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PubMed2005

Axonal transport of rubidium and thallium in the olfactory nerve of mice.

Following intranasal administration of radioactive (86)Rb(+) and (201)Tl(+) in mice, we observed this direct transport via the olfactory nerve pathway. The (86)RbCl and (201)TlCl solutions were administered to two groups of mice, the unilateral intranasal and intravenous administration groups. After sacrifice, their heads were divided into the right and left side, which were then subdivided into seven parts; the nasal mucosa and brain regions were separated. Following the unilateral intranasal administration, uptake after 6 h by the olfactory bulb was significantly higher on the ipsilateral side ((86)Rb, 0.7 %dose; (201)Tl, 0.5 %dose) than on the contralateral side ((86)Rb, 0.08 %dose; (201)Tl, 0.15 %dose). Moreover, the (86)Rb and (201)Tl that accumulated in the olfactory bulb were gradually transported to other brain regions of the olfactory tract, the telencephalon and the diencephalon on the side corresponding to the nostril used for administration. Significant differences were observed between the right and left side of the brain regions 6 and 12 h after administration. Further, (201)Tl autoradiography clearly showed striped patterns of dense accumulation, localized in the region around the glomerular layer and granule cell layer of the olfactory bulb and around the olfactory cortex. These results provide clear evidence of axonal transport via the olfactory nerve pathway, from nasal cavity to the olfactory bulb, as well as to the olfactory cortex through the synaptic junctions. The olfactory transport of the (86)Rb(+) and (201)Tl(+) is thought to represent the behavior of K(+) in the olfactory system.

Animals↗
PubMed2000

Dopaminergic modulation at the olfactory nerve synapse.

Dopamine can change the membrane potential, regulate cyclic nucleotides, and modulate transmitter release in central neurons. In the olfactory bulb (OB), the dopamine synthetic enzyme, tyrosine hydroxylase, is largely confined to neurons in the glomerular layer. After demonstrating dopamine D2 receptors in the glomerular and olfactory nerve (ON) layers, Nickell et al. [W.T. Nickell, A.B. Norman, L.M. Wyatt, M.T. Shipley, Olfactory bulb DA receptors may be located on terminals of the olfactory nerve, NeuroReport, 2 (1991) 9-12.] proposed that these receptors may reduce transmitter release due to their localization to ON presynaptic boutons. We have previously demonstrated that olfactory receptor neurons use glutamate to excite OB neurons through activation of glutamate receptors subtypes, NMDA and AMPA/kainate [D.A. Berkowicz, P.Q. Trombley, G.M. Shepherd, Evidence for glutamate as the olfactory receptor cell neurotransmitter. J. Neurophysiol., 71 (1994) 2557-2561]. Here, we used a hemisected turtle OB preparation and patch-clamp recording techniques to assess dopamine modulation of the ON/OB neuron synapse. We found that dopamine (10-300 microM) reversibly decreased the excitatory postsynaptic response to ON stimulation. This effect could be overcome by recruiting additional nerve fibers by increasing the intensity of ON stimulation. Quinpirole (10 microM), a D2 agonist, mimicked the effects of dopamine. Conversely, sulpiride (300 microM), a D2 antagonist, prevented the inhibitory effects of dopamine on synaptic transmission. Whereas dopamine appeared to equally affect the NMDA and AMPA/kainate receptor-mediated components of the synaptically evoked response, it had no direct effect on membrane currents evoked by exogenous glutamate, kainate or NMDA applied to cultured OB neurons. Our data, therefore, support the notion that dopamine modulates synaptic transmission between olfactory receptor neurons and OB neurons via a presynaptic mechanism involving D2 receptor activation. Our abstract (Berkowicz et al. (1994) Neuroscience Abs. 20:328) is the first report of these results.

Action Potentials↗
PubMed2006

Axon behavior in the olfactory nerve reflects the involvement of catenin-cadherin mediated adhesion.

