Genetics:
Protein Reverses Chromatin Engineering

Biological Chemistry:
Molecule Implicated in Transcription Termination

Structural Biology:
DNA Splicing Enzyme Observed in Action

Scientific Symposium:
Fashions Change in Modeling Disease

Chronic Periodontitis Differs at the Microbial Level in Populations Worldwide

Brain Structure for Reward and Punishment Smaller in Cocaine Addicts

Brigham Celebrates 50th Anniversary of First Human Organ Transplant

Beth Israel Assumes Academic Oversight of Mass. Mental Health Faculty

Joslin Names Conley Chairman of the Board

Academic Officer Tapped for HMI Dubai Project

Macklis Receives Javits Neuroscience Investigator Award

Global Citizen Award Goes to Bill Moyers

HMS Family Health Guide Published in Paperback

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Honors and Advances

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Chronic Periodontitis Differs at the Microbial Level in Populations Worldwide

"One can't just assume that the same clinical condition can be treated exactly the same way in different populations. It's important to know what bugs are actually causing the disease in each patient in order to get the optimum clinical response."

Researchers have assumed that a given treatment for chronic periodontitis would be equally effective in patients across the globe. Clinical trials, however, have revealed significant differences in response. Haffajee and Socransky had previously shown that healthy individuals and patients with chronic periodontitis harbor similar periodontal bacterial species, but those with the disease have these species present at different levels. In the current study, the researchers extend their work to patients from different populations. "We wanted to ask if the same disease in different populations in the world would look different at the microbial level," said Haffajee, who heads the Forsyth Department of Periodontology and, with Socransky, is a senior member of the institute staff.

A total of 300 patients with chronic disease were drawn from populations in Boston and in Chile, Sweden, and Brazil. The researchers took microbial samples from patients' teeth and used DNA hybridization to identify the levels of 40 bacterial species present in each sample; all the samples from within a population were then averaged. Although they expected only minor differences to appear among populations, the authors found pronounced differences in the proportions of several bacterial species, including three key disease-producing bugs.

The findings may change the way chronic periodontitis is diagnosed and treated. "One can't just assume that the same clinical condition can be treated exactly the same way in different populations," said Haffajee. "It's important to know what bugs are actually causing the disease in each patient in order to get the optimum clinical response."

--Jillian Lokere

Brain Structure for Reward and Punishment Smaller in Cocaine Addicts

The amygdala has been a structure of interest in addiction biology because of its role both in drug craving and in reward/punishment-based decision-making. Existing studies of the brain structure of addicts have found abnormalities only in regions connected to the amygdala, but these studies used less sophisticated imaging techniques. "We wanted to use a technique that would allow us to put together a detailed topological map," said Breiter.

The researchers used segmentation-based morphometric analysis in capturing MRI scans of the brains of 27 subjects who had been using cocaine for one to 27 years. They also scanned the brains of 27 matched healthy volunteers. The anterior and superior aspects of the addicts' amygdalas were found to have significantly less volume than those of healthy controls. Reinforcing the amygdala's correlation with craving, those cocaine users with the largest volume reductions reported the highest levels of daily craving.

The study could not determine if the brain differences were a predisposing factor for addiction or whether they were caused by cocaine use. Scans revealed, however, that the normal left-right asymmetry that arises in the amygdala during adolescence was not seen in any of the cocaine addicts, whose amygdalas showed nearly perfect symmetry. Such similar and precise reductions are unlikely to be due to varying degrees of cocaine usage, an argument that suggests the abnormalities are a predisposing factor for addiction.

"Further research on other addictions will help us understand their structural basis, enabling better methods to prevent, diagnose, and treat them," said Breiter.

--Jillian Lokere