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At least 19 recordsLinked to original sources
PubMed1975

Nuclear characteristics and phylogeny in the protistan phylum Ciliophora.

Ciliates possess a number of nuclear characteristics which, in combination, are unique among the Protista. Nevertheless, attempts to understand the origin - presumably from a flagellate ancestry - of the Ciliophora as a phylum must be made, as well as efforts to elucidate phylogenetic pathways within the large and diverse assemblage represented by its present-day forms. The macronucleus may provide an important clue to early ciliate phylogeny, since we still have, among extant species, groups of distinct "karyological relicts" exhibiting the very features expected in hypothetical forms corresponding to postulated stages in macronuclear origin and evolution. The relationship of the groups of "relict" species to the predominant polyploid-macronucleate forms, with a direct impact on the classification system as well as ciliate evolution and phylogeny in general, is discussed in some detail. Arguments are presented for taxonomic separation of the relatively primitive homokaryotic and diploid-macronucleate forms, which also share other features in common related to their being members of the interstitial fauna, from the more advanced ciliates. The problem is complicated by the non-nuclear structural complexities of these sand-dwelling forms, apparently secondarily-derived specializations which, by convergence, have come to resemble certain non-homologous features of the allegedly more highly evolved groups.

Biological Evolution↗
PubMed1975

Mitosis and early meiosis in Tetrahymena pyriformis and the evolution of mitosis in the phylum Ciliophora.

The micronuclear mitotic spindle of Tetrahymena pyriformis contains several distinctive elements. The 150 or so continuous microtubules (MTs) form a peripheral sheath just inside the inner nuclear membrane while the kinetochore bundles traverse the center of the nucleoplasm. A new set of microtubules, the separation spindle, appears during the 10-fold nuclear elongation which occurs during the late anaphase. Both the separation spindle and peripheral sheath MTs are present in the macronucleus during macronuclear division but there are no definite kinetochore MTs. In the cresent stage of meiotic prophase both peripheral sheath and kinetochore MTs are present in the micronucleus. By using our own, and other workers', data in conjunction with the phylogenetic scheme for the ciliates which has been designed by Corliss (1974, 1975), we have attempted to trace out the evolutionary history of the various elements of the ciliate mitotic spindle. For example, the micronuclear separation spindle can be followed, from its point of origin within the primitive gymnostomes, throughout the phylum. The separation spindle of the macronucleus, by contrast, is lost at the level of the heterotrichs. Similarly, the anaphase breakdown and reconstitution of the nuclear envelope, which occurs in the primitive Loxodes magnus, can be followed up some phyletic branches, such as the heterotrichs, but in the suctorians and some other groups this feature seems to have been lost. Tracing the evolution of the ciliate mitotic spindle is made very difficult both by the incompleteness of the data and by what appear to be a number of cases of secondary reduction and parallel evolution. In general, however, the evolution of mitosis correlates well with the phylogeny of the ciliates constructed by Corliss and we consider this an independent substantiation of the general correctness of his phylogeny.

Biological Evolution↗
PubMed1978

Size increase and form allometry during evolution of ciliate species in the genera Colpoda and Tillina (Ciliophora: Colpodida).

With the absence of a fossil record to provide direct evidence of evolutionary relationships, many researchers have inferred by circular reasoning that body size increase and form allometry have occurred during the evolution of ciliated protozoa. This study establishes ancestor-descendant relationships among five species of the related genera Colpoda and Tillina using ultrastructural characteristics which are not apparently dependent on size and form. This independent test suggests that phylogenetic size increase and phylogenetic form allometry have occurred during the evolution of these ciliates. Interrelationships of body size increase, increase in number of cortical organelles, and form allometry are discussed in reference to the divergence of these ciliate species.

Animals↗
PubMed2026

Detection of endocytobionts inhabiting the macronucleus of Frontonia paramagna (Ciliophora, Peniculida).

