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At least 883 records · Page 49Linked to original sources
PubMed1981

Ruffed cell: a new type of neuron with a distinctive initial unmyelinated portion of the axon in the olfactory bulb of the goldfish (Carassius auratus). III. Three-dimensional structure of the ruffed cell dendrite.

The three-dimensional structure of the ruffed cell dendrite in the olfactory bulb of the goldfish (Carassius auratus) was studied by means of light and high-voltage electron microscopy of Golgi-impregnated material, combined Golgi-electron microscopy, and electron microscopy of serial thin sections. Ruffed cell dendrites ramify in the glomerular area with tufted branching patterns. They give rise to many appendages of various shapes and sizes: sheetlike processes, fingerlike projections, or small tuftlike appendages. These appendages, singly or together, appear to entwine or cover other neuronal processes. In thin sections ruffed cell dendritic appendages frequently look like glial processes; that is, they appear to conform in shape to the contours of surrounding neuronal elements, such as mitral and granule cell dendrites. Ruffed cell dendrites display intimate relationships with mitral cell dendrites. The former appear to coil around and cover the latter. Nothwithstanding the intimate relationship between ruffed cell dendrites and mitral cell dendrites, there seem to be no synaptic connection between them. Ruffed cell dendrites bear a rather small number of presynaptic and postsynaptic sites, most of which area with granule cell dendrites. Ruffed cell dendrites seem to receive no synapses from olfactory nerve terminals.

Animals↗
PubMed1984

Experimental transcerebral fistula. Perineural olfactory CSF flow in the normal, hydrocephalic, and postoperative hydrocephalic dog shown by radionuclide ventriculography.

Cerebrospinal fluid dynamics were studied in eight dogs during normal, hydrocephalic, and postoperative phases. Radionuclide-labeled substances introduced into the normal ventricular system flow out of the exits from the fourth ventricle to the convexity subarachnoid spaces superiorly to be absorbed in the sagittal sinus, and basorostrally to the exits from the perineural olfactory sheath into the nose to produce physiological cerebrospinal fluid (CSF) rhinorrhea. Serial radionuclide ventriculography of the head following intraventricular isotope injection of labeled proteins and chelate into the kaolin-induced hydrocephalic system shows a high degree of ventricular stasis with no perineural olfactory nerve flow (rhinorrhea). An operative transcerebral fistula, fashioned from a dilated lateral ventricle to the convexity subarachnoid space, reestablishes perineural olfactory flow of CSF into the nose, as demonstrated by the radionuclide ventriculography studies. This suggests a potential method for treatment of hydrocephalus. Serial imaging studies in this surgically modified system clearly demonstrate radionuclide flow through the patent fistula to distal absorption sites, thereby bypassing the basal obstruction. Moreover, augmented CSF pressures associated with obstructive hydrocephalus can be controlled by such treatment. The application of this method in treating clinical hydrocephalus is discussed with emphasis on fistula arachnoid closure to assure fistula patency.

Animals↗
PubMed1991

The formation of axonal pathways in developing cranial nerves.

The roles of a variety of molecules including cell adhesion molecules and growth factors in the development of cranial nerves have begun to be understood in detail. In the course of embryonic development, cranial nerves are differentiated in concordance with the development of the metameric facial structure called 'ectomeres'. Each ectomere parallels the segmentation of the hindbrain called the 'rhombomere', in which pairs of metameric units cooperate to generate the repeating sequence of cranial branchiomotor nerves. A number of genes, including homeobox genes, are expressed in a rhombomere-specific pattern. For the formation of the olfactory nerve, it is suggested that several carbohydrate residues play important roles in receptor-target specificity. In the optic nerve, a combination of multiple cell adhesion molecules contributes to neurite growth in a developmental stage-specific manner. The development of the trigeminal nerve is under the control of both cell adhesion molecules and several growth factors. There is evidence that some of the adhesion molecules are expressed in a modality-specific way. There are also several molecules, such as 11p15 or TAG1/SNAP which are expressed only in selected cranial nerves. The growth rate of neurites also varies according to the individual nerves. Thus each cranial nerve has its own intrinsic properties and their outgrowth is the outcome of these properties and their interactions with surrounding non-neuronal tissues.

