401
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Liao LD, Tsytsarev V, Delgado-Martínez I, Li ML, Erzurumlu R, Vipin A, Orellana J, Lin YR, Lai HY, Chen YY, Thakor NV. Neurovascular coupling: in vivo optical techniques for functional brain imaging. Biomed Eng Online 2013; 12:38. [PMID: 23631798 PMCID: PMC3655834 DOI: 10.1186/1475-925x-12-38] [Citation(s) in RCA: 75] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2013] [Accepted: 03/25/2013] [Indexed: 01/21/2023] Open
Abstract
Optical imaging techniques reflect different biochemical processes in the brain, which is closely related with neural activity. Scientists and clinicians employ a variety of optical imaging technologies to visualize and study the relationship between neurons, glial cells and blood vessels. In this paper, we present an overview of the current optical approaches used for the in vivo imaging of neurovascular coupling events in small animal models. These techniques include 2-photon microscopy, laser speckle contrast imaging (LSCI), voltage-sensitive dye imaging (VSDi), functional photoacoustic microscopy (fPAM), functional near-infrared spectroscopy imaging (fNIRS) and multimodal imaging techniques. The basic principles of each technique are described in detail, followed by examples of current applications from cutting-edge studies of cerebral neurovascular coupling functions and metabolic. Moreover, we provide a glimpse of the possible ways in which these techniques might be translated to human studies for clinical investigations of pathophysiology and disease. In vivo optical imaging techniques continue to expand and evolve, allowing us to discover fundamental basis of neurovascular coupling roles in cerebral physiology and pathophysiology.
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Affiliation(s)
- Lun-De Liao
- Singapore Institute for Neurotechnology (SINAPSE), National University of Singapore, 28 Medical Drive, #05-COR, Singapore 117456, Singapore
| | - Vassiliy Tsytsarev
- Department of Anatomy and Neurobiology, University of Maryland School of Medicine, 20 Penn street, HSF-2, Baltimore, MD 21201, USA
| | - Ignacio Delgado-Martínez
- Singapore Institute for Neurotechnology (SINAPSE), National University of Singapore, 28 Medical Drive, #05-COR, Singapore 117456, Singapore
| | - Meng-Lin Li
- Department of Electrical Engineering, National Tsing Hua University, No. 101, Sec. 2, Kuang-Fu Rd, Hsinchu 300, R.O.C, Taiwan
| | - Reha Erzurumlu
- Department of Anatomy and Neurobiology, University of Maryland School of Medicine, 20 Penn street, HSF-2, Baltimore, MD 21201, USA
| | - Ashwati Vipin
- Singapore Institute for Neurotechnology (SINAPSE), National University of Singapore, 28 Medical Drive, #05-COR, Singapore 117456, Singapore
| | - Josue Orellana
- Singapore Institute for Neurotechnology (SINAPSE), National University of Singapore, 28 Medical Drive, #05-COR, Singapore 117456, Singapore
| | - Yan-Ren Lin
- Department of Emergency Medicine, Changhua Christian Hospital, 135 Nanshsiao Street, Changhua 500, R.O.C, Taiwan
| | - Hsin-Yi Lai
- Department of Physical Medicine and Rehabilitation, Chang Gung Memorial Hospital and Chang Gung University, Taoyuan 333, R.O.C, Taiwan
| | - You-Yin Chen
- Department of Biomedical Engineering, National Yang Ming University, No.155, Sec.2, Linong St, Taipei 112, R.O.C, Taiwan
| | - Nitish V Thakor
- Singapore Institute for Neurotechnology (SINAPSE), National University of Singapore, 28 Medical Drive, #05-COR, Singapore 117456, Singapore
- Department of Biomedical Engineering, Johns Hopkins University, Traylor 701/720 Rutland Ave, Baltimore, MD 21205, USA
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402
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Pérez-Alvarez A, Araque A, Martín ED. Confocal microscopy for astrocyte in vivo imaging: Recycle and reuse in microscopy. Front Cell Neurosci 2013; 7:51. [PMID: 23658537 PMCID: PMC3647290 DOI: 10.3389/fncel.2013.00051] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2013] [Accepted: 04/07/2013] [Indexed: 02/01/2023] Open
Abstract
In vivo imaging is one of the ultimate and fundamental approaches for the study of the brain. Two-photon laser scanning microscopy (2PLSM) constitutes the state-of-the-art technique in current neuroscience to address questions regarding brain cell structure, development and function, blood flow regulation and metabolism. This technique evolved from laser scanning confocal microscopy (LSCM), which impacted the field with a major improvement in image resolution of live tissues in the 1980s compared to widefield microscopy. While nowadays some of the unparalleled features of 2PLSM make it the tool of choice for brain studies in vivo, such as the possibility to image deep within a tissue, LSCM can still be useful in this matter. Here we discuss the validity and limitations of LSCM and provide a guide to perform high-resolution in vivo imaging of the brain of live rodents with minimal mechanical disruption employing LSCM. We describe the surgical procedure and experimental setup that allowed us to record intracellular calcium variations in astrocytes evoked by sensory stimulation, and to monitor intact neuronal dendritic spines and astrocytic processes as well as blood vessel dynamics. Therefore, in spite of certain limitations that need to be carefully considered, LSCM constitutes a useful, convenient, and affordable tool for brain studies in vivo.
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403
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Olson JP, Kwon HB, Takasaki KT, Chiu CQ, Higley MJ, Sabatini BL, Ellis-Davies GCR. Optically selective two-photon uncaging of glutamate at 900 nm. J Am Chem Soc 2013; 135:5954-7. [PMID: 23577752 DOI: 10.1021/ja4019379] [Citation(s) in RCA: 130] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
We have synthesized a 7-diethylaminocoumarin (DEAC) derivative that allows wavelength-selective two-photon uncaging at 900 nm versus 720 nm. This new caging chromophore, called DEAC450, has an extended π-electron moiety at the 3-position that shifts the absorption spectrum maximum of DEAC from 375 to 450 nm. Two-photon excitation at 900 nm was more than 60-fold greater than at 720 nm. Two-photon uncaging of DEAC450-Glu at 900 nm at spine heads on pyramidal neurons in acutely isolated brain slices generated postsynaptic responses that were similar to spontaneous postsynaptic excitatory miniature currents, whereas significantly higher energies at 720 nm evoked no currents. Since many nitroaromatic caged compounds are two-photon active at 720 nm, optically selective uncaging of DEAC450-caged biomolecules at 900 nm may allow facile two-color optical interrogation of bimodal signaling pathways in living tissue with high resolution for the first time.
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Affiliation(s)
- Jeremy P Olson
- Department of Neuroscience, Mount Sinai School of Medicine, New York, New York 10029, USA
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404
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Petersen C, Crochet S. Synaptic Computation and Sensory Processing in Neocortical Layer 2/3. Neuron 2013; 78:28-48. [DOI: 10.1016/j.neuron.2013.03.020] [Citation(s) in RCA: 184] [Impact Index Per Article: 16.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/22/2013] [Indexed: 11/26/2022]
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405
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Dunn KW, Sutton TA, Sandoval RM. Live-animal imaging of renal function by multiphoton microscopy. ACTA ACUST UNITED AC 2013; Chapter 12:Unit12.9. [PMID: 23042524 DOI: 10.1002/0471142956.cy1209s62] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Intravital microscopy, microscopy of living animals, is a powerful research technique that combines the resolution and sensitivity found in microscopic studies of cultured cells with the relevance and systemic influences of cells in the context of the intact animal. The power of intravital microscopy has recently been extended with the development of multiphoton fluorescence microscopy systems capable of collecting optical sections from deep within the kidney at subcellular resolution, supporting high-resolution characterizations of the structure and function of glomeruli, tubules, and vasculature in the living kidney. Fluorescent probes are administered to an anesthetized, surgically prepared animal, followed by image acquisition for up to 3 hr. Images are transferred via a high-speed network to specialized computer systems for digital image analysis. This general approach can be used with different combinations of fluorescent probes to evaluate processes such as glomerular permeability, proximal tubule endocytosis, microvascular flow, vascular permeability, mitochondrial function, and cellular apoptosis/necrosis.
