Stalagmite study tells a story of past storms
When studying climate patterns of the past, geoscientists often look at samples of ice cores, soil, and tree rings. Now, a Boston College researcher and colleagues have found that stalagmites from caves can also offer a detailed look into the past. The stalagmites preserve an accurate record of individual storms and could provide much needed data to help resolve the controversy over the possible link between climate change and hurricane intensity.
In a paper in this month’s Geology, Amy Benoit Frappier of Boston College and colleagues show that chemical analysis of a stalagmite from a cave in Belize revealed a record of the storms in the region from 1977 to 2000. A stalagmite is formed when minerals crystallize out of water that has seeped into the cave. Over time, the stalagmite slowly grows wider, layer by layer, forming rings like a tree.
It’s known that an isotope of oxygen, oxygen-18, is present at lower levels in rainwater from tropical cyclones. So the researchers measured the levels of this isotope in microsamples taken from the various layers of the stalagmite. They found that they could see the effects of individual storms with a resolution of a couple weeks’ time. (Earlier measurements from stalagmites had a time resolution of decades or more.)
Each cyclone caused an abrupt drop in the amount of oxygen-18 in a specific layer of the stalagmite. When they compared their data with storm records from the region, they found that the magnitude of the decrease in oxygen-18 levels was strongly linked to the intensity of the storm.
The researchers say that measurements from older stalagmites could provide a long-term record of storms, potentially stretching back a million years or more, which could help settle the debate about the influence of global warming on storm intensity. Mason Inman
Constant surveillance reveals the secret lives of lab mice
The mice in Susan Lindquist’s lab at the Whitehead Institute may be forgiven for feeling a little paranoid—someone is watching them all the time.
Researchers videotaped the animals 24 hours a day to see if they could detect signs of neurodegenerative disease earlier or even spot new ones. Lindquist and colleagues developed software that automatically classifies and tallies up the mouse movements according to categories like resting, walking, running, jumping, or hanging upside down.
The animals under watch had a neurodegenerative prion disease or the mouse equivalent of Huntington’s disease. In most labs, researchers observe mice when put through their paces in mazes and swimming pools, or using special exercise equipment. But such tests are just snapshots of the animal’s behavior, the researchers write, which can be highly variable and may not allow researchers to detect subtle changes.
Continuous monitoring of animals in their cages, on the other hand, revealed known habits associated with brain-wasting disease at an earlier age than previously observed. For example, the mice models for Huntington’s spent less time hanging, jumping, or stretching in their cages. Some behaviors seen in the mice with prion disease had never been observed before: increased walking, sniffing, and jumping.
This new kind of behavioral profiling could be useful for evaluating the effects of experimental therapies in animals or for behavioral analysis in large-scale mouse genetics projects, the researchers write in this week’s Proceedings of the National Academy of Sciences. Pat McCaffrey
Protein analysis of human eyeball fluid uncovers possible cause of diabetic eye damage
More than half of diabetics eventually go blind from malfunctioning blood vessels that feed the retina, the light-sensitive tissue at the back of the eye. Leaks in the vessels lead to swelling of the retina, which destroys vision.
In analyzing proteins from the eye, researchers from the Joslin Diabetes Center have found a new culprit in retinal swelling. Their results, published in Nature Medicine, also suggest that the same protein is involved in the brain swelling that occurs after stroke or head injury. Targeting the protein, an enzyme called carbonic anhydrase could lead to new treatments for these conditions.
Edward Feener and colleagues collected vitreous, the gel-like fluid that fills the eyeball and bathes the retina, from 25 people during eye surgery. Using proteomics methods, they identified 117 proteins in the fluid.
In people with diabetic retinopathy, they found that carbonic anhydrase was up to 15 times more abundant compared to nondiabetics.
When the investigators injected the protein into rat vitreous, it caused a rapid increase in blood vessel leakage and swelling of the retina. They found that in the rat eye, carbonic anhydrase was involved in regulating vessel permeability.
The investigators showed that blocking either the enzyme or its downstream effectors prevented the changes. And when they injected the protein into rat brain, it caused vascular leakage there, too. Pat McCaffrey
