Growth control by cell to cell contact.

Control of cell growth by cell to cell contact is reviewed with particular emphasis on two systems--contact inhibition of growth observed with Swiss 3T3 cells and the mitogenic stimulation of Schwann cells by dorsal root ganglia neurites. In both cases the biological effect can be reproduced by the addition of surface membranes to the corresponding cells. In the case of contact inhibition of 3T3 cells, biological activity appears to correlate with membrane binding to the cells. An octylglucoside extract of 3T3 plasma membranes retains the biological activity (growth inhibition) of the original membranes.     

Stimulants from gardeniae fructus for cultured endothelial cell proliferation.

Bioassay-guided fractionation of Gardeniae Fructus extract (GFE), which stimulates the proliferation of cultured endothelial cells, led to the isolation of glycerol and D-mannitol. Both compounds significantly increased the incorporation of [3H]thymidine and [14C]leucine into the acid-insoluble fraction of bovine aortic endothelial cell layers in culture. This clearly indicated that glycerol and D-mannitol are active components of GFE on endothelial cell proliferation. On the other hand, they did not change the number of cultured vascular smooth muscle cells from bovine aorta. Glycerol and D-mannitol may be beneficial drugs for vascular disorders.     

Synthesis and cellular uptake of cell delivering PNA-peptide conjugates

The synthesis and cellular uptake of fluorescently labelled PNA-peptide conjugates is described; Dde/Mmt protected PNA monomers, fully orthogonal to Fmoc chemistry, were used to develop a flexible strategy to give Peptide Nucleic Acids conjugated to tri- and hepta-arginine and the short basic Tat(48-57) peptide as examples of cellular penetrating peptides, thereby allowing efficient cellular delivery of PNA into cells.     

Growth inhibition in animal cell culture

Eight independent cell lines accumulated ammonia in culture to concentrations between 1.3 and 2.9 mM. The growth inhibition of such concentrations of ammonium chloride when added to culture medium was variable. The cell lines tested could be divided into 3 groups depending on their growth response to 2 mM added NH4Cl. In the first group (293, HDF, Vero, and PQXB1/2) little (less than 14%) or no growth inhibition occurred. In the second group (McCoy and MDCK) a reduction in final cell yield of 50-60% was observed. The third group (HeLa and BHK) was most sensitive to the effects of NH4Cl with growth inhibition (greater than 75%) compared to controls. The growth inhibitory effect of added lactate up to 20 mM was negligible (less than 10%) for 3 cell lines, although one cell line (PQXB1/2) showed greater sensitivity. The interactive effects of ammonia and lactate were determined in a matrix experiment. At lactate (greater than 12 mM) and ammonia (1-4 mM), the growth inhibitory effects of the two components were synergistic. However, at low concentrations of lactate (less than 12 mM) the toxic effect of ammonia was reduced. A proposed mechanism for the sparing effect of lactate on ammonia toxicity is discussed. This may have importance in developing strategies for the optimal growth of ammonia-sensitive cell lines.     

Substituted oxines inhibit endothelial cell proliferation and angiogenesis

Two substituted oxines, nitroxoline (5) and 5-chloroquinolin-8-yl phenylcarbamate (22), were identified as hits in a high-throughput screen aimed at finding new anti-angiogenic agents. In a previous study, we have elucidated the molecular mechanism of antiproliferative activity of nitroxoline in endothelial cells, which comprises of a dual inhibition of type 2 human methionine aminopeptidase (MetAP2) and sirtuin 1 (SIRT1). Structure-activity relationship study (SAR) of nitroxoline offered many surprises where minor modifications yielded oxine derivatives with increased potency against human umbilical vein endothelial cells (HUVEC), but with entirely different as yet unknown mechanisms. For example, 5-nitrosoquinolin-8-ol (33) inhibited HUVEC growth with sub-micromolar IC(50), but did not affect MetAP2 or MetAP1, and it only showed weak inhibition against SIRT1. Other sub-micromolar inhibitors were derivatives of 5-aminoquinolin-8-ol (34) and 8-sulfonamidoquinoline (32). A sulfamate derivative of nitroxoline (48) was found to be more potent than nitroxoline with the retention of activities against MetAP2 and SIRT1. The bioactivity of the second hit, micromolar HUVEC and MetAP2 inhibitor carbamate 22 was improved further with an SAR study culminating in carbamate 24 which is a nanomolar inhibitor of HUVEC and MetAP2.     

