bluuebunny/crossref_metadata_2025_split huggingface dataset:
The importance of the techniques employed during the enzymatic preparation of isolated liver parenchymal cells
Authors: Labrecque Douglas R. , Bachur Nicholas R. , Peterson Janice A. , Howard Roger B. 
Published: February 2005

AbstractThe endogenous respiration of isolated rat liver parenchymal cells prepared by two enzymatic techniques has been measured. Despite the production of a high percentage of viable cells by both methods, as measured by the exclusion of trypan blue, the cells obtained by one of the techniques consume oxygen at only one‐half the rate of those obtained by the other technique. It is suggested that the lower rate is the result of an insufficient oxygen supply and also a lack of control of the pH of the incubation medium during the preparation of the cells.
Deoxyglucose transport by uninfected, murihe sarcoma virus‐transformed, and murine leukemia virus‐infected mouse cells
Authors: Plagemann Peter G. W. 
Published: February 2005

AbstractThe initial rates of deoxy‐D‐glucose transport by cultures of growing and density‐inhibited mouse embryo cells and lines of mouse cells transformed spontaneously or after infection by murine leukemia virus or murine sarcoma virus were investigated as a function of the deoxyglucose concentration. The apparent Km for deoxyglucose transport was about the same for all types of cells (1–2 mM). The Vmax of secondary cultures of mouse embryo cells decreased from 6 nmoles/106 cells/minute for sparse cultures to less than 1 nmole/106 cells/minute for density‐inhibited cultures. The Vmax was about the same whether estimated in monolayer culture or in suspensions of cells dispersed by treatment with trypsin. The Vmax for deoxyglucose transport by the established cells, whether transformed spontaneously or by virus infection, was 4 to 25 times higher than that for density‐inhibited mouse embryo cells and was independent of the cell density of the cultures. Deoxyglucose transport was competitively inhibited by Cytochalasin B, Persantin, glucose and 3‐O‐methyl‐D‐glucose and the apparent Ki values of inhibition were similar for the mouse embryo cells and the various cell lines. Similarly, the sensitivity of the glucose transport systems to inactivation by p‐chloromercuribenzoate was about the same for all types of cells. The results suggest that the glucose transport system of the normal mouse embryo cells and the cells of the various established lines is qualitatively the same, but that the number of functional transport sites differs for the various cell lines and decreases markedly in mouse embryo cells with an increase in cell density of the cultures.
Anion transport in the Ehrlich ascites tumor cell: The effect of 2,4,6‐trinitrobenzene sulfonic acid
Authors: Levinson Charles , Villereal Mitchel L. 
Published: February 2005

AbstractWe have investigated the effects of the amino reactive reagent, 2,4,6‐trinitrobenzene sulfonic acid (TNBS) on anion transport (chloride and sulfate) and on the K+ content of Ehrlich ascites tumor cells. Incubation of tumor cells with TNBS (3 mM or 10 mM) results in a time dependent uptake of this molecule. Tightly bound TNBS caused a loss of K+ as well as inhibition of sulfate uptake. Although sulfate transport was inhibited by tightly bound TNBS (40% inhibition with 20 nmoles bound per 107 cells), reversibly bound TNBS exerted much greater inhibition. Kinetic analysis of sulfate transport in the presence and absence of TNBS suggests that: (1) tightly bound TNBS exerts a competitive inhibition by occupying membrane sites remote from the specific transport site, (2) TNBS reversibly interacts with a separate site also in a competitive fashion.Increasing amounts of tightly bound TNBS resulted in an enhanced chloride influx. However, reversibly bound TNBS was without effect. These results are in contrast to the effect of TNBS on sulfate transport and show that TNBS, at least in this cell type, is not a general inhibitor of anion transport.
Macromolecular requirements for the initiation and maintenance of DNA synthesis during the cell cycle of Tetrahymena pyriformis
Authors: Jeffery William R. 
Published: February 2005

