Friday, February 26, 2010

Crazy artificial genetish

This is just crazy.  I'm still not decided whether it's mad-scientist, what-could-they-possibly-be-thinking? crazy or it's brilliant, why-didn't-they-think-of-this-sooner, life-is-now-complete crazy.

According to a recent post at, scientists have recently created an artificial system in which a bizarre, created ribosome reads codons in mRNA that are four bases long. You read the correctly . . . instead of reading bases three at a time (like in real life), these little monsters can read a whole different form of genetic language—or genetish, as author Matt Ridley calls it.

This breakthrough allows scientists to build a whole new system of creating proteins—one in which there could be up to 256 different possible amino acids available.  This means that instead of being limited to using only the 22 naturally-occurring amino acids currently available for playing around to produce crazy new proteins, scientists can now also use synthetically modified amino acids with a variety of chemical properties. Modified or synthetic amino acids have no 3-base codons to represent them in natural genetish.

Just a few months ago, we were lauding the Nobel laureates who helped us figure out the structure of the ribosome.  Now we're seeing the creation of artificial ribosomes that translate artificial genetish. I guess this is a huge breakthrough for chemists hoping to synthesize new types of proteins.  It may also provide opportunities for synthetic biologists (scientists attempting to create artificial cells, tissues, and organisms).  It certainly is a great starting point for a sci-fi novel!

Want to know more?

Genetic coding revamp
Jef Akst 14 Feb 2010
[Summary of development of a new genetic language.]

Some background from the primary literature:

A chemical toolkit for proteins — an expanded genetic code
Jianming Xie et al.
Nature Reviews Molecular Cell Biology 7, 775-782 (October 2006) doi:10.1038/nrm2005

An evolved ribosome for genetic code expansion
Caroline Köhrer et al.
Nature Biotechnology 25, 745 - 746 (2007) doi:10.1038/nbt0707-745

A network of orthogonal ribosome·mRNA pairs
Oliver Rackham et al.
Nature Chemical Biology 1, 159 - 166 (2005) doi:10.1038/nchembio719

Monday, February 22, 2010

FREE digestion images
Although there's still a lot more to go, I have recently updated the library of images for digestion in the FREE Image Library at The A&P Professor website.

In a previous post I outlined a few of the many ways you could use supplemental images like these.  In this batch, there are some dramatic images of gall stones, laparoscopic views of digestive organs that I may use to spice up our classroom discussions a bit.

Thursday, February 18, 2010

New discovery about sperm's ability to swim

Scientists have found the trigger that gets sperm swimming in the female reproductive tract.

Sperm cells in the testis are pretty quiet . . . they don't seem very interested in swimming.  However, after they are ejaculated into the female reproductive tract they become activated and get with the program. We already knew that the sperm cells need to raise their pH in order to kick into their swimming mode . . . but we didn't know how that is actually done.

In an article in the journal Cell, researchers report that they have the answer . . . one-way proton (H+) channels called Hv1 that open when sperm enter the female reproductive tract.  Increasing the intracellular pH triggers the influx of calcium ions, which in turn activate the sperm flagellum.  And they're off!

The increase in intracellular sperm pH also enables the sperm's acrosome to become activated and get ready to do its job, too.

Hv1 may be a key to triggering the hyperactivation and capacitation of sperm necessary for male fertility.

The researchers also found that a chemical similar to the active ingredient in marijuana inhibits the Hv1 channels and thus reduced fertility.  Perhaps this explains low fertility among males who are chronic users of marijuana.  And perhaps this opens the door to discovering chemicals that can be used to regulate the sperm fertility.

Want to know more?
Science News web edition : Thursday, February 4th, 2010
[Summary article includes a cool fluorescent micrograph.]

Acid extrusion from human spermatozoa is mediated by flagellar voltage-gated proton channel. 
Lishko, P.V. et al.
Cell Volume 140, Issue 3, 327-337, 5 February 2010
[Original research article with some fabulous images in the graphical abstract and an excellent movie that features the scientists explaining their discovery. ]

Sunday, February 14, 2010

Any dopes in Vancouver?

If you're like me, I mention the concept of blood doping when covering the life cycle of red blood cells (RBCs) and the homeostatic mechanisms that regulate the population numbers of RBCs.

