bluuebunny/crossref_metadata_2025_split huggingface dataset:
The transport of chloride in ehrlich ascites tumor cells
Authors: Levinson Charles , Villereal Mitchel L. 
Published: February 2005

AbstractThe steady state transport and distribution of chloride between the intracellular and extracellular phases was investigated when the extracellular chloride concentration was varied by isosmotic replacement with nitrate, bromide and acetate. The results of these experiments show that chloride transport, measured by uptake of 36Cl, is sensitive to the replacement anion. In the presence of nitrate, chloride transport is a linear function of the extracellular chloride concentration. The relationship between chloride transport and extracellular chloride in the presence of bromide is concave upward which suggests that this anion inhibits chloride movement. However, when acetate replaces chloride, the relationship between chloride transport and extracellular chloride is concave downward. The chloride distribution ratio of cells incubated in 145–155 mM chloride medium is 0.386 and is not effected by the replacement of chloride with nitrate, bromide or acetate.These findings are consistent with the assertion that chloride transport is composed of two parallel pathways, a diffusional plus a saturating, mediated component. Of the total chloride flux (9.1 mmoles Cl‐/kg dry weight per minute) measured in chloride medium (145–155 mM Cl ‐), the mediated component represents 40% and the diffusional component 60%.
Effect of 5‐bromodeoxyuridine on the appearance of cytoplasmic poly‐A containing RNA
Authors: Pawlowski Philip J. 
Published: February 2005

AbstractCytoplasmic poly‐A containing RNA, synthesized by cultured chick embryo cells, was examined during growth in 5‐bromodeoxyuridine. The kinetics of 3H‐adenosine incorporation into this species of RNA, when compared to the rest of the cytoplasmic RNA, and to control cells, indicates that the rate of synthesis of this RNA is slower in BrdU treated cells. An examination of the rate at which a steady state distribution of radioactivity, between the poly‐A segment and non‐poly‐A portion of poly‐A containing RNA is reached also indicated that this species is synthesized at a lower rate in BrdU treated cells.
Growth abnormalities of cultured human skin fibroblasts derived from individuals with hereditary adenomatosis of the colon and rectum
Authors: Pfeffer Lawrence , Lipkin Martin , Stutman Osias , Kopelovich Levy 
Published: February 2005

AbstractA heritable propensity to develop malignant lesions is found in individuals with familial adenomatosis of the colon and rectum (ACR) and the Gardner's syndrome variant, an autosomal dominant trait. In the present study, the growth characteristics of cultured skin fibroblasts (SF) derived from normal‐appearing flat skin biopsies of ACR families, representing all phenotypes, and appropriate controls were investigated. SF were obtained from stocks between the second and fifth passages and grown to confluency in Eagle's Minimal Essential Medium (EMEM) supplemented with 15% fetal calf serum (FCS). Following trypsinization, cells were replanted in EMEM supplemented with either 1% or 15% FCS at an initial density of 4 × 103 cells/cm2 and counted daily for five days. Normal SF representing several age groups (both sexes) and those obtained from non‐afflicted individuals of ACR families grew only in 15% FCS. In contrast, SF from ACR subjects and from embryonal skin grew both in 1% and 15% FCS. SF from several clinically asymptomatic adults, children of ACR patients, grew in 1% FCS as well. Cell cultures from ACR individuals showed regions of criss‐crossed arrays and multilayered pattern. These growth properties were not observed in normal cell cultures. The SF from ACR individuals did not grow in methocel, nor did they form tumors in athymic mice. These results suggest the occurrence of previously undetected biochemical alterations in SF taken from ACR genotypes.
Effect of ESF preparations on different types of erythroblasts
Authors: Hegemann F. , Döurmer P. 
Published: February 2005

