bluuebunny/crossref_metadata_2025_split huggingface dataset:
Rates of incorporation of radioactive molecules during the cell cycle
Authors: Gray J. W. , Pallavicini M. G. , George Y. S. , Groppi V. , Look M. , Dean P. N. 
Published: February 2005

AbstractWe report measurements of the incorporation of radioactive molecules during short labeling periods, as a function of cell‐cycle stage, using a cell‐sorter‐based technique that does not require cell synchronization. We have determined: (1) tritiated thymidine (3H‐TdR) incorporation throughout S‐phase in Lewis lung tumor cells in vitro both before and after treatment with cytosine arabinoside; (2) 3H‐TdR incorporation throughout S‐phase in KHT tumor cells in vitro and in vivo; (3) 3H‐TdR incorporation throughout S‐phase in Chinese hamster ovary cells and compared it with DNA synthesis throughout S‐phase; (4) a mathematical expression describing 3H‐TdR incorporation throughout S‐phase in Chinese hamster M3‐1 cells; and (5) the simultaneous incorporation of 3H‐TdR and 35S‐methionine as they are related to cell size and DNA content in S49 mouse lymphoma cells. In asynchronously growing cells in vitro and in vivo, 3HH‐TdR incorporation was generally low in early and late S‐phase and highest in mid‐S‐phase. However, in Lewis lung tumor cells treated with cytosine arabinoside 3H‐TdR incorporation was highest in early and late S‐phase and lowest in mid‐S‐phase. Incorporation of 35S‐methionine increased continuously with cell size and DNA content. Incorporation of 3H‐TdR in CHO cells was proportional to DNA synthesis.
Trifluoperazine inhibits spreading and migration of cells in culture
Authors: Connor Charles G. , Brady Richard C. , Brownstein Barbara L. 
Published: February 2005

AbstractTrifluoperazine (TFP) blocks spreading and migration of cultured mammalian cells. These are calcium‐dependent and microfilament‐mediated processes. Calmodulin, a regulator of many calcium‐dependent processes in cells, is selectively inhibited by TFP. Cell spreading on a plastic‐ or collagen‐coated substratum was reversibly inhibited by 10 μM TFP. The drug blocks cell spreading even in the presence of 1 mM cAMP. TFP is as effective as cytochalasin B (CB), an inhibitor of microfilament function, in blocking cell spreading. All cell lines tested, whether “normal” or virally transformed, failed to spread in TFP. The drug, at a concentration sufficient to inhibit spreading, does not interfere with the initial attachment of a cell to a plastic surface. Cells plated in the presence of 10 μM TFP attach at a rate and to an extent equal to untreated controls. TFP added to already spread cells results in a reversible cell rounding. Detection of fibronectin by indirect immunofluorescence suggests TFP‐induced cell rounding is not due to shedding of fibronectin from the cell surface. TFP reversibly blocks cell migration into a wound edge almost as effectively as CB. We suggest that TFP interferes with these microfilament‐mediated functions by direct action on the microfilaments or indirect action by inactivating calmodulin.
Expression of angiotensin‐converting enzyme activity in cultured pulmonary artery endothelial cells
Authors: del Vecchio Peter J. , Smith James R. 
Published: February 2005

AbstractAngiotensin‐converting enzyme (EC 3.4.15.1) is a carboxyterminal dipeptidyl peptidase. The enzyme catalyzes the conversion of the decapeptide angiotensin I to the octapeptide angiotensin II. In addition, the enzyme catabolizes bradykinin. Because of these actions, the enzyme is of pivotal importance in blood pressure homeostasis. Numerous investigators have demonstrated the presence of the enzyme in association with endothelial cells but relatively little is known concerning the factors controlling the expression of enzyme activity by endothelial cells in culture. We have demonstrated that endothelial cells in culture do not express significant amounts of enzyme activity until several days after growth ceases due to high cell density. This is important because it demonstrates a change in function with stage of growth in culture and a possible difference in functional capabilities between nondividing endothelial cells and cells that are dividing in response to injury. Since density‐dependent expression of differentiated traits does not appear to be unique to endothelial cells an understanding of the mechanisms underlying this phenomenon may provide a general explanation for the expression of differentiated traits by cultured cells.
Precursor of mast cells fixed in the skin of mice
Authors: Matsuda Hiroshi , Kitamura Yukihiko , Sonoda Takashi , Imori Tatsuo 
Published: February 2005

