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Philosophical Transactions of the Royal... Dec 2000Zonal organization is one of the characteristic features observed in both main and accessory olfactory systems. In the main olfactory system, most of the odorant... (Review)
Review
Zonal organization is one of the characteristic features observed in both main and accessory olfactory systems. In the main olfactory system, most of the odorant receptors are classified into four groups according to their zonal expression patterns in the olfactory epithelium. Each group of odorant receptors is expressed by sensory neurons distributed within one of four circumscribed zones. Olfactory sensory neurons in a given zone of the epithelium project their axons to the glomeruli in a corresponding zone of the main olfactory bulb. Glomeruli in the same zone tend to represent similar odorant receptors having similar tuning specificity to odorants. Vomeronasal receptors (or pheromone receptors) are classified into two groups in the accessory olfactory system. Each group of receptors is expressed by vomeronasal sensory neurons in either the apical or basal zone of the vomeronasal epithelium. Sensory neurons in the apical zone project their axons to the rostral zone of the accessory olfactory bulb and form synaptic connections with mitral tufted cells belonging to the rostral zone. Signals originated from basal zone sensory neurons are sent to mitral tufted cells in the caudal zone of the accessory olfactory bulb. We discuss functional implications of the zonal organization in both main and accessory olfactory systems.
Topics: Animals; Axons; Chemoreceptor Cells; Humans; Mammals; Olfactory Bulb; Olfactory Mucosa; Perception; Receptors, Odorant; Vomeronasal Organ
PubMed: 11205342
DOI: 10.1098/rstb.2000.0736 -
International Journal of Radiation... May 2020The various microenvironments that exist within the brain combined with the invasive nature of glioblastoma (GBM) creates the potential for a topographic influence on...
PURPOSE
The various microenvironments that exist within the brain combined with the invasive nature of glioblastoma (GBM) creates the potential for a topographic influence on tumor cell radiosensitivity. The aim of this study was to determine whether specific brain microenvironments differentially influence tumor cell radioresponse.
METHODS AND MATERIALS
GBM stem-like cells were implanted into the right striatum of nude mice. To measure radiosensitivity, proliferation status of individual tumor cells was determined according to the incorporation of 5-chloro-2'-deoxyuridine delivered at 4, 12, and 20 days after brain irradiation. As an additional measure of radiosensitivity, the percentage of human cells in the right hemisphere and the olfactory bulb were defined using digital droplet polymerase chain reaction. Targeted gene expression profiling was accomplished using NanoString analysis.
RESULTS
Tumor cells were detected throughout the striatum, corpus callosum, and olfactory bulb. After an initial loss of proliferating tumor cells in the corpus callosum and striatum after irradiation, there was only a minor recovery by 20 days. In contrast, the proliferation of tumor cells located in the olfactory bulb began to recover at 4 days and returned to unirradiated levels by day 12 postirradiation. The percentage of human cells in the right hemisphere and the olfactory bulb after irradiation also suggested that the tumor cells in the olfactory bulb were relatively radioresistant. Gene expression profiling identified consistent differences between tumor cells residing in the olfactory bulb and those in the right hemisphere.
CONCLUSIONS
These results suggest that the olfactory bulb provides a radioresistant niche for GBM cells.
Topics: Animals; Glioblastoma; Mice; Olfactory Bulb; Radiation Tolerance; Stem Cell Niche; Tumor Microenvironment
PubMed: 31987963
DOI: 10.1016/j.ijrobp.2020.01.007 -
Brain Imaging and Behavior Aug 2017Repeated exposure to odors modifies olfactory function. Consequently, "olfactory training" plays a significant role in hyposmia treatment. In addition, numerous studies...
Repeated exposure to odors modifies olfactory function. Consequently, "olfactory training" plays a significant role in hyposmia treatment. In addition, numerous studies show that the olfactory bulb (OB) volume changes in disorders associated with olfactory dysfunction. Aim of this study was to investigate whether and how olfactory bulb volume changes in relation to lateralized olfactory training in healthy people. Over a period of 4 months, 97 healthy participants (63 females and 34 males, mean age: 23.74 ± 4.16 years, age range: 19-43 years) performed olfactory training by exposing the same nostril twice a day to 4 odors (lemon, rose, eucalyptus and cloves) while closing the other nostril. Before and after olfactory training, magnetic resonance imaging (MRI) scans were performed to measure OB volume. Furthermore, participants underwent lateralized odor threshold and odor identification testing using the "Sniffin' Sticks" test battery.OB volume increased significantly after olfactory training (11.3 % and 13.1 % respectively) for both trained and untrained nostril. No significant effects of sex, duration and frequency of training or age of the subjects were seen. Interestingly, PEA odor thresholds worsened after training, while olfactory identification remained unchanged.These data show for the first time in humans that olfactory training may involve top-down process, which ultimately lead to a bilateral increase in olfactory bulb volume.
