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Comment by Dr. Krishna Kumari Challa on October 6, 2021 at 9:57am

New study uncovers brain circuits that control fear responses

Researchers  have discovered a brain mechanism that enables mice to override their instincts based on previous experience.

The study, published today in Neuron, identifies a new brain circuit in the ventral lateral geniculate nucleus (vLGN), an inhibitory structure in the brain. The neuroscientists found that when activity in this brain region was suppressed, animals were more likely to seek safety and escape from perceived danger, whereas activation of vLGN neurons completely abolished escape responses to imminent threats.

While it is normal to experience fear or anxiety in certain situations, we can adjust our fear responses depending on our knowledge or circumstances. For example, being woken up by loud blasts and bright lights nearby might evoke a fear reaction. But if you have experienced fireworks before, your knowledge will likely prevent such reactions and allow you to watch without fear. On the other hand, if you happen to be in a war zone, your fear reaction might be strongly increased.

While many brain regions have previously been shown to be involved in processing perceived danger and mediating fear reactions, the mechanisms of how these reactions are controlled are still unclear. Such control is crucial since its impairment can lead to anxiety disorders such as phobias or post-traumatic stress disorders (PTSD), in which the circuits in the brain associated with fear and anxiety are thought to become overactive, leading to pathologically increased fear responses.

The new study took advantage of an established experimental paradigm in which mice escape to a shelter in response to an overhead expanding dark shadow. This looming stimulus simulates a predator moving towards the animal from above.

The researchers found that the vLGN could control escape behavior depending on the animal's knowledge gained through previous experience, and on its assessment of risk in its current environment. When mice were not expecting a threat and felt safe, the activity of a subset of inhibitory neurons in the vLGN was high, which in turn could inhibit threat reactions. In contrast, when mice expected danger, activity in these neurons was low, which made the animals more likely to escape and seek safety.

vLGN specifically inhibits neurons in the superior colliculus that respond to visual threats and thereby specifically blocks the pathway in the brain that mediates reactions to such threats—something the animal sees that could pose a danger like an approaching predator.

Flexible inhibitory control of visually-evoked defensive behaviour by the ventral lateral geniculate nucleus, Neuron (2021). DOI: 10.1016/j.neuron.2021.09.003

https://medicalxpress.com/news/2021-10-uncovers-brain-circuits-resp...

Comment by Dr. Krishna Kumari Challa on October 6, 2021 at 9:06am

Within the environment of the nucleus, it would make sense that genes regulated by the same type of information would be concentrated in close proximity so that they might share resources, potentially lowering the energetic cost of regulation. Several previous experiments have shown a level of organization in the nucleus where genes occupy discrete domains. However, many of these studies use biochemical methods to define domains, rather than actually observing the physical position of the active genes within the nucleus.

In the Current Biology study, the researchers demonstrated that they could accurately identify the physical position of the active genes using a microscopy imaging procedure and fruit flies, a model organism commonly used in genetic and molecular research. The researchers examined how a fertilized fruit fly egg develops into a fully formed organism, a process that requires the activity of sets of genes, which become progressively activated during embryonic development.

Focusing on the earliest set of genes appearing in 90-minute-old fruit fly embryos, the researchers observed how a protein called Zelda regulates the genes' transcription by recruiting the enzyme RNA Polymerase II (Pol-II). Using high resolution microscopy and antibody staining, they visualized Pol-II at sites of nascent transcription on chromosomes.

By observing the positions of many genes using this method, they asked the question: Are genes found in clusters? The answer was no.

The researchers performed a series of follow-up experiments to test the notion of functional clustering, such as looking for gene expression changes when genes were found in close proximity, or signs of resources being shared among the genes visualized. Once again, they did not find evidence of clustering.

In contrast to the idea that genes are spatially clustered and share transcriptional resources—what one might call a "collectivist" model—the authors conclude that the data support an "individualist" model of gene control at early genome activation in fruit flies.

Spatial organization of transcribing loci during early genome activation in Drosophila, Current Biology (2021). DOI: 10.1016/j.cub.2021.09.027

https://phys.org/news/2021-10-genes-individualists-collectivists-ea...

Comment by Dr. Krishna Kumari Challa on October 6, 2021 at 9:05am

Genes are individualists, not collectivists, during early fruit fly development

Active genes do not form clusters and share resources during early development in the fruit fly, according to a new study by researchers published in the journal Current Biology.

The study changes the way we think about how the molecular machinery functions in basic cellular mechanisms during the development of organisms.

The nucleus is the portion of the cell containing the vast majority of genetic information—including the complex jumble of long cables of DNA that make up the genome—in order to determine the behavior of that organism. Genes stored in the sequence of DNA encode not just the protein sequence required to express the trait associated with that gene, but also the information for when that protein sequence should be manufactured.

"The nucleus is an elaborate switchboard—the connection point for the vast array of information about the state of the cell's environment, which will be processed and responded to by a defined set of expressed protein products. Within this framework, this study asked if there exists cooperation between these hundreds of logic gates making individual decisions about when to manufacture their respective proteins.

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Comment by Dr. Krishna Kumari Challa on October 6, 2021 at 8:53am

Announcement of the 2021 Nobel Prize in Physics

Three scientists won the Nobel Prize in physics Tuesday for work that found order in seeming disorder, helping to explain and predict complex forces of nature, including expanding our understanding of climate change.

