bluuebunny/crossref_metadata_2025_split huggingface dataset:
TGF‐β blocks early but not late differentiation‐specific gene expression and morphologic differentiation of 3T3 T proadipocytes
Authors: Sparks Rodney L. , Allen Blake J. , Strauss Ethan E. 
Published: February 2005

AbstractTransforming growth factor‐β (TGF‐β) inhibits morphologic differentiation of BALB/c 3T3 T cells as well as other proadipocyte models. Our prior studies suggested that TGF‐β may act only during the early stages of differentiation induction. However, we did not determine whether TGF‐β was differentially effecting expression of any of the various differentiation‐specific genes or if it could cause down‐regulation of these genes in differentiated cells. Therefore, in the current study we tested the effects of exogenous TGF‐β (0.01–5.0 ng/ml) on morphologic differentiation and on differentiation‐dependent gene expression (Northern and slot blot analyses) at various times during differentiation. When induced to differentiate, 3T3 T cells first undergo predifferentiation growth arrest and from this state molecular, biochemical, and morphological differentiation proceeds. Here it was found that when added prior to the onset of differentiation, TGF‐β was a potent inhibitor of morphologic differentiation as well as of the expression of differentiation‐specific genes such as lipoprotein lipase (LPL) and glycerol‐3‐phosphate dehydrogenase (GPD). However, once morphologic differentiation began, TGF‐β was ineffective in blocking differentiation. In addition, exposure of fully differentiated cells to TGF‐β for up to 72 hours caused no decrease of differentiation‐specific genes and even a 7‐day treatment caused no morphologic dedifferentiation. Tumor necrosis factor also had no detectable effect on fully differentiated cells.
Cyclic AMP potentiates bFGF‐induced neurite outgrowth in PC12 cells
Authors: Ho Paulo Lee , Raw Isaias 
Published: February 2005

AbstractWe report here that basic fibroblast growth factor (bFGF)‐elicited neurite outgrowth in PC12 cells is potentiated by dibutyryl cyclic adenosine monophosphate (dbcAMP) or forskolin. This property was also described for nerve growth factor (NGF), suggesting that both NGF and bFGF may share common intracellular events leading to neurite outgrowth and synergism with dbcAMP and forskolin. The synergistic effect of dbcAMP and forskolin is specific, since treatment of PC12 cells with bFGF and dibutyryl cyclic guanosine monophosphate (dbcGMP) or phorbol ester did not change the neurite outgrowth response of cells treated with bFGF alone. Furthermore, neurite outgrowth depends on cellular adhesion. Increasing adhesion by plate treatment with poly‐d‐lysine increases the neurite outgrowth elicited by bFGF alone or bFGF plus dbcAMP. On the other hand, decreasing cellular adhesiveness by plating PC12 cells in semi‐solid agarose renders the cells unable to develop neuritic processes. In addition, 3H‐methylthymidine incorporation studies showed that bFGF‐treated PC12 cells cease growth only when they become fully differentiated after 3–5 days of treatment. In contrast, dbcAMP, which is a poor differentiation factor, is able to block cellular growth after 24 hour treatment. These results suggest that when PC12 cells become differentiated, they stop growing. However, growth inhibition does not necessarily lead to differentiation.
Zinc transport into endothelial cells is a facilitated process
Authors: Bobilya Dennis J. , Briske‐Anderson Mary , Reeves Philip G. 
Published: February 2005

