bluuebunny/crossref_metadata_2025_split huggingface dataset:
Differential effects of hydrocortisone on both growth and collagen metabolism of human fibroblasts from normal and keloid tissue
Authors: Russell James D. , Russell Shirley B. , Trupin Kathryn M. 
Published: February 2005

AbstractCultured fibroblasts isolated from normal and keloid tissue do not differ in their growth characteristics or in the rate of collagen synthesis under routine culture conditions. The addition of hydrocortisone to the culture media results in significant differences in both growth and collagen synthesis between these cell types. Collagen syntehsis is inhibited 60% in normal cultures by hydrocortisone (0.5 μg/ml) and the population size at which density‐dependent growth inhibition is achieved is increased. Keloid‐derived fibroblasts grow to a lower maximum density in the presence of hydrocortisone, while their rate of collagen syntehsis is not significantly reduced. The rate of non‐collagen protein synthesis is increased significantly by hydrocortisone in both cell types.Comparison of normal and keloid‐derived cultures obtained from a single individual suggests that the keloid phenotype with respect to both growth and collagen synthesis is restricted to the fibroblasts isolated from the keloid nodule.
Osmotic properties of ehrlich ascites tumor cells during the cell cycle
Authors: Dupre Ann M. , Hempling H. G. 
Published: February 2005

AbstractEhrlich ascites tumor cells were grown and maintained in continuous spinner culture. The population of dividing cells was synchronized by a double thymidine block technique. Cell cycle phases were determined graphically by plotting mitotic index, cell number, and DNA synthesis against time. Changes in the osmotic properties of Ehrlich ascites tumor cells during the cell cycle are described. Permeability to water is highest at the initiation of S and progressively decreases to its lowest value just after mitosis. Heats of activation for water permeability vary during the cell cycle, ranging from 9–14 kcal/mole. Results may imply changes in the state of water in the membrane during the cycle. The volume of osmotically active cell water is highest during S and early G2 and decreases during the mitotic phase, as cells undergo division. Total water content remains stable at 82% (w/w) during the cycle. Total concentration of the three major ions (Na, K, Cl), expressed as mEq/liter total cell volume, does not change. The fraction of total cell water which is osmotically active (Ponder's R) decreased gradually from 0.75 at S to about 0.56 following mitosis. Findings suggest that a fraction of the total water within the cell exists in a “bound” form and is, therefore, incapable of being shifted under the driving force of osmotic pressure. This fraction of bound water increases during the cell cycle. Possible alterations in membrane fluidity and the state of water in the cell are discussed.
Regulation of dihydrofolate reductase gene expression in mouse fibroblasts during the transition from the resting to growing state
Authors: Johnson Lee F. , Fuhrman Carolyn L. , Wiedemann Leanne M. 
Published: February 2005

AbstractThe rate of accumulation of dihydrofolate reductase (DHFR) was studied in resting, growing and serum stimulated mouse 3T6 fibroblasts by first exposing the cells briefly to 10−6 M methotrexate (MTX) to inactivate specifically and irreversibly the pre‐existing enzyme, then determining the rate of recovery of reductase activity after removal of MTX. DHFR activity was quantitated by measuring the ability of a cell extract to reduce 3H‐folic acid or to bind 3H‐MTX. In all cases, recovery of enzyme activity was inhibited by cyclo‐heximide, indicating that the recovery was due to de novo synthesis of reductase.We found that the rate of accumulation of DHFR was high in exponentially growing cells, as expected, but about 40‐fold lower in resting (G0) 3T6 cells. When resting 3T6 cells were induced to re‐enter the cell cycle following serum stimulation, we found that the rate of accumulation of DHFR increased sharply about ten hours after serum stimulation. DNA replication also began at this time. When resting cells were serum stimulated in the presence of inhibitors of DNA synthesis (hydroxyurea or cytosine arabinoside), the increase in DHFR synthesis was the same as in control stimulated cells. This indicates a lack of tight coupling between DNA synthesis and reductase gene expression. The increase in DHFR accumulation was inhibited by Actinomycin D (5 μg/ml) if the drug was added 7.5 hours after stimulation, but was not inhibited if the drug was added 15 hours after stimulation. This is consistent with the idea that DHFR gene expression is regulated at the level of transcription, and that reductase mRNA is transcribed only between 7.5 and 15 hours following stimulation.
Increased ouabain‐sensitive glycolysis of lymphocytes treated with phytohemagglutinin: Relationship to potassium transport
Authors: Segel George B. , Androphy Elliot J. , Lichtman Marshall A. 
Published: February 2005