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Affiliation(s)
- Kenneth W Dunn
- Indiana University School of Medicine, Indianapolis, IN, USA
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406
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Improving spinning disk confocal microscopy by preventing pinhole cross-talk for intravital imaging. Proc Natl Acad Sci U S A 2013; 110:3399-404. [PMID: 23401517 DOI: 10.1073/pnas.1216696110] [Citation(s) in RCA: 57] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
A recent key requirement in life sciences is the observation of biological processes in their natural in vivo context. However, imaging techniques that allow fast imaging with higher resolution in 3D thick specimens are still limited. Spinning disk confocal microscopy using a Yokogawa Confocal Scanner Unit, which offers high-speed multipoint confocal live imaging, has been found to have wide utility among cell biologists. A conventional Confocal Scanner Unit configuration, however, is not optimized for thick specimens, for which the background noise attributed to "pinhole cross-talk," which is unintended pinhole transmission of out-of-focus light, limits overall performance in focal discrimination and reduces confocal capability. Here, we improve spinning disk confocal microscopy by eliminating pinhole cross-talk. First, the amount of pinhole cross-talk is reduced by increasing the interpinhole distance. Second, the generation of out-of-focus light is prevented by two-photon excitation that achieves selective-plane illumination. We evaluate the effect of these modifications and test the applicability to the live imaging of green fluorescent protein-expressing model animals. As demonstrated by visualizing the fine details of the 3D cell shape and submicron-size cytoskeletal structures inside animals, these strategies dramatically improve higher-resolution intravital imaging.
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407
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Two-photon optogenetic toolbox for fast inhibition, excitation and bistable modulation. Nat Methods 2013; 9:1171-9. [PMID: 23169303 PMCID: PMC5734860 DOI: 10.1038/nmeth.2215] [Citation(s) in RCA: 210] [Impact Index Per Article: 19.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2012] [Accepted: 09/24/2012] [Indexed: 12/11/2022]
Abstract
Optogenetics with microbial opsin genes has enabled high-speed control of genetically specified cell populations in intact tissue. However, it remains a challenge to independently control subsets of cells within the genetically targeted population. Although spatially precise excitation of target molecules can be achieved using two-photon laser-scanning microscopy (TPLSM) hardware, the integration of two-photon excitation with optogenetics has thus far required specialized equipment or scanning and has not yet been widely adopted. Here we take a complementary approach, developing opsins with custom kinetic, expression and spectral properties uniquely suited to scan times typical of the raster approach that is ubiquitous in TPLSMlaboratories. We use a range of culture, slice and mammalian in vivo preparations to demonstrate the versatility of this toolbox, and we quantitatively map parameter space for fast excitation, inhibition and bistable control. Together these advances may help enable broad adoption of integrated optogenetic and TPLSMtechnologies across experimental fields and systems.
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408
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Abstract
Multiphoton microscopy has enabled unprecedented dynamic exploration in living organisms. A significant challenge in biological research is the dynamic imaging of features deep within living organisms, which permits the real-time analysis of cellular structure and function. To make progress in our understanding of biological machinery, optical microscopes must be capable of rapid, targeted access deep within samples at high resolution. In this Review, we discuss the basic architecture of a multiphoton microscope capable of such analysis and summarize the state-of-the-art technologies for the quantitative imaging of biological phenomena.
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Affiliation(s)
- Erich E. Hoover
- Center for Microintegrated Optics for Advanced Bioimaging and Control, Colorado School of Mines, 1523 Illinois Street, Golden, Colorado 80401, USA
- Department of Physics, Colorado School of Mines, 1523 Illinois Street, Golden, Colorado 80401, USA
| | - Jeff A. Squier
- Center for Microintegrated Optics for Advanced Bioimaging and Control, Colorado School of Mines, 1523 Illinois Street, Golden, Colorado 80401, USA
- Department of Physics, Colorado School of Mines, 1523 Illinois Street, Golden, Colorado 80401, USA
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409
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Yaseen MA, Sakadžić S, Wu W, Becker W, Kasischke KA, Boas DA. In vivo imaging of cerebral energy metabolism with two-photon fluorescence lifetime microscopy of NADH. BIOMEDICAL OPTICS EXPRESS 2013; 4:307-21. [PMID: 23412419 PMCID: PMC3567717 DOI: 10.1364/boe.4.000307] [Citation(s) in RCA: 71] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/06/2012] [Revised: 01/17/2013] [Accepted: 01/17/2013] [Indexed: 05/04/2023]
Abstract
Minimally invasive, specific measurement of cellular energy metabolism is crucial for understanding cerebral pathophysiology. Here, we present high-resolution, in vivo observations of autofluorescence lifetime as a biomarker of cerebral energy metabolism in exposed rat cortices. We describe a customized two-photon imaging system with time correlated single photon counting detection and specialized software for modeling multiple-component fits of fluorescence decay and monitoring their transient behaviors. In vivo cerebral NADH fluorescence suggests the presence of four distinct components, which respond differently to brief periods of anoxia and likely indicate different enzymatic formulations. Individual components show potential as indicators of specific molecular pathways involved in oxidative metabolism.
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Affiliation(s)
- Mohammad A. Yaseen
- Optics Division, MGH/MIT/HMS Athinoula A. Martinos Center for
Biomedical Imaging, Massachusetts General Hospital/Harvard Medical School, Charlestown,
Massachusetts 02129, USA
| | - Sava Sakadžić
- Optics Division, MGH/MIT/HMS Athinoula A. Martinos Center for
Biomedical Imaging, Massachusetts General Hospital/Harvard Medical School, Charlestown,
Massachusetts 02129, USA
| | - Weicheng Wu
- Optics Division, MGH/MIT/HMS Athinoula A. Martinos Center for
Biomedical Imaging, Massachusetts General Hospital/Harvard Medical School, Charlestown,
Massachusetts 02129, USA
| | - Wolfgang Becker
- Becker & Hickl GmbH, Nahmitzer Damm 30, 12277 Berlin,
Germany
| | - Karl A. Kasischke
- Department of Neurology, University of Ulm Medical Center, Oberer
Eselsberg 45, 89075 Ulm, Germany
| | - David A. Boas
- Optics Division, MGH/MIT/HMS Athinoula A. Martinos Center for
Biomedical Imaging, Massachusetts General Hospital/Harvard Medical School, Charlestown,
Massachusetts 02129, USA
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410
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Lee SJ, Rao AS, Shin YH, Chung HJ, Huh Y, Ahn KH, Jung J. A novel method using an acedan-based Zn(DPA) probe to monitor ATP localization in an in vivo system. J Mol Histol 2012; 44:241-7. [PMID: 23264110 DOI: 10.1007/s10735-012-9474-3] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2012] [Accepted: 12/14/2012] [Indexed: 01/31/2023]
Abstract
In in vitro and in vivo systems, understanding localization and the functional role of ATP is essential, but effective methods to monitor ATP in cells and tissues are limited. Although quinacrine dihydrochloride is a well-known fluorescent dye used to detect ATP, it is limited in its use because it shows non-specific nuclear staining both in vitro and in vivo. A commercial luciferin-luciferase bioluminescence assay has also been used to detect ATP, but it can not be easily used in vivo. Thus, to effectively monitor ATP in vivo, we employed a novel two-photon ATP fluorescent probe, acedan-based Zn(DPA). Using the acedan-based Zn(DPA) probe, we show that this probe produces high quality images of ATP in lung, spleen, liver and spinal cord tissues.
