bluuebunny/crossref_metadata_2025_split huggingface dataset:
Satellite DNA in differentiating chick tissues
Authors: Ayres Kathleen Nelson 
Published: February 2005

AbstractEmbryonic chick DNA from different tissues was examined for differences which might indicate specific DNA amplification in somatic cells. The problem was approached by determining the DNA compositional heterogeneity and searching for possible variation in different tissues of the 12‐day chick. Neural retina, muscle, and whole decapitated (general) chick DNA were analyzed in CsCl and Cs2SO4 density gradients. While overloaded CsCl gradients showed a main band (ρ = 1.701 g/cm3) and a heavy shoulder (ρ = 1.716 g/cm3), overloaded Cs2SO4 gradients displayed a main band (ρ = 1.426 g/cm3) and a discrete heavy satellite (ρ = 1.447 g/cm3) This satellite, comprising approximately 1% of the whole cell DNA, appeared to be of nuclear origin and not related to mitochondrial DNA, which was found to have a density of 1.426 g/cm3 in Cs2SO4. No differences were found in the densities of the main band or the satellite DNA in the DNA samples isolated from the different tissues. However, the method of DNA isolation was found to be of crucial importance when comparing satellite DNA's among different tissues.
Factors influencing endothelial cell proliferation in vitro
Authors: Wall Robert T. , Harker Laurence A. , Quadracci Leonard J. , Striker Gary E. 
Published: February 2005

AbstractThe relative roles of blood cell products and plasma factors on endothelial cell proliferation were evaluated by studying the proliferative response of human umbilical vein endothelial cells to cell free plasma derived serum (CFPDS), whole blood serum (WBS), platelet released factors, fibroblast growth factor and macrophage conditioned medium in vitro. Human adult arterial smooth muscle cells were treated in a similar manner for comparison. The rate of endothelial cell proliferation was directly related to the concentrations of both WBS and CFPDS. Growth rate in WBS was marginally greater than that observed in CFPDS during early culture, however, similar confluent densities were achieved. The addition of platelet released factors to CFPDS did not further stimulate endothelial cell proliferation. In contrast smooth muscle cells were quiescent in CFPDS despite increasing serum concentrations, but proliferated actively in response to platelet released factors. Both human macrophage conditioned medium and fibroblast growth factor increased endothelial cell proliferation significantly when compared with CFPDS alone. It is concluded that endothelial cell proliferation in preconfluent cultures is dependent on plasma factors while human vascular smooth muscle cells also require cell derived mitogens such as platelet growth factor to proliferate. The release of a substance by human macrophages mitogenic for endothelial cells may be involved in endothelial cell proliferation in vivo.
Dna replication in human lymphocytes during aging
Authors: Agarwal Shyam S. , Tuffner Margaret , Loeb Lawrence A. 
Published: February 2005

AbstractAn analysis of the accuracy of protein and DNA synthesis in human lymphocytes with respect to aging has been carried out. The response of human peripheral lymphocytes, from young and old adults, to phytohemagglutinin was measured at varying temperatures. This should provide a sensitive test for the accumulation of altered thermolabile proteins that are rate limiting in the response to phytohemagglutinin. At 37°C the rate of thymidine incorporation as well as the induction of DNA polymerase in phytohemagglutinin‐stimulated lymphocytes from old and young adults were similar. Also at elevated temperatures, the thermosensitivity of DNA replication in lymphocytes from young and old adults was the same.DNA polymerase was purified from PHA‐stimulated lymphocytes from young and old adults. The fidelity of DNA synthesis using poly (dC) as a template was similar with both enzymes. However, DNA polymerase‐α purified from old adults was thermolabile compared to the enzyme from young adults. Thus, while the lymphocytes from old individuals may have heat labile proteins, they do not limit their proliferative capacity.
A human serum protein system affecting muscle contractility: Characterization of the five components and their reaction sequence
Authors: Hajdu Stephen , Leonard Edward J. 
Published: February 2005

