bluuebunny/crossref_metadata_2025_split huggingface dataset:
Calcium‐mediated effects of calcitonin on cyclic AMP formation and lymphoblast proliferation in thymocyte populations exposed to prostaglandin E1
Authors: Whitfield J. F. , MacManus J. P. , Franks D. J. , Braceland B. M. , Gillan D. J. 
Published: February 2005

AbstractThe calcitonin (SCT) from salmon ultimobranchial bodies which (like mammalian calcitonins) lowers the plasma calcium concentration in mammals can also affect cyclic AMP (cyclic adenosine 3′,5′‐monophosphate) metabolism and proliferation of lymphoblasts in normal and prostaglandin E1 (PGE1)‐treated rat thymocyte populations in three different ways. In the first case, low concentrations (0.5–5.0 ng per milliliter) of SCT lower (by a calcium‐mediated process) the ability of PGE1 to transiently increase cyclic AMP synthesis, but the reduced surge of cyclic AMP production is still ample to stimulate lymphoblasts in the cell population to initiate deoxyribonucleic acid (DNA) synthesis. Secondly, these low SCT concentrations affect the eventual progression of the PGE1‐stimulated, DNA‐synthesizing lymphoblasts into mitosis by a calcium‐mediated process. Depending on the extracellular calcium concentration and the magnitude of the initial increment in the intracellular cyclic AMP content, SCT can either promote or inhibit the progression of the stimulated cells into mitosis. SCT's third action is a rapid (within 5 minutes), calcium‐independent elevation of the cellular cyclic AMP content in otherwise untreated thymic lymphocyte populations exposed to a very high concentration (100 ng per milliliter) of the hormone. This early, transient rise in the cyclic AMP level is followed by a calcium‐dependent increase in lymphoblast proliferation. An attempt is made to interrelate and explain the different actions of SCT on cyclic AMP metabolism and mitogenesis.
Cell size distribution in the thymus as a function of age
Authors: Salinas F. A. , Smith L. H. , Goodman J. W. 
Published: February 2005

AbstractAlthough it is well known that thymus function changes with age, it is not known whether these changes are associated with specific thymocyte populations. Since one criterion of specificity is cell size, we studied the size distribution of thymocytes from mice 0.5 days to 30.5 months of age. Body weight, thymus weight, and thymocyte yield were also measured. The mean cell volume of thymocytes from 8.5 to 13 week old mice was 326 μ3, with two detectable subpopulations. Mean thymocyte size was found to change with age. During the first postnatal week, the mean cell volume of the whole thymocyte population increased from 200 to 350 μ3, and the percentage of large cells increased greatly and constituted 90% of the whole population at four days of age. A rather slow decline in mean cell volume with some fluctuation occurred throughout the remaining life span, and at 30.5 months the mean had dropped to about 190 μ3. We suggest on the basis of these data that large thymocytes are involved in the contribution of the thymus to early postnatal development of the immune system and that the age‐related functional capacity of the thymus is related to the size of the thymocyte population.
Biochemical characteristics of normal and virally transformed mouse cell lines
Authors: Yoshikawa‐Fukada M. , Nojima T. 
Published: February 2005

AbstractNormal and virally transformed mouse cells respond differently in vitro to high concentrations of potassium. A higher potassium concentration is required to inhibit multiplication of SV40 transformed 3T3 cells to the same extent as that of normal 3T3 cells. This potassium effect correlates to specific activity of Na‐K dependent ATPase in membranous fraction, normal 3T3 cells having the higher enzyme activity being more sensitive to potassium than SV40‐3T3 cells which have the lower specific activity of the enzyme.Contact inhibition of growth and changes of concanavalin A binding sites which are characteristics of viral transformation influence specific activities of Na‐K dependent ATPase and of adenyl cyclase. Incubation with trypsinized concanavalin A causes SV40‐3T3 to show contact inhibition of growth and at the same time, higher specific activities of both enzymes than the observed in untreated cells. Cellular content of cyclic 3′,5′‐AMP of contact inhibited 3T3 is higher than that in transformed SV40‐3T3, but no difference is detectable in ATP content.
Calcium accumulation by isolated sarcoplasmic reticulum of skeletal muscle during development in tissue culture
Authors: Lough John W. , Entman Mark L. , Bossen Edward H. , Hansen James L. 
Published: February 2005

