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A 25-year-old female California sea lion (Zalophus californianus) reared in an aquarium died following a history of anorexia, lethargy, abnormal protrusion of the skin, and oral respiration. At necropsy, multiple yellowish-white nodules with diameters of 0.1-0.5 cm were disseminated in the thoracic cavity and lungs. Histopathologically, the nodules were continuous with normal mesothelium and were characterized by the proliferation of spindle-shaped to polygonal neoplastic cells with prominent atypia. The neoplastic cells exhibited diffuse, strong staining for vimentin and partial, weak to moderate staining for cytokeratin AE1/AE3. Based on these findings, the lesions were diagnosed as pleural mesothelioma. This study reports the first case of pleural mesothelioma in California sea lion.

The concept of "stem cell pathology" is to establish the role of the stem cells by exploring their contribution to lesion development. The somatic stem cells are present in the body. Malignant fibrous histiocytoma (MFH; recently named "undifferentiated pleomorphic sarcoma") includes pluripotential undifferentiated mesenchymal stem cells as a cell element. An antibody (A3) generated by using rat MFH cells as the antigen labels somatic stem cells such as bone marrow stem cells and immature endothelial cells and pericytes, as well as immature epithelial cells in epithelialization. By using A3 and other antibodies recognizing somatic stem cells, it is considered that myofibroblasts appearing in rat fibrotic lesions are developed partly from immature hepatic stellate cells in hepatic fibrosis, immature pancreatic stellate cells in pancreatic fibrosis, pericytes/endothelial cells in neovascularization in injured tissues, as well as via the epithelial-mesenchymal transition. These progenitors may be in the stem cell lineage. In this review, the author introduces the histogenesis of MFH and the characteristics of myofibroblasts appearing in fibrosis, based mainly on the author's studies.

Properties of macrophages and lymphocytes appearing in renal fibrosis remains to be investigated. F344 rats were injected once a week with cisplatin (2 mg/kg body weight) for 8 weeks and examined at post-final injection weeks 1, 3, 6, 9, and 12. Rats developed progressive renal fibrosis at weeks 1 to 6 as fibrosis-progress phase, and subsequent amelioration at weeks 9 and 12. CD68 + M1-macrophages and major histocompatibility complex (MHC) class II + macrophages remarkably increased persistently, whereas CD163 + M2-macrophages slightly increased. MHC class II + /CD68 + and MHC class II + /CD163 + macrophages were present, indicating that MHC class II + macrophages might have both functions of M1- and M2-macrophages. In the fibrosis-progress phase, interleukin (IL)-6, tumor necrosis factor (TNF)-α, and interferon (IFN)-γ for M1-factors, and transforming growth factor (TGF)-β1 and IL-10 for M2-factors tended to increase; tissue injury by M1 and fibrosis by M2 might have occurred simultaneously. Lots of CD4 + and CD8 + T cells appeared in close relation with MHC class II + macrophages, and mainly CD4 + T cells formed aggregations. In the lymphocyte aggregates collected by laser microdissection, expression of IL-17A (for Th17 cells) and forkhead box P3 (FoxP3) (for Treg) significantly increased at weeks 1 and 6, respectively; presumably, Th17 cells might be involved in tissue injury, whereas Treg might be related to fibrosis amelioration. These results suggested that macrophages and T cells may contribute interrelatedly to renal fibrosis.

The administration with high dose (close to LD 50 ) of thioacetamide (TAA), a hepatotoxicant used widely to induce experimental liver lesions, develops hepatocellular necrosis and subsequent inflammation (mainly M1-/M2-macrophages without neutrophil infiltration) in rats. We analyzed rat livers treated with a low dose TAA (50 mg/kg/body weight) at 6, 12, 18, 24 and 48 hr. The lesions in the affected centrilobular areas consisted of slight hepatocyte degeneration at 12 hr, and inflammatory cell infiltration at 18 and 24 hr; the lesions recovered until 48 hr. Translocation of intranuclei to cytoplasm of HMGB1, a representative molecule of damage-associated molecular patterns, was seen in some hepatocytes mainly at 6, 12, and 18 hr. As an interesting finding, at 12 hr, myeloperoxidase-positive neutrophil infiltration was observed in the affected centrilobular area. Additionally, CD68 M1-/CD163 M2-macrophages increased consistently at 12 to 48 hr. CXCL1, a chemokine for induction of neutrophils, began to increase at 6 hr and gradually increased at 12, 18 and 24 hr, apparently corresponding to the appearance of neutrophils. Collectively, the present findings at the low dose TAA indicated that along with M1-/M2-macrophages, neutrophils were characteristically seen, which might be elicited by cytoplasmic translocation of HMGB1 from nuclei. These finding would be useful for evaluation of hepatotoxicity at the early stages.

A 16 years old neutered male Miniature Dachshund with 1-year history of repetitive administration of zonisamide for treatment of epileptic seizure was presented for vomiting, anorexia and diarrhea. Serum biochemistry showed a markedly elevated ALP level. The dog died 6 days after the presentation and a necropsy was performed. Histopathologically, random, focal to extensive necrosis, formation of regenerative hepatocellular nodules surrounded by fibrous septa and proliferation of bile ducts were seen in the liver. From these findings, the hepatic lesion was diagnosed as hepatocellular necrosis with prominent regenerative reactions due to the chronic persistent liver injury. Hepatic lesions were considered to be induced by zonisamide, based on the history of continuous administration, and clinical and histopathological findings.

