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INTRANUCLEAR MICROTUBULE ORGANIZING CENTER IN EARLY PROPHASE NUCLEI OF THE PLASMODIUM OF THE SLIME MOLD, PHYSARUM POLYCEPHALUM

Authors
Journal
The Journal of Cell Biology
0021-9525
Publisher
The Rockefeller University Press
Publication Date
Keywords
  • Brief Notes
  • Article
Disciplines
  • Biology

Abstract

INTRANUCLEAR MICROTUBULE ORGANIZING CENTER IN EARLY PROPHASE NUCLEI OF THE PLASMODIUM OF THE SLIME MOLD, PHYSARUM POLYCEPHALUM KENJI TANAKA . From the Institute of Applied Microbiology, The University of Tokyo, Tokyo, Japan INTRODUCTION The nuclei of the plasmodial phase of the true slime mold (myxomycetes) perform intranuclear mitosis which is not accompanied by centrioles, while those of the myxamoebae exhibit an astral type of mitosis with centrioles and nuclear en- velope breakdown (2) . In fungal mitoses of cen- triole-lacking styles, the microtubules composing the metaphase spindle arise, in most instances, in the vicinity of variously shaped microtubule or- ganizing centers (MTOC) (13) or spindle pole bodies (1) . These may take the form of circular or rectangular, electron-opaque, layered plaques as in yeasts and mycelial ascomycetes (14, 17), or vaguely textured spherical structures repeatedly described in basidiomycetes (5, 10, 11) . No such structure has been described in myxo- mycetes but recently one has been found, sur- prisingly, deep inside prophase nuclei of Physarum (15) . The present study provides independently made observations confirming the occurrence of this novel type of MTOC in Physarum . MATERIALS AND METHODS Cultures of Physarum polycephalum, kindly supplied by Professor J . Ohta, Ochanomizu University, Tokyo, were maintained plasmodia on sterile, semidefined medium according to the method of Daniel and Rusch (3), slightly modified by Okada and Ohta (12) . Surface plasmodia were obtained by the fusion of microplasmodia growing on filter paper (TOYO No . 4, Toyo Roshi Co . Ltd., Tokyo) supported by a layer of glass beads in a Petri dish according to Guttes and Guttes (6) . The nuclei of plasmodia divide in syn- chrony and the course of mitosis can be reconstructed from samples taken at closely spaced intervals . Nu- clear behavior in the growing plasmodium was moni- 220 tored by examinin

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