bluuebunny/crossref_metadata_2025 huggingface dataset:
Glutathione Depletion, Lipid Peroxidation, and Liver Necrosis following Bromobenzene and lodobenzene Intoxication
Authors: Casini Alessandro F. , Pompella Alfonso , Comporti Mario
Published: September 2009

NMRI Albino mice, in which the hepatic glutathione (GSH) content was decreased by nearly 50% by either the administration of a pure glucose diet or by starvation, were intoxicated with aryl halides, bromobenzene, and iodobenzene (13 and 9 mmol/kg body weight, respectively, p.o.). After both intoxications, the hepatic glutathione content decreased rapidly to very low values, and liver necrosis, as assessed by serum transaminase levels, occurred in about 45 or 60% of the animals (in the case of bromobenzene or iodobenzene, respectively) after a lag phase of 9 or 6 hr. In both instances liver necrosis was evident only when the hepatic GSH depletion reached a threshold value (3.5-2.5 nmols/mg protein). The same threshold value was evident for the occurrence of lipid peroxidation (measured as both carbonyl functions and conjugated dienes in liver phospholipids). The possibility that the depletion in hepatic GSH level is capable of inducing lipid peroxidation and necrosis could be supported by the fact that similar results were obtained after the administration of diethylmaleate (12 mmol/kg, p.o.), a drug which is expected to conjugate directly with GSH without previous metabolism. The covalent binding of reactive metabolites to cellular macromolecules was determined in the case of bromobenzene poisoning. A dissociation between liver necrosis and covalent binding was observed in experiments in which Trolox C, a lower homolog of vitamin E, was administered (270 μmol/kg) 9 and 13 hr after bromobenzene poisoning. The treatment with Trolox C, in fact, almost completely prevented both liver necrosis and lipid peroxidation, while the extent of the covalent binding of bromobenzene metabolites to liver proteins was not altered.
Protection of Hepatocytes with Hyperoxia against Carbon Tetrachloride-induced Injury
Authors: Bernacchi Adriana , Myers Roy , Trump Benjamin F. , Marzella Louis
Published: September 2009

Hyperbaric oxygen (HPO) was administered to rats (100% O2at 2.8 atm for 90 min) immediately or 1 hr after severe carbon tetrachloride (CCl4) intoxication in order to study the mechanisms of protection against hepatocellular injury by hyperoxia. Slight to moderate hepatocellular injury was observed, particularly by morphologic criteria, 4 hr after CCl4intoxication. Little cell death was observed; 24 hr after CCl4, 20% of the untreated animals died. In the survivors, the following typical changes occurred in the liver: extensive hepatocellular swelling, vacuolization and necrosis; severe ultrastructural alterations; binding of CCl4to microsomal lipids; elevation of lipid peroxidation products (conjugated dienes); little decrease in cytochrome b5 and severe decrease in cytochrome P-450 levels. Serum (ransaminase (alanine aminotransferase and aspar-tate aminotransferase) levels were elevated. Immediate treatment with HPO prevented the mortality and markedly decreased the hepatocellular necrosis 24 hr after intoxication. Immediate HPO treatment did not lower the levels of free CCl4in the liver. However, the rise in lipid peroxidation products caused by CCl4intoxication at 4 hr was reduced. Delayed treatment with HPO (1 hr after CCl4) prevented the mortality but was less effective in preventing necrosis. Some hepatocellular protection was still demonstrable. In particular, the rise in lipid peroxidation products was reduced.

Hyperoxia protects hepatocytes against CCl4toxicity. The rapid decline in protective effect within 60 min of intoxication suggests that hyperoxia inhibits CCl4activation and/or damage from molecular intermediates. Hyperoxia has little effect on the progression of sublethal injury to cell death in the livers of CCl4-intoxicated rats.
Lipid Composition, Physical State, and Lipid Peroxidation of Tumor Membranes
Authors: Galeotti Tommaso , Borrello Silvia , Minotti Giorgio , Palombini Guglielmo , Masotti Lanfranco , Sartor Giorgio , Cavatorta Paolo , Arcioni Alberto , Zannoni Claudio
Published: September 2009

Studies were carried out on microsomes isolated from the highly differentiated (slow-growing) Morris hepatoma 9618A, on microsomes and plasma membranes from the poorly differentiated (fast-growing) Morris hepatoma 3924A, and rat liver used as control. The lipid composition (phospho-lipid and cholesterol content, degree of fatty acid unsaturation) and peroxidation of such membranes has been correlated with the order and fluidity of the membrane bilayer. The results indicate that substrate availability is the rate-limiting step in microsomal and plasma membrane lipid peroxidation of hepatoma 3924A. From diphenylhexatriene fluorescence depolarization measurements it appears that the changes in lipid composition cause an increase in the order of the lipid bilayer on going from the control to hepatoma 9618A and 3924A microsomes, while fluidity is virtually unchanged. Conversely, for similar chemical changes, in plasma membranes from hepatoma 3924A the order is nearly the same and there is a decrease in fluidity. The changes in the above parameters of tumor membranes might be partly related to the loss of protective enzymes against oxygen radicals. This is supported by the observation that inhibition of liver superoxide dismutase and glutathione reductase, by treatment of rats with diethyldithiocarbamate and chloroethyl nitrosourea, respectively, renders the microsomal membranes more resistant to lipid peroxidation in vitro.
Mechanism of Action of Divicine in a Cell-free System and in Glucose-6-phosphate Dehydrogenase-deficient Red Cells
Authors: Baker Margaret A. , Bosia Amalia , Pescarmona Gianpiero , Turrini Franco , Arese Paolo
Published: September 2009

