Role of neurofibromin in modulation of expression of the tyrosinase-related protein 2 gene

Tyrosinase-related protein 2 (TRP-2)/DOPAchrome tautomerase is an enzyme involved in melanin biosynthesis and plays an important role in cytoprotection by preventing the production of a toxic melanin precursor, 5,6-dihydroxyindole. Neurofibromin is the protein product of a gene linked to neurofibromatosis type 1 (NF1), which is characterized by multiple neurofibromas and abnormalities in skin pigmentation. To explore the pathogenesis of NF1, we studied the role of neurofibromin in the regulation of TRP-2 gene expression. By means of transient cotransfection assays, we show that the expression of a reporter gene under the control of the TRP-2 gene promoter was increased by a neurofibromin-dependent signal through the 71-bp region (positions -415 to -345). A Lys-to-Glu substitution at position 1425 in neurofibromin abrogated this activating function. A dominant negative Ki-ras inhibitor mimics neurofibromin's function, and additively increases TRP-2 promoter activity when coexpressed with neurofibromin. Therefore, we suggest that neurofibromin is involved in the regulation of TRP-2 gene expression. Moreover, we found a single case of a glioblastoma multiforme that expresses TRP-2 mRNA but not tyrosinase mRNA, suggesting that TRP-2 may function in human neural tissues under certain conditions.     

Coagulation and sedimentation of bacteria using a highly biodegradable polymeric coagulant

Copolymer of acrylamide with N‐benzyl‐4‐vinylpyridinium chloride (PAAM‐co‐BVP) produced coagulation and sedimentation of Escherichia coli, Bacillus subtillus, Pseudomonas aeruginosa, and Staphylococcus aureus. Addition of more than 50 mg L^?1 of PAAM‐co‐BVP produced bacterial flocks that precipitated at a rate of around 200 cm h^?1. Supernatant population reduced in the range 1/30,000–1/25,000,000. Reduction of supernatant population was most effective when about 200 mg L^?1 of PAAM‐co‐BVP was added. PAAM‐co‐BVP was highly biodegradable and the half‐life estimated was 2.4 days when treated with activated sludge. The ratio of biochemical oxygen demand for 5 days (BOD₅) to total organic carbon (TOC) was 0.607. Coagulation and sedimentation of bacteria using PAAM‐co‐BVP is expected to improve the water disinfection processes by saving chlorine and other hazardous chemical fungicides and by reducing the formation of trihalomethanes and other toxic chemical materials. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 1618–1623, 2006     

Possible mechanisms of superior resistance of polyamide nanocomposites to partial discharges and plasmas

Degradation profiles induced by partial discharges and those induced by oxygen plasmas are compared for polyamide/mica nanocomposites. Both the resistances to partial discharges and to plasmas improve with an increase in nanofiller content. On the other hand, the partial discharge resistance is not improved if mum-sized glass fibers are added to polyamide. In order to investigate these phenomena, the superior resistance mechanism of nanocomposites is discussed, focusing on the effects of the nanofillers on the bulk and surface structures of the resin. It was revealed from X-ray diffraction and permittivity measurements that the nanofiller loading increases crystallinity of the resin and restricts the molecular motion. This should enhance the resistance to degradation. Furthermore, observation results by scanning electron microscopy, energy dispersive X-ray spectroscopy, and X-ray diffraction revealed that the nanofillers had piled up themselves to form a layered structure on the sample surface in an early stage of degradation. Such a structure acts as a barrier against impact of charged particles and diffusion of gases such as oxygen, which should contribute to the improvement of resistance to degradation as its direct effect and also as its indirect effect by suppressing the oxidation of resin. Moreover, it was also revealed from scanning electron microscopy that the nanofillers impede the growth of surface cavities by partial discharges drastically.     

