Hepatoblastoma in a cat.

Hepatoblastomas are neoplasms that originate from putative pluripotential stem cells of the liver. A hepatic mass from an 8-year-old Abyssinian cat was composed of cords and sheets of neoplastic cells, with scattered rosettes and small ductal structures. Most neoplastic cells had a pale eosinophilic cytoplasm and a round to ovoid nucleus. The tumor also had short spindle cells with an oval nucleus. Immunohistochemically, neoplastic cells were weakly positive for embryonic hepatocellular markers, such as alpha-fetoprotein and cytokeratin (CK) 8/18, but negative for the hepatocellular marker Hepatocyte Paraffin 1. The cells were also positive for CD56/neural cell adhesion molecule and for the biliary epithelial markers CK 7, CK 8/18, CK CAM5.2, and vimentin, but negative for CK 20. Some neoplastic cells expressed neuroectodermal or neuroendocrine markers, such as protein gene product 9.5 and synaptophysin, but were negative for chromogranin A and not argyrophilic by the Grimelius technique. The cat died soon after the biopsy without clinical improvement.

Dental caries and caries-related periodontitis in type 2 diabetic mice.

Diabetic patients are predisposed to periodontal disease as well as dental caries; however, there are contradictory reports about the possible association between dental caries and diabetes. Thus, the authors set out to determine whether diabetes affects onset of dental caries and periodontal disease and to clarify whether dental caries and periodontal disease are associated with each other in diabetic db/db mice. Oral tissue was examined from 68 male mice (diabetic db/db and nondiabetic db/+; aged 20, 30, 40, and 50 weeks) and 20 female mice (db/db and db/+; aged 50 weeks). Macroscopically, caries were seen developing in the diabetic mice by 20 weeks of age. The number of teeth with dental lesions increased with age in the db/db mice at a significantly higher incidence than that of db/+ mice. Histologically, dental caries were detected in 30 of 120 molars in 17 of 20 db/db mice at 50 weeks of age and in 4 of 108 molars in 4 of 18 db/+ mice of the same age. The severity of dental caries in db/db mice was significantly higher than it was in db/+ mice. Dental caries were a primary change that led to bacterial gingivitis and pulpitis. These lesions spread to the dental root and periodontal connective tissue through the apical foramen. Apical periodontitis was more frequent and severe when occurring in close association with dental caries. In conclusion, there is a strong relationship between diabetes and dental caries, but in this model, it is highly probable that the onset of periodontal disease was a secondary change resulting from dental caries.

Cardiac vascular hamartoma in two slaughtered cattle.

Two cases of cardiac vascular hamartoma were detected in slaughtered cattle. In each case, a single nodular protrusion (ca 2.5 cm in diameter) was located in the same part of the right atrium. Tortuous vessels of variable size with irregular lumina were seen on the cut surface of each nodule. Microscopically, there were many dysplastic vascular structures within the nodules. The vascular structures showed various changes such as irregular thickening of the tunica intima and the tunica media, walls with variable amounts of fibres (elastic, collagen and smooth muscle), some of which were disarranged. Mature adipose tissue and fibrous connective tissue were seen close to the vascular structures and intervascular tissue. In the nodules, bundles of cardiac muscle were disorganized, intermingled with connective tissue, and in some areas embedded within fibrous connective tissue.

Renal dysplasia unrelated to claudin-16 deficiency in Japanese Black cattle.

Renal lesions of the type usually found in claudin-16 (CL-16) defective Japanese Black cattle (homozygous for CL-16 deficiency) were identified in six animals of this breed, aged 28-59 months, which were either heterozygous for CL-16 deficiency (type 1) or normal, as judged by a DNA-based test associated with the CL-16 gene. Histopathologically, all six cases showed elongated focal lesions which ran through the cortex to terminate in the outer zone of the medulla. The lesions contained components that included: (1) immature tubules, (2) small irregularly shaped tubules with thickening of the basement membrane, (3) mesenchymal cells in an increased interstitium, (4) small atrophic glomeruli, and (5) immature glomeruli. The glomeruli were noticeably reduced in number, and large glomeruli with an increased number of mesangial cells were observed throughout the entire cortical area. Cystic dilation of tubules and flattening of the epithelium were noted in all areas of the kidney. Histopathologically, the renal lesions in the six cases were indistinguishable from those reported previously in cattle homozygous for CL-16 deficiency. These findings demonstrate that such renal lesions in Japanese Black cattle are not necessarily associated with homozygous deletion of the CL-16 gene.

Pigmented cutaneous papillomatosis (pigmented epidermal nevus) in three pug dogs; histopathology, electron microscopy and analysis of viral DNA by the polymerase chain reaction.

