Work on Telomeres Wins Nobel Prize in Physiology or Medicine

The 2009 Nobel Prize in Physiology or Medicine will go to three American geneticists—Elizabeth Blackburn, Carol Greider, and Jack Szostak. They discovered telomeres, the genetic code that protects the ends of chromosomes, and telomerase, the enzyme that assists in this process, findings that are important in the study of cancer, aging and stem cells.
The work for which they received the award illuminated key aspects of the DNA replication process. As genetic material is copied from the chromosome during cell division, the whole DNA strand must be duplicated from end to end; otherwise, portions of genetic information will be lost. Until the 1980s, it was a mystery as to how the chromosomes could be reliably copied the whole way through without missing bits and pieces at the very end of each strand. Work completed by this year’s laureates demonstrated how, if parts of the end-cap telomeres were missing, DNA would eventually be shortened and cut off in the replication process.
Blackburn and Szostak in 1982 demonstrated that the telomere sequence could be isolated, inserted into another organism and still serve the same function. Working with Blackburn, Greider helped in 1989 to identify the RNA-based telomerase—the enzyme that creates the crucial telomeres. The findings have since been applied in studies of aging, stem cells and cancer.

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Some Women Have Duplex Uterus!

Many mammals, including pigs, dogs, rabbits and cats have two uteruses. In these animals, multiple foetuses can grow in each uterus. The foetuses share the placenta, but each one has its own umbilical cord. All primates have single uteruses.

One in about every 2,000 women worldwide has a double uterus. About one in 25,000 women with uterus didelphys gets pregnant with twins, one to each uterus. (Hence the likelihood of any given woman growing two babies in two separate wombs is about one in 50 million).

In the embryonic stage of human development, a female has more than one "uterine horn," or tubes that ultimately fuse into one uterus. In people with this condition, somewhere in the developmental process the tubes didn't come together, most likely because there was an error in the signals cells received instructing them to migrate to certain places.

Some people with uterus didelphys also have two cervices (cervix is the narrow outer end of the uterus at its junction with vagina) and two vaginas, but some only have one vagina. (Most women with two vaginas do not get surgery to fuse them, because one side is typically bigger than the other, so they have intercourse using just that one side)

Most women aren't even aware they have the condition until they become pregnant and get an ultrasound exam. If she gets an ultrasound about eight weeks into her pregnancy (as most ob–gyns recommend), chances are the ultrasound technician would spot the extra womb. But if the woman doesn't get an ultrasound until 20 weeks or more into her pregnancy, the uterus housing the foetus might have grown big enough to overshadow the extra uterus in which case the ultrasound technician might not see it.

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Alternative to Honeybees for Pollination

According to an article published in June 2009 Edition of Scientific American, honeybees have been dying in record numbers, yet many commercial crops depend on them for pollination. Entomologists who have been struggling to find an alternative now report that another bee might fill the void.

The blue orchard bee, also known as the orchard mason bee, is undergoing intensive study by the U.S. Department of Agriculture pollinating insect research unit at Utah State University at Logan. A million blue orchards are now pollinating crops in California. Like honeybees, the species can pollinate a variety of flora, including almond, peach, plum, cherry and apple trees. Unlike honeybees, however, they tend to live alone, typically in boreholes made by beetles in dead trees. In cultivation, the bees will happily occupy holes drilled into lumber or even Styrofoam blocks.

The blue orchards rarely sting and, because of their solitary nature, do not swarm. They are incredibly efficient pollinators: for fruit trees, 2,000 blue orchards can do the work of 100,000 honeybees. Their biggest drawback is that beekeepers can increase their population only by a factor of three to eight a year; a honeybee colony can expand from several dozen individuals to 20,000 in a few months.

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A Cockroach Can Live without Its Head!

Cockroaches can live without their heads. Entomologist Christopher Tipping at Delaware Valley College in Doylestown, Pa., has actually decapitated American cockroaches (Periplaneta americana) very carefully under microscopes. He sealed the wound with dental wax, to prevent them from drying out. A couple lasted for several weeks in a jar. And it is not just the body that can survive decapitation; the lonely head can thrive, too, waving its antennae back and forth for several hours until it runs out of steam.

