bluuebunny/crossref_metadata_2025_split huggingface dataset:
Hemoglobin synthesis in murine virus‐induced leukemic cells in vitro. III. Effects of 5‐bromo‐2′‐deoxyuridine, dimethylformamide and dimethylsulfoxide
Authors: Scher William , Preisler Harvey D. , Friend Charlotte 
Published: February 2005

AbstractErythroid differentiation of Friend leukemia cells is enhanced when the cells are grown for four days in the presence of dimethylsulfoxide (DMSO). Dimethylformamide (DMF) has a similar though less marked effect. 5‐Bromo‐2′‐deoxyuridine (BUdR) (10−5M) inhibits both DMF‐ and DMSO‐stimulated differentiation. For maximum inhibition, BUdR must be present during the first two days of growth, during which time DNA synthesis is maximal. The addition of BUdR after the third day has no effect.Since BUdR is incorporated into DNA and thymidine prevents BUdR inhibition of DMSO‐stimulated differentiation, it is likely that BUdR acts by virtue of its incorporation into DNA. Although BUdR alone had little effect upon cell multiplication, in combination with DMSO, cell growth was inhibited up to 40%. Since the BUdR‐inhibition of the DMSO effect was approximately 70%, it is unlikely that its effect on differentiation is due to selective killing of those cells which are stimulated to differentiate.
Serum dependent growth of primary cultured differentiated fetal rat hepatocytes in arginine‐deficient medium
Authors: Leffert H. L. , Paul D. 
Published: February 2005

AbstractFetal rat hepatocytes in primary monolayer cultures multiply in arginine‐deficient medium. Both the “recovery efficiency” and the final cell density of the cultured cells are proportional to the concentration (0–15%, v/v) of dialyzed fetal bovine serum in the medium. Stationary‐phase cells divide again following addition of fresh serum to the culture. After two to three generations of growth, the chromosome number of these cells remains diploid [2N = 42].Cross‐feeding (of a subpopulation of arginine‐requiring liver‐derived cells by parenchymal arginine‐synthesizing cells) and cellular degradation of various serum proteins do not account for sources of arginine required for cell multiplication in this culture system. Because these cultured hepatocytes utilize ornithine for arginine biosynthesis, and because ornithine enhances the rate and the amount of cell multiplication, it is more likely that the multiplying cells are parenchymal arginine‐synthesizing hepatocytes.At least two classes of serum factors are required for the growth of cultured fetal rat hepatocytes: one stimulates cell multiplication; the other is required for cellular survival and/or attachment to the culture dish. These factors have been partially separated by fractionation with ammonium sulfate; they are non‐dialyzable, heat labile, and sensitive to changes in pH.
Studies on the nature of the subcellular localization of lactate dehydrogenase and glyceraldehyde‐3‐phosphate dehydrogenase in chicken skeletal muscle
Authors: Melnick Ronald L. , Hultin H. O. 
Published: February 2005

AbstractThe elucidation of the subcellular localization of enzymes by the classical technique of homogenization followed by differential centrifugation is limited in that it is difficult to determine the effect of the severe disruptive procedures on the normal relationship of the enzymes to their subcellular environment. Attempts have been made to study this problem under less severe limitations; one of the approaches used has been the use of pressure on whole muscle tissue to extract the cellular fluids. In this report we introduce the concept of “comparative extraction” for evaluation of results obtained by this procedure. By comparing the efflux of enzymes of similar solubility and similar size and shape, it is possible to determine the minimal amount of the less easily extractable enzyme which cannot be removed due to compartmentation or binding to cellular particulate structures.Using this concept of “comparative extraction,” we show in this report that at least 35% of the lactate dehydrogenase of chicken breast muscle is restricted in its removal. The data do not definitely resolve the problem of whether the restriction is due to compartmentation of the enzyme within subcellular organelles or binding to subcellular structures.
Isolation and characterization of some of the proteins that shuttle between cytoplasm and nucleus in Amoeba proteus
Authors: Jelinek Warren , Goldstein Lester 
Published: February 2005

