Pseudo-cerebrospinal fluid rhinorrhea after skull base surgery

A 41-year-old female underwent complete resection of a left petroclival meningioma via an anterior transpetrosal approach, during which the greater superficial petrosal nerve was divided. On the 14th day after the operation, she first noticed leakage of clear fluid from her right nostril whenever the ambient room temperature rose. This pseudo-cerebrospinal fluid rhinorrhea may have developed because of parasympathetic hypersensitivity due to division of the greater superficial petrosal nerve.

Spatiotemporal appearance of developing LHRH neurons in the rat brain

To obtain insight into the development of the heterogeneous intracerebral populations of luteinizing hormone-releasing hormone (LHRH) neurons, their spatiotemporal appearance was examined at different stages in normal rat embryos, in nasal epithelial explants in vitro, and in intrauterine nasal-operated embryos. Following the appearance of nerve cell adhesion molecule in the nasal placode at embryonic day (E) 12.5, LHRH neurons, generated in the nasal placode at E13.5, penetrated the forebrain vesicle (FV) by E14.5-15.5. After E16.5, as the FV elongated to form the olfactory bulb, the migrating neurons traversed posteriorly through the interhemispheric space to penetrate the septopreoptic (S-P) area. By E18.5, LHRH neurons were detected in the preoptic-diagonal band (P-D) area as well as in the S-P region, along with some scattered extrahypothalamic LHRH neurons. To determine the source of these neurons, we separately cultured dissected parts of E12.5 nasal pit epithelium. Neuronal generation was predominantly from the medial wall epithelium (NAP), but some LHRH neurons originated in the roof epithelium. Cocultures of the NAP (E12.5) with the FV, median eminence-arcuate complex, Rathke's pouch, mesencephalon, or medulla oblongata from E14.5 embryos revealed the ability of LHRH cells to penetrate all of these tissues. Uni- or bilateral nasal destruction was conducted at E16.5 or E15.5, respectively, and examined at E18.5 and E21.5. In the operated embryos, most LHRH neurons were present in the P-D system and some in the S-P area. This finding suggests that the neurons generated before E15.5 are primarily predisposed to form the P-D system, whereas those derived afterward form the S-P system.

Identification of carbonic anhydrase activity in bullfrog olfactory receptor neurons: histochemical localization and role in CO2 chemoreception

The objectives of this study were to determine: (1) the frequency and distribution of carbonic anhydrase (CA) activity in the bullfrog nasal cavities, and (2) whether inhibition of nasal CA affects the olfactory receptor response to CO2 or other odorants. It was found, using Hansson's staining technique, that some olfactory receptor neurons exhibited CA activity and that these CA-positive receptors were distributed throughout the nasal cavity with peak densities in the dorsal and ventral sensory epithelial regions. To test for the role of CA in olfactory transduction, electro-olfacto-grams (EOGs) were recorded from the surface of the ventral sensory epithelium in response to 2-s pulses of 5% CO2 and amyl acetate before and after topical CA inhibition with acetazolamide (10(-3) mol.l-1). In 52 bullfrogs, 1222 sites on the ventral epithelium were tested resulting in 23 locations that exhibited a response to 5% CO2. Inhibition of CA caused an immediate 65% reduction in the EOG response to CO2 while the response to amyl acetate was not affected. These results, along with the histochemical localization of CA in some olfactory receptor neurons, indicate that CA plays a role in the detection of CO2 in frog olfactory neurons and that only a small population of olfactory receptor neurons are CO2 sensitive.

Luteinizing hormone-releasing hormone and innervation pathways in human prenatal nasal submucosa: factors of importance in evaluating Kallmann's syndrome

A previous study has demonstrated that luteinizing hormone-releasing hormone (LHRH) is localized in the human bilateral vomeronasal organs in the nasal septum during a 4-week period of intrauterine life (22). The purpose of the present study was to elucidate the location of LHRH-expressing cells outside the vomeronasal organs, with special emphasis on the submucosa of the medial wall and roof of the nasal cavity. An additional aim was to study the innervation pathways in the same regions. Both regions can be affected in Kallmann's syndrome, which is characterized by hypogonadotropic hypogonadism (lack of LHRH) and often associated with anosmia. Histological sections of craniofacial regions (49 normal human fetuses, 6-19 weeks) were examined by immunohistochemical techniques for LHRH and for neuronal tissue (protein gene product 9.5, PGP 9.5). LHRH reactions were only seen in the septal submucosa extending from the vomeronasal organs to the olfactory bulb. There was a close spatiotemporal association between the occurrence of LHRH and neuronal tissue. From the rhino-olfactory epithelium separate nerve tissue extended to the olfactory bulb. It is suggested that the medial region of the nasal placode giving rise to the septal wall is always affected in Kallmann's syndrome, and in cases in which the phenotypic features are associated with anosmia, also the more lateral part of the nasal placode, from which the rhino-olfactory region originates, is affected.

