sábado, 8 de enero de 2011

Desentrañan un efecto que condiciona toda la química de los azúcares

“No había dudas sobre la existencia del efecto anomérico, pero nunca se había podido caracterizar”, explica Emilio J. Cocinero, investigador de la Universidad del País Vasco/Euskal Herriko Unibertsitatea (UPV/EHU) . Este profesor del Departamento de Química Física, en colaboración con la Universidad de Oxford, ha conseguido, por primera vez aislarlo y medirlo. El resultado de la investigación se publica en la revista Nature, en el artículo titulado ‘Sensing the anomeric effect in a solvent-free environment’.

UPV/EHU

País Vasco

05.01.2011 19:00

Emilio J. Cocinero. Imagen UPV/EHU

Las moléculas que forman los seres vivos, las biomoléculas, se dividen en cuatro grandes familias: proteínas, lípidos, ácidos nucleicos y los glúcidos o azúcares, que son los encargados de suministrar la energía al organismo. Toda la química de los azúcares se ve afectada por el efecto anomérico, que juega un papel clave en la estabilización de los mismos.

Este efecto se identificó en 1955 pero, a pesar de su importancia tanto en química como en biología, su origen físico continúa sin estar claro y un análisis pormenorizado de dicho efecto todavía no había sido posible. En su investigación Cocinero ha conseguido medir, por primera vez, el grado de influencia del efecto anomérico en un azúcar y ha probado que, al contrario de lo que se pensaba hasta ahora, el efecto anomérico exo predomina sobre el endo.

La investigación codirigida por Cocinero se llevó a cabo mediante la unión de un azúcar y un pequeño péptido como modelo del sistema glúcido-proteína presente en los seres vivos. “La investigación se hizo en fase gas y en este medio podemos estudiar y analizar las propiedades que son intrínsecas del azúcar”, explica el investigador, que se doctoró en Química por la Universidad de Valladolid.

Para llevar a cabo este estudio se utilizó una combinación de espectroscopia láser y análisis computacional. “Los resultados sugieren que será importante reevaluar la influencia del efecto anomérico tanto en química como en biología, ya que está presente en la mayoría de los azúcares y altera las proporciones de estos en la naturaleza”. También puede ayudar a esclarecer por qué el organismo selecciona unos determinados azúcares a pesar de que haya otros más abundantes en la naturaleza.

Emilio J. Cocinero se incorporó a la UPV/EHU en 2009, tras una estancia de tres años en la Universidad de Oxford, centro con el que sigue colaborando. “En nuestras investigaciones estudiamos “los ladrillos”, las unidades más básicas que forman estas biomoléculas, que a pesar de su importancia no se comprenden totalmente.

Empezamos caracterizando azúcares aislados, para posteriormente ir añadiendo complejidad a los sistemas de estudio, con disacáridos, azúcares de tres unidades… A continuación investigamos la influencia del disolvente en los azúcares, estudiando el efecto del agua en varios de ellos. Nuestro objetivo es ir hacia el estudio de sistemas cada vez más complejos que den una visión más real de lo que pasa en nuestro organismo”.

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Referencia bibliográfica:

Emilio J. Cocinero, Pierre Çarçabal, Timothy D. Vaden, John P. Simons y Benjamin G. Davis. "Sensing the anomeric effect in a solvent-free environment". Nature, 6 de enero de 2011 (doi:10.1038/nature09693).

Fuente: UPV/EHU

Las lágrimas envían señales químicas que reducen el deseo sexual del hombre

El estudio se publica en el último número de la revista 'Science'

Las lágrimas envían señales químicas que reducen el deseo sexual del hombre

Las lágrimas que derraman las mujeres cuando estan tristes podrían transmitir una señal química que reduce los niveles de testosterona y excitación sexual en los hombres, según un nuevo estudio del Instituto Weizmann de Ciencias (Israel).

