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The question: Burning excess calories post exercise

in SciWorld/That Makes Sense by

Combining resistance and endurance exercises potentiates fat loss and muscle hypertrophy

You don’t burn calories while working out alone, body continues to burn calories even after the cessation of the workout. It was attributed to excess post-exercise oxygen consumption (EPOC), which remains high after aerobic exercise as well as anaerobic exercise. In addition, lactic acid produced, during strenuous exercise, in muscle cells has to be diverted/oxidized back to other metabolites, which might also contribute to the excess calorie consumption after the workout. These 2 hypotheses however could not completely explain burning of more calories after exercise.

pic-1

The science behind

Researchers at Harvard University detailed the science behind these hypotheses. They found that endurance induces a hormone which converts white adipose tissue (tissue which stores fat) into brown adipose tissue (tissue which burns fat). Irisin is the hormone produced upon endurance exercise in mice and human subjects which regulates this process. Irisin has been in the news ever since as an exercise hormone. In another study, by the same group, they found the scientific reason why resistance exercise induces muscle hypertrophy. When human subjects performed resistance exercises such as leg press, chest press etc., Insulin like growth factor (a hallmark protein for muscle hypertrophy) production was enhanced.

Interestingly, both the endurance and resistance exercise benefits were under the control of a master protein called PGC1 α. This protein is differentially produced in the body according the nature of the exercise performed. If endurance exercise is performed it produces the beneficial effects of burning fat; if resistance exercise is done muscle hypertrophy results.

PGC1 α is very important protein, a person’s athletic performance is determined in part by it. Genetic mutations in this protein affect athletic performance of the individual.

Kill two birds with one stone: resistance and endurance exercise

It was also reported that PGC1-α is induced at a higher level when resistance (anaerobic) exercise is performed after endurance (aerobic) exercise, which is called concurrent training. Combining both exercises, thus, will have a synergistic effect on overall health.

The future

There has been no golden rule for how much workout has to be done for achieving desirable health benefits- either fat loss or muscle gain. It could be possible, in future, that amount of production might be used as readout for endurance or resistance exercise for each individual. Proper exercise regime and nutritious diet could help maintain general wellbeing and attain dream physique.

 

 

About the Author:

srinvas

 

Srinivas Aluri is postdoc at Albert Einstein College, NY. He is a fitness enthusiast, exercise and diet expert. He is also an international sports science association certified fitness trainer as well as American Heart Association’s CPR/AED certified professional.

P.S: This article was blogged at an untraceable place. It’s been edited and published here.

 

Photo source: builtlean.com and Pixabay

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My story on how I got my H1B

in SciWorld by

Hello everyone, I would like to share my experience towards getting the H1B visa. I’m happy to let you know that I am joining the University of Michigan, Ann Arbor, as a postdoctoral fellow. I am very grateful to CSG, as early discussions on this forum encouraged me to begin applications even before thesis submission. My PI offered to do an expedited processing of the H1B visa, and I was also assigned an immigration lawyer for the same.

I chose Mumbai as the city of choice for my visa interview, but there were no dates for H1B available until Feb 2017!! (They have now increased availability, but from July-Oct it was tough to get dates within 3 months for this visa category). So I did the biometrics at the VAC in Mumbai, and had my consular interview at Kolkata,as that was the only place where dates were available. I’m sure many of you know this already, but just for the benefit of the minority (I was one of them) who don’t, it is perfectly fine to take visa appointments anywhere in India, as long as you mention the same city on your DS-160. In case you have already submitted the DS-160 and then see no dates available in your city of choice, or if you need to correct and/or update information, you can select the “Retrieve an Application” option on the site where you filled the form, enter your previous visa application ID, and then select “Create a New Application”. Your personal information will then populate into the new application. In the new application, update the details and proceed further. Applicants who have completed a new DS-160 after scheduling an appointment are required to carry both the old and new DS-160 confirmation pages to their Visa Application Center appointment for biometrics. 

At the Kolkata consulate, I was given a few minutes to explain my current research in IISc and future research in USA, and I was told that further administrative processing would be needed before they could grant me the visa. They kept my passport, and handed me a form which stated that my application was pending under section 221G, and I needed to email them a detailed word document describing my current research as well as proposed research in USA and its practical applications, following which I would get my visa in 2-4 weeks. Two other postdoctoral candidates at the consulate were also given the same form, and this is pretty common for researchers working in fields belonging to the ‘Technology Alert List’ that includes biomedical research, nuclear physics, chemical engineering among others. After a very tense and frustrating wait where I kept imagining the worst case scenario (that my visa would get rejected), I finally got my visa after 3 weeks 🙂

Take home message – Visa processing takes time, but it is rarely rejected.

 

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Awanti has done her PhD in Systems Biology at the Indian institute of Science,Bangalore, and will be joining the University of Michigan for postdoctoral research. She identifies as a compulsive chatterbox

Of clothes, clocks and lice

in SciWorld by

We humans are the only species who wear clothes. And, it is obvious that we are obsessed with clothes – about the designing, making and procuring of clothes and materials that are used to make clothes. As the ‘Page 3’ would testify, we are fascinated about who wears what, and also who did not wear what!!

But, how did it all come about? What were the first ‘baby’ steps? When did we start wearing clothes?

The trouble with this kind of investigation is the paucity of ‘hard’ evidence. Clothes, unlike bones, do not fossilize, and unlike stone and metal, they perish fast. Thus, except under special environmental conditions in which some paleo-humans (such as iceman Ӧtzi) have been unearthed, the direct evidence of prehistoric clothing is scanty and so the origins of clothes have been lost in the mists of Time.

But, as always, there is evidence – it is only about properly looking for it. In this case, the evidence lies in the well-known pest – the human louse.

THE PEST FAMILY

Almost all mammalian and avian species are host to various species of lice. But, humans are among the few species that are host to, not one, but 3 species (or subspecies) of lice! The human head louse (Pediculus humanus capitis), the body louse (P. humanus corporis, also considered P. humanus humanus) and the pubic louse (Pthirus pubis) are obligate ectoparasites (Figure 1) to the human body and cannot survive on other species, including pets. Head louse are slightly smaller in size than body louse and usually have a darker pigmentation. There are subtle differences in the lengths and widths of the antennae and the front legs. But, not surprisingly, the head louse and body louse have considerable morphological similarity. Their main difference lies in the choice of habitat.

fig-1

The head louse is a blood-sucking insect that lives only on the head scalp and lays eggs only on scalp hair. The body louse, in contrast, doesn’t venture towards the head. It feeds from the skin and notably, it lives and lays eggs in human clothing. The head louse and the body louse are fastidious about their habitats – neither encroaches into the other’s ‘territory’ (in fact, the head louse cannot live on clothes). And, neither species can survive away from a human host for long – the head louse perishes within 24 hours, while the body louse (which reside on clothing) can live without human contact for about a week. Noted biologist Mark Stoneking (Figure 2) – who had already made a name for himself by studies on the ‘mitochondrial Eve’ – got interested to study the migration of these obligate parasites across the globe hoping that would lead to insights about human migrations. Stoneking hypothesized that the head louse was the ancestral species and body louse have evolved from head louse only when a new ecological niche got available – in the folds and creases of human clothes. When did this happen? – the most likely answer is when humans started regular wearing of clothes. This leads to the intriguing possibility that finding out the time when the body louse evolved from head louse would (by inference) correspond to the beginning of extensive use of clothing by ancestral human populations. The answer, as was elegantly shown, lay in using a molecular clock approach to calculate the origin of body louse.

