bluuebunny/crossref_metadata_2025_split huggingface dataset:
The relation of endogenous adenosine cyclic 3′:5′‐monophosphate to the antagonistic effects of adenosine and colchicine on cell shape
Authors: Yin H. H. , Berlin R. D. 
Published: February 2005

AbstractAdenosine and colchicine have antagonistic effects on cell shape. When Chinese Hamster lung fibroblasts (CHE36‐6) or SV40 transformed 3T3 (SV3T3) cells are incubated with colchicine (1 μM) for one hour at 37°C, they round up into spheres with short spikes. Cells treated with adenosine (1 μM–4 mM) for one hour become refractile and develop spindly processes. However, when the two compounds are added simultaneously, the characteristic responses to either drug are abolished and the cells appear normal. The counteraction is specific for adenine and its derivatives, adenosine being the most effective of the compounds we tested. Accumulation of colchicine or adenosine is not altered significantly by the presence of the other drug, ruling out decreases in uptake as the basis of the mutual antagonism. The morphological changes can be observed under conditions where there are no changes in intracellular cAMP levels (such as incubation with low concentrations of adenosine or cordycepin, an adenosine analog that cannot be directly converted to cAMP). Colchicine does not alter cAMP content of control or adenosine‐treated cells. These data show that adenine compounds have potent effects on cell shape, and the antagonistic effects of adenosine and colchicine on cell shape are not mediated through changes in intracellular cAMP levels.
Glucose utilization, pH reduction and density dependent inhibition in cultures of chick embryo fibroblasts
Authors: Fodge D. W. , Rubin H. 
Published: February 2005

AbstractThe multiplication rate of sparse cultures of chick embryo cells is only slightly lower at pH 6.9 than at pH 7.4. There is, however, a marked reduction in the multiplication rate of the pH 6.9 cultures before they reach confluency. Cultures at pH 7.4 continue to multiply beyond confluency with only a slight decrease in the multiplication rate.Eighty to ninety percent of the glucose taken up by the cells growing at each pH is converted to lactic acid which is released into the medium. Metabolic reduction in pH of the medium is almost entirely accounted for by the amount of lactic acid produced by the cells. Neither the intracellular nor extracellular accumulation of lactic acid nor the accompanying reduction in pH is sufficient to explain density dependent inhibition of the rate of multiplication of chick cells.The rate of lactic acid production and the multiplication rate of chick cells are independent of glucose concentration in the range of 2–16 mM. In view of the kinetic parameters for the uptake of glucose, this shows that glycolysis is not limited by the rate of glucose uptake and that depletion of glucose from the medium cannot account for the onset of density dependent inhibition of multiplication. However, when cells reach very high population densities, conventional glucose concentrations of 5 mM can be depleted overnight by chick cells. Since the multiplication rate of cells is dependent on glucose concentration when it falls below 2 mM, depletion of glucose may cause some growth inhibition in crowded cultures supplied with conventional medium.
Transient erythropoietic spleen colonies: Effects of erythropoietin in normal and genetically anemic W/Wv mice
Authors: Gregory C. J. , McCulloch E. A. , Till J. E. 
Published: February 2005

AbstractProperties of the cells (TE‐CFU) that give rise within four to six days to transient endogenous erythropoietic spleen colonies in irradiated mice have been investigated. The results obtained indicate that (1) erythropoietic maturation within such colonies is highly erythropoietin‐dependent, (2) the population size of TE‐CFU is not erythropoietin‐dependent, (3) initial exposure to a high dose of erythropoietin followed by continuing exposure to lower doses is required for maximal efficiency of colony formation by TE‐CFU, (4) successful transplantation of TE‐CFU has not been achieved, but they appear among the progeny of transplanted hemopoietic cells, (5) TE‐CFU are defective in mice of genotype W/Wv. These findings are consistent with the view that the TE‐CFU assay detects a class of early erythropoietin‐sensitive progenitor cells committed to erythropoietic differentiation, rather than “abortive” colony formation by pluripotent stem cells.
Studies on the regulation of the three enzymes of the leloir pathway in cultured mammalian cells II. A Search for quantitative interrelationships between the three enzymes activities
Authors: Stern Elizabeth Sell , Krooth Robert S. 
Published: February 2005

