A Simplified Chatton-Lwoff Silver Impregnation Procedure for Use in Experimental Studies with Ciliates

Abstract

A modified and simplified version of the Chatton-Lwoff silver impregnation technique, which allows one to handle a large amount of material in a relatively short time, is described and discussed. Concentrated ciliates are fixed in centrifuge tubes with Champy's fixative, and then washed into DaFano's fixative. Slides are made on a slide warmer set at 40-45 C. A tiny drop of concentrated cells is placed on a warm slide, and a larger drop of liquefied gelatin is added. A warm needle is used to stir and spread the preparation, the thickness of which is regulated by the degree of spreading. The liquefied preparation is solidified by cooling on a moist cold surface, then rinsed with distilled water, and placed on a slide rack within a cold 3% silver nitrate bath. The slides are kept in silver nitrate for ½-24 hr, and then simultaneously dehydrated and reduced by passage of the slide racks through cold alcohol mixtures (70-80-95-100%) while they are exposed to sunlight or other strong light. The slides are then placed in xylene for 10-15 min, and mounted. The mounted slides are placed on a white pan and exposed, on both sides, to bright light for several hours, to complete reduction of silver. The critical steps of the technique are discussed.