AbstractThe presence and origin of mast‐cell precursors fixed in the skin tissue of mice were investigated. Giant granules of beige (C57BL/6‐bgj/bgj, Chediak‐Higashi syndrome) mice were used to distinguish different populations of mast cells. Pieces of the skin were grafted from the intact WBB6F1 (WB × C57BL/6)F1−+/+ mice onto the back of the WBB6F1−+/+ mice which had been irradiated and injected with bone marrow cells of C57BL/6‐bgj/bjj mice (bgj/bgj −+/+ chimeras). Although the number of mast cells in the skin grafts decreased after the transplantation, the mast‐cell precursors circulating in the bloodstream of bgj/bgj −+/+ chimeras (bgj/bgj type) did not seem to enter into the skin grafts, because most of mast cells were of +/+ type after the recovery of mast‐cell number to pregrafting levels. As a considerable proportion of +/+‐type mast cells was labeled with 3H‐thymidine, the recovery of mast‐cell number in the grafts was attributed to the proliferation and differentiation of +/+‐type precursor cells fixed in the skin tissue of the donor. On the other hand, the skin of WBB6F1‐W/Wv mice seemed to be depleted of fixed precursors, because most of mast cells were of bgj/bgj type in skin grafted from WBB6F1‐W/Wv mice to bgj/bgj−+/+ chimeras. Since the fixed precursor cells which proliferate and differentiate into mast cells after skin grafting may be transferred to WBB6F1‐W/Wv mice by bone marrow transplantation, such precursor cells seem to have been derived from the bone marrow.
Identification of the glucose/glycosylation‐regulated proteins as those which accumulate in the temperature‐sensitive cell line K12
Authors: Melero José A. 
Published: February 2005

AbstractThe analysis of proteins synthesized by the temperature‐sensitive cell line K12 at the restrictive temperature or after glucose starvation revealed that two main polypeptides were enhanced under both conditions. Besides having the same apparent molecular weights, these new proteins showed identical patterns of partial proteolysis products, irrespective of being isolated from cells incubated at the nonpermissive temperature or from glucose‐starved cultures. These results identified the proteins overproduced by K12 cells at 39.5 °C as those described in other cell systems, called „glucose/glycosylation regulated proteins”︁ (GR proteins). In addition, it is shown that K12 cells are defective in some step of the glycosylation pathway; this defect may be responsible for the overproduction of GR proteins in K12.
Effect of substrata and fibroblast growth factor on the proliferation in vitro of bovine aortic endothelial cells
Authors: Gospodarowicz D. , Lui G.‐M. 
Published: February 2005

AbstractThe hypothesis that, in the case of clonal or low‐density cultures, cells which do not readily proliferate are those that do not produce an extracellular matrix (ECM), while those that proliferate actively are cells that have retained their ability to produce it, has been tested using low‐density vascular endothelial cell cultures maintained on either plastic or ECM‐coated dishes and exposed to various combinations of media and sera.Proliferation of low‐density vascular endothelial cell cultures seeded on plastic and exposed to DMEM, RPMI‐1640, or medium 199 plus thymidine is a function of the batch of calf serum used to supplement the various media. In all three cases, such cultures proliferated at a slow rate and fibroblast growth factor (FGF) greatly accelerated their proliferation. In contrast, when similar cultures were seeded on ECM‐coated dishes, they actively proliferated regardless of the batch of calf serum to which they were exposed. FGF was no longer required in order for cultures to be come confluent. In the case of cultures exposed to RPMI‐1640 or medium 199 plus thymidine, it was even toxic.When cultures were exposed to either medium 199 or Waymouth medium, cells did not proliferate, regardless of the substrate (either plastic or ECM) upon which they were maintained and of the batch of serum to which they were exposed. Addition of FGF to such media had no effect. It is therefore likely that nutrient limitations in both of these media restrict the ability of low‐density vascular endothelial cells to respond to the mitogenic stimuli provided by either serum of FGF. These restrictions cannot be relieved by maintaining cells on ECM‐coated dishes, and modifications of the nutrient composition of both media is required in order to allow cells to respond to either FGF or serum when maintained on plastic or to serum alone when maintained on ECM.These results suggest that, when low‐density cell cultures are maintained on plastic and exposed to an adequate medium, their proliferation will be a function of both serum and FGF. When maintained on ECM, their proliferation will depend only on serum. It is therefore possible that the inability of serum to stimulate optimal cell proliferation when cells are maintained on plastic results from an inability of the cells to produce an ECM, and that FGF could induce such production.
Patterns of cell communication and differentiation in SV40 transformed human keratinocytes
Authors: Steinberg Mark , Defendi Vittorio 
Published: February 2005

