Modified Lactic Acid Shows Promise as Anti-HIV Drug

A research team led by Brown Medical School Assistant Professor Bharat Ramratnam has genetically modified lactic acid bacteria, which help make yogurt and other fermented foods, to produce a protein proven to block HIV infection in monkeys. The results offer hope for a microbicide that can prevent the spread of HIV, which affects about 40 million people.

Ramratnam, a researcher at the Center for AIDS Research, oversaw the experiments, results of which were published in December in the Journal of Acquired Immune Deficiency Syndromes.

A microbicide using these modified bacteria will be tested in monkeys beginning this summer. Human trials of these topical treatments will follow.

From Polar Snow to Tropical Glaciers on Mars

Recent images beamed from Mars reveal intriguing evidence of glacial deposits in the tropics of the Red Planet.

How did this Martian ice form so far from the poles? Ancient snows, according to research conducted by planetary geologist James Head III.

The discovery ends a thirty-year Martian mystery. In 1976, cameras aboard NASA's Viking Mission to Mars captured unprecedented views of the planet's canyons and craters, including polar ice caps. Data from Mars Express and other recent missions reveal curious ice-rich deposits at the foot of volcanoes and mountains close to the equator.

In a January Science article, Professor Head and an international team showed how the ice formed so close to the tropics. A few million years ago, the axis of Mars was tilted so that the poles pointed significantly closer to the sun. Sun rays hit the ice caps nearly head on, releasing massive amounts of vapor. Winds carried the vapor south. The vapor cooled, condensed, and fell in the form of snow. Over time, the snow turned to ice, the ice formed glaciers, and the glaciers created the deposits seen today.

Surprising Findings on Mysterious Eye Cells

A type of retinal photoreceptor discovered by Brown researchers adjusts its sensitivity in different lighting conditions, according to results from the laboratory of neuroscientist David Berson, where the eye cells were discovered in 2002.

Published in Neuron in December, the results were a surprise. Though rods and cones, their biological cousins in the retina, clearly adjust to light levels, these new cells - intrinsically photosensitive retinal ganglion cells, or ipRGCs - were assumed not to adapt this way.

The work, which sheds important light on these mysterious eye cells, was conducted by Berson, the Sidney A. Fox and Dorothea Doctors Fox Professor of Ophthalmology and Visual Sciences, postdoctoral student Kwoon Wong, and former undergraduate Felice Dunn.

The Brain's Electrical Synapses Can Change

Plasticity - the brain's ability to change based on experience and its own activity - is a key to critical functions such as making memories. Chemical synapses, junctions where neurons communicate using chemical substances, have long been implicated in plasticity. Now, for the first time, neuroscience Professor Barry Connors, along with former Brown lab investigator Carole Landisman, have demonstrated that electrical synapses also are subject to long-term changes in the brains of mammals.

Their work appeared in Science in December.

Salt Marsh Serial Killer

Periwinkles, the spiral-shelled snails commonly found along rocky shorelines, play a primary role in the unprecedented disappearance of salt marshes in the southeastern states, according to research conducted in the lab of Professor Mark Bertness and published in December in Science.

Based on extensive field studies, the work challenges six decades of salt marsh science. Ecologists have long thought that stressed soil was the main killer of this critical marine habitat. But Brian Silliman, a Bertness lab research fellow, said drought-stressed soils pave the way for periwinkles that spread fungal disease as they graze on cordgrass.

"Snails can transform healthy marsh to mudflats in a matter of months," said Silliman. "Drought makes the marsh vulnerable, then the snails move in."

Since 2000, thousands of acres of salt marsh have disappeared from South Carolina to Texas, posing a serious threat to the ecology and economy of the southeastern seaboard and the Gulf Coast. Bertness, chair of the Department of Ecology and Evolutionary Biology, said a better understanding of the causes of salt marsh loss will point to better ways to protect salt marshes.