 

fig-2

BOX: What is a molecular clock?

The molecular clock is a method to determine when 2 species/ sequences diverged from a common ancestor. It is based on the principle that, as time passes, random errors/substitutions take place during DNA replication and get transmitted down the generations. More the time since the 2 sequences diverged greater the number of differences between them (as substitutions happen independently). Thus, if the ‘number of substitutions per million years’ is known, it is possible to estimate how many years have passed since the 2 sequences had a common ancestor. This calibration can be done by knowing the number of substitutions that have accumulated in 2 DNA sequences whose divergence-time is actually well-established from other lines of evidence, for eg, fossil record. Assuming the error rate stays constant across time and in different species, this allows to calculate the unknown time points (Figure 3).

fig-3

THE GENETIC TALES OF THE LICE…

The molecular clock for dating the evolution of lice was built by using 2 mitochondrial DNA and 2 nuclear DNA segments. To avoid any bias in their investigation, the scientists collected lice from 12 geographical regions – Ethiopia, Panama, Germany, Philippines, Iran, Ecuador, Laos, Papua New Guinea, Florida (USA), Taiwan, Nepal and the United Kingdom – and extracted nuclear and mitochondrial DNA. They also collected DNA from chimpanzee head louse. Since it is well known that hosts and their parasites often co-evolve, it was assumed that the chimpanzee louse (Pediculus schaeffi) and P. humanus must have co-speciated with their respective hosts, and this must have happened at around 5.5. MYA – the scientifically-established period when humans and chimps diverged. Thus, the differences between DNA sequences of chimp louse and human head louse must have accumulated over 5.5 million years. Using this specific time period as a calibration point for the clock, the time when head louse and body louse diverged could be estimated.

For the sequence analysis, Stoneking’s group first analysed segments of the genes ND4 and CYTB present in mitochondrial DNA of the louse. They followed it up with comparative sequence analysis of 2 bits of nuclear sequence – from the important genes of elongation factor EF-1α and RNA polymerase II subunit RPII. The size of fragments ranged between 400-600bp. The results obtained were fascinating to say the least.

The first result (Table 1) showed that genetic diversity of the African louse (although collected only from Ethiopia) is significantly greater than the global samples of non-African louse. The finding mirrored the greater genetic diversity of humans seen in Africa compared to that in other continents. Since greater genetic diversity almost invariably occurs at the source, the results indicate, as in the case of humans, the African origin of the human louse.

Table 1: Comparing genetic diversity of African versus Non-African lice (adapted from data present in Kittler et al (2003))

Genetic Diversity

African louse Non-African louse
mtDNA 3.31 1.76
EF-1α 0.29 0.10
RPII 0.94 0.56

 

The next set of results (Table 2) similarly showed that human head louse was far more genetically diverse compared to its cousin, the body louse – proving that the head louse was the ancestral species.

Table 2: Comparing genetic diversity of Head louse and Body louse (adapted from data present in Kittler et al (2003))

Genetic diversity

Head louse Body louse
mtDNA 3.42 0.19
EF-1α 0.23 0.18
RPII 0.93 0.61

 

(BOX: A few definitions: Phylogenetic tree: a tree-like diagrammatic representation that describes the evolutionary relationships between the organisms/sequences being studied (Figure 4).

fig-4

Monophyletic sequences: Two or more DNA sequences that have evolved from a common ancestral DNA sequence.

Clade: A group of monophyletic sequences that consists of all the sequences included in the analysis that are descended from the ancestral sequence at the root of the clade.

Outgroup: a homologous sequence that has originated from a common ancestor as the sequences under investigation, but is not as closely related to the being-studied sequences as they are to each other. In this case, the DNA from chimp louse serves as an outgroup and helps to locate the root of the tree)

 

THE FINGERPRINTS ON THE TREE…

Next, a phylogenetic tree was constructed using all these mitochondrial sequences of human lice (Figure 5). The tree showed presence of number of clades. The deepest clades contained only head louse sequences, confirming that body louse had originated from head louse. Notably, one particular clade contained all body louse and 16 head louse sequences and included samples from all over the world. The molecular clock, calculated using the sequences from the chimp louse as an outgroup, showed that this clade is 72000 +/- 42000 years old. Since it contained all body louse sequences, the estimated age of this clade has to be the upper limit for the time since body louse originated. And, since body louse exclusively inhabits human clothing, this must be the time period when modern humans started regular use of clothes.

fig-5

Very similar results were obtained from studying the nuclear sequences, in spite of the fact that DNA recombination can make such analysis difficult compared to that for mitochondrial DNA. As a final piece of evidence, Stoneking’s team also analysed parts of the Cytochrome oxidase (COX) gene, also present in mitochondrial DNA and showed that the results were in agreement with that obtained from ND4-CYTB i.e. anatomically modern humans, residents of Africa, started wearing clothes around 70,000 years ago.

In a latter study, David Reed’s group from the University of Florida carried out a more robust analysis using a Multilocus Bayesian isolation-with-migration coalescent method and concluded that body louse had diverged around 170,000 years ago, and certainly not after 83,000 years ago. The difference between the two sets of data is not surprising given the different methodologies used (moreover, Reed et al also used 18S ribosomal RNA from louse nuclear genome for their analysis), but they are in broad agreement. Importantly, both conclude that the body louse evolved in presence of anatomically modern humans in Africa because of the availability of a new ecological niche – clothes.

But, what if clothing originated much earlier, and louse colonized this ecological niche later? This is an intriguing possibility and cannot be discounted entirely. Stoneking et al believe that, since a new ecological niche is colonized fairly rapidly, it is unlikely that clothing could have existed for thousands of years before body louse occupied it. Indeed, the molecular data also corresponds well with the archaeological finding that the earliest eyed needles – the only prehistoric tools that can be definitely associated with clothing – are ~ 40000 years old, and they have been found only in settlements of modern humans and not archaic humans like Neanderthals.

TO SUMMARIZE,

The genetic and archaeological data converge on the conclusion that the chimp louse and the human head louse are close cousins who must have originated from a common ancestor. The human head louse got confined to one relatively small habitat (i. e. scalp) when ancestral humans lost significant amount of body hair/fur ~1.2 million years ago. However, sometime between 70,000-170,000 years ago, anatomically modern humans started stitching and wearing clothes and the lice could now colonize a new niche. Indeed, it is quite possible that clothing protected the modern humans against the vagaries of environment and allowed them to explore the world out of Africa ~50000-80000 years ago – a time period that has been validated by the latest studies. And, along with humans and their clothes, the human lice have spread across the globe.

