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Zhang WT, Chao THH, Yang Y, Wang TW, Lee SH, Oyarzabal EA, Zhou J, Nonneman R, Pegard NC, Zhu H, Cui G, Shih YYI. Spectral fiber photometry derives hemoglobin concentration changes for accurate measurement of fluorescent sensor activity. CELL REPORTS METHODS 2022; 2:100243. [PMID: 35880016 PMCID: PMC9308135 DOI: 10.1016/j.crmeth.2022.100243] [Citation(s) in RCA: 17] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/14/2021] [Revised: 04/08/2022] [Accepted: 06/08/2022] [Indexed: 12/22/2022]
Abstract
Fiber photometry is an emerging technique for recording fluorescent sensor activity in the brain. However, significant hemoglobin absorption artifacts in fiber photometry data may be misinterpreted as sensor activity changes. Because hemoglobin exists widely in the brain, and its concentration varies temporally, such artifacts could impede the accuracy of photometry recordings. Here we present use of spectral photometry and computational methods to quantify photon absorption effects by using activity-independent fluorescence signals, which can be used to derive oxy- and deoxy-hemoglobin concentration changes. Although these changes are often temporally delayed compared with the fast-responding fluorescence spikes, we found that erroneous interpretation may occur when examining pharmacology-induced sustained changes and that sometimes hemoglobin absorption could flip the GCaMP signal polarity. We provide hemoglobin-based correction methods to restore fluorescence signals and compare our results with other commonly used approaches. We also demonstrated the utility of spectral fiber photometry for delineating regional differences in hemodynamic response functions.
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Affiliation(s)
- Wei-Ting Zhang
- Center for Animal MRI, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
- Biomedical Research Imaging Center, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
- Department of Neurology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Tzu-Hao Harry Chao
- Center for Animal MRI, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
- Biomedical Research Imaging Center, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
- Department of Neurology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Yue Yang
- Center for Animal MRI, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
- Biomedical Research Imaging Center, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
- Department of Neurology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
- Department of Biostatistics, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Tzu-Wen Wang
- Center for Animal MRI, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
- Biomedical Research Imaging Center, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Sung-Ho Lee
- Center for Animal MRI, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
- Biomedical Research Imaging Center, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
- Department of Neurology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Esteban A. Oyarzabal
- Center for Animal MRI, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
- Biomedical Research Imaging Center, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
- Department of Neurology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Jingheng Zhou
- In Vivo Neurobiology Group, Neurobiology Laboratory, National Institute of Environmental Health Sciences, National Institutes of Health, Durham, NC 27709, USA
| | - Randy Nonneman
- Center for Animal MRI, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
- Biomedical Research Imaging Center, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
- Department of Neurology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Nicolas C. Pegard
- Department of Applied Physical Sciences, UNC Neuroscience Center, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
- Department of Biomedical Engineering, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Hongtu Zhu
- Biomedical Research Imaging Center, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
- Department of Biostatistics, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
- Department of Computer Science, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Guohong Cui
- In Vivo Neurobiology Group, Neurobiology Laboratory, National Institute of Environmental Health Sciences, National Institutes of Health, Durham, NC 27709, USA
| | - Yen-Yu Ian Shih
- Center for Animal MRI, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
- Biomedical Research Imaging Center, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
- Department of Neurology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
- Department of Biomedical Engineering, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
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Chao THH, Zhang WT, Hsu LM, Cerri DH, Wang TW, Shih YYI. Computing hemodynamic response functions from concurrent spectral fiber-photometry and fMRI data. NEUROPHOTONICS 2022; 9:032205. [PMID: 35005057 PMCID: PMC8734587 DOI: 10.1117/1.nph.9.3.032205] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/01/2021] [Accepted: 11/15/2021] [Indexed: 05/31/2023]
Abstract
Significance: Although emerging evidence suggests that the hemodynamic response function (HRF) can vary by brain region and species, a single, canonical, human-based HRF is widely used in animal studies. Therefore, the development of flexible, accessible, brain-region specific HRF calculation approaches is paramount as hemodynamic animal studies become increasingly popular. Aim: To establish an fMRI-compatible, spectral, fiber-photometry platform for HRF calculation and validation in any rat brain region. Approach: We used our platform to simultaneously measure (a) neuronal activity via genetically encoded calcium indicators (GCaMP6f), (b) local cerebral blood volume (CBV) from intravenous Rhodamine B dye, and (c) whole brain CBV via fMRI with the Feraheme contrast agent. Empirical HRFs were calculated with GCaMP6f and Rhodamine B recordings from rat brain regions during resting-state and task-based paradigms. Results: We calculated empirical HRFs for the rat primary somatosensory, anterior cingulate, prelimbic, retrosplenial, and anterior insular cortical areas. Each HRF was faster and narrower than the canonical HRF and no significant difference was observed between these cortical regions. When used in general linear model analyses of corresponding fMRI data, the empirical HRFs showed better detection performance than the canonical HRF. Conclusions: Our findings demonstrate the viability and utility of fiber-photometry-based HRF calculations. This platform is readily scalable to multiple simultaneous recording sites, and adaptable to study transfer functions between stimulation events, neuronal activity, neurotransmitter release, and hemodynamic responses.
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Affiliation(s)
- Tzu-Hao H. Chao
- University of North Carolina at Chapel Hill, Center for Animal MRI, Chapel Hill. North Carolina, United States
- University of North Carolina at Chapel Hill, Biomedical Research Imaging Center, Chapel Hill. North Carolina, United States
- University of North Carolina at Chapel Hill, Department of Neurology, Chapel Hill. North Carolina, United States
| | - Wei-Ting Zhang
- University of North Carolina at Chapel Hill, Center for Animal MRI, Chapel Hill. North Carolina, United States
- University of North Carolina at Chapel Hill, Biomedical Research Imaging Center, Chapel Hill. North Carolina, United States
- University of North Carolina at Chapel Hill, Department of Neurology, Chapel Hill. North Carolina, United States
| | - Li-Ming Hsu
- University of North Carolina at Chapel Hill, Center for Animal MRI, Chapel Hill. North Carolina, United States
- University of North Carolina at Chapel Hill, Biomedical Research Imaging Center, Chapel Hill. North Carolina, United States
- University of North Carolina at Chapel Hill, Department of Neurology, Chapel Hill. North Carolina, United States
| | - Domenic H. Cerri
- University of North Carolina at Chapel Hill, Center for Animal MRI, Chapel Hill. North Carolina, United States
- University of North Carolina at Chapel Hill, Biomedical Research Imaging Center, Chapel Hill. North Carolina, United States
- University of North Carolina at Chapel Hill, Department of Neurology, Chapel Hill. North Carolina, United States
| | - Tzu-Wen Wang
- University of North Carolina at Chapel Hill, Center for Animal MRI, Chapel Hill. North Carolina, United States
- University of North Carolina at Chapel Hill, Biomedical Research Imaging Center, Chapel Hill. North Carolina, United States
| | - Yen-Yu I. Shih
- University of North Carolina at Chapel Hill, Center for Animal MRI, Chapel Hill. North Carolina, United States
- University of North Carolina at Chapel Hill, Biomedical Research Imaging Center, Chapel Hill. North Carolina, United States
- University of North Carolina at Chapel Hill, Department of Neurology, Chapel Hill. North Carolina, United States
- University of North Carolina at Chapel Hill, Department of Biomedical Engineering, Chapel Hill. North Carolina, United States
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3
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Lee SH, Broadwater MA, Ban W, Wang TWW, Kim HJ, Dumas JS, Vetreno RP, Herman MA, Morrow AL, Besheer J, Kash TL, Boettiger CA, Robinson DL, Crews FT, Shih YYI. An isotropic EPI database and analytical pipelines for rat brain resting-state fMRI. Neuroimage 2021; 243:118541. [PMID: 34478824 PMCID: PMC8561231 DOI: 10.1016/j.neuroimage.2021.118541] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2021] [Revised: 08/08/2021] [Accepted: 08/30/2021] [Indexed: 12/24/2022] Open
Abstract
Resting-state functional magnetic resonance imaging (fMRI) has drastically expanded the scope of brain research by advancing our knowledge about the topologies, dynamics, and interspecies translatability of functional brain networks. Several databases have been developed and shared in accordance with recent key initiatives in the rodent fMRI community to enhance the transparency, reproducibility, and interpretability of data acquired at various sites. Despite these pioneering efforts, one notable challenge preventing efficient standardization in the field is the customary choice of anisotropic echo planar imaging (EPI) schemes with limited spatial coverage. Imaging with anisotropic resolution and/or reduced brain coverage has significant shortcomings including reduced registration accuracy and increased deviation in brain feature detection. Here we proposed a high-spatial-resolution (0.4 mm), isotropic, whole-brain EPI protocol for the rat brain using a horizontal slicing scheme that can maintain a functionally relevant repetition time (TR), avoid high gradient duty cycles, and offer unequivocal whole-brain coverage. Using this protocol, we acquired resting-state EPI fMRI data from 87 healthy rats under the widely used dexmedetomidine sedation supplemented with low-dose isoflurane on a 9.4 T MRI system. We developed an EPI template that closely approximates the Paxinos and Watson's rat brain coordinate system and demonstrated its ability to improve the accuracy of group-level approaches and streamline fMRI data pre-processing. Using this database, we employed a multi-scale dictionary-learning approach to identify reliable spatiotemporal features representing rat brain intrinsic activity. Subsequently, we performed k-means clustering on those features to obtain spatially discrete, functional regions of interest (ROIs). Using Euclidean-based hierarchical clustering and modularity-based partitioning, we identified the topological organizations of the rat brain. Additionally, the identified group-level FC network appeared robust across strains and sexes. The "triple-network" commonly adapted in human fMRI were resembled in the rat brain. Through this work, we disseminate raw and pre-processed isotropic EPI data, a rat brain EPI template, as well as identified functional ROIs and networks in standardized rat brain coordinates. We also make our analytical pipelines and scripts publicly available, with the hope of facilitating rat brain resting-state fMRI study standardization.
