The vomeronasal duct has a protracted postnatal development in the mouse

Recent evidence suggests that the accessory olfactory system (AOS) may mediate chemoreception before birth. Such a capability may allow the fetus to begin to sample chemical stimuli from the outside world, a possibility that has important developmental and evolutionary implications. Herein we describe the development in the mouse of the duct that connects the vomeronasal organ (VNO), containing the primary receptor neurons of the AOS, with the nasal cavity and thus with external stimuli. Twenty-four mice, four at each of six different ages from the last day of gestation through 25 days of age, were fixed and embedded in glycol methacrylate. Serial sections were examined under the light microscope so that the VNO duct could be reconstructed in three dimensions. Results confirm an earlier study which demonstrated that the VNO duct is not patent before birth. The duct becomes patent sometime after the first day of life but remains in an immature condition throughout the normal prepubertal period. During this period the duct is characterized by an internal surface that is rapidly desquamating such that the lumen of the duct contains sloughed tissue. These results suggest that the VNO is unlikely to function in the prenatal period, since the route for external stimuli to reach its receptor surface is blocked. The protracted period of VNO duct development reported here is consistent with the great bulk of data on the AOS of mammals which firmly establishes its role in the detection of pheromones which coordinate reproduction. © 1993 Wiley-Liss, Inc.     

Magnetic resonance imaging of the vomeronasal organ

The vomeronasal organ of mice and frogs was studied by highspatial resolution magnetic resonance imaging. By this techniquethe presence of material in the vomeronasal lumen can be evidencedin vivo.     

The vomeronasal organ of the male ferret.

The vomeronasal organ (VNO) is known to play a major role in sexual behavior in many mammals. This study is the first report that the adult male ferret has a VNO, which is considerably smaller and morphologically different from the usually crescent-shaped epithelium in several mammalian species, particularly rodents. There were no differences in the size or structure of the ferret VNO between the mating season in spring and the sexually quiescent season in autumn, although plasma testosterone, testis size and brain size are dramatically increased in spring and behavior changes significantly. The histological data suggest that the VNO might be not as important a structure in male ferret sexual behavior as in rodents.     

The flow of bile in the human cystic duct

Clinical studies suggest that the flow of bile in the biliary system may be a contributing factor in the pathogenesis of cholelithiasis, but little is known about its transport mechanism. This paper reports a numerical study of steady flow in human cystic duct models. In order to obtain parametric data on the effects of various anatomical features in the cystic duct, idealised models were constructed, first with staggered baffles in a channel to represent the valves of Heister and lumen. The qualitative consistency of these findings are validated by modelling two of the real cystic ducts obtained from operative cholangiograms. Three-dimensional (3D) models were also constructed to further verify the two-dimensional (2D) results. It was found that the most significant geometric parameter affecting resistance is the baffle clearance (lumen size), followed by the number of baffles (number of folds in the valves of Heister), whilst the least significant ones are the curvature of the cystic duct and the angle between the neck and the gallbladder. The study presented here forms part of a larger project to understand the functions of the human cystic duct, especially the influence of its various anatomical structures on the resistance to bile flow, so that it may aid the assessment of the risk of stone formation in the gallbladder.     

Histoarchitecture of the human parotid duct. Light-microscopic study

A light-microscopical study of the histoarchitecture of the human parotid duct was carried out. The parotid duct, much like other excretory passages, possessed three histological coats: mucosa, muscular layer and adventitia. The mucous epithelium was composed of the innermost tall columnar cells and the basal cubical cells. Numerous, circular elastic fibers were in close vicinity to the epithelium. The muscular layer consisted of smooth muscular fibers running in longitudinal direction. The adventitia consisted of lipofibrous connective tissue and contained many vessels. The result of the present study suggests that the parotid duct contributes to control of salivary secretion, since its architecture is basically similar to that of other excretory passages which have peristaltic activity.     

Microvasculature of the human testis and excurrent duct system

Summary The vascular microarchitecture of the human testis and excurrent duct system was examined by use of a casting method combined with scanning electron microscopy. In the testicular parenchyma, the capillaries form a fine plexus around the seminiferous tubules. The commonly described rope-ladder-like pattern of the peritubular capillaries is absent in the human testis. The microvasculature of the rete testis consists of a poorly organized plexus. Throughout the epididymis including the ductuli efferentes, the peritubular capillary network encircles each tubule cylindrically. In the cauda epididymidis, a coarse venous network surrounds the capillary network externally. Small arteries of the epididymis not only penetrate the connective tissue septa, but also run along the surface. In the ductus deferens, three distinct microvascular systems are distinguished: (1) a venous network located in the connective tissue surrounding the muscular coat, (2) a microvascular plexus within the muscular coat, and (3) a peritubular capillary network. The plexus within the muscular coat interconnects the venous and the peritubular capillary networks.     

Presence of the vomeronasal system in aquatic salamanders

Previous reports have indicated that members of the proteid family of salamanders lack a vomeronasal system, and this absence has been interpreted as representing the ancestral condition for aquatic amphibians. I examined the anatomy of the nasal cavities, nasal epithelia, and forebrains of members of the proteid family, mudpuppies (Necturus maculosus), as well as members of the amphiumid and sirenid families (Amphiuma tridactylum and Siren intermedia). Using a combination of light and transmission electron microscopy, I found no evidence that mudpuppies possess a vomeronasal system, but found that amphiuma and sirens possess both vomeronasal and olfactory systems. Amphiumids and sirenids are considered to be outgroups relative to proteids; therefore, these data indicate that the vomeronasal system is generally present in salamanders and has been lost in mudpuppies. Given that the vomeronasal system is generally present in aquatic amphibians, and that the last common ancestor of amphibians and amniotes is believed to have been fully aquatic, I conclude that the vomeronasal system arose in aquatic tetrapods and did not originate as an adaptation to terrestrial life. This conclusion has important implications for the hypothesis that the vomeronasal organ is specialized for detection of non-volatile compounds.     