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Affiliation(s)
- Seo Jin Lee
- Department of Anatomy, College of Medicine, Kyung Hee University, Heogi-Dong 1, Dongdaemun-Gu, Seoul 130-701, Republic of Korea
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411
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Amyloid plaque formation precedes dendritic spine loss. Acta Neuropathol 2012; 124:797-807. [PMID: 22993126 PMCID: PMC3508278 DOI: 10.1007/s00401-012-1047-8] [Citation(s) in RCA: 61] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2012] [Revised: 09/07/2012] [Accepted: 09/09/2012] [Indexed: 11/01/2022]
Abstract
Amyloid-beta plaque deposition represents a major neuropathological hallmark of Alzheimer's disease. While numerous studies have described dendritic spine loss in proximity to plaques, much less is known about the kinetics of these processes. In particular, the question as to whether synapse loss precedes or follows plaque formation remains unanswered. To address this question, and to learn more about the underlying kinetics, we simultaneously imaged amyloid plaque deposition and dendritic spine loss by applying two-photon in vivo microscopy through a cranial window in double transgenic APPPS1 mice. As a result, we first observed that the rate of dendritic spine loss in proximity to plaques is the same in both young and aged animals. However, plaque size only increased significantly in the young cohort, indicating that spine loss persists even many months after initial plaque appearance. Tracking the fate of individual spines revealed that net spine loss is caused by increased spine elimination, with the rate of spine formation remaining constant. Imaging of dendritic spines before and during plaque formation demonstrated that spine loss around plaques commences at least 4 weeks after initial plaque formation. In conclusion, spine loss occurs, shortly but with a significant time delay, after the birth of new plaques, and persists in the vicinity of amyloid plaques over many months. These findings hence give further hope to the possibility that there is a therapeutic window between initial amyloid plaque deposition and the onset of structural damage at spines.
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412
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A Novel Fluorescent Protein Pair for Dual-color Two-photon Laser Scanning Microscopy*. PROG BIOCHEM BIOPHYS 2012. [DOI: 10.3724/sp.j.1206.2012.00027] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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413
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Intravital Microscopy Reveals Differences in the Kinetics of Endocytic Pathways between Cell Cultures and Live Animals. Cells 2012; 1:1121-32. [PMID: 24710546 PMCID: PMC3901136 DOI: 10.3390/cells1041121] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2012] [Revised: 11/06/2012] [Accepted: 11/07/2012] [Indexed: 01/01/2023] Open
Abstract
Intravital microscopy has enabled imaging of the dynamics of subcellular structures in live animals, thus opening the door to investigating membrane trafficking under physiological conditions. Here, we sought to determine whether the architecture and the environment of a fully developed tissue influences the dynamics of endocytic processes. To this aim, we imaged endocytosis in the stromal cells of rat salivary glands both in situ and after they were isolated and cultured on a solid surface. We found that the internalization of transferrin and dextran, two molecules that traffic via distinct mechanisms, is substantially altered in cultured cells, supporting the idea that the three dimensional organization of the tissue and the cues generated by the surrounding environment strongly affect membrane trafficking events.
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414
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Kozai TDY, Vazquez AL, Weaver CL, Kim SG, Cui XT. In vivo two-photon microscopy reveals immediate microglial reaction to implantation of microelectrode through extension of processes. J Neural Eng 2012; 9:066001. [PMID: 23075490 DOI: 10.1088/1741-2560/9/6/066001] [Citation(s) in RCA: 154] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
OBJECTIVE Penetrating cortical neural probe technologies allow investigators to record electrical signals in the brain. Implantation of probes results in acute tissue damage, and microglia density increases around implanted devices over weeks. However, the mechanisms underlying this encapsulation are not well understood in the acute temporal domain. The objective here was to evaluate dynamic microglial response to implanted probes using two-photon microscopy. APPROACH Using two-photon in vivo microscopy, cortical microglia ∼200 µm below the surface of the visual cortex were imaged every minute in mice with green fluorescent protein-expressing microglia. MAIN RESULTS Following probe insertion, nearby microglia immediately extended processes toward the probe at (1.6 ± 1.3) µm min(-1) during the first 30-45 min, but showed negligible cell body movement for the first 6 h. Six hours following probe insertion, microglia at distances <130.0 µm (p = 0.5) from the probe surface exhibit morphological characteristics of transitional stage (T-stage) activation, similar to the microglial response observed with laser-induced blood-brain barrier damage. T-stage morphology and microglia directionality indexes were developed to characterize microglial response to implanted probes. Evidence suggesting vascular reorganization after probe insertion and distant vessel damage was also observed hours after probe insertion. SIGNIFICANCE A precise temporal understanding of the cellular response to microelectrode implantation will facilitate the search for molecular cues initiating and attenuating the reactive tissue response.
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415
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Yasuda R. Studying signal transduction in single dendritic spines. Cold Spring Harb Perspect Biol 2012; 4:cshperspect.a005611. [PMID: 22843821 DOI: 10.1101/cshperspect.a005611] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Many forms of synaptic plasticity are triggered by biochemical signaling that occurs in small postsynaptic compartments called dendritic spines, each of which typically houses the postsynaptic terminal associated with a single glutamatergic synapse. Recent advances in optical techniques allow investigators to monitor biochemical signaling in single dendritic spines and thus reveal the signaling mechanisms that link synaptic activity and the induction of synaptic plasticity. This is mostly in the study of Ca2+-dependent forms of synaptic plasticity for which many of the steps between Ca2+ influx and changes to the synapse are now known. This article introduces the new techniques used to investigate signaling in single dendritic spines and the neurobiological insights that they have produced.
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Affiliation(s)
- Ryohei Yasuda
- Neurobiology Department, Howard Hughes Medical Institute, Duke University Medical Center, Durham, North Carolina 27710, USA.
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416
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Riemann I, Le Harzic R, Mpoukouvalas K, Heimann A, Kempski O, Charalampaki P. Sub-cellular tumor identification and markerless differentiation in the rat brain in vivo by multiphoton microscopy. Lasers Surg Med 2012; 44:719-25. [PMID: 23018677 DOI: 10.1002/lsm.22079] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/04/2012] [Indexed: 11/07/2022]
Abstract
OBJECTIVE/BACKGROUND Aim of the current study was to localize and differentiate between tumor (glioma) and healthy tissue in rat brains on a cellular level. Near-infrared multiphoton microscopy takes advantage of the simultaneous absorption of two or more photons to analyze various materials such as cell and tissue components via the observation of endogenous fluorophores such as NAD(P)H, FAD, porphyrins, melanin, elastin, and collagen, with a very high resolution, without inducing the problems of photo-bleaching on out-of-focus areas. METHODS In vitro and in vivo studies on healthy rat brains as well as C6 glioma cell line allografts have been performed. Near-infrared laser pulses (λ = 690-1060 nm, τ ~140 fs) generated by an ultrafast Ti:Sapphire tunable laser system (Chameleon, Coherent GmbH, Santa Clara, CA) were coupled into a laser scanning microscope (LSM 510 META, Carl Zeiss, Germany) to observe high quality images. RESULTS Several image acquisitions have been performed by varying the zoom scale of the multiphoton microscope, image acquisition time and the wavelength (765, 840 nm) to detect various tissue components. With a penetration depth of ~200 µm in vitro and about 30-60 µm in vivo into the brain tissue it was possible to differentiate between tumor and healthy brain tissue even through thin layers of blood. CONCLUSION Near-infrared multiphoton microscopy allows the observation and possibly differentiation between tumor (glioma) and healthy tissue in rat brains on a cellular level. Our findings suggest that a further miniaturization of this technology might be very useful for scientific and clinical applications in neurosurgery.
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Affiliation(s)
- Iris Riemann
- Fraunhofer Institute for Biomedical Engineering, Ensheimer Str 48, 66386 St Ingbert, Germany.
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417
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Abstract
Optical methods for manipulation of cellular function have enabled deconstruction of genetic and neural circuits in vitro and in vivo. Plasmonic gold nanomaterials provide an alternative platform for external optical manipulation of genetic circuits. The tunable absorption of gold nanoparticles in the infrared spectral region and straightforward surface functionalization has led to applications in intracellular delivery and photorelease of short RNAs, recently enabling bidirectional photothermal modulation of specific genes via RNA interference (RNAi). We discuss recent advances in optical gene circuit engineering and plasmonic nanomaterials, as well as future research opportunities and challenges in photothermal gene manipulation.
