bluuebunny/crossref_metadata_2025_split huggingface dataset:
Interferon‐Gamma inhibits proliferation, but not commitment, of murine granulocyte‐macrophage progenitors
Authors: Koike Kenichi , Ma Feng , Shiohara Masaaki , Kubo Tetsuo , Takagi Mineo , Amano Yoshiro , Nakahata Tatsutoshi , Komiyama Atsushi 
Published: February 2005

AbstractWe investigated the effects of interferon γ (IFN‐γ) on the growth of murine hematopoietic progenitors. IFN‐γ inhibited granulocyte colony‐stimulating factor (G‐CSF)‐ and interleukin‐3 (IL‐3)‐dependent colony growth by granulocyte‐macrophage (GM) progenitors derived from the bone marrow cells of normal mice. However, the number of IL‐3‐dependent GM colonies formed by the bone marrow cells of 5‐fluorouracil (5‐FU)‐treated mice was not influenced by the addition of IFN‐γ. Replating experiments suggested that IFN‐γ suppressed GM colony growth directly and that it exerted an inhibitory effect on the proliferation, but not on the commitment, of GM progenitors. In contrast, IFN‐γ failed to suppress colony growth by mast cell progenitors. Erythroid and megakaryocytic progenitors exhibited different responses to IFN‐γ depending on mouse strains. These results suggest that potent negative regulators are not always inhibitors of hematopoietic progenitors. © 1992 Wiley‐Liss, Inc.
Coordinate regulation of mRNAs from multiple calmodulin genes during myoblast differentiation in vitro
Authors: Christenson Mark A. , Means Anthony R. 
Published: February 2005

AbstractMultiple genes encoding identical calmodulin molecules have been found in all mammalian species so far examined, but little is known regarding the factors involved in regulating the expression of this gene family. We have investigated the possibility of differential regulation under conditions of cell cycle withdrawal and differentiation in the nonfusing BC3H1 myoblast. Transcripts from the three genes are expressed in myoblasts and myocytes and each of the mRNA species decreases during BC3H1 differentiation. Calmodulin protein levels also decrease, although with distinct kinetics with respect to the mRNAs. Previous studies indicated that a decrease in transcription is involved (Epstein et al., Molecular Endocrinology 3:193–202, 1989). In this study, an increase in stability for each of the mRNA species is also shown to contribute to overall mRNA levels. The calmodulin mRNAs are also found to decrease under conditions of cell cycle withdrawal when differentiation is blocked. This demonstrates that the expression of mRNA from all three genes is directly coupled with the proliferation state but only indirectly with the differentiation state. Consistent with this, calmodulin expression decreases in serum deprived fibroblasts as they exit the cell cycle. © 1993 Wiley‐Liss, Inc.
Modulation of the epidermal growth factor receptor by basic fibroblast growth factor
Authors: Maher Pamela A. 
Published: February 2005

AbstractTreatment of Swiss 3T3 fibroblasts with basic fibroblast growth factor (bFGF) lead to a rapid reduction in epidermal growth factor (EGF) binding and a slower inhibition of EGF receptor autophosphorylation. The reduction in binding was due to a complete loss of the highest affinity EGF binding sites and a reduction in the lower affinity binding sites. Neither the inhibition of EGF binding nor the inhibition of EGF receptor autophosphorylation required protein kinase C. Treatment of cells with bFGF stimulated the phosphorylation of the EGF receptor, which persisted for several hours. The inhibition of EGF receptor autophosphorylation by bFGF was reduced in the presence of cycloheximide. However, cycloheximide had no effect on the reduction of EGF binding by bFGF. In contrast to these results with Swiss 3T3 fibroblasts, treatment of PC12 cells with bFGF lead to a reduction in EGF binding but no inhibition of EGF receptor autophosphorylation. Thus inhibited of EGF receptor autophosphorylation and inhibition of EGF binding can be uncoupled. © 1993 Wiley‐Liss, Inc.
Deregulation of granulocyte‐macrophage colony‐stimulating factor (GM‐CSF) receptor in murine macrophage cell line J774A.1
Authors: Fan Kai , Barendsen Nelleke , Sensenbrenner Lyle , Chen Ben D. M. 
Published: February 2005

