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The article presents a proposal for a two-tier histologic grading system for canine cutaneous mast cell tumors (MCTs) for a more accurate prediction of biological behavior. It evaluated the consistency of microscopic grading among veterinary pathologists and the prognostic significance of the Patnaik grading system. The study showed significant interobserver variation in MCT grading among pathologists, suggesting unreliability in the current histologic grading system while the proposed system is found to offer higher consistency and less ambiguity.

In this study, we describe a novel approach for collecting bile from dogs and cynomolgus monkeys for metabolite profiling, ultrasound-guided cholecystocentesis (UCC). Sampling bile by UCC twice within 24 hours was well tolerated by dogs and monkeys. In studies with atorvastatin (ATV) the metabolite profiles were similar in bile obtained through UCC and from bile duct-cannulated (BDC) dogs. Similar results were observed in UCC and BDC monkeys as well. In both monkey and dog, the primary metabolic pathway observed for ATV was oxidative metabolism. The 2-hydroxy- and 4-hydroxyatorvastatin metabolites were the major oxidation products, which is consistent with previously published metabolite profiles. S-cysteine and glucuronide conjugates were also observed. UCC offers a viable alternative to bile duct cannulation for collection of bile for metabolite profiling of compounds that undergo biliary excretion, given the similar metabolite profiles in bile obtained via each method. Use of UCC for metabolite profiling may reduce the need for studies using BDC animals, a resource-intensive model.

Introduction: Low intrinsic solubility leading to poor oral bioavailability is a common challenge in drug discovery that can often be overcome by formulation strategies, however, it remains a potential limitation that can pose challenges for early risk assessment and represent a significant obstacle to drug development. We identified a selective inhibitor (BMS-986126) of the IL-1 receptor-associated kinase 4 (IRAK4) with favorable properties as a lead candidate, but with unusually low intrinsic solubility of <1 μg/mL., Methods: Conventional histopathology identified the issue of crystal formation in vivo. Subsequent investigative work included confocal Raman micro-spectroscopy, MALDI-MS, polarized light microscopy of fresh wet-mount tissue scrapings and transmission electron microscopy., Results: BMS-986126 was advanced into a 2-week toxicology study in rats. The main finding in this study was minimal granulomatous inflammation in the duodenum, associated with the presence of birefringent crystals at the highest dosage of 100 mg/kg/day. Considering the safety margin, and the single location of the lesion, BMS-986126 was further progressed into IND-enabling toxicology studies where tolerability deteriorated with increasing dosing duration. Birefringent crystals and granulomatous inflammation were detected in multiple organs at dosages ≥20 mg/kg/day. Raman spectroscopy confirmed the identity of the crystals as BMS-986126. Therefore, follow up investigations were conducted to further characterize drug crystallization and to evaluate detection methods for their potential to reliably detect in vivo crystallization early., Discussion: The purpose of our efforts was to identify critical factors influencing in vivo drug crystallization and to provide a preliminary assessment (based on one compound) which method would be best suited for identifying crystals. Results indicated a combination of methods was required to provide a complete assessment of drug crystallization and that a simple technique, scraping of freshly collected tissue followed by evaluation under polarizing light was suitable for detecting crystals. However, dosing for 2 weeks was required for crystals to grow to a clearly detectable size., (Copyright © 2018 Elsevier Inc. All rights reserved.)

