Biomedical subjects

M R Elwell

Publications and source records attributed to M R Elwell.

At least 19 recordsLinked to original sources

PubMed1999

Toxicology and humoral immunity assessment of octamethylcyclotetrasiloxane (D4) following a 28-day whole body vapor inhalation exposure in Fischer 344 rats.

Octamethylcyclotetrasiloxane, D4, is a low viscosity, silicone fluid consisting of four dimethyl-siloxy units ((CH3)2SiO)4 in a cyclic structure. It is primarily used as a building block in the industrial synthesis of long chain silicone polymers. The combination of D4 with decamethylcyclopentasiloxane (D5) is commonly referred to as cyclomethicone which has a wide range of applications as a formulation aid in personal care products. To extend the existing database regarding the biological activities of D4, a 28 day whole body vapor inhalation study was conducted using Fischer 344 rats at 0 (room air), 7, 20, 60, 180 and 540 ppm for 6 hours/day, 5 days/week. Parameters measured included body weights, organ weights, gross pathology, histopathology, serum chemistries, and urinalysis. In addition to these standard toxicological endpoints, the ability of D4 exposed animals to mount an IgM antibody response was evaluated by a splenic antibody forming cell (AFC) assay and a serum enzyme-linked immunosorbant assay (ELISA). The results of this 28-day inhalation study indicate that D4 exposure caused no adverse effects on body weight, food consumption, or urinalysis parameters. In addition, there were no exposure related histopathological alterations at any site for any exposure group. A statistically significant increase in liver weight and the liver to body weight ratio was observed in both male (180-540 ppm) and female (20-540 ppm) rats, which was not observed in the 14-day recovery group animals. There were no other significant organ weight changes. Although statistically significant changes were observed in several hematological and serum chemistry parameters in both the terminal and 14-day recovery animals, the changes were marginal and within the normal range of values for the rat. Under these experimental conditions, there were no alterations noted in immune system function at any of the D4 exposure levels.

Adjuvants, Immunologic↗

PubMed1998

Lipopolysaccharide augments IgG and IgE responses of mice to the latex allergen Hev b 5.

BACKGROUND: LPS is a common contaminant in the health care environment and in latex examination gloves. OBJECTIVE: We sought to investigate the role of LPS in enhancing the immune responses of mice to inhaled latex allergen. METHODS: As our model allergen, we used a fusion protein containing the potent latex allergen Hev b 5. BALB/c mice were lightly anesthetized and given repeated intranasal doses of saline, LPS, and/or Hev b 5. The doses were given in 2 courses separated by a 6-week period, with the first course consisting of 6 doses and the second consisting of 3 doses. RESULTS: After the first set of immunizations, mice given Hev b 5 alone had no detectable IgG1 or IgE responses to Hev b 5, whereas mice given the antigen along with LPS had significant responses (IgG1, 0.73 U +/- 0.05; IgE, 0.88 U +/- 0.2). No enhancement of specific IgG2a was observed. A stimulatory effect of LPS on all 3 immunoglobulin types was apparent after the second course. Lymphocytes from mice immunized with LPS and Hev b 5 had increased proliferation to Hev b 5 and its fusion partner. CONCLUSIONS: LPS may be an important immunoadjuvant for the development of allergic reactions to latex protein allergens.

Adjuvants, Immunologic↗

PubMed1997

The effects of dietary boron on bone strength in rats.