AbstractJ774A.1 immortalized macrophage tumor cells display several phenotypes and functional capacities similar to that of murine peritoneal exudate macrophages (PEM). Both populations display comparable number of M‐CSF receptors. Yet the number of GM‐CSF receptors on J774A.1 cells is only one‐fourth that of PEM (1,500 vs. 6,000 per cell). Unlike J774A.1 cells, which constitutively express c‐myc transcripts, normal PEM required rMuGM‐CSF for the induction of c‐myc expression. Nevertheless, the growth of J774A.1 cells can be further enhanced in the presence of exogenous rMuGM‐CSF, rHuM‐CSF, and rMulL‐3. Treatment with either rMulL‐3 (20 ng/ml) and rHuTGF‐β1 (1.0 ng/ml) for 24 hr at 37°C, markedly enhanced the expression of GM‐CSF receptors on normal PEM but not leukemic J774A.1 cells. J774A.1 cells also did not respond by autologous upregulation of GM‐CSF receptors as seen in PEM following treatment with rMuGM‐CSF. Treatment with either pertussis toxin (20–100 ng/ml) or H‐8 (50 μM) for 24 hr led to an enhanced expression of GM‐CSF receptors on J774A.1 cells in a time‐and dose‐dependent manner but did not result in enhanced receptor expression on normal PEM. These findings suggest that the expression of GM‐CSF receptors may be regulated by mechanisms involving Gi‐and their downstream elements, which in turn are linked to regulatory pathways of other cytokine receptors. In J774A.1 cells, such regulatory interaction may not exist. © 1993 Wiley‐Liss, Inc.
Rapid and reversible tubulin tyrosination in human neutrophils stimulated by the chemotactic peptide, fMet‐Leu‐Phe
Authors: Rothwell Stephen W. , Nath Jayasree , Wright Daniel G. 
Published: February 2005

AbstractNeutrophil activation by specific stimuli, such as the oligopeptide chemotactic factor fMet‐Leu‐(fMLF), is associated with an increased enzymatic addition of tyrosine to tubulin α ‐subunits, as measured by 14C tyrosine uptake. In studies using immunoblots we have found that this increased tyrosine uptake into tubulin in activated neutrophils reflects an increase in the proportion of cellular tubulin that is tyrosinated rather than simply an increase in the turnover of tyrosinated subunits. However, the increased accumulation of tyrosinated tubulin was also found to follow an initial depletion of tyrosinated tubulin and concomitant increase in detyrosinated tubulin between 0 and 60 sec following stimulation of neutrophils with fMLF. Immunogold electron microscopy studies of intact micro tubules recovered from activated neutrophils demonstrated that these rapid changes in the relative content of tubulin isoforms in the cells were not associated with the formation or disappearance of microtubule microdomains composed of only one form of tubulin. Previously, we have shown that under conditions of fMLF‐stimulated exocytosis there is an increased binding of neutrophil granules to endogenous microtubules. Since neutrophil activation by fMLF is associated with increased tyrosination of α ‐tubulin subunits, we speculated that rapid changes in the levels of tyrosinated tubulin in the microtubules of activated neutrophils might have a role in the regulation of granule‐microtubule interactions. When the binding of purified neutrophil granules to reconstituted rat brain microtubules containing approximately 50% tyrosinated tubulin was measured by electron microscopy and compared with granule binding to microtubules that contained no detectable tyrosinated tubulin, granule‐microtubule associations were found to be significantly favored by detyrosinated vs. tyrosinated tubulin. These findings indicate that interactions between cytoplasmic granules and microtubules in activated neutrophils may be modulated by rapid changes in the relative content of detyrosinated and tyrosinated tubulin in the microtubule network of the cells. © 1993 Wiley‐Liss, Inc.
Strontium induces murine keratinocyte differentiation in vitro in the presence of serum and calcium
Authors: Li Luowei , Kruszewski Francis H. , Punnonen Kari , Tucker Robert W. , Yuspa Stuart H. , Hennings Henry 
Published: February 2005