An 11-year-old female French Bulldog was presented with a mass at the base of the heart, detected by X-ray and echocardiography. Clinical abnormality included abdominal retention by ascites. Radiation therapy was performed for 5 weeks. The mass volume didn't change during the radiotherapy. The condition became worse and the dog died 6 months after the initial presentation and necropsy was performed. Grossly, the mass, 12.5 × 6.5 × 6.0 cm in size, was found at the base of the heart. Histopathological examination revealed that cardiac mass was composed of alveolar, bundle and diffuse proliferation of neoplastic cells. Most of the neoplastic cells showed a spindle morphology; in some areas small round or polyhedral neoplastic cells were observed. Occasional cartilage metaplasia was seen multifocal in the mass, and it was surrounded by the sarcomatoid proliferation. Electron microscopy revealed a few neuroendocrine granules in the cytoplasm of spindle and polyhedral neoplastic cells. Metastatic cells in the lungs which had not irradiated demonstrated typical morphology of aortic body tumors. Based on these findings, the case was diagnosed as an aortic body carcinoma with sarcomatoid morphology and chondroid metaplasia.

Leiomyoma is the most common mesenchymal tumor in the gastrointestinal (GI) tract. Leiomyomas usually have a single or multinodular mass of various sizes, and affected animals can develop alimentary symptoms depending on the location and size. A 3-year old female miniature dachshund died after a history of refractory rectal prolapse, esophagectasis and aspiration pneumonia. At necropsy, the GI wall at the gastroesophageal and anorectal junctions was circumferentially thickened. Histologically, both GI lesions were composed of bundles of well-differentiated smooth muscles without mass formation or invasive growth. The neoplastic cells had little cellular atypia and low proliferative activity, and were positive for α-smooth muscle actin. The lesions were diagnosed as diffuse leiomyomatosis with circumferential thickening of the GI wall and has not been described in the veterinary literature.

This study represents cases with spontaneous neuritis of peripheral nerves in electric eels. Two electric eels were presented with abnormal swimming behavior and loss of appetite. Electric eels had extensive histopathologic lesions in the splenic and cardiac nerves. The lesions were characterized by swelling of neuronal cells, central chromatolysis and marked inflammatory cell infiltration consisting mainly of lymphocytes around the affected nerves. To the best of our knowledge, this is the first case report of spontaneous neuritis of peripheral nerves in electric eels.

An 8-year-old female Magellanic penguin (Spheniscus magellanicus) started to show epilepsy-like seizures. Subsequent magnetic resonance imaging (MRI) examinations did not reveal any responsible lesions. The neurological symptoms worsened at the age of 10. This penguin became recumbent and died 6 months later after the apparition of the recumbency. At necropsy, only multiple yellowish necrotic lesions in the air sacs and lungs were found. Histopathological evaluation of the brain showed a marked loss of Purkinje cells and many hypertrophied parvalbumin-positive basket/stellate cells were seen in the cerebellar cortex. Calbindin immunohistochemistry demonstrated disrupted arrangement of dendrites in the Purkinje cells. This case was diagnosed as cerebellar cortical degeneration with a very late onset and a slow progression in a Magellanic penguin.

Fibrotic lesion is formed by myofibroblasts capable of producing collagens. The myofibroblasts are characterized by immunoexpressions of vimentin, desmin and α-smooth muscle actin (α-SMA) in varying degrees. The cellular characteristics remain investigated in myocardial fibrosis. We analyzed immunophenotypes of myofibroblasts appearing in isoproterenol-induced myocardial fibrosis in rats until 28 days after injection (10 mg/kg body weight); the lesions developed as interstitial edema and inflammatory cell reaction on 8 hr and days 1 and 3, and fibrosis occurred on days 1, 3, 7, 14, and 21 by gradual deposition of collagens, showing the greatest grade on day 14; the lesions gradually reduced with sporadic scar until day 28. Myofibroblasts expressing vimentin and α-SMA increased with a peak on day 3, and then, gradually decreased onwards. Interestingly, Thy-1 expressing cells appeared in the affected areas, apparently being corresponding to the grade similar to vimentin- and α-SMA-positive cells. Thy-1 is expressed in immature mesenchymal cells such as pericytes with pluripotent nature. The immunoreactivity for A3-antigen, a marker for immature mesenchymal cells, was seen in some surrounding cells. There were no cells reacting with antibodies to nestin or glial fibrillary acidic protein, although hepatic myofibroblats have been reported to react with these antibodies. Collectively, myofibroblasts appearing in rat myocardial fibrosis may have been derived from immature mesenchymal cells positive for Thy-1 or A3-antigen, with thereafter showing expressions of vimentin and α-SMA in differentiation.

Neuroaxonal dystrophy (NAD) is a neurodegenerative disease characterized by severe axonal swelling (spheroids) throughout the nervous system. In dogs, NAD has been reported in several breeds and a missense mutation in PLA2G6 gene has recently been identified in the Papillon dog NAD. Here we performed ultrastructural analysis to clarify the detailed ultrastructural features of the Papillon dog NAD. Dystrophic axons consisted of accumulation of filamentous materials, tubulovesicular structures, and swollen edematous mitochondria with degenerated inner membranes were often observed in the central nervous system. At axonal terminals, degeneration of presynaptic membrane was also detected. As reported in Pla2g6 knockout mice, mitochondrial and presynaptic degeneration may be related with the pathogenesis of NAD in Papillon dogs.

