bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of Glutathione and N-Acetylcysteine on Hepatocellular Modifications Induced by 2-Acetylaminofluorene
Authors: Cesarone Carmelo F. , Scarabelli Linda , Orunesu Mauro
Published: September 2009

The exposure of rats to a dietary regimen containing 2-acetylaminofluorene induces a sequence of hepatocellular alterations leading to the development of preneoplastic nodules. Groups of 2-acetylaminofluorenetreated rats were given glutathione or N-acetylcysteine to evaluate the effects of these different thiols on the sequence of events that originate transformed cells. It is well known that intracellular thiols protect biological macromolecules from scavenging free radicals and electrophilic compounds produced by the metabolism of chemical agents. Male Wistar rats were maintained on a feeding regimen containing 0.05% 2-acetylaminofluorene. The diet of 2 groups of 2-acetylaminofluorene-treated animals was supplemented with either 0.1% glutathione or N-acetylcysteine. The effects in the liver of the exogenously supplied thiols during 2-acety-laminofluorene treatment were assessed evaluating DNA damage, glutathione levels, activity of marker enzymes glucose-6-phosphatase, γ-glutamyltranspeptidase, and glutathione-S-transferase, survival rates, and development of salivary gland tumors. Our results demonstrate that the mortality due to 2-acetylaminofluorene exposure was reduced or completely abolished by thiols and that the development of salivary gland tumors was inhibited. Exogenously supplied thiols significantly reduced DNA damage as assessed by alkaline elution. At the doses employed, glutathione and N-acetylcysteine induce early stimulation of glutathione-S-transferase, had little effect on the loss of glucose-6-phosphatase activity and scanty influence on the net increase in γ-glutamyltranspeptidase activity.
Quantitative Assessment of Trimethyltin Induced Pathology of the Hippocampus
Authors: Robertson Donald G. , Gray Robert H. , De LaIglesia Felix A.
Published: September 2009

The pathology induced by trimethyltin in the hippocampus was investigated using a detailed morphometric model. Male Long-Evans rats were dosed with 3 mg/kg trimethyltin chloride (TMT) for three consecutive days and sacrificed at subsequent interim periods. Total brain volume was not significantly affected; hippocampus volume decreased within 4 days after completion of dose. Pyramidal cells were more sensitive to the toxic effects of TMT than granule cells, in addition, dorsal pyramidal cells appeared to be more sensitive than ventral pyramidal cells. The dorsal CA4 region appeared to be the most susceptible to cell loss, although the dorsal CA1 region also exhibited significant reductions. The most dramatic reduction in cell numbers occurred between 14 and 28 days post-dose. Cell loss within the CA3c and CA4 but not the CA1 region was preceded by decreased nuclear volume. In addition cellular loss within the dorsal CA1 region appeared to be most pronounced within a well defined rectangular patch of cells immediately adjacent to the CA3-CA1 junction. The data further suggest that TMT is a potent toxicant to the hippocampus. This toxicity is delayed, and selectively affects well defined groups of cells within the structure. Additionally, differences in nuclear pathology suggest that more than one mechanism may be involved in the destruction of these target cell populations.
Transplantation of Preneoplastic Rat Hepatoeytes by Intraportal Injection
Authors: Sæter Gunnar , Schwarze Per E. , Nesland Jahn M. , Seglen Per O.
Published: September 2009

Hepatocyte suspensions prepared from inbred male Wistar-Kyoto rats were transplanted to the livers of syngeneic recipients by injection into the portal venous system immediately after partial hepatectomy. Donor cells were labelled with 51Cr in vitro before transplantation. Animals were sacrificed 1 hr, 10 hr, 48 hr, or 1 week later and the liver radioactivity was measured in a gamma counter. Total liver radioactivity declined rapidly during the first 10 hr after transplantation, and then stabilized. After 1 week, 15–20% of the injected radioactivity still remained, indicating that this fraction of the injected cells was retained by the liver. The percentage was unaffected by the number of cells injected. In another experiment, 106 hepatocytes from a carcinogen-treated rat were transplanted to syngeneic rats fed 0.05% phenobarbital in the diet. Recipients developed liver carcinomas from 7 weeks after transplantation, and at 5 months 4 out of 5 animals showed severe debility and had large hepatocellular carcinomas. This model generates tumors considerably faster than those previously described, and is well suited for the study of the tumorigenic potential of subclasses of cells in liver carcinogenesis.
Endocytosis of Asialo-glycoproteins and Attachment to Asialo-glycoproteins of Hepatocytes from Carcinogen-Treated Rats
Authors: Schwarze Per E. , Tolleshaug Helge , Seglen Per O.
Published: September 2009

Endocytosis and degradation of asialo-glycoprotein were investigated in hepatocytes from carcinogen-treated rats. The cells were isolated at an early stage of carcinogenesis after a sequential treatment with diethylnitrosamine and 2-acetylaminofluorene. Hepatocytes at this pre-nodular stage take up asialo-orosomucoid at a lower rate than hepatocytes from normal rats, whereas degradation of the protein occurs at a similar rate in the two populations. The lower rate of uptake appears to result from a decreased binding capacity in treated hepatocytes. The reduced binding capacity leads to slower kinetics of cell attachment to a substratum of asialo-glycoprotein. The lower number of receptors did not seem to be confined to a particular subpopulation of hepatocytes. Diploid and tetraploid hepatocytes, isolated by centrifugal elutriation, displayed the same reduction in binding capacity.
Biochemical Properties of Carcinogen-Metabolizing Enzymes in Cultured Hepatoma Cells
Authors: Ferro Margherita , Marinari Umberto M. , Bassi Anna M. , Nanni Giorgio
Published: September 2009