AbstractA new method of quantitative 14C‐autoradiography was applied for evaluating possible effects of erythropoietin (ESF) on the DNA synthesis rate of differentiated erythroid murine bone marrow cells identified as proerythroblasts, basophilic and polychromatic erythroblasts. Eosinophilic myelocytes were used as a control cell population. ESF was prepared from the urine of a patient with chronic aplastic anemia; an inactive urinary preparation served as control. The potency of the preparations was estimated by the 59Fe‐incorporation assay. The materials to be tested were injected into polycythemic mice 4, 8 and 16 hours before in vitro short‐term incubation of the bone marrow cells with 14C‐thymidine and Methotrexate. Animals without test material were taken as additional controls. Autoradiographic grains were counted by an incident light microscope photometer.Eight hours after injection of ESF a significant increase in the mean 14C‐thymidine incorporation was found in all three erythroid cell types when compared either with the inactive control preparation (excess incorporation 30–40%) or with the untreated control animals (excess incorporation 10–20%). It could be shown that the increase is due to an immediate action of ESF on already differentiated cells and cannot –‐ at least not solely –‐ be attributed to its action on hemopoietic stem cells. The control preparation which was inactive in terms of 59Fe incorporation exerted a slight inhibition of DNA synthesis rate in all erythroid cells as well as in cells not committed to erythroid differentiation.
Argon laser microirradiation of mitochondria in rat myocardial cells in tissue culture. VII. Fibrillation in ventricle and auricle cells
Authors: Waymire Katrina , Kitzes Margarita , Meredith Stephanie , Twiggs Gary , Berns Michael W. 
Published: February 2005

AbstractRat myocardial cells in vitro were irradiated in individual mitochondria with an argon ion laser microbeam. The contractile response termed fibrillation in single and multicellular groups of both ventricle and auricle cells were compared. Specific correlations were made between fibrillation duration, the number of cells in the group, and the number of times the cells had fibrillated. Correlations were also made for the number of laser shots needed to induce fibrillation and the number of cells in the group. Another set of correlations were made between the pre‐irradiation beat frequency and the beat frequency following recovery. Several differences and similarities of the above parameters were detected between auricle and ventricle cells. A comparison of the morphology and ultrastructure of auricle and ventricle cells also revealed significant differences.
Endotoxin‐induced size change in bone marrow progenitors of granulocytes and macrophages
Authors: Metcalf D. , Wilson J. W. 
Published: February 2005

AbstractInjection of 5 μg endotoxin to adult C57BL mice caused a marked increase in the sedimentation velocity of granulocytic and macrophage progenitor (colony‐forming) cells in the bone marrow. This change was maximal two days after injection and was not accompanied by corresponding changes in total marrow nucleated cell populations. The endotoxin‐induced shift was not dependent on the presence of the thymus but did not occur in mice challenged after preinjection with endotoxin. No changes in buoyant density, cell cycle status, pattern of differentiation and responsiveness of granulocytic and macrophage progenitor cells were observed after the injection of endotoxin. The increased sedimentation velocity of progenitor cells appears to indicate an increase in cell volume but the mechanisms involved have not been identified.
Potassium transport in normal and transformed mouse 3T3 cells
Authors: Spaggiare Santa , Wallach Michael J. , Tupper Joseph T. 
Published: February 2005

AbstractThe components of unidirectional K influx and efflux have been investigated in the 3T3 cell and the SV40 transformed 3T3 cell in exponential and stationary growth phase. Over the cell densities used for transport experiments the 3T3 cell goes from exponential growth to density dependent inhibition of growth (4 × 104 to 4 × 105 cell cm−2) whereas the SV40 3T3 maintains exponential or near exponential growth (4 × 104 to 1 × 106 cell cm−2). In agreement with previous observations, volume per cell and mg protein per cell decrease with increasing cell density. Thus, transport measurements have been expressed on a per volume basis. Total unidirectional K influx and efflux in the 3T3 cell is approximately double that of the SV40 3T3 cell at all cell densities investigated. Both cell types have similar volumes initially and show similar decreases with increasing cell density. Thus, in this clone of the 3T3 cell SV40 transformation specifically decreases unidirectional K flux. The magnitude of the total K flux does not change substantially for either cell line during transition from sparse to dense cultures. However, the components of the K transport undergo distinct changes. Both cell lines possess a ouabain sensitive component of K influx, presumably representing the active inward K pump. Both also possess components of K influx and efflux sensitive to furosemide. The data suggest this component represents a one‐for‐one K exchange mechanism. The fraction of K influx mediated by the ouabain sensitive component is reduced to one half its value when exponential versus density inhibited 3T3 cells are compared (63% versus 31% of total influx). No comparable drop occurs in the SV40 3T3 cell at equivalent cell densities (64% versus 56% of total influx). Thus, the pump mediated component of K influx would appear to be correlated with growth. In contrast, the furosemide sensitive component represents approximately 20% of the total unidirectional K influx and efflux in both cell lines in sparse culture. At high cell densities, where growth inhibition occurs in the 3T3 cell but not the SV40 3T3, the furosemide sensitive component doubles in both cell lines. Thus, the apparent K‐K exchange mechanism is density dependent rather than growth dependent.
Carbohydrate uptake by escherichia coli
Authors: Kornberg Hans L. 
Published: February 2005