SINC

Asia

06.01.2011 20:00

Los hombres que olieron las lágrimas fueron más proclives a considerar a mujeres en fotografías menos atractivas sexualmente que aquellos que olieron una solución salina. Foto: Lara Danielle.

Investigadores del Instituto Weizmann de Ciencias, liderados por la científica Shani Gelstein, sugieren que las lágrimas de las mujeres podrían contener una señal química que reduce los niveles de testosterona y excitación sexual en los hombres.

“La importancia funcional de este tipo de lágrimas, que creemos que son únicamente humanas, han desconcertado a biólogos durante años. En ratones, las lágrimas contienen compuestos químicos específicos que transmiten señales a otros ratones que las ‘huelen’”, explican los expertos.

Para el estudio, que publica la revista Science, los investigadores recogieron las lágrimas de mujeres que lloraron con una película triste, junto con una solución salina y se las expusieron a un grupo voluntario de varones para que oliera dichas gotas y posteriormente observara fotografías de mujeres.

Las ‘quimioseñales’ de las lágrimas disminuyen la atracción sexual

“Los hombres manifestaron que las lágrimas no tenían olor. Sin embargo, los hombres que olieron las lágrimas fueron más proclives a considerar a mujeres en fotografías menos atractivas sexualmente que aquellos que olieron la solución salina”, aseguran los expertos.

El experimento fue doblemente oculto, es decir, ni los hombres ni el investigador que entregó los líquidos sabía si estaban recibiendo lágrimas o solución salina.

“Los varones que olieron las lágrimas también experimentaron bajadas en sus niveles de excitación fisiológica y testosterona salival. Además, los que olieron las lágrimas y luego vieron una película triste dentro de una máquina de imágenes por resonancia magnética funcional mostraron menos actividad en las partes del cerebro típicamente asociadas con excitación sexual”, apunta el estudio.

Pese a que el estudio no investiga las lágrimas recolectadas de hombres, los investigadores especulan que las lágrimas de varones (y posiblemente las lágrimas de niños) podrían contener quimioseñales similares.

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Referencia bibliográfica:

S. Gelstein; Y. Yeshurun; L. Rozenkrantz; S. Shushan; I. Frumin; N. Sobel. "Human Tears Contain a Chemosignal", Science, enero de 2011 10.1126/science.1198331.

Fuente: SINC

Dificultades para diferenciar depresión y alzhéimer incipiente

Científicos de la Universidad de Salamanca y del Hospital Universitario han llevado a cabo un estudio clínico para mejorar los diagnósticos de pacientes con alzhéimer incipiente y depresión a través de pruebas de memoria episódica no verbal. La investigación constató que estas herramientas eran eficaces a la hora de distinguir a las personas con estas patologías de las que no las tienen, pero confirmó también la dificultad que existe para distinguir a los pacientes que tienen alzhéimer de los que tienen depresión, puesto que en este último caso también existen funciones cognitivas como la memoria que se ven afectadas.

DICYT

Castilla y León

07.01.2011 17:48

Personas con demencias realizan dibujos (Foto: DiCYT).

Todo ello ha quedado plasmado en un artículo publicado recientemente en la revista científica Applied Neuropsychology. "Intentamos probar, en Atención Especializada, cómo funcionaban ciertas tareas de memoria para diferenciar pacientes con enfermedad de alzhéimer temprana y los que tenían depresión", explica a DiCYT Israel Contador, experto de la Facultad de Psicología y uno de los autores del artículo. "Intentamos ver si esas pruebas nos permitían discriminar entre estos dos grupos a través de un tipo de tareas de memoria no verbal, asociada a dibujos o diseños pictóricos", señala.