The purpose of this study was to establish a 2-stage model of urinary bladder carcinogenesis in male Sprague-Dawley rats to identify tumor promoters. In phase 1 of the study, rats ( n = 170) were administered 100 mg/kg of the tumor initiator, N-butyl-N-(4-hydroxybutyl)-nitrosamine (BBN), twice weekly by oral gavage (po) for a period of 6 weeks. Phase 2 consisted of dividing rats into 4 groups ( n = 40 per group) and administering one of the following for 26 weeks to identify putative tumor promoters: (1) vehicle po, (2) 25 mg/kg/day rosiglitazone po, (3) 5% dietary sodium l-ascorbate, and (4) 3% dietary uracil. Rats were necropsied after 7.5 months, and urinary bladders were evaluated by histopathology. BBN/vehicle treatments induced the development of urothelial hyperplasia (83%) and papillomas (15%) but no transitional cell carcinomas (TCCs). Rosiglitazone increased the incidence and severity of papillomas (93%) and resulted in TCC in 10% of treated rats. Uracil was the most effective tumor promoter in our study and increased the incidence of papillomas (90%) and TCC (74%). Sodium ascorbate decreased the incidence of urothelial hyperplasia (63%) and did not increase the incidence of urothelial papillomas or TCC. These data confirm the capacity of our 2-stage model to identify urinary bladder tumor promoters.

BMS-986094, a 2'-C-methylguanosine prodrug that was in development for treatment of chronic hepatitis C infection was withdrawn from Phase 2 clinical trials because of unexpected cardiac and renal adverse events. Investigative nonclinical studies were conducted to extend the understanding of these findings using more comprehensive endpoints. BMS-986094 was given orally to female CD-1 mice (25 and 150 mg/kg/d) for 2 weeks (53/group) and to cynomolgus monkeys (15 and 30 mg/kg/d) for up to 6 weeks (2-3/sex/group for cardiovascular safety, and 5/sex/group for toxicology). Endpoints included toxicokinetics; echocardiography, telemetric hemodynamics and electrocardiography, and tissue injury biomarkers (monkey); and light and ultrastructural pathology of heart, kidney, and skeletal muscle (mouse/monkey). Dose-related and time-dependent findings included: severe toxicity in mice at 150 mg/kg/d and monkeys at 30 mg/kg/d; decreased left ventricular (LV) ejection fraction, fractional shortening, stroke volume, and dP/dt; LV dilatation, increased QTc interval, and T-wave flattening/inversion (monkeys at ≥ 15 mg/kg/d); cardiomyocyte degeneration (mice at 150 mg/kg/d and monkeys at ≥ 15 mg/kg/d) with myofilament lysis/myofbril disassembly; time-dependent proteinuria and increased urine β-2 microglobulin, calbindin, clusterin; kidney pallor macroscopically; and tubular dilatation (monkeys); tubular regeneration (mice 150 mg/kg/d); and acute proximal tubule degeneration ultrastructurally (mice/monkeys); and skeletal muscle degeneration with increased urine myoglobin and serum sTnI. These studies identified changes not described previously in studies of BMS-986094 including premonitory cardiovascular functional changes as well as additional biomarkers for muscle and renal toxicities. Although the mechanism of potential toxicities observed in BMS-986094 studies was not established, there was no evidence for direct mitochondrial toxicity., (© The Author 2016. Published by Oxford University Press on behalf of the Society of Toxicology. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.)

The objective of this work was to investigate the mechanisms of hepatobiliary toxicity caused by thienopyrimidone MCHR1 antagonists using BMS-773174 as a tool molecule. Co-administration of the pan CYP inhibitor 1-aminobenzotriazole with BMS-773174 prevented hepatobiliary damage, and direct delivery of the diol metabolite BMS-769750 caused hepatobiliary toxicity, identifying the diol and possibly its downstream hydroxyacid (BMS-800754) metabolite as the toxic species. Rat liver gene expression revealed treatment-related changes in hepatic transporters and induction of oval cell-specific genes including deleted malignant tumor 1 (Dmbt1). The metabolites did not alter hepatic transporter activities, suggesting that transporter-mediated cholestasis was not involved. Because injury to biliary epithelium can result in adaptive hyperplasia, rat biliary epithelial cells (BECs) were isolated and exposed to the oxidative metabolites. BMS-769750 was cytotoxic to BECs, but not rat hepatocytes, suggesting a role of the diol in biliary epithelial injury. BMS-800754 was cytotoxic to rat hepatocytes therefore its contribution to hepatocyte injury in rats is a possibility. Induction of Dmbt1 in rat BECs was investigated because of its role in hepatic progenitor cell differentiation/proliferation during injury. Dmbt1 mRNA was induced by BMS-769750, but not BMS-800754 in BECs; this induction and cellular injury was confirmed with diol metabolites formed by other compounds with the same hepatobiliary liability. In conclusion, hepatobiliary injury by thienopyrimidinone MCHR1 antagonists was driven through a CYP-mediated bioactivation pathway. Induction of Dmbt1 mRNA coupled with cellular injury suggests that injury of biliary epithelium may be the first step toward an adaptive proliferative response causing BDH by these compounds., (© The Author 2016. Published by Oxford University Press on behalf of the Society of Toxicology. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.)

