bluuebunny/crossref_metadata_2025_split huggingface dataset:
Selective utilization of ω 6 and ω 3 polyunsaturated fatty acids by human skin fibroblasts
Authors: Rosenthal Miriam D. , Whitehurst M. Candace 
Published: February 2005

AbstractIncorporation of exogenous [14C] arachidonate by human skin fibroblasts was found to be significantly greater than that of either [14C] linoleate or α‐[14C] linolenate. Arachidonate was preferentially esterified in the PI + PS and PE classes of phospholipids. Over 40% of the incorporated [14C] arachidonate was chain elongated in 24 hours. Cells were also grown in lipid‐free medium to enhance PUFA desaturation and elongation and the utilization of various ω 6 and ω 3 metabolites examined. Whereas [14C] linoleate partitioned approximately 50:50 between PL and TAG, eicosatrienoate (20:3 ω 6) was selectively sequestered in TAG. Arachidonate and docosatetraenoate (22:4 ω 6) were preferentially incorporated into phospholipids; the PI + PS fraction was most highly enriched with arachidonate. Modification of α‐[14C] linolenate was more extensive than that of [14C] linoleate. Docosapentaenoate (22:5 ω 3) was the major ω 3 [14C] PUFA of PI + PS and PE. Eicosapentaeonate was not selectively incorporated into phospholipids; within phospholipids the 20:5 ω 3 was primarily in PC. These results indicate that human skin fibroblasts exhibit acyl specificity in the esterification of polyunsaturated fatty acids, including preferential utilization of arachidonate rather than other prostaglandin precursors in the PI + PS fraction.
Antigen‐specific stimulation of amino acid transport in bovine lymphocytes
Authors: Tate Emily H. 
Published: February 2005

AbstractTreatment of bovine lymphocytes isolated from animals which were either infected with Mycobacterium bovis or sensitized to a purified protein derivative (PPD‐B) from this organism induced an increase in the transport of α‐aminoisobutyric acid (AIB) and α‐methylaminoisobutyric acid (MeAIB). PPD‐B did not stimulate these transport activities in lymphocytes from nonsensitized animals. The transport stimulation was first measurable after about 7 hours of treatment, reached about a two‐fold enhancement after 20 hours, and continued to increase to 30‐ to 40‐fold after 6 days. The stimulation of AIB transport was inhibited by both ouabain and cycloheximide. Experiments to determine transport system specificities in nonstimulated lymphocytes showed that MeAIB transport was primarily by the Na+‐dependent, A‐system, and leucine transport was mostly by Na+‐independent system(s). In contrast, AIB transport was about 25% by the A‐system, 25% by at least one Na+‐dependent, non‐A‐system, and 50% by one or more Na+‐independent system(s). Analysis of the three components of AIB transport after treatment with PPD‐B showed that: (1) transport by both the A‐system and the Na+‐independent system(s) was stimulated; (2) A‐system transport was stimulated to a larger extent than Na+‐independent transport; and (3) Na+‐dependent, non‐A‐system transport was not stimulated significantly.
Enhancement of altered‐cell foci in baby mouse skin cultures by antitubulin treatment: Nuclear mechanisms
Authors: Cooper Peter D. , Marshall Susan A. , Masinello Gillian R. 
Published: February 2005

AbstractWhen primary baby mouse skin (BMS) cultures were subcultured for 48 hours into media containing 10−6 to 10−7 M colchicine or demecolcine, the number of altered cell foci appearing after 3–4 weeks' maintenance at 36°C was substantially enhanced over drug‐free controls. This applied whether or not the primary cultures had been irradiated with white fluorescent light. The additional presence of cytochalasin D and 12‐O‐tetradecanoyl‐phorbol‐l3‐acetate (TPA) sometimes improved and sometimes partly suppressed the enhancing effect of the antitubulin drugs, and these drugs were omitted for reproducible focus enhancement. The enhancement depended on passage through DNA synthesis in presence of colchicine, which did not prevent concurrent or subsequent DNA synthesis but induced a substantial proportion (>33%) to replicate in the tetraploid (4n to 8n) chromosome configuration. Another effect was to induce widespread asymmetric nuclear division, allowing the potential for chromosome loss. All these effects occurred within the first one or few cell cycles after removal of the antitubulin drugs. The results suggest that the generation of tetraploidy perhaps followed by chromosome loss may be an important factor in the rapid induction of altered cell foci. Pre‐existing DNA damage is another important factor.
Mg2+‐sensitive alterations in Ca2+ regulation associated with cell transformation
Authors: Vidair Charles , Rubin Harry 
Published: February 2005

