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SCIENCE
Broughton, writing in Ornithological Monographs, said his most recent study of bird consumption showed the same pattern as his earlier studies of mammals and fish.
He said the lowest strata had the largest number of big animals, but number and size both decreased over time: "Longevity decreased due to harvest pressure."
  Researchers conduct an excavation at the Emeryville Shell Mound, where many bird bones are buried. (City Of Emeryville, Calif.) |
Broughton acknowledged that European settlers speak of a "land of plenty," but they were latecomers, he said. Wildlife probably had rebounded after European diseases thinned the Native American population starting in the 1500s.
-- Guy Gugliotta
Stomach Hormone Boosts Brain
A hormone produced by the stomach can boost the number of connections between neurons in a part of the brain involved in forming new memories, providing new evidence for the close connection between the brain and the gut.
The recently discovered hormone, ghrelin, is released into the bloodstream by the stomach when it is empty and travels to the brain, where it stimulates appetite. But the hormone's function in other parts of the brain has been unknown.
In new experiments, Tamas Horvath of Yale Medical School and colleagues found that mice genetically engineered to lack the gene necessary to produce ghrelin have 25 percent fewer connections in a part of the brain known as the hippocampus, which is involved in forming new memories.
When normal mice are injected with extra ghrelin, they form extra connections in that part of the brain. Moreover, tests show that the animals have enhanced ability to learn and remember, the researchers reported in a paper published online yesterday by the journal Nature Neuroscience.
More research is needed to explore why the hormone has that effect, the researchers said. The findings suggest the hormone might be useful for treating learning and memory problems, such as those caused by aging and brain ailments such as Alzheimer's disease, they said.
-- Rob Stein
