Transcript tetrodotoxin

Nick Lowe & Emily Bauer
One fish,
Red fish,
Blow fish…
Two fish,
Introduction
History
Source
Mechanism of Action
Chemistry
Case Studies
Tetrodotoxin
Deadly toxin that blocks voltage activated Na+ Channels.
The Puffer Fish
Tetrodotoxin(TTX) is
named after the order
of fish from which it is
most commonly
associated, the
Tetraodontiformes or
the tetraodon
pufferfish.
Discovery
The deadly blowfish has been feared for thousands of
years.
The tomb of an Egyptian Pharoah was engraved with the
blowfish’s image.
The Bible warned against eating fish without fins and scales, like
the Red Sea puffer.
The structure of tetrodotoxin was determined by Robert Woodward in
1964.
Eating the
Honorable Fugu
Fugu has been eaten
in China and Japan
for thousands of
years.
Fugu is one of the most
expensive foods in Japan.
A single fish served in a
restaurant, it can bring in
$200.
Fugu's trade volume is
rising because of people's
curiosity in eating the
toxic fish.
A Fugu Chef
There are over 1,500 fugu
restaurants in Tokyo.
Fugu chefs in Japan must
pass a test and eat the fugu
he/she has prepared.
Only 25% of the applicants
pass the test.
Voodoo + Tetrodotoxin=?
• Voodoo is the predominant religion in Haiti
• Many believe in the existence of zombies
• Two explainations
1. Religious
2. Scientific
• Does Voodoo or drugs make zombies?
The Serpent and The Rainbow
• In ’83, ethnobotanist Wade Davis reported
existence of “Zombies” in Haiti
• Named one of National Geographic’s “Explorers
for the Millennium”
• Many remain skeptical of his findings
• Stresses “psychobiological” aspect of his
hypothesis
•
•
www.universalstudios.com/horror/video/serp4.mov
www.universalstudios.com/horror/video/serp3.mov
Is there experimental proof of
Zombies?
• “Zombie” powder given to rats in the lab of
Leon Roizin
• Some rats appeared “comatose”
• Certain rats immobilized for 24 hrs, then
recovered
• Similar response in monkey
• RESULTS NEVER PUBLISHED!!!!!!
Animals That Contain
Tetrododoxin
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California newt
Taricha salamander
Parrotfish
Frogs of the genus
Atelopus
Starfish
Blue-ringed octopus
Angelfish
Triggerfish
Goby
Cod
Xanthid crabs
Boxfish
Porcupine fish
Globefish
Horseshoe crab
Marine snails
What makes Tetrodotoxin
Bacteria inside these animals make the toxin.
These bacterial species, include strains of the family Vibrionaceae,
Pseudomonas sp., and Photobacterium phosphoreum.
Supporting Evidence
Puffer fish grown in culture do not produce tetrodotoxin.
The blue-ringed octopus accummulates tetrodotoxin in a
special salivary gland and infuses its prey with toxin by bite.
Xanthid crabs contain tetrodotoxin.
Tetrodotoxin in algae species Jania is produced by a bacteria
species Alteromas.
Puffer fish do not have the genes coding for the synthesis
tetrodotoxin molecules.
The TTX-producing bacteria and host
organisms offer advantages to both partners.
The bacteria get a safe place to live, eat,
and reproduce The hosts use the toxin for
predation or defense.
The blue-ringed
octopuses employ TTX
as a potent venom for
securing prey.
Newts arch their backs,
revealing a red-and-black
surface, a common
warning sign in nature.
Why aren’t host organisms effected?

A single point mutation in the amino acid
sequence of the sodium-ion channel makes it
immune from being bound by TTX.
Tetrodotoxin will not recognize
the channel in these organisms.
The only known predators
resistant to this toxin is the
common garter snake.
Toxicity
"Weight-for-weight, tetrodotoxin is ten times as
deadly as the venom of the many-banded krait of
Southeast Asia. It is 10 to 100 times as lethal as
black widow spider venom when administered to
mice, and more than 10,000 times deadlier than
cyanide. William H. Light
One blow fish is enough to kill more than 30 people.
The estimated lethal dose for an adult, is one to
two milligrams.
Action
Tetrodotoxin acts directly on the electrically active
sodium channel in nerve tissue.
It blocks diffusion of sodium through the sodium
channel.
