bluuebunny/crossref_metadata_2025_split huggingface dataset:
Characterization of human megakaryocytic colony formation in human plasma
Authors: Solberg L. A. , Jamal N. , Messner H. A. 
Published: February 2005

AbstractWe have analysed the contribution to megakaryocyte colony formation in methylcellulose made by human plasma, serum, media conditioned by phytohemagglutinin (PHA) stimulated leukocytes (PHA‐LCM), erythropoietin (EPO) preparations, and platelets. The culture system was used as a bioassay for megakaryocyte colony stimulating activity (Meg‐CSA) in plasma samples of patients with perturbed megakaryocytopoiesis. Preparations of heparinized platelet‐poor plasma yielded the most consistent results. Platelet‐poor plasma of normal subjects will at best facilitate the occasional growth of small megakaryocyte colonies. Colony frequency and size are reproducibly enhanced in the presence of PHA‐LCM as a source of exogenous Meg‐CSA. Commercially available EPO preparations may vary in their content of activities that influence megakaryocyte colony formation. Addition of these preparations to cultures that contain plasma and PHA‐LCM usually does not enhance colony formation. In contrast to platelet‐poor plasma, platelet rich plasma and serum are less supportive of megakaryocyte colony growth. It is suggested that this loss of activity may be related to the release of inhibitors by activated platelets or alternatively caused by absorption of activities by platelets. Plasma samples from patients with megakaryocytopoietic dysfunction may contain components that promote colony formation without addition of PHA‐LCM or EPO. This phenomenon is consistently observed for patients with severe aplastic anemia and bone marrow transplant recipients after completion of their ablative preparative regimen.
Epidermal growth factor promotes the chemotactic migration of cultured rat intestinal epithelial cells
Authors: Blay Jonathan , Brown Kenneth D. 
Published: February 2005

AbstractThe RIE‐1 cell line is an untransformed, epithelial cell line derived from the rat small intestine. We report that epidermal growth factor (EGF), which regulates the proliferation of RIE‐1 cells, also directs their movement. We measured cell migration through gelatin‐coated filters in blind‐well Boyden chambers. The migration of RIE‐1 cells was stimulated up to ˜ 100‐fold by EGF, with a half‐maximal response at 1–2 ng/ml and a maximal effect at 10 ng/ml. Further analysis showed that the RIE‐1 cells responded directionally to a gradient of EGF in solution. Other growth factors tested did not stimulate RIE‐1 cell migration, and EGF did not stimulate the migration of fibroblasts in this assay. We conclude that EGF is a potent and specific chemo‐attractant for RIE‐1 intestinal epithelial cells and suggest that EGF might influence epithelial cell migration in vivo.
Permissive role of interleukin 3 (IL‐3) in proliferation and differentiation of multipotential hemopoietic progenitors in culture
Authors: Suda Toshio , Suda Junko , Ogawa Makio , Ihle James N. 
Published: February 2005

AbstractWe studied the effects of interleukin‐3 (IL‐3) on colony formation by hemopoietic progenitors in methylcellulose cultures of spleen cells from 5‐fluorouracil (FU)‐treated mice. Purified IL‐3 supported the growth of various types of multilineage colonies including blast cell colonies. The types of colonies were similar to those supported by pokeweed‐mitogen spleen cell conditioned medium (PWM‐SCM), except that IL‐3 supported eosinophil and neutrophil expression better. Delayed addition of IL‐3 to cultures 7 days after cell plating decreased the number of colonies to one‐half the number in cultures with IL‐3 added on day 0. It did not alter the proliferative and differentiation characteristics of late emerging multipotential blast cell colonies. These observations suggest that IL‐3 does not trigger hemopoietic progenitors into active cell proliferation but is necessary for their continued proliferation. This permissive role of IL‐3 is consistent with a stochastic model of stem cell proliferation which features random entry into cell cycle. IL‐3 also supported the growth of multilineage colonies from single cells isolated from blast cell colonies by micromanipulation. This result shows that IL‐3 acts directly on multipotential progenitors. Analysis of colonies derived from paired progenitors revealed disparate lineage expression and was in accordance with the stochastic model of stem cell differentiation.
Induction of DNA polymerase α in senescent cultures of normal and Werner's syndrome cultured skin fibroblasts
Authors: Pendergrass W. R. , Saulewicz A. C. , Salk D. , Norwood T. 
Published: February 2005

