Science  01 Jun 2012:
Vol. 336, Issue 6085, pp. 1083

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  1. Jet Lag Disrupts Pregnancies in Mice


    What happens when you give a mouse jet lag? If she's pregnant, the results could be disastrous. Researchers placed laboratory mice that had recently copulated on a regimen of artificial daylight. Then they shifted the rodents' exposure to this light forward by 6 hours every 5 to 6 days—the equivalent of flying from Chicago to London. Four time shifts later, only 22% of the mice gave birth compared with 90% in a control group. Mothers may have reabsorbed their pregnancies or fertilized eggs might never have implanted, the team reported online 23 May in PLoS ONE.

    The result fits with previous studies which found that mice with mutations in genes that regulate their circadian rhythms have irregular estrous cycles and more pregnancy failures. Shift workers and flight attendants, whose own body clocks are disrupted, also report increased miscarriages and menstrual changes. But there may be hope: When mice were clock-shifted backward rather than forward, the effect was less severe. So even if circadian changes lead to fertility problems in women, careful scheduling might limit the turbulence.

  2. No New Neurons in Adult Olfactory Area

    For decades, scientific wisdom held that the birth of new neurons, called neurogenesis, wasn't possible in the adult brain. But studies since the late 1990s have shown that neurogenesis occurs in humans in a memory nexus known as the hippocampus. Now, a surprising study shows that the same may not be true for the olfactory bulb—a known hot spot of neurogenesis in other animals.

    Jonas Frisén and colleagues at the Karolinska Institute in Stockholm used radiocarbon dating to test human brain tissue taken in autopsies. The technique takes advantage of nuclear testing during the 1950s and early 1960s, which released massive amounts of the isotope carbon-14 (14C) into the atmosphere. Because 14C is taken up into the cells of plants and animals, and thus the humans that eat them, the isotope acts as a date stamp for the formation of new cells. In the 23 May issue of Neuron, the researchers report that olfactory neurons are all the same age—the age of the individual they were taken from.

  3. Tippy-Top Target for Next Mars Rover


    When NASA's rover Curiosity arrives at Mars on 6 August, its prime target will be Mount Sharp, the 5-kilometer-high mound of sediments in the middle of Gale crater. Mars researchers have no idea how those sediments got there. But a pair of geologists is now suggesting that at least the top third of Mount Sharp is volcanic ash that fell out of the sky surprisingly early in Mars's history.

    The Medusae Fossae Formation (left) covers one-third of the martian equatorial region, with patches near Gale crater. The formation bears a striking resemblance to layered deposits high on Mount Sharp (right), the researchers noted online 24 May in Science. By counting accumulated impact craters, the team has also found that the two deposits were laid down at about the same time: 3.8 billion years ago. When it arrives, Curiosity can probe beneath the thin coating of dust that obscures the deposit to confirm its true nature.