In 2008 and 2009,  beginning around the time of the Beijing Olympics, I wrote a series of articles on doping in this blog and an extended version at The A&P Professor website.

I recently updated that extended doping article with a link to a recent news story from the Canadian Press service regarding the possibility of doping with the experimental anemia drug Hematide.

The doping issue is a great way to tie an unfortunately unending series of "real life" high-profile cases to the concepts of blood physiology.

Check out my Doping article, which includes several resources from major anti-doping agencies plus hints for incorporating doping issues in your A&P course.

You may also be interested in the PBS video Doping for Gold, which chronicles doping in a generation of European athletes. In the 1970s, female East German athletes came from nowhere to dominate international sport. Behind their success lay a secret, state-sponsored doping program that distributed untested steroids to athletes as young as 12. Many of these girls had no knowledge that they were being doped, and now, their damaged bodies and psyches deal with the cruelty of a government that pursued international glory at the expense of its most acclaimed citizens.

Wednesday, February 10, 2010

Prions are our friends

OK, let's see if I can remember what I just read about prion proteins (PrPs) . . . I think I read that they can help us store memories.  Oh yeah, that's right . . . and it turns out that they are needed to maintain the insulating myelin sheath around neurons that enables proper conduction of action potentials.

In my Anatomy & Physiology textbook I define a prion as
a term that is short for “proteinaceous infectious particles,” which are proteins that convert normal proteins of the nervous system into abnormal proteins, causing loss of nervous system function; the abnormal form of the protein also may be inherited; a newly discovered type of pathogen, not much is known about how the prion works; see bovine spongiform encephalopathy, variant Creutzfeldt-Jakob Disease (vCJD)

Well, it turns out that prions are not all bad, after all.  In a recent article in Nature Neuroscience, scientists report that certain prions are needed for the axonal signaling to Schwann cells that is needed to maintain the myelin sheath (pictured) and thus maintain normal conduction of nerve impulses.

In another finding reported in the journal Cell, scientists working with prions in sensory neurons of the sea slug found that the clumping of prions that we previously associated only with prion diseases plays a role in preserving memory.  Typically, when prions clump, they for tangles called amyloid plaques in a cell. Apparently, the clumping of certain prions at synapses increase the length of time that a memory is stored at that synapse.

Researchers also found that the neurotransmitter serotonin promotes the formation of the memory-preserving clumps.

More work needs to be done, of course, but these findings may lead to the discovery of a central role for prions in retaining long-term memories.

Want to know more?
Axonal prion protein is required for peripheral myelin maintenance. 
Bremer, J., et al.
Nature Neuroscience. 24 January 2010. doi:10.1038/nn.2483
[Original research article]

Prion protein is not all bad
Tina Hesman Saey
Science News February 13th, 2010; Vol.177 #4 (p. 17) 
[Summary article describing the role of prions in maintaining the myelin sheath, as well as some general insights on the emerging new view of prions.]
Aplysia CPEB Can Form Prion-like Multimers in Sensory Neurons that Contribute to Long-Term Facilitation
Kausik Si, et al.
Cell Volume 140, Issue 3, 421-435, 5 February 2010
[Original research article included a nifty graphical summary of the central findings.]
Click here for an audio interview with the scientist about this breakthrough

Protein clumps like a prion, but proves crucial for long-term memory
Tina Hesman Saey
Science News web edition : Thursday, February 4th, 2010
[Summary article explaining new research findings and their importance.]

Saturday, February 6, 2010

FREE respiratory images

You already know that I'm slowly adding to the Free Image Library at The A&P Professor website.  I've recently added a few images related to the Respiratory System to the collection.

All the images are either copyright-free or provide a free license to re-use them with permission.  So you can use them to . . .
  • Add them to your PowerPoint slides.

  • Use them in handouts or outlines.

  • Use them in tests or worksheets. Many of them have numbered and/or unlabeled versions that make this easy for you.

  • Provide them to students to use for their reports, projects, or concept maps.

  • Use them as icons for your website or learning management system.

  • Illustrate case studies with medical images or clinical procedures.

  • Use pathology images to hammer home concepts of normal anatomy and physiology.

  • Make your own anatomy T-shirts using iron-on transfer paper to print the images.

  • Receive inspiration to become a scientific illustrator.  (Then call me, I can use your help!)
Why not just use the images provided by the publisher of your textbook?
  • No textbook contains all the variations of how to draw a structure or concept.  Use alternate images to help drive home a particular point.