Favism is an acute hemolysis occurring in glucose-6-phosphate dehydrogenase (G6PD)-deficient (Mediterranean variant) individuals after intake of fava beans. Divicine (D), 2,6-diamino-4,5-dihydroxypyrimidine, is present in high amounts in the beans, and is suspected to play a role in hemolysis. Its mechanism of action was studied in a cell-free system and in G6PD (Mediterranean variant)-deficient red cells (RBC). Upon hydrolysis of the inactive β-glucoside vicine, reduced divicine is formed. Oxygen acts as a one- or two-electron acceptor; superoxide anion and hydrogen peroxide are formed, respectivley, together with the semiquinoid free-radical form of D. This free radical gives an electron spin resonance (ESR) signal, which is similar to that of the alloxan free radical. Added reduced glutathione (GSH) is rapidly oxidized with a stoichiometry of one to one, and the ESR signal is abolished. Additional GSH is oxidized by hydrogen peroxide and by a slow redox cycle which continuously regenerates oxidized D. The fast-direct and the slow-indirect oxidation result in nonstoichiometric oxidation of GSH.

D added to G6PD-deficient RBC rapidly oxidizes GSH with an end point kinetics and a stoichiometry of one to one. Hydrogen peroxide and superoxide anion are scavenged in the RBC and no redox cycling is taking place. No GSH is regenerated even after long incubation periods. After the primary event, i.e., oxidation of GSH and —SH groups, a number of metabolic, rheologic, and membrane modifications, together with increased erythrophagocytosis take place in G6PD-deficient, D-treated RBC only. There is almost complete correspondence between D effects and RBC changes during the favic crisis. Among these effects, increased erythrophagocylosis, membrane cross-bonding, and formation of Heinz bodies seem to be causally related with the hemolytic process.
Comparison of Different Models of Rat Liver Carcinogenesis: Conclusions from a Systemic Analysis
Authors: de Gerlache Jacque , Lans Marc , Préat Veronique , Taper Hendryk , Roberfroid Marcel
Published: September 2009

Different protocols of chemically induced hepatocarcinogenesis were applied to Wislar rats under identical experimental conditions. The following conclusions may be drawn after an analytic comparison of these results. Various chemical carcinogens show different carcinogenic capacities. Diethylnitrosamine is more potent than N-nitrosomorpholine which is more active than 2-acetylaminofluorene. A short-term exposure to such carcinogens is sufficient to initiate but not necessarily to complete the carcinogenic process. It can be promoted to completion by either a noncarcinogenic promoter or a carcinogen. From a systemic point of view, it appears that, as in the skin models, two-step protocols are not always equivalent to protocols using the same agent during the whole treatment. Moreover, the results observed with a multistep protocol indicate that during the initiating phase the carcinogen plays a selective role distinct both from a pure initiating role and from the promoting effect. The results obtained lead to the conclusion that the distinction between initiation and promotion remains purely operational as it still does not correspond to the nature of well-established biologic processes.
Significance of Various Enzymes in the Control of Mutagenic and Carcinogenic Metabolites Derived from Aromatic Structures
Authors: Oesch Franz
Published: September 2009

One important early contribution to the control of chemical carcinogenesis is provided by the enzyme pattern responsible for the generation and disposition of reactive metabolites. Especially well studied is the important group of enzymes responsible for the control of reactive epoxides. Many natural as well as man-made foreign compounds, including Pharmaceuticals, possess olefinic or aromatic double bonds. Such compounds can be transformed to epoxides by microsomal monooxygenases present in very many mammalian organs. By virtue of their electrophilic reactivity such epoxides may spontaneously react with nucleophilic centers in the cell and thus covalently bind to DNA, RNA, and protein. Such alterations of critical cellular macromolecules may disturb the normal biochemistry of the cell and lead to cytotoxic, allergenic, mutagenic, and/or carcinogenic effects. Whether such effects will be manifested depends on one hand on the chemical reactivity as well as other properties (geometry, lipophilicity) of the epoxide in question. On the other hand, enzymes controlling the concentration of such epoxides are another important contributing factor. Several microsomal monooxygenases exist differing in activity and substrate specificity. With respect to large substrates, some monooxygenases preferentially attack at one specific site different from that attacked by others. Some of these pathways lead to reactive products, others are detoxification pathways. Moreover, enzymes metabolizing such epoxides represent a further determining factor. These enzymes include epoxide hydrolases and glutathione transferases. These enzymes do not play a pure inactivating role, but can in some cases also act as coactivating enzymes. Enzymes involved in biosynthesis and further metabolism of epoxides differ in quantity and sometimes also in substrate specificity between organs, developmental stages, sexes, and animal species. They therefore represent one important contributing factor to differences in susceptibilities between species and individuals.
Early Stages of Nodular Transformation of the B6C3F1 Mouse Liver Induced by Choline Deficiency
Authors: deCamargo Joao L. V. , Punyarit Phaibul , Newberne Paul M.
Published: September 2009