We have previously demonstrated the inducibility of both cytochrome P-448- and P-450-dependent mono-oxygenases in the differentiated rat hepatoma cell line MH1C1. Further experiments with these cells on the expression of different forms of cytochrome P-450, inducible not only by phenobarbital (PB) and 3-methylcholanthrene (MC), but also by metyrapone (MP), ethanol (E), and beta-naphthoflavone (BNF) are reported here. The effects of the in vitro addition of the inhibitors alpha-naphthoflavone and beta-naphthoflavone on the aryl hydroxylase activity (AHH) and the influence of protein synthesis on the induction of cytochrome P-450 were also assessed. Cultures were exposed to the inducers PB, MC, BNF, and MP during the last 6 days of culture and to E for 10 days. The inhibition of protein synthesis was obtained by adding cycloheximide (CY) to the cultured cells during the last 24 hr. The exposure of MH1C1cells to various concentrations of MP resulted in a dose-dependent increase in AHH activity. The treatment of MH1C1cells with different concentrations of ethanol produced a significant dose-dependent increase of monooxygenases. AHH activity, induced by the various treatments, was inhibited in a dose-dependent way by alpha-naphthoflavone and beta-naphthoflavone. CY reduced the concentration of cytochrome P-450 and the AHH activity induced by the various treatments, thus indicating an implication of the protein synthesis in the mechanism(s) of induction.
Sulfation of N-hydroxy-2-acetylaminofluorene in Normal and Nodular Liver from Male Wistar Rats
Authors: Blanck Agneta , Wicksell Lottie , Eriksson Lennart C.
Published: September 2009

Hepatocyte nodules produced by cyclic feeding of the rat liver carcinogen 2-acetylaminofluorene to male rats have been shown to exhibit specific metabolic characteristics. None of the characteristics of nodular tissue so far investigated has provided any explanation why initiated cells, such as in the “resistant hepatocyte model,” were resistant to the mitoinhibitory effects of 2-acetylaminofluorene. In the present study, hepatocyte nodules are produced by cyclic feeding of 0.05% 2-AAF in the diet to male Wistar rats. N-hydroxy-2-acetylaminofluorene sulfotransferase levels were determined in the postmicrosomal supernatant prepared from nodules and from control rat liver. The average sulfotransferase activities were 0.29 and 4.75 nmol p-nitrophenol formed/min × mg protein, respectively. We suggest that the low sulfotransferase activity in preparations from nodular tissue might be an important part of the explanation for the resistance of focal and nodular tissue to the mitoinhibitory effects of 2-acetylaminofluorene.
The Variations of S-adenosyl-L-methionine Content Modulate Hepatocyte Growth During Phenobarbital Promotion of Diethylnitrosamine-Induced Rat Liver Carcinogenesis
Authors: Feo Francesco , Garcea Renato , Pascale Rosa , Pirisi Lucia , Daino Lucia , Donaera Anna
Published: September 2009

A decrease in liver S-adenosyl-L-methionine (SAM) content and an increase in ornithine decarboxylase (ODC) activity occurred between the 2nd and the 5th week after starting 2-acetylaminofluorene (AAF) feeding in diethylnitrosamine (DENA)-initiated rats. These rats then received a 0.05% phenobarbital (PB)-containing diet for 18 weeks after the end of AAF feeding. Two weeks after starting AAF, an increase in the hepatocyte labeling index (LI) also occurred in γ-glutamyl-transpeptidase (GGT)-positive foci and surrounding tissue. LI returned to control values in a few days in surrounding tissue, while it remained high for at least 4 weeks in the foci. Analogous changes were observed, but for a shorter period of time, in the rats subjected to partial hepatectomy (PH) plus AAF, in which no GGT-positive foci developed. Twenty-four weeks after starting AAF, 30% of the liver was occupied by visible nodules. ODC activity and LI were high and SAM was low in nodules, but they were near to control values in surrounding liver. SAM administration reconstituted the liver SAM pool, inhibited ODC activity, and prevented visible nodule development. SAM inhibition of ODC activity occurred in vitro only after preincubation with liver homogenate and was enhanced by adenine, an inhibitor of methylthioadenosine (MTA) phosphorylase. MTA addition to the reaction of mixture for ODC determination was inhibitory. The SAM decrease in both liver and nodules was coupled with a decrease of MTA content. SAM administration caused MTA accumulation in the liver. It is suggested that liver SAM content by influencing MTA level, could be a rate-limiting factor for growth and promotion, through a modulation of polyamine synthesis.
Histologic Changes in Nude Mouse Skin and Human Skin Xenografts Following Exposure to Sulfhydryl Reagents: Arsenicals
Authors: McGown Evelyn L. , van Ravenswaay Theodore , Dumlao Cecilio R.
Published: September 2009

