In the January issue of the American Journal of Psychiatry, researchers reported that heritability of depression is higher in women - approximately 42 percent -- than in men, where it is approximately 29 percent.
"Our work, together with colleagues at the Karolinska Institute in Sweden, represents the largest epidemiological study of depression in twins done to date. In addition, it broadly replicates what has been shown by our earlier work using the Virginia Twin Registry. In particular, we have shown that depression is a moderately heritable disorder, suggesting that genetic factors are important, but by no means overwhelming," said Kenneth S. Kendler, M.D., a professor of psychiatry and human genetics in VCU's School of Medicine and lead author on the study.
The research team employed twin study models to evaluate lifetime major depression of approximately 42,000 twins, including 15,000 complete pairs from the Swedish National Twin Registry.
According to Kendler, the sex-effects are of two kinds - quantitative and qualitative. He said that quantitative sex-effects examine whether heritability is different in males compared with females, and if the overall importance of genetic factors differs between the sexes; whereas qualitative sex-effects examine whether the same genes are playing a role in males and females.
For example, Kendler said there may be genes that alter the risk for depression in a woman's response to cyclic sex hormones, particularly in the postpartum period. Such genes would impact a woman's risk for major depression, but would not be active in men because men lack the relevant hormonal milieu.
The Virginia Twin Registry is now part of the VCU Mid-Atlantic Twin Registry (MATR), which contains a population-based record of twins from Virginia, North Carolina and South Carolina.
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The research team has tested the current virus in 10 passages in mice, and it remained safe while retaining its potency. Dr. Dietzschold notes that the likelihood of a mutation occurring is extremely low. While different varieties of rabies virus exist, they maintain enough similarities in the all-important outer glycoprotein, that a vaccine that takes advantage of immune reactions to this protein can be effective.
Dr. Dietzschold explains that the current wildlife rabies vaccine used in the United States is ineffective in a chief carrier: skunks. The vaccine developed by his team is much broader, showing efficacy in such animals as raccoon, skunk and mongoose. One of the problems with current vaccines is the fact that several varieties are used, depending on the particular species of animal. The scientists hope their vaccine will prove useful for rabies prevention in several species.
The newer virus and vaccine currently are being evaluated by Molecular Targeting Technologies, Inc., of West Chester, Pa. The researchers are asking for permission from the United States Department of Agriculture and the Environmental Protection Agency to perform field trials. These would entail placing food baits containing the vaccine in the wild, then later capturing and testing animals for antibodies against the rabies virus.
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