26 July 2011

Arizona Part 3: Still on the Water Thing

I realized I wasn’t done with water.  Don’t worry, even I’m growing bored of it.  I’ll be on to bigger, better Arizona things soon.

I just wanted to let you know not to cry for me over the fact that we never got snow days as kids.  And no, we didn’t get heat days, either, even though in a hundred and ten I can tell you that school swamp coolers just don’t cut it.

(Aside: Swamp coolers.  Would you believe that when it’s really hot and dry, you can run water over a pad and then draw air through it into a house, and as that water evaporates it cools that house?  People have made these machines (also less inventively known as ‘evaporative coolers’) for bone-dry places like Arizona, and in practice they even kind of work.  In June.  For a while.  Husband and I used to have a swamp cooler in our house, and in July and August we sweated buckets late into the night playing Dance Dance Revolution in our unders in the privacy of our living room while the swamp cooler pumped in heavy, wet, not remotely cool air that smelled of local sewage treatment plant.  Delightful.  End aside.)

This is a swamp cooler.  The pigeons love that it drips water, and probably love less the way their insides feel after trying to drink it.

So we didn’t get snow days, and we didn’t get heat stroke days.  But we did get a couple of flood days.

Arizonans don’t know what the hell to do with precipitation of any sort when they do get it.  Worse, it only comes in deadly bombardments and not in manageable drizzles.  Flash flood warnings are a regular occurrence, and annually a number of people have to get pulled by firemen out of cars stalled in underpasses that look like this:

Taken this week.

There’s little adequate drainage to speak of anywhere in our city.  The water is supposed to be channeled along the sides of roads and dumped into gutters, but the gutters are too small and fill fast with debris, and soon even the main streets become filled with running water.  It inevitably drains off onto secondary streets, which city planners have elected to allow to dip into the deep drainage washes (now running feet deep) rather than build more drainage tubes and run the roads over them.  I mean bridges, those are like, expensive, right?  And you can see from the picture above how well these ditches work.  They speak for themselves, really.

So if you live anywhere, pretty much anywhere in the city, when it starts really raining you’re unlikely to be able to drive anywhere else of real import because your car will get stuck in the water.  This is especially true of the boonies where we lived, as we had to cross no fewer than four major washes running straight off the mountain before we could get out of our suburban corner and into the proper city.  And by the way, our city planners may suck at planning for water, but our drivers are even worse at driving in it.  If you could get past the washes, you’d probably get sideswiped by a hydroplaning idiot trying to turn left. 

(That idiot was me, I admit, when I was sixteen and full of newly-licensed hubris on the back streets of Minneapolis during a summer storm – I almost took out two entire branches of my extended family driving my cousins and sister to rent some DVDs.  Hell, they might have been VHS tapes, come to think of it.)

So on flood days, we got to stay home.  It was beautiful.

And I have had one “snow day” in my life.  I was living for two months with the parents after college, it was winter time, and by some miraculous force of Higher Power, we woke up one morning to see the sky had snowed and sleeted and the world was covered in a very thin film of icy powder.  My dad and I were carpooling to work then, and we got in his car and made a valiant effort for two straight hours to try and cross either of the two bridges leading from my parents’ house into town, both now covered in ice and snow that still, bizarrely, had not melted even by ten o’clock.  There is no way to get into town without crossing one of these two bridges.  And my dear city has, to its name, exactly one snow plow.  And I think they were trying to de-ice something on the bridge too or something, which is the extent of my knowledge on the subject because I am a native Arizonan and know nothing at all about precipitation (I had never even heard of a roof rake until I was in my second quarter century on this earth).  No one was getting across those bridges.  So we gave up and went home.  And yes, I may have had a bachelor’s degree already under my belt when it happened, but I might as well have been five for how excited I was to finally get a single mostly-legit snow day in my life.

Picture courtesy of my dad.  Gorgeous, right?  And yes, this shut down an entire corner of the city for half a day.

25 July 2011

Arizona Part 2: The power of water

We’re moving out of Arizona at year’s end.  I’m already missing it. 