AbstractFluorescein dye microinjection was used to demonstrate changes in communication between human epidermal keratinocytes grown in vitro after infection by the oncogenic virus, SV40. Whereas keratinocytes are normally fully coupled to each other, dye spread becomes progressively restricted to small cell subpopulations after infection, although dye coupling is increased when the infected cells attain high densities. Reduction or enhancement of dye coupling is correlated with similar changes in the extent of cytochemical differentiation and cornified envelope formation.
The synthesis of protein(S) for chromosome condensation may be regulated by a post‐transcriptional mechanism
Authors: Nishimoto Takeharu , Ishida Ryoji , Ajiro Kozo , Yamamoto Susumu , Takahashi Taijo 
Published: February 2005

AbstractA temperature sensitive mutant of BHK21, tsBN2, showed a premature chromosome condensation (PCC) upon the temperature shift of 40.5°, even in the absence of DNA replication. The induction of PCC requires new protein synthesis, but not necessarily new RNA synthesis. Our data suggested that the messenger RNA for chromosome condensation starts to be transcribed at the beginning of Sphase. At the permissive temperature (33.5°), the messenger RNA for chromosome condensation translated with a very slow rate during S phase and rapidly in G2‐M phase. At the nonpermissive temperature (40.5°), however, those messenger RNAs were translated anytime, so that various figures of PCC appeared depending on the cell cycle. On the way of PCC induction, ribosomal RNA synthesis was inhibited at first, as expected from mitosis. Our data suggested that the synthesis of protein(s) for chromosome condensation was regulated by the post‐transcriptional mechanism, in which tsBN2 might be defective, especially at the translational level.
Pulmonary macrophages alter the collagen phenotype of lung fibroblasts
Authors: Kelley Jason , Trombley Lucy , Kovacs Elizabeth J. , Davis Gerald S. , Absher Marlene 
Published: February 2005

AbstractCultured lung fibroblasts produced and secreted interstitial collagen types I and III. The relative proportion of type III collagen increased as a linear function of cell density, with confluent cultures producing 8.6% type III collagen. When human lung fibroblasts were cultured in the presence of newly harvested lung macrophages, the proportion of type III collagen secreted rose to 15.5%. This high level of type III collagen synthesis was greater than could be induced by withdrawal of serum, a perturbation known to alter the proportion of types I and III collagen synthesized by fibroblasts. This effect on fibroblast phenotype was independent of cell density, as both low and high density cultures of fibroblasts responded similarly when cultured with macrophages. There was no evidence that fibroblasts synthesize new or different collagen types (such as type I trimer) in response to macrophages. Optimal conditions for eliciting an effect on fibroblast connective tissue metabolism required interaction of the two cell types for 5–8 days. These in vitro changes are analogous to the sequence of interactions and changes in connective tissue metabolism seen during recovery from tissue injury.
In vitro differentiation of chicken embryo skin cells transformed by rous sarcoma virus
Authors: Yoshimura Mokoto , Kaji Akira , Iwasaki Yuzo 
Published: February 2005

AbstractThe epidermal cells isolated from 14‐day chicken embryo shank skin epidermis were infected in vitro with Rous sarcoma virus (RSV). Within a few weeks, rapidly growing colonies of epithelial cells appeared among the sea of transformed fibroblastic cells. When isolated and subcultured, these cells were found to possess typical markers of skin epidermis. The presence of major keratin and typical epithelial cell type morphology strongly suggested that these cells were transformed epidermal cells retaining their differentiated characteristics but having the capacity to propagate in cell culture. If RSV tsNY68, an RSV mutant having a temperature lesion in the src gene, was used, similar transformed epidermal cells were obtained at 36°C (permissive temperature). At the nonpermissive temperature (41°C) the growth rate of these cells decreased and additional keratin species appeared. At 41°C the cells were flattened and lost the refractivity in their peripheries. All the keratins which are synthesized at the nonpermissive temperature were present in normal differentiated shank skin of 19‐day old chick embryo. These cells also had “cornified envelop,” indicating extensive differentiation. Viral production was as efficient as transformed fibroblasts during the rapid growth phase, while it declined significantly after the cells reached confluency, exhibiting the differentiated characteristics. Since no normal epidermal cells could be cultured under our experimental conditions, these results represent examples in which the src gene is essential for propagation of differentiated cells in cell culture while it abolishes only a part of differentiated characteristics.
Post‐transcriptional control of protein synthesis in Balb/C‐3T3 cells by platelet‐derived growth factor and platelet‐poor plasma
Authors: Cochran Brent H. , Lillquist Jay S. , Stiles Charles D. 
Published: February 2005

