Hepatic jaundice in a colony of nude mice.

A colony of nude mice was maintained under controlled standards of care for 12 months, at which time a rapidly escalating liver disease developed in the animals, characterized by jaundice, emaciation, and rapid death. Histologically, the livers had swollen, vacuolated hepatic cells and increased numbers of enlarged Kupffer cells. Mouse hepatitis virus was not isolated from the livers of sick mice. Although the nature of the lesions suggested toxicity, efforts to reproduce the lesions by increased exposure to chemical compounds used for colony husbandry were unsuccessful. A definitive determination of the causative agent was not made.

Clinical and pathologic conditions of female nude (athymic) mice in two conventional maintained colonies.

Two colonies of female outbred nude (athymic) mice were maintained by conventional standards of husbandry, but with special sanitary methods and segregation from other rodents. A total of 1,526 mice entered the colonies. Of these, 802 were untreated and most remained healthy. Necropsies were performed on 312 untreated mice that were sick and were killed or died naturally, and the tissues were examined microscopically. Clinical and pathologic conditions in the untreated mice included subcutaneous abscessation, dermatitis, subcutaneous edema due to glomerulonephritis (nephrotic syndrome), rectal prolapse, and lymphomas and other neoplasms.

An approach to C-type virus immunoprevention of spontaneously occurring tumors in laboratory mice.

A review of our current progress in C-type virus vaccine research is presented. This includes the findings of C-type virus or its antigen expressions in every naturally occurring tumor of two strains of "low-incidence" laboratory mice, the BALB/cCr mouse and the NIH Swiss mouse. Vaccine preparation methods are described including the inactivation of C-type virus infectivity with optimal maintenance of the antigen titers of at least two of the polypeptides of the C-type virus, gp69/71 and p30. The cell-mediated immune response of the mouse to C-type virus vaccines, as measured by a footpad assay for delayed-type hypersensitivity and an in vitro lymphocyte transformation assay, is described. Studies with two murine C-type viruses (Rauscher leukemia and Gross leukemia) a simian C-type virus, and an avian C-type virus (avian myeloblastosis virus) showed that the cell-mediated immune response of the animal includes type-specific, group-specific, and interspecies-specific reactivity. The mouse gave a cell-mediated immune response to at least one of the polypeptides of the C-type virus, the gp69/71, whether this polypeptide was presented to the immune system of the mouse as whole virus, Tween-ether-treated virus, or a purified polypeptide. One measure of the effectiveness of the C-type virus vaccines was provided by immunization of the mouse with Rauscher leukemia virus preparation that induced resistance to challenge with both live Rauscher leukemia virus and a naturally occurring BALB/c leukemia virus. Evidence is presented that the C-type virus can act as an effective transplantation antigen in syngeneic tumor cell lines resulting in the immunogenicity and loss of tumorigenicity of these cell lines. An approach to the viral immunoprevention of spontaneously occurring tumors is discussed.

Incidence of spontaneous neoplasms in F344 rats throughout the natural life-span.

The age-related incidence of spontaneously occurring neoplasms and degenerative diseases in the F344 inbred rat strain was established from the histologic examination of tissues from 160 male and 192 female rats kept throughout their natural life-span. The most common neoplasms were leukemias (25%), mammary tumors (females, 40.6%; males, 23.1%), pituitary adenomas (females, 35.9%; males, 23.8%), and testicular interstitial cell tumors (males, 85%). Various less common neoplasms were observed: thyroid interstitial cell tumors, adrenocortical adenomas, carcinomas of the genitourinary tract, representative central nervous system tumors, pheochromocytomas, and tumors of mesodermal origin including mesotheliomas, myoblastomas, fibromas, and fibrosarcomas. Multiple tumor types were found in 176 of the rats; metastatic tumors were uncommon. Degenerative diseases including myocardial degeneration and nephrosis were often observed. The incidence rate of these neoplasms and degenerative diseases generally increased with advancing age of the animals.

An improved method for enumeration of X-C cell assay for murine leukemia virus.

A modification for the enumeration of X-C syncytia is described wherein the projected image of the entire infected culture is observed. This method is rapid, reliable, and reproducible.

Epizootiology of tropical canine pancytopenia.

Tropical canine pancytopenia (TCP) is a newly recognized infectious disease of dogs in diverse tropical and subtropical areas. The disease is characterized by hemorrhage, pancytopenia, severe emaciation and persistent infection. Dogs with TCP are often presented with epistaxis, which is the most dramatic sign of the disease; however, a large number of affected dogs develop severe pancytopenia and die without manifesting clinical signs of hemorrhage. The disease has been reported most frequently in the German Shepherd. Pathological findings consist of petechial and ecchymotic hemorrhages on serosal and mucosal surfaces of numerous organs. The most prominent histological finding is a perivascular plasma cell infiltrate in most organs. Disease, indistinguishable from the natural disease, has been produced in laboratory dogs inoculated with whole blood from affected dogs. Ehrlichia canis has been consistently recovered from all experimentally infected dogs. Attempts to transmit the disease to other laboratory animals and to propagate the agent in cell cultures and embryonating eggs have been unsuccessful. The tick is the probable vector of the disease.