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Comment by Dr. Krishna Kumari Challa on March 22, 2024 at 9:30am

How cells in plant leaves organize themselves to ensure optimal area for photosynthesis

Plant leaves need a large surface area to capture sunlight for photosynthesis. Researchers  have now discovered which genetic mechanisms control leaves' growth into a flat structure capable of efficiently capturing sunlight.

A kind of built-in GPS informs each cell about its relative position in the growing leaf. The order corresponds to a biological concept of self-organization.

When cells divide and multiply, the result is usually a clump of cells. So researchers wanted to know how, in the case of a leaf, cell division leads to a large flat area.

To this end, a team of mathematicians and experimental biologists worked together to track the processes using computer models, methods of molecular genetics, and imaging techniques on living organisms.

The basis of such pattern formation is polarity; that is, the ability to distinguish, in this case, between top and bottom. It is usually created by a concentration gradient of a substance, called morphogen, that is low on one side and higher on the other.

The team discovered that "small RNAs" play a decisive role in controlling the growing leaf. As mobile messengers, they are used for communication between the cells and help the cells to perceive their relative position to each other in the structure—like a GPS. In addition, the small RNAs transmit information that coordinates which genes need to be activated or inhibited on the top and bottom side to give the leaf the right shape and function.

This regulatory mechanism works autonomously in the growing leaf; there is no central control in the plant.

The small RNA molecules in the cells of the growing leaf set in motion a genetic process that enables the cells to perceive and interpret their environment. The genes' activities are coordinated among the cells in such a way that each leaf is divided in a sharply defined top and bottom part that form a perfectly flat canvas for photosynthesis.

Emanuele Scacchi et al, A diffusible small-RNA-based Turing system dynamically coordinates organ polarity, Nature Plants (2024). DOI: 10.1038/s41477-024-01634-x

Comment by Dr. Krishna Kumari Challa on March 22, 2024 at 9:19am

Neuralink shows quadriplegic playing chess with brain implant

Neuralink recently streamed a video of its first human patient playing computer chess with his mind and talking about the brain implant making that possible.

Comment by Dr. Krishna Kumari Challa on March 21, 2024 at 11:46am

Researchers find evidence of 68 'forever chemicals' in food packaging around the world

A team of environmental scientists with the Food Packaging Forum Foundation, based in Zürich, has found evidence of 68 "forever chemicals" in food packaging used around the world. For their study, published in the journal Environmental Science & Technology, the group mapped evidence of per- and polyfluoroalkyl substances (PFASs) in food contact materials using information from databases.

PFASs are a group of manmade chemical compounds that are known as "forever" chemicals because it takes them so long to break down in the environment. To date, approximately 4,730 distinct PFASs have been created. Manufacturers began using them several decades ago for their water-resistance properties. They have typically been used in such products as nonstick stain-resistant fabrics, cookware, water-repellent clothing, carpeting, cosmetics, firefighting foams, electronics and food packaging.

Over the past several decades, many PFASs have been found to have adverse health impacts on animals, including humans. Because of that, many of them have been banned around the world.

In this new study, the research team looked into the use of PFASs in food packaging around the world, as recent research has shown that the compounds can migrate into the food.

The researchers collected records from the FCCmigex database involving food packaging and any known PFAS. They found 68 of the compounds, 61 of which have been specifically banned from use in such packaging. They were only able to find potential hazards for just 57% of the compounds they found.

In looking at the compounds they found in the packaging, the research team notes that little evidence is available to explain how or why they wound up where they did. They suggest a comprehensive review of packaging be undertaken and new rules and a means for enforcing them be established.

Drake W. Phelps et al, Per- and Polyfluoroalkyl Substances in Food Packaging: Migration, Toxicity, and Management Strategies, Environmental Science & Technology (2024). DOI: 10.1021/acs.est.3c03702

Comment by Dr. Krishna Kumari Challa on March 21, 2024 at 10:06am

Decades of research have revealed trends in how the shapes and structures of different surfaces affect water's freezing point. In an earlier study on ice-nucleating proteins within bacteria, researchers found that the distances between the groups of proteins could impact the temperature at which ice formed. There were distances that were very favorable for ice formation, and distances that were completely opposite.

Similar trends had been observed for other surfaces, but no mathematical explanation had been found.

