Wednesday
May172017

The science of super-agers

According to the Guinness World Records the oldest person ever living on earth was 122 years and 164 days old Jeanne Louise Calment, who was born on 21 February 1875 and died on 4 August 1997 [1]. Today’s oldest living person, with an authenticated date of birth, appears to be Emma Martina Luigia Morano of Vercelli, who was born on 29 November 1899 [2].

The life expectancy in the whole population steadily increased since the 19th century (see Figure 1a, adapted from [3]), foremost attributable to a sharp decrease of infant-mortality, but also to a reduction in late-life mortality.

However, despite better access to health care, clean water, enough food and an increasing consciousness of a ‘healthy lifestyle’ (decreasing number of smokers, being physically active until an old age, …) this didn’t change the mean of the very old ages significantly, as well as the age of the oldest person ever didn’t change since Jeanne Louise Calment died in 1997, leading to the assumption of a biological limit of human ageing.

As you can see in Fig. 1b the relative changes of people reaching a specific age drop at the very old ages, emphasizing the hypothesis of a limit in human life expectancy.

Scientists hope that following years will let them gain more insights into this area of research, as more people with authenticated dates of birth reach these old ages.

Furthermore, they are looking for mechanisms of this hypothesized limit and possible interventions in order to find ways of improving life expectancy even further…

- NS

 

[1] http://www.guinnessworldrecords.com/world-records/oldest-person (05/14/2017)

[2] http://www.guinnessworldrecords.com/news/2016/5/guinness-world-records-announces-emma-martina-luigia-morano-as-worlds-oldest-liv-428983 (05/14/2017)

[3] X Dong et al. Nature 1–3 (2016) doi:10.1038/nature19793 (05/14/2017)

Monday
May012017

A Plastic Eating Caterpillar: An Accidental Discovery with Potential?

Humans produced 311 million tons of plastic in 2014, and that number is expected to double in the next two decades. About 40 percent of this is plastic bags, containers, and other products made of polyethylene [2]. Much of this plastic is discarded in landfills, and new solutions for plastic degradation are urgently needed.
Federica Bertocchini, a beekeeper and researcher in Spain, found her hives infested with waxworms, a type of caterpillar that feeds on beeswax. She placed the worms in a plastic bag while she cleaned out the hives, and when she returned to the bag, it was full of holes! Surprised, Bertocchini created a waxworm homogenate and applied that to a polyethylene plastic bag. After half a day, the bag had about 13% less mass, demonstrating that the breakdown was not purely mechanical. She worked with biochemists at the University of Cambridge to analyze the chemistry more closely. They determined using FTIR that polyethylene treated with worm homogenate had ethylene glycol present, suggesting that the polyethylene was being broken down into ethylene glycol.   
 
Other organisms with plastic degrading abilities have been discovered in recent years. In 2016, a Japanese team identified a bacterium that can degrade polyethylene terephthalate [5]. In 2014, Chinese scientists found that two species of bacteria from the gut of Indian mealmoths can degrade polyethylene. However, these microbes worked over the course of weeks or months [3]. Federica’s waxworms shredded polyethylene shopping bags within hours.
 
Bertocchini believes the waxworms may have evolved an ability to degrade polyethylene because of its carbon bond similarity to wax. Others are not convinced of the waxworm’s promise. Ramani Narayan says that the degradation, even if it is producing ethylene glycol, is “not a magical solution to plastics waste management”. The worms could pass microplastics into the environment and transport these toxins up the food chain.
 
Bertocchini says that the application of these worms could stem from identifying the enzymes that are actually degrading the polyethylene. Researchers do not know what exactly allows these worms to degrade polyethylene. The responsible enzyme could then be produced at high volumes, rather than using millions of actual worms. This wax worm discovery is still far from a solution to our planet’s growing piles of plastic, but I hope it can lead to an advancement with a real environmental impact.
 
--CJW
                                                                                                                       
References
1. Bombelli P, Howe CJ, Bertocchini F. Polyethylene bio-degradation by caterpillars of the wax moth Galleria mellonella. Current Biology. April 2017.
2. Neufeld L, Stassen F, Sheppard R, Gilman T. The New Plastics Economy: Rethinking the future of plastics. World Economic Forum. January 2016.
3. Yang J, Yang Y, Wu WM, Zhao J, Jiang L. Evidence of polyethylene biodegradation by bacterial strains from the guts of plastic-eating waxworms. Environ. Sci. Technol. November 2014.
4. Yong E. The Very Hungry Plastic-Eating Caterpillar. The Atlantic. April 24, 2017.
5. Yoshida S, Hiraga K, Takehana T, Taniguchi I, Yamaji H, Maeda Y, Toyohara K, Miyamoto K, Kumura Y, Oda K. A bacterium that degrades and assimilates poly (ethylene terephthalate). Science. March 2016.
 
Images: Wayne Boo/ USGS Bee Inventory and Monitoring Lab (waxworm)
Federica Bertocchini (waxworm chewing plastic)

 

Saturday
Apr222017

Bumblebees playing soccer – an example of behavioral flexibility and social learning in insects

Have you ever seen bumblebees playing soccer? In a recent study done by Loukola et al. [1], bumblebees were taught to transfer a ball in marked location and bees were rewarded after a successful performance. The aim of this study was not only to enjoy some nice playtime with bees but also to observe behavioral flexibility and social learning. Social learning is a phenomenon in which a new behavior is learned by the observation and imitation of others, whereas behavioral flexibility is considered to reflect one’s ability to change a pattern of behavior and create novel solutions to a problem. These features are thought to be common in mammals and birds, but are not well understood in insects.

