Macro- and micromorphological remodeling of olfactory organs throughout the ontogeny of the fire salamander Salamandra salamandra (Linnaeus, 1758)

This article studies the morphological remodeling of olfactory organs in the fire salamander (Salamandridae, Caudata), from the larval stages of ontogeny to the adult and throughout the course of the annual cycle. The fire salamander exhibits adaptations to the aquatic environment during premetamorphic life and terrestrial adaptations after metamorphosis. During adulthood, the annual activity of this species is divided into three seasonal periods: a breeding period, a nonbreeding period, and hibernation. We observed significant differences in morphology of olfactory organs between developmental stages as well as between each period within the annual cycle. For the first time in caudates, we examined the morphology of olfactory organs during the winter period (wintering larvae, hibernating adults). The results show that the remodeling of olfactory organs during the life of the fire salamander occurs both on macro- and micromorphological levels. Macromorphological ontogenetic variability includes the shape of the main olfactory chamber (MOC) and the distribution of olfactory epithelium (OE) in the MOC and in the vomeronasal organ (VNO). In larvae, the vomeronasal epithelium (VNE) is in a separate cavity, while in the post-metamorphic stages of ontogeny, the VNE occurs in the diverticulum of the MOC. In adult fire salamanders, both olfactory organs are most developed during the breeding season and reduced during hibernation. The VNE and OE in the MOC are also reduced during hibernation. Micro-morphological changes included different types/subtypes of olfactory receptor neurons (ORNs) in the OE in particular stages of ontogeny and periods within the annual cycle, for example, ciliate ORNs are present in the VNE only in the larval stages and giant ORNs occur only in nonbreeding adults. Also, there was a variable set of types of olfactory supporting cells in the VNO of the fire salamander during pre- and postmetamorphic life stages.     

Olfactory epithelia differentially express neuronal markers

All three olfactory epithelia, the olfactory epithelium proper (OE), the septal organ of Masera (SO), and the vomeronasal organ of Jacobson (VNO) originate from the olfactory placode. Here, their diverse neurochemical phenotypes were analyzed using the immunohistochemical expression pattern of different neuronal markers. The olfactory bulb (OB) served as neuronal control. Neuronal Nuclei Marker (NeuN) is neither expressed in sensory neurons in any of the three olfactory epithelia, nor in relay neurons (mitral/tufted cells) of the OB. However, OB interneurons (periglomerular/granule cells) labeled, as did supranuclear structures of VNO supporting cells and VNO glands. Protein Gene Product 9.5 (PGP9.5 = C-terminal ubiquitin hydrolase L1 = UCHL1) expression is exactly the opposite: all olfactory sensory neurons express PGP9.5 as do OB mitral/tufted cells but not interneurons. Neuron Specific Enolase (NSE) expression is highest in the most apically located OE and SO sensory neurons and patchy in VNO. In contrast, the cytoplasm of the most basally located neurons of OE and SO immunoreacted for Growth Associated Protein 43 (GAP-43/B50). In VNO neurons GAP-43 labeling is also nuclear. In the cytoplasm, Olfactory Marker Protein (OMP) is most intensely expressed in SO, followed by OE and least in VNO neurons; further, OMP is also expressed in the nucleus of basally located VNO neurons. OB mitral/tufted cells express OMP at low levels. Neurons closer to respiratory epithelium often expressed a higher level of neuronal markers, suggesting a role of those markers for neuronal protection against take-over. Within the VNO the neurons show clear apical–basal expression diversity, as they do for factors of the signal transduction cascade. Overall, expression patterns of the investigated neuronal markers suggest that OE and SO are more similar to each other than to VNO.     