Pheromone transduction in the vomeronasal organ

Single-cell physiology and cloning efforts have extended studies of the vomeronasal organ to cellular and molecular levels. Recent work has shown that transduction in the vomeronasal organ is probably mediated by signalling pathways distinct from those that mediate transduction in the main olfactory system. An advance in understanding transduction has come with the cloning from rat vomeronasal organ of a family of putative pheromone receptor genes that bear no sequence similarity to previously cloned receptors. Other work has examined the expression of putative signalling components and found a zonal organization of the epithelium. Patch-clamp studies have described the basic electrical properties of vomeronasal neurons and explored second-messenger pathways.

A transgenic mouse model to study transsynaptic regulation of tyrosine hydroxylase gene expression

Previous studies demonstrated that 9 kb of the rat tyrosine hydroxylase (TH) 5' flanking sequence directed appropriate spatiotemporal expression of a lacZ reporter gene to catecholaminergic cells in the CNS of transgenic mice. In the present study, specificity of transgene expression was further extended to demonstrate cell type-specific functional regulation of lacZ expression using manipulations known to alter endogenous TH expression. Alterations in lacZ reporter expression should parallel changes in endogenous TH levels if the DNA elements mediating these functional changes of TH expression in vivo reside within the 9 kb of the TH promoter region. Naris closure induced an activity-dependent decrease of TH expression in dopaminergic periglomerular cells in the olfactory bulb that was paralleled by down-regulation of lacZ expression in the transgenic mice. Densitometry and image analysis were used to quantify lacZ expression following acute reserpine administration (5 mg/kg s.c.), which up-regulates endogenous TH. At 48 h postinjection, analysis of OD values indicated a significant increase of X-gal staining in the locus coeruleus and ventral tegmental area but not in the substantia nigra or olfactory bulb of reserpine-treated transgenic animals. These data showed that the 9-kb sequence also mediates cell type-specific transsynaptic regulation of reporter gene expression. Analysis of this transgenic animal offers a useful model system to study in vivo regulation of TH gene expression.

Aqueous tear production in patients with neurotrophic keratitis

The purpose of this study was to determine whether corneal epithelial defects and epitheliopathy in patients with unilateral dysfunction of the ophthalmic division of the trigeminal nerve (neurotrophic keratitis) is associated with reduced aqueous tear production. Sensation of the skin, cornea, and nasal mucosa, aqueous tear production by Schirmer 1 testing, nasal-lacrimal reflex, and exposure zone rose bengal staining were evaluated in the affected and fellow eyes of subjects with neurotrophic keratitis (n = 5), eyes of subjects who had recent herpes zoster ophthalmicus (HZO) and who did not develop neurotrophic keratitis (n = 4), and normal controls (n = 10). Sensation in the brow and upper lid skin and nasal mucosa was absent on the affected side of patients with neurotrophic keratitis, but was intact in all other groups. Corneal sensation and Schirmer 1 test values were significantly reduced (p < or = 0.05) in eyes with neurotrophic keratitis compared with the other groups. The nasal-lacrimal reflex was absent on the involved side of subjects with neurotrophic keratitis but was intact in subjects with HZO without keratopathy, and in normal controls (p < 0.008). Rose bengal keratitis staining scores were significantly increased in eyes with neurotrophic keratitis compared with the other groups (p < 0.05). We conclude that neurotrophic keratitis is associated with reduced cutaneous, nasal mucosal, and corneal sensation on the affected side, as well as marked reduction in aqueous tear production with loss of the nasal-lacrimal reflex. It is possible that the corneal epithelial pathology in neurotrophic keratitis is due in part to aqueous tear deficiency.