Topics: Adult; Female; Functional Laterality; Humans; Learning; Longitudinal Studies; Magnetic Resonance Imaging; Male; Neuronal Plasticity; Neuropsychological Tests; Odorants; Olfactory Bulb; Olfactory Perception; Organ Size; Young Adult
PubMed: 27448159
DOI: 10.1007/s11682-016-9567-9 -
Journal of Neurochemistry Jul 2010Because the olfactory system plays a major role in food consumption, and because 'food addiction' and associated morbidities have reached epidemic proportions, we tested...
Because the olfactory system plays a major role in food consumption, and because 'food addiction' and associated morbidities have reached epidemic proportions, we tested the hypothesis that dietary energy restriction can modify adverse effects of cocaine on behavior and olfactory cellular and molecular plasticity. Mice maintained on an alternate day fasting (ADF) diet exhibited increased baseline locomotion and increased cocaine-sensitized locomotion during cocaine conditioning, despite no change in cocaine conditioned place preference, compared with mice fed ad libitum. Levels of dopamine and its metabolites in the olfactory bulb (OB) were suppressed in mice on the ADF diet compared with mice on the control diet, independent of acute or chronic cocaine treatment. The expression of several enzymes involved in dopamine metabolism including tyrosine hydroxylase, monoamine oxidases A and B, and catechol-O-methyltransferase were significantly reduced in OBs of mice on the ADF diet. Both acute and chronic administration of cocaine suppressed the production of new OB cells, and this effect of cocaine was attenuated in mice on the ADF diet. Cocaine administration to mice on the control diet resulted in up-regulation of OB genes involved in mitochondrial energy metabolism, synaptic plasticity, cellular stress responses, and calcium- and cAMP-mediated signaling, whereas multiple olfactory receptor genes were down-regulated by cocaine treatment. ADF abolished many of the effects of cocaine on OB gene expression. Our findings reveal that dietary energy intake modifies the neural substrates underlying some of the behavioral and physiological responses to repeated cocaine treatment, and also suggest novel roles for the olfactory system in addiction. The data further suggest that modification of dietary energy intake could provide a novel potential approach to addiction treatments.
Topics: Animals; Behavior, Animal; Cell Proliferation; Cocaine; Diet; Dopamine; Energy Intake; Fasting; Gene Expression; Male; Mice; Mice, Inbred C57BL; Motor Activity; Neurons; Olfactory Bulb; Stem Cells
PubMed: 20456017
DOI: 10.1111/j.1471-4159.2010.06782.x -
Trends in Neurosciences Aug 2008In adult rodents, subventricular zone (SVZ) astrocytes (B cells) function as primary progenitors in the generation of new neurons that migrate to the olfactory bulb... (Review)
Review
In adult rodents, subventricular zone (SVZ) astrocytes (B cells) function as primary progenitors in the generation of new neurons that migrate to the olfactory bulb (OB), where they differentiate into multiple types of interneurons. It has been generally considered that individual adult SVZ stem cells are capable of generating different types of neurons and glial cells. However, recent studies indicate that these adult SVZ primary progenitors are heterogeneous and predetermined to generate specific types of neurons. Surprisingly, OB interneurons are generated by stem cells not only in the walls of the lateral ventricle facing the striatum but also in the rostral migratory stream and walls of the lateral ventricle facing the cortex and the septum. SVZ B cells in different locations within this extensive germinal region generate different kinds of interneurons. General physiological characteristics of major classes of OB interneurons have begun to emerge, but the functional contribution of each subtype remains unknown. The mosaic organization of the SVZ offers a unique opportunity to understand the origin of interneuron diversity and how this assortment of neurons contributes to plasticity of postnatal olfactory circuits.