 

POSTSCRIPT:

Not surprisingly, this is not the end of ‘louse research’. Lice found in 1000 year-old Peruvian mummies have subsequently given insights into how and when humans migrated to the New World…..just imagine the unearthed treasury if we could genetically score for lice present in the various populations of the Indian subcontinent.

 

ACKNOWLEDGMENTS:

Prof. Mark Stoneking; Eugene Dubois Foundation.

 

REFERENCES:

  1. Kittler, R., Kayser, M. and Stoneking, M. (2003) Molecular Evolution of Pediculus humanus and the Origin of Clothing. Biol. 13, 1414-1417.
  2. CARTA: Unique Features of Human Skin – Mark Stoneking: The Molecular Evolution of Human Lice https://www.youtube.com/watch?v=S9rl8o8cGZ8
  3. https://en.wikipedia.org/wiki/Louse
  4. https://en.wikipedia.org/wiki/Head_louse
  5. https://en.wikipedia.org/wiki/Body_louse
  6. Whitfield, J. (2003) Lice date first human clothes. http://www.nature.com/news/2003/030818/full/news030818-7.html
  7. Toups, MA. et al (2011) Origin of Clothing Lice Indicates Early Clothing Use by

Anatomically Modern Humans in Africa. Mol. Biol. Evol. 28, 29-32.

  1. Choi, CQ (2011) Humans Got Lice When We Clothed Our Naked, Hairless Bodies. http://www.livescience.com/9225-humans-lice-clothed-naked-hairless-bodies.html
  2. Choi, CQ (2008) Lice Shed Light on Ancient History of Americas. http://www.livescience.com/2291-lice-shed-light-ancient-history-americas.html
  3. https://en.wikipedia.org/wiki/Ӧtzi#Clothes_and_shoes
  4. Venkateswaran, TV (2011) Clothing is distinctly human. But how old is it? http://beta.bodhicommons.org/article/clothing-is-distinctly-human-but-how-old-is-it
  5. Eugene Dubois Foundation, Eijsden, The Netherlands http://www.eugenedubois.org/en/lecture-by-mark-stoneking-archaic-genomes-and-insights-into-human-evolution/
  6. Zimmer, C. A Single Migration From Africa Populated the World, Studies Find. New York Times, Sept 21, 2016. http://www.nytimes.com/2016/09/22/science/ancient-dna-human-history.html?_r=1

Featured Image source: http://imgur.com/gallery/2ELegP1

Author Profile:

for sciwri

Anirban Mitra, Ph.D

Anirban Mitra did his PhD from the Department of Microbiology and Cell Biology, Indian Institute of Science (IISc), Bengaluru and is now a teacher of biology, based in Kolkata. His interests range from biological evolution to history of science and facets of India’s past.

 

 

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From writing to reviewing…. my story, my experience

in SciWorld/That Makes Sense by

bh_doskcmaeh_bm

 

Image source:“Piled Higher and Deeper” by Jorge Cham www.phdcomics.com

How to write a scientific article for a journal? Does writing require training? Does the training come with experience or does one take courses for that? How does one write it so that lucidity is maintained and the scientific message is still conveyed straight across? How much does writing PhD thesis help beforehand?

 

As any other beginner I had the same questions with my first-ever scientific article as a 2 years old PhD student at the Max Planck Institute for Biology of Aging, Cologne, Germany. I was still figuring out best ways to interpret results, optimize protocols, and busy learning new things, when I was invited by my boss to participate in writing a review. On the one hand, I was overwhelmed with joy at the opportunity to face this new challenge. On the other hand, I was confronting the pressure to prove my writing skills not only to my ambitious and detail-oriented supervisor but also to my ambitious self. The task was made easy by two facts. First, it was an invited review from the journal, and was supposed to be short. Second, my highly organized supervisor divided the review into two equal parts and allowed me the option to choose mine. I chose the introduction and the first topic. She was responsible for the last two topics. Since I was naïve I decided to follow directions. I was first directed to read up past and current literature regarding my parts and draft a very rough plan on what I was going to write and whom I was going to cite (with proper justifications regarding the latter). I had strict time limits and needed to fulfill this task within two days. This strict deadline helped me to be structured and to streamline my reading. After getting a green signal on the rough draft, I was given a week to hand over the final draft. I had to make sure I read most of the articles I cited, followed a scientific diction of that from leading journals, and that it made a smooth reading. It felt like a herculean task as a beginner and required utilizing all my scientific fervor and burning my night oils. First of all, I read up reviews written by my supervisor, just to have an idea of her writing so that the review doesn’t read completely foreign when both the parts are combined as a final article. I made sure that I stayed close to the topic and included past and current knowledge as well as discussed contradictions wherever applicable. Of course flair for writing and a bit of talent was necessary to fulfill the task in that short time. Her honest feedback and constructive criticisms were very beneficial, and it was a huge relief to hear that it was well written. After combining both the parts, we still went through several editing sessions, which is part of the ball game anyway. Finally, it was accepted and published, without a single correction or suggestion from the editor. That was a big exercise!! Looking back at that article I always feel a sense of accomplishment, as it smells the sweet fragrance of my hard work and learning.

 

The next challenge was to write my first manuscript ever during the first few months of my Post Doc. This was now a different lab than my PhD lab. Two things helped again. First, by this time I had finished my PhD, hence by now I was a pro in literature survey, and second, I already went through the review writing and thesis writing. As anyone else would do, I started first with writing the results part and prepared the figures. Preparing figures with the adobe illustrator was a part of my PhD learning, hence it was easy now. Next, I wrote the easiest part, the materials and methods. The introduction was a bit challenging because I was pretty new to the topic and needed to read up past and current literature, but having written the review on a strict time schedule helped. The challenge was the discussion because I needed to discuss all past and present contradictions, conundrums and speculate possible mechanisms. Another point was the format. In certain journals, the discussion is written like one long story, putting the results in a bigger perspective. In some others, each result is discussed under a separate heading. Hence, I needed to first decide which journal we were going to communicate this manuscript to, in order to be able to choose one format over the other. Since ours was a specific topic, hence we narrowed down to a few journals dealing with this topic. Next, we chose the one that was closest to our interest in terms of peer review, audience spectrum and impact. I then wrote the discussion according to the norms of our chosen journal. In all, I took a good one month in preparing the entire manuscript for this journal. The manuscript writing was a fun learning, more so because my Post Doc supervisor gave me complete freedom to explore my writing skills. She edited and improved certain parts but thankfully the overall story was narrated in my style and therefore I feel a strong ownership to this one. The story has just been accepted!

