bluuebunny/crossref_metadata_2025_split huggingface dataset:
Growth‐promoting actions of extracts from mouse submaxillary glands on human endothelial cells in culture
Authors: Johnson Alice R. , Boyden Nit Ton , Wilson Carol M. 
Published: February 2005

AbstractExtracts of submaxillary glands from two different strains of inbred mice were mitogenic for human endothelial cells in culture. The mitogenic activity of extracts from glands of males of the SWR/J and C57BL/10J strains were equivalent, and the growth stimulating effect was unrelated to renin or esteroproteolytic activity. Mitogenic activity in extracts from SWR/J females was less than that from males, and extracts from C57BL/10J females were inactive. The polypeptide growth factors, epidermal (EGF) and fibroblast (FGF) growth factors, also stimulated replication of endothelial cells. Cells from either umbilical arteries or veins responded to submaxillary extracts, EGF, or FGF with a similar increase in cell number, increase in protein and enhanced uptake of 3H‐thymidine. The proliferative response was associated with decreased activity of angiotensin I converting enzyme which is localized on the endothelial surface. Nerve growth factor (NGF) was not mitogenic for endothelial cells. Extracts of submaxillary glands from male mice of either strain contained approximately 20 times more EGF than extracts from females, as determined by immunodiffusion. Mitogenic activity of the extracts was completely inhibited by antiserum to EGF, suggesting that the active component of these preparations is EGF.
An X‐ray microanalysis survey of the concentration of elements in the cytoplasm of different mammalian cell types
Authors: Cameron Ivan L. , Pool Thomas B. , Smith Nancy K. R. 
Published: February 2005

AbstractElectron probe energy dispersive X‐ray microanalysis was performed on freeze‐dried tissue sections. The dry weight concentration of elements (mmole/kg dry weight) was measured in the cytoplasm of several cell types from adult mice and rats. This comparative investigation showed: (1) That the energy dispersive X‐ray spectrum of element concentration from the cytoplasm of a specific cell type allows one to distinguish this specific cell type from other cell types with considerable accuracy. (2) That there is a relationship between the concentration of the various elements and the ultrastructural features of the cytoplasmic regions being analyzed. For example, areas rich in ribosomes are also rich in P, K and Mg. (3) These data support the idea that K is directly involved in the control of protein synthesis. The catalog of element concentrations in the cytoplasm of 13 cell types from both mice and rats should be of value to others who seek to answer various questions about these cell types.
Protein synthesis in transformed 3T3 cells permeabilized by exogenous ATP
Authors: Kitagawa Takayuki 
Published: February 2005

AbstractExogenous ATP has been shown to cause a rapid and reversible increase in permeability in transformed 3T3 cells (3T6 and SV3T3) but not in untransformed 3T3 cells. The cells remain viable, but lose intracellular acid‐soluble pools. Treatment of transformed cells with ATP greatly reduces incorporation of 14C‐leucine into protein, which is restored by the incubation of the cells with Dulbecco's modified Eagle's medium or by the external additions of certain ions and energy sources. tRNA is not required for the restoration of protein synthesis. In the permeabilized cells the energy for protein synthesis can be provided by glycolysis, oxidative phosphorylation, or direct addition of ATP. These studies demonstrate the usefulness of this method for studying the control of metabolism and macromolecular synthesis in monolayer cultures of transformed mammalian cells.
Concanavalin A induces an intraluminal alkalinization of thymocyte membrane vesicles
Authors: Mikkelsen Ross B. , Schmidt‐Ullrich Rupert , Wallach Donald F. H. 
Published: February 2005

AbstractWeak acid distribution methods demonstrate that mitogenic levels of concanavalin A induce an intravesicular alkalinization of isolated thymocyte membrane vesicles. Experiments with chemical reagents that crosslink the high affinity concanavalin A receptor and extensive correlation with known cellular events suggest that a “membrane Bohr effect” may participate in the initiation of mitogenesis.
Formation of low molecular weight RNA species in HeLa cells
Authors: Eliceiri George L. 
Published: February 2005