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Affiliation(s)
- Polina Anikeeva
- Department of Materials Science and Engineering & Research Laboratory of Electronics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
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418
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Drocco JA, Wieschaus EF, Tank DW. The synthesis-diffusion-degradation model explains Bicoid gradient formation in unfertilized eggs. Phys Biol 2012; 9:055004. [PMID: 23011646 DOI: 10.1088/1478-3975/9/5/055004] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Precise formation of morphogen gradients is essential to the establishment of reproducible pattern in development. Mechanisms proposed for obtaining the requisite precision range from simple models with few parameters to more complex models involving many regulated quantities. The synthesis-diffusion-degradation (SDD) model is a relatively simple model explaining the formation of the Bicoid gradient in Drosophila melanogaster, in which the steady-state characteristic length of the gradient is determined solely by the rates of diffusion and degradation of the morphogen. In this work, we test the SDD model in unfertilized D. melanogaster eggs, which contain a single female pronucleus and lack the nuclear division cycles and other zygotic regulatory processes seen in fertilized eggs. Using two-photon live imaging as well as a novel method for quantitative imaging based on decorrelation of photoswitching waveforms, we find that the Bicoid gradient is longer and shallower in unfertilized eggs as compared to the gradient at the same time points in fertilized eggs. Using a means of measuring the Bicoid lifetime by conjugation to a photoconvertible fluorophore, we find that the lifetime is correspondingly longer in unfertilized eggs, providing qualitative and quantitative agreement with the predictions of the SDD model.
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Affiliation(s)
- J A Drocco
- Joseph Henry Laboratories of Physics, Princeton University, Princeton, NJ 08544, USA
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419
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Abstract
Neurons in the mammalian brain receive thousands of synaptic inputs on their dendrites. In many types of neurons, such as cortical pyramidal neurons, excitatory synapses are formed on fine dendritic protrusions called spines. Usually, an individual spine forms a single synaptic contact with an afferent axon. In this protocol, we describe a recently established experimental procedure for measuring intracellular calcium signals from dendritic spines in cortical neurons in vivo by using a combination of two-photon microscopy and whole-cell patch-clamp recordings. We have used mice as an experimental model system, but the protocol may be readily adapted to other species. This method involves data acquisition at high frame rates and low-excitation laser power, and is termed low-power temporal oversampling (LOTOS). Because of its high sensitivity of fluorescence detection and reduced phototoxicity, LOTOS allows for prolonged and stable calcium imaging in vivo. Key aspects of the protocol, which can be completed in 5-6 h, include the use of a variant of high-speed two-photon imaging, refined surgery procedures and optimized tissue stabilization.
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420
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Masedunskas A, Milberg O, Porat-Shliom N, Sramkova M, Wigand T, Amornphimoltham P, Weigert R. Intravital microscopy: a practical guide on imaging intracellular structures in live animals. BIOARCHITECTURE 2012; 2:143-57. [PMID: 22992750 PMCID: PMC3696059 DOI: 10.4161/bioa.21758] [Citation(s) in RCA: 73] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/28/2012] [Revised: 08/05/2012] [Accepted: 08/07/2012] [Indexed: 01/05/2023]
Abstract
Intravital microscopy is an extremely powerful tool that enables imaging several biological processes in live animals. Recently, the ability to image subcellular structures in several organs combined with the development of sophisticated genetic tools has made possible extending this approach to investigate several aspects of cell biology. Here we provide a general overview of intravital microscopy with the goal of highlighting its potential and challenges. Specifically, this review is geared toward researchers that are new to intravital microscopy and focuses on practical aspects of carrying out imaging in live animals. Here we share the know-how that comes from first-hand experience, including topics such as choosing the right imaging platform and modality, surgery and stabilization techniques, anesthesia and temperature control. Moreover, we highlight some of the approaches that facilitate subcellular imaging in live animals by providing numerous examples of imaging selected organelles and the actin cytoskeleton in multiple organs.
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Affiliation(s)
- Andrius Masedunskas
- Intracellular Membrane Trafficking Unit; Oral and Pharyngeal Cancer Branch; National Institute of Dental and Craniofacial Research; National Institutes of Health; Bethesda, MD USA
- Department of Biology; University of North Carolina at Chapel Hill; Chapel Hill, NC USA
| | - Oleg Milberg
- Intracellular Membrane Trafficking Unit; Oral and Pharyngeal Cancer Branch; National Institute of Dental and Craniofacial Research; National Institutes of Health; Bethesda, MD USA
- Department of Chemical and Biochemical Engineering; Rutgers University; Piscataway, NJ USA
- Department of Biomedical Engineering; Rutgers University; Piscataway, NJ USA
| | - Natalie Porat-Shliom
- Intracellular Membrane Trafficking Unit; Oral and Pharyngeal Cancer Branch; National Institute of Dental and Craniofacial Research; National Institutes of Health; Bethesda, MD USA
| | - Monika Sramkova
- Intracellular Membrane Trafficking Unit; Oral and Pharyngeal Cancer Branch; National Institute of Dental and Craniofacial Research; National Institutes of Health; Bethesda, MD USA
| | - Tim Wigand
- Intracellular Membrane Trafficking Unit; Oral and Pharyngeal Cancer Branch; National Institute of Dental and Craniofacial Research; National Institutes of Health; Bethesda, MD USA
| | - Panomwat Amornphimoltham
- Intracellular Membrane Trafficking Unit; Oral and Pharyngeal Cancer Branch; National Institute of Dental and Craniofacial Research; National Institutes of Health; Bethesda, MD USA
| | - Roberto Weigert
- Intracellular Membrane Trafficking Unit; Oral and Pharyngeal Cancer Branch; National Institute of Dental and Craniofacial Research; National Institutes of Health; Bethesda, MD USA
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421
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Morales AR, Yanez CO, Zhang Y, Wang X, Biswas S, Urakami T, Komatsu M, Belfield KD. Small molecule fluorophore and copolymer RGD peptide conjugates for ex vivo two-photon fluorescence tumor vasculature imaging. Biomaterials 2012; 33:8477-85. [PMID: 22940216 DOI: 10.1016/j.biomaterials.2012.06.082] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2012] [Accepted: 06/27/2012] [Indexed: 01/13/2023]
Abstract
We report the use of small molecule and block copolymer RGD peptide conjugates for deep ex vivo imaging of tumor vasculature in "whole" excised tumors using two-photon fluorescence microscopy (2PFM). The fluorescent probes were administered to mice via tail-vein injection, after which the tumors were excised, fixed, and imaged without further sample preparation. Both RGD conjugates demonstrated specific targeting to tumor blood vessels, and this selectivity imparted excellent contrast in 2PFM micrographs that captured high-resolution 3-D images of the tumor vasculature up to depths of 830 μm in Lewis Lung Carcinoma (LLC) tumors. 2PFM ex vivo fluorescence micrographs clearly revealed tumor vessels, while differences in the sensitivity of tumor vessel imaging were apparent between the small molecule and block copolymer conjugates. Both the small molecule and polymer-based two-photon absorbing probe conjugate are valuable for deep tissue tumor microvasculature imaging.
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Affiliation(s)
- Alma R Morales
- University of Central Florida, Department of Chemistry, P.O. Box 162366, Orlando, FL 32816-2366, USA
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422
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Random-access Two-photon Microscopy for Neural Activity Observation*. PROG BIOCHEM BIOPHYS 2012. [DOI: 10.3724/sp.j.1206.2012.00234] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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423
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Dendritic spines: from structure to in vivo function. EMBO Rep 2012; 13:699-708. [PMID: 22791026 DOI: 10.1038/embor.2012.102] [Citation(s) in RCA: 214] [Impact Index Per Article: 17.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2012] [Accepted: 06/22/2012] [Indexed: 12/19/2022] Open
Abstract
Dendritic spines arise as small protrusions from the dendritic shaft of various types of neuron and receive inputs from excitatory axons. Ever since dendritic spines were first described in the nineteenth century, questions about their function have spawned many hypotheses. In this review, we introduce understanding of the structural and biochemical properties of dendritic spines with emphasis on components studied with imaging methods. We then explore advances in in vivo imaging methods that are allowing spine activity to be studied in living tissue, from super-resolution techniques to calcium imaging. Finally, we review studies on spine structure and function in vivo. These new results shed light on the development, integration properties and plasticity of spines.
