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Tikhomirov R, Oakley RH, Anderson C, Xiang Y, Al Othman S, Smith M, Yaar S, Torre E, Li J, Wilson LR, Goulding DR, Donaldson I, Harno E, Soattin L, Shiels HA, Morris GM, Zhang H, Boyett MR, Cidlowski JA, Mesirca P, Mangoni ME, D'Souza A. Cardiac GR Mediates the Diurnal Rhythm in Ventricular Arrhythmia Susceptibility. Circ Res 2024. [PMID: 38533639 DOI: 10.1161/circresaha.123.323464] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/03/2023] [Accepted: 03/13/2024] [Indexed: 03/28/2024]
Abstract
RATIONALE Ventricular arrhythmias (VAs) demonstrate a prominent day-night rhythm, commonly presenting in the early morning. Transcriptional rhythms in cardiac ion channels accompany this phenomenon, but their role in the morning vulnerability to VAs and the underlying mechanisms are not understood. OBJECTIVE The objectives are to investigate the recruitment of transcription factors to time-of-day differentially accessible chromatin that underpins day-night ion channel rhythms and to assess the significance of this for the heart's day-night rhythm in VA susceptibility. METHODS AND RESULTS Assay for transposase-accessible chromatin with sequencing performed in mouse ventricular myocyte nuclei at the beginning of the inactive (zeitgeber time, time of lights on, start of sleep period) and active (time of lights off, start of awake period [ZT12]) periods revealed differentially accessible chromatin sites annotating to rhythmically transcribed ion channels and transcription factor binding motifs in these regions. Notably, motif enrichment for the glucocorticoid receptor (GR; transcriptional effector of corticosteroid signaling) binding site in open chromatin profiles at ZT12 was observed, in line with the well-recognized ZT12 peak in circulating corticosteroids. Molecular, electrophysiological, and in silico biophysically detailed modeling approaches demonstrated GR-mediated transcriptional control of ion channels (including Scn5a underlying the cardiac Na+ current, Kcnh2 underlying the rapid delayed rectifier K+ current, and Gja1 responsible for electrical coupling) and their contribution to the day-night rhythm in the vulnerability to VA. Strikingly, both pharmacological block of GR and cardiomyocyte-specific genetic knockout of GR blunted or abolished ion channel expression rhythms and abolished the ZT12 susceptibility to pacing-induced VA in isolated hearts. CONCLUSIONS Our study registers a day-night rhythm in chromatin accessibility that accompanies diurnal cycles in ventricular myocytes. Our approaches directly implicate the cardiac GR in the myocyte excitability rhythm and mechanistically link the ZT12 surge in glucocorticoids to intrinsic VA propensity at this time.
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Affiliation(s)
- Roman Tikhomirov
- Division of Cardiovascular Sciences, The University of Manchester, United Kingdom. (R.T., C.A., S.A.O., M.S., S.Y., L.S., H.A.S., G.M.M., A.D.)
| | - Robert H Oakley
- National Institute of Environmental Health Sciences, National Institutes of Health (R.H.O., J.L., L.R.W., D.R.G., J.A.C.)
| | - Cali Anderson
- Division of Cardiovascular Sciences, The University of Manchester, United Kingdom. (R.T., C.A., S.A.O., M.S., S.Y., L.S., H.A.S., G.M.M., A.D.)
| | - Yirong Xiang
- Department of Physics and Astronomy, The University of Manchester, United Kingdom. (Y.X., H.Z.)
| | - Sami Al Othman
- Division of Cardiovascular Sciences, The University of Manchester, United Kingdom. (R.T., C.A., S.A.O., M.S., S.Y., L.S., H.A.S., G.M.M., A.D.)
| | - Matthew Smith
- Division of Cardiovascular Sciences, The University of Manchester, United Kingdom. (R.T., C.A., S.A.O., M.S., S.Y., L.S., H.A.S., G.M.M., A.D.)
| | - Sana Yaar
- Division of Cardiovascular Sciences, The University of Manchester, United Kingdom. (R.T., C.A., S.A.O., M.S., S.Y., L.S., H.A.S., G.M.M., A.D.)
| | - Eleonora Torre
- IGF, CNRS, INSERM, Université de Montpellier, France (E.T., P.M., M.E.M.)
| | - Jianying Li
- National Institute of Environmental Health Sciences, National Institutes of Health (R.H.O., J.L., L.R.W., D.R.G., J.A.C.)
| | - Leslie R Wilson
- National Institute of Environmental Health Sciences, National Institutes of Health (R.H.O., J.L., L.R.W., D.R.G., J.A.C.)
| | - David R Goulding
- National Institute of Environmental Health Sciences, National Institutes of Health (R.H.O., J.L., L.R.W., D.R.G., J.A.C.)
| | - Ian Donaldson
- Bioinformatics Core Facility, The University of Manchester, United Kingdom. (I.D.)
| | - Erika Harno
- Division of Diabetes, Endocrinology and Gastroenterology, The University of Manchester, United Kingdom. (E.H.)
| | - Luca Soattin
- Division of Cardiovascular Sciences, The University of Manchester, United Kingdom. (R.T., C.A., S.A.O., M.S., S.Y., L.S., H.A.S., G.M.M., A.D.)
| | - Holly A Shiels
- Division of Cardiovascular Sciences, The University of Manchester, United Kingdom. (R.T., C.A., S.A.O., M.S., S.Y., L.S., H.A.S., G.M.M., A.D.)
| | - Gwilym M Morris
- Division of Cardiovascular Sciences, The University of Manchester, United Kingdom. (R.T., C.A., S.A.O., M.S., S.Y., L.S., H.A.S., G.M.M., A.D.)
- John Hunter Hospital, Newcastle, NSW, Australia (G.M.M.)
| | - Henggui Zhang
- Department of Physics and Astronomy, The University of Manchester, United Kingdom. (Y.X., H.Z.)
| | - Mark R Boyett
- Faculty of Life Sciences, University of Bradford, United Kingdom (M.R.B.)
| | - John A Cidlowski
- National Institute of Environmental Health Sciences, National Institutes of Health (R.H.O., J.L., L.R.W., D.R.G., J.A.C.)
| | - Pietro Mesirca
- IGF, CNRS, INSERM, Université de Montpellier, France (E.T., P.M., M.E.M.)
| | - Matteo E Mangoni
- IGF, CNRS, INSERM, Université de Montpellier, France (E.T., P.M., M.E.M.)
| | - Alicia D'Souza
- Division of Cardiovascular Sciences, The University of Manchester, United Kingdom. (R.T., C.A., S.A.O., M.S., S.Y., L.S., H.A.S., G.M.M., A.D.)
- National Heart and Lung Institute, Imperial College London, United Kingdom (A.D.)
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Wilson LR, Plummer NW, Evsyukova IY, Patino D, Stewart CL, Smith KG, Konrad KS, Fry SA, Deal AL, Kilonzo VW, Panda S, Sciolino NR, Cushman JD, Jensen P. Partial or Complete Loss of Norepinephrine Differentially Alters Contextual Fear and Catecholamine Release Dynamics in Hippocampal CA1. Biol Psychiatry Glob Open Sci 2024; 4:51-60. [PMID: 38058990 PMCID: PMC10695841 DOI: 10.1016/j.bpsgos.2023.10.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2023] [Revised: 09/28/2023] [Accepted: 10/05/2023] [Indexed: 12/08/2023] Open
Abstract
Background Contextual fear learning is heavily dependent on the hippocampus. Despite evidence that catecholamines contribute to contextual encoding and memory retrieval, the precise temporal dynamics of their release in the hippocampus during behavior is unknown. In addition, new animal models are required to probe the effects of altered catecholamine synthesis on release dynamics and contextual learning. Methods We generated 2 new mouse models of altered locus coeruleus-norepinephrine (NE) synthesis and utilized them together with GRABNE and GRABDA sensors and in vivo fiber photometry to investigate NE and dopamine (DA) release dynamics in the dorsal hippocampal CA1 during contextual fear conditioning. Results Aversive foot shock increased both NE and DA release in the dorsal CA1, while freezing behavior associated with recall of fear memory was accompanied by decreased release. Moreover, we found that freezing at the recent time point was sensitive to both partial and complete loss of locus coeruleus-NE synthesis throughout prenatal and postnatal development, similar to previous observations of mice with global loss of NE synthesis beginning postnatally. In contrast, freezing at the remote time point was compromised only by complete loss of locus coeruleus-NE synthesis beginning prenatally. Conclusions Overall, these findings provide novel insights into the role of NE in contextual fear and the precise temporal dynamics of both NE and DA during freezing behavior and highlight complex relationships between genotype, sex, and NE signaling.
