Kiyokazu Ozaki

Mast cell tumors of the gastrointestinal tract in 39 dogs

Mast cell tumors (MCTs) of gastrointestinal origin that had been surgically removed from 39 dogs were examined to evaluate their pathologic features. Miniature breeds, especially Maltese, were most frequently affected. The average age of affected dogs was 9.7 ± 2.6 years. No sex difference was apparent. The most frequently affected sites were in the upper digestive tract, and the prognosis was very poor. Grossly, the gastrointestinal wall was prominently thickened, and the lumen of the affected gut was usually narrowed. Microscopically, there was diffuse transmural invasion of round to pleomorphic tumor cells. Tumor cells had moderate to abundant cytoplasm, round to ovoid nuclei with scattered chromatin, and mitotic figures. Fibrous stroma was observed in about half of the tumors. There was variable infiltration of eosinophils. In all tumors, cytoplasmic granules showed weak metachromasia, but the number of granules was very small. Immunohistochemical staining for c-kit and mast cell tryptase was positive in 77% and 62% of tumors, respectively. All tumors were positive for at least two of these markers. Immunohistochemical staining for p53 was positive in 13% of the tumors. Reactivity for staining markers and p53 was unrelated to cell pleomorphism, vessel invasion, or survival time. Gastrointestinal MCTs have histologic and immunohistochemical features completely different from those of other primary or metastatic gastrointestinal tumors. The combination of immunostaining for mast cell tryptase and c-kit and histochemical staining for metachromasia appears to be a powerful tool for the diagnosis of gastrointestinal MCTs.

Iron Lactate-Induced Osteopenia in Male Sprague-Dawley Rats

Osteopenia was induced in rats fed a diet containing 50,000 ppm (5%) iron lactate for 2 or 4 weeks. Blood chemistry, urinalysis, and bone histomorphometry of the proximal tibial metaphysis were performed. Urinary pyridinoline and deoxypyridinolin e and the osteoclast number per bone surface were selected for the measurement of dynamic resorption. The osteoclast surface, eroded surface, and osteoblast surface increased at both ends of the exposure periods, and bone resorption and formation both increased. The bone volume, trabecular thickness, and trabecular number decreased, and the secondary spongiosa of proximal metaphysis showed a marked bone loss. However, no mineralization defect was observed. At the end of the 2-week exposure period, biomarkers of osteoclasts and osteoblasts had increased the most, and the osteoblast surface, osteoclast surface, and osteoclast number per bone surface increased with prolonged exposure. The pathological changes of the bone lesion in iron lactate-overloaded rats were similar to those in rats of the osteoporotic model, because they consisted of changes reflecting the increase of bone resorption and formation without an osteomalacic change. However, the decline of serum parathyroid hormone (PTH) levels was different from that of the osteoporosi s model rat. We concluded iron-induced bone lesions probably differ from those of low turnover bone diseases.

Mitochondrial abnormalities of muscle tissue in mice with juvenile visceral steatosis associated with systemic carnitine deficiency.

A mouse with juvenile visceral steatosis (the JVS mouse) has been recognized as a novel animal model for systemic carnitine deficiency. We examined cardiac, skeletal and smooth muscle cells in JVS and control mice by light and electron microscopy. Cardiac and skeletal muscle cells of these mice at 4 weeks of age exhibited a ragged-red appearance after trichrome staining. Electron microscopy, demonstrated increased numbers of mitochondria and lipid droplets in the cells. Compression or distortion of the myofibril bundles, primarily due to the increased number of mitochondria, suggests the possible existence of a functional disturbance of the cardiac and skeletal muscle. In the urinary bladder, only one or two large lipid droplets and slightly increased number of mitochondria were recognized in the perinuclear region of the smooth muscle cells. At 8 weeks of age, the mouse enzyme histochemistry specific for mitochondria, such as cytochrome c oxidase and succinic dehydrogenase, and oil red O staining, confirmed further increases in the number of mitochondria and lipid droplets in the heart. However, the accumulation of these organelles in the skeletal and smooth muscle cells was no greater than that noted in JVS mice at 4 weeks of age. In the cardiac muscle cells, autolysosomes or autophagic vacuoles containing electron-dense membranous, lamellar or whorled structures closely associated with mitochondria and pseudoinclusion bodies in the nucleus were recognized, and bundles of myofibrils were buried under numerous mitochondria, suggesting the existence of disturbed contractile function in the heart of JVS mice. These results indicate that this murine strain associated with systemic carnitine deficiency exhibits a generalized mitochondrial abnormality in the muscle system especially in the heart.