AbstractThe calcium uptake and ATPase activities of isolated sarcoplasmic reticulum were studied during the first six days of chick skeletal muscle maturation in tissue culture. Statistically significant increases in these activities were observed between the second and the sixth day of maturation. Increases in oxalate‐dependent calcium uptake were demonstrated at concentrations of 2.5 × 10−5 M calcium and 10−4 M calcium. Calcium‐binding determinations conducted in the absence of oxalate displayed changes manifested by an increase at day 5 followed by a significant decrease at day 6. Increases in total ATPase activity during maturation paralleled the sequential increases in calcium uptake. Calcium‐stimulated ATPase activity, however, did not change significantly during periods of marked increase in calcium uptake, suggesting that these activities are dissociated during development of the sarcoplasmic reticulum. These data demonstrate that calcium uptake and total ATPase activity increase during muscle maturation in tissue culture and that these activities are present prior to spontaneous contractions.
Effect of AMP and related compounds on glycogen content of Tetrahymena
Authors: Blum J. J. 
Published: February 2005

AbstractAddition of AMP to cultures of Tetrahymena pyriformis caused an increase in glycogen content of the cells and a small inhibition of growth. Adenine, adenosine, ADP, and ATP also increased glycogen content. Inosine and GMP were less effective; cytidine and uridine were ineffective. The increase in glycogen content was also observed in cultures supplemented with ribose, fructose, or glycerol, and when glyconeogenesis was increased by partial anaerobiosis. Adenine itself did not serve as a glycogen precursor, nor could the lipids of the cell have been the source of the carbon for the increased glycogen. The specific activity of glycogen from cultures supplemented with labelled amino acids was lower in AMP‐treated cells than in controls. AMP‐treatment had little effect on 14CO2 production from labelled glucose, acetate, or pyruvate, but baused a marked inhibition of the oxidation of labelled glyoxylate. It was suggested that AMP increases the rate of glyconeogenesis from precursors other than amino acids and interferes with malate synthase activity or malate transfer from peroxisomes to mitochondria.
Heats of activation for the exosmotic flow of water across the membrane of leucocytes and leukemic cells
Authors: Hempling Harold G. 
Published: February 2005

AbstractThe permeability of the membranes of different types of leucocytes from several mammalian species to the exosmotic flow of water has been measured at different temperatures. Heats of activation for the process have been calculated. Results indicate that the leucocyte has an unusually high heat of activation for the osmotic movement of water across its outer membrane, ranging between 13 to 18 kcal/mole. Unconstrained water movement usually has values between 3 to 5 kcal/mole. This property characterizes all leucocytes examined to date, regardless of species or type. It is apparent that water is intimately associated with the outer boundary of the cell and that this association is quite sensitive to the structural changes which must occur in response to changes in temperature.
A low molecular weight factor in lung‐conditioned medium stimulating granulocyte and monocyte colony formation in vitro
Authors: Sheridan J. W. , Metcalf D. 
Published: February 2005

AbstractMedium conditioned by excised whole lungs from endotoxin‐injected C57BL mice was highly active in stimulating hemopoietic colony formation, particularly of granulocytic type, in agar cultures of mouse bone marrow cells. The colony stimulating factor (CSF) in this material had an α1‐α2 electrophoretic mobility, was eluted from calcium phosphate gel by 0.04 M phosphate buffer and had an unusually low apparent S20W of 1.9. Sequestered polymor‐phonuclear neutrophils were excluded as a major source of this CSF. The high specific activity and ease of preparation of lung conditioned medium make it valuable both for the large scale production of CSF and as a source of an unusual type of CSF.
The response of normal and polyoma virus‐transformed BHK/21 cells to exogenous purines
Authors: Clarke G. D. , Smith Carole 
Published: February 2005

