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Comment by Dr. Krishna Kumari Challa on January 12, 2024 at 11:30am

Lab-grown retinas explain why people see colours some animals can't

With human retinas grown in a petri dish, researchers discovered how an offshoot of vitamin A generates the specialized cells that enable people to see millions of colors, an ability that dogs, cats, and other mammals do not possess.

These retinal organoids allowed scientists for the first time to study this very human-specific trait. It's a huge question about what makes us human, what makes us different.

The findings, published in PLOS Biology, increase understanding of color blindness, age-related vision loss, and other diseases linked to photoreceptor cells. They also demonstrate how genes instruct the human retina to make specific color-sensing cells, a process scientists thought was controlled by thyroid hormones. By tweaking the cellular properties of the organoids, the research team found that a molecule called retinoic acid determines whether a cone will specialize in sensing red or green light. Only humans with normal vision and closely related primates develop the red sensor.

Scientists for decades thought red cones formed through a coin toss mechanism where the cells haphazardly commit to sensing green or red wavelengths—and research from researchers recently hinted that the process could be controlled by thyroid hormone levels. Instead, the new research suggests red cones materialize through a specific sequence of events orchestrated by retinoic acid within the eye.

The team found that high levels of retinoic acid in early development of the organoids correlated with higher ratios of green cones. Similarly, low levels of the acid changed the retina's genetic instructions and generated red cones later in development.

There still might be some randomness to it, but the big finding is that you make retinoic acid early in development.This timing really matters for learning and understanding how these cone cells are made.

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Comment by Dr. Krishna Kumari Challa on January 12, 2024 at 10:06am

Copy and taste

There is still much that needs to be understood about the interplay of obvious enjoyment and the liking of food. For example, the researchers have focused on adults, and while this has not been tested for on this occasion, they said that given the power of negative facial expressions and because children tend to be less willing to try vegetables by default, these findings could generalize to kids.

"For example, if a child sees their parent showing disgust while eating vegetables, this could have negative consequences on children's vegetable acceptance.

In the present study, participants also watched short video clips rather than watching people eat in front of them. This allowed them to observe the dynamic nature of reactive facial expressions, which is more realistic than looking at static pictures; however, in the future, an important focus will be to examine the effect of watching live food enjoyment on eating behavior, the researchers said.

"We also need more research to see whether the findings from this study translate to adults' actual intake of vegetables.

Katie L. Edwards et al, Facial expressions and vegetable liking, Frontiers in Psychology (2024). DOI: 10.3389/fpsyg.2023.1252369

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Comment by Dr. Krishna Kumari Challa on January 12, 2024 at 10:04am

Watching others visibly dislike vegetables might make onlookers dislike them, too

Humans learn which behaviours pay off and which don't from watching others. Based on this, we may draw conclusions about how to act—or eat. In the latter's case, people may use each other as guides to determine what and how much to eat. This is called social modeling and is one of the most powerful social influences on eating behaviour.

In a new study, researchers  investigated whether observing others' facial expressions while eating raw broccoli influenced young women's liking and desire to eat raw broccoli.

They show that watching others eating a raw vegetable with a negative facial expression reduces adult women's liking of that vegetable, but not their desire to eat it. This highlights the power of observing food dislike on adults' eating behaviour. 

Previous research shows that behaviors are more likely to be imitated if positive consequences are observed, while the reverse is true if negative outcomes are witnessed. In the present study, however, this correlation was observed only partially: Exposure to models eating broccoli while conveying negative facial expressions resulted in a greater reduction in liking ratings, whereas the reverse did not hold. Watching others eating a raw vegetable with a positive facial expression did not increase adults' vegetable liking or eating desire.

One possible explanation may be that avoiding any food—irrespective of whether it is commonly liked or disliked—that appears disgusting can protect us from eating something that tastes bad or is harmful. Another reason may be that smiling while eating is perceived as an untypical display of liking a certain food.

"This might imply that watching someone eating a raw vegetable with positive facial expressions does not seem an effective strategy for increasing adults' vegetable consumption.

Part 1

Comment by Dr. Krishna Kumari Challa on January 12, 2024 at 9:57am

In a new paper, scientists describe a new peptide that binds directly to MYC with what is called sub-micro-molar affinity, which is getting closer to the strength of an antibody. In other words, it is a very strong and specific interaction.

Researchers now improved the binding performance of this peptide over previous versions by two orders of magnitude. This makes it closer to their drug development goals.

Currently, the researchers are using lipid nanoparticles to deliver the peptide into cells. These are small spheres made of fatty molecules, and they are not ideal for use as a drug. Going forward, the researchers are developing chemistry that improves the lead peptide's ability to get inside cells.

