Knowledge Update

​London, Feb 28 (IANS) In a first, researchers have found evidence of planetary debris surrounding a double sun that resembles Tatooine -- Luke Skywalker's home world in the "Star Wars" film.

A scene in "Star Wars", where Skywalker looks at the horizon with the setting of two suns is regarded as one of the most iconic images in cinema.

In a study published in the journal Nature Astronomy, the researchers described the remains of shattered asteroids orbiting a double sun consisting of a white dwarf and a brown dwarf roughly 1000 light-years away in a system called SDSS 1557.

The debris appears to be rocky and suggests that terrestrial planets like Tatooine might exist in the system, according to the researchers.

"With the discovery of asteroid debris in the SDSS 1557 system, we see clear signatures of rocky planet assembly via large asteroids that formed, helping us understand how rocky exoplanets are made in double star systems," said lead study author Jay Farihi from University College London.

To date, all exoplanets discovered in orbit around double stars are gas giants, similar to Jupiter, and are thought to form in the icy regions of their systems.

In contrast to the carbon-rich icy material found in other double star systems, the planetary material identified in the SDSS 1557 system has a high metal content, including silicon and magnesium. 

These elements were identified as the debris flowed from its orbit onto the surface of the star, polluting it temporarily with at least 1.1 trillion tonnes of matter, equating it to an asteroid at least four km in size.

"Building rocky planets around two suns is a challenge because the gravity of both stars can push and pull tremendously, preventing bits of rock and dust from sticking together and growing into full-fledged planets," Farihi said.

The team studied the binary system and the chemical composition of the debris by measuring the absorption of different wavelengths of light or 'spectra', using the Gemini Observatory South telescope and the European Southern Observatory Very Large Telescope, both located in Chile.

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New Delhi, Feb 27 (IANS) The WHO on Monday said it it has published the first-ever list of antibiotic-resistant "priority pathogens", 12 families of bacteria that pose the greatest threat to human health, to guide and promote research and development of new antibiotics.

The Geneva-based World Health Organisation (WHO) said that list was drawn up as part of its efforts to address growing global resistance to antimicrobial medicines.

According to the global health body, the list is divided into three categories according to the urgency of need for new antibiotics: critical, high and medium priority.

"The most critical group of all includes multi-drug resistant bacteria that pose a particular threat in hospitals, nursing homes, and among patients whose care requires devices such as ventilators and blood catheters. They include Acinetobacter, Pseudomonas and various Enterobacteriaceae (including Klebsiella, E. coli, Serratia, and Proteus)," said a WHO statement.

It said that all the bacteria can cause severe and often deadly infections such as bloodstream infections and pneumonia.

"These bacteria have become resistant to a large number of antibiotics, including carbapenems and third generation cephalosporins - the best available antibiotics for treating multi-drug resistant bacteria," said the report.

The second tier which includes antibiotics of high priority includes for Enterococcus faecium, which is vancomycin-resistant, Staphylococcus aureus which is methicillin-resistant, Helicobacter pylori which is clarithromycin-resistant, Campylobacter spp which is fluoroquinolone-resistant, Salmonellae which is fluoroquinolone-resistant, Neisseria gonorrhoeae which is cephalosporin and fluoroquinolone-resistant.

The third tier which includes medium priority includes Streptococcus pneumoniae which is penicillin-non-susceptible, Haemophilus influenzae, which is ampicillin-resistant and Shigella spp which is fluoroquinolone-resistant.

"This list is a new tool to ensure research and development responds to urgent public health needs," said WHO's Assistant Director-General for Health Systems and Innovation Marie-Paule Kieny in the statement.

Evelina Tacconelli, Head of the Division of Infectious Diseases at the University of Tübingen and a major contributor to the list, said :"New antibiotics targeting this priority list of pathogens will help to reduce deaths due to resistant infections around the world. 

"Waiting any longer will cause further public health problems and dramatically impact on patient care."

New York, Feb 26 (IANS) Although the last Neanderthal died tens of thousands years ago, their DNA sequences still influence how genes are turned on or off in modern humans, and their effects can contribute to traits such as height and susceptibility to schizophrenia or lupus, says a study.

Experts know that after leaving Africa, our ancestors -- the homo sapiens -- mated with Neanderthals thousands of years ago, and today Neanderthal DNA makes up one to four per cent of the genomes of modern non-African people. 

