Study on the Role of Histochemical Stains in Identifying Merkel Cells in Dogs

Merkel cells (MCs) are neuroendocrine cells involved with tactile sense, growth, differentiation, and homeostasis of the skin as well as in different cutaneous diseases. Specific staining techniques are required for their identification because they are not easily visible in paraffin sections stained with hematoxylin and eosin. The present study assess the histochemical features of the MCs in dogs comparing with those described for other mammals in the literature and with the use of immunohistochemistry. A systematic study of samples from MCs-rich areas from healthy dogs was carried out by use of several histologic stains, including metachromatic staining, silver stains, methylene blue, periodic acid-Schiff stain, and osmium-based staining method. MCs were detected by the Grimelius argyrophilic stain in 86.7% of the specimens. The staining was showed as dark-brown granular cytoplasmic and consistently polarized to the basal cell cytoplasm matching with the cellular distribution of the characteristic neurosecretory granules. Some modifications in the standard staining protocol, including rinsing, silver reimpregnation, and counterstain dye, enhanced the MCs identification in stratified squamous epithelium. When compared with Cytokeratin 20-immunolabeled serial sections several MCs appeared nonstained with the argyrophilic method. These differences in MC numbers between stains were statistically significant. Other histologic stains failed to identify MCs in the specimens. The results of this study indicate that Grimelius argyrophilic stain is a suitable method for demonstration of MCs in the stratified squamous epithelium of skin and mucosa. Discussion on its utility when compared with immunohistochemistry and a review of the scientific literature is also presented. Anat Rec, 302:1458-1464, 2019. © 2018 Wiley Periodicals, Inc.

Mandibular odontogenic sarcoma (ameloblastic fibrodentinosarcoma) in an aged cat - Short communication

A 13-year-old male cat presented with an ill-defined mass in the rostral mandible causing destruction and loss of alveolar bone. Microscopically, the mass consisted of cords or islands of benign odontogenic epithelium and a malignant, pleomorphic spindle-shaped cell component with dysplastic dentine formation. Immunohistochemically, neoplastic mesenchymal cells proved to be strongly positive for vimentin and negative for cytokeratins, desmin, actin and S100 protein; the Ki67 proliferation index was high. Morphological and immunohistochemical features largely overlap those reported for ameloblastic fibrodentinosarcoma, an uncommon histologic subtype of odontogenic sarcoma recognised in humans but no reported previously in animals. Ki-67 expression assessment may help to discriminate between malignant and benign forms of odontogenic tumours but the final diagnosis is mainly morphological.

Assessing Marine Microbial Induced Corrosion at Santa Catalina Island, California

High iron and eutrophic conditions are reported as environmental factors leading to accelerated low-water corrosion, an enhanced form of near-shore microbial induced corrosion. To explore this hypothesis, we deployed flow-through colonization systems in laboratory-based aquarium tanks under a continuous flow of surface seawater from Santa Catalina Island, CA, USA, for periods of 2 and 6 months. Substrates consisted of mild steel – a major constituent of maritime infrastructure – and the naturally occurring iron sulfide mineral pyrite. Four conditions were tested: free-venting “high-flux” conditions; a “stagnant” condition; an “active” flow-through condition with seawater slowly pumped over the substrates; and an “enrichment” condition where the slow pumping of seawater was supplemented with nutrient rich medium. Electron microscopy analyses of the 2-month high flux incubations document coating of substrates with “twisted stalks,” resembling iron oxyhydroxide bioprecipitates made by marine neutrophilic Fe-oxidizing bacteria (FeOB). Six-month incubations exhibit increased biofilm and substrate corrosion in the active flow and nutrient enriched conditions relative to the stagnant condition. A scarcity of twisted stalks was observed for all 6 month slow-flow conditions compared to the high-flux condition, which may be attributable to oxygen concentrations in the slow-flux conditions being prohibitively low for sustained growth of stalk-producing bacteria. All substrates developed microbial communities reflective of the original seawater input, as based on 16S rRNA gene sequencing. Deltaproteobacteria sequences increased in relative abundance in the active flow and nutrient enrichment conditions, whereas Gammaproteobacteria sequences were relatively more abundant in the stagnant condition. These results indicate that (i) high-flux incubations with higher oxygen availability favor the development of biofilms with twisted stalks resembling those of marine neutrophilic FeOB and (ii) long-term nutrient stimulation results in substrate corrosion and biofilms with different bacterial community composition and structure relative to stagnant and non-nutritionally enhanced incubations. Similar microbial succession scenarios, involving increases in nutritional input leading to the proliferation of anaerobic iron and sulfur-cycling guilds, may occur at the nearby Port of Los Angeles and cause potential damage to maritime port infrastructure.

