Archive for the ‘lifespan’ Category

fly-getty

Sexually frustrated fruit flies die earlier, new research suggests.

Scientists made the discovery by genetically modifying male flies to release female sex pheromones. Other males were left nearby and therefore instantly aroused by the pheromones. Some were allowed to mate, but others weren’t.

The findings, published in the journal Science, show that the sexually frustrated flies’ lives were 40 per cent shorter, while those who did mate suffered less stress.

Dr Scott Pletcher, Assistant Professor of Molecular & Integrative Physiology at the University of Michigan, co-authored the research. He told the BBC: “We immediately observed that (the non-mating flies) looked quite sick very soon in the presence of these effeminised males.”

A brain chemical, neuropeptide F (NPF), appeared to play a big role. NPF levels went up once flies were aroused. It would normally go down again upon mating.

But when it stayed high, it caused the stress and apparently the premature deaths.

Dr Pletcher went on: “Evolutionarily we hypothesise the animals are making a bet to determine that mating will happen soon.

“Those that correctly predict may be in a better position, they either produce more sperm or devote more energy to reproduction in expectation, and this may have some consequences [if they do not mate].”

http://www.independent.co.uk/news/science/sexual-frustration-will-give-you-a-shorter-and-more-stressful-life-if-you-are-a-fruit-fly-8972673.html

Thanks to Dr. D for bringing this to the attention of the It’s Interesting community.

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

Talk about a longevity strategy no man wants to pursue. A recent study published in the journal Current Biology finds that Korean eunuchs — castrated men — lived 14 to 19 years longer than other men, suggesting that male sex hormones play a role in life span.

In the study, the researchers used a genealogy record called the Yang-Se-Gye-Bo that tracked eunuchs who worked in the Korean imperial court during the Chosun Dynasty, which ruled from the 14th to early 20th centuries.

Researchers were able to identify 81 eunuchs, who were castrated as boys, and determined that they lived to an average age of 70, significantly longer than other men of similar social status. Even kings didn’t typically make it to age 50.

Three of the 81 eunuchs lived to 100, a centenarian rate that’s far higher than would be expected in modern society. The current incidence of centenarians is 1 per 3,500 people in Japan, and 1 per 4,400 people in the United States, for instance; thus, the incidence of centenarians among Korean eunuchs was at least 130 times higher than that of present-day developed countries, according to the paper.

TIME.com: Want to live longer? Don’t try caloric restriction

“Our study supports the idea that male sex hormones decrease the lifespan of men,” the authors write.

Based on earlier research, the authors argue that one explanation for this could be that male sex hormones may negatively influence the immune system and “predispose men to adverse cardiovascular attacks.” They note further that the theory helps explain why females — in many species — live longer than males.

But while animal studies have suggested that castration (which removes the testes, the source of male hormones) results in longer lives, studies in humans have been spotty. In one study of castrati singers, there was no difference in lifespan between them and non-castrated singers; in another study of institutionalized, mentally ill men, however, those who were castrated lived some 14 years longer than those who weren’t.

And there are other reasons that women may outlive men, including for example the presence of estrogen, which may help enhance longevity. Also, as ABC News reports:

“Females may have an advantage in longevity because they have a back-up X chromosome, (Dr. L. Stephen Coles, a co-founder of the Los Angeles Gerontology Research Group,) said. A woman’s body is a mixture of cells, half containing an active X chromosome from her mother and the other half from her father, he said. If there is a defect on one X chromosome, half of her cells will be unaffected.”

TIME.com: Health checkup: How to live 100 years

Further, the longevity of the Korean eunuchs could be attributable to lifestyle factors the study didn’t track, like diet, exercise and stress.

The authors think the men’s long lives can’t be chalked up solely to a privileged lifestyle, however. “Except for a few eunuchs, most lived outside the palace and spent time inside the palace only when they were on duty,” study author Kyung-Jin Min of Inha University told Reuters. Meanwhile, they still tended to outlive other royalty who spent their whole lives inside the palace.

Obviously, the study authors don’t advocate becoming a eunuch. There are more sensible and reliable ways to up your chances of a long, healthy life: don’t smoke, eat a healthy diet, get plenty of exercise.

“For better health and longevity, stay away from stresses and learn what you can from women,” the authors said in a statement.

http://www.cnn.com/2012/09/25/health/eunuchs-lifespan/index.html?hpt=hp_bn12