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Rozofsky JP, Pozzuto JM, Byrd-Jacobs CA. Mitral Cell Dendritic Morphology in the Adult Zebrafish Olfactory Bulb following Growth, Injury and Recovery. Int J Mol Sci 2024; 25:5030. [PMID: 38732248 PMCID: PMC11084181 DOI: 10.3390/ijms25095030] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2024] [Revised: 05/03/2024] [Accepted: 05/04/2024] [Indexed: 05/13/2024] Open
Abstract
The role of afferent target interactions in dendritic plasticity within the adult brain remains poorly understood. There is a paucity of data regarding the effects of deafferentation and subsequent dendritic recovery in adult brain structures. Moreover, although adult zebrafish demonstrate ongoing growth, investigations into the impact of growth on mitral cell (MC) dendritic arbor structure and complexity are lacking. Leveraging the regenerative capabilities of the zebrafish olfactory system, we conducted a comprehensive study to address these gaps. Employing an eight-week reversible deafferentation injury model followed by retrograde labeling, we observed substantial morphological alterations in MC dendrites. Our hypothesis posited that cessation of injury would facilitate recovery of MC dendritic arbor structure and complexity, potentially influenced by growth dynamics. Statistical analyses revealed significant changes in MC dendritic morphology following growth and recovery periods, indicating that MC total dendritic branch length retained significance after 8 weeks of deafferentation injury when normalized to individual fish physical characteristics. This suggests that regeneration of branch length could potentially function relatively independently of growth-related changes. These findings underscore the remarkable plasticity of adult dendritic arbor structures in a sophisticated model organism and highlight the efficacy of zebrafish as a vital implement for studying neuroregenerative processes.
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Affiliation(s)
- John P. Rozofsky
- Department of Biological Sciences, Western Michigan University, 1903 W Michigan Ave., Kalamazoo, MI 49009, USA;
| | - Joanna M. Pozzuto
- Department of Biology, Kalamazoo Valley Community College, 6767 W O Ave., Kalamazoo, MI 49009, USA;
| | - Christine A. Byrd-Jacobs
- Department of Biological Sciences, Western Michigan University, 1903 W Michigan Ave., Kalamazoo, MI 49009, USA;
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2
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Serrano GE, Walker JE, Tremblay C, Piras IS, Huentelman MJ, Belden CM, Goldfarb D, Shprecher D, Atri A, Adler CH, Shill HA, Driver-Dunckley E, Mehta SH, Caselli R, Woodruff BK, Haarer CF, Ruhlen T, Torres M, Nguyen S, Schmitt D, Rapscak SZ, Bime C, Peters JL, Alevritis E, Arce RA, Glass MJ, Vargas D, Sue LI, Intorcia AJ, Nelson CM, Oliver J, Russell A, Suszczewicz KE, Borja CI, Cline MP, Hemmingsen SJ, Qiji S, Hobgood HM, Mizgerd JP, Sahoo MK, Zhang H, Solis D, Montine TJ, Berry GJ, Reiman EM, Röltgen K, Boyd SD, Pinsky BA, Zehnder JL, Talbot P, Desforges M, DeTure M, Dickson DW, Beach TG. SARS-CoV-2 Brain Regional Detection, Histopathology, Gene Expression, and Immunomodulatory Changes in Decedents with COVID-19. J Neuropathol Exp Neurol 2022; 81:666-695. [PMID: 35818336 PMCID: PMC9278252 DOI: 10.1093/jnen/nlac056] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Brains of 42 COVID-19 decedents and 107 non-COVID-19 controls were studied. RT-PCR screening of 16 regions from 20 COVID-19 autopsies found SARS-CoV-2 E gene viral sequences in 7 regions (2.5% of 320 samples), concentrated in 4/20 subjects (20%). Additional screening of olfactory bulb (OB), amygdala (AMY) and entorhinal area for E, N1, N2, RNA-dependent RNA polymerase, and S gene sequences detected one or more of these in OB in 8/21 subjects (38%). It is uncertain whether these RNA sequences represent viable virus. Significant histopathology was limited to 2/42 cases (4.8%), one with a large acute cerebral infarct and one with hemorrhagic encephalitis. Case-control RNAseq in OB and AMY found more than 5000 and 700 differentially expressed genes, respectively, unrelated to RT-PCR results; these involved immune response, neuronal constituents, and olfactory/taste receptor genes. Olfactory marker protein-1 reduction indicated COVID-19-related loss of OB olfactory mucosa afferents. Iba-1-immunoreactive microglia had reduced area fractions in cerebellar cortex and AMY, and cytokine arrays showed generalized downregulation in AMY and upregulation in blood serum in COVID-19 cases. Although OB is a major brain portal for SARS-CoV-2, COVID-19 brain changes are more likely due to blood-borne immune mediators and trans-synaptic gene expression changes arising from OB deafferentation.
