Fine structure of the epithelia of the vomeronasal organ of horse and cattle. A comparative study

Histological evaluation of the alpaca (Vicugna pacos) vomeronasal organ

Little is known about the neuronal structure of the vomeronasal organ (VNO), a receptor organ responsible for pheromone perception, in the alpaca (Vicugna pacos). This study was performed to determine the localization of neuronal elements, including protein gene product 9.5 (PGP 9.5), a pan-neuronal marker, olfactory marker protein (OMP), a marker of mature olfactory receptor cells, and phospholipase C beta 2 (PLC-β2), a marker of solitary chemoreceptor cells (SCCs), in the VNO. OMP was identified in receptor cells of the vomeronasal sensory epithelium (VSE), while PGP 9.5 and PLC-β2 were localized in both the VSE and vomeronasal non-sensory epithelium. Collectively, these results suggested that the alpaca VNO possesses SCCs and olfactory receptor cells, which recognize both harmful substances and pheromones.

Immunohistological study of the unexplored vomeronasal organ of an endangered mammal, the dama gazelle (Nanger dama)

Dama gazelle is a threatened and rarely studied species found primarily in northern Africa. Human pressure has depleted the dama gazelle population from tens of thousands to a few hundred individuals. Since 1970, a founder population consisting of the last 17 surviving individuals in Western Sahara has been maintained in captivity, reproducing naturally. In preparation for the future implementation of assisted reproductive technology, certain aspects of dama gazelle reproductive biology have been established. However, the role played by semiochemical-mediated communications in the sexual behavior of dama gazelle remains unknown due partially to a lack of a neuroanatomical or morphofunctional characterization of the dama gazelle vomeronasal organ (VNO), which is the sensory organ responsible for pheromone processing. The present study characterized the dama gazelle VNO, which appears fully equipped to perform neurosensory functions, contributing to current understanding of interspecies VNO variability among ruminants. By employing histological, lectin-histochemical, and immunohistochemical techniques, we conducted a detailed morphofunctional evaluation of the dama gazelle VNO along its entire longitudinal axis. Our findings of significant structural and neurochemical transformation along the entire VNO suggest that future studies of the VNO should take a similar approach. The present study contributes to current understanding of dama gazelle VNO, providing a basis for future studies of semiochemical-mediated communications and reproductive management in this species. RESEARCH HIGHLIGHTS: This exhaustive immunohistological study of the vomeronasal organ (VNO) of the dama gazelle provides the first evidence of notable differences in the expression of neuronal markers along the rostrocaudal axis of the VNO. This provides a morphological basis for the implementation of pheromones in captive populations of dama gazelle.

Morphological and histological features of the vomeronasal organ in the brown bear

The vomeronasal organ (VNO) is a peripheral receptor structure that is involved in reproductive behavior and is part of the vomeronasal system. Male bears exhibit flehmen behavior that is regarded as the uptake of pheromones into the VNO to detect estrus in females. However, the morphological and histological features of the VNO in bears have not been comprehensively studied. The present study investigated the properties and degree of development of the VNO of the brown bear by histological, histochemical and ultrastructural methods. The VNO of bears was located at the same position as that of many other mammals, and it opened to the mouth like the VNO of most carnivores. The shape of the vomeronasal cartilages and the histological features of the sensory epithelium in the bear VNO were essentially similar to those of dogs. Receptor cells in the VNO of the bear possessed both cilia and microvilli like those of dogs. The dendritic knobs of receptor cells were positive for anti-G protein alpha-i2 subunit (Gαi2 ) but negative for anti-G protein alpha-o subunit, indicating preferential use of the V1R-Gαi2 pathway in the vomeronasal system of bears, as in other carnivores. The VNO of the bear possessed three types of secretory cells (secretory cells of the vomeronasal gland, multicellular intraepithelial gland cells and goblet cells), and the present findings showed that the secretory granules in these cells also had various properties. The vomeronasal lumen at the middle region of the VNO invaginated toward the ventral region, and this invagination contained tightly packed multicellular intraepithelial gland cells. To our knowledge, this invagination and intraepithelial gland masses in the VNO are unique features of brown bears. The VNO in the brown bear, especially the secretory system, is morphologically well-developed, suggesting that this organ is significant for information transmission in this species.