AbstractAdenosine (10 μM) stimulates the initial growth rate of BHK/21 cells seeded at low but not high density in monolayer culture; it does not affect final cell density or permit growth in agar. In labelling experiments With tritiated thymidine, adenosine also increases the response of quiescent cells to low concentrations of serum. Dialysis of serum to remove oxypurines only marginally reduces its effect on quiescent cell labelling or growth, indicating that BHK/21 cells are able to synthesise purines. The response of quiescent cells to 5% serum is inhibited by high MW (2 × 106) dextran sulphate at 2 μg per milliliter. Low MW dextran sulphate (30,000) and heparin at 20 μg per milliliter produce the same effect. Exogenous adenosine (10 μM) prevents this inhibition. Many other purine derivatives replace adenosine for all the above activities but xanthine is completely inactive in all. It, therefore, appears that nucleotide synthesis is a necessary function of these compounds.The growth of cells of a polyoma‐virus‐transformed BHK/21 line in monolayer is not stimulated by exogenous purine, though their colony‐forming ability in agar is increased five‐fold. The stimulating effects of exogenous purines on normal BHK/21 cells and the absolute requirement for them in the presence of polyanions is discussed in relation to possible mechanisms of growth control.
Histone mediated changes in morphology and confluent density of cultured cells
Authors: Kolodny G. M. 
Published: February 2005

AbstractCalf thymus histones and histone subfractions were added to media overlying subconfluent mouse fibroblast cells in culture. The histones caused significantly higher cell densities at confluence than control cultures and disruption of the normal ordered arrangement of cells. These changes were seen on application of histones to growing cells but not confluent cells and were reversed when the histones were removed and the cells replated with more growth area. The slightly lysine rich histone fraction had the greatest effect and the lysine rich fraction had the least effect on cell morphology and cell number at confluence. These effects could not be duplicated with other highly charged basic proteins.
The ability of calcium to change cyclic AMP from a stimulator to an inhibitor of thymic lymphoblast proliferation
Authors: Whitfield J. F. , MacManus J. P. , Gillan D. J. 
Published: February 2005

AbstractCalcium is a major regulator of thymic lymphoblast proliferation in vivo and in vitro. The proliferative activity of the lymphoblasts in thymic lymphocyte (thymocyte) populations in vitro is both constant and low in the presence of calcium concentrations between 0 and 1.0 mM, but higher concentrations increase proliferation by an endogenous cyclic AMP‐mediated promotion of the initiation of DNA synthesis.Lower concentrations (10−7 to 10−5 M) of exogenous cyclic AMP (but not 5′‐AMP) stimulate lymphoblast proliferation in a low‐calcium (0.5 mM) medium, but higher concentrations do not. However, all exogenous cyclic AMP concentrations between 10−7 and 10−3 M (but again not 5′‐AMP) block the stimulation of lymphoblast proliferation in a high‐calcium (1.5 mM) medium. Exogenous cyclic AMP does not prevent calcium from “activating” lymphoblasts, but it reversibly blocks the reaction responsible for the initiation of DNA synthesis in these stimulated cells. Finally, cyclic AMP's inhibitory action, in contrast to its stimulatory action in low‐calcium medium, is not specific for the cyclic nucleotide since a low, non‐mitogenic concentration of cyclic GMP also prevents calcium from stimulating DNA synthesis and cell proliferation.
The effect of trypsin on membrane transport of non‐electrolytes
Authors: Tsan Min‐Fu , Taube Rebekah A. , Berlin Richard D. 
Published: February 2005

AbstractTrypsinization of alveolar macrophages depresses lysine transport but has no effect on nucleoside transport. The depression of the initial rate of lysine transport is due to a decreased rate of exchange diffusion presumably secondary to lowered intracellular pools of amino acids. It is shown directly that trypsinization accelerates the efflux of amino acids but not certain other metabolites, and reduces the capacity of the cell to concentrate amino acids.
A Calcium‐sensitive lanthanum inhibition of amoeboid movement
Authors: Hawkes R. B. , Holberton D. V. 
Published: February 2005

AbstractThe effects of lanthanum ions upon amoeboid movement and upon the redistribution of dense cytoplasmic inclusions following centrifugation were investigated in Amoeba discoides. Treatment with low lanthanum concentrations produced a characteristic inhibited condition in which locomotion ceased while saltatory movements continued. The resorting of stratified cytoplasm by local internal cytoplasmic flow was unaffected. This contrasted with p‐hydroxymercuribenzoate treatment which inhibited both locomotion and saltatory movements. The inhibitory effects of lanthanum ions were antagonised by calcium ions but not by magnesium ions. It is reasoned that lanthanum competes for a peripheral binding site thereby disrupting a calcium‐mediated regulatory mechanism of amoeboid movement.
Cellular responsiveness to stimulation in vitro: Strain differences in hemopoietic colony forming cell responsiveness to stimulating factor and suppression of responsiveness by glucocorticoids
Authors: McNeill T. A. , Fleming W. A. 
Published: February 2005