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Affiliation(s)
- Geidy E Serrano
- From the Banner Sun Health Research Institute, Sun City, Arizona, USA
| | - Jessica E Walker
- From the Banner Sun Health Research Institute, Sun City, Arizona, USA
| | - Cécilia Tremblay
- From the Banner Sun Health Research Institute, Sun City, Arizona, USA
| | - Ignazio S Piras
- Neurogenomics Division, Translational Genomics Research Institute, Phoenix, Arizona, USA
| | - Matthew J Huentelman
- Neurogenomics Division, Translational Genomics Research Institute, Phoenix, Arizona, USA
| | | | - Danielle Goldfarb
- From the Banner Sun Health Research Institute, Sun City, Arizona, USA
| | - David Shprecher
- From the Banner Sun Health Research Institute, Sun City, Arizona, USA
| | - Alireza Atri
- From the Banner Sun Health Research Institute, Sun City, Arizona, USA.,Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts, USA
| | - Charles H Adler
- Mayo Clinic College of Medicine, Mayo Clinic Arizona, Scottsdale, Arizona, USA
| | - Holly A Shill
- Barrow Neurological Institute, Phoenix, Arizona, USA
| | | | - Shyamal H Mehta
- Mayo Clinic College of Medicine, Mayo Clinic Arizona, Scottsdale, Arizona, USA
| | - Richard Caselli
- Mayo Clinic College of Medicine, Mayo Clinic Arizona, Scottsdale, Arizona, USA
| | - Bryan K Woodruff
- Mayo Clinic College of Medicine, Mayo Clinic Arizona, Scottsdale, Arizona, USA
| | | | - Thomas Ruhlen
- Banner Boswell Medical Center, Sun City, Arizona, USA
| | - Maria Torres
- Banner Boswell Medical Center, Sun City, Arizona, USA
| | - Steve Nguyen
- Banner Boswell Medical Center, Sun City, Arizona, USA
| | - Dasan Schmitt
- Banner Boswell Medical Center, Sun City, Arizona, USA
| | | | | | | | | | - Richard A Arce
- From the Banner Sun Health Research Institute, Sun City, Arizona, USA
| | - Michael J Glass
- From the Banner Sun Health Research Institute, Sun City, Arizona, USA
| | - Daisy Vargas
- From the Banner Sun Health Research Institute, Sun City, Arizona, USA
| | - Lucia I Sue
- From the Banner Sun Health Research Institute, Sun City, Arizona, USA
| | | | - Courtney M Nelson
- From the Banner Sun Health Research Institute, Sun City, Arizona, USA
| | - Javon Oliver
- From the Banner Sun Health Research Institute, Sun City, Arizona, USA
| | - Aryck Russell
- Uniformed Services University of the Health Sciences, Bethesda, Maryland, USA
| | | | - Claryssa I Borja
- From the Banner Sun Health Research Institute, Sun City, Arizona, USA
| | - Madison P Cline
- From the Banner Sun Health Research Institute, Sun City, Arizona, USA
| | | | - Sanaria Qiji
- From the Banner Sun Health Research Institute, Sun City, Arizona, USA
| | - Holly M Hobgood
- From the Banner Sun Health Research Institute, Sun City, Arizona, USA
| | - Joseph P Mizgerd
- Pulmonary Center, Boston University School of Medicine, Boston, Massachusetts, USA
| | - Malaya K Sahoo
- Department of Pathology, Stanford University, Stanford, California, USA
| | - Haiyu Zhang
- Department of Pathology, Stanford University, Stanford, California, USA
| | - Daniel Solis
- Department of Pathology, Stanford University, Stanford, California, USA
| | - Thomas J Montine
- Department of Pathology, Stanford University, Stanford, California, USA
| | - Gerald J Berry
- Department of Pathology, Stanford University, Stanford, California, USA.,From the Banner Sun Health Research Institute, Sun City, Arizona, USA
| | | | - Katharina Röltgen
- Department of Pathology, Stanford University, Stanford, California, USA
| | - Scott D Boyd
- Department of Pathology, Stanford University, Stanford, California, USA
| | - Benjamin A Pinsky
- Department of Pathology, Stanford University, Stanford, California, USA.,Division of Infectious Disease & Geographic Medicine, Department of Medicine, Stanford University, Stanford, California, USA
| | - James L Zehnder
- Department of Pathology, Stanford University, Stanford, California, USA
| | - Pierre Talbot
- Laboratory of Neuroimmunology, Centre Armand-Frappier Santé Biotechnologie, Institut National de la Recherche Scientifique, Laval, Quebec, Canada
| | - Marc Desforges
- Laboratory of Virology, Centre Hospitalier Universitaire Sainte-Justine, Montréal, Quebec, Canada.,Département de microbiologie, infectiologie et Immunologie, Université de Montréal, Montréal, Quebec, Canada
| | - Michael DeTure
- Mayo Clinic College of Medicine, Mayo Clinic Florida, Jacksonville, Florida, USA
| | - Dennis W Dickson
- Mayo Clinic College of Medicine, Mayo Clinic Florida, Jacksonville, Florida, USA
| | - Thomas G Beach
- From the Banner Sun Health Research Institute, Sun City, Arizona, USA
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3
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Lakshmanan HG, Miller E, White-Canale A, McCluskey LP. Immune responses in the injured olfactory and gustatory systems: a role in olfactory receptor neuron and taste bud regeneration? Chem Senses 2022; 47:bjac024. [PMID: 36152297 PMCID: PMC9508897 DOI: 10.1093/chemse/bjac024] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
Sensory cells that specialize in transducing olfactory and gustatory stimuli are renewed throughout life and can regenerate after injury unlike their counterparts in the mammalian retina and auditory epithelium. This uncommon capacity for regeneration offers an opportunity to understand mechanisms that promote the recovery of sensory function after taste and smell loss. Immune responses appear to influence degeneration and later regeneration of olfactory sensory neurons and taste receptor cells. Here we review surgical, chemical, and inflammatory injury models and evidence that immune responses promote or deter chemosensory cell regeneration. Macrophage and neutrophil responses to chemosensory receptor injury have been the most widely studied without consensus on their net effects on regeneration. We discuss possible technical and biological reasons for the discrepancy, such as the difference between peripheral and central structures, and suggest directions for progress in understanding immune regulation of chemosensory regeneration. Our mechanistic understanding of immune-chemosensory cell interactions must be expanded before therapies can be developed for recovering the sensation of taste and smell after head injury from traumatic nerve damage and infection. Chemosensory loss leads to decreased quality of life, depression, nutritional challenges, and exposure to environmental dangers highlighting the need for further studies in this area.
