bluuebunny/crossref_metadata_2025_split huggingface dataset:
Studies on a fractionated murine fibrosarcoma: Proliferative potential of the separated cells
Authors: Sheridan J. W. , Finlay‐Jones J. J. 
Published: February 2005

AbstractA transplantable methylcholanthrene‐induced fibrosarcoma of female BALB/c mice (the MC‐2 fibrosarcoma) was dissociated by combined mechanical and enzymatic means, then fractionated by isopycnic centrifugation in linear albumin gradients.In some experiments recovered cells were both cultured in soft nutrient agar and inoculated subcutaneously into syngeneic recipients. In these experiments a highly significant correlation was observed between subsequent colony number and rapid growth phase tumor size suggesting identity of clonigenic and tumorigenic cells.It was consistently found that clonigenic cells were markedly depleted from the low density extremes of the cell density distribution profiles suggesting that the low density neoplastic cells had irreversibly left the growth fraction.With increasing tumor age, sequential studies showed that both total and clonigenic cell density distribution profiles were variable, showing no obvious trend, suggesting that in the age (13–35 days) and size (2–8 g) range studied growth fraction changes had little selective effect on cells of any specific density. These results imply that a marked selective depletion of low density clonigenic cells (or selective accumulation of low density non‐proliferative cells) must mainly occur during an earlier phase of tumor growth. Studies on several other murine solid tumors also showed maximal depletion of clonigenic cells from the least dense fractions, suggesting that this situation may be common.
Perturbation of growth and differentiation of friend murine erythroleukemia cells by 5‐bromodeoxyuridine incorporation in early S phase
Authors: Brown Eric H. , Schildkraut Carl L. 
Published: February 2005

AbstractCultured Friend murine erythroleukemia cells (Friend cells) are induced to undergo erythroid differentiation when grown in the presence of dimethylsulfoxide (DMSO) and other compounds. The effects of unifilar substitution of bromouracil (BU) for thymidine in the DNA (BU‐DNA) of Friend cells were examined. Cells were grown in the presence of 5‐bromodeoxyuridine (BrdU) for one generation, then centrifuged and resuspended in medium containing DMSO without BrdU. These cells exhibited a delay in the appearance of heme‐producing, benzidine‐reactive (B+) cells and a decreased rate of cell proliferation in comparison to the control not containing BU‐DNA. A transient inhibition of entry into S phase was observed when control cells or cells containing BU‐DNA were grown in the presence of DMSO for 10 to 20 hours. This transient inhibition was increased in the BrdU culture. Thus, BU‐substitution in Friend cells alters other cellular functions in addition to erythroid differentiation. The rate of increase in the percent of cells committed to differentiate (those forming B+ colonies in plasma clots) was similar in the BrdU and control cultures until 40 to 50 hours. After this time, a delay in the appearance of committed cells was observed in the BrdU culture. The effect of BrdU on the appearance of B+ cells was more pronounced and occurred earlier than its effect on the rate of commitment. Therefore, the delay in the appearance of B+ cells in the BrdU culture was due primarily to perturbation of post‐commitment events such as the accumulation of hemoglobin.We also examined the effect on growth and differentiation after BrdU was incorporated during different intervals of S phase in cells synchronized by centrifugal elutriation or by double thymidine block and hydroxyurea treatment. The delay in the appearance of B+ cells and inhibition of cell proliferation were only observed when BrdU was incorporated in the first half of S phase. BrdU (10 μM) had no effect on growth or differentiation when present during late S or G1 and G2. These results, using two very different methods to achieve cell synchrony, indicate that the effects of BrdU on growth and differentiation described above are due to its incorporation into DNA sequences replicating during early S.
Production of factors required for cell attachment and spreading is a constitutive property in mouse A9 cells
Authors: Dairkee Shahnaz Hashmi , Gilbert Michael W. 
Published: February 2005

AbstractIt is demonstrated here that cells in a suspension culture of an established mammalian cell line release non‐dialyzable factors into their growth medium. These factors are capable of promoting the adhesion and spreading of these cells on a generally non‐attachable substratum and also promote spreading on an adhering substrate. Evidence in presented which demonstrates that the spreading promotion activity of the conditioned medium is dependent on the cell density of the culture from which it was derived. Dilution of the conditioned medium results in a proportionate dilution of the spreading promotion activity. The results clearly demonstrate that the production of this spreading promotion factor is continued even in the absence of cell to substrate attachment.
Neurotrophic effect of nerve extract on development of tetrodotoxin‐sensitive spike potential in skeletal muscle cells in culture
Authors: Kano Masaakira , Suzuki Nobuyuki , Ojima Hisayuki 
Published: February 2005

