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Comment by Dr. Krishna Kumari Challa on June 19, 2023 at 11:48am

NASA finds key building block for life in a moon of Saturn

Scientists have discovered that phosphorus, a key building block of life, lies in the ocean beneath the icy surface of Saturn's moon Enceladus. The finding was based on a review of data collected by NASA's Cassini probe, and was published Wednesday in the prestigious journal Nature.

Cassini started exploring Saturn and its rings and moons in 2004, before burning up in the gas giant's atmosphere when its mission ended in 2017.

NASA found abundant phosphorus in plume ice samples spraying out of the subsurface ocean.

Scientists previously found other minerals and organic compounds in the ejected ice grains, but not phosphorus, which is an essential building block for DNA and RNA, and is also found in the bones and teeth of people, animals, and even ocean plankton.

Simply put, life as we know it would not be possible without phosphorus.

It's the first time this essential element has been discovered in an ocean beyond Earth.

With this finding, the ocean of Enceladus is now known to satisfy what is generally considered to be the strictest requirement for life. The next step is clear –- we need to go back to Enceladus to see if the habitable ocean is actually inhabited.

Frank Postberg, Detection of phosphates originating from Enceladus's ocean, Nature (2023). DOI: 10.1038/s41586-023-05987-9. www.nature.com/articles/s41586-023-05987-9

Comment by Dr. Krishna Kumari Challa on June 17, 2023 at 10:36am

At each stage of its life cycle, the parasite must logically pick up signals that enable it to react correctly.

There are small molecules  absent in the blood but present in the mosquito that the parasite is able to detect. Starting from this single known element, scientists have identified a sensor that enables the parasite to detect the presence of these molecules when it is ingested by a mosquito.

This sensor is made up of five proteins. In its absence, the parasite does not realize that it has left the bloodstream for the mosquito, and is therefore unable to continue its development.

Surprisingly, this sensor is also present at other stages of the parasite lifecycle, notably when the parasite has to leave the red blood cell. Scientists then observe exactly the same mechanism: without this sensor, Plasmodium is trapped in the red blood cells, unable to continue its infection cycle.

The protein complex discovered here is absent in humans, but is found in the entire family of apicomplexan parasites to which Plasmodium belongs, as well as Toxoplasma, the agent of toxoplasmosis. By identifying this sensor, scientists can now imagine how to scramble the signals perceived by the parasite at different stages of its development, thus disorienting it and blocking its multiplication and transmission.

Ronja Kühnel et al, A Plasmodium membrane receptor platform integrates cues for egress and invasion in blood forms and activation of transmission stages, Science Advances (2023). DOI: 10.1126/sciadv.adf2161. www.science.org/doi/10.1126/sciadv.adf2161

Part 2

Comment by Dr. Krishna Kumari Challa on June 17, 2023 at 10:33am

Scientists think disorienting the malaria parasite may prevent it from causing harm

With almost 250 million cases a year, 621,000 of them fatal, malaria remains a major public health problem, particularly in sub-Saharan Africa. Malaria is a parasitic disease transmitted by mosquitoes and caused by a microbe of the genus Plasmodium. On its journey from mosquito to human, Plasmodium must adapt to the specificities of the many organs and cells it parasitizes. Microbes do not have sensory organs; instead, they have sensors made of proteins to detect molecules specific to the environments they colonize. While most living organisms share the same types of sensors, Plasmodium is an exception.

Biologists have identified a new type of sensor that enables Plasmodium to know precisely where it is and what to do. This work, published in the journal Science Advances, opens up the possibility of scrambling the signals perceived by this sensor to disorient the parasite and thus prevent its replication and transmission.

When a human is bitten by a Plasmodium-infected mosquito, the parasite enters the bloodstream and travels to the liver, where it thrives for around 10 days without causing any symptoms. After this period, Plasmodium re-enters the bloodstream, where it parasitizes red blood cells. Once inside the red blood cells, the parasites multiply in a synchronized 48-hour cycle.

At the end of each multiplication cycle, the newly-formed parasites leave their host red blood cells, destroying them and infecting new ones. It is this destruction of red blood cells that causes the waves of fever associated with malaria. Severe forms of malaria are linked to the obstruction of blood vessels by infected red blood cells.

When a mosquito bites a human whose blood is infected with Plasmodium, the parasite changes its development program to colonize the intestine of its new host. After a further period of multiplication, Plasmodium returns to the mosquito's salivary glands, ready to infect a new human.