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Affiliation(s)
- Sung-Ho Lee
- Center for Animal MRI, University of North Carolina, Chapel Hill, NC, USA,Biomedical Research Imaging Center, University of North Carolina, Chapel Hill, NC, USA,Department of Neurology, University of North Carolina, Chapel Hill, NC, USA,Bowles Center for Alcohol Studies University of North Carolina, Chapel Hill, NC, USA,Corresponding authors at: Center for Animal MRI, 125 Mason Farm Road, CB# 7513, University of North Carolina, Chapel Hill, NC 27599, USA. (S.-H. Lee), (Y.-Y.I. Shih)
| | - Margaret A. Broadwater
- Center for Animal MRI, University of North Carolina, Chapel Hill, NC, USA,Biomedical Research Imaging Center, University of North Carolina, Chapel Hill, NC, USA,Department of Neurology, University of North Carolina, Chapel Hill, NC, USA,Bowles Center for Alcohol Studies University of North Carolina, Chapel Hill, NC, USA
| | - Woomi Ban
- Center for Animal MRI, University of North Carolina, Chapel Hill, NC, USA,Biomedical Research Imaging Center, University of North Carolina, Chapel Hill, NC, USA
| | - Tzu-Wen Winnie Wang
- Center for Animal MRI, University of North Carolina, Chapel Hill, NC, USA,Biomedical Research Imaging Center, University of North Carolina, Chapel Hill, NC, USA
| | - Hyeon-Joong Kim
- Center for Animal MRI, University of North Carolina, Chapel Hill, NC, USA,Biomedical Research Imaging Center, University of North Carolina, Chapel Hill, NC, USA,Department of Neurology, University of North Carolina, Chapel Hill, NC, USA
| | - Jaiden Seongmi Dumas
- Center for Animal MRI, University of North Carolina, Chapel Hill, NC, USA,Department of Neurology, University of North Carolina, Chapel Hill, NC, USA,Department of Quantitative Biology, University of North Carolina, Chapel Hill, NC, USA
| | - Ryan P. Vetreno
- Bowles Center for Alcohol Studies University of North Carolina, Chapel Hill, NC, USA,Department of Pharmacology, University of North Carolina, Chapel Hill, NC, USA
| | - Melissa A. Herman
- Bowles Center for Alcohol Studies University of North Carolina, Chapel Hill, NC, USA,Department of Pharmacology, University of North Carolina, Chapel Hill, NC, USA
| | - A. Leslie Morrow
- Bowles Center for Alcohol Studies University of North Carolina, Chapel Hill, NC, USA,Department of Psychiatry, University of North Carolina, Chapel Hill, NC, USA,Department of Pharmacology, University of North Carolina, Chapel Hill, NC, USA
| | - Joyce Besheer
- Bowles Center for Alcohol Studies University of North Carolina, Chapel Hill, NC, USA,Department of Psychiatry, University of North Carolina, Chapel Hill, NC, USA
| | - Thomas L. Kash
- Bowles Center for Alcohol Studies University of North Carolina, Chapel Hill, NC, USA,Department of Pharmacology, University of North Carolina, Chapel Hill, NC, USA
| | - Charlotte A. Boettiger
- Bowles Center for Alcohol Studies University of North Carolina, Chapel Hill, NC, USA,Department of Psychiatry, University of North Carolina, Chapel Hill, NC, USA,Department of Psychology and Neuroscience, University of North Carolina, Chapel Hill, NC, USA
| | - Donita L. Robinson
- Bowles Center for Alcohol Studies University of North Carolina, Chapel Hill, NC, USA,Department of Psychiatry, University of North Carolina, Chapel Hill, NC, USA
| | - Fulton T. Crews
- Bowles Center for Alcohol Studies University of North Carolina, Chapel Hill, NC, USA,Department of Psychiatry, University of North Carolina, Chapel Hill, NC, USA,Department of Pharmacology, University of North Carolina, Chapel Hill, NC, USA
| | - Yen-Yu Ian Shih
- Center for Animal MRI, University of North Carolina, Chapel Hill, NC, USA,Biomedical Research Imaging Center, University of North Carolina, Chapel Hill, NC, USA,Department of Neurology, University of North Carolina, Chapel Hill, NC, USA,Bowles Center for Alcohol Studies University of North Carolina, Chapel Hill, NC, USA,Corresponding authors at: Center for Animal MRI, 125 Mason Farm Road, CB# 7513, University of North Carolina, Chapel Hill, NC 27599, USA. (S.-H. Lee), (Y.-Y.I. Shih)
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Jiang Y, Zhang Z, Wu Z, Sun S, Fu Y, Ke B. Change and Recovery of Choroid Thickness after Short-term Application of 1% Atropine Gel and Its Influencing Factors in 6-7-year-old Children. Curr Eye Res 2021; 46:1171-1177. [PMID: 33390025 DOI: 10.1080/02713683.2020.1863431] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
Abstract
PURPOSE To investigate the change and recovery of choroid thickness after short-term application of 1% atropine gel and its influencing factors in 6-7-year-old children. MATERIALS AND METHODS 71 right eyes of 71 children were enrolled and divided into myopia and control group. 1% atropine gel was administered twice a day for one week and then stopped. Spherical equivalent (SE), accommodative amplitude (AA), keratometry (K), axial length (AL), and choroidal thickness (CT) were obtained at baseline and 1st, 4th, and 8th weeks. CT was measured at subfovea and 1 mm, 2 mm, and 3 mm temporal, superior, nasal, and inferior from the fovea using spectral-domain optical coherence tomography. RESULTS In both groups, all CTs increased following the change in SE, AA, and AL after administration of 1% atropine for one week. They gradually recovered to baseline levels seven weeks after withdrawal. The change (Δ) in CT at 3 mm superior from the fovea was significantly higher in the myopia group than in the control group. In both groups, ΔCT at subfovea had no significant correlation with SE, AA, and AL, both at baseline and one week. However, ΔCT at subfovea was negatively correlated with ΔAL in the control group. CONCLUSIONS One-week application of 1% atropine gel may increase CT in 6-7-year-old Chinese children. Meanwhile, the recovery process after withdrawal lasts seven weeks. During the recovery process, the changes in structural parameters (AL, CT) and functional parameters (AA, SE) in both groups occurred synchronously. The SE, AA, and AL at baseline may not predict the extent of atropine's effect on CT.
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Affiliation(s)
- Yunjia Jiang
- Department of Ophthalmology, Shanghai General Hospital of Nanjing Medical University, Shanghai, China.,Department of Ophthalmology, The Affiliated Wuxi No. 2 People's Hospital of Nanjing Medical University, Wuxi, Jiangsu Province, China.,Department of Ophthalmology, The Affiliated Wuxi Clinical College of Nantong University, Wuxi, Jiangsu Province, China
| | - Zhengwei Zhang
- Department of Ophthalmology, Shanghai General Hospital of Nanjing Medical University, Shanghai, China.,Department of Ophthalmology, The Affiliated Wuxi No. 2 People's Hospital of Nanjing Medical University, Wuxi, Jiangsu Province, China.,Department of Ophthalmology, The Affiliated Wuxi Clinical College of Nantong University, Wuxi, Jiangsu Province, China
| | - Zhifeng Wu
- Department of Ophthalmology, The Affiliated Wuxi No. 2 People's Hospital of Nanjing Medical University, Wuxi, Jiangsu Province, China.,Department of Ophthalmology, The Affiliated Wuxi Clinical College of Nantong University, Wuxi, Jiangsu Province, China
| | - Song Sun
- Department of Ophthalmology, The Affiliated Wuxi No. 2 People's Hospital of Nanjing Medical University, Wuxi, Jiangsu Province, China.,Department of Ophthalmology, The Affiliated Wuxi Clinical College of Nantong University, Wuxi, Jiangsu Province, China
| | - Yuting Fu
- Department of Ophthalmology, The Affiliated Wuxi No. 2 People's Hospital of Nanjing Medical University, Wuxi, Jiangsu Province, China.,Department of Ophthalmology, The Affiliated Wuxi Clinical College of Nantong University, Wuxi, Jiangsu Province, China
| | - Bilian Ke
- Department of Ophthalmology, Shanghai General Hospital of Nanjing Medical University, Shanghai, China.,Department of Ophthalmology, Shanghai General Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai, China.,National Clinical Research Center for Eye Diseases, Shanghai, China.,Shanghai Key Laboratory of Fundus Disease, Shanghai, China.,Shanghai Engineering Center for Visual Science and Photomedicine, Shanghai, China.,Shanghai Engineering Center for Precise Diagnosis and Treatment of Eye Diseases, Shanghai, China
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5
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Measurement of Retinal Microvascular Blood Velocity Using Erythrocyte Mediated Velocimetry. Sci Rep 2019; 9:20178. [PMID: 31882799 PMCID: PMC6934793 DOI: 10.1038/s41598-019-56239-8] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2019] [Accepted: 12/07/2019] [Indexed: 01/08/2023] Open
Abstract
Changes in retinal blood flow may be involved in the pathogenesis of glaucoma and other ocular diseases. Erythrocyte mediated velocimetry (EMV) is a novel technique where indocyanine green (ICG) dye is sequestered in erythrocyte ghosts and autologously re-injected to allow direct visualization of erythrocytes for in vivo measurement of speed. The purpose of this study is to determine the mean erythrocyte speed in the retinal microvasculature, as well as the intravisit and intervisit variability of EMV. Data from 23 EMV sessions from control, glaucoma suspect, and glaucoma patients were included in this study. In arteries with an average diameter of 43.11 µm ± 6.62 µm, the mean speed was 7.17 mm/s ± 2.35 mm/s. In veins with an average diameter of 45.87 µm ± 12.04 µm, the mean speed was 6.05 mm/s ± 1.96 mm/s. Intravisit variability, as measured by the mean coefficient of variation, was 3.57% (range 0.44-9.68%). Intervisit variability was 4.85% (range 0.15-8.43%). EMV may represent reliable method for determination of retinal blood speed, potentially allowing insights into the effects of pharmacologic agents or pathogenesis of ocular diseases.
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6
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Nesper PL, Lee HE, Fayed AE, Schwartz GW, Yu F, Fawzi AA. Hemodynamic Response of the Three Macular Capillary Plexuses in Dark Adaptation and Flicker Stimulation Using Optical Coherence Tomography Angiography. Invest Ophthalmol Vis Sci 2019; 60:694-703. [PMID: 30786274 PMCID: PMC6383834 DOI: 10.1167/iovs.18-25478] [Citation(s) in RCA: 28] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
Purpose To assess retinal microvascular reactivity during dark adaptation and the transition to ambient light and after flicker stimulation using optical coherence tomography angiography (OCTA). Methods Fifteen eyes of 15 healthy participants were dark adapted for 45 minutes followed by OCTA imaging in the dark-adapted state. After 5 minutes of normal lighting, subjects underwent OCTA imaging. Participants were then subjected to a flashing light-emitting diode (LED) light and repeat OCTA. Parafoveal vessel density and adjusted flow index (AFI) were calculated for superficial (SCP), middle (MCP), and deep capillary plexuses (DCP), and then compared between conditions after adjusting for age, refractive error, and scan quality. SCP vessel length density (VLD) was also evaluated. Between-condition capillary images were aligned and subtracted to identify differences. We then analyzed images from 10 healthy subjects during the transition from dark adaptation to ambient light. Results SCP vessel density was significantly higher while SCP VLD was significantly lower during ambient light and flicker compared to dark adaptation. There was a significant positive mean value for DCP “flicker minus dark or light,” suggesting more visible vessels during flicker due to changes in flow, dilation, or vessel recruitment. We found a significant, transient increase in SCP and decrease in both MCP and DCP vessel density during the transition from dark to light. Conclusions We show evidence suggesting constriction of deeper vessels and dilation of large SCP vessels during the transition from dark to light. This contrasts to redistribution of blood flow to deeper layers during dark adaptation and flicker stimulation.
