Potential for human exposure to Beta-N-methylamino-L-alanine in a freshwater system

β-N-methylamino-L-alanine (BMAA) is a non-proteinogenic amino acid associated with human neurodegenerative diseases. The content of BMAA in cyanobacteria is modulated by nitrogen in laboratory cultures. In order to evaluate the potential for human exposure, the nitrogen modulation of BMAA content ne...

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Main Author: Scott, Laura Louise
Format: Others
Language:English
Published: Nelson Mandela Metropolitan University 2014
Subjects:
Online Access:http://hdl.handle.net/10948/5159
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spelling ndltd-netd.ac.za-oai-union.ndltd.org-nmmu-vital-208162017-12-21T04:22:32ZPotential for human exposure to Beta-N-methylamino-L-alanine in a freshwater systemScott, Laura LouiseWater quality biological assessmentCyanobacteriaNeurotoxic agentsβ-N-methylamino-L-alanine (BMAA) is a non-proteinogenic amino acid associated with human neurodegenerative diseases. The content of BMAA in cyanobacteria is modulated by nitrogen in laboratory cultures. In order to evaluate the potential for human exposure, the nitrogen modulation of BMAA content needed verification in a natural environment. In accordance with laboratory culture studies, data presented in this study show that combined nitrogen was the most significant modulator of both cellular microcystin (MC) and BMAA content in phytoplankton in an environmental cyanobacterial bloom. While BMAA is produced upon nitrogen deprivation, MC is only produced at a specific nitrogen threshold where the rate of increase of nitrogen in the cell exceeds the carbon fixation rate. As BMAA and MC were detected in phytoplankton sourced from the Hartbeespoort Dam reservoir, the transfer of these cyanotoxins to organisms of higher trophic levels was investigated. Both BMAA and MC were detected at high concentrations in the liver and muscle tissue of fish sourced from the Hartbeespoort Dam reservoir indicating that consumption of fish from this reservoir constitutes a serious risk of exposure to cyanotoxins. In addition to the dietary exposure route to BMAA, two recent studies reported a correlation between Amyotrophic Lateral Sclerosis (ALS) incidence and the potential for aerosol exposure to cyanobacteria. With the absence of any evidence of the systemic distribution of BMAA following inhalation, an evaluation of the potential exposure risk associated with living in close proximity to this reservoir was deemed premature. A laboratory experiment investigating the effect and systemic fate of inhaled aerosolised BMAA was therefore conducted in order to determine the feasibility of inhalation as a potential BMAA exposure route. Data from the rat inhalation exposure study, however, showed that in rats BMAA inhalation may not constitute a significant mechanism of toxicity at environmental BMAA levels.Nelson Mandela Metropolitan UniversityFaculty of Science2014ThesisMastersMScvi, 87 leaves: illustrationspdfhttp://hdl.handle.net/10948/5159vital:20816EnglishNelson Mandela Metropolitan University
collection NDLTD
language English
format Others
sources NDLTD
topic Water quality biological assessment
Cyanobacteria
Neurotoxic agents
spellingShingle Water quality biological assessment
Cyanobacteria
Neurotoxic agents
Scott, Laura Louise
Potential for human exposure to Beta-N-methylamino-L-alanine in a freshwater system
description β-N-methylamino-L-alanine (BMAA) is a non-proteinogenic amino acid associated with human neurodegenerative diseases. The content of BMAA in cyanobacteria is modulated by nitrogen in laboratory cultures. In order to evaluate the potential for human exposure, the nitrogen modulation of BMAA content needed verification in a natural environment. In accordance with laboratory culture studies, data presented in this study show that combined nitrogen was the most significant modulator of both cellular microcystin (MC) and BMAA content in phytoplankton in an environmental cyanobacterial bloom. While BMAA is produced upon nitrogen deprivation, MC is only produced at a specific nitrogen threshold where the rate of increase of nitrogen in the cell exceeds the carbon fixation rate. As BMAA and MC were detected in phytoplankton sourced from the Hartbeespoort Dam reservoir, the transfer of these cyanotoxins to organisms of higher trophic levels was investigated. Both BMAA and MC were detected at high concentrations in the liver and muscle tissue of fish sourced from the Hartbeespoort Dam reservoir indicating that consumption of fish from this reservoir constitutes a serious risk of exposure to cyanotoxins. In addition to the dietary exposure route to BMAA, two recent studies reported a correlation between Amyotrophic Lateral Sclerosis (ALS) incidence and the potential for aerosol exposure to cyanobacteria. With the absence of any evidence of the systemic distribution of BMAA following inhalation, an evaluation of the potential exposure risk associated with living in close proximity to this reservoir was deemed premature. A laboratory experiment investigating the effect and systemic fate of inhaled aerosolised BMAA was therefore conducted in order to determine the feasibility of inhalation as a potential BMAA exposure route. Data from the rat inhalation exposure study, however, showed that in rats BMAA inhalation may not constitute a significant mechanism of toxicity at environmental BMAA levels.
author Scott, Laura Louise
author_facet Scott, Laura Louise
author_sort Scott, Laura Louise
title Potential for human exposure to Beta-N-methylamino-L-alanine in a freshwater system
title_short Potential for human exposure to Beta-N-methylamino-L-alanine in a freshwater system
title_full Potential for human exposure to Beta-N-methylamino-L-alanine in a freshwater system
title_fullStr Potential for human exposure to Beta-N-methylamino-L-alanine in a freshwater system
title_full_unstemmed Potential for human exposure to Beta-N-methylamino-L-alanine in a freshwater system
title_sort potential for human exposure to beta-n-methylamino-l-alanine in a freshwater system
publisher Nelson Mandela Metropolitan University
publishDate 2014
url http://hdl.handle.net/10948/5159
work_keys_str_mv AT scottlauralouise potentialforhumanexposuretobetanmethylaminolalanineinafreshwatersystem
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