Effect of tetracosahexaenoic acid on the content and release of histamine, and eicosanoid production in MC/9 mouse mast cell

6,9,12,15,18,21-Tetracosahexaenoic acid (24∶6n−3) was isolated from a brittle star, Ophiura sarsi Lütken, at>95% purity to evaluate its physiological functions. The effects of 24∶6n−3 on the production of leukotriene (LT)-related compounds such as LTB₄, LTC₄ and 5-hydroxyeicosatetraenoic acid, and the accumulation and release of histamine in an MC/9 mouse mast cell line were studied. We found that 24∶6n−3 could inhibit the antigen-stimulated production of LT-related compounds as well as other n−3 polyunsaturated fatty acids (PUFA) such as eicosapentaenoic acid (20∶5n−3) and docosahexaenoic acid (22∶6n−3), which are major n−3 PUFA in fish oils; 24∶6n−3 was also shown to reduce the histamine content in MC/9 cells at 25 μM (27% reduction from the control), and the effect was diminished with increase of the fatty acid concentration (up to 100 μM). These two n−3 PUFA, 20∶5n−3 and 22∶6n−3, also reduced the histamine content (16 and 20% reduction at 25 μM, respectively), whereas arachidonic acid (20∶4n−6) increased it (18% increase at 25 μM). Spontaneous- and antigen-induced release of histamine was not influenced with these PUFA (at 25 μM). Ionophore-stimulated release of histamine was suppressed by the PUFA (13,9,15, and 11% reduction with 20∶4n−6, 20∶5n−3, 22∶6n−3, and 24∶6n−3, respectively). The patterns of the effects of 24∶6n−3 on the synthesis of eicosanoids and histamine content were more similar to those of 22∶6n−3 than 20∶5n−3. From these results, 24∶6n−3 can be expected to have anti-inflammatory activity and antiallergic activities similar to those of 22∶6n−3.     

Characterization of β-Silicon Carbide Powders Synthesized by the Carbothermal Reduction of Silicon Carbide Precursors

Boron-doped and nondoped ultrafine β-silicon carbide (β-SiC) powders were synthesized via the carbothermal reduction of SiC precursors at temperatures of 1773–1973 K. Although the reaction rate of carbothermal reduction was generally higher when a boron-doped precursor was used, the reaction rate for the boron-doped precursor was reduced considerably at 1873 K. For boron-doped and nondoped precursors, the reaction rates were almost the same. Powder characterization via transmission electron microscopy indicated that the suppression of the reaction rate for boron-doped precursor at 1873 K was due to the formation of a special coexistent system with two types of particle agglomerates. As expected, boron doping inhibited the particle growth in the synthesis of SiC powder.     

Antimicrobial resistance and serotype distribution of Streptococcus pneumoniae strains causing childhood infections in Bangladesh, 1993 to 1997

Three hundred sixty-two Streptococcus pneumoniae strains were isolated from children under 5 years of age at Dhaka Shishu (Children) Hospital from 1993 to 1997. The strains were isolated from blood (n = 105), CSF (n = 164), ear swab (n = 61), eye swab (n = 20), and pus (n = 12). Of the 362 isolates, 42 (11.6%) showed intermediate resistance (MIC, <0.1 microgram/ml) and only 4 (1.1%) showed complete resistance (MIC, >2.0 microgram/ml) to penicillin. Penicillin resistance exhibited a strong relationship with serotype 14; 47.8% of the penicillin-resistant strains belonged to this type. A remarkably high (64.1%) resistance to co-trimoxazole was observed, along with a significant increase during the time period studied; there was no relationship to capsular type. By way of contrast, penicillin resistance did not show any significant change during the study period. Resistance to chloramphenicol (2.2%) and erythromycin (1.1%) was rare. The high resistance to co-trimoxazole and its increasing trend demand elucidation of the clinical impact of pneumonia treatment by this antimicrobial and reconsideration of the World Health Organization recommendation for co-trimoxazole administration to children with community-acquired pneumonia at the health care worker level in Bangladesh.     

Direct deposition of nanostructured Pt particles onto a Ni foam from lyotropic liquid crystalline phase by displacement plating

Nanostructured Pt particles are directly deposited onto a Ni foam by utilizing displacement plating after a lyotropic liquid crystalline phase including Pt species was prepared within macropores of the Ni foam. The EDS mapping of Pt after deposition corresponds to the macroscopic framework of the Ni foam, indicating the uniform displacement plating of Pt on the surface of the Ni foam. The Pt particles of 150-250 nm in size are formed over the entire area of the surface of the Ni foam. The TEM images prove that the nanoscale rods (width: about 3 nm) are aggregated with each other to form nanoscale porosity. The active area of Pt can be estimated to be ca. 12 m²/g by using the cyclic voltammogram in sulfuric acid. Our method realizes one-step production of hierarchical macro-meso type porous electrodes.     

Theoretical discharge coefficient of a critical circular-arc nozzle with laminar boundary layer and its verification by measurements using super-accurate nozzles

The discharge coefficient of a circular-arc critical Venturi nozzle is derived theoretically by combining theories to calculate mass flow defects caused by the core flow distribution and the laminar boundary layer. The equation obtained is verified by measurements using a constant volume tank system and nozzles of similar shape machined by super accurate lathes, which achieved mirror finish without polishing thus resulting in a machining error of less than 1 μm. The agreement of the theoretical and measured discharge coefficients is better than 0.04% at Reynolds numbers larger than 8×10⁴, the minimum used. The equation derived is in an analytical form, which enables an estimation of the effects of specific heat ratio as well as nozzle shape.     

Preparation of TiO2 nanocrystalline electrode for dye-sensitized solar cells by 28 GHz microwave irradiation

Microwave preparation of TiO₂ nanocrystalline electrode for use in dye-sensitized solar cells is examined. A multi-mode microwave heating system operating at a frequency of 28 GHz is used to produce rapid processing. Well-sintered TiO₂ nanocrystalline thin film is successfully fabricated on transparent conductive FTO glass electrode. Photoelectron energy conversion efficiency of 5.51% is achieved in an electrode prepared by 28 GHz microwave irradiation at 0.7 kW for 5 min.     

Photoactivity of ternary lead-group IVB oxides for hydrogen and oxygen evolution

The relative photocatalytic activity of a series of lead-IVB group oxides (PbCrO₄, PbMoO₄, and PbWO₄) was studied for hydrogen evolution from aqueous methanol solution and for oxygen evolution from aqueous silver nitrate solution. Among the compounds, only PbMoO₄ and platinized PbMoO₄ powders acted as photocatalysts for oxygen and hydrogen evolution reactions from aqueous solutions, with an activity for oxygen evolution on PbMoO₄ comparable to that observed on TiO₂.     

Test Model for Studying Sun Drying of Rough Rice Using Far-Infrared Radiation

The effect of heat input, mixing at regular intervals, airflov over the surface and the relative humidity were investigated within a radiation chamber. Likening to sun drying as practiced in the tropics, the chamber was constructed to study the direct radiant heat drying of rough rice under various bed thicknesses. Graphic results showing the variations of rough rice surface temperature during the experiments are presented. Comparisons are also made between the relative contributions of bed depth and mixing on the drying rate. A non-mixed bed of 3 cm dried just as fast as a 6 cm mixed bed although moisture content was nonuniform in the former case. After drying, the grains were dehusked by hand and examined for physical defects like cracks. Possible constraints involved in drying thick beds of rough rice under direct radiation were investigated with the aim of defining suitable strategies for improving actual sun drying.