AbstractA human serum protein system that affects muscle contractility, previously reported to be a calcium transport system (CTS), was fractionated into five protein components, A, B1, Bf1, B3 and C. The system was assayed on frog heart muscle in vitro by its capacity to increase contractile force and at high concentrations to cause contracture. With separated fractions, the reaction sequence was divided into three separate steps: B1 and B3 interacted with the heart in the first step, B2 and B3 in the second, and A and C in the third. Increased contractility occurred only after the third step. Partial purification, with preservation of biological activity, was achieved for B1, B2, A and C. B1 has a M.W. of about 170,000, as determined by its elution from Sephadex G‐200. B2, a labile protein of M.W. 220,000, was one of the few serum proteins precipitated by M.W. 500,000 dextran sulfate at pH 8.0. This was the basis for the preparation of highly purified B2, which was used to produce rabbit anti‐B2 antibody. Experiments with this antibody proved that B2 became bound to the heart surface. CTS‐A, the smallest protein of the system, had a M.W. of approximately 130,000. The M.W. of C was over 300,000. Purified C antigen induced rabbit antibody that inhibited the action of C without affecting the other components.
Glucose and amino acid metabolism in an established line of skeletal muscle cells
Authors: Pardridge William M. , Davidson Mayer B. , Casanello‐Ertl Delia 
Published: February 2005

AbstractThe suitability of an established myogenic line (L6) for the study of skeletal muscle intermediary metabolism was investigated. Myoblasts were grown in tissue culture for ten days at which time they had differentiated into multinucleated myotubes. Myotube preparations were then incubated for up to 96 hours in 10 ml of Dulbecco's modified Eagle medium containing 10% fetal calf serum. Glucose was utilized at a nearly linear rate, 3.0 nmol/min/mg protein. Intracellular glucose was detectable throughout the incubation, even when medium glucose was as low as 16 mg%. During the initial 28 hours of incubation, when net lactate production was observed, only 35% of the glucose utilized was converted to lactate. Alanine was produced in parallel to lactate at an average rate of 0.6 nmol/min/mg protein. In concert with active glutamine utilization, high rates of ammoniagenesis were observed as medium glutamine decreased from 3.3 mM to 0.49 mM and medium ammonia increased from 2.3 mM to 6.2 mM, between zero time and 96 hours of incubation, respectively. The cells maintained stable ATP and citrate levels, and physiologic intracellular lactate/pyruvate ratios (10–24) throughout 96 hours of incubation. These results suggest (1) glucose utilization by skeletal muscle in tissue culture is limited by phosphorylation, not transport; (2) as much as 50% of glucose‐derived pyruvate enters mitochondrial pathways; (3) glutamine carbon may be utilized simultaneously with glucose consumption and this process accounts for high rates of ammoniagenesis.
Amphibian cells in culture. I. Nutritional studies
Authors: Chinchar Giovina D. , Sinclair John H. 
Published: February 2005

AbstractNutritional requirements of amphibian cells in culture were studied for the purpose of modifying a minimal medium in which frog cells could proliferate and which could be used for obtaining drug‐resistant and auxotrophic variants. The serum, purine, CO2, and amino acid requirements for ICR 2A (a Rana pipiens haploid cell strain) have been investigated employing two different media: L‐15, a nonbicarbonate, amino acid‐buffered medium and Eagle's MEM, a bicarbonate‐buffered medium.In this paper we present evidence to support the following conclusions: (1) With L‐15 as the base medium, 10% fetal calf serum (FCS) supports optimal cell growth during exponential phase. Calf serum, whole, dialyzed, or heat‐inactivated, cannot substitute for FCS and, in fact, is inhibitory. (2) Purines are required by ICR 2A cells only if grown in a nonbicarbonate‐buffered medium, since the cells under these conditions cannot produce enough endogenous CO2 to support de novo purine synthesis. (3) In addition to the amino acids considered essential for mammalian cells in culture, ICR 2A cells depend upon exogenous asparagine. Glutamine and/or aspartic acid cannot replace the asparagine requirement. However, ICR 2A cells do utilize exogenous glutamine as an oxidative substrate.
Hormonal activation of adenylate cyclase in mouse melanoma metastatic variants
Authors: Niles R. M. , Makarski J. S. 
Published: February 2005