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Affiliation(s)
- Peter L Nesper
- Department of Ophthalmology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, United States
| | - Hee Eun Lee
- Department of Ophthalmology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, United States
| | - Alaa E Fayed
- Department of Ophthalmology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, United States.,Department of Ophthalmology, Kasr Al-Ainy School of Medicine, Cairo University, Cairo, Egypt
| | - Gregory W Schwartz
- Department of Ophthalmology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, United States.,Department of Physiology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, United States.,Department of Neurobiology, Weinberg College of Arts and Sciences, Northwestern University, Chicago, Illinois, United States
| | - Fei Yu
- Department of Biostatistics, Fielding School of Public Health, University of California-Los Angeles, Los Angeles, California, United States
| | - Amani A Fawzi
- Department of Ophthalmology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, United States
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7
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Blair NP, Tan MR, Felder AE, Teng PY, Wanek J, Shahidi M. Retinal tissue oxygen tension and consumption during light flicker stimulation in rat. Exp Eye Res 2018; 175:207-211. [PMID: 30121195 DOI: 10.1016/j.exer.2018.08.007] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2018] [Revised: 08/09/2018] [Accepted: 08/12/2018] [Indexed: 10/28/2022]
Abstract
Light flicker stimulation has been shown to increase inner retinal oxygen metabolism and supply. The purpose of the study was to test the hypothesis that sustained light flicker stimulation of various durations alters the depth profile metrics of oxygen partial pressure in the retinal tissue (tPO2) but not the outer retinal oxygen consumption rate (QO2). In 17 rats, tPO2 depth profiles were derived by phosphorescence lifetime imaging after intravitreal injection of an oxyphor. tPO2 profile metrics, including mean inner retinal tPO2, maximum outer retinal tPO2 and minimum outer retinal tPO2 were determined. QO2 was calculated using a one-dimensional oxygen diffusion model. Data were acquired at baseline (constant light illumination) and during light flicker stimulation at 10 Hz under the same mean illumination levels, and differences between values obtained during flicker and baseline were calculated. None of the tPO2 profile metrics or QO2 differences depended on the duration of light flicker stimulation (R2 ≤ 0.03). No significant change in any of the tPO2 profile metrics was detected with light flicker compared with constant light (P ≥ 0.08). Light flicker decreased QO2 from 0.53 ± 0.29 to 0.38 ± 0.30 mL O2/(min*100 gm), a reduction of 28% (P = 0.02). The retinal compensatory responses to the physiologic challenge of light flicker stimulation were effective in maintaining the levels of oxygen at or near baseline in the inner retina. Oxygen availability to the inner retina during light flicker may also have been enhanced by the decrease in QO2.
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Affiliation(s)
- Norman P Blair
- Department of Ophthalmology and Visual Sciences, University of Illinois at Chicago, 1855 West Taylor Street, Chicago, IL, 60612, USA.
| | - Michael R Tan
- Department of Ophthalmology and Visual Sciences, University of Illinois at Chicago, 1855 West Taylor Street, Chicago, IL, 60612, USA.
| | - Anthony E Felder
- Department of Ophthalmology and Visual Sciences, University of Illinois at Chicago, 1855 West Taylor Street, Chicago, IL, 60612, USA.
| | - Pang-Yu Teng
- Department of Ophthalmology and Visual Sciences, University of Illinois at Chicago, 1855 West Taylor Street, Chicago, IL, 60612, USA.
| | - Justin Wanek
- Department of Ophthalmology and Visual Sciences, University of Illinois at Chicago, 1855 West Taylor Street, Chicago, IL, 60612, USA.
| | - Mahnaz Shahidi
- Department of Ophthalmology and Visual Sciences, University of Illinois at Chicago, 1855 West Taylor Street, Chicago, IL, 60612, USA.
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8
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Broadwater MA, Lee SH, Yu Y, Zhu H, Crews FT, Robinson DL, Shih YYI. Adolescent alcohol exposure decreases frontostriatal resting-state functional connectivity in adulthood. Addict Biol 2018; 23:810-823. [PMID: 28691248 PMCID: PMC5760482 DOI: 10.1111/adb.12530] [Citation(s) in RCA: 49] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2017] [Revised: 05/18/2017] [Accepted: 05/23/2017] [Indexed: 12/11/2022]
Abstract
Connectivity of the prefrontal cortex (PFC) matures through adolescence, coinciding with emergence of adult executive function and top-down inhibitory control over behavior. Alcohol exposure during this critical period of brain maturation may affect development of PFC and frontolimbic connectivity. Adult rats exposed to adolescent intermittent ethanol (AIE; 5 g/kg ethanol, 25 percent v/v in water, intragastrically, 2-day-on, 2-day-off, postnatal day 25-54) or water control underwent resting-state functional MRI to test the hypothesis that AIE induces persistent changes in frontolimbic functional connectivity under baseline and acute alcohol conditions (2 g/kg ethanol or saline, intraperitoneally administered during scanning). Data were acquired on a Bruker 9.4-T MR scanner with rats under dexmedetomidine sedation in combination with isoflurane. Frontolimbic network regions-of-interest for data analysis included PFC [prelimbic (PrL), infralimbic (IL), and orbitofrontal cortex (OFC) portions], nucleus accumbens (NAc), caudate putamen (CPu), dorsal hippocampus, ventral tegmental area, amygdala, and somatosensory forelimb used as a control region. AIE decreased baseline resting-state connectivity between PFC subregions (PrL-IL and IL-OFC) and between PFC-striatal regions (PrL-NAc, IL-CPu, IL-NAc, OFC-CPu, and OFC-NAc). Acute ethanol induced negative blood-oxygen-level-dependent changes within all regions of interest examined, along with significant increases in functional connectivity in control, but not AIE animals. Together, these data support the hypothesis that binge-like adolescent alcohol exposure causes persistent decreases in baseline frontolimbic (particularly frontostriatal) connectivity and alters sensitivity to acute ethanol-induced increases in functional connectivity in adulthood.
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Affiliation(s)
| | - Sung-Ho Lee
- Department of Neurology, University of North Carolina, Chapel Hill, NC, USA
- Departments of Biomedical Research Imaging Center and Biomedical Engineering, University of North Carolina, Chapel Hill, NC, USA
| | - Yang Yu
- Department of Statistics and Operations, University of North Carolina, Chapel Hill, NC, USA
- Departments of Biomedical Research Imaging Center and Biomedical Engineering, University of North Carolina, Chapel Hill, NC, USA
| | - Hongtu Zhu
- Department of Biostatistics, University of North Carolina, Chapel Hill, NC, USA
- Departments of Biomedical Research Imaging Center and Biomedical Engineering, University of North Carolina, Chapel Hill, NC, USA
| | - Fulton T. Crews
- Bowles Center for Alcohol Studies, University of North Carolina, Chapel Hill, NC, USA
- Department of Pharmacology, School of Medicine, University of North Carolina, Chapel Hill, NC, USA
| | - Donita L. Robinson
- Bowles Center for Alcohol Studies, University of North Carolina, Chapel Hill, NC, USA
- Department of Psychiatry, University of North Carolina, Chapel Hill, NC, USA
| | - Yen-Yu Ian Shih
- Department of Neurology, University of North Carolina, Chapel Hill, NC, USA
- Departments of Biomedical Research Imaging Center and Biomedical Engineering, University of North Carolina, Chapel Hill, NC, USA
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9
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Ahn J, Ahn SE, Yang KS, Kim SW, Oh J. Effects of a high level of illumination before sleep at night on chorioretinal thickness and ocular biometry. Exp Eye Res 2017; 164:157-167. [PMID: 28887137 DOI: 10.1016/j.exer.2017.09.001] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2016] [Revised: 08/10/2017] [Accepted: 09/04/2017] [Indexed: 10/18/2022]
Abstract
The choroid is affected by many factors. One of the factors, change in illumination has been suggested to influence choroidal thickness. However, the effects of bright light before sleep at night on the human eye are not well established. The purpose of this study was to investigate the effects of a high level of illumination in the evening on ocular measurements. Twenty-seven men with myopia spent seven consecutive nights in the sleep laboratory. During the first two nights, subjects were exposed to light at 150 lux between 20:00 and midnight. Then, for five consecutive nights, they were exposed to ambient light at 1000 lux between 20:00 and midnight. Ocular parameters and their diurnal variations were compared between the two periods and the effects of a high level of illumination were analyzed. After subjects were exposed to 1000 lux of illumination, axial length increased with borderline significance (p = 0.064). Macular volume and retinal thickness did not change. However, subfoveal choroidal thickness after exposure to 1000 lux of illumination (245.37 ± 52.84 μm) was significantly lower than that after 150 lux of illumination (268.00 ± 57.10 μm), (p < 0.001). Significant diurnal variations were found in mean keratometry (p = 0.039), intraocular pressure (IOP, p = 0.003), ocular perfusion pressure (OPP, p < 0.0001), macular volume (p = 0.019), and subfoveal choroidal thickness (p < 0.0001). A high level of illumination had significant effects on only IOP and OPP (p = 0.027 and 0.017, respectively). Bright light exposure before sleep at an intensity as high as 1000 lux reduced subfoveal choroidal thickness in healthy young men. In conclusion, diurnal variation in choroidal thickness can be affected by bright light exposure before sleep.
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Affiliation(s)
- Jaemoon Ahn
- Department of Ophthalmology, Korea University College of Medicine, 73, Inchon-ro, Sungbuk-gu, Seoul 02841, South Korea
| | - Soh-Eun Ahn
- Sungmo Eye Hospital, 409, Haeundae-ro, Haeundae-gu, Busan 48064, South Korea
| | - Kyung-Sook Yang
- Department of Biostatistics, Korea University College of Medicine, 73, Inchon-ro, Sungbuk-gu, Seoul 02841, South Korea
| | - Seong-Woo Kim
- Department of Ophthalmology, Korea University College of Medicine, 73, Inchon-ro, Sungbuk-gu, Seoul 02841, South Korea
| | - Jaeryung Oh
- Department of Ophthalmology, Korea University College of Medicine, 73, Inchon-ro, Sungbuk-gu, Seoul 02841, South Korea.
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10
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Berkowitz BA, Schmidt T, Podolsky RH, Roberts R. Melanopsin Phototransduction Contributes to Light-Evoked Choroidal Expansion and Rod L-Type Calcium Channel Function In Vivo. Invest Ophthalmol Vis Sci 2017; 57:5314-5319. [PMID: 27727394 PMCID: PMC5063053 DOI: 10.1167/iovs.16-20186] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Purpose In humans, rodents, and pigeons, the dark → light transition signals nonretinal brain tissue to increase choroidal thickness, a major control element of choroidal blood flow, and thus of photoreceptor and retinal pigment epithelium function. However, it is unclear which photopigments in the retina relay the light signal to the brain. Here, we test the hypothesis that melanopsin (Opn4)-regulated phototransduction modulates light-evoked choroidal thickness expansion in mice. Methods Two-month-old C57Bl/6 wild-type (B6), 4- to 5-month-old C57Bl/6/129S6 wild-type (B6 + S6), and 2-month-old melanopsin knockout (Opn4−/−) on a B6 + S6 background were studied. Retinal anatomy was evaluated in vivo by optical coherence tomography and MRI. Choroidal thickness in dark and light were measured by diffusion-weighted MRI. Rod cell L-type calcium channel (LTCC) function in dark and light (manganese-enhanced MRI [MEMRI]) was also measured. Results Opn4−/− mice did not show the light-evoked expansion of choroidal thickness observed in B6 and B6 + S6 controls. Additionally, Opn4−/− mice had lower than normal rod cell and inner retinal LTCC function in the dark but not in the light. These deficits were not due to structural abnormalities because retinal laminar architecture and thickness, and choroidal thickness in the Opn4−/− mice were similar to controls. Conclusions First time evidence is provided that melanopsin phototransduction contributes to dark → light control of murine choroidal thickness. The data also highlight a contribution in vivo of melanopsin phototransduction to rod cell and inner retinal depolarization in the dark.