Bacterial endosymbionts of Frontonia, a widely distributed ciliate genus, remain poorly characterized. Here, we investigated the endosymbiotic microbiota of a Shanghai population of Frontonia paramagna using an integrated morphological and molecular approach. Fluorescence in situ hybridization (FISH) targeting the 16S rRNA gene, coupled with V3-V4 high-throughput sequencing, consistently identified Caedimonas as the bacterial symbiont, specifically localized within the host macronucleus. FISH and transmission electron microscopy confirmed this intramacronuclear colonization with high prevalence and revealed that the symbionts lack flagella and R-bodies. Phylogenetic analysis of full-length 16S rRNA gene sequences placed the F. paramagna symbionts within a well-supported clade containing Caedimonas from divergent hosts. Comparative analysis of the 16S rRNA internal excised element (IEE) showed substantial sequence and secondary structural divergence between the Frontonia-associated lineage and other Caedimonas strains from different ciliates. We conservatively designate this lineage as Caedimonas varicaedens Fpa. These distinct molecular features suggest that the diversity and host distribution of Caedimonas are far from fully described, and genomic approaches will be necessary to evaluate species delimitation within the genus and the possible presence, distribution, and horizontal transfer of R-body genetic determinants.

16S rRNA gene↗
PubMed1976

[Balantidium coli infection of the female genitals (author's transl)].

Two cases of therapy-resistant fluorine are reported in which Balantidium coli from the class of the cilia (Ciliophora, Ciliata, Infusoria) was identified. After a personal experiment, the Balantidia must be considered extremely pathogenic. In international literature, no further indication of a ciliata infection of the female genitals was found.

Adult↗
PubMed1975

Pattern formation in ciliary organelle systems of ciliated protozoa.

Genetic, morphometric, and microsurgical investigations of the pattern of ciliary organells in ciliate protozoa support the view that ther are two types of developmental process responsible for the positioning of these organelles. The first is exemplified by the propagation of ciliary rows through localized addition of new ciliary units along the axis of the row, a process which is responsible for the maintenance of the pre-existing number of rows in clonal lineages over a large number of fissions. The second is illustrated by two examples: (1) Ciliary units are distributed among ciliary rows of Euplotes minuta according to an invariant geometrical pattern that is independent both of the total number of units and of the number of rows. (2) Microsurgical alteration of the topographical contours of a related ciliate, Paraurostyla weissei, brings about a shift in the sites of formation of certain specific ciliary rudiments to new positions that are determined in relation to the newly constructed form. The two modes of pattern formation in ciliates are discussed from both genetic and developmental viewpoints. The localized positional mechanisms within the ciliary rows allow for a 'configurational heredity' shich is, however, subject to constraints of nuclear genic control both of the stable range of number of rows and of the positioning mechanism itself. The large-scale systems of pattern determination are probably more closely related to the field properties of developing multicellular organisms. In ciliates such systems are almost certainly located in the cell membrane or in the relatively fixed cytoplasmic layer just beneath the membrane.

Animals↗
PubMed1975

Myonemal contraction of spirostomum. II. Some mechanical properties of the contractile apparatus.

In several respects, notably the high velocity of shortening, Ca(2+) dependence, and ATP independence, contraction of Spirostomum resembles the spasmonemal mechanism of the peritrich ciliates. In this report further mechanical properties of the contractile apparatus are described that extend this comparison. The velocity-load characteristic is more appropriate to an elastomer than to a muscle where contraction force is load-dependent. Active tension is found to relate linearly to cell length for extensions up to and beyond resting length (1r), an elastic limit is reached around 1.5 1r. At resting length this tension, measured by the deformation of a glass microbalance, is similar to that predicted from consideration of the hydrodynamic forces normally resisting shortening. The tension-length relation for the unstimulated (passive) cell is also linear between 1r and the elastic limit, but is displaced from the active tension-length curve and is of reduced stiffness. Kinetic studies suggest that maximum tension and maximum velocity coincide. Calculations are presented that support a model of contraction in Spirostomum in which the myonemes behave as a mechanochemical engine powered directly by the chemical potential of Ca(2+).

Animals↗
PubMed1976

Cell surface control in Blepharisma intermedium (Protozoa Ciliata). Blocking of gamone II-induced homotypic interacting ligands.

PHA, Con-A, or anti-tubulin antibodies inhibit homotypic pair formation, in B, intermedium mating type-I cells in the presence of suboptimal concentrations of gamone II. The inhibition is dependent on the dose of gamone added; the structural conformation and the relative concentration of the inhibitor; and the time of addition of the inhibitor. The block can be selectively prevented by competitive inhibitors of each ligand. The receptors for the inhibitors are distinctive and there is no cross-reaction between the ligands. It is concluded that ligand binding and subsequent receptor-ligand aggregation must induce a change within the cell-surface membrane, which distorts the distribution and/or affects an optimal conformational aspect of a specific membrane-receptor system for the gamon, a prerequisite for cell pair formation.

Acetylgalactosamine↗
PubMed1977

Carchesium stalk fibrillar matrix as a highly filled polymer network.