AbstractIn contrast to active transport, the uptake of carbohydrates via the phosphoenolpyruvate‐dependent phosphotransferase system (PTS) leads to the appearance in the cell of the sugar initially as a 1‐ or 6‐ phosphate ester. The components of the PTS that transfer phosphate to the sugar are not absolutely specific for any one sugar. Both their synthesis and their activity are controlled; in the latter, “fine” control, glucose‐6‐phosphate appears to play an important role. Studies of growth on, and uptake of, galactose by E.coli mutants devoid of components of the PTS and also devoid of active transport systems for galactose, suggest that proteins effecting facilitated diffusion of hexoses may be part of, or be closely associated with, the sugar‐specific components of the PTS.
Regulation of amino acid and glucose transport activity expressed in isolated membranes from untransformed and SV 40‐transformed mouse fibroblasts
Authors: Lever Julia E. 
Published: February 2005

AbstractMembrane vesicles isolated from untransformed Balb/c and Swiss mouse fibroblasts and their SV 40‐transformed derivatives were shown to catalyze carrier‐mediated, intravesicular uptake of α‐aminoisobutyric acid and D‐glucose. Concentrative uptake of α‐aminoisobutyric acid required the presence of a Na+‐gradient (external >internal) and could occur independently of endogenous (Na+ + K+)ATPase activity. A K+ diffusion gradient (internal > external) in the presence of valinomycin, or the addition of the Na+ salt of a highly permeant anion, conditions expected to create an interior‐negative membrane potential, stimulated Na+‐gradient‐dependent uptake, suggesting this process is electrogenic. D‐Glucose uptake was nonconcentrative and did not require ion gradients or metabolic conversion.Na+‐gradient‐dependent transport of α‐aminoisobutyric acid was reduced both in initial rate and extent of uptake in vesicles from confluent untransformed cells and increased in those from SV 40‐transformed cells, compared with activities observed in vesicles from proliferating untransformed cells. No changes in D‐glucose carrier activity were observed when assayed at low glucose concentrations.
Amino acid transport by membrane vesicles of virally transformed and nontransformed cells: Effects of sodium gradient and cell density
Authors: Parnes Jane R. , Garvey Thomas Q. , Isselbacher Kurt J. 
Published: February 2005

AbstractMixed membrane vesicle populations composed of plasma membrane and endoplasmic reticulum were prepared from Balb/c 3T3 and simian virus 40‐transformed Balb/c 3T3 mouse fibroblasts. The initial rates of uptake of L‐leucine and α‐aminoisobutyric acid by these vesicles were stimulated by a NaCl gradient (external > internal). Cation specificity for stimulation of L‐leucine uptake was Na+ > Li+ > K+. NaSCN was as effective as NaCl. Stimulation of uptake of both amino acids by a NaCl gradient was twice as great in vesicles from transformed as compared to non‐transformed cells. The NaCl gradient produced transient accumulation of both L‐leucine and α‐aminoisobutyric acid to twice the equilibrium level in vesicles from transformed cells. No such “overshoot” was observed in vesicles from nontransformed cells. In vesicles from the contact‐inhibitable Balb/c 3T3 cells, transport of α‐aminoisobutyric acid, but not L‐leucine, exhibited a density‐dependent decrease in Na+ gradient induced stimulation, from 248% for sub‐confluent to 109% with confluent cells. No density‐related changes in uptake were noted with vesicles from the transformed cells. These studies suggest that variations in amino acid uptake associated with viral transformation may be related, at least in part, to alterations in Na+ permeability of the surface membrane.
Uptake of amino acids in reconstituted vesicles derived from plasma membranes of ehrlich ascites cells
Authors: Johnstone R. M. , Bardin Claudette 
Published: February 2005