Previous studies from our laboratory found that when boric acid (BA) was administered in the diet to rats, boron levels in bone were approximately fourfold greater than serum levels. The current studies were undertaken to determine if these elevations produced adverse effects on several bone-related measures, including serum electrolyte levels, bone structure, and bone strength. Data from two studies are presented: in the first study, young adult male rats consumed a powdered diet containing 0, 3000, 4500, 6000, or 9000 ppm BA for 9 weeks. Endpoints were serum calcium, phosphorous, potassium, and chloride, as well as blood and bone boron concentrations ([B]) measured weekly during the 9-week exposure period, and at 8, 16, 24, and 32 weeks after the end of exposure. In the second study, the male and female young adult rats diet contained 0, 200, 1000, 3000, or 9000 ppm BA for 12 weeks; endpoints measured weekly were serum levels of calcium, phosphorous, and magnesium, bone [B], and bone structure (humerus) and strength (tibia, femur, and lumbar vertebrae). In treated rats, calcium was reduced in the first study but not the second. Serum phosphorous was reduced in both studies; potassium was unchanged, chloride was increased by 1%, and magnesium was reduced in all BA-exposed groups in the second study, to a maximal 19% reduction. Bone [B] was consistently increased in all treated groups, to concentrations approximately fourfold those of serum. After cessation of exposure, serum and urinary boron concentrations dropped to within control values within a week. However, even 32 weeks after the end of exposure, bone [B] remained threefold greater than controls. Male tibia and femur resistance to bending was unchanged. However, vertebral strength in compression was significantly increased by 5-10% in all dose groups (200 to 9000 ppm). The pattern was substantially similar in females. Only the humerus was examined by light microscopy and was found to be unchanged at any level of BA consumption. These data show that, despite a reduction in some serum electrolyte levels, BA consumption increased vertebral resistance to crush force, without detectably altering the microscopic structure of the humerus or the resistance of femur and tibia to a bending load. This increase in compression resistance occurred at exposure levels substantially below those that were previously reported to be reproductively toxic.

Animals↗

PubMed1997

Comparative pulmonary absorption, distribution, and toxicity of copper gallium diselenide, copper indium diselenide, and cadmium telluride in Sprague-Dawley rats.

Copper gallium diselenide (CGS), copper indium diselenide (CIS), and cadmium telluride (CdTe) are novel compounds used in the photovoltaic and semiconductor industries. This study was conducted to characterize the relative toxicities of these compounds and to evaluate the pulmonary absorption and distribution after intratracheal instillation. Female Sprague-Dawley rats were administered a single equimolar dose (70 mM) of CGS (21 mg/kg), CIS (24 mg/kg), CdTe (17 mg/kg), or saline by intratracheal instillation. Bronchoalveolar lavage fluid (BALF) protein, fibronectin, inflammatory cells, lung hydroxyproline, and tissue distribution were measured 1, 3, 7, 14, and 28 days after instillation. Relative lung weights were significantly increased in CIS- and CdTe-treated rats at most time points. Inflammatory lesions in the lungs consisting of an influx of macrophages, lymphocytes, and PMNs were most severe in CdTe-treated rats, intermediate in CIS-treated rats, and minimal in rats receiving CGS. Hyperplasia of alveolar type 2 cells was present in CIS- and CdTe-treated rats and was greatest in CdTe-treated rats. Pulmonary interstitial fibrosis was observed in CdTe-treated rats at all time points. All three compounds caused marked increases in total BALF cell numbers, with the greatest increase observed in CIS-treated rats. BALF protein, fibronectin, and lung hydroxyproline were significantly increased in all treated animals and were highest in CdTe-treated animals. There was no apparent pulmonary absorption or tissue distribution of CGS. Indium levels increased in extrapulmonary tissues of CIS-treated rats, although Cu and Se levels remained unchanged. CdTe was absorbed from the lung to a greater extent than CGS and CIS. Cd and Te levels decreased in the lung and increased in extrapulmonary tissues. Of these compounds CdTe presents the greatest potential health risk because it causes severe pulmonary inflammation and fibrosis and because it is readily absorbed from the lung may potentially cause extrapulmonary toxicity.

Absorption↗

PubMed1997

Effects of the carcinogen, acrylonitrile, on forestomach cell proliferation and apoptosis in the rat: comparison with methacrylonitrile.

