bluuebunny/crossref_metadata_2025_split huggingface dataset:
Colony formation in agar by multipotential hemopoietic cells
Authors: Metcalf D. , Johnson G. R. , Mandel T. E. 
Published: February 2005

AbstractAgar cultures of CBA fetal liver, peripheral blood, yolk sac and adult marrow cells were stimulated by pokeweed mitogen‐stimulated spleen conditioned medium. Two to ten percent of the colonies developing were mixed colonies, documented by light or electron microscopy to contain erythroid, neutrophil, macrophage, eosinophil and megakaryocytic cells. No lymphoid cells were detected. Mean size for 7‐day mixed colonies was 1,800‐7,300 cells.When 7‐day mixed colonies were recloned in agar, low levels of colony‐forming cells were detected in 10% of the colonies but most daughter colonies formed were small neutrophila and/or macrophage colonies. Injection of pooled 7‐day mixed colony cells to irradiated CBA mice produced low numbers of spleen colonies, mainly erythroid in composition. Karyotypic analysis using the T6T6 marker chromosome showed that some of these colonies were of donor origin. With an assumed f factor of 0.2, the mean content of spleen colony‐forming cells per 7‐day mixed colony was calculated to vary from 0.09 to 0.76 according to the type of mixed colony assayed.The fetal and adult multipotential hemopoietic cells forming mixed colonies in agar may be hemopoietic stem cells perhaps of a special or fetal type.
Fast and slow fractions of K+ flux in human lymphocytes
Authors: Negendank William , Shaller Calvin 
Published: February 2005

AbstractPotassium influx and efflux were studied in human peripheral blood lymphocytes equilibrated over a wide range of external K+ levels. The absence of a net ion movement throughout the flux study was established, trapped space was measured with polyethylene glycol, and cells were separated from incubation media without exposure to any washing solution. There are both rapid and slow cellular fractions of 42K influx and efflux, with half‐times of exchange of around 2 minutes, and 400 minutes, respectively. The rapid component is identical in magnitude to the smaller non‐saturable component of cell K+, while the slow component is identified with the larger, sigmoidal, saturable component of cell K+ that was previously shown to follow a cooperative adsorption isotherm. These results support the association‐induction hypothesis, which predicts (a) a rapid fraction of K+ flux due to equilibration of ion within cell water existing in a state of polarized multilayers, and (b) a slower component of K+ flux limited by adsorption onto, or desorption from, fixed anionic sites existing throughout the cell. K+ influx, as a function of external K+, showed a triphasic relation with a peak around 1 mM K, then a trough around 4 mM K, and then a gradual rise. This relation was readily explained, in terms of the association‐induction hypothesis, by the cooperative interaction between, and ion occupancy of, fixed anionic sites that absorb K+ or Na+.
Glucocorticoids enhance the mitogenic action of insulin in serum‐free cultures of chick embryo cells
Authors: Baker Joffre B. , Simmer Robert L. , Glenn Kevin C. , Cunningham Dennis D. 
Published: February 2005

AbstractAddition of insulin to nonproliferating serum‐free cultures of secondary chicken embryo (CE) cells caused a 30% to 50% increase in cell number. Addition of any one of several glucocorticoids (dexamethasone, cortisol, or corticosterone) to the cultures two days before insulin addition increased the mitogenic effect of insulin by about twofold at each insulin concentration tested. This glucocorticoid stimulation of cell proliferation was “permissive” because in the absence of insulin glucocorticoids caused little increase in cell number (usually less than 15%). Glucocorticoids were maximally active at low concentrations (e.g., 10−10 M dexamethasone). Steroids without glucocorticoid activity were inactive over a wide range of concentrations. Glucocorticoids increased the mitogenic response to insulin largely by increasing the percentage of cells that insulin stimulated to synthesize DNA.The maximum mitogenic effect of insulin upon CE cells rapidly decreased after the cells were serially subcultured. After only nine population doublings (4 passages) in culture, the response to insulin was diminished by about 70%. The mitogenic effect of insulin plus dexamethasone declined similarly during serial subculture, and was always about twofold greater than the effect of insulin alone. The cells maintained their mitogenic responsiveness to serum as these responses decreased.In contrast to the growth promoting influence of glucocorticoids in the presence of insulin, glucocorticoids inhibited the mitogenic response of CE cells to serum. This result may resolve our above findings with reports that glucocorticoids inhibit the proliferation of CE cells.
Growth of human embryonic fibroblasts at clonal density: Concordance with results from mass cultures
Authors: Smith James R. , Braunschweiger Karen I. 
Published: February 2005

