Sedimentation counting of particles via electron microscopy

Abstract

Electron microscope counts of virus particles have usually required highly concentrated, purified, preparations with a minimum of extraneous material (2, 4, 6). Isaacs has thoroughly reviewed these results recently (5). But, the virologist frequently does not require such purity. He generally deals with crude tissue extracts, plasmas, chorioallantoic fluids, etc., in which virus activity may be 10⁶ to 10⁹ ID₅₀ per ml. It is rarely greater than 10¹⁰. This paper will describe electron microscope counting of two viruses in just such crude form.

This investigation was supported in part by a research grant RGE-5177 from the Division of Research Grants, US Public Health Service and further aided by a gift of equipment from the Ivan Sorvall, Inc., Norwalk, Conn.