Glucokinase (GK) catalyzes the initial step in glycolysis and is a key regulator of glucose homeostasis. Therefore, glucokinase activators (GKa) have potential benefit in treating type 2 diabetes. Administration of a Bristol-Myers Squibb GKa (BMS-820132) to healthy euglycemic Sprague-Dawley (SD) rats and beagle dogs in 1 mo toxicology studies resulted in marked and extended hypoglycemia with associated clinical signs of toxicity and degenerative histopathological changes in the stomach, sciatic nerve, myocardium, and skeletal muscles at exposures comparable to those expected at therapeutic clinical exposures. To investigate whether these adverse effects were secondary to exaggerated pharmacology (prolonged hypoglycemia), BMS-820132 was administered daily to male Zucker diabetic fatty (ZDF) rats for 1 mo. ZDF rats are markedly hyperglycemic and insulin resistant. BMS-820132 did not induce hypoglycemia, clinical signs of hypoglycemia, or any of the histopathologic adverse effects observed in the 1 mo toxicology studies at exposures that exceeded those observed in SD rats and dogs. This indicates that the toxicity observed in euglycemic animals was secondary to the exaggerated pharmacology of potent GK activation. This study indicates that ZDF rats, with conventional toxicity studies, are a useful disease model for testing antidiabetic agents and determining toxicities that are independent of prolonged hypoglycemia., (© 2015 by The Author(s).)

Glucagon-like peptide 1-based therapies, collectively described as incretins, produce glycemic benefits in the treatment of type 2 diabetes. Recent publications raised concern for a potential increased risk of pancreatitis and pancreatic cancer with incretins based in part on findings from a small number of rodents. However, extensive toxicology assessments in a substantial number of animals dosed up to 2 years at high multiples of human exposure do not support these concerns. We hypothesized that the lesions being attributed to incretins are commonly observed background findings and endeavored to characterize the incidence of spontaneous pancreatic lesions in three rat strains (Sprague-Dawley [S-D] rats, Zucker diabetic fatty [ZDF] rats, and rats expressing human islet amyloid polypeptide [HIP]; n = 36/group) on a normal or high-fat diet over 4 months. Pancreatic findings in all groups included focal exocrine degeneration, atrophy, inflammation, ductular cell proliferation, and/or observations in large pancreatic ducts similar to those described in the literature, with an incidence of exocrine atrophy/inflammation seen in S-D (42-72%), HIP (39%), and ZDF (6%) rats. These data indicate that the pancreatic findings attributed to incretins are common background findings, observed without drug treatment and independent of diet or glycemic status, suggesting a need to exercise caution when interpreting the relevance of some recent reports regarding human safety.

Animal models of human disease are commonly utilized to gain insight into the potential efficacy and mode of action of novel pharmaceuticals. However, conventional (healthy) rodent and nonrodent models are generally utilized in nonclinical safety testing. Animal models of human disease may be helpful in understanding safety risks of compounds in nonclinical or clinical development, with their greatest value being in targeted or hypothesis-driven studies to help understand the mechanism of a particular toxicity. Limitations of animal models of disease in nonclinical safety testing include a lack of historical control, heterogeneity in disease expression, a limited life span, and confounding effects of the disease. In most instances, animal models of human disease should not be utilized to supplant testing in conventional animal models. While of potential benefit, testing in an animal model of human disease should only be taken after adequate consideration of relevance along with benefits and limitations of the proposed model.

