Pathological analysis of lesions in the exocrine pancreas of rats induced by Zinc Maltol.

The pancreas plays an important role in the homeostasis of zinc (Zn), a nutritionally essential metal. In several previous studies, Zn ions induced inflammatory changes in the exocrine pancreas; however, little is known about Zn complexes. In this study, we microscopically, immunohistochemically, and ultrastructurally examined pancreatic lesions in Sprague-Dawley (SD) rats induced by a 4-week repeated oral dose toxicity study of Zinc Maltol (ZM), a zinc (II) complex. ZM induces acinar atrophy and increases the number of duct-like structures. Immunohistochemistry revealed a decrease in the number of trypsin-positive cells, and an increase in the number of SOX9-positive cells. Interstitial fibrosis and macrophage infiltration also correlated with the degree of acinar atrophy. Electron microscopic evaluation revealed that the acinar cells that lost granules were surrounded by fibroblasts and collagen fibers. In conclusion, we provided a detailed description of ZM-induced pancreatic lesions in SD rats.

Morphological characteristics and notes of the skin in preclinical toxicity assessment.

In this review, the histological structures of the skin are summarized for fundamental knowledge for toxicological assessment. The skin is composed of epidermis, dermis, subcutaneous tissue, and associated adnexa. In the epidermis, keratinocytes comprise four layers, and three other cell types, besides keratinocytes, play various roles. Epidermal thickness varies with species and body site. In addition, it can be affected by tissue preparation procedures, which can render toxicity assessments difficult. Bulge stem cells are the origin of sebaceous glands, epidermal basal layer, and hair follicle formation, and they play an important role in the maintenance of the basic structure of the skin. Stem cells and appendages formed from stem cells sometimes become toxic targets, and it is useful to study the origins of the hair follicle/hair cycle to interpret their toxicity. Irritant contact dermatitis and allergic contact dermatitis are the main adverse reactions in topical application studies. The mechanism involves direct chemical irritation of the skin, and histologically, epidermal necrosis and accompanying inflammatory cell infiltration. In allergic contact dermatitis, an inflammatory reaction and intercellular or intracellular edema, histologically represented by lymphocytic infiltration of the epidermis and dermis, are observed. Regional and species differences exist in the dermal absorption of compounds, and differences in the thickness of the stratum corneum substantially contribute to these differences. Learning the basic structures, functions, and possible artifacts will contribute to the evaluation of skin toxicity by topical and systemic applications.

Four-week repeated oral dose toxicity study of zinc maltol in rats.

Zinc (Zn) is one of the trace elements, and Zn deficiency causes many adverse effects. Zn complexes are used for Zn supplementation, but there are few toxicity reports. Zn maltol (ZM) was orally administered for 4 weeks to male rats at a dose of 0, 200, 600, or 1000 mg/kg to assess its toxicity. As a ligand group, maltol was administered at a dose of 800 mg/kg/day. General conditions, ophthalmology, hematology, blood biochemistry, urinalysis, organ weights, necropsy, histopathology, and plasma Zn concentration were investigated. Plasma Zn concentration increased with dose levels of ZM. The following toxicities were observed at 1000 mg/kg. Pancreatitis was observed with histopathological lesions and increases in white blood cell parameters and creatine kinase. Anemia was observed with changes in red blood cell parameters and extramedullary hematopoiesis in the spleen. Decreases in the trabecula and growth plate in the femur were observed. On the other hand, no toxicities were observed in the ligand group. In conclusion, these toxicities induced by ZM have been reported as Zn-related toxicities. It was considered that these results will be helpful for a creation and development of new Zn complexes as well as supplements.

Databases for technical aspects of immunohistochemistry: 2021 update.

With the aim of sharing information about the technical aspects of immunohistochemistry (IHC) and facilitating the selection of suitable antibodies for histopathological examination, this technical report describes the results of a questionnaire distributed during the period of 2018 to 2019 among members of the Conference on Experimental Animal Histopathology. Additionally, it describes the immunological properties and supplier details (clone, supplier, catalog number, species reactivity, etc.) as well as the IHC staining conditions (fixing solution, fixing time, embedding, antigen retrieval method, antibody dilution, incubation time, incubation temperature, positive control tissue, blocking condition, secondary antibody information, etc.) for a total of 509 primary antibodies (comprising 220 different types). These survey results were an update on the contents reported by CEAH in 2017.

A spontaneously occurring malignant pituicytoma in a male sprague dawley rat.