Olfactory marker protein during ontogeny: Immunohistochemical localization

Specific immunohistochemical staining for the olfactory marker protein (OMP) is first demonstrated in rat olfactory receptor neurons at embryonic day 18, at which age no OMP can be seen in the olfactory bulb or vomeronasal epithelium. At 21 days OMP staining in the olfactory epithelium is more extensive and is evident in the fibrous and glomerular layers of the bulb as well. Staining intensity increases progressively until the full adult pattern is seen by 1 month postnatally. In the vomeronasal organ, staining is not observed until the fourth postnatal day and, even then, only with higher antiserum concentrations. In mice, very similar results are obtained, except for a much earlier appearance of OMP, on embryonic day 14. Olfactory epithelium from 12- and 13-day rat embryos maintained in organ culture for up to 2 weeks did not exhibit OMP staining, nor did several neural or nonneural tissues from adult animals. The temporal and causal interrelationships between OMP and other indicators of olfactory receptor cell maturation are considered.     

Identification of an olfactory receptor neuron subclass: cellular and molecular analysis during development

Development of olfactory receptor neuron populations was studied using the previously described monoclonal antibody (Mab) 2B8 which binds to cell surface glycoproteins of presumptive olfactory receptor neurons. In order to definitively demonstrate that the cells recognized were olfactory receptor neurons and to better characterize these cells during development, a well-established receptor cell marker, olfactory marker protein (OMP), was studied at the same time as the 2B8 antigens in double-label immunofluorescence analyses of olfactory structures in rats from Day 13 of gestation (E13) to the early postnatal period. Olfactory epithelium cryostat sections of E13 rats showed binding of the 2B8 Mab to bipolar cells in caudal regions of the nasal cavity. The 2B8 Mab also recognized a large number of cells in the vomeronasal organ (VNO) at this stage. No specific binding of anti-OMP was seen until E15. At this time approximately half of the 2B8 reactive cells also expressed OMP. By birth, greater than 90% of the 2B8 reactive cells expressed OMP. The percentage of total fluorescent labeled cells which are double labeled remained relatively constant at 23-33% as the total number of cells increased between E15 and 2 days postnatal. 2B8 immunoreactivity can be found in the olfactory nerve layer of the olfactory bulb and the presumptive accessory olfactory bulb at E15. In double-label experiments the 2B8 Mab did not bind to all anti-OMP-labeled glomeruli of postnatal to adult rats. In summary, the 2B8 Mab recognizes cells early during development and appears to recognize a subclass of olfactory receptor cells and their axon terminals. Developmental changes in the electrophoretic profile of the olfactory 2B8 antigens were also studied. In the olfactory epithelium a single band at Mr of 200,000 was seen at E19. After birth three bands at 220,000, 180,000 and 110,000 were observed but in adults only two bands of Mr 215,000 and 163,000 were detected. During olfactory bulb development the Mr of the two major 2B8 reactive bands did not change but remained the same as the two major bands seen in the adult olfactory epithelium. The olfactory bulb band at Mr of 215,000 showed a 3 to 4-fold increase and the band at 163,000 showed a 10-fold increase in specific activity from birth to adulthood.     

Neurogenesis in the vomeronasal epithelium of adult garter snakes: 3. Use of H3-thymidine autoradiography to trace the genesis and migration of bipolar neurons

Use of H3-thymidine autoradiography and unilateral vomeronasal (VN) axotomy has permitted us to demonstrate directly the existence of VN stem cells in the adult garter snake and to trace continuous bipolar neuron development and migration in the normal VN and deafferentated VN epithelium in the same animal. The vomeronasal epithelium and olfactory epithelium of adult garter snakes are both capable of incorporating H3-thymidine. In the sensory epithelium of the vomeronasal organ, H3-thymidine-labeled cells were initially restricted to the base of the undifferentiated cell layer in animals surviving 1 day following H3-thymidine injection. With increasing survival time, labeled cells progressively migrated vertically within the receptor cell column toward the apex of the bipolar neuron layer. In both the normal and denervated VN epithelium, labeled cells were observed through the 56 days of postoperative survival. In the normal epithelium, labeled cells were always located within the matrix of the intact receptor cell columns. However, labeled cells of the denervated epithelium were always located at the apical front of the newly formed cell mass following depletion of the original neuronal cell population. In addition, at postoperative days 28 and 56, labeled cells of the denervated VN epithelium achieved neuronal differentiation and maturation by migrating much farther away from the base of the receptor cell column than the labeled cells on the normal, unoperated contralateral side. This study directly demonstrates that basal cells initially incorporating H3-thymidine are indeed stem cells of the VN epithelium in adult garter snakes.(ABSTRACT TRUNCATED AT 250 WORDS)     