Researchers now  gathered hundreds of previously reported measurements on how the angles between microscopic bumps on a surface affected water's freezing temperature.  They then tested theoretical models against the data. They used the models to consider factors that would encourage ice crystal formation, such as how strongly water binds to the surfaces and angles between structural features.

In the end, they identified a mathematical expression that shows that certain angles between surface features makes it easier for water molecules to gather and crystallize at relatively warmer temperatures. 

They say their model can help design materials with surfaces that would make ice form more efficiently with minimal energy input. Examples include snow or ice makers, or surfaces that are suitable for cloud seeding.

The researchers plan to use this model to return to their studies of ice-nucleating proteins in bacteria.

https://www.acs.org/pressroom/presspacs/2024/march/new-model-clarif...

Comment by Dr. Krishna Kumari Challa on March 21, 2024 at 10:00am

Why water freezes at a range of temperatures

 Water's freezing point is generally accepted to be 32 degrees Fahrenheit. But that is due to ice nucleation—impurities in everyday water raise its freezing point to this temperature. Now, researchers unveil a theoretical model that shows how specific structural details on surfaces can influence water's freezing point.

Ice nucleation is one of the most common phenomena in the atmosphere. "In the 1950s and 1960s, there was a surge of interest in ice nucleation to control weather through cloud seeding and for other military goals. Some studies addressed how small shapes promote ice nucleation, but the theory was undeveloped, and no one has done anything quantitative.

When temperatures drop, the molecules in liquid water, which normally speed around and zip past one another, lose energy and slow down. Once they lose enough energy, they grind to a halt, orient themselves to avoid repulsions and maximize attractions, and vibrate in place, forming the crystalline network of water molecules we call ice.

When liquid water is completely pure, ice may not form until the temperature gets down to a frigid –51 degrees Fahrenheit; this is called supercooling. But when even the tiniest impurities—soot, bacteria or even particular proteins—are present in water, ice crystals can form more easily on the surfaces, resulting in ice formation at temperatures warmer than –51 degrees Fahrenheit.

Part 1

Comment by Dr. Krishna Kumari Challa on March 21, 2024 at 9:56am

Life's building blocks are surprisingly stable in Venus-like conditions: Study

If there is life in the solar system beyond Earth, it might be found in the clouds of Venus. In contrast to the planet's blisteringly inhospitable surface, Venus' cloud layer, which extends from 30 to 40 miles above the surface, hosts milder temperatures that could support some extreme forms of life.

If it's out there, scientists have assumed that any Venusian cloud inhabitant would look very different from life forms on Earth. That's because the clouds themselves are made from highly toxic droplets of sulfuric acid—an intensely corrosive chemical that is known to dissolve metals and destroy most biological molecules on Earth.

But a new study by  researchers may challenge that assumption. Published today in the journal Astrobiology, the study reports that, in fact, some key building blocks of life can persist in solutions of concentrated sulfuric acid.

The study's authors have found that 19 amino acids that are essential to life on Earth are stable for up to four weeks when placed in vials of sulfuric acid at concentrations similar to those in Venus' clouds. In particular, they found that the molecular "backbone" of all 19 amino acids remained intact in sulfuric acid solutions ranging in concentration from 81% to 98%.

What is  surprising is that concentrated sulfuric acid is not a solvent that is universally hostile to organic chemistry.

We are finding that building blocks of life on Earth are stable in sulfuric acid, and this is very intriguing for the idea of the possibility of life on Venus.

It doesn't mean that life there will be the same as here. In fact, we know it can't be. But this work advances the notion that Venus' clouds could support complex chemicals needed for life.

The search for life in Venus' clouds has gained momentum in recent years, spurred in part by a controversial detection of phosphine—a molecule that is considered to be one signature of life—in the planet's atmosphere. While that detection remains under debate, the news has reinvigorated an old question: Could Earth's sister planet actually host life?

In search of an answer, scientists are planning several missions to Venus, including the first largely privately funded mission to the planet, backed by California-based launch company Rocket Lab. That mission aims to send a spacecraft through the planet's clouds to analyze their chemistry for signs of organic molecules.

