扬子鳄鼻腔上皮光学显微镜及扫描电镜观察

本文通过光镜和扫描电镜研究了爬行动物扬子鳄鼻腔上皮的组织学。结果表明:其嗅觉上皮的组成细胞类型与两栖类、鸟类和哺乳类基本相似,但嗅细胞纤毛形状则有所不同;扬子鳄与两栖类、鸟类嗅纤毛相似,呈丝状,而哺乳类嗅觉纤毛则呈棍棒状;据外,扬子鳄鼻腔不同部位可发现不同类型嗅纤毛,鸟兽则无此现象,扬子鳄嗅觉上皮的分布仅局限于鼻腔中部前甲区和鼻甲区狭小范围,而兽类嗅觉上皮一般分布较广;扬子鳄呼吸上皮下未见兽类具有的混合型粘液腺,也未见兽类用以温暖空气的静脉丛,这和扬子鳄属外温动物而兽类为恒温动物密切相关。     

Distribution of epithelia and glands of the nasal septum mucosa in the rat.

A histotopographic study of the nasal septum mucosa in rats was made using semi-serial sections stained with PAS-hematoxylin, reconstructed in form of maps representing the structure in a sagittal plane. The stratified squamous, respiratory and olfactory epithelia and Masera's organ cover 14.8, 43.6, 41.6 and 1.8%, respectively, of the septal surface (117.1 mm2). In the vestibular region, only ducts of PAS-negative glands of the respiratory region are found, and below the septum there is the infraseptal gland with PAS-negative acini. In the respiratory region, PAS-negative acinous glands form two groups: the superior and the inferior one occupying 10.5 and 1.5%, respectively, of the septal area. PAS-positive acinous glands are in the inferior half of the respiratory region and in a small anteroinferior portion of the olfactory region. Besides goblet cells broadly distributed, the respiratory epithelium presents scattered intraepithelial PAS-positive glands which are concentrated in the anterior portion and close to the nasopharyngeal duct. In the olfactory region prevail Bowman's PAS-positive glands which are also present in the mucosa of Masera's organ, but are not seen in the olfactory mucosa of Jacobson's organ. In the latter, PAS-positive glands are found in the respiratory mucosa. Globular leukocytes, cells of connective tissue origin, are constantly infiltrating the superior regions of the respiratory and olfactory epithelia, being more numerous in female rats.     

Localization of CYP4B1 in the rat nasal cavity and analysis of CYPs as secreted proteins

CYP4B1 is highly expressed in rat nasal respiratory mucosa, and to a lesser extent in olfactory mucosa. Examination of high-power photomicrographs suggests that CYP4B1 may be a secreted protein, based on the fact that immunoreactivity appears to be present in the lumens of ducts of Bowman's glands (rather than intracellular localization, as we observed with an antibody recognizing CYP2F4) and in secretory granules in respiratory mucosa. Furthermore, anti-CYP4B1 immunoreactivity is present on the surface of both respiratory and olfactory mucosa. We used SignalP 3.0 analysis to ascertain the likelihood that rat CYP4B1 is a secreted protein. While this analysis does not suggest that rat CYP4B1 is a secreted protein, several other cytochrome P450 enzymes were predicted to be secreted proteins. The observation that multiple human cytochrome P450s appear to be secreted proteins helps to explain the appearance of anti-cytochrome P450 antigens in cases of human autoimmune liver diseases.     

Biochemical quantitation and histochemical localization of glucose-6-phosphate dehydrogenase activity in the olfactory system of adult and aged rats

