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Archive - Mar 30, 2012

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Intestinal Stem Cell Marker Functions As Tumor Suppressor

Tales from the crypt are supposed to be scary, but new research from Vanderbilt University, the HudsonAlpha Institute for Biotechnology and collaborating institutions shows that crypts can be places of renewal too: intestinal crypts, that is. Intestinal crypts are small areas of the intestine where new cells are formed to continuously renew the digestive tract. By focusing on one protein expressed in our intestines called Lrig1, the researchers have identified a special population of intestinal stem cells that respond to damage and help to prevent cancer. The research, published in the March 30, 2012 issue of Cell, also shows that the diversity of stem cells in the intestines is greater than previously thought. "Identification of these cells and the role they likely play in response to injury or damage will help advance discoveries in cancer," said Shawn Levy, Ph.D., faculty investigator at the HudsonAlpha Institute and an author on the study. The intestines and colon are normally lined with a single layer of cells to absorb nutrients from food. There are regular small pockets in the intestines called crypts, where stem cells are gathered. Rapid turnover of the lining cells and replacement by new lining cells made in the crypt, keep the intestines and colon healthy and keep damaged cells from turning into cancerous ones. The new paper demonstrates that, although the makeup of stem cells in the crypt is still controversial, one protein called Lrig1 can distinguish a group of long-lived cells at the base of the crypt. These Lrig1-positive stem cells do not regularly replace lining cells, but instead are only activated when there is damage or injury to the intestine. In addition, the researchers show that the Lrig1 protein functions to prevent cancer as a tumor suppressor molecule.

Dengue Infection Alters Gene Expression in Mosquito Salivary Glands

Mosquitoes infected with dengue virus experience an array of changes in the activity of genes and associated functions of their salivary glands, and these changes may lead to increased virus transmission, according to a recent study led by George Dimopoulos, Ph.D., of the Malaria Research Institute and Bloomberg School of Public Health at Johns Hopkins University. Some of these changes involve the mosquito's immune system and affect its susceptibility to infection with the virus. Others involve factors that enhance the mosquito's capacity to feed on blood, possibly leading to greater transmission of dengue virus to humans, the study authors write. According to the World Health Organization, each year, dengue virus infects about 50 million to 100 million people and causes between 10,000 and 15,000 deaths, most of them in children. Symptoms include high fever and pain in the muscles and joints, and in severe cases can include bleeding under the skin, damage to blood vessels, and death. The disease, which is prevalent in tropical and subtropical regions of the world, has been reported recently in parts of the United States, such as Hawaii, Puerto Rico, and Florida. There is no vaccine or drug treatment for dengue. The only way to prevent infection is to avoid being bitten by Aedes mosquitoes, which can carry the virus in their salivary glands. The Hopkins researchers sought to learn how dengue virus affects the way the glands function during virus transmission. They compared the expression of several thousand genes in Aedes aegypti mosquitoes that either were or were not infected with dengue virus.

Honey Bees Self-Medicate When Infected by Pathogenic Fungus

Research from North Carolina State University shows that honey bees “self-medicate” when their colony is infected with a harmful fungus, bringing in increased amounts of antifungal plant resins to ward off the pathogen. “The colony is willing to expend the energy and effort of its worker bees to collect these resins,” says Dr. Michael Simone-Finstrom, a postdoctoral research scholar in NC State’s Department of Entomology and lead author of a paper describing the research. “So, clearly this behavior has evolved because the benefit to the colony exceeds the cost.” When faced with pathogenic fungi, bees line their hives with more propolis, a waxy, yellow substance. Wild honey bees normally line their hives with propolis, a mixture of plant resins and wax that has antifungal and antibacterial properties. Domesticated honey bees also use propolis, to fill in cracks in their hives. However, researchers found that, when faced with a fungal threat, bees bring in significantly more propolis – 45 percent more, on average. The bees also physically removed infected larvae that had been parasitized by the fungus and were being used to create fungal spores. Researchers know propolis is an effective antifungal agent because they lined some hives with a propolis extract and found that the extract significantly reduced the rate of infection. And apparently bees can sometimes distinguish harmful fungi from harmless ones, because colonies did not bring in increased amounts of propolis when infected with harmless fungal species. Instead, the colonies relied on physically removing the spores. However, the self-medicating behavior does have limits. Honey bee colonies infected with pathogenic bacteria did not bring in significantly more propolis – despite the fact that the propolis also has antibacterial properties.