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Biology Park

A time to write!

I am Lakshmi. I am a researcher and an instructor. I am also an avid reader, love music and cooking. As a researcher, I wrote a lot of technical stuff and it was an enjoyable exercise. I love to learn about new topics and write about interesting and complex science and make it accessible to everyone.

If you are visiting, hope you check out some of the posts and leave a comment.

Featured post

Hidden Figures no more!

Hidden Figures by Margot Lee Shetterly is a must read! The women featured in the book are such an inspiration. Gifted mathematicians, as black women during the Jim crow era, there were few avenues available to them to fulfill their thirst to best apply their skills. War brought these women to National Advisory Committee for Aeronautics (NACA), the institution on the forefront of Aeronautical research specifically to cater to the high air craft demands of warfare. They were employed as manual computers or number crunchers that made sure an engineer’s calculations in airplane design were accurate. Although they were surrounded by people who were also exceptionally well educated and brilliant and mostly male scientists, these women went through double the discrimination for being female and black. Even still, the women went about doing their jobs with quiet dignity and where they could, waged small battles against discrimination and scored a few wins too. Here is one example at the very beginning of the book that was inspiring to me.

Thirty minutes and back to work. Just enough time for a hot lunch and a little conversation. Most groups sat together out of habit. For the West Computers, it was by mandate. A white sign beckoned them, its crisply stenciled black letters spelling out the lunchroom hierarchy: COLORED COMPUTERS…..

It was Miriam Mann who finally decided it was too much to take…..The West Computers watched their colleague remove the sign and banish it to the recesses of her purse, her small act of defiance inspiring both anxiety and a sense of empowerment……When Miriam snatched  the sign, it took its leave for a few days, perhaps a week, may be longer, before it was replaced with an identical twin, the letters of the new sign just as blankly menacing as its predecessor’s……

….At some point during the war, the COLORED COMPUTERS sign disappeared into Miriam Mann’s purse and never came back……the unseen hand had been forced to concede victory to its petite but relentless adversary.

The black men faced discrimination from not only their peers but also the white blue collar workers. For instance, one black engineer James William had to spend a long time on his first day trying to convince the guards at the security gate that he was an engineer and they should let him pass through so he could go do his job!

The chief protagonists Dorothy Vaughn, Mary Jackson and Katherine Johnson were always walking a fine line between being patriotic, and serving a country that was treating them as second class citizens. Much before the civil rights movement that many of us associate with Martin Luther King Jr, there were other leaders who pushed for inclusion of black men and women in lucrative war jobs such as A. Philip Randolph, the leader of the largest black labor union. “Hidden Figures” pays homage to Mr Randolph’s efforts and vision that led to the signing of two important executive orders by President Roosevelt and opened doors to employment at the federal defense industry to black people. The black men and women at NACA were always having to be better at everything for a chance to be treated equally to their white peers. The women also kept up with changing times in the form of introduction of electronic computers that could do their work faster and the needs of the research in focus which changed from air to space research. After a full day’s work, they also took courses on Aerodynamics, Differential Equations, Theory of equations etc. Most of these courses were taught at NACA and some in the whites-only school. Although these women were gaining this additional knowledge for the technological betterment of their country, they had to still obtain permission to enter the premises (the whites-only school) where the courses were being taught. All this was apart from their life of being a mother and wife in their families. But they did whatever it took! What grit!

What several of us take for granted now including the ability to obtain an education in any institution one chooses to go to, were hard fought battles forced on ordinary people. Particularly for the discriminated, every rule made by the privileged class boxed them in so tight that any fight they got into was so much more hard to win. Having always led a privileged life and having never had to face discrimination, I am humbled by reading the experiences of black men and women in this country and reminded of the discrimination faced by Dalits in my birth country India. Margot Shetterly gives a glimpse of how the world perceived America at that time. Black and brown nations newly freed from colonization watched closely America’s treatment of its black population and saw in them their own future. They felt Russians would be better allies. The work at NACA including that of the women featured in Hidden figures contributed significantly to making sure America emerged as the world leader post World war II. The author also describes how Russians invested in training women to be scientists many of whom would have contributed to big technological advancements such as designing ballistic missiles and launching the first ever earth satellite ‘Sputnik’ into orbit. America’s treatment of women and black people made sure that a significant proportion of great minds were either not being used at all or under-used leaving it trailing behind the Russians in conquering the outer space! Ultimately, the work of many ‘Hidden Figures’ made sure America emerged triumphant in the space race.

Go on this journey with Margot Shetterly, and discover the unseen contributions made by these incredible women to science!

ES+TS+ECM = Mouse embryo!

