Sexual Abnormalities in an Inbred Strain of Mice

Abstract

An interesting sexual abnormality was observed in the Little-Murray dilute brown strain of mice. To date this abnormality has been observed in 10 animals, and is evidently hereditary. All the abnormal individuals were descendants of the same pair of mice, the ancestors of which were inbred by brother to sister matings for many generations. A pedigree chart (Table I) gives further details.

Mouse No. 6 was 23 months old when killed. Externally the animal was a normal female. Internally no female sex organs were present. A large nodule was found in the peritoneal cavity. Microscopical sections showed that the nodule was surrounded by a fibrous capsule. A few definitely recognizable but atrophic seminiferous tubules were present near the periphery. The rest of the tissue was composed of diffusely distributed large cells, of embryonal type, and was diagnosed as embryonal carcinoma of the testis (Fig. 1).

Mouse No. 323 was 20 months old when killed. At autopsy a large, yellow, necrotic nodule was found on the right side, half way between the kidney and the bladder. On the left side a small oval body was found in the same position. Inserting a probe into the vagina, a blind ending could be felt. No other sex organs could be found. Examined microscopically the yellow nodule of the right side showed almost complete necrosis. Only a very small peripheral area was still cellular, and showed faint outlines of seminiferous tubules. The small body of the left side was surrounded by a fibrous capsule and contained seminiferous tubules in which actively dividing spermatogonia and spermatocytes were present, but there were no spermatozoa.