- Banned Chemical May Interfere With Pregnancy
- Recreational Drug Creates Out-of-Body Illusions
- Sometimes Invasive Species Are Good
- Scientists Buy Rocket Rides to Suborbital Space
Posted: 01 Mar 2011 07:00 AM PST
PCB exposure may interfere with a woman's ability to get pregnant, a new study of women undergoing in vitro fertilization suggests. The study of 765 women found that those whose blood contained the highest levels of a particular form of polychlorinated biphenyl — one known as PCB 153 — were 41 percent less likely to give birth than women with the lowest levels.
One contributing factor: Fertilized eggs were half as likely to implant in women if blood concentrations of PCB-153 fell in the top 25 percent of those measured among all participants. The study appeared online February 24 in Environmental Health Perspectives.
In women not undergoing IVF it would be difficult to know when to test for implantation, says John Meeker, who led the new study. So the new data may provide a window into a subtle fertility risk that would be almost impossible to find in the general population, explains Meeker, an environmental and reproductive epidemiologist at the University of Michigan School of Public Health in Ann Arbor.
His team studied blood and urine that had been collected from 765 women treated at fertility clinics in the Boston area between 1994 and 2003. Together, the women had gone through a total of 827 cycles of attempted fertilization — processes that led to 297 live births, 229 implantation failures and 301 pregnancies that naturally terminated within 20 weeks of implantation.
The researchers went into the study suspecting that the risk of implantation failure might be elevated among the most highly exposed women, based on earlier studies by others showing a similar problem in PCB-exposed rodents. Two years ago, Meeker's team also showed that in women, PCBs can enter follicles, structures that hold egg cells. So this "does suggest that these chemicals can make it to a place where they would be in contact with the maturing egg," he says.
More than 200 related PCBs exist. Most people inadvertently encounter a broad mix of these, including traces of PCB-153, through food and the environment. Because some of these pollutants are difficult and costly to measure in blood, the researchers tested for the sum of all PCBs as well as for a narrow spectrum of specific ones or mixes of several with related functional attributes, such as binding to hormone receptors in cells or — in PCB-153's case — an ability to turn on certain detoxifying enzymes.
The authors caution that although they found the strongest signs of potential fertility risks associated with PCB-153, there were hints that other PCBs might also impair fertility. The team notes that PCB-153 might even serve as a marker for one or more other reproductively toxic PCBs — or related pollutants — that co-occur in the environment.
"I find the data intriguing — and think they have something here," says David Carpenter, director of the Institute for Health and the Environment at the University at Albany in New York. "I'm also underwhelmed," he adds.
The researchers probed for a number of different reproductive endpoints, he says, including miscarriage, and what are known as chemical pregnancies — where a fertilized egg dies before a fetal heartbeat can be detected. Only implantation failures appeared at rates greater than would be expected by chance. And only for PCB-153, he adds, not for any of several different PCBs or PCB combinations.
The data would be more convincing, Carpenter says, if the authors could point to some mechanism by which PCBs might impair reproduction — such as changing the permeability of the outer membrane of egg cells.
Several years ago, Carpenter's team showed that some cells — nerve cells and immature immune cells — can incorporate PCBs, including PCB-153, altering the fluidity of the cells' membranes. "Something as fundamental as changing the fluidity of the membrane in the oocyte [egg cell] or uterus could, in fact, have dramatic effects on implantation," Carpenter says.
Until their U.S. production was banned in 1979, most PCBs were used as insulating liquids in electrical transformers. Over the years, PCBs also have found use in other applications, including as an ingredient of exterior building caulk and in some floor finishes. Because many PCB-containing materials are still in use and because any PCBs that enter the environment do not readily break down, people continue to encounter exposure to these potentially toxic compounds, most often through contaminated food.
Posted: 28 Feb 2011 03:30 PM PST
A popular "club drug" promises to open a scientific window on the strange world of out-of-body experiences, researchers say.
Recreational users of a substance called ketamine often report having felt like they left their bodies or underwent other bizarre physical transformations, according to an online survey conducted by psychologist Todd Girard of Ryerson University in Toronto and his colleagues.
Ketamine, an anesthetic known to interfere with memory and cause feelings of detachment from one's self or body, reduces transmission of the brain chemical glutamate through a particular class of molecular gateways. Glutamate generally jacks up brain activity. Ketamine stimulates sensations of illusory movement or leaving one's body by cutting glutamate's ability to energize certain brain areas, the researchers propose in a paper published online Feb. 15 in Consciousness and Cognition.
"Ketamine may disrupt patterns of brain activation that coalesce to represent an integrated body and self, leading to out-of-body experiences," Girard says.
National surveys indicate that 1.6 percent of high school seniors in Canada and the United States have used ketamine at least once. An estimated 70 percent of Toronto rave-goers now report taking ketamine at these all-night parties, Girard notes.
In the new survey, use of marijuana, LSD and MDMA, also known as ecstasy, displayed modest links to volunteers' reports of illusions of walking or moving rapidly up and down while actually remaining still. But only ketamine use exhibited a strong relationship with having had a range of out-of-body experiences, regardless of any other drugs ingested at the time of those sensations, researchers say.
Neuroscientist Olaf Blanke of the Swiss Federal Institute of Technology in Lausanne calls ketamine "an interesting candidate to further understand some of the brain mechanisms in out-of-body experiences." Blanke, who like a growing number of scientists studies these phenomena in controlled experiments (SN: 6/5/10, p. 10), says that drugs such as ecstasy and amphetamines also deserve close scrutiny.
Blanke has linked out-of-body experiences to reduced activity in brain areas that integrate diverse sensations into a unified perception of one's body and self. Ketamine and other recreational drugs act throughout the brain, making it difficult to explain how any one drug might specifically affect sensation-integrating tissue, Blanke says.
