ELECTRON MICROSCOPIC OBSERVATIONS ON THE THYROID GLANDS OF NORMAL, HYPOPHYSECTOMIZED, COLD-EXPOSED AND THIOURACIL-TREATED RATS¹

Abstract

RECENT advances in fixation (Palade, 1951) embedding (Newman, Borysko and Swerdlow, 1949) and sectioning (Pease and Baker, 1948; Latta and Hartman, 1950; Dempsey and Lansing, 1953) have made it possible to prepare thin sections of almost any mammalian tissue for use in the electron microscope. With the current techniques and instruments, resolutions of 100 Å are easily possible, so that approximated twenty times the definition available with the ordinary microscope can now be attained. We have initiated, in this laboratory, a program of electron microscopy of various tissues and organs the physiological activity of which can be controlled by experimental means, with the intent of correlating changes in function with whatever alteration occurs in the morphological elements of cells. The present investigation concerns the submicroscopic structure of the rat’s thyroid gland. In the following passages we shall describe the appearance of the thyroid follicular cells in states of inactivity and in stages during which thyroid colloid is being formed rapidly.