The B6C3F1 strain of mice is prone to develop liver nodules as animals grow older. This spontaneous tumor development is enhanced by dietary lipotrope deficiency. The present studies were performed to evaluate the liver of the B6C3F1 mice in early periods of lipotrope deficiency and before the nodules appear. Mice were fed high levels of dietary fat (cotton seed oil or beef fat) without choline or vitamin B12. The livers of these mice were compared with those of mice subjected to partial hepatectomy or dietary phenobarbital both of which enhance liver nodule formation. The ability of putative preneoplastic hepatocytes to exclude parenteral-administered iron was used to detect this eventual phenotype. A lipotrope-deficient condition was established which typically exhibited fatty liver and increased cell proliferation, the latter measured by autoradiography. In the time periods evaluated the lipotrope-devoid diets were not sufficient to induce nodular or putative preneoplastic lesions. An excessively high activity of p-nitroanisole- O-demethylase and a single small fatty nodule were obtained when phenobarbital was added to the lipotrope-deficient diet. Scattered eosinophilic hepatocytes were seen in every experimental group when the histologic slides were stained for iron pigments, but their biologic significance in the present experiments could not be established. Under the conditions of this study, the liver of the B6C3F1 strain of mouse exhibited only minor indications of future tumor development.
Morphologic Changes in the Gastric Mucosa of Rats and Dogs Treated with an Analog of Prostaglandin E1
Authors: Kramer Alfred W. , Dougherty William J. , Belson Alan R. , Iatropoulos Michael J.
Published: September 2009

American Cyanamid compound CL 115,574, a synthetic analog of prostaglandin E1, is active orally in inhibiting gastric acid secretion and in protecting against gastric ulcers induced by stress, ethanol, and nonsteroidal anti-inflammatory drugs. CL 115,574 was administered to rats for 6 months and to dogs for 1 year. Diarrhea occurred in both species and transient hyperthermia was observed in dogs. In rats, the only gross finding related to treatment was limited to the gastric mucosa and consisted of a dose-related widening of the cuticular ridge in the mid (2 mg/kg/day) and high (20 mg/kg/day) dose groups. Microscopically, there was a proliferation of the cuticular ridge stratified squamous epithelium. Morphologic findings in the dogs showed a multifocal proliferation of the foveolar epithelium in the pyloric antrum. Neither species had atypical cellular changes associated with the proliferative process. Furthermore, the changes in the dog consisted of well differentiated cells and occurred without pseudostratification of cells and increased mitotic activity. The “pseudoproliferative” character of these changes may be the result of a prolonged life span of most cell types of the gastric mucosa. These tissue adaptations reflect a true manifestation of the cytoprotective effect of prostaglandin E1 on the gastric mucosa.
Canine Ovarian Fibroma Associated with Prolonged Exposure to Mibolerone
Authors: Seaman William J.
Published: September 2009

A study to determine the efficacy and safety of mibolerone following prolonged oral administration in the female dog was terminated after 9.6 yr. Histopathologic examination revealed the presence of small dense tumors in the ovaries of 12 of 92 dogs given mibolerone at the approximate efficacious dose. No such tumors were found in 60 vehicle control animals or 55 animals given exaggerated doses of mibolerone. The tumors were composed of dense fibrous connective tissue and incorporated occasional ovarian medullary tubules. The tumors appeared to grow by expansion with no evidence of invasion or metastasis and were diagnosed as fibromas.
Morphofunctional Investigations on Spontaneous Pituitary Tumors in Wistar Rats
Authors: Barsoum Nabila J. , Moore John D. , Gough Alec W. , Sturgess Jennifer M. , De LaIglesia Felix A.
Published: September 2009

Adenoma of the pituitary gland represents one of the commonest spontaneous tumors in strains of laboratory rats. In a retrospective survey of pituitary glands from 2165 albino Wistar rats, the total number of pituitary adenomas was 501, representing an overall incidence of 23% with females showing a higher incidence (32%) than males (13%). Pituitary adenoma was rare from 6–52 weeks of age and accounted for only 0.2% of the total incidence. The first pituitary tumors in this series were observed at 32 weeks in 2 female rats and at 40 weeks in a male rat. From 52–85 weeks of age, incidence remained low, and then increased progressively in animals that died from 85–110 weeks of age. In a series of 200 Wistar rats, detailed evaluation was completed for neoplastic and hyperplastic lesions of the pituitary gland. The immunocytochemical characteristics of the pituitary adenoma were investigated using markers for prolactin, growth hormone, and thyrotropic hormone. Positive immunoperoxidase staining revealed an incidence of 59% prolactinomas in both male and female rats. Forty-one percent of pituitary adenomas did not stain for prolactin, thyrotropic, or growth hormone and showed no specific morphologic differences from prolactinomas. The application of immunoperoxidase-staining techniques of fers a useful tool for characterizing secretory activity of pituitary adenomas and evaluating histopathologic changes of the pituitary gland.
Spontaneous Vesicular and Prostatic Gland Epithelial Squamous Metaplasia, Hyperplasia, and Keratinized Nodule Formation in Rabbits
Authors: Zwicker Gary M. , Killinger Joanne M. , Mcconnel Robert F.
Published: September 2009

Histopathology of the reproductive system of 76 young adult Dutch Belted and 22 young adult or adult male New Zealand White rabbits was conducted as part of fertility studies. Thirty-five (46%) of the Dutch Belted and 11 (50%) of the New Zealand White males had multifocal vesicular gland basal epithelial cell atypia and hyperplasia without metaplasia. The affected cells were taller with pale cytoplasm and a prominent basophilic nucleus longitudinally oriented and increased in number compared to more normal adjacent epithelium. Thirty-one (41%) of the Dutch Belted and 10 (45%) of the New Zealand White males showed one or more nodules of squamous metaplasia in the alveolar epithelial lining or seen occasionally within alveolar walls of the vesicular gland. The prostate was less commonly affected and none of the early cellular atypia or later cornification changes were seen. A few cornified nodules with mitotic figures resembled “carcinoma in situ,” but the morphology and available biologic data supported the judgment that the lesion was benign, metaplastic, proliferative, and clinically silent.
Comparative Effects of Carcinogens on the Induction of Placental Glutathione S-Transferase-positive Liver Nodules in a Short-term Assay and of Hepatocellular Carcinomas in a Long-term Assay
Authors: Ogiso Tadashi , Tatematsu Masae , Tamano Seiko , Tsuda Hiroyuki , Ito Nobuyuki
Published: September 2009

