Donald J. Svoboda

Acute exposure to cadmium causes severe liver injury in rats

Abstract The acute cardiotoxicity of Cd was studied in rats injected iv with 3.9 mg Cd/kg (LD99). Electrocardiogram, blood pressure, and heart rate were recorded intermittently from 9 hr after Cd administration until death. No changes were observed in cardiac indices. Microscopic examination of the major tissues revealed histologically normal myocardium but severely damaged liver. To evaluate further the observed hepatotoxic effects of Cd, time course (1 to 10 hr after 3.9 mg Cd/kg, iv) and dose-response (10 hr after 0.9 to 3.9 mg Cd/kg, iv) studies were conducted. Liver was examined for histopathologic changes; plasma enzyme activities of aspartate (AST) and alanine (ALT) aminotransferases and alkaline phosphatase (AP) were determined to assess liver damage. Pronounced eosinophilia, hepatocyte swelling, and an increase of mitotic figures in hepatocytes were present within 1 hr after Cd. Increased AST and ALT activities were also observed, but AP activity and plasma glucose concentration were unchanged. At later times, severe liver injury was evidenced by necrosis of hepatocytes, striking elevation of serum enzymes (AST, ALT, and AP), and a 50% decrease in plasma glucose concentration. Doseresponse data indicated that doses greater than 1.1 mg Cd/kg produced pathologic changes similar to those observed in the time course study 1 hr after 3.9 mg Cd/kg. Doses above 3.5 mg Cd/kg caused massive hepatic necrosis and increased ALT, AST, and AP activities 60-, 100-, and 3-fold, respectively. A 50% decrease in plasma glucose concentration was also observed at doses above 2.9 mg Cd/kg. These results do not suggest that Cd is cardiotoxic after acute exposure, but rather that the liver is a major target organ for acute Cd toxicity.

Time course of cadmium-induced ultrastructural changes in rat liver.

Ultrastructural changes in rat liver were studied 1, 2, 4, 6, 8, and 10 hr after administration of a single, high dose of Cd (3.9 mg Cd/kg, iv) or after repeated administration of a lower dose (0.5 mg Cd/kg, sc, 6 days/week for 6 months). These dosing regimens have been previously shown to produce hepatotoxicity and result in large accumulations of Cd in liver. In addition to light and electron microscopy, plasma enzyme activities indicative of liver injury, namely alanine (ALT) and aspartate (AST) aminotransferase, were determined at the aforementioned times. One hour after an acute dose of Cd, electron photomicrographs of liver showed dilation of the rough endoplasmic reticulum with concomitant loss of membrane-associated ribosomes, nucleolar condensation, and an increase in the number of perichromatin granules. At later times (4 and 6 hr), ultrastructural changes included mitochondrial swelling associated with matrical inclusions, further dilation and vesiculation of rough endoplasmic reticulum, and presence of a fibrillar material within cytoplasm. In contrast to changes observed after single administration of Cd, the predominant hepatic lesions in rats injected repeatedly with the metal over 6 months were interstitial fibrosis, nuclear enlargement, and an increase in number and predominance of nucleoli. Ultrastructural evidence of nuclear alterations included condensation of nucleoli and an increase in the number of perichromatin granules. These results indicate that Cd interferes with hepatic protein synthesis early after injection of a large dose, and that further degenerative changes occur later and possibly in response to protein inhibition. Although severe degenerative changes in liver were not evident in rats chronically exposed to the metal, Cd-induced changes in nuclei and nucleoli also indicate the likelihood of altered protein synthesis.

Microbody proliferation in liver induced by nafenopin, a new hypolipidemic drug: comparison with CPIB.

Abstract Nafenopin (2-methyl-2[P-(1,2,3,4-tetrahydro-1 naphthyl) phenoxy]- propionic acid, a phenolic ether with hypolipidemic properties, when administered by gavage at 100 mg/kg b wt daily for 1 to 2 weeks, caused a significant increase in the number of microbody profiles and simultaneous increase in catalase activity in livers of male rats. The concentration of catalase protein and the rate of incorporation of H3-δ-aminolevulinic acid into catalase fraction, as determined by immunochemical methods were approximately twice that of controls. The microbody proliferation resulting from nafenopin treatment was comparable to that induced by CPIB.

Variations in ultrastructural nuclear changes in hepatocarcinogenesis

Abstract The ultrastructural changes observed in the nuclei and nucleoli of liver cells following the acute and chronic administration of several hepato-carcinogens are discussed. Three major types of nucleolar change have been observed following acute administration: 1. 1. Macrosegregation—following aflatoxin, lasiocarpine and tannic acid. 2. 2. Microsegregation—following DMN and 3′Me DAB. 3. 3. Enlargement—following thioacetamide and ethionine. In chronic toxicity nucleolar macrosegregation was not observed in precancerous liver or in tumours but some degree of microsegregation and nucleolar enlargement persisted. The significance of these changes in the light of reported biochemical data on the action of these carcinogens is discussed, with special reference to DNA binding. It is concluded that neither the nucleolar nor the nuclear changes observed in both acute and chronic intoxication can be regarded as specific manifestations related to the carcinogenic process, in view of their apparent ability to regress and lack of consistency in chronic carcinogenesis.

