Electron Microscopy of Nuclear and Cytoplasmic Events during Division in Tetrahymena pyriformis Strains W and HAM 3*

Abstract

Amicronucleate (strain W) and micronucleate (strain HAM 3) Tetrahymena pyriformis have been studied by light and electron microscopy. Numerous interphase and individually‐sectioned organisms in division stages have been examined. In macronuclei of the amicronucleate organisms (strain W) the time of division is characterized by a rather marked chromatin condensation, by morphological changes in nucleoli, and by the presence of dense granules. In macro‐nuclei of the micronucleus‐possessing organisms (strain HAM 3) little alteration of the interphase morphology is observed at division. Mitochondrial changes and an increase in the amount and complexity of the endoplasmic reticulum are observed in division in the amicronucleate strain. These results show that macronuclear division is more complex than a simple “pinching‐in‐two” and that loss of the micronucleus may alter the mitotic events of the macronucleus.

On cell organelles in Tetrahymena. With special reference to mitochondria and peroxisomes

“…Mitochondria divide by binary fission (60) and they are sensitive to treatment with ethidium bromide (16,81,58,77). The organelles may play a role in the intracellular control of ions (56, 101 ), thus isolated mitochondria accumulate calcium at the expense of energy (22); the electron dense core found in mitochondria under unfavourable conditions (117,32,36,33,92,101)may represent accumulated inorganic material (101). For reviews on the respiration of Tetrahymena and the respiratory components of its mitochondria see J. F. RYLEY (118), W. F. DANFORTH (29), and D. LLOYD (77).…”

ELECTRON-MICROSCOPIC OBSERVATION ON NUCLEAR EVENTS DURING BINARY FISSION IN <i>BLEPHARISMA WARDSI</i> (CILIATA, HETEROTRICHIDA)

“…Microtubules were observed in the stage of the macronuclear division in several species of ciliate (Roth and Minick 1961, Roth and Shigenaka 1964, Raikov 1965, Carasso and Favard 1965, Suganuma and Inaba 1967.…”

“…In most of the ciliates investigated by electron microscopy such as Tetrahymena (Roth and Minick 1961), Nassula and Nassulopsis (Raikov 1965), Campanella (Carasso and Favard 1965) and Urostyla (Suganuma and Inaba 1967), microtubules were found between the chromonemata inside the dividing macronucleus. In Diplodium (Roth and Shigenaka 1964) they were found on the inside as well as on the outside of the macronucleus during division.…”

“…Some of them, however, were on changes of the nucleoli rather than of the chromonemata (Ehret and Powers 1955, Roth and Minick 1961, Elliott et al 1962, Elliott 1963. Flickinger (1965) studied the morphology of the chromonemata throughout the cell cycle of Tetrahymena pyriformis, but he did not find any correlation between the morphological changes in the chromonemata and DNA synthesis.…”

Osmium tetroxide vapor fixation of dividing and regenerating Blepharisma

“…For many years, the study of dividing ciliates did not disclose the presence of discrete filaments in either the macro-or micronucleus (Roth, 1959;Roth and Minick, 1961;Elliot, ^ , 1962;Elliot, 1963); only the observations of Roth, and Roth and Minick indicated the possible presence of filaments associated with the amitotic macronuclear division.…”