This report documents the histological changes in nude mouse skin and in human skin xenografts on nude mice following exposure to phenyldichloroarsine (PDA), a vesicant arsenical. Under light microscopy, we observed in PDA-treated human skin grafts: 1) degeneration of epidermal cell nuclei (apparent by 2 hr after exposure with increasing severity through 48 hr); 2) loss of epidermal cytoplasmic basophilia (apparent by 4 hr, maximal within 12 hr); 3) epidermal cytoplasmic vacuolization (vacuoles appeared within 4 hr and increased in size through 24 hr); 4) cleft formation within the basement membrane zone (apparent by 12 hr, increasing in severity through 24 hr); 5) inflammation evidenced by polymorphonuclear leukocyte (PMN) infiltration (apparent by 4 hr and increasing through 48 hr). The PMNs frequently formed a wall around the lesion, but did not infiltrate the treated area. Nude mouse skin reacted faster to PDA than did the grafts, but the histological changes were similar. Nude mouse hair follicles and sebaceous glands showed similar cellular changes at approximately the same time as did epidermal cells. Transmission electron microscopy of mouse skin exposed to PDA revealed a widening of intercellular spaces with attenuation of desmosomes. The subepidermal clefts resulted from separation within the lamina lucida with the lamina densa forming the base of the cleft. Diphenylchloroarsine caused lesions histologically indistinguishable from those of PDA. Lesions resulting from exposure to other sulfhydryl-binding compounds were very different from arsenical lesions. The arsenical-sensitive cellular constituents were not identified.
Spontaneous Mesotheliomas in Fischer Rats—A Histological and Electron Microscopic Study
Authors: Tanigawa Hiroyuki , Onodera Hiroshi , Maekawa Akihiko
Published: September 2009

Seventeen mesotheliomas from 395 untreated male Fischer 344/DuCrj rats were studied by light and electron microscopy to define the morphological characteristics of the tumors. In 16 out of 17 rats, mesotheliomas were observed in the abdominal and/or scrotal sac, and the other one was localized on the pleura. Grossly, tumors were yellow-brown with various-sized multiple modules growing irregularly over the surface of the serosa. Microscopically, they varied from complex papillary to sessile nodular growths. Tumor cells were cuboidal to polygonal with round to oval nuclei, and were sometimes arranged in tubule-like structures. Occasionally, the cells contained Mowry's colloidal iron positive materials, which were negative following prior incubation with hyaluronidase. Furthermore, intracellular keratins were detected using the peroxidase-antiperoxidase method. Ultrastructural features of tumor cells included numerous microvilli, a basement membrane, junctional complexes, abundant cytofilaments, dilated rough surfaced endoplasmic reticulum cisternae, and a well-developed Golgi apparatus. The morphological characteristics of these tumors in Fischer 344 rats were consistent with those in humans and with experimentally induced counterparts in rats. The histogenesis of these tumors and the variability in their incidence following oral administration of chemical carcinogens is discussed.
Inhibition by Dehydroepiandrosterone of Liver Preneoplastic Foci Formation in Rats After Initiation-Selection in Experimental Carcinogenesis
Authors: Garcea Renato , Daino Lucia , Pascale Rosa , Frassetto Serenella , Cozzolino Patrizia , Ruggiu Maria E. , Feo Francesco
Published: September 2009

The effect of dehydroepiandrosterone (DHEA) on the development of liver preneoplastic foci was evaluated. The experimental protocol used initiation by diethylnitrosamine (DENA), followed by selective growth induced by partial hepatectomy (PH), in rats fed an N-acetylamino-fluorene (AAF)-containing diet, and followed by a standard diet with or without 0.05% phenobarbital (PB). DHEA (0.6%) was administered in the diet for 4 or 7 weeks after DENA injection (treatments A and B) or for 3 weeks after the end of AAF feeding (treatment C). On the 7th week after DENA injection, DHEA treatments A and C caused slight decrease of body weight and 40–60% increase in liver weight and cell size; number of nuclei per g of liver was not changed. The dietary treatment also caused a marked decrease of liver glucose-6-phosphate dehydrogenase (G6PD) activity and of the percentage of the γ-glutamyltranspeptidase (GGT)-positive liver. PB increased G6PD activity and GGT-positive liver. This effect was oblated by DHEA treatments A and C. On the 7th week, the labeling index (LI) was low in surrounding liver, and high in GGT-positive foci. PB had an enhancing effect, while DHEA treatments A and C were inhibitory. G6PD was low at the end of DHEA treatment B, but it returned to normal values 4 weeks after the end of this treatment. At this time no effect of DHEA treatment B was observed on the extent of GGT-positive liver and LI. The observation that an inhibition of GGT-positive liver formation occurs when DENA is given at the end of the AAF/PH treatment in DENA initiated rats could indicate that the DHEA antipromoting effect depends more on growth inhibition than on interference with carcinogen metabolism.
Lipid Changes Associated with Erythroid Differentiation of Friend Erythroleukemia Cells
Authors: Fallani Anna , Arcangeli Annarosa , Ruggieri Salvatore
Published: September 2009

