Research Roundup

• Big Cities and Small Towns: Similar Risks of Gun Death
• T Cell's Memory: Immunity to Leishmaniasis
• Common Butterfly: Actually 10 Different Species
• Artistic Expression: Need Not End After Brain Damage

Click here to see Resarch Roundups from previous issues.

Big Cities and Small Towns: Similar Risks of Gun Death

Americans in small towns are as likely to die from gunfire as people in major cities, according to a new study from  Penn's School of Medicine—with one key distinction. "The difference is who does the shooting," says lead author Dr. Charles C. Branas, assistant professor of epidemiology. Dr. Branas and his colleagues found that when looking at all deaths by firearms, the risk of being murdered with a gun in large cities and the risk of committing suicide with a gun in rural areas were almost identical.

After adjusting for income, education, employment rates, and other factors, the most rural counties had over 1.5 times the rate of gun suicides compared to the most urban counties. At the same time, urban areas experienced almost twice the gun homicide rate of the most rural counties.

The investigators analyzed urban-rural differences in deaths—homicides and suicides—using over 580,000 death certificates from 1989 to 1999 in all counties in the United States. Their findings are reported in the October issue of the American Journal of Public Health.

In the 1990s, a great deal of legislation was aimed at reducing gun homicide, which decreased in the U.S. by about 5 percent per year. Much of this decrease was in big cities. But almost no attention has been paid to gun suicide, which increased by about 1 to 2 percent per year, most starkly in rural areas, over the same period.

The study also found that the same trend for gun death did not hold true for urban-versus-rural differences in non-gun methods of suicide or homicide. Thus, guns clearly functioned differently from other methods. But why the urban-rural difference? "We didn't directly account for differences in availability of guns by location, but we can speculate how that might have affected our results," says Dr. Branas, referring to the larger percentage of gun owners in rural areas versus cities. "A major take-home message from these findings is that although prevention efforts must be continued in big cities, dispelling the urban myth that gun death does not touch areas outside of big cities should be a high priority."

T Cell's Memory: Immunity to Leishmaniasis

Researchers at Penn have discovered a "central memory" form of "helper" T cells that can offer immunity to leishmaniasis, a disease that causes a significant number of deaths and disfigurement across the globe and has been found in U.S. military personnel returning from Afghanistan and Iraq.         

In the October issue of Nature Medicine, the researchers describe how the discovery can offer immunity to leishmaniasis, even without the persistent presence of the parasite that caused the disease. Their findings encourage a new approach to creating a vaccine against leishmaniasis and other immune cell mediated diseases such as tuberculosis and HIV/AIDS.Attempts to create a vaccine for leishmaniasis have long been stymied by the fact that helper T cells, which coordinate the immune response against a pathogen, need constant stimulation from the pathogen in order to remain effective against the disease.

Most common in North Africa, the Middle East and Asia, leishmaniasis is a parasitic disease spread by the bite of sand flies infected with the protozoan Leishmania. The Centers for Disease Control report that each year the world sees 1.5 million new cases of cutaneous leishmaniasis, which infects the skin, causing scarring boils, and 500,000 new cases of visceral leishmaniasis, which infects internal organs, causing death if left untreated.           

While people who recover from leishmaniasis generally develop lifelong immunity to reinfection, this has been thought to depend upon the continued presence of the Leishmania parasite. Indeed, it has been shown in mice that if the parasite is entirely removed, the host can become reinfected. Dr. Phillip Scott of pathobiology at the School of Veterinary Medicine and his colleagues wondered if, despite the apparent loss of immunity when the parasites disappeared, there were any T cells that still retained memory of Leishmania. Recent studies have shown that memory T cells may be of more than one type, including a "central memory" T cell variation found in lymph nodes. Since little is known about CD4+ T cell memory during chronic disease, the Penn researchers set out to find if such central memory cells exist in Leishmaniasis. The hunt for the theoretical CD4+ central memory T cells began by transferring T cells from mice infected with Leishmaniasis to mice who had never faced the disease. Tests revealed that some of the transferred T cells went to the lymph nodes, and had the characteristics of central memory cells.       

"We see that these central memory T cells—but not the effector T cells—persist in the absence of obvious parasites for as long as five months, " Dr.  Scott said. "Since we still do not know much about these new T cells, our next step is to find out how we can encourage the proliferation of central memory cells and stimulate them to fight disease."

