Protein Acts as Cell Transport

Like the pipes, wires and sewers hidden beneath any city street, every cell in our bodies contains a complex communication and transportation system to keep everything running smoothly.

In recent years, researchers have begun to understand how this works, discovering, for example, the components of a tiny biological transportation system. Now, scientists have determined how a protein that acts like a motor for this cellular machinery does its job.

The protein, called kinesin, links with another kinesin protein to create a two-molecule ferry, which carries cellular cargo along the equivalent of tracks made of minuscule filaments called microtubules, which crisscross a cell's interior.

Ronald D. Vale, of the University of California at San Francisco, and colleagues used several techniques to study kinesin, which is about one-ten-millionth of an inch across, as it works. The researchers determined that a tiny part of the kinesin protein, dubbed the "neck linker," stiffens when it attaches to an energy molecule called ATP. The stiffening throws the neck linker forward, providing the force that starts the kinesin molecule moving, the researchers report in the Dec. 16 issue of Nature.

"The kinesin walks along the microtubules much like a person walks along steppingstones across a pond," said Vale in a statement. "Just as a person has to step from stone to stone, there are only certain points where kinesin molecules can attach to a microtubule. Basically, the neck linker zippers up and throws its rearward partner forward to the next attachment site, like swinging the rear leg forward to the next steppingstone."

The insights could lead to new treatments for diseases in which the transport system is malfunctioning, Vale said.

For Icthyosaurs, the Eyes Had It

Ichthyosaurs, marine reptiles that lived about between 250 million and 90 million years ago, apparently had gigantic eyeballs--bigger than those of any other known vertebrates.

Ryosuke Motani of the University of California Museum of Paleontology in Berkeley and colleagues estimated the size of the eyeballs of parvipelvians, a group of ichthyosaurians with tuna-shaped bodies.

The largest eyeball socket the researchers found--nearly 10 inches in diameter--belonged to the Temnodontosaurus, which was about 27 feet long. That's slightly larger than the eyeball of the giant squid Architeuthis, which is believed to have the largest eyeball of any animal living today. Another creature, the Ophthalmosaurus, had the largest eyes--nearly 9 inches in diameter--for its body length.

Based on the size of the eyeballs, the researchers estimated these animals could see as well in dim light as a cat. The creatures probably needed very good eyesight so they could locate prey in dark, deep waters.

"Absolute size is an important property of eyes, because larger eyes can house more retinal photoreceptive cells and receive more light per solid angle of image space," the researchers wrote in the Dec. 16 issue of the journal Nature. "Eye size also usually reflects the importance of vision in animals: for example, the horse has among the largest eyeballs of any land animal alive today."

Sax Playing May Be Health Risk

Saxophone playing may be hazardous to a jazz musician's health.

An analysis of biographical information about 813 musicians born between 1882 and 1974 found that "saxophone players were more at risk of death than other musicians," Sanjay Kinra, of the South and West Devon Health Authority, and Mona Okasha, of the University of Bristol, report in the Dec. 18-25 issue of the British Medical Journal.

The pair speculate that this might be due to a technique sax players use called "circular breathing," in which the musician inhales through the nose while simultaneously inflating the cheeks and neck with air to produce smooth playing.

"This is a demanding and possibly dangerous exercise," the researchers write, noting that it can increase pressure in the neck, possibly reducing blood flow to the brain or increasing the risk of deadly blood clots.

Blocking Senses Prolongs Life

Sometimes the world can seem overwhelming, inundating our senses with information overload. For at least one kind of creature, cutting off that sensory onslaught appears to make it live longer--a lot longer.

A tiny dirt-dwelling nematode worm, known as Caenorhabditis elegans, typically lives just 18 days. But those with a genetic defect that cuts off their ability to "smell" and "taste" through sensory organs on their head and tail lived nearly twice as long--about 30 days. Otherwise, they seemed normal.

"Our findings imply that sensory perception regulates the lifespan of this animal, and suggest that in nature, its lifespan may be regulated by environmental cues," Javier Apted and Cynthia Kenyon, of the University of California at San Francisco, write in the Dec. 16 issue of Nature.

The researchers speculate that some kind of chemical signal from the environment, perhaps pheromones, influences the nematode's rate of aging.

CAPTION: Saxaphonist Grover Washington Jr., 56, who died Friday of an apparent heart attack.