The formal cycloaddition adduct of 1,4-benzoquinone with two equivalents of cyclopentadiene is a scaffold with two non-conjugated alkenes. Both alkenes undergo endo [4+2] cycloaddition with a diene to form a rigid U-shaped molecular cleft. Here we show experimental, computational and structural evidence that π interactions between the alkenes affect structural rigidity, Diels–Alder reactivity, cleft formation and host–guest capture.

Background In October 2004, Manam Island volcano in Papua New Guinea erupted, causing over 10 000 villagers to flee to internally displaced person (IDP) camps, including 550 from Dugulaba village. Following violence over land access in March 2010, the IDPs fled the camps, and four months later concurrent outbreaks of acute watery diarrhea and unusual neurological complaints were reported in this population. Materials and Methods A retrospective case-control study was conducted to identify the risk factors for peripheral neuropathy. Rectal swabs were collected from cases of acute watery diarrhea. Hair and serum metals and metalloids were analyzed by Inductively Coupled Plasma-Mass Spectrometry (ICP-MS). Results There were 17 deaths among the 550 village inhabitants during the outbreak period at a crude mortality rate 21-fold that of a humanitarian crisis. Vibrio cholerae O1 El Tor Ogawa was confirmed among the population. Access to community-level rehydration was crucial to mortality. Peripheral neuropathy was diagnosed among cases with neurological symptoms. A balanced diet was significantly protective against neuropathy. A dose-response relationship was seen between peripheral neuropathy and a decreasing number of micronutrient- rich foods in the diet. Deficiencies in copper, iron, selenium and zinc were identified among the cases of peripheral neuropathy. Conclusions Cholera likely caused the mostly preventable excess mortality. Peripheral neuropathy was not caused by cholera, but cholera may worsen existing nutritional deficiencies. The peripheral neuropathy was likely caused by complex micronutrient deficiencies linked to non-diversified diets that potentially increased the vulnerability of this population, however a new zinc-associated neuropathy could not be ruled out. Reoccurrence can be prevented by addressing the root cause of displacement and ensuring access to arable land and timely resettlement.

Cyanobacterial blooms represent one of the most conspicuous and widespread waterborne microbial hazards to human and ecosystem health. Investigation of a cyanobacterial bloom in a shallow brackish water recreational cable ski lake in south-eastern Queensland, Australia revealed the dominance of the toxigenic species Nodularia spumigena. The bloom spanned three months, during which time cell concentrations exceeded human guideline thresholds for recreational risk, and concentrations of the hepatotoxic cyanotoxin nodularin exceeded 200 µg L−1. Cyanotoxin origin and identification was confirmed by amplification of the ndaF-specific PCR product and sequencing of the 16S rRNA gene. From the limited data available leading up to, and throughout the bloom, it was not possible to establish the set of causative factors responsible for its occurrence. However a combination of factors including salinity, hydraulic retention time and nutrient status associated with an extended period of drought are likely to have contributed. This was the first known occurrence of this species in bloom proportions from sub-tropical Australia and as such represents a hitherto uncharacterized risk to human and ecosystem health. It highlights the need for adaptive monitoring regimes to ensure a comprehensive understanding of the potentially toxic cyanobacteria likely to inhabit any given region. Such monitoring needs to recognize that cyanobacteria have a significant capacity for range expansion that has been facilitated by recent changes in global climate.

Fish collected after a mass mortality at an artificial lake in south-east Queensland, Australia, were examined for the presence of nodularin as the lake had earlier been affected by a Nodularia bloom. Methanol extracts of muscle, liver, peritoneal and stomach contents were analysed by HPLC and tandem mass spectrometry; histological examination was conducted on livers from captured mullet. Livers of sea mullet (Mugil cephalus) involved in the fish kill contained high concentrations of nodularin (median 43.6 mg/kg, range 40.8–47.8 mg/kg dry weight; n = 3) and the toxin was also present in muscle tissue (median 44.0 μg/kg, range 32.3–56.8 μg/kg dry weight). Livers of fish occupying higher trophic levels accumulated much lower concentrations. Mullet captured from the lake 10 months later were also found to have high hepatic nodularin levels. DNA sequencing of mullet specimens revealed two species inhabiting the study lake: M. cephalus and an unidentified mugilid. The two mullet species appear to differ in their exposure and/or uptake of nodularin, with M. cephalus demonstrating higher tissue concentrations. The feeding ecology of mullet would appear to explain the unusual capacity of these fish to concentrate nodularin in their livers; these findings may have public health implications for mullet fisheries and aquaculture production where toxic cyanobacteria blooms affect source waters. This report incorporates a systematic review of the literature on nodularin measured in edible fish, shellfish and crustaceans.