From the warmth of the red blood cell to the depths of the mosquito's intestine via the liver, how does Plasmodium perceive changes in its environment in order to change its development program? Understanding this very specific biological mechanism is an important step towards countering the parasite.

Part 1

Comment by Dr. Krishna Kumari Challa on June 17, 2023 at 10:01am

Study finds that the human brain reactivates mental representations of past events during new experiences

Neuroscience studies have showed that as mice and other rodents navigate a maze, their brain often "replays" relevant past events. This mental replaying of events, such as the route taken until reaching their current position, could help rodents create a mental map of the spatial environment, and understand their position in it.

Researchers  recently explored the possibility that the human brain also replays past events to make sense of evolving, non-spatial experiences. Their findings, published in Nature Neuroscience, confirms this hypothesis and suggests that the process through which the human brain reactivates these events might be far more complex than that observed in rodents.

Researchers tried to devise an experiment that might elicit the replay of past events as observed in rodents, but during non-spatial daily experiences. Ultimately, they decided to ask their participants to watch a movie or listen to audio recordings of a narrated story while recording their brain activity using a functional magnetic resonance imaging (fMRI) scanner.

Movies and stories simulate real world experiences, as they are composed of events that should be linked together to understand the overall narrative.

Interestingly, researchers  found that as participants were engaged in the narrative of a movie or story, representations of past events, which were needed to make sense of each present scene, were reactivated in their brain. Unlike in rodents, these reactivations appeared while the participants were watching the movie or listening to the story, rather than during periods of rest from the task.

They found that the same brain regions that replay spatial information in the rodent brain also replay narrative events in the human brain. In other words, replay, previously thought to mainly support spatial navigation, could also underlie the human ability to make sense of narratives.  

Overall, the recent work by this team of researchers suggests that while humans are trying to make sense of their present experiences, their brain may continuously reactivate relevant past events. 

Avital Hahamy et al, The human brain reactivates context-specific past information at event boundaries of naturalistic experiences, Nature Neuroscience (2023). DOI: 10.1038/s41593-023-01331-6

Comment by Dr. Krishna Kumari Challa on June 16, 2023 at 12:50pm

Endometriosis could be caused by bacteria

Endometriosis could be caused by Fusobacterium. The severely painful condition, in which tissue similar to the uterus lining grows outside the uterus, affects up to 10% of women. In a study of 155 women, the bacterium was found in around 64% of those with endometriosis a.... Experiments with Fusobacterium-infected mice showed that antibiotics could reduce the size and frequency of the lesions that are associated with the disease. A clinical trial is now under way to find out whether antibiotics could relieve some endometriosis symptoms.

https://www.science.org/doi/10.1126/scitranslmed.add1531

https://www.nature.com/articles/d41586-023-01956-4?utm_source=Natur...

Comment by Dr. Krishna Kumari Challa on June 16, 2023 at 12:36pm

Modern high dynamic range televisions create bright white regions that are over 10,000 times brighter than their darkest black, approaching the contrast levels of natural scenes.

How our eyes and brains can handle this contrast is a puzzle because tests show that the highest contrasts we humans can see at a single spatial scale is around 200:1.

Even more confusingly, the neurons connecting our eyes to our brains can only handle contrasts of about 10:1.

This new  model shows how neurons with such limited contrast bandwidth can combine their signals to allow us to see these enormous contrasts, but the information is 'compressed'—resulting in visual illusions.

The model shows how our neurons are precisely evolved to use of every bit of capacity.

"For example, some neurons are sensitive to very tiny differences in gray levels at medium-sized scales, but are easily overwhelmed by high contrasts.

"Meanwhile, neurons coding for contrasts at larger or smaller scales are much less sensitive, but can work over a much wider range of contrasts, giving deep black-and-white differences.

"Ultimately this shows how a system with a severely limited neural bandwidth and sensitivity can perceive contrasts larger than 10,000:1."

 A model of colour appearance based on efficient coding of natural images, PLoS Computational Biology (2023). DOI: 10.1371/journal.pcbi.1011117

Part 2

Comment by Dr. Krishna Kumari Challa on June 16, 2023 at 12:35pm

New research shows illusions are in the eye, not the mind's neurons

Numerous visual illusions are caused by limits in the way our eyes and visual neurons work—rather than more complex psychological processes, new research shows.

Numerous visual illusions are caused by limits in the way our eyes and visual neurons work—rather than more complex psychological processes, new research shows.

The new study suggests simple limits to neural responses—not deeper psychological processes—explain these illusions.

Our eyes send messages to the brain by making neurons fire faster or slower. However, there's a limit to how quickly they can fire, and previous research hasn't considered how the limit might affect the ways we see color.

