bluuebunny/crossref_metadata_2025_split huggingface dataset:
Enhancement of chemotactic response and microtubule assembly in human leukocytes by ascorbic acid
Authors: Boxer Laurence A. , Vanderbilt Burton , Bonsib Stephen , Jersild Ralph , Yang Hsin‐Hsin , Baehner Robert L. 
Published: February 2005

AbstractThe incubation of human leukocytes with ascorbic acid increased chemotaxis of the cells. In addition, ascorbic acid promoted the assembly of intracellular polymorphonuclear leukocyte (PMN) microtubules as assessed by transmission electron microscopy. Prior incubation of the PMN with colchicine blocked the effect of ascorbic acid on promoting microtubule assembly. Not only did ascorbic acid promote the assembly of microtubules in vivo, but it enhanced the assembly of bovine brain tubulin into microtubules in vitro as quantitated by a glass‐fiber filtration assay and by promotion of viscosity changes. The enhancement in leukocyte mobility by ascorbate at concentrations achievable in normal tissues correlates with its ability to assemble microtubule organelles.
Plasma membrane phosphoproteins in normal and Rous sarcoma virus transformed chick embryo fibroblasts: Characterization by in vitro phosphorylation
Authors: Branton Philip E. , Landry‐Magnan Johanne 
Published: February 2005

AbstractPlasma membranes isolated from normal and RSV transformed chick embryo fibroblasts were phosphorylated in vitro using endogenous protein kinase and ATP (γ32P) and the labeled phosphoproteins were analyzed by SDS‐PAGE. A number of protein phosphorylation changes were observed following transformation, however in most cases they were relatively small quantitative differences. The four major changes were in proteins of 47,000, 58,000, 75,000 and 135,000 daltons. Decreased phosphorylation of the 47,000 dalton polypeptide was found in transformed cell membranes but this alteration was shown to be due to differences in cell growth rather than transformation. Increased phosphorylation of the 75,000 dalton protein was at least partially related to virus infection. However, increased phosphorylation of the 58,000 and 135,000 dalton polypeptides were entirely transformation specific.
Involvement of glutathione in the inhibition of sea urchin egg mitosis by phenyl glyoxal
Authors: Amy Christopher M. , Rebhun Lionel I. 
Published: February 2005

AbstractCell division in fertilized sea urchin eggs was reversibly inhibited when the ketoaldehyde phenyl glyoxal (PG) at a concentration of 0.1 mM was added to eggs for ten minutes prior to the formation of the mitotic spindle. We investigated whether inhibition of mitosis was due to PG binding to the cell surface (as previously suggested by Stein and Berestecky, '74) or to some intracellular effect. When 14C‐PG was added to eggs, label was readily taken up into the egg cytoplasm; very little label was associated with the egg surface. In the cytoplasm PG combined with equimolar amounts of reduced glutathione (GSH), decreasing the levels of cellular GSH to less than 15% of normal and accounting for at least 50% of the PG taken up by eggs. The concentrations of oxidized and protein‐bound glutathione were unaffected by PG treatment. We showed that glyoxalase enzymes were present in sea urchin eggs and were capable of metabolizing the PG‐GSH complex, thereby restoring GSH to normal levels after PG was removed from the sea water. Though some other effect of PG cannot be ruled out, the major fate of PG in eggs was to combine with GSH, and the transient decrease in GSH which resulted could lead to inhibition of mitosis. While other reports (Nath and Rebhun, '76; Oliver et al., '76) have shown that reagents which oxidize GSH disrupt microtubule‐related events, our results showed that such inhibition could be caused by decreased GSH levels alone.
Effect of serum on prostaglandin production during the co‐culture of human thyroid cells and peripheral blood mononuclear cells
Authors: Herman E. A. , Yamamoto M. , Rapoport B. 
Published: February 2005

