Development of an in vitro Batch-type Closed Gas Exposure Device with an Alveolar Epithelial Cell Line, A549, for Toxicity Evaluations of Gaseous Compounds

To simply evaluate toxicity for various types of exhaust-gas samples collected in various locations, we developed a small-scale (150 mL) batch-type completely closed gas exposure device incorporated with an air-liquid interface culture of a human alveolar epithelial cell line, A549. On the basis of cell viability tests using an acid phosphatase assay after 48 h of gas exposure, the developed device was able to measure clear dose-response relationships for volatile organic and inorganic compounds, such as benzene, trichloroethylene (TCE), acetone, SO(2) and NO(2) gases, but not CO gas. Although the 50% effective concentration values in the device were much higher than 50% lethal concentration values reported in animal experiments, the tendency of the toxic intensity observed in the former was roughly consistent with that of the acute toxicity in the latter. We further applied the device to evaluate the toxicity of cigarette smoke as an example of actual environmental gases, and successfully measured acute cell death from the gas after 48 h of exposure. The present small device is expected to be one of good tools not only in simultaneously assessing various gaseous chemicals or samples, but also in studying acute toxicity expression mechanisms in human lung epithelia.     

Laser-induced fluorescence and microwave-optical double-resonance study of the B1Σ+-X1Σ+ system of magnesium monoxide

Doppler-limited, laser-induced fluorescence spectra on the B¹Σ⁺-X¹Σ⁺ (v′ = v″ = 0 and 1) system of MgO have been obtained. The results of the optical analysis were merged with our microwave-optical double-resonance measurements to produce the following set of spectroscopic parameters for the B and X states, where the units are in cm^?1, and the uncertainties represent 95% confidence limits: T′_0.0 = 20003.594(2); B′₀ = 0.58004(3); D′₀ = 1.13(2) × 10^?6; B″₀ = 0.57198(3); D″₀ = 1.20(2) × 10⁶; T′_1.1 = 20043.423(2); B′₁ = 0.57528(4); D′₁ = 1.14(11) × 10⁶; B″₁ = 0.56674(4); D″₁ = 1.22(10) × 10⁶.     

Synthesis, Photoreactivity and Cytotoxic Activity of Caged Compounds of L-Leucyl-L-Leucine Methyl Ester, an Apoptosis Inducer

I,-Leucyl-L-leucine methyl ester (Leu-Leu-OMe), an apoptosis inducer in natural killer cells and macro-phages, was caged with trans -o-hydroxycinnamoyl (3ad), trans-o -mercaptocinnamoyl (4) and o -nitrobenzyl derivatives (5a, b), and the photochemical reactivity of these derivatives in phosphate-buffered saline containing 1% dimethyl sulfoxide and their immunological properties were studied. All of the derivatives exhibited absorplion at wavelengths longer than the UVB region. Although 3a–d and 4 were expected to isomerize to a cis isomer, which thgn cyclizes intramolecularly to give Leu-Leu-OMe and a coumarin derivative, cyclization efficiency was not satisfactory except for 3a. However, 3a itself caused necrosis (cell swelling) of U937 cells (a myeloid cell line). In contrast, 5a and b released Leu-Leu-OMe quickly and efficiently and did not affect U937 cells. Although irradiated 5b induced necrosis, irradiated 3a and 5a induced apoptosis in these cells, as evidenced by a decrease in cell size.     

Reactions of quinolinium and pyridinium N-imines with cyclopentadienone derivatives

The novel reactions of quinolinium and pyridinium N-imines with cyclopentadienones are described.     

Radiation-induced solid-state polymerization of methacrylic acid. I. Crystalline transition of the monomer

The anomalous crystalline transition of methacrylic acid found by broad-line NMR measurements was studied in connection with the build-up and decay of trapped radicals. The build-up of radicals is smaller and the decay rate of the trapped radicals is faster in the low-temperature range (phase II), which gave the narrower maximum slope distance ΔH_msl of the NMR spectrum, than those in the higher temperature range (phase I), which gave the broader ΔH_msl. From these experiments it was concluded that in phase I the crystals have a more closely packed structure, resulting in a more rigid matrix for the trapped radicals than those in phase II. This interpretation is consistent with the temperature dependence of the ESR spectrum of the trapped propagating radicals previously reported. The existence of the crystalline transition was also confirmed by DSC measurements, and the effects of the crystallization conditions on the transition were investigated and were discussed with reference to the results of broad line NMR measurements.     

Diels-alder reaction of cyclopropenylketone

The Diels-Alder reactions of tris(trifluoromethyl)trifluoroacetyl-cyclopropene with dienes gave syn-adducts mainly, due to the electronic effects of the fluorinated substituents.     

Synthesis of 24,24-difluoro- and 24ξ-fluoro-25-hydroxyvitamin D3

From cholenic acid 24,24-difluoro-25-hydroxyvitamin D₃ and 24ξ-fluoro-25-hydroxyvitamin D₃ were prepared.     

Determination of hydrogen concentration in amorphous silicon films by nuclear elastic scattering (NES) of 100 MeV 3He2+

Nuclear elastic scattering (NES) of 100 MeV ³He²⁺ ions was used to determine the amount of hydrogen atoms in hydrogenated amorphous silicon film fabricated by reactive sputtering. The total amount of hydrogen in this film was determined to be (1.12 ± 0.1) x 10²² cm^-3 within the accuracy of ～ 10%.     

Near-field Raman imaging and electromagnetic field confinement in the self-assembled monolayer array of gold nanoparticles

Spatial distribution of surface enhanced Raman activity is visualized for two-dimensional (2D) nearly close-packed and well-ordered monolayer array of gold nanoparticles by using scanning near-field optical microscope. The 2D arrays exhibit highly nonuniform enhancement in Raman scattering, i.e., the regions along the edge of the 2D array are preferentially enhanced. We demonstrate that the spatial distribution of the localized electric field is also nonuniform and agrees well with that of the Raman enhancement.