摘要:

AbstractCompound 48/80 (poly‐p‐methoxyphenethylmethylamine), an agent commonly used to trigger degranulation of mast cells, at concentrations of 5–20 μg/ml suppresses the proliferation of L1210 and Friend leukemic cells in vitro, inducing the formation of giant cells, which are polykaryons. Both the proportion of polykaryons in cultures and their size (which reflects the number of nuclei per polykaryon) increase during growth in the presence of 48/80 up to 48 hr; thereafter, the cells lose viability. A predominant number of nuclei in these polykaryons contain a 4C, or higher DNA content. The data indicate that compound 48/80 impairs the cleavage (cytokinesis) and perhaps mitotic processes. Mechanisms by which compound 48/80 induces the described effects are unknown but may be related to the polycationic nature of the polymer and its interaction with the cell membrane. Certain attributes of compound 48/80 suggest that this or similar polymers may have value as research tools for the study of regulatory mechanisms involved in cell di

ISSN:0021-9541    

DOI:10.1002/jcp.1041190102

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1984

数据来源: WILEY

摘要:

AbstractThe anion requirement for toxic action of diphtheria toxin and modeccin was studied. In Cl−‐free Hepes buffer made isotonic with mannitol, cells were insensitive to diphtheria toxin and modeccin. Just 2 mM NaCl was sufficient to obtain full toxic activity of modeccin, whereas 140 mM NaCl was required for maximal intoxication with diphtheria toxin. Br−could substitute for Cl−. NO3−, I−and ClO3−were less efficient than Cl−, whereas SO42−and SCN−were unable to replace Cl−. Cl−deprivation both reduced the ability of cells to bind diphtheria toxin and prevented bound toxin from intoxicating the cells. The binding of modeccin was not reduced. SITS (4‐acetamide‐4′‐isothio‐cyano‐stilbene‐2,2′‐disulfonic acid), an inhibitor of Cl−entry, protected against diphtheria toxin and modeccin, indicating tha

ISSN:0021-9541    

DOI:10.1002/jcp.1041190103

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1984

数据来源: WILEY

摘要:

AbstractL cells and mouse 3T3 cells, which are very sensitive toPseudomonas aeruginosaexotoxin A (PEA), were protected with weak bases and low concentrations of monensin. BHK cells and a number of other cell lines which are much less sensitive to PEA were much less protected under these conditions. Trifluoperazine, dansylcadaverine, and several other calmodulin antagonists strongly sensitized BHK cells to the toxin whereas they did not affect the sensitivity of the mouse 3T3 and L cells. The sensitization of the BHK cells was counteracted by treatment with weak bases or low concentrations of monensin. Calmodulin antagonists also sensitized cells to toxin which had become inaccessible to antitoxin, indicating that the effect of the calmodulin antagonists is exerted on a process taking place after the toxin is endocytosed.

ISSN:0021-9541    

DOI:10.1002/jcp.1041190104

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1984

数据来源: WILEY

摘要:

AbstractUDPgalactose inhibits the growth of mouse leukemic L1210 cells. In calf serum supplemented Dulbecco's medium (CS‐DMEM), 1.2 mM UDPgalactose (UDPgal) inhibited cell growth by 50% (IC50), and 5 mM UDPgalactose inhibited cell growth by 92%. Other nucleotide sugars as well as galactose, glucose, and galactose‐1‐phosphate had little or no effect on cell growth. Uridine nucleotides, which inhibit galactosyltransferase activity, protected L1210 cells from the growth inhibitory effect of UDPgalactose when both were added simultaneously to culture media. Unlike mouse 3T12 cells, in which no inhibition of cell growth was observed with heat‐inactivated calf serum (HICS)‐DMEM, 5 nM UDPgalactose inhibited L1210 cell growth in HICS‐DMEM to the same degree as that observed in CS‐DMEM. In contrast to 3T12 cells, L1210 cells secrete significant galactosyltransferase activity into the media. Complete inhibition of 3T12 cell growth by UDPgal was observed if HICS‐DMEM medium was first conditioned by L1210 cells for 48 hours. No difference in cell growth or [3H]thymidine uptake was detected after 6 hours of exposure to UDPgalactose, but both were significantly decreased at 24 and 48 hours. Flow cytometric analysis of UDPgalactose effects on L1210 cells revealed no differences in the distribution of cells in G1, S, or G2‐M of the cell cycle after 6 hours of incubation, but after 16 hours of UDPgalactose treatment, L1210 cells were arrested in early S phase. These cells were completely viable and morphologically similar to control L1210 cells. Normal growth was resumed when UDPgal was removed. The data suggest that UDPgalactose inhibition of cell growth requires extracellular galactosyltransferase activity and that the effect is mediated via