 

The most recent learning however has been the review of another manuscript. Many PIs request their senior PhD students or post docs to review a few articles to relieve some workload. I look at it as a symbiotic act because the post doc gets trained to be objective, improve his/her analytical skills and becomes even more critical without being biased and the PI saves his/her time. Since I had no experience or opportunity in reviewing during my PhD, I had once mentioned it as one of my interests to my Post Doc supervisor. One fine day, she gave me an article to review and I took this task happily to my stride. I was naïve, therefore, my boss advised me to judge the following points in the manuscript:

  1. If the abstract is making justice to the title.
  2. Is the introduction justified, too long or too short according to the journal norms?
  3. Are the experiments performed with proper controls, if statistics are sound, if the conclusions are drawn well or are there over interpretations?
  4. Are the techniques sufficient to answer the question or other ones could have been used?
  5. Have they discussed adequately.

I took into account all the above points. Since the manuscript was a small story and was quiet close to our field, it was easy to judge as a beginner. Ideally speaking, a Post Doc is not a beginner in reviewing anymore. By this time he/she has critically evaluated his/her own data, has discussed the data of peers during lab/departmental seminars and has attended numerous scientific talks from speakers around the world and hopefully participated in stimulating scientific discussions. It is only that one has not penned down the critical points in a structured manner. Hence, I began. It was not too difficult to find the strong points of the story as well as the deficiencies. First of all I wrote down what kind of controls or experiments were missing. Next I checked if the techniques they used were justified, if not, what else could have answered their question better. I spotted the over conclusions/under statements in their data as compared to the numbers on their graphs. And finally I assessed the contribution of their work in the field by doing a little bit of background check on the exact topic. I wrote down all the above points in a well-structured way and discussed with my boss, who also came up with her own judgment. Finally, we came to a unified conclusion and she gave the verdict.

Overall, it was a very unique experience to be on the other side of the coin, to be able to be unbiased and critical and to be able to judge as a peer.

 

So this was my small journey with my baby steps from writing a review to writing my first manuscript and to reviewing a small article. With these steps I not only came to realize my interests in scientific writing, but also that we all can learn new things and venture into the unknown if we are passionate, determined, and focused. And yes, every single small step counts! I hope that, through my tiny story, I could somehow inspire the beginners and the skeptical. So….what are you waiting for? Grab the opportunity or create one!

sushmita-headshot

About the author: Sushmita Ghatak completed her PhD from Max Planck Institute for Biology of Ageing (Cologne, Germany) in 2015. As a graduate student, she worked on the role of the ageing niche in regulating skin stem cell homeostasis. She is currently a postdoctoral fellow at Uniklinik (Cologne). She is exploring the domain of skin wound healing and fibrosis by studying the role of collagen binding integrin receptors in skin homeostasis.

 

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Ten years of sailing aboard a cockroach

in SciWorld by

The story of the cockroach milk protein started about a decade ago with the ‘curiosity of discovering’ and continues with the ‘curiosity of understanding and developing’. While observing these minute crystals inside the embryos of pregnant cockroach females, little did Nathan or Prof. Ramaswamy know that one day it will be popularly known for being the future protein supplement. During these years, while all the authors of the paper collaborated towards the understanding of the protein, we all marveled at the Biology of these cockroaches and the fascinating crystallographic features that the milk proteins exhibited.

cockroach-birth

Image: Diploptera punctata cockroach (source: livescience.com)

Generally, As an advantage for the organisms, the proteins are under negative natural selection pressure for crystallizing inside their cells. However, the knowledge of several proteins crystallizing inside an organism (in vivo, either in cellulo or ex cellulo) is also known. These proteins are proposed to be under positive selection pressure for crystallizing in vivo with functional importance. The crystals observed by us in the Pacific Beetle cockroaches, usually found near Hawaiian regions, are one of the examples of in vivo crystals. Cockroaches are known to be very sturdy organisms having survived for over 300 million years. During this period, one of the features that it has evolved for higher survival chances is its nature of reproduction. There are three types of reproduction found in the cockroaches; oviparous (eggs-laying), ovo-viviparous (fertilized eggs laid in maternal brood sac without her nourishment) and viviparous (fertilized eggs with maternal brood sac protection and nourishment). The pacific beetle cockroach, scientifically known as Diploptera punctata, is the only known viviparous cockroach till date which gives birth to the young ones like mammals and provides nourishment to the developing embryos. In-keeping with the nomenclature of “milk” used for the maternal nutrition in new-born of mammals, the nourishment provided to the embryos in these cockroaches is also termed the same. The brood sac of the pregnant females secretes this ‘cockroach milk’, which is taken up by the embryos. As the embryos continue to drink the milk, there is a surplus of the protein in their gut. This excess amount is stored inside the embryos’ gut in the form of crystals, which maintain equilibrium with the liquid milk in solution that is readily available to be ingested. Storage of food in the form of crystals allows for a high concentration of food to be stored as well as controlled release of nutrients as needed by the embryos.

Cockroach crystals

Image: From the research article jt5013, showing in vivo-grown Lili-Mip crystals from D. punctata. Polarized microscopy reveals birefringent protein crystals enclosed inside the embryo midgut and an enlarged view of the extracted crystals (inset).

In vivo crystallography is one of the new facets of Structural Biology that deals with structure determination of in vivo protein crystals. Apart from naturally occurring crystals, scientists have also engineered a baculovirus based system to induce in vivo crystal formation. Recent advancements in X-ray free electron lasers (XFEL) and serial femtosecond crystallography (SFX) have resulted in the increase of structures from in vivo crystals. One of the major challenges of in vivo crystallography has been the size of the in vivo-grown crystals that are limited by the volume of the cells that are usually of the micro-nanometer range. However, since these crystals were formed in the gut of the embryos, their sizes were not limited by cellular volumes and were comparatively larger. Therefore, single crystal X-ray diffraction was possible but obtaining the phases of the atoms was tricky. The structure was finally solved using sulfur single wavelength anomalous dispersion method. The protein is a lipocalin with β-barrel forming the lipid binding pocket and a single α-helix. Mass spectrometric and crystallographic studies revealed that each crystal was a heterogeneous mixture of not just multiple protein sequences, but also the sugars bound to these proteins in the form of glycosylation and the fatty acids bound at the binding pocket. More than three sequences of similar proteins (85-95% sequence identity) were found in these crystals. Additionally, multiple N-linked glycosylation sites (3-4 sites) with pauci-mannose and high-mannose structures and variable branching were observed. Further, the fatty acid bound at the pocket was found to be either an oleic acid or linoleic acid. With such an extent of heterogeneity, we were amazed to see that the crystals diffracted X-rays to atomic resolutions of 1.2-1.8 Å.