Histological and lectin histochemical studies of the vomeronasal organ of horses

The morphological characteristics and glycoconjugate composition of the vomeronasal organ (VNO) of the horse was investigated using histological, immunohistochemical, and lectin histochemical methods. The VNO is bilaterally located at the base of the nasal septum, has a tubular structure surrounded by cartilage, and consists of sensory and non-sensory epithelia. Immunohistochemical examination showed that the vomeronasal sensory epithelium (VSE) consisted of receptor cells positive for both olfactory marker protein (OMP) and protein gene product 9.5 (PGP 9.5), supporting cells, and basal cells. VNO receptor cells were positive for G protein Gαi2 (vomeronasal receptor type 1 marker), but not Gαo (vomeronasal receptor type 2 marker). Lectin histochemical studies using 21 biotinylated lectins showed that the free border of the VSE was positive for 20 lectins. The receptor and supporting cells reacted with 16 lectins while the basal cells reacted with 15 lectins, with varying intensities. In the vomeronasal non-sensory epithelium, the free border was positive for 19 lectins. The cilated cells were positive for 17 lectins and the basal cells were positive for 15 lectins. The vomeronasal glands, positioned in the lamina propria, were stained with both periodic acid Schiff (PAS) and alcian blue (pH 2.5). Eighteen lectins stained the acinar cells of the vomeronasal glands with various binding patterns. These findings suggest that horse VNO receptor cells express vomeronasal receptor type 1, and the VNO glands have mucous to seromucous characteristics. Moreover, each lectin differentially binds each cell type in both the VNO sensory and non-sensory epithelia.

Phylogenic studies on the olfactory system in vertebrates

The olfactory receptor organs and their primary centers are classified into several types. The receptor organs are divided into fish-type olfactory epithelium (OE), mammal-type OE, middle chamber epithelium (MCE), lower chamber epithelium (LCE), recess epithelium, septal olfactory organ of Masera (SO), mammal-type vomeronasal organ (VNO) and snake-type VNO. The fish-type OE is observed in flatfish and lungfish, while the mammal-type OE is observed in amphibians, reptiles, birds and mammals. The MCE and LCE are unique to Xenopus and turtles, respectively. The recess epithelium is unique to lungfish. The SO is observed only in mammals. The mammal-type VNO is widely observed in amphibians, lizards and mammals, while the snake-type VNO is unique to snakes. The VNO itself is absent in turtles and birds. The mammal-type OE, MCE, LCE and recess epithelium seem to be descendants of the fish-type OE that is derived from the putative primitive OE. The VNO may be derived from the recess epithelium or fish-type OE and differentiate into the mammal-type VNO and snake-type VNO. The primary olfactory centers are divided into mammal-type main olfactory bulbs (MOB), fish-type MOB and mammal-type accessory olfactory bulbs (AOB). The mammal-type MOB first appears in amphibians and succeeds to reptiles, birds and mammals. The fish-type MOB, which is unique to fish, may be the ancestor of the mammal-type MOB. The mammal-type AOB is observed in amphibians, lizards, snakes and mammals and may be the remnant of the fish-type MOB.

A morphological study of the vomeronasal organ and the accessory olfactory bulb in the Korean roe deer, Capreolus pygargus

The vomeronasal organ (VNO) and accessory olfactory bulb (AOB) of the Korean roe deer (Capreolus pygargus) were studied histologically to evaluate their morphological characteristics. Grossly, the VNO, encased by cartilage, has a paired tubular structure with a caudal blind end and a rostral connection through incisive ducts on the hard palate. In the VNO, the vomeronasal sensory epithelium (VSE) consists of galectin-3-positive supporting cells, protein gene product (PGP) 9.5-positive receptor cells, and basal cells. The vomeronasal respiratory epithelium (VRE) consists of a pseudostratified epithelium. The AOB strata included a vomeronasal nerve layer (VNL), a glomerular layer (GL), a mitral/tufted cell layer, and a granular cell layer. All lectins used in this study, including Bandeiraea simplicifolia agglutinin isolectin B4 (BSI-B4), soybean agglutinin (SBA), Ulex europaeus agglutinin I (UEA-I), and Triticum vulgaris wheat germ agglutinin (WGA), labeled the VSE with varying intensity. In the AOB, both the VNL and the GL reacted with BSI-B4, SBA, and WGA with varying intensity, but not with UEA-I. This is the first morphological study of the VNO and AOB of the Korean roe deer, which are similar to those of goats.

