Keiko Shibata

Long-term variation of chemical composition of atmospheric aerosol on the Oki Islands in the Sea of Japan

Abstract Chemical composition in aerosols collected on the Oki Islands, which are located in the Sea of Japan, were measured for 4 1 2 years (1983–1988) and their variations were investigated from the viewpoints of aerosol background level and transport of aerosols from both the mainland of Japan and the Asian Continent. Kosa, which is soil dust from the Asian deserts, strongly influenced the variations of the concentration of soil-derived components in aerosol, which showed high concentrations every spring and November. Sulfate had a good correlation with V in the variation and their concentrations increased in summer as the result of the transport of the aerosol from the mainland of Japan. Whereas high Pb concentration in winter was presumed to be attributed to the contribution of lead-enriched aerosol transported from the Asian Continent by the northwest monsoon. The differences of aerosol composition between summer and winter were seen in the ratios of Pb/Zn and Sulfate/V, which may be good indicators for the characterization of aerosol in Asian region. Long-term trends of changing of aerosol composition were also studied, and only C indicated a slight increase for 4 years.

Distribution, localization, and pulmonary effects of yttrium chloride following intratracheal instillation into the rat.

Metabolic behavior and pulmonary toxicity of yttrium chloride (YCl3) deposited in the lung was investigated. Yttrium chloride was instilled intratracheally into rats and the time-course and dose-related changes in distribution of Y between lung tissue and bronchoalveolar lavage fluid (BALF) and pulmonary inflammatory responses were investigated. Pulmonary clearance of Y was very slow and the half-life was estimated to be 168 days. Yttrium content in the supernatant of BALF did not exceed 5 micrograms Y/lung even when a dose of 200 micrograms Y/rat was administered, suggesting that the alveolar surface fluid could retain at most 5 micrograms Y. On the other hand, Y content in the pellet of BALF changed with the number of macrophages retrieved in BALF in both time-course and dose-response experiments. Transmission electron microscopy and X-ray microanalysis suggested that Y was localized in lysosomes of alveolar and interstitial macrophages, and basement membranes. These results clearly explain the long pulmonary half-life of Y. beta-Glucuronidase activity and calcium and phosphorous contents in the supernatant of BALF increased significantly even at the lowest dose (10 micrograms Y/rat). Comparative dose-effect profiles of lactate dehydrogenase activity in BALF supernatant revealed that 1 mol of YCl3 is equivalent to about one-third mole of cadmium compounds and about 3 mol of zinc oxide in the potency for acute pulmonary toxicity.

Lead accumulation and location in the shoots of the aquatic liverwort Scapania undulata (L.) Dum. in stream water at greenside mine, England

Lead accumulation in the shoots of the aquatic liverwort Scapania undulata (L.) Dum. collected from a stream at an abandoned lead mine in England was studied with respect to its concentration, localization and chemical forms in the cells. The concentration of Pb in the stream water was 0.02 mg 1−1, and that of Pb in the shoots ranged from 0.7 to 2.4% Pb on a dry weight basis, giving an enrichment ratio of 3.5×105-1·2×106, Energy-dispersive X-ray microanalysis (XMA) of the cells showed localization of Pb in the cell wall, while Pb was not detected in the nucleus and other cell components. A study of sulphur speciation in the shoot showed that sulphide-S, which would indicate the presence of PbS, was undetectable at a distinguishable concentration ( <5 μg g−1). A insoluble sulphate-S concentration of 78 μg g−1, which may occur as PbSO4 was equivalent to about 3% of total Pb in the shoots of S. undulata.

Differential cytotoxic effects of methylmercury and organotin compounds on mature and immature neuronal cells and non-neuronal cells in vitro.

The neurotoxicity of methylmercury and organotin compounds was evaluated in vitro on the basis of their differential cytotoxic effects on neuronal cells (rat phaeochromocytoma cell PC12h, human neuroblastoma cell NB-1 and primary cultures of rat cerebellar cells) and non-neuronal cells (normal rat kidney epithelial cell NRK-52E and primary cultures of rat hepatocyte). In this system, neuronal cells show consistently higher sensitivity to the toxicity of methylmercury, trimethyltin and triethyltin, which are known to be neurotoxic, than non-neuronal cells, as judged by the 50% lethal concentrations (LC(50)) of these compounds after 48 hr treatment. Tributyltin and triphenyltin, which have not yet been confirmed to be neurotoxic, also show higher toxicity to neuronal cells; their LC(50) values for neuronal cells are generally lower than those for non-neuronal cells, suggesting that they could be neurotoxic. Differential cytotoxic effects of these compounds on mature and immature neuronal cells were also investigated using nerve growth factor (NGF)-treated PC12h and cerebellar cells precultured for 15 days in vitro as mature neuronal cells. With this system, cerebellar cells precultured for 1 day in vitro and NGF-untreated PC12h as immature neuronal cells were shown to be more sensitive to the toxicity of methylmercury than mature neuronal cells, which is consistent with the higher vulnerability of the developing neural system to the toxicity of methylmercury. This assessment system for neurotoxic compounds based on differential cytotoxicity to neuronal and non-neuronal cells may be useful as a primary screening system for the neurotoxicity of environmental contaminants.

