Maneb causes pro-oxidant effects in the hippocampus of Nrf2 knockout mice

The effects of maneb were investigated in C57BL/6 Nrf2 wildtype and knockout mice. Treated KO mice showed significant weight loss as compared to WT counterparts. ICPAAS analysis demonstrated a significant increase in manganese concentration in the tissues of treated KO mice as compared to WT. Biochemical analysis revealed significant decreases of antioxidants including glutathione, glutathione reductase and heme oxygenase-1. Levels of TBARS were significantly increased in hippocampal tissue in Nrf2 KO mice at the 30 and 60mg doses. qPCR demonstrated that the only gene mediated by the Nrf2 transcription pathway that was significantly modulated by at least 1.5 fold was glutathione peroxidase 4. GPX4 was significantly upregulated in Nrf2 WT mice treated with 30mg/kg maneb and significantly downregulated in Nrf2 KO mice treated with the same dose. Microscopy revealed neuronal pyknosis and eosinophilia of the cytoplasm in the hippocampi of both WT and KO animals treated with 60mg/kg maneb.

Proliferative and nonproliferative lesions of the rat and mouse central and peripheral nervous systems

Harmonization of diagnostic nomenclature used in the pathology analysis of tissues from rodent toxicity studies will enhance the comparability and consistency of data sets from different laboratories worldwide. The INHAND Project (International Harmonization of Nomenclature and Diagnostic Criteria for Lesions in Rats and Mice) is a joint initiative of four major societies of toxicologic pathology to develop a globally recognized nomenclature for proliferative and nonproliferative lesions in rodents. This article recommends standardized terms for classifying changes observed in tissues of the mouse and rat central (CNS) and peripheral (PNS) nervous systems. Sources of material include academic, government, and industrial histopathology databases from around the world. Covered lesions include frequent, spontaneous, and aging-related changes as well as principal toxicant-induced findings. Common artifacts that might be confused with genuine lesions are also illustrated. The neural nomenclature presented in this document is also available electronically on the Internet at the goRENI website (http://www.goreni.org/).

Nonlesions, unusual cell types, and postmortem artifacts in the central nervous system of domestic animals

In the central nervous system (CNS) of domestic animals, numerous specialized normal structures, unusual cell types, findings of uncertain or no significance, artifacts, and various postmortem alterations can be observed. They may cause confusion for inexperienced pathologists and those not specialized in neuropathology, leading to misinterpretations and wrong diagnoses. Alternatively, changes may mask underlying neuropathological processes. "Specialized structures" comprising the hippocampus and the circumventricular organs, including the vascular organ of the lamina terminalis, subfornical organ, subcommissural organ, pineal gland, median eminence/neurohypophyseal complex, choroid plexus, and area postrema, are displayed. Unusual cell types, including cerebellar external germinal cells, CNS progenitor cells, and Kolmer cells, are presented. In addition, some newly recognized cell types as of yet incompletely understood significance and functionality, such as synantocytes and aldynoglia, are introduced and described. Unusual reactive astrocytes in cats, central chromatolysis, neuronal vacuolation, spheroids, spongiosis, satellitosis, melanosis, neuromelanin, lipofuscin, polyglucosan bodies, and psammoma bodies may represent incidental findings of uncertain or no significance and should not be confused with significant microscopic changes. Auto- and heterolysis as well as handling and histotechnological processing may cause postmortem morphological changes of the CNS, including vacuolization, cerebellar conglutination, dark neurons, Buscaino bodies, freezing, and shrinkage artifacts, all of which have to be differentiated from genuine lesions. Postmortem invasion of micro-organisms should not be confused with intravital infections. Awareness of these different changes and their recognition are a prerequisite for identifying genuine lesions and may help to formulate a professional morphological and etiological diagnosis.

Preparation and Analysis of the Central Nervous System

For many pathologists, neuropathology is intimidating. Practical approaches for nervous tissue histologic evaluations to meet both routine and advanced study designs can lead to rewarding neuropathology efforts. Cost-effective, high-quality histologic evaluations can occur if animals are exsanguinated quickly, brains removed carefully to maintain structural integrity and avoid dark neuron artifact, immersion-fixed quickly and thoroughly, and trimmed and processed to consistently survey multiple areas. While brightfield examination of H&E-stained sections is generally sufficient for survey evaluations, epifluorescent assessment of neuronal autofluorescence facilitates recognition of neurodegeneration in H&E-stained sections. Fluoro-Jade B or specialized immunohistochemical stains may be required to answer specific questions. Evaluations require that both technical staff and pathologists have a working knowledge of a few easily identified neuroanatomic landmarks and familiarity with use of a detailed brain atlas. At least four coronal sections should be routinely surveyed from young adult rats, with evaluation of comparable areas in other laboratory animal species. This number should be at least doubled if there is reason to suspect morphologic changes in the CNS. This article focuses on technical details of efficient specimen preparation for neuropathologic evaluations involving relatively large numbers of rodents, as well as a practical approach to basic neuroanatomic site identification.