Tuesday, July 19, 2011

Want to keep your brainpower? Exercise, Hawai`i!

Hawai`i has among the most active citizens in the nation, but there's way more to do, according to a cluster of recent scientific and research reports.

The U.S. Centers for Disease Control reports all four counties in the Islands have among the lowest rates of physical inactivity in the nation.

Is there a benefit to that exercise? The CDC study says it's good for reduced diabetes risk, but new studies indicate it's also significant for a healthy brain.

Regular physical activity is linked to lower loss of cognitive function in older adults, according to two studies in Online First by Archives of Internal Medicine, a JAMA/Archives journal.

There has long been an association between exercise and good mental function, but much of the previous research has been based on self-reported data and thus questionable. The newest information addresses those shortfalls and still comes to a similar result.

In a French study, researchers followed a group of nearly 3,000 women with risk factors for heart disease, part of the Women's Antioxidant Cardiovascular Study. They found increased exercise resulted in reduced brainpower loss. The lead researcher was Marie-Noël Vercambre, of Foundation of Public Health, Mutuelle Generale de l'Education Nationale, Paris.

Briefly, the report found that something equivalent to a half-hour walk daily was associated with a statistically reduced risk of cognitive function loss.

"Various biologic mechanisms may explain the positive relation between physical activity and cognitive health," said Vercambre's group, in a press release from the Archives of Internal Medicine, of the Journal of the American Medical Association. "If confirmed in future studies, physical activity recommendations could yield substantial public health benefits given the growing number of older persons with vascular conditions and their high risk of cognitive impairment."

A second report looked at 197 participants averaging nearly 75 years of age in the Health, Aging and Body Composition study in Canada. Researchers were led by Laura E. Middleton, of the Heart and Stroke Foundation Centre for Stroke Recovery, Sunnybrook Research Institute, Toronto.

Interestingly, these researchers subtracted the individuals' resting metabolic rate from their total energy expenditure. They found that the participants who had the highest net energy expenditure tended to have the lowest cognitive loss.

"The mechanisms by which physical activity is related to late-life cognition are likely to be multifactorial,” Middleton's group said. "We are optimistic that even low-intensity activity of daily living may be protective against incident cognitive impairment."

Find the studies here: Arch Intern Med. Published July 19, 2011. doi:10.1001/archinternmed.2011.282; doi:10.1001/archinternmed.2011.277.

In an Alzheimer's study, exercise was listed as one of the keys to reducing the likelihood of suffering from the disease. A report in the journal Lancet said the key risk factors internationally for Alzheimer's disease are, in this order: low education, smoking, physical inactivity, depression, hypertension in midlife, diabetes and mid-life obesity. They are associated with half of all cases of Alzheirmer's.

Mental health researcher Deborah Barnes, of the San Francisco VA Medical Center, analyzed data from a massive pool of patients internationally—hundreds of thousands.

Among Americans, physical activity rises to the top as the biggest single modifiable risk factor listed in the study.

"What's exciting is that this suggests that some very simple lifestyle changes, such as increasing physical activity and quitting smoking, could have a tremendous impact on preventing Alzheimer's and other dementias in the United States and worldwide," said Barnes, who is also an associate professor of psychiatry at the University of California, San Francisco.

She had one caution about the research: "We are assuming that when you change the risk factor, then you change the risk," Barnes said. "What we need to do now is figure out whether that assumption is correct."

In the Islands, although we do well on the activity scale, we can do far better.

According to the state Department of Health's Hawai`i Physical Activity and Nutrition Plan:

“In 2005, almost 48 percent of adults in Hawaii did not meet the recommended guidelines for physical activity (moderate intensity physical activity for at least 30 minutes on five or more days of the week or vigorous intensity physical activity for 20 or more minutes on three or more days per week).”

© Jan TenBruggencate 2011

Tuesday, July 12, 2011

Hawai`i causes vast ocean eddies, and whales take advantage of them

As winds and currents sweep across the central Pacific, the Islands cause disruptions in their flow—creating vast eddies.

Those eddies can bring nutrient-rich waters up from the deep, and create an extensive food chain.

(Image: Three melon-headed whales. Credit: © Robin W. Baird.)

New research indicates that melon-headed whales take advantage of this food resource. Satellite tagging indicates they regularly feed around the fringes of some eddies, and near the centers of others.

Researchers placed satellite tags on 10 adult melon-headed whales that are part of a population that stays around the main Hawaiian Islands.

In analyzing the tracks of the whales, they found that several of them spent significant amounts of time around several of the major eddies around the Hawaiian Islands, and were presumably feeding there, since it is known that these eddies concentrate fishery resources.

The whales tended to use the edges of counter-clockwise (cyclonic) eddies that have cold centers, and to go to the hearts of clockwise-turning (anticyclonic) eddies that have warm centers.

What’s going on at these locations? The authors write of the fringes of one such eddy: “This edge region is characterized by convergence of nutrients and phytoplankton upwelled in the eddy’s divergent center. Several studies identify this convergence zone as a fruitful foraging ground for species such as sea turtles, marlin and tuna, seabirds, and cetaceans.”