AbstractDNA polymerase α activity was determined following serum stimulation of early and late passages of human diploid fibroblast‐like (HDFL) cultures derived from apparently normal donors (two strains) and from a patient with Werner's syndrome (one strain). Induction of this enzyme was observed in both low passage, actively proliferating cultures and in postmitotic “senescent” cultures from all three strains. The maximal polymerase activity of early and late passage cells of each strain were nearly identical when normalized to the number of cells present. However, the activity of the enzyme was observed to be significantly lower in late passage cultures when normalized to total protein content apparently because of enlargement of the senescent cells. The behavior of Werner derived cells was similar to that of the normal cells. The induction of DNA polymerase α in senescent cultures indicates that they retain the capacity to carry out some complex metabolic responses to mitogen stimulation. In addition, these results suggest the possibility that dilution of DNA polymerase α and/or other DNA replication factors may play a role in the onset or maintenance of the postmitotic state in the enlarged senescent HDFL cells.
The possible cyclic AMP‐dependence of an early prereplicative event that determines mitosis in regenerating rat liver
Authors: Rixon R. H. , Whitfield J. F. 
Published: February 2005

AbstractThe β‐adrenergic blocker dl‐propranolol prevented a large proportion of regenerating rat liver cells from entering the mitotic phase of their first cell divisions cycle without affecting their ability to initiate or complete DNA replication. The drug, at a dose of 20 or 50 mg/kg of body weight, was most effective in reducing mitosis when injected between 1 and 2 hours after the proliferatively activating partial hepatectomy, which was 22 to 23 hours before the peak of DNA‐synthetic activity. Propranolol also inhibited the early prereplicative surge of total liver cyclic AMP, which occurs shortly after partial hepatectomy, but this effect was not correlated to the mitosis‐inhibiting activity. However, cyclic AMP or dibutyryl cyclic AMP completely reversed propranolol's mitosis‐inhibiting action when injected between 1.5 and 2 hours (but not sooner or later) after partial hepatectomy, which was just before the total liver cyclic AMP content began to rise. Thus, there appears to be a transient, propranolol‐inhibitable, probably cyclic AMP‐initiated event in the early prereplicative development of rat hepatocytes that determines entry into mitosis rather than the initiation of DNA replication.
The mechanism of iron uptake by the rat placenta
Authors: McArdle Harry J. , Douglas Andrea J. , Bowen Barbara J. , Morgan Evan H. 
Published: February 2005

AbstractThe mechanism of iron uptake from transferrin by the rat placenta in culture has been studied. Transferrin endocytosis preceded iron accumulation by the cells. Both transferrin internalisation and iron uptake were inhibited by low temperature. Transferrin endocytosis was less susceptible to the effects of metabolic inhibitors such as sodium fluoroacetate, potassium cyanide, 2,4, dinitrophenol or carbonylcyanide M‐chlorophenyl hydrazone (CCCP) than was iron uptake. Iron accumulation was decreased if the cells were incubated in the presence of weak bases such as chloroquine or ammonium chloride. These results suggest that, following internalisation, the vesicles containing the transferrin and iron became acidified, and that this acidification was a necessary prerequisite for the accumulation of iron by the cell. Further, the results indicate that the intravesicular pH was maintained at the expense of metabolic energy, suggesting that a pump may be involved. The importance of the permeability properties of the vesicle membrane in the iron uptake process was investigated by incubating the cells with labelled transferrin and iron in the presence of different cation and anion ionophores. Irrespective of the normal cation that the ionophores carried, all inhibited iron uptake without altering transferrin levels. In contrast, phloridzin, a Cl‐ transport inhibitor, did not affect either the levels of transferrin within the cells or the amount of iron accumulated.
Adenosine receptor‐mediated changes in cyclic AMP production and DNA synthesis in cultured arterial smooth muscle cells
Authors: Jonzon Bror , Fredholm Bertil B. , Nilsson Jan 
Published: February 2005