AbstractIt has been previously shown that newly synthesized nuclear low molecular weight RNA species C and D are first detected in the cytoplasm for a few minutes before they are finally found in the nucleus. The following are some of the observations made in the present study, regarding the formation of C and D RNA: (1) The 5′ end cap ribose methylation of the C RNA precursor is complete in its cytoplasmic stage; the internal ribose methylation of the precursor seems to be completed about the time of its apparent transition from cytoplasm to nucleus. (2) The few nucleotides lost from the D RNA precursor during maturation seem to be excised sometime near its apparent cytoplasmic → nuclear transition. Newly synthesized C RNA also appears to lose some of its non‐conserved nucleotides about the time of that transition, while the other extra nucleotides are lost later, in the nucleus. (3) The maturation of C and D RNA is inhibited early during suppression of protein synthesis by cycloheximide, while their synthesis is not. (4) The cytoplasmic precursors of C and D RNA are not associated with ribonucleoprotein particles as large as those reported for mature C and D RNA, although they do not appear to be free in the cytoplasm. (5) When the cellular UTP pool is depleted by exposure of the cells to amino sugars, and the synthesis of C, D, and other RNA species decreases, the level of[3H]uridine labeling of C and D RNA increases, while that of 4 S and 5 S RNA does not. These data are compatible with the existence of more than one nuclear UTP pool.
Changes in the cell cycle during culture of mouse‐Chinese hamster cell hybrids
Authors: Graves Jennifer A. Marshall , Koschel Kenneth W. 
Published: February 2005

AbstractCell cycle studies, using PLM analysis, were carried out on a mouse‐Chinese hamster cell hybrid and its derivatives which stably retained all parental chromosomes during the year of study. Parameter estimates were obtained from the PLM curves, using conjugate gradient curve fitting procedures. The hybrid initially grew very slowly, and all phases (especially G1) were longer than those of either parent. During propagation, mean generation time decreased progressively, and the phase times approached those of the mouse parent (which had the longer G1 and S). DNA replication could be scored separately in mouse and hamster chromosome sets; initially termination was highly asynchronous, but during growth asynchrony was progressively reduced as DNA synthesis in the hamster set was prolonged.We conclude that cell hybrids may undergo progressive modifications of the cell cycle, even in the absence of significant chromosome segregation, and suggest that such changes may at least partly account for the great variety of relationships between the growth rates and phase times of parent and hybrid cells which have been reported. Because of the complexity of these changes in the cycles of interspecific cell hybrids, we believe that somatic cell genetic analysis of the regulation of the cell cycle would be more usefully applied to intraspecific hybrids whose parents differ in only one specific cycle characteristic.
Fetal hemoglobin synthesis in culture of early erythroid precursors (BFU‐E) from the blood of normal adults
Authors: Vainchenker William , Dubart Anne , Bouguet Jacqueline , Testa Ugo , Tsapis Andréas , Tonthat Hoi , Henri Annie , Monplaisir Nicole , Beuzard Yves , Rochant Henri , Rosa Jean 
Published: February 2005

AbstractBFU‐E from the blood of 14 normal adults have been grown by the plasma clot technique. The hemoglobins synthesized in burst colonies were purified from other proteins by affinity chromatography on Sepharose‐haptoglobin. The radioactivity incorporated in the globin chains was estimated by CM‐cellulose chromatography in urea. The number of bursts scored at the 14th day of culture fluctuated between 50‐130 (average 86, s: 29) for 106 mononuclear plated cells. A constant reactivation of fetal hemoglobin was found (from 1.4% to 11%, mean value 5.8%, s: 3.07), but was lower than previously described, mainly because of the highly selective purification of Hb. This reactivation of fetal hemoglobin was not dependent upon the concentration of erythropoietin (from 1 U/ml to 6 U/ml) nor on the purity of the erythropoietin preparations (from 6 U/mg of protein to 70 000U/mg of protein). In addition, the same subject exhibited a constant proportion of Hb F synthesized in culture over a period of time up to 6 months. A positive correlation exists between the proportion of Hb F in culture and that of F cells present in the blood, with the exception of two subjects. Such findings suggest that Hb F in culture is a characteristic of each individual and that this reactivation often represents an amplification of the Hb F synthesis in vivo.
Pactamycin resistance in CHO cells: Morphological changes induced by the drug in the wild‐type and mutant cells
Authors: Gupta Radhey S. , Siminovitch Louis 
Published: February 2005

