Knowledge Update

New York, Oct 10 (IANS) An adolescent's ability to learn and form memories is closely linked to the reward-seeking behaviour of the brain, researchers have found.

"Studies of the adolescent brain often focus on the negative effects of teenagers' reward-seeking behaviour," said Daphna Shohamy, Associate Professor of psychology at New York's Columbia University. 

However, the study found that this tendency may be tied to better learning as well as a critical feature of adolescence and the maturing brain.

"We identified patterns of brain activity in adolescents that support learning -- serving to guide them successfully into adulthood," Shohamy added.

For the study, the team involved 41 teenagers and 31 adults and scanned the brains of each participant with functional magnetic resonance imaging (fMRI) while they were performing the learning tasks. 

The fMRI analysis revealed an uptick in hippocampal (brain's memory centre) activity for teenagers -- but not adults -- during reinforcement learning -- a reward signal that helps the brain learn how to repeat the successful choice again. 

Moreover, that activity seemed to be tightly coordinated with activity in the striatum -- a critical component of the brain's reward system. 

The researchers also slipped in random and irrelevant pictures of objects into the learning tasks, such as a globe or a pencil. 

When asked later on, both adults and teens remembered seeing some of the objects. However, only in the teenagers the memory of the objects was associated with reinforcement learning.

"The findings showed that teenagers do not necessarily have better memory, in general, but rather the way in which they remember is different," Shohamy said. 

The results of this research were published in the journal Neuron.

​New York, Oct 10 (IANS) Researchers have identified an enzyme that has caused rifampicin -- a popular antibiotic used to treat bacteria that causes tuberculosis, leprosy, and Legionnaire's disease -- to become less effective and develop more resistance.

The actions of the enzyme Rifampicin monooxygenase -- a flavoenzyme which is a family of enzymes that catalyze chemical reactions essential for microbial survival -- have been found responsible for the antibiotic's resistance.

"Antibiotic resistance is one of the major problems in modern medicine," said Heba Adbelwahab, graduate student at Virginia Polytechnic Institute in the US. 

Rifampicin, also known as Rifampin, has been used to treat bacterial infections for more than 40 years. It works by preventing the bacteria from making RNA, a step necessary for growth.

The findings represent the first detailed biochemical characterisation of a flavoenzyme involved in antibiotic resistance, the researchers said.

"Our studies have shown how this enzyme deactivates rifampicin. We now have a blueprint to inhibit this enzyme and prevent antibiotic resistance," Adbelwahab added.

Tuberculosis, leprosy, and Legionnaire's disease are infections caused by different species of bacteria. While treatable, the diseases pose a threat to children, the elderly, people in developing countries without access to adequate health care, and people with compromised immune systems.

For the study, the team used a special technique called X-ray crystallography to describe the structure of this enzyme. 

They also reported the biochemical studies that allow them to determine the mechanisms by which the enzyme deactivates this important antibiotic.

The results were published in the Journal of Biological Chemistry and PLOS One.

London, Oct 9 (IANS) The absence of a particular molecule from cells can make tumours recur even after immunotherapy, a group of researchers from Germany has found.

Immunotherapy is a new and highly promising form of treatment for cancer.

A team of researchers from the Max Delbruck Center for Molecular Medicine in the Helmholtz Association (MDC) and the Berlin Institute of Health (BIH) and Charite -- Universitatsmedizin Berlin will help doctors in selecting suitable target points for immunotherapy.

One form of immunotherapy for cancer is T-cell receptor gene therapy that involves removing T-cells (a type of immune cell) from the blood and altering them in the test tube to enable them to target cancer cells.

"The tumours are not recognised by the T-cells. We want to find out how to reduce the frequency with which the cancer recurs after treatment," biologist Ana Textor said.

To achieve this, the researchers trained two different types of T-cell. One of the T-cell types permanently destroyed the tumours in a mouse model. After treatment with the other T-cell type, initial tumour regression was followed by recurrence.

The researchers found that when the tumour recurred, a particular molecule on the cell surface -- called the epitope -- was no longer present on the cell surface in sufficient quantity.

This was because the epitopes in these cancer cells were no longer correctly trimmed enzymatically -- in this case by the enzyme ERAAP.

By contrast, the epitopes on the cells of the successfully treated tumour did not require processing by ERAAP and were therefore also not dependent on stimulation by interferon gamma.

According to Textor, epitopes that do not need processing by the enzyme ERAAP are therefore, likely to be a better choice for immunotherapy.

The findings were published in the Journal of Experimental Medicine.

