Temores por polémica terapia para la esclerosis múltiple

BBC Ciencia

La EM afecta la transferencia de mensajes en el sistema nervioso central.

Expertos han expresado "seria preocupación" por un controvertido tratamiento que se está ofreciendo a pacientes con esclerosis múltiple (EM).

El procedimiento consiste en el ensanchamiento de las venas que drenan el sistema nervioso central, basado en una teoría -que no ha sido comprobada científicamente- de que la EM es causada por el bloqueo de las venas que abastecen al cerebro.

Una investigación llevada a cabo por la BBC descubrió que un médico que lleva a cabo el procedimiento en Egipto no tiene licencia para practicar medicina en ese país.

Y en el Reino Unido, el estudio encontró a un facultativo -que ya ha sido reportado al Consejo Médico General- organiza sin licencia el procedimiento en su clínica privada, con un costo de unos US$13.000.

También se ofrecen "paquetes todo incluido" para viajar a México y someterse a la terapia por unos US$10.000.

La operación ha sido bautizada como el "tratamiento de liberación" por algunas personas que dicen que éste les ayudó a aliviar sus síntomas de EM, una enfermedad incurable.

Por los expertos advierten que esas "mejorías" podrían ser resultado del efecto placebo de la terapia y de que los síntomas de la enfermedad pueden desaparecer temporalmente para volver más tarde.

Sin comprobar

El polémico tratamiento consiste en insertar pequeñísimos "globos" en el organismo por medio de una incisión en la ingle. Los globos son dirigidos hacia venas en el torso y el cuello, y una vez allí son inflados para ensanchar los vasos sanguíneos.

En algunos pacientes se insertan también pequeños tubos -o stents- para dilatar las venas.

Éste es un procedimiento que no ha sido comprobado y hasta que se lleven a cabo ensayos clínicos es imposible decir si funciona o si es seguro para la gente que sufre esclerosis múltiple

Dr. Doug Brown, MS Society

El procedimiento está basado en una nueva teoría, no comprobada, de que la EM es causada por anormalidades en las venas que provocan deficiencias en el abastecimiento de sangre al cerebro.

Se trata de una hipótesis muy radical, que se aleja mucho de la visión aceptada entre la comunidad científica de que se ignora la causa de la EM.

Se piensa que varios miles de pacientes ya han sido "liberados" en clínicas privadas en muchos países del mundo, incluidos India, Polonia, Bulgaria y México.

En internet circulan videos de pacientes "antes y después" del procedimiento, en los que muestran sus aparentes mejoras.

Pero tal como le dijo a la BBC el doctor Dough Brown, jefe de investigación biomédica de la MS Society del Reino Unido, "uno de los factores más complicados es el efecto placebo, con el cual la persona se siente bien después de someterse al tratamiento pero que esto no necesariamente se debe al procedimiento".

"Éste es un procedimiento que no ha sido comprobado y hasta que se lleven a cabo ensayos clínicos es imposible decir si funciona o si es seguro para las personas que sufren esclerosis múltiple", afirma el experto.

Teoría de la insuficiencia venosa

La teoría de las venas bloqueadas como causa de la EM fue propuesta hace dos años por un médico italiano, Paolo Zamboni.

Su investigación pareció mostrar que sólo las personas con la enfermedad tenían múltiples anormalidades en determinadas venas del torso, que provocaban una deficiencia en el flujo sanguíneo hacia el cerebro.

La EM causa daños en la capa que protege a las neuronas, la mielina

Zamboni llamó a este supuesto trastorno "insuficiencia venosa cerebro espinal crónica" (CCSVI, por sus siglas en inglés) y afirmó que su estudio había demostrado que el problema no ocurría en las personas sanas.

Posteriormente, en 2010, un investigador estadounidense afirmó que había encontrado CCSVI en poco más de la mitad de personas con EM estudiadas, pero el trabajo no ha sido publicado.

Lo que si ha sido publicado son otros siete estudios de científicos independientes, ninguno de los cuales logró apoyar la teoría de Zamboni.

