A Device for Staining Tissue Sections for Electron Microscopy

It has been the experience of this laboratory that the lead hydroxide stain of Watson (1) gives excellent results in increasing contrast in thin sections of tissue, but that the stain is inconvenient to use because on contact with air it forms an insoluble precipitate which contaminates both the stored solution and the sections. 1 Contamination introduced in transferring the solution from the storage vessel to the staining vessel and the excessive amount of solution wasted in filling even the smallest of ordinary staining vessels can be mentioned as additional shortcomings of common methods of using any staining solutions. These difficulties can be minimized by the technique reported here which involves the use of a plastic syringe both as an air-free storage container for the staining solution 2 and as a staining vessel. The syringes used are of a disposable variety and are commercially available2 They have a capacity of 2.5 cc, and are supplied complete with needles and protective needle covers. Modification of the syringes for staining consists of removing the needle by cutting around the tip of the syringe about 2 ram. back from the needle collar, and boring a staining well about 4 mm. in diameter and about 2 mm. deep in the cut end of the syringe (see Fig. 1). Best results are obtained if the well is reasonably well centered. The needle cap is used as a dust cover for the staining well and as a CO2-trap. The latter is prepared by packing the cover with a sodium hy-droxide pellet, some anhydrous calcium chloride to reduce the amount of water vapor that gets to the hydroxide, and some cotton. There is a small hole and a cotton plug in the end of the cap as it is supplied, and these are left intact to allow free * Received for publication, March 11, 1959. i This precipitate is probably lead carbonate, rather than lead oxide, as can be shown by passing 5 per cent CO2 in air over one drop of the lead hydroxide solution and pure oxygen over another: a precipitate forms only with the CO2. 2 The use of a disposable syringe for air-free storage of staining solutions was suggested to the author by FIG. 1. Sectional views of modification of plastic syringe to staining vessel, a. Syringe with needle, b. End cut away and needle removed, c. Staining well drilled in cut end. …