bluuebunny/crossref_metadata_2025_split huggingface dataset:
Separation of proximal tubule cells from suspensions of rat kidney cells by free‐flow electrophoresis
Authors: Kreisberg Jeffrey I. , Sachs George , Pretlow Thomas G. , McGuire Robert A. 
Published: February 2005

AbstractSuspensions of rat kidney cells obtained by disaggregation of the kidney with 0.25% trypsin were separated by electrophoresis. Previously, we found a correlation between cells with histochemically demonstrable alkaline phosphatase (HDAP) and cells with brush borders which established that HDAP is a useful marker for rat proximal tubule cells (Kreisberg et al., '77). The starting suspension of cells for electrophoresis consisted of 38.4 ± 5.7% nucleated cells with HDAP, 39.8 ± 5.7% nucleated cells without HDAP, and 20.8 ± 9.2% red blood cells. After electrophoresis, the purest fraction contained 85.8 ± 3.5% nucleated cells with HDAP, 8.4 ± 2.2% nucleated cells lacking HDAP, and 5.8 ± 2.8% red blood cells; 91.9 ± 2.4% of the nucleated cells in the purest fractions had HDAP.
Expression of nervous system antigen‐3 by lines of mouse fibroblasts and kidney cells and continued expression in hybrid cells
Authors: Doyle Jane M. , Schachner Melitta , Davidson Richard L. 
Published: February 2005

AbstractIn a survey of the expression on cultured mouse cells of the cell surface antigen known as nervous system antigen‐3 (NS‐3), it was found that RAG, a renal adenocarcinoma line, expressed that antigen. It was also observed that 3T3, a fibroblast line of unknown tissue origin, expressed NS‐3. Cells of these two lines were hybridized with cells of two mouse L cell lines that did not express NS‐3. Four hybrid clones were tested for both the 3T3 × L cell cross and the RAG × L cell cross, and all the hybrids were found to be NS‐3 positive. All the hybrids had at least 40% as much activity as the NS‐3 positive parent. Of the four parental mouse cell lines used, only 3T3 expressed Thy‐1.2 antigen on the cell surface. In contrast to the continued expression of NS‐3 on hybrid cells, Thy‐1.2 antigen was not detectable on two clones of 3T3 × L cell hybrids that were tested.
Glucocorticoid binding and mechanism of resistance in some clones of mouse myeloid leukemic cells resistant to induction of differentiation by dexamethasone
Authors: Honma Yoshio , Kasukabe Takashi , Okabe Junko , Hozumi Motoo 
Published: February 2005

AbstractSeveral clones of dexamethasone‐resistant cells, which could not differentiate even in a high concentration of dexamethasone, were isolated from glucocorticoid‐sensitive myeloid leukemic cells. Some of them were shown to be deficient in steroid binding to specific cytoplasmic receptors, while the others contained glucocorticoid‐specific cytoplasmic receptors that might be the same as those in sensitive cells. One of the resistant clones was found to be almost completely deficient in nuclear acceptor sites for cytoplasmic steroid‐receptor complexes. The remaining clones were also characterized by significantly reduced amounts of nuclear‐bound glucocorticoid. These results suggest that resistibility to glucocorticoids in the resistant clones of myeloid leukemic cells is due mainly to a defect in some steps of intracellular transfer of the steroid. Dexamethasone‐sensitive cells, which could differentiate in the presence of dexamethasone, could be also induced to differentiate by protein factor(s) in ascitic fluid. Although all the resistant cells showed a low response to ascitic fluid, some of them showed 10‐fold enhancement of phagocytic activity which is a typical character of differentiated cells. These results suggest that response to steroids is not directly correlated with that to protein inducer(s).
Reversible inhibition of the norepinephrine induction of lactate dehydrogenase by cytochalasin B in rat glial C6 cells
Authors: Bennett Kimberly , De Vellis Jean 
Published: February 2005

