Survey of strontium in mineral waters sold in Japan

The concentrations of strontium, calcium, and magnesium in 33 brands of natural mineral waters commercially available in Japan were determined by inductively coupled plasma-atomic emission spectrometry. The geometric mean values were 94.4 microg/L for strontium, 19.1 mg/L for calcium, and 2.82 mg/L for magnesium. Wide confidence intervals of 1.96-4539 microg/L for strontium, 0.865-421 mg/L for calcium, and 0.064-123 mg/L for magnesium were observed. The significant linear relationships among the three elements over a wide distribution range suggest that the synchronized variations of these elements are regulated by the natural ecosystem and not from accidental contamination from human activities or exceptionally high natural sources. Using the results of multiple linear regression analysis, the strontium concentration can be predicted by that of calcium with the appropriate power function. The results of this study suggest that mineral water can be an important nutritional source of strontium. As trace elements imbalance is often found in older patients with chronic renal failure, we propose that close attention of trace elements intake from trendy foods or beverages is necessary to prevent this hidden problem of a rapidly aging society.     

Urinary and serum titanium: assessment as an indicator of exposure to ammonium citratoperoxotitanate (IV) and its influence on renal function

Ammonium citratoperoxotitanate IV (TAS-FINE) is a water-soluble titanium complex used to synthesize a photocatalytic titanium(IV) oxide film. This study was aimed to investigate the LD50, dose-response, time-course response, and renal toxicity of TAS-FINE using an animal model. Serum titanium (S-Ti) and its 24-h urinary excretion (U-Ti) were determined by inductively coupled plasma-argon emission spectrometry (ICPAES) after a single oral TAS-FINE administration to male Wistar rats. The LD50 of TAS-FINE was 7.97 g/kg body weight in 24 h, and its half-life was 3.78+/-1.28 d for S-Ti and 2.19+/-0.09 d for U-Ti. Although TAS-FINE was not easily absorbed in the gastrointestinal tract, it was distributed into the bloodstream in a dose-dependent manner. Within 24 h, 0.189% of administrated Ti was excreted via urine. It was speculated that TAS-FINE formed conjugates with serum constituents that resulted in nephrotoxicity resulting from an allergic reaction. The observed indices in this study were revealed to be good indicators for TAS-FINE exposure. The analytical method and animal model described in this study will help to further elucidate details about human exposure to TAS-FINE, which in recent times has become an occupational and environmental toxicant of concern.     

Self-assembled monolayer of light-harvesting core complexes of photosynthetic bacteria on an amino-terminated ITO electrode

Light-harvesting antenna core (LH1-RC) complexes isolated from Rhodospirillum rubrum and Rhodopseudomonas palustris were successfully self-assembled on an ITO electrode modified with 3-aminopropyltriethoxysilane. Near infra-red (NIR) absorption, fluorescence, and IR spectra of these LH1-RC complexes indicated that these LH1-RC complexes on the electrode were stable on the electrode. An efficient energy transfer and photocurrent responses of these LH1-RC complexes on the electrode were observed upon illumination of the LH1 complex at 880 nm.     

Optimization of wastewater feeding for single-cell protein production in an anaerobic wastewater treatment process utilizing purple non-sulfur bacteria in mixed culture condition

Impacts of operation timing of feeding and withdrawal on anaerobic wastewater treatment utilizing purple non-sulfur bacteria have been investigated in mixed culture condition with acidogenic bacteria. Simulated wastewater containing glucose was treated in a laboratory-scale chemostat reactor, changing the timing of wastewater feeding and withdrawal. Rhodopseudomonas palustris, which does not utilize glucose as a substrate, was inoculated in the reactor. Rps. palustris was detected by a fluorescent in situ hybridization (FISH) technique using the specific Rpal686 probe. As a result, population ratios of Rps. palustris were over 20% through the operation. Rps. palustris could grow by utilizing metabolites of acidogenic bacteria that coexisted in the reactor. A morning feed was effective for a good growth of purple non-sulfur bacteria. A protein content of cultured bacteria was the highest when wastewater was fed in the morning. Dissolved organic carbon (DOC) removal was 94% independent of the timing control. Consequently, feeding in the morning is the optimum feed-timing control from the aspects of growth of purple non-sulfur bacteria and single-cell protein production.     

Atmospheric Phosphorus Deposition in Ashiu, Central Japan – Source Apportionment for the Estimation of True Input to a Terrestrial Ecosystem

Atmospheric bulk depositions of soluble reactive phosphorus (SRP), soluble unreactive phosphorus (SUP), particulate inorganic phosphorus (PIP), particulate organic phosphorus (POP), total phosphorus (TP) and some other dissolved and particulate components were monitored for 3 years in Ashiu, Central Japan. The mean bulk depositions of SRP, SUP, PIP, POP, TP, dissolved components (Na, Mg, nss-Ca, K, V, Mo, nss-SO₄) and particulate components (Al, Fe, Ti, Ca, Mg, Mn, Ba, Sr, Zn) were 175, 76, 136, 397, 783, 156,000, 10,900, 7450, 5470, 10.3, 1.52, 40,100, 13,200, 3590, 2630, 576, 624, 42.3, 30.2, 17.4, 8.2 μmol m⁻² year⁻¹, respectively. The value for TP deposition was in the lower range of previous literature. The low P deposition probably reflected the method applied to reduce the contribution of local particles, including (1) placement of samplers off the ground surface, (2) installation of multiple samplers, and (3) rejection of contaminated samples. Al data suggested that 15 ± 5% of TP was brought by lithogenic dust from East Eurasia. Nss-SO₄ and Mo data and air-mass backward trajectories suggested that 39 ± 4% of TP was derived from coal combustion in China. It was speculated that the rest (47 ± 6%) of the TP deposition might be predominantly attributed to the contribution of local biogenic particles. Net atmospheric TP input (lithogenic dust and fossil fuel combustion) was almost equal to the TP outflow from Japanese forests on granitic soils.     