AbstractProstaglandin generation by human peripheral blood mononuclear cells is enhanced during co‐culture with human thyroid cells. The objective of the present study was to determine the influence of various sera on this process.Human thyroid adenoma cell monolayers were cultured with normal human peripheral blood mononuclear cells for three days in the presence of a variety of sera, or serum fractions. Prostaglandin E (PGE) in the medium was measured by bioassay or by radioimmunoassay. Significantly more PGE was generated in cultures containing fetal calf serum than in those containing human serum. This difference was not abolished by dialysis of the human serum. When the 50% (NH4) 2SO4 precipitate of the serum was used, PGE generation was similar to that in fetal calf serum, indicating the presence of an inhibitory factor in human serum. The degree of this inhibitory activity was similar in autologous and heterologous human serum, as well as in normal subjects and patients with Graves' disease. Gel filtration and ion‐exchange chomatography of human serum showed the inhibitor to co‐migrate with albumin. Evidence presented suggests that the inhibitor is not albumin itself but is, instead, a factor tightly bound to albumin. Inhibitory activity was also found in rabbit, goat, rat and cow serum.Prostaglandins are potent modulators of immune‐cell function. These data indicate that this process may be modulated by a factor in mammalian serum. The relative absence of this factor in fetal serum may have important implications in regard to the profound changes which occur in the immune system after birth.
Studies on the mechanism of Ca2+ stimulation of plasminogen activator synthesis/release by swiss 3T3 cells
Authors: Chou Iih‐Nan (George) , Cox Robert , Black Paul H. 
Published: February 2005

AbstractStimulation of postconfluent Swiss 3T3 cells in serum‐free medium with 4.3 mM Ca2+ results in marked increases in both released and cell‐associated plasminogen activator (PA). Increased release of PA commenced approximately 10 to 12 hours post‐stimulation and continued to increase steadily until 48 hours at which time the stimulated cells (4.3 mM Ca2+) released approximately 14 times more PA than control cells (1.8 mM Ca2+). Sr2+, like Ca2+, also stimulates PA synthesis/release either in the presence or in the absence of 1.8 mM Ca2+ whereas an excess of Mg2+ inhibits Ca2+ stimulation. Supranormal [Pi] in the medium stimulates PA synthesis/release in the presence of 1.8 mM Ca2+. Further, optimal stimulation by 4.3 mM Ca2+ requires a normal level of Pi (1.0 mM). Elevation of medium [Ca2+] or [Pi] results in an enhanced uptake of Ca2+. The facts that cycloheximide treatment completely abolishes the Ca2+ stimulatory effect and that an increase in cell associated PA precedes release indicate that PA release is coupled to synthesis of new PA. Ca2+ stimulation of PA synthesis/release also requires continuous energy production and RNA as well as protein synthesis. A hypothesis is proposed to explain the relationship between stimulation of PA production and its enhanced release from cells stimulated by elevated [Ca2+] or [Pi] in the media. The possibility that PA release may be an example of the phenomenon of membrane shedding as opposed to secretion is discussed.
Effects of low electrolyte media on salt loss and hemolysis of mammalian red blood cells
Authors: Zeidler R. B. , Kim H. D. 
Published: February 2005

AbstractCation loss and hemolysis of various mammalian red cells suspended in isotonic non‐electrolyte media were investigated. Sucrose buffered with 10 mM Tris‐Hepes, pH 7.4 was used as the non‐permeable non‐electrolyte. Mammals from which the red cells were derived include the human, guinea pig, rat, rabbit, newborn calf, newborn piglet and pig, all of which contain K as the predominant cation species (HK type) and the dog, cat, sheep and cow, all of which possess Na as the predominant cation species (LK type). Of HK cells, a rapid efflux of K takes place from humans, rats and guinea pigs. Of LK type cells, the dog and cat exhibit an augmented membrane permeability to Na. The governing factors which influence cation permeability are the change in pH, temperature, and ionic strength. In response to increase in pH, the red cells of humans, dogs and cats become more permeable to cations, whereas the red cells of rat and rabbit are unaffected. In response to increase in temperature, HK type cells exhibit augmented K efflux, while the Na loss from the dog and cat cells manifest a well‐defined maximum at near 37°C. In all cases, a small substitution of sucrose by an equal number of osmoles of salts results in a dramatic decrease in cation loss. By contrast, the red cells of the rabbit, newborn calf, adult cow, newborn piglet, adult pig and sheep display no discernible increase in ion‐permeability under the conditions alluded to above. In some species including the newborn calf, dog and cat, an extensive hemolysis occurs usually within an hour in isotonic buffered sucrose solution. The osmolarity of sucrose solution affects these cells differently in that as the osmolarity increases from 200‐500 mM, hemolytic rates of the calf and dog reach a saturation near 300 mM sucrose, whereas the hemolytic rate of the cat decreases progressively. Common features pertaining to this hemolysis are (1) the intracellular alkalinization process; and (2) the diminution of the cell volume which take place prior to and onset of hemolysis. SITS, a potent anion transport inhibitor, completely protects the cells from hemolysis by inhibiting chloride flux and the concomitant rise in intracellular pH.
Somatic cell hybrids between totipotent mouse teratocarcinoma and rat hepatoma cells
Authors: Litwack Gerald , Croce Carlo M. 
Published: February 2005

