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Showing posts with label Biology. Show all posts
Showing posts with label Biology. Show all posts

Tuesday, 5 November 2019

How do bacteria alter Drosophila behavior?

 Confronted with microorganisms that share their environment, eukaryotes have mechanisms to contain them. When this immune barrier is crossed and the animal is infected, other biological processes are triggered that limit the consequences of the infection. In a study published in the eLife journal , researchers show that Drosophila females infected with bacteria lay fewer eggs than healthy females. They provide evidence that this behavioral adaptation is due to the direct detection of a universal compound present in the bacterial wall , called peptidoglycan , by only a few neurons present in the brain of flies.

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Anyone who has been victim of a viral or bacterial infection knows the side effects that result in a loss of appetite , a fragmented sleep and, in extreme cases, a depressive state. While these "side effects" that reflect the impact of microorganisms on the host's nervous system have been clearly established, the nature of the microbial vectors of the effect and the precise identity of the targeted neurons remain, in most cases, unknown.

Figure: (Left): In the absence of infection, fertilized female Drosophila eggs. (Right): During an infection, the proliferating bacteria produce fragments of peptidoglycan, a component of their wall, in the extracellular medium. By unknown mechanisms, this compound of the bacterial wall enters the brain. Its detection by only one or two neurons (framed), of the 100,000 or so contained in the brain of a Drosophila, causes their inhibition (lowering of calcium levels) and, ultimately, a slowdown in egg deposition. It is likely that this drop in egg yield allows the infected Drosophila to allocate as much energy as fight against infection. Once infection is controlled, the level of spawning returns to normal. This is a case of behavioral immunity.
© Ambra Masuzzo.

The researchers had shown in a previous study that egg-laying behavior of fruit-infected Drosophila was modified, with infected females laying fewer eggs than their healthy counterparts. This work provided evidence that the detection of a major and universal component of the bacterial wall, the peptidoglycan, by infected Drosophila neurons alters their behavior. The next step was to identify precisely these neurons and to demonstrate how this bacterial compound could modify their activity.

In this new publication, researchers use the powergenetic and molecular tools available in Drosophila to demonstrate that by acting on only one or two of the 100,000 neurons contained in the Drosophila brain, the bacterial compound alters the behavior of the host. Using calcium imaging to measure intracellular calcium concentration, the authors demonstrate that direct application of bacterial peptidoglycan in vivo or ex vivo is sufficient to block the activity of these neurons. It remains to understand the mechanisms by which the detection of peptidoglycan and activationNF-kB signaling pathway block their activity. The cellular mechanisms that allow the peptidoglycan to reach these neurons by crossing the blood-brain barrier also remain to be elucidated.

The question now arises of the generalization of these discoveries to vertebrates . Several elements suggest that the mechanism could be conserved beyond invertebrates. On the one hand, the peptidoglycan of bacteria produced by the microbiota of mice was detected in the circulationblood and is able to cross the blood-brain barrier. In addition, mutant mice for peptidoglycan receptors exhibit behavioral disorders and social interactions. The recently published work adds an important piece to the complex puzzle that governs interactions between the microbial world and the nervous system of eukaryotes.


Sunday, 3 November 2019

Brain recognizes familiar music at lightning speed

One snippet of music suffices: our brain recognizes familiar songs with surprising speed. It takes only 100 to 300 milliseconds to classify a piece of music as known, as experiments reveal. But the recognition does not only show in the brain: Our pupils react too. They widen with excitement when we hear a familiar and popular song.

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Music is deeply rooted in our human nature: There is hardly a culture worldwide that knows no music, and unborn children in the womb react to melodious sounds. Above all, the sound of music develops a strong emotional effect . It can make us cry, awaken memories - or cause uproar.

How certain music affects a person, however, is completely different. This is evidenced, for example, by the fact that everyone has a different favorite song. Where one of them turns off the radio annoyed, the other one turns up loud and sings along at the top of his voice.

Song recognized?

Interestingly enough, our most popular pieces of music seem to be anchored in the brain in a special way: often just a few notes are enough to recognize the song. But how fast can the thinking organ identify familiar melodies? Robert Jagiello from University College London and his colleagues have now taken the test.

For their study, the researchers recruited five men and five women, each of whom named five pop songs known to them, connecting them with positive feelings and memories. For each of these songs, Jagiello's team chose a counterpart - a song that sounded similar in tempo, melody, harmony, and song, but was unknown to the participants.

A matter of milliseconds

In the crucial experiment, the scientists then alternately played less than a second of the known and unknown songs to the study participants. They used electroencephalography (EEG) to observe how the brain responded to these musical snippets. They also measured the dilation of the pupils, which is considered a sign of excitement.

The results revealed that the mind recognized familiar songs surprisingly quickly. It took only 100 to 300 milliseconds to classify a music excerpt as known. This was shown on the one hand by a clear pupil reaction. On the other hand, Jagiello and his colleagues found an activation of cortical brain regions involved in recalling memories.

Benefit for the therapy

"Our results show that familiar music is recognized remarkably quickly. This points to a fast temporal circuit and underlines how deeply such pieces of music are anchored in our memory, "says Jagiello's colleague Maria Chait. The scientists suspect that this particular reaction to the music has to do with the positive emotions associated with it.

According to the team, the results may also be relevant to therapeutic approaches: "Understanding how the brain recognizes familiar melodies can be very useful for music therapy. For example, there is a growing interest in learning about people with dementia through music. Because the memory of music is often kept for a surprisingly long time, "explains Chait.

Identifying the neural processes that enable the recognition of music could thus help to better understand this and other phenomena.


Saturday, 2 November 2019

New powerful ranavirus discovered that can spread among amphibians

Of the invasive pathogens that are decimating the reptile populations in various areas the United States we have already mentioned and now a new study, appeared in the journal Ecological Modeling and produced by researchers of the University of Tennessee, shows the existence of a new ranavirus similar to a Frog virus 3 (FV3).

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The new ranavirus, called RCV-Z2, can, according to researchers who have developed a specific model to predict its spread, spread just as quickly in a tadpole population of North American wood frogs ( Lithobates sylvaticus ) and transmission can occur in a very efficient through direct contact, through necrophagy (if the subjects feed on the bodies of other infected subjects) or even by water.

The ranaviruses are pathogens that are emerging globally and affect mainly reptiles, amphibians and fish threatening the ecological diversity of these species and therefore all the eco-environments in which they are found.
To combat the ranavirus emergency, which has become global, researcher Matt Gray founded and directs the Global Ranavirus Consortium.

The same Gray states in the press release published on the University of Tennessee website:
"In our previous work, we discovered that RCV-Z2 is a recombinant ranavirus that has the DNA of a strain in North America and one from Europe and Asia. We think these viruses mixed DNA on a frog farm in South Georgia: the result was a highly virulent hybrid virus. The point of this modeling effort was to demonstrate how this virus evolved with the DNA of the eastern hemisphere can infect and spread into a kind of amphibian. The news is not good ".

And this without counting the trade in amphibians and other wild animals that may be subject to these infections: with a trade of this type their pathogens can be moved around the world, something that could make the infection truly global.

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