Glycerolated stalks of the sessile peritrich ciliate Carchesium sp. were treated with 10(-6) g ion/1 Ca2+ to disrupt the contractile spasmoneme. The resulting preparation consisted primarily of the fibrillar matrix, a dense extra-cellular meshwork of microfibrils. Some mechanical properties of this preparation have been investigated. The matrix tensile force-extension ratio relation for an initial stretch was characteristic of a soft, swollen polymer network, elastic modulus in young stalks 1.7 X 10(5) Nm-2, in mature stalks 4.0 X 10(5) Nm-2. The higher elastic modulus in mature stalks implies an increase in the interchain cross-link frequency. In young stalks, elastic modulus was found to be independent of the ambient Ca2+ concentration in the threshold range for spasmonemal contraction. Stalk relaxation was pronouncedly irreversible, showing stress softening and permanent hysteresis on repeated loading. Hysteresis was time independent and stiffness was not recovered after four hours at zero strain. Hysteresis was enhanced by repeated loading to the same tensile force. Stress-strain hysteresis at a low extension is characteristic of highly filled polymer networks in which polymer chains are interconnected via rigid filler particles as well as directly cross-linked.

Biopolymers↗
PubMed1977

Measurements of contraction latencies to mechanical and electrical stimulation of the protozoan, Spirostomum ambiguum.

Measurements made on contraction latencies in Spirostomun suggest that mechanical stimulation causes contractions to be initiated by the release of small amounts of calcium from a store tightly coupled to the contractile apparatus. Contraction to electrical stimulation appears to result from the gross electrophoretic mobilization of large amounts of calcium from a loosely coupled store. Contraction latencies to mechanical stimulation were three milliseconds and were independent of stimulus strength, previous stimulation, and contraction probability. For 0.5-millisecond biphasic electrical stimulation the contraction latencies varied widely. Latencies to initial contractions were dependent on stimulus strength: from 1.0 milliseconds for a stimulus that caused a 100% probability of contraction to 2.0 milliseconds for a stimulus that caused a 10% probability of contraction. Latencies of contraction to electrical stimulation were also dependent upon previous stimulation, lengthening to over 300 milliseconds after ten minutes of stimulation. Initial contraction latencies were not affected by previous stimulation to the other (electrical or mechanical) stimulus modality. Repeated electrical stimulation also reduced the animal's resting length and slowed the rate of post contraction re-extension, whereas mechanical stimulation did not have these effects.

Animals↗
PubMed1977

Electron microbeam analysis of calcium distribution in the ciliated protozoan, Spirostomum ambiguum.

Electron microprobe analyses of calcium distribution in the ciliated protozoan, Spirostomum ambiguum, indicated several calcium rich sites. One site was an endoplasmic distribution of calcium coincident with phosphorus which corroborates previous findings of hydroxyapatite deposits within Spirostomum. These apatite deposits were distributed throughout the endoplasm, but not within the nuclei or the contractile vacuole. Calcium was also detected within the cortical region. Cortical calcium was in greater concentration in the anterior portion of the organism and decreased towards the posterior end (region containing the contractile vacuole). Phosphorus and potassium were also detected as gradients from the anterior end, whereas magnesium was detected in the same density throughout the cortical region. Line scans of cortical regions suggested (1) distributions of calcium within mitochondria and/or vesicles, and (2) calcium associated with bundles of microfilaments.

Animals↗
PubMed1975

Conjugation in Oxytricha bifaria: cell interaction.

As a model of cell interaction, the mating process of Oxytricha bifaria has been investigated. Mating involves several distinct and sterotyped stages, each lasting a determined time, and ending with the formation of firmly united pairs. A "waiting period" intervenes between the mixture of complimentary mating types and the onset of cell interaction. A proper starvation shortens the waiting period (25 min vs 120 min). Treatment of properly starved cells with heterologous cell-free fluid further reduces the waiting period. Certain enzyme treatments (pronase, trypsin and lipase) dramatically increase the waiting period in both washed enzyme-treated cells and in unwashed cells. Trypsin inhibits the first two stages of the mating process, while lipase inhibits membrane fusion between mates.

Cell Division↗
PubMed1975

Comparative physiology of cellular ion and volume regulation.