Nasal receptors responding to cold and l-menthol airflow in the guinea pig

The aim of this study was to demonstrate the presence of nasal 'cold' receptors, through recordings of action potentials from the ethmoidal nerve (EN), in guinea pigs and to characterize their responsiveness to l-menthol and capsaicin. Constant flows (400 ml/min) of room air (20 degrees C), warm air (45 degrees C), room air containing l-menthol, and cold air (-5 degrees C) were directed into the nasal cavity in the inspiratory direction via a nasopharyngeal catheter in the anesthetized guinea pigs breathing spontaneously through a tracheostomy. The ethmoidal afferent activity was increased by cold air, and to a greater extent by l-menthol but hardly by warm air. After topical anesthesia of the nasal cavity with 2% lidocaine, cold air and l-menthol no longer stimulated the EN. L-menthol noticeably stimulated the EN even after repeated capsaicin instillation into the nose, but these values were lower than those following the l-menthol stimulus before the 1st capsaicin treatment. These results suggest that the ethmoidal nerve in guinea pigs has cold-sensitive receptors which consist of both small myelinated fibers and C-fiber endings.

Two classes of olfactory receptors in Xenopus laevis

Xenopus laevis possess a gene repertoire encoding two distinct classes of olfactory receptors: one class related to receptors of fish and one class similar to receptors of mammals. Sequence comparison indicates that the fish-like receptors represent closely related members of only two subfamilies, whereas mammalian-like receptors are more distantly related, most of them representing a different subfamily. The fish-like receptor genes are exclusively expressed in the lateral diverticulum of the frog's nose, specialized for detecting water-soluble odorants, whereas mammalian-like receptors are expressed in sensory neurons of the main diverticulum, responsible for the reception of volatile odors.

The migration of luteinizing hormone-releasing hormone neurons in the developing rat is associated with a transient, caudal projection of the vomeronasal nerve

Luteinizing hormone-releasing hormone (LHRH) neurons originate in the olfactory placode and vomeronasal organ and migrate to the brain from embryonic day 14 (E14) in the rat. We investigated the development of the vomeronasal nerve and its role as a guide for migrating LHRH neurons. Using fluorescent, lipophilic dye tracing methods, we observed axons that emerge from the vomeronasal organ and cross the nasal septum as several large fascicles. At E14-15, these fascicles converge as they enter the region of the cribriform plate and subsequently disperse, projecting dorsally and caudally across the olfactory bulb and rostral forebrain. At E16, the dorsal branch of the vomeronasal nerve forms a more tightly fasciculated projection; the caudal fibers remain dispersed, extending along the medial forebrain. The number of caudally directed axons decreases during development, leaving four or five present at postnatal day 4 (P4). Immunohistochemical studies indicate that the vomeronasal nerve can be divided into four spatially distinct subpopulations of fibers. One subset, composed of caudal fibers that terminate in the lamina terminalis, selectively expresses TAG-1, a transient axonal surface glycoprotein and PSA-N-CAM, a highly polysialated form of neural cell adhesion molecule. The extension and subsequent retraction of this branch of the vomeronasal nerve corresponds spatially and temporally with the migration of LHRH neurons from the nasal cavity to the brain. Our studies show that between E14 and E18, LHRH neurons migrate in contact with the TAG-1+, PSA-N-CAM+ caudal branch of the vomeronasal nerve.

Coculture of the vomeronasal organ and olfactory bulb of the fetal rat

The vomeronasal organ and the olfactory bulb of the rat were cocultured from 15-day embryo siblings on collagen-coated membrane in Dulbecco's modified Eagle's medium containing fetal calf serum, horse serum, and antibiotics. At 4 days in vitro (DIV), vomeronasal axons forming two to three large fascicles were seen originating from the explants of the vomeronasal organ. Differential axonal growth was observed. Some fascicles made connections with the explants of the olfactory bulb. Twenty percent of the cocultures studied here showed the formation of connections. At 6-10 DIV many fascicles that did not connect with the olfactory bulb had degenerated, and large fascicles that were connected with the olfactory bulb survived for more than 10 DIV. The formation of connections between the vomeronasal organ and the olfactory bulb in coculture favors the survival of large nerve fascicles, but it could not be determined whether or not the presence of the olfactory bulb affects the initial orientation of the fibers and fascicles from the explants of the vomeronasal organ.

