bluuebunny/crossref_metadata_2025_split huggingface dataset:
Differential effects of abrin on normal and tumor cells
Authors: Chan Lee‐Nien Lillian , Li Jiann‐Shyong , Liu Su‐Yin 
Published: February 2005

AbstractThe effects of the plant toxin abrin on normal mouse embryonic fibroblasts (MEF), an untransformed mouse cell line (NIH 3T3), and two mouse tumor cell lines (LMTK− and S‐180) were studied. Measurements of cell growth and colony formation showed that MEF and S‐180 cells were more sensitive to abrin intoxication than NIH 3T3 and LMTK− cells. Also, the effects of abrin on the inhibition of [3H]leucine and [3H]thymidine incorporation were more evident in MEF and S‐180 cells. The basis for these varying responses to abrin by the four different cells was examined. The number of abrin binding sites per cell was determined from [125]abrin binding studies: NIH 3T3 and LMTK− cells had significantly fewer abrin binding sites than MEF and S‐180 cells. The fate of the [125l]abrin after internalization was examined by gel electrophoresis and autoradiography. A pattern of time‐dependent degradation was observed, degradation being more rapid in NIH 3T3 and S‐180 cells than in LMTK− and MEF cells. We conclude that the varying responses of different cells to the toxin abrin may be due to several factors, including the relative number of abrin binding sites on the cell surface and the rate of degradation of the toxin once internalized. The results also show that the sensitivities of the cells to abrin do not necessarily correlate with their normal or neoplastic state.
Phenotypic transformation of normal rat kidney cells in a growth‐factor‐defined medium: Induction by a neuroblastoma‐derived transforming growth factor independently of the EGF receptor
Authors: van Zoellen Everardus J. J. , van Oostwaard Theodora M. J. , van der Saag Paul T. , de Laat Siegfried W. 
Published: February 2005

AbstractPolypeptide growth factor activity in serum can be destroyed by treatment with dithiothreitol. When such growth‐factor‐inactivated serum is used as a supplement of culture media instead of regular serum, normal rat kidney (NRK) cells become quiescent unless defined polypeptide growth factors like insulin and epidermal growth factor (EGF) are added. On this basis a growth‐factor‐defined medium has been developed for NRK cells, which permits cell proliferation as rapidly as in media supplemented with serum, even at low cell densities. Moreover, cells can be serially passaged in this medium. NRK cells can be induced to grow in semisolid media when incubated with transforming growth factors. The growth‐factor‐defined medium permits soft agar growth experiments of NRK cells, without interference from polypeptide growth factors in serum. Using this assay system we have shown that EGF alone is unable to induce any degree of anchorage‐independent growth in NRK cells. However, a recently identified transforming growth factor from mouse neuroblastoma cells which does not compete with EGF for receptor binding is able to induce progressively growing colonies of NRK cells in soft agar, even without additional EGF.
Two receptor classes for epidermal growth factor on pheochromocytoma cells, distinguishable by temperature, lectins, and tumor promoters
Authors: Boonstra Johannes , Mummery Christine L. , van der Saag Paul T. , de Laat Siegrfried W. 
Published: February 2005

AbstractRat pheochromocytoma cells (clone PC12) display cell surface receptors for both nerve growth factor (NGF) and epidermal growth factor (EGF) and therefore provide a useful model system with which to study the role of these receptors in the regulation of proliferation and differentiation. In this paper PC12 cells are demonstrated to possess two classes of EGF receptors, a high‐affinity class with 7,600 sites per cell and an apparent dissociation constant (Kd) of 0.05 nM, and a low‐affinity class with 62,000 sites per cell and a Kd of 14.1 nM. These findings are contrary to literature data (Huff et al., 1981; Vale and Shooter, 1983) but can be explained in part by differences in experimental conditions. Binding studies at 37°C compared with room temperature demonstrated similar affinities of both classes, but during prolonged incubation at 37°C, the binding capacities of both classes decreased. Furthermore the high‐affinity class was sensitive to lectins, such as concanavalin A (Con A), and to the tumor‐promoting phorbol ester 12‐O‐tetradecanoylphorbol‐13‐acetate (TPA). Both compounds caused a decrease of the affinity of the high‐affinity class without affecting the low‐affinity class. At high concentrations of Con A or TPA, a decrease of the apparent number of binding sites of the low‐affinity class was also observed. The similarities between the characteristics of EGF binding and NGF binding in PC12 cells are striking and will be discussed.
Enterocytic differentiation and glucose utilization in the human colon tumor cell line Caco‐2: Modulation by forskolin
Authors: Rousset Monique , Laburthe Marc , Pinto Moïse , Chevalier Guillemette , Rouyer‐Fessard Christiane , Dussaulx Elisabeth , Trugnan Germain , Boige Nathalie , Brun Jean‐Louis , Zweibaum Alain 
Published: February 2005