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Affiliation(s)
- Hari G Lakshmanan
- Department of Neuroscience and Regenerative Medicine, Medical College of Georgia, Augusta University, Augusta, GA, USA
| | - Elayna Miller
- Department of Medical Illustration, Medical College of Georgia, Augusta University, Augusta, GA, USA
| | - AnnElizabeth White-Canale
- Department of Medical Illustration, Medical College of Georgia, Augusta University, Augusta, GA, USA
| | - Lynnette P McCluskey
- Department of Neuroscience and Regenerative Medicine, Medical College of Georgia, Augusta University, Augusta, GA, USA
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4
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Hardy K, Amariutei AE, De Faveri F, Hendry A, Marcotti W, Ceriani F. Functional development and regeneration of hair cells in the zebrafish lateral line. J Physiol 2021; 599:3913-3936. [PMID: 34143497 PMCID: PMC7612129 DOI: 10.1113/jp281522] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2021] [Accepted: 06/03/2021] [Indexed: 12/22/2022] Open
Abstract
Hair cells are mechanosensory receptors responsible for transducing auditory and vestibular information into electrical signals, which are then transmitted with remarkable precision to afferent neurons. Different from mammals, the hair cells of lower vertebrates, including those present in the neuromasts of the zebrafish lateral line, regenerate following environmental or chemical insults. Here we investigate the time-course of regeneration of hair cells in vivo using electrophysiology, 2-photon imaging and immunostaining applied to wild-type and genetically-encoded fluorescent indicator zebrafish lines. Functional hair cells drive spontaneous action potentials in the posterior lateral line afferent fibres, the frequency of which progressively increases over the first 10-days post-fertilization (dpf). Higher firing-rate fibres are only observed from ~6 dpf. Following copper treatment, newly formed hair cells become functional and are able to drive APs in the afferent fibres within 48 hours in both early-larval (≤8 dpf) and late-larval (12-17 dpf) zebrafish. However, the complete functional regeneration of the entire neuromast is delayed in late-larval compared to early-larval zebrafish. We propose that while individual regenerating hair cells can rapidly become active, the acquisition of fully functional neuromasts progresses faster at early-larval stages, a time when hair cells are still under development. At both ages, the afferent terminals in the regenerating neuromast appear to make initial contact with supporting cells. The ablation of the lateral line afferent neurons prevents the timely regeneration of supporting cells and hair cells. These findings indicate that the afferent system is likely to facilitate or promote the neuromast regeneration process.
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Affiliation(s)
- Katherine Hardy
- Department of Biomedical Science, University of Sheffield, Sheffield, UK
| | - Ana E Amariutei
- Department of Biomedical Science, University of Sheffield, Sheffield, UK
| | | | - Aenea Hendry
- Department of Biomedical Science, University of Sheffield, Sheffield, UK
| | - Walter Marcotti
- Department of Biomedical Science, University of Sheffield, Sheffield, UK.,Sheffield Neuroscience Institute, University of Sheffield, Sheffield, UK
| | - Federico Ceriani
- Department of Biomedical Science, University of Sheffield, Sheffield, UK
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5
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Diving into the streams and waves of constitutive and regenerative olfactory neurogenesis: insights from zebrafish. Cell Tissue Res 2020; 383:227-253. [PMID: 33245413 DOI: 10.1007/s00441-020-03334-2] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2020] [Accepted: 11/02/2020] [Indexed: 02/06/2023]
Abstract
The olfactory system is renowned for its functional and structural plasticity, with both peripheral and central structures displaying persistent neurogenesis throughout life and exhibiting remarkable capacity for regenerative neurogenesis after damage. In general, fish are known for their extensive neurogenic ability, and the zebrafish in particular presents an attractive model to study plasticity and adult neurogenesis in the olfactory system because of its conserved structure, relative simplicity, rapid cell turnover, and preponderance of neurogenic niches. In this review, we present an overview of the anatomy of zebrafish olfactory structures, with a focus on the neurogenic niches in the olfactory epithelium, olfactory bulb, and ventral telencephalon. Constitutive and regenerative neurogenesis in both the peripheral olfactory organ and central olfactory bulb of zebrafish is reviewed in detail, and a summary of current knowledge about the cellular origin and molecular signals involved in regulating these processes is presented. While some features of physiologic and injury-induced neurogenic responses are similar, there are differences that indicate that regeneration is not simply a reiteration of the constitutive proliferation process. We provide comparisons to mammalian neurogenesis that reveal similarities and differences between species. Finally, we present a number of open questions that remain to be answered.
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6
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Var SR, Byrd-Jacobs CA. Microglial response patterns following damage to the zebrafish olfactory bulb. IBRO Rep 2019; 7:70-79. [PMID: 31650065 PMCID: PMC6804743 DOI: 10.1016/j.ibror.2019.08.002] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2019] [Accepted: 08/23/2019] [Indexed: 12/11/2022] Open
Abstract
The inherent plasticity of the zebrafish olfactory system serves as a useful model for examining immune cell responses after injury. Microglia are the resident immune cells of the CNS that respond to damage by migrating to the site of injury and phagocytizing neuronal debris. While the olfactory system is renowned for its ability to recover from damage, the specific mechanisms of microglial involvement in olfactory system plasticity are unknown. To approach the potentially time-dependent effects of microglial activation after injury, we performed a time course analysis of microglial response profiles and patterns following different forms of damage: deafferentation by cautery ablation of the olfactory organ, deafferentation by chemical ablation of the olfactory epithelium, and direct lesioning of the olfactory bulb. Our aim was to demonstrate that immunocytochemistry and microscopy methods in zebrafish can be used to determine the timing of distinct microglial response patterns following various forms of injury. We found that permanent and temporary forms of damage to the olfactory bulb resulted in different microglial response profiles from 1 to 72 h after injury, suggesting that there may be critical timepoints in which microglia are activated that contribute to tissue and neuronal repair with a regenerative outcome versus a degenerative outcome. These distinctions between the different forms of damage suggest temporal changes relative to the potential for regeneration, since cautery deafferentation is permanent and unrecoverable while chemical ablation deafferentation and direct lesioning is reversible and can be used to observe the microglial relationship in neural regeneration and functional recovery in future studies.