AbstractThe kinetics of zinc transport were examined by measuring the uptake of 65Zn into cultured endothelial cells. This served as a suitable model for characterizing the transport of zinc across a biological membrane (i.e., the plasma membrane). The transport process was saturable under physiological conditions, which indicates a facilitating transport mechanism. Within the physiological range of zinc concentrations, the maximum zinc transport rate was 27 pmoles zinc/(min × mg protein) and it was half maximal at 4.1 μM zinc. Cadmium competitively inhibited zinc transport (Ki = 6.5 μM), while equimolar concentrations of copper and manganese were ineffectual. The rate of zinc transport was substantially reduced at lower temperatures and in the presence of sulfhydryl blockers (sodium iodoacetate and N‐ethylmaleimide). Inhibitors of energy metabolism (2,4‐dinitrophenol and sodium azide) failed to disrupt zinc transport. These results demonstrate that zinc transport into endothelial cells is a facilitated process (i.e., it is carrier mediated and energy‐independent). © 1992 Wiley‐Liss, Inc.
Distinct effects of phorbol esters and exogenous diacylglycerols in the induction of murine thymocyte proliferation
Authors: Stoeck Michael , Howe Rawleigh C. , MacDonald H. Robson 
Published: February 2005

AbstractMurine thymocytes were stimulated with the protein kinase C activating agents Phorbol‐12‐myristate‐13‐acetate (PMA) or a more physiological membrane permeant diacylglycerol (dioctanoyl‐sn‐glycerol, DiC8) in the presence or absence of exogenous lymphokines (rlL‐1β, rlL‐2). Whereas PMA directly induced reactivity to rlL‐2, DiC8 did not but had to synergize with the calcium ionophore lonomycin. Expression of the p55 chain of the IL‐2 receptor behaved similarly. In the absence of exogenous rlL‐2, thymocytes proliferated in response to a combination of lonomycin and PMA; however, replacing PMA by a single addition of DiC8 did not result in proliferation. Stimulation with lonomycin plus repeated addition of DiC8 induced a low level of thymocyte proliferation and further addition of rIL‐1β resulted in a significant increase. Purified immature (L3T4−Lyt2−) thymocytes behaved similarly, but showed an increased sensitivity to rIL‐1β. Taken together, the data support the idea that PMA and the more physiological diacylglycerols do not possess totally equivalent activities in lymphocyte stimulation. © 1992 Wiley‐Liss, Inc.
Growth and motility of microvascular endothelium are modulated by the relative concentration of gangliosides in the medium
Authors: Alessandri G. , de Cristan G. , Ziche M. , Cappa A. P. M. , Gullino P. M. 
Published: February 2005

AbstractThe data reported were obtained as an attempt to understand whether the change in total concentration and relative ratios of the 3 major corneal gangliosides (GM3, GM2, GD3) previously observed in corneas stimulated by an angiogenic molecule (Ziche et al., 1989) was a relevant event in the angiogenic response of the tissue. The effect on endothelial cell growth was tested for the 3 corneal gangliosides added singly to the culture medium, and GM3 was found to possess a substantial growth inhibitory effect as compared to GM2 and GD3. The growthlimiting effect of GM3 was counteracted to a different degree by the addition of a second ganglioside to the culture medium. A mixture of GM3 + GM2 + GD3 in the proportion similar to that found in the cornea stimulated by an angiogenic molecule was able to sustain a sharp increment in cell growth and motility when added to cultures of capillary endothelium. On the contrary, when the 3 components of the mixture were in the proportion present in the normal cornea, the increment in growth or motility did not occur. A simple change in the relative proportions of the 3 gangliosides was sufficient to trigger or prevent an increment in growth and motility of the endothelial cells. These data in vitro suggest that the changes in concentration and relative ratios of the 3 major corneal gangliosides observed in vivo when the cornea was stimulated by an angiogenic molecule were an event targeted to favour growth and mobilization of the capillary endothelium located within the limbal vessels at the periphery of the cornea. © 1992 Wiley‐Liss, Inc.
Inhibition of heat shock gene expression does not block the development of thermotolerance
Authors: Bader Stephen B. , Price Brendan D. , Mannheim‐Rodman Laura A. , Calderwood Stuart K. 
Published: February 2005

