Tag Archives: PubMed

MR-guided joint reconstruction of activity and attenuation in brain PET-MR.






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MR-guided joint reconstruction of activity and attenuation in brain PET-MR.

Neuroimage. 2017 Sep 13;162:276-288

Authors: Mehranian A, Zaidi H, Reader AJ

Abstract
With the advent of time-of-flight (TOF) PET scanners, joint maximum-likelihood reconstruction of activity and attenuation (MLAA) maps has recently regained attention for the estimation of PET attenuation maps from emission data. However, the estimated attenuation and activity maps are scaled by unknown scaling factors. We recently demonstrated that in hybrid PET-MR, the scaling issue of this algorithm can be effectively addressed by imposing MR spatial constraints on the estimation of attenuation maps using a penalized MLAA (P-MLAA(+)) algorithm. With the advent of simultaneous PET-MR systems, MRI-guided PET image reconstruction has also gained attention for improving the quantitative accuracy of PET images, usually degraded by noise and partial volume effects. The aim of this study is therefore to increase the benefits of MRI information for improving the quantitative accuracy of PET images by exploiting MRI-based anatomical penalty functions to guide the reconstruction of both activity and attenuation maps during their joint estimation. We employed an anato-functional joint entropy penalty function for the reconstruction of activity and an anatomical quadratic penalty function for the reconstruction of attenuation. The resulting algorithm was referred to as P-MLAA(++) since it exploits both activity and attenuation penalty functions. The performance of the P-MLAA algorithms were compared with MLAA and the widely used activity reconstruction algorithms such as maximum likelihood expectation maximization (MLEM) and penalized MLEM (P-MLEM) both corrected for attenuation using a conventional MRI segmentation-based attenuation correction (MRAC) method. The studied methods were evaluated using simulations and clinical studies taking the PET image reconstructed using reference CT-based attenuation maps as a reference. The simulation results showed that the proposed method can notably improve the visual quality of the PET images by reducing noise while preserving structural boundaries and at the same time improving the quantitative accuracy of the PET images. Our clinical reconstruction results showed that the MLEM-MRAC, P-MLEM-MRAC, MLAA, P-MLAA(+) and P-MLAA(++) algorithms result in, on average, quantification errors of -13.5 ± 3.1%, -13.4 ± 3.1%, -2.0 ± 6.5%, -3.0 ± 3.5% and -4.2 ± 3.6%, respectively, in different regions of the brain. In conclusion, whilst the P-MLAA(+) algorithm showed the best overall quantification performance, the proposed P-MLAA(++) algorithm provided simultaneous partial volume and attenuation corrections with only a minor compromise of PET quantification.

PMID: 28918316 [PubMed – as supplied by publisher]

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Controlled, synchronized actuation of microdroplets by gravity in a superhydrophobic, 3D-printed device.






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Controlled, synchronized actuation of microdroplets by gravity in a superhydrophobic, 3D-printed device.

Anal Chim Acta. 2017 Oct 02;988:50-57

Authors: Oomen PE, Mulder JPSH, Verpoorte E, Oleschuk RD

Abstract
Droplet manipulation over open surfaces allows one to perform assays with a large degree of control and high throughput, making them appealing for applications in drug screening or (bio)analysis. However, the design, manufacturing and operation of these systems comes with high technical requirements. In this study we employ a commercial, low-friction, superhydrophobic coating, Ultra-Ever Dry(®), on a 3D-printed microfluidic device. The device features individual droplet compartments, which allow the manipulation of discrete droplets (10-50 μL) actuated by gravity alone. Simply by angling the device to normal in a 3D-printed holder and rocking in a “to and fro”-fashion, a sequence of droplets can be individually transferred to an electrochemical microelectrode detector and then to waste, while preserving the (chronological) order of samples. Multiple biological fluids (i.e. human saliva, urine and rat blood and serum) were successfully tested for compatibility with the device and actuation mechanism, demonstrating low slip angles and high contact angles. Biological matrix (protein) carryover was probed and effectively mitigated by incorporating aqueous rinse droplets as part of the analysis sequence. As a proof-of-concept, the enzyme-coupled, amperometric detection of glucose was carried out on individual rat serum droplets, enabling total analysis in ≈30 min, including calibration. The device is readily customizable, and the integration of droplet generation techniques and other sensor systems for different analytes of interest or applications can be realized in a plug and play fashion.

PMID: 28916103 [PubMed – in process]

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Coupled reactions by coupled enzymes: alcohol to lactone cascade with alcohol dehydrogenase-cyclohexanone monooxygenase fusions.






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Coupled reactions by coupled enzymes: alcohol to lactone cascade with alcohol dehydrogenase-cyclohexanone monooxygenase fusions.

