[Comparison of shaping ability of 4 nickel-titanium rotary instruments in preparation of curved root canals].

PRUPOSE: To compare the shaping ability of 4 nickel-titanium rotary instruments in preparation of curved root canals. METHODS: Forty extracted human maxillary first or second molars with mesiobuccal root canal curvature ranging from 20°-40° were selected. The teeth were randomly equally divided into 4 groups(n=10). Mesial root canals were separately prepared using Protaper Universal, Protaper Next, TF, and S3 nickel-titanium instruments. A series of preoperative and postoperative images were taken by Micro-CT． Mimics 17.0 software was used to analyze the following parameters: canal transportation, centering ratio values, root canal volume, volume of removed dentin, and canal/root width ratio. Data analysis was performed by using SPSS 20.0 software package. RESULTS: In terms of canal transportation after preparation at 1, 3 and 5 mm from the apex, Protaper Universal was more than the other three groups(P＜0.05). The centering ratio value of Protaper Universal was significantly smaller than that of the other three groups at 1 mm from the apex(P＜0.05). The amount of dentin removal was significantly different after instrumentation with the four test systems(P＜0.05). Protaper Universal had the highest mean volume of removed dentin. After preparation, all root canals had a diameter that was not larger than 39% of the root diameter at the coronal and middle segments. CONCLUSIONS: Under the conditions of this study, Protaper Next, TF, S3 systems seem to be better choices than Protaper Universal system in preparing curved root canals.

Response of phytoplankton assemblages to nitrogen reduction in the Laizhou Bay, China.

The response of phytoplankton assemblages to decreases in nitrogen loading is an essential index to assess the recovery of aquatic ecosystems from eutrophic status. However, a positive signal is hard to observe from short-term operations considering ecosystem complexity. Here, we used decadal data from the Laizhou Bay, China to track the seasonal and annual variations in phytoplankton assemblages after ammonia reduction in the Xiaoqing and Yellow Rivers. Annual trends show reduced phytoplankton abundance and a decline in harmful algal blooms, indicating the positive recovery of phytoplankton assemblages. Phytoplankton assemblage in the sea region adjacent to the Xiaoqing River shows a lower H' index, higher cell abundance, and higher seasonal variability than the sea region neighbouring the Yellow River. The spatial variability might result from the differences of nitrogen species, runoff and sediment contents between the two rivers; this finding indicates a demand for more aggressive decreases in nitrogen loads.

Application of a bacterial whole cell biosensor for the rapid detection of cytotoxicity in heavy metal contaminated seawater.

A toxicity biosensor Acinetobacter baylyi Tox2 was constructed with the host strain A. baylyi ADP1 harboring a new and medium-copy-number plasmid pWH1274_lux, and was applied to detect the cytotoxicity of heavy metal contaminated seawater. The gene cassette luxCDABE was controlled by constitutively expressed promoter Ptet on pWH1274_lux and the bioluminescence intensity of the biosensor reduces in proportional to the concentrations of toxic compounds. A. baylyi Tox2 exhibits tolerance to salinity, hence it is applicable to seawater samples. A. baylyi Tox2 and Mugilogobius chulae were exposed to different concentrations of heavy metals (Hg2+, Zn2+, Cu2+, and Cd2+) in artificial seawater for performance comparison and Pearson correlation analysis showed a significant correlation (p < 0.01) between A. baylyi Tox2 toxicity detection and the fish (M. chulae) exposure test. This suggests that the performance of A. baylyi Tox2 is comparable to the conventional fish toxicity test in terms of cytotoxicity detection of heavy metal contaminated seawater. Furthermore, A. baylyi Tox2 was used to evaluate cytotoxicity of field-collected seawater samples. The results indicate that there was a significant correlation between the luminescence inhibition ratio (IR) of A. baylyi Tox2 and heavy metal concentrations detected by ICP-MS in the samples. Two seawater samples, which contained a high concentration of total heavy metals, exhibited stronger cytotoxicity than the samples containing low concentrations of heavy metals. In conclusion, A. baylyi Tox2 can be used as an alternative tool to aquatic animals for the evaluation of the cytotoxicity of heavy metal contamination in the marine environment.

Seasonal and spatial variation of Deuteromycetes population in polluted cost of Kiaochow Bay.

Objective: To reveal the relationship between Deuteromycetes community and the environmental in Kiaochow Bay of the Yellow Sea. Methods: Using recorded pollution survey, we used molecular methods to study seasonal and spatial variation of Deuteromycetes community diversity in different polluted waters of Kiaochow Bay of the Yellow Sea, China. Results: Denaturing gradient gel electrophoresis fingerprints varied obviously among different sites of similar level of pollution. Moreover, sequence analysis of recovered dominant bands exhibited the existence of plenty of uncultivable fungi, among which Penicillium was the dominant genus. Furthermore, in heavily polluted estuary, there were abundant animal pathogens such as amoeba and Pythium as well as Deuteromycetes. These discoveries demonstrate that the Deuteromycetes community structure is closely related to marine environment, and are indicative of different level of marine contamination. Conclusion: The relationship between Deuteromycetes community and different level of pollution and seasons varied were closely related.

Molecular detection of Penicillium griseofulvum as the coastal pollution indicator.

Molecular methods were carried out to detect Penicillium griseofulvum, a dominant species related to heavy metal pollution, which was screened from marine contaminated sediments. Based on differences in internal transcribed spacer (ITS) sequences of Penicillium genus and specific isoamyl alcohol oxidase (IAO) sequences, species-specific primers AS1/RS4 and IAO1/IAO2 of Penicillium griseofulvum were designed and synthesized which were then employed in optimized PCR systems. The detection sensitivities were compared through ordinary PCR and nested-PCR using two pairs of primers, respectively. Both primer pairs could exclusively amplify destined DNA fragment from contaminated environmental samples in our researches. As for primers AS1/RS4, the detection sensitivity for spores (pure spore DNA) could be 10 fg/µl and 10 spores, respectively, and the detection sensitivity for the sediments was 10² spores/0.25 g sediments. While the detection sensitivity of IAO1/IAO2 primers was lower than that of AS1/RS4. Despite the difference in detection sensitivity, it is feasible that the species-specific primers could be used as probes for the detection of environmental pollution dominant species, Penicillium griseofulvum, since the frequency of occurrence and amount of this strain could preferably indicate the pollution degree.