bluuebunny/crossref_metadata_2025_split huggingface dataset:
The relation between cell division rate and 3HTdR incorporation in organ culture
Authors: Simnett John D. , Fisher Jean M. 
Published: February 2005

AbstractRates of incorporation of labelled thymidine (RIT), radioautographic labelling index for DNA synthesis (LI) and mitotic incidence following colcemid metaphase arrest (MI) were measured in organ cultures of newborn and adult rat lung. In adult cultures these three parameters correlated well, being low after explantation and reaching a maximum after two to three days. In newborn cultures RIT fell several fold over the first 24 hours after explantation and, in this respect, did not correlate with LI and MI. The changes in RIT over the first 24 hours appear to be due to changes in the degree of competition between endogenous TdR and exogenous labelled TdR, probably caused by leakage of the intracellular thymidine pool following explantation. The report emphasizes the need to check RIT data against radioautographic evidence before accepting it as an index of DNA synthesis.
Relationship between the ratio of parental chromosomes and parental doubling times in chinese hamster‐mouse somatic cell hybrids
Authors: Labella T. , Amati P. , Marin G. 
Published: February 2005

AbstractSomatic hybrids obtained by the selective method of Littlefield between a permanent line of Chinese hamster cells (Wg3) and one of mouse cells (3TP) showed a preponderance of biarmed (hamster) chromosomes. Under normal culture conditions (37°) the doubling time of the parental mouse cells was twice as long as that of the parental hamster cells. If the temperature of incubation was lowered (31°), the relative difference in doubling times was reduced; in hybrid lines obtained under these conditions, the proportion of biarmed chromosomes was also reduced.Upon extended cultivation the average number of telocentric chromosomes progressively decreased in all hybrid lines tested, regardless whether these were started and maintained at 37° or at 31°. An inverse correlation was observed in hybrid cells between doubling time and relative proportion of biarmed chromosomes, suggesting that the karyotypic changes observed after extended culture were due to the selective overgrowth of cells with a high biarmed to telocentric ratio.
The temperature dependence of the exchange transport of glucose in human erythrocytes
Authors: Lacko L. , Wittke B. , Geck P. 
Published: February 2005

AbstractThe temperature dependence of the uptake of glucose by exchange transport is investigated at two pH values (7.5 and 5). The Arrhenius's energy of activation, the heat of activation, the free energy of activation and the entropy of activation are calculated. The parameters are different at pH 7.5 and 5. For both pH levels the heat of activation and the entropy of activation change abruptly at 20°C. This finding leads us to assume that at this temperature a change in the structure of the membrane takes place.
The effects of zinc and lanthanum on calcium uptake by mitochondria and fragmented sarcoplasmic reticulum of frog skeletal muscle
Authors: Batra S. 
Published: February 2005

AbstractCalcium uptake by mitochondria and fragmented sarcoplasmic reticulum (FSR) isolated from frog skeletal muscle was studied. These fractions were characterized by electron microscopy, succinic dehydrogenase assay and by using mitochondrial inhibitors. With high (100 μM) Ca in the medium, the Ca accumulating capacity of the two fractions was similar. Zinc in concentrations of 5–10 μM in the medium had no effect on Ca uptake by either fraction whereas higher concentration of Zn (25 μM) reduced Ca uptake in both fractions. Five micromolar lanthanum lowered Ca uptake by 70% in mitochondria but had no effect on Ca uptake by FSR. With 10 and 25 μM La, Ca uptake by FSR decreased by 12 and 20% respectively. Addition of La (5 μM) to Ca‐loaded mitochondria had no effect indicating that La could only interfere with the Ca binding step and was unable to release Ca that was already stored. In the medium that originally contained low (10 μM) Ca FSR was able to reduce the Ca concentration below 0.1 μM. In contrast mitochondria, although possessing an equal capacity for Ca uptake were unable to accumulate Ca from the medium when Ca was lowered to approximately 4 μM. Presence of 5–10 μM La in the low Ca medium had no effect on the total amount of Ca taken up by FSR in two minutes but reduced the rate of Ca uptake significantly. The relation of the effects of Zn and La on the isolated fractions to their reported effects on the contractile response of skeletal muscle is discussed.
Electrophysiological observations on immature rat nerve cells grown in tissue culture
Authors: Lawson Sarah N. , Biscoe T. J. 
Published: February 2005

