Following up on last week's post concerning the relationship between elevated levels of arsenic in drinking water and a diminished immune response to certain types of influenza (swine flu?), I ran across the following article describing the use of nanorust (actually tiny particles of iron oxide coated on sand) to provide a possible low cost means of removing arsenic from water. You can’t get much more inorganic than this.
In a previous post, I discussed my general reluctance for taking drugs, somewhat skeptical that it might be possible to develop a drug which didn’t cause some problem somewhere else in the body. Now, Derek Lowe has written a column describing how much we don’t know about drugs and their mechanisms inside the body. He even says:” I try not to take any medication unless I feel it's absolutely needed, and I'm often not very happy about taking it even then.” A man after my own heart! I just might finally consider throwing out all that aspirin I’ve been suspicious of for a while now.
Showing posts with label Poisons. Show all posts
Showing posts with label Poisons. Show all posts
Tuesday, June 2, 2009
Wednesday, June 18, 2008
Poisons of the Day - Part Ia
News Flash! Napoleon probably did not die of arsenic poisoning. I would like to say that I’m surprised by this, but I can’t since I had never heard of the “Napoleon was poisoned by arsenic” theory in the first place. Apparently, arsenic had previously been found in a sample of Napoleon’s hair, and when combined with reports of his severe stomach pain (a symptom of arsenic poisoning), it had been speculated that Napoleon was either poisoned by the British during his captivity or had been exposed to poisonous arsenic fumes generated by mold infested wallpaper containing an arsenic-based dye. But a team of Italian scientists has now cast considerable doubt on this theory. By collecting samples of Napoleon’s hair at various stages of his life, along with hair from his son and first wife, they were able to show that all three of them had had elevated levels of arsenic in their bodies long before Napoleon’s imprisonment.
What made the story interesting was that the levels of arsenic in Napoleon’s hair were 100 times greater than expected today. Apparently, back in the day, consuming small amounts of arsenic was a highly regarded practice. It was supposed to make the body more vigorous, it was believed to be a sexual stimulant, and its tendency to produce bright, rosy cheeks was much in demand by the women of the time. (The rosy cheeks were a result of blood vessel damage in the skin.) The knowledge that arsenic was a poison, and that it caused severe stomach pain, was apparently not much of a deterrent. (To make things worse, facial powders were often loaded with white lead, Pb3(CO3)2(OH)2, in order to make the face more pale -- a sign of nobility.)
Now the reason I mention this story relates to the “Poisons of the Day” post from last week in which I mentioned that much of arsenic’s toxicity arises from its tendency to replace phosphorus in the body. My question was: How could people continue to survive the continuous ingestion of arsenic if it’s slowly replacing the body’s phosphorus? In fact, anecdotal reports suggest that it is possible to build up some immunity to arsenic by regularly ingesting it -- although some experts reject that possibility. Now, I know that you can build up an immunity to the poison "iocane" (warning: Princess Bride reference ;) ), but how would that work with arsenic? One theory involves metallothioneins, which are proteins produced by the body that seem to bond to ions of dangerous elements like arsenic and cadmium and help minimize their effects. Constant exposure to arsenic might increase the levels of metallothioneins produced by the body. I don’t think anyone knows the answer just yet.
By the way, I found a few references to a second mechanism by which arsenic can be toxic. It tends to bind to the sulfhydryl (thiol) groups (-SH) in proteins, which as you can imagine, really screws up the operation of these proteins.
What made the story interesting was that the levels of arsenic in Napoleon’s hair were 100 times greater than expected today. Apparently, back in the day, consuming small amounts of arsenic was a highly regarded practice. It was supposed to make the body more vigorous, it was believed to be a sexual stimulant, and its tendency to produce bright, rosy cheeks was much in demand by the women of the time. (The rosy cheeks were a result of blood vessel damage in the skin.) The knowledge that arsenic was a poison, and that it caused severe stomach pain, was apparently not much of a deterrent. (To make things worse, facial powders were often loaded with white lead, Pb3(CO3)2(OH)2, in order to make the face more pale -- a sign of nobility.)
Now the reason I mention this story relates to the “Poisons of the Day” post from last week in which I mentioned that much of arsenic’s toxicity arises from its tendency to replace phosphorus in the body. My question was: How could people continue to survive the continuous ingestion of arsenic if it’s slowly replacing the body’s phosphorus? In fact, anecdotal reports suggest that it is possible to build up some immunity to arsenic by regularly ingesting it -- although some experts reject that possibility. Now, I know that you can build up an immunity to the poison "iocane" (warning: Princess Bride reference ;) ), but how would that work with arsenic? One theory involves metallothioneins, which are proteins produced by the body that seem to bond to ions of dangerous elements like arsenic and cadmium and help minimize their effects. Constant exposure to arsenic might increase the levels of metallothioneins produced by the body. I don’t think anyone knows the answer just yet.
By the way, I found a few references to a second mechanism by which arsenic can be toxic. It tends to bind to the sulfhydryl (thiol) groups (-SH) in proteins, which as you can imagine, really screws up the operation of these proteins.
Thursday, June 12, 2008
Poisons of the Day - Part I
I’ve decided to start a little series called “Poisons of the Day.” This series is not to discuss the use of poisons to remove irritating coworkers in the chemical laboratory, but to understand why many elements and simple compounds are poisonous, something I’ve never really thought about before. Ever since I ran into an article describing the mechanism of arsenic poisoning, I’ve been interested in the subject. After doing some research I have come to the conclusion that there appears to be four main ways in which an element can be poisonous.
