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El Cheikh Hussein L, Fontanaud P, Mollard P, Bonnefont X. Nested calcium dynamics support daily cell unity and diversity in the suprachiasmatic nuclei of free-behaving mice. PNAS NEXUS 2022; 1:pgac112. [PMID: 36741435 PMCID: PMC9896879 DOI: 10.1093/pnasnexus/pgac112] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 02/11/2022] [Accepted: 07/05/2022] [Indexed: 02/07/2023]
Abstract
The suprachiasmatic nuclei (SCN) of the anterior hypothalamus host the circadian pacemaker that synchronizes mammalian rhythms with the day-night cycle. SCN neurons are intrinsically rhythmic, thanks to a conserved cell-autonomous clock mechanism. In addition, circuit-level emergent properties confer a unique degree of precision and robustness to SCN neuronal rhythmicity. However, the multicellular functional organization of the SCN is not yet fully understood. Indeed, although SCN neurons are well-coordinated, experimental evidences indicate that some neurons oscillate out of phase in SCN explants, and possibly to a larger extent in vivo. Here, to tackle this issue we used microendoscopic Ca2+ i imaging and investigated SCN rhythmicity at a single cell resolution in free-behaving mice. We found that SCN neurons in vivo exhibited fast Ca2+ i spikes superimposed upon slow changes in baseline Ca2+ i levels. Both spikes and baseline followed a time-of-day modulation in many neurons, but independently from each other. Daily rhythms in basal Ca2+ i were highly coordinated, while spike activity from the same neurons peaked at multiple times of the light cycle, and unveiled clock-independent coactivity in neuron subsets. Hence, fast Ca2+ i spikes and slow changes in baseline Ca2+ i levels highlighted how multiple individual activity patterns could articulate within the temporal unity of the SCN cell network in vivo, and provided support for a multiplex neuronal code in the circadian pacemaker.
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Affiliation(s)
- Lama El Cheikh Hussein
- Institut de Génomique Fonctionnelle, Université de Montpellier, CNRS, INSERM, IGF, 141 Rue de la Cardonille, F-34094 Montpellier, Cedex 5, France,BioCampus Montpellier, Université de Montpellier, CNRS, INSERM, 141 Rue de la Cardonille, F-34094 Montpellier, Cedex 5, France
| | - Pierre Fontanaud
- Institut de Génomique Fonctionnelle, Université de Montpellier, CNRS, INSERM, IGF, 141 Rue de la Cardonille, F-34094 Montpellier, Cedex 5, France,BioCampus Montpellier, Université de Montpellier, CNRS, INSERM, 141 Rue de la Cardonille, F-34094 Montpellier, Cedex 5, France
| | - Patrice Mollard
- Institut de Génomique Fonctionnelle, Université de Montpellier, CNRS, INSERM, IGF, 141 Rue de la Cardonille, F-34094 Montpellier, Cedex 5, France,BioCampus Montpellier, Université de Montpellier, CNRS, INSERM, 141 Rue de la Cardonille, F-34094 Montpellier, Cedex 5, France
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Abstract
The scientific community has searched for years for ways of examining neuronal tissue to track neural activity with reliable anatomical markers for stimulated neuronal activity. Existing studies that focused on hypothalamic systems offer a few options but do not always compare approaches or validate them for dependence on cell firing, leaving the reader uncertain of the benefits and limitations of each method. Thus, in this article, potential markers will be presented and, where possible, placed into perspective in terms of when and how these methods pertain to hypothalamic function. An example of each approach is included. In reviewing the approaches, one is guided through how neurons work, the consequences of their stimulation, and then the potential markers that could be applied to hypothalamic systems are discussed. Approaches will use features of neuronal glucose utilization, water/oxygen movement, changes in neuron-glial interactions, receptor translocation, cytoskeletal changes, stimulus-synthesis coupling that includes expression of the heteronuclear or mature mRNA for transmitters or the enzymes that make them, and changes in transcription factors (immediate early gene products, precursor buildup, use of promoter-driven surrogate proteins, and induced expression of added transmitters. This article includes discussion of methodological limitations and the power of combining approaches to understand neuronal function. © 2020 American Physiological Society. Compr Physiol 10:549-575, 2020.
