Terrorists’ toxin?
David Evans: Pennsylvania College
of Technology
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It is important to give the reader an orientation to the setting of my course and of
its special challenges. Therefore, I will tell you a little about my situation.
I teach at Pennsylvania College of Technology (or Penn College), a whollyowned subsidiary of the Pennsylvania State University. We have about 6,500
students pursuing a variety of majors including everything from welding to
physician assistant. Many of the programs are open admission but a few such as
our world-class dental hygiene major are highly selective. Our placement tests
are intended to direct weaker students into remediation. The lowest grade level
we allow for mathematics, for instance, is fifth grade. We offer certificates,
associates, and bachelors degrees with a subtle shift over the last 10 years from
most student pursuing certificates to more aiming for the bachelors. The age
cohorts of our students are also shifting from many being of non-traditional age to
many more of traditional age. We draw most of our students from the ten
counties surrounding ours but have had a lot of foreign students too.
I will be using the ricin case in two different courses and in two different ways.
However, as you read through this paper please note that I am using different
ideas I picked up from other class members. One of these is the animation you
watch but another is the notion of dividing my class into teams and having them
compete.
A. Science 260: Biology and Modern Society
Biology and Modern Society is a 3-credit, lecture only science course which I
designed myself in 1991 and have had it run successfully, most often in multiple
sections every regular semester since. It is a sophomore human biology course
but the only prerequisite is college English. Most students would have had many
other courses in their majors by the time they take me, an important qualification
for a primarily biology course since language skills are closely linked to success
in the life sciences. Only one other person ever offered the course from Penn
College and that was only one semester at an off-campus site. On the other
hand, Penn State University offers a course with the identical name and
description but I have never had any contact with whoever is teaching that
course (they are forty-five miles away!).
This course, in addition to offering science credit to the students, is also a
science technology and society course (or STS). Every student enrolled in a
state-related institution must take an STS course by Pennsylvania law. The aim
of STS courses is to encourage students to make the connections between
scientific discoveries, technological applications, and their impacts on society.
I offer Science 260 in both face-to-face and distance learning format. The “script”
I offer here will go on-line, but I will be presenting similar activities in the face-toface version. The placement of this section will be obvious as one reads the
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script. The reader will find the Biology 115 (anatomy and physiology) material
immediately following the SCI 260 script.
Unit V, section 3: “Biological and Chemical Terrorism”
Learning objectives: In this unit, the class will review earlier aspects of population
biology, digestion, and cell biology and then explore one case of chemical
terrorism.
As you will remember from Unit III (population biology) plants make numerous
substances that are secondary to the major metabolic pathways (e.g., burning
sugars, making proteins, etc.). The function of many of these chemicals is to
ward off feeding by other organisms by making the plant poisonous or otherwise
objectionable. In Unit IV we learned that our sense of taste is adapted to pick up
on these noxious chemicals and our brain interprets these as tasting bitter so as
to protect us (Evans and Schmidt 1990).
Assignment question: In your usual 3 well thought-out sentences, list three things
that most people would say taste bitter but which are not likely to kill in
reasonable amounts. Submit your answer to: [email protected].
Let’s bring in some other facts from earlier in the semester. Since we are going to
be talking about terrorism, really a type of warfare, which in turn is really just
another kind of game, let’s review something about Game Theory. Remember
that opponents who are significantly weaker in resources will intelligently either
submit to the greater force or seek to use methods seen by others as “cheating”
or “unfair” to achieve their ends (Maynard-Smith1982). The military would say
such warfare is between unequal contestants.
In addition to the events of September 11, 2001, what other occasions can you
think of where terrorists have used unexpected, innovative, or unfair practices to
gain headlines? Write 3 well thought-out sentences and submit them to the
Angel® discussion area below this lesson on your course Homepage. Expect to
be able to defend your choices to the other members of the class.
We are currently looking at cell biology in Unit 6 so how does all of this fit into
that topic? Naturally one of the biggest concerns is that the United States will be
attacked once again by anthrax as happened in October, 2001. Here is a
summary of some possible agents: WEBSITE imbedded for biological and
chemical terrorism: http://www.cdc.gov/ncidod/EID/vol5no4/kortepeter.htm. We
are going to be examining one case of chemical and biological warfare but use it
as a way to better understand how normal cells go about their business.
Read the above site and then answer these questions in your usual 3 clear, wellthought out way. Why did the cult in Oregon use food-borne Salmonella?
Consider the impact on your restaurant should a similar group target your
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community. What countermeasures could you adopt that would absolutely
protect your business? Submit them to the Angel® discussion area below this
lesson on your course Homepage. Expect to be able to defend your choices to
the other members of the class.
However, instead of concentrating on germ-based attacks, let’s look at a simpler,
cheaper technology: ricin from castor beans.