AbstractStudies on a normal human diploid cell strain revealed that the specific activity of the cell protein, for each of the three enzymes of the Leloir pathway, changed significantly as the cells grew. The kinetics of change in specific activity varied according to the enzyme being studied, and the kinetics for each enzyme varied from experiment to experiment.Within each experiment, there was no consistent correlation between specific activity for any one enzyme and specific activity for the other two. The ratios between the specific activities did not tend to remain constant as the absolute levels of specific activity changed. Hence, the activities did not behave coordinately. The kinetics of change in these ratios varied from experiment to experiment.The failure of galactose to stimulate increased cellular activity for the three enzymes (shown in the preceding paper), and the absence of a coordinate relationship between the activities, represent a striking difference between the behavior of these enzymes in human diploid cell strains and their behavior in E. coli.
Effects of metabolites present during growth of Tetrahymena pyriformis on the subsequent secretion of lysosomal hydrolases
Authors: Blum J. J. 
Published: February 2005

AbstractTetrahymena were grown in proteose‐peptone medium supplemented with glucose, mannose, fructose, galactose, acetate, succinate, or pyruvate and then washed and resuspended in a non‐nutrient salt solution and the amounts of 7 acid hydrolases secreted into the medium in a one hour incubation were measured. Cells that had been grown in the presence of glucose secreted about half the amounts of acid phosphatase, β‐N‐acetylglucosaminidase and acid protease as did control cells grown in unsupplemented medium. Pyruvate was about as effective as glucose and both were slightly more effective than acetate or fructose. Succinate had little effect. Similar experiments showed that α‐mannosidase, β‐fucosidase, and β‐galactosidase are secreted into the salt solution and that secretion is reduced by prior growth of the cells in medium supplemented with glucose or mannose but not galactose. Except for α‐mannosidase, these reductions in amounts of hydrolase secreted were not accompanied by appreciable changes in intracellular activity, and therefore demonstrate a persistent effect of growth in the presence of certain metabolites on the subsequent secretion of lysosomal hydrolases. Since the inhibition of subsequent secretion depended on both the individual metabolite and the particular hydrolase examined, it appears that the effect of metabolites is not limited to a general inhibition of secretion but may differentially alter some properties of lysosomal subpopulations. A preliminary characterization of the secreted acid protease of Tetrahymena suggests that there may be two acid proteases released, since up to 25% of the activity was not inhibited by high concentrations of pepstatin, leupeptin, or chymostatin.
Interaction of the fluorescent probe, 1‐anilino‐8‐napthalene sulfonate, with the sulfate transport system of ehrlich ascites tumor cells
Authors: Levinson Charles , Villereal Mitchel L. 
Published: February 2005

AbstractThe addition of the fluorescent dye, ANS, to intact ascites tumor cells results in an enhancement of fluorescence intensity. The increase in fluorescence intensity as a function of time is biphasic which suggests that at least two processes occur. The first associated with the rapid initial rise in fluorescence represents binding to the cell surface while the second or slower phase reflects entrance of ANS into the intracellular phase. The relationship between bound and free ANS in 0.50 mM sulfate medium was used to calculated the apparent dissociation constant of ANS‐membrane complex (Kd = 6.53 × 10−5 M) and the total number of ANS binding sites (4.49 nmoles/mg dry weight).Kinetic analysis of steady state sulfate transport in the presence and absence of ANS suggests that (1) sulfate exchange can be described by Michaelis Menten type kinetics (Km = 2.05 × 10−3 M), (2) a small fraction of surface associated ANS competitively inhibits sulfate exchange (Ki = 4.28 × 10−6 M) and (3) the transport system has a higher affinity for ANS than for sulfate.These data are consistent with the hypothesis that inhibition of sulfate exchange is related to the direct, reversible interaction of the negatively charged sulfonate group of ANS with superficial positively charged membrane sites.
ITP pyrophosphohydrolase and idp phosphohydrolase in rat tissue
Authors: Vanderheiden Bernardo S. 
Published: February 2005

AbstractThe existence of a nucleoside triphosphate pyrophosphohydrolase specific for ITP has been demonstrated in the cytosol fraction of a variety of rat tissues. The enzyme, stable to moderate heat treatment, was present in erythrocytes as well as brain, heart, kidney, liver, lung, muscle, ovaries, spleen, testes and thymus. The specific activity of the enzyme ranges from 26 to 150 m̈moles/min/g protein. In addition, evidence is given for a heat labile nucleoside diphosphate (IDP) phosphohydrolase present in most rat tissues, and particularly high in the adrenal (137 m̈moles/min/g protein). An “ITP‐IMP cycle” is proposed as a regulating mechanism for intracellular levels of ATP.
Concurrent development of resistance to 6‐azauridine and adenosine in a mouse cell line
Authors: Hashmi S. , May S. R. , Krooth R. S. , Miller O. J. 
Published: February 2005