Acrylonitrile (AN) and methacrylonitrile (MAN) are two major industrial nitriles used in the production of plastics and acrylic fibers. Whereas AN is a potent acute toxin and carcinogenic in rats, little is known regarding MAN. Current work is part of an overall effort designed to assess the potential toxicity/carcinogenicity of MAN. The present study compares the ability of the two chemicals to induce epithelial proliferation and apoptosis in the forestomach (FS; a target of AN carcinogenicity), liver and glandular stomach (non-targets of AN carcinogenicity) of male F344 rats. AN was administered to rats daily, by gavage, for 6 weeks, at 0.43 and 0.22 mmol/kg. MAN was administered at 0.87 and 0.43 mmol/kg. Both AN and MAN induced a dose-dependent increase in epithelial cell proliferation in the FS of male F344 rats as determined by bromodeoxyuridine (BrdU) incorporation into DNA. In contrast, AN, but not MAN caused a dose-dependent increase in the thickness of the forestomach squamous mucosa. This increased thickness (hyperplasia) was reflected by an increase in the number of total epithelial cells per unit length of mucosa. At doses of AN and MAN which induced a 2.3-fold increase in BrdU incorporation, apoptosis was 5- and 18-fold greater than controls, respectively. Although both MAN and AN caused a similar increase in cell proliferation, the relatively more prominent increase in the apoptotic index of the squamous epithelium of rats exposed to MAN may explain the lack of a detectable increase in the thickness of the mucosa compared to that seen with AN. The disruption of the balance between FS mucosal cell proliferation and apoptosis in favor of a net increase in the number of FS epithelial cells per unit length may contribute to the carcinogenicity of AN. In conclusion, present work demonstrated that AN selectively induced a net enhancement in FS cell proliferation, a site of its carcinogenicity. On the other hand, MAN-induced FS cell proliferation was associated with a parallel increase in apoptosis. The relatively greater increase in apoptosis by MAN may have compensated for the increase in FS mucosal cell proliferation and the lack of observable change in the FS thickness.

Acrylonitrile↗

PubMed1996

Effects of D&C yellow no. 11 ingestion on F344/N rats and B6C3F1 mice.

D&C yellow no. 11 (CAS no. 8003-22-3) was administered in the feed at concentrations of 500-50,000 ppm to groups of F344/N rats and B6C3F1 mice of each sex for 13 wk to determine the toxicity. In addition, a perinatal study was conducted to determine the effects of feeding diets containing D&C yellow no. 11 to female rats during reproduction and to their offspring. Although the estimated intake (g/kg) of D&C yellow no. 11 of mice was more than twice that of rats, the results were generally similar for both rats and mice. In both species, D&C yellow no. 11 caused no mortality, but it did reduce body weight gain slightly in both sexes of rats exposed to 17,000 and 50,000 ppm. Absolute and relative liver weights were significantly increased in all groups of rats and mice administered D&C yellow no. 11 in the feed. There was minimal to mild degeneration of the periportal hepatocytes in rats at doses of 1700 ppm and higher and in mice at 5000 ppm and above. A dose-related yellow-brown pigment was observed in hepatocytes, Kupffer cells, and biliary epithelium of the liver of both sexes of both species and in the renal tubule epithelium in both sexes of rats. In male rats, all treated groups had increased number and size of hyaline droplets in the renal tubule epithelium of the cortex and outer medulla. To determine if these renal and hepatic lesions were reversible, male rats were administered 5000 ppm dietary D&C yellow no. 11 for 70 d and then examined at 3, 14, and 28 d after the chemical was removed from the diet. Pigment persisted in the kidney and liver for as long as 28 d following removal of D&C yellow no. 11 from the diet, but hepatocellular degeneration and cytoplasmic alteration in the kidney completely resolved by d 3 and 14, respectively. In the perinatal toxicity study, body weight gain in rat dams given diets containing as much as 50,000 ppm D&C yellow no. 11 for 4 wk before mating to untreated males was similar to that of controls at the time of mating but was lower at parturition and weaning. However, fertility, gestation length, litter size, and pup birth weights were unaffected by treatment. At weaning, there was a significant dose-related decrease in pup body weights from the 5000, 17,000, and 50,000 ppm groups. At 8 wk of age, pups fed the same dosed-feed concentrations as the dams had depressed body weights in the 17,000 and 50,000 ppm treated groups. Microscopic lesions in the liver and kidney of the pups in all dose groups were similar to those described in the 13-wk study. The results of these studies indicate that compound-related effects occurred at all dietary concentrations of D&C yellow no. 11. Liver weights were increased in dosed rats and mice, minimal to mild hepatocellular degeneration was seen in rats receiving dietary concentrations of 1700 ppm and above and in mice at 5000 ppm and above, and there was an increase in the number and size of hyaline droplets in all dosed groups of male rats. Similar compound-related effects were also seen in all dosed rats in the perinatal toxicity study. With the exception of pigment accumulation, the treatment-related kidney and liver lesions in male rats were reversible by 14 d after chemical was withdrawn from the diet.