AbstractThe Rapidly Migrating Proteins (RMP) which shuttle nonrandomly between nucleus and cytoplasm and equilibrate in approximately equal amounts in each compartment, were isolated from Amoeba proteus by implanting 3H‐protein containing nuclei into unlabeled cells and some time later extracting the labeled material from the cytoplasms of such cells. The labeled material was subsequently fractionated by gel filtration in Sephadex G‐100 columns. The RMP are soluble in dilute salt solutions and appear as a heterogenous group of molecules, one component of which seems to be a single species of protein accounting for ca. one‐third of the RMP fraction. Because of its distinctness this component, called the LR fraction, received the major attention in this study. LR was found to comprise ca. 17% of the aqueous‐soluble proteins of the nucleus and ca. 3–4% of the total cell protein.LR has a very low molecular weight as determined, e.g., by its elution from a Sephadex G‐100 column. Because of its low molecular weight, LR could be purified by taking advantage of the fact that LR is (1) soluble in a saturated Solution of ammonium sulfate and (2) insoluble in butanol, diethyl ether, and 10% trichloroacetic acid.LR migrates toward the anode as a single band when subjected to electrophoresis on “standard disc” and SDS polyacrylamide gels. It does not enter a gel designed to separate basic proteins (at pH 4.0). When subjected to Sephadex G‐25 gel filtration LR migrates through the gel as a single band and elutes from the gel at a position in the middle of the linear separation range that indicates its molecular weight is ca. 2300. The only N‐terminal amino acid found in the LR fraction is proline.Evidence is presented to show that LR is not the product of a non‐specific breakdown of protein produced during its isolation, but the possibility that it results from the cleavage of a single chemical bond of a larger polypeptide, has not been eliminated.When injected into non‐labeled amebae, purified radioactive LR concentrates in the nucleus — just as radioactive RMP concentrates in a recipient cell nucleus when an amino acid‐labeled nucleus is implanted into an unlabeled cell.
Conditionally lethal mutations in chinese hamster cells. I. Isolation of a temperature‐sensitive line and its investigation by cell cycle studies
Authors: Scheffler I. E. , Buttin G. 
Published: February 2005

AbstractThe isolation of a temperature sensitive cell line from the Chinese hamster line CCL39 of the American Type Culture Collection is described. At the nonpermissive temperature (39°C) the cells become attached to the surface of tissue culture dishes, but no microscopically observable colonies are formed upon prolonged incubation. Exposure to the high temperature for more than 24 hours leads to an almost complete loss in viability. A karyotypic analysis showed that this new line has lost one of the medium‐sized metacentric chromosomes, although no proof is available so far to show that this loss is not simply coincidental.In nonsynchronized cultures transferred to 39°C DNA synthesis stops first, RNA synthesis shortly thereafter, while protein synthesis (turnover) continues for a longer time. After such a shift the cell number increases by less than 15% as measured with the Coulter counter.Studies with synchronized cultures give the following results: (1) one round of DNA synthesis can occur at 39°C when the cells are released from serum starvation or a hydroxyurea block, or when mitotic cells are placed at 39°C; (2) the entry of cells into metaphase of mitosis at 39°C is almost normal when the preceding time interval at 39°C is only eight hours (release of cells from G1/S boundary), but considerably reduced when the cells spend an additional 12 to 15 hours at 39°C in G1 (release from serum starvation).Infection by SV40 virus temporarily induces DNA synthesis after it has come to a stop at the nonpermissive temperature, but cells permanently transformed by SV40 still exhibit the temperature‐sensitive phenotype.
Investigations of the mechanism of decreased tumorigenicity of cells grown in BrdU
Authors: Rothschild Henry , Black Paul H. 
Published: February 2005

AbstractTransplantable SV40‐transformed hamster cells cultivated in the presence of low concentrations of BrdU for prolonged periods of time and cells made deficient in the enzyme thymidine kinase (dTK) by continued exposure to BrdU became less tumorigenic. In both instances, when grown in BrdU the cells contained analog substituted DNA. The tumorigenicity of dTK+ cells exposed to low concentrations of BrdU, but not the dTK− cells, returned to control values when the cells were grown in medium devoid of BrdU. A tumorigenic mouse cell line made dTK deficient also had diminished oncogenicity. However, transformed hamster cells made deficient in another salvage pathway enzyme, hypoxanthineguanine phosphoribosyl‐transferase by growth in eight azaguanine, retained their tumorigenicity. Two of five revertant cell lines, in which thymidine kinase activity was restored, transplanted more readily to hamsters than the dTK− cells from which they were derived. It is concluded that there is a relative loss of tumorigenicity when BrdU is incorporated into the DNA of tumorigenic cell lines, or when there is a genetic modification of thymidine kinase activity.
Contact inhibition and gene expression in HTC/L cell hybrid lines
Authors: Levisohn Steven R. , Thompson E. Brad 
Published: February 2005