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Affiliation(s)
- Bruce A Berkowitz
- Department of Anatomy and Cell Biology, Wayne State University, Detroit, Michigan, United States 2Department of Ophthalmology, Wayne State University, Detroit, Michigan, United States
| | - Tiffany Schmidt
- Department of Neurobiology, Northwestern University, Evanston, Illinois, United States
| | - Robert H Podolsky
- Department of Family Medicine and Public Health Sciences, Wayne State University, Detroit, Michigan, United States
| | - Robin Roberts
- Department of Anatomy and Cell Biology, Wayne State University, Detroit, Michigan, United States
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11
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Van Den Berge N, Albaugh DL, Salzwedel A, Vanhove C, Van Holen R, Gao W, Stuber GD, Shih YYI. Functional circuit mapping of striatal output nuclei using simultaneous deep brain stimulation and fMRI. Neuroimage 2017; 146:1050-1061. [PMID: 27825979 PMCID: PMC5322177 DOI: 10.1016/j.neuroimage.2016.10.049] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2016] [Revised: 09/08/2016] [Accepted: 10/31/2016] [Indexed: 01/11/2023] Open
Abstract
The substantia nigra pars reticulata (SNr) and external globus pallidus (GPe) constitute the two major output targets of the rodent striatum. Both the SNr and GPe converge upon thalamic relay nuclei (directly or indirectly, respectively), and are traditionally modeled as functionally antagonistic relay inputs. However, recent anatomical and functional studies have identified unanticipated circuit connectivity in both the SNr and GPe, demonstrating their potential as far more than relay nuclei. In the present study, we employed simultaneous deep brain stimulation and functional magnetic resonance imaging (DBS-fMRI) with cerebral blood volume (CBV) measurements to functionally and unbiasedly map the circuit- and network level connectivity of the SNr and GPe. Sprague-Dawley rats were implanted with a custom-made MR-compatible stimulating electrode in the right SNr (n=6) or GPe (n=7). SNr- and GPe-DBS, conducted across a wide range of stimulation frequencies, revealed a number of surprising evoked responses, including unexpected CBV decreases within the striatum during DBS at either target, as well as GPe-DBS-evoked positive modulation of frontal cortex. Functional connectivity MRI revealed global modulation of neural networks during DBS at either target, sensitive to stimulation frequency and readily reversed following cessation of stimulation. This work thus contributes to a growing literature demonstrating extensive and unanticipated functional connectivity among basal ganglia nuclei.
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Affiliation(s)
- Nathalie Van Den Berge
- Department of Neurology, University of North Carolina, Chapel Hill, NC, USA; Biomedical Research Imaging Center, University of North Carolina, Chapel Hill, NC, USA; Medical Image and Signal Processing Group, Ghent University, Ghent, Belgium
| | - Daniel L Albaugh
- Department of Neurology, University of North Carolina, Chapel Hill, NC, USA; Biomedical Research Imaging Center, University of North Carolina, Chapel Hill, NC, USA; Curriculum in Neurobiology, University of North Carolina, Chapel Hill, NC, USA
| | - Andrew Salzwedel
- Biomedical Imaging Research Institute, Department of Biomedical Sciences and Imaging, Cedars-Sinai Medical Center, Los Angeles, CA, USA
| | - Christian Vanhove
- Medical Image and Signal Processing Group, Ghent University, Ghent, Belgium
| | - Roel Van Holen
- Medical Image and Signal Processing Group, Ghent University, Ghent, Belgium
| | - Wei Gao
- Biomedical Imaging Research Institute, Department of Biomedical Sciences and Imaging, Cedars-Sinai Medical Center, Los Angeles, CA, USA
| | - Garret D Stuber
- Curriculum in Neurobiology, University of North Carolina, Chapel Hill, NC, USA; Department of Psychiatry, University of North Carolina, Chapel Hill, NC, USA
| | - Yen-Yu Ian Shih
- Department of Neurology, University of North Carolina, Chapel Hill, NC, USA; Biomedical Research Imaging Center, University of North Carolina, Chapel Hill, NC, USA; Curriculum in Neurobiology, University of North Carolina, Chapel Hill, NC, USA; Department of Biomedical Engineering, University of North Carolina, Chapel Hill, NC, USA.
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12
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Coordination of Brain-Wide Activity Dynamics by Dopaminergic Neurons. Neuropsychopharmacology 2017; 42:615-627. [PMID: 27515791 PMCID: PMC5240174 DOI: 10.1038/npp.2016.151] [Citation(s) in RCA: 42] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/10/2016] [Revised: 07/15/2016] [Accepted: 07/26/2016] [Indexed: 01/21/2023]
Abstract
Several neuropsychiatric conditions, such as addiction and schizophrenia, may arise in part from dysregulated activity of ventral tegmental area dopaminergic (THVTA) neurons, as well as from more global maladaptation in neurocircuit function. However, whether THVTA activity affects large-scale brain-wide function remains unknown. Here we selectively activated THVTA neurons in transgenic rats and measured resulting changes in whole-brain activity using stimulus-evoked functional magnetic resonance imaging. Applying a standard generalized linear model analysis approach, our results indicate that selective optogenetic stimulation of THVTA neurons enhanced cerebral blood volume signals in striatal target regions in a dopamine receptor-dependent manner. However, brain-wide voxel-based principal component analysis of the same data set revealed that dopaminergic modulation activates several additional anatomically distinct regions throughout the brain, not typically associated with dopamine release events. Furthermore, explicit pairing of THVTA neuronal activation with a forepaw stimulus of a particular frequency expanded the sensory representation of that stimulus, not exclusively within the somatosensory cortices, but brain-wide. These data suggest that modulation of THVTA neurons can impact brain dynamics across many distributed anatomically distinct regions, even those that receive little to no direct THVTA input.
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13
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Linsenmeier RA, Zhang HF. Retinal oxygen: from animals to humans. Prog Retin Eye Res 2017; 58:115-151. [PMID: 28109737 DOI: 10.1016/j.preteyeres.2017.01.003] [Citation(s) in RCA: 143] [Impact Index Per Article: 20.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2016] [Revised: 01/13/2017] [Accepted: 01/17/2017] [Indexed: 10/20/2022]
Abstract
This article discusses retinal oxygenation and retinal metabolism by focusing on measurements made with two of the principal methods used to study O2 in the retina: measurements of PO2 with oxygen-sensitive microelectrodes in vivo in animals with a retinal circulation similar to that of humans, and oximetry, which can be used non-invasively in both animals and humans to measure O2 concentration in retinal vessels. Microelectrodes uniquely have high spatial resolution, allowing the mapping of PO2 in detail, and when combined with mathematical models of diffusion and consumption, they provide information about retinal metabolism. Mathematical models, grounded in experiments, can also be used to simulate situations that are not amenable to experimental study. New methods of oximetry, particularly photoacoustic ophthalmoscopy and visible light optical coherence tomography, provide depth-resolved methods that can separate signals from blood vessels and surrounding tissues, and can be combined with blood flow measures to determine metabolic rate. We discuss the effects on retinal oxygenation of illumination, hypoxia and hyperoxia, and describe retinal oxygenation in diabetes, retinal detachment, arterial occlusion, and macular degeneration. We explain how the metabolic measurements obtained from microelectrodes and imaging are different, and how they need to be brought together in the future. Finally, we argue for revisiting the clinical use of hyperoxia in ophthalmology, particularly in retinal arterial occlusions and retinal detachment, based on animal research and diffusion theory.
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Affiliation(s)
- Robert A Linsenmeier
- Biomedical Engineering Department, Northwestern University, 2145 Sheridan Road, Evanston 60208-3107, IL, USA; Neurobiology Department, Northwestern University, 2205 Tech Drive, Evanston 60208-3520, IL, USA; Ophthalmology Department, Northwestern University, 645 N. Michigan Ave, Suite 440, Chicago 60611, IL, USA.
| | - Hao F Zhang
- Biomedical Engineering Department, Northwestern University, 2145 Sheridan Road, Evanston 60208-3107, IL, USA; Ophthalmology Department, Northwestern University, 645 N. Michigan Ave, Suite 440, Chicago 60611, IL, USA.
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14
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Merkle CW, Leahy C, Srinivasan VJ. Dynamic contrast optical coherence tomography images transit time and quantifies microvascular plasma volume and flow in the retina and choriocapillaris. BIOMEDICAL OPTICS EXPRESS 2016; 7:4289-4312. [PMID: 27867732 PMCID: PMC5102529 DOI: 10.1364/boe.7.004289] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/30/2016] [Revised: 08/19/2016] [Accepted: 09/16/2016] [Indexed: 05/18/2023]
Abstract
Despite the prevalence of optical imaging techniques to measure hemodynamics in large retinal vessels, quantitative measurements of retinal capillary and choroidal hemodynamics have traditionally been challenging. Here, a new imaging technique called dynamic contrast optical coherence tomography (DyC-OCT) is applied in the rat eye to study microvascular blood flow in individual retinal and choroidal layers in vivo. DyC-OCT is based on imaging the transit of an intravascular tracer dynamically as it passes through the field-of-view. Hemodynamic parameters can be determined through quantitative analysis of tracer kinetics. In addition to enabling depth-resolved transit time, volume, and flow measurements, the injected tracer also enhances OCT angiograms and enables clear visualization of the choriocapillaris, particularly when combined with a post-processing method for vessel enhancement. DyC-OCT complements conventional OCT angiography through quantification of tracer dynamics, similar to fluorescence angiography, but with the important added benefit of laminar resolution.
