bluuebunny/crossref_metadata_2025_split huggingface dataset:
Lack of selective killing by steroids in normal and malignant cells
Authors: Weichselbaum R. R. , Little J. B. , Nove J. , Hellman S. , Piro A. J. 
Published: February 2005

AbstractUsing a colony formation assay, the cytotoxic effects of steroids and an anit‐steroid on an established human breast tumor line and two human diploid fibroblast strains were studied. Experiments involving 17 a‐estradiol, 17 β‐estradiol, dexamethasone, cortisone, dihydrotestosterone, and the anti‐estrogen Tamoxifen showed no killing at concentrations below 10–7M following a 24‐hour exposure to these agents. A maximum of 80% killing was observed at 10–5M with dexamethasone in one fibroblast strain and at the same dose of 17 β‐estradiol in the breast tumor line. The extent of killing observed is insufficient to account for many of the clinical remissions observed with steroid therapy. The data also suggest that at therapeutic doses, there is no selective killing of malignant cells by these agents.
Membrane‐associated ribosomes in producing and nonproducing mouse myeloma cells
Authors: Cieplinski William , Scharff M. D. 
Published: February 2005

AbstractMouse myeloma cell lines synthesize large amounts of immunoglobulin on their membrane‐associated polyribosomes. Variants which no longer synthesize immunoglobulins have been studied and shown to have the same number of tightly bound membrane‐associated polyribosomes as the parental cell lines. These polyribosomes are still active in the synthesis of nonimmunoglobulin proteins.
Increased neurite development and plasminogen activator expression by exposure of human neuroblastoma cells to a plasminogen‐deficient growth medium
Authors: Becherer P. R. , Wachsman J. T. 
Published: February 2005

AbstractGrowth of human neuroblastoma strain SK‐N‐SH in a plasminogen‐deficient medium results in about a 40% increase in the number of differentiated cells (cells with a neurite‐like process at least 50 μm in length) and about a five‐fold increase in the amount of plasminogen activator liberated per cell. Plasminogen deficiency has no effect on the growth rate of SK‐N‐SH cells. These results are consistent with the hypothesis that plasminogen activator is involved in neuroblast development.
Discrimination of a colony stimulating factor subclass by a specific receptor on a macrophage cell line
Authors: Das S. K. , Stanley E. R. , Guilbert L. J. , Forman L. W. 
Published: February 2005

AbstractUtilizing the high affinity interactions between pure 125I‐L cell colony stimulating factor and its receptor(s) on the murine macrophage cell line J774, a murine radioreceptor assay (RRA) has been developed. The murine RRA selectively detects a colony stimulating factor (CSF) subclass (CSF‐1) previously defined by murine radioimmunoassay (RIA) (E.R. Stanley, Proc. Nat. Acad. Sci., USA, 76:2969–2973 ('79)). CSF‐1 stimulates macrophage production exclusively, and the occurrence of the CSF‐1 receptor(s) appears to be restricted to cells of the mononuclear phagocytic system (L.J. Guilbert and E.R. Stanley, J. Cell Biol. 85:153–160 ('80)). The murine CSF‐1 RRA failed to detect a variety of other CSF subclasses, growth factors, and hormones. In contrast to data obtained with the murine CSF‐1 RIA, human CSF‐1 (e.g., human urinary CSF) is detected by the mouse CSF‐1 RRA almost as sensitively as murine CSF‐1. In addition, there was an absolute correlation between CSF‐1 levels determined by murine CSF‐1 RRA and those determined by a human CSF‐1 RIA for a variety of human CSF‐1 sources. The murine CSF‐1 RRA is a sensitive (sensitivity 5 units or 1.0 femtomole of CSF‐1 protein), rapid, and highly specific assay for CSF‐1 in both murine and human sources.
Divergent effects of long acting cyclic nucleotides and lysine vasopressin on the release of matrix sulfated proteoglycans into the medium of fetal rat chondrocytes in monolayer culture
Authors: Miller R. P. , Erickson‐Lucas M. 
Published: February 2005

