bluuebunny/crossref_metadata_2025_split huggingface dataset:
Lectin‐dependent neutrophil cytotoxicity: Enhanced susceptibility of desialylated red cells
Authors: Tsan Min‐Fu , Scheffel Ursula , Denison Rebecca C. 
Published: February 2005

AbstractLectin‐dependent neutrophil cytotoxicity against autologous human red cells was studied using an 111In(indium)‐release assay. Human red cells were not readily killed by neutrophils in the presence of phytohemagglutinin (PHA). However, removal of red cell membrane sialic acids (desialylation) markedly enhanced their susceptibility to PHA‐dependent neutrophil cytotoxicity. This neutrophil cytotoxicity was dependent on the energy supplied by anaerobic glycolysis, but it was independent of erythrophagocytosis. Catalase, superoxide dismutase, KCN, and Na azide did not inhibit PHA‐dependent neutrophil cytotoxicity. Neutrophils from a patient with chronic granulomatous disease, in the presence of PHA, also killed desialylated red cells normally. On the other hand, desialylation of neutrophils had no effect on the expression of their cytotoxic effect. The results suggest that desialylated red cells are much more susceptible to lectin‐dependent neutrophil cytotoxicity than normal red cells, and that lectin‐dependent neutrophil cytotoxicity is independent of reactive oxygen species.
Cultured animal cells exposed to amino acid analogues or puromycin rapidly synthesize several polypeptides
Authors: Hightower Lawrence E. 
Published: February 2005

AbstractFour major acidic polypeptides, with molecular weights of 88, 72, 71, and 23 thousand, and minor polypeptides with molecular weights of 110, 50, 38, and 30 thousand rapidly accumulated in cultured chick embryo (CE) cells which were exposed for three hours to the arginine analogue canavanine. P110, P88, P71,72, and P23 had unique peptide maps. Evidence of a 27,000 dalton precursor to P23 was obtained. The analogue‐stimulated proteins were not related to another set of inducible avian polypeptides known as the glucose‐regulated proteins. In mammalian cells, the rate of accumulation of several polypeptides, which were similar in size to the avian proteins, sharply increased after canavanine treatment.Proteins with the same electrophoretic mobilities, isoelectric points, and peptide maps as the analogue‐stimulated proteins were expressed at low levels in untreated cultures. To determine the time courses of the canavanine‐mediated increases in protein accumulation and the recovery of protein metabolism after analogue treatment, radioactively labeled proteins were extracted from CE cells and analyzed on SDS‐polyacrylamide gels. In cultures exposed to canavanine, the rates of accumulation of P88 and P71,72 increased from basal to new plateau levels in about 1.5 hours, while P23 required about 2.5 hours. When added with the analogue, actinomycin D and cordycepin blocked the increases in protein accumulation. These inhibitors also blocked the rapid decline in the rates of accumulation of the enhanced proteins which occurred after removal of canavanine. Studies of the metabolic stability of the enhanced proteins indicated that the changes in their accumulation were caused by alterations in their rates of synthesis. Thus, the analogue‐mediated response fulfilled several of the criteria for inducible eucaryotic gene expression.The amino acid analogue p‐fluorophenylalanine and the chain‐terminating analogue of amino acyl‐tRNA puromycin stimulated the synthesis of the same set of proteins induced by canavanine. The enhanced synthesis of these proteins appeared to be a cellular response to either the presence or catabolism of abnormal proteins and puromycyl peptides.
The stimulation of the initiation of DNA synthesis by fibroblast growth factor in swiss 3T3 cells: Interactions with hormones during the pre‐replicative phase
Authors: Richmond K. M. Veronica , Kubler Anne‐Marie , Martin Francisco , De Asua Luis Jimenez 
Published: February 2005

AbstractFibroblast Growth Factor (FGF) stimulates quiescent Swiss 3T3 cells to initiate DNA synthesis and divide. Cells begin to enter the S‐phase after a lag of 13–15 hr, and the rate of initiation of DNA synthesis in the population can be quantified by a first order rate constant, k. A subsaturating concentration of FGF may establish the lag phase, while the value of k is dependent on the FGF concentration present during the second half of the lag phase. Insulin and hydrocortisone enhance the effect of FGF by increasing k without changing the lag phase, and they can act when added at any time after FGF. Prostaglandin E1 (PGE1) causes a decrease in k and a lengthening of the lag phase, and acts only when added during the first 8 hr. None of these agents stimulate DNA synthesis in the absence of FGF.These results show that the stimulation of growth by FGF follows the same basic pattern as was previously shown with Prostaglandin F2α (PGF2α). However, since hydrocortisone inhibits stimulation by PGF2α when added during the first 4 hr of the lag phase, there are clearly differences in some events stimulated by the two growth factors.
Changes in RNA polymerase II in a cell cycle‐specific temperature‐sensitive mutant of hamster cells
Authors: Rossini Mara , Baserga Susan , Huang C. H. , Ingles C. James , Baserga Renato 
Published: February 2005