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Affiliation(s)
- Susanna R Var
- Western Michigan University, Kalamazoo, Michigan, 49008-5410 USA
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7
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Calvo-Ochoa E, Byrd-Jacobs CA. The Olfactory System of Zebrafish as a Model for the Study of Neurotoxicity and Injury: Implications for Neuroplasticity and Disease. Int J Mol Sci 2019; 20:ijms20071639. [PMID: 30986990 PMCID: PMC6480214 DOI: 10.3390/ijms20071639] [Citation(s) in RCA: 37] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2019] [Revised: 03/26/2019] [Accepted: 03/29/2019] [Indexed: 12/30/2022] Open
Abstract
The olfactory system, composed of the olfactory organs and the olfactory bulb, allows organisms to interact with their environment and through the detection of odor signals. Olfaction mediates behaviors pivotal for survival, such as feeding, mating, social behavior, and danger assessment. The olfactory organs are directly exposed to the milieu, and thus are particularly vulnerable to damage by environmental pollutants and toxicants, such as heavy metals, pesticides, and surfactants, among others. Given the widespread occurrence of olfactory toxicants, there is a pressing need to understand the effects of these harmful compounds on olfactory function. Zebrafish (Danio rerio) is a valuable model for studying human physiology, disease, and toxicity. Additionally, the anatomical components of the zebrafish olfactory system are similar to those of other vertebrates, and they present a remarkable degree of regeneration and neuroplasticity, making it an ideal model for the study of regeneration, reorganization and repair mechanisms following olfactory toxicant exposure. In this review, we focus on (1) the anatomical, morphological, and functional organization of the olfactory system of zebrafish; (2) the adverse effects of olfactory toxicants and injury to the olfactory organ; and (3) remodeling and repair neuroplasticity mechanisms following injury and degeneration by olfactory toxicant exposure.
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Affiliation(s)
- Erika Calvo-Ochoa
- Department of Biological Sciences, Western Michigan University, Kalamazoo, MI 49008-5410, USA.
| | - Christine A Byrd-Jacobs
- Department of Biological Sciences, Western Michigan University, Kalamazoo, MI 49008-5410, USA.
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8
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Scheib JJ, Pozzuto JM, Byrd-Jacobs CA. Reversible deafferentation of the zebrafish olfactory bulb with wax plug insertion. J Neurosci Methods 2018; 311:47-56. [PMID: 30316892 DOI: 10.1016/j.jneumeth.2018.10.014] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2018] [Revised: 10/08/2018] [Accepted: 10/10/2018] [Indexed: 11/26/2022]
Abstract
BACKGROUND Deafferentation of the zebrafish olfactory bulb allows investigation of neuroplasticity in a particularly dynamic brain region of a popular model animal known for its regenerative abilities. Current methods to remove sensory input to the zebrafish olfactory bulb differ in the extent of deafferentation and potential for recovery. NEW METHOD We present a novel method of olfactory bulb deafferentation using continuous wax plug insertions into the nasal cavity of zebrafish. Wax plugs were placed in the nasal cavity and replaced if needed over 1wk or 3wk survival periods. Wax plugs were removed from fish after 1wk of occlusion to analyze the potential recovery of the olfactory organ and bulb. RESULTS Wax plug insertions caused a dramatic reduction in olfactory organ size and structure and significantly reduced afferent input to the olfactory bulb after 1wk and 3wk. Removal of the wax plugs after 1wk allowed for recovery of the olfactory organ and subsequent reinnervation of the olfactory bulb. COMPARISONS WITH EXISTING METHODS Chemical ablation with detergent causes partial, temporary deafferentation of the olfactory bulb. Cautery ablation causes complete, permanent deafferentation of the olfactory bulb. Wax plug insertions cause nearly complete, temporary deafferentation, allowing both significant deafferentation and the potential for reinnervation of the olfactory bulb. CONCLUSIONS The wax plug insertion method of deafferentation described here is unique in that it destroys almost completely the structure of the olfactory organ and removes almost completely sensory input to the olfactory bulb, yet the organ returns to its typical morphology and afferent innervation returns.
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Affiliation(s)
- Jackson J Scheib
- Department of Biological Sciences, Western Michigan University, 1903 W. Michigan Ave., Kalamazoo, MI, 49008-5410, USA
| | - Joanna M Pozzuto
- Department of Biological Sciences, Western Michigan University, 1903 W. Michigan Ave., Kalamazoo, MI, 49008-5410, USA
| | - Christine A Byrd-Jacobs
- Department of Biological Sciences, Western Michigan University, 1903 W. Michigan Ave., Kalamazoo, MI, 49008-5410, USA.
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9
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Pozzuto JM, Fuller CL, Byrd-Jacobs CA. Deafferentation-induced alterations in mitral cell dendritic morphology in the adult zebrafish olfactory bulb. J Bioenerg Biomembr 2018; 51:29-40. [PMID: 30215151 DOI: 10.1007/s10863-018-9772-x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2018] [Accepted: 09/07/2018] [Indexed: 11/30/2022]
Abstract
The removal of afferent input to the olfactory bulb by both cautery and chemical olfactory organ ablation in adult zebrafish results in a significant decrease in volume of the ipsilateral olfactory bulb. To examine the effects of deafferentation at a cellular level, primary output neurons of the olfactory bulb, the mitral cells, were investigated using retrograde tract tracing with fluorescent dextran using ex vivo brain cultures. Morphological characteristics including the number of major dendritic branches, total length of dendritic branches, area of the dendritic arbor, overall dendritic complexity, and optical density of the arbor were used to determine the effects of deafferentation on mitral cell dendrites. Following 8 weeks of permanent deafferentation there were significant reductions in the total length of dendritic branches, the area of the dendritic arbor, and the density of fine processes in the dendritic tuft. With 8 weeks of chronic, partial deafferentation there were significant reductions in all parameters examined, including a modified Sholl analysis that showed significant decreases in overall dendritic complexity. These results show the plasticity of mitral cell dendritic structures in the adult brain and provide information about the response of these output neurons following the loss of sensory input in this key model system.
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Affiliation(s)
- Joanna M Pozzuto
- Department of Biological Sciences, Western Michigan University, 1903 W. Michigan Ave, Kalamazoo, MI, 49008-5410, USA
| | - Cynthia L Fuller
- Department of Biological Sciences, Western Michigan University, 1903 W. Michigan Ave, Kalamazoo, MI, 49008-5410, USA
| | - Christine A Byrd-Jacobs
- Department of Biological Sciences, Western Michigan University, 1903 W. Michigan Ave, Kalamazoo, MI, 49008-5410, USA.
