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Comment by Dr. Krishna Kumari Challa on June 25, 2025 at 11:16am

Sharks freeze when you turn them upside down

The freeze response—called "tonic immobility"—can be a lifesaver. Possums famously "play dead" to avoid predators. So do rabbits, lizards, snakes, and even some insects.

But what happens when a shark does it?

Researchers explored this strange behavior in sharks, rays and their relatives. In this group, tonic immobility is triggered when the animal is turned upside down—it stops moving, its muscles relax, and it enters a trance-like state. Some scientists even use tonic immobility as a technique to safely handle certain shark species. 

The reasons behind tonic immobility remain murky—especially in the ocean. It is generally thought of as an anti-predator defense. 

Three main hypotheses try to explain this immobility in sharks:

Anti-predator strategy—"playing dead" to avoid being eaten

Reproductive role—some male sharks invert females during mating, so perhaps tonic immobility helps reduce struggle

Sensory overload response—a kind of shutdown during extreme stimulation.

But research results don't support any of these explanations.

 So, scientists offer a simpler explanation. Tonic immobility in sharks is likely an evolutionary relic.

Evolutionary analysis suggests tonic immobility is "plesiomorphic"—an ancestral trait that was likely present in ancient sharks, rays and chimeras. But as species evolved, many lost the behavior.

Whatever may be the reason if you want to handle the sharks safely, just turn them upside down!

 Joel H. Gayford et al, Tonic immobility in cartilaginous fishes (Chondrichthyes): function, evolutionary history, and future directions, Reviews in Fish Biology and Fisheries (2025). DOI: 10.1007/s11160-025-09958-3

Comment by Dr. Krishna Kumari Challa on June 25, 2025 at 11:06am

Scientists use gene editing to correct harmful mitochondrial mutations in human cells

In a step toward treating mitochondrial diseases, researchers  have successfully edited harmful mutations in mitochondrial DNA using a genetic tool known as a base editor. The results, published in the open-access journal PLOS Biology, offer new hope for people with rare genetic conditions.

Mitochondria have their own small set of DNA. Mutations in this mitochondrial DNA can lead to a wide range of maternally inherited diseases, cancer, and aging-related conditions. While the development of CRISPR technology has given scientists new ways to correct mutations in nuclear DNA, this system cannot effectively cross the mitochondrial membrane and reach mitochondrial DNA.

In the new study, the researchers used a tool called a base editor—specifically, a DdCBE (double-stranded DNA deaminase toxin A-derived cytosine bas editor). This tool allows scientists to change a single letter in the DNA code without cutting it, and it works on mitochondrial DNA.

The team showed that they could effectively generate and correct mitochondrial DNA mutations in multiple disease-linked cell types in the lab. First, they engineered liver cells to carry a mitochondrial mutation that impairs energy production. Then they showed they could fix a different mutation in skin cells taken from a patient with the mitochondrial disorder Gitelman-like syndrome, restoring key signs of healthy mitochondrial function.

To help move the therapy toward clinical use, the researchers also tested the efficacy of delivering the mitochondrial base editors in mRNA form, rather than as DNA, and within lipid nanoparticles for delivery.

They showed that these approaches are more efficient and less toxic to cells than older methods like DNA plasmids. Importantly, the edits were highly specific, with minimal off-target changes detected in nuclear DNA and multiple detected in mitochondrial DNA.

Joore IP, et al. Correction of pathogenic mitochondrial DNA in patient-derived disease models using mitochondrial base editors. PLOS Biology (2025). DOI: 10.1371/journal.pbio.3003207

Comment by Dr. Krishna Kumari Challa on June 25, 2025 at 10:56am

Why AI and humans see objects differently: Meaning versus visual features

While humans concentrate on the meaning of objects, artificial intelligence focuses on visual characteristics.

These dimensions represent various properties of objects, ranging from purely visual aspects, like 'round' or 'white,' to more semantic properties, like 'animal-related' or 'fire-related,' with many dimensions containing both visual and semantic elements.

 While humans primarily focus on dimensions related to meaning—what an object is and what we know about it—AI models rely more heavily on dimensions capturing visual properties, such as the object's shape or color. Researchers call this phenomenon 'visual bias' in AI.

"Even when AI appears to recognize objects just as humans do, it often uses fundamentally different strategies. This difference matters because it means that AI systems, despite behaving similarly to humans, might think and make decisions in entirely different ways, affecting how much we can trust them.

 Florian P. Mahner et al, Dimensions underlying the representational alignment of deep neural networks with humans, Nature Machine Intelligence (2025). DOI: 10.1038/s42256-025-01041-7

Comment by Dr. Krishna Kumari Challa on June 25, 2025 at 9:42am

New evidence map shows normal use of plastic packaging contaminates food with micro- and nanoplastics

In an article published in npj Science of Food, scientists led by the Food Packaging Forum show that the normal and intended use of plastic food packaging and other food contact articles (FCAs), such as opening a plastic bottle or chopping on a plastic cutting board, can contaminate foodstuffs with micro- and nanoplastics (MNPs).

