Knowledge Update

New York, March 15 (IANS) Scientists have developed a high-resolution retinal prosthesis using nanowires and wireless electronics that may aid neurons in the retina to respond to light.

The technology could help tens of millions of people worldwide suffering from neurodegenerative diseases that affect eyesight, including macular degeneration, retinitis pigmentosa and loss of vision due to diabetes.

In the study, detailed in the Journal of Neural Engineering, the researchers demonstrated this response to light in a rat retina interfacing with a prototype of the device in vitro.

"We want to create a new class of devices with drastically improved capabilities to help people with impaired vision," said Gabriel A. Silva, Professor at the University of California San Diego in the US.

The new prosthesis relies on two ground-breaking technologies. One consists of arrays of silicon nanowires that simultaneously sense light and electrically stimulate the retina accordingly.

The nanowires give the prosthesis higher resolution than anything achieved by other devices -- closer to the dense spacing of photoreceptors in the human retina. 

The other is a wireless device that can transmit power and data to the nanowires over the same wireless link at record speed and energy efficiency.

Further, the new system does not require a vision sensor outside of the eye to capture a visual scene and then transform it into alternating signals to sequentially stimulate retinal neurons.

Instead, the silicon nanowires mimic the retina's light-sensing cones and rods to directly stimulate retinal cells.

Nanowires are bundled into a grid of electrodes, directly activated by light and powered by a single wireless electrical signal. 

The power provided to the nanowires from the single wireless electrical signal gives the light-activated electrodes their high sensitivity while also controlling the timing of stimulation.

Seoul, March 15 (IANS) Challenging a commonly held theory that changes in the Earth's orbit triggered Sahara desertification, a new study suggests that humans may have played an active role in the transition of a lush green landscape into the world's largest hot desert thousands of years ago.

The desertification of the Sahara has long been a target for scientists trying to understand climate and ecological tipping points. 

Most studies done to date point to changes in the Earth's orbit or natural changes in vegetation as the major driving forces.

In a new paper published in the journal Frontiers in Earth Science, David Wright from Seoul National University in South Korea challenges the conclusions of these studies.

"In East Asia there are long established theories of how Neolithic populations changed the landscape so profoundly that monsoons stopped penetrating so far inland," said Wright. 

Evidence of human-driven ecological and climatic change has been documented in Europe, North America and New Zealand, said Wright who believed that similar scenarios could also apply to the Sahara.

To test his hypothesis, Wright reviewed archaeological evidence documenting the first appearances of pastoralism across the Saharan region, and compared this with records showing the spread of scrub vegetation, an indicator of an ecological shift towards desert-like conditions. 

The findings confirmed his thoughts.

Beginning approximately 8,000 years ago in the regions surrounding the Nile River, pastoral communities began to appear and spread westward, increasing at the same time the spread of scrub vegetation, the study said.

Growing agricultural addiction had a severe effect on the region's ecology. As more vegetation was removed by the introduction of livestock, it increased the albedo (the amount of sunlight that reflects off the earth's surface) of the land, which in turn influenced atmospheric conditions sufficiently to reduce monsoon rainfall. 

The weakening monsoons caused further desertification and vegetation loss, promoting a feedback loop which eventually spread over the entirety of the modern Sahara, the study said.

London, March 15 (IANS) Stimulating the brain with electricity may synchronise brain waves and help improve short-term working memory that could improve treatments for people with traumatic brain injury, stroke or epilepsy, a study has found.

According to researchers, applying a weak electrical current through the scalp can align different parts of the brain, synchronising brain waves and enabling people to perform better on tasks involving working memory.

"What we observed is that people performed better when the two waves had the same rhythm and at the same time," said lead author Ines Ribeiro Violante, a neuroscientist at the Imperial College London.

"The hope is that it could eventually be used for patients with brain injury, or even those who have suffered a stroke or who have epilepsy," Violante added. 

For the study, published in the journal eLife, the team used a technique called transcranial alternating current stimulation (TACS) to manipulate the brain's regular rhythm in 10 volunteers.

Using TCAS, the researchers targeted two brain regions -- the middle frontal gyrus and the inferior parietal lobule -- known to be involved in working memory.

The findings revealed that when the brain regions were stimulated in sync, reaction times on the memory tasks improved.

Functional MRI images of the brain showed changes in activity occurring during stimulation, with the electrical current potentially modulating the flow of information.

"The results show that when the stimulation was in sync, there was an increase in activity in those regions involved in the task. When it was out of sync, the opposite effect was seen.

"The hope is that it could eventually be used for patients with brain injury, or even those who have suffered a stroke or who have epilepsy," Violante added.

​Buenos Aires, March 14 (IANS) The worlds first fluorescent frog has been discovered in the Amazon basin in Argentina, a media report said on Tuesday.