AbstractThe effects of adenosine and two analogs, L‐phenylisopropyladenosine (L‐PIA) and 5′‐N‐ethylcarboxamidoadenosine (NECA), on cAMP production and on platelet‐derived growth factor (PDGF)‐stimulated initiation of DNA synthesis in growth‐arrested cultures of rat arterial smooth muscle cells (SMC) were studied. The intracellular cAMP concentration was dose‐dependently enhanced by micromolar concentrations of adenosine and its analogs, with the potency order NECA > adenosine > L‐PIA. The effect was antagonized, in a competitive manner, by the adenosine receptor antagonist 8‐phenyltheophylline (8‐PT). The stimulatory effect of adenosine was enhanced by 3 μM dipyridamole an adenosine‐uptake blocker. DNA synthesis was inhibited in a parallel manner, showing the same potency order. The inhibition was antagonized by 8‐PT. Forskolin, a diterpene with the ability to stimulate the catalytic unit of adenylate cyclase and thereby cAMP formation, potentiated the effects of micromolar concentrations of NECA and L‐PIA. Forskolin, by itself, stimulated cAMP production and inhibited DNA synthesis. The forskolin‐stimulated increase in cAMP was inhibited by L‐PIA at nanomolr concentrations. L‐PIA in the nanomolar concentration range also stimulated DNA synthesis when initiation was stimulated with suboptimal concentrations of PDGF. These findings suggest the presence of adenosine receptors of both the A1‐ and A2‐subtype on SM‐mediating bidirectional changes of cAMP and DNA synthesis.
Partial purification of a low‐molecular‐weight growth factor from chicken brain
Authors: Carlone Robert L. , Rathbone Michel P. 
Published: February 2005

AbstractThe regenerating amphibian limb serves as a useful model for studying factors influencing cell proliferation and differentiation. In particular, peripheral nerves are thought to provide a stimulus for growth of the blastema, presumably via the elaboration of an as yet unidentified neurotrophic factor. In the present study, pressure ultrafiltration coupled with chromatofocusing have proven to be effective methods of partially purifying a neurotrophic factor from adult chicken brains. This chick brain growth factor (CBGF) appears to be a heat‐stable, basic peptide of low molecular weight (<6,000). It is a potent mitogen in vitro, at nanomolar concentrations, for both blastema cells and Swiss mouse 3T3 fibroblasts. CBGF is apparently distinct from other peptide mitogens and/or neuromodulators that have been reported to stimulate blastema growth in vivo and in vitro. These include substance P, FGF from bovine brain and pituitary, EGF, transferrin (sciatin), and spinal cord growth factor (SCGF). The possible relationship of CBGF to other neural regulatory molecules is discussed.
125I‐EGF binding to responsive and nonresponsive cells in culture: Loss of cell‐associated radioactivity relates to growth induction
Authors: Schaudies R. Paul , Harper Robert A. , Savage C. Richard 
Published: February 2005

AbstractA comparison of the binding and overall processing of epidermal growth factor (EGF) was made in ten mammalian fibroblast‐like and three epithelial‐like cell lines. EGF stimulated the growth of five fibroblastic cell lines (132 to 224%) after 10 days in the constant presence of EGF and were termed “responsive”. Eight of the lines did not respond or were growth inhibited by EGF (−64 to + 21%) and were listed as “nonresponsive”. Both “responsive” and “nonresponsive” cell lines possessed specific saturable membrane receptors for EGF, but no consistent differences were found between the number of apparent receptors per cell or the concentrations of 125I‐EGF required for half maximal binding. However, a consistent difference between the “responsive” and “nonresponsive” cell lines was observed when the amount of cell associated 125I‐labeled EGF was measured as function of incubation time at 37°C in the constant presence of the hormone. In every cell line we classified as responsive, the binding of 125I‐EGF reached a maximum after 30 minutes incubation at 37°C and the cell associated radiolabel subsequently decreased by 42‐68% within 4 hours. In contrast, the “nonresponsive” cell lines required 1‐2 h to reach maximal binding and showed a minimal decrease of 1–10% during the 4‐h period. These data indicate that a variety of different cell lines can possess receptors with similar binding properties but process EGF in a dissimilar manner. This difference in processing may reflect the specific events which are necessary for the induction of cell growth.
Growth factor production during multistage transformation of epithelium in vitro. I. Partial purification and characterisation of the factor(s) from a fully transformed epithelial cell line
Authors: Wigley Caroline B. , Trejdosiewicz Ludwik K. , Southgate Jennifer , Coventry Ruth , Ozanne Brad 
Published: February 2005

