About Johns Hopkins

Recent news from The Johns Hopkins University

This section contains regularly updated highlights of the news from around The Johns Hopkins University. Links to the complete news reports from the nine schools, the Applied Physics Laboratory and other centers and institutes are to the left, as are links to help news media contact the Johns Hopkins communications offices.

 

Chilean Miners/Biological Clocks: Johns Hopkins Expert

Reporters working on stories about the impact of the Chilean miners’ long ordeal underground should consider speaking with Samer Hattar, an assistant professor of biology at The Johns Hopkins University. An expert on how exposure to light – or lack thereof – affects mammals’ biological clocks and health, Hattar can discuss the likely impact that 69 days without natural light had on the miners’ physiology, especially their sleep-wake cycles.

Tick, Tock: Rods Help Set Internal Clocks, Johns Hopkins Biologist Says

We run our modern lives largely by the clock, from the alarms that startle us out of our slumbers and herald each new workday to the watches and clocks that remind us when it’s time for meals, after-school pick-up and the like. In addition to those ubiquitous timekeepers, though, we have internal “clocks” that are part of our biological machinery and which help set our circadian rhythms, regulating everything from our sleep-wake cycles to our appetites and hormone levels. Light coming into our brains via our eyes set those clocks, though no one is sure exactly how this happens. Johns Hopkins biologist Samer Hattar, in collaboration with scientists at the University of Southern California and Cornell University, however, has unlocked part of that mystery recently in a study that found that rod cells – one of three kinds of exquisitely photosensitive cells found in the retina of the eye – are the only ones responsible for “setting” those clocks in low light conditions. What’s more, the study found that rods – which take their name from their cylindrical shape – also contribute (along with cones and other retinal cells) to setting internal clocks in bright light conditions. The study appeared in a recent issue of Nature Neuroscience.