Experimental chlamydial pneumonia in pigs

Naturally occurring disease in pigs associated with chlamydial infections has not been reported in Britain, though evidence of chlamydial challenge has been demonstrated in two separate serological surveys. An isolate of Chlamydia psittaci (28/68) from an ovine pneumonia produced pneumonia in pigs following intratracheal inoculation. Transient pyrexia at 24 hr was followed by increased respiratory rates and inappetance which lasted for a further 48 hr in challenged pigs. Histologically acute exudative reactions were present in the lungs by 24 hr with proliferative changes predominating after 10 days. While variations in the concentrations of inocula were reflected by corresponding increases and/or decreases in gross lung damage, clinical signs and histological reactions were unaltered. Chlamydial organisms were recovered only from lung tissues.     

Cryptosporidiosis in guinea pigs: a retrospective study

Cryptosporidiosis was diagnosed in 81 guinea pigs (Cavia porcellus) from 1979 through 1985 at a research animal diagnostic laboratory. Most of the guinea pigs were juveniles of Hartley stock and originated from 6 commercial laboratory animal suppliers or from one pet store supplier. Common clinical signs reported were failure to gain weight, weight loss, diarrhea, and death. At necropsy, macroscopic findings included emaciation, hyperemia of the small intestine, serosal edema of the cecal wall, and increased fluidity of ingesta throughout the intestines. Oval to round cryptosporidia (1 to 4 microns) were seen microscopically within or on the brush border of mucosal epithelial cells from the duodenum through the cecum. Acute histologic lesions consisted of necrosis and sloughing of enterocytes at the villus tips, inflammation, hyperemia and edema of the lamina propria, and hyperplasia of crypt epithelium. More chronic lesions consisted of marked villus bridging or villus fusion and blunting, metaplasia of the mucosal epithelium, and lymphocytic infiltration of the lamina propria.     

Post-natal maturation of acinar cells of the guinea pig pancreas: an ultrastructural morphometric study

The morphological maturation of the acinar cells of the guinea pig pancreas during post-natal development was characterized morphometrically by determining the intracytoplasmic accumulation of rough endoplasmic reticulum (RER) and zymogen granules. The following results were obtained for the period analysed, i.e., from 2 to 70 days of post-natal life: (a) the acinar cell volume increased by 210% (P < 0.01); (b) the mostly cisternal RER occupied more than 30% of the cytoplasm at any age studied and their total volume and surface in the cell were increased by 300 and 534% (P < 0.01), respectively; (c) maturation in the morphological pattern of the RER was observed; (d) the mean number of zymogen granules per cell increased from 261 at 2 days to 422 at 70 days (P < 0.01), while their mean diameter increased from 0.52 to 0.94 micron (P < 0.01) during the same period; (e) these increases in granule number and size were responsible for a 500% (P < 0.01) increase in total volume from 2 to 70 days and for a 304% increase (P < 0.01) in total surface from 2 to 35 days; (f) the RER and the zymogen granules together occupied 44, 54, 55 and 57% of the cytoplasm at 2, 14, 35 and 70 days of age, respectively. We conclude that although the pancreatic acinar cells of the guinea pig are morphologically well differentiated at 2 days of age, with the cytoplasm already showing a large amount of RER and zymogen granules, they are still immature. Morphological maturation of the acinar cell occurs during the first months of post-natal life and is characterized by a substantial gain in cell volume and intracytoplasmic accumulation of RER and zymogen granules, which significantly increase of both their absolute volume and total surface, with a higher growth rate being observed during the period from 2 to 14 days of post-natal life.     

Experimental Tonsillophilus suis granuloma in rats and guinea pigs.

Rats and guinea pigs were experimentally infected by intradermal and intraperitoneal inoculation of T. suis. These animals were observed for pathologic changes at various stages. Macroscopic observation disclosed visible grayish white soft nodules at the injection site in those inoculated intradermally and many grayish white nodules in the peritoneum of those inoculated intraperitoneally. Histopathological examination revealed the presence of characteristic microbial elements in the centre of the lesions. Various stages of the lesions were recognized; the early stage being abscess, the advanced stage being pus-forming granuloma and the final stage being residual granuloma. The microbial elements were composed of spores, thalli and multilocular tubers. Clubs were formed around microbial elements in rats inoculated intradermally and in guinea pigs inoculated intraperitoneally. The characteristic T. suis lesions in pigs were reproduced by experimental infection of this organisms in rats and guinea pigs, and thus the pathogenicity of T. suis was confirmed.     

Early histopathologic and ultrastructural alterations in femorotibial joints of partial medial meniscectomized guinea pigs

The articular cartilage from femorotibial joints of partial medial meniscectomized male guinea pigs was evaluated at 24, 48, 72, and 96 hours post-surgery to determine the sequential histopathologic and ultrastructural alterations. At 24 hours post-surgery, histopathologic alterations were in the superficial and middle layers and consisted of degeneration and necrosis of chondrocytes and minimal decreased intensity of toluidine blue matrix staining. Changes in chondrocytes and matrix became progressively more extensive 48 hours after surgery. Ultrastructurally, the changes in the superficial matrix appeared to be the result of loss of the fine granular material interspersed between collagen fibers. At 72 and 96 hours post-surgery, chondrocyte loss was extensive and surface fibrillation was seen. These findings suggested that chondrocyte death was the initial important event which led to progressive severe cartilage degeneration in this model.     

Experimental infection by Vibrio anguillarum in mice and guinea pigs.

The fish pathogen Vibrio anguillarum causes a lethal infection in farmed fish characterized by hemorrhagic septicemia. There are no reports of experimental laboratory infections in warm-blooded animals. We investigated the effects of an intraperitoneal infection with different doses of a V. anguillarum suspension in mice and guinea pigs. The infection caused a 95-100% of mortality in 24-48 h. Hemorrhagic septicemia was observed at necropsy and confirmed by histological and hematological examination. Immunohistochemically positive bacterial clumps were detected exclusively in vessel lumen in all examined organs, including brain, and V. anguillarum was reisolated in pure culture from all organs, particularly from the kidney. Blood analysis showed erythropenia and leukopenia with granulocytosis in mice, platelet reduction and leukopenia with lymphocytosis in guinea pigs.