Brain's on-off thirst switch identified

January 27, 2015

Brains on-off

Washington, Jan 27: Scientists have identified neurons that trigger our sense of thirst and those that turn it off.

For years, researchers have suspected that thirst is regulated by neurons in the subfornical organ (SFO), in the hypothalamus. But it has been difficult to pinpoint exactly which neurons are involved.

“When researchers used electrical current to stimulate different parts of the SFO of mice, they got confusing results,” said lead author Yuki Oka, a postdoctoral research scientist in the laboratory of Charles S Zuker, a Howard Hughes Medical Institute Investigator at Columbia University Medical Center (CUMC).

The CUMC team hypothesised that there are at least two types of neurons in the SFO, including ones that drive thirst and others that suppress it.

“Those electrostimulation experiments were probably activating both types of neurons at once, so they were bound to get conflicting results,” said Oka.

To test their hypothesis, Oka and Zuker turned to optogenetics, a more precise technique for controlling brain activity. With optogenetics, researchers can control specific sets of neurons in the brain after inserting light-activated molecules into them.

Shining light onto these molecules turns on the neurons without affecting other types of neurons nearby.

These “mind-control” experiments revealed two types of neurons in the SFO that control thirst: CAMKII neurons, which turn thirst on, and VGAT neurons, which turn it off.

When the researchers turned on CAMK11 neurons, mice immediately began to seek water and to drink intensively.

This behaviour was as strong in well-hydrated mice as in dehydrated ones. Once the neurons were shut off – by turning off the light – the mice immediately stopped drinking.

The researchers also found that light-stimulation of the CAMKII neurons did not induce feeding behaviour. In addition, light-induced thirst was specific for water and did not increase the animals’ consumption of other fluids, including glycerol and honey.

Similar experiments with VGAT neurons showed that these neurons act to turn off thirst. When the researchers turned on these neurons with light, dehydrated mice immediately stopped drinking, even if they were drinking water.

“Together, these findings show that the SFO is a dedicated brain system for thirst,” said Oka.

“The SFO is one of few neurological structures that is not blocked by the blood-brain barrier – it’s completely exposed to the general circulation,” said Oka.

“This raises the possibility that it may be possible to develop drugs for conditions related to thirst,” Oka added.

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Agencies
June 20,2020

The World Health Organisation has warned that the COVID-19 pandemic is entering a "new and dangerous" phase. Thursday saw the most cases in a single day reported to the WHO.

Tedros Adhanom Ghebreyesus said the day had seen 150,000 new cases with half of those coming from the Americas and large numbers also from the Middle East and South Asia, the BBC reported.

He said the virus was still spreading fast and the pandemic accelerating.

He acknowledged people might be fed up with self-isolating and countries were eager to open their economies but he said that now was a time for extreme vigilance.

Maria van Kerkhove, technical lead of the WHO's COVID-19 response, told a press conference the pandemic is "accelerating in many parts of the world".

"While we have seen countries have some success in suppressing transmission and bringing transition down to a low level, every country must remain ready," she said.

Mike Ryan, the head of the WHO's Health Emergencies Programme, said that some countries had managed to flatten the peak of infections without bringing them down to a very low level.

"You can see a situation in some countries where they could get a second peak now, because the disease has not been brought under control," he said.

"The disease will then go away and reduce to a low level, and they could then get a second wave again in the autumn or later in the year."

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Agencies
February 24,2020

Singapore, Feb 24: Last week Singapore's Ministry of Trade and Industry revised their 2020 GDP growth projections downwards to -0.5 to 1.5 per cent, confirming fears of economic fallout from the coronavirus COVID-19. Just three days earlier, while visiting Changi Airport, the Prime Minister told the media that the country is bracing for a significant hit on the economy and the possibility of a recession.

In the budget announcement on February 18, various measures to help affected companies were announced.

This included a jobs support scheme to help companies retain workers that will see the government offset 8 per cent of wages up to SGD3,600(USD2,600) per worker, per month, for a three-month period. Companies will also get a 25 per cent rebate on their taxes for the year capped at SGD15,000 (USD10,800) per company.

There will be additional support for sectors directly affected by the virus outbreak such as tourism, aviation and retail. Qualifying companies will be given property tax rebates and can apply for temporary bridging loans to ease cash flow. Rebates will be offered on aircraft landing and parking charges as well as rental rebates for shops and cargo agents at Changi Airport.

Overall, the economic package will cost Singapore some USD 4.6 billion, well in excess of the USD 500 million some analysts had predicted. The resulting spending plan including the virus economic package will see a budget deficit of SGD 10.9 billion or 2.1 per cent of GDP, the highest since the Asian financial crisis of 1997.

It is hoped that with financial support, companies in Singapore will not only be able to ride through the current rough patch but be able to position themselves better to take off once the economic crisis brought upon by the contagion is over.

Which then are the Singapore companies that can potentially ride out the current storm and emerge stronger?

Aviation and hospitality firms are among those most impacted by the virus outbreak and Singapore Airlines (SIA) comes to mind. SIA is a well-run company but has seen its share price fall about 5.2 percent since the beginning of the year. In the short term, revenue and profits will no doubt be affected but it will recover in the long run.

Hospitality sector companies like Ascott Residence whose main sponsor is Capitaland, Southeast Asia's largest landlord, and CDL Hospitality, have seen 1.5 and 5.5 percent (respectively) shaved off their share prices since the start of the year.

In reporting financial results for the quarter which ended in December on February 14, Alibaba CEO Daniel Zhang said that due to the virus, they are seeing large changes in buying patterns. With widespread home confinement, there is a growing demand for delivery services including online food and grocery delivery, as well as office apps and streaming entertainment.

Similarly, in Singapore, with more people staying and working from home, the three main food delivery services, Grab Food, Foodpanda and Deliveroo, are doing roaring business. All three are privately held.

In late January, as the scale of the outbreak became more apparent, investors began pouring money into health-product firms in Asia that they think will benefit from the virus outbreak.

Bloomberg reported that when Chinese pharmaceutical companies like Da An Gene Co, Xilong Scientific and Shanghai Kehua Bio-Engineering said they have developed kits for detecting the virus, their stocks soared to hit the 10 per cent daily limit. Firms manufacturing protection gear and air-cleaning equipment climbed more than 10 per cent in Japan, while Malaysian rubber gloves producers climbed at least 5 per cent.

Naturally, many would view that pharmaceutical companies that have the technology and expertise to develop drugs to treat patients with the virus or are able to develop a vaccine, would stand to benefit from the coronavirus outbreak.

Firms like and Johnson & Johnson, Pfizer, MSD, GlaxoSmithKline (GSK) and Sanofi are the pharmaceutical behemoths that dominate the global vaccine market.

However, industry experts speaking to the BBC warned that a pot of gold is not necessarily waiting for any company that successfully develops a vaccine. Although the global vaccine market is expected to grow to USD60 billion this year, it is costly and time-consuming to develop and pass it through for use by the general public.

It is also unclear if Indian pharmaceutical firms will be able to benefit from the demand for medicines that can treat or prevent the virus.

India is the world's largest manufacturer of generic drugs and it supplies 20 percent of the world's drugs by volume. However, it sources 70 percent of its raw material from China. If supplies are disrupted beyond a month to a month and a half, they may see a slow-down in production. According to a CNN report, the companies that are most impacted by material shortages are GSK India, Pfizer (PFE) and Cipla. Other companies like Aurobindo Pharma, Cadila Healthcare and Sun Pharma are said to be carefully monitoring the situation.

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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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