Sudden Death Associated with Clostridium sordellii in Captive Lions (Panthera leo)

In the spring of 2003, a series of sudden deaths in a group of adult lions ( Panthera leo) with a previous history of depression, inanition, and lethargy, was investigated. Five animals died within 24 to 36 hours after onset of signs of disease. Serologic screening for viral disease detection was negative, evidence of parasites was not detected, and results of a complete blood count and serum biochemical analysis were within reference intervals in all lions. The most relevant lesions observed were multiple areas of necrosis and hemorrhage in the intestinal outer muscular layer, and cellulitis with an intense bloody edema in the mesenteric and the pericardial fat tissue. On the basis of the fulminant course of the disease, the gross and histologic findings, and the isolation and identification of Clostridium sordellii, a diagnosis of infectious myositis and cellulitis associated with acute clostridiosis was made. To the authors' knowledge, this is the first report of sudden death associated with C. sordellii in felines.

Temperature and Redox Effect on Mineral Colonization in Juan de Fuca Ridge Flank Subsurface Crustal Fluids

To examine microbe-mineral interactions in subsurface oceanic crust, we evaluated microbial colonization on crustal minerals that were incubated in borehole fluids for 1 year at the seafloor wellhead of a crustal borehole observatory (IODP Hole U1301A, Juan de Fuca Ridge flank) as compared to an experiment that was not exposed to subsurface crustal fluids (at nearby IODP Hole U1301B). In comparison to previous studies at these same sites, this approach allowed assessment of the effects of temperature, fluid chemistry, and/or mineralogy on colonization patterns of different mineral substrates, and an opportunity to verify the approach of deploying colonization experiments at an observatory wellhead at the seafloor instead of within the borehole. The Hole U1301B deployment did not have biofilm growth, based on microscopy and DNA extraction, thereby confirming the integrity of the colonization design against bottom seawater intrusion. In contrast, the Hole U1301A deployment supported biofilms dominated by Epsilonproteobacteria (43.5% of 370 16S rRNA gene clone sequences) and Gammaproteobacteria (29.3%). Sequence analysis revealed overlap in microbial communities between different minerals incubated at the Hole U1301A wellhead, indicating that mineralogy did not separate biofilm structure within the 1-year colonization experiment. Differences in the Hole U1301A wellhead biofilm community composition relative to previous studies from within the borehole using similar mineral substrates suggest that temperature and the diffusion of dissolved oxygen through plastic components influenced the mineral colonization experiments positioned at the wellhead. This highlights the capacity of low abundance crustal fluid taxa to rapidly establish communities on diverse mineral substrates under changing environmental conditions such as from temperature and oxygen.

Ultrastructural characterization of normal Merkel cells in the dog

BACKGROUND

Involvement of Merkel cells (MKs) in different cutaneous diseases as well as in the growth, differentiation and homeostasis of the skin has been previously documented.

HYPOTHESIS/OBJECTIVES

The aim was to assess the ultrastructural features of MKs in canine skin, including morphometrics, highlighting their similarities with and differences from those described for other mammals.

