الجمعة، 5 فبراير 2010

A brief history of neuroimaging From prints on papyrus to MRI scans, Man has spent millennia trying to map and understand the human bra


Sir Charles Bell exposes the anatomy of the brain in a series of watercolour plates from 1823

Medicate a smashed skull with grease and bind a head wound with fresh meat. These are just two of the treatments laid out in the Edwin Smith Surgical Papyrus, unearthed in the 19th century. Drawing on texts from 3000BC, the Ancient Egyptian document represents one of our earliest attempts to understand the brain.

By the 2nd century AD, Claudius Galen, a Roman physician, was experimenting on gladiators and primates. About 800 years later, Abu al-Qasim al-Zahrawi, a Moor, documented surgical procedures in al-Tasrif. Their work dominated medical teaching for centuries.

A lull came during the Middle Ages, when the Church prohibited dissection. But the Renaissance brought the brain to the attention of Leonardo da Vinci. He produced detailed studies of the organ and pioneered theories about its ventricular structure by injecting hot wax into an ox brain. Next came influential textbooks. In 1543 Andreas Vesalius, an anatomist who worked with artists to ensure accurate illustrations, wrote On the Fabric of the Human Body. The hands behind some of the finest sketches of the time remain unknown, but some trace them back to the pupils of Titian.

But not all portrayals advanced knowledge. In 1810 Francis Gall, the father of phrenology, thought that he had mapped the bumps of the skull that predict personality. A movement that encouraged voting for MPs based on their head shape has since abated.

As the Victorian era approached, knowledge about the brain accelerated. When Sir Charles Bell wasn’t operating at the Battle of Waterloo or giving his name to Bell’s palsy, he studied the role of nerves. His illustrations still speak to the beauty of our brains.

Images shifted from the artistic to the photographic in the 1900s. Pumping air into the brain sounds terrifying, but when Walter Dandy introduced ventriculography in 1918 it enabled surgeons to pinpoint a tumour using X-rays.

In 1927, scientists were able to visualise blood vessels in the brain for the first time when Egas Moniz pioneered cerebral angiography. This important discovery would be overshadowed by his more enduring legacy: the lobotomy.

CAT scans replaced more invasive neuroimagery techniques in the 1970s. By taking multiple X-rays and blending them into one, they can create a detailed picture of the brain. The decade also saw the development of PET scans, which trace the passage of radioactive isotopes injected into the body.

Today the MRI is often the scan of choice. The machines, which magnetise the body and then send powerful radio waves through it to create images, enable surgeons to make greater distinction between different types of tissue.

Our understanding of the brain is still superficial. Scientists now hope to map the wiring that connects our billions of neurons. A huge task, but these images would be fit to hang beside those of Bell and Leonardo.

ناسا: كوكب بلوتو أصبح أكثر لمعانا واحمرارا


واشنطن، الولايات المتحدة الأمريكية (CNN) -- قالت وكالة الفضاء الأمريكية "ناسا،" الخميس إن كوكب بلوتو يصبح أكثر لمعانا واحمرارا حيث تؤدي دورته حول الشمس التي تستمر 248 عاما، والتي على وشك أن تبدأ من جديد إلى تغيير مواسمه.

ونشرت ناسا صورا جديدة التقطها المنظار الفضائي المداري "هابل" تظهر أن النصف الشمالي لبلوتو يصبح أكثر لمعانا وان الكوكب بأكمله يبدو أكثر احمرار، بعد ذوبان بعض الثلوج في جزئه الشمالي.
روابط ذات علاقة

* "ناسا" تكشف عن صورة تثبت وجود سوائل في عالم آخر
* اكتشاف أصغر كوكب خارج المجموعة الشمسية
* اكتشاف "كوكب خارق" مشابه لكوكب الأرض

وقال بيان لمعهد علم مناظير الفضاء التابع لناسا في بالتيمور "هذه التغيرات من المرجح جدا أن تكون نتيجة لذوبان الجليد على سطح القطب المواجه للشمس ثم تجمده مرة أخرى على القطب الآخر أثناء دخول الكوكب القزم المرحلة التالية في دورته الموسمية التي تستمر 248 عاما."

وأضاف البيان "صور هابل تؤكد أن تغييرا ديناميكيا في الغلاف الجوي لبلوتو، وتظهر أن الكوكب ليس مجرد كرة من الجليد والصخور."
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وبمقارنة صور للكوكب أخذت عام عام 1994 مع أخرى التقطت عامي 2002 و2003، قالت الوكالة إن أدلة تظهر على أن المنطقة القطبية الشمالية قد أصبحت أكثر إشراقا، بينما في نصف الكرة الجنوبي مظلمة.