AbstractIn the past, it has been difficult to grow human diploid fibroblast cells at clonal densities. Newly devised cell culture media and rigorously controlled environmental conditions have greatly increased the ease with which such cells can be cloned. The present work was undertaken to determine whether, under appropriate conditions, diploid fibroblast cells from human embryonic lung, grow as well at clonal densities as in mass culture. The parameters studied were: (1) population doubling time, (2) in vitro proliferative capacity, (3) attachment, (4) percentage of non‐dividing cells. In all cases essentially the same results were obtained for cultures at clonal densities and mass cultures. These results indicate that the behavior of these types of cells in clonal culture can be used to infer the behavior of individual cells and clones within a mass culture.
Effects of hydrostatic pressure in the range 100–300 atmospheres on cell division and protein synthesis in synchronized Tetrahymena pyriformis: A comparison with cycloheximide and emetine
Authors: Walker Eric , Wheatley Denys N. 
Published: February 2005

AbstractHeat‐synchronized Tetrahymena pyriformis have been subjected to 5‐, 15‐ and 30‐minute pulses of hydrostatic pressure in the range 100–300 atm, without being simultaneously subjected to significant heats of compression. The pressure‐induced division delays depend on (1) the level of pressure used, (2) the length of pressure pulse and (3) the time after the synchronizing treatment at which the pressure is applied. A pressure‐dependent inhibition of 3H‐leucine incorporation into protein was also measured. Comparison of the effects of pressure with those of pulse treatments of cycloheximide and emetine on cell division and protein synthesis revealed that the physical agent produced characteristically different responses from those of the chemical agents. Of particular interest was the fact that the division delays induced by pressures of 200 atm and above were greater than those observed after treatments with cycloheximide and emetine which produced comparable levels of protein synthesis inhibition. Pressure also delayed cells if it was applied at a time when addition of chemical inhibitors had little effect on the first synchronous division. The results show that inhibition of protein synthesis by pressure cannot entirely account for pressure‐induced effects on cell division. The possibility that pressure may also directly affect other processes, such as the assembly of proteins into structures required for division, is discussed.
Amino acid transport in normal and Rous sarcoma virus‐transformed chicken embryo fibroblasts
Authors: Nakamura Kenji D. , Weber Michael J. 
Published: February 2005

AbstractA study was made of the transport of a variety of amino acids by uninfected and Rous sarcoma virus‐infected chicken embryo fibroblasts. Following a period of amino acid starvation, transformed, but not normal cells, showed increased levels of transport for α‐aminoisobutyric acid, proline and alanine, three amino acids which are transported primarily by the A transport system. There was no starvation‐induced increase in the transport of leucine, phenylalanine, lysine, or cycloleucine. In the absence of starvation, normal and transformed cells exhibited comparable rates of amino acid transport. Cycloheximide was able to block the increase in uptake. The enhanced uptake was characterized by an increase in Vmax for transport and little change in Km.The data demonstrate that an alteration in the regulation of the A amino acid transport system is an early event in malignant transformation by Rous sarcoma virus. However, since this alteration is made manifest only following a period of starvation, our findings suggest that increased amino acid uptake does not play a role in generating the other manifestations of the transformed state seen in cell culture.
Effect of phagocytosis by human polymorphonuclear leukocytes and rabbit alveolar macrophages on 2‐deoxyglucose transport
Authors: Tsan Min‐Fu 
Published: February 2005

