Worth all the sweat

Thanks to Gioia A for the link - deals with calorie restriction and exercise, longevity and health.

From the economist

Worth all the sweat
Just why exercise is so good for people is, at last, being understood

ONE sure giveaway of quack medicine is the claim that a product can treat any ailment. There are, sadly, no panaceas. But some things come close, and exercise is one of them. As doctors never tire of reminding people, exercise protects against a host of illnesses, from heart attacks and dementia to diabetes and infection.

How it does so, however, remains surprisingly mysterious. But a paper just published in Nature by Beth Levine of the University of Texas Southwestern Medical Centre and her colleagues sheds some light on the matter.

Dr Levine and her team were testing a theory that exercise works its magic, at least in part, by promoting autophagy. This process, whose name is derived from the Greek for “self-eating”, is a mechanism by which surplus, worn-out or malformed proteins and other cellular components are broken up for scrap and recycled.

To carry out the test, Dr Levine turned to those stalwarts of medical research, genetically modified mice. Her first batch of rodents were tweaked so that their autophagosomes—structures that form around components which have been marked for recycling—glowed green. After these mice had spent half an hour on a treadmill, she found that the number of autophagosomes in their muscles had increased, and it went on increasing until they had been running for 80 minutes.

To find out what, if anything, this exercise-boosted autophagy was doing for mice, the team engineered a second strain that was unable to respond this way. Exercise, in other words, failed to stimulate their recycling mechanism. When this second group of modified mice were tested alongside ordinary ones, they showed less endurance and had less ability to take up sugar from their bloodstreams.

There were longer-term effects, too. In mice, as in people, regular exercise helps prevent diabetes. But when the team fed their second group of modified mice a diet designed to induce diabetes, they found that exercise gave no protection at all.

Dr Levine and her team reckon their results suggest that manipulating autophagy may offer a new approach to treating diabetes. And their research is also suggestive in other ways. Autophagy is a hot topic in medicine, as biologists have come to realise that it helps protect the body from all kinds of ailments.

The virtues of recycling

Autophagy is an ancient mechanism, shared by all eukaryotic organisms (those which, unlike bacteria, keep their DNA in a membrane-bound nucleus within their cells). It probably arose as an adaptation to scarcity of nutrients. Critters that can recycle parts of themselves for fuel are better able to cope with lean times than those that cannot. But over the past couple of decades, autophagy has also been shown to be involved in things as diverse as fighting bacterial infections and slowing the onset of neurological conditions like Alzheimer’s and Huntington’s diseases.

Most intriguingly of all, it seems that it can slow the process of ageing. Biologists have known for decades that feeding animals near-starvation diets can boost their lifespans dramatically. Dr Levine was a member of the team which showed that an increased level of autophagy, brought on by the stress of living in a constant state of near-starvation, was the mechanism responsible for this life extension.

The theory is that what are being disposed of in particular are worn-out mitochondria. These structures are a cell’s power-packs. They are where glucose and oxygen react together to release energy. Such reactions, though, often create damaging oxygen-rich molecules called free radicals, which are thought to be one of the driving forces of ageing. Getting rid of wonky mitochondria would reduce free-radical production and might thus slow down ageing.

A few anti-ageing zealots already subsist on near-starvation diets, but Dr Levine’s results suggest a similar effect might be gained in a much more agreeable way, via vigorous exercise. The team’s next step is to test whether boosted autophagy can indeed explain the life-extending effects of exercise. That will take a while. Even in animals as short-lived as mice, she points out, studying ageing is a long-winded process. But she is sufficiently confident about the outcome that she has, in the meantime, bought herself a treadmill.

Aye-aye lemur 'heats up' its special foraging finger

from BBC nature
By Ella Davies

Madagascar's mysterious aye-aye warms up its extra-long finger when searching for dinner, scientists have found.

The lemur, the world's largest nocturnal primate, taps its specialised middle finger on tree trunks to find nutritious beetle larvae.

Studying thermal images, researchers found that the digit was colder than the others but warmed by up to 6C during foraging.

Scientists suggest that the aye-aye saves energy by keeping the digit cool.

The findings are published in the International Journal of Primatology.

The team from Dartmouth College in New Hampshire, US, wanted to investigate the surface temperature of sensitive structures.

The aye-aye's unusual middle finger has already been found to be super-sensitive to vibrations, so provided the perfect subject for their study.