AbstractThe ability of melanocyte stimulating hormone (MSH), adrenocorticotropic hormone (ACTH), and prostaglandin E1 (PGE1) to stimulate the accumulation of cyclic AMP was examined in intact mouse melanoma cells of varying metastatic potential. F1 cells (low metastatic potential) had significantly greater cyclic AMP levels in response to all three hormones than F5 (intermediate metastatic potential) and F10 (high metastatic potential) cells. The ranking of the response was as follows: MSH, F1 > F5 > F10, ACTH, F1 > F5 > F10, PGE, F1 > F10 > F5. In contrast to the above, the degree of hormonal stimulation of adenylate cyclase in broken cell preparations was virtually identical in all three melanoma cell lines. Control enzyme activity was depressed in both F5 and F10 relative to F1. The conflicting results between studies of intact vs. broken cell preparations could not be explained by increased cyclic AMP phosphodiesterase activity in F5 and F10 cells. We conclude that as the melanoma cells increase in metastatic potential, there is a significant loss in the ability of their cyclic AMP system to respond appropriately to hormonal stimuli.
Red cell aging II. Anomalous electrophoretic properties of neuraminidase treated human erythrocytes
Authors: Nordt F. J. , Knox R. J. , Seaman G. V. F. 
Published: February 2005

AbstractDesialylation of human red blood cells (RBC) by Vibrio cholerae neuraminidase (VCN) was found to produce cells with electrophoretic properties which were inconsistent with the view of simple loss of N‐acetyl‐neuraminic acid (NANA) as the sole effect of VCN treatment. Modification of human RBC with 50–350 U VCN/1010 RBC for one hour at 37°C releases 90–100% of the NANA and produces a progressive decrease towards zero in their electrophoretic mobilities when measured in 0.15 M NaCl (pH 7.2) at 25°C. The appearance of positive groups on the desialylated cells was indicated by the VCN‐treated cells displaying positive mobilities below ∼ pH 5.5 and increased negative mobilities at ∼ pH 9 as well as substantial increases in their mobility at neutral pH following treatment with formaldehyde. Adsorption of about 95% of the VCN activity at 0°C to the RBC did not produce any significant change in their electrophoretic mobilities thus indicating that the observed changes in the electrophoretic properties of the RBC following VCN treatment could not be attributable to adsorption of VCN.These studies indicate that the cationic charge groups which appear at the electrophoretic surface of the RBC after VCN treatment are probably of endogenous origin. It is suggested that this alteration rather than simple NANA release may operate to shorten the in vivo survival time of desialylated red cells.
Inhibition of basal protein degradation in rat embryo fibroblasts by cycloheximide: Correlation with activities of lysosomal proteases
Authors: Amenta J. S. , Sargus M. J. , Baccino F. M. 
Published: February 2005

AbstractRat embryo fibroblasts were grown in medium containing 14C‐leucine and 3H‐thymidine. After a 24‐hour chase in nonlabeled medium, cultures were placed in either fresh growth medium or medium containing 10–20 μg/ml cycloheximide. Cell monolayers were processed at daily intervals for three days. Four hours prior to processing, cultures were placed in fresh medium and the accumulation rate of trichloracetic acid soluble 14C in the media assayed. Cycloheximide effects a progressive decrease in the fractional degradation rate of the labeled cell protein, primarily during the first 24 hours. The specific activities of cathepsin D, cathepsin B, and neutral protease correlate closely with the fractional degradation rate. Other lysosomal hydrolases show little change during this period. The activities of the lysosomal proteases approach a new steady state which is correlated with the new steady state leve of protein synthesis. A model is proposed which relates the rate of protein break‐down in the cell to the level of protein synthesis. The data also suggests the possibility that subpopulations of high turnover and low turnover cells exist in these cultures.
Transport and phosphorylation of hexoses in normal and rous sarcoma virus‐transformed chick embryo fibroblasts
Authors: Singh Malathy , Singh Vishwa Nath , August J. T. , Horecker B. L. 
Published: February 2005

AbstractEffects of transformation by Rous sarcoma virus on sugar uptake and activity and the subcellular distribution of hexokinase isozymes in chick embryo fibroblasts were examined. Transformation caused a several‐fold increase in the maximum velocity for uptake of 2‐deoxyglucose without a significant change in Km. Cytochalasin B (CB), was used to differentiate between the effects of transformation on facilitated diffusion and the nonsaturable (CB‐insensitive) mode. Transformation was found to stimulate 2‐deoxyglucose transport by both mechanisms, but the increase in transport by the CB‐insensitive mode was greater.Transformation enhances the activity of hexokinase, the enhancement being confined to the particulate fraction of the enzyme. Heat‐inactivation and electrophoretic mobility studies showed that although hexokinase Type I is the major form in both normal and transformed fibroblasts, there is a significant increase in the proportion of the Type II isozyme in the transformed cells.
Polyene macrolide antibiotic cytotoxicity and membrane permeability alterations I. Comparative effects of four classes of polyene macrolides on mammalian cells
Authors: Fisher Paul B. , Bryson Vernon , Schaffner Carl P. 
Published: February 2005