ISSN:0021-9541    

DOI:10.1002/jcp.1041190105

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1984

数据来源: WILEY

摘要:

AbstractMethionine dependence is a metabolic defect found thus far only in transformed and malignant cells. The defect is manifested as the inability of cells to grow in media in which methionine (Met) is replaced by its immediate precursor homocysteine (Hcy). We have termed this Met−Hcy+media. We demonstrate here that methionine‐dependent cells derived from human tumors, compared to normal methionine‐independent cells, have low levels of free Met, low levels of S‐adenosylmethionine (AdoMet) and elevated levels of S‐adenosylhomocysteine (AdoHcy) when incubated in Met−Hcy+medium. Methionine‐independent human tumor cells also have very low levels of free Met compared to normal cells but generally have levels of AdoMet and AdoHcy comparable to normal cells in Met−Hcy+medium. All tumor cell types incorporate amounts of Met into protein similar to normal methionine‐pindependent human fibroblasts when incubated in Met−Hcy+medium, thereby indicating apparently normal levels of Met synthesis in the tumor cells. The methionine‐independent tumor cell lines in Met−Hcy+medium seem able to regulate their AdoMet/AdoHcy ratios normally despite this defect in having very low levels of free Met. Thus, in a diverse set of human tumor cell lines, all are defective in at least one aspect of Met metabolism, giving rise to the possibility of a general met

ISSN:0021-9541    

DOI:10.1002/jcp.1041190106

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1984

数据来源: WILEY

摘要:

AbstractProstaglandin F2α(PGF2α); which stimulates DNA synthesis in resting 3T3 cells, also stimulates the incorporation of [32P]PO4into phosphatidylinositol. The effect is selective for PGF2αwhen compared with PGE1, PGE2, and PGF2α. Epidermal growth factor (EGF) also stimulates DNA synthesis but does not affect phosphatidylinositol turnover. PGE1, which acts synergistically with PGF2αto enhance DNA synthesis, does not affect the ability of PGF2αto enhance the incorporation of [32P]PO4into phosphatidylinositol. PGF2αalso causes a small increase in the cellular content of 1,2‐diacylglycerol. This effect is not shared by EGF or PGE1. Stimulation of phosphatidylinositol metabolism resulting in an increase in the cellular content of 1,2‐diacylglycerol may thus constitute an event in the pathway leading to the initiation of DNA synthesis in which PGF2αdiffers in its acti

ISSN:0021-9541    

DOI:10.1002/jcp.1041190107

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1984

数据来源: WILEY

摘要:

AbstractAdenylate cyclase activity in cultured rat aortic vascular smooth muscle cells showed a linear correlation with the rate of DNA synthesis. When smooth muscle cells were rendered quiescent by shifting them from a serum‐supplemented medium to a medium containing low concentrations of plasma, the cells could be stimulated to proliferate by the addition of serum or by addition of a crude preparation of platelet‐derived growth factor. DNA synthesis began at 16 hours and was maximal at 24 hours. Prior to synthesis of DNA there was an increase in adenylate cyclase activity with a peak at 12 hours. Adenylate cyclase activity returned to basal level before DNA synthesis began. The increase in adenylate cyclase activity was not blocked by cycloheximide. Adenylate cycase activity could also be increased by incubating vascular smooth muscle cells with cholera toxin; however, the time course and magnitude of this increase was different from that caused by growth stimulants. Cholera toxin caused a slight increase in DNA synthesis at 16 hours, but was also cytotoxic to smooth muscle cells. An increase in adenylate cyclase activity may be a prerequisite for the progression from G1t

