Modulation of EphA receptor function by coexpressed ephrinA ligands on retinal ganglion cell axons.
(9/1321)
The Eph family is thought to exert its function through the complementary expression of receptors and ligands. Here, we show that EphA receptors colocalize on retinal ganglion cell (RGC) axons with EphA ligands, which are expressed in a high-nasal-to-low-temporal pattern. In the stripe assay, only temporal axons are normally sensitive for repellent axon guidance cues of the caudal tectum. However, overexpression of ephrinA ligands on temporal axons abolishes this sensitivity, whereas treatment with PI-PLC both removes ephrinA ligands from retinal axons and induces a striped outgrowth of formerly insensitive nasal axons. In vivo, retinal overexpression of ephrinA2 leads to topographic targeting errors of temporal axons. These data suggest that differential ligand expression on retinal axons is a major determinant of topographic targeting in the retinotectal projection. (+info)
MR appearance of rhinoscleroma.
(10/1321)
BACKGROUND AND PURPOSE: We describe the MR imaging appearance of rhinoscleroma, an endemic, chronic, granulomatous disease whose causative agent is Klebsiella rhinoscleromatis. METHODS: The study included 15 patients (nine males and six females; mean age, 25 years; range, 13-36 years) with rhinoscleroma. MR imaging was performed in all patients. The signal intensity of the nasal masses was compared with that of fat, muscle, and CSF on both T1- and T2-weighted images. All cases were proved by histopathologic examination. RESULTS: The nasal masses were bilateral and symmetrical (n = 6), asymmetrical (n = 4), or unilateral (n = 5). They extended through the anterior nares (n = 9) or posterior choana into the nasopharynx (n = 3). They obstructed the ostiomeatal units with retained secretions in the related sinuses (n = 10). On T1-weighted images, rhinoscleroma showed striking (n = 9) or mild (n = 6) high signal intensity relative to muscle and CSF, but less hyperintensity than fat. On T2-weighted images, the nasal masses showed homogeneous high signal intensity (n = 10) or heterogeneous high signal intensity associated with hypointense foci (n = 5). They were hyperintense relative to fat and muscle, but less hyperintense than CSF. CONCLUSION: The hypertrophic stage of rhinoscleroma has characteristic mild to marked high signal intensity on both T1- and T2-weighted MR images. (+info)
Sensory perception is related to the rate of change of volatile concentration in-nose during eating of model gels.
(11/1321)
The relationship between perceived aroma and the volatile concentration measured in-nose was investigated during eating of a model food. Sensory ranking and time-intensity analysis (TI) were used to measure perceived aroma, while in-nose volatile concentration was monitored by atmospheric pressure ionization mass spectrometry, which produced time release data. A gelatine-sucrose gel with a range of gelatine concentrations (2-8% w/w) and flavoured with furfuryl acetate was used as the model food. Sensory scaling showed decreased flavour intensities and TI showed a decrease in the flavour perceived over time, as the gelatine concentration increased. Studies in model systems and in people demonstrated that the different rates of release observed for different gelatine concentrations were not due to binding of volatile to protein in the gel, nor to mucous membranes, but were due to different rates of gel breakdown in-mouth. There were no significant differences in the maximum in-nose volatile concentrations for the different gelatine concentrations, so the amount of volatile present did not correlate well with the sensory analysis. However, the rates of volatile release were different for the different gels and showed a good correlation with sensory data. (+info)
Driver distance from the steering wheel: perception and objective measurement.
(12/1321)
OBJECTIVES: This study assessed the accuracy of driver perceptions of the distance between the driver's nose and the steering wheel of the vehicle as a factor in considering driver disconnection of an airbag contained in the steering wheel for preventing injury to the driver in an accident. METHODS: A cross-sectional survey of 1000 drivers was done to obtain perceived and objective measurements of the distance between the driver's nose and the steering wheel of the vehicle. RESULTS: Of 234 drivers who believed that they sat within 12 inches of the steering wheel, only 8 (3%) actually did so, whereas of 658 drivers who did not believe that they sat within 12 inches of the wheel, 14 (2%) did so. Shorter drivers were more likely than taller ones to both underestimate and overestimate their seating distance. CONCLUSIONS: Considerable misperception of drivers' distance from the wheel indicates that drivers should objectively measure this distance. (+info)
The olfactory origin of luteinizing hormone-releasing hormone (LHRH) neurons. A new era in reproduction physiology.
(13/1321)
This paper reviews those studies which conceived the concept that the brain LHRH-synthesizing neurons originate in the nasal placode. LHRH isolated from mammalian hypothalamus in 1971 was first shown immunohistochemically two years later in the hypothalamic neurons which project processes to the median eminence, to release it into the portal capillaries in the guinea pig. At an early stage of development, the LHRH cells were found in the nasal placode but not in the hypothalamus as shown in in vivo and in vitro developmental studies. The cells arising in the brain were delayed. This discrepancy was solved in 1989-1990 by findings that the cells derived in the placode at an early stage left the site and migrated to the forebrain vesicles along the placode-derived terminal and vomeronasal nerve fibers, both of which were found to express immunoreactive cell adhesion molecules. The neurons, after reaching the surface of the forebrain vesicles, entered into the brain by the guidance of the cell adhesion molecule-positive fibers, and came to be distributed not only in the hypothalamus but also in the telencephalon cortex, midbrain, limbic brain, and main and accessory olfactory bulbs. The attention to these heterogeneties led to discussion of the possible neurobiological significance of this peculiar peripheral neurogenesis from an evolutionary viewpoint. (+info)
A technique to measure the ability of the human nose to warm and humidify air.
