bluuebunny/crossref_metadata_2025_split huggingface dataset:
Hemopoietic progenitor cells with limited potential for differentiation: Erythropoietic function of mouse marrow “lymphocytes”
Authors: Bennett Michael , Cudkowicz Gustavo 
Published: February 2005

AbstractFiltration of mouse marrow cell suspensions over columns of glass wool increased the frequency of small and medium‐sized lymphocytes (SML) and of erythropoietic progenitor units (EPU) by about the same factor. Identical results were obtained when erythropoiesis was assayed by isotope uptake (59FeCl3 and 125IUdR) or by the spleen‐colony techniques.Transfusion of prospective donor mice with erythrocytes virtually eliminated morphologically recognizable erythroid cells from marrow without affecting the frequency of EPU. Injection of prospective donors with cortisol decreased the frequency of SML in marrow but not that of EPU or erythropoietin‐sensitive cells. However, glass wool filtration of lymphocyte‐poor marrow taken from mice pretreated with cortisol resulted in a similar increase in frequency of residual SML and of EPU. Therefore, it appears that a subpopulation of marrow SML are EPU.Whereas glass wool filtration increased the frequency of erythropoietic progenitor and colony‐forming units, the filtration failed to change the frequency of leukopoietic progenitor or colony‐forming units (assayed in mice hypertransfused with erythrocytes to suppress erythropoiesis). It follows that separate progenitor cells for erythropoiesis and leukopoiesis are present in bone marrow of adult mice, in addition to pluripotent stem cells.
Energy‐limitation of a sodium‐independent amino acid transport in ovarian oocytes of the frog
Authors: Merriam R. W. , Pollack Gerald 
Published: February 2005

AbstractThe frog, Rana pipiens, hibernates through the winter with ovaries containing oocytes which, in size and appearance, are ready for ovulation and maturation. From November through April, the normal time of egg laying, ovulation and maturation can be induced by interrupting hibernation and administering gonadotropic hormones. In the studies reported here, it has been found that oocytes taken from hibernating animals in early winter take up amino acids from a saline medium at a relatively rapid rate. Respiratory inhibition produced by such agents as dinitrophenol (DNP) and anaerobiosis, does not completely stop uptake but slows it down markedly.In late winter, amino acid uptake tends to be slower in normal cells and when DNP or cyanide is added, a marked acceleration of the rate of uptake is observed. The uptake in poisoned cells is accumulative, producing internal concentrations higher than that of the medium. At this concentration of DNP, amino acid incorporation is almost completely stopped. Fluoride abolishes the DNP stimulation of amino acid uptake. Removal of sodium ion from the incubating medium has no effect on either uptake or incorporation.These data are interpreted to mean that a capacity for oxidative phosphorylation in oocytes diminishes during winter hibernation. In the spring either an anaerobic capacity comes into being or becomes capable of being switched on. During this time the rate of amino acid uptake, even in the downhill phase, is limited by energy availability and is not dependent on a sodium gradient.
The effect of temperature on ATP levels in cells of an ascitic Hepatoma
Authors: Jones P. C. T. 
Published: February 2005

AbstractThe effect of temperature on intracellular ATP levels in cells of the ascitic Hepatoma 129 has been determined using an UV‐enzymic method. ATP levels are found to vary inversely with temperature over the range (4°–37°C) studied, and this variation is found to be reversible. An indication of a possible direct correlation of ADP level with temperature was also obtained.A correlation is deduced between rise in intracellular ATP level and decrease in cytoplasmic viscosity, both from the present results, and from similar effects recently reported by Landau ('61) for increase in pressure.The significance of these observations is discussed with reference to the model for cytoplasmic viscosity proposed by Marsland ('56) and the wider biological significance of this effect is explored.
Water diffusion and water permeation in eggs from three Anuran species
Authors: Haglund Birgit , Loeffler Clarence A. 
Published: February 2005