I spent a good part of the last decade studying Wnt signaling, a cascade of proteins acting in a sequential manner in our cells that instruct cells on what to do and how to behave. Wnt signaling and a few other protein cascades like it are conserved across species and are one of the earliest group of proteins that make sure embryos develop normally and have the right beginnings to make a complete organism. Pioneering work by many developmental biologists on various animal model systems brought to light the importance of these players in shaping the embryo. Mouse embryos are the closest mammalian versions that scientists have used to extrapolate and understand the development of human embryos. Embryonic stem cells, the first cells that arise from the fusion of sperm with egg, are capable of giving rise to many different type of cells of our body given the right environment and proteins to nudge them into a specific fate. Mouse embryonic stem cells have been used precisely for this purpose to test the roles of various proteins that help in directing the cells to choose one fate over another. Being able to study embryonic cell behavior in a petri dish allows us to understand what really goes on in living organisms. The authors of a new paper published in Science this week build an embryo in the lab using a few cells from the mouse embryo and a supporting gel matrix. They use these embryos to reconstruct the sequence of events and shine a focus light on players directing these events, that occur a few days into the embryo’s journey to becoming a complete organism.

A freshly fertilized egg travels from the site of fertilization to the uterus to be implanted. During this time, it divides and gives rise to two types of cells – the embryonic stem cells (ES) that will give rise to all cells of the body and the trophoblast stem cells (TS) that will form the placenta and yolk sac. The proper and complete development of an organism from an embryo requires an exchange of information between the ES and the TS cells. In the study, the authors mix a few ES and TS cells and provide a gel matrix or extracellular matrix (ECM) to allow the development of the lab embryo referred to as ETS embryo. The gel matrix is sort of a replacement to the uterus where the embryo would get implanted if it were in a live organism, and it also provides a mix of nourishing proteins to the developing embryo. Upon mixing, the ES and TS cells rearranged themselves into distinct compartments as they would in a live embryo 22% of the time the authors attempted the experiment (see Fig.1 bottom panel).

embryo

Fig.1 Comparison of the lab-constructed ETS embryos with natural embryos

One of the first events of interaction between the ES and TS cells is the formation of a common and continuous hollow space or cavity between the two cell compartments and occurs approximately 6days post implantation. The chance of the cavities merging was greatly increased when ES cells were present in the mix as embryos made exclusively of TS cells initiated no cavity formation. They also show that the ES cells provide a crucial protein signal that induces TS cells to form the cavity. Next they observed whether the ETS embryo was capable of forming mesodermal cells that would go on to give rise to many tissues of the body including muscle, bone, linings of blood vessels, kidneys and other organs. The ETS embryos not only expressed proteins that would be expressed by the mesodermal cells in a normal embryo, but the chance that they would express these proteins increased greatly if TS cells were present in the ETS embryo thus reinforcing the importance of exchange of crucial early signals between ES and TS cells. From previous studies, they knew that one obvious candidate for the signal that could be provided by the TS cells is Wnt, the bread and butter of my graduate studies! In the study, the authors show that Wnt protein is indeed required for the ES cells of the ETS embryo to express mesoderm specific proteins setting the stage for the development of all those tissues that these mesodermal cells would give rise to later in development. The next major event in embryo development would be the generation of primordial germ cells (PGCs), the precursor cells that would ultimately become sperms or eggs. The 15 ETS embryos they observed were able to form cells that expressed the same proteins expressed by PGCs and this was again dependent on the cells receiving two important signals, Wnt and BMP.

The authors show that they are able to recapitulate some of the major early events of the developing embryo and identify important early precursor cells in their lab-constructed ETS embryo. Even though the ETS embryos lack the structure that provides the signals to ensure directionality to the developing embryo, about 70% of them were still able to express mesodermal proteins in the appropriate compartment. Although by no means perfect, the authors make a case that their ETS embryos would allow scientists to dig deeper into these early protein signals, uncover whether they come from ES cells or the TS cells and expose the intricate cross talk between these two cell types that basically govern how we ultimately develop. While the nerd in me was excited to read this paper that recaptures early embryonic development using a mix of stem cells and an artificial matrix, I also realized it won’t be too long before someone attempts to do this with human ES cells. Human ES cells are more complex to deal with and their optimal conditions of growth are different from those of mouse ES cells, but the seeds of possibility have been sown!

References

  1. Assembly of embryonic and extraembryonic stemcells to mimic embryogenesis invitro –embryos_in_dish

Ever experience musical “Chills”? How does your brain do it?