Olfactory receptors and signalling elements in the Grueneberg ganglion

The Grueneberg ganglion (GG) is a cluster of neurones present in the vestibule of the anterior nasal cavity. Although its function is still elusive, recent studies have shown that cells of the GG transcribe the gene encoding the olfactory marker protein (OMP) and project their axons to glomeruli of the olfactory bulb, suggesting that they may have a chemosensory function. Chemosensory responsiveness of olfactory neurones in the main olfactory epithelium (MOE) and the vomeronasal organ (VNO) is based on the expression of either odorant receptors or vomeronasal putative pheromone receptors. To scrutinize its presumptive olfactory nature, the GG was assessed for receptor expression by extensive RT-PCR analyses, leading to the identification of a distinct vomeronasal receptor which was expressed in the majority of OMP-positive GG neurones. Along with this receptor, these cells expressed the G proteins Go and Gi, both of which are also present in sensory neurones of the vomeronasal organ. Odorant receptors were expressed by very few cells during prenatal and perinatal stages; a similar number of cells expressed adenylyl cyclase type III and G(olf/s), characteristic signalling elements of the main olfactory system. The findings of the study support the notion that the GG is in fact a subunit of the complex olfactory system, comprising cells with either a VNO-like or a MOE-like phenotype. Moreover, expression of a vomeronasal receptor indicates that the GG might serve to detect pheromones.     

Localization of G protein alpha subunits and morphology of receptor neurons in olfactory and vomeronasal epithelia in Reeve's turtle, Geoclemys reevesii

Most vertebrates have two nasal epithelia: the olfactory epithelium (OE) and the vomeronasal epithelium (VNE). The apical surfaces of OE and VNE are covered with cilia and microvilli, respectively. In rodents, signal transduction pathways involve G alpha olf and G alpha i2/G alpha o in OE and VNE, respectively. Reeve's turtles (Geoclemys reevesii) live in a semiaquatic environment. The aim of this study was to investigate the localization of G proteins and the morphological characteristics of OE and VNE in Reeve's turtle. In-situ hybridization analysis revealed that both G alpha olf and G alpha o are expressed in olfactory receptor neurons (ORNs) and vomeronasal receptor neurons (VRNs). Immunocytochemistry of G alpha olf/s and G alpha o revealed that these two G proteins were located at the apical surface, cell bodies, and axon bundles in ORNs and VRNs. Electron microscopic analysis revealed that ORNs had both cilia and microvilli on the apical surface of the same neuron, whereas VRNs had only microvilli. Moreover G alpha olf/s was located on only the cilia of OE, whereas G alpha o was not located on cilia but on microvilli. Both G alpha olf/s and G alpha o were located on microvilli of VNE. These results imply that, in Reeve's turtle, both G alpha olf/s and G alpha o function as signal transduction molecules for chemoreception in ORNs and VRNs.     