AbstractWater exchange has been studied in ovarian and body cavity eggs of three Anuran species (Rana esculenta, R. pipiens and R. temporaria) with the isotope exchange method using the automatically recording diver balance. In order to estimate the rate of water diffusion in egg cytoplasm (D), a factor required to determine the rate of water permeation (= the exchange coefficient, E), three different chemical treatments (digitonin, ethanol and formaldehyde) have been used to remove the surface barrier to water flow. The obtained mean value of D, 5 × 10−6 cm2 sec−1, has been accepted as a close approximation of water diffusion in the egg cytoplasm. This value has been used to determine the exchange coefficients in the egg types of the above mentioned species. Comparisons have been made between the calculated values of E both within and between species, and some suggestions have been made concerning the influence of microvilli on the rate of water exchange. Although, on the average, water exchange proceeds at a greater rate in ovarian than in body cavity eggs, a measurable diffusion barrier at the surface can be demonstrated.
Impairment of deoxyribonucleic acid synthesis by dietary zinc deficiency in the rat
Authors: Sandstead Harold H. , Rinaldi Robert A. 
Published: February 2005

AbstractDietary zinc deficiency has been shown to decrease the in vivo incorporation of thymidine into the nuclear DNA of liver parenchymal cells in the rat. A single injection of 100 μg of zinc was sufficient to rapidly reverse the effect of zinc deficiency on the synthesis of DNA.
The dependence of DNA synthesis on protein synthesis in HeLa S3 cells
Authors: Weiss Barbara G. 
Published: February 2005

AbstractThe rate of DNA synthesis in HeLa S3 cells, as measured by incorporation of C14‐labeled thymidine, is strongly dependent on protein synthesis at all times during the S phase. The relation between the rate of DNA synthesis and the rate of protein synthesis is linear when measured two or three hours after reducing the rate of protein synthesis with either puromycin or cycloheximide. The effect is manifested rapidly, is found in both random and synchronized cultures, and is independent of the method of synchronization.
Transformation of chick fibroblast cultures with avian myeloblastosis virus
Authors: Moscovici C. , Moscovici M. G. , Zanetti M. 
Published: February 2005

AbstractCellular transformation was induced with avian myeloblastosis virus strain BAI‐A (standard AMV) and with a strain of AMV containing subgroup B only. Cultures of muscle tissues from either chick embryo or day old chicks were used for this study. Results were similar in C/O and C/A cells. Leukemogenic virus was continuously produced by these transformed cultures.
Lethal effects of fluorodeoxyuridine on cultured mammalian cells at various stages of the cell cycle
Authors: Lozzio Carmen B. 
Published: February 2005

AbstractThe lethal damage induced by the exposure of synchronized Chinese hamster cells to various concentrations of 5‐fluoro‐2′deoxyuridine (FUdR) was not selectively restricted to cells exposed during the period of DNA synthesis S. The colony survival fraction observed after treatment for one hour with 5 × 10−5 M FUdR was very low (0.0001–0.0003) whether the drug was administered during early G1, late G1, early S or in middle S. The survival of cells treated with the same concentration of FUdR during mitosis, however, was significantly higher (0.62) showing that mitotic cells were less sensitive to FUdR. Administration of 10−7M thymidine or “conditioned” medium for one hour reversed the lethal effect of FUdR or improved the survival, depending on the time after removal of the FUdR at which these substances were given.
Chemical modification of crayfish axons by protein crosslinking aldehydes
Authors: Shrager Peter G. , Strickholm Alfred , Macey Robert I. 
Published: February 2005

AbstractA series of aldehydes of varying protein crosslinking strengths have been tested on intact and internally perfused crayfish axons. Non‐crosslinking aldehydes have no effect, or cause a gradual decline in resting potential and overshoot with no widening of the spike. Strong crosslinking compounds, such as acrolein, crotonaldehyde, and glutaraldehyde, widen the action potential significantly while reducing its amplitude. Differences in the shapes of the resulting action potentials and accompanying impedance changes suggest that each crosslinking aldehyde exerts different effects on the axon. Glutaraldehyde, the strongest crosslinking agent tested, slows both rising and falling phases of the spike, and also of the impedance change, suggesting a prolongation of the transient increase in sodium conductance. The ability of protein crosslinking agents to alter excitability, and particularly to slow the various phases of the action potential, provides support for the hypothesis that a conformational change in a protein or protein‐phospholipid complex is involved in excitation.
The relationship of protein synthesis to cell division and oral development in synchronized Tetrahymena pyriformis GL‐C: An analysis employing cycloheximide
Authors: Frankel Joseph 
Published: February 2005