Friend erythroleukemia cells were induced to differentiate by dimethyl sulfoxide (DMSO) and hexamethylene-bis-acetamide (HBMA) in order to investigate whether their lipid characteristics, common to other systems of transformed cells, revert to a normal differentiation pattern. DBA/2 mouse erythrocytes were examined as a model of terminal differentiation in erythroid lineage. Variants of erythroleukemia cells not inducible to erythroid differentiation by DMSO and HMBA were also used in this study, in order to test whether lipid modifications occurring in differentiated erythroleukemia cells were related to the differentiation process or caused by specific effects of the inducers. Friend erythroleukemia cells showed the same lipid characteristics as those found in other transformed cell types. That is, a high level of ether-linked lipids and low percentages of long chain polyunsaturated fatty acids along with an accumulation of monoenoic fatty acids in phospholipids. These lipid characteristics remained unchanged when erythroleukemia cells were induced to differentiation by either DMSO or HMBA. However, other lipid components of erythroleukemia cells, e.g., phosphatidylethanolamine and triglycerides, were affected by erythroid differentiation. There were also changes of some lipid components of erythroleukemia cells, such as cholesteryl esters, which were related to specific effects of the inducers. Both DMSO- and HMBA-resistant variants differed from the inducible erythroleukemia cells, mainly in their ether-linked phospholipid pattern.
Detection of Free Radical Intermediates in the Oxidative Metabolism of Carcinogenic Hydrazine Derivatives
Authors: Tomasi Aldo , Albano Emanuele , Botti Barbara , Vannini Vanio
Published: September 2009

Hydrazine derivatives are widely used in agriculture, in industry, as rocket propellants, and in medicine. Hydrazines also occur naturally in tobacco and mushrooms. Many hydrazines tested in animal studies appear to be carcinogenic and induce tumors in various target tissues in mice, hamsters, and rats. The use of hydrazine derivatives in humans is of ten complicated by adverse side-effects such as liver injury and rheumatoid arthritis. A number of studies have demonstrated that hydrazine derivatives are activated to reactive intermediates, such as free radicals, through a variety of cellular oxidative metabolic pathways. The aim of this work is to demonstrate the occurrence of free radical intermediates during the metabolic activation of various hydrazine derivatives and to characterize the enzymatic system(s) responsible for the activation to free radical species. The hydrazines studied are acetylhydrazine, isoniazid, isopropylhydrazine, iproniazid, methylhydrazine, 1,1-dimethylhydrazine, and 1,2-dimethylhydrazine. The model systems chosen are those of rat liver microsomes and isolated hepatocytes. Free radical intermediates have been demonstrated by the electron spin resonance spectroscopy coupled to spin trapping technique. The activation mechanism has been characterized using inhibitors of the mixed function oxidase system and of the FAD-dependent oxygenase system. Glutathione was able to scavenge, with high efficiency, the free radicals produced.
The Physical State of Intranuclear Water and Ions: Changes During Cell Proliferation and Chemically Induced Carcinogenesis
Authors: Nicolini Claudio , Carlo Pia , Ridella Sandro
Published: September 2009

The complex dielectric constant of small quantities of liver nuclei in various functional states was measured in the frequency range of 50–2,000 MHz using an Automatic Network Analyzer. From these measurements, through an electric model of macromolecules in solution, several quantities such as ion content, bound water, and free water have been estimated. Unique changes in the physical state of intranuclear water and ions were then apparent in the resting liver nuclei immediately following induced cell proliferation, as compared to nuclei either from early carcinogen-altered hepatocytes or from late selected carcinogen-initiated hepatocytes. Possible implications of these findings are discussed in terms of the molecular events controlling chemically-induced neoplastic transformation.
Certain Aspects of Hepatocarcinogenesis in the Infant Mouse Model
Authors: Vesselinovitch Stan D.
Published: September 2009

The studies related to the kinetics of hepatocarcinogenesis and the effect of sex hormones upon hepatocarcinogenesis have been presented. The objective was to clarify the carcinogen- and time-dependent events leading to the development of liver tumors and the role of sex hormones regarding the rate of development of focal and nodular liver lesions. Kinetics of hepatocarcinogenesis were evaluated in B6C3F1 mice using the mathematical-graphic approach. Low-dose levels (0.0, 0.3125, 0.625, 1.25, 2.5, and 5.0 μg/g body weight) of diethylnitrosamine (DEN) were injected once intraperitoneally into 15-day-old males. Subgroups of 8 to 20 animals were killed from each treatment level at 4 to 6 week intervals. In addition, a series of male and female mice was administered 2.5 μg DEN/kg body weight and a fraction of each sex was gonadectomized. The analysis of dose-response data showed first order kinetics (single event) regarding the induction of intermediate basophilic foci (IBF) and hepatocellular carcinomas (HCC). The difference in the transformation probabilities between these two lesions was of 3 orders of magnitude, indicating a qualitative difference between the original events. Time-dose kinetics showed that twice as many time-dependent events were required for the development of HCC than for the development of IBF. Therefore, the carcinogen influenced not only the nature and degree of initiation of hepatocytes but also programmed the rate of cascading events, and the time being the limiting factor of morphologic expression. In relation to the role of sex hormones, the study demonstrated that the male hormonal environment accelerated and the female hormonal environment delayed the rate of focal morphologic expression and neoplastic progression.
Influence of Dehydroepiandrosterone on G-6-PD Activity and 3H-Thymidine Uptake of Human Lymphocytes In Vitro
Authors: Ennas Maria Grazia , Laconi Sergio , Dessí Sandra , Milia Giovanna , Murru Maria Rita , Manconi Paolo Emilio
Published: September 2009