  • Students aren't really learning their anatomy and physiology if they memorize a particular diagram.  Using alternate diagrams on worksheets and tests pushes them to learn where things really are in the body. . . not where they happen to be labeled in the book.

  • Textbooks must conserve space to remain a practical tool.  There are many images that would be great to show students . . . such as medical images, portraits of A&P heroes or sources of eponyms, or amazing micrographs . . . that are simply not appropriate for a beginning-level textbook.

This image of an iron lung is not appropriate for a textbook, perhaps, but it might help you explain the concept of how pressure affects the mechanics of breathing.

Please send me your ideas for images that you need (maybe I can find them for you).

I'll be updating you when I add more topics to the Free Image Library.

If you have any suggestions for additional subjects for images, let me know and I'll try to find them for you.

Tuesday, February 2, 2010

Lipid rafts

Having lived most of my life near the river banks at the confluence of the Mississippi and Missouri Rivers, I guess I have a special place in my heart for rafts. A few years ago, when scientists discovered organized domains within cell membranes and named them rafts, I guess it all felt pretty obvious to me . . . and comfortable.

I was thinking about rafts today when I received this month's issue of  The Scientist, which features a cover story on the evolution of the lipid raft concept.

My Life on a Raft
Kai Simmons
The Scientist Volume 24 Issue 2  Page 24 February 2010
[Brief article by a pioneer in the discovery and study of lipid rafts]

In my textbook Anatomy & Physiology I define a membrane raft as . . .
"a structure made up of groupings of molecules (cholesterol, certain phospholipids, proteins) within a cell membrane that travel together on the surface of the cell, something like a log raft on a lake; also called lipid raft"
 When I first added the concept of lipid rafts to our introductory chapter on cellular structure a number of years ago, some of my colleagues were a bit put off by this addition.  Some reviewers suggested that I drop it because it wasn't, well, standard in the texts with which they were familiar.

First, I think that when we form our own cohesive idea of what a cell is, it's hard to break that apart easily to accommodate changes and (especially) radical new concepts.  It's even harder to imagine that any new concepts of cell structure and function have any place in an introductory conversation about cells. 

Second, it isn't always immediately clear that a beginning student is really going to encounter significant applications of such a new concept in their studies . . . or in their practice.

With lipid rafts, the concept was used several times in other parts of the book to understand such central ideas as endocytosis.  As a science, we continue to learn about significant medical application opportunities, such as a possible effective therapy for HIV infection and other viral conditions (for example, see New non-drug fix for HIV).

Similarly, come colleagues question my textbook's coverage of the cytoskeleton and motor molecules, when this dynamic system seems to play a basic, central (and increasingly well understood) role in many mechanisms typically covered in a beginning A&P course . . . not to mention applications in clinical science.

So updating a textbook can be quite challenging when it comes to deciding how to handle new ideas that come along. 

When, if ever, is a new biological concept ready to be put into an introductory textbook?  If one puts it in early, then some users are alienated by the unfamiliar.  Some may even be suspect of something different than the orthodox and time-tested A&P curriculum. If one waits until everyone has already become familiar with the new idea, then isn't it a bit late to be first introducing into a textbook?

For me, the central question is, "Do textbook authors have any responsibility to introduce new concepts into the curriculum?"   I think the answer is yes.  Of course, curriculum issues are guided by more than just textbook content.  Many agents interacting on many levels help guide the evolution of curriculum in anatomy and physiology (and any other discipline).  I think textbook authors are in an unusual . . . and sometimes scary . . . position of offering some of the latest ideas available.

Of course, introducing additional concepts has to be balanced with the concern that too much information, no matter how up-to-date or relevant, may make it hard for the beginning learner to establish a meaningful foundation upon which to build later, fuller understanding of human structure and function.  Another difficult and scary task, then, is to determine what is essential at the beginning level and what can be held off for a later time when the additional information will be more easily incorporated into a student's understanding.

I'd love to hear your comments!   What is the role of the textbook author when in comes to incorporating new or changed concepts in the A&P curriculum?  How can one determine which concepts are better left for later learning?

NOTE: Get some FREE images of lipid rafts to use for your class at The A&P Professor FREE Image Library.