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10
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Hawkins SJ, Weiss L, Offner T, Dittrich K, Hassenklöver T, Manzini I. Functional Reintegration of Sensory Neurons and Transitional Dendritic Reduction of Mitral/Tufted Cells during Injury-Induced Recovery of the Larval Xenopus Olfactory Circuit. Front Cell Neurosci 2017; 11:380. [PMID: 29234276 PMCID: PMC5712363 DOI: 10.3389/fncel.2017.00380] [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] [Received: 09/08/2017] [Accepted: 11/13/2017] [Indexed: 01/08/2023] Open
Abstract
Understanding the mechanisms involved in maintaining lifelong neurogenesis has a clear biological and clinical interest. In the present study, we performed olfactory nerve transection on larval Xenopus to induce severe damage to the olfactory circuitry. We surveyed the timing of the degeneration, subsequent rewiring and functional regeneration of the olfactory system following injury. A range of structural labeling techniques and functional calcium imaging were performed on both tissue slices and whole brain preparations. Cell death of olfactory receptor neurons and proliferation of stem cells in the olfactory epithelium were immediately increased following lesion. New olfactory receptor neurons repopulated the olfactory epithelium and once again showed functional responses to natural odorants within 1 week after transection. Reinnervation of the olfactory bulb (OB) by newly formed olfactory receptor neuron axons also began at this time. Additionally, we observed a temporary increase in cell death in the OB and a subsequent loss in OB volume. Mitral/tufted cells, the second order neurons of the olfactory system, largely survived, but transiently lost dendritic tuft complexity. The first odorant-induced responses in the OB were observed 3 weeks after nerve transection and the olfactory network showed signs of major recovery, both structurally and functionally, after 7 weeks.
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Affiliation(s)
- Sara J Hawkins
- Institute of Neurophysiology and Cellular Biophysics, University of Göttingen, Göttingen, Germany.,Institute of Animal Physiology, Department of Animal Physiology and Molecular Biomedicine, Justus Liebig University Giessen, Giessen, Germany
| | - Lukas Weiss
- Institute of Neurophysiology and Cellular Biophysics, University of Göttingen, Göttingen, Germany.,Institute of Animal Physiology, Department of Animal Physiology and Molecular Biomedicine, Justus Liebig University Giessen, Giessen, Germany
| | - Thomas Offner
- Institute of Neurophysiology and Cellular Biophysics, University of Göttingen, Göttingen, Germany.,Center for Nanoscale Microscopy and Molecular Physiology of the Brain (CNMPB), Göttingen, Germany
| | - Katarina Dittrich
- Institute of Neurophysiology and Cellular Biophysics, University of Göttingen, Göttingen, Germany.,Institute of Animal Physiology, Department of Animal Physiology and Molecular Biomedicine, Justus Liebig University Giessen, Giessen, Germany
| | - Thomas Hassenklöver
- Institute of Neurophysiology and Cellular Biophysics, University of Göttingen, Göttingen, Germany.,Institute of Animal Physiology, Department of Animal Physiology and Molecular Biomedicine, Justus Liebig University Giessen, Giessen, Germany.,Center for Nanoscale Microscopy and Molecular Physiology of the Brain (CNMPB), Göttingen, Germany
| | - Ivan Manzini
- Institute of Neurophysiology and Cellular Biophysics, University of Göttingen, Göttingen, Germany.,Institute of Animal Physiology, Department of Animal Physiology and Molecular Biomedicine, Justus Liebig University Giessen, Giessen, Germany.,Center for Nanoscale Microscopy and Molecular Physiology of the Brain (CNMPB), Göttingen, Germany
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11
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Trimpe DM, Byrd-Jacobs CA. Patterns of olfactory bulb neurogenesis in the adult zebrafish are altered following reversible deafferentation. Neuroscience 2016; 331:134-47. [PMID: 27343831 DOI: 10.1016/j.neuroscience.2016.06.026] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2015] [Revised: 06/13/2016] [Accepted: 06/14/2016] [Indexed: 11/17/2022]
Abstract
Adult brain plasticity can be investigated using reversible methods that remove afferent innervation but allow return of sensory input. Repeated intranasal irrigation with Triton X-100 in adult zebrafish diminishes innervation to the olfactory bulb, resulting in a number of alterations in bulb structure and function, and cessation of the treatment allows for reinnervation and recovery. Using bromodeoxyuridine, Hu, and caspase-3 immunoreactivity we examined cell proliferation, differentiation, migration, and survival under conditions of acute and chronic deafferentation and reafferentation. Cell proliferation within the olfactory bulb was not influenced by acute or chronic deafferentation or reafferentation, but cell fate (including differentiation, migration, and/or survival of newly formed cells) was affected. We found that chronic deafferentation caused a bilateral increase in the number of newly formed cells that migrated into the bulb, although the amount of cell death of these new cells was significantly increased compared to untreated fish. Reafferentation also increased the number of newly formed cells migrating into both bulbs, suggesting that the deafferentation effect on cell fate was maintained. Reafferentation resulted in a decrease in newly formed cells that became neurons and, although death of newly formed cells was not altered from control levels, survival was reduced in relation to that seen in chronically deafferented fish. The potential effect of age on cell genesis was also examined. While the amount of cell migration into the olfactory bulbs was not affected by fish age, more of the newly formed cells became neurons in older fish. Younger fish displayed more cell death under conditions of chronic deafferentation. In sum, our results show that reversible deafferentation affects several aspects of cell fate, including cell differentiation, migration, and survival, and age of the fish influences the response to deafferentation.
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Affiliation(s)
- Darcy M Trimpe
- Department of Biological Sciences, Western Michigan University, 1903 W Michigan Ave, Kalamazoo, MI 49008-5410, USA.
| | - Christine A Byrd-Jacobs
- Department of Biological Sciences, Western Michigan University, 1903 W Michigan Ave, Kalamazoo, MI 49008-5410, USA.