Algunas de estas investigaciones revelan que lo que el italiano interpretó como anormalidades son, de hecho, variaciones anatómicas normales e inocuas que se encuentran en todas las personas.

"Entiendo que los pacientes están desesperados", le comenta a la BBC el profesor John Zajicek, experto en neurociencia clínica de la Escuela Médica Peninsula, de Inglaterra.

"Pero virtualmente cada año surge un nuevo tratamiento que alienta a los pacientes con EM, sólo para comprobar que no son efectivos".

"Por ahora no sé de ninguna evidencia que muestre que este procedimiento y su explicación para la esclerosis múltiple tenga algún valor en absoluto".

Avance "crucial" para vacunas contra el cáncer

Científicos británicos descubrieron por qué hasta ahora ha sido tan difícil preparar al sistema inmune para atacar a tumores cancerosos.

El estudio identificó una célula que protege al tumor de la respuesta inmune.

Los investigadores de la Universidad de Cambridge, Inglaterra, identificaron un tipo de célula que protege a las células cancerosas de la respuesta inmune del organismo "saboteando" las defensas del paciente.

Es por eso que muchos de los intentos que se han hecho con vacunas y otras terapias para combatir el cáncer, basadas en esta respuesta inmune, han fracasado, afirman los científicos en la revista Science.

Los investigadores creen que el hallazgo podría conducir a nuevos tratamientos más efectivos para combatir el cáncer.

El estudio, financiado por la Fundación Wellcome Trust, descubrió que las llamadas células del estroma, un tipo de célula del tejido conectivo que se encuentra en muchos tipos de cáncer, juegan un papel crucial suprimiendo la respuesta inmune en los tumores cancerosos.

Tal como explican los investigadores, las vacunas que se han desarrollado para provocar que el sistema inmune ataque a las células cancerosas han logrado activar la respuesta inmune pero casi nunca han logrado tener un impacto en el crecimiento de los tumores.

Y hasta ahora no se sabía por qué ocurría esto, pero se sospechaba que de alguna forma la actividad de las células inmunes quedaba suprimida dentro del tumor.

Ahora descubrieron que un compuesto que se encuentra en las células del estroma encargado de producir una proteína, llamada proteína activadora del fibroblasto o FAP, juega un papel crucial en ese proceso.

En la nueva investigación, llevada a cabo con ratones modificados, los científicos destruyeron las células del estroma en los tumores de ratones con un tipo de cáncer pulmonar.

Descubrieron que el tumor comenzó a "morir" rápidamente.

Paso importante

Las próximas investigaciones sobre el proceso que utilizan estas células para llevar a cabo este efecto podrían contribuir a mejores terapias inmunológicas que nos permitirán retirar una de las barreras que el cáncer ha construido

Prof. Douglas Fearon

"El hallazgo de células específicas dentro de la compleja mezcla del estroma del cáncer que previene el ataque inmune es un paso importante" expresa el profesor Douglas Fearon, del Departamento de Medicina de la Universidad de Cambridge.

"Las próximas investigaciones sobre el proceso que utilizan estas células para llevar a cabo este efecto podrían contribuir a mejores terapias inmunológicas que nos permitirán retirar una de las barreras que el cáncer ha construido", afirma el científico.

Los investigadores planean ahora llevar a cabo más estudios con animales que padezcan un tipo de cáncer más similar al cáncer humano y también analizarán el efecto en tumores humanos.

Según los científicos, como las células productoras de FAP se encuentran en la mayoría de los tumores cancerosos, podrían ser un buen blanco para el ataque con una nueva vacuna u otra terapia anticancerosa.

La doctora Claire Knight de la organización Cancer Research Uk afirma que el estudio ofrece "claves importantes" sobre cómo los tumores reclutan células sanas para ayudarlos a esconderse del sistema inmune.

Agrega que "la Inmunoterapia es un área prometedora de investigación pero su uso en el tratamiento de cáncer es limitado porque los tumores pueden esconderse del sistema inmune".