1. Intracellular [K+]i in most cells is around 100-150 mOs. This is true in invertebrate or vertebrate muscle or any other tissue, and the only known exceptions being the axons of some invertebrates (Burton, '73). 2. When cell volume is increased due to hypoosmotic swelling, cell volume is regulated back toward normal in almost all cells. In cells with an osmolality of 300-350 mOs, the regulatory volume decrease is caused primarily by a passive efflux of potassium and anions due to increased membrane permeability to potassium. In cells with a higher osmolality, regulatory volume decrease is caused by the passive efflux of small organic molecules. 3. When cell volume is decreased due to hyperosmotic shrinking, volume is not always regulated back toward normal in in vitro experiments carried out for several hours. However, it appears from the in vivo experiments that some cell volume control is always present. The volume control in the flounder red cells took place through increased sodium influx brought about by a relative increase in cell membrane permeability to sodium. This mechanism also appears to be dominant in the mammalian renal papilla, where the [Na+]i increases in proportion to the increase in cellular osmolality with no change in [K+]i. 4. Cells which remain shrunken in vitro, or cells which only partly restore their volume in vivo, do not exhibit increased [K+]i. This finding means that potassium is lost from the cell and, in most cases, exchanged for sodium when the volume is decreased, even though the osmotic concentration in the extracellular fluid is elevated. 5. Finally, it appears that the maintenance of a rather constant [K+]i is important for all cells. This constancy may be due to the fact that certain enzymes are sensitive to the intracellular potassium concentration. Thus, the DNA synthesis is blocked in mammalian kidney cells when [K+]i is increased (Bygrave, '67). Furthermore, Lubin ('64) has shown that low [K+]i concentrations also cause a decrease in DNA, RNA, and protein synthesis. An optimal concentration appears to be necessary for protein synthesis.

Amoeba↗
PubMed1976

Differential cortical degradation in the two members of early conjugant pairs of Oxytricha fallax.

A differential resorption of the anterior ventral cortical structures is shown to occur in early conjugating pairs of Oxytricha. The member on the pair's left resorbs the collar membranelles and the frontal and right marginal cirri; the member on the pair's right resorbs the central and posterior membranelles (lapel) of the adoral zone of membranelles. The lapel of the left member then aligns with the collar of the right member to form a composite structure which appears with light and scanning electron microscopy to be completely integrated. Consequently, a 4-5-hour-old pair contains slightly more than one complete set of anterior ventral organelles (viz., one extra set of undulating membranes) and two complete sets of ventral and anal cirri. Analysis of conjugant pairs in which the two members are joined in abnormal positions suggests that neither the proximity of certain cortical organelles to the region of cytoplasmic bridge formation, the specific pairing position, nor the relocation of certain cortical organelles into a different cortical region is directly responsible for determining which resorption pattern occurs. Furthermore, analysis of the cortical events in conjugating doublets suggests that neither nuclear determination nor differential gene expression can account for the phenomena observed in Oxytricha.

Animals↗
PubMed1977

The role of cortical pattern in timing of cell division and morphogenesis in Stentor.

This paper describes experiments involving reciprocal exchange of the oral apparatus between a large (L) and a small (S) strain of Stentor coeruleus. Mature L-strain stentors given and S-strain oral apparatus formed an oral primordium in response to the presence of abnormally small oral structures and mostly divided although a few reorganized instead. Conversely, when S-strain stentors in early division were given a large L-strain oral apparatus, they resorbed the developing primordium and returned to interphase. When combined with previous results, these findings provide evidence for the hypothesis that the time of cell division in Stentor is determined by a "critical" ratio between the size of the oral apparatus and the size of the cell body (somatic) cortex. This ratio develops because the somatic cortex grows during interphase and the oral apparatus does not. Cell division in Stentor therefore appears to be initiated by a cortical pattern change resulting from cell surface growth during interphase.

Animals↗
PubMed1977

Control of shape and pattern during the assembly of a large microtubule bundle. Evidence for a microtubule-nucleating-template.

Microtubules are packed and linked together in a well defined hexagonal arrangement in the cytopharyngeal microtubule bundles of the ciliate Nassula. Early stages in the morphogenesis of these bundles have been examined. Elements which nucleate assembly of bundle microtubules are apparently closely associated before tubule assembly commences. These nucleating elements seem to be bound together in highly ordered arrays to form microtubule-nucleating-templetes. Each array of elements is attached to the proximal end of a basal body and appears to establish the pattern of tubule packing and cross-sectional shape of a tubule bundle. A self-assembly procedure which accounts for the anisometric growth and shaping of a template and its microtubule bundle is proposed.

Animals↗