Administration, Oral↗

PubMed1996

Decreased incidence of spontaneous mammary gland neoplasms in female F344 rats treated with amphetamine, methylphenidate, or codeine.

Three drugs that affect the neuroendocrine system (amphetamine, methylphenidate, and codeine) caused decreases in body weights and in the incidence of spontaneously occurring mammary gland neoplasms in the female F344/N rat in 2-year carcinogenicity studies. Using a mathematical model that relates body weight changes to the incidence of mammary gland neoplasms, we find that the decrease in mammary gland tumours seen in female rats cannot be fully explained by body weight decreases relative to control animals. Further, the observed decreases in body weight in treated female rats were not a function of differences in feed consumption between treated and control groups. These pharmaceuticals are thought to affect the biologic system through interaction with membrane receptors. This interaction and/or subsequent cell signaling events may play a role in the observed decrease in spontaneously occurring mammary gland neoplasms in the female rat treated with amphetamine, methylphenidate, or codeine.

Amphetamine↗

PubMed1996

Toxicity of inhaled chloroprene (2-chloro-1,3-butadiene) in F344 rats and B6C3F(1) mice.

Chloroprene (2-chloro-1,3-butadiene) is a high production chemical used almost exclusively in the production of polychloroprene (neoprene) elastomer. Because of its structural similarity to isoprene (2-methyl-1,3-butadiene) and to 1,3-butadiene, a potent trans-species carcinogen, inhalation studies were performed on chloroprene to characterize its toxicological potential and to provide a basis for selecting exposure concentrations for chronic toxicity and carcinogenicity studies. Thirteen-week inhalation toxicology studies were conducted in male and female F344 rats and B6C3F(1) mice at exposure concentrations of 0, 5, 12, 32 or 80 ppm (6 h/day; 5 days/week). A 200 ppm exposure group was also included for rats only, because a previous study showed that this concentration of chloroprene is lethal to mice. In mice, exposure to 80 ppm chloroprene caused a marginal decrease in body weight gain in males and epithelial hyperplasia of the forestomach in males and females. This lesion has been observed in mice exposed to isoprene or 1,3-butadiene. In rats, exposure to 80 ppm chloroprene or higher concentrations caused degeneration and metaplasia of the olfactory epithelium and exposure to 200 ppm caused anemia, hepatocellular necrosis and reduced sperm motility. These lesions have not been observed in rats exposed to isoprene or 1,3-butadiene. The profile of toxic effects of chloroprene is considerably different from that of isoprene or 1,3-butadiene; this may be due to differences in exposure concentrations that were used in toxicology studies of these compounds and /or to the influence of the chlorine substitution on the toxicokinetics of these compounds, on their biotransformation, or on the reactivity of metabolic intermediates with tissue macromolecules.

Administration, Inhalation↗

PubMed1996

Frequency and relationships of clinical chemistry and liver and kidney histopathology findings in 13-week toxicity studies in rats.