AbstractAfter cells have been exposed to a nonlethal heat shock, they develop an enhanced resistance to subsequent prolonged heat shock. This process, termed thermotolerance, correlates with the expression of a group of proteins called the heat shock proteins. When cells are exposed to heat, protein synthesis is rapidly turned off and takes 5–6 hr to recover. In thermotolerant cells, protein synthesis is not blocked by heat. The heat shock proteins are thought to be responsible for the development of thermotolerance and the protection of the protein synthesis machinery from heat inactivation. To test the hypothesis that the heat shock proteins are involved in the heat shock response, we used two inhibitors to block their transcription and expression during heating and then monitored the effect on the development of thermotolerance and on protein synthesis. Camptothecin inhibits DNA topoisomerase I and blocks transcription of all actively transcribed genes, whereas dichloro‐D‐ribofuranosylbenzimidazole (DRB) inhibits only those genes transcribed by RNA polymerase II. Both DRB and camptothecin blocked the heat‐induced expression of the heat shock proteins, but the absence of these proteins did not block either the development of thermotolerance or the protection of protein synthesis after heating. The data indicate that thermotolerance can develop in the absence of new protein synthesis. © 1992 Wiley‐Liss, Inc.
Fibrin contact increases endothelial permeability to albumin
Authors: Lo Siu K. , Vecchio Peter J. Del , Lum Hazel , Malik Asrar B. 
Published: February 2005

AbstractWe studied the effects of contact of bovine pulmonary artery endothelial cell monolayers with fibrin on the endothelial barrier function. Fibrin formed by clotting purified fibrinogen (0.5 to 3.0 mg/ml) with α‐thrombin (1 U/ml) was added to endothelial monolayers and permeability measurements were made after fibrin removal. Fibrin incubation for 3 hours resulted in 2‐ to 5‐fold increases in transendothelial 125l‐albumin permeability. Permeability returned to baseline value within 3 hours after fibrin removal. Direct contact with fibrin was necessary for the response, since fibrin separated from the endothelium did not increase permeability. Contact with agarose (2 mg/ml) or fibrinogen (0.5 to 3.0 mg/ml) also did not increase endothelial permeability. Transmission electron microscopic examination indicated normal appearance of interendothelial junctions at a time when albumin permeability was increased and no overt evidence of endothelial injury. Incubation of fibrin with endothelial monolayers at 4°C prevented the increase in albumin permeability. We examined the possibility that increased albumin transcytosis was responsible for fibrin's effect using 14C‐sucrose (Mr = 342D), a lipid insoluble tracer. Fibrin increased sucrose flux by 1.5‐fold compared to 2‐to 5‐fold increases in albumin flux. The results indicate that fibrin contact with the endothelial cell increases endothelial permeability. The effect of fibrin may involve activation of temperature‐sensitive bulk phase transcytosis of albumin. © 1992 Wiley‐Liss, Inc.
Release of cell surface‐associated basic fibroblast growth factor by glycosylphosphatidylinositol‐specific phospholipase C
Authors: Bashkin Pnina , Neufeld Gera , Gitay‐Goren Hela , Vlodavsky Israel 
Published: February 2005