 

Generally, in macromolecular X-ray crystallography the rate-limiting step is the crystallization of proteins and obtaining good quality crystals. Usually, when we purify and crystallize recombinant proteins in vitro, we make several modifications such that the protein solutions are homogenous and monodisperse. This usually drives the protein away from its native state in which it naturally occurs. Further, proteins with post-translational modifications have been observed to be heterogeneous and mostly polydisperse in physiological conditions. Hence, when we make these proteins in vitro, we tend to remove all possible glycosylation to enable crystallization of the protein. The high-resolution diffraction of the milk protein crystals and its successful structure determination is till date the first structure reported with this amount of heterogeneity. The precise role for heterogeneity optimized for crystallization in a single lattice is currently unclear. Understanding the molecular structure of these in vivo grown milk protein crystals enables us to appreciate the evolution of viviparity in these cockroaches.

 

Analysis of the calorific value of these crystals shows that it has three-four times more the energy provided by the equivalent masses of cow, buffalo and other mammalian milks. This cockroach milk protein with proteins, sugars and lipids is a complete food for the embryos. The heterogeneity in the protein sequences provides all the essential amino acids to the embryos. The knowledge of the high energy values gave us an idea that if we produce these milk proteins in vitro in yeast, these recombinant proteins could be used for human consumption as a protein supplement. The curiosity still continues and we hope that this wonderful system can be used for multiple innovations in the future.

Below is the table showing comparison of milk calorific values:

Species

kcal (per 100 g)

Lili-Mip

230-300

Cow

66

Goat

60

Sheep

95

Water Buffalo

110

Human

72

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About the author: After completing her Ph.D. from Molecular Biophysics Unit, Indian institute of Science in 2014, Sanchari worked in Syngene International Limited for a very short time. Then she joined the Institute of Stem Cell Biology and Regenerative Medicine (Bangalore, India) as a postdoc. Since the time of joining she has been involved with the cockroach milk protein project. The other areas that interest her are in teaching and education. Her hobbies include dancing and cooking.
To know more, read her paper here: jt5013

Maria Sibyllia Merian, who rendered science pretty

in SciWorld/Theory of Creativity by

Maria Sibyllia Merian was an illustrator and entomologist (1647-1717). At a time when education was scant for women, she learnt miniature painting from her step father. She used this skill to depict her observations on insect metamorphosis across a variety of specimens. Her work contributed to the shift in belief from theory of spontaneous generation prevalent at the time. She travelled to the forests of Surinam where she spent six years studying insects and plants. She worked at a time, when illustrations were the only ‘photographs’ available. For financial support, she sold her work as art and published books. Linneaus later used her work to classify insects. Here are recreation of four of her plates.

maria betonien rose 1

Bentonein rose

 

maria chocolate tree

Chocolate pod

maria lime tree with butterfly

Lime tree with insect metamorphosis

maria insect of surinam

Insect metamorphosis

 

While Maria used copperplate etching for her illustrations, here Adobe illustrator software has been used to revisit those.

 

IMG_20151008_111034_1444282874501

About the illustrator: Ipsa is pursuing a Ph.D. at Indian Institute of Science. She loves to draw and paint. Biologist by training. Wants to gather and spread interestingness.

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The Earliest Englishman who never was

in Sci-Pourri/SciWorld by

 

Piltdown_gang_(dark)

    • 1912 – the meeting of the Geological Society, London. Charles Dawson, an amateur anthropologist, stuns the world by presenting bone fragments which, he claims, are that of an extinct species of ancestral humans!
    • The find – from a gravel pit at Piltdown village of Sussex – includes parts of a skull and lower jawbone, a canine and prehistoric tools made from bones. They are estimated to be about half a million years old.
    • Arthur Woodward, head of the department of Geology of the Natural History Museum, reconstructs the skull and announces that it had belonged to a ‘missing link’ between apes and humans – it is named Eoanthropus dawsoni, after the discoverer.

piltdown-image-1160x435

    • The crux of the discovery is that the skull indicates that the brain size would have been about two-thirds that of a modern human. It is quite similar to a human skull, except for the occiput (the part of the skull that sits on the vertebral column). BUT, apart from two human-like molar teeth, the jaw bone is identical to that of a modern, young chimpanzee.
    • ‘Piltdown Man’ stuns the world. And the British rejoice. Many of them had been sad that no fossils of ancestral humans had been unearthed in the British isles, while Neanderthals and Cro-Magnon fossils had been found in Germany and France respectively. Now, here is THE EARLIEST ENGLISHMAN AND THE EARLIEST EUROPEAN.

PSM_V82_D210_Reconstruction_of_Eoanthropus_dawsoni

    • And of course, Piltdown Man is an EURASIAN and not of African origin. [in the days of colonial imperialism and racism, Darwin’s 1871-hypothesis that human origins lay in Africa had caused much controversy; here was proof that Darwin had been wrong].
    • And the evidence nicely fits into the predominant hypothesis that the cranium had evolved first followed by jaws i.e. the large brain preceded the omnivorous diet . That also implies that the British were the ‘first to be smart’ and the first to start eating like humans, not beasts.
    • And Piltdown Man loved sports too – a sculpted elephant bone, discovered alongside the skull and jaw, is even interpreted as being the prehistoric cricket bat!
    • But, not all is rosy – many scientists, including the famous anthropologist Sir Arthur Keith, are skeptical (some of them in continental Europe and the US had ‘extra-academic reasons’ to be so too). And even The Royal College of Surgeons demonstrates that the bone fragments can be reconstructed differently such that it’d be identical to a modern human skull.
    • It is even suggested that the skull bones and the jawbones belonged to two different species and had accidentally come in close juxtaposition in the pit!
    • Besides, could an ape-like canine snugly fit into a jawbone that had human-like molars?   Scientists doubt – heated debates rage.
    • But, in 1915, Dawson discovers 3 more skull fragments from a site 2 miles away from Piltdown. And they look convincing. Now, even skeptics have to accept the data…grudgingly.
    • Dawson dies in 1916. Woodward digs more, but the Piltdown pit has nothing more to unearth.
    • Over the decades, more fossils come up – predominantly in Africa…and the line-of-evidence they present is rather different from the Piltdown Man. ‘He’ seems to be a strange, ill-explained aberration – almost an outlier…odd…funny…but, 40 years go by…
    • November, 1953. TIME magazine publishes the findings of Kenneth Oakley, Sir Wilfrid Le Gros Clark and Joseph Weiner. The article is titled ‘End as a Man’. Using the latest techniques, including Fluorine absorption dating, the trio proves that the Piltdown Man is a forgery.
    • The paleoanthropological hoax-‘fossil’ is a composite of bones from 3 species – a medieval-era human skull, a medieval-era orangutan’s lower jaw and fossilized teeth of a chimpanzee!!!
    • They were made to look prehistoric by staining the bones in a solution of Iron and Chromic acid.
    • Microscopic examination of the teeth shows file-marks – they had been modified as if they used to chew a human diet – Eoanthropus dawsoni had never existed. It was a scientific fraud, crafted with sinister care and then deliberately thrown at the world.
    • WHODUNIT?? – more than a century later, it is still unclear. Dawson was certainly involved (later investigations showed that many of the antiques and artifacts he had collected were hoaxes – a serial bluffmaster ? ), but probably there were others too.
    • WHY? – no one knows. Perhaps Dawson, an amateur, yearned for international recognition – maybe fellowship of the Royal Society….we will never be sure of the motive…
    • What had been achieved? People – researchers and commoners – had wasted a LOT of time and money and enthusiasm had been funneled into a ‘blind lane of knowledge’ for years. An estimated 250+ papers had been written on the topic!
    • No use at all? – well, it shows science can never compromise on its stringency – especially when cultural, natural or ideological emotions and the pursuit-of-glory may tend to cloud judgment. A successful hoax is one that ‘presents what one expects to see’ – and the Piltdown Man was just that.
    • And, of course, the great thing is that it was rigorous science that finally unearthed the hoax.