The relative sensitivities of eight commonly used clinical chemistry end points and histopathology to detect potential toxic effects in liver and kidney were evaluated for a series of 61 13-week rat toxicity studies conducted for the National Toxicology Program. The data consisted of 1-,2- to 3-, and 13 week clinical chemistry measurements and 13-week histopathological assessments of liver and kidney. Except for serum alkaline phosphatase, treatment-related alterations of individual clinical chemistry variables occurred in 20-48% of the studies, depending on the analyte, sampling time, and sex. Liver and kidney lesions were reported for 31% and 41% of the studies respectively. There was an association between treatment-related increases in alanine aminotransferase (ALT) and sorbitol dehydrogenase (SDH) activities and histopathological changes in the liver. SDH activity had greater positive and negative predictive values than similar changes in ALT; by week 1 in females and weeks 2-3 in both sexes. SDH predicted morphological hepatic change at study termination with 75% or better accuracy. If increases in activities of both enzymes occurred simultaneously, however, terminal histopathological changes could be predicted, in both sexes, with 75% accuracy by week 1, increasing to 100% by weeks 2-3. There also was an association between treatment-related increases in urea nitrogen (UN) and creatinine (Cre) concentrations and morphological kidney change. Cre concentration had greater positive predictive values than similar changes in UN; by weeks 2-3 in males and week 13 in both sexes. Cre predicted morphological renal change at study termination with 56% or better accuracy. UN concentration was associated and predictive of morphological kidney change only in females at week 13. Depending on time point and sex, serum alkaline phosphatase activity increased in 5-22% of the studies. Increases in total bile acid concentration occurred in 33-48% of the studies. Because both tests are used as markers of cholestasis, this marked discrepancy was unexpected. Treatment-related decreases in alkaline phosphatase activity occurred, however, in 39-56% of the studies; serum alkaline phosphatase may be more useful as an indicator of decreased food intake (decreased activity) than of cholestasis (increased activity). In summary, treatment-related alterations of clinical chemistry and histopathology occurred frequently in this series of toxicity studies in rats. Changes in the chemistry end points also occurred frequently at interim time points, indicating that clinical chemistry evaluations can be useful for detecting potential treatment effects throughout a study. This observation is important, since histopathological evaluations are limited to animal termination and not useful for detecting transient responses or the onset of treatment-related effects.

Alanine Transaminase↗

PubMed1996

Evaluation of false positive and false negative outcomes in NTP long-term rodent carcinogenicity studies.

The decision-making process used by the National Toxicology Program (NTP) in its evaluation of long-term rodent carcinogenicity studies was investigated to determine whether or not this procedure resulted in an excessive number of false positive or false negative outcomes. All site-specific tumor incidences that were found to be significantly (p < 0.05) increased either by a trend test or by pairwise comparisons of each dosed group against the controls in 218 NTP 2-year studies with Fischer 344 rats and/or B6C3F1 mice were tabulated and compared to the number of statistically significant tumor increases expected to occur by chance. Our evaluation suggests that false positive rates are fairly low in NTP long-term studies. Assessing false negative rates is more difficult because of the limited sensitivity of the bioassay for detecting subtle carcinogenic effects. Moreover, reduced body weights frequently occur in dosed animals, and the positive correlation between the incidences of certain site-specific tumors and body weight may mask the detection of carcinogenic effects. Despite these difficulties, our analysis did identify one tumor showing evidence of false negative outcomes: interstitial cell tumors of the testis in male Fischer 344 (F344) rats. This tumor showed considerably more significant (p < 0.05) increased incidences than expected by chance, yet none were considered to be chemically-related. However, the biological significance of interstitial cell tumor increases in F344 rats is uncertain because of the high background rate of neoplasia (> 90%) for this target site.

Animals↗

PubMed1995

Comparative carcinogenic effects of nickel subsulfide, nickel oxide, or nickel sulfate hexahydrate chronic exposures in the lung.