Figure legend: Castor bean flowers and immature fruit—the mottled seeds will
come out when these red structures dry and turn brown. The term “fruit” is used
only in the technical, botanical sense—don’t put them over your ice cream! Photo
source: Cornell University
The castor bean grows from a lovely tropical shrub (Ricinis communis) and
contains oil used as a commercial fine machine lubricant; the most familiar
product is Castrol®. There is a mealy material left over after the oil is extracted
and this material contains an extremely toxic protein named ricin (Franz and Jaax
1997). Ricin’s toxic properties have been known since ancient times and it is, in
fact, possible that Alexander the Great was killed with it. More recently Georgi
Markov, a Bulgarian dissident was assassinated in 1978 during the Cold War
using ricin. The ricin was embedded into a metal ball and the ball was thrust into
the back of Markov’s leg with a weapon disguised as an umbrella. It made an
ideal assassin’s weapon: cheap, light, and almost impossible to treat or trace in
time—the killer was never brought to justice. It is possible to administer the toxin
other ways such as a fine mist to the face or orally. Mist will be drawn into the
lungs but the drawback is that the assassin may accidentally inhale it! However,
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for various reasons (whole castor beans just taste horrible, for one), the oral
route is just not as effectively deadly as others.
In early 2008, a man was found unconscious in a Las Vegas hotel room with
vials of ricin. The person was delivered to a local hospital in respiratory distress,
the hotel evacuated, a hazardous waste team called in, and seven others were
taken to area hospitals as well (Friess 2008). Nobody seems to know what the
man was planning to do with all of that ricin but the FBI currently sees ricin as the
number one potential chemical threat that terrorists might use: it is easy to grow
the plant and refine the toxin from the beans. Even those not in warmer areas of
the United States can carry beans from the south or even quite legally buy them
at plant nurseries.
How can you tell if you have been ricin-poisoned? Unfortunately, there is no
single sign and it can depend on how the stuff got into you. Looking at ricin from
a terrorist’s perspective, here is yet another “advantage” to using it: the
symptoms are varied so that, at least with the initial cases, health care
professionals will be at a loss to diagnose it. Fortunately, work seems to be going
forward to develop a quick-detection kit which would promptly identify the toxin. It
would not pass through unbroken skin since it is a fairly large, water soluble
compound. On the other had, if you swallow it, there will be digestive symptoms:
vomiting, diarrhea, and dehydration, followed by eventual failure of the kidneys,
spleen, and liver. If the person inhales ricin, there will be labored breathing and
pulmonary edema (=fluid build-up in the lungs), and possible eventual death. The
Centers for Disease Control and Prevention have more information on this:
http://www.bt.cdc.gov/agent/ricin/facts.asp.
Here is a brief outline of ricin’s effects on a cell: Ricin is able to cross into the cell
membranes of many different types of cells and then will attack to the ribosomes
and make it impossible to “read” the m-RNA coming out from the nucleus. Ricin
then goes to other ribosomes and does the same thing to them, all in a very short
time. The cell will eventually become completely non-functional and kills itself.
Discussion board question: Some researchers have tried to use ricin against
cancer. Why do you think the efforts have had a fairly high mortality rate? Write 3
well thought-out sentences and submit them to the Angel® discussion area
below this lesson on your course Homepage. This is a fairly difficult question so I
will look at your ability to deal with it in a creative way.
Fortunately, it may be possible to develop vaccinations against ricin in the future
(Maddaloni, et al, 2004).
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B. BIO 115: Anatomy and Physiology, first semester
This is a freshman course intended for the student wishing to pursue a career in
one of the health professions. The only prerequisites are that a person be ready
to take college-level English and mathematics.
The following is a text to be given to students; alternatively, the professor can
use this presentation as lecture notes. I would employ it in a lab session and
spend around 30 minutes on it, keeping in mind that students will be spending
more time reviewing the material from other perspectives.
Learning objectives:
We will learn how the toxin ricin destroys cells primarily to review our lecture
information about cell biology.
Some ideas you may want to review from your lecture notes:
Apoptosis, endoplasmic reticulum, enzyme, eukaryotic, galactose, Golgi body,
polypeptide, prokaryotic, ribosome, tissue, Vmax
Ricin is a protein derived from the castor bean consisting of two polypeptide
chains (review this information from unit II: “Living chemistry”): the A and B
polypeptides. Ricin is extremely toxic and there is at least one case of it being
used in an assassination but potentially it could serve as weapon used by
terrorists. There is also some possibility of it being used in some form in the
future as a chemotherapeutic agent.
Each polypeptide has different roles in poisoning. The B chain helps the entire
protein to gain entrance to a cell; this seems like an insignificant issue but we
have seen in our virus biology lecture, this is actually a big problem. The B chain
can attach to the galactose portion of a membrane polysaccharide (Bradberry et
al. 2003). Since that monosaccharide is very common, many different types of
cell membranes are affected so ricin can damage lots of different tissue types.
The poison really travels in the opposite way that most proteins do so its action is
said to be retrograde (=backwards). The cell will then take the entire protein in
and transfer it to an endosome and then on to the Golgi complex. After the Golgi
complex, it goes to the endoplasmic reticulum (ER) where the A and B chain
separate (Lord, et al. 2003, Sanvig and van Deur 1999).