Nanometer-scale patterned surfaces for control of cell adhesion.

A novel cell-adhesion surface, controlled by nanometer-scale topography and chemical patterning, was developed using semiconductor fabrication methods and the formation of self-assembled monolayers. The patterned surface had a sharp contrast between the adsorption and non-adsorption of proteins and cells, and the contrast could be maintained for more than 10 days. The patterning method could easily realize a single cell array and control of the cell morphology. The nanometer-scale patterned surface could control cell adhesion and proliferation. Using the patterned surface will contribute to studies about cell-surface interactions.     

The existance of a group translocation transport mechanism in animal cells: uptake of the ribose moiety of inosine.

After exposure to inosine, transport-competent plasma membrane vesicles isolated from SV-40-transformed Bal/c 3T3 cells accumulate intravesicular ribose 1-PO4 at a concentration 200-fold greater than the extravesicular concentration. An analysis of the purine nucleoside phosphorylase activity distribution in various subcellular fractions, relative to other enzyme activities, indicated the presence of plasma membrane-associated purine nucleoside phosphorylase activity. The plasma membrane vesicles appear relatively impermeable to hypoxanthine. However, hypoxanthine, which is a competitive inhibitor of the transport reaction, is the only compound tested capable of mediating efflux of already accumulated ribose 1-PO4. In addition, hypoxanthine does not result in the efflux of transported uridine which is accumulated in these membrane vesicles as uridine. Exogenous ribose 1-PO4 neither results in counterflow nor does it inhibit the original uptake reaction. The following transport reaction is proposed: uptake occurs by group translocation, mediated by membrane-localized purine nucleoside phosphorylase. The data are consistent with sites for inosine and hypoxanthine being on the outer membrane surface whereas the ribose 1-PO4 site is only on the inner surface.     

Intracellular self-assembly of nanoparticles for enhancing cell uptake

A radioactive probe (1) has been developed and applied to a condensation reaction and self-assembly of radioactive nanoparticles (i.e., (125)I-NPs) intracellularly. Upon 160 min cellular efflux, the radioactivity retained in cells incubated with 1 was 4-fold more higher than that of those cells treated with a scrambled control probe (1-Scr).     

Nanocoating of CsgA protein for enhanced cell adhesion and proliferation

Immune rejection, poor biocompatibility and cytotoxicity have seriously stalled the widespread application of biometallic materials. To overcome these problems, biometallic materials with fast and sufficient osseointegration, antibacterial properties and long-term stability have attracted the attention of researchers worldwide. Surface modification is currently used as a general strategy to develop material coatings that will overcome these challenging requirements and achieve the successful per...     

On-line monitoring and active control of dye uptake in dye-sensitised solar cells

Real-time monitoring of dye loading (N3 and N719) under continuous flow conditions on TiO(2) photoanodes for dye-sensitized solar cells has been applied to quantitatively investigate dye uptake kinetics, demonstrating that static impregnation provides in all cases higher dye loading and, as a consequence, better working devices.     

Active transport of Na + and K + through animal cell membranes

The transport of Na⁺ out of the cell and K⁺ into the cell against a concentration gradient is catalyzed by a (Na⁺ + K⁺)-activated ATPase. The way in which the cations pass through the cell membrane has not yet been elucidated. Studies on the ATP hydrolysis revealed a Na⁺-dependent phosphorylation of the enzyme protein; the conformation of the enzyme also appears to change. The energy required for transport of the cations against their concentration gradients is probably provided by K⁺-dependent hydrolysis of the enzyme-bound phosphate. The enzyme can synthesize ATP from inorganic phosphate and ADP on reversal of the cation concentration gradient. By keeping the enzyme in a particular conformation, the cardiac glycoside ouabain specifically inhibits the Na⁺ pump.     

