Apr 122011
 

Here’s the first in a series of science essays from NC’s resident scientist (also painter, author, musician, mountain woman), Simon Fraser University gene biologist Lynne Quarmby, who promises to lead us into that fierce nexus of mystery, art, literature, beauty and science. Lynne has already contributed aphorisms, a “What it’s like living here” piece and paintings to the pages of NC. It seems only fitting that she now extend our reach into the laboratory, into the cell and atom. Lynne wrote her own short intro to the series. DG could do no better.

dg

It’s amazing all
this motion going
on and
water can lie still
in glasses and the gas
can in the
garage doesn’t rattle.

—AR Ammons

Have you ever watched a sunset and reminded yourself that you are standing on a ball that is spinning and that you are flying backwards away from the sun? It totally changes the experience. Try flying into a “sunrise”-– that’s really wild. On the evolutionary timescale, it has been the blink of an eye since Copernicus realized — and Galileo observed — that we have day and night because we live on a spinning world that orbits the Sun. We’re still trying to get used to the idea.

Our direct sensory experience of the world evolved with us; in our hearts the world is what our sensory organs tell us it is. Our senses are superbly effective for helping us function in the everyday world—that’s why we’re still here—so it’s understandable that when science reveals something counter-intuitive or paradoxical, we have difficulty integrating the new ideas into our worldview. But if we can recognize and acknowledge that our direct biological senses, as wonderful as they are, give us only a tightly pinched and cloudy view of the world, then we open ourselves to unimagined beauty.

From where I view the spinning world—as a cell biologist—I see our experience of the world expanding so much that what it means to be human is changing as profoundly as it did when Copernicus and Galileo bumped Earth out of the centre of the Universe. Our intellectual peripheral vision has picked up on the shift, but as usual, our spirits and souls are lagging behind, as though they fear that there isn’t a place for them. —LQ

Stem Cells and the Fountain of Youth

By Lynne Quarmby

 

I hope I die before I get old
—Pete Townshend (from “My Generation”)

In some societies the aged are venerated, in none are they envied. The inevitable decay of our bodies and minds is something we prefer not to contemplate. There is nothing appealing about decreased mobility, loss of muscle and bone mass, reduced immune function, decreasing liver, kidney and brain function, decline in ability to respond to stress and an increasing susceptibility to stroke, heart attack, diabetes and neurodegenerative disorders. A dollop of increased wisdom seems meager compensation.

Everyday we are witness to the inevitability of decay; our buildings and roads crumble, landscapes erode and holes appear in our socks. It is something we know more deeply as we grow older: if we manage to dodge the proverbial bus, our bodies will decay until one day we die. The idea of reversing this decay goes entirely against our experiential knowledge of the world. Yet time and again the tools of science reveal that the world is not as it seems. We are learning that ageing is not simply the inevitable decay we’ve assumed it to be.

Our bodies are not static structures. The cells lining our intestine turn over approximately every five days. Similarly, our skin cells last on average two weeks, our blood cells a few months and the cells in our liver turn over approximately once/year. The average age of our muscles is estimated at 15 years. Cells of the heart are longer lived, but they too turn over. There is a large variation in the lifetime of our brain cells: Olfactory neurons are short-lived, but the neurons of our visual and cerebral cortices may be the ones we were born with. The average age of the cells in an adult has been estimated to be something like 10 years.

Old cells die and new ones are born. The dying cells are those that have done specialized service (filtering urine, absorbing glucose, detoxifying drugs, secreting milk, engulfing bacteria, detecting odors, and so on). At the end of their life span cells undergo a process known as apoptosis, or programmed cell death, and housekeeping cells clear the debris away. New cells go through a program of specialization (known as differentiation) and assume the duties of the old cells.

The new cells are born from adult stem cells that reside in special niches in every tissue. Stem cells can divide indefinitely and with each division one of the daughters replaces the stem cell and the other becomes a progenitor for the differentiated cells of the tissue. Embryonic stem cells have the potential to produce any cell in the body – that is how we develop from sacs of cells – but so far as we know, adult stem cells are restricted in the variety of cells they can produce.

About five years ago scientists discovered that adding extra copies of a specific set of genes could convert differentiated adult cells (from your skin, for example) back into pluripotent stem cells – called iPSCs for induced Pluripotent Stem Cells. These cells earned the name “pluripotent” because their daughters can be enticed (by various combinations of hormones) to become any of a wide variety of differentiated cell types. iPSCs were big news medically because they suggested the possibility of grow-your-own replacements for diseased or damaged tissues. The original iPSCs caused cancer (in mice) and while it isn’t clear yet whether we will be able to overcome all of the problems that are hindering the use of iPSCs in tissue regeneration, these cells have already become hugely valuable for research. Ageing is one of the research areas that is benefitting from iPSCs.

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