You go to sleep at night, you wake up in the morning—the definition of sleep doesn’t seem so complicated. But start asking questions and things start getting thorny: Are dolphins that never stop swimming sleeping? Are migrating birds that “shut down” half their brains sleeping? Is someone under general anesthesia sleeping? And what about babies in the womb?
Unborn human babies in the womb are pretty difficult to monitor 24/7, so the researchers interested in that last question got ahold of unhatched chicken eggs. In a new Current Biology paper, they report that chicks show higher-brain activity patterns similar to sleep, and the cries of a hen could “wake up” the chick even when other loud but not chicken-salient sounds could not. These higher-brain activity patterns only appear in the last stage of incubation, presumably after their brains become well developed.
To monitor brain activity in the chicks, the scientists carefully made a small hole in the top of the egg and injected radioactive sugars onto the egg’s inner membrane. The developing embryo absorbed these sugars, which the team could then track with a PET scan. Active neurons need energy, which they get from sugar, so mapping the radioactivity in the brain shows what parts of the brain are active.
Fossilized dinosaur embryos, found still in their eggshells, have claimed the title of the oldest vertebrate embryos ever seen–they were fossilized in the early Jurassic Period, around 190 million years ago, researchers say. The embryos are from the species Massospondylus, a prosauropod, the family of dinosaurs which gave rise to iconic sauropods like the Brachiosaurus.
Robert Reisz and his team found the embryos when analyzing a clutch of fossilized eggs collected in South America in 1976. The find was just published in the Journal of Vertebrate Paleontology.
“This project opens an exciting window into the early history and evolution of dinosaurs,” said Professor Reisz. “Prosauropods are the first dinosaurs to diversify extensively, and they quickly became the most widely spread group, so their biology is particularly interesting as they represent in many ways the dawn of the age of dinosaurs.” [BBC News]
Earlier today we noted that Robert Edwards won a 2010 Nobel Prize for his work developing in vitro fertilization. But more than three decades after Edwards’ work came to fruition with the first IVF child’s birth, the technique is still somewhat haphazard—two-thirds of the time, it doesn’t lead to a live birth. Now, with a new approach to watching the first day or two of an embryo’s existence, scientists may be able to take a leap forward in both their understanding of a life’s first moments and in the success rate of IVF.
In a study published in Nature Biotechnology, Connie Wong and colleagues watched nearly 250 embryos develop over six days. They made the videos like the one seen above using time-lapse photography at the microscopic level, which showed the key differences between successful and failed embryos.
Successful embryos had an initial cytokinesis, or division of the cell’s cytoplasm, lasting between 0 and 33 minutes, a gap between first and second cell divisions lasting 7.8 – 14.3 hours, and an interval between second and third cell divisions of 0 – 5.8 hours. The pattern was so uniform that it was possible to automate the analytical process, using a computer algorithm to predict whether embryos would go on to develop successfully. [Nature]