Common Butterfly: Actually 10 Different Species

A common butterfly, found in a variety of habitats from the southern U.S. to northern Argentina, is actually comprised of at least 10 separate species, according to researchers from Penn. 

Astraptes fulgerator, a medium-large skipper butterfly, is a routine visitor to urban gardens and tropical rainforests. While the "species" has been known to science since 1775, only now has examination of a small and standardized signature piece of the genome—a technique called DNA barcoding—shown that this "species" is really an amalgam of a number of genetically distinct lineages, each with different caterpillars and preferences in food plant and ecosystem. 

Dr. Daniel Janzen, the Thomas G. and Louise E. DiMaura Endowed Term Professor of Conservation Biology, and co-author of the study, and his colleagues reported their findings in the September 29 issue of the Proceedings of the National Academy of Sciences. Their research began during a 25-year-long inventory of the wildlife in the Area de Conservación Guanacaste, a large conservation zone of dry, rain and cloud forests in northwestern Costa Rica. They noticed that, amid the more than 2,500 wild-caught caterpillars of A. fulgerator, many could be separated by slight variations in color, which then could be linked to the particular plants the caterpillars ate. 

It soon became obvious that A. fulgerator was, indeed, a complex of a number of separate species whose adult forms looked remarkably similar. When the centuries-old method of telling insects apart—the examination of their genitalia by John Burns at the Smithsonian Institution—proved inconclusive, the team turned to a recently emerging method for discriminating species: DNA "barcoding."

Dr. Paul Hebert, of the University of Guelph, and Erin Penton, a student at the University of Guelph, were able to extract the necessary DNA from 484 adult butterflies—all raised from the much larger pool of caterpillars caught in Costa Rica by Dr. Janzen, Winnie Hallwachs and a team of 17 Costa Rican parataxonomists—despite the fact that these butterflies have been dried museum specimens for as long as 23 years. Where possible, they included at least 20 individuals from each group of food plant, color variation and preferred habitat. As a result, they found 10 distinct species within the group known as A. fulgerator in an area the size of the greater Philadelphia area and as many as six species in a place no larger than the 262-acre Penn campus.

Artistic Expression: Need Not End After Brain Damage

What happens to visual artists that experience brain damage? And what can it tell us about how humans represent the world? According to Dr. Anjan Chatterjee, associate professor in the Center for Cognitive Neuroscience at the School of Medicine, brain damage does not necessarily end the ability to produce compelling works of art; additionally, artists with brain damage can provide useful information on the nature of artistic expression. In a review article published in Neuropsychologia (Volume 42, Issue 11), Dr. Chatterjee draws on nearly 50 research articles and books, and finds that, "Artists with neuropsychological deficits do not necessarily produce art of lesser quality. Rather, their art may change in content or in style, sometimes in surprising and aesthetically pleasing ways." Not only does this collection illustrate various forms and changes in perception, but it also suggests that continuing research in the field could bring about new therapies that could help patients with brain damage.

Dr. Chatterjee finds that artists are still susceptible to visuo-spatial deficits caused by brain damage but, because of their skill, they are "often quite eloquent in expressing these deficits."

For instance, those that suffer from aphasia have difficulties communicating verbally. However, rather than having a uniform effect, the impact of aphasia on communicating through art can be quite variable. Dr. Chatterjee cites a description of a French painter that did not experience any changes in his artistic skills or style; critics did believe that he had found a "more intense and acute expression." The painter explained: "When I am painting I am outside my life; my way of seeing things is even sharper than before; I find everything again; I am a whole man. ..."

Dr. Chatterjee asks if artists who suffer from diffuse cognitive impairment, such as from Alzheimer's and autism, experience a drastic impairment of their artistic production. Surprisingly, this is not the case. As seen with artists who suffer from selective neuropsychological deficits, artistic skills are relatively preserved and sometimes even enhanced.

By bringing all of these scattered accounts into one body of literature, Dr. Chatterjee raises intriguing themes relevant to the nature of artistic expression and proposes that art is worth considering as a neuropsychological probe. Continuing research that focuses on these themes could bring exciting developments in various therapies for brain damage—including, of course, art therapy—and unlock perceptual mysteries of the mind.

  Almanac, Vol. 51, No. 7, October 12, 2004

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