AbstractTransforming growth factor (TGF)‐like activity is characterised from one of a series of salivary epithelial cell lines, CSG 211, chemically transformed in vitro. In this transformation system, we can demonstrate multiple stages in the acquisition of a malignant phenotype by normal diploid ductal epithelial cells from male mouse submandibular gland. The fully transformed, tumorigenic cell TGF‐like activity in serum‐free supernatants resembles no other well‐characterised growth factor and has an apparent molecular weight (Mr) of 14 kd. There is also evidence of a higher Mr activity, which is separable by anion exchange chromatography. We show that the premalignant, nontumorigenic progenitor cells of this line do not produce demonstrable TGF‐like activity and that this property is therefore acquired as CSG 211 cells become carcinoma producing.
Expression of tracheal differentiated functions in serum‐free hormone‐supplemented medium
Authors: Wu Reen , Nolan E. , Turner C. 
Published: February 2005

AbstractMost dissociated airway epithelial cells in culture express few of their in vivo functions and only to a limited degree. In this report, we demonstrate that hamster tracheal epithelial (HTE) cells cultured on a collagen gel substratum in a serum‐free hormone‐supplemented medium differentiate to cilia‐beating and mucus‐secreting cell types. The medium is Ham's F‐12 supplemented with insulin, epidermal growth factor, transferrin, hydrocortisone, cholera toxin, bovine hypothalamus extract, and vitamin A. Under these culture conditions, HTE cells exhibit a growth rate of 24 h/population doubling and reach confluency, at a density of 2–5 × 104 cells/cm2, within 2 weeks. Both the collagen gel substratum and vitamin A of this culture system are important to the growth and differentiation of HTE cells in vitro. Evidence of HTE cell differentiation has been obtained at both the ultrastructural and the histochemical levels. In addition, a variety of biochemical studies (gel filtration, ion exchange column chromatography, enzyme digestion, nitrous acid treatment, and composition analysis) indicate the production of mucin‐like glycoprotein in the HTE cultures. The levels of mucin‐like glycoprotein were found to closely correlate with the histochemically quantitated levels of the mucous cell type. Kinetic studies demonstrate that HTE cells rapidly lose their differentiated features during the attachment stage of primary culture but redifferentiation occurs after the cultures reach confluency. The ability of HTE cells to grow and differentiate in this serum‐free culture system in the absence of other cell types should greatly facilitate the study of mucociliary functions in vitro.
Human spreading factor: Synthesis and response by HepG2 hepatoma cells in culture
Authors: Barnes David W. , Reing Janet 
Published: February 2005

AbstractHuman serum spreading factor (SF) is a cell adhesion and spreading‐promoting glycoprotein purified from serum or plasma that mediates effects in a wide variety of animal cell culture systems. HepG2 human hepatoma cells were found to synthesize and secrete SF into culture medium. Quantitative immunoassay of the protein indicated a concentration of about 1 μg/ml in 48 hr‐conditioned medium from confluent cultures. Although fibronectin also was synthesized and secreted into the culture medium, HepG2 cell spreading was observed in response to human serum SF, but not in response to human plasma fibronectin. Immunoprecipitation of SF from culture medium of cells metabolically‐labeled with leucine, fucose or glucosamine identified a single from of the molecule of approximately 70,000 daltons. Treatment of cultures with tunicamycin inhibited incorporation of fucose and glucosamine into immunoprecipitated SF, but did not prevent synthesis and secretion of the protein. Electrophoretic analysis and cell spreading assays showed that SF secreted by tunicamycin‐treated HepG2 cells was of molecular weight (mw) approximately 60,000, and was biologically active.
Reversible effects of dibutyryl cAMP on laminin and type IV collagen secretion from retinoic acid treated F9 cells
Authors: Morita Akihito , Kitagawa Yasuo , Sugimoto Etsuro 
Published: February 2005