Every time I hear the piece called “Swara Kakali” from the album “West Meets East” by sitar maestro Ravi Shankar and violinist Yehudi Menuhin, I get transported to a different world. My husband says that I experience musical orgasm! Intense feelings that people experience upon hearing music have been variously described as chills, frission, thrills and even skin orgasm. Studies have shown previously that things that induce pleasurable feelings such as food and sex cause the brain to release chemicals known as opiods which bind to their receptors and trigger the release of the dopamine neurotransmitter in the brain resulting in intensifying these feelings. A rewarding experience such as listening to music apparently has two phases, as found by a 6yr old study (1). In the first phase, there is anticipation for the reward (say a favorite part of in the music piece) and the second phase is the pleasure one gets while experiencing the reward (when the favorite part actually plays). Both phases are regulated by dopamine. Other studies involving food and sex as rewards have found that the second ‘pleasure’ phase involves the binding of opiods to opiod receptors and activating them to trigger further release of dopamine. It was not clear if a similar chemical reaction is triggered upon listening to music.

A recent study published in Scientific Reports attempts to answer this by using an opiod receptor antagonist drug called Naltrexone or NTX (2).  NTX likes to bind to the opiod receptors and prevent binding of opiods produced by our body in response to pleasure thus stopping the subsequent increase in dopamine release. The authors conducted a double-blind cross over study which means that all the 15 participants received NTX or a placebo before the experiment and neither they nor the investigators knew what they got until after the study was fully completed. The participants were asked to bring two pieces of their favorite music that instills ‘chills’ whenever they listen to it. The authors also used previously tested neutral music that the participants had not heard before as a control. First, they measured any differences in nerve conductivity or relay of electrical signals from the nerves of facial muscles involved in smiling and frowning while they hear pleasurable music (of their choice) and neutral music (selected by authors). Second, they measured the pleasure experienced by the participants in real time by asking them to use slider buttons scaled from 1 to 10 to indicate their level of pleasure as they listen to the two kinds of music.

They find that upon taking NTX, the participants experienced a decrease in the nerve conductivity of both smiling and frowning muscles indicating that NTX affects both positive and negative feelings triggered by listening to music. This decrease was especially stark when they listened to pleasurable music. The authors suggest that this is because the feelings associated with pleasurable music of the participant’s choice are more intense than the ones experienced upon listening to the neutral music. Next, they also find that pleasure that the participants experienced real time upon listening to their favorite music was also significantly attenuated whenever they took NTX, further confirming that the opiods are indeed involved in experiencing musical ‘chills’.  Our bodies therefore use opiods to not only experience the pleasure of eating good food and having sex but also to experience the positive and negative emotions triggered by our favorite music. I often wonder why many musicians are addicted to prescription opiates. May be taking these drugs offers a way to sustain intense feelings of pleasure and sadness beyond music to their everyday lives.

Music pervades all aspects of our lives and as attempts to use it to effectively manage pain become popular, it is immensely interesting and important to understand the nature of the various chemical reactions that it elicits in us. This study is yet another step in that direction.

References

  1. Anatomically distinct dopamine release during anticipation and experience of peak emotion to music
  2. Anhedonia to music and mu-opioids: Evidence from the administration of naltrexone – music_scientific_report
  3. Cover image courtesy
  4. Swara-Kakali from West Meets East

Now you can be B positive in 2 mins! – A new blood typing method

In the Microbiology lab I teach, blood typing is one of the labs that my students enjoyed doing as it directly applies to their own life. Our blood consists of red blood cells (RBCs), white blood cells, platelets and serum (the liquid, non-cellular portion). On the surface of the RBCs, there are specific proteins attached, sort of like ID cards. These are called antigens. For example, if your blood group is B+ve, then you have the ‘B’ antigen and ‘D’ antigen on your RBCs (See Fig 1). You might have also heard that you can only accept blood from another person who has the same blood type as you. Why? That is because in the serum or non-cell part of your blood there are other proteins called as antibodies whose job is to detect any antigens/ID cards that are foreign and destroy them. It is therefore crucial to be able to quickly test if blood types are compatible between a donor and a recipient, even if they share the same blood type to avoid any unnecessary complications resulting from destruction of RBCs. In the lab class, my students mixed synthetic blood samples (which would contain the antigens) and various serum antibodies and observed for a reaction which can be visualized as small clumps or in scientific terms called as agglutination. Sometimes the agglutination was not easily visible leading to some confusion about the blood typing. However, in a large hospital/diagnostic center setting, a reasonably quick, effective and reliable method is of utmost importance as there can be no room for confusion and, mistakes would be costly. Such methods exist already but a newly published paper in Science Translational Medicine shows the discovery of a new assay that allows one to find out their blood type within 2 mins by observing a color change on a piece of paper.

