Category Archives: biology

Electric Faces

From here:

For the first time, Tufts University biologists have reported that bioelectrical signals are necessary for normal head and facial formation in an organism and have captured that process in a time-lapse video that reveals never-before-seen patterns of visible bioelectrical signals outlining where eyes, nose, mouth, and other features will appear in an embryonic tadpole.

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The folks who made The Life of the Cell made a new video last year:

Nuclear Pore Complex

Click on the image to see some more neat pics

Classic Cell Animation

You have probably seen the 3 minutes version, but I just found out that the complete 8 minute version is on youtube:

Also, the narrated version is below the fold:
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Taste the Cold

Something of interest from a couple of years ago:

Several years ago, the specific receptors that allow us to detect heat were identified in nerve cells.  Closely related to the capsaicin receptor (TRPV1), TRPV2 is an ion channel that, upon activation by heat, allows positively-charged ions to enter neurons.  This creates a potential difference across the cell membrane and therefore an electrical current.  Given that these two receptors are closely related, it isn’t that surprising that exposure to capsaicin, the active ingredient in chili peppers, is sensed as “hot.”

Now a new paper published in Nature has shown that on the other end of the temperature spectrum, cold is detected by the same ion channel that is activated by menthol.  Known as TRPM8, the ion channel is activated both by menthol, a compound found in mint, and by temperatures below 26? C.  The researchers from UCSF, the Medical College of Wisconsin, and Yale have shown that isolated, cultured nerve cells that express TRPM8 react to cooling stimuli, but cells cultured from mice lacking TRPM8 do not.  Further, the mice lacking TRPM8 are much less sensitive to cold than their normal equivalents.

Where It All Begins

So what do the special senses all share in common?  They all begin with cilia, the little hair-like projections that extend off the surface of cells.  When it comes to the sense of smell and taste, the cilia bind molecules and an electrical change in the membrane is produced.  When it comes to the sense of hearing and balance, the cilia are bent and an electrical change in the membrane is produced.  When it comes to the sense of sight, photopigments arrayed within the cilia absorb light and an electrical change in the membrane is produced.  Below is a figure of the three different cilia (shaded in green) tailored to detect changes in three different forms of energy:

Figure from Tomer Avidor-Reiss, Andreia M. Maer, Edmund Koundakjian, Andrey Polyanovsky, Thomas Keil, Shankar Subramaniam and Charles S. Zuker.  2004. Defining Specialized Genes Required for Compartmentalized Cilia Biogenesis Cell (04) 117:527-539.

We know these cilia are essential to our senses.

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Special Sense Quiz

There are five special senses located in our heads: taste, smell, hearing, vision, and equilibrium (balance).  These senses provide the majority of information about our environment and together can detect changes in three different forms of energy – chemical, light, and mechanical.

So now it is quiz time.  There is something that all these special senses share in common.  Do you know what it is? Below the fold is a hint: figures that illustrate the core detection components of all five senses.

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Metazoan extremophiles

Deep under the Mediterranean Sea, small animals have been discovered that live their entire lives without oxygen and surrounded by ‘poisonous’ sulphides.

Also, from the same article:

“These extreme environments,” said Danovaro, “have been thought to be exclusively inhabited by viruses, Bacteria and Archaea. The bodies of multicellular animals have previously been discovered, but were thought to have sunk there from upper, oxygenated, waters. Our results indicate that the animals we recovered were alive. Some, in fact, also contained eggs.”

So contrary to conventional biological wisdom, metazoan life can thrive in extreme environments.  This new research also helps us appreciate how another popular belief is also probably false….

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The spliceosome is a dynamic molecular machine that removes the introns from protein-coding genes in eukaryotes.  It is composed of 5 small RNA molecules and around 300 proteins.  Here is a video that shows you how the spliceosome works:

Quiz Time

I have a question you can ponder over the holiday weekend. Below is a picture of Tetrahymena, a single-celled eukaryotic organism that is related to the paramecium you might have seen in a high school biology class.

And here’s what the critter looks like with an electron microscope:

Time for your quiz.

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