La memoria episódica es uno de los indicadores más precoces de alzhéimer, según los especialistas, ya que esta información se almacena en estructuras del lóbulo temporal medial, concretamente en el hipocampo, que se ven afectadas desde las fases más tempranas de la enfermedad. "En el estudio se intentó contrastar la eficacia de las tareas de memoria episódica de tipo no verbal, a través de estímulos visuales complejos y poco familiares para el sujeto, como las letras alfabeto chino, para diferenciar entra un grupo de pacientes con alzhéimer incipiente y otro grupo con depresión mayor unipolar", comenta Israel Contador.

"A diferencia de otras tareas basadas en el recuerdo de palabras, estas pruebas están menos mediadas por procesos lingüísticos, en los que interviene el hemisferio izquierdo, y parecen menos influidas por las variables socio-demográficas, como la edad y escolaridad de los sujetos", indica.

Perfiles diferentes

La investigación contó con la participación de varias decenas de sujetos (30 controles, 27 con enfermedad de Alzheimer y 19 con depresión). Los resultados fueron eficaces para detectar pacientes con alzhéimer incipiente, pero algunas dificultades para diferenciar este grupo y que sufre depresión. "Esto plantea la necesidad de seguir investigando en el perfil neuropsicológico diferencial de éstos pacientes con alzhéimer y depresión, uno de los retos actuales en el ámbito clínico", asegura el científico.

La clave del problema está en que muchas veces la depresión viene acompañada de deterioro cognitivo y la memoria se ve afectada. "La depresión afecta significativamente al rendimiento cognitivo de las personas, pero las pruebas sí fueron buenas para discriminar a las personas con alzhéimer incipiente de las normales", apunta.

Por eso, considera que merece la pena profundizar en este tipo de pruebas que pueden ayudar a detectar en fases más tempranas los posibles casos de alzhéimer y otras demencias. Se trata de presentarle al sujeto "diseños no verbalizables", por ejemplo, colocación de objetos en un determinado espacio o recordar figuras como letras chinas. "Las pruebas que se utilizan habitualmente son de memoria verbal, pero nosotros intentamos abrir el campo para averiguar cosas nuevas del funcionamiento de la memoria", comenta.

Dibujos y palabras

"Los mecanismos neurocognitivos son diferentes entre palabras y dibujos", según Israel Contador. La memoria episódica de las palabras comprende sobre todo la actividad de ciertas estructuras cerebrales como el lóbulo temporal. Esto también ocurre con los dibujos, pero a diferencia de las palabras, resultan difícilmente codificables.

Una ventaja del uso de pruebas de memoria no verbal es que, en teoría, podrían servir para diagnosticar a todo tipo de personas, sin que influya su educación o su cultura, algo que sí puede suceder con las pruebas verbales. "Intentamos que estas pruebas de memoria no verbal se puedan aplicar para todos los niveles educativos y culturales, aunque también hay estudios que denotan que están influidas por la cultura", reconoce.

Fuente: DICYT

Nosing into the emerging national parks of China's Yunnan province

They're as yet largely undeveloped and typically toured by bus, but that doesn't stop one determined hiker.

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Nearly 8,000 members of the Lisu ethnic group, including this family, live inside Laojunshan. (Mike Ives)

By Mike IvesSpecial to the Los Angeles Times

January 9, 2011

Reporting from Yunnan province, China —

One spring morning last year, I stuffed my rucksack with things I bring on camping trips in the U.S.: fleece, books 'n' socks, toothbrush, bug spray, sunshades. Then I shouldered my mandolin case, unlatched my apartment gate and stepped into the sunshine.

I suspected this trip would be a bit different from my previous trips to American national parks. OK, a lot different: I live in Hanoi, and I was heading to fledgling national parks in southwestern China.

My first challenge was getting to the parks on a shoestring budget — that is, without flying. A sultry overnight train ride left me at the Vietnam-China border. From there I hopped an all-day bus to Kunming, the capital of Yunnan province. During the next two weeks, I would spend more than 30 hours riding more buses and minibuses.