AbstractWe have produced somatic cell hybrids between totipotent mouse teratocarcinoma cells and rat hepatoma cells. These hybrids were tested for the expression of liver specific functions expressed in the hepatoma cell parent and for their ability to differentiate when injected into nude mice. The results of this study indicate that hybrid cell clones do not resemble either of the parental cells, since they do not produce albumin and tyrosine aminotransferase that are expressed in the rat hepatoma parent, and are incapable of forming either teratocarcinoma or hepatomas when injected in experimental animals.
Potassium fluxes and ouabain binding in growing, density‐inhibited and rous sarcoma virus‐transformed chicken embryo cells
Authors: Johnson Marcia A. , Weber Michael J. 
Published: February 2005

AbstractPotassium fluxes, ouabain binding, and Na+ and K+ intracellular concentrations were determined for cultures of growing normal, density‐inhibited and Rous sarcoma virus‐transformed chicken embryo fibroblasts. No significant differences in K+ influx or ouabain binding were detected between growing normal cells and Rous sarcoma virus‐transformed cells; however, ouabain binding and ouabain‐sensitive K+ influx were 1.5‐ to 1.8‐fold lower in density‐inhibited cells. Thus, potassium influx in this system can be classified as a growth‐related, but not transformation‐specific change. As determined by both flame photometry and radioisotopic (42K) equilibration, growing normal and density‐inhibited cells had similar potassium contents, whereas transformed cells exhibited 1.4‐fold higher potassium levels. Sodium ion levels, as measured by flame photometry, were also 2‐ to 4.5‐fold higher in transformed than normal or density‐inhibited cells. Complementary studies of potassium efflux showed a 1.3‐ to 1.5‐fold higher rate (based on the percentage of pool exiting the cell) in growing normal versus density‐inhibited or transformed fibroblasts. Because of the larger potassium pool in transformed cells, efflux based on absolute number of potassium ions is similar in normal and transformed chicken embryo fibroblasts.
Studies on the penetration of mammalian cells by deoxyribonucleoside‐5′‐phosphates
Authors: Waqar M. Anwar , Taber Robert L. , Huberman Joel A. 
Published: February 2005

AbstractWe have tested the ability of [5′‐32P]‐deoxyribonucleoside monophosphates (dNMPs) to penetrate living mouse fibroblast L cells and human HeLa cells. Under the conditions of our experiments, small numbers of apparently intact dNMP molecules appeared to penetrate into the interior of L cells and be incorporated into DNA. This incorporation was not due to mycoplasma contamination nor to extracellular hydrolysis of the dNMPs followed by resynthesis inside the cell. Under these same conditions, penetration of HeLa cells by intact dNMPs did not occur to a significant extent. However, HeLa cells were capable of hydrolyzing extracellular dNMPs to Pi and deoxyribonucleosides at a much faster rate than L cells.These experiments provide a starting point for attempts to specifically label the DNA in intact, living eukaryotic cells with [32P]‐dNMPs.
Reversible inactivation of autosomal alleles in chinese hamster cells
Authors: Bradley W. E. C. 
Published: February 2005

