The Structure of the Centrioles and Spindle Body as Observed Under the Electron and Phase Contrast Microscope S-A New Extension-fiber Theory Concerning Mitotic Mechanism in Animal Cells

Abstract

Various cellular organella, especially the centrioles, the Golgi body, and the spindle body in regard to their activity in mitosis were studied under the phase contrast and electron microscopes and herewith a new viewpoint of mitotic mechanism, a neo-extension-fiber theory was offered.1. The centriole of the mitotic cells as observed under the EMS consists of following three components, namely, a central clear sphere, b. shell zone with high electron density, and c. centrosomal capsule zone (C1 internal capsule and C2 external halo).2. The centriole of the interkinetic cells has a cylindrical form, whose transverse section coinciding the structure just described in 1, whereas in longitudinal section it was revealed that the cylinder (120-160mμ in diameter and ca 350mμ in length) consist of nine parallel running canaliculi sur-rounding clear space in the center. Each canaliculus has a size of 20mμ in diameter having a sheath of RNA-like substance with high electron density.The further extension of these canaliculi going out from the RNA sheath, run around the centrioles and form a net-work corresponding the canaliculi of the Golgi body (Golgi protofilaments according to our nomen-clature), which may be demonstrated most evidently in plasma cells. The fact also explains the reason why the parallel running Golgi canaliculi or protofilaments are enumerated usually 4-6 in ultra-thin sections and maximally nine.3. In mitosis, nine canaliculi intermediating two centrioles develop particularly and form the skeletal structure of the spindle body. These correspond to the nine neo-extension- fibers of the spindle body of animal cells observed under the phase contrast microscope. Therefore, neo-extension-fibers here defined correspond to nine continuous fibers between the centriole; thus the previously proposed development of the connective fibers between the paired kinetochores has been abandoned.These nine neo-extension-fibers work always as extending craft through the period of the mitosis.This understanding postulates the rise of half spindle fibers (between centrosomes and kinetochores) probably from the centrosomes in a different way as the neo-extension fibers.4. Therefore, the chromosomes of the mitotic animal cells arrange on the equatorial plate supported by the half spindle fibers and their separation is taken place through the elongation of the neo-extension-fibers principally. In this case, the kinetochores of the chromosomes connect with the half spindle fibers without any direct relation to the neo-extension-fibers and play a role as a tonicity center for the neighbouring organella, as it is demonstrate-under electron microscopic pictures.5. As the neo-extension-fibers in respect to thier structure are induced from the fundamental structure of the centriole, they have nothing to do with the mitosis of plant cells. The essential characteristics of the animal cells differentiating from the plant cells in the course of the mitosis may be attributed to the existence of these neo-extension-fibers. Therefore, we have reached to a view-point which enable us to classify animal and plant cells as refer to the structure of the mitotic organella, the centrioles.