bluuebunny/crossref_metadata_2025_split huggingface dataset:
Cation fluxes and volume regulation by human lymphocytes
Authors: Bui A. H. , Wiley J. S. 
Published: February 2005

AbstractThe ionic basis of volume regulation by human peripheral blood lymphocytes in hypotonic Tyrode's medium has been studied. The intracellular water space of lymphocytes increased to a maximum after 1 min in 0.68 × isotonic Tyrode's but returned to the isotonic value by 20 min at 37°C. During this phase of volume regulation (1–20 min) both 42K+ efflux and 42K+ influx were stimulated severalfold, but the increase in 42K+ efflux exceeded the influx, resulting in a net loss of 20% of the lymphocyte K+. The increase in 42K+ efflux during the phase of cell shrinkage was unaffected by ouabain or by quinidine. Hypotonicity increased both the ouabain‐sensitive (active) and ouabain‐insensitive components of 42K+ influx by 76% and 123% respectively. Hypotonic shock stimulated 22Na+ influx by only 25%, but cell Na+ content was unchanged at 1 min and even decreased after 20 min. Thus active K+ influx and Na+ extrusion is increased by hypotonicity, but greater pumping cannot explain the net decrease in cell cations that leads to volume regulation. The 45Ca2+ uptake was not significantly changed by hypotonicity. Although volume regulation was abolished in a hypotonic high K medium, 42K+ efflux was still stimulated 2‐fold by the reduction in tonicity. These findings support the hypothesis that volume regulation in hypotonic media occurs largely by a passive loss of cell K+, which results from a selective increase in membrane permeability to this ion. The increase in K+ permeability in hypotonic media is observed even in the absence of volume regulation by the cell.
The hexose transport system in the human K‐562 chronic myelogenous leukemia‐derived cell
Authors: Dozier J. C. , Diedrich D. F. , Turco S. J. 
Published: February 2005

AbstractKinetics of glucose transport in K‐562 cells was studied using 3‐0‐methylglucose, a nonmetabolizable analog of glucose. A Km of 3.7 mM and Vmax of 32.0 nmoles/minute/106 cells was found for the process. D‐Glucose, phloretin, and phlorizin competitively inhibit the transport of 3‐0‐methylglucose with Ki values of 4.1 mM, 4.1 μM and 225 μM, respectively, whereas L‐glucose did not inhibit transport at all. The results indicate that K‐562 cells, which are known to have erythropoietic characteristics, possess a glucose carrier system similar to the one in adult human erythrocytes. However, the Vmax data suggest that more copies of the carrier are present in the malignant cell, presumably to support the high rate of anaerobic glycolysis.
Control of cellular proliferation in HeLa‐S3 suspension cultures. Characterization of cultures utilizing acridine orange staining procedures
Authors: Bauer Kenneth D. , Dethlefsen Lyle A. 
Published: February 2005

AbstractGrowth control is investigated in detail in fed and unfed HeLa‐S3 suspension cultures. Two‐step acridine orange staining and flow cytometric analysis indicate declines in cellular red fluorescence (proportional to RNA content) of 40–50% between exponential and plateau phase in both culture types. Cellular green fluorescence (DNA content) assessed simultaneously indicates an increment of cells with G1‐DNA content in plateau phase in the unfed cultures, while fed cultures show a brief increment in G1‐phase cells in the transition phase followed by a recovery in plateau phase to a value similar to that of exponential cultures. Temporal declines in the 3H‐thymidine pulse‐labeling index are observed in both culture systems. These data along with the flow cytometry data indicate a distinct G1‐arrest in the unfed plateau cultures and suggest a random arrest of cells about the cell cycle in fed plateau cultures. Acidic acridine orange staining and flow cytometric analysis furthermore indicate the occurrence of a quiescent population comprising approximately 34% of the total cells and consisting of both dead and viable cells in plateau phase unfed cultures. In contrast, fed plateau cultures show approximately 14% quiescent, mostly dead cells. Also, both culture systems show temporal declines in the clonogenic index and a longer cell‐cycle transit time in plateau phase relative to exponential phase. These findings confirm earlier work which indicates that the environment has a profound influence on the mode of growth control for mammalian cells in vitro.
Sodium fluxes in human fibroblasts: Kinetics of serum‐dependent and serum‐independent pathways
Authors: Villereal Mitchel L. 
Published: February 2005