AbstractThe macromolecular reguirements for the initiation and maintenance of macronuclear DNA replication were studied in heat synchronized Tetrahymena pyriformis GL‐C. Previous work had established that macronuclear S periods could occur in a consecutive fashion without intervening cell divisions during a multiple heat shock treatment, as well as immediately following the synchronized cell divisions. Cycloheximide treatment prior to or during the S period which follows the first synchronized cell division resulted in abolition of the initiation of DNA synthesis or an almost immediate cessation of DNA synthesis in progress. Temporary inhibition of DNA synthesis occurred when cycloheximide was added late in the S period. Treatment with actinomycin D was found to block the initiation of DNA synthesis but did not appreciably affect the continuation of the S period. It was concluded that RNA synthesis was required for the initiation but not the maintenance of DNA replication, whereas protein synthesis was necessary for both processes.The dependency of the initiation of an S period on prior RNA and protein synthesis was also shown to exist when a second consecutive S period was initiated without a preceding cell division. Treatment with actinomycin or cycloheximide prior to a supernumerary S period during a multiple heat shock treatment completely abolished the initiation of DNA synthesis. In T. pyriformis the synthesis of RNA and protein related to the initiation of the S period is tightly coupled to each cycle of DNA replication.
Primitive erythropoiesis in chick embryogenesis. III. Effect of FUdR on Hb synthesis
Authors: Campbell Graham Lem , Weintraub Harold , Holtzer Howard , Mayhall B. H. 
Published: February 2005

AbstractA single hematocytoblast in the yolk sac of the chick embryo has been shown previously to give rise on the average to a clone of 128 erythrocytes. Furthermore, in any given generation the erythroid cell synthesizes a characteristic amount of hemoglobin (Hb). In these experiments day 4 embryos were treated with FUdR for 12 hours, and then reversed with thymidine. We have monitored both the passage of these erythroblasts through the cell cycle, and the effect of this perturbation on the Hb content of single cells. As a result of this disruption the amount of Hb synthesized in a given generation can be varied, but the final amount of Hb/cell in the mature erythrocyte is the same as in the untreated controls. Apparently the total amount of the Hb/cell does not in itself influence the passage of the cell through the cycle. The coefficients of variation of the Hb values in the mature erythrocytes from both normal an perturbed embryos are similar.
Alkaline phosphatase activity and the regulation of growth in transformed mammalian cells
Authors: Sela Ben‐Ami , Sachs Leo 
Published: February 2005

AbstractThe relationship between alkaline phosphatase activity and cell growth has been studied in hamster cells transformed by different carcinogens. About 90% of normal hamster embryo cells were constitutively positive for alkaline phosphatase activity (AP+). However, there were no AP+ cells in cell lines transformed after treatment with the chemical carcinogens dimethylnitrosamine or 4‐nitro‐quinoline‐N‐oxide and 0.02% and 4% AP+ cells in cell lines transformed by polyoma virus or Simian virus 40. The glucocorticoid hormone, prednisolone, induced alkaline phosphatase activity in 12% and 44% of the enzyme‐negative (AP−) cells in cell lines transformed by polyoma or Simian virus 40, but this hormone did not induce alkaline phosphatase activity in AP− cells from cell lines transformed after treatment with the chemical carcinogens. Treatment of polyoma transformed AP− cells with the mutagen N‐methyl‐N′‐nitro‐N‐nitro‐soguanidine produced AP+ cells, whereas no AP+ cells were found after mutagen treatment of AP− cells from the chemically transformed cell lines. Studies on spontaneous segregation in the polyoma transformed cell line has shown that AP+ cells segregated AP− cells both in vitro and in vivo, although no spontaneous segregation was observed from AP− to AP+ cells.AP+ cells, compared to AP− cells, showed a decrease in DNA synthesis, cell multiplication, the ability to form colonies in soft agar and tumorogenicity in animals. AP− cells induced for alkaline phosphatase activity by prednisolone, showed the same growth properties in vitro as uninduced AP− cells. The decreased cell growth found in AP+ cells which were constitutive for alkaline phosphatase activity was therefore not found in the hormone induced AP− cells. The results indicate that constitutive alkaline phosphatase activity appears to be related to the regulation of cell growth and that AP− cells have a selective advantage over AP+ cells.
The non‐equivalence of mouse and human marrow culture in the assay of granulopoietic stimulatory factors
Authors: Lind D. E. , Bradley M. L. , Gunz F. W. , Vincent P. C. 
Published: February 2005

