A survey for paralytic shellfish poisoning (PSP) in Vancouver Harbour

Shellfish samples were collected from seven inter-tidal and two sub-tidal sites between 23 May and 8 June 1999 in Vancouver Harbour and were analysed for paralytic shellfish poisoning (PSP) using a mouse bioassay. PSP was detected in mussels collected at four sampling sites in English Bay and Burrard Inlet, at a concentration below 20 mug saxitoxin equivalents (STXeq)/100 g wet weight. (C) 2003 Elsevier Ltd. All rights reserved.

Investigation of Extration Method for Paralytic Shellfish Poisoning Toxins in Shellfish

Me optimal conditions were established for the extraction of paralytic shellfish poisoning toxins from gonad of Chlamys nobills using acetic acid and hydrochloric acid in the concentration range of 0.04-1.0 mol/L. A 10-g portion of gonad of Chlamys nobilis was extracted by boiling for 5 min with 1.0 mL acetic acid and hydrochloric acid in a 50-mL beaker. Meanwhile, a portion of gonad of Chlamys nobilis was extracted by sonication in the solution of 0.3 mol/L HAc + 0.2 mol/L HCl for a total period of 5-30 min. The raw extract was centrifuged at 3500 r/min for 5 min and the pH of supernatant was adjusted from 2.0 to 4.0 by 0.1 mol/L NaOH or 5 mol/L HCL After passing through a Millipore ultrafiltration membrane (10000 MW cut-off), ultrafiltrate was then analyzed by HPLC. The results showed that hydrochloric acid in the concentration range of 0.25-1.0 mol/L caused a significant decrease of N-sulfocarbarnoyl-11-hydroxysulfate toxin C1 (C1), C2 and gonyautoxin 5 (GTX5) and the concomitant increase of GTX2,3. However, the amount of the three unstable toxins did not show any change using the extraction with acetic acid. Under the same concentration of acetic acid (0.3 mol/L) and hydrochloric acid (0.2 mol/L), the amount of C1 in the ultrasonic extraction was obviously lower than the boiling one, while C2 showed slightly higher than the latter.

Nitrate and phosphate supplementation to increase toxin production by the marine dinoflagellate Alexandrium tamarense

Alexandrium tamarense toxins have great value in biotechnology research as well as important in connection with shellfish poisoning. The influence of nitrate or nitrate and phosphate supplementation on cell biomass and toxin content were investigated in batch cultures. When cultures at low nitrate (88.2 mu M NaNO3) Were supplemented with 793.8 mu M NaNO3 at day 10 the cell density and cellular toxin contents were increased by 6-29% and 20-76%, respectively, compared with controls, and maximal values were 43,600 cells/ml (day 38) and 0.91 pg/cell (day 31). Supplementation with nitrate at day 14 or with nitrate and phosphate at day 10/14 to the cultures did not increase the cell density compared with the non-supplemented middle nitrate or high phosphate (108 mu M NaH2PO4) cultures, respectively, but increased the cellular toxin contents by an average of 52%. The results showed that supplementation with nitrate or with nitrate and phosphate at different growth phases of the cultures increased toxin yield by an average of 46%. Supplementation with nitrate at selected times to maintain continuous low level of nitrate might contribute to the effective increase of toxin yield of A. tamarense. (c) 2005 Elsevier Ltd. All rights reserved.

Small fish communities in two regions of the Liangzi Lake, China, with or without submersed macrophytes

Small fish communities were compared between the vegetated and vegetation-free regions of the Liangzi Lake, a shallow lake along the middle reach of the Yangtze River, China. Fish were sampled using 10 x 10 m(2) block nets and poisoning. Three samples were taken from either the near shore area or lake centre of each region. A total of 19 fish species were collected; all species occurred in the vegetated region but only 12 occurred in the vegetation-free region. The dominant small fish were Carassius auratus auratus in the vegetated region and Ctenogobius giurinus in the vegetation-free region. Diversity, density and biomass of small fishes were significantly higher in the vegetated region than in the vegetation-free region in both near shore and lake centre areas. In the vegetated region, density and biomass of small fishes was significantly higher, while species diversity significantly lower in the near shore area than in the lake centre. In the vegetation-free region, density of small fishes was significantly higher in the near shore area than in the lake centre area, but species diversity or biomass was unaffected by location.