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Affiliation(s)
- Leslie R. Wilson
- Neurobiology Laboratory, NIEHS, National Institutes of Health, Department of Health and Human Services, Research Triangle Park, North Carolina
- Neurobehavioral Core Laboratory, NIEHS, National Institutes of Health, Department of Health and Human Services, Research Triangle Park, North Carolina
| | - Nicholas W. Plummer
- Neurobiology Laboratory, NIEHS, National Institutes of Health, Department of Health and Human Services, Research Triangle Park, North Carolina
| | - Irina Y. Evsyukova
- Neurobiology Laboratory, NIEHS, National Institutes of Health, Department of Health and Human Services, Research Triangle Park, North Carolina
| | - Daniela Patino
- Neurobiology Laboratory, NIEHS, National Institutes of Health, Department of Health and Human Services, Research Triangle Park, North Carolina
| | - Casey L. Stewart
- Neurobiology Laboratory, NIEHS, National Institutes of Health, Department of Health and Human Services, Research Triangle Park, North Carolina
| | - Kathleen G. Smith
- Neurobiology Laboratory, NIEHS, National Institutes of Health, Department of Health and Human Services, Research Triangle Park, North Carolina
| | - Kathryn S. Konrad
- Social and Scientific Systems, Inc., a DLH Holdings Corp Company, Durham, North Carolina
| | - Sydney A. Fry
- Neurobehavioral Core Laboratory, NIEHS, National Institutes of Health, Department of Health and Human Services, Research Triangle Park, North Carolina
| | - Alex L. Deal
- Neurobiology Laboratory, NIEHS, National Institutes of Health, Department of Health and Human Services, Research Triangle Park, North Carolina
| | - Victor W. Kilonzo
- Neurobiology Laboratory, NIEHS, National Institutes of Health, Department of Health and Human Services, Research Triangle Park, North Carolina
| | - Sambit Panda
- Neurobehavioral Core Laboratory, NIEHS, National Institutes of Health, Department of Health and Human Services, Research Triangle Park, North Carolina
| | - Natale R. Sciolino
- Department of Physiology and Neurobiology, Department of Biomedical Engineering, Institute for System Genomics, Connecticut Institute for the Brain & Cognitive Sciences, University of Connecticut, Storrs, Connecticut
| | - Jesse D. Cushman
- Neurobehavioral Core Laboratory, NIEHS, National Institutes of Health, Department of Health and Human Services, Research Triangle Park, North Carolina
| | - Patricia Jensen
- Neurobiology Laboratory, NIEHS, National Institutes of Health, Department of Health and Human Services, Research Triangle Park, North Carolina
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Bridge MF, Wilson LR, Panda S, Stevanovic KD, Letsinger AC, McBride S, Cushman JD. FiPhA: an open-source platform for fiber photometry analysis. Neurophotonics 2024; 11:014305. [PMID: 38406178 PMCID: PMC10885510 DOI: 10.1117/1.nph.11.1.014305] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/21/2023] [Revised: 01/19/2024] [Accepted: 01/23/2024] [Indexed: 02/27/2024]
Abstract
Significance Fiber photometry (FP) is a widely used technique in modern behavioral neuroscience, employing genetically encoded fluorescent sensors to monitor neural activity and neurotransmitter release in awake-behaving animals. However, analyzing photometry data can be both laborious and time-consuming. Aim We propose the fiber photometry analysis (FiPhA) app, which is a general-purpose FP analysis application. The goal is to develop a pipeline suitable for a wide range of photometry approaches, including spectrally resolved, camera-based, and lock-in demodulation. Approach FiPhA was developed using the R Shiny framework and offers interactive visualization, quality control, and batch processing functionalities in a user-friendly interface. Results This application simplifies and streamlines the analysis process, thereby reducing labor and time requirements. It offers interactive visualizations, event-triggered average processing, powerful tools for filtering behavioral events, and quality control features. Conclusions FiPhA is a valuable tool for behavioral neuroscientists working with discrete, event-based FP data. It addresses the challenges associated with analyzing and investigating such data, offering a robust and user-friendly solution without the complexity of having to hand-design custom analysis pipelines. This application thus helps standardize an approach to FP analysis.
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Affiliation(s)
- Matthew F. Bridge
- Social & Scientific Systems, Inc., a DLH Holdings Corp. Company, Durham, North Carolina, United States
| | - Leslie R. Wilson
- National Institute of Environmental Health Sciences, National Institutes of Health, Neurobiology Laboratory, Division of Intramural Research, Durham, North Carolina, United States
| | - Sambit Panda
- National Institute of Environmental Health Sciences, National Institutes of Health, Neurobiology Laboratory, Division of Intramural Research, Durham, North Carolina, United States
| | - Korey D. Stevanovic
- National Institute of Environmental Health Sciences, National Institutes of Health, Neurobiology Laboratory, Division of Intramural Research, Durham, North Carolina, United States
| | - Ayland C. Letsinger
- National Institute of Environmental Health Sciences, National Institutes of Health, Neurobiology Laboratory, Division of Intramural Research, Durham, North Carolina, United States
| | - Sandra McBride
- Social & Scientific Systems, Inc., a DLH Holdings Corp. Company, Durham, North Carolina, United States
| | - Jesse D. Cushman
- National Institute of Environmental Health Sciences, National Institutes of Health, Neurobiology Laboratory, Division of Intramural Research, Durham, North Carolina, United States
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Bridge MF, Wilson LR, Panda S, Stevanovic KD, Letsinger AC, McBride S, Cushman JD. FiPhA: An Open-Source Platform for Fiber Photometry Analysis. bioRxiv 2023:2023.07.21.550098. [PMID: 37546723 PMCID: PMC10401953 DOI: 10.1101/2023.07.21.550098] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/08/2023]
Abstract
Significance Fiber photometry is a widely used technique in modern behavioral neuroscience, employing genetically encoded fluorescent sensors to monitor neural activity and neurotransmitter release in awake-behaving animals, However, analyzing photometry data can be both laborious and time-consuming. Aim We propose the FiPhA (Fiber Photometry Analysis) app, which is a general-purpose fiber photometry analysis application. The goal is to develop a pipeline suitable for a wide range of photometry approaches, including spectrally resolved, camera-based, and lock-in demodulation. Approach FiPhA was developed using the R Shiny framework and offers interactive visualization, quality control, and batch processing functionalities in a user-friendly interface. Results This application simplifies and streamlines the analysis process, thereby reducing labor and time requirements. It offers interactive visualizations, event-triggered average processing, powerful tools for filtering behavioral events and quality control features. Conclusions FiPhA is a valuable tool for behavioral neuroscientists working with discrete, event-based fiber photometry data. It addresses the challenges associated with analyzing and investigating such data, offering a robust and user-friendly solution without the complexity of having to hand-design custom analysis pipelines. This application thus helps standardize an approach to fiber photometry analysis.
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Affiliation(s)
- Matthew F. Bridge
- Social & Scientific Systems, Inc., a DLH Holdings Corp. Company, Durham, NC, United States
| | - Leslie R. Wilson
- Neurobiology Laboratory, Division of Intramural Research, National Institute of Environmental Health Sciences, National Institutes of Health, Durham, NC, United States
| | - Sambit Panda
- Neurobiology Laboratory, Division of Intramural Research, National Institute of Environmental Health Sciences, National Institutes of Health, Durham, NC, United States
| | - Korey D. Stevanovic
- Neurobiology Laboratory, Division of Intramural Research, National Institute of Environmental Health Sciences, National Institutes of Health, Durham, NC, United States
| | - Ayland C. Letsinger
- Neurobiology Laboratory, Division of Intramural Research, National Institute of Environmental Health Sciences, National Institutes of Health, Durham, NC, United States
| | - Sandra McBride
- Social & Scientific Systems, Inc., a DLH Holdings Corp. Company, Durham, NC, United States
| | - Jesse D. Cushman
- Neurobiology Laboratory, Division of Intramural Research, National Institute of Environmental Health Sciences, National Institutes of Health, Durham, NC, United States
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Shaw RD, Goldwag JL, Wilson LR, Ivatury SJ, Tsapakos MJ, Pauli EM, Wilson MZ. Retrorectus mesh reinforcement of ileostomy site fascial closure: stoma closure and reinforcement (SCAR) trial phase I/II results. Hernia 2022; 26:1645-1652. [PMID: 36167868 DOI: 10.1007/s10029-022-02681-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2022] [Accepted: 09/05/2022] [Indexed: 11/29/2022]
Abstract
PURPOSE Loop ileostomy (LI) is commonly employed during colorectal surgeries to reduce the consequences of anastomotic leak. Unfortunately, LI is associated with a 10-30% incisional hernia (IH) rate after closure. We hypothesized that prophylactic mesh reinforcement during LI takedown would safely prevent subsequent IH formation. METHODS This single-center, phase I/II prospective study evaluated adult patients undergoing LI closure after left-sided colorectal cancer procedures. After LI closure, the posterior rectus sheath was mobilized and reapproximated with absorbable suture. A reduced-weight, macroporous, polypropylene mesh (Softmesh, BD) was placed in the retrorectus position to allow 3 cm of overlap and secured with fibrin sealant. The anterior fascia was closed with slowly absorbable suture. CT images obtained for cancer surveillance were reviewed by a radiologist blinded to the study intervention to evaluate for evidence of hernia or surgical site occurrence (SSO). RESULTS Twenty patients were included with mean defect and mesh sizes of 11.2 cm2 and 64.2 cm2, respectively. Mean operative time for LI takedown and mesh augmented closure was 84 min with mesh implantation time being 16.4 min. Two patients were readmitted within 30 days for ileus, no patient required procedural intervention. Over a mean follow-up period of 20 ± 7 months, no SSO or hernias were observed clinically or on CT imaging. CONCLUSION In our small series, retromuscular mesh reinforcement of LI closure appears feasible, safe and effective. This mesh reinforcement approach should be further investigated to evaluate its long-term effectiveness.
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Affiliation(s)
- R D Shaw
- Department of Surgery, Dartmouth Hitchcock Medical Center, One Medical Center Drive, Lebanon, NH, 03756, USA
| | - J L Goldwag
- Department of Surgery, Dartmouth Hitchcock Medical Center, One Medical Center Drive, Lebanon, NH, 03756, USA
| | - L R Wilson
- Department of Surgery, Dartmouth Hitchcock Medical Center, One Medical Center Drive, Lebanon, NH, 03756, USA.,Geisel School of Medicine, Hanover, NH, USA
| | - S J Ivatury
- Dell Medical School, UT Health, Austin, TX, USA
| | - M J Tsapakos
- Geisel School of Medicine, Hanover, NH, USA.,Department of Radiology, Dartmouth Hitchcock Medical Center, Lebanon, NH, USA
| | - E M Pauli
- Department of Surgery, Penn State Hershey Medical Center, Hershey, PA, USA
| | - M Z Wilson
- Department of Surgery, Dartmouth Hitchcock Medical Center, One Medical Center Drive, Lebanon, NH, 03756, USA. .,Geisel School of Medicine, Hanover, NH, USA.
