bluuebunny/crossref_metadata_2025_split huggingface dataset:
Purified multiplication‐stimulating activity from rat liver cell conditioned medium: Comparison of biological activities with calf serum, insulin, and somatomedin
Authors: Smith Gary L. , Temin Howard M. 
Published: February 2005

AbstractMultiplication‐stimulating activity (MSA) for chicken embryo fibroblasts was purified from serum‐free medium conditioned by the growth of a line of rat liver cells (CRL), The biological activities of purified CRL MSA for chicken embryo fibroblasts were compared with those of calf serum to determine which activities are important for the stimulation of DNA synthesis and mitosis. In a balanced salt solution, only glucose and amino acids were needed in addition to purified CRL MSA to stimulate DNA synthesis maximally. Purified CRL MSA stimulated the rates of uptake of glucose and α‐aminoisobutyric acid. Only the stimulation of the rate of glucose uptake appeared to be a primary response to purified CRL MSA since the stimulation was not inhibited by actinomycin D or cycloheximide. The stimulation of the rate of uptake of α‐aminoisobutyric acid was inhibited by actinomycin D.CRL MSA differed from calf serum in its inability to commit cells irreversibly to synthesize DNA after the removal of CRL MSA and in its lack of the ability to stimulate the migration or prolong the survival of chicken embryo fibroblasts.Comparative studies indicated that purified CRL MSA had functional similarities to insulin and somatomedin. CRL MSA may be representative of a family of small polypeptide hormones having insulin‐like activity which are involved in the control of cell multiplication.
Adenosine diphosphate and calcium stimulation of respiration in mitochondria from alloxan diabetic rats
Authors: Garrick Rita Anne , Hall James C. 
Published: February 2005

AbstractLiver mitochondria from normal and alloxan diabetic rats, isolated in 0.25 M sucrose, were assayed with an oxygen electrode for ADP/O and Ca+2/O ratios, respiratory ratio, and respiratory control index. Mitochondria were incubated with two substrates, succinate and β‐hydroxybutyrate; two types of ionic media, Na+ medium (Na+ the major monovalent cation) and K+ medium (K+ the major monovalent cation); and two respiratory stimulants, ADP (352 μM) and Ca+2 (187 μM). Significant differences between respiratory rates and ADP/O ratios were dependent upon the substrate and ionic medium employed. The results confirm previous studies which showed no alteration in ADP/O ratio but decreased State 3 respiratory rates under similar conditions of K+ medium with ADP stimulation in the diabetic. Furthermore, the State 3 respiration was prolonged compared to normal. Ca+2 stimulation was the same in normal and diabetic mitochondria in K+ medium. Studies in Na+ media revealed more significant differences in RCI's, respiratory rates, and ADP/O ratios that were substrate dependent as well as ion dependent. The results from these various studies can be accounted for by an hypothesis linking mitochondrial K+ interaction with alterations in the diabetic mitochondria.
Biochemical criteria for the in vitro differentiation of embryoid bodies produced by a transplantable teratoma of mice. The production of acetylcholine esterase and creatine phosphokinase by teratoma cells
Authors: Levine Arnold J. , Torosian Michael , Sarokhan Alan J. , Teresky Angelika K. 
Published: February 2005

AbstractWhen embryoid bodies are grown in suspension culture in vitro, they undergo only a limited amount of morphological development. When these same embryoid bodies are permitted to attach to the surface of a culture dish, a wide variety of new morphological cell types appear.Suspension cultures of embryoid bodies do not contain significant detectable levels of acetylcholine esterase or creatine phosphokinase. These same enzymes however are produced in cell cultures derived from embryoid bodies attached to the culture dish surface. Polyacrylamide gel electrophoresis has been employed to demonstrate that the electrophoretic form of creatine phosphokinase produced by teratoma cells in culture is the brain form of the enzyme.Solid transplantable tumors containing only embryonal carcinoma cells (stem cells) do not contain either of these enzymatic activities. Well differentiated transplantable teratomas contain both enzymes.
Morphological criteria for the in vitro differentiation of embryoid bodies produced by a transplantable teratoma of mice
Authors: Teresky Angelika K. , Marsden Margery , Kuff Edward L. , Levine Arnold J. 
Published: February 2005

