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Comment by Dr. Krishna Kumari Challa yesterday

Why are men usually taller than women?

A recent study, analyzing genetic data from nearly a million individuals, sheds light on why men are typically taller than women. Researchers focused on the SHOX gene, located on both X and Y chromosomes, and its role in height determination.

While scientists have long suspected that genetics contribute to these differences, the biological mechanisms behind this sexual dimorphism independent of hormones remained unclear, until a team of researchers from the U.S. shed some light onto it with their study published in PNAS.

The team analyzed a large-scale dataset with 928,605 adult participants, including 1,225 adults with sex chromosome aneuploidies (SCAs)—genetic conditions where individuals have an abnormal number of X or Y chromosomes, either extra or missing.

They found that having an extra Y chromosome led to a greater increase in height compared to an additional X chromosome, regardless of the influence of male hormones.

The sex chromosomes X and Y are non-homologous, meaning they do not share many gene sequences or structures, but both contain a gene called SHOX located in pseudoautosomal region 1 (PAR1), a small section where X and Y chromosomes share sequence identity and work like a regular chromosome. The SHOX gene is a key player in influencing height.

In human females, most of the X chromosome is inactivated, except for PAR1, which escapes X-inactivation, and both human males and females typically have two active copies of PAR1 genes.

Research indicated that the SHOX and other genes in the PAR1 region have lower levels of expression in the inactive X chromosome (Xi), suggesting they are only partially protected from silencing.

This partial silencing means that males (46,XY) may have higher levels of SHOX since it is expressed in both the X and Y chromosomes, compared to females (46,XX) with two X chromosomes. This difference in gene expression is especially noticeable in musculoskeletal tissues, thus explaining sex differences in growth and height.

The findings indicated that the height contribution of the Y chromosome was larger than that of a second X chromosome, irrespective of hormonal differences.

The researchers highlight that understanding genetic underpinnings of sex dimorphisms is crucial not just for traits like height, but also for uncovering the biological mechanisms behind sex-based disparities in the occurrence of autoimmune, neuropsychiatric, and other medical conditions.

Alexander S. F. Berry et al, X and Y gene dosage effects are primary contributors to human sexual dimorphism: The case of height, Proceedings of the National Academy of Sciences (2025). DOI: 10.1073/pnas.2503039122

Comment by Dr. Krishna Kumari Challa yesterday

Could Mitochondria Be Rewriting the Rules of Biology?

Comment by Dr. Krishna Kumari Challa on Wednesday

Markers in blood and urine may reveal how much ultra-processed food we are eating

Molecules in blood and urine may reveal how much energy a person consumes from ultra-processed foods, a key step to understanding the impact of the products, a new study finds.

It's the first time that scientists have identified biological markers that can indicate higher or lower intake of the foods, which are linked to a host of health problems. The study is published   this week in the journal PLOS Medicine.

It can potentially give us some clues as to what the underlying biology might be between an ultraprocessed food association and a health outcome.

Ultraprocessed foods—sugary cereals, sodas, chips, frozen pizzas and more—are products created through industrial processes with ingredients such as additives, colours and preservatives not found in home kitchens. 

The scientists found that hundreds of metabolites—products of digestion and other processes—corresponded to the percentage of energy a person consumes from ultra-processed foods. From those, they devised a score of 28 blood markers and up to 33 urine markers that reliably predicted ultra-processed food intake in people consuming typical diets.

The researchers  found this signature that was sort of predictive of this dietary pattern that's high in ultra-processed food and not just a specific food item here and there.

A few of the markers, notably two amino acids and a carbohydrate, showed up at least 60 times out of 100 testing iterations. One marker showed a potential link between a diet high in ultraprocessed foods and type 2 diabetes, the study found.

The research team found that they could use the metabolite scores to tell when the individual participants were eating a lot of ultra-processed foods and when they weren't eating those foods.

The results suggested the markers were "valid at the individual level".

With more research, these metabolic signatures can begin to untangle the biologic pathways and harms of UPF and also differences in health effects of specific UPF food groups, processing methods and additives.

Abar L, et al. Identification and validation of poly-metabolite scores for diets high in ultra-processed food: An observational study and post-hoc randomized controlled crossover-feeding trial.PLOS Medicine (2025). DOI: 10.1371/journal.pmed.1004560

Comment by Dr. Krishna Kumari Challa on Wednesday

Stopping infections before they can start: Promising approach blocks bacteria from binding to cells

As concerns about waning antibiotic effectiveness grow, researchers are using unique tools to search for new ways to keep bacteria from causing infections in both humans and animals.

Researchers used the Canadian Light Source (CLS) at the University of Saskatchewan to visualize the structure of long, thin proteins called adhesins, which most bacteria have, and which bind to a sugar molecule on the surface of a cell. Once attached, the bacteria start to form a colony and then eventually a biofilm. This is how they get started in an infection.

The goal of the research, recently published in the journal mBio, is to find a way to interrupt that attachment process—to "put something in there that would fool them (bacteria) and not allow them to bind to the host cells."

