Chiyo Doi

Histopathology of streptozotocin-induced diabetic DBA/2N and CD-1 mice

Histopathological examinations were carried out on female DBA/2N and CD-1 mice which were autopsied 4 and 12 weeks after six daily intraperitoneal injections of streptozotocin (SZ). Histopathological changes related to SZ treatment were found in the pancreas, liver and kidneys. Little difference was observed between the two strains in the histological changes of the pancreas (a decrease in size of the islets, and degranulation and a decrease in the number of B cells) and liver (hypertrophy of hepatocytes and cytoplasmic invagination into hepatocyte nuclei). With regard to the changes in the kidneys, DBA/2N mice showed characteristic inclusions positive to periodic acid-Schiff reagent in the distal tubule epithelial cells, while CD-1 mice showed remarkable luminal dilatation and epithelial cell deformation of distal tubules. SZ-induced diabetes had no innuence on the development of spontaneous cardiovascular lesions in DBA/2N mice under the present experimental conditions.

Age-related non-neoplastic lesions in the heart and kidneys of Syrian hamsters of the APA strain

Spontaneous cardiac and renal lesions in APA hamsters were examined histopathologically. Myocardial degeneration, valvular thickening, coronary arterial degeneration and increase in heart weight were common in old hamsters. These changes, which suggest cardiac failure, seem to be related to cardiac thrombosis which predominantly affected the left atrium and was found in over 40% of each sex over 16 months of age. Neither glomerular amyloidosis nor arteriolar nephrosclerosis was detected. In general the histopathology of renal lesions in APA hamsters resembled that of the condition known as glomerulonephrosis in rats. Renal lesions occurred more frequently and more severely and developed more rapidly in females than in males. There was no apparent correlation between cardiac thrombosis and renal disease.

Mouse strain difference in bile duct lesions induced by swine serum injections

The mouse strain difference in bile duct lesions was studied on male A/J, BALB/c, C57BL/6, C3H/He, DBA/2 and DDY mice 4 weeks old given intraperitoneal injections of swine serum (0·05 or 0·2 ml per mouse) twice a week for 4 weeks. The hepatic lesions were restricted to the portal tract. Biliary epithelial cells showed hypertrophy and hyperplasia, and eosinophilic and homogeneous or needle-shaped material appeared in the cytoplasm of such hypertrophied epithelial cells and in the ductular lumen. Around these damaged biliary epithelia, eosinophil leukocyte and plasma cell infiltration with proliferation of collagen fibres was commonly detected. These changes became more apparent with increasing size of bile duct. Such histopathological characteristics of hepatic lesions were essentially the same in all strains, but the severity showed a clear strain difference: the lesion was marked in the DDY, A/J and BALB/c strains, moderate in C3H/He and slight in C57BL/6 and DBA/2. A high production of anti-swine-serum antibodies associated with a marked increase in the number of mouse IgG-producing lymphocytes in the spleen was detected in the strains showing the marked hepatic lesions.

Encephalomyocarditis (EMC) virus infection in the common vole, Microtus arvalis

Encephalomyocarditis (EMC) virus infection in the common vole was examined for the first time. Sixteen 8-week-old males inoculated intraperitoneally with 105 plaque-forming units (pfu)/animal of the D variant of EMC virus were killed 3 and 7 days after inoculation (3 and 7 DAI). Viral replication was detected in the brain (105 pfu/g), heart (104 pfu/g) and pancreas (107 pfu/g) of all 8 animals at 3DAI. It was found in the pancreas (103 pfu/g) of all 8 animals and in the brain (104 pfu/g) of 2 of 8 animals at 7 DAI. Histopathological changes were observed in the brain (mild mononuclear cell infiltration around capillaries and sporadic pyknosis of neurons), heart (minimal myocardial necrosis) and pancreas (prominent acinar cell necrosis with inflammatory exudation) at 3DAI. At 7 DAI, replacement of necrotic tissues by mesenchymal cells and regeneration of acinar cells were conspicuous in the pancreas. Throughout the experimental period, no evidence for diabetogenic effect was found.

Transmissibility of the D variant of encephalomyocarditis virus (EMC-D) in mice

Transmissibility of the D variant of encephalo-myocarditis virus (EMC-D) was examined. Eight-week-old ICR:CD-1 male mice inoculated with 105 plaque forming units (PFU)/animal of EMC-D intranasally, orally or intraperitoneally showed marked viraemia and prominent pancreatic lesions at 2 days after inoculation (2 DAI), and excreted virus in faeces from 2 to 8 DAI (virus titre:l03-l05 PFU/g). Only a small proportion of control mice housed with EMC-D-inoculated mice for 10 days developed viraemia and pancreatic lesions.