A histological study of the facial hair follicles in the pygmy sperm whale (Kogia breviceps).

In the pygmy sperm whale (Kogia breviceps, Blainville 1838), vibrissae are present in neonates, but within a few months the hairs are lost, and the structures remain as empty vibrissal crypts (VCs). In this work, we have studied histologically the facial vibrissal follicles of two juveniles and one adult specimens stranded dead. A few VCs with no visible hairs were found grouped in a row rostral to each eye. The follicular lumen, covered by a simple squamous epithelium, showed invaginations in the most superficial part. Beneath the epithelium, the follicle walls were made of loose connective tissue and were encircled by a thick capsule of dense connective tissue. In juveniles, a dermal papilla was found basally and, from it, a non-keratinized pseudo hair grew upwards but did not reach the skin surface. The VCs were richly innervated and irrigated. Many lamellated corpuscles were identified in the subluminal connective tissue of the crypt walls. A large venous cavernous plexus was located beneath and around the hair papilla. The main differences observed in the adult specimen were the degeneration and calcification of both the dermal papilla and the pseudo hair, and the absence of the venous cavernous plexus, albeit maintaining a rich vascularization and innervation. Our study revealed that VCs of the pygmy sperm whale possess features of fully functional sensory structures, with a microanatomy different from those described in other species. In addition, they undergo a postnatal morphological transformation, which implies functional differences between the VCs of neonates and adults.

Visceral leishmaniasis with cardiac involvement in a dog: a case report.

A dog presented with cutaneous nodules, enlarged lymph nodes and oedema in limbs, face and abdomen. The diagnosis of visceral leishmaniasis was established by identification of Leishmania amastigotes within macrophages from skin and popliteal lymph node biopsies. At necropsy, lesions were found in different organs, but it was particularly striking to observe large areas of pallor in the myocardium. Histological examination revealed an intense chronic inflammatory reaction in many organs, and numerous macrophages were found to contain amastigote forms of Leishmania. The inflammatory reaction was especially severe in the heart, where large areas of the myocardium appeared infiltrated with huge numbers of mononuclear immune cells, causing cardiac muscle atrophy and degeneration. Despite the severe inflammation, the number of parasitized macrophages was low in the myocardium, as revealed by immunohistochemical staining of Leishmania amastigotes. Because cardiac involvement is not usually described in this condition, this dog represents a very rare case of canine visceral leishmaniasis with affection of the myocardium.

Pseudorabies virus infection in mink: a host-specific pathogenesis.

Pseudorabies virus (PRV) is an alphaherpesvirus that causes a neurological disease in many wild and domestic animals. The neuropathology elicited by PRV is quite consistent regardless of the host with the only exception of mink, in which it is characterized by a vasculopathy rather than by an encephalitis. In this study, we aimed to investigate the underlying pathogenic mechanism(s) of PRV infection in mink by using immunohistochemistry and laser capture microdissection (LCM) on material from naturally and experimentally infected animals. The inflammatory reaction induced by PRV was minimal or absent not only in the nervous system, where we identified a low number of macrophages and a few T lymphocytes, but also in the primary replication site, the oropharyngeal mucosa; however, the number of PRV-infected cells detected by immunohistochemistry was extremely high both in the peripheral mucosa and in the nervous tissue. On the other hand, the vascular pathology included parenchymal hemorrhages of various degrees and, in specific cortical areas of the brain, fibrinoid degeneration of the capillary walls. Detection of viral antigens by immunohistochemistry revealed infection of endothelial cells of capillaries situated both in the oropharyngeal mucosa and in the brain stem; the presence of PRV DNA in vessels was further demonstrated by PCR performed on LCM samples of brain capillaries. These results can be interpreted as supporting the idea that the different pathology of the disease in mink may be the consequence of an increased endotheliotropism of PRV in this species. Infection of the vessel wall may then lead to vascular pathology and impairment in endothelial cell function, resulting in a weak immune response to infection.

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.

Pseudorabies virus induces a rapid up-regulation of nitric oxide synthases in the nervous system of swine.

Nitric oxide (NO) is a free radical gas with important roles in the host's immune response against viral infections. In this study, we examined the kinetics and distribution of nitric oxide synthase (NOS) expression during the early steps of infection of the porcine nervous system by the alphaherpesvirus pseudorabies virus (PRV). To this end, we examined changes in the expression of the three major NOS isoforms, neuronal NOS (nNOS), endothelial NOS (eNOS) and inducible NOS (iNOS), by immunohistochemistry in the trigeminal ganglia and brain of pigs inoculated intranasally with a virulent PRV strain. The results obtained show that infection of the porcine nervous system by PRV induced a rapid and progressive increment in NOS expression that coincided in timing, location, and magnitude with those of virus propagation in the nervous tissue. A major finding of this study was that PRV caused not only nNOS and iNOS induction in a variety of cell types, but also eNOS up-regulation in endothelial cells and neurons; therefore, all possible sources of NO are activated and probably contribute to the overproduction of NO during infection with the neurotropic alphaherpesvirus PRV in its natural host.

