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Comment by Dr. Krishna Kumari Challa on August 2, 2024 at 12:05pm

Comment by Dr. Krishna Kumari Challa on August 2, 2024 at 11:56am

Paper cut physics: the physics behind why some paper is more prone to cut fingers

We all know what it’s like to pick up a sheet of paper, only to get a painful paper cut. The injury is usually small and shallow, but it can really hurt!
Your body has hundreds of nerves. These nerves are spread throughout your body, from head to toe.
In your hands and fingers, though, the nerve endings are densely packed together. So, they’re more sensitive than other areas, like your back or arm.
This explains why paper cuts hurt so much. They commonly affect the hands and fingers, which have a higher density of nerve endings.
But what about all the blood? Well, the capillaries in your hands and fingers are closely packed together. This means paper cuts can cause a lot of bleeding because of how concentrated blood can be in your hands.

In experiments with a gelatin replica of human tissue, researchers found that a thin sheet of paper tended to buckle before it could cut. Thick paper typically indented the material but didn’t pierce it: Like a dull knife blade, it didn’t concentrate force into a small enough area. A thickness of around 65 micrometers was a paper cut sweet spot — or sore spot — physicist Kaare Jensen and colleagues report in a paper to appear in Physical Review E.

That makes dot matrix printer paper the most treacherous, the researchers say. (That paper is seldom used today ). Paper from various magazines was a close second in the scientists’ tests. 

The angle of slicing also played a role. Paper pressed straight down into the gelatin was less likely to cut than paper that cleaved across and down.

S.F. Arnbjerg-Nielsen, M.D. Biviano and K.H. Jensen. Competition between slicing and buckling underlies the erratic natu.... Physical Review E, in press, 2024.

Comment by Dr. Krishna Kumari Challa on August 2, 2024 at 9:35am

One outcome of the study could be that "health care providers might more strongly consider recommending aspirin to patients who have less healthy lifestyles.
Previous studies have found evidence to suggest aspirin can reduce the production of pro-inflammatory proteins, known as prostaglandins, that can promote the development of cancer. Aspirin may also block signaling pathways that cause cells to grow out of control, influence the immune response against cancer cells, and block the development of blood vessels that supply nutrients to cancer cells.

Aspirin likely prevents colorectal cancer through multiple mechanisms.
The study did not assess potential side effects of daily aspirin use, such as bleeding. In addition, while the study tried to control for a wide range of risk factors for colorectal cancer, in comparing non-aspirin and aspirin-taking groups with the same level of risk factors, because this was an observational study, it is possible there may have been additional factors that influenced the findings.

 Aspirin Use and Incidence of Colorectal Cancer According to Lifestyle Risk, JAMA Oncology (2024). DOI: 10.1001/jamaoncol.2024.2503

Part 2

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Comment by Dr. Krishna Kumari Challa on August 2, 2024 at 9:32am

Study finds regular aspirin use associated with greatest reduction in colorectal cancer among those most at risk

Regular aspirin may help lower risk of colorectal cancer in people with greater lifestyle-related risk factors for the disease, according to a study by researchers. 

 The study, published in JAMA Oncology, could encourage a more nuanced approach to preventive aspirin use.

The U.S. Preventive Services Task Force previously recommended daily low-dose aspirin to prevent cardiovascular events and colorectal cancer in all adults ages 50 to 59 (the highest risk age group for colorectal cancer). In 2016, they withdrew the recommendation in part due to concerns about aspirin increasing the risk of gastrointestinal bleeding.

For the study, researchers analyzed the health data from 107,655 participants from the Nurses' Health Study and Health Professionals Follow-Up Study. They compared the colorectal cancer rates in those who took aspirin regularly with those who did not take aspirin regularly. Regular aspirin use was defined as either two or more standard dose (325 mg) tablets per week or daily low-dose (81 mg) aspirin.

Study participants were followed starting from an average age of 49.4 years. Those who regularly took aspirin had a colorectal cancer 10-year cumulative incidence of 1.98%, compared to 2.95% among those who did not take aspirin.

The benefit of aspirin was largest among those with the unhealthiest lifestyles. Those with the lowest healthy lifestyle scores (unhealthiest) had a 3.4% chance of getting colorectal cancer if they did not take regular aspirin and a 2.12% chance of getting colorectal cancer if they took aspirin regularly.

By contrast, in those with the highest healthy lifestyle scores (healthiest), the colorectal cancer rates were 1.5% in regular aspirin-taking group and 1.6% in the non-regular aspirin group. This means that in the least healthy group, treating 78 patients with aspirin would prevent one case of colorectal cancer over a 10-year period, while it would take treating 909 patients to prevent one case for the healthiest group.

