biology

Around my heart: The Pericardium

A two-walled sac hugs my heart (yours, too).

The pericardium, aptly named:

Peri, or around; Cardion, or heart.

The outer layer – fibrous, rigid – bears the brunt of the work. Holds my heart steady to avoid its swings, tethers it in the expanse of my chest cavity. Keeps it from beating right out.

orange peel

This layer is tough, just enough for safety purposes. Like the hard peel around an orange, it shields my heart. From infections, so prone to developing in nearby lungs. From my heart itself, which could overfill with blood and too big. My heart may be eager, but this fibrous layer knows everything has its limits.

Inside that hard exterior is an inner layer, cushioned and kind. After all, to do its work, my heart cannot have friction building up with nearby tissues. Even the strongest parts need a bit of softness.

Like anywhere, things can go wrong here, in the pericardium. Fluid can build, cysts can grow, layers can swell. Nothing is perfect. Nothing is guaranteed.

But still my heart pulses. And still my pericardium guards every beat.

 

 

 

A frog's life

Frogs live all over the world: from rainforests to deserts, and from the suburbs to the Arctic Circle. Which means they have to withstand some pretty cold and pretty hot weather.

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And that brings us to two cool things frogs can do: they can hibernate through the cold, or estivate (go dormant) through the heat.

In hibernation, a frog finds a safe place to hangout all winter, then its metabolism slows dramatically. A land frog might dig a burrow to get below the frost line or crawl into a crevice and cover itself with dead leaves. A water frog might sink to the bottom of a pond and partially immerse itself in mud, but not too much to cut off all the oxygen soaking through its skin from that H2O.

Some frogs can survive being frozen: though ice crystals may form under their skin or in their body cavities, they've lowered the freezing point of cells in important organs by pumping in extra glucose so those don't turn to ice (sorry, Elsa, they have you beat on this one). The frog no longer breathes, its heart no longer beats; and yet, as soon as it warms up, it comes back to life. 

I don't know if these green tree frogs are hibernating but they look cool. Photo by  judygva  on  Foter.com  

I don't know if these green tree frogs are hibernating but they look cool. Photo by judygva on Foter.com 

In super hot areas, some frogs estivate, which is similar to hibernation. They burrow into the soil and go dormant, shedding several layers of skin over the months that follow. These layers of skin form a tight barrier around the frog, keeping moisture from evaporating. Only the frog's nostrils are exposed to air, allowing it to breathe.

In addition to these special skills, frogs can drink and breathe through their skin, have tongues that attach at the front of their mouths, and have teeth. Some are nearly see-through, some can almost fly, and one type has enough poison in its skin to kill 10 to 20 men.

So, yeah, frogs are pretty interesting. I might just have to start another blog category about them. 

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Photo of tree frogs by judygva on Foter.com | other photos from pixabay.com

 

For the love of plants

Alice Eastwood was a self-taught botanist who published more than 310 science articles, authored 395 scientific names for land plants, and once risked her life to save her plant collection.

Alice Eastwood, circa 1910

Alice Eastwood, circa 1910

Granted, these weren't just any plants - these were type specimens: an example of a species that clearly shows that species' defining features. And there were around 1,500 of them.

But still, she risked everything to save her work.

It was 1906 in San Francisco. Early in the morning on April 18, the massive earthquake struck, resulting in widespread fires that consumed hundreds of city blocks and destroyed thousands of buildings. A small group of staff and curators with the California Academy of Sciences worked to save what they could. For Eastwood, who was procurator and head of the Biology Department, that meant entering the burning building, climbing to the sixth floor on a metal railing, and saving her type specimens. The feat was possible not just because of her bravery, but because she had used an ingenious new method to store her specimens: she had segregated the type specimens from the rest of the collection.

She still lost years of work, years of effort in the fire. But afterwards, she wrote a letter in Science that said:

"My own destroyed work I do not lament, for it was a joy to me while I did it, and I can still have the same joy in starting it again."

I can't help but think that her perspective applies, in a small way, to writing. We can spend hours crafting and cutting and writing and revising a piece that never makes it past our own computer screen. It may not be destroyed by a fire, but it's abandoned to languish in a series of 1s and 0s, or possibly in a stack of papers stuffed into a closet. 

And yet, if we have Eastwood's perspective - that though a piece may be lost, it gave us joy while we did it - well, that changes everything.

It's especially motivating for me as I consider the six books I've written over the past eight years, all of which may never see the light of day. Joy in the process, joy in creating - there's value in that alone.

And by the way, after that fire, Eastwood kept collecting. By 1942, her collection hit more than 300,000 samples... three times the number of specimens that had been lost. 