AbstractThe effects of cycloheximide on synchronized Tetrahymena pyriformis strain GL‐C were investigated at concentrations ranging from 0.01 to 10 μg/ml. The initial inhibition of protein synthesis was nearly total (>85%) at 1 μg/ml and above, partial (50–80%) at 0.2 to 0.05 μg/ml, and slight (<30%) at 0.02 μg/ml. Eventual recovery of protein synthesis to a rate approaching that of the controls took place at concentrations of 1 μg/ml and less. When the drug was added before a “transition point” at 55 minutes after the end of the synchronizing treatment (EST), cell division was blocked by 10 μg/ml, and delayed at concentrations of 1 μg/ml or less. The duration of delay was related to the degree of initial inhibition, and to the time required for recovery of protein synthesis; it also depended on the time after EST at which the drug was added. At a given concentration, maximum division delay was observed just prior to the “transition point;” this maximum delay was correlated with resorption of differentiating oral primordia, followed by the appearance of new primordia. The lesser delays observed at earlier times were correlated with temporary blockage of development of primordia in the “stomatogenic field” stage. Resumption of oral primordium development was, in both cases, temporally correlated with a substantial recovery of protein synthesis. After the “transition point,” cell division, and completion of oral development, was delayed slightly at the lower concentrations, and more substantially at 1 and 10 μg/ml, with some division‐arrest at the latter concentration. Except for the recovery phenomenon, the developmental responses elicited by cycloheximide were similar to those observed earlier with puromycin.The bearing of these findings on the mechanism of synchronization in Tetrahymena is considered in the Discussion.
The expression of differentiation by chick embryo thyroid in cell culture. I. Functional and fine structural stability in mass and clonal culture
Authors: Spooner Brian S. 
Published: February 2005

AbstractThe stability of glandular epithelial cells has been investigated utilizing the techniques of cell culture. Embryonic chick thyroid was chosen as a representative cell type and methods were developed for the successful clonal culture of thyroid follicular cells.Thyroid cells were found to be morphologically and functionally stable while undergoing rapid division in both dense (monolayer) and dilute (clonal) cell culture. Differentiated features were retained for a minimum of 32 days of primary clonal culture (approximately 17 generations under clonal conditions). During the culture period, the cells retained their epithelial morphology, retained their cytoplasmic rough endoplasmic reticulum, and continued to produce chromatographically detectable thyroid hormones. Hormone production in culture was a specific thyroid characteristic since control cultures of embryonic heart and liver did not contain the hormones.
Recovery of proliferative capacity of agar colonyforming cells and spleen colony‐forming cells following ionizing radiation or vinblastine
Authors: Chen Michael G. , Schooley John C. 
Published: February 2005

AbstractThe effects of sublethal radiation and the mitotic inhibitor, vinblastine sulphate, on the number of cells in mouse bone marrow capable upon transplantation of forming macroscopic colonies on the surface of the spleens of irradiated recipient mice (CFU) and on the number of cells capable of forming colonies in soft agar after cell culture (ACFU) were studied as a function of time after injury. The results show that ACFU are radiosensitive and vinblastine‐sensitive cells, comparable in sensitivity to erythropoietin‐sensitive cells. The temporal pattern of recovery following radiation of ACFU, different from that for CFU, is compatible with the concept that these are two distinct but closely related stem cell populations. The relevance of these findings to models of hematopoiesis and to studies on the precursors of macrophages and monocytes in inflammatory exudates is discussed.
The possible mediation by cyclic AMP of parathyroid hormone‐induced stimulation of mitotic activity and deoxyribonucleic acid synthesis in rat thymic lymphocytes
Authors: Whitfield J. F. , MacManus J. P. , Rixon R. H. 
Published: February 2005