blood_types

Traditionally, to be able to test for the presence of antigens on the RBCs and the antibodies in the serum, the blood is first spun at a high speed to separate the blood components. The USP of this new paper-based method is that there is no prior blood preparation needed. The method takes advantage of the presence of a protein called human serum albumin (HSA) in the serum of the blood and its ability to react with a dye called bromocrecol green (BCG). The HSA-BCG dye complex produces a teal color. Whole blood which contains both RBCs and HSA in the serum reacts with the dye to give a brown color. Both reactions absorb light at specific wavelengths and produce distinct spectra which the authors find especially useful to automate this process and ensure accuracy by removing the need for manual color distinction. Let us visualize this using our previous example of B blood type which will have B antigen on the RBCs and antibodies ready to destroy the A antigen in the serum (Fig. 1). As the blood moves along the paper, imagine its constituents undergoing reactions progressively. First, the B antigens on the RBCs would react with the immobilized anti-B antibody on the paper. Now the blood is free of RBCs and the serum contains antibodies against the A antigen and HSA. Next, the antibodies against A would react with the A type red cells confirming that it is indeed B blood group. Finally, devoid of any RBCs and antibodies, the serum now only contains HSA which reacts with the BCG dye resulting in a teal color. If the sample was not the B blood type, then HSA and BCG dye would react to form a brown color and none of the other reactions would occur. The whole process takes about 2 minutes and just a few microliters of blood.  Using this Dye Assisted Paper-based method (DAP), the authors tested more than 3500 blood samples and achieved 99% accuracy in blood typing and the method showed a similar accuracy when performed side by side with the commonly used gel card method of blood typing.

Since this is a new paper-based method, the authors conduct many quality control tests to show that their method is robust and reproducible. For instance, they test a bunch of different papers and membranes for suitability to effectively separate the RBCs and serum. They also test various dilutions of RBCs (antigens) and antibodies to determine the ideal ratio needed to produce reproducible results and the stability of the immobilized antibodies on the paper (6months). They examine if longer interactions between antigens and antibodies affect color change (maximum intensity was seen at 10mins), investigate how long after blood collection the test result is reliably accurate (7 days), if the pH of the blood influences the reaction (no) and whether various temperature, light and humidity conditions during experiment affect the results (no). Although they suggest ways to overcome challenges of testing blood with varying number of RBCs (think anemic conditions or newborns who typically have higher number of RBCs), they acknowledge their inability to predict if the DAP method would be affected by samples from people with any changes in their serum proteins due to disease or medications. They also realize that their method needs to be made better at detecting some of the rare RBC antigens that are weakly expressed.

The DAP assay appears to be a better, easier and quicker mouse trap for blood typing and will probably replace some of the current blood typing methods in the near future.

 

References

A dye-assisted paper-based point-of-care assay for fast and reliable blood grouping – blood_typing

Image courtesy – inline image, gel card method of blood typing – cover image

Honey, you on birth control?- A contraceptive for men

A recent executive order signed by the US president would not allow any foreign non-profits that receive health funds from the US to use it for providing abortion services (1) . This order which was signed by a man surrounded by men, re-started highly polarized debates and opinions on the role of government in limiting access to methods of birth control and a woman’s right to safe abortion. Women bear the emotional and physical consequences of reproductive decisions that they often unfortunately don’t get to make. Let us for a minute shine the focus light on men and their role in reproductive control. What if there is a procedure that allows for men to contribute to birth control in a big way? There has been considerable interest in the pharmaceutical industry to produce a male contraceptive pill. Although pills are a profitable bet for the pharma industry, they are a pain for the users. You need to remember to take them every day, worry about side-effects however minimal they are made out to be, and the physical consequence of forgetting to take one will overwhelmingly fall on the woman. Vindicating some of these points, the most recent clinical trial met with an unhappy ending as some men participating in the study reported side effects (2). While women have been experiencing side effects of varying degrees because of taking birth control pills since their introduction, one might argue that men may not be as willing to take the risk of experiencing side effects for a physical result (pregnancy) that they will never experience.

There is however a glimmer of hope. Invented by Dr. Sujoy Guha of IIT (Indian Institute of Technology, Kharagpur, India), a procedure called RISUG (Reversible Inhibition of Sperm Under Guidance) offers men a way to limit sperm from fertilizing an egg. The procedure includes a one-time injection of a polymer called styrene maleic anhydride (SAM) in the vas deferens, a man’s sperm-carrying vehicle which transports sperm from their site of origination to their storage site where they remain until ejaculation. The SAM polymer is believed to serve as a sieve to prevent the sperm from passing through and/or alters the sperm in such a way that they are unable to fertilize an egg (3). Although various animal studies propose possibilities of how this polymer works to limit sperms from passing into the ejaculation fluid, the exact mechanism is still not fully understood.  In a recent short term study conducted on rabbits, the sperm count decreased shortly after injection and some of the sperm that managed to pass through the polymer had abnormal morphology (4). Most importantly, there were no pregnancies reported for 1 year post SAM injection. One cool thing about this process is that it is reversible; the sperms can be allowed to do their job with a simple injection of a chemical that apparently dissolves the SAM polymer. The rabbit study observed that the sperms showed normal morphology after reversal, could fertilize eggs and the next generation of rabbits that they produced were normal (4). However, whether the next generation of rabbits developed normally later and if their reproductive capacity was unaffected were not examined. Future animal studies must show that for at least a few generations, the progeny born out of reversing this procedure are normal and functional with no adverse effects on their fecundity.

