SOME APPLICATIONS OF THE ULTRA‐VIOLET AND INTERFERENCE MICROSCOPES IN ELECTRON MICROSCOPY

Abstract

SYNOPSIS An ultra‐violet microscope of high resolution, using radiation of wavelength 2570 Å, is described. This makes it useful to the electron microscopist for giving information about the concentration of nucleic acids in different parts of an organism. Three different types of application are described. Firstly, a comparison of ultra‐violet pictures with electron micrographs of identical bacteria (Mycobacterium phlei); secondly, a comparison of light microscope pictures of Feulgen‐stained organisms (Streptomyces cœlicolor ) with ultra‐violet pictures as well as with electron micrographs of these bacteria at the same stage of growth. The third application concerns a comparative study in the ultra‐violet and electron microscopes of locust testis in order to assist in interpreting the electron microscope picture of the nucleus in these cells. The interference microscope was used for measuring accurately the thickness and refractive index of thin sections. A special grid for mounting thin sections to be measured in the interference microscope was designed. The method was used to investigate the effect of the electron beam on thin sections of four different embedding materials (Methacrylate, Araldite, Vestopal, Aquon). It was found that all sections become thinner, the loss of thickness ranging from 25–60 per cent according to the nature of the material and the amount of irradiation.