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Affiliation(s)
- Gloria E. Hoffman
- Department of Biology, Morgan State University, Baltimore, Maryland, USA
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3
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Harvey JRM, Plante AE, Meredith AL. Ion Channels Controlling Circadian Rhythms in Suprachiasmatic Nucleus Excitability. Physiol Rev 2020; 100:1415-1454. [PMID: 32163720 DOI: 10.1152/physrev.00027.2019] [Citation(s) in RCA: 50] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Animals synchronize to the environmental day-night cycle by means of an internal circadian clock in the brain. In mammals, this timekeeping mechanism is housed in the suprachiasmatic nucleus (SCN) of the hypothalamus and is entrained by light input from the retina. One output of the SCN is a neural code for circadian time, which arises from the collective activity of neurons within the SCN circuit and comprises two fundamental components: 1) periodic alterations in the spontaneous excitability of individual neurons that result in higher firing rates during the day and lower firing rates at night, and 2) synchronization of these cellular oscillations throughout the SCN. In this review, we summarize current evidence for the identity of ion channels in SCN neurons and the mechanisms by which they set the rhythmic parameters of the time code. During the day, voltage-dependent and independent Na+ and Ca2+ currents, as well as several K+ currents, contribute to increased membrane excitability and therefore higher firing frequency. At night, an increase in different K+ currents, including Ca2+-activated BK currents, contribute to membrane hyperpolarization and decreased firing. Layered on top of these intrinsically regulated changes in membrane excitability, more than a dozen neuromodulators influence action potential activity and rhythmicity in SCN neurons, facilitating both synchronization and plasticity of the neural code.
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Affiliation(s)
- Jenna R M Harvey
- Department of Physiology, University of Maryland School of Medicine, Baltimore, Maryland
| | - Amber E Plante
- Department of Physiology, University of Maryland School of Medicine, Baltimore, Maryland
| | - Andrea L Meredith
- Department of Physiology, University of Maryland School of Medicine, Baltimore, Maryland
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Min C, Kim H, Choi W, Lee KJ. Diversity in the structure of action potential-mediated neural connectivity within rat supra chiasmatic nucleus. Eur J Neurosci 2019; 50:2814-2829. [PMID: 30968479 DOI: 10.1111/ejn.14417] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2018] [Revised: 03/14/2019] [Accepted: 03/21/2019] [Indexed: 11/30/2022]
Abstract
Action potential (AP)-mediated cell-to-cell communication is essential for the frequency-locking and phase-synchronization of the clock cells within the biological master clock, suprachiasmatic nucleus (SCN). Nevertheless, the morphology of its network connectivity is largely unexplored. Here, with an optimized optogenetic light-stimulation and scanning protocol, we report some key characteristics of the inhibitory receptive field (IRF), the area which brings inhibitory synaptic currents to a given target cell, and basic statistics of the inhibitory network connections of rat SCN clock cells. ChR2 transfected, slice cultures of rat SCN were stimulated by a blue power LED light in a repetitive box-scanning modes, while a target cell was whole-cell patched. The registered inhibitory postsynaptic currents, which were brought by light-induced APs of presynaptic neurons, were mostly GABAergic. The sizes and shapes of IRFs of SCN cells were very diverse, and the number of presynaptic cells making up the IRF of a given target cell followed an exponential distribution with an average value of 8.9 approximately, according to our clustering analysis which is based on a hybrid measure D, combining the physical distance r and the difference in the current amplitudes of two different sites. Although this estimate inevitably depends on the construct of the measure D, it is found not so sensitive on the parameter w, which weighs the relative significance of the current amplitude different with respect to the physical distance r: The average number of presynaptic neurons varies < 26% over a significant range of 0 < w < 30. On average, the presynaptic connection number density around a target cell falls off as an exponentially decreasing function of r. But, its space constant (~210.7 μm) is quite large that long-range (>210.7 μm) neural connections are abundant (>66.9%) within the SCN.
