Medical Bulletin 25/ December/ 2024 - Video

Published in the journal Scientific Reports, researchers have created realistic, skin-like replicas made of Ecoflex, a type of silicone rubber that can potentially serve as a platform to evaluate risks of bacterial infections from intravenous catheters and test wearable sensors, among other biomedical applications. The study found that EcoFlex-based skin replicas can be engineered to mimic actual skin textures, wettability, and elasticity, simulating the conditions where bacteria grow and adhere.

“We have been slow in finding solutions for preventing infections from intravenous catheters,” said Majed Othman Althumayri, a graduate student in the Texas A&M Department of Biomedical Engineering and primary author of the paper. “A reason could be that we lack good platforms to test new catheter designs or wearable biosensor technologies and train staff so that the number of infections can be reduced.”

To address this gap, the researchers turned to Ecoflex 00-35, a fast-curing, biocompatible rubber used for various applications, including prosthetics for special effects. First, they created molds of common intravenous insertion sites, such as the elbows, hands and forearms. Then, by pouring Ecoflex into the molds that contained artificial bones and tubes acting as veins, the researchers created skin-like replicas.

Next, the researchers tested if the Ecoflex skin replicas had properties that matched that of real skin. They measured the replicas’ wettability, bacterial adhesion and mechanical properties, such as elasticity and resilience. The researchers found that the Ecoflex models could replicate human skin roughness within a 7.5% error margin. Further, high-resolution imaging showed that bacteria could adhere to the skin replica and grow on it.

Then, in a key experiment, the researchers simulated an intravenous catheter insertion into an Ecoflex hand replica that they created. This artificial hand effectively modeled phases of bacterial growth, showing promise that these replicas can be used for implementing infection control measures and improving the design of medical devices like catheters.

However, the researchers noted that their current experiments do not entirely model real-world conditions.

Reference: Althumayri, M.O., Tarman, A.Y. & Ceylan Koydemir, H. Bioinspired skin-like in vitro model for investigating catheter-related bloodstream infections. Sci Rep 14, 26167 (2024). https://doi.org/10.1038/s41598-024-76652-y

A new study published in the journal Metabolism reveals brain circuits and chemical messengers that contribute to the regulation of meal initiation and food intake. The findings have implications for the development of improved therapies to manage obesity, a worldwide epidemic.

“It’s well known that serotonin, a neurotransmitter in the brain, can suppress food intake. This finding led to the development of drugs that interact with serotonin or its receptors to regulate food consumption and obesity,” said corresponding author Dr. Yong Xu, professor of pediatrics – nutrition and associate director of basic sciences at the USDA/ARS Children’s Nutrition Research Center at Baylor. “However, some of these drugs have unwanted side effects, and they are no longer offered to patients. There is a need to better understand how the brain regulates food intake to improve drug design.”

In this study, researchers focused on a little-known component of the serotonin regulation of food intake. They looked for brain circuits and neurotransmitters that regulate the activity of serotonin-producing neurons, activating or inhibiting them at the appropriate periods to reach balanced food consumption

Serotonin is primarily synthesized by neurons in the dorsal Raphe nucleus (DRN) in the midbrain. Serotonin neurons in the DRN project to numerous brain regions, including the arcuate of the hypothalamus (ARH). The team showed that the ARH circuit and two neurotransmitters, GABA and dopamine, play a key role in meal initiation.

“Working with animal models, we found that when the animals are hungry, serotonin-producing neurons in the DRN are inhibited by GABA and dopamine. This reduces the levels of serotonin in the brain, which allows the initiation of a meal,” Xu explained. “As the animals feed and reach satiety, the inhibitory signals on serotonin neurons are reduced and more serotonin is produced to inhibit feeding via projections to the ARH.”

“What's unique about this is that GABA and dopamine act synergistically – when both are present, serotonin neurons appear to be more inhibited than when only one of the neurotransmitters is present,” Xu said.

Reference: Serotonin neurons integrate GABA and dopamine inputs to regulate meal initiation, Conde, Kristine M. et al., Metabolism - Clinical and Experimental, Volume 163, 156099

Giving more blood to anemic patients after a heart attack may save lives, according to a Rutgers Health–led study. The study, published in NEJM Evidence, affirms research conducted in 2023 that suggested mortality rate or recurrent heart attacks were more frequent in anemic patients who received less blood.

Researchers acquired data from the four clinical trials evaluating blood transfusion in 4,311 patients with heart attacks. These trials included patients who had a heart attack and low blood count. Half the patients received less blood transfusions and the other half received more blood transfusions. The trials compared the frequency of death at 30 days or recurrent heart attacks and death at six months.

The results of this analysis, didn’t definitively establish that giving less blood transfusions increased a patients’ risk of death or heart attack at 30 days, but did suggest that using less transfusions was associated with an increased risk of death at six months.

In the original clinical trial, a large percentage of patients had suffered a previous heart attack, heart failure, diabetes or kidney disease. The average age of participants was 72, with 45% women.

The researchers compared the frequency of the main outcome of death or recurrent heart attack at 30 days after enrollment into the trial. Although not statistically significant, the study found the frequency of mortality or recurrent heart attack was 2.4% lower when a liberal approach was used.

“The results of this analysis show that giving more blood to anemic patients with heart attacks can save lives at six months,” Jeffrey L. Carson, provost and Distinguished Professor of medicine at Rutgers Robert Wood Johnson Medical School, said.

Propranolol, is a beta-blocker that inhibits the action of stress hormones. It was developed for high blood pressure and heart arrhythmias, has been around for a long time, and is already used as a standard treatment for essential tremor -- a condition in which people experience tremors without other neurological symptoms. There were already indications that propranolol might reduce tremors in Parkinson's, but until now, no thorough research has explored its potential effects.

Researchers studied 27 people with Parkinson's who experienced tremors. They were given propranolol on one day and a placebo on another day. A device on their hands measured the intensity of their tremors, while an MRI scan mapped brain activity. This was done both at rest and during a task involving stressful mathematical calculations. The stress response was measured by pupil size and heart rate, both of which increased during the calculations. As expected, without medication, tremors worsened during stress.

The study showed that propranolol reduced tremors both at rest and during stress. The MRI scans revealed how this works: after taking the medication, the brain circuit responsible for tremors showed less activity.

Researchers also noted that propranolol worked to reduce tremors at rest as well.

Reference: https://www.radboudumc.nl/en/news-items/2024/propranolol-reduces-tremors-in-parkinson-s-disease