Once the peptide is in the cell, it will bind to MYC, changing MYC's physical properties and preventing it from performing transcription activities.

MYC represents chaos, basically, because it lacks structure. That, and its direct impact on so many types of cancer make it one of the holy grails of cancer drug development.

Zhonghan Li et al, MYC-Targeting Inhibitors Generated from a Stereodiversified Bicyclic Peptide Library, Journal of the American Chemical Society (2024). DOI: 10.1021/jacs.3c09615

Part 2

Comment by Dr. Krishna Kumari Challa on January 12, 2024 at 9:55am

Scientists tame chaotic protein fueling 75% of cancers

MYC is the shapeless protein responsible for making the majority of human cancer cases worse. Researchers have now found a way to rein it in, offering hope for a new era of treatments.

In healthy cells, MYC helps guide the process of transcription, in which genetic information is converted from DNA into RNA and, eventually, into proteins. Normally, MYC's activity is strictly controlled. In cancer cells, it becomes hyper active, and is not regulated properly.

MYC is less like food for cancer cells and more like a steroid that promotes cancer's rapid growth. That is why MYC is a culprit in 75% of all human cancer cases.

In 2018, the researchers noticed that changing the rigidity and shape of a peptide improves its ability to interact with structureless protein targets such as MYC.

Peptides can assume a variety of forms, shapes, and positions. Once you bend and connect them to form rings, they cannot adopt other possible forms, so they then have a low level of randomness. This helps with the binding.

Part 1

Comment by Dr. Krishna Kumari Challa on January 11, 2024 at 12:32pm

Is Vitamin D that importnat?
For a time, vitamin D was touted as a potential miracle vitamin, thought to prevent everything from heart disease to cancer to diabetes. But several recent randomized controlled trials showed no significant benefit of vitamin D for any major condition. To be sure, vitamin D plays a vital role in health, but most people get all they need in several minutes of daily sunlight.

Why this matters: Overtesting by doctors of vitamin D serum levels remains widespread. Experts disagree about how to interpret the test and many doctors still unnecessarily recommend vitamin D supplements. The supplements represent more than a $1 billion market, despite the lack of evidence that they are necessary for the majority of people (not to mention the fact that vitamins are not independently tested for purity or dosing).

What the experts say: “There’s a religiosity around vitamin D,” says Clifford Rosen, an endocrinologist at the Maine Medicine Center's Research Institute. “The evidence is out there. People don’t want to pay attention to it.”

 no significant benefit of vitamin D

Comment by Dr. Krishna Kumari Challa on January 11, 2024 at 11:58am

Higher viral load during HIV infection can shape viral evolution

A new paper in Molecular Biology and Evolution finds that HIV populations in people with higher viral loads also have higher rates of viral recombination. In effect, the more HIV in the blood, the easier it is for the virus to diversify.

One of the reasons HIV has historically been so difficult to combat is the virus's exceptionally high rate of recombination. Recombination enables the exchange of genetic information across strains of the virus and drives HIV's evolution within people. This genetic exchange helps the virus evade the immune system and become resistant to many drugs designed to treat HIV.

More generally, recombination is an important evolutionary driver, permitting organisms to purge destructive mutations and combine beneficial ones.

Understanding the factors that impact recombination rate in a well-studied system such as HIV can help uncover some of the effects that recombination has on evolution more broadly.

One important yet understudied step in HIV recombination is coinfection, in which two different virus particles infect the same cell.

The researchers involved with the new study hypothesized that people with higher viral loads (more HIV in the blood) would have more cells that were coinfected, which would lead to higher rates of recombination for the virus. To investigate this hypothesis, they developed a new approach called Recombination Analysis via Time Series Linkage Decay (RATS-LD) to quantify recombination using genetic associations between mutations over time.

This investigation found that while HIV populations with viral loads in the lowest third of the data set have recombination rates in line with previous estimates, while populations with viral loads in the upper third have a median recombination rate that is nearly six-fold higher. Furthermore, the researchers observe patterns of viral load and effective recombination rate increasing simultaneously within single individuals.

 Elena Romero et al, Elevated HIV viral load is associated with higher recombination rate in vivo, Molecular Biology and Evolution (2023). DOI: 10.1093/molbev/msad260. academic.oup.com/mbe/article-l … .1093/molbev/msad260

Comment by Dr. Krishna Kumari Challa on January 11, 2024 at 11:17am

More than 900 chemicals, many found in consumer products and the environment, display breast-cancer causing traits

With tens of thousands of synthetic chemicals on the market, and new ones in development all the time, knowing which ones might be harmful is a challenge both for the federal agencies that regulate them and the companies that use them in products. Now scientists have found a quick way to predict whether a chemical is likely to cause breast cancer based on whether the chemical harbors specific traits.