Animals↗
PubMed1992

[Immunohistochemical study of the human olfactory system].

Taurine (2-aminoethane sulfonic acid) and carnosine (beta-alanyl-L-histidine) are found in large quantities in the olfactory epithelium and bulb. Taurine is a structurally simple amino acid, and has been reported to have several putative roles, such as neurotransmitter, neuromodulator, neurogrowth factor and to function in membrane stabilization. Carnosine, on the other hand, has been suggested as a putative neurotransmitter in the olfactory system. We have succeeded in visualizing taurine- and carnosine-like immunoreactivities (LI) in the human olfactory mucosa, and also carnosine-LI in the human olfactory bulb. For this investigation, we collected specimens of the human olfactory bulb by autopsy and from the olfactory mucosa by biopsy, and compared localization of taurine- and carnosine-LI in several cases. By means of biopsy using Nakano's forceps, samples of olfactory mucosa were obtained from 5 cases: a 17 year old female, 23 year old male, 46 year old male, 47 year old male, and a 57 year old male. The olfactory bulb of a 1 month old male was collected at autopsy. These specimens were processed for immunohistochemical study according to the peroxidase-antiperoxidase (PAP) method. In the olfactory epithelium, taurine-LI was demonstrated in some primary olfactory neurons, and in basal cells. Carnosine-LI was observed only in primary olfactory neurons, i.e., dendrites, vesicles and axonal bundles of olfactory receptor cells, but not in basal cells. In the olfactory bulb, the olfactory nerve layer and the glomerular layer showed carnosine-LI positive reactions. Therefore, taurine and carnosine may possibly coexist in some olfactory neurons. Olfactory receptor cells are classified as sensory neurons.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1999

[Persistent primitive olfactory artery: report of 5 cases].

Five cases of a persistent primitive olfactory artery are reported. The anomalous artery coursed anteromedially along the ipsilateral olfactory nerve and made a hairpin turn, supplying the circulation of the anterior cerebral artery. It was proposed that a primitive embryonic olfactory artery had remained as this artery. A cerebral aneurysm was located at the hairpin curve of the artery. Hemodynamic stress is considered to have an important role in aneurysm formation. Any aneurysm occurring at an artery should be considered for surgical treatment.

Aged↗
PubMed2004

Nasal toxicity of manganese sulfate and manganese phosphate in young male rats following subchronic (13-week) inhalation exposure.

Growing evidence suggests that nasal deposition and transport along the olfactory nerve represents a route by which inhaled manganese and certain other metals are delivered to the rodent brain. The toxicological significance of olfactory transport of manganese remains poorly defined. In rats, repeated intranasal instillation of manganese chloride results in injury to the olfactory epithelium and neurotoxicity as evidenced by increased glial fibrillary acidic protein (GFAP) concentrations in olfactory bulb astrocytes. The purpose of the present study was to further characterize the nasal toxicity of manganese sulfate (MnSO(4)) and manganese phosphate (as hureaulite) in young adult male rats following subchronic (90-day) exposure to air, MnSO(4) (0.01, 0.1, and 0.5 mg Mn/m(3)), or hureaulite (0.1 mg Mn/m(3)). Nasal pathology, brain GFAP levels, and brain manganese concentrations were assessed immediately following the end of the 90-day exposure and 45 days thereafter. Elevated end-of-exposure olfactory bulb, striatum, and cerebellum manganese concentrations were observed following MnSO(4) exposure to > or = 0.01, > or = 0.1, and 0.5 mg Mn/m(3), respectively. Exposure to MnSO(4) or hureaulite did not affect olfactory bulb, cerebellar, or striatal GFAP concentrations. Exposure to MnSO(4) (0.5 mg Mn/m(3)) was also associated with reversible inflammation within the nasal respiratory epithelium, while the olfactory epithelium was unaffected by manganese inhalation. These results confirm that high-dose manganese inhalation can result in nasal toxicity (irritation) and increased delivery of manganese to the brain; however, we could not confirm that manganese inhalation would result in altered brain GFAP concentrations.

Air Pollutants↗
PubMed2005

Inhibition [corrected] of olfactory receptor neuron input to olfactory bulb glomeruli mediated by suppression of presynaptic calcium influx.