AbstractThe cyclic AMP mediated induction of lactate dehydrogenase (LDH: E.C. 1.1.1.27) activity by norepinephrine in the rat glial cell line C6 is inhibited by cytochalasin B. Doses of 5, 15, and 25 μg/ml of cytochalasin B inhibited the induction equally. Twenty‐five μg/ml of cytochalasin B inhibited the induction reversibly, and had no effect on basal enzyme level. No effect of cytochalasin B on general protein synthesis was found, nor did it increase the rate of decline of enzyme activity in deinduced cells. It therefore appears to block LDH induction by selectively inhibiting its synthesis. Cytochalasin B had no effect on the transient (intracellular and extracellular) rise in cyclic AMP generated in response to norepinephrine treatment. Cytochalasin B was effective when added during the transcription dependent phase (first 3 hours) but not during the translation dependent phase (after 3 hours) of LDH induction. The suggestion is discussed that cytochalasin B inhibits one of the early events of the inductive process.
Gel filtration analysis of vanadium in Ascidia nigra blood cell lysate
Authors: Gilbert Katharine , Kustin Kenneth , McLeod Guy C. 
Published: February 2005

AbstractFractions from a Sephadex gel filtration of homogenized Ascidia nigra blood cell lysate were analyzed for vanadium by atomic absorption spectroscopy. The results were unaffected by temperature from 4–21°C, and by ionic strength in the range 0.09‐1.0 M (NaCl). Appreciable loss of vanadium in the supernatant was experienced above pH 2.2. Experiments at pH 2.1 under anaerobic conditions show that the green chromogen and the vanadium‐containing bands elute separately. Under these experimental conditions, the vanadium‐containing species is of relatively low (⋍ 1,000) molecular weight.
On the mechanism of the crabtree effect in mouse ascites tumor cells
Authors: Sauer Leonard A. 
Published: February 2005

AbstractThe addition of glucose to ELD and ELT/B1 mouse ascites tumor cell suspensions caused a 2.3‐fold increase in the phosphorylation state ratio, (ATP)/(ADP)(Pi), because of a decrease in the intracellular Pi concentration. The addition of glucose to these cell suspensions has been reported by Chance and Hess ('59) to cause an increase in the steady state reduction of cytochrome b and an increase in the steady state oxidation of cytochrome c. On a quantitative basis these two independent measurements suggest that a near equilibrium exists between the oxidation‐reduction state of the mitochondrial electron carriers and the reactions of ATP synthesis (as expressed by the phosphorylation state ratio) both before and after glucose addition. We conclude that the mechanism of the inhibition of respiration by glycolysis (the Crabtree effect) is a decrease in the rate of electron transport caused by the mass action effect of the elevated phosphorylation state ratio.
Modulation of protein synthesis during the growth cycle of a culture of scarlet rose
Authors: Ramagopal S. , Huang B. , Marcus A. 
Published: February 2005

AbstractDilution of a stationary phase culture of Scarlet Rose results in an increased rate of protein synthesis. This study compares the time course of this increase with the changes in polyribosome content and the levels of adenine and guanine nucleotides.During the first two hours after dilution, protein synthesis increases 2‐ to 3‐fold; much of the large monoribosome pool that characterizes the stationary state disappears and a steady state situation is reached in which 70% of the ribosomes are in polyribosomes. Between two and eight hours, there is no further change in polyribosome content although the rate of protein synthesis increases an additional 2‐ to 3‐fold. During this initial 8‐hour period there is little change in the levels of ATP and GTP. An explanation consistent with these observations is that the initial activation (within the first 2 hours), characterized by the monoribosome to polysome transition, is at the level of a component(s) of the initiation system, and that between two and eight hours, since neither mRNA availability nor energy level are primary determinants, protein synthesis is augmented by the activation of a translational component, perhaps an elongation factor.After 24 hours, there is a proliferative phase characterized by the onset of ribosome accumulation. By day 5, maximum ribosome levels, 5‐fold that of 24‐hour cells, are reached, but the rate of protein synthesis increases only 2.5‐fold during this period. The lack of quantitative coincidence between the changes in polyribosome content and the rates of protein synthesis again suggests that factors other than mRNA availability are involved in determining the overall rate of protein synthesis. Finally at days 6–8, while the growth of the culture is still in the exponential phase, the rate of protein synthesis per unit fresh weight drops markedly concomitant with a decline in ribosome content. At days 11–12, the monoribosome to polysome ratio begins to change with the monoribosome pool increasing.Presence of either actinomycin D or cordycepin inhibits increased protein synthesis in direct relation to the ability of these compounds to inhibit RNA synthesis. This suggests that the protein synthetic processes occurring after dilution require either the synthesis of the mRNA that is being translated or of an RNA functioning in a closely linked reaction.
Inhibition of mammalian ribonucleotide reductase by a dinucleotide produced in eucaryotic cells
Authors: Lewis William H. , McNaughton David R. , Goh Swee Han , Lejohn Herb B. , Wright Jim A. 
Published: February 2005