AbstractRelease of sulfated proteoglycans into the medium of fetal rat chondrocytes in monolayer culture was studied by contrasting the effects of 10% calf serum, long‐acting cyclic nucleotides (8 Br‐cAMP or DBcAMP), and lysine vasopressin (LVP). Eight hours after initiation of the experiment, the monolayer was pulsed for 2 hours with Na2[35SO], the radioactivity was chased, and the monolayer was reincubated for 6 hours with conditioned medium from replicate cultures. Immediately after labelling, the amount of newly synthesized sulfated proteoglycans was invariably higher in the insoluble matrix than in the medium compartment. Both additives selectively enhanced sulfate incorporation into chondroitin sulfate of the matrix when compared to serum controls, but only LVP stimulation caused increases in the medium. Remodeling (loss of cell layer and release into the medium at 6 hours) was suppressed by cAMP analogues and increased by LVP. This process was more active in cultures of lower cell density. Utilizing calibrated gel columns, no size difference of the glycosaminoglycans was found between the medium and cell layer compartments of the three treatment groups at the two time points. Because the cAMP analogues inhibit, while LVP stimulates cell division, our observations imply that the rate of degradation of the constraining matrix is increased when replication is favored, even when chondroitin sulfate synthesis is selectively stimulated.
Protein synthesis and the presence or absence of a measurable G1 in cultured chinese hamster cells
Authors: Liskay R. Michael , Kornfeld Bruce , Fullerton Paul , Evans Ronald 
Published: February 2005

AbstractV79‐8 cells lack a measurable G1 interval under normal growth conditions. We found that partial inhibition of protein synthesis using low levels of cycloheximide (0.05 μ/ml) could induce a measurable G1 in these cells without any significant effects on S, G2, or M. In view of these findings, recessive mutants selected from the V79‐8 cell line, which each express G1, were analyzed for their rates of protein synthesis and degradation/loss. Three of the four mutants showed a decreased rate of protein synthesis sufficient to account for their G1 lengths. A fourth mutant, however, showed parental rates of both protein synthesis and degradation/loss. These results suggest not only that a G1 interval can be expressed as a result of a decreased rate of protein synthesis, but that other alterations (mutations) other than those simply affecting overall protein synthesis can result in the expression of a measureable G1 interval.
The effects of steel mutation on testicular germ cell differentiation
Authors: Nishimune Yoshitake , Haneji Tatsuji , Kitamura Yukihiko 
Published: February 2005

AbstractThe effects of artificial cryptorchidism and its surgical reversal on spermatogenesis were examined in germ cell mutant, S1/+ and wild type, +/+, mice. In cryptorchid testes no difference was found between S1/+ and +/+ mice in the number of undifferentiated type A spermatogonia. The activity of type A spermatogonia in mutant mice appeared normal as judged by its mitotic cell number and DNA synthesis. The surgical reversal of cryptorchidism resulted in regenerative differentiation of mature germ cells in both types of mice, but the pattern of cellular differentiation in the mutant testes was completely different from that of the wild type testes. At two steps of cellular differentiation, intermediate or type B spermatogonia and spermatid, the numbers of cells were much smaller in the S1/+ testes than those in the +/+ testes. The steel gene was therefore suggested to exert its effects on the differentiation of type A spermatogonia to intermediate or type B spermatogonia, on meotic division and/or the survival rate of these cells, but not on the undifferentiated type A spermatogonia or stem cells.
Endogenously produced CO2 induces stationary phase in tetrahymena cultures
Authors: Gillies R. J. , Deamer D. W. 
Published: February 2005

AbstractMedia concentration of total soluble CO2 increases with culture age of Tetrahymena pyriformis. CO2 is a weak acid and is capable of acidifying intracellular pH (pHi). Changes in pHi have been demonstrated to affect cell metabolism and growth in many systems. For these reasons, we investigated whether the concentrations of CO2 produced in vitro were sufficient to affect cell proliferation and pHi in Tetrahymena. In this study, we used DMO to mimic the weak acid properties of CO2. DMO is freely permeable to membranes in its uncharged form and has a pKa similar to that of CO2/HCO. In addition, it has the advantages of being metabolically inert and non‐volatile. At concentrations similar to endogenously produced CO2, DMO acidifies pHi and arrests culture growth. In addition, procedures are described which decrease the media CO2 concentrations in both growing and non‐growing cultures. These conditions lead to increased maximum culture density at stationary phase. The data indicate that, under our conditions, accumulation of CO2 in the culture leads to cessation of growth, probably through elimination of transmembrane pH gradients, which are necessary for regulation of metabolism and growth.
Correlation between growth rate, cell density, and intracellular concentrations of cyclic nucleotides in chemsostat cultures of mouse L1210 cells
Authors: Tovey Michael G. , Rochette‐Egly Cécile , Castagna Monique 
Published: February 2005

