A look at the Supreme Court decisions this term reveals that corporations don't always win, employees don't always lose, and Antonin Scalia and Clarence Thomas don't always agree.

U.S.MARCH 23, 2011

Mural of Maine’s Workers Becomes Political Target

By STEVEN GREENHOUSE

Gov. Paul LePage has opened a new — and unlikely — front in the battle between some lawmakers and unions: a 36-foot-wide mural in the state’s Department of Labor building in Augusta.

OPINIONMARCH 23, 2011

Townies: My Dog Days Are Over

By DOREE SHAFRIR

My dog was always there for me, and then I was there for her in her last days.

SCIENCEMARCH 25, 2011

Tools Suggest Earlier Human Arrival in America

By JOHN NOBLE WILFORD

Researchers say the tools may be as old as 15,500 years, retiring a hypothesis that the so-called Clovis people arrived first.

10.

MOVIESMARCH 24, 2011

Elizabeth Taylor, 1932-2011: A Lustrous Pinnacle of Hollywood Glamour

By MEL GUSSOW

Elizabeth Taylor, whose name was synonymous with Hollywood glamour, dazzled generations of moviegoers with her beauty.

11.

HOME & GARDENMARCH 24, 2011

In the Garden: Heirloom Seeds or Flinty Hybrids?

By MICHAEL TORTORELLO

Business is booming in heirloom seeds. But for backyard gardeners, are they actually better than hybrids?

12.

TECHNOLOGYMARCH 24, 2011

State of the Art: Portable, but Not Puny, Speakers

By DAVID POGUE

Portable wireless speakers connect to your phone, tablet or laptop and set free the formerly muted music in your collection, from Basie to Bieber.

13.

U.S.MARCH 24, 2011

Once Rare in Rural America, Divorce Is Changing the Face of Its Families

By SABRINA TAVERNISE and ROBERT GEBELOFF

Forty years ago, divorced people were more concentrated in cities and suburbs. But now, for the first time, rural Americans are just as likely to be divorced as city dwellers.

14.

BUSINESS DAYMARCH 25, 2011

But Nobody Pays That: G.E.’s Strategies Let It Avoid Taxes Altogether

By DAVID KOCIENIEWSKI

General Electric is skilled at avoiding taxes, lately to the extent that the Treasury owes the company money.

15.

WORLDMARCH 24, 2011

Drug Wars Push Deeper Into Central America

By RANDAL C. ARCHIBOLD and DAMIEN CAVE

Aggressive crackdowns on criminal organizations in Mexico and Colombia have increasingly brought the powerful drug syndicates into Central America.

16.

EDUCATIONMARCH 22, 2011

For Law Students With Everything, Dog Therapy for Stress

By TIMOTHY WILLIAMS

For three days, a pup named Monty will be available for Yale law students to check out of the library for half-hour “stress-therapy” sessions.

17.

OPINIONMARCH 24, 2011

Op-Ed Contributor: A Digital Library Better Than Google’s

By ROBERT DARNTON

Don’t let a for-profit company monopolize knowledge. Create a public — and free — online collection of our books.

18.

WORLDMARCH 24, 2011

Shady Dealings Helped Qaddafi Build Fortune and Regime

By ERIC LICHTBLAU, DAVID ROHDE and JAMES RISEN

Since the United States reopened trade with Col. Muammar el-Qaddafi’s government in 2004, businesses have witnessed a Libyan culture rife with kickbacks, strong-arm tactics and political patronage.

19.

TECHNOLOGYMARCH 24, 2011

Swiping Is the Easy Part

By TARA SIEGEL BERNARD and CLAIRE CAIN MILLER

With cellphones ready to act as credit cards, banks, carriers and card issuers are fighting for control.

20.

HEALTHMARCH 23, 2011

The New Old Age: Simple Rules for Better Sleep

By PAULA SPAN

Observing four easy guidelines helps older people get more sleep, a new study finds.

21.

HEALTHMARCH 24, 2011

Recipes for Health: Carrot and Leek Frittata With Tarragon

By MARTHA ROSE SHULMAN

Tarragon brings a hint of sweetness to this frittata.

22.

OPINIONMARCH 23, 2011

Thomas L. Friedman: Tribes With Flags

By THOMAS L. FRIEDMAN

Are the new revolutions brewing in the Arab world democracy movements, or are they civil wars?

23.

U.S.MARCH 25, 2011

In a Southern California Suburb, Layoffs for Nearly Half the Staff

By JENNIFER MEDINA

Officials in Costa Mesa say they are just trying to solve a budget problem, but some see a political motive.

24.

WORLDMARCH 24, 2011

News Analysis: Germany Steps Away From European Unity

By STEVEN ERLANGER and JUDY DEMPSEY

Chancellor Angela Merkel has raised questions about Germany’s ability to play a global role in foreign policy.

25.

OPINIONMARCH 24, 2011

Op-Ed Contributor: It Could Happen Here

By FRANK N. VON HIPPEL

The Fukushima crisis provides a chance to reform America’s nuclear power regulations.

Los científicos logran crear espermatozoides en el laboratorio

Los científicos logran crear espermatozoides en el laboratorio
Investigadores de la Universidad de la Ciudad de Yokohama (Japón) han conseguido producir espermatozoides en laboratorio, un hito científico que los biólogos de la reproducción perseguían desde el origen de los tratamientos de reproducción asistida en los años 70. El avance, presentado en la revista científica Nature, abre una vía de esperanza para el tratamiento de la infertilidad masculina.
FUENTE \| La Vanguardia Digital	24/03/2011

Por ahora, la investigación se ha realizado en ratones, por lo que la producción de espermatozoides en laboratorio aún no puede ofrecerse a hombres infértiles. Pero el equipo de Yokohama ya ha comprobado que la técnica que han desarrollado produce espermatozoides funcionales. Y que las crías concebidas con estos espermatozoides crecen con normalidad, sin problemas de salud aparentes, y que son fértiles al llegar a adultas.