AbstractSodium influx in serum‐deprived human fibroblasts is by way of a pathway which shows saturation kinetics. A plot of initial Na influx versus [Na]o ([Na]i = 10 mM) gives a simple Michaelis‐Menten type of curve with a K1/2 = 70.0 ± 8.1 mM and a Vmax = 14.5 ± 1.9 /mol/g prot/min. A similar plot of initial Na influx versus [Na]o in the presence of 10% fetal bovine serum (FBS) gives a nonsatu‐rating curvilinear response which appears to be biphasic. A plot of the serum‐dependent Na influx versus [Na]o (obtained by subtracting the curve in the absence of FBS from the curve in the presence of 10% FBS) shows that there is a linear relationship between serum‐induced Na influx and external [Na]. At physiological Na concentrations, in the presence of FBS, the serum‐induced Na influx is equal to the amiloride‐sensitive Na flux, whereas in the absence of serum amiloride inhibits less than 10% of the Na influx. The effect of intracellular Na on Na flux was tested by preloading cells with Na in a digitoxin‐containing medium prior to measurement of Na flux. A plot of steady‐state Na exchange flux versus [Na]o ([Na]i ≈︁ [Na]o) in the absence of serum gives a curve that appears to saturate at approximately 100 mM Na (flux = 100 /μmol/g prot/min) and then declines with increasing [Na] (flux = 40 /μmol/g prot/min at 150 mM). In contrast to Na influx in control serum‐deprived cells, Na flux in Na‐loaded cells is dramatically inhibited by the presence of amiloride. Since the peak Na exchange flux of 100 μmol/g prot/min is greatly in excess of the Vmax for Na influx in control serum‐deprived cells and the enhanced Na flux is amiloride‐sensitive, elevating intracellular Na must somehow activate the amiloride‐sensitive Na transport system, which is normally only minimally active in the absence of serum.
Cellular regulatory role of leukotriene B4: Its effects on cation homeostasis in rabbit neutrophils
Authors: Sha'Afi R. I. , Naccache P. H. , Molski T. F. P. , Borgeat P. , Goetzl E. J. 
Published: February 2005

AbstractWe have found that exogenous leukotriene B4 modifies calcium homeostasis in rabbit neutrophils in a manner essentially analogous to that of the chemotactic peptide f‐Met‐Leu‐Phe. Leukotriene B4 causes a rapid and dose‐dependent increase in membrane permeability to calcium and a release of calcium from previously unexchangeable intracellular pool(s). The net result of these changes is to transiently elevate the intracellular level of exchangeable calcium. A stereoisomer of leukotriene B4 with greatly reduced secretory activity toward neutrophils (5S, 12S‐di HETE) is essentially without effect on the rate of 45Ca uptake at concentrations equal to those that produce near maximal enhancement by leukotriene B4. Leukotriene B4, in addition to its effects on calcium metablolism, also increases the rate of 22Na influx into rabbit neutrophils. The relationships between the action of leukotriene B4 on calcium homeostasis and the neutrophil‐directed activities of arachidonic acid and its lipoxygenase metabolites are discussed.
Regulation of the prereplicative changes in the synthesis and transport of messenger and ribosomal RNA in regenerating livers of normal and hypocalcemic rats
Authors: Walker P. Roy , Whitfield James F. 
Published: February 2005

AbstractPartial hepatectomy induces increases in the synthesis of both messenger (poly(A)+) and ribosomal (poly(A)−) RNA, which precede the initiation of DNA synthesis. The increase in poly(A)+RNA, which commences soon after surgery and reaches a peak 1–3 hours later is particularly striking. Disruption of this early increase in poly(A)+RNA synthesis by colchicine (and other microtubule disrupters) or indomethacin results in a failure to initiate DNA synthesis. This suggests that prostaglandins and the microtubules are involved in the mechanism of proliferative activation. Hypocalcemia, which also prevents the initiation of DNA synthesis, has no effect on the prereplicative changes in either messenger or ribosomal RNA synthesis. These results help to define the critical stages of prereplicative development and give some insight into their regulation.
Cytochalasin inhibition of isolated rat gastric parietal cell function
Authors: Rosenfeld Gary C. , McAllister Ellen , Thompson W. Joseph 
Published: February 2005

