Comment

Comment by Dr. Krishna Kumari Challa 31 minutes ago

Patients with implants also exhibited higher levels of chromium, titanium, niobium, and zirconium in blood and serum. In cerebrospinal fluid, titanium, niobium, and zirconium levels were significantly elevated, but only when serum levels of these metals were also increased. This is an important finding as it supports the accuracy of less invasive blood sampling as an indicator of possible cerebrospinal fluid inundation.

Patients with implant components containing cobalt-chromium-molybdenum alloys had the highest cerebrospinal fluid concentrations of both cobalt and chromium. Cobalt levels in cerebrospinal fluid were significantly elevated even among patients with implants in place for less than ten years. Pain in the joint containing the implant was also associated with higher cobalt levels in cerebrospinal fluid.

No increase in cerebrospinal fluid metal levels was observed in patients with implants lacking cobalt-chromium-molybdenum components. Patients with cemented implants showed elevated levels of zirconium in blood and serum, though not in cerebrospinal fluid. Aluminum did not appear elevated in the implant group despite being present in certain implant alloys.
Blood-brain barrier integrity, assessed by serum S-100B levels, appeared unaffected and uncompromised in the implant group. Among those with elevated cerebrospinal fluid cobalt or zirconium, serum S-100B levels were lower than in matched controls.

Findings indicate that metal particles released from joint implants can accumulate in the central nervous system, especially those containing cobalt-chromium-molybdenum.
Results suggest that arthroplasty-related metal exposure is not confined to local tissues but extends systemically and may involve the brain. While blood-brain barrier dysfunction was not evident, the presence of these metals in cerebrospinal fluid raises questions about long-term neurological safety.

Anastasia Rakow et al, Metal Concentrations in Blood and Cerebrospinal Fluid of Patients With Arthroplasty Implants, JAMA Network Open (2025). DOI: 10.1001/jamanetworkopen.2025.2281

Part 2

Comment by Dr. Krishna Kumari Challa 33 minutes ago

Implant-derived metals found in cerebrospinal fluid

New research has found that metal particles from artificial joint implants can enter the central nervous system and accumulate in cerebrospinal fluid, raising concerns about potential neurological effects.

Joint replacement surgery has transformed orthopedic care, improving mobility and quality of life for millions of people. Modern implants, made from combinations of metals, are designed for durability and biocompatibility.

Over time, wear and corrosion of these materials can release microscopic particles into surrounding tissue. These byproducts have been linked to problems near the implant  site, including inflammation, tissue damage, and loosening of the joint.

Emerging concerns point to the possibility of metal particles entering the bloodstream and affecting organs far from the implant. Case reports have described serious effects on the heart, thyroid, and nervous system in patients with elevated levels of certain metals, particularly cobalt and chromium. Neurological changes have been reported in some patients following joint replacement.

Previous research has largely focused on these  metals and has relied on blood and serum measurements, leaving open the question of whether such particles reach the central nervous system.

In the study, "Metal Concentrations in Blood and Cerebrospinal Fluid of Patients With Arthroplasty Implants," published in JAMA Network Open, researchers conducted a single-site cross-sectional study to determine whether metals from joint implants can be found in cerebrospinal fluid and bloodstream.

A cohort was assessed of 204 adult participants, 102 with an existing large joint implant (median age 71.7) and 102 in a control group that had never received joint replacement surgery (median age 67.2).

Samples were collected during elective surgery under spinal anesthesia or during lumbar puncture for routine diagnostic or therapeutic reasons. Inductively coupled plasma mass spectrometry measured concentrations of ten metals in blood, serum, and cerebrospinal fluid, including cobalt, chromium, titanium, niobium, zirconium, and others known to be used in implant materials.

Cobalt levels in cerebrospinal fluid were significantly higher in patients with joint implants than in matched controls. Median cobalt concentrations were 0.03 μg/L in the implant group and 0.02 μg/L in the control group. Strong correlations were observed between cobalt levels in cerebrospinal fluid and those in serum and whole blood, suggesting systemic exposure may be reaching the central nervous system.

Part 1

Comment by Dr. Krishna Kumari Challa 22 hours ago

How Microorganisms looks under the microscope

Comment by Dr. Krishna Kumari Challa yesterday

How perceptions are influenced by expectations: Songbird study draws parallels with human speech processing

Past neuroscience and psychology studies have shown that people's expectations of the world can influence their perceptions, either by directing their attention to expected stimuli or by reducing their sensitivity (i.e., perceptual acuity) to variations within the categories of stimuli we expect to be exposed to.

Researchers carried out a study involving songbirds aimed at better understanding how expectation-fueled biases in perception shape brain activity and behaviour.  

Their findings, published in Nature Neuroscience, suggest that the perceptions of songbirds, like those of humans, are influenced by expectations, with peripheral sensory systems utilizing expectations to enhance sensory perception and retain high-fidelity representations of the world.

Human speakers are known to have different voices, while also pronouncing many words differently. Past studies suggest that the human brain possesses robust underlying mechanisms designed to address these differences, by grouping speech sounds into stable perceptual categories, a process referred to as "categorical perception". 

