Yuji Takeuchi

Antibody-regulated neurotoxic function of cell-surface β-amyloid precursor protein

APP is a transmembrane precursor of beta-amyloid, and its mutations cause early-onset familial Alzheimers disease. We report a toxic function of normal wild-type APP (wtAPP). Treatment of neuronal F11 cells, immortalized embryonic day 13 neurons, overexpressing wtAPP with anti-APP antibodies caused death. Death was not induced by antibody in parental F11 cells. Death by antibody occurred through cell-surface APP, not through secreted APP, in a pertussis toxin-sensitive manner and was typical apoptosis, not observed in primary astrocytes or glioma cells overexpressing wtAPP, but observed in primary cortical neurons. Cell-surface APP thus performs a toxic function as an extracellularly controllable regulator of neuronal death. This study provides a novel insight into the normal and pathological functions of cell-surface wtAPP.

PLP-I: a novel prolactin-like gene in rodents.

In this report, we describe molecular cloning and characterization of cDNAs encoding a novel rat prolactin-like protein. The rat cDNAs were isolated from the decidua and the gene was named PLP-I. cDNAs for the mouse equivalent were also cloned by the cross-hybridization technique. Pregnancy-specific expression of the rat PLP-I gene was observed in the rat placenta by Northern analysis. Location of signal peptide cleavage sites in rat and mouse pre-PLP-I proteins was predicted using a theoretical method. A molecular phylogenetic tree for the growth hormone-prolactin superfamily including the novel member, PLP-I, constructed using the neighbor-joining method, places rat/mouse PLP-I closest to rat/mouse placental lactogen I and II.

Immunohistochemical study of localization of γ-glutamyl transpeptidase in the rat brain

Abstract γ-glutamyl transpeptidase (γ-GTP) is a membrane-bound enzyme which is known to play a crucial role in active transport of amino acids across membrane barriers. We prepared a monoclonal antibody recognizing specifically rat γ-GTP and investigated localization of the enzyme in the rat brain by immunohistochemistry with this antibody. The antigen was localized on the ependyma, epithelia of the choroid plexus and microvessels. More precise localization of γ-GTP was examined with immuno-electron microscopy. The antigen was recognized on the microvilli and cilia of the ependymal cells, microvilli of the choroid epithelial cells and luminal membranes of the vascular endothelial cells.

Cell‐associated IL‐8 in human blood monocytes: Analysis by flow cytometry

Several cell-associated cytokines, such as interleukin-1 (IL-1) and tumor necrosis factor, exist on the cell surface and are biologically active. Although extracellular IL-8, a potent chemotactic factor for primarily neutrophils, has been studied extensively, cell-associated IL-8 has barely been studied. In this study, we analyzed the intracellular and cell-surface IL-8 in human blood monocytes in vitro by using flow cytometry and predicted the biological activity of the cell-associated IL-8 in vivo. After fixation with paraformaldehyde, mononuclear cells were divided into two subgroups. One subgroup was left untreated to study cell-associated antigens, and the other subgroup was permeabilized with saponin to detect intracellular antigens. In lipopolysaccharide (LPS)-stimulated monocytes, IL-8 was detected solely intracellularly, whereas both the intracellular and cell-surface IL-1 beta was detectable. In a time-course study, the intracellular IL-8 increased in response to LPS stimulation, but the cell-surface IL-8 was undetectable throughout the course. In an LPS-stimulated monocytic cell line, both ELISA and flow cytometry detected the quantitative change of the intracellular IL-8. The dissimilar localization between IL-8 and IL-1 beta within cells was confirmed by the immunohistochemical analysis. In summary, LPS stimulation induced a time-dependent increase in intracellular but not cell-surface IL-8 in monocytes. Thus, it is unlikely that the cell-associated IL-8 is functioning physiologically. The semiquantitative flow cytometric procedure may be useful for simultaneous examination for cell-surface and intracellular cytokines.

Annealing effects on the electrical properties and microscopic structure of semi‐insulating polycrystalline silicon films

The dependence of the electrical properties and microscopic structure of semi‐insulating polycrystalline silicon (SIPOS) films prepared by low‐pressure chemical‐vapor deposition on annealing temperature has been investigated, and the electrical conduction mechanisms have been clarified. As‐deposited SIPOS films were crystallized from an amorphous matrix by annealing, which changes the structure to polycrystalline films at annealing temperatures above 1100 °C. The electrical conduction mechanisms in films annealed at temperatures above 1000 °C can be explained by thermionic emission theory over a wide range of temperatures from high temperatures to those below room temperature, and by hopping conduction through the trap states at the grain boundaries at sufficiently low temperatures. For films annealed below 1000 °C, the electrical conduction mechanisms can be explained by conduction in the extended states over the high‐temperature range, and by hopping conduction through the localized states below room te...

Energy distribution of grain boundary traps in semi-insulating polycrystalline silicon films doped with oxygen

Abstract The energy distribution of the grain boundary traps in semi-insulating polycrystalline silicon (SIPOS) films prepared by low pressure chemical vapor deposition (LPCVD) is determined for various oxygen contents taking account of the segregation effect of phosphorus. The energy distribution of the grain boundary traps is expressed as a Gaussian distribution. The surface trap density of the grain boundary and the energy band gap of the films increase with increasing oxygen content. Both peaks of the energy distribution of the donor- and acceptor-type traps are located at 0.49 eV over the valence band in case of poly-Si films, but moves toward the midgap as oxygen content increases in case of SIPOS films.