AbstractSubmicrogram concentrations (0.04‐‐0.29 μM) of the microfilament disrupting agents cytochalasins D, E, and B (CD, CE, CB) were shown to inhibit secretagogue‐stimulated 14C‐aminopyrine accumulation (AP) in isolated rat gastric mucosal parietal cells. The microtubule disrupting agent colchicine had little influence on AP accumulation. Histamine‐ and dibutyryl cyclic AMP (DbcAMP)‐stimulated AP accumulation was inhibited with an order of potency CD > CE ≈︁ CB. CB inhibition of these secretagogue actions was, however only approximately 65‐‐70% of the maximal stimulated response, whereas CD and CE caused 100% inhibition. On the other hand, carbamylcholine‐stimulated AP accumulation was inhibited 100% by all cytochalasins tested with an order of potency CD ≈︁ CE > CB. These data are discussed in relation to acid secretagogue‐induced morphological changes involving actin filament organization in parietal cells.
Effects of thyroliberin (TRH) on cell proliferation and prolactin secretion by GH3/B6 rat pituitary cells: A comparison between serum‐free and serum‐supplemented media
Authors: Brunet N. , Rizzino A. , Gourdji D. , Tixier‐Vidal A. 
Published: February 2005

AbstractNumerous studies have shown that prolactin (PRL) production by GH3 cells grown in serum supplemented media is regulated by several hormones including thyroliberin (TRH). The recent availability of hormonally defined, serum‐free media for the growth of GH3 cells has made it possible to determine the effect of TRH in absence of other prolactin regulating hormones. Here we demonstrate that transfer of GH3/B6 cells from serum‐supplemented medium to serum‐free media results in several important changes: (1) altered growth response to TRH, (2) altered cell attachment and morphology, (3) greatly reduced prolactin production, and (4) greater stimulation of prolactin production by TRH. After 4 days in serum‐free medium, TRH stimulates prolactin production by as much as 5‐fold instead of approximately 2‐fold in serum‐supplemented medium. Furthermore, this increased responsiveness to TRH in serum‐free medium is accompanied by a 10‐fold decrease in the ED50 for TRH (concentration needed for half‐maximal response) and paradoxically by a 2‐fold reduction in the number of high‐affinity TRH binding sites without significant change of their association constant.
Adhesive substrates for fibronectin
Authors: Klebe Robert J. , Bentley Kevin L. , Schoen Robert C. 
Published: February 2005

AbstractIn order to promote cell attachment, fibronectin must first undergo activation by a suitable substrate. In this study, 52 materials have been surveyed for their ability (a) to bind fibronectin, (b) to activate the cell‐adhesive property of fibronectin, and (c) to support the growth of cells. Many plastics, polysaccharides, metals, and ceramics were found to support cell growth as well as the fibronectin‐dependent attachment of cells. Several other substrates have been identified that were inactive in promoting either cell attachment or growth. Hydrophobic substrates were found to be active in fibronectin activation, whereas hydrophilic substrates were found to be inactive.Since fibronectin binds to substrata of extremely varied chemical composition, it is clear that the binding of fibronectin to such substrata is nonspecific in nature. Since protein pretreatment of all substrata, except collagen and poly(L‐lysine), abolished the physical binding of fibronectin, the binding of fibronectin to artificial substrata is probably ascribable to a nonspecific hydrophobic protein‐substratum interaction. In contrast, several lines of evidence indicate that the interaction between fibronectin and collagen displays biological specificity.Poly(hydroxyethylmethacrylate)(poly(HEMA)), which has previously been shown to be nonadhesive for cells, is demonstrated here to be unique in its inability to bind fibronectin. Addition of one part per million of an adhesive polymer to poly(HEMA) permits fibronectin binding to occur.
Hb Switching in neonatal cultures. Increase of Hb A synthesis in presence of an erythroid potentiating activity (EPA)
Authors: Testa Ugo , Vainchenker William , Guerrasio Angelo , Beuzard Yves , Breton‐Gorius Janine , Rosa Jean , Lusis A. J. , Golde David 
Published: February 2005

AbstractThe role of EPA (erythroid potentiating activity) on the growth and on the pattern of hemoglobin synthesis in erythroid colonies from human neonates was investigated. Conditioned medium from the Mo cell line was used as a source of EPA. The results have shown that the addition of Mo medium to cultures determined a significant enhancement of the number and size of BFU‐E and an increase of β chain synthesis. The acceleration of hemoglobin switching is not related to an amelioration of the maturation of the erythroid colonies when grown in the presence of Mo medium. The enhancement of Hb A synthesis induced by Mo medium can directly be related to its EPA, which may operate by two different mechanisms: (1) the recruitment of early erythroid progenitors already preprogrammed to synthesize prevalently β chains, or (2) the modulation of β and γ gene activity in cord blood BFU‐E. Some evidence suggests that the first mechanism does operate.
Effects of Ca ions on action potentials in immature cultured neurons from chick cerebral cortex
Authors: Mori Junko , Ashida Hiroshi , Maru Eiichi , Tatsuno Jiro 
Published: February 2005