AbstractPlatelet‐derived growth factor (PDGF) and platelet‐poor plasma, which lacks PDGF, both induce a rapid increase in the rate of total protein synthesis within quiescent, density‐arrested Balb/c‐3T3 cells. This stimulation of protein synthesis is associated with an increased aggregation of ribosomes into polyribosomes. Nuclear functions are not required for this response, as demonstrated by the observation that this stimulation of protein synthesis occurs in cells pretreated with actinomycin D and in enucleated cells (cytoplasts). The response to PDGF persists even after PDGF has been removed from the culture medium, but in contrast, when plasma is removed from the medium, polysomes dissaggregate and protein synthesis declines. PDGF and plasma do not function synergistically to increase protein synthesis, whereas they do to induce optimum DNA synthesis. Thus stimulation of the translational apparatus may be necessary for the mitogenic response of Balb/c‐3T3 cells to growth factors, but it is not by itself sufficient.
A molecular mechanism of regulation for granulocyte macrophage colony stimulating factor from T lymphocytes
Authors: Frölich Marianne 
Published: February 2005

AbstractWe have partially purified a mitogenic factor, termed colony stimulating factor, which is secreted from a human T lymphocytic cell line, and which stimulates in vitro formation of colonies of macrophages and granulocytes by human bone marrow cells. Colony stimulating factor (CSF) produced by cells grown in serum supplemented media has a molecular weight of 60,000. It easily dissociates into a low (20,000) and a high (40,000) molecular weight component. The low molecular weight component, F I, initiates colony formation by a subset of the marrow cells. F II, the high molecular weight component, is inactive by itself, but reconstitution of F I with F II causes a dramatic increase in the number of target cells that form colonies. In serum‐free media the T‐cell line secretes only F I, which can be activated by F II. F II is only present when serum has been added to the medium, yet it is not present in the serum. Therefore, either the lymphocytes modify a component of the serum or they are stimulated to secrete F II by the serum. The molecular properties of this CSF suggest a possible mechanism of regulation of similar factors in that dissociation and reassociation may be physiologically important in determining which cell population is activated in hematopoesis.
Large‐scale preparation and characterization of human colony‐stimulating factor
Authors: Okabe Tetsuro , Nomura Hitoshi , Sato Noriharu , Ohsawa Nakaaki 
Published: February 2005

AbstractIn order to obtain human granulocytic colony‐stimulating factor (G‐CSF) in large quantities, a large‐scale culture system of human G‐CSF‐producing cells has been established. The cell used for this system was T3M‐1, which grew in a monolayered sheet in F‐10 synthetic medium supplemented with 10% fetal bovine serum. T3M‐1 cells grew in rolling bottles at the velocity of 0.5 r.p.m. with about 22 hr. of population doubling time. When the culture reached confluency, it was incubated in a serum‐free medium supplemented with 1% bovine serum albumin. The conditioned medium was harvested every week, concentrated by Amicon PM‐10 membrane, and loaded on a Sephadex G‐75 column. The molecular weight of G‐CSF was estimated at about 30,000. This G‐CSF was stable over a pH range of 1.0 to 11.0 at 4°C for 21 hr. The CSF activity was destroyed by either trypsin or chymotrypsin, but resisted to RNase and DNase. A slight decrease in the activity was produced by treatment with neuramidase. G‐CSF stimulated granulocytic colony formation of human and mouse marrow cells. By using the roller bottle culture system, we could obtain more than 100 liters of cultured medium in a month, which was able to form about 150,000,000 colonies of human bone marrow cells. The recovery of the human G‐CSF activity from gel‐filtration column was very high (91.7%), and a large increase of specific activity was obtainable (13.3‐fold). This culture system is therefore expected to aid in the large‐scale preparation of human G‐CSF, thereby facilitating further studies on this granulopoietic factor.
Defective basal lamina formation by transformed mammary epithelial cells: A reduced effect of collagen on basal lamina (heparan sulfate‐rich) proteoglycan degradation
Authors: David Guido , Bernfield Merton 
Published: February 2005

