993 Wiley‐Liss, Inc.
Inducers of the heat shock response stimulate phospholipase C and phospholipase A2 activity in mammalian cells
Authors: Calderwood Stuart K. , Stevenson Mary Ann 
Published: February 2005

AbstractAlthough the mammalian heat shock response has been well characterized, the processes that mediate the induction of the response and the regulation of heat shock protein function are not completely understood. We have investigated the potential role in heat‐shocked cells of phosphoinositide‐specific phospholipase C (PLC), a membrane enzyme activity involved in transmembrane signal transduction. Our studies indicate that heat shock activates PLC in each of seven cell lines, including cells of human, rat, mouse, and hamster origin. Heat shock produced increases in inositol phosphate concentrations comparable in magnitude to those achieved after simulation with growth factors, indicating that heat shock might initiate transmembrane signaling cascades of potential importance in cellular regulation. Common cellular responses to heat and growth factors also included feedback modulation of PLC by its products and the parallel stimulation of phospholipase A2 activity. In addition to heat shocki, other agents that induce the stress response stimulated PLC activity. The data indicate a close correlation between expression of the mammalian heat shock response and stimulation of PLC activity and indicate a possible role for this enzyme activity in the regulation of some aspects of the stress response. © 1993 Wiley‐Liss, Inc.
Expression and loss of the transferrin receptor in growing and differentiating HD3 cells
Authors: Grdisa Mira , Mathew Anu , Johnstone R. M. 
Published: February 2005

AbstractDuring induced differentiation and maturation of HD3 cells (a chicken erythroblast cell line infected with a temperature‐sensitive mutant of the avian erythroblastosis virus), the levels of transferrin receptor (TFR) and nucleoside transporter increase. Both these activities increase before elevated levels of hemoglobin are detected. Shortly after induction, as cellular TFR levels rise, a native‐size TFR is detected in the cell‐free culture medium, associated with an exosome fraction (100,000 xg pellet). Nucleoside transporter (measured as NBMPR‐binding activity) is not increased in this pellet with induction. Previous studies have suggested that exosome formation in peripheral reticulocytes may be a significant route for loss of specific membrane proteins (Johnstone et al., 1991). Although the present experiments in HD3 cells do not address the quantitative importance of exosome formation, the studies suggest that exosome formation is an early event in commitment to the red cell lineage and is not a phenomenon restricted to the terminal stages of red cell maturation. © 1993 Wiley‐Liss, Inc.
Expression of basic fibroblast growth factor and its receptor in an invasive bladder carcinoma cell line
Authors: Allen Lynn E. , Maher Pamela A. 
Published: February 2005

AbstractBasic fibroblast growth factor (bFGF) is a multifunctional growth factor that can stimulate cell proliferation, production of proteases, and angiogenesis. Loss of mechanisms that regulate bFGF activity could result in tumor development. To test this idea, cells derived from an invasive bladder carcinoma (EJ) were compared with cells derived from a noninvasive bladder carcinoma (RT4) for the expression of bFGF and high and low affinity FGF receptors. bFGF was produced by the invasive EJ cells but not by the noninvasive RT4 cells, suggesting that bFGF could act in an autocrine fashion in the EJ cells to promote their invasion and growth in the surrounding tissue. The two cells lines also showed differences in FGF receptor expression. The EJ cells expressed both high and low affinity FGF receptors as determined by Scatchard analysis, whereas the RT4 cells expressed only high affinity receptors. The high affinity receptors on the RT4 cells expressed recognized by an antibody to known FGF receptors. Furthermore, in contrast to the EJ cells, bFGF did not induce protein tyrosine phosphorylation in the RT4 cells. Thus these data suggest that the invasive potential of bladder carcinoma cells may be regulated by the expression of both bFGF and its receptors. © 1993 Wiley‐Liss, Inc.
Growth regulation of primary rat tracheal epithelial cell cultures by endogenous transforming growth factor‐βs
Authors: Rundhaug Joyce E. , Nettesheim Paul 
Published: February 2005