AbstractMouse bone marrow forms colonies of granulocytes and monocytic phagocytes when cultured in the presence of human plasma, urine or “feeder layers” prepared from human leukocytes. By contrast, human marrow produces colonies in the presence of leukocyte feeder layers but not in the presence of plasma or urine. It has been tacitly assumed that the response of mouse marrow to human blood leukocyte feeder layers is a measure of physiological substances released by those leukocytes which might control human granulopoiesis. This assumption however, has never been put to the test by comparing the response of mouse and human marrow to stimulation by leukocytes from the same individual. This has been done in the present study by using leukocytes from normal and leukemic subjects. Different human marrows responded similarly to stimulation by the same normal feeder layers, but there was no quantitative or qualitative correlation between the response of human and mouse marrows. Feeder layers from patients with acute granulocytic leukemia did not stimulate colony growth in normal human marrow but were as potent in stimulating mouse marrow colony growth as were feeder layers of normal leukocytes.We conclude that different factors may stimulate human and mouse marrows and that assays of granulopoietic factors of human origin should in future be carried out in human rather than mouse marrows.
Chinese hamster cells exhibiting a temperature dependent alteration in purine transport
Authors: Harris J. F. , Whitmore G. F. 
Published: February 2005

AbstractThis paper reports the isolation of a phenotypically stable line of Chinese hamster ovary cells which exhibits a temperature dependent alteration in the transport of some purines. The alteration manifests itself for the uptake of guanine, hypoxanthine, azaguanine and guanosine but not for adenine, adenosine or thymidine. Studies with crude cell extracts suggest that, at the temperature the alteration is being expressed, the HGPRT activity is within the normal range. In cell‐cell hybridization studies the alteration behaves as a recessive genetic trait.
The localization of enzymatic activities involved in uridine nucleotides reactions in human erythrocytes
Authors: Boninsegna A. , Deana R. , Siliprandi Dagmar 
Published: February 2005

AbstractEnzymatic activities involved in the transformations of uridine nucleotides by intact erythrocytes and their subfractions have been studied and the following enzymatic activities have been identified: UTPase, UDPase, UMPase and uridylate kinase.UTPase activity was present exclusively in the stromal fraction while UMPase and uridylate kinase activities were specific in the soluble fraction. UDPase was present in both the stromal and soluble fractions.This compartmentation in erythrocytes differs from that reported for the enzymes involved in adenine nucleotides transformations. Due to its sensitivity to Zn2+, uridylate kinase could be differentiated from adenylate kinase.
Selection for temperature‐sensitive mutants of diploid and tetraploid mammalian cells
Authors: McBurney Michael W. , Whitmore Gordon F. 
Published: February 2005

AbstractMammalian cell populations may be enriched for temperature‐sensitive (ts) mutants by the tritiated thymidine (3H‐TdR) suicide procedure (Thompson et al., '71). Such procedures were carried out on the near‐diploid Chinese hamster ovary (CHO) cell line and on a line made “tetraploid” by Colcemid treatment. Clones of ts mutants were obtained from the diploid line, but in spite of repeated attempts, no ts mutants were isolated from the tetroploid line. The phenotypes of the new diploid ts mutants recovered were consistent with the particular selection regime employed.
The role of humoral factors in the regression of leukemia in chickens as measured by in vitro colony formation
Authors: Silva R. F. , Dodge W. H. , Moscovici C. 
Published: February 2005

AbstractLeukemic myeloblasts induced by avian myeloblastosis virus in the chicken formed small compact (type II) colonies in semi‐solid agar medium. Normal yolk sac cells from 12‐day old embryos formed large diffuse (type I) colonies under the same conditions. Type I colony formation (but not type II) was strictly dependent upon the presence in the medium of a colony stimulating factor (CSF) present in fresh chicken serum or conditioned medium. Serum CSF levels were determined for normal, leukemic, and birds which had spontaneously regressed from myeloblastic leukemia. When type I colony formation was used as the assay, serum CSF levels of leukemic birds were found to be significantly lower than levels in either normal or regressed birds. When the same sera were tested for their ability to induce type II colonies, leukemic birds demonstrated a significantly higher CSF level than either normal or regressed sera. Regressed chickens had serum CSF levels similar to normal birds.
Changes in the uptake of 2‐deoxy‐D‐glucose in Balb/3T3 cells chemically transformed in culture
Authors: Oshiro Y. , Dipaolo J. A. 
Published: February 2005

