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15 August 2003

Anesthetizing Microorganisms for Study

Excerpted from "A Bit of Basic Microtechnique As Applied to Protists"
by Richard L. Howey

A wide range of chemicals has been used by microscopists to "anesthetize" micro-organisms. Some of these compounds were used with a fairly good understanding of the possible biochemical reactions and effects; but, in many instances, with early microscopists and more recent amateurs, there was a large element of trial and error. Curiosity is a fascinating, but sometime dangerous, even deadly, aspect of the human psyche. There are some individuals who just can't seem to resist the temptation: "Gee, I wonder what would happen if I mix this compound with that compound?" Well, maybe nothing drastic, but, on the other hand, you might get an explosion or produce a deadly gas or ignite your curtains--so, don't mix things randomly; always be aware of the potential safety hazards. Some of the older books on microtechnique don't contain specific warnings about dangerous substances or reactions, either because the seriousness of the hazards was not known at the time or because the author, rather naively, assumed that the person using the procedures would already be aware of any potential dangers or would be under the supervision of someone who would.

The major protists that swim rapidly enough to be a problem are a number of ciliates and certain flagellates. Two chemicals that can be useful are either nickel sulfate in a 0.5% to 1.5% solution (experiment!), or a 0.5% to 1.5% solution of potassium iodide. These substances affect the mechanisms that are involved in ciliary action and, in the right concentration for a particular organism (trial and error), can be quite effective.

Occasionally magnesium sulfate (Epsom salts) is effective with ciliates and here is a chance to experiment extensively, since different organisms vary widely in their tolerance to this substance. For example, I have found that Lacrymaria olor has a very high tolerance for this salt. Some organisms--Stentor, Spirostomum, Vorticella, to mention just a few--are highly contractile and this makes them especially difficult to study. In professional scientific circles, a substance is regarded as a true anesthetic only if its effects are completely reversible. The substances which may accomplish this feat with protists are virtually unobtainable by the amateur and consist almost exclusively of legally restricted and expensive compounds. However, for those of you who are determined to experiment, certain over-the-counter medications or leftover prescription drugs which you have sitting around, just might provide some interesting results. Take notes and let us all know if you succeed. For example, neosynephrine has been successfully used as an anesthetic for certain micro-invertebrates. A 10% solution of grain alcohol (dilute down a bit of vodka) has proven effective with a variety of micro-critters. Ingenuity and lots of patience will likely yield results--not likely a Nobel Prize--but who cares, we do all this stuff because we love it, not for the fame or fortune. (Please send all contributions to the Howey Microscope Fund).