Abstract2‐Deoxyglucose transport was characterized in human polymorphonuclear leukocytes (PMN) and rabbit alveolar macrophages (AM). The Km was 1 mM for human PMN and 1.6 mM for rabbit AM, and the Vmax was 0.66 × 10−3 μmoles/45 sec/106 PMN and 5.09 × 10−4 μmoles/45 sec/106 AM. The rate of 2‐deoxyglucose transport was the same before and after phagocytosis in PMN from normal individuals and three patients with chronic granulomatous disease, as well as rabbit AM. Studies of the kinetics of 2‐deoxyglucose transport and intracellular fate of 2‐deoxyglucose in human PMN indicate that the nature of the membrane transport system is not altered by phagocytosis. The results support the concept that the plasma membrane is mosaic in character with geographically separate transport and phagocytic sites.
Defective transient endogenous spleen colony formation in S1/S1d mice
Authors: Wiktor‐Jedrzejczak W. , Ahmed A. , Sharkis S. J. , McKee A. , Sell K. W. 
Published: February 2005

AbstractWCB6F1 mice of the genotype S1/S1d did not form transient 5‐day endogenous spleen colonies following midlethal irradiation, either spontaneously or in response to postirradiation bleeding. Their hematologically normal (+/+) littermates produced colonies equivalent in number and morphologic type to a normal strain (D2B6F1), as evaluated by both macroscopic and microscopic criteria. Bone marrow cells from S1/S1d mice, when transplanted into lethally irradiated +/+ mice, were able to generate equivalent numbers of transient endogenous spleen colonies (TE‐CFUs), as compared to that obtained when syngeneic +/+ marrow cells were injected into lethally irradiated +/+ recipients. A defective growth of an early class of hematopoietic progenitor cells, resulting in the clinical course of the S1/S1d anemia is suggested and confirms previous reports on the microenvironmental nature of this abnormality.
Selective inhibition of preribosomal RNA synthesis by puromycin aminonucleoside in transformed human fibroblasts: Studies of the nature of the inhibition in isolated nuclei and nucleoli
Authors: Albanese Ernest A. , Studzinski George P. 
Published: February 2005

AbstractPuromycin aminonucleoside selectively inhibits the synthesis of ribosomal RNA in human lung fibroblasts transformed by the oncogenic virus SV40. The mechanism of this inhibition was studied utilizing nuclei and nucleoli isolated from cells treated for 18 hours with 100 μg/ml of this compound. It was established that for a limited period of time nuclei and nucleoli isolated from the fibroblasts continue synthesis of RNA of size classes seen in intact cells, and that the inhibitory effect of aminonucleoside persists after isolation of these organelles. The inhibition was shown to be directed primarily to the activity of RNA polymerase I.Studies of the mechanism of this inhibition have indicated that the decreased rate of the polymerase reaction is not due to the impairment of the template function of nucleolar chromatin, and that unbound, as well as chromatin‐bound, RNA polymerase I is present in both control and treated nucleoli. Analysis of the size distribution of the products of cell‐free RNA synthesis showed that aminonucleoside pretreatment results in marked reduction in the synthesis of preribosomal 45S RNA, abnormal accumulation of 32S RNA, and reduced formation of mature ribosomal RNA species in the in vitro system. The data suggest that the inhibitory effect of aminonucleoside on ribosomal synthesis is due in part to a lower rate of transcription by RNA polymerase I of preribosomal RNA, and in part to its impaired maturation.
The kinetics of chick cell population aging in vitro
Authors: Ryan J. M. 
Published: February 2005

AbstractWe have examined the kinetics of chick cell population aging in vitro using the percentage of labeled nuclei, the number of colonies formed from a low density inoculum and the number of cells/colony to monitor culture age. The results from these studies showed a gradual age‐associated decline in each of the parameters which was first detected early in the culture lifespan and well in advance of changes in total cell number at confluency. Our results also indicated that each of the above parameters, in addition to the calendar time cells had been in culture, could be used to estimate the percentage of lifespan completed by the culture. A comparison of the methods used to estimate the remaining culture lifespan indicated that the percentage of labeled nuclei was the most accurate in describing cell age.
Rapid separation of mouse T and B lymphocytes using wheat germ agglutinin
Authors: Bourguignon Lilly Y. W. , Rader Richard L. , McMahon James T. 
Published: February 2005