The activity of glucose-6-phosphate dehydrogenase, the rate-limiting enzyme of the hexose monophosphate shunt, was examined in olfactory epithelium, respiratory epithelium, olfactory bulb, and occipital cortex in Fisher 344 rats aged 4 and 24 months. Marked differences in this enzyme were found in olfactory compared to nonolfactory tissues. Olfactory epithelium and olfactory bulb have much greater glucose-6-phosphate dehydrogenase activity than respiratory epithelium and occipital cortex at both ages. Glucose-6-phosphate dehydrogenase remains fairly constant between adulthood and senescence in respiratory epithelium and occipital cortex. However, glucose-6-phosphate dehydrogenase activity decreases during the same time in both of the olfactory tissues examined. Previous studies of changes in this enzyme with aging have shown increases in enzyme activity in some brain regions, but never the decreases that we describe in olfactory tissues. Glucose-6-phosphate dehydrogenase histochemistry revealed intense staining of both the apical layer of olfactory epithelium and of Bowman's glands along with their ducts. Histochemistry of the olfactory bulb showed strongest staining in the nerve and glomerular layers of the bulb. The functional implications of these findings are discussed.     

Distribution of cytochrome P-450 monoxygenase enzymes in the nasal mucosa of hamster and rat

Deposition of inhaled particulates onto the respiratory mucosa is relatively great in that portion of the nasal cavity unprotected by ciliated, goblet, or keratinized superficial cells. The cytochrome P-450 system is an important enzyme system involved in the biotransformation of xenobiotics into metabolites that are more readily absorbed. To examine the transitional region caudal to the nasal vestibule, nasal tissues of hamster and rat were prepared for immunocytochemistry. Blocks of tissue representing four levels along the long axis of the nasal cavity were examined. Paraffin sections were processed through the avidin-biotin peroxidase procedure, with diaminobenzidine tetrahydrochloride as the chromagen. Enzyme localization was accomplished through the use of antibodies for three rabbit cytochrome P-450 isozymes; 2, 5, and 6 (subfamilies IIB, IVB, and IA, respectively); and for rabbit NADPH-cytochrome P-450 reductase. Enzyme distribution was similar in both hamster and rat nasal tissues except in cells of striated and intercalated ducts of nasal glands and in cells of the nasolacrimal duct where immunoreactivity was greater in the hamster. Immunoreactivity for reductase and isozyme 2 was intense in nonciliated cells lining the nonolfactory epithelium, in sustentacular cells of the olfactory epithelium, and in acinar cells of olfactory glands. Distribution of reaction products to isozyme 5 and 6 were similar to but not so intense as those of reductase and isozyme 2. Reaction products for reductase and isozyme 2 occurred generally in the same cellular and intracellular regions with the following exceptions: isozyme 2 was more concentrated in cells of striated ducts and of the nasolacrimal duct, and reductase was more abundant in intercalated ducts of nasal glands.(ABSTRACT TRUNCATED AT 250 WORDS)     

Qualitative and quantitative freeze-fracture studies on olfactory and nasal respiratory structures of frog,ox, rat,and dog

Summary A comparative study using freeze-fracturing has been made of surface structures of olfactory and nasal respiratory epithelia of frog, ox, rat and dog. Special attention has been paid to cilia and microvilli present at these surfaces, although the observations include various other structures such as small intracellular vacuoles present in the olfactory receptor endings and infrequent brush cells. Within the mucus overlying the olfactory epithelium membranous vesicles, often attached to olfactory cilia, are seen. Some of these show intramembranous particle distributions similar to those of the rest of the cilia, whereas others are devoid of particles. Smooth vesicles are also found in the mucus of other types of epithelium (respiratory epithelium and Bowman's glands). The freeze-fracture morphology of intracellular secretory vacuoles present in olfactory supporting, Bowman's and respiratory glandular cells of the frog is similar in all these epithelia. Quantitative comparisons are made of the different structures of interest. When corrected for cilia which were not observed, mammalian receptor endings bear 17 cilia on average, whereas frog receptor endings have 6 cilia. The relative magnitudes of the diameters of the cilia and microvilli are, except for frog, the same for all species studied. Dimensions of other structures e.g., axons, dendrites and dendritic endings are compared in the various species. Freeze-fracture diameters are usually larger than those seen by techniques using dehydration. Dendritic ending densities range from 4.5 × 10⁶ (frog) to 8.3 × 10⁶ (dog) endings per cm². Possible sex-dependent differences are only found for these densities and dendritic ending diameters.     