Pancreatic fibrosis develops as the results of the activity of myofibroblasts capable of producing collagens. The myofibroblasts derive from pancreatic interstitial cells, including pancreatic stellate cells (PSCs), which can express glial fibrillary acidic protein (GFAP). First, we investigated the expression patterns of vimentin, desmin, α-smooth muscle actin (α-SMA), Thy-1 and GFAP in the developing rat pancreas (in fetuses at 18 and 20 days, neonates from 1 to 21 days, and adults). Interstitial cells in the developing pancreas expressed vimentin, desmin, GFAP and Thy-1 at varying degrees; interestingly, the reactivity for desmin and vimentin was the highest in fetuses. GFAP expression was consistent between fetuses and neonates, and Thy-1 reactivity transiently increased after birth; however, α-SMA-positive interstitial cells were rarely seen. Next, we analyzed the immunophenotypical characteristics of myofibroblasts appearing in pancreatic fibrosis in dogs and cats. With increasing fibrotic grade, myofibroblasts showed increased expression of vimentin, desmin and α-SMA, in addition to increased GFAP expression. Collectively, pancreatic interstitial cells and myofibroblasts may have similar immunophenotypes, and myofibroblasts might originate partly from GFAP-expressing PSCs.

β-catenin, E-cadherin and N-cadherin are adhesion molecules that play important roles in organogenesis, tissue homeostasis, renal epithelial integrity and polarity. The present study demonstrated their immunolocalization in adult and neonate rat kidney. Membranous or cytoplasmic expression of β-catenin, E-cadherin and N-cadherin were seen in adult and developing renal tubular epithelial cells. Particularly, in adult kidney, E-cadherin and β-catenin were intensively expressed in distal renal tubules, whereas N-cadherin was expressed in proximal renal tubules. In neonate rat kidney on 1 and 4 days old, developing renal tubular epithelial cells were mainly reacted with E-cadherin and very weakly expressed N-cadherin; β-catenin was expressed in developing renal tubules and mesenchymal blastemal cells. Interestingly, β-catenin-positive renal tubular epithelial cells simultaneously expressed E-cadherin in the kidney of adult and developing rats. Collectively, the adhesion molecules were differentially distributed in the renal tubules of adult rats and β-catenin and E-cadherin are predominant adhesion molecules in developing kidney. The present findings would provide the basic information of evaluating renal tubular toxicity using rats, in addition to renal genesis, in terms of adhesion molecules.

A white, lobular mass was found in the right ovary of a pregnant Risso's dolphin (Grampus griseus) at necropsy. The mass was unilateral and occupied most of the pre-existing ovarian tissue. Histologically, the mass was composed of diffuse sheets of polyhedral cells with abundant eosinophilic cytoplasm and oval nuclei, separated by fibrous connective tissue. Only a few ovarian follicles were observed at the periphery of the mass. Immunohistochemically, the large eosinophilic cells were positive for vimentin and negative for pan-cytokeratins. Based on the histopathological features, the present case was diagnosed as luteoma. In human medicine, luteoma of pregnancy, a tumor-like proliferative lesion occurring in pregnant women, is well described. In veterinary medicine, luteoma associated with pregnancy has never been described. The present study would provide useful information for understanding the characteristics of luteoma in animals.

An 11-year-old female golden retriever dog had a mass at the right corner of the upper lip, which gradually increased in size and protruded into the oral cavity. The mass was removed surgically. The cut surface of the mass was smooth, whitish and solid, and covered by the oral mucosal membrane. Histopathologically, the mass consisted mainly of reticular pattern of short spindle cells that stained positively for cytokeratin AE1/AE3, α-smooth muscle actin and p63, suggestive of a myoepithelial cell phenotype. Between the neoplastic cords, there was myxoid or edematous connective tissue. Additionally, neoplastic cells with luminal epithelial and basal cell phenotypes were arranged in ducts and small islands, respectively. Based on the diverse histological and immunohistochemical features, the tumor was diagnosed as pleomorphic adenoma of the labial gland. To our knowledge, the reticular proliferation pattern of myoepithelial cells has not been described in salivary gland tumors of domestic animals.

A Bengal tiger was presented for evaluation of weakness, ataxia and inappetance. Computed tomography (CT) and magnetic resonance imaging (MRI) revealed a mass extending from the T7-8 vertebral body to the left rib and compressing the spinal cord. On CT, the bone destruction and sequestrum were shown. On MRI, the multilobulated mass appeared hypo- to isointense in T1-weighted and hyperintense in T2-weighted images. The tiger died after imaging, most likely from renal failure. Chordoma without metastasis was diagnosed on necropsy. The imaging characteristics were similar to those found in chordoma in humans. This report describes the use of CT and MRI in an exotic species.

A 19-year-old female Bengal tiger (Panthera tigris tigris) was presented with hind limb weakness, ataxia and respiratory distress. Computed tomography revealed a mass between the left side of the T7 vertebra and the base of the left 7th rib. The tiger then died, and necropsy was performed. Grossly, the vertebral mass was 6 × 5.7 × 3 cm, and invaded the adjacent vertebral bone and compressed the T7 spinal cord. Histologically, the mass was composed of large, clear, vacuolated and polygonal cells with osteochondral matrix. Cellular and nuclear atypia were moderate. The vacuolated cells stained positively for cytokeratin and vimentin and negatively for S-100. Based on these findings, the present case was diagnosed as a vertebral chordoma; the first report in a tiger.