The relative toxicity and carcinogenicity of nickel sulfate hexahydrate (NiSO4.6H2O), nickel subsulfide (Ni3S2), and nickel oxide (NiO) were studied in F344/N rats and B6C3F1 mice after inhalation exposure for 6 h/day, 5 days/week for 2 years. Nickel subsulfide (0.15 and 1 mg/m3) and nickel oxide (1.25 and 2.5 mg/m3) caused an exposure-related increased incidence of alveolar/bronchiolar neoplasms and adrenal medulla neoplasms in male and female rats. Nickel oxide caused an equivocal exposure-related increase in alveolar/bronchiolar neoplasms in female mice. No exposure-related neoplastic responses occurred in rats or mice exposed to nickel sulfate or in mice exposed to nickel subsulfide. These findings are consistent with results from other studies, which show that nickel subsulfide and nickel oxide reach the nucleus in greater amounts than the do water-soluble nickel compounds such as nickel sulfate. It has been proposed that the more water-insoluble particles are phagocytized, whereas the vacuoles containing nickel migrate to the nuclear membrane, where they release nickel ions that effect DNA damage. The findings from these experimental studies show that chronic exposure to nickel can cause lung neoplasms in rats, and that this response is related to exposure to specific types of nickel compounds.

Animals↗

PubMed1995

Development and persistence of placental glutathione-S-transferase-positive foci in livers of male F344 rats exposed to o-nitrotoluene.

In a previous 13-week study of o-nitrotoluene, a chemical-related increase in liver weight, hepatocellular vacuolization, and oval cell hyperplasia in male F344 rats was reported. In this study, the occurrence and change in number and size of hepatic foci in male F344 rats fed a diet containing 5000 ppm o-nitrotoluene or a control diet for 13 weeks, 26 weeks, and 13 weeks followed by a 13-week recovery period (26-week stop-exposure) were evaluated. The livers were stained immunohistochemically for placental glutathione S-transferase (PGST), a marker of hepatic preneoplasia, and quantified stereologically using computer-assisted image analysis. Exposure to o-nitrotoluene induced PGST-positive (PGST-positive (PGST+) liver foci in all treatment groups. The 26-week continuous-exposure group produced more PGST+ liver foci (961.4 foci/cm3 versus 445.4 foci/cm3) and greater mean focus volume (4.34 microns3 versus 1.34 microns3) than the 13-week continuous-exposure group. In the 26-week stop-exposure group, there were fewer PGST+ liver foci (181.4 foci/cm3) than observed with continuous exposure at 13 weeks or 26 weeks; however, the mean focal volume in the stop-exposure group at 26 weeks (5.33 microns3) was greater than that at 13 weeks (1.34 microns3) or 26 weeks of continuous exposure (4.34 microns3). These findings demonstrate that (1) PGST+ foci are observed after only 13 weeks of exposure to o-nitrotoluene; (2) the number and size of foci increase with continued exposure for 26 weeks; and (3) although the number of PGST+ foci decreases with time after chemical exposure is discontinued, many PGST+ foci do not regress but increase in size during the recovery of 13 weeks. The persistence and increase in size of these foci, even in the absence of chemical exposure, suggest the potential for a hepatocarcinogenic effect in long-term studies for o-nitrotoluene.

Animals↗

PubMed1995

Induction of thymic lymphoma in mice administered the dideoxynucleoside ddC.

Groups of 10 male and 20 female B6C3F1 mice received 0, 500, or 1000 mg/kg/day 2'3'-dideoxycytidine (ddC) by gavage for 13 weeks. At the end of the 13-week exposure period all males and 10 females per group were necropsied while the remaining females were held for 1 month without further treatment. Thymic atrophy was present at the 13-week necropsy in male and female mice administered 1000 mg/kg/day and in females administered 500 mg/kg/day, but was not present in females following 1 month of recovery. Thymic lymphoma was present in 1 female that received 500 mg/kg/day and 1 female that received 1000 mg/kg/day. In a follow-up study groups of 70 female mice received 0, 500, or 1000 mg/kg/day for 13 weeks. At the end of the 13-week exposure period 20 mice per group were necropsied and the remaining animals held for 3 months without further treatment. Thymic atrophy was observed in ddC-exposed groups at the 13-week necropsy but not in mice allowed to recover for 13 weeks. Thymic lymphoma occurred in 3/50 mice that received 500 mg/kg/day and in 17/50 mice that received 1000 mg/kg/day but did not occur in mice from the vehicle control group.

