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Research Roundup
April 27, 2010, Volume 56, No. 31

A Brain-Recording Device that Melts into Place

Penn Medicine scientists and colleagues have developed a brain implant that essentially melts into place, snugly fitting to the brain’s surface. The technology could pave the way for better devices to monitor and control seizures, and to transmit signals from the brain past damaged parts of the spinal cord.

The ultrathin flexible implants, made partly from silk, can record brain activity more faithfully than thicker implants embedded with similar electronics. “The focus of our study was to make ultrathin arrays that conform to the complex shape of the brain, and limit the amount of tissue damage and inflammation,” said coauthors Brian Litt, associate professor of neurology and associate professor of bioengineering in the School of Engineering and Applied Science, and PhD student Jonathan Viventi.

The silk-based implants, developed by Dr. Litt and colleagues at Tufts University and the University of Illinois, can hug the brain like shrink wrap, collapsing into its grooves and stretching over its rounded surfaces. The study appears this month in Nature Materials.

For more information, refer to the National Institute of Neurological Disorders and Stroke news release: www.ninds.nih.gov/news_and_events/news_articles/melting_brain_implant.htm.

Gene Therapy Cures Canines of Inherited Form of Day Blindness

Veterinary ophthalmology researchers from the University of Pennsylvania have used gene therapy to restore retinal cone function and day vision in two canine models of congenital achromatopsia, also called rod monochromacy or total color blindness.

Achromatopsia is a rare autosomal recessive disorder with an estimated prevalence in human beings of about 1 in 30,000 to 50,000. It primarily affects the function of the cone photoreceptors in the retina and serves as a representative model for other more common inherited retinal disorders affecting cones. Cone function is essential for color vision, central visual acuity and most daily visual activities, which underlines the importance of the newly developed treatment.

The treatment cured younger canines regardless of the mutation that caused their achromatopsia. It was effective for the 33 months of the study and most likely is permanent; however, researchers also observed a reproducible reduction in the cone therapy success rate in dogs treated at 54 weeks of age or older.

The successful therapy in dogs was documented by the restoration of the cone function using electroretinography and by objective measure of day vision behavior. The behavioral results suggest that inner retinal cells and central visual pathways were able to usefully process the input from the recovered cones.

The results represent the second successful cone-directed gene replacement therapy in achromatopsia animal models and the first outside of mouse models. The gene therapy targets mutations of the CNGB3 gene, the most common cause of achromatopsia in humans. Achromatopsia-affected dogs represent the only natural large animal model of CNGB3-achromatopsia.

The results hold promise for future clinical trials of cone-directed gene therapy in achromatopsia and other cone-specific disorders.

Many vision-impairing disorders in humans result from genetic defects, and, to date, mutations have been identified in approximately 150 genes out of 200 mapped retinal disease loci. This wealth of genetic information has provided fundamental understanding of the multiple and specialized roles played by photoreceptors and the retinal pigment epithelium in the visual process and how mutations in these genes result in disease. Together with the development of gene-transfer technologies, it is now possible to realistically consider the use of gene therapy to treat these previously untreatable disorders.

The article is available online in advance of its publication in the journal Human Molecular Genetics.

Low-Fat Diets Outlast Low-Carb Diets

A new report from the University of Pennsylvania School of Medicine showed that people who followed a low-carbohydrate diet lost more weight in the first year, but tended to regain most of the weight during the next two years. In contrast, people who stuck to a low-fat diet maintained their weight loss over three years.

The report, which appeared in the March 2 edition of the Annals of Internal Medicine, suggests that the difference in weight regain between groups reflects the initial weight loss, because greater weight loss within the first year was associated with greater weight regain from 12 to 36 months.

If you want to take it off and keep it off, a slow and steady low-fat diet may be right for you.

For more information, see the Annals of Internal Medicine announcement, online at www.acponline.org/journals/annals/tipsheets/02mar10.htm.


Increasingly Violent Content Assigned to PG-13 Movies

Research conducted by the Annenberg Public Policy Center (APPC) has found that the Motion Picture Association of America’s (MPAA’s) rating system increasingly has assigned violent content to the PG-13 rating category. The PG-13 category was established in 1984 to warn parents about content in PG films that might not be appropriate for a child under 13. Instead of shielding young people from such content, however, the research found that some content that previously would have received a restrictive R-rating is now assigned a PG-13 rating.

For example, a 13 year old today could see a movie like “Mission Impossible 2” (2000) with intense gun and fist fighting, but in the years before 1985, prior to the introduction of the PG-13 category, the same 13-year old would not have been allowed to view a movie with comparable explicit violence such as the R-rated movie “Magnum Force” (1974), or even an R rated movie with less explicit violence such as “48 Hours” (1982), unless he or she was accompanied by a parent or other adult.

Although violent content increasingly has been assigned to the PG-13 category, the MPAA system has been more consistent in screening explicit sexual content. Such content has consistently been assigned to the R category (children under 17 not admitted without a parent or guardian).

Released in the Journal of Adolescent Health, the study examined trends in rating assignments since 1968, when the MPAA rating system was initiated. It found that the explicitness of violent and sexual content in films significantly increased since the system was put in place. However, during the period from 1984 to 2006, explicit violence that would have previously been rated R was increasingly assigned to PG-13. Although violence increased in both PG-13 and R-rated films, recent PG-13 movies from 2001 to 2006 were significantly higher in violent content than earlier R-rated movies from 1977 to 1984. This “ratings creep” was evident only for films with explicit violence. Although sexually explicit content increased in R-rated films, the study did not find evidence of ratings creep in the assignment of sexually explicit content.

“The finding that PG-13 movies are becoming increasingly violent is worrisome given the fact that PG-13 movies now account for more than half of top-grossing film sales,” said Dr. Patrick E. Jamieson, associate director of the Adolescent Risk Communication Institute of the APPC. “Adolescents are more likely to engage in violent behavior as a result of viewing media models of violence, and films may reinforce the message that violence is an acceptable solution to people’s problems.”

Repeated exposure to explicit media violence is not only associated with increased aggression in youths but it also can cause fear in some viewers. It can also desensitize people to victimization by violence. Repeated exposure to explicit sexual content has been associated with teen pregnancy, early sexual initiation and unhealthy sexual attitudes among adolescents.

The study was conducted by the Adolescent Risk Communication Institute at the Annenberg Public Policy Center of the University of Pennsylvania.

Almanac - April 27, 2010, Volume 56, No. 31