Improvement of the vomeronasal organ ablation in the rat

The vomeronasal organ (VNO) in most mammalian species consists of a bilaterally paired tubular structure lying on either side at the base of the nasal septum. Functionally, the VNO receives chemosensory informations and conveys it to its parts of the hypothalamus thought to be important in the regulation of reproductive physiology and behavioral functions. Here the authors report an improvement of the VNO ablation in the rat. With the exception of restraint of a rat, this operation method is fundamentally similar to those reported by Saito and Mennella (1986). The rat was anesthetized and placed supine on a home-made operating board with some accessories, and its extremities and head were fixed. It should be emphasized that the restraint of its lower incisor and tongue to keep the mouth open was performed with home-made restraint devices. The above method enabled us to remove the VNO easily. In addition, it could be useful in this field of oral surgery in small animals.     

Imaging and the new fabric of the human body

A short historical survey recalls the main techniques of medical imaging, based on modern physico-chemistry and computer science. Imagery has provided novel visions of the inside of the body, which are not self-obvious but require a training of the gaze. Yet, these new images have permeated the contemporary mind and inspired esthetic ventures. The popularity of these images may be related to their ambiguous status, between real and virtual. The images, reminiscent of Vesalius' De humani corporis fabrica, crosslink art, science and society in a specific way: which role will they play in the "empowerment" of the tomorrow patient?     

Chiropteran vomeronasal complex and the interfamilial relationships of bats

Within the extant orders of living mammals, the distribution of the vomeronasal organ (VNO) and associated structures is very stable, being universally present in the vast majority or universally absent in cetaceans and sirenians. Chiroptera is the most noteworthy exception, with variation in the absence or presence of the vomeronasal complex occurring even at the species level in some instances. The VNO and/or its component structures, such as the accessory olfactory bulb, were studied in serially sectioned snouts and brains from 114 genera and 292 species representing all extant chiropteran families except Myzopodidae and Antrozoidae. Taxa were scored for the following characters: (1) degree of formation of the vomeronasal epithelial tube, (2) shape of the vomeronasal cartilage, (3) occurrence of the nasopalatine duct, and (4) occurrence of the accessory olfactory bulb. To reconstruct the evolutionary history of the bat vomeronasal complex, the distributions of these four characters were mapped, using the computer program MacClade, onto chiropteran phylogenies in the literature derived from other data sets. In all phylogenies, these four characters exhibit a high degree of homoplasy, only part of which is accounted for by several polymorphic taxa. However, perhaps the most remarkable result is that in the most parsimonious solutions the absence of the vomeronasal epithelial tube and accessory olfactory bulb is identified as primitive for Chiroptera, with both structures reevolving numerous times: such a scenario would be unique to bats among mammals. An alternative, though less parsimonious interpretation, which does not require reevolution of this very complex system, is that a well-developed vomeronasal epithelial tube is primitive for Chiroptera, as in nearly all other orders of mammals, but has been reduced or lost in the majority of families. Explication of the peculiar evolutionary history of the vomeronasal system in bats awaits studies on the adult morphology in the more than 630 species not yet examined and, in particular, on ontogeny, which to date is known for only a handful of taxa.A preliminary account of this research was presented at the Tenth International Bat Research Conference and Twenty-Fifth North American Bat Research Symposium held at Boston University, Massachusetts, on 6–11 August 1995.     

The vomeronasal epithelia of NMRI mouse

Summary The features of the apical and lateral surfaces of cells of the vomeronasal epithelium were studied in adult male mice by scanning electron microscopy. Supporting cells and receptor cells of the neuroepithelium are covered with microvilli. Microvilli of the sensory cells are longer and thinner than those of the supporting cells. Additionally, the former differ in local distribution, orientation, occurrence of branching and appearance of the cell coat. The receptor-free epithelium consists most likely of one cell type only, which shows different structural modifications including the presence, number and length of microvilli and cilia. In the transitional region, between the neuroepithelium and the receptor-free epithelium, immature receptor cells are present.This paper is dedicated to Prof. A. JinoSupported by grants from the Alexander von Humboldt-Stiftung and the Deutsche Forschungsgemeinschaft (Br. 358/5-1)     

High-resolution magnetic resonance spectroscopy of the mouse vomeronasal organ

The chemical composition of the vomeronasal organ (VNO) was investigated by means of in vitro proton magnetic resonance spectroscopy (MRS) in prepubertal and adult mice of both sexes. Results demonstrate that MRS detects several chemical constituents in the VNO, showing their age- and sex-associated changes in concentration. Preliminary experiments also suggest the ability of MRS to show compositional changes in the VNO after pheromonal stimulation. MRS can serve as a useful technique to investigate vomeronasal chemoreception.     

Encoding pheromonal signals in the mammalian vomeronasal system

The past few years have delivered substantial progress in understanding the molecular logic of the mammalian vomeronasal system. Selective expression of vomeronasal receptors and high response selectivity of vomeronasal receptor neurons suggest that pheromones are encoded by labeled lines at the level of the vomeronasal organ: each pheromonal compound is represented by the activation of a small and exclusive subset of receptor neurons. Labeled lines might be transferred to the accessory olfactory bulb through convergent connections. The key challenges ahead will be to identify the pheromonal ligands of the receptors and unravel the functional connectivity from the vomeronasal organ to the hypothalamus.     

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.