ISSN:0021-9541    

DOI:10.1002/jcp.1041190108

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1984

数据来源: WILEY

摘要:

AbstractProcedures to isolate plasma membrane, Golgi apparatus, and endoplasmic reticulum from a single homogenate of mouse liver are described. Fractions contain low levels of contaminating membranes as determined from morphometry and analyses of marker enzymes. The method requires only 2–3 gm of liver as starting material and yields approximately 0.7, 0.7, and 0.5 mg protein/gm liver, respectively, for endoplasmic reticulum, Golgi apparatus, and plasma membrane. Golgi apparatus fractions show high levels of galactosyltransferase activity and consist of cisternal stacks and associated secretory vesicles and tubules. Endoplasmic reticulum fractions are enriched in both glucose‐6‐phosphatase and nicotinamide adenine dinucleotide phosphate (reduced) (NADPH)‐cytochromecreductase and contain membrane vesicles with attached ribosomes. K+‐stimulated p‐nitrophenyl phosphatase and (Na+K+) adenosine triphosphatase activity are enriched in the plasma membrane fraction. This fraction consists of membrane sheets, many with junctional complexes, and bile canaliculi that are representative of the total hepatocyte plasma membrane. The fractionation procedure is designed to utilize small amounts of tissue (e.g., with liver slices), to reduce the total time required for fractionation, and to permit comparisons of constituents of plasma membrane, Golgi apparatus, and endoplasmic reticulum prepared from the same starting

ISSN:0021-9541    

DOI:10.1002/jcp.1041190109

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1984

数据来源: WILEY

摘要:

AbstractExperiments were carried out to test the hypothesis that cell spreading and phagocytosis are similar cell responses to different‐sized substrata. The following morphological and biochemical studies provided evidence for this supposition. Cells phagocytosed 1.09‐μm and 5.7‐μm latex beads, but were unable to completely ingest 15.8‐μm or 25.7‐μm beads. With the larger beads, the cells spread around the bead surfaces with an appearance typical of cells spread on culture dishes. Biochemical studies with cytochalasin D, azide, and iodoacetate, as well as temperature‐dependence studies, demonstrated similar responses of cell spreading and phagocytosis to these treatments. Similar cell surface receptors were involved in cell spreading and phagocytosis based upon experiments using antibodies to baby hamster kidney (BHK) cell wheat germ agglutinin receptors. And finally, BHK cell variants with defective plasma fibronectin (pFN) receptors were unable to spread on pFN‐coated dishes or ingest pFN‐coated beads. Evidence also is presented concerning the “contact” process in cell adhesion. It was found that azide and low temperature inhibited cell attachment per se but did not block fibronectin‐receptorinter actions based upon cell binding of pFN‐coated beads. A possible explanation for the contact process is presented based upon the resistance of cell

ISSN:0021-9541    

DOI:10.1002/jcp.1041190110

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1984

数据来源: WILEY

摘要:

AbstractCM‐S is an autonomous cell line of human hemopoietic precursor cells inducible to monocyte‐macrophage differentiation in response to appropriate inducing agents. CM‐S cells produce factors that stimulate their own growth and proliferation, and are also capable of stimulating clonal proliferation of human, but not mouse, monocytic and granulocytic bone marrow progenitor cells in viscous medium. Preliminary purification steps have demonstrated at least two species, one of which (MW 30,000–50,000) retains both these activities, while the other (MW ≤ 10,000) apparently retains only the autostimulatory activity. CM‐S cells could thus be a useful source for the purification of human colony stimulating factors (CSFs). CM‐S cells also respond to factors present in human placenta conditioned medium, known to contain human CSF. This suggests that CM‐S cells could provide a homogeneous target cell population for testing CSFs from othe

ISSN:0021-9541    

DOI:10.1002/jcp.1041190111

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1984

数据来源: WILEY