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Affiliation(s)
- Conrad W. Merkle
- Department of Biomedical Engineering, University of California Davis, Davis, California, USA
| | - Conor Leahy
- Department of Biomedical Engineering, University of California Davis, Davis, California, USA
| | - Vivek J. Srinivasan
- Department of Biomedical Engineering, University of California Davis, Davis, California, USA
- Department of Ophthalmology and Vision Science, University of California Davis School of Medicine, Sacramento, California, USA
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15
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Albaugh DL, Salzwedel A, Van Den Berge N, Gao W, Stuber GD, Shih YYI. Functional Magnetic Resonance Imaging of Electrical and Optogenetic Deep Brain Stimulation at the Rat Nucleus Accumbens. Sci Rep 2016; 6:31613. [PMID: 27601003 PMCID: PMC5013271 DOI: 10.1038/srep31613] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2016] [Accepted: 07/25/2016] [Indexed: 01/16/2023] Open
Abstract
Deep brain stimulation of the nucleus accumbens (NAc-DBS) is an emerging therapy for diverse, refractory neuropsychiatric diseases. Although DBS therapy is broadly hypothesized to work through large-scale neural modulation, little is known regarding the neural circuits and networks affected by NAc-DBS. Using a healthy, sedated rat model of NAc-DBS, we employed both evoked- and functional connectivity (fc) MRI to examine the functional circuit and network changes achieved by electrical NAc stimulation. Optogenetic-fMRI experiments were also undertaken to evaluate the circuit modulation profile achieved by selective stimulation of NAc neurons. NAc-DBS directly modulated neural activity within prefrontal cortex and a large number of subcortical limbic areas (e.g., amygdala, lateral hypothalamus), and influenced functional connectivity among sensorimotor, executive, and limbic networks. The pattern and extent of circuit modulation measured by evoked-fMRI was relatively insensitive to DBS frequency. Optogenetic stimulation of NAc cell bodies induced a positive fMRI signal in the NAc, but no other detectable downstream responses, indicating that therapeutic NAc-DBS might exert its effect through antidromic stimulation. Our study provides a comprehensive mapping of circuit and network-level neuromodulation by NAc-DBS, which should facilitate our developing understanding of its therapeutic mechanisms of action.
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Affiliation(s)
- Daniel L. Albaugh
- Department of Neurology, University of North Carolina, Chapel Hill, NC, 27599, USA
- Biomedical Research Imaging Center, University of North Carolina, Chapel Hill, NC, 27599, USA
- Curriculum in Neurobiology, University of North Carolina, Chapel Hill, NC, 27599, USA
| | - Andrew Salzwedel
- Biomedical Research Imaging Center, University of North Carolina, Chapel Hill, NC, 27599, USA
- Department of Radiology, University of North Carolina, Chapel Hill, NC, 27599, USA
- Biomedical Imaging Research Institute, Department of Biomedical Sciences and Imaging, Cedars-Sinai Medical Center, Los Angeles, CA, 90048, USA
| | - Nathalie Van Den Berge
- Department of Neurology, University of North Carolina, Chapel Hill, NC, 27599, USA
- Biomedical Research Imaging Center, University of North Carolina, Chapel Hill, NC, 27599, USA
- Medical Image and Signal Processing Group, Ghent University, Ghent, 9000, Belgium
| | - Wei Gao
- Biomedical Research Imaging Center, University of North Carolina, Chapel Hill, NC, 27599, USA
- Department of Radiology, University of North Carolina, Chapel Hill, NC, 27599, USA
- Biomedical Imaging Research Institute, Department of Biomedical Sciences and Imaging, Cedars-Sinai Medical Center, Los Angeles, CA, 90048, USA
| | - Garret D. Stuber
- Curriculum in Neurobiology, University of North Carolina, Chapel Hill, NC, 27599, USA
- Department of Psychiatry, University of North Carolina, Chapel Hill, NC, 27599, USA
| | - Yen-Yu Ian Shih
- Department of Neurology, University of North Carolina, Chapel Hill, NC, 27599, USA
- Biomedical Research Imaging Center, University of North Carolina, Chapel Hill, NC, 27599, USA
- Curriculum in Neurobiology, University of North Carolina, Chapel Hill, NC, 27599, USA
- Department of Biomedical Engineering, University of North Carolina, Chapel Hill, NC, 27599, USA
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16
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Zhou ZC, Salzwedel AP, Radtke-Schuller S, Li Y, Sellers KK, Gilmore JH, Shih YYI, Fröhlich F, Gao W. Resting state network topology of the ferret brain. Neuroimage 2016; 143:70-81. [PMID: 27596024 DOI: 10.1016/j.neuroimage.2016.09.003] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2016] [Revised: 08/17/2016] [Accepted: 09/01/2016] [Indexed: 12/22/2022] Open
Abstract
Resting state functional magnetic resonance imaging (rsfMRI) has emerged as a versatile tool for non-invasive measurement of functional connectivity patterns in the brain. RsfMRI brain dynamics in rodents, non-human primates, and humans share similar properties; however, little is known about the resting state functional connectivity patterns in the ferret, an animal model with high potential for developmental and cognitive translational study. To address this knowledge-gap, we performed rsfMRI on anesthetized ferrets using a 9.4T MRI scanner, and subsequently performed group-level independent component analysis (gICA) to identify functionally connected brain networks. Group-level ICA analysis revealed distributed sensory, motor, and higher-order networks in the ferret brain. Subsequent connectivity analysis showed interconnected higher-order networks that constituted a putative default mode network (DMN), a network that exhibits altered connectivity in neuropsychiatric disorders. Finally, we assessed ferret brain topological efficiency using graph theory analysis and found that the ferret brain exhibits small-world properties. Overall, these results provide additional evidence for pan-species resting-state networks, further supporting ferret-based studies of sensory and cognitive function.
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Affiliation(s)
- Zhe Charles Zhou
- Department of Psychiatry, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, United States; Neurobiology Curriculum, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, United States
| | - Andrew P Salzwedel
- Biomedical Imaging Research Institute, Cedars-Sinai Medical Center, Los Angeles, CA 90048, United States; Department of Biomedical Sciences, Cedars-Sinai Medical Center, Los Angeles, CA 90048, United States
| | - Susanne Radtke-Schuller
- Department of Psychiatry, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, United States
| | - Yuhui Li
- Department of Psychiatry, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, United States
| | - Kristin K Sellers
- Department of Psychiatry, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, United States; Neurobiology Curriculum, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, United States
| | - John H Gilmore
- Department of Psychiatry, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, United States
| | - Yen-Yu Ian Shih
- Department of Biomedical Engineering, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, United States; Department of Neurology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, United States; Biomedical Research Imaging Center, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, United States; Small Animal Imaging Facility, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, United States; Neuroscience Center, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, United States; Neurobiology Curriculum, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, United States
| | - Flavio Fröhlich
- Department of Psychiatry, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, United States; Department of Cell Biology and Physiology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, United States; Department of Biomedical Engineering, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, United States; Department of Neurology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, United States; Neuroscience Center, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, United States; Neurobiology Curriculum, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, United States
| | - Wei Gao
- Biomedical Imaging Research Institute, Cedars-Sinai Medical Center, Los Angeles, CA 90048, United States; Department of Biomedical Sciences, Cedars-Sinai Medical Center, Los Angeles, CA 90048, United States.
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17
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Kam JH, Jeffery G. To unite or divide: mitochondrial dynamics in the murine outer retina that preceded age related photoreceptor loss. Oncotarget 2016; 6:26690-701. [PMID: 26393878 PMCID: PMC4694945 DOI: 10.18632/oncotarget.5614] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2015] [Accepted: 08/27/2015] [Indexed: 12/18/2022] Open
Abstract
Mitochondrial function declines with age and is associated with age-related disorders and cell death. In the retina this is critical as photoreceptor energy demands are the greatest in the body and aged cell loss large (~30%). But mitochondria can fuse or divide to accommodate changing demands. We explore ageing mitochondrial dynamics in young (1 month) and old (12 months) mouse retina, investigating changes in mitochondrial fission (Fis1) and fusion (Opa1) proteins, cytochrome C oxidase (COX III), which reflects mitochondrial metabolic status, and heat shock protein 60 (Hsp60) that is a mitochondrial chaperon for protein folding.Western blots showed each protein declined with age. However, within this, immunostaining revealed increases of around 50% in Fis1 and Opa1 in photoreceptor inner segments (IS). Electron microscope analysis revealed mitochondrial fragmentation with age and marked changes in morphology in IS, consistent with elevated dynamics. COX III declined by approximately 30% in IS, but Hsp60 reductions were around 80% in the outer plexiform layer.Our results are consistent with declining mitochondrial metabolism. But also with increased photoreceptor mitochondrial dynamics that differ from other retinal regions, perhaps reflecting attempts to maintain function. These changes are the platform for age related photoreceptor loss initiated after 12 months.
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Affiliation(s)
- Jaimie Hoh Kam
- Institute of Ophthalmology, University College London, London, UK
| | - Glen Jeffery
- Institute of Ophthalmology, University College London, London, UK
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18
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Chandra S, Muir ER, Deo K, Kiel JW, Duong TQ. Effects of Dorzolamide on Retinal and Choroidal Blood Flow in the DBA/2J Mouse Model of Glaucoma. Invest Ophthalmol Vis Sci 2016; 57:826-31. [PMID: 26934140 PMCID: PMC4777278 DOI: 10.1167/iovs.15-18291] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
PURPOSE To test the hypothesis that acute topical dorzolamide (DZ) decreases intraocular pressure (IOP) and increases retinal and choroidal blood flow in the DBA/2J mouse model of glaucoma. METHODS Retinal and choroidal blood flow were measured in 4- and 9-month-old DBA/2J mice, and 4-month C57BL/6 (control) mice under isoflurane anesthesia using magnetic resonance imaging. Ocular blood flow was measured at baseline, and 1 and 2 hours after topical dorzolamide. Intraocular pressure was measured using a rebound tonometer in a subset of animals at the same time points. RESULTS Baseline IOP in the 4-month-old DBA/2J mice and C57BL/6 mice was not significantly different (P > 0.05), and IOP in both groups was less than in the 9-month-old DBA/2J mice (P < 0.05 for both). Compared to baseline, dorzolamide reduced IOP at 1 and 2 hours after dorzolamide in the 4- (P < 0.05) and 9-month-old (P < 0.01) DBA/2J mice, but not in the C57BL/6J mice (P > 0.05). Baseline retinal blood flow was lower in the 4-month and 9-month-old DBA/2J mice compared with the 4-month-old C57BL/6J mice (P < 0.05). Baseline choroidal blood flow in the 9-month-old DBA/2J mice was less than in the C57BL/6J mice (P < 0.05). Compared with baseline, both retinal and choroidal blood flow increased at 1-hour post-dorzolamide and remained elevated 2 hours later in the 9-month-old DBA/2J mice (P < 0.05). CONCLUSIONS Dorzolamide lowers IOP and raises retinal and choroidal blood flow in older DBA/2J mice, consistent with the study hypothesis.
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19
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Alagöz C, Pekel G, Alagöz N, Sayın N, Yüksel K, Yıldırım Y, Yazıcı AT. Choroidal Thickness, Photoreceptor Thickness, and Retinal Vascular Caliber Alterations in Dark Adaptation. Curr Eye Res 2016; 41:1608-1613. [PMID: 27159535 DOI: 10.3109/02713683.2015.1135961] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
PURPOSE Our aim was to evaluate the alterations of subfoveal choroidal thickness (SFCT), photoreceptor layer thickness (PRT), and retinal vessel diameter in the dark and light adaptation. METHODS Twenty-four eyes of 24 healthy volunteers (12 males, 12 females) were included in this cross-sectional and observational study. The SFCT, PRT, retinal arteriole, and venule caliber measurements were performed with spectral domain optical coherence tomography in the dark (0.0 cd/m2) and under light (80 cd/m2) adapted conditions. RESULTS The mean age of the participants was 30.4 ± 4.4 years (range: 22-42). The SFCT increased statistically significantly in dark adaptation (p < 0.001), then returned to baseline values following light adaptation. The PRT, retinal arteriole, and venule caliber measurements were similar in the dark and light (p > 0.05). CONCLUSIONS While SFCT increased, PRT, and retinal vessel diameter did not change following transition from light to dark.
