Re: Thimerosal and methylmercury

[Guest guest]

It should be noted that this research study compared equal doses of

methylmercury and thimerosal. However, thimerosal is only 1/2 mercury

(ethylmercury), so the authors should have compared 1/2 dose thimerosal

with 1 dose methylmercury. The conclusion would then be that

ethylmercury is equally potent to methylmercury in increasing Ca2++. The

study also says that unlike methylmercury (which is usually bound to

cysteine in a cell) thimerosal's potency is unaffected by presence of

L-cysteine in the neuron, so under in vivo conditions the effects of

ethylmercury are likely greater (by a factor or 2) than methyl. Finally,

the study shows that thimerosal is more potent than methyl in decreasing

glutathione levels in the cell, which is what other researchers have/are

finding as well.

Donna wrote:

>Methyl-mercury, usually from contaminated food, is very dangerous to

>pregnant women. Methyl-mercury causes profound mental retardation,

>cerebral

>palsy, seizures, spasticity, tremors, and incoordination, along with

>eye and

>hearing damage in the unborn baby as a result of the mother's

>exposure.

>Organic mercury passes into the breast milk as well.

>

>

>

>The effect of thimerosal, an organomercurial preservative in

>vaccines, on cerebellar neurons dissociated from 2-week-old rats was

>compared with those of methylmercury using a flow cytometer with

>appropriate fluorescent dyes. Thimerosal and methylmercury at

>concentrations ranging from 0.3 to 10 microM increased the

>intracellular concentration of Ca2+ ([Ca2+]i) in a concentration-

>dependent manner. The potency of 10 microM thimerosal to increase

>the [Ca2+]i was less than that of 10 microM methylmercury. Their

>effects on the [Ca2+]i were greatly attenuated, but not completely

>suppressed, under external Ca(2+)-free condition, suggesting a

>possibility that both agents increase membrane Ca2+ permeability and

>release Ca2+ from intracellular calcium stores. The effect of 10

>microM thimerosal was not affected by simultaneous application of 30

>microM L-cysteine whereas that of 10 microM methylmercury was

>significantly suppressed. The potency of thimerosal was similar to

>that of methylmercury in the presence of L-cysteine. Both agents at

>1 microM or more similarly decreased the cellular content of

>glutathione in a concentration-dependent manner, suggesting an

>increase in oxidative stress. Results indicate that thimerosal

>exerts some cytotoxic actions on cerebellar granule neurons

>dissociated from 2-week-old rats and its potency is almost similar

>to that of methylmercury.

>

>

>

>

>

>=======================================================

>

[Guest guest]

So, the study compared twice the dose of methylmercury to ethylmercury and

then tried to draw conclusions between the two.

To my way of thinking, that's a very basic and fundamental error.

At 03:50 PM 9/05/2004, you wrote:

>It should be noted that this research study compared equal doses of

>methylmercury and thimerosal. However, thimerosal is only 1/2 mercury

>(ethylmercury), so the authors should have compared 1/2 dose thimerosal

>with 1 dose methylmercury. The conclusion would then be that

>ethylmercury is equally potent to methylmercury in increasing Ca2++. The

>study also says that unlike methylmercury (which is usually bound to

>cysteine in a cell) thimerosal's potency is unaffected by presence of

>L-cysteine in the neuron, so under in vivo conditions the effects of

>ethylmercury are likely greater (by a factor or 2) than methyl. Finally,

>the study shows that thimerosal is more potent than methyl in decreasing

>glutathione levels in the cell, which is what other researchers have/are

>finding as well.

>

>Donna wrote:

>

> >Methyl-mercury, usually from contaminated food, is very dangerous to

> >pregnant women. Methyl-mercury causes profound mental retardation,

> >cerebral

> >palsy, seizures, spasticity, tremors, and incoordination, along with

> >eye and

> >hearing damage in the unborn baby as a result of the mother's

> >exposure.