AbstractPurified parathyroid hormone (PTH) strongly stimulates the initiation of deoxyribonucleic acid (DNA) synthesis and thereby raises the flow of cells into mitosis in rat thymic lymphocyte populations maintained in vitro. These actions of PTH are potentiated by caffeine and inhibited by imidazole which indicates that the hormonal action is mediated by cyclic adenosine 3′,5′,‐monophosphate (cyclic AMP). The feasibility of cyclic AMP being the mediator of PTH action is established by the observation that a low concentration (10−7 M) of dibutyryl cyclic AMP precisely mimics the stimulatory action of the hormone on DNA synthesis and cell proliferation.
Differential proliferation of erythroid and granuloid spleen colonies following sublethal irradiation of the bone marrow donor
Authors: Wolf Norman S. , Trentin John J. 
Published: February 2005

AbstractSpleen colonies produced by sublethally irradiated mouse bone marrow cells were compared to those produced by unirradiated marrow cells in lethally irradiated mice. Sublethally irradiated marrow cells gave rise to many fewer spleen colonies. At seven days of colony age, the ratio of erythroid colonies to granuloid colonies was lower (< 1) than for colonies formed by unirradiated marrow (2 to 3 or more). Delay of harvest of colonies to day 10 or 12 resulted in 6 to 11 fold increase in the ratio of erythroid to granuloid colonies due largely to the belated appearance of erythroid colonies.
Fetal erythroid cell development: Density gradients and size distributions
Authors: Zucker Robert M. 
Published: February 2005

AbstractElectronic size distributions of erythroid cells from fetal C57BL‐6J mice during the eleventh through twentieth days of gestation indicate that the erythropoietic cell populations are constantly changing. The mean volume of the liver derived non‐nucleated erythroid population decreases from four times the mean adult erythrocyte volume on the thirteenth gestation day to twice the adult erythrocyte volume at birth. The mean volume of the nucleated erythroid cell is about ten times the mean adult erythrocyte volume. The gestation age of an embryo can be determined from blood cell size distributions. The mode of the non‐nucleated population and the percentage of each population indicates the gestation age.Size distribution of cells in density gradient fractions apparently indicate two size populations of non‐nucleated cells between the thirteenth and fifteenth days. The density of the non‐nucleated cells increases during gestation. It is suggested that the decrease in size and increase in density of non‐nucleated cells is due to the release of successively smaller reticulocytes from the liver.
Membrane phosphatase and active transport in red cells from different species
Authors: Vigliocco Ana M. , Rega Alcides F. , Garrahan Patricio J. 
Published: February 2005

AbstractThe K+‐dependent phosphatase activity from red cell membranes from different mammalian species shows a close relationship with both the rate of active potassium influx and (Na+ + K+)‐dependent ATPase activity. This finding supports the view that membrane phosphatase activity is related to the cation transport system.
In vitro immune response of primed mouse spleen cells as affected by the time of antigenic stimulation
Authors: Meiss H. K. , Agarossi G. , Martinozzi M. , Doria G. 
Published: February 2005

AbstractNormal and primed spleen cells stimulated in vitro with sheep RBC showed a different behaviour in the 19 S PFC response. The immunologic capacity of primed cells, unlike that of unprimed cells, was impaired if the antigen addition to culture had been delayed for more than six hours. The requirement of primed cells for immediate reexposure to antigen varied with the time of preimmunization and was maximum when spleen cells had acquired in the donor the ability to display the highest response in vitro upon optimal restimulation. This phenomenon of antigen requirement of primed cells in vitro is at variance with the known immunologic behaviour of primed cells grown in vivo, and can be attributed to cellular changes unmasked by in vitro cultivation.
A new method of cloning mammalian tissue culture cells in suspension
Authors: Walters R. A. , Hutson J. Y. , Burchill B. R. 
Published: February 2005

AbstractChinese hamster cells (line CHO) were cloned in suspension with a carboxymethylcellulose‐containing medium, and the colonies were counted with an electronic particle counter after enzymatically degrading the carboxymethylcellulose with cellulase. Survival of x‐irradiated cells was determined by both the standard plating technique and the suspension technique, and comparable results were obtained.
The influence of diffusion in the external medium upon the determination of cytoplasmic diffusion coefficients
Authors: Løvtrup Søren , Mild Kjell Hansson , Berglund André 
Published: February 2005