Expression and distribution of facilitative glucose (GLUTs) and monocarboxylate/H+ (MCTs) transporters in rat olfactory epithelia

Cell-to-cell metabolic interactions are crucial for the functioning of the nervous system and depend on the differential expression of glucose transporters (GLUTs) and monocarboxylate transporters (MCTs). The olfactory receptor neurons (ORNs) and supporting cells (SCs) of the olfactory epithelium exhibit a marked polarization and a tight morphological interrelationship, suggesting an active metabolic interaction. We examined the expression and localization of MCTs and GLUTs in the olfactory mucosa and found a stereotyped pattern of expression. ORNs exhibited GLUT1 labeling in soma, dendrites, and axon. SCs displayed GLUT1 labeling throughout their cell length, whereas MCT1 and GLUT3 localize to their apical portion, possibly including the microvilli. Additionally, GLUT1 and MCT1 were detected in endothelial cells and GLUT1, GLUT3, and MCT2 in the cells of the Bowman's gland. Our observations suggest an energetic coupling between SCs and Bowman's gland cells, where glucose crossing the blood-mucosa barrier through GLUT1 is incorporated by these epithelial cells. Once in the SCs, glucose can be metabolized to lactate, which could be transported by MCTs into the Bowman's gland duct, where it can be used as metabolic fuel. Furthermore, SCs may export glucose and lactate to the mucous layer, where they may serve as possible energy supply to the cilia.     

The distribution of dopamine-like immunoreactivity in the thoracic and abdominal ganglia of the locust (Schistocerca gregaria)

Summary An indirect gold-labeling method utilizing the lectin from Limax flavus was employed to characterize the subcellular distribution of sialic acid in glycoconjugages of the salamander olfactory mucosa. The highest density of lectin binding sites was in secretory vesicles of sustentacular cells. Significantly lower densities of lectin binding sites were found in secretory granules of acinar cells of both Bowman's and respiratory glands. Lectin binding in acinar cells of Bowman's glands was confined primarily to electron-lucent regions and membranes of secretory granules. In the olfactory mucus, the density of lectin binding sites was greater in the region of mucus closest to the nasal cavity than in that closest to the epithelial surface. At the epithelial surface, the density of lectin binding sites associated with olfactory cilia was 2.4-fold greater than that associated with microvilli of sustentacular cells or non-ciliary plasma membranes of olfactory receptor neurons, and 7.9-fold greater than non-microvillar sustentacular cell plasma membranes. Lectin binding sites were primarily associated with the glycocalyx of olfactory receptor cilia. The cilia on cells in the respiratory epithelium contained few lectin binding sites. Thus, sialylated glycoconjugates secreted by sustentacular cells are preferentially localized in the glycocalyx of the cilia of olfactory receptor neurons.     

Larval development and metamorphosis of the olfactory and vomeronasal organs in the toad Rhinella (Bufo) arenarum (Hensel, 1867)

Jungblut, L.D., Pozzi, A.G. and Paz, D.A. 2010. Larval development and metamorphosis of the olfactory and vomeronasal organs in the toad Rhinella (Bufo) arenarum (Hensel, 1867). — Acta Zoologica (Stockholm) 92 : 305–315. The olfactory and the vomeronasal system are the two major chemosensory systems found in terrestrial vertebrates. Among tetrapods, amphibians are unique in having an aquatic larval stage, followed by metamorphosis to a terrestrial adult. In the present work, we studied the histological development of the olfactory and vomeronasal organ and associated multicellular glands of the toad Rhinella (Bufo) arenarum, from early poshatching larva to postmetamorphic toadlets. As in other bufonids, the olfactory epithelium of R. arenarum in larvae is divided into dorsal and ventral branches in the rostral and mid‐nasal regions. At metamorphic climax, the larval pattern changes drastically and the adult olfactory configuration develops. Bowman’s glands appear in the olfactory epithelium of R. arenarum at the onset of metamorphic climax. The vomeronasal epithelium develops early in larval development in R. arenarum, around the time of operculum development. Interestingly, a novel sensory epithelium develops in the floor of the principal chamber of R. arenarum at metamorphic climax. This novel sensory epithelium resembles larval sensory epithelium lacking Bowman’s glands, and suggests that these animals would be able to sense not only air‐borne, but also water‐borne odors during their adult terrestrial life.     

