bluuebunny/crossref_metadata_2025_split huggingface dataset:
Genetic control of lipopolysaccharide induced generation of serum colony stimulating factor and proliferation of splenic granulocyte/macrophage precursor cells
Authors: Apte Ron N. , Pluznik Dov H. 
Published: February 2005

AbstractAdministration of bacterial lipopolysaccharides (LPS) to mice causes a rise in tissue and serum colony stimulating factor (CSF) levels and in bone marrow and splenic colony forming cells (CFC). Two inbred strains of mice differing in their response to LPS were used to study the genetic control of LPS induced granulopoietic responses: a high responder strain (C3H/eB) which reacts to LPS by an elevation in serum CSF and by an increase in splenic CFC levels, and a low responder strain (C3H/HeJ) which fails to show these responses. The ability to generate serum CSF after administration of LPS is controlled by a single autosomal dominant gene, while the splenic CFC response to LPS follows the characteristic patterns of a polygenic inheritance control. The associated relationships of CSF and CFC responsiveness have been investigated in backcross (F1 x C3H/HeJ) and F2 mice. Most mice which generated high levels of CSF showed a high or intermediate CFC response and most mice which did not generate any detectable levels of serum CSF showed a low splenic CFC response. The results suggest that CSF may play a physiologic role in vivo as a granulopoietin. In addition it was shown that the genetic control mechanisms governing the CSF/CFC responses are determined by the lipid A‐KDO portion of the LPS molecule, suggesting that lipid A is the active part of the LPS molecule in stimulating granulopoiesis.
Adaptive enhancement of amino acid uptake and exodus by thymic lymphocytes: Influence of ph
Authors: Peck William A. , Rockwell Linda H. , Lichtman Marshall A. 
Published: February 2005

AbstractEntry of certain free amino acids (alpha aminoisobutyric acid (AIB), alanine and proline), but not of leucine into rat thymic lymphocytes increased progressively when the cells were incubated in amino acid deficient medium. Actinomycin D, cycloheximide, or a high concentration of AIB abolished the time‐related increase in AIB accumulation, whereas exposure to a high concentration of leucine had no effect. This phenomenon could not be attributed to a progressive alteration in the nature of the incubation medium nor to reduced transinhibition of AIB uptake. The exodus of AIB also increased with time, but to a smaller degree than AIB entry.Initial rates of AIB entry and exodus increased with increases in the pH of the incubation medium over the range 6.5–8.0. The effects of pH on entry and exodus were time‐related, increasing progressively over a 180‐minute period. Actinomycin D, cycloheximide, and 5 mM AIB nullified the magnified time related increments in AIB transport caused by prolonged incubation at pH 8.0. The influence of a given pH on transport of AIB decreased rapidly when the cells were transferred to medium of another pH, but this tendency diminished the longer the cells were exposed to the initial pH. pH influenced the entry of alanine and proline in the same fashion as that of AIB, but did not affect leucine entry.These results indicate that thymic lymphocytes exhibit adaptive enhancement in the accumulation of free amino acids that are transported largely by the A or alanine‐preferring system, and that the adaptive process involves both entry and exodus. Moreover, alterations in pH modify entry and exodus of these same amino acids, profoundly affect the magnitude of time‐released increases, and may induce fundamental changes in the mechanism(s) serving amino acid transport.
Human erythroid colony formation in vitro: Evidence for clonal origin
Authors: Prchal Jaroslav F. , Adamson John W. , Steinmann Laura , Fialkow Philip J. 
Published: February 2005

AbstractHuman marrow cells, suspended in methylcellulose medium containing erythropoietin, give rise to discrete colonies of hemoglobin synthesizing cells. The presumption that such colonies originate from single progenitor cells has been tested directly in females with X‐chromosome inactivation mosaicism using glucose‐6‐phosphate dehydrogenase (G‐6‐PD) as a marker. When individual colonies were grown from marrow cells obtained from two black females heterozygous for G‐6‐PD, only one or the other isoenzyme type was observed, but not both. These results are most consistent with the interpretation that human erythroid colonies arise from single cells.
Nucleoside transport systems in Escherichia coli K12: Specificty and regulation
Authors: Munch‐Petersen Agnete , Mygind Benete 
Published: February 2005