AbstractAn early increase in lymphocyte plasma membrane K+ transport is essential for PHA stimulated lymphocytes to divide. Little is known about the specific source and amount of energy required to support the increased transport by activated lymphocytes. Since ouabain, a cardiac glycoside, specifically inhibits the transport ATPase, we have measured the decrement in glycolysis and tricarboxylic acid cycle activity when untreated and PHA treated lymphocytes were exposed to ouabain. This metabolic decrement represents the portion of metabolism associated with monovalent cation transport and closely related processes. Since TCA cycle activity accounted for only 0.2% of glucose consumption, aerobic glycolysis was the major source of energy, i.e., ATP, for increased transport. Approximately one‐third of the total lactate production in both control and PHA stimulated lymphocytes was ouabain‐sensitive. Ouabain sensitive lactate production in control, 105 μmol/1010 cells/hour, increased 1.8‐fold to 193 μmol/1010 cells/hour after PHA treatment. Active K+ influx in similar cell populations increased from 40 μmol/1010 cells/hour to 74 μmol/1010 cells/hour (1.9‐fold) after PHA treatment. The increment in ouabain‐sensitive energy production and K+ transport were closely correlated and, therefore, 0.38 moles of K+ are transported for each mole of ATP generated in both control and PHA treated cells. The increased requirement for transport related energy is provided by increasing the ouabain‐sensitive ATP production rather than altering the efficiency of ATP transduction.
Coordinate control of balb/c3T3 cell survival and multiplication by serum or calcium pyrophosphate complexes
Authors: Rubin A. Harry , Bowen‐Pope Daniel F. 
Published: February 2005

AbstractBalb/c3T3 cells in crowded cultures detach from the dish when deprived of serum, and the survivors incorporate 3H‐thymidine at a reduced rate. The detachment becomes pronounced two hours after removal of serum, and reaches its maximum rate between two and four hours. Cells in sparse culture are not detached by serum removal, and their rate of 3H‐thymidine incorporation is only slightly reduced. As the sparse cultures grow into more crowded cultures, and the serum is depleted, increasing numbers detach. The detached cells are incapable of reattaching when placed in a new dish with ample fresh serum. The cells are leaky to cellular constituents and appear to be dead. Detachment is a consequence rather than the cause of cell death, and can be produced by agents which inhibit cellular energy metabolism. The cells on the dish which survive serum deprivation are fully viable and grow rapidly when serum is added. When they become crowded they are as sensitive to serum deprivation as was the original population. They are therefore not selected for a low serum requirement but apparently survive because they spread into the space vacated by the detaching cells and then behave as sparse cultures in response to serum variations. Insoluble complexes of Ca2+ and pyrophosphate (Ca2+‐PPi) show the same concentration dependence in promoting cell survival as in stimulating 3H‐thymidine incorporation, showing that a single substance can be responsible for both activities. It is concluded that survival and growth are part of the coordinate response of 3T3 cells to single external effectors. The results are discussed in terms of a simple model in which the coordinate response is regulated by the availability of Mg2+ for transphosphorylation reactions within the cell, and the availability depends on the binding affinity of cellular membranes for Mg2+. The difference between survival and multiplication is postulated to be in the intensity and duration rather than the kind of stimulus.
Potassium‐sodium distribution in human lymphocytes: Description by the association‐induction hypothesis
Authors: Negendank William , Shaller Calvin 
Published: February 2005

