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FYI: Thimerosal neurotoxicity and protection with N-Acetylcysteine supplementati

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FYI: Thimerosal neurotoxicity and protection with N-Acetylcysteine supplementati

Posted by R. [27.1490] on January 08, 2005 at 17:19:59:

In the 1930s, Eli Lily developed Thimerosal as a reservative and it was widely used in vaccines. Until the removal of Thimerosal, which contains 49.9% ethyl mercury by weight, from most pediatric vaccines in 2001, the source of the largest human exposure to mercury in the US was in children under 18 months of age undergoing routine childhood
immunization schedules. Before 2001, a child may have received a cumulative dose of over 200 mg/kg (micrograms per kilogram) in the first 18 months of life.

Although Thimerosal has been removed from most childhood vaccines, it is still present in the flu vaccine, which is given to pregnant women, the elderly, and children. Also, many vaccines given to children in developing countries still contain Thimerosal.

In the 2005 issue of NeuroToxicology, the authors of a study examine the toxicity of Thimerosal within the body including neurons. They examine the neurotoxic mechanisms, how the body detoxifies mercury, and the use of N-Acetylcysteine, or NAC for short, in facilitating the detoxification pathway within the body.

Glutathione, a tripeptide composed of cysteine, glutamate, and glycine, is manufactured in the liver and also in the brain. Normally, the concentrations of glutathione in the cells are quite high providing for detoxification of a variety of heavy metals including mercury. However, when this essential antioxidant is depleted the excess mercury can bind to internal cellular proteins leading to toxic damage. Studies have shown that, “low micromolar concentrations of Thimerosal induced DNA strand breaks, caspase-3 activation, membrane damage and cell death.”

Although the brain can produce glutathione, it can only manufacture this from its immediate precursor cysteine. The liver, on the other hand, is able through a long series of biochemical steps to create glutathione from methionine. Methionine is an essential amino acid that supplies the body with sulfur and methyl groups. The liver uses a number of enzyme systems along with various B vitamins to produce
glutathione. The liver then exports the glutathione to the blood that then is broken down to cystine. Cystine crosses the blood-brain barrier to be used by the brain to make glutathione. Thus, the brain is reliant on the liver to manufacture chemicals to keep it free from toxins.

The brain contains neurons and other cells called astrocytes. Astrocytes use the cystine that crosses the blood-brain barrier to make glutathione. The astrocytes then export the glutathione to the space between the cells where it is broken down to cysteine. The neurons take up the cysteine and manufacture glutathione. This complex series of
biochemical events is what is necessary to keep the brain free from heavy metal damage.

The authors first examined the level of Thimerosal that would cause toxic damage to cells. They found that the higher the concentration of Thimerosal the greater the number of cells that were killed although the nerve cell response occurred with only a 3 hour exposure, whereas
the other cell line required a 48 hour exposure demonstrating that nerve cells are more sensitive to Thimerosal toxicity. “In both cell lines, a progressive increase in cytotoxicity (decrease in viability) was observed when Thimerosal dose was progressively doubled from 2.5 mmol/L [micromoles per liter] to 5, 10, and 20 mmol/L. Viability was reduced more than 50% in both cell lines with exposure to 10 mmol/L Thimerosal and less than 10% of cells survived a dose of 20 mmol/L.”

The authors then pretreated cells with NAC before adding a dose of 15 mmol/L Thimerosal. They found that, “Thimerosal alone induced more than a 6-fold decrease in viability”, and that NAC, “provided significant protection against cell death”. The authors note, “Thimerosal induces oxidative stress and apoptosis by activating mitochondrial cell death
pathways. A subsequent study using cultured human neuron and fibroblast cell lines similarly showed that low micromolar concentrations of Thimerosal induced DNA strand breaks, caspase-3 activation, membrane damage and cell death.”

The authors conclude that, “numerous clinical studies have demonstrated the efficacy of NAC in increasing intracellular glutathione levels and reducing oxidative stress in humans. Since cytotoxicity with both ethyl- and methyl- mercury have been shown to be mediated by glutathione depletion, dietary supplements that increase intracellular glutathione could be envisioned as an effective intervention to reduce previous or anticipated exposure to mercury. This approach would be especially valuable in the elderly and in pregnant women receiving Rho D immunoglobulin shots, and individuals who regularly consume mercury-containing fish.”

SOURCE: NeuroToxicology, Vol. 26, 2005, pp. 1-8



Re: FYI: Thimerosal neurotoxicity and protection with N-Acetylcysteine supplementati

Posted by Mel [461.4] on January 08, 2005 at 21:18:21:

In Reply to: FYI: Thimerosal neurotoxicity and protection with N-Acetylcysteine supplementati posted by R. [27.1490] on January 08, 2005 at 17:19:59:

Thimerosal was also used in saline solutions which I used for my contacts back in the late seventies. This caused permanent damage to my corneas since I was allergic to it. My ophthamologist says I am losing my stem cells and now I know why.



Thimerosal neurotoxicity--protection with N-Acetylcysteine supplement Archive.

Posted by Walt Stoll [9.1465] on January 09, 2005 at 07:05:47:

In Reply to: FYI: Thimerosal neurotoxicity and protection with N-Acetylcysteine supplementati posted by R. [27.1490] on January 08, 2005 at 17:19:59:

Thanks, R.

Walt

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Re: FYI: Thimerosal neurotoxicity and protection with N-Acetylcysteine supplemen

Posted by R. [27.1490] on January 09, 2005 at 15:16:56:

In Reply to: Re: FYI: Thimerosal neurotoxicity and protection with N-Acetylcysteine supplementati posted by Mel [461.4] on January 08, 2005 at 21:18:21:

How does he know you are losing your stem cells? Can their number be measured?

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Re: FYI: Thimerosal neurotoxicity and protection with N-Acetylcysteine supplementati

Posted by Mel [461.4] on January 09, 2005 at 21:29:24:

In Reply to: FYI: Thimerosal neurotoxicity and protection with N-Acetylcysteine supplementati posted by R. [27.1490] on January 08, 2005 at 17:19:59:

Well, he has done a few cornea surgeries on both eyes,and examines me about every three months. He told me this after my last procedure. When I asked him about cornea transplant he said no way would it work b/c I'm losing my stem cells and what I do have are not healthy to maintain a successful transplant in either eye.

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