Fashions come and go
Hairstyles, music we listen to, travel destinations, even words and expressions that we use are subject to fashion. Biology has its fashions, too. Right now it is fashionable to specialize in Molecular Genetics or Biotechnology. And who wouldn’t be fascinated by reports on unravelling the genome of Neanderthal man or by prospects of re-creating extinct species like mammoths or Tasmanian tigers. Genetically engineered food stuffs and cloned animals, after all, are already part of our lives.
At a time I studied Biology, electrophysiology was fashionable. Could there be anything more exciting than measuring the responsiveness of single sensory cells to stimuli like a puff of air, slight noise, odours, or a flash of light? In 1972 I was probably the first who succeeded in inserting an electrode into the visual cells of a caterpillar, recording these cells’ visual fields and sensitivity. I used a technique, which, since then, has not changed, but the equipment, of course, has. To produce the flashes of light to test colour and polarization sensitivities, one used a xenon arc lamp in those days (now one uses light emitting diodes of specific colours).
To examine a cell’s sensitivity to UV, quartz lenses were needed that focused the stimulating light onto a light guide (which ended just in front of the insect’s eye). A set of grey filters to adjust the light’s intensity in precise steps was also part of the set-up. Then there was (and still is) the problem of the electrodes. For cruder, extracellular work sharpened steel or tungsten needles were adequate (sometimes a wet cotton wick or a silver wire pressed against the outside of the eye would do); the preparation, meanwhile, had to be earthed. For intracellular recordings, however, no metal needle would be sharp enough and glass pipettes with tip diameters of 0.1 micrometer were (and still are) required. To obtain such finely tapered glass tubes one uses so-called electrode pullers, which heat and soften a 1- 1.5 mm wide glass tube in one place and then mechanically pull it into two very fine tips. Such electrodes, filled with 2.5 Molar KCl-solution by capillary action, subsequently have electrical resistances of ca. 200 Mega Ohm. Peering through a microscope and operating a micromanipulator, the researcher then has to find a suitable place in the eye to insert the electrode. All of this occurs in an electrically-shielded Faraday Cage.
In order to record any responses at all from a cell, a high quality pre-amplifier and an oscilloscope are required. This has not changed, but nowadays the cell’s responses are computerized and recorded digitally, while in the 70s, I still had to work with a photographic camera in front of the oscilloscope screen. Since every living cell has an electrically-negative charge inside with regard to the cell’s outer environment, the first hurdle was and still is to penetrate a cell’s membrane with the electrode, but causing minimal damage to the cell. However, not every cell is a sensory cell and only after flashing a light onto the impaled cell and noticing its depolarization response, one knows that the electrode is actually inside a photoreceptive cell. Then the experiment can begin.
The excitement, the utter and glorious feeling of joy that then filled my body every time I obtained a useful recording, is something that I can still re-live today when I think about this work. I’m left with the thought whether students of molecular genetics experience the same kind of awesome thrill when they nowadays carry out their DNA-studies. I think they do, for whether a field is fashionable or not is irrelevant: what matters is the joy of discovery.
© Dr V.B. Meyer-Rochow and http://www.bioforthebiobuff.wordpress.com, 2015.
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