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Sciolino NR, Hsiang M, Mazzone CM, Wilson LR, Plummer NW, Amin J, Smith KG, McGee CA, Fry SA, Yang CX, Powell JM, Bruchas MR, Kravitz AV, Cushman JD, Krashes MJ, Cui G, Jensen P. Natural locus coeruleus dynamics during feeding. Sci Adv 2022; 8:eabn9134. [PMID: 35984878 PMCID: PMC9390985 DOI: 10.1126/sciadv.abn9134] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/31/2021] [Accepted: 07/07/2022] [Indexed: 06/15/2023]
Abstract
Recent data demonstrate that noradrenergic neurons of the locus coeruleus (LC-NE) are required for fear-induced suppression of feeding, but the role of endogenous LC-NE activity in natural, homeostatic feeding remains unclear. Here, we found that LC-NE activity was suppressed during food consumption, and the magnitude of this neural response was attenuated as mice consumed more pellets throughout the session, suggesting that LC responses to food are modulated by satiety state. Visual-evoked LC-NE activity was also attenuated in sated mice, suggesting that satiety state modulates LC-NE encoding of multiple behavioral states. We also found that food intake could be attenuated by brief or longer durations of LC-NE activation. Last, we found that activation of the LC to the lateral hypothalamus pathway suppresses feeding and enhances avoidance and anxiety-like responding. Our findings suggest that LC-NE neurons modulate feeding by integrating both external cues (e.g., anxiogenic environmental cues) and internal drives (e.g., satiety).
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Affiliation(s)
- Natale R. Sciolino
- Neurobiology Laboratory, National Institute of Environmental Health Sciences, National Institutes of Health, Department of Health and Human Services, Research Triangle Park, NC, USA
| | - Madeline Hsiang
- Neurobiology Laboratory, National Institute of Environmental Health Sciences, National Institutes of Health, Department of Health and Human Services, Research Triangle Park, NC, USA
| | - Christopher M. Mazzone
- Neurobiology Laboratory, National Institute of Environmental Health Sciences, National Institutes of Health, Department of Health and Human Services, Research Triangle Park, NC, USA
| | - Leslie R. Wilson
- Neurobiology Laboratory, National Institute of Environmental Health Sciences, National Institutes of Health, Department of Health and Human Services, Research Triangle Park, NC, USA
| | - Nicholas W. Plummer
- Neurobiology Laboratory, National Institute of Environmental Health Sciences, National Institutes of Health, Department of Health and Human Services, Research Triangle Park, NC, USA
| | - Jaisal Amin
- Neurobiology Laboratory, National Institute of Environmental Health Sciences, National Institutes of Health, Department of Health and Human Services, Research Triangle Park, NC, USA
| | - Kathleen G. Smith
- Neurobiology Laboratory, National Institute of Environmental Health Sciences, National Institutes of Health, Department of Health and Human Services, Research Triangle Park, NC, USA
| | - Christopher A. McGee
- Comparative Medicine, National Institute of Environmental Health Sciences, National Institutes of Health, Department of Health and Human Services, Research Triangle Park, NC, USA
| | - Sydney A. Fry
- Neurobiology Laboratory, National Institute of Environmental Health Sciences, National Institutes of Health, Department of Health and Human Services, Research Triangle Park, NC, USA
| | - Cindy X. Yang
- Neurobiology Laboratory, National Institute of Environmental Health Sciences, National Institutes of Health, Department of Health and Human Services, Research Triangle Park, NC, USA
| | - Jeanne M. Powell
- Neurobiology Laboratory, National Institute of Environmental Health Sciences, National Institutes of Health, Department of Health and Human Services, Research Triangle Park, NC, USA
| | - Michael R. Bruchas
- Departments of Anesthesiology and Pharmacology, Center for the Neurobiology of Addiction, Pain, and Emotion, University of Washington, Seattle, WA, USA
| | | | - Jesse D. Cushman
- Neurobiology Laboratory, National Institute of Environmental Health Sciences, National Institutes of Health, Department of Health and Human Services, Research Triangle Park, NC, USA
| | - Michael J. Krashes
- National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Department of Health and Human Services, Bethesda, MD, USA
| | - Guohong Cui
- Neurobiology Laboratory, National Institute of Environmental Health Sciences, National Institutes of Health, Department of Health and Human Services, Research Triangle Park, NC, USA
| | - Patricia Jensen
- Neurobiology Laboratory, National Institute of Environmental Health Sciences, National Institutes of Health, Department of Health and Human Services, Research Triangle Park, NC, USA
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Foster AP, Hallett D, Iorsh IV, Sheldon SJ, Godsland MR, Royall B, Clarke E, Shelykh IA, Fox AM, Skolnick MS, Itskevich IE, Wilson LR. Tunable Photon Statistics Exploiting the Fano Effect in a Waveguide. Phys Rev Lett 2019; 122:173603. [PMID: 31107076 DOI: 10.1103/physrevlett.122.173603] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/22/2018] [Indexed: 06/09/2023]
Abstract
A strong optical nonlinearity arises when coherent light is scattered by a semiconductor quantum dot coupled to a nanophotonic waveguide. We exploit the Fano effect in such a waveguide to control the phase of the quantum interference underpinning the nonlinearity, experimentally demonstrating a tunable quantum optical filter which converts a coherent input state into either a bunched or an antibunched nonclassical output state. We show theoretically that the generation of nonclassical light is predicated on the formation of a two-photon bound state due to the interaction of the input coherent state with the quantum dot. Our model demonstrates that the tunable photon statistics arise from the dependence of the sign of two-photon interference (either constructive or destructive) on the detuning of the input relative to the Fano resonance.
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Affiliation(s)
- A P Foster
- Department of Physics and Astronomy, University of Sheffield, Sheffield S3 7RH, United Kingdom
| | - D Hallett
- Department of Physics and Astronomy, University of Sheffield, Sheffield S3 7RH, United Kingdom
| | - I V Iorsh
- ITMO University, St. Petersburg 197101, Russia
| | - S J Sheldon
- Department of Physics and Astronomy, University of Sheffield, Sheffield S3 7RH, United Kingdom
| | - M R Godsland
- Department of Physics and Astronomy, University of Sheffield, Sheffield S3 7RH, United Kingdom
| | - B Royall
- Department of Physics and Astronomy, University of Sheffield, Sheffield S3 7RH, United Kingdom
| | - E Clarke
- EPSRC National Epitaxy Facility, University of Sheffield, Sheffield S1 3JD, United Kingdom
| | - I A Shelykh
- ITMO University, St. Petersburg 197101, Russia
- Science Institute, University of Iceland, Dunhagi 3, IS-107 Reykjavik, Iceland
| | - A M Fox
- Department of Physics and Astronomy, University of Sheffield, Sheffield S3 7RH, United Kingdom
| | - M S Skolnick
- Department of Physics and Astronomy, University of Sheffield, Sheffield S3 7RH, United Kingdom
- ITMO University, St. Petersburg 197101, Russia
| | - I E Itskevich
- Department of Engineering, University of Hull, Hull HU6 7RX, United Kingdom
| | - L R Wilson
- Department of Physics and Astronomy, University of Sheffield, Sheffield S3 7RH, United Kingdom
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Hurst DL, Price DM, Bentham C, Makhonin MN, Royall B, Clarke E, Kok P, Wilson LR, Skolnick MS, Fox AM. Nonreciprocal Transmission and Reflection of a Chirally Coupled Quantum Dot. Nano Lett 2018; 18:5475-5481. [PMID: 30080970 DOI: 10.1021/acs.nanolett.8b01869] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
We report strongly nonreciprocal behavior for quantum dot exciton spins coupled to nanophotonic waveguides under resonant laser excitation. A clear dependence of the transmission spectrum on the propagation direction is found for a chirally coupled quantum dot, with spin up and spin down exciton spins coupling to the left and right propagation directions, respectively. The reflection signal shows an opposite trend to the transmission, which a numerical model indicates is due to direction-selective saturation of the quantum dot. The chiral spin-photon interface we demonstrate breaks reciprocity of the system and opens the way to spin-based quantum optical components such as optical diodes and circulators in a chip-based solid-state environment.