AbstractEmbryoid bodies are produced when a transplantable testicular teratoma from strain 129 mice is serially passaged in the peritoneal cavity of these mice. These bodies are roughly spherical containing two morphologically distinct cell types. Scanning and transmission electron microscopy have been employed to show that the endodermal cells of embryoid bodies, like those of the mouse embryo, are on the outer surface and have highly convoluted surfaces containing numerous microvilli‐like projections. The inner, embryonal carcinoma cells, are the pluripotent stem cells of this tumor.Intracisternal A‐type particles have been observed in electron micrographs and are almost exclusively located in the endodermal cells of the embryoid bodies. The A‐type complement‐fixing antigen has been identified in extracts prepared from this tumor.When embryoid bodies are placed in culture and allowed to attach to the surface of a petri dish, a large number of new morphologically distinct cell types appear. Attachment to the petri dish surface is required for the generation of these new cell types. Cells of similar morphology in culture, display a distinctly “clonal” distribution on the petri dish surface.
Effect of hyperthermia on protein biosynthesis in L5178Y murine leukemic lymphoblasts
Authors: Fuhr J. E. 
Published: February 2005

AbstractThe effects of elevated temperatures upon protein biosynthesis were determined in L5178Y murine leukemic lymphoblasts. The rate of protein synthesis was inhibited proportionately to the increase in temperature. Efforts were made to determine the mechanism of heat inactivation of protein synthesis by studying the requirements for recovery of activity after the cells were returned to 37°C. The ability of actinomycin to block the recovery process suggests that elevated temperatures destroy or inactivate a species of RNA required for protein synthesis. Loss of RNA during heating of the cells is apparently at least partially dependent on protein synthesis, since the presence of cycloheximide during heat shock, is capable of ameliorating the effects of short duration heat treatment.
The transport of sulfate ions across the membrane of the ehrlich ascites tumor cell
Authors: Levinson Charles , Villereal Mitchel L. 
Published: February 2005

AbstractThe applicability of the membrane fixed charge hypothesis to anion transport in Ehrlich ascites tumor cells was studied by investigating the dependence of steady state sulfate transport on the extracellular pH, chloride and sulfate concentration. When the extracellular sulfate was maintained at 10 mM both cellular sulfate and sulfate transport increased with decreasing pH and chloride concentration. The dependence of sulfate transport on the cellular sulfate concentration suggests a saturation phenomenon.The relationship between sulfate transport and cellular sulfate was also studied as a function of extracellular sulfate, both in the presence and absence of chloride. In both cases, sulfate transport is a saturable function of the cellular sulfate. However, in the presence of chloride the maximal flux is twice that in its absence. The discrepancy between the maximal fluxes suggests that the transport system mediates chloride‐sulfate exchange in addition to sulfate self exchange. Unidirectional sulfate effluxes into chloride and sulfate‐free medium; into 50 mM sulfate medium or 50 mM chloride medium were: 0.38, 1.95 and 3.91 nmoles/107 cells min‐1, respectively. These results indicate that in the absence of either sulfate or chloride the net efflux, of sulfate is low. However, chloride or sulfate on the trans side of the membrane is effective in accelerating unidirectional sulfate efflux. Taken together, the results of this investigation cannot be explained in terms of the membrane fixed charge hypothesis. Rather, they support the contention that sulfate transport across the tumor cell membrane is a carrier‐mediated process.
Phosphorylation but not transport of sugars is enhanced in virus‐transformed mouse 3T3 cells
Authors: Colby C. , Romano A. H. 
Published: February 2005

AbstractThe transport and phosphorylation of 2‐deoxy‐D‐glucose are separate and sequential events in both normal and virus‐transformed 3T3 cells. The apparent enhancement of 2‐dOG uptake by 3T3 cells accompanying virus transformation is not due to an effect on the transport process but to enhanced phosphorylation by intracellular kinases. Phosphorylation of 3‐O‐methyl‐D‐glucose does not occur in these cells. Both the rate and extent of transport of this glucose analog is the same in normal cells, SV40 virus‐transformed cells and sarcoma virus‐transformed cells. The appropriateness of using 3‐O‐MeG for studies of the glucose transport system of animal cells is examined and discussed.
Adaptation of potassium metabolism and restoration of mitosis during prolonged treatment of mouse lymphoblasts with ouabain
Authors: Cuff Joyce M. , Lichtman Marshall A. 
Published: February 2005