AbstractStable mutants resistant to pactamycin (PacR), a polypeptide chain initiation inhibitor, have been selected in a single step in Chinese hamster ovary (CHO) cells. The sensitivity of protein synthesis in mutant cell extracts to pactamycin indicates that resistance involves an alteration in the permeability of this drug. The failure of PacR mutants to show cross‐resistance to other compounds provides further indication that the lesion is presumably specific for pactamycin. Cell hybrids formed between PacR × PacS lines show intermediate sensitivity towards pactamycin, suggesting that the PacR lesion behaves codominantly under these conditions. In the presence of subinhibitory concentrations of pactamycin, CHO cells, which are normally short, polygonal and disoriented, became greatly elongated and aligned themselves in parallel fashion to produce highly oriented colony morphologies, reminiscent of normal diploid fibroblasts. This effect of pactamycin on cellular morphology was seen much more clearly with the PacR mutants, although somewhat higher concentrations of the drug were required to produce this change.
Secretion and partial degradation of granulocyte‐macrophage colony‐stimulating factor (GM‐CSF) of mouse L‐P3 cells
Authors: Tsuneoka K. , Shikita M. 
Published: February 2005

AbstractSecretion of a granulocyte‐macrophage colony‐stimulating factor (GM‐CSF) was accomplished by L‐P3 cells in culture with a serum‐free medium. Cell proliferation per se was not requisite for the production of GM‐CSF; the cells continued secreting GM‐CSF even after their growth had been suspended. The amount of GM‐CSF accumulated in the conditioned medium was reasonably accounted by the daily rate of production, and the addition of a proteinase inhibitor such as leupeptin and pepstatin did not result in greater accumulation of GM‐CSF in the culture. It is thus postulated that there is no significant proteolytic inactivation of the secreted GM‐CSF in the culture. However, when partially purified GM‐CSF preparation was chromatographed on a gel‐filtration column in the presence of 0.1% Triton X‐100, a derivative of the GM‐CSF was yielded which had been diminished in the molecular weight and altered in the isoelectric point. On the other hand, when leupeptin was included in the solution during production and isolation of the factor, the yielded GM‐CSF did not manifest such a detergent‐induced transformation and maintained its isoelectric point at pH 3.5. It is thus assumed that, in the presence of the detergent, GM‐CSF suffers deterioration by an endogenous proteinase and releases a sialoglycopeptide fragment without loosing its colony‐stimulating activity.
A study of metabolic cooperation with rat peritoneal macrophages
Authors: Kane A. B. , Bols N. C. 
Published: February 2005

AbstractRat peritoneal macrophages were studied for their ability to undergo metabolic cooperation. Macrophages were unable to cooperate with human fibroblasts. This was true for macrophages which had been activated in vivo as well as for macrophages treated with various agents in vitro. Macrophages were also unable to undergo metabolic cooperation with rat fibroblasts or with other macrophages. In contrast, rat reticular cells, mesothelial cells, and fibroblasts were able to cooperate with human fibroblasts.
Fibronectin from aged fibroblasts is defective in promoting cellular adhesion
Authors: Chandrasekhar Srinivasan , Millis Albert J. T. 
Published: February 2005

AbstractLate passage fibroblasts show decreased cell‐substrate adhesion. We provide evidence that the reduced adhesion is due to a defect in the adhesive glycoprotein fibronectin. Late passage cells become more adhesive in culture media that has been conditioned by the growth of early passage cells. Analysis of fibronectins purified from early and late passage cell conditioned media indicates that there are striking differences in their abilities to promote cell adhesion. Young cell fibronectin supports the maximal adhesion of both young and old cells. However, old cells require quantitatively more fibronectin. In contrast, old cell fibronectin is less effective in supporting the adhesion of either cell type. In addition, neither cell type achieves a normal morphology in the presence of old cell fibronectin. The results support the conclusion that the fibronectin released by late passage cells is defective and does not support normal cell‐substrate interactions.
A critical temperature transition of K+‐Na+ exchange in human lymphocytes
Authors: Negendank William , Shaller Calvin 
Published: February 2005