AbstracttsAF8 cells are a temperature‐sensitive mutant of BHK cells that arrest at the nonpermissive temperature in the G1 phase of the cell cycle. The activity of solubilized RNA polymerase II and its ability to bind [3H]‐γ‐amanitin decrease in tsAF8 cells at 40.6°, with a half‐life of ∼ 10 hr. No appreciable changes occur in these two parameters in tsAF8 cells at 34° or in BHK cells at either 34° or 40.6°. Protein synthesis is not appreciably affected for at least 24 hr after tsAF8 cells are shifted to 40.6°. These results indicate that in tsAF8 cells at the nonpermissive temperature, there is a defect in either the synthesis, the assembly, or the stability of RNA polymerase II, and that the loss of RNA polymerase II molecules is not due to widespread cellular damage.
Relationships between polyamine metabolism and RNA synthesis in post‐ischemic liver cell repair
Authors: Ferioli Maria E. , Schiaffonati Luisa , Scalabrino Giuseppe , Cairo Gaetano , Bernelli‐Zazzera Aldo 
Published: February 2005

AbstractIn liver cells recovering from reversible ischemia the increase in RNA synthesis by isolated nuclei is preceded by activation of ornithine decarboxylase, leading in turn to an increase in putrescine concentration. Treatment of the animals with 1,3‐diaminopropane and putrescine prevents ornithine decarboxylase activation but does not hinder the enhancement of RNA synthesis in post‐ischemic liver nuclei; therefore, ornithine decarboxylase activation does not seem to be a necessary prerequisite for the increase in RNA synthesis. Hypophysectomy does not prevent the post‐ischemic increases of ornithine decarboxylase and RNA synthesis; but pre‐treatment of the animals with cycloheximide—which has a dual effect on the activity of ornithine decarboxylase—abolishes the post‐ischemic enhancement of RNA synthesis. In contrast with regenerating liver, changes in ornithine decarboxylase activity and putrescine concentrations in reversible ischemia are not associated to changes in S‐adenosylmethionine decarboxylase activity and in spermine and spermidine concentrations that seem to be characteristic of tissues where increases in RNA synthesis are followed by DNA synthesis and cell multiplication.
The stimulation by epidermal growth factor (Urogastrone) of the growth of neonatal rat hepatocytes in primary tissue culture and its modulation by serum and associated pancreatic hormones
Authors: Draghi Enrica , Armato Ubaldo , Andreis Paola G. , Mengato Loreta 
Published: February 2005

AbstractEpidermal growth factor (EGF) added in a single dose (between 10–16 and 1.7 ± 10–9M) to neonatal rat hepatocytes in primary culture with subsequent incubation for 12 and 24 hours in Eagle's MEM fortified with 10% (v/v) FBS stimulated their entry into S and M phases, as shown by (3H)thymidine labeling and autoradiography and by a 1‐hour exposure to colchicine (0.1 mM). Growth stimulation by EGF was detectable after 4 hours, peaking between 12 and 16 hours, and thereafter declining in intensity. Rat hepatocytes exposed for 72 hours (between the fourth and the seventh day in vitro) to no serum or to 10% fresh FBS possessed similar growth rates and absolute numbers in the cultures. A 24‐hour exposure to 20 to 50% FBS stimulated hepatocytic DNA synthesis and mitotic activity and resulted (except for the 50% FBS treatment) in increased hepatocytes' numbers, which were relatively greater than the concurrent increases in connective tissue cell numbers. In serum‐devoid medium EGF (10–11M) enhanced hepatocytic mitotic, but not DNA‐synthetic activity. To be fully effective EGF required a 10% FBS addition to the medium, then eliciting within 24 hours a marked increase in hepatocytes' number with respect to cultures incubated with 10% serum only. When associated with 20 to 30% FBS, EGF stimulated parenchymal cell growth at rates slightly higher, but not significantly different, than those elicited by the same serum concentrations alone. However, when used in conjunction with 10 to 30% FBS, EGF preferentially increased the number of hepatocytes rather than that of non‐parenchymal cells. Moreover, comparative proliferation kinetic studies showed that in the presence of 10% FBS, an equimolar (10–14M) mixture of EGF, insulin, and glucagon promoted an early and marked increase in the DNA‐synthetic and mitotic activities of hepatocytes, which peaked after 8 hours. Within a 24‐hour time lag this growth stimulation was as effective in increasing the final hepatocytes' number as was a 1000‐fold higher EGF concentration, and was twice as active as either an equimolar (10–14M) mixture of the two pancreatic hormones or EGF by itself at 10–14M.These results show that the growth‐promoting effect of EGF on primary neonatal rat hepatocytes is modulated by serum factor(s) and can be additively amplified by the simultaneous administration of subphysiological doses of glucagon and insulin.
Maintenance of glucokinase activity in primary hepatocyte cultures
Authors: Spence Joseph T. , Pitot Henry C. 
Published: February 2005

