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PubMed1995

Pitfalls in the pterional approach to the parasellar area (review).

The pterional approach is commonly employed in surgery of the anterior circulation and upper basilar artery aneurysms, as well as for the tumors of orbital, retroorbital, sellar, chiasmatic, subfrontal and prepontine areas and lesions around the sella especially for lesions behind the clivus. Also tumors arising from the medial sphenoid ridge, the superior orbital fissure, the anteromedial temporal surface, or the cavernous sinus region are approached through a pterional exposure. The surgical technique is based on the experience, training and observation of the neurosurgeon. One technique is not necessarily better than another. Regardless of the surgical technique, the end results depend on a rigorous, methodical, systematic, and step-by-step approach to the target, securing it with minimal injury to surrounding structures. In this study, we have analyzed the intraoperative anatomical findings of the Sylvian vein and fissure, lenticulostriatal artery, olfactory nerve, and recurrent artery of Heubner and showed the surgical pitfalls in 700 patients with different diagnoses that were operated on with the pterional approach. The findings were recorded during surgical interventions and through the slides and videotapes of the operations. Also, we have stressed the preservation of the frontotemporal branch of the facial nerve, the delicate retraction of frontal lobe, the cottonoid retraction in temporal lobe and the preservation of olfactory nerve functions.

Cerebral Arteries↗
PubMed2002

EphA receptors and ephrin-A ligands exhibit highly regulated spatial and temporal expression patterns in the developing olfactory system.

The spatiotemporal expression patterns of the chemorepulsive EphA receptors, EphA4 and EphA7, and three ephrins-A2, A4 and A5, were examined in the developing rat primary olfactory system. Unlike the visual system that has simple and stable gradients of Ephs and ephrins, the olfactory system demonstrates complex spatiotemporal expression patterns of these molecules. Using immunohistochemistry, we demonstrate that expression of these molecules is dynamic and tightly regulated both within and between different cell types. We reveal restricted targeting of these proteins within subcellular compartments of some neurons. EphA4, ephrin-A2 and ephrin-A5 were expressed by primary olfactory axons during the embryonic formation of the olfactory nerve. There were no gradients in expression along the rostrocaudal or ventrodorsal axes in the nasal cavity and olfactory bulb. However, during the early neonatal period, axons expressing different levels of ephrin-A5 sorted out and terminated in a subpopulation of glomeruli that were mosaically dispersed throughout the bulb. The expression of EphA4 and ephrin-A2 was dramatically down-regulated on all axons during the early neonatal period of glomerular formation. The uniform co-expression of receptors and ligands before glomerular formation suggests they play a generic role in axon-axon interactions in the olfactory nerve and nerve fibre layer. In contrast, loss of EphA4 from axons during glomerular formation may facilitate the interaction of ephrin-A5 with Eph receptors on target cells in the bulb. While EphA4, EphA5 and EphA7 are not mosaically expressed by bulbar neurons, other Eph receptors may have expression patterns complementary to the ephrin-A5-positive subpopulation of glomeruli.

Animals↗
PubMed1997

Glutamatergic deafferentation of olfactory bulb modulates the expression of mGluR1a mRNA.

Glutamate (Glu) released by olfactory nerve axons acts on postsynaptic ionotropic and metabotropic glutamate receptors expressed by principal neurones and interneurones of the olfactory bulb (OB). Using ZnSO4 lesioning of the rat olfactory mucosa and semiquantitative RT-PCR, we examined the effect of removal of the glutamatergic input to the OB on the expression of mGluR1a, mGluR1b and GluR1 mRNAs. Two days after lesioning, mGluR1a mRNA levels in OB increased by 45%. At this time, the expression of tyrosine hydroxylase (TH) mRNA, which is strictly dependent on olfactory nerve input, was still unchanged. In contrast, 16 days after lesioning, deafferented OB exhibited a decrease in both mGluR1a (-30%) and TH (-40%) mRNAs. GluR1 and mGluR1b mRNA levels were not affected at either time point. These results suggest that alterations in glutamatergic input to OB selectively modulate the expression of the mGluR1 splicing form possessing a longer C-terminal domain.

Animals↗
PubMed1992

Immunolocalization of B-50 (GAP-43) in the mouse olfactory bulb: predominant presence in preterminal axons.