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Affiliation(s)
- D L Hurst
- Department of Physics and Astronomy , University of Sheffield , Hounsfield Road , Sheffield , S3 7RH , United Kingdom
| | - D M Price
- Department of Physics and Astronomy , University of Sheffield , Hounsfield Road , Sheffield , S3 7RH , United Kingdom
| | - C Bentham
- Department of Physics and Astronomy , University of Sheffield , Hounsfield Road , Sheffield , S3 7RH , United Kingdom
| | - M N Makhonin
- Department of Physics and Astronomy , University of Sheffield , Hounsfield Road , Sheffield , S3 7RH , United Kingdom
| | - B Royall
- Department of Physics and Astronomy , University of Sheffield , Hounsfield Road , Sheffield , S3 7RH , United Kingdom
| | - E Clarke
- EPSRC National Epitaxy Facility, Department of Electronic and Electrical Engineering , University of Sheffield , Sheffield S1 3JD , United Kingdom
| | - P Kok
- Department of Physics and Astronomy , University of Sheffield , Hounsfield Road , Sheffield , S3 7RH , United Kingdom
| | - L R Wilson
- Department of Physics and Astronomy , University of Sheffield , Hounsfield Road , Sheffield , S3 7RH , United Kingdom
| | - M S Skolnick
- Department of Physics and Astronomy , University of Sheffield , Hounsfield Road , Sheffield , S3 7RH , United Kingdom
| | - A M Fox
- Department of Physics and Astronomy , University of Sheffield , Hounsfield Road , Sheffield , S3 7RH , United Kingdom
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Bishop ZK, Foster AP, Royall B, Bentham C, Clarke E, Skolnick MS, Wilson LR. Electro-mechanical control of an on-chip optical beam splitter containing an embedded quantum emitter. Opt Lett 2018; 43:2142-2145. [PMID: 29714766 DOI: 10.1364/ol.43.002142] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/07/2018] [Accepted: 03/29/2018] [Indexed: 05/28/2023]
Abstract
We demonstrate electro-mechanical control of an on-chip GaAs optical beam splitter containing a quantum dot single-photon source. The beam splitter consists of two nanobeam waveguides, which form a directional coupler (DC). The splitting ratio of the DC is controlled by varying the out-of-plane separation of the two waveguides using electromechanical actuation. We reversibly tune the beam splitter between an initial state, with emission into both output arms, and a final state with photons emitted into a single output arm. The device represents a compact and scalable tuning approach for use in III-V semiconductor integrated quantum optical circuits.
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10
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Wilson LR, Panda S, Schmidt AC, Sombers LA. Selective and Mechanically Robust Sensors for Electrochemical Measurements of Real-Time Hydrogen Peroxide Dynamics in Vivo. Anal Chem 2018; 90:888-895. [PMID: 29191006 PMCID: PMC5750107 DOI: 10.1021/acs.analchem.7b03770] [Citation(s) in RCA: 32] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Hydrogen peroxide (H2O2) is an endogenous molecule that plays several important roles in brain function: it is generated in cellular respiration, serves as a modulator of dopaminergic signaling, and its presence can indicate the upstream production of more aggressive reactive oxygen species (ROS). H2O2 has been implicated in several neurodegenerative diseases, including Parkinson's disease (PD), creating a critical need to identify mechanisms by which H2O2 modulates cellular processes in general and how it affects the dopaminergic nigrostriatal pathway, in particular. Furthermore, there is broad interest in selective electrochemical quantification of H2O2, because it is often enzymatically generated at biosensors as a reporter for the presence of nonelectroactive target molecules. H2O2 fluctuations can be monitored in real time using fast-scan cyclic voltammetry (FSCV) coupled with carbon-fiber microelectrodes. However, selective identification is a critical issue when working in the presence of other molecules that generate similar voltammograms, such as adenosine and histamine. We have addressed this problem by fabricating a robust, H2O2-selective electrode. 1,3-Phenylenediamine (mPD) was electrodeposited on a carbon-fiber microelectrode to create a size-exclusion membrane, rendering the electrode sensitive to H2O2 fluctuations and pH shifts but not to other commonly studied neurochemicals. The electrodes are described and characterized herein. The data demonstrate that this technology can be used to ensure the selective detection of H2O2, enabling confident characterization of the role this molecule plays in normal physiological function as well as in the progression of PD and other neuropathies involving oxidative stress.
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Affiliation(s)
- Leslie R. Wilson
- Department of Chemistry, North Carolina State University, Raleigh, North Carolina 27695, United States
| | - Sambit Panda
- Department of Chemistry, North Carolina State University, Raleigh, North Carolina 27695, United States
| | - Andreas C. Schmidt
- Department of Chemistry, North Carolina State University, Raleigh, North Carolina 27695, United States
| | - Leslie A. Sombers
- Department of Chemistry, North Carolina State University, Raleigh, North Carolina 27695, United States
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11
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Foster AP, Maguire JK, Bradley JP, Lyons TP, Krysa AB, Fox AM, Skolnick MS, Wilson LR. Tuning Nonlinear Mechanical Mode Coupling in GaAs Nanowires Using Cross-Section Morphology Control. Nano Lett 2016; 16:7414-7420. [PMID: 27960503 DOI: 10.1021/acs.nanolett.6b02994] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
We investigate the nonlinear mechanical properties of GaAs nanowires with anisotropic cross-section. Fundamental and second order flexural modes are studied using laser interferometry with good agreement found between experiment and theory describing the nonlinear response under mechanical excitation. In particular, we demonstrate that the sign of the nonlinear coupling between orthogonal modes is dependent on the cross-section aspect ratio. The findings are of interest for applications such as amplitude to frequency conversion and vectorial force sensing.
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Affiliation(s)
- A P Foster
- Department of Physics and Astronomy, University of Sheffield , Sheffield S3 7RH, United Kingdom
| | - J K Maguire
- Department of Physics and Astronomy, University of Sheffield , Sheffield S3 7RH, United Kingdom
| | - J P Bradley
- Department of Physics and Astronomy, University of Sheffield , Sheffield S3 7RH, United Kingdom
| | - T P Lyons
- Department of Physics and Astronomy, University of Sheffield , Sheffield S3 7RH, United Kingdom
| | - A B Krysa
- Department of Electronics and Electrical Engineering, University of Sheffield , Sheffield S1 3JD, United Kingdom
| | - A M Fox
- Department of Physics and Astronomy, University of Sheffield , Sheffield S3 7RH, United Kingdom
| | - M S Skolnick
- Department of Physics and Astronomy, University of Sheffield , Sheffield S3 7RH, United Kingdom
| | - L R Wilson
- Department of Physics and Astronomy, University of Sheffield , Sheffield S3 7RH, United Kingdom
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12
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Qi L, Thomas E, White SH, Smith SK, Lee CA, Wilson LR, Sombers LA. Unmasking the Effects of L-DOPA on Rapid Dopamine Signaling with an Improved Approach for Nafion Coating Carbon-Fiber Microelectrodes. Anal Chem 2016; 88:8129-36. [PMID: 27441547 DOI: 10.1021/acs.analchem.6b01871] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
L-DOPA has been the gold standard for symptomatic treatment of Parkinson's disease. However, its efficacy wanes over time as motor complications develop. Very little is known about how L-DOPA therapy affects the dynamics of fluctuating dopamine concentrations in the striatum on a rapid time scale (seconds). Electrochemical studies investigating the effects of L-DOPA treatment on electrically evoked dopamine release have reported conflicting results with significant variability. We hypothesize that the uncertainty in the electrochemical data is largely due to electrode fouling caused by polymerization of L-DOPA and endogenous catecholamines on the electrode surface. Thus, we have systematically optimized the procedure for fabricating cylindrical, Nafion-coated, carbon-fiber microelectrodes. This has enabled rapid and reliable detection of L-DOPA's effects on striatal dopamine signaling in intact rat brain using fast-scan cyclic voltammetry. An acute dose of 5 mg/kg L-DOPA had no significant effect on dopamine dynamics, demonstrating the highly efficient regulatory mechanisms at work in the intact brain. In contrast, administration of 200 mg/kg L-DOPA significantly increased the amplitude of evoked dopamine release by ∼200%. Overall, this work describes a reliable tool that allows a better measure of L-DOPA augmented dopamine release in vivo, measured using fast-scan cyclic voltammetry. It provides a methodology that improves the stability and performance of the carbon-fiber microelectrode when studying the molecular mechanisms underlying L-DOPA therapy and also promises to benefit a wide variety of studies because Nafion is so commonly used in electroanalytical chemistry.
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Affiliation(s)
- Lingjiao Qi
- Department of Chemistry, North Carolina State University , Raleigh, North Carolina 27695, United States
| | - Elina Thomas
- Department of Chemistry, North Carolina State University , Raleigh, North Carolina 27695, United States
| | - Stephanie H White
- Department of Chemistry, North Carolina State University , Raleigh, North Carolina 27695, United States
| | - Samantha K Smith
- Department of Chemistry, North Carolina State University , Raleigh, North Carolina 27695, United States
| | - Christie A Lee
- Department of Chemistry, North Carolina State University , Raleigh, North Carolina 27695, United States
| | - Leslie R Wilson
- Department of Chemistry, North Carolina State University , Raleigh, North Carolina 27695, United States
| | - Leslie A Sombers
- Department of Chemistry, North Carolina State University , Raleigh, North Carolina 27695, United States
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13
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Makhonin MN, Foster AP, Krysa AB, Fry PW, Davies DG, Grange T, Walther T, Skolnick MS, Wilson LR. Homogeneous array of nanowire-embedded quantum light emitters. Nano Lett 2013; 13:861-865. [PMID: 23398085 DOI: 10.1021/nl303075q] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
The potential for scale-up coupled with minimized system size is likely to be a major determining factor in the realization of applicable quantum information systems. Nanofabrication technology utilizing the III-V semiconductor system provides a path to scalable quantum bit (qubit) integration and a materials platform with combined electronic/photonic functionality. Here, we address the key requirement of qubit-site and emission energy control for scale-up by demonstrating uniform arrays of III-V nanowires, where each nanowire contains a single quantum dot. Optical studies of single nanowire quantum dots reveal narrow linewidth exciton and biexciton emission and clear state-filling at higher powers. Individual nanowire quantum dots are shown to emit nonclassically with clear evidence of photon antibunching. A model is developed to explain unexpectedly large excited state separations as revealed by photoluminescence emission spectra. From measurements of more than 40 nanowire quantum dots, we find emission energies with an ensemble broadening of 15 meV. The combination of deterministic site control and the narrow distribution in ensemble emission energy results in a system readily capable of scaling for multiqubit quantum information applications.
