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A blog on scientific imaging, science, pseudoscience, the politics of science, and other things which catch my interest.
Bryan
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- March 3, 2010
- 12:42 PM
- 415 views
Porn is good for you
by Bryan in Imaging Geek
Science has some good news for any pornhounds that may be out there. Porn may be good for you.Its long been though that porn is associated with a range of negative social attitudes; including promoting sexual violence and negative attitudes towards women. Turns out that, at least in the case of these two issues, this doesn't appear to be the case.In a finding sure to piss off some feminists:Now let’s look at attitudes towards women. Studies of men who had seen X-rated movies found that they were significantly more tolerant and accepting of women than those men who didn’t see those movies, and studies by other investigators—female as well as male—essentially found similarly that there was no detectable relationship between the amount of exposure to pornography and any measure of misogynist attitudes.So apparently watching porn makes men less mysogynist, not more. It may even promote attitudes conducive to making for a long-lasting relationship.Not only that, but viewing porn may actually act to prevent sex crimes. Quoting the article:Over the years, many scientists have investigated the link between pornography (considered legal under the First Amendment in the United States unless judged “obscene”) and sex crimes and attitudes towards women. And in every region investigated, researchers have found that as pornography has increased in availability, sex crimes have either decreased or not increased.So men, grab your...mice.For a more technical review of the literature, click here.Diamond, M. (2009). Pornography, public acceptance and sex related crime: A review International Journal of Law and Psychiatry, 32 (5), 304-314 DOI: 10.1016/j.ijlp.2009.06.004... Read more »
Diamond, M. (2009) Pornography, public acceptance and sex related crime: A review. International Journal of Law and Psychiatry, 32(5), 304-314. DOI: 10.1016/j.ijlp.2009.06.004
- March 3, 2010
- 12:14 PM
- 488 views
Porn is Good For You
by Bryan in Imaging Geek
Its long been though that porn is associated with a range of negative social attitudes; including promoting sexual violence and negative attitudes towards women. Turns out that, at least in the case of these two issues, this doesn't appear to be the case.... Read more »
Diamond, M. (2009) Pornography, public acceptance and sex related crime: A review. International Journal of Law and Psychiatry, 32(5), 304-314. DOI: 10.1016/j.ijlp.2009.06.004
- February 11, 2010
- 10:19 AM
- 485 views
Its g-g-g-genetic
by Bryan in Imaging Geek
Pardon the title, but it somewhat shocking news (to me, anyways), it turns out stuttering is genetic. A study released today in the New England Journal of Medicine has identified mutations in two genes - GNPTAB and GNPT - that seem to cause stuttering. These mutations seem to be found in stutterers around the world, although the initial mutations were identified in a Pakistani family.The real odd thing though is what these genes do - they're involved in sending proteins to lysosomes; our cells version of a garbage bin. Lysosomes are nasty places, where parts of our cells go to die - they're acidic, full of oxidents, and full of enzymes whose sole job is to destroy anything that fall into their maw.Genetic diseases involving lysosomes are somewhat common, and while the exact symptoms vary depending on the gene(s) which are mutated, they all have a common thread - neurological problems. In fact, most of these disorders have profound - often lethal - effects on a patients neurology. So in some ways the link between stuttering and lysosomes makes sense - lysosomal mutations often have neurological outcomes - the mildness, and limited affected area (speach, not much else) is very, very odd.So what exactly does GNPTAB and GNPT do? Turns out both are pieces of a large complex whose job is to tag proteins that need to be sent to lysosomes. This tag is a sugar (GlcNAc), and acts as a sorting signal that tells our body "this protein should go to a lysosome". Proteins tagged in this way are generally not being sent to lysosomes for degradation, but rather are the active components of lysosomes. So mutations in these genes should make for less active lysosomes, which in turn may lead to the buildup of damaged cell components in affected individuals.How and why these mutations lead to stuttering remains a mystery. In fact, other mutations in GNPTAB are known to cause two severe disorders called "mucolipidosis types II and III"; disorders which cause sever cardiac, skeletal and eye issues. The fact that these mutations seem to selectively affect one region of the brain (presumably the speech centre) is particularity hard to explain, given the diverse effects of other mutations in the same gene.Whether or not this discovery does anything to help stutterers is an open question - although it does get overbearing teachers and parents off the hook.Kang, C., Riazuddin, S., Mundorff, J., Krasnewich, D., Friedman, P., Mullikin, J., & Drayna, D. (2010). Mutations in the Lysosomal Enzyme-Targeting Pathway and Persistent Stuttering New England Journal of Medicine DOI: 10.1056/NEJMoa0902630... Read more »