The dose-dependent effects of three hepatocarcinogens were investigated by measuring the number and area of glutathione S-transferase placental form (GST-P)-positive foci and nodules appearing in the liver under short-term conditions (Experiment I) and evaluating the incidence of hepatocellular carcinoma after long-term chronic administration (Experiment II). For these purposes, three different doses of 2-acetylaminofluorene (2-AAF), 3'-methyl-4-dimethylaminoazobenzene (3'-Me-DAB), and DL-ethionine (ethionine) were given to male F344 rats for 6 weeks after a single injection of diethylnitrosamine (DENA) in Experiment I or for 104 weeks without initiation by DENA in Experiment II. In Experiment I, the induction of GST-P-positive foci and nodules by 2-AAF and 3'-Me-DAB was clearly dose-dependent. In contrast, ethionine showed enhancing effects inducing GST-P-positive foci and nodules only in groups given the highest dose level. Similarly, in Experiment II, induction of hepatocellular carcinomas by 2-AAF and 3'-Me-DAB was clearly dose-dependent, whereas liver neoplasms were only induced by the highest dose level of ethionine. These results indicate that degree of induction of GST-P positive foci and nodules in a short-term in vivo test for liver carcinogens corresponds with the incidences of hepatocellular carcinomas revealed in a long-term in vivo assay.
Orally Induced Adjuvant-like Arthritis in the Rat
Authors: Gray Jack E. , Larsen Erik R. , Fast Patricia E. , Hamilton Ramon D.
Published: September 2009

Adjuvant-like arthritis was produced in Sprague-Dawley rats during 14 days of oral administration of 2-amino-5-bromo-6-(3-fluorophenyl)-4(3 H)-pyrimidinone. Inflammatory changes about and in the hindlimb joints were similar to those described by Pearson for adjuvant-induced polyarthritis. Lymphoid hyperplasia, elevation of serum IgG levels, and localization of fluorescein-labeled globulin in disseminated inflammatory lesions implicate an immunologic effect. Rats treated twice weekly for 64 days developed lymphocytic thyroiditis and showed less inflammation in the joints.
Regression of Pathologic Changes Induced by the Long-term Administration of Contraceptive Steroids to Rodents
Authors: Lumb George , Mitchell Lorelie , De La Iglesia Felix A.
Published: September 2009

The induction of pathologic changes with hormone steroids has been studied in rodents, although comprehensive studies are lacking on the potential reversibility of these lesions. For these purposes, groups of rats were treated with quingestanol acetate and quinestrol, a progestogen-estrogen combination, for 50 weeks and observed for a subsequent 30-week period. Treatment resulted in a significant body weight gain suppression and reduction of food consumption which recovered after withdrawal. Other significant treatment-related effects were hair loss, ataxia due to pituitary enlargement, mammary chain masses with histologic adenocarcinoma, lens opacities, ovarian atrophy with follicular arrest, and uterine atrophic changes with suppurative inflammation throughout 50 weeks. Cessation of treatment did not effect hair loss or lens opacities, while mammary chain masses decreased in size and in incidence; mammary gland tumors showed regressive changes including the disappearance of adenocarcinoma, and the incidence of ataxia diminished together with reduced pituitary weights. Chromophobe cell hyperplasia with decreased eosinophils and acidophils and hemorrhage into the pituitary was observed up to 50 weeks and the tinctorial affinity of basophils and acidophils returned after withdrawal. Ovaries and uteri, which become atrophic and sustained chronic suppurative inflammation in the treatment phase, showed reduction of inflammatory reaction and disappearance of suppuration after withdrawal, and endometrial regeneration occurred with luteal cells seen in the ovaries. These results revealed the regressive characteristics of some of the mammary gland carcinomas as well as steroid-induced endocrine and pathologic lesions other than tegumentary and ocular changes in rats receiving high levels of steroids for prolonged periods of time.
Kidney Morphology: Update 1985
Authors: Bulger Ruth Ellen
Published: September 2009

Many new observations have been made correlating changes in renal morphology with changes in renal function. These changes have led to a better definition of the various segments which make up the renal tubule. These morphological patterns vary in different species as is documented by morphologic studies and by differences in the patterns of enzymes in various nephron segments. The subdivision of cells located in the mesangial region of the glomerulus into several types may provide new areas to study with respect to disease processes.
Drug-Associated Glomerulopathies
Authors: Hill Gary S.
Published: September 2009