AbstractThe intracellular Ca2+ content of nontransformed Balb/c3T3 cells is two to three times higher than that of a spontaneously transformed derivative. Depriving either cell type of extracellular Mg2+ causes a 2‐ to 3‐fold increase in their Ca2+ content over a 24‐hr period. Restoring Mg2+ to the medium decreases the Ca2+ content of the cells to their original values in about the same time. The increase in Ca2+ content is not blocked by cycloheximide suggesting that normal rates of protein synthesis are not required to produce this effect. Mg2+ deprivation also decreases the initial rate of Ca2+ efflux from the transformed cells and increases the size of the slowly exchanging fraction of Ca2+ to the levels found in the nontransformed cells. Since Mg2+ deprivation normalizes the appearance and growth behavior of the transformed cells, the possible intermediary role of Ca2+ in this normalization was studied. Large changes in extracellular Ca2+ produced large changes in the Ca2+ content of the transformed cells with little change in appearance or thymidine incorporation rate. Ca2+ deprivation did inhibit thymidine incorporation in early passage nontransformed cells; however with repeated passage, this effect decreased, as did the Ca2+ content of these cells. The possible role of Mg2+ in regulating cellular Ca2+ content and distribution is discussed, as is the relation of Ca2+ content and distribution to the development of the transformed state.
Membrane potential and sodium flux in neuroblastoma X glioma hybrid cells: Effects of amiloride and serum
Authors: O'Donnell Martha E. , Villereal Mitchel L. 
Published: February 2005

AbstractThe Na+ uptake into neuroblastoma x glioma hybrid cells was measured in Hepes‐buffered EMEM containing 10% calf serum and 5 mM ouabain in the presence and absence of amiloride (1.0 mM). Amiloride was found to markedly inhibit net Na+ influx (by approximately 50%). Examination of the effect of amiloride on net Na+ influx in the absence of calf serum revealed that a significant amiloride‐sensitive Na+ influx remains even under serum‐deprived conditions, although the degree of amiloride inhibition (35%) is substantially lower than that found in the presence of serum. The amiloride‐insensitive portion of Na+ influx was found to be independent of serum effects. Estimation of resting membrane potential was made by measurement of the steady state distribution of the lipophilic cation, TPP+, in the presence and absence of amiloride. A large, immediate increase in TPP+ uptake, indicative of a membrane hyperpolarization, was seen upon addition of amiloride. Determination of the effect of amiloride on resting membrane potential of serum‐deprived cells showed that cells are hyperpolarized to a greater extent in the presence than in the absense of amiloride, and that serum exerts a depolarizing effect on the cells. Thus, serum‐stimulation of Na+ influx results in a depolarization of resting membrane potential, while amiloride inhibition of Na+ influx causes a hyperpolarization. These data strongly suggest that NG108‐15 cells possess an electrogenic Na+ influx pathway that is sensitive to amiloride inhibition and enhanced by serum.
Hereditary orotic aciduria, Lesch‐Nyhan syndrome, and xeroderma pigmentosum probed by herpes simplex virus: 125I‐Iododeoxycytidine incorporation as an assay for viral growth
Authors: Campisi Judith , Hafner Julianne , Boorstein Robert , Pardee Arthur B. 
Published: February 2005

Abstract125I‐Iododeoxycytidine (125IdC) incorporation into acid‐insoluble material was a sensitive, rapid, and quantitative assay for the growth of herpes simplex virus type 1 (HSV‐1) in human fibroblasts. Cellular utilization of the isotope was 10 to 25% of the incorporation by infected cells and could be 80% inhibited by tetrahydrouridine (THU). Viral utilization was inhibited by acycloguanosine, thioguanine (TG), and cytosine arabinoside. Isotope was incorporated equally well by growing or quiescent infected cells. HSV‐1 was used to probe the metabolic capabilities of three mutant human fibroblast strains. 125IdC incorporation quantitatively measured the ability of the virus to grow in these cells. Viral 125IdC incorporation was sensitive to TG in normal fibroblasts but showed a 8‐ to 10‐fold greater resistance to TG in fibroblasts derived from patients with Lesch‐Nyhan syndrome (LN). Similarly, the growth of ultraviolet irradiated HSV‐1 in normal fibroblasts, as judged by 125IdC incorporation, was 5‐fold greater than in fibroblasts derived from patients with xeroderma pigmentosum. In fibroblasts derived from patients with hereditary orotic aciduria, viral 125IdC incorporation was sensitive to adenosine (AD) at concentrations which were slightly stimulatory in normal fibroblasts. This was a 2‐fold difference in AD sensitivity, which the radioassay reliably and quantitatively documented. Previous attempts to quantify and characterize this difference by immunofluorescence were unsuccessful. HSV‐1 infected cells could be individually identified by their incorporated 125IdC; such cells had blackened nuclei in autoradiograms prepared 12 hr after infection. Normal cells infected in the presence of TG had many fewer labeled nuclei than LN cells similarly infected in the presence of the drug. Thus, this viral assay can be a rapid and accurate probe of cellular function and has potential for the identification of mutant cells in amniocentesis samples or tumor speciments. Towards this end, we determined that the AD and TC dose responses of infected amniotic fluid cells closely paralleled that of the normal human fibroblasts.
DNA synthesis and cell division related to adipose differentiation of 3T3 cells
Authors: Kuri‐Harcuch Walid , Marsch‐Moreno Meytha 
Published: February 2005