AbstractThe human colon cancer line Caco‐2 exhibits after confluency a concomitant increase of glycogen accumulation and an enterocytic differentiation. The purpose of this work was to investigate whether forskolin (FK), an activator of adenylate cyclase, would induce a permanent glycogenolysis and, if so, whether it would result in modifications of the differentiation pattern of the cells. FK activates adenylate cyclase in Caco‐2 cells with an ED50 of 7 × 10−6M. Three different treatment protocols with FK (10−5M) were applied: (1) the cells were treated during all the time in culture (20 days); (2) the treatment was started after confluency; (3) the treatment was interrupted after confluency. The presence of FK results in a permanent stimulation of cAMP accumulation (10 to 20 fold the basal values) and in a permanently reduced glycogen content (30 to 50% of the control values). The rates of glucose consumption are increased three and five fold in protocols 1 and 3 respectively. These metabolic changes are associated with morphological changes (tightening of the intercellular spaces and shortening of the brush border microvilli) and with a dual inhibition of the activities of brush border hydrolases: (a) an inhibition of the post‐confluent increase of activity of sucrase, aminopeptidase N and alkaline phosphatase in the brush border enriched fraction; (b) an inhibition of the post‐confluent increase of activity of sucrase in the cell homogenate. A comparison of the results obtained in each protocol shows that the morphological modifications and the decrease of the enzyme activities in the brush border fraction are regularly associated with an increased cAMP accumulation, whereas the inhibition of the differentiation of sucrase is a direct consequence of the increase in glucose consumption and decrease in glycogen stores.
Carbohydrate metabolism in transforming lymphocytes from the aged
Authors: Tollefsbol Trygve O. , Cohen Harvey J. 
Published: February 2005

AbstractThere is an age‐related decline in immune capacity which has been linked to a decreased response of lymphocytes to mitogens in vitro. During transformation, lymphocytes require a marked increase in energy production and biosynthesis which is supplied primarily by glycolysis. In the elderly, the glycolytic enzymes increase significantly in transforming lymphocytes at least 24 hr later than in the young and then at significantly reduced levels. Glucose utilization is also impaired in stimulated lymphocytes from the elderly but follows the impairment of glycolysis. In stimulated cells from the young, increases in glycolytic enzyme activity levels accompany sharp increases in blastogenesis while a delayed increase in glycolytic enzyme activity in the elderly is accompanied by a delay in blastogenesis. Maximal glycolytic enzyme activity levels are significantly reduced in transformed lymphocytes from the elderly though the number of transformed cells is also significantly reduced. However, glycolytic enzyme activity levels are significantly lower in the elderly than in the young even on a per transformed cell basis. Thus, this reduction cannot be attributed to the lower number of transformed cells that are present in the elderly. This defect in the increase of glycolysis in stimulated cells from the elders suggests an intracellular mechanism which could be related to the impaired lymphocyte stimulation in vitro in the aged.
Diacylglycerol treatment rapidly decreases the affinity of the epidermal growth factor receptors of Swiss 3T3 cells
Authors: Sinnett‐Smith James W. , Rozengurt Enrique 
Published: February 2005