See, I’m a native here, and by that I mean I was born somewhere else but I don’t remember much of it.  Home to me has always been here, in this little patch of dirt ringed by purple remnants of an old volcano.  Home is washes that only run with water a few months of every year – torrential flash floods of mud in summer, frigid snowmelt in winter.  Home is saguaros and javelinas and creosote and knowing how to pronounce all of them.  Home is just the right amount of sky.  Home is sun, and sun and sun, with a few miraculous moments of weather.  Home is where precipitation is considered nothing short of blessed, all the time.  Home is one day of snow every seven years, snow that never sticks, snow that dances and falls and disappears instantly.  Home is coyotes howling and cicadas buzzing and frogs chirping in raucous chorus and the morning call of mourning doves.  Oh, the mourning doves!  My heart cries already.  Home is mesas and roadrunners and pico de gallo and temperatures too hot for thermometers and cracked pavement and cacti and swimming pools and year-round flip flops and only owning casual wear and painfully gorgeous sunsets.  How am I going to survive living anywhere else?

Water.  In the desert it all comes back to water.  It’s the precious thing.  I have so many memories about water.  How are people going to understand my lust for water?  Can I give you some Scenes from the Life of Me, sort of thing, and maybe you can harbor some of that lust with me?

When I was a wee babe, solid water was something that came in trays out of a freezer.  I was shocked, delighted, aghast when I found it also in the open trunk of my red-and-yellow toy car in the back yard one uncharacteristically frigid winter morning.  I was young, so young, and I could never claim that to be my first experience with natural ice but it’s the first I remember.  It was just so weird.  Water wasn’t supposed to do that.  I was so giddy about frozen water my neurons hardwired that memory into something I still have all these many years after I’ve forgotten the majority of my childhood.

The first time I remember seeing snow falling was in fourth grade.  Maybe it was fifth.  It snowed in the courtyard outside our classroom and the teachers let us all out to play in it – because when were we ever going to get that chance as children again?  We were mesmerized.  It almost stuck to the ground. 

In school we learned all about water.  I knew from the age of seven that to qualify as a desert a place has to get less than twelve inches of water a year, and our place got eleven.  Well, back then it got eleven.  Now it’s becoming sort of a joke to say we’re still in a longstanding drought, as we fail year after year to reach our mark, as the water table falls ever farther and we import more and more foreign water via aqueducts from other states… 

But I digress – back to those school days.  We attended special assemblies all about water and how to conserve water.  There was a duck.  A guy in a duck suit, whatever.  We learned to conserve water and we did a damn fine job of it, too.  When we went to visit my cousins out of state, my aunt was I think a little appalled that my sister and I would spit our toothpaste into the sink before washing it away with a short burst from the tap.  I was appalled they were willing to just let the water run a full two minutes for no reason.  It was one of those cultural things.

The only award I ever received for a school science project was about water.  It was second grade, and we were trying to figure out what kind of water helped bean plants grow best.  The answer, according to our results, was tap water.  Little did we know at the time (well, okay, I didn’t know – maybe my two collaborators were better informed than I was) that tap water had become quite politically charged that year.  They were just getting the Central Arizona Project water system online, pumping water in from Colorado, and the whole project was fraught with problems and most of the town wanted it canned.  Needless to say, CAP gave us an award for our work and we got to go up on stage and collect a plaque and everything.

Water, water, it was all about water – about the ebb and flow of nature, all governed, wholly and mercilessly, by water.  Seasons were measured not by temperature so much as by water.  And there was no better example of that than at the creek by my parents’ house. 

The creek

(People who live in Arizona haven’t invented any new words for dry washes – we still call them rivers and creeks and whatnot, even when they don’t have any water in them.)

The creek was – and is – a magical place.  It runs off from the adjacent mountain canyon, cutting into the valley and joining the aptly named Rillito River that runs through town.  And when I say The Creek, I’m speaking of a particular one-block section or so surrounding the point where it intersects a horse trail leading up from our neighborhood into the mountains.  This section is bounded on one side by the white rocks – a waterfall of, well, big white rocks that sit on someone’s private property.  (When we were little we scarce knew of the white rocks, because we didn’t dare step past the private property line with its intimidating yellow warning signs full of bullet holes.  And when we were older, it became our actual duty as kids to cross that same property line and see what we’d been missing.)  The creek is bounded on the other side by, um, I guess by more wash, which we tended to access from the other side of our neighborhood and which is therefore a distinct entity called the Meadow. 

The creek is dry most of the year, but in summer when the monsoons come it has water in it.  It flows for a few days, sometimes, after a heavy rain.  And in the winter it runs for even weeks at a time as the snow melts up on the mountains.