Salvianolic acid A inhibits PDGF-BB induced vascular smooth muscle cell migration and proliferation while does not constrain endothelial cell proliferation and nitric oxide biosynthesis

Proliferation and migration of vascular smooth muscle cells (VSMCs) are critical events in the initiation and development of restenosis upon percutaneous transluminal coronary angioplasty (PTCA). Polyphenols have been suggested to ameliorate post-angioplasty restenosis. Salvianolic A (SalA) is one of the most abundant polyphenols extracted from salvia. In this study, we investigated the effect of salvianolic A (SalA) on the migration and proliferation of VSMCs. We found a preferential interaction of SalA with cellular systems that rely on the PDGF signal, but not on the EGF and bFGF signal. SalA inhibits PDGF-BB induced VSMC proliferation and migration in the concentration range from 0.01 to 0.1 μM. The inhibition of SalA on VSMC proliferation is associated with cell cycle arrest. We also found that SalA inhibits the PDGFRβ-ERK1/2 signaling cascade activated by PDGF-BB in VSMCs. In addition, SalA does not influence the proliferation of endothelial cells, the synthesis of NO and eNOS protein expression. Our results suggest that SalA inhibits migration and proliferation of VSMCs induced by PDGF-BB via the inhibition of the PDGFRβ-ERK1/2 cascade, but that it does not constrain endothelial cell proliferation and nitric oxide biosynthesis. Thus, the present study suggests a novel adjunct pharmacological strategy to prevent angioplasty-related restenosis.     

Detection of the cell viability and proliferation using two-signal electrochemical method

Two electrochemical signals of the MCF-7 cell were simultaneously detected by using multiwall carbon nanotubes and room temperature ionic liquid composite film modified electrode. The signal at +0.726 V due to the oxidation of xanthine and guanine, was obviously improved. And the signal at +1.053 V due to the oxidation of hypoxanthine and adenine was found for the first time. This two-signal electrochemical method is credible to detect cell viability and proliferation.     

Changes in cell proliferation due to environmental non-ionizing radiation 1. ELF electromagnetic fields

To study the effect of extremely low frequency (ELF) magnetic fields on cell growth, human cells (AMA cells) and K14 skin fibroblasts cells, growing in monolayer culture, were exposed to a sinusoidal 50 Hz, 80 μT field. Exposure times varied from 15 to 90 min. Changes in cell proliferation rates were then studied during subsequent field-free incubation, for 24 h.The results showed that a 30 min exposure resulted in a much higher increase in proliferation rates in the AMA cells compared with non-exposed cells or cells exposed to electromagnetic fields for shorter or longer times. The magnitude of the increase also depended on the initial proliferation rate and confluency. The exposure to varying field densities showed that the greatest increase in proliferation occurred at 80 μT.     

Changes in cell proliferation due to environmental non-ionizing radiation: 2. Microwave radiation

Due to the use of mobile telephones, there is an increased exposure of the environment to weak radiofrequency (RF) electromagnetic fields, emitted by these devices. This study was undertaken to investigate if the microwave radiation from these fields will have a similar effect on cell proliferation as weak electromagnetic (ELF) fields. The field was generated by signal simulation of the Global System for Mobile communications (GSM) of 960 MHz. Cell cultures, growing in microtiter plates, were exposed in a specially constructed chamber, a Transverse Electromagnetic (TEM) cell. The Specific Absorption Rate (SAR) values for each cell well were calculated for this exposure system. Experiments were performed on cell cultures of transformed human epithelial amnion cells (AMA), which were exposed to 960 MHz microwave fields at three different power levels and three different exposure times, respectively. It was found that cell growth in the exposed cells was decreased in comparison to that in the control and sham exposed cells. Cell proliferation during the period following exposure varied not only with the various SAR levels, but also with the length of exposure time. On the other hand, repeated periods of exposure did not seem to change the effects. There was a general linear correlation between power level and growth change. However, the exposure time required to obtain the maximum effect was not the same for the various power levels. It turned out that at low power level, a maximum effect was first reached after a longer exposure time than at higher power level. A similar phenomenon was registered in the studies on ELF electromagnetic fields. Here, it was found that there was a linear correlation between the length of exposure time to obtain maximum effect and field strength.     

