PTEE
Aula 10
imortalidade
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mortalidade
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senescência
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imortalidade
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dados
Amoebae leave no fossils. They haven't any bones. (No teeth, no belt buckles, no wedding rings.) It is
impossible, therefore, to determine how long amoebae have been on Earth.
Quite possibly they may have been here since the curtain opened. Amoebae may even have
dominated the stage, early in the first act. On the other hand, they may have come into existence only
three years - or three days or three minutes - before they were discovered by Anton van Leeuwnhoek in
1674. It can't be proven either way.
One thing is certain, however: because amoebae reproduce by division, endlessly, the first amoebae
that ever lived is still alive. Whether four billion years old or merely three hundred, he/she is with us today.
Where?
Well, the first amoeba may be floating on his/her back in a luxurious pool in Hollywood, California. The
first amoeba may be hiding among the cattail roots and peepers in the muddy shallows of Siwash Lake.
The first amoeba may recently have dripped down your leg. It is pointless to speculate.
The first amoeba, like the last and the one after that, is here, there, and everywhere, for its vehicle,
its medium, its essence is water.
Water - the ace of elements. Water dives from the clouds without a parachute, wings or safety net.
Water runs over the steepest precipice and blinks not a lash. Water is buried and rises again; water walks
on fire and fire gets the blisters. Stylishly composed in any situation - solid, gas, or liquid - speaking in
penetrating dialects understood by all things - animal, vegetable or mineral - water travels intrepidly
through four dimensions, sustaining (Kick a lettuce in the field and it will yell "Water!"), destroying (The
Dutch boy's finger remembered the view from Ararat) and creating (It has even been said that human
beings were invented by water as a device for transporting itself from one place to another, but that's
another story). Always in motion, ever-flowing (whether at stream rate or glacier speed), rhythmic,
dynamic, ubiquitous, changing and working its changes, a mathematics turned wrong side out, a
philosophy in reverse, the ongoing odyssey of water is virtually irresistible. And wherever water goes,
amoeboe go along for the ride.
Sissy Hankshaw once taught a parakeet to hitchhike. There is not much in that line she could teach an
amoeba.
For its expertise as a passenger, as well as for its near-perfect resolution of sexual tensions, the
amoeba (and not the whooping crane) is hereby proclaimed the official mascot of Even Cowgirls Get the
Blues.
And to the first amoeba, wherever it may be, Even Cowgirls Get the Blues would like to say happy
birthday. Happy birthday to you.
- Tom Robbins, Even Cowgirls get the Blues
mortalidade
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não a estocástica
“acúmulo de pequenos acidentes”
Weissmann
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mecanismo evolutivo
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imortalidade é intrínseca
mortalidade
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notáveis imortais
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bactérias?
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amebas?
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Hydra?
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planárias?
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HeLa
senescência
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envelhecimento
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estresse oxidativo (multicell)
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telômeros (células)
telômeros e telomerase
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região repetitiva no fim do cromossomo
Elizabeth Blackburn, Carol Greider e Jack
Szostak, Nobel 2009
telômerase
Elizabeth Blackburn, Carol Greider e Jack
Szostak, Nobel 2009
dados
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1890 – 1920
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ciliados
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dualismo nuclear
destino de linhagens clonais
destino de linhagens clonais
imortais?
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telomerase?
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problemas experimentais
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“slides were wiped with a very clean cloth”
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“dead lineages were substituted”
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estatística?
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espécies crípticas?
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e em não ciliados?