We investigated the cellular mechanism underlying presynaptic regulation of olfactory receptor neuron (ORN) input to the mouse olfactory bulb using optical-imaging techniques that selectively report activity in the ORN presynaptic terminal. First, we loaded ORNs with calcium-sensitive dye and imaged stimulus-evoked calcium influx in a slice preparation. Single olfactory nerve shocks evoked rapid fluorescence increases that were largely blocked by the N-type calcium channel blocker omega-conotoxin GVIA. Paired shocks revealed a long-lasting suppression of calcium influx with approximately 40% suppression at 400-ms interstimulus intervals and a recovery time constant of approximately 450 ms. Blocking activation of postsynaptic olfactory bulb neurons with APV/CNQX reduced this suppression. The GABA(B) receptor agonist baclofen inhibited calcium influx, whereas GABA(B) antagonists reduced paired-pulse suppression without affecting the response to the conditioning pulse. We also imaged transmitter release directly using a mouse line that expresses synaptopHluorin selectively in ORNs. We found that the relationship between calcium influx and transmitter release was superlinear and that paired-pulse suppression of transmitter release was reduced, but not eliminated, by APV/CNQX and GABA(B) antagonists. These results demonstrate that primary olfactory input to the CNS can be presynaptically regulated by GABAergic interneurons and show that one major intracellular pathway for this regulation is via the suppression of calcium influx through N-type calcium channels in the presynaptic terminal. This mechanism is unique among primary sensory afferents.

2-Amino-5-phosphonovalerate↗
PubMed1979

Neuronal degeneration and regeneration in the olfactory epithelium of pigeon following transection of the first cranial nerve.

The pigeon olfactory nerve has been sectioned to explore the course of retrograde degeneration of the sensory neurons' perikarya, which are located in the olfactory neuroepithelium. Both light- and electron-microscopic observations have shown that from 3 to 8 days after axotomy the sensory neurons undergo retrograde, irreversible degeneration. Following disappearance of the mature neurons, the basal cells of the neuroepithelium actively divide and differentiate into mature olfactory sensory neurons. Consequently, the basal cells represent true stem cells of the olfactory sensory neurons. The olfactory mucosa regains a structural organization close to normal in a period of 30-50 days after axotomy. These observations indicate that, when the primary olfactory neurons degenerate as a consequence of the experimental section of their axons, restitutio ad integrum of the sensory olfactory connections can be reestablished by new elements which differentiate from basal cells of the olfactory neuroepithelium.20

Animals↗
PubMed1987

Serotonergic afferents to the rat olfactory bulb: I. Origins and laminar specificity of serotonergic inputs in the adult rat.

This is a study of the chemoanatomical organization of the projection from the raphe nuclei to the main olfactory bulb in the rat. A heavy projection from the dorsal and median raphe nuclei to the main olfactory bulb was shown by both retrograde and anterograde tracing techniques. Following injections of 1% wheat germ agglutinin-horseradish peroxidase (WGA-HRP) into the main olfactory bulb, up to 1300 neurons were retrogradely labeled in the dorsal and median raphe nuclei, a much larger number than has been suggested by previous studies. By combining 5-HT immunofluorescence with True blue retrograde fluorescent labeling, it was determined that the vast majority of raphe neurons that project to the olfactory bulb contain serotonin. Injections of WGA-HRP into dorsal and/or median raphe produced dense anterograde labeling in the glomeruli, while fewer labeled fibers were observed in the external plexiform layer, internal plexiform layer, and granule cell layer. In contrast to the number of other centrifugal afferents to the bulb, a significant contingent of fibers from the raphe nuclei enters the main olfactory bulb (MOB) from outside in, i.e., via the olfactory nerve layer. Serotonergic fibers in MOB were visualized by immunocytochemistry, and the distribution of specific 5-HT fibers closely matched the distribution of anterograde terminal label resulting from injections of WGA-HRP in the raphe nuclei. The serotonergic fibers have a specific laminar distribution and morphology in MOB. Thus, the density of the serotonergic innervation to the glomerular layer is 2-3 times that of any other layer in MOB. In addition to their preferential innervation of the glomeruli, glomerular and infraglomerular serotonergic fibers are morphologically different. Serotonergic fibers located in the glomerular layer are generally thick (0.25-0.60 micron) compared to the thinner (0.25-0.35 micron) fibers that predominate in infraglomerular layers. Another difference is that the glomerular fibers often contain varicosities that are greater than 1 micron in diameter, while varicosities along infraglomerular fibers are usually barely larger than the axonal diameter. Finally, glomerular fibers are much more intensely stained than infraglomerular fibers. Electrolytic lesions of the dorsal and median raphe caused a total depletion of serotonin fiber staining in the bulb, demonstrating that the raphe nuclei are the sole source of the serotonergic input to the main olfactory bulb. Thus, it has been demonstrated that serotonergic neurons in dorsal and median raphe project very heavily to glomeruli and less heavily to other layers in the main olfactory bulb.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1994