Then there was the question of what to do. In 2008, China's State Forestry Administration declared Yunnan, a biodiverse area bordering Vietnam, Laos, Myanmar and Tibet, a demonstration area for the country's first national parks. And in 2009, an official at the Yunnan National Park Management Office told me that five of province's planned 12 or 13 parks were drafting development plans.

Several U.S. and Chinese conservation experts say these aren't national parks in the American sense, partly because China doesn't have the equivalent of a National Park Service. The Yunnan government has embraced the national park concept, noting in a 2009 memorandum, "Establishing national parks is an important measure for Yunnan government to build the good image of ecological conservation."

Westerners wouldn't know, because for all its enthusiasm for "national parks" the Yunnan government isn't aggressively marketing them to English-speaking tourists.

Before hitting the trail in Yunnan last April, I met with Yue Wang, acting director of the Yunnan program at the Nature Conservancy China, which reportedly introduced the "national park" concept to Yunnan officials in the late 1990s.

"Which of these national parks do Chinese hikers like?" I asked the conservation policy expert. We were sipping Pu'er in a posh Kunming tea garden. Wang, who wore a white blouse and a red skirt, considered my ripped jeans and dusty rucksack. Then she laughed.

"For now," she said, "Chinese tourists don't travel like you, carrying a backpack into the mountains and going camping. A very small group of Chinese people are doing that, but most of them are just getting on buses and going to overlooks."

Into thinner air

Despite Yue Wang's advisory, I was determined to do some Thoreau-style exploring.

A few days and minibus rides after my Kunming orientation, I landed in Shangri-La (a.k.a. Zhongdian), a city in northwest Yunnan that Chinese officials claim is the actual fictional setting of James Hilton's 1933 novel, "Lost Horizon." From Zhongdian, I planned to visit a protected area that the Nature Conservancy reports is slated to become the beautiful-sounding Meili Snow Mountain National Park.

Yue Wang had said that when visiting Meili, I should be flexible — no one knew when local officials would close a crucial access road for construction. In Zhongdian, a travel agent said Meili-bound travelers could be stranded in Diqing, the nearest city, for as long as 10 days.

I couldn't risk that delay, so I opted for Plan B: Pudacuo National Park. Yue Wang had cautioned me that the 4-year-old protected area, one hour by minibus from Zhongdian, feels more like a city park. But I figured that any park so close to Tibet was bound to be some shade of spectacular.

The road to Pudacuo was flanked by boxy Tibetan-style houses, and the roadside fields were crawling with yaks. As my minibus climbed above 8,000 feet, sunlight graced the snow-capped Henduan Mountains, and the air rushing through my window felt crisp and cold.

I was riding with a friendly Taiwanese couple whose new hiking boots and breathable jackets suggested a commitment to outdoorsiness. When the minibus stopped at Pudacuo's visitor center, I followed them inside, hoping they would lead me to good hiking trails.

But after we each paid $27 in park fees, a man in a suit directed us to an "environment shuttle bus." Boarding it, I saw a dozen more smartly dressed hikers — none of whom, apparently, preferred to walk. Celine Dion was crooning in surround-sound.

As the bus rolled through the park, we saw alpine hillsides, fluttering Tibetan prayer flags, crumbly thatch huts and real-live subsistence farmers. "It's like the movies," my new Taiwanese friends said. Soon a park representative was lecturing us via onboard microphone. Cameras clicked.

This place is a bit city-park-ish, I thought. Scenery aside, I felt like a Midwesterner cruising Manhattan on a double-decker.

They're as yet largely undeveloped and typically toured by bus, but that doesn't stop one determined hiker.

Finally the bus stopped at an alpine lake that reminded me of landscapes in Montana's Glacier National Park. But after 20 minutes of turtle-slow progress on a lakeside boardwalk, our group leader crouched down for an extended photo shoot.

"What gives?" I asked.

"A wild animal," someone whispered in English.

The animal's name translated to "many colored mouse" — a.k.a. chipmunk. More photography. A woman from the mega-city Shenzhen approached me with a bag of sunflower seeds.

