Sunday, March 29, 2009

Bacteria can run but they can't hide

I just stumbled across a video ( of a neutrophil chasing down and engulfing a bacterium. Although it’s one of those old, slightly grainy science films from the 1950s, there is something really compelling about the frantic vibrations of the bacterium, the remorseless pursuit by the neutrophil, and their eerily silent battle among the red blood cells. It’s a little Hitchcockian, don't you think? I leaned forward while I watched it, and now I can’t help anthropomorphizing the heck out of it while I discuss it. Although that isn’t completely out of line, since this very scene is being repeated a million times over right now inside me and you and every human. At any rate, it was interesting enough to get me to Google around a bit to refresh my memory on just what a neutrophil is and does. So you go, 1950s filmstrip.

As is so often the case in biology, what looks like a simple process – see bacteria, catch bacteria, kill bacteria – is actually quite complex. Neutrophils are one variety of a kind of white blood cells called granular leucocytes, which form a major part of the immune system. The cell membrane of each neutrophil is studded with chemical receptors. These receptors are specialized to detect the proteins that immune cells release when they encounter an infection or inflammation. When neutrophils receive such calls for help, they follow their chemical gradient back to the source with great speed. Upon arrival, foreign bacteria are destroyed through phagocytosis – the neutrophils engulf and then digest the invaders. The bacteria do get revenge of a sort. Eventually the neutrophils die, and are themselves phagocytosed and subsequently turned into pus, which isn’t a particularly glorious end for such staunch defenders.

Neutrophil (yellow) engulfing anthrax bacteria (orange). Scale bar is 5um. From PLoS Pathogens Vol. 1(3) November 2005.

Sunday, March 15, 2009

Those who can, doodle

JFK's White House Doodles
I’ve been seeing lots of news stories lately about a research study that suggests that doodling improves memory. A group of test subjects who were directed to doodle while listening to a series of long, dull conversations remembered the details much better than the group who simply sat and listened. It seems that the brain is adapted to be active, and if the world doesn’t supply enough stimulation to keep it going, it’ll make it’s own through daydreaming. Doodling keeps the brain just busy enough that it continues to pay attention to the outside world. Daydreaming takes more mental effort, and distracts the mind from its surroundings.

There are obvious implications for teaching in this. As a biology student, I doodled a lot – the citric acid cycle, that would do it. The electron transport chain, every time. But I mainly did it when I thought I could do it on the down low, sitting in the back of the room or in a large lecture hall. In a smaller class, I became the master of the glassy stare and the falsely inquisitive head tilt instead.

As a teacher, I’m sure I’ve given more than one doodler the skunk eye. Now I wonder if I should encourage it. Every lecture has its boring bits – anything that keeps a student learning through the dull spots is worth using. Maybe I need to add doodles to the hands-on demo, the small-group discussion pause, the five-minute stretch and soda break, and all the other straighten up and pay attention tricks. At the least, I'll try and see doodling as a genuine attempt to learn rather than as a surefire sign of slacking.