AbstractEvidence is presented which suggests that a CHO‐derived thymidine kinase (Tk) heterozygote, ts201, can reversibly inactivate the wild type Tk allele, and that this event may result in simultaneous inactivation of a linked allele, galactokinase (Glk). The clone ts201 was isolated as a revertant of a stable Tk− 5‐bromodeoxyuridine (BrdU)‐resistant mutant of CHO. The reacquired Tk activity differed from that of the wild type with respect to Km and heat resistance, supporting the contention that ts201 was genetically heterozygous (Tk+/−). At frequencies varying from 0.02–0.5, segregants of ts201 could be isolated by cloning in BrdU at 39°. These derivatives were phenotypically Tk− (by enzymology and by autoradiography of 3H‐dT labeled cells), but after removal of BrdU, reacquired the Tk+ phenotype at frequencies varying randomly from clone to clone. From mutagenized populations of Ts201 two variants were isolated, 71t and 72c, by selection at 39° in 2‐deoxygalactose (2‐dgal). Resistance to 2‐dgal has been correlated with a mutation in the gene for Glk, which is syntenic with that for Tk and evidence is presented suggesting that 71t and 72c are Glk+/−. Cloning efficiencies in doubly selective media and autoradiographic data showed that at 39° a coordination existed between the levels of Tk and Glk, which in 71t was inverse, and in 72c, direct. These data led to the hypothesis that pairs of linked alleles can be inactivated or re‐expressed simultaneously. The inactivating effect was temperature‐sensitive, since at 33°, the cloning efficiency in BrdU and in 2‐dgal was very low.
DNA synthesis: Evaluation of a hydrodynamic method for measuring the rate of replication fork movement
Authors: Richter Andrea , Hand Roger 
Published: February 2005

AbstractWhen replicating DNA is labeled sequentially with radioactive and density tracers and analyzed by equilibrium centrifugation, the fraction banding at heavier than normal density is inversely proportional to the rate of replication fork movement if there is a sharp transition from one tracer to the other on the newly synthesized chains (Painter and Schaefer, '69). Primate CV‐1 DNA labeled for 5 to 30 minutes with 3H‐dThd and then for three hours with BrdUrd in the presence of FdUrd bands in a bimodal distribution in alkaline CsCl, rather than in a continuous distribution with a skew toward heavier density seen when FdUrd is omitted and centrifugation is in neutral CsCl. The heavy density peak represents interspersion of both tracers in the DNA and is caused by slow transition from dThd to BrdUrd incorporation when the tracers are switched in the labeling medium. This may result from preferential uptake and incorporation of dThd over BrdUrd. Because of the interspersion, calculation of the rate of replication fork movement is inaccurate. Reversal of the labeling sequence with administration of the long density pulse before the radioactive pulse reduces the problem of interspersion. Using this sequence of labeling, estimates of the rate of fork movement of 0.36–0.38 μm/min are obtained when the 3H pulse time is long enough to allow accurate measurement of the fraction of heavy DNA. Analysis by fiber autoradiography yields a rate of 0.56 μm/min in the same cell line. If appropriate precautions are taken to minimize mixing of the two tracers in the precursor pool and to ensure that the fraction of heavy DNA is measured accurately, the hydrodynamic technique provides an objective method of measuring rate of fork movement that gives values only slightly lower than those obtained by autoradiography.
Phenotypic characterization of ouabain‐resistant Aedes albopictus cells
Authors: Mento Steven J. , Malinoski Frank , Stollar Victor 
Published: February 2005

AbstractThe phenotype of a ouabain‐resistant Aedes albopictus cell line has been partially characterized. Treatment of ouabain‐sensitive cells with 0.005–1.0 mM ouabain resulted in an 80% reduction in the uptake of 86rubidium (86Rb+), an ion with an affinity for the K+ pump binding site; ouabain‐resistant cells showed only a 40% reduction with 1.0 mM ouabain. When ouabain‐sensitive cells were incubated in the presence of ouabain (0.1 mM) for one and one‐half to three hours, the molar ratio of intracellular Na+/K+ rose from 0.2 to 4.2. In ouabain‐resistant cells, a similar treatment had very little effect. Based on [3H] ouabain‐binding studies, ouabain‐resistant cells were estimated to have 60% fewer binding sites per cell than ouabain‐sensitive cells. The spontaneous mutation rate from ouabain sensitivity to ouabain resistance was calculated to be 1–6 X 10−8 mutations/cell/generation, a value similar to that reported for mammalian cells at the analogous locus.
Serum of lipopolysacharide‐treated mice contains two types of colony‐stimulating factor, separable by affinity chromatography
Authors: Staber F. G. , Burgess A. W. 
Published: February 2005