Maxwell D. Seager et al, Stability of 20 Biogenic Amino Acids in Concentrated Sulfuric Acid: Implications for the Habitability of Venus' Clouds, Astrobiology (2024). DOI: 10.1089/ast.2023.0082

Comment by Dr. Krishna Kumari Challa on March 21, 2024 at 7:19am

What are retroviruses?

A retrovirus is a type of RNA virus. RNA viruses have genes encoded in RNA instead of DNA. Like other viruses, retroviruses need to use the cellular machinery of the organisms they infect to make copies of themselves. Infection by a retrovirus, however, requires an additional step.

Retroviruses are "retro" because they reverse the direction of the normal gene-copying process. Usually, cells convert DNA into RNA so that it can be made into proteins. But with retroviruses, the process has to start by going backward.

A retrovirus replicates itself by first reverse-coding its genes into the DNA of the cells it infects. It does this with an enzyme called reverse transcriptase.

Retroviruses use reverse transcriptase to transform their single-stranded RNA into double-stranded DNA. DNA molecules store the genetic information of human cells and cells from other life forms.

Once transformed from RNA to DNA, the viral DNA is integrated into the genome of the infected cells. When this happens, the cells are tricked into copying these genes as part of the normal replication process.

The cell can also transcribe the DNA back into RNA as the first step in making viral proteins.

Retroviruses are sometimes used as gene delivery methods in gene therapy. This is because these viruses are both easy to modify and easily integrated into the host genome.

This means that, in theory, retroviruses can be used to make cellular machinery to produce proteins in an ongoing way. For example, scientists have used retroviruses to help diabetic rats make their own insulin.

Many retroviruses have been identified that infect non-human animals. Only a few retroviruses are known to cause illness in human beings, however. The most well-known of these are HIV and human T-cell lymphotropic virus.

Part 4

Comment by Dr. Krishna Kumari Challa on March 21, 2024 at 7:10am

Myelin is a coating of fat and protein that encases long nerve fibers known as axons. The coating works a bit like the insulation around an electrical wire: Nerves sheathed in myelin can send electrical signals faster than uninsulated nerves can.

Coated nerve fibers can also be thinner and grow longer than they would without insulation, enabling animals to grow bigger. And thinner fibers can be packed into the nervous system more efficiently.

As a result of myelin, brains became more complex and vertebrates became more diverse. If myelination hadn’t happened in early vertebrate evolution, we wouldn’t have the whole galaxy of vertebrate diversity that we see now.

T. Ghosh et al. A retroviral link to vertebrate myelination through retrotransposon.... Cell. Published online February 15, 2024. doi: 10.1016/j.cell.2024.01.011.

Part 3

Comment by Dr. Krishna Kumari Challa on March 21, 2024 at 7:08am

Ancient viruses helped speedy nerves evolve

The trick happened multiple independent times in jawed animals

One particular retrovirus — embedded in the DNA of jawed vertebrates — helps turn on production of a protein needed to insulate nerve fibers, researchers report February 15 in Cell. Such insulation, called myelin, may have helped make speedy thoughts and complex brains possible.

The retrovirus trick was so handy, in fact, that it showed up many times in the evolution of vertebrates with jaws, the team found.

Retroviruses are RNA viruses that make DNA copies of themselves to embed in a host’s DNA. Rarely, these insertions can become a permanent part of who we are, being passed down from parent to offspring. Scientists once thought remnants of of these ancient viruses — known as jumping genes or retrotransposons — as genetic garbage, but that impression is changing.

 Scientists are finding more and more evidence that these retrotransposons and retroviruses have influenced the evolution of life on the planet.

Remains of retroviruses were already known to have aided the evolution of the placenta, the immune system and other important milestones in human evolution . Now, they’re implicated in helping to produce myelin.

Part 2

Comment by Dr. Krishna Kumari Challa on March 21, 2024 at 7:04am

Virus helped brain evolution
Remnants of an ancient viral infection are essential for producing myelin, a protein that insulates nerve fibres, in most vertebrates. Certain viruses insert DNA into the genetic material of the cells they invade. Sometimes, these insertions become permanent and even aid evolutionary processes. Myelin helps nerves to send electrical signals faster, grow longer and thinner so they can be packed in more efficiently. “As a result of myelin, brains became more complex and vertebrates became more diverse,” says stem-cell biologist and study co-author Robin Franklin.

Part 1

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