CYCLIC PEPTIDE HEPATOTOXINS FROM FRESH-WATER CYANOBACTERIAL (BLUE-GREEN-ALGAE) WATERBLOOMS COLLECTED IN CENTRAL CHINA

Toxic cyanobacteria (blue-green algae) waterblooms have been found in several Chinese water bodies since studies began there in 1984. Waterbloom samples for this study contained Anabaena circinalis, Microcystis aeruginosa and Oscillatoria sp. Only those waterblooms dominated by Microcystis aeruginosa were toxic by the intraperitoneal (i.p.) mouse bioassay. Signs of poisoning were the same as with known hepatotoxic cyclic peptide microcystins. One toxic fraction was isolated from each Microcystis aeruginosa sample. Two hepatotoxic peptides were purified from each of the fractions by high-performance liquid chromatography and identified by amino acid analysis followed by low and high resolution fast-atom bombardment mass spectrometry (FAB-MS). LD50 i.p. mouse values for the two toxins were 245-mu-g/kg (Toxin A) and 53-mu-g/g (Toxin B). Toxin content in the cells was 0.03 to 3.95 mg/g (Toxin A) and 0.18 to 3.33 mg/kg (Toxin B). The amino acid composition of Toxin A was alanine [1], arginine [2], glutamic acid [1] and beta-methylaspartic acid [1]; for Toxin B it was the same, except one of the arginines was replaced with a leucine. Low- and high-resolution FAB-MS showed that the molecular weights were 1,037 m/z (Toxin A) and 994 m/z (Toxin B), with formulas of C49H76O12N13 (Toxin A) and C49H75O12N10 (Toxin B). It was concluded that Toxin A is microcystin-RR and Toxin B is microcystin-LR, both known cyclic heptapeptide hepatotoxins isolated from cyanobacteria in other parts of the world. Sodium borohydride reduction of microcystin-RR yielded dihydro-microcystin-RR (m/z = 1,039), an important intermediate in the preparation of tritium-labeled toxin for metabolism and fate studies.

NOx storage-reduction over Pt/Mg-Al-O catalysts with different Mg/Al atomic ratios

A series of Pt/Mg-Al-O catalysts with different Mg/Al atomic ratios were prepared. The NOx storage capacities of these catalysts were measured by isothermal storage at 350 degreesC. It was found that the NOx storage capacity increased with increasing Mg/Al atomic ratios. The catalytic behaviors of Pt/Mg-Al-O and Pt/MgO were studied with storage-reduction cycles at 400 degreesC. Under oxidizing conditions, NOx concentration in the outlet gas gradually increased with time, which indicated the catalysts could store NOx effectively. After a switch from oxidizing conditions to reducing conditions, NOx desorption peak emerged immediately due to the incomplete reduction of stored NOx, which lowered the total NOx conversion. With increasing Mg/Al atomic ratio in the catalysts, NOx conversion increases. Pt/MgO has the highest NOx conversion because of its best activity in the reduction of NOx by C3H6. It seems that with an increasing amount of MgO in the catalysts, the self-poisoning of Pt-sites by adsorbed species during the reaction of NOx with C3H6 may be inhibited effectively.

过量Mg~(2+)对农作物种子萌发特性的影响(英文)

[Objective] The research aimed to reveal the effects of excessive Mg2+ on the germination characteristics of maize and soybean. [Method] Eleven concentration gradients of Mg2+ including 0,40,80,120,160,200,240,280,320,360 and 400 mmol/L were set up to study the effects of different treatments on such indices as the germination potential,germination rate,fresh weight,dry weight,root length,plant height and stem diameter of maize and soybean. [Result] With the increasing of Mg2+ concentration,the germination of maize delayed and the germination rate of soybean obviously decreased,reaching the significant difference at 0.05 level. When Mg2+ concentration increased,the fresh weight and dry weight of maize and soybean decreased,but maize and soybean showed some adaptability. The growth of radicles and seedlings in maize and soybean were obviously inhibited by Mg2+,and atrophy and dysplasia phenomena appeared. [Conclusion] Excessive Mg2+ stress has different effects on the germination potential and germination rate of different crops and has obvious poisoning effects on the root and stem growth of crops.

