Archive for the ‘longevity’ Category

Five places in the world are now considered so-called “Blue Zones” – geographic areas where people are living much longer and more active lives. The first Blue Zone identified was Sardinia’s Nuoro province, which researchers Gianni Pes and Michel Poulain found to have the greatest number of male centenarians. Four other Blue Zones have since been identified by National Geographic explorer Dan Buettner and his team of longevity researchers. In these Blue Zones people are reaching the age of 100 at a much greater rate than anywhere else in the world. So what exactly sets these places apart from the rest? In his book The Blue Zones: Lessons for Living Longer From the People Who’ve Lived the Longest, Dan Buettner discusses the lessons he learned from the people inhabiting the Blue Zones and what specific lifestyle characteristics allow these people to live longer and better lives.

Ikaria, Greece

The tiny Mediterranean island boasts nearly non-existent rates of dementia and chronic disease and an isolated culture with a focus on socialization. Residents often drink goat’s milk and herbal teas and eat a Mediterranean diet full of fruits and vegetables, whole grains, beans, potatoes, and olive oil. Because this population is comprised traditionally of Greek Orthodox Christians, many fast for nearly half the year (caloric restriction has been linked to a slowing of the aging process in mammals). They also exercise by gardening, walking, or completing yard work but also nap regularly.

Loma Linda, CA

It may be surprising that one of the Blue Zones is located in the U.S., but Loma Linda is home to about 9,000 Seventh-day Adventists who form an extremely close community. Many Seventh-day Adventists adhere to a vegetarian diet rich in fruits and vegetables and consume water and nuts in lieu of soda and unhealthy snacks. They also spend time with family and friends, particularly during the weekly 24-hour Sabbath, and give back by volunteering.

Nicoya, Costa Rica

Besides their diet, the secret to a longer life for Nicoyans may be in their sense of purpose and strong social connections. They eat a traditional diet of fortified maize and beans, drink water with the country’s highest calcium levels, and eat a light dinner early in the early evening. Nicoyan residents often live with family members for support and strongly wish to contribute to a greater good. Their physical work keeps them fit and is embraced in everyday life.

Okinawa, Japan

Although this area is experiencing a decline in life expectancies from the influence of factors like fast food, older residents have consumed a plant-based, soy-rich diet most of their lives and eat pork only for infrequent ceremonial occasions in small amounts. Okinawans spend time outside every day and nearly all grow or have grown gardens (a source of vitamin D and fresh vegetables). It is also traditional to form a moai, or social network, for emotional and financial support.

Shuri Castle in Okinawa, Japan

Shuri Castle in Okinawa, Japan

Sardinia, Italy

Sardinia has nearly 10 times more centenarians per capita than the U.S., which could be attributed to a combination of genetics and a traditional lifestyle. The rare genetic M26 marker is common in this population and has been associated with longevity; due to the geographic isolation of the island, this gene is not prevalent in other areas worldwide. Sardinians eat a plant-based diet with pecorino cheese made from grass-fed sheep that is high in omega-3 fatty acids and drink wine in moderation. Laughter may be good medicine on this island – men in particular here are known for their afternoon laughing sessions in the street.

View of Cala Domestica beach, Sardinia, Italy

View of Cala Domestica beach, Sardinia, Italy

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palm

For centuries, humans have been exploring, researching, and, in some cases, discovering how to stave off life-threatening diseases, increase life spans, and obtain immortality. Biologists, doctors, spiritual gurus, and even explorers have pursued these quests — one of the most well-known examples being the legendary search by Ponce de León for the “Fountain of Youth.” Yet the key to longevity may not lie in a miraculous essence of water, but rather in the structure and function of cells within a plant — and not a special, mysterious, rare plant, but one that we may think of as being quite commonplace, even ordinary: the palm.

As an honors botany student at the University of Leeds, P. Barry Tomlinson wrote a prize-winning essay during his final year titled, “The Span of Life.” Fifty years later, Tomlinson (now a Distinguished Professor at The Kampong Garden of the National Tropical Botanical Garden, Miami, FL) teamed up with graduate student Brett Huggett (Harvard University, MA) to write a review paper exploring the idea that palms may be the longest-lived tree, and whether this might be due to genetic underpinnings. Having retained his essay in his personal files, Tomlinson found that it provided an excellent literature background for working on the question of cell longevity in relation to palms. Together, Tomlinson and Huggett published their review in the December issue of the American Journal of Botany.

