- SCIENCE NEWS - This Week

Research in Dubna, Russia, reported cre- ating a different form of element 116. Just 2 weeks ago, adds Dubna’sYuri Ts. Oganes- sian, signs of a lone atom of element 118 turned up in the group’s preliminary analy- sis of a new experiment. -P. WElSS

Sleepy Heads Low fuel may drive brain’s need to sleep 7

Why animals must sleep is a mystery to scientists. But a new study suggests that a vital function of sleep is to refuel the brain.

Canadian scientists report that energy stores in the brains of rats decline when the animals are forced to stay awake and the stock rebuilds while the animals sleep. The findings support a hypothesis that dwin- dling energy stores in the waking brain induce sleep (SN: 5/24/97, p . 316).

Most past attempts to test the hypothe- sis failed because there was no good way to measure brain-energy stores, says Jonathan D. Geiger of the University of Manitoba in Winnipeg, a coauthor of the report. Glyco- gen, the complex carbohydrate that pro- vides short-term energy storage for brain and muscle, rapidly deteriorates in tissue taken from an animal. So, scientists can’t measure glycogen concentrations accu- rately. Geiger and his colleagues dodged this problem by applying powerful microwaves to rat brains, killing the ani- mals and instantlyinactivatingthe enzymes that break down glycogen &er death. The scientists then removed the rats’ brains and measured glycogen concentrations.

The scientists tested some rats at their usual bedtime and kept others awake for 6, 12, or 24 hours bygentlyplayingwith them. The scientists then microwaved and removed each animal’s brain and measured brain glycogen. They found that glycogen concentrations were 38 percent lower in the rats that were sleep-deprived for 12 or 24 hours compared with the other two groups.

When other rats deprived of sleep for 12 or 24 hours were permitted to sleep with- out restriction, their brain glycogen rebounded to above-normal concentra- tions. The brain may be bracing itself for future bouts of sleep deprivation, the authors speculate in the July 1 Journal of Neuroscience. Skeletal muscles similarly overload glycogen when they’re recovering from strenuous exercise, Geiger notes.

The scientists treated sections of frozen brain tissue from the rats with a chemical that stains areas of high glycogen concen- tration. They found that glycogen was dis- tributed unevenly in the brains of rats both with and without sleep deprivation. During sleeplessness, brain areas varied in their decreases in glycogen.

“This work opens a whole new area of sleep research, as well as research in under- standing what role brain glycogen plays in maintaining normal brain function,” says Rolf Gruetter of the University of Minnesota at MinneaDolis St. Paul. His team studies brain glycogen in rats stressed by low con- centrations of blood sugar. The group’s results suggest that brain-glycogen reserves are critical to survival. Like Geiger’s team, Gruetter’s group has found that the brain tends to overstock glycogen following stress.

“I’m excited that the glycogen hypothe- sis is continuing to receive attention,” says H. Craig Heller of Stanford University, a coauthor of the hypothesis that brain- energy stores control sleep. “I’m encour- aged that our original idea held.”

However, the story is complex, Heller cau- tions. In an experiment simiiar to Geiger’s, Heller’s team failed to see brain-glycogen changes from sleep deprivation in the cor- tex of rats’ brains, one of the areas where Geiger’s team reported a large change. The finding appears in the JulyAmerican Jwr- nal ofPhyssiology -Regulatory, Integrative, and Comparative Physiology.

The results don’t necessarily conflict, Heller says, because his group used weaker microwaves and younger animals than Geiger’s team did. Also, glycogen depletion may vary from one brain area to another according to an animal’s circumstances, says Heller. For example, the part that con- trols a rat’s movements may become depleted if the animal is kept awake by physical activity, whereas sensory brain cen- ters may become depleted if an animal is kept awake by loud noises or flashing lights.

Heller concludes, “It’s a continuing story, and this is just the beginning.” -K. COB6

The Original Cocoa Treat Chemistry pushes back first use of the drink

It’s a triumph of bad housekeeping. Chem- ical analysis of residues from ancient Maya vessels that had been unwashed for 2 mil- lennia has revealed that the pots held cocoa almost 1,000 years before its previously known earliest use.

Madefromthebeans ofthetropid plant Theobroma cacao, cocoa was a favorite drink of ancient Maya and Aztec people in

CHOCOLATE POT A Maya vessel, dated 600 B.C. to A.D. 250, contains cocoa residue.

Mesoamerica. That helps explain why archaeologists have long referred to certain spouted Maya vessels as “chocolate pots,” even though these predated chemical evi- dence of cocoa consumption, says Terry G. Powis of the University of Texas in Austin.

Until now, the earliest leftovers of cocoa consumption were in residues from a Maya tomb in Guatemala from AD. 460 to 480. The newly examined spouted vessels, from 600 B.C. to A.D. 250, were discovered at an archaeological site called Colha in Belize. Similar vessels date back as far as 900 B.C.

Analysis of 14 Colhavessels indicated that 3 contained theobromine and caffeine, markers for cocoa, says team member W. JefFrey Hurst ofthe Hershey Foods Tech- nical Center in Hershey, Pa. Archaeologists hadn’t previously cleaned these three pots because they have narrow necks, Powis adds. Unfortunately, archaeologists had washed the other pots, which might have once harbored the marker molecules. Powis, Hurst, and their coworkers describe their findings in the July 18 Nature.

Spanish explorers in the 1500s reported that the Mesoamericans mixed cocoa with water, maize, chili, and honey. Powis says he’s now interested in determining what ingredients the earlier Maya combined with their cocoa. He’d also like to discover the geography of ancient cocoa consumption.

These steps will be important to figuring out how and where the processing of cocoa drinks first developed, comments Patrick McGovern of the University of Pennsylva- nia Museum of Archaeology and Anthro- pology in Philadelphia. “Both honey and chocolate could be very important for the development of civilization and culture in the Americas,” says McGovern, who ana- lyzed food and beverage residues from King Midas’ tomb (SN: 11/4/00, p . 296). “ m e n these fermented beverages are right at the focal point of feasting and religious activi- I?

ties,” he says. -J. GORMAN 5 38 JULY 20. 2002 V O L . 1 6 2 SCIENCE N E W S