AbstractContact‐inhibited somatic cell hybrids were formed between two malignant cell lines lacking contact inhibition of growth. One cell line was HTC‐AR1, an azaguanine‐resistant subline from the rat hepatoma line HTC +; the other line was the BUDR‐resistant mouse L‐cell subline L‐B82. Hybrids were obtained from selective medium and characterized by chromosomal and enzymic analysis. The hybrids lacked the inducible rat enzyme tyrosine aminotransferase.
6,8‐Dihydroxypurine: A novel growth factor for mammalian cells in vitro, isolated from a commercial peptone
Authors: Yamane Isao , Murakami Osamu 
Published: February 2005

AbstractA substance promoting the growth of mammalian cells in vitro has been isolated from Bacto‐peptone (Difco Labs., Detroit) and identified as 6,8‐dihydroxypurine. This compound, which is isomeric with xanthine(2,6‐dihydroxypurine), enhances the growth of one Chinese hamster and some other cell lines; xanthine itself is inactive. The biological action of the compound is discussed.
Evidence for similar biochemical requirements for bioluminescence among the coelenterates
Authors: Cormier Milton J. , Hori Kazuo , Karkhanis Y. D. , Anderson James M. , Wampler John E. , Morin James G. , Hastings J. W. 
Published: February 2005

AbstractWe present evidence that the chemical requirements among all the bioluminescent coelenterates that have been examined are very similar or identical to those already described for Renilla by Cormier and associates. Components required for luminescence in Renilla were also found in a number of bioluminescent coelenterates examined such as Aequorea, Obelia, Cavernularia, Ptilosarcus, Stylatula, Acanthoptilum, Parazoanthus and Mnemiopsis. Depending on the organism these include one or more of the following: luciferyl sulfate, luciferase, and luciferin sulfokinase. These isolated components were found to be indistinguishable from those found in Renilla as evidenced by their reactivity in the Renilla bioluminescent system, by the spectral characteristics of the isolated luciferyl sulfates, by the molecular weights of the luciferases, and by the colors of the bioluminescence produced in vitro.
Stimulation of density‐inhibited cell cultures by insulin
Authors: Vaheri Antti , Ruoslahti Erkki , Hovi Tapani , Nordling Stig 
Published: February 2005

AbstractCell proliferation in density‐inhibited chick embryo cell cultures was induced by microgram quantities of insulin, neuraminidase, trypsin or papain. Other proteins tested, including albumin, fetuin, ribonuclease and hyaluronidase were inactive except in very high concentrations (> 100 μg/ml).The insulin chick embryo model was selected for detailed analysis of the initiation of proliferation. Insulin insolubilized by conjugation with Sepharose particles was also active, but only in so far as it was released in soluble form from the particles. This was measured by a radioimmunoassay. Under the conditions giving maximal cell proliferation less than 0.002‐0.2% of insulin was taken up by the cells. This suggests that an interaction of insulin with the cell surface only is sufficient to stimulate the cells. Insulin released the density‐inhibited cells from G1 phase to produce an almost synchronous wave of proliferation. The following sequence of events was characteristic of the cells after stimulation by insulin: an early increase in sugar uptake and decrease in leucine uptake, increase in cell volume, stimulation of RNA and protein synthesis, increase in thymidine uptake, DNA synthesis, mitosis and cell division.
Ionic basis of volume regulation in mammalian cells following osmotic shock
Authors: Shank Brenda Buckhold , Rosenberg Howard M. , Horowitz Carolyn 
Published: February 2005

