The Experts below are selected from a list of 7929 Experts worldwide ranked by ideXlab platform
Jenny Ekberg - One of the best experts on this subject based on the ideXlab platform.
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reliable cell purification and determination of cell purity crucial aspects of Olfactory ensheathing cell transplantation for spinal cord repair
Neural Regeneration Research, 2020Co-Authors: Ronak Reshamwala, Megha Shah, Lucy Belt, Jenny Ekberg, James Anthony St JohnAbstract:Transplantation of Olfactory ensheathing cells, the glia of the primary Olfactory Nervous System, has been trialed for spinal cord injury repair with promising but variable outcomes in animals and humans. Olfactory ensheathing cells can be harvested either from the lamina propria beneath the neuroepithelium in the nasal cavity, or from the Olfactory bulb in the brain. As these areas contain several other cell types, isolating and purifying Olfactory ensheathing cells is a critical part of the process. It is largely unknown how contaminating cells such as fibroblasts, other glial cell types and supporting cells affect Olfactory ensheathing cell function post-transplantation; these cells may also cause unwanted side-effects. It is also, however, possible that the presence of some of the contaminant cells can improve outcomes. Here, we reviewed the last decade of Olfactory ensheathing cell transplantation studies in rodents, with a focus on Olfactory ensheathing cell purity. We analyzed how purification methods and resultant cell purity differed between Olfactory mucosa- and Olfactory bulb-derived cell preparations. We analyzed how the studies reported on Olfactory ensheathing cell purity and which criteria were used to define cells as Olfactory ensheathing cells. Finally, we analyzed the correlation between cell purity and transplantation outcomes. We found that Olfactory bulb-derived Olfactory ensheathing cell preparations are typically purer than mucosa-derived preparations. We concluded that there is an association between high Olfactory ensheathing cell purity and favourable outcomes, but the lack of Olfactory ensheathing cell-specific markers severely hampers the field.
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the link between Olfactory ensheathing cell survival and spinal cord injury repair a commentary on common limitations of contemporary research
Neural Regeneration Research, 2020Co-Authors: Ronak Reshamwala, James Anthony St John, Megha Shah, Jenny EkbergAbstract:Olfactory ensheathing cells (OECs) are crucial players in the continuous regeneration of the Olfactory Nervous System that occurs through out life and are thought to have unique growth-promoting properties. For this reason, OEC transplantation has been thoroughly explored for the potential to promote neural repair after both central and peripheral Nervous System injuries. Numerous studies have shown that OEC transplantation is safe and can promote recovery after spinal cord injury (SCI), both in animal models and in human clinical trials. To date, a variety of injury types and time-points after injury, as well as different delivery methods, have been tested. Outcomes have been encouraging (in rodent models including, for example, restoration of locomotion, breathing and climbing ability along with induction of axonal sprouting and some axonal regeneration) but highly variable (Barnett and Riddell, 2007; Gomez et al., 2018). In their natural environment of the primary Olfactory Nervous System (the Olfactory nerve and outer layer of the Olfactory bulb), OECs provide structural support for Olfactory axons and secrete a range of growth and guidance factors as well as basement membrane components. OECs also phagocytose debris arising from degenerating axons (Ekberg and St John, 2014). In the injured spinal cord, OECs (in addition to these functions) also exhibit a unique capacity for migration into scar tissue and for integration with astrocytes (Barnett and Riddell, 2007; Gomez et al., 2018). For these neural repair effects to occur, it is essential that the transplanted cells survive over time. The key factor for success is thus that the OECs must not only arrive at the right place within the injury site, but must also over time integrate and interact with the injured tissue.
