bluuebunny/crossref_metadata_2025_split huggingface dataset:
Transformation of human cystinotic fibroblasts by SV40: Characteristics of transformed cells with limited and unlimited growth potential
Authors: Oshima Robert G. , Pellett Ocean L. , Robb James A. , Schneider Jerry A. 
Published: February 2005

AbstractHuman skin fibroblasts derived from patients with nephropathic cystinosis were transformed with SV40 virions, cloned and permitted to enter the degenerative stage of growth termed “crisis,” characteristics of SV40 transformed human cells. Nephropathic cystinosis is an autosomal recessively inherited metabolic disorder resulting in the intracellular accumulation of the amino acid cystine. A transformed cystinotic cell line which was recovered from the crisis stage was indistinguishable from its transformed precrisis parental cell strain in growth rate in media containing either 1% or 10% serum, cloning efficiency on plastic, in semisolid media, or upon confluent monolayers of normal skin fibroblasts, expression of SV40 T antigen, or production of virus. However, the modal DNA content of the recovered postrisis transformed cystinotic cell line was different from that the cloned parental precrisis transformed cell strain, suggesting that the postcrisis line was derived from a small subpopulation of the precrisis strain. The DNA content of the established cystinotic cell line continued to be unstable during subsequent subculturing and gave rise to subclones with both more and less DNA per cell. This line now has an apparently infinite growth potential and still has the hallmark of the cystinotic parental line, the storage of abnormally large amounts of intracellular nonprotein cystine.
Repetitive DNA in differntiating chick tissues
Authors: Ayres Kathleen Nelson 
Published: February 2005

AbstractEmbryonic chick DNA from different tissues was examined for diferences in relative content of highly repetitive DNA which might indicate specific DNA amplification in somatic cells. The content of repetitive sequences in DNA isolated from cerebrum, muscle, and neural retina tissues, at the same and at different embryonic stages, was determined by hydroxyapatite fractionation of partially reassociated DNA samples. An unrenatured marker DNA (C14‐labeled E. coli DNA) was added to each chick DNA sample in order to monitor the nonspecific single‐stranded DNA retention by each hydroxyapatite column. When chick DNA samples were sheared to a double‐stranded length of 1,300 nucleotide pairs, an average of 20.2% ± 2.2% of the DNA was found to reassociate at a Cot value of 10. The quantity of the fast reassociating sequences was found to constitute the same fraction of the DNA in all the tissues studied. In addition, all the reassociated DNA samples exhibited the same CsCl density classes. The studies also indicated that most chick DNA repetitive sequences are interspersed with nonrepetitive sequences.
Interrelationships between water and cellular metabolism in Artemia cysts VII. Free amino acids
Authors: Clegg James S. , Lovallo Jeffrey 
Published: February 2005

AbstractThe concentration of total ninhydrin‐positive material (NPM) soluble in 5% trichloroacetic acid was measured in cysts of the brine shrimp, Artemia salina, as a function of hydration level. No net change in NPM was observed until the cysts had achieved a water content of about 0.65 g H2O/g of initially dry cysts. Above this hydration threshold the NPM content increased markedly. Examination of the free amino acid composition of cysts incubated at selected hydration levels revealed that almost all of the amino acids underwent net change above the hydration threshold. However, just below this threshold, the free amino acid composition was essentially the same as in fully dried cysts. The activity generating net changes in the concentration of free amino acids above the hydration threshold was shown to be metabolic in nature and restricted to the cellular component of the cyst.
Effects of multiplication stimulating activity (MSA) on AIB transport into myoblast and myotube cultures
Authors: Merrill Gary F. , Florini James R. , Dulak Norman C. 
Published: February 2005