Appl Microbiol Biotechnol. 2017 Sep 15;:

Authors: Aalbers FS, Fraaije MW

Abstract
The combination of redox enzymes for redox-neutral cascade reactions has received increasing appreciation. An example is the combination of an alcohol dehydrogenase (ADH) with a cyclohexanone monooxygenase (CHMO). The ADH can use NADP(+) to oxidize cyclohexanol to form cyclohexanone and NADPH. Both products are then used by CHMO to produce ε-caprolactone. In this study, these two redox-complementary enzymes were fused, to create a self-sufficient bifunctional enzyme that can convert alcohols to esters or lactones. Three different ADH genes were fused to a gene coding for a thermostable CHMO, in both orientations (ADH-CHMO and CHMO-ADH). All six fusion enzymes could be produced and purified. For two of the three ADHs, we found a clear difference between the two orientations: one that showed the expected ADH activity, and one that showed low to no activity. The ADH activity of each fusion enzyme correlated with its oligomerization state. All fusions retained CHMO activity, and stability was hardly affected. The TbADH-TmCHMO fusion was selected to perform a cascade reaction, producing ε-caprolactone from cyclohexanol. By circumventing substrate and product inhibition, a > 99% conversion of 200 mM cyclohexanol could be achieved in 24 h, with > 13,000 turnovers per fusion enzyme molecule.

PMID: 28916997 [PubMed – as supplied by publisher]

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Uric acid in major depressive and anxiety disorders.






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Uric acid in major depressive and anxiety disorders.

J Affect Disord. 2017 Sep 06;225:684-690

Authors: Black CN, Bot M, Scheffer PG, Snieder H, Penninx BWJH

Abstract
BACKGROUND: Uric acid has neuroprotective effects, owing to its antioxidant properties. Lowered antioxidant capacity, causing increased oxidative stress, may be involved in affective disorders and might be altered by antidepressants. This study investigated the association of plasma uric acid, the greatest contributor to blood antioxidant capacity, with major depressive disorder (MDD) and anxiety disorders.
METHODS: Data were from the Netherlands Study of Depression and Anxiety including patients with current (N = 1648), remitted (N = 609) MDD and/or anxiety disorders (of which N = 710 antidepressant users) and 618 controls. Diagnoses were established with the Composite International Diagnostic Interview. Symptom severity was assessed with the Inventory of Depressive Symptoms-Self Report, Beck Anxiety Inventory and Fear Questionnaire. Uric acid was measured in plasma. Analyses were adjusted for sociodemographic, health and lifestyle variables.
RESULTS: Plasma uric acid adjusted mean levels were lower in current MDD and/or anxiety disorder(s) (289μmol/l) compared to remitted disorders (298μmol/l, p < .001) and controls (299μmol/l, p < .001; Cohen’s d .10). This finding was independent of antidepressant use. Depressive (β-.05, p = .0012), anxiety (β-.04, p = .009) and phobic (β-.03, p = .036) symptom severity, and symptom duration (β-.04, p = .009) were negatively associated with uric acid.
LIMITATIONS: Limitations include the lack of data on dietary intake which could be a potential confounding factor. From these cross-sectional findings, the association between uric acid and psychopathology cannot be inferred to be causal.
CONCLUSION: This large scale study finds plasma uric acid levels are lower in current, but not remitted, MDD and/or anxiety disorders, according to a dose-response gradient. This suggests the involvement of decreased antioxidant status in affective disorders, and points to their potential as an avenue for treatment.

PMID: 28917195 [PubMed – as supplied by publisher]

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Changes in acid-base and ion balance during exercise in normoxia and normobaric hypoxia.






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Changes in acid-base and ion balance during exercise in normoxia and normobaric hypoxia.

Eur J Appl Physiol. 2017 Sep 15;:

Authors: Lühker O, Berger MM, Pohlmann A, Hotz L, Gruhlke T, Hochreiter M

Abstract
PURPOSE: Both exercise and hypoxia cause complex changes in acid-base homeostasis. The aim of the present study was to investigate whether during intense physical exercise in normoxia and hypoxia, the modified physicochemical approach offers a better understanding of the changes in acid-base homeostasis than the traditional Henderson-Hasselbalch approach.
METHODS: In this prospective, randomized, crossover trial, 19 healthy males completed an exercise test until voluntary fatigue on a bicycle ergometer on two different study days, once during normoxia and once during normobaric hypoxia (12% oxygen, equivalent to an altitude of 4500 m). Arterial blood gases were sampled during and after the exercise test and analysed according to the modified physicochemical and Henderson-Hasselbalch approach, respectively.
RESULTS: Peak power output decreased from 287 ± 9 Watts in normoxia to 213 ± 6 Watts in hypoxia (-26%, P < 0.001). Exercise decreased arterial pH to 7.21 ± 0.01 and 7.27 ± 0.02 (P < 0.001) during normoxia and hypoxia, respectively, and increased plasma lactate to 16.8 ± 0.8 and 17.5 ± 0.9 mmol/l (P < 0.001). While the Henderson-Hasselbalch approach identified lactate as main factor responsible for the non-respiratory acidosis, the modified physicochemical approach additionally identified strong ions (i.e. plasma electrolytes, organic acid ions) and non-volatile weak acids (i.e. albumin, phosphate ion species) as important contributors.
CONCLUSIONS: The Henderson-Hasselbalch approach might serve as basis for screening acid-base disturbances, but the modified physicochemical approach offers more detailed insights into the complex changes in acid-base status during exercise in normoxia and hypoxia, respectively.

PMID: 28914359 [PubMed – as supplied by publisher]

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Platelets as Modulators of Liver Diseases.






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Platelets as Modulators of Liver Diseases.
Semin Thromb Hemost. 2017 Sep 12;:
Authors: Lisman T, Luyendyk JP
PMID: 28898899 [PubMed – as supplied by publisher]

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Assessment of CT dose to the fetus and pregnant female patient using patient-specific computational models.






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Assessment of CT dose to the fetus and pregnant female patient using patient-specific computational models.

Eur Radiol. 2017 Sep 08;:

Authors: Xie T, Poletti PA, Platon A, Becker CD, Zaidi H

Abstract
PURPOSE: This work provides detailed estimates of the foetal dose from diagnostic CT imaging of pregnant patients to enable the assessment of the diagnostic benefits considering the associated radiation risks.
MATERIALS AND METHODS: To produce realistic biological and physical representations of pregnant patients and the embedded foetus, we developed a methodology for construction of patient-specific voxel-based computational phantoms based on existing standardised hybrid computational pregnant female phantoms. We estimated the maternal absorbed dose and foetal organ dose for 30 pregnant patients referred to the emergency unit of Geneva University Hospital for abdominal CT scans.
RESULTS: The effective dose to the mother varied from 1.1 mSv to 2.0 mSv with an average of 1.6 mSv, while commercial dose-tracking software reported an average effective dose of 1.9 mSv (range 1.7-2.3 mSv). The foetal dose normalised to CTDIvol varies between 0.85 and 1.63 with an average of 1.17.
CONCLUSION: The methodology for construction of personalised computational models can be exploited to estimate the patient-specific radiation dose from CT imaging procedures. Likewise, the dosimetric data can be used for assessment of the radiation risks to pregnant patients and the foetus from various CT scanning protocols, thus guiding the decision-making process.
KEY POINTS: • In CT examinations, the absorbed dose is non-uniformly distributed within foetal organs. • This work reports, for the first time, estimates of foetal organ-level dose. • The foetal brain and skeleton doses present significant correlation with gestational age. • The conceptus dose normalised to CTDI vol varies between 0.85 and 1.63. • The developed methodology is adequate for patient-specific CT radiation dosimetry.

PMID: 28887589 [PubMed – as supplied by publisher]

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Sexual dimorphism in the genetic influence on human childlessness.






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Sexual dimorphism in the genetic influence on human childlessness.
Eur J Hum Genet. 2017 Sep;25(9):1067-1074
Authors: Verweij RM, Mills MC, Tropf FC, Veenstra R, Nyman A, Snieder H
Abstract
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Cognitive behavioral therapy and predictors of weight loss in bariatric surgery patients.






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Cognitive behavioral therapy and predictors of weight loss in bariatric surgery patients.
Curr Opin Psychiatry. 2017 Aug 08;:
Authors: Paul L, van der Heiden C, Hoek HW
Abstract
PURPOS… Continue reading






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The effects of normal aging on multiple aspects of financial decision-making.






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The effects of normal aging on multiple aspects of financial decision-making.
PLoS One. 2017;12(8):e0182620
Authors: Bangma DF, Fuermaier ABM, Tucha L, Tucha O, Koerts J
Abstract
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Inflammatory Bowel Diseases: Review of Known Environmental Protective and Risk Factors Involved.






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Inflammatory Bowel Diseases: Review of Known Environmental Protective and Risk Factors Involved.
Inflamm Bowel Dis. 2017 Aug 02;:
Authors: van der Sloot KWJ, Amini M, Peters V, Dijkstra G, Alizadeh BZ… Continue reading






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Evidence-based clinical guidelines for eating disorders: international comparison.