AbstractThe effect of the presence of nerve extracts on the development of tetrodotoxin (TTX)‐sensitive sodium channels in cultures of dissociated embryonic chick skeletal muscle cells was examined by measuring the maximum rate of rise of TTX‐sensitive spike potential. The addition of the nerve extract prepared from brain or spinal cord of chick embryos to the culture medium caused an increase in the channel density. Extracts of non‐neural tissues, i.e., lung, kidney, and muscle, were ineffective Liver extract, however, produced an effect similar to the nerve extracts. These resutls suggest that the TTX‐sensitive sodium channels in the muscle cell membrane are regulated by a diffusible chemical substance independently of innervation, and that this substance resides in neural tissues, and perhaps also in liver.
Endogenous membrane phosphorylation increases in serum‐stimulated 3T3 cells
Authors: Mastro Andrea M. 
Published: February 2005

AbstractAutophosphorylation of 3T3 cells, utilizing endogenous membrane protein kinase, can be detected by incubating the cells with μgM32P‐ATP. The phosphorylation activity of growing cells is two to four‐fold greater than quiescent ones. In this study, the increased phosphorylation activity of serum‐stimulated cells was examined. Phosphorylation, measured at times after serum stimulation of quiescent cultures, was found to increase in early G1 and to reach a maximum prior to DNA synthesis. This increase in stimulated cells was dependent on RNA and protein synthesis but not on DNA synthesis. The increased activity decayed quickly (half‐life approximately 2–3 hours) in the presence of cycloheximide, while the basal activity in quiescent cells was relatively unchanged. Insulin, prostaglandin E1 or prostaglandin F2α were also found to bring about the same increase in phosphorylation as serum, although in contrast with serum they caused only a small percentage of the culture to synthesize DNA. The results suggest that enhanced phosphorylation activity is a G1 event. It does not depend on subsequent DNA synthesis. Phosphorylation may be one of the biochemical steps in G1, necessary but not sufficient for cells to move into S phase.
Tyrosinase maturation and pigment expression in B16 melanoma: Relation to theophylline treatment and intracellular cyclic AMP
Authors: White Roger , Hanson Gary C. , Hu Funan 
Published: February 2005

AbstractWe have studied the effects of theophylline treatment on pigmentation characteristics and growth of two B16 melanoma cell lines, HFH‐18 and P/140. Cell counts of control and theophylline‐treated cultures confirmed that the drug inhibits cell growth. Light and electron microscope cytochemistry with the L‐dopa reaction indicated that the two cell lines differ in their ability to transfer Golgi‐associated tyrosinase to developing premelanosomes. The results of these experiments, considered with results of electrophoretic analyses and activity measurements by the Pomerantz method, also provide evidence that increased tyrosinase synthesis occurs in response to theophylline treatment. In addition, results indicate that theophylline induces changes in the rate of synthetic or degradative posttranslational modification of tyrosinase. Measurements of intracellular cyclic AMP levels by radioimmunoassay in control cultures and in theophylline‐ and α‐MSH‐treated cultures were made. Although the hormone induced spectacular increases in cyclic AMP levels, theophylline produced no detectable change. These results indicate that theophylline differs from α‐MSH because theophylline‐induced changes in pigmentation may not require the participation of intracellular cyclic AMP.
Specific esterase activity induced in mouse Friend erythroleukemia cells by dimethylsulfoxide
Authors: Revoltella Roberto P. , Bertolini Luisa , Fioritoni Giuseppe , Torlontano Glauco 
Published: February 2005