AbstractHeparan sulfate proteoglycans (HSPG) are ubiquitous constituents of mammalian cell surfaces and most extracellular matrices. A portion of the cell surface HSPG is anchored via a covalently linked glycosyl‐phosphatidylinositol (PI) residue, which can be released by treatment with a glycosyl‐PI specific phospholipase C (PI‐PLC). We report that exposure of bovine aortic endothelial and smooth muscle cells to PI‐PLC resulted in release of cell surface‐associated, growth‐promoting activity that was neutralized by antibasic fibroblast growth factor (bFGF) antibodies. Active bFGF was also released by treating the cells with bacterial heparitinase. Under the same conditions there was no release of mitogenic activity from cells (BHK‐21, NIH/3T3, PF‐HR9) that expressed little or no bFGF, as opposed to PI‐PLC‐mediated release of active bFGF from the same cells transfected with the bFGF gene. The released bFGF competed with recombinant bFGF in a radioreceptor assay. Addition of PI‐PLC to sparsely seeded vascular endothelial cells resulted in a marked stimulation of cell proliferation, but there was no mitogenic effect of PI‐PLC on 3T3 fibroblasts. Studies with exogenously added 125I‐bFGF revealed that about 6.5% and 20% of the cell surface‐bound bFGF were released by treatment with PI‐PLC and heparitinase, respectively. Both enzymes also released sulfate‐labeled heparan sulfate from metabolically labeled 3T3 fibroblasts. PI‐PLC failed to release 125I‐bFGF from the subendothelial extracellular matrix (ECM), as compared to release of 60% of the ECM‐bound bFGF by heparitinase. Our results indicate that 3–8% of the total cellular content of bFGF is associated with glycosyl‐PI anchored cell surface HSPG. This FGF may exert both autocrine and paracrine effects, provided that it is released by PI‐PLC and adequately presented to high affinity bFGF cell surface receptor sites. © 1992 Wiley‐Liss, Inc.
Stimulatory and inhibitory effects of catecholamines on DNA synthesis in primary rat hepatocyte cultures: Role of alpha1‐ and beta‐adrenergic mechanisms
Authors: Refsnes Magne , Thoresen G. Hege , Sandnes Dagny , Dajani Olav F. , Dajani Laila , Christoffersen Thoralf 
Published: February 2005

AbstractPrevious studies suggest that catecholamines may be involved in the regulation of liver growth. Considerable evidence implicates α1‐adrenergic mechanisms in the initiation of hepatocyte proliferation, while the role of β‐adrenoceptors is less clear. We have examined further the adrenergic regulation of hepatocyte DNA synthesis, using primary monolayer cultures. In hepatocytes that were also treated with epidermal growth factor and insulin, epinephrine or norepinephrine added early after the seeding strongly accelerated the rate of S phase entry. The β‐adrenergic agonist isoproterenol and the α‐adrenergic agonist phenylephrine also stimulated the DNA synthesis, but were less efficient than epinephrine and norepinephrine. Experiments with the α1‐receptor blocker prazosine and the β‐receptor blocker timolol showed that the stimulatory effect of norepinephrine consisted of both an α1‐ and a β‐adrenergic component. The α1‐component was most prominent in terms of maximal response at high concentrations of the agonist, but the β‐component contributed significantly and predominated at low concentrations (< 0.1 μM) of norepinephrine. At later stages (about 40 h) of culturing norepi nephrine strongly but reversibly inhibited the cells, acting at a point late in the G1 phase. This inhibition was mimicked by isoproterenol and abolished by timolol but was unaffected by prazosine, suggesting a β‐adrenoceptor‐mediated effect. The results confirm the α1‐adrenoceptor‐mediated stimulatory effect, but also show that β‐adrenoceptors may contribute to the growth stimulation by catecholamines. Furthermore, catecholamines, via β‐adrenoceptors and cyclic AMP, inhibit the G1‐S transition, and may thus play a role in the termination of hepatic proliferation. © 1992 Wiley‐Liss, Inc.
Modulation of tumor cell susceptibility to cytokine‐induced cell death by hormones, growth factors, and cell density
Authors: van der Bosch Jürgen , Horn Daniel , Rüller Stephan , Schlaak Max 
Published: February 2005

