Monday, September 30, 2013

Larks vs. Night-Owls: What Your Sleep Patterns Say About You

Ugh, Monday morning really kicked my butt. Even my strong coffee failed to wake me up completely. Of course, I drag-ass most mornings, being almost useless before 10 a.m. On the flip side, I have always been wonderfully alert and productive after 7 p.m. A night owl I am, and this seems like a good topic for discussion. What determines your circadian rhythms and what does that mean for your personality?

A circadian rhythm is an endogenous, near 24 hour cycle in the process of living organisms (plants, animals, fungi, cyanobacteria). They have clear patterns and are important in determining physiological processes and activities. They are adjusted to the local environmental cues, like the light-dark cycle. I point this one out specifically because we are looking at the sleep-wake rhythm. Now, as with all things, there are individual variations, and a diurnal preference (or “morningness-eveningness (M-E) dimension” or nocturnality) is one of them. Your preference categorizes you into one of two chronotypes: (1) a lark or early riser who goes to sleep early in the evening and wakes up early in the morning or (2) a night owl who goes to sleep late in the evening and wakes up late in the morning.

Did you know that this preference is actually genetically controlled? Yeah. A paper published in Science in 2007 by Godinho et al. used N-ethyl-N-nitrosourea (ENU) mutagenized mice and screened alterations in circadian wheel-running activity. These screenings revealed a group of animals with a longer than average circadian period. They named the mutant gene “after hours” (Afh) and mapped the dominant phenotype. Then they selected those mice displaying the most extreme circadian phenotype for a genome scan. This scan revealed that the Afh mutation results in the substitution of serine for Cys358 (C358S) in Fbxl3, an F-box protein with leucine-rich repeats. Basically, Afh is a variant of the Fbxl3 gene, one of a large gene family that controls the breakdown of specific proteins in the body’s cells. After the identification of this variant, the researchers looked at the circadian expression profiles using in situ hybridization, immunohistochemistry, and Western blotting. They found that Afh affected steady-state levels of the principal negative-feedback regulators of the clock (Period genes Per1 and Per2, Cryptochrome gene Cry1, and the positive regulator Bmal1). One of the key components was the Cry1 gene which delayed the Cry protein breakdown, slowing the molecular feedback loops and lengthening the circadian cycle.

Now that we have our genotype (and resulting sleep-wake phenotype) explanation, let’s move on to personality traits. There is a rather expansive amount of literature showing that larks exhibit optimal cognitive function earlier in the day and night owls later in the day (hmmm…maybe I can coin the term “morning drag-ass syndrome”? MDAS? Pronounce that Midas because it’s gold!) A paper published in 1999 by Roberts and Kyllonen examined these cognitive differences, notabally intelligence, in a study of 420 participants. The participants were United States Air Force recruits undergoing their six week basic training and, as such, had known, homogeneous sleep-wake cycles, dietary intake and social constraints. These recruits completed two self-report measures of circadian type (Morningness-Eveningness Questionnaire and Composite Circadian Scale), a standardized intelligence test (Armed Services Vocational Aptitude Battery or ASVAB), and a standardized memory and processing test (Cognitive Abilities Measurement Battery or CAM-IV). The results of this study showed that night owls scored higher in measures of memory, processing speed, and general intelligence. I almost feel like I need to insert an immature, raspberry-accompanied I’m-smarter-than-you dance in here. Almost.

Admittedly, this final topic was the genesis for this post. I came across a newly published paper about the “Dark Triad” and just had to stop and read it. I mean, Dark Triad? Sounds like something Harry Potter might battle. Basically, the Dark Triad is a psychological term that describes a set of traits that include the tendency to seek admiration and special treatment (narcissism), to be callous and insensitive (psychopathy), and to manipulate others (Machiavellianism). Lovely. Granted, there are other determinations (google The Dirty Dozen Scale….awesome name!), but summing them all up gives you a picture of a person who is basically a giant toolbag. And there is some evidence suggesting there may be a genetic correlation to these traits. This new paper by Jonason, Jones, and Lyons looks at how the Dark Triad may be associated with the night owl chronotype. They had at 263 participants take online assessments that measured the three traits as well as the Morningness-Eveningness Questionnaire. The results of this study showed a correlation between being a night owl and the Dark Triad. The authors do a pretty good job at attempting to explain why this is so, hypothesizing that these Dark Triad traits may be evolutionarily important. They posit that these traits may give some type of night-time specialization, facilitate a cheater strategy, and enable a protean social style. They did not find any sex differences which eliminates sexual selection from their argument. This is sad because they were only able to use male “night-time adventures” once in their explanation. An overall interesting study that both allowed me to say Dark Triad a lot while removing all want to immaturely dance around.

