A Method for the Study of Cultured Cells by Thin Sectioning and Electron Microscopy

Some years before thin sectioning techniques were developed, a number of investigators, notably Porter and his associates (6-8), made some new and interesting observations on cell structure by examining in the electron microscope fixed and dried preparations of whole cells grown on form-vat-coated glass surfaces. The method depends on the fact that the peripheral regions of such cells are often extremely thin and consequently show fairly good detail in the electron microscope. The detail, however, does not compare favourably with that obtainable with the thin sectioning methods that were subsequently developed. The present paper describes a procedure that allows cells grown in vitro to be sectioned in a plane parallel to the glass surface to which they are attached. The resulting micrographs have the high resolution associated with sectioned material and have the added advantage of presenting the cells in the aspect in which they are observed in the light microscope and in the whole-cell type of preparation referred to above. This facilitates comparison of the structures revealed by the present method with those observed by other techniques. Moreover, the method is applicable to the study of small numbers of cells or even to single cells, and promises to be very useful in studying the effects of different agents on cells growing in vitro or of variations in the procedures used for preserving the cells. The method is essentially a modification of the methods described by Borysko and Sapranauskas (1), and by Gay (2). The former authors, however , used a double embedding procedure and sectioned the cells in a plane perpendicular to the one in which they were growing. The latter author described a method suitable for studying smears. Materials and Methods Cdls.-Cell strains derived from monkey kidney cortex formed the source of material described here, but the method is applicable to all cells growing in contact with glass surfaces. The cells were grown in Petri dishes of diameter 5 or I0 cm. in a medium consisting of 80 per cent solution CMRL-1066 s and 20 per cent horse serum. A continuous flow of moist air containing 5 per cent CO2 was maintained in the cabinet in which the cells were incubated. The cells multiply while adhering to the surface of the Petri dish, forming isolated colonies or a more or less continuous sheet according to the size of the inocu-him and the period of cultivation. To prepare cells …