Morphology of the nasal fossae and associated structures of the hamster (Mesocricetus auratus)

The hamster nasal cavity consists of vestibular, non-olfactory and olfactory portions. Much of the non-olfactory nasal cavity surface is lined by cuboidal, stratified cuboidal, and low columnar epithelia, devoid of cilia. Goblet cells and ciliated respiratory epithelium are present over only a small portion of the nasal cavity surface. The largest glandular masses in the hamster nose are the maxillary recess glands, the vomeronasal glands and the lateral nasal gland 1; these three glands contain neutral mucopolysaccharides (PAS-positive). Other nasal glands contain both acidic and neutral mucopolysaccharides; the staining reaction for acidic mucopolysaccharide is stronger in goblet cells and olfactory glands than in the other nasal glands. The ducts which open into the nasal vestibule are the excretory ducts of compound tubuloacinar serous glands. The one major PAS-positive gland whose duct opens into the nasal vestibule is the lateral nasal gland 1. The ducts of the compound tubuloacinar vomeronasal glands open into the lumen of the vomeronasal organ, which is connected to the ventral nasal meatus by means of the vomeronasal duct. The ducts of the branched tubuloacinar maxillary recess glands open into the maxillary recess. Few ducts open into the caudal half of the nasal cavity.     

Development of the Olfactory Epithelium and Nasal Glands in TMEM16A-/- and TMEM16A+/+ Mice

TMEM16A/ANO1 is a calcium-activated chloride channel expressed in several types of epithelia and involved in various physiological processes, including proliferation and development. During mouse embryonic development, the expression of TMEM16A in the olfactory epithelium is dynamic. TMEM16A is expressed at the apical surface of the entire olfactory epithelium at embryonic day E12.5 while from E16.5 its expression is restricted to a region near the transition zone with the respiratory epithelium. To investigate whether TMEM16A plays a role in the development of the mouse olfactory epithelium, we obtained the first immunohistochemistry study comparing the morphological properties of the olfactory epithelium and nasal glands in TMEM16A^-/- and TMEM16A^+/+ littermate mice. A comparison between the expression of the olfactory marker protein and adenylyl cyclase III shows that genetic ablation of TMEM16A did not seem to affect the maturation of olfactory sensory neurons and their ciliary layer. As TMEM16A is expressed at the apical part of supporting cells and in their microvilli, we used ezrin and cytokeratin 8 as markers of microvilli and cell body of supporting cells, respectively, and found that morphology and development of supporting cells were similar in TMEM16A^-/- and TMEM16A^+/+ littermate mice. The average number of supporting cells, olfactory sensory neurons, horizontal and globose basal cells were not significantly different in the two types of mice. Moreover, we also observed that the morphology of Bowman’s glands, nasal septal glands and lateral nasal glands did not change in the absence of TMEM16A. Our results indicate that the development of mouse olfactory epithelium and nasal glands does not seem to be affected by the genetic ablation of TMEM16A.     

Differential expression of Alpha,Mu, and Pi classes of glutathione S-transferases in chemosensory mucosae of rats during development