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Affiliation(s)
- Cengiz Alagöz
- a Beyoglu Eye Training and Research Hospital, Eye Clinic , Istanbul , Turkey
| | - Gökhan Pekel
- b Pamukkale University , Ophthalmology Department , Denizli , Turkey
| | - Neşe Alagöz
- a Beyoglu Eye Training and Research Hospital, Eye Clinic , Istanbul , Turkey
| | - Nihat Sayın
- c Kanuni Sultan Suleyman Training and Research Hospital, Eye Clinic , Istanbul , Turkey
| | - Kemal Yüksel
- a Beyoglu Eye Training and Research Hospital, Eye Clinic , Istanbul , Turkey
| | - Yusuf Yıldırım
- a Beyoglu Eye Training and Research Hospital, Eye Clinic , Istanbul , Turkey
| | - Ahmet Taylan Yazıcı
- a Beyoglu Eye Training and Research Hospital, Eye Clinic , Istanbul , Turkey
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Application of Arterial Spin Labelling in the Assessment of Ocular Tissues. BIOMED RESEARCH INTERNATIONAL 2016; 2016:6240504. [PMID: 27066501 PMCID: PMC4811053 DOI: 10.1155/2016/6240504] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/05/2015] [Accepted: 02/07/2016] [Indexed: 11/17/2022]
Abstract
Arterial spin labelling (ASL) is a noninvasive magnetic resonance imaging (MRI) modality, capable of measuring blood perfusion without the use of a contrast agent. While ASL implementation for imaging the brain and monitoring cerebral blood flow has been reviewed in depth, the technique is yet to be widely used for ocular tissue imaging. The human retina is a very thin but highly stratified structure and it is also situated close to the surface of the body which is not ideal for MR imaging. Hence, the application of MR imaging and ASL in particular has been very challenging for ocular tissues and retina. That is despite the fact that almost all of retinal pathologies are accompanied by blood perfusion irregularities. In this review article, we have focused on the technical aspects of the ASL and their implications for its optimum adaptation for retinal blood perfusion monitoring. Retinal blood perfusion has been assessed through qualitative or invasive quantitative methods but the prospect of imaging flow using ASL would increase monitoring and assessment of retinal pathologies. The review provides details of ASL application in human ocular blood flow assessment.
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Berkowitz BA, Bissig D, Roberts R. MRI of rod cell compartment-specific function in disease and treatment in vivo. Prog Retin Eye Res 2015; 51:90-106. [PMID: 26344734 DOI: 10.1016/j.preteyeres.2015.09.001] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2015] [Revised: 08/26/2015] [Accepted: 09/01/2015] [Indexed: 10/23/2022]
Abstract
Rod cell oxidative stress is a major pathogenic factor in retinal disease, such as diabetic retinopathy (DR) and retinitis pigmentosa (RP). Personalized, non-destructive, and targeted treatment for these diseases remains elusive since current imaging methods cannot analytically measure treatment efficacy against rod cell compartment-specific oxidative stress in vivo. Over the last decade, novel MRI-based approaches that address this technology gap have been developed. This review summarizes progress in the development of MRI since 2006 that enables earlier evaluation of the impact of disease on rod cell compartment-specific function and the efficacy of anti-oxidant treatment than is currently possible with other methods. Most of the new assays of rod cell compartment-specific function are based on endogenous contrast mechanisms, and this is expected to facilitate their translation into patients with DR and RP, and other oxidative stress-based retinal diseases.
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Affiliation(s)
- Bruce A Berkowitz
- Dept. of Anatomy and Cell Biology, Wayne State University School of Medicine, Detroit, MI, USA; Dept. Of Ophthalmology, Wayne State University School of Medicine, Detroit, MI, USA.
| | - David Bissig
- Dept. of Anatomy and Cell Biology, Wayne State University School of Medicine, Detroit, MI, USA
| | - Robin Roberts
- Dept. Of Ophthalmology, Wayne State University School of Medicine, Detroit, MI, USA
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22
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Muir ER, Chandra SB, De La Garza BH, Velagapudi C, Abboud HE, Duong TQ. Layer-Specific Manganese-Enhanced MRI of the Diabetic Rat Retina in Light and Dark Adaptation at 11.7 Tesla. Invest Ophthalmol Vis Sci 2015; 56:4006-12. [PMID: 26098468 DOI: 10.1167/iovs.14-16128] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
PURPOSE To employ high-resolution manganese-enhanced MRI (MEMRI) to study abnormal calcium activity in different cell layers in streptozotocin-induced diabetic rat retinas, and to determine whether MEMRI detects changes at earlier time points than previously reported. METHODS Sprague-Dawley rats were studied 14 days (n = 8) and 30 days (n = 5) after streptozotocin (STZ) or vehicle (n = 7) injection. Manganese-enhanced MRI at 20 × 20 × 700 μm, in which contrast is based on manganese as a calcium analogue and an MRI contrast agent, was obtained in light and dark adaptation of the retina in the same animals in which one eye was covered and the fellow eye was not. The MEMRI activity encoding of the light and dark adaptation was achieved in awake conditions and imaged under anesthesia. RESULTS Manganese-enhanced MRI showed three layers, corresponding to the inner retina, outer retina, and the choroid. In normal animals, the outer retina showed higher MEMRI activity in dark compared to light; the inner retina displayed lower activity in dark compared to light; and the choroid showed no difference in activity. Manganese-enhanced MRI activity changed as early as 14 days after hyperglycemia and decreased with duration of hyperglycemia in the outer retina in dark relative to light adaptation. The choroid also had altered MEMRI activity at 14 days, which returned to normal by 30 days. No differences in MEMRI activity were detected in the inner retina. CONCLUSIONS Manganese-enhanced MRI detects progressive reduction in calcium activity with duration of hyperglycemia in the outer retina as early as 14 days after hyperglycemia, earlier than any other time point reported in the literature.
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Affiliation(s)
- Eric R Muir
- Research Imaging Institute, University of Texas Health Science Center, San Antonio, Texas, United States 2Departments of Ophthalmology, Radiology, and Physiology, University of Texas Health Science Center, San Antonio, Texas, United States
| | - Saurav B Chandra
- Research Imaging Institute, University of Texas Health Science Center, San Antonio, Texas, United States
| | - Bryan H De La Garza
- Research Imaging Institute, University of Texas Health Science Center, San Antonio, Texas, United States
| | - Chakradhar Velagapudi
- Department of Medicine, University of Texas Health Science Center, San Antonio, Texas, United States
| | - Hanna E Abboud
- Department of Medicine, University of Texas Health Science Center, San Antonio, Texas, United States
| | - Timothy Q Duong
- Research Imaging Institute, University of Texas Health Science Center, San Antonio, Texas, United States 2Departments of Ophthalmology, Radiology, and Physiology, University of Texas Health Science Center, San Antonio, Texas, United States 4South Texas Ve
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23
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Sun N, Ly A, Meding S, Witting M, Hauck SM, Ueffing M, Schmitt-Kopplin P, Aichler M, Walch A. High-resolution metabolite imaging of light and dark treated retina using MALDI-FTICR mass spectrometry. Proteomics 2014; 14:913-23. [PMID: 24459044 DOI: 10.1002/pmic.201300407] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2013] [Revised: 12/06/2013] [Accepted: 12/20/2013] [Indexed: 11/06/2022]
Abstract
MS imaging (MSI) is a valuable tool for diagnostics and systems biology studies, being a highly sensitive, label-free technique capable of providing comprehensive spatial distribution of different classes of biomolecules. The application of MSI to the study of endogenous compounds has received considerable attention because metabolites are the result of the interactions of a biosystem with its environment. MSI can therefore enhance understanding of disease mechanisms and elucidate mechanisms for biological variation. We present the in situ comparative metabolomics imaging data for analyses of light- and dark-treated retina using MALDI-FTICR. A wide variety of tissue metabolites were imaged at a high spatial resolution. These include nucleotides, central carbon metabolism pathway intermediates, 2-oxocarboxylic acid metabolism, oxidative phosphorylation, glycerophospholipid metabolism, and cysteine and methionine metabolites. The high lateral resolution enabled the differentiation of retinal layers, allowing determination of the spatial distributions of different endogenous compounds. A number of metabolites demonstrated differences between light and dark conditions. These findings add to the understanding of metabolic activity in the retina.
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Affiliation(s)
- Na Sun
- Research Unit Analytical Pathology, Institute of Pathology, Helmholtz Zentrum München, German Research Center for Environmental Health GmbH, Neuherberg, Germany
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24
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Berkowitz BA, Gorgis J, Patel A, Baameur F, Gurevich VV, Craft CM, Kefalov VJ, Roberts R. Development of an MRI biomarker sensitive to tetrameric visual arrestin 1 and its reduction via light-evoked translocation in vivo. FASEB J 2014; 29:554-64. [PMID: 25351983 DOI: 10.1096/fj.14-254953] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Rod tetrameric arrestin 1 (tet-ARR1), stored in the outer nuclear layer/inner segments in the dark, modulates photoreceptor synaptic activity; light exposure stimulates a reduction via translocation to the outer segments for terminating G-protein coupled phototransduction signaling. Here, we test the hypothesis that intraretinal spin-lattice relaxation rate in the rotating frame (1/T1ρ), an endogenous MRI contrast mechanism, has high potential for evaluating rod tet-ARR1 and its reduction via translocation. Dark- and light-exposed mice (null for the ARR1 gene, overexpressing ARR1, diabetic, or wild type with or without treatment with Mn2+, a calcium channel probe) were studied using 1/T1ρ MRI. Immunohistochemistry and single-cell recordings of the retinas were also performed. In wild-type mice with or without treatment with Mn2+, 1/T1ρ of avascular outer retina (64% to 72% depth) was significantly (P < 0.05) greater in the dark than in the light; a significant (P < 0.05) but opposite pattern was noted in the inner retina (<50% depth). Light-evoked outer retina Δ1/T1ρ was absent in ARR1-null mice and supernormal in overexpressing mice. In diabetic mice, the outer retinal Δ1/T1ρ pattern suggested normal dark-to-light tet-ARR1 translocation and chromophore content, conclusions confirmed ex vivo. Light-stimulated Δ1/T1ρ in inner retina was linked to changes in blood volume. Our data support 1/T1ρ MRI for noninvasively assessing rod tet-ARR1 and its reduction via protein translocation, which can be combined with other metrics of retinal function in vivo.