If you have stayed with me this long then I commend you! In my defense, you did get three papers instead of the usual one. But anyway, what are we to take from all of this? That because I’m a night owl I am also an intelligent jerk, and that I can’t help it because it’s all genetic? Oh dear, I hope not. While I like to think I am intelligent, I hope that I am not a narcissistic ass-hat. So, what I guess that I’m saying is take of this what you will, and maybe read more studies.

ResearchBlogging.orgSofia I. H. Godinho, et al. (2007). The After-Hours Mutant Reveals a Role for Fbxl3 in Determining Mammalian Circadian Period Science, 316 (5826), 897-900 DOI: 10.1126/science.1141138

ResearchBlogging.orgRichard D. Roberts, & Patrick C. Kyllonen (1999). Morningness±eveningness and intelligence: early to bed, early to rise will likely make you anything but wise! Personality and Individual Di€fferences, 27, 1123-1133 DOI: 10.1016/S0191-8869(99)00054-9

ResearchBlogging.orgPeter K. Jonason, Amy Jones, & Minna Lyons (2013). Creatures of the night: Chronotypes and the Dark Triad traits Personality and Individual Di€fferences, 55, 538-541 DOI: 10.1016/j.paid.2013.05.001

(image via the Sleepio blog)

Thursday, September 19, 2013

Avast Me Hearties! It's International Talk Like a Pirate Day!

Ahoy, Matey, it be that wonderous of days where even th' weakest of landlubbers can spout the talk o' the pirate! Arrrr!! What? Now, don' go tellin' me ye havenna been practicin' yer pirate-slang, ya scurvy scum! The Cap'n'll be havven ya swab the decks for that'un. Scurry on over to me past page to brush up on yer pirate-talk and plunder some information on ITLAPD beginnins:

Happy International Talk Like a Pirate Day! (2011 post)

For the rest of ye ole salty sea-dogs and saucy wenches that have been sailin' with me for a while, here be some ITLAPD booty to enjoy! Yarrr!!

Pyrates! be a sea faring band from the shores of the Olde Lowlands of Holland. They be a notorious band of buccaneers who be playin' pirate themed folk music!

This bein' the modern age ye must be knowin' how to rap like a pirate too!

We ARR Who We ARR, a Ke$ha parody just for ITLAPD!

Tom Mason and The Blue Buccaneers be singin' "Talk Like a Pirate"!

Here be yer home ports for ITLAPD...

The Official Site for International Talk Like a Pirate Day

Talk Like a Pirate Day UK Headquarters

...and some articles for ye to gaze at...

Zerve's "How to Celebrate International Talk Like a Pirate Day"

Huffington Post's "Talk Like A Pirate Day 2013: Avast Me Hearties"

...and because ye twisted me arm, some more videos on how to talk like a pirate...

Real Pirates' Guide to "Arrrgh!" Volume 1

Real Pirates' Guide to "Arrrgh!" Volume 2

Real Pirates' Guide to "Arrrgh!" Volume 3

Thursday, September 12, 2013

Dealing with Drought: How Do Plants Cope?

Have you noticed how often drought has been in the news lately? You don’t have to be a scientist to know that drought is bad. But, if you’re a plant, how bad is bad? I mean, you’re a plant; it isn't like you can pick up your roots and go looking for the nearest water source. You must have ways to cope, strategies that will let you survive until water arrives. A new paper in Tree Physiology caught my eye today that examines how plants handle drought in our changing climate.

We know that drought and elevated temperatures have all sorts of effects on ecosystems worldwide. The ecosystem level is a bit broad so let's narrow the scope a bit, just looking at plants. The average person tends to think about plants as just that: plants. They are green, they grow. Okay, but we really need to think of them as different species that have their own strengths, weaknesses, and strategies to cope with hard times. Different species of plants react to drought and elevated temperatures differently, some are better able to cope than others. It is known that drought and temperature influence seedling and sapling establishment and survivorship. To anthropomorphize a bit, some infant and toddler plants survive to grow up into adults and others...well...don't. The results of this survivorship will profoundly affect the composition of the community (collectively, which species are there) and how that community changes over time. Additionally, drought and elevated temperatures may affect our efforts to restore habitats. If newly planted saplings die within the first few years of planting then the restoration fails. If we get even more doom-and-gloom with it, extreme drought will cause massive forest dieback, releasing huge amounts of stored carbon and exacerbating the problem.

