Карта сайта

Motivation for lifestyle changes - Second mole rat species has different mechanism for resisting cancer

Motivation for lifestyle changes

"If we can point to an increased risk of diabetes in a middle-aged individual of normal weight using a simple blood test, up to ten years before the disease develops, this could provide strong motivation to them to improve their lifestyle to reduce the risk", says Anders Rosengren, adding:

"In the long term, our findings could also lead to new methods of treating type 2 diabetes by developing ways of blocking the protein SFRP4 in the insulin-producing beta cells and reducing inflammation, thereby protecting the cells."

The research results have been published in the journal Cell Metabolism: 'Secreted Frizzled-Related Protein 4 Reduces Insulin Secretion and is Overexpressed in Type 2 Diabetes' http://www.sciencedirect.com/science/article/pii/S1550413112004093


A little radiation is good for mice

Low doses of radioactivity led to healthier pups

By Tina Hesman Saey

X-rays may not heal broken bones, but low doses of ionizing radiation may spark other health benefits, a new study of mice suggests.

Radiation in high doses has well-known harmful effects. Scientists had thought low doses would do less extensive damage but could add up to big problems later. But radiation acts differently at low doses, producing health benefits for mice with an unusual genetic makeup, Randy Jirtle of the University of Wisconsin–Madison and colleagues report online November 1 in the FASEB Journal. Antioxidant vitamins, such as vitamins C and E, erased those health gains.

“What goes on at high doses is not very predictive of what happens at low doses,” says Edward Calabrese, a toxicologist at the University of Massachusetts-Amherst. Chemicals that are poisons at high doses may be growth or health promoters at low concentrations. “It’s a major observation that is still to be appreciated,” he says.

Jirtle’s group studies mice known as viable yellow agouti mice. Scientists use them to gauge how diet, chemicals and other environmental conditions affect gene activity in animals, probably including humans. Agouti mice have a genetic quirk that causes the agouti gene to be turned on in all their body tissues. This results in yellow coats, obesity, diabetes and more cancer than normal. But attaching chemical tags to the DNA, a process called DNA methylation, around the agouti gene shuts the gene’s activity down, leading to lean, brown, healthy mice. Chemicals, stress or other factors that interfere with methylation shift the coat color and health status of the mice.

The scientists irradiated pregnant mice so that developing fetuses received doses between 0.4 centigrays and 7.6 centigrays. (A human dental X-ray delivers about 0.4 to 0.8 centigrays.) Some mice were put in the scanner but not irradiated. Mother mice that got radiation doses between 0.7 and 3 centigrays had more pups with browner coats than did sham-irradiated mice. Browner coat colors among mice exposed to low-dose radiation were associated with higher levels of DNA methylation on the agouti gene, indicating that radiation does something to alter the chemical tagging.

Giving mother mice antioxidants blocked the tagging. That finding could mean that radiation is creating oxidants, chemicals that are hungry to interact with other molecules. Too many hungry molecules in a cell can tear apart proteins, DNA and other components, but small numbers of oxidants serve as chemical messengers for cells. In this case, low-level radiation may have signaled cells to shut down agouti activity, thus making the mice healthier. Vitamins and other antioxidants that intercept that message would promote the unhealthy state.

Jirtle wasn’t exactly excited about the result at first. “Nobody wants to think that low dose radiation could be advantageous and the stuff you put in your vitamin pill would be bad,” he says.

Although the mice in Jirtle’s experiments have a specific genetic quirk that may make low levels of radiation helpful to them, people may also get some benefits from such exposure, Calabrese says. Before antibiotics became widespread, some doctors treated ear and sinus infections and gangrene with low dose X-rays. Low doses of radiation are also sometimes used to treat arthritis in people who can’t take anti-inflammatory drugs. Radiation may help modulate the immune system by altering epigenetic tags on DNA in immune cells, he says.

A.J. Bernal et al. Adaptive radiation-induced epigenetic alterations mitigated by antioxidants. FASEB Journal. doi: 10.1096/fj.12-220350. [Go to]


Concern over 'souped up' human race

A race of humans who can work without tiring and recall every conversation they've ever had may sound like science fiction, but experts say the research field of human enhancement is moving so fast that such concepts are a tangible reality that we must prepare for.

By Michelle Roberts Health editor, BBC News online

People already have access to potent drugs, originally made for dementia patients and hyperactive children, that boost mental performance and wakefulness. Within 15 years, experts predict that we will have small devices capable of recording our entire life experience as a continuous video feed - a life log that we can reference when our own memory fails.

