Showing posts with label humans. Show all posts
Showing posts with label humans. Show all posts

Friday, March 28, 2008

Bones show humans in Europe 1.2 mln years ago

Early humans may have roamed Europe as much as 1.2 million years ago, far earlier than previously thought, scientists said on Wednesday, based on fossils they found in northern Spain.

Researchers excavated a jaw bone, teeth and simple tools in a cave near the city of Burgos dated around 400,000 years older than the previously oldest-known remains found at a nearby site 14 years ago, a paper published in the journal Nature said.

The remains are accurately dated and lay to rest doubts about when early humans first lived in Europe, said Andreu Olle, who has worked at the Atapuerca site since 1990.

"These are the oldest human remains in Europe. With this fossil, we can say it (Europe) was populated earlier than was thought," he told Reuters.

The bones are similar to fossils thought to be 800,000 years old found at the same site in 1994, suggesting a continuous human presence in Western Europe.

Up to now archaeologists had found evidence of human activity in Spain, France and Italy around 1 million years ago but no human remains, only animal bones and stone tools.

Scientists generally agree that modern humans spread out of Africa starting about 50,000 years ago, quickly establishing Stone Age cultures throughout Europe, Asia and Australia.

However the fossil, thought to be from the 'Homo antecessor' species, would have shared common ancestors with modern man and may have mixed with the more recent newcomers from Africa.

Flakes of flint embedded in animal bones, suggesting the use of a crude knife, were amongst the finds discovered at the site last June.

The find adds weight to the theory that early humans spread from Africa via the Middle East, not across the Straits of Gibraltar separating Africa from Europe, because the jaw was a similar shape to one unearthed in the central Asian country of Georgia thought to be 1.7 million years old.

Wednesday, March 19, 2008

Growth hormone no benefit to athletes

People who take human growth hormone in the hope of boosting athletic performance are not only breaking the law and risking their health, but likely are not even achieving their objective, U.S. researchers reported on Monday.

While some reports show that some illegal steroids may help athletes bulk up and train harder, human growth hormone is not one of them, the report in the Annals of Internal Medicine suggests.

"What we saw is that while there was a change in body composition, we didn't find evidence that growth hormone improves athletic performance," Dr. Hau Liu of Stanford University in California, who led the study, said in a telephone interview.

Liu's team looked at 27 studies covering 303 people aged 13 to 45. They found that, overall, those who took growth hormone did develop more lean body mass, but this did not translate to either more strength or exercise capacity.

People who took growth hormone had swelling of their tissues and more fatigue compared to people not taking the drug, they added.

Use of growth hormone is banned by the International Olympic Committee, Major League Baseball and the National Football League. U.S. law prohibits its use for sports enhancement.

When the hormone is given to people with growth hormone deficits caused by pituitary tumors or other conditions, it can improve strength. But it does not enhance strength in normal, healthy people.

For example, people given hormone generated more lactate, a byproduct of exercise that can cause pain and muscle fatigue. In one study meant to see if human growth hormone might boost strength or endurance, two cyclists given the hormone stopped a workout because of fatigue.

"The key takeaway is that we don't have any good scientific evidence that growth hormone improves athletic performance," Dr. Andrew Hoffman, a professor of endocrinology, gerontology and metabolism who worked on the study, said.

Hoffman noted that other hormones have been shown to benefit athletes -- notably testosterone.

"Athletes probably take much more hormone than the investigators felt that they could ethically try to give to healthy people; in addition, some athletes combine growth hormone with other anabolic hormones like testosterone," Hoffman added in an e-mail.

Hoffman said people get side-effects from high doses of hormones. "You you get fluid accumulating in the legs, you get pain in the joints," he said in a telephone interview.

"From what we hear the athletes are taking very, very large doses," he added.

Other hormones do, however bulk up athletes -- although not without risk, Hoffman said. "The findings with growth hormone absolutely do not extend to other hormones like testosterone which work through entirely different mechanisms," he said.

Pain lasts long after traumatic injury

A surprising number of people -- more than 60 percent -- still suffer significant pain a year after a traumatic injury in a car crash or other cause, showing the need for better pain treatment, researchers said.

In a study published on Monday in the journal Archives of Surgery, researchers tracked 3,047 patients ages 18 to 84 from 14 U.S. states who survived an acute traumatic injury.