AbstractHS3, a highly phosphorylated dinucleoside originally purified from the fungus Achlya, has been isolated from Chinese hamster ovary cells undergoing glutamine starvation. The HS3 compounds obtained from the fungal and mammalian sources exhibited similar physical and chemical properties. This unusual dinucleotide may be an important regulator of eucaryotic ribonucleoside diphosphate reductase activity; for 50 μm HS3, isolated from either mammalian or fungal cells, significantly inhibited CDP reduction in Achlya or hamster cell preparations, but only marginally affected the activity of the enzyme from E. coli. Studies with HS3 isolated from Achlya and partially purified mammalian ribonucleotide reductase indicated that the compound noncompetitively inhibited the reduction of varying concentrations of the substrates CDP, ADP and GDP with Ki values of 23 μm, 14 μM and 16 μM respectively. These inhibitor concentrations are well below the estimated intracellular levels of HS3 in glutamine starved cells and suggest that HS3 inhibition of ribonucleotide reduction may be responsible for the rapid inhibition of DNA synthesis seen under these culture conditions.
Possible regulation of macromolecular biosynthesis in mammalian cells by a novel dinucleoside polyphosphate (HS3) produced during step‐down growth conditions
Authors: Goh Swee Han , Wright Jim A. , LéJohn Herb B. 
Published: February 2005

AbstractShortly after the withdrawal of L‐glutamine from the growth medium of Chinese hamster ovary (CHO) cells, the rate of synthesis of a bizarre dinucleoside polyphosphate, HS3, increased by 5‐ to 6‐fold. This elevated rate of synthesis was maintained for six hours before it gradually declined to basal level 22 hours later. The pool size of HS3 increased and decreased coincidentally with rate changes. Withdrawal of L‐isoleucine did not affect HS3 biosynthesis. A glycine, adenosine, thymidine (GAT−) auxotroph of CHO cells accumulated HS3 when adenosine, not glutamine, was withdrawn. Replenishment of either glutamine (“wild type” cells) or adenosine (GAT− cells) caused an immediate depletion of HS3 intracellularly.When HS3 accumulated in CHO cells, DNA and RNA synthesis decreased and, vice versa. A similar correlation was not seen for protein synthesis. But, inhibition of protein synthesis by either puromycin or cycloheximide, and of RNA biosynthesis by actinomycin D facilitated HS3 depletion in L‐glutamine starved cells.Mutant CHO cells that are deficient in purine salvage metabolism, HGPRT− (hypoxanthine‐guanine phosphoribosyltransferase) failed to deplete their accumulated HS3 when fed with hypoxanthine, whereas the “wild type” CHO cells responded accordingly. The available data suggest that HS3 metabolism is connected with de novo and salvage pathways of nucleotide biosynthesis, and may play a crucial role in regulating nucleic acid metabolism in CHO cells under conditions of nutritional stress.
Serum‐mediated regulation of amino acid transport in cultured chick embryo fibroblasts
Authors: Tramacere Mariarosaria , Borghetti Angelo F. , Guidotti Guido G. 
Published: February 2005

AbstractWhen chicken serum was added to serum‐deprived quiescent cultures of chick embryo fibroblasts the activity of amino acid transport by means of the A system, as measured by α‐aminoisobutyric acid and L‐proline uptake after discrimination of the contribution of interacting systems, increased with time of exposure to serum between 30 and 120 minutes (remaining constantly high thereafter). Under the same conditions, DNA synthesis, as measured by thymidine incorporation, increased abruptly six to eight hours after the addition of serum. Serum‐mediated increases of transport activity by the A system have also been detected with glycine, L‐alanine and L‐serine. Transport activities of systems ASC, L and Ly+ did not change appreciably (or decreased slightly) after the addition of serum. The stimulation of amino acid transport was apparently proportional to the length of exposure to serum; its rate declined progressively with time after withdrawal of serum from the culture medium. Kinetic analysis indicated that stimulation of the activity of transport system A by serum occurred through a mechanism affecting Vmax rather than Km; stimulation was prevented by inhibitors of protein synthesis. Our results indicate that the A transport system is the only system which is regulated by serum in cultured avian fibroblasts. Remarkably, the A transport system appears to be the target on which widely different factors and conditions converge to regulate amino acid transport in eukaryotic cells.
Development of hormonal regulation of ion transport in embryonic chick red cells
Authors: Wacholtz M. , Chan L. N. , Sha'Afi R. I. 
Published: February 2005

