bluuebunny/crossref_metadata_2025_split huggingface dataset:
Early and late volume changes during erythroid differentiation of cultured friend leukemic cells
Authors: Loritz Frank , Bernstein Alan , Miller Richard G. 
Published: February 2005

AbstractFriend erythroleukemic cells (FLC) can be induced to differentiate in vitro by addition of dimethylsulfoxide (DMSO). We have studied the kinetics of induction by measuring cell volume, volume coefficient of variation and cell doubling time. Two distinct volume changes (early and late) are observed after the addition of the inducing agent. The early change occurs after ten hours and consists of a 10–20% decrease in volume compared to an untreated control population. This shift persists for two days and its magnitude is proportional to both the concentration of DMSO and the number of differentiated cells seen on day 5. FLC lines which induce weakly or not at all with DMSO exhibit a reduced or absent early volume shift. Inclusion of a local anaesthetic in the culture prevents the appearance of differentiated cells and also counteracts the early volume shift. The exact time of the early volume change is a function of cell growth rate and appears to be cell cycle related. Synchronized cell populations exposed to DMSO during G2 and S phase undergo one round of mitosis before expression of the volume change whereas cells in G2‐M express the change only after a second mitosis.A later, more gradual decrease in volume is observed in those cultures which begin to produce hemoglobin. It occurs after approximately five doubling times and coincides with the first appearance of hemoglobin‐containing cells. Volume distribution parameters indicate that only a proportion of the population becomes smaller in size.
Microfluorometric analysis of cellular DNA following incorporation of bromodeoxyuridine
Authors: Swartzendruber Douglas E. 
Published: February 2005

AbstractBromodeoxyuridine (BrdU) incorporation into cellular DNA has a differential effect on the cell‐associated fluorescence of several DNA‐specific dyes. After cells were treated with BrdU, flow microfluorometry was used to study the relative increase or decrease in fluorescence of stained cells. Bromodeoxyuridine incorporation into CHO cells increased the fluorescence of mithramycin‐, olivomycin‐, or chromomycin‐stained cells, decreased that of propidium iodide‐stained cells, and had little, if any, effect on the fluorescence of acriflavine Feulgen‐stained cells. Changes in relative fluorescence of cell‐associated dyes are due to changes in the amounts of dye bound to cells with BrdU‐substituted DNA. Colorimetric and absorbance measurement of DNA content showed that BrdU does not alter the diploid DNA content of CHO cells; however, BrdU induces perturbations in the distribution of cells about the cell cycle which cause an increase in average DNA content.
Sulphonated polystyrene as an optimal substratum for the adhesion and spreading of mesenchymal cells in monovalent and divalent saline solutions
Authors: Maroudas N. G. 
Published: February 2005

AbstractCell adhesion and spreading were studied on sulphonated polystyrene dishes in serum‐free saline (Mn, Na, Cl, buffer) i.e., without an intervening protein layer. Spreading as a function of surface charge density, SCD, peaked around 2–10 negative charges per square nanometer, corresponding to a monomolecular layer of sulphonate ions. At optimal SCD, macrophages, BHK‐C13 and whole mouse embryo secondary cells all showed considerable spreading, even in monovalent saline–more so than on a conventional tissue‐culture surface. But outside this narrow range of SCD, or on protein‐coated surfaces, the divalent cation was indispensable.The biphasic effect of sulphonation on cell adhesion is consistent with the theory that a substratum need not be biochemically specific, provided it is physicochemically polar, rigid and dense. According to this theory, polystyrene of sub‐optimal SCD would not be sufficiently polar, while supra‐optimal sulphonation would produce a hydrogel surface, lacking in local rigidity and density, due to osmotic swelling. The principle of polymer exclusion, by a surface hydrogel layer, is also consistent with observations on the inhibitory effects of adsorbed proteins–viz., albumin, collagen, serum and cellular exudate, respectively–contrasted with the ready attachment of cells to a bare, optimally charged substratum, in this minimal in vitro system.
Cell density‐dependent secretion of plasminogen activator by 3T3 cells
Authors: Chou Iih‐Nan , O'Donnell Sara P. , Black Paul H. , Roblin Richard O. 
Published: February 2005