3-hydroxy-3-methylglutaryl coenzyme-A reductase (HMGR) inhibitors, more commonly known as statins, represent the gold standard in treating hypercholesterolemia. Although statins are regarded as generally safe, they are known to cause myopathy and, in rare cases, rhabdomyolysis. Statin-dependent effects on plasma lipids are mediated through the inhibition of HMGR in the hepatocyte, whereas evidence suggests that myotoxicity is due to inhibition of HMGR within the myocyte. Thus, an inhibitor with increased selectivity for hepatocytes could potentially result in an improved therapeutic window. Implementation of a strategy that focused on in vitro potency, compound polarity, cell selectivity, and oral absorption, followed by extensive efficacy and safety modeling in guinea pig and rat, resulted in the identification of compound 1b (BMS-644950). Using this discovery pathway, we compared 1b to other marketed statins to demonstrate its outstanding efficacy and safety profile. With the potential to generate an excellent therapeutic window, 1b was advanced into clinical development.

Statins, because of their excellent efficacy and manageable safety profile, represent a key component in the current armamentarium for the treatment of hypercholesterolemia. Nonetheless, myopathy remains a safety concern for this important drug class. Cerivastatin was withdrawn from the market for myotoxicity safety concerns. BMS-423526 [{(3R,5S)-7-[4-(4-fluorophenyl)-6,7-dihydro-2-(1-methylethyl)-5H-benzo[6,7]cyclohepta[1,2-b]pyridin-3-yl]-3,5-dihydroxy-heptenoic acid} sodium salt], similar to cerivastatin in potency and lipophilicity, was terminated in early clinical development due to an unacceptable myotoxicity profile. In this report, we describe the guinea pig as a model of statin-induced cholesterol lowering and myotoxicity and show that this model can distinguish statins with unacceptable myotoxicity profiles from statins with acceptable safety profiles. In our guinea pig model, both cerivastatin and BMS-423526 induced myotoxicity at doses near the ED(50) for total cholesterol (TC) lowering in plasma. In contrast, wide differences between myotoxic and TC-lowering doses were established for the currently marketed, more hydrophilic statins, pravastatin, rosuvastatin, and atorvastatin. This in vivo model compared favorably to an in vitro model, which used statin inhibition of cholesterol synthesis in rat hepatocytes and L6 myoblasts as surrogates of potential efficacy and toxicity, respectively. Our conclusion is that the guinea pig is a useful preclinical in vivo model for demonstrating whether a statin is likely to have an acceptable therapeutic safety margin.

There are two major defects in type 2 diabetes: 1) insulin resistance and 2) insulin deficiency due to loss of beta-cell function. Here we demonstrated that treatment with muraglitazar (a dual peroxisome proliferator-activated receptor alpha/gamma activator), when initiated before or after the onset of diabetes in mice, is effective against both defects. In study 1, prediabetic db/db mice were treated for 12 weeks. The control mice developed diabetes, as evidenced by hyperglycemia, hyperinsulinemia, reduced insulin levels in the pancreas, blunted insulin response to glucose, and impaired glucose tolerance. The muraglitazar-treated mice had normal plasma glucose, and insulin levels, equivalent or higher pancreatic insulin content than normal mice, showed a robust insulin response to glucose and exhibited greater glucose tolerance. In study 2, diabetic db/db mice were treated for 4 weeks. The control mice displayed increased glucose levels, severe loss of islets, and their isolated islets secreted reduced amounts of insulin in response to glucose and exendin-4 compared with baseline. In muraglitazar-treated mice, glucose levels were reduced to normal. These mice showed reduced loss of islets, and their isolated islets secreted insulin at levels comparable to baseline. Thus, muraglitazar treatment decreased both insulin resistance and preserved beta-cell function. As a result, muraglitazar treatment, when initiated before the onset of diabetes, prevented development of diabetes and, when initiated after the onset of diabetes, prevented worsening of diabetes in db/db mice.