The renal glomeruli are vulnerable to injury by a number of drugs and other toxic agents. These agents may lead to damage by one of two basic mechanisms: 1) direct, dose-related toxic injury; 2) indirect, immunologically mediated injury, largely dose-independent. Proteinuria is the simplest and most important functional indicator of glomerular injury. It occurs almost immediately in direct toxic injury, but there is a latent period of weeks to months with immunologically mediated processes. Of the two mechanisms, the second is by far the more common in clinical settings. The best studied experimental agent causing direct toxic injury is the aminonucleoside of puromycin. Clinically, perhaps the most important agent is Cyclosporine A. Although this agent is usually thought of primarily as a tubular toxin, it is capable of giving rise to a microangiopathic glomerular lesion similar to that in the hemolytic uremic syndrome. The classic model for immunologic glomerular lesion is Heymann nephritis, which produces a membranous glomerulopathy. Clinically, most drug mediated glomerulopathies also take the form of a membranous nephropathy, usually with a frank nephrotic syndrome. Among the more common of fenders are penicillamine, gold salts used in rheumatoid arthritis, and captopril used in hypertension. The other common type of drug-related glomerulopathy occurs as part of a lupus-like syndrome induced by a variety of drugs, including hydralazine, procainamide, and penicillamine. All of these give rise to a variety of antibodies, most prominently antinuclear antibodies, and in the more severe cases there may be lupus-like glomerular lesions as well.
Nephrotoxic Tubular and Interstitial Lesions: Morphology and Classification
Authors: Racusen Lorraine C. , Solez Kim
Published: September 2009

Nephrotoxic renal injury, and especially drug nephrotoxicity is now a common cause of acute renal failure. The most common patterns of renal injury produced by nephrotoxins, tubular damage, and interstitial nephritis, are discussed here. Toxic agents which are primarily tubular toxins include certain antibiotics, cis-platinum, anesthetics, and radiocontrast agents. In tubules injured by toxins, alterations range from subtle ultrastructural abnormalities to extensive tubular necrosis. Mechanisms of tubular injury include direct tubular cell toxicity, and alterations in intrarenal blood flow producing secondary tubular damage. Other commonly used therapeutic agents, including the penicillins, other antibiotics, and non-steroidal anti-inflammatory agents, produce renal dysfunction by inducing interstitial nephritis. Long-term analgesic abuse is associated with a particularly striking interstitial damage with frank papillary necrosis. Criteria for differentiating primary tubular injury with inflammation and primary interstitial nephritis with tubular injury are discussed. Individual commonly-used therapeutic agents are considered in some detail, with discussion of both clinical and morphological aspects of drug nephrotoxicity.
Renal Damage Caused by Heavy Metals
Authors: Bulger Ruth Ellen
Published: September 2009

Studies of tubular injury and necrosis caused by heavy metals have indicated involvement by various parts of the proximal tubule. This paper describes the patterns of injury seen after administration of mercuric chloride, uranyl nitrate, and cisplatin to animal models. Studies describing a possible role of the mesangium of the renal corpuscle in proximal tubular injury are included.
Spontaneous Nephropathies in Rats
Authors: Peter Chennekatu P. , Burek Joe D. , Zwieten Matthew J. Van
Published: September 2009

Spontaneously occurring diseases of the kidneys are very common in laboratory rats. These diseases include chronic progressive nephrosis, nephrocalcinosis, renal tubular epithelial hyaline droplets, renal tubular hypertrophy, and renal tubular basophilia. As increasing numbers of rats are used in long-term toxicity and carcinogenicity studies, recognizing spontaneously occurring renal lesions and understanding their etiology and pathogenesis are important in making an assessment of the safety of drugs and chemicals that are being tested. The purpose of this paper is to review the incidence, morphology, and pathogenesis of these spontaneous diseases. Some of the factors that alter the incidence and/or severity of these spontaneous diseases will also be discussed.
Functional-Morphologic Correlations in Assessing Renal Toxicity
Authors: Hottendorf Girard H.
Published: September 2009

Evaluation of the correlation of functional and morphologic assessments of renal toxicity are obviously important to the toxicologic pathologist. All clinical assessments of the nephrotoxicity of drugs are based on renal function tests while preclinical assessments involve functional and/or morphologic assessments in laboratory animals. However, there are considerable concerns about the sensitivity of the tests available to monitor renal function. In an attempt to assess the relative sensitivity of functional and morphologic indicators of nephrotoxicity, three data bases were examined for their ability to rank the nephrotoxicity of the three most widely used aminoglycosides. The functional data base was comprised of reported comparative clinical trial data and the morphologic data base was composed of preclinical studies available in the literature which used morphology as the basis of comparison. A third data base involved biochemical or mechanistic comparisons of aminoglycosides and represented data that was not based on clinical function test results or morphologic analysis. When these three data bases were compared, it was obvious that clinical function tests could not discriminate between the nephrotoxic liability of the three aminoglycosides. The preclinical renal morphology data base and the biochemical mechanistic data base both clearly discriminated the drugs one from another and ranked the three aminoglycosides in the same order. Several conclusions were suggested by these results. Comparisons of the nephrotoxic potentials of drugs in patients utilizing available renal function tests may be inconclusive primarily because clinical renal function tests are insensitive. Comparisons of the nephrotoxic liabilities of drugs in laboratory animals utilizing morphologic assessments of renal tissue damage may be the best comparison available. Such comparisons indicate that amikacin is less nephrotoxic than tobramycin which is less nephrotoxic than gentamicin.
Exaggerated Response to Gentamicin-Induced Nephrotoxicity in Sprague-Dawley Rats: Identification of a Highly Sensitive Outlier Population
Authors: Frazier Donita L. , Carver Mike P. , Dix Lynn P. , Thompson Carol A. , Riviere J. Edmond
Published: September 2009

