bluuebunny/crossref_metadata_2025_split huggingface dataset:
Growth kinetics and collagen synthesis of normal skin, normal scar and keloid fibroblasts in vitro
Authors: Diegelmann Robert F. , Cohen I. Kelman , McCoy Barbara J. 
Published: February 2005

AbstractFibroblasts were isolated from keloid, normal skin, and normal scar and maintained in tissue culture for four passages. Growth kinetics were the same for all groups on days 2 through 12. However, the rate of collagen synthesis per fibroblast was greater in keloid derived cells than any controls at all growth phases. Keloid fibroblasts have an autonomous capacity to synthesize collagen at a significantly increased level in vitro, which may explain in part why these lesions are characterized by increased collagen deposition.
Correlation of the effect of Ca+2 on Na+ and K+ permeability and membrane potential of Ehrlich ascites tumor cells
Authors: Smith Thomas C. , Vernon Kim D. 
Published: February 2005

AbstractThe effect of Ca+2 on the transport and intracellular distribution of Na+ and K+ in Ehrlich ascites tumor cells was investigated in an effort to establish the mechanism of Ca+2‐induced hyperpolarization of the cell membrane. Inclusion of Ca+2 (2mM) in the incubation medium leads to reduced cytoplasmic concentrations of Na+, K+ and Cl− in steady state cells. In cells inhibited by ouabain, Ca+2 causes a 41% decrease in the rate of net K+ loss, but is without effect on the rate of net Na+ accumulation. Net K+ flux is reduced by 50%, while net Na+ flux is unchanged in the transport‐inhibited cells. The membrane potential of cells in Ca+2‐free medium (‐13.9 ± 0.8 mV) is unaffected by the addition of ouabain. However, the potential of cells in Ca+2‐containing medium (‐23.3 ± 1.2 mV) declines in one hour after the addition of ouabain to values comparable to those of control cells (‐15.2 ± 0.7 mV).The results of these experiment are consistent with the postulation that Ca+2 exerts two effects on Na+ and K+ transport. First, Ca+2 reduces the membrane permeability to K+ by 25%. Second, Ca+2 alters the coupling of the Na/K active transport mechanism leding to an electrogenic hyperpolarization of the membrane.
Electrophysiological properties of human oviduct smooth muscle cells in dissociated cell culture
Authors: Sinback C. Nelson , Shain William 
Published: February 2005

AbstractIntracellular recordings were made from human oviduct smooth muscle maintained in cell culture. Solitary cells isolated from one another and cells in contact with one another retained electrical properties of smooth muscle in vivo. Membrane potential of solitary cells and connected cells was −35 mV. Connected cells formed electrotonic junctions which transmitted current from one cell to another. This current spread was responsible for differences in input resistance and time constant in solitary cells, 66 MΩ and 96 msec, compared to connected cells, 26 MΩ and 56 msec. All cells expressed delayed rectification to depolarizing current pulses. Some cells generated action potentials spontaneously or in response to intracellular current puleses. Action potentials were abolished by cobalt or by EGTA. Slow wave potentials, 5‐20 mV in amplitude, occurred continuously once every 15 to 45 seconds in connected cells.
The requirement of DNA synthesis for the induction of alkaline phosphatase by bromodeoxyuridine in a derivative of the HeLa cell line
Authors: Morrow John , Stocco Douglas M. , Fralick Joe A. 
Published: February 2005

AbstractNon‐lethal concentrations of bromodeoxyuridine induce a 2‐ to 5‐fold increase in the specific activity of alkaline phosphatase in HeLa subclone, S3G. Experiments employing 10‐hour pulses of BRdU showed that 48 hours were required before induction commenced, and that maximal induction was attained by 96 hours. Under conditions in which DNA synthesis was prevented with hydroxyurea induction did not occur. Upon removal of hydroxyurea both DNA synthesis and induction were rapidly reestablished. Furthermore, experiments employing radiolabelled BRdU demonstrated that the kinetics of the induction process paralleled the incorporation of the analogue into cellular DNA.These results indicate that DNA synthesis, or some process intimately linked to DNA synthesis, is required for the induction of alkaline phosphatase, and suggest that the mode of the induction may be through the incorporation of the analogue into cellular DNA.
The importance of ornithine as a precursor for proline in mammalian cells
Authors: Smith Robert J. , Phang James M. 
Published: February 2005

