2,625 research outputs found

    TFE and Spt4/5 open and close the RNA polymerase clamp during the transcription cycle

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    Transcription is an intrinsically dynamic process and requires the coordinated interplay of RNA polymerases (RNAPs) with nucleic acids and transcription factors. Classical structural biology techniques have revealed detailed snapshots of a subset of conformational states of the RNAP as they exist in crystals. A detailed view of the conformational space sampled by the RNAP and the molecular mechanisms of the basal transcription factors E (TFE) and Spt4/5 through conformational constraints has remained elusive. We monitored the conformational changes of the flexible clamp of the RNAP by combining a fluorescently labeled recombinant 12-subunit RNAP system with single-molecule FRET measurements. We measured and compared the distances across the DNA binding channel of the archaeal RNAP. Our results show that the transition of the closed to the open initiation complex, which occurs concomitant with DNA melting, is coordinated with an opening of the RNAP clamp that is stimulated by TFE. We show that the clamp in elongation complexes is modulated by the nontemplate strand and by the processivity factor Spt4/5, both of which stimulate transcription processivity. Taken together, our results reveal an intricate network of interactions within transcription complexes between RNAP, transcription factors, and nucleic acids that allosterically modulate the RNAP during the transcription cycle

    Metacognition and Motivation in Anatomy and Physiology Students

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    The purpose of this study was to use a grounded theory, qualitative approach to gain a deeper understanding of students’ self-regulated learning processes in a required first-year gateway Anatomy and Physiology (A&P) course that is critical for success in health care-related academic programs and professions. At the end of a two-semester sequence in A&P, students were recruited to participate in individual 30-minute semi-structured interviews based on questions related to their metacognitive beliefs and behaviors. Investigators reviewed verbatim transcripts from 25 primarily first-year students and identified four major themes: 1) career orientation, 2) relevance of Anatomy and Physiology, 3) success as the ability to earn good grades, as well as retention and ability to apply materials, and 4) student behaviors referring to the learning and metacognitive strategies reported by students. Within the theme of student behaviors, four sub-themes emerged: collaborative work with peers, self-responsibility, self-awareness, and evolution as learners. The results of this study will help investigators to design and implement strategies to improve success in this course for pre-health professional students

    Variation in Mating Dynamics across Five Species of Leiobunine Harvestmen (Arachnida: Opliones)

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    The study of mating choices often focuses on correlates of traits to the overall outcome of a mating interaction. However, mating interactions can proceed through a series of stages, with opportunities for assessment at each stage. We compared whether male or female size predicted mating interaction outcome across several stages of mating in five species of North American leiobunine harvestmen (commonly known as daddy longlegs). Leiobunine harvestmen have been previously shown to exhibit incredible morphological diversity consistent with a spectrum of male–female antagonism. Across all of the species, we found a general progression of female size predicting the outcome (success and timing) of early stages of interactions, and male size or male size relative to female size predicting the outcome and timing of later stages of interactions. We also found that size was not a strong predictor of outcome in the two species on the lower end of the antagonism spectrum. The variation in how female and male size predicted outcomes across species and stages of mating suggests that multiple mechanisms may operate to shape mating dynamics within and across species. Given the close relatedness of the species studied, the patterns we uncovered suggest a rapid evolution of the traits and processes predicting the outcome of mating interactions

    Retrospective Analysis of Methotrexate Elimination When Coadministered With Levetiracetam

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    Background: Delayed elimination of methotrexate was previously reported in 2 patients receiving concomitant levetiracetam. Objective: To explore the potential interaction between methotrexate and levetiracetam in patients receiving high-dose methotrexate. Methods: This retrospective study reviewed the records of 81 adults receiving 280 cycles of methotrexate to determine the effects of levetiracetam on methotrexate elimination. Institutional review board approval was obtained. Results: Levetiracetam was administered in 33 (12%) cycles of methotrexate. Patients receiving levetiracetam had significantly lower 24-hour methotrexate concentrations compared with those not receiving levetiracetam (2.91 vs 7.37 µmol/L, P = 0.005). Despite this difference, concentrations at 48 and 72 hours were similar between groups. Times to nontoxic methotrexate concentration (\u3c0.1 µmol/L) were the same regardless of the presence of levetiracetam. The frequency of delayed elimination at 24, 48, and 72 hours was similar in both groups as was the frequency of delayed elimination at any time point. Cox regression demonstrated that levetiracetam was not a significant predictor of time to nontoxic methotrexate concentration (P = 0.796; HR = 1.058; 95% CI = 0.692-1.617), and logistic regression demonstrated that levetiracetam was not a significant predictor of delayed elimination at any time point. Levetiracetam use was similar between groups when comparing patients experiencing delayed elimination at any time point with those without delayed elimination (13% vs 10%, respectively, P = 0.527). Conclusion: This study does not support the previous reports of a significant interaction between levetiracetam and methotrexate. A clinically significant interaction is unlikely in those without additional risk factors for delayed elimination

    Prospectus, September 11, 2002

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    https://spark.parkland.edu/prospectus_2002/1021/thumbnail.jp

    Prospectus, February 27, 2004

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    https://spark.parkland.edu/prospectus_2004/1005/thumbnail.jp
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