A number of factors have been shown to predispose patients treated with aminoglycosides to nephrotoxicity. In a previous study in our laboratory investigating the interaction of prior renal dysfunction with gentamicin toxicokinetics, 9.4% of rats in all treatment groups were relatively more sensitive to gentamicin-induced nephrotoxicity. To determine if these outliers had an underlying disease or physiological abnormality, serum was collected from 99 Sprague-Dawley rats prior to daily treatment with 75 mg/kg gentamicin for seven days. Urea nitrogen, creatinine, Na, K, Ca, Mg, P, total protein, albumin, aspartate transaminase, serum osmolality, total white and red blood cell count, hematocrit, hemoglobin, blood gases, and thyroxine were measured. Blood was collected one and four hours after the first dose of gentamicin for pharmacokinetic analysis. Elevations in post-treatment creatinine and nitrogen were significantly greater in the outliers (4.10 ± 0.24 mg/dl (n = 12) vs 1.92 ± 0.06 mg/dl (n = 87) and 146.4 ± 7.2 mg/dl (n = 12) vs 71.5 ± 2.0 mg/dl (n = 87); both p = 0.0001) and served as criteria for identifying this subgroup. Post-treatment creatinine and urea nitrogen were not normally distributed in the entire study population. However, when the population was divided into normal and sensitive subgroups, both subgroup values were normally distributed. The gentamicin pharmacokinetic profiles were similar in both groups. Postmortem histopathology showed significant increases in tubular casts and tubular necrosis ( p = 0.01) in the sensitive rats, compared to the normally responding subgroup. Clinical tests on pre-treatment serum revealed significant differences only in serum osmolality ( p = 0.04), total protein ( p = 0.02), and oxygen tension ( p = 0.01). The pre-treatment creatinine/urea nitrogen ratio was marginally decreased in the sensitive rats ( p = 0.057).
A New Diagnostic Immunoassay for Proximal Tubule Injury
Authors: Thompson Russell E. , Piper Donna J. , Kidd Kathryn A.
Published: September 2009

Adenosine deaminase binding protein (AdAbp), a glycoprotein found in the epithelial cells of the brush border of the proximal tubule, is shed into urine following kidney damage. A sandwich enzyme immunoassay is described that uses two monoclonal antibodies, URO-4 (S27) and URO-4a (S23), which react with different epitopes on AdAbp (2, 24). Release of AdAbp into the urine appears to reflect the severity of the insult to the nephron and its measurement may assist in distinguishing between tubular disease and glomerular disease and may be useful in indicating renal toxicity.
Mammary Gland Tumors in Irradiated Untreated Guinea Pigs
Authors: Hoch-Ligeti Cornelia , Liebelt Annabel G. , Congdon Charles C. , Stewart Harold L.
Published: September 2009

This is a report of mammary gland tumors from 62 guinea pigs. The tumors arose in the terminal ductal-lobular units as either lobular acinar carcinoma or cystadenocarcinoma or 2) as papillary carcinomas within large ducts near the mammilla. About half the number of the males had terminal ductal-lobular carcinomas and all but 2 of the papillary duct carcinomas also arose in males. Large tumors frequently-exhibited squamous, chondromatous, osseous, fatty and myoepitheliomatous types of tissues. In 2 irradiated males and 1 female the tumors metastasized. Whole-body irradiation did not produce significant changes in the number or sex distribution or in the morphology of mammary gland tumors in inbred or outbred guinea pigs. All females had cystic ovaries without increase in granulosa cells, 24 (66.6%) had uterine tumors and 13 (34.2%) had adrenal gland tumors; all males had atrophic testes, 5 (16.5%) had testicular and 6 (22.2%) had adrenal gland tumors.
Promoting and Anticarcinogenic Effects of Phenobarbital and DDT in the Rat Hepatocarcinogenesis
Authors: Kitagawa Tomoyuki
Published: September 2009

The possible discrepancy between the dose level required for promoting action (when given after the initiation process, and that needed to exert an anticarcinogenic effect when given simultaneously with a carcinogen) of hepatic promoters were investigated in an attempt to obtain a “practical” threshold dose of promoters. Phenobarbital (PB) and dichlorophenyltrichlorethane (DDT) were used as promoters and 3‘-methyl-4-(dimethylamino)-azobenzene (3’-Me-DAB) was used as the carcinogen. Male weanling rats were treated with either 600 ppm 3‘-Me-DAB for 3 weeks followed by a diet containing a promoter at various dose levels (5–500 ppm), or the animals were treated with a low dose (100 ppm) of 3’-Me-DAB plus a promoter at various dose levels (20–500 ppm). The effects of promoters were measured by scoring size and number of enzyme-altered islands (EAIs) at 12 and 24 weeks of age. The promoting effect of PB and DDT was demonstrated in dose-dependent fashion, in the dose range of 10–500 ppm and 20–500 ppm, respectively. On the other hand, promoters given simultaneously with a low dose of carcinogen enhanced carcinogenesis at all the dose levels tested, in contrast with the inhibitory effect on carcinogenesis when given together with relatively high doses of carcinogens.
Modifying Effects of Antioxidants on Chemical Carcinogenesis
Authors: Ito Nobuyuki , Hirose Masao , Fukushima Shoji , Tsuda Hiroyuki , Tatematsu Masae , Asamoto Makoto
Published: September 2009