Neural drive to nasal dilator muscles: influence of exercise intensity and oronasal flow partitioning

Our aim was to test the following hypotheses: 1) neural drive to the muscles of the alae nasi (AN) is proportional to nasal airflow and is independent of the overall level of central respiratory drive, and 2) the switch from nasal to oronasal breathing corresponds to the onset of marked flow turbulence in the nasal airway. Total and nasal inspired ventilation rates (VI) and the electromyogram (EMG) of the AN muscles were measured in seven subjects during progressive-intensity bicycling exercise. In separate experiments in six subjects the nasal VI corresponding to the transition from laminar to turbulent airflow was determined by measuring the pressure-flow relationship of the nasal airway with anterior rhinomanometry. Nasal VI accounted for 70 +/- 11% of total VI at rest and 27 +/- 8% (SE) at 90% of the maximal attainable power (max). Nasal VI and integrated AN EMG activities increased linearly with exercise intensity up to 60% of the max power, but both variables plateaued at this level even though total VI (and central respiratory drive) began to increase exponentially as exercise intensity increased to 90% max. The onset of the exponential rise in total VI was associated with a sharp increase in oral VI and with the onset of marked flow turbulence in the nasal airway. The results suggest that during incremental exercise 1) changes in AN EMG activities are highly correlated with changes in nasal VI, 2) turbulent flow in the nose may be the stimulus for the switch to oronasal breathing so that total pulmonary resistance is minimized, and 3) the correlation between nasal airflow and neural drive to the AN muscles is probably mediated by mechanisms that monitor airway resistance. Although these mechanisms were not identified, the most likely possibilities are receptors in the upper and/or lower airways that are sensitive to negative transmural pressure, or to effort sensations leading to greater corollary motor discharge to nasal dilator muscle motoneurons.

An intact glutamatergic trigeminal pathway is essential for the cardiac response to simulated diving

Nasal water flow plus concomitant expiratory apnea in anesthetized (Innovar-Vet), paralyzed, and artificially ventilated rats produces immediate bradycardia. To investigate the origin of this response, four procedures were used to block the trigeminal pathway. 1) Trigeminal receptors within the nasal passages were anesthetized by infusing local anesthetic through the external nares. 2) Trigeminal nerves that innervate the nasal passages were sectioned bilaterally as they passed through the orbit. 3) The trigeminal neural pathway was blocked within the brain stem by either electrolytically lesioning or infusing local anesthetic into the spinal trigeminal nucleus interpolaris (Sp5I). 4) Synaptic transmission within Sp5I was prevented by infusing glutamate receptor antagonists D-2-amino-7-phosphonoheptanoic acid and 6,7-dinitroquinoxaline-2,3-dione. After each of the procedures was completed, the cardiovascular responses to nasal water flow plus apnea were either attenuated or eliminated. The major conclusion of this study is that an intact glutamatergic trigeminal pathway is required for manifestation of the cardiovascular responses to nasal stimulation. Evidence also suggests that N-methyl-D-aspartate (NMDA) and non-NMDA glutamate receptors are both required for synaptic neurotransmission within Sp5I.

Regional differences of CGRP-immunoreactive nerve fibers in nasal epithelium of the rat

The regional distribution of calcitonin gene-related peptide (CGRP)-immunoreactive nerve fibers in the epithelium throughout the nasal cavity was determined using semiserial cryostat sections and whole mount preparations. Both respiratory and olfactory epithelia displayed, in their basal portion, an extensive nerve plexus projecting beaded nerve fibers toward the luminal surface. However, the density of the intraepithelial CGRP nerve fibers conspicuously varied according to regions. They were abundant on the septal mucosa, the ventromedial side of the nasoturbinates and the dorsal surface of the maxilloturbinates, while less numerous on the lateral side of the naso- and maxilloturbinates and on the lateral nasal wall. Another difference in the regional distribution of nerves was recognized between the anterior and posterior portions of the respiratory area: the anterior portion received a denser supply of intraepithelial CGRP fibers than the posterior portion. Characteristically, the transepithelial CGRP-immunoreactive nerve fibers were densest on the anteroventral aspect of the nasoturbinates and on the anterodorsal surface of the maxilloturbinates. Some of them appeared to penetrate through the epithelium to come into contact with the lumen of the nasal cavity. These results suggest that the CGRP fibers in the epithelium display a region-specific distribution, apparently disposed more densely over the areas which are more directly exposed to inhaled air, possibly that containing irritants and toxicants.

