Proliferative and Nonproliferative Lesions of the Rat and Mouse Central and Peripheral Nervous Systems: New and Revised INHAND Terms

Harmonization of diagnostic terminology used during the histopathologic analysis of rodent tissue sections from nonclinical toxicity studies will improve the consistency of data sets produced by laboratories located around the world. The INHAND Project (International Harmonization of Nomenclature and Diagnostic Criteria for Lesions in Rats and Mice) is a cooperative enterprise of 4 major societies of toxicologic pathology to develop a globally accepted standard vocabulary for proliferative and nonproliferative lesions in rodents. A prior manuscript (Toxicol Pathol 2012;40[4 Suppl]:87S-157S) defined multiple diagnostic terms for toxicant-induced lesions, common spontaneous and age-related changes, and principal confounding artifacts in the rat and mouse central nervous system (CNS) and peripheral nervous system (PNS). The current article defines 9 new diagnostic terms and updates 2 previous terms for findings in the rodent CNS and PNS, the need for which has become evident in the years since the publication of the initial INHAND nomenclature for findings in rodent neural tissues. The nomenclature presented in this document is also available electronically on the Internet at the goRENI website (http://www.goreni.org/).

Macrophage-Associated Gelatinase Degrades Basement Membrane at the Optic Fissure Margins During Normal Ocular Development in Mice

Purpose

Basement membrane degradation and macrophage aggregation at the optic fissure margins are crucial to optic fissure closure during normal murine eye development. Basement membrane degradation is also an essential step in cancer development, and matrix metalloproteinases (MMPs) play an important role. In this study, we investigated MMP alteration at the degrading basement membrane of optic fissure margins in mice and attempted to clarify the relationship between MMP activity and macrophages.

Methods

Serial coronal frozen sections of eyes from BALB/c fetuses were prepared and gelatinase activity was examined using in situ zymography techniques. The frozen sections were immunohistochemically stained with anti-F4/80, anti-MMP 2, and anti-MMP 9 antibodies. Serial coronal paraffin sections were also immunohistochemically stained with anti-type IV collagen and anti-F4/80, and basement membrane disintegration and macrophage aggregation at the optic fissure margins were examined.

Results

The basement membrane of optic fissure margins was rapidly degraded during gestational days (GDs) 12.0 to 12.5. Meanwhile, gelatinase activity at F4/80-positive macrophages significantly increased during GDs 11.5 to 12.0 and declined thereafter; some of those were also positive for MMP2. The number of macrophages was also increased and decreased at nearly the same time.

Conclusions

Intramacrophage MMPs may be responsible for basement membrane degradation at the optic fissure margins during normal eye development in mice.

Suspected lily toxicosis in a meerkat (Suricata suricatta): a case report

Lilies are considered nephrotoxic only to domestic cats, which belong to the family Felidae of the suborder Feliformia. However, a 7-month-old female meerkat, belonging to the family Herpestidae of the suborder Feliformia, presented with oliguria, seizure, tachypnea, self-biting, and nystagmus after it ingested lilies. The meerkat died approximately 40 hr after lily ingestion. Gross and histopathologic lesions consistent with acute renal failure were conspicuous in the animal. The renal lesions were acute tubular necrosis, corresponding to the typical pathological changes of lily toxicosis in cats. In addition, massive hepatocyte necrosis and pulmonary congestion/edema were observed. These findings suggest that lily toxicosis in meerkats is characterized by pulmonary and hepatic failure, in addition to the renal failure observed in domestic cats.

Effect of combined dyslipidemia and hyperglycemia on diabetic peripheral neuropathy in alloxan-induced diabetic WBN/Kob rats

Clinical and experimental research have suggested that dyslipidemia aggravates diabetic peripheral neuropathy (DPN). However, whether dyslipidemia is a risk factor for DPN remains unclear. To investigate the effect of dyslipidemia on DPN, morphological features of peripheral nerves were analyzed in diabetic rats treated with a high-fat diet (HFD). Male rats were divided into four groups: nondiabetic rats (N), alloxan-induced diabetic rats (AL), diabetic rats treated with an HFD (AH), and nondiabetic rats treated with an HFD (HF). Combined hyperglycemia and dyslipidemia (AH group) induced a significant increase in plasma triglyceride and cholesterol levels. In addition, the combined effects contributed to a reduction in myelin size and a reduction in myelin thickness as indicated on sensory sural nerve histograms. There was also a reduction in the size of motor nerve axons when compared with the effects of hyperglycemia or dyslipidemia alone. However, the sensory nerve conduction velocity in the AH group was slightly but not significantly lower than those in the HF and AL groups. These results suggest that combined hyperglycemia and dyslipidemia induced mild peripheral motor and sensory nerve lesions, without significantly affecting sensory nerve conduction velocity.

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.

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.