The creek after it rains

When we were very little, my mom would get us in our swimsuits and we’d go splash about in the foot or two of water flowing lazily through the broad section of creek right where the big trail crosses it, made broader by a rock dam built so that hikers could get across even on those few days when they needed a bridge to do so.  There were little fishes and tadpoles swimming in the creek and I never understood how they got there or where they went when the water went away. 

When we were much older my friend and I found out where they went.  We had trekked out to the white rocks, to the pool at their base which was much deeper than the rest of the creek, and there found the last few remaining inches of water evaporating away weeks after the latest rain.  And in that algae-filled slime writhed hundreds of fish, flopping helplessly body-to-body, asphyxiating slowly, squirming against each other in an effort to reach the last vestiges of fetid water.  It was a horror I don’t think either of us has forgotten.  And there was nothing at all we could do.

So I figured out where the fish went.  I never figured out how they got there.  They spawned seemingly out of nothing, growing to fill that deepest pool in the creek at the base of the white rocks.  The same white rocks where we once found a rattlesnake curled up sleeping in a cranny, the white rocks that had that one perfect groove for a butt and a lower back, the white rocks with a just-obscured view of the house over the hill where sometimes you could hear voices or dogs barking, the hill I didn’t want to admit I looked warily up at more often than my overconfident sheltered preteen attitude felt was strictly necessary. 

My only picture of the white rocks: the obscure patch of white hidden behind the brush just over the left ear of the equally obscure deer.  You might remember this picture.

The white rocks were the best place to be in the winter, when the snowmelt was six feet deep and you could make a show of jumping in with all your clothes on and shocking the crap out of your nervous system.  It was cold.  One of my very best memories of those preteen years was formed when my best friend and I convinced some classmates to jump in with us.  The two of us seasoned veterans just jumped right in all brazen and casual about it, and the rest followed like good lemmings.  I still remember the look on one boy’s face when he came up gasping for air yelling “oh shit” repeatedly, poor desert rat with no sense for ice water.  And I think I kind of fell a little in love with another of them when I saw how stoically he handled the experience.  That was one of those testing-ground kind of days, you know?  It was a bonding thing.  I held onto some of those friends for years.

We had some beautiful times at that creek.  It makes me emotional, thinking about the creek.  If you took the trail to the creek and turned right, you’d reach the white rocks, but if you turned left you’d reach our three rocks.  We had these three rocks, and we may have named them but I don’t remember now.  I just remember the feel of them, the big flat one and the tall craggy one and the little one, and the way they made this perfect shallow pool and the way you could lie on them and stare up at the sky and let your feet dangle in the water.

There existed a Moment, on those rocks.  You know how Moments go.  They’re a little piece of perfection encapsulated in a single image or sentence or smell or feeling, a memory too good to let go.  This Moment was perfect because the air was clear and everything was green and the water was flowing and the sun felt just warm enough on skin and it heated the rocks just right, and we were lying there poised like Abercrombie models on the big flat rock and all of a sudden a duck flew by.  A bloody mallard duck.  For those of you who don’t understand, I will let you know that mallard ducks don’t happen in Arizona, not out in the wilderness.  That mallard made it a Moment and I won’t readily forget it.

The creek hasn’t been the same since it flooded.  I don’t remember how many years ago it flooded, but it did, and all our favorite spots were terraformed beyond recognition by a wall of inconsiderate water.  Nature at her best, the bitch.  She gouged a whole new path for the water to go and marred everything we loved irreparably, in a single night.  Out here in the desert, the water commands respect.

Interjection: Fast Things

Oops!  I interrupted my (ironically very slowly generated) theme about fast biological things to tell you my lament about Arizona.  And now I’m interrupting my lament series about Arizona to wrap up the Fast Things theme.  Fast.

All I wanted to say was: Blah blah blah eyes are also complicated blah blah now imagine how much has to happen for you to slam on your brakes at an intersection blah blah blah be a safe driver.  Fin.

24 July 2011

Arizona, I love you (Part 1)

I’m going to miss this place.

I’m sitting in my living room listening to the pounding of rain on the roof.  And now I’m not.  That span of a sentence was the full length of that first foreboding burst of rain.  And now it’s back.  See how quickly the weather changes in Arizona?

Now it’s coming down hard, blowing in all directions, really drenching the pavement outside.  I can’t see the mountains in the distance.  It’s still light out, like anyone else’s normal sunny day.  And it is pouring.