Studies were made on the carcinogenic activity of butylated hydroxyanisole (BHA) in rats, mice, and hamsters and the effect of the antioxidants BHA, butylated hydroxytoluene (BHT), ethoxyquin (EQ), sodium L-ascorbate (SA), ascorbic acid (AA), sodium erythorbate (SE), propyl gallate (PG), and α-tocopherol, on two-stage chemical carcinogenesis in rats initiated with N-methyl-N'-nitro-N-nitrosoguanidine (MNNG), 1,2-dimethylhydrazine (DMH), diethylnitrosamine (DEN), 7,12-dimethylbenz(a)anthracene (DMBA), N-butyl-N-(4-hydroxybutyl)nitrosamine (BBN), N-ethyl-N-hydroxyethylnitrosamine (EHEN), or N-methylnitrosourea (MNU). BHA clearly induced squamous cell carcinomas in both the rat and hamster forestomach. The tumorigenic action of crude BHA on the forestomach is largely due to 3- tert-BHA. In two-stage chemical carcinogenesis, BHA promoted MNNG or MNU-initiated forestomach and BBN- or MNU-initiated urinary bladder carcinogenesis and inhibited DEN- or EHEN-initiated liver and DMBA-initiated mammary carcinogenesis. BHT demonstrated promotion potential for urinary bladder and MNU-initiated thyroid carcinogenesis and inhibited DMBA-initiated ear duct carcinogenesis. EQ promoted EHEN-initiated kidney carcinogenesis and inhibited DMBA-initiated mammary and EHEN-initiated liver carcinogenesis. SA promoted forestomach and urinary bladder carcinogenesis and SE likewise enhanced urinary bladder carcinogenesis. α-Tocopherol inhibited ear duct carcinogenesis. No effects of any of the antioxidants on glandular stomach carcinogenesis were found. The results clearly demonstrated that antioxidants have different effects (promoting or inhibitory influences) depending on the organ studied and suggest the importance of a whole body approach to their investigation.
Evidence for a Special Relationship Between Proteolysis and Single Cell Necrosis
Authors: Amenta Joseph S. , Brocher Steffanie C. , Mehta Jasbir , Manjunath Dodomanine , Baccino Franco M.
Published: September 2009

A high rate of single cell necrosis is a common phenomenon in neoplastic and preneoplastic lesions, accounting for growth rates that are significantly less than the cell birth rate. We present data relating the process of protein turnover to single cell necrosis. Cells were labeled with 3H-leucine and 14C-thymidine; the loss of radioactivity from the cell protein and DNA was then measured for 3–6 days. Preliminary experiments showed that cell necrosis by freeze-thawing cells did not significantly contribute to the degradation of cell proteins. Similar results were observed with dying 3T3-SV40 cells at high density. L-cells, however, showed a progressive increase in cell loss as higher cell densities were attained on the monolayer. Although proteolysis remained constant in the culture, analysis of the cells recovered from the high density monolayers showed little loss of labeled protein after adjustment for loss of label in the DNA. Three possible explanations are proposed: (1) DNA turns over with cell protein (unlikely), (2) single cell necrosis involves a special mechanism that facilitates reutilization of amino acids, or (3) single cell necrosis includes only cells that are selectively involved in protein turnover. A unique relationship between single cell necrosis and proteolysis is suggested.
Changes in Cellular Ploidy and Autophagic Responsiveness During Rat Liver Carcinogenesis
Authors: Seglen Per O. , Schwarze Per E. , Saeter Gunnar
Published: September 2009

Liver carcinogenesis was initiated in young rats by diethylnitrosamine/partial hepatectomy and promoted by dietary 2-acetylaminofluorene (for 4 weeks). Eight weeks after initiation, hepatocytes were isolated by means of collagenase perfusion and analyzed by means of flow cytometry. Whereas cells and cell nuclei from normal or hepatectomized livers were predominantly tetraploid, most of the hepatocytes/nuclei from carcinogen-treated rats were diploid. Neoplastic liver nodules and hepatocellular carcinomas also contained almost exclusively diploid nuclei, suggesting that diploidization may be an essential feature of liver carcinogenesis. Two-parametric analysis (simultaneous flow cytometric determination of DNA and protein content within the same cell) revealed that the diploid cells were only half as big as the tetraploid cells. They could therefore be separated from the latter by centrifugal elutriation. Normal, isolated hepatocytes responded to amino acid deprivation by increasing their rates of autophagic sequestration (measured with electroinjected (14C)sucrose as a probe) and endogenous protein degradation, the resulting protein loss eventually leading to cell death. Hepatocytes from carcinogen-treated rats were much less responsive to amino acid deprivation, preserved their protein better, and survived for longer periods of time in culture than did normal cells. The reduced autophagic responsiveness may conceivably give carcinogen-altered cells a survival advantage even in vivo, that could contribute to their outgrowth during carcinogenesis.
Inhibition of Tumor Development by Dehydroepiandrosterone and Related Steroids
Authors: Schwartz Arthur G. , Pashko Laura , Whitcomb Jeannette M.
Published: September 2009

The naturally occurring adrenal steroid, dehydroepiandrosterone (DHEA), is a potent non-competitive inhibitor of mammalian glucose-6-phosphate dehydrogenase (G6PDH). Oral administration of DHEA to mice inhibits spontaneous breast cancer and chemically induced tumors of the lung and colon. Topical application of DHEA to mouse skin inhibits 7,12-dimethylbenz(a)anthracene (DMBA)-initiated and tetra-decanoylphorbol-13-acetate (TPA)-promoted papillomas and DMBA-induced carcinomas at both the initiation and promotion phase. Evidence is presented that critical steps in the initiation process (mixed-function oxidase activation of a carcinogen) and promotion process (enhanced rates of cell proliferation and superoxide formation) all require NADPH and may be inhibited by DHEA and structural analogs as a result of a lowering of the NADPH cellular pool. Results obtained by others with fibroblasts and lymphocytes from individuals with the Mediterranean variant of G6PDH deficiency also indicate that a reduction in the NADPH cellular pool confers resistance to benzo(a)pyrene. Preliminary data suggest that food restriction may depress G6PDH levels and this may contribute to the tumor preventive effect of underfeeding.
Characterization of the Promoting Activity of Thiobenzamide on Liver Carcinogenesis
Authors: Malvaldi Gino , Chieli Elisabetta , Saviozzi Michela
Published: September 2009