AbstractGranulocyte‐macrophage colony formation from bone marrow cells in soft agar is dependent upon the presence of a stimulating factor and the number of colonies is related to its concentration. This dose‐response effect provided a measurement of the responsiveness to stimulation of colony forming cell populations in marrows from different sources. There were significant differences between the responsiveness of cells from different strains of mice which paralleled the previously observed myelopoietic and immune responsiveness of these strains to stimulation in vivo.Low concentrations of hydrocrotisone reduced the responsiveness of colony forming cells (a) when added to cultures of normal marrow or (b) when cells were taken from hydrocortisone‐treated mice and cultured in its absence. The reduction which followed inoculation was not apparent until the 4th day and occurred irrespective of mouse strain, type of drug or route of inoculation and with a dose (100 μg) which did not affect the actual number of colony forming cells in the marrow.
The effect of extracellular calcium and magnesium on the proliferation of murine lymphoblasts
Authors: Brennan James K. , Lichtman Marshall A. 
Published: February 2005

AbstractWe have shown that the murine lymphoblast, L5178Y, requires extracellular magnesium or calcium for proliferation in suspension culture. Although both cations produce biphasic effects on growth, magnesium is the more potent since it: (1) stimulates proliferation at lower concentrations; (2) supports optimal proliferation over a wider concentration range; (3) maintains higher cell densities at stationary phase; and (4) produces less inhibition at high concentration.At suboptimal concentrations, calcium facilitates the effect of magnesium but at optimal concentration, no facilitation is evident. A concentration of 3.2 mM calcium or magnesium inhibits growth, while the same concentration composed of equimolar calcium and magnesium does not inhibit proliferation.Extracellular calcium and magnesium may influence proliferation by effecting changes in intracellular calcium and magnesium since: (1) reduction in extracellular concentrations sufficient to produce decreased growth rate is associated with decreased cell calcium and magnesium; (2) cell magnesium and growth rate are related such that an exponential decrease in relative doubling time occurs with decrease in cellular magnesium.Cells cultured at 37°C in magnesium and calcium‐deprived medium will proliferate at a normal rate if either or both cations are replaced within six to 10 hours; however, with longer deprivation the doubling time in restored medium is progressively lengthened.
Isolation and characterization of revertant cell lines. IV. Direct selection of serum‐revertant sublines of SV40‐transformed 3T3 mouse cells
Authors: Vogel A. , Pollack R. 
Published: February 2005

AbstractSV101, the SV40‐transformed subline of the mouse fibroblast line 3T3, is both serum‐ and density transformed, since it grows in both 1% and 10% calf serum, and grows beyond confluence in 10% calf serum. Negative selection at low cell density in 1% calf serum or in 10% agamma‐depleted serum permits direct recovery of serum‐revertant sublines of SV101. These sublines are unable to grow in 1% calf serum.Although negative selection at high cell density in 10% calf serum is known to permit recovery of density‐revertant sublines of SV101, most density‐revertants are not serum‐revertant. However, all serum‐revertants isolated so far are density‐revertant as well.
ph, serum and Zn++ in the regulation of DNA synthesis in cultures of chick embryo cells
Authors: Rubin H. 
Published: February 2005

AbstractVariations in pH, serum concentration and the availability of Zn++ in the medium markedly influence the initiation of DNA synthesis in cultured chick embryo cells. This report considers the interplay of these factors with one another and with other factors such as type of medium, cell population density and the malignaut transformation in an attempt to better define the variables of the growth control system. Conditioned medium seems to protect the cells against the inhibitory effects of lowered pH. Increased serum concentration has a similar, but more striking effect. Increased serum concentration and pH, as well as decreased population density, which stimulate DNA synthesis, also lower the sensitivity of DNA synthesis to inhibition by Zn++ deprivation. Likewise, cell transformation by infection with Rous sarcoma virus lowers the sensitivity of DNA synthesis to inhibition by Zn++ deprivation and by pH reduction. The response of DNA synthesis to pH varies with the type and concentration of buffer used. It is concluded that there are a number of mutually interacting variables involved in the regulation of animal cell multiplication.
The effect of endotoxin on murine stem cells
Authors: Quesenberry Peter J. , Morley Alec , Ryan Marie , Howard Donald , Stohlman Frederick 
Published: February 2005