Morphology of non-sensory epithelium during post-natal development of the rabbit vomeronasal organ

The vomeronasal organ (VNO), because of its ability to detect pheromones, has an important role in many social and sexual behaviours in mammals. It also mediates defensive behaviours through detection of protein pheromone homologues. A detailed morphological description of the post-natal development of the 'non-sensory' epithelium (NSE) of the female rabbit is recorded. Histological techniques were used to study the NSE of the VNO in post-natal development of female rabbits. The study focused on the following post-natal ages: newborn, 1 week, 2 weeks and 1 month (five animals each) beside to two adult animals. The rabbit VNO was surrounded externally by bony capsule and internally by cartilaginous capsule. NSE was pseudostratified columnar partially ciliated epithelium without goblet cells. In addition to basal cells, NSE contained ciliated and three types of non-ciliated columnar cells (dark, pale and light). At birth, dark cells may have primary cilia. By 1 month, the cytoplasm became lighter with less free ribosomes. The pale cells had electron-lucent cytoplasm, which contained a few organelles. Mitotic figures were observed in basal and columnar cells, particularly during the first 2 weeks of post-natal development. Light columnar cells were common during the first week. Numerous leucocytes and a few nerve endings were detected intra-epithelial. Scanning electron microscope revealed a gradual increase in height of microvilli of non-ciliated cells. Ciliated cells had cilia and microvilli. Cells were arranged singly, in clumps or in a dense population of cells. The rabbit VNO-NSE had a unique morphological structure.

Developmental changes affecting lectin binding in the vomeronasal organ of domestic pigs, Sus scrofa

This study investigated the developmental changes of glycoconjugate patterns in the porcine vomeronasal organs (VNOs) and associated glands (Jacobson's glands) from prenatal (9 weeks of gestation) and postnatal (2 days after birth) to the sexually mature stage (6 months old). The VNO of pigs (Sus scrofa) was examined using the following: Dolichos biflorus agglutinin (DBA), Bandeiraea simplicifolia agglutinin isolectin B4 (BSI-B4), Triticum vulgaris agglutinin (WGA), Ulex europaeus agglutinin I (UEA-I), and soybean agglutinin (SBA). At the fetal stage, all lectins examined were detected mainly in the free border of the vomeronasal epithelium, but few (WGA and UEA-I) and or absent in the VNO cell bodies. At the postnatal and sexually mature stages, the reactivity of some lectins, including WGA, UEA-I, DBA and SBA, were shown to increase in the VNO sensory epithelium as well as the free border. The increased reactivity of lectins as development progressed was also observed in Jacobson's gland acini. These findings suggest that binding sites of lectins, including those of WGA, UEA-I, DBA, and SBA, increase during development from fetal to postnatal growth, possibly contributing to the increased ability of chemoreception in the pig.

Phylogenic outline of the olfactory system in vertebrates

Phylogenic outline of the vertebrate olfactory system is summarized in the present review. In the fish and the birds, the olfactory system consists only of the olfactory epithelium (OE) and the olfactory bulb (B). In the amphibians, reptiles and mammals, the olfactory system is subdivided into the main olfactory and the vomeronasal olfactory systems, and the former consists of the OE and the main olfactory bulb (MOB), while the latter the vomeronasal organ (VNO) and the accessory olfactory bulb (AOB). The subdivision of the olfactory system into the main and the vomeronasal olfactory systems may partly be induced by the difference between paraphyletic groups and monophyletic groups in the phylogeny of vertebrates.