AbstractPrimary mouse keratinocytes in culture are induced to terminally differentiate by increasing extracellular Ca2+ concentrations (CaO) from 0.05 mM to ≥ 0.1 mM. The addition of Sr2+ (≥ 2.5 mM) to medium containing 0.05 mM Ca2+ induces focal stratification and terminal differentiation, which are similar to that found after increasing the CaO to 0.12 mM. Sr2+ in 0.05 mM Ca2+ medium induces the expression of the differentiation‐specific keratins, keratin 1 (K1), keratin 10 (K10), and the granular cell marker, filaggrin, as determined by both immunoblotting and immunofluorescence. Sr2+ induces the expression of those differentiation markers in a dose dependent manner, with an optimal concentration of 5 mM. In the absence of Ca2+ in the medium, the Sr2+ effects are reduced, and Sr2+ is ineffective when both Ca2+ and serum are deleted from the medium. Sr2+ treatment increases the ratio of fluorescence intensity of the intracellular Ca2+ sensitive probe, fura‐2, indicating an associated rise in the level of intracellular free Ca2+ and/or Sr2+. At doses sufficient to induce differentiation, Sr2+ also increases the level of inositol phosphates in primary keratinocytes within 30 min. The uptake curves of 85Sr2+ by primary keratinocytes are similar to those of 45Ca2+. At low concentrations, the initial uptake of both 45Ca2+ and 85Sr2+ reaches a plateau within 1 hr; at higher concentrations, the uptake of both 45Ca2+ and 85Sr2+ increases continuously for 12 hr. In keratinocytes pre‐equilibrated with 45Ca2+ in 0.05 mM Ca2+ medium, Sr2+ causes an increase of 45Ca2+ uptake, which is dependent on the presence of serum. These results suggest that Sr2+ utilizes the same signalling pathway as Ca2+ to induce keratinocyte terminal differentiation and that Ca2+ may be required to exert these effects. © 1993 Wiley‐Liss, Inc.
Fibronectin promotes the elongation of microvessels during angiogenesis in vitro
Authors: Nicosia Roberto F. , Bonanno Elena , Smith Marion 
Published: February 2005

AbstractFibronectin is a component of the extracellular matrix of developing microvessels whose role in angiogensis is poorly understood. This study evaluated the effect of plasma fibronectin on angiogenesis in serum‐free collagen gel culture of rat aorta. Aortic explants embedded in collagen gels generated microvascular outgrowths. Fibronectin incorporated in the collagen gel promoted a selective dose‐dependent elongation of the newly formed microvessels without stimulating vascular proliferation. The fibronectin‐treated microvessels were longer due to a proportional increase in the number of microvascular cells. However, fibronectin had no effect on microvascular DNA synthesis and mitotic activity. Fibronectin stimulated microvascular length also in cultures in which mitotic activity was suppressed and angiogenesis was markedly reduced by pretreating the aortic explants with mitomycin C. The synthetic peptide Gly‐Arg‐Asp‐(GRGDS), which competes for the binding of fibronectin to its cell receptors and inhibits the adhesion of endothelial cells to substrates, arrested the elongation of developing microvessels causing regression and inhibition of angiogenesis. Conversely, Gly‐Arg‐Glu‐(GRGES), which lacks the RGD sequence, had no inhibitory effect. These data support the hypothesis that fibronectin promotes angiogenesis and suggest that developing microvessels elongate in response to fibronectin as a result of an adhesion‐dependent migratory recruitment of endothelial cells that does not require increased cell proliferation. © 1993 Wiley‐Liss, Inc.
Activation of the Ca2+ “receptor” on the osteoclast by Ni2+ elicits cytosolic Ca2+ signals: Evidence for receptor activation and inactivation, intracellular Ca2+ redistribution, and divalent cation modulation
Authors: Shankar Vijai S. , Bax Christopher M. R. , Bax Bridget E. , Alam A. S. M. Towhidul , Moonga Baljit S. , Simon Bruce , Pazianas Michael , Huang Christopher L.‐H. , Zaidi Mone 
Published: February 2005