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Affiliation(s)
- M N Makhonin
- Department of Physics and Astronomy, University of Sheffield, Sheffield S3 7RH, United Kingdom.
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14
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Couto ODD, Sercombe D, Puebla J, Otubo L, Luxmoore IJ, Sich M, Elliott TJ, Chekhovich EA, Wilson LR, Skolnick MS, Liu HY, Tartakovskii AI. Effect of a GaAsP shell on the optical properties of self-catalyzed GaAs nanowires grown on silicon. Nano Lett 2012; 12:5269-5274. [PMID: 22989367 DOI: 10.1021/nl302490y] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
We realize the growth of self-catalyzed core-shell GaAs/GaAsP nanowires (NWs) on Si substrates using molecular-beam epitaxy. Transmission electron microscopy of single GaAs/GaAsP NWs demonstrates their high crystal quality and shows domination of the GaAs zinc-blende phase. Using continuous-wave and time-resolved photoluminescence (PL), we make a detailed comparison with uncapped GaAs NWs to emphasize the effect of the GaAsP capping in suppressing the nonradiative surface states. Significant PL enhancement in the core-shell structures exceeding 3 orders of magnitude at 10 K is observed; in uncapped NWs PL is quenched at 60 K, whereas single core-shell GaAs/GaAsP structures exhibit bright emission even at room temperature. From analysis of the PL temperature dependence in both types of NW we are able to determine the main carrier escape mechanisms leading to the PL quench.
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Affiliation(s)
- O D D Couto
- Department of Physics and Astronomy, University of Sheffield, Sheffield S3 7RH, United Kingdom.
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15
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Zibik EA, Grange T, Carpenter BA, Porter NE, Ferreira R, Bastard G, Stehr D, Winnerl S, Helm M, Liu HY, Skolnick MS, Wilson LR. Long lifetimes of quantum-dot intersublevel transitions in the terahertz range. Nat Mater 2009; 8:803-807. [PMID: 19684587 DOI: 10.1038/nmat2511] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/15/2009] [Accepted: 07/14/2009] [Indexed: 05/28/2023]
Abstract
Carrier relaxation is a key issue in determining the efficiency of semiconductor optoelectronic device operation. Devices incorporating semiconductor quantum dots have the potential to overcome many of the limitations of quantum-well-based devices because of the predicted long quantum-dot excited-state lifetimes. For example, the population inversion required for terahertz laser operation in quantum-well-based devices (quantum-cascade lasers) is fundamentally limited by efficient scattering between the laser levels, which form a continuum in the plane of the quantum well. In this context, semiconductor quantum dots are a highly attractive alternative for terahertz devices, because of their intrinsic discrete energy levels. Here, we present the first measurements, and theoretical description, of the intersublevel carrier relaxation in quantum dots for transition energies in the few terahertz range. Long intradot relaxation times (1.5 ns) are found for level separations of 14 meV (3.4 THz), decreasing very strongly to approximately 2 ps at 30 meV (7 THz), in very good agreement with our microscopic theory of the carrier relaxation process. Our studies pave the way for quantum-dot terahertz device development, providing the fundamental knowledge of carrier relaxation times required for optimum device design.
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Affiliation(s)
- E A Zibik
- [1] Department of Physics and Astronomy, University of Sheffield, Sheffield S3 7RH, UK [2] Present addresses: Oclaro (Switzerland) AG, Binzstrasse 17, CH-8045 Zürich, Switzerland (E.A.Z.); Walter Schottky Institut, Technische Universität München, 85748 Garching, Germany (T.G.); Department of Electronic & Electrical Engineering, University College London, London WC1E 7JE, UK (H.Y.L.) [3] These authors contributed equally to this work
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16
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Wilson LR, Richards BS. Measurement method for photoluminescent quantum yields of fluorescent organic dyes in polymethyl methacrylate for luminescent solar concentrators. Appl Opt 2009; 48:212-220. [PMID: 19137031 DOI: 10.1364/ao.48.000212] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
A method for measuring the photoluminescent quantum yields (PLQY) of luminescent organic dyes is presented. The self-absorption probability calculated at different dye concentrations is used to determine the absolute quantum yield from the observed values. The results for a range of commercially available dyes show high quantum yields, even at high concentrations, and an absence of quenching. The PLQY of several dye mixtures are also presented. The results indicate an absence of any reduction of PLQY in a dye mixture as compared with the individual PLQY of the dyes.
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Affiliation(s)
- L R Wilson
- School of Engineering and Physical Sciences, Heriot-Watt University, Edinburgh, EH14 4AS, UK.
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17
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Moreau V, Bahriz M, Colombelli R, Perahia R, Painter O, Wilson LR, Krysa AB. Demonstration of air-guided quantum cascade lasers without top claddings. Opt Express 2007; 15:14861-14869. [PMID: 19550765 DOI: 10.1364/oe.15.014861] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
We report on quantum cascade lasers employing waveguides based on a predominant air confinement mechanism in which the active region is located immediately at the device top surface. The lasers employ ridge-waveguide resonators with narrow lateral electrical contacts only, with a large, central top region not covered by metallization layers. Devices based on this principle have been reported in the past; however, they employed a thick, doped top-cladding layer in order to allow for uniform current injection. We find that the in-plane conductivity of the active region - when the material used is of high quality - provides adequate electrical injection. As a consequence, the devices demonstrated in this work are thinner, and most importantly they can simultaneously support air-guided and surface-plasmon waveguide modes. When the lateral contacts are narrow, the optical mode is mostly located below the air-semiconductor interface. The mode is predominantly air-guided and it leaks from the top surface into the surrounding environment, suggesting that these lasers could be employed for surface-sensing applications. These laser modes are found to operate up to room temperature under pulsed injection, with an emission spectrum centered around l (1/4) 7:66 mum.
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18
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Cai Y, Ludeman SM, Wilson LR, Chung AB, Dolan ME. Effect of O6-benzylguanine on nitrogen mustard-induced toxicity, apoptosis, and mutagenicity in Chinese hamster ovary cells. Mol Cancer Ther 2001; 1:21-8. [PMID: 12467235] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/27/2023]
Abstract
O6-Benzylguanine (BG) inactivates O6-alkylguanine-DNA alkyltransferase (AGT), resulting in an increase in the sensitivity of cells to the toxic effects of O6-alkylating agents. BG significantly enhances the cytotoxicity and decreases the mutagenicity of nitrogen mustards [i.e., phosphoramide mustard (PM), melphalan, and chlorambucil], a group of alkylating agents not known to produce O6-adducts in DNA. The enhancement is observed in cells irrespective of AGT activity. Exposure of Chinese hamster ovary cells to 100 microM BG results in enhancement in the cytotoxicity of PM (300 microM), chlorambucil (40 microM), and melphalan (10 microM) by 9-, 7-, and 18-fold, respectively. In contrast, mutation frequency after treatment with 300 microM PM is decreased from 259 mutants/10(6) cells to 22 mutants/10(6) cells when cells are pretreated with BG. The enhancement of toxicity of these bis-alkylating agents appears to involve cross-link formation, because neither cytotoxicity nor mutagenicity of a monoalkylating PM analogue is significantly altered when combined with BG. Enhanced cytotoxicity and decreased mutagenicity is concomitant with a dramatic increase in the number of cells undergoing apoptosis when BG is combined with PM, melphalan, or chlorambucil at 72-94 h after treatment. Cell cycle analysis demonstrates that BG alone or combined with nitrogen mustards arrests cells in G1 phase of the cell cycle. At 16 h after treatment, 11 and 57% of cells treated with PM alone or with BG plus PM are in G1 phase, respectively. Our data suggest that treatment with BG causes G1 arrest and drives noncycling cells treated with nitrogen mustards into apoptosis, thus protecting against mutagenic DNA damage introduced by nitrogen mustards.
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Affiliation(s)
- Y Cai
- Section of Hematology-Oncology, Department of Medicine, Committee on Clinical Pharmacology, Cancer Research Center, University of Chicago, Chicago, Illinois 60637, USA
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19
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Lince DP, Wilson LR, Carlson GA, Bucciferro A. Effects of gasoline formulation on methyl tert-butyl ether (MTBE) contamination in private wells near gasoline stations. Environ Sci Technol 2001; 35:1050-1053. [PMID: 11347913 DOI: 10.1021/es0010305] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
UNLABELLED The extent of methyl tert-butyl ether (MTBE) contamination in private wells near gasoline stations, which lack the relative protection afforded many public waters supplies through zoning and routine testing, was examined. Samples were collected from 74 private wells near 21 randomly selected gasoline stations and from 21 control wells, one per facility. Two hypotheses are tested: (1) private wells downgradient and close (<0.5 mi) to gasoline stations (case wells) are more likely to have MTBE contamination than private wells upgradient and distant (>1.5 mi) (control wells); and (2) private wells near gasoline stations selling oxygenated gasoline are more likely to have MTBE contamination than private wells near gasoline stations selling conventional gasoline. Data on the concurrence of MTBE and other gasoline constituents are presented. RESULTS MTBE concentrations ranged from <1.0 micro/L (microg/L) to 61 microg/L, with a mean of 12.0 microg/L. MTBE contamination of > or =1 microg/L was detected more frequently in case wells (28%) than control wells (5%) (p = 0.015). MTBE contamination of > or =1 microg/L occurred more frequently in private wells near facilities selling oxygenated gasoline (38%) than private wells near facilities selling conventional gasoline (20%) (p = 0.11). Statistical significance may have been achieved with a larger sample size. Benzene (0.5 microg/L) was found concurrently with MTBE in only one well, which also had the highest concentration of MTBE.
