Granular cell tumors of the central nervous system of rats.

On the basis of our study of 12 cases of granular cell tumors in the brains of rats of different inbred strains, it seems that granular cell tumors are not rate in the central nervous system of untreated, aging BN/Bi rats. In none were metastases found. Awareness of the occurrence of these tumors in the central nervous system of these rats may stimulate further studies into the cellular origin of granular cell tumors that form in the central nervous system of the rat and might help to elucidate the origin of these tumors in general.

Argyrophilic carcinoids in two Syrian hamsters (Mesocricetus auratus).

Argyrophilic carcinoids were found in 2 Syrian hamsters (Mesocricetus auratus). A solitary neoplasm was located in the glandular stomach of a 25.5-month-old animal that had ingested for 12 months laboratory chow to which arecoline and calcium hydroxide [Ca(OH)2] had been added. In the other hamster, a primary carcinoid of the pancreas had metastasized to the mesenteric lymph nodes and liver; this was in a 22-month-old animal that had ingested for 16 months chow containing added snuff and Ca(OH)I. It is not known whether the carcinoids were spontaneous or induced by the treatment. Argyrophilic carcinoids have previously been reported in only one other rodent species.

Spontaneous diseases in a closed colony of Praomys (Mastomys) natalensis.

In comparison with other rodents, the mastomys is unique as regards the patterns of neoplastic and non-neoplastic diseases that it develops, some of which may constitute suitable animal models for corresponding diseases of man. Among the spontaneous diseases commonly encountered in necropsies of 600 mastomys maintained in a closed colony were: (1) degenerative joint disease of diarthroses and interventricular disks, which develops regularly in the second year of life; (2) renal disease, a type of immune-complex glomerulonephritis, affecting approximately 80% of mastomys in the age bracket 18-36 months; (3) thymomas and thymic hyperplasia affecting 30% of mastomys by the time they are 2 years old or older; (4) a combination of thymoma and polymyositis in a mastomys showing serum-globulin reactivity, presumably auto-antibody against striated muscle; (5) beginning before the age of 1 year, replacement of the normal cell population of the lymphoid tissues by plasma cells, and intense plasma cell infiltration at many other organ and tissue sites; (6) haematopoietic neoplasms, without leukaemic blood, in 10% of mastomys; and (7) histamine-producing argyrophilic carcinoid tumours of the glandular stomach in approximately 60% of old male and 30% of old female mastomys. Additionally, other neoplasms not infrequently encountered in mastomys rarely occur in other rodent species; conversely some neoplasms commonly found in other rodents, including especially tumours of the lung and mammary gland and leukaemia, are rare or absent in mastomys.

Histamine production by transplantable argyrophilic gastric carcinoid of Praomys (Mastomys) natalensis.

A transplantable argyrophilic gastric carcinoid of Praomys (Mastomys) natalensis contained appreciable amounts of histamine. Dialyzed, microsome-free supernatant of tumor tissue produced definite amounts of histamine in the presence of L-histidine and pyridoxal phosphate. These findings may relate to hypersecretion of gastric acid and formation of multiple ulcers in the stomach and duodenum of Mastomys bearing carcinoids.

Malignant argyrophilic gastric carcinoids of Praomys (Mastomys) natalensis.

Cells of carcinoid tumors which arise in the glandular stomach of old male and female Praomys (Mastomys) natalensis contain argyrophil granules when tissues fixed in formalin are colored with solutions of silver salts. The carcinoids metastasize in about 25 percent of cases, and are transplantable to other Mastomys. Tumor-bearing animals may show gastric and duodenal ulcers and multiple endocrine adenomas.