Mercury amalgam fillings and the brain

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Mercury amalgam fillings and the brain

How is a snail like a typewriter? This absurd riddle sounds a bit like a playground joke circulated by seven-year-oldsÛor the Mad HatterÌs ÏHow is a raven like a writing-desk?Ó But University of Calgary neuroscientist Dr. Naweed Syed says the snailÒtypewriter comparison is a good analogy for the studies he is conducting on brain development and regeneration.

ÏIf you look at the keyboard of a typewriter and that of a computer, everything is almost identical,Ó explains the AHFMR Senior Scholar, a researcher in the University of CalgaryÌs Respiratory and Neuroscience Research Groups. ÏBut if you want to understand how the computer functions, the access is still through the keyboard. We are in a situation now where we first have to understand the keyboards, so we use simple animals, like snails. The snails are like typewriters. They provide us with the basic, fundamental information as to how Mother Nature may have configured things in the computersÛthe higher animals. These lower animals offer greater opportunity to understand or define the role of any given gene, and then one can extrapolate their function in human or other animal models.Ó

Dr. SyedÌs research looks at how brain cells (neurons) recognize and connect with their partners, how they establish the intricate network of synapses that forms the basis of brain function, and how the brain repairs itself during regeneration. Though we flatter ourselves with the belief that we are higher beings, from a genetic perspective we are kissing cousins to worms, flies, and Dr. SyedÌs humble snails. We enjoy only twice as many genes as the worm; when we move up the ladder from worms and snails to flies, the gap narrows even further.

Snails as models

These resemblances made the snail model a particularly useful one for Dr. SyedÌs collaborator at the University of Calgary, Dr. Fritz Lorscheider, who studies the effects of mercury amalgam tooth fillings on the brain.

In landmark research in the early 1980s, Dr. Lorscheider and his team in the Department of Physiology and Biophysics showed that mercury vapour is released from fillings when we chew. In follow-up studies conducted on rats in 1997, his team and a group of researchers from the University of Kentucky showed that inhaling mercury vapour leads to the development of molecular lesions in the brain that are similar to the lesions found in 80% of Alzheimer-diseased brains. Because more than 90% of the amino acids that make up the microtubules (the main protein in the structure of the neuron) are the same across species, Dr. SyedÌs snails provided a rare opportunity to observe exactly how mercury affects the healthy brain cells. From these findings, Drs. Syed and Lorscheider would be able to extrapolate how it might be affecting the nervous systems of those of us who have mercury amalgam fillings, which are made from 50% mercury, 35% silver and 15% other metals.

Dr. Syed and AHFMR Summer Student Christopher Leong isolated and cultured neurons from snails. They then exposed the neurons to the same concentration of mercury that would be present in the urine of anyone who had seven or eight amalgam fillings. The mercury soon took effect on the bundles of microtubules that make up a healthy neuron. Within 30 minutes, the microtubules started to break down, and the neuron began to shrink. About 15 minutes later, the irreversibly damaged neurons were tangled together in a disordered structure resembling the brain lesions found in those with AlzheimerÌs disease. The researchers repeated the study using aluminum, lead, cadmium, and manganese, none of which caused this type of degeneration in the neurons.

International attention

As the cover story of AprilÌs issue of NeuroReport, the research garnered international attention and a flood of mail. The accompanying time-lapse video recording provided graphic evidence of their findings.

ItÌs no secret that mercury is a highly potent neurotoxin. Tremors and twitches, memory loss, and loss of manual dexterity have long been associated with prolonged exposure to toxic levels of the metal. With his perplexing riddles and eccentric behaviour, Lewis CarrollÌs Mad Hatter in AliceÌs Adventures in Wonderland was a fanciful depiction of the effects of mercury on hat-makers, who suffered mercury poisoning from inhaling the fumes of the mercurous nitrate used in curing felt. More than a century later, evidence continues to mount against exposure to mercury in any form, whether ingested or inhaled as a vapour.

ÏMercury toxicity has now been linked to autism in children and basic deformities to the neurosystem, to learning disabilities, and to many other forms of health hazards,Ó says Dr. Syed. Another concernÛand a personal interest of Dr. SyedÌsÛis the Third World practice of using mercury to clean smoke-blackened cooking pots and utensils. ÏWhen the pots have been cleaned this way,Ó he adds, Ïthese people are consuming huge amounts of mercury in their food on a daily basis.Ó

These uses of mercury aside, research over the past 15 years has clearly demonstrated that the biggest contributor to increased levels of mercury in humans is amalgam fillings. In one study, participants with mercury fillings were still excreting mercury in their urine years after the fillings had been put in place.

Challenges for dentists

The findings of this research raise red flags for the scientific community and some serious challenges for dentists, who are now trying to establish a policy that would see amalgam fillings banned in children under the age of 18. But the alternatives are expensive, and insurance companies would have to be prepared to shoulder the costs.

Dr. Syed is quick to point out that further studies are needed to determine the effects of mercury on brain cells with established connections and to show that the metal has the same effect in higher animalsÛÏthe computerÓÛas it does in his ÏtypewriterÓ snails.

ÏI would be very surprised if this didnÌt turn out to be the case,Ó he says. ÏThese animals are more likely to be exposed to heavy metals like mercury in the water, and yet they still show enormous sensitivity to such compounds. Since we are normally not likely to be exposed to these compounds, I suspect that we would be even more susceptible to any changes caused by exposure to mercury.Ó


Dr. Syed is an AHFMR Senior Scholar, and an Associate Professor in the Department of Cell Biology & Anatomy and the Department of Physiology & Biophysics at the University of Calgary. His research is also supported by the Canadian Institutes for Health Research, the Canadian Institutes of Health Research, and the National Science and Engineering Council of Canada.

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