Author Profile:

for sciwri

Anirban Mitra, Ph.D

Anirban Mitra did his PhD from the Department of Microbiology and Cell Biology, Indian Institute of Science (IISc), Bengaluru and is now a teacher of biology, based in Kolkata. His interests range from biological evolution to history of science and facets of India’s past.

*This blog summarizes the findings from the research articles that can be found in this link. http://www.clarku.edu/~piltdown/map_prim_suspects/ABBOTT/Abbot_defense/piltman_englishmystery.html

*The overall conclusion derived from these studies have been voiced at the website of Natural History Museum http://www.nhm.ac.uk/our-science/departments-and-staff/library-and-archives/collections/piltdown-man.html

One man’s Junk is another man’s treasure or the secret art of cellular talking

in SciWorld by

Like begets like. And so bags of membranes shed other bags of membranes. A cell during its course of its short (or long) tortuous life is expected to shed membranous structures. After all it is the primary container in which all life processes are carried. Does this process have a higher purpose is a question that had been pondered over and decided that it must be how the cells get rid of unwanted stuff. A few years ago, If I were offered to investigate these cellular garbage bags, my answer would have been an enthusiastic “Thanks but No thanks”.

Rit2 Rit1

 

(Image courtesy Johan Skog and Casey Maguire, Massachusetts General Hospital. I have met Johan, who is a wonderful person and is the CSO of exosome diagnostics.)

 

And hence I focused on disparate variety of things with no relations to the above, specifically on how neutrophils co-ordinate movement in complex tissue spaces. Neutrophils are the SWAT teams of the body. They are the first emergency responders that reach the site of a pathogen attack or injury to initiate a wide variety of inflammatory responses. Their modus operandi can be described right out of a scene of CSI. A police officer patrolling the highway smells a faint smell of smoke. He turns his head to detect the direction of the smoke and determines to be coming out of the wood. He decides to go into the wood to investigate, and in the meantime calls for a backup. He fears his backup wouldn’t know the direction he has taken into the woods and decides he should light up flares as he goes. As he approaches the scene of crime, shots ring out and he is fatally wounded. Before he dies, he shoots his flare gun into the air and calls for help from the backup that has arrived in wood’s edge. Seeing their comrade dead, the crack police team come out with guns blazing shooting down any one in their path.

Rit3

Now replace the officer with neutrophil, smoke with bacterial peptides released by a pathogen, highway as the blood vessel, wood with interstitial tissue space, guns with the deadly neutrophil proteases. What was not known till a few years ago, is the nature of the flares or simply put how does neutrophil coordinate during subsequent neutrophil swarming during an inflammatory response. The answer turned out to be a rather unintuitive molecule called leukotriene B4 or LTB4. I call the molecule unintuitive not because it is not a potent molecule, it is one of prime targets in asthma medication, but because it is a lipid. And that is a problem. Let me illustrate.

In a perfect world, neutrophils sense a gradient of chemoattractant (e.g. Bacterial peptide) and move towards a region of higher concentration, a process that is called chemotaxis. In situation where the gradient is too shallow for the following cells to detect, it would release a second molecule which now can diffuse far and wide to recruit other neutrophil, hence increasing the range of response. This phenomenon was dubbed as signal relay. This second molecule was found to be LTB4. But being lipid it doesn’t diffuse well. It does not play very well with aqueous environment of the tissue and of course, it would not create a defined gradient (remember neutrophil can find its way by comparing differences or gradients of attractants in space). Unless of course there is something that facilitates in doing its job.

 

Rit4

(from New paradigms in the establishment and maintenance of gradients during directed cell migration Current Opinion in Cell Biology, Volume 30, Pages 33-40 Ritankar Majumdar, Michael Sixt, Carole A Parent)

We started to find the facilitator by trying to locate where LTB4 was in the cell. We traced the location of the site of its active synthesis by mapping the proteins that were responsible for making this molecule. We found that these proteins were localized on atypical vesicular structures not found in a neutrophil’s natural repertoire. We took a very close look and found these were special bags-in-a-bag arrangement called multivesicular bodies. These are big bag that contains smaller bags which under certain conditions fuse with the cell membrane and release their content of smaller bags. These released smaller bags (or vesicles if you may) are called as exosomes. After painstaking ultrastructure sectioning of neutrophils migrating towards a bacterial tripeptide, we deciphered a series of events showing the genesis of the bag at the nuclear envelope to the fusion with the plasma membrane releasing smaller vesicles.

The rest of the story comprises of relatively boring monotonous sequence of validating the hypothesis by purifying exosomes, quantitating their content, knocking down the production of exosomes and their effects in chemotaxis etc. But one of the key insights came from a form of mixed cell experiments where we found cells talked to each other while they migrated. They talked through LTB4 by releasing them in exosomes. Without them the cells lose their sense of directionality. Without exosome, the dying police officers would have shot a very short feeble flare that the other police officers would have never seen. The exosomes acted as molecular beacons to the guardians of our body.

Rit5

 

 

 

Very few engaged in biological research would believe exosomes to be the garbage bag of cells. They have been shown to be carrier of extracellular miRNA, they can transfer genetic material between cells, and even active proteins. They have been heralded as the best candidate for liquid biomarkers in cancer especially in glioblastomas where getting biopsies mean boring through your skull or spinal cord. Researchers who work with exosomes have an immensely difficult task of unravelling these microcosm of things, especially when one encounters the very fundamental question of “Did I just purify exosomes or some other stuff that the cells throws out?” The lack of standardization of markers and the tedious pain-in-the-butt purification process pose additional challenges. (It took ~ 500 ml of blood to purify ~ half a billion neutrophils to yield ~ 50-100 ug of pure exosomes)

All said, working on exosomes gives a feeling that a genome researcher would have felt in the last decade of the last millennia or the geneticist of the last century. The path to research is full of promise and is littered with red herrings, where paradigms change in matter of days and the rule of the game is that there is no rule. For me the moral of story is that One man’s junk is other man’s treasure. Literally.

Rit6

(From Exosomes: secreted vesicles and intercellular communications, an excellent article by Clotilde Thery)

A few good reads and see.

