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Archive - Mar 9, 2010

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Green Tea May Help Protect Against Glaucoma and Other Eye Diseases

In a rat model, Hong Kong scientists have shown that powerful antioxidants in green tea can penetrate the eye, raising the possibility that the tea may help protect against glaucoma and other common eye diseases that may be related to oxidative stress. The authors point out that so-called green tea "catechins" have been among a number of antioxidants thought capable of protecting the eye. Until now, however, nobody knew if the catechins in green tea actually passed from the stomach and gastrointestinal tract into the tissues of the eye. In this new research, the scientists resolved this uncertainty in experiments with laboratory rats that drank green tea. Analysis of eye tissues showed beyond a doubt that eye structures absorbed significant amounts of individual catechins. The retina, for example, absorbed the highest levels of gallocatechin, while the aqueous humor tended to absorb epigallocatechin. The effects of green tea catechins in reducing harmful oxidative stress in the eye lasted for up to 20 hours. "Our results indicate that green tea consumption could benefit the eye against oxidative stress," the report concluded. This new research was published on January 19, 2010 in the Journal of Agricultural and Food Chemistry, an American Chemical Society publication. [Press release] [JAFC abstract]

New Form of Prion Disease Described

NIH scientists investigating how prion diseases destroy the brain have observed a new form of the disease in mice that does not cause the hole-filled, sponge-like brain deterioration typically seen in prion diseases. Instead, the disease resembles a form of human Alzheimer's disease, cerebral amyloid angiopathy, that damages brain arteries. The study results, reported by NIH scientists at the National Institute of Allergy and Infectious Diseases (NIAID), are similar to findings from two newly reported human cases of the prion disease Gerstmann-Straussler-Scheinker syndrome (GSS). The mouse findings represent a new mechanism of prion disease brain damage, according to study lead author Dr. Bruce Chesebro, chief of the Laboratory of Persistent Viral Diseases at the NIAID’s Rocky Mountain Laboratories in Montana. The role of a specific cell anchor for prion protein is at the crux of the NIAID study. Normal prion protein uses a specific molecule, glycophosphoinositol (GPI), to fasten to host cells in the brain and other organs. In their study, the NIAID scientists genetically removed the GPI anchor from study mice, preventing the prion protein from fastening to cells and thereby enabling it to diffuse freely in the fluid outside the cells. The scientists then exposed those mice to infectious scrapie and observed the mice for up to 500 days to see if they became sick. The researchers documented signs typical of prion disease including weight loss, lack of grooming, gait abnormalities, and inactivity. But when they examined the brain tissue, they did not observe the sponge-like holes in and around nerve cells typical of prion disease.

Desert Ant Uses Stereo Odor “Landscape” Detection in Navigation

The desert ant Cataglyphis fortis, which is native to the inhospitable salt-pans of Tunisia, is already well-known for its remarkable navigational abilities. It uses a sun compass along with a step counter and visible landmarks to locate its nest (a tiny hole in the desert ground) after foraging for food. Now, researchers at the Max-Planck Institute for Chemical Ecology in Germany have shown that these ants have another tool in their navigational toolbox. After the scientists recently discovered that these ants also use olfactory cues to pinpoint their nests, they conducted new experiments that revealed that the ants cannot only locate an odor source, but they also use the distribution of different odors in the vicinity of their nests in a map-like manner. The scientists found that the ants need both their antennae for this odor-guided navigation, that is, they smell the landscape scenery in stereo. "We conducted two key experiments," said Kathrin Steck, a Ph.D. student at the Institute. "First we marked four odor sources surrounding the nest entrance with the substances methyl salicylate, decanal, nonanal, and indole, and got the ants trained on them. If these four odor points were shifted away from the nest in the original arrangement, the ants repeatedly headed for the odors, even though the nest wasn't there anymore. If we rearranged the odor sources relative to each other, the ants were completely confused." Therefore the researchers assumed that ants do not "think" one-dimensionally--i.e., they do not associate the nest with only one smell--but multi-dimensionally, i.e., they relate an odor “landscape” to their nest. Spatial perception can easily be acquired if two separate sensory organs are available, such as two eyes for visual orientation. In the case of the ants, this would be their two antennae.

Blindness Gene Therapy in Second Eye Shown Safe in Animal Studies

Gene therapy for a severe inherited blindness disorder (Leber's congenital amaurosis or LCA), which produced dramatic improvements last year in twelve children and young adults who received the treatment in a clinical trial, has cleared another hurdle. The same research team that conducted the human trial has now reported that a study in large animals has shown that a second injection of the normal gene (RPE65) into the opposite, previously untreated, eye is safe and effective, with no signs of interference from unwanted immune reactions following the earlier injection. LCA is an autosomal recessive retinal disease that progresses to total blindness by adulthood and that can be caused by mutation in any one of a variety of different genes, including the RPE65 gene. Approximately 3,000 people in the United States are estimated to have the disease. In the current study, the research team found no evidence of toxic side effects in the blood or the eyes of the ten animals—six dogs and four monkeys—that received the gene therapy (with the normal RPE65 gene). Each animal received an injection first in the right eye, then in the left eye 14 days later. All six dogs, which had been specially bred to have congenital blindness, had improved vision, in addition to showing no toxic effects from the gene therapy. The monkeys, which were not blind, also showed no toxic effects from the therapy. These new findings suggest that LCA patients who benefit from gene therapy in one eye may experience similar benefits from treatment in the other eye. Researchers had exercised caution by treating only one eye in the human trial. "We designed this study to investigate the immunological consequences of administering the gene therapy injection to the second eye after treating the first one," said senior author Dr.