AbstractOrnithine aminotransferase catalyzes the reversible transamination of L‐ornithine to δ1‐pyrroline‐5‐carboxylate, the immediate precursor of proline. The direction and flux through this pathway in mammalian cells has not been established. Glutamate has generally been considered to be the most important precursor for proline biosynthesis, but recent studies in xiphoid cartilage indicate that a significant fraction of cellular proline is derived from ornithine. Using newly isolated mutant Chinese hamster ovary cells with defined defects in the proline biosynthetic pathways, we now have established that cells can grow at a maximal rate with ornithine as the sole source of proline. Furthermore, we have measured the rate of proline formation from ornithine (1.6 nmol/h/106 cells). Future studies with these mutant Chinese hamster ovary cells may offer insight into the regulatory mechanism which coordinates proline biosynthesis from ornithine and glutamate.
Ordered replication of DNA sequences: Synthesis of mouse satellite and adjacent main band sequences
Authors: Dooley Douglas C. , Ozer Harvey L. 
Published: February 2005

AbstractThe replication of mouse satellite DNA was delayed when synchronized 3T3 cells were exposed to low concentrations of hydroxyurea during S phase. It appears that the onset of satellite replication is not a time dependent event, but instead requires that a certain amount of main band DNA be synthesized first. Using hydroxyapatite chromatography and S1 nuclease digestion, a procedure was developed to quantitate the synthesis of both satellite and neighboring main band sequences. The replication kinetics of satellite determined by this method agree with previous estimates. Main band sequences adjacent to satellite appear to replicate in concert with satellite DNA. The results are discussed and related to the limitations of the techniques utilized.
Induction of human choriogonadotropin and follitropin in HeLa cell cultures by hyperosmolality
Authors: Fallon Robert J. , Cox Rody P. , Ghosh Nimai K. 
Published: February 2005

AbstractThe growth of cervical carcinoma cell (HeLa) cultures in a hyperosmolar environment stimulates increased production of the onco‐developmental peptides human choriogonadotropin (hCG) and follitropin (FSH). This effect was observed in two sublines examined in this study, HeLa65 and HeLa71. hCG and FSH were measured by radioimmunoassay using antiserum against the β‐subunit of the hormone dimer, thus insuring immunochemical specificity. The amounts of hCG and FSH produced by HeLa65 and HeLa71 cells cultured in hyperosmolar medium were 2‐ to 50‐fold higher than corresponding hormone levels in basal cultures. Synthesis of gonadotropins depended on concentration and duration of exposure to hyperosmolar medium. Levels of culture medium osmolality effective in inducing hormone production also inhibit the incorporation of 14C‐thymidine into acid‐insoluble macromolecules. Hyperosmolality thus stimulates the ectopic production of gonadotropic hormones while retarding cellular growth and nucleic acid synthesis.
The effect of hexose on chloramphenicol sensitivity and resistance in chinese hamster cells
Authors: Ziegler Michael L. , Davidson Richard L. 
Published: February 2005

AbstractThe toxicity and extent of growth inhibition produced by chloramphenicol (CAP) in CAPs Chinese hamster cells (line V79‐5) was found to be dependent on the type and concentration of hexose in the medium. In high levels of glucose (6.5 mM), cultures of CAPs cells underwent 7–8 population doublings in the presence of 100 μg/ml CAP and viability then dropped rapidly. In contrast, lower concentrations of glucose (1.0 mM) permitted only limited growth (2–3 doublings) in the presence of 100 μg/ml CAP, but the cells remained viable and apparently quiescent for prolonged periods of time. The growth potential of V79‐5 cells in CAP appeared specifically dependent on glucose, as mannose and galactose could not substitute for glucose. The toxicity of CAP to these cells seemed to be determined primarily by the number of cell doublings in the presence of the drug.A CAPR derivative of V79‐5, designated 5‐3, was analyzed in order to determine whether the requirement for glucose for cell growth in the presence of CAP also occurred in cells that were isolated as resistant to the drug. In order to rigorously control the hexose in the medium, some experiments were performed with medium containing dialysed, instead of whole, fetal calf serum. It was seen that the growth of the CAPR line in the presence (but not the absence) of 100 μg/ml CAP was dependent on glucose in the medium. Thus, resistance to CAP in these cells appears to be a conditional state, dependent on glucose for expression. Furthermore, the glucose auxotrophy of these cells in the presence of CAP suggests that CAP is still affecting some activities in cells isolated as CAPR.
Tunicamycin‐mediated depletion of insulin receptors in 3T3‐L1 adipocytes
Authors: Rosen O. M. , Chia G. H. , Fung C. , Rubin C. S. 
Published: February 2005

