ABSTRACT
Gastrin and cholecystokinin-B receptor (CCK-B) were co-expressed in human gastric carcinoma tissues, suggesting that a functional autocrine loop, the gastrin and CCK-B receptor loop, may be presented in gastric cancer cells and play an important role in the pathogenesis and progression of gastric carcinomas. The present study was aimed at studying the effects of blocking the gastrin and CCK-B receptor loop on cell proliferation and apoptosis in gastric cancer cell line SGC-7901 cells (SGC-7901 cells). First, the expression of gastrin and CCK-B receptor mRNAs and gastrin protein in SGC-7901 cells were measured by RT-PCR and immunocytochemistry, respectively. Radioimmunoassay (RIA) was used to detect the concentrations of gastrin in culture medium. The gastrin-CCK-B receptor axis was blocked by using a specific neutralizing antibody against human gastrin and siRNA specifically targeting human CCK-B receptors, respectively. Flow cytometry was used to measure the cell cycle and apoptotic cells, and western blotting was used to measure the expression of CCK-B receptor, caspase-3, and matrix metalloproteinase-2 (MMP-2) in cells. The results showed that SGC-7901 cells not only coexpressed gastrin and CCK-B receptor mRNAs, but also endogenously secreted gastrin protein into the culture medium, thus forming gastrin-CCK-B receptor autocrine loop. Biologically, disrupting gastrin-CCK-B receptor autocrine loop by neutralizing the endogenous gastrin or by knocking down CCK-B receptor expression significantly inhibited the cell proliferation and decreased the percentage of cells residing in the S-phase of the cell cycle, and meanwhile promoted cell apoptosis and increased caspase-3 expression as well as decreased MMP-2 expression. An autocrine loop between endogenously secreted gastrin and CCK-B receptors may play a key role in the regulation of cell proliferation and apoptosis in SGC-7901 cells.
Subject(s)
Apoptosis , Cell Proliferation , Gastrins/antagonists & inhibitors , Receptor, Cholecystokinin B/antagonists & inhibitors , Base Sequence , Blotting, Western , Cell Line , Colorimetry , DNA Primers , Flow Cytometry , Gene Knockdown Techniques , Humans , In Vitro Techniques , RNA Interference , Radioimmunoassay , Receptor, Cholecystokinin B/genetics , Reverse Transcriptase Polymerase Chain Reaction , Signal TransductionABSTRACT
Granular sludge membrane bioreactor (GMBR), operated with alternating anaerobic-aerobic mode, showed good organics removal and simultaneous nitrification and denitrification (SND) performances during 120 days operation. Moreover, sludge size distribution examination showed that the increase of sludge concentration in GMBR was mostly due to the increase of small granular sludge with diameter between 0.18 - 0.45 mm and flocculent sludge smaller than 0.18 mm, and most of granular sludge larger than 0.45 mm was stably existed in GMBR, at the end of operation granular sludge with diameter larger than 0.18mm remained 60%-65% in GMBR. Sludge surface negative charge increased with the sludge size distribution variation, and surface charge remained -0.42 - -0.80 meq x g(-1) after 80 days operation. The increase of sludge surface negative charge was mostly caused by sludge smaller than 0.45 mm, thereinto sludge smaller than 0.18 mm had the greatest effect. Moreover, results revealed that the sludge surface negative charge decreased as the sludge size increased, and a linear correlation can be obtained between sludge surface negative charge and sludge size. Sludge in GMBR had good settleability, and SVI was about 60-90 mL/g. Furthermore results showed that sludge surface charge was correlated with SVI, sludge SVI increased with surface negative charge increased.
Subject(s)
Bacteria, Aerobic/metabolism , Bioreactors/microbiology , Oxygen/metabolism , Sewage/microbiology , Waste Disposal, Fluid/methods , Aerobiosis , Membranes, Artificial , Oxygen/analysis , Water Purification/methodsABSTRACT
An aerobic granular sludge membrane bioreactor(GMBR) had been stably operated for 71 days, and it showed good organics removal and simultaneous nitrification and denitrification (SND) performances. TOC, ammonium and total nitrogen removal efficiencies of GMBR remained 84.7% - 91.9%, 85.4% - 99.7% and 41.7% - 78.4% respectively as influent TOC were 56.8 - 132.6 mg/L and ammonium nitrogen were 28.1 - 38.4 mg/L. Moreover, further batch tests of different size sludge revealed that floclike sludge nearly had not SND ability, the SND performances of GMBR was mostly come from granular sludge, and denitrification rate and total nitrogen removal efficiencies under aerobic condition increased with sludge size increased. Analyzing the morphology and section characteristics of granular sludge under scan electron microscope, the SND process was also described.