AbstractA variant of the hypoxanthine‐guanine phosphoribosyltransferase deficient, and adenine phosphoribosyltransferase deficient mouse A9 cell line has been obtained by selecting cells which are resistant to 6‐azauridine. These cells are not only resistant to 6‐azauridine (5 × 10−4 M), but also to adenosine (10−3 M). Resistance persists indefinitely even in the absence of both compounds. The resistant cells are killed by 5‐fluorouridine (10−6 M), indicating that the part of the salvage pathway for pyrimidine ribonucleotide biosynthesis which is relevant to the action of 6‐azauridine is intact. The heritable change producing concurrent resistance to 6‐azauridine and adenosine probably involves the de novo pyrimidine biosynthetic pathway.
Hemopoietic colony forming cells in regenerating mouse liver
Authors: Hays Esther F. , Firkin Frank C. , Koga Yoshiko , Hays Daniel M. 
Published: February 2005

AbstractCells from regenerating mouse liver removed 2–25 days post 68% hepatic resection have been assayed for in vitro colony forming capacity in soft agar (CFU‐C), proliferative capacity in liquid culture, and in vivo spleen colony forming capacity (CFU‐S).These studies demonstrated low concentrations of CFU‐C and CFU‐S in normal and sham‐operated liver, with an appreciable increase of both in regenerating liver, reaching maximum values in tissue removed 5–7 days post hepatic resection. Colony formation in agar by regenerating liver cells occurred in the absence of exogenous colony stimulating factor. Separation of liver cells on the basis of adherent properties prior to culture indicated concentration of CFU‐C in the nonadherent fraction, while cells producing colony stimulating factor were concentrated in the adherent fraction. Foci of actively dividing cells of the macrophage and granulocyte series arose in liquid culture from preparations of sham operated and regenerating liver, although total cell formation was greater with regenerating liver. A small proportion of the colonies formed in agar from regenerating liver consisted of cords of epithelioid cells, which resembled hepatocytes and differed from the macrophages or granulocytes found in the majority of colonies, raising the possibility that regenerating hepatocytes form colonies in agar culture.
A comparative study of the effects of lucanthone (miracil D) and actinomycin d on the chinese hamster cells grown in cultures
Authors: Epifanova Olga I. , Makarova G. F. , Abuladze M. K. 
Published: February 2005

AbstractChinese hamster cells of an established clone line grown in monolayers were incubated for up to two hours with either lucanthone (0.3–30 m̈g/ ml) or actinomycin D (0.06–0.10 m̈g/ml) and subjected to radioautographic investigations with 3H‐uridine during the period of treatment.At concentration of 9 m̈g/ml lucanthone selectively inhibited the synthesis of nucleolar (ribosomal) RNA while the extranucleolar RNA synthesis proceeded at a high level. Similar results were obtained with 0.08 m̈g/ml actinomycin D. Protein synthesis and mitotic activity were also affected by lucanthone but the drug did not markedly interfere with DNA synthesis.Lucanthone appeared to be much less effective in cell killing than actinomycin D and its inhibitory effects on the nucleolar RNA synthesis and other cellular processes proved readily reversible. The results allow to conclude that lucanthone may be useful as a tool for studying RNA synthesis in animal cells.
The stimulation of 2‐deoxy‐D‐glucose transport in control and virus‐transformed cells by ethidium bromide
Authors: Soslau Gerald , Nass Margit M. K. 
Published: February 2005

AbstractRecently we demonstrated that ethidium bromide altered the plasma and subcellular membrane glycoproteins in control and virus transformed cells. It is reported here that ethidium bromide also stimulated the membrane associated process of sugar transport. The Km of the virus transformed cells and the ethidium bromide treated cells is the same as that of the control cells while the maximum velocity as compared to the control cells is significantly increased. The transport of 2‐deoxy‐D‐glucose was inhibited by glucose, cytochalasin B and neuraminidase but was unaffected by variations in cell density or pH of the incubation medium.
N6‐(Δ2‐Isopentenyl)adenosine, an inhibitor of cellular transport of uridine and cytidine
Authors: Hakala Maire T. , Slocum Harry K. , Gryko George J. 
Published: February 2005

