New view of how bubonic plague attacks victims
Scientists have thought the bacteria that cause the bubonic plague hijack host cells at the site of a fleabite and are then taken to the lymph nodes, where the bacteria multiply and trigger severe disease.
But UNC School of Medicine researchers discovered that this accepted theory is off base. The bacteria do not use host cells; they traffic to lymph nodes on their own and not in great numbers. In fact, most of the plague-causing bacteria – Yersinia pestis – get trapped in a bottleneck either in the skin, while en route to the lymph node, or in the node itself. Only a few microbes break free to infect the lymph node and cause disease.
Virginia Miller, UNC professor of microbiology and immunology, said, “We found that only one or two of the 10 bacteria made it to the lymph node,” Miller said. "But they got there fast – within five or 10 minutes after the bacteria were introduced. We know that if a bacterium is traveling in a host cell, it would not move that fast because host cells are slow; they kind of crawl through the lymphatic system instead of flowing through fluid like bacteria can.”
Miller, senior author of the paper in PLoS Pathogens, said, “If we can understand how the host and the bacteria contribute to this bottleneck, then this could become something we'd target so we could either ramp up what's causing the bottleneck or slow down the infection.”
The plague, which killed millions of people during the Middle Ages, is contracted by several people each year in the western United States. Outbreaks have occurred in the recent past in India and Africa. med.unc.edu
How beavers naturally resist tooth decay
Beavers don't brush their teeth, and they don't drink fluoridated water. But they do have protection against tooth decay built into the chemical structure of their teeth: iron. Researchers at Northwestern University found this pigmented enamel is harder and more resistant to acid than regular enamel, including that treated with fluoride.
Layers of well-ordered hydroxylapatite “nanowires” are the core structure of enamel, but the researchers discovered that material surrounding the nanowires, where small amounts of amorphous minerals rich in iron and magnesium are located, control enamel’s acid resistance and mechanical properties. This discovery could lead to a better understanding of human tooth decay, earlier detection of the disease and improving on current fluoride treatments.
The Northwestern study will be published Feb. 13 in the journal Science. northwestern.edu
Dogs can discriminate emotions in human faces
It’s been proven that dogs can discriminate human faces on pictures. But can they do that for human emotional expressions?
Austrian researchers presented photos of happy and angry women’s faces side by side on a touchscreen to 20 dogs. During the training phase, dogs from one group were trained to touch images of happy faces. The other group was rewarded for choosing angry faces.
In the study by Messerli Research Institute and the University of Veterinary Medicine-Vienna, dogs trained to choose the happy faces mastered the task significantly faster than those who had to choose the angry faces. “It seems that dogs dislike approaching angry faces,” said study director Ludwig Huber.
“We believe that dogs draw on their memory during this exercise. They recognize a facial expression which they have already stored,” said Corsin Müller, Huber’s colleague at Messerli and first author of the paper to be published in February in the journal Current Biology. “We suspect that dogs that have no experience with people would perform worse or could not solve the task at all.” vetmeduni.ac.at