Dehydroepiandrosterone (DHEA) was found to inhibit experimental cancer development in mouse and rat lung, colon and mammary gland. Since DHEA is a potent inhibitor of mammalian G-6-PD, the hypothesis that the compound could inhibit cell proliferation through an inhibition of the pentose phosphate pathway has been formulated. We studied the effects of DHEA on the proliferation in vitro of human lymphocytes induced by several mitogens (PHA, ConA and PWM), measuring 3H-thymidine uptake. DHEA inhibited 3H-thymidine uptake of mitogen-stimulated cells from both G-6-PD+ and G-6-PD- (mediterranean type deficiency) individuals in a dose-dependent and reversible fashion. The inhibitory effect was found even if DHEA was added to cells in the last hours of culture, simultaneously with the addition of 3H-thymidine. These data suggest that the inhibition of thymidine uptake induced by DHEA on human lymphocytes probably does not depend on the inhibition of G-6-PD.
Structure and Function of the Immune System
Authors: Schultz Kevin T. , Grieder Franziska
Published: September 2009

The major function of the immune system is to protect the host from environmental agents such as microbes or chemicals, thereby preserving the integrity of the body. This is done by the recognition of self and response to non-self. The immune response has been artificially divided into innate immunity (resistance) and specific immunity. Specific immunity is further divided into humoral immunity, the one involved with antibody, and cellular immunity, which is orchestrated by T cells. It is essential to understand that although these divisions have helped in understanding and analyzing the immune response, the system functions as a single unit rather than as a separate entity. In this paper, a simplified analysis of specific immunity will be given. However, the importance of nonspecific immunity, especially as it pertains to its role in preventing exposure of environmental substances, should not be forgotten.
Immunotoxicology: An Overview
Authors: Dean Jack H. , Thurmond Linda M.
Published: September 2009

It is now known that chemicals and drugs may induce selective toxicity which may alter the interactions between immunocompetent cells, especially if the toxicity occurs during proliferation and differentiation. Hence, a flexible panel of sensitive in vivo and in vitro assays has been developed and validated to assess the immunotoxicity or immunopharmacology of suspect agents in rodents. The combined use of such sequential analysis methods with host resistance assays can effectively define immunomodulation following exposure to xenobiotics. Methods development, refinement and validation will be an ongoing requirement because of our rapidly expanding knowledge of the cell biology of the immune system. Classic studies of the comparative preclinical toxicology of several immunosuppressive drugs have substantiated species similarities and have contributed significantly to the development of predictive rodent models for extrapolation to humans. Studies of immunopharmacology and immunotoxicity of cyclosporin A, for example, produced both the desired pharmacology and the undesired toxicity at similar doses in both rodents and humans. When species differences are observed during toxicology studies they are most probably due to differences in absorption, disposition, metabolism, excretion, or delivered dose at the target tissue, rather than major species differences in cellular targets or cell physiology. This assumption is the basis for using rodent species to predict the toxicity of chemicals and drugs under development. The next few years will present novel and exciting challenges to the field of toxicology as safety assessment issues emerge regarding the use of species-specific recombinant biologicals (e.g., growth hormones, interferons, interleukins, tumor necrosis factor, and defined vaccines), biological and biochemical pesticides (e.g., recombinant microbes), immunopharmacologically active drugs, and monoclonal antibody reagents designed as drug delivery or detoxification vehicles. These agents will require the thoughtful application of flexible toxicology protocols designed to reveal whether they are immunotoxic, immunopharmacologically active, or immunogenic. The design of such immunotoxicology studies will be based on an understanding of the potential targets within the immune system and the interactions of chemicals with immunocompetent cells.
The Role of Conventional Pathology and Toxicology in Evaluating the Immimotoxic Potential of Xenobiotics
Authors: Bloom John C. , Thiem Patricia A. , Morgan D. Gwyn
Published: September 2009

Investigating the immunotoxic potential of candidate drugs as part of a preclinical safety evaluation poses several problems. These include the need for practical, validated tests, the difficulty in establishing the toxicologic significance of positive findings, and a poor understanding of the predictive value such findings hold for drug effects in man. A key component of this investigation is the toxicologic profile generated through preclinical toxicity and safety studies. As this “routine” assessment becomes increasingly comprehensive and sophisticated, most toxicologically significant drug-associated effects are revealed. Such findings may serve as “triggers” for investigating possible immune mechanisms. Decisions to test specifically for immunotoxicity may also be influenced by the molecular structure and pharmacologic profile of the compound, as well as the intended use of the drug. Examples of such indications and follow–up studies are discussed in this review. We are presently poorly equipped to effectively screen drugs indiscriminately for an immunotoxic potential. We are better prepared, however, to investigate whether a drug-associated change is due to an adverse effect on the immune system. This problem-oriented approach to immunotoxicology challenges us as diagnosticians and immunopathologists, and requires a close working relationship among the toxicologic pathologist, the basic immunologist, the immunopharmacologist, and the clinician.
Immune Responses in the Central Nervous System
Authors: Griffin Diane E. , Hess Jay L. , Moench Thomas R.
Published: September 2009