Immunohistochemical distribution of galectin-1, galectin-3, and olfactory marker protein in human olfactory epithelium

The expression pattern of galectin-1 and galectin-3 in the human olfactory epithelium was investigated in relation to olfactory marker protein (OMP) using confocal laser immunofluorescence in human specimens and postmortem biopsies. OMP expression was found in olfactory receptor neurons (ORNs) in the olfactory mucosa and in fibers of the olfactory nerve crossing the submucous connective tissue. Galectin-1 was expressed in both the connective tissue of the nasal cavity and in the basal layer of the olfactory epithelium. In contrast, galectin-3 expression was limited to cells of the upper one-third of the olfactory epithelium. Expression of galectin-3 occurred in a subset of OMP-positive cells. However, between areas of galectin-1 and galectin-3 expression in the lower and upper portion of the epithelium, OMP-positive ORNs did not stain for both galectins. Considering the potential role of galectin-1 and galectin-3 in cell differentiation and maturation, the differential localization of galectins in the olfactory epithelium appears to be consistent with a significant role of these molecules in the physiological turnover of ORNs. Accepted: 20 December 1999     

Light and electron microscopic observations on the normal structure of the vomeronasal organ of garter snakes

The vomeronasal epithelium of adult garter snakes (Thamnophis sirtalis and T. radix) was studied by light and electron microscopy. The sensory epithelium is extraordinarily thick, consisting of a supporting cell layer, a bipolar cell layer, and an undifferentiated cell layer. The supporting cell layer is situated along the luminal surface and includes supporting cells and the peripheral processes (dendrites) of bipolar neurons. The luminal surfaces of both supporting cells and bipolar neurons are covered with microvilli. Specializations of membrane junctions are always observed between adjacent cells in the subluminal region. Below the supporting cell layer, the epithelium is characterized by a columnar organization. Each column contains a population of bipolar neurons and undifferentiated cells. These cells are isolated from the underlying vascular and pigmented connective tissue by the presence of a thin sheath of satellite cells and a basal lamina. Heterogeneity of cell morphology occurs within each cell column. Generative and undifferentiated cells occupy the basal regions and mature neurons occupy the apical regions. Transitional changes in cell morphology occur within the depth of each cell column. These observations suggest that the vomeronasal cell column is the structural unit of the organ and may represent the dynamic unit for cell replacement as well. A sequential process of cell proliferation, neuronal differentiation, and maturation appears to occur in the epithelium despite the adult state of the animal.     

Evidence for neural progenitor cells in the human adult enteric nervous system

Putative neural stem cells have been identified within the enteric nervous system (ENS) of adult rodents and cultured from human myenteric plexus. We conducted studies to identify neural stem cells or progenitor cells within the submucosa of adult human ENS. Jejunum tissue was removed from adult human subjects undergoing gastric bypass surgery. The tissue was immunostained, and confocal images of ganglia in the submucosal plexus were collected to identify protein gene product 9.5 (PGP 9.5) - immunoractive neurons and neuronal progenitor cells that coexpress PGP 9.5 and nestin. In addition to PGP-9.5-positive/nestin-negative neuronal cells within ganglia, we observed two other types of cells: (1) cells in which PGP 9.5 and nestin were co-localized, (2) cells negative for both PGP 9.5 and nestin. These observations suggest that the latter two types of cells are related to a progenitor cell population and are consistent with the concept that the submucosa of human adult ENS contains stem cells capable of maintenance and repair within the peripheral nervous system.     

Goα expression in the vomeronasal organ and olfactory bulb of the tammar wallaby

The vomeronasal organ (VNO) detects pheromones via 2 large families of receptors: vomeronasal receptor 1, associated with the protein Giα2, and vomeronasal receptor 2, associated with Goα. We investigated the distribution of Goα in the developing and adult VNO and adult olfactory bulb of a marsupial, the tammar wallaby. Some cells expressed Goα as early as day 5 postpartum, but by day 30, Goα expressing cells were distributed throughout the receptor epithelium of the VNO. In the adult tammar, Goα appeared to be expressed in sensory neurons whose nuclei were mostly basally located in the vomeronasal receptor epithelium. Goα expressing vomeronasal receptor cells led to all areas of the accessory olfactory bulb (AOB). The lack of regionally restricted projection of the vomeronasal receptor cell type 2 in the tammar was similar to the uniform type, with the crucial difference that the uniform type only shows expression of Giα2 and no expression of Goα. The observed Goα staining pattern suggests that the tammar may have a third accessory olfactory type that could be intermediate to the segregated and uniform types already described.     

