The circadian rhythm that quietly pulses inside us all, guiding our daily cycle from sleep to wakefulness and back to sleep again, may be doing much more than just that simple metronomic task, according to Stanford researchers. Working with Siberian hamsters, biologist Norman Ruby has shown that having a functioning circadian system is critical to the hamsters’ ability to remember what they have learned. Without it, he said, “They can’t remember anything.”
A new study uncovers a previously unrecognized, species-specific impact of circadian rhythms on the production of mobilized stem cells. The research, published by Cell Press in the October 9th issue of the journal Cell Stem Cell, suggests that when it comes to collecting human stem cells for clinical transplantation, picking the right time of day to harvest cells may result in a greater yield. A variety of organisms have evolved an endogenous timing system, called a circadian clock, to regulate metabolic activities in a day/night cycle. In mice, the cells that give rise to mature blood cells, called hematopoietic stem cells (HSC), are regulated under the influence of rhythmic circadian signals that influence expression of Cxcl12, a gene involved in white blood cell migration.
It’s hard being a mussel: you have to worry about hungry starfish and even hungrier humans, not to mention an environment that can change your body temperature 50 degrees Fahrenheit in just a few hours.
“They spend part of the day respiring, and doing metabolic processes, and then the other part of the day switching to cell division,” Gracey explained.
Because their environment is so unpredictable–at low tide mussels could scorch on a sunny day and get soaked on a stormy one–these regular cycles were unexpected.