Lifestyle scores were calculated based on  body mass index, frequency of cigarette and alcohol use, physical activity, and adherence to a high-quality diet.

These results show that aspirin can proportionally lower the markedly elevated risk in those with multiple risk factors for colorectal cancer.

In contrast, those with a healthier lifestyle have a lower baseline risk of colorectal cancer, and, therefore, their benefit from aspirin was still evident, albeit less pronounced.

Part1

Comment by Dr. Krishna Kumari Challa on August 2, 2024 at 8:47am

Warming breaks down symbiosis

Hotter conditions prevent two tiny organisms working together for mutual benefit, new research shows.

Scientists studied a single-celled organism (Paramecium bursaria) which can absorb and host algae (Chlorella spp). This pairing is common in freshwater worldwide, and their symbiotic relationship provides benefits including trading of nutrients and protection for the algae.

But when scientists made the water 5°C warmer, the partnership stopped working—and the results suggest the algae may even become parasitic.

The breakdown of such relationships could have a major impact on ecosystems.

The paper, published in the journal Aquatic Biology, is titled "One year of warming leads to the total loss of productivity in a widespread photosymbiosis."

This kind of relationship—called photosymbiosis—is an important part of freshwater and ocean ecosystems.

To illustrate their importance, these relationships provide around half of all marine photosynthesis.

A well-known example is found in coral reefs—where the reef-building corals host resident photosynthetic partners. In recent years, we have seen many high-profile 'bleaching' events—when corals expel these partners, often due to high temperatures, leaving them at risk of stress and mortality.

B Makin et al, One year of warming leads to the total loss of productivity in a widespread photosymbiosis, Aquatic Biology (2024). DOI: 10.3354/ab00769

Comment by Dr. Krishna Kumari Challa on August 2, 2024 at 8:22am

the new study showed that for geographically restricted strains, whether a person has ancestors who lived where the strain is common was an even bigger predictor of infection risk than bacterial load in the sputum. In the cases analyzed in the study, this risk of common ancestry even outweighed the risk stemming from having diabetes and other chronic diseases previously shown to render people more susceptible to infection.

The findings add to a growing body of evidence of the importance of paying attention to the wide variation between different lineages of tuberculosis and to the details of how different lineages of tuberculosis interact with different host populations.

Previous studies have shown that some genetic groups of TB are more prone to developing drug resistance and that TB vaccines appear to work better in some places than others. There is also evidence that some treatment regimens might be better suited to some strains of TB than others.

"These findings emphasize how important it is to understand what makes different strains of TB behave so differently from one another, and why some strains have such a close affinity for specific, related groups of people.

In addition to the analysis of clinical, genomic, and public health data, the researchers also tested the ability of different strains of TB to infect human macrophages, a type of immune cell that TB hijacks to cause infection and disease. The researchers grew cells from donors from different regions. Once again, cell lines from people with ancestry that matched the native habitat of a restricted strain of tuberculosis bacteria were more susceptible to the germs than cells from people from outside the area, mirroring the results of their epidemiologic study.

Differential rates of Mycobacterium tuberculosis transmission associate with host–pathogen sympatry, Nature Microbiology (2024). DOI: 10.1038/s41564-024-01758-y

Part 2

Comment by Dr. Krishna Kumari Challa on August 2, 2024 at 8:21am

Study links TB strain infectivity to shared geographic background

For some forms of tuberculosis, the chances that an exposed person will become infected depend on whether the individual and the bacteria share a hometown, according to a new study comparing how different strains move through mixed populations in cosmopolitan cities.

Results of the research, led by Harvard Medical School scientists and published in Nature Microbiology, provide the first hard evidence of long-standing observations that have led scientists to suspect that pathogen, place, and human host collide in a distinctive interplay that influences infection risk and fuels differences in susceptibility to infection.

The study strengthens the case for a long-standing hypothesis in the field that specific bacteria and their human hosts likely co-evolved over hundreds or thousands of years, the researchers said.

The findings may also help inform new prevention and treatment approaches for tuberculosis, a wily pathogen that sickens more than 10 million people and causes more than a million deaths worldwide each year, according to the World Health Organization.

In the current analysis, believed to be the first controlled comparison of TB strains' infectivity in populations of mixed geographic origins, the researchers custom built a study cohort by combining case files from patients with TB in New York City, Amsterdam, and Hamburg. Doing so gave them enough data to power their models.

The analysis showed that close household contacts of people diagnosed with a strain of TB from a geographically restricted lineage had a 14% lower rate of infection and a 45% lower rate of developing active TB disease compared with those exposed to a strain belonging to a widespread lineage.