AbstractTwo nucleoside transport systems have been verified and separated by mating and recombination experiments. The recipient strain was a mutant which is negative for transport of all nucleosides.The two systems differ in specificity and in regulation. One system transports pyrimidine and adenine in specificity and in regulation. One system transports pyrimidine and adenine nucleosides, but not guanine nucleosides. It is regulated by the cytR gene. The other system transports all nucleosides and is regulated by the cytR as well as by the deoR genes.Enzyme assays performed on whole cells of strains, able or unable to transport nucleosides, indicate that the nucleoside catabolizing enzymes are located inside the permeability barrier of the cell.
Stimulation of sugar uptake in cultured fibroblasts by epidermal growth factor (EGF) and EGF‐binding arginine esterase
Authors: Barnes David , Colowick Sidney P. 
Published: February 2005

AbstractMouse epidermal growth factor causes a rapid increase in 2‐deoxyglucose uptake in stationary phase mouse (3T3) cells or human fibroblasts. Maximum effect is approximately two fold over control levels for 3T3 cells and about 50% over controls for human fibroblasts. Maximum effect on 3T3 cells is seen about two hours after addition of 10 ng/ml EGF to the culture medium. Stimulation is easily measurable within the first fifteen minutes after addition of the hormone and may be detected at hormone concentrations as low as 0.1 ng/ml. The EGF‐binding arginine esterase found associated with EGF in the mouse submaxillary gland causes an enhancement of the EGF effect. In serum‐free medium, the EGF effect is still readily observed, but no enhancement by the esterase is seen. SV40 virus‐transformed 3T3 cells show no effect on deoxy‐glucose uptake after addition of 10 ng/ml EGF to the culture medium, but a response may be demonstrated after these cells are incubated for 12 hours or more in serumless medium. EGF stimulates transport of 3‐0‐methylglucose in stationary phase 3T3 and human fibroblasts but no EGF stimulation of α‐amino‐isobutyrate uptake in 3T3 cells is seen under conditions in which EGF clearly stimulates sugar uptake. Ammonium chloride, which is reported to inhibit intracellular degradation of human EGF by human fibroblasts, does not diminish the EGF effect on deoxyglucose uptake in human fibroblasts.
Transport of D‐allose by isolated fat‐cells: An effect of adenosine triphosphate on insulin stimulated transport
Authors: Loten E. G. , Regen D. M. , Park C. R. 
Published: February 2005

AbstractD‐allose, a glucose analogue, is not metabolized by isolated fatcells and its distribution space at equilibrium in the cells is the same as that of tritiated water. Uptake of allose is inhibited by glucose and 3‐0‐methylglucose, stimulated by insulin and virtually eliminated by cytochalasin B. Counter transport of allose out of fat‐cells against a concentration gradient can be induced by exogenous glucose but not by pyruvate. It is concluded that allose is transported into fat‐cells by the same carrier mediated transport system as glucose and that it is a suitable analogue with which to study the glucose transport system. Insulin stimulated allose transport, into or out of the cell, but not basal transport, is inhibited by a brief exposure of isolated fat‐cells to exogenous ATP or ADP (but not AMP or AMP‐PNP). The antilipolytic effect of insulin is not affected. The ATP inhibition is slowly reversible.It is suggested that ATP phosphorylates a membrane component and thereby blocks transmission of signal from the insulin receptor to the carrier system. Indirect evidence suggests that ATP does not alter the affinity of the insulin or glucose binding sites.Insulin decreases the Km of glucose metabolism to CO2 and lipid in isolated fat‐cells and increases the Vmax. However, the hormone has no effect on the Ki of glucose as an inhibitor of allose transport. The glucose analogue, 3‐0‐methylglucose, also inhibits both glucose metabolism and allose transport. The Ki for both these processes is similar and is not affected by insulin. These results support the view that the effect of insulin on glucose transport is to raise the Vmax without a change in the Km. It appears further that sugar transport is not the major rate limiting step in metabolism at high glucose concentrations in the absence of insulin, or at most glucose concentrations in the presence of the hormone.
A novel mechanism for group translocation: Substrate‐product reutilization by γ‐glutamyl transpeptidase in peptide and amino acid transport
Authors: Prusiner Stanley , Doak Carola W. , Kirk Gerald 
Published: February 2005