Synthesis and screening of N-alkyl hydroxamates for inhibition of cancer cell proliferation

A small library of N-alkylated amino acid-derived sulfonamide hydroxamates was synthesized on solid phase and tested for inhibition of proliferation of the highly invasive breast cancer cell line MDA-MB-231. The most active compound 4317 inhibited cell growth at IC(50) 30 microM. N-alkylation of N-H hydroxamate-based MMP inhibitors, a modification known to eliminate MMP activity, enhanced cell proliferation inhibition potency.     

Construction of a biomimetic zwitterionic interface for monitoring cell proliferation and apoptosis

A new zwitterionic monolayer film of sulfobetaine was constructed by grafting novelly designed N,N-dimethyl (beta-hydroxyethyloxyethyl) ammonium propanesulfonate (DHAPS) to hydroxyl groups of glass in the presence of hexamethylene diisocyanate (HDI) as a coupling agent and dibutyltin dilaurate (DBTDL) as a catalyst. Experiments of blood adhesion proved that the zwitterionic film possessed excellent hydrophilicity and very good biocompatibility and provided an appropriate biomimetic interface for adhesion and proliferation of cells. Thus, the monitoring of the cell proliferation and apoptotic processes on the zwitterionic surface during an incubation process was achieved, using different techniques, such as electrochemical impedance spectroscopy, scanning electron microscopy, flow cytometric assay, and Trypan blue staining. K562 leukemia cells, as a model, cultured in vitro on the zwitterionic surface kept their viability for 5 days and remained healthy and undifferentiated, indicating that the zwitterionic surface did not have a deleterious effect on cell growth in normal conditions. Thus, this man-made interface would be applicable to the growth of cells and the study of biomaterial-cell interaction and has potential applications in medicine and cytobiology.     

Photocontrol of cell adhesion and proliferation by a photoinduced cationic polymer surface

In this study photoinduced cation generation, based on the photochemical properties of malachite green (MG), was used for the surface design and in vitro photochemical control of cell adhesion and proliferation. The MG-derivatized surface was prepared by coating a photoreactive polymer as a substrate onto a poly(ethylene terephthalate) (PET) sheet. The photoreactive polymer was radical copolymer of styrene with the MG-derivatized monomer diphenyl(4-vinylphenyl)methane leucohydroxide (degree of substitution of MG unit: 12.4 mol%). Water contact angle measurements and X-ray photoelectron spectroscopy revealed high hydrophobicity and homogeneous distribution of the MG groups on the outermost surface of the coated film, respectively. When the coated film was exposed to ultraviolet light (UV) irradiation at wavelengths of 290-410 nm, a time-dependent color change of the film was observed from pale yellow, before irradiation, to green. These results indicated generation of cations on the film surface by photochemical cation generation of the MG groups, which was quantitatively characterized by force versus distance curves measurements in atomic force microscopic (AFM) observation using a carboxylated AFM tip. The seeding and culture of endothelial cells showed a marked reduction in adhesion on the nonirradiated coated film surface, whereas the UV-irradiated surface promoted cell adhesion and proliferation except for incubation in serum-free medium, which was similar to commercial tissue culture PET sheet. These observations may be due to adsorption of cell adhesive proteins, typified by fibronectin, in serum-containing medium onto the cationized photoreactive copolymer surface by electrostatic interactions.