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Affiliation(s)
- D P Lince
- New York State Department of Health, Bureau of Environmental Exposure Investigation, Troy 12180, USA.
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20
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Ewesuedo RB, Wilson LR, Friedman HS, Moschel RC, Dolan ME. Inactivation of O6-alkylguanine-DNA alkyltransferase by 8-substituted O6-benzylguanine analogs in mice. Cancer Chemother Pharmacol 2001; 47:63-9. [PMID: 11221964 DOI: 10.1007/s002800000202] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
PURPOSE The purpose of this study was to determine the usefulness of various 8-substituted O6-benzylguanine (BG) analogs as modulators of the DNA repair protein. O6-alkylguanine-DNA alkyltransferase (AGT). More specifically, the degree of inactivation of AGT in mouse brain, liver, kidney and tumor by O6-benzyl-8-oxoguanine (8-oxoBG), 8-aza-O6-benzylguanine (8-azaBG), O6-benzyl-8-bromoguanine (8-bromoBG) and O6-benzyl-8-trifluoromethylguanine (8-tfmBG) was compared to inactivation by BG, a modulator in phase II clinical trials. BG is converted rapidly to 8-oxoBG in rodents, monkeys and humans. It was reasoned that 8-substituted analogs of BG would exhibit different pharmacological properties compared to BG which could influence tissue bioavailability and, thus, the extent of AGT inactivation in vivo. We compared the tissue distribution of these agents and AGT activity following administration of the 8-substituted analogs. MATERIALS AND METHODS At various time points up to 24 h after i.p. administration of the BG analogs, tissues (i.e. brain, liver, kidney), A549 lung tumor xenografts (i.p.) or D456 brain tumor xenografts (i.c.) were harvested from athymic nude mice for AGT analysis. AGT activity was quantified in tissue extracts using a biochemical assay with [3H]methylated DNA as a substrate. In addition, concentrations of BG and 8-oxoBG were determined by HPLC with fluorescence detection in mouse tissues following administration of drug. RESULTS Each of the 8-substituted analogs of BG demonstrated variable AGT inactivation capabilities that were comparable to or better than those of BG especially in kidney and brain tissues. There was a more pronounced depletion of AGT inactivation in brain and D456 brain tumor xenografts following administration of BG compared to 8-oxoBG that could be explained by a much greater concentration of AGT-inactivating drug (BG plus the metabolite 8-oxoBG for mice treated with BG versus 8-oxoBG for mice treated with 8-oxoBG) present in these tissues. The AUCs for brain, kidney and liver were 3.2, 6.9 and 1 1.8 times greater for BG than for 8-oxoBG. CONCLUSIONS 8-substituted analogs of BG possess unique AGT-inactivation profiles in vivo that are different from that of BG. The AGT-inhibitory activities of BG and its major metabolite, 8-oxoBG, are related to tissue disposition of both drugs.
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Affiliation(s)
- R B Ewesuedo
- Department of Pediatrics, University of Chicago, IL 60637, USA
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21
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Schilsky RL, Dolan ME, Bertucci D, Ewesuedo RB, Vogelzang NJ, Mani S, Wilson LR, Ratain MJ. Phase I clinical and pharmacological study of O6-benzylguanine followed by carmustine in patients with advanced cancer. Clin Cancer Res 2000; 6:3025-31. [PMID: 10955780] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/17/2023]
Abstract
O6-benzylguanine (BG) is a potent inactivator of the DNA repair protein O6-alkylguanine-DNA alkyltransferase (AGT) that enhances sensitivity to nitrosoureas in tumor cell lines and tumor-bearing animals. The major objectives of this study were to define the optimal modulatory dose and associated toxicities of benzylguanine administered alone and in combination with carmustine; to define the maximally tolerated dose and associated toxicities of carmustine administered with benzylguanine and to describe the pharmacokinetics of BG in humans and its effects on AGT depletion and recovery in peripheral blood mononuclear cells. Patients with histologically confirmed advanced solid tumors or lymphoma that had failed to respond to standard therapy or for which no standard therapy was available were eligible to participate in this study. Patients initially received BG as a 1-h i.v. infusion without carmustine. After a 14-day washout (ie., without therapy) period, patients received BG as a 1-h i.v. infusion followed, 1 h later, by a 15-min i.v. infusion of carmustine. Cycles of chemotherapy were repeated every 6 weeks. Cohorts of patients received BG doses ranging from 10 to 120 mg/m2 and carmustine doses ranging from 13 to 50 mg/m2. Plasma and urine samples were collected and analyzed for BG, and O6-benzyl-8-oxoguanine concentrations and AGT activity was determined in peripheral blood mononuclear cells. There was no toxicity attributable to BG alone at any dose tested. Bone marrow suppression was the primary and dose-limiting toxicity of BG combined with carmustine and was cumulative in some patients. The neutrophil nadir occurred at a median of day 27, with complete recovery in most patients by day 43. Nonhematological toxicity included fatigue, anorexia, increased bilirubin, and transaminase elevation. Recommended doses for Phase II testing are 120 mg/m2 BG given with carmustine at 40 mg/m2. BG rapidly disappeared from plasma and was converted to a major metabolite, O6-benzyl-8-oxoguanine, which has a 2.4-fold higher maximal concentration and 20-fold higher area under the concentration versus time curve than BG. AGT activity in peripheral blood mononuclear cells was rapidly and completely suppressed at all of the BG doses. The rate of AGT regeneration was more rapid for patients treated with the lowest dose of BG but was similar for BG doses ranging from 20-120 mg/m2. In conclusion, coadministration of BG and carmustine is feasible in cancer patients, but the maximal dose of carmustine that can be safely administered with BG is approximately one-third of the standard clinical dose. Bone marrow suppression, which may be cumulative, is the dose-limiting toxicity of the combination. Prolonged AGT suppression is likely attributable primarily to the effect of O6-benzyl-8-oxoguanine.
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Affiliation(s)
- R L Schilsky
- Department of Medicine, Cancer Research Center and Committee on Clinical Pharmacology, University of Chicago, Illinois 60637, USA.
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22
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Fry PW, Itskevich IE, Mowbray DJ, Skolnick MS, Finley JJ, Barker JA, O'Reilly EP, Wilson LR, Larkin IA, Maksym PA, Hopkinson M, Al-Khafaji M, David JP, Cullis AG, Hill G, Clark JC. Inverted electron-hole alignment in InAs-GaAs self-assembled quantum dots. Phys Rev Lett 2000; 84:733-736. [PMID: 11017359 DOI: 10.1103/physrevlett.84.733] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/05/1999] [Indexed: 05/23/2023]
Abstract
New information on the electron-hole wave functions in InAs-GaAs self-assembled quantum dots is deduced from Stark effect spectroscopy. Most unexpectedly it is shown that the hole is localized towards the top of the dot, above the electron, an alignment that is inverted relative to the predictions of all recent calculations. We are able to obtain new information on the structure and composition of buried quantum dots from modeling of the data. We also demonstrate that the excited state transitions arise from lateral quantization and that tuning through the inhomogeneous distribution of dot energies can be achieved by variation of electric field.
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Affiliation(s)
- P W Fry
- Department of Physics and Astronomy, University of Sheffield, Sheffield S3 7RH, United Kingdom
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23
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Abstract
Weakness, loss of dexterity and exaggerated reflex responses to proprioceptive and cutaneous stimuli are typical features of hemiparetic stroke. Since the extent to which altered fusimotor drive contributes to these deficits has not been established, this study was designed to assess fusimotor function in stroke patients by comparing three aspects of muscle spindle afferent behaviour (background discharge rate, responses to reflex inputs and responses to voluntary contractions) in 11 subjects affected by recent cerebrovascular lesions, with those in 18 healthy volunteers. The mean background discharge rates of muscle spindle afferents in the radial nerve when subjects attempted to relax the recorded limb completely were 6.6 +/- 5.3 Hz (n = 26) in patients and 6.4 +/- 6.1 Hz (n = 76) in control subjects. The variability of discharge rate of active afferents was also similar (0.12 +/- 0.07 and 0.09 +/- 0. 10, respectively). Reflex activation of fusimotor neurons was assessed using trains of electrical stimuli to the superficial radial nerve or to the palm of the hand, and using natural skin stimuli. Neither type of cutaneous stimulation affected muscle spindle afferent discharge in the absence of an EMG response. During deliberate voluntary contractions muscle spindle discharge rates were enhanced similarly in both the control and patient groups, indicating that volitional drives could access fusimotor neurons in the patients. Qualitatively, spindle behaviour was similar in patients and control subjects. These findings suggest that fusimotor function is not disturbed any more or less than skeletomotor function in hemiparetic patients and it is concluded that fusimotor dysfunction probably contributes little to their deficit.
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Affiliation(s)
- L R Wilson
- Department of Clinical Neurophysiology, The Prince Henry and Prince of Wales Hospitals and Prince of Wales Medical Research Institute, University of New South Wales, Sydney, Australia
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Abstract
To study fusimotor function in stroke patients, we compared the amplitude of stretch reflexes elicited in flexor carpi radialis (FCR) after contraction of FCR with the wrist held flexed ('hold-short') or extended ('hold-long'). Seven subjects with impaired hand function and spasticity due to stroke, and seven healthy subjects were investigated. Surface electrodes recorded electromyographic activity of wrist flexors and extensors while subjects performed isometric wrist flexions with the wrist alternately in 15 degrees of flexion or extension. After contractions the wrist was moved passively to the mid-position, and stretch reflexes were elicited via controlled mechanical taps delivered over the FCR tendon. For both groups, the amplitude of the stretch reflex was greater after 'hold-short' than 'hold-long' contractions. This finding is consistent with the 'after-effects' of intrafusal fibre activation, and suggests that fusimotor neurones are activated during voluntary contractions of the paretic limb, just as in the limb of a healthy subject.