AbstractA separation procedure has been developed for mouse splenic T and B lymphocytes which is based on their differential agglutination by wheat germ agglutinin (WGA). In the presence of 50‐100 μg/ml of WGA, multicellular aggregates are formed which are enriched in B cells. These aggregates can be separated from monodisperse T cells by gravity sedimentation and subsequently dissociated into single cells by treatment with N‐acetylglucosamine (NAG). Immunocytochemical analyses and mitogenic assays indicate approximately 10‐15% cross contamination of the resultant B and T cell fractions. The separation procedure is not only convenient and rapid but also allows the simultaneous recovery of viable T and B cells from the same spleen preparation.
Regulation of epidermal growth factor (EGF) receptor activity during the modulation of protein synthesis
Authors: Carpenter Graham 
Published: February 2005

AbstractThe capacity of cultured human fibroblasts to bind 125I‐labeled epidermal growth factor (EGF) was measured during protein synthesis inhibition and reinitiation. Protein synthesis was inhibited by incubation of human fibroblasts in histidine‐free medium supplemented with L‐histidinol to produce a stringent amino acid starvation. Under these conditions 125I‐EGF binding activity decreased with a half‐life of 14.5 hours. Protein synthesis could be rapidly reinitiated by the addition of L‐histidine to human fibroblasts which had been preincubated in histidinol containing media for 36 to 48 hours. 125I‐EGF binding activity rapidly increased upon the reinitiation of protein synthesis. In the presence of serum 100% of the original binding capacity was recovered ten hours after the renitiation of protein synthesis, while 70% of the binding capacity was recovered in 12 hours in serum‐free media. The recovery of 125I‐EGF binding activity after the reinitiation of protein synthesis, was not blocked by the presence of Actinomycin D, indicating that the messenger RNA for the EGF receptor may accumulate during the period of histidinol‐mediated inhibition of protein synthesis. The time course of recovery of 125I‐EGF binding activity after the reinitiation of protein synthesis is very similar to that observed during the recovery of receptor activity following “down regulation” of EGF receptor activity. Recovery from down regulation, however, was markedly sensitive to Actinomycin D.
Ultrastructural localization of wheat germ agglutininbinding sites on surfaces of chick embryo cells during early differentiation
Authors: Sanders E. J. , Anderson A. R. 
Published: February 2005

AbstractThe objective of this work was to examine changes in a surface component of cells from the chick embryo during morphogenetic migrations of gastrulation. Two electron microscope techniques were used to localize cell‐bound wheat germ agglutinin (WGA), a lectin which specifically binds N‐acetyl glucosamine residues. One technique involved conjugation of peroxidase to WGA before reaction with the cells; the other technique used glucose oxidase to mark WGA which was already cell‐bound. In both cases, binding was revealed using diaminobenzidine. Before formation of the primitive streak, all surfaces of the two‐layered embryo bound WGA. After migration of cells through the streak, to form the three‐layered embryo, not all cell surfaces bound WGA equally. Epiblast cells generally bound WGA lateral to the primitive streak but not during passage through the streak. Mesenchyme cells, after passage through the streak, bound WGA increasingly as they migrated away from the streak. A WGA‐binding matrix was observed in the vicinity of the mesenchyme cells and on the dorsal surface of the endoblast. The ventral surface of the endoblast bound the lectin very poorly. In some instances, a peroxidase reaction product was consistently seen on certain surfaces which was not removable by addition of the simple hapten N‐acetyl glucosamine. In these cases, the density of the deposit was lessened by use of diacetyl chitobiose as a hapten. This result, together with the reduction of reaction product following certain hyaluronidase treatments, suggests that WGA may be binding to hyaluronic acid as well as membrane glycoproteins.
Regulation of DNA replication by serum and the transforming function in cultured rat fibroblasts transformed by Rous sarcoma virus
Authors: Magun Bruce E. , Thompson Richard L. , Gerner Eugene W. 
Published: February 2005