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424
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Weimer RM, Hill TC, Hamilton AM, Zito K. Imaging synaptic protein dynamics using photoactivatable green fluorescent protein. Cold Spring Harb Protoc 2012; 2012:771-777. [PMID: 22753605 DOI: 10.1101/pdb.prot070029] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Considerable evidence has accumulated that structural changes in dendritic spines and their synapses are associated with adaptive functional changes in cortical circuits, such as during circuit refinement in young animals and in learning and memory in adults. Understanding the mechanisms of circuit plasticity requires detailed investigation of the structural dynamics of dendritic spines and how they are regulated by neural activity and sensory experience. Studying the dynamic localization of synaptic proteins in dendritic spines and how their stabilization and exchange rates influence spine structural plasticity is also important. This protocol describes imaging approaches to study synaptic protein dynamics in dendritic spines of the rodent cerebral cortex. It gives a strategy for generating photoactivatable green fluorescent protein (PA-GFP)-tagged synaptic proteins and in vitro and in vivo transfection methods for coexpression of these proteins with a spectrally separable cell-filling marker (DsRed-Express). Methods for tracking synaptic protein localization using photoactivation and time-lapse imaging of PA-GFP in spiny pyramidal neuron dendrites are given. A discussion of imaging hardware and software preferences is also included. The methods described here can be used to study the dynamic processes underlying spine synapse development during the formation and plasticity of neural circuits in the mammalian brain.
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425
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Devor A, Sakadžić S, Srinivasan VJ, Yaseen MA, Nizar K, Saisan PA, Tian P, Dale AM, Vinogradov SA, Franceschini MA, Boas DA. Frontiers in optical imaging of cerebral blood flow and metabolism. J Cereb Blood Flow Metab 2012; 32:1259-76. [PMID: 22252238 PMCID: PMC3390808 DOI: 10.1038/jcbfm.2011.195] [Citation(s) in RCA: 111] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
In vivo optical imaging of cerebral blood flow (CBF) and metabolism did not exist 50 years ago. While point optical fluorescence and absorption measurements of cellular metabolism and hemoglobin concentrations had already been introduced by then, point blood flow measurements appeared only 40 years ago. The advent of digital cameras has significantly advanced two-dimensional optical imaging of neuronal, metabolic, vascular, and hemodynamic signals. More recently, advanced laser sources have enabled a variety of novel three-dimensional high-spatial-resolution imaging approaches. Combined, as we discuss here, these methods are permitting a multifaceted investigation of the local regulation of CBF and metabolism with unprecedented spatial and temporal resolution. Through multimodal combination of these optical techniques with genetic methods of encoding optical reporter and actuator proteins, the future is bright for solving the mysteries of neurometabolic and neurovascular coupling and translating them to clinical utility.
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Affiliation(s)
- Anna Devor
- Department of Neurosciences, UCSD, La Jolla, CA, USA.
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426
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Holtmaat A, de Paola V, Wilbrecht L, Trachtenberg JT, Svoboda K, Portera-Cailliau C. Imaging neocortical neurons through a chronic cranial window. Cold Spring Harb Protoc 2012; 2012:694-701. [PMID: 22661440 PMCID: PMC9809922 DOI: 10.1101/pdb.prot069617] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
The rich structural dynamics of axonal arbors and neuronal circuitry can only be revealed through direct and repeated observations of the same neuron(s) over time, preferably in vivo. This protocol describes a long-term, high-resolution method for imaging neocortical neurons in vivo, using a combination of two-photon laser scanning microscopy (2PLSM) and a surgically implanted chronic cranial window. The window is used because the skull of most mammals is too opaque to allow high-resolution imaging of cortical neurons. Using this method, it is feasible to image the smallest neuronal structures in the superficial layers of the neocortex, such as dendritic spines and axonal boutons. Because the surface area of the craniotomy is relatively large, this technique is even suitable for use when labeled neurons are relatively uncommon. The surgery and imaging procedures are illustrated with examples from our studies of structural plasticity in the developing or adult mouse brain. The protocol is optimized for adult mice; we have used mice up to postnatal day 511 (P511). With minor modifications, it is possible to image neurons in rats and mice from P2. Most of our studies have used the Thy1 promoter to drive expression of fluorophores in subsets of cortical neurons.
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427
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Kanamori A, Catrinescu MM, Belisle JM, Costantino S, Levin LA. Retrograde and Wallerian axonal degeneration occur synchronously after retinal ganglion cell axotomy. THE AMERICAN JOURNAL OF PATHOLOGY 2012; 181:62-73. [PMID: 22642911 DOI: 10.1016/j.ajpath.2012.03.030] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/21/2011] [Revised: 03/05/2012] [Accepted: 03/15/2012] [Indexed: 01/23/2023]
Abstract
Axonal injury and degeneration are pivotal pathological events in diseases of the nervous system. In the past decade, it has been recognized that the process of axonal degeneration is distinct from somal degeneration and that axoprotective strategies may be distinct from those that protect the soma. Preserving the cell body via neuroprotection cannot improve function if the axon is damaged, because the soma is still disconnected from its target. Therefore, understanding the mechanisms of axonal degeneration is critical for developing new therapeutic interventions for axonal disease treatment. We combined in vivo imaging with a multilaser confocal scanning laser ophthalmoscope and in vivo axotomy with a diode-pumped solid-state laser to assess the time course of Wallerian and retrograde degeneration of unmyelinated retinal ganglion cell axons in living rats for 4 weeks after intraretinal axotomy. Laser injury resulted in reproducible axon loss both distal and proximal to the site of injury. Longitudinal polarization-sensitive imaging of axons demonstrated that Wallerian and retrograde degeneration occurred synchronously. Neurofilament immunostaining of retinal whole-mounts confirmed axonal loss and demonstrated sparing of adjacent axons to the axotomy site. In vivo fluorescent imaging of axonal transport and photobleaching of labeled axons demonstrated that the laser axotomy model did not affect adjacent axon function. These results are consistent with a shared mechanism for Wallerian and retrograde degeneration.
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Affiliation(s)
- Akiyasu Kanamori
- Maisonneuve-Rosemont Hospital Research Center and Department of Ophthalmology, University of Montreal, Quebec, Canada
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428
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Hayes JA, Wang X, Del Negro CA. Cumulative lesioning of respiratory interneurons disrupts and precludes motor rhythms in vitro. Proc Natl Acad Sci U S A 2012; 109:8286-91. [PMID: 22566628 PMCID: PMC3361386 DOI: 10.1073/pnas.1200912109] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
How brain functions degenerate in the face of progressive cell loss is an important issue that pertains to neurodegenerative diseases and basic properties of neural networks. We developed an automated system that uses two-photon microscopy to detect rhythmic neurons from calcium activity, and then individually laser ablates the targets while monitoring network function in real time. We applied this system to the mammalian respiratory oscillator located in the pre-Bötzinger Complex (preBötC) of the ventral medulla, which spontaneously generates breathing-related motor activity in vitro. Here, we show that cumulatively deleting preBötC neurons progressively decreases respiratory frequency and the amplitude of motor output. On average, the deletion of 120 ± 45 neurons stopped spontaneous respiratory rhythm, and our data suggest ≈82% of the rhythm-generating neurons remain unlesioned. Cumulative ablations in other medullary respiratory regions did not affect frequency but diminished the amplitude of motor output to a lesser degree. These results suggest that the preBötC can sustain insults that destroy no more than ≈18% of its constituent interneurons, which may have implications for the onset of respiratory pathologies in disease states.
