Comparative histomorphological review of rat and human hepatocellular proliferative lesions

In this comparative review, histomorphological features of common nonneoplastic and neoplastic hepatocyte lesions of rats and humans are examined using H&E-stained slides. The morphological similarities and differences of both neoplastic (hepatocellular carcinoma and hepatocellular adenoma) and presumptive preneoplastic lesions (large and small cell change in humans and foci of cellular alteration in rats) are presented and discussed. There are major similarities in the diagnostic features, growth patterns and behavior of both rat and human hepatocellular proliferative lesions and in the process of hepatocarcinogenesis. Further study of presumptive preneoplastic lesions in humans and rats should help to further define their role in progression to hepatocellular neoplasia in both species.

Proliferative and nonproliferative lesions of the rat and mouse hepatobiliary system

The INHAND Project (International Harmonization of Nomenclature and Diagnostic Criteria for Lesions in Rats and Mice) is a joint initiative of the Societies of Toxicologic Pathology from Europe (ESTP), Great Britain (BSTP), Japan (JSTP) and North America (STP) to develop an internationally-accepted nomenclature for proliferative and non-proliferative lesions in laboratory animals. The purpose of this publication is to provide a standardized nomenclature and differential diagnosis for classifying microscopic lesions observed in the hepatobiliary system of laboratory rats and mice, with color microphotographs illustrating examples of some lesions. The standardized nomenclature presented in this document is also available for society members electronically on the internet (http://goreni.org). Sources of material included histopathology databases from government, academia, and industrial laboratories throughout the world. Content includes spontaneous and aging lesions as well as lesions induced by exposure to test materials. A widely accepted and utilized international harmonization of nomenclature for lesions of the hepatobiliary system in laboratory animals will decrease confusion among regulatory and scientific research organizations in different countries and provide a common language to increase and enrich international exchanges of information among toxicologists and pathologists.

Gastric neuroendocrine tumors in a 2-year oncogenicity study with CD-1 mice

Descriptions of two rare gastric neuroendocrine tumors (carcinoids) of enterochromaffin (ECL) cells in CD-1 mice (2/50) from a 104-week oncogenicity study of a serotonergic/dopaminergic compound are presented. These tumors were detected at necropsy and confirmed by histopathology in hematoxylin and eosin- and Chromogranin A-stained slides. ECL cell counts of the glandular stomachs were determined by quantitative image analysis and did not reveal any hyperplastic changes as possible predisposing lesions for carcinoid formation. To investigate the possibility of drug-induced hypergastrinemia as the cause of tumor formation of ECL cells, gastrin blood levels were measured after treating mice for 7 days with the test substance. In this study, Omeprazole, the positive control, raised gastrin levels, while the test material did not. It was concluded that these two tumors were an example of "late-life"-occurring, spontaneous neuroendocrine tumors in the stomachs of aged CD-1 mice.

BrdUrd labeling of S-phase cells in testes and small intestine of mice, using microwave irradiation for immunogold-silver staining: an immunocytochemical study

In this study, BrdUrd labeling of S-phase cells in the small intestine and testes was accomplished using microwave irradiation. In this way crypt cells, spermatogonia, and Leydig cells could be labeled using removable plastic-embedded sections and immunogold-silver staining (IGSS). By using short periods of microwave irradiation for incubation of the monoclonal antibodies and the protein A-colloidal gold solution, the detection of BrdUrd-labeled cells could be remarkably enhanced. A comparative study of BrdUrd labeled spermatogonia in the testis of a Cpb-N mouse that received both [3H]-thymidine and BrdUrd proved that 90% of the BrdUrd-labeled cells also showed [3H]-thymidine labeling. The radioactive [3H]-thymidine labeling was a time-consuming method of 4 weeks' duration, whereas the BrdUrd-labeled cells could be labeled, fixed, enhanced, and counterstained in less than 3 hr. This investigation proves that BrdUrd labeling of S-phase cells can be a reliable, reproductive, rapid, and non-radioactive alternative method for [3H]-thymidine labeling of proliferating cells.