AbstractThe expression of extracellular fibrinolytic activity in untransformed 3T3 cell cultures depends on the growth state of the cells. Actively growing 3T3 cultures exhibit a relatively high level of fibrinolysis, which decreases progressively as the cells become confluent and density‐inhibited. The low level of fibrinolytic activity in confluent 3T3 cultures is due to a diminution in secretion of plasminogen activator since the intracellular level of plasminogen activator remains high. The amount of plasminogen activator observed in growing 3T3 cultures varies depending upon whether the cells are passaged with trypsin/EDTA solution, or with the Ca++ selective chelating agent, ethylene‐bis (oxyethylenenitrilo) tetraacetic acid (EGTA). However, in cells passaged using either agent, the amount of plasminogen activator secreted is always greatest when the cells are actively growing and decreases thereafter. In contrast to confluent 3T3 cultures, dense cultures of SV40‐virus transformed 3T3 cells continued to secrete relatively large amounts of plasminogen activator. The ability to decrease secretion of plasminogen activator as cells become dense may be an important characteristic of cells which demonstrate density‐dependent inhibition of cell multiplication in vitro.
Transport enhancement and reversal: Glucose and 3‐O‐methyl glucose
Authors: Musliner Thomas A. , Chrousos George P. , Amos Harold 
Published: February 2005

AbstractIn chick embryo fibroblast cultures the 15‐ to 30‐fold enhancement of D‐glucose uptake observed when cells are starved of glucose for 24 hours is not duplicated for derivatives of glucose that compete effectively for uptake and have generally been considered to use the same carrier. 2‐deoxy‐D‐glucose, D‐mannose, D‐galactose and D‐glucosamine are derepressed progressively less sharply in that order with glucosamine uptake never more than doubled by starvation. D‐glucose at a concentration of 5.5 mM in the 24‐hour conditioning medium is a strong “repressor” resulting in low “transport” behavior for each of the five sugars cited. D‐glucosamine is equally effective at the same concentration. A 10‐fold reduction in the concentration of glucosamine (0.55 mM) allows for the escape from repression of mannose, glucose, and deoxyglucose uptake while the others remain repressed. Mannose uptake escapes as well when the glucose concentration in the “conditioning” medium is similarly reduced.Under certain conditions of starvation and cell density dramatic effects of supplemental stimulation by insulin can be achieved. Insulin withdrawal interrupts the supplemental stimulation process. Cycloheximide, actinomycin D and cordycepin block both non‐insulin and insulin‐induced derepression. Short exposure (15–30 minutes) of 24‐hour starved cells to glucose (5.5 mM) reduces glucose sharply but does not affect 3‐O‐methyl glucose uptake. If the exposure is to 2‐deoxyglucose (5.5 mM) further derepression of glucose uptake results.
Regulation of intracellular calcium in chick embryo fibroblast: Calcium uptake by the microsomal fraction
Authors: Moore Leon , Pastan Ira 
Published: February 2005

AbstractThe total membrane fraction of a chick embryo fibroblast (CEF) homogenate accumulates calcium in an energy‐dependent manner. This activity can be dissociated into azide‐sensitive and azide‐insensitive components. The azide‐sensitive component of calcium uptake is believed to represent mitochondrial calcium uptake. The azide‐insensitive component of calcium uptake is enhanced by the presence of a calcium trapping agent such as oxalate, and cannot utilize, ADP, inorganic phosphate and a Krebs cycle substrate to support uptake. The distribution of the azide‐insensitive calcium uptake in subcellular fractions suggests that this uptake occurs in other than mitochondrial membranes. The membranes most likely to contribute to the azide‐insensitive component of calcium uptake are the endoplasmic reticulum and plasma membrane. A microsomal preparation from CEF cells is essentially devoid of the azide‐sensitive calcium uptake activity. This microsomal activity is similar in characteristics to the sarcoplasmic reticulum of skeletal muscle. However the specific activity of CEF microsomal calcium uptake system is much less than that found in the skeletal muscle system. The transport of calcium by these membranes provide a mechanism for the regulation of cytosol calcium levels and may play a role in the control of movement and growth of cultured cells.
Proline oxidase in cultured mammalian cells
Authors: Downing Sylvia J. , Phang James M. , Kowaloff Edward M. , Valle David , Smith Robert J. 
Published: February 2005

