Toxicity of adriamycin-oxidized dextran (ADM-OXD), a newly developed antineoplastic macromolecule, was compared with that of adriamycin (ADM). ADM-OXD (0.7, 2.0mgADM/kg) and ADM (0.7mg/kg) were administered intravenously to male and female Wistar rats daily for 28 days. Upon observation of morphological changes at the same dose level (0.7mg/kg), toxic effects on the heart, kidney, hematopoietic-lymphatic system (lymph nodes, thymus, bone marrow, spleen), digestive tract (stomach) were found to be more pronounced in the ADM groups. Furthermore, hematological changes such as decrease in erythrocyte count and leucocyte count, were more significant in the ADM groups than in the ADM-OXD groups. On the other hand, the effect on the liver was specific to ADM-OXD, especially in the high dose groups. Not only hepatic dysfunction such as elevation of transaminase activities, but also morphological changes such as single cell necrosis, hyaline degeneration, and congestion, were found in these groups. To confirm these hepatotoxicities of ADM-OXD, ADM was monitored daily up to day 4. Here too, hepatotoxicity was specific to ADM-OXD. Since increase in TBA-reactive substances in the liver homogenate was found in close proportion to the induction of hepatic dysfunction, it was suggested that lipid peroxidation was one of the factors which caused hepatotoxicity.

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Clofibric acid, a peroxisome proliferator and non-genotoxic hepatocarcinogen in rodents, was administered to old rats at 9, 000, 4, 500, and 1, 500 ppm in diet for 1 or 13 weeks to investigate hepatocyte proliferation and its relationship to hepatocarcinogenesis. The cumulative number of Sphase hepatocytes over 1 week was scored prior to necropsy at both weeks 1 and 13 by BrdU immunohistochemistry. At week 13, the total number of hepatocytes per liver was determined by stereological procedures and used to calculate the total number of S-phase hepatocytes per liver. Hepatomegaly was evident in the 4, 500 and 9, 000ppm groups at week 1 and in all doses at week 13. During the first week of treatment, a significant burst of hepatocyte proliferation was induced in a dose-dependent manner. However, there was no increase in the number of hepatocytes per liver in any dose groups at week 13, and the hepatomegaly at week 13 was the result of hepatocyte hypertrophy and not hyperplasia. On the contrary, an opposite effect was observed with the hepatocyte labeling index as well as total number of labeled hepatocytes per liver being decreased below the control levels in a dose-related fashion. These data indicate that clofibric acid appears to inhibit DNA synthesis of rat hepatocytes when administered over an extended period of time, and suggest the possible effect as a promoter on rat hepatocarcinogenesis through the mechanism of differential mitoinhibition.

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Feeding rats orotic acid as l o of a semisynthetic high sucrose diet induced a specific defect in hepatic lipid secretion and resulted in hepatic fatty degeneration. This inhibition of hepatic lipid secretion by ortic acid was investigated in rat primary cultured hepatocytes. The addition of 6.4 mM orotic acid to culture system within 20 hours decreased lipid secretion, triglyceride by 49%, phospholipid by 71%, and cholesterol by 81%. In the same experiment, cellular triglyceride decreased by 81%. Microscopic studies show the addition of orotic acid to increase extraordinary hepatocytes including Sudan III positive small lipid droplets. In orotic acid-treated groups, hepatocytes including Sudan III positive small lipid droplets increased in number. Ultrastructural studies demonstrated marked dilatation of Golgi apparatus during 20 hours incubation with orotic acid. This ultrastructual change means inhibition of lipid secretion by orotic acid. These observations indicate that in rat primary cultured hepatocytes, orotic acid induces lipid secretion as in animal experiments, both biochemically and pathologically.

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In order to demonstrate the species differences in the effects of a hypolipidemic agent, bezafibrate, on hepatic peroxisomes and mitochondria, bezafibrate a hypolipidemic agent was administered orally to rats, mice, guinea pigs, rabbits, and dogs for two weeks, and to monkeys for 13 weeks. Peroxisomes in the livers were visualized using a cytochemical staining method for catalase with diaminobenzidine. Morphometric comparison of the hepatic peroxisomes and mitochondria was made to examine by point counting method. Peroxisome proliferation was the highest among male rats (4.15 fold) and then male and female mice (3.68 fold and 4.47 fold respectively), with a more moderate increase of this organelle in guinea pigs and monkeys, whereas no change was seen in rabbits and dogs. A slight increase in the volume density of mitochondria was observed for female rats, guinea pigs, and male and female monkeys. These results show that there are marked species differences in the effects of bezafibrate on hepatic peroxisomes and mitochondria. We considered that the species differences are very important to elucidate the mechanism of peroxisomal proliferation, hypolipidemic action, carcinogenicity, and their relationship.

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Two new chemical compounds (MY-7816 and MY-7674) induced a lipometabolic disorder in rats and dogs. The characteristic histological lesions in rats administered orally with MY-7876 or MY-7674 were cytoplasmic vacuolation in hepatic cells, Kupffer cells, convoluted tubular epithelial cells, adrenal cortical cells, and other parenchymal cells. Similar cytoplasmic vacuolation and eosinophilic cytoplasmic inclusions were observed in the hepatic cells of dogs treated with MY-7674. The cytoplasmic vacuoles in the hepatic cells of both rats and dogs examined were stained bluish black with Baker stain and consisted of myelinosomes by electron microscope. These changes were similar to those in the drug-induced lipidosis.
However, no vacuolated cells were found in the lymphoid organs, hematopoietic system, and nervous system. In general, such organs and systems were involved in the drug-induced lipidosis. These different findings caused by the present chemicals might result from a variability in the drug-distribution or concentration in the metabolizing process.

