Xenophilia (True Strange Stuff)

Blog of the real Xenophilius Lovegood, a slightly mad scientist

Archive for December 19th, 2009

Researchers link calorie intake to cell lifespan, cancer development

Posted by Anonymous on December 19, 2009

Researchers from the University of Alabama at Birmingham (UAB) have discovered that restricting consumption of glucose, the most common dietary sugar, can extend the life of healthy human-lung cells and speed the death of precancerous human-lung cells, reducing cancer’s spread and growth rate.

The research has wide-ranging potential in age-related science, including ways in which calorie-intake restriction can benefit longevity and help prevent diseases like cancer that have been linked to aging, said principal investigator Trygve Tollefsbol, Ph.D., D.O., a professor in the Department of Biology.

“These results further verify the potential health benefits of controlling calorie intake.” Tollefsbol said. “Our research indicates that calorie reduction extends the lifespan of healthy human cells and aids the body’s natural ability to kill off cancer-forming cells.”

Researchers from the University of Alabama at Birmingham (UAB) have discovered that restricting consumption of glucose, the most common dietary sugar, can extend the life of healthy human-lung cells and speed the death of precancerous human-lung cells. Credit: Jamie Cottle/UAB

The UAB team conducted its tests by growing both healthy human-lung cells and precancerous human-lung cells in laboratory flasks. The flasks were provided either normal levels of glucose or significantly reduced amounts of the sugar compound, and the cells then were allowed to grow for a period of weeks.”In that time, we were able to track the cells’ ability to divide while also monitoring the number of surviving cells. The pattern that was revealed to us showed that restricted led the healthy cells to grow longer than is typical and caused the to die off in large numbers,” Tollefsbol said.

In particular, the researchers found that two key genes were affected in the cellular response to decreased glucose consumption. The first gene, , encodes an important enzyme that allows cells to divide indefinitely. The second gene, p16, encodes a well known anti-cancer protein.

“Opposite effects were found for these genes in healthy cells versus precancerous cells. The healthy cells saw their telomerase rise and p16 decrease, which would explain the boost in healthy cell growth,” Tollefsbol said. “The gene reactions flipped in the precancerous cells with telomerase decreasing and the anti-cancer protein p16 increasing, which would explain why these cancer-forming cells died off in large numbers.”

The UAB research into the links between calorie intake, aging and the onset of diseases related to aging is thought to be a first of its kind given that it used the unique approach of testing human cells versus laboratory animals.

“Our results not only support previous findings from the feeding of animals but also reveal that human longevity can be achieved at the cellular level through caloric restriction,” Tollefsbol said.

“The hope is that this UAB breakthrough will lead to further discoveries in different cell types and facilitate the development of novel approaches to extend the of humans,” he added.via Researchers link calorie intake to cell lifespan, cancer development (w/ Video).

A few things to remember:

Vitamin C is structurally similar to glucose and the vitamin has a short half-life in the blood stream. – iw

Except for one mutated gene, we could turn glucose into vitamin C. Other animals do this.- nhaa

Vitamin C is an antioxidant – av

Considerable laboratory evidence from chemical, cell culture, and animal studies indicates that antioxidants may slow or possibly prevent the development of cancer. – cancer



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The Known Universe

Posted by Anonymous on December 19, 2009

Posted in Space | 1 Comment »

Tiny whispering gallery

Posted by Anonymous on December 19, 2009

Nanotechnology has already made it to the shelves of your local pharmacy and grocery: nanoparticles are found in anti-odor socks, makeup, makeup remover, sunscreen, anti-graffiti paint, home pregnancy tests, plastic beer bottles, anti-bacterial doorknobs, plastic bags for storing vegetables, and more than 800 other products.

How safe are these products and the flood of new ones about to spill out of labs across the world? A group of researchers at Washington University is devising instruments and protocols to assess the impact of nanoparticles on the environment and human health before they are sent to market

As part of this effort, a team led by Lan Yang, Ph.D., assistant professor of electrical and systems engineering, has devised a sensor on a chip that can not only detect but also measure single particles. They expect the sensor will be able to measure nanoparticles smaller than 100 nanometers in diameter (about the size of a virus particle) on the fly.

The new sensor, an improved version of a sensor called a whispering-gallery microresonator, is described in the December 13 edition of Nature Photonics’s advanced online publication.