Probiotic (yogurt) containing Lactobacillus gasseri OLL2716 is effective for preventing Candida albicans-induced mucosal inflammation and proliferation in the forestomach of diabetic rats

Oral and esophageal candidiasis sometimes leads to mucosal hyperplasia, and progresses to carcinoma. We have produced an animal model for hyperplastic mucosal candidiasis in the forestomach that has a proliferative lesion of the squamous epithelium with chronic inflammation and C. albicans infection, some of which advanced to squamous cell carcinoma. There are many reports of the antibacterial effects of probiotics, but consensus about their antifungal effect has not been reached. In the present study, we investigate whether probiotic (yogurt) containing Lactobacillus gasseri OLL2716 (LG21 yogurt) can prevent proliferative and inflammatory changes caused by C. albicans in this mucosal candidiasis animal model. Diabetes was induced in 8-week-old WBN/Kob rats by intravenous administration of alloxan. One group of diabetic rats received a saline containing C. albicans and LG21 yogurt orally (DC+LG21 group) for 30 weeks, and another group received only C. albicans (DC group) for 30 weeks. They were sacrificed at 40 weeks of age, and analyzed histopathologically. In the DC+LG21 group, squamous hyperplasia at the greater curvature was significantly milder, and the Ki-67 positive index was significantly lower compared with the DC group. Suppurative inflammation with C. albicans also tended to be suppressed at the greater curvature. These findings suggest that probiotic (yogurt) containing Lactobacillus gasseri OLL2716 can suppress squamous hyperplastic change and inflammation associated with C. albicans infection in the forestomach.

Effect of deoxycorticosterone acetate-salt-induced hypertension on diabetic peripheral neuropathy in alloxan-induced diabetic WBN/Kob rats

The relationship between hypertension and diabetic peripheral neuropathy (DPN) has recently been reported in clinical research, but it remains unclear whether hypertension is a risk factor for DPN. To investigate the effects of hypertension on DPN, we analyzed morphological features of peripheral nerves in diabetic rats with hypertension. Male WBN/Kob rats were divided into 2 groups: alloxan-induced diabetic rats with deoxycorticosterone acetate-salt (DOCA-salt) treatment (ADN group) and nondiabetic rats with DOCA-salt treatment (DN group). Sciatic, tibial (motor) and sural (sensory) nerves were subjected to qualitative and quantitative histomorphological analysis. Systolic blood pressure in the two groups exhibited a higher value (>140 mmHg), but there was no significant difference between the two groups. Endoneurial blood vessels in both groups presented endothelial hypertrophy and narrowing of the vascular lumen. Electron microscopically, duplication of basal lamina surrounding the endothelium and pericyte of the endoneurial vessels was observed, and this lesion appeared to be more frequent and severe in the ADN group than the DN group. Many nerve fibers of the ADN and DN groups showed an almost normal appearance, whereas morphometrical analysis of the tibial nerve showed a significant shift to smaller fiber and myelin sizes in the ADN group compared with DN group. In sural nerve, the fiber and axon-size significantly shifted to a smaller size in ADN group compared with the DN group. These results suggest that combined diabetes and hypertension could induce mild peripheral nerve lesions with vascular changes.

Hepatic Lesions Caused by Large Granular Lymphocyte Leukemia in Fischer 344 Rats: Similar Morphologic Features and Morphogenesis to Those of Nodular Regenerative Hyperplasia (NRH) in the Human Liver

To characterize the hepatic lesions in Fischer 344 (F344) rats afflicted with large granular lymphocyte (LGL) leukemia, the livers of rats with LGL leukemia at various stages were examined histopathologically and immunohistochemically. The morphologic features in the livers of rats afflicted with LGL leukemia were diffuse, uniform-sized, granular, or micronodular lesions consisting of hepatocytes showing centrilobular atrophy and perilobular hypertrophy (CAPH) without fibrosis. With progression in the stage of the LGL leukemia, the severity of the CAPH of hepatocytes increased resulting in fatty change and/or single-cell necrosis, along with compensatory hyperplasia of the hepatocytes, finally resulting in lesions similar to those seen in nodular regenerative hyperplasia (NRH) in the human liver. The CAPH of hepatocytes was a nonspecific tissue adaptation against ischemia or hypoxemia and/or imbalance in blood supply due to disturbance in the portal circulation and hemolytic anemia induced by the leukemia cells. In addition, direct and/or indirect hepatocellular injuries by leukemia cells were considered to be necessary for the formation of human NRH-like lesions. Morphogenetic investigation of the livers of rats afflicted with LGL leukemia may be helpful to clarify the pathogenesis of NRH in the human liver.

Insulin-ameliorated peripheral motor neuropathy in spontaneously diabetic WBN/Kob rats

Rodent models of diabetes develop a slowing of nerve conduction velocity and mild axonal atrophy, but generally lack overt degenerative neuropathy. Spontaneously diabetic Wistar Bonn Kobori (WBN/Kob) rats develop severe diabetic peripheral motor neuropathy with a slowing of nerve conduction velocity. We examined the effect of glycemic control, using insulin implant, on neuropathic changes in these rats. Animals were divided into 2 groups: WBN group (spontaneously occurring diabetes rats) and WBN + insulin group (spontaneously occurring diabetes rats treated with insulin implants until 90 weeks of age). Conduction velocity was measured in sciatic–tibial motor nerves. These nerves also underwent qualitative and quantitative histomorphologic analysis. Mild to severe hyperglycemia (>200 mg/dl) and glycosuria (>100 mg/dl) were observed in the WBN group. In contrast, the blood glucose level of the WBN + insulin group fluctuated between normoglycemia (<200 mg/dl) and hyperglycemia. Conduction velocity significantly decreased in WBN group compared with WBN + insulin group. Morphologic analysis of the sciatic and tibial nerves of WBN group showed severe changes, including axonal degeneration, myelin distention, endoneurial fibrosis and microangiopathy. Insulin treatment corrected these changes without microangiopathy. These results suggest that insulin could decrease axonal atrophy and myelin distension of peripheral nerve in diabetic WBN/Kob rats. Observation of WBN/Kob rats revealed changes of axon, myelin and capillary caused by diabetes, thus indicating that this animal is a suitable model for investigating diabetic peripheral neuropathy.