AbstractAdipose differentiation of 3T3‐F442A cells in surface cultures depends on adipogenic factor present in the culture medium. We found that after stimulation with adipogenic serum, 3T3T442A cell underwent a burst of DNA synthesis before adipose conversion was manifested by an augmented li‐pogenic enzyme activity. In differentiating cells, DNA synthesis, judged by a 100‐fold higher rate of [3H]thymidine incorporation into TCA‐insoluble material, was followed by a 100‐fold increase in the activity of glycero‐phosphate acyltransferase. Cytosine arabinoside, added to the cultures at a concentration of 3 μg/ml, exerted 95% inhibition of [3H]thymidine incorporation and also inhibited adipose conversion. The burst of DNA synthesis correlated with a 2.5‐fold increase in the amount of DNA and in the number of cells in the culture. The DNA content was the same in differentiated and nondifferentiated cells. We conclude that after the interaction with the adipogenic factor, the cells go through DNA synthesis and cell division essential for adipose conversion.
Tunicamycin inhibits the expression of surface Na+ channels in cultured muscle cells
Authors: Bar‐Sagi Dafna , Prives Joav 
Published: February 2005

AbstractWe have investigated the effect of tunicamycin (TM), an inhibitor of protein glycosylation, on surface Na+ channels in cultured chick skeletal muscle cells. The expression of Na+ channels, estimated by the measurement of batrachotoxin (BTX)‐activated 22Na+ uptake, was found to be significantly diminished after exposure of muscle cells to TM. This effect is partially reversed by the protease inhibitor leupeptin and is associated with a markedly enhanced rate of disappearance of Na+ channels from the surface of TM‐treated cells. Our findings suggest that protein glycosylation contributes to the metabolic stability of voltage‐sensitive Na+ channels.
Analysis of myogenesis by somatic cell hybridization. II. Retention of myogenic competence and suppression of transformed properties in hybrids between differentiation competent and incompetent rat L6 myoblasts
Authors: Lawrence Jeanne Bentley , Coleman John R. 
Published: February 2005

AbstractThis study describes the characteristics of hybrids between two closely related rat myoblast lines, which differ both in the ability to express their program of differentiation and in the expression of neoplastic properties. Myogenic, nonneoplastic L6J1‐S cells were hybridized with nonmyogenic, neoplastic L6J1‐N1 cells. Six hybrid clones were isolated and expanded for analysis of myogenic competence, and four of these clones were also evaluated for parameters of transformation, including tumorigenicity, ability to clone in agar, and surface fibronectin. In addition to our analysis of isolated clones, we also assessed myogenic differentiation in colonies representing 226 early hybrid clones. Results of all these analyses demonstrate that the myogenic phenotype is retained and that the tumorigenic/transformed phenotype is suppressed in the hybrids. Furthermore, our results indicate that when the programs for myogenesis and neoplastic transformation are confronted within a single cell, they are expressed as mutually exclusive alternatives. In contrast to these results on myogenic × nonmyogenic L6 hybrids, it has been reported that isolated clones of A9 × L6 exhibited extinction of myogenic competence and retention of transformed properties. We have evaluated myotube formation in over 300 early hybrid clones between A9 and either diploid or subtetraploid L8 rat myoblasts. Our results demonstrate that all of these hybrid clones exhibit extinction regardless of the ploidy of the myoblast parent, and they further indicate that extinction is not a consequence of chromosome loss. These results support the conclusion that in A9 × L6 hybrids, the nonmyogenic, transformed phenotype is dominant.
RNA turnover in cultured hamster embryo cells: Identification of modified nucleoside end products
Authors: Lothrop Clinton D. , Uziel Mayo 
Published: February 2005