AbstractAction potentials evoked by depolarizing pulses were studied in immature cultured cerebral cortical neurons from chick embryos. The majority of action potentials were rather small, and they were still elicited in the presence of 10−7 gm/ml tetrodotoxin (TTX), but were almost completely abolished in Na+‐free solution or by 10−5 gm/ml TTX in Tyrode's solution. The elevation of external Ca2+ concentration not only increased the maximum rates of rise of action potentials in normal Tyrode's solution with and without low (10−7 gm/ml) TTX but also regenerated action potentials in high (10−5 gm/ml) TTX‐containing Tyrode's solution or in Na+‐free solution. These high Ca2+ effects were blocked by Mn2+ or Co2+. These results suggest that action potentials, which were predominantly Na‐dependent, are partially contributed by Ca ions in immature chick cerebral cortical neurons.
The relationship between the insulin content and inhibitory effects of bovine colostrum on protein breakdown in cultured cells
Authors: Ballard F. J. , Nield M. K. , Francis G. L. , Dahlenburg G. W. , Wallace J. C. 
Published: February 2005

AbstractProtein degradation in ten mammalian cell lines is markedly inhibited by small amounts of bovine colostrum. This response is consistent with the growth‐promoting activity of colostrum that has been reported previously. Fractionation of colostrum on DEAE cellulose showed that most of the inhibitory activity against protein breakdown in H35 cells coeluted with insulin. Insulin concentrations in different batches of bovine colostrum ranged from 0.67 nM to 5.7 nM, approximately 100‐fold higher than in blood. The sensitivity of protein breakdown in H35 or MH1C1 hepatoma lines to these colostrum samples was proportional to their insulin concentrations and could largely be accounted for by the amount of insulin present. Removal of insulin from colostrum by means of a protein A‐anti‐insulin antibody affinity column was accompanied by a loss of the ability of colostrum to inhibit protein breakdown in H35 or MH1C1 cells. However, in IMR90 fibroblasts, a cell line with a similar sensitivity to colostrum as the two hepatomas but very insensitive to insulin, protein breakdown was still inhibited by the insulin‐free colostrum. These results suggest that, whereas the effect of bovine colostrum in H35 or MH1C1 cells is actually a response to insulin, different growth factors in colostrum account for the inhibition of protein breakdown in other cell lines.
Changes of ornithine decarboxylase activity and polyamine content upon differentiation of mouse NB‐15 neuroblastoma cells
Authors: Chen Kuang Yu , Presepe Vincent , Parken Nancy , Liu Alice Y.‐C. 
Published: February 2005

AbstractThe possible functions of ornithine decarboxylase (ODC) and polyamines in the differetiation of mouse NB‐15 neuroblastoma cells were investigated by examining the changes of these parameters in the differentiaton and nondifferentiating NB‐15 cells over a 5‐day culture period. Differentiation of NB‐15 cells was induced by the addition of dibutyryl cyclic AMP and 3‐isobutyl‐1‐methylxanthin (IBMX) to the growth medium and was monitored by neurite outgrowth, increase of acetylcholinesterase (AChE), and RI cAMP‐binding protein. Plating of NB‐15 cells in fresh serum‐containing growth medium was accompanied by rapid growth and a marked increase of ODC activity, this early increase of ODC activity was attenuated, both in duration and in magnitude, in the differentiating cells. The spermidine content of the differentiating neuroblastoma cell was significantly lower than that of the nondifferentiating cells. In the fully differentiated neuroblastoma cells, the ODC activity and spermidine content were lower than that of the undifferentiated cells by approximately 15‐fold and five‐fold, respectively. Based on these results it is proposed that changes of polyamine metabolism may be of significance in the differentiation of mouse neuroblastoma cells.
Cytoplasts can transfer factor(s) that stimulate quiescent fibroblasts to enter S phase
Authors: Mercer W. Edward , Schlegel Robert A. 
Published: February 2005

AbstractCytoplasts prepared from fibroblasts arrested by hydroxyurea were fused with serum‐arrested, quiescent fibroblasts. In contrast to unfused mon‐nucleated cells in the same culture, a sizable fraction of these cybridoids entered S phase in the absence of extracellular serum stimulation. Because DNA synthesis commenced only after a considerable lag following fusion, it was concluded that the cytoplasts contain factors which initiate the progression of quiescent cells toward S phase.
Selective inhibition of DNA synthesis by a protein released from spleen cells
Authors: Miyata Shohei , Kihara Hirozi K. 
Published: February 2005