"Necesitamos extender nuestros métodos a otras especies, incluida la humana, antes de poder aplicar estos resultados al tratamiento de personas", ha declarado por correo electrónico Takehiko Ogawa, director de la investigación. Aunque es posible que la técnica exacta que ha permitido obtener espermatozoides de ratón en laboratorio no sea efectiva en otras especies, admite Ogawa, "confío en que podremos lograrlo con alguna modificación del medio de cultivo".

Producir espermatozoides es "uno de los procesos más largos y complejos (...) que tienen lugar en el cuerpo", escriben los investigadores en Nature. Se trata de un proceso que pasa por varias etapas y que, en el cuerpo humano, requiere más de un mes.

Para reproducirlo en el laboratorio, Ogawa y su equipo extirparon minúsculos fragmentos de testículos de ratones de menos de tres días de edad. "Nos bastan fragmentos muy pequeños, de menos de un miligramo", ha explicado Ogawa. Recurrieron a ratones tan jóvenes porque la producción de células precursoras de espermatozoides se inicia pocos días después de nacer y los investigadores querían asegurarse de que podían realizar todo el proceso en el laboratorio.

Situaron el tejido extirpado en un medio de cultivo a 34 grados, la temperatura óptima para el crecimiento de espermatozoides de ratón. Dos detalles técnicos facilitaron el éxito del experimento. Uno es que colocaron el tejido de manera que una parte estuviera en contacto con un medio de cultivo líquido y otra parte, en contacto con el aire; el líquido le aportó los nutrientes necesarios para que vivieran las células y el aire le permitió el intercambio de gases necesario para la espermatogénesis.

El segundo detalle es que, tras un primer intento fallido, añadieron una proteína llamada KSR al medio de cultivo. Esta proteína se había empleado anteriormente en investigaciones de células madre. En este caso, permitió obtener espermatozoides maduros, dotados de una cola móvil, tras cultivar el tejido en el laboratorio entre 27 y 45 días.

Los investigadores mantuvieron el experimento en curso durante unas semanas más para averiguar si el tejido que habían utilizado se agotaba tras haber producido su primera hornada de espermatozoides o bien seguía produciendo células sin cesar como ocurre en un ser vivo. Según los resultados presentados en Nature, "nuestro sistema de cultivo ha sido capaz de inducir y mantener la espermatogénesis durante más de dos meses".

Llegados a este punto, faltaba demostrar que los espermatozoides obtenidos con esta técnica pudieran utilizarse para fertilizar óvulos y que fueran capaces de engendrar crías sanas. Entraban en la fase decisiva de la investigación. Si no nacían crías, o no nacían sanas, habría que renunciar a utilizar la técnica para tratar la infertilidad en personas.

Los investigadores recuperaron algunos de los espermátides y espermatozoides que habían obtenido en laboratorio y con ellos intentaron fertilizar 58 óvulos in vitro. Los espermátides son células precursoras de los espermatozoides y son igualmente útiles para la fecundación in vitro, ya que tienen el mismo número de cromosomas, aunque deben manipularse de manera diferente. Los embriones obtenidos se implantaron en hembras. Según los resultados del experimento, la tasa de nacimiento fue algo más alta con espermátides que con espermatozoides. En total, nacieron cuatro machos y ocho hembras.

Un sus primeros días de vida, aún no estaba claro si estas crías estaban sanas o si iban a ser enfermizas. Los investigadores dejaron que crecieran hasta llegar a la edad de reproducción y, durante su crecimiento, no apreciaron que tuvieran ningún problema relevante de salud. Para comprobar si eran fértiles, dejaron que se aparearan entre ellas. Los doce ratones concebidos con espermatozoides de laboratorio resultaron ser fértiles.

Finalmente, con el objetivo de aplicar esta técnica a pacientes infértiles en el futuro, los investigadores estudiaron si podían congelar el tejido en nitrógeno líquido y después repetir el experimento con éxito. Este es un requisito imprescindible para que la técnica pueda ofrecerse a niños que corren el riesgo de quedar infértiles a causa del tratamiento que reciben por un cáncer. En estos casos, sería preciso extirpar tejido testicular antes del tratamiento, conservarlo en nitrógeno líquido y descongelarlo cuando el paciente quisiera tener hijos años más tarde.

El experimento mostró que, incluso tras la congelación con nitrógeno líquido, el tejido testicular conserva la capacidad de producir espermatozoides en el laboratorio. Estos resultados, concluyen los investigadores, "contribuirán a desarrollar nuevas técnicas de diagnóstico y de tratamiento para la infertilidad masculina".

Autor: Josep Corbella

salud

DOCTOR AND PATIENT

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Why patients can relax if they see a young doctor-in-training following their gurney into the operating room.

VITAL SIGNS

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Anxiety Up as Tokyo Issues Warning on Its Tap Water

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Under a new law, women seeking abortions in South Dakota must go to consultations at “pregnancy help centers” like the Alpha Center in Sioux Falls.

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South Dakota became the first state to require all women seeking abortions to first attend a consultation at a “pregnancy help center.”

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F.D.A. Bans Some Food Imports From Japan

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18 AND UNDER

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Arts

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