The expression of three classes of glutathione S-transferases (GSTs), Alpha, Mu, and Pi was investigated in the nasal mucosae of rats during development using immunohistochemical methods. GST Alpha and Mu were first detected in the supranuclear region of sustentacular cells on embryonic days 16. The Bowman's glands expressed differential patterns of immunoreactivity during development, beginning at postnatal day (P) 2 and P6 for Alpha and Mu classes, respectively and being greatest at P11 for both. The acinar cells of vomeronasal glands in the vomeronasal organ expressed Alpha and Mu classes of GSTs from P11 onwards. In the septal organ of Masera, the supranuclear region of sustentacular cells expressed GSTs from P11 with little or no variation during development. In the respiratory mucosa, Alpha and Mu classes of GSTs were detected at the brush borders of ciliated cells and in the acinar cells of posterior septal glands, but not in anterior septal or respiratory glands located on the turbinates. Compared to olfactory mucosa, the changes in immunoreactivity for GSTs were less pronounced in the respiratory mucosa during development. Specific GST Pi immunoreactivity was not detected in the nasal mucosae at any stage of development studied. The occurrence of GSTs in the nasal mucosa, including olfactory, vomeronasal, septal, and respiratory epithelia, suggests that the GSTs are actively involved in the biotransformation of xenobiotics including odorants and pheromones, and may also participate in perireceptor processes such as odorant clearance. In addition, we have developed a working model describing the cellular localization of certain phase I (e.g., cytochrome P-450s) and phase II (e.g., GSTs, -glutamyl transpeptidase) biotransformation enzymes in the olfactory mucosa and their proposed roles in xenobiotic metabolism.     

Expression patterns of anoctamin 1 and anoctamin 2 chloride channels in the mammalian nose

Calcium-activated chloride channels are expressed in chemosensory neurons of the nose and contribute to secretory processes and sensory signal transduction. These channels are thought to be members of the family of anoctamins (alternative name: TMEM16 proteins), which are opened by micromolar concentrations of intracellular Ca²⁺. Two family members, ANO 1 (TMEM16A) and ANO 2 (TMEM16B), are expressed in the various sensory and respiratory tissues of the nose. We have examined the tissue specificity and sub-cellular localization of these channels in the nasal respiratory epithelium and in the five chemosensory organs of the nose: the main olfactory epithelium, the septal organ of Masera, the vomeronasal organ, the Grueneberg ganglion and the trigeminal system. We have found that the two channels show mutually exclusive expression patterns. ANO 1 is present in the apical membranes of various secretory epithelia in which it is co-localized with the water channel aquaporin 5. It has also been detected in acinar cells and duct cells of subepithelial glands and in the supporting cells of sensory epithelia. In contrast, ANO 2 expression is restricted to chemosensory neurons in which it has been detected in microvillar and ciliary surface structures. The different expression patterns of ANO 1 and ANO 2 have been observed in the olfactory, vomeronasal and respiratory epithelia. No expression has been detected in the Grueneberg ganglion or trigeminal sensory fibers. On the basis of this differential expression, we derive the main functional features of ANO 1 and ANO 2 chloride channels in the nose and suggest their significance for nasal physiology.     

Aquaporin pathways and mucin secretion of Bowman's glands might protect the olfactory mucosa

The sense of smell is conveyed by the olfactory sensory neurons of the olfactory mucosa. Uniquely for sensory systems, the olfactory neurons directly face the external environment and are thus vulnerable to infections and changes in the airway surface liquid, but the surface liquid production and maintenance is not well understood. Here we show in rats and mice that Bowman's glands secrete the mucin MUC5AC. Aquaporin-5 was present at the apical face of the olfactory epithelium, completing a water transport pathway to the surface of the epithelium. Immunogold electron microscopy analysis revealed an intricate network of fine Aquaporin-1-positive fibroblast processes that surround Bowman's glands, whereas deeper blood vessels were unlabeled for Aquaporin-1. Our results show how the olfactory mucosa might be protected against infections and dehydration generally and how neuronal function is protected against ion concentration changes in the airway surface liquid by rapid replacement of water losses through the aquaporin pathways.     