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Affiliation(s)
- L R Wilson
- Prince of Wales Medical Research Institute, Prince of Wales Hospital, University of New South Wales, Sydney, Australia
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25
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Abstract
1. Using microneurography with a conventional monopolar electrode, the action potentials of ten myelinated axons in the peripheral nerves of human subjects were followed while they developed conduction block. 2. The action potentials had initially (n = 6) or developed (n = 4) a positive double-peaked morphology. The time interval between the two positive peaks represents the conduction time across the impaled internode. 3. When the interpeak interval was < 500 micros, conduction across the site of impalement was secure, even if the conduction time was markedly prolonged. When the interval was > 600 microseconds, intermittent conduction failure occurred. For all units the longest interpeak interval recorded just prior to complete conduction failure was, on average, 1.12 ms (range, 0.8-1.4 ms). 4. For five axons, there was evidence that natural activity triggered the conduction failure. 5. Impalement of the nerve fibre by the microelectrode impairs the ability of the axon to conduct impulses across the site of injury, but impulse transmission can be secure even when the conduction time across individual internodes is prolonged to 500 microseconds. These findings are therefore relevant to the conduction deficits that occur in focal injuries of human axons.
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Affiliation(s)
- J T Inglis
- Department of Clinical Neurophysiology, Prince of Wales Hospital and Prince of Wales Medical Research Institute, University of New South Wales, Sydney, Australia
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Lince DP, Wilson LR, Carlson GA. Methyl tert-butyl ether (MTBE) contamination in private wells near gasoline stations in upstate New York. Bull Environ Contam Toxicol 1998; 61:484-488. [PMID: 9811953 DOI: 10.1007/s001289900788] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Affiliation(s)
- D P Lince
- New York State Department of Health, Bureau of Environmental Exposure Investigation, II University Place, Room 205, Albany, NY 12203, USA
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27
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Macefield VG, Williamson PM, Wilson LR, Kelly JJ, Gandevia SC, Whitworth JA. Muscle sympathetic vasoconstrictor activity in hydrocortisone-induced hypertension in humans. Blood Press 1998; 7:215-22. [PMID: 9858113 DOI: 10.1080/080370598437240] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/16/2022]
Abstract
AIM This study was undertaken to test the hypothesis that increased sympathetic vasomotor drive is responsible for cortisol-induced hypertension. METHODS Ten healthy male subjects on a fixed sodium diet (150 mmol/day) were randomized to five days of treatment with cortisol (200 mg/day) or placebo in a double-blind crossover study. On day 5 of each treatment, multi-unit muscle sympathetic activity was recorded from the common peroneal nerve. Resting muscle sympathetic activity (MSA) was measured in the recumbent position and stimulated MSA was measured in the final 20 sec of end-inspiratory capacity apnoea and end-expiratory apnoea and in the second minute of a cold pressor stimulus. A subgroup of six subjects also underwent identical MSA measurements following 5 days treatment with dexamethasone (3 mg/day). MAJOR FINDINGS Cortisol, but not placebo, significantly increased systolic (115+/-2 vs 129+/-3 mmHg precortisol vs cortisol day 5, p < 0.001) and diastolic blood pressure (53+/-3 vs 61+/-3, p < 0.05). Resting MSA was significantly reduced by cortisol (23.9+/-2.3 to 5.0+/-2.0 bursts/min, placebo vs cortisol, p < 0.01). Cortisol significantly attenuated the increase in MSA observed at end-inspiratory apnoea (56.3+/-3.9 vs 35.4+/-6.6, p < 0.05) and end-expiratory apnoea (50.5+/-3.5 vs 26.3+/-6.2 bursts/min, n = 8, p < 0.05), and during the cold pressor response (55.0+/-12.7 vs 21.4+/-7.6, n = 5, p < 0.05). Dexamethasone significantly increased systolic blood pressure and suppressed resting and stimulated MSA. No changes in body weight, haematocrit or angiotensin II concentrations occurred during dexamethasone treatment. CONCLUSION MSA is significantly suppressed by cortisol treatment. As suppression of MSA is also observed during treatment with the pure glucocorticoid dexamethasone, suppressed MSA cannot be attributed to increased plasma volume or to changes in angiotensin II concentration. We conclude that cortisol-induced hypertension is not due to increased muscle sympathetic vasomotor drive.
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Affiliation(s)
- V G Macefield
- Prince of Wales Medical Research Institute, Randwick, Australia
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Wilson LR, Good RT, Panaccio M, Wijffels GL, Sandeman RM, Spithill TW. Fasciola hepatica: characterization and cloning of the major cathepsin B protease secreted by newly excysted juvenile liver fluke. Exp Parasitol 1998; 88:85-94. [PMID: 9538862 DOI: 10.1006/expr.1998.4234] [Citation(s) in RCA: 79] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Proteolytic activity present in the excreted/secreted (ES) material of newly excysted juvenile (NEJ) Fasciola hepatica was biochemically analyzed. By gelatin substrate SDS-PAGE, only one region of activity was observed in the NEJ ES material at a molecular mass of 29 kDa. Both the secreted cathepsin L from adult fluke and the 29-kDa proteolytic activity of NEJ ES show a common pH optimum of 7.5, a cysteine protease inhibition profile, and preference for the N-benzyloxycarbonyl (Z)-Phe-Arg-NHMec fluorogenic substrate over Z-Arg-Arg-NHMec and Z-Arg-NHMec. In vitro analysis revealed that the NEJ protease activity digested sheep immunoglobulin heavy chain and bovine serum albumin but not bovine hemoglobin. Amino-terminal protein sequence analysis of the 29-kDa NEJ protease band revealed two sequences with homology to the cathepsin B family of proteases. Using degenerate oligonucleotides designed from the N-terminal sequence, reverse transcriptase polymerase chain reaction with NEJ RNA amplified a cDNA sequence encoding the first 236 amino acids of mature cathepsin B. Using this cDNA fragment an overlapping cDNA was isolated from a LambadaZAP cDNA library constructed with poly(A)+ RNA from immature 5-week-old liver fluke. Together with the N-terminal sequence, these cDNAs predict a mature cathepsin B sequence of 254 amino acids which shows 48-51% sequence identity to mammalian and Schistosoma mansoni cathepsin B. We conclude that, in contrast to the major proteases released by adult fluke, the major secreted protease of NEJ of F. hepatica is of the cathepsin B class.
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Affiliation(s)
- L R Wilson
- Victorian Institute of Animal Science, Attwood, Australia.
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Gandevia SC, Wilson LR, Inglis JT, Burke D. Mental rehearsal of motor tasks recruits alpha-motoneurones but fails to recruit human fusimotor neurones selectively. J Physiol 1997; 505 ( Pt 1):259-66. [PMID: 9409487 PMCID: PMC1160109 DOI: 10.1111/j.1469-7793.1997.259bc.x] [Citation(s) in RCA: 86] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
1. As mental rehearsal of movements activates multiple cortical areas associated with movement, we assessed whether this increases fusimotor drive and whether enhanced muscle spindle activity could contribute to the improvement in skill that accompanies mental rehearsal. 2. Microneurographic recordings were made from six muscle spindle afferents innervating extensor muscles in the forearm or tibialis anterior, which were selected because their discharge increased during very weak contractions. Activity was monitored while subjects imagined performing a range of activities including simple and complex movements involving the relevant muscles. 3. No activation of muscle spindle afferents occurred during imagined motor tasks without EMG. When the relevant muscles contracted during mental rehearsal, spindle discharge increased, much as in weak contractions. 4. Mental rehearsal increased background EMG in the involved muscles and also increased H reflex amplitude independently of EMG changes. 5. Although there was no evidence for selective fusimotor activation during imagined movement, skeletomotor activity and reflex excitability increased. Similar changes occur with preparation for movement following a cue. It is likely that mental rehearsal usually involves unintentional performance of the planned motor task.
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Affiliation(s)
- S C Gandevia
- Department of Clinical Neurophysiology, Prince Henry and Prince of Wales Hospitals, Sydney, NSW, Australia.
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Abstract
1. There are discrepancies in the literature about the reproducibility of forces at which human muscle spindle afferents accelerate their discharge during isometric voluntary contractions. The aim of this study was to determine for single muscle spindle afferents both the reproducibility of the 'acceleration threshold' and the factors contributing to variability of 'acceleration threshold'. 2. Microneurographic recordings were made from muscle spindle afferents innervating tibialis anterior while subjects performed isometric ankle dorsiflexions. Subjects matched the force of their contractions with a visually displayed 'ramp-and-hold' template. Template parameters were determined by the force of maximal isometric ankle dorsiflexion (MVC), and expressed as per cent MVC. The required 'ramp' rate and 'hold' force was adjusted between trials (range, 0.5-5% MVCs-1 and 0.5-20% MVC, respectively). The duration of the hold phase was 4 s and, following each contraction, stretch was applied transversely to the tendon to minimize the influence of any 'after-effects' on spindle afferent responses in subsequent contractions. 3. For each contraction, the force at which the rate of muscle spindle discharge increased was defined as the 'acceleration threshold'. Of twenty-six muscle spindle afferents innervating tibialis anterior, all but two increased their discharge in the test contractions. In 90% of contractions, acceleration thresholds were less than 3.2% MVC (range, 0.01-11.9% MVC). 4. Individual muscle spindle afferents increased their discharge at similar but not identical forces in repeated contractions. There was a positive correlation between the rate of contraction and the acceleration threshold (P < 0.001), but the strength of the target contraction had no effect on the threshold, and there was no trend for thresholds to change over time. 5. The results suggest, first, that most muscle spindle endings in the human pretibial muscles receive a significant increase in fusimotor drive during relatively weak isometric efforts and secondly, that when fusimotor after-effects are controlled, much of the residual variability in 'acceleration threshold' for any one spindle in repeated contractions is due to extrafusal factors, particularly variability in contraction rate.
