Newsgroup: it.sport.ciclismo
Titolo: [Hamilton] Gemello scomparso o doping? Mistero nel ciclismo

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Il ciclista statunitense Tyler Hamilton, accusato di doping dopo che un 
prelievo ha rilevato nel suo sangue tracce del sangue di un'altra 
persona, ha dato la colpa al suo gemello scomparso. Una follia? La 
giuria sportiva dice di sì, ma alcuni scienziati sostengono il 
contrario. All'incredibile vicenda ha dato molto risalto il New York Times.
Hamilton, sospettato di ricorrere a trasfusioni di sangue per aumentare 
l’apporto di ossigeno fornito dal suo sangue e migliorare così 
artatamente le sue performance, si è preso una squalifica di 2 anni, che 
alla sua età (34 anni) potrebbe voler dire la fine ingloriosa di una 
carriera. Il ciclista sostiene che non si tratta di doping, ma delle 
tracce ematiche lasciate da un suo fratello gemello morto in utero che 
prima di morire avrebbe ‘passato’ al feto di Hamilton alcune cellule, 
tuttora attive nel suo organismo e responsabili della produzione di 
sangue apparentemente non appartenente all’organismo di Hamilton.
La giuria sportiva incaricata di decidere sul caso non ha dato credito a 
questa tesi difensiva e ha squalificato il ciclista statunitense, che ha 
preannunciato che presenterà ricorso alla sentenza. Travis T. Tygart 
della United States Anti-Doping Agency sostiene che l’evidenza 
scientifica è contro Hamilton: “Il nostro unico interesse è la 
giustizia. Non portiamo avanti procedure sul doping se non riteniamo di 
avere un’evidenza scientifica che provi le accuse”.
In realtà esiste un fenomeno detto chimerismo che consiste in effetti 
nella coesistenza di cellule di 2 individui diversi in un unico 
paziente, e una delle possibili cause è proprio la scomparsa di un 
gemello in utero. Helain Landy della Georgetown University ha scoperto 
che il 20-30 per cento delle gravidanze che iniziano come gemellari 
finiscono come singole, e uno dei due feti gemelli viene riassorbito 
dalla madre durante le prime settimane di gestazione. Altre ricerche nel 
campo hanno dimostrato che prima che questi feti vengano riassorbiti, 
alcune cellule migrano nel feto sopravvissuto e rimangono al suo interno 
per tutta la vita. Alcune di queste cellule possono essere cellule 
staminali del midollo osseo, capaci di generare cellule ematiche. Un 
altro possibile percorso del chimerismo risiede nello scambio ematico 
tra madre e feto. Ann Reed, reumatologa della Mayo Clinic, utilizzando 
un test del DNA, ha scoperto che una percentuale tra il 50 ed il 70 per 
cento della popolazione sana presenta chimerismo: più gli scienziati 
affinano i metodi di ricerca, più i risultati sembrano confermare la 
grande diffusione del fenomeno. “Se cerchi abbastanza a lungo puoi 
trovare chimerismo in chiunque”, afferma la Reed.
Ma l’idea che i risultati positivi al doping di Tyler Hamilton possano 
essere spiegati con un caso di chimerismo viene rigettata da Ross Brown, 
ematologo del Royal Prince Alfred Hospital e consulente medico di molte 
agenzie anti-doping: “L’unica ragionevole spiegazione è una trasfusione. 
Le Banche del sangue non hanno mai trovato casi di chimerismo”. A chi 
ritiene che questa mancanza di riscontri sia dovuta all’utilizzo di test 
poco sensibili, Brown fa sapere di aver lui stesso effettuato un test di 
citometria a flusso molto sensibile su 20.000 campioni di sangue senza 
riscontrare alcun caso di chimerismo. Oltretutto, fanno notare dalla 
United States Anti-Doping Agency, anche il compagno di squadra di 
Hamilton Santiago Perez è risultato positivo ai test. “Mi sembra 
inconcepibile che ci siano due persone con chimerismo nella stessa 
squadra”, conclude scettico Brown. David Housman, biologo molecolare del 
Massachusetts Institute of Technology, non è così categorico: “Non credo 
affatto che la spiegazione che viene proposta per i risultati del test 
del sangue di Hamilton sia l’unica possibile. Il chimerismo non è 
assolutamente raro come si crede”.
Un caso di doping apparentemente banale (?!) si trova insomma ad aver 
scatenato una avvincente querelle scientifica. Intanto Hamilton si 
allena da solo, sperando di essere scagionato.
-- 
Il segreto della felicita' non e' di far sempre cio' che si vuole, ma di 
voler sempre cio' che si fa. (Lev Tolstoj)

