Archive for the ‘Circadian Rhythms’ Category
Dormivigilia’s “Official” Website
November 18, 2009
Hollah to Gagan!
October 30, 2009
Today, my lab mate, Gagandeep Kaur successfully defended her dissertation: “Phase regulation of the circadian clock: neuropeptidergic and serotonergic mechanisms.” You can read about figments of her dissertation in a recently published article investigating rapid circadian re-entrainment to a new photocycle (i.e. time zone) following brief, constant light exposure and systemic administration of serotonergic agonists. The administration of serotonergic agonists (i.e. antidepressants) advances circadian rhythms by means of advancing the time of activity onset. When exposing nocturnal animals to constant conditions of light, the extent of advance of activity onset is potentiated.This type of accelerated re-entrainment would be beneficial for travel to far time-zones.
Dr. Kaur is off to work at a nearby veterinary clinic, applying her circadian experience towards better veterinary animal care.
This Just In: Rodents Take Jello Shots, Engage in Risk-Taking Behavior
September 27, 2009
I am extremely ecstatic about a recent PNAS publication investigating the effects of adolescent alcohol exposure on risk-taking behavior. Rats, yes rats, were co-administered alcohol and gelatin (i.e. Jello shots) during adolescence and then engaged in a lever-pressing protocol designed to administer sugar pellets, another hedonistic, pleasurable treat, during adulthood. To measure risk-taking behavior, lever-pressing did not necessarily coincide with two pellets. Lever pressing would either administer two, four, or no pellets. Rats that had taken Jello shots as a “teenager” were more likely to engage in risk-taking behavior and would routinely press the lever, knowing that no pellets may be present. For more information, see the article.
In the meantime, I may have to develop another experiment assessing the effects of long-term alcohol exposure on circadian timing of awakening and the consolidation of locomotor activity. Perhaps the hedonistic properties of both alcohol and sugar will augment alcohol consumption and exacerbate alcohol-induced disruptions of the circadian timing system. There is only one way to find out. Plus, I may develop a reputation for being the coolest cat/graduate student in the department.
Alcohol Exacerbates Jet-Lag: A Hamster Model per the Glass Lab
September 1, 2009
An intriguing study was published today in The American Journal of Physiology; the effects of chronic alcohol consumption and alcohol withdrawal on circadian entrainment in the Syrian hamster (you’ll recognize a familiar name or two or three or four or five….booyah!)
A prelude of today’s publication was broadcasted on Manswers, the hybrid of MythBusters and Jimmy Kimmel’s The Man Show, in December. Though the pre-report did not focus on circadian rhythm research, it truly showed that these “booze-soaked fluffballs” willingly consume copious amount of alcohol. Aha! The perfect model to investigate alcohol addiction and reward.
Jet-Lagged? No Doritos for You.
September 1, 2009
Today in PLOS, researchers have discovered that circadian dysregulation disrupts bile homeostasis. This may explain the unsettling stomach you had after eating General Tso’s chicken in the food court of Newark via LA.
Bile is critically important for the metabolism of lipids. Before the ascent of modern Gray’s Anatomy medicine, Greco-Roman doctors of Hippocrates’s era considered bile homeostasis to govern personality. Yellow and black bile, blood, and phlegm comprised the four humors. Individuals with too much yellow bile were characterized as ornery, while individuals with excessive black bile were described as melancholic.
In this study, circadian desynchronization was independent of environmental changes. The mice lacked clock genes, which assist in maintaining a circadian rhythm near 24 hours (hence, why it’s defined as circadian; circa=about; dia=day). Similar mouse lines are currently used in our lab for a top secret project. Yes, it’s top secret, unless you happen to be a philanthropist….
William C. Dement Retreat 2009: SHY, PVT, mTOR, and PPD
August 21, 2009
The 3 day sleep/circadian retreat held in the scenic W. Alton Jones Campus was “acronymonyous.” In addition to the impressive 10 minute presentations given by the Dement fellows, including discussions on the evolution of sleep and sleep in autistic children, the young investigators were off the hook. Dr. Erin Henlon, a post-doc in Ciara Chirelli and Julio Tuononi’s lab at Wisconsin-Madison, nicely summarized the role of BDNF in the learning process, and the SHY theory of synaptic plasticity across sleep and wake; during the waking day, there is incredibly high synaptic potentiation (LTP), and rewiring of synapses that are facilitated through mGlu1 activity. During sleep, LTP across wake is counterbalanced by synaptic depotentiation (LTD) mediated through the phosphorylation of serine. This suggests that sleep resets neuronal processing, serving as a protective mechanism against overstimulation and subsequent neuronal death.
Dr. Dan Mollicone from Pulsar Informatics in Philly uses mathematical modeling to explain detriments in performance related to sleep debt and shifted circadian phases. His model is incredibly reliable; he assured us that he could spend a day in the international terminal at JFK, and know which time zone the sleepy, jet-lagged traveler had arrived from based on his/her performance on the psychomotor vigilance test (PVT); a simple, Gameboy-esque device used to test reaction times. The bottom line is that even though a sleepy traveler may objectively appear alert after taking the PVT at one time of the day, this above-average performance can drastically change within 2 hours. Hence, the circadian timing system is a potent mediator of wakefulness and sleepiness.