Researchers  learned how to recognize those parts of the protein that stick to the surface of cells and begin causing infections. The researchers noted one spot on the protein that attaches to a simple sugar called fucose found on human blood cells and other organisms.

Special imaging at the CLS—called crystallography—confirmed the model and revealed a possible way to inhibit bacteria from binding to cells. 

Adding more fucose in with the bacterium disrupts the binding process "because they're confused by all of this free fucose floating around" . The protein sensorsrs "that are looking out for the sugar on our cells" are unable to bind "because we're flooding the market with fucose."

The next steps in the research will be to produce compounds that mimic fucose "but that cannot be metabolized by either the bacteria or by the human cells that scientists are trying to protect" .  We won't have to put so much sugar in the system.

Qilu Ye et al, Aeromonas hydrophila RTX adhesin has three ligand-binding domains that give the bacterium the potential to adhere to and aggregate a wide variety of cell types, mBio (2025). DOI: 10.1128/mbio.03158-24

Comment by Dr. Krishna Kumari Challa on Wednesday

Color-correcting algorithm removes the effect of water in underwater scenes

The ocean is teeming with life. But unless you get up close, much of the marine world can easily remain unseen. That's because water itself can act as an effective cloak: Light that shines through the ocean can bend, scatter, and quickly fade as it travels through the dense medium of water and reflects off the persistent haze of ocean particles. This makes it extremely challenging to capture the true color of objects in the ocean without imaging them at close range.

Now, a team has developed an image-analysis tool that cuts through the ocean's optical effects and generates images of underwater environments that look as if the water had been drained away, revealing an ocean scene's true colors. The team paired the color-correcting tool with a computational model that converts images of a scene into a three-dimensional underwater "world," that can then be explored virtually.

The researchers have dubbed the new tool SeaSplat, in reference to both its underwater application and a method known as 3D Gaussian splatting (3DGS), which takes images of a scene and stitches them together to generate a complete, three-dimensional representation that can be viewed in detail, from any perspective.

Daniel Yang et al, SeaSplat: Representing Underwater Scenes with 3D Gaussian Splatting and a Physically Grounded Image Formation Model, arXiv (2024). DOI: 10.48550/arxiv.2409.17345

Comment by Dr. Krishna Kumari Challa on Wednesday

Climate change emerges as third major threat to global wildlife, scientists warn

New research published in BioScience reveals that climate change is rapidly emerging as a third major threat to Earth's wild animals, joining habitat alteration and overexploitation in what scientists call a shift from "twin to triple threats."

The research team analyzed data for 70,814 animal species from 35 classes, using two publicly available biodiversity datasets to assess climate change vulnerability among the world's wild animal populations.

Their findings indicate that 5.1% of all assessed animal species are threatened by climate change, with six animal classes having at least 25% of assessed species at risk. The researchers note that these figures likely underestimate the true scale of the crisis.

"We are entering an existential crisis for the world's wild animals," say the authors. Although some species might benefit, increases in global temperature can lead to a variety of impacts on wild animals, including changes in their physiology, behavior, life cycle, distribution, and interactions among species.

"Rapid and effective climate mitigation is crucial now more than ever for saving the world's biodiversity," the researchers conclude.

 William Ripple et al, Climate change threats to Earth's wild animals, BioScience (2025). DOI: 10.1093/biosci/biaf059

Comment by Dr. Krishna Kumari Challa on Tuesday

World’s first bladder transplant
A 41-year-old man has become the first person to receive a bladder transplant. Surgeons in the United States transplanted the bladder, together with a kidney, earlier this month, in an operation that lasted eight hours.

https://www.nytimes.com/2025/05/18/health/bladder-transplant-human....

Comment by Dr. Krishna Kumari Challa on Tuesday

Physicists determine how to cut onions with fewer tears

A team of physicists, biologists and engineers  has discovered some of the factors that lead to more or less spray when cutting onions and found a couple of ways to reduce the amount of eye irritation. The group has published a paper describing their study on the arXiv preprint server.

Prior research has shown that eye irritation when cutting onions is caused by the release of syn-propanethial-S-oxide into the air along with other juices in the onion. For this new study, the team in New York wanted to know what factors led to more or less of the juices being spewed into the air during slicing.

To find out, the research team outfitted a special guillotine that could be fitted with different types of blades. They also coated onion chunks with paint to allow for better viewing of the cutting process. They used the guillotine to cut samples, each of which was recorded. Trials varied knife size, sharpness and cutting speed. They even used an electron microscope to accurately measure the knives before use.

The videos revealed that the differences in the amount of spray released, and thus the amount of eye irritation, were due to the sharpness of the knife and the speed at which it cut the onion. The sharper the knife, and slower the cut, the less spray. This was because duller knives tended to push down on the onion, forcing its layers to bend inward—as the cut ensued, the layers sprang back, forcing juice out into the air.

They also noted that as the juice droplets were flung into the air, they tended to fragment into smaller drops, which allowed them to persist longer. Faster cutting also resulted in more juice generation, and thus more mist to irritate the eyes.

They conclude that onion cutters use the sharpest knife they can find and cut their onions slowly.