Scientists at the Bernardino Rivadavia Natural Sciences Museum in Buenos Aires made the discovery by accident while studying the pigment of polka-dot tree frogs, a species common to the rainforest, the Guardian said in the report.

In normal light the frog appears to have a dull, mottled brown-green skin with red dots, but under UV light it glows a bright fluorescent green.

Fluorescence -- the ability to absorb light at short wavelengths and re-emit it at longer wavelengths -- is uncommon in creatures that live on land.

The translucent frog was found to use a combination of lymph and glandular emissions to fluoresce.

The researchers, who published their discovery on Monday in Proceedings of the National Academy of Sciences, found that the trait enhanced the brightness of the frog by 19-29 per cent depending on the level of ambient light in its surroundings, the daily said.

The compound causing the blue-green glow of the polka-dot tree frog was not previously thought to exist in vertebrates and its discovery has excited researchers.

"This is very different from fluorophores found in other vertebrates, which are usually proteins or polyenic chains," Maria Gabriella Lagoria, a photochemist at the University of Buenos Aires and study co-author, told Chemistry World.

The discovery opens up the possibility that other amphibians may be able to fluoresce, particularly those with translucent skin similar to that of the tree frog.

Speaking to the journal Nature, which first published news of the fluorescent frog, co-author Julian Faivovich expressed his hope that the discovery would inspire interest in the phenomenon, saying he hoped scientists would "start carrying a UV flashlight to the field".

​London, March 14 (IANS) Although parenthood may have its share of woes, it could also hold the key to long life, particularly in older age, when health and capacity may start to decline, finds a new study.

The findings suggested that the risks of death were lower among those who had had at least one child than they were among those who were childless -- and more so among men than among women -- and were not affected by the sex of the child(ren).

"We started first at the age of 60 and we looked all the way up to the age of 100," Karin Modig from Karolinska Institute Sweden was quoted as saying by guardian.com.

At age 60, the difference in the one-year risk of death was 0.06 per cent among men and 0.16 per cent among women.

The one-year risk of death for an 80-year-old man with a child was 7.4 per cent, for example, compared with 8.3 per cent for a childless man of the same age.

The gap in absolute death risks between the two groups rose with increasing age, and was somewhat larger for men than it was for women.

By the age of 90, these differences had risen to 1.47 per cent among men and to 1.10 per cent among women.

Further, the difference in death risk was 1.2 per cent among unmarried men and 0.6 per cent among those who were married.

"Our finding that the association grew stronger when parents became older is further in agreement with study suggesting that childless people face support deficits only towards the end of life," the researchers noted, in the paper published online in the Journal of Epidemiology & Community Health.

For the study, the team tracked the lifespan from the age of 60 onwards of all men (704,481) and women (725,290) in Sweden.

Tokyo, March 14 (IANS) Japanese authorities sent a robot to the Fukushima nuclear plant on Tuesday to measure radiation levels inside and evaluate its condition ahead of a future dismantling of a reactor.

The self-propelled, remotely-operated robot is equipped with a video camera, thermometer as well as dosimeter -- to measure radiation -- among other sensors, said the Tokyo Electric Power Company (TEPCO), the maker of the bot, in a statement.

Using the recorded data and footage, experts will try to ascertain the presence of melted fuel that could have leaked from the reactor core and accumulated at the bottom of the containment vessel, something they have been unable to verify so far, Efe news reported.

Determining the exact conditions inside the reactor is a necessary step for drafting a plan on the future recovery of the nuclear fuel; a task that has been made difficult by fatal radiation levels at the heart of the nuclear installations.

TEPCO had introduced two bots into the reactor earlier but while the first one could not make it out of the reactor, the second one became inoperative due to extreme radiation.

Another robot that TEPCO sent was also damaged by radiation, but managed to record footage that supplied important information on conditions inside, said the company.

Reactors No. 1, 2 and 3 had suffered partial meltdowns due to an earthquake and a tsunami that hit Japan in March 2011.

The Fukushima nuclear accident is considered the world's worst since Ukraine's Chernobyl disaster in 1986. 

​New York, March 14 (IANS) Scientists have, in a monkey model of HIV, discovered that a dual-antibody therapy can boost the immune system to effectively control the infection and prevent deadly virus from returning for an extended period.

There are more than 25 drugs to control HIV, yet the virus remains one of the world's biggest health problems. 

In the study, the researchers used two drugs -- 3BNC117 and 10-1074 -- belonging to a class of molecules called broadly neutralising antibodies, where each antibody binds to a different site of the virus, preventing its damaging effects from different angles.

"This form of therapy can induce potent immunity to HIV, allowing the host to control the infection," said Michel Nussenzweig from the Howard Hughes Medical Institute -- a US-based non-profit. 

"It works by taking advantage of the immune system's natural defenses, similar to what happens in some forms of cancer immunotherapy," Nussenzweig added.