AbstractSerum from mice traated with bacterial lipopolysaccharide (LPS) was fractionated by Con A‐Sepharose affinity chromatography, and assayed in vitro for colony‐stimulating factor (CSF) using mouse bone marrow cells. The CSF failing to bind to concanavalin A‐Sepharose (pool A) had similar biological properties to the unfractionated serum, i.e., it stimulated the formation of about equal numbers of granulocytic, mixed granulocyte‐macrophage and macrophage colonies. The fraction eluted from the Con A‐Sepharose column with α‐methyl‐D‐glucopyranoside (pool B) had a steeper dose‐response curve than either the unfractionated serum or the pool A CSF and most of the colonies were composed of macrophages. A mixture of the pool A and pool B CSFs stimulated colonies in a similar way as unfractionated serum and pool A. The apparent molecular weights of the two types of CSF were determined by two different gel‐filtration procedures. Sephacryl S‐200 gel‐filtration suggested an apparent molecular weight of 85,000 for pool A CSF and 180,000 for pool B CSF. Gel‐filtration on Sepharose CL‐6B in the presence of guanidine hydrochloride (6M) yielded an apparent molecular weight of approximately 23,000 for pool A CSF and 33,000 for pool B CSF. The colony‐forming cells (CFC) responding to pool B CSF were found to have a relatively high sedimentation velocity (peak sedimentation velocity 5.6–6.2 mm/hr) compared to the CFC responding to mouse‐lung conditioned medium (MLCM) whose peak sedimentation velocity was between 4.0–4.5 mm/hour. The CFC responding to pool A CSF had an intermediate sedimentation velocity (peak 4.6–5.2 mm/hour). A time‐course analysis of the morphology of clones or colonies in cultures stimulated with either MLCM or pool B CSF showed that the proporation of different colony types depends significantly on the incubation period and suggested that pool B CSF induced an early commitment of CFC towards macrophage differentiation.
Transcriptional activity of nuclei from WI‐38 cells at various passages
Authors: Nose Kiyoshi , Okamoto Hiroshi 
Published: February 2005

AbstractTranscriptional activity of nuclei from human diploid fibroblast (WI‐38) cells at different passage levels was studied with endogenous RNA polymerase. The rate and extent of the RNA synthesis decreased when the nuclei were were prepared from senescent cells. The decreased activity of RNA synthesis in senescent cell nuclei was demonstrated from both the transcriptional assay and the estimation of the processing activity, i.e., polyadenylation of the transcripts.
Effect of phagocytosis on guinea pig granulocyte membrane markers
Authors: Smolen James E. , Karnovsky Manfred L. 
Published: February 2005

AbstractThe internalization of membrane markers during phagocytosis was followed in guinea pig granulocytes as a function of the extent of particle ingestion. The plasmalemma was carefully labeled with diazotized 35S‐sulfanilate, or by treatment with periodate and sodium 3H‐borohydride. These treatments provided general membrane markers. More specific markers used were 5′‐nucleotidase, neuraminidase‐releasable membrane sialate, and concanavalin A binding sites. In all cases except the last, internalization of membrane was directly determined on isolated phagosomes; disappearance of binding sites from the cell surface was followed in the last instance. Both phagosomal levels and disappearance from the surface were measured in the case of 5′‐nucleotidase, permitting balance studies. Phagocytosis was determined as uptake of paraffin emulsions labeled with Oil‐Red 0. “Marker/particle” ratios were determined as the percent external marker internalized per mg paraffin ingested.The “marker/particle” ratios for cells with chemically labeled membranes were considered to reflect random internalization of membrane entities. Colchicine had no effect on those ratios. Internalization of 5′‐nucleotidase and neuraminidase‐releasable sialate gave “marker/particle” ratios similar to those of the random markers, and these increased in the presence of colchicine. Concanavalin A binding sites did not appear to be removed from the cell surface in the absence of colchicine, but disappearance was observed in its presence. Control experiments indicated that these changes due to colchicine must be very cautiously interpreted. Our results differ from those obtained by others, and the reasons due to species, cell type, experimental design, etc. are discussed. Maximal particle uptake was computed to require internalization of one‐fifth to one‐third of the total external membrane of the cells—based on the assumption of random internalization of markers.