To characterize the promoting activity of thiobenzamide (TB), a thiono-sulfur-containing xenobiotic, rats of both sexes were treated with the compound for 4 or 8 weeks after an initiating dose of diethyl-nitrosamine. The number, area (volume), and phenotypic complexity of the enzyme-altered hepatocyte foci were studied in serial sections stained with hematoxylin/eosin and reacted for glycogen, iron, and gamma-glutamyltrans-peptidase activity. The TB-induced changes on the drug metabolizing systems were also investigated. The main findings were: 1) When fed in a dose range of 500–2,000 mg/kg of diet, TB induced a number of foci greater than controls, especially in female rats. Benzamide, a major TB metabolite, was ineffective. 2) The appearance of hepatocyte foci upon TB feeding was nearly synchronized. 3) An increase of the phenotypic complexity of the hepatocyte foci occurred only during the first 4 weeks of TB administration; it correlated with an increase in size. 4) The liver microsome content of cytochrome P-450 as well as the activity of many monooxygenases was decreased, some of the phase II reactions being increased. In conclusion TB behaves as an efficient promoter of liver carcinogenesis, possibly as a consequence of an induced adaptive response.
Comparison of the Acute Toxicity of N-nitrosocimetidine with Three Structurally Related Carcinogens in the Rat
Authors: Ogiu Toshiaki , Hard Gordon C. , Magee Peter N. , Jensen David E.
Published: September 2009

The acute toxicity of N-nitrosocimetidine, the nitrosated derivative of the histamine H2-receptor blocking agent cimetidine, was compared with the toxicities of three structurally related nitroso compounds known to be potent carcinogens, namely N-methyl-N'-nitro-N-nitrosoguanidine, N-methyl-N-nitrosourea, and N-methyl-N-nitrosourethane, and also with the parent drug cimetidine. The acute toxicity of each compound was investigated in 6-week-old female Fischer-344 rats by estimating the median lethal doses via three different routes of administration, and by assessing the sequence of histopathological alterations induced. According to median lethalities, all three known carcinogens were substantially more toxic than nitrosocimetidine whether administered by the intravenous, intraperitoneal, or oral routes. The widest margin of difference was represented by orally administered N-methyl-N-nitrosourea, the median lethal dose being 59 times greater than oral N-nitrosocimetidine. By this method, the acute toxicities of N-nitrosocimetidine and the parent drug cimetidine were virtually identical for each of the three routes of administration. Sequential histological assessment indicated that the three known carcinogens induced specific pathological alterations mainly in organs which were also known to be targets for their carcinogenic activity. In contrast, no tissue lesions of a specific nature were associated with N-nitrosocimetidinc or cimetidine in this study. The comparable results with N-nitrosocimetidine and the parent drug provide biological support for previously obtained biochemical data which suggested that N-nitrosocimetidine is rapidly denitrosated to cimetidine in the rat.
Rapid Changes in Glucose Metabolism Following the Administration of Ethionine: Its Role in Regulating Hepatic Protein Synthesis
Authors: Lyon Andrew W. , Kisilevsky Robert
Published: September 2009

The relationship between the changes in portal glucagon, insulin, glucose, and hepatic protein synthesis were investigated during ethionine intoxication. There was a 50% decrease in blood glucose, a seven-fold increase in portal glucagon and a 90% increase in portal insulin, all of which coincided temporally with the inhibition of hepatic protein synthesis. When reversal of ethionine intoxication was initiated with adenine it simultaneously restored blood glucose, insulin, glucagon, and protein synthesis. Protein synthesis could not be adequately restored by glucose, but in this case hepatic ATP levels did not increase. In addition, glucose given by stomach tube prior to ethionine did not prevent the action of ethionine, though it did maintain plasma glucose levels and prevented the decrease in plasma insulin and increase in plasma glucagon. These results show that in vivo regulation of hepatic protein synthesis during ethionine intoxication is not likely to be mediated by portal insulin, glucose, and glucagon.
Interaction of Halocompounds with Nucleic Acids
Authors: Prodi Giorgio , Arfellini Giancarlo , Colacci Annamaria , Grilli Sandro , Mazzullo Mario
Published: September 2009

The binding of epichlorohydrin, 1,2-dichloroethane, 1,2-dibromoethane, chlorobenzene, bromobenzene, and benzene to nucleic acids and proteins of different murine organs was studied in in vivo and in vitro systems. The extent of in vivo enzymatic activation of brominated compounds was higher than that of chlorinated chemicals. Aryl halides were bound mainly to liver DNA whereas interaction of alkyl halides with DNA of liver, kidney, and lung gave rise to similar binding extent. In vitro activation of all chemicals was mediated by microsomal P-450-dependent mixed function oxidase system which is present in rat and mouse liver and, in smaller amount, in mouse lung. Activation of alkyl halides by liver cytosolic GSH-transferases even occurred. The relative reactivity of chemicals in vivo, expressed as Covalent Binding Index (CBI) to rat liver DNA, was: 1,2-dibromoethane > bromobenzene > 1,2-dichloroethane > chlorobenzene > epichlorohydrin > benzene. On the whole, it agreed with in vitro activation of chemicals, with genotoxicity data from other short-term assays and also with oncogenicity of benzene, epichlorohydrin, 1,2-dichloroethane, and 1,2-dibromoethane. CBI values of chlorobenzene and bromobenzene gave the first clear evidence of genotoxicity and of possible carcinogenicity of these two chemicals.