The projection of olfactory sensory neuron (OSN) axons to the olfactory bulb (OB) is a complex but well-regulated process. Although odorant receptor proteins, and other molecules, are implicated in this process, our understanding remains incomplete. We demonstrate that axons remain restricted to the outer olfactory nerve layer (ONLo) until they are proximal to their target glomeruli, where they enter the inner ONL (ONLi), dividing the ONL into extension and sorting zones. Sorting is likely contingent on cell:cell interactions mediated in part by cell adhesion molecules. The cadherins are a large family of adhesion molecules whose function is contingent on their intracellular binding partners, the catenins, which in turn link to the cytoskeleton. We previously demonstrated that the organization of the cytoskeleton changed as olfactory sensory neuron axons moved from the ONLo to the ONLi. To further assess the role of cadherin mediated adhesion in the developing mouse ONL, we localized alpha-, beta-, gamma-, delta-, and p120-catenins as well as neural cadherin (N-cadherin; CDH2) in the OB. alpha- and beta-catenins are found throughout the OB and are uniform throughout the ONL. In contrast, gamma-catenin and CDH2 are expressed predominantly in the ONLo during perinatal development, but are uniform across the ONL beginning at P7 and into adulthood. Finally, p120- and delta-catenins are expressed in nonoverlapping patterns by olfactory axons and OB neuronal dendrites, respectively. We conclude that gamma-catenin-mediated CDH2 adhesion may influence OSN targeting by restricting axons to the ONLo until they reach the appropriate domain of the OB.

Animals↗
PubMed1999

Adult rat olfactory nerve ensheathing cells are effective promoters of adult central nervous system neurite outgrowth in coculture.

A coculture method is described for ensheathing glial cells from adult rat olfactory nerve, serving as a substrate for the regrowth of neurites from adult rat retinal ganglion cells. Immunocytochemically identified phenotypes present in primary cultures of olfactory nerve cells are described, and their ability to promote neurite outgrowth is compared with neonatal astrocytes and Schwann cells, with other nonglial cells, and with laminin. Ensheathing cell cultures were more effective than any other substrate tested and also directed the orientation of regrowing neurites. In comparison with cultured Schwann cells, which released neurotrophic factors into the culture medium, there was no evidence of a similar activity in ensheathing cell cultures. Combinations of ensheathing cell-conditioned medium and substrates of laminin, merosin, or 3T3 cells also failed to show the release of factors enhancing either survival or neurite outgrowth from retinal ganglion cells. Evidence is presented for a partial inhibition of neurite outgrowth in the presence of calcium channel antagonists or an intracellular calcium-chelating reagent. This provides evidence for a contribution from an intracellular calcium signaling mechanism, possibly implicating ensheathing cell adhesion molecules in promoting neurite outgrowth.

Animals↗
PubMed1979

The recovery heat production in non-myelinated garfish olfactory nerve fibres.

1. The recovery heat production of the non-myelinated fibres of garfish olfactory nerve has been measured. 2. At about 20 degrees C the total recovery heat was 381 +/- 26 microcal g-1 impulse-1 at a stimulation frequency of 2 sec-1. 3. The time constant of decay of the recovery heat production after a brief period of stimulation was 78.7 +/- 3.1 sec at about 20 degrees C. 4. Changing the temperature (by +/- 5 degress C) had little effect on the total recovery heat produced. 5. However, lowering the temperature reduced both the rate of rise, and the maximum rate of recovery heat production whereas the time constant of decay was increased. Raising the temperature produced corresponding changes in the opposite direction. 6. the recovery heat production measured in the present experiments is consistent with the previously measured oxygen consumption in the same preparation.

Animals↗
PubMed1988

Electrical stimulation of primary olfactory nerve induces two types of variations in the extracellular potassium activity within the glomerulus of the rat olfactory bulb in vivo.