"Even 50,000 years after the last human-Neanderthal mating, we can still see measurable impacts on gene expression," said study co-author Joshua Akey from the University of Washington School of Medicine in Seattle.

"And those variations in gene expression contribute to human phenotypic variation and disease susceptibility," Akey added.

Previous studies have found correlations between Neanderthal genes and traits such as fat metabolism, depression, and lupus risk.

In this study, published in the journal Cell, researchers analysed RNA sequences in a dataset called the Genotype-Tissue Expression (GTEx) Project, looking for people who carried both Neanderthal and modern human versions of any given gene -- one version from each parent. 

For each such gene, the investigators then compared expression of the two alleles head-to-head in 52 different tissues.

"We find that for about 25 per cent of all those sites that we tested, we can detect a difference in expression between the Neanderthal allele and the modern human allele," added Rajiv McCoy, post-doctoral researcher at the University of Washington.

One example uncovered by this study is a Neanderthal allele of a gene called ADAMTSL3 that decreases risk of schizophrenia, while also influencing height.

"Hybridisation between modern humans and Neanderthals increased genomic complexity," Akey explained.

"Hybridisation wasn't just something that happened 50,000 years ago that we don't have to worry about anymore. Those little bits and pieces, our Neanderthal relics, are influencing gene expression in pervasive and important ways," Akey said.

New York, Feb 25 (IANS) Researchers have found a 700-per cent surge in infections caused by bacteria that is resistant to multiple kinds of antibiotics among children in the US.

According to researchers, these antibiotic resistant infections -- caused by Enterobacteriaceae, a family of bacteria that also include such pathogens as Salmonella and Escherichia coli -- are linked to longer hospital stays and potentially greater risk of death.

The findings showed that the proportion of these infections in children caused by bacteria increased from 0.2 per cent in 2007 to 1.5 per cent in 2015, a more than 700 per cent increase in prevalence over the eight-year period.

"There is a clear and alarming upswing throughout US of antibiotic resistant Enterobacteriaceae infections in kids and teenagers," said lead author Sharon B. Meropol, a pediatrician and epidemiologist at Case Western Reserve University in the US. 

Bacterial infections resistant to multiple drugs are especially concerning in children, for whom there are a limited number of stronger antibiotics currently approved for use compared to adults, putting kids at higher risk for worse outcomes, the researchers said. 

For the study, published in the Journal of the Pediatric Infectious Diseases Society, the team analysed data from 48 children's hospitals throughout the US, focusing on approximately 94,000 patients under the age of 18 who were diagnosed with Enterobacteriaceae - associated infections between 2007 and 2015. 

More than 75 per cent of the antibiotic-resistant infections were already present when the young people were admitted to the hospital, upending previous findings that the infections were mostly picked up in the hospital. 

This suggested that the bacteria may be increasingly spreading in the community. 

In addition, the bacterial infection may also cause a greater mortality risk among pediatric patients.

"Health care providers have to make sure we only prescribe antibiotics when they're really needed. It's also essential to stop using antibiotics in healthy agricultural animals", Meropol added.

New York, Feb 24 (IANS) Fructose -- simple sugar found in fruits, vegetables, table sugar, and many processed foods -- is converted in the human brain from glucose, according to a new study.

Previous studies have established that excess consumption of fructose contributes to high blood sugar and chronic diseases like obesity. But it was not known whether fructose was produced in the brain or crossed over from the bloodstream.

"In this study, we show for the first time that fructose can be produced in the human brain," said first author Janice Hwang, Assistant Professor at Yale University, in the US.

The study showed that high concentration of fructose in the brain was due to a metabolic pathway called the polyol pathway that converts glucose to fructose.

"By showing that fructose in the brain is not simply due to dietary consumption of fructose, we've shown fructose can be generated from any sugar you eat. It adds another dimension into understanding fructose's effects on the brain," Hwang added, in the paper published in the journal JCI Insight. 

Glucose in the brain sends signals of fullness, but that is not the case with fructose. The conversion of glucose to fructose in the brain also occurs in other parts of the body.

This polyol pathway may be one other mechanism by which high blood sugar can exert its adverse effects.

The finding also raises questions about fructose's effects on the brain and eating behaviour, Hwang said.

For the study, the team gave eight healthy, lean individuals infusions of glucose over a four-hour period, where the sugar concentrations in the brains and blood of the participants were assessed.

The results revealed that cerebral fructose levels rose significantly in response to a glucose infusion, with minimal changes in fructose levels in the blood

​New York, Feb 24 (IANS) Astronomers have spotted an enormous, glowing blob of gas in the distant universe, with no obvious source of power for the light it is emitting.