Kang, C., Riazuddin, S., Mundorff, J., Krasnewich, D., Friedman, P., Mullikin, J., & Drayna, D. (2010) Mutations in the Lysosomal Enzyme-Targeting Pathway and Persistent Stuttering. New England Journal of Medicine. DOI: 10.1056/NEJMoa0902630
- February 2, 2010
- 04:08 PM
- 976 views
Arthritis, platelets, and inflammation
by Bryan in Imaging Geek
As I mentioned in my last post, this has been a watershed week in two areas I'm greatly interested in. Two major discoveries were published last week that are in areas of great interest for myself. My first post concentrated on one of my favourite parts of the cell - mitochondria. The second article I want to blog about is a blast from my past, and involves inflammation - the major way our immune system gets rid of bacteria, and ironically, the cause of many human diseases.This paper discusses the role platelets - the miniature cells that help our blood clot - play in making some forms of arthritis worse. It also addresses the role of a biological mystery - microparticles - play in mediating disease.Platelets main role is to form blood clots - upon breaking a blood vessel they encounter the proteins that "glue" our cells together. Upon identifying these proteins (and protein products formed when this "glue" is exposed to blood) platelets glom together, forming a clot. At the same time they release chemical signals that inform our bodies that the blood vessel is damaged and that an immune response is needed. In many cases those chemical signals are the first warnings our immune system has that something is wrong. But in a few cases damage caused by the immune system results in platelet activation, in which case those chemicals tend to aggravate the underlying condition.The second half of this story surrounds microparticles (image at left) - microscopic sized fragments of cells that are found in the various fluid of our bodies. Even today the source, cause and purpose of these particles remains elusive. Whether they're deliberate products that have an evolutionarily-derived purpose, or whether they're an abnormality caused by biological malfunction, is not known. A large range of cells are known to produce these particles, but in only a small number of cases do we know how, and why, these are made.The authors of this paper have tested a couple of fairly simply hypotheses - do plateltes form microparticles during an inflammatory disease (arthritis), and do those microparticles alter the disease itself?The answer to the former question is a resounding 'yes'; the number of platelet-derived microparticles increases by a huge amount during arthritis. Not only that, but the researchers were able to determine that one single receptor - the collagen receptor GPVI. Collagen, by the way, is one of the glues which hold our cells together. By blocking the interaction of GPVI with collagen this group was able to both stop microparticle generation, and reduce the severity of arthritis. The image to the left shows a platelet releasing microparticles.Which leads us to the second question they asked - do these microparitcles affect the disease? Obviously the answer is 'yes', as removing the particles reduced the severity of the disease. Exactly how this occurs is a bit of a mystery - although we know a chemical signal called "interleukin-1" is involved.What this means for patients is twofold - first of all, it validates the idea that the presence of these microparticles may be a way to detect disease. Emphasis on the "may" - we simply do not know enough about these particles to really make any firm predictions at this point. The second thing this does for patients is open the door to new therapies, targeting either GPVI or the microparticles themselves.Boilard E, Nigrovic PA, Larabee K, Watts GF, Coblyn JS, Weinblatt ME, Massarotti EM, Remold-O'Donnell E, Farndale RW, Ware J, & Lee DM (2010). Platelets amplify inflammation in arthritis via collagen-dependent microparticle production. Science (New York, N.Y.), 327 (5965), 580-3 PMID: 20110505... Read more »
Boilard E, Nigrovic PA, Larabee K, Watts GF, Coblyn JS, Weinblatt ME, Massarotti EM, Remold-O'Donnell E, Farndale RW, Ware J.... (2010) Platelets amplify inflammation in arthritis via collagen-dependent microparticle production. Science (New York, N.Y.), 327(5965), 580-3. PMID: 20110505
- February 2, 2010
- 01:18 PM
- 546 views
The cause of Parkinsons?