Differential expression of two cell surface proteins, neuropilin and plexin, in Xenopus olfactory axon subclasses

Immunohistochemistry by using monoclonal antibodies named A5 and B2, which specifically recognize cell surface proteins the neuropilin and the plexin, respectively, revealed that olfactory axons in Xenopus tadpoles were classified into several subgroups by virtue of the expression levels of these two cell surface molecules. The vomeronasal axons expressed the plexin but not the neuropilin. The plexin-positive and neuropilin-negative vomeronasal axons form a discrete fiber bundle, even after they joined with the principal olfactory axons. However, the principal olfactory axons were divided into at least two subclasses; the neuropilin-predominant axons which expressed high levels of the neuropilin and low levels of the plexin, and the plexin-predominant axons which expressed high levels of the plexin and low levels of the neuropilin. Within the olfactory nerve the pathways for these two principal olfactory axon subclasses were initially intermingled with each other, but were gradually segregated throughout their courses from the nose to the cerebrum. Eventually, the neuropilin-predominant and the plexin-predominant principal olfactory axon subclasses projected to specified glomeruli in topographically related regions within the main olfactory bulb. Neuroanatomical tracings of the olfactory projection also confirmed the gradual segregation of the pathways for the principal olfactory axons. These results allow us to speculate that both the neuropilin and the plexin are involved in axon interactions, and play roles in the organization of the precise patterns of the olfactory pathway and projection.

The distribution of nasal airflow sensitivity in normal subjects

Nasal airflow modifies the pattern of ventilation presumably due in part to nervous signals arising in the nose and transmitted along the trigeminal nerve to the respiratory centre. Nasal receptor tissue must also be important in determining the sensation of airflow at a conscious level but little attention has been paid to the distribution and function of these receptors. An experimental model to deliver a pulse of air at different velocities to various nasal test sites is described. In this way nasal sensitivity to an air jet can be mapped out. Sensitivity of the nose to an air jet is greatest at the entrance to the nose--the region of the nasal vestibule.

c-fos expression in vomeronasal pathways of mated or pheromone-stimulated male golden hamsters: contributions from vomeronasal sensory input and expression related to mating performance

The vomeronasal system projects to the accessory olfactory bulb (AOB), to the medial (Me) and posterior medial cortical nuclei (PMCN) of the amygdala, to the bed nucleus of the stria terminalis (BNST), and to other central structures shown to be important in mating behavior, including the medial preoptic area (MPOA). In these experiments c-fos expression was used as a marker of neural activity to identify the contribution of vomeronasal sensory input during mating behavior in male golden hamsters, either intact or with vomeronasal organs removed (VNX). Inexperienced hamsters were either stimulated with a receptive female and allowed to mate, exposed to female hamster vaginal fluid (HVF), which contains stimuli known to act through the VN system, or placed in a clean cage alone. Densely stained Fos-positive nuclei were evident in mated animals in the central VN pathway [AOB, Me, posterior medial BNST (pmBNST)] and a VN target area (MPOA). HVF-exposed animals showed Fos expression in the AOB, Me, and BNST but not MPOA. Unstimulated animals showed almost no activation. Most VNX animals exposed to females did not mate, but performed intense chemoinvestigation. They had few Fos-positive nuclei in any of these areas except the caudal pmBNST. A few VNX animals that did mate had patterns of Fos activation that were similar but less intense than those of intact mating animals, suggesting a selective activation of VN central pathways during mating regardless of VN sensory input. The main olfactory system showed low levels of Fos expression in all animals (stimulated and unstimulated). Fos expression in the MPOA and rostral pmBNST was seen only in mated animals, suggesting that these regions are concerned with mating performance or its consequences, rather than the chemosensory input that triggers it. Fos expression in the caudal encapsulated pmBNST was evident in all groups of animals that performed chemosensory investigation, regardless of VN status or mating, suggesting that this region either directs or responds to chemosensory investigation.

