With the leaves having changed color and falling
into a thick carpet, the sun shines through early morning mist at a low angle
leaving us to wistfully recall the cozier mornings of the summer months. Later
on, the sun will sparkle on frost and snow and look pretty, then we’ll take lots
of photographs as a test of our artistic talents.
We have a love/hate relationship with the sun. On
one hand we love to bask in its rays like turtles, but only after we’ve
slathered ourselves with sunscreen to prevent damage to the DNA in our skin
cells. Sancar and colleagues from North Carolina have just published a study of
the effects of UV radiation on bald mice (1). They observed that the time of
day that the mice were indulging in tanning was important in the likelihood
that they would get skin cancer.
Our epidermis, and those of mice, has a cell
proliferation rate that cycles with our circadian clocks. Remember that cell
proliferations means lots of DNA replication. They noted that the DNA repair
rate speeded up and slowed to the same rhythm. The repair mechanism is the
chopping out of damaged sections that are then rebuilt. Un-repaired DNA can
lead to mutations and cancerous outbreaks.
Now, mice are nocturnal, so their clock is 12-hour
shifted from ours and the safest time for them to get tanned is also shifted by
12-hours from when we may get away with exposing ourselves. For the
sun-worshippers among us, 7 AM may be the safest time to dance naked in the
sunshine.
Note that this is currently just a speculation
until a large number of people are studied in a detailed study like the bald
mice, so until then, it may be wise to slather on the sunscreen prior to your
morning dance.