AbstractBalb/3T3 cells transformed in culture by chemical carcinogens were shown to multiply in a medium supplemented with 2% calf serum or with 10% agamma new‐born calf serum. The cell lines that multiply well in medium supplemented with 10% agamma serum produced a higher incidence of tumors in X‐irradiated weanling mice than the lines that multiply poorly. The difference in 2‐deoxy‐D‐glucose uptake into exponentially growing transformed and un‐transformed cells was 50–100%. In crowded cultures untransformed Balb/3T3 cells ceased taking up the sugar, while chemically transformed cells continued at the same rate even at high cell densities; thus, the difference became greater in crowded cultures. When the serum concentration in the media was reduced from 10% to 2%, untransformed Balb/3T3 cells took up the sugar at a reduced rate, while chemically transformed cells were only slightly affected; agamma new born calf serum supplemented medium had no effect on sugar uptake in any of the cells. When the serum concentration was changed from 2% to 10%, untransformed cells increased sugar uptake followed by cell division. The immediacy (within 15 min) of the response in the sugar uptake to 10% serum concentration suggested that the increased uptake rate and the consequent higher concentration of the sugar (D‐glucose in normal situation) within Balb/3T3 cells triggered the cell cycle. Chemical carcinogens appear to alter permanently the uptake mechanism for a key nutrient.
Viral probe into the events of cellular (in vitro) aging
Authors: Pitha Josef , Adams Robert , Pitha Paula M. 
Published: February 2005

AbstractViral infection by vesicular stomatitis virus (VSV) as well as cellular protection against it were studied in cultured human diploid fibroblast cells (WI38 strain) of varying senescence (passage) level. Full protection against viral infection can be achieved by pretreatment of cells with an interferon inducer (complex of polycytidylate and polyinosinate) or by pretreatment with concentrates of interferon itself. The late passages (over 45) require higher concentration of both agents than the medium passages (25–45); a complete failure of protective mechanisms occurs only close to cellular death. Furthermore, effects of confluency and of duration of induction impulse were studied. WI38 cells are sensitive to VSV infection through their entire life span; however, during the last passage before their death by senescence, VSV replication is significantly decreased. It is concluded that even in relatively senescent cells (a) protection mechanisms which were not used previously can be activated, (b) synthesizing machinery necessary for efficient support of viral replication is sustained, and (c) release of lysosomal enzymes ending the viral replication does not begin sooner than with cells of earlier passage level.
Effect of 5‐bromodeoxyuridine on incorporation of RNA precursors in sea urchin embryos
Authors: Fitzmaurice Leona C. , Baker Robert F. 
Published: February 2005

AbstractExposure of early sea urchin embryos to 5‐bromodeoxyuridine (at concentrations up to 100 μg per ml) severely decreases the uptake of exogenous 3H‐uridine into RNA. However, the actual gross rate of DNA or RNA synthesis in these embryos appears not to be affected by the presence of 5‐bromodeoxyuridine.
Interaction of alcohols with the transport system of glucose in human erythrocytes
Authors: Lacko L. , Wittkeand B. , Geck P. 
Published: February 2005

AbstractAlcohols inhibit the exchange transport of glucose in human erythrocytes. Comparing the inhibition by monohydroxy‐alcohols, which have different distribution coefficients between medium and membrane, shows that the degree of inhibition depends mainly upon the concentration of the alcohol in the membrane.1‐butanol exerts a mixed‐type inhibition; Vmax decreases and Km increases. Since also the Km of the equilibrium transport increases upon the addition of the alcohol, the changes in the Km of exchange transport cannot be attributed solely to the differently affected mobilities of the loaded and free carrier, but the affinity of glucose to the transport system is reduced.The transport system can bind two alcohol molecules. With one alcohol molecule bound the affinity of the transport system for the second alcohol molecule already increases.The nature of the bond of the alcohols to the transport system is discussed and possible explanations for the cooperative effect upon the binding of the second alcohol molecule are offered.
The influence of sex steroids on calcium‐ and magnesium‐induced mitogenesis in isolated rat thymic lymphocytes
Authors: Morganand J. I. , Perris A. D. 
Published: February 2005