Heterogeneity in the accessory olfactory system

The mammalian accessory olfactory bulb (AOB) is chemoarchitecturally heterogeneous in that it stains differentially with a number of markers; the receptor cells that project to the AOB are similarly heterogeneous. What is the significance of this heterogeneity? We have found that the AOB of the gray, short-tailed opossum, Monodelphis domestica, stains differentially with a number of 'markers': antibodies to olfactory marker protein (OMP) and the alpha subunit of the G protein Gi2, the lectin of Vicia villosa and NADPH-diaphorase. These markers stain the rostral AOB more strongly than the caudal AOB whereas, the G protein subunit G(o) alpha is located predominantly in the posterior subdivision of the AOB. This heterogeneity in the chemoarchitecture of the AOB may reflect a fundamental organizational dichotomy within the vomeronasal system that corresponds to a functional dichotomy. The vomeronasal sensory epithelium also exhibits a chemoarchitectural heterogeneity: receptor cells in the basal third are G(o) alpha-immunoreactive whereas the cells in the middle third are Gi2 alpha-immunoreactive. Tracing studies using WGA-HRP demonstrate that the neurons in the middle third of the vomeronasal sensory epithelium project their axons to the anterior AOB whereas those in the basal third appear to project to the posterior AOB.      

Cell turnover in the vomeronasal epithelium: evidence for differential migration and maturation of subclasses of vomeronasal neurons in the adult opossum

Previous investigations of cell turnover in the mammalian vomeronasal sensory epithelium (VN-SE) raised two issues. First, if, in addition to the already demonstrated vertical migration, horizontal migration from the edges of the VN-SE participates in neuronal replacement. Second, whether or not migration and maturation is differential in upper and lower populations of vomeronasal neurons, since these two cell populations are chemically, physiologically, functionally, and perhaps evolutionarily different. By injecting bromodeoxyuridine (BrdU) into adult opossum (Monodelphis domestica) and permitting different survival times, the pattern of distribution of BrdU-labeled cells was analyzed. No evidence of horizontal migration in neuronal replacement was found. To investigate vertical migration and maturation of subclasses of vomeronasal neurons, double immunohistochemistry of BrdU and markers of the lower (G(oalpha) protein) and upper [G(i2alpha) protein and olfactory marker protein (OMP)] cell populations were performed. Three days after administration of BrdU, some mature neurons were observed in both lower and upper layers of the VN-SE, as demonstrated by coexpression of BrdU with G(oalpha) protein and OMP, respectively. The data on vertical distribution, however, indicate that most of the daughter cells enter the G(oalpha)-protein-expressing zone of the VN-SE by day 5, whereas most daughter cells do not reach the G(i2alpha)-protein-expressing zone until day 7, suggesting that these two populations mature at slightly different rates. These results are the first evidence of differential neurogenesis of subclasses of vomeronasal neurons.     

Olfactory metamorphosis in the coastal tailed frog Ascaphus truei (Amphibia,Anura, Leiopelmatidae)