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Affiliation(s)
- John A. Hayes
- Departments of Applied Science and
- Biology, College of William and Mary, Williamsburg, VA 23187-8795
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429
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Superpenetration optical microscopy by iterative multiphoton adaptive compensation technique. Proc Natl Acad Sci U S A 2012; 109:8434-9. [PMID: 22586078 DOI: 10.1073/pnas.1119590109] [Citation(s) in RCA: 120] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
Biological tissues are rarely transparent, presenting major challenges for deep tissue optical microscopy. The achievable imaging depth is fundamentally limited by wavefront distortions caused by aberration and random scattering. Here, we report an iterative wavefront compensation technique that takes advantage of the nonlinearity of multiphoton signals to determine and compensate for these distortions and to focus light inside deep tissues. Different from conventional adaptive optics methods, this technique can rapidly measure highly complicated wavefront distortions encountered in deep tissue imaging and provide compensations for not only aberration but random scattering. The technique is tested with a variety of highly heterogeneous biological samples including mouse brain tissue, skull, and lymph nodes. We show that high quality three-dimensional imaging can be realized at depths beyond the reach of conventional multiphoton microscopy and adaptive optics methods, albeit over restricted distances for a given correction. Moreover, the required laser excitation power can be greatly reduced in deep tissues, deviating from the power requirement of ballistic light excitation and thus significantly reducing photo damage to the biological tissue.
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430
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431
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Zhao J, Wang D, Wang JH. Barrel cortical neurons and astrocytes coordinately respond to an increased whisker stimulus frequency. Mol Brain 2012; 5:12. [PMID: 22537827 PMCID: PMC3465214 DOI: 10.1186/1756-6606-5-12] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2012] [Accepted: 04/26/2012] [Indexed: 02/01/2023] Open
Abstract
Background Nerve cells program the brain codes to manage well-organized cognitions and behaviors. It remains unclear how a population of neurons and astrocytes work coordinately to encode their spatial and temporal activity patterns in response to frequency and intensity signals from sensory inputs. Results With two-photon imaging and electrophysiology to record cellular functions in the barrel cortex in vivo, we analyzed the activity patterns of neurons and astrocytes in response to whisker stimuli with increasing frequency, an environmental stimulus pattern that rodents experience in the accelerated motion. Compared to the resting state, whisker stimulation caused barrel neurons and astrocytes to be activated more synchronously. An increased stimulus frequency up-regulated the activity strength of neurons and astrocytes as well as coordinated their interaction. The coordination among the barrel neurons and astrocytes was fulfilled by increasing their functional connections. Conclusions Our study reveals that the nerve cells in the barrel cortex encode frequency messages in whisker tactile inputs through setting their activity coordination.
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Affiliation(s)
- Jun Zhao
- Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China
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432
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Beretta CA, Dross N, Guiterrez-Triana JA, Ryu S, Carl M. Habenula circuit development: past, present, and future. Front Neurosci 2012; 6:51. [PMID: 22536170 PMCID: PMC3332237 DOI: 10.3389/fnins.2012.00051] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2012] [Accepted: 03/27/2012] [Indexed: 12/23/2022] Open
Abstract
The habenular neural circuit is attracting increasing attention from researchers in fields as diverse as neuroscience, medicine, behavior, development, and evolution. Recent studies have revealed that this part of the limbic system in the dorsal diencephalon is involved in reward, addiction, and other behaviors and its impairment is associated with various neurological conditions and diseases. Since the initial description of the dorsal diencephalic conduction system (DDC) with the habenulae in its center at the end of the nineteenth century, increasingly sophisticated techniques have resolved much of its anatomy and have shown that these pathways relay information from different parts of the forebrain to the tegmentum, midbrain, and hindbrain. The first part of this review gives a brief historical overview on how the improving experimental approaches have allowed the stepwise uncovering much of the architecture of the habenula circuit as we know it today. Our brain distributes tasks differentially between left and right and it has become a paradigm that this functional lateralization is a universal feature of vertebrates. Moreover, task dependent differential brain activities have been linked to anatomical differences across the left–right axis in humans. A good way to further explore this fundamental issue will be to study the functional consequences of subtle changes in neural network formation, which requires that we fully understand DDC system development. As the habenular circuit is evolutionarily highly conserved, researchers have the option to perform such difficult experiments in more experimentally amenable vertebrate systems. Indeed, research in the last decade has shown that the zebrafish is well suited for the study of DDC system development and the phenomenon of functional lateralization. We will critically discuss the advantages of the zebrafish model, available techniques, and others that are needed to fully understand habenular circuit development.
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Affiliation(s)
- Carlo A Beretta
- Department of Cell and Molecular Biology, Medical Faculty Mannheim, Heidelberg University Mannheim, Germany
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433
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Local dendrodendritic inhibition regulates fast synaptic transmission in visual thalamus. J Neurosci 2012; 32:2513-22. [PMID: 22396424 DOI: 10.1523/jneurosci.4402-11.2012] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Inhibition from thalamic interneurons plays a critical role in modulating information transfer between thalamus and neocortex. Interestingly, these neurons yield inhibition via two distinct outputs: presynaptic dendrites that innervate thalamocortical relay neurons and axonal outputs. Since the dendrites of thalamic interneurons are the primary targets of incoming synaptic information, it has been hypothesized that local synaptic input could produce highly focused dendritic output. To gain additional insight into the computational power of these presynaptic dendrites, we have combined two-photon laser scanning microscopy, glutamate uncaging, and whole-cell electrophysiological recordings to locally activate dendritic terminals and study their inhibitory contribution to rat thalamocortical relay neurons. Our findings demonstrate that local dendritic release from thalamic interneurons is controlled locally by AMPA/NMDA receptor-mediated recruitment of L-type calcium channels. Moreover, by mapping these connections with single dendrite resolution we not only found that presynaptic dendrites preferentially target proximal regions, but such actions differ significantly across branches. Furthermore, local stimulation of interneuron dendrites did not result in global excitation, supporting the notion that these interneurons can operate as multiplexors, containing numerous independently operating input-output devices.
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434
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Mancuso JJ, Chen Y, Li X, Xue Z, Wong STC. Methods of dendritic spine detection: from Golgi to high-resolution optical imaging. Neuroscience 2012; 251:129-40. [PMID: 22522468 DOI: 10.1016/j.neuroscience.2012.04.010] [Citation(s) in RCA: 55] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2011] [Revised: 03/30/2012] [Accepted: 04/05/2012] [Indexed: 12/18/2022]
Abstract
Dendritic spines, the bulbous protrusions that form the postsynaptic half of excitatory synapses, are one of the most prominent features of neurons and have been imaged and studied for over a century. In that time, changes in the number and morphology of dendritic spines have been correlated to the developmental process as well as the pathophysiology of a number of neurodegenerative diseases. Due to the sheer scale of synaptic connectivity in the brain, work to date has merely scratched the surface in the study of normal spine function and pathology. This review will highlight traditional approaches to the imaging of dendritic spines and newer approaches made possible by advances in microscopy, protein engineering, and image analysis. The review will also describe recent work that is leading researchers toward the possibility of a systematic and comprehensive study of spine anatomy throughout the brain.
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Affiliation(s)
- J J Mancuso
- Department of Systems Medicine and Bioengineering, The Methodist Hospital Research Institute, Weill Cornell Medical College, Houston, TX 77030, USA; Ting Tsung and Wei Fong Chao Center for Bioinformatics Research and Imaging in Neurosciences, USA
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435
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Zhang X, Ma Y, Zhang L, Zhu J, Jin F. The development of a novel dry powder inhaler. Int J Pharm 2012; 431:45-52. [PMID: 22543053 DOI: 10.1016/j.ijpharm.2012.04.019] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2011] [Revised: 03/26/2012] [Accepted: 04/03/2012] [Indexed: 01/08/2023]
Abstract
A novel active and multi-dose dry powder inhaler (DPI) was developed and evaluated to deliver a small quantity (100-500 μg) of pure drug without any excipient. This dry powder inhaler utilized two compressed air flows to dispense and deliver drug powder: the primary flow aerosolizes the drug powder from its pocket and the secondary flow further disperses the aerosol. In vitro tests by Anderson Cascade Impactor (ACI) indicated that the fine particle fraction (FPF) (<4.7 μm) of drug delivery could reach over a range of 50-70% (w/w). Emitted dose tests showed that delivery efficiency was above 85% and its relative standard deviation (RSD) was under 10%. Confocal microscopy was used to confirm the deposition of fluorescently labeled spray-dried powder in rabbit lungs. Also, a chromatographic method was used to quantify drug deposition. The results of animal tests showed that 57% of aerosol deposited in the rabbit lung and 24% deposited in its trachea. All the results implied that this novel active dry powder inhaler could efficiently deliver a small quantity of fine drug particles into the lung with quite high fine particle fraction.