Proliferative and nonproliferative lesions of the rat and mouse central and peripheral nervous systems

Harmonization of diagnostic nomenclature used in the pathology analysis of tissues from rodent toxicity studies will enhance the comparability and consistency of data sets from different laboratories worldwide. The INHAND Project (International Harmonization of Nomenclature and Diagnostic Criteria for Lesions in Rats and Mice) is a joint initiative of four major societies of toxicologic pathology to develop a globally recognized nomenclature for proliferative and nonproliferative lesions in rodents. This article recommends standardized terms for classifying changes observed in tissues of the mouse and rat central (CNS) and peripheral (PNS) nervous systems. Sources of material include academic, government, and industrial histopathology databases from around the world. Covered lesions include frequent, spontaneous, and aging-related changes as well as principal toxicant-induced findings. Common artifacts that might be confused with genuine lesions are also illustrated. The neural nomenclature presented in this document is also available electronically on the Internet at the goRENI website (http://www.goreni.org/).

Histopathology of incidental findings in beagles used in toxicity studies

The purpose of our publication is to widely communicate the pictures of spontaneous findings occurring in beagles. Spontaneous arteritis occurs commonly in beagles. Frequent sites of arteritis are the heart, spleen, pancreas, epididymis and spinal cord. Morphological similarities between spontaneous and drug-induced arterial lesions may cause confusion when evaluating vascular toxicity of chemicals such as vasodilating agents. Focal and minimal inflammatory lesions are occasionally seen in the lung and may be associated with aspiration of food particles or of unknown causes. A cystic change with copious mucin production occurs occasionally in the mucosal epithelium of the gall bladder. Nesidioblastosis is seen rarely in the pancreas of beagles. C-cell complex and lymphocytic thyroiditis are common thyroid lesions. Spontaneous focal hypospermatogenesis and lobular Sertoli-cell-only seminiferous tubules occurring frequently in beagles must be distinguished from drug-induced damage of the seminiferous tubules in toxicity studies. The morphological differences of the female genital system in each cycle need to be understood; therefore, we present the normal features of the cyclic changes of the female genital organs. Further, we provide more information on spontaneous findings in beagles for exact diagnoses in toxicity studies.

Iridal coloboma induces dyscoria during miosis in FLS mice

OBJECTIVE

Fatty liver Shionogi (FLS) mice exhibit characteristic retinochoroidal coloboma because of a failure in fusion of the embryonic optic fissure. However, the same pathogenesis should result in iridal coloboma that has not been reported in this strain. The purpose of this study was to describe the physiologic and morphometric changes in iridal tissue involved in ocular coloboma in FLS mice.

PROCEDURES

The miotic response after light exposure was evaluated in three strains of live mice, and the shape and location of the pupil were judged macroscopically. Subsequently, macroscopic abnormalities in the anterior segment and fundus were observed postmortem in all mice. During miotic and mydriatic responses in the eyes of live male FLS mice with dyscoric and normal pupils, each iris was measured in four radial directions. The enucleated eyes were examined morphometrically and histologically in both sexes of FLS mice.

RESULTS

Inferior corectopia upon light-induced miosis was clearly detected in live FLS mice. The deviated pupils were not round but oval-shaped. Clinical and postmortem examination revealed that all dyscoric eyes had hypoplastic and dysfunctional irides inferiorly in FLS mice. Histopathological examination confirmed that both the dilator and sphincter muscles and iris stroma were quantitatively diminished in the affected inferior iris. Meanwhile, the rate of fundus (retinochoroidal) coloboma in eyes exhibiting dyscoria was remarkably high, although some dyscoric eyes had no fundus coloboma.

CONCLUSIONS

Fatty liver Shionogi mice had iridal coloboma, resulting in inferior corectopia upon light-induced miosis as an indicator of ocular coloboma.