AbstractEarlier studies have demonstrated that a high (mM) extracellular Ca2+ concentration triggers intracellular [Ca2+] signals with a consequent inhibition of bone resorptive activity. We now report that micromolar concentrations of the divalent cation, Ni2+, elicited rapid and concentration‐dependent elevations of cytosolic [Ca2+]. The peak change in cytosolic [Ca2+] increased monotonically with the application of [Ni2+] in the 50–5,000 μM range in solutions containing 1.25 mM‐[Ca2+] and 0.8 mM‐[Mg2+]. The resulting concentration‐response function suggested Ni2+‐induced activation of a single class of binding site (Hill coefficient = 1). The triggering process also exhibited a concentration‐dependent inactivation in which conditioning Ni2+ applications in the range 5–1,500 μM‐[Ni2+] inhibited subsequent responses to a maximally effective [Ni2+] of 5,000 μM. Ni2+‐induced cytosolic [Ca2+] responses were not dependent on extracellular [Ca2+]. Thus, when 5,000 μM‐[Ni2+] was applied to osteoclasts in Ca2+‐free, ethylene glycol bis‐(aminoethyl ether) tetraacetic acid (EGTA)‐containing medium (≤5 nM‐[Ca2+] and 0.8 mM‐[Mg2+]), cytosolic [Ca2+] responses resembled those obtained in the presence of 1.25 mM‐[Ca2+]. Prior depletion of intracellular Ca2+ stores by ionomycin prevented Ni2+‐induced cytosolic [Ca2+] responses, suggesting a major role for intracellular Ca2+ redistribution in the response to Ni2+. The effects of Ni2+ were also modulated by the extracellular concentration of the divalent cations, Ca2+ and Mg2+. When these cations were not added to the culture medium (0 μM‐[Ca2+] and [Mg2+]), even low [Ni2+] ranging between 5 pM and 50 μM elicited progressively larger cytosolic [Ca2+] transients. However, the response magnitude decreased at higher, 250–5,000 μM‐[Ni2+], resulting in a “hooked” concentration‐response curve. Furthermore, increasing extracellular [Mg2+] or [Ca2+] (0–1 mM) diminished the response to 50 μM‐[Ni2+], a concentration on the rising phase of the “hook.” Similar increases (0–10 mM) in extracellular [Mg2+] or [Ca2+] increased the response to 5,000 μM‐[Ni2+], a concentration on the falling phase of the “hook”. These findings are consistent with the existence of a membrane receptor strongly sensitive to Ni2+ as well as the divalent cations, Ca2+ and Mg2+. Receptor occupancy apparently activates intracellular Ca2+ release followed by inactivation. Furthermore, repriming is independent of intracellular Ca2+ stores, suggesting that such inactivation operates at a transduction step between receptor occupancy and intracellular Ca2+ release. © 1993 Wiley‐Liss, Inc.
Regulation of insulin‐like growth factor‐II expression and its role in autocrine growth of human neuroblastoma cells
Authors: Martin D. M. , Feldman E. L. 
Published: February 2005