"Si encontramos formas de atacar estas células sanas recién reclutadas podremos ayudar a que la inmunoterapia sea más efectiva en el futuro, pero todavía hacen falta muchas más investigaciones".

Cientistas encontram novas pistas sobre origem genética dos infartos

Um grupo internacional de cientistas identificou 13 novas variantes genéticas associadas ao risco de sofrer cardiopatia isquêmica (infarto do miocárdio), o que permite aprofundar o conhecimento sobre a doença, a principal causa de morte nos países industrializados. 

Se estima que os fatores genéticos expliquem 40% do risco de apresentar a doença na população, explicou à agênciaEFE Roberto Elosua, coordenador do grupo de Pesquisa em Epidemiologia e Genética Cardiovascular do Instituto de Pesquisa Hospital del Mar (IMIM), que colabora no trabalho. 

Em estudos anteriores, nos quais também participou esse centro de pesquisa espanhol, já se encontraram 12 variantes vinculadas à doença. "Agora se identificaram 13 novas características genéticas associadas a uma maior probabilidade de apresentar um infarto do miocárdio, de modo que na atualidade conhecemos 25 variantes associadas a esta doença", destacou. 

Embora com este estudo tenham conseguido duplicar, estas 25 características genéticas só explicam 10% dos fatores genéticos relacionados com a cardiopatia isquêmica. Por enquanto, os pesquisadores não conhecem o 90% restante, apesar de já terem dado passos para seu estudo. Tais 90% podem estar relacionados com variantes genéticas raras ou pouco frequentes na população que, embora afetem menos de 5%, implicam um grande risco de sofrer infarto, ou outras características genéticas que modificam a estrutura do DNA que estão começando a serem estudados, indicou Elosua. 

As 25 variantes identificadas até agora são variantes comuns, presentes em mais de 10 % da população. Em cada uma destas há uma característica genética que indica o excesso de risco cardiovascular. Cada pessoa pode apresentar esta característica genética 0 vezes (não herdada de seus pais), 1 vez (herdada de seu pai ou mãe) ou 2 vezes (herdada de seu pai e mãe). 

Para cada vez que se apresente uma destas características genéticas de risco, a probabilidade de apresentar cardiopatia isquêmica aumenta entre 6% e 17%. Este estudo também constou que das 13 características genéticas novas, só três estão relacionadas com fatores de risco cardiovascular clássicos: dois com colesterol e um com hipertensão. Elosua explicou que as outras 10 poderiam estar associadas a fatores de risco desconhecidos até agora. Destacou, além disso, que quando aprofundarem o conhecimento genético sobre esta doença, isto permitirá identificar e entender melhor suas causas, o que, em um futuro, possibilitará desenvolver novos fármacos, assim como quantificar melhor o risco de uma pessoa ter a doença. 

Apesar da patologia ter um componente genético, 60% depende de fatores ambientais. "As recomendações sobre um estilo de vida saudável seguem tendo a mesma relevância, e inclusive mais, porque é o único que podemos ser modificado, não assim os genes", ressaltou. A pesquisa, cujos resultados foram publicados na revista "Nature Genetics", está emoldurada em Cardiogram, projeto no qual participam mais de 100 instituições internacionais.

Migraine drug hikes birth defect risk, FDA says

WASHINGTON — A headache medication for migraines increases the risk for birth defects in babies born to pregnant mothers taking the medication, U.S. health officials said on Friday.

The Food and Drug Administration said new data shows the drug, sold generically and as Johnson & Johnson's Topamax, can cause cleft lips or cleft palate deformities.

Officials called on doctors to warn their female patients of childbearing age who are taking the medicine about its risks.

FDA's Russell Katz, who heads the agency's Division of Neurology Products, said doctors should think carefully before prescribing the drug to women and "alternative medications that have a lower risk of birth defects should be considered."

Cleft lips and cleft palates occur when the mouth does not fully form, causing a "split lip" or a hole in the roof of the mouth.

They can lead to multiple development issues because they can make it nearly impossible for babies to get adequate nutrition. They can be corrected with surgery, although sometimes several operations are needed.