> >Organic mercury passes into the breast milk as well.

> >

> >

> >

> >The effect of thimerosal, an organomercurial preservative in

> >vaccines, on cerebellar neurons dissociated from 2-week-old rats was

> >compared with those of methylmercury using a flow cytometer with

> >appropriate fluorescent dyes. Thimerosal and methylmercury at

> >concentrations ranging from 0.3 to 10 microM increased the

> >intracellular concentration of Ca2+ ([Ca2+]i) in a concentration-

> >dependent manner. The potency of 10 microM thimerosal to increase

> >the [Ca2+]i was less than that of 10 microM methylmercury. Their

> >effects on the [Ca2+]i were greatly attenuated, but not completely

> >suppressed, under external Ca(2+)-free condition, suggesting a

> >possibility that both agents increase membrane Ca2+ permeability and

> >release Ca2+ from intracellular calcium stores. The effect of 10

> >microM thimerosal was not affected by simultaneous application of 30

> >microM L-cysteine whereas that of 10 microM methylmercury was

> >significantly suppressed. The potency of thimerosal was similar to

> >that of methylmercury in the presence of L-cysteine. Both agents at

> >1 microM or more similarly decreased the cellular content of

> >glutathione in a concentration-dependent manner, suggesting an

> >increase in oxidative stress. Results indicate that thimerosal

> >exerts some cytotoxic actions on cerebellar granule neurons

> >dissociated from 2-week-old rats and its potency is almost similar

> >to that of methylmercury.

> >

> >

> >

> >

> >

> >=======================================================

> >

[Guest guest]

Boy your good! I got a letter from the FDA, They tried to tell me

that there is not enough evidence that ethylmercury can cause brain

damage...I sent my part to them...Im going to copy what you

wrote...I know they will come up with some other excuse regarding

the ethylmercury! ITS THE TUNA! Or ITS THE AIR! I think they

should ALL be fired!

> >

> > >Methyl-mercury, usually from contaminated food, is very

dangerous to

> > >pregnant women. Methyl-mercury causes profound mental

retardation,

> > >cerebral

> > >palsy, seizures, spasticity, tremors, and incoordination, along

with

> > >eye and

> > >hearing damage in the unborn baby as a result of the mother's

> > >exposure.

> > >Organic mercury passes into the breast milk as well.

> > >

> > >

> > >

> > >The effect of thimerosal, an organomercurial preservative in

> > >vaccines, on cerebellar neurons dissociated from 2-week-old

rats was

> > >compared with those of methylmercury using a flow cytometer with

> > >appropriate fluorescent dyes. Thimerosal and methylmercury at

> > >concentrations ranging from 0.3 to 10 microM increased the

> > >intracellular concentration of Ca2+ ([Ca2+]i) in a

concentration-

> > >dependent manner. The potency of 10 microM thimerosal to

increase

> > >the [Ca2+]i was less than that of 10 microM methylmercury. Their

> > >effects on the [Ca2+]i were greatly attenuated, but not

completely

> > >suppressed, under external Ca(2+)-free condition, suggesting a

> > >possibility that both agents increase membrane Ca2+

permeability and

> > >release Ca2+ from intracellular calcium stores. The effect of 10

> > >microM thimerosal was not affected by simultaneous application

of 30

> > >microM L-cysteine whereas that of 10 microM methylmercury was

> > >significantly suppressed. The potency of thimerosal was similar

to

> > >that of methylmercury in the presence of L-cysteine. Both

agents at

> > >1 microM or more similarly decreased the cellular content of

> > >glutathione in a concentration-dependent manner, suggesting an

> > >increase in oxidative stress. Results indicate that thimerosal

> > >exerts some cytotoxic actions on cerebellar granule neurons

> > >dissociated from 2-week-old rats and its potency is almost

similar

> > >to that of methylmercury.

> > >

> > >

> > >

> > >

> > >

> > >=======================================================

> > >