Antimicrobial agent, tetracycline, enhanced upper alimentary tract Candida albicans infection and its related mucosal proliferation in alloxan-induced diabetic rats

Alloxan-induced diabetic rats showed proliferative changes in the forestomach, accompanied by chronic inflammation, and one lesion progress to squamous cell carcinoma (SCC) without distant metastasis. The authors demonstrated that these lesions might be caused by Candida albicans infection. Antimicrobial therapy, particularly tetracycline treatment, has been blamed for a reduction in the number of competing bacterial organisms, which is frequently mentioned as a cause of candidiasis. The objective of this study is to ascertain whether or not tetracycline treatment can accelerate early-onset of C. albicans infection and the proliferative changes in this diabetic model. Alloxan-induced diabetic rats were given chlorinated water (AL group) and tetracycline solution (0.1% during week 1 and 0.01% thereafter) as drinking water (AT group). They were sacrificed after 25 weeks of drinking the treated water. The infection rate with C. albicans in the AT group was significantly higher than in the AL group. The incidence and severity of the squamous cell hyperplasia were enhanced in the AT group compared to the AL group. The proliferative lesions were consistently accompanied by inflammation and C. albicans infection in both groups. SCC was detected in one case in the AT group. These findings demonstrate that tetracycline induces C. albicans infection and enhances forestomach proliferative lesions in alloxan-induced diabetic rats.

Histopathology of incidental findings in cynomolgus monkeys ( macaca fascicularis ) used in toxicity studies

The purpose of our publication is to widely communicate pictures of spontaneous findings occurring in cynomolgus monkeys. Focal lymphoplasmacytic infiltration is commonly seen in the general organs. The frequency and severity of these lesions may be influenced by the administration of drugs with an effect on the immune system. Lymphoplasmacytic infiltration in the lamina propria of the stomach is also frequently seen in cynomolgus monkeys, and it is caused mainly by a Helicobacter pylori infection. Various degrees of brown pigments are observed in various organs, and it is possible to distinguish the material of the pigments by its morphological features and site. A focal/segmental glomerular lesion is occasionally seen in a section of the kidney, and the minimal lesion has no influence on the urinalysis. We showed the common glomerular lesions in HE-stained sections, as well as in PAM- or PAS-stained sections, for understanding the details. Young and pubertal monkeys are usually used in toxicity studies; therefore, understanding various maturation stages of the genital system is important. In particular, the female genital system needs to be understood in the morphology, because their cyclic changes are different from other laboratory animals. Thus, we present the normal features of the cyclic changes of the female genital organs. Furthermore, we provide more information on spontaneous findings in cynomolgus monkeys for exact diagnoses in toxicity studies.

Organogenesis of mild ocular coloboma in FLS mice: failure of basement membrane disintegration at optic fissure margins

Fatty Liver Shionogi (FLS) mice have been shown to develop a hereditary disorder characterized by localized retinochoroidal defects of the ventral fundus very similar to human typical ocular coloboma without microphthalmia. The objective of this study was to determine when and how the failure of the optic fissure closure occurs, and to clarify the disturbed mechanism of basement membrane disintegration during embryonal stage in FLS mice. Fetuses at day 11.5-15.5 of gestation were obtained from dams of FLS and BALB/c strain of mice. Coronal serial sections through the eye were examined by light and electron microscopy. The sections were followed by observation of the basement membrane using reaction with periodic acid-Schiff (PAS) reagent and immunohistochemical staining with anti-Laminin and anti-Type IV collagen antibodies. Both optic fissure margins closely approached each other up to GD 11.5 in all FLS and BALB/c embryos. The inner and outer layers of the optic cup did not normally fuse at midlenticular levels of the optic fissure in almost 70% of FLS fetuses by GD 15.5, whereas both margins were completely fused in all BALB/c fetuses of the same gestational day. In the FLS fetuses at GD 12.5, rolling on one side of fissure margins and consequent asymmetry were observed at the ventral optic fissure. The basement membrane persisted after the close contact of both sides of the fissure margins during GD 11.5 and 15.5. Ultrastructurally, the basal lamina was not disintegrated and mesenchymal cells intervened between the two neuroepithelial layers, resulting in complete separation of both fissure margins at GD 13.0. It is highly probable that the disturbed basement membrane disintegration right before optic fissure closure causes mild ocular coloboma without microphthalmia in FLS mice.

Inferior ectopic pupil and typical ocular coloboma in RCS rats

Ocular coloboma is sometimes accompanied by corectopia in humans and therefore ectopic pupil may indicate ocular coloboma in experimental animals. The RCS strain of rats has a low incidence of microphthalmia. We found that inferior ectopic pupil is associated exclusively with small-sized eyes in this strain. The objective of the current study was to evaluate whether inferior ectopic pupil is associated with iridal coloboma and other types of ocular coloboma in RCS rats. Both eyes of RCS rats were examined clinically, and those with inferior ectopic pupils underwent morphologic and morphometric examinations. In a prenatal study, coronal serial sections of eyeballs from fetuses at gestational day 16.5 were examined by using light microscopy. Ectopic pupils in RCS rats were found exclusively in an inferior position, where the iris was shortened. Fundic examination revealed severe chorioretinal coloboma in all cases of inferior ectopic pupil. The morphologic characteristics closely resembled those of chorioretinal coloboma in humans. Histopathologic examination of primordia showed incomplete closure of the optic fissure in 4 eyeballs of RCS fetuses. Neither F(1) rats nor N(2) (progeny of RCS × BN matings) displayed any ocular anomalies, including ectopic pupils. The RCS strain is a suitable model for human ocular coloboma, and inferior ectopic pupil appears to be a strong indicator of ocular coloboma.