Immune responses occurring within the central nervous system (CNS) have unique features attributable to the cellular and functional organization of the CNS and to the presence of the blood-brain barrier. Immune responses to viral infection of the CNS involve the participation of most immunologically important cells: T and B lymphocytes, monocytes, and natural killer cells. Normally, helper/inducer T lymphocytes are predominant in the cerebrospinal fluid (CSF) and in perivascular cuffs. After stimulation with antigen in tissue, these cells produce lymphokines, which stimulate mast cells to open capillary tight junctions, stimulate proliferation of lymphocytes, and attract monocytes and B lymphocytes. B lymphocytes mature into immunoglobulin-producing cells that secrete antibody locally which appears in the CSF. Cytotoxic/suppressor T lymphocytes, which damage antigen-containing cells, are predominant in immunopathologic reactions. In other situations the immune response targets normal CNS tissue rather than foreign antigens. Two general types of reactions may be seen: (1) vasculitis with destruction of vessel walls and infarction, and (2) perivascular inflammation with demyelination. The former is associated with immune complex deposition, and the cellular infiltrate includes polymorphonuclear leukocytes. The inflammation associated with perivenular demye-lination is composed almost exclusively of mononuclear leukocytes. In the diseases for which pathogenetic mechanisms are understood, cells become sensitized to myelin constituents and induce local demyelinating lesions in which the damage is effected by macrophages. It is not clear whether macrophages are directed in this destructive effort by lymphokines or immunoglobulins or both.
Quantitative Immunocytochemistry by Digital Image Analysis: Application to Toxicologic Pathology
Authors: Levine Gary M. , Brousseau Pauline , O'Shaughnessy Donald J. , Losos George J.
Published: September 2009

Recent advances in immunocytochemical techniques allow the localization of specific antigens in tissue sections. The work reported here attempts to evaluate the application of antibody-labeled, disease-related protein, followed by microscopy and computerized image analysis. Using an experimental anti-tumor, polyclonal antibody (anti-oncomodulin) as a model, various tissues were prepared for light microscope immunocytochemistry. Sections were incubated with primary antibody, then biotinylated secondary antibody. This was followed by incubation with avidin-biotin-peroxidase (ABC method). Marker was visualized by the presence of precipitated diaminobenzidine. Samples were evaluated using a Zeiss/Kontron IBAS I & II semi-automatic digital image analysis system. Statistical analyses were performed on output data. Results demonstrated the localization and determined optical density of immunolabel. Statistical comparisons showed significant differences between control and experimental sections. The practical application of these combined techniques provides the toxicologic pathologist with a powerful tool for accurate and objective determination of the location and relative amount of selected proteins in normal and abnormal tissues.
Experimental T-2 Toxicosis in Swine Following Inhalation Exposure: Effects on Pulmonary and Systemic Immunity, and Morphologic Changes
Authors: Pang Victor F. , Lambert Richard J. , Felsburg Peter J. , Beasley Val R. , Buck William B. , Haschek Wanda M.
Published: September 2009

Thirty-four, 9-to 11-week-old, male castrated, crossbred, specific pathogen-free derived pigs were exposed to a T-2 toxin aerosol at a nebulized dose of 0 or 9 mg/kg in pairs, each pair consisting of 1 control and 1 T-2 treated pig which were exposed on the same day. Twenty to 30% of the toxin (1.8 to 2.7 mg/kg) was retained by the pigs. Five pairs were killed on each of 1, 3 and 7 days after dosing. Two pairs of pigs were designated as a 0.33-day group when one T-2 treated pig died and the other was killed in a moribund state at 8 to 10 hours after dosing. The pulmonary and systemic immunity and morphologic changes of the lungs and other organs were examined. Bronchoalveolar lavage was performed to obtain alveolar macrophages (AM) and pulmonary lymphocytes (PL). The phagocytic ability of AM and mitogen-induced blastogenic responses of enriched PL and peripheral blood lymphocytes were evaluated. Clinically, all of the T-2 treated pigs vomited and were cyanotic, anorexic, lethargic and laterally recumbent. In the 0.33-, 1-, and 3-day T-2 treated pigs, there was a marked reduction in AM phagocytosis and mitogen-induced blastogenic responses of PL but not of peripheral blood lymphocytes. Mild to moderate, multifocal interstitial pneumonia was seen in the majority of the T-2 treated pigs. In pigs dying following inhalation of T-2 toxin, there was a more severe pneumonia, as well as marked necrosis of lymphoid tissues, severe necrohemorrhagic gastroenteritis and edema of the gall bladder wall, and multifocal necrosis of the heart and pancreas. Thus, inhalation exposure to T2 toxin can result in clinical signs and morphologic changes resembling those reported previously in pigs given T-2 toxin intravascularly (iv) at a dose of 1.2 mg/kg (approximate LD50) or greater, as well as death. Mild pulmonary injury as well as transient impairment of pulmonary immunity was present in pigs surviving inhalation exposure.
The Immunopharmacology of Immunotoxicology, and Immunorestoration
Authors: Caspritz Gert , Hadden John
Published: September 2009

The first part of this paper focuses on the secondary immunodeficiencies caused by immunosuppressive drugs and environmental chemicals. The mechanism of action and the therapeutic effects of azathioprine, glucocorticosteroids, cyclophosphamide, cyclosporin A, and anticancer drugs will be discussed. The immunotoxic actions of benzene, polychlorinated and polybrominated biphenyls, tetrachlorodibenzo-para-dioxin, polycyclic aromatic hydrocarbons, various insecticides, metals and abused drugs or drugs with side effects are also described. Immunorestorative approaches are discussed in the second part, based on our current knowledge of the immune system and the lymphokines and hormones involved in its function. The usefulness of thymic hormones, interleukin 2, macrophage growth factor/colony stimulating factor, and interferons as immunotherapeutic agents is considered. In addition, we address chemically defined drugs, such as levamisole, diethyldithiocarbamate, isoprinosine, muramyl dipeptides, azimexon, ciamexon, bestatin, tuftsin, and pyrimidinoles, and finally conclude that combined use of different immunostimulants may be the most effective way to treat the above mentioned immunodeficiencies.
Carcinogenicity Studies with Medroxalol Hydrochloride in Rats and Mice
Authors: Sells Donald M. , Gibson John P.
Published: September 2009