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Wang M, Banerjee K, Baker H, Cave JW. Nucleotide sequence conservation of novel and established cis-regulatory sites within the tyrosine hydroxylase gene promoter. ACTA ACUST UNITED AC 2014; 10:74-90. [PMID: 25774193 DOI: 10.1007/s11515-014-1341-z] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Tyrosine hydroxylase (TH) is the rate-limiting enzyme in catecholamine biosynthesis and its gene proximal promoter ( < 1 kb upstream from the transcription start site) is essential for regulating transcription in both the developing and adult nervous systems. Several putative regulatory elements within the TH proximal promoter have been reported, but evolutionary conservation of these elements has not been thoroughly investigated. Since many vertebrate species are used to model development, function and disorders of human catecholaminergic neurons, identifying evolutionarily conserved transcription regulatory mechanisms is a high priority. In this study, we align TH proximal promoter nucleotide sequences from several vertebrate species to identify evolutionarily conserved motifs. This analysis identified three elements (a TATA box, cyclic AMP response element (CRE) and a 5'-GGTGG-3' site) that constitute the core of an ancient vertebrate TH promoter. Focusing on only eutherian mammals, two regions of high conservation within the proximal promoter were identified: a ∼250 bp region adjacent to the transcription start site and a ∼85 bp region located approximately 350 bp further upstream. Within both regions, conservation of previously reported cis-regulatory motifs and human single nucleotide variants was evaluated. Transcription reporter assays in a TH -expressing cell line demonstrated the functionality of highly conserved motifs in the proximal promoter regions and electromobility shift assays showed that brain-region specific complexes assemble on these motifs. These studies also identified a non-canonical CRE binding (CREB) protein recognition element in the proximal promoter. Together, these studies provide a detailed analysis of evolutionary conservation within the TH promoter and identify potential cis-regulatory motifs that underlie a core set of regulatory mechanisms in mammals.
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Affiliation(s)
- Meng Wang
- Burke Medical Research Institute, White Plains, NY 10605, USA
| | | | - Harriet Baker
- Burke Medical Research Institute, White Plains, NY 10605, USA ; Weill Cornell Medical College Brain and Mind Research Institute, NY 10065, USA
| | - John W Cave
- Burke Medical Research Institute, White Plains, NY 10605, USA ; Weill Cornell Medical College Brain and Mind Research Institute, NY 10065, USA
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Kishimoto N, Asakawa K, Madelaine R, Blader P, Kawakami K, Sawamoto K. Interhemispheric asymmetry of olfactory input-dependent neuronal specification in the adult brain. Nat Neurosci 2013; 16:884-8. [PMID: 23685722 DOI: 10.1038/nn.3409] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2013] [Accepted: 04/25/2013] [Indexed: 02/07/2023]
Abstract
The vertebrate brain is anatomically and functionally asymmetric. The left and right cerebral hemispheres harbor neural stem cell niches at the ventricular-subventricular zone (V-SVZ) of the ventricular walls, where new neurons are continuously generated throughout life. However, any interhemispheric asymmetry of neural stem cell niches remains unclear. We performed gene-trap screens in adult zebrafish to identify genes that are differentially expressed in the two hemispheres and found that adult-born neurons expressing the neural zinc-finger protein Myt1 exist predominantly in the left V-SVZ. This lateralization could be reversed by left olfactory sensory deprivation-induced inactivation of Notch signaling. The olfactory behavioral preference for attractive amino acids was also impaired by sensory deprivation of the left olfactory system, but not of the right olfactory system. Our findings suggest that olfactory input generates interhemispheric differences in the fate of adult-born neurons in the zebrafish brain.
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Affiliation(s)
- Norihito Kishimoto
- Department of Developmental and Regenerative Biology, Nagoya City University Graduate School of Medical Sciences, Nagoya, Japan
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14
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Kress S, Wullimann MF. Correlated basal expression of immediate early gene egr1 and tyrosine hydroxylase in zebrafish brain and downregulation in olfactory bulb after transitory olfactory deprivation. J Chem Neuroanat 2012; 46:51-66. [DOI: 10.1016/j.jchemneu.2012.09.002] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2012] [Revised: 09/10/2012] [Accepted: 09/11/2012] [Indexed: 02/02/2023]
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15
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Paskin TR, Byrd-Jacobs CA. Reversible deafferentation of the adult zebrafish olfactory bulb affects glomerular distribution and olfactory-mediated behavior. Behav Brain Res 2012; 235:293-301. [PMID: 22963994 DOI: 10.1016/j.bbr.2012.08.018] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2012] [Revised: 08/08/2012] [Accepted: 08/12/2012] [Indexed: 10/28/2022]
Abstract
The olfactory system is a useful model for studying central nervous system recovery from damage due to its neuroplasticity. We recently developed a novel method of deafferentation by repeated exposure of Triton X-100 to the olfactory organ of adult zebrafish. This long-term, reversible method of deafferentation allows both degeneration and regeneration to be observed in the olfactory bulb. The aim of the present study is to examine olfactory bulb innervation, glomerular patterns, and olfactory-mediated behavior with repeated Triton X-100 treatment and the potential for recovery following cessation of treatment. Olfactory bulbs of control, chronic-treated, and recovery animals were examined for the presence or absence of glomeruli that have been identified in the zebrafish glomerular map. Following chronic treatment, the number of glomeruli was dramatically reduced; however, partial innervation remained in the lateral region of the bulb. When animals were given time to recover, complete glomerular distribution returned. A behavioral assay was developed to determine if innervation remaining correlated with behavior of the fish. Chronic-treated fish did not respond to odorants involved with social behavior but continued to react to odorants that mediate feeding behavior. Following recovery, responses to odorants involved with social behavior returned. The morphological and behavioral effects of chronic Triton X-100 treatment in the olfactory system suggest there may be differential susceptibility or resistance to external damage in a subset of sensory neurons. The results of this study demonstrate the remarkable regenerative ability of the olfactory system following extensive and long-term injury.
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Affiliation(s)
- Taylor R Paskin
- Department of Biological Sciences, Western Michigan University, 1903 W Michigan Ave, Kalamazoo, MI 49008-5410, USA.