Testicular gonadoblastoma in two pet domestic rabbits (Oryctolagus cuniculus domesticus)

Testicular gonadoblastoma is an uncommon tumor in domestic animals. The current study describes a testicular gonadoblastoma in 2 pet domestic rabbits ( Oryctolagus cuniculus domesticus) based on the histomorphological, immunohistochemical, and ultrastructural characteristics of the tumor. The tumor tissue consisted of discrete tubular structures separated by a fibrous stroma. The tubular structures were composed of large round cells similar in appearance to germ cells in the seminiferous tubules, and small spindle cells with oval or elongated nuclei resembling Sertoli cells. The spindle cells showed peculiar structural patterns arranged in a coronal or follicular pattern, often forming Call–Exner bodies like those in an ovarian granulosa cell tumor. One case was concomitant with seminoma. Immunohistochemistry revealed large round cells that were positive for c-kit and placental alkaline phosphatase, while spindle cells were positive for vimentin and Wilms tumor protein. Ultrastructurally, the spherical eosinophilic material (Call–Exner body) consisted of duplicated basal lamina, and sex cord components surrounded a single degenerative cell similar to a germ cell.

Diabetes enhances dental caries and apical periodontitis in caries-susceptible WBN/KobSlc rats

Many epidemiologic studies have suggested that diabetes may be an important risk factor for periodontal disease. To determine whether diabetes induces or enhances periodontal disease or dental caries, dental tissue from diabetic male and nondiabetic female WBN/KobSlc rats and male and female age-matched nondiabetic F344 rats was analyzed morphologically and morphometrically for these 2 types of lesions. Soft X-ray examination revealed that the incidence and severity of both molar caries and alveolar bone resorption were much higher in male WBN/KobSlc rats with chronic diabetes than in nondiabetic female rats of the same strain. Histopathologic examination showed that dental caries progressed from acute to subacute inflammation due to bacterial infections and necrosis in the pulp when the caries penetrated the dentin. In the most advanced stage of dental caries, inflammatory changes caused root abscess and subsequent apical periodontitis, with the formation of granulation tissue around the dental root. Inflammatory changes resulted in resorption of alveolar bone and correlated well with the severity of molar caries. Our results suggest that diabetic conditions enhance dental caries in WBN/KobSlc rats and that periodontal lesions may result from the apical periodontitis that is secondary to dental caries.

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.

Emperipolesis-like invasion of neoplastic lymphocytes into hepatocytes in feline T-cell lymphoma

Twelve cases of feline malignant lymphoma with emperipolesis-like invasion of neoplastic lymphocytes were examined microscopically, immunohistochemically and ultrastructurally. Intracytoplasmic invasion of neoplastic cells varied in severity between the cases, between hepatic lobules and between areas within the lobules. The number of infiltrating neoplastic cells ranged from one to several per hepatocyte. Neoplastic cells exhibited widely varying morphology from case-to-case and cell-to-cell within each case, and contained eosinophilic cytoplasmic granules in four cases. Immunohistochemical examination revealed that neoplastic cells in 11 of the 12 cases expressed one or both T-cell markers (CD3 and TIA-1). Diagnosis of T-cell lymphoma was also confirmed by assessment of clonality by polymerase chain reaction. Ultrastructural analysis revealed that the neoplastic lymphocytes were contained within an invagination of the cell membrane of the hepatocyte, rather than directly infiltrating into the cytoplasm of the cell. There was no evidence that the invasive neoplastic lymphocytes had a cytotoxic effect.

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.

Insulin-induced hypoglycemic peripheral motor neuropathy in spontaneously diabetic WBN/Kob rats

Intensive insulin therapy can lead to hypoglycemia, with patients sometimes developing hypoglycemic neuropathy. Spontaneously diabetic Wistar Bonn Kobori (WBN/Kob) rats develop diabetic peripheral motor neuropathy characterized by segmental demyelination and axonal degeneration. We examined the short-term effects of hypoglycemia on neuropathic changes in these rats. Spontaneous diabetic WBN/Kob rats received insulin implants for 40 d and were divided into 3 groups based on blood glucose levels: group N, normoglycemic to slightly hyperglycemic (150 to 250 mg/dL); group H, hypoglycemic to slightly hyperglycemic (50 to 200 mg/dL); and group D, nontreated spontaneously diabetic (350 to 420 mg/dL). Conduction velocity was measured in sciatic-tibial motor nerves; these nerves also underwent qualitative and quantitative histomorphologic analysis. Conduction velocity was not significantly different in N, D, and H groups. Morphologic analysis of the sciatic nerves of H rats showed severe changes, including axonal degeneration, myelin distention, and endoneurial fibrosis, that tended to occur in large, myelinated fibers. N and D rats showed relatively mild changes. The degree and distribution of degenerated nerve fibers in H rats were significantly higher than in N and D rats. These results suggest that hypoglycemia of less than 50 mg/dL induced severe peripheral neuropathy. Hypoglycemic lesions differed from the hyperglycemic lesions in diabetic WBN/Kob rats. This rat strain is an appropriate model for investigating the hypoglycemic peripheral neuropathy that can be associated with a diabetic condition.