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Affiliation(s)
- Bruce A Berkowitz
- Department of Anatomy and Cell Biology and Department of Ophthalmology, Wayne State University, Detroit, Michigan, USA;
| | | | | | - Faiza Baameur
- Department of Pharmacology, Vanderbilt University, Nashville, Tennessee, USA
| | - Vsevolod V Gurevich
- Department of Pharmacology, Vanderbilt University, Nashville, Tennessee, USA
| | - Cheryl M Craft
- Mary D. Allen Laboratory for Vision Research, USC Eye Institute, and Department of Ophthalmology and Department of Cell and Neurobiology, Keck School of Medicine of the University of Southern California, Los Angeles, California, USA; and
| | - Vladimir J Kefalov
- Department of Ophthalmology and Visual Sciences, Washington University in St. Louis, St. Louis, Missouri, USA
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25
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Teng PY, Wanek J, Blair NP, Shahidi M. Response of inner retinal oxygen extraction fraction to light flicker under normoxia and hypoxia in rat. Invest Ophthalmol Vis Sci 2014; 55:6055-8. [PMID: 25183761 DOI: 10.1167/iovs.13-13811] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
PURPOSE Oxygen extraction fraction (OEF), defined by the ratio of oxygen metabolism (MO2) to delivery (DO2), determines the level of compensation of MO2 by DO2. In the current study, we tested the hypothesis that inner retinal OEF remains unchanged during light flicker under systemic normoxia and hypoxia in rats due to the matching of MO2 and DO2. METHODS Retinal vascular oxygen tension (PO2) measurements were obtained in 10 rats by phosphorescence lifetime imaging. Inner retinal OEF was derived from vascular PO2 based on Fick's principle. Measurements were obtained before and during light flicker under systemic normoxia and hypoxia. The effects of light flicker and systemic oxygenation on retinal vascular PO2 and OEF were determined by ANOVA. RESULTS During light flicker, retinal venous PO2 decreased (P < 0.01, N = 10), while inner retinal OEF increased (P = 0.02). Under hypoxia, retinal arterial and venous PO2 decreased (P < 0.01), while OEF increased (P < 0.01). The interaction effect was not significant on OEF (P = 0.52), indicating the responses of OEF to light flicker were similar under normoxia and hypoxia. During light flicker, OEF increased from 0.46 ± 0.13 to 0.50 ± 0.11 under normoxia, while under hypoxia, OEF increased from 0.67 ± 0.16 to 0.74 ± 0.14. CONCLUSIONS Inner retinal OEF increased during light flicker, indicating the relative change in DO2 is less than that in MO2 in rats under systemic normoxia and hypoxia. Inner retinal OEF is a potentially useful parameter for assessment of the relative changes of MO2 and DO2 under physiologic and pathologic conditions.
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Affiliation(s)
- Pang-yu Teng
- Department of Ophthalmology & Visual Sciences, University of Illinois at Chicago, Chicago, Illinois, United States
| | - Justin Wanek
- Department of Ophthalmology & Visual Sciences, University of Illinois at Chicago, Chicago, Illinois, United States
| | - Norman P Blair
- Department of Ophthalmology & Visual Sciences, University of Illinois at Chicago, Chicago, Illinois, United States
| | - Mahnaz Shahidi
- Department of Ophthalmology & Visual Sciences, University of Illinois at Chicago, Chicago, Illinois, United States
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26
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Imaging neurovascular function and functional recovery after stroke in the rat striatum using forepaw stimulation. J Cereb Blood Flow Metab 2014; 34:1483-92. [PMID: 24917039 PMCID: PMC4158660 DOI: 10.1038/jcbfm.2014.103] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/11/2013] [Revised: 05/05/2014] [Accepted: 05/07/2014] [Indexed: 12/19/2022]
Abstract
Negative functional magnetic resonance imaging (fMRI) response in the striatum has been observed in several studies during peripheral sensory stimulation, but its relationship between local field potential (LFP) remains to be elucidated. We performed cerebral blood volume (CBV) fMRI and LFP recordings in normal rats during graded noxious forepaw stimulation at nine stimulus pulse widths. Albeit high LFP-CBV correlation was found in the ipsilateral and contralateral sensory cortices (r=0.89 and 0.95, respectively), the striatal CBV responses were neither positively, nor negatively correlated with LFP (r=0.04), demonstrating that the negative striatal CBV response is not originated from net regional inhibition. To further identify whether this negative CBV response can serve as a marker for striatal functional recovery, two groups of rats (n=5 each) underwent 20- and 45-minute middle cerebral artery occlusion (MCAO) were studied. No CBV response was found in the ipsilateral striatum in both groups immediately after stroke. Improved striatal CBV response was observed on day 28 in the 20-minute MCAO group compared with the 45-minute MCAO group (P<0.05). This study shows that fMRI signals could differ significantly from LFP and that the observed negative CBV response has potential to serve as a marker for striatal functional integrity in rats.
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27
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Abcouwer SF, Gardner TW. Diabetic retinopathy: loss of neuroretinal adaptation to the diabetic metabolic environment. Ann N Y Acad Sci 2014; 1311:174-90. [PMID: 24673341 DOI: 10.1111/nyas.12412] [Citation(s) in RCA: 162] [Impact Index Per Article: 16.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Diabetic retinopathy (DR) impairs vision of patients with type 1 and type 2 diabetes, associated with vascular dysfunction and occlusion, retinal edema, hemorrhage, and inappropriate growth of new blood vessels. The recent success of biologic treatments targeting vascular endothelial growth factor (VEGF) demonstrates that treating the vascular aspects in the later stages of the disease can preserve vision in many patients. It would also be highly desirable to prevent the onset of the disease or arrest its progression at a stage preceding the appearance of overt microvascular pathologies. The progression of DR is not necessarily linear but may follow a series of steps that evolve over the course of multiple years. Abundant data suggest that diabetes affects the entire neurovascular unit of the retina, with an early loss of neurovascular coupling, gradual neurodegeneration, gliosis, and neuroinflammation occurring before observable vascular pathologies. In this article, we consider the pathology of DR from the point of view that diabetes causes measurable dysfunctions in the complex integral network of cell types that produce and maintain human vision.
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Affiliation(s)
- Steven F Abcouwer
- Department of Ophthalmology and Visual Sciences, University of Michigan Kellogg Eye Center, Ann Arbor, Michigan
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28
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Wanek J, Teng PY, Blair NP, Shahidi M. Inner retinal oxygen delivery and metabolism in streptozotocin diabetic rats. Invest Ophthalmol Vis Sci 2014; 55:1588-93. [PMID: 24550355 DOI: 10.1167/iovs.13-13537] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
PURPOSE The purpose of the study is to report global measurements of inner retinal oxygen delivery (DO2_IR) and oxygen metabolism (MO2_IR) in streptozotocin (STZ) diabetic rats. METHODS Phosphorescence lifetime and blood flow imaging were performed in rats 4 (STZ/4 wk; n = 10) and 6 (STZ/6 wk; n = 10) weeks following injection of STZ to measure retinal arterial (O2A) and venous (O2V) oxygen contents and total retinal blood flow (F). DO2_IR and MO2_IR were calculated from measurements of F and O2A and of F and the arteriovenous oxygen content difference, respectively. Data in STZ rats were compared to those in healthy control rats (n = 10). RESULTS Measurements of O2A and O2V were not significantly different among STZ/4 wk, STZ/6 wk, and control rats (P ≥ 0.28). Likewise, F was similar among all groups of rats (P = 0.81). DO2_IR measurements were 941 ± 231, 956 ± 232, and 973 ± 243 nL O2/min in control, STZ/4 wk, and STZ/6 wk rats, respectively (P = 0.95). MO2_IR measurements were 516 ± 175, 444 ± 103, and 496 ± 84 nL O2/min in control, STZ/4 wk, and STZ/6 wk rats, respectively (P = 0.37). CONCLUSIONS Global inner retinal oxygen delivery and metabolism were not significantly impaired in STZ rats in early diabetes.
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Affiliation(s)
- Justin Wanek
- Department of Ophthalmology and Visual Sciences, University of Illinois at Chicago, Chicago, Illinois
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29
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Werkmeister RM, Vietauer M, Knopf C, Fürnsinn C, Leitgeb RA, Reitsamer H, Gröschl M, Garhöfer G, Vilser W, Schmetterer L. Measurement of retinal blood flow in the rat by combining Doppler Fourier-domain optical coherence tomography with fundus imaging. JOURNAL OF BIOMEDICAL OPTICS 2014; 19:106008. [PMID: 25321400 DOI: 10.1117/1.jbo.19.10.106008] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/24/2014] [Accepted: 09/22/2014] [Indexed: 05/22/2023]
Abstract
A wide variety of ocular diseases are associated with abnormalities in ocular circulation. As such, there is considerable interest in techniques for quantifying retinal blood flow, among which Doppler optical coherence tomography (OCT) may be the most promising. We present an approach to measure retinal blood flow in the rat using a new optical system that combines the measurement of blood flow velocities via Doppler Fourier-domain optical coherence tomography and the measurement of vessel diameters using a fundus camera-based technique. Relying on fundus images for extraction of retinal vessel diameters instead of OCT images improves the reliability of the technique. The system was operated with an 841-nm superluminescent diode and a charge-coupled device camera that could be operated at a line rate of 20 kHz. We show that the system is capable of quantifying the response of 100% oxygen breathing on the retinal blood flow. In six rats, we observed a decrease in retinal vessel diameters of 13.2% and a decrease in retinal blood velocity of 42.6%, leading to a decrease in retinal blood flow of 56.7%. Furthermore, in four rats, the response of retinal blood flow during stimulation with diffuse flicker light was assessed. Retinal vessel diameter and blood velocity increased by 3.4% and 28.1%, respectively, leading to a relative increase in blood flow of 36.2%. The presented technique shows much promise to quantify early changes in retinal blood flow during provocation with various stimuli in rodent models of ocular diseases in rats.