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Evidence-based clinical guidelines for eating disorders: international comparison.
Curr Opin Psychiatry. 2017 Aug 01;:
Authors: Hilbert A, Hoek H, Schmidt R
Abstract
PURPOSE OF REVIEW:… Continue reading






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Revealing Oft-cited but Unpublished Papers of Colin Pittendrigh and Coworkers.






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Revealing Oft-cited but Unpublished Papers of Colin Pittendrigh and Coworkers.
J Biol Rhythms. 2017 Jul 01;:748730417716685
Authors: Tackenberg MC, Johnson CH, Page TL, Daan S
Abstract
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Structural Biology of the Immune Checkpoint Receptor PD-1 and Its Ligands PD-L1/PD-L2.






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Structural Biology of the Immune Checkpoint Receptor PD-1 and Its Ligands PD-L1/PD-L2.

Structure. 2017 Aug 01;25(8):1163-1174

Authors: Zak KM, Grudnik P, Magiera K, Dömling A, Dubin G, Holak TA

Abstract
Cancer cells can avoid and suppress immune responses through activation of inhibitory immune checkpoint proteins, such as PD-1, PD-L1, and CTLA-4. Blocking the activities of these proteins with monoclonal antibodies, and thus restoring T cell function, has delivered breakthrough therapies against cancer. In this review, we describe the latest work on structural characterization of the checkpoint proteins, their interactions with cognate ligands and with therapeutic antibodies. Structures of the extracellular portions of these proteins reveal that they all have a similar modular structure, composed of small domains similar in topology to the domains found in antibodies. Structural basis for blocking the PD-1/PD-L1 interaction by small molecules is illustrated with the compound BMS-202 that binds to and induces dimerization of PD-L1.

PMID: 28768162 [PubMed – in process]

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Interim FDG-PET in lymphoma, a questionable practice in hematology.






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Interim FDG-PET in lymphoma, a questionable practice in hematology.
Eur J Nucl Med Mol Imaging. 2017 Jul 31;:
Authors: Adams HJA, Kwee TC
PMID: 28761975 [PubMed – as supplied by publisher]

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Costly comorbidities of COPD: the ignored side of the coin?






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Costly comorbidities of COPD: the ignored side of the coin?
Eur Respir J. 2017 Jul;50(1):
Authors: van Boven JFM
PMID: 28751418 [PubMed – in process]

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Comments on: Cernes, R. & Zimlichman, R. Role of Paced Breathing for Treatment of Hypertension. Curr Hypertens Rep (2017) 19: 45.






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Comments on: Cernes, R. & Zimlichman, R. Role of Paced Breathing for Treatment of Hypertension. Curr Hypertens Rep (2017) 19: 45.
Curr Hypertens Rep. 2017 Aug;19(8):65
Authors: Landman GWD, van Ha… Continue reading






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Electrically controlled cloud of bulk nanobubbles in water solutions.






Electrically controlled cloud of bulk nanobubbles in water solutions.

PLoS One. 2017;12(7):e0181727

Authors: Postnikov AV, Uvarov IV, Lokhanin MV, Svetovoy VB

Abstract
Using different experimental techniques we visualize a cloud of gas in water that is produced electrochemically by the alternating polarity process. Liquid enriched with gas does not contain bubbles strongly scattering visible light but its refractive index changes significantly near the electrodes. The change of the refractive index is a collective effect of bulk nanobubbles with a diameter smaller than 200 nm. Any alternative explanation fails to explain the magnitude of the effect. Spatial structure of the cloud is investigated with the optical lever method. Its dynamics is visualised observing optical distortion of the electrode images or using differential interference contrast method. The cloud covers concentric electrodes, in a steady state it is roughly hemispherical with a size two times larger than the size of the electrode structure. When the electrical pulses are switched off the cloud disappears in less than one second. The total concentration of gases can reach very high value estimated as 3.5 × 1020 cm-3 that corresponds to an effective supersaturation of 500 and 150 for hydrogen and oxygen, respectively.

PMID: 28727812 [PubMed – in process]

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An unexpected role for bile acid synthesis in adaptation to low temperature.






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An unexpected role for bile acid synthesis in adaptation to low temperature.
Nat Med. 2017 Jul 11;23(7):800-802
Authors: Kuipers F, Groen AK
PMID: 28697185 [PubMed – in process]

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Construct validity and test-retest reliability of the revised Upper Extremity Work Demands (UEWD-R) Scale.






Construct validity and test-retest reliability of the revised Upper Extremity Work Demands (UEWD-R) Scale.
Occup Environ Med. 2017 Jul 08;:
Authors: Cavalini MA, Berduszek RJ, van der Sluis CK
Abstract
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