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Comment by Dr. Krishna Kumari Challa on May 29, 2025 at 2:02pm

By elucidating the neural basis of individual differences in fear plasticity, this study highlights the central role of brain states in stress adaptation.

Xuemei Liu et al, Neural circuit underlying individual differences in visual escape habituation, Neuron (2025). DOI: 10.1016/j.neuron.2025.04.018

Part 2

Comment by Dr. Krishna Kumari Challa on May 29, 2025 at 1:47pm

Neural circuit mechanism may explain why people have different fear levels

In a study published in Neuron, a research team revealed the neural circuit underlying individual differences in visual escape habituation.

Emotional responses, such as fear behaviors, are evolutionarily conserved mechanisms that enable organisms to detect and avoid danger, ensuring survival. Since Darwin's "On the Origin of Species" (1859) proposed that individual differences drive natural selection, understanding behavioral adaptation has become essential for unraveling biodiversity and survival strategies.

Repeated exposure to predators can elicit divergent coping strategies—habituation or sensitization—that are dependent on sensory inputs, internal physiological states, and prior experiences. However, the neural circuits underlying individual variability in the regulation of internal states and habituation to repeated threats remain poorly understood.

To address this question, researchers employed advanced techniques such as in vivo multichannel recording, fiber photometry, pupillometry and optogenetic manipulation to investigate how individual differences in arousal and internal states influence visual escape habituation.

Researchers found that distinct subcortical pathways from the superior colliculus to the amygdala and insula cortical pathways that govern two visual escape behaviors in two groups of mice. They identified two distinct defensive behaviors—sustained rapid escape (T1) and rapid habituation (T2).

T1 involves the superior colliculus (SC)/insular cortex-ventral tegmental area (VTA)-basolateral amygdala (BLA) pathway, whereas T2 relies on the SC/insula-dorsomedial thalamus (MD)-BLA circuit. The MD integrates inputs from the SC and insula to regulate arousal and fear responses, while beta oscillations in BLA modulate fear states.
Dysregulation of innate fear circuits is closely linked to many mental health conditions, including phobias, anxiety, and post-traumatic stress disorder (PTSD). Elucidating the neural circuitry underlying innate fear not only enhances our understanding of emotional disorders but also provides promising therapeutic targets for clinical interventions.

Comment by Dr. Krishna Kumari Challa on May 29, 2025 at 1:43pm

Intestinal bacteria influence aging of blood vessels

The aging of the innermost cell layer of blood vessels leads to cardiovascular diseases. Researchers at UZH have now shown for the first time that intestinal bacteria and their metabolites contribute directly to vascular aging.

As people age, the bacterial composition in their gut changes, resulting in fewer "rejuvenating" and more harmful substances in the body.

Cardiovascular diseases are the most common cause of death worldwide. Even if known traditional risk factors such as diabetes or high blood pressure are treated, the disease worsens in half of all cases, especially in older patients.

In a study published in Nature Aging, researchers at UZH have now shown for the first time that intestinal bacteria and their metabolites can accelerate the aging of blood vessels and trigger cardiovascular disease.

The human body consists of around 30 to 100 trillion bacteria that reside in our organs. Ninety percent of these bacteria live in the intestine, processing the food we eat into metabolic products, which in turn affect our bodies.

Half of these substances have not yet been recognized. 

Using data from more than 7,000 healthy individuals aged between 18 and 95 as well as a mouse model of chronological aging, the researchers found that the breakdown product of the amino acid phenylalanine—phenylacetic acid—accumulates with age.

In several series of experiments, researchers were able to prove that phenylacetic acid leads to senescence of endothelial cells, in which the cells that line the inside of blood vessels do not proliferate, secrete inflammatory molecules, and exhibit an aging phenotype. As a result, the vessels stiffen up and their function is impaired.

By conducting a comprehensive bioinformatic analysis of the microbiome of mice and humans, the researchers were able to identify the bacterium Clostridium sp.ASF356, which can process phenylalanine into phenylacetic acid.

When the researchers colonized young mice with this bacterium, they subsequently showed increased phenylacetic acid levels and signs of vascular aging. However, when the bacteria were eliminated with antibiotics, the concentration of phenylacetic acid in the body decreased.