AbstractThe synthetic diacylglycerol 1‐oleoyl‐2‐acetyl glycerol (OAG) and phorbol esters activate protein kinase C in intact cells. We report here that OAG inhibits the binding of 125I‐labelled epidermal growth factor (125I‐EGF) to Swiss 3T3 cells. The inhibition was detected as early as 1 min after treatment at 37°C and persisted for at least 120 min. The effect of OAG was reversed upon removal of this diacylglycerol. Detailed Scatchard analysis of 125I‐EGF binding to Swiss 3T3 cells at 4°C after a 1 h incubation with a saturating dose of OAG at 37°C, demonstrates that this OAG pretreatment does not change the apparent number of EGF receptors but causes a marked decrease in their apparent affinity for the ligand. Prolonged treatment (40 h) of the cells with phorbol dibutyrate (PBt2) which causes a marked decrease in the number of phorbol ester binding sites and in the activity of protein kinase C, prevented the inhibition of 125I‐EGF binding by both PBt2 and OAG. The results support the possibility that protein kinase C plays a role in the transmodulation of the EGF receptor in intact cells.
Reduction of DNA synthesis in aging but still proliferating cells
Authors: Collins James M. , Chu Annie K. 
Published: February 2005

AbstractIt is well known that cell proliferation (and hence, DNA synthesis) declines in human diploid fibroblast‐like cells with increasing passage number. It is not clear whether DNA synthesis declines in the remaining cells that are still actively proliferating. Estimations of cell kinetic parameters permitted extrapolations to be made that reflected the declining numbers of cells still capable of DNA replication. DNA synthesis declined with culture age in intact cells, permeabilized cells, and in the isolated nuclear matrix even when corrected for declining numbers of proliferating cells. With age, DNA polymerase alpha and beta activity in cell lysates declined, but when corrected for the remaining proliferating cells, only polymerase alpha activity declined; DNA polymerase alpha and beta activity bound to the nuclear matrix declined, but when corrected for declining proliferation, no decline was apparent for either enzyme. There was an increase in the number of S1‐nuclease sensitive sites and breaks in the parental DNA of the dividing cells in older cultures. It is suggested that in aging cultures, not only does overall DNA synthesis decline owing to decreasing cell proliferation, but also that DNA synthesis declines in the remaining proliferating cells, that this decline is not due to decreasing amounts of DNA polymerase bound to the nuclear matrix, and that alterations in DNA structure occur.
The metabolism of cobalamin bound to transcobalamin II and to glycoproteins that bind Cbl in HepG2 cells (human hepatoma)
Authors: Hall Charles A. , Green‐Colligan Pamela D. , Begley James A. 
Published: February 2005

AbstractThe binding, internalization, processing and release of labeled cyanocobalamin (CN[57Co]Cbl) bound to human transcobalamin II (TC II) were studied in HepG2 cells, a line of hepatocytes derived from a human hepatoma. The cells bound the TC II‐Cbl by specific, high affinity receptors. Within the cell, the CN‐Cbl was promptly freed from TC II and the CN‐Cbl converted to more active forms including adenosyl Cbl (AdoCbl) and methyl Cbl (MeCbl). Whereas free labeled Cbl was still present at 72 hours after entry, the cells also bound Cbl to an intracellular binder (ICB) presumed to represent the holo enzymes dependent on Cbl. At levels of TC II that saturated the receptors for TC II‐Cbl, much of the Cbl entering the cells remained free and was converted to AdoCbl. Under these circumstances the cells released free Cbl, mostly AdoCbl.Human R type binders of Cbl, which are glycoproteins and some having a terminal galactose, were bound by the HepG2 cells. The binding was characteristic of the receptor system responsive to a terminal galactose, or asialoglycoproteins, but was inconsistent and of low affinity. Cbl bound to R binder was internalized and converted to coenzyme forms of Cbl, but the process was much less effective than when the Cbl entered via the TC II receptor system. It was concluded that the receptors for R‐Cbl were unlikely to contribute to the physiologic transport of Cbl in man, but may function in some yet unknown way.
A reduction in the in situ rates of oxygen and glucose consumption of cells in EMT6/Ro spheroids during growth
Authors: Freyer J. P. , Sutherland R. M. 
Published: February 2005