Teva Pharmaceutical Industries Ltd, Watson Pharmaceuticals Inc, Mylan Inc and other generic drug makers also sell the drug under its chemical name topiramate.

FDA issued the warning based on data collected from the North American Antiepileptic Drug Pregnancy Registry, it said.

updated 3/4/2011 2:38:02 PM ET

Definition of life: Arsenic debate just won't die An essential element? Some scientists think so, but others still skeptical

Life on Earth is composed of a handful of essential elements from the periodic table. Recently, one group of researchers claimed that this ingredient list should be expanded, having found a bacteria that presumably switches poisonous arsenic in for phosphorous.

Other scientists are skeptical, but they still entertain the thought of switching the rules in the biochemistry playbook.

The human body contains around 60 elements, but only about a third of those are considered necessary for survival. Looking across all species, the most fundamental elements are carbon, hydrogen, oxygen, nitrogen, phosphorous and sulfur, since these make up the basic molecules of terrestrial life: DNA, proteins and carbohydrates.

This is why the little microbe, GFAJ-1, has caused such a stir. It was isolated from arsenic-rich Mono Lake in California by Felisa Wolfe-Simon of the NASA Astrobiology Institute and her colleagues. In a recent Science journal paper, the researchers reported that GFAJ-1 can apparently build its DNA and proteins using arsenicin the spots usually held by phosphorus.

Arsenic is located right below phosphorous in the periodic table, because their chemistries are similar. But that is exactly why arsenic is so deadly: it replaces phosphorous in chemical reactions, but the resulting arsenic compounds are a poor substitute.

The GFAJ-1 claim "seems to be incompatible with 150 years of understanding the chemistry of arsenic," says William Bains of Rufus Scientific in Cambridge, UK and MIT.

Many scientists like Bains contend that GFAJ-1 survives in arsenic-rich conditions by sequestering the element somewhere in its cell. They don't believe there's enough proof yet to say that the bacteria is actually encoding its genes on arsenic-laced DNA.

"Arsenic DNA is exceptional, so it demands exceptional evidence," says Steve Benner of the Foundation for Applied Molecular Evolution.

However, Benner and Bains are not immune to the idea of life written out with a different chemical formula. They just think it's probably happening on an entirely different world.

Biochemistry on Titan Benner for his part has tried to fabricate arsenic DNA in the lab, but without any luck. He blames it on the fact that arsenic esters break down a million billion times faster than phosphorous esters. (These esters are needed to make the DNA backbone.)

However, this doesn't completely rule out a role for arsenic in biology. On Saturn's moon Titan, where temperatures hover around minus-180 degrees Celsius, arsenic could make a fine replacement.

"Phosphorous-containing molecules would be too stable on Titan," Benner says. "The reactivity of arsenic in this case becomes a virtue."

Titan has other properties that make it an interesting test-bed for alternative life theories. Dirk Schulze-Makuch of Washington State University has considered thelakes of liquid methane and ethane that dot the Titan landscape.

"We can ask: what could make a living there?" Schulze-Makuch says. "How different can the life be?"

Methane has often been considered as a possible substitute for water as a life-sustaining liquid. Large complex molecules often disintegrate in water, but that is less of a problem in methane and other hydrocarbon solvents, explains Schulze-Makuch. Another difference is that carbon might not be the only element of choice.

"Silicon works nicely with methane," says Schulze-Makuch.

Silicon sits underneath carbon in the periodic table, so it can form many of the same complex molecular structures for which carbon is famous.

Silicon is the second-most-abundant element in the Earth's crust (outnumbering carbon atoms by a factor of 1,000), and yet none of our neighbors are silicon-based life-forms. The reason is that silicon typically forms silicon oxides in water, and these oxides eventually turn into rock, which is a dead-end for silicon biochemistry. But in a cold landscape where water is frozen, one can imagine silicon analogues of our biochemicals emerging from a primordial soup of liquid methane or liquid nitrogen. Bains is currentlystudying this very possibility.

Extremes of habitability This is all familiar terrain for Star Trek fans. In the "Devil in the Dark" episode from 1967, Dr. Spock befriends a silicon-based life form called the Horta.