This prevents the firing of action potentials in
nerve cells.
Tetrodotoxin acts on both the central and the
peripheral nervous systems, ultimately paralyzing
muscles.
Respiratory arrest is the cause of death.
Action potential
The flow of Na₊ ions
into the axon leads
the axon to become
positively charged.
The inside grows
increasingly more
positive.
Sodium Channels
Within the channel are two types of charged
particles forming the gates that control the
diffusion of Na+.
The gate closes at polarization and opens
at depolarization.
open
closed
Depolarization
As Na+ ions flow into the axon the
action potential is initiated.
Repolarization
The membrane of the axon is repolarized by
the closing of Na+ channels and the opening of
K+ channels.
Transmission
Muscle contraction
When Na+ Channels are blocked an action
potential can not be initiated and muscles
can not contract. This is important for things
like…
Breathing
Effect on the Heart
Tetrodotoxin can block neural and
skeletal muscle Na+ channels at
10 nM.
It takes 100 times more to block
cardiac channels.
Cardiac muscle skeletal muscle Na +
channels differ in structure and
protein composition.
Symptoms of TTX poisoning
• Symptoms occur within 30 min
• Initial tingling sensation in mouth
• Followed by high fever, headache,vomiting,
lightheadedness, dizziness, feelings of doom,
anxiety, and weakness
• Elevated blood pressure
• Bleeding lesions may occur over much of the body
• Respiratory arrest
Structures
TTX and STX inhibit
Na+ channels.
Both bind the outer
enzyme complex.
TETRODOTOXIN
Produce similar
physiological responses.
Local anesthetics are
also selective for some
Na+ channels.
PROCAINE
SAXITOX
Biosynthesis of TTX
Synthesis of Tetrodotoxin
Isolation of TTX
• Extracted from the gonads,
liver, intestines, and skin of
pufferfish
Tetrodotoxin Mechanism
• Guanidinium moiety present on molecule
• + charge at physiological pH
• Selective, complete, and reversible binding
Binding Conformations of Tetrodotoxin and Saxitoxin
Tetrodotoxin
Saxitoxin
These toxins bind to same sites on sodium channel
Tetrodotoxin binds to the outside of the
sodium channel on a one-to-one basis.
Uses of Tetrodotoxin
Tetrodotoxin is used as a tool because of its selective
blocking of the voltage-gated Na+-channel.
It was used to isolate channels, and identify the
structures of Na+ channels.
Researchers have synthesized a labeled 3Htetrodotoxin and a photoactivatable form which may
help locate the tetrodotoxin-binding site.
In diluted from it is also used as a painkiller for
victims of neuralgia, arthritis and rheumatism.
Antidotal Evidence
A 69-year-old woman was admitted to the Casualty
Dept. for food poisoning. Prognosis was bleak…
In 1998, three chefs in southern California collapsed
soon after eating small amounts of puffer fish brought
back from Japan by a co-worker.
Two women nearly died after eating puffer fish in a
Los Angeles restaurant.
In Australia, several people recently died soon after being
bitten by the blue-ringed octopuses.
In July 1979, a 29-year-old college student in Oregon
suddenly collapsed at a party and later died.
TTX
+
=
Thanks!
Have a great day
any questions?
References
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http://www.chm.bris.ac.uk/motm
• http://www.britney .com
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Booth, William, “Voodoo Science,” Science. (1988)
Hille, Beritle, Ionic Channels of Excitable Mebranes. (1992)
http://www.vet.purdue.edu/depts/bms/courses/bms513/drgact01.htm
http://www.american.edu/projects/mandala/TED/BLOWFISH.HTM
http://www.macalester.edu/~psych/whathap/diaries/diariess98/tal/tetro.html
http://vm.cfsan.fda.gov/~MOW/chap39.html
http://home.earthlink.net/~zh32/ttx.html
http://gened.emc.maricopa.edu/bio/bio181/BIOBK/BioBookMUSSKEL.html
http://www.cellsalive.com/
http://fugu.hgmp.mrc.ac.uk/fugu/pffp/tetrodotoxin.html
http://vm.cfsan.fda.gov/~mow/tet.html
http://psych.hanover.edu/Krantz/neural/actionpotential.html
http://www.chm.bris.ac.uk/motm/ttx/ttx.htm
http://www.owlnet.rice.edu/~psyc521/lectures/lec2/sld010.htm