Because the growth-associated protein B-50 (GAP-43) has been implicated in neurite outgrowth as well as in synaptic plasticity, we studied its light and electron microscopical distribution in the mouse olfactory bulb, an area of the nervous system which exhibits a high degree of synaptic plasticity. Immunofluorescent staining with monospecific affinity-purified anti-B-50 antibodies revealed that B-50 is most abundantly expressed in the olfactory nerve fibre layer and the granule cell layer neuropil, while little staining was observed in the external plexiform layer and in cell bodies. B-50 is absent from dendrites and myelinated axons as indicated by double labelling with monoclonal antibodies against microtubule-associated protein 2 and the large neurofilament protein, respectively. Using post-embedding immunogold labelling on ultrathin Lowicryl sections, B-50 was found to be highly concentrated in presumed growth cones in the olfactory nerve fibre layer and in thin unmyelinated axons and presynaptic terminals in the granule cell layer neuropil. Near background immunolabelling was seen in perikarya, dendrites and myelinated axons. In view of the implication of B-50 in plasticity-related phenomena, its abundance in the thin unmyelinated preterminal axons suggests that these are potential sites of extrasynaptic plasticity.

Animals↗
PubMed1990

Organization of projections from olfactory epithelium to olfactory bulb in the frog, Rana pipiens.

One hypothesis for the coding of olfactory quality is that regions of the olfactory epithelium are differentially sensitive to particular odor qualities and that this regional sensitivity is conveyed to the olfactory bulb in a topographic manner by the olfactory nerve. A corollary to this hypothesis is that there is a sufficiently orderly connection between the epithelium and the olfactory bulb to convey this topographical coding. Thus we examined topography in the projection from epithelium to bulb in the frog, which has been the subject of numerous electrophysiological studies but has not yet been examined using modern neuroanatomical techniques. The tracer WGA-HRP was applied to the ventral or to the dorsal olfactory epithelium, or both. Anterograde transport of label to the olfactory bulb was seen after as few as 2 days; label was still present in the bulb as long as 21 days postinjection. In cases where WGA-HRP was applied to the entire epithelium, there was dense anterograde labelling of the ipsilateral olfactory bulb. In addition, a small medial portion of the contralateral bulb was labelled. Injections limited to either the ventral or dorsal epithelium produced patterns of anterograde labelling in the glomerular layer of the olfactory bulb, which varied with the size and location of the injection. With very large injections in either the dorsal or ventral epithelium, label appeared to be evenly distributed in the glomerular layer. With smaller injections in the ventral epithelium, there was heavier labelling in the lateral than in the medial portions of the glomerular layer, although light labelling was found in all regions of the glomerular layer. In contrast, injection sites restricted to the dorsal epithelium produced more anterograde labelling in the medial than lateral portions of the glomerular layer. These patterns extended throughout the dorsal-ventral extent of the bulb. Within the limits of the anterograde tracing technique used, we were unable to detect any systematic relationship between the pattern of labelling in the glomerular layer and the medial-lateral or rostral-caudal location of the injection site in either the ventral or dorsal epithelium. We conclude that in the frog, as in other amphibia, there is only a limited degree of topographic order between the epithelium and the olfactory bulb.

Animals↗
PubMed1991

The olfactoretinalis system = terminal nerve?

Immunohistochemistry revealed a distinct terminal nerve (nT) from the olfactoretinalis system (ORS) in several gymnotid species. The ganglion (NOR) of the ORS is a cluster of FMRF-amide immunoreactive neurones located on the olfactory nerve and bulb. The NOR projects to the olfactory bulb and optic nerve but not to the olfactory epithelium. In contrast, the nT is a small substance P or GnRH immunoreactive fibre bundle which originates from a ganglion located rostral to the olfactory epithelium, courses caudally with the olfactory nerve and terminates as glomeruli in the olfactory bulb. Peripherally the ganglion projects to the epithelium of the anterior nostril. Thus, the terminal nerve appears to be a cranial nerve, clearly distinct from the ORS which consequently should no longer be considered as the terminal nerve.

Animals↗
PubMed1988

A macromolecular approach to excitation phenomena: mechanical and thermal changes in nerve during excitation.