Stillbirth and neonatal mortality are significant problems in captive breeding of dolphins, however, the causes of these problems are not fully understood. Here, we report a case of meconium aspiration syndrome (MAS) in a male neonate of bottlenose dolphin (Tursiops truncates) who died immediately after birth. At necropsy, a true knot was found in the umbilical cord. The lungs showed diffuse intraalveolar edema, hyperemic congestion and atelectasis due to meconium aspiration with mild inflammatory cell infiltration. Although the exact cause of MAS in this case was unknown, fetal hypoxia due possibly to the umbilical knot might have been associated with MAS, which is the first report in dolphins. MAS due to perinatal asphyxia should be taken into account as a possible cause of neonatal mortality and stillbirth of dolphin calves.

A 10-year-old female sea otter exhibited convulsions, arrhythmia, hyperthermia, forced breathing and anorexia and died after a week. Histopathological examination revealed neoplastic proliferation of small round cells with scant cytoplasm and round or oval nuclei distributed mainly in the thalamus. The proliferation of neoplastic cells was observed in the cerebral parenchyma and perivascular areas. The neoplastic cells were immunopositive for CD3, but not CD20. No neoplastic proliferation of T-cells was found in other organs. Taken together, we diagnosed this case as a primary cerebral T-cell lymphoma. To our knowledge, this is the first case of primary cerebral T-cell lymphoma in a sea otter.

A 9-year-old male Yellow-headed Amazon (Amazona oratrix) with a history of anorexia and vomiting died of a liver tumor. The tumor consisted of neoplastic cells with hepatocellular and cholangiocellular differentiations and their intermingled areas. Neoplastic hepatocytes showed islands or trabecular growth with vacuolated eosinophilic cytoplasm. Cells showing biliary differentiation formed ducts or tubules lined by cytokeratin AE1/AE3-positive epithelia, accompanied by desmoplasia consisting of myofibroblasts reacting to α-smooth muscle actin and desmin. The tumor was diagnosed as a combined hepatocellular-cholangiocarcinoma, which is very rare in the avian.

Histopathologically, fibrosis in Fasciola-infected cattle livers was characterized by inflammatory cell infiltration, such as eosinophils and macrophages, pseudo-lobule, pseudo-bile ducts and fibrotic bridges separating pseudo-lobules; the fibrotic lesions were developed in the Glisson's sheath. Pseudo-bile ducts consisting of epithelial cells reacted clearly to cytokeratin (CK) 19, indicating cholangiocyte origin. Immunophenotypes of macrophages and myofibroblasts were investigated in the fibrotic livers. Macrophages positive for CD68 (reflecting phagocytosis) and CD163 (representing proinflammatory cytokine production) were increased, and those for CD204 (implying lipid metabolism) and Iba-1 (a calcium-binding protein playing role in chemotaxis) decreased in fibrotic livers compared to control livers. Spindle-shaped myofibroblasts positive for vimentin, desmin and α-smooth muscle actin (α-SMA) increased in the peribiliary connective tissues, although the desmin-positive cells were fewer. In addition to the usefulness of these antibodies for macrophage detection in cattle livers, this study shows that macrophages with different immunophenotypes participate in Fasciola-infected cattle livers, in relation to development of myofibroblasts expressing mainly vimentin and α-SMA.

A 20-year-old Gentoo penguin was found dead with a clinical history of inappetence and dyspnoea. At necropsy, the lungs showed severe congestion/hemorrhage and atelectasis. Histopathologically, fibrosis was observed exclusively around parabronchi with severe collagen deposition. In fibrotic lesions, there were numerous depositions of crystalline structures accompanied by epithelioid cells and multinucleated giant cells (foreign body type). In addition to irregularly lamellar structures as the morphology, the crystals were demonstrated calcium oxalate (CaOx) by the Alizarin red S staining with and without polarized light and von Kossa's staining. Myocobacteria and fungi were not found by special and immuohistochemical stainings. Pulmonary dystrophic oxalosis is a very rare lesion in Gentoo penguin.

A 16-year-old male mixed-breed dog was euthanized due to progression of renal failure caused by renal adenocarcinoma in the left kidney. Apart from main symptomatic lesion, accumulation of transparent jelly-like fluid was observed between the right femoral muscles. Gross examination of the right hindlimb revealed multiple nodules in the articular surface and capsule of the stifle joints, which extended into the crural muscles. Histopathologically, the joint and intermuscular masses were characterized by variously-sized hypocellular nodules consisting of spindle to stellate cells suspended in an abundant myxoid matrix. There were cystic structures within the intermuscular masses, lined by synoviocyte-like cells. Based on the gross and histopathologic findings, the case was diagnosed as synovial myxoma with extensive intermuscular infiltration. Synovial myxoma should be considered in the differential diagnosis of dogs with myxomatous tumor between skeletal muscles, even in absence of joint or muscle symptoms.

