Quorum quenching bacteria protect Macrobrachium rosenbergii larvae from Vibrio harveyi infection.

AIMS: In this study, we investigated the effect of N-acyl homoserine lactone-degrading bacterial enrichment cultures (ECs) on larviculture of the giant freshwater prawn Macrobrachium rosenbergii. METHODS AND RESULTS: The larval performance in terms of larval growth, larval survival, larval quality, duration of the larval rearing process and microflora levels in the rearing water as well as inside the prawn gut was investigated. The application of the EC bacteria was performed in two ways: by adding them directly into the larval rearing water and via enriched Artemia nauplii used for larval feeding. The results of the study demonstrated that both ECs that were tested had a similar positive effect on larval survival and larval quality, whereas they did not affect larval growth or the duration of the larval rearing process. CONCLUSIONS: Under normal hatchery conditions, the optimal EC densities were found to be 10(6) CFU ml(-1) for adding into the rearing water and 5 × 10(8) CFU ml(-1) for enrichment of Artemia nauplii used for feeding of the larvae. In the hatchery, the ECs can be grown on waste streams of Artemia hatching. SIGNIFICANCE AND IMPACT OF THE STUDY: Application of this kind of ECs could lead to a more sustainable aquaculture production, by replacing the use of antibiotics to control diseases.

Prevalence of and factors associated with Helicobacter pylori infection in children in the north of Vietnam.

The study aimed at evaluating the seroprevalence of and sociodemographic, health, lifestyle, and environmental hygiene conditions associated with Helicobacter pylori infection in Vietnamese children. Data from 824 children, aged from 6 months to 15 years and gastrointestinal symptom free when consulted, admitted to a university hospital, were collected using a structured questionnaire and ELISA test for H. pylori infection. The data were examined using univariate and multivariate analyses. H. pylori seroprevalence was 34.0%. Age groups from 3 to 6 years and older than 6, and number of offspring were positively and independently associated with H. pylori seropositivity [adjusted OR (95% CI): 2.9 (1.5-5.5); 1.9 (1.1-3.1) and 1.8 (1.1-2.6), respectively]. Breastfeeding more than 6 months was negatively and independently associated with H. pylori seropositivity [adjusted OR (95% CI): 0.5 (0.3-0.9)]. Mother's age, history of allergy, gastro-duodenal disease history in the past, initiating collective life before 6 years, sharing bed with parents and time of bed sharing with parents > 24 months were positively but not independently associated with H. pylori seropositivity. None of the other environmental or lifestyle conditions examined was associated with H. pylori infection. Our results support person-to-person transmission and the role of sociodemographic factors in H. pylori infection.

Extraction of hydrocarbons from seaweed samples using sonication and microwave-assisted extraction: a comparative study.

A sonication method is compared with a microwave-assisted extraction method for recovering polycyclic aromatic hydrocarbons and aliphatic hydrocarbons from seaweed and acid humic samples. Different extracting solvents and adsorbents for the purification step are tested. For the sonication extraction, 10 g of the sample are extracted in an ultrasonic bath (60 degrees C for 15 min with 20 mL of hexane). For the microwave-assisted extraction two steps are carried out, each step at 90 degrees C under pressure in closed vessels with 20 mL of hexane for 10 min at 950 W. A clean-up step is performed for both extraction techniques. The results indicate that the recovery of hydrocarbons is dependent on both the extraction technique and the type of matrix. The most suitable technique appears to be sonication employing hexane as the extraction solvent. The recoveries obtained for aliphatic hydrocarbons are higher than those achieved for the polycyclic aromatic hydrocarbons, with values ranging within 81-109% and 40-76%, respectively.

Solid-phase microextraction and gas chromatography-mass spectrometry for the determination of polycyclic aromatic hydrocarbons in environmental solid matrices.

A solid-phase microextraction (SPME) and gas chromatography-mass spectrometry method for determining polycyclic aromatic hydrocarbons (PAHs) in environmental solid matrices is developed. Investigated matrices include seaweed (Undaria pinnatifida and Himanthalia elongata), humic substances (isolated from a wetland out-flow and purchased from Aldrich), and soil. Optimal conditions for a good SPME efficiency of 16 hydrocarbon compounds are obtained using a 100- micro m polydimethylsiloxane fiber directly immersed in aqueous carrier medium. The method is remarkable for presenting short extraction times and considerably high sensitivities. The SPME results obtained by using internal calibration give the total analyte concentration based on the identical partitioning behavior of native and spiked pollutants. The detection limits range from 0.001 to 0.1 mg of PAH per kilogram of dry matrix. SPME external calibration provides information regarding freely dissolved analytes. The detection limits range from 0.001 to 0.05 micro g of PAH per liter of carrier medium. The SPME with external calibration procedure can be applied to measure free concentrations of a target compound spiked into a carrier medium and onto a matrix. Based on a comparison of results obtained for the two samples, the partitioning of the target analyte between the matrix and the carrier medium is calculated.