To understand why cockroaches—and many other insects—can survive decapitation, it helps to understand why humans cannot, explains physiologist and biochemist Joseph Kunkel at the University of Massachusetts Amherst, who studies cockroach development.

Why Humans Can't Survive Decapitation?	Why Cockroaches Can Survive Decapitation?
Decapitation in humans results in blood loss and a drop in blood pressure hampering transport of oxygen and nutrition to vital tissues.	Cockroaches have open circulatory system with low blood pressure. They don't have a huge network of blood vessels like that of humans, or tiny capillaries. After you cut their heads off, very often their necks would seal off just by clotting. There's no uncontrolled bleeding.
A drop in blood pressure hampering transport of oxygen and nutrition to vital tissues.	Insect blood does not carry oxygen. The spiracles carry air directly to tissues through tracheae.
Humans breathe through their mouth or nose.	Cockroaches breathe through spiracles, located in each body segment.
The brain controls that breathing, so breathing would stop.	Their brain does not control this breathing. Insects have ganglia distributed within each body segment capable of performing the basic nervous functions responsible for reflexes.
The human body cannot eat without the head, ensuring a swift death from starvation should it survive the other ill effects of head loss.	Cockroaches are also poikilotherms, or cold-blooded, meaning they need much less food than humans do. An insect can survive for weeks on a meal they had one day.

Source: Scientific American

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The Origin of Oxygen in the Atmosphere

Cyanobacteria Bloom: Thanks to algal blooms like this one, the Earth's atmosphere is 21 percent oxygen.

It's hard to keep oxygen molecules around, despite the fact that it's the third-most abundant element in the universe, forged in the superhot, superdense core of stars. That's because oxygen wants to react; it can form compounds with nearly every other element on the periodic table. So how did Earth end up with an atmosphere made up of roughly 21 percent of the stuff?

The answer is tiny organisms known as cyanobacteria, or blue-green algae. These microbes conduct photosynthesis: using sunshine, water and carbon dioxide to produce carbohydrates and, yes, oxygen. In fact, all the plants on Earth incorporate symbiotic cyanobacteria (known as chloroplasts) to do their photosynthesis for them down to this day.

For some untold eons (eon is the longest division of geologic time, containing two or more eras) prior to the evolution of these cyanobacteria, during the Archean eon, more primitive microbes lived the real old-fashioned way: anaerobically. These ancient organisms—and their "extremophile" descendants today—thrived in the absence of oxygen, relying on sulfate for their energy needs.

But roughly 2.45 billion years ago, the isotopic ratio of sulfur transformed, indicating that for the first time oxygen was becoming a significant component of Earth's atmosphere, according to a 2000 paper in Science. At roughly the same time (and for eons thereafter), oxidized iron began to appear in ancient soils and bands of iron were deposited on the seafloor, a product of reactions with oxygen in the seawater.

"What it looks like is that oxygen was first produced somewhere around 2.7 billion to 2.8 billon years ago. It took up residence in atmosphere around 2.45 billion years ago," says geochemist Dick Holland, a visiting scholar at the University of Pennsylvania. "It looks as if there's a significant time interval between the appearance of oxygen-producing organisms and the actual oxygenation of the atmosphere."

So a date and a culprit can be fixed for what scientists refer to as the Great Oxidation Event, but mysteries remain. What occurred 2.45 billion years ago that enabled cyanobacteria to take over? What were oxygen levels at that time? Why did it take another one billion years—dubbed the "boring billion" by scientists—for oxygen levels to rise high enough to enable the evolution of animals?

Most important, how did the amount of atmospheric oxygen reach its present level? "It's not that easy why it should balance at 21 percent rather than 10 or 40 percent," notes geoscientist James Kasting of Pennsylvania State University. "We don't understand the modern oxygen control system that well."

Climate, volcanism, plate tectonics all played a key role in regulating the oxygen level during various time periods. Yet no one has come up with a rock-solid test to determine the precise oxygen content of the atmosphere at any given time from the geologic record. But one thing is clear—the origins of oxygen in Earth's atmosphere derive from one thing: life.

