Metallothionein expression in canine and feline mammary and melanotic tumours.

Moderate to strong immunohistochemical metallothionein (MT) positivity (MT expression) is associated with a poor prognosis in some human tumours. The aim of this study was to determine MT expression in mammary tumours and cutaneous melanomas in dogs and cats. Canine (67) and feline (47) mammary tumours, and cutaneous melanomas (canine 40, feline 26) were immunolabelled with MT monoclonal antibody E9. The overall incidence of MT expression of these tumours was similar to that observed in various human neoplasms. However, a striking interspecies difference was detected. In dogs, MT expression occurred in 100% of benign and 57% of malignant mammary tumours. In cats, however, 30% of malignant mammary tumours expressed MT but benign mammary tumours and cases of fibroadenomatous hyperplasia did not. Moderate to strong MT immunoreactivity was detected in 30% of benign and 25% of malignant cutaneous melanomas in dogs, and in 6% of malignant melanomas in cats. The findings in feline mammary tumours resembled findings reported in human breast cancer, but the cause of tumour-associated MT expression is unknown. Studies are in progress to determine whether the MT state (apo [metal-free] or holo [metal-bound]) accounts for the paradoxical association of MT expression with individual types of tumours and the animal species in which they arise.

Copper toxicosis in the Bedlington terrier: a diagnostic dilemma.

Diagnosis of copper toxicosis (CT) in Bedlington terriers by the quantitative and qualitative assessment of copper (Cu) in, and pathology of, biopsies has been largely superseded by a DNA-based assay which uses a microsatellite marker (C04107) linked to the CT disease allele. A retrospective study was conducted comprising 154 liver biopsies from Bedlington terriers with 22 matched DNA markers to compare the two methods in the diagnosis of CT. For the biopsy method, three categories (phenotypes) were identified based on analytical and morphological criteria: 'unaffected' in 83 samples (54 per cent), where Cu was much less than 400 microg/g, and there was an absence of visual Cu or liver damage; 'intermediate' in 18 samples (12 per cent), where Cu was less than 400 microg/g, and there was limited histochemical Cu and no/equivocal damage; and 'affected' in 53 samples (34 per cent), where Cu was greater than 400 microg/g, there was histochemical Cu and liver damage was poorly related to Cu content. In the DNA assay, which was used alone on unrelated individuals, the microsatellite marker failed to identify the CT status of any of the groups. Liver biopsy remains a reliable indicator of Cu accumulation and progressive liver disease in individual dogs. The microsatellite marker C04107 has a predictive value only when supported by a pedigree.

Eccrine adenocarcinoma of the footpads in 2 cats.

Adenocarcinoma of sweat glands of the footpads was diagnosed in 2 cats. Clinical signs included lameness and swelling of multiple digits. Pulmonary metastasis was detected in one case. Diagnosis was based on histopathological and immunohistochemical findings. Eccrine adenocarcinoma should be included in the differential diagnosis of footpads lesions in aged cats.

Purification and partial characterization of a cadmium-binding protein from the liver of rainbow trout (Onchorynchus mykiss).

This study describes the isolation and partial characterization of a low molecular weight (approximately 14 kDa), cadmium-binding protein from rainbow trout (Onchorynchus mykiss) liver. Rainbow trout were injected intraperitoneally with 3.5 mg/kg cadmium chloride (total body dose) twice weekly for 3 wk. Livers were removed and a cadmium-binding protein was isolated. Monoclonal antibodies produced against this protein were used in the affinity purification process. Amino acid analysis showed the protein contained 3.8 mol% cysteine, 3.5 mol% phenylalanine, 2.2 mol% tyrosine and 1.9 mol% histidine. The low cysteine content suggests that it was distinct from metallothionein. The monoclonal antibodies were also used to identify the protein in liver homogenates from both cadmium-exposed and control fish and in the testes of cadmium-exposed mice lacking the gene for both metallothionein-1 and metallothionein-II. The compound identified in this study represents a non-metallothionein cadmium-binding protein that appears to be highly conserved.

Immunohistochemical demonstration of metallothionein in benign and malignant canine mammary tumours.

Immunocytochemical demonstration of metallothionein (MT) has been reported as a useful prognostic tool in human breast cancer. The aim of this study was to determine the immunohistochemical location of MT in canine mammary tumours and its possible correlation with the morphologic characteristics of these tumours. Surgical specimens from spontaneous malignant (n = 20) and benign mammary neoplasms (n = 20) were processed for routine histological examination and immunohistochemical study. An indirect immunoperoxidase technique, using monoclonal antibody E9 against horse MT was employed. Intensity of the stain, the percentage of immunoreactive tumour cells and immunohistochemical overexpression of MT was estimated for each case. Metallothionein over-expression, defined as those cases with more than 10% immunopositive cells, was detected in both benign and malignant mammary tumours. However, strong immunostaining intensity was seen in benign tumours, whereas in malignant tumours immunopositive cells stained weakly. Positive MT immunostaining occurred in neoplastic epithelial cells, and some chondrocytes present in mixed mammary tumours. However, staining intensity was variable in immunopositive cells. Differences in staining intensity between the primary malignant mammary tumour, tumour emboli and metastatic cells within a lymph node were also noted. Myoepithelial cells and connective tissue did not stain for MT. We concluded that metallothionein immunostaining cannot be used as a diagnostic or prognostic tool in canine mammary neoplasms. However, results of this study support the hypothesis that MT has a role in tumour proliferation and tumour progression.

Hepatic lesions in rabbits infected with Encephalitozoon cuniculi administered per rectum.

Microsporidia have been recognized recently as opportunistic pathogens in acquired immunodeficiency syndrome patients. In an attempt to develop an animal model of enteric microsporidiosis, adult (5 to 6 months old) male Flemish Giant rabbits from a closed New York colony were administered 5 x 10(3), 5 x 10(5), and 5 x 10(7) Encephalitozoon cuniculi per rectum. Rabbits given 5 x 10(5) and 5 x 10(7) E. cuniculi had moderate granulomatous periportal infiltrates, characterized by the presence of numerous macrophages, epithelioid cells and a few multinucleated giant cells, lymphocytes, and plasma cells. Inflammatory cells also were seen infiltrating the tunica adventitia and tunica media of hepatic portal veins and branches of the hepatic artery. This study demonstrates that administration of E. cuniculi per rectum to rabbits results in infection that is characterized by high frequency and severity of hepatic lesions.

Endometrial adenocarcinoma in a mare.

An endometrial adenocarcinoma with metastases to the lung, liver, spleen, mesentery and serosal peritoneal surfaces was found in an 11-year-old Arabian mare. Clinical signs included generalized weight loss, depression, anorexia, ventral edema and abdominal distension. Ascites was due to thrombosis of the caudal vena cava. The diagnosis of endometrial adenocarcinoma was based on the histological appearance of uterine glandular epithelium and the presence of similar tissue in the metastatic tumors.