AbstractWe sought a cultured cell line with Proline Oxidase activity to study the regulation and physiologic role of the enzyme in mammalian tissues. Among the cell lines tested, only LLC‐RK1 cells, derived from rabbit kidney, had significant Proline Oxidase activity; the Km for proline of the enzyme from these cells was similar to that for the liver enzyme. LLC cells, Proline Oxidase positive, were able to convert proline to CO2. In contrast, CHL cells, Proline Oxidase negative, did not have this capability. The presence of Proline Oxidase in LLC cells and the absence of the enzyme in fibroblasts suggest that Proline Oxidase may serve as a marker enzyme for distinguishing parenchymal kidney cells from fibroblasts in culture. Cells transformed by SV40 virus and cells transformed by methylcholanthrene had activities higher than the parent cell line, but this effect of transformation could not be generalized to all transformed cells. Finally, L‐hydroxy proline at 100‐fold greater concentration than substrate L‐proline failed to decrease proline oxidation. This finding suggests distinct degradative enzymes for these two amino acids.
Control of proliferation of bovine vascular endothelial cells
Authors: Gospodarowicz Denis , Moran John S. , Braun Debra L. 
Published: February 2005

AbstractThe effects of Fibroblast Growth Factor (FGF) and Epidermal Growth Factor (EGF) on the proliferation of bovine vascular endothelial cells has been examined. FGF induces the initiation of DNA synthesis and cell proliferation in cloned endothelial cells of fetal and adult origin at concentrations as low as 1 ng/ml and is saturating at 50 ng/ml. EGF had no effect over the same range of concentrations. The mitogenic effect of FGF is blocked by a crude extract of cartilage. Platelet extract is also mitogenic for vascular endothelial cells although to a lesser extent than the purified FGF. In contrast to vascular endothelial cells, both EGF and FGF are mitogenic for vascular smooth muscle cells although EGF is less mitogenic than FGF at 100 ng/ml. The mitogenic effect of EGF and FGF on vascular smooth muscle is not blocked by the addition of a crude extract of cartilage, thus demonstrating the specificity of the chalone like effect of cartilage crude extract for endothelial cells.
Fibrinolysis and liver regeneration
Authors: Rixon R. H. , Walker P. R. , Whitfield J. F. 
Published: February 2005

AbstractThe plasmin and plasminogen activator proteases of the plasma fibrinolytic system were investigated as potential blood‐borne mediators of the proliferative activation of hepatocytes by partial hepatectomy. Partial (68%) liver resection, as well as proliferatively activating the remaining hepatocytes, rapidly (by 30 minutes) doubled the level (or activity) of circulating plasminogen activator but later (2 hours) greatly depressed this level. This later depression of the activity of circulating plasminogen activator lasted for eight to ten hours before returning to the normal level two to four hours before the hepatocytes in the liver remnant began to synthesize DNA. This sequence of changes in the fibrinolytic potential was not abolished by prior thyroparathyroidectomy which is known to inhibit the initiation of hepatocyte DNA synthesis and to prevent the secretion of the calcium homeostatic hormones, another early systemic consequence of partial liver resection. Since the early rise in plasminogen activator activity did not cause the appearance of active (free) circulating plasmin, and since the injection of large doses of the fibrinolytic and protease inhibitors, EACA and Trasylol®, during this early, post‐operative period of hyperfibrinolytic potential did not prevent hepatocytes from initiating DNA synthesis, it is unlikely that either plasmin or its activator protease are blood‐borne initiators of hepatocyte proliferative development.
Rapid cell surface‐related stimulation of alkaline phosphatase in HeLa cells by dimethyl DL‐2,3‐distearoyloxypropyl‐2′‐hydroxyethylammonium acetate (Rosenthal's inhibitor)
Authors: Melnykovych G. , Lopez I. C. 
Published: February 2005

AbstractCultures of HeLa cells, strains S3G (HeLa65) and S3K (HeLa71) were grown in plastic dishes until firmly attached and were then treated with sonic dispersions of Rosenthal's phospholipase inhibitor. A rapid increase in alkaline phosphatase activity occurred following this treatment in the S3G strain (low inducible alkaline phosphatase) but not in the S3K strain (high constitutive alkaline phosphatase). The stimulatory effect was dependent on the presence of bovine serum in the medium. No stimulation of alkaline phosphatase was observed in a variety of soluble preparations of this enzyme.
Phosphate uptake and control of fibroblast growth
Authors: Barsh Gregory S. , Greenberg Deborah B. , Cunningham Dennis D. 
Published: February 2005