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16
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Paskin TR, Iqbal TR, Byrd-Jacobs CA. Olfactory bulb recovery following reversible deafferentation with repeated detergent application in the adult zebrafish. Neuroscience 2011; 196:276-84. [PMID: 21933699 DOI: 10.1016/j.neuroscience.2011.09.005] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2011] [Revised: 08/29/2011] [Accepted: 09/06/2011] [Indexed: 10/17/2022]
Abstract
The neuroplasticity and regenerative properties of the olfactory system make it a useful model for studying the ability of the nervous system to recover from damage. We have developed a novel method for examining the effects of long-term deafferentation and regeneration of the olfactory organ and resulting influence on the olfactory bulb in adult zebrafish. To test the hypothesis that repeated damage to the olfactory epithelium causes reduced olfactory bulb afferent input and cessation of treatment allows recovery, we chronically ablated the olfactory organ every 2-3 days for 3 weeks with the detergent Triton X-100 while another group was allowed 3 weeks of recovery following treatment. Animals receiving chronic treatment showed severe morphological disruption of the olfactory organ, although small pockets of epithelium remained. These pockets were labeled by anti-calretinin, indicating the presence of mature olfactory sensory neurons (OSNs). Following a recovery period, the epithelium was more extensive and neuronal labeling increased, with three different morphologies of sensory neurons observed. Repeated peripheral exposure to Triton X-100 also affected the olfactory bulb. Bulb volumes and anti-tyrosine hydroxylase-like immunoreactivity, which is an indicator of afferent activity, were diminished in the olfactory bulb of the chronically treated group compared to the control side. In the recovery group, there was little difference in bulb volume or antibody staining. These results suggest that repeated, long-term nasal irrigation with Triton X-100 eliminates a substantial number of mature OSNs and reduces afferent input to the olfactory bulb. It also appears that these effects are reversible and regeneration will occur in both the peripheral olfactory organ and the olfactory bulb when given time to recover following cessation of treatment. We report here a new method that allows observation not only of the effects of deafferentation on the olfactory bulb but also the effects of reinnervation.
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Affiliation(s)
- T R Paskin
- Department of Biological Sciences, Western Michigan University, Kalamazoo, MI 49008-5410, USA
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17
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Villanueva R, Byrd-Jacobs CA. Peripheral sensory deafferentation affects olfactory bulb neurogenesis in zebrafish. Brain Res 2009; 1269:31-9. [PMID: 19302984 DOI: 10.1016/j.brainres.2009.03.005] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2008] [Revised: 02/05/2009] [Accepted: 03/02/2009] [Indexed: 11/26/2022]
Abstract
The potential effects of the removal of olfactory input on adult neurogenesis in the olfactory bulb were examined. Olfactory organs of adult zebrafish were permanently and completely ablated by cautery and animals were exposed to bromodeoxyuridine then examined following short (4-hour) or long (3-week) survival periods. Short survival times allowed analysis of cell proliferation in the olfactory bulb. Long survival times permitted investigation of survival of adult-formed cells. Deafferentation did not immediately affect the dividing cells in the bulb but did affect the number of adult-formed cells, some of which expressed a neuronal marker, present in the bulb 3 weeks later. Thus, afferent removal influenced the fate of newly formed cells by impacting subsequent divisions, maturation, or survival of those cells. One week of deafferentation altered the pattern of cell genesis, with a significant increase in the number of dividing cells located in the olfactory bulb and also in the ventral telencephalic proliferation zone. Sham surgery did not impact either proliferation or survival of adult-formed cells in the olfactory bulb, suggesting that the deafferentation effect is specific. Thus, afferent innervation is necessary for normal cell proliferation and maintenance of the olfactory bulb in adult zebrafish.
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Affiliation(s)
- Ruth Villanueva
- Department of Biological Sciences, Western Michigan University, 1903 W. Michigan Ave., Kalamazoo, MI 49008, USA
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18
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Fuller CL, Yettaw HK, Byrd CA. Mitral cells in the olfactory bulb of adult zebrafish (Danio rerio): morphology and distribution. J Comp Neurol 2006; 499:218-30. [PMID: 16977629 DOI: 10.1002/cne.21091] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
The mitral cell is the primary output neuron and central relay in the olfactory bulb of vertebrates. The morphology of these cells has been studied extensively in mammalian systems and to a lesser degree in teleosts. This study uses retrograde tract tracing and other techniques to characterize the morphology and distribution of mitral cells in the olfactory bulb of adult zebrafish, Danio rerio. These output neurons, located primarily in the glomerular layer and superficial internal cell layer, had variable-shaped somata that ranged in size from 4-18 microm in diameter and 31-96 microm2 in cross-sectional area. The mitral cells exhibited two main types of morphologies with regard to their dendrites: the unidendritic morphology was a single primary dendrite with one or more tufts, but multidendritic cells with several dendritic projections also were seen. The axons of these cells projected to either the medial or the lateral olfactory tract and, in general, the location of the cell on the medial or lateral side of the bulb was indicative of the tract to which it would project. Further, this study shows that the majority of zebrafish mitral cells likely innervate a single glomerulus rather than multiple glomeruli. This information is contrary to the multiple innervation pattern suggested for all teleost mitral cells. Our findings suggest that mitral cells in zebrafish may be more similar to mammalian mitral cells than previously believed, despite variation in size and structure. This information provides a revised anatomical framework for olfactory processing studies in this key model system.
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Affiliation(s)
- Cynthia L Fuller
- Western Michigan University, Department of Biological Sciences, Kalamazoo, Michigan 49008-5410, USA
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Fuller CL, Villanueva R, Byrd CA. Changes in glutamate receptor subunit 4 expression in the deafferented olfactory bulb of zebrafish. Brain Res 2005; 1044:251-61. [PMID: 15885223 DOI: 10.1016/j.brainres.2005.03.012] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2004] [Revised: 03/01/2005] [Accepted: 03/02/2005] [Indexed: 01/21/2023]
Abstract
The distribution of ionotropic glutamate receptor subunit 4 (iGluR4) was examined in both normal and deafferented olfactory bulbs of adult zebrafish, Danio rerio. With the exception of the olfactory nerve layer, there was extensive labeling with antibodies to iGluR4 in the olfactory bulbs, specifically in juxtaglomerular cell bodies and their processes. These results are consistent with previous work, which has suggested differential distribution of glutamate receptors in the vertebrate olfactory system. Analysis of bulbs following olfactory organ removal revealed a significant loss of iGluR4 immunoreactivity by 24 h post-deafferentation. At 48 h after denervation, iGluR4 labeling had returned to normal levels and was retained through 3 weeks post-surgery. Thus, afferent input plays a role in reduced labeling of this protein immediately following injury, but return of immunoreactivity can occur even without sensory innervation.