The structure of the olfactory organ in larvae and adults of the basal anuran Ascaphus truei was examined using light micrography, electron micrography, and resin casts of the nasal cavity. The larval olfactory organ consists of nonsensory anterior and posterior nasal tubes connected to a large, main olfactory cavity containing olfactory epithelium; the vomeronasal organ is a ventrolateral diverticulum of this cavity. A small patch of olfactory epithelium (the “epithelial band”) also is present in the preoral buccal cavity, anterolateral to the choana. The main olfactory epithelium and epithelial band have both microvillar and ciliated receptor cells, and both microvillar and ciliated supporting cells. The epithelial band also contains secretory ciliated supporting cells. The vomeronasal epithelium contains only microvillar receptor cells. After metamorphosis, the adult olfactory organ is divided into the three typical anuran olfactory chambers: the principal, middle, and inferior cavities. The anterior part of the principal cavity contains a “larval type” epithelium that has both microvillar and ciliated receptor cells and both microvillar and ciliated supporting cells, whereas the posterior part is lined with an “adult‐type” epithelium that has only ciliated receptor cells and microvillar supporting cells. The middle cavity is nonsensory. The vomeronasal epithelium of the inferior cavity resembles that of larvae but is distinguished by a novel type of microvillar cell. The presence of two distinct types of olfactory epithelium in the principal cavity of adult A. truei is unique among previously described anuran olfactory organs. A comparative review suggests that the anterior olfactory epithelium is homologous with the “recessus olfactorius” of other anurans and with the accessory nasal cavity of pipids and functions to detect water‐borne odorants. J. Morphol. 2011. © 2011 Wiley Periodicals, Inc.     

Distinct axonal projections from two types of olfactory receptor neurons in the middle chamber epithelium of <Emphasis Type="BoldItalic">Xenopus laevis</Emphasis>

Most vertebrates have two olfactory organs, the olfactory epithelium (OE) and the vomeronasal organ. African clawed frog, Xenopus laevis, which spends their entire life in water, have three types of olfactory sensory epithelia: the OE, the middle chamber epithelium (MCE) and the vomeronasal epithelium (VNE). The axons from these epithelia project to the dorsal part of the main olfactory bulb (d-MOB), the ventral part of the MOB (v-MOB) and the accessory olfactory bulb, respectively. In the MCE, which is thought to function in water, two types of receptor neurons (RNs) are intermingled and express one of two types of G-proteins, Golf and Go, respectively. However, axonal projections from these RNs to the v-MOB are not fully understood. In this study, we examined the expression of G-proteins by immunohistochemistry to reveal the projection pattern of olfactory RNs of Xenopus laevis, especially those in the MCE. The somata of Golf- and Go-positive RNs were separately situated in the upper and lower layers of the MCE. The former were equipped with cilia and the latter with microvilli on their apical surface. These RNs are suggested to project to the rostromedial and the caudolateral regions of the v-MOB, respectively. Such segregation patterns observed in the MCE and v-MOB are also present in the OE and olfactory bulbs of most bony fish. Thus, Xenopus laevis is a very interesting model to understand the evolution of vertebrate olfactory systems because they have a primitive, fish-type olfactory system in addition to the mammalian-type olfactory system.     

Development of olfactory marker protein and N-CAM expression in chemosensory systems of the opossum,Monodelphis domestica

Using olfactory marker protein (OMP) and neural cell adhesion molecule (N-CAM) immunohistochemistry, the present study describes development of olfactory and vomeronasal systems in pre- and postnatal opossums, Monodelphis domestica. As revealed by OMP expression, development of the main olfactory system precedes that of the vomeronasal system by 1–2 weeks. OMP is expressed throughout (homogeneously) the nerve and glomerular layers of the main (MOB) but is expressed more strongly (heterogeneously) in the anterior as compared to the posterior accessory (AOB) olfactory bulb. N-CAM expression is homogeneous in both MOB and AOB. The heterogeneity in the AOB is developmentally regulated, since in the 30-day-old AOB the expression of OMP is homogeneous, becoming heterogeneous during the second month of life. Maximal expression of N-CAM precedes maximal expression of OMP in the VNS by about 2 weeks. From 7 to 21 days of age only, there is a small population of OMP-positive, N-CAM-negative olfactory and vomeronasal axon terminals that penetrate deep into the brain parenchyma, overgrowing their normal targets in the MOB and AOB, respectively. J. Morphol. 234:109–129, 1997. © 1997 Wiley-Liss, Inc.     