AbstractPrevious studies have shown that growth to quiescence of fibroblast‐like cells is accompanied by a large decrease in the rate of phosphate uptake. Since 3T3 cells can be arrested in the G1 (or G0) phase of the cell cycle by lowering the concentration of phosphate in the medium, we examined the possibility that the decline in phosphate uptake observed during growth to quiescence might be a key event in the inhibition of DNA synthesis and cell division.The experimental approach consisted of controlling the rate of phosphate uptake by varying the phosphate concentration in the medium. Kinetic experiments showed that phosphate uptake in both growing and quiescent cells was partly accounted for by simple diffusion as well as carrier‐mediated uptake. In fact, diffusion of phosphate into the growing cells was 2.5‐fold greater than in the quiescent cells.When phosphate uptake was measured in 3T3 cells plated at different initial densities, we found an inverse relationship between phosphate uptake and cell density, showing that phosphate uptake was correlated with growth rate and did not decline simply as a consequence of time in culture.Measurements of phosphate demonstrated that the lowered rate of phosphate uptake by quiescent cells was not due merely to a reduction of phosphate in the medium. To check the possibility that release of a previously described transport inhibitor might account for the decline in phosphate uptake observed as cells grow to quiescence, we removed media from growing and non‐growing cultures and tested its ability to support phosphate uptake. We found that the medium from growing cultures supported a higher rate of phosphate uptake than the medium from the quiescent cultures did, indicating that a transport inhibitor was being released. In addition, we found that the amount of inhibitor released was proportional to the concentration of phosphate in the medium.To directly determine if the decline in phosphate uptake was a key event in the decline in DNA synthesis as cells grew to quiescence, we switched growing cultures to a medium with low phosphate immediately after cell attachment. This lowered the rate of phosphate uptake to a level below that of quiescent cells grown in the usual concentration of phosphate. This was done for 3T3, Polyoma virus‐transformed 3T3, human diploid foreskin, and secondary chick embryo cells. Measurements of DNA synthesis and cell number showed that this lowered rate of phosphate uptake had virtually no effect on cell growth, directly demonstrating that the decline in phosphate uptake observed during growth to confluency was not causing the decline in DNA synthesis. In addition, measurements of intracellular phosphate pool size showed that changes in phosphate uptake were not directly paralleled by changes in intracellular phosphate pool size, and that intracellular phosphate pool size was not regulating DNA synthesis or cell division during growth to quiescence.
Bacterial, serum and cellular modulation of granulopoietic activity
Authors: Bolin Rex W. , Robinson William A. 
Published: February 2005

AbstractThe interaction of human peripheral blood lymphocytes, monocytes, gram‐positive bacteria and human serum in the release of colony stimulating activity (CSA) has been studied. CSA was assayed by the soft agar technique using human and murine bone marrow cells. It has been demonstrated that gram‐positive organisms and their products can stimulate release of CSA by mononuclear cells. Human serum is also effective in promoting release of CSA. Release is further modulated by interactions between lymphocytes and monocytes, and lymphocytes may serve to control the modulation. The serum component is sensitive to temperature inactivation suggesting that it may have a specific physiologic role in regulation. Bacterial products, on the other hand, are not subject to temperature inactivation and require the presence of human serum for activity to be expressed.
The detection of in vitro monocyte‐macrophage colony‐forming cells in mouse thymus and lymph nodes
Authors: MacVittie T. J. , McCarthy K. F. 
Published: February 2005

AbstractIn vitro moocyte‐macrophage colony‐forming cells (CFC) have been detected in the thymus (30/106 cells) and in the cervical (22/106) and mesenteric (20/106) lymph nodes (LN) of the mouse. Thymus and LN derived CFC differed from bone marrow derived CFU‐c in several characteristic parameters: (1) sole specificity of PMUE to induce colony formation (CF), (2) apparent singular line of monocyte‐macrophage differentiation, (3) a marked 6‐ to 10‐day lag period prior to initiation of CF, and (4) significantly slower rates of appearance of colonies in culture after initiation of CF. Two of these parameters are shared with those CFC detected within alveolar space, peritoneal exudate and pleural effusion. These are the delay prior to CF and the singular monocyte‐macrophage differentiation. These similarities suggested that T‐CFC and LN‐CFC are probably of similar origin and represent, as suggested by Lin and Stewart ('74), a population of progenitor cells exclusively for monocyte‐macrophages.
The control of human WI‐38 cell proliferation by extracellular calcium and its elimination by SV‐40 virus‐induced proliferative transformation
Authors: Boynton A. L. , Whitfield J. F. , Isaacs R. J. , Tremblay R. 
Published: February 2005