Giant mitochondria in pancreatic acinar cells of alloxan-induced diabetic rats

This was a study of the microscopic, ultrastructural, immunohistochemical, and enzyme cytochemical features of giant eosinophilic granules encountered in pancreatic acinar cells of alloxan-induced diabetic rats. Seven male F344 rats with diabetes induced by a single i.v. dose of alloxan were sacrificed after twenty-five weeks of treatment. Histologically, the pancreatic acini were diffusely atrophied, and the islets showed marked atrophy or had disappeared, and giant eosinophilic granules and small vacuoles were observed in almost all acinar cells. The eosinophilic granules showed negative reactions for periodic acid-Schiff (PAS) and acid phosphatase, as well as fat stains such as Nile blue, Oil red O, and Sudan III. Ultrastructurally, the giant eosinophilic granules were huge structures surrounded by a double membrane containing many irregular cristae. A large amount of small lipid droplets was also apparent in the basal area of the acinar cells. Immunohistochemical analysis of prohibitin, a kind of protein located in the mitochondrial inner membrane, was partially positive in the marginal area of some giant eosinophilic granules, but negative for the central area. The enzyme activity for succinic dehydrogenase (SDH), one of the mitochondrial enzymes, showed a localizing pattern similar to that of prohibitin. These findings confirmed that the giant eosinophilic granules in the exocrine pancreas of alloxan-induced diabetic rats were giant mitochondria.

Enhanced tumorigenesis of forestomach tumors induced by N-Methyl-N'-nitro-N-nitrosoguanidine in rats with hypoinsulinemic diabetes

Hyperinsulinemia and hyperglycemia in prediabetic and diabetic patients are thought to increase the risk of developing neoplasms because insulin is a growth factor with pre-eminent metabolic but also mitogenic effects. To determine the effect of hypoinsulinemic diabetic conditions on carcinogenesis, we examined N-Methyl-N'-nitro-N-nitrosoguanidine (MNNG)-induced forestomach carcinogenesis in hypoinsulinemic diabetic WBN/Kob rats aged about 45 weeks (DM) compared with non-diabetic younger WBN/Kob rats (C1), non-diabetic Wistar rats age-matched to DM (C2), and non-diabetic Wistar rats age-matched to C1 (C3). All rats were treated with MNNG by gavage and were killed at 40 weeks after dosing. Various-sized tumors were disseminated throughout the forestomach of all rats, and the ratio of the area of tumors to the whole forestomach area was 23.3% in the DM group and was higher than in the C1-3 (4.2-14.3%) groups. The incidence of carcinoma was much higher in the DM group (36.8%) than in the C1-3 (7.1-16.7%) groups, and the incidence of papilloma was also significantly higher in the DM group (84.2%) than in the C1-3 (28.5-50.0%) groups. The average thickness of the squamous epithelium in the non-neoplastic mucosa was significantly greater in the DM group (50.8 mum) than in the C1-3 (29.6-37.9 microm) groups. Immunohistochemically, the Ki-67-positive index in the non-tumorous mucosa of the DM group (42.0%) was significantly higher than that of the C1-3 groups (18.8-33.3%). These results suggest that prolonged hyperglycemic conditions without hyperinsulinemia enhance tumorigenesis of MNNG-induced tumors by enhanced proliferative activity of the squamous epithelium in the rat forestomach.

Diabetic retinopathy and choroidal angiopathy in diabetic rats (WBN/Kob)

Retinopathy and choroidal angiopathy were both detected in aged male rats of the WBN/Kob strain with sustained diabetes. Hyperglycemia and glucosuria were found starting from 12 months of age and lasted through 24 months of age. Macroscopically, the vitreous body was partially or entirely replaced by white mass in 3 of 9 diabetic males. Histopathologically, the intravitreal white mass consisted of collagen fibers accompanied by numbers of newly formed vessels. Intraretinal angiopathy was accompanied with newly formed vessels, which were observed within the retina in 5 of 9 diabetic males, and marked hyalinization of intraretinal vessels was detected in 6 of 9 males irrespective of the presence of intravitreal neovascularization. Furthermore, hyperglycemia-related choroidal angiopathy was also seen with newly formed blood vessels originating from the choroid penetrating the retinal pigment epithelial layer and invading the retina in 8 of 9 diabetic males. Focal proliferation or degeneration of the pigment epithelial cells was associated in the region with choroidal angiopathy. In females, choroidal vessels slightly raised the pigment epithelial layer; however, they were localized in the choroid. The present study indicates that the WBN/Kob strain of rats is a useful model for both diabetic retinopathy and diabetic choroidal angiopathy.

Merkel cell carcinoma in a cat

A 17-year-old spayed female Japanese domestic cat presented with a solitary cutaneous mass in the right thoracic area. Histopathologically, the mass consisted mainly of round tumor cells that had infiltrated throughout the dermis and deep subcutaneous tissue. The proliferating pattern of tumor cells was solid but also trabecular or cord-like in some areas, and lined with small cells resembling mature lymphocytes or basal cells. The tumor cells were positive for cytokeratin 20 and synaptophysin. The positive reaction for cytokeratin 20 showed localized to diffuse pattern. This is the first report describing now cytokeratin 20 was clearly beneficial for the differential diagnosis of feline Merkel cell carcinoma.