AbstractThe mechanisms controlling “spontaneous” cellular death rates in normal and tumorigenic tissues are largely unknown. An important parameter in this respect is the susceptibility of the target cell to induction of the lytic pathway by appropriate signals. In the present article it is demonstrated in a serum‐free in vitro system that the susceptibility of human tumor cells (TC) to induction of lysis by cytokine signals generated during interaction of TC with elutriated human monocytes (MO) is a highly dynamic parameter subject to modulation by hormones, growth factors, and tumor cell density. It was found that growth stimulatory signals such as insulin, and especially epidermal growth factor (EGF), increase lytic susceptibility, whereas hydrocortisone, which does not exert significant growth modulatory effects in these examples, protects TC against the induction of lysis. Increasing TC density above confluence dramatically enhances lytic susceptibility, suggesting interactions between TC to be involved in the induction of their death. In conjunction with previous data demonstrating the insusceptibility of TC, which are forced out of the cell cycle into the quiescent state (G0), the hypothesis is put forward that growth stimulatory factors increase a TC's lytic susceptibility by preventing its transit from G1 to G0 in response to growth inhibitory signals generated during MO/TC interaction. The data support the concept that TC susceptibility to the induction of cell death is a consequence of simultaneously activated growth stimulatory and growth inhibitory signalling pathways. © 1992 Wiley‐Liss, Inc.
Elevated cAMP is required for stimulation of eicosanoid synthesis by interleukin 1 and bradykinin in BALB/c 3T3 fibroblasts
Authors: Burch Ronald M. , Connor Jane R. 
Published: February 2005

AbstractIn Swiss 3T3, murine fibroblasts, interleukin 1 (IL‐1) and bradykinin stimulate prostaglandin E2 (PGE2) synthesis. However, in the present study, we found that neither agonist stimulated PGE2 synthesis in BALB/c 3T3 murine fibroblasts, this in spite of expression of similar numbers of receptors for each agonist compared to Swiss 3T3 cells. When BALB/c 3T3 cells were preincubated with cAMP analogs, both IL‐1 and bradykinin stimulated PGE2 synthesis to levels similar to those observed in Swiss 3T3 cells. Similarly, when the cells were preincubated with forskolin, which activates the catalytic subunit of adenylate cyclase directly, or NECA, which stimulates cellular cAMP accumulation by activating adenosine receptors, IL‐1 and bradykinin stimulated PGE2 synthesis. Rp‐cAMPS, an inhibitor of cAMP‐dependent protein kinase, blocked the ability of cAMP or NECA to render cells responsive to IL‐1 and bradykinin. In basal BALB/c 3T3 cells, bradykinin and IL‐1 stimulated arachidonate release in the absence of cAMP, but little conversion of released arachidonate to PGE2 occurred. cAMP, forskolin, and NECA all increased cyclooxygenase activity in the cells. SV‐T2 is a clonal line originating from BALB/c 3T3 transformed with SV‐40. In these cells, IL‐1 and bradykinin stimulated PGE2 svnthesis despite basal intracellular cAMP concentrations similar to BALB/c, and cAMP only modestly potentiated the response. In summary, cyclooxygenase expression appears to be regulated by cAMP in BALB/c 3T3 cells, and SV‐40 transformation results in increased cyclooxygenase expression, apparently independent of cAMP. © 1992 Wiley‐Liss, Inc.
Initial characterization of heat‐induced excess nuclear proteins in HeLa cells
Authors: Laszlo A. , Wright W. , Roti J. L. Roti 
Published: February 2005

AbstractExposure of mammalian cells to hyperthermia is known to cause protein aggregation in the nucleus. The presence of such aggregates has been detected as the relative increase in the protein mass that is associated with nuclei isolated from heated cells. We have characterized these excess nuclear proteins from the nuclei of heated HeLa cells by two‐dimensional gel electrophoresis. The abundance of cytoskeletal elements which co‐purify with the nuclei did not increase with exposure to hyperthermia, indicating that these proteins are not part of the excess nuclear proteins. In contrast, several specific polypeptides become newly bound or increase in abundance in nuclei isolated from heated cells. Members of the hsp 70 family were identified as a major component of the excess nuclear proteins. Among the other excess nuclear proteins we identified ten that had apparent molecular weights of 130, 95, 75, 58, 53, 48, 46, 37, 28, and 26 kilodaltons. Since hsp 70 is mainly cytoplasmic in non‐heated cells, its association with nuclei in heated cells indicates that one mechanism accounting for the heat‐induced excess nuclear proteins is the movement of cytoplasmic proteins to the nucleus. We also obtained evidence that increased binding of nuclear proteins is another mechanism for this effect. No overall increase or decrease in the phosphorylation of nuclear proteins was found to be associated with such altered binding or movement from the cytoplasm to the nucleus. © 1992 Wiley‐Liss, Inc.
Leukemia inhibitory factor/differentiation‐stimulating factor (LIF/D‐factor): Regulation of its production and possible roles in bone metabolism
Authors: Ishimi Yoshiko , Abe Etsuko , Jin Cheng He , Miyaura Chisato , Hong Mei Hua , Oshida Midori , Kurosawa Hisashi , Yamaguchi Yuri , Tomida Mikio , Hozumi Motoo , Suda Tatsuo 
Published: February 2005

