495 research outputs found
Studies on the flight medical aspects of the German Lufthansa non-stop route from Frankfurt to Rio de Janeiro, part 1
The problem of crew size for regularly scheduled flights between Frankfurt and Rio de Janeiro is discussed. Factors affecting crew performance are examined, comparisons are drawn to regulations of other countries and crew questionnaires and tests are presented
A unique DNA entry gate serves for regulated loading of the eukaryotic replicative helicase MCM2-7 onto DNA.
The regulated loading of the replicative helicase minichromosome maintenance proteins 2–7 (MCM2–7) onto replication origins is a prerequisite for replication fork establishment and genomic stability. Origin recognition complex (ORC), Cdc6, and Cdt1 assemble two MCM2–7 hexamers into one double hexamer around dsDNA. Although the MCM2–7 hexamer can adopt a ring shape with a gap between Mcm2 and Mcm5, it is unknown which Mcm interface functions as the DNA entry gate during regulated helicase loading. Here, we establish that the Saccharomyces cerevisiae MCM2–7 hexamer assumes a closed ring structure, suggesting that helicase loading requires active ring opening. Using a chemical biology approach, we show that ORC–Cdc6–Cdt1-dependent helicase loading occurs through a unique DNA entry gate comprised of the Mcm2 and Mcm5 subunits. Controlled inhibition of DNA insertion triggers ATPase-driven complex disassembly in vitro, while in vivo analysis establishes that Mcm2/Mcm5 gate opening is essential for both helicase loading onto chromatin and cell cycle progression. Importantly, we demonstrate that the MCM2–7 helicase becomes loaded onto DNA as a single hexamer during ORC/Cdc6/Cdt1/MCM2–7 complex formation prior to MCM2–7 double hexamer formation. Our study establishes the existence of a unique DNA entry gate for regulated helicase loading, revealing key mechanisms in helicase loading, which has important implications for helicase activation
An ORC/Cdc6/MCM2-7 Complex Is Formed in a Multistep Reaction to Serve as a Platform for MCM Double-Hexamer Assembly
In Saccharomyces cerevisiae and higher eukaryotes, the loading of the replicative helicase MCM2-7 onto DNA requires the combined activities of ORC, Cdc6, and Cdt1. These proteins load MCM2-7 in an unknown way into a double hexamer around DNA. Here we show that MCM2-7 recruitment by ORC/Cdc6 is blocked by an autoinhibitory domain in the C terminus of Mcm6. Interestingly, Cdt1 can overcome this inhibitory activity, and consequently the Cdt1-MCM2-7 complex activates ORC/Cdc6 ATP-hydrolysis to promote helicase loading. While Cdc6 ATPase activity is known to facilitate Cdt1 release and MCM2-7 loading, we discovered that Orc1 ATP-hydrolysis is equally important in this process. Moreover, we found that Orc1/Cdc6 ATP-hydrolysis promotes the formation of the ORC/Cdc6/MCM2-7 (OCM) complex, which functions in MCM2-7 double-hexamer assembly. Importantly, CDK-dependent phosphorylation of ORC inhibits OCM establishment to ensure once per cell cycle replication. In summary, this work reveals multiple critical mechanisms that redefine our understanding of DNA licensing
Comparative study between LMA supreme with I-gel in anaesthetised adult patient on effectiveness and safety
Background: Supreme laryngeal mask airway (SLMA) and I-gel airway devices are second generation supraglottic airway devices (SAD) and are good alternatives to intubation during surgeries. The study was conducted with the objective to compare two supraglottic airway devices for ease of insertion, number of attempts of insertion, hemodynamic changes, incidence of adverse effects like regurgitation, lip and dental trauma and post-operative sore throat, dysphagia or hoarseness.Methods: This study was conducted at Topiwala National Medical College and BYL Nair hospital, Mumbai. 80 patients of ASA class 1 and 2 with Mallampati grading 1 and 2, between age group of 18-60 years and with BMI 0.05). Postoperatively no significant complications were observed in terms of dental injury, laryngospasm. Complication like sore throat after 1 hour and after 24 hours was comparatively more in I-gel group but difference was not significant at 1 hr (p>0.05). Dysphagia was reported more in SLMA group (8 cases) than I-gel group (1 case) at one hour and the difference was statistically significant (p=0.013).Conclusions: SLMA and I-GEL are better airway management option for patients undergoing short surgical procedures under general anaesthesia
Cryo-EM structure of a helicase loading intermediate containing ORC-Cdc6-Cdt1-MCM2-7 bound to DNA
In eukaryotes, the Cdt1-bound replicative helicase core MCM2-7 is loaded onto DNA by the ORC-Cdc6 ATPase to form a prereplicative complex (pre-RC) with an MCM2-7 double hexamer encircling DNA. Using purified components in the presence of ATP-γS, we have captured in vitro an intermediate in pre-RC assembly that contains a complex between the ORC-Cdc6 and Cdt1-MCM2-7 heteroheptamers called the OCCM. Cryo-EM studies of this 14-subunit complex reveal that the two separate heptameric complexes are engaged extensively, with the ORC-Cdc6 N-terminal AAA+ domains latching onto the C-terminal AAA+ motor domains of the MCM2-7 hexamer. The conformation of ORC-Cdc6 undergoes a concerted change into a right-handed spiral with helical symmetry that is identical to that of the DNA double helix. The resulting ORC-Cdc6 helicase loader shows a notable structural similarity to the replication factor C clamp loader, suggesting a conserved mechanism of action