AbstractElevated calcium and magnesium concentrations promoted mitotic activity in rat thymic lymphocyte cultures. Oestradiol inhibited calcium‐ but not magnesium‐induced mitogenesis. One prerequisite for the mitogenic action of calcium is a raised intracellular concentration of cyclic adenosine 3′5′ monophosphate (cyclic AMP) but cyclic AMP‐induced mitogenesis was insensitive to oestradiol. This suggests that the steroid blocks the mitogenic process at a stage preceding the endogenous cyclic AMP elevation. Furthermore the mitogenic actions of adrenaline, which stimulates adenylate cyclase (the enzyme responsible for cyclic AMP biosynthesis), and caffeine, which inhibits phosphodiesterase (the enzyme which degrades cyclic AMP) were also insensitive to oestradiol inhibition. This precludes a direct effect of the steroid on these enzymes. However, oestradiol did inhibit the mitogenic action of parathyroid hormone (PTH). Since the mitogenic action of PTH probably involves increased calcium entry to the cell, oestradiol may block this ion influx.The inhibition of calcium‐ and PTH‐induced mitogenesis must be attributable to some structurally specific action of oestradiol. The steroids cholesterol, progesterone and testosterone all failed to reduce calcium‐induced mitogenesis, whereas both α and β oestradiol were effective.In addition to its insensitivity to oestradiol inhibition, magnesium‐stimulated mitosis was unaffected by both imidazole and calcitonin at concentrations which significantly reduced calcium‐stimulated proliferation. These findings are compatible with the thesis that magnesium‐induced mitogenesis does not involve the elevation of cyclic AMP concentrations.
The deoxyribonucleoside transport systems of cultured Novikoff rat hepatoma cells
Authors: Plagemann Peter G. W. , Erbe John 
Published: February 2005

AbstractThe transport of various deoxyribonucleosides by cultured Novikoff rat hepatoma cells (subline N1S1‐67) follows normal Michaelis‐Menten kinetics. The transport reactions are competitively inhibited by most heterologous deoxy‐ and ribonucleosides and by Persantin and Cytochalasin B. Comparisons of the transport kinetics of the various deoxyribonucleosides (Km and Vmax ) and of the Km/Ki ratios for the inhibitions indicate that deoxythymidine, deoxyuridine and 5‐fluordeoxyuridine are transported by a single system, whereas deoxycytidine and the purine deoxyribonucleosides are transported by other systems. The data suggest that deoxyadenosine, deoxyguanosine and deoxyinosine, are not transported by a single system, but the number of transport systems involved could not be established unequivocally. Similar comparisons also suggest that the deoxyribonucleosides are transported by different systems than the ribonucleosides. All deoxyribonucleoside transport systems are inhibited to about the same extent by Persantin (Ki = 1–2 μM) and Cytochalasin B (Ki = 4–12 μM). The inhibitions of deoxynucleoside transport resulted in corresponding apparent competitive inhibitions of their incorporation into nucleic acids.
Chromosome patterns of nontransformed variants from chemically transformed Balb/3T3 cells
Authors: Olinici C. D. , Evans C. H. , DiPaolo J. A. 
Published: February 2005

AbstractNine variant cell lines isolated from cloned 7,12‐dimethylbenz(a) ‐ahthracene transformed Balb/3T3 mouse cells by treatment with FUdR had growth parameters closely resembling nontransformed cells. Chromosome analysis of the variant lines demonstrated that six variants had a diminished number and three variants had an increased number of chromosomes compared to the parental transformed cell line. All variants had unique marker chromosomes not present in the parental transformed Balb/3T3 cells. The distribution of marker chromosomes and heterochromatin suggested that the initial event in variant formation was a reduction in chromosome number with a subsequent polyploidization of the reduced chromosome complement.
The effect of calcium concentration on ACTH stimulation of steroidogenesis in mouse adrenal tumor cells
Authors: Wishnow Rodney M. , Feist Patty 
Published: February 2005

AbstractCalcium is required for ACTH stimulated steroidogenesis in adrenal tumor cells in tissue culture. In the absence of calcium, the dose of ACTH required to induce half maximum steroidogenesis was increased 30 fold. In contrast to intact adrenal glands or isolated adrenal cells, high doses of ACTH (50 mU/ml) maximally stimulated steroidogenesis in the absence of calcium. Growth for up to six days in medium with low calcium did not affect basal or ACTH induced steroidogenesis. The addition of calcium to cells incubated with ACTH produced a maximum steroidogenic response in 15 minutes. In contrast to intact adrenal glands, calcium is not required for adenosine‐3′,5′‐cyclic monophosphate (cyclic AMP) stimulated steroidogenesis in adrenal tumor cells. These experiments support the concept that calcium is important at the level of ACTH‐membrane receptor site interaction or activation of adenyl cyclase in adrenal tumor cells.