Nasal receptors responding to noxious chemical irritants

This study was performed to investigate the chemoreception of trigeminal afferents in the nose. Single unit activity was recorded from the anterior ethmoidal nerve in the anesthetized guinea pig breathing through a tracheostomy during nasal instillation of capsaicin (0.3 mM), nicotine (6 mM) and ammonia (1.5 M) solutions or with distilled water. Out of 36 fibers recorded, nineteen were stimulated by capsaicin, six by nicotine and seventeen by ammonia. Among those fibers, two were stimulated by both capsaicin and nicotine, six by both capsaicin and ammonia and one nicotine-responsive fiber was also stimulated by ammonia. A large proportion of capsaicin- and nicotine-responsive fibers exhibited long lasting discharges (170.4 +/- 17.7 sec and 120.7 +/- 29.3 sec, respectively), and were not stimulated by the second application of the same substance. However, fibers responding to ammonia discharged for a shorter time (31.5 +/- 6.5 sec), indicating a rapid adaptation. These results indicate that the ethmoidal nerve possesses a well-developed responsiveness to noxious stimuli. The nociceptive component of this nerve may be related to the various cardiorespiratory responses that can be elicited from the nasal cavity and also to local axonal reflexes (neurogenic inflammation) due to the release of chemical mediators from C-fiber endings.

Biocytin: a neuronal tracer compatible with rapid decalcification procedures

The compatibility of neuronal tract-tracing and decalcification procedures was examined in salamander nasal chemosensory systems. Biocytin, but not horseradish peroxidase, retained its labeling capacity following rapid decalcification of the cranial bone. The combination of biocytin tract-tracing and decalcification procedures allows the visualization of labeled neurons and/or their projections within bony regions of intact specimens.

A unique achiasmatic anomaly detected in non-albinos with misrouted retinal-fugal projections

In mammals with binocular vision, projections of retinal axons to primary retino-recipient nuclei establish a strict visuotopic and eye-segregated arrangement. Normal primate visual pathway organization is characterized by orderly hemiretina separation in which nasal-retinal axons cross at the optic chiasm and project to primary contralateral subcortical and cortical structures while temporal-retinal fibres project ipsilaterally to corresponding visual structures. We report here, in two unrelated children, an unusual visual pathway malformation in which nasal-retinal cortical projections, unable to decussate due to the inborn absence of an optic chiasm, erroneously route ipsilaterally to visual projection targets. We have termed this newly documented achiasmatic condition the non-decussating retinal-fugal fibre syndrome (Apkarian et al., Invest. Ophthalmol. Vis. Sci., 34, Suppl., 711, 1993).

Histochemical and immunocytochemical study of the migration of neurons from the rat olfactory placode

Immunocytochemical and histochemical methods have been used to describe the neuronal population migrating from the rat olfactory placode and to analyze the spatio-temporal evolution of this neuronal migration during development. Several neuronal markers, such as binding to the lectin Ulex europaeus (UEA I) and the presence of neuron-specific enolase (NSE), olfactory marker protein (OMP), and luteinizing hormone-releasing hormone (LHRH), have been tested in order to determine whether migrating neurons originate from both the medial and the lateral parts of the placode and whether they all express LHRH. Our data show that a large population of differentiated migrating neurons can be identified with an antibody against NSE from the 14th day of gestation and with UEA I one day later. Migrating neurons are closely associated with both the vomeronasal axon fascicles emerging from the medial pit and the olfactory axons originating from the lateral pit. However, the neuron migration from the lateral pit appears to be more discrete than that from the medial pit. No LHRH immunoreactivity has been detected among neurons migrating from the lateral pit. Some neurons accompanying the olfactory axon fascicles exhibit a high level of maturation as shown by their OMP-positivity. Numerous neurons positive for both NSE and UEA I have also been observed within the presumptive olfactory nerve layer in early embryonic stages.