AbstractHuman lymphocytes were equilibrated for 48 hours over a wide range of external potassium levels, and their contents of potassium, sodium, and water determined. As external potassium rose from zero, cell potassium rose steeply in a sigmoidal fashion, reached half‐saturation at 0.4 mM external potassium, and then saturated at 129 mmoles/kg cells. The saturable cell potassium exchanged mole‐for‐mole with sodium. Analysis of the saturable components by a statistical‐mechanical adsorption model demonstrated a cooperative interaction between sites determining equilibrium potassium‐sodium distribution. Superimposed upon the saturable fraction of cell potassium was a smaller one that was non‐saturable with increasing external potassium to at least 64 mM, and that, when expressed as mmoles/liter cell water, existed in a ratio to external potassium of 0.6. The results strongly support the association‐induction hypothesis, which predicts a small non‐saturable component of ions determined by exclusion from oriented cell water and a cooperative interaction between sites throughout the cell that associate with potassium or sodium.
Binding of Salmonella minnesota R‐form glycolipid mR595 to rat fibroblasts and its effect on cell metabolism and cell behaviour
Authors: Lallier Réal , Trudel Michel , Brailovsky Carlos A. , Nigam Vijai N. 
Published: February 2005

AbstractTrypsinized normal rat embryo fibroblasts and untrypsinized and trypsinized transformed rat fibroblasts have two orders of binding sites for bacterial glycolipid mR595. The high order sites fix 1–3 μg glycolipid mR595/105 cells and those of the low order fix about 6 μg glycolipid mR595/106 cells. Ca++ is required for the low order glycolipid mR595 binding to be trypsinized but not to the untrypsinized transformed rat fibroblasts. The low order binding but not to the untrypsinized transformed rat fibroblasts. The low order binding is temperature dependent with the transition temperature lying between 25 and 37°C. Exogenously added ganglioside and glycoproteins contained in the fetal calf serum do not inhibit fixation of glycolipid mR595. Only β‐lipoprotein at high concentrations is slightly inhibitory.Glycolipid mR595 fixation to transformed fibroblast does not alter their morphology and appears to slightly improve cell attachment to substratum. Glycolipid mR595 fixation results in a lengthening of the S‐phase of the cell cycle and a reduction in 2‐deoxyglucose uptake. Uptake of inorganic phosphate is not affected. Inhibition of phospholipid synthesis is observed in mR595 fixed fibroblasts whereas synthesis of cell surface glycoproteins and the content of cellular gangliosides is not affected.
Studies on intercellular adhesion. III. Adhesion of cells to isotypic or heterotypic collecting particles and monolayers
Authors: Pessac Bernard , Girard Arlette , Alliot Françoise 
Published: February 2005

AbstractAdhesion between cells of different tissues from chick embryos was studied by the modified collecting particle (Pessac et al., 1977a) and stationary monolayer assays. These assays measure the number of 3H labeled cells that adhere to the surface of cell aggregates and tissue fragments or on top of cell monolayers. The numbers of cells from a given suspension that adhere to identical or different cells can be compared. Intercellular adhesion may be considered as tissue specific if, in identical conditions, more cells adhere to identical cells than to cells from different tissues. Neural retina, cerebrum, optic tectum, liver and kidney cells from 9‐day‐old chick embryos showed no tissue specificity of adhesion, while heart cells adhered preferentially to collecting heart fragments.
Evidence for a high molecular weight factor(s) in serum which increases alkaline phosphatase specific activity in HeLa
Authors: Carlson Charles W. 
Published: February 2005

AbstractHeLa (substrain Ho) grown in serum free medium showed an increase in the specific activity of alkaline phosphatase when fetal calf serum (10%) was added to the medium (9.7 nmoles/sec/mg protein to 86.8). Under the same conditions, eight intracellular enzymes showed no increase in activity. Similar results were obtained using a different serum or medium, and with a second strain of HeLa (substrain ATC).For a given set of growth conditions, the effect of serum was dependent on its concentration and required one or more culture generations to develop. The type of isozyme expressed did not change. Neither zinc nor a total serum lipid extract would substitute for serum. The enzyme expressed by HeLaHo was not induced by prednisolone, while that in HeLaATC was. However, for cells grown in excess prednisolone without serum, the specific activity was 25% of that found for cells grown with prednisolone and serum. Cortexolone, an antagonist of prednisolone, was without effect for HeLaHo grown in A3 medium with or without serum.The serum factor had the following characteristics. It was not lost on dialysis, treatment with DNase and RNase, or removal of lipoproteins. It was reduced after heating by 65% and after treatment with Pronase by 82%.The data are interpreted to indicate the presence of a factor (s) in serum, probably a protein, which is involved in stimulating alkaline phosphatase specific activity.
Metabolic correction of fucosidosis fibroblasts by human α‐L‐fucosidase
Authors: Turner Bryan M. , Turner Virginia S. , Hirschhorn Kurt 
Published: February 2005