Primary olfactory nerve stimulation induces a two-step increase in extracellular potassium, as recorded by K+-sensitive microelectrodes inserted into single glomeruli of the rat olfactory bulb. The second rise in K+ (K-peak) occurs in a graded, activity-dependent manner at the basal pole of the glomerular neuropile. This phenomenon appears to be directly related to the rate of extracellular K+ accumulation and is accompanied by a substantial depression of the mitral cell firing rate.

Animals↗
PubMed1989

Rapid mechanical and thermal changes in the garfish olfactory nerve associated with a propagated impulse.

Mechanical and thermal changes associated with a propagated nerve impulse were determined using the garfish olfactory nerve. Production of an action potential was found to be accompanied by swelling of the nerve fibers. The swelling starts nearly at the onset of the action potential and reaches its peak at the peak of the action potential. There is a decrease in the length of the fibers while an impulse travels along the fibers. The time-course of the initial heat was determined at room temperature using heat-sensors with a response-time of 2-3 ms. Positive heat production was found to start and reach its peak nearly simultaneously with the action potential. The rise in temperature of the nerve was shown to be 23 (+/- 4) mu degrees C. In the range between 10 degrees and 20 degrees C, the temperature coefficient of heat production is negative, primarily due to prolongation of the period of positive heat production at low temperatures. The amount of heat absorbed during the negative phase varies widely between 45 and 85% of the heat evolved during the positive phase. It is suggested that both mechanical and thermal changes in the nerve fibers are associated with the release and re-binding of Ca-ions in the nerve associated with action potential production.

Action Potentials↗
PubMed2006

Response of matrix metalloproteinase-9 to olfactory nerve injury.

Matrix metalloproteinases function in the remodeling of the extracellular matrix during growth and development as well as in injury and disease processes. We examined the role of matrix metalloproteinase-9 in a model of olfactory nerve injury in mice. We measured changes in matrix metalloproteinase-9 protein levels for up to 60 days following olfactory nerve transection. Matrix metalloproteinase-9 levels increased within hours after injury, peaked at day 1 and were elevated for approximately 2 weeks before returning to control levels over the 60-day time period. The increase in matrix metalloproteinase-9 was temporally associated with the degeneration of olfactory neurons that follows nerve transection and with increased gliosis. Our results demonstrate a temporal relationship between matrix metalloproteinase-9 elevation, degeneration of olfactory neurons and gliosis.

Animals↗
PubMed1975

The movement of potassium ions during electrical activity, and the kinetics of the recovery process, in the non-myelinated fibres of the garfish olfactory nerve.

1. An electrophysiological study was made with the sucrose gap of the compound action potential of the non-myelinated fibres of the garfish olfactory nerve at temperatures between 8 and 22 degrees C. The efflux of 42K with stimulation, and the post-tetanic hyperpolarization following a period of repetitive stimulation, were also studied. 2. At 22 degrees C the compound action potential (at zero conduction distance) reached its peak in about 5 msec and lasted about 12 msec; the conduction velocity was 19.4 cm/sec. The corresponding extrapolated values at 0 degrees C were: time to peak, 16 msec; duration, 37 msec; conduction velocity, 4.2 cm/sec. 3. The rate constant for resting potassium efflux (kr) was 0.0108 min-1 at 22 degrees C and 0.00489 min-1 at 0 degrees C. 4. The extra fractional loss of potassium with stimulation (ks) was 2.02 x 10(-4) impulse-1 at 22 degrees C and 4.41 x 10(-4) impulse-1 at 0 degrees C. 5. Raising the external potassium concentration, or addition of ouabain (1 mM), raised the resting rate of efflux of potassium. 6. The post-tetanic hyperpolarization, which reflects the electrogenic extrusion of sodium ions, indicated a rate constant for active sodium efflux at 22 degrees C of 0.47 min=1. 7. The rate constant was decreased by a 10 degrees C fall in temperature by a factor of 1.73. 8. Increasing the external potassium concentration increased the rate constant, apparently by potassium combining with some site with an equilibrium dissociation constant of 1.2 mMM. 9. The rate constant was decreased slightly in acidic solutions and increased slightly in alkaline solutions. 10. 14C-labelled ouabain was found to bind to the garfish olfactory nerve with an equilibrium dissociation constant of about 0.5 muM. The maximum saturable binding capacity, 22.3 p-mole/mg dry, suggests that there are about 350 sodium pumping sites per square micron membrane.