Mercury sulphide (HgS) crystals in the cell walls of the aquatic bryophytes, Jungermannia vulcanicola Steph. and Scapania undulata (L.) Dum.

Abstract The chemical and physical forms of mercury compounds accumulated in the cell wall of the liverwort, Jungermannia vulcanicola Steph. and Scapania undulata (L.) Dum. in an acid stream, Kashiranashigawa (pH 4.2–4.7), were studied employing high-resolution electron microscopy with X-ray microanalysis. The accumulation rates of mercury in both liverworts were studied in the stream by a transplanting technique and by energy-dispersive X-ray fluorescence spectrometry. High-resolution transmission electron microscopy revealed the distribution of single crystalline particles with a diameter of 5–15 nm and polycrystalline particles with a diameter of 10–200 nm in the cell wall of J. vulcanicola and S. undulata. Electron micro-diffraction measurements of the crystals showed the diffraction pattern of mercury sulphide (cubic metacinnabar, HgS, black) which is insoluble in water and non-toxic to organisms. The accumulation rate of mercury from water by both liverworts, obtained by transplanting the shoots from the mid- and downstream site to an upstream site in which mercury levels were ∼0.6 μg 1−1 water, was ∼300–1000 μg g−1 month−1.

p-chloromercuribenzoate-induced dissociation of cytoskeletal proteins in red blood cells of rats

Effects of p-chloromercuribenzoate (PCMB) on the cytoskeletal organization of rat red blood cells were studied. Upon incubation with 50 microM PCMB in 10 mM Tris-HCl (pH 7.4) at 37 degrees C for 30 min, 80% of actin and 45% of spectrin were released from the ghosts, resulting in the fragmentation of ghost membranes. Addition of 2 mM Mg2+ or 0.1 M KCl, or lowering incubation temperature to 0 degree C substantially inhibited the solubilization of the cytoskeletal proteins and the fragmentation of ghost membranes, which enable to examine the effects of PCMB on the interaction between transmembrane proteins and the peripheral cytoskeletal network. Decreased recoveries of transmembrane proteins, such as band 3 and glycophorin, in Triton shell fraction were observed in the ghosts incubated with PCMB either in the presence of Mg2+ or at 0 degree C. PCMB also inhibited the in vitro association of purified spectrin with spectrin-depleted inside-out vesicles through interaction with proteins in the vesicle, such as bands 2.1 and 3. In the PCMB-treated ghosts, intramembrane particles were highly aggregated, which further supports the PCMB-induced dissociation of the transmembrane proteins from the cytoskeletal network. The decreased recovery of glycophorin in the Triton shell fraction also observed in intact red blood cells upon incubation with PCMB. These results suggest that the main action of PCMB on red cell membranes under physiological condition, at higher ionic strength and in the presence of Mg2+, is to dissociate transmembrane proteins from the peripheral cytoskeletal network, which may modify functions of these proteins.

Elemental composition of the sub-aquatic liverwort Pellia endiviifolia (Dicks.) Dum. in relation to heavy metal contamination

The concentrations of fifteen elements (B, Na, Mg, Al, P, K, Ca, Ti, Mn, Fe, Cu, Zn, Sr, Cd, Pb) in thalli of the sub-aquatic liverwort Pellia endiviifolia (Dicks.) Dum. collected from seven sites in Japan, were analyzed by inductively coupled plasma atomic emission spectrometer (ICP). The average concentration of major essential elements in the thalli was: 49 600 µg g−1 K, 9 140 µg g−1 Na, 6740 µg g−1 Ca, 3 840 µg g−1 P, and 3 060 µg g−1 Mg. Thalli of P. endiviifolia from sites polluted by heavy metals (Cu, Zn, Pb) contained high concentrations of these elements (maxima 0.88% Cu, 0.55% Zn and 0.36% Pb in the older thallus), thus demonstrating the potentiality of this liverwort as an indicator for heavy metal contamination.