Determination of petroleum hydrocarbons in contaminated soils using solid-phase microextraction with gas chromatography-mass spectrometry.

Manual solid-phase microextraction (SPME) coupled with gas chromatography-mass spectrometry is investigated as a possible alternative for the determination of petroleum hydrocarbons in soils. Spiked onto an agricultural soil is a commercial diesel fuel (DF) with the following composition by weight: 12% linear alkanes, 52% saturated hydrocarbons (branched and cyclic), 21% alkylated aromatic hydrocarbons, 6% polycyclic aromatic hydrocarbons, and 9% unidentified compounds. The spiked soil samples are aged three days at room temperature before analysis. The optimal conditions for the SPME of DF from soils are examined and maximum sensitivity is obtained using a 100-microm polydimethylsiloxane fiber at a sampling temperature of 47 degrees C by sonication both in the headspace and directly through a water medium. The reproducibility of the whole technique showed a relative standard deviation of 10%. The parameters that can influence the recovery of DF (such as the time of SPME extraction, the presence of organic solvent and water, and the matrix) are investigated. The linearity is verified in the range of 40 to 1200 mg/L for the direct injection of DF, 0.1 to 1 mg/L for the SPME of DF from water, and 1 to 50 mg/Kg of dry soil for the SPME of DF from soils. The detection limits are respectively 0.5 mg/L, 0.02 mg/L, and 0.1 mg/Kg of dry soil. The method is corroborated by comparing the results with those obtained by the traditional way.

Determination of polycyclic aromatic hydrocarbons in sediment using solid-phase microextraction with gas chromatography-mass spectrometry.

Manual solid-phase microextraction (SPME) coupled with gas chromatography-mass spectrometry (GC-MS) is applied for the determination of polycyclic aromatic hydrocarbons (PAHs) from natural matrix through a distilled water medium. Seven of the 16 PAH standards (naphthalene, acenaphthene, fluorene, anthracene, fluoranthene, pyrene, benzo[a]anthracene) are spiked on a marine muddy sediment. The samples, containing PAHs in the range of 10-20 ppm, are then aged at room temperature more than 10 days before analysis. The influence of the matrix, SPME adsorption time, pH, salt content, and SPME adsorption temperature are investigated. The reproducibility of the technique is less than 13% (RDS) for the first 6 considered PAHs and 28% (RDS) for benzo(a)anthracene with a fiber containing a 100-micron poly dimethylsiloxane coating. Linearity extended in the range of 5-50 picograms for PAHs direct injection, 5-70 picograms for PAHs in water, and 1-170 picograms for PAHs in sediment. The detection limit is estimated less than 1 microgram/kg of dry sample for the first 6 considered PAHs in sediment and 1.5 micrograms/kg of dry sample for benzo(a)anthracene using the selected ion monitoring mode in GC-MS. The recoveries of the considered PAHs are evaluated.

Degradation of high molecular weight poly(L-lactide) in alkaline medium.

To study the effect of molecular weight and morphology on hydrolytic degradation, four poly(L-lactide)s (PLLAs) with average molecular weight of 3.0 x 10(5), 4.5 x 10(5), 6.5 x 10(5) and 3 x 10(6) were used. PLLA films with different morphologies were obtained by solution casting. Degradation of the films was performed at 37 degrees C in 0.01 N NaOH solution and this alkaline hydrolysis seemed to simulate well the real case while offering significant acceleration of the degradation process. Diverse microscopy techniques (light, polarizing and scanning electron) were used to study the surface change of morphology and erosion of the PLLA films. Swelling was visualized by scanning electron microscopy, particularly on the spherulites, which were eroded from the centre by hydrolysis. In the case of highly amorphous film, crystallization took place as degradation proceeded. The reduction in transparency of PLLA films, measured by a spectrophotometer at 570 nm, was ascribed to the increased density of spherulites. Differential scanning calorimetry revealed that the crystallinity of PLLA increased with degradation time, in accordance with accelerated spherulite formation.

Medical care of doctors.

AIM: To describe doctors' attitudes towards their own medical care. METHODS: Postal survey asking 2564 doctors about their access to, and use of, medical services. The sample, 14% of all New South Wales doctors, was randomly selected from the NSW Register of Medical Practitioners. To ensure anonymity, non-respondents were not followed up. RESULTS: The response rate was 44%. Only 42% of respondents had a general practitioner and most had self-prescribed medication. Nineteen per cent reported marital disturbances, 18% emotional disorders, 3% alcohol problems and 1% drug abuse, but not many had discussed these problems with their doctor. Twenty-six per cent had a condition warranting a medical consultation but felt inhibited about consulting a doctor. CONCLUSION: Many doctors lack adequate medical care. RECOMMENDATIONS: We recommend that doctors have their own general practitioner, avoid "corridor consultations" and not self-prescribe drugs that affect mental function. Teaching of appropriate help-seeking responses should be part of medical education.