AbstractPrevious studies showed that after 5 μg of Salmonella typhosa endotoxin there was an increase in colony stimulating factor temporally related to a fall in murine marrow in vitro colony forming cells (CFC). This was followed by differentiation along the marrow granulocytic pathway. The present studies showed that after 5 μg of endotoxin the peripheral blood CFC fell by approximately 50% at one hour, rose to a level ten fold that of control at six hours and then returned to control values by 48 hours. There was a progressive increase in the number of splenic CFC to ten fold that of control from 24 to 72 hours after endotoxin. These data imply a migration of CFC from the marrow to the spleen along with an in‐situ increase in splenic CFC. Thus, either migration or differentiation may explain the fall in marrow CFC after endotoxin.Spleen colony forming units (CFU) in the marrow were measured by a transplantation technique and the transplantation fraction (f Fx) determined. A decrease in marrow CFU at 24 hours after endotoxin was secondary to a change in the f Fx. from 11.1% to 7.6%. There was however, an increased percentage of CFU in DNA synthesis in the interval of 6–48 hours after endotoxin, as judged by the hydroxyurea technique. As the marrow CFC fell within 20 minutes of endotoxin administration, the data suggest the CFC may be affected initially and that changes in the generative cycle of the CFU may be of a secondary nature.
A comparison of the effect of cytotoxic agents on agar colony forming cells, spleen colony forming cells, and the erythrocytic repopulating ability of mouse bone marrow
Authors: Millard R. E. , Blackett N. M. , Okell S. F. 
Published: February 2005

AbstractThree assays for bone marrow progenitor cells have been used to determine the effect of single doses of two cytotoxic agents, cyclophosphamide and vinblastine. The assays employed were the agar colony forming and spleen colony forming assays and the crythroid repopulating ability.In normal mice, there was little difference between the response of the progenitor cells assayed by the three methods, following cyclophosphamide: and no detectable difference following vinblastine.Bone marrow from continuously irradiated mice and bone marrow regenerating seven days following transplantation was also studied: in both these situations the proliferation rate of the progenitor cells is increased. Cyclophosphamide was found to be only slightly proliferation dependent with each assay. However, vinblastine was strikingly proliferation dependent. In irradiated mice and also in regenerating marrow the agar colony forming cells were many times more sensitive to this agent than were the other progenitor cells.These results show that under some but not all circumstances the agar colony forming and spleen colony forming cells behave similarly in C57BL mice, but are not a single population of cells.
The role of sulfhydryl groups in human neutrophil adhesion, movement and particle ingestion
Authors: Giordano Gerald F. , Lichtman Marshall A. 
Published: February 2005

AbstractRecent studies have suggested that ectosulfhydryl groups may play a role in cell contact phenomena.We have studied the possible role of ecto‐ and endosulfhydryl groups in the morphology, adhesiveness, random and directed (chemotaxis) motility and phagocytosis of human polymorphonuclear neutrophils. The rapidly penetrating sulfhydryl binding reagents HgCl2 and NEM inhibited adhesiveness, motility and phagocytosis when studied at > 0.1 mM in plasma or > 0.01 mM in buffer. The difference in inhibitory concentration was shown to be due to the difference in albumin content of the two media. D‐cysteine prevented the effect of HgCl2 and NEM on cell morphology, adhesiveness, motility and phagocytosis indicating that their effects were on cell sulfhydryl groups. PCMBS, a very slowly penetrating organic mercurial, had no effect on neutrophil morphology, adhesiveness, motility or phagocytosis. However, PCMBS inhibited platelet aggregation, assuring its potency. These studies indicate that ectosulfhydryl groups are either not present or not participants in the maintainence of structure and functions of human neutrophilic granulocytes.