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Affiliation(s)
- Cheolhong Min
- Department of Physics, Korea University, Seoul, Korea
| | - Hyun Kim
- Department of Physics, Korea University, Seoul, Korea
| | - Wonshik Choi
- Department of Physics, Korea University, Seoul, Korea.,Center for Molecular Spectroscopy and Dynamics, Institute for Basic Science, Seoul, Korea
| | - Kyoung J Lee
- Department of Physics, Korea University, Seoul, Korea
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Martí Ruiz MC, Hubbard KE, Gardner MJ, Jung HJ, Aubry S, Hotta CT, Mohd-Noh NI, Robertson FC, Hearn TJ, Tsai YC, Dodd AN, Hannah M, Carré IA, Davies JM, Braam J, Webb AAR. Circadian oscillations of cytosolic free calcium regulate the Arabidopsis circadian clock. NATURE PLANTS 2018; 4:690-698. [PMID: 30127410 PMCID: PMC6152895 DOI: 10.1038/s41477-018-0224-8] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/13/2016] [Accepted: 07/17/2018] [Indexed: 05/04/2023]
Abstract
In the last decade, the view of circadian oscillators has expanded from transcriptional feedback to incorporate post-transcriptional, post-translational, metabolic processes and ionic signalling. In plants and animals, there are circadian oscillations in the concentration of cytosolic free Ca2+ ([Ca2+]cyt), though their purpose has not been fully characterized. We investigated whether circadian oscillations of [Ca2+]cyt regulate the circadian oscillator of Arabidopsis thaliana. We report that in Arabidopsis, [Ca2+]cyt circadian oscillations can regulate circadian clock function through the Ca2+-dependent action of CALMODULIN-LIKE24 (CML24). Genetic analyses demonstrate a linkage between CML24 and the circadian oscillator, through pathways involving the circadian oscillator gene TIMING OF CAB2 EXPRESSION1 (TOC1).
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Affiliation(s)
| | - Katharine E Hubbard
- Department of Plant Sciences, University of Cambridge, Cambridge, UK
- School of Biological, Biomedical and Environmental Sciences, University of Hull, Hull, UK
| | - Michael J Gardner
- Department of Plant Sciences, University of Cambridge, Cambridge, UK
| | - Hyun Ju Jung
- Department of Plant Sciences, University of Cambridge, Cambridge, UK
| | - Sylvain Aubry
- Department of Plant Sciences, University of Cambridge, Cambridge, UK
- Department for Plant and Microbial Biology, University of Zürich, Zürich, Switzerland
| | - Carlos T Hotta
- Department of Plant Sciences, University of Cambridge, Cambridge, UK
- Departamento de Bioquímica, Instituto de Química, Universidade de São Paulo, São Paulo, SP, Brazil
| | - Nur Izzati Mohd-Noh
- Department of Plant Sciences, University of Cambridge, Cambridge, UK
- Department of Bioscience and Health Science, Faculty of Bioscience and Medical Engineering, Universiti Teknologi Malaysia, Skudai, Johor, Malaysia
| | - Fiona C Robertson
- Department of Plant Sciences, University of Cambridge, Cambridge, UK
- Department of Biochemistry, University of Zimbabwe, Harare, Zimbabwe
| | - Timothy J Hearn
- Department of Plant Sciences, University of Cambridge, Cambridge, UK
| | - Yu-Chang Tsai
- Biochemistry and Cell Biology, Rice University, Houston, TX, USA
| | - Antony N Dodd
- Department of Plant Sciences, University of Cambridge, Cambridge, UK
- School of Biological Sciences, Bristol Life Sciences Building, University of Bristol, Bristol, UK
| | - Matthew Hannah
- Bayer CropScience NV Innovation Center, Trait Discovery, Gent, Belgium
| | | | - Julia M Davies
- Department of Plant Sciences, University of Cambridge, Cambridge, UK
| | - Janet Braam
- Biochemistry and Cell Biology, Rice University, Houston, TX, USA
| | - Alex A R Webb
- Department of Plant Sciences, University of Cambridge, Cambridge, UK.