The article describes how the authors systematically evaluated 103 previously published studies investigating plastic particles less than 10 mm in foodstuffs or food simulants that had been in contact with an FCA made partly or entirely of plastic.

Food contact articles are a relevant source of MNPs in foodstuffs; however, their contribution to human MNP exposure is underappreciated, the researchers say.

 Food contact articles as source of micro- and nanoplastics: a systematic evidence map, npj Science of Food (2025). DOI: 10.1038/s41538-025-00470-3

Comment by Dr. Krishna Kumari Challa on June 25, 2025 at 9:38am

500 bird species face extinction within the next century, researchers warn

Climate change and habitat loss could cause more than 500 bird species to go extinct in the next 100 years, researchers  have found.

Their study, published in Nature Ecology & Evolution, reveals this number is three times higher than all bird extinctions recorded since 1500 CE. The extinction of vulnerable birds such as the bare-necked umbrellabird, the helmeted hornbill, and the yellow-bellied sunbird-asity would greatly reduce the variety of bird shapes and sizes worldwide, harming ecosystems that depend on unique birds like these for vital functions.

The scientists found that even with complete protection from human-caused threats like habitat loss, hunting and climate change, about 250 bird species could still die out.

Many birds are already so threatened that reducing human impacts alone won't save them. These species need special recovery programs, like breeding projects and habitat restoration, to survive.

We face a bird extinction crisis unprecedented in modern times. We need immediate action to reduce human threats across habitats and targeted rescue programs for the most unique and endangered species, the researchers say.

The researchers examined nearly 10,000 bird species using data from the IUCN Red List. They predicted extinction risk based on the threats each species faces. The study found that large-bodied birds are more vulnerable to hunting and climate change, while birds with broad wings suffer more from habitat loss.

This research also identified which conservation actions will best preserve both the number of bird species and their ecological functions.

Stopping the destruction of habitats would save the most birds overall. However, reducing hunting and preventing accidental deaths would save birds with more unusual features, which are especially important for ecosystem health.

Threat reduction must be coupled with targeted recovery programmes to conserve global bird diversity, Nature Ecology & Evolution (2025). DOI: 10.1038/s41559-025-02746-z

Comment by Dr. Krishna Kumari Challa on June 25, 2025 at 9:05am

The researchers analyzed more than 30 tomato samples collected from distinct geographic locations across the islands. They found that plants on eastern islands produced the same alkaloids found in modern cultivated tomatoes. But on western islands, the tomatoes were churning out a different version with the molecular fingerprint of eggplant relatives from millions of years ago.

That difference comes down to stereochemistry, or how atoms are arranged in three-dimensional space. Two molecules can contain exactly the same atoms but behave entirely differently depending on how those atoms are arranged.

To figure out how the tomatoes made the switch, the researchers examined the enzymes that assemble these alkaloid molecules. They discovered that changing just four amino acids in a single enzyme was enough to flip the molecule's structure from modern to ancestral.
They proved it by synthesizing the genes coding for these enzymes in the lab and inserting them into tobacco plants, which promptly began producing the old compounds.

The pattern wasn't random. It aligned with geography. Tomatoes on the eastern, older islands, which are more stable and biologically diverse, made modern alkaloids. Those on the younger, western islands where the landscape is more barren and the soil is less developed, had adopted the older chemistry.

The researchers suspect the environment on the newer islands may be driving the reversal. It could be that the ancestral molecule provides better defense in the harsher western conditions.
To verify the direction of the change, the team did a kind of evolutionary modeling that uses modern DNA to infer the traits of long-extinct ancestors. The tomatoes on the younger islands matched what those early ancestors likely produced.

Still, calling this "reverse evolution" is bold. While the reappearance of old traits has been documented in snakes, fish, and even bacteria, it's rarely this clear, or this chemically precise.
And this kind of change might not be limited to plants. If it can happen in tomatoes, it could theoretically happen in other species, too.
It wouldn't happen in a year or two, but over time, maybe, if environmental conditions change enough.
And if you change just a few amino acids, you can get a completely different molecule. That knowledge could help us engineer new medicines, design better pest resistance, or even make less toxic produce.

Adam Jozwiak et al, Enzymatic twists evolved stereo-divergent alkaloids in the Solanaceae family, Nature Communications (2025). DOI: 10.1038/s41467-025-59290-4

Part 2

Comment by Dr. Krishna Kumari Challa on June 25, 2025 at 9:02am

Tomatoes in the Galápagos are quietly de-evolving

On the younger, black-rock islands of the Galápagos archipelago, wild-growing tomatoes are doing something peculiar. They're shedding millions of years of evolution, reverting to a more primitive genetic state that resurrects ancient chemical defenses.

These tomatoes, which descended from South American ancestors likely brought over by birds, have quietly started making a toxic molecular cocktail that hasn't been seen in millions of years, one that resembles compounds found in eggplant, not the modern tomato.