AbstractIntracellular measurements were made on immature cultured rat neurons using single or double barrelled microelectrodes; 361 dorsal root ganglion, DRG, cells, 105 spinal cord cells and 12 cerebellar cells were studied. Membrane potentials recorded were in the range −25 mV to −50 mV. A statistically significant increase in membrane potentials with time in culture was found for DRG cells during 32 days in culture. This was not found for spinal cord cells.Voltage‐current curves showed a non‐linearity in about 50% of DRG and spinal cord cells similar to anomalous rectification. Measurements made in DRG and spinal cord cells at ± 10 nA showed significantly greater average cell input resistance during hyperpolarising pulses than during depolarising pulses.The calculated values of Rm and Cm for DRG and spinal cord cells were similar in magnitude to values given for other cells by other workers. The value for L, the dimensionless electrotonic length, was slightly higher than that calculated for motoneurones by other workers. Differences between these results and those of others working on neurons in vitro are ascribed to the immature nature of the cells studied here.
Myoglobin synthesis in cell cultures of red and white muscle
Authors: Heywood Stuart M. , Havaranis Amalia S. , Herrmann Heinz 
Published: February 2005

AbstractMyoglobin synthesis was compared in cell cultures of leg (red) and breast (white) muscle of chick embryos. In leg muscle cultures a rapidly increasing amino acid incorporation into myoglobin begins two days after muscle cell fusion; in breast muscle cultures no comparable increase was observed. This qualitative difference in cultures of the two muscle cell types provides possibilities for the further study of the mechanism of myoglobin synthesis.
Isolation of temperature sensitive mammalian cells by selective detachment
Authors: Roscoe D. H. , Read Moira , Robinson Hildred 
Published: February 2005

AbstractTemperature sensitive cells have been isclated from Syrian and Chinese hamster cells using a method based on selective detachment from a glass substrate. The Syrian hamster isolates occurred at a high frequency (about 1 in 103) and reverted rapidly; polyoma virus transformation conferred on cells the ability to grow, perhaps abnormally, in agar suspension. A slightly modified isolation technique was applied to Chinese hamster cultures and resulted in the isolation of at least one mutant (from a starting population of 5 × 108 cells) with a spontaneous reversion rate of less than one in 6 × 107. Treatment of the mutant with ethyl methane sulphonate induced reversion. It was concluded that selective detachment provided a useful method for the isolation of conditional lethal mutants of mammalian cells.
Factors affecting pH‐dependent photo‐inhibition of division in Euglena gracilis
Authors: Cook J. R. , Kaiser H. 
Published: February 2005

AbstractVisible light of moderate intensity (1200 ft‐cd) can severely inhibit cell division of a non‐photosynthetic mutant of Euglena gracilis when growth is supported by butanol, ethanol, or fumarate as sole carbon source. The degree of inhibition is pH dependent, being greatest at pH 4 to 5. A wide variety of other carbon sources permitted growth in the light without inhibition.
Density dependent regulation of growth in L cell suspension cultures. III. Elevation of specific activity of acetylcholinesterase
Authors: Glinos André D. , Bartos Edwin M. 
Published: February 2005

AbstractHigh density L cell suspension cultures were previously shown to remain viable for indefinite periods of time and to exhibit marked inhibition of DNA synthesis and mitosis while the fraction of total protein synthesis represented by collagen is increased. The present study demonstrates that regulation in this system extends to the activity of acetylcholinesterase found to be approximately 100‐fold greater in the high density populations than in low density exponentially growing cultures. Kinetic studies of the increase of the activity, its fluctuation over an extended period of time and its decrease upon resumption of exponential growth after dilution of the cultures were performed. The data obtained indicate that the enzyme does not accumulate in high density populations merely as a result of the absence of net protein synthesis and cell division but that changes of its rates of synthesis and possibly degradation are involved. The expression of regulated acetylcholinesterase activity in a cell line of connective tissue origin is considered in relation to phenotype reprogramming and to cell membrane associated growth control mechanisms.
Calcium and flagellar response during the chemotaxis of bracken spermatozoids
Authors: Brokaw C. J. 
Published: February 2005