AbstractThe effects of ouabain on the growth of murine lymphoblasts in vitro have been studied. Exposure of cells to ouabain (0.1 mM) initially inhibited 86Rb+ uptake rate, reduced the intracellular potassium concentration, and decreased population growth rates. Continued exposure to the same ouabain concentration resulted in an increase of 86Rb+ uptake rate, intracellular potassium content and population growth rates to control values (adaptation). When treated cells were resuspended in medium free of ouabain after 12 to 15 hours of ouabain treatment, 86Rb+ uptake rates and intracellular potassium levels exceeded those of untreated cells. Adaptation was inhibited by cycloheximide (3 μg/ml) and by actinomycin D (0.05 μg/ml). Kinetic analysis of transport suggested that while the total capacity of the Na+, K+ transport system increased, the affinity for both the cation (86Rb+) and ouabain decreased.
The effect of potassium on the cell membrane potential and the passage of synchronized cells through the cell cycle
Authors: Stambrook Peter J. , Sach Howard G. , Ebert J. D. 
Published: February 2005

AbstractThe cell membrane potential of cultured Chinese hamster cells is known to increase at the start of the S phase. The putative role of the cell membrane potential as a regulator of cell proliferation was examined by following the cell cycle traverse of synchronized Chinese hamster cells in the presence or absense of high exogenous levels of potassium. An increase in external potassium levels results in a depressed membrane potential and a reduced rate of cell proliferation. A potassium concentration of 115 mM was used in experiments with synchronized cells since at that level cell proliferation is almost completely halted, recovery of growth is rapid and complete, and the membrane potential is reduced to a level well below that normally found in cells in the G1 phase.A mitotic population was divided into four aliquots and plated in either control medium or medium containing 115 mM K+. Cells placed directly into high K+ medium were retarded in their exit from mitosis and displayed a delayed and abnormal entry into the S phase. If control medium was added after two hours, cell cycle traverse was normal, but delayed by two hours compared to control cells. If the mitotic cells were plated directly into control medium and two hours later were shifted to high K+ medium, the cells entered the S phase in the absence of the normally observed increase in membrane potential and proceeded to the next mitosis normally. It was concluded that the increase in membrane potential observed at the start of the S phase in isolated synchronized cells is not a requirement for the initiation of DNA synthesis. In addition, sensitivity to the high potassium regimen was found at two different times during the cell cycle. In one case, cells were impeded in their transit through mitosis. Such cells displayed an altered chromosome structure which may account for the partial mitotic block. In the second case, synchronized cells displayed a sensitivity to the high potassium regimen in early G1 which appeared to be separate from the block in mitosis and independent of a change in the membrane potential.
Dissociation by cytochalasin B of movement, DNA synthesis and transport in 3T3 cells
Authors: Brownstein Barbara L. , Rozengurt Enrique , de Asua Luis Jimenez , Stoker Michael 
Published: February 2005

AbstractCytochalasin B was used as a tool to study the inter‐relationships between cell movement, the reinitiated DNA synthesis and the enhanced transport of specific small molecules stimulated by serum in quiescent 3T3 cells. Cytochalasin at concentrations of less than 1 μg/ml inhibits serum‐stimulated movement within the monolayer and migration into a wound. Even at ten times this concentration there is little effect on the increase in DNA in the culture, indicating that movement away from neighboring cells is not required for the initiation of DNA synthesis.While DNA synthesis is not inhibited by concentrations of cytochalasin up to 10 μg/ml, the increased thymidine transport which is associated with the onset of the S phase of the cell cycle is inhibited and DNA synthesis cannot be measured by the labelling of nuclei with radioactive thymidine.Cytochalasin has a differential effect on the early transport changes produced by serum addition. Glucose transport is inhibited by low concentrations of the drug (< 1 μg/ml) while the enhanced uptake of phosphate and uridine is unaffected by a 10‐fold increase in concentration. Although the doses of cytochalasin required for 50% inhibition of hexose uptake and of cell movement are the same, no causal relationship between sugar transport and locomotion can be demonstrated.Cytochalasin affects membrane functions in at least two different ways. The drug inhibits the uptake of glucose directly but affects only the S‐phase associated increase in thymidine transport.
Control of normal differentiation of myeloid leukemic cells. VI. Inhibition of cell multiplication and the formation of macrophages
Authors: Lotem Joseph , Sachs Leo 
Published: February 2005