However, the microbiome in the gut also produces substances that are beneficial to vascular health. Short-chain fatty acids such as acetate, which are produced by fermentation of dietary fibers and polysaccharides in the intestine, act as natural rejuvenating agents.

The research group used in-vitro experiments to show that adding sodium acetate can restore the function of aged vascular endothelial cells. When analyzing intestinal bacteria, they found that the number of bacteria that produce such rejuvenating agents decreases with age.

"The aging process of the cardiovascular system can therefore be regulated via the microbiome", say the researchers.

The researchers are also working on ways to reduce phenylacetic acid in the body through medication.

Seyed Soheil Saeedi Saravi et al, Gut microbiota-dependent increase in phenylacetic acid induces endothelial cell senescence during aging, Nature Aging (2025). DOI: 10.1038/s43587-025-00864-8

Comment by Dr. Krishna Kumari Challa on May 29, 2025 at 12:14pm

Earth's magnetic field typically deflects the majority of these blasts of charged particles, but during periods of intense activity, some manage to get through. Merging of the magnetic fields in the solar wind, arriving from the sun as a result of the expansion of its atmosphere into space, with the magnetic fields of Earth inject energy into near-Earth space and power space weather and the dancing northern (and southern) lights.

In order to generate the aurora, accelerated particles, mostly electrons, rain down towards Earth and then collide with atoms and molecules in the upper atmosphere, between 100 and 250 kilometers above Earth's surface. In the period after these collisions, when the particles drop back down into a lower-energy state, "they spit out a photon of light."
You have these energy conversion processes occurring at the solar surface, but then you also have something similar occurring in Earth's magnetic field. That's ultimately the origin of the energy for accelerating the charged particles that rain into Earth's atmosphere and cause this sort of glowing effect.
The palette of brilliant colors we see from the ground is a result of different gases involved in the collisions. Green, by far the most common hue, comes from particles colliding with oxygen atoms. Higher-energy collisions involving oxygen can have a red hue, and nitrogen is the gas responsible for blue and purple-tinted displays.
Part 2

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Comment by Dr. Krishna Kumari Challa on May 29, 2025 at 12:10pm

Science behind the surge in northern lights

If you feel like you've seen more of the northern lights painting the night sky lately, you'd be right. 

We're currently in a period of solar maximum, which is good news for aurora borealis enthusiasts. If you want to watch beautiful shows of the dancing northern lights, solar max is an ideal time to do that, say the experts.

The sun operates on a roughly 11-year cycle of magnetic activity. 

As the sun's magnetic field flips its north and south poles over this time, it switches between periods of lower magnetic activity (solar minimum) and periods of higher magnetic activity (solar maximum).

Surrounding the north and south magnetic poles of Earth are regions referred to as the "auroral ovals"—areas where aurora displays typically happen. During periods of solar max, these zones tend to expand a bit closer towards the equator, moving into areas where more people live.

There's more energy available, so they're more powerful, but they also move so they're at locations where they're more visible. 

Before any colors appear in the night skies over Earth, things need to turn explosive—literally—on the sun. The sun's surface is permeated by bundles of strong magnetic fields which poke out into the solar atmosphere. The ends of such magnetic loops represent cooler regions of the solar surface called sunspots. 

Loops can be stable for days and then suddenly they'll explode and launch a whole mass of charged particles into space—that's called a coronal mass ejection. It's basically a rapid release of the energy in these magnetic loops, but in the form of charged particles, which get a lot of kinetic energy and exceed the escape velocity of the sun's gravity field, blasting outwards into the solar system. 

Part 1

Comment by Dr. Krishna Kumari Challa on May 29, 2025 at 11:50am

Filtered car emissions still turn toxic after sunlight exposure, study reveals

A new international study reveals that emissions from modern gasoline cars—despite meeting the currently strictest European emission standards EURO 6d—can become significantly more harmful after being released into the atmosphere. The findings, published in Science Advances, challenge the assumption that filtered exhaust from EURO 6d-compliant vehicles is inherently safe.

The research focused on a gasoline vehicle equipped with a gasoline particulate filter (GPF), designed to drastically reduce primary particulate emissions. Freshly emitted exhaust showed no detectable cytotoxic effects on human lung cells. However, once the exhaust underwent "photochemical aging"—a natural transformation process driven by sunlight and atmospheric oxidants—it became substantially more toxic.

