Behzad Yamini

Mutations in the Juxtamembrane Domain of c-KIT Are Associated with Higher Grade Mast Cell Tumors in Dogs

Mast cell tumors are among the most commonly seen tumors of the skin in dogs and are more highly aggressive than mast cell tumors of other species. Some breeds display a markedly higher incidence of mast cell tumor development than others and appear to have some genetic predisposition. Recently, mutations have been found in canine mast cell tumor tissues and cell lines within the juxtamembrane domain of the protooncogene c-KIT. In previous studies utilizing a small number of cases, no association between the presence of a mutation and the breed of dog or grade of the tumor could be identified. An expanded study with a larger sample set was performed to explore this possibility. The juxtamembrane domain of c-KIT was amplified using the polymerase chain reaction from genomic DNA preparations of 88 paraffin-embedded mast cell tumors from selected breeds. Mutations, consisting of duplications and deletions, were found in 12 of the tumors. A significant association was found between the presence of a mutation and a higher grade of tumor but not between breed and grade or between breed and the presence of a mutation.

Effects of waterborne exposure of 17 β-estradiol on secondary sex characteristics and gonads of fathead minnows (Pimephales promelas)

Abstract Environmental contaminants with estrogenic activity have recently received attention because of their potential effects on the reproductive efficiency of humans and wildlife. This study was conducted with the endogenous estrogen, 17 β-estradiol (E2), to establish the histologic response of the fathead minnow (Pimephales promelas) as a model organism. Sexually mature fathead minnows were exposed for 14 days to waterborne concentrations of 1000, 100, 10, 2, 1, 0.5, 0.25, 0.125, 0.1 or 0.0625 nM E2. Exposure to E2 caused a reduction in size of the prominent male secondary sex characteristics, the fatpads and nuptial breeding tubercles. Histological lesions observed in the testes included proliferation of Sertoli cells and degenerative changes. Electron microscopy of seminiferous tubules and their Sertoli cells revealed large phagolysosomes filled with degenerating spermatozoa and other cellular debris. Females had ovaries in which most of the follicles were in the primary stage of development. There were also more atretic follicles and fewer secondary and Graafian follicles than in unexposed females. These findings demonstrate components of sexually mature fish which may be altered by compounds that mimic E2. To determine if lesions observed in males were permanent, 50 sexually mature males and females were exposed to a single concentration of 10 nM E2 for 10 days. Samples were collected from males on the final day of E2 exposure and over a period of 16 weeks after the exposure was stopped. No E2-induced lesions were observed beyond 16 weeks post E2 exposure. Results of these studies suggest that histological lesions could occur at ecologically-relevant exposures to ‘estrogenic’ compounds. However, certain lesions caused by exposure of adult fathead minnows are not permanent.

Dietary exposure of mink (Mustela vison) to fish from the Housatonic River, Berkshire County, Massachusetts, USA: Effects on reproduction, kit growth, and survival

We evaluated the effects of feeding farm-raised mink (Mustela vison) diets containing polychlorinated biphenyl (PCB)-contaminated fish from the Housatonic River (HR; Berkshire County, MA, USA) on adult reproductive performance and kit growth and survival. Diets contained 0.22-3.54% HR fish, providing 0.34-3.7 microg total PCBs (TPCB)/g feed wet wt (3.5-68.5 pg toxic equivalence [TEQ]/g). Female mink were fed diets before breeding through weaning of kits. Twelve kits from each treatment were maintained on their respective diets for an additional 180 d. Dietary PCBs had no effect on the number of offspring produced, gestation period, or other measures of adult reproductive performance. Mink kits exposed to 3.7 microg TPCB/g feed (68.5 pg TEQ/ g) in utero and during lactation had reduced survivability between three and six weeks of age. The lethal concentrations to 10 and 20% of the population (LC10 and LC20, respectively) were estimated to be 0.231 and 0.984 microg TPCB/g feed, respectively. Because inclusion of PCB-contaminated fish that composed approximately 1% of the diet would reduce mink kit survival by 20% or more, it is likely that consumption of up to 30-fold that quantity of HR fish, as could be expected for wild mink, would have an adverse effect on wild mink populations.

Dietary exposure of mink (Mustela vison) to fish from the Housatonic River, Berkshire County, Massachusetts, USA: Effects on organ weights and histology and hepatic concentrations of polychlorinated biphenyls and 2,3,7,8-tetrachlorodibenzo-p-dioxin toxic equivalence