AbstractSpleen cells cultured release proteins into the culture medium, some of which shows both binding activity to single stranded DNA (ss‐DNA) and inhibitory activity to 3H‐thymidine incorporation into cells. The inhibitory protein of DNA synthesis was purified to near homogeneity by ammonium sulfate precipitation, ss‐DNA‐cellulose affinity chromatography, and gel filtration chromatography. The molecular weight of the major band of this protein, as estimated by sodium dodecyl‐sulfate gel electrophoresis, was approximately 14,000. The effect of the protein was compared with various cell lines and primary cell culture, and it was found that the protein strongly inhibited DNA synthesis of HeLa, L, and HEp2 cells, but only inhibited to a minor extent synthesis of Ehrlich cells and primary culture of mouse embryo.
Fibroblasts from Retinoblastoma patients: Enhanced growth in fetal calf serum and a normal response to ionizing radiation
Authors: Kossakowska A. E. , Gallie B. L. , Phillips R. A. 
Published: February 2005

AbstractRetinoblastoma is a rare malignant eye tumor found almost exclusively in young children. In 30% of cases, the tumor is bilateral and is inherited as an autosomal dominant trait. In such patients, all of the cells in the body must carry the mutation predisposing to retinoblastoma. To search for the expression of the gene in cells outside the retina, we have studied several in vitro properties of skin fibroblasts from patients with bilateral retinoblastoma. Measurement in low concentrations of fetal calf serum of the initial growth rate and the plating efficiency show that fibroblasts from retinoblastoma donors grow significantly better than those from normal donors. However, we were unable to confirm the results of other investigators that fibroblasts from donors with bilateral retinoblastoma are unusually sensitive to ionizing radiation. In family studies, skin fibroblasts from normal siblings had the same radiation sensitivity as fibroblasts from sibling with retinoblastoma.
Stimulation of thymidine kinase activity by chloramphenicol in Naegleria
Authors: Corff Sondra , Yuyama Shuhei , Young Paul G. 
Published: February 2005

AbstractIn the present study, the possible association of thymidine kinase (TK) with mitochondria in Naegleria was investigated by treating growing and differentiating cells with chloramphenicol (CAP), an inhibitor of mitochondrial protein synthesis. In some systems, CAP causes an overproduction of mitochondrial proteins coded for in the nucleus. The present results show that in growing Naegleria, CAP stimulates a dramatic increase in TK activity while growth and division is gradually inhibited. CAP does not stabilize the enzyme in vivo or in vitro. The stimulation is cycloheximide (CHI)‐sensitive and specific since nucleoside phosphotransferase activity does not increase. In cells stimulated to differentiate, CAP does not prevent differentiation or the expected decrease in TK activity. Using polyacrylamide gel electrophoresis, a comparison of TK in mitochondrial and postmitochondrial fractions of CAP‐treated and untreated cells was made. Results suggest some processing of the enzyme, resulting in a slight change in electrophoretic mobility. No mitochondrial TK was found. The stimulation of a cytoplasmic enzyme by CAP suggests a form of mitochondrial control of nuclear transcription for other than mitochondrial proteins. DNA synthesis in CAP‐treated cells was not stimulated, suggesting (since TK and DNA synthesis are usually tightly coupled) an uncoupling of these two events, most likely, at the beginning of the S phase.
6‐Deoxy‐D‐glucose and D‐xylose: Analogs for the study of D‐glucose transport by mouse 3T3 cells
Authors: Romano Antonio H. , Connell Nancy D. 
Published: February 2005

Abstract6‐Deoxy‐D‐glucose and D‐xylose, structural homomorphs of D‐glucose that lack a 6‐hydroxyl group or a 6‐hydroxymethyl group, respectively, are transported efficiently by mouse 3T3 cells, with good affinity and high specificity for the D‐glucose transport system. Since these analogs lack the 6‐hydroxyl group, which is the site of phosphorylation of glucose by hexokinase, they are taken up and are recoverable from cells in an unchanged state. Thus, 6‐deoxy‐D‐glucose and D‐xylose offer advantages as transport substrates over 2‐deoxy‐D‐glucose, which is phosphorylated by intercellular hexokinases, and 3‐O‐methyl‐D‐glucose, which shows a lower specificity for the D‐glucose transport system.