Brain Pathology in Adult Rats Treated With Domoic Acid.

Domoic acid (DA) is a neurotoxin reported to produce damage to the hippocampus, which plays an important role in memory. The authors inoculated rats intraperitoneally with an effective toxic dose of DA to study the distribution of the toxin in major internal organs by using immunohistochemistry, as well as to evaluate the induced pathology by means of histopathologic and immunohistochemical methods at different time points after toxin administration (6, 10, and 24 hours; 5 and 54 days). DA was detected by immunohistochemistry exclusively in pyramidal neurons of the hippocampus at 6 and 10 hours after dosing. Lesions induced by DA were prominent at 5 days following treatment in selected regions of the brain: hippocampus, amygdala, piriform and perirhinal cortices, olfactory tubercle, septal nuclei, and thalamus. The authors found 2 types of lesions: delayed death of selective neurons and large areas of necrosis, both accompanied by astrocytosis and microgliosis. At 54 days after DA exposure, the pathology was characterized by still-distinguishable dying neurons, calcified lesions in the thalamus, persistent astrocytosis, and pronounced microgliosis. The expression of nitric oxide synthases suggests a role for nitric oxide in the pathogenesis of neuronal degeneration and chronic inflammation induced by DA in the brain.

Histochemical identification of carbohydrate moieties in the accessory olfactory bulb of the mouse using a panel of lectins.

Lectin binding patterns in the olfactory bulb of the mouse were investigated using 12 biotinylated lectins. Three, with specificities for galactose, N-acetylgalactosamine and L-fucose, stained only the nervous and glomerular layers of the accessory olfactory bulb; four, with specificities for galactose or N-acetylglucosamine, stained these layers in both the accessory and the main olfactory bulbs; three, with specificities for N-acetylgalactosamine or L-fucose, effected general staining with little contrast between the background and the accessory olfactory bulb or other structures; the remaining two, both of them specific for mannose, stained no part of the tissue studied. In the nervous and glomerular layers of the accessory olfactory bulb six lectins stained the anterior and posterior halves with different intensities and two of these six similarly differentiated between rostral and caudal regions of the posterior half. We conclude that: (i) three lectins binding to different monosaccharides are specific stains for the vomeronasal system when used in this area of the mouse brain; (ii) it may be appropriate to distinguish three parts in the mouse accessory olfactory bulb, instead of the hitherto generally accepted two.

A descriptive and comparative lectin histochemical study of the vomeronasal system in pigs and sheep.

The accessory olfactory bulb (AOB) is the primary target of the sensory epithelium of the vomeronasal organ (VNO), and thus constitutes a fundamental component of the accessory olfactory system, which is involved in responses to behaviour-related olfactory stimuli. In this study we investigated the characteristics of the AOB, VNO, vomeronasal nerves (VNNs) and caudal nasal nerve (CdNN) in pigs and sheep, species in which olfaction plays a key behavioural role both in the neonatal period and in adulthood. The patterns of staining of the AOB by the Bandeiraea simplicifolia and Lycopersicon esculentum lectins were the same in the 2 species, whereas the Ulex europeus and Dolichos biflorus lectins gave different patterns. In both species, lectin staining of the AOB was consistent with that of the VNNs, while the CdNN did not label any of the structures studied. The entire sensory epithelium of the pig was labelled by Ulex europeus and Lycopersicum esculentum lectins, and all 4 lectins used labelled the mucomicrovillar surface of the sensory epithelium in sheep.

The accessory olfactory bulb of the mink, Mustela vison: a morphological and lectin histochemical study.

The distribution of binding sites for the lectins Ulex europaeus agglutinin I, Soybean agglutinin, Bandeiraea simplicifolia agglutinin I-isolectin B4, and Vicia villosa agglutinin in the mink olfactory bulb was investigated. All lectins except Ulex europaeus agglutinin I bound exclusively and systematically to a single area of the olfactory bulb. This area corresponded to that in which the vomeronasal nerves terminate, indicating that it is the accessory olfactory bulb, as confirmed by microdissection and by the study of transverse and parasagittal series of the olfactory bulb. The results, moreover, indicate that the accessory olfactory bulb of the mink comprises three isolated eminences, the largest in the dorsal part of the olfactory bulb, and the other two in the lateral and medial parts.