AbstractThe attraction of fern spermatozoids by secretions from the female reproductive structures, and by salts of malic acid, has long been known as a classic example of precise chemotactic orientation by motile cells. Spermatozoids of the bracken fern are attracted by the partially ionized form of malic acid, bimalate ion, and also by calcium ions. Both calcium and bimalate ions must be present for chemotactic response and for response to voltage gradients, Spermatozoids swimming up a bimalate concentration gradient swim in helical paths of abnormally small radius; if they accidentally swim down the concentration gradient the radii of their path helices become abnormally large.These observations suggest that changes in the direction of flagellar beating in response to the rate of change of bimalate ion concentration with time may be the basis for chemotactic orientation. A “coupled diffusion” hypothesis for chemo‐reception is presented, which postulates a membrane carrier which can only circulate freely in the membrane if it binds both bimalate and calcium ions. This hypothesis could explain time‐differentiation of the stimulus, the coupling of a specific stimulus — bimalate ions — to a general mediator of intracellular response — calcium ions — and the quantitative relationship between response of the spermatozoids and the chemical potential of “calcium bimalate.”
Control of normal differentiation of myeloid leukemic cells. IV. Induction of differentiation by serum from endotoxin treated mice
Authors: Fibach Eitan , Sachs Leo 
Published: February 2005

AbstractSera from different strains of mice injected with endotoxin induced clones (D+) from a cultured line of myeloid leukemic cells to undergo normal differentiation to mature granulocytes and macrophages. Other clones (D−) derived from the same cell line were not inducible by these sera to undergo normal cell differentiation. Sera from the same strains of mice that had not been injected with endotoxin, increased the cloning efficiency of D+ and D − clones but did not induce differentiation. Endotoxin serum induced differentiation in D+ cells at dilutions up to 1:64, but increased the cloning efficiency of these cells at dilutions up to 1:2048. The end point of the dilution of endotoxin serum that induced differentiation in D+ cells, was also the end point that induced the formation of colonies with differentiation from normal bone marrow cells. The results indicate that serum from endotoxin treated animals can serve as a good in vivo source to induce normal differentiation in D+ myeloid leukemic cells; that the progeny of a single leukemic cell was induced to undergo differentiation to both macrophages and granulocytes; that endotoxin serum contained two activities, one that increased cloning efficiency and the other that induced cell differentiation; and that the same material in endotoxin serum induced cell differentiation in normal and leukemic cells.
Inhibition of development of transformation by rous Sarcoma virus in cultures of high cell density
Authors: Clark Joseph M. , Bader John P. 
Published: February 2005

AbstractThe effect of cell density on morphological transformation of chick embryo cells by Rous Sarcoma Virus (RSV) was examined in this study, and a cell density optimum for transformation was found. Less than 10% of the transformed foci appearing at the optimum density (2.5 × 104 cells per cm2) developed at high cell densities, and the diameters of the foci (an indication of the number of cells per focus) decreased with increasing cell density. No correlation was found between the decrease in transformation at high cell densities and the effect of cell density on the initial rate of cell proliferation, although dissociation of transformation from incorporation of radioactive precursors into nucleic acids could not be established. Redistribution of cells infected at high density showed that only a small proportion of successfully infected cells developed into foci. The results indicate that transformation of cells containing the RSV genome can be suppressed by physiological factors accompanying high cell density.
Studies on the surface of chick blastoderm cells. III. Calcium binding to ionogenic sites
Authors: Harris Harriet L. , Zalik Sara E. 
Published: February 2005

AbstractThe effect of increasing calcium concentrations on the electrophoretic mobility of cells obtained from early chick blastoderms at successive developmental stages was studied. Cells had zero mobilities at calcium concentrations in the range of 1 to 2 × 10−2 M CaCl2, and became positively charged when calcium concentrations between 2 and 5 × 10−2 M CaCl2 were used. Results using trypsin suggest that while some calcium binding sites disappear from the surface ionogenic layer, the majority of them are not removed by this enzyme. The calcium binding capacity did not vary appreciably in the stages studied. Charge reversal induced by calcium is reversible.
Autoradiographic studies of pyridine nucleotide metabolism in human culture cells
Authors: Rechsteiner Martin , Lund Keith , Hillyard David , Olivera Baldomero 
Published: February 2005