The study also showed that strains with narrow geographic ranges are much more likely to infect people with roots in the bacteria's native geographic region than people from outside the region.

The researchers found that the odds of infection dropped by 38% when a contact is exposed to a restricted pathogen from a geographic region that doesn't match the person's background, compared with when a person is exposed to a geographically restricted microbe from a region that does match their home country. This was true for people who had lived in the region themselves and for people whose two parents could each trace their heritage to the region.

This pathogen-host affinity points to a shared evolution between humans and microbes with certain biological features rendering both more compatible and fueling the risk for infection, the researchers said.

Part 1

Comment by Dr. Krishna Kumari Challa on August 1, 2024 at 10:03am

Study uncovers unique brain plasticity in people born blind

A study by neuroscientists reveals that the part of the brain that receives and processes visual information in sighted people develops a unique connectivity pattern in people born blind. They say this pattern in the primary visual cortex is unique to each person—akin to a fingerprint.

The findings, described July 30, 2024, in PNAS, have profound implications for understanding brain development and could help launch personalized rehabilitation and sight restoration strategies.

For decades, scientists have known that the visual cortex in people born blind responds to a myriad of stimuli, including touch, smell, sound localization, memory recall and response to language. However, the lack of a common thread linking the tasks that activate primary areas in the visual cortex has perplexed researchers.

The new study offers a compelling explanation: differences in how each individual's brain organizes itself.

We don't see this level of variation in the visual cortex connectivity among individuals who can see—the connectivity of the visual cortex is usually fairly consistent, say the researchers.

The connectivity pattern in people born blind is more different across people, like an individual fingerprint, and is stable over time—so much so that the individual person can be identified from the connectivity pattern.

Lénia Amaral et al, Longitudinal stability of individual brain plasticity patterns in blindness, Proceedings of the National Academy of Sciences (2024). DOI: 10.1073/pnas.2320251121

Comment by Dr. Krishna Kumari Challa on August 1, 2024 at 9:58am

Engineered microbes found to repel mosquitoes

Genetically-engineered human skin bacteria can make mice less attractive to mosquitoes for 11 days. Mosquitoes transmit a host of deadly diseases, including malaria, West Nile, dengue, yellow fever, and Zika. Female mosquitoes on the hunt for a blood meal tune into scents released by skin microbes that live on their targets.

Researchers engineered versions of the common human  skin commensals Staphylococcus epidermidis and Corynebacterium amycolatum to produce much less of a form of lactic acid known to attract mosquitoes. The work is published in the journal PNAS Nexus.

The authors tested the microbes alone and found the engineered version of S. epidermidis attracted about half as many Aedes aegypti and Anopheles gambiae mosquitoes and about 22% fewer Culex quinquefasciatus as the wildtype versions of the microbes.

The authors also tried the engineered microbes on mice. Painting the mice with wildtype S. epidermidis attracted mosquitos. However, painting the mice with engineered S. epidermidis reduced mosquito attraction by up to 64.4%, compared with wildtype, starting three days after the microbe was applied.

The effect lasted for 11 days. Trials with engineered C. amycolatum had similar results. In addition, a smaller proportion of mosquitoes that landed on mice painted with engineered microbes bit the mice. According to the authors, the results suggest the feasibility of creating a living and long-lasting engineered microbiome-based mosquito repellent.

 Feng Liu et al, Engineered skin microbiome reduces mosquito attraction to mice, PNAS Nexus (2024). DOI: 10.1093/pnasnexus/pgae267

Comment by Dr. Krishna Kumari Challa on August 1, 2024 at 9:46am

Why men and women feel touch differently

Why women generally seem to have a more acute sense of touch than men?

 Women are better than men at touch discrimination—although not because they have smaller fingers, but because in general they have softer fingers. 

But demonstrating the "why" behind the gender difference, first published in November 2023 in the Journal of Physiology, continues to be a cited topic of interest. The insight could be useful as engineers develop softer sensor materials for wearable technology, improve prosthetics with a sense of touch, or design better interfaces for surgical robots.

The experimental design combined novel 3D imaging and biomechanical observations of skin and how it deforms when pressed, statistical analysis and machine learning, and experiments to test how the participants used touch to perceive objects.
They found that softer skin resulted in greater rates of change in surface contact with objects, which correlated with a greater ability to distinguish small changes in the objects' stiffness.

"The mechanism seems to be that attributes of surface contact control the recruitment of sensory nerve fibers in the skin".

For those who'd like to improve their touch perception, the researchers said, apply hyaluronic acid, an effective skin moisturizer and softener.

Bingxu Li et al, An individual's skin stiffness predicts their tactile discrimination of compliance, The Journal of Physiology (2023). DOI: 10.1113/JP285271

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