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Abstract
Intracellular calcium signals in neurons frequently derive from the stimulation of G protein-coupled receptors (GPCR) by neurotransmitters, neuropeptides, and neurohormones. GPCR stimulation in neurons leads to generation of inositol 1,4,5-trisphosphate (IP3), which in turn activates endoplasmic reticulum (ER)-localized IP3 receptors. The IP3 receptor (IP3R) is a ligand-gated Ca2+ channel, which releases Ca2+ from ER stores. In Drosophila neurons it has been shown that depletion of ER Ca2+ store is followed by store-operated Ca2+ entry (SOCE) through STIM and Orai, the ER Ca2+ sensor and the plasma membrane Ca2+ channel respectively. The elucidation of this Ca2+ signaling pathway in neurons has in part been possible due to the ease of genetic manipulation in Drosophila, which has allowed neuron-specific knockdown of various proteins of interest. This has been followed by standardization of conditions for culturing neurons from dissected brains of the relevant genotypes, such that they could be used for robust Ca2+ measurements by imaging with standard Ca2+ indicator dyes. Protocols for measurement of IP3-mediated Ca2+ release, passive depletion of ER Ca2+ store, and SOCE in primary cultures of Drosophila neurons are described here.
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Chen Y, Huang LYM. A simple and fast method to image calcium activity of neurons from intact dorsal root ganglia using fluorescent chemical Ca 2+ indicators. Mol Pain 2017; 13:1744806917748051. [PMID: 29212403 PMCID: PMC5731619 DOI: 10.1177/1744806917748051] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
Chemical calcium indicators have been commonly used to monitor calcium (Ca2+) activity in cell bodies, i.e., somata, of isolated dorsal root ganglion neurons. Recent studies have shown that dorsal root ganglion somata play an essential role in soma–glia interactions and actively participate in the transmission of nociceptive signals. It is therefore desirable to develop methods to study Ca2+ activity in neurons and glia in intact dorsal root ganglia. In our previous studies, we found that incubation of intact dorsal root ganglia with acetoxymethyl dye resulted in efficient Ca2+ dye loading into glial cells but limited dye loading into neurons. Here, we introduce a useful method to load Ca2+ dyes in intact dorsal root ganglion neurons through electroporation. We found that electroporation greatly facilitated loading of Fluo-4 acetoxymethyl, Oregon green bapta-1-488 acetoxymethyl, and Fluo-4 pentapotassium salt into dorsal root ganglion neurons. In contrast, electroporation did not further facilitate dye loading into glia. Using electroporation followed by incubation of acetoxymethyl form Ca2+ dye, we can load acetoxymethyl Ca2+ dye well in both neurons and glia. With this approach, we found that inflammation induced by complete Freund’s adjuvant significantly increased the incidence of neuron–glia interactions in dorsal root ganglia. We also confirmed the actions of capsaicin and morphine on Ca2+ responses in dorsal root ganglion neurons. Thus, by promoting the loading of Ca2+ dye in neurons and glia through electroporation and incubation, Ca2+ activities in neurons and neuron–glia interactions can be well studied in intact dorsal root ganglia.