One of my favorite video made by David Rogers in 1950s. This gives an idea of the persistence of a neutrophil chasing a bacterium. https://www.youtube.com/watch?v=I_xh-bkiv_c

An excellent review on leukocyte migration. For advanced readers I am afraid http://www.nature.com/nri/journal/v14/n4/full/nri3641.html

The finding of evidence of signal relay in neutrophils and how LTB4 plays a critical role. http://www.cell.com/action/showRelatedArticles?pii=S1534-5807%2812%2900084-6

The reason why I am writing this piece. “Exosomes Mediate LTB4 Release during Neutrophil Chemotaxis.” http://journals.plos.org/plosbiology/article?id=10.1371/journal.pbio.1002336

Richard Robinson has done a wonderful job of explaining the findings in the above paper in layman terms. “To Attract Others, Immune Cells Release a Packet Which Releases a Signal” http://journals.plos.org/plosbiology/article?id=info:doi/10.1371/journal.pbio.1002337.

An excellent review on the current standing and status of exosome research by Clotilde Thery. http://f1000.com/prime/reports/b/3/15

About the author: Ritankar Majumdar is a Post-Doctoral fellow at the National Cancer Institute, NIH. He has been trained as a biochemical engineer, although after completing his thesis on  structure-function relationship of GPCRs from IISc, he refuses to identify himself as an one. He enjoys working on complex chemotactic systems, good music, decent food and living the fresh breathe of science.

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Conformational selection in vision

in SciWorld by

Kaly1

The moment we step into an unlit room from sun we are blinded for a couple of seconds. After some time our eyes adjust to the low light and then we can see in the dark room. This is because the light sensors in our eyes, the rhodopsin molecules, go on overdrive in presence of strong light. The importance of the adapter protein recoverin lies in the light-adaptation mechanism. In presence of excess light, when the cellular calcium concentration is high, recoverin binds the amino-terminal helix of rhodopsin kinase. The amino-terminal helix of rhodopsin kinase is required for reactivating rhodopsin so that it can sense light. This plugging action by recoverin on rhodopsin kinase prevents over-excitation of rhodopsin, allowing us to adjust to the low light level. How does recoverin bind rhodopsin kinase? The recoverin structure clearly changes upon binding rhodopsin kinase. Does the structure change due to binding, or, recoverin has a minor conformation which the rhodopsin kinase binds selectively? In order to answer this, the first step is to look at the structures.

In the morning of 10th January, 2016, the Protein Data Bank contains a total of 114741 structures of biomolecules. The majority of this high resolution structural information comes from x-ray crystallography. The other major technique that contributes high resolution structural information is nuclear magnetic resonance (NMR) spectroscopy. This huge number of protein structures point to the power of structural biology. However, some scientists think that the large number can give us a false sense of complacency. They argue that in order to function many proteins need more than one structure. Not only that, they argue further that the structures that are biologically active are invisible to the structural methods because of minor population.

The underlying idea is more than 50 years old; the classic studies on hemoglobin binding oxygen molecules yielded two competing mechanisms, the induced fit and the conformational selection. In the induced fit model, the protein binds a ligand to form an unstable pre-complex, which than goes on to the final stable structure. In case of recoverin this model will predict that the structure changes due to binding rhodopsin kinase. Schematically,

P + L PL P*L

In conformational selection model a minor population of the free protein already exists in the “bound-like” conformation. The ligand binds to this minor conformation selectively. As a result of binding the equilibrium is driven towards the bound conformation. In terms of recoverin and rhodopsin kinase system this model will predict that recoverin has a second conformation and rhodospin kinase binds to this minor conformation selectively. Schematically:

P P* + L P*L

The induced fit mechanism is the popular choice for explaining structural plasticity seen in proteins. But scientists working on kinetics noticed evidence of conformational selection or, in most cases noted that the kinetic data can be explained by both induced fit and conformational selection mechanisms.

This debate has been reopened in recent times with the evidence for previously undetected minor conformations by fluorescence spectroscopy, new technique of x-ray crystallography and NMR spectroscopy. Fluorescence spectroscopy can measure local information about the protein dynamics by measuring interaction between strategically positioned tags. The classical x-ray crystallography is done at cold temperature. Only recently there are techniques that allow x-ray crystallography to be done at room temperature, which allows visualization of the minor conformations.

However, the most powerful technique to study minor conformations is NMR spectroscopy. For example, a typical NMR experiment measures dynamics of the entire protein backbone. NMR spectroscopy manipulates the nuclear spins using radio-frequency pulses in presence of strong (upto 662,500 times earth’s magnetic field) magnetic field. Imagine a bunch of indefatigable runners in a track who run at different but constant speed. Before the race begins, all the runners are in the same position, or, they are “in-phase”, as an NMR spectroscopist would say. As soon as the race starts the runners will start to spread out, or they will start “de-phasing”. Next, after a certain time t, the runners are turned around by 180°. So after exactly time t all the runners will be back at the starting point together. In the NMR experiment the runners are nuclear spins and this phenomenon is called the “spin-echo”. The turning by 180° is performed by the application of a radio-frequency pulse. If we go back to the racing analogy again, if the time t is sufficiently long such that some of the runners have finished the race before being turned-around, then only the small number of runners still running will be back at the starting block. Now if t is decreased in steps, then with our shenanigan more and more runners will be collected at the staring block. And finally, when t is so small that even the fastest runner cannot complete the race before being turned around, we will get back all the runners at the starting block. This is the idea behind the relaxation dispersion experiment in NMR, where increasing frequencies (decreasing t) of 180° pulses are applied on nuclear spins. The resulting “dispersion” profiles can be fit to obtain thermodynamic, kinetic and structural information of the conformations at the same time! Recent developments in NMR methodology and hardware allow us to apply the 180° pulses at high enough frequency so that we can reliably measure functionally relevant dynamics.