The vomeronasal organ of the tammar wallaby

The vomeronasal organ is the primary olfactory organ that detects sexual pheromones in mammals. We investigated the anatomy of the vomeronasal organ of the tammar wallaby (Macropus eugenii), a small macropodid marsupial. Pheromones may be important for activation of the hypothalamo-pituitary axis of tammar males at the start of the breeding season because plasma testosterone and luteinizing hormone concentration in males rise concurrently with pregnancy and the post-partum ovulation in females. The gross anatomy and the connection to the brain of the vomeronasal organ were examined by light and electron microscopy in adult male and female tammars. The vomeronasal organ was well developed in both sexes. The vomeronasal organ is a tubular organ connected at the rostral end via the nasopalatine duct (incisive duct) to the mouth and nasal cavity. At the rostral end the lumen of the vomeronasal organ was crescent shaped, changing to a narrow oval shape caudally. Glandular tissue associated with the vomeronasal organ increased towards the blind end of the organ. The tammar has the typical pattern of mammalian vomeronasal organs with electron-dense supporting cells and electron-lucent receptor cells. Microvilli were present on the surface of both epithelia while cilia were only found on the surface of the non-receptor epithelium. Some non-receptor epithelial cells appeared to secrete mucus into the vomeronasal organ lumen. The vomeronasal organ shows a high degree of structural conservation compared with eutherian mammals. The degree of vomeronasal organ development makes it likely that, as in other mammals, pheromones are important in the reproduction of the tammar.

Anatomical, immnunohistochemical and physiological characteristics of the vomeronasal vessels in cows and their possible role in vomeronasal reception

The general morphology of the vomeronasal vessels in adult cows was studied following a classic protocol, including optical, confocal and ultrastructural approaches. This anatomical work was completed immunohistochemically. The vomeronasal organ in cows is well developed, and its vessels are considerable in size. This fact allowed some functional properties of the vomeronasal arteries to be evaluated and, for the first time, their isometric tension to be recorded. Our functional studies were in agreement with the immunohistochemistry, and both corroborated the morphological data on the similarity between the vomeronasal vessels and those of the typical erectile tissue. In consequence, the vasoconstriction and vasodilation of the vomeronasal vessels would facilitate an influx and outflow of fluids in the vomeronasal organ, that is to say, this organ in cows would be able to work as a pump mechanism to send chemical signals to the vomeronasal receptor neurones.

Morphological characteristics of the vomeronasal organ of the newborn Asian elephant (Elephas maximus)

The 6-week-old Asian elephant (Elephas maximus) has a well-documented precocious flehmen response to pheromones, suggesting that the pheromone-detecting vomeronasal organ (VNO) is functional very early in the life of this species. To further document this, the VNOs of two newborn elephants were examined in situ and analyzed by light microscopy (LM) to ascertain their structural maturity at birth. A tubular, cartilage-encased VNO was located along the anterior base of each side of the nasal septum. Its rostral end was connected to a duct to the roof of the mouth; the caudal end was attached to a well-defined vomeronasal nerve projecting toward the brain. LM revealed distinctive differences in the mucosae bordering the horseshoe-shaped lumen: a concave, sensory mucosa, and a convex, nonsensory mucosa. Small groups of receptor neurons were observed among ciliated columnar cells in the sensory epithelium. Numerous unmyelinated nerve bundles and blood vessels filled the underlying lamina propria (LP) and a small section of the vomeronasal nerve was conspicuous at one edge. The nonsensory mucosa manifested a thinner epithelium that principally consisted of ciliated columnar cells, some of which showed a granular cytoplasm, and a conspicuous row of basal cells. The LP was replete with acinar glands and ducts that opened into the lumen. This study shows that the VNO of the newborn elephant has reached an advanced stage of structural maturity, closely resembling that of the adult. Its composition supports the view that flehmen at 6 weeks delivers pheromones to a functional VNO.

The vomeronasal organ of the South American armadillo Chaetophractus villosus (Xenarthra, Mammalia): anatomy, histology and ultrastructure

The vomeronasal organ (VNO) is a chemoreceptive structure that has not been extensively studied in the Xenarthran order. Tissue samples from the VNO of the armadillo Chaetophractus villosus were prepared for light and electron microscopy. The VNO is located in the anterior part of the base of the nasal septum. It is tubular in shape, approximately 18 mm in length and opens in the rostral region of the nasal cavity and with a blind caudal end. Its lumen is lined by sensory (SE) and nonsensory (NSE) epithelium. The SE shows sensory, supporting and basal cells whereas the NSE contains ciliated and nonciliated secretory cells and basal cells. At the ultrastructural level, the sensory cells appear as bipolar neurons with conspicuous microvilli on their free surface. The supporting cells of the SE contain numerous membrane-bound vesicles in their apical regions. A peculiar feature not found in other mammals, is the presence of concentric whorls of RER cisterns frequently observed in their basal expansions. Infiltrating plasma cells can be detected in the SE basal region close to the dorsal junctional area. This region also exhibits an unusual type of basal cell, probably responsible for the generation of new vomeronasal receptor neurons. The ciliated NSE cells exhibit numerous ovoids or irregularly shaped membranous protrusions projecting from the plasma membrane of the cilia. As far as we know, this is the first study reporting the presence of this feature in ciliated NSE cells. The nonciliated cells are characterised by scarce large secretory granules and apical microvilli. The vomeronasal glands are compound-branched tubuloacinar glands with serous acinar cells. Four types of secretory granules are present. The ducts of these glands reach the lumen in the dorsolateral region between the NSE and SE. Hypolemmal nerve terminals were observed contacting secretory cells. Fenestrated and nonfenestrated capillaries constitute the vascular supply to these glands. Plasma cells, intimately associated with acinar cells, were frequently observed.