AbstractTo obtain a clearer concept of the mechanism of organic solute transport in mammalian cells, we have attempted to reconstitute a functional transport system for amino acids from plasma membranes of Ehrlich ascites cells. Purified plasma membranes were dissolved in 2% Na cholate—4 M urea, a mixture which brought over 85% of the membrane proteins into solution. After centrifugation of the solubilized material for 2 hrs at 100,000 × g, the supernatant was dialyzed in the cold for 20 hrs with additional lipid. The reformed vesicles were tested for the ability to transport amino acids. The preliminary results obtained show that the uptake of α‐aminoisobutyric acid can be inhibited by L‐methionine and much less by L‐leucine as would be predicted from the known properties of α‐aminoisobutyrate transport in the intact cells. In addition, it has been possible to show accelerated efflux of intravesicular phenylalanine when phenylalanine is added to the trans side (medium side). The data are consistent with the conclusion that there is carrier mediated transport in the reconstituted vesicles.
Nature of lectin‐induced alteration of potassium transfer in Ehrlich ascites tumor cells
Authors: Aull Felice , Nachbar Martin S. , Oppenheim Joel D. 
Published: February 2005

AbstractThe way in which the lectins concanavalin A (Con A) and Ricinus communis agglutinin (Ricin) alter the K+ content of Ehrlich ascites tumor cells was investigated. Unidirectional and net fluxes were determined in unwashed cells during a time course following lectin addition. Total influx, ouabain sensitive influx, Mg++‐ and Na+‐K+‐ATPase activity were all unaffected. Cell ATP content was normal for at least 19 minutes after exposure to Con A. Early after contact with Ricin or Con A efflux was stimulated 2‐3‐fold, resulting in net K+ loss, but after 20 minutes efflux had returned to normal. Ricin and Con A acted similarly although Ricin was present at only 1/50 the concentration of Con A. When the findings are evaluated together with previous work it is suggested that a particular membrane glycoprotein may be concerned in the efflux alteration observed.
Studies on intercellular adhesion. II. Promoting effect of serum and proteins on adhesion of neural retina cells to isotypic aggregates
Authors: Pessac Bernard , Alliot Françoise , Cornet Monique , Girard Arlette 
Published: February 2005

AbstractThe quantitative assay described in the preceding paper (Pessac et al., 1977) was used to study the effects of serum and various proteins on isotypic adhesion of chick embryo neural retina cells. Fetal bovine, chicken, horse, rabbit and human sera promoted cell adhesion to the same extent. The same sera also enhanced isotypic adhesion of cells from other organs showing that the cell adhesion promoting activity of sera was not organ specific. Neural retina (NR) cell collection in serum supplemented medium was not modified by protein synthesis or metabolic inhibitors and was temperature dependent with a maximum at 38°C. The higher temperature does not seem to be required for repair of the cell surface after dissociation, but for the process of adhesion itself. Various serum fractions and egg albumin showed a cell adhesion promoting activity similar to that of sera.
Glycoprotein synthesis in a temperature‐sensitive Chinese hamster cell cycle mutant
Authors: Tenner A. , Zieg J. , Scheffler I. E. 
Published: February 2005

AbstractA temperature‐sensitive mutant of Chinese hamster cells is described which has two interesting properties: (1) it is a cell cycle mutant and (2) glycoprotein synthesis appears to be affected at the non‐permissive temperature (40°C). Synchronized cells shifted to 40°C in the beginning of their G1 phase do not incorporate [3H]‐thymidine into DNA during the expected S‐phase, but once DNA synthesis has been initiated (∼ 10 hours after termination of serum starvation) a shift to 40°C no longer leads to an arrest of DNA synthesis. Flow microfluorimetric analysis of DNA content/cell supports this conclusion and indicates that a majority of cells become arrested in the G1 phase of the cell cycle when a non‐synchronized population of cells is transferred to 40°C. Apparently at all times in the cell cycle there is a drastic reduction of incorporation of labeled sugars (particularly fucose) into glycoproteins. The uptake of fucose and its conversion to GDP‐fucose appears to be normal at 40°C. Chromatographic analysis indicates that all classes of glycoproteins are affected, and we do not find any evidence for partially completed oligosaccharides at 40°C. Overall protein synthesis is not reduced at the nonpermissive temperature during the time interval under consideration and the number of polysomes attached to membranes (RER) is also normal at 40°C. This suggests that the defect is at an early step in the synthesis or regulation of synthesis of glycoproteins. The mutation is a recessive mutation in hybrid cells and mutagen induced revertants can be obtained which grow normally at 40°C and in which glycoprotein synthesis at 40°C is restored to normal, wild type levels.
Rapid decline in thymidine kinase activity during differentiation of Naegleria
Authors: Bols N. C. , Corff Sondra , Yuyama Shuhei 
Published: February 2005