AbstractWhen primary cultures of hepatocytes are maintained for 2 weeks from the time of perfusion, the activity of the enzyme glucokinase decreases rapidly, so that the activity can no longer be detected after the fourth day in culture. Concomitantly, there occurs an increase in the activity of hexokinases, the low‐KM isozymes, which predominate in fetal liver. We have made several modifications of the culture medium in an attempt to prevent the decrease in glucokinase activity. When the medium was supplemented with a mixture of insulin, thyroxine, glucagon, dexamethasone, testosterone, and estradiol, the activity of the enzyme in the hepatocytes was present at approximately 15% of in vivo levels after 2 weeks in culture. When this hormone mixture was present during the first 4 hrs of culture and when the hepatocytes were allowed to attach to the collagen support and were maintained thereafter in medium supplemented with fetal bovine serum, insulin, and dexamethasone, the activity of glucokinase increased after an initial decrease for 3 days and was maintained thereafter at levels comparable to those observed in vivo. This effect of the hormone mixture was found to be the result of the presence of glucagon in the mixture, since the presence of glucagon with no other hormones added, except insulin, during the attachment period produced the same pattern of increased glucokinase activity. Immunoprecipitation of glucokinase from the hepatocytes, using monospecific antibody, indicated that the increase in enzyme activity was the result of increased glucokinase enzyme protein and not an increased synthesis of the other hexokinase isozymes. These studies demonstrate the specific hormonal requirements for the maintenance of glucokinase levels in primary hepatocyte culture at those seen in vivo and lends support to the hypothesis that fetal gene expression in primary hepatocyte cultures is selectively regulated rather than being a general effect with a common regulatory mechanism.
Serum stimulation of potassium fluxes, ouabain binding, and sodium fluxes in quiescent chicken embryo fibroblasts
Authors: Johnson Marcia A. , Weber Michael J. 
Published: February 2005

AbstractGrowth‐contingent alterations in potassium and sodium fluxes, ouabain binding, and potassium ion content were examined following serum stimulation of quiescent, density‐inhibited chicken embryo fibroblasts. Serum stimulation resulted in very rapid 1.5‐ to 1.8‐fold increases in ouabain‐sensitive potassium influx and lesser 1.4‐ to 1.5‐fold increases in potassium efflux and sodium influx. Potassium influx stimulation was maximal after addition of 5–20% calf serum and was unaffected by cycloheximide inhibition of protein synthesis. Reflecting the slightly greater stimulation of potassium influx versus potassium efflux, potassium ion levels were 10–15% higher in serum‐stimulated compared to unstimulated cells. Specific ouabain binding levels in stimulated and unstimulated control cells were initially similar, however, by four hours after stimulation a 40–50% increase in specific ouabain binding was observed. Incubation with ouabain was found also to inhibit later serum‐stimulated hexose uptake and thymidine incorporation; this blockage may be a consequence of subnormal potassium levels rather than ouabain inhibition of the serum‐stimulated potassium influx.
Differences between rat liver epithelial and fibroblast cells in metabolism of purines
Authors: Berman Jules J. , Tong Charles , Williams Gary M. 
Published: February 2005