AbstractThe rates of consumption of oxygen and glucose by EMT6/Ro cells in multi‐cellular spheroids were measured at various times during normal growth. In situ spheroid cellular consumption rates were similar to those of exponentially growing single cells up to a spheroid diameter of 150 μm. Further growth resulted in decreases in the rates of both oxygen and glucose consumption which were correlated with the increase in spheroid diameter and cell number. At a diameter of 1300 μm, both rates of cellular consumption had decreased by a factor of 2.5. The rates of consumption per unit of nonnecrotic spheroid volume decreased in a similar manner. Measurements with single cells demonstrated that the rate of oxygen consumption was coupled with glucose concentration, and vice versa. The rates of consumption for cells dissociated from small spheroids indicated that there was some effect of the spheroid environment. As the spheroids grew, however, association in the spheroid structure accounted for a smaller proportion of the total observed reduction in the rates of nutrient consumption. The presence of central necrosis also appeared to have no effect on the rates of consumption of these nutrients. Spheroid‐derived cells showed a decrease in cell volume with growth as the cells accumulated in a quiescent state. Measurements with single cells demonstrated that oxygen and glucose consumption were correlated with cell volume and with the development of nonproliferating cells. We conclude that the observed decrease in oxygen and glucose consumption with growth in spheroids is largely due to the progressive accumulation of cells in a quiescent state characterized by an inherently lower cellular rate of nutrient utilization.
Continuous growth and phosphatidylcholine synthesis of rat hepatoma cells in choline‐deprived chemically defined medium
Authors: Yamamoto Katsuhiko , Niwa Akira , Yasumura Yosihiro 
Published: February 2005

AbstractA choline non‐required cell line was established from a rat hepatoma cell line. The line designated R‐Y121B·cho was able to grow in choline‐deprived medium without serum and lipid. Choline is necessary for the biosynthesis of phosphatidylcholine, which is a main component of cell membranes. Phosphatidylcholine can be synthesized by the methylation of phosphatidyletha‐nolamine in liver cells. Phospholipid composition and incorporation of radiolabeled serine into phosphatidylserine or phosphatidylethanolamine were quite similar in R‐Y121B cho and its parental cells. However R‐Y121B cho cells had higher phosphatidylcholine synthesis activity from radiolabeled methionine than parental cells. These results indicate that choline requirement of mammalian cells depends on the activity of phosphatidylethanolamine methyltransferase.
The synergistic action of the copper chelator bathocuproine sulphonate and cysteine in enhancing growth of L1210 cells in vitro
Authors: Ishii Tetsuro , Bannai Shiro 
Published: February 2005

AbstractThe growth stimulating effect of a copper‐specific chelator, 2,9‐dimethyl‐4,7‐diphenyl‐1, 10‐phenonthroline‐sulfonic acid on mouse lymphoma L1210 cells in vitro has been studied. Since they are defective in cystine transport, these cells require cysteine for their growth in vitro. However, addition of cysteine does not greatly enhance cell growth because it is rapidly oxidized to cystine. We have observed that the copper chelator potently inhibited oxidation of cysteine in culture medium and that simultaneous addition of cysteine and the chelator greatly enhanced cell growth. The chelator alone stimulated cell growth slightly by stabilizing a small amount of cysteine effluxed from the cells to the medium. The chelator also enhanced the growth promoting activity of 2‐mercaptoethanol by stabilizing cysteine produced in the medium during culture. These results suggest that the chelator stimulates cell growth by inhibiting copper mediated oxidation of cysteine in culture medium.
Potassium‐induced reverse transformation of cells infected with a temperature‐sensitive transformation mutant virus
Authors: Lai Chiu‐Nan , Becker Frederick F. 
Published: February 2005

AbstractHigh potassium concentrations altered the morphology and the ability to grow in soft agar in 6m2 cells, a clone of rat kidney cells infected with a temperature‐sensitive mutant of Moloney sarcoma virus. Approximately 60% of cells exhibited normal morphology in the presence of 94.8 mM potassium in isotonic medium at the temperature permissive for transformation, whereas 100% were normal at 72 mM potassium in hypertonic media. A significant reduction of growth in soft agar was also induced with these conditions. However, the synthesis ratio of virus‐specified transforming protein to marker viral protein was not altered. Na+K+ ‐ATPase might play a role in this reversetransformation process.
Functional properties of normal and inverted rat thyroid follicles in suspension culture
Authors: Tacchetti Carlo , Zurzolo Chiara , Monticelli Antonella , Nitsch Lucio 
Published: February 2005