The anatomy and functional role of the circumvallate papilla/von Ebner gland complex

We suggest that the description of the reciprocal relationships between the circumvallate papilla (CP) and von Ebner glands (VEGs) reported in most textbooks of anatomy must be rewritten. In the past, the VEG was described as a gland ancillary to the taste buds, mainly involved in the washing of the vallum around the CP or in perireceptorial events. Recent data obtained in our laboratory or reported in the literature indicate that both these structures form a single functional unity which could be called circumvallata papilla/von Ebner gland (CP/VEG) complex. The CP/VEG complex seems to represent an important enzyme- and pheromone-producing system composed of a sensitive (taste buds) and an effectory (VEG) branch linked by feedback mechanisms of control. In our hypothesis, the taste buds located in the distal portion of the VEG ductal system can be considered similar to the chemoreceptory cells located in other portions of the digestive apparatus such as pancreatic and bile ducts. Therefore, the CP/VEG complex represents a rare example of chemoreceptor-secretory organ.

Isolation of mouse vomeronasal receptor genes and their co-localization with specific G-protein messenger RNAs

Four mouse vomeronasal receptors (mV1Rs) have been isolated by similarity to rat vomeronasal receptor (V1R) motifs. The four mV1Rs identified in this study are members of two distinct subfamilies. Specific in situ hybridization probes (ISH) derived from the 3' non-coding regions of the mV1R genes, were used to detect expression of a single receptor and probes from the homologous coding regions were used to detect expression of subfamily members. The ISH results showed that the mV1Rs expressing neurons were scattered in the middle/upper layer of the vomeronasal organ (VNO) sensory epithelium in serial VNO sections but were excluded from the deeper layers of the VNO sensory epithelium and these neurons were found to co-express the mRNA for the G-protein Galphai2, and were distinct from the deeper layers of the VNO sensory epithelium where the mRNA for Galphao positive neurons was located.

Atomic force microscopy of histological sections using a new electron beam etching method

In order to examine histological sections of the rat vomeronasal epithelium with the atomic force microscope (AFM), we developed an electron beam etching method that improves the resolution of AFM images. This method results in AFM images comparable to those obtained with the transmission electron microscope (TEM). Ultrathin tissue sections embedded in epoxy resin were observed before and after the treatment with electron beam radiation. Before electron beam treatment, epithelial structures such as the microvilli surface, dendritic processes, the supporting cell layers and the neuronal cell layers were all visible using the AFM. However, only a few subcellular structures could also be resolved. The AFM images were not as clear as those obtained with the TEM. After electron beam treatment, however, the resolution of AFM images was greatly improved. Most of the subcellular structures observed in TEM images, including the inner membrane of mitochondria, ciliary-structure precursor body, junctional complexes between the neurons and supporting cells, and individual microvilli were now visible in the AFM images. The electron beam treatment appeared to melt the embedding resin, bringing subcellular structures into high relief. The result of this study suggests that electron beam etching of histological samples may provide a new method for the study of subcellular structure using the AFM.

Sensory epithelium of the vomeronasal organ express TrkA-like and epidermal growth factor receptor in adulthood. An immunohistochemical study in the horse

BACKGROUND

The medial wall of the vomeronasal organ (VNO) is lined with a sensory epithelium that is closely related to the olfactory epithelium, which is developed from the olfactory placode. It undergoes continuous replacement during its life span. In other sensory epithelia, cell proliferation is under the control of some trophic factors. Whether these proteins are involved in the continuous turnover of the VNO epithelium is unknown. This study approaches this topic by analyzing the occurrence of signal-transducing receptor proteins for neurotrophins (Trk proteins) and epidermal growth factor (EGFr).