AbstractEpithelial and fibroblast cells from adult rat liver were found to differ markedly in their metabolism of the purine hypoxanthine. Both cell types took up hypoxanthine and possessed hypoxanthine‐guanine phosphoribosyl transferase for phosphoribosylating the purine. However, in the transferase assay, lysates from epithelial cells converted hypoxanthine predominantly to inosine monophosphate, with small amounts of the nucleoside inosine as product, whereas fibroblast cell lysates converted hypoxanthine predominantly to inosine. The inosine appeared not to be produced by direct ribosylation of the base, since fibroblast cell lysates had less purine nucleoside phosphorylase activity than epithelial cell lysates. Rather, the inosine produced by fibroblast lysates appeared to be derived from inosine monophosphate through catabolism of the mononucleotide by 5′ nucleotidase. An inhibitor of 5′ nucleotidase, thymidine triphosphate, reduced the amount of inosine formed.
Stimulation of macrophage plasminogen activator activity by colony‐stimulating factors
Authors: Hamilton J. A. , Stanley E. R. , Burgess A. W. , Shadduck R. K. 
Published: February 2005

AbstractColony‐stimulating factors (CSFs) stimulate granulocyte‐macrophage production from single hemopoietic progenitor cells. Various preparations of purified CSFs of two different subclasses have been shown here to stimulate a plasminogen‐dependent fibrinolytic (plasminogen activator) activity from resident and starch‐induced mouse peritoneal macrophages. Lymphocyte supernatants also stimulate macrophage plasminogen activator (PA) activitty. Since they contain colony stimulating activity, it is possible that one or more sublcasses of CSF in these supernatants is responsible for this effect. Since both colony‐stimulating and macrophage growth activities have been detected at inflammatory sites, these findings could reflect a role for CSF in inflammatory processes.
On the effect of inhibitors of mitochondrial macromolecular‐synthesizing systems and respiration on the growth of cultured chick embryo cells
Authors: Morais Réjean 
Published: February 2005

AbstractWe have found that chick embryo fibroblasts (DEF) cultivated in the presence of tryptose phosphate broth (TPB) are inherently resistant to the growth inhibitory effect of ethidium bromide (EB). As demonstrated by cytochrome oxidase activity and oxygen consumption measurements, analyses of reduced‐minus‐oxidized cytochrome spectra and electron microscopic observations, TPB did not seem to prevent the inhibitory effect of EB on mitochondrial DNA transcription. EB‐treated chick cell populations cultivated in the presence of TPB behave essentially the same as populations treated with chloramphenicol (CAM) and grow with mitochondria devoid of a functional respiratory chain. In contrast to CAM‐trreated CEF populations, however, the respiratory activity of EB‐treated cell populations did not reappear when the cells were shifted back to EB‐free medium. Attempts to demonstrate that TPB confers resistance to the growth inhibitory effect of carbomycin and mikamycin, inhibitors of the mitochondrial protein‐synthesizing system, have failed, the drugs being cytotoxic at doses where protein synthesis on mitoribosomes is not suppressed. On the other hand, the present results demonstrated that chick cell populations proliferate in the presence of the respiratory inhibitors rotenone, antimycin A, amytal and oligomycin whether or not TPB is present in the growth medium.
Identification of a distinct phase during melanogenesis that is sensitive to extracellular pH and ionic strength
Authors: Laskin Jeffrey D. , Mufson R. Allan , Weinstein I. Bernard , Engelhardt Dean L. 
Published: February 2005

AbstractThe cell line B16/C3 will undergo melanogenesis at a specific time after plating. We have found that this time can be modulated by varying the pH of the culture medium. At high pH levels (8.2–8.6) the onset of melanogenesis occurs in 3 or 4 days, while at lower pH (6.7–7.2) it occurs in 7 or 8 days. Furthermore, the time of onset is also sensitive to the extracellular ionic strength. The addition of sodium lactate, sodium chloride, or any other salt tested delays or blocks completely the onset of melanogenesis. These effects are not simply consequence of growth inhibition, nor can they be correlated with patterns of lactate accumulation.These cells are sensitive to pH or ionic strength after entering the stationary phase just prior to the time of onset of melanogenesis. The existence of a specific pH‐and ionic‐strength‐sensitive phase may provide an important clue to the events responsbile for differentiation in this system.
Paradoxical effects of protein synthesis inhibitors on uridine uptake in cultured cells: Possible role of uncharged tRNA in regulating metabolism
Authors: Martin Thomas F. J. 
Published: February 2005