The effects of feeding ranch mink (Mustela vison) diets containing polychlorinated biphenyl (PCB)-contaminated fish (88 gold fish [Carassius auratus] weighing a total of 70.3 kg and 16 carp [Cyprinus carpio] weighing a total of 77.3 kg) collected from the Housatonic River (HR; Berkshire County, MA, USA) in October 1999 on organ weights and histology and hepatic concentrations of total PCBs (sigmaPCBs) and 2,3,7,8-tetrachlorodibenzo-p-dioxin toxic equivalence (TEQ) were evaluated. Diets contained 0.22 to 3.54% HR fish, which provided 0.34 to 3.7 microg sigmaPCBs/g feed (3.5-69 pg TEQ/g feed). Female mink were fed the diets eight weeks before breeding through weaning of kits at six weeks of age. Offspring were maintained on their respective diets for an additional 180 d. The dietary concentration of PCBs that caused a decrease in kit survival (3.7 microg EPCBs/g feed [69 pg TEQ/g]) resulted in a maternal hepatic concentration of 3.1 microg sigmaPCBs/g wet weight (218 pg TEQ/g). Organ weights were not consistently affected. Mandibular and maxillary squamous cell proliferation was apparent in 31-week-old juveniles exposed to as low as 0.96 microg sigmaPCBs/g feed (9.2 pg TEQ/g). Juveniles in this treatment group had a liver concentration of 1.7 microg sigmaPCBs/g wet weight (40 pg TEQ/g). Because inclusion of PCB-contaminated fish, which comprised approximately 1% of the diet, resulted in mandibular and maxillary squamous cell proliferation, it is possible that consumption of up to 30-fold that quantity of HR fish, as could be expected for wild mink, would result in more severe lesions characterized by loss of teeth, thus impacting survivability.

Disseminated Rhodococcus equi infection in two goats.

Rhodococcus equi infection was diagnosed in two goats from the same herd. At necropsy, numerous caseating granulomas were disseminated throughout the liver, lungs, abdominal lymph nodes, medulla of right humerus, and the right fifth rib of goat No. 1, and the liver of goat No. 2. Histopathologic examination confirmed the presence of multiple caseating granulomas in these organs. Numerous gram-positive and Giemsapositive coccobacilli were identified within the cytoplasm of macrophages. Aerobic bacterial cultures of the liver and lung from both goats yielded a pure growth of R. equi. R. equi antigens were immunohistochemically identified in caseating granulomas from both goats. However, the 15- to 17-kd virulence antigens of R. equi were not detected, suggesting possible infection by an avirulent strain of this organism.

A 12-year retrospective study of equine abortion in Michigan.

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Characterization of an Undifferentiated Malignancy as a Mast Cell Tumor Using Mutation Analysis in the Proto-Oncogene c-KIT

A 6.5-year-old female Boxer was euthanized and presented for necropsy following rapid clinical decline concomitant with the development of numerous tumor masses. The largest of these masses was in the same location as a mast cell tumor that had been previously removed from this dog. Gross examination revealed the presence of nodules 5–200 mm in diameter throughout the body, including the lymph nodes. Histologic analysis showed an influx of round cells with no granules, leading to the provisional diagnosis of systemic lymphosarcoma. Immunohistochemical staining for B- and T-lymphocyte antigens was negative. Molecular tests were used to identify a tandem duplication in the c-KIT proto-oncogene from both the earlier mast cell tumor and the current nodules, implicating a common origin. Addition of molecular testing to conventional necropsy evaluations allowed a definitive diagnosis of mast cell tumors.

Sarcocystosis in mink (Mustela vison).

This report describes the clinical, microscopic, and ultrastructural findings in mink with muscular sarcocystosis. Three 2-3-mo-old mink were killed because they were ill with signs of progressive neurological disease. One mink had variable numbers of sarcocysts in multiple skeletal muscles. Sarcocysts were up to 300 microm in long and 20 microm wide. Ultrastructurally, the sarcocyst wall had numerous elongated 1.7-2.0-microm x 250-nm villar protrusions (VP). The VP had microtubules and irregularly distanced minute undulations. Both metrocytes and bradyzoites were present in sarcocysts. The mink with sarcocysts in muscles also had nonsuppurative meningoencephalitis and meningomyelitis. Similar brain lesions were found in other 2 mink from the same farm, but sarcocysts were not observed in the skeletal muscle of these animals. This is the first report of muscular sarcocystosis in mink.

Equine Colonic Lipomatosis

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Cerebrospinal Nematodiasis and Vertebral Chondrodysplasia in a Calf

from vasculitis and tissue infiltration of leukocytes to necrosis with granulation tissue. The age of these primary lesions was estimated to be less than 1 day and up to a week or more.9 The inflammatory process had started before slaughter, and the affected valves were less elastic and somewhat fragile. The fact that erythrocyte destruction, erythrophagocytosis, and hemosiderosis were not observed indicates that the hemorrhages were fresh and had developed shortly before or during the slaughter procedure. The great fluctuations in blood pressure as a consequence of stress, stunning, and sudden massive bleeding (hypovolemic shock4,14) probably caused greater vascular strain than these altered valves could bear. Demonstration of an Erysipelothrix sp. and a Streptococcus sp. in 4 out of the 6 valves investigated is in accordance with the earlier reports that these bacteria are the most common cause of valvular endocarditis in the pig.11,15 The findings presented indicate that hemorrhages in the left atrioventricular valves of conventionally slaughtered pigs reveal an apparent early phase of valvular endocarditis and thus provide material suitable for morphological studies. Even if the material presented here is limited, the findings indicate that inflammation in a previously undamaged valve may start as vasculitis within the spongiosa of the valve. Acknowledgement. The assistance of Mr. Christer Rundberg is gratefully acknowledged.