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optimizing Olfactory ensheathing cell transplantation for spinal cord injury repair
Journal of Neurotrauma, 2020Co-Authors: Aaron D Gilmour, Jenny Ekberg, Ronak Reshamwala, Alison Wright, James Anthony St JohnAbstract:Cell transplantation constitutes an important avenue for development of new treatments for spinal cord injury (SCI). These therapies are aimed at supporting neural repair and/or replacing lost cells at the injury site. To date, various cell types have been trialed, with most studies focusing on different types of stem cells or glial cells. Here, we review commonly used cell transplantation approaches for spinal cord injury (SCI) repair, with focus on transplantation of Olfactory ensheathing cells (OECs), the glial cells of the primary Olfactory Nervous System. OECs are promising candidates for promotion of neural repair given that they support continuous regeneration of the Olfactory nerve that occurs throughout life. Further, OECs can be accessed from the nasal mucosa (Olfactory neuroepithelium) at the roof of the nasal cavity and can be autologously transplanted. OEC transplantation has been trialed in many animal models of SCI, as well as in human clinical trials. While several studies have been promising, outcomes are variable and the method needs improvement to enhance aspects such as cell survival, integration, and migration. As a case study, we include the approaches used by our team (the Clem Jones Centre for Neurobiology and Stem Cell Research, Griffith University, Nathan, QLD, Australia) to address the current problems with OEC transplantation and discuss how the therapeutic potential of OEC transplantation can be improved. Our approach includes discovery research to improve our knowledge of OEC biology, identifying natural and synthetic compounds to stimulate the neural repair properties of OECs, and designing three-dimensional cell constructs to create stable and transplantable cell structures.
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the plant natural product 2 methoxy 1 4 naphthoquinone stimulates therapeutic neural repair properties of Olfactory ensheathing cells
Scientific Reports, 2020Co-Authors: Mo Chen, J A St John, Marielaure Vial, L Gee, Rohan Andrew Davis, Jenny EkbergAbstract:Olfactory ensheathing cells (OECs) are crucial for promoting the regeneration of the primary Olfactory Nervous System that occurs throughout life. Transplantation of OECs has emerged as a promising therapy for Nervous System injuries, in particular for spinal cord injury repair. Functional outcomes in both animals and humans are, however, highly variable, primarily because it is difficult to rapidly obtain enough OECs for transplantation. Compounds which can stimulate OEC proliferation without changing the phenotype of the cells are therefore highly sought after. Additionally, compounds which can stimulate favourable cell behaviours such as migration and phagocytic activity are desirable. We conducted a medium-throughput screen testing the Davis open access natural product-based library (472 compounds) and subsequently identified the known plant natural product 2-methoxy-1,4-naphthoquinone as a stimulant of OEC viability. We showed that 2-methoxy-1,4-naphthoquinone: (i) strongly stimulates proliferation over several weeks in culture whilst maintaining the OEC phenotype; (ii) stimulates the phagocytic activity of OECs, and (iii) modulates the cell cycle. We also identified the transcription factor Nrf2 as the compound’s potential molecular target. From these extensive investigations we conclude that 2-methoxy-1,4-naphthoquinone may enhance the therapeutic potential of OECs by stimulating proliferation prior to transplantation.
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survival and integration of transplanted Olfactory ensheathing cells are crucial for spinal cord injury repair insights from the last 10 years of animal model studies
Cell Transplantation, 2019Co-Authors: Ronak Reshamwala, James Anthony St John, Megha Shah, Jenny EkbergAbstract:Olfactory ensheathing cells (OECs), the glial cells of the primary Olfactory Nervous System, support the natural regeneration of the Olfactory nerve that occurs throughout life. OECs thus exhibit unique properties supporting neuronal survival and growth. Transplantation of OECs is emerging as a promising treatment for spinal cord injury; however, outcomes in both animals and humans are variable and the method needs improvement and standardization. A major reason for the discrepancy in functional outcomes is the variability in survival and integration of the transplanted cells, key factors for successful spinal cord regeneration. Here, we review the outcomes of OEC transplantation in rodent models over the last 10 years, with a focus on survival and integration of the transplanted cells. We identify the key factors influencing OEC survival: injury type, source of transplanted cells, co-transplantation with other cell types, number and concentration of cells, method of delivery, and time of transplantation after the injury. We found that two key issues are hampering optimization and standardization of OEC transplantation: lack of (1) reliable methods for identifying transplanted cells, and (2) three-dimensional Systems for OEC delivery. To develop OEC transplantation as a successful and standardized therapy for spinal cord injury, we must address these issues and increase our understanding of the complex parameters influencing OEC survival.
Tetsuji Moriizumi - One of the best experts on this subject based on the ideXlab platform.