AbstractThree cell lines of mouse erythroleukemia transformed by Friend virus (FLC), namely 745, F4‐1, and 3BM‐78, were grown for six days in the absence or in the presence of 1.5% (v/v) dimethylsulfoxide (DMSO) and compared cytochemically for naphtol‐AS D‐chloroacetate esterase (E), alkalinephosphatase (AP), myeloperoxidase (MP) and periodic acid Schiff (PAS) reaction activity. In the absence of inducer only 1–2% of slightly E positive cells could be found. E positivity greatly increased in 3BM‐78 and F4‐1 but poorly in 745 cells, after treatment with DMSO. Unlike E reaction, AP and MP reactions were positive in about 5% 3BM‐78 and F4‐1 cells without DMSO, but there were no positive cells after DMSO treatment. All three lines were always PAS negative. Hemoglobin synthesis (benzidine staining) was intensively induced by DMSO in all three lines. Morphologically after DMSO treatment, FLC matured displaying characteristics of basophilic megaloblastoid cells. The emergence of specific esterase activity, a marker of granulocytes, in FLC differentiating along the erythroid pathway, suggests that in these leukemia cells the genetic determinants for leukopoietic differentiation are retained and capable of being expressed phenotypically.
Degradation of proteins microinjected into cultured mammalian cells
Authors: Zavortink Michael , Thacher Thomas , Rechsteiner Martin 
Published: February 2005

AbstractIodinated proteins were degraded after injection into HeLa cells at first‐order rates with half‐lives varying from three hours for the trout nonhistone chromosomal protein, HMG‐T, to 60 hours for whale myoglobin. Fluoresceinated‐bovine serum albumin (fl‐BSA) was degraded almost twice as fast as unmodified BSA. The rate of degradation of 125I‐BSA was very similar in eight cell lines of mouse, human, monkey and rat origin. Microinjected proteins were analyzed on SDS‐acrylamide gels after injection, and for BSA and immunoglobin G, all remaining intracellular 125I migrated at the molecular weight of the injected proteins. By contrast, more than 80% of the extracellular 125I chromatographed as iodotyrosine. With the exception of fl‐BSA, which exhibited perinuclear accumulation in approximately one‐half of the injected cells, autoradiography showed that throughout the period of study the injected proteins remained dispersed in the cytoplasm.
α‐Amanitin and 5‐fluorouridine inhibition of serumstimulated DNA synthesis in quiescent AKR‐2B mouse embryo cells
Authors: Wells David J. , Stoddard Linda S. , Getz Michael J. , Moses Harold L. 
Published: February 2005

AbstractAKR‐2B mouse embryo cells undergoing the serum‐stimulated transition from a quiescent to a proliferating state exhibit an increase in the rate of hnRNA synthesis which appears to be mediated through an increase in the actual number of RNA polymerase II molecules. α‐Amanitin, administered early in the prereplication interval following stimulation, effectively inhibits hnRNA synthesis, polysomal mRNA accumulation, polyribosome formation, and subsequent DNA synthesis, and cell division. Unexpectedly, α‐amanitin treatment also produces almost complete inhibition of the synthesis of 45SrRNA precursor and the increase in accumulation of cytoplasmic rRNA following serum stimulation. In order to determine whether the inhibition of new ribosomal synthesis might in itself be sufficient to prevent serum‐stimulated DNA synthesis, the effects of 5‐fluorouridine (5‐FU), a specific inhibitor of 45SrRNA processing, were investigated. If added within eight hours following serum stimulation, 5‐FU was found to completely inhibit subsequent DNA synthesis. These results suggest that quescent AKR‐2B cells do not contain a sufficient excess of ribosomes to support the synthesis of proteins which are required for DNA synthesis in response to serum growth factors. Furthermore, an early polymerase II mediated synthesis of mRNA (s) coding for some factor(S) necessary for ribosomal gene transcription may be an essential step in the serum‐stimulated synthesis of new ribosomes.
Cell cycle dependence of transformation expression in mouse cells transformed by a thermosensitive mutant (Ts‐121) of polyoma virus
Authors: Okada Yasuhiro S. , Hakura Akira 
Published: February 2005

AbstractChange in division capability as a phenotypic expression of cellular transformation was investigated by using one of the temperature‐sensitive (ts) mutants of the polyoma virus‐transformed cell line, the 121‐6‐5 cells of BALB/3T3. When contact ‐inhibited cells were treated with hyaluronidase at 39°C, a single round of cell division was induced after which cell growth was inhibited by cell density. However, if the cells were incubated at 35°C, after the enzyme treatment, density‐inhibition block disappeared and the cells entered a second division. This indicates that the release of cells from density‐inhibition depends on the low temperature incubation. The ability of cells to complete a second division was examined by shifting the cells from 39°C to 35°C during different phases of the first division cycle after the enzyme‐treatment. A 6‐hour incubation of S phase cells at 35°C resulted in a second cycle of division, while the 24‐hour incubation of G1 cells at 35°C did not induce a second round of division. These results suggest that expression of the transformed phenotype in 121‐6‐5 cells is clearly dependent upon both the temperature and the phase of the division cycle.
A growth factor from spinal cord
Authors: Jennings Thomas , Jones R. David , Lipton Allan 
Published: February 2005