The clinical trials conducted so far in India are a decade old, limited and although effective have not led to approval of the drug for marketing. The bureaucracy in India is frustratingly slow and the limited information from the clinical trials is not helping in advancing this further.  A few years ago, a US based non-profit licensed RISUG from Dr. Guha, rechristened it Vasalgel and is working on getting it approved by the FDA (Food and Drug Administration) (5). There are several phases of approval that Vasalgel needs to go through before being given the green by FDA for marketing in the US. It must be shown to be effective in animal studies, should have toxicology studies done to show that it does not have any toxic side effects in animals to even begin testing in humans. Since there is already prior knowledge from the trials in India that can be used as start points, the hope is that this process might not take as long. But drug trials are inherently very expensive and quite prolonged. We can be cautiously optimistic about having this available by 2020.

The availability of Vasalgel would hopefully shift the onus of birth control from women to men and allow both genders to be its active advocates. Let us envision a bill being signed by a woman surrounded by women and men of all colors to allow access to Vasalgel all over the world! Oh, what a nice picture!

 

  1. https://www.washingtonpost.com/news/to-your-health/wp/2017/01/23/trump-reverses-abortion-related-policy-to-ban-funding-to-international-health-groups/?utm_term=.20bdc7a0b17e)
  2. http://www.npr.org/sections/health-shots/2016/11/03/500549503/male-birth-control-study-killed-after-men-complain-about-side-effects)
  3. RISUG: An intravasal injectable male contraceptive – review_RISUG
  4. Contraception with RISUG® and functional reversal through DMSO and NaHCO3 in male rabbits –RISUG_rabbit_study
  5. https://www.parsemusfoundation.org/projects/vasalgel/vasalgel-faqs/

 

Bite me – How a malarial patient attracts more mosquito bites!

Last year when we visited my native country India, my 2yr old daughter was bitten by a lot of mosquitos while I, who slept right next to her, was avoided by them! While discussing this, my mom-in-law casually remarked that mosquitos’ preference for O blood group individuals rendered her a victim of their vicious bites too. I was intrigued and found that a previous study had indeed found that the Aegus albopictus mosquito which can harbor viruses that cause chikungunya, dengue etc, does have a preference for certain blood types. The female Anopheles mosquito, a carrier of the malarial parasite, is apparently more attracted to take its blood meal from people already infected with the malarial parasite and it was not clear why. That is the central point of interest in a new short and neat study by Emami and colleagues (1).  They found that the female Anopheles mosquitos prefer Red Blood Cells (RBCs) that contain a key compound secreted by the malaria causing parasite Plasmodium falciparum. It has a crazy long name and so for short it will be referred to as HMBPP and the RBCs containing it as HmbRBCs. HMBPP is a compound that contributes to the production of many other chemical compounds including aromatic ones (think compounds that give eucalyptus and ginger their unique smell).

When mosquitos were given a choice of consuming regular RBCs verses HmbRBCs, 95% of mosquitos chose the latter option. The malarial parasite Plasmodium falciparum goes through a complex life cycle that is shared between humans and mosquitos. When presented with RBCs laden with the Plasmodium parasite in two different developmental stages that it goes through in the human host, the likelihood that a mosquito fed on these RBCs doubled. When they blocked HMBPP synthesis by Plasmodium, the mosquitos did not care for such RBCs any more than the unsupplemented RBCs. The mosquitos also did not care for feeding on RBCs that were supplemented with a different compound, leading the authors to infer that HMBPP secreted by the malarial parasite needs to be present in the mosquito feeding attraction concoction.

