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发表于 2005-4-13 15:01:56
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回复: 【小哀科学院】[禁水]Science Fans进来乱弹(04.10·祝猫生日快乐·生日礼物DN
DING......
迅速逃回实验室的老头子，附送早上扫描NATURE的新文章
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Cancer test stretches limits /Roxanne Khamsi
A device that detects cancerous cells by measuring their stretchiness has been developed by researchers in Germany. The highly sensitive device, which is the size of a shoebox, uses a laser to take its measurements.
Traditional methods of testing for cancer require 10,000-100,000 abnormal cells in order to work. But the new technique can provide an answer with as few as 50 tumour cells, so that much smaller samples would need to be taken from patients.
So far, testing of the new technology has focused on diluted cell mixtures in the lab, but its creators hope to see its eventual use in hospitals. "We really have a clinical application in mind," says Josef Käs of the University of Leipzig, Germany, who helped to build the device.
The laser test relies on the fact that healthy cells contain an inner scaffolding called the cytoskeleton that helps to hold their contents in place. When cells become cancerous, the cytoskeleton recedes and they become more elastic as a result.
Momentous light
When a laser beam from the device enters a cell, the light gains momentum because of the different conditions inside. According to the law of conservation of momentum, the cell must lose an equal but opposite amount, so its membrane bends towards the light source. "The cell gets a kick backwards," explains Käs. When the laser light leaves the cell, it loses momentum and drags the cell's opposite edge along with it. By applying a continuous beam, the cell gets stretched to its limit.
Without a strong cytoskeleton, cancerous cells are 40% easier to extend than their healthy counterparts. And cells from 'metastasized' tumours — those that have spread through the body — are an additional 30% more stretchy than early-stage cancer cells. This means that the laser could potentially assess how far the disease has advanced. "The softest ones are the most aggressive," says Käs.
Currently, doctors cannot diagnose metastasis without discovering the location of the secondary tumours. The new laser-based method would pick up on metastasis based on cell elasticity alone, he says. In breast cancer, for example, the researchers believe this would mean fewer mastectomies carried out unnecessarily on the basis of guesswork about how far the disease has spread.
Sensitive issue
The test should be much more sensitive than cancer tests that simply use molecular markers to tag renegade cells. Käs explains that when cancer-causing genes begin to act in a cell they produce a small change in its structural proteins, but this has an exponential impact on elasticity. The underlying changes in the cell's DNA, which are the focus of current cancer-detection methods, are nowhere near as dramatic.
Given a sample that contains at least 50 tumour cells, the laser can spot cancer more than 90% of the time, its creators claim. Nevertheless, further studies are needed to determine whether it can spot all types of cancer. "That will take years of testing," says Käs, who presented the findings at a meeting of the Institute of Physics in Warwick, UK, this week.
Talk that such a machine could replace a microscope for cancer screening is "rather premature", says Peter Sasieni, a spokesman for London-based charity Cancer Research UK. He adds, however, that the "highly innovative" device could have future clinical applications. |
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发表于 2005-4-14 19:19:44