The analysis of reproductive hormones in faecal samples is a possibility for non-invasive monitoring of reproductive status in free-ranging or intractable species. In the present study, faecal samples from three black rhinoceroses (Diceros bicornis michaeli) were collected at about weekly intervals during oestrous cycles and pregnancy. Daily samples were taken during the week after parturition. Total immunoreactive progestagens in faecal extracts were analysed with three different enzymeimmunoassays (EIA) that had considerable specificity for progestagens containing either a 20\g=a\-hydroxyl or a 20-keto group. With each EIA it was possible to distinguish between the follicular and luteal phases of the oestrous cycle. Mating corresponded with low concentrations of faecal progestagens. Samples from five and six consecutive cycles were available from two rhinoceroses and cycle lengths of 24 and 26.5 days were calculated. All three animals became pregnant and the duration of gestation ranged from 440 to 470 days. After fertilization, the concentration of progestagens increased continuously, as in the luteal phase, reaching values 5\p=n-\10times higher between days 60 and 250. During the two weeks before parturition faecal progestagens declined and within 3\p=n-\4 days post partum had reached follicular phase values. It was concluded that several immunoreactive progestagens are present in the faeces of black rhinoceroses and that their measurement with EIA enables non-invasive monitoring of the oestrous cycle and pregnancy.

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A 34-year-old female orangutan (Pongo pygmaeus) developed renal failure and became uremic. At necropsy, large gastric masses were present around the cardia and in the corpus. Abdominal metastases occurred in the liver, pancreas, and right ovary. Light microscopic examination of the tumor revealed polygonal cells with vesicular nuclei and prominent nucleoli. The growth pattern was predominantly solid. Focal areas contained excentric cytoplasmic intermediate filament inclusions, as identified by immunohistochemistry and electron microscopy. Immunohistochemical procedures demonstrated mainly the vimentin type of intermediate filaments. Except for occasional cytokeratin, other intermediate filament markers and neural, lymphocytic, and histiocytic markers stained negative. The morphologic and ultrastructural characteristics are typical for a malignant rhabdoid tumor, a term used in human pathology to describe a rare and extremely aggressive malignancy of uncertain histogenesis. Although usually located in the infant kidney, a few reports have documented the occurrence of similar lesions in extrarenal sites of adults. In human tumors, vimentin is often combined with the expression of cytokeratins. The sparsity of the cytokeratin filaments in this case might be due to species-specific variations and/or may reflect the hypothesis of a phenotypic concept encompassing a spectrum of histogenetic diversity.

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