B-50/GAP-43 expression by the olfactory receptor cells and the neurons migrating from the olfactory placode in embryonic rats.

B-50/GAP-43 is a growth-associated phosphoprotein that is commonly expressed in all developing neuronal systems. Using an immunocytochemistry approach, we have investigated the expression of this protein in the rat olfactory system during embryogenesis and neonatal development with a particular emphasis on the early developmental stages of the olfactory placode. Data show that already at embryonic day 12 (E12), a strong B-50/GAP-43 immunoreactivity was detected in few olfactory receptor cells well-recognizable by their positive short neuritic processes. The B-50/GAP-43 expression in the placodal epithelium thus appeared to coincide with the onset of neurite outgrowth. From E13 onwards, there was a rapid increase in the number of B-50/GAP-43-positive olfactory neurons and from E18, the protein was strongly expressed by nearly all neurons. In addition, results clearly demonstrate that as early as E13, B-50/GAP-43 was strongly expressed by many migrating cells which were seen leaving the pit epithelium in association with the first olfactory axons that penetrated the nasal mesenchyme. Many immunoreactive cells were also observed in the presumptive olfactory nerve layer. Experiments of double-labeling showed that B-50/GAP-43-immunostained migrating cells were also stained with anti-neuron-specific enolase (NSE). This confirms the neuronal nature of these early labeled migrating cells. The progressive disappearance of migrating neurons noted during the late stages of embryonic development is discussed in relation with their possible function in the early stages of development of the peripheral olfactory system.

Animals↗
PubMed1985

Immunolocalization of a neuronal growth-dependent membrane glycoprotein.

Monoclonal antibody (mAb) 5B4 recognizes in the rat a large, developmentally regulated membrane glycoprotein. The larger form of this antigen (185-255 kD) occurs in the developing nervous system and is present in membranes of nerve growth cones, as determined by analysis of a growth cone particle fraction. An immunochemical characterization of this antigen and of a smaller form (140 kD), sparsely present in the mature nervous system, has been described (Ellis, L., I. Wallis, E. Abreu, and K. H. Pfenninger, 1985, J. Cell. Biol., 101:1977-1989). The present paper reports on the localization by immunofluorescence of 5B4 antigen in cultured cortical neurons, developing spinal cord, and the mature olfactory system. In culture, mAb 5B4 stains only neurons; it is sparsely present in neurons at the onset of sprouting while, during sprouting, it appears to be concentrated at the growth cone and in regions of the perikaryon. In the developing spinal cord, 5B4 labeling is faintly detectable on embryonic day 11 but is intense on fetal day 13. At this stage, the fluorescence is observed in regions of the cord where axonal growth is occurring, while areas composed of dividing or migrating neural cells are nonfluorescent. With maturation of the spinal cord, this basic pattern of fluorescence persists initially, but the staining intensity decreases dramatically. In the adult, faint fluorescence is detectable only in gray matter, presumably indicating the presence of the 140 kD rather than the fetal antigen. The only known structure of the adult mammalian nervous system where axonal growth normally occurs is the olfactory nerve. mAb 5B4 intensely stains a variable proportion of olfactory axons in the mucosa as well as in the olfactory bulb. Based on both immunochemical and immunofluorescence data, the 5B4 antigen of 185-255 kD is associated specifically with growing neurons, i.e., neurons that are generating neurites.

Animals↗
PubMed1981

Chemical deafferentation of the olfactory bulb: plasticity of the levels of tyrosine hydroxylase, dopamine and norepinephrine.