AbstractThe effects of a somatomedin analog, Temin's multiplication stimulating activity (MSA), on amino acid transport into muscle cells have been characterized in a series of experiments on myoblasts and myotubes in culture. Addition of MSA to serum‐starved L6 myoblasts increased the rate of aminoisobutyrate (AIB) uptake 50‐150% within five hours. This early effect on transport was followed by increases in cell number, protein content and 3H‐thymidine incorporation. Kinetic analyses indicated that MSA increased the maximal velocity of AIB uptake but had no effect on the KM for AIB. When myoblasts were allowed to fuse (and dividing cells eliminated by addition of 10−4 M cytosine arabinoside) the AIB transport system(s) remained similarly responsive to MSA. In myoblasts and in myotubes, both the basal and MSA‐stimulated rate of AIB uptake were sodium‐dependent processes; little stimulation occurred if sodium was absent from the labeling medium. Further suggesting the involvment of cations in response to hormone, MSA stimulated uptake of the potassium analog, 86Rb+, and increased net intracellular potassium in both myoblasts and myotubes. MSA was active at concentrations equivalent to in vivo levels of somatomedins; neither insulin nor growth hormone had any effect at or near physiological concentrations.
The presence of cyclic AMP, and its effects on oral regeneration and in situ ciliary regeneration in stentor coeruleus
Authors: Maloney Michael S. , Burchill Brower R. 
Published: February 2005

AbstractWe have found cyclic AMP in the large, heterotrichous ciliate Stentor coeruleus in amounts per milligram protein similar to those found in another ciliate, Tetrahymena pyriformis. The possible function of cyclic AMP in Stentor was first examined by determining its effects on oral regeneration, the process by which Stentor can replace a missing oral apparatus in eight to ten hours. Once begun (by brief exposure to a 15% sucrose solution, causing shedding of the oral apparatus) regeneration follows eight specific morphological stages visible with the dissecting microscope. Continuous exposure of regenerating cells to either N6, 2′‐0‐dibutyryl adenosine cyclic 3′:5′‐monophosphate (DBC) or theophylline begun at the onset of oral regeneration (stage 0) caused delays in the completion of regeneration. The delays induced by DBC occurred in the early stages prior to stage 5. Regenerating cells exposed to DBC or theophylline at various stages of development were delayed, even at stages 5 and 6. Both DBC and theophylline reversibly bleached the cortical pigment of the cells. Guanosine 3′:5′‐cyclic monophosphate (cyclic GMP), AMP, GMP, and sodium butyrate neither delayed oral regeneration nor bleached the cortical pigment. Excess extracellular calcium ions alone had no effect on oral regeneration, but 10 mM calcium and DBC caused more delay than DBC alone. Thus, the delay of oral regeneration in Stentor caused by cyclic AMP may involve calcium ions.To determine if cyclic AMP can retard in situ ciliary regeneration by Stentor, as it does in Tetrahymena, a new technique, more accurate than past methods, was developed to monitor ciliary regrowth. Using this procedure we found that both DBC and theophylline significantly delayed the in situ ciliary regeneration by Stentor.
Reversible regulation by magnesium of chick embryo fibroblast proliferation
Authors: Rubin A. H. , Chu Berbie 
Published: February 2005

AbstractThe rates of 3H‐thymidine incorporation and of cell proliferation in chick embryo fibroblast cultures are reduced coordinately when the [Mg2+] of the external medium is reduced below the physiological concentration of about 0.8 mM. These effects of moderately reduced [Mg2+] and the accompanying change in appearance of the cells, resemble the effects produced by lowering the [serum] of the medium. Cells subjected to severe Mg2+ deprivation, especially at low [Ca2+], die and detach from the culture dish. Cells kept at a reduced rate of proliferation for three days by moderate Mg2+ deprivation are quickly restored to rapid proliferation upon restoration of the normal [Mg2+] of the medium. The rate of proliferation of the chick embryo cells is reduced markedly by lowering [Ca2+] about 100‐fold, but unlike the case of Mg2+‐deprivation this can occur without significant effect on the rate of 3H‐thymidine incorporation. More severe Ca2+ deprivation, which does lower the rate of 3H‐thymidine incorporation, produces retraction of cells from one another and from the dish, and results in a distinctly abnormal, rounded appearance. The results lend weight to the thesis that free [Mg2+] plays a central role within the cell in the coordinate control of metabolism and growth. They also suggest that the effects produced by varying [Ca2+] in the medium are caused by changes at the external surface of the cell.
Arginase activity and other cellular events associated with epidermal hyperplasia
Authors: Redmond Audrey F. , Rothberg Simon 
Published: February 2005