AbstractWe have found that cation transport in red cells from chick embryos is stimulated by the hormone epinephrine and that this response develops as the embryonic definitive cells mature. Sodium efflux and potassium influx are significantly stimulated (50%) by epinephrine in red cells from embryos incubated ten days or longer, whereas cation fluxes in erythroid cells from 8‐ or 9‐day embryos are stimulated little or not at all.The effect of epinephrine may be mediated by cyclic AMP as adenylate cyclase activity in membranes isolated from embryonic red cells is only slightly stimulated at nine days, but the response increases as the cells mature to a maximum of about 180%. Also the stimulation of cation transport by epinephrine is blocked by propranolol, but not by phentolamine. Although the younger cells respond poorly to epinephrine, cyclic AMP significantly stimulates transport.The enhancement of cation fluxes by epinephrine or cyclic AMP occurs even in the presence of ouabain. Since both K influx and Na efflux are enhanced by these agents, their action is most likely on some form of the “Na‐K” pump which is not ouabain sensitive resulting in a significant increase in the maximum velocity of the pump. We suggest the hypothesis that there are two classes of “Na‐K” pump in these embryonic cells. One pump is similar to that found in many erythrocytes including mammalian cells in that it selectively pumps potassium in and sodium out, is ouabain‐sensitive, and is primarily involved in maintaining intracellular cation concentrations. The second pump is enhanced by epinephrine via cyclic AMP, is not inhibited by ouabain, and may have lower ion selectivity. This hormone sensitive pump activity is lost as the cells mature, a process which is completed when the animal is fully grown and no longer has significant numbers of embryonic cells in its circulation.
Effects of cyclic AMP on the growth of differentiating and undifferentiated friend erythroleukemic cells
Authors: Rubin Charles S. 
Published: February 2005

AbstractElevated concentrations of cyclic AMP elicit only minor reductions in growth rate and saturation density in undifferentiated Friend erythroleukemic cells. During the course of dimethylsulfoxide (DMSO)‐induced differentiation, Friend cells convert from a cyclic AMP‐tolerant state to a phenotype characterized by a high degree of sensitivity to cyclic AMP‐mediated growth arrest.Conversion to cyclic AMP sensitivity is detectable after 30 hours growth in medium containing 2% DMSO, and either 0.5 mM 8‐Br‐cyclic AMP or 5 nM cholera toxin. Cultures of differentiating Friend cells achieved a stationary phase density that was approximately 8‐fold higher than the cell density observed in parallel, differentiating cultures treated with 0.5 mM 8‐Br‐cyclic AMP. Temporally, the appearance of cyclic AMP‐sensitivity corresponds to the early expression of in vitro erythroid differentiation (Ross et al., ′74), but growth arrest does not alter the subsequent accumulation of hemoglobin in non‐dividing DMSO‐induced cells. Since growth arrest is preceded by a round of cell division, these observations are consistent with the concept that DMSO must be present during DNA replication for the subsequent expression of hemoglobin synthesis (McClintock and Papaconstantinou, ′74; Levy et al., ′75; Harrison, ′76).
Polyamine metabolism in regenerating livers from normal and hypocalcemic rats
Authors: Walker P. Roy , Whitfield James F. , Sikorska Marianna 
Published: February 2005

AbstractThere is a marked increase in the concentration of putrescine during the first ten hours following partial hepatectomy in rats. The concentration of spermidine also increases but to a smaller degree. Putrescine levels return to normal between 10 and 24 hours after the operation, whereas the increased spermidine level is maintained. The production of putrescine and spermidine appears to be initiated by the induction of ornithine decarboxylase which shows a single peak of activity at four hours after hepatectomy. The activity of S‐adenosylmethionine decarboxylase shows little change following hepatectomy. The changes in polyamine levels and the activities of the enzymes of polyamine metabolism are not affected by thyroparathyroidectomy 72 hours prior to hepatectomy. Thus although these hypocalcemic conditions considerably reduce and delay DNA synthesis and mitosis, the prereplicative changes in polyamine metabolism still occur. These data suggest that the hepatocytes in hypocalcemic animals have become activated and moved to an advanced stage of prereplicative development before being blocked.
Different red cell populations in newborn, genetically low potassium sheep: Relation to hematopoietic, immunologic and physiologic differentiation
Authors: Valet G. , Franz G. , Lauf P. K. 
Published: February 2005