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Affiliation(s)
- Yong Chen
- 1 Department of Neuroscience, Cell Biology and Anatomy, 12338 University of Texas Medical Branch, Galveston , TX, USA
| | - Li-Yen M Huang
- 1 Department of Neuroscience, Cell Biology and Anatomy, 12338 University of Texas Medical Branch, Galveston , TX, USA
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Beesley S, Noguchi T, Welsh DK. Cardiomyocyte Circadian Oscillations Are Cell-Autonomous, Amplified by β-Adrenergic Signaling, and Synchronized in Cardiac Ventricle Tissue. PLoS One 2016; 11:e0159618. [PMID: 27459195 PMCID: PMC4961434 DOI: 10.1371/journal.pone.0159618] [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: 12/18/2015] [Accepted: 07/06/2016] [Indexed: 11/18/2022] Open
Abstract
Circadian clocks impact vital cardiac parameters such as blood pressure and heart rate, and adverse cardiac events such as myocardial infarction and sudden cardiac death. In mammals, the central circadian pacemaker, located in the suprachiasmatic nucleus of the hypothalamus, synchronizes cellular circadian clocks in the heart and many other tissues throughout the body. Cardiac ventricle explants maintain autonomous contractions and robust circadian oscillations of clock gene expression in culture. In the present study, we examined the relationship between intrinsic myocardial function and circadian rhythms in cultures from mouse heart. We cultured ventricular explants or dispersed cardiomyocytes from neonatal mice expressing a PER2::LUC bioluminescent reporter of circadian clock gene expression. We found that isoproterenol, a β-adrenoceptor agonist known to increase heart rate and contractility, also amplifies PER2 circadian rhythms in ventricular explants. We found robust, cell-autonomous PER2 circadian rhythms in dispersed cardiomyocytes. Single-cell rhythms were initially synchronized in ventricular explants but desynchronized in dispersed cells. In addition, we developed a method for long-term, simultaneous monitoring of clock gene expression, contraction rate, and basal intracellular Ca2+ level in cardiomyocytes using PER2::LUC in combination with GCaMP3, a genetically encoded fluorescent Ca2+ reporter. In contrast to robust PER2 circadian rhythms in cardiomyocytes, we detected no rhythms in contraction rate and only weak rhythms in basal Ca2+ level. In summary, we found that PER2 circadian rhythms of cardiomyocytes are cell-autonomous, amplified by adrenergic signaling, and synchronized by intercellular communication in ventricle explants, but we detected no robust circadian rhythms in contraction rate or basal Ca2+.
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Affiliation(s)
- Stephen Beesley
- Center for Circadian Biology, University of California San Diego, La Jolla, California, United States of America
- Department of Psychiatry, University of California San Diego, La Jolla, California, United States of America
| | - Takako Noguchi
- Center for Circadian Biology, University of California San Diego, La Jolla, California, United States of America
- Department of Psychiatry, University of California San Diego, La Jolla, California, United States of America
- * E-mail:
| | - David K. Welsh
- Center for Circadian Biology, University of California San Diego, La Jolla, California, United States of America
- Department of Psychiatry, University of California San Diego, La Jolla, California, United States of America
- Veterans Affairs San Diego Healthcare System, San Diego, California, United States of America
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Singh U, Kumar S, Shelkar GP, Yadav M, Kokare DM, Goswami C, Lechan RM, Singru PS. Transient receptor potential vanilloid 3 (TRPV3) in the ventral tegmental area of rat: Role in modulation of the mesolimbic-dopamine reward pathway. Neuropharmacology 2016; 110:198-210. [PMID: 27084697 DOI: 10.1016/j.neuropharm.2016.04.012] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2016] [Revised: 04/04/2016] [Accepted: 04/10/2016] [Indexed: 12/29/2022]
Abstract
While dopamine (DA) neurons in the ventral tegmental area (VTA) drive the mesolimbic-reward pathway, confluent lines of evidence underscore the importance of transient receptor potential vanilloid (TRPV) channels as novel regulators of these neurons. Among the TRPV-subfamily, TRPV3 is of particular interest in reward, since active ingredients of flavour-enhancing spices in food serve as TRPV3 agonists and modulate DAergic neurotransmission. The nature of TRPV3 elements in the VTA and their role in driving the mesolimbic-DA-reward pathway has however, remained unexplored. We observed TRPV3 mRNA as well as TRPV3-immunoreactive neurons in the VTA of Wistar rats. We therefore explored whether these ion channels participate in modulating mesolimbic-DA reward pathway. In the posterior VTA (pVTA), 82 ± 2.6% of the TRPV3 neurons co-express tyrosine hydroxylase and 68 ± 5.5% of these neurons project to the nucleus accumbens shell (Acb shell). While ex vivo treatment of midbrain slices with TRPV3-agonist, thymol increased [Ca(2+)]i-activity in pVTA neurons, intra-pVTA injections of thymol in freely-moving, satiated rats enhanced positive reinforcement for active lever pressings in an operant chamber to self-administer sweet pellets. This behavior was attenuated by prior treatment with intra-Acb shell DA D1- and D2-like receptor antagonists. These results demonstrate a role for TRPV3 in driving mesolimbic-DA food-reward pathway, and underscores the importance of these channels in the VTA as key components processing reward.