By observing how bumblebees learned to play soccer, it was found that social learning is the best way for bees to learn the game [1].  Bees were not only copying the demonstrated ball transport method but also, were able to improve upon learned methods and develop more a convenient approach[1]. This kind of behavioral flexibility has not been noted before in insects, although behavior and cognition of insects has been widely studied [2,3]. But back to our first question; if you have not seen how a bee plays soccer, check out the videos from the supplementary material of Loukola et al. (http://science.sciencemag.org/content/355/6327/833), or see collected clips https://www.youtube.com/watch?v=ToZDCo51c_I

- JR 


References:

[1] Loukola OJ, Perry CJ, Coscos L, Chittka L. Bumblebees show cognitive flexibility by improving on an observed complex behavior. Science. 2017, 355(6327):833-836. doi: 10.1126/science.aag2360.

[2] Chittka L, Niven J. Are bigger brains better? Curr Biol. 2009, 19(21):R995-R1008. doi: 10.1016/j.cub.2009.08.023.

[3] Giurfa M. Cognition with few neurons: higher-order learning in insects. Trends Neurosci. 2013, 36(5):285-94. doi: 10.1016/j.tins.2012.12.011

Monday
Apr172017

An early event in Autism Spectrum Disorder: Increase in Brain Surface Area

Observations of increased brain size and head circumference in autism spectrum disorder (ASD) are certainly nothing new [1, 2], with previous work having suggested accelerated growth rates as potential early warning signs of risk of ASD [3]. However, an interesting study published in Nature reports additional evidence, including timing of this event and its relationship with behavioral symptoms [4].

 Hazlett and colleagues conducted a prospective anatomical MRI study of infants at high vs. low familial risk of ASD and found evidence that early post-natal hyper-expansion of cortical surface area may play a role in the development of ASD [4]. Furthermore, this cortical surface area increase (which was observed between 6-12 months) was linked with increases in total brain volume (at 12 - 24 months) and social deficits (at 24 months).

 In terms of potential underlying mechanisms the authors discuss previously suggested mechanisms such as increase proliferation of neural progenitor cells, increase in number of mini-columns and decreased pruning.

 - NRZ

 

 References

 - Piven, J. et al. An MRI study of brain size in autism. Am. J. Psychiatry 152, 1145–1149. 1995.

- Courchesne, E. et al. Unusual brain growth patterns in early life in patients with autistic disorder: an MRI study. Neurology 57, 245–254. 2001.

- Courchesne et al. Evidence of brain overgrowth in the first year of life in autism. JAMA. 2003.

- Hazlett et al . Early brain development in infants at high risk for autism spectrum disorder. Nature. 2017.

Wednesday
Apr052017

How should we be using exercise as a tool to protect our brains?

It is well-accepted that physical exercise is beneficial for your health, but researchers are still investigating how exactly these benefits translate in the brain.  Many studies have shown that aerobic exercise increases neurogenesis and improves cognitive performance, but the exact mechanism connecting these two observations is still unclear. Two recent publications have reported interesting results describing how exercise type, genetic variance, and external stress affect the brain. The experiments are both done in rodents, so take the results with a grain of salt.

What the best type of exercise I can do for my brain?

While most clinicians are likely to encourage any physical activity, Nokia et al investigated the effects of three different types of exercise on neurogenesis in the hippocampus, the region of the brain critical for memory, learning, and stress response. Rodent exercise research generally employs a running wheel to simulate aerobic exercise, but here the authors compared three different exercise regimens: 1) sustained aerobic endurance exercise (ie. Voluntary running wheel or motorized treadmill), 2) high-intensity interval training (speed intervals on treadmill) and, 3) anaerobic resistance training (ie. weighted climbing). Interestingly, the authors found markers of cell proliferation, maturation, and survival- all indicative of neurogenesis- were only significant in rats that had completed the endurance training, which included voluntary running on a running wheel 3 times per week for 6 weeks. Moreover, they found the effects were most significant in rats genetically predisposed to respond to physical exercise (ie. maximal running distance increased following 8 weeks of treadmill training as opposed to no change). Take home: Sustained aerobic exercise is the most effective training paradigm to promote hippocampal neurogenesis, especially if you are running voluntarily and genetically predisposed to show gains in aerobic fitness with training.

Can exercise protect my brain?

Stress is known to negatively impact mood and impair memory, while simultaneously eliminating dendritic spines in the brain. Because exercise is known to improve memory function, Chen et al investigated whether exercise could rescue the negative effects of stress on behavior and spine stability. This study was carried out in mice who expressed fluorescent protein in their cortical neurons enabling in vivo transcranial monitoring of dendritic spine dynamics before and after exercise/stress intervention. Mice were physically stressed for 14days with or without one hour of continuous treadmill exercise, followed by behavioral testing, imaging, and brain protein/transcript quantification. The results showed that exercise not only prevented stress-induced anxiety and working memory loss, but also physically prevented spine elimination and enhancing survival of newly formed spines. The authors confirmed that the observed neuroprotective effects of exercise were conferred through the BDNF/TrkB pathway. Take home: Regular sustained aerobic activity can prevent the deleterious effects of stress on your brain.

Better get moving!

MMR

Chen et al. Treadmill exercise suppressed stress0induced dendritic spine elimination in mouse barrel cortex and improved working memory via BDNF/TrkB pathway. Transl Psychiatry (2017) 7, e1069.

Nokia et al. Physical exercise increases adult hippocampal neurogenesis in male rats provided it is aerobic and sustained. J. Physiol 594. (2016) pp 1855-1873.