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Affiliation(s)
- René M Werkmeister
- Medical University of Vienna, Center for Medical Physics and Biomedical Engineering, Währinger Gürtel 18-20, 1090 Vienna, Austria
| | - Martin Vietauer
- Medical University of Vienna, Center for Medical Physics and Biomedical Engineering, Währinger Gürtel 18-20, 1090 Vienna, AustriabVienna University of Technology, Institute of Applied Physics, Wiedner Hauptstrasse 8-10/134, 1040 Vienna, Austria
| | - Corinna Knopf
- Medical University of Vienna, Center for Medical Physics and Biomedical Engineering, Währinger Gürtel 18-20, 1090 Vienna, Austria
| | - Clemens Fürnsinn
- Medical University of Vienna, Department of Internal Medicine II, Währinger Gürtel 18-20, 1090 Vienna, Austria
| | - Rainer A Leitgeb
- Medical University of Vienna, Center for Medical Physics and Biomedical Engineering, Währinger Gürtel 18-20, 1090 Vienna, Austria
| | - Herbert Reitsamer
- Paracelsus University, Department of Ophthalmology, Müllner Hauptstraße 48, 5020 Salzburg, Austria
| | - Martin Gröschl
- Vienna University of Technology, Institute of Applied Physics, Wiedner Hauptstrasse 8-10/134, 1040 Vienna, Austria
| | - Gerhard Garhöfer
- Medical University of Vienna, Department of Clinical Pharmacology, Währinger Gürtel 18-20, 1090 Vienna, Austria
| | | | - Leopold Schmetterer
- Medical University of Vienna, Center for Medical Physics and Biomedical Engineering, Währinger Gürtel 18-20, 1090 Vienna, AustriaeMedical University of Vienna, Department of Clinical Pharmacology, Währinger Gürtel 18-20, 1090 Vienna, Austria
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Shih YYI, De La Garza BH, Huang S, Li G, Wang L, Duong TQ. Comparison of retinal and cerebral blood flow between continuous arterial spin labeling MRI and fluorescent microsphere techniques. J Magn Reson Imaging 2013; 40:609-15. [PMID: 24227681 DOI: 10.1002/jmri.24407] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2013] [Accepted: 08/05/2013] [Indexed: 01/09/2023] Open
Abstract
PURPOSE To compare basal retinal and cerebral blood flow (BF) values using continuous arterial spin labeling (CASL) MRI and fluorescent microspheres. MATERIALS AND METHODS A total of 41 animals were used. BF was measured using an established microsphere technique (a mixture of 2.5 million 8 μm green and 0.5 million 10 μm blue fluorescent microspheres) and CASL MRI blood flow measurement in the rat retina and brain at 7 Tesla (T) and 11.7T, respectively. RESULTS Retinal BF by MRI was 1.18 ± 0.57 mL/g/min and choroidal BF was 8.14 ± 1.8 mL/g/min (n = 6). Microsphere retinal BF was 9.12 ± 2.8 μL/min per tissue and choroidal BF was 73.38 ± 44 μL/min per tissue (n = 18), corresponding to a retinal BF value of 1.22 ± 0.36 mL/g/min by means of a wet weight conversion. The wet-weight of the choroid could not be determined. To corroborate our findings, cerebral BF (CBF) by MRI was also analyzed. In the cerebral cortices, CBF was 0.91 ± 0.29 mL/g/min (n = 14) by CASL MRI and 1.09 ± 0.37 mL/g/min (n = 6) by microspheres. There were no significant differences found between MRI and microsphere blood flow in the retina and brain. CONCLUSION BF values in the rat retina and cerebral cortex by MRI are in agreement with those obtained by the microsphere technique.
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Affiliation(s)
- Yen-Yu I Shih
- Departments of Neurology, Biomedical Research Imaging Center, and Biomedical Engineering, University of North Carolina, Chapel Hill, North Carolina, USA; Research Imaging Institute, University of Texas Health Science Center at San Antonio, San Antonio, Texas, USA
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31
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Shih YYI, Yash TV, Rogers B, Duong TQ. FMRI of deep brain stimulation at the rat ventral posteromedial thalamus. Brain Stimul 2013; 7:190-3. [PMID: 24309153 DOI: 10.1016/j.brs.2013.11.001] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2013] [Revised: 09/25/2013] [Accepted: 11/01/2013] [Indexed: 10/26/2022] Open
Abstract
BACKGROUND Functional magnetic resonance imaging (fMRI) of deep brain stimulation (DBS) has potentials to reveal neuroanatomical connectivity of a specific brain region in vivo. OBJECTIVE This study aimed to demonstrate frequency and amplitude tunings of the thalamocortical tract using DBS fMRI at the rat ventral posteromedial thalamus. METHODS Blood oxygenation level dependent (BOLD) fMRI data were acquired in a total of twelve rats at a high-field 11.7 T MRI scanner with modulation of nine stimulus frequencies (1-40 Hz) and seven stimulus amplitudes (0.2-3.6 mA). RESULTS BOLD response in the barrel cortex peaked at 25 Hz. The response increased with stimulus amplitude and reached a plateau at 1 mA. Cortical spreading depolarization (CSD) was observed occasionally after DBS that carries >10% BOLD waves spanning the entire ipsilateral cortex. CONCLUSION fMRI is sensitive to the frequency effect of DBS and has potential to investigate the function of a particular neuroanatomical pathway.
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Affiliation(s)
- Yen-Yu Ian Shih
- Research Imaging Institute, University of Texas Health Science Center at San Antonio, San Antonio, TX 78229, USA; Department of Neurology, University of North Carolina, Chapel Hill, NC 27599, USA; Biomedical Research Imaging Center, University of North Carolina, Chapel Hill, NC 27599, USA; Department of Biomedical Engineering, University of North Carolina, Chapel Hill, NC 27599, USA.
| | - Tiwari V Yash
- Research Imaging Institute, University of Texas Health Science Center at San Antonio, San Antonio, TX 78229, USA; Department of Biomedical Engineering, University of Texas at San Antonio, San Antonio, TX 78249, USA
| | - Bill Rogers
- Research Imaging Institute, University of Texas Health Science Center at San Antonio, San Antonio, TX 78229, USA
| | - Timothy Q Duong
- Research Imaging Institute, University of Texas Health Science Center at San Antonio, San Antonio, TX 78229, USA; South Texas Veterans Health Care System, Department of Veterans Affairs, USA.
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Lai HY, Younce JR, Albaugh DL, Kao YCJ, Shih YYI. Functional MRI reveals frequency-dependent responses during deep brain stimulation at the subthalamic nucleus or internal globus pallidus. Neuroimage 2013; 84:11-8. [PMID: 23988274 DOI: 10.1016/j.neuroimage.2013.08.026] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2013] [Revised: 07/20/2013] [Accepted: 08/13/2013] [Indexed: 11/15/2022] Open
Abstract
Deep brain stimulation (DBS) represents a widely used therapeutic tool for the symptomatic treatment of movement disorders, most commonly Parkinson's disease (PD). High frequency stimulation at both the subthalamic nucleus (STN) and internal globus pallidus (GPi) has been used with great success for the symptomatic treatment of PD, although the therapeutic mechanisms of action remain elusive. To better understand how DBS at these target sites modulates neural circuitry, the present study used functional blood-oxygenation-level-dependent (BOLD) functional magnetic resonance imaging (fMRI) to map global brain responses to DBS at the STN and GPi of the rat. Robust activation centered in the ipsilateral motor cortex was observed during high frequency stimulation at either target site, with peak responses observed at a stimulation frequency of 100Hz. Of note, frequency tuning curves were generated, demonstrating that cortical activation was maximal at clinically-relevant stimulation frequencies. Divergent responses to stimulation were noted in the contralateral hemisphere, with strong cortical and striatal negative BOLD signal during stimulation of the GPi, but not STN. The frequency-dependence of the observed motor cortex activation at both targets suggests a relationship with the therapeutic effects of STN and GPi DBS, with both DBS targets being functionally connected with motor cortex at therapeutic stimulation frequencies.
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Affiliation(s)
- Hsin-Yi Lai
- Department of Neurology, University of North Carolina, Chapel Hill, NC, USA; Biomedical Research Imaging Center, University of North Carolina, Chapel Hill, NC, USA
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Wanek J, Teng PY, Blair NP, Shahidi M. Inner retinal oxygen delivery and metabolism under normoxia and hypoxia in rat. Invest Ophthalmol Vis Sci 2013; 54:5012-9. [PMID: 23821203 DOI: 10.1167/iovs.13-11887] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022] Open
Abstract
PURPOSE Retinal hypoxia is a common pathological condition usually caused by ischemia that may result in alterations in oxidative energy metabolism. We report measurements of oxygen delivery by the retinal circulation (DO2_IR) and inner retinal oxygen metabolism (MO2_IR) under systemic normoxia and hypoxia in rat. METHODS Rats were ventilated with fractions of inspired oxygen (FiO2) to induce either normoxia (n = 10), moderate hypoxia (n = 14), or severe hypoxia (n = 10). Oxygen tension was measured in retinal vessels using phosphorescence lifetime imaging and converted to arterial (O2A) and venous (O2V) oxygen contents. Total retinal blood flow (F) was assessed by red-free and fluorescent microsphere imaging. DO2_IR and MO2_IR were calculated as the products of F and O2A, and F and the arteriovenous oxygen content difference (O2A-V), respectively. RESULTS Measurements of O2A, O2V, and O2A-V were significantly reduced with decreased FiO2 (P < 0.001). In response to reduced oxygen availability, F increased under moderate hypoxia (P < 0.001) but did not increase further under severe hypoxia (P = 0.5). DO2_IR was similar under normoxia and moderate hypoxia (P = 0.7), but significantly lower under severe hypoxia (P < 0.001). Likewise, MO2_IR under normoxia and moderate hypoxia was similar (P = 0.1), but significantly reduced under severe hypoxia (P ≤ 0.02). CONCLUSIONS DO2_IR and MO2_IR were maintained during moderate hypoxia, but reduced under severe hypoxia, indicating blood flow compensation became insufficient for the reduced oxygen availability. Future studies may aid our understanding of retinal metabolic function in ischemic conditions.
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Affiliation(s)
- Justin Wanek
- Department of Ophthalmology and Visual Sciences, University of Illinois at Chicago, Chicago, Illinois 60612, USA
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Di Y, Lu N, Liu R, Chu R, Zhou X, Zhou X. The effect of various levels of stroboscopic illumination on the growth of guinea pig eyes. Clin Exp Optom 2013; 97:55-61. [PMID: 23844603 DOI: 10.1111/cxo.12079] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2012] [Revised: 02/07/2013] [Accepted: 02/22/2013] [Indexed: 11/29/2022] Open
Abstract
BACKGROUND The aim was to investigate various levels of stroboscopic illumination effect on the growth of guinea pig eyes. METHODS Thirty-six two-week-old guinea pigs were randomised to one of three treatment groups (n = 12 for each). Two stroboscopic-reared groups were raised with a duty diurnal cycle of 50 per cent at a flash rate of 0.5 Hz. Illumination intensity varied between zero-to-250 lux or zero-to-500 lux during each cycle in each group, respectively. The third control group was exposed to 250 lux illumination. Refraction and biometric measurements were taken for each animal prior to and after two, four, six and eight weeks of treatment. Finally, retinal microstructure was examined. RESULTS There was significant correlation between refractive errors and axial elongation. After eight weeks of treatment, illumination with flickering light 0-250 lux caused a larger myopic shift with increased axial length than illumination of continuous 250 lux. Stroboscopic illumination with zero-to-500 lux caused a further myopic shift and longer axial length than stroboscopic illumination with zero-to-250 lux. In animals raised in flickering light of zero-to-250 lux or zero-to-500 lux for eight weeks, the outer segment disc membranes in photoreceptor layers were found deformed and detached. CONCLUSION Chronic exposure to low-frequency temporally modulated illumination-induced histological damage in the retina and induced exaggerated axial length elongation.
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Affiliation(s)
- Yue Di
- Jinshan Hospital, Fudan University, Shanghai, China; Eye Ear Nose and Throat Hospital, Fudan University, Shanghai, China.
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