Binding of S-layer homology modules from Clostridium thermocellum SdbA to peptidoglycans

S-layer homology (SLH) module polypeptides were derived from Clostridium josui xylanase Xyn10A, Clostridium stercorarium xylanase Xyn10B, and Clostridium thermocellum scafoldin dockerin binding protein SdbA as rXyn10A-SLH, rXyn10B-SLH, and rSdbA-SLH, respectively. Their binding specificities were investigated using various cell wall preparations. rXyn10A-SLH and rXyn10B-SLH bound to native peptidoglycan-containing sacculi consisting of peptidoglycan and secondary cell wall polymers (SCWP) prepared from these bacteria but not to hydrofluoric acid-extracted peptidoglycan-containing sacculi (HF-EPCS) lacking SCWP, suggesting that SCWP are responsible for binding with SLH modules. In contrast, rSdbA-SLH interacted with HF-EPCS, suggesting that this polypeptide had an affinity for peptidoglycans but not for SCWP. The affinity of rSdbA-SLH for peptidoglycans was confirmed by a binding assay using a peptidoglycan fraction prepared from Escherichia coli cells. The SLH modules of SdbA must be useful for cell surface engineering in bacteria that do not contain SCWP.     

Microbial production of optically active β-phenylalanine ethyl ester through stereoselective hydrolysis of racemic β-phenylalanine ethyl ester

The ability to produce (R)- or (S)-β-phenylalanine ethyl ester (3-amino-3-phenylpropionic acid ethyl ester, BPAE) from racemic BPAE through stereoselective hydrolysis was screened for in BPAE-assimilating microorganisms. Sphingobacterium sp. 238C5 and Arthrobacter sp. 219D2 were found to be potential catalysts for (R)- and (S)-BPAE production, respectively. On a 24-h reaction, with 2.5% (w/v) racemic BPAE (130 mM) as the substrate and wet cells of Sphingobacterium sp. 238C5 as the catalyst, 1.15% (w/v) (R)-BPAE (60 mM) with enantiomeric purity of 99% e.e. was obtained, the molar yield as to racemic BPAE being 46%. On a 48-h reaction, with 2.5% (w/v) racemic BPAE (130 mM) as the substrate and wet cells of Arthrobacter sp. 219D2 as the catalyst, 0.87% (w/v) (S)-BPAE (45 mM) with enantiomeric purity of 99% e.e. was obtained, the molar yield as to racemic BPAE being 35%. The enzyme stereoselectively hydrolyzing (S)-BPAE was purified to homogeneity from the cell-free extract of Sphingobacterium sp. 238C5. The enzyme was a monomeric protein with a molecular mass of about 42,000. The enzyme catalyzed hydrolysis of β-phenylalanine esters, while the common aliphatic and aromatic carboxylate esters were not catalyzed.     

Characteristics of bacteria showing high denitrification activity in saline wastewater

AIMS: Denitrification efficiency at 10% salinity was compared with that at 2% salinity. The characteristics of bacterial strains isolated from the denitrification system, where an improvement of denitrification efficiency was observed at a high salinity were investigated. METHODS AND RESULTS: Two continuous feeding denitrification systems for saline solutions of 2% and 10% salinity, were operated. Denitrification efficiency at 10% salinity was higher than that at 2% salinity. The bacterial strains were isolated using the trypticase soy agar (TSA) medium at 30 degrees C. The phylogenetic analysis of 16S rRNA gene sequences of isolates indicated that halophilic species were predominant at 10% salinity. CONCLUSIONS: The improvement of denitrification efficiency at a high salinity was demonstrated. The strains isolated from the denitrifying system with 10% salinity were halophilic bacteria, Halomonas sp. and Marinobacter sp., suggesting that these bacteria show a high denitrifying activity at 10% salinity. SIGNIFICANCE AND IMPACT OF THE STUDY: The long-term acclimated sludge used in this study resulted in high denitrification performance at a high salinity, indicating that the design of a high-performance denitrification system for saline wastewater will be possible.     

Capacity of dental pulp differentiation after tooth transplantation

Under pathological conditions, dental pulp elaborates both bone and dentin matrix in which the contribution of periodontal tissue cannot be excluded. This study has aimed to clarify the capability of dental pulp to deposit bone matrix in an auto-graft experiment by using (1) immunohistochemistry for 5-bromo-2′-deoxyuridine (BrdU) and nestin and (2) histochemistry for tartrate-resistant acid phosphatase (TRAP). Following the extraction of the molars of 3-week-old mice, the roots and pulp floor were resected and immediately transplanted into the sublingual region. On Days 5–7, tubular dentin formation commenced next to the pre-existing dentin at the pulp horn in which nestin-positive odontoblast-like cells were arranged. Up until Day 14, bone-like tissue formation occurred in the pulp chamber in which intense TRAP-positive cells appeared. These results suggest that odontoblast- and osteoblast-lineage cells reside in the dental pulp. Overall, specific dental pulp regeneration should provide fundamental knowledge for the realization of human tooth regeneration in the near future.This work was supported in part by a grant from MEXT to promote the 2001-multidisciplinary research project (in 2001–2005), KAKENHI (B) (no. 16390523 to H.O.) from MEXT, and the Japan-Korea Joint Research Project from JSPS and KOSEF (no. F01-2005-000-10212-0).