Differential binding patterns of three antibodies (VOBM1, VOBM2, and VOM2) in the rat vomeronasal organ and accessory olfactory bulb

Immunohistochemical properties of monoclonal antibodies raised against the rat vomeronasal epithelium were examined in adult rats. Three monoclonal antibodies, VOBM1, VOBM2, and VOM2, reacted specifically to the luminal surface of the sensory epithelium of the vomeronasal organ. In addition, the reactivities of VOBM1 and VOBM2 were detected in the vomeronasal nerve layer and the glomerular layer of the accessory olfactory bulb. Electron-microscopic study revealed differential patterns of the immunoreactivity of the three antibodies to the microvilli of vomeronasal sensory epithelium. VOBM1 immunoreactivity was found on the microvilli of the supporting cells, whereas VOBM2 immunoreactivity was found on those of the sensory cells. VOM2 immunoreactivity was observed on the microvilli of both the sensory and supporting cells. These results suggest that the three antibodies recognize different antigens on the vomeronasal sensory epithelium. In particular, VOBM2 antibody appears to react to an antigen specific to the microvilli of the vomeronasal sensory cells.     

Immunohistochemical localization of protein gene product 9.5, ubiquitin, and neuropeptide Y immunoreactivities in epithelial and neuroendocrine cells from normal and hyperplastic human prostate.

This study was designed to investigate (a) the presence of protein gene product 9.5 (PGP 9.5), ubiquitin, and neuropeptide Y (NPY) in the neuroendocrine and secretory epithelium of the human normal prostate and its secretions, and (b) the changes in immunoreactivity to these proteins in men with benign prostatic hyperplasia. Western blotting and light microscopic immunohistochemistry techniques were used and the numerical density of immunoreactive neuroendocrine cells, and the volume fractions of immunostained secretory epithelium were evaluated. Western blotting revealed the presence of the three antigens in both tissue homogenates and prostate secretion. Some neuroendocrine cells immunoreacted to PGP 9.5 and NPY in all the prostate regions of control specimens. Ubiquitin immunoreactivity was detected in the nuclei from both basal cells and secretory epithelial cells. The cytoplasm of the secretory cells and the glandular lumen also showed immunostaining for the three proteins. The numerical densities of both PGP 9.5 and NPY neuroendocrine cells were lower in hyperplasia than in controls. No differences in the volume fraction occupied by epithelial immunostaining to both proteins was found between hyperplastic and control prostates. We concluded that (a) PGP 9.5 and NPY, but not ubiquitin, are common antigens in both neuroendocrine and secretory prostate cells, (b) the three immunoreactive proteins contribute to the prostate secretions, and (c) the secretion of ubiquitin is markedly diminished in the hyperplastic epithelium.(J Histochem Cytochem 48:1121-1130, 2000)     

Immunocytochemistry of glutathione S-transferase in taste bud cells of rat circumvallate and foliate papillae

Immunocytochemistry was used to investigate the distribution of cells reacting with specific antibodies against glutathione S-transferase (GST) mu and pi in rat circumvallate and foliate taste buds; the findings were confirmed by Western blotting. Double immunofluorescence staining for protein gene product (PGP) 9.5 and GST subunits allowed the classification of taste bud cells of both papillae into: (i) cells immunoreactive to either PGP 9.5 or GST subunit antibody; (ii) cells immunoreactive to both antibodies; and (iii) cells that did not react with either of these antibodies. Immunoelectron microscopy revealed that most GST subunit-immunoreactive cells seemed to be either type II or type III cells based on their ultrastructure. Since PGP 9.5 is now widely used as a marker for type III cells in mammalian taste buds, it seems reasonable to believe that most GST subunit-immunoreactive cells are type II cells. Whether cells immunoreactive for both PGP 9.5 and GST subunits constitute a small subpopulation of type III cells or whether they are intermediate forms between type II and III cells is under investigation. No type I cells reacted with antibodies against GST subunits in the present study. GST subunits in taste bud cells may participate in xenobiotic metabolism of certain substances exposed to taste pits, as already shown for olfactory epithelium.