The study was conducted on heroin-addicted rats. But the researchers now think that, within a few years, better treatments will become available to human heroin users who cannot quit due to insidious cycles of relapse.

“Many people try to stop taking heroin, but in a few months almost all of them go back to using the drug,” said Ivan Diamond, at the Ernest Gallo Clinic and Research Center in California, US, and one of the research team.

David Shurtleff, director of the Division of Basic Neuroscience and Behavioral Research at the National Institute on Drug Abuse in Maryland, US, is encouraged by the research. “It will take creativity and additional research to translate this into usable therapies, but it does provide hope that we will be able to prevent compulsive drug seeking behaviour,” he told New Scientist.

Reward circuitry

Previous research has indicated that a section of the midbrain called the nucleus accumbens plays a central role in the “mental reward circuitry” of animals, such as rats and humans. This circuitry generates feelings of pleasure in response to drugs, as well as in response to other things, including food, sex and, in humans, work accomplishments.

Drugs like heroin, however, seem to over-stimulate the normal reward process to the point where users value their next fix more highly than food, water and other essentials. In 2004, a study revealed that cocaine causes a gene in the nucleus accumbens, called AGS3, to rapidly encode masses of proteins that are involved in the cravings and pleasure associated with the drug.

Diamond and his team isolated AGS3 genes and proteins in nucleus accumbens cells taken from newborn baby rats. After cloning and studying the cells in the lab, the researchers determined that AGS3’s drug-related functions are most active in the inner nucleus accumbens core as opposed to its outer shell region.

An AGS3 blocker was then created from a herpes virus. This temporarily binds to proteins within the reward circuit and blocks the cravings-pleasure cycle until the virus “washes out” of the body a few weeks later.

Eliminated desires

Heroin-addicted rats that were trained to give themselves the drug using a lever were injected with the AGS3 blocker into their nucleus accumbens after they had gone through a short period of withdrawal. A small dose of heroin then was administered to each rat.

Normally even such a tiny “taste” of the drug leads to cravings for more, but the blocker prevented the addiction relapse by eliminating these desires. The treatment produced no other observed behavioural side effects.

Diamond told New Scientist that a related treatment could become available to humans within the next couple of years. His colleague Krista McFarland, at the Medical University of South Carolina, added that one of the challenges will be to find a safe method of administering the blocker to people.

Journal reference: Proceedings of the National Academy of Sciences ()

While this may not surprise political analysts, the objective analysis contradicts the US Code, which outlines US laws and suggests a just system in which all legislation receives a fair hearing from politicians who put the country’s interests ahead of their political party’s. The words “non-partisan” and “unbiased” appear frequently in the code.

Among the study’s findings is that the membership of the Select Committee on Homeland Security, formed after the terrorist attacks of September 11, 2001, is closely tied to the House Rules Committee, a powerful group involved in the regulation of all committees and House members. But, contrary to expectation, the Homeland Security committee does not have many members in common with the Permanent Select Committee on Intelligence.

The paper identifies the House Rules, Judiciary, and Homeland Security committees as being the most partisan while the Intelligence committee is one of the least partisan.

The analysis also identifies the House’s most partisan members. They include Republican representatives Tancredo, Shadegg, Ryun, and Schaffer, and Democrat representatives Schakowsky, McGovern, Solis, Pelosi, and Woolsey.

Pure mathematics

All the conclusions emerge solely from mathematical data, and not from any particular political viewpoint, according to mathematicians Mason Porter, and Peter Mucha, at the Georgia Institute of Technology, Atlanta, US, and colleagues.

Porter’s team first constructed a model of how the House would operate if committee members were chosen on a random basis. They then compared this with the actual membership of the committees. They also created a chart showing the ties between the committees based on how many common members they had.

The researchers discovered committee member selection was not random, but instead was stacked. For example, they discovered that a bipartisan subcommittee of the Permanent Select Committee on Intelligence first handled homeland security, “yet none of the members of that subcommittee ended up on the Select Committee on Homeland Security”, Porter told New Scientist. “And this was despite established protocol for assigning Representatives to these things,” he added. This select committee ended up with a very partisan membership.

Connection king

James Fowler, a political scientist at the University of California, Davis, US, agrees with the findings. He recently conducted network research that concluded Senator John McCain is the most connected member of the current Congress.