by Bryan in Imaging Geek
One of the more frustrating things about being a scientist is we often spend weeks, even months, between discovering (or reading about discoveries) that make a real impact in fields we're interested in. The last week was far from a frustrating week, in fact large advances were made in two areas I'm interested in (plus a bunch of cool stuff in other area's, like figuring out the colouration of some dinosaurs). Weeks like this are rare, so I'm dedicating the next two posts simply to what happened last week.This post is on an amazing discovery in regards to Parkinsons disease, a degenerative neurological disease that affects many of the elderly. Parkinsons itself has been known to be partially a defect in mitochondria - the energy-generating parts of our cells. For reasons that are still a mystery, the buildup of broken mitochondria leads to neurodegenerative diseases like Parkinsons. We've known for a long time that Parkinsons is partially genetic, and a few genes have been identified as culprits. Two in particular have been known to be major players and - PINK1 and Parkin. But while these two genes have been known to be important for a while, exactly what they did to cause Parkinsons disease was unknown - until last week.As it turns out these two genes play a role in regulating the removal of damaged mitochondria. PINK1 has been known to be stuck to mitochondria, where it is though to phosphorylate proteins on mitochondria that are no longer functioning properly. For those of you who are not bio majors, phosphoryaltion simply attaches a little chemical tag to a protein. That tag can be recognised by other proteins, or can modify the activity of the tagged protein itself. Exactly what that tag did, in terms of getting rid of damaged mitochondria, has long been a mystery.As it turns out the purpose of that tag is to bring in another protein, called Parkin, to the mitochondria. As odd as it may seem, Parkin's job is to attach another kind of tag onto proteins - a tag called "ubiquitin" (picture to right). On the surface tagging a tag may seem a little redundant, at least it does until you realise that ubiquitin is a very special kind of tag - ubiquitin is usually used by our cells to tag things for destruction. So PARK1 and Parkin act as a team; PARK1 sits on mitochondria and acts as a sensor. When PARK1 detects that a mitochondria is not functioning properly it phosphorylates (tags) the mitochondria. This tag brings in Parkin which then adds the final tag that leads to the destruction of the defective mitochondria, through a process called autophagy (literally "self-eating).You'd think that figuring out how these proteins work would be enough to make a scientist happy - but no, this group had to take things a little further. Not only did they discover how these two genes act to destroy defective mitochondria (and thus prevent Parkinsons), but they also showed that the mutations in these genes most often found in people with Parkinsons prevent this process from occurring.What is really exciting is what this potentially offers for patients. At the very least this discovery may lead to genetic tests that would allow us to detect potential Parkinsons patients decades before they become symptomatic - perhaps allowing us to treat the disease before it happens. But it also opens up the door to other options - new drug regimens, gene therapies, even stem cell therapies, to treat - or even better - prevent Parkinsons.Geisler S, Holmström KM, Skujat D, Fiesel FC, Rothfuss OC, Kahle PJ, & Springer W (2010). PINK1/Parkin-mediated mitophagy is dependent on VDAC1 and p62/SQSTM1. Nature cell biology, 12 (2), 119-31 PMID: 20098416... Read more »
Geisler S, Holmström KM, Skujat D, Fiesel FC, Rothfuss OC, Kahle PJ, & Springer W. (2010) PINK1/Parkin-mediated mitophagy is dependent on VDAC1 and p62/SQSTM1. Nature cell biology, 12(2), 119-31. PMID: 20098416
- January 27, 2010
- 11:52 AM
- 537 views
Game changer
by Bryan in Imaging Geek
I'll apologise now for the geek-out, but sometimes a little piece of science comes around that sets my nerd-senses tingling. One such event happened a few days ago, and I'm still working it into my world view - this is a game changer (at least in the little corner of the scientific world in which I live. Sorry, but I need to yell for a second:
INTEGRINS CAN ENGAGE G-PROTEINS!!!!!!!
