NOT PICTURING IT
Memory fades with age, and now imagination seems to disappear with it, too. Harvard University researchers asked volunteers in their 20s and those around 70 to construct within three minutes a future event using as much detail as possible. The younger adults created significantly richer scenarios. The results, presented in the January Psychological Science, support the notion that picturing what is to come requires the ability to recall past experiences and piece them together to form a coherent scenario. Imagine that—if you can.
As men grow older, their testosterone levels gradually but progressively wane, a decline linked with an increase in fat and drops in strength, cognition and bone mass. Unfortunately, testosterone supplements seem to do little to thwart these changes. Researchers found that testosterone supplements did decrease body fat and increase lean body mass in older men with low testosterone levels. But the subjects were no stronger and showed no improvement in mobility, cognition or bone mineral density. The January 2 Journal of the American Medical Association describes the outcomes.
MUTANTS FROM THE AIR
Mice kept downwind from two steel mills and a major highway developed 60 percent more mutations in their sperm than their brethren inhaling HEPA-filtered air did. The sperm stem cells became damaged after just three weeks of exposure, perhaps because of oxidative stress triggered by the particulates. Because the sperm were still functional, the mutations could be passed on to offspring. The findings show up in the January 15 Proceedings of the National Academy of Sciences USA.
Magnetic Control of Cells
To sense their environment, cells rely on the receptor proteins that stud their surface. These receptors latch onto specific molecules, triggering a cascade of biochemical events that lead to cell behaviors, such as the secretion of hormones or the destruction of pathogens. But before receptors can switch on, they often have to bump into one another. Donald Ingber of Harvard Medical School and his colleagues demonstrated that they could control this activation using particles of iron oxide attached to dinitrophenyl (DNP) molecules, which attach to the receptors on histamine-producing mast cells. When magnetized, the 30-nanometer-wide beads would attract one another, forcing the receptors to huddle and activate. The researchers detected a spike in the calcium levels inside the cells, which is the first step in histamine secretion. The technique could lead to lighter-weight, lower-power biosensors for detecting pathogens or to novel ways of delivering drugs in the body. The work appears in the January Nature Nanotechnology.
New World, New Disease
New genetic evidence supports the view that Columbus introduced syphilis to Europe. The first recorded syphilis epidemic happened in 1495, fueling centuries of debate as to whether the germ came from the Americas or existed previously in the Old World but had not been distinguished from other skin-lesion diseases until 1500. To uncover syphilis’s origins, scientists at Emory University and their colleagues genetically compared strains of the microbe from around the world with related bacteria. They found that syphilis’s closest kin were South American variants of yaws, a disease spread by skin contact and limited to hot and humid areas. One theory suggests that syphilis became sexually transmitted only after it reached Europe, where more clothing and cooler climes limited the ways it could otherwise spread. Ultimately the progenitors of syphilis may be as old as humanity, hitching a ride with migrants to the Americas millennia before Columbus, speculate researchers in the January 15 PLoS Neglected Tropical Diseases.
Better Ethanol through Grass
For making ethanol, switchgrass appears to be a feasible choice—and a better one than corn. Working with the U.S. Department of Agriculture, farmers grew and monitored the native North American perennial, which often naturally grows on the borders of croplands. Specifically, they tracked the seed used to establish the plant, the fertilizer used to boost its growth, the fuel consumed to farm it and the overall rainfall that the areas received. The five-year study showed that switchgrass grown on plots three to nine hectares in size would yield from 5.2 to 11.1 metric tons of grass bales per hectare, depending on rainfall. If processed by appropriate biorefineries (now being built), the yields would have delivered 540 percent more energy than was used to produce them, compared with the at most 25 percent more energy returned by corn-based ethanol. The January 15 Proceedings of the National Academy of Sciences USA has the findings.