Whispering galleries

The sensor belongs to a class of devices charmingly called whispering-gallery-mode resonators.

One famous whispering gallery is St. Paul’s Cathedral in London. If you stand under the dome close to the wall and speak softly to the wall, someone on the opposite side of the gallery is able to hear what you say.

The reason is the sound bounces along the wall of the gallery with very little loss of energy and so can be heard at a great distance.

However, if you speak at normal volume, what you say can no longer be understood. The sound travels around the dome more than once, and the recirculating signal gets mixed up and garbled.

Whispering-gallery microresonators

In a miniature version of a whispering gallery, laser light is coupled into a circular “waveguide,” such as a glass ring. When the light strikes the boundary of the ring at a grazing angle it is reflected back into the ring.

The light wave can make many trips around the ring before it is absorbed, but only frequencies of light that fit perfectly into the circumference of the ring can do so. If the circumference is a whole number of wavelengths, the light waves superimpose perfectly each trip around.

This perfect match between the frequency and the circumference is called a resonance, or whispering-gallery mode.

The glass resonator can serve as a particle detector because the faint outer edge of the light wave, called its “evanescent tail, ” penetrates the ring’s surface, probing the surroundings. So when a particle attaches to the ring, it disturbs the light wave, changing the resonant frequency. This change can be used to measure the size of the particle.

There are two problems with these microresonators, says Yang. One is that they are finicky. Lots of things can shift the resonant frequency, including vibration or temperature changes.

The other is that the frequency shift depends on where the particle lands on the ring. A particle that happens to land on a node (the dark blue areas reflected on the base of the pedestal in the accompanying image) will disturb the light wave less and appear smaller than a particle of the same size that happens to land on an anti-node (the red spots visible on the base).

For this reason the frequency shift is not a reliable measure of particle size.

The ultra-high-Q microresonator

The way around these problems is a self-referring sensing scheme possible only in an exceptionally good resonator, one with virtually no optical flaws.

Yang’s lab uses surface tension to achieve the necessary perfection. The microresonators are etched out of glass layers on silicon wafers by techniques borrowed from the integrated circuit industry. These techniques allow the rings to be mass produced but leave them with rough surfaces.

In a crucial finishing step, the microresonators are reheated with a pulsed laser until the glass reflows. Surface tension then pulls the rings into smooth toruses.

“Nature helps us create the perfect structure,” says Yang.

“This quality factor gives the sensor a resonance as beautiful as the pure tone form the finest musical instrument,” says Jiangang Zhu, a graduate student in Yang’s lab.

The Q value, or quality factor, of the reflowed resonators, a measure of microscopic imperfections that sap energy from the resonating mode, is about 100 million, meaning that light circles the ring many time. Because recirculation dramatically increases the interaction of the light wave and particles on the ring’s surface, a different approach to particle detection is possible: mode splitting.

Each whispering-gallery mode is actually two modes: the light travels both clockwise and counterclockwise around the resonator. These modes are usually “degenerate,” meaning they have the same frequency.

When a particle lands on a resonator, it acts as a scattering center that couples energy between the modes. The two modes re-arrange themselves so that the particle lies on a node of one and an anti-node of the other. As a result, one wave is much more perturbed than the other, and this “lifts the degeneracy,” or “splits the mode.”

In a low-Q resonator, the split mode can’t be resolved. But in the high-Q resonator it is easily seen.

A sensor that relies on mode splitting is much less finicky than a frequency-shifting sensor. Because the clockwise and counterclockwise light waves share the same resonator, they share the same noise. Any jitter or jiggle that biases one biases the other by the same amount. Because it is self-referring, the sensor is more accurate and reliable.

Mode splitting also solves the particle location problem. The light scattering that perturbs the mode also broadens it. The mode split still varies with the location of the particle, but the ratio of the mode split and the difference between the linewidths (the breadth) of the two modes depends only on the particle’s size.

To test the sensor, Daren Chen, Ph.D., associate professor of energy, environmental and chemical engineering, helped the team generate nanoparticles within specifc size ranges. In experiments with nanoparticles of salt or nanospheres of plastic, the resonator’s size estimates were within one or two percent of the actual values.

“Size is a key parameter that significantly affects the physical and chemical properties of nanoparticles,” says Yang. “It plays a crucial role in the applications of nanoparticles both in science and in industry, all of which will benefit from the ability to measure these particles accurately.”

via Tiny whispering gallery.

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