The carcinogenic potential of medroxalol hydrochloride, an antihypertensive agent with β1 adrenergic cardiac blocking properties, and β2 and some α1 vasodilating activity, was studied by dietary administration. Long Evans rats were treated for 2 years and CD-1 mice for 18 months at dosages of 0, 50, 250 or 500 mg/kg/day. Medroxalol did not produce any evidence of a tumorigenic effect in the Long Evans rat, but graying of pigmented hair was noted at 250 and 500 mg/kg/day and is probably related to melanin binding of the drug. In the CD-1 mouse, there was a dose related increase in uterine leiomyomas that was statistically significant ( p < 0.05) at doses of 250 and 500 mg/kg/day. The incidence at 50 mg/kg/day was not different from control. Endometrial stromal sarcomas were observed only in treated mice, and pairwise comparison with controls indicated a statistically significant difference ( p < 0.05) only at the lowest dosage (50 mg/kg/day). The latter finding may not be related to treatment since there was no dose response and the incidence in the two higher dose groups was neither statistically significant nor higher than occasionally seen in other control groups.
2,2,2-Trifluoroethanol Toxicity in Aged Rats
Authors: Kim James C. S. , Kaminsky Laurence S.
Published: September 2009

Various anesthetics are metabolized by different forms of cytochrome P-450 yielding the same toxic metabolite, 2,2,2-trifluoroethanol (TFE). The. toxicity of TFE is a consequence of its metabolism catalyzed by cytochrome P-450. Since a marked age difference exists in the composition and inducibility of the hepatic mixed function oxidase system, we have elucidated the toxicity of TFE in 36-month-old aged Wistar rats. The aged rats were injected with sublethal doses of TFE (0.10 g/kg once per week for 5 weeks), after which they were sacrificed for pathologic examination. The major TFE-related lesions observed were severe hepatocyte degenerative changes such as basophilic, eosinophilic, vacuolated hepatocytes, bile duct hyperplasia, accumulation of lipofuscin pigments, and preneoplastic nodules. Other changes seen were the hyalinization of gastric submucosal wall, generalized testicular atrophy due to the loss of seminiferous tubules, coagulation necrosis of intestinal mucosal wall, hyperpigmentation, and more advanced and severe chronic progressive glomerulonephropathy in the TFE-treated rats. More severe lipofuscin and vacuolation of white matter of thalamic area, pons, midbrain, and cerebellum reflective of enhanced aging were also seen. Ultrastructural studies of liver from TFE-treated rats revealed rather diffuse loss of glycogen, fragmentation of endoplasmic reticulum, mineralization of mitochondria, and loss of other organelles within the hepatocytes versus salinetreated aged rats. Hepatic cytochrome P-450 concentrations, measured as a possible index of endoplasmic reticulum damage, were not affected by TFE administration.
Intestinal and Hepatobiliary Disposition of Drugs
Authors: Klaassen Curtis D.
Published: September 2009

Biliary excretion of xenobiotics is a complex process involving uptake into liver, intracellular sequestration and/or biotransformation, and transport into bile. A description of liver morphology is included to aid in the understanding of how chemical and physiological factors affect hepatic uptake and biliary excretion. Data will be presented with morphine and nalorphine that illustrate how efficient the intestinal and hepatobiliary system is in clearing drugs from the body. However, enterohepatic circulation can interfere with these processes.
Mucosal Biotransformation
Authors: Schwenk Michael
Published: September 2009

About 4 million compounds have been described by chemists, and some 60,000 are presently on the market. The search for new chemicals with better properties and less toxicity continues, and future life quality will depend on our ability to find the safest compounds in each field of application. During development of new drugs and chemicals, studies on biotransformation should be done very early, and with adequate analytical tools, in order to get an early understanding of data on bioavailability, metabolic pattern, and toxicity. Though the liver is generally the organ with the highest drug metabolizing activity, it becomes increasingly evident that some extrahepatic organs, such as intestine, kidney, skin, and lung also participate in drug metabolism (17). The peculiar property of intestinal metabolism is the fact that it modifies chemicals before they enter the circulation. Therefore, an understanding of intestinal metabolism is important for proper interpretation of all pharmacological and toxicological data during development of a new compound. Mucosal biotransformation has recently been reviewed (14, 33, 34, 43, 60). The present work gives a schematic survey on the topic, shows new trends, and discusses the consequences for toxicological testing of new chemicals.
Forestomach Carcinogens: Pathology and Relevance to Man
Authors: Wester Peter W. , Kroes Robert
Published: September 2009