In a study published recently in Nature Communications, scientists at the University of California, Riverside, describe this unexpected development as a possible case of "reverse evolution," a term that tends to be controversial among evolutionary biologists.

That's because evolution isn't supposed to have a rewind button. It's generally viewed as a one-way march toward adaptation, not a circular path back to traits once lost. While organisms sometimes re-acquire features similar to those of their ancestors, doing so through the exact same genetic pathways is rare and difficult to prove.

However, reversal is what these tomato plants appear to be doing.

The key players in this chemical reversal are alkaloids. Tomatoes, potatoes, eggplants, and other nightshades all make these bitter molecules that act like built-in pesticides, deterring insect predators, fungi, and grazing animals.

While the Galápagos are famous as a place where animals have few predators, the same is not necessarily true for plants. Thus, the need to produce the alkaloids.

What makes these Galápagos tomatoes interesting isn't just that they make alkaloids, but that they're making the wrong ones, or at least, ones that haven't been seen in tomatoes since their early evolutionary days.

Part 1

Comment by Dr. Krishna Kumari Challa on June 24, 2025 at 11:30am

Recycled plastics can affect hormone systems and metabolism, study shows

A single pellet of recycled plastic can contain over 80 different chemicals. A new study by researchers shows that recycled polyethylene plastic can leach chemicals into water, causing impacts on the hormone systems and lipid metabolism of zebrafish larvae.

The work is published in the Journal of Hazardous Materials.

The plastic pollution crisis has reached global levels, threatening both planetary and human health, and recycling is proposed as one of the solutions to the plastics pollution crisis. However, as plastics contain thousands of chemical additives and other substances that can be toxic, and these are almost never declared, hazardous chemicals can indiscriminately end up in recycled products.

In a new study, researchers bought plastic pellets recycled from polyethylene plastic from different parts of the world and let the pellets soak in water for 48 hours. After which, zebrafish larvae were exposed to the water for five days. The experimental results show increases in gene expression relating to lipid metabolism, adipogenesis, and endocrine regulation in the larvae.

These short leaching times and exposure times are yet another indicator of the risks that chemicals in plastics pose to living organisms. The impacts that we measured show that these exposures have the potential to change the physiology and health of the fish.

Previous research has shown similar effects to humans, including threats to reproductive health and obesity, from exposure to toxic chemicals in plastics. Some chemicals used as additives in plastics and substances that contaminate plastics are known to disturb hormones, with potential impacts on fertility, child development, links to certain cancers, and metabolic disorders including obesity and diabetes.

Azora König Kardgar et al, Effects of leachates from black recycled polyethylene plastics on mRNA expression of genes involved in adipogenesis and endocrine pathways in zebrafish embryos, Journal of Hazardous Materials (2025). DOI: 10.1016/j.jhazmat.2025.138946

Comment by Dr. Krishna Kumari Challa on June 24, 2025 at 11:22am

Scientists find new blood type in Guadeloupe woman

A French woman from the Caribbean island of Guadeloupe has been identified as the only known carrier of a new blood type, dubbed "Gwada negative," France's blood supply agency has announced.

The announcement was made 15 years after researchers received a blood sample from a patient who was undergoing routine tests ahead of surgery, the French Blood Establishment (EFS) said on Friday.

"The EFS has just discovered the 48th blood group system in the world!" the agency said in a statement on social network LinkedIn.

"This discovery was officially recognized in early June in Milan by the International Society of Blood Transfusion (ISBT)."

The scientific association had until now recognized 47 blood group systems.

Thierry Peyrard, a medical biologist at the EFS involved in the discovery, told AFP that a "very unusual" antibody was first found in the patient in 2011.

Scientists were finally able to unravel the mystery in 2019 thanks to "high-throughput DNA sequencing," which highlighted a genetic mutation

The patient, who was 54 at the time and lived in Paris, was undergoing routine tests before surgery when the unknown antibody was detected.

She is the only person in the world who is compatible with herself

The woman inherited the blood type from her father and mother, who each had the mutated gene.

Comment by Dr. Krishna Kumari Challa on June 24, 2025 at 10:57am

Antimicrobial resistance genes hitch rides on imported seafood

Colistin is a potent, last-resort antibiotic used only to treat people with dangerous, life-threatening bacterial infections that have developed resistance to other drugs. But it's not foolproof. Worldwide, resistance to colistin is spreading, further diminishing treatment options and putting infected people at higher risk.

Researchers have identified a way that colistin  resistance genes are spreading: imported seafood.

In a new study, microbiologists  have reported the first isolation of colistin-resistance genes in bacteria found in imported shrimp and scallops, purchased from eight food markets around Atlanta, GA.

 Some countries do not have strict regulations for using antibiotics in food animal production, so imported food can be a vehicle for transmission of resistance,

The researchers presented the findings in Los Angeles at ASM Microbe 2025, the annual meeting of the American Society for Microbiology. An accompanying paper will be published in the journal mSphere.

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