AbstractD+ but not D− myeloid leukemic cells can be induced by the appropriate conditioned medium or by serum from endotoxin treated mice, to undergo cell migration in agar, cell attachment to the surface of a Petri dish and differentiation to mature macrophages and granulocytes. Inhibition of cell multiplication by cytosine arabinoside, hydroxyurea, mitomycin C, thymidine, 5‐bromodeoxyuridine, 5‐iododeoxyuridine, 5‐fluorodeoxyuridine or actinomycin D, but not by vinblastine or cycloheximide, induced cell migration, cell attachment to the Petri dish and the formation of macrophages in D+ cells. There was no induction of cell migration or formation of macrophages and a much lower induction of cell attachment in D− cells. The induction of these changes in D+ cells required protein synthesis and the inhibitors showed the same toxicity for D+ and D− cells. The results indicate, that the inhibitors induced specific surface membrane changes in D+ but not in D− cells.
Somatic genetic analysis of cyclic AMP action: Characterization of unresponsive mutants
Authors: Bourne Henry R. , Coffino Philip , Tomkins Gordon M. 
Published: February 2005

AbstractN6,O2′‐dibutyryl adenosine 3′,5′‐monophosphate kills cultured mouse lymphosarcoma cells, but not resistant mutants derived by a single‐step clonal selection. Resistant clones lack the cyclic AMP binding proteins present in wild type, cyclic AMP sensitive clones. Both endogenous cyclic AMP, accumulated in response to isoproterenol or cholera toxin, and exogenous dibutyryl cyclic AMP induce cyclic AMP phosphodiesterase, slow growth, and eventually kill wild type cells. In the resistant mutants, however, the endogenous and exogenous cyclic nucleotides appear to be completely inactive. These results indicate that an intracellular receptor for cyclic AMP, previously shown to be associated with a cyclic AMP‐dependent protein kinase, mediates cyclic AMP's regulation of growth and phosphodiesterase synthesis.
Difference in transport of leucine in attached and suspended 3T3 cells
Authors: Otsuka Haruki , Moskowitz Merwin 
Published: February 2005

Abstract3T3 cells in subconfluent culture take up leucine through a transport system which has a relatively high affinity for leucine (M system). When the culture becomes confluent, the M system is turned off and leucine is transported by another system which has a low affinity for leucine (S system). The M system is reactivated by transferring the cells into subconfluent cultures.In suspension cultures 3T3 cells, initiated from confluent cultures, the M system is not activated and leucine is transported by the S system. In cells suspended from subconfluent culture, the M system continues to operate at a high level for four hours and then is gradually turned off.Tumor virus transformed 3T3 cells (SV3T3 and Py3T3) grow quite well in suspension culture and transport leucine both in monolayer and suspension through a high affinity system, with a high Vmax value. A derivative of 3T3, 3T3/41, which grows in suspension much more slowly than tumor virus transformed 3T3 cells, also takes up leucine through a high affinity transport system both in monolayer and suspension but its Vmax value is lower than that of the transformed cells.
The inhibition of DNA‐dependent RNA synthesis in yoshida ascites cells by bovine follicular fluid
Authors: Moore G. P. M. , Lintern‐Moore Sue , Peters Hannah , Byskov Anne Grete , Andersen Mette , Faber M. 
Published: February 2005

AbstractFollicular fluid aspirated from large cow follicles inhibits endogenous, DNA‐dependent RNA polymerase activity in Yoshida ascites cells. The inhibitory component of follicular fluid is probably a protein and appears to affect specifically the activity of the nucleoplasmic polymerase II.
Early cellular responses to diverse growth stimuli independent of protein and RNA synthesis
Authors: Rubin H. , Koide T. 
Published: February 2005