AbstractPrimary rat tracheal epithelial (RTE) cell cultures have previously been shown to secrete transforming growth factor‐β (TGFβ) and to be growth inhibited by exogenous TGFβ. The purpose of the present studies was to determine whether the endogenous TGFβ(s) were regulating the growth of RTE cell cultures and, if so, which isoforms were involved. Neutralizing antibodies specific to TGFβ1 and TGFβ2 were added to cultures, and their effects on several growth parameters were measured. Addition of antibodies to early cultures (day 1), resulted in 1.8‐and 3‐fold increases in colony formation and cell number, respectively, above control IgG‐treated cultures. Antibody dose‐response experiments revealed that TGFβ2 was the predominant isoform inhibiting early RTE cell growth. The antibody treatments resulted in similar stimulation of early growth at low and high seeding densities, suggesting that the endogenous TGFβs were acting locally. Anti‐TGFβ1 treatment of cultures at various stages of growth resulted in 1.2–1.7‐fold increases in DNA synthesis above controls, whereas anti‐TGFβ2 treatment resulted in increased DNA synthesis only in early and late cultures (1.7‐ and 2.5‐fold, respectively), but not during midlogarithmic growth. Continuous treatment with a combination of both antibodies resulted in increased growth and decreased exfoliation in early cultures, but had no effect on the slow down of growth in late cultures. Thus endogenous TGFβs inhibited primarily early growth and contributed to, but did not appear to be responsible for, plateau of growth in late stage cultures. Antibody treatment of secondary cultures resulted in 4–70‐fold increases in colony formation, depending on the age of the primary cultures when replated, indicating that endogenous production of both TGFβ1 and TGFβ2 greatly inhibits the subculturability of primary RTE cells. Other experiments suggested that cholera toxin enhances RTE cell growth in part by counteracting the inhibitory effects of endogenous TGFβs. © 1993 Wiley‐Liss, Inc.
CSF‐1 stimulates nucleoside transport in S1 macrophages
Authors: Meckling‐Gill Kelly A. , Guilbert Larry , Cass Carol E. 
Published: February 2005

AbstractWe have examined nucleoside transport (NT) in a cell line derived from primary day 7 murine bone marrow macrophages (S1 macrophages) in response to the macrophage growth factor, colony‐stimulating factor 1 (CSF‐1). Adenosine and uridine transport in quiescent S1 macrophages occurred primarily by two facilitated diffusional routes, one that was sensitive and one that was relatively resistant to the inhibitor nitrobenzylthioinosine (NBMPR). Addition of CSF‐1 to quiescent cultures resulted in increased adenosine and uridine transport with biphasic kinetics with respect to the cell cycle. Basal NT activity was elevated (about twofold) within 15 min of CSF‐1 addition, returned to near basal levels by 1 h, and then increased again (three‐ to fourfold) 8–12 h later, returning again to basal levels by 48 h post CSF‐1 stimulation. We propose that the large increase in NT activity at 8–12 h corresponded with the time when cultures synchronously began to enter the S phase of the cell cycle. In addition to these changes in the absolute rates, the proportions of NBMPR‐sensitive and NBMPR‐insensitive transport also change after CSF‐1 addition. Quiescent cultures exhibited primarily NBMPR‐insensitve transport while logrithmically growing cultures exhibited primarily NBMPR‐sensitive nucleoside transport activity. The increase in the NBMPR‐sensitive component of the transport process paralleled a similar increase in the number of high‐affinity NBMPR binding sites, suggesting that the mechanism for upregulating NBMPR‐sensitive NT activity involves increases in the number of NBMPR‐sensitive transporter sites. Interestingly, we were unable to detect Na+‐dependent concentrative uptake of adenosine, uridine, or formycin‐B either in the S1 macrophage cell line or in primary (day 7) murine macrophages. Thus these bone marrow derived macrophages did not display the characteristically large Na+‐dependent transport systems observed by others in peritoneal macrophages, implying that these two populations of macrophages are, indeed, functionally distinct. © 1993 Wiley‐Liss, Inc.
Isoprenoid regulation of cell growth: Identification of mevalonate‐labelled compounds inducing DNA synthesis in human breast cancer cells depleted of serum and mevalonate
Authors: Wejde Johan , Carlberg Magdalena , Hjertman Magnus , Larsson Olle 
Published: February 2005

AbstractGrowth arrest induced by serum depletion and/or treatment with mevinolin (an inhibitor of mevalonate synthesis) in the human breast cancer cell line Hs578T was overcome by exogenous mevalonate, indicating that some product or metabolite of mevalonate may be involved in the mediation of serum‐regulated growth of these cells. In the search for such compounds we first tested a variety of known end products of mevalonate with respect to their ability to counteract the inhibition of DNA synthesis caused by serum‐free medium and mevinolin. Thereby high doses (10 μg/ml) of dolichol‐20 were found to cause a partial counteraction. After straight‐phase HPLC purification of endogenous lipids, isolated from 3H‐ or 14C‐mevalonate‐labelled Hs578T cultures, we found that non‐sterol lipids co‐eluting with dolichols efficiently induced DNA synthesis. After further purification with reverse‐phase HPLC it was confirmed that virtually all of this effect was achieved by compound(s) (seen as a single UV and radioactive peak) co‐eluting with dolichol‐20. Nanogram doses, at most, of this (these) compound(s) elicited a substantial stimulation of DNA synthesis. The lipid(s) also counteracted the inhibition by mevinolin of N‐linked glycosylation, indicating that it (they) also interfere(s) with this processing. Since treatment with tunicamycin (an inhibitor of N‐linked glycosylation) abolished this growth‐stimulative effect, N‐linked glycosylation seems to be a necessary event in the processes leading to lipid‐induced initiation of DNA synthesis.
Paradoxical biological effects of overexpressed insulin‐like growth factor‐1 receptors in chinese hamster ovary cells
Authors: Kato Hisanori , Faria Teresa N. , Stannard Bethel , Levy‐Toledano Rachel , Taylor Simeon I. , Roberts Charles T. , Leroith Derek 
Published: February 2005