Morphological study on dental caries induced in WBN/KobSlc rats (Rattus norvegicus) fed a standard laboratory diet

In our previous studies, WBN/KobSlc was characterized as a rat strain in which only males began to develop pancreatitis, and then presented with diabetic symptoms. In the course of studying their pancreatic inflammation, we detected molar caries in prediabetic males feeding on a standard diet (CRF-1) widely used for experimental animals. The purpose of this study is to confirm whether the WBN/KobSlc strain is caries-susceptible to the diet reported to be non-cariogenic, and to examine the effect of a prediabetic condition on their dental caries. For a morphological study, 25 male WBN/KobSlc rats aged 3.2–7.8 months and 24 females of the same strain aged 3.3–6.6 months were used, along with 10 males and 10 females of 8.2-month-old F344 rats. Marked dental caries were detected in the mandibular molars of male and female WBN/KobSlc rats regardless of pancreatitis, although no similar changes were observed in any teeth of the F344 strain fed the same diet. Soft X-ray examination revealed that the caries began in the crown and progressed horizontally and vertically, and that a severe radiolucent lesion extensively expanded to the entire crown, corresponding to a macroscopically deleted molar. The caries had gradually developed mainly in the second mandibular molar from more than 3.5 months of age, while none were seen in any rats before that time. The WBN/KobSlc rats were caries-susceptible even to the standard laboratory diet, and pancreatitis was not directly associated with the onset of dental caries in this strain.

Malignant Lymphoma with Severe Infiltrative Growth into Skeletal Muscles in WBN/Kob Rats

Although spontaneously occurring neoplasms have been reported repeatedly in F344, SD and Wistar rats, which are commonly used strains for routine toxicologic and carcinogenicity studies, there are only a few reports of malignant lymphoma or lymphatic leukemia except for large granular lymphocytic leukemia (LGL) in F344 rats. Malignant lymphoma (lymphosarcoma) is thought to be uncommon in F344 rats. The authors encountered malignant lymphomas of the non-LGL leukemia type with characteristic pathologic features in WBN/Kob rats. The mean age at onset of the disease in all 13 affected rats (8 males and 5 females) was about 60 weeks. Common and characteristic clinical signs were abnormal gait with hind limb paralysis. Macroscopically, the enlargement of the lymph nodes, spleen and liver was slight to moderate. Scattered multiple white-to-gray nodules encompassed the aorta and assumed a bead-like appearance near the thoracic and lumbar vertebrae. Histopathologically, neoplastic proliferative changes were predominant in the bone marrow tissue of the entire body, and many tumor cells infiltrated the spleen and several lymph nodes. The most striking histological features were constant and severe infiltration of tumor cells in the adipose tissue and skeletal muscle adjacent the thoracic and lumber vertebrae. Immunohistochemically, all tumor cells were positive for B-cell markers (PAX-5, CD79a and CD45) and negative for CD3. From the results of immunohistochemistry and morphological examination, these tumors were diagnosed as malignant B-cell lymphomas.

Effects of the antifungal agent itraconazole on proliferative changes of the forestomach mucosa in alloxan-induced diabetic rats

Alloxan-induced diabetic rats frequently exhibit proliferative lesions of squamous hyperplasia accompanied by chronic inflammation and Candida albicans infection in the forestomach, and some lesions progress to squamous cell carcinoma (SCC). Candida infection causes not only hyperplastic changes with inflammation but might also lead to SCC in human oral mucosa. Thus, the present study was conducted to examine the effects of the antifungal agent itraconazole (ITCZ) on proliferative and inflammatory changes of the forestomach in alloxan-induced diabetic WBN/Kob rats. Diabetes was induced by alloxan at fifteen weeks of age. Rats were allocated to three groups at forty-five weeks of age and were given ITCZ by gavage 0 (vehicle control), 5, and 10 mg/kg/day for four weeks, and they were sacrificed at the sixty-fifth week of age. Mucosal hyperplastic changes were consistently accompanied by inflammation and Candida infections in the 0 mg/kg group. These lesions were reduced by ITCZ (0 mg/kg; 100%, 5 mg/kg; 53.5%, 10 mg/kg; 61.5%). Squamous cell carcinoma was detected in three rats from the 0 mg/kg, but only one rat from the 10 mg/kg dose groups in this study. Itraconazole reduced the degree of mucosal hyperplasia, inflammatory changes, and Candida infection. Therefore, C. albicans infection was an important factor in pathogenesis of mucosal proliferation and inflammation.

Nephrotic Syndrome Induced by Dibasic Sodium Phosphate Injections for Twenty-eight Days in Rats

Sprague-Dawley rats received once daily tail-vein injections of 360 mM dibasic sodium phosphate solution at 8 mL/kg for fourteen or twenty-eight days. Clinical examination revealed persistent proteinuria from three days after the first dosing and thereafter severe proteinuria from eight days or later in the phosphate-treated groups. Proteinuria developed without remission even after fourteen-day withdrawal in the fourteen-day dosed group. Phosphate-treated animals developed lipemia, hypercholesterolemia, anemia, higher serum fibrinogen levels, and lower serum albumin/globulin ratios on day 29. Renal weight increased significantly compared with control animals, and the kidneys appeared pale and enlarged with a rough surface. Histopathologically, glomerular changes consisted of mineralization in whole glomeruli, glomerular capillary dilatation, partial adhesion of glomerular tufts to Bowman’s capsule, and mesangiolysis. Ultrastructural lesions such as an increased number of microvilli, effacement of foot processes, and thickening of the glomerular basement membrane, and immunocytochemical changes in podocytes, mainly decreased podoplanin-positive cells and increased desmin expression, were also conspicuous in the phosphate-treated rats for twenty-eight days. Marked tubulointerstitial lesions were tubular regeneration and dilatation, protein casts, mineralization in the basement membrane, focal interstitial inflammation, and fibrosis in the cortex. These clinical and morphological changes were similar to features of human nephrotic syndrome.