(1) Nerve fibers and cells were shown to swell when they develop action potentials. Both in the squid giant axon and in the garfish olfactory nerve, the peak of swelling coincides with the peak of the action potential recorded from the site of mechanical recording. Substitution of univalent cations for the bivalent cations (Ca) bound to multi-anion sites in the membrane macromolecules is considered to be at the base of the phenomenon of swelling. (2) Measurements of heat production by the garfish olfactory nerve indicate that the rate of temperature rise is maximal at the peak of the action potential. Since heat production lasts for the entire depolarizing phase of the action potential, the "condenser theory" of heat production is abandoned. Again, substitution of the bound bivalent cations in the membrane macromolecules with univalent cations is regarded as the origin of nerve heat. (3) The two stable states of the nerve membrane, which are readily demonstrable in TEA-treated or internally perfused squid giant axons, are shown to represent bivalent cation-rich and univalent cation-rich states of the nerve membrane. (4) A physicochemical theory is described that explains macromolecular transitions between two stable states. The mechanism of nerve excitation is explained on a physicochemical basis. (5) The importance of the role played by water molecules in the process of nerve excitation is emphasized.

Action Potentials↗
PubMedDate not supplied

Immunocytochemical localization of calretinin in the olfactory system of the adult lamprey, Lampetra fluviatilis.

The distribution of calretinin immunoreactive (CR-ir) structures in the adult lamprey (Lampetra fluviatilis) olfactory system was studied by using immunocytochemical techniques. In the olfactory epithelium, a subpopulation of olfactory receptor cells was CR-ir. In the olfactory bulbs, three different cell populations were observed. Large CR-ir cells (mitral cells) were located medially to the olfactory glomeruli and occasionally between them. In the inner cellular layer, two types of CR-ir perikarya were found: numerous small CR-ir cells (granule cells) and some medium-sized CR-ir cells (putative displaced periglomerular cells). In addition, different intensities of CR-ir fibers were present in particular rootlets of the olfactory nerves, as well as in particular glomeruli. The presence of CR-ir cells and fibers in all layers of the lamprey olfactory bulbs supports the idea that this protein is present in pathways underlying the processing of sensory information throughout evolution.

Animals↗
PubMed1991

The ontogeny of luteinizing hormone-releasing hormone (LHRH) producing neurons in the chick embryo: possible evidence for migrating LHRH neurons from the olfactory epithelium expressing a highly polysialylated neural cell adhesion molecule.

The development of neurons expressing luteinizing hormone-releasing hormone (LHRH) has been studied immunohistochemically in the chick embryo from the 3.5 embryonic day (ED) to the day of hatching. At ED-3.5, LHRH-immunoreactive neurons were first detected in the medial epithelium of the olfactory pit, but their appearance in the brain was delayed to ED-4.5. On EDs-6-7, cords of the LHRH-immunoreactive cells extended across the nasal septum towards the ventromedial forebrain with the olfactory nerve. By double staining for LHRH and, a highly polysialylated form of neural cell adhesion molecule (NCAM-H), the LHRH-positive neurons in the olfactory-forebrain system were found strongly NCAM-H-positive. At ED-8, a marked decrease in the number of LHRH-positive cells in the olfactory epithelium and a concomitant increase in the LHRH-positive cells in the forebrain area were noted. From ED-11 to the day of hatching, the majority of LHRH-positive neurons tended to move into their usual adult position, whereas the LHRH-positive cells had almost disappeared in the olfactory epithelium. No LHRH-immunoreactive neurons were found strongly positive to NCAM-H. These results suggest that LHRH neurons originate from the olfactory placode, then as they develop they migrate across the nasal septum and enter the forebrain with the olfactory nerve. The close association of NCAM-H with the developing LHRH neurons raises the possibility that NCAM-H plays some role in guiding the migrating LHRH neurons from the olfactory epithelium to the forebrain.

Animals↗
PubMed1992

Origin of luteinizing hormone-releasing hormone (LHRH) neurons in the chick embryo: effect of the olfactory placode ablation.

A unilateral olfactory placodectomy resulted in the absence of luteinizing hormone-releasing hormone-immunoreactive (LHRH-ir) cells in the olfactory-forebrain axis of the operated side, whereas the development of the LHRH neuronal system was not disturbed on the unoperated side. In the embryos in which a fragment of the medial olfactory epithelium was spared the damage, a small number of LHRH-ir cells were detected in the nasal region of the operated side, where the lack of the central projection of the olfactory nerve caused stagnation of LHRH-ir cells, no ir-cells being found in the brain area. These results suggest that LHRH neurons originate in the olfactory placode and then migrate into the forebrain along the olfactory nerve.

Animals↗
PubMed2005

Ultrastructural study of the primary olfactory pathway in Macaca fascicularis.