AbstractThe unknown biochemical role of arginase in epidermal metabolism was probed by examining the association of elevated arginase activty with epidermal hyperplasia and hyperkeratinization. Epidermal hyperplasia as induced experimentally by topical application of 1‐decanol to the right side of male hairless mice while the contralateral side served as control. Arginase activity, incorporation of 3 H‐thymidine into DNA, DNA and protein content were measured in the separated control and experimental epidermis six hours and on days 1 through 5 and 7 after 1‐decanol application. After six hours, the epidermis appears damaged histologically, and DNA synthesis is inhibited. By day 1, incoporation of 3 H‐thymidine into DNA is elevated and a new hyperplastic epidermis has formed beneath the original epidermis. Epidermal arginase is elevated two through seven days after 1‐decanol application and always is associated with continuing epidermal hyperplasia. The stimulation of DNA synthesis, which parallels the induction of epidermal hyperplasia by 1‐decanol, precedes the induction of epidermal arginase activity. An attempt to relate these results with polyamine synthesis and other metabolic events is made.
Interrelationships between water and cellular metabolism in Artemia cysts. VIII. Sorption isotherms and derived thermodynamic quantities
Authors: Clegg James S. 
Published: February 2005

AbstractAn analysis of water vapor sorption by cysts of the brine shrimp, Artemia salina, has shown that at environmental water activities (aw) of 0.95 or less, the cysts equilibrate with the aw of their environment. Above this aw the metabolic activity of the cysts participates directly in their water content, and equilibration does not occur. In contrast, dried cysts killed by heat treatment or exposure to ammonia fumes equilibrated with all values of aw examined. Analysis of the temperature dependence of sorption isotherms revealed that below cyst hydrations of about 0.3 g H2O/g dried weight the temperature coefficient for water sorption was negative, but became positive at hydrations appreciably in excess of this value. Estimates for the differential and integral net enthalpy and entropy changes accompanying the sorption of water have been calculated from isotherms. These results have been interpreted and integrated with those from previous work on the hydration‐dependence of metabolic activity. All of the examined hydration properties of the cysts have been shown to be due chiefly to the cellular component, and not the acellular shell. Analysis of the data by the Bradley equation has shown that the hydration behavior of the shell obeys this relationship, whereas that of the cellular component does not.
The selection of a stable rat hepatoma variant with concomitant increase in ploidy and permeability to glycerol
Authors: Li C. C. , Lin E. C. C. , Karnovsky M. J. , Lin P. S. 
Published: February 2005

AbstractBy repeated selection for longer survival in an isotonic solution of glycerol, a stable subline of Novikoff rat hepatoma cells has been isolated. The cells exhibit markedly increased resistances to osmotic lysis in isotonic solutions of glycerl. They are twice as large and have twice as many chromosomes as cells of the parental line. It is suggested that the osmotic stress procedure can be extended for the selection of numerous kinds of mutants and can be used as a method of analysis of membrane properties.
Early transport changes during erythroid differentiation of friend leukemic cells
Authors: Mager Dixie , Bernstein Alan 
Published: February 2005

AbstractEarly transport changes occurring during Friend erythroleukemic cell differentiation are reported. A decrease in the rate of 86Rb transport was observed beginning approximately five hours after stimulation with 1.5% dimethylsulfoxide (DMSO), a potent inducer of Friend cell differentiation. By 12 to 14 hours after DMSO addition, the transport rate had stabilized at close to 60% of control level. This decrease in the rate of 86Rb transport preceded a previously reported decrease in cell volume. Other chemical inducers of Friend cells, such as hypoxanthine and ouabain, also caused early decreases in 86Rb influx. In contrast, xanthine, which does not induce Friend cell differentiation, also did not affect 86Rb influx.The transport of two amino acid analogues, αaminoisobutyric acid and 2‐aminobicyclo [2,2,1]‐heptane‐2‐carboxylic acid, which differ in their mode of uptake, was also measured following induction by DMSO. The transport rates of both compounds decreased after a 12‐hour exposure to DMSO. In contrast, the uptake of 3H‐colchicine, a drug which diffuses passively across the cell membrane, was not significantly affected.Studies with several variant cell lines which do not synthesize hemoglobin in response to DMSO indicate that these non‐inducible cells can be divided into two classes—those that demonstrate early changes in transport very similar to the changes observed in inducible cell lines and those which exhibit only small changes in transport. Results obtained using a revertant clone have helped to distinguish between those transport changes which are associated with the induction of hemoglobin synthesis and those which are not. In addition, these early transport changes may be useful in defining the stage in the differentiation process at which a particular variant line is blocked.
Effect of hydrocortisone on cell morphology in C6 cells
Authors: Berliner Judith A. , Bennett Kimberly , De Vellis Jean 
Published: February 2005

