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achterover
10-27-2001, 10:48 PM
I've run into 8 zillion medical journal shtuff about the effects of lead, arsenic, etc poisoning, but how exactly do these elements affect the nervous system and why?

Dank U wel!

achterover

SenorBeef
10-28-2001, 08:59 AM
Originally posted by achterover
I've run into 8 zillion medical journal shtuff about the effects of lead, arsenic, etc poisoning, but how exactly do these elements affect the nervous system and why?

Dank U wel!

achterover

I think it has something to do with the body mistaking these substances for other things critical to the body's function.

For example, I think the body mistakes lead as calcium, and so it 'passes' on taking up new calcium, because it think's it has enough, while the lead actually doesn't do anything.

Or something like that. I don't know what I'm talking about.

astro
10-28-2001, 09:14 AM
IIRC all have somewhat different mechanisms

http://pevsnerlab.kennedykrieger.org/lead.htm

"Lead poisoning
Human exposure to lead (Pb2+), especially at a young age, impairs a range of neurological functions. A blood Pb2+ level above 10 ug/dL (~ 0.5 uM) is considered potentially hazardous. Recently it has been reported that approximately 5% of children in the U.S. have blood Pb2+ levels greater than or equal to 10 ug/dL. Thus Pb2+ poisoning is one of the most critical environmental health hazards affecting children today. The mechanism of Pb2+ toxicity remains poorly understood. One possible mechanism of its effects may be its influence on synaptic activity. We are studying the molecular basis of lead neurotoxicity in the brain.

Since the early 1970s, it has been appreciated that lead blocks evoked neurotransmitter release while dramatically promoting spontaneous release. These effects have been observed in a variety of experimental paradigms including tissue culture, slice preparations, and synaptosomes. It is also known that lead potently activates protein kinase C (PKC), possibly acting via its calcium-binding C2 domain. We hypothesized that a mechanism by which lead affects neuronal function is by binding directly to synaptotagmin:

Lead interacts with PKC at picomolar concentrations
PKC has a C2 domain which promotes calcium-sensitive phospholipid binding
Synaptotagmin has a pair of C2 domains through which lead might act
Synaptotagmin is a synaptic vesicle protein that is a calcium sensor, and it is poised to regulate exocytotic release of neurotransmitter
We have found that lead interacts with synaptotagmin potently. While lead is likely to interact with many proteins to disrupt cellular function, its effects on synaptotagmin suggest a direct mechanism for its modulation of neurotransmission. This could partially account for lead's global effects on behavior."

etc etc

Here is an interesting website re

"VIOLENCE, ACCIDENTS, POISONING
Ed Friedlander, M.D., Pathologist"

http://www.pathguy.com/lectures/env-23.htm

choosybeggar
10-28-2001, 09:31 AM
I found one thing. In Cecil's (No relation to C. Adams)Textbook of Medicine it says:
Lead interferes with a variety of red cell enzyme systems, including delta-aminolevulinic acid dehydratase and ferrochelatase.

Inhibiting these enzymes decreases haemoglobin (hey, the British spelling is fuunnnn!) formation and ultimately results in anaemia (too few red blood cells.

Unfortunately, Cecil didn't comment on the neurotoxicological mechanisms.

I'll be back if I find more.

Squink
10-28-2001, 09:50 AM
How Does Lead Effect the Nervous System? (http://serendip.brynmawr.edu/bb/neuro/neuro00/web2/Patel.html)
The short, massively oversimplified and misleading, answer is that lead mimics calcium and messes with the electrical potential of neurons. A more detailed explanation involves lots of biochemical gobblydegook of the sort given by astro.
Arsenic reacts with sulphydryl groups (sulfur) in proteins, and inhibits several ensymes which are critical for energy production.

choosybeggar
10-28-2001, 09:52 AM
Goetz'Textbook of Clinical Neurology chimes in on arsenic poisoning:

Arsenic rapidly leaves the bloodstream for storage in the liver, kidneys, intestines, spleen, lymph nodes, and bones, and within 2 weeks it is deposited in the hair, remaining there for years. It also remains in the bones for extended periods of time. Excretion through the kidneys and feces is slow. A single dose may require up to 10 days to be excreted. Pathways involved in oxidative metabolism are sensitive to arsenic toxicity. Arsenic also prevents the transformation of thiamine into acetyl-CoA, causing patients to become clinically thiamine deficient. Organic arsenicals release the poison slowly and are therefore less likely to produce acute symptoms than the elemental form. Neuropathological findings in patients with fatal arsenic encephalopathy include cerebral congestion, multiple hemorrhagic lesions throughout the white matter, and areas of necrosis. Decreased numbers of myelinated fibers are seen in the peripheral nerves, and degenerative changes, consisting of swelling, granularity, and a reduction in the number of axons, are present.

I think the bit about thiamine is an error, though. Thiamine is not transformed into acetyl-CoA, pyruvate and fatty acids are. Even if it were, I can't see how that result in thiamine deficiency.

achterover
10-28-2001, 08:27 PM
thanks guys...i guess i'll have to quit chewing on the molding of old houses for good...sigh...

Niobium Knight
10-28-2001, 11:39 PM
what about Cadmium and Mercury? what do they do to you?

Broomstick
10-29-2001, 05:51 AM
Cadmium replaces the calcium in your bones. Problem is, cadmium is much more brittle than calcium, so after awhile your bones start to break and your vertebrae collapse, causing your standing height to plummet. All of which is horribly painful.

Not so sure about the mercury, except that it has bad effects on the central nervous system. If you inhale mercury vapor it can destroy your lung tissue, which case you die of slow suffocation (or not so slow, if you really got dosed) rather than some other problem

Niobium Knight
10-29-2001, 08:36 AM
ooh Cadmium sounds nasty. :(

erislover
10-29-2001, 12:40 PM
I just wanted to say: ouch. OUCH. That would, so they say, suck.

easy e
10-29-2001, 04:18 PM
Originally posted by choosybeggar



I think the bit about thiamine is an error, though. Thiamine is not transformed into acetyl-CoA, pyruvate and fatty acids are. Even if it were, I can't see how that result in thiamine deficiency.

Pyruvate and fatty acids become the acetyl part of acetyl-CoA, but thiamine is necessary to form the factor CoA. Thiamine deficiency can cause lethargy, because without CoA, the Kreb's cycle and the electron transport chain can't occur, which supplies the bulk of ATP (read: energy) from glucose metabolism.

I just had an exam in this stuff last week.

Winkie
10-29-2001, 09:27 PM
Mercury screws with your nervous system -- something about crossing the blood/brain barrier and being very slow to leave. I'd say more but I don't understand it too well -- instead, here's a webite with some good mercury information:

Mercury: A Fact Sheet for Health Professionals (http://www.orcbs.msu.edu/AWARE/pamphlets/hazwaste/mercuryfacts.html)

Scroll down for toxicity information.