Origin and regional distribution of the arterial vessels of the vomeronasal organ in the sheep. A methodological investigation with scanning electron microscopy and cutting-grinding technique.

The origin and location of the arteries of the vomeronasal organ (VNO) in the sheep were studied by means of dissection, scanning electron microscopy of corrosion casts, and the cutting-grinding technique after injection with Araldite CY23-HY2967 via one of the carotid arteries. Dissection revealed that the most ventral of the three main branches of the sphenopalatine artery is responsible for the blood supply to the VNO. Scanning electron microscopy of corrosion casts revealed that the arterioles of the vomeronasal organ form a microvascular network. Cross sections of the region of the nasal cavity containing the VNO, obtained by the cutting-grinding technique, showed that the arterioles of the vomeronasal plexus are located medial and ventral to the vomeronasal duct. These results confirm the usefulness of the cutting-grinding technique as a complementary procedure in morphological studies of structures containing hard tissues.

The soft-tissue components of the vomeronasal organ in pigs, cows and horses.

The soft-tissue components of the vomeronasal organ of the pig, the cow and the horse were studied with the aid of dissection, microdissection, and light microscopy and immunohistochemistry of series of transverse sections. In horses, the rostral end of the incisive duct was blind: thus, unlike in pigs and cows, there was no communication between the vomeronasal organ and the oral cavity. In all three species, the central part of the vomeronasal duct bore the 'typical' respiratory/ receptor epithelium lining on its lateral and medical walls. The rostral part of the duct was characterized by stratified columnar epithelium, while more caudal parts bore simple columnar type. The patterns of distribution of glands, blood vessels and nerves were closely associated with the patterns of distribution of duct linings. The distribution of soft-tissue components in pigs was less clearly defined than in cows and horses. Of the three species, nerves were detected in the rostral half of the vomeronasal parenchyma only in the horse.

The organization of pyramidal cells in area 18 of the rhesus monkey.

The aim of this study was to investigate the vertical organization of axons and pyramidal cells in area 18, and to compare it with that in area 17. In area 18 there are regularly spaced vertical bundles of myelinated axons that have an average center-to-center spacing of 21 microns. This arrangement of axons resembles that in area 17. Pyramidal cells in area 18 and their apical dendrites are less regularly arranged. The apical dendrites of the pyramidal cells of layer 6A aggregate with those from layer 5 pyramids to form swathes of apical dendrites that pass into layer 4. There they are joined by the apical dendrites of the small layer 4 pyramids, so that much of the neuropil of layer 4 is occupied by apical dendrites. Most of these apical dendrites form their terminal tufts in layer 3. Very few of them reach layer 1, which is dominated by the apical dendrites of layer 2/3 pyramids. Thus, there are two tiers of apical dendrites and their apical tufts, a deep one formed by the layer 4, 5 and 6 apical dendrites that terminate in layer 3, and a second one formed by the apical dendrites of layer 2/3 pyramids that terminate in layer 1. In contrast, in area 17 the apical dendrites of layer 5 pyramids form discrete clusters that have a center-to-center spacing of 23 microns. These clusters are joined by the apical dendrites of the layer 2/3 pyramids and all of these apical dendrites form their apical tufts in layer 1. Based upon the dispositions of the apical dendrites of the pyramidal cells in area 17 and 18, we speculate that the influences of, and the interactions between, the feed-forward and feed-back signals in the two areas are quite different, because in the two areas different postsynaptic targets are available to these afferents.

Distribution of the arterial supply to the vomeronasal organ in the cat.