AbstractConstant intracellular concentration of both adenosine 3′,5′ cyclic monophosphate (cyclic AMP) and guanosine 3′,5′ cyclic monophosphate (cyclic GMP) were obtained when mouse leukemia L1210 cells were cultivated under steady‐state conditions in the chemostat. When L1210 cells were maintained at a constant growth rate in the chemostat, the mean steady‐state intracellular concentration of cyclic AMP decreased with increasing cell density, while the concentration of cyclic GMP remained unchanged. When cell growth rate was increased by three‐fold, independently of cell density, in the chemostat, then the mean steady‐state intracellular concentration of cyclic GMP increased by 3.6‐fold, whereas that of cyclic AMP increased by only 22%. The ratio of cyclic AMP to cyclic GMP was found to decrease with increasing cell growth rate in the chemostat. Our results show that a close correlation exists between the steady‐state intracellular concentrations of cyclic nucleotides and changes in both cell growth rate and cell density in chemostat cultures of L1210 tumour cells.
Intracellular degradation of hemoglobin transferred into fibroblasts by fusion with red blood cells
Authors: Hendil Klavs B. 
Published: February 2005

AbstractHamster fibroblast protein and rabbit hemoglobin were labelled by incubation of fibroblasts (BHK21) or reticulocytes with [3H]leucine. Alternatively, human or rabbit hemoglobin was labelled by carbamoylation of erythrocytes with K14CNO. The labelled hemoglobins were introduced into fibroblasts by virus‐mediated fusion between the blood cells and fibroblasts. The hemoglobins became uniformly distributed throughout the cytoplasm.Degradation was assessed from release of acid‐soluble radioactivity into the medium. Radioactivity from [14C]‐carbamoylhemoglobin was released as carbamoylvaline and homocitrulline, and these compounds were not metabolized or reincorporated by the cells.Intermediate degradation products could not be detected.The degradation of hemoglobin followed first‐order kinetics. The half‐life of both carbamoylated and native rabbit hemoglobin in hamster fibroblasts was 28 h, and the half‐life of carbamoylated human hemoglobin was about 150 h in fibroblasts from hamster (BHK21), mouse (Balb/3T3), and man (MRC 5), corresponding to that of the more stable endogenous proteins.Phenylhydrazine increased the intracellular degradation of carbamoylated human hemoglobin about 13 times, whereas the degradation of endogenous proteins was little affected. Hemoglobin was degraded in homogenates at 31% h−1 at pH 5 and 0.3% h−1 at pH 7.4. Phenylhydrazine increased these rates to 45% h−1 and 9.7% h−1, respectively.Growing hamster fibroblasts, which are brought into quiescence by serum deprivation or by high culture density, increase the degradation of endogenous protein and of hemoglobin in parallel.
Cell surface molecules of friend erythroleukemias: Decrease in T200 glycoprotein expression after induction
Authors: Hyman Robert , Trowbridge Ian , Cunningham Kristie 
Published: February 2005

AbstractMonoclonal antibodies against the Thy‐1 and T200 glycoproteins were used to study the expression of cell surface molecules on mouse hematopoietic cell lines. Friend erythroleukemias express T200 glycoprotein but do not express significant amounts of Thy‐1 glycoprotein on their cell surface. The rate of T200 glycoprotein synthesis in maximally‐induced Friend erythroleukemia 745.6 cells is less than 10% that in noninduced cells, although total protein synthesis shows only a twofold decline and induced cells express 2‐6‐fold less T200 glycoprotein on their surface compared to noninduced cells. T200 glycoprotein expression is reduced in a variant cell line obtained by selection for growth in dimethylsulfoxide, showing that the reduction in T200 glycoprotein synthesis characteristic of induced cells is an event that can be dissociated from commitment and hemoglobin synthesis. Analysis of T200 glycoprotein negative cell lines, isolated by cytotoxic immunoselection against T200 glycoprotein, indicates that the presence of T200 glycoprotein on the cell surface is not necessary for induction of hemoglobin synthesis and terminal differentiation of Friend erythroleukemias.
Phorbol ester tumor promoters block the transition from the early to the heme‐dependent late program of friend cell differentiation
Authors: Mager Dixie , Bernstein Alan 
Published: February 2005

