Mast cell tumor in dogs--incidence and histopathological characterization.

Incidence of mast cell tumors, their distribution according to sex, breed, age and localisation in Croatia is not established yet. Also, the statistical significance of the various histopathological parameters according to Patnaik's scheme, in the diagnostics of the tumor grade was not performed. Investigation analysed mast cell tumors histopathologicaly characterized at the Department of General Pathology and Pathological Morphology of the Veterinary Faculty Zagreb from January 1st 2002 to December 31st 2006. Sex, age, breed, localisation and tumor grade of each animal with tumor was recorded and statisticaly evaluated. Each histopathological variable was scored and compared with tumor grade. In the analyzed period, totally 1630 tumors were recorded, and mast cell tumors were found in 106 animals or in 6.5% of all cases. With statistically significant difference, this tumor was found in more cases in male dogs, and average age was 6.96 years. Boxers and retrievers were most frequent breeds, and localization was mostly on legs. Grade I tumor was found in 15.09%, grade II in 44.34% and grade III in 28.3% of animals. There were no significant correlations between tumor grade and age, breed, sex or localization. Considering the lesion scores compared with grade, statistically significant differences were found in cell shape, number of nucleoli, anisocytosis, anisokariosis, karyomegaly, mitoses, necroses, hemorrhages, cellularity, cell borders and collagenolysis.

Comparison of genomic damage caused by 5-nitrofurantoin in young and adult mice using the in vivo micronucleus assay.

The antibiotic 5-nitrofurantoin (5-NF) has been used widely for the treatment of urosepsis in children during the last 20 years. Recent experimentation suggests the need for reevaluating its genotoxic potential. Because of possible differences in the metabolism and clearance of 5-NF in young and adult animals, we conducted a study to determine whether micronuclei caused by 5-NF were age-related. The in vivo micronucleus (MN) assay was performed on 3- and 8-week-old mice given single intraperitoneal injections of 5, 10, and 50 mg/kg 5-NF. Blood samples from the tail vein were taken before injection (baseline) and at 48, 96, 168, and 336 hr (2 weeks) after the treatment. One thousand reticulocytes were analyzed for micronuclei from each animal. Compared to similar baseline values for young and adult mice, 5-NF caused a significant increase in MN frequency in both age groups. The mean MN frequency in the young animals was higher than in the adult animals for each dose and sampling time. MN frequencies remained significantly elevated in young animals even 2 weeks after exposure to 5-NF. The results of the study confirm the genotoxic potential of 5-NF in young and adult animals, and indicate that young animals are more sensitive to the genotoxic effects of 5-NF than adult mice and that the response in young mice persists for a significantly longer time. These findings may be related to poorly developed mechanisms of xenobiotic detoxification and renal elimination in young animals.