An even earlier attempt at imagining the limits of alien biochemistry was the 1953 sci-fi novel Iceworld by Hal Clement, in which a superhot planet hosts life that breathes gaseous sulfur and drinks copper chloride.

We now have proof that superhot planets like this exist and are perhaps quite common. The first confirmedrocky exoplanet, Kepler 10b, orbits so close to its host star that surface temperatures are estimated to rise above 1,000 degrees Celsius, enough to melt iron.

"Is it reasonable to look for life on the dayside of Kepler 10b?" asks Bains. He doesn't think it is, but pondering life in seemingly impossible environments can help astrobiologists narrow their search.

Reshuffling the chemistry deck Besides silicon, other element swaps have also been considered. A combination of nitrogen and phosphorous can form a diverse set of long-chain molecules and therefore might replace carbon on, for example, a planet with an ammonia atmosphere. Boron, too, has carbon-like properties, but there's relatively little of this light element in the universe.

The role of oxygen in organic chemistry could be filled by chlorine or sulfur. Indeed, some microbes are known to occasionally replace one oxygen in their DNA with sulfur. What's even more common is sulfur itself losing its spot to selenium in particular proteins.

However, Bains and Schulze-Makuch stress that the swapping that scientists have observed in Earth's biology is only occasional. None of these organisms could survive a complete substitution. As a matter of fact, experiments have shown that replacing hydrogen with its isotope deuterium will sicken a microbe and even kill a larger animal. This is somewhat surprising since deuterium has essentially the same chemical properties as hydrogen.

"Any switching of elements has got to be accompanied with major changes in everything else," Benner says.

So if you plan to dream up your own hypothetical biochemistry, you are going to need to start from scratch and show how your elemental ingredients can come together to make a diverse set of large molecules that evolution can play with.

"We should be very open-minded when we only know of one kind of life," says Schulze-Makuch. "Let's not check anything off the list yet."

Life in meteorites? Study stirs debate

A field-emission scanning electron micrograph shows one of the filaments that was found in the Ivuna CI1 carbonaceous meteorite. The image includes labels for data about elemental composition. The bar at lower left shows the 1-micron scale. The filament looks similar to those seen in earthly cyanobacteria.

By Alan Boyle

Are there traces of ancient bacteria trapped inside meteorites that fell to Earth decades ago? You can add that question to the list of unresolved issues surrounding the search for life beyond Earth, thanks to a just-published study by a NASA researcher.

The new study, published in the Journal of Cosmology, focuses on structures that look like the filaments that biologists typically see on micro-organisms known as cyanobacteria. Richard Hoover, an astrobiologist at NASA's Marshall Space Flight Center in Alabama, found the filamentary structures inside samples of meteorites that are thought to date back to the solar system's beginnings, more than 4 billion years ago.

If the structures are confirmed to be of biological but unearthly origin, that would serve as fresh evidence that life can make its way through outer space and "seed" planets, including our own, Hoover told me today.

"Life may have a wider planetary distribution than simply being limited to the planet Earth," he said. In the paper, Hoover said the evidence suggests that microbial life could well exist on comets or icy worlds such as Europa or Enceladus.

Most astrobiologists might be willing to go along with that broad conclusion. However, Hoover's specific claims could well end up in the same sort of limbo that surrounds the claims made 15 years ago about microfossils inside a meteorite from Mars.

The initial evidence was the subject of dramatic news conferences and huge headlines, but as time went on, doubts about the findings grew. Today, few astrobiologists see the Mars meteorite as containing any conclusive evidence for the existence of past or present Martian life.

Cautious and skeptical reactions
"This may turn out to be another one of those cases where it's controversial but remains unproven," Seth Shostak, senior astronomer at the California-based SETI Institute, told me today.

Shostak said Hoover's findings would be "important, if true." But he noted that the research paper relied on a highly technical interpretation of electron microscope images and chemical analyses. "Is it true? I'm not qualified to say that," Shostak said.