BACKGROUND: The main goal of this work was to investigate the general distribution of arterial blood around and inside the vomeronasal organ (VNO) of the cat. METHODS: Macro- and microdissection methods together with light and scanning electron microscopy were used. Heads were injected with an India ink/agar mixture (the VNO subsequently being cut in transverse, sagittal and horizontal sections), with clear latex (the VNO subsequently being cut in transverse sections), or with an epoxy resin to obtain casts for examination by scanning electron microscopy. RESULTS: Dissection and microdissection show that the infraorbital, minor palatine, and descending palatine arteries have a common origin, rostral to the Rete mirabile arteria maxillaris. In transverse series and in the rostral half of the VNO, an arteriole is consistently observed between the vomeronasal duct and the lateral sheet of the vomeronasal cartilage. In this same segment, arterial branches with different orientations (perpendicular, horizontal, or transverse with respect to the main axis of the organ) are observed. Scanning electron microscopy of arterial casts shows that arterial vessels of the mucosa of the nasal septum have a direct relationship with the VNO. CONCLUSIONS: Branches of the sphenopalatine artery are the chief route of blood supply to the VNO. The vomeronasal parenchyma has few arterial vessels, and these are usually situated in the same position. Differences observed between the arteries inside and outside the VNO and the dilation of both by isoproterenol support the idea that the VNO is similar to erectile tissue organs and that it may act as a physiological pump.

The vomeronasal organ of the cat.

The vomeronasal organ of the cat was studied macroscopically, by light microscopy and by immunohistochemical techniques. Special attention was paid to the general distribution of the various soft tissue components of this organ (duct, glands, connective tissue, blood vessels and nerves.) Examination of series of transverse sections showed that the wall of the vomeronasal duct bears 44 different types of epithelium: simple columnar in the caudal part of the duct, respiratory and receptor respectively on the lateral and medial walls of the middle part of the duct, and stratified squamous rostrally. The pattern of distribution of other soft tissue components was closely associated with that of epithelium types. In areas where the duct wall was lined with receptor epithelium, nerves and connective tissue were present between the epithelium and the medial sheet of the vomeronasal cartilage. Most glands and blood vessels were located lateral to those areas of the duct wall lined with respiratory epithelium. Numerous basal cells were present in the sensory epithelium. Understanding of the distribution of the soft tissue components of this organ may shed light on its function.

Comparative anatomy of the vomeronasal cartilage in mammals: mink, cat, dog, pig, cow and horse.

The vomeronasal cartilages of mink, cat, dog, pig, cow and horse were studied by dissection, microdissection and by means of series of transverse sections. In all the species studied the cartilage is of hyaline type and the medial sheet is well-defined and perfectly moulded to the adjacent bone. However, interspecies differences are apparent in the manner in which the medial sheet associates and eventually fuses with the cartilage of the incisive duct; the morphology of the horse vomeronasal cartilage is particularly distinctive in this respect. The lateral sheet of the vomeronasal cartilage, although always present, has a different arrangement in each species studied. Similarly, the gaps in the lateral sheet (corresponding to the opening of the vomeronasal organ) differ among the species studied in form, location and number.

Structural, morphometric, and immunohistological study of the accessory olfactory bulb in the dog.

BACKGROUND: The study of the morphological, morphometric, and immunohistological characteristics of the accessory olfactory bulb (AOB) in the dog is the main goal of this work. METHODS: Horizontal sections of the AOB where stained by four different methods (haematoxilin/eosin, Tolivia, Nissl, and Bielchowsky). The avidin-biotin-peroxidase complex (ABC) was used, whereas the monoclonal antibodies to neuron-specific enolase, neurofilaments, glial fibrillary acidic protein, and synaptophysin were selected for the immunohistological study. A computer-assisted image analysis was employed in order to define the morphometric characteristics of de AOB. RESULTS: The general morphology of the AOB indicates that it comprises a thick glomerular layer and a thinner internal layer containing mitral/tufted, granular, and glial cells. The mitral/tufted cells have large pale-staining nuclei with intensely staining nucleoli. There does not appear to be a clearly defined granular layer. No reactivity with antibodies to neuron-specific enolase or to neurofilaments was observed in any part of the AOB, but there was some reactivity with an antibody to glial fibrillary acidic protein and widespread reactivity with an antibody to synaptophysin. CONCLUSIONS: The stratification of the AOB is simpler and less well defined than that of the main olfactory bulb (MOB), unlike in rodents in which the structure of the AOB corresponds closely to that of the MOB. According to the scale of Frahm and Bhatnagar (1980. J. Anat., 130: 349-365) the AOB of the adult dog has an intermediate position.

The vomeronasal system of the mink, Mustela vison. I. The vomeronasal organ.