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Riporto il testo originale Nel NYT, lungo
************
Cheating, or an Early Mingling of the Blood?
Last month, when the champion American cyclist Tyler Hamilton was 
accused of blood doping, or transfusing himself with another person's 
blood to increase his oxygen-carrying red cells, he offered a surprising 
defense: the small amount of different blood found mixed in with his own 
must have come from a "vanishing twin."
Jack Dempsey/Associated Press
Tyler Hamilton has been suspended from competitive cycling for two years.
In other words, his scientific expert argued, Mr. Hamilton had a twin 
that died in utero but, before dying, contributed some blood cells to 
him during fetal life. And those cells remained in his body, producing 
blood that matched the dead twin and not Mr. Hamilton. Or perhaps it was 
his mother's blood that got mixed in during fetal life.
An arbitration panel did not believe those hypotheses and said there was 
a "negligible probability" that Mr. Hamilton was anything but guilty.
The test, they concluded in a 2-to-1 decision, shows a blood transfusion 
and that meant that Mr. Hamilton was suspended from racing for two 
years, the first and only person convicted for that offense. At age 34, 
near the end of his career, it could mean his championship days are over.
Mr. Hamilton has said he will appeal the decision. If he can prove the 
test was flawed, then not only might he return to cycling and his 
multimillion-dollar career, but other athletes could use the same 
defense. The new test, developed over two years by the World Anti-Doping 
Agency and the United States Anti-Doping Agency, would be all but useless.
Travis T. Tygart, the general counsel for the United States Anti-Doping 
Agency, which prosecuted Mr. Hamilton, says the scientific evidence was 
against the cyclist.
"Our interest is only justice," Mr. Tygart said. "We don't blindly bring 
doping cases. We look at the evidence, and if we think there is enough 
evidence to go forward we present that to an arbitration panel."
Whether Mr. Hamilton is guilty or innocent, his defense does refer to a 
real phenomenon. Researchers who have no involvement in Mr. Hamilton's 
case say it actually is possible for someone to have two types of blood 
in his body, without doping. They emphasize that they do not know 
whether this is the case with Mr. Hamilton.
One route to this odd state, called chimerism, is the vanishing twin. 
Dr. Helain Landy of Georgetown University, who has no involvement in the 
Hamilton case, has found that 20 to 30 percent of pregnancies that start 
out as twins end up as single babies, with one twin being absorbed by 
the mother during the first trimester.
Others researchers have found that in some cases, before the twin is 
absorbed, some of its cells enter the body of the other fetus and remain 
there for life. The cells can include bone marrow stem cells, the 
progenitors of blood cells.
Another route to chimerism is through the cells that routinely pass from 
a mother to fetus and remain there for life.
Dr. Ann Reed, chairwoman of rheumatology research at the Mayo Clinic, 
who uses sensitive DNA tests to look for chimerism, finds that about 50 
to 70 percent of healthy people are chimeras. The more scientists look 
for chimerism, the more they find it. It seemed not to exist in the 
past, she said, because no one was explicitly looking for small amounts 
of foreign cells in people's bodies.
"Some believe that if you look hard enough you can find chimerism in 
anybody," said Dr. Reed, who also has not been involved in the Hamilton 
case. It is so common that she thinks there must be a biological reason 
for it. It also may cause problems, she and others say.
Chimerism may be why bone marrow from a seemingly perfectly matched 
donor relentlessly attacks a patient who receives it in a transplant - 
the attackers may be a small percentage of cells in the marrow that come 
from someone else. It also may help explain autoimmune diseases, when 
the body's own immune cells attack. The attacking cells may be the 
foreign ones that arise from someone else.
The Hamilton case involves a test developed by Dr. Margaret Nelson and 
her colleagues at the Royal Prince Alfred Hospital in Australia. It was 
based on a simple idea: if an athlete got a transfusion, he would have 
to make sure the blood was the right match using the blood antigens A, B 
and O. But blood cells have other surface proteins, so-called minor 
antigens, that do not matter in blood typing for transfusions but can be 
used to distinguish one person's blood from another's. The investigators 
said they could use a sensitive test, flow cytometry, to search for 
small amounts of blood with minor antigens different from those in the 
athlete's own blood.
It was an important advance, anti-doping agency officials said. They 
knew that athletes, including cyclists, had used blood transfusions in 
the past to boost their performance but had no test to prove it.
The principal hematologist working with the anti-doping agencies, Dr. 
Ross Brown of Royal Prince Alfred Hospital, rejects the idea that the 
test could be finding chimeras instead of transfusions. In his testimony 
at Mr. Hamilton's hearing and in an e-mail message Dr. Brown, who is Dr. 
Nelson's immediate supervisor, said chimerism was so rare as to be 
inconceivable as an explanation for Mr. Hamilton's results. "The only 
reasonable explanation is a transfusion," he wrote by e-mail.
Dr. Brown, the only outside scientist that the anti-doping agency 
suggested to present its point of view, said that blood banks almost 
never found chimeras. The blood banks used a less sensitive test, but 
Dr. Brown testified that he himself, using the more sensitive flow 
cytometry on at least 20,000 blood samples, never found a chimera.
And, he said, reports of people with small amounts of foreign cells do 
not signify that an athlete with a second population of blood cells had 
someone else's blood stem cells in his bone marrow. Moreover, he said, 
Mr. Hamilton tested negative a few months after his positive test last 
fall. That is consistent with an athlete who had transfusions, was 
caught, and then stopped.
In addition, Dr. Brown said, another rider on Mr. Hamilton's team, 
Santiago Perez, also tested positive. (He did not show up for his 
hearing and was pronounced guilty in absentia.)
"It seems inconceivable to me that there would be two people who were 
rare chimeras on the same cycling team," Dr. Brown wrote by e-mail.
Dr. Olivier Rabin, the scientific director of the World Anti-Doping 
Agency, said the onus was on Mr. Hamilton to prove he was innocent. "It 
is up to the defending party to prove it is anything other than blood 
doping," he said.
The story of Mr. Hamilton's scientific defense began last September, 
when the blood doping allegations were first made public. He had just 
won a gold medal in the Athens Olympics and had competed in a bicycle 
race in Spain when the World Anti-Doping Agency said his blood revealed 
transfusions.
"I was so calm," Mr. Hamilton recalled, thinking the result was a 
mistake. "I knew something was wrong and we would get to the bottom of it."
The next morning, Dr. David Housman, a molecular biology professor at 
the Massachusetts Institute of Technology and an avid Red Sox fan, was 
reading the sports pages for baseball news and came across an article on 
Mr. Hamilton.
Dr. Housman, who never took much interest in bicycle racing, was jolted 
by what he read.
"I read it and said: 'Wait a second. I don't think the explanation they 
give for the blood test is the only possible explanation,' " he said.
He knew the science showing that chimeras are not so unusual. And he 
knew that stem cells turn off and on throughout life so that a stem cell 
from a twin, for example, might be producing red blood cells and then 
stop, making a tiny amount of foreign blood come and go at random.
So Dr. Housman looked up Mr. Hamilton's father, Bill, on the Internet 
and wrote him a letter offering to help, for no fee.
Bill Hamilton was astonished.
"We were so grateful," he said. "At the time, we didn't know which way 
to turn, and then out of the blue came this brilliant scientist from 
M.I.T. wanting to help."
Not only was a vanishing twin or chimerism a real possibility, Dr. 
Housman decided, but he had real questions about whether the test was 
reliable enough to use to look for blood doping.
Dr. S. Gerald Sandler, a professor of medicine and pathology at 
Georgetown University Hospital, who previously was medical director for 
the national reference laboratory for blood group serology at the 
National Red Cross and who has no involvement in the Hamilton case, said 
the test was acceptable for research. But, he said, its results could 
easily differ from lab to lab. It "is being misapplied," he said, when 
it is used to accuse athletes of blood doping.
Dr. V. K. Gadi, a hematologic oncologist at the Fred Hutchinson Cancer 
Center in Seattle, who uses flow cytometry in his research, says that 
"the test can be quite finicky from experiment to experiment," and that 
the results can vary depending on how the experimenter sets up the test.
But the two arbitrators who ruled against Mr. Hamilton said they were 
confident that the test was accurate. Although, they wrote, "There are 
no scientific studies that detect false positives in the use of the 
HBTT," referring to the test, "there is no need to do so because there 
is no suggestion in the use of the HBTT that it produces false positives."
Mr. Hamilton hopes to be vindicated on appeal. In the meantime, 
preparing to race again, he is training in Boulder, Colo. After riding 
for four to seven hours a day he e-mails his training files to a coach 
in Italy who oversees his program.
Bicycling, his wife, Haven, said, is his life. "He still loves it," she said