A 10-year-old female false killer whale (Pseudorca crassidens) developed skin lesions in the left breast fin. Histopathologically, the lesions consisted of multiple granulomas spread diffusely into the deep dermis and bone; characteristically, each granuloma had septate, branching fungal hyphae and chlamydospores surrounded by eosinophilic Splendore-Hoeppli materials. Macrophages, epithelioid cells and multinucleated giant cells in the granulomas reacted mainly to anti-SRA-E5 antibody against human macrophage scavenger receptor type I. Fusarium solani was isolated and its gene was detected from the skin samples. Mycotic skin lesions by Fusarium spp. reported so far in marine mammals were regarded as superficial dermatitis; therefore, the present case is very uncommon in that the lesions spread deeper into the skin.

A 6-month-old male miniature pinscher dog developed chronic ascites, formation of fibrous membrane covering the abdominal organs, and numerous adhesions between the intestinal loops. The membrane and adhesions were surgically removed twice, but the dog died 1 month after initial presentation. Necropsy revealed recurrence of the membrane and intestinal adhesions. The fibrous membrane was composed of a thick layer of mature collagenous connective tissue, covered by immature collagenous connective tissue with mild lymphoplasmacytic infiltration, prominent neovascularization, and fibrin exudation. Similar fibrotic lesions were observed in the serosa of the liver, spleen, stomach and intestines. These findings are consistent with encapsulating peritoneal fibrosis reported in humans and dogs. The dog also had a maldeveloped liver, which is characterized by disorganized hepatic lobules and disarranged hepatic cords.

A 3-year-old, spayed female miniature dachshund was presented for vomiting and anorexia. Thoracic radiographs and CT scan revealed abnormal pulmonary opacities at bilateral caudal lobe. Cytological analysis of the pulmonary mass revealed the presence of large lymphohistiocytic cells and small lymphocytes with occasional neutrophils and plasma cells. An open lung biopsy was performed and a diagnosis of pulmonary lymphomatoid granulomatosis (LYG) was made. The dog was administered CHOP based therapy (modified UW-25), and it survived for 1,022 days after admission. Immunohistochemistry revealed pulmonary lesions consisted of many CD79a positive B cells aggregation and proliferation with prominent angiocentric pattern. This was the first case of canine pulmonary LYG managed by CHOP chemotherapy.

A 10-year-old miniature sow was died, showing inappetence and weight loss. Grossly, neoplastic enlargement of the uterus was found. Histopathologically, the lesions consisted of acinar, ductular and cystic proliferations of mono- and multilayered epithelial cells; these cells reacted immunohistochemically strongly with three different cytokeratin antibodies, and occasionally to vimentin. Myofibroblastic desmoplastic cells, positive to alpha-smooth muscle actin, were present among neoplastic cells. Metastatic lesions were seen in the lungs and liver. Based on these findings, a diagnosis of uterine adenocarcinoma with marked desmoplasia was made. This case is the second report of uterine adenocarcinoma in the miniature pig.

An adult female Aldabra giant tortoise (Geochelone gigantea) was found dead with a 2 month-history of decreased appetite. At necropsy, multiple ulcers were seen in the mucosa of stomach and colon. Histopathologically, the ulcers were characterized by extensive necrosis, hemorrhage, and marked edema, along with numerous chlamidospores and aseptate fungal hyphae. Fungal structures infiltrated into the lamina propria, submucosa and muscle layer; their invasion into blood vessels formed thrombosis. Immunohistochemically, the fungal structures were strongly positive with an antibody against Candida spp. This case is the first report on gastrointestinal candidiasis in an Aldabra giant tortoise.

A female Japanese domestic shorthair cat showed gait abnormality at 5 months of age, and head shaking and tremor became apparent from 6 months of age. Serum biochemistry at 13 months of age revealed markedly elevated ALT and ALP. The cat died at 16 months of age. Histopathologic examination revealed prominent cytoplasmic swelling of neurons with accumulation of yellowish pigments. The storage pigments stained positively with periodic acid Schiff reaction, Schmorl method, and Oil red O stain. Ultrastructurally, the neuronal storage consisted of aggregates of dense materials, similar to the granular osmiophilic deposits in infantile ceroid-lipofuscinosis in humans. Hepatocytes were markedly swollen and contained faintly eosinophilic inclusion. To our knowledge this case is the sixth case of feline ceroid-lipofuscinosis, which is characterized by granular osmiophilic dense bodies in the neurons and prominent involvement of hepatocytes.

Human BRCA1 is familial breast cancer susceptibility gene. Recently, decreased BRCA1 mRNA and protein expression has been identified in sporadic breast tumors. In the reported human BRCA1 splicing variants, delta11b lacks the majority of exon11 and is suspected to have a distinct function in normal tissues. The splicing variants display a variety of expression pattern in breast cancer samples. Although mammary gland tumor is important disease in dog, there are few reports for BRCA1 in the canine tumors. In this study, we examined the relative amounts of BRCA1 splicing variants mRNA in canine normal and mammary tumor samples by RT-PCR to investigate whether there is the altered expression of variant mRNAs in the canine tumor as reported in human. The exon11b-defecting RT-PCR products were observed in all the normal tissues examined and the nucleotide sequence was quite similar to that of human BRCA1 delta11b. In some tumor samples, we did not detect the products targeted for exon10-13 and exon14-15, while these products were observed in all the normal samples examined. Especially, the relative amounts of the exon11-defecting products were remarkably decreased in most of the tumors (11/16).

