(1) Tyr-tubulin is principally at the bases of cirri and membranelles.
(2) These sets, however, are incomplete, with certain structures, most notably cirri of the right marginal type, missing near the line of symmetry.
(3) The laterofrontal (LF) cirri on isolated gill filaments of Mytilus edulis, prepared in natural seawater, are active and initially beat with an average frequency of about 8 Hz (with a range of 6-14 Hz).
(4) The cirri of the ciliate Euplotes all asslumne the "reversed" orientation whenever the cell is depolarized and the "forward" orientation whenever the cell is hyperpolarized.
(5) This results in the differentiation of maxillary structures like cirri and mouth hooks in places where they normally do not appear, and represents a phenomenon of autocatalysis of homeotic gene function that differs from the normal activation process.
(6) 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.
(7) Under these conditions, the threshold of the LF cirri arrest response is again found to occur as the L cilia attain a beat frequency of 12-14 Hz.
(8) When a mirror-image doublet is bisected longitudinally to separate the RH and LH components physically, each fragment undergoes a regeneration process that restores a complete set of cortical structures, including the previously missing cirri of the right marginal type.
(9) The orientation responses of thte cirri are appatently independent of intracellular "neuromotor" fibrils previously assigned a coordinating function, as they persist after the fibrils are transected.
(10) 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.
(11) A combination of 10(-7) M 5HT and 0.5 mM IBMX in ASW mimics high (greater than 10(-6) M) 5HT concentrations by arresting the LF cirri and increasing the beat frequency of the L cilia.
(12) Exposure to higher concentrations of 5HT (greater than 10(-7) M) elevates the beat frequency of the L cilia and simultaneously inhibits the activity of the LF cirri, leading to their arrest in a position at the end of the effective stroke.
(13) A concentration of 0.5 mM IBMX mimics low 5HT concentrations (about 10(-7) M) by stimulating the L cilia to beat without affecting the beat frequency of the LF cirri.
(14) We document a novel approach for quantitative assessment of ciliary activity, exemplified in rapid three-dimensional cyclic motion of the frontal cirri of Stylonychia.
(15) These results suggest that the mechanisms of LF cirri arrest and L cilia activation are mediated by 5HT-induced changes in intracellular cyclic AMP levels.
(16) The influence of 5HT on the L cilia and the LF cirri can be reversibly mimicked or enhanced by the phosphodiesterase inhibitor 3-isobutyl-1-methylxanthine (IBMX).
(17) The exposure of the gill to low levels of 5-hydroxytryptamine (5HT) (10(-8) less than 5HT less than 10(-7) M) has no effect on the activity of the LF cirri but stimulates the L cilia to beat.
(18) In the resulting LH cell, all ciliary structures are present in an arrangement that is globally reversed in relation to that found in RH cells; in particular, marginal cirri of the left-marginal type are formed at the cell's right margin, and marginal cirri of the right-marginal type are produced at the cell's left margin.
(19) Motor responses of the frontal cirri of the ciliate Stylonychia were recorded at the axial view of the ciliary base with high-speed cinematography.
(20) Perfusion of the filament with artificial seawater (ASW), with or without 1% ethanol, has little or no biological effect on the activity of the LF cirri, although a transitory decrease in frequency often accompanies the perfusion process.
Protist
Definition:
(n.) One of the Protista.
Example Sentences:
(1) Thus, a plant alpha-tubulin exhibits a high degree of homology to the alpha-tubulins of protists and animals.
(2) Molecular distances were computed between the aligned nucleotides of all presently available protist sequences and were used to derive a tentative dendrogram.
(3) The microsporidia are a group of unusual, obligately parasitic protists that infect a great variety of other eukaryotes, including vertebrates, arthropods, molluscs, annelids, nematodes, cnidaria and even various ciliates, myxosporidia and gregarines.
(4) Actin genic regions were isolated and characterized from the heterokont-flagellated protists, Achlya bisexualis (Oomycota) and Costaria costata (Chromophyta).
(5) An RNA polymerase III in vitro transcription system has been developed from the protist Acanthamoeba castellanii.
(6) Unlike the actin-encoding genes (act) of other filamentous fungi, no introns are obvious in the coding region, a feature shared with the act genes of certain protists.
(7) We have undertaken the construction of a broad molecular phylogeny of protists through the comparison of 28S rRNA molecules.
(8) Parasitic amitochondriate protists, representatives of early branches of eukaryote evolution, differ considerably in their central, energy metabolism from mitochondrion-bearing cells.
(9) The emonctory structures, functions and stereotype and their component parts are studied in protists, spongia, coelenterata and coelomata: lower worms, annelids, their hyponeurian descendents (arthropods, molluses) and epineurian descedents echinoderms and protochordates (Stomochordata, Tunicata, Cephalochordata).
(10) The most probable hypothesis is that of a symbiotic origin of the first zygote by association of two protists one signifying a spherical oocell and the other a flagellated spermatozoan; this could be the first step of the metazoan ontogenesis and therefore also of the phylogenesis.
(11) The folding for the D3, D7a and D10 divergent domains has been refined and a consensus model for the protist 24-26S rRNA structure is proposed.
(12) The classification thus seeks to offer a compromise between the protist and protoctist kingdoms of Whittaker and Margulis and to combine a full listing of phyla with grouping of these for synoptic treatment.
(13) The E. gracilis divergence far antedates a period of massive evolutionary radiation that gave rise to the plants, animals, fungi, and certain groups of protists such as ciliates and the acanthamoebae.
(14) It is suggested that, in line with comparable situations in other protists, expansion of the nuclear envelope is chiefly responsible for separation of the nucleus into two daughter nuclei.
(15) This simple binary immunological character was superimposed on a number of published protist phylogenies and seen to fit very well with some of them.
(16) The data show that the cytochrome c oxidase of the protist Euglena is different from other eukaryotic cytochrome c oxidases in number and size of subunits, and also with regard to kinetic properties and substrate specificity.
(17) The ciliated protists (ciliates) offer a unique opportunity to explore the relationship between chemoreception and cell structure.
(18) Glucokinase activities that phosphorylate glucose and glucosamine are inhibited by N-acetyl-glucosamine and xylose, were found to be present in the non-sulphur photosynthetic bacteria Rhodospirillum rubrum, the blue-green algae Anacystis montana, and the protists Chlorella pyrenoidosa and Chlamydomonas reinhardtii (green algae), Hypochytrium catenoides (Hypochytridiomycete) and Saprolegnia Iitoralis (Oomycete).
(19) This interpretation of the identity of nucleus-associated membranes differs from those previously reported for other protists, including members of the Plasmodiophorales.
(20) The reduction of flagella (cilia) is occurring in different taxa independent of the transition of protists from the flagellate type of locomotion to the amoeboid, gliding of metabolizing ones, and in the number of metazoan cells.