 

Alice Eastwood may have seen views like this as she led Arthur Russel Wallace up Grays Peak.

Alice Eastwood may have seen views like this as she led Arthur Russel Wallace up Grays Peak.

Skin deep

Act I: Epidemermis

Aka - Boundary Line. Death Zone. Bacterial breeding grounds.

This is my boundary line. Where I separate from the outside world. Where I become me.

My outermost layer, very strong wall that it is, virtually impermeable to all on the outside. It keeps the enemies out, and keeps my inside parts in.

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The living claim the bottom parts, and then slowly rise, shoved up and pushed out as new life begins below. On their way up, these cells release proteins, lipids, keratin. Strengthening the whole, fulfilling their duty even as they march to their death.

Then, it is time. They die, dry, flake, slough, fall off. Millions every day. I leave tiny bits of me everywhere I go.

And there among the sloughing skin, live my bosom buddies, the bacteria. Thousands of them, crowded in, claiming their plot. In between fingers and toes, inside nostrils and ears, belly button, too. Tucked into the far corners of me and spread along the remaining surface, like a well-iced cake. My skin's flora, as though I am a walking botanical garden. 

More than 80 species reside on the heel; about 40 between the toes; 60 in nail clippings. They munch away at my sweat, releasing the stink under my arms. I am not smelly on my own.

Mostly, my bacteria in residence are good, or at least, they do no harm. They keep the bad guys away, secreting nasty chemicals and calling my immune system into action. But I never  get too comfortable with these nice guys: let some in, and they'll wreak havoc, infecting lungs and bones and gut and joints. 

 

Intermission: The Basement Membrane

Thin, fibrous sheet. Made by both the layer above and the layer below. Bumpy and folded to allow nutrients to pass from bottom to top. Reservoir for supplies in times of skin repair.

 

Act II: Dermis

Lots of action here, but we'll be quick. It is Act 2, after all. 

Dense connective tissue that cushions the body. Life-filled cells surrounded by a thick substance that gives strength and snap-ability to the skin. Little ropes and proteins and hyaluronic acid, a third of which is degraded and remade each day.

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The necessary bits live here: hair follicles and sweat glands, lymphatic vessels and blood vessels. The dermis is home to many.

Including feeling. The myriad nerve endings that communicate touch and heat and pressure and vibration and more to me. They're how I know to drop the burning pan. How I know that my child's hair is silky smooth. How I know the wet slide of a tear, the tight squeeze of a hug, the warmth of a fire.

 

Act III: Hypodermis

The grand finale now. The part that holds it all together, attaching the slim skin layers to the muscle and bone beneath. Fat lives here, too, keeping me warm and buffered from winter winds, sometimes making my clothes squeeze tight. If this layer gave up, threw in the towel, quick, then everything else - my boundary with the world - would slip off and fall away.

And I would be lost.

 

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Creative Commons/Pixabay

 

 

The Virus

Life, but not it’s own,

borrowed from another.

A shady spot – chemical or life form or just entirely

different.

 

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Tiny, tiny thing

(millions on a pinhead, for scale).

Mere genes in a protein coat

coming in an array of beautiful shapes and flavors,

all so the virus can pop onto a cell and then enter

without knocking.

 

Once inside, it commandeers and reprograms the cell’s own hard-earned organelles

making them, eager slaves that they are, do its dirty work:

Copy down the viral recipe. Then use it to make more of the one thing the host cell does not want:

viruses.

Even the ingredients called for belong to the cell:

nucleotides, enzymes, ribosomes, tRNAs, amino acids, DNA mixers, energy.

The virus comes empty handed

and requires everything.

 

Suddenly, spontaneously, viral bits begin to self-assemble inside the host cell

poor, poor host that it is

And then, hundreds or thousands of the new viruses leave,

exit

usually destroying their host in the process.

The damage is not yet finished

for the new viruses move on to the host cell’s neighbors,

friends and family,

and take them over, too.

 

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Our defenses are strong,

but so are viruses.

That one flu – remember – killed 40 million of us in the span of

two years.

 

But sometimes we can use viruses,

harness their power

to kill off bacterial infections.

Use the enemy to fight another enemy,

and hope it doesn’t then come for us.

 

 

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Creative Commons/Pixabay

The Super Smart Crow

For a long time, I rolled my eyes at crows. They were just big black birds that screeched and cawed and messed with other birds' nests. But now I know better.

Crows are smart in lots of ways, with problem-solving skills that rival those of a young child (see my earlier post). One example of their smarts is their use of tools.