A good Arizona monsoon day starts with a cloudless, stifling, muggy summer morning.  It’s a hundred and five and the humidity is forty percent.  Scoff if you want, but in a desert forty percent might as well be a steam room.  The cicadas are loving it – their constant deafening buzz rings from every tree, cutting like knives through still, thick air.

And then, on toward afternoon, the clouds start building.  Huge mushrooms of white billowing out of bright blue nothing off in the distance.  They start lumping together, forming a black mass on the horizon, a wall of water coming closer.  It starts to get darker.  The cicadas go quiet.  And then you catch a whiff of that smell, that fabled desert rain smell everyone talks about in poems and songs, the one you have to live to understand.  The smell of wet creosote.  It’s still sweltering.  The wind starts to pick up, short sharp bursts of air rattling tree branches, kicking up dust.  And the clouds get closer.  Lightning flashes in the darkness, you hear that gentle roll of distant thunder.

One big, heavy drop of rain thuds onto the ground.  Another, another, smacking hard into hot pavement.  They dapple the ground, steaming.  You look up and you can see that gray wall heading right for you, obscuring the houses down the block. 

And then the sky breaks open and a torrent of water descends, a whole ocean all at once, a downpour of epic proportions.  Heavy gusts of wind knock the rain about, water dancing sideways through the air.  The sky goes dark.  And it keeps coming.  In moments the streets turn to rivers, waterfalls cascade from rooftops.  Lighting cracks overhead, instantaneous flash-boom ripping through the atmosphere.

It’s over in minutes.  Soon the flood becomes a drizzle, last wringing of straggling leaden clouds as the storm passes onward.  Suddenly the only water still dropping is off of roof edges, parched earth soaking it in greedily the moment it hits.  Rivers become rivulets, which give way again to already drying streets.

The next morning you can hardly even tell it rained at all. 

And then the clouds start building.

The scene from our front door

05 July 2011

The ephemeral lives of synaptic vesicles

So I already talked about how muscles are insane and you would never believe that they can work as fast as they do once you see how they work.  This is even truer of your brain.

We all (hopefully) know that your brain is filled with cells called neurons and that the things you call thoughts are really electrical impulses traveling among those neurons.  Good. 

So for now I’m going to leave aside just how that electrical impulse travels through a single neuron, because while that is cool and also mind-boggling in its speed-despite-complexity, it doesn’t make for a very interesting blog post (well, I think it does, but that’s me and not everyone else in the universe).  What does make for a marginally more interesting blog post is what happens between neurons  how that signal hops from one neuron to the next.

Here’s why it’s more interesting.  While a signal traveling within a neuron is essentially an electrical signal, propagating quickly like any electrical signal would (you know, like in a copper wire or something), the transmission that goes on between neurons is chemical.  There’s a very small space between the end of one neuron and the start of the next, and this space is called a ‘synapse’.  And somehow the signal from the first neuron has to jump across that space and start a new electrical signal in the next neuron. 

The neuron accomplishes this by releasing little packets of chemicals (aptly named neurotransmitters) that make their way across the synapse and bind onto the surface of the next neuron, catalyzing a whole cascade of crazy events and eventually (possibly and with all standard biological “nothing works exactly the way I say it does” caveats) resulting in the instigation of another electrical signal in the next neuron.

Quickly, some terminology.  And I made some pretty pictures to show it to you!  

Like I already said, the space between neurons is the synapse.  The first neuron is the presynaptic neuron, which has a very long fiber called an axon, which has an end called an axon terminal.  The second neuron is the postsynaptic neuron (which also has its own axon, but that’s not important right now).  

The chemical being transmitted is a neurotransmitter.  (There are many kinds of neurotransmitter, and you’ve probably heard of a few of them: dopamine and serotonin and adrenaline and the like.  Ironically, none of these are the standard neurotransmitter  used by 9 out of every 10 neurons  which is glutamate.  Have you even heard of glutamate?  I didn’t think so.  Poor glutamate...)  The ‘packets’  I mentioned earlier are really called vesicles, and they’re bubbles made of cell membrane.  I’ll define other new terms as I go.

Okay, this is taking way too long already.  I need to get to the point.

In case you get bored before you reach the end of this post, the point is this: vesicle recycling is awe-inspiring. 