Fowler told New Scientist that political analysts “have known for a long time that there is a great deal of partisanship in the House. Some voters will benefit from partisanship. For example, strong Republicans are happy the Republican majority is currently voting together to pass many Republican policies. Others will not be happy, such as the moderates who believe both parties are too extreme.”

The researchers hope similar methods will be used in future to provide additional insights into the working of the US government, and other political bodies.

Journal reference: Proceedings of the National Academy of Sciences (DOI: 10.1073/pnas.0500191102)

The testosterone-derived chemical AND is found in male sweat and is believed to be a pheromone. It activated the anterior hypothalamus and medial preoptic area of gay men and straight women alike. Researchers led by Ivanka Savic at the Karolinska University Hospital in Sweden believe this brain region integrates the hormonal and sensory cues used in guiding sexual behaviour.

The research demonstrates a likely link between brain function and sexual orientation, Savic suggests. But she told New Scientist that the study “does not answer the cause-and-effect question”.

So the brain-activation of gay men by AND may contribute to sexual orientation of those men, or simply be the result of their orientation and sexual behaviour. She added that the brain scans revealed no anatomical differences between any of the participant’s brains.

Lavender and cedar

The team observed 36 healthy men and women, who were exposed in turn to AND, the oestrogen-derived compound EST and other odours, including lavender oil, cedar oil, eugenol and butanol.

While the subjects were consciously aware of each unidentified smell as it was presented, Savic does not believe the reactions in the subjects brains were intentional in any way: “The pattern of activation does not suggest cognitive processing,” she says.

PET and MRI scans revealed that the ordinary odours activated parts of the brain associated with smelling in all test subjects. But in addition to that activation, AND excited the brain areas associated with sexual behaviour for female and gay male participants, as did the EST for straight men.

Open minded

Ada Frumerman, a psychotherapist based in New York, US, who has presented papers on related topics, says sexual orientation is probably determined by a mixture of biological and psychological influences.

“I think we should be open minded,” she says. “It would not be advisable to focus solely on biological causes. Similarly, it would do a disservice to only look for psychodynamic causes.”

Savic’s team has also conducted similar experiments with gay women and the researchers are currently analysing the results.

Journal reference: Proceedings of the National Academy of Sciences (DOI: 10.1073/pnas.0407998102)

These genes show signs of positive natural selection in both branches of the evolutionary tree and are changing more swiftly than would be expected through random mutation alone. Lead scientist Rasmus Nielsen and colleagues at the University of Copenhagen, Denmark, examined the 13,731 chimp genes that have equivalent genes with known functions in humans.

Research in 2003 revealed that genes involved with smell, hearing, digestion, long bone growth, and hairiness are undergoing positive natural selection in chimps and humans. The new study has found that the strongest evidence for selection is related to disease defence and apoptosis – or programmed cell death – which is linked to sperm production.

Plague and HIV

Nielsen, a professor of bioinformatics, believes immune and defence genes are involved in “an evolutionary arms race with pathogens”.

“Viruses and other pathogens evolve very fast, and the human immune system is constantly being challenged by the emergence of new pathogenic threats,” he told New Scientist. “The amount of selection imposed on the human population by pathogens – such as the bubonic plague or HIV – is enormous. It is no wonder that the genes involved in defence against such pathogens are evolving very fast.”

Harmit Singh Malik, a researcher at the Fred Hutchinson Cancer Research Center in Seattle, Washington, US, agrees. Both Malik and Nielsen, however, expressed surprise over the findings concerning tumour suppression, which is linked to apoptosis – or programmed cell death – which can reduce the production of healthy, mature sperm.

Selfish mutation

The discovery by Nielsen that genes involved in apoptosis show strong evidence for positive natural selection may be due, in part, to the evolutionary drive for sperm cells to compete.

Cells carrying genes that hinder apoptosis have a greater chance of producing mature sperm cells, so Nielsen believes these genes can become widespread in populations over time.

But because primates also use apoptosis to eliminate cancerous cells, positive selection in this case may not be favourable for the mature animal: “The selfish mutations that cause apoptosis avoidance may then also reduce the organism’s ability to fight cancer,” Nielsen explains.

Journal reference: Public Library of Science Biology (vol 3, issue 6)