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How the tests survive
Sep 1, 2010

1- How the “fit” tests survive

Original Article: Lewis, G.D. et al., Science Translational Medicine 2, 33 (2010).

Visits to biochemistry labs are frequent in our lives. Often we give blood to know levels of different metabolites, such as glucose or cholesterol. Instead of looking at a handful of metabolites, a group of scientists from Harvard Medical School has screened more than 200 metabolites before and after exercise. Interestingly, the levels of 21 of these metabolites changed significantly following exercise. The study also showed significant differences between physically more fit and less fit individuals after exercise. Following exercise, more fit people had greater increases in the biological markers of fat-burning and had decreased oxidative stress -a state where the balance between oxidants and antioxidants shift towards damaging oxidant side. Hence, fit people can get better results following exercise by efficiently removing waste materials. Moreover, exercise increased the levels of “niacinamide”, a compound which modulates insulin sensitivity. This increase was more prominent in leaner individuals and was maximized in fast marathon runners after exercise. It has been long known that obese and less-active individuals had greater tendencies to develop Type II diabetes where insulin action is impaired due to decreased sensitivity of the body to this molecule. Understanding the biochemistry behind the exercise may lead to identification of small molecules mediating its beneficial effects. These molecules may then be used to boost up metabolism or treat diseases. Until then, it is best to exercise and stay fit.

2- Our scents make us targets

Original Article: Carey, A.F. et al., Nature 464, 66 (2010).

Are you avoiding spending time outdoors in summer evenings because most of your time has to be spent chasing away the unwelcomed attention of mosquitoes? If so, then you must be one of those “lucky” people whose perspiration contains a key chemical that makes you irresistible to the six-legged bug. Scientists at Yale University have identified a key chemical compound that is detected by one of the mosquitoes’ 27 smell-receptors in their antenna. These smell-receptors are tuned to detect the key chemicals from hundreds of meters away which make people who secrete large amounts of these key chemicals in their sweat vulnerable to frequent mosquito attacks. Depending on the species, usually only the female mosquitoes bite humans, mainly on their feet or lower legs. More importantly, mosquitoes carry several deadly diseases such as Malaria and West-Nile dengue fever. In fact, Malaria is one of the deadliest and the most neglected diseases, affecting more than 500 million people and killing more than 3 million every year, mostly in sub-Saharan Africa. Sadly, the majority of deaths occur among children. Therefore, these types of studies, far from being trivial, may in fact lead to a better understanding of those mosquito-borne diseases, and hopefully may lead to the production of more effective drugs both for the prevention and the cure of diseases as well as better mosquito repellents and traps.

3- We are not alone in our body: Genomes of microbes living with us

Original Articles: Qin, J. et al., Nature 464, 59 (2010) & The Human Microbiome Jumpstart Reference Strains Consortium, Science 328, 994 (2010).

New advancements in DNA sequencing technology allow scientists to sequence genomes of microorganism living in their natural habitat. Human body contains roughly ten times as many microbes as human cells. As part of Human Microbiome Project, scientists are decoding the DNA sequences of all microbes living in several parts of our body such as skin, mouth, gut, respiratory tract and urogenital tract. Two independent teams from US and Europe have produced the first results of DNA sequences of microbes living with us. The projects have initially focused on bacterial genomes but intent to sequence viral and fungal genomes as well. The US team has generated a set of 178 bacterial reference genomes and is aiming to generate many more. In the second project funded by European Union, scientists sequenced the entire microbial DNA in the gut instead of sequencing them individually. They have sequenced more than 3 million bacterial genes, nearly 150 times more than our own (humans have only ~20 thousand genes). Importantly they have found that bacterial species are different in healthy individuals compared to the individuals with inflammatory bowel disease. Throughout these projects, scientists are trying to reveal significant information about the role of different microbial species in health and disease states.

4- Seeing with the sound

Original Article: Yovel Y et al., Science 327, 701 (2010).

Bats, dolphins, shrews and swiftlets use sound waves for navigation and hunting. They emit short sonar pulses and listen to the echoes reflecting back from solid objects. Microsecond differences in the arrival times of echoes are coded by detector neurons and used as a main cue for positioning objects in an environment. This phenomenon is known as biosonar. A recent study published in Science reveals one unknown part of this perfect sound processing strategy. The study shows that bats do not center the sonar beam on the target. Instead, they aim to match the maximum slope of the beam to the target in order to increase the signal-to- noise ratio. Around the sharp edge, small variations of the target position can be detected as a clear signal change in reflected sound intensity. Furthermore, the researchers showed that if the environment is very noisy, bats could bias this critical point to increase amplitude of the echoes. As it turns, this powerful technique has already been employed by humans in engineering and used in various technological tools such as atomic force microcopy. Whether this strategy is used in general by other echolocating animals remains to be answered.