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Adult Neurogenesis and Gliogenesis in the Rat Olfactory Nervous System
2015Co-Authors: Nanae Fukushima, Kumiko Yokouchi, Takashi Kato, Tetsuji MoriizumiAbstract:Key words: cell fate, granule cells, Olfactory bulb, periglomerular cells, rostral migratory strea
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Adult neurogenesis and gliogenesis in the rat Olfactory Nervous System.
Chemical Senses, 2005Co-Authors: Nanae Fukushima, Kumiko Yokouchi, Takashi Kato, Tetsuji MoriizumiAbstract:In the Olfactory Nervous System, it is well established that neural stem cells continually proliferate in the periventricular region, migrate along the rostral migratory stream (RMS) and differentiate into neurons of the glomerular (OB-GL) and granule cell (OB-GCL) layers of the Olfactory bulb (OB). In this paper, we will answer the following questions regarding adult neurogenesis of the Olfactory Nervous System. (i) What is the fate of newly generated bulbar neurons? (ii) Does neuronal regeneration occur after neuronal cell death of the forebrain regions in and around the RMS? (iii) Does neurogenesis occur within the OB independently of migrating neural stem cells? If intrabulbar neurogenesis occurs, are there some differences in neurogenesis and gliogenesis by the neural stem cells of different origins?
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cell dynamics of calretinin immunoreactive neurons in the rostral migratory stream after ibotenate induced lesions in the forebrain
Neuroscience Research, 2002Co-Authors: Zhiyou Li, Nanae Fukushima, Kumiko Yokouchi, Kyutaro Kawagishi, Takashi Kato, Tetsuji MoriizumiAbstract:It is now apparent that adult neurogenesis is taking place during life in the Olfactory bulb (OB) of the rodent brain. In the Olfactory Nervous System, the precursor cells of the subventricular zone are known to continually proliferate, migrate through the rostral migratory stream (RMS) and differentiate into the bulbar neurons. The RMS, consisting of heterogenous cell populations of the neural and neuronal precursor cells, is the unique forebrain structure that provides a long-distance migratory route for the precursor cells. The present study was undertaken to examine whether neuronal regeneration, focusing on calretinin-immunoreactive (+) cells, may proceed in the RMS following lesions induced by an excitotoxin. Two days after ibotenate injections, massive degeneration of calretinin (+) cells occurred in the RMS and its adjacent forebrains. Thereafter, calretinin (+) cells gradually increased in the RMS and reached above their control value 2 weeks after ibotenate injections. Removal of the OB also produced a marked increase in calretinin (+) cells in the RMS. Autoradiographic experiments using 3H-thymidine showed that calretinin (+) cells were continually generated in the RMS and underwent neuronal turnover within 8 weeks in a normal condition. The results indicate that, in terms of calretinin (+) cells, neuronal differentiation and replacement is continually taking place within the RMS, and that the RMS is capable of repopulating those cells which were injured by ibotenate.
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the minimum number of neurons in the central Olfactory pathway in relation to its function a retrograde fiber tracing study
Chemical Senses, 2002Co-Authors: Nanae Fukushima, Kumiko Yokouchi, Kyutaro Kawagishi, Susumu Oikawa, Tetsuji MoriizumiAbstract:The present study was aimed at determining the functionally essential size of the neuronal population in the central Olfactory Nervous System. Using conditioned rats who had learnt to avoid repellent (cycloheximide) solution by olfaction, varying degrees of injuries were made to the lateral Olfactory tract, a major central Olfactory pathway connecting the Olfactory bulb to the Olfactory cortex. After examining their Olfactory ability to discriminate cycloheximide solution from water, intact bulbar projection neurons (mitral cells) with fiber connections to the Olfactory cortex were quantified using a retrograde fiber tracing technique. The numbers of retrogradely labeled mitral cells from the rats with normal olfaction ranged between 20 and 92% of the control value, while those numbers from the anosmic rats ranged between 0 and 22%. We conclude that the functionally essential neuronal population is approximately one-fifth of the total in the central Olfactory pathway, a presumed threshold value in terms of the ability to avoid cycloheximide solution by Olfactory discrimination.
James Anthony St John - One of the best experts on this subject based on the ideXlab platform.