وأشارت "ناسا" إلى أن صور هابل الجديدة تعطي الفلكيين أدلة أساسية حول مواسم بلوتو ومصير غلافه الجوي، وتمكنهم من تفسير أكثر من ثلاثة عقود من الملاحظات والصور حول بلوتو من عدد من المناظير.

السبت، 10 أكتوبر 2009

Vaccine heralds new dawn in the fight against Aids

The scientific naysayers who claimed a vaccine against HIV would never be possible have received their comeuppance. After years of setbacks and growing doubts, a jab to prevent the worst disease of modern times, which currently affects 33 million people worldwide, may be in prospect after all.

The world's largest HIV prevention trial, involving 16,000 people in Thailand, reported yesterday that giving a combination of two vaccines lowered the risk of contracting the virus by 31.2 per cent. That is not enough for a viable vaccine that could be used globally against HIV but it is the first indication that an effective jab – one that provides at least a 50 per cent reduction in risk – might be possible.
The World Health Organisation and the Joint United Nations Programme on HIV/Aids hailed the result as a "significant scientific breakthrough". Seth Berkley, president of the International Aids Vaccine Initiative, said it was "very exciting news".
The advance comes after more than 20 years of research, the expenditure of billions of pounds and four previous vaccine trials with single agents which failed to demonstrate any protective effect. It is a victory for the US and Thai researchers who pushed through the $120m trial in the face of heavyweight scientific opposition. One of the chief critics was Robert Gallo, a discoverer of HIV, who had scoffed: "We'd learn more if we had extract of maple leaf in the vaccine."

Another blow came when a group of two dozen scientists wrote to the journal Science in 2004 that the inclusion of one of the candidate vaccines, made by Vaxgen – which had failed a previous trial – was "completely incapable of preventing or ameliorating" HIV infection. The group questioned "the wisdom of the US government's sponsoring" the Thailand trial.

A poll of 35 international Aids researchers published by The Independent in April 2008 revealed a mood of "deep pessimism" within the scientific community, with a substantial minority admitting an HIV vaccine might never be developed. Aids organisations had called for the funds spent on the search for a vaccine to be diverted to other prevention efforts. Now the results of the Thai trial are in, its critics may have to eat their words.

The first vaccine used in the trial, called ALVAC, is based on a canarypox virus that has been disabled which is used as a "Trojan horse" to smuggle three genetic fragments of HIV into the body, priming the immune system to recognise and kill HIV-infected cells. The second vaccine, AidsVAX, contains a protein designed to encourage the body to produce neutralising antibodies to destroy HIV before it infects healthy cells. The researchers warned that the two vaccine components might not work in other parts of the world, such as sub-Saharan Africa, where different strains of HIV are circulating and the population has a different genetic make-up.

Thailand was chosen 18 years ago by the WHO for HIV vaccine trials that were then thought to be imminent. Scientists predicted that a vaccine to prevent the infection would be ready long before a treatment for the symptoms could be developed but the opposite turned out to be true.
Millions of people are keeping the virus under control with drugs. But these are not a cure. In contrast to virtually every other microbe known, there is no documented case of anyone who has ultimately cleared the virus from their body completely. That is why developing a vaccine to prevent the infection has been a priority.
The trial, funded by the US Army and the US National Institute for Allergy and Infectious Diseases, was run in Thailand because it is a country with a high rate of HIV, with a good health infrastructure and the Thai government was willing to host it.
Sheena McCormack, senior clinical scientist at the UK Medical Research Council, and the African-European HIV Vaccine Development Network, said the results of the Thai trial were statistically significant. "This is encouraging. It is proof of concept and strongly suggests we may be able to achieve a vaccine. It will help us select and design vaccine candidates for the future," she said.

The next stage would be to examine the immune response generated by the vaccine in the Thai trial. Each volunteer received four doses of one vaccine and two of the other – six jabs in all. Some got strong immune responses which failed to protect them from HIV infection while others with weaker immune responses were protected.

"Obviously, if the immune response is very strong but it is not protective that is no good. The next task is to analyse the immune responses. But with 16,000 participants in the trial that is a challenge," she added.

1981 Aids is identified as a new disease among gays in California and New York

1984 HIV identified as cause of Aids

1984 Aids is discovered to be widespread in parts of Africa

1987 AZT is licensed as the first drug to treat Aids

1990 Around 8 million people are living with HIV worldwide
1996 Combination treatment – a cocktail of three drugs – is shown to be highly effective in preventing HIV progressing to Aids


2003 The first Aids vaccine to undergo a major trial is found to be ineffective

2007 Another major HIV vaccine trial is halted after results show no benefit

2009 World's largest vaccine trial among 16,000 volunteers in Thailand shows the risk of infection reduced by 31.2 per cent