STRATEGI MEMBANGUN MODERASI BERAGAMA MELALUI PERAYAAN HARI BESAR KEAGAMAAN DI SMK NEGERI 2 KAIMANA
Konflik tentang perbedaan agama masih saja hangat untuk dibicarakan karena itu penguatan moderasi beragama dapat dijadikan sebagai sarana untuk meminimalisir terjadinya konflik agama dan sifat fanatik sempit antara satu agama dengan agama yang lainnya. Sekolah adalah salah satu tempat bertemunya beberapa agama yang memungkinkan terjadinya pemahaman yang berbeda-beda tentang suatu agama. Strategi moderasi beragama sebagai pilihan untuk mengelola keragaman peserta didik sehingga hak untuk menikmati pendidikan secara bebas tanpa ada tekanan, diskriminasi dan kekerasan. Salah satu strategi membangun moderasi beragama dapat dilakukan melalui perayaan hari besar keagamaan di sekolah. Hal ini penting dilakukan sebagai kebijkan kepala sekolah untuk memutuskan sikap radikalisme dengan pendekatan edukatif dalam rangka mengimplementasikan kultur sekolah dengan kurikulum yang cintai damai sehingga siswa memiliki karakter yang terbuka terhadap agama lain, saling menghormati dan menerima perbedaan yang ada dalam lingkungan belajar mereka
Mechanism and timing of Mcm2–7 ring closure during DNA replication origin licensing
The opening and closing of two ring-shaped Mcm2-7 DNA helicases is necessary to license eukaryotic origins of replication, although the mechanisms controlling these events are unclear. The origin-recognition complex (ORC), Cdc6 and Cdt1 facilitate this process by establishing a topological link between each Mcm2-7 hexamer and origin DNA. Using colocalization single-molecule spectroscopy and single-molecule Förster resonance energy transfer (FRET), we monitored ring opening and closing of Saccharomyces cerevisiae Mcm2-7 during origin licensing. The two Mcm2-7 rings were open during initial DNA association and closed sequentially, concomitant with the release of their associated Cdt1. We observed that ATP hydrolysis by Mcm2-7 was coupled to ring closure and Cdt1 release, and failure to load the first Mcm2-7 prevented recruitment of the second Mcm2-7. Our findings identify key mechanisms controlling the Mcm2-7 DNA-entry gate during origin licensing, and reveal that the two Mcm2-7 complexes are loaded via a coordinated series of events with implications for bidirectional replication initiation and quality control.National Institutes of Health (U.S.) (Grant R01 GM52339)National Institutes of Health (U.S.) (Pre-Doctoral Training Grant GM007287)National Cancer Institute (U.S.) (Koch Institute Support Grant P30-CA14051
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A comprehensive analysis of coherent rainfall patterns in China and potential drivers. Part II: intraseasonal variability
The causes of subseasonal precipitation variability in China are investigated using observations and reanalysis data for extended winter (November–April) and summer (May–October) seasons from 1982 to 2007. For each season, the three dominant regions of coherent intraseasonal variability are identified with Empirical Orthogonal Teleconnection (EOT) analysis. While previous studies have focused on particular causes for precipitation variability or on specific regions, here a comprehensive analysis is carried out with an objective method. Furthermore, the associated rainfall anomaly timeseries are tied to specific locations in China, which facilitates their interpretation. To understand the underlying processes associated with spatially coherent patterns of rainfall variability, fields from observations and reanalysis are regressed onto EOT timeseries. The three dominant patterns in winter together explain 43% of the total space–time variance and have their origins in midlatitude disturbances that appear two pentads in advance. Winter precipitation variability along the Yangtze River is associated with wave trains originating over the Atlantic and northern Europe, while precipitation variability in southeast China is connected to the Mediterranean storm track. In summer, all patterns have a strong relationship with the Boreal Summer Intraseasonal Oscillation and are modulated by the seasonal cycle of the East Asian summer monsoon. The wet and dry phases of the regional patterns can substantially modulate the frequency of daily rainfall across China. The discovered links between weather patterns, precursors, and effects on local and remote precipitation may provide a valuable basis for hydrological risk assessments and the evaluation of numerical weather prediction models
Aspectos Moleculares da Regeneração de Fígado de Rato. I - Atividade da Aspartato Transcarbamilase em Função do Tempo de Regeneração em Fígado de Ratos Submetidos a Hepatectomia Parcial
A Aspartato Transcarbamilase foi estudada em fígado de rato em regeneração. Sua atividade sofre um aumento em função do tempo de regeneração, com aumento de até 47% sobre sua atividade basal na décima segunda hora após a hepatectomia
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