ANIMALS

Hard palate, nasal planum, lower lip and whisker pad samples were taken from two healthy young dogs destined for academic purposes.

METHODS

Ultrathin sections of samples fixed in osmium tetroxide and embedded in Epon 812 resin were stained with uranyl acetate and lead citrate and examined using a JEOL JEM 2010 transmission electron microscope.

RESULTS

Ultrastructural characteristics included the following: (i) arrangement in clusters in the basal layer of the epidermis, oral mucosa and external follicular root sheath; (ii) inconstant link with nerve terminal; (iii) oval (10.27 ± 1.64 μm major axis) cell shape with large lobulated nuclei (5.98 ± 1.16 μm major axis); (iv) spine-like and thick cytoplasmic processes interdigitating with surrounding keratinocytes; (v) presence of desmosomes in the cell body or at the base of spine-like processes attaching to neighbouring keratinocytes; and (vi) cytoplasm containing loosely arranged intermediate filaments (10.04 ± 1.17 nm) and numerous dense-core granules (100.1 ± 17.12 nm) arranged in the basal portion of the cytoplasm.

CONCLUSIONS AND CLINICAL IMPORTANCE

This study provides the first complete description of the ultrastructural characteristics of MKs in the dog, enhancing our knowledge of the skin structure in this species and providing a basis for future physiological and pathological studies of the role of these cells in normal and damaged canine tissues.

Adrenohepatic fusion in domestic ferrets (Mustela putorius furo)

We describe two cases of adrenohepatic fusion (AHF) in domestic ferrets (Mustela putorius furo). This condition is defined as the union of hepatic tissue with the adrenal gland with close fusion of the respective parenchymal cells and lack of a fibrous capsule between the two cell populations. AHF is believed to be a congenital anomaly caused by failure of retroperitoneal mesenchyme to stimulate capsule formation, promoting the fusion of the structures. Two male domestic ferrets had a mass adherent to the liver, comprising adrenal gland with areas of fusion between the liver parenchyma and adrenal cortex. There was no evidence of a capsule separating the hepatic and adrenal cell populations. Clinical signs related to either the liver or adrenal gland were not observed, so this was considered to be an incidental finding.

Naturally acquired visceral leishmaniosis in a captive Bennett's wallaby (Macropus rufogriseus rufogriseus)

A high prevalence of leishmaniosis has been reported from an increasing number of domestic and wild mammals around the world. In Australian macropods, Leishmania spp infection has been occasionally described in its cutaneous form only. The purpose of this report is to present a case of fatal visceral leishmaniosis in a captive Bennett's wallaby in Madrid, Spain, which was investigated by detailed macroscopic, histologic, and immunohistochemical examinations.

Intraepidermal glandular carcinoma of the nipple (mammary Paget-like disease) in 2 dogs

Mammary Paget disease, characterized by diffuse infiltration of the nipple and areolar epidermis by carcinoma cells, develops in 1% to 3% of human mammary carcinomas. The purpose of this article is to present 2 cases of intraepidermal adenocarcinoma that resembled human mammary Paget disease, histologically and immunohistochemically, in dogs with underlying mammary carcinoma.

Clinical and histopathological features of a thymolipoma in a dog

This study presents a case of a canine thymolipoma, which is a rare, slow-growing, benign tumor of the thymus composed of mature adipose tissue and thymic tissue. A 9-year-old spayed, female miniature pinscher presented with chronic cough and dyspnoea. Radiology revealed pleural effusion and a mediastinal mass with a fatty appearance. The mass was attached to, and silhouetted, the adjacent pericardium. Microscopically, the mass was composed of adipose tissue with numerous cords and nests of thymic tissue without corticomedullary arrangement. To the authors' knowledge, this is the first description of this uncommon neoplasm in a dog. The gross and histological findings are similar to those described for thymolipomas in humans. The possible histogenesis for this neoplasia in a dog is also discussed.