Diversity of the vomeronasal system in mammals: the singularities of the sheep model.

The enormous morphological diversity and heterogeneity of the vomeronasal system (VNS) in mammals--as well as its complete absence in some cases--complicates the extrapolation of data from one species to another, making any physiological and functional conclusions valid for the whole Mammalian Class difficult and risky to draw. Some highly-evolved macrosmatic mammals, like sheep, have been previously used in interesting behavioral studies concerning the main and accessory olfactory systems. However, in this species, certain crucial morphological peculiarities have not until now been considered. Following histological, histochemical and immunohistochemical procedures, we have studied the vomeronasal organ (VNO) and the accessory olfactory bulb (AOB) of adult sheep. We have determined: (1) that all structures which classically define the VNO in mammals are present and well developed, providing the morphological basis for functional activity. (2) that, conversely, there is only a scant population of scattered mitral/tufted cells. One morphological consequence of both details is that the strata of the AOB in adult sheep are not as sharply defined as in other species; moreover, the small number of the mitral/tufted cells in the AOB may imply that the VNS of adult sheep is not capable of functioning in the way a well-developed VNS does in other species. (3) the zone to zone projection from the apical and basal sensory epithelium of the VNO to the anterior and posterior part of the AOB, respectively, typical in rodents, lagomorphs and marsupials, is not present in adult sheep.

The prenatal maturity of the accessory olfactory bulb in pigs.

The morphological development of the accessory olfactory bulb of the fetal pig was studied by classical and histo-chemical methods, and the vomeronasal organ and nasal septum were studied histochemically. Specimens were obtained from an abattoir and their ages estimated from their crown-to-rump length. The accessory olfactory bulb was structurally mature in fetuses of crown-to-rump length 21-23 cm, by which time the lectin Lycopersicum esculentum agglutinin stained the same structures as in adults (in particular, the entire sensory epithelium of the vomeronasal organ, the vomeronasal nerves, and the nervous and glomerular layers of the accessory olfactory bulb). These results suggest that the vomeronasal system of the pig may, like that of vertebrates such as snakes, be functional at birth.

Development of the vomeronasal receptor epithelium and the accessory olfactory bulb in sheep.

The morphological development of the vomeronasal organ (VNO) and accessory olfactory bulb (AOB) of the sheep from anlage to birth were studied by classical and histochemical methods using embryos and fetuses obtained from an abattoir with ages estimated from crown-to-rump length. Both VNO and AOB developed in a biologically logical sequence and completed their morphological development around day 98, at entry into the last third of the gestation period. A lectin with specificity for oligomeric N-acetylglucosamine labeled the sensory epithelium of the VNO, the vomeronasal nerves, and the nervous and glomerular layers of the AOB before birth. These results suggest that the vomeronasal system, which is well developed and functional in adult sheep, may be able to function at or even before birth in these animals (whereas in rodents, for example, this is precluded by the AOB not completing its development until after birth).

Morphogenesis and growth of the soft tissue and cartilage of the vomeronasal organ in pigs.

The morphology of the soft tissue and supporting cartilage of the vomeronasal organ of the fetal pig was studied from early stages to term. Specimens obtained from an abattoir were aged by crown-to-rump distance. Series of transverse sections show that some time before birth all structures--cartilage, connective tissue, blood vessels, nerves, glands and epithelia--are well developed and very similar in appearance to those of the adult. Furthermore, in transmission electron microscopy photomicrographs obtained at this stage the vomeronasal glands exhibit secretory activity.

L-particle production during primary replication of pseudorabies virus in the nasal mucosa of swine.

Different tissue culture cell lines infected with a number of alphaherpesviruses produce, in addition to virions, light particles (L particles). L particles are composed of the envelope and tegument components of the virion but totally lack the proteins of the capsid and the virus genome; therefore, they are noninfectious. In this electron microscopy report, we show that L particles are produced during primary replication of the alphaherpesvirus pseudorabies virus (PRV) in the nasal mucosa of experimentally infected swine, its natural host. Although PRV infected different types of cells of the respiratory and olfactory mucosae, PRV L particles were found to be produced exclusively by epithelial cells and fibroblasts. We observed that formation of noninfectious particles occurred by budding of condensed tegument at the inner nuclear membrane and at membranes of cytoplasmic vesicles, resulting in intracisternal and intravesicular L particles, respectively. Both forms of capsidless particles were clearly distinguishable by the presence of prominent surface projections on the envelope and the higher electron density of the tegument, morphological features which were only observed in intravesicular L particles. Moreover, intravesicular but not intracisternal L particles were found to be released by exocytosis and were also identified extracellularly. Comparative analysis between PRV virion and L-particle morphogenesis indicates that both types of virus particles share a common intracellular pathway of assembly and egress but that they show different production patterns during the replication cycle of PRV.