Advances in bionics and engineering will mean we could all boast enhanced night vision allowing us to see clearly in the dark.

While it may be easy to count the potential gains, experts are warning that these advances will come at a significant cost - and one which is not just financial.

'Smart' pills

Improve memory and mental performance

One commonly used "smart" drug is modafinil

(brand name Provigil), which is normally

prescribed for sleep disordersAnother is the

drug methylphenidate (brand name Ritalin),

which is given to people with ADHD

Potential harm

Four professional bodies - the Academy of Medical Sciences, the British Academy, the Royal Academy of Engineering and the Royal Society - say that while human enhancement technologies might improve our performance and aid society, their use raise serious ethical, philosophical, regulatory and economic issues.

In a joint report, they warn that there is an "immediate need" for debate around the potential harms.

Chairwoman of the report's steering committee Prof Genevra Richardson said: "There are a range of technologies in development and in some cases already in use that have the potential to transform our workplaces - for better or for worse." There may be an argument for lorry drivers, surgeons and airline pilots to use enhancing drugs to avoid tiredness, for example. But, in the future, is there a danger that employers and insurers will make this use mandatory, the committee asks.


As our population ages, it is accepted that we will all be expected to work further into old age. Human enhancement could enable older workers to keep pace with younger colleagues. But there is also the risk that those who fail to join the technological elite would be sidelined as dinosaurs, says Prof Jackie Leach Scully, professor of social ethics at Newcastle University's Policy, Ethics & Life Sciences Research Centre.

Several surveys reveal that many students now use brain-enhancing "smart" pills to help boost their exam grades, which raises the question about whether colleges and universities should insist candidates are "clean" in the same way that Olympic athletes have to prove they are drug-free to compete.

Many people buy them over the internet, which is risky because they don't know what they're getting.

And we know little about their long-term effects on healthy, young brains.

Dr Robin Lovell-Badge, of the Medical Research Council and who chaired one of the workshop sessions that formulated the report, said: "It was clear from discussions that cognitive-enhancing drugs present the greatest immediate challenge for regulators and other policymakers. "They are simple to take, already available without prescription, and are increasingly being used by healthy individuals.

"However, other forms of enhancement, including physical methods, will follow. Some were on show at the Paralympics, some are being explored by the military and others may become a serious option in the clinic in the not too distant future.

"It is good to see and to be excited by many of these developments, but there must be an equally watchful eye and care taken to ensure that the workforce can capitalise on the benefits, but not suffer the harms that could come about by their inappropriate use."


Corals attacked by toxic seaweed use chemical 911 signals to summon help

Bodyguard fish

Corals under attack by toxic seaweed do what anyone might do when threatened – they call for help. A study reported this week in the journal Science shows that threatened corals send signals to fish "bodyguards" that quickly respond to trim back the noxious alga – which can kill the coral if not promptly removed.

Scientists at the Georgia Institute of Technology have found evidence that these "mutualistic" fish respond to chemical signals from the coral like a 911 emergency call – in a matter of minutes. The inch-long fish – known as gobies – spend their entire lives in the crevices of specific corals, receiving protection from their own predators while removing threats to the corals.

This symbiotic relationship between the fish and the coral on which they live is the first known example of one species chemically signaling a consumer species to remove competitors. It is similar to the symbiotic relationship between Acacia trees and mutualist ants in which the ants receive food and shelter while protecting the trees from both competitors and consumers.

A juvenile Gobidon fish is shown on an Acropora coral. These fish spend their entire lives with the same coral, and protect the coral from encroaching seaweed.

Georgia Tech Photo: Joao Paulo Krajewski

"This species of coral is recruiting inch-long bodyguards," said Mark Hay, a professor in the School of Biology at Georgia Tech. "There is a careful and nuanced dance of the odors that makes all this happen. The fish have evolved to cue on the odor released into the water by the coral, and they very quickly take care of the problem."

The research, supported the National Science Foundation, the National Institutes of Health and the Teasley Endowment at Georgia Tech, was reported November 8 in the journal Science. The research was done as part of a long-term study of chemical signaling on Fiji Island coral reefs aimed at understanding these threatened ecosystems and discovering chemicals that may be useful as pharmaceuticals.

