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PNAS highlights for the week of April 18 - 22

Proceedings of the National Academy of Sciences

Happiness Related to Biological Function

Researchers report that happiness may be related to the functioning of the body in key processes, such as those of the cardiovascular system and those controlling hormone levels.

Previous studies have shown that depressed people often have more health problems, while happier people tend to live longer. Yet the mechanism of these effects has been unclear.

To look more closely at this psychobiological connection, Andrew Steptoe and colleagues studied emotions and health of more than 200 middle-aged Londoners in their daily lives. The authors found that those who reported more everyday happiness had healthier biological functions in a few key systems. For one, the happier subjects had lower levels of cortisol, a stress hormone related to conditions such as type II diabetes and hypertension. Happier individuals also showed lower responses to stress in plasma fibrinogen levels, a protein that in high concentrations often signals future problems with coronary heart disease. Finally, happy men had lower heart rates over the day and evening, which suggests good cardiovascular health.

These results were independent of psychological distress, the authors say, which implies that positive well-being is directly related to the biological processes relevant to health.

Chinese Herbal Medicine Component Arrests Cancer Growth

Derivatives of indirubin, the active component of a traditional Chinese herbal medicine used to treat leukemia, can potently inhibit the growth of certain types of cancers, according to researchers.

In many cancer types, the Stat3 protein, known to play a role in tumor cell survival and proliferation, is activated by c-Src, an enzyme implicated in tumor formation and metastasis.

Richard Jove, Gerhard Eisenbrand, and colleagues synthesized and characterized 10 indirubin derivatives. One derivative, E804, inhibited Stat3 activity in breast and prostate cancer cell lines, and in vitro E804 blocked c-Src activity. Cancer cells treated with E804 showed a decrease in the levels of activated Stat3. The authors also showed that E804 induced apoptosis (programmed cell death) in breast cancer cells by down-regulating the expression of Mcl-1 and Survivin, proteins known to block apoptosis.

The authors suggest that the indirubin derivative E804 has potential as a cancer therapeutic agent.

Altruistic Punishment May Make Evolutionary Sense

In a newly published report, an evolutionary model of human behavior suggests that "moralists" who voluntarily pay a cost to punish misbehavers can come to dominate a population and ensure cooperation among its members.

The origin of cooperative behavior has puzzled researchers, since natural selection favors "free-riders" over those who make personal sacrifices to get along with others. Some researchers have suggested that cooperation may make sense in a society with altruistic punishers--essentially, moralists who are willing to pay a personal cost to punish free-riders.

To examine how altruistic punishment could take root in a society, James Fowler developed a mathematical model that simulates interacting behaviors in a society over time. He found altruistic punishers can enter a population of cooperators and noncooperators and change the dynamics of the group. Under certain conditions, altruistic punishment is so beneficial to the population that it will come to dominate the behavior of the group and keep noncooperators at bay.

These results may help to explain the origins of cooperation and punishment. Previous studies have shown that altruistic punishment stimulates the reward center in the brain, suggesting that humans may have physically or developmentally evolved this behavior.


Nerve Poison Detoxifier Identified

Researchers have found a brain enzyme that appears to break down and potentially detoxify a specific organophosphorus (OP) compound, which is part of a major class of insecticides and chemical warfare agents.

Nonnative Vertebrates Are Successful Invaders

Although only a small proportion of North American and European animal species have been introduced to foreign lands, a relatively large percentage of these have become successful invaders.

Retinal Gene Therapy May Not Help Everyone

Some patients suffering from blindness caused by Leber congenital amaurosis may benefit more than others from gene therapy to restore photoreceptors to the retina.


The Proceedings of the National Academy of Sciences (PNAS) is the multi-disciplinary, peer-reviewed journal of the National Academy of Sciences. Founded in 1914, PNAS publishes daily online and weekly in print. The preceding highlights are not intended to substitute for articles as sources of information. The articles in PNAS report original research by independent authors and do not necessarily represent the views of the National Academy of Sciences or the National Research Council.

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