A component of an organism’s life span that biologists have been particularly interested in is whether longevity is genetically determined and adaptive. For botanists, discovering genetic links to increasing crop production and the reproductive lifespan of plants, especially long-lived ones such as trees, would be invaluable.

In their paper, Tomlinson and Huggett emphasize that in many respects, an organisms’ life span, or longevity, is determined by the period of time in which its cells remain functionally metabolically active. In this respect, plants and animals differ drastically, and it has to do with how they are organized — plants are able to continually develop new organs and tissues, whereas animals have a fixed body plan and are not able to regenerate senescing organs. Thus, plants can potentially live longer than animals.

“The difference in potential cell longevity in plants versus animals is a significant point,” states Tomlinson. “It is important to recognize that plants, which are so often neglected in modern biological research, can be informative of basic cell biological features in a way that impacts human concern at a fundamental level.”

The authors focused their review on palm trees because palms have living cells that may be sustained throughout an individual palm’s lifetime, and thus, they argue, may have some of the longest living cells in an organism. As a comparison, in most long-lived trees, or lignophytes, the main part, or trunk, of the tree is almost entirely composed of dead, woody, xylem tissues, and in a sense is essentially a supportive skeleton of the tree with only an inner ring of actively dividing cells. For example, the skeleton of Pinus longaeva may be up to 3000 years old, but the active living tissues can only live less than a century.

In contrast, the trunks of palms consist of cells that individually live for a long time, indeed for the entire life of an individual.

Which brings up the question of just how long can a palm tree live? The authors point out that palm age is difficult to determine, primarily because palms do not have secondary growth and therefore do not put down annual or seasonal growth rings that can easily be measured. However, age can be quite accurately assessed based on rate of leaf production and/or visible scars on the trunk from fallen leaves. Accordingly, the authors found that several species of palm have been estimated to live as long as 100 and even up to 740 years. The important connection here is that while the “skeleton” of the palm may not be as old as a pine, the individual cells in its trunk lived, or were metabolically active, as long as, or longer than those of the pine’s.

Most plants, in addition to increasing in height as they age, also increase in girth, putting down secondary vascular tissue in layers both on the inner and outer sides of the cambium as they grow. However, palms do not have secondary growth, and there is no addition of secondary vascular tissue. Instead, stem tissues are laid down in a series of interconnected vascular bundles — thus, not only is the base of the palm the oldest and the top the youngest, but these tissues from old to young, from base to top, must also remain active in order to provide support and transport water and nutrients throughout the tree.

Indeed, the authors illustrate this by reviewing evidence of sustained primary growth in two types of palms, the coconut and the sago palm. These species represent the spectrum in tissue organization from one where cells are relatively uniform and provide both hydraulic and mechanical functions (the coconut) to one where these functions are sharply divided with the inner cells functioning mainly for transporting water and nutrients and the outer ones for mechanical support (the sago palm). This represents a progression in specialization of the vascular tissues.

Moreover, there is evidence of continued metabolic activity in several types of tissues present in the stems of palms, including vascular tissue, fibers, ground tissue, and starch storage. Since the vascular tissues in palms are nonrenewable, they must function indefinitely, and Tomlinson and Huggett point out that sieve tubes and their companion cells are remarkable examples of cell longevity as they maintain a long-distance transport function without replacement throughout the life of the stem, which could be for centuries.

Despite several unique characteristics of palms, including the ability to sustain metabolically active cells in the absence of secondary tissues, seemingly indefinitely, unlike conventional trees, in which metabolically active cells are relatively short-lived, the authors do not conclude that the extended life span of palms is genetically determined.

“We are not saying that palms have the secret of eternal youth, and indeed claim no special chemical features which allows cells in certain organisms to retain fully differentiated cells with an indefinite lifespan,” states Tomlinson. “Rather, we emphasize the distinctive developmental features of palm stems compared with those in conventional trees.”

Tomlinson indicates that this reflects the neglect of the teaching of palm structure in modern biology courses. “This paper raises incompletely understood aspects of the structure and development of palms, emphasizing great diversity in these features,” he concludes. “This approach needs elaborating in much greater detail, difficult though the subject is in terms of conventional approaches to plant anatomy.”

Journal Reference:

1.P. B. Tomlinson, B. A. Huggett. Cell longevity and sustained primary growth in palm stems. American Journal of Botany, 2012; 99 (12): 1891 DOI: 10.3732/ajb.1200089

http://www.sciencedaily.com/releases/2012/12/121219092842.htm