Animals↗

PubMed1995

Early changes in sex hormones are not evident in mice exposed to the uterine carcinogens chloroethane or bromoethane.

Chloroethane and bromoethane have been shown to cause a marked uterine tumor response in B6C3F1 mice exposed for 2 years. These chemicals are nearly unique in this regard among the nearly 400 chemicals studied by the National Toxicology Program, and the reasons for this carcinogenic activity are unclear. The possible relationship of changes in blood concentrations of sex hormones to this response was evaluated by examining the estrous cycle of mice prior to and during a 21-day exposure to concentrations of the haloethanes which resulted in the tumorigenic response in the 2-year studies. Serum concentrations of estradiol and progesterone were determined at the termination of the exposures and compared to exposure group and stage of the estrous cycle. No consistent patterns of change were found in estrous cyclicity or in blood concentrations of sex hormones. Thus, the findings suggest that early changes in circulating sex hormones are not important contributing factors in the uterine neoplasia caused by these chemicals.

Animals↗

PubMed1995

Role of tumor necrosis factor-alpha in cadmium-induced hepatotoxicity.

Liver and kidney injury following acute or chronic exposure to cadmium is well characterized. While hepatocytes and endothelial cells of the sinusoids are thought to be the primary cellular targets in the liver, ultrastructural changes may vary depending upon the exposure regimen and the time following administration. Since acute and chronic liver disease is often associated with the presence of cytokines, we investigated the role of proinflammatory cytokines in cadmium-induced hepatotoxicity. Supernatants from cultured liver slices obtained from acute or subchronic cadmium-exposed rats and mice were collected and cytokine secretion was examined. In addition, mRNA transcripts for IL-1 alpha, IL-1 beta, IL-6, TNF-alpha, MIP-2, IFN-gamma, and ICAM-1 from livers of treated mice were quantitated by reverse transcription-polymerase chain reaction. Modest increases in secretion of TNF-alpha, IL-1 alpha, and IL-6 were observed in response to cadmium which were enhanced in LPS-primed mice. Additionally, cadmium exposure increased IL-1 alpha, IL-1 beta, TNF-alpha, MIP-2, IL-6, and ICAM-1 mRNA transcripts in the liver. Immunohistochemical analysis revealed that TNF-alpha was associated with nonparenchymal cells in livers of cadmium-treated mice. Cadmium exposure produced a marked increase in plasma hepatocellular enzyme levels (i.e., AST, LDH, SDH), acute phase proteins (i.e., serum amyloid A), and foci formation in the liver, while focal inflammation and serum amyloid A (SAA) secretion, but not plasma enzymes, were further increased in cadmium-exposed mice primed with LPS. SAA secretion and focal inflammation were prevented by pretreatment with antibodies to TNF-alpha, indicating that these pathological manifestations are cytokine dependent. These data indicate that TNF-alpha, released from nonparenchymal cells as well as associated cytokines, are responsible for certain manifestations observed with cadmium-induced hepatotoxicity.

Animals↗

PubMed1995

Cadmium-induced renal damage and proinflammatory cytokines: possible role of IL-6 in tubular epithelial cell regeneration.