Action Potentials↗
PubMed2000

In goldfish the discriminative ability for odours persists after reduction of the olfactory epithelium, and rapidly returns after olfactory nerve axotomy and crossing bulbs.

Goldfish are ideal vertebrates for the study of regeneration within the peripheral and the central olfactory system. The present behavioural investigations studied the effects of bilateral lesions on the animals' ability to qualitatively discriminate two amino acids (10(-6) M) and their performance in two more difficult tasks: (i) rewarded amino acid applied in a lower concentration, and (ii) rewarded stimulus contaminated. A 50 and 85% reduction of the olfactory epithelium resulted in no recordable behavioural deficit. After axotomy of olfactory nerves and lateral olfactory tractotomy, fishes were anosmic for seven to ten days. Following replacement of sensory cells in the epithelium, and after regeneration of olfactory tract fibres a full functional recovery i.e. a highly specific regeneration, was recorded. After three surgical modifications of the olfactory bulbs' position, (i) crossing olfactory tracts and bulbs, (ii) crossing tracts and turning bulbs, and (iii) turning bulbs upside down, a full functional recovery was recorded for amino-acid discrimination in a similar concentration. A permanent, and similar slight deficit was, however, found during application of different concentrations, and of contaminated stimuli when medial lateral halves of the bulb were in 'incorrect' position (i) and (ii), or olfactory bulbs were positioned in the vicinity of the contralateral epithelium (i) and (ii).

Animals↗
PubMed1996

Low-affinity NGF-receptor and E-N-CAM expression define two types of olfactory nerve ensheathing cells that share a common lineage.

Previously, we have shown that the O4 antibody can be used to define and purify olfactory nerve ensheathing cells (ONECs) from the rat olfactory bulb by fluorescence-activated cell sorting. In this study, using a larger panel of neural markers, we demonstrate that this apparently homogeneous population of ONECs possess a heterogeneous antigenic profile both in vivo and in vitro. The antigenic profile of the sorted cells initially correlated with their antigenic profile in vivo, although expression of some of the markers was either lost or gained during time in culture. These changes were influenced by the culture conditions, with a greater loss of "typical" ONEC markers in serum-containing medium. In serum-free medium, which maintains the cells in a phenotype that closely resembles their in vivo counterparts, we were able to reclassify the ONECs into two cell types based on morphology and antigenic phenotype by using antibodies to polysialic acid (correlating with the embryonic form of N-CAM expression) and the low-affinity nerve growth factor receptor. A detailed immunocytochemical study of the developing olfactory system showed that these two cell types could also be detected along the entire length of the olfactory nerve and the outer layer of the olfactory bulb from Embryonic Day 14 to adulthood, suggesting they were not an in vitro artefact. To address the relationship between the two cell types we constructed a clonal ONEC cell line by retroviral infection with the temperature-sensitive mutant gene of the large T antigen. This clonal cell line contained cells that expressed antigenic phenotypes of both classes of ONECs, suggesting that both cell types are related and share a common lineage.

Animals↗
PubMed1974

Ion fluxes through the sodium channels of garfish olfactory nerve membranes.