Robust pharmaceutical treatment of obesity has been limited by the undesirable side-effect profile of currently marketed therapies. This paper describes the synthesis and optimization of a new class of pyrazinoisoindolone-containing, selective 5-HT2C agonists as antiobesity agents. Key to optimization of the pyrazinoisoindolone core was the identification of the appropriate substitution pattern and functional groups which led to the discovery of (R)-9-ethyl-1,3,4,10b-tetrahydro-7-trifluoromethylpyrazino[2,1-a]isoindol-6(2H)-one (58), a 5-HT2C agonist with >300-fold functional selectivity over 5-HT2B and >70-fold functional selectivity over 5-HT2A. Oral dosing of 58 reduced food intake in an acute rat feeding model, which could be completely reversed by a selective 5-HT2C antagonist and caused a reduction in body weight gain in a 4-day rat model.

Fatal meningoencephalitis caused by equine herpesvirus-1 (EHV-1) was diagnosed in a reticulated giraffe (Giraffa camelopardalis reticulate). The giraffe died following a history of stumbling, incoordination, and abdominal pain. Gross examination of the brain revealed asymmetric edema and red-brown discoloration, predominantly within the telencephalon. Microscopically, there was perivascular lymphohistiocytic cuffing, multifocal gliosis, and neuronal necrosis in the cerebrum. Necrotic neurons contained acidophilic intranuclear inclusions. EHV-1 was isolated from the brain of the giraffe, and polymerase chain reaction was positive on sections of the brain. Immunohistochemistry using an EHV-1-specific antibody identified positive staining in neurons, astrocytes, and endothelial cells. The giraffe had been housed with a group of zebras that were serologically positive for EHV-1 and suspected as the source of infection. This raises concerns for cross-species transmission of EHV-1 when housing equids together with other species in zoologic collections.

Objective: To determine whether the increasing prevalence of feline hyperthyroidism is the result of aging of the cat population and whether consumption of canned foods at various times throughout life is associated with increased risk of hyperthyroidism., Design: Retrospective and case-control studies., Study Population: Medical records of 169,576 cats, including 3,570 cats with hyperthyroidism, evaluated at 9 veterinary school hospitals during a 20-year period, and 109 cats with hyperthyroidism (cases) and 173 cats without hyperthyroidism (controls)., Procedure: Age-adjusted hospital prevalence of hyperthyroidism was calculated by use of Veterinary Medical Database records. On the basis of owners' questionnaire responses, logistic regression was used to evaluate associations between consumption of canned food and development of hyperthyroidism., Results: Age-specific hospital prevalence of feline hyperthyroidism increased significantly from 1978 to 1997. Overall, consumption of pop-top canned (vs dry) food at various times throughout life and each additional year of age were associated with greater risk of developing hyperthyroidism. In female cats, increased risk was associated with consumption of food packaged in pop-top cans or in combinations of pop-top and non-pop-top cans. In male cats, increased risk was associated with consumption of food packaged in pop-top cans and age., Conclusions and Clinical Relevance: These findings suggest that the increasing prevalence of feline hyperthyroidism is not solely the result of aging of the cat population and that canned foods may play a role.

Asian pox was diagnosed in three sanderlings (Calidris alba) on Sanibel Island, Florida (USA) in February 1997. All three cases had large tumor-like lesions which contributed significantly to their mortality. Poxvirus infection was confirmed by cytology, histopathology, and electron microscopy. This is the first report of poxvirus infection in sanderlings.