AbstractRat thyroid follicles in both the normal and the inverted configuration have been cultured in suspension. It has been found that normal follicles (i.e., those having a structural organization similar to the follicles in vivo) express most functional properties of the thyroid gland. They trap iodide, synthesize, secrete, and iodinate thyroglobulin, and secrete thyroid hormone into the culture medium. On the contrary, in inverted follicles (i.e., those having a cell polarity reversed with respect to normal) we were unable to detect expression of some of these functions. We conclude that both the follicular organization and the proper cell polarity are needed for the full expression of thyroid functional properties.
Hematopoiesis in the rat: Quantitation of hematopoietic progenitors and the response to iron deficiency anemia
Authors: Kimura Hideo , Finch C. A. , Adamson John W. 
Published: February 2005

AbstractTo determine the quantitative effects of iron deficiency on erythropoiesis and to assess the response of erythroid progenitors to sustained anemia, we developed quantitative assays for various hematopoietic progenitors in the adult, Sprague‐Dawley rat including erythroid colony‐ and burst‐forming cells (CFU‐E and BFU‐E), granulocyte/macrophage colony‐forming cells (CFU‐GM), and megakaryocytic colony‐forming cells (CFU‐Meg). CFU‐E were cultured in methylcellulose and grew best in the presence of fetal calf serum. CFU‐GM, BFU‐E, and CFU‐Meg grew better in normal rat plasma and required the presence of pokeweed mitogen‐stimulated rat spleen cell conditioned medium. The numbers of progenitors and nucleated erythroblasts in total marrow were estimated by the ratios of radioactivity in the humerus to the total skeleton as determined by radioiron dilution. The numbers of progenitors and erythroblasts in the spleen were measured by simple dilution. Sustained anemia was brought about through chronic iron deficiency. The response to iron deficiency anemia (IDA) was monitored by the numbers of the various progenitors and their cell cycle characteristics as measured by the tritiated thymidine suicide technique. With IDA, the number of CFU‐E in the body (marrow plus spleen) was increased to 3.5 times control, whereas the numbers of BFU‐E and CFU‐GM were unchanged. There was no difference in the percentage of CFU‐E, BFU‐E, and CFU‐GM in DNA synthesis (68%, 19.4%, and 18.8%, respectively). With iron therapy of IDA, CFU‐E numbers in marrow began to decrease by day 1 and fell in a manner reciprocal to changes in the hematocrit. Marrow and spleen erythroblasts, 1.7 times control in IDA, increased further to 3.9 times control by the fourth day after iron administration. There was no change in BFU‐E or CFU‐GM numbers in response to iron repletion, although the fraction of progenitors increased in the spleen. Thus, IDA does not limit the increase in CFU‐E seen with anemia, but does restrict erythroid maturation. Furthermore, the increase in CFU‐E and the state of chronic anemia occur without detectable changes in the number or cell cycle state of the more primitive BFU‐E.
Anchorage‐independent growth of primary rat embryo cells is induced by platelet‐derived growth factor and inhibited by type‐beta transforming growth factor
Authors: Anzano Mario A. , Roberts Anita B. , Sporn Michael B. 
Published: February 2005

AbstractSeveral growth factors implicated in the process of cellular transformation were tested for their ability to induce anchorage‐independent (AI) growth of primary rat embryo (RE) cells. Our results show that in the presence of 10% calf serum, platelet‐derived growth factor (PDGF), 1–30 ng/ml, has the strongest effect of all growth factors tested on Al growth. Type‐β transforming growth factor (TGF‐β), by itself, does not stimulate Al growth, and it inhibits the PDGF‐induced colony formation in a dose‐dependent manner (ED50 ∼ 0.03 ng/ml). Qualitatively similar responses are obtained by using an established line of fibroblasts, NIH 3T3 cells; the principal difference between the response of the primary cells and the established cell line is in colony‐forming efficiency in soft agar culture (15% and 90%, respectively, for growth of colonies > 1,500 μm2 diameter in the presence of 10 ng/ml PDGF). Since Al growth has been shown to correlate well with tumorigenicity in vivo, our results suggest that the transforming potential of PDGF in an appropriate responsive cell can be controlled not only through its interaction with its own receptor, but also by the presence of inhibitory factors such as TGF‐β.