1. It binds to and/or removes necessary elements or compounds from the body
2. It replaces an element already in the body, but cannot fulfill the same role.
3. It’s a necessary element for life in small amounts but causes trouble when too much is around.
4. It interferes with the chemical reactions in the body.
I’ll start out with four poisons today.
ARSENIC
This is the element which got me started on this series. Arsenic does not attack the body directly, it operates by replacing the phosphorus in the body. Since it sits just below P in the periodic table, it tends to bind to the same compounds that phosphorus does. As you might expect, the arsenic analogues do not work very well, if at all. ATP, the molecule responsible for storing and releasing energy, is particularly susceptible to arsenic poisoning. In the presence of arsenic, cells tend to die from energy starvation.
LEAD
Lead is another poison which works by slowly replacing other metals used by the body, in particular, calcium, iron, and zinc which are cofactors in many enzymatic reactions. Lead tends to bind to the same enzymes as these metals, but the resulting molecules fail to function properly, usually because the shape of the protein is no longer correct. It is known to interfere both with the production of heme (Zn replacement), which leads to anemia, as well as the transmission of electrical impulses in the brain (Ca replacement) which impairs brain function.
BARIUM
Barium apparently causes problems in a lot of ways, but its primary role occurs because it interferes with the sodium-potassium pump used by our muscles. Apparently it reduces the permeability of muscles to potassium entry. This can lead to paralysis, and if the affected muscles include the heart and respiratory muscles, death. Barium does also appear to replace calcium in the body, but this is a minor effect.
I hadn’t really appreciated how toxic barium is, assuming that it’s in the form of a soluble salt. Barium carbonate is a common rat poison. Barium sulfate is so insoluble that you can drink it with no ill effects.
D2O
I include this compound because I used D2O (deuterated or heavy water) back as an undergraduate for isotope labeling experiments. My undergraduate advisor used to tell me that if you drank enough of it, it would kill you. Apparently he was correct, although you would have to work really hard to get your body deuterated enough to have an effect. If you can replace between 25 and 50% of the water in your body with D2O, then you’ll notice the health effects, but this will require the drinking of nothing but large quantities of D2O for at least a week according to Wikipedia. The poisoning mechanism is pretty simple. Deuterium has slightly different hydrogen bonding properties than hydrogen (which is why we use D2O in the lab in the first place). Our bodies consist of large number of proteins, including DNA, which depend upon hydrogen bonding to hold them in the rather complicated conformations which are necessary for certain enzymatic reactions to occur. Start changing the hydrogen bonding in our bodies and you can imagine what kind of problems would result.
I’ll have more poisons to discuss at a later date.
1. It binds to and/or removes necessary elements or compounds from the body
2. It replaces an element already in the body, but cannot fulfill the same role.
3. It’s a necessary element for life in small amounts but causes trouble when too much is around.
4. It interferes with the chemical reactions in the body.
I’ll start out with four poisons today.
ARSENIC
This is the element which got me started on this series. Arsenic does not attack the body directly, it operates by replacing the phosphorus in the body. Since it sits just below P in the periodic table, it tends to bind to the same compounds that phosphorus does. As you might expect, the arsenic analogues do not work very well, if at all. ATP, the molecule responsible for storing and releasing energy, is particularly susceptible to arsenic poisoning. In the presence of arsenic, cells tend to die from energy starvation.
LEAD
Lead is another poison which works by slowly replacing other metals used by the body, in particular, calcium, iron, and zinc which are cofactors in many enzymatic reactions. Lead tends to bind to the same enzymes as these metals, but the resulting molecules fail to function properly, usually because the shape of the protein is no longer correct. It is known to interfere both with the production of heme (Zn replacement), which leads to anemia, as well as the transmission of electrical impulses in the brain (Ca replacement) which impairs brain function.
BARIUM
Barium apparently causes problems in a lot of ways, but its primary role occurs because it interferes with the sodium-potassium pump used by our muscles. Apparently it reduces the permeability of muscles to potassium entry. This can lead to paralysis, and if the affected muscles include the heart and respiratory muscles, death. Barium does also appear to replace calcium in the body, but this is a minor effect.
I hadn’t really appreciated how toxic barium is, assuming that it’s in the form of a soluble salt. Barium carbonate is a common rat poison. Barium sulfate is so insoluble that you can drink it with no ill effects.
D2O
I include this compound because I used D2O (deuterated or heavy water) back as an undergraduate for isotope labeling experiments. My undergraduate advisor used to tell me that if you drank enough of it, it would kill you. Apparently he was correct, although you would have to work really hard to get your body deuterated enough to have an effect. If you can replace between 25 and 50% of the water in your body with D2O, then you’ll notice the health effects, but this will require the drinking of nothing but large quantities of D2O for at least a week according to Wikipedia. The poisoning mechanism is pretty simple. Deuterium has slightly different hydrogen bonding properties than hydrogen (which is why we use D2O in the lab in the first place). Our bodies consist of large number of proteins, including DNA, which depend upon hydrogen bonding to hold them in the rather complicated conformations which are necessary for certain enzymatic reactions to occur. Start changing the hydrogen bonding in our bodies and you can imagine what kind of problems would result.
I’ll have more poisons to discuss at a later date.
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