Not impressed? You should be - unless, of course, you don't know what integrins or g-proteins are.
As per usual, some background first.... Read more »
Gong H, Shen B, Flevaris P, Chow C, Lam SC, Voyno-Yasenetskaya TA, Kozasa T, & Du X. (2010) G protein subunit Galpha13 binds to integrin alphaIIbbeta3 and mediates integrin "outside-in" signaling. Science (New York, N.Y.), 327(5963), 340-3. PMID: 20075254
- January 27, 2010
- 11:01 AM
- 416 views
Evolving Robots
by Bryan in Imaging Geek
Creationists often like to claim that complex traits cannot arise from the "simple" processes of mutation and selection. They often claim that these processed are not even observable (even though we've been observing them since we began breeding plants and animals).
Anyone with even a basic grasp of science knows the above claims are pure BS, but not being content with simply being right, some scientists have now gone the extra mile and used evolution to make ROBOTS.
And not just any robots - robots that walk, hunt each other, evolve their shape, and which are even altruistic - a distinctly mammalian trait. All of that was evolved; starting with nothing more than a collection of parts and a simple mutation/selection algorith.... Read more »
Floreano, D., & Keller, L. (2010) Evolution of Adaptive Behaviour in Robots by Means of Darwinian Selection. PLoS Biology, 8(1). DOI: 10.1371/journal.pbio.1000292
- December 30, 2009
- 12:46 PM
- 734 views
T-Cells: Beyond the Resolution Line
by Bryan in Imaging Geek
I have a diverse set of research interests - high-end microscopy, immunology, infectious disease, cancer, etc. Its rare that a paper hits the "awesome" end of the scale in most of those categories, but this week Nature Immunology published a paper that got the nerd senses tingling. In this tour-de-force, Mark Davis's group uses a new form of microscopy to analyse how T-cells work.As usual, a bit of background first.T-cells are the major regulatory cell of our immune system. The express special receptors, called T cell receptors, which they can use to identify cells which have been infected by bacteria or viruses. After detecting an infection, some T-cells (called CD4 t-cells, or helper t-cells) initiate and regulate the immune response. Another type of T-cell (CD8 T-cells, or cytotoxic T-cells) go out and destroy infected cell.The t-cell receptors (TCRs) themselves are complex things, with multiple parts (see pic on right). There is the alpha/beta chains that detect the infected cell, and then the CD3 chains and the zeta chains which transmit the signal from the receptor into the cell, and the CD4 (or CD8) co-receptor which helps stabilise the interaction between the TCR and the target cell. Upon engagement these receptors signal by recruiting proteins from within the cell, including one called Linker of Activated T-Cells (LAT), which acts as a scaffold for the rest of the proteins to bind to.This paper studies the interactions between LAT and the zeta chain portion of the TCR.The second cool part of the paper is HOW they looked at the TCR. Microscopy is plagued with one major issue - there is a distinct resolution (diffraction) limit, below which we cannot resolve. We've all experienced this ourselves, with our own eyes. Think of driving at night. When you see a car far off you see only one headlight (a, image to the left) - its not until the car comes closer that you can see two (c, image to left). Where the one light becomes two is the resolution limit of your eye; microscopes experience a similar limitation. Under optimal conditions this limit is 200-300nm, while proteins interact in spaces of 30nm or less, meaning we're lacking about 10X the resolution we need to study protein-interactions.We scientists have a few tricks to get around this limitation. This paper uses one of the newer of these tricks, called PALM. The way this works is you use a photoactivatable dye - basically a florescent marker which needs to be activated by a specific wavelength of light before it becomes fluorescent. The way PALM works is you use a weak activating beam to activate a small portion of the dye. You then image the dye using a high-powered laser, and you image until all of the active dye is photobleached (the microscopy version of burning out light bulb). The resulting image will be a pattern of dots. You repeat this process time-and-time again, and then mix the dot "images" together to get a single, complete image.Normally this wouldn't produce anything other than what you would get if you just activated all the dye and then imaged it - you'd end up with nothing more than a resolution-limited image. But there's a trick here - known as "math" - which lets us break that resolution limit. Diffraction-limited dots have a specific shape, as you can see in the image above. This shape is always the same, and the "tip" of the peak lies exactly over the fluorescent molecule. So by mapping the peak of each dot, we can "break" the resolution limit and see much finer detail - in the case of this paper, down to 25nm!So what did they find?We've known for a while that many of the proteins in our cells membranes are not evenly spread out, but instead float around in little "islands". The clustering of these little "islands" is often what activates these receptors. But in many cases - like the T-cell receptor - we didn't know what was in these little islands, or what happened to them when they clustered. There really were three options:The TCR and signalling components like LAT are in the same islands, and clustering activates them through mass-action.The TCR and signalling components like LAT are in separate islands which come together and mix; activating the receptor by mixing normally separate proteins.The TCR and signalling components like LAT are in separate islands which come together but don't mix; activating the receptor by simply bringing things close together, but without actually mixing.Davis's group has answered this question. The first image shows the TCR before (left) and after (middle) activation. You can see several small islands on the left, that come together into "super islands" on the right. The right-most image is a control of randomly distributed particles, to show they are looking at islands, not spread-out single molecules.LAT looks almost the same (image on right), with lots of small islands before activation, and fewer big islands after activation. And while its not obvious when you compare the TCR image with the LAT image, the pre-activation TCR "islands" do not overlap with the pre-activation LAT "islands".So that answers the first half of our question, LAT and the TCR are in separate islands before activation. But do they mix, or are they wall flowers?How this was demonstrated is hard to explain; but they used two mathematical measures to figure it out; Ripleys K-function, and cross-correlation, both of which measure how well two distributions overlap. Without going into a lot of boring detail, the TCR and LAT cluster togeather upon activation, but the individual clusters of TCR and LAT remain separate; think of a cookie - both chocolate chips and peanuts are in the cookie, but the chips and nuts remains separate.... Read more »
Lillemeier, B., Mörtelmaier, M., Forstner, M., Huppa, J., Groves, J., & Davis, M. (2009) TCR and Lat are expressed on separate protein islands on T cell membranes and concatenate during activation. Nature Immunology, 11(1), 90-96. DOI: 10.1038/ni.1832
- December 11, 2009
- 01:37 PM
- 712 views
Walking the line, using a microscope
by Bryan in Imaging Geek
Things need to get transported around inside of our cells. For example, proteins meant to detect extracellular signals like hormones must move to the cell surface; otherwise they won't work. Much of this cargo gets moved through small balloon-like structures called vesicles. Rather than drifting randomly, these "balloons" move along tracks in the cell called microtubules; long, filamentous proteins that form a skeleton within the cell. ike a train, these "balloons" require a motor to pull them along the microtubule tracks. In a cell this job is mediated by motor proteins. While there are a few kinds of motor proteins, this paper deals with one kind called kinesins.
One outstanding question in the biology of kinesins is how do they know where to go - as you can see in the picture of the cytoskeleton at the beginning of this post, microtubules go everywhere, which makes it hard to understand how things can be selectively moved to specific points in the cell. As it turns out, microtubules are not quite as simple as I outlined here - they're dynamic, as in they continually grow and shrink. But among those ever-changing tracks there are a small number of microtubules that are modified in a way which makes them stable. Furthermore, these stable microtubules do tend to go to specific places - for example, in neurons they lead to the junctions between one neuron and the next. Perhaps these modified microtubules act as highways that allow cells to specifically move proteins to important places.... Read more »
Cai D, McEwen DP, Martens JR, Meyhofer E, & Verhey KJ. (2009) Single molecule imaging reveals differences in microtubule track selection between Kinesin motors. PLoS biology, 7(10). PMID: 19823565
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