1. The efflux of (22)Na from garfish olfactory nerves, after treatment with ouabain and equilibration with (22)Na, occurs in two components of almost equal size. One component represents efflux from the extracellular space and the other, much slower, component represents efflux from the intracellular space through the axonal membrane.2. The rate of efflux of (22)Na through the membrane is increased from 0.038 to 0.055 min(-1) by veratrine, and restored back to 0.036 min(-1) by the additional application of tetrodotoxin or saxitoxin (10(-7)M).3. 50% inhibition of this increased sodium ion flux occurs at tetrodotoxin and saxitoxin concentrations of 12 and 6 nM respectively.4. The tetrodotoxin-sensitive efflux of (22)Na is almost unchanged in nerves equilibrated with hypertonic 0.85 M-NaCl, whereas it is largely eliminated in nerves equilibrated with 0.85 M-LiCl. We interpret this to indicate that there exists within the sodium channel a specific metal cation site which is responsible for the co-ordination of the ions during their passage through the membrane. Lithium ions bind to this site relatively strongly, with a dissociation constant of 0.2-0.3 M, whereas sodium ions bind less strongly, with a dissociation constant greater than 0.75 M. Other evidence indicates that this site is the site at which tetrodotoxin and saxitoxin act.5. Batrachotoxin has a similar action to veratrine but is effective in concentrations at least 100 times lower.

Animals↗
PubMed1981

Partial purification and characterization of (Na+ + K+)-ATPase from garfish olfactory nerve axon plasma membrane.

The (Na+ + K+)-ATPase of garfish olfactory nerve axon plasma membrane was purified about sixfold by treatment of the membrane with sodium dodecyl sulfate followed by sucrose density gradient centrifugation. The estimated molecular weights of the two major polypeptide components of the enzyme preparation on sodium dodecyl sulfate gels were 110,000 and 42,000 daltons, which were different from those of the corresponding peptides of rabbit kidney (Na+ + K+)-ATPase. No carbohydrate was detected in the 42,000-dalton component either by the periodic acid-Schiff reagent or by the more sensitive concanavalin A-peroxidase staining procedure. The molecular properties of the garfish (Na+ + K+)-ATPase, such as the Km for ATP, pH optimum, energies of activation, Na and K ion dependence and vanadium inhibition, were, however, similar to those of the kidney enzyme. The partially purified garfish (Na+ + K+)-ATPase was reconstituted into phospholipid vesicles by a freeze-thaw-sonication procedure. The reconstituted enzyme was found to catalyze a time and ATP dependent 22Na+ transport. The ratio of 22Na+ pumped to ATP hydrolyzed was about 1; under the same reconstitution and assay conditions, eel electroplax (Na+ + K+)-ATPase, however, gave a 22Na+ pumped to ATP hydrolyzed ratio of nearly 3.

Animals↗
PubMed2004

Balamuthia mandrillaris, an opportunistic agent of granulomatous amebic encephalitis, infects the brain via the olfactory nerve pathway.

Balamuthia mandrillaris is a free-living ameba and an opportunistic agent of lethal granulomatous amebic encephalitis (GAE) in humans and other mammals. Its supposed routes of infection have been largely assumed from what is known about Acanthamoeba spp. and Naegleria fowleri, other free-living amebae and opportunistic encephalitis agents. However, formal proof for any migratory pathway, from GAE patients or from animal models, has been lacking. Here, immunodeficient mice were infected with B. mandrillaris amebae by intranasal instillation, the most likely natural portal of entry. By means of classical and immunohistology, the amebae are shown to adhere to the nasal epithelium, progress along the olfactory nerves, traverse the cribriform plate of the ethmoid bone, and finally infect the brain. A similar invasion pathway has been described for N. fowleri. The data suggest that the olfactory nerve pathway is a likely route for natural infection of the brain by B. mandrillaris amebae.

Amebiasis↗
PubMed2004

X-ray scattering study of pike olfactory nerve: elastic, thermodynamic and physiological properties of the axonal membrane.