Squamous cell carcinomas of the forestomach have been observed in many carcinogenicity studies in rodents, especially after oral or gavage exposure. The histopathological diagnosis of forestomach lesions and the relevance of the data for human risk estimation can be controversial. The pathological classification may be troublesome because of the low-grade malignancy and the pseudoepitheliomatous hyperplasia that may develop after ulceration and inflammation. For human risk estimation it is important to understand the mechanism of action; this is illustrated by examples using butylated hydroxyanisole, methyl bromide, and epichlorohydrin. Another feature that complicates risk estimation is the absence of a homologue for the forestomach in man. The potential risk from non-genotoxic forestomach carcinogens in man involves exposure of the mouth, pharynx, and esophagus at dose levels that exert irritating action. It is assumed that exposure to non-genotoxic chemicals at concentrations far below those having irritating potential is not hazardous to humans.
Forestomach Lesions Induced by Butylated Hydroxyanisole and Ethylene Dibromide: A Scientific and Regulatory Perspective
Authors: Moch Ronald W.
Published: September 2009

Selected pathology lesions from 9 studies, 5 with butylated hydroxyanisole (BHA) and 4 with ethylene dibromide (EDB) are reviewed and their relative importance in regulatory evaluation is discussed. When Fischer 344 (F344) rats were fed BHA at 0.5% and 2.0% of the diet for 2 years, an increased number of rats of both sexes had epithelial hyperplasia of the forestomach at both treatment levels, compared to controls. At the 2.0% level, an increased number of rats had forestomach papilloma or forestomach squamous cell carcinoma. In a second study, in which F344 rats were fed BHA at 1.0% and 2.0% of the diet for 2 years, increased numbers of rats in both treatment groups were reported to have hyperplasia or papilloma of the forestomach. At the 2.0% level, increased numbers of rats developed squamous cell carcinoma of the forestomach. More Syrian golden hamsters fed BHA at 1.0% and 2.0% of the diet for 2 years reportedly had hyperplasia, papilloma or squamous cell carcinoma of the forestomach than did nontreated animals. Ingestion of BHA at 0.5% and 1.0% of the diet by B6C3F1 mice for 2 years was reported to produce an increase of animals with hyperplasia or papilloma of the forestomach at both dosage levels, compared to nontreated mice. When beagle dogs were fed BHA at 1.0% and 1.3% of the diet for 180 days, no lesions/tumors of the distal esophagus or stomach were identified at gross necropsy or by light or electron microscopy. When EDB was administered by gavage to Osborne-Mendel rats and B6C3F1 mice under conditions of the National Toxicology Bioassay Program, more rats and mice, both male and female, developed squamous cell carcinoma of the forestomach than did nontreated groups. EDB administered via inhalation to F344 rats and B6C3F1 mice did not cause squamous cell carcinoma of the forestomach; however, other neoplasms occurred which were considered to be treatment-related. Information gleaned from the BHA and EDB studies with multiple animal species facilitated regulatory decision-making regarding the potential toxicity/carcinogenicity of these compounds to man.
The Influence of Food Additives and Related Materials on Lower Bowel Structure and Function
Authors: Newberne Paul M. , Conner Michael W. , Estes Paul
Published: September 2009

Food additives, drugs, and other chemicals are known to influence the lower gastrointestinal tract under some defined conditions, resulting in morphological alterations in the mucosa and other tissues, deranged absorption and excretion of nutrients, and, in some cases, injury to other organs and tissues as a secondary phenomenon. Generally, in rats, hamsters, and dogs, there is increased absorption and urinary excretion of calcium, soft stools or diarrhea, and cecal enlargement. In the rat, hamster, and dog, renal lesions accompany the hypercalcemia and elevated excretion of calcium. These signs, symptoms, and lesions are typical of exposure to sugar alcohols (sorbitol, mannitol, xylitol, lactitol), lactose and caramel, some of the chemically modified food starches, and synthetic polydextrose. Soft stools and diarrhea, as well as cecal enlargement and variable hyperplasia of the colon mucosa, occur frequently when substances are absorbed incompletely in the small intestine and subjected to microbial metabolism in the cecum and colon. The remarkable cecal enlargement, mucosal hyperplasia and, when present, colonic mucosal hyperplasia are reversible, even when long-standing. Renal lesions are reversible only if exposure is of short duration, before significant mineralization and scarring has occurred. Morphological and functional anomalies associated with some of these substances are described and illustrated.
Intestinal Cancer Induced by N-Nitroso Compounds
Authors: Lijinsky William
Published: September 2009

Several N-nitroso compounds induce tumors of the colon, and some induce tumors in other parts of the intestinal tract as well. The nitrosamines that induce colon tumors are beta oxidized n-propyl-nitrosamines. These require metabolic activation, as do 1,2-dimethylhydrazine, azomethane, and azoxymethane, another group of colon carcinogens. Several nitrosoalkylureas induce tumors in rat colons after oral administration, although the monoalkylnitrosoureas are fairly unstable and might not be expected to reach the colon. However, monoalkylnitrosoureas are equally effective with the much more stable dialkylnitrosoureas. Although nitrosomethylurea did not induce colon tumors under these conditions, nitrosoethylurea did, together with nitrosodiethylurea and other nitrosoethylalkylureas. Nitroso-n-butyl-, n-amyl-, n-hexyl-urea, and nitrosohydroxyethylurea also induced colon tumors, but the last, like nitrosoethylurea, also induced tumors of the duodenum and ileum. In most of these experiments male rats were more susceptible to induction of intestinal tumors than female rats. An explanation for the differences between these compounds of similar structure might be found in variations in their ability to alkylate DNA in intestinal cells, or in differences in stability of the alkylated product between the compounds. The physical properties of the compounds might also modulate the process of carcinogenesis, however.