Anti-ageing pill activates telomerase

Peter Pan stayed forever young in Neverland. In real life, some scientists are looking at telomeres, or regions of repetitive DNA at the ends of our chromosomes, to try to arrive at something like a real version of this story.

Telomeres consist of up to 3,300 repeats of the DNA sequence TTAGGG. They protect chromosome ends from being mistaken for broken pieces of DNA that would otherwise be fixed by cellular repair machinery. But every time our cells divide, the telomeres shrink. When they get short enough, our cells no longer divide and our body stops making those cells. Over time, this leads to aging and death.

New York-based T.A. Sciences claims to be the only company in the world manufacturing a supplement in a pill form that has been lab tested and shown to stop telomeres from shortening, in hopes of halting the aging process. The product, TA-65, comes from extracts of the Chinese herb astragalus, which has been used for medicinal purposes for more than 1,000 years, says Noel Patton, chief executive officer of the company.

TA-65 is produced at very low levels in the astragalus plant, but the company purifies and concentrates the substance, which is thought to "turn on" the enzyme telomerase (hTERT) that acts to maintain or lengthen telomeres. hTERT is usually "off" in adult cells, except in immune, egg and sperm cells, and in malignant cancer-forming cells.

Telomerase is the same enzyme that allows cancer cells to stop aging or to become immortal, so there is a chance that TA-65 could keep alive cancer cells that would otherwise die.

However, telomerase activation should keep all telomeres longer in the first place, and that actually reduces the chances of cells becoming cancerous. The enzyme should keep immune cells, which can fight off most cancerous cells, alive longer.

Appendix is not a vestigial organ!

Duke University Medical Center researchers said that the supposedly useless appendix is actually where good gut bacteria safely hide out during some unpleasant intestinal conditions.

Now the research team has looked at the appendix over evolutionary history. They found that animals have had appendixes for about 80 million years. And the organ has evolved separately at least twice, once among the weird Australian marsupials and another time in the regular old mammal lineage that we belong to.

Darwin thought that only a few animals have an appendix and that the human version was what was left of a digestive organ called the cecum. But the new study found that 70 percent of rodent and primate groups have species with an appendix. And some living animals have a cecum and an appendix. If Darwin had known about species that had both organs, he probably would have revised his views of the appendix, the researchers note.

Ironically, it’s natural selection that keeps the human appendix from shrinking away completely. Because smaller ones are more likely to become infected. And keep your genes out of the pool.

—Steve Mirsky

Jellyfish help mix the world's oceans

Small sea creatures such as jellyfish may contribute to ocean mixing by pulling water along as they swim, according to a new study. The collective movement of animals could generate stirring of the same order as winds and tides.

Pulsating jellyfish stir up the oceans with as much vigor as tides and winds, scientists have found. The new study, which is published in the July 30 issue of the journal Nature, reveals a mixing mechanism first described by Charles Darwin's grandson that is actually enhanced by the ocean's viscosity, making these tiny sea creatures major players in ocean mixing.

In their field experiments, the researchers squirt fluorescent dye into the water in front of the Mastigias jellyfish and watched what happened as the animals swam through the dyed water. Rather than being left behind as the jellyfish swam by, the dyed water travelled along with the swimming creatures.

As the jellyfish swims, water gets pulled along with the animal, seen as swirls of red or green dye that was injected into the water.

Here's how the researchers think it works: As a jellyfish swims, it pushes water aside and creates a high-pressure area ahead of the animal. The region behind the jellyfish becomes a low-pressure zone. Then, the ocean water rushes in behind the animal to fill in this lower pressure gap. The result: Jellyfish drag water with them as they swim.

Jelliy fishes have huge variation in their body shapes. Moon jellyfish (the kind typically seen at aquariums) have saucer-shaped bodies and can carry a lot of water with them. But other bullet-shaped jellyfish would drag smaller volumes of water.

Global impact
The ocean churning has broader implications.
With this mechanism the animals can pull nutrient-rich fluid up to nutrient-poor areas and pull oxygen-rich fluid down to oxygen-poor regions,".
On larger scales, the biologic blender could impact the ocean circulation, which affects the Earth's climate.