The aged emissions caused notable DNA damage and oxidative stress in both cancerous alveolar and normal bronchial epithelial cells. This toxicity was not only associated with newly formed particles, known as secondary organic and inorganic aerosols (SOA and SIA), but also with oxygenated volatile compounds, such as carbonyls, generated during their residence in the atmosphere.

 These findings point to a critical shortfall in current vehicle emissions testing and regulation.

While EURO 6d standards ensure low emissions at the tailpipe, they do not account for the chemical transformations those emissions undergo once released into the environment.

This new study shows that we are missing a big part of the picture by not considering how exhaust gases change—and become more harmful—after they leave the car.

The results have important implications for how air quality standards are set and monitored. Current regulations focus primarily on the emissions measured directly after combustion, without factoring in how these emissions interact with sunlight and atmospheric chemicals to form new, more harmful pollutants.

Mathilde N. Delaval et al, The efficiency of EURO 6d car particulate filters is compromised by atmospheric aging: In vitro toxicity of gasoline car exhaust, Science Advances (2025). DOI: 10.1126/sciadv.adq2348

Comment by Dr. Krishna Kumari Challa on May 29, 2025 at 11:34am

Humans are seasonal creatures, according to our circadian rhythms

It's natural to think that, with our fancy electric lights and indoor bedrooms, humanity has evolved beyond the natural influence of sunlight when it comes to our sleep routines.

But new research  shows that our circadian rhythms are still wild at heart, tracking the seasonal changes in daylight. Humans really are seasonal, even though we might not want to admit that in our modern context. 

Day length, the amount of sunlight we get,  really influences our physiology. The study shows that our biologically hardwired seasonal timing affects how we adjust to changes in our daily schedules.

This finding could enable new ways to probe and understand seasonal affective disorder, a type of depression that's connected to seasonal changes. It could also open new areas of inquiry in a range of other health issues that are connected to the alignment of our sleep schedules and circadian clocks.

Researchers have previously shown that our moods are strongly affected by how well our sleep schedules align with our circadian rhythms. 

This work may have deeper implications for mental health issues, like mood and anxiety, but also metabolic and cardiovascular conditions as well.

The research also showed there is a genetic component of this seasonality in humans, which could help explain the vast differences in how strongly individuals are affected by changes in day length.

For some people they might be able to adapt better, but for other people it could be a whole lot worse.

Exploring this genetic component will help researchers and doctors understand where individuals fall on that spectrum, but getting to that point will take more time and effort. For now, this study is an early but important step that reframes how we conceive of human circadian rhythms.

A lot of people tend to think of their circadian rhythms as a single clock. What  the researchers are showing is that there's not really one clock, but there are two. One is trying to track dawn and the other is trying to track dusk, and they're talking to each other.

The fact that circadian rhythms  in people exhibited a seasonal dependence is a compelling argument for just how hardwired this feature is in humans, which isn't altogether surprising, the researchers say.

Seasonal timing and interindividual differences in shiftwork adaptation, npj Digital Medicine (2025). DOI: 10.1038/s41746-025-01678-z

Comment by Dr. Krishna Kumari Challa on May 29, 2025 at 10:41am

The researchers studied a number of antibiotic classes and how body weight affects the drugs' metabolism. Drug classes analyzed in the study included β-lactams, aminoglycosides, glycopeptides, lipoglycopeptides, and quinolones, among others. Yet, not all antibiotics require special guidelines for the obese.
Obesity modestly alters the pharmacokinetics of β-lactam antibiotics, so evidence does not support routine dose adjustments [because of body weight].
For aminoglycosides and glycopeptides, the impact of obesity on pharmacokinetics is evident and weight-based dosing is recommended.
β-lactam antibiotics include such widely prescribed drugs as the penicillins, cephalosporins, carbapenems and monobactams. They are chemically characterized by a β-lactam ring in their chemical structure. The drugs are used against a wide range of bacterial infections, including Gram-positive and Gram-negative species. But there's no need to treat obese patients differently when it comes to β-lactam medications.

Doctors, meanwhile, frequently turn to aminoglycosides to treat extremely serious infections, especially those caused by Gram-negative bacteria. Aminoglycosides include such medications as gentamicin, streptomycin, and neomycin. These drugs work by disrupting critical protein production activity inside the bacterial cell. The drugs enter bacteria and bind to the 30S ribosomal subunit, resulting in flawed protein synthesis and death of the pathogens.