"It was striking to see how much cooler the third digit was while not in use and how quickly it warmed to [match] the other digits when engaged in an active foraging task," said graduate student Gillian Moritz, who carried out the study under the guidance of her supervisor, Dr Nathaniel Dominy.

Black and white
When not in use, the finger appeared black on thermal images. This indicated a large difference in temperature between it and the white (hot) ears and eyes.

But when the animal was looking for food, the finger rose in temperature by up to 6C.
"We think the relatively cooler temperatures of the digit when not in use could be related to its [long, thin] form," said Ms Moritz.

"This form results in a relatively high surface-to-volume ratio [but] such a ratio is bad for retaining heat."

In order to sense the vibrations of beetle larvae through the bark of a tree, the finger is "packed with sensitive nerve endings", the scientist explained.

Because of its specialist sense receptors, using this tapping tool is very costly in terms of energy.
"Like any delicate instrument, it is probably best deactivated when not in use," Ms Moritz told BBC Nature.

Kink in the flow
The question of how the lemur controls the heat of a single digit remains unclear.
Ms Moritz suggested two explanations. The first was simply that the blood vessels that supplied the digit could be constricted or dilated.

The second more unusual possibility, she said, was that the creature might employ temperature control method that was linked to the flexibility of its finger.

Ms Moritz explained: "Because the finger is fragile and vulnerable to injury, it is often extended back and out of the way during locomotion and periods of inactivity," she said.

This extension could cause a "kink" in the artery that supplies warm blood to the digit.

In the same way a bent garden hose supplies less water, the artery could supply less blood, keeping the finger much colder than its fully supplied neighbouring digits.

Aye-ayes are the only primates known to have this strange adaptation.

The species is listed as Near Threatened by the International Union for Conservation of Nature (IUCN), mainly because of threats to its habitat.

But the odd-looking primate also suffers direct persecution. Superstition in Madagascar describes the species as a bad omen. Those that are pointed at by the creature's mysterious finger are said to meet their death.

Vegetarian orang-utans eat world's cutest animal

by Michael Marshall
from the New Scientist
Thanks to Tracy K for the link!




When fruit is scarce, try chomping on a slow loris. That seems to be the strategy adopted by the normally vegetarian orang-utans, which have been spotted knocking the small primates out of trees and killing them with a bite to the head.

Sumatran orang-utans (Pongo abelii) get almost all their nutrients from fruit and other plant products, but there are a few isolated reports of them eating meat (American Journal of Primatology, vol 43, p 159). Madeleine Hardus of the University of Amsterdam in the Netherlands and colleagues have now observed three more cases, bringing the total to nine.

In 2007 Hardus was tracking two orangs in the canopy above her – a female called Yet and her infant Yeni – when Yet abruptly changed direction and approached a slow loris (Nycticebus coucang). She knocked it out of the tree, crashed down to the ground, bit the stunned loris's head, then carried the body back into the tree to eat it. When Yeni begged, she was allowed to share the meat. The great apes each chomped on opposite ends of the dead primate, sharing it between them like lovers might a strand of spaghetti.

Searching through the scientific literature, Hardus found detailed studies of six orang-utan hunts. All stunned their prey before eating it, which Hardus thinks may be to avoid being bitten. Slow lorises are unique among primates in that their saliva is toxic.

All the documented hunts took place when there was little fruit available, which may push the apes to meat-eating, says Hardus.

By contrast, chimpanzees hunt more when fruit is abundant, perhaps because it doesn't matter if they waste energy on a failed hunt.

The sample is unavoidably small, but the data have been thoughtfully analysed, says Richard Wrangham of Harvard University.

Only five individual orang-utans have been observed hunting. Yet has so far been caught in the act four times – three times by Hardus, and once by another researcher – making her the best documented hunter.

In other accounts, the apes stumbled upon their prey, but Yet systematically changed direction and headed straight for the loris, which Hardus says may be because she has learned to smell them. Because a few cases have been documented within a 40-kilometre range, all using the same killing method, she thinks it may be a cultural behaviour, passed from orang-utan to orang-utan.