Electrodeposition of platinum nanoclusters on type I collagen modified electrode and its electrocatalytic activity for methanol oxidation

We firstly reported a novel polymer matrix fabricated by type I collagen and polymers, and this matrix can be used as nanoreactors for electrodepositing platinum nanoclusters (PNCs). The type I collagen film has a significant effect on the growth of PNCs. The size of the platinum nanoparticles could be readily tuned by adjusting deposition time, potential and the concentration of electrolyte, which have been verified by field-emitted scanning electron microscopy (FE-SEM). Furthermore, cyclic voltammetry (CV) has demonstrated that the as-prepared PNCs can catalyze methanol directly with higher activity than that prepared on PSS/PDDA film, and with better tolerance to poisoning than the commercial E-TEK catalyst. The collagen-polymer matrix can be used as a general reactor to electrodeposit other metal nanostructures.

Highly efficient electrocatalytic oxidation of formic acid by electrospun carbon nanofiber-supported PtxAu100-x bimetallic electrocatalyst

Electrospun carbon nanofiber-supported bimetallic PtxAu100-x electrocatalysts (PtxAu100-x/CNF) were prepared by electrochemical codeposition method. The composition of PtAu bimetallic nanoparticles could be controlled by varying the ratio of H2PtCl6 and HAuCl4. Scanning electron microscopy images showed that bimetallic nanoparticles had coarse surface morphology with high electrochemically active surface areas. X-ray diffraction analysis testified the formation of PtAu alloys. PtxAu100-x/CNF electrocatalysts exhibited improved electrocatalytic activities towards formic acid oxidation by providing the selectivity of the reaction via dehydrogenation pathway and suppressing the formation/adsorption of poisoning CO intermediate, indicating that PtxAu100-x/CNF is promising electrocatalyst in direct formic acid fuel cells.

Platinum-macrocycle co-catalyst for electro-oxidation of formic acid

In this work, a new promoter, tetrasulfophthalocyanine (FeTSPc), one kind of environmental friendly material, was found to be very effective in both inhibiting self-poisoning and improving the intrinsic catalysis activity, consequently enhancing the electro-oxidation current during the electro-oxidation of formic acid. The cyclic voltammograms test showed that the formic acid oxidation peak current density has been increased about 10 times compared with that of the Pt electrode without FeTSPc. The electrochemical double potential step chronoamperometry measurements revealed that the apparent activity energy decreases from 20.64 kJ mol(-1) to 17.38 kJ mol(-1) after Pt electrode promoted by FeTSPc. The promoting effect of FeTSPc may be owed to the specific structure and abundant electrons of FeTSPc resulting in both the steric hindrance of the formation of poisoning species (CO) and intrinsic kinetic enhancement. In the single cell test, the performance of DFAFC increased from 80 mW cm(-2) mg(-1) (Pt) to 130 mW cm(-2) mg(-1) after the anode electrode adsorbed FeTSPc.

FLOW-INJECTION ANALYSIS OF GLUCOSE AT AN AMPEROMETRIC GLUCOSE SENSOR-BASED ON ELECTROCHEMICAL CODEPOSITION OF PALLADIUM AND GLUCOSE-OXIDASE ON A GLASSY-CARBON ELECTRODE

A glassy carbon electrode (GCE) modified with palladium provides excellent electrocatalytic oxidation of hydrogen peroxide. When the electrolyte contains palladium chloride and glucose oxidase, the GCE can be modified by electrochemical codeposition at a given potential. The resulting modified surface was coated with a thin film of Nation to form a glucose sensor. Such a glucose sensor was successfully used in the flow-injection analysis of glucose with high stability and anti-poisoning ability. It gave a detection limit of 1 X 10(-7) M injected glucose, with a linear concentration range of 0.001-8 mM. There is no obvious interference from substances such as ascorbate and saccharides.

MEASUREMENT OF CATALYTIC ACTIVITY VARIATION FOR H2O2 OXIDATION AT A COBALT PORPHYRIN COATED ELECTRODE

A rapid rotation-scan method was used for the electrocatalytic oxidation of H2O2 at a cobalt protoporphyrin modified pyrolytic graphite electrode (CoPP/PG). The rate constant of H2O2 oxidation at the CoPP/PG electrode at different potentials and in different pH solutions was measured. The variation of catalytic activity with reaction charges (Q) passed through the electrode was analyzed. This provided a convenient electrochemical method to study the passivation and poisoning of catalytic sites with time.