A female adult bottlenose dolphin suddenly died at 17 days after the capture. Macroscopically, severe pulmonary congestive edema was found. Histopathology revealed many lungworms in the bronchioli and the worms were identified as Stenurus ovatus. Variously sized vessels proliferated around the lesioned bronchioli. Based on these findings, chronic bronchopneumonia due to the lungworm was diagnosed and vascular proliferation was similar to angiomatosis recently reported in Atlantic bottlenose dolphin.

Slit, a secreted protein, functions as a chemorepellent factor in axon guidance and neuronal migration and as an inhibitor in leukocyte chemotaxis. In humans, slit2 protein attracts endothelial cells and promotes tube formation in the tumor angiogenic mechanism. In this study, we cloned a part of the canine slit subfamily and examined the expression of slit subfamily mRNAs in 3 normal canine mammary glands and 11 mammary tumor samples by RT-PCR. The cloned part of the slit gene sequences showed high similarity to those of the human, mouse, and rat. The mRNAs were expressed at low levels in the normal mammary gland. The expression levels of slit1 mRNA were low in both the normal and tumor tissues. In contrast, the expression of slit2 mRNA increased in most of the malignant mammary tumors, and an increase in slit3 mRNA expression was observed in 2 of the malignant mixed tumors. These results suggest that the expression of slit2 plays an important role in tumor angiogenesis in canine mammary gland tumors and that slit2 can be a putative marker for malignancy diagnosis of these tumors.

A 4-year-old male Shiba dog initially presented with pain of an undetermined origin and hypersensitivity to touch. Seven days later, the dog developed ataxia, hind-leg weakness and knuckling. The dog died on 20 days after presentation. Postmortem examination revealed a mass in the body of thoracic vertebra. Histopathologically, the mass consisted of granulomatous inflammation, including fungal organisms that were immunohistochemically positive for Candida albicans. Similar granulomatous lesions were observed in the systemic lymph nodes, kidneys, pancreas, spleen, prostate gland, thyroid glands and heart. This case was diagnosed as systemic candidiasis with spondylitis.

A 19.5-year-old male mongrel dog developed a progressive lameness and swelling around the right carpus. A tumor (6 x 3 x 3 cm) was found in the caudal of distal antebrachium of the right forelimb, including tendons of the superficial digital flexor muscle and deep digital flexor muscle. No joint destruction was observed. The tumor consisted of round and spindle cells arranged in a compact sheet. There were occasional slit-like spaces or lumina, and areas rich in collagen fibers giving an appearance of tendon tissues. Neoplastic cells gave a positive immunoreaction to vimentin, but negative reactions to antibodies against S-100 protein, cytokeratin and myoglobin. Based on these findings, this tumor was diagnosed as a synovial sarcoma generating from the tendon and tendon sheath, which is very uncommon in dogs.

An 11-year-old thoroughbred gelding was euthanatized because of right nasal cavity tumor. The tumor consisted of round to oval cells with a scanty cytoplasm and hyperchromatic nuclei. Homer-Wright rosettes and pseudorosettes, as well as microcysts were seen. Neoplastic cells were immunoreactive to vimentin, S-100 protein, and neuron-specific enolase, glial fibrillary acidic protein and microtube-associated protein in varying degrees, indicating neurogenic nature. Based on these findings, this tumor was diagnosed as an olfactory neuroblastoma. Since this type is an uncommon tumor showing histological variety, the nature is discussed.

A 6-year-old female ferret had a firm mass 2 cm in diameter in the pyloric region of the stomach. Histopathologically, the mass was composed of neoplastic proliferation of well-differentiated epithelial cells, showing tubular or glandular growth patterns. Osseous metaplastic foci were often found in the tumor. Tumor cells showed a positive reaction for immunohistochemistry against bone morphogenetic protein-6, an osteogenic factor. A diagnosis of gastric adenocarcinoma with ossification was made.

Details of morphology and distribution of hepatic macrophages in cetaceans were investigated using the immunohistochemistry with an antibody (SRA-E5) generated against human macrophage scavenger receptor antigen. Liver samples were obtained from five species of cetaceans (Baird's beaked whales, short-finned pilot whales, Risso's dolphins, bottlenose dolphins, and pantropical spotted dolphins). Except for two species of whales, the number of SRA-E5-positive Kupffer cells was greatest in the perivenous zone (zone 3), followed by the mid-zonal (zone 2) and periportal (zone 1) zones; this distribution pattern was different from that in cattle examined here and previously reported rodents with the highest number in zone 1. The frequency of Kupffer cell in each of zones was significantly different among species, and interestingly, the total mean of the Kupffer cell number in three zones increased as the body-length of species was small. In cetaceans, Kupffer cells in zone 1 appeared larger and more stellate in shape, whereas those in zone 3 were smaller and rounder. All cetaceans but Baird's beaked whales had the black pigment-containing Kupffer cells, with the greatest number in zone 3, and macrophages with the similar pigments were also seen in the hepatic intermediate septa, indicating an active phagocytosis. Most of the black pigments were considered to be lipofuscin and such pigments were not seen in the bovine livers. These results indicate that cetacean hepatic macrophages show differences in the distribution and phagocytosis among hepatic lobular zones, or between cetacean species and terrestrial animals.