HMBPP mixed with salt water or serum still attracted about 80% of mosquitos to check out these RBC-free meals. It is clear that HMBPP is an attractant but since mosquitos like to take blood meals and not RBC-free meals, what is the role of RBCs? RBCs usually release CO2. Now CO2 release by a host organism had been shown before to have an attractive effect on mosquitos. The authors speculated that HMBPP released by the malarial parasite sitting in the RBCs could be increasing the CO2 released by these RBCs thus making them attractive for the mosquito to consume. To test this, they captured the gaseous compounds released by the RBCs, HmbRBCs and RBCs containing the malarial parasite. As hypothesized, the amount of CO2 released increased by 16% in the HmbRBCs compared to the unsupplemented RBCs. Apart from CO2, a few other compounds were also found to be released in significantly higher amounts by HmbRBCs and parasite-containing RBCs. Interestingly, a synthetic concoction of these compounds and CO2 was as attractive to the mosquitos as HmbRBCs indicating that the right mixture of these compounds is all it takes for the mosquito to land and take its meal. Presence of HMBPP also moderately but significantly increased the meal size per mosquito.

So what is the consequence of mosquitos being attracted to take larger blood meals of RBCs containing HMBPP? Does it affect the mosquito in anyway? According to this study, no. The mosquitos survived and reproduced just fine even though they had now consumed RBCs laden with this compound. You might wonder why the mosquitos don’t get malaria? Read my other blog post to know why! Very briefly, the mosquito’s defense system makes sure that most of the parasites that land in the mosquito gut after it takes a blood meal, are cleared out. The few that escape are able to lodge themselves in the mosquito salivary gland and are transformed into a developmental phase that is now ready to infect humans and other hosts. According to this study, more of the mosquitos that consume HMBPP supplemented, parasite-laden RBCs are infection ready. That means, a higher percentage of the mosquitos that took this type of blood meal have their salivary glands teeming with the malarial parasite.

In the very last segment, they test for changes in the kind of genes expressed in the mosquito at various time points post consumption of HmbRBCs. They observed changes in genes that send messages between neurons and infer that these neurological changes might be directing the mosquito towards a malarial parasite infected host. They also observed changes in genes that control the mosquito’s innate defense response indicating that their immune response could be changed to allow a greater number of malarial parasites to survive, multiply and reside in the mosquito salivary gland. So the big take home story for us is that when given a choice of taking a blood meal from a person who is affected with malaria and an unaffected person, the mosquito might end up choosing the former 95% of the time. Such mosquitos are highly likely to pass on the parasite to whoever they take their next blood meal from. This work by Emami and colleagues uncovers HMBPP secretion as yet another trick in the malarial parasite Plasmodium falciparum’s survival tool kit that cleverly scapegoats the mosquito!

Reference

  1. A key malaria metabolite modulates vector blood seeking, feeding, and susceptibility to infection – malaria_susceptibility

Gut bacteria help bees buzz off E. coli!

Innate immune response is our first line of defense against foreign bodies. For instance, when our bodies sense foreign microbes, we produce small proteins called Anti-microbial peptides (AMPs) that help trigger our first responder immune cells to mount a response. These cells detect the bacteria as non-self and jump into action to clear them away. All organisms armed with innate immunity have AMPs  as part of their tool kit. AMPs are able to disrupt bacterial colonization and establishment by disrupting bacteria’s cell wall or interfering with the process of making new DNA and proteins. Although bacteria have become unpopular over the years due to their disease causing ability, there are millions of them that are essential to our development. For example, an earlier study found that germ free mice or mice born without any resident microbial population in their bodies have a poorly developed immune system including the inability to secrete AMPs. The authors of the current study want to understand if Apis mellifera, the African honey bee’s normal gut resident microbes have a role in triggering AMP production and if that is beneficial enough to fight infection caused by disease causing bacteria (1).

First, they test if AMPs are produced by honey bees by comparing the haemolymphs (blood equivalent in insects) obtained from honey bees that have been microbe free since birth with microbe free honeybees inoculated with a common type of honey bee gut microbe Snodgrassella alvis or with the digested guts of worker honeybees (which would contain normal microbial flora of honey bees). Out of the four common AMP classes produced by honeybees, apidaecin and hymenoptacein were found to be strongly induced in the haemolymph and intestinal lumen of the microbe exposed honeybees with apidaecin showing a 2.4fold increase in production. They suggest that apidaecin production in the haemolyph could trigger innate response of honey bees while their production in the gut lumen could modulate the gut microbial population to help respond to infections better. Next, they show that unlike the pathogenic E. coli bacteria, the resident microbial population is largely immune to the two forms of apidaecin. As mentioned above, this is important because bees have to fine tune AMP production so that it is selectively harmful to the invading pathogen while maintaining a good mix of the resident gut microbial population.