Thymoma in a Java sparrow (Padda oryzivora)

Thymoma is described in a 3-year-old female Java sparrow (Padda oryzivora). Histopathologically, the subcutaneous mass from the cervical region consisted of epithelial cells characterized by large polyhedral cells and spindle cells, which sometimes showed squamous differentiation, and small lymphocytes without apparent atypical forms. Immunohistochemically, the epithelial cells possessed cytokeratin in their cytoplasm and proliferating cell nuclear antigen.

Nasal and paranasal adenocarcinomas with neuroendocrine differentiation in dogs

Tumors of the nasal cavity or paranasal sinuses of 18 dogs were examined histopathologically, immunohistochemically, and histochemically. The tumors were classified histologically as 13 adenocarcinomas, 3 transitional carcinomas, 1 squamous cell carcinoma, and 1 adenosquamous carcinoma. Tumor cells were strongly immunoreactive for broad-spectrum cytokeratins in all cases, for cytokeratin 8/18 in 16 cases, and for cytokeratin 19 in 17 cases. None of the 18 carcinomas had cytologic or histologic features indicative of neuroendocrine differentiation, yet tumor cells in 5 of the 13 adenocarcinomas were argyrophilic and immunohistochemically positive for synaptophysin and chromogranin A. Results of this study indicate that neuroendocrine markers may be detected immunohistochemically and histochemically in canine nasal or paranasal adenocarcinomas despite the lack of typical histologic features of neuroendocrine differentiation.

Polypoid eosinophilic cystitis with pseudosarcomatous proliferative tissue in a dog

A dog presented with hematuria, and two small polypoid masses were detected in the urinary bladder. Histopathologically, the masses were located in the mucosal or submucosal layer. That tissue consisted of a random proliferation of spindle-shaped, round and pleomorphic cells with single or multiple large atypical nuclei and abundant cytoplasm, and eosinophil infiltration. These large cells were confirmed by immunohistochemical staining as fibroblasts, myofibroblasts and macrophages. Mitotic figure was rarely seen. These masses were diagnosed as eosinophilic polypoid cystitis with pseudosarcomatous proliferative tissue, since they consisted of a wide variety of cells and showed low growth activity.

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.

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.

Induction of squamous cell carcinoma of forestomach in diabetic rats by single alloxan treatment

Male rats of WBN/Kob strain are one of the diabetic model animals and develop long-lasting diabetic symptoms and some complications from about 40 weeks of age without any treatment. A single intravenous dose of alloxan, a non-genotoxic diabetogenic chemical, frequently induced proliferative lesions of squamous epithelium in tongue, esophagus and forestomach of male and female WBN/Kob rats, and hastened the onset and acceleration of diabetic conditions. Histopathologically, proliferative changes of squamous cell of forestomach varied with the severity of hyperplasia in alloxan-treated rats (100% of 31 males and 94.1% of 17 females) and progressed to SCC in approximately 20% of all rats. Metastasis to regional lymph nodes was also observed in two cases. Proliferative changes were most severe in the forestomach and were constantly accompanied with chronic suppurative inflammation of the mucosal epithelium with infection of filamentous fungi and/or bacterial colonies. In contrast, forestomach of the spontaneously diabetic male rats showed only slight hyperplasia of the mucosal epithelium confined to the limiting ridge in approximately 30% of the cases. All non-diabetic female rats showed neither proliferative changes nor the inflammatory process in the mucosa. Immunohistochemically, COX-2 and iNOS were positive in these chronic suppurative inflammatory lesions accompanied by proliferative squamous epithelium. From these results, it is suggested that chronic inflammatory processes play an important role in the pathogenesis of alloxan-induced SCC. An experimental system of alloxan-induced SCC might serve as a suitable model for the study of the inflammation-related promotion of carcinogenesis.

Pulmonary intravascular hemangiosarcoma in a cat

A 9-year-old, castrated male Japanese domestic cat presented with a complaint of exertional dyspnea. Based on the radiographic findings, presumptive diagnosis of aspiration pneumonia or primary diffuse pulmonary neoplasia in the right middle lobe was made. Histologically, the pulmonary lesion was characterized by diffuse thickening of alveolar wall with the proliferation of apparently atypical irregular-shaped cells. Immunohistochemical staining using anti-human factor VIII-related antigen antiserum showed positive reaction in the cytoplasm of the atypical cells. According to the findings, the lesion was diagnosed as pulmonary intravascular hemangiosarcoma.