Fish eyes may hold key to blindness cure: study

March 11, 2017

Washington, Mar 11: Scientists, including one of Indian-origin, have identified a chemical signal in the zebrafish brain that helps it regenerate retina, a finding that may help cure blindness in humans.

fisheye

The discovery raises the possibility that human retinas can be induced to regenerate, naturally repairing damage caused by degenerative retinal diseases and injury, including age-related macular degeneration and retinitis pigmentosa, researchers said.

"The prevailing belief has been that the regeneration process in fish retinas is triggered by secreted growth factors, but our results indicate that the neurotransmitter GABA might initiate the process instead," said James Patton, Professor at Vanderbilt University in the US.

"All the regeneration models assume that a retina must be seriously damaged before regeneration takes place, but our studies indicate that GABA can induce this process even in undamaged retinas," said Patton.

It turns out that the structure of the retinas of fish and mammals are basically the same.

Although the retina is very thin - less than 0.5 millimetres thick - it contains three layers of nerve cells: photoreceptors that detect the light, horizontal cells that integrate the signals from the photoreceptors and ganglion cells that receive the visual information and route it to the brain.

In addition, the retina contains a special type of adult stem cell, called Muller glia, that span all three layers and provide mechanical support and electrical insulation. In fish retinas, they also play a key role in regeneration.

When regeneration is triggered, the Muller glia dedifferentiate, begin proliferating, and then differentiate into replacements for the damaged nerve cells. Muller glia are also present in mammalian retinas, but do not regenerate.

Graduate student Mahesh Rao got the idea that GABA - normally a fast-acting neurotransmitter best known for its role of calming nervous activity by inhibiting nerve transmission in the brain - might be the trigger for retinal regeneration.

He was inspired by the results of a study in the mouse hippocampus which found that GABA was controlling stem cell activity.

Working with Patton and assistant professor Dominic Didiano, Rao designed a series of experiments with zebrafish which determined that high concentrations of GABA in the retina keep the Miller glia quiescent and that they begin dedifferentiating and proliferating when GABA concentrations drop.

They tested their hypothesis in two ways: By blinding zebrafish and injecting them with drugs that stimulate GABA production and by injecting normal zebrafish with an enzyme that lowers the GABA levels in their eyes.

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Agencies
March 16,2020

New Delhi, Mar 16: A recent survey across 140 districts of the country shows that about 54 per cent of Indians are finding travelling to be unsafe as the deadly coronavirus (COVID-19) pandemic sweeps globally.

The big worry that people have is community transmission, something that researchers from around the world have approximated at 10 per cent of total infections and more common in places like Wuhan in China, South Korea, Iran and Italy.

The months of March to June have historically been high travel season for most Indians, largely due to the summer vacations in schools. "But it seems that Indians do not want to take a chance with this rather scary virus and are either cancelling or postponing their travel plans," concluded the survey by LocalCircles.

The survey gathered more than 22,000 responses from participants in tier one, two and three cities. It said 48 per cent Indians plan to cancel their international business travel for the next four months.

Besides, nearly 38 per cent of respondents said they had to pay cancellation fee to the website, travel agent, airline or railways.

"These are testing times for the entire travel and tourism industry -- airlines, hotels, travel agents as well as small tour and taxi operators. The best solution at this point is to adjust cost structures, stay flexible and work with a collective approach to minimise the period of impact to both citizens and business," said LocalCircles.

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Agencies
July 14,2020

UN, Jul 14: There will be no return to the "old normal" for the foreseeable future as a result of the ongoing COVID-19 pandemic, and too many countries were still headed in the wrong direction, the chief of the World Health Organization (WHO) warned.

"The virus remains public enemy number one, but the actions of many governments and people do not reflect this," Xinhua news agency quoted WHO Director-General Tedros Adhanom Ghebreyesus at as saying a regular briefing on Monday.

He noted that mixed messages from leaders are undermining trust, which is the most critical ingredient of any response, while the only aim of the virus is to find people to infect.

Things are going to "get worse and worse and worse", he warned, unless governments communicate clearly with their citizens and roll out a comprehensive strategy focused on suppressing transmission and saving lives, while populations follow the basic public health principles of physical distancing, hand washing, wearing masks, coughing etiquette and staying home when sick.

COVID-19 has been gaining its momentum lately.

According to Tedros, Sunday saw a record of 230,000 cases reported to WHO, of which almost 80% were from just 10 countries and about half from just two countries.

"But it does not have to be this way," he said, asking every single leader, government and individual "to do their bit to break the chains of COVID-19 transmission and end the collective suffering".

To control the disease and get on with people's lives, Tedros said, three things are required. The first is to focus on reducing mortality and suppressing transmission; the second is to focus on an empowered, engaged community that takes individual behaviour measures in the interest of each other.

And the third is a strong government leadership and coordination of comprehensive strategies that are communicated clearly and consistently.

"We weren't prepared collectively, but we must use all the tools we have to bring this pandemic under control. And we need to do it right now," he added.

At the WHO briefing on Monday, health experts also said there was evidence to suggest that children under the age of 10 were only very mildly affected by Covid-19, while those over 10 seemed to suffer similar mild symptoms to young adults.

To what extent children can transmit the virus, while it appears to be low, remains unknown.

On Tuesday, the number of global coronavirus cases cross the 13 million mark, according to the Johns Hopkins University.

The total number of cases currently stood at 13,070,097, while the fatalities rose to 572,411, the University's Center for Systems Science and Engineering (CSSE) revealed in its latest update.

The US accounted for the world's highest number of infections and fatalities at 3,363,056 and 135,605, respectively, according to the CSSE.

Brazil came in the second place with 1,884,967 infections and 72,833 deaths.

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Agencies
February 27,2020

Washington D.C, Feb 27: New research shows that adults who have low fruit and vegetable intake are more likely to be diagnosed with an anxiety disorder.

"For those who consumed less than 3 sources of fruits and vegetables daily, there was at least at 24% higher odds of anxiety disorder diagnosis," says the lead author of the Canadian Longitudinal Study, Karen Davison, who is a health science faculty member, nutrition informatics lab director at Kwantlen Polytechnic University, (KPU) and North American Primary Care Research Group Fellow.

"This may also partly explain the findings associated with body composition measures. As levels of total body fat increased beyond 36%, the likelihood of anxiety disorder was increased by more than 70%," states co-author Jose Mora-Almanza, a Mitacs Globalink intern who worked with the study at KPU.

"Increased body fat may be linked to greater inflammation. Emerging research suggests that some anxiety disorders can be linked to inflammation," says Davison.

In addition to diet and body composition measures, the prevalence of anxiety disorders also differed by gender, marital status, income, immigrant status and several health issues.

An important limitation of the study was that the assessment of anxiety disorders was mostly based upon self-reporting of a medical diagnosis.

"It is estimated that 10% of the global population will suffer from anxiety disorders which are a leading cause of disability," says Karen Davison

"Our findings suggest that comprehensive approaches that target health behaviours, including diet, as well as social factors, such as economic status, may help to minimize the burden of anxiety disorders among middle-aged and older adults, including immigrants," she concluded.

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