AbstractPrevious studies with mammalian cultured cells have shown that volume regulation in hypotonic medium requires active Na transport. In the present study, determinations of intracellular Na and K content were made in cultured mouse lymphoblasts during the process of swelling and subsequent shrinking (volume regulation) in hypotonic medium. Na and K content were measured in cells in which the shrinking phase was inhibited by the cardiac glycoside, ouabain. In osmotically‐shocked cells, an initial permeability increase to K, and not Na, was observed, which allowed K to diffuse out rapidly, down its gradient. Na, meanwhile, rapidly flowed inward with water entry during the swelling process, and was later lost with the same kinetics as the cell shrinkage. This loss of Na was prevented in the presence of ouabain. The results imply that volume regulation is achieved by pumping Na gained during swelling out of the cells, while any K taken up by the pump is rapidly lost through a more permeable membrane. The loss of osmotically active Na, presumably with accompanying anions, allows water to passively diffuse down its osmotic gradient, reducing cell volume subsequent to the initial passive swelling, during which K was rapidly lost.
Effects of colchicine and 2‐Br‐α‐Ergocryptine‐methane‐sulfonate (CB 154) on the release of prolactin and growth hormone by functional pituitary tumor cells in culture
Authors: Gautvik Kaare M. , Hoyt Richard F. , Tashjian Armen H. 
Published: February 2005

AbstractThe effects of colchicine and 2‐Br‐α‐ergocryptine‐methane‐sulfonate (CB 154) on the release of prolactin and growth hormone have been studied in a clonal strain of rat pituitary tumor cells (GH3) in monolayer culture. These cultures produce both prolactin and growth hormone and release both proteins spontaneously into the medium without storing them in large amounts. Immunological methods were used to measure both intracellular and extracellular concentrations of the hormones. Colchicine (5 × 10−6 M for 3 hours) caused a 2‐ to 3‐fold increase in intracellular concentrations of prolactin and growth hormone but, under basal conditions, had little or no measurable effect on the amounts of hormone accumulated in the medium during the course of the standard three hour treatment period. This latter finding evidently is due to a lag in the onset of drug action. Colchicine had little or no effect on accumulation of extracellular prolactin during the first two hours of treatment whereas such accumulation was depressed by over 60% during the third hour of treatment. Previous studies have shown that treatment of GH3 cells with thyrotropin releasing hormone (TRH) and hydrocortisone (HC) increases both intra and extracellular levels of prolactin and growth hormone, respectively. In cultures treated with TRH (5 × 10−8 M), colchicine (5 × 10−6 M for 3 hours) increased intracellular prolactin by about 70% and decreased extracellular hormone by 10%. In cultures treated with HC (3 × 1O−6 M), colchicine increased intracellular growth hormone by more than 100% and decreased medium concentrations of the hormone by 15%. Colchicine did not significantly alter total hormone (intracellular + extracellular) accumulation, cellular uptake of 3H‐amino acids, or total cell protein synthesis. The synthetic ergot alkaloid, CB 154, (3.3 × 10−6 M for 3 hours) caused an 80% increase in intracellular, and a nearly 50% decrease in extracellular, prolactin without affecting the accumulation of growth hormone, the uptake of 3H‐labeled amino acids, or overall protein synthesis in the cultures. Elevation of medium potassium concentration from a basal value of 5.3 mM to 3–5 × 10−2 M (by addition of KCl) decreased intracellular levels of prolactin by 85% and growth hormone by 55%. These effects of high potassium were blocked by colchicine and by CB 154. We conclude that colchicine, after a lag period of two hours, acts to inhibit the release of prolactin and growth hormone from GH3 cells. By the end of three hours of treatment, this inhibition is over 60% complete in the case of prolactin. The qualitatively different effects of colchicine and CB 154 on prolactin and growth hormone release suggest that these two secretory blocking agents probably act on GH3 cells by different mechanisms.
Stimulation of differentiation and proliferation of haemopoietic cells in vitro
Authors: Dexter T. M. , Allen T. D. , Lajtha L. G. , Schofield R. , Lord B. I. 
Published: February 2005