Pituicytoma is an extremely rare neoplasm derived from pituicytes, which are glial cells in the posterior lobe of the pituitary gland. A malignant pituicytoma was found in the intracranial cavity of a 55-week-old male Sprague-Dawley rat. Macroscopically, the tumor was located on the sphenoid bone and involved the pituitary gland. The tumor was composed of sheets of fusiform cells with spindle- or pleomorphic-shaped nuclei and abundant eosinophilic cytoplasms. The cells were arranged in a whirling or irregular growth pattern. Some tumor cells were bizarre multinucleated giant cells with cytoplasmic eosinophilic hyaline droplets. Many tumor cells were strongly positive for vimentin and glial fibrillary acidic protein, and some cells were positive for ED-1 and S-100. These findings closely resembled those of a giant cell glioblastoma derived from the pituitary gland, suggesting anaplastic pituicytoma. From our review of the literature, we believe this is the first report of a spontaneous malignant pituicytoma in a rodent.

Morphological analysis of the pancreas and liver in diabetic KK-A(y) mice treated with zinc and oxovanadium complexes.

The relationship between biometals, such as zinc (Zn(2+)), vanadium, copper, cobalt, and magnesium ions, and diabetes therapy has been recognized for several years. In particular, the antidiabetic activities of Zn(2+) and oxovanadium (VO(2+)) complexes have been measured using biochemical approaches. In the present study, diabetic KK-A(y) mice were treated with bis(1-oxy-2-pyridine-thiolato)Zn(2+) (Zn(opt)2) and bis(1-oxy-2-pyridine-thiolato)VO(2+) (VO(opt)2) for 4 weeks, and the antidiabetic activities of these metal complexes were evaluated using biochemical and morphological methods. Additionally, zinc gluconate (Zn(glc)2) and bis(ethylmaltolato)VO(2+) (VO(emal)2) were used as reference compounds. Pancreatic islet cells were smaller, and there was a tendency towards a lower islet cell area ratio in Zn(opt)2-treated mice compared with nontreated KK-A(y) mice. Furthermore, plasma insulin concentrations were significantly reduced to 27.2% of insulin concentrations in nontreated KK-A(y) mice. These results suggest that Zn(opt)2 administration provides morphological and biochemical improvements in hyperinsulinaemia. In contrast, in mice that received Zn(glc)2 and VO(2+) complexes, the islet cell size and islet cell area ratio did not differ from those in nontreated controls. Zn(opt)2- and VO(opt)2-treated mice exhibited significantly lower fat deposition and fat deposition area ratio in the liver (63.6% and 65.8% of nontreated KK-A(y) mice, respectively) compared to those observed in nontreated KK-A(y) mice. The differences in morphological improvements of the pancreas and liver owing to Zn(opt)2 or VO(opt)2 treatment may be explained by differences in the sites of actions of Zn(2+) and VO(2+) complexes in different organs in KK-A(y) mice. In conclusion, Zn(opt)2 exhibited superior antidiabetic effects over those of VO(opt)2, and this was owing to greater amelioration of the morphological parameters of the liver and pancreas.

Testicular Mineralization in KK-A(y) Mice Treated with an Oxovanadium Complex.

Vanadium has potential for use in diabetes therapy. Many investigators have reported toxic effects of inorganic vanadium salts; however, there are few reports on toxic effects of oxovanadium(VO(2+)) complexes. Therefore, we studied VO(2+) toxicity by examining histological changes and measuring the vanadium concentration in the testis after repeated oral administration of bis(1-oxy-2-pyridine-thiolato)oxovanadium(VO(2+)) (VO(opt)2) for 2 or 4 weeks in KK-A(y) mice. Severe mineralization and degeneration/necrosis of the seminiferous tubules were detected after either 2 or 4 weeks of administration. Vacuolar changes in Sertoli cells and the seminiferous epithelia, and hyperplasia of Leydig cells were observed in the testes of some animals. Vanadium concentrations in the mineralized testis were much higher than those in the testis of untreated KK-A(y) mice. These results represent the first report of the possibility for seminiferous tubules mineralization induced by VO(opt)2 administration. Therefore, our research provides important information about the potentially toxic effects of VO(2+) complexes.

Morphological characterization of systemic changes in KK-Ay mice as an animal model of type 2 diabetes.

BACKGROUND: KK-Ay mice, a relevant model of human type 2 diabetes mellitus, are used worldwide for the assessment of pharmacological effects of new anti-diabetes drugs. MATERIALS AND METHODS: KK-Ay mice were examined at five weeks of age (non-hyperglycemic condition) and at 10 and 14 weeks of age (hyperglycemic condition). RESULTS: Islet cell hypertrophy was observed in 10- and 14-week-old mice. The area ratio of islet cells to total pancreas significantly increased compared to that of age-matched C57BL/6J mice. Plasma insulin concentration increased in 14-week-old KK-Ay mice. Enlargement of mesangial matrix and increased glomerular area were seen in kidneys of KK-Ay mice. Fatty changes were observed in the liver. Total plasma cholesterol and triglyceride levels increased compared to that of five-week-old KK-Ay mice. CONCLUSION: The present results on young/adult KK-Ay mice indicate that the hyperglycemic state developing at the early stage of diabetes mellitus is due to related changes in systemic organs.