An 8-year-old female Shetland sheep dog had hyperproteinemia with a monoclonal gammopathy and a solid mass on the liver, which was histologically diagnosed as a plasma cell tumor. After the treatment of surgery and chemotherapy, serum protein level reduced to the normal range and the gammopathy was disappeared. These findings indicate the plasma cell tumor developed primarily from the liver.

A transplantable rat pulmonary carcinoma line (IP) in F344 rats is a useful animal model for humoral hypercalcemia of malignancy (HHM). The present study analyzed the degree of HHM by implanting IP into F344 female rats aged 6, 20 or 45 weeks. IP-bearing females developed elevated plasma parathyroid hormone-related protein levels, hypercalcemia and increased osteoclastic activity as well as calcification in various organs. The severity of such HHM differed depending on age; particularly, calcification showed age-dependent reduction. HHM development in IP-bearing females may be influenced by age-related factors.

A monoclonal antibody (B9) was generated by using a rat malignant fibrous histiocytoma (MFH)-derived cloned cell line (MT-8) as the immunogen. Immunohistochemically, B9 reacted specifically with a cytoplasmic antigen of MT-8 cells. Furthermore, B9 immunolabeled another MFH-derived cloned cells (MT-9) and histiocytic sarcoma cells, as well as macrophages/histiocytes in normal and diseased tissues of rats. These findings suggest the presence of a common antigen recognized by B9 between MFH cells and macrophages/histiocytes. This suggests that MFH cells may express histiocytic nature.

In order to establish base-line data on angiogenic factors in development of mesenchymal tumors, expressions of vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (bFGF) in implanted MT-8 and MT-9 tumors, both derived from a transplantable malignant fibrous histiocytoma (MFH) in the F344 rat, were investigated by immunohistochemistry and Western blotting method. MT-8 and MT-9 tumors were developed in syngeneic rats by implant of a tumor tissue fragment. MT-8 tumors were examined on post-implantation (PI) days 3, 6, 9 and 17, and MT-9 tumors were on PI days 9, 14, 17 and 23. The growth of MT-8 tumors was faster than that of MT-9 tumors. Histologically, MT-8 tumors were features of undifferentiated sarcomas, whereas MT-9 tumors exhibited a typical storiform growth pattern of MFH. Immunohistochemically, all cells constituting MT-8 and MT-9 tumors reacted with antibodies to VEGF and bFGF, indicating production of these factors by mesenchymal neoplastic cells. However, there were no marked differences in these immunoreactions between tumors examined. Thus, the bands obtained in the Western blotting methods were densitometrically scanned. The expression levels of VEGF and bFGF gradually increased PI day 3 to 9 in MT-8 tumors and PI day 9 to 17 in MT-9 tumors. On last examination day, the levels of bFGF in both tumors and of VEGF in MT-9 tumors decreased, but the VEGF expression level in MT-8 tumors was still increased. These findings indicated that VEGF and bFGF may contribute cooperatively to angiogenesis in an early growth of mesenchymal tumor development.

A 9-month-old male Shih-Tzu dog had a right mandibular tumor composed of strands, or nest-like proliferation of epithelial cells with abundant fibrous stroma characterized by spheroid to large nodular deposition of amyloid with Congo-red stain. Globule calcification was also seen throughout the tumor tissue and the spheroid depositions often had a concentrically laminated structure (Liesegang rings). The case was diagnosed as amyloid-producing odontogenic tumor in a dog.

The kinetics of T-cells (CD3 positive (+), CD4+ and CD8+ cells) and B-cells (IgG+, IgM+ and IgA+ cells) in chicken trachea were studied immunohistochemically and histopathologically following an intratracheal inoculation of infectious bronchitis virus (IBV). Viral antigen was detected in the cytoplasm of tracheal epithelium from 16 hr to 6 days post-inoculation (p.i.) with a peak on 4 days p.i. A few IgG+, IgM+ and IgA+ cells were detected in the submucosa from 8 hr p.i. Thereafter IgG+ and IgM+ cells were gradually increased in number, and dramatically increased from 3 days p.i., peaked on 4 days p.i., and gradually decreased after 5 days p.i. IgA+ cells were detected in a small number than IgG+ and IgM+ cells during the all experimental period. These B cells mainly existed in the lamina propria, and some cells were recognized in the interepithelial space. After 14 days p.i., small number of IgG+ and IgM+ cells were detected in the germinal center of lymph follicles in the lamina propria. From 24 to 60 hr p.i., a few number of CD3+, CD4+ and CD8+ cells were detected at the perivascular area in the lamina propria. After 3 or 4 days p.i., each positive T-cells increased rapidly in number, and reached on the peak at 5 days p.i. CD3+, CD4+ and CD8+ cells tend to distribute diffusely, perivascular area, and surrounding area of CD4+ cells, respectively. CD4+ cells were dramatically decreased from 7 days p.i., and CD3+ and CD8+ cells were decreased from 14 days p.i. No T-cells were detected in the lymph follicles in the lamina propria.