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Almost anything can be a tool in a crow's beak. They even take advantage of cars, dropping hard-to-crack nuts at strategic spots on roads. Cars roll over the nuts, popping them open and saving the crow a lot of work.

New Caledonian crows are the only animal (besides us people) that are known to make hooks in the wild. They pull off a thin branch, then remove small bits of wood near the the joint that had connected the branch to the tree or bush. The resulting hook can then be used to forage for bugs.

In experiments, these crows quickly and instinctively fashion hooks out of wire to do things like lift a tiny pail of meat from a clear plastic tube. In one example, two crows were presented with a hooked wire and a straight wire. One crow immediately grabbed the hooked wire, which was needed to get a tiny pail with food from a tube. But then the second crow bent the straight wire, making a hook to get the food. Neither crow had seen wire before.

New Caledonian crows can also use tools to get other tools, completing complex series of tasks to get to their final goal. In the video below, a crow completes eight distinct steps to get to his treat.

I'm thinking about conducting my own unscientific experiment at my home. Maybe I'll set up a platform with hard-to-get food and a few thin wires. If I can get a few crows to stop by, I'll sit back and watch what they do. The crows around here aren't quite as clever as those New Caledonian crows. But they're still smart. And they might just teach me something in the process.

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 pixabay.com

 

Hello, my blood

I nicked my finger on a knife

That day before dinner

and while the toddler howled and the dog whined

and peas boiled over and pizza burned,

I watched it:

thin red liquid line.

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A few drops of blood.

Millions of erythrocytes – red blood cells.

A staggering loss

except that, at the same moment, 25 trillion red blood cells (minus these few million)

were speeding through my body.

Small disks without a brain or a powerhouse

because there simply isn’t room.

Not when you have a single job: pack yourself with oxygen.

One small red blood cell has 250 million molecules of hemoglobin clasping 1 billion molecules of oxygen.

They hold tight through arteries and blood vessels, until the capillaries, where oxygen – the unsocial, dissociative molecule it is – checks out, goes its own way, to where it’s actually needed.

Red blood cells are designed to not even use the oxygen they carry on their journey.

The body does not like to waste.

These millions of escapee cells, loosed by the slip of my knife will be quickly replaced.

Perhaps death to open air is preferred to being eaten by a phagocytic cell, which would’ve happened anyway after three or four months of constant service – clock in when you’re born and out at your death.

But it wasn’t just red blood cells lost in my carelessness:

there was water

and salts and proteins and hormones and wastes.

And there were the fighters,

those white blood cells always on patrol for enemies, ready to destroy.

Fingers crossed and prayers said they will only ever identify the

real enemies

otherwise, they might just take my whole ship down.

The dog howled again

and I picked up the toddler and

stuck my finger in my mouth

quelling the bleeding (knowing that platelets and fibrin were already doing their sticky work to plug the slender cut)

tasting that metallic, iron flavor

that is the cornerstone

of my life.

I turned off the peas, finger still in mouth,

then dumped the pizza into the trash

and called

for takeout.

 

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commonfund.nih.gov

nsf.gov, quantitative light imaging gallery

 

Gambel's Oak

gambel oak 2

You’ve likely walked by these scraggly trees, lichen nestled in the knobs and ridges of their dark bark. They’re the last trees to sprout green leaves in spring, forming a low, tight canopy overhead. By autumn, their leaves turn orange, complementing the golden aspens. And finally, as winter settles in, tangles of black branches are exposed, giving our woods an otherworldly feel. 

They go by many names: scrub oak, oak brush, white oak. Quercus gambelii, formally. Which in turn is shortened into their common name: Gambel oaks. 

That is the name that caught my attention, for it points back to a budding naturalist whose own life was cut short by a twist of ill fate. A twist not unlike the turning branches of the tree itself.

William Gambel was born near Philadelphia in 1823 to an impoverished Irish family; his father died when he was nine. At age 16, he joined naturalist Thomas Nuttall on a collecting trip in North Carolina. The trip sparked an interest in the world around him, and a few years later, Gambel set off for California, crossing the country by foot and observing plants and birds and other animals along the way. He was 18 years old.

He collected along the California coast and eventually returned to the east coast, became a physician and married, then decided to head back to California to begin his medical career – after all, it was 1849 and the Gold Rush was on. He made a plan with his wife: he’d establish his practice, then she would travel out to meet him. And finally, he began the long journey west with a small group of settlers for company.

But their pace was a bit quick for his liking: after all, there were so many species to observe and record. So Gambel made a fateful decision to join a slower-moving group. It would give him more time to collect samples. It would also turn out to be his demise.