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reliable cell purification and determination of cell purity crucial aspects of Olfactory ensheathing cell transplantation for spinal cord repair
Neural Regeneration Research, 2020Co-Authors: Ronak Reshamwala, Megha Shah, Lucy Belt, Jenny Ekberg, James Anthony St JohnAbstract:Transplantation of Olfactory ensheathing cells, the glia of the primary Olfactory Nervous System, has been trialed for spinal cord injury repair with promising but variable outcomes in animals and humans. Olfactory ensheathing cells can be harvested either from the lamina propria beneath the neuroepithelium in the nasal cavity, or from the Olfactory bulb in the brain. As these areas contain several other cell types, isolating and purifying Olfactory ensheathing cells is a critical part of the process. It is largely unknown how contaminating cells such as fibroblasts, other glial cell types and supporting cells affect Olfactory ensheathing cell function post-transplantation; these cells may also cause unwanted side-effects. It is also, however, possible that the presence of some of the contaminant cells can improve outcomes. Here, we reviewed the last decade of Olfactory ensheathing cell transplantation studies in rodents, with a focus on Olfactory ensheathing cell purity. We analyzed how purification methods and resultant cell purity differed between Olfactory mucosa- and Olfactory bulb-derived cell preparations. We analyzed how the studies reported on Olfactory ensheathing cell purity and which criteria were used to define cells as Olfactory ensheathing cells. Finally, we analyzed the correlation between cell purity and transplantation outcomes. We found that Olfactory bulb-derived Olfactory ensheathing cell preparations are typically purer than mucosa-derived preparations. We concluded that there is an association between high Olfactory ensheathing cell purity and favourable outcomes, but the lack of Olfactory ensheathing cell-specific markers severely hampers the field.
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the link between Olfactory ensheathing cell survival and spinal cord injury repair a commentary on common limitations of contemporary research
Neural Regeneration Research, 2020Co-Authors: Ronak Reshamwala, James Anthony St John, Megha Shah, Jenny EkbergAbstract:Olfactory ensheathing cells (OECs) are crucial players in the continuous regeneration of the Olfactory Nervous System that occurs through out life and are thought to have unique growth-promoting properties. For this reason, OEC transplantation has been thoroughly explored for the potential to promote neural repair after both central and peripheral Nervous System injuries. Numerous studies have shown that OEC transplantation is safe and can promote recovery after spinal cord injury (SCI), both in animal models and in human clinical trials. To date, a variety of injury types and time-points after injury, as well as different delivery methods, have been tested. Outcomes have been encouraging (in rodent models including, for example, restoration of locomotion, breathing and climbing ability along with induction of axonal sprouting and some axonal regeneration) but highly variable (Barnett and Riddell, 2007; Gomez et al., 2018). In their natural environment of the primary Olfactory Nervous System (the Olfactory nerve and outer layer of the Olfactory bulb), OECs provide structural support for Olfactory axons and secrete a range of growth and guidance factors as well as basement membrane components. OECs also phagocytose debris arising from degenerating axons (Ekberg and St John, 2014). In the injured spinal cord, OECs (in addition to these functions) also exhibit a unique capacity for migration into scar tissue and for integration with astrocytes (Barnett and Riddell, 2007; Gomez et al., 2018). For these neural repair effects to occur, it is essential that the transplanted cells survive over time. The key factor for success is thus that the OECs must not only arrive at the right place within the injury site, but must also over time integrate and interact with the injured tissue.