AbstractN6(Δ2‐Isopentenyl)adenosine (IPAR) inhibited severely the incorporation of uridine and cytidine into S‐180 cells in culture. When IPAR and the nucleosides were simultaneously present in the medium the inhibition was competitive (Ki 3.4 m̈M) and indicated inhibition of transport. However, the inhibition occurred even in the absence of extracellular IPAR if the cells had been preincubated with IPAR. Since 5′‐IPAMP was the product which accumulated in large quantities in S‐180 cells when incubated with IPAR, the effects of this AMP analog on the intracellular metabolism of uridine had to be considered. No direct correlation between the amount of intracellular IPAMP and the degree of inhibition of uridine utilization was observed and the relative distribution of uridine nucleotides in the acid soluble pool of the cells was unaltered in cells treated with IPAR. Also, IPAMP was not an inhibitor of uridine kinase in a cell free system nor was the activity of this enzyme affected by treatment of cells with IPAR. In addition, a profound inhibition of uridine utilization was also observed in a resistant subline of S‐180 cells, which is unable to form IPAMP. These data suggest that IPAMP was not the inhibitory agent. Furthermore, the observation that the inhibition in both sensitive and resistant cells was caused even by a 15‐second exposure to 100 m̈M IPAR, followed by rinsing, suggests that IPAR itself is the effective agent.It is concluded that IPAR exerts its inhibitory effect on uridine and cytidine utilization by becoming lodged in the cell membrane and thereby preventing the passage of these nucleosides into the cells. It is also shown that the inhibition of uridine and cytidine utilization by IPAR and by other potent nucleoside uptake inhibitors is unrelated to inhibition of growth or of RNA‐synthesis when the cells do not depend on an extracellular source of a nucleoside for growth.
DNA replication in homogenates of Physarum polycephalum
Authors: Brewer E. N. , Ting Pauline 
Published: February 2005

AbstractHomogenates of Physarum polycephalum incorporate [3H] dATP into nuclear DNA at an initial rate of approximately 15% of the in vivo rate. To attain this level of synthesis, cultures are homogenized in a medium containing Mg++, EGTA, glucose and spermine. Incorporation is strongly stimulated by the addition of ATP and all four deoxyribonucleoside triphosphates to homogenates prior to incubation. Various inorganic cations other than Mg++ either do not affect synthesis or are inhibitory. Incorporation is inhibited by a nonionic detergent, Triton X‐100. DNA synthesis in this cell‐free nuclear system is similar in several respects to that which occurs in vivo: (1) The rate of DNA synthesis in the intact organism at a given time in the mitotic cycle is reflected by the level of synthesis in homogenates prepared from cultures at that time of the cycle; (2) DNA strands labeled in vitro exhibit alkaline sucrose density gradient sedimentation properties similar to those of daughterstrand DNA pulse‐labeled in vivo; and (3) Homogenates of cultures which were pre‐treated with cycloheximide incorporate [3H]dATP at about 60% of the level observed in homogenates of untreated controls.
Development of excitability in embryonic chick skeletal muscle cells
Authors: Kano Masaakira 
Published: February 2005

AbstractDuring embryonic and early postnatal development, the chick leg muscle cells undergo a series of changes in their electrical responses in the following sequence: passive response, plateau response, plateau plus spike response and spike response. This suggests that the electrogenetic mechanism of muscles matures during development; a mechanism producing the plateau may first be induced, and then that producing the spike. The plateau is sensitive to manganese or cobalt ions, while the spike to tetrodotoxin. This suggests that the plateau is related to the increase in permeability to calcium ions, while the spike to sodium ions.
Evidence contrary to the protein error hypothesis for in vitro senescence
Authors: Pendergrass William R. , Martin George M. , Bornstein Paul 
Published: February 2005