AbstractMitogenic activity is present at a variety of sites in the central nervous system. A growth factor was purified from neonatal bovine spinal cord. It has a pI of 9.5‐9.8 and a molecular weight of about 11,000 daltons. Spinal cord growth factor is a basic polypeptide that is inactivated by extremely acid or basic conditions. Its mobility on SDS polyacrylamide gels suggests that this factor is different from pituitary FGF and brain FGF‐1.
Insulin effects on protein synthesis and secretion in primary cultures of amphibian hepatocytes
Authors: Stanchfield James E. , Yager James D. 
Published: February 2005

AbstractThe objective of the present study was to determine the effects of insulin on amphibian hepatocytes in primary culture. Hepatocytes were isolated from adult bullfrogs by collagenase perfusion and maintained as monolayers in serum‐free medium. Cells cultured in the continuous presence of insulin exhibited a relatively constant rate of protein secretion over the first four to five days, whereas controls showed an almost three‐fold decrease over the same time period. The decline in secreted proteins was equally represented in most exported proteins, except that serum albumin secretion showed twice as much of a decrease relative to the other proteins.The maintenance of protein secretion by insulin was the result of its effect on protein synthesis. The rate of protein synthesis was measured by the incorporation of (3H)‐leucine into protein using culture medium containing 0.5 mM leucine, a condition where the specific radioactivity of leucyl‐tRNA was shown to be equal to that of (3H)‐leucine in the medium. Cultures maintained with insulin for 60 hours synthesized protein at two to three times the rate found in non‐insulin treated controls whose rate of protein synthesis was first detectably decreased after nine hours of culture in the insulin‐free medium.Sedimentation profiles of polyribosomes from hepatocytes maintained for 60 hours without insulin showed proportionately fewer ribosomes in large polysomes and more in monosomes and free ribosomal subunits than ribosomes from cells cultured with insulin. This result suggests that the decrease in protein synthesis found in the absence of insulin is due to a defect in initiation. Insulin does not exert its effect by regulating cellular levels of ATP; no change in ATP content was found in cells maintained with or without insulin.The results show that insulin maintains high levels of protein synthesis and secretion in amphibian hepatocytes. The hepatocytes in monolayer culture provide a system to study the molecular mechanisms involved in the translational control of protein synthesis by insulin.
Polyene macrolide antibiotic cytotoxicity and membrane permeability alterations. II. Phenotypic expression in intraspecific and interspecific somatic cell hybrids
Authors: Fisher Paul B. , Bryson Vernon , Schaffner Carl P. 
Published: February 2005

AbstractCytotoxicity and membrane permeability alterations induced by the polyene macrolide antibiotics filipin (FIL) and pimaricin (PIM) have been compared in parental intraspecific and interspecific somatic cell hybrids. B82 (mouse) and B1 (hamster) cells were found to be more resistant than RAG (mouse) parental cells to both polyene macrolides as indicated by 24‐hour survival, 72‐hour viability, and growth rate. Analysis of both intraspecific and interspecific somatic cell hybrids indicated that polyene macrolide resistance was being expressed even in the presence of the polyene macrolide‐sensitive (RAG) genome. Where one of the two parental cell types is relatively polyene macrolide resistant, the use of specific polyene macrolides may prove efficacious as half‐selective agents in cell hybridization.
Characterization of factor(s) in culture supernatants affecting cell social behavior
Authors: Weston James A. , Yamada Kenneth M. , Hendricks Karen L. 
Published: February 2005

