Seventy-nine spontaneous neoplasms in Dunkin-Hartley guinea pigs were observed over a 9-year period in the Fort Detrick guinea pig colony. Sixty-three of the neoplasms were found during approximately 8,500 necropsies performed on animals under 27 months of age. The remaining 16 tumors were in 34 breeders maintained after 27 months of age on a natural life-span study. Of this group, 10 (29.4%) developed neoplasms by the termination of the study, when the animals were 80 months of age. The skin tumor, trichofolliculoma, of which there were 29, comprised the largest tumor classification.
189Summary A case of opocephaly in inbred guinea-pig strain 2jN and another in strain 13jN, a conjoined twin and an opocephaly concurrent with conjoined twins in the Dunkin-HartleyjFD strain are described. The incidence of congenital malformations in the inbred strain 2jN and strain 13jN was 0,0013 and 0,0073 % respectively. The incidence in the random-bred Dunkin-HartleyjFD strain was 0'0007%.Spontaneous congenital malformation of the guineapig have rarely been reported (Hoar, 1976). This is especially remarkable in view of the enormous numbers of guinea-pigs that are constantly being raised as laboratory animals. In a recent review of Case I. A conjoined twin Dunkin-HartleyjFD strain guinea-pig was found dead shortly after birth. The female twins had a single head with a broad face and 2 eyes. The upper abdomen was shared; the lower abdomen and hind quarters were separate and normally developed (Fig. ]). The fused thoracic cavities had 2 sterna, but only] normal respiratory system of larynx, trachea and lungs. There was a
The cause of a fatal condition characterized by hemorrhagic cardiomyopathy, hemothorax, and coagulation defects in hysterectomy-derived male mice was investigated. Microscopic heart alterations included multifocal hemorrhage and necrosis with variable degrees of acute inflammation and fibroplasia that were most severe in the region of the atrioventricular junction. A spontaneous outbreak was arrested by increasing menadione Na-bisulfite (vitamin K) in the feed to 20 ppm. The complete syndrome including hemorrhagic cardiomyopathy was readily reproduced in germ-free male mice given a vitamin K-free diet, and in conventional male and female mice given Warfarin in the diet. We concluded that the cause of this condition was vitamin K deficiency.
A major cause of male reproductive failure in a C57BL/6N mouse production colony is self-inflicted mutilation of the penis. The extent of the damage ranged from loss of the distal end to loss of the entire penis. From January 1974 to August 1976, 645 adult male mice with mutilated penis were removed from this colony--where the monthly census was 9500 mice, mated 1 male to 4 females using a continuous mating system. On necropsy, it was observed that the substance blocking the urethra in the penile stump resulted in urine retention, grossly distending the urinary bladder. Proteus mirabilis and other bacteria isolated from the urethral plugs were considered secondary invaders.
16 cases of intestinal volvulus were observed in a total of 200 inbred C57BL/6N, GR/N, and DBA/2N germfree mice during the course of 2 years. The volvulus was a twisting of the caecum at the junction of the ileum, caecum and colon, resulting in occlusion and death. In each case the caecum was greatly enlarged. During the same period no intestinal volvulus was seen in 5 other germfree strains or in F1 to F4 generations of identical strains of microflora-associated and conventionalized mice.
Thirty-six hundred ninety-eight guinea pigs of the Dunkin-Hartley strain from the breeding colony at Fort Detrick were necropsied. Four females had mesenchymomas of the heart. The tumors were similar histologically and were composed of multiple benign mesenchymal tissues which were amalgamated into a single mass. One tumor was composed of fibrous, angiomatous, adipose, cartilagenous, osscous, hematopoietic, myxomatous, and possibly smooth muscle tissues. Smooth muscle and myxomatous tissues were not found in the other tumors. All were benign and probably originated from the primitive mesenchyme of the heart.
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