Antioxidant status of the rat nasal cavity

Despite extensive interest in the rodent nasal cavity as a target organ for toxicity, there is very limited information regarding nasal defenses against oxidative stress and xenobiotic-derived oxidants. Using immunohistochemistry, we have examined the distribution of Cu,Zn and Mn superoxide dismutase (SOD), catalase, glutathione (GSH) peroxidase, and DT-diaphorase in rat nasal tissues. In addition, we have determined the concentrations of ascorbate and alpha-tocopherol and the activities of SOD (combined Cu,Zn and Mn forms), catalase, GSH peroxidase, GSH reductase, and DT-diaphorase in nasal respiratory epithelium (RE), olfactory epithelium (OE), and in lung. Immunohistochemistry demonstrated that all four enzymes were similarly distributed, with the greatest staining intensity in dorsal-medial regions of the nasal cavity. In respiratory epithelium, ciliated columnar cells and subepithelial glands stained positively, while in olfactory tissue the enzymes were detected in the sustentacular cells and Bowman's glands. With the exception of SOD, enzyme activities were higher in RE than OE, while concentrations of ascorbate and alpha-tocopherol were higher in OE than RE. With the exception of catalase, nasal activities were either higher than or comparable to those of the lung. Thus, the rat nasal cavity appears to be well protected against oxidative damage.     

Metabolism-dependent activation and toxicity of chemicals in nasal glands

The mucosae of the nasal passages contain a large amount of glands which express secretory proteins as well as phase I and phase II biotransformation enzymes. In this review the metabolic activation, covalent binding and toxicity of chemicals in the Bowman's glands in the olfactory mucosa, in the sero-mucous glands in the nasal septum and in the lateral nasal glands and maxillary glands around the maxillary sinuses are discussed. Light microscopic autoradiographic studies have demonstrated a selective covalent binding of nasal toxicants and carcinogens such as halogenated hydrocarbons and N-nitrosamines, especially in the Bowman's glands following a single systemic exposure, suggesting a high rate of metabolic activation of chemicals in these glands. Special attention is put on the herbicide dichlobenil which induces necrosis in the olfactory mucosa following a cytochrome-P450-mediated metabolic activation and covalent binding in the Bowman's glands.     

Peptidergic regulation of secretory activity in amphibian olfactory mucosa: Immunohistochemistry,neural stimulation,and pharmacology

Summary The role of substance P in the regulation of secretion from sustentacular cells, Bowman's glands and deep glands in the amphibian olfactory mucosa was investigated using immunohistochemical, electrophysiological, and pharmacological methods. Substance P-like immunoreactive varicose fibers extended through the olfactory epithelium, terminating at or near the surface. In addition, immunoreactive varicose fibers innervated Bowman's glands, deep glands, and blood vessels in the lamina propria. Innervation of Bowman's gland was sparse, with fibers terminating on basal acinar cell membranes; deep gland innervation was abundant, with fibers often extending between acinar cells almost to the lumen. Stimulation of the ophthalmic branch of the trigeminal nerve resulted in slow potentials recorded at the surface of the olfactory epithelium. When the olfactory mucosae from trigeminal-stimulated animals were examined histologically, morphological signs of secretory activity were observed, suggesting that substance P was released from the trigeminal nerve terminals. Topical application of 10^-5 to 10^-3 mol substance P resulted in morphological signs of secretion that were very similar to those seen as a result of trigeminal stimulation. Thus, substance P released from trigeminal fibers may modulate secretory activity within the olfactory mucosa.     

Inflammatory obstruction of the olfactory clefts and olfactory loss in humans: a new syndrome?

The first step in the olfactory perception is the activation by odorants of sensory neurones in the olfactory epithelium. In humans, this sensory epithelium is located at 2 narrow passages, the olfactory clefts, at the upper part of the nasal cavities. Little is known about the physiology of these clefts. We examined, in 34 patients, the impact of obstructed clefts upon detection and postlearning identification of 5 odorants. The location and extension of the obstructions were assessed using endoscopy, CT scans, and MRI. The inflammatory obstruction was usually bilateral, extending anteroposteriorly, and confined to the clefts, with no sign of obstruction or any inflammatory disease in the rest of the nasal cavities and sinuses. When tested with 5 odorants, these patients showed greatly impaired olfaction compared with a group of 73 normosmic subjects. The majority of these 34 patients had sensory deficits equivalent to that found in another group of 41 congenital anosmic patients, where inspection with MRI indicated the lack of olfactory bulbs. This study demonstrates that the olfactory clefts, in human, function as an entity that is different from other regions of the nasal cavity and is the target for local inflammatory events that are apparently not responding to corticoid and antibiotic treatments.