AbstractThree red cell populations have been distinguished in genotypically low potassium (LK) newborn sheep by an improved electrical sizing method and were best approximated by a logarithmic normal distribution. Labeling studies with 51Cr and 59Fe exclude transformation of the three red cell populations into each other. Population I, consisting of large red cells (mean volume 36 μm3), with a comparatively slow electrophoretic mobility is present at birth and disappears within three to four weeks from circulation. These cells possess a high potassium (HK) steady state concentration, a K+ pump influx activity at least 5‐fold greater than observed in adult LK red cells, very low amounts of the L antigens generally associated with the LK property, and do not respond to the stimulatory action of the L antibody. The first population is gradually replaced by population II comprising small red cells (mean volume 28 μm3) of intermediate electrophoretic mobility and with a peak production around day 20 after birth. The potassium concentration, [K+]c, in these cells appears to be lower than in the cells of population I but the L antigen content is increased. Formation of population III (mean volume 30 μm3 and comparatively fast electrophoretic mobility) follows closely that of population II and is preceded by a sharp increase in reticulocytosis. The red cells of population III exhibit parameters characteristic for adult LK cells: low [K+]c and K+ pump activity, fully developed L antigen content, and an almost maximal response to the K+ pump stimulating effect of anti‐L. In L and M antigen positive LK red cells of newborn sheep, the development of the M antigen parallels that of the L antigen. The data are consistent with the hypothesis that cellular replacement and not maturation is the major factor in controlling the HK‐LK transition in newborn sheep.
Growth requirements of calf lens epithelium in culture
Authors: Taylor‐Papadimitriou J. , Shearer M. , Watling D. 
Published: February 2005

AbstractThe in vitro life span and rate of growth of calf lens cells cultured in serum‐supplemented 199 medium can be markedly increased by growing the cells with a layer of mitomycin‐killed 3T6 feeders. In the absence of feeders, the epithelial cells are partially blocked in the S period of the cell cycle but show a normal distribution of cells in G1 and G2 when grown with fibroblasts. Increased growth rates and division potential can also be achieved by growing the lens in 199 medium containing 10−5 M thymidine, and cells grown under these conditions show a normal growth cycle. Our results suggest that lens epithelial cells cultured in medium 199 show a deficient endogenous synthesis of thymidylic acid, and fibroblast feeders or exogenously added thymidine enable them to overcome this deficiency. When grown in the presence of 10−5 M thymidine, the lens epithelial cells show a very low serum requirement for cell division in short term culture.
In vitro and in vivo actions of zinc ion affecting cellular substances which influence host metabolic responses to inflammation
Authors: Mapes Carol A. , Bailey Paul T. , Matson Charles F. , Hauer Edward C. , Sobocinski Philip Z. 
Published: February 2005

AbstractGlycogen‐stimulated rabbit peritoneal exudate cells (polymorphonuclear leukocytes, PMN) produce prostaglandins (PG) and substances which induce alterations (mediators) in experimental animals characteristics of host metabolic responses to infection and other acute inflammatory stresses. The effect of Zn2+ on mediator production and PG synthesis was examined because: Zn homeostasis is perturbed during infection, Zn is known to regulate some cellular functions, and there appears to be an interrelationship between PG synthesis and mediator productionUsing exudate cells, 2 mM Zn2+ causec complete inhibition of in vitro PG synthesis as assessed by conversion of [1−14C] arachidonic acid into PG. This concentration of Zn2+ also inhibited production of substances mediating plasma Zn depression, hepatic amino acid "uptake," fever, and neutrophil release from bone marrow. Conversely, Zn2+ did not inhibit in vivo metabolic responses to these mediators. Zn‐pretreatment of rabbits or simultaneous injection of Zn2+ and crude PMN‐derived pyrogenic activity resulted in prolongation of fever. It is suggested that this action of Zn2+ may be attributed to either stabilization of cyclic AMP through inhibition of phosphodiesterase or a Zn‐mediator interaction which stabilizes crude endogenous pyrogenThe potential physiological significance of these results includes: possible potentiation of the host's defense mechanisms by Zn2+ and its utilization for prolongation of fever to determine its effect on potentially temperature‐dependent host defense mechanisms.