In November 1996, a 14-yr-old captive male African lion (Panthera leo) had sudden onset of left-sided hemiparesis and mydriasis of the left eye. After 24 hr of supportive care, the lion showed no improvement and was euthanized. At necropsy, the right cerebral hemisphere was diffusely and irregularly swollen and malacic. Histopathology revealed extensive acute necrosis and edema of the portion of the right cerebral hemisphere that received blood from the right middle cerebral artery. Gross and histopathologic cerebral findings resembled those of feline ischemic encephalopathy.

Intact female Beagles from life-span studies in the Lovelace Respiratory Research Institute colony were examined for mammary tumor incidence. The breeding colony, founded in 1963, produced five generations from 28 founder females. After proportional hazards analysis, two maternal families were shown to have markedly different phenotypes, one susceptible and one resistant to mammary neoplasia, as compared with the entire colony. When tumors were subdivided into benign and malignant based on local invasiveness, familial differences in tumor incidence were preserved for each tumor type. Fifty-seven females in the susceptible family developed 149 benign and 39 malignant tumors, and 95 females in the resistant family developed 70 benign and 20 malignant tumors. The ratio of benign to malignant tumors of about 4:1 for both families was higher than expected. Using Kaplan-Meier and log-rank analyses, the susceptible family had a 50% malignant tumor incidence by age 13.6 years, whereas the resistant family did not have a 50% incidence until 17.0 years (P = 0.0065). Because of marked censoring, Kaplan-Meier analyses could not provide an estimate of the 50% benign tumor incidence; mean incidence age was calculated instead. These estimates for benign tumors for susceptible and resistant families were 10.8 and 13.8 years (P = 0.0001), respectively. Using chi(2) tests, families had no differences in the occurrence of the types of benign (P = 0.098) or malignant (P = 0.194) tumors or in the ratio of benign to malignant tumors (P = 0.778). Immunohistochemical analysis of malignant tumors from both families did not demonstrate differences in p53 mutation rate or p185erbB-2 expression. These results suggest that 1) genetic factors produce familial differences in the age of onset of both benign and malignant mammary tumors; histologic types do not segregate by family; 2) the ratio of benign to malignant tumors is greater than formerly reported; and 3) neither p53 nor p185erbB-2 alterations are the basis for the familial predisposition.

Pseudorabies (Aujeszky's disease) was diagnosed in three adult captive coyotes (Canis latrans) from southern Indiana (USA). The coyotes died in their outdoor enclosure within a 48 hr period. Histopathology revealed multifocal, nonsuppurative meningioencephalitis and eosinophilic intranuclear inclusion bodies within neurons. Samples of brain were positive for pseudorabies virus by fluorescent antibody testing and virus isolation. Source of infection was the probable consumption of pseudorabies virus-infected pig carcasses.

In November 1995, a malignant mast cell tumor (mastocytoma) was diagnosed in an adult African hedgehog (Atelerix albiventris) from a zoological park (West Lafayette, Indiana, USA). The primary mast cell tumor presented as a firm subcutaneous mass along the ventrum of the neck. Metastasis to the right submandibular lymph node occurred.

Sarcomas at vaccination sites in cats were first reported in 1992. Recent retrospective studies have confirmed an association between these vaccination-site sarcomas (VSS) and feline leukemia virus (FeLV) and/ or rabies vaccines. In most cases, VSS are locally invasive fibrosarcomas that tend to recur but rarely metastasize. We report the mediastinal and pulmonary metastases of a VSS in a FeLV-and feline immunodeficiency virus-negative, 8-year-old, domestic short-haired cat. The primary sarcoma was removed from an interscapular vaccination site and diagnosed as a VSS 3 months prior to radiographic lesions suggestive of pulmonary and mediastinal metastases. At necropsy, there were multiple pulmonary and mediastinal nodules that histologically and ultrastructurally were fibrosarcomas, cytomorphologically similar to the VSS. In addition, immunohistochemical staining patterns of the VSS and metastatic sites were consistent with that described for VSS. Recent reports of pulmonary and mediastinal metastases of interscapular VSS emphasize the importance of early diagnosis and treatment of these tumors.