(14/1321)
To assess the ability of the nose to warm and humidify inhaled air, we developed a nasopharyngeal probe and measured the temperature and humidity of air exiting the nasal cavity. We delivered cold, dry air (19-1 degrees C, <10% relative humidity) or hot, humid air (37 degrees C, >90% relative humidity) to the nose via a nasal mask at flow rates of 5, 10, and 20 l/min. We used a water gradient across the nose (water content in nasopharynx minus water content of delivered air) to assess nasal function. We studied the characteristics of nasal air conditioning in 22 asymptomatic, seasonally allergic subjects (out of their allergy season) and 11 nonallergic normal subjects. Inhalation of hot, humid air at increasingly higher flow rates had little effect on both the relative humidity and the temperature of air in the nasopharynx. In both groups, increasing the flow of cold, dry air lowered both the temperature and the water content of the inspired air measured in the nasopharynx, although the relative humidity remained at 100%. Water gradient values obtained during cold dry air challenges on separate days showed reproducibility in both allergic and nonallergic subjects. After exposure to cold, dry air, the water gradient was significantly lower in allergic than in nonallergic subjects (1,430 +/- 45 vs. 1,718 +/- 141 mg; P = 0.02), suggesting an impairment in their ability to warm and humidify inhaled air. (+info)
The effect of inhibition of aldehyde dehydrogenase on nasal uptake of inspired acetaldehyde.
(15/1321)
At exposure concentrations of 750 ppm or more, acetaldehyde is a rodent inhalation carcinogen that induces nasal tumors. Aldehyde dehydrogenase (ALDH) is thought to be an important detoxifying enzyme for aldehydes. Although nasal tissues express ALDH, the importance of this enzyme relative to delivered dosage rates at high-inspired concentrations is not well defined. To provide such information, uptake of inspired acetaldehyde was measured at an inspiratory flow rate that approximated the minute ventilation rate in the surgically isolated nasal cavity of F 344 rats pretreated with either saline (control) or the ALDH inhibitor, cyanamide (10 mg/kg s.c.). ALDH activities (substrate concentration 3 times the K(m)) in anterior (respiratory mucosa) and posterior (olfactory mucosa) nasal tissues averaged 160 and 210 nmol/min), respectively, in control animals (total activity 370 nmol/min), compared to 60 and 80 nmol/min, respectively, in cyanamide-pretreated rats (p < 0.05), indicating that approximately 60% inhibition was obtained. Nasal uptake was measured at 3 inspired concentrations: 10, 300, and 1500 ppm. At these concentrations, acetaldehyde uptake efficiency averaged 54, 37, and 34% in saline-pretreated rats, respectively (p < 0.05). In absolute terms, the delivered dosage rates at these exposure concentrations averaged 21, 420, and 1990 nmol/min. The concentration dependence on uptake suggests a saturable process was involved. At inspired concentrations of 300 ppm or more, the delivered dosage rates exceeded the measured specific activity for nasal ALDH of 370 nmol/min. Cyanamide pretreatment abolished the concentration dependence. Specifically, uptake efficiencies in cyanamide-pretreated rats averaged 30, 27, and 31% at inspired concentrations of 10, 300, and 1500 ppm, respectively (p > 0.05); delivered dosage rates were 12, 310, and 1780 nmol/min. Thus, cyanamide pretreatment reduced nasal-delivered dosage rates at inspired concentrations of 10, 300, and 1500 ppm, respectively by 9, 110, and 210 nmol/min, values that correspond well with the total nasal ALDH activity of 370 nmol/min. In toto, these results suggest that inspired acetaldehyde is metabolized in situ by ALDH, but at exposure concentrations of 300 ppm or greater, the delivered dosage rate may equal or exceed the capacity of this enzyme. (+info)
Johanson-Blizzard syndrome: a prenatal ultrasonographic diagnosis.
(16/1321)
Johanson-Blizzard syndrome is a rare autosomal recessive disorder characterized by aplasia of alae nasi, pancreatic insufficiency, aplasia cutis, anorectal anomalies and postnatal growth restriction. In this case report, we describe the prenatal sonographic findings of Johanson-Blizzard syndrome in a 21-week pregnancy of a consanguineous couple. Sonographic findings of aplastic alae nasi (beak-like nose) and dilated sigmoid colon led to the prenatal diagnosis. This is the first report of the prenatal sonographic diagnosis of Johanson-Blizzard syndrome. (+info)