AbstractA logarithmically growing population of Naegleria gruberi differentiate into flagellates synchronously in about 85 to 90 minutes after the stimulation. Using this system, two separate enzymes that phosphorylate thymidine were assayed. Thymidine kinase activity decreases rapidly after the stimulation, while nucleoside phosphotransferase activity remains approximately constant. The possibility that this observed decrease in thymidine kinase activity is due to an expanded thymidine pool or to an increased phosphatase activity has been ruled out. Mixing experiments indicated that there is neither an activator of thymidine kinase in growing cells nor an inhibitor in differentiating cells. Thus, the observed decrease is likely to be due to an inactivation of the enzyme. Addition of actinomycin D or cycloheximide does not prevent the decrease in thymidine kinase activity suggesting that neither transcription nor translation is involved in the putative inactivation of thymidine kinase enzyme. There is very good correlation between the degree (or rate) of decrease in thymidine kinase activity and the percent of cells differentiating into flagellates. Thus, it appears certain that the residual thymidine kinase activity is primarily due to some portion of cells which did not respond to the stimulation and did not differentiate. Since there is an early termination of nuclear DNA synthesis in differentiating Naegleria, the decrease in thymidine activity (but no change in nucleoside phosphotransferase) suggests a correlation between thymidine kinase and DNA synthesis in Naegleria.
Action of FdUrd and dCyd on the incorporation of brdurd in Chinese hamster somatic cell DNA and the isolation of auxotrophic mutants
Authors: Labrecque Romain , Thirion Jean‐Paul 
Published: February 2005

AbstractChinese hamster somatic cells grown in the presence of bromodeoxyuridine, deoxycytidine and fluorodeoxyuridine incorporate more bromodeoxyuridine in their DNA than cells grown in the presence of bromodeoxyuridine alone. Thus they become more sensitive to light irradiation. Our data suggest that 0.05 mM–0.2 mM bromodeoxyuridine, 0.05 mM deoxycytidine and 10 mμg/ml fluorodeoxyuridine is one of the best possible combinations for the selection of Chinese hamster somatic cells mutants. Auxotrophs for proline, inositol or both were thus isolated at high frequency.
Altered morphology and increased cell adhesiveness of Chinese hamster ovary cells cultured on fibrin
Authors: Nozawa Ryushi T. 
Published: February 2005

AbstractChinese hamster ovary cells cultivated on fibrin exhibited different characteristics from cells growing on plastic.While sparsely plated cells on plastic dishes had an epithelioid morphology, cells on fibrin assumed a round shape and then converted to a stretched form with protruded processes that increased with cell density. Within a few days, cells fibrinolysed adjacent fibrin and returned to the morphology seen in plastic dishes. When fibrinolysis was inhibited by ϵ‐aminocaproic acid (EACA), cells continued to grow on the fibrin for a longer period and showed dense, criss‐crossed fibroblast‐type congestion. Whereas, cells on plastic maintained pavement‐like epithelioid appearance when they grew to a confluent monolayer.The other altered characteristics on fibrin was increased accumulation of cells in multilayers. Normally as Chinese hamster cells on plastic proliferate, many cells float into the medium instead of piling up after they form a monolayer. On the other hand, cells on fibrin, being maintained by the addition of EACA, remained adherent, piling up multilayers instead of floating into the medium. A possible explanation of these findings is that the surface properties of the stretched cells on fibrin are altered to make them more adhesive.A possible link of these characteristics of the cells on fibrin to tumor cell behavior in vivo is discussed.