AbstractTunicamycin, an antibiotic that inhibits protein glycosylation, elicited a rapid depletion of insulin binding activity at the surface of 3T3‐L1 adipocytes. Disappearance of insulin receptors occurred more rapidly in the presence of tunicamycin than when protein synthesis was inhibited by cycloheximide and was accompanied by a diminution in sensitivity of the adipocytes to the acute effects of insulin and anit‐insulin receptor antibody on hexose uptake and metabolism.
Transmembrane electrical and pH gradients across human erythrocytes and human peripheral lymphocytes
Authors: Deutsch C. J. , Holian A. , Holian S. K. , Daniele R. P. , Wilson D. F. 
Published: February 2005

AbstractTransmembrane electrical and pH gradients have been measured across human erythrocytes and peripheral blood lymphocytes using equilibrium distributions of radioactively labelled lipophilic ions, and of weak acids and weak bases, respectively. The distributions of methylamine, trimethylamine, acetic acid and trimethylacetic acid give calculated transmembrane pH gradients (pHe‐pHi) for erythrocytes of between 0.14‐0.21 for extracellular pH values of 7.28‐7.16. The distributions of trimethylacetic acid, DMO and trimethylamine were determined for lymphocytes, establishing upper and lower limits of the calculated pH gradient over he external pH range of 6.7 to 7.7.Tritiated triphenylmethyl phosphonium ion (TPMP) and 14C‐thiocyanate ion (SCN) equilibrium distributions were measured in order to calculate transmembrane electrical potentials, using tetraphenylboron as a catalyst to facilitate TPMP equilibrium. Transmembrane potentials of −7 to −10 mV were calculated from SCN and TPMP, respectively for red cells, and −35 to −52 mV respectively, in the case of lymphocytes. Distributions of TPMP and potassium ions were determined in the presence of valinomycin over a wide range of extracellular potassium concentrations for red cells and the calculated Nernst potentials for TPMP compared to the calculated potential using the Goldman equation for chloride and potassium ions. Distributions of TPMP, SCN and potassium ions were also determined for lymphocyte suspensions as a function of extracellular potassium and the calculated Nernst potentials for TPMP and SCN compared to the calculated potassium diffusion potential.
Two distinct mechanisms for ornithine decarboxylase regulation by polyamines in rat hepatoma cells
Authors: McCann Peter P. , Tardif Chantal , Hornsperger Jean‐Marie , Böhlen Peter 
Published: February 2005

AbstractExogenous diamines and polyamines added to rat hepatoma (HTC) cells in culture rapidly decrease ornithine decarboxylase (ODC) activity. Previous evidence has suggested that these amines act either at the level of blocking new enzyme synthesis or by the induction of a non‐competitive protein inhibitor, termed antizyme, which complexes with ODC to form an inactive complex. With the use of HMOA cells, a recently cloned rat hepatoma cell line that has a greatly stabilized ODC, it has been possible to demonstrate that 10−5 M of exogenous putrescine blocks the increase in ODC activity, but unlike in the parent HTC cell line, without induction of the antizyme or formation of any inactive ODC‐antizyme complex. However, complete blockade of ODC at 10−2 M putrescine is effected by induction of antizyme and formation of the ODC‐antizyme complex, as now evidenced by the isolation of the active enzyme and antizyme components after Sephadex column chromatography in the presence of 250 mM NaCl. These findings indicate clearly that two polyamine‐regulatory mechanisms for ODC exist and are separable in this cell line.
The effects of Clostridium perfringens enterotoxin on morphology, viability, and macromolecular synthesis in vero cells
Authors: McClane Bruce A. , McDonel James L. 
Published: February 2005

AbstractVero (African green monkey kidney) cells grown in tissue culture monolayer were sensitive to Clostridium perfringens enterotoxin. Within 30 minutes of exposure to the enterotoxin gross morphological damage was observed and within 40 minutes approximately 75% of the cells had detached. Nearly half of the cells were nonviable following 35 to 40 minutes incubation with the enterotoxin. Doses as low as 0.1 ng caused small but detectable inhibition of plating efficiency of the cells while more than 100 ng caused the inhibition to approach 100%. Total inhibition of DNA, RNA, and protein synthesis occurred within 30 minutes exposure to enterotoxin. Heat inactivated enterotoxin had no apparent effects upon cellular morphology, detachment, viability, plating efficiency, or incorporation. We propose that the enterotoxin induces structural damage to the cytoplasmic membrane which results in loss of electrolytes and other essential substances from the cells. The outcome of this process is shut down of macromolecular synthesis, gross morphological damage, and eventual death of the cell.
Sulfated mucopolysaccharides from normal and virus transformed rodent fibroblasts
Authors: Chiarugi Vincenzo P. , Dietrich Carl P. 
Published: February 2005