AbstractInsulin‐like growth factor‐II (IGF‐II) is highly expressed in fetal tissues and may act as an autocrine growth factor during early embryogenesis. The SH‐SY5Y human neuroblastoma cell line also expresses IGF‐II and its receptors and responds to exogenous IGF‐II with increased DNA synthesis, cell division, and neuritic outgrowth. For this study, we tested the hypothesis that IGF‐II mediates autocrine growth of SH‐SY5Y cells in serum‐free media. SH‐SY5Y cells plated at high densities proliferated in serum‐free media, whereas sparsely plated cells did not. IGF‐II mRNA levels increased within 24 hours of serum deprivation and were associated with increased immunoreactive IGF‐II protein. Exogenous addition of IGF‐II increased 3H‐TdR incorporation and cell number in a dose‐ and time‐dependent fashion. By nuclear labelling experiments using 5‐Bromo‐2′ deoxyuridine (BrdU), we detected a twofold higher percentage of S phase nuclei after a 24‐hour incubation in IGF‐II. Treatment of SH‐SY5Y cells with anti‐IGF‐II antibodies in serum‐free media inhibited cell proliferation, and this inhibition was partially overcome by the addition of increasing concentrations of IGF‐II. Collectively, our results indicate that IGF‐II mediates an autocrine growth mechanism in SH‐SY5Y cells that is associated with increased IGF‐II expression. © 1993 Wiley‐Liss, Inc.
Autocrine/paracrine regulation of keratinocyte urokinase plasminogen activator through the TGF‐α/EGF receptor
Authors: Jensen Pamela J. , Rodeck Ulrich 
Published: February 2005

AbstractTransforming growth factor‐α (TGF‐α) appears to be an important autocrine/paracrine regulator of keratinocyte function. Not only does TGF‐α induce keratinocyte proliferation and migration in vitro, but it also has been detected in normal human epidermis and at elevated levels in hyperproliferative epidermis. In the present study we report that exogenous TGF‐α increases urokinase‐type plasminogen activator (uPA) in cultured human keratinocytes. Furthermore, in the absence of exogenous growth factors, the “basal” levels of uPA are decreased by an antagonist monoclonal antibody to the receptor shared by TGF‐α and epidermal growth factor (EGF). These results suggest that an endogenous factor serves as an autocrine/paracrine regulator of keratinocyte uPA. We hypothesize that activation of the TGF‐α/EGF receptor may coordinately regulate the keratinocyte response to cutaneous wounding, which includes enhanced uPA expression, migration, and proliferation. © 1993 Wiley‐Liss, Inc.
Mevalonate controls cytoskeleton organization and cell morphology in thyroid epithelial cells
Authors: Bifulco Maurizio , Laezza Chiara , Aloj Salvatore M. , Garbi Corrado 
Published: February 2005

AbstractBlockade of mevalonate synthesis by the 3‐hydroxy‐3‐methylglutaryl Coenzyme A reductase inhibitor mevinolin (lovastatin) causes FRTL‐5 thyroid cells to undergo significant morphological changes; these include a transition from a flat, polygonal to a round shape, the development of cytoplasmic arborizations, and the loss of contact between neighboring cells. Immunofluorescence studies of cytoskeletal structures show that, at early times after administering the drug, and before the round phenotype develops, stress fibers disassemble while the peripheral actin filaments, which are adjacent to the cytoplasmic face of the plasma membrane, appear largely unaffected. Subsequently, when this cortical actin network becomes fragmented, cells start to round up and become separated from neighbors. Microtubules become disconnected from the plasma membrane and retract toward the cell center, although they do not appear depolymerized; indeed, at this stage, cytoplasmic elongations contain mostly intact microtubules. After exposure to mevinolin FRTL‐5 cells also lose vinculin‐related substrate contacts. Treatment of cells with either cycloheximide or colchicine abolishes morphological changes induced by mevinolin, suggesting that ongoing protein synthesis and microtubule integrity are prerequisites for the drug to be effective. Both cytoskeletal and morphological perturbations can be reversed by mevalonate, but not by cholesterol or the non‐sterol derivatives of mevalonate such as dolichol, ubiquinone, and isopentenyladenine, individually or in combination. It is suggested that mevalonate deficiency may impair formation of isoprenylated proteins important for cytoskeletal organization and stability. © 1993 Wiley‐Liss, Inc.
Growth state‐regulated expression of p52(PAI‐1) in normal rat kidney cells
Authors: Ryan Michael P. , Higgins Paul J. 
Published: February 2005