The spatial organization of the peripheral olfactory system of the hamster. Part II: Receptor surfaces and odorant passageways within the nasal cavity

The spatial organization of olfactory receptor surfaces and odorant passageways within the nasal cavity was studied in hamsters through descriptive and morphometric analyses of a complete stereotaxically defined series of coronal, sagittal, and horizontal sections through the snout. These analyses reveal that the caudal two-thirds of each cavity is divided into two longitudinally oriented medial and lateral channels. The olfactory mucosa that lines these two channels projects selectively onto the medial and lateral halves of the main olfactory bulb (MOB), respectively. Moreover, the ethmoturbinates of the caudal recesses create highly convoluted channels, lined by ventrally projecting mucosa, that lie ventral, lateral, and dorsal to a relatively smooth central channel lined by dorsally projecting mucosa. The rhinotopic map makes equivalent representations of medial and lateral olfactory space to the MOB but gives the smooth space lined by dorsally projecting mucosa a disproportionately larger representation on the MOB than the convoluted space lined by the more expansive ventrally projecting mucosa. Recent descriptions of the spatial distribution of probes for odorant receptor proteins conform closely to this organization, giving credence to the idea that rhinotopy is a basis for representing to the MOB the specific molecular features of odorant molecules.

Use of the incisive canal as a recipient site for root form implants: preliminary clinical reports

A technique is described for utilization of the augmented incisive canal as a recipient site for a root form implant. A mixture of four parts of demineralized freeze-dried bone and one part of tricalcium phosphate is used as the augmentation material. Preliminary case reports are presented that describe the placement of an implant adjacent to an augmented canal and in the incisive canal in conjunction with implants placed in newly formed bone following a sinus lift procedure. Long-term clinical evaluation of this new procedure is necessary to justify its use.

Asymmetric reflex responses of the nasal and tracheal vasculatures of the dog

Both sides of the nasal vasculature of the dog in vivo were perfused separately, with measurement of vascular resistance responses to stimulation of various nerves. Stimulation of the central end of a cut superior laryngeal nerve caused an ipsilateral vasodilation (-4.98%) and a contralateral vasoconstriction (+3.96%), the difference being statistically significant (P < 0.01). Stimulation of a glossopharyngeal nerve caused vasodilation on both sides, the ipsilateral (-17.52%) being greater than the contralateral (-6.33%) response (P < 0.05). Mechanical stimulation of the nasal mucosa caused little ipsilateral change (+0.47%) and a weak contralateral vasoconstriction (+3.78%; P < 0.01). Stimulation of the central end of a cervical vagus nerve caused vasodilations on both sides, the ipsilateral (-9.75%) being greater than the contralateral (-5.73%) change (P < 0.05). With bilateral perfusions of the cervical tracheal arteries, stimulation of a superior laryngeal nerve caused vasodilation on both sides, the ipsilateral (-10.1%) being greater than the contralateral (-7.4%) response (P < 0.05). Stimulation of the central end of a vagus nerve caused vasoconstrictions on both the sides, the ipsilateral (+37.4%) being greater than the contralateral (+10.8%) change (P < 0.05). Thus various nervous inputs from the nose, pharynx, larynx, and vagal distribution cause asymmetric vascular responses both in the nose and in the cervical trachea.

Experimental evidence for an early commitment of gonadotropin-releasing hormone neurons, with special regard to their origin from the ectoderm of nasal cavity presumptive territory

The origin and the migration of gonadotropin-releasing hormone (GnRH)-producing neurons were studied using the indirect immunoperoxidase method in normal and surgically operated chick embryos. In normal embryos, during early embryonic development, GnRH neurons were located only in the respiratory and the olfactory epithelia. Then, these neurons followed the nearest nerve bundle and occupied, thereafter, the dorsal, medial or ventral part of the olfactory nerve according to the time and area of the olfactory epithelium they emerged from. At the junction with the forebrain, the majority of GnRH neurons passed ventromedially round the olfactory bulb. Therefore, they penetrated through the interhemispheric space and coursed obliquely toward caudal and dorsal telencephalon from where they will be later distributed to reach their adult-like position. In view of the large distribution of these neurons in the nasal region, unilateral surgical ablation either of the whole or of each presumptive territory of nasal structures was performed from 2 to 4 somite stages. As expected, when both olfactory placode and ectoderm of nasal cavity presumptive territories were unilaterally removed, olfactory nerve, nasal structures and GnRH neurons failed to develop in the operated side. After the unilateral removal of the olfactory placode anlage, the distribution pattern of GnRH neurons was not disturbed in the operated as well as in the control side although ipsilateral olfactory structures were greatly reduced. In contrast, when the presumptive ectoderm of nasal cavity was unilaterally removed, GnRH neurons were detected only in the control side where this territory was left intact. Therefore, from early neurogenesis, GnRH neurons seem to be already committed, and they originate from the ectoderm of nasal cavity presumptive territory.