Cadmium exposure in humans and experimental animals produces renal damage characterized by degeneration and necrosis of tubular epithelial cells followed by interstitial inflammation and eventual regeneration of proximal tubular cells. Since chronic kidney diseases are often associated with the presence of inflammatory cytokines and cadmium has been reported to alter cytokine expression in monocytes and the Kupffer cells of the liver, we investigated the role of proinflammatory cytokines in cadmium-induced nephrotoxicity. Increases in TNF-alpha and IL-6 cytokine mRNA transcripts and secretion were observed in the kidney following exposure of LPS-primed mice to a total of 21 mg/kg body weight cadmium administered over a 14-week period. IL-6 was the predominant cytokine expressed and was found to be present in mesangial cells. Cadmium, in the presence of LPS, was able to induce IL-6 secretion in vitro from mouse glomerular mesangial cells. Proliferative cell nuclear antigen (PCNA) staining revealed increases in regeneration of tubular epithelial cells following cadmium exposure. Furthermore, renal tubular epithelial cells responded to IL-6 by marked proliferation. Taken together, these data suggest that cadmium-induced IL-6 secretion in the kidney may act to support the regeneration of renal tubular epithelial cells that occurs in the course of cadmium nephrotoxicity.

Animals↗

PubMed1995

Chemically induced mammary gland cancer in the National Toxicology Program's carcinogenesis bioassay.

Incidences of breast cancer change in populations as people migrate from one area of the world to another, suggesting that environmental factors contribute to this disease. There is a continuing effort to identify these environmental factors and the role that exposures to specific chemicals play in this disease. Results from experimental studies show that chemicals identified to cause mammary gland cancer in rodents are frequently mutagenic chemicals, suggesting that genetic damage is an important mechanism for the induction of this cancer. Prevalent classes of chemicals that were identified to cause mammary gland cancer in rodents in studies by the National Toxicology Program include halogenated hydrocarbons, aromatic amino/nitro compounds and epoxide-forming chemicals. Results from these experimental studies will help to elucidate mechanisms and possible causes of breast cancer in humans.

Animals↗

PubMed1995

Bile duct-specific lectins, Dolichos biflorus agglutinin and peanut agglutinin, as probes in mouse hepatocarcinogenesis.

BACKGROUND: It is well established that alterations in the expression of cell surface glycoproteins occur during the course of tumorigenesis and can be detected immunohistochemically. However, no consistent markers of malignancy in mouse hepatocellular tumors have yet been identified. EXPERIMENTAL DESIGN: Lectin histochemistry, using three bile duct-specific lectins, Dolichos biflorus agglutinin (DBA), peanut agglutinin (PNA) and soybean agglutinin (SBA), and anti-epidermal keratin immunohistochemistry, was conducted on formalin-fixed, paraffin-embedded tissues of a spectrum of benign and malignant hepatocellular proliferative lesions of mice, including hepatocholangiocarcinomas. DBA- and PNA-binding glycoproteins in normal livers and in bile and liver tumors of mice were verified by SDS-PAGE and Western blot analysis. RESULTS: Normal bile duct cells stained strongly with DBA but minimally to moderately with PNA and SBA. DBA-positive tumor cells were present in 96% of hepatocholangiocarcinomas, 89% of hepatocellular carcinomas, and 35% of hepatocellular adenomas. In comparison, 43% of hepatocholangiocarcinomas, 37% of hepatocellular carcinomas, and 24% of hepatocellular adenomas exhibited PNA staining. SBA did not specifically stain tumor cells. Normal hepatocytes and those in altered foci were consistently negative for these three lectins. Keratin-positive staining was found only in normal bile ductular cells and ductal elements in 70% of hepatocholangiocarcinomas. Electrophoresis and Western blot analysis demonstrated that, in normal livers, DBA and PNA bound to the 13- to 16-kDa and 27- to 30-kDa glycoproteins believed to be of bile duct cell origin and commonly present in hepatocellular adenomas, hepatocellular carcinomas, and hepatocholangiocarcinomas, with strongest expression in the last. In addition, hepatocholangiocarcinomas had the same high molecular mass glycoprotein (> 200 kDa) labeled with DBA as detected in bile. CONCLUSIONS: Our results suggest that some malignant hepatocytes, especially in mouse hepatocholangiocarcinomas, have the potential of biliary differentiation. DBA is a sensitive marker for malignant hepatocytes in mice.

Adenoma↗