Guidelines were recommended for the use of this class in the obese as well as for glycopeptide antibiotics, which include the highly potent cell-wall-disrupting drug vancomycin.
Maintenance doses [of vancomycin] should be individualized and guided by therapeutic drug monitoring to increase the probability of achieving therapeutic yet non-toxic drug exposures, the researchers say.
The team did not provide a guideline based on total body weight for the quinolones, the drug class that includes the fluoroquinolones. However, the team's recommendations stressed special consideration for administering fluoroquinolones.
Higher or more frequent dosing resulting in higher systemic exposure should be considered for patients with obesity and severe deep-seated infections to reach adequate tissue concentration," the team asserted.

Data were sparse for other antibiotic classes and will require additional study, according to findings from the research.
When making decisions on dosing in obesity, the severity of illness, site of infection, susceptibility of the pathogen, and potential toxicity of the antibiotics should be considered, they concluded.

Anne-Grete Märtson et al, The pharmacokinetics of antibiotics in patients with obesity: a systematic review and consensus guidelines for dose adjustments, The Lancet Infectious Diseases (2025). DOI: 10.1016/S1473-3099(25)00155-0

Part 2

Comment by Dr. Krishna Kumari Challa on May 29, 2025 at 10:37am

Size matters when it comes to antibiotics. Obese patients may need customized doses of certain drugs

Obesity can have a distinct impact on the absorption, effectiveness and excretion of antibiotics, medications that have been in use for more than 80 years, but only now have consensus guidelines been proposed on prescribing the drugs for patients with substantial fat mass.

The new research arrives amid two major global health crises: In 2022, the World Health Organization declared that 43% of the global adult population is overweight, and an estimated 16% of adults are considered obese, some severely so. Also, in recent years, the WHO has stressed the need for more efficient use of antibiotics to preserve their usefulness as drug-resistant superbugs become an increasingly lethal threat.

Now, an international team of medical investigators reports that obesity can interfere with antibiotics, resulting in too much or too little drug exposure to treat infections. And because dosages that effectively work in normal weight individuals don't seem to treat the obese, the research team has developed obesity-specific antibiotic dosing guidelines for certain classes of the drugs.

Writing in The Lancet Infectious Diseases, the team describes its research as an in-depth systematic review of the medical literature on dosing and antibiotics. Conclusions drawn from the research created the framework for the guidelines.

Obesity can alter antibiotic pharmacokinetics due to physiological changes, such as body composition and organ dysfunction that result in increased or decreased drug exposures in plasma or at the site of infection, say the researchers.

Researchers used the standard definition of obesity, a BMI of 30 or higher, and underscored that "substantial changes can occur in the volume of [systemic antibiotic] distribution due to increased fat and muscle mass." In other words, obesity can alter how antibiotics are absorbed, distributed and excreted from the body.

The team began its systematic investigation with a review of 6,113 studies on obesity and antibiotic dosing. After eliminating duplicate studies, the team narrowed that number to 128 studies from which conclusions in the study were drawn.

A pictorial chart in the study illustrated problems facing the obese when it comes to taking antibiotics: increased fat mass, impaired kidney and/or liver function. Of special concern in the liver is the dysfunction of cytochrome P450, the group of enzymes responsible for metabolizing drugs.

Part 1

Comment by Dr. Krishna Kumari Challa on May 28, 2025 at 3:35pm

Trees May Be Able to Warn Us When a Volcano Is About to Erupt

The science of predicting volcanic eruptions can genuinely save lives – potentially, a lot of lives – and researchers have shown that tree leaf colors can act as warning signals around a volcano that's about to blow. As volcanoes get more active and closer to an eruption, they push magma up closer to the surface, releasing higher levels of carbon dioxide. That in turn can boost the health of the surrounding trees, making leaves greener. And those changes – specifically in the measurement known as the normalized difference vegetation index (NDVI) – can be spotted by satellites in space. We could be looking at an early warning system for eruptions that doesn't require any local field work or ground sensors, so it could work in remote and difficult-to-access areas.

https://www.sciencedirect.com/science/article/abs/pii/S003442572400...

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