Because they control the growth of seaweeds that damage coral, the importance of large herbivorous fish to maintaining the health of coral reefs has been known for some time. But Georgia Tech postdoctoral fellow Danielle Dixson suspected that the role of the gobies might be more complicated. To study that relationship, she and Hay set up a series of experiments to observe how the fish would respond when the coral that shelters them was threatened.

They studied Acropora nasuta, a species in a genus of coral important to reef ecosystems because it grows rapidly and provides much of the structure for reefs. To threaten the coral, the researchers moved filaments of Chlorodesmis fastigiata, a species of seaweed that is particularly chemically toxic to corals, into contact with the coral. Within a few minutes of the seaweed contacting the coral, two species of gobies – Gobidon histrio and Paragobidon enchinocephalus – moved toward the site of contact and began neatly trimming away the offending seaweed.

"These little fish would come out and mow the seaweed off so it didn't touch the coral," said Hay, who holds the Harry and Linda Teasley Chair in Environmental Biology at Georgia Tech. "This takes place very rapidly, which means it must be very important to both the coral and the fish. The coral releases a chemical and the fish respond right away."

In corals occupied by the gobies, the amount of offending seaweed declined 30 percent over a three-day period, and the amount of damage to the coral declined by 70 to 80 percent. Control corals that had no gobies living with them had no change in the amount of toxic seaweed and were badly damaged by the seaweed.

To determine what was attracting the fish, Dixson and Hay collected samples of water from locations (1) near the seaweed by itself, (2) where the seaweed was contacting the coral, and (3) from coral that had been in contact with the seaweed – 20 minutes after the seaweed had been removed. They released the samples near other corals that hosted gobies, which were attracted to the samples taken from the seaweed-coral contact area and the damaged coral – but not the seaweed by itself.

"We demonstrated that the coral is emitting some signal or cue that attracts the fish to remove the encroaching seaweed," Hay said. "The fish are not responding to the seaweed itself."

Similar waters collected from a different species of coral placed in contact with the seaweed did not attract the fish, suggesting they were only interested in removing seaweed from their host coral.

Finally, the researchers obtained the chemical extract of the toxic seaweed and placed it onto nylon filaments designed to stimulate the mechanical effects of seaweed. They also created simulated seaweed samples without the toxic extract. When placed in contact with the coral, the fish were attracted to areas in which the chemical-containing mimic contacted the coral, but not to the area contacting the mimic without the chemical.

By studying the contents of the fish digestive systems, the researchers learned that one species – Gobidon histrio – actually eats the noxious seaweed, while the other fish apparently bites it off without eating it. In the former, consuming the toxic seaweed makes the fish less attractive to predators.

The two species of fish also eat mucus from the coral, as well as algae from the coral base and zooplankton from the water column. By defending the corals, the gobies are thus defending the home in which they shelter and feed.

"The fish are getting protection in a safe place to live and food from the coral," Hay noted. "The coral gets a bodyguard in exchange for a small amount of food. It's kind of like paying taxes in exchange for police protection."

As a next step, Hay and Dixson would like to determine if other species of coral and fish have similar symbiotic relationships. And they'd like to understand more about how the chemical signaling and symbiotic relationship came into being.

"These kinds of positive interactions needs to be better understood because they tell us something about the pressures that have gone on through time on these corals," said Hay. "If they have evolved to signal these gobies when a competitor shows up, then competition has been important throughout evolutionary time."

CITATION: Danielle L. Dixson and Mark E. Hay, Corals chemically signal mutualistic fishes to remove competing seaweeds, Science (2012).

This research has been supported by the National Science Foundation (NSF) under grant OCE-0929119 and by the National Institutes of Health under grant U01-TW007401. The content of this article is solely the responsibility of the authors and does not necessarily represent the official views of the NSF or the NIH.


2014-07-19 18:44
  • Контрольная работа
  • Контрольная работа
  • Контрольная работа
  • Контрольная работа
  • Контрольная работа
  • Контрольная работа
  • Контрольная работа
  • Контрольная работа
  • Контрольная работа
  • Контрольная работа
  • Контрольная работа
  • Контрольная работа
  • Контрольная работа
  • Контрольная работа
  • Контрольная работа
  • Контрольная работа
  • Контрольная работа
  • Контрольная работа
  • Контрольная работа
  • Контрольная работа
  • Контрольная работа
  • Контрольная работа
  • Контрольная работа
  • Контрольная работа
  • Контрольная работа
  • © sanaalar.ru
    Образовательные документы для студентов.