AbstractA liquid culture system, for haemopoietic cells, has been developed using bone marrow cells alone, or co‐cultures of thymus and bone marrow cells, inoculated into four ounce medical bottles. After several days growth, such cultures consisted of an attaching population of cells, forming discrete colonies, and a non‐attaching population. In the (co‐cultures) there was a 2 X enhancement of monolayer colony development compared with the combined total present in the (marrow alone) plus (thymus alone) cultures. Also, better maintenance of non‐attaching cells was seen in the (co‐cultures). Normal CFUS and CFUC were present in both the (marrow alone) and the (co‐cultures) for at least 14 days.In the (marrow alone) cultures, granulocytes in all stages of development were present for the first week, but by 12 days the culture consisted mainly of mono‐nuclear cells. In the (co‐cultures), however, at 12 days more than 60% of the cells were granulocytes, in all stages of differentiation. (Co‐cultures) established using lethally irradiated thymus cells were not able to support this prolonged myeloid differentiation.By feeding the (co‐cultures) it was possible to maintain production of (granulocytic) cells for at least ten weeks, although no fully mature granulocytes were observed. After the second feeding, no CFUS were detectable, but variable numbers of agar colony forming cells (not classical CFUC) were present at least for ten weeks.
Inactivation of protein synthesis stimulating activity in serum by cells
Authors: Kaminskas Edvardas 
Published: February 2005

AbstractWhen Ehrlich ascites cells were cultivated in serum‐free media their cellular protein synthetic rate declined to a new steady‐state level and the cells stopped multiplying. On addition of serum the cellular protein synthetic rate increased to the level before serum starvation and cells resumed multiplication. The activity in serum stimulating protein synthesis was inactivated on incubation with cells. At cell concentrations of the usual culture conditions this inactivation took several hours; at very high cell concentrations it was complete in ten minutes. Serum‐starved cells inactivated low serum (2%–6%) media in the same length of time. Studies of inactivation of high serum media demonstrated that cells had a limted capacity to inactivate. Cells grown in 10% serum were unable to inactivate. Inactivation was not due to accumulation in the medium of either low molecular or macromolecular cell products. Inactivation was strongly inhibited at 4° or by treatment of cells with fluoride or cycloheximide (long exposure): less inhibited by treatment with 2‐deoxyglucose or glutaraldehyde; and slightly inhibited by treatment with cyanide or cycloheximide (short exposure). Inactivating ability was unaffected by trypsinization. These findings are best explained by the hypothesis that cells take up the serum activity by endocytosis.
Influence of the explantation milieu on intranuclear [Na], [K] and [Mg] of Chironomus thummi salivary gland cells
Authors: Kroeger Heinrich , Trösch Walter 
Published: February 2005

AbstractIntranuclear Na, K and Mg concentrations were determined in cells of salivary glands incubated for 1h in selected NaCl/KCl/MgCl2 media. By variation of the external milieu beyond “physiological” limits the intranuclear electrolytes can be shifted between ca 100 and 280 mM [K]i, between ca 8 and 100 mM [Na]i and between ca 5 and 75 mM [Mg]i. No significant competition or interactions of the 3 ionic species are apparent. The relationships [K]e : [K]i and [Na]e : [Na]i can best be described by a positive and linear, that between [Mg]e : [Mg]i by a negative and exponential function. Regression parameters are given which permit a computation of intranuclear [Na], [K] and [Mg] as induced by NaCl/KCl/MgCl2 in any binary or triple combination that is tolerated by the explanted gland without visible damage.
Nucleoside diphosphate kinase at the cell surface of neoplastic human cells in culture
Authors: Ågren G. , Pontén J. , Ronquist G. , Westermark B. 
Published: February 2005

AbstractStrong evidence is given that a nucleoside diphosphate kinase is present to some extent on the surface of intact neoplastic cells in culture. Experiments could be performed with cells cultured in a few plates to which an incubation medium was added. The cells were firmly attached to the supporting medium and remained viable during the incubation procedure.Determinations of lactate dehydrogenase were carried out to rule out any possible contamination from the culturing medium as well as from the cell interior. From these analyses, a procedure was developed which easily removed the last traces of the culturing medium and which showed that there was no leakage of intracellular lactate dehydrogenase during the incubation procedure. There was a rather insignificant diffusion of nucleoside diphosphate kinase into the incubation medium. In common with other nucleoside diphosphate kinases, the glioma cell surface enzyme seemed to be nonspecific with regard to nucleotide substrates.