The Journal of Cosmology's editor-in-chief, Rudy Schild of the Harvard-Smithsonian Center for Astrophysics, said in a note accompanying Hoover's study that 100 experts were invited to critique the research, and that any commentaries would be published beginning Monday. The overall tone of the commentaries is likely to be skeptical: Lynn Rothschild, an astrobiologist at NASA's Ames Research Center in California, said many biologists were "very concerned" about the claims.

More than one expert wondered why the research merited any news coverage at all.

"Many scientists have examined thousands of meteorites in detail over the past 50 years without finding any evidence of fossil life," David Morrison, senior scientist at the NASA Astrobiology Institute at Ames Research Center, told me in an e-mail. "Further, we know a great deal about the conditions on the parent objects of the meteorites, which (not counting the few meteorites from the moon and Mars) were rather small, not at all like planets.

"I would therefore invoke Carl Sagan's famous advice that extraordinary claims require extraordinary evidence. At a bare minimum this would require publication in a prestigious peer-refereed scientific journal — which this is not. Cyanobacteria on a small airless world sounds like a joke. Perhaps the publication came out too soon; more appropriate would have been on April 1," Morrison said.

Questions about origin
The debate over the validity of Hoover's claims is likely to concentrate over whether the filamentary structures are truly biological in origin, and if so, whether they're the result of earthly contamination.

Hoover said that the filaments, which can measure more than 20 microns long, are of the right size and shape to match the characteristic structures seen in types of cyanobacteria.

"Because of the fact that they are so large and so complex, and many of them have specialized cells, these cyanobacteria can be identified — sometimes to genus and species — just on the basis of certain specialzed cells," he explained. One of the structures found in the meteorites is similar to that seen in the giant bacterium known as Titanospirillum velox, for example.

If the structures are so similar to those seen in earthly organisms, could that be because they're actually the traces of cyanobacteria that found their way into the meteorite? Hoover argues that they're not the result of contamination. He said that cyanobacteria are generally found in aquatic environments, but the meteorites are made of stuff that falls apart when exposed to liquid water. He also said chemical tests on the filaments could find no evidence of nitrogen, which should have been present if earthly cyanobacteria infiltrated the meteorites. One of the meteorites, for example, is known to have fallen to Earth in France in 1864.

"The inability to detect nitrogen in the filaments indicates that they are ancient, and since the meteorite came to Earth in 1864, that indicates that they were in the meteorite when it fell," Hoover said.

Previous analyses of the meteorites' chemical composition have concluded that they were formed during the solar system's earliest epoch, perhaps as comets. But Hoover said that doesn't necessarily mean the structures were present from the very beginning. They could have been picked up from debris that was knocked into space by cosmic impacts. They could even have come from Earth itself, as the result of a meteor blast that occurred millions or billions of years ago.

"That's absolutely possible," Hoover acknowledged. "I have no reason to say I could rule that out."

Hoover has made provocative claims before, and he fully expects that others will contest his conclusions this time as well. "I can only make my observations, based on the scientific results that I see," he told me.

What do you think? Is this a significant advance for the study of life beyond Earth, or a blip hardly worth writing about? Feel free to weigh in with your comments below.

Update for 6 p.m. ET: Rocco Mancinelli, senior research scientist at the Bay Area Environmental Research Institute, weighed in with this e-mailed critique of Hoover's paper:

"As a microbiologist who has looked at thousands of microbes through a microscope, and done some of my own electron microscopy, I see no convincing evidence that these particles are of biological origin.  

"The techniques used may not have been appropriate for these types of analyses. It is stated that the implements were flame-sterilized, with no details of how this was performed.  Were the implements placed in the flame of a Bunsen burner? If so, sometimes soot can get on them at the microscopic level. The usual procedure for flame sterilization is to dip the implements in ethanol then burn the ethanol off. Yet, these would be inappropriate for this type of analysis. You need to have everything clean and then bake at 550 degrees C overnight.  These missing details would cause me to question not just about the photos, but the elemental analyses as well.  I am also disturbed about the lack of nitrogen. There should be more. There are many technical flaws in this paper."