Silent mutations can also be harmful

Single-letter changes to the DNA, known as point mutations, can therefore change a codon to one that specifies the wrong amino acid (known as a missense mutation) or to a stop signal (nonsense mutation), causing the final protein to be truncated. A single-base change can also alter a stop codon so that it then encodes an amino acid (sense mutation), resulting in a lengthened protein. And a final change is possible: a mutation that alters a nucleotide but yields a synonymous codon. These mutations are the ones termed “silent.”
The classic view assumed that what are termed “silent” mutations were inconsequential to health, because such changes in DNA would not alter the composition of the proteins encoded by genes.
Only in the 1980s did scientists realize that silent mutations could also affect protein production—at least in bacteria and yeast. A key discovery at the time was that the genes of those organisms did not use synonymous codons in equal numbers. When the bacterium Escherichia coli specifies the amino acid asparagine, for instance, the codon AAC appears in its DNA much more often than AAT. The reason for this biased usage of codons soon became apparent: cells were preferentially employing certain codons because those choices enhanced the rate or accuracy of protein synthesis.
It turned out that tRNAs corresponding to those synonymous codons typically are not equally abundant within the cell. Most important, then, a gene that contains more of the codons matching the relatively abundant tRNAs would be translated faster, because the higher concentration of those tRNAs would make them more likely to be present when needed. In other cases, a single tRNA variety matches more than one synonymous codon but binds more readily to one codon in particular, so the use of that codon maximizes the accuracy of translation. Consequently, a cell has good reasons not to use all codons equally. As expected, in bacteria and yeast the genes that encode especially abundant proteins exhibit the greatest codon bias, with the preferred codons matching the most common or better-binding tRNAs.
Lately, studies of human disease have indicated that silent disease-causing mutations interfere with several stages of the protein-making process, from DNA transcription all the way through to the translation of mRNA into proteins.
One example involves silent mutations changing how a gene transcript is edited. Shortly after a gene is transcribed into RNA form, that transcript is trimmed to remove noncoding regions (introns) and then splice the coding regions (exons) together to produce the final mRNA version of the gene. Research over the past few years has revealed that exons not only specify amino acids, they also contain within their sequences cues necessary for intron removal. Chief among these are exonic splicing enhancer (ESE) motifs—short sequences of about three to eight nucleotides that sit near the ends of the exons and define the exon for the cellular splicing machinery. The need for such motifs can in fact explain a preference for certain nucleotides in human genes. Although the codons GGA and GGG, which encode glycine, can both occur in splicing enhancers, the former codon acts as a more potent enhancer, leading to more efficient splicing. GGA is also correspondingly more common close to the ends of exons.

Michael Jackson Dies of Cardiac arrest

Michael Jackson, the moon-walking pop star who once patented "anti-gravity" shoes to enhance his stage performances, died of cardiac arrest on 25th June, 2009 at age 50.
What is the difference between cardiac arrest and heart attack?
Christie Ballantyne, interim chief of cardiology at Baylor College of Medicine in Houston, Tex., tells Scientific American that cardiac arrest just means that someone has lost their blood pressure and their pulse. "Usually, this means there has been a collapse of the circulatory systems and many times, it is due to an [accelerated] heartbeat," he says. When the heart is contracting so quickly, blood can no longer be squeezed from the pumping chamber and circulate to the brain, leading to death within minutes.
This accelerated heartbeat, or arrhythmia, can be a sign of a heart attack, which stems from buildup of plaque in the arteries. But not all heart attacks lead to cardiac arrest, and they are not the only cause of cardiac arrests, Ballantyne says. Cardiac arrest can occur from a major blood clot in the lung or a heart enlarged from infection or other damage. Previous heart attacks can also leave scars that injure the heart's pacemaking electrical system.

Birds of a feather

The size of flighted birds is limited by the demands of feather maintenance.

Sievert Rohwer at the University of Washington in Seattle and his colleagues studied 43 species of bird, assessing size, the length of flight feathers and timing of moulting cycles.

Flight-feather length is proportional, they say, to body mass raised to the one-third power, so that feather length roughly doubles with a tenfold increase in a bird's weight. But feather growth rate is proportional to body mass raised only to the one-sixth power. The trade-offs in time and energy required to replace long feathers therefore limit maximum bird size.