24 research outputs found
Histopathology of Incidental Findings in Cynomolgus Monkeys (Macaca Fascicularis) Used in Toxicity Studies
The purpose of our publication is to widely communicate pictures of spontaneous findings
occurring in cynomolgus monkeys. Focal lymphoplasmacytic infiltration is commonly seen in
the general organs. The frequency and severity of these lesions may be influenced by the
administration of drugs with an effect on the immune system. Lymphoplasmacytic
infiltration in the lamina propria of the stomach is also frequently seen in cynomolgus
monkeys, and it is caused mainly by a Helicobacter pylori infection.
Various degrees of brown pigments are observed in various organs, and it is possible to
distinguish the material of the pigments by its morphological features and site. A
focal/segmental glomerular lesion is occasionally seen in a section of the kidney, and the
minimal lesion has no influence on the urinalysis. We showed the common glomerular lesions
in HE-stained sections, as well as in PAM- or PAS-stained sections, for understanding the
details. Young and pubertal monkeys are usually used in toxicity studies; therefore,
understanding various maturation stages of the genital system is important. In particular,
the female genital system needs to be understood in the morphology, because their cyclic
changes are different from other laboratory animals. Thus, we present the normal features
of the cyclic changes of the female genital organs. Furthermore, we provide more
information on spontaneous findings in cynomolgus monkeys for exact diagnoses in toxicity
studies
Malignant Lymphoma with Severe Infiltrative Growth into Skeletal Muscles in WBN/Kob Rats
Although spontaneously occurring neoplasms have been reported repeatedly in F344, SD and
Wistar rats, which are commonly used strains for routine toxicologic and carcinogenicity
studies, there are only a few reports of malignant lymphoma or lymphatic leukemia except
for large granular lymphocytic leukemia (LGL) in F344 rats. Malignant lymphoma
(lymphosarcoma) is thought to be uncommon in F344 rats. The authors encountered malignant
lymphomas of the non-LGL leukemia type with characteristic pathologic features in WBN/Kob
rats. The mean age at onset of the disease in all 13 affected rats (8 males and 5 females)
was about 60 weeks. Common and characteristic clinical signs were abnormal gait with hind
limb paralysis. Macroscopically, the enlargement of the lymph nodes, spleen and liver was
slight to moderate. Scattered multiple white-to-gray nodules encompassed the aorta and
assumed a bead-like appearance near the thoracic and lumbar vertebrae.
Histopathologically, neoplastic proliferative changes were predominant in the bone marrow
tissue of the entire body, and many tumor cells infiltrated the spleen and several lymph
nodes. The most striking histological features were constant and severe infiltration of
tumor cells in the adipose tissue and skeletal muscle adjacent the thoracic and lumber
vertebrae. Immunohistochemically, all tumor cells were positive for B-cell markers (PAX-5,
CD79a and CD45) and negative for CD3. From the results of immunohistochemistry and
morphological examination, these tumors were diagnosed as malignant B-cell lymphomas