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November 18, 2002
A: FROM MENTOR MARTY CHINTALA
RI
Alexis, that is a great question, particularly since there
are a couple
of different camps on this issue and all the details have
not been
worked out yet. Pfiesteria piscicida (and other related Pfiesteria
species) is a free swimming, single-celled alga and has a
complex life
cycle. The life cycle includes at least 24 flagellated, amoeboid,
and
encysted (it is a dormant stage- means that they make a protective
covering and sink to the bottom) stages. Most of the time,
Pfeisteria
is nontoxic, but it will become toxic when it detects enough
of a
substance that is a cue for it. One of the cues is thought
to be large
schools of menhaden (oily fish) that come to an area to feed
and the
excreted and secreted substances trigger the dormant cells
to emerge and
feed. These outbreaks are very short, usually lasting no longer
than a
few hours. So unless conditions are just right, the cells
won't emerge
and thus you won't have an incidence of disease. The lesions
that fish
get from the Pfeisteria can last for days after the cells
are gone. HOW
the Pfeisteria acts on fish is a main source of contention
now.
Researchers from the North Carolina State University think
that when the
cells become activated (flagellated cells), they swim toward
the fish,
secrete potent toxins into the water that make the fish lethargic
so
that they remain in the area where the Pfiesteria cells are.
The toxins
will also destroy the fish skin, which causes open sores and
incapacitates the fish. The Pfiesteria cells then feed on
the epidermal
tissue, blood and other substances that leak from the sores.
When the
fish are dead, the flagellated form turns to an amoeboid form
that feeds
on the fish remains. When conditions are unfavorable, the
cells will
then make protective cysts and become dormant until triggered
again. A
couple of good webpages that detail this are:
http://www.pfiesteria.org/pfiesteria
and
http://www.epa.gov/owow/estuaries/pfiesteria/fact.html.
The scientists at Virginia Institute of Marine Science (VIMS)
have a
different theory. The toxins that are supposedly secreted
by Pfiesteria
piscicida and its related species Pfiesteria shumwayae have
never been
isolated or characterized. They did a series of experiments
and suggest
that the Pfiesteria don't secrete toxins, but instead are
"micropredators", that they swarm to the fish skin,
feed on the skin and
remove the epidermis. They question the role that Pfiesteria
plays in
fish lethargic behavior and mortality. Their study has recently
been
published in the journal Nature. Their website can give you
more
information, and has cool video clips of the cells attacking
fish:
http://www.vims.edu/pfiesteria/
So the debate on Pfiesteria is far from over, which leads
me to your
second question. One thing for sure, science will be very
political as
long grant money is involved. Many scientists survive their
whole
career on grant money, and in order to keep going, they have
to keep
getting grant money. Depending on the administration (President,
Congress, etc.), sometimes money is tighter than others. Scientists
are
always competing against each other for dollars to do their
research, so
who you know and how famous you are helps to determine how
many grants
you will end up getting (despite what some people say to the
contrary
because you often have to prove that you are qualified to
conduct the
research in order to get the money for the research). This
topic
(Pfiesteria) is a hot one, because the basic tenet of the
findings to
date are being questioned. This could lead to more $$ for
one side and
less for the other. I know that it hasn't been a particularly
pleasant
argument.
As for your third question, I think that depends on whether
you are
involved in politics or are being attacked by a nasty, disease-causing
cell! I think both have their downsides, particularly when
politics
prevents people from getting the help that they need or prevents
research from being done that is beneficial to mankind as
a whole.
(somehow, I don't think you want to get me started on this
point!) From
an egocentric viewpoint, the nasty cell might not affect me
as much,
because there has not been a case of illness from eating fish
exposed to
Pfiesteria. But you can show symptoms when exposed to water
where
Pfiesteria's toxic forms are active (however where I live
in the NE,
it's not an issue). But I love a good political argument,
and I don't
like when politics is harmful to people (that could be a topic
onto
itself!).
********************
November 15, 2002
A: FOLLOW-UP FROM MENTOR SUZANNE FRANKS IN KS
Alexis, after I sent my original reply, I thought I really
should
address your last question as well. In my opinion, politics
(the kind
of politics that gets in the way of getting things done, or
that prevents
appropriate action) is worse than a nasty disease causing
cell,
because at least we can hope to find cures for the disease!