AbstractHuman lymphocytes were equilibrated for 48 hours at 5‐6 mM K+ex over a range of temperatures between 0 and 37°C, and at 5°C over a range of external K+ levels between 0 and 32 mM. Cell K+ and Na+ contents are normal between 37 and 10′. Below 10′ there is a critical thermal transition in ion contents centering around 3°C. This and the steep sigmoidal isotherms of K+ and Na+ at 5°C confirm the cooperative nature of ion exchange. At 0′, cell K+ is maintained at a concentration that is seven to eight times that of the external medium. Isotopic K+ influx shows smaller, rapidly‐exchanging, and larger, slowly‐exchanging fractions. The latter, which correspond to the saturable, sigmoidal components of cell K+, are slowed by decreasing temperature. Although there is a critical temperature transition of K+‐Na+ exchange, there is no corresponding transition for isotopic K+ exchange, which has an activation energy of 11.6 kcal/mole. The combined ion content and flux data are readily understood by reference to two major concepts of the association‐induction hypothesis: that of rapid solute exclusion from cell water existing in a state of polarized multilayers, and that of solute accumulation limited by adsorption onto and desorption from fixed anionic sites that interact with one another in a critical, cooperative fashion.
Hormonal regulation of amino acid transport and cAMP production in monolayer cultures of rat hepatocytes
Authors: Kelley Darshan S. , Shull James D. , Potter Van R. 
Published: February 2005

AbstractThe effects of insulin, glucagon or Dexamethasone (DEX) and of glucagon with insulin or DEX were examined on the uptake of 2‐amino [1‐14C]isobutyric acid (AIB) and N‐Methyl‐2‐amino [1‐14C]isobutyric acid (NMe AIB) in monolayer cultures of rat hepatocytes. Insulin and glucagon stimulated the uptake of both the amino acids and DEX inhibited it, showing that all three of these hormones regulate the A system (the sodium‐dependent system that permits the transport of NMe AIB) for amino acid transport in these cultures. Experiments investigating the transport of aminocyclopentane‐1‐carboxylic acid, 1‐ [carboxyl‐14C] in the presence of excess AIB or in the absence of sodium showed that insulin had no effect on the activity of the L system (the sodium‐independent system that prefers leucine). Experiments on the uptake of AIB in the presence of excess NMe AIB showed insulin had no effect on the transport activity of the ASC system (the sodium‐dependent system that does not transport NEe AIB). Insulin concentrations ranging from 0.1 nM to 100 nM did not antagonize the stimulatory effect of optimum or suboptimum concentrations of glucagon on the uptake of either AIB or NMe AIB. Similarly, glucagon did not antagonize the stimulatory effect of optimum or suboptimum concentrations of insulin on the uptake of both the amino acids. The combined effect of insulin and glucagon was additive on the rate as well as the cumulative uptake of both AIB and NMe AIB. DEX alone inhibited the transport of both AIB and NMe AIB by about 25%, while glucagon caused a 2–3‐fold increase; however, the addition of glucagon to cultures containing DEX caused a 7–8‐fold increase in the uptake of both AIB and NMe AIB when compared to cultures containing DEX alone. The effect of insulin on the levels of cAMP was also investigated. Insulin had no effect on the cAMP levels in cultures treated or untreated with optimum or suboptimum concentrations of glucagon.
The regulation of RNA metabolism in suspended and reattached anchorage‐dependent 3T6 fibroblasts
Authors: Benecke Bernd‐Joachim , Ben‐Ze'ev Avri , Penman Sheldon 
Published: February 2005

AbstractSuspending anchorage‐depent fibroblasts in methocel results in marked reduction in a number of macromolecular metabolic processes. These are restored when cells make contact with a solid substrate and are allowed to spread. The response of 3T6 cells to suspension culture and their recovery upon reattachment has been extensively studied. (Benecke et al., '78; Farmer et al., '78). In these cells, message production and its turnover rate both drop abruptly when cells are suspended, while protein synthesis declines very slowly but extensively. Recovery of protein synthesis in 3T6 cells only requires surface contact and not cell spreading and proceeds rapidly, reaching control values within a few hours. The recovery of messenger RNA production in spread cells is much slower, and commences about 18 hours after cells are replated.The present report extends the studies on RNA regulation in suspended and reattached 3T6 fibroblasts. All RNA synthesis systems respond to cell suspension. Production of small nuclear RNA species is shown to behave very similarly to the production of messenger RNA, suggesting these may be coordinately regulated. Ribosomal precursor RNA synthesis ceases promptly upon cell suspension and recovers only slowly after reattachment. The control of ribosome formation appears independent of the regulation of protein synthesis in this system. The products of polymerase III including transfer RNA, 5S RNA, and species K and L are all regulated together and show a distinct pattern of behavior unlike that of any other RNA species. Their formation is rapidly inhibited at the beginning of suspension, but then recovers to the level of control cells, even during continued suspension culture. This unusual property of polymerase III RNA species is quite different from the behavior of the small nuclear (snRNA) RNA species, which strengthens the previous suggestion that these two classes of RNA molecules are formed by different mechanisms and regulated independently.
Mitochondrial protein synthesis in chinese hamster cells (line CHO) synchronized by isoleucine deprivation
Authors: Ley K. D. 
Published: February 2005