Korean Yellow Clay (Whangto) can be used to efficiently remove the cyanobacterial toxin microcystin-LR when present in water. This removal technique can be employed by rural and remote communities when surface water is contaminated with a toxic Microcystis sp. bloom. In most cases two sequential applications of clay can bring the dissolved microcystin toxin content below WHO guidelines for drinking water (1 ug/L) (WHO, 1998). The removal process is characterised by adsorption to the clay particle, with the Langmuir isotherm fitting the results marginally better than the Freundlich isotherm.

Chemical by-products arising from water disinfection may be harmful to human health. Although there are potentially innumerable individual chemical species arising from the water disinfection process, the risk to human health is considered small when compared to the risks associated with drinking water which has not been treated for pathogen removal. The purpose of this study was to assess the prevalence of the four regulated trihalomethanes, as well as the potently carcinogenic nitrosamine, N-nitrosodimethylamine (NDMA) (whose regulation has been proposed by the NHMRC in the draft 2010 Australian Drinking Water Guidelines) in South East Queensland (SEQ) drinking water supplies. Toward this objective, NDMA and trihalomethane (THM) formation potential experiments were undertaken using source waters from a number of SEQ water treatment plants (WTPs), as well as directly from the Logan River, Teviot Brook and Mary River. The relationship between water parameters such as dissolved organic carbon (DOC) and dissolved organic nitrogen (DON), disinfection method, and the final concentration of particular disinfection by-products (DBPs) in the finished water were examined, with a number of general trends becoming apparent. NDMA formation potentials were consistently quite low (5 – 21 ng/L) from chloramination of raw waters, and not detected (< 5 ng/L) in chlorinated waters. NDMA was not detected in any SEQ finished waters (< 5 ng/L).THM formation potentials were consistently below the Australian Drinking Water Guideline of 250 µg/L, however levels were higher for chlorinated waters than for chloraminated waters.

This study was undertaken to evaluate the protective efficacy of the antioxidants vitamin E and Trolox (a water-soluble vitamin E derivative) against the toxicity of microcystin-LR (MC-LR), Microcystis aeruginosa aqueous extract (CE), and a reference toxin, menadione sodium bisulfite (MSB), in Artemia franciscana nauplii. This was achieved by using the well-established brine shrimp bioassay. The experiment was conducted in 2 stages, with (1) 12-h mortality time course and (2) LC50 determination for 12- and 24-h exposures. Treatments consisted of MC-LR, CE, and MSB alone and with 4-h pretreatments of either vitamin E or Trolox. Sensitivity of A. franciscana nauplii with 24-h LC50 values of 11 (10.1–12.1) μg/ml for MSB and 9.5 (8.8–10.4) μg/ml for MC-LR were in general agreement with values reported for Artemia sp. Both antioxidant pretreatments resulted in significant reductions in mortality of approximately 50% at 9 h postexposure when challenged by either 40 μg/ml MC-LR or 20 μg/ml MSB. In contrast, the antioxidant pretreatments offered little to no protection from CE, suggesting that other uncharacterized bioactive compounds contributed to overall toxicity. The described bioassay is easily accessible, inexpensive, rapid, and complies with animal ethics guidelines of many countries, and thus provides a potential alternative to the mouse bioassay for the initial screening for chemoprotectants against MC-LR toxicity.

A referee analysis method for the detection and quantification of Pacific ciguatoxins in fish flesh has recently been established by the public health analytical laboratory for the State of Queensland, Australia. Fifty-six fish samples were analysed, which included 10 fillets purchased as negative controls. P-CTX-1 was identified in 27 samples, and P-CTX-2 and P-CTX-3 were found in 26 of those samples. The range of P-CTX-1 concentrations was 0.04-11.4 mu g/kg fish flesh; coefficient of variation from 90 replicate analyses was 7.4%. A liquid chromatography/tandem mass spectrometry (HPLC-MS/MS) method utilising a rapid methanol extraction and clean-up is reliable and reproducible, with the detection limit at 0.03 mu g/kg fish flesh. Some matrix effects are evident, with fish oil content a likely signal suppression factor. Species identification of samples by DNA sequence analysis revealed some evidence of fish substitution or inadvertent misidentification, which may have implications for the management and prevention of ciguatera poisoning. Blinded inspection of case notes from suspect ciguatera poisoning cases showed that reporting of ciguatera-related paraesthesias was highly predictable for the presence of ciguatoxins in analysed fish, with 13 of 14 expected cases having consumed fish that contained P-CTX-1 (p < 0.001, Fishers Exact Test). Crown Copyright (C) 2009 Published by Elsevier Ltd. All rights reserved.