At the ER, unit A has to have its shape changed so that it can cross the
membranes and then be changed back afterward. Upon entering the ER, the A
unit attacks and destroys an adenine in a specific set of nucleotides in the r-RNA,
this set found in the larger (or 60s section of the ribosome) part of the eukaryotic
ribosome. The 60s section looks like a catcher’s mitt from the perspective we see
in the lecture book. The A chain does not attack prokaryotic ribosomes because
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their ribosomal structures are different. When that adenine near the beginning of
the r-RNA is destroyed, the ribosome having that r-RNA portion in it no longer will
receive an m-RNA and no more protein synthesis occurs there. The A chain goes
on to other ribosomes and disables them in an enzymatic way until the whole cell
becomes disabled and eventually undergoes apoptosis. Ricin’s Vmax (=enzyme
optimum) is approximately 2000 ribosomes destroyed/sec under normal, or
physiological, conditions (Sanvig and van Deur 1999), similar to many other
enzymes.
There are attempts to harness ricin’s ghastly cell poisoning capacity as a
chemotherapeutic agent. All you have to do is get it into the right cells and that is
where the hard part comes in—getting it to attack ONLY the cancer cells and not
every other cell it bumps into! Therefore, any but experimental therapeutic use
seems to be years down the road.
We are going to divide into teams and compete but first, with your group, make a
flow chart of ricin’s action beginning with the cell membrane, naming each
structure in its proper sequence:
A unit attaches to cell membrane > endocytosis > ___________________ >
_____________________ > _____________> _____________ > polypeptides
separate >
_____________________ > ribosome disabled > > apoptosis
When everyone is finished, one member from each group will be called on to
supply their group’s answer to one of the blanks.
Now we’ll have some fun with the flow chart: teams will race to give the normal
sequence of protein synthesis:
m-RNA synthesis from DNA template > ________________ > ____________>
________________ > _________________ > exocytosis from cell membrane
As a summary, you can look at the animation during lab but I will also be sending
out to all by College E-mail an animation of the actions of ricin.
End of student section.
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Assessment
In face-to-face classes, I prefer the Socratic method for students as they mature
through the semester. The method of course presumes a knowledge base. Since
cell biology and introductory biochemistry come early in the semester for Biology
115, I would minimize playing Socrates at that time in that course. On the other
hand, the Science 260 classes should be able to deal with the method by the
time they get to this topic.
The embedded questions in the SCI 260 distance learning script show how I
would initiate assessment in the distance learning class. It should be obvious that
those questions can be turned into quiz and test questions. Additionally, several
students every year choose to do their term projects on chemical and biological
warfare.
In Biology 115, my cooperative learning exercise will initiate study along with
similar multiple choice and fill-in the blank questions on tests and quizzes. Once
again, students in this course may start choosing chemical and biological warfare
issues for their projects too. I believe I will try the team exercise out for one
semester without formal grading and hope that emotional rewards and peer
pressure will insure participation as it seemed to work that way when my
teachers used it.
Answers:
A unit attaches to cell membrane > endocytosis > endosome >
Golgi complex > vesicles > Endoplasmic reticulum > polypeptides separate >
Ribosome (or r-RNA) > ribosome disabled > > apoptosis
When everyone is finished, one member from each group will be called on to
supply their group’s answer to one of the blanks.
Note the retrograde (=backward) flow of actions.
Now we’ll have some fun with the flow chart: teams will race to give the normal
sequence of protein synthesis:
m-RNA synthesis from DNA template > Ribosome (or r-RNA) >
Endoplasmic reticulum > vesicles > Golgi complex > exocytosis from cell
membrane
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Literature cited
Bradberry, S.M., K.J. Dickers, P. Rice, G.D. Griffiths, and J.A. Vale. 2003. Ricin
poisoning. Toxicol. Rev. 22: 65-70.
Evans, D.L. and J.O. Schmidt, eds. 1990. Insect defenses. Albany, NY: SUNY
Press.
Franz, D.R. and N.K. Jaax. 1997. Ricin toxin. In: Textbook of military medicine.
Washington: Office of the Surgeon General.
Friess, S. 2008. Man in critical condition in ricin case. The New York Times Feb.
29, 2008.
Lord, M.J., N.A. Joliffe, C.J. Marsden, C.S.C. Pateman, D.C. Smith, R.A.
Spooner, P.D. Watson, and L.M. Roberts. 2003. Ricin: mechanisms of
cytotoxicity. Toxicol. Rev. 22: 53-64/
Maddaloni, M., C. Cooke, R. Wilkinson, A.V. Stout, L. Eng, and S.H. Pincus.
2004. Immunological characteristics associated with protective efficacy of
antibodies to ricin. J. Immunol. 172: 6221-6228.
Maynard-Smith, J.1982. Evolution and the Theory of Games. Cambridge:
Cambridge University Press.
Sandvig, K. and B. van Deurs. 1999. Endocytosis and intracellular transport of
ricin: recent discoveries. FEBS lett. 452: 67-70.
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