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.

Total mandibular reconstruction with cancellous cellular bone graft, allogeneic bone crib, and endosseous implants.

It is not often that the oral and maxillofacial surgeon is faced with the challenge of restoring a defect that involves the entire mandible. The case presented in this article illustrates the management of such a case. Trauma, infection, neoplasm, and congenital malformations can lead to a discontinuous, deficient, or even absent mandible. In planning the reconstruction of a discontinuity of the mandible, the surgeon may need to manage one or more problems, including loss of adequate denture-bearing bone, loss of speech articulation, loss of control of the tongue and masticatory function, xerostomia as a result of the loss of sublingual and submandibular glands, loss of an intact deglutition mechanism, and a loss of facial form.

Effect of age and sex on liver damage due to excess dietary copper in Fischer 344 rats.

OBJECTIVE: The aim of this study was to investigate the morphologic and biochemical effects of excess dietary copper in young and adult rats of different sex. METHODS: Adult Fischer 344 male and female rats were given a diet containing 1500 ppm copper for 18 weeks. Young male and female rats were fed a similar copper-loaded diet from birth until 16 weeks of age. Age- and sex-matched control rats were fed a normal rodent diet (<10 ppm copper). Serum liver enzyme activity was determined in all rats. Livers were sampled for histology, histochemistry (rhodanine), immunohistochemical detection of metallothionein and copper analysis by atomic absorption spectrophotometry. Hepatic metallothionein and zinc concentrations were measured in adult rats. RESULTS: Excess dietary copper caused substantial liver injury, as evidenced by morphologic changes and increased activity of serum ALT, GGT, and SDH. All copper-loaded rats had significantly (p< 0.05) increased hepatic copper concentrations compared to controls. However, young copper-loaded rats accumulated more hepatic copper, had more severe liver changes, and had higher serum liver enzyme activities than adult rats. Histologic changes in copper-loaded rats consisted of multifocal hepatitis and widespread single-cell necrosis. Cytoplasmic copper was detected histochemically in centroacinar zone 1 (portal) and mid-zone in copper-loaded rats. Immunoreactivity for metallothionein was prominent in necrotic hepatocytes and within inflammatory foci in copper-loaded rats. However, differences in hepatic metallothionein concentrations were not detected between adult copper-loaded and control rats. CONCLUSIONS: Young Fischer 344 rats are more susceptible than adults to copper-induced liver injury.

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.

Immunohistochemical detection of metallothionein in liver, duodenum and kidney after dietary copper-overload in rats.

Metallothionein (MT) has been used in immunohistochemical techniques to indicate presence and distribution of heavy metals within biological tissues. This study describes a comparison of the pattern of MT-immunostaining in the liver, duodenum and kidney during dietary copper overload in rats. Sixteen male 10-week-old Wistar rats were randomly allocated into groups of four. Two groups were fed a pelleted diet containing 1,500 mg/kg copper and two control groups received a rodent diet containing 10 mg/kg copper. After 6 weeks samples of liver, kidney and duodenum were collected for immunohistochemistry and histology. An indirect immunoperoxidase technique, using monoclonal antibody E9 against horse MT and polyclonal sera against rabbit MT, was employed. Copper-loaded rats had marked MT-immunoreactivity within the nucleus and cytoplasm of many periportal hepatocytes, renal proximal convoluted tubule epithelial cells, intestinal columnar epithelial cells and Paneth cells. Immunohistochemical staining was similar using either mouse anti-MT polyclonal serum, or monoclonal antibody E9. Hepatocytes surrounding inflammatory foci were positive for MT, supporting the proposed role of this protein in free radical scavenging. The presence of MT in the kidney appears to be associated with renal excretion of copper-metallothionein (Cu-MT) in copper-loaded rats. Paneth cells were easily detected using MT-immunostaining. MT may play a part in absorption of copper from intestinal contents and possible storage as Cu-MT in Paneth cells. The function of Paneth cells remains unknown but the presence of marked MT-immunoreactivity in these cells, observed in copper-loaded rats, suggests their involvement in homeostasis and metabolism of copper.