1,878 research outputs found
Cofactor regeneration by a soluble pyridine nucleotide transhydrogenase for biological production of hydromorphone
We have applied the soluble pyridine nucleotide transhydrogenase of Pseudomonas fluorescens to a cell-free system for the regeneration of the nicotinamide cofactors NAD and NADP in the biological production of the important semisynthetic opiate drug hydromorphone. The original recombinant whole-cell system suffered from cofactor depletion resulting from the action of an NADP(+)-dependent morphine dehydrogenase and an NADH-dependent morphinone reductase. By applying a soluble pyridine nucleotide transhydrogenase, which can transfer reducing equivalents between NAD and NADP, we demonstrate with a cell-free system that efficient cofactor cycling in the presence of catalytic amounts of cofactors occurs, resulting in high yields of hydromorphone. The ratio of morphine dehydrogenase, morphinone reductase, and soluble pyridine nucleotide transhydrogenase is critical for diminishing the production of the unwanted by-product dihydromorphine and for optimum hydromorphone yields. Application of the soluble pyridine nucleotide transhydrogenase to the whole-cell system resulted in an improved biocatalyst with an extended lifetime. These results demonstrate the usefulness of the soluble pyridine nucleotide transhydrogenase and its wider application as a tool in metabolic engineering and biocatalysis
Inferring a consensus problem list using penalized multistage models for ordered data
A patient\u27s medical problem list describes his or her current health status and aids in the coordination and transfer of care between providers, among other things. Because a problem list is generated once and then subsequently modified or updated, what is not usually observable is the provider-effect. That is, to what extent does a patient\u27s problem in the electronic medical record actually reflect a consensus communication of that patient\u27s current health status? To that end, we report on and analyze a unique interview-based design in which multiple medical providers independently generate problem lists for each of three patient case abstracts of varying clinical difficulty. Due to the uniqueness of both our data and the scientific objectives of our analysis, we apply and extend so-called multistage models for ordered lists and equip the models with variable selection penalties to induce sparsity. Each problem has a corresponding non-negative parameter estimate, interpreted as a relative log-odds ratio, with larger values suggesting greater importance and zero values suggesting unimportant problems. We use these fitted penalized models to quantify and report the extent of consensus. For the three case abstracts, the proportions of problems with model-estimated non-zero log-odds ratios were 10/28, 16/47, and 13/30. Physicians exhibited consensus on the highest ranked problems in the first and last case abstracts but agreement quickly deteriorates; in contrast, physicians broadly disagreed on the relevant problems for the middle and most difficult case abstract
Checkpoint Inhibitors and Therapeutic Vaccines for the Treatment of Chronic HBV Infection
Treatment of chronic hepatitis B virus (HBV) infection is highly effective in suppressing viral replication, but complete cure is rarely achieved. In recent years, substantial progress has been made in the development of immunotherapy to treat cancer. Applying these therapies to improve the management of chronic HBV infection is now being attempted, and has become an area of active research. Immunotherapy with vaccines and checkpoint inhibitors can boost T cell functions in vitro, and therefore may be used to reinvigorate the impaired HBV-specific T cell response. However, whether these approaches will suffice and restore antiviral T cell immunity to induce long-term HBV control remains an open question. Recent efforts have begun to describe the phenotype and function of HBV-specific T cells on the single epitope level. An improved understanding of differing T cell specificities and their contribution to HBV control will be instrumental for advancement of the field. In this review, we outline correlates of successful versus inadequate T cell responses to HBV, and discuss the rationale behind therapeutic vaccines and checkpoint inhibitors for the treatment of chronic HBV infection
Letter from A. C. Van Raalte to His Wife Christina Johanna de Moen
A letter of Albertus C. Van Raalte to his wife, Christina Johanna de Moen, to inform her of his travels thus far. He has learned from Judge Kellogg that there is land available at Ada and Ionia and six townships in Allegan are still for sale by the government. Van Raalte is very thankful that he has come into contact with M. I. Colt, Theodore Romeyn, Rev. Ova P. Hoyt and Judge Kellogg all of whom are God fearing men. More and more I think that the state of Michigan is the place in which we shall make our home. p. 32. He also admonishes his children to be obedient to Mrs. Van Raalte. He signs the letter as Your loving friend, brother, and husband.https://digitalcommons.hope.edu/vrp_1840s/1067/thumbnail.jp
Understanding dyadic promoter-stakeholder relations in complex projects
In this study, we propose a Bilateral Double Motive framework of stakeholder cooperation in complex projects. The framework analyses and explains dyadic promoter-stakeholder relationships at a micro level by acknowledging both transactional and relational motives. We demonstrate the framework’s usefulness by illustrating its explanatory power in two instances of cooperation and two of non-cooperation within two health information technology projects. The study contributes to project management theory through its combined focus on transactional and relational motives. Further, the study contributes to practice by providing a tool for planning and evaluating cooperation in health Information Technology projects and similar complex multi-stakeholder environments
A modular framework for early-phase seamless oncology trials