AbstractMore than 80% of the intracellular pyridine metabolite pool of human culture cells is trapped by OsO4 fixation. The fixed pyridine metabolites fully exchange with nicotinamide and nicotinic acid but not with nicotinamide adenine dinucleotide. Yet, chromatography of the exchanged compounds reveals that NAD and NADP constitute more than 95%. of the fixed material. Although the mechanism of OsO4 fixation is not fully understood, such fixation has permitted the autoradiographic detection of intracellular pyridine metabolites. Cells of the human cell line, D98/AH2, synthesize pyridine nucleotides during all phases of the cell cycle at rates which do not vary by more than six‐fold. There is no difference in the apparent concentration of pyridine metabolites between nucleus and cytoplasm after ten minute or three day pulses with 3H‐nicotinic acid. The 3H‐labeled pyridine ring is lost from D98/AH2 cells upon transfer to unlabeled medium. In general, the rate of loss is uniform among cells in the population. However, in a small proportion of cells there is little or no loss. Non‐dividing cells lose the pyridine ring at approximately the same rate as dividing cells, yet the intracellular concentration of pyridine metabolites is 50% greater in non‐dividing cells.
Density dependent regulation of growth in L‐cell suspension cultures. IV. Adaptive and nonadaptive respiratory decline
Authors: Vail James M. , Glinos André D. 
Published: February 2005

AbstractRespiration as an index of oxidative energy production was investigated in a L‐cell suspension culture system previously shown to exhibit density‐dependent inhibition of growth. It was found that as cultures progressed from exponential growth to high density nongrowing populations (6−10 × 106 cells/ml) over a 2‐week period, the respiratory rate determined from the total amount of oxygen consumed during the daily medium renewal cycle, declined from 5.4 to 1.8 fmoles O2/cell/min. There are two components in this decrement. The first consists of a daily recurrent decline of oxygen uptake resulting from decreased availability of medium oxygen and glutamine and is readily reversed by medium supplementation. The second component which is refractory to medium supplementation and accounts for approximately 50% of the total respiratory decline, is considered to indicate an adaptive change of the respiratory capacity of the cells. This change is reversed during the lag period which precedes resumption of exponential growth upon subculture to low cell densities. The significance of these results is discussed in relation to recent reports indicating a marked depression of respiratory activity in nongrowing dense attached cultures as well.
Cell volume regulation in ehrlich ascites tumor cells
Authors: Hendil Klavs B. , Hoffmann Else K. 
Published: February 2005

AbstractEhrlich cells subjected to anisoosmolar media show very rapid volume changes. In hypertonic media they shrink. In hypotonic media they swell but the rapid initial swelling is followed by a regulatory shrinkage lasting ca. 30 minutes.Cells suspended in media with identical ionic concentrations but different total osmolarity (adjusted by sucrose) were compared. These studies revealed that swollen cells adjust their volume by decreasing the amount of intracellular K+ and ninhydrin positive substances. Intracellular Na+ and ATP concentrations were unchanged. Accordingly 42K+ flux analysis showed that the (passive) cell membrane permeability for K+ is increased to a minor degree and the Na+ permeability unaffected. The increased K+ permeability could not be correlated to an increase in 45Ca2+ influx.
Peritoneal exudate cells II. Kinetics of appearance of colony‐forming cells
Authors: Lin Hsiu‐San 
Published: February 2005

AbstractA transient increase in the number of peritoneal colony‐forming cells in agar (PCFC) was noted in the peritoneal cavity of mice given one intraperitoneal injection of thioglycollate medium. This increase of PCFC was not accompanied by a similar degree of increase in the number of either pluripotent hemopoietic stem cells or committed hemopoietic stem cells for granulocytes and/or macrophages that are normally present in the peritoneal cavity in small numbers. Other substances, such as glycogen, starch, Freund's adjuvant, sheep red blood cells and lectins, were also capable of increasing PCFC, but to different degrees. The ability of thioglycollate medium as well as other stimulatory agents to increase PCFC appeared to be dose‐dependent.
Proliferative capacity and DNA content of aging human diploid cells in culture: A cytophotometric and autoradiographic analysis
Authors: Yanishevsky Rosalind , Mendelsohn Mortimer L. , Mayall Brian H. , Cristofalo Vincent J. 
Published: February 2005