AbstractThe onset and rate of semiconservative DNA replication were measured in stimulated cultured rat fibroblasts and their Rous sarcoma virus‐transformed derivatives after a period of serum deprivation. Rat‐1 (tsLA24/RSV) cells initiated DNA synthesis following a shift to the permissive temperature or addition of serum at the non‐permissive temperature. Their rate of DNA replication was unaffected by the presence of serum at the permissive temperature, however, there was a serum requirement at the non‐permissive temperature. The transition probability was less at the permissive temperature, independent of serum, than at the non‐permissive temperature in the presence of serum. The amount of DNA induced to replicate by addition of serum at the non‐permissive temperature or by a shift to the permissive temperature was similar. Using the untransformed Rat‐1 cells and these cells transformed by wild‐type RSV (Rat‐1 (wt/RSV)), it was confirmed that the rate of entry into S phase (transition probability) was always lower in the transformed cell line at both 39° and 35°. In both cell lines the rate of DNA replication was independent of temperature, but the onset was delayed at the lower temperature. These results indicate that in the cell lines examined, (1) serum was able to commit the cells to replicate DNA (alter the transition probability) in both transformed and untransformed cells, but the transforming function was able to supplant a serum‐dependent process during G1 necessary for the initiation of DNA replication, and (2) the effects of the transforming function and serum factor(s) on the alteration of the transition probability are not additive, suggesting that the transforming function initiates a process which acts at the level of the commitment to DNA replication which may render the normal serum‐related control mechanisms ineffective in the regulation of growth.
Inosine di‐ and triphosphate synthesis in erythrocytes and cell extracts
Authors: Vanderheiden Bernardo S. 
Published: February 2005

AbstractThe ability to synthesize inosinetriphosphate was demonstrated in blood cells as well as in a variety of tissue extracts in spite of the presence of ITP pyrophosphohydrolase. At the expense of having sub‐optimal conditions, an assay system was selected that completely repressed the hydrolyzing enzyme, thus permitting the accumulation of ITP.In an attempt to define the biosynthetic pathway of ITP, and since guanylate kinase has been implicated in the formation of ITP, the rate of synthesis of ITP and GTP in cell extracts was compared.The comparison of the specific activities of the [14C]‐labeled hypoxanthine and guanine moieties of the inosine and guanosine phosphates formed during incubation with [8‐14C]‐inosine and [8‐14C]‐guanosine respectively, revealed striking differences in the relative rates of isotope incorporation. Tentative mechanisms are proposed to explain these differences.The data obtained thus far does not discard the possibility that ITP may be formed by stepwise phosphorylation and (or) by direct pyrophosphorylation of IMP.
Early decrease of 2‐deoxy glucose and α‐amino isobutyric acid transport are among the first events in differentiating synchronized murine erythroleukemia cells
Authors: Gazitt Yair 
Published: February 2005

AbstractMurine erythroleukemic cells were induced to differentiate along the erythroid pathway by Me2SO and HMBA. These inducers caused an early decrease in the transport of glucose and amino acids, both in non‐synchronized and in synchronized cultures. Careful analysis of the transport parameters in synchronized cultures showed a cyclic fluctuation of the Vmax but no significant change of the Km. In the presence of the inducers, however, a modification of the Km and Vmax of both carriers was observed which was not dependent on cell cycle. This modification is very early and precedes the transient arrest of the cells in G1 reported previously. In addition, a Me2SO‐resistant cell line (DR10) does not show any changes in the transport of glucose and amino acids when incubated with Me2SO. However, there is an effect on the transport when incubated with HMBA which induces differentiation of 50% of the cells.These data support the hypothesis that an early effect of the inducers on the plasma membrane may be a necessary prerequisite for initiation of differentiation in murine erythroleukemic cells.