AbstractIn normal rat kidney (NRK) cells, synthesis of the 52‐kDa substrate‐associated type 1 inhibitor of plasminogen activator [p52(PAI‐1)] is linked to alterations in cell shape and substrate adhesion. Subconfluent NRK cells accumulated significantly more ventral undersurface‐associated p52(PAI‐1) compared to newly confluent or 1 ‐ to 2‐day postconfluent cultures, suggesting that p52(PAI‐1) expression was also growth state‐modulated. Since cytoarchitectural constraints function in cell growth control, changes in p52(PAI‐1) synthesis were assessed with respect to defined morphologic events that accompany growth activation of cultured NRK cells. Stimulation of low population density, quiescent NRK cells with 20% serum‐containing medium resulted in a rapid increase in matrix p52(PAI‐1) protein content (6‐ and 26‐fold after 1 and 5 hr, respectively). Growth activation in response to serum reflected elevations in p52(PAI‐1) cytoplasmic mRNA abundance, which peaked at 2 hr (125‐fold increase) and subsequently declined (100‐fold increase) at 5 hr poststimulation. Morphologic analysis indicated that quiescent NRK cells were devoid of transcytoplasmic actin filaments and focal contact‐associated vinculin. A marked increase in the fraction of cells that eleborated transcytoplasmic microfilaments and vinculin‐containing focal adhesions was evident within 5 min of serum addition. Such cytoarchitectural restructuring preceded p52(PAI‐1) induction. Morphologic reorganization and p52(PAI‐1) induction occurred prior to progression of cells through the S‐phase, indicating they are early events associated with serum stimulation in the NRK cell system. The relevance of p52(PAI‐1) induction during this growth state transition is not clear but may influence the established cytoarchitectural changes observed prior to p52(PAI‐1) induction by regulating pericellular proteolysis and, thereby, cell‐to‐substrate adhesion. © 1993 Wiley‐Liss, Inc.
Regulation of polyamine transport by polyamines and polyamine analogs
Authors: Kramer D. L. , Miller J. T. , Bergeron R. J. , Khomutov R. , Khomutov A. , Porter C. W. 
Published: February 2005

AbstractRegulation of polyamine transport in murine L1210 leukemia cells was characterized in order to better understand its relationship to specific intracellular polyamines and their analogs and to quantitate the sensitivity by which it is controlled. Up‐regulation of polyamine uptake was evaluated following a 48‐hr treatment with a combination of biosynthetic enzyme inhibitors to deplete intracellular polyamine pools. The latter declined gradually over 48 hr and was accompanied by a steady increase in spermidine (SPD) and spermine (SPM) transport as indicated by rises in Vmax to levels ∼4.5 times higher than control values. Restoration of individual polyamine pools during a 6‐hr period following inhibitor treatment revealed that SPD and SPM uptake could not be selectively affected by specific pool changes. The effectiveness of individual polyamines in reversing inhibitor‐induced stimulation of uptake was as follows: putrescine < SPD < SPM = the SPM analog, N1, N12‐bis(ethyl)spermine (BESPM). In contrast to stimulation of transport, down‐regulation by exogenous polyamines or analogs occurred rapidly and in response to subtle increases in intracellular pools. Following a 1‐hr exposure to 10 μM BESPM, Vmax values for SPD and SPM fell by 70%, whereas the analog pool increased to only 400–500 pmol/106 cells—about 15–20% of the total polyamine pool (∼2.8 nmol/106 cells). SPM produced nearly identical regulatory effects on transport kinetics. Both BESPM and SPM were even more effective at down‐regulating transport that had been previously stimulated four to fivefold by polyamine depletion achieved with enzyme inhibitors. A dose response with BESPM at 48 hr revealed a biphasic effect on uptake whereby concentrations of analog < 3 μM produced an increase in SPD and SPM Vmax values, whereas concentrations 3 μM and higher produced a marked suppression of these values. Cells treated with 3 μM BESPM for 2 hr and placed in analog‐free medium recovered transport capability in only 3 hr. Thus, whereas stimulation of polyamine transport is a relatively insensitive and slowly responsive process that tends to parallel polyamine depletion, down‐regulation of polyamine transport by exogenous polyamines and analogs and its reversal are rapidly responsive events that correlate with relatively small (i.e., 15–20%) changes in intracellular polyamine pools.