T-Cell Lymphoma with Eosinophilic Infiltration Involving the Intestinal Tract in 11 Dogs

Among the intestinal tumors of hematopoietic cell origin, lymphoma is the most common in the dog. Herein, we characterized the clinical and pathologic features of 11 dogs (average age, 10.6 ± 2.5 years) with T-cell lymphoma of the intestinal tract with eosinophil infiltrates. No sex predominance was apparent. All had localized tumor masses in the small intestine. Grossly, the intestinal wall was thickened, and the lumen of the affected intestine was usually narrowed. Microscopically, we observed transmural diffuse invasion of round to pleomorphic tumor cells. Tumor cells showed varying morphology, from scanty to abundant cytoplasm, and round to ovoid nuclei with scattered to dense chromatin. In seven of the dogs, tumor cells had infiltrated into the epithelium. All showed infiltration of eosinophils and all 11 tumors had a T-cell phenotype (CD3+,CD79-). Only one tumor stained positive for the mast cell marker c-kit and none was positive for mast cell tryptase. We did not observe ultrastructurally apparent granules in any of the tumor cells. These results suggest that, in dogs, T-cell lymphomas of intestinal origin resemble mast cell tumors of intestinal origin with respect to cell structure and eosinophil infiltration. Therefore, in the absence of epitheliotropism, it is difficult to confirm the differential diagnosis without immunostaining for mast cell and lymphocyte markers, including mast cell tryptase, c-kit, CD3, and CD79.

Mitochondrial abnormalities in a murine model of primary carnitine deficiency. Systemic pathology and trial of replacement therapy.

Mitochondrial abnormalities and effectiveness of replacement therapy were examined in a murine model of systemic carnitine deficiency, namely the juvenile visceral steatosis (JVS) mouse. Homozygous JVS mice revealed severe lipid deposition and abnormal mitochondria in liver, heart, skeletal muscle, and kidney, but there was no pathological change in the nervous system, though they showed cerebral signs. There were numerous ragged-red fibers in muscles, but enzyme activities of the respiratory chain were intact. Histograms of oxidative and nonoxidative muscle fibers showed an increase in small and oxidative muscle fibers in 4-week-old JVS mice, but this difference no longer existed in 8-week- or 1-year-old JVS mice. On the contrary, Mn-superoxide dismutase immunostaining of muscle showed a focal increase in every age of JVS mice. With L-carnitine treatment, JVS mice could survive for a year, but to some extent, there were the same pathological changes as those seen in untreated mice.

Abscess-Forming Inflammatory Granulation Tissue with Gram- Positive Cocci and Prominent Eosinophil Infiltration in Cats: Possible Infection of Methicillin-resistant Staphylococcus

We occasionally encounter feline cervical or mesenteric lesions diagnosed histopathologically as abscess or inflammatory granulation tissue with eosinophil infiltration. Gram-positive cocci accompany the lesions. In the present study, such lesions obtained from 27 cats were examined to evaluate the histopathologic features and the nature of the causative bacteria. The average age was 7.3 ± 3.5 years. No sex predilection was observed. Most frequent locations of the lesions included the abdominal cavity with/without mesenteric lymph nodes (11/ 27, 41%) and subcutaneous tissue or lymph nodes of the neck (9/27, 33%). Common clinical presentation was a localized mass. Grossly, the lesions contained abscesses in the center and were surrounded by fibrous tissue. Microscopically, the necrotic zone contained bacterial colonies. Large numbers of eosinophils and macrophages infiltrated the area surrounding the necrotic tissue. The surrounding connective fiber-rich granulation tissue demarcated the eosinophilic abscess. The bacteria were Gram-positive cocci in 23 of the 27 cats and were positive for anti-staphylococcus antiserum in 19 of the 23 cats. In 15 out of 17 lesions, the colonies expressed immunoreactivity to penicillin-binding protein 2′, which is a drug-resistance gene product of methicillin-resistant Staphylococcus (MRS) species. These findings suggest strongly that MRS causes this type of infectious lesion.