The vomeronasal organ (VNO) of the mink is restricted to the area of the Fissura palatina and thus always topographically related to the Ductus incisivus (DI). The VNO and DI have also a functional relation because the vomeronasal duct ends in the incisive duct. On the other hand, as the DI has its mouth in the Papilla incisiva there is a communication between the VNO and the oral cavity. The vomeronasal cartilage, approximately in 1/6 of its length, wraps completely the parenchyma of the VNO whose main structure is the vomeronasal duct, with two different epithelia: sensory receptor in the medial wall, and respiratory in the lateral one. Nevertheless the variations of epithelia belong to the segment of the duct because in its rostral and caudal parts the medial and lateral epithelia are very similar. Branches and tubular PAS positive glands stand out in three points: superior, inferior and medial areas of the vomeronasal duct in which they end. An important number of vessels, mainly veins of different diameter, are located around the duct, while the nervous fibers are close to the medial wall of the duct and very easy to identify in the caudal third of the organ. Two immunohistochemical techniques were used to identify the nerve fibers and the receptor cells.

Anatomical and immunohistological demonstration of the primary neural connections of the vomeronasal organ in the dog.

Macro- and microdissection methods together with conventional histology and lectin immunohistochemistry have been used to identify the course of the vomeronasal nerves and their site of termination (accessory olfactory bulb; AOB) in the dog. The AOB in this species is small and variable in size, situated on the medial surface of the main olfactory bulb, and has an anatomical structure unlike that described for other mammals. The vomeronasal nerves and their terminal glomeruli in the AOB are easily identifiable by selective immunohistochemical staining using Ulex europeus agglutinin I.

The nucleus of the tractus solitarius of the dog. A morphological and morphometric analysis.

The neuronal and fibrous architecture of the nucleus of the tractus solitarius (NTS) of the dog has been studied in transversely cut Nissl, myelin and reduced silver stained serial sections. Eight distinct subdivisions, clearly delimited both by their cytoarchitectonic and fibrous characteristics, have been identified. They are: the commissural, gelatinous, lateral, interstitial, dorsolateral, ventrolateral, intermediate and medial subdivisions. Their rostrocaudal extensions and locations in relation to the obex are summarised in Table 1. A morphometric analysis was additionally done. The frequency distributions of cell areas and cell form factor of each subdivision are represented by histograms in Figures 8 and 9 respectively.

Vascularization of the vomeronasal organ in the dog.

Blood is led to the vomeronasal organ via the large palatine and sphenopalatine arteries and returns via the veins of the same names. Under the microscope, transverse sections exhibit large numbers of veins and lymph vessels and relatively few arteries. The prominent veins are characterized by their thick, muscular wall; the arteries are smaller in proportion and likewise muscular, while the typical lymph vessels are dilated in sections of organ prepared by injection of latex or Araldite. Due to the presence of erectile tissue, the arrangement of the parenchyma depends on the functional state of the organ.

Macroscopical and microscopical anatomy of the hippocampus in the dog.

In this article we have studied the topography, relationship and projection of the hippocampus in the dog by means of 1 mm thick transverse, horizontal and parasagital sections stained with Mulligan's reagent and 50 microns transverse sections (Nissl). The macroscopical disposition of this part of the CNS was completed by means of a gross dissection. Horizontal sections of 10 microns through the middle or limbic part were used to determine the general microscopic anatomy and to define the morphometry of its cells. From this point of view the Hippocampus of the dog appears to be intermediate between the rat and primates, species better studied.

The thalamus of the dog: a tridimensional and cytoarchitectonic study.

The organization of the thalamus varies considerably from species to species. This article reports a tridimensional study of the canine thalamus in which 18 nuclei were distinguished on the basis of their delimitation in sections and their differing cytoarchitectonic characteristics, the latter having been objectively quantified by means of an image analyser. On the basis of their location and/or mutual similarities, these 18 nuclei are classified in 5 groups. The thalamus of the dog is similar to that the cat, but differs considerably from those of other well-studied species.

Spavin: a proposed term for a non-fracture associated canine hock lesion.

In accordance with macroscopic and microscopic features of the tarsal joint degeneration in the greyhound dog, the possibility of establishing a direct relation between this process and spavin or bone spavin is proposed. To date this has been considered limited to equine and occasionally bovine stock. This investigation has been carried out on three different levels: macroscopic, radiological and histological and has been completed with the corresponding graphic documentation.