Called an "enormous Lyman-alpha nebula" (ELAN), it is the brightest and among the largest of these rare objects, only a handful of which have been observed, the researchers said.

The newly discovered nebula was found at a distance of 10 billion light years in the middle of a region with an extraordinary concentration of galaxies. 

Researchers found this massive overdensity of early galaxies, called a "protocluster," through a novel survey project led by Zheng Cai, Hubble postdoctoral fellow at University of California, Santa Cruz in the US.

"Our survey was not trying to find nebulae. We're looking for the most overdense environments in the early universe, the big cities where there are lots of galaxies," said Cai, who is first author of a paper on the discovery to be published in the Astrophysical Journal.

"We found this enormous nebula in the middle of the protocluster, near the peak density," Cai said.

ELANs are huge blobs of gas surrounding and extending between galaxies in the intergalactic medium. 

They are thought to be parts of the network of filaments connecting galaxies in a vast cosmic web. 

Previously discovered ELANs are likely illuminated by the intense radiation from quasars, but it is not clear what is causing the hydrogen gas in the newly discovered nebula to emit Lyman-alpha radiation (a characteristic wavelength of light absorbed and emitted by hydrogen atoms), the researchers said.

The newly discovered ELAN is known as MAMMOTH-1.

"It's a terrifically energetic phenomenon without an obvious power source," said study co-author J. Xavier Prochaska, Professor at University of California, Santa Cruz.

​London, Feb 24 (IANS) Have a sweet tooth? Beware, you may be at risk of developing Alzheimer's disease, as a study has found a specific molecular link between abnormally high blood sugar levels, or hyperglycaemia -- a key characteristic of diabetes and obesity -- and Alzheimer's disease.

The findings showed that excess glucose damages a vital enzyme involved with inflammation response to the early stages of Alzheimer's and that is the reason behind diabetes patients having an increased risk of developing the disease compared to healthy individuals.

"Excess sugar is well known to be bad for us when it comes to diabetes and obesity, but this potential link with Alzheimer's disease is yet another reason that we should be controlling sugar intake in our diets," said Omar Kassaar, from the University of Bath in Britain.

For the study, published in the journal Scientific Reports, the team studied brain samples from people with and without Alzheimer's using a sensitive technique to detect glycation -- the bonding of a sugar molecule.

The results showed that in the early stages of Alzheimer's, glycation damages an enzyme called MIF (macrophage migration inhibitory factor) which plays a role in immune response and insulin regulation.

MIF is involved in the build-up of abnormal proteins in the brain during Alzheimer's. This inhibition and reduction of MIF activity caused by glycation could be the "tipping point" in disease progression, the researchers said.

"Normally MIF would be part of the immune response to the build-up of abnormal proteins in the brain and we think that because sugar damage reduces some MIF functions and completely inhibits others that this could be a tipping point that allows Alzheimer's to develop," explained Jean van den Elsen, Professor at the University of Bath.

The study may be vital to developing a chronology of how Alzheimer's progresses and help identify those at risk of Alzheimer's and lead to new treatments or ways to prevent the disease, the researchers noted.

Sydney, Feb 24 (IANS) Sweating depends on body size, weight and not on gender, meaning that larger individuals sweat more than smaller ones during exercises in warm and tolerable conditions, a study has found, negating the conventional belief that gender influences sweat.

The body cools itself down in two main ways: Sweating and increasing circulation to the skin's surface. Body shape and size dictates which of these two is relied upon for heat loss, the researchers said. 

"Gender has long been thought to influence sweating and skin blood flow during heat stress. We found that these heat loss responses are, in fact, gender independent during exercise in conditions where the body can successfully regulate its temperature," said lead author Sean Notley from the University of Wollongong in Australia.

The study found that smaller males and females with more surface area per kg of body mass are more dependent on heat loss through increasing circulation and less dependent upon sweating.

For the study, published in the journal Experimental Physiology, the team looked at skin blood flow and sweating responses in 36 men and 24 women.

They performed two trials -- one of light exercise and the other of moderate -- at 28 degrees Celsius and 36 per cent humidity. 

These are conditions where the body is able to mitigate the additional heat produced during exercise and prevent further rises in body temperature by increasing sweating and blood flow to the skin.

The results showed that the body temperature changes were same in all participants within each trial regardless of the gender.