Abstractγ‐Glutamyl transpeptidase (γ‐GTP) is suggested to act as a carrier in the group translocation of oligopeptides and possibly some amino acids across cellular membranes. It is proposed that the process may involve the repetitive transfer of γ‐glutamyl groups to acceptor peptides which are being translocated from the exterior of the cell to its interior. After group translocation of the peptides has occurred with concomitant formation of γ‐glutamyl peptide products, it is suggested that the products might then be utilized as substrate for the enzyme in order to permit the translocation of other peptides from the exterior. The system is economical and requires only that it be primed with an appropriate source of γ‐glutamyl peptides, such as glutathione. In contrast to most group translocation systems previously described, substrate‐product reutilization by γ‐GTP would not be expected to accumulate peptides against a concentration gradient. Mechanisms for maintaining low intracellular concentrations of the translocated peptides are described.Studies on acceptor substrate specificity of γ‐GTP from bovine choroid plexus and rat kidney show some glycyl peptides are much better substrates than free amino acids in accord with the proposal that γ‐GTP might be primarily involved in peptide translocation. Both kinetic and topological evidence support the suggestion that repetitive transfer of γ‐glutamyl moieties by γ‐GTP could occur during group translocation of peptides and possibly some amino acids.
The pH and temperature dependence of the interaction of steroid hormones with the transport system of glucose in human erythrocytes
Authors: Lacko L. , Wittke B. , Lacko I. 
Published: February 2005

AbstractThe thermodynamic parameters ΔH°, ΔF°, ΔS° and the pH dependence of the interaction between steroids and the glucose carrier in human erythrocytes have been studied. The results indicate that, according to the structure of the steroids, hydrophilic as well as hydrophobic bonds can be involved in the association. For the binding of the C‐21‐steroids to the carrier the polarity rule has been observed to be valid. On the basis of the thermodynamic parameters it has been found that in the association process of the steroids with the carrier, simultaneous randomization of ordered water molecules is important.
A serum factor requirement for the passage of cultured Vero cells through G2
Authors: Engelhard Dean L. , Jen‐Hao Mao 
Published: February 2005

AbstractWhen Vero cells, a line derived from an African Green Monkey kidney, are grown under conditions where the saturation density is limited by serum, they deplete the growth medium of a factor necessary for cell division. The factor is a component of serum. When Vero cells are plated at low density (2 × 104/cm2) in this depleted growth medium (after dialysis against serum‐free Dulbecco's Modified Eagle's Medium) they initiate an unbalanced program of growth. Protein synthesis proceeds at the same rate as parallel cells in fresh serum, and the cells accumulate protein as a function of time. DNA synthesis is also initiated in these cells, and the amount of DNA per cell increases for the next four days after plating. However the cells quickly stop dividing. Measurements of DNA per cell using microspectrofluorometry show that the cells are accumulating in the late S and G2 period during this time. Thus we conclude that these cells cannot pass through a transition point in G2. When fresh serum is added to cells after three days in depleted growth medium, they divide before they begin to synthesize DNA. This further confirms that they are in late S and G2. Cell division is promoted in Vero cells in depleted growth medium by bovine fetuin, and to a lesser extent by bovine albumin. Cell division is not promoted by insulin, hydrocortisone, dexamethasone, linolenic acid, calcium, and trypsin inhibitor from ovomucoid. From these data we conclude that transit through G2 requires the presence of an extracellular factor.
Alterations in differentiation and pyrimidine pathway enzymes in 5‐azacytidine resistant variants of a myoblast line
Authors: Ng S. K. , Rogers Jackilynn , Sanwal B. D. 
Published: February 2005