Peripheral neuropathy in the spontaneously diabetic WBN/Kob rat

Abstract We report that the morphological characteristics of the periperhal neuropathy in WBN/Kob rat, a diabetic animal model that develops persistent diabetes, were primary segmental demyelination and secondary axonal degeneration. These findings are similar to those in human patients with diabetes mellitus and unlike those in rodents with streptozotosin-induced diabetes. However, these changes were also indistinguishable from those of age-dependent neuropathy. In the spontaneous peripheral motor neuropathy of rats, pressure neuropathy from housing in wire-mesh cages has also been reported to be indistinguishable from the peripheral neuropathy in plantar nerve or tibial nerve. Therefore, we examined phrenic nerves that were free from the pressure of body weight in rats and described the changes with light and electron microscopy. The morphological changes of the nerve fibers consisted of myelin blebbing or distention, and early remyelination. The changes were seen with age. On morphometric analysis, a marked reduction of fiber occupancy was observed in WBN/Kob rats over 23 months old. The present study demonstrated that the peripheral neuropathy of WBN/Kob rats is myelinopathy. Since the phrenic nerve was not affected by pressure neuropathy anatomically, this study indicates that the peripheral neuropathy of WBN/Kob rats is not pressure neuropathy.

Iron lactate-induced osteomalacia in association with osteoblast dynamics

Osteomalacia was induced in rats fed a diet containing 50,000 ppm (5%) iron lactate for 13 weeks. The histopathology and histomorphometrical dynamics of osteoblasts under this condition were examined. Bone histomorphometry of the proximal tibial metaphysis revealed that the osteoblast surface, osteoid volume, osteoid surface and labeled surface ratio, which are the parameters of bone formation had increased. The blood chemistry revealed the greatest elevation in the osteocalcin level; however, the parathyroid hormone (PTH) secretion and inorganic phosphorus level were very low. From the serum biochemical, histopathological and histomorphometrical findings, the bone lesion in iron lactate-overloaded rats was considered to be similar to low turnover osteomalacia showing decreased trabeculae in secondary spongiosa and increased lamellar osteoid. Furthermore, an iron-positive reaction was detected at the interface between osteoid and mineralized bone. In the bone lesions induced by chronic iron overload, osteoblast recruitment exceeded that of mineralization or, alternatively, the iron within osteoblasts along the trabecular bone suppressed the remodeling and led to an increase in osteoid thickness.

Chediak-Higashi syndrome in rats : Light and electron microscopical characterization of abnormal granules in beige rats

Chediak-Higashi syndrome (CHS) is a rare disease occurring in several animal species. Recently, mutant beige rats with CHS were found among DA strain rats in Japan. In the present study, histological examination of beige rats revealed giant granules in the hepatocytes, renal proximal tubules, submandibular ducts, thyroid follicular cells, granulocytes, mast cells, melanocytes, retinal pigment epithelial cells and globular leucocytes. Ultrastructurally, these granules varied from enlarged lysosomes, which were amorphous, granular or filamentous, to giant mast cell granules, crystalloid granules of eosinophils and slightly enlarged neutrophil granules. These findings bore many similarities to those in the beige mouse, which is a well known animal model for CHS, but some differences were apparent. Thus the giant granules of beige rats were larger and more easy to observe than those in beige mice. The study indicated that the beige rat may prove useful as an animal model for CHS.

Eosinophilic Gastroenterocolitis in Iron Lactate-Overloaded Rats

Eosinophilic gastroenterocolitis with peripheral eosinophilia was induced in rats fed a diet containing 2.5% or 5.0% iron lactate for 3 mo. Additional findings consistent with iron overload were also observed. Microscopically, the lesions consisted of eosinophilic infiltrations in the mucosa and submucosa along the whole length of the gastrointestinal tracts, increased surface area of the gastric mucosal propria covered with mucous cells, and increased apoptotic bodies in the gastric glandular neck of rats in the 2.5% and 5.0% groups. An increased number of intraepithelial globule leukocytes in the gastric and intestinal lamina propria was also observed in the 5.0% group. Globule leukocytes in the gastric mucosa contained obviously enlarged granules in their cytoplasm in these rats. The granules of the globule leukocytes were positive for rat mast cell protease II, suggesting the mastocyte origin of these cells. Although severe infiltration of eosinophils and globule leukocytes suggested a type-1 hypersensitivity reaction, other features such as an increasing vascular permeability were not detected. Serum IgE levels in the 5.0% and control groups were <3 ng/ml. Final body weights of male and female rats of the 5.0% group were suppressed to 70% and 90%, respectively, of those of the control rats, whereas food consumption was comparable to that of the control group. The morphologic characteristics of the gastrointestinal lesions and peripheral eosinophilia induced in rats fed iron lactate were very similar to those in some cases of eosinophilic gastroenterocolitis in humans and other animals.