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Affiliation(s)
- Uday Singh
- School of Biological Sciences, National Institute of Science Education and Research (NISER)-Bhubaneswar, 752050, Odisha, India
| | - Santosh Kumar
- School of Biological Sciences, National Institute of Science Education and Research (NISER)-Bhubaneswar, 752050, Odisha, India
| | - Gajanan P Shelkar
- Department of Pharmaceutical Sciences, R.T.M. Nagpur University, Nagpur, 440033, Maharashtra, India
| | - Manoj Yadav
- School of Biological Sciences, National Institute of Science Education and Research (NISER)-Bhubaneswar, 752050, Odisha, India
| | - Dadasaheb M Kokare
- Department of Pharmaceutical Sciences, R.T.M. Nagpur University, Nagpur, 440033, Maharashtra, India
| | - Chandan Goswami
- School of Biological Sciences, National Institute of Science Education and Research (NISER)-Bhubaneswar, 752050, Odisha, India
| | - Ronald M Lechan
- Division of Endocrinology, Diabetes and Metabolism, Department of Medicine, Tupper Research Institute, Tufts Medical Center, Boston, MA, USA; Department of Neuroscience, Tufts University School of Medicine, Boston, MA, USA
| | - Praful S Singru
- School of Biological Sciences, National Institute of Science Education and Research (NISER)-Bhubaneswar, 752050, Odisha, India.
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Francis M, Waldrup J, Qian X, Taylor MS. Automated analysis of dynamic Ca2+ signals in image sequences. J Vis Exp 2014:51560. [PMID: 24962784 PMCID: PMC4195352 DOI: 10.3791/51560] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
Intracellular Ca(2+) signals are commonly studied with fluorescent Ca(2+) indicator dyes and microscopy techniques. However, quantitative analysis of Ca(2+) imaging data is time consuming and subject to bias. Automated signal analysis algorithms based on region of interest (ROI) detection have been implemented for one-dimensional line scan measurements, but there is no current algorithm which integrates optimized identification and analysis of ROIs in two-dimensional image sequences. Here an algorithm for rapid acquisition and analysis of ROIs in image sequences is described. It utilizes ellipses fit to noise filtered signals in order to determine optimal ROI placement, and computes Ca(2+) signal parameters of amplitude, duration and spatial spread. This algorithm was implemented as a freely available plugin for ImageJ (NIH) software. Together with analysis scripts written for the open source statistical processing software R, this approach provides a high-capacity pipeline for performing quick statistical analysis of experimental output. The authors suggest that use of this analysis protocol will lead to a more complete and unbiased characterization of physiologic Ca(2+) signaling.