Abstract5‐azacytidine at concentrations higher than 5 μM inhibited the differentiation of a rat myoblast line in vitro. It was also somewhat cytotoxic at this level. Variants resistant to the cytotoxic effect of 5‐azacytidine were obtained which were simultaneously unable to differentiate into myotubes and exhibited altered morphology. These characteristics were retained by the variants when subcultured in the absence of the drug for over 700 generations. Several of the azacytidine resistant cells were more susceptible than the parental line to the lethal action of 5‐bromodeoxyuridine and adenosine, but not that of cytosine arabinoside, ouabain or 8‐azaguanine.The variants were capable of transporting uridine, thymidine and 5‐azacytidine. The uridine kinase activity was one‐half to one‐third of that in the parental cells but it was not missing completely in any of the variants. Two independently isolated variants selected for detailed study showed a 2‐ to 3‐fold increase in the activity of orotidylic acid decarboxylase. This enzyme in the variants in contrast to that of the parental cells was completely insensitive to the inhibitory effect of a nucleotide generated from ATP and 5‐azacytidine in cell extracts (probably 5‐azacytidine monophosphate). These observations point to the possibility that 5‐azacytidine resistance arises in myoblasts due to an alteration of the components of two target pathways of this drug, viz., the de novo pyrimidine pathway and an undefined sequence leading to the synthesis of membrane components.
RNA synthesis and processing as a measure of phenotypic variability in cytodifferentiation and neoplasia
Authors: Bynum John W. , Regan James D. , Volkin Elliot 
Published: February 2005

AbstractNeoplastic cell lines exhibit RNA synthesis and process patterns which are related to phenotypic attributes more complex than merely the rate of proliferation. Mouse neuroblastoma cells of the same genotype but different differentiated states have different ribosomal RNA precursor processing patterns, while plasmacytoma cells of different genotypes but the same differentiated state have the same pre‐ribosomal RNA processing pattern. In addition, our observations indicate that chromatin‐associated RNA is involved in cytodifferentiation and is closely related to phenotypic variability. When neuroblastoma cells are induced to differentiate, there is a 2‐ to 3‐fold increase in the labeling of chromatin‐associated RNA. Both of the differentiated cell lines, human myeloma and mouse neuroblastoma, have slow‐labeling, stable chromatin‐associated RNA while this same fraction from HeLa cells is labeled rapidly and is unstable.
Glycogen metabolism in adult rat liver parenchymal cell primary cultures
Authors: Walker P. Roy 
Published: February 2005

AbstractParenchymal cells were isolated from adult rat liver with an enzyme perfusion technique. The single‐cell suspension, representing 40–50% of the liver's hepatocytes was suspended in medium and maintained in primary culture for up to four days. The cells were found to carry out glycogen synthesis for the first eight hours in culture after which time the accumulated glycogen was gradually degraded. The ability of the liver cell cultures to accumulate glycogen was found to be dependent upon the metabolic state of the animal prior to cell isolation. Cells prepared during the feeding period from animals on the 8 + 16 feeding schedule had markedly different capacities for glycogen accumulation. Changes in glycogen metabolism were found to be due, in part, to changes in the fraction of cells involved in metabolism at any given time. High concentrations of glucose stimulated the cells to deposit glycogen but the response was reduced the longer the cells were in culture over a 3‐day period. This loss of glycogen synthesizing capacity appears to be due to a decrease in glycogen synthetase activity. The activities of pyruvate kinase, hexokinase and aldolase also decrease during the culture period.
A serum factor capable of stimulating hyaluronic acid synthesis in cultured rat fibroblasts
Authors: Tomida Mikio , Koyama Hideki , Ono Tetsuo 
Published: February 2005

AbstractCalf serum as well as rat and mouse sera has a factor that stimulates hyaluronic acid synthesis in cultured rat fibroblasts. Such a factor was partially purified from calf serum and characterized. It has a molecular weight of approximately 150,000. The activity of the factor is lost by treatment with pronase and by periodate oxidation. It is suggested, therefore, that the factor is a glycoprotein. Its susceptibility to α‐mannosidase and affinity for Con A‐Sepharose may suggest that the factor contains a mannose residue(s) which is essential for the activity to induce hyaluronic acid synthesis.
Proteases stimulate proliferation of human fibroblasts
Authors: Pohjanpelto Pirkko 
Published: February 2005

AbstractIncubation of primary human fibroblasts in serum‐free medium with small concentrations of thrombin, trypsin or plasmin resulted in manyfold increase in total DNA synthesis and in the number of 3H‐thymidine labelled cells. Rise in the frequency of mitoses indicates that the proteases stimulated also cell division. Because proteases induced only a fraction of cells to proliferate increase in the total number of cells remained moderate. Calf, horse and rabbit serum inhibited the growth stimulating effect of trypsin but chicken, dog and monkey serum were permissive. Specific inhibitors of proteases prevented the stimulation of cell proliferation suggesting strongly that proteases act in virtue of their enzymatic activity.
Alterations of acetylcholine enzymes in neuroblastoma cells persistently infected with lymphocytic choriomeningitis virus
Authors: Oldstone Michael B. A. , Holmstoen James , Welsh Raymond M. 
Published: February 2005