The group was excruciatingly slow.  They didn’t make it to Nevada until the end of fall, and worry built as they realized winter was at hand. They were in bad shape.  The long autumn months had been dry.  Most of their cattle and horses had been lost.  But with no motel to check into, they pushed forward. They hit the eastern edge of the Sierras after the first snowfall and were certain they could make it no further. But onward they went. 

Somehow Gambel and a few others survived the treacherous mountains, reaching a gold-mining camp on the Yuba River.  But this was not the end to their struggles. For a typhoid epidemic had taken hold, working its way through the miners. Gambel, the good doctor that he was, stopped to help the sick. But his efforts were for naught as he soon caught typhoid himself and died. He was 26 years old.

His name lives on, in the scrub oak as well as Gambel’s Quail, mountain chickadee and a genus of lizard. It’s no wonder that, on early morning or late evening walks through stands of these low, twisted trees, I can’t help but imagine what it was like so many years ago, when so much land had yet to be explored, when every journey carried immense risk, and when so-called "small" decisions had the power to lead to life or to death. 

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Richard G. Beidleman | California’s Frontier Naturalists

Apoptosis

Cells are programmed to do lots of things... including to die. Below is a tribute to apoptosis, the technical term for self-directed cell death.

 

Every day, bits of me

Are dying.

I don’t mean figuratively – like lost

Dreams, or hopes, or ideals –

This is not the scenario of a broken winged bird that cannot fly.

Rather, bits of me, quite literally, are dying. Constantly.

Have died every second of every day. 

Will keep dying. On purpose. As planned. For the good of the whole.

 

Every cell in my body

has a death switch

a big red button, or rather, a miniscule receptor

just waiting for the signal

to kill itself.

 

When the signal comes, whether before breakfast or after a bath, in the middle of a good movie or under a star-filled sky,

my cell is ready.

 

My cell already holds all of the components of self warfare.

Fifteen types of enzymes on pause, just waiting to do what they were created for.

And when it’s time, they leap to attention

soldiers on the front lines.

Some, like cytochrome C, are first used in life

Until the switch is flipped, and they become agents of death:

Chopping up DNA

Tearing apart organelles

Fragmenting bits of life

No mercy, no pause, no second guessing.

 

My chosen cell shrinks and blebs, its parts packaged neatly

In vesicles then left for the scavengers

Which engulf and digest, leaving

No trace behind.

 

The signal to die can come from a neighbor

Or from inside the cell itself:

If a cell’s DNA is damaged beyond repair, or its proteins have misfolded so much, too much,

Then the cell gives

itself

the signal.

 

Don’t cry over the death switch for it is

vital to life.

Diseased cells, infected cells, damaged cells,

Cells at the end of their functional life spans –

It would do no good for any of these to let go and simply deteriorate,

Leaking their bits of life all around:

Caustic digestive enzymes

Myriad strange particles.

Anyway, cell death has made me who I am: Without it, my fingers would still be webbed together

Flippers not hands.

 

Strangely, the death switch is most like a brake.

When the cell is living, the death switch is halting the process of dying.

Which means death is the default.

 

To be or not to be?

Each cell in my body must ask itself this question every day.

If the answer is not to be, then the work of apoptosis

Or falling off

Or death

Begins.

And life

Follows.

Thirsty crows and true fables

Remember Aesop's fable about the thirsty crow? The one that finds a half-filled glass of water, but isn't able to reach it's beak down into the glass to drink. Not to be discouraged, the crow gathers rocks and stones, dropping them into the glass and raising the level of water, until at last, it's able quench its thirst.

I read the fable at some point, probably in English class, and always thought it was a lesson in persistence and creative thinking. I didn't know it was a real phenomenon.

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But it is. When presented with a similar situation - this time, with a bit of meat on a styrofoam disk floating in a tube of water for extra motivation - New Caledonian crows  drop in rocks to raise the water level until they can reach the meat.

Through a range of challenges, the crows prove their causal thinking skills. If researchers set out heavy stones and "imposter" styrofoam stones, the crows preferentially choose the the heavy stones that will raise the water level. And if crows are presented with two tubes with food, but one with an already high water level and the other with a low water level, they go first to the tube with higher water.

Crows are smart. Their intelligence rivals that of dolphins and orangutans, and is up there with that of young children.

I used to think of crows as pests. After all, they made a mess at dumpsters and ate Robin eggs and blared their loud "caws" in nearby trees. But now, when I see a crow, I watch carefully to see what it's going to do next. Because it just might be something really interesting.

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some info from: Jelbert SA, Taylor AH, Cheke LG, Clayton NS, Gray RD (2014) Using the Aesop's Fable Paradigm to Investigate Causal Understanding of Water Displacement by New Caledonian Crows.