Dr. Jonathan Lipton from Harvard Medical School is a neuroscientist/neurologist (M.D./Ph.D.) who balances research and clinical practice. He spends most of his week studying the circadian expression of mTOR, the mammalian target of rapamycin that mediates cell growth and apoptosis, and possibly responsible for the etiology of cancer, and one day diagnosing pediatric sleep disorders . His clinical passion is the role of sleep in the onset and perpetuation of autism.
Finally, Dr. Hawley Montgomery-Downs (bonus points for the awesome name) studies sleep in women post-child birth. Poor sleep following child birth is independent of time in bed and total sleep time. It’s sleep fragmentation across the night that leads to severe sleepiness. As Dr. “The Crusader Dement” has recapitulated over and over again…SLEEPINESS IS RED ALERT! This retreat he even brought us mini squirt guns with his motto engraved on the side. Handy for rest stops…..
3 Day Haitus for a 3 Day Retreat
August 17, 2009
You will notice an absence of new posts within the next day or two. I will be spending the next 3 days at the W.Alton Jones Campus in West Greenwich, Rhode Island for the annual Dement Fellowship sleep/circadian rhythm retreat. The retreat is at the scenic ecological wetland reserve owned by the University of Rhode Island. In addition to hanging out with Dr. D, the discoverer of REM sleep, I will be preoccupied with finding turtles, water snakes, and other native Rhode Island flora and fauna.
Climate Change Does Not Affect The Timing of Bird Migration
August 11, 2009
Yesterday, I attended Science Cafe Cleveland, an international monthly science colloquium sponsored by Sigma Xi. The topic of burning interest this month was bird migration. Though a general overview of the vast and profound physiological processes required for migration were narrated by Dr. Sarah Nabey of Hiram College and Harvey Webster of the Cleveland Museum of Natural History, the audience was nonetheless concerned with an assumed looming issue: the effect of global climate change on the timing of bird migration.
As a chronobiologist, I would argue that global climate change does not affect the timing of bird migration. Emphasis on timing. Sarah agreed. Why? Migrating bird species have adapted to plastic weather, climate, and food availability by relying on the single, least plastic, most constant, reliable phenomenon on mother Earth; the hours of light (photoperiod) and dark (scotoperiod) in a given day. Of course, we all know that the lengths of photo and scotoperiods vary seasonally due to the Earth’s tilt. Unless global climate change alters the Earth’s tilt, then the timing of migration and return home will not change. Yes, the suprachiasmic nuclei’s abilities to integrate photic information and modulate behavior and physiology accordingly are that awesome.
Another intriguing question was whether the length of the photo or scotoperiod is a more important determinant of the timing of migration. From a chronobiological perspective, I would postulate that the scotoperiod is more influential. Why? The onset of all reproductive phenomena and related physiological stress, which is highly important for the mobilization of energy resources during the migratory process (on average, an 80 hour, non-stop flight, with no meals, drinks, and in-flight entertainment), are mediated by melatonin, the hormone of darkness. In mammalian species, the pineal gland, responsible for nocturnal melatonin secretion, is indirectly wired to the retina, the locus of photic integration, via the spinal cord. In avian species, the pineal gland is directly wired to the retina, minimizing interferences of transmitted photic information from other indirectly projecting brain areas. This suggests that melatonin secretion from the pineal gland in avian species is critically involved in the timing and onset of physiological phenomena influenced by the lengths of daylight and/or darkness.
For trivial purposes: The two prominent killers of birds, migratory and non-migratory, are felis catus (the domestic cat) and illuminating, ambient lights of skyscrapers.
Below is a picture from www.montegraphia.com of a migratory Copper’s Hawk, we saw in Letchworth State Park near Rochester, New York.
Do Brown-Eyed Girls Have Exacerbated Jet Lag?
August 8, 2009
A month ago, I published that the length of the internal circadian day varies among races; African-Americans have a shorter internal circadian day relative to Caucasians, evoking public health concerns about both productive and error-prone work times, and adjustment to shift-work. The same research group, very near and dear to the Carskadon lab, has just observed that phase-resetting of the circadian day, comparable to that experienced during travel across time zones, is independent of eye color.
Why was eye color a salient concern worthy of scientific merit in the first place? It has been shown that melatonin release triggered by the pineal gland’s sensitivity to dim-light and/or darkness is mediated by eye color.
The two eye colors of interest were brown and blue eyes, but what about green and hazel? For those with hazel eyes, myself included, the eye color changes with lighting intensities, or at least mine do; in bright sunlight and ambient light, my eyes are aquamarine, and in dimmer light, are forest green.
Hmmmm, I wonder what about my mice’s (pronounced meces) beady eyes…..
Less Sleep, More Wake With Age
August 5, 2009
Sleep has been a sexy, salient topic on NPR this week. My labmate passed along an article that nicely summarizes changes in sleep architecture with age. One of the interviewees was my undergraduate advisor, Dr. Mary A. Carskadon; her lab investigates adolescent sleep and its changes across puberty; the internally generated circadian rhythm within the SCN and melatonin release from the pineal gland are increasingly delayed across puberty, which behaviorally means that teenagers have a natural, biological tendency to fall asleep late and awake late….though school districts have yet to understand….or care…..). Below is a beautiful schematic from the Basics of Sleep Handbook, provided by the Sleep Research Society, showing a remarkable loss of REM and slow wave sleep with age.
Dormivigilia 