All stages of degeneration and regeneration in chicken tracheal epithelium were studied morphologically following an intratracheal inoculation of infectious bronchitis virus (IBV). Viral antigen was detected in the cytoplasm of tracheal epithelium from 1 to 7 days post-inoculation (d.p.i.) with a peak on 3 d.p.i. At 1 d.p.i., almost all epithelial cells were involved in the degeneration. At this time, labelling index of bromodeoxyuridine (BrdU) in the basal cells showed significantly high value compared with control. At 2 and 3 d.p.i., a great number of basal cells were recognized, but the BrdU labelling index tended to decrease. At 4 and 5 d.p.i., the BrdU labelling index of basal cells significantly decreased than 1 d.p.i., and a few number of regenerated immature ciliated epithelia appeared. At 6 to 11 d.p.i., the ciliated columnar epithelia increased rapidly in number, and returned to the normal appearance except for non-ciliated patch by 13 d.p.i. These results suggested that the tracheal epithelial cells infected with IBV degenerated within 24 hours and proliferating activity of basal cells functioned immediately, and 3 to 4 days later, these basal cells were differentiated to the ciliated epithelia.

Peripheral nerve sheath tumor was found in a 7-year-old male mongrel dog. The tumors were located in the right cheek subcutis and oral submucosa. Histologically, neoplastic cells were arranged in streaming bundles, occasionally interlacing bundles or whorls of elongated and spindle cells. Cellular atypia was poor and mitotic figures were rarely observed. Ultrastructurally, neoplastic cells had basement membrane, typical of Schwann cells. One bundle of normal peripheral nerve fibers and some myelinated axons were seen within the tumor tissues. Immunohistochemically, neoplastic cells reacted to vimentin, glial fibrillary acidic protein, S-100 protein and neuron specific enolase. In addition to the above immunoreactions, the included nerve fibers were positive for myelin basic protein and neurofilament protein. This paper also discusses immunohistochemical findings on differential diagnosis in comparison with those of canine hemangiopericytomas reported hitherto.

A 13-month-old female Newfoundland dog suffered from urinary bladder tumor. Histologically the tumor consisted of round or fusiform cells, occasionally having eosinophilic cytoplasms. Apparent mature rhabdomyoblasts possessing elongated eosinophilic cytoplasm and cross striations were infrequently observed. The tumor cells exhibited immuno-positive for anti-myoglobin, desmin and vimentin antibodies. Ultrastructurally, tumor cells have abundant myofibrils in their cytoplasm and Z bands were also detected. The present tumor was diagnosed as a urinary bladder rhabdomyosarcoma in a Newfoundland dog, which has not been frequently reported in dogs.

A thyroid gland tumor, showing unusual histology, was identified in a 13-year-old male Andalusian horse. Microscopically, the tumor consisted of neoplastic proliferation of C-cell (parafollicular cell) with cytoplasmic fine granules, containing diffusely distributed, variously sized colloid-containing follicles. Immunohistochemically, the neoplastic C-cell were positive for calcitonin and follicleforming epithelial cells showed a positive reaction for thyroglobulin. Ultrastructurally, membrane-bound secretory granules up to 250 nm in diameter were found in the cytoplasm of the parafollicular cells, whereas the follicular epithelial cells had microvilli, junctional complex, and well-developed endoplasmic reticulum.

A six-month-old male Golden Retriever with a three-month history of polyuria and polydipsia was examined. Hematological examinations revealed nonregenerative anemia, azotemia, high serum creatinine level, hypercalcemia, hyperphosphatemia, hypercholesterolemia, hyperamylasemia, and low level of total serum protein. Urinalysis indicated mild proteinuria, and low specific gravity. Radiographic and ultrasonographic examinations revealed bilateral small sized kidneys. Histological examination by renal biopsy confirmed the diagnosis of renal dysplasia. Treatment with a dietary protein restriction, oral adsorbents, and dried aluminum hydroxide gel have been performed in this dog, and then, azotemia, high serum creatinine level, hypercalcemia, and hyperphosphatemia were improved. During 10 months after the initiation of treatments, no significant clinical change except polydipsia and polyuria has been observed.

To investigate a possible phenotypic modulation, MT-8L and MT-9L cells were induced by in vitro culture of undifferentiated MT-8 and fibrohistiocytic MT-9 cells, which had been established from a rat malignant fibrous histiocytoma (MFH), in the medium containing 10 micrograms lipopolysaccharide (LPS)/ml. MT-8L and MT-9L gave greater positive reactions for histiocytic lysosomal markers and showed ultrastructures of histiocytic natures. In MT-8L, alpha-smooth muscle actin-positive myofibroblastic cells also significantly increased in number. MT-8L expressed both histiocytic and myofibroblastic phenotypes. MT-8L-induced tumors consisted mainly of storiform type MFH, differing from undifferentiated sarcoma type induced by MT-8. MT-9L and MT-9 tumors showed a storiform pattern. A phenotypic modulation of MFH cells was easily induced by LPS treatment.

Hereditary cerebellar vermis defect rats (CVD), a new neurological mutant, developed disorganized cerebellar cortical tissues. The postnatal development of the cerebellum in the CVD was examined histologically and immunohistochemically. A main pathological change in the CVD was abnormal perivascular cell aggregations, beginning to be observed from postnatal day 5. Around postnatal day 14, perivascular cells increased in number and many of them showed vigorous bromodeoxyuridine incorporation activities, as seen in the normal external granule cells (EGCs). The perivascular cells and EGCs were strongly positive for low affinity nerve growth factor receptor. These immunohistochemical results revealed that abnormal perivascular cells were heterotopic EGCs. The perivascular cells led to dysplastic abnormalities of lamination and abnormal cell positioning in the CVD. These findings indicate that abnormal perivascular aggregations of EGCs play an important role in the pathogenesis for cerebellar cortical dysplasia of CVD.