- Beta-methylamino L-alanine
" that live on the plant's roots.
Neurotoxicity
BMAA is considered a possible cause of the
amyotrophic lateral sclerosis /parkinsonism –dementia complex (ALS/PDC) that has an extremely high rate of incidence among the Chamorro people ofGuam . [Cox, P.A., S.A. Banack, S.J. Murch, U. Rasmussen, G. Tien, R.R. Bidigare, J.S. Metcalf, L.F. Morrison, G.A. Codd, B. Bergman 2005. Diverse taxa of cyanobacteria produce β-N-methylamino-L-alanine, a neurotoxic amino acid. "Proceedings of the National Academy of Sciences of the United States of America" 102: 5074-5078. [http://dx.doi.org/10.1073/pnas.0501526102] ] The Chamorro call the condition "lytico-bodig".Miller, G. July 2006. [http://dx.doi.org/10.1126/science.313.5786.428 Guam's Deadly Stalker: On the Loose Worldwide?] "Science" 28 (313): 428-431.]ources of BMAA
In the 1950s, ALS/PDC prevalence ratios and death rates for Chamorro residents of Guam and Rota were 50–100 times that of developed countries, including the United States. No demonstrable
heritable orviral factors were found for the disease, and a subsequent decline of ALS/PDC after 1955 on Guam, led to the search for responsible environmental agents. The use of cycad ("Cycas circinalis") seeds in food and traditional medicine had decreased as the Chamorro population became more Americanized following World War II.Spencer, P.S., P.B. Nunn, J. Hugon, A.C. Ludolph, S.M. Ross, D.N. Roy, and R.C. Robertson July 1987. Guam amyotrophic lateral sclerosis-parkinsonism-dementia linked to a plant excitantneurotoxin . "Science" 31 (237): 517-522.]In addition to eating the seeds directly, BMAA may have found its way into human diets by way of
biomagnification .Fruit bats , a Chamorrodelicacy , may feed on cycad seeds and concentrate the toxin in their flesh. Three museum specimen bats, collected in Guam in the 1950s, contained hundreds of times more BMAA, gram for gram, than cycad seeds.BMAA neurotoxic effects
Degenerative locomotor diseases had been described in animals grazing on cycad species, fueling interest in a possible link between the plant and the
etiology of ALS/PDC . Subsequent laboratory investigations discovered the presence of BMAA. BMAA induced severe neurotoxicity inrhesus macaques , including:
*limb muscleatrophy
*nonreactive degeneration ofanterior horn cells
*degeneration and partial loss ofpyramidal neuron s of themotor cortex
*behavioral dysfunction
*conduction deficits in the central motor pathway
*neuropathological changes of motor cortexBetz cell sThere are reports that low BMAA concentrations can selectively kill cultured motor neurons from mouse
spinal cord s. In the motor neurons, BMAA activates AMPA-kainateglutamate receptor s and boosted production ofoxygen radicals .Worldwide concerns
The presence of BMAA in cyanobacteria, among the most populous organisms in the world, has raised concerns that humans worldwide may be exposed to levels of BMAA that could be potentially harmful. Cyanobacteria from soil and water samples collected around the world produce BMAA, giving rise to speculative biomagnification in
food chain s.References
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