AbstractLeukemia inhibitory factor/differentiation‐stimulating factor (LIF/D‐factor), expression of its mRNA, and possible roles in bone metabolism were studied in murine primary and clonal osteoblast‐like cells. Local bone‐resorbing factors such as IL‐1, TNFα, and LPS strongly induced expression of LIF/D‐factor mRNA in both clonal MC3T3‐E1 cells and primary osteoblast‐like cells. Neither parathyroid hormone nor 1α,25‐dihydroxyvitamin D3 stimulated expression of LIF/D‐factor mRNA. LIF/D‐factor per se did not stimulate expression of its own mRNA.Appreciable amounts of LIF/D‐factor were detected in synovial fluids from rheumatoid arthritis (RA) patients but not in those with osteoarthritis (OA). Simultaneous treatment with LIF/D‐factor, IL‐1, and IL‐6 at the concentrations found in synovial fluids from RA patients greatly enhanced bone resorption, though these cytokines did not stimulate bone resorption when separately applied. This suggests that LIF/D‐factor produced by osteoblasts is in concert with other boneresorbing cytokines such as IL‐1 and IL‐6 involved in the bone resorption seen in the joints of RA patients.LIF/D‐factor specifically bound to MC3T3‐E1 cells with an apparent dissociation constant of 161 pM and 1,100 binding sites/cell. LIF/D‐factor dose‐dependently suppressed incorporation of [3H]thymidine into MC3T3‐E1 cells. In addition, it potentiated the alkaline phosphatase activity induced by retinoic acid, though LIF/D‐factor alone had no effect on enzyme activity. These results suggest that LIF/D‐factor is involved in not only osteoclastic bone resorption but also osteoblast differentiation in conjugation with other osteotropic factors. © 1992 Wiley‐Liss, Inc.
Development of acute thermotolerance in 1929 cells: Lack of HSP28 synthesis and phosphorylation
Authors: Lee Yong J. , Hou Zi‐Zheng , Curetty Lindali , Borrelli Michael J. 
Published: February 2005

AbstractWe investigated the correlation between the development of acute thermotolerance and the phosphorylation, synthesis, and expression of the HSP28 family in murine L929 cells. Following heating at 43° for 30 min, thermotolerance developed rapidly in exponential‐phase cells and reached its maximum 4–9 h after heat shock. Maximal thermal resistance was maintained for 24 h and then gradually decayed. However, heat‐induced phosphorylation of HSP28 was not detected. Furthermore, HSP28 synthesis during incubation at 37°C for 12 h following heat shock was not detected by [3H]‐leucine labeling followed by two‐dimensional polyacrylamide gel electrophoresis. In addition, Northern blots failed to demonstrate expression of the HSP28 gene. Unlike HSP28, the expression of constitutive and inducible HSP70 genes, along with the synthesis of their proteins, was observed during incubation at 37° after heat shock. These results demonstrate that HSP28 synthesis and its phosphorylation are not required to develop acute thermotolerance in L929 cells. © 1992 Wiley‐Liss, Inc.