The model combines this "limited bandwidth" with information on how humans perceive patterns at different scales, together with an assumption that our vision performs best when we are looking at natural scenes.

The model was developed by researchers from the Universities of Exeter and Sussex to predict how animals see color, but it was also found to correctly predict many visual illusions seen by humans.

Part 1

Comment by Dr. Krishna Kumari Challa on June 16, 2023 at 12:19pm

Right-handed building blocks of life

Scientific research may have solved the puzzle of how life became molecularly right-handed. In the paper, "Origin of biological homochirality by crystallization of an RNA precursor on a magnetic surface," published in Science Advances, the researchers explain how it all might have started with the right kind of rocks.

Molecules can be left-handed, right-handed or both. RNA and the sugars that makeup DNA are right-handed molecules. Nobody knows why or if there is a reason beyond chance that life started right-handed.

As an analogy, human hands can be left or right, and they are mirror images of each other, which means that they cannot be superimposed without one facing the wrong way. Molecules can have similar structural symmetry.

In much the same way that right-handed people have difficulty with left-handed scissors, or left-handed guitar players need to reverse strings and play the instrument the other way round, molecules do not interact the same way when they are left or right-handed. Once started, it makes sense that the building blocks of life should continue with the same handedness.

One intriguing idea is that cosmic rays with left-handed spin destroyed left-handed DNA precursors just as life started on Earth.

Ribo-amino oxazoline (RAO) is a crucial RNA precursor for two of RNA's nucleotides, cytosine and uracil. RAO also happens to form a crystalline structure that can be either right-handed or left-handed that, once the crystal starts forming, right or left, only binds with other molecules of the same handedness.

By placing RAO on magnetite (Fe₃O₄) surfaces, researchers could achieve 100% handedness of RAO crystallization, either left or right, depending on the spin-exchange interaction and degree of spin alignment (magnetization) at the active surface.

Earth's most abundant natural magnetic mineral, magnetite, would have had plenty of interaction opportunities with RAO in primordial times. However, the researchers say the effect is not likely to occur in particle solution contact like mud but rather on sedimentary rock surfaces.

Even with the current findings possibly unlocking two of the four RNA nucleotide components, two more are still missing. So far, The origin story finds that common, naturally occurring components at room temperatures can start the process. If the next two are found to have similar requirements, it would indicate that life on any Earth-like planet in the universe could have started just as easily.

S. Furkan Ozturk et al, Origin of biological homochirality by crystallization of an RNA precursor on a magnetic surface, Science Advances (2023). DOI: 10.1126/sciadv.adg8274

S. Furkan Ozturk et al, Chirality-Induced Magnetization of Magnetite by an RNA Precursor, arXiv (2023). DOI: 10.48550/arxiv.2304.09095

Comment by Dr. Krishna Kumari Challa on June 16, 2023 at 11:01am

Seeing Dead Flies Makes Other Flies Die Faster

There might be a weird benefit to leaving dead flies where they fall .

Research has shown that when fruit flies of the species Drosophila melanogaster are exposed to the carcasses of their dead friends, their lifespan shrinks in a significant and measurable way.

They start acting withdrawn, lose body fat, and their aging accelerates to the point that they die sooner than fruit flies that don't see their dead buddies just lying where they fall like some macabre fruit fly graveyard.

And now scientists have a better idea about why this happens. Two neuron types receptive to the neurotransmitter serotonin become activated when fruit flies perceive dead comrades, and this increased activity accelerates the flies' aging process.

Scientists have seen similar effects in other animals: necrophoresis, or the removal of dead conspecifics, in eusocial insects; vocalization and corpse inspection in elephants; or an increase in levels of regulatory hormones called glucocorticoids in nonhuman primates.

https://journals.plos.org/plosbiology/article?id=10.1371/journal.pb...

Comment by Dr. Krishna Kumari Challa on June 16, 2023 at 9:00am

To form the vesicles and to get the nanostructures inside these vesicles, the team used an established method, placing the nanostructures in a solution of water and sugar (sucrose) and adding this to a layer of oil and lipids and another layer of glucose.

Spinning (centrifuging) this combination of substances resulted in droplets of oil with a membrane composed of a double layer of lipids, mimicking the membrane that separates cells from the outside world, with the nanostructures migrating inside these droplets.

Nishkantha Arulkumaran et al, Creating complex protocells and prototissues using simple DNA building blocks, Nature Communications (2023). DOI: 10.1038/s41467-023-36875-5

Part 2

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