AbstractThe sulfated mucopolysaccharide composition of normal and virus transformed Balb 3T3 and BHK21 cell lines is reported. It is shown that normal 3T3 cells contain mainly chondroitin sulfate B and heparitin sulfate. Relatively higher amounts of chondroitin sulface AC were observed in polyoma virus transformed 3T3 cells, besides an absolute increase of all the three sulfated mucopolysaccharides in the polyoma and SV 40 transformed cells. It is shown also that the three sulfated mucopolysaccharides are at least in part at the cell surface. Similar differences in sulfated mucopolysaccharide composition of normal and virus transformed BHK cell lines were also observed.
Pyrimidine nucleoside, pseudouridine, and modified nucleoside excretion by growing and resting fibroblasts
Authors: Uziel Mayo , Selkirk J. K. 
Published: February 2005

AbstractWe are examining the relationship of RNA metabolism and de novo pyrimidine synthesis as parameters of malignant transformation. These initial experiments on normal hamster embryo fibroblasts have shown that excreted nucleosides are markers for intracellular RNA metabolism. We employed affinity chromatography to concentrate the nucleosides in the medium and sensitive column chromatographic procedures to quantitatively measure them. The excretion of pyrimidine nucleoside from hamster embryo fibroblasts in culture was found to be dependent on the growth stage of the cells, with the greatest accumulation occurring during cell quiescence. The major nucleoside excretion products, uridine and cytidine, were both normal end products of RNA metabolism and the major nucleoside excretion products from cultured cells. The modified nucleosides N‐1‐methylguanosine, N‐2‐methylguanosine, N‐2‐dimethylguanosine, N‐4‐acetylcytidine, N‐1‐methylinosine, pseudouridine, N‐1‐methyladenosine, N‐3‐methylcytidine, and 5‐methylcytidine were found, as were several unidentified nucleosides.
Relationship between histidyl‐tRNA level and protein synthesis rate in wild‐type and mutant chinese hamster ovary cells
Authors: Lofgren Don J. , Thompson Larry H. 
Published: February 2005

AbstractA preliminary investigation was carried out to determine how conditional lethal mutants affected in particular aminoacyl‐tRNA synthetases may be used to study the role of tRNA charging levels in protein synthesis. The relationship between rate of protein synthesis and level of histidyl‐tRNA in wild‐type cultured Chinese hamster ovary cells was determined using the analogue histidinol to inhibit histidyl‐tRNA synthetase activity. This response was compared with that obtained using a mutant strain with a defective histidyl‐tRNA synthetase that phenotypically shows decreased rates of protein synthesis at reduced concentrations of histidine in the growth medium. The approach used was based on measuring the histidyl‐tRNA levels in live cells. The percentage charging was estimated by comparing [14C]histidine incorporated into alkali‐labile material in paired samples, one of which was treated with cycloheximide, five minutes before terminating during the incubation, to produce maximal aminoacylation. Wild‐type cells under histidinol inhibition exhibited a sensitive, sigmoidal relationship between the level of histidyl‐tRNA and the rate of protein synthesis. A decrease in the relative percentage of acylated tRNAHis from 46% to 35% elicited a large reduction in the rate of protein synthesis from 90% to 30% relative to untreated cells. An unpredicted result was that the relationship between protein synthesis and histidyl‐tRNA in the mutant was essentially linear. High acylation values for tRNAHis were associated with rates of protein synthesis that were not nearly as high as in wild‐type cells. These findings suggest that the charging levels of tRNAHis isoacceptors could play a regulatory role in determining the rate of protein synthesis under conditions of histidine starvation in normal cells. The mutant appears to be a potentially useful system for studying the pivotal role of tRNA charging in protein synthesis, assuming that the altered response in the mutant is caused by its altered synthetase.
Pyridine nucleotide synthesis in 3T3 cells
Authors: Jacobson Elaine L. , Lange Richard A. , Jacobson Myron K. 
Published: February 2005