-
optimizing Olfactory ensheathing cell transplantation for spinal cord injury repair
Journal of Neurotrauma, 2020Co-Authors: Aaron D Gilmour, Jenny Ekberg, Ronak Reshamwala, Alison Wright, James Anthony St JohnAbstract:Cell transplantation constitutes an important avenue for development of new treatments for spinal cord injury (SCI). These therapies are aimed at supporting neural repair and/or replacing lost cells at the injury site. To date, various cell types have been trialed, with most studies focusing on different types of stem cells or glial cells. Here, we review commonly used cell transplantation approaches for spinal cord injury (SCI) repair, with focus on transplantation of Olfactory ensheathing cells (OECs), the glial cells of the primary Olfactory Nervous System. OECs are promising candidates for promotion of neural repair given that they support continuous regeneration of the Olfactory nerve that occurs throughout life. Further, OECs can be accessed from the nasal mucosa (Olfactory neuroepithelium) at the roof of the nasal cavity and can be autologously transplanted. OEC transplantation has been trialed in many animal models of SCI, as well as in human clinical trials. While several studies have been promising, outcomes are variable and the method needs improvement to enhance aspects such as cell survival, integration, and migration. As a case study, we include the approaches used by our team (the Clem Jones Centre for Neurobiology and Stem Cell Research, Griffith University, Nathan, QLD, Australia) to address the current problems with OEC transplantation and discuss how the therapeutic potential of OEC transplantation can be improved. Our approach includes discovery research to improve our knowledge of OEC biology, identifying natural and synthetic compounds to stimulate the neural repair properties of OECs, and designing three-dimensional cell constructs to create stable and transplantable cell structures.
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survival and integration of transplanted Olfactory ensheathing cells are crucial for spinal cord injury repair insights from the last 10 years of animal model studies
Cell Transplantation, 2019Co-Authors: Ronak Reshamwala, James Anthony St John, Megha Shah, Jenny EkbergAbstract:Olfactory ensheathing cells (OECs), the glial cells of the primary Olfactory Nervous System, support the natural regeneration of the Olfactory nerve that occurs throughout life. OECs thus exhibit unique properties supporting neuronal survival and growth. Transplantation of OECs is emerging as a promising treatment for spinal cord injury; however, outcomes in both animals and humans are variable and the method needs improvement and standardization. A major reason for the discrepancy in functional outcomes is the variability in survival and integration of the transplanted cells, key factors for successful spinal cord regeneration. Here, we review the outcomes of OEC transplantation in rodent models over the last 10 years, with a focus on survival and integration of the transplanted cells. We identify the key factors influencing OEC survival: injury type, source of transplanted cells, co-transplantation with other cell types, number and concentration of cells, method of delivery, and time of transplantation after the injury. We found that two key issues are hampering optimization and standardization of OEC transplantation: lack of (1) reliable methods for identifying transplanted cells, and (2) three-dimensional Systems for OEC delivery. To develop OEC transplantation as a successful and standardized therapy for spinal cord injury, we must address these issues and increase our understanding of the complex parameters influencing OEC survival.
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the grueneberg Olfactory organ neuroepithelium recovers after injury
Brain Research, 2018Co-Authors: James Anthony St John, Fatemeh Chehrehasa, Angela Jacques, Jenny EkbergAbstract:Abstract The Grueneberg organ (also termed Grueneberg ganglion) is an Olfactory subSystem at the rostral nasal septum of rodents, and has been suggested to exist also in humans. Grueneberg organ neurons respond to coldness and alarm pheromones, but the anatomical arrangement and regenerative capacity are not fully characterised. We examined the relationship between the glia and the neurons using crosses of two transgenic mouse lines, S100s-DsRed and OMP-ZsGreen, to visualise Olfactory ensheathing cells (OECs) and Grueneberg Olfactory neurons, respectively. Within the epithelium, Grueneberg organ OECs were in direct contact with Grueneberg organ neuron cell bodies. Individual axons from the neurons initially grew over the surface of the OECs before forming larger fascicles consisting of numerous axons and OECs. Considering the location of the Grueneberg organ so close to the external environment, it may be that the Grueneberg neurons are likely to be subject to damage suggesting that as in other Olfactory regions there is a capacity for recovery after injury. Here, we used a well characterised model of Olfactory Nervous System injury, unilateral bulbectomy, to determine whether Grueneberg organ neurons degenerate after injury. We found that Grueneberg organ neurons degenerated in response to the axotomy, yet by 11 days post injury neurons and/or axons were detected again within the epithelium. Our results demonstrate that while Grueneberg organ neurons and glia have a distinct relationship in the epithelium, they have largely similar characteristics to that of the main Olfactory neurons and glia.
Nathaniel L. Scholz - One of the best experts on this subject based on the ideXlab platform.