Cyanobacteria can produce groups of structurally and functionally unrelated but highly potent toxins. Cyanotoxins are used in multiple research endeavours, either for direct investigation of their toxicologic properties, or as functional analogues for various biochemical and physiological processes. This paper presents occupational safety guidelines and recommendations for personnel working in field, laboratory or industrial settings to produce and use purified cyanotoxins and toxic cyanobacteria, from bulk harvesting of bloom material, mass culture of laboratory isolates, through routine extraction, isolation and purification. Oral, inhalational, dermal and parenteral routes are all potential occupational exposure pathways during the various stages of cyanotoxin production and application. Investigation of toxicologic or pharmacologic properties using in vivo models may present specific risks if radiolabelled cyanotoxins are employed, and the potential for occupational exposure via the dermal route is heightened with the use of organic solvents as vehicles. Inter- and intra-national transport of living cyanobacteria for research purposes risks establishing feral microalgal populations, so disinfection of culture equipment and destruction of cells by autoclaving, incineration and/or chlorination is recommended in order to prevent viable cyanobacteria from escaping research or production facilities.

The cyanobacterial toxin cylindrospermospin (CYN) was shown to inhibit the eukaryotic protein synthesis apparatus with similar potency in plant and mammalian cell extracts, IC50 of 334 nM in wheat germ extract and 110 nM in reticulocyte lysate. [14C] CYN binding was assessed in reticulocyte lysates, following separation of ribosomes from free toxin on Sephadex G-50 size exclusion columns. While toxin binding was shown to be concentration-dependent (60–600 nM [14C] CYN), it did not correlate with ribosome content. The molar ratio of toxin to ribosomes was 0.02:1 at the binding plateau. Significant binding of [14C] CYN was identified in both the ribosome fraction (>90% total ribosomes) and the first wash fraction eluting from the Sephadex G-50 column, despite the low ribosome content (<10% total ribosomes) in the latter. Bound [14C] CYN could be partially displaced by incubation with an excess of unlabelled CYN in both the ribosome and wash fractions, indicating a non-covalent linkage. Molecular weight cut-off filters identified that [14C] CYN was associated with high molecular weight material >100 kDa. These results suggest that CYN's target may not be the ribosome itself, but rather one of the soluble proteins associated with the eukaryotic translation system.

Cylindrospermopsin and its deoxy analogue have been detected in a number of cyanobacteria throughout the world. Previously in Australia these toxins have been reported in Cylindrospermopsis raciborskii and Aphanizomenon ovalisporum. In both these species the deoxycylindrospermopsin levels are less than 10 % of the predominant toxin, cylindrospermopsin. Lyngbya wollei specimens from several streams in South East Queensland were found to contain deoxycylindrospermopsin as the predominant toxin with only low levels of cylindrospermopsin. The level of toxin in the water was below the detection level of 0.2 micrograms per Litre in contrast to the other two species mentioned which often give toxin levels in the surrounding water at similar concentrations to the toxin content of the cells. This is the first report of these toxins being detected in a benthic cyanobacterial species.

Lyngbya wollei (Farlow ex Gomont) Speziale and Dyck is a common mat-forming benthic cyanobacterium from freshwater habitats. We found that two populations from southeast Queensland (Australia) produce the potent cyanotoxin cylindrospermopsin (CYN) and its analogue, deoxy-cylindrospermopsin (deoxy-CYN). The highest concentrations in environmental samples were 20 and 550μgg−1 dry weight for CYN and deoxy-CYN, respectively. A sub-sample maintained in culture for over 16 months yielded concentrations of 33 and 308μgg−1 dry weight for CYN and deoxy-CYN, respectively. The concentration of deoxy-CYN in L. wollei was 10–300 times higher than CYN, suggesting that, unlike many other CYN-producing cyanobacteria, the primary compound produced by L. wollei is deoxy-CYN. The production of CYN and deoxy-CYN by L. wollei represents a potential human health risk and an additional source of these toxins in freshwaters. This is the first report of the production of CYN and deoxy-CYN by L. wollei or any species of the Oscillatoriales.

The occurrence of toxic cyanobacterial blooms has been reported worldwide and poses a threat to human health through drinking water exposure. The toxins they produce are highly water soluble and can leach into the water body. To eliminate any risk of drinking water exposure, removal of these toxins is essential before the water is consumed. Conventional water treatment techniques such as chlorination, if managed well, can be effectively used to remove some of these toxins, however, saxitoxin and its derivatives pose a problem. Little toxicological data are available to evaluate the real threat of these toxins.