​New York, Oct 9 (IANS) Motivation can act as the best defence against distractions that arise while performing activities that are both difficult as well as an easy, a study has found.

In the study, the researchers from the University of Illinois, have challenged the popular notion that people become more distractible as they tackle increasingly difficult tasks.

On the contrary, they found that it is the simpler tasks that causes individuals to become distracted more easily.

Those who get engaged in an easy tasks were more likely to have distractions than those engaged in an extremely challenging tasks.

Further, the more complex the activity, the more attention you have to give to the task at hand, and the less time you have for outside distractions, the study stated.

"This suggests that focus on complex mental tasks reduces a person's sensitivity to events in the world that are not related to those tasks," said Simona Buetti, Professor at University of Illinois.

"When the need for inner focus is high, we may have the impression that we momentarily disengage from the world entirely in order to achieve a heightened degree of mental focus," Buetti added.

This finding corroborates a phenomenon called "inattentional blindness", in which people involved in an engaging task often fail to notice strange and unexpected events.

The bigger the task, the less likely they are to notice their surroundings, the researchers observed.

For the study, the team tracked eye movements of volunteers as they solved math problems of various difficulty while looking at neutral photographs.

The results showed that the more difficult the math problem, the more likely the volunteers' eyes were to wander.

The ability to avoid being distracted is not driven primarily by the difficulty of the task, but is likely the result of an individual's level of engagement with the endeavour, the researchers concluded.

​Washington, Oct 7 (IANS) Using NASA's Hubble space telescope data, scientists, including one of Indian-origin, have detected superhot blobs of gas, each twice as massive as the planet Mars, being ejected near a dying star.

The plasma balls are zooming so fast through space it would take only 30 minutes for them to travel from Earth to the moon, NASA said in a statement on Thursday.

Astronomers have estimated that this stellar "cannon fire" has continued once every 8.5 years for at least the past 400 years.

"We knew this object had a high-speed outflow from previous data, but this is the first time we are seeing this process in action," said lead author of the study Raghvendra Sahai of NASA's Jet Propulsion Laboratory in Pasadena, California.

The fireballs present a puzzle to astronomers, because the ejected material could not have been shot out by the host star, called V Hydrae. 

The star is a bloated red giant, residing 1,200 light years away and which has probably shed at least half of its mass into space during its death throes. 

Red giants are dying stars in the late stages of life that are exhausting their nuclear fuel that makes them shine. They have expanded in size and are shedding their outer layers into space.

The current best explanation suggests the plasma balls were launched by an unseen companion star. 

According to this theory, the companion would have to be in an elliptical orbit that carries it close to the red giant's puffed-up atmosphere every 8.5 years. 

As the companion enters the bloated star's outer atmosphere, it gobbles up material. This material then settles into a disk around the companion, and serves as the launching pad for blobs of plasma, which travel at roughly a half-million miles per hour.

This star system could be the archetype to explain a dazzling variety of glowing shapes uncovered by Hubble that are seen around dying stars, called planetary nebulae, the researchers said. 

A planetary nebula is an expanding shell of glowing gas expelled by a star late in its life.

"We suggest that these gaseous blobs produced during this late phase of a star's life help make the structures seen in planetary nebulae," Sahai noted.

Sahai's team used Hubble's Space Telescope Imaging Spectrograph (STIS) to conduct observations of V Hydrae and its surrounding region over an 11-year period, first from 2002 to 2004, and then from 2011 to 2013. 

The results appeared in The Astrophysical Journal.

​New York, Oct 8 (IANS) Mother's milk may boost the immunity of a newborn in such a way that it may work against certain diseases like tuberculosis (TB) just as vaccination does, suggests new research.

"Some vaccines are not safe to give a newborn baby and others just don't work very well in newborns," said lead researcher Ameae Walker, Professor at the University of California, Riverside School of Medicine in the US. 

"If we can instead vaccinate mom or boost her vaccination shortly before she becomes pregnant, transferred immune cells during breastfeeding will ensure that the baby is protected early on," Walker explained.

Scientists have long understood that mother's milk provides immune protection against some infectious agents through the transfer of antibodies, a process referred to as "passive immunity." 

The new research, published in the Journal of Immunology, showed that mother's milk also contributes to the development of the baby's own immune system by a process the team calls "maternal educational immunity."

Specific maternal immune cells in the milk cross the wall of the baby's intestine to enter an immune organ called the thymus. Once there, they "educate" developing cells to attack the same infectious organisms to which the mother has been exposed.

"While our work has used mouse models because we can study the process in detail this way, we do know that milk cells cross into human babies as well," Walker pointed out.