Canine pigmented epidermal nevus (CPEN) is a skin disorder of some breeds of dog characterized by multiple black plaques of the haired and non-haired skin. Three cases of pigmented cutaneous papillomatosis (previously described also as CPEN) in pug dogs were investigated histopathologically, immunohistochemically and electron microscopically. Additionally, DNA analyses with the polymerase chain reaction (PCR) were performed in two cases. Many nuclei of the stratum granulosa were diffusely immunolabelled for specific structural antigens of bovine papillomavirus (subgroup A), but nuclear inclusion bodies were not detected by retrospective examination of haematoxylin and eosin-stained sections of the affected skin. Aggregates of small numbers of viral particles (ranging from 37 to 43 nm in diameter) with a hexagonal structure were sparsely scattered throughout the nuclei of some of the superficial keratinocytes. PCR amplification targeted for the L1 gene of papillomavirus cloned from a case of CPEN yielded an expected fragment of 194-bp in the two CPEN cases examined but not in a case of canine oral papilloma.

Otsuka Long-Evans Tokushima fatty (OLETF) rat is not a suitable animal model for the study of angiopathic diabetic retinopathy.

We have previously shown that the peak latency of oscillatory potential (OP), the earliest electroretinographic manifestation of diabetic retina, was prolonged in Otsuka Long-Evans Tokushima Fatty (OLETF) rat, a model of non-insulin-dependent diabetes. These observations suggest that retinal neuronal dysfunction revealed by the OP abnormality in the electroretinogram takes place prior to the angiopathic diabetic changes in this animal model. However whether acellular capillaries and pericyte ghosts, one of the histopathological hallmarks of early diabetic retinopathy in humans, could occur in OLETF rat remains to be elucidated. In the present study, we first prepared the retinal trypsin digests of OLETF and control Long-Evans Tokushima Otsuka (LETO) rats at 45 weeks old and then compared the number of acellular capillaries and pericyte ghosts in the retinas of OLETF rats with that in LETO rats. Blood glucose levels were higher in the OLETF rats than those in LETO rats. Retinal capillaries of OLETF rats were found to remain morphologically normal and pericyte ghosts were barely detectable. There was no difference in the number of acellular capillaries in the retinas between OLETF and LETO rats. The present study indicates that acellular capillaries and pericyte ghosts, the characteristic morphological changes in early diabetic retinopathy, are not accelerated in OLETF rats. Our data suggest that OLETF rat is not a suitable animal model for the study of angiopathic diabetic retinopathy.

Enhancement of tumor growth under short light/dark cycle in mouse lung.

We examined whether a change in daily light/dark cycle affected DNA synthesis and tumor growth in mouse lung. Both CD-1 and A/J mice, which were treated with urethane and maintained under the short light/dark cycle (6 h light, 6 h dark), developed significantly larger sizes of lung tumors than the mice maintained under the standard light/dark cycle (12 h light, 12 h dark), indicating that short and frequent light/dark cycles enhanced tumor growth. When 3H-labeled thymidine was injected and incorporated radioactivity in the lung tissue was measured, two peaks of DNA synthesis in the lung were observed in a day under the short light/dark cycle, and both peaks were during light periods, while only one peak was observed during the dark period under the standard light/dark cycle. Although the level of [3H]thymidine incorporation into the lung tissue in the short light/dark cycle is lower than that in the standard cycle, frequent or unbalanced DNA synthesis may have promoted the growth of lung tumors.

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.

Developmental study on reduction and kinks of the tail in a new mutant knotty-tail mouse.

The knotty-tail (knt/knt) mouse has a short and knotty tail. The tail deformity is caused by a decrease in the number of caudal vertebrae and a deformity of them in the distal part of the tail. The objective of the study was to determine how reduction and kinks of the tail region were formed during secondary body formation. By day 12.0 pc, the somitogenesis of knt/knt embryos was completed; the number of caudal somites more or less agreed with those of the caudal vertebrae in knt/knt mice and were similar to those of knt/+ embryos. On the other hand, the somitogenesis of knt/+ embryos continued up to day 12.5 pc. The somites below about the sixth caudal somite were wedge-shaped with a dorsal apex in knt/knt embryos. The location of abnormal somites also corresponded well to that of deformed caudal vertebrae. Abnormal somitogenesis was always preceded by abnormalities in the presomitic region. Under gross observation, this could be seen to become markedly thickened, and histologically its dorsoventral diameter increased in the transverse plane on days 10.5-12.0 pc. In the mesenchyme there was often obvious cell death at the boundary of the unsegmented area and the tail bud after day 10.5 pc. These results suggested that the shortness of tail was primarily caused by the agenesis of distal caudal vertebrae following the agenesis of distal caudal somites, and partly by the disappearance of the presomitic part due to cell death, while the tail kinks were caused by the deformation of each caudal vertebra following disturbances of the caudal somites. Also, it is highly probable that the prominent cell death at the boundary of the unsegmented area and the tail bud may involve a defect or deformity of somites in this mutant.