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chemosensory deprivation in juvenile coho salmon exposed to dissolved copper under varying water chemistry conditions
Environmental Science & Technology, 2008Co-Authors: Jenifer K Mcintyre, David H. Baldwin, James P Meador, Nathaniel L. ScholzAbstract:Dissolved copper is an important nonpoint source pollutant in aquatic ecoSystems worldwide. Copper is neurotoxic to fish and is specifically known to interfere with the normal function of the peripheral Olfactory Nervous System. However, the influence of water chemistry on the bioavailability and toxicity of copper to Olfactory sensory neurons is not well understood. Here we used electrophysiological recordings from the Olfactory epithelium of juvenile coho salmon (Oncorhynchus kisutch) to investigate the impacts of copper in freshwaters with different chemical properties. In low ionic strength artificial fresh water, a short-term (30 min) exposure to 20 µg/L dissolved copper reduced the Olfactory response to a natural odorant (10−5 M L-serine) by 82%. Increasing water hardness (0.2–1.6 mM Ca) or alkalinity (0.2–3.2 mM HCO3−) only slightly diminished the inhibitory effects of copper. Moreover, the loss of Olfactory function was not affected by a change in pH from 8.6 to 7.6. By contrast, Olfactory capacit...
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Dose-additive inhibition of chinook salmon acetylcholinesterase activity by mixtures of organophosphate and carbamate insecticides.
Environmental Toxicology and Chemistry, 2006Co-Authors: Nathaniel L. Scholz, Nathan K. Truelove, Jana S. Labenia, David H. Baldwin, Tracy K. CollierAbstract:Organophosphate and carbamate insecticides are widely detected in surface waters of the western United States. These chemicals interfere with acetylcholine-mediated synaptic transmission in the Nervous Systems of fish and other aquatic animals via the inhibition of AChE (acetylcholinesterase) enzyme activity. Anticholinesterase insecticides commonly co-occur in the environment. This raises the possibility of antagonistic, additive, or synergistic neurotoxicity in exposed fish, including threatened and endangered species of Pacific salmon. We extracted AChE from the Olfactory Nervous System of chinook salmon (Oncorhynchus tshawytscha) and investigated the inhibitory effects of organophosphates (the oxon derivatives of diazinon, chlorpyrifos, and malathion) and carbamates (carbaryl and carbofuran), alone and in two-way combinations. We found that the joint toxicity of anticholinesterase mixtures can be accurately predicted from the inhibitory potencies of individual chemicals within a mixture. This indicates that organophosphate and carbamate insecticides are noninteractive in terms of AChE inhibition and that it might be possible to estimate the cumulative neurotoxicity of mixtures by simple dose addition. Because organophosphates and carbamates are likely to have additive effects on the neurobehavior of salmon under natural exposure conditions, ecological risk assessments that focus on individual anticholinesterases might underestimate the actual risk to salmon in watersheds in which mixtures of these chemicals occur.
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sublethal effects of copper on coho salmon impacts on nonoverlapping receptor pathways in the peripheral Olfactory Nervous System
Environmental Toxicology and Chemistry, 2003Co-Authors: David H. Baldwin, Jana S. Labenia, Jason F Sandahl, Nathaniel L. ScholzAbstract:The sublethal effects of copper on the sensory physiology of juvenile coho salmon ( Oncorhynchus kisutch) were evaluated. In vivo field potential recordings from the Olfactory epithelium (electro-olfactograms) were used to measure the impacts of copper on the responses of Olfactory receptor neurons to natural odorants ( L-serine and taurocholic acid) and an odorant mixture (L-arginine, L-aspartic acid, L-leucine, and L-serine) over a range of stimulus concentrations. Increases in copper impaired the neurophysiological response to all odorants within 10 min of exposure. The inhibitory effects of copper (1.0-20.0 mg/L) were dose- dependent and they were not influenced by water hardness. Toxicity thresholds for the different receptor pathways were determined by using the benchmark dose method and found to be similar (a 2.3-3.0 mg/L increase in total dissolved copper over background). Collectively, examination of these data indicates that copper is broadly toxic to the salmon Olfactory Nervous System. Consequently, short-term influxes of copper to surface waters may interfere with Olfactory-mediated behaviors that are critical for the survival and migratory success of wild salmonids.
