Diffusion-limited transport of I- 3 through nanoporous TiO2-polymer gel networks.

Tri-iodide transport in a polymer gel electrolyte embedded in nanoporous TiO(2) networks and its diffusion limits are investigated by means of current-voltage (I-V) characteristics of simple Pt-gel-Pt sandwich devices with a thin porous TiO(2) layer sintered directly onto one of the Pt electrodes. At voltages between 0.2 and 0.7 V, the I-V curves of such devices show the typical plateau of diffusion-limited redox reactions, in this case I(-)/I(3) (-), at the platinum electrodes. From the dependence of the limiting current density on layer thickness, the diffusion constants D(bulk) and D(p,eff) of tri-iodide in the bulk polymer gel and through a polymer gel penetrated TiO(2) network, respectively, have been found to be D(bulk)=3.2(+/-0.2)x10(-6) cm(2)/s and D(p,eff)=1.5(+/-0.1)x10(-6) cm(2)/s. Temperature-dependent measurements show diffusion in the gel to be activated by about 0.16 eV. The results are discussed in comparison to diffusion in liquid electrolytes as well as with respect to the implications for dye-sensitized solar cell devices.

A common epithelial cell surface antigen (EPM-1) on gastrointestinal tumors and in human sera.

A common epithelial cell surface marker (EPM-1) was defined by two monoclonal antibodies (Pa-25 and Pa-42), raised against a pancreatic tumor cell line (Capan-1). Both monoclonal antibodies were tested on 49 cultured human cell lines and 244 tissue samples and reacted with all 76 tissue samples of 20 different normal epithelial cell types and with 57 of 63 epithelial tumor tissue samples of nonendocrine origin. Included were eight exocrine pancreatic carcinomas. There the percentage of EPM-1 positive tumor cells correlated with tumor grading. EPM-1 was detectable on the cell surface of cultured human cell lines of the pancreas, liver, colon, and mamma. Some epithelial tumor cell lines did not express EPM-1 on the cell surface, but in the cytoplasm. 100 nonepithelial and epithelial endocrine tissue samples as well as 25 nonepithelial cultured tumor and normal cells were unreactive with monoclonal antibodies Pa-25 and Pa-42. These included cells of neuronal, endocrine, and mesenchymal origin. EPM-1 activity was purified from pancreas tumor cells Capan-1 and from human sera by high-performance liquid chromatography and its molecular weight amounts to about Mr 400,000. EPM-1 was detectable in bronchial, intestinal, and pancreatic secretions and saliva and serum by an enzyme-linked immunosorbent assay test. EPM-1 values were high in the sera of normal individuals, but low or not detectable in most sera (21 of 31) of patients with gastrointestinal tumors. EPM-1 represents a novel differentiation marker for epithelial cell types, which should have a central role in the biology of normal and tumorous epithelial cells.

Signet ring stomach cancer: morphological characterization and antigenic profile of a newly established cell line (Mz-Sto-1).

A human gastric signet ring cancer cell line (Mz-Sto-1) was established in tissue culture from the ascites fluid of a 54-year-old patient. The tumor cells growing in tissue culture exhibit the morphological characteristics of signet ring cells in phase contrast and transmission electron microscopy. Mz-Sto-1 cells grow as monolayer with a population doubling time of 28-36 hr during exponential growth phase and show a chromosome number between 72 and 74. In the cellular DNA of Mz-Sto-1 cells no amplification of 19 oncogenes studied is observed, c-myc included. Mz-Sto-1 cells secrete 150-250 ng CEA per 10(7) cell in 3 days, but no AFP. In addition Mz-Sto-1 cells and 2 already established gastric cancer cell lines MKN-28 and MKN-45 express HLA- and blood group related antigens (A, Lewis). HLA-DR antigens, which are regularly detected on normal stomach epithelium, are not found on any of the 3 cultured gastric cell lines. Mz-Sto-1 cells represent the first human gastric cancer cell characterized ultrastructurally as signet ring cells. This line will be a valuable tool to study the biology and genetics of gastric carcinoma, to test cytostatic drugs and to define new antigenic markers for stomach cancer.