Malignant peripheral nerve sheath tumour (malignant schwannoma) in the diaphragm of a goat

This report describes a malignant schwannoma in the diaphragm of a 2-year-old goat. The immunohistochemical and histological features indicated a diagnosis of malignant schwannoma rather than neurofibrosarcoma. The diaphragm represents an unusual location for neoplasia in both domestic animals and human beings. A possible anatomical origin from the phrenic nerve is discussed.

Expression of maspin in mammary gland tumors of the dog

Maspin is a serine protease inhibitor that inhibits tumor invasion and metastasis in human breast cancer and is consistently expressed by mammary myoepithelial cells (MECs). To analyze the value of maspin as a marker of the MEC layer of the normal and tumoral canine mammary gland, the immunohistochemical expression of maspin was studied in formalin-fixed tissues from 55 benign and malignant tumors (40 tumors also contained the surrounding normal mammary gland) using a commercially available monoclonal antibody. Periacinar and periductal MECs of all 40 normal mammary glands were stained by the anti-human maspin monoclonal antibody, and immunoreactivity was observed in the nucleus and cytoplasm of these cells. In addition, maspin was found in 53 (98%) of the tumors studied, reacting with the MECs in 100% of benign tumors and 93% of malignant tumors and to the epithelial cells of 16% of benign and 73% of malignant tumors. In the MEC compartment, immunoreactivity was observed in the cytoplasm of hypertrophic MECs, fusiform MECs, stellate MECs, rounded (myoepithelial) cells, and chondroblasts. In the epithelial cell compartment, immunoreactivity was observed in the cytoplasm of cells with and without squamous differentiation. Stromal myofibroblasts were unreactive. Maspin appears to be a very sensitive marker of the normal and neoplastic myoepithelium that, contrary to smooth muscle differentiation markers, does not stain stromal myofibroblasts. In addition, a subset of neoplastic epithelial cells reacted with the maspin antibody. The relationship between maspin expression in different cellular compartments of canine mammary carcinomas and the biologic aggressiveness of the disease remains to be elucidated.

Immunohistochemical Labelling of Cytokines in Lung Lesions of Pigs Naturally Infected with Mycoplasma hyopneumoniae

Mycoplasma hyopneumoniae (Mh) is the primary agent of porcine enzootic pneumonia (PEN), a chronic respiratory disease endemic to pig farms, and characterized histologically by infiltration of mononuclear cells in airways and prominent hyperplasia of the bronchus-associated lymphoid tissue (BALT). To gain further insight into the pathogenesis of PEN, cytokine expression in the lung, with particular attention to the BALT, was examined immunohistochemically in pigs naturally infected with Mh. An increase (P < 0.05) in proinflammatory and immunoregulatory cytokines (especially interleukin [IL]-2, IL-4 and tumour necrosis factor [TNF]-alpha, and to a lesser extent IL-1 [alpha and beta] and IL-6) was detected in the BALT, which showed intense lymphoid hyperplasia. IL-1beta and TNF-alpha were also detected in the bronchoalveolar exudate of infected pigs, and IL-6 and IL-8 were demonstrated in mononuclear cells of the alveolar septa. The results showed that in Mh infection, macrophage and lymphocyte activation results in the expression of a number of cytokines capable of inducing lung lesions and lymphoreticular hyperplasia of the BALT.

Lipid-rich carcinomas of the mammary gland in seven dogs: clinicopathologic and immunohistochemical features

Lipid-rich carcinomas occurred in seven female dogs. Affected dogs were purebred (all but one), intact (all but one), and between 4 and 13 years of age. Five of them had a history of parity, one had pseudopregnancy, and none had received contraceptive steroids. The tumors were single (five cases) or multiple (two cases) well-circumscribed masses of different sizes (varying from 1 to 6 cm in diameter), composed of solid nests and cords of tumor cells separated by a moderate amount of stroma. The tumor cells contained either multiple and small or large and solitary vacuoles that pushed the nucleus to the periphery of the cell (signet-ring cell). A glandular epithelial immunophenotype (cytokeratins 5 and 8 and 8 and 18) was observed in the majority of tumor cells. All tumors lacked both estrogen and progesterone receptors, and five out of seven tumors gave rise to local recurrence and proximal or distant metastases or both.