AbstractHuman α‐L‐fucosidase, purified from placenta, was taken up from the culture medium by skin fibroblasts from patients with fucosidosis (α‐L‐fucosidase deficiency). The rate of uptake was low (uptake coefficient = 6 × 10−4 ml.mg−1.h−1). Intracellular α‐L‐fucosidase activity was directly proportional to enzyme in the medium up to an activity of at least 40 nmoles/min/ml. No evidence for saturation of specific cell‐surface receptors was seen. However, uptake was reduced by 75% by 1 mM mannose‐6‐phosphate and by 50% by 1 mM glucose‐6‐phosphate, suggesting that uptake may be mediated by a receptor recognising a phosphorylated sugar or an analagous compound. Enzyme taken up by the cells was most active in subcellular fractions enriched with lysosomes and had an isozyme pattern, by isoelectric focusing, identical to that of the original enzyme preparation.Fucosidosis fibroblasts were shown to accumulate low molecular‐weight, fucose‐containing compounds to a level several times greater than control cells. This stored material was eluted from Sephadex G‐25 as an asymmetrical peak with an elution volume of approximately twice the void volume of the column. Addition of placental α‐L‐fucosidase to the culture medium of fucosidosis fibroblasts prevented excessive accumulation of fucose‐containing material and accelerated the breakdown of material accumulated prior to enzyme uptake.
The accumulation of manganese from the environmental medium by the egg of Oryzias latipes
Authors: Michibata H. , Hori R. 
Published: February 2005

AbstractThe manganese content of the egg and embryo of the Medaka, Oryzias latipes was determined by activation analysis. A remarkable increase in the amount of manganese in the egg was observed within one hour after fertilization. The rate of increase was reduced by the gastrula stage and the concentration of manganese remained unchanged at a later stage. The accumulation of manganese by the Oryzias egg was discussed in relation to the effect of manganese on respiratory enzyme systems.
Amino acid transport in chick embryo fibroblasts: Evidence for transcriptional regulation of transport following serum addition
Authors: Borghetti Angelo F. , Tramacere Mariarosaria , Piedimonte Giuseppe , Guidotti Guido G. 
Published: February 2005

AbstractChanges in amino acid transport activity by system A (a Na+‐dependent agency with affinity for a discrete group of neutral amino acids) caused by the addition of serum to serum‐deprived cultured chick embryo fibroblasts have been evaluated by measurements of 14C‐labeled L‐proline and α‐methylaminoisobutyric acid uptake under conditions approaching initial entry rates. Dialysed serum was as effective as undialysed serum in stimulating amino acid transport. This effect was inhibited by 7 μM cycloheximide, by 80 nM actinomycin D and by 40 μM cordycepin, but not by 0.3 mM cytosine arabinoside. Cultured avian fibroblasts previously incubated in a cycloheximide‐containing medium (phase of inhibited translation) in the presence of serum, subsequently exhibited a net increase of proline transport activity when transferred to a medium containing actinomycin D (phase of inhibited transcription). Omission of serum in the cycloheximide‐phase prevented the increase of transport activity during subsequent incubation in the actinomycin D‐phase; omission of serum in the actinomycin D‐phase allowed a shorter and less pronounced increase of transport activity than in the presence of serum. Additions of actinomycin D or cycloheximide slightly increased the rate of decay of amino acid transport caused by serum withdrawal. These observations suggest that in cultured avian fibroblasts, serum modulates the activity of transport system A by a mechanism acting at the transcription level.
Effects of angiotensin II and angiotensin II antagonist saralasin on cell growth and renin in 3T3 and SV3T3 cells
Authors: Schelling Pierre , Ganten Detlev , Speck Georg , Fischer Hans 
Published: February 2005