Background: As our understanding of the etiology and mechanisms of cancer becomes more sophisticated and the number of therapeutic options increases, phase I oncology trials today have multiple primary objectives. Many such designs are now \u27seamless\u27, meaning that the trial estimates both the maximum tolerated dose and the efficacy at this dose level. Sponsors often proceed with further study only with this additional efficacy evidence. However, with this increasing complexity in trial design, it becomes challenging to articulate fundamental operating characteristics of these trials, such as (i) what is the probability that the design will identify an acceptable, i.e. safe and efficacious, dose level? or (ii) how many patients will be assigned to an acceptable dose level on average? Methods: In this manuscript, we propose a new modular framework for designing and evaluating seamless oncology trials. Each module is comprised of either a dose assignment step or a dose-response evaluation, and multiple such modules can be implemented sequentially. We develop modules from existing phase I/II designs as well as a novel module for evaluating dose-response using a Bayesian isotonic regression scheme. Results: We also demonstrate a freely available R package called seamlesssim to numerically estimate, by means of simulation, the operating characteristics of these modular trials. Conclusions: Together, this design framework and its accompanying simulator allow the clinical trialist to compare multiple different candidate designs, more rigorously assess performance, better justify sample sizes, and ultimately select a higher quality design
Identification of the contribution of the ankle and hip joints to multi-segmental balance control
Background\ud
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Human stance involves multiple segments, including the legs and trunk, and requires coordinated actions of both. A novel method was developed that reliably estimates the contribution of the left and right leg (i.e., the ankle and hip joints) to the balance control of individual subjects. \ud
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Methods\ud
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The method was evaluated using simulations of a double-inverted pendulum model and the applicability was demonstrated with an experiment with seven healthy and one Parkinsonian participant. Model simulations indicated that two perturbations are required to reliably estimate the dynamics of a double-inverted pendulum balance control system. In the experiment, two multisine perturbation signals were applied simultaneously. The balance control system dynamic behaviour of the participants was estimated by Frequency Response Functions (FRFs), which relate ankle and hip joint angles to joint torques, using a multivariate closed-loop system identification technique. \ud
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Results\ud
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In the model simulations, the FRFs were reliably estimated, also in the presence of realistic levels of noise. In the experiment, the participants responded consistently to the perturbations, indicated by low noise-to-signal ratios of the ankle angle (0.24), hip angle (0.28), ankle torque (0.07), and hip torque (0.33). The developed method could detect that the Parkinson patient controlled his balance asymmetrically, that is, the right ankle and hip joints produced more corrective torque. \ud
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Conclusion\ud
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The method allows for a reliable estimate of the multisegmental feedback mechanism that stabilizes stance, of individual participants and of separate leg
Reliability of transcranial magnetic stimulation evoked potentials to detect the effects of theta-burst stimulation of the prefrontal cortex
Background: Transcranial magnetic stimulation (TMS) with simultaneous electroencephalography (EEG) is a novel method for assessing cortical properties outside the motor region. Theta burst stimulation (TBS), a form of repetitive TMS, can non-invasively modulate cortical excitability and has been increasingly used to treat psychiatric disorders by targetting the dorsolateral prefrontal cortex (DLPFC). The TMS-evoked potentials (TEPs) and local mean field power (LMFP) analyses have been used to evaluate local cortical excitability changes after TBS. However, it remains unclear whether TEPs can detect the neuromodulatory effects of TBS. Objectives: To confirm the reliability of TEP components and LMFP within and between sessions and to measure changes in neural excitability induced by intermittent (iTBS) and continuous TBS (cTBS) applied to the left DLPFC. Methods: Test-retest reliability of TEPs/LMFP and TBS-induced changes in cortical excitability were assessed in twenty-four healthy participants by stimulating the DLPFC in five separate sessions, once with sham and twice with iTBS and cTBS. EEG responses were recorded of 100 single TMS pulses before and after TBS, and the reproducibility measures were quantified with the concordance correlation coefficient (CCC). Results: The N100 and P200 components presented substantial reliability within the baseline block (CCCs>0.8) and moderate concordance between sessions (CCCmax> 0.6). Both N40 and P60 TEP amplitudes showed little concordance between sessions. Similar results were achieved using LMFP responses. Changes in TEP amplitudes after iTBS were marginally reliable for N100 (CCCmax = 0.52), P200 (CCCmax = 0.47) and P60 (CCCmax = 0.40), presenting only fair levels of concordance at specific time points. LMFP changes showed poor reproducibility after iTBS and cTBS. Conclusions: The present findings show that only the N100 and P200 components had good concordance between sessions. The reliability of earlier TEP components and LMF responses may have been affected by a sub-optimal removal of TMS-related artefacts. The poor reliability in detecting changes in neural excitability induced by TBS indicates that TEPs/LMFP do not provide a precise estimate of the changes in excitability in the DLPFC or, alternatively, that TBS did not induce consistent changes in neural excitability
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