AbstractFourteen methylated nucleosides (N‐2‐dimethylGuo, N‐2‐methylGuo, N‐1‐methylGuo, N‐5‐methylUrd, N‐3‐methylUrd, N‐1‐methylAdo, N‐3‐methylCyd, N‐5‐methylCyd, N‐1‐methyllno, 2′‐0methyl‐Cyd, 2′‐0‐methylUrd, 2′‐0‐methylGuo, 2′‐0‐methyllno, and thymidine) and one methylated base (m7Gua) have been identified as normal excretion products of cultured hamster embryo cells. The methylated nucleosides are excreted in the culture media subsequent to RNA turnover. The excretion pattern of the base‐methylated nucleosides was determined by continuous labeling of serum‐stimulated quiescent hamster embryo cells with [3H‐CH3]methionine and measurement of radioactivity in the excreted nucleosides between 23 and 811/2 hours after the label was added. These nucleosides accumulate exponentially until a maximum level is reached after 60 hours. These maximum levels were maintained for at least an additional 20 hours.
Cultured endothelial cells increase their capacity to synthesize prostacyclin following the formation of a contact inhibited cell monolayer
Authors: Eldor Amiram , Vlodavsky Israel , Hy‐Am Esther , Atzmon Ruth , Weksler Babette B. , Raz Amiram , Fuks Zvi 
Published: February 2005

AbstractThe synthesis of the prostaglandins (PG), prostacyclin (PGI2), PGE2, and thromboxane A2 (TXA2), has been investigated in actively growing and contact‐inhibited bovine aortic endothelial cell cultures. Cells were stimulated to synthesize prostaglandins by exposure to exogenous arachidonic acid or to the endoperoxide PGH2 and by the liberation of endogenous arachidonic acid from cellular lipids with melittin or ionophore A23187. Increased capacity of the cells to synthesize PGI2 and PGE2 was observed as a function of time in culture, regardless of the type of stimulation. TXA2 production increased with time only upon stimulation of the cells with ionophore A23187. This increased PG synthetic capacity was independent of cell density since it was mainly observed in confluent, nondividing endothelial cell cultures. The fact that increased PGI2 production in confluent cells was also observed with PGH2, a direct stimulator of PGI2 synthetase, implies that this process is independent of the arachidonate concentration within the cells or in the culture medium. This increased capacity is likely to reflect an increased activity of the PG synthetase system associated with the formation of a contact inhibited endothelial cell monolayer. A similar time‐dependent increase in the PGI2 production capacity was also observed during growth of cultured bovine corneal endothelial cells.
Treatment of human tumor cells with ADP or ATP yields arrest of growth in the S phase of the cell cycle
Authors: Rapaport Eliezer 
Published: February 2005

AbstractTreatment of a variety of cultured human tumor cells with low levels (40–80 μM) of adenosine 5′‐dephosphate (ADP) or adenosine 5′ ‐triphosphate (ATP) has produced arrest of these cells in the S phase of their cycle followed by cellular death. ADP and ATP are demonstrated to be incorporated into the cellular acid‐soluble nucleotide pools, presumably by permeation through the plasma membrane of these cells. Since AMP, adenosine, 3′,5′ cycle AMP, or a variety of diadenosine polyhosphates do not produce similar cytostatic effects or similar alterations of the cellular acid‐soluble nucleotide pools, we suggest that the effects of ADP and ATP are not due to their prior breakdown or modification. Cultured animal cells have been widely acknowledged not to incroporte acid‐soluble adenine nucleotides although incorporation of exogenous intact nucleoside monophosphate into cellular pools has been demonstrated in a few cases. A 48‐hour treatment of logarithmically growing human tumor cells with 40mUM of ADP or ATP produced substantial arrest of cell populations in the S phase of their cycle and a dramatic reduction in total cellular uridine 5′ ‐triphosphate (UTP) pools. AMP, adenosine, 3′,5′ cyclic AMP, Ap3A, Ap4A or Ap5A produced small and dissimilar effects. The experiments reported here suggest that the plasma membranes of several lines of human tumor cells are premeable to low levels of intact ADP and ATP. The suggestion of en bloc incorporation of low ADP and ATP levels into human tumor cells is supported by the almost identical effects of ADP and ATP on total cellular acid‐soluble nucleotide pools and cellular growth. The rapid conversion of intracellular ADP pools into ATP in tumor cells has been reported.
Analysis of angiotensin‐stimulated sodium transport in cultured smooth muscle cells from rat aorta
Authors: Smith Jeffrey Bingham , Brock Tommy A. 
Published: February 2005