Finally, they test if AMP production could increase the survival chances of honey bees infected with E. coli.  They infect germ free bees or bees inoculated with two different types of gut resident microbes (S. alvi and Gilliamella apicola) with E. coli and after a 3hr and 6hr interval, obtain haemolyph to check for how much of the injected E. coli was cleared as a result of the activation of first defense response triggered by AMP production. The bees that received inoculations of S. alvi and G. apicola were able to significantly clear out E. coli after 6hrs in two out of three trials. The second test they do is to check how long the bees survive post E. coli infection and in only two out of five total trials conducted, the gut microbe exposed bees were able to significantly increase their survival time. They suggest that this variability in trials show that having gut microbiota is not harmful to bees but can be useful in some instances to fight infection. It is indeed not ideal to get such a mix of outcomes in what was supposed to be their role defining experiment.

Why were some microbe free bees able to fight off E. coli as well as their gut microbe injected peers? They attribute it to seasonal differences and differences in the groups of bees used for the experiment which may very well have played a role in generating variability between trials. However, it is also possible that sustained AMP production and as a result better outcome for bees may require more than one type of gut resident microbe to be present.  I also wondered if passage of immune response-eliciting proteins from the original mother bee to her eggs has a role in modulating immune response in the next generation. I am no bee research expert and this is just something I was thinking about while reading this paper. Passive adaptive immunity occurs in humans (and in other animals) where the mom is able to pass on germ fighting antibodies to babies during pregnancy, and after via breast feeding. Since bees do not make antibodies, other studies have shown that pieces of bacterial cells (dead or alive) from both disease causing and non-disease causing bacteria can be passed on via the eggs to the next generation, a phenomena called as trans-generational immune priming. What if these immune-eliciting bacterial proteins induce a response that is sufficient to tackle E. coli infection even in the absence of gut microbiota? Well, we will have to wait for the next research paper to add more weight to the proposed symbiotic relationship between bees and their gut bacteria in warding off infections.

Recently I began reading Ed Yong’s “I contain multitudes: The Microbes Within Us and a Grander View of Life”, a fascinating and superbly written book about animals’ intrinsic relationship with microbes that is beneficial at so many levels. Excellently researched, the book referenced a paper on how mouse specific and not human specific resident gut bacteria successfully induced a defense response in germ free mice infected with Salmonella (2). This study on bees shows how this relationship possibly extends to insects as well.

References

  1. Immune system stimulation by the native gut microbiota of honey bees – bee_immune_system_stimulation
  2. Gut immune maturation depends on colonization with a host-specific microbiota – gut-immune-maturation

A Mosquito’s defense against Malaria

When a female Anopheles mosquito has its blood meal from a person containing the Malarial parasite, the gametes (parasite equivalent of eggs and sperm) are passed on to the mosquito’s gut cells. There, the cells fuse to form an ookinete which goes through a few more steps of development transforming itself into a form that subsequently lodges in the salivary gland of the mosquito. When the mosquito takes its next blood meal from an unsuspecting human, the parasite is successfully transferred to her resulting in Malaria. Why does the mosquito never get Malaria?

Just as in humans, mosquitos also have immune cells circulating in their hemolymph (blood equivalent in mosquito) that descend on the parasite infected gut cells and initiate a chain of reactions to clear out the ookinetes. Although the proteins that the mosquito gut cells make as well as recruit from the hemolymph in order to clear out the parasites is known, a new study explores the immune cells’ role in kicking off this cascade (1). The immune cells of the mosquito were labelled with a dye and then the mosquito was subsequently allowed to take a blood meal from a mouse infected with one of the Malarial parasites. When the authors observed the infected gut cells, they found that about ­­­­33% of them were found associated with a dye-labelled piece from the immune cells. This piece of the cell in scientific terms is referred to as a vesicle, and usually carries proteins and other molecules. Greater the number of ookinetes in the mosquito midgut, higher the number of vesicle forming immune cells found associated with them. However, in the same gut, the non-infected gut cells were not found to be associated with these immune cell-derived vesicles.

Upon sensing parasite infection, the mosquito gut cells activate a bunch of proteins that attach a nitro functional group (-NO2) to the parasite proteins. This process called as nitration ‘tags’ the parasite ookinetes and is then followed by the death of the infected gut cells and leaking of the ookinetes into the surrounding lumen. There another patrolling protein called TEP1, whose job is to clear out pathogens like the malarial parasite, springs into action. TEP1 protein breaks into a smaller piece and starts coating the surface of the ookinete thus marking it for clearing. So the mosquito clears out most of the ookinetes to be able to warrant a Malarial infection (2). The few that escape, are able divide multiple times to generate thousands of sporozoites that ultimately rest in the mosquito salivary gland (2). Going back to the study, the authors asked what would happen if they blocked the formation of these vesicles by the immune cells. Would it affect the subsequent clearing of the ookinetes? They found that the levels of the proteins required for nitration of the ookinete as well as the coating protein TEP1 were unaffected when immune cell-derived vesicle formation was thwarted. However, TEP1 did not bind well to the ookinetes and TEP1 bound ookinetes decreased from 90% to 50%. So they were not cleared out efficiently.