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Affiliation(s)
- Xi Zhang
- Chemical and Biochemical Engineering, University of Western Ontario, 1151 Richmond Street, London N6A 5B9, Canada
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436
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Examining form and function of dendritic spines. Neural Plast 2012; 2012:704103. [PMID: 22577585 PMCID: PMC3345238 DOI: 10.1155/2012/704103] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2011] [Accepted: 01/10/2012] [Indexed: 12/20/2022] Open
Abstract
The majority of fast excitatory synaptic transmission in the central nervous system takes place at protrusions along dendrites called spines. Dendritic spines are highly heterogeneous, both morphologically and functionally. Not surprisingly, there has been much speculation and debate on the relationship between spine structure and function. The advent of multi-photon laser-scanning microscopy has greatly improved our ability to investigate the dynamic interplay between spine form and function. Regulated structural changes occur at spines undergoing plasticity, offering a mechanism to account for the well-described correlation between spine size and synapse strength. In turn, spine structure can influence the degree of biochemical and perhaps electrical compartmentalization at individual synapses. Here, we review the relationship between dendritic spine morphology, features of spine compartmentalization and synaptic plasticity. We highlight emerging molecular mechanisms that link structural and functional changes in spines during plasticity, and also consider circumstances that underscore some divergence from a tight structure-function coupling. Because of the intricate influence of spine structure on biochemical and electrical signalling, activity-dependent changes in spine morphology alone may thus contribute to the metaplastic potential of synapses. This possibility asserts a role for structural dynamics in neuronal information storage and aligns well with current computational models.
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437
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Jiang R, Zhou Z, Lv X, Zeng S. Wide-band acousto-optic deflectors for large field of view two-photon microscope. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2012; 83:043709. [PMID: 22559541 DOI: 10.1063/1.4705972] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Acousto-optic deflector (AOD) is an attractive scanner for two-photon microscopy because it can provide fast and versatile laser scanning and does not involve any mechanical movements. However, due to the small scan range of available AOD, the field of view (FOV) of the AOD-based microscope is typically smaller than that of the conventional galvanometer-based microscope. Here, we developed a novel wide-band AOD to enlarge the scan angle. Considering the maximum acceptable acoustic attenuation in the acousto-optic crystal, relatively lower operating frequencies and moderate aperture were adopted. The custom AOD was able to provide 60 MHz 3-dB bandwidth and 80% peak diffraction efficiency at 840 nm wavelength. Based on a pair of such AOD, a large FOV two-photon microscope was built with a FOV up to 418.5 μm (40× objective). The spatiotemporal dispersion was compensated simultaneously with a single custom-made prism. By means of dynamic power modulation, the variation of laser intensity within the FOV was reduced below 5%. The lateral and axial resolution of the system were 0.58-2.12 μm and 2.17-3.07 μm, respectively. Pollen grain images acquired by this system were presented to demonstrate the imaging capability at different positions across the entire FOV.
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Affiliation(s)
- Runhua Jiang
- Britton Chance Center for Biomedical Photonics, Wuhan National Laboratory for Optoelectronics, Huazhong University of Science and Technology, Wuhan, 430074, China
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438
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439
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Siegel F, Lohmann C. Probing synaptic function in dendrites with calcium imaging. Exp Neurol 2012; 242:27-32. [PMID: 22374356 DOI: 10.1016/j.expneurol.2012.02.007] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2011] [Revised: 11/22/2011] [Accepted: 02/13/2012] [Indexed: 11/19/2022]
Abstract
Calcium imaging has become a widely used technique to probe neuronal activity on the cellular and subcellular levels. In contrast to standard electrophysiological methods, calcium imaging resolves sub- and suprathreshold activation patterns in structures as small as fine dendritic branches and spines. This review highlights recent findings gained on the subcellular level using calcium imaging, with special emphasis on synaptic transmission and plasticity in individual spines. Since imaging allows monitoring activity across populations of synapses, it has recently been adopted to investigate how dendrites integrate information from many synapses. Future experiments, ideally carried out in vivo, will reveal how the dendritic tree integrates and computes afferent signals. For example, it is now possible to directly test the concept that dendritic inputs are clustered and that single dendrites or dendritic stretches act as independent computational units.
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440
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Rao AS, Kim D, Nam H, Jo H, Kim KH, Ban C, Ahn KH. A turn-on two-photon fluorescent probe for ATP and ADP. Chem Commun (Camb) 2012; 48:3206-8. [PMID: 22331239 DOI: 10.1039/c2cc17629g] [Citation(s) in RCA: 105] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
An acedan derivative containing Zn(II)-DPA has been developed as a two-photon probe for nucleoside phosphates, which shows enhanced fluorescence toward ATP and ADP at physiological pH 7.4 among other competing anions including AMP; the probe is permeable to cell membranes and thus can be directly used for two-photon imaging of ATP and ADP in live cells.
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Affiliation(s)
- Alla Sreenivasa Rao
- Department of Chemistry and the Center for Electro-Photo Behaviors in Advanced Molecular Systems, POSTECH, San 31, Hyoja-dong, Pohang, 790-784, Republic of Korea
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441
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Aberration-free three-dimensional multiphoton imaging of neuronal activity at kHz rates. Proc Natl Acad Sci U S A 2012; 109:2919-24. [PMID: 22315405 DOI: 10.1073/pnas.1111662109] [Citation(s) in RCA: 141] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Multiphoton microscopy is a powerful tool in neuroscience, promising to deliver important data on the spatiotemporal activity within individual neurons as well as in networks of neurons. A major limitation of current technologies is the relatively slow scan rates along the z direction compared to the kHz rates obtainable in the x and y directions. Here, we describe a custom-built microscope system based on an architecture that allows kHz scan rates over hundreds of microns in all three dimensions without introducing aberration. We further demonstrate how this high-speed 3D multiphoton imaging system can be used to study neuronal activity at millisecond resolution at the subcellular as well as the population level.
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442
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Hou X, Cheng W. Detection of single fluorescent proteins inside eukaryotic cells using two-photon fluorescence. BIOMEDICAL OPTICS EXPRESS 2012; 3:340-53. [PMID: 22312586 PMCID: PMC3269850 DOI: 10.1364/boe.3.000340] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/07/2011] [Revised: 01/15/2012] [Accepted: 01/15/2012] [Indexed: 05/24/2023]
Abstract
Imaging single fluorescent proteins in a live cell is a challenging task because of the strong cellular autofluorescence. Autofluorescence can be minimized by reducing fluorescence excitation volume. Total internal reflection fluorescence (TIRF) microscopy has been routinely used to reduce excitation volume and detect single protein molecules in or close to cell membrane. However, the limited penetration depth of evanescent field excludes imaging of single fluorescent proteins that reside deep inside a eukaryotic cell. Here we report detection of single fluorescent proteins inside eukaryotic cells by two-photon fluorescence (TPF) microscopy. TPF has an excitation volume less than 0.1 femtoliter (fL). Cell autofluorescence under TPF is low and thus enables us to detect single enhanced green fluorescent proteins (EGFP) and single monomeric teal fluorescent proteins (mTFP1.0) that reside several microns deep inside the cell. Discrete stepwise photobleaching of TPF was observed for both proteins inside the cell. Quantitative analysis of single-molecule fluorescence trajectories show that mTFP1.0 is about twofold brighter than EGFP, while its fluorescence on-time before bleaching is about 10 fold shorter. These findings demonstrate the sensitivity of TPF for imaging of eukaryotic cells at single-molecule level and will be useful for measurement of protein stoichiometry inside the cell.