For the study, published in the journal Nature, the team analysed 13 macaque monkeys, who were inoculated with simian-human immunodeficiency virus (SHIV) and then given three intravenous infusions of the two antibodies over a two-week period. 

The treatment suppressed the virus to levels near or below the limit of detection and its effect lasted for as long as six months. 

These monkeys were also able to maintain healthy levels of key immune cells after receiving the antibody infusions.

In those, who did not regain complete control of the virus, the treatment helped them maintain extremely low viral loads and healthy levels of key immune cells for two to three years after infection.

Although this model does not precisely mimic human HIV infection, the findings suggest that immunotherapy should be explored as a way of controlling the virus and boosting an immune response that might be capable of controlling the infection in people.

London, March 14 (IANS) In a first, scientists have created the three-dimensional (3-D) structures of intact mammalian genomes from individual cells, leading to a potential advance of stem cells in medicine.

The 3-D structure shows how the DNA from all the chromosomes intricately folds to fit together inside the cell nuclei.

The new approach, detailed in the journal Nature, also enables researchers to determine the structures of active chromosomes inside the cell and how they interact with each other to form an intact genome.

"Visualising a genome in 3D at such an unprecedented level of detail is an exciting step forward in research and one that has been many years in the making. This detail will reveal some of the underlying principles that govern the organisation of our genomes - for example how chromosomes interact or how structure can influence whether genes are switched on or off," said Tom Collins from Wellcome trust -- a London-based non-profit. 

The genome's structure controls when and how strongly genes -- particular regions of the DNA -- are switched 'on' or 'off,' while playing a critical role in the development of organisms and also, when it goes awry, in disease.

The study may help study how this changes as stem cells differentiate and how decisions are made in individual developing stem cells, which may be key to realising the potential of stem cells in medicine.

"If we can apply this method to cells with abnormal genomes, such as cancer cells, we may be able to better understand what exactly goes wrong to cause disease, and how we could develop solutions to correct this," Collins said.

​New York, March 14 (IANS) US researchers have developed a new hormone-based test that can better distinguish between the symptoms of depression and schizophrenia.

Depression is thought to affect over 300 million people worldwide and schizophrenia affects as many as 51 million people. 

Clinically, it is difficult to distinguish between these two diseases in their early phases, because symptoms are non-specific and relatively mild. 

In the study, led by researchers from Yale University in Connecticut, US, the researchers infused patients with a high concentration salt solution to induce the release of the hormone arginine-vasopressin (AVP), and then measured the level of the hormone in their blood. 

The results, reported in Experimental Physiology, revealed that AVP release can distinguish schizophrenia from depression.

Depressed patients showed an increased release of the hormone, while patients with schizophrenia showed a decreased response. 

Further, the novel method will help identify people whose depression or schizophrenia involves signalling via a receptor called NMDAR, and differentiate between the two diseases. 

In patients with schizophrenia the NMDA receptor signalling may be decreased, while it might be high in those with depression. 

This hormone test may be a simple way to distinguish and identify patients with NMDA receptor malfunction in each disorder, the researchers said. 

"This is the first objective, physiological marker for two major psychiatric disorders that, once fully developed into a clinical test, can allow for earlier and more accurate diagnosis, and selection of more appropriate medications for patients," said Handan Gunduz-Bruce from Yale University.

Distinguishing this specific form of these diseases could allow for earlier and more accurate diagnoses as well as more targeted treatment, Gunduz-Bruce added.

New York, March 14 (IANS) Researchers have found evidence of a white dwarf star orbiting a likely black hole at a distance of only 961,000 km -- just about 2.5 times the distance between the Earth and the Moon.

In a tightest orbital dance ever witnessed for a black hole and a companion star, the star whips around the black hole at an astonishing speed -- about two orbits an hour, said the study published in the journal Monthly Notices of the Royal Astronomical Society.

"This white dwarf is so close to the black hole that material is being pulled away from the star and dumped onto a disk of matter around the black hole before falling in," said study lead author Arash Bahramian, affiliated with the University of Alberta in Canada and Michigan State University in the US. 

"Luckily for this star, we don't think it will follow this path into oblivion, but instead will stay in orbit," Bahramian said.

Although the white dwarf does not appear to be in danger of falling in or being torn apart by the black hole, its fate is uncertain.

The stellar system, known as X9, is located in the globular cluster 47 Tucanae, a dense cluster of stars in our galaxy about 14,800 light years away from the Earth. 

"For a long time astronomers thought that black holes were rare or totally absent in globular star clusters," study co-author Jay Strader from Michigan State University said. 

"This discovery is additional evidence that, rather than being one of the worst places to look for black holes, globular clusters might be one of the best," Strader added.

For the study, the researchers used data from the Australia Telescope Compact Array as well as NASA's Chandra X-ray Observatory and NuSTAR telescope.