AbstractSerum, elevated pH, excess Zn++, 9,10 dimethyl‐1,2 dibenzanthracene (DMBA) and insulin accelerate the progress of growth‐inhibited chick embryo cells into the S‐period of DNA synthesis. A comparative study was made of their capacity to elicit other cellular responses within two hours after their application. All the agents studied stimulated the uptake of the glucose analogue 2‐deoxy‐D‐glucose (2‐dGlc). Elevated pH elicited a more striking increase than the other agents in the uptake of the amino acid analogue α‐amino isobutyric acid (AIB). The application of subtoxic concentrations of Zn++ or DMBA did not stimulate the uptake of uridine by cells nor its incorporation into RNA when tested at 2 hours. However, it was found that the stimulation of uridine utilization did occur but was delayed several hours. Similarly, the accelerated onset of DNA synthesis was also delayed for several hours by these agents. Insulin acted like serum in stimulating the utilization of 2‐dGlc, AIB and uridine. Serum and DMBA were particularly effective in stimulating the utilization of choline. It was concluded that the utilization of 2‐dGlc, uridine and thymidine are affected similarly by all the agents, but that there may be differential effects in the utilization of AIB and choline.The inhibition of RNA synthesis by actinomycin D did not prevent the relative stimulation of 2‐dGlc, AIB and choline utilization by serum and pH treatment. The inhibition of protein synthesis by cycloheximide did not prevent the relative stimulation of 2‐dGlc and choline utilization by serum and pH treatment. It partially blocked the increased uptake of AIB and had erratic effects on the utilization of uridine. It was concluded that neither RNA nor protein synthesis is required for some, if not all, the early responses to growth stimuli measured here. The inhibited cell appears to be a poised system which carries out a programmed array of reactions characteristic of the cell type following perturbation by a variety of unrelated agents. In vivo specificity is provided by the physiological reagents available (i.e., hormones) and their capacity to interact with different cell types.
Effect of cell trypsinization on nuclear proteins of WI‐38 fibroblasts in culture
Authors: Maizel Abby , Nicolini Claudio , Baserga Renato 
Published: February 2005

AbstractWhen resting confluent monolayers of WI‐38 fibroblasts are trypsinized and replated at a lower density they are stimulated to proliferate again with an interval of 18 hours between replating and the onset of DNA synthesis. Trypsinization of resting cells causes a 40% loss of nuclear proteins as well as of cytoplasmic proteins. The amount of nuclear proteins remains low for the first six hours after the cells have been replated and then it increases rapidly, reaching the same level of non‐trypsinized resting cells by ten hours after plating. The proteins that are lost from the nucleus immediately after trypsinization are chromatin‐associated proteins and most of them are non‐histone chromosomal proteins, although a modest loss of histones cannot be ruled out. The loss of non‐histone chromosomal proteins from cells that have been trypsinized causes changes in the structure of chromatin that can be detected by circular dichroism and by viscosity measurements. These results show that cell trypsinization causes an extensive loss of proteins from chromatin and that the loss is restored only several hours after the cells have been replated at a lower density.
The effects of metabolic inhibitors on the synthesis of inducible tyrosine aminotransferase in cultured hepatoma cells
Authors: Dethlefsen Lyle A. 
Published: February 2005

AbstractThe effects of actinomycin‐D and 3′‐deoxyadenosine (cordycepin) on the steroid‐mediated induction of tyrosine aminotransferase (TAT) synthesis have been reexamined in view of recent reports that the primary inhibitory action of these compounds may affect synthesis of proteins as well as RNA. The present results confirm that cordycepin blocks the steroid‐mediated induction of TAT in rat hepatoma cells (HTC), but unlike actinomycin‐D, cordycepin neither increases nor maintains the levels of TAT found in HTC cells preinduced with dexamethasone. Indeed, cordycepin added to preinduced cells, either in the presence or absence of steroid, causes a prompt decline in TAT activity. These data also confirm that both actinomycin‐D and cordycepin have an early inhibitory effect on protein synthesis, but the cordycepin effect is observed sooner and the extent of inhibition is greater. When actinomycin‐D and cordycepin are added simultaneously to preinduced cells with the steroid removed, the actinomycin‐D produced maintenance of preinduced levels of TAT persists. Also, the inhibition of protein synthesis in cultures with both inhibitors approaches that for the cells treated with actinomycin‐D alone instead of cordycepin alone. These data suggest that cordycepin inhibits TAT synthesis in preinduced cells by its inhibition of protein synthesis, and this inhibitory effect of cordycepin is blocked by actinomycin‐D. It is possible that actinomycin‐D does this by preventing the incorporation of cordycepin into RNA. However, regardless of the correctness of this speculation, the multiple effects of cordycepin indicate that this inhibitor cannot be used either to prove or rule out the post‐transcriptional model for regulation of gene expression. Also, this requirement that protein synthesis must continue in order to maintain pre‐induced levels of TAT is inconsistent with the assumption that the maintenance of these induced TAT levels by actinomycin‐D is due to inhibition of TAT degradation.