The large oligotrich rumen protozoa Diplodiniurn ecaudatum and Ophryoscolex caudatus have been studied by electron microscopy during interphase and division. The structure of mature cilia is contrasted with that seen during their formation particularly in a tuft where development lags and is arrested. Here the shaft is only a few micra long and is composed of filaments that have circular cross-sections not in the typical circular arrangement. In their diameter and appearance the filaments are similar to filaments associated with the nuclei during division. The macronucleus has within it randomly directed filaments, while the micronuclcus contains well aligned filaments and other arrangements typical of an intranuclear mitotic process. An extranuclear filament system is also present and is elaborated during division. The infraciliary filament system is particularly elaborate in these organisms.Filaments ranging from 14 to 22 m# have been observed with some tendency for a bimodal distribution in diameters of 15 and 21 m#. Formation of such filaments has been observed and consists of an initial orientation of very fine elements followed by filament formation. The observations are discussed in relation to filament involvements in cell movements. The concepts are discussed that filaments are metastable structures and that the transitions from one state to another are functionally significant.
Summary.The green paramecium Paramecium bursaria has many endosymbiotic algae in its cytoplasm. Here, we cloned and characterized endosymbiotic algae from P. bursaria and examined in detail the interaction between the cloned algae and algae-free paramecia. Homogenates of P. bursaria were cultured on agar plates containing various kinds of media to establish clones of the endosymbiotic algae. Many algal colonies were obtained from poorly nutritious medium (CA medium) after one month in culture. Algae were picked up from these colonies and inoculations were repeated 9 times on agar plates containing CA medium. On enriched media including bacto-peptone, glucose, proteose-peptone and/or yeast extract, however, bacteria and mold grew rapidly and no algal colonies were formed. When tile cloned algae were cultured in liquid CA medium, they grew faster than on agar plates and the numbers stayed constant at 1 • 107 algae/ml after 7 day s in culture. They revealed high infectivity to algae-free paramecia, and an incubation period of 24 h and at least 1 • 103 algae/paramecium were required to achieve successful infection (80-90%). The growth and infection rate did not change through 74 repeated inoculations of algae in liquid CA medium. Optical microscopic observations revealed marked morphological similarity between endosymbiotic algae and free-living Chlorella, but the latter showed no infectivity to algae-free paramecia. The cloned endosymbiotic algae presented here will provide an excellent opportunity to examine the mechanism of symbiont-host interaction.
SYXOPSIS.A study of the 'longitudinal fibrillar bundle' (LFB) and the 'contractile fibrillar system' (CFS) of a large protozoan ciliate, Spirostomum ambiguunt, has been performed by means of an electron microscope. .4 system of sub-pellicutar fibrils has been newly found and its function is discussed. Each LFB runs parallel with a longitudinal row of ciliary bases. I t seems to be identical with the so-called kinetodesma. I t is composed of tubular fibrils arranged in layered sheets, each of which contains 13 to 3. 5 fibrils with the same diameter as the intra-ciliary fibrils and has a close connection to each EVERAL large ciliates that are capable of rapid S change of form in response to stimuli-Condylostoma, Stentor, Vorticella, Carchesium, Zoothamnium and others-have special cell organelles which are directly instrumental in their body contraction. The fibrous structures of these organelles have been studied since nearly a century ago, and since Lieberkuhn ( 3 ) found 'Muskelfasern' in the ectoplasm of Stentor, the corresponding structures have been recognized in several contractile ciliates and named mvoneme, myophane, neurophane, neuroid and the like. At present, the term myoneme seems to be generally and widely used for the structure considered as a contractile element, but it is still doubtful whether or not such fibrous structures actually contract. As far as we know, the so-called myoneme of Spirostomum
As the species name indicates, the large heterotrichous ciliate Spirostomum umbiguum is characterized by a twisting contraction of the cell body that is easily triggered by various kinds of external stimuli. On the basis of morphological studies, contraction and extension of this organism have been considered to result from antagonistic actions of myoneme and microtubular ribbons. After many trials, we have succeeded in preparing cell models to examine induced contractions and extensions of the cell body. The contraction of this model was induced by increasing the free Ca2+ concentrationc even in the absence of Mg-ATP and was reversed by adding Mg-ATP without Ca2' . Using dynein ATPase inhibitors such as vanadate and ATP analogs, furthermore, the experiments revealed that the ATPase that generated the force between the two neighboring microtubular ribbons might be a dynein-like ATPase.
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