241 research outputs found

    PF15p Is the Chlamydomonas Homologue of the Katanin p80 Subunit and Is Required for Assembly of Flagellar Central Microtubules

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    Numerous studies have indicated that the central apparatus plays a significant role in regulating flagellar motility, yet little is known about how the central pair of microtubules or their associated projections assemble. Several Chlamydomonas mutants are defective in central apparatus assembly. For example, mutant pf15 cells have paralyzed flagella that completely lack the central pair of microtubules. We have cloned the wild-type PF15 gene and confirmed its identity by rescuing the motility and ultrastructural defects in two pf15 alleles, the original pf15a mutant and a mutant generated by insertional mutagenesis. Database searches using the 798-amino-acid polypeptide predicted from the complete coding sequence indicate that the PF15 gene encodes the Chlamydomonas homologue of the katanin p80 subunit. Katanin was originally identified as a heterodimeric protein with a microtubule-severing activity. These results reveal a novel role for the katanin p80 subunit in the assembly and/or stability of the central pair of flagellar microtubule

    Titanium and Aluminum in Biotite From High-Grade Archaean Gneisses, Langø, West Greenland

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    Biotite grains from a variety of gneiss types were analyzed by electron microprobe techniques for Na, Mg, Al, Si, K, Ca, Ti, Mn, Fe, Zn, F & Cl. TiO_2- and Al_2O_3-contents range continuously from < 0.1 to 6.0 and 13.9 to 20.6 wt % respectively. Most occur with ilmenite, but a few coexist with rutile. Biotite in pyribolite contains the least Al, and that in Kfeld-sill gneiss contains the most, suggesting that Al-content of biotite is related to the bulk composition of the host rock. For a given rock type, Ti in biotite tends to decrease as Mg/Fe and Al increase

    Cytokinesis in bloodstream stage Trypanosoma brucei requires a family of katanins and spastin

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    Microtubule severing enzymes regulate microtubule dynamics in a wide range of organisms and are implicated in important cell cycle processes such as mitotic spindle assembly and disassembly, chromosome movement and cytokinesis. Here we explore the function of several microtubule severing enzyme homologues, the katanins (KAT80, KAT60a, KAT60b and KAT60c), spastin (SPA) and fidgetin (FID) in the bloodstream stage of the African trypanosome parasite, Trypanosoma brucei. The trypanosome cytoskeleton is microtubule based and remains assembled throughout the cell cycle, necessitating its remodelling during cytokinesis. Using RNA interference to deplete individual proteins, we show that the trypanosome katanin and spastin homologues are non-redundant and essential for bloodstream form proliferation. Further, cell cycle analysis revealed that these proteins play essential but discrete roles in cytokinesis. The KAT60 proteins each appear to be important during the early stages of cytokinesis, while downregulation of KAT80 specifically inhibited furrow ingression and SPA depletion prevented completion of abscission. In contrast, RNA interference of FID did not result in any discernible effects. We propose that the stable microtubule cytoskeleton of T. brucei necessitates the coordinated action of a family of katanins and spastin to bring about the cytoskeletal remodelling necessary to complete cell divisio

    Earth's oldest mantle fabrics indicate Eoarchaean subduction

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    The extension of subduction processes into the Eoarchaean era (4.0-3.6 Ga) is controversial. The oldest reported terrestrial olivine, from two dunite lenses within the ~3,720 Ma Isua supracrustal belt in Greenland, record a shape-preferred orientation of olivine crystals defining a weak foliation and a well-defined lattice-preferred orientation (LPO). [001] parallel to the maximum finite elongation direction and (010) perpendicular to the foliation plane define a B-type LPO. In the modern Earth such fabrics are associated with deformation of mantle rocks in the hanging wall of subduction systems; an interpretation supported by experiments. Here we show that the presence of B-type fabrics in the studied Isua dunites is consistent with a mantle origin and a supra-subduction mantle wedge setting, the latter supported by compositional data from nearby mafic rocks. Our results provide independent microstructural data consistent with the operation of Eoarchaean subduction and indicate that microstructural analyses of ancient ultramafic rocks provide a valuable record of Archaean geodynamics

    Fluticasone/formoterol combination therapy is as effective as fluticasone/salmeterol in the treatment of asthma, but has a more rapid onset of action: an open-label, randomized study

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    <p>Abstract</p> <p>Background</p> <p>The inhaled corticosteroid (ICS) fluticasone propionate (fluticasone) and the long-acting β<sub>2</sub>-agonist (LABA) formoterol fumarate (formoterol) are being made available as a combination product (fluticasone/formoterol, <b><it>flutiform</it></b><sup>®</sup>) in a single aerosol inhaler. This 12-week, open-label, randomized, active-controlled, parallel-group, multicentre, phase 3 study compared the efficacy and safety of fluticasone/formoterol with the commercially available combination product fluticasone/salmeterol.</p> <p>Methods</p> <p>Patients aged ≥ 18 years (N = 202) with mild-to-moderate–severe, persistent asthma for ≥ 6 months prior to screening were included in the study. After a screening phase (4–10 days), eligible patients were randomized 1:1 to receive fluticasone/formoterol or fluticasone/salmeterol during the 12-week treatment period. The primary objective was to demonstrate non-inferiority of fluticasone/formoterol versus fluticasone/salmeterol, measured by pre-dose forced expiratory volume in the first second (FEV<sub>1</sub>), at week 12.</p> <p>Results</p> <p>Fluticasone/formoterol was comparable to fluticasone/salmeterol for the primary efficacy endpoint, mean pre-dose FEV<sub>1 </sub>at week 12. The new combination was also comparable to fluticasone/salmeterol for change from baseline to week 12 in pre-dose FEV<sub>1</sub>, change from pre-dose FEV<sub>1 </sub>at baseline to 2-hour post-dose FEV<sub>1 </sub>at week 12 and discontinuations due to lack of efficacy. Importantly, fluticasone/formoterol was superior to fluticasone/salmeterol in time to onset of action throughout the duration of the study. The two treatments demonstrated similar results for various other secondary efficacy parameters, including other lung function tests, patient-reported outcomes, rescue medication use, asthma exacerbations and Asthma Quality of Life Questionnaire scores. Fluticasone/formoterol was well tolerated and had a good safety profile that was similar to fluticasone/salmeterol.</p> <p>Conclusions</p> <p>The results of this study indicate that fluticasone/formoterol is as effective as fluticasone/salmeterol, and has a more rapid onset of action, reflecting the faster bronchodilatory effects of formoterol compared with those of salmeterol. If patients perceive the benefits of therapy with fluticasone/formoterol more rapidly than with fluticasone/salmeterol, this could have a positive impact on preference and adherence.</p> <p>Trial Registration</p> <p>ClinicalTrials.gov: <a href="http://www.clinicaltrials.gov/ct2/show/NCT00476073">NCT00476073</a></p
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