MICROBODIES (PEROXISOMES) IDENTIFICATION IN INTERSTITIAL CELLS OF THE TESTIS

cence. The minimal detectable amount of the histidyl-peptides was approximately 0.3 jzg/cm’. The excitation and emissiomi maxima of the OPTinduced polypeptide fluonophores were very similar. Thus, maximal excitation was at 415 (410-430) m . Excitation with the 365-mj limies gave maximal emission at 460 with a temudency to a secomud peak at 480-490 m u; excitation with the 405-m lines gave only one peak, at 480-490 m (Fig. 1). There was only a slight concentrationdependent ned shift of the emission maxima. The OPT-induced fluorescence was not affected by subsequemit formaldehyde treatment. Formaldehyde pretreatment, which did not result in detectable fluorescence with glucagon, secretin on VIP, failed to prevent the subsequent OPT-miduced fluorescence. The spectral properties were the same as after exposure to OPT alone. Comiceivably, all peptides with NH2-terminal histidine give fluonophones upon condenisatiomi with OPT. This principle is currently beimug applied in the fluorescence histochemical demonstratiomu of histidyl-peptides in general and of glucagon, secretin and VIP in particular. OPT has been foumid to induce fluorescence in pancreatic A cells (4, 11). The fluorescence characteristics are different from those of the histamine fluorophone (9). From the present results, it is suggested that the fluonogenic compound in the islet cells is glucagon and that the reactive part of the molecule is the NH,-terminal histidine.

Alterations in pancreatic and hepatic ultrastructure following acute cycloheximide intoxication.

Cycloheximide, an inhibitor of protein synthesis at the polysomal level, produces ultrastructural changes in rat liver and pancreas which closely resemble ultrastructural changes attributed solely to inhibition of DNA-dependent RNA synthesis. Nucleolus-like structures and collections of ribosomes in “hook-like” configurations of the endoplasmic reticulum are two unusual changes found in the cytoplasm following cycloheximide treatment. The ultrastructural effects of cycloheximide indicate the importance of diminished protein synthesis in drug-induced nuclear and nucleolar ultrastructural changes, regardless of the stage at which the protein synthetic process is inhibited—directly at translation or indirectly at transcription. By selective use of agents which inhibit RNA and protein synthesis, correlative biochemical and ultrastructural investigations may add further meaning to the complex nuclear changes produced by some carcinogens and antimetabolites.

Stimulation of liver catalase synthesis in rats by ethyl-α-p-chlorophenoxyisobutyrate

Abstract In male rats fed 0.25% CPIB in diet 1 to 2 weeks, the concentration of catalase protein in liver extract was 2.1 times that of controls. With immunochemical methods, it was shown that CPIB enhances the rate of synthesis of hepatic catalase by more than 80% in three days and maintains this enhanced synthesis throughout the duration of its administration.

Multiple congenital mesenchymal tumors. Multiple vascular leiomyomas in several organs of a newborn.

A case of multiple congenital mesenchymal tumors is described. The tumors involved the lungs, the small intestine, the colon, and the subcutaneous tissues. Twenty cases are reviewed, and comparisons are made. The features in the 20 cases are basically similar, and resemble one another; the tumors are multiple, congenital, and mesenchymal in origin. It is felt that the present case, perhaps as well as Bartletts 4 cases, represents a different age of the tumors from those of the other cases, and shows a greater degree of differentiation.

ULTRASTRUCTURE OF NASOPHARYNGEAL CARCINOMAS IN AMERICAN AND CHINESE PATIENTS; AN APPLICATION OF ELECTRON MICROSCOPY TO GEOGRAPHIC PATHOLOGY.

Abstract Fourteen carcinomas of the nasopharynx from Chinese and American patients were selected for electron-microscopic study in order to compare the fine structure of tumors from the two groups and to determine, if possible, the cell of origin. The undifferentiated tumors, by light microscopy, were of transitional cell, spindle cell, or lymphoepithelioma type. By electron microscopy, all three types were composed of cells forming keratin fibrils even though lacking recognizable squamous characteristics by light microscopy. It is suggested that many undifferentiated tumors of nasopharynx, especially lymphoepithelioma, are, in fact, squamous cell carcinomas.

MICROBODIES IN LEYDIG CELL TUMORS OF RAT TESTIS

Spontaneous Leydig cell tumors (interstitial cell tumors) of the testis arising in aged rats have been studied by cytochemical procedures for identification of microbodies. Large numbers of microbodies with diameters ranging from 0.1 to 0.4 µ were present in tumor cells. The size of the tumor did not appear to have any effect on the microbody number in neoplastic Leydig cells. Examination of large numbers of microbodies in tumor cells revealed continuities between adjacent microbodies. The microbodies in Leydig cell tumors lacked a typical crystalline core or nucleoid, but some of the elongated forms contained cylindrical or tubular structures with periodicity. The nature of these inclusions remains obscure because urate oxidase activity was not detected in these tumors, by either biochemical or histochemical methods. In view of the presence of numerous microbodies, it is suggested that these tumors serve as a rich source of microbodies for studying their functional significance in Leydig cells of the testis.