Arsenic accumulation and speciation in Japanese paddy rice cultivars

We examined arsenic (As) accumulation and speciation in the major cultivars currently grown in Japan, because differences in grain As levels among cultivars may influence dietary As exposure in Japanese people. Ten major cultivars (Oryza sativa L.) were grown under flooded conditions in a paddy field with a background level of As (low-As soil) or in pots filled with soil containing a high level of As (high-As soil). In the low-As soil, the total grain As ranged from 0.11 to 0.17?mg?kg^?1, with a mean concentration of 0.14?mg?kg^?1, and inorganic As was the major species in all cultivars. There were few genotypic differences in the levels of either total As or inorganic As in the grain. In the high-As soil, total grain As increased to a mean level of 2.4?mg?kg^?1 in the 10 cultivars, with markedly increased levels of dimethylarsinic acid. The genotypic variations among cultivars in the levels of both total As and dimethylarsinic acid were statistically significant. However, the genotypic variability of inorganic As levels was quite small, and these levels remained low (at about 0.2?mg?kg^?1) even when total As levels increased markedly. These results suggest that differences in grain As levels among Japanese cultivars may not influence dietary As exposure, because there is little genotypic difference in the accumulation of inorganic As, which is considered more toxic than organic As to humans. We discuss the possible mechanism of As accumulation in Japanese paddy rice, in the context of the accumulation of As species in the developing grain and in other plant tissues.     

ABSTRACTS of the Articles Printed in Journal of the Science of Soil and Manure,Japan

In the preceding paper (1), it was reported that even under aerobic shaking conditions, if R. capsulatus were mixed with Bacillus megaterium, the bacterial growth of both and nitrogen fixation were accelerated remarkably.     

Nitrogen-fixing microoganisms in paddy soils XVI

1. It was proved that under aerobic shaking conditions of the system of R. capsulatus mixed with Az. agilis or R. capsulatus mixed with B. megaterium, the bacterial growth of both and the nitrogen fixation were promoted markedly, comp:ired with the non-shaking culture. However, in the system of R. capsulatus mixed with B. subtilis under aerobic shaking conditions. such remarkable stimulative effects were not recognized altough some slow effects were recognized in the nonshaking culture.

2. It was also proved that under aerobic shaking conditions of the system of R. capsulatus mixed with Az. agilis or R. capsulatus mixed with B. megaterium the assimilative activity of carbon dioxide increased over 10 times more than in the separate pure culture.

From these results, it is conceivable that a very good environment was created for the internal metabolism of R. capsulatus in such mixing systems (R-Az and R-Bm).     

Nucleic acids in the culture fluids of Rhodopseudomonas capsulatus and other heterotrophic bacteria

In previous papers (1,2), it was reported that in cultures of R. capsulatus mixed with other heterotrophic bacteria nitrogen fixation is accelerated and there is some production of slime substances (3), exchange of pyruvic acid (4–6), amino acids, carbohydrates (7) and others in these mixed systems. There is also symbiotic association between R. capsulatus and other heterotrophic bacteria (Azotobacter) in nature (8).     

Effect of presowing seed treatments on germination and early seedling growth of wheat varieties under saline conditions

The effect of presowing wheat seed treatments was investigated for the salt-sensitive variety Blue Silver and relatively salt-tolerant variety PARI-73 at the germination and early seedling stages. Seeds were treated with distilled water (DW) or 10/50 mm KCl, KNO₃ , CaCl₂, Ca(NO₃)₂ and then germinated in DW or 200 mm NaCl. Treatment with calcium (Ca) or potassium (K) did not lead to a significantly higher rate for final germination than the DW treatment. Ca salt treatments significantly improved shoot growth during the early seedling establishment stage in both varieties, especially in the salt-sensitive variety Blue Silver. There were significant differences in the Ca content of seeds after various presowing treatments. There were also significant differences between both varieties in the ion contents after seed treatment. However, these differences appeared to be related to the improvement of shoot growth during the early seedling establishment stage and not to the effectiveness of pres owing seed treatments in increasing germination.     