Cross-reactivity of human and bovine antibodies in striped dolphin paraffin wax-embedded tissues

This study evaluates the cross-reactivity of seven anti-human and one anti-bovine antibodies in formalin-fixed, paraffin-embedded tissue samples of liver and mesenteric lymph nodes of 13 striped dolphins (Stenella coeruleoalba). Four antibodies (CD3, IgG, lysozyme and S100 protein) reacted with striped dolphin lymph nodes in a similar pattern to that observed in the species of origin. The anti-human MHC class II mAb reacted strongly with macrophages and dendritic-like cells of striped dolphins, whereas a small number of lymphocytes were labelled with this antibody. These antibodies were used to study the immunophenotype of the inflammatory infiltrated in non-specific chronic reactive hepatitis (eight cases) and chronic parasite cholangitis (two cases) and normal liver (three cases) of striped dolphins. Non-specific chronic reactive hepatitis was composed of inflammatory infiltration of CD3+ T lymphocytes and IgG+ plasma cells in portal spaces and hepatic sinusoids. Lymphonodular aggregates observed in chronic parasitic cholangitis showed a cellular distribution similar to that found in lymph node cortex, including the presence of S100+ and MHC class II+ dendritic-like cells in lymphoid follicles and interfollicular areas. This result suggests that those inflammatory infiltrates are highly organised to enhance antigen presentation to B and T cells.

Left ventricular outflow tract-right atrial communication (Gerbode type defect) associated with bacterial endocarditis in a dog

Left ventricular (LV) outflow tract-right atrial (RA) communication associated with bacterial endocarditis is described in a 6-year-old intact male Great Pyrenees dog with a 4- to 5-day history of fever, lethargy, weight loss, severe regenerative anemia, and asplenia. Typical vegetative mural endocardial lesions were observed grossly. Histologic evaluation revealed small gram-negative coccobacilli that were consistent with Bordetella avium-like organisms. These bacteria were associated with severe endocardial inflammation characterized by neutrophilic infiltration, extensive necrosis of endocardium, and fibrin deposition. LV-RA shunt (Gerbode defect) is a rare cardiac defect in humans that can be either congenital or, more rarely, secondary to septic endocarditis, valve replacement procedures, or thoracic trauma. B. avium-like organisms causing septicemia and endocarditis in immunocompromised and asplenic human patients have been described. To our knowledge, no previous descriptions of Gerbode defect associated with bacterial endocarditis in domestic animals have been reported in veterinary literature.

Immunohistochemical detection of Mycoplasma agalactiae in formalin-fixed, paraffin-embedded tissues from naturally and experimentally infected goats

Samples from the mammary tissue of 14 lactating goats (12 naturally infected and two experimentally infected) were examined for the presence of Mycoplasma agalactiae. A monoclonal antibody (5G12) was applied to formalin-fixed, paraffin-wax-embedded sections and labelled by the avidin-biotin peroxidase complex (ABC) method. Histological examination of tissue sections revealed strong immunoreactivity in all animals included in the study. Mycoplasma agalactiae antigen was mainly detected in the cellular debris at the periphery of purulent exudates present within lactiferous sinuses, and lactiferous and interlobular ducts. In addition, M. agalactiae organisms appeared in the cytoplasm of the epithelium of ducts, and in infiltrating macrophages and neutrophils within the ducts, alveoli, interstitial tissue and regional lymph node sinuses. It is concluded that this monoclonal antibody-based immunohistochemical technique is an efficient and specific method for the post-mortem detection of M. agalactiae in cases of clinical mastitis as well as being a useful tool for the study of the route of infection and cellular types involved during mastitis caused by this organism.