AbstractIn this study, the mechanism of inhibition of differentiation of Friend erythroleukemia cells by the phorbol ester tumor promoter, 12‐O‐tetradecanoylphorbol‐13‐acetate (TPA), has been examined. These studies indicate that some early events associated with Friend cell differentiation, including an early change in 86Rb+ transport and a decrease in cell volume, still occur in the presence of TPA. However, several late events in the program of Friend cell differentiation, including the induction of heme synthesis and the loss of proliferative capacity, are inhibited by TPA. These effects of TPA can be reversed by hemin, which alone does not induce Friend cells to differentiate. The addition of hemin to cultures grown in the presence of inducer plus TPA for several days results in the rapid restoration of hemoglobin synthesis, and also causes a parallel decrease in colony‐forming ability. These results suggest that tumor promoters may inhibit only heme‐dependent events, rather than the entire program of Friend cell differentiation.
Modulation of the G0 to S phase transit time by insulin: Potential involvement of protein phosphorylation
Authors: Kletzien Rolf F. , Day Philip 
Published: February 2005

AbstractBHK fibroblasts can be growth arrested by incubation in low serum (0.1%) medium. Growth is initiated by incubating cells in high serum (10%) medium. We have found that if the quiscent cells in low serum medium are incubated with insulin, the G0 to S transit time is decreased by two to six hours when serum (10%) is added back to the culture. The effect of insulin treatment of quiescent cells on the cellular phosphoprotein profile was examined. It was found that insulin stimulated the phosphorylation of a 96,000 dalton cytosol protein. This protein is also intensely phosphorylated in proliferating cells and may be one of the critical intracellular events to occur when a cell initiates growth.
Comparative aspects of oxidative metabolism of neutrophils from human blood and guinea pig peritonea: Magnitude of the respiratory burst, dependence upon stimulating agents, and localization of the oxidases
Authors: Badwey J. A. , Curnutte J. T. , Robinson J. M. , Lazdins J. K. , Briggs R. T. , Karnovsky M. J. , Karnovsky M. L. 
Published: February 2005

AbstractWe have compared the subcellular sites of H2O2 and presumably also superoxide‐(O2−) production, and certain aspects of metabolic responses (O2 consumption, O2− production) of stimulated neutrophils from human blood and those elicited into guinea pig peritonea. Stimulation was accomplished with either opsonized zymosan or phorbol‐12‐myristate‐13‐acetate (PMA). Striking quantitative differences were observed between these cell types with regard to the increased respiration and O2− production observed during stimulation. These differences were most apparent when opsonized zymosan served as the stimulating agent. They were minimized when the soluble stimulating agent, PMA, was used. With either stimulus, the subcellular sites of H2O2 production were the same for both types of neutrophils, i.e., the plasmalemma and phagosomal membranes. No H2O2 production could be detected cytochemically in the absence of stimulation.Treatment of both unstimulated human blood and elicited guinea pig peritoneal neutrophils with the nonpenetrating, covalently linking reagent, p‐diazobenzenesulfonic acid, failed to diminish O2− production upon subsequent stimulation, in contrast to a previous report. These data are discussed in terms of the possible cytological arrangements of the respiratory enzyme(s), and the different modes of stimulation of neutrophil metabolism by various agents. Ancillary data on elicited mouse peritoneal neutrophils are presented.
Stimulation of autophosphorylation of liver cell membrane proteins by calcium and partial hepatectomy
Authors: MacManus J. P. , Whitfield J. F. 
Published: February 2005

AbstractPartial hepatectomy in the rat stimulated the phosphorylation of three proteins (Mr 100,000, 48,000, and 35,000) in the plasma membranes of the proliferatively activated cells of the liver remnant. The autophosphorylation of these plasma membrane proteins began to rise about 8 hours after surgery, peaked at 14 hours, and then returned to the original low level by 24 hours. This increase in autophosphorylation was not evident in isolated plasma membranes from other proliferatively activated liver cells, such as those in fetal liver or hepatomas. The protein kinase responsible for the phosphorylation of the three membrane proteins was activated by calcium but appeared both cyclic‐AMP‐ and calmodulinindependent.
Amphotericin B resistance is recessive in Chinese hamster hybrid cells
Authors: Hidaka Katsuhiko , Akiyama Shin‐Ichi , Kuwano Michihiko 
Published: February 2005