AbstractTreatment of embryonic chick heart fibroblast cultures with 0.2 M urea reversibly increases cellular overlap. The increase in cellular overlapping over that in control cultures may be quantitated by the overlap ratio (R), the ratio of the number of superimposed nuclei observed, to the number expected to occur when cells are assumed to be distributed randomly over the culture substratum (R = observed/expected overlaps). Reversal of the urea‐induced increase in R is blocked by 0.2 μg/ml cycloheximide. In the presence of cycloheximide, normal (low) overlap ratios are restored to urea‐treated cultures by adding non‐dialyzable material recovered by washing fibroblast monolayers with serum‐free medium. The overlap ratio assay revealed no effect of supernatant material added either to urea‐treated cultures in the continued presence of urea, or to untreated cultures. Although unfiltered supernatants were shown by SDS‐polyacrylamide gel electrophoresis to contain fibronectin (CSP; LETS; MWappar. = 220,000 d) and smaller proteins, the ability to reverse the urea‐induced increase in overlap ratio was present in Diaflo and Millipore filtrates of culture supernatants in which fibronectin was greatly depleted or absent. In contrast, purified fibronectin preparations failed to lower urea‐induced increases in overlap‐ratio. Partially purified, biologically active supernatants, prepared from 14C‐leucine or 125I‐labeled cultures, contained several macromolecules smaller than fibronectin that were labeled by both radioisotopes. In particular, one band (MWappar. = 58‐60,000 d) was present in polyacrylamide gels of active supernatant and also depleted in gels of homogenates from urea‐treated cultures. These results indicate that external macromolecules other than fibronectin are synthesized by culture fibroblasts and can affect cell social behavior or culture morphology.
A calcium requirement for movement of cultured cells
Authors: Moore Leon , Pastan Ira 
Published: February 2005

AbstractWhen calcium is removed from culture medium, motility of cultured cells is decreased. The effect is rapid, reversible and pronounced. Decreased motility is observed with normal mouse Balb/c 3T3 cells, mouse L929 cells, rat kidney fibroblasts and chick embryo fibroblasts. The calcium dependence of movement can be observed both with individual cells and with the movement of the margin of a monolayer into a wound. Magnesium will not substitute for calcium to maintain motility. Strontium will substitute, but is not as effective as calcium for maintaining cell movement. Low concentrations of the divalent cation ionophore A23187 (0.5–1 μm) partially reverse the reduced migration observed at low calcium concentrations. These results are consistent with the hypothesis that movement of non‐muscle cells occurs through mechanisms similar to those important in the contraction of muscle.
Selective high metabolic lability of uridine, guanosine and cytosine triphosphates in response to glucose deprivation and refeeding of untransformed and polyoma virus‐transformed hamster fibroblasts
Authors: Rapaport Eliezer , Christopher C. William , Svihovec Sandra K. , Ullrey Donna , Kalckar Herman M. 
Published: February 2005

AbstractSugar deprivation of hamster fibroblasts (NILAbbreviations: ATP, ADP and AMP, adenosine 5′‐tri‐, di‐ and monophosphate respectively; CTP, CDP and CMP, cytosine 5′‐tri‐, di and monophosphate respectively; GTP, GDP and GMP, guanosine 5′‐tri‐, di‐ and monophosphate respectively; IMP, inosine 5′‐monophosphate; Gal‐1‐P, α‐D‐galactose‐1‐phosphate; UDP‐Gal, uridine 5′‐diphosphogalactose; D‐MEM, Dulbecco's modified Eagle's minimal essential medium; D‐PBS, Dulbecco's phosphate‐buffered saline (pH 7.2); NIL, a line of Syrian hamster fibroblasts; PyNIL, a polyoma virus‐transformed line of NIL cells.
) affected the steady state levels (pool sizes) of cellular acid soluble nucleotides in the following fashion; the pools of UTP, GTP and CTP decreased to a much greater extent than the cellular ATP pools, with the UTP pools undergoing the most dramatic reduction. Sugar deprivation of polyoma‐transformed NIL cells (PyNIL) yielded even sharper decreases in the nucleoside triphosphate pools with relative changes similar to those of the untransformed cells. Inhibition of protein synthesis by cycloheximide, initiated at the onset of (and continued during) sugar deprivation, prevented the reduction in pool sizes and yielded values slightly higher than those observed for pool sizes in cells cultured in sugar‐supplemented medium. Refeeding glucose to sugar‐depleted hamster fibroblasts led to rapid increases (within 1 hour) in the UTP and CTP pools to levels well above the pool sizes observed in cells which were continuously cultured (16 hours) in sugar supplemented medium. Feeding NIL or PyNIL cells with fructose instead of glucose as the only hexose source did not appreciably affect any of the ribonucleoside triphosphate pool sizes. Measurements of hexose uptake by NIL and PyNIL cells under a variety of conditions suggest that hexose transport is not regulated by the total cellular pools of ATP or any of the other ribonucleoside triphosphates.