The paper, “Eddies as offshore foraging grounds for melon-headed whales (Peponocephala electra),” was written by: Phoebe Woodworth of NOAA’s Pacific Islands Fisheries Science Center in Honolulu; Gregory Schorr, Robin Baird and Daniel Webster off the Cascadia Research Cooperative; Daniel McSweeney of Wild Whale Research Foundation; Bradley Hanson of NOIAA’s Northwest Fisheries Science Center in Seattle; Russel Andrews of the University of Alaska Fairbanks’ School of Fisheries and Ocean Sciences; and Jeffrey Polovina, of the Pacific Islands Fisheries Science Center in Honolulu. It was published in the journal Marine Mammal Science.

“Both warm and cold core eddies are continually recurring features in the lee of the Hawaiian Islands. Wind stress from easterly trade winds is intensified by the islands’ topography, leading to the formation of eddies,” the paper says.

These kinds of research often turn up other mysteries that need solving. In this case, some of the whales went to feed in an area west of Ni`ihau, where no eddies are known to occur. What’s happening there? That’s a new subject for inquiry.

“The melon-headed whale tracks … indicate a potentially favorable habitat southwest of the Hawaiian island of Ni‘ihau, although the factors contributing to this area’s desirability are unclear,” the authors wrote.

© Jan TenBruggencate 2011

Friday, July 8, 2011

New `opihi science: lots to know about limpets

An 'opihi came to the Hawaiian archipelago, and evolved into three distinct species, each with specific characteristics built for their specific habitats.

You may not have thought much about 'opihi, but there's a lot to know about these limpets--besides that they are growing so rare due to overharvesting that they're priced like gold. That's because `opihi is a prized item at any Hawai`i gathering--a salty, crunchy condiment served raw, and delicious grilled with a little butter and garlic.

But we digress. Back to the science.

One thing: There's nothing to prevent their seagoing larvae from invading other shores, but Hawai`i's three edible `opihi are only found in Hawai`i.

Another: Since the original migrants could readily cross with others of their species, how and why did they evolve into three distinct species.

Speciation seems highly improbable under these circumstances,” writes author Christopher E. Bird, of the Hawai`i Institute of Marine Biology at the University of Hawai`i. His paper is “Morphological and Behavioral Evidence for Adaptive Diversification of Sympatric Hawaiian Limpets (Cellana spp.)” The paper is in the journal Integrative and Comparative Biology: Integrative and Comparative Biology, pp. 1–8 doi:10.1093/icb/icr050

But they did evolve, and probably they did it, he argues, due to natural selection—the individuals found environments to which they could adapt, and they and their offspring stayed there.

Still, it seems odd that you can find three different species of 'opihi on the same slab of rock—the exarata or makaiauli baking in the sun above the tide; the sandwicensis, `alinalina or yellowfoot taking the brunt of the wave force at the interface between air and sea; and the talcosa or ko`ele fighting off marine predators below the surface.

Bird argues that those locations below to above the water define their ecological niches: “Overall, C. talcosa is regularly exposed to pelagic predatory fish, C. sandwicensis is subject to the greatest amount of wave energy and mechanical stress, and C. exarata is subject to the most extreme temperatures and desiccating conditions.”

The ko`ele is sometimes called the kneecap `opihi. It's much bigger than the others, and its shell can be very thick—perhaps a trait developed to protect it from marine snails and predatory fish.

In another just-published article, this one in Molecular Ecology, Bird teamed up with Brenden Holland, Brian Bowen and Robert Toonen, all of the University of Hawai'i. This paper is “Diversification of sympatric broadcast-spawning limpets (Cellana spp.) within the Hawaiian archipelago,” Molecular Ecology (2011) 20, 2128–2141 doi: 10.1111/j.1365-294X.2011.05081.x

They say genetic studies suggest that the limpets first arrived in the Hawaiian archipelago between 3.4 and 7.2 million years ago—back in a time when Kaua`i, Ni`ihau and Nihoa were young islands

They probably arrived from the vicinity of Japan as free-floating larvae, and the original migrant was probably an inhabitant of the high shoreline, like Cellana exarata. Their nearest relative outside Hawai`i are probably the Japanese limpets, Cellana nigrolineata, C. mazatlandica and C. grata.

As little as six years ago, when this article was written, those things weren't known. http://the.honoluluadvertiser.com/article/2005/Jun/01/ln/ln08p.html

The researchers found that the Hawaiian 'opihi technically can hybridize but rarely do. They also found that they have different ranges throughout the island chain. All three are found in the main Hawaiian Islands, but talcosa doesn't go beyond Kaua`i and Ni`ihau. Sandwicensis stops at the basalt bastion, La Perouse Pinnacle. And exarata extends to the northewestern most Hawaiian land that still has volcanic rock above the surface, Gardner Pinnacles.

To confuse things, there are a couple of other `opihi reported from Hawaii. One is the small false `opihi, `opihi `awa, or Siphonaria normalis, which isn't eaten and isn't closely related to the others. The other is sometimes called Cellana melanostoma, which characteristically has steep sided shells, but genetic tests suggest it's a form of exarata.

© Jan TenBruggencate 2011