AbstractThe biosynthesis of NAD has been examined in 3T3 cells. The net synthesis of pyridine nucleotides does not occur when cells are cultured in the absence of performed pyridine ring compounds; however, growth continues normally for up to four cell doublings resulting in cells with a total pyridine nucleotide content that is reduced by as much as 12‐fold. The mechanism that adjust the relative amounts of NADP and NAD are also altered such that the amount of NADP relative to NAD increases 5‐fold. Both nicotinate and nicotinamide can be used as a precursor for NAD biosynthesis, however nicotinate is utilized less efficiently than nicotinamide. The presence of functional pathways for the biosynthesis of NAD from nicotinate via nicotinate mononucleotide and nicotinate adenine dinucleotide and from nicotinamide via nicotinamide mononucleotide has been demonstrated by identification of biosynthetic intermediates following short term exposure of cells to radiolabelled precursors. When cells are grown in Dulbecco's modified Eagle's medium which contains 33 μM nicotinamide the biosynthesis of NAD proceeds by a single pathway with nicotinamide mononucleotide as the only intermediate. Nicotinamide ribonucleoside which previously has been postulated to be an intermediate in the conversion of nicotinamide to NAD is not an intermediate in NAD biosynthesis.
Properties of Na‐K pump in primary cultures of kidney cells
Authors: Becker John H. , Willis John S. 
Published: February 2005

AbstractActivities related to Na‐K transport were measured in cell cultures of ground squirrel kidney cortex in order to compare these cells with those of intact kidney and of continuous cell lines. A microsomal preparation containing plasma membrane Na,K‐ATPase from fresh kidney showed twice the activity of a similar preparation from 72‐hour cultured cells. Na,K‐ATPase of homogenates of 72‐hour cells showed one‐third to one‐fourth the specific activity of that from 6‐hour cultured cells. The associated K‐dependent phosphatase activity also declined as a function of time in culture. The ouabain‐sensitive influx of K into 6‐hour cultured cells was twice as great as the K influx into 72‐hour cells. The number of sites binding 3H‐ouabain in intact cultured cells declined 81% on a cell protein basis between 6 and 72 hours in culture. This decline in ouabain binding sites was relatively greater than that of K influx, so that the K turnover number increased over this same time period.The decline in ouabain‐sensitive K influx during culture was complementary to an increase in furosemide‐sensitive K influx. Measurements of unidirectional and net K fluxes showed that there were three components of K influx into 3‐day cultured cells: ouabain‐sensitive Na:K exchange, furosemide‐sensitive K:K exchange, and K diffusion. In the 6‐hour cultures, however, there was no furosemide‐sensitive K:K exchange.Thus, after three days in culture ground squirrel kidney cells lose a feature characteristic of the original parent cells (high Na,K‐ATPase activity), and gain a feature common to many undifferentiated cultured cells (furosemidesensitive K:K exchange).
Membrane effects of tumor promoters: Stimulation of sugar uptake in mammalian cell cultures
Authors: Lee Lih‐Syng , Weinstein I. Bernard 
Published: February 2005

AbstractPhorbol esters stimulate 2‐deoxy‐D‐glucose (DG) uptake in rodent and human cell cultures. The potent tumor promoting agent, 12‐0‐tetradecanoyl phorbol‐13 acetate (TPA), induces a 12‐fold stimulation in confluent 3T3 cells and a 2.5‐fold stimulation in HeLa cells. When a series of macrocyclic diterpenes are assayed, their relative potencies in stimulating DG uptake in 3T3 cells correlate with other known biologic effects of these compounds. On a molar basis, TPA is a much more potent stimulator of DG transport than insulin or epidermal growth factor. In HeLa cells, the ED50 value of the TPA effect is 0.2 nM. The increase in DG uptake occurs immediately after the addition of TPA, reaches a maximum at 90 minutes, persists for at least three hours after removal of TPA from the medium, and is temperature dependent. The stimulation is not inhibited by cycloheximide or actinomycin D. As in control cells, DG uptake in TPA treated cells is inhibited by p‐hydroxymercuribenzoate, phloridzin, cytochalasin B, and dexamethasone. Although the precise mechanism is not known, evidence is presented that the TPA stimulation of DG uptake is due to enhanced transport of the sugar rather than to effects of intracellular metabolism. The enhanced transport may be secondary to a more generalized change in membrane structure.