AbstractOne major approach to the study of growth factor receptor action has been to overexpress wild‐type or mutant receptors in cultured cells and to evaluate biological responses to exogenous ligand. Studies of this type with insulin and insulin‐like growth factor‐I (IGF‐I) receptors often use Chinese hamster ovary (CHO) cells. We have compared the effect of receptor overexpression in CHO cells and in NIH‐3T3 fibroblasts in order to assess the suitability of CHO cells for studies of this nature and the contribution of cell type‐specific factors to those responses generally assayed. Overexpression of IGF‐I receptors in NIH‐3T3 cells resulted in increased sensitivity and maximal responsiveness of thymidine incorporation, 2‐deoxyglucose uptake, and phosphatidylinositol‐3 (PI3) kinase activation to IGF‐I stimulation. In CHO cells, on the other hand, overexpression of either IGF‐I or insulin receptors increased the sensitivity of thymidine incorporation to ligand, but maximal responsiveness was unchanged or decreased. Overexpression of the insulin receptor increased sensitivity of glucose uptake and the maximal response of PI3 kinase activation to insulin. Overexpression of the IGF‐I receptor did not affect sensitivity or maximal responsiveness of glucose uptake or PI3 kinase activation to IGF‐I. These data suggest that IGF‐I and insulin signal pathways may differ in CHO cells, and that there may even be divergent IGF‐I signaling pathways for short vs. long‐term effects. Whether this is a result of differences in the number of endogenous receptors, hybrid receptor formation, or defects in post‐receptor signaling, the use of CHO cells to assess receptor function must be approached with caution. © Wiley‐Liss, Inc.
Effect of thermotolerance on heat‐induced excess nuclear‐associated proteins
Authors: Borrelli Michael J. , Stafford Diane M. , Rausch Cynthia M. , Lee Yong J. , Corry Peter M. 
Published: February 2005

AbstractEarlier studies reported that thermotolerance had two effects on the heat‐induced increase in nuclear‐associated proteins (NAPs); reduction in NAP levels immediately following hyperthermia and facilitation of NAP recovery to control levels. It has also been demonstrated that there are two phases of thermotolerance; one that requires newly synthesized proteins (protein synthesis dependent thermotolerance; PSDT), and another that does not (protein synthesis independent thermotolerance; PSIT). This study was designed to determine if these two phases of thermotolerance affected NAP binding in a similar or different manner. The results demonstrated that protein synthesis during thermotolerance development was not required to reduce NAP levels measured immediately following hyperthermia, but was required to facilitate NAP recovery to control levels following hyperthermia. Reducing NAP levels was the predominant mechanism by which thermotolerance protected cells from this lesion at 43.0°C while facilitated NAP recovery predominated in protecting against exposure to 45.5°C. The facilitated recovery of NAPs required only proteins synthesized following thermotolerance induction and prior to the second heat challenge. Proteins synthesized following the second heat challenge were not requisite. Finally, the processes that facilitate NAP recovery were inhibited at 3°C, suggesting that they are enzymatically mediated. © 1993 Wiley‐Liss, Inc.
Plasma membrane lipid packing and leukocyte function‐associated antigen‐1‐dependent aggregation of lymphocytes
Authors: Smith Douglas M. , Williamson Patrick L. , Schlegel Robert A. 
Published: February 2005

AbstractA simple model system for study of adhesion mediated by leukocyte function‐associated antigen‐1 (LFA‐1) is aggregation of lymphocytes stimulated in vitro. Although aggregation is blocked by monoclonal antibodies to LFA‐1, not all lymphocytes expressing LFA‐1 aggregate, indicating that LFA‐1 is necessary but not sufficient for aggregation. To investigate whether the lipid bilayer plays a role in the functional activation of LFA‐1, human peripheral blood lymphocytes and murine splenic lymphocytes were stimulated in culture, and measurements made of aggregation vs. packing of plasma membrane lipids. Progression of cells into aggregates was paralleled by a decrease in lipid packing of the population as a whole, as monitored by increased staining with the fluorescent probe merocyanine 540. Cells from aggregates stained more intensely than nonaggregated cells from the same population, indicating that aggregates are preferentially formed from cells in the population with the loosest packed membrane. In contrast, aggregated cells were found to express equivalent or even lower amounts of LFA‐1 than nonaggregated cells. Looser lipid packing is therefore associated with the development of LFA‐1‐dependent aggregation, and might be involved in the functional activation of this cell adhesion molecule. © 1993 Wiley‐Liss, Inc.