Enthesopathy of the radial tuberosity in two thoroughbred racehorses.

Two cases of enthesopathy of the radial tuberosity in Thoroughbred racehorses are described. Soft X-ray pictures revealed separated bony fragments at the anterior aspect of the radial tuberosity, resembling the lesions of Osgood-Schlatter disease in children. Osgood-Schlatter lesions result from detachment of a portion of the apophysis of the tibial tuberosity. However, in the affected horses, the detached bony fragments consisted of cortical bone tissue composed of trabeculae with osteons similar to lamellar bone, the main component of the radial tuberosity. Tendon fibrils were inserted into the anterior parts of the detached fragments, and scar tissue filled the gap between the posterior part of the fragments and the radial tuberosity. The bone fragments may have originated from an avulsion fracture at the site of attachment of the tendinous portion of the biceps brachii muscle to the bone tissue of the radial tuberosity, a site at which high-tensile force is repeatedly exerted by muscle contraction.

Accumulation of pigment granules in lacrymal gland epithelium in practolol-treated beagle dogs.

A 6-month oral toxicity test of practolol was carried out in beagle dogs as a reference control for a newly developed beta blocker. No significant drug-induced changes were detected in any animals by various ophthalmological examinations such as ERG, tear flow, lysozymal activity in tears, etc. However, an unusual pathological change was detected in the lacrymal gland of all five dogs treated with practolol and not in control animals. Macroscopically, the lacrymal glands assumed a blackish brown to deep black colour on both the outside and the cut surface. Microscopically, fine, dark-brown pigment granules were present in the apical and supra-nuclear portion of the cytoplasm of predominantly serosal type epithelial cells. These pigments reacted positively to Schmorl's method for lipofuscin, but gave a negative PAS reaction for polysaccharide, Prussian blue for iron and Ziehl-Neelsen method for ceroid pigment. They were detected as membrane-bound electron-dense bodies by electron microscopy. Similar pigments were also deposited in the cytoplasm of the apocrine sweat gland. Although the mechanism of the accumulation of these granules is far from clear, concentration of practolol in the lacrymal gland is considered to be very closely related to the presence of these granules. A possible mechanism for ocular toxicity by practolol, involving this change, is discussed.

Relationship between cellular morphology and immunocytological findings of spontaneous pituitary tumours in the aged rat.

A total of 339 spontaneous pituitary tumours from 284 aged rats were studied by light microscopy. Based on the cellular morphology in preparations stained by haematoxylin and eosin, tumour cells were classified into 4 types: granular; agranular small; agranular large polygonal; and agranular large slender cells. Eight tumours consisted of mixed neoplastic masses of 2 types of cells. A total of 85 cases representative for each tumour type was used for special staining and immunocytochemistry. All tumours of the granular cell type and some tumours of the agranular large polygonal cell type had granules which stained red by azocarmine and were positive for prolactin. All agranular small cell type tumours were also positive for prolactin and agranular slender cell type tumours were positive for adrenocorticotropic hormone. Only tumours of the agranular large polygonal cell type gave an indefinite or negative reaction for all the various pituitary hormones. These results indicate a relatively good correlation between the cellular morphology and the immunocytochemistry of spontaneous pituitary tumours in aged rats.

The morphogenesis of a papillomatous gastric polyp in the crab-eating monkey (Macaca fascicularis).

The histopathology of gastric papillomas in 17 crab-eating monkeys from Indonesia and Malaysia was investigated. The changes in the affected mucosa consisted of papillomatous proliferation with accidental heterotopia, desquamation or necrosis of the epithelium associated with eggs or adults of the small nematode Nochtia nochti, inflammatory cell infiltration and haemorrhage or oedema and fibrosis. The primary pathogenic effect of this parasite was due to its irritant action on the gastric mucosa. Hyper-regeneration, with a downward shift of the proliferating zone in the gastric gland and an inflammatory process, appeared to play a significant role in the morphogenesis of this lesion. It is concluded that the gastric papilloma associated with Nochtia nochti in the monkey is a parasitic inflammatory polyp.

Amoebosis in the flat-shelled spider tortoise (Acinixys planicauda).