METHODS

VNO samples were obtained from adult horses (n = 9) and processed for Western blot or immunohistochemical detection of TrkA, TrkB, TrkC, and EGFr. For immunohistochemistry, both frozen and formalin-fixed, paraffin-embedded sections were used. Antibodies against Trk proteins were polyclonal antibodies that map within the intracytoplasmic domain. Antibodies against EGFr were monoclonal antibodies that map within the external (clone EGFR1) or the cytoplasmic (clone F4) domains.

RESULTS

TrkA-like, but not TrkB- or TrkC-like, protein was detected in the VNO. By using immunoblotting, protein bands of TrkA-like protein with estimated molecular weights of 43-45, 55, and 60 kDa were found. In agreement with these findings, the sensory epithelium lining the VNO displayed strong TrkA-like immunoreactivity. On the other hand, regular protein bands with estimated molecular weights of 100 and 170 kDa, corresponding with immature and full-length EGFr, respectively, were found with the clone F4, whereas the clone EGFR1 was ineffective in detecting EGFr with Western blot analysis. Positive EGFr immunolabelling was observed regularly in the supranuclear pole of the sensory epithelial cells, and the pattern was identical with both antibodies used.

CONCLUSIONS

The present results provide evidence for the occurrence of EGFr in the VNO of the adult horse, suggesting a role for their ligands (EGF and transforming growth factor-alpha) in this organ, probably in continuous cell replacement, during the adult life span. However, although immunoreactivity for TrkA-like protein was regularly observed, because the full-length protein was not found, whether or not its putative ligands (nerve growth factor and neurotrophin-3) act on these cells remains to be demonstrated.

Ultrastructure of the olfactory organ of the newt, Cynops pyrrhogaster

The ultrastructure of the nasal sacs of the Japanese newt, Cynops pyrrhogaster, was studied by scanning and transmission electron microscopy. The paired nasal sacs of the newt are dorsoventrally flattened with a lateral nasal sinus off the main cavity of each sac. Throughout each sac is a series of ridges and grooves. In the main cavity, sensory epithelium with ciliated and microvillous receptor cells lines the grooves, and a thin, ciliated non-sensory epithelium lines the ridges. Secretory glands are present in the lamina propria. In the lateral nasal sinus, the ridges are lined with a thick, non-ciliated sensory epithelium that lacks glands. This region resembles and may function as a primitive vomeronasal organ.

An immuno-electron microscopic comparison of olfactory marker protein localization in the supranuclear regions of the rat olfactory epithelium and vomeronasal organ neuroepithelium

Immuno-electron microscopy was used to examine olfactory marker protein (OMP) ultrastructural localization in the supranuclear regions of the rat olfactory epithelium (OE) and vomeronasal organ (VNO) neuroepithelium. In the OE, OMP immuno-reaction product was observed within the cytoplasm of olfactory chemoreceptor cell dendrites, vesicles and cilia. Reaction product was absent from olfactory microvillar cells and their unique microvillar projections. In the neuroepithelium of the VNO, immuno-reaction product was seen within the dendrites of the chemoreceptor cells, and in the bases of their attached microvilli; the remaining distal portions of these microvilli were unlabeled. These results demonstrate a difference in the distribution of OMP immunoreactivity over the surfaces of the rat OE and VNO. They also show that OMP immunoreactivity does not exist in the rat olfactory microvillar cells.

Subdivisions of the accessory olfactory bulb, as demonstrated by lectin-histochemistry in the golden hamster

Lectin-binding patterns in the accessory olfactory bulb (AOB) of the golden hamster were investigated histochemically with 21 biotinylated lectins. The AOB was divided into rostral and caudal halves according to binding patterns of 16 lectins, WGA, s-WGA, LEL, STL, DSL, BSL-II, DBA, SBA, BSL-I, VVA, SJA, PNA, ECL, UEA-I, Con A and PSA. The caudal half of the AOB was further subdivided into anterior 2/3 and posterior 1/3 by 10 lectins, WGA, s-WGA, BSL-II, DBA, SBA, BSL-I, VVA, SJA, PNA and ECL. In addition, the rostral half of the AOB was subdivided into anterior 1/4 and posterior 3/4 by one lectin, PNA. Thus, the AOB of the golden hamster was divided into 4 divisions on the basis of lectin-binding patterns.