One of these mechanisms is that we use context to cue and bias our perception.

The researchers examined the vocal behaviour and perceptions of songbirds. This is because songbirds are known to share many similarities with humans in terms of their vocal behaviour, thus studying them can help to better understand human speech and speech-related perceptions.

The team's initial experiments utilizing synthesized birdsongs showed that, similarly to humans who are listening to others speak, the perceptions of songbirds while listening to birdsongs are biased by their expectations.

Overall, this study confirmed the hypothesis that the song perceptions of songbirds closely resemble the speech perceptions of humans. Specifically, it gathered strong evidence suggesting that the vocal perceptions of songbirds are also biased and influenced by expectations.

The second important finding of this study emerged from the team's second experiment probing the neural basis of context-dependent categorical perception in songbirds. While their first experiment showed that the birds' expectations influenced how they classified songs, the second was aimed at determining whether the birds' sensory systems reflected this shift in perception.

The findings showed that  the sensory brain appears to use expectation in a more clever way, by rededicating neural responses to focusing on relevant, expected signals, improving perceptual acuity.

"It then leaves the bias to downstream processing like motor and decision-making regions of the brain. In this way, the brain can retain high-fidelity, unbiased, representations of the world, while still incorporating bias to make optimal decisions.

Tim Sainburg et al, Expectation-driven sensory adaptations support enhanced acuity during categorical perception, Nature Neuroscience (2025). DOI: 10.1038/s41593-025-01899-1.

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Comment by Dr. Krishna Kumari Challa yesterday

New study validates lower limits of human heat tolerance

A new study has confirmed that the limits for human thermoregulation—our ability to maintain a stable body temperature in extreme heat—are lower than previously thought.

The findings are published in the journal Proceedings of the National Academy of Sciences.

The study found that many regions may soon experience heat and humidity levels that exceed the safe limits for human survival

Utilizing a widely used technique known as thermal-step protocols, researchers  exposed 12 volunteers to various heat and humidity conditions to identify the point at which thermoregulation becomes impossible. What made this study different was that participants returned to the laboratory for a daylong exposure to conditions just above their estimated limit for thermoregulation. Participants were subjected to extreme conditions, 42°C with 57% humidity, representing a humidex of approximately 62°C.

The results were clear. The participants' core temperature streamed upwards unabated, and many participants were unable to finish the 9-hour exposure. This data provides the first direct validation of thermal step protocols, which have been used to estimate upper limits for thermoregulation for nearly 50 years.

The implications of this research extend beyond academia. As cities prepare for hotter summers, understanding these limits can help guide health policies and public safety measures.

Robert D. Meade et al, Validating new limits for human thermoregulation, Proceedings of the National Academy of Sciences (2025). DOI: 10.1073/pnas.2421281122

Comment by Dr. Krishna Kumari Challa yesterday

Short-term reactivation of brain between encoding of memories enhances recall, study finds

Past neuroscience and psychology studies have shown that after the human brain encodes specific events or information, it can periodically reactivate them to facilitate their retention, via a process known as memory consolidation. The reactivation of memories has been specifically studied in the context of sleep or rest, with findings suggesting that during periods of inactivity, the brain reactivates specific memories, allowing people to remember them in the long term.

Researchers  recently conducted a study exploring the possibility that the brain engages in a similar reactivation process during wakefulness to store important information for shorter periods of time. Their findings, published in Nature Neuroscience, suggest that the spontaneous reactivation of specific stimuli in the brain during the brief intervals between their encoding predicts the accuracy with which people remember them at the end of a memory task.

David J. Halpern et al, Study-phase reinstatement predicts subsequent recall, Nature Neuroscience (2025). DOI: 10.1038/s41593-025-01884-8.

Comment by Dr. Krishna Kumari Challa on Saturday

Adverse outcomes increased with long-term inhaled corticosteroids in COPD

For patients with chronic obstructive pulmonary disorder (COPD), long-term inhaled corticosteroid (ICS) treatment is associated with increased rates of adverse composite and specific individual outcomes, according to a study published in the March/April issue of the Annals of Family Medicine.

examined electronic health record data for individuals older than 45 years with COPD to assess long-term ICS risks. The prevalent cohort had a COPD diagnosis any time during the observation period (318,385 individuals), and the inception cohort had a COPD diagnosis after entry into the database (209,062 individuals).

A composite outcome of any new diagnosis of type 2 diabetes, cataracts, pneumonia, osteoporosis, or nontraumatic fracture and recurrent event outcomes of repeated pneumonia or nontraumatic fracture were compared for long- versus short-term ICS exposure (>24 months versus <4 months).

The researchers found that the composite dichotomous outcome was significantly greater for long- versus short-term ICS use for both the prevalent and inception cohorts (hazard ratios, 2.65 and 2.60, respectively). The absolute risk difference of the composite outcome was 20.26% for the inception cohort, with a number needed to harm of five.