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Affiliation(s)
- Cynthia L Fuller
- Department of Biological Sciences, Western Michigan University, 1903 W. Michigan Avenue, Kalamazoo, MI 49008-5410, USA
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Liu Q, Marrs JA, Azodi E, Kerstetter AE, Babb SG, Hashmi L. Differential expression of cadherins in the developing and adult zebrafish olfactory system. J Comp Neurol 2004; 478:269-81. [PMID: 15368532 DOI: 10.1002/cne.20293] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Cadherins are cell adhesion molecules that play important roles in development of a variety of tissues and maintenance of adult structures. Although cadherin expression has been studied in detail in the central nervous system of several vertebrate species, little is known of their distribution in the developing and adult olfactory structures, and there is no published report, to our knowledge, of cadherin expression in fish olfactory system. In this study, we examined expression patterns of three cadherins, cadherin-1 (E-cadherin), cadherin-2 (N-cadherin), and cadherin-4 (R-cadherin), in the olfactory system of developing and adult zebrafish by using both in situ hybridization and immunocytochemical methods. Cadherin-1 is detected in the newly formed olfactory placode, and its expression is maintained in the developing and adult olfactory epithelium and olfactory nerve. Cadherin-2 is expressed in the olfactory epithelium, olfactory nerve, and olfactory bulb of the embryonic and larval zebrafish, and its expression is reduced in the adult olfactory system. In contrast to the cadherin-1 and cadherin-2 expression, cadherin-4 is not found in the olfactory epithelium, but it is detected in the larval and adult olfactory bulb, in the olfactory tract, and its targets in the telencephalon. We hypothesize that the differential expression of these three cadherins in the developing zebrafish major olfactory structures reflects functionally different roles in the development of the vertebrate olfactory system.
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Affiliation(s)
- Qin Liu
- Department of Biology, University of Akron, Akron, Ohio 44325-3908, USA.
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Singru PS, Sakharkar AJ, Subhedar N. Neuronal nitric oxide synthase in the olfactory system of an adult teleost fish Oreochromis mossambicus. Brain Res 2003; 977:157-68. [PMID: 12834876 DOI: 10.1016/s0006-8993(03)02626-x] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
The aim of the present study is to explore the distribution of nitric oxide synthase in the olfactory system of an adult teleost, Oreochromis mossambicus using neuronal nitric oxide synthase (nNOS) immunocytochemistry and nicotinamide adenine dinucleotide phosphate diaphorase (NADPHd) histochemistry methods. Intense nNOS immunoreactivity was noticed in several olfactory receptor neurons (ORNs), in their axonal extensions over the olfactory nerve and in some basal cells of the olfactory epithelium. nNOS containing fascicles of the ORNs enter the bulb from its rostral pole, spread in the olfactory nerve layer in the periphery of the bulb and display massive innervation of the olfactory glomeruli. Unilateral ablation of the olfactory organ resulted in dramatic loss of nNOS immunoreactivity in the olfactory nerve layer of the ipsilateral bulb. In the olfactory bulb of intact fish, some granule cells showed intense immunoreactivity; dendrites arising from the granule cells could be traced to the glomerular layer. Of particular interest is the occurrence of nNOS immunoreactivity in the ganglion cells of the nervus terminalis. nNOS containing fibers were also encountered in the medial olfactory tracts as they extend to the telencephalon. The NADPHd staining generally coincides with that of nNOS suggesting that it may serve as a marker for nNOS in the olfactory system of this fish. However, mismatch was encountered in the case of mitral cells, while all are nNOS-negative, few were NADPHd positive. The present study for the first time revealed the occurrence of nNOS immunoreactivity in the ORNs of an adult vertebrate and suggests a role for nitric oxide in the transduction of odor stimuli, regeneration of olfactory epithelium and processing of olfactory signals.
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Affiliation(s)
- Praful S Singru
- Department of Pharmaceutical Sciences, Nagpur University Campus, Nagpur 440 033, India
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Vankirk AM, Byrd CA. Apoptosis following peripheral sensory deafferentation in the olfactory bulb of adult zebrafish. J Comp Neurol 2003; 455:488-98. [PMID: 12508322 DOI: 10.1002/cne.10502] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Removal of the olfactory organ in adult zebrafish results in a significant decrease in volume of the ipsilateral olfactory bulb. The current study investigated the potential role of apoptosis in this phenomenon. It was hypothesized that cells in the adult olfactory bulb normally undergo minimal apoptosis and that apoptosis increases upon removal of sensory stimulation. By using both the terminal transferase-mediated deoxyuridine nick-end labeling method and bis-benzimide labeling, the current study showed that, in the normal adult olfactory bulb, cells exhibiting apoptotic profiles were scarce and were localized to the outer layers of the bulb. However, in deafferented animals, there was a significant increase in the number of apoptotic cells. The apoptotic response occurred in two phases and was confined to the rostral half of the bulb. The first phase of cell death peaked at 1 hour postsurgery. These apoptotic profiles appeared to be primarily nonneuronal in nature, in that they exhibited no immunohistochemical labeling to the neuron-specific protein Hu. The second phase of cell death peaked at 24 hours and declined to normal levels by 1 week. At the 24 hour time point, only a fraction of the apoptotic cells was neuronal in nature. Thus, apoptosis of nonneuronal and neuronal elements accounts for at least part of the deafferentation-induced volume decrease in the zebrafish olfactory bulb. This model of anterograde transneuronal degeneration will be useful in elucidating the afferent signals involved in survival and maintenance of mature brain neurons.
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Affiliation(s)
- Akiko M Vankirk
- Department of Biological Sciences, Western Michigan University, Kalamazoo, Michigan 49008-5410, USA
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