Binding and regulation of thrombopoietin to human megakaryocytes

Thrombopoietin (TPO, c-Mpl ligand) is considered to play an important role in the regulation of megakaryocytopoiesis and platelet production by activating the cytokine receptor c-Mpl. We have examined the binding of 125I-TPO to the human megakaryocytic cell line, CMK, and to primary human megakaryocytes. Scatchard analysis of TPO binding to its cognate receptor in megakaryocytic cells suggested the existence of a single class of c-Mpl receptors. CMK cells exhibited 1223 receptors per cell with a dissociation constant (Kd) of Kd = 223 pM, whereas primary human megakaryocytes exhibited 12140 receptors per cell and a dissociation constant of Kd = 749 pM. The pretreatment of CMK cells and primary bone marrow megakaryocytes with TPO resulted in a decreased binding of TPO to the c-Mpl receptors. This down-regulation was observed within 3 h and was not inhibited by cycloheximide. Phorbol ester, an activator of protein kinase C, also inhibited TPO binding to the c-Mpl receptors by reducing the number of these receptors. The pretreatment of CMK cells with IL-3, IL-6 and DMSO, all of which induced the differentiation of CMK cells, did not affect the binding of TPO to the c-Mpl receptors. These results suggest an additional mechanism, where protein kinase C may help to regulate the binding of TPO to these cells.     

Pulmonary histoplasmosis in a Japanese male: report of a case

A case of pulmonary histoplasmosis, which is rare in Japan, is reported herein. A 43-year-old man who had worked in Mexico for 2 years and had come back to Japan 3 months earlier, presented at our hospital because of an abnormal shadow on his chest roentogenogram with no symptoms. His chest roentogenogram as well as chest computed tomograms revealed a 2-cm-diameter nodule in the anterior basal segment of his right lung and an enlargement of the subcarinal lymph node. Although these pictures seemed to indicate an advanced lung cancer, no malignant cells were found based on the brushing cytology findings after bronchoscopy. An exploratory thoracoscopic tumor resection and biopsy of the enlarged lymph node led to a histological diagnosis of an abscess due to histoplasma. The hospital course was uneventful. Postoperatively, amphotericin B was administered for 1 year. This is the eighth case of pulmonary histoplasmosis reported in Japan. A pulmonary nodule together with mediastinal lymphoadenopathy seems to be characteristic in these patients. Histoplasmosis should therefore be considered in the differential diagnosis, since overseas travel has now become common-place for the Japanese.     

A physically based base pushout model for submicrometer BJTs in thepresence of velocity overshoot

By using a two-dimensional relaxation time approximation device simulator, base pushout phenomena for submicrometer bipolar junction transistors (BJTs) are analyzed. From the numerical analysis, it was clarified that, under the base pushout condition, the electron velocity exceeds the saturation velocity in most of the epi-collector region. Considering this velocity overshoot effect with two-dimensional carrier behavior, a base pushout model was developed. This model is applicable to the BJT equivalent circuit model. The model utility was verified for a 0.8 μm emitter-width BIT, and excellent agreement with measured I-V characteristics was obtained over wide injection conditions. Scaling effects on the velocity overshoot are also calculated, based on the constant current scaling. It is shown that the base pushout is suppressed due to the increased velocity overshoot level as the device sizes are scaled down     

Approximate method for calculating the impedances of multiconductors with cross sections of arbitrary shapes

This paper proposes an approximate impedance formula of a conductor with an arbitrary cross section, and also a method of approximating the conductor by an equivalent circular conductor. Thus, a multiconductor system consisting of arbitrary cross section conductors is represented by circular cross section conductors, the impedance of admittance of which are evaluated by the existing impedance and admittance formulas. The calculated results by the proposed method agree satisfactorily with measured results and numerical results by a finite-element method which is, at present, the only way of calculating such impedance, but requires a large computation time and large memory. The proposed method might be very useful in evaluating the impedance and admittance of a multiconductor system consisting of arbitrary cross section conductors.     

Near-term location planning of hydrogen refueling stations in Yokohama City

Establishing hydrogen refueling stations is key to transition into a hydrogen economy. To achieve this, a near-term, city-level roll-out plan is required, as Japan is shifting from the demonstration to implementation stage of a hydrogen economy. The aim of this study was to devise a plan to identify near-term locations to build hydrogen refueling stations in Yokohama City, Japan. Our plan provides information on the potential location of hydrogen refueling stations for 2020–2030. We considered mobile and parallel-siting type refueling stations; the locations of these stations were determined by matching the supply and demand estimated from hybrid vehicle ownership data and the available space in existing gas stations based on a safety perspective. The results reaffirmed the importance of planning the locations of hydrogen refueling stations and highlighted the suitability of using mobile-type stations. This was based on the uncertainty in fuel demand for fuel cell vehicles during the implementation stage of the hydrogen economy.