Let's narrow the scope a bit more. The survivorship of plants is related to their physiology and productivity. In general, growth is the most sensitive to drought. This is followed by photosynthesis and then respiration. The timing and extent of these declines is governed by changes and coping methods for water balance (water supply vs. water use), carbon balance, and strategies to balance the water loss and carbon gain. Most climate models predict that with increased atmospheric carbon dioxide (CO2) and warming the intensity and timing of droughts will go up. Now, carbon dioxide is good for plants because they use it like we use oxygen, to make energy. Give plants more CO2 and you see increased leaf area, productivity, photosynthesis, and carbon storage (in this case we are talking about non-structural carbohydrates (TNC)). Warming under well-watered conditions isn't too bad either, but under drought, warming will decrease photosynthesis and carbon storage while increasing water loss. But increasing CO2, warming, and drought are not solitary factors; you need to look at them in combination. Elevated CO2 will lessen drought stress, but warming worsens it. Based on what we know of the individual factors, the effects of elevated CO2 plus warming plus drought may vary depending on the trade-offs a plant makes. This new study in Tree Physiology looks at how drought alone and in combination with CO2 and warming affects carbon dynamics (growth, photosynthesis, respiration, TNC).

To do this they raised Blue Gum (Eucalyptus globulus) seedlings under ambient CO2 and temperature conditions. After one month they transplanted and separated them into their various treatment groups. These treatment groups were put in whole-tree growth chambers where the conditions could be very carefully controlled. There were four CO2 and temperature combinations: two CO2 levels (400 and 640 μl l−1) and two temperatures (28/17 and 32/21°C day/night, a.k.a.ambient and ambient + 3°C). Within each of these treatments, seedlings were designated to a drought regime: well-watered/control, sustained drought, rewatered drought (watering after sustained drought), and progressive drought (on rewatered and sustained treatments). They were able to maintain the "sustained drought" condition by adding just enough water to maintain leaf stomatal conduction (a measure of the rate of CO2 entering and water vapor exiting the stomata/pores of the leaf).

The researchers took gas exchange measurements, specifically looking at leaf net photosynthesis and leaf respiration rates. They also randomly selected individuals at various times during the experiment’s duration to be harvested for dry mass measurements (leaf, stems and roots). TNC concentration was calculated as the sum of starch and soluble sugar concentrations.

The results showed effects of progressive drought to be similar in rewatered and sustained drought plants. These plants were limited in growth, photosynthesis and respiration. However, there was not a decrease in TNC, although the drought plants did convert quite a bit of their starch into soluble sugar. This means that the plants consumed less TNC, and the soluble sugars likely serve some other function apart from a respiratory carbon source during drought (perhaps osmotic adjustment and/or hydraulic transport). They also found that elevated CO2 ameliorated the stress of their plants in the moderate drought treatments. These plants showed increased photosynthesis and TNC reserves. This suggests that the plants have the capacity to withstand drought, having sugar available for osmotic adjustment (think: better water movement, which is good for growth and photosynthesis). Conversely, elevated temperature exacerbated moderate drought stress by reducing photosynthesis, increasing leaf respiration and decreasing TNC reserves, and reducing the plants’ capacity to withstand drought. The combined effect of elevated CO2 and increased temperature is a little more complex. This study found only moderate benefits to plants, with similar/lower carbon uptake and greater carbon loss during the moderate drought treatment. TNC was found to be higher which suggests that there may be some carbon storage going on. However, these benefits went away when the plants were subjected to extreme drought. I suppose that is to be expected. They don’t call it extreme for nothin’ right?

Perhaps we can find a silver lining from this story. Plants are resilient organisms that have the capacity to withstand more than we had thought even when they are hit with multiple stressors. They can deal with moderate droughts, but extreme is still extreme and nothing survives everything. I didn’t say it would be a thick silver lining, but we can potentially use this knowledge to help us mitigate some of the effects of climate change and work to better restore lost habitats.

ResearchBlogging.orgDuan, Honglang, Jeffrey S. Amthor, Remko A. Duursma, Anthony P. O’Grady, Brendan Choat, & David T. Tissue (2013). Carbon dynamics of eucalypt seedlings exposed to progressive drought in elevated [CO2] and elevated temperature Tree Physiology, 33 (8), 779-792 DOI: 10.1093/treephys/tpt061

(image via TrendsUpdates)
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