AbstractHydrocortisone has been found to induce cell spreading in rat glial C6 cells by 24 hours after its addition. This spreading phenomenon is correlated with an increase in the fraction of the peripheral cytoplasm occupied by microfilaments. Cytochalasin B causes disorganization of microfilaments in the peripheral cytoplasm of the cells. Additionally, it also prevents cell spreading in response to hormonal stimulation. High levels of calcium prevent recovery of normal microfilament organization and cell spreading following removal of cytochalasin B, but have no effect on normal microfilament organization alone. Additionally both the hydrocortisone induced spreading of C6 cells and increases in peripheral microfilaments are shown to be dependent on RNA and protein synthesis. The levels of protein co‐electrophoresing with actin are not effected by hydrocortisone.
Growth dependence of phosphoglyceric acid dehydrogenase activity in cultured rat liver cells
Authors: Isom Harriet C. , Pizer Lewis I. 
Published: February 2005

AbstractRat liver epithelial cells in culture (WIRL‐3C) have the enzymes that synthesize serine from 3‐phosphoglyceric acid. Both phosphoglyceric acid dehydrogenase (PGAD) and serine‐phosphate (serine‐P) forming activities fluctuate with time after subculture and are higher in growing than confluent cells. This activity pattern was not common for other dehydrogenases in WIRL‐3C cells, nor was it common for PGAD activity in other cultured cells. At time of sub‐culture, cells are removed from spent medium, treated with trypsin, and fed fresh medium. None of these parameters causes the rise in activity; in contrast, reduction in cell density and the accompanying stimulation of growth do. PGAD activity decreases when growth is slowed either as the cells progress to the end of the culture cycle, when cells are treated with dexamethasone‐phosphate (Dx‐P) or dibutyryl cyclic AMP (cAMP) and theophylline or when the serum concentration of the medium is reduced to 0.2%. Under these conditions, decreased PGAD activity is paralleled by a decline in growth and DNA accumulation. PGAD activity in WIRL‐3C cells is regulated in a manner closely resembling what has been observed previously in rat liver from the whole animal. The possible use of this system in studying regulation of gene expression in mammalian cells is discussed.
Early changes in the membrane of HeLa cells adsorbing sendai virus under conditions of fusion
Authors: Fuchs P. , Spiegelstein M. , Haimsohn M. , Gitelman J. , Kohn A. 
Published: February 2005

AbstractAdsorption of Sendai virus at high multiplicity (500‐1,000 HAU/106 cells) to HeLa cells grown in monolayers causes immediate changes in the ion barrier of the cell membrane, as well as changes in the morphology of the virus‐treated cells. Within minutes of adsorption the cells begin to lose potassium and an extensive influx of ions into the cells occurs. Concomitantly with these changes, the cell membrane becomes depolarized, and the resting potential across its membrane decreases. Twenty to sixty minutes post adsorption the damage to the cell membrane is repaired, and both the potassium uptake and the resting potential return to their pre‐exposure values. Scanning electron‐micrographs of Sendai infected cells incubated at 37°C show formation of bridging microvilli in a zipper‐like fashion within two to five minutes post‐adsorption; 30 to 60 minutes thereafter the majority of cells in the monolayer are fused. Biochemical changes induced by virus adsorption and the role of Ca++ ions in the observed effects are discussed.
Polyamine biosynthesis and DNA synthesis in cultured mammary gland explants from virgin mice
Authors: Sakai Tadashi , Lundgren David W. , Oka Takami 
Published: February 2005