********************
November 14, 2002
A: FROM MENTOR SUZANNE FRANKS
IN KS
Alexis, I am going to leave the question about why the cells
don't
always cause disease to a bacteriologist or a cell biologist
to answer!
However, I do want to talk a little about "why science
gets poltiical."
Science gets political because it is political! What I mean
by that, is
that science is a set of activities and actions and decisions
and
investigations and projects, all of which are undertaken by
human
beings, for the purpose of doing something to affect or change
the way
we live and how we understand things. All of that makes it
a political act.
Some would argue that there is nothing any human being can
do that is
not, in some sense, political. But science is all about understanding
and
improving our lives, and that is political work. I think,
however, that you
are asking "why do people let their political beliefs
get in the way of
science?" Well, political beliefs and ideas are part
of what human
beings use to figure out what kind of action should be taken.
One can
never really decide "just" on the basis of science
because what we
learn from science must always be interpreted in the context
of
a particular society and state of affairs. And we must consider
what
the impact will be of any decision for action that we take.
Science, for
example, was able to tell us that spraying DDT on crops would
kill
pests that were destroying the crops. It was also able to
tell us that
DDT was making the shells of eggs of bald eagles and many
other
birds so fragile that the eggs could not last until birds
were hatched,
and that other kinds of environmental impacts were taking
place.
But science could not tell us whether we should then stop
using DDT,
and who should be responsible to repair the damage that was
caused,
and what kind of rules about pollution and insecticides we
should have.
Those decisions all require political input. Science can inform
our
decision making process, but it cannot substitute for that
process.
So when it looks sometimes like politics are getting in the
way of
science, it may actually be the case that science cannot substitute
for politics, but can only guide it. We are responsible for
being
scientifically literate enough to make good informed decsions
but we
can't escape politics or the fact that the decisions we make,
aren't made
in a vacuum, but are made in a particular societal context
and have
implications far beyond what the scientific data can say.
********************
A: FROM MENTOR JOAN LUSK IN
RI
I don't know, but since the disease is caused by a toxin,
perhaps the
Pfiesteria only makes the toxin under certain conditions.
(How would
you test this?)
In the case of diphtheria,
http://www.bact.wisc.edu/Bact330/lecturediphth
the bacterium has the gene to make the diphtheriotoxin but,
to quote
from the URL:
"Two factors have great influence on the ability of Corynebacterium
diphtheriae to produce the diphtheria toxin: (1) low extracellular
concentrations of iron and (2) the presence of a lysogenic
prophage in the bacterial
chromosome. The gene for toxin production occurs on the chromosome
of
the prophage, but a bacterial repressor protein controls the
expression
of this gene. The repressor is activated by iron, and it is
in this
way that iron influences toxin production. High yields of
toxin are
synthesized only by lysogenic bacteria under conditions of
iron
deficiency. "
I knew about this, so by analogy I would investigate what
controls
toxin production by Pfiesteria - it might be something quite
different, of course. And I could be totally off-base! Toxin
production might not be the variable. What other variables
can you
think of that could explain different responses to the same
rate of
toxin production?
As for the second part of your question:
Science may be purely rational in theory, but it is only carried
out
by human beings - who are by nature political. Politics has
to do
with the division of responsibilities, rights, wealth and
power, and
no one is immune from having her self-interest color the way
she sees
the world. Scientists worthy of the name try to avoid letting
their
biases affect their results and interpretation of results,
but
scientist are only human and can be blind to the fact that
what they
expect and want to observe can influence what they think they
do
observe. Self-interest can also influence how we interpret
what we
see. This is why we have to disclose potential conflicts of
interest. Readers of our scientific paper on the beneficial
effects
of smoking should know that the work was funded by a cigarette
company.
There are also political struggles for power between scientists
in
laboratories, where the struggle is less concerned with the
science
itself than simply with who's to be boss.
Politics _can_ be fair - the free exchange of ideas, "may
the best
man (or woman) win," but fairness has nothing to do with
disease and
death. So I think we just need to leave the nastiness to the
disease
itself and try to keep our political struggles clean and separate
from our science as much as possible!
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