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443
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Lasserre S, Hernando J, Hill S, Schümann F, Anasagasti PDM, Jaoudé GA, Markram H. A neuron membrane mesh representation for visualization of electrophysiological simulations. IEEE TRANSACTIONS ON VISUALIZATION AND COMPUTER GRAPHICS 2012; 18:214-227. [PMID: 21383404 DOI: 10.1109/tvcg.2011.55] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
We present a process to automatically generate three-dimensional mesh representations of the complex, arborized cell membrane surface of cortical neurons (the principal information processing cells of the brain) from nonuniform morphological measurements. Starting from manually sampled morphological points (3D points and diameters) from neurons in a brain slice preparation, we construct a polygonal mesh representation that realistically represents the continuous membrane surface, closely matching the original experimental data. A mapping between the original morphological points and the newly generated mesh enables simulations of electrophysiolgical activity to be visualized on this new membrane representation. We compare the new mesh representation with the state of the art and present a series of use cases and applications of this technique to visualize simulations of single neurons and networks of multiple neurons.
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Affiliation(s)
- Sébastien Lasserre
- EPFL - Blue Brain Project, AAB 201 - station 15, Lausanne 1015, Switzerland.
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444
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Abstract
Synaptic plasticity, or changes in synaptic strength, is thought to underlie learning and memory. Imaging studies, mainly in brain slices, have revealed that long-term synaptic plasticity of excitatory synapses in hippocampal neurons is coupled with structural plasticity of dendritic spines, which is thought to be essential for inducing and regulating functional plasticity. Using pharmacological and genetic manipulation, the signalling network underlying structural plasticity has been extensively studied. Furthermore, the recent advent of fluorescence resonance energy transfer (FRET) imaging techniques has provided a readout of the dynamics of signal transduction in dendritic spines undergoing structural plasticity. These studies reveal the signalling pathways relaying Ca2+ to the functional and structural plasticity of dendritic spines.
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Affiliation(s)
- Michael Patterson
- Department of Neurobiology, Howard Hughes Medical Institute, Duke University Medical Center, Durham, NC 27710, USA
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445
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Masedunskas A, Porat-Shliom N, Weigert R. Regulated exocytosis: novel insights from intravital microscopy. Traffic 2012; 13:627-34. [PMID: 22243493 DOI: 10.1111/j.1600-0854.2012.01328.x] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2011] [Revised: 01/11/2012] [Accepted: 01/13/2012] [Indexed: 12/20/2022]
Abstract
Regulated exocytosis is a fundamental process that every secretory cell uses to deliver molecules to the cell surface and the extracellular space by virtue of membranous carriers. This process has been extensively studied using various approaches such as biochemistry, electrophysiology and electron microscopy. However, recent developments in time-lapse light microscopy have made possible imaging individual exocytic events, hence, advancing our understanding of this process at a molecular level. In this review, we focus on intravital microscopy (IVM), a light microscopy-based approach that enables imaging subcellular structures in live animals, and discuss its recent application to study regulated exocytosis. IVM has revealed differences in regulation and modality of regulated exocytosis between in vitro and in vivo model systems, unraveled novel aspects of this process that can be appreciated only in in vivo settings and provided valuable and novel information on its molecular machinery. In conclusion, we make the case for IVM being a mature technique that can be used to investigate the molecular machinery of several intracellular events under physiological conditions.
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Affiliation(s)
- Andrius Masedunskas
- Intracellular Membrane Trafficking Unit, Oral and Pharyngeal Cancer Branch, National Institute of Dental and Craniofacial Research, National Institutes of Health, 30 Convent Dr. 303A, Bethesda, MD 20892-4340, USA
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446
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Davalos D, Akassoglou K. In vivo imaging of the mouse spinal cord using two-photon microscopy. J Vis Exp 2012:e2760. [PMID: 22258623 DOI: 10.3791/2760] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
In vivo imaging using two-photon microscopy in mice that have been genetically engineered to express fluorescent proteins in specific cell types has significantly broadened our knowledge of physiological and pathological processes in numerous tissues in vivo. In studies of the central nervous system (CNS), there has been a broad application of in vivo imaging in the brain, which has produced a plethora of novel and often unexpected findings about the behavior of cells such as neurons, astrocytes, microglia, under physiological or pathological conditions. However, mostly technical complications have limited the implementation of in vivo imaging in studies of the living mouse spinal cord. In particular, the anatomical proximity of the spinal cord to the lungs and heart generates significant movement artifact that makes imaging the living spinal cord a challenging task. We developed a novel method that overcomes the inherent limitations of spinal cord imaging by stabilizing the spinal column, reducing respiratory-induced movements and thereby facilitating the use of two-photon microscopy to image the mouse spinal cord in vivo. This is achieved by combining a customized spinal stabilization device with a method of deep anesthesia, resulting in a significant reduction of respiratory-induced movements. This video protocol shows how to expose a small area of the living spinal cord that can be maintained under stable physiological conditions over extended periods of time by keeping tissue injury and bleeding to a minimum. Representative raw images acquired in vivo detail in high resolution the close relationship between microglia and the vasculature. A timelapse sequence shows the dynamic behavior of microglial processes in the living mouse spinal cord. Moreover, a continuous scan of the same z-frame demonstrates the outstanding stability that this method can achieve to generate stacks of images and/or timelapse movies that do not require image alignment post-acquisition. Finally, we show how this method can be used to revisit and reimage the same area of the spinal cord at later timepoints, allowing for longitudinal studies of ongoing physiological or pathological processes in vivo.
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Affiliation(s)
- Dimitrios Davalos
- Gladstone Institute of Neurological Disease, University of California, San Francisco, USA.
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447
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Optogenetic reporters: Fluorescent protein-based genetically encoded indicators of signaling and metabolism in the brain. PROGRESS IN BRAIN RESEARCH 2012; 196:235-63. [PMID: 22341329 DOI: 10.1016/b978-0-444-59426-6.00012-4] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Fluorescent protein technology has evolved to include genetically encoded biosensors that can monitor levels of ions, metabolites, and enzyme activities as well as protein conformation and even membrane voltage. They are well suited to live-cell microscopy and quantitative analysis, and they can be used in multiple imaging modes, including one- or two-photon fluorescence intensity or lifetime microscopy. Although not nearly complete, there now exists a substantial set of genetically encoded reporters that can be used to monitor many aspects of neuronal and glial biology, and these biosensors can be used to visualize synaptic transmission and activity-dependent signaling in vitro and in vivo. In this review, we present an overview of design strategies for engineering biosensors, including sensor designs using circularly permuted fluorescent proteins and using fluorescence resonance energy transfer between fluorescent proteins. We also provide examples of indicators that sense small ions (e.g., pH, chloride, zinc), metabolites (e.g., glutamate, glucose, ATP, cAMP, lipid metabolites), signaling pathways (e.g., G protein-coupled receptors, Rho GTPases), enzyme activities (e.g., protein kinase A, caspases), and reactive species. We focus on examples where these genetically encoded indicators have been applied to brain-related studies and used with live-cell fluorescence microscopy.
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448
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Neural activity imaging with genetically encoded calcium indicators. PROGRESS IN BRAIN RESEARCH 2012; 196:79-94. [PMID: 22341322 DOI: 10.1016/b978-0-444-59426-6.00005-7] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Genetically encoded calcium indicators (GECIs), together with modern microscopy, allow repeated activity measurement, in real time and with cellular resolution, of defined cellular populations. Recent efforts in protein engineering have yielded several high-quality GECIs that facilitate new applications in neuroscience. Here, we summarize recent progress in GECI design, optimization, and characterization, and provide guidelines for selecting the appropriate GECI for a given biological application. We focus on the unique challenges associated with imaging in behaving animals.
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449
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Specht A, Bolze F, Donato L, Herbivo C, Charon S, Warther D, Gug S, Nicoud JF, Goeldner M. The donor–acceptor biphenyl platform: A versatile chromophore for the engineering of highly efficient two-photon sensitive photoremovable protecting groups. Photochem Photobiol Sci 2012; 11:578-86. [DOI: 10.1039/c2pp05360h] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
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450
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Maschio MD, Beltramo R, De Stasi AM, Fellin T. Two-Photon Calcium Imaging in the Intact Brain. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2012; 740:83-102. [DOI: 10.1007/978-94-007-2888-2_4] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
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