AbstractA strain of diploid fibroblasts, obtained from the skin of a male infant, was cultured in vitro and cells were tested throughout their lifespan for the appearance of altered glucose‐6‐phosphate dehydrogenase (G‐6‐PD) detected either by thermostability studies or by immunotitration. No significant difference was found in the proportion of thermolabile enzyme in 31 young cultures (4.8 ± 1%, S.E.), in comparison with that in 19 old cultures (4.9 ± 1%, S.E.). Old cultures had ceased active cell division (49–60 doublings); DNA replication, measured by [3H] thymidine uptake over a period of 24 hours, was limited to less than 5% of these cells. Young cells (5–22 doublings) had a [3H] thymidine labeling index of 75–85%. Titration of G‐6‐PD activity in extracts of young and old cells with neutralizing antibody directed specifically against G‐6‐PD failed to detect an increment of enzymatically defective G‐6‐PD in old cells. The thermostability studies were capable of detecting altered G‐6‐PD in skin fibroblasts from a female heterozygous for a thermolabile mutant of G‐6‐PD, and in fibroblasts treated with a proline analogue, azetidine carboxylic acid. The immunotitration technique was also capable of detecting catalytically altered G‐6‐PD from the thermolabile mutant and G‐6‐PD inactivated with N‐ethylmaleimide. These findings argue against a protein error catastrophe as the cause of in vitro clonal senescence.
Control of phenylalanine hydroxylase synthesis in tissue culture by serum and insulin
Authors: Tourian Ara 
Published: February 2005

AbstractStationary‐phase, minimal deviation hepatoma H4‐II‐E‐C3 cell cultures that are serum‐deprived respond with a biphasic time course of phenyl‐alanine hydroxylase induction when dialyzed fetal calf serum or insulin is added. These two agents induce phenylalanine hydroxylase additively, during both the initial 3‐hour and the delayed 24‐hour phases. The initial phase of induction by insulin is inhibited by cycloheximide but not by actinomycin D. The delayed induction by both dialyzed fetal calf serum and insulin is inhibited by 10−6 M cycloheximide and 0.20 μg/ml actinomycin D.H4‐II‐E‐C3 cells in culture do not synthesize the factor(s) in serum that induce phenylalanine hydroxylase.
Calcium‐dependent stimulation of BALB/c 3T3 mouse cell DNA synthesis by a tumor‐promoting phorbol ester (PMA)
Authors: Boynton A. L. , Whitfield J. F. , Isaacs R. J. 
Published: February 2005

AbstractDuring the first six passages after their arrival in this laboratory, BALB/c 3T3 mouse cells did not proliferate in serum containing‐medium having an ionic calcium concentration of 0.05 mM or less, but by the ninth passage they had become able to multiply in the presence of these lower calcium levels. In low calcium (e.g., 0.02 mM) medium, passage 1–6, cells in sparse cultures were blocked at the Gl/S boundary of their cycle. These blocked cells could be induced to start making DNA within only one hour either by returning the ionic calcium level to a normal range of values (1.25 mM), or by adding 0.05 μg/ml of PMA (12‐O‐tetradecanoyl‐phorbol‐13‐acetate). PMA probably acted by sensitizing the blocked cells to calcium rather than replacing the ion, because it was ineffective in ionic calcium‐free medium. Finally, PMA did not by itself induce proliferation of cells (regardless of the number of passages) which had been proliferatively inactivated by density‐dependent factors in confluent cultures. However, PMA did promote DNA synthesis by these cells during their brief transition to the “cycling” state caused by exposure to fresh serum‐containing medium.
Lipid A, the active part of bacterial endotoxins in inducing serum colony stimulating activity and proliferation of splenic granulocyte/macrophage progenitor cells
Authors: Apte Ron N. , Pluznik Dov H. , Galanos Chris 
Published: February 2005

AbstractAn analysis of which component of lipopolysaccharides (LPS), the lipid or the poly saccharide (PS), is active in stimulating the murine granulopoietic system has been performed. LPS with different structures, isolated from different mutant strains of Salmonella and chemical degradation products of lipopolysaccharides have been used. Lipid A obtained by acid hydrolysis of the LPS and complexed to bovine serum albumin (BSA) (lipid A‐BSA) was shown to be active in generating serum colony stimulating factor (CSF) and in increasing the splenic colony forming cells (CFC) levels, although it was less active than the parent LPS. The polysaccharide (PS) showed no significant activity at the concentrations used. LPS (glycolipids) from R mutants of Salmonella minnesota were active to the same extent as the LPS. The fact that even the most defective LPS from the R mutant R595 which contains lipid A and KDO only is a potent endotoxin, points unequivocally, to lipid A, as the active principle in stimulating the granulopoietic system.