The fellowship provides support to advance research, enabling winners to study with prominent U.S. scientists and then establish laboratories in their home countries.
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.
With every sunrise and sunset, our eyes make note of the light as it waxes and wanes, a process that is critical to aligning our circadian rhythms to match the solar day so we are alert during the day and restful at night. Watching the sun come and go sounds like a peaceful process, but Johns Hopkins scientists have discovered that behind the scenes, millions of specialized cells in our eyes are fighting for their lives to help the retina set the stage to keep our internal clocks ticking.
The old adage “Looks can be deceiving” certainly rings true when it comes to people. But it is also accurate when describing special, light-sensing cells in the eye, according to a Johns Hopkins University biologist. In a study recently published in Nature, a team led by Samer Hattar of the Department of Biology at the Krieger School of Arts and Sciences and Tudor Badea at the National Eye Institute found that these cells, which were thought to be identical and responsible for both setting the body’s circadian rhythm and the pupil’s reaction to light and darkness, are actually two different cells, each responsible for one of those tasks.
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.
It would make the perfect question for the popular television show “Are You Smarter than a 5th Grader:” What parts of the eye allow us to see? The conventional wisdom: rods and cones. The human retina contains about 120 million rods, which detect light and darkness, shape and movement, and about 7 million cones, which in addition detect color. Without them, or so we are taught, our eyesight simply would not exist. But that might not be true, according to a study — published July 15 in the journal Neuron and led by Johns Hopkins biologist Samer Hattar — that provides new hope to people who have severe vision impairments or who are blind.