The laminar distribution of tyrosine hydroxylase activity, dopamine and norepinephrine was determined in the dog olfactory bulb. The levels of tyrosine hydroxylase activity and dopamine were highest in the glomerular layer, whereas norepinephrine appeared to be more uniformly distributed across the layers. A similar distribution was observed within the mouse olfactory bulb. Following deafferentation of the mouse olfactory bulb, the levels of tyrosine hydroxylase activity and dopamine declined, while norepinephrine levels showed a transient increase. Subsequent to regeneration of the olfactory nerve, these levels returned to control values. The levels of tyrosine hydroxylase activity and of dopamine were very low or non-detectable in the olfactory epithelium, which contains the olfactory receptor neuron perikarya. The data obtained indicate that tyrosine hydroxylase activity and dopamine content in the bulb are more tightly coupled to each other than either is to norepinephrine content. Since the two catecholamines are in two different classes of neurons, this implies that the bulk of the tyrosine hydroxylase activity in the bulb is associated with the dopamine-containing neurons. Finally, our data are consistent with a transsynaptic control mechanism of the tyrosine hydroxylase activity and dopamine level in the olfactory bulb.

Afferent Pathways↗
PubMed2005

Ontogeny of GnRH-like immunoreactive neuronal systems in the forebrain of the Indian major carp, Cirrhinus mrigala.

GnRH immunoreactivity appeared in the medial olfactory placode very early in the development of Cirrhinus mrigala. The immunoreactive elements were divisible into distinct migratory and non-migratory components. The migratory component appeared as a patch of intensely immunoreactive cells located close to the olfactory epithelium in day 6 post-fertilization larvae. Subsequently, these neurons migrate caudally along the ventromedial aspect of the developing forebrain and enroute give rise to GnRH immunoreactive neurons in the (1) nervus terminalis located in ventral and caudal part of the olfactory bulb (day 8), and (2) basal telencephalon (day 9). The non-migratory GnRH immunoreactive component appeared in the olfactory placode of day 1 post-fertilization larvae. It consisted of few olfactory receptor neuron (ORN)-like cells with distinct flask-shaped somata, dendrites that communicate with the periphery and a single axon on the basal side; GnRH immunoreactivity was seen throughout the neuron. Considerable increase in the number of immunoreactive ORNs was encountered in day 2 post-fertilization larvae. On day 3, the dendrites of ORNs sprout bunches of apical cilia, while on the basal side the axonal outgrowths can be traced to the olfactory bulb. GnRH immunoreactive fibers were distributed in the olfactory nerve layer in the periphery of the bulb and glomeruli-like innervation was clearly established in 5 days old larvae. The innervation to the olfactory bulb showed a considerable increase in GnRH immunoreactivity in 9 and 19 days old larvae. However, GnRH immunoreactivity in non-migratory as well as migratory components gradually diminished and disappeared altogether by the age of 68 days. Results of the present study suggest that GnRH may serve a neurotransmitter role in the ORNs during early stages of development in C. mrigala.

Animals↗
PubMed1988

Putative glutamatergic and/or aspartatergic cells in the main and accessory olfactory bulbs of the rat.

The "transmitter-specific" retrograde axonal tracer 3H-D-aspartate has been used to demonstrate neurons in the olfactory bulb which putatively utilize aspartate and/or glutamate as their neurotransmitter and which send an axon either to the piriform cortex or within the bulb itself. Injections of 3H-D-aspartate into layer I of the anterior piriform cortex, in the zone of termination of axons from the olfactory bulb, labeled only a few cells in the main olfactory bulb, located in the mitral and external plexiform layers. Although these cells resembled mitral and tufted cells, they tended to have smaller somata than other mitral or tufted cells and apparently form a distinct subpopulation of relay cells. In contrast, many of the mitral cells of the accessory olfactory bulb were labeled by the same injections of 3H-D-aspartate, probably as a result of involvement of the accessory olfactory tract or its bed nucleus in the injection site. Similar injections of the "nonspecific" tracer HRP into the anterior piriform cortex labeled most of the cells in the mitral cell layer of both the main and accessory olfactory bulbs, and some tufted cells in the external plexiform layer. It is concluded that only a small, distinct subpopulation of the mitral or tufted cells of the main olfactory bulb are aspartatergic and/or glutamatergic, while many (at least) of the mitral cells of the accessory olfactory bulb use the excitatory amino acids as transmitters. Injections of 3H-D-aspartate directly into the main olfactory bulb also failed to label the mitral and deeply situated tufted cells. However, a few cells were labeled in the periglomerular region, the superficial external plexiform layer, and the granule cell layer near the injection site. These labeled cells were smaller than mitral and tufted cells but generally larger than periglomerular or granule cells. They may represent a population of glutamatergic or aspartatergic short axon cells. In addition, small cells of an unknown type were labeled in the olfactory nerve layer following injections in the deepest part of the bulb. These cells do not correspond to any of the well characterized cell types of the olfactory bulb.