Amoebosis is one of the most common protozoal diseases of reptiles, but has rarely been reported in tortoises. Six cases of amoebosis were identified in flat-shelled spider tortoises immediately after their importation from Madagascar to Japan. Necropsy revealed an extensive green pseudomembrane of ulceration along the length of the thickened wall of the colon, and disseminated green foci in the liver. Histologically, the colonic wall was severely ulcerated and covered with a fibrinonecrotic pseudomembrane, and many amoebic trophozoites were seen in the submucosa. Multifocal necrosis with intralesional amoebic trophozoites corresponded to the disseminated green foci in the liver. Amoebic trophozoites invaded many blood vessels in the colon and liver. All tortoises exhibited severe colonic lesions, but the severity of the hepatic lesions varied. These findings suggest that amoebic colitis was the primary lesion with spread of amoebae to the liver via the portal system.

Naturally occurring Tyzzer's disease in a clean mouse colony: high mortality with coincidental cardiac lesions.

Light and electron microscopic examinations were performed on tissues from 12 young mice which were affected by naturally-occurring Tyzzer's disease. Eight of the 12 mice had cardiac lesions which have not previously been reported in mice and which caused a high mortality. The cardiac lesions were detected in mice which had severe and advanced intestinal lesions which penetrated the deeper mucosa and muscular layer with active regeneration of the mucosal epithelium. Periodical serological tests to monitor the bacterial and viral status of this colony showed that it was free of other agents of murine disease such as mouse hepatitis virus, Corynebacterium kutscheri and Salmonella spp. until the onset of Tyzzer's disease and that no mixed infection occurred at the onset. It is considered that an advanced intestinal lesion is essential for the formation of cardiac lesions in Tyzzer's disease in mice.

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.

Glomerular lesions in spontaneously occurring diabetic WBN/Kob rats.

Glomerular lesions in WBN/Kob male rats with spontaneous diabetes were examined histopathologically. The glomerulopathy caused by diabetes was compared with lesions in chronic progressive nephropathy of non-diabetic SD and F344 male aged rats. Diffuse and global thickening of the mesangial area was observed only in WBN/Kob rats and showed a statistically significant correlation with serum glucose concentrations. Therefore, it suggested that the mesangial thickening was a result of hyperglycaemia. Fibrin cap-like lesions were seen in both WBN/Kob and non-diabetic SD or F344 male rats. The severity of these lesions was closely related to that of chronic progressive nephropathy and, therefore, the fibrin cap-like lesions were considered to be due to the chronic progressive nephropathy.

Histological and topographical characteristics of canine granulomatous leptomeningitis.

Histological and topographical characteristics of granulomatous leptomeningitis were studied in 14 laboratory beagle dogs (12 males, two females), 8 to 19 months old. The dogs, which were either saline-treated controls or drug-treated animals in four different toxicity studies, remained clinically normal during the experimental period, and granulomatous leptomeningitis was identified as an incidental finding by routine histopathological examination. There were no macroscopical lesions in the brain or other organs. Microscopical lesions of the central nervous system were of three types, namely (1) a diffuse inflammatory type, characterized by diffuse infiltration of macrophages, (2) a granulomatous type, characterized by non-caseating granulomas, or (3) a fibrotic type, featuring dense connective tissue. Each of the 14 cases fell into one of three disease phases, early, fulminating and healing. In the early phase, only diffuse inflammatory-type lesions were seen. In the fulminating phase, all three types of lesion were present. In the healing phase, discrete granulomas were relatively few and fibrosis was prominent.

Glycogen accumulation in the renal tubular cells of spontaneously occurring diabetic WBN/Kob rats.

Cytoplasmic and nuclear accumulation of glycogen granules in the kidney cells of 72 male WBN/Kob rats with a long-term diabetic condition was studied histologically and by electron microscopy. The incidence and degree of the accumulation showed good correlation with the blood glucose concentration. In the kidneys, there was evidence of two types of lesion, cytoplasmic glycogen accumulation in the distal convoluted tubules and nuclear accumulation in the ascending thick segment of Henle's loops. Electron microscopically, the cytoplasmic glycogen accumulation was often associated with an increased number of lysosomal bodies containing lamellar bodies. Glycogen bodies, the halo of which was thought to be identical with that of nuclear bodies, were frequently observed in the nuclei containing the glycogen granules. These morphological and topographical differences between the two types of lesion were considered suggestive of different pathogenetic mechanisms for glycogen accumulation in the kidney cells.

Cutaneous papillomatosis associated with papillomavirus infection in a dog.

A 7-year-old female Kerry blue terrier dog developed 20 cutaneous nodules, up to 4 mm in diameter, over the body. Light and electron microscopy demonstrated that they were virus-associated inverted papillomas and they are described because canine skin viral papillomas have not been frequently reported.