Zixuan Wu et al, Droplet Outbursts from Onion Cutting, arXiv (2025). DOI: 10.48550/arxiv.2505.06016

Comment by Dr. Krishna Kumari Challa on Tuesday

Positive proof-of-concept experiments may lead to the world's first treatment for celiac disease

An investigational treatment for celiac disease effectively controls the condition—at least in an animal model—in a first-of-its-kind therapeutic for a condition that affects approximately 70 million people worldwide.

Currently, there is no treatment for celiac disease, which is caused by dietary exposure to gluten, a protein in wheat, barley and rye. The grains can produce severe intestinal symptoms, leading to inflammation and bloating.

A series of innovative experiments has produced "a cell soothing" technique that targets regulatory T cells, the immune system components commonly known as T_regs.

The cell-based technique borrows from a form of cancer therapy and underlies a unique discovery that may eventually lead to a new treatment strategy, data in the study suggests.

In an animal model, Porret and his global team of researchers have tested the equivalent of CAR T cell therapy against celiac disease. The team acknowledged that the "Treg contribution to the natural history of celiac disease is still controversial," but the researchers also demonstrated that at least in their animal model of human celiac disease, the treatment worked.

CAR T cell therapy is a type of cancer immunotherapy in which a patient's T cells are genetically modified in the laboratory to recognize and kill cancer cells. The cells are then infused back into the patient to provide a round-the-clock form of cancer treatment. In the case of celiac disease, the T cells are modified to affect the activity of T cells that become hyperactive in the presence of gluten.

To make this work, the researchers had to know every aspect of the immune response against gluten. "Celiac disease, a gluten-sensitive enteropathy, demonstrates a strong human leukocyte antigen association, with more than 90% of patients carrying the HLA-DQ2.5 allotype, the researchers wrote, describing the human leukocyte antigen profile of most patients with celiac disease.

As a novel treatment against the condition, the team engineered effector T cells and regulatory T cells and successfully tested them in their animal model. Scientists infused these cells together into mice and evaluated the regulatory T cells' ability to quiet the effector T cells response to gluten. They observed that oral exposure to gluten caused the effector cells to flock to the intestines when they were infused without the engineered T_regs.

However, the engineered regulatory T cells prevented this gut migration and suppressed the effector T cells' proliferation in response to gluten. Although this is a first step, the promising early results indicate that cell therapy approaches could one day lead to a long-sought treatment for this debilitating intestinal disorder.

 Raphaël Porret et al, T cell receptor precision editing of regulatory T cells for celiac disease, Science Translational Medicine (2025). DOI: 10.1126/scitranslmed.adr8941

Comment by Dr. Krishna Kumari Challa on Tuesday

Better than stitches: Researchers develop biocompatible patch for soft organ injuries

Researchers developed an injectable sealant for rapid hemostasis and tissue adhesion in soft, elastic organs.

Formulated with methacryloyl-modified human recombinant tropoelastin (MeTro) and Laponite silicate nanoplatelets (SNs), the engineered hydrogel demonstrated substantial improvements in tissue adhesion strength and hemostatic efficacy in preclinical models involving lung and arterial injuries.

Injuries to soft tissues such as lungs, heart, and blood vessels complicate surgical closure due to their constant motion and elasticity. Sutures, wires, and staples are mechanically fixed, risking blood loss when applied to tissues that expand and contract with each breath or heartbeat. Existing hemostatic agents, including fibrin-based sealants, aim to stem blood flow but may trigger intense coagulation responses in patients with clotting disorders.
In the study, "Rapid closure and hemostasis of ruptured soft tissues using a modified human tropoelastin-based sealant in preclinical models," published in Science Translational Medicine, researchers conducted preclinical testing of an engineered hydrogel combining MeTro and Laponite SNs to assess tissue adhesion and hemostatic efficacy in soft tissues.

Preclinical testing involved arterial injury models in rat and lung injury in pig subjects to assess the sealant's performance in soft, elastic organs. Researchers measured adhesion strength, clotting time, and tissue response to evaluate the effectiveness of the MeTro/SN formulation under dynamic physiological conditions.

Prepolymer solutions of MeTro and varying concentrations of SNs were prepared and cross-linked using visible light. Rat and pig subjects underwent injury procedures to assess the sealant's efficacy.

Testing involved ex vivo adhesion strength measurements on pig skin, lung, and heart tissues, with burst pressure evaluated on punctured collagen sheets. Hemostatic performance was assessed through clotting time analysis using fresh human blood treated with MeTro/SN hydrogels and commercial hemostatic agents.

Integration of SNs reduced clotting time without inducing inflammatory responses, supporting the hydrogel's potential for rapid intervention in hemorrhagic wounds. Biocompatibility analysis demonstrated minimal immune response and tissue damage after implantation, suggesting a low-risk profile for clinical translation.

Mahsa Ghovvati et al, Rapid closure and hemostasis of ruptured soft tissues using a modified human tropoelastin-based sealant in preclinical models, Science Translational Medicine (2025). DOI: 10.1126/scitranslmed.adr6458

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