AbstractThe exchange of isotopic water has been studied in ovarian eggs from three Anuran species (R. esculenta, R. pipiens and R. temporaria) by the automatic diver balance technique. The oocytes were treated with chemicals (digitonin, ethanol and formaldehyde) to remove the plasma membrane. The cytoplasmic diffusion coefficient for water was calculated with and without allowance for the influence of diffusion in the external medium. The former expedient was found necessary in order to obtain correct values. The chemical treatments gave different values, but there are sound reasons to believe that those obtained with digitonin (8.9, 15.3 and 10.8.10−6 cm2sec−1 for R. esculenta, R. pipiens and R. temporaria, respectively) are the correct ones. These results indicate that the rate of diffusion in the oocyte cytoplasm amounts to 50–75% of that of free diffusion.
Extraction of an actomyosin‐like protein from amoebae of Dictyostelium discoideum
Authors: Woolley David E. 
Published: February 2005

AbstractAn actomyosin‐like protein has been extracted from amoebae of Dictyostelium discoideum, V‐12. The purified protein exhibited a reversible change in viscosity upon addition of ATP, indicating an ATP sensitivity of 75–85% and a specific viscosity of 0.1. At low ionic strength in the presence of Mg++ and ATP the amoeba protein displayed the phenomenon of superprecipitation. The protein extract was found to be an adenosinetriphosphatase (ATP'ase) hydrolyzing ATP to ADP and inorganic phosphate. Both Mg++ and Ca++ at low ionic strength accelerated the ATP ase activity whereas at high ionic strength only Ca++ stimulated ATP hydrolysis. The ATP'ase activity was inhibited by ethylene‐diamine‐tetraacetic‐acid, Mersayl and p‐chloromercuribenzoate. The physico‐chemical and enzymatic properties of the extracted amoeba protein are qualitatively comparable to those of muscle actomyosin, and very similar in quantitative properties to smooth muscle actomyosin and the actomyosin‐like proteins of blood platelets, leucocytes and slime mold plasmodia. The significance of the presence of this actomyosin‐like protein in Dictyostelium amoebae is discussed in relation to amoeboid form and movement.
Correlation of adenosine phosphate levels with cellular morphology in Dictyostelium discoideum amoebae
Authors: Woolley David E. , Jones Peter C. T. 
Published: February 2005

AbstractPrior to completion of aggregation and the beginning of multicellular differentiation, the amoebae of Dictyostelium discoideum assume two distinct phases with characteristic changes in cellular movement, shape and adhesiveness. These two phases of amoeboid behaviour have been studied with respect to the quantitative analysis of the intracellular adenosine phosphates, using both enzymatic and chromatographic techniques. A higher intracellular ATP level and energy‐charge has been found for the actively moving, non‐adhesive amoebae as compared to the flattened, mutually adhesive cells. The importance and possible role of ATP in regulating amoeboid form, movement and cell adhesion is discussed.
Argon laser micro‐irradiation of mitochondria in rat myocardial cells in tissue culture
Authors: Berns Michael W. , Gamaleja Nicolai , Olson Robert , Duffy Cecilia , Rounds Donald E. 
Published: February 2005

AbstractThree types of lesions produced by argon laser micro‐irradiation of single mitochondria are described. A correlation between lesion severity and optical phase density and/or laser output power was observed. Cell survival was generally not affected by mitochondrial irradiation. As many as ten mitochondria were irradiated without cell death resulting. Absorption of the laser radiation was attributed to the natural chromophores, cytochromes c and c1.
From cell biology to immunology—A short trip
Authors: Herzenberg Leonard A. 
Published: February 2005

AbstractImmunologic memory and immunoglobulin allotype suppression are discussed as problems in Cell Biology. Memory, the ability of an animal after a first antigenic exposure to give a heightened and faster immune response upon a second exposure to the same antigen, is shown to be a property of bone marrow‐derived cell lines. Expression of this memory depends on interaction with thymus‐derived cells from either non‐immunized or immunized mice.Chronic allotype suppression is described for the first time. It is initiated by in utero or neonatal exposure of (SJL × BALB/c)F1 mice, allotype a/b, to anti b antibody. Suppression lasts for long periods and continues in irradiated recipients which have received lymphoid cells from suppressed donors. Selection against b allotype producing cell precursors can explain suppression.