A year after the injury, 63 percent reported that they still experienced pain related to the injury, with most having pain in more than one region of the body.

On average, the patients assessed their pain at 5.5 on a 10-point scale -- a level at which they would be expected to have moderate to severe interference with daily activities.

"I was surprised that the pain was as common and as severe as they reported it to be," said Dr. Frederick Rivara of the University of Washington in Seattle, who led the study.

"The implications are that we need to do a much better job of identifying pain in these patients, treating it adequately and treating it early," Rivara added in a telephone interview.

The people in the study sustained head injuries, broken limbs, chest or abdominal trauma and other injuries in motor vehicle crashes, falls and other circumstances.

Pain was most commonly seen in joints and limbs (44 percent of patients), the back (26 percent), the head (12 percent) and neck (7 percent).

Rivara noted that people who experience chronic pain are at higher risk for depression and for being unable to work or function normally.

"The focus up until now in a lot of our care is on whether you live or die, which is obviously important. But we can't just stop there. And I think we need to look at what are the things we can do to improve people's lives after serious illness or injury," Rivara added.

The American Pain Foundation, a Baltimore-based advocacy group, said the financial cost exacted by chronic pain in the United States -- including health-care expenses, lost income and lost productivity -- is estimated at $100 billion a year.

The group said back pain is the leading cause of disability in Americans under 45 years old.

"There are hundreds of thousands, if not millions, of people who have had traumatic injury when the focus has been the injury and the destruction of tissue and not the pain. Pain has been a secondary consideration (during treatment)," said Will Rowe, American Pain Foundation chief executive officer.

"In many instances, the injury heals and the pain persists. That's the story that needs to be told," Rowe said.

Folate helps keep men's sperm normal

Vitamins known as folates that prevent birth defects when consumed by women also help to keep men's sperm normal, researchers reported on Wednesday.

Men who took folic acid supplements and who ate folate-rich foods such as leafy greens had fewer abnormal sperm, the team at the University of California, Berkeley said.

Specifically, the men had fewer abnormal sperm in which a chromosome had been lost or gained, known as aneuploidy, they reported in the journal Human Reproduction.

"We found a statistically significant association between high folate intake and lower sperm aneuploidy," said Brenda Eskenazi, who helped lead the study.

"There was increasing benefit with increasing intake, and men in the upper 25th percentile who had the highest intake of folate between 722-1150 micrograms, had 20 percent to 30 percent lower frequencies of several types of aneuploidy compared with men with a lower intake," Eskenazi added in a statement.

She said larger studies were needed to confirm the findings.

Sperm aneuploidy can cause failure to conceive, causes up to a third of miscarriages and causes children to be born with Down's syndrome and other rare chromosomal syndromes.

Chemotherapy for cancer and exposure to pesticides also can damage sperm in this way but diet had not been investigated, the researchers said.

Folic acid can prevent nerve damage in growing babies and is so important that it is added to flour, rice and other staples in many countries.

But few studies had looked its effects on fathers.

Eskenazi's team said estimates suggest that between 1 percent and 4 percent of sperm in a healthy man have some type of aneuploidy but this varies from man to man.

Her team analyzed sperm samples from 89 healthy, non-smoking men of all ages and also questioned them about their daily total intake of zinc, folate, vitamin C, vitamin E and beta-carotene in both food and supplements.

Eskenazi said her team and others had previously shown that vitamin intake may help make men more fertile by improving the quality of the sperm. "This study is the first to suggest that paternal diet may play a role after conception in the development of healthy offspring," she said.

The current U.S. recommended daily intake of folate for men aged over 19 is 400 micrograms. Men seeking to become fathers may need more, Eskenazi said.

Men who ate the most zinc and beta-carotene also had fewer instances of some sperm abnormalities, but not aneuploidy, the researchers found.

Fresher blood poses fewer surgery risks

People who got old, stale blood during surgery were 30 percent more likely to die than people who got fresh blood, U.S. researchers reported on Wednesday.

Two weeks seemed be the cutoff, with older blood causing more complications, the researchers reported in the New England Journal of Medicine.

"We report that the relative risk of postoperative death is increased by 30 percent in patients given blood that has been stored for more than two weeks," the researchers wrote.

