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“…conventional wisdom now holds that aging really is just wearing out over time because the body’s normal maintenance and repair mechanisms simply wane. Evolutionary natural selection, the logic goes, has no reason to keep them working once an organism has passed its reproductive age.

“Yet we and other researchers have found that a family of genes involved in an organism’s ability to withstand a stressful environment, such as excessive heat or scarcity of food or water, have the power to keep its natural defense and repair activities going strong regardless of age. By optimizing the body’s functioning for survival, these genes maximize the individual’s chances of getting through the crisis. And if they remain activated long enough, they can also dramatically enhance the organism’s health and extend its life span. In essence, they represent the opposite of aging genes – longevity genes…

“One of the first longevity genes to have been identified, SIR2 is the best characterized, so we will focus here on its workings. They illustrate how a genetically regulated survival mechanism can extend life and improve health, and growing evidence suggests that SIR2 may be the key regulator of that mechanism…

“The Calorie Connection
Restricting an animal’s calorie intake is the most famous intervention known to extend life span. Discovered more than 70 years ago, it is still the only one absolutely proven to work. The restricted regime typically involves reducing an individual’s food consumption by 30 to 40 percent compared with what is considered normal for its species. Animals ranging from rats and mice to dogs and possibly primates that remain on this diet not only live longer but are far healthier during their prolonged lives. Most diseases, including cancer, diabetes and even neurodegenerative illnesses, are forestalled. The organism seems to be supercharged for survival. The only apparent trade-off in some creatures is a loss of fertility…

“Having seen how life-extending biological stress increases SIR2 activity, the question became, is SIR2 necessary for longevity? The answer appears to be a resounding ‘yes’…

“Both our labs are running carefully controlled mouse experiments that should soon tell us whether the SIRT1 gene controls health and life span in a mammal. We will not know definitely how Sirtuin genes affect human longevity for decades. Those who are hoping to pop a pill and live to 130 may have therefore been born a bit too early. Nevertheless, those of us already alive could live to see medications that modulate the activity of Sirtuin enzymes employed to treat specific conditions such as Alzheimer’s, cancer, diabetes and heart disease. In fact, several such drugs have begun clinical trials for treatment of diabetes, herpes and neurodegenerative diseases.

“And in the longer term, we expect that unlocking the secrets of longevity genes will allow society to go beyond treating illnesses associated with aging and prevent them from arising in the first place. It may seem hard to imagine what life will be like when people are able to feel youthful and live relatively free of today’s disease well into their 90s. Some may wonder whether tinkering with human life span is even a good idea. But at the beginning of the 20th century, life expectancy at birth was around 45 years. It has risen to about 75 thanks to the advent of antibiotics and public health measures that allow people to survive or avoid infectious diseases. Society adapted to that dramatic change in average longevity, and few people would want to return to life without those advances. No doubt, future generations accustomed to living past 100 will also look back at our current approaches to improving health as primitive relics of a bygone era.”

To read the complete article, click on http://www.sciam.com and then on our title under “FEATURE ARTICLES.”

“EAR’S SPIRAL RESPONDS TO BASS
New theory explains why our hearing machinery is coiled up.
by Philip Ball”

Our quotes are from a posting on http://www.nature.com/nature/index.html

“Daphne Manoussaki of Vanderbilt University in Nashville, Tennessee, and her colleagues believe that the snail-shell curve of the cochlea focuses sound waves at the spiral’s outer edge, making it easier for vibration-sensitive cells to detect them.

“If the researchers are right, then the ear is more sophisticated than we thought. ‘It would show we need to take a step back from the cell biology and see how the cochlea works as an integrated system,’ says Karl Grosh of the University of Michigan at Ann Arbor, who studies the ear’s structure.

“The findings also suggest that artificial cochlear implants for the hard of hearing could be improved. Grosh, who is working on such microscopic devices, says that the work will encourage him to think about the coiled structure, which was thought previously to have no real function.

‘The cochlea is a fluid-filled, coiled tube, about one centimeter in volume, that narrows toward the end. Sitting in the inner ear, it separates the different frequencies of a sound, picking up sound waves from 20 to 20,000 hertz.

“Different frequencies peak at different positions along the tube: high frequencies near the spiral’s broad mouth, and low frequencies further up the tube….

“But Manoussaki and her colleagues have calculated the way that sound waves travel in a cochlear tube with a realistic coiled shape. They find that the wave energy is not evenly distributed throughout the tube, but becomes concentrated along the outer wall, the more so the further up the duct the wave travels.

“The researchers say this is similar to the way sound in a cylindrical space such as St Paul’s cathedral in London, UK, gets concentrated around the walls; known as the ‘whispering gallery’ effect, it allows a listener at one part of the wall to hear a speaker on the other side of the cathedral.

“The concentration of energy in one part of the tube could help the membrane cells to detect sound, if they are clustered in that region. Thus the cochlea may be more sensitive further up the tube, where lower frequencies are detected.

“The researchers estimate that this amplification means that sounds at the inner tip of the spiral is boosted by 20 decibels relative to sound at the outer face: the difference between the volume of a normal conversation and that of a vacuum cleaner.

“A boost of 20 decibels would be significant in an artificial cochlea, says Grosh: ‘we’d love that.’ He says that it would be relatively easy to make miniaturized channels in the shape of a coil.”

To read the complete article, click on http://www.nature.com/nature/index.html and then the headline of our article under “NEWS@NATURE.COM”

“SEPARATION OF MAN AND APE DOWN TO GENE EXPRESSION”

Our title and quotes are from a 03/09/06 posting in SCIENTIFIC AMERICAN.COM:

“Humans and chimpanzees have in common more than 98 percent of DNA and 99 percent of genes. Yet, in looks and behavior we are very different from them. For more than 30 years – well before either the human or chimpanzee genome had been sequenced – scientists have speculated that this might be due to the way that the common genes express themselves rather than differences in the genes themselves. A new comparison published in Nature seems to prove that theory.

“Geneticist Yoav Gilad of the University of Chicago and his colleagues used a new technique to examine the genes in the liver cells of four primates: humans, chimpanzees, orangutans and macaques. The researchers were able to compare more than 900 genes for each of the four and assess how they differed in terms of expression. More than half – 60 percent – did not vary at all; the researchers found the same levels of mRNA – the molecule that links a gene and the protein it helps build – in all four for most genes. But 19 genes showed significant shifts in expression between humans and apes.

“‘When we looked at gene expression, we found fairly small changes in 65 million years of the macaque, orangutan and chimpanzee evolution,’ Gilad explains. ‘[This was] followed by rapid change, along the five million years of the human lineage, that was concentrated on these specific groups of genes.’”…

To read the entire article, click on http://www.sciam.com and then on title under LATEST SCIENCE NEWS.

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