"Would you like to feed him?" she asked.

"No, thanks," I said. I was ready to visit a different park.

Field of beans

Busing south from Zhongdian, I watched snow-capped peaks fade into rice paddies. A four-hour minibus ride brought me to Lijiang, a popular urban destination for Chinese and Western tourists. In the morning I caught a minibus that puttered west from the Lijiang bus station.

Backpackers who visit Lijiang typically hike the nearby Tiger Leaping Gorge, but I was going to a protected area called Laojunshan National Park, a hiking spot that wasn't listed in my guidebook.

The minibus struggled up winding roads, showing vistas of terraced farms and mountain streams. By lunchtime I was walking through Liming, a one-horse town with a national park-style visitor center. The park, a 419-square-mile,UNESCO-recognized area of rolling forests and red sandstone formations, suggested a lusher version of Utah's Arches National Park.

Established in 2007, Laojunshan National Park may be China's next great eco-tourism destination. In partnership with the Nature Conservancy China, the Kunming Mountain Expedition Assn. helps design the park's hiking trails, and the American nonprofit Global Parks has sent retired U.S. National Park Service professionals here to help design interpretive systems.

Although Laojunshan may eventually acquire a sleek network of hiking trails and interpretive signs, it still feels wild.

On my second day in the park, an English-speaking guide took me walking for four hours on a dusty access road. The only beverage he drank was beer. There were no trailheads or signposts, and none of the Lisu farmers we met — nearly 8,000 members of that ethnic group reside inside Laojunshan's borders — knew they lived in a nascent national park.

Around dusk, we reached a no-frills Lisu hut overlooking a sun-drenched bean field. Wood smoke was pushing through cracks in the roof. Once my guide and I were settled by the cooking fire, our hosts handed us chopsticks and insisted that we spend the night.

When they fed us homegrown beans, I thought of the bean field Thoreau wrote about in "Walden." I reflected that if the 19th century essayist were still alive, this protected area — with its friendly farmers, sublime vistas and lack of signage — would make a great backup muse.

Chang to the rescue

A natural park with undeveloped infrastructure can also be dangerous. On my fourth afternoon in Laojunshan, I found myself standing on a cliff with my friend Alyssa. She had bused in from Lijiang the previous afternoon. All day we had blissfully rambled along a sandstone ridgeline, but now we were famished, and all we had to eat were soy nuts and chocolate.

The night before, a Lisu villager named Chang Zhen Hu had offered us beds in his makeshift guestroom. But now it was almost dark, we couldn't see any huts, we were sunburned and dehydrated, and Alyssa felt lightheaded.

We backtracked until we reached Chang's simple hut. Chickens and pigs were running around the yard, but there was no sign of our ex-host. We weren't sure if he was home, or if he would shelter us again.

Then he emerged from the woods, wearing a green jacket with yellow stripes. "If you try to walk back to Liming now, it'll be night when you arrive," Chang told Alyssa in Chinese. "So stay."

Chang and his family had eaten, but his wife offered to cook us dinner. As she fried pork gristle over a wood fire, Alyssa went to lie down, Chang fed his chickens, and I tuned my mandolin.

Sitting on a wooden bench, I imagined I was back in Glacier or Arches. Hiking in China was nothing like hiking in America, I thought, but the basic idea was the same: Take a walk, share a meal and sing a few songs.

I sang the first one that seemed apropos:

"My ol' hen, she's a good ol' hen

"But she ain't laid an egg since I don't know when

"Old hen cacklin', cacklin' a lot

"Next time she cackles, gonna cackle in the pot."

Chang Zhen Hu sat down to listen. He grinned, and I think I saw him tap a foot. He couldn't have understood the lyrics, but when I finished the tune and put down my instrument, he placed it back in my hands and smiled.