The researchers showed that you can vaccinate the mother and this results in vaccination of the baby through this process.

One of the infectious agents the research team studied was the organism that causes tuberculosis. Generally, babies directly vaccinated against TB do not have a very good response. 

"We hope that by vaccinating the mother, who will eventually nurse the baby, we will improve infant immunity against TB," Walker said. 

"It's like vaccinating the baby without actually vaccinating the baby. In some instances, our work has shown that immunity against TB is far more effective if acquired through the milk than if acquired through direct vaccination of the baby," Walker noted.

"Of course, clinical trials will need to be conducted to test whether this is the case in humans," Walker said.

​New York, Oct 8 (IANS) Some fungicides, often regarded as safe for bees, could be a major contributor to honey bee colony losses, and the number of different pesticides within a colony -- regardless of dose -- closely correlates with colony deaths, suggests new research.

"Our results fly in the face of one of the basic tenets of toxicology: that the dose makes the poison," said senior author of the study Dennis van Engelsdorp, Assistant Professor at the University of Maryland in the US.

"We found that the number of different compounds was highly predictive of colony deaths, which suggests that the addition of more compounds somehow overwhelms the bees' ability to detoxify themselves," van Engelsdorp noted.

The researchers followed 91 honey bee colonies in the US, owned by three different migratory commercial beekeepers, for an entire agricultural season. 

The colonies began their journey in Florida and moved up the East Coast, providing pollination services for different crops along the way. 

A total of 93 different pesticide compounds found their way into the colonies over the course of the season, accumulating in the wax, in processed pollen known as bee bread and in the bodies of nurse bees. 

The study, published online in the journal Scientific Reports, showed that colonies with very low pesticide contamination in the wax experienced no queen events or colony death, while all colonies with high pesticide contamination in the wax lost a queen during the beekeeping season.

The study results also suggest that some fungicides, which have led to the mortality of honey bee larvae in lab studies, could have toxic effects on colony survival in the field. 

In the current study, pesticides with a particular mode of action also corresponded to higher colony mortality. 

For example, the fungicides most closely linked to queen deaths and colony mortality disrupted sterols -- compounds that are essential for fungal development and survival.

"We were surprised to find such an abundance of fungicides inside the hives, but it was even more surprising to find that fungicides are linked to imminent colony mortality," lead author on the study Kirsten Traynor from the University of Maryland said.

"These compounds have long been thought to be safe for bees," Traynor noted

​Washington, Oct 7 (IANS) Globally, life expectancy increased from about 62 years to nearly 72 from 1980 to 2015, thanks to improvements in sanitation, immunisations, indoor air quality and nutrition in poor countries, and several nations in sub-Saharan Africa rebounding from high death rates due to HIV/AIDS, says a new report.

However, such progress is threatened by increasing numbers of people suffering serious health challenges related to obesity, high blood sugar, and alcohol and drug abuse, said the Global Burden of Disease 2015 study published in The Lancet.

The study analysed 249 causes of death, 315 diseases and injuries, and 79 risk factors in 195 countries and territories between 1990 and 2015. 

The progress in India, however, has not been very impressive, according to the report.

All countries in the South Asian region did much worse than expected at reducing deaths in children under five, with India recording the largest number of under-five deaths of any country in 2015, at 1.3 million.

Globally, 5.8 million children under age five died in 2015, representing a 52 per cent decline in the number of under-five deaths since 1990. 

"Over the past 25 years, there have been important and impressive gains in the number of children surviving past their fifth birthdays, a significant milestone," said one of the study authors Haidong Wang, Associate Professor at Institute for Health Metrics and Evaluation (IHME) at the University of Washington in Seattle.

"Regrettably, many nations -- especially those low on the Socio-demographic Index -- have not made such gains and need to hasten the pace of progress, including availability of cost-effective vaccines, expanded access to clean water, and other interventions," Wang noted.

The study draws on the work of more than 1,800 collaborators in over 120 countries.

Bangladesh has improved maternal survival much faster than expected, while India and Nepal fared poorly.

Most countries in the South Asian region -- including India and Pakistan -- did better than expected at reducing health loss from stroke and lower respiratory infections. India also performed much worse than expected on tuberculosis, the report said.

The number of maternal deaths globally dropped by roughly 29 per cent since 1990, and the ratio of maternal deaths fell 30 per cent, from 282 per 100,000 live births in 1990 to 196 in 2015.

Between 2005 and 2015, death rates from HIV/AIDS decreased 42 per cent, malaria 43 per cent, preterm birth complications 30 per cent, and maternal disorders 29 per cent, according to the study.