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A life-span study with 900 female virgin Han:NMRI mice (300 outbred controls, 300 of a fat subline and 300 of a lean subline) was carried out to determine the occurrence of spontaneous diseases with ad libitum or restricted feeding. Rare non-neoplastic lesions of the lungs (1-8%) were secondary inflammations, focal ossification and subintimal arterial 'plaques'. More frequent were age-dependent pulmonary mineralizations similar to psammoma bodies (3-18%) and crystal formations (4-22%). Food restriction did not affect the incidence of these lesions directly. Crystals were observed furthermore within infoldings of the tracheobronchial mucosa and intra- as well as extracellularly in the nasal cavities.

Efficiency of indirect immunofluorescence microscopy (IFM) for detection of M. pulmonis antibody (IgG) in rats was compared with results of enzyme-linked immunosorbent assay (ELISA), complement fixation (CF), cultural isolation and histopathology. IFM was carried out on M. pulmonis infected BHK-21 cells grown on cover slips or multitest slides. After acetone fixation these antigen carriers could be stored at -20 degrees C for several months so that serological tests could be done at any time and completed within 2 h. The IFM was strain specific and the sensitivity of the test was comparable with that of the ELISA, whereas the CF-test proved to be very insensitive. For routine monitoring, only in cases of fresh infections should time consuming cultural procedures be preferred to serological tests. Chronic disease stages were readily detected by histological examination.

A life span study of 900 female virgin Han:NMRI mice (300 outbred controls, 300 of a fat subline, and 300 of a lean subline) was done to determine the occurrence of spontaneous disease with ad libitum or restricted feeding. Major nonneoplastic lesions in the glandular stomach were erosions, ulcers and adenomatous hyperplasia of the fundus. Ulcers, ranging in incidence with ad libitum feeding from 5 to 9% and with food restriction from 13 to 34%, either occurred secondary to other diseases or were due to stress associated with food restriction, causing death mainly in the lean subline. Adenomatous hyperplasia was most common in the control group (41%); the frequency increased with age and was significantly reduced by food restriction. The etiology of adenomatous gastric hyperplasia is yet unknown. However, a lack of antiparietal cell antibodies, as determined by an immunofluorescent technique, indicates that an autoimmune disorder is not involved and an increase in antral gastrin cells, as determined by avidin-biotin peroxidase immunocytochemistry, suggests a hormonal involvement in pathogenesis.

A variety of sex-dependent urinary proteins of low molecular weight, absent in females and in castrated males, can be identified in male rats by disc electrophoresis. In the urine of male rats of age 5.5 months, albumin comprises only 1-2% of the total protein. Albumin excretion increases greatly with age and associated kidney disease. Total protein excretion, however, stays the same or even decreases slightly as the rat ages, due to a loss of low molecular weight, sex-dependent, proteins. These are virtually absent in senescent rats (38 months of age), although total protein excretion rises tenfold in these animals due to high molecular weight plasma proteins passing into the urine; the glomerular filtration rate decreases to 70% of the value measured at 5.5 months of age.

Hereditary polycystic kidney disease (PKD) was seen in Han:SPRD rats and identified as an autosomal, incomplete dominant trait. Homozygous animals died at 3 to 4 weeks of age, while heterozygous males were severely ill or moribund within about 6 months. Heterozygous females developed PKD to a lesser extent than males and survived longer. Renal secondary hyperparathyroidism and osteodystrophia fibrosa were seen in most males but were absent in females. In male rats metastatic calcification was found in kidneys, lungs, glandular and forestomach, blood vessels, and heart. In a few uremic males ulcerative enteritis occurred in cecum and colon. Blood urea nitrogen values were significantly increased in both sexes.

A life span study with 900 female virgin Han:NMRI mice (300 outbred controls, 300 of a fat subline and 300 of a lean subline) was carried out to determine the occurrence of spontaneous disease with ad libitum or restricted feeding. The major age-dependent non-neoplastic alteration of the thyroid was a cystic distension of the ultimobranchial bodies (up to 90% in the oldest age groups). Most of the severely cystic thyroids were found in animals of the fat sublines and development seemed to be slightly delayed by food restriction. The cyst walls were composed of ciliated and non-ciliated granular or highly attenuated cells. The cysts contained Alcian blue and periodic acid Schiff positive substances.

The histopathological features of 2 atypical epithelial thymomas found in female Han: SPRD rats are described. The neoplasms were characterized by well-circumscribed epithelial nests and islands. One tumour showed local invasion in lymph vessels.

Tumours of the seminal vesicles were found in 11 of 182 male Han:Chin hamsters kept in a life-span study from weaning to their natural death. Histologically they were classified as adenocarcinoma (n = 10) and hemangiosarcoma (n = 1). The histopathological features of the neoplasms are described.

In a longevity study on 320 male and 320 female specified-pathogen-free Han:Wistar rats, 119 (39.0%) of 305 females evaluated developed spontaneous metastatic uterine adenocarcinomas. These tumors caused a great difference between the mortality rates of males and females. Thirty five percent of the females died of adenocarcinomas of the uterus. The tumors began as small nodules in one or both horns near the bifurcation. Large tumors extended through the uterine wall and produced wide-spread transcoelomic metastases. Early lesions were well-differentiated adenocarcinomas but advanced tumors were more poorly differentiated.