AbstractThe relationship between polyene macrolide‐induced early membrane damage and cytotoxicity in B1 (hamster), B82 (mouse), and RAG (mouse) cells has been investigated. Filipin (FIL) induced the greatest immediate damage, as monitored by 51Cr release, followed by mediocidin (MED), amphotericin B‐deoxycholate (Fungizone®) (FZ) and pimaricin (PIM). For long term effect, PIM was the least toxic followed by MED, FZ, and FIL as indicated by 24‐hour survival, 72‐hour viability, and growth rate of cells. In evaluating polyene macrolide‐induced permeability alterations and cytotoxicity two types of interactions with mammalian cells were found: (1) cell toxicity at polyene macrolide levels not eliciting immediate membrane permeability changes; and (2) immediate membrane damage without long range toxicity.
The proliferative response in vitro of vascular endothelial and smooth muscle cells exposed to wound fluids and macrophages
Authors: Greenburg Gary B. , Hunt Thomas K. 
Published: February 2005

AbstractThe ability of wound‐derived macrophages and of fluids obtained from wounds to stimulate the proliferation of vascular endothelial cells and vascular smooth muscle cells in vitro has been investigated. Sparse cultures of endothelial and smooth muscle cells maintained in the presence of optimal concentrations of serum and wound fluid showed a 25‐fold increase and a 10‐fold increase, respectively, in final cell density when compared to cultures maintained in the presence of serum alone. The response of both endothelial and smooth muscle cells to the wound fluid was dependent on the serum or plasma‐serum concentrations in which they were maintained. The ability of the wound fluid to stimulate endothelial cell proliferation was compared to that of fibroblast growth factor (FGF), which has already been shown to be a potent mitogen for endothelial cells in vitro. The growth response of endothelial cell cultures, when exposed to either 2% wound fluid or 100 ng/ml of FGF, was found to be similar, and the normal cell morphology was maintained. To examine the possibility that the growth stimulating activity present in the wound fluid originated from macrophages, endothelial cells or smooth muscle cells were co‐cultured with macrophages obtained from the wound fluid. A significant stimulation of both endothelial and smooth muscle cells was observed with 2 × 106 macrophages, which would suggest that macrophages may be the source of the mitogenic activity of the wound fluid in vivo.
5‐fluorotryptophan resistant mutants affecting the A and L transport systems in the mouse L cell line A9
Authors: Taub Mary , Englesberg Ellis 
Published: February 2005

AbstractTryptophan transport has been examined in A9 and in mutants resistant to 5‐fluorotryptophan (5‐FT). Evidence indicates that in A9 cells two systems are present for tryptophan transport, which are analogous to the A and L systems found in Ehrlich ascites cells differing, however, in terms of amino acid specificity. Tryptophan uptake via the L system, a high affinity, low capacity system, is Na+ independent and occurs by a counter transport mechanism, while uptake via the A system, a low affinity, high capacity system, is Na+ dependent. Alanine, arginine, lysine, proline, asparagine, and aspartate (listed in order of decreasing inhibitory effect) inhibit tryptophan uptake via the A system from approximately 80‐50% while having no inhibitory effect on the L system. In addition, glutamine which inhibits tryptophan uptake by 80% via the L system only inhibits to the extent of 20% via the A system. Previous kinetic studies of 5FT resistant clone FTr37 indicated system A was altered while the analysis of the effects of the mutation on system L was inconclusive. However, in these studies Na+ independent uptake was not altered in FTr 37 indicating system L was not affected. Amino acid competition studies confirmed this observation and suggested that a change in the specificity of system A had occurred in FTr 37. The amino acid competition studies in FTr 23, indicated that the specificities of both systems differed from A9. The possibility that this change may be due to a single mutational event is discussed.
RNA synthesis by nuclei and nucleoli from ischemic liver cells
Authors: Schiaffonati Luisa , Cairo Gaetano , Bernelli‐Zazzera Aldo 
Published: February 2005