AbstractComponents of the renin‐angiotensin system were studied in established cell culture lines of 3T3 and SV3T3 mouse fibroblasts. The renin content in 3T3 cells was significantly higher than in virus‐transformed SV3T3 cells. With time after infection, renin decreased in Simian virus 40 transformed cells, while it increased steadily in mock‐infected 3T3 cells. In contrast to renin, angiotensinase activity was higher in SV3T3 cells.Angiotensin II stimulated cell proliferation in 3T3 mouse fibroblasts and decreased their renin content in a dose‐related manner. In contrast, saralasin, an angiotensin receptor antagonist, inhibited cell growth in 3T3 and SV3T3 cells and caused an increase of cellular renin concentration. The angiotensin fragments angiotensin (2–8) heptapeptide and angiotensin (4–8) pentapeptide had no effect on cell growth. A significant negative correlation was found between cell proliferation and renin levels in 3T3 and SV3T3 cells irrespective of the treatment.Our results indicate (1) that angiotensin II may be involved in cell growth regulation, (2) that a negative feedback exists between angiotensin II added and intracellular renin content, and (3) that virus infection causes a decrease in intracellular renin synthesis, while non‐specific angiotensinase activity is increased under this condition.
Evidence suggesting that a cyclic AMP‐dependent protein kinase is a positive regulator of proliferation in Cloudman S91 melanoma cells
Authors: Pawelek John M. 
Published: February 2005

AbstractWild‐type Cloudman S91 melanoma cells have a retarded rate of division when agents which raise cyclic AMP levels such as melanotropin, protaglandin E1, or cholera toxin are supplemented to the culture medium. A mutant cell line was isolated which had the opposite response, i.e., the mutant grew very slowly unless agents which raised cyclic AMP levels were present (Pawelek et al., '75a). In this report evidence is presented indicating that the molecular basis for the mutant phenotype resides in the major cyclic AMP‐dependent protein kinase found in the cells. The mutant kinase had increased thermolability and an elevated activation constant for cyclic AMP over the corresponding wild‐type kinase. It is proposed that the elevated requirement for cyclic AMP for the proliferation of cAdep cells is related to the elevated activation constant of this kinase, suggesting that the kinase is a positive regulator of proliferation in Cloudman S91 cells.
Electrophysiology of differentiating mouse spermatozoa
Authors: McGrady Angels 
Published: February 2005

AbstractThe morphological aspects of spermatogenesis are well described in many mammalian species, but functional changes are not completely understood. Electrophysiological parameters were investigated in primary spermatocytes and early and late spermatids isolated from the seminiferous tubules of the mouse. Substantial changes were not detected in membrane potential between different developmental stages. Membrane potential was dependent on both potassium and sodium ion concentration gradients, but not on chloride gradients. The ratio of the permeabilities PNa/PK varied according to the extracellular concentrations of sodium and potassium. Ouabain, a specific inhibitor of Na+, K+‐activated ATPase, produced a maximal reduction in membrane potential of 20% Comparisons were drawn between differentiating germ cells and previously determined properties of mature spermatozoa.
Alterations in chloride transport during differentiation of Friend virus‐transformed cells
Authors: Harper Patricia A. , Knauf Philip A. 
Published: February 2005

AbstractFriend erythroleukemic cells can be induced by a variety of agents to synthesize hemoglobin and to exhibit other characteristics suggesting erythroid maturation. Upon induction of hemoglobin synthesis with dimethyl‐sulfoxide (DMSO), the chloride flux in Friend cells gradually increases, until after five days of exposure to DMSO (when the hemoglobin content of the cells approaches that of the mature erythrocyte) the flux is three times the value in non‐induced cells. A similar flux increase is observed in the presence of a different type of inducer, hypoxanthine, but no increase in flux is seen in the mutant cell line, TG‐13, which does not synthesize hemoglobin after DMSO treatment. Thus, the flux increase seems to be associated with the induction process, rather than being a direct effect of the inducing agent. After DMSO treatment, the sulphate flux decreases and the chloride/sulphate selectivity increases, as would be expected if the cells were becoming more like red cells. On the other hand, the sensitivity of the chloride flux to the inhibitor, furosemide, and to temperature is the same in the induced as in the non‐induced Friend cells, and different from that of the mature red cell. Thus, the anion transport properties of the induced Friend cell are different from those of both the non‐induced Friend cell and the mature erythrocyte. Either the system in the induced cell represents an intermediate stage in the development of the mature red cell characteristics, or else the maturation of transport function in the Friend cell differs from that in normal erythrocyte precursors.