Girard's team administered online surveys about drug use and drug-related experiences to 192 volunteers, ages 14 to 48. Almost half the sample reported having used marijuana, alcohol, ecstasy, ketamine and amphetamines. Roughly two-thirds had taken ketamine, and nearly everyone had used marijuana and alcohol.
Almost three-quarters of all participants reported having had a feeling of temporarily leaving their bodies, usually on several occasions. About 42 percent had experienced seeing their own bodies from an outside vantage point. Feelings of rapidly moving up and down, falling, flying or spinning had affected more than 60 percent of volunteers. Another 41 percent reported illusions of sitting up, moving a limb or walking around a room, only to realize that they had not moved.
Of those reporting feelings of leaving their bodies, 58 percent were under the influence of ketamine at the time. Ketamine use also displayed a close association with other unusual bodily sensations.
Apparent effects of drugs such as ecstasy on out-of-body experiences were largely explained by associated ketamine use, Girard says.
Image: nick see/Flickr
Posted: 28 Feb 2011 02:43 PM PST
Invasive species are the stock villains of conservation biology, disrupting ecosystems and throwing native populations into disarray. But in certain cases, they're actually quite beneficial, and perhaps it's time to recognize that.
In California, for example, native butterflies feed on non-native plants. In Puerto Rico, alien trees help restore abandoned pastures to a condition suitable for native plants. Even the much-maligned zebra mussel helps filter toxins from lakes.
"We predict the proportion of non-native species that are viewed as benign or even desirable will slowly increase over time," write ecologist Martin Schlaepfer of the State University of New York and colleagues in a paper published Feb. 22 in Conservation Biology.
According to Schlaepfer's group, biologists are often biased against invasives, and decline to notice or report instances of beneficial invasions.
They support their unorthodox perspective by reviewing dozens of papers on plants and animals introduced, accidentally or otherwise, outside their historical ranges. A variety of underappreciated invasive roles are described: providing ecosystem services, replenishing human-damaged regions, and generally helping to sustain some semblance of natural health even as many ecosystems struggle to survive.
Schlaepfer and colleagues admit to a certain bias of their own. "Negative roles listed here are not exhaustive and include only those that directly oppose the listed positive roles," they write. "Many of the non-native species listed have other negative effects on conservation objectives."
Their goal, however, isn't to do a conclusive analysis of the pros and cons of invasives, but to encourage a more open-minded consideration of benefits — and not just cost — for species often described in militarized, even xenophobic terms.
After all, many now-beloved native creatures were once invasives. Among them are dozens of honeybee species introduced to North America since the 16th century. Far from declaring war on bees, people now worry that these invading aliens might vanish.
Image: Thomas Bresson/Flickr.
Citation: "The Potential Conservation Value of Non-Native Species." By Martin Schlaepfer, Dov Sax and Julian Olden. Conservation Biology, published online Feb. 22, 2011.
Posted: 28 Feb 2011 12:00 PM PST
Two companies promising routine suborbital access have signed the first-ever contracts to ferry researchers beyond the Earth's limb and into space.
Virgin Galactic, a suborbital-spaceflight company that's building a spaceport in New Mexico, will fly at least two Southwest Research Institute researchers and their experiments into space at a cost of $200,000 per person. The institution has also reached a deal with XCOR Aerospace for six researcher seats on suborbital flights at $100,000 each.
"No one has ever offered any contracts to fly scientific researchers into suborbital space before," said planetary scientist Alan Stern of SwRI. "This breaks the ice and not in a small way. This is the beginning to what I think is going to be a huge market for routine access to space."
Virgin Galactic's suborbital vehicle, SpaceShipTwo, will rocket two pilots and six paying customers about 68 miles above the Earth to provide about four minutes of zero-gravity flight. The company is building six ships, and each can haul more than 2,000 pounds of cargo into space.
Accounting for the weight of pilots and passengers, that leaves hundreds of pounds for scientific experiments.
"We could be flying weekly or daily, once we finish safety flights," said George Whitesides, president and CEO of Virgin Galactic. "That will allow researchers incredibly fast and routine access to the space environment."
Parabolic airplane flights can re-create microgravity, but only for 20 to 25 seconds at a time. Sounding rockets are another option to create microgravity, but average around $2.5 million per launch.
"No matter how you slice it, these vehicles are significantly cheaper than any other access to microgravity," Whitesides said.
Stern, who will be one of the first researchers to fly, said SwRI has the option to reserve nine more seats between the two spacecraft for a total of 17.
Once in space, the researchers will perform three different experiments. One involves a biomedical device that will monitor a person's vital signs during flights, similar to equipment astronauts wear today on space shuttle missions. An ultraviolet-imaging device will also be flown to look at the upper atmosphere, as well as an experiment designed to study asteroid-like dust in microgravity.
"These aren't hypothetical experiments. They exist, and we've flown some of them before at high altitudes," Stern said. "We're ready to fly, although the vehicles aren't quite ready."
In preparation for hundreds of customers who have purchased tickets, including the SwRI researchers, Virgin Galactic hopes to perform full test flights of SpaceShipTwo within a year. XCOR, which is building four one-pilot, one-passenger Lynx spacecraft, also plans to begin demonstration spaceflights in a year.
Whitesides said SwRI's researchers will be among the first 200 passengers to hop on board.
"We're being cautious about giving a timeline, because this is still a new vehicle," Whitesides said. "Flight testing is one of those things that's impossible to predict with certainty."
A rendering of XCOR Aerospace's Lynx spacecraft. (XCOR Aerospace)
Top photo: Virgin Galactic's SpaceShipTwo during a test flight. (Virgin Galactic)
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