Immunohistochemical demonstration of protein gene product 9.5 (PGP 9.5) in the primary olfactory system of the rat

Immunohistochemical localization of protein gene product 9.5 (PGP 9.5) was examined in the primary olfactory system of the rat. Receptor cells were intensely immunopositive in the olfactory epithelium, vomeronasal organ and septal olfactory organ of Masara. The mitral cells and some of the short-axon cells of the main olfactory bulb (MOB) were also intensely immunopositive, while the tufted cells of the MOB and the mitral/tufted cells of the accessory olfactory bulb varied in immunoreactivity.

Fine structure of the vomeronasal and septal olfactory epithelia and of glandular structures

The vomeronasal and septal olfactory organs are two neurosensory structures in the mammalian nasal septum which are poorly understood relative to the main olfactory system. The vomeronasal organ is a paired, blind-ending tubular structure that opens rostrally into the nasal cavity in some species and into the incisive ducts in others. When present in mammals, the septal olfactory organ is an island of olfactory mucosa positioned such that it is in the primary air pathway in the caudal portion of the nasal cavity. Mammalian nasal glands, with a diverse histochemical and ultrastructural morphology, secrete a variety of substances onto the mucosal surface. One of these substances, odorant binding protein, localized in bovine nasal glands and lateral nasal glands of rodents, may be important in the capture and conveyance of odorant molecules to olfactory receptors. The objectives of this paper are to present original data while reviewing the literature on the ultrastructure of vomeronasal and septal olfactory neuroepithelia, and of vomeronasal, bovine nasal, and lateral nasal glands. Nasal tissues from pigs, calves, and hamsters were prepared for electron microscopy. Neurosensory epithelia of the porcine vomeronasal organ and the hamster septal olfactory organ are similar to that described for the vomeronasal and septal olfactory organs of other mammals. Bovine nasal and rodent lateral nasal glands consist of subregions which differ morphologically; the most abundant acinar cell type in the bovine nasal gland contains lightly electron dense secretory granules while that of the rodent lateral nasal gland contains both small electron dense and large, electron lucent granules. The porcine vomeronasal gland contains numerous small, dense granules of a diverse morphology.

Phylogeny of the vomeronasal system and of receptor cell types in the olfactory and vomeronasal epithelia of vertebrates

In this paper, the evolutionary origin of the vomeronasal system as a discrete sensory system separate from olfaction is examined. The presence of a discrete vomeronasal system appears to be a derived character in tetrapods, and its presence in larval amphibians indicates that the system did not arise as a terrestrial adaptation. The vomeronasal system has been lost independently in several taxa, including crocodilians, some bats, cetaceans, and some primates. The presence of microvillar receptor cells in the vomeronasal epithelium appears to be the ancestral condition for tetrapods, and alternative hypotheses concerning the ancestral condition for receptor cell types in the vertebrate olfactory epithelium are discussed. Finally, the possibility that the vomeronasal system is present in some fishes in a form that has not been recognized is discussed in relation to the phylogenetic distribution of receptor cell types in vertebrates.

The role of the Flehmen response in the behavioral repertoire of the stallion

The role of the Flehmen response in equine behavior was investigated under field and laboratory conditions. In Experiment 1, a field study made of five stallions on pasture with between three and eighteen mares each during the season indicated the following: 1) The Flehmen response was most frequently preceded by nasal, rather than oral, investigation of substances; 2) The stallions' rate of Flehmen varied with the estrous cycles of the mares; 3) The rate of Flehmen response did not show a variation with time of day; and 4) The Flehmen response was most frequently followed by marking behaviors rather than courtship behaviors. The results suggest that the Flehmen response is not an immediate component of sexual behavior, e.g., courtship of the stallion but may be involved in the overall monitoring of the mare's estrous cycle. Therefore the Flehmen response may contribute to the chemosensory priming of the stallion for reproduction. In Experiment 2 stallions were presented with urine or feces of mares in various stages of the reproductive cycle as well as with their own or other males' urine or feces. The occurrence of sniffing and Flehmen was used to determine the discriminatory ability of the stallions. Stallions can differentiate the sex of a horse on the basis of its feces alone, but cannot differentiate on the basis of urine. This ability may explain the function of fecal marking behavior of stallions.