This can cause a dilemma, as many blood banks and hospitals cannot keep enough blood on hand that is so fresh.

The U.S. Food and Drug Administration allows blood to be held for as long as six weeks, and blood banks typically give out the oldest blood first.

One solution may be to use the freshest blood first. Another is to use techniques to reduce the need for a transfusion in the first place, said Dr. Colleen Gorman Koch of the Cleveland Clinic Foundation, who led the study.

Her team studied 6,002 patients who received heart surgery at the Cleveland Clinic Foundation. Koch and her colleagues compared the outcome with the storage time of the blood transfused in each operation.

The rate of death while in the hospital was 1.7 percent among fresh blood recipients versus 2.8 for older blood. Rates for kidney failure, infection, respirator use and multiorgan failure were also higher if older blood was used.

However, a system that uses blood no older than two weeks would make it harder to keep blood banks properly stocked, and much more blood would be discarded. There are times when the blood supply falls to critically low levels, even with the current six-week limit.

SUPPLY VERSUS DEMAND

"It is just not feasible to shorten storage time significantly without restricting the blood supply," Dr. John Adamson of the University of California at San Diego wrote in a commentary.

Adamson also said there are important unanswered questions about whether the results would apply to other medical procedures where transfusions are common. For example, the process of sending blood through a heart-lung machine may be causing damage to blood cells, reducing the shelf-life of each pint.

Older blood may be acceptable for other uses.

Koch said patients should be asking their surgeons if the hospital has a blood management program in place.

"For cardiac surgery there are a lot of things you can do in the operating room to minimize the risk of receiving a blood transfusion at all," Koch said. One method scavenges and recycles blood that would normally be lost in an operation.

And if surgery is being done on a nonemergency basis, doctors should first be treating any underlying anemia a patient might have, Koch said. "So they're getting themselves in tip-top shape prior to surgery to decrease their need for blood."

In October, researchers reported that donated blood quickly loses nitric oxide in red blood cells -- which is key to transferring oxygen in the blood to tissues.

But if nitric oxide is restored, banked blood appears to regain its power, the team at Duke University in North Carolina found.

Currently, about 5 million Americans receive blood transfusions each year, according to the National Institutes of Health.

Better to walk away than punish

Harvard study

Punishing a lazy team member can be counterproductive and it may be better to simply walk away, researchers said on Wednesday.

The researchers at Harvard University found that people who go to the trouble of punishing colleagues, co-workers or others in one-on-one situations do not profit from their revenge.

Such behavior does not pay off for a group, either, they reported in the journal Nature.

"Put simply, winners don't punish," said David Rand, who worked on the study. "Punishment can lead to a downward spiral of retaliation with destructive outcomes for everybody involved."

Rand works in Harvard's Program for Evolutionary Dynamics and Department of Systems Biology, which combines the study of evolution with economics.

His team studied people playing the so-called prisoner's dilemma computer-based game, in which 104 Boston-area students could choose to cooperate, defect or punish.

"Cooperation meant paying one unit for the other person to receive two units," the researchers wrote. So if both players cooperated, each got two units. Defectors could take off with three units, unless the other player defected too, in which case both ended up with only one.

"That makes defection tempting for most people and cooperation generally breaks down at some point in a prisoner's dilemma game," Manfred Milinski and Bettina Rockenbach of the Max-Planck-Institute for Evolutionary Biology in Ploen, Germany wrote in a commentary.

The Harvard game added two dimensions -- punishment and familiarity. The five top-ranked players never used costly punishment, while players who won the least amount had punished the most often.

An equivalent situation might be in the workplace, Rand said.

"Say you have a project that you have to complete with someone else and you feel like someone else is not contributing as much as they should; they are not pulling their weight," Rand said in a telephone interview.

"The thing that is best for you is to stop contributing, to walk away, as opposed to expending a lot of effort insulting them, threatening them or taking aggressive action."

Punishing someone else in a situation where both parties are equal creates an "opportunity cost," Rand said. "The time that you are spending being punitive toward the other person could be spending doing things that are more productive."

But it also does not pay to let the freeloader ride along. "It's not quite turn the other cheek," Rand said. "We are saying you should only do as much as the other person is doing."

He said the findings only apply in one-on-one situations -- not to societies or cultures as a whole, or situations in which one person is more powerful than the other.

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