AbstractAngiotensin peptides (AI, AII, AIII) increased the rate of Na+ accumulation by smooth muscle cells (SMC) cultured from rat aorta. The stimulatory effect of All on Na+ uptake was observed which Na+ exodus via the Na+/K+ pump was blocked either by ouabain or by the removal of extracellular K+. All was at least ten times more potent than AIII and about 100 times more potent than AI in stimulating Na+ uptake. Saralasin had little effect on Na+ uptake by itself but almost completely blocked the increase caused by All. The stimulation of net Na+ entry by AI, but not AII, was prevented by protease inhibitors. The stimulation of Na+ uptake was almost completely blocked by amiloride. Tetrodotoxin, which prevented veratridine from increasing Na+ uptake, had no effect on the response to AII. Angiotensin increased the rate of ouabain‐sensitive 86Rb+ uptake (Na+/K+ pump activity) but had no effect on ouabain‐sensitive ATPase activity in frozen‐thawed SMC or in microsomal membranes isolated from cultured SMC. The stimulation of ouabain‐sensitive 86Rb+ uptake by All was blocked by saralasin. Omitting Na+ from the external medium prevented All from increasing 86Rb+ uptake. All had no effect on cell volume or cyclic AMP levels in the cultured SMC. These results suggest that angiotensin peptides activate an amiloride‐sensitive Na+ transporter which supplies the Na+ /K+ pump with more Na+, its rate‐limiting substrate.
Differential calcium dependence of contractile responses and 86Rb efflux from the rabbit aorta induced by vasoactive stimuli
Authors: Martin W. , Gordon J. L. 
Published: February 2005

Abstract86Rb was used to monitor potassium movements in strips of rabbit aorta simultaneously with measurements of tension. Histamine, noradrenaline, the prostaglandin endoperoxide analogue U46619, angiotensin II, and 144 mM K+ each induced an increase in 86Rb efflux concomitantly with contraction. For the first four agonists there was a rank‐order correlation between the contractile response and 86Rb efflux, but 144 mM K+ induced a massive increase in 86Rb efflux although it was the weakest contractile stimulus. Contraction and increase in 86Rb efflux‐induced K+ were both reduced by verapamil, which blocks voltage‐sensitive calcium channels, implying that both effects of K+ were mediated mainly by a depolarisation‐induced influx of calcium. Noradrenaline increased both tension and 86Rb efflux through an action on alpha‐adrenoceptors, but its effect on efflux, unlike its effect on tension, was apparently totally dependent on the presence of extracellular calcium. Experiments performed in the presence of lanthanum, which blocks calcium influx, showed that the intracellular store of calcium released by noradrenaline apparently played no role in inducing 86Rb efflux, although it could trigger contraction. Lanthanum also blocked contraction induced by K+ but less effect on the increase in 86Rb efflux induced by K+. Thus, agonist‐induced vascular contraction and 86Rb efflux can be dissociated, but under normal conditions all the contractile stimuli tested induced 86Rb efflux.
Variables controlling somatomedin production by cultured human fibroblasts
Authors: Clemmons David R. , Shaw Debra S. 
Published: February 2005

AbstractSomatomedin is secreted by multiple types of cultured cells including human fibroblasts. Since the control of somatomedin (Sm) production by fibroblasts may be an important regulatory step in cell division, we undertook studies to define the variables in tissue culture experimental design that may have significant effects on the secretion of Sm. Cell density was an important parameter in determining basal Sm production rates. Cultures plated at 2.5 × 104 cells/well produced 0.38 ± 0.06 U/ml/105 cells whereas an increase in culture density to 6.2 × 104 cells/well was associated with a decrease in Sm production per cell to 0.23 ± 0.04 U/ml/105 cells (P < .01). Cultures stimulated by platelet‐derived growth factor (PDGF) showed a similar reduction in Sm production with increasing cell density. Epidermal growth factor was stimulatory (5.4‐fold increase) in low‐density cultures but had no effect when high‐density cultures were used. If the experiments were initiated between 2 and 4 days after the last media change there were no significant differences in basal or PDGF‐stimulated Sm concentrations. Between days 5 and 9 however, there was a progressive increase in the basal Sm production rate. The duration of incubation was an important variable since Sm production increased during the first 12 h in noncycling cells and showed an accelerated increase between 4 and 8 h in cycling cells. Cells between the eighth and 12th passage had similar basal Sm production (0.22 ± 0.04 U/ml/105 cells) rates; cells between the 19th and 20th passages had significantly higher basal Sm production rates (0.41 ± 0.05 U/ml/105 cells) (P < .01). These results suggest that several variables, particularly cell density and passage number, are critical variables when quantitating the effect of hormones and growth factors on Sm production by cultured fibroblasts.