AbstractInvasive, spontaneously transformed mammary epithelial cells derived from the normal NMuMG cell line have lost the ability of their parental cells to respond in vitro to the presence of a collagen substratum by forming a continuous glycosaminoglycan (GAG)‐rich basal lamina. On collagen, the cells synthesize 35S‐GAG at the same rates, but the transformed cells accumulate less 35S‐GAG than the normal cells because a larger fraction of their newly synthesized 35S‐GAG is rapidly degraded. Chromatography of the 35SO4‐containing materials from cultures on collagen indicates that the reduced accumulation of 35S‐GAG by the transformed cells reflects less of a heparan sulfate‐rich proteoglycan fraction which has been found in the basal lamina. On plastic substrata, however, the normal and transformed cells have near identical rates of 35S‐GAG synthesis and degradation and they accumulate similar low amounts of the basal lamina proteoglycan fraction, which is rapidly degraded.Thus, transformation appears to impair the ability of the cells to reduce basal lamina proteoglycan degradation in response to collagen. This impairment may prevent the neoplastic cells from forming a complete basal lamina and, therefore, allow local invasion.
Factors involved in the control of proliferation of bovine corneal endothelial cells maintained in serum‐free medium
Authors: Giguère L. , Cheng J. , Gospodarowicz D. 
Published: February 2005

AbstractExperimental conditions have been defined that allow bovine corneal endothelial (BCE) cells to grow in the complete absence of serum. Low density BCE cell cultures maintained on extracellular matrix (ECM)‐coated dishes and plated in the total absence of serum proliferate actively when exposed to a synthetic medium supplemented with high density lipoprotein (HDL 500 μg protein/ml), transferrin (10 μg/ml), insulin (5 μg/ml), and fibroblast (FGP) or epidermal growth factor (EGF) added at concentrations of 100 or 50 ng/ml, respectively. Omission of any of these components results in a lower growth rate and/or final cell density of the cultures. BCE cell cultures plated on plastic dishes and exposed to the same synthetic medium grow very poorly. The longevity of BCE cultures maintained on plastic versus ECM and exposed to serum‐free versus serum‐containing medium has been studied. The use of ECM‐coated dishes extended the life span of BCE cultures maintained in serum‐supplemented medium to over 120 generations, as compared to less than 20 generations for cultures maintained on plastic. Likewise, BCE cells maintained on ECM and exposed to a synthetic medium supplemented with optimal concentrations of HDL, transferrin, insulin, and FGF underwent 85 generations, whereas control cultures maintained on plastic could not be passaged. The enhancing effect of ECM on BCE cell growth and culture longevity clearly illustrates the importance of the cell substrate in the control of proliferation of these cells.
Mitogenic activity elaborated by macrophage‐like cell lines acts as competence factor(s) for BALB/c 3T3 cells
Authors: Wharton Walker , Gillespie G. Yancey , Russell Stephen W. , Pledger W. J. 
Published: February 2005

AbstractThe culture medium from several murine macrophage‐like cell lines contained a mitogenic activity that functioned synergistically with platelet‐poor plasma to induce DNA synthesis in quiescent density‐inhibited BALB/c 3T3 fibroblasts. This mitogenic activity was generated by P388D1 (and other established lines of) macrophage‐like cells that were cultured either in medium alone or in medium supplemented with platelet‐poor plasma. The amount of mitogenic activity produced was directly related to the length of time the macrophage‐like cells were maintained in the medium. Serum‐free medium conditioned by macrophage‐cells did not stimulate DNA synthesis in density‐inhibited 3T3 cells in the absence of plasma; however, a transient (4‐hr) exposure to serum‐free macrophage‐conditioned medium allowed quiescent cells to respond to plasma‐derived progression factors. The addition of plasma to 3T3 cells that had been treated with the macrophage‐conditioned medium brought about DNA synthesis after a 12‐hr lag. The mitogenic activity that was in macrophage‐conditioned medium bound to DEAE‐Sephadex and eluted in a single peak using a linear NaCl gradient. This macrophage‐derived competence factor was not mitogenic for lymphocytes and was clearly separated by DEAE‐Sephadex chromatography from the major peak of the previously described mitogenic monokine, Interleukin‐I (lymphocyte activating factor).