So before the electrical signal reaches the terminal, here is what is already in place in the presynaptic axon terminal.  There are a whole bunch of “docked” vesicles, full of glutamate, already lined up (docked) along the synapse.  There are a lot of closed calcium channels sitting right next to those vesicles.  There is also a whole host of other vesicles waiting in a pool right behind the docked vesicles.  Okay.

Docked vesicle with a green calcium channel next to it

When the electrical signal reaches the axon terminal, the change in voltage opens the calcium channels, which let a lot of calcium into the terminal.  This calcium binds onto some proteins called SNAREs which are holding the docked vesicles in place.  That binding causes the SNAREs to torque and shove the vesicle into the cell membrane, and they fuse with the cell membrane and spew their contents (glutamate) out into the synapse.  The glutamate floats over to the other side and starts a chain reaction in the postsynaptic neuron which is incredible but irrelevant to this story.

Before another signal can get propagated, new vesicles have to come and dock up against the calcium channels lining the synapse.  These vesicles come from the vesicle pool.  Now, because this is your brain and because neurons are firing like all the time, if this pool didn’t get replenished constantly your neurons would cease to function in a matter of moments.

I know.  Whenever I realize things like this I start freaking out that this process which was going on perfectly fine my whole life without me knowing it is suddenly at dire risk of stopping just because I now know that without it I’d die.  I understand if you want to hyperventilate a little.  Nevertheless rest assured that nothing’s going to stop your neurons from doing this any time soon.

But here’s what has to happen in order for that pool to get replenished.

First, those vesicles that fused with the cell membrane and spewed their contents, they’re now fully fused and make up part of that membrane.  So to compensate, new vesicles have to come out of the cell membrane.

This is achieved using proteins called clathrin, which all link up together and start yanking on the membrane, surrounding a little blob of it and molding that blob into a clathrin-coated sphere. 

Then this other protein called dynein comes along and pinches off the last little bit of membrane, and you’re left with a ball of membrane that looks suspiciously like a vesicle (because it is).

Then the clathrin breaks up and that vesicle sits around looking silly with nothing in it.

To put something in it, you need some channels I neglected to mention, which are sitting in the membrane all the time just hanging out waiting to be taken up into a vesicle (this is kind of true and kind of not, but just go with it).  These channels are glutamate channels, and they sit in the membrane of the vesicle and pump glutamate into the vesicle.

It’s been too long since I took basic neurobiology to remember just how the channels know they’ve reached the ideal amount of glutamate in the vesicle, but take it from me  they know, and they stop pumping.  And there you have it, a nice shiny new vesicle waiting to enter the pool.

So let’s go through those many steps again and follow the Life Cycle of a Vesicle (the worst part is I’ve skipped a few steps for brevity so you’re going to see some previously unmentioned steps here!). 

First, here’s the picture.  Go ahead, admire it:

As usual, click to enlarge

You start with a neuronal membrane.  And suddenly, out of nowhere a little patch of membrane is encountered by clathrins (1).  And the clathrins start binding to each other and a chain reaction happens, and in a beautiful and miraculous turn of events a cute little sphere of membrane ends up caged in a soccer ball of clathrins (23).  And good old dynein comes along and cuts the cord (2), and the clathrins fall off (4), and behold, a brand-new empty vesicle!

This vesicle starts filling with glutamate (5), and when it reaches that Goldilocks-perfect concentration (6) it gets transported over to the pool to take its place at the back of the line (7).  It waits patiently while other older vesicles get pulled to the synapse ahead of it, and finally, finally it’s this loaded vesicle’s time to shine!  It gets transported straight to the membrane, where it is loosely tethered (8).  Then it is formally and properly docked (9).  Then it is ‘primed’, meaning it’s not only docked in the right place but it is dressed up all pretty for the ball and by God, it will be fused (10). 

Then the electrical signal comes (11).  Calcium floods into the terminal and binds to the proteins holding the primed vesicle.  The tortured proteins wrench violently, and the vesicle fuses and spills its guts like Snowden’s secret.  Thus ends the life of the vesicle, because it becomes One with the membrane and all its little parts go floating into the all-encompassing vastness of the cell and whatnot.  (Would you believe I’m still leaving out a few steps with this description?)

And now for the moment you’ve all been waiting for  this whole process, start to finish, happens on the order of milliseconds (ms).  Last I checked someone had calculated it at about twenty ms.  That’s twenty thousandths of a second. 

I mean wow, right?