AbstractThe mammary cells in virgin mice are essentially non‐proliferative, but they can be induced to undergo DNA synthesis in vitro in the presence of insulin. Time course studies on polyamine biosynthesis and DNA synthesis showed that insulin elicits sequential stimulation of the activity of the polyamine biosynthetic enzymes, ornithine decarboxylase, S‐adenosyl‐L‐methionine decarboxylase (SAMDC) and spermidine synthase, and an increase in the concentration of spermidine prior to the augmentation of DNA synthesis. At 48 to 72 hours of culture when DNA synthesis is maximal, the concentration of spermidine increased 2− to 3‐fold, whereas the level of spermine remained unchanged. Addition of methyl glyoxal bis(guanylhydrazone) (5—10 μM), a potent inhibitor of SAMDC, to the medium at the onset of culture resulted in inhibition of spermidine formation and DNA synthesis, but when added at 24 hours or 48 hours of culture, the inhibitory effect on DNA synthesis was greatly reduced. The drug, however, produced little inhibition of RNA and protein synthesis. Inhibition of DNA synthesis by the drug can be reversed by addition of spermidine or other polyamines such as putrescine, cadaverine and spermine to the culture. Spermidine is, however, the only polyamine that is effective at physiological concentrations (100∼150 pmoles/mg tissue). These results suggest a possibility that spermidine may play a key role in the regulation of mammary cell proliferation.
Induction of erythroid differentiation in friend leukemia cells by bromodeoxyuridine
Authors: Adesnik Milton , Snitkin Harriet 
Published: February 2005

AbstractTreatment of Friend leukemia cells with BrdU, the thymidine analog which interferes with DMSO induced differentiation in these cells as well as the expression of differentiated character in many other cell systems, is capable of inducing erythroid differentiation. Globin mRNA, as assayed by hybridization to globin cDNA, increases 2.5− to 30−fold after appropriate treatment with BrdU. This effect was observed with several different subclones of three independent Friend tumor cell lines. After BrdU treatment, globin mRNA content may reach up to 10—20% of the levels in DMSO induced cultures. The induction of erythroid differentiation is also apparent when accumulated heme content or the appearance of benzidine positive cells is monitoredOne Friend cell line (745) we examined was not induced by BrdU although it incorporated an amount of BrdU into its DNA comparable to that incorporated by the other cell lines. In addition, BrdU did interfere with DMSO induction in this cell lineThese results suggest that two different mechanisms may be operative in regulating erythroid differentiation in Friend leukemia cells. While BrdU interferes with the mechanism activated by DMSO treatment, this analog could independently activate an alternative mechanism.
Alterations in the protein synthetic apparatus of friend erythroleukemia cells during their erythroid differentiation
Authors: Nishioka Yutaka , Silverstein Saul 
Published: February 2005

AbstractThe changes in rate of protein synthesis and cell division and the distribution of polyribosomes and globin mRNA on the polyribosomes of Friend erythroleukemia (FL) cells exposed to 2% DMSO and maintained at low cell density, were examined at different times after exposure to DMSO. The rate of protein synthesis and the capacity of cells to divide declined in concert to 50% of the level found in untreated cell cultures at 24 hours after exposure. Thereafter these rates recovered to 70% of the rate found in untreated control cultures until 96 hours post‐exposure and then irreversibly declined as the cells lost the capacity to divide. The proportion of ribosomes present as polyribosomes in cells exposed to DMSO paralleled the capacity of these cells to synthesize protein. The distribution of polyribosomes analyzed by sedimentation in sucrose gradients demonstrated that a discrete, abundant class of polyribosomes composed of pentamers to heptamers appeared as early as 48 hours after exposure to DMSO. The appearance of an abundant class of polyribosomes was correlated with globin synthesis be demonstrating that a discrete class of polyribosomes arises in cells treated with the inducers hexamethylene bisacetamide and hemin.