AbstractNuclei and nucleoli were isolated from rat livers subjected to an interruption of the blood supply for periods of different duration, as well as after restoration of the blood supply. They were assayed for RNA synthesis under conditions of diverse ionic strengths, and in the presence of an exogenous template, such as poly d (A–T), and actinomycin to inactivate the endogenous template; α‐amanitin was made used of to distinguish polymerase I and polymerase II dependent RNA synthesis. Nuclei and nucleoli from ischemic livers showed a severe impairment of RNA synthesis, which is likely to be due to decreased initiation frequency of the engaged polymerases, while free polymerases were essentially unchanged. Both form I and II polymerase were equally involved. After restoration of the blood supply RNA synthesis recovered with an overshooting well above normal levels of activity, lasting for at least 24 hours. Increased RNA synthesis was not followed by thymidine incorporation into DNA.
Purification and properties of human erythrocyte inosine triphosphate pyrophosphohydrolase
Authors: Vanderheiden Bernardo S. 
Published: February 2005

AbstractInosine triphosphate pyrophosphohydrolase from human erythrocytes was purified and characterized. The enzyme is highly specific for ITP and shows optimal activity in glycine buffer pH 9.6 and 50 mM MgCl2. The Km of the enzyme is 1.3 × 10−4, the Vmax = 1.2 × 10−9 and the Keq = 3.8 × 104. Human erythrocyte ITP pyrophosphohydrolase does not require SH compounds for activation. The enzyme is inhibited by Cd++, Co++, and Ca++ ions and by phydroxymercuribenzoate.
The initiation and elongation steps in protein synthesis: Relative rates in chinese hamster ovary cells during and after hyperthermic and hypothermic shocks
Authors: Oleinick Nancy L. 
Published: February 2005

AbstractThe relative rates of the initiation and elongation phases of protein synthesis have been determined in heat‐ and cold‐shocked CHO cells from measurements of the incorporation of 35S‐methionine into N‐terminal and internal positions of growing peptides by a modified Edman degradation. When the cells are shifted from 37°C to temperatures between 10°C and 34°C, the rate of initiation is at first reduced more extensively than that of elongation. After 20 to 30 minutes at the lower temperature, however, the cells undergo a metabolic adjustment which includes increasing the rate of initiation until it corresponds to the rate of elongation at that temperature. Calculated apparent energies of activation for initiation and elongation are in reasonable agreement with those determined in other mammalian cells. When the cooled cells are returned to 37°C, the rates of initiation and elongation recover immediately but do not exceed the control values. Exposure to elevated temperature (43°C) causes an immediate cessation of initiation and thus a delayed inhibition of elongation; upon return to 37°C, the rate of initiation is transiently elevated above the control rate, and the rate of elongation returns to the control rate after a 2‐ to 3‐minute delay. Hence, a factor which leads to supranormal rates of initiation may accumulate at high but not at low temperatures.
Dexamethasone induces irreversible G1 arrest and death of a human lymphoid cell line
Authors: Harmon Jeffrey M. , Norman Michael R. , Fowlkes Betty Jo , Thompson E. Brad 
Published: February 2005

AbstractGrowth of a human leukemic T‐cell line (CEM C7) in 10−6 M dexamethasone results in inhibition of growth and rapid loss of cell viability after a delay of approximately 18 to 24 hours. Analysis of dexamethasonetreated cells by flow‐microfluorometry showed that they were arrested in the G1 phase of the cell cycle. Loss of cell viability began at the same time as G1 accumulation was first detectable, and 20% of all cells were found to be blocked in G1 at this time suggesting that loss of viability and G1 arrest were coincident events. Half‐maximal and maximal effects on both viability and G1 arrest after 48 hours in steroid were nearly identical with respect to steroid concentration and corresponded to half‐maximal and full occupancy of glucocorticoid specific receptor by hormone, consistent with a glucocorticoid receptor mediated mechanism for both phenomena. Most non‐viable cells were arrested in G1, and accumulation of cells in G1 was irreversible; removal of steroid in the presence of colcemid did not result in a decreased fraction of G1 cells. Furthermore, dexamethasone treatment did not protect cells against the effects of 33258 Hoechstamplified killing of bromodeoxyuridine substituted cells exposed to light. These results show that dexamethasone arrests these leukemic cells in G1 and strongly suggest that dexamethasone‐treated cells are killed upon entry into G1.