A University of Calgary Faculty of Medicine research team has found that exposure to mercury causes degeneration of brain neurons in animals.
The scientific findings are being published in a cover story in the April edition of the British journal NeuroReport. The researchers' academic paper is supported by a time-lapse video recorded from a microscope camera showing how neurons degenerate when they are exposed to mercury.
"Our study illustrates how mercury ions alter the cell membrane structure of developing neurons," says Fritz Lorscheider, professor of physiology and biophysics, University of Calgary. "This discovery provides visual evidence of our previous findings that mercury produces a molecular lesion in the brain."
The research paper, co-authored by U of C professors Fritz Lorscheider and Naweed Syed as well as medical student Christopher Leong, looks at brain neurons from snails. The researchers added mercury ions to cell cultures of developing neurons and observed the neurons undergoing rapid degeneration.
Nerve processes in snails and other animals, specifically the microtubules in neurons, are similar to those of humans.
The team has identified how this degeneration takes place:
* Mercury ions attach to a neuron, causing its microtubules to disassemble or break down and, ultimately, leave that neuron stripped of its protective membrane;
* Some of these stripped neurons then form aggregates;
* These aggregates are damaged neurons that are clumped or tangled together;
* The damaged neurons cease to function as healthy neurons would.
Other metals - aluminum, lead, cadmium and manganese -– did not produce this type of degeneration.
"Mercury has long been known to be a potent neurotoxic substance, whether it is inhaled as vapor or consumed in the diet as a food contaminant," says Lorscheider. "This research provides visual confirmation of that."
Medical research laboratories, over the past 15 years, have established that dental amalgam tooth fillings are a major contributor to mercury body burden.
In 1997, research done by Lorscheider and colleagues at the universities of Calgary and Kentucky demonstrated that mercury vapor inhalation in rats produced a molecular lesion in the brain -- similar to a lesion seen in 80% of human Alzheimer-diseased brains.
This work has been funded by the Alberta Heritage Foundation for Medical Research, the Canadian Institutes of Health Research and the International Academy of Oral Medicine & Toxicology. - By Karen Thomas
[Contact: Fritz Lorscheider, Karen Thomas ]