AbstractPrevious studies from our laboratory have shown that Chinese hamster V79 cells mutated to high level resistance to amphotericin B have a lower cellular level of cholesterol, the target molecule for the polyene antibiotic. Two amphotericin B‐resistant (AMBR) mutants were each hybridized to their parental amphotericin B‐sensitive (AMBS) V79 cells. All the hybrids derived from AMBR/AMBS fusions were as sensitive to polyene antibiotics (amphotericin B, filipin, and pimaricin) as AMBS/AMBS hybrids. The AMBR/AMBS hybrids were found to contain cholesterol per phospholipids that is comparable to those in AMBS or AMBS/AMBS. The analysis of hybrids formed between mutant and wild‐type cells thus indicated that resistance to amphotericin B is a recessive marker, and that the cellular level of cholesterol is compensated in the AMBS/AMBR hybrids. Hybrids of AMBR and AMBR cells were all resistant, so that the three AMBR mutants all fell into a single complementation group.
Aging in vitro and D‐glucose uptake kinetics of diploid human fibroblasts
Authors: Cremer T. , Werdan K. , Stevenson A. F. G. , Lehner K. , Messerschmidt O. 
Published: February 2005

AbstractBy use of a rapid technique, initial rates of D‐glucose transport were obtained during the lifespan in vitro of a commercially available strain of human embryo lung fibroblasts (Flow 2000). The apparent Km of the D‐glucose carrier did not change during senescence in vitro: x̄ = 1.8 mM (range 1.3–2.3) in phase II, x̄ = 1.8 mM (range 1.5–2.2) in phase III. Transport rates remained constant in stationary phase II cultures, which had completed between 30% and 80% of their replicative lifespan. A wide variation, however, was observed in terminally differentiated cells (phase III), which showed a two‐ to threefold increase in average cell size and protein content. In some senescent cultures, glucose transport calculated on a per cell basis was also two‐to threefold increased, while it was strongly decreased (‐75%) in others. When calculated per unit of cell water, protein, and surface area, respectively, transport rates in phase III cultures ranged from values established for stationary phase II cultures down to very low values. Detaching cells flushed off from senescent cultures did not show measurable rates of glucose transport into the inulin impermeable cell space. Present evidence argues against the idea that an impairment of D‐glucose transport might precede loss of replicative potential in aging human fibroblasts. Instead our data indicate that the transport capacity of cell membrane finally decreases during postreplicative senescence in terminally differentiated cells.
Development of capping ability during differentiation of HL‐60 human promyelocytic leukemia cells
Authors: Brown William J. , Norwood Cynthia F. , Smith R. Graham , Snell William J. 
Published: February 2005

AbstractDevelopmental changes in cell surface and cytoskeletal elements have been studied in human promyelocytic leukemia cells (line HL‐60) which differentiate into functionally mature myeloid cells when grown in dimethyl sulfoxide (DMSO)‐supplemented medium. Both differentiated and undifferentiated HL‐60 cells bind fluorescent concanavalin A (F‐Con A) in a diffuse pattern over the entire cell surface. As with normal neutrophils, pretreatment of the differentiated HL‐60 cells with colchicine before incubation with Con A causes the formation of large cytoplasmic protrusions over which the lectin associates into a cap. On the other hand, similarly treated undifferentiated HL‐60 cells do not form the cytoplasmic protuberances and are unable to cap the Con A. Transmission electron microscopy reveals that the number and distribution of microtubules and microfilaments change during differentiation. Thus, developing myeloid cells undergo important alterations in the structure and function of the cytoskeleton as they differentiate into mature phagocytes.
Control and virus‐transformed baby hamster kidney cells resistant to ethidium bromide. II. Membrane properties
Authors: Soslau Gerald , Conover Thomas E. , Schneider Richard F. , Zavodny Paul J. 
Published: February 2005

AbstractAspects of membrane stucture and functions were studied in ethidium bromide resistant cells. Submitochondrial particles were solubilized and electrophoresed. The gel patterns, representing mitochondiral membrane proteins, demonstrated qualitative and quantitative alterations in mitochondrial preparations derived from virus‐transformed cells and ethidium bromide resistant cells as compared to the control cells. The plasma membrane glycoproteins were labelled by the sodium borohydride method. The glycoporteins were released with Triton X‐100 and electrophoresed. Fluorograms of the gels demonstratred some marked differences between the ethidium bromide resistant cells and their parental strain. The observed alterations in the membrane glycoproteins did not result in altered glucose transport properties or in the elution patterns of plasma membrane glycopeptides as analyzed by Sephadex G‐50 chromatography. Dye uptake and binding studies with intact parental and drug resistant cells and their isolated mitochondria demonstrated no alteration of the membrane permeability or the number of binding sites for ethidium bromide. Similar results were also obtained with a cyanine dye. This latter finding was significant in that it permitted one to exclude dye exclusion as a mechanism for ethidium bromide resistance.