The molecular logic of endocannabinoid signalling

The endocannabinoids are a family of lipid messengers that engage the cell surface receptors that are targeted by Δ9-tetrahydrocannabinol, the active principle in marijuana (Cannabis). They are made on demand through cleavage of membrane precursors and are involved in various short-range signalling processes. In the brain, they combine with CB1 cannabinoid receptors on axon terminals to regulate ion channel activity and neurotransmitter release. Their ability to modulate synaptic efficacy has a wide range of functional consequences and provides unique therapeutic possibilities. © 2003, Nature Publishing Group. All rights reserved

Efficiency of UV Treatment with and without the photocatalyst titanium dioxide for the degradation of the cyanotoxin cylindrospermopsin

Cylindrospermopsin is a potent hepatotoxin, produced by several cyanobacteria including Cylindrospermopsis raciborskii, a species commonly found in water supplies in Queensland, Australia. This study focussed on an assessment of the effectiveness of ultra violet (UV) irradiation as a water treatment procedure for the degradation of cylindrospermopsin. Enhancement of UV treatment with the addition of the photocatalyst titanium dioxide was also examined. Results indicate that UV irradiation (>4750 μW cm) degrades cylindrospermopsin over an initial toxin concentration range of 50-350 μg L. In addition, there was an influence on the degradation rate from solution pH (4, 7 and 9), but less so from solution temperature (19, 28 and 35°C). Degradation was a first order kinetic relationship and the calculated half-life of cylindrospermopsin under UV irradiation (unbuffered, pH 6.5, 22 ± 2°C) was 14 ± 2 minutes. The addition of titanium dioxide (0.1 g L) to samples greatly increased the degradation rate to produce a calculated half-life of 2.8 ± 1 minutes

Photocatalytic degradation of the cyanotoxin cylindrospermopsin, using titanium dioxide and UV irradiation

Cylindrospermopsis raciborskii produces the cyanotoxin cylindrospermopsin, which is commonly found in SouthEast Queensland water reservoirs, and has been responsible for the closure of these reservoirs as a source of drinking water in recent times. Thus, alternative more effective treatment methods need to be investigated for the removal of toxins such as cylindrospermopsin. This study examined the effectiveness of two brands of titanium dioxide under UV photolysis for the degradation of cylindrospermopsin. Results indicate that titanium dioxide is an efficient photocatalyst for cylindrospermopsin degradation. The titanium dioxide (TiO2), brand Degussa P-25 was found to be more efficient than the alternate brand Hombikat UV-100. There was an influence from solution pH (4, 7, and 9) with both brands of titanium dioxide, with high pH resulting in the best degradation rate. Importantly, there was no adsorption of cylindrospermopsin to titanium dioxide particles as seen with other cyanotoxins, which would adversely influence the degradation rate. Degradation rates were not influenced by temperature (19-34é when P-25 was the source of TiO2, some temperature influence was observed with UV-100. Dissolved organic carbon concentration will reduce the efficiency of titanium dioxide for cylindrospermopsin degradation, however the presence of other inorganic matter in natural waters greatly assists the photocatalytic process. With minimal potentially toxic by-product formation expected with this treatment, and the effective degradation of cylindrospermopsin, titanium dioxide UV photolysis is a promising speculative alternative water treatment method.No Full Tex