Madeleine E. Hardus, Adriano R. Lameira, Astri Zulfa, S. Suci Utami Atmoko Han de Vries, Serge A Wich (2012) Behavioral, Ecological, and Evolutionary Aspects of Meat-Eating by Sumatran Orangutans (Pongo abelii). International Journal of Primatology, DOI: 10.1007/s10764-011-9574-z

Abstract
Meat-eating is an important aspect of human evolution, but how meat became a substantial component of the human diet is still poorly understood. Meat-eating in our closest relatives, the great apes, may provide insight into the emergence of this trait, but most existing data are for chimpanzees. We report 3 rare cases of meat-eating of slow lorises, Nycticebus coucang, by 1 Sumatran orangutan mother–infant dyad in Ketambe, Indonesia, to examine how orangutans find slow lorises and share meat. We combine these 3 cases with 2 previous ones to test the hypothesis that slow loris captures by orangutans are seasonal and dependent on fruit availability. We also provide the first (to our knowledge) quantitative data and high-definition video recordings of meat chewing rates by great apes, which we use to estimate the minimum time necessary for a female Australopithecus africanus to reach its daily energy requirements when feeding partially on raw meat. Captures seemed to be opportunistic but orangutans may have used olfactory cues to detect the prey. The mother often rejected meat sharing requests and only the infant initiated meat sharing. Slow loris captures occurred only during low ripe fruit availability, suggesting that meat may represent a filler fallback food for orangutans. Orangutans ate meat more than twice as slowly as chimpanzees (Pan troglodytes), suggesting that group living may function as a meat intake accelerator in hominoids. Using orangutan data as a model, time spent chewing per day would not require an excessive amount of time for our social ancestors (australopithecines and hominids), as long as meat represented no more than a quarter of their diet.

What The Panda Won't Tell Us

by Robert Krulwich
from NPR


Every giant panda, said evolutionary biologist Stephen J. Gould, is a riddle. A contradiction. Each one is, first, a soft, furry ball of adorableness "with a large, round head and clumsy, cuddly body" that we all want to hug. That panda, said Gould, "exists in our mind."

Then there's the hidden panda, the real one that isn't as we imagine, that lives in the wild — and that panda, Gould wrote, "has remained essentially a mystery."

Thirty years ago, scientists knew next to nothing about pandas. Because the animals live in dense forests thick with bamboo, in 1980, when George Schaller from the Bronx Zoo and a team of Chinese scientists spent four years searching in Sichuan, they saw pandas rarely, only 16 times in the first two years. Most viewings, they wrote later, "were brief — a glimpse as an animal crossed an opening or ambled up a trail."

So what do biologists do when close encounters are few? They turn to indirect evidence of behavior. Which, in the panda's case, meant poo. Pandas defecate constantly.

Schaller weighed, measured and examined that poo. He checked the bamboo shoots. (How much did they eat? How much did they digest?) It was exacting, exhausting work, often boring. But Schaller kept at it. Here's his map of one panda moving along a trail on May 31, 1982. The little black dots are poop deposits, all carefully counted.

After four years in the field, Schaller and his team were able to report that giant pandas spend about 60 percent of the day eating, and the rest of the time sleeping or resting (mostly to emit what they ate), plus a few minutes grooming and scent-marking, but almost no time playing or gamboling, as we like to think. Pandas in the wild are rarely romantic, don't cuddle and are certainly not like the pandas of our minds.

As to what goes on in a real panda's mind, Schaller says he has no idea. After years spent tracking, poop collecting and bamboo measuring, he says pandas remain deeply strange to him. He knows everything they do, but he can't say much about who they are. In his book, The Last Panda, he imagines getting a letter from one of them. It's respectful, but the panda tells him, this "science" you do? It will never describe the real me. ....

But in Schaller's defense (and the typing panda should know this), those scientific studies did have consequences.

Before he set out, conservationists thought that pandas were losing population because their food source was untrustworthy, because wild bamboo goes through cycles, and sometimes there's not enough to eat. But Schaller found no evidence of starvation. Instead, he found that human poachers were to blame. So, according to Wikipedia, "Schaller would hand out cards to wildlife hunters that read:

All beings tremble at punishment, to all, life is dear. Comparing others to oneself, one should neither kill nor cause to kill."

After Schaller's first few expeditions, predation went down, the Chinese government stepped up enforcement, and since then, the Wiki entry says, "the panda population has increased in the wild by 45 percent."

So that imaginary panda should go back to his imaginary typewriter and crank out another imaginary "Dear Dr. Schaller" letter, and if Schaller would let him, I'd have him add just a couple of extra words — nothing grand — but right at the end, I'd let the panda say something like, "Thank you."
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George Schaller's newest essay and the panda field notes I showed you appear in a 2011 collection edited by Michael R. Canfield, from Harvard University Press. The book is called Field Notes on Science & Nature. Stephen Jay Gould's essay "How does the Panda fit?" can be found in his collection, An Urchin in the Storm: Essays About Books and Ideas.