Nanae Fukushima - One of the best experts on this subject based on the ideXlab platform.
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Adult Neurogenesis and Gliogenesis in the Rat Olfactory Nervous System
2015Co-Authors: Nanae Fukushima, Kumiko Yokouchi, Takashi Kato, Tetsuji MoriizumiAbstract:Key words: cell fate, granule cells, Olfactory bulb, periglomerular cells, rostral migratory strea
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Adult neurogenesis and gliogenesis in the rat Olfactory Nervous System.
Chemical Senses, 2005Co-Authors: Nanae Fukushima, Kumiko Yokouchi, Takashi Kato, Tetsuji MoriizumiAbstract:In the Olfactory Nervous System, it is well established that neural stem cells continually proliferate in the periventricular region, migrate along the rostral migratory stream (RMS) and differentiate into neurons of the glomerular (OB-GL) and granule cell (OB-GCL) layers of the Olfactory bulb (OB). In this paper, we will answer the following questions regarding adult neurogenesis of the Olfactory Nervous System. (i) What is the fate of newly generated bulbar neurons? (ii) Does neuronal regeneration occur after neuronal cell death of the forebrain regions in and around the RMS? (iii) Does neurogenesis occur within the OB independently of migrating neural stem cells? If intrabulbar neurogenesis occurs, are there some differences in neurogenesis and gliogenesis by the neural stem cells of different origins?
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cell dynamics of calretinin immunoreactive neurons in the rostral migratory stream after ibotenate induced lesions in the forebrain
Neuroscience Research, 2002Co-Authors: Zhiyou Li, Nanae Fukushima, Kumiko Yokouchi, Kyutaro Kawagishi, Takashi Kato, Tetsuji MoriizumiAbstract:It is now apparent that adult neurogenesis is taking place during life in the Olfactory bulb (OB) of the rodent brain. In the Olfactory Nervous System, the precursor cells of the subventricular zone are known to continually proliferate, migrate through the rostral migratory stream (RMS) and differentiate into the bulbar neurons. The RMS, consisting of heterogenous cell populations of the neural and neuronal precursor cells, is the unique forebrain structure that provides a long-distance migratory route for the precursor cells. The present study was undertaken to examine whether neuronal regeneration, focusing on calretinin-immunoreactive (+) cells, may proceed in the RMS following lesions induced by an excitotoxin. Two days after ibotenate injections, massive degeneration of calretinin (+) cells occurred in the RMS and its adjacent forebrains. Thereafter, calretinin (+) cells gradually increased in the RMS and reached above their control value 2 weeks after ibotenate injections. Removal of the OB also produced a marked increase in calretinin (+) cells in the RMS. Autoradiographic experiments using 3H-thymidine showed that calretinin (+) cells were continually generated in the RMS and underwent neuronal turnover within 8 weeks in a normal condition. The results indicate that, in terms of calretinin (+) cells, neuronal differentiation and replacement is continually taking place within the RMS, and that the RMS is capable of repopulating those cells which were injured by ibotenate.
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the minimum number of neurons in the central Olfactory pathway in relation to its function a retrograde fiber tracing study
Chemical Senses, 2002Co-Authors: Nanae Fukushima, Kumiko Yokouchi, Kyutaro Kawagishi, Susumu Oikawa, Tetsuji MoriizumiAbstract:The present study was aimed at determining the functionally essential size of the neuronal population in the central Olfactory Nervous System. Using conditioned rats who had learnt to avoid repellent (cycloheximide) solution by olfaction, varying degrees of injuries were made to the lateral Olfactory tract, a major central Olfactory pathway connecting the Olfactory bulb to the Olfactory cortex. After examining their Olfactory ability to discriminate cycloheximide solution from water, intact bulbar projection neurons (mitral cells) with fiber connections to the Olfactory cortex were quantified using a retrograde fiber tracing technique. The numbers of retrogradely labeled mitral cells from the rats with normal olfaction ranged between 20 and 92% of the control value, while those numbers from the anosmic rats ranged between 0 and 22%. We conclude that the functionally essential neuronal population is approximately one-fifth of the total in the central Olfactory pathway, a presumed threshold value in terms of the ability to avoid cycloheximide solution by Olfactory discrimination.