Topics: Animals; Cell Differentiation; Cell Movement; Cell Proliferation; Cerebral Ventricles; Humans; Interneurons; Olfactory Bulb; Olfactory Pathways; Stem Cells
PubMed: 18603310
DOI: 10.1016/j.tins.2008.05.006 -
PLoS Biology Oct 2018Odor-guided behaviors, including homing, predator avoidance, or food and mate searching, are ubiquitous in animals. It is only recently that the neural substrate...
Odor-guided behaviors, including homing, predator avoidance, or food and mate searching, are ubiquitous in animals. It is only recently that the neural substrate underlying olfactomotor behaviors in vertebrates was uncovered in lampreys. It consists of a neural pathway extending from the medial part of the olfactory bulb (medOB) to locomotor control centers in the brainstem via a single relay in the caudal diencephalon. This hardwired olfactomotor pathway is present throughout life and may be responsible for the olfactory-induced motor behaviors seen at all life stages. We investigated modulatory mechanisms acting on this pathway by conducting anatomical (tract tracing and immunohistochemistry) and physiological (intracellular recordings and calcium imaging) experiments on lamprey brain preparations. We show that the GABAergic circuitry of the olfactory bulb (OB) acts as a gatekeeper of this hardwired sensorimotor pathway. We also demonstrate the presence of a novel olfactomotor pathway that originates in the non-medOB and consists of a projection to the lateral pallium (LPal) that, in turn, projects to the caudal diencephalon and to the mesencephalic locomotor region (MLR). Our results indicate that olfactory inputs can induce behavioral responses by activating brain locomotor centers via two distinct pathways that are strongly modulated by GABA in the OB. The existence of segregated olfactory subsystems in lampreys suggests that the organization of the olfactory system in functional clusters may be a common ancestral trait of vertebrates.
Topics: Animals; Brain; Diencephalon; GABA Modulators; Lampreys; Locomotion; Mesencephalon; Neural Pathways; Neurons; Odorants; Olfactory Bulb; Smell
PubMed: 30286079
DOI: 10.1371/journal.pbio.2005512 -
European Archives of... Jan 2024Post-infectious olfactory dysfunction (PIOD) is one of the most common causes of olfactory impairment but has limited treatment options. Recently, olfactory training...
PURPOSE
Post-infectious olfactory dysfunction (PIOD) is one of the most common causes of olfactory impairment but has limited treatment options. Recently, olfactory training (OT) has been considered an effective treatment method; however, several questions have arisen regarding its optimal scheme. The aim of this study was to assess whether an OT scheme with 8 odors is more effective than the classic OT scheme with 4 odors by comparing psychophysical test results and olfactory bulb (OB) volumetrics.
METHODS
In this prospective cohort study, 72 patients with PIOD were included. The patients followed either the classic 4-odor OT scheme (COT; n = 34 patients) or an extended 8-odor scheme (EOT; n = 38 patients) for 16 weeks. All patients underwent olfactory testing with a Sniffin'Sticks battery test at 0, 8, and 16 weeks. Of the patients, 38 underwent brain magnetic resonance imaging for OB volumetric assessment before and after treatment.
RESULTS
The comparison of the olfactory test results did not show any significant difference between the two study groups, in agreement with the OB volumetrics. The convex OB showed better test results than the non-convex OB, with significantly better improvement after treatment regardless of OT type. The EOT group presented significantly better adherence than the COT group.
CONCLUSION
The number of odors did not appear to play a significant role in the effect of the OT. However, the training scheme with more than four odors showed better adherence among the patients in a long-term treatment plan. The shape of the OB may have prognostic value in clinical assessment and warrants further investigation.
Topics: Humans; Odorants; Olfactory Bulb; Olfactory Training; Prospective Studies; Smell; Olfaction Disorders
PubMed: 37924364
DOI: 10.1007/s00405-023-08283-4 -
Chemical Senses Sep 2009To investigate factors that influence the degree of neural regeneration and recovery, we studied 2 olfactory nerve injury models. Transection of the olfactory nerves...