Animals↗
PubMed1999

Role of polysialic acid on outgrowth of rat olfactory receptor neurons.

Towards elucidating the role of polysialic acid (PSA) in developing olfactory neuron of the rat, we injected neuraminidase (endo-N) into the olfactory nerve pathway under whole embryo culture, then employed immunohistochemistry to (i) detect expression of highly sialylated neural cell adhesion molecules (NCAM-H) and (ii) identify olfactory neurons via anti-microtubule-associated protein 1B (MAP1B) antibody. Olfactory axonal outgrowth from basal lamina occurred at the 31-somite stage and reached the olfactory bulb primordium at the 42-somite stage, being coincident with the timing and expression of NCAM-H immunoreactivity. Enzymatic removal of PSA by endo-N remarkably affected developmental processes of axonal outgrowth, extension, and pathfinding, i.e. individual axons appeared to have become stuck in the mesenchyme. Results indicate that PSA is critically involved with anti-adhesion cues associated with individual axonal growth during olfactory system development.

Animals↗
PubMed1997

Long-term recording of olfactory and vomeronasal stimulant-induced waves from the turtle main olfactory bulb and accessory olfactory bulb.

Recording of stimulant-induced waves (bulbar responses) from the main olfactory bulb is a useful tool for measuring quantitative stable olfactory responses. There is a good relationship between the olfactory bulbar response, olfactory nerve response and electroolfactogram (EOG), suggesting that the bulbar response reflects events in receptor cells. The modern whole-cell recording technique offers direct information on olfactory transduction in single cells, but it requires long experimental periods and many animals. On the other hand, analysis of bulbar responses provides useful information and requires the use of few animals. For example, we found that cAMP-increasing and IP3-increasing odorants were not distinctly received by the turtle olfactory organ by measuring olfactory bulbar responses and analyzed with a multidimensional scaling from about 60 animals. However, to record similar odor responses from isolated turtle olfactory neurons, at least 200 animals would be necessary. Bulbar responses are recorded with electrodes implanted into or located on the main olfactory bulb. When electrodes are located on the olfactory bulb surface, it is possible to record stable responses over a period of 3 days. These methods were applied successfully to the accessory olfactory bulb. In this paper, we describe the protocols used for recording of the stimulant-induced waves from the main and accessory olfactory bulb.

Adaptation, Physiological↗
PubMed1996

Olfactory evoked potentials: experimental and clinical studies.

Olfactory evoked potentials (OEPs), obtained by electrical stimulation of the olfactory mucosa, were recorded in dogs and humans to develop an objective method for evaluating olfactory functions. In dogs, OEPs were recorded from the olfactory tract and the scalp. The latency of the first negative peak was approximately 40 msec. A response was not obtained after stimulation of the nasal mucosa and disappeared after sectioning of the olfactory nerve. With increasing frequencies of repetitive stimulation, the amplitude was reduced, suggesting that the response was synaptically mediated. These results demonstrate that evoked potentials from the olfactory tract and the scalp following electrical stimulation of the olfactory mucosa originate specifically from the olfactory system. In humans, a stimulating electrode with a soft catheter was fixed on the olfactory mucosa. The OEPs from the olfactory tract, recorded with a negative peak of approximately 27 msec, had similar characteristics to OEPs found in dogs. The OEPs from the olfactory tract in humans also originate specifically from the olfactory system. The authors postulate that OEPs obtained by electrical stimulation of the olfactory mucosa may prove useful for intraoperative monitoring of olfactory functions.

Animals↗