So what is the implication if there is a minor conformation detected for some proteins? A group of scientists in Brandeis University in Waltham, MA were interested in looking at the implications for recoverin of having a minor conformation. I was a part of this group led by the Howard Hughes Medical Institute investigator and professor of Biochemistry department, Dorothee Kern. Our NMR results showed that 3% of recoverin exists in a minor conformation, which has lifetime in the order of milliseconds. The NMR results also showed that the minor conformation is very similar to the bound structure of the protein. Interestingly, the protein did not show exchange with the minor conformation when bound to the partner protein. This is a strong hint that the minor state is required for binding. However, the skeptics among us were not completely convinced, arguing that the formation of the minor state can be just an unnecessary excursion in the energy landscape; while the conformational exchange is a necessary condition for conformational selection, it is not a sufficient condition. So with the help of my colleagues I measured the actual rate of binding of recoverin with rhodopsin kinase using stopped-flow fluorescence spectroscopy. At this point we already knew the rate of formation of the minor conformation from NMR. Now if the mechanism underlying the binding is conformational selection, then the maximum rate of binding has to be equal to the rate of formation of the minor state. We found exact correlation of the rate of formation of the minor state measured using NMR with the rate of binding measured using stopped-flow fluorescence. We repeated the whole set of measurements at a different temperature to be doubly sure. Our results unambiguously show that the rate of formation of the minor conformation is the rate determining step of binding. While the results fit the conformational selection model beautifully, is it still possible that the data can be explained by induced fit model? Turns out, the answer is no in the case of recoverin. The thermodynamics is fundamentally different in the two models. In the conformational selection model, the actual binding step is much tighter than the overall binding, because the minor conformation is present in very small amount. In case of induced fit, however, the actual binding step is much weaker than the overall binding, because the exchange in the complex drives the equilibrium strongly towards the final stable complex. We determined the thermodynamics of binding using Isothermal calorimetry and the result rules out the possibility of induced fit binding. Additionally, in the induced fit model the expectation is that the rate of binding can be increased by increasing the ligand concentration. Also from this perspective, recoverin did not show any contribution of induced fit in binding rhodopsin kinase. Till date this is the clearest example of conformational selection mechanism. This works has been published in December in Cell Reports (http://www.cell.com/cell-reports/abstract/S2211-1247(15)01423-0).

 

Figure: Recoverin (Rv) exists in an equilibrium with a minor population (3%) existing as the active conformation Rv*. The ligand, the amino-terminal helix of rhodopsin kinase, selectively binds Rv* to form the final complex Rv*RK. The rate of formation of the Rv* from Rv (30 s-1) is the rate of complex formation in presence of excess rhodopsin kinase. Reprinted from Chakrabarti et al. (2015) Cell Reports, 14, 32-42.

http://dx.doi.org/10.1016/j.celrep.2015.12.010

 

Why would anybody need to care about the detailed mechanism of binding of a protein that is not involved in a disease? Can we apply this knowledge to develop a drug molecule? Not immediately. But the importance of the observation that some proteins exist in an inactive major conformation, while the minor conformation is active, cannot be overstated. Because then at least for some proteins, the structure that we know is of the inactive form and is a wrong target for drug development efforts. How common is this mechanism? Future research in more systems, when looking beyond the structure, will tell. For now, the message is that dynamics is very important for structural biology!

About the author: Kalyan Chakrabarti is a postdoc at the Department for NMR-based Structural Biology, Max Planck Institute for Biophysical Chemistry (MPIBPC), Gottingen, Germany. The work described here was carried out in Howard Hughes Medical Institute and Dept of Biochemistry, Brandeis University, Waltham, MA, USA.

Kaly2

About the image: The author in front of the 900 MHz NMR spectrometer in MPIBPC.

Reference: Chakrabarti KS, Agafonov, RV, Pontiggia F, Otten R, Higgins MK, Schertler GF, Oprian DD and Kern D (2016) Conformational selection in a protein-protein interaction revealed by dynamic pathway analysis. Cell Reports, 14, 32-42.  doi: 10.1016/j.celrep.2015.12.010.

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Unpicking the autism puzzle by linking empathy to reward

in SciWorld by

Unpicking the autism puzzle by linking empathy to reward

Bhismadev Chakrabarti, University of Reading

Empathy is at the heart of human social life. It allows us to respond appropriately to others’ emotions and mental states. A perceived lack of empathy is also one of the symptoms that defines autism. Understanding this is key to devising effective therapies.

While empathic behaviour takes many forms, it is worthwhile to note at least two main sets of processes that are involved in empathising. One of these processes is a bottom-up, automatic response to others’ emotions. The classic example of this is breaking into giggles upon seeing another person giggle, without really knowing the reason why. The other is a top-down response, where we need to work out what another person must be feeling – a bit like solving a puzzle.

My research focuses on the bottom-up automatic component of empathy. This component is sometimes called “emotional contagion”. Emotional contagion happens spontaneously, and has important consequences for social behaviour. It helps us understand another person’s emotion expression better by “embodying” their emotion.

It also helps build social bonds; we bond more with those who smile and cry with us. But what factors determine who we spontaneously imitate? And what makes some people spontaneously imitate more than others? This is particularly relevant for understanding some of the behavioural features of autism, which has been associated with a lack of this spontaneous imitation.

Empathy and autism

One factor that has been suggested to play a central role in how much we spontaneously mimic another person is how rewarding that other person is to us. Anecdotally, it is noted that people spontaneously imitate their close friends more than strangers. In a set of experiments, we tested this suggestion by manipulating the value participants associate with different faces, using a classic conditioning task.

Some faces were paired with rewarding outcomes (for example these faces would appear most of the times you win in a card game) while others were paired with unrewarding outcomes (these faces would appear most times you lose). Following the conditioning task, people were shown happy faces made by the high-reward and the low-reward faces. Using facial electromyography (a technique that records tiny facial muscular movements that can not often be detected by the naked eye), we found that individuals showed greater spontaneous imitation of rewarding faces compared to faces conditioned with low reward.

Crucially, this relationship between reward and spontaneous imitation varied with the level of autistic traits. Autistic traits measure the symptoms of autism in the general population. These are distributed across the population, with individuals with a clinical diagnosis of autism represented at one end of this spectrum. In our study, people with high autistic traits showed a similar extent of spontaneous imitation for both types of face, while those with low autistic traits showed significantly greater imitation for high-reward faces.

What does the face say?
mistermundo, CC BY

In another group of volunteers, we did this same experiment inside the MRI scanner. We found that autistic traits predicted how strongly the brain areas involved in imitation and reward were connected to each other, when people were looking at the high-reward and the low-reward faces.

The emerging picture from this set of studies suggests the reduced spontaneous imitation seen in autism may not represent a problem with imitation as such, but one due to how the brain regions involved in imitation are connected to those that are involved in processing rewards. This has important implications for designing of autism therapy, many of which use a reward-learning model to encourage socially appropriate behaviour.

The future of brain imaging

New technologies are constantly expanding the scope of experiments and the inferences we draw from them. Human brain imaging is now being done at a resolution higher than ever before in multiple international initiatives (for example in the Human Brain Project).

A high resolution map of the human brain will allow a more detailed insight into the nature of these neural connections. This, in turn, could provide targets for potential future interventions. Another aspect where new technologies will change the landscape of this research is computational, one that will allow us to combine insights from different techniques.

At this point, there is no standard model to combine data across different techniques that we use routinely in our research (for example facial electromyography, functional MRI, eyegaze tracking). Using computers to build such models that allow a combination of the results from different techniques will help generate insights far beyond that possible for each individual technique.

Decoding the brain, a special report produced in collaboration with the Dana Centre, looks at how technology and person-to-person analysis will shape the future of brain research. Click here to read more Conversation UK articles on why behaviour tells us more about the brain than scans and chattering brain cells in autism.

The Conversation

Bhismadev Chakrabarti, Associate Professor of Neuroscience, University of Reading

This article was originally published on The Conversation. Read the original article.

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