This new study provides a roadmap for regulators and manufacturers to quickly flag chemicals that could contribute to breast cancer in order to prevent their use in consumer products and find safer alternatives.

The study titled "Application of the Key Characteristics framework to identify potential breast carcinogens using publicly available in vivo, in vitro, and in silico data," published in Environmental Health Perspectives.

The researchers identified a total of 921 chemicals that could promote the development of breast cancer. Ninety percent of the chemicals are ones to which people are commonly exposed in consumer products, food and drink, pesticides, medications, and workplaces.

A breakdown of the list revealed 278 chemicals that cause mammary tumors in animals. More than half of the chemicals cause cells to make more estrogen or progesterone, and about a third activate the estrogen receptor.

Breast cancer is a hormonal disease, so the fact that so many chemicals can alter estrogen and progesterone is concerning.

Since damage to DNA can also trigger cancer, the researchers searched additional databases and found that 420 of the chemicals on their list both damage DNA and alter hormones, which could make them riskier. What's more, the team's analysis found that chemicals that cause mammary tumors in animals are more likely to have these DNA-damaging and hormone-disrupting characteristics than ones that don't.

These findings show that screening chemicals for these hormonal traits could be an effective strategy for flagging potential breast carcinogens.

Application of the Key Characteristics framework to identify potential breast carcinogens using publicly available in vivo, in vitro, and in silico data, Environmental Health Perspectives (2024). DOI: 10.1289/EHP13233. ehp.niehs.nih.gov/ehp13233

Comment by Dr. Krishna Kumari Challa on January 11, 2024 at 11:09am

To overcome those limitations, Researchers containing over 40  research groups that are part of a larger data-sharing initiative, pooled together their brain imaging scans to study PTSD as broadly and universally as possible. The group ended up with images from 4,215 adult MRI scans, about a third of whom had been diagnosed with PTSD.

The result of this thorough methodology was a fairly simple and consistent finding: PTSD patients had cerebellums about 2% smaller.

The results are an important first step at looking at how and where PTSD affects the brain.

Smaller Total And Subregional Cerebellar Volumes In Posttraumatic Stress Disorder: A Mega-Analysis By The ENIGMA-PGC PTSD Workgroup, Molecular Psychiatry (2024). DOI: 10.1038/s41380-023-02352-0. www.nature.com/articles/s41380-023-02352-0

Part 2

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Comment by Dr. Krishna Kumari Challa on January 11, 2024 at 11:07am

New study finds that traumatic stress is associated with a smaller cerebellum

Adults with posttraumatic stress disorder (PTSD) have smaller cerebellums, according to new research from a brain imaging study.

The cerebellum, a part of the brain well-known for helping to coordinate movement and balance, can influence emotion and memory, which are impacted by PTSD. What isn't known yet is whether a smaller cerebellum predisposes a person to PTSD or PTSD shrinks the brain region.

The differences were largely within the posterior lobe, where a lot of the more cognitive functions attributed to the cerebellum seem to localize, as well as the vermis, which is linked to a lot of emotional processing functions.

PTSD is a mental health disorder brought about by experiencing or witnessing a traumatic event, such as a car accident, sexual abuse, or military combat.

Though most people who endure a traumatic experience are spared from the disorder, about 6% of adults develop PTSD, which is often marked by increased fear and reliving the traumatizing event.

Researchers have found several brain regions involved in PTSD, including the almond-shaped amygdala that regulates fear, and the hippocampus, a critical hub for processing memories and routing them throughout the brain.

The cerebellum (Latin for "little brain"), by contrast, has received less attention for its role in PTSD.

A grapefruit-sized lump of cells that looks like it was clumsily tacked underneath the back of the brain as an afterthought, the cerebellum is best known for its role in coordinating balance and choreographing complex movements, like walking or dancing. But there is much more to it than that.

It's a really complex area. If you look at how densely populated with neurons it is relative to the rest of the brain, it's not that surprising that it does a lot more than balance and movement.

Dense may be an understatement. The cerebellum makes up just 10% of the brain's total volume, but packs in more than half of the brain's 86 billion nerve cells.

Researchers have recently observed changes to the size of the tightly-packed cerebellum in PTSD. Most of that research, however, is limited by either a small dataset (fewer than 100 participants), broad anatomical boundaries, or a sole focus on certain patient populations, such as veterans or sexual assault victims with PTSD.

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