The effects of several agents, sugars, isotonic KCl, and a variety of drugs, on the structure of the axonal membranes of unmyelinated pike olfactory nerve have been studied by synchrotron radiation X-ray scattering experiments. The main effects of the sugars are: (i) to increase the electron density of the extra-axonal space and thereby yield the absolute scale of the electron density profile; (ii) to osmotically stress the membrane and thus yield its elastic modulus of area compressibility, since the related strain, thickness dilation, is directly determined by the X-ray scattering experiments. Exposure to isotonic KCl, a depolarizing agent, induces membrane thickness to increase. The energy liberated in this process is a function of the amplitude of the dilation and of the elastic modulus of the membrane. This energy turns out to be close to the thermal energy liberated by the pike olfactory nerve during the initial phase of action potential that has previously been measured by others. Electrical depolarization thus seems to be accompanied by a thickness dilation of the axonal membrane. Another effect of isotonic KCl is to induce a large fraction of the membranes to pair by tight apposition of their extra-axonal faces. Local anaesthetics and some drugs have the effect of altering membrane thickness. All these observations are interpreted in terms of a modulation of the conformational disorder of the hydrocarbon chains of the lipid molecules.

Anesthetics, Local↗
PubMed1995

Wavelet analysis of olfactory nerve response to stimulus.

Multiunit electrophysiological activity recorded by gross electrodes from the olfactory nerve was analyzed by wavelet decomposition, a relatively new method of signal processing. The analysis was run on data from the unstimulated olfactory system as well as on data evoked in response to six different odorant stimuli. Like Fourier analysis, wavelet analysis provides a spectral decomposition of the signal. Unlike Fourier, wavelet analysis also locates the dominant spectral features in time. The output of a wavelet analysis can be further processed to enhance selected features. The increased amplitude of the nerve response evoked by stimulation was the most obvious feature, but efforts to learn from it were unproductive. The temporal pattern of receptor cell activity was much more yielding. The analysis resolved the nerve activity into three classes of events based on duration. On wavelet maps these classes of events separate out into three shifting and overlapping but distinct bands, one of which was interpreted as being associated with individual receptor cell firings and the other two as short and somewhat longer duration bursts of activity that was attributed to the synchronized firing of a group of receptor cells. This interpretation is supported by experiments in which waveforms simulating action potentials and bursts of action potentials are added to recorded data. Stimulation of the olfactory system with odorant molecules evokes a significant increase in the number of short duration bursts, and an amplitude increase that can be related to the number of receptor cells responding. Changes in the patterns of wavelet events can be associated with synchrony of cell firing, reset times for bursts of firing, and possibly other physiological dynamics. A number of differences in activity patterns with different odorants were observed, but without sufficient repeatability to allow reliable discrimination among them. While this study is clearly preliminary in that regard, it shows the potential of the wavelet method for contributing to the understanding of olfaction.

Animals↗
PubMed1988

[Neuroblastoma of the olfactory nerve. Radiotherapy experiences in 6 patients].

Six patients with neuroblastomas of the olfactory nerve (esthesioneuroblastoma) are presented who were irradiated between 1983 and 1986 at the Medical Radiologic Institute of Tübingen. Clinical manifestations, diagnostics, histology, therapy, and courses are compared and discussed with regard to a survey of literature. An attempt is made to find out the value of radiotherapy in the treatment of this rare disease. In stage A (tumor restricted to the nasal cavity, 1 patient), a local tumor control of up to now 28 months could be achieved by a treatment combination of surgery and radiotherapy. A treatment consisting of surgery or radiotherapy alone should even in this stage only be performed in connection with a close follow-up because of the increased local recurrence risk. Tumors of stage B (manifestation in the nasal cavity and the paranasal sinuses) did not occur in this group of patients. Five patients suffered from tumors of stage C (tumor extent beyond the paranasal sinuses). A good palliative effect was obtained temporarily by radiotherapy alone in three out of these patients showing large inoperable tumors and rapidly progressing clinical symptoms. A complete remission now lasting 16 months was achieved only in one patient by radical surgery with unilateral evisceration of orbit and homogeneous postirradiation. In case of stage C tumors it is recommended to perform, if possible, a radical tumor excision with evisceration of orbit in case of unilateral manifestation in the orbit and a postirradiation applying a radical, large volume technique. In order to reduce the risk of radiogenic cerebral necroses, it should be attempted to avoid dose maxima as they can occur when applying a combined ventro-dorsal and lateral irradiation technique.

Adult↗