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Affiliation(s)
| | - Josh Waldrup
- Department of Physiology, University of South Alabama
| | - Xun Qian
- Department of Physiology, University of South Alabama
| | - Mark S Taylor
- Department of Physiology, University of South Alabama;
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Francis M, Qian X, Charbel C, Ledoux J, Parker JC, Taylor MS. Automated region of interest analysis of dynamic Ca²+ signals in image sequences. Am J Physiol Cell Physiol 2012; 303:C236-43. [PMID: 22538238 DOI: 10.1152/ajpcell.00016.2012] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Ca(2+) signals are commonly measured using fluorescent Ca(2+) indicators and microscopy techniques, but manual analysis of Ca(2+) measurements is time consuming and subject to bias. Automated region of interest (ROI) detection algorithms have been employed for identification of Ca(2+) signals in one-dimensional line scan images, but currently there is no process to integrate acquisition and analysis of ROIs within two-dimensional time lapse image sequences. Therefore we devised a novel algorithm for rapid ROI identification and measurement based on the analysis of best-fit ellipses assigned to signals within noise-filtered image sequences. This algorithm was implemented as a plugin for ImageJ software (National Institutes of Health, Bethesda, MD). We evaluated the ability of our algorithm to detect synthetic Gaussian signal pulses embedded in background noise. The algorithm placed ROIs very near to the center of a range of signal pulses, resulting in mean signal amplitude measurements of 99.06 ± 4.11% of true amplitude values. As a practical application, we evaluated both agonist-induced Ca(2+) responses in cultured endothelial cell monolayers, and subtle basal endothelial Ca(2+) dynamics in opened artery preparations. Our algorithm enabled comprehensive measurement of individual and localized cellular responses within cultured cell monolayers. It also accurately identified characteristic Ca(2+) transients, or Ca(2+) pulsars, within the endothelium of intact mouse mesenteric arteries and revealed the distribution of this basal Ca(2+) signal modality to be non-Gaussian with respect to amplitude, duration, and spatial spread. We propose that large-scale statistical evaluations made possible by our algorithm will lead to a more efficient and complete characterization of physiologic Ca(2+)-dependent signaling.
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Affiliation(s)
- Michael Francis
- Department of Physiology, University of South Alabama, Mobile, Alabama, USA
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Hong JH, Jeong B, Min CH, Lee KJ. Circadian waves of cytosolic calcium concentration and long-range network connections in rat suprachiasmatic nucleus. Eur J Neurosci 2012; 35:1417-25. [PMID: 22501027 DOI: 10.1111/j.1460-9568.2012.08069.x] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The suprachiasmatic nucleus (SCN) is the master clock in mammals governing the daily physiological and behavioral rhythms. It is composed of thousands of clock cells with their own intrinsic periods varying over a wide range (20-28 h). Despite this heterogeneity, an intact SCN maintains a coherent 24 h periodic rhythm through some cell-to-cell coupling mechanisms. This study examined how the clock cells are connected to each other and how their phases are organized in space by monitoring the cytosolic free calcium ion concentration ([Ca(2+)](c)) of clock cells using the calcium-binding fluorescent protein, cameleon. Extensive analysis of 18 different organotypic slice cultures of the SCN showed that the SCN calcium dynamics is coordinated by phase-synchronizing networks of long-range neurites as well as by diffusively propagating phase waves. The networks appear quite extensive and far-reaching, and the clock cells connected by them exhibit heterogeneous responses in their amplitudes and periods of oscillation to tetrodotoxin treatments. Taken together, our study suggests that the network of long-range cellular connectivity has an important role for the SCN in achieving its phase and period coherence.
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Affiliation(s)
- Jin Hee Hong
- Center for Cell Dynamics and Department of Physics, Korea University, Anam-Dong 5-1, Sungbuk-Gu, Seoul 136-713, Korea
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Fluorescent Genetically Encoded Calcium Indicators and Their In Vivo Application. FLUORESCENT PROTEINS II 2011. [DOI: 10.1007/4243_2011_29] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
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