AbstractMitochondrial protein synthesis was measured in line CHO cells after phases of the cell cycle were synchronized by isoleucine deprivation or mitotic selection. Maximum incorporation of [3H] leucine into mitochondrial polypeptides occurred within 2 hours after isoleucine was added to initiate G1 traverse. In cells synchronized in G1 by mitotic selection, the rate of mitochondrial protein synthesis was fairly constant throughout the cell cycle. SDS‐polyacrylamide gel electrophoretic profiles of labeled mitochondrial polypeptides were similar in cells synchronized by either isoleucine deprivation or mitotic selection. Obvious changes in the distribution of polypeptides were not detected during various phases of the cell cycle. The increased rate of incorporation of [3H] leucine into mitochondrial polypeptides after reversal of G1‐arrest may indicate that mitochondrial protein synthesis and possibly mitochondrial biogenesis are synchronized in CHO cells deprived of isoleucine.
Nature of permeability changes in membrane of HeLa cells adsorbing sendai virus
Authors: Fuchs Pinchas , Gruber Eva , Gitelman Janina , Kohn Alexander 
Published: February 2005

AbstractAdsorption of Sendai virus to HeLa cells induced in them an increased permeability to K+, Na+, Ca++, deoxyglucose, but not to fluorescein. The stimulation of uptake of 42K was temperature‐dependent, did not occur below 15°C, and was not inhibited by ouabain.The virus‐induced increase in the uptake and release of 42K and of 3H deoxyglucose could not be mimicked by treatment of cells with linoleic acid, a procedure which increased the fluidity of the cellular membranes. The stimulatory effect of 0.5 mM ATP on the release of deoxyglucose was enhanced several fold in the presence of Sendai virus. These results seem to indicate the possible involvement of membranal enzymes such as e.g. protein kinase in the permeability changes induced by Sendai virus.
Electron probe analysis of cultured vascular smooth muscle
Authors: James‐Kracke M. R. , Sloane B. F. , Shuman H. , Karp R. , Somlyo A. P. 
Published: February 2005

AbstractMitochondrial and cytoplasmic composition were determined with electron probe analysis in freeze‐dried guinea pig aortic smooth muscle cells cultured on stainless steel grids. The mitochondrial calcium content in normal cells was low: not significantly different from that detected in the cytoplasm. Mitochondrial calcium granules were found in less than 3% of the cells, and in these the cytoplasmic K/Na ratio was reduced, indicating that they were damaged. There were no major differences between the cytoplasmic concentrations of K, Cl, Ca, Mg, and S of cultured cells and those previously found in adult vascular smooth muscle (Somlyo et al. '79). There was no evidence of nuclear Na or Ca sequestration in cultured cells, and the transmitochondrial Na, Cl, and K gradients were small.Attempts to selectively remove adhering, extracellular ions with a 2‐second wash with isotonic ammonium acetate were unsuccessful because they were accompanied by loss of cell K.
Age‐related decrease in repair of oxidative damage to surface sulfhydryl groups on rat adipocytes
Authors: Hughes B. A. , Roth G. S. , Pitha J. 
Published: February 2005

AbstractAdipocytes were isolated from the Wistar and Sprague‐Dawley strains of rats of different ages. An impermeable reagent, mercury‐[3H] dextran, was used to quantitate the sulfhydryl groups on the surface of these cells. The application of this reagent after the pre‐reduction of cells with 2‐mercaptoethanol yielded a measure of the total sulfhydryl and disulfide groups located there. Aging was found to significantly decrease the ratio of the number of exofacial sulfhydryl groups to the total number of exofacial sulfhydryl and disulfide groups.