AbstractThe proliferative activity of diploid human WI‐38 cells in sparse cultures depends on the extracellular concentration of free (or physiologically available) calcium, and cultivation in a medium having a calcium concentration of 0.1 mM or less gradually, but reversibly, arrest their proliferative development in the prereplicative (G1) phase of the cell cycle. Calcium's proliferative control of this cell type is eliminated by proliferative and morphological transformation by the oncogenic SV‐40 virus, and the proliferative activity of SV‐WI‐38 cells in sparse cultures is unaffected by variation of the extracellular free calcium concentration between 0.00 and 1.25 mM.
Interaction of local anesthetics with the transport system of glucose in human erythrocytes
Authors: Lacko L. , Wittke B. , Lacko I. 
Published: February 2005

AbstractLocal anesthetics inhibit the exchange transport of glucose in human erythrocytes. All compounds tested showed a competitive inhibition except lidocaine and baycaine causing a non‐competitive one. Moreover the transport system can bind two inhibitor molecules to one transport site as described for tetracaine and oxybuprocaine.
Mechanism of Regulation of fibroblastic cell replication. IV. An analysis of the serum dependence of cell replication based on michaelis‐menten kinetics
Authors: Ellem K. A. O. , Gierthy J. F. 
Published: February 2005

AbstractThe quantitative dependence of the initiation of DNA synthesis in nonreplicating cultures of human diploid fibroblasts (HDFs) on the concentration of fresh serum present in the stimulating medium has been analyzed. A simple formal analysis of the system suggested that the theory of dissociation reactions should lead to a model analogous to the Michaelis‐Menten formulation. Accumulation of enough data for statistical analysis became possible by innovations in the culture techniques and isotope incorporation methods. The data were shown to conform to this model, and parameters Vm and K′m were calculated, together with appropriate statistical functions, from a weighted linear regression of the double reciprocal transformation of the data. Several variables in the culture system were assessed for their effects on the kinetic parameters. The results were consistent with the hypothesis that Vm is a measure of the maximum population of cells capable of responding to the stimulation, and K′m is an estimate of the interaction between the mitogenic factors in serum and the cell surface.Different strains of HDFs had different parameter values. Of several culture variables tested, the Vm was found to be influenced by the type of serum used, and by overall cell density as well as density variations within the monolayer. K′m showed significant changes only in response to cell density, and the evidence suggests that the affinity of cells for serum factors decreases as the cell density increases in confluence.
Adaptation to trichodermin and anisomycin in Physarum polycephalum
Authors: Gorman Jessica A. 
Published: February 2005

AbstractThe effects of the protein synthesis inhibitors trichodermin and anisomycin on the growth of the eucaryotic myxomycete Physarum polycephalum have been examined. When either of these drugs is added to log phase monoxenic cultures of myxamoebae, cell division is immediately arrested, but on continued incubation, growth resumes at a rate only slightly lower than that of drug free cultures. The length of the drug induced growth lag is roughly proportional to drug concentration. When adapted cells are transferred to fresh drug containing medium, growth is not inhibited. However, if the drug concentration is increased, transient inhibition is again exhibited. Measurement of the antibiotic concentration in used media demonstrates no significant external inactivation of either drug during adaptation. The resumption of growth cannot be attributed to the selection of stable drug‐resistant mutants: single amoebal colonies arising on drug plates are found to be as drug‐sensitive as control colonies when retested after subculture. In addition, when adapted cells are transferred to drug free medium, the phenotypic drug‐resistance is completely lost after several generations of growth. As recovery occurs in the continuous presence of drug and is not due to the accumulation of drug‐resistant mutants, this response appears to be an example of drug adaptation. Cross adaptation between anisomycin and trichodermin is also demonstrated, suggesting a common system is involved in adaptation to these structurally dissimilar, but functionally similar, drugs.