Olfactory ensheathing glial cells (OEGs) interact with a wide repertoire of cell types and support extension of olfactory axons (OAs) within the olfactory pathway. OEGs are thought to exclude OAs from contact with all other cells between the olfactory epithelium and the glomerulus of the olfactory bulb. These properties have lead to testing to determine whether OEGs support axonal growth following transplantation. The cellular interactions of transplanted OEGs will probably resemble those that occur within the normal pathway where interactions between OEGs and fibroblasts are prominent. No previous primate studies have focused on these interactions, knowledge of which is important if clinical application is envisioned. We describe the detailed intercellular interactions of OAs with supporting cells throughout the olfactory epithelium, the lamina propria, the fila olfactoria, and the olfactory nerve layer by using transmission electron microscopy in adult Macaca fascicularis. Patterns of OEG ensheathment and variations of the endo- and perineurium formed by olfactory nerve fibroblasts are described. OAs mainly interacted with horizontal basal cells, OEGs, and astrocytes. At both transitional ends of the pathway seamless intercellular interactions were observed, and fibroblast processes were absent. Perineurial cells produced surface basal lamina; however, endoneurial, epineurial, and meningeal fibroblasts did not. Perineurial cells contained intermediate filaments and were distinct from other fibroblasts and meningeal cells. OAs had direct contacts with astrocytes near the glia limitans. The properties of OEGs differed depending on whether astrocytic or fibroblastic processes were present. This indicates the importance of the cellular milieu in the structure and function of OEGs in primates.

Animals↗
PubMed1976

The polypeptide and the phospholipid components of axon plasma membranes.

The axon plasma membrane fraction isolated from garfish olfactory nerve was analyzed for its polypeptide composition by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. There were present over 20 well-resolved polypeptide components in this membrane, and eleven of them, with an apparent molecular weight range of 22,000-130,000, accounted for most of the membrane proteins. None of the major polypeptide species present in the membrane appeared to be glycoprotein. Based on electrophoretic mobility on sodium dodecyl sulfate-polyacrylamide gel, eight of the major polypeptides found in garfish nerve membrane appeared to be also present in the axon plasma membrane isolated from lobster walking leg nerve. Both garfish and lobster nerve membranes contained high concentration of lipids (66-76%) which were essentially cholesterol and phospholipids. The classes of phospholipids present were phosphatidylethanolamine, phosphatidylcholine, phosphatidylserine, phosphatidylinositol and sphingomyelin. Lobster nerve membrane also contained about 3% phosphatidic acid. Assays for acetylcholinesterase in axon plasma membrane fractions isolated from different nerve sources showed a wide variation, ranging from a specific activity of 2.4 for garfish nerve to 312.5 for lobster nerve membrane.

Acetylcholinesterase↗
PubMed1996

The role of olfaction in oil preference in the chicken.

The role of olfaction on the preference of diets containing 20% medium-chain (MCT) or long-chain triacylglycerol (LCT) was investigated in the chicken. Olfactory bulbectomized, sham-operated (Sham) or intact (Intact) birds were offered a choice between LCT or MCT diet and food intake was measured over a short time period. Intact and Sham groups showed a significant preference for LCT over MCT diet, but olfactory-bulbectomized chickens lost the preference for LCT over MCT. The bilateral cutting of the olfactory nerves confirmed the results taken in olfactory bulbectomy. It is concluded that olfaction plays a major role in the preference of diets containing MCT or LCT in chickens.

Animals↗
PubMedDate not supplied

Selective infections of olfactory and respiratory epithelium by vesicular stomatitis and Sendai viruses.

Following intranasal instillation of vesicular stomatitis virus (VSV) in mice there was an extensive infection of the olfactory epithelium in contrast to a minimal involvement of the respiratory epithelium. Sendai virus (SV), on the other hand, caused an extensive infection of the respiratory epithelium and only minimal infection of the olfactory mucous membrane. VSV budded from basolateral surfaces of supporting cells and olfactory neurons, but not from their apical surfaces or the ciliated bulbous endings of the olfactory neuron dendrites. This asymmetric release of VSV favoured neuroinvasion. The virus spread along the olfactory nerves to the glomeruli in the olfactory bulbs after which it propagated transneuronally into the rest of the brain. SV budded only from the apical surface of respiratory epithelial cells, was released into the air passages, and there were no signs of invasion into the olfactory bulbs. Inoculation of the olfactory mucous membrane is a useful procedure for studies on selectivity of attack on peripheral neurons by viruses and on mechanisms of virus invasion of the nervous system in vivo.