A retrospective study of 195 feline sarcomas diagnosed histologically between July 1988 and June 1994 showed that 170 (87.2%) were fibrosarcomas. Cats with vaccination site (VS) fibrosarcomas were younger (8.6 +/- 3.9 years; median = 8 years) than cats with non-vaccination site (NVS) fibrosarcomas (10.2 +/- 4.7 years; median = 11 years) (P = 0.03), but there was no such association with breed, sex, or "neuter status". Microscopical features more characteristic of VS fibrosarcomas than of NVS fibrosarcomas were (1) subcutaneous location (P < 0.001), (2) necrosis (P < 0.001), (3) inflammatory cell infiltration (P < 0.001), (4) increased mitotic activity (P < 0.02), (5) pleomorphism (P < 0.001), and (6) variability in the density of the extracellular matrix (P < 0.001). When these data were fitted to a logistic regression model, younger age (P = 0.003), subcutaneous location of the fibrosarcoma (P = 0.0002), and the presence of inflammation (P = 0.017) were more characteristic of VS fibrosarcomas than of NVS fibrosarcomas. The study showed that in the absence of any vaccination history, the age of a cat, coupled with certain histological characteristics (e.g., tumour location in skin, and inflammation), may help in distinguishing VS fibrosarcomas from NVS fibrosarcomas. The characteristic histological features of VS fibrosarcomas, such as necrosis, increased mitotic activity and pleomorphism, are those of aggressive tumours.

Baylisascaris larva migrans (LM) has been recognized as a cause of central nervous system (CNS) disease in puppies. A presumptive antemortem diagnosis is based on a history of raccoon exposure, clinical signs, cerebrospinal fluid eosinophilic pleocytosis, and peripheral blood eosinophilia. Early diagnosis is critical for treatment or prevention of disease in other dogs, animals, or humans exposed to the suspected contaminated area. In the present case, an antemortem diagnosis was not made, emphasizing the importance of postmortem examination in cases of CNS disease in puppies.

Seven cats with thyroid carcinomas that had previously undergone surgical removal of neoplastic tissue were treated with 30 mCi of radioactive iodine (131I). Six of the cats had clinical signs of hyperthyroidism; 1 did not. There were no complications associated with 131I treatment, and clinical signs resolved in all cats. Technetium scans of 4 cats made after treatment did not have evidence of isotope uptake. In the remaining 3 cats, small areas of isotope uptake, the intensity of which was equal to or less than the intensity of uptake in the salivary glands, were seen. All 7 cats became hypothyroid after treatment; 4 required L-thyroxine supplementation. One cat was alive 33 months after treatment. The other 6 cats were euthanatized because of unrelated diseases 10 to 41 months after treatment.

Heat-labile Pasteurella multocida toxin (PMT) is an important virulence factor of some isolates from rabbits. To determine whether protective immunity to PMT could be induced in rabbits by intranasal immunization with heat-inactivated PMT, we immunized groups of rabbits intranasally at days 0, 7, 14, and 21 with inactivated PMT, with or without cholera toxin, an adjuvant for the mucosal immune system. Significant increases in anti-PMT IgA in nasal lavage samples and anti-PMT serum IgG, as determined by enzyme-linked immunosorbent assay, developed within 2 weeks after initial immunization. Coadministration of cholera toxin with inactivated PMT enhanced anti-PMT activity in the samples. Rabbits similarly immunized on days 0, 7, and 14 were challenged with PMT, and tissues were graded histologically on a numeric scale of lesion severity. Immunization conferred partial protection against development of pneumonia, pleuritis, hepatic necrosis, and testicular atrophy in rabbits challenged 16 days after initial immunization. Thus, immunization with inactivated PMT stimulates a protective response to PMT challenge in rabbits that is enhanced by coadministration of cholera toxin.