AbstractPrevious studies (J. Biol. Chem, 253: 99–105, 1978) showed that thyrotropin‐releasing hormone (TRH) acutely stimulated uridine uptake in pituitary cell (GH4C1) cultures. Studies on the role of protein synthesis in this response to TRH led to the finding that an inhibitor of ribosomal translation, cycloheximide, also stimulated uridine uptake acutely. Studies reported here attempt to determine the mechanism of cycloheximide action and whether cycloheximide and hormone stimulation of uridine uptake occurred by similar pathways. The experiments presented indicate that: (1) seven inhibitors of ribosomal translation stimulated uridine uptake; (2) in contrast, inhibition of protein synthesis at tRNA aminoacylation resulted in reduced rates of uridine uptake; (3) inhibition of tRNA aminoacylation blocked cycloheximide but not TRH stimulation of uptake; (4) cycloheximide stimulation of uptake was restricted to amino acid‐depleted cultures; (5) amino acid supplementation stimulated uridine uptake with a time‐course identical to that of cycloheximide; (6) cycloheximide and amino acid supplementation promoted reacylation of cellular tRNAs in amino acid‐depleted cultures; and (7) cycloheximide stimulation of uridine uptake resulted from enhanced nucleoside phosphorylation rather than increased uridine transport. We conclude that cycloheximide and amino acid stimulation of uridine phosphorylation may be mediated through a common pathway involving the extent of amino‐acylation of cellular tRNAs. Furthermore, cycloheximide and TRH stimulate uridine phosphorylation by pathways that are distinguishable. It is apparent that not all cellular effects of cycloheximde can be attributed solely to inhibition of the synthesis of proteins.
Nerve growth factor may stimulate either division or differentiation of cloned C1300 neuroblastoma cells in serum‐free cultures
Authors: Revoltella Roberto P. , Butler Richard H. 
Published: February 2005

AbstractTwo clone of mouse C1300 neuroblastoma cells (clones NB1R and NB6R) bind mouse 2.5S Nerve Growth Factor (NGF) in vitro. The ligand is then capped and internalized by the cells. This step requires active cell processing. In serum‐free or low serum conditions, clear effects of NGF are seen with both clones. Cultured NB1R cells are stimulated, after a lag interval of a few hours, to synthesize DNA and to proliferate, whereas NB6R cells are stimulated to cell differentiation and maintain viability under these conditions much longer than similar cultures in the absence of NGF. Stimulation of clone NB1R occurs within an optimal dose concentration of the same order as that used in the Levi‐Montalcini bioassay with 8‐day‐old chick embryo‐sensitive ganglia; the effects of clone NB6R, however, need higher NGF concentrations. Both effects are protein‐specific since they are inhibited in the presence of added anti‐NGF antibodies. This system could provide a convenient means to study the control of cell division in susceptible malignant neuroblastoma clones and to correlate NGF binding to receptors and biological activity.
Two candidate G1 polypeptides in chick embryo fibroblasts
Authors: Rudert William A. , Graves Mark W. , Chadwick David E. , Lieberman Irving 
Published: February 2005

AbstractResting cultures of primary chick embryo cells have been labeled with 3H‐leucine for the first 2 or 3 hours after feeding basal medium or basal medium supplemented with 10% dialyzed serum. The labeling patterns of the 3H‐polypeptides of the soluble cell fraction have been compared by fluorography of two‐dimensional gels. Large and consistent differences are seen in only three of the more than 900 spots that can visualized. This report concerns two of the three spots. The 3H contents of the two polypeptides (41,000 daltons, pI 7.1, designated 41–7.1, and 34,000 daltons, pI 6.2, designated 34–6.2) are increased by serum by about ten‐fold. The highly selective effect of serum on the labeling of the two spots does not appear to be an artifact related to the extractability, solubility, or state of aggregation of the polypeptides. The radio‐intensities of both polypeptides decrease markedly when the cells are labeled later than 3 hours after “shift‐up”.Drugs that inhibit RNA synthesis and are known to stop the progression of the chick cells through the G1 period, camptothecin, cordycepin and 5,6‐dichloro‐β‐D‐ribofuranosylbenzimidazole, depress, with great specificity, the enhanced labeling of polypeptide 41–7.1 in the stimulated cells, and all but camptothecin have a similar action on polypeptide 34–6.2. A high level of actinomycin D (10 μg/ml), but neither a low level of the drug (0.02 μg/ml) nor 5‐fluorouridine prevents the increased labeling of the two polypeptides in serum‐fed cells. That 5‐fluorouridine enters the chick cells and is converted to its active form is shown by the inhibition of the processing of pre‐ribosomal RNA.The observations with the RNA inhibitors are at least consistent with the conclusions that the enhanced labeling of the two sports results from increased rates of synthesis of the polypeptïdes that depend upon mRNA production but not on the formation of ribosomal RNAs, and that the polypeptides play a role in the regulation of DNA replication in the chick cells.