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Affiliation(s)
- L R Wilson
- Department of Clinical Neurophysiology, Prince Henry Hospital, Sydney, Australia.
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31
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Abstract
1. The aim of this study was to assess the incidence of lasting alterations in discharge rate of muscle spindle afferents innervating human ankle and toe dorsiflexor muscles following isometric contractions. 2. The subjects performed controlled isometric ankle dorsiflexions maintained for approximately 5 s. During the contraction the discharge of all but one spindle afferent increased above the precontraction level. After complete relaxation, there was prolonged enhancement of the discharge rate of nineteen of fifty-five muscle spindle afferents and none of three Golgi tendon organ afferents. Ten of the nineteen spindle afferents had been silent prior to the contraction. For the population of fifty-five spindle afferents, the mean 'postcontraction' discharge rate was 65% higher than the mean precontraction discharge rate, with the mean rate increasing from 2.3 to 3.9 Hz (P < 0.001). The mean duration of the enhanced postcontraction discharge was 52 s (range, 8-240 s). 3. Stretch applied to the tendon of the receptor-bearing muscle in twelve of fourteen spindle afferents with an enhanced postcontraction discharge rate eliminated or reduced the enhanced discharge rate. 4. The high incidence of an enhanced spindle discharge after voluntary contraction (35% of spindle afferents) suggests that muscle 'history' should be taken into account when interpreting changes in spindle discharge rates. The enhanced discharge rates following contraction probably reflect a long-lasting effect of the contraction-associated increase in fusimotor drive on intrafusal stiffness, rather than the persistence of fusimotor drive following relaxation.
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Affiliation(s)
- L R Wilson
- Department of Clinical Neurophysiology, Prince Henry and Prince of Wales Hospitals, University of New South Wales, Sydney, Australia
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Creaney J, Spithill TW, Thompson CM, Wilson LR, Sandeman RM, Parsons JC. Attempted immunisation of sheep against Fasciola hepatica using gamma-irradiated metacercariae. Int J Parasitol 1995; 25:853-6. [PMID: 7558572 DOI: 10.1016/0020-7519(94)00204-2] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
The potential of gamma-irradiated Fasciola hepatica metacercariae to vaccinate sheep against fascioliasis was examined. The effect of the size of the inocula of irradiated metacercariae and the level of gamma-irradiation on the recovery of non-irradiated fluke was assessed following homologous challenge. Groups of Merino wethers were vaccinated with a single infection of either 500 or 2000 metacercariae, previously exposed to either 30, 100 or 400 Gy of gamma-irradiation. No significant reduction of fluke burdens were observed in any group, although a nonsignificant 20% reduction was observed in sheep vaccinated with 2000 metacercariae irradiated with 100 Gy. A second trial was conducted in which groups of sheep were vaccinated with 2 doses, given 4 weeks apart, of 2000 metacercariae, previously irradiated at either 70, 100 or 150 Gy. In both trials parasite viability was severely affected by doses of gamma-irradiation of 30 Gy or greater and no mature flukes were recovered from control sheep given metacercariae attenuated with 70 Gy or greater. A strong humoral immune response to somatic F. hepatica antigens was observed in all sheep. Only sera from sheep receiving 70 Gy irradiated metacercariae recognised the 2 candidate liver fluke vaccine molecules, F. hepatica glutathione S-transferase and cathepsin-L proteases. No reduction was observed in either the number of flukes or the production of fluke eggs in any vaccinated group. Vaccination appeared to affect the development of the challenge fluke population, resulting in reduced hepatic damage during migration, as measured by levels of serum glutamate dehydrogenase, and an increase in mean fluke weight.
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Affiliation(s)
- J Creaney
- Victorian Institute of Animal Science, Attwood, Australia
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Abstract
The response of a muscle afferent to the mechanical stimulus produced by a twitch contraction of the receptor-bearing muscle is an important test for differentiating between muscle spindle endings and Golgi tendon organs. The present study demonstrates that active alpha-motor axons can behave in a similar manner to spindle afferents, presumably responding not to the mechanical event per se, but reflexly to the change in afferent discharge created by the mechanical event. alpha-Motor axons were unequivocally identified during microneurography using spike-triggered averages of EMG. Caution is required when the twitch test is utilized to assist in the classification of muscle afferents during an intentional or unintentional voluntary contraction.
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Affiliation(s)
- J T Inglis
- Faculty of Applied Health Science, Department of Physical Therapy, Elborn College, University of Western Ontario, London, Canada
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Panaccio M, Wilson LR, Crameri SL, Wijffels GL, Spithill TW. Molecular characterization of cDNA sequences encoding glutathione S-transferases of Fasciola hepatica. Exp Parasitol 1993; 77:385. [PMID: 8224094 DOI: 10.1006/expr.1993.1097] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
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Panaccio M, Wilson LR, Crameri SL, Wijffels GL, Spithill TW. Molecular characterization of cDNA sequences encoding glutathione S-transferases of Fasciola hepatica. Exp Parasitol 1992; 74:232-7. [PMID: 1740183 DOI: 10.1016/0014-4894(92)90051-b] [Citation(s) in RCA: 30] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Affiliation(s)
- M Panaccio
- Victorian Institute of Animal Science, Department of Agriculture, Attwood, Australia
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36
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Abstract
We have identified a period during early Xenopus development when several different genes transcribed by RNA polymerase III (class III genes) are coordinately inactivated. During the late gastrula stage a major reduction in the number of active transcription complexes gives rise to a pattern of class III gene activity typical of adult somatic cells. This event is referred to as the Gastrula-Neurula Transition and involves the inactivation of genes encoding oocyte-type tRNAs and 5S RNA, along with several heterogeneous RNAs expressed during the blastula and gastrula stages of embryogenesis.
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Affiliation(s)
- M T Andrews
- Department of Genetics, North Carolina State University, Raleigh 27695-7614
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Abstract
Streptobacillus moniliformis is an uncommon human pathogen contracted from exposure to rodents. It usually produces a mild, protracted illness (rat-bite fever, Haverhill fever, erythema arthriticum epidemicum) that has either a favorable response to antibiotic therapy or spontaneously resolves. This report describes a fatal case of Streptobacillus moniliformis in an infant bitten by a wild rat. The autopsy findings included an interstitial pneumonia, fibrinous endocarditis, mild mononuclear meningitis, hepatosplenomegaly and lymphadenopathy, erythrophagocytosis, and sinusoidal mononuclear cell infiltrates in regional lymph nodes and the liver. To the authors' knowledge, this is the first report of the autopsy pathology findings of this agent.
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Affiliation(s)
- M A Sens
- Department of Pathology, Medical University of South Carolina, Charleston
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Roberts BR, Wilson LR, Cascino JJ, Smith GP. Autoradiographic studies of ethylenediurea distribution in woody plants. Environ Pollut 1987; 45:81-86. [PMID: 15092753 DOI: 10.1016/0269-7491(87)90050-9] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/09/1986] [Revised: 10/01/1986] [Accepted: 10/14/1986] [Indexed: 05/24/2023]
Abstract
Carbon-14-labelled ethylenediurea (EDU), synthesised from diethylenetriamine and (14)C-urea, was stem-injected into 2-year-old seedlings of sugar maple, white ash, flowering dogwood and flowering crabapple. At time intervals ranging from 1 h to 42 days after treatment, macroautoradiographs of leaf, stem and root tissue were made to determine relative distribution patterns of labelled chemical. Translocation of (14)C-EDU was very rapid and predominantly acropetal, especially after the first few hours. Maximum quantities of (14)C were found in leaf tissue approximately 7-10 days following injection, after which the intensity of the labelled chemical declined over the remainder of the study (42 days). Distribution patterns of (14)C-EDU were correlated with observed levels of protection afforded most plants when the chemical is injected 7 days before fumigation with ozone.
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Affiliation(s)
- B R Roberts
- United States Department of Agriculture, Agricultural Research Service, Ohio Wesleyan University, Delaware, OH 43015, USA
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Larson M, Leigh J, Wilson LR. Detecting compartmental syndrome using continuous pressure monitoring. Focus Crit Care 1986; 13:51-6. [PMID: 3639828] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
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40
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Abstract
Children with ( N = 30) and children without ( N = 30) visual-motor handicaps, defined by the Bender-Gestalt test, were matched on IQ and MA and given a successive discrimination task involving 2 stimuli varying only on spatial orientation. The handicapped Ss learned at a significantly (p < .05) slower rate with no recall deficit 3 min. after acquisition. Their slower learning may have been produced by weaknesses in verbal mediation, raising the possibility that language contributes to their limited academic progress and thus also underlies the reported correlations between school achievement and perceptual-motor scores. Similar comments could be made about limited brief-memory storage and inadequate perception of spatial orientation, both of which may have also impeded their successive discrimination learning. Thus, the frequent tacit assumption of a simple cause and effect relationship between achievement and perceptual-motor development seems questionable.
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