Responses of antioxidant enzymes in the needles of hinoki cypress (Chamaecyparis obtusa) seedlings to nutrient solutions containing various calcium/aluminum ratios

An attempt was made to examine the possible connection between the various ratios of calcium/aluminum (Ca/Al) in the nutrient solution of plant cultures and the active oxygen scavenging system of hinoki cypress (Chamaecyparis obtusa) seedlings. The hinoki cypress seedlings were transferred to nutrient solutions containing 5 mM AlCl₃ together with various concentrations of Ca(NO₃)₂ in pots containing glass beads and Teflon tips. The activities of superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX) and glutathione reductase (GR) in the needles were estimated at several stages during the 7-day treatment. The samples treated with the lower Ca/Al solutions show the highest SOD activities. The activities of APX and GR, both of them involved in the ascorbate-glutathione cycle, showed the same tendency with decrease to higher Ca/Al ratio. These results indicate that rhizospheric Ca might compete with Al and ameliorate Al toxicity on and in the roots, the Al stress is not transformed to the needles after a few days, and the ascorbate-glutathione cycle in the hinoki cypress needles might fluctuate and be suppressed by the rhizospheric Al stress during the 7 days. This work was supported in part by funding from the Japan Science & Technology Corporation, the CREST program 1996–2001, and the Center for Forest Decline Studies.     

Automatic detection of a damaged cutting tool during machining I: method to detect damaged bandsaw teeth during sawing

This paper presents an on-line method for detecting damaged teeth in the bandsaw using acoustic emission (AE) signal energy. The method is based on an analysis of differences in AE energies generated by normal and damaged teeth during sawing. Because of the difference in the amount of sawing, the AE energy was low for sawing by the damaged tooth and high for sawing by the normal tooth immediately after the damaged tooth. The ratio of AE energy for two successive teeth — a normal tooth immediately following a damaged tooth — was much greater than 1, whereas the ratio of AE energy for two successive normal teeth was close to 1. The results demonstrate that the technique using the AE energy ratio for two successive teeth is effective for on-line detection of damaged bandsaw teeth.Part of this paper was presented at the 9th Annual Meeting of the Chugoku Skikoku Branch of the Japan Wood Research Society, Tottori, October 1997     

Sparing effect of tramadol,lidocaine, dexmedetomidine and their combination on the minimum alveolar concentration of sevoflurane in dogs

BackgroundProblems associated with using inhalational anaesthesia are numerous in veterinary anaesthesia practice. Decreasing the amount of used inhalational anaesthetic agents and minimising of cardiorespiratory disorders are the standard goals of anaesthetists.ObjectiveThis experimental study was carried out to investigate the sparing effect of intravenous tramadol, lidocaine, dexmedetomidine and their combinations on the minimum alveolar concentration (MAC) of sevoflurane in healthy Beagle dogs.MethodsThis study was conducted on six beagle dogs. Sevoflurane MAC was determined by the tail clamp method on five separate occasions. The dogs received no treatment (control; CONT), tramadol (TRM: 1.5 mg kg^-1 intravenously followed by 1.3 mg kg^-1 h^-1), lidocaine (LID: 2 mg kg^-1 intravenously followed by 3 mg kg^-1 h^-1), dexmedetomidine (DEX: 2 μg kg^-1 intravenously followed by 2 μg kg^-1 h^-1), and their combination (COMB), respectively. Cardiorespiratory variables were recorded every five minutes and immediately before the application of a noxious stimulus.ResultsThe COMB treatment had the greatest sevoflurane MAC-sparing effect (67.4 ± 13.9%) compared with the other treatments (5.1 ± 25.3, 12.7 ± 14.3, and 40.3 ± 15.1% for TRM, LID, and DEX treatment, respectively). The cardiopulmonary variables remained within the clinically acceptable range following COMB treatment, although the mean arterial pressure was higher and accompanied by bradycardia.ConclusionsTramadol-lidocaine-dexmedetomidine co-infusion produced a remarkable sevoflurane MAC-sparing effect in clinically healthy beagle dogs and could result in the alleviation of cardiorespiratory depression caused by sevoflurane. Cardiorespiratory variables should be monitored carefully to avoid undesirable side effects induced by dexmedetomidine.     

Histologic features of the carotid artery trifurcation in thoroughbreds.

The common, external, and internal carotid and occipital arteries were examined histologically at the trifurcation of the common carotid arteries in 13 Thoroughbred foals (0 to 30 days old) and 64 Thoroughbred adults (2 to 4 years old). Calcification in the media of the common carotid and external carotid arteries was observed in 3 of the 13 foals and in 30 of the 64 adult horses. Calcification resembled that seen in M?nckeberg's arteriosclerosis in human beings, the cause of which is unknown.