For recurrent pneumonia and recurrent fracture, the hazard ratios were significantly increased in the prevalent and inception cohorts (hazard ratios, 2.88 and 2.85 for pneumonia, respectively; 1.77 and 1.57 for fracture, respectively).

"The clinical use of and indications for ICS therapy in COPD should be carefully considered for each individual before initiation of long-term ICS therapy," the authors write.

Wilson D. Pace et al, Adverse Outcomes Associated With Inhaled Corticosteroid Use in Individuals With Chronic Obstructive Pulmonary Disease, The Annals of Family Medicine (2025). DOI: 10.1370/afm.240030

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Comment by Dr. Krishna Kumari Challa on Saturday

Measles outbreak leads to dangerous vitamin A toxicity

As a measles outbreak spreads across the U.S., doctors are now seeing a new and unexpected danger: children getting sick from taking too much vitamin A.

At Covenant Children's Hospital in Lubbock, Texas, several unvaccinated children showed signs of liver problems after taking large amounts of vitamin A, according to Dr. Lara Johnson, the hospital's chief medical officer.

U.S. Department of Health and Human Services Secretary Robert F. Kennedy Jr. has promoted vitamin A during the outbreak, even suggesting it might help prevent measles. But doctors say this isn't true.

If people have the mistaken impression that you have an either-or choice of MMR vaccine or vitamin A, you're going to get a lot of kids unnecessarily infected with measles. That's a problem, especially during an epidemic.

And second, you have this unregulated medicine in terms of doses being given and potential toxicities, say the doctors.

The measles, mumps and rubella (MMR) vaccine is the only proven way to prevent measles. It is 97% effective after two doses. 

Vitamin A can be helpful as a supplement for people with measles when given the right dose by a doctor. But taking too much, especially without medical supervision, can be dangerous.

Vitamin A is fat-soluble and can build up in the body. This can lead to dry skin, blurry vision, bone problems and liver damage. In pregnant women, it can even cause birth defects.

If kids are well nourished,  they don't need extra vitamin A.

Recovery for patients with acute toxicity can be rapid when the vitamin is discontinued. Sadly, some of the more serious problems with vitamin A toxicity are not always reversible.

The Council for Responsible Nutrition (CRN), a group representing supplement makers, also warned parents not to give their children high doses of vitamin A.

"While vitamin A plays an important role in supporting overall immune function, research hasn't established its effectiveness in preventing measles infection. CRN is concerned about reports of high-dose vitamin A being used inappropriately, especially in children," it said in a statement.

Doctors say some parents may be following questionable advice from social media or health influencers.

Source: News agencies

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Comment by Dr. Krishna Kumari Challa on Saturday

They found that population, environment, and language all significantly contribute to the variation in hearing across human groups, but it wasn't clear whether this was due to the whole body being affected by the environment or due to long-term adaptations to varying soundscapes, noise levels, or exposure to pollution.

The researchers suggest that people living in forests could have higher sensitivity because they've adapted to soundscapes with lots of non-human sounds, where vigilance is essential for survival. Or it could be due to being exposed to lower levels of pollution.

People living at higher altitudes may have reduced sensitivity due to a number of reasons, including the impact of lower atmospheric pressure on measurements, potential sound reduction in high altitude environments, or physiological adaptations to lower oxygen levels.

The team also found a difference between urban and rural populations, with those living in cities having a shift towards higher frequencies, possibly due to filtering out low-frequency traffic noise.

Patricia Balaresque et al, Sex and environment shape cochlear sensitivity in human populations worldwide, Scientific Reports (2025). DOI: 10.1038/s41598-025-92763-6

Part 2

Comment by Dr. Krishna Kumari Challa on Saturday

Women can hear better than men: Researchers find amplitude more influenced by sex than age

Scientists have found that sex is the leading factor explaining differences in hearing sensitivity, with women having significantly more sensitive hearing than men.

Hearing problems are on the rise worldwide, and while hearing sensitivity is well known to decrease with age, little research has been done on the other biological and environmental factors that influence them, such as sex, ear side, language, ethnicity, and local environment.

So researchers conducted hearing tests for 450 individuals across 13 global populations—Equador, England, Gabon, South Africa, and Uzbekistan. These populations were selected to capture a wide range of ecological and cultural contexts, including underrepresented rural and non-European groups.

They investigated the sensitivity of the cochlea in the ear, looking at how it transmitted brain signals in response to different amplitudes and frequencies of sound by measuring so-called Transient-Evoked Otoacoustic Emissions (TEOAE).

It's already well known that people generally have better hearing in their right ear, compared with their left, and that hearing usually declines with age. However, the researchers were surprised by their results on the effects of sex and the environment.

Their findings, published in the journal Scientific Reports, show that hearing amplitude is more influenced by sex than age, with women showing an average of two decibels more sensitive hearing than men across all the populations studied.

The second most significant influence was the environment, which not only affected the response to volume but also the range of frequencies of sound perceived. People living in forest areas had the highest hearing sensitivity and those living at high altitudes had the lowest.

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