AbstractThe effects of dibutyryl cAMP on the differentiation of embryonal carcinoma F9 cells were studied mainly using the secretion of laminin and type IV collagen as the marker. For this purpose, F9 cells were labeled with 35Smethionine and radioactive proteins in the medium were analyzed by SDS‐polyacrylamide gel electrophoresis. Treatment of F9 cells with retinoic acid alone induced differentiation into cells secreting type IV collagen. The combination of retinoic acid and dibutyryl cAMP stimulated laminin secretion in addition to type IV collagen secretion. This effect of dibutyryl cAMP was observed only 16 h after adding dibutyryl cAMP. Immunofluorescence staining demonstrated that the majority of the cells in culture were converted into cells secreting laminin under these conditions. In contrast to the irreversible effect of retinoic acid, the effect of dibutyryl cAMP on laminin and type IV collagen secretion was reversible at least during the first 5 days of maintaining cells in the medium containing retinoic acid plus dibutyryl cAMP. Removal of dibutyryl cAMP from the culture medium decreased the protein secretion to the basal levels within 2 days. This reversibility was not due to a change in cell number. An in vitro translation assay also suggested the reversible effect of dibutyryl cAMP on the levels of laminin mRNA. Coinciding with variations of the protein secretion, a reversible and homogeneous change in the morphology of retinoic acid generated F9 cells was observed by dibutyryl cAMP.
Glucocorticoid receptors and cell cycle progression in human melanoma cell lines
Authors: Osman A.‐M. , Jansen P. W. M. , Smets L. A. , Benckhuijsen C. 
Published: February 2005

AbstractProliferation of six established human melanoma cell lines was inhibited after treatment for 1 h with a high dose of glucocorticoid. Four of the lines with the capacity of colony formation were used to quantify final plating efficiency. Specific glucocorticoid binding sites in these cell lines ranged from 51,000 to 170,000 sites per cell as measured with a whole‐cell assay. Growth inhibition was completely reversible in one cell line, irreversible in another, and partially reversible in two lines. Receptor content er cell correlated with the reduction in final plating efficiency of glucocorticoid‐treated cells, suggesting a receptor‐mediated event. A more than 90% growth inhibition and a 40% reduction in cell survival in the most sensitive cell line, M‐5A, was accompanied by a dual blockage in G1 and G2/M phase that lasted till at least 96 h after treatment with 2.5 μM dexamethasone for 1 h. Evidence is presented of a real arrest of M‐5A cells in G1 phase and a markedly retarded progression through G2; the blockage of G1‐S transition was immediate and complete. Accumulation of G1 cells was observed in two other cell lines but was inconsistent in the fourth line studied by fiow cytometry; in none of the three cell lines was G2/M accumulation observed. Stimulated melanogenesis after glucocorticoid treatment of M‐5A and NKI‐26 cells suggested differentiation of the cells during glucocorticoid‐induced arrest.
Neurite formation by neuroblastoma‐glioma hybrid cells (NG108–15) in defined medium: Stochastic initiation with persistence of differentiated functions
Authors: Krystosek Alphonse 
Published: February 2005

AbstractNeurite formation and proliferation by NG108‐15 cells were studied in shortterm serum‐free N2 medium. Neuritogenesis by individual cells was observed at widely differing times, suggesting a stochastic component to initiation of differentiation. Cells with and without neurites could also enter one or more rounds of proliferation at varying times. The initial choice between these divergent behaviors influenced subsequent growth. Cells initially extending neurites had a high probability of continuing neuritic elongation. Cells initially dividing had a high probability of yielding further progeny. Addition of dibutyryl cyclic AMP to cells cultured in N2 medium rapidly increased the probability of differentiating and decreased the probability of proliferating. To test whether or not cells with highly differentiated morphologies had irreversibly lost the capacity for proliferation, induced cultures were washed and challenged by the addition of serum‐containing medium. The length of time required for individual cells to divide increased with increasing time of preincubation in the induction medium. However, few cells appeared to be permanently removed from the proliferative pool. These observations suggest that differentiating cells exhibit persistence, a tendency to continue on the differentiation pathway. Persistence is extinguished following one round of proliferation in serum‐contianing medium.