Dinner was still cookin', so I sang him another.

travel@latimes.com

Gabrielle Giffords shooting stirs outpouring of concern and support

Leaders react to the shooting of the Arizona congresswoman. Obama: 'We are going to get to the bottom of this, and we're going to get through this.'

By Rong-Gong Lin II, Los Angeles Times

January 8, 2011, 4:37 p.m.

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In the hours after Arizona Rep. Gabrielle Giffords and several others were shot in Tucson Saturday, politicians across the country, including President Obama, Sarah Palin and John McCain, offered sympathies to the victims.

An excerpt of the remarks:

President Obama — "Gabby Giffords was a friend of mine. She is not only an extraordinary public servant, but she is also somebody who is warm and caring. She is well liked by her colleagues and well liked by her constituents. Her husband,Mark Kelly, is a Navy captain and one of America's valiant astronauts.

"It's not surprising that today Gabby was doing what she always does — listening to the hopes and concerns of her neighbors. That is the essence of what our democracy is all about. That is why this is more than a tragedy for those involved. It is a tragedy for Arizona and a tragedy for our entire country.

"What Americans do at times of tragedy is to come together and support each other. So at this time I ask all Americans to join me and Michelle in keeping all the victims and their families, including Gabby, in our thoughts and prayers. Those who have been injured, we are rooting for them. And I know Gabby is as tough as they come, and I am hopeful that she's going to pull through.

"Obviously our hearts go out to the family members of those who have been slain. We are going to get to the bottom of this, and we're going to get through this. But in the meantime, I think all of us need to make sure that we're offering our thoughts and prayers to those concerned."

Sarah Palin — "My sincere condolences are offered to the family of Rep. Gabrielle Giffords and the other victims of today's tragic shooting in Arizona. On behalf of Todd and my family, we all pray for the victims and their families, and for peace and justice."

Janet Napolitano, Secretary of Homeland Security: "I am deeply saddened by reports that Congresswoman Gabrielle Giffords, Chief Judge John Roll and others were attacked this afternoon in Tucson, Ariz. There is no place in our society or discourse for such senseless and unconscionable acts of violence. Gabby is a steadfast representative for southern Arizona and both she and John are dedicated public servants."

Sen. John McCain (R-Ariz): "I am horrified by the violent attack on Rep. Gabrielle Giffords and many other innocent people by a wicked person who has no sense of justice or compassion. I pray for Gabby and the other victims, and for the repose of the souls of the dead and comfort for their families. I beg our loving Creator to spare the lives of those who are still alive, heal them in body and spirit, and return them to their loved ones.

"Whoever did this; whatever their reason, they are a disgrace to Arizona, this country and the human race, and they deserve and will receive the contempt of all decent people and the strongest punishment of the law."

House Speaker John A. Boehner (R- Ohio): "I am horrified by the senseless attack on Congresswoman Gabrielle Giffords and members of her staff. An attack on one who serves is an attack on all who serve. Acts and threats of violence against public officials have no place in our society. Our prayers are with Congresswoman Giffords, her staff, all who were injured, and their families. This is a sad day for our country."

House Minority Leader Nancy Pelosi (D- San Francisco): "Our prayers and thoughts are will all of them. ... Congresswoman Giffords is a great patriotic American."

Arizona Gov. Jan Brewer: "I am just heartbroken. Gabby is more than just a colleague, she's actually a friend. She's always been a noble public servant."

Sen. Jon Kyl (R-Ariz.): "Caryll and I send our most heartfelt condolences to the family of Judge John Roll and the others who were killed and injured today in Tucson. Judge Roll, who presided over the federal District Court in Arizona, was an exceptional judge and a good friend.

"We pray for the recovery of Rep. Giffords and the others who remain in critical condition. Congresswoman Giffords is also a good friend, and I find it especially saddening that such a heinous crime would occur while she was fulfilling her congressional responsibilities.

"All of us will work to ensure that justice will be served fully and swiftly."

The Associated Press contributed to this report.