Co-occurrence of beta-N-methylamino-L-alanine, a neurotoxic amino acid with other cyanobacterial toxins in British waterbodies, 1990-2004.
ABSTRACT The neurotoxic amino acid, beta-N-methylamino-L-alanine, was found to be present in all of 12 analysed samples of cyanobacterial blooms, scums and mats, which had been collected in seven years between 1990 and 2004 inclusive and stored at -20 degrees C. BMAA identification was by high performance liquid chromatography with fluorescence detection and by triple quadrapole mass spectrometry after derivatization. The samples originated from 11 freshwater lakes and 1 brackish waterbody, used either for drinking water, recreation, or both. BMAA was present at between 8 and 287 microg g(-1) cyanobacterial dry weight and was present as both the free amino acid and associated with precipitated proteins. Ten of the samples contained additional cyanotoxins (including microcystins, anatoxin-a, nodularin and saxitoxin) at the time of sample collection. Five of the samples were associated with animal deaths, attributable at the time of sample collection, to microcystins, nodularin or anatoxin-a. The data demonstrate the presence of BMAA by high performance liquid chromatography and mass spectrometry in a diverse range of cyanobacterial bloom samples from high resource waterbodies. Furthermore, samples collected over several years shows that BMAA can co-occur with other known cyanotoxins in such waterbodies. Health risk assessment of cyanobacterial BMAA in waterbodies is suggested.
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ABSTRACT: The Lesser Flamingo (Phoeniconaias minor) is known to use cyanobacteria (primarily Arthrospira) as a major food source in the East African Rift Valley lakes. Periodically, mass mortalities have occurred, associated with the cyanobacterial toxins (cyanotoxins), microcystins and anatoxin-a. Deposition of these cyanotoxins into P. minor feathers has been shown to occur, consistent with the presence of cyanotoxins in the livers, stomach and faecal contents after dietary intake. As cyanobacteria have been shown to also produce the neurotoxins β-N-methylamino-l-alanine (BMAA) and 2,4-diaminobutyric acid (DAB), stored wing feathers, previously recovered from flamingos which had been exposed to microcystins and anatoxin-a and had subsequently died, were analysed for these neurotoxic amino acids. Trace amounts of BMAA were detected in extracts from Lake Nakuru flamingo feathers, with DAB also present at concentrations between 3.5 and 8.5μgg(-1) dry weight in feathers from both lakes. Toxin recovery by solid-phase extraction of feather digests was tested with spiked deuterated BMAA and showed good recovery when analysed by LC-MS/MS (80-94%). This is the first report of these neurotoxic amino acids in birds. We discuss the origin and significance of DAB, alongside other cyanotoxins of dietary origin, in the feathers of the Lesser Flamingo.Chemosphere 10/2012; 90(2). DOI:10.1016/j.chemosphere.2012.09.094 · 3.50 Impact Factor
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ABSTRACT: Ensembles of mutually coupled ultradian cellular oscillators have been proposed by a number of authors to explain the generation of circadian rhythms in mammals. Most mathematical models using many coupled oscillators predict that the output period should vary as the square root of the number of participating units, thus being inconsistent with the well-established experimental result that ablation of substantial parts of the suprachiasmatic nuclei (SCN), the main circadian pacemaker in mammals, does not eliminate the overt circadian functions, which show no changes in the phases or periods of the rhythms. From these observations, we have developed a theoretical model that exhibits the robustness of the circadian clock to changes in the number of cells in the SCN, and that is readily adaptable to include the successful features of other known models of circadian regulation, such as the phase response curves and light resetting of the phase.Bulletin of Mathematical Biology 06/1997; 59(3):517-32. DOI:10.1007/BF02459463 · 1.29 Impact Factor