AbstractUsing a combination of DNA‐cytophotometry and tritiated thymidine‐autoradiography, we have shown that the majority of nondividing cells in serially propagated human diploid cell populations have the 2C DNA content consistent with their being arrested in the G1 phase of the diploid cell cycle. Unlabeled 4C cells appear increasingly with time in culture. These may be arrested G2 diploids or they may be G1 tetraploids, since there is an associated increase in polyploidy in older cultures as evidenced by the appearance of labeled 8C cells.
Metabolic cooperation in cell culture: Studies of the mechanisms of cell interaction
Authors: Cox Rody P. , Krauss Marjorie R. , Balis M. E. , Dancis Joseph 
Published: February 2005

AbstractMetabolic cooperation is a form of cell communication in which the mutant phenotype of enzyme deficient cells, as determined by incorporation of labeled substrates, is corrected in culture by contact with normal cells. Previous studies showed that metabolic cooperation between normal and hypoxanthine phosphoribosyl transferase deficient cells (HPRT−) was the result of transfer of product of the enzyme, nucleotide or nucleotide derivative, from normal to mutant cells rather than transfer of enzyme or informational macromolecules leading to the synthesis of the enzyme.In the present study the nature and mechanisms involved in these cell interactions were investigated. Effective communication is observed within one hour of cell contact. Modifications of the extracellular environment including changes in osmolarity, concentration of sodium and divalent ions failed to interfere significantly with transfer. Changes of cell shape induced by cyclic nucleotides, hormones and urea also did not affect communication. Cytochalasin B which dissociates microfilaments and binds to cell membranes reduced metabolic cooperation while colcemide which dissociates microtubules had little effect. Enzymatic oxidation and iodination of cell surface structures abolished metabolic cooperation. The subcellular localization of label in donor cells is important in determining efficiency of transfer. Metabolic cooperation is efficient when radioactive label is primarily located in the nucleus and inefficient if the label is cytoplasmic. Cell lines previously classified as “non‐communicating” because they lack gap junctions, ionic coupling and metabolic cooperation were shown in the present study to communicate when incubated with labeled substrates for 20 hours rather than 3. Cell communication is a more generalized phenomenon among cells in contact than previously appreciated.
Cellular binding of 3H‐cytochalasin B
Authors: Mayhew E. , Poste G. , Cowden M. , Tolson N. , Maslow D. 
Published: February 2005

AbstractThe binding of tritium‐labelled cytochalasin B (3H‐CB) to a variety of mammalian cells was investigated. Binding studies revealed near‐equilibrium binding of 3H‐CB within 5 to 10 minutes, but the equilibrium level was influenced by 3H‐CB concentration. Binding kinetics revealed strong temperature dependence. Rapid release of up to 70% of cell‐bound 3H‐CB molecules occurred when cells were washed and returned to fresh medium without CB. The remaining 30% of cell‐bound 3H‐CB molecules dissociated more slowly. Equilibrium binding studies on a variety of diploid, heteroploid and transformed cells treated with 1 μg/ml 3H‐CB revealed between 1.7 X 107 to 5.3 X 107 3H‐CB binding sites per cell. Cellular binding of 3H‐CB was not affected by inhibition of cellular energy metabolism, RNA or protein synthesis. Modification of the cell surface by proteases, neuraminidase, hyaluronidase, ribonuclease, or occupation of cell surface saccharide residues by a variety of plant lectins did not significantly alter the pattern of 3H‐CB binding. Surface pressure measurements on CB‐treated lipid monolayers indicated that CB can interact with lipid molecules. The partition of CB in hydrophobic lipid regions of cell membrane systems as a possible mechanism of cellular binding of CB is discussed. Fractionation of 3H‐CB‐treated cells revealed binding of 3H‐CB to both the plasma membrane and by intracellular membranes.