To investigate factors that influence the degree of neural regeneration and recovery, we studied 2 olfactory nerve injury models. Transection of the olfactory nerves along the surface of the olfactory bulb was performed in OMP-tau-lacZ mice using either a flexible Teflon blade (mild injury) or a stainless steel blade (severe injury). Histological assessment of recovery within the olfactory bulb was made at 5, 14, and 42 days after injury. We used X-gal staining to label the degenerating and regenerating olfactory nerve fibers and immunohistochemical staining to detect the presence of reactive astrocytes and macrophages. Areas of injury-associated tissue were significantly smaller in the mild injury model, and at 42 days, the regenerated nerves had reestablished connections to the glomerular layer of the bulb. With severe injury, there were larger areas of injury-associated tissue, more astrocytes and macrophages, and a decrease in regenerated nerve fibers. When dexamethasone (DXM) was injected after severe injury, there was a significant reduction in injury-associated tissue, better nerve recovery, and fewer astrocytes and macrophages. These results demonstrate that recovery in the olfactory system varies with the severity of injury and that DXM treatment may have therapeutic value by reducing injury-associated tissue and improving recovery outcome.
Topics: Animals; Anti-Inflammatory Agents; Dexamethasone; Mice; Mice, Transgenic; Nerve Regeneration; Olfactory Bulb; Olfactory Nerve; Olfactory Nerve Injuries
PubMed: 19578153
DOI: 10.1093/chemse/bjp038 -
International Journal of Molecular... Oct 2012Successful nerve regeneration after nerve trauma is not only important for the restoration of motor and sensory functions, but also to reduce the potential for abnormal... (Review)
Review
Successful nerve regeneration after nerve trauma is not only important for the restoration of motor and sensory functions, but also to reduce the potential for abnormal sensory impulse generation that can occur following neuroma formation. Satisfying functional results after severe lesions are difficult to achieve and the development of interventional methods to achieve optimal functional recovery after peripheral nerve injury is of increasing clinical interest. Olfactory ensheathing cells (OECs) have been used to improve axonal regeneration and functional outcome in a number of studies in spinal cord injury models. The rationale is that the OECs may provide trophic support and a permissive environment for axonal regeneration. The experimental transplantation of OECs to support and enhance peripheral nerve regeneration is much more limited. This chapter reviews studies using OECs as an experimental cell therapy to improve peripheral nerve regeneration.
Topics: Animals; Axons; Disease Models, Animal; Nerve Fibers, Myelinated; Nerve Regeneration; Olfactory Bulb; Peripheral Nerve Injuries; Spinal Nerves
PubMed: 23202929
DOI: 10.3390/ijms131012911 -
Brain Pathology (Zurich, Switzerland) Sep 2015Olfactory dysfunction is common in multiple sclerosis (MS). Olfactory bulb and tract pathology in MS and other demyelinating diseases remain unexplored. A human autopsy...
Olfactory dysfunction is common in multiple sclerosis (MS). Olfactory bulb and tract pathology in MS and other demyelinating diseases remain unexplored. A human autopsy cohort of pathologically confirmed cases encompassing the spectrum of demyelinating disease (MS; n = 17), neuromyelitis optica [(NMO); n = 3] and acute disseminated encephalomyelitis [(ADEM); n = 7] was compared to neuroinflammatory [herpes simplex virus encephalitis (HSE); n = 3], neurodegenerative [Alzheimer's disease (AD); n = 4] and non-neurologic (n = 8) controls. For each case, olfactory bulbs and/or tracts were stained for myelin, axons and inflammation. Inferior frontal cortex and hippocampus were stained for myelin in a subset of MS and ADEM cases. Olfactory bulb/tract demyelination was frequent in all demyelinating diseases [MS 12/17 (70.6%); ADEM 3/7 (42.9%); NMO 2/3 (66.7%)] but was absent in HSE, AD and non-neurologic controls. Inflammation was greater in the demyelinating diseases compared to non-neurologic controls. Olfactory bulb/tract axonal loss was most severe in MS where it correlated significantly with the extent of demyelination (r = 0.610, P = 0.009) and parenchymal inflammation (r = 0.681, P = 0.003). The extent of olfactory bulb/tract demyelination correlated with that found in the adjacent inferior frontal cortex but not hippocampus. We provide unequivocal evidence that olfactory bulb/tract demyelination is frequent, can occur early and is highly inflammatory, and is specific to demyelinating disease.
Topics: Adolescent; Adult; Aged; Aged, 80 and over; Axons; Cerebral Cortex; Child; Demyelinating Diseases; Encephalitis; Female; Humans; Male; Middle Aged; Myelin Sheath; Olfactory Bulb; Young Adult
PubMed: 25230202
DOI: 10.1111/bpa.12209