The organic or methylated form of mercury (Hg), consisting of one methyl group
bound to each atom of Hg, (methylmercury; MeHg), accounts for most of the Hg to
which humans are exposed. MeHg, by virtue of its lipophilicity is highly neurotoxic to
both the developing and mature central nervous system (CNS). Historically, MeHg has
been implicated in high morbidity and mortality rates over the last 40 years in Japan,
Iraq, Pakistan and Guatemala. The most common symptom exhibited in these exposure
episodes was cerebellar ataxia. Recent in vitro studies using cultured granule cells
showed that MeHg alters intracellular calcium ion ([Ca2+]i) homeostasis, potentiates
reactive oxygen species (ROS) generation and loss of mitochondrial membrane potential
leading to apoptotic death of cerebellar granule neurons. To better understand the
neurotoxic mechanisms of MeHg on cerebellum, changes with respect to biochemical
processes in cerebellar granule cells and associated behavior changes were investigated.
The aims of this dissertation were: (1) to assess mercury concentrations in mouse
brain using different routes of administration and different tissue preparations, (2) to
determine the behavior effects of in vivo MeHg exposure in young adult mice. (3) to understand specific biochemical processes leading to granule cell death/dysfunction due
to in vivo MeHg toxicity in mice, and (4) to determine the toxic effects of in vivo MeHg
exposure on mice aged between 16-20 months.
The present results showed that repeated oral exposure to MeHg results in greater
accumulation of Hg in brain tissue when compared to single oral or subcutaneous
exposures at the same concentration of MeHg. Behavior analysis revealed that MeHg at
the concentrations used in this study had profound effects on motor coordination and
balance in young adult and aged mice. Investigation of biochemical processes in
cerebellar granule cells of mice exposed to MeHg showed an increase in ROS
generation, alteration of ([Ca2+]i (in young adult mice) and loss of MMP in young adult
and aged mice. However, these changes did not lead to apoptotic cell death of granule
cells at the concentrations of MeHg used and at the specific time point it was
investigated in young adult mice.
| Identifer | oai:union.ndltd.org:tamu.edu/oai:repository.tamu.edu:1969.1/4992 |
| Date | 25 April 2007 |
| Creators | Bellum, Sairam |
| Contributors | Abbott, Louise C |
| Publisher | Texas A&M University |
| Source Sets | Texas A and M University |
| Language | en_US |
| Detected Language | English |
| Type | Book, Thesis, Electronic Dissertation, text |
| Format | 1762455 bytes, electronic, application/pdf, born digital |
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