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Five-week-old JCR: CD rats were administered either with 10% sodium chloride (NaCI) or with 10% ethanol in drinking water after a single dose of 20 Gy of X-irradiation exposed to the gastric region. One year after X-irradiation, the animals were sacrificed. The incidence of gastric tumors was 19% in the X-ray group, 37% in the X-ray plus NaCI, and 10% in the X-ray plus ethanol (X-ray+NaCl vs. X-ray+ethanol p<0.05). The frequency of intestinal metaplasia with alkaline phosphatase (ALP) positive foci in X-ray+NaCl was significantly decreased compared to those of the X-ray or X-ray+ethanol group. The heights of pyloric and fundic mucosa were increased in NaCI groups. It was concluded that 10% NaCI worked as a promotive for the gastric tumorigeneis induced by X-ray but was inhibitory for the appearance of intestinal metaplasia.

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Lectin histochemical characteristics of the kidney of experimentally induced diabetic mice were investigated. Mice were divided into the following 4 groups: control (C), streptozotocin (SZ)induced diabetes (D), unilateral nephrectomy (UN), and unilateral nephrectomy-SZ-induced diabetes (UN-D) groups, and killed at 12 weeks after completion of the SZ-injection. No lectin histochemical differences were observed in the glomeruli of all groups. Stainabilities of Bowman's capsules lined with cuboidal to columnar epithelia seen in C and UN groups were the same as those of proximal tubules, and they were different from those of Bowman's capsules lined with flattened epithelia generally seen in D and UN-D groups. In D and UN-D groups, distal tubules and collecting ducts increased their affinities to Canavalia ensiformis A, Dolichos bifiorus agglutinin, Griffonia simplicifolia agglutinin-I, Glycine max agglutinin, and Triticum vulgaris agglutinin, compared with C and UN groups. Conclusively, this study showed that unilateral nephrectomy enhanced SZ-induced kidney lesions without a prominent histochemical modification.

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Sex-dependent protein reabsorption droplets (PRD) were observed in the kidneys of beagle dogs. Seventy-six untreated males and seventy-eight untreated females were examined histologically. Microscopically, two types of PRD were detected in the proximal tubules (P3 segment). One was large and palely eosinophilic, and the other was small and deeply eosinophilic. Ultrastructural features of the large droplets were cytoplasmic vacuoles filled with electron lucent, proteinaceous, fine granular material. The small droplets were irregular clumps of electron lucent material without a boundary membrane. These PRD are likely to arise from intense reabsorption of protein from the urine by tubular cells as evident by histological or ultrastructural forms and response to various staining methods. The incidence of PRD in male beagle dogs was 36.8% (28/76), but there was no PRD in females. The highest incidence of PRD occurred in males 9-11 months of age. Since this finding was seen only in males and since no glomerular changes were evident, it was suggested that male beagle dogs have a low-molecular-weight, sex-dependent urinary protein like α 2μ-globulin in adult male rats.

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It is well known that an acute or subacute exposure to p-dichlorobenzene (p-DCB) is capable of inducing α_2u-globulin-mediated nephropathy and that its continuous administration accelerates the development of age-associated chronic progressive nephrosis (CPN). In the present study, in order to investigate the necessity of continued p-DCB exposure for CPN induction, kidneys of male F344 rats maintained for a 6 month-recovery period after cessation of 9 months exposure at concentrations of 600, 300 or 75 ppm by inhalation were histologically examined. Development of CPN lesions was accelerated as compared to the control in spite of the lack of any persisting α_2u-globulin-mediated nephropathy. Therefore, the present results support the hypothesis that the induced CPN is a secondary effect of kidney tubule damage.

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In order to clarify the characteristics of the toxic effects of endotoxins on various organs and tissues, single and multiple doses studies of commercial endotoxins were carried out using Fischer and SD rats for the purpose of microscopic examination. In the single dose study using a dose of 10 mg/kg of endotoxin Salmonella typhimurium, changes of the lungs, liver, gastrointestinal tract, and thymus were observed primarily in a tme-dependent manner. After onset of hemorrhagic changes of some organs and tissues at the early stage after dosing, hepatic changes such as activation of Kupffer cells, formation of thrombi and necrosis of hepatocytes, activation of alveolar macrophages and polymorphonuclear cell infiltration in the lungs, and lymphoid depletion of the thymus were observed from 2 or 4 hours after dosing. On the other hand, in the multiple doses study using doses from 0.1 to 1.0mg/kg/day of the same endotoxin, activation of Kupffer cells in the liver and activation of alveolar macrophages in the lungs, and lymphoid depletion of the thymus were observed primarily. We concluded that the endotoxin-modified changes should be taken into consideration when we interprete and judge the results of a general toxicity study of an agent, which has effects related to generation of endotoxins from intestinal flora. Moreover, it is also necessary to understand the different sensitivity to endotoxin among the animal strain for this situation, because the microscopic changes in SD rats due to endotoxin were more prominent to be compared with those in Fischer rats in a single dose study.

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Subcellular changes of mouse thymocytes after T-2 intoxication were observed for up to 48 hours after injection (HAI). The following changes were observed mainly in cortical lymphocytes at 8 and 16HAI: (1) nuclear projections, (2) nuclear macrocleft, and (3) characteristic features of apoptosis. Conclusively, it is suggested that apoptosis is partially involved in the early development of thymic lesions by T-2 toxin.

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