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
June 11,2020

The World Health Organisation (WHO) Director-General Tedros Adhanom Ghebreyesus said that more research needs to be done to better understand the extent to which COVID-19 is being spread by people who don't show symptoms.

"Since early February, we have said that asymptomatic people can transmit COVID-19, but that we need more research to establish the extent of asymptomatic transmission," the WHO chief said at a virtual press conference from Geneva on Wednesday, Xinhua news agency reported.

"That research is ongoing, and we're seeing more and more research being done," he added.

Saying that the world has been achieving a lot in knowing the new virus, the WHO chief told reporters that "there's still a lot we don't

"WHO's advice will continue to evolve as new information becomes available," he said.

Tedros stressed that the most critical way to stop transmission is to find, isolate and test people with symptoms, and trace and quarantine their contacts.

"Many countries have succeeded in suppressing transmission and controlling the virus doing exactly this," Tedros said.

Meanwhile, Michael Ryan, executive director of WHO Health Emergencies Program, said Wednesday that the COVID-19 pandemic is still evolving.

"If we look at the numbers... this pandemic is still evolving. It is growing in many parts of the world," he said. "We have deep concerns that health systems of some countries are struggling, under a huge strain and require our support, our help and our solidarity."

He said "each and every country has a different combination of risks and opportunities, and it's really down to national authorities to carefully consider where they are in the pandemic."

In Europe, the risk issue now are about travels and the opening of the schools, around risk management, mass gathering, surveillance and contact tracing, said the WHO official.

In Southeast Asian countries, where to a great extent transmissions have been under control, governments are more concerned about the re-emergence of clusters, while in South America, the issue of PPE for health workers has not gone away, said Ryan.

As regards Africa, Ryan said the death rates have been very low in the past week, but the health system can be overwhelmed, as it would have to cope with other diseases such as malaria.

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January 25,2020

Washington D.C., Jan 25: A new study conducted by a team of researchers reveals why individuals who have a history of early life adversity (ELA) are disproportionately prone to opioid addiction.

The study conducted examined how early adversities interact with factors such as increased access to opioids to directly influence brain development and function, causing a higher potential for opioid addiction.

The study was lead by UCI researchers and was published in Molecular Psychiatry.

Tallie Z. Baram, MD, PhD, the Danette Shepard Chair in Neurological Sciences at the UCI School of Medicine and one of the senior researchers for the study, was on the take that the widely known factor genetics that plays major role in addiction vulnerability, cannot be solely held responsible for the recent rise in opioid abuse.

To further clarify, the researchers simulated ELA in rats by limiting bedding and nesting materials during a short, postnatal period of time.

In female rats, this led to striking opioid addiction-like characteristics including an increased relapse- behaviour, for example.

As observed in addicted humans, the rats were willing to work very hard (pay a very high price) to obtain the drug.

Baram said: "Ultimately, we found that conditions during sensitive developmental periods can lead to vulnerability to the addictive effects of opioid drugs, especially in females, which is consistent with the prevalence of ELA in heroin-addicted women."

These findings can be used to highlight the importance given to sex differences in future ELA-related studies on opioid addiction, and in future prevention or intervention strategies being developed to address the growing opioid crisis.

The study conducted examined how early adversities interact with factors such as increased access to opioids to directly influence brain development and function, causing a higher potential for opioid addiction.

The study was lead by UCI researchers and was published in Molecular Psychiatry.

The study found that unpredictable, fragmented early life environments may lead to abnormal maturation of certain brain circuits, which profoundly impacts brain function and persists into adolescence and adulthood.

Tallie Z. Baram, MD, PhD, the Danette Shepard Chair in Neurological Sciences at the UCI School of Medicine and one of the senior researchers for the study, was on the take that the widely known factor genetics that plays major role in addiction vulnerability, cannot be solely held responsible for the recent rise in opioid abuse.

To further clarify, the researchers implanted ELA in rats by limiting bedding and nesting materials during a short, postnatal period of time.

In female rats, this led to striking opioid addiction-like characteristics including an increased relapse- behaviour, for example.

As observed in addicted humans, the rats were willing to work very hard (pay a very high price) to obtain the drug.

Baram said: "Ultimately, we found that conditions during sensitive developmental periods can lead to vulnerability to the addictive effects of opioid drugs, especially in females, which is consistent with the prevalence of ELA in heroin-addicted women."

These findings can be used to highlight the importance given to sex differences in future ELA-related studies on opioid addiction, and in future prevention or intervention strategies being developed to address the growing opioid crisis.

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Agencies
April 4,2020

Washington D.C., Apr 4: While consuming a high-diet salt can result in high blood pressure, a recent study has revealed a link between salt-rich diet and weaker immune system.

The study was conducted under the leadership of the University Hospital Bonn, and the results were published in the journal Science Translational Medicine.

The research was conducted on mice that were fed a high-salt diet. Later, they were found to suffer from much more severe bacterial infections.

Human volunteers who consumed an additional six grams of salt per day also showed pronounced immune deficiencies.

The World Health Organization (WHO) has recommended a maximum amount of five grams of salt a day.

It corresponds approximately to one level teaspoon. In reality, however, many Germans exceed this limit considerably. 

Figures from the Robert Koch Institute suggest that on average men consume ten, and women more than eight grams a day.

This means that we reach for the salt shaker much more than is good for us. After all, sodium chloride, which is its chemical name, raises blood pressure and thereby increases the risk of heart attack or stroke.

"We have now been able to prove for the first time that excessive salt intake also significantly weakens an important arm of the immune system," said Prof. Dr. Christian Kurts from the Institute of Experimental Immunology at the University of Bonn.

This finding is unexpected, as some studies point in the opposite direction. For example, infections with certain skin parasites in laboratory animals heal significantly faster if these consume a high-salt diet.

The study also sheds light on the fact that the skin serves as a salt reservoir.

"Our results show that this generalization is not accurate," emphasized Katarzyna Jobin, lead author of the study.

The body keeps the salt concentration in the blood and in the various organs largely constant. Otherwise important biological processes would be impaired. The only major exception is the skin which functions as a salt reservoir of the body. This is why the additional intake of sodium chloride works so well for some skin diseases.

However, other parts of the body are not exposed to the additional salt consumed with food. Instead, it is filtered out by the kidneys and excreted in the urine.

"We examined volunteers who consumed six grams of salt in addition to their daily intake," said Prof. Kurts. This is roughly the amount contained in two fast-food meals, i.e. two burgers and two portions of French fries.

After one week, from the results, it showed that the immune cells coped much worse with bacteria after the test subjects had started to eat a high-salt diet.

In human volunteers, excessive salt intake also resulted in increased glucocorticoid levels.

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