Trabecular bone morphometry in beagles with hyperadrenocorticism and adrenal adenomas.

Trabecular bone morphometry was done on rib samples of beagles with hyperadrenocorticism and adrenal adenomas to evaluate bone loss and the remodeling changes responsible. Beagles diagnosed as having clinical hyperadrenocorticism and those with milder or subclinical hyperadrenocorticism diagnosed on the basis of adrenal and pituitary lesions at necropsy had increased adrenal and pituitary gland weights. In a group of dogs with adrenal cortical adenomas there was atrophy of remaining cortex, and the combined weight of adrenal glands or pituitary weights were not increased. In dogs with clinical hyperadrenocorticism, mean trabecular bone volume was 25% less than controls (P = 0.10). In both clinical and subclinical hyperadrenocorticism groups, the extent of trabecular surface with unmineralized osteoid matrix and osteoblasts was significantly reduced. There were no changes in resorption surfaces or number of osteoclasts present. No bone changes were seen in dogs with adrenal adenomas. In dogs with hyperadrenocorticism it appeared that decreased bone formation was primarily responsible for the relative osteopenia that developed. Although parathyroid glands were moderately enlarged in those dogs for which weights were available, the bone changes were not those of increased remodeling expected in hyperparathyroidism.

Neoplasms in young dogs after perinatal irradiation.

For a study of the life-time effects of irradiation during development, 1,680 beagles were given single, whole-body exposures to 60Co gamma-radiation at one of three prenatal (preimplantation, embryonic, and fetal) or at one of three postnatal (neonatal, juvenile, and young adult) ages. Mean doses were 0, 0.16, or 0.83 Gy. For comparison with data on childhood cancer after prenatal irradiation, examination was made of tumors occurring in young dogs in this life-span experiment. Up to 4 years of age, 18 dogs had neoplasms diagnosed, 2 of these being in controls. Four dogs that were irradiated in the perinatal (late fetal or neonatal) period died of cancers prior to 2 years of age. This risk was of significant increase compared to the risks for other experimental groups and for the canine population in general. Overall, 71% (5 of 7) of all cancers and 56% (10 of 18) of all benign and malignant neoplasms seen in the first 4 years of life occurred in 29% (480 of 1,680) of the dogs irradiated in the perinatal period. These data suggest an increased risk for neoplasia after perinatal irradiation in dogs.

Spontaneous cor pulmonale in laboratory beagles.

Right heart failure associated with postmortem evidence of pulmonary hypertension (cor pulmonale) was observed in nearly 1% of the young beagles of a large research colony. During the past 18 years, 176 dogs with cor pulmonale were observed. Most cases occurred between September and April of each year. Nearly equal numbers of males and females were involved, and some siblings were affected. Ninety-six percent of known affected dogs died, and 85% of the deaths occurred by 5 weeks of age. Clinically, most dogs were stunted and exhibited ascites, subcutaneous edema, hypothermia, dyspnea, cyanosis, and systolic murmur. Radiography revealed cardiomegaly, and electrocardiography revealed right axis deviation and an enlarged right atrium. Postmortem evidence of cor pulmonale included subcutaneous edema, ascites, hydrothorax, mediastinal and mesenteric edema, splenomegaly, centrolobular hepatic congestion and necrosis, right ventricular hypertrophy, interstitial pneumonia, and medial hypertrophy of pulmonary arteries and arterioles. The specific cause of the disease was not determined.

Relationship of hypothyroidism to diabetes mellitus, renal amyloidosis, and thrombosis in purebred beagles.

Review of 484 records for colony Beagles revealed an association between hypothyroidism and diabetes mellitus. The average time between first notation of hypothyroidism and later development of diabetes mellitus was 2.8 years. An association was also made with hypothyroidism, renal amyloidosis, and thrombosis. Hypothyroidism was significantly related to thrombosis, thrombosis was significantly related to renal amyloidosis, but hypothyroidism and renal amyloidosis were not significantly related. Of 62 hypothyroid dogs, 11 were diabetic and 7 others had thrombosis. Six hypothyroid dogs had renal amyloidosis, 4 of which had thrombosis. One dog had renal amyloidosis and thrombosis in the absence of hypothyroidism. There does not appear to be an association with any of the lesions and previous low-dose, whole-body gamma, or sham irradiation.