cosa non si fa x pur di scampare alla giustizia...
--
Cordialmente
---------------------------------------------------------------
De Marchi Stefano
the.mt...@virgilio.it
www.tmb.135.it
---------------------------------------------------------------

 persona, ha dato la colpa al suo gemello scomparso.
Ma un minimo di dignità, questa gente, proprio no?
 --
"Look around again, it's the same old circle"
David Crosby

 Santiago Perez è risultato positivo ai test. “Mi sembra
Lol che sfiga.. pure nello stesso team!
Bah.. han veramente toccato il fondo.. era meglio la storia delle caramelle 
^^ 

 dice di sì, ma alcuni scienziati sostengono il contrario. [CUT]
Di bello c'è che a seguire le vicende di doping e antidoping si diventa 
cultori della medicina e non solo (anche del cunnilingus :-P ).
Dovreste ringraziarli; con questa farvida fantasia molti ciclisti lavorano 
per accrescere la nostra cultura. Nel mondo d'oggi meriterebbero una bella 
laurea Honoris Causa. Se l'hanno data a Jean Todt e Vasco Rossi...
Ciao
-- 
Sculler,   ICQ# 147722075 MSN: icchi78[at]
hotmail.it
"Ove c'è molta luce, l'ombra è più cupa"
"Le cose che amiamo, ci modellano"
                               Wolfgang Goethe 

 persona, ha dato la colpa al suo gemello scomparso. 
Eh, ma che sfiga !!
Anche Rumsas nel 2002 venne rovinato dalla suocera dopata.
Oh, non ci si puo' piu' fidare neppure dei parenti. :-DD