Comment by Dr. Krishna Kumari Challa on October 5, 2021 at 10:03am

Our DNA is becoming the world's tiniest hard drive

Our genetic code is millions of times more efficient at storing data than existing solutions, which are costly and use immense amounts of energy and space. In fact, we could get rid of hard drives and store all the digital data on the planet within a couple hundred pounds of DNA.

Using DNA as a high-density data storage medium holds the potential to forge breakthroughs in biosensing and biorecording technology and next-generation digital storage, but researchers haven't been able to overcome inefficiencies that would allow the technology to scale.

Now, researchers at Northwestern University propose a new method for recording information to DNA that takes minutes, rather than hours or days, to complete. The team used a novel enzymatic system to synthesize DNA that records rapidly changing environmental signals directly into DNA sequences, a method the paper's senior author said could change the way scientists study and record neurons inside the brain.

The research, "Recording Temporal Signals with Minutes Resolution Using Enzymatic DNA Synthesis," was published Thursday (Sept. 30) in the Journal of the American Chemical Society.

Namita Bhan et al, Recording Temporal Signals with Minutes Resolution Using Enzymatic DNA Synthesis, Journal of the American Chemical Society (2021). DOI: 10.1021/jacs.1c07331

https://phys.org/news/2021-10-dna-world-tiniest-hard.html?utm_sourc...

Comment by Dr. Krishna Kumari Challa on October 5, 2021 at 9:58am

The researchers combined infrared satellite imagery and readings from thousands of ground instruments to determine maximum daily heat and humidity readings in 13,115 cities, from 1983 to 2016. They defined extreme heat as 30 degrees Centigrade on the so-called "wet-bulb globe temperature" scale, a measurement that takes into account the multiplier effect of high humidity on human physiology. A wet-bulb reading of 30 is the rough equivalent of 106 degrees Fahrenheit on the so-called "real feel" heat index—the point at which even most healthy people find it hard to function outside for long, and the unhealthy might become very ill or even die.

To come up with a measure of person-days spent in such conditions, the researchers matched up the weather data with statistics on the cities' populations over the same time period.

The analysis revealed that the number of person-days in which city dwellers were exposed went from 40 billion per year in 1983 to 119 billion in 2016—a threefold increase. By 2016, 1.7 billion people were being subjected to such conditions on multiple days.

The most-affected cities tend to cluster in the low latitudes, but other areas are being affected, too. The worst-hit city in terms of person-days was Dhaka, the fast-growing capital of Bangladesh; it saw an increase of 575 million person-days of extreme heat over the study period. Its ballooning population alone—4 million in 1983, to 22 million today—caused 80 percent of the increased exposure. This does not mean that Dhaka did not see substantial warming—only that population growth was even more rapid. Other big cities showing similar population-heavy trends include Shanghai and Guangzhou, China; Yangon, Myanmar; Bangkok; Dubai; Hanoi; Khartoum; and various cities in Pakistan, India and the Arabian Peninsula.

https://phys.org/news/2021-10-exposure-deadly-urban-worldwide-tripl...

Part 2

Comment by Dr. Krishna Kumari Challa on October 5, 2021 at 9:56am

Exposure to deadly urban heat worldwide has tripled in recent decades, says study

A new study of more than 13,000 cities worldwide has found that the number of person-days in which inhabitants are exposed to extreme combinations of heat and humidity has tripled since the 1980s. The authors say the trend, which now affects nearly a quarter of the world's population, is the combined result of both rising temperatures and booming urban population growth. The study was published today in the Proceedings of the National Academy of Sciences.

Over recent decades, hundreds of millions have moved from rural areas to cities, which now hold more than half the world's population. There, temperatures are generally higher than in the countryside, because of sparse vegetation and abundant concrete, asphalt and other impermeable surfaces that tend to trap and concentrate heat —the so-called urban heat island effect.

 This has broad effects. It increases morbidity and mortality. It impacts people's ability to work, and results in lower economic output. It exacerbates pre-existing health conditions.

 Global urban population exposure to extreme heat, Proceedings of the National Academy of Sciences (2021). doi.org/10.1073/pnas.2024792118

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Comment by Dr. Krishna Kumari Challa on October 5, 2021 at 9:33am

2 win medicine Nobel for showing how we react to heat, touch

Two scientists won the Nobel Prize in medicine on Monday for their discoveries into how the human body perceives temperature and touch, revelations that could lead to new ways of treating pain or even heart disease.

 David Julius and Ardem Patapoutian separately identified receptors in the skin that respond to heat and pressure, and researchers are working on drugs to target them. Some hope the discoveries could eventually lead to pain treatments that reduce dependence on highly addictive opioids. 

Julius, of the University of California at San Francisco, used capsaicin, the active component in chili peppers, to help pinpoint the nerve sensors that respond to heat, the Nobel Committee said. Patapoutian, of Scripps Research Institute at La Jolla, California, found pressure-sensitive sensors in cells that respond to mechanical stimulation.

This really unlocks one of the secrets of nature. It's actually something that is crucial for our survival, so it's a very important and profound discovery.

Announcement of the 2021 Nobel Prize in Physiology or Medicine

https://medicalxpress.com/news/2021-10-nobel-prize-honors-discovery...

Comment by Dr. Krishna Kumari Challa on October 4, 2021 at 11:20am

The promise of medical science

Understanding and treating Necrotizing Enterocolitis in babies

Comment by Dr. Krishna Kumari Challa on October 3, 2021 at 1:55pm

Mystery of the Pulsating Spider

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