Since the process of nitration was previously shown to be at the start of this anti-parasite activity, the authors also tested if nitration triggers the release of these vesicles from the immune cells. A loss of proteins required for nitration in the gut cells, resulted in a 7fold decrease in the formation of the vesicles from the immune cells. Increasing nitration had the opposite effect; vesicle formation increased by 2 fold. They also found that putting the immune cells in contact with pre-nitrated gut cells was sufficient to promote vesicle formation by the immune cells. So what might be the ‘secret sauce’ in these immune cell-derived vesicles that might help mosquitos get rid of the parasite before Malaria sets in? Vesicles contain enzymes and other proteins and the authors imply that there could be one or several of them functioning to promote efficient binding of the TEP1 protein to the ookinete surface and help clearing it away.

Malaria affects millions of people each year and the parasite’s complex life cycle shared between mosquitos and humans is part thwarted in the mosquito successfully. How can we take advantage of a mosquito’s ability to fight off the malarial parasite and prevent transmission into humans? What about the role of the mosquito gut microbiota that also contribute positively to this process? Scientists continue to be busy uncovering the mosquito’s clever means to mount an effective defense against the evasive malarial parasite.

References

Activation of mosquito complement antiplasmodial response requires cellular immunity  – mosquito_malaria

The Plasmodium bottleneck: malaria parasite losses in the mosquito vector

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The bodacious cop – Constance Kopp

I am a big fan of books featuring strong female leads. Of late, I have been excitedly following the life of Constance Kopp, a reluctant farmer turned cop from Wyckoff, New Jersey.  She and her sisters more or less live a quiet life on the outskirts of Paterson, NJ with no close neighbors until their buggy gets hit by a motor car driven by a rich thug. When Constance repeatedly but politely demands in writing that he reimburse her family for the loss of their only mode of transport, he chooses not to. She finally decides to ask him in person but when he refuses again and threatens to harm her little sister, Constance does not hesitate to take him by the collar and threaten him back!  This only enrages him more so he along with his friends start intimidating the sisters. I could imagine how difficult it must have been for women in the early 1900s to live by themselves as everyone is always wondering why, judging the prudence of the decision and thinking that anything that happens to them is because they deserved it. While reading the challenges they face, I kept thinking that for many women around the world, the situation still remains the same almost a century later!

Due to their troubles, the sisters get introduced to the sympathetic and emphatically duty bound town sheriff who offers them protection. He takes it upon himself to teach Constance how to use a gun, encourages her to press charges against the culprit-in-chief and helps her doggedly pursue him. The first book titled “Girl waits with Gun” is amazingly written and although the situation for the ladies is difficult, there is plenty of humor and Constance is a super cool woman. In pursuing this rich thug, she discovers her knack for detective work and is really good at it too. She takes lead, makes smarter choices and thinks to look where others don’t and succeeds (Yes!!). A well-built woman, she is not afraid to chase after wrongdoers and catch them – all while wearing a corset, long flowing skirts and uncomfortable shoes :). All this work gets her the job of a ‘deputy sheriff’.

In the equally colorful and adventurous sequel “Lady cop makes trouble”, as the sheriff works to get her a deputy badge, Constance works as the jail matron. She is very good at that job too but yearns to get her badge soon and officially do detective work. Back in 1915, she was one of the few women working in law enforcement that were actually paid a salary, allowing her to support her family. It would be no easy task for the sheriff to convince the county officials (referred to as freeholders in New Jersey) that a woman deserves to serve in the police department much less as the deputy to a sheriff, a job considered totally inappropriate for a woman (although many men in the department were less than capable and did not have much training). The 37year old Constance often gets referred to as the ‘girl’ in the press. Even when she catches a culprit after a chase and a fierce fight (see image below), some of the papers of the day take it upon themselves to make her actions read lady like. Take for instance the headline “Girl deputy sheriff “pinches” a minister!”. The report goes further to completely change what really occurs and publishes that “she stepped up to a husky well-dressed man in front of Borough Hall and tapped him on the shoulder”. Constance takes these in her stride and continues being a totally bodacious cop!

lady-cop-drawing-of-constance-fighting-von-matthesius

Last year, I was looking at NPR’s book recommendations and chanced upon Amy Stewart’s “Girl waits with Gun”. Amy Stewart’s descriptions of Brooklyn and the suburban areas in the early 20th century and the factual notes of Constance’s life and times, are all a treat for the reader. Both the novels she has penned in this series are absolutely delightful. Constance Kopp is one cop you want to read about 🙂

For more fun details:

Amy stewart’s website on the characters featured in the books- http://www.amystewart.com/characters/

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