A 2-year-old Standardbred gelding was examined because of prolapse of the third eyelid; myoclonus of the muscles of the head, neck, and forelimbs; and persistent tail swishing. The horse had a high plasma sodium concentration but was not drinking water. The hypernatremia could not be corrected by means of IV administration of fluids, and the horse became worse and, 6 days later, died. At necropsy, a tumor was found to be compressing the neurohypophysis and the area in the brain in which the thirst centers are believed to be located. It is believed that hypernatremia in this horse was a result of altered thirst.

The ability of subcutaneous, prostatic, and nonprostatic intraabdominal organ microenvironments to influence local tumor growth and metastasis of PC-3 human prostate carcinoma cells in athymic mice was determined. Tumorigenesis and metastasis of PC-3 were evaluated 60 days after subcutaneous and intraprostatic (orthotopic) implantation of 5 x 10(5) PC-3 cells in 6-week-old, male athymic mice. Intraprostatic implantation of PC-3 cells resulted in paraaortic lymph node metastases in 10 of 10 (100%) mice with prostatic tumors, whereas metastases were present in only 2 of 9 (22%) mice after subcutaneous implantation. Next, we determined whether the urinary bladder (nonprostatic, urogenital microenvironment) or stomach (nonurogenital, intraabdominal microenvironment) would facilitate the metastasis of PC-3 cells in athymic mice. Tumorigenesis and metastasis were 100% after subserosal implantation of PC-3 cells within the wall of the urinary bladder (n = 6 mice). Subserosal implantation of PC-3 cells into the stomach wall (n = 7 mice) also resulted in tumor formation and metastasis to regional lymph nodes in 100% of mice. In all experiments, regional lymph nodes were the most frequent site of metastasis, regardless of implantation site. We conclude that tumor microenvironment factors responsible for the metastasis of PC-3 cells in athymic mice may not be organ-specific, since nonprostatic visceral microenvironments are sufficient for predictable metastasis. Use of these models may further our understanding of how tumor microenvironment modulates expression of the metastatic phenotype by human prostate carcinoma cells.

Most reports of neosporosis associated with abortion in cattle are in dairy cattle and infected calves do not survive beyond 7 days of age. This paper reports neosporosis in a 4-week-old Hereford calf. The calf was full term and appeared clinically normal at birth. At 2 weeks of age, the calf had weakened and was unable to nurse unassisted. The calf was killed at 4 weeks because of paralysis. The primary lesions were in the brain and were associated with Neospora caninum tachyzoites. The diagnosis was confirmed by immunohistochemical staining with anti-Neospora rabbit serum.

Oronasal squamous cell carcinoma was diagnosed in an adult African hedgehog (Erinaceidae albiventris). Clinically, the carcinoma presented as a firm right maxillary swelling with deviation of the nose to the left. The carcinoma was attached to the hard palate and protruded into the oral cavity. At necropsy, the carcinoma appeared centered in the right maxillary sinus, and had replaced the maxilla and extended into the nasal cavity. Metastatic foci were not found.

Copper toxicosis was diagnosed in 7 veal calves, 10-16 weeks old, from 5 separate farms. All calves died without specific clinical signs, although 4 of the calves were icteric. The calves' dietary rations had been supplemented with various copper-containing hematinics. Peritoneal hemorrhage was reported at post-mortem in 2 calves. Microscopic evidence of hepatopathy consisted of hepatocellular degeneration and necrosis, hemorrhage, and fibrosis. Concentrations of copper in livers from intoxicated calves ranged from 277 to 684 ppm and in kidneys from 1.1 to 82.0 ppm. The extent and severity of lesions in livers appeared to correlate with concentrations of copper. Nephrosis was minimal, without evidence of hemoglobinuria.

Lymphoblastic lymphosarcoma with disseminated skeletal involvement was diagnosed in a 15-week-old Golden Retriever. The skeletal disease was characterized by diffuse, irregular areas of radiolucency most evident in the diaphyseal portion of long bones and was associated with gait abnormalities and signs of pain. Necropsy also revealed involvement of the spleen, liver, kidneys, and mesenteric lymph nodes.