Animals↗
PubMed1968

Homing orientation by olfaction in newts (Taricha rivularis).

Newts displaced after perfusion of the olfactory epithelium with formaldehyde failed to orient toward home, whereas control animals subjected to oral perfusion with formaldehyde oriented as readily as did untreated controls. Newts with surgically extirpated olfactory nerves failed to home unless their nerves had regenerated. These results strongly suggest a critical role for olfaction in homing behavior.

Animals↗
PubMed1996

Role of olfaction in the formation of preference for high-fat foods in mice.

Male albino mice were given access to both high- and low-fat food mixtures in the home cage for 4 days. Mice were then divided into three groups and given a choice test in which all groups demonstrated a significant preference for the high-fat food mixture. One group was then bilaterally olfactory nerve sectioned. Seven days following surgery, all groups were given a second choice test. Olfactory nerve-sectioned mice (while anosmic) showed no preference, whereas high-fat food preference in the two control groups strengthened. However, high-fat food preference returned to recovered nerve-sectioned mice by 21 days postsurgery. It appears that preference for many high-fat foods in mice requires olfaction. This is in good agreement with earlier work that reported the loss of the novel food effect in olfactory nerve-sectioned mice while anosmic, and points to an important role for olfaction in the formation of preference for many high-fat foods.

Animals↗
PubMed2002

Role for mucosal immune responses and cell-mediated immune functions in protection from airborne challenge with Venezuelan equine encephalitis virus.

Venezuelan equine encephalitis virus (VEEV) replicates in lymphoid tissues following peripheral inoculation and a high titre viraemia develops. Encephalitis develops after the virus enters the central nervous system from the blood, with the earliest neuronal involvement being via the olfactory nerve. Following aerosol challenge with virulent VEEV, the virus is thought to replicate in the nasal mucosa and there could be direct entry into the olfactory nerve via infected neuroepithelial cells. Protection from VEEV infection is believed to be primarily mediated by virus specific antibody. The correlation between protection and neutralising serum antibody titres is, however, inconsistent when the virulent virus is administered by the airborne route. This study demonstrates a link between antibody in serum and the nasal mucosa and protection by means of passive immunisation studies. Intra-nasal administration of antibody increased protection against airborne virus in Balb/c mice. Vaccination of mu MT strain mice that do not have functional B cells and cannot produce antibody revealed normal proliferation of spleen cells in vitro and robust cytokine production. Aerosol challenge of mu MT mice demonstrated that complete protection was only achieved when passive immunisation with antibody was supplemented with active immunisation with the TC-83 vaccine strain of the virus. This implies that cell-mediated immune functions are required for protection against airborne challenge with virulent VEEV.

Administration, Intranasal↗
PubMed1990

Participation of the olfactory system in the control of approach behavior of the female rat to the male.

The amounts of time spent by females in the sector of an open field close to the cage housing a normal male or a castrated male were measured in order to quantitate the tendency of the female to reach physical proximity to a sexually active male (androtropism). Intact proestrous or ovariectomized females primed with 100 micrograms of estradiol benzoate/kg b. wt. (EB) or EB plus 2 mg progesterone/kg b. wt. (P) spent significantly more time close to the sexually active (intact) male than in the proximity of the orchidectomized male. In order to determine whether olfactory clues were sufficient for female rats to distinguish between intact and castrated males, the males were removed from the stimulus cages, leaving the soiled bedding in place. Ovariectomized rats primed with EB or EB plus P clearly preferred proximity to the cage where the intact male had been living. No preference was evident after transection of olfactory nerves in proestrous rats or in ovariectomized rats primed with EB plus P. Resection of the vomeronasal organ also suppressed preference. These results indicate that olfactory input is necessary and sufficient for androtropism to occur, and suggest that the accessory olfactory system is involved in the analysis of olfactory signals used by female rats to identify the endocrine status of prospective sexual partners. In a different group of animals, it was demonstrated that destruction of the posteromedial cortical amygdaloid nucleus also suppressed preference for the intact male. It is proposed that this structure serves as a relay station for the analysis and integration of olfactory input significant for the motivational control of sexual behavior in the female rat.(ABSTRACT TRUNCATED AT 250 WORDS)

Amygdala↗