Circadian Wound Healing

Welcome back. I’ve got a fascinating topic, but before I begin, you’ll have to promise not to try to verify the findings of the research study I’ll be reviewing--you know, don’t try this at home, kids. Agreed? OK.

The study found that daytime wounds heal faster than nighttime wounds. It’s all very logical when you realize that wound healing falls under the spell of circadian rhythms. Here’s the story.

Circadian Rhythms
I wrote briefly about circadian rhythms in a blog post on the cause of Roosters’ Crowing. Circadian rhythms are physical, mental and behavioral changes that follow the 24-hour diurnal cycle and are found in most living things--microbes, animals and plants.

Our bodies’ biological clocks.
(Graphic by Katherine Streeter
for National Public Radio, 2015)

Circadian rhythms are produced and their timing regulated by each organism’s biological clocks. Note that “clocks” is plural. The biological clocks are composed of specific protein molecules that interact in cells in nearly every tissue and organ in the body. The brain synchronizes all those the clocks.

(By the way, the 2017 Nobel Prize in Physiology or Medicine was given for discoveries of molecular mechanisms controlling circadian rhythm.)

Although natural factors within the body produce circadian rhythms, they’re also affected by external factors, especially daylight. Jet lag is one example of how altering the cycle can speed, slow or reset the body’s clocks as well as circadian rhythms.

What Happens with a Wound?

My scraped
knee (selfie).

Ouch! You cut your finger (or scrape your knee). Fibroblast cells, which are responsible for making an extracellular matrix and collagen to help skin cells with the repair, waste no time in getting to the wound.

Movement of the fibroblast cells relies on actin, a protein that, in addition to being involved in cell migration, shares the responsibility for forming the contractile filaments of muscle cells.

Circadian Rhythm Healing
To investigate the circadian influence on healing, researchers from the UK’s Medical Research Council’s Laboratory of Molecular Biology in Cambridge first led experiments with cells in lab petri dishes. They found fibroblasts filled scratches faster during the day than at night apparently because genes that control actin are more active during the day.

They then found similar results in experiments with mice. Fibroblasts took twice as long to reach a new wound site if the wound occurred during the mice’s normal rest period of their 24-hour cycle than during the mice’s active waking period.

Pursuing these findings further with humans, the researchers analyzed cases from the International Burn Injury Database. They observed that the time of burn injury significantly affected the rate of healing. Daytime wounds healed about 60% faster than comparable nighttime wounds.

Wrap Up
While the study extends our understanding of circadian rhythms and cell-based biological clocks, the authors emphasize the need for additional research.

If the results are confirmed, how could that affect medical decisions? Should a patient’s circadian rhythm be considered when scheduling surgery? Can drugs be formulated to put a site of injury into daytime status?

Interesting, no? Thanks for stopping by.

P.S.
Example articles on circadian rhythms:
www.nigms.nih.gov/education/pages/Factsheet_CircadianRhythms.aspx
www.sciencealert.com/your-body-has-trillions-of-clocks-in-its-cells
Background on fibroblasts:
www.news-medical.net/health/What-are-Fibroblasts.aspx
en.wikipedia.org/wiki/Fibroblast
Study on circadian influence on fibroblasts in Science Translational Medicine journal: stm.sciencemag.org/content/9/415/eaal2774
Article on study on New Scientist website: www.newscientist.com/article/2152754-daytime-injuries-heal-twice-as-fast-as-wounds-sustained-at-night/
International Burn Injury Database: www.ibidb.org/

A version of this blog post appeared earlier on www.warrensnotice.com.

Roosters’ Crowing

When your rooster crows at the break of dawn
Look out your window and I’ll be gone…

Like the lyrics from Bob Dylan’s “Don’t Think Twice, It’s All Right,” I always thought roosters started crowing at or just before sunrise.

Some chickens behind the barn.
(Photo by Vicki)

Welcome back. As I mentioned in an earlier blog post, my father-in-law, a retired dairy farmer, is not fond of chickens, live or cooked (Save the Barn!). Nevertheless, he’s renting an unused barn and an adjacent field to his grandnephew, who with his wife and a partner are raising beef cattle and free-range chickens. (They also had a goat for a spell, but her penchant for hanging out in the cattle trough became too much of a problem.)

The first batch of chickens seemed to go reasonably well, and they’re now on a second batch. Whether intentional or not, this dozen or so has at least a couple of roosters, which, judging from the lack of crowing, the first batch didn’t. And it’s not just during the day. When I step out to do my predawn jogging and walking, I sometimes hear crowing.

Isn’t 3:30 AM a bit early for crowing? I was curious. Wouldn’t you be? OK, maybe not. Anyway, here’s what I learned.

Chickens and Me
I should mention that I have no experience with chickens. When I was growing up, there was a small chicken farm nearby, though I was never inside. There was also Chi-Chi, a neighbor’s pet rooster. I only saw him from a distance and not when he chased our dog Lassie (Time for Pets--Dogs).

The closest I’ve come to chickens was in Puerto Rico, when I was working at the Arecibo Observatory in the mid-1960s. I would occasionally see a hen or two hunting and pecking in peoples’ yards, but once, I did go to the cockfights at a local gallera (cockpit). Watching the men handling the birds, strapping on the spurs and especially betting was much more interesting than watching the cocks fighting.

Cockfight action at Gallera La Paloma, Guaynabo, Puerto Rico, 2013. (Photo from video: www.youtube.com/watch?v=ppn6ppU6vcA)

Cockfighting in Puerto Rico dates back to the 18th century and is regulated under the Department of Recreation and Sports. The island’s nearly 130 galleras are listed under the U.S. National Register of Historic Places. A 2012 government report noted that, annually, over one million people attended cockfights, generating over $100 million in bets, admission, food and other expenses.

Crowing Research
Searching online, I didn’t find a long list of research reports on the topic (hmmm…I wonder why). A few years ago, however, researchers from Japan’s Nagoya University did take on the challenge.

They conducted a series of well-designed experiments with caged roosters in light- and sound-controlled environments, monitoring the birds under 24 hour continuous dim light; split 12 hour light–12 hour dim light; different intensities of external light stimuli; and different amplitudes of external sound stimuli (other roosters crowing).

The study found that crowing was driven by the roosters' circadian rhythm, their biological clocks. (Circadian rhythms, you’ll recall, are internal changes that generally track a 24-hour cycle, responding primarily to light and darkness.) External stimuli, such as light and crowing by other roosters, induce roosters to crow, but that crowing is also influenced by a circadian clock.

Wrap Up
In keeping with circadian rhythm, roosters might start crowing as early as two hours before sunrise. The birds in the barn could be confused by external lighting. Just past the edge of the field, there’s a church parking lot with a bright light that’s on all night (see first photo, left-center). It’s also natural for roosters to alert the hens if predators are out and about. I doubt that’s the case, yet fox, coyote and even a wolf have been seen in our area.

There’s also the possibility that one of the birds crows because he just feels like crowing. Don’t you get that way sometimes? Thanks for stopping by.

P.S.
Research report on rooster crowing in Current Biology journal:
www.cell.com/current-biology/fulltext/S0960-9822(13)00186-3
Article on the study in National Geographic: news.nationalgeographic.com/news/2013/03/130318-rooster-crow-circadian-clock-science/
Puerto Rico galleras: www.nps.gov/nr/feature/places/64501213.htm (see link to full file)
Example article on roosters crowing in the middle of the night: animals.mom.me/mean-roosters-crow-middle-night-6686.html
Note: The Chinese Year of the Rooster begins 28 Jan 2017.