AbstractPersistent infection of murine neuroblastoma cells with a relatively non‐cytopathic virus, lymphocytic choriomeningitis virus (LCMV), significantly lowered the cells' concentrations of choline acetyl transferase (CAT) and acetylcholine esterase (ACHE), enzymes which make or degrade acetylcholine. Quantities of acetylcholine enzymes remained depressed during the observation period of more than two years. This cellular luxury function was turned off without observable alterations in the cells' vital functions – growth rates, protein and RNA synthesis. Cloning experiments showed that CAT and ACHE levels were altered in the majority of LCMV infected neuroblastoma cells in culture and not limited to a specific subpopulation. Cells persistently infected with virus also contained receptors for neurotoxin A and α bungarotoxin. Six months after becoming infected, neuroblastoma cells having significant alterations in luxury functions stopped making infectious virus. Instead these cells now produced a defective interfering virus component.Similar events to those seen in vitro with neuroblastoma cells also occurred in vivo. Mice inoculated with LCMV at birth carried high titers of LCMV in brain tissues and viral antigens in neuronal cells as adults. Some of these mice also showed significant alterations in their ability to make and degrade acetylcholine when compared to age and sex matched controls.
Rapid increase in poly(A) (+) mRNA content following inhibition of protein synthesis
Authors: Johnson Lee F. , Meister Richard 
Published: February 2005

AbstractWhen resting 3T6 cells undergo a serum‐induced transition to the growing state, the cytoplasmic content of ribosomal, transfer and messenger RNA increase as the cells prepare for DNA synthesis. The normal linear increase in mRNA content occurs even when the production of ribosomes is blocked. In this paper we determine the effect of inhibiting protein synthesis on the increase in poly(A) (+) mRNA content. Resting cells were serum stimulated in the presence of cycloheximide or puromycin at levels which inhibit protein synthesis by greater than 95%. Cytoplasmic poly(A) (+) mRNA content was determined at various times thereafter. We found that mRNA content increased five to ten times more rapidly in drug treated cells than in control cells stimulated in the absence of inhibitors. mRNA content increased 50–70% by one hour, and 60–90% by two hours following stimulation in the presence of inhibitor, and remained more or less constant thereafter. In contrast, mRNA content increased linearly in control stimulated cultures and did not double until about 15 hours after stimulation. The rapid increase in mRNA content is most likely the result of inhibition of protein synthesis rather than a secondary effect of the drug since the same observations were made in growth stimulated cells if protein synthesis was blocked with either puromycin or cycloheximide.A similar effect was also observed with resting 3T6, exponentially growing 3T6 and growing HeLa cells following exposure to cycloheximide, although the magnitude of the increase was less than that observed with growth stimulated cells. Puromycin had negligible effect on mRNA content in resting or exponentially growing cells.The rapid increase in cytoplasmic poly(A) (+) mRNA content was not due to rapid unbalanced export of nuclear poly(A) (+) RNA into the cytoplasm since there was no decrease in nuclear poly(A) content following serum stimulation in the presence of cycloheximide.
Induced alteration in uptake properties of Tetrahymena and its association with the development of mating competency
Authors: Adair W. Steven , Wolfe Jason 
Published: February 2005

AbstractThe rate of uridine uptake in Tetrahymena declines by an order of magnitude by two hours after shiftdown to a non‐nutrient buffer. This alteration in uptake properties cannot be accounted for by an increase in the intracellular pool of uridine, an increase in apparent Km for uptake or a decline in the rate in which uridine is processed intracellularly.It is argued that the decrease in uridine uptake is due to a reduction in numbers of functional transport molecules exposed at the cell surface and is a reflection of a developmentally related cell surface transformation.In addition, the putative decline in functional transport molecules cannot be entirely explained by metabolic turnover of these molecules in the absence of replacement, nor does it require the synthesis of new protein. We discuss the possibility that a shift in equilibrium between accessible and inaccessible transporters is operating.Finally, a close correlation between conditions which elicit the transport alteration and those which allow the development of mating competency suggests that the two phenomena may be coordinately regulated.