Multi-organ carcinogenicity by inhalation exposure to 2-Bromopropane in rats

OBJECTIVE

The purpose of this study was to investigate the carcinogenicity of 2-bromopropane (2-BP) in rats.

METHODS

Male and female F344 rats were exposed by whole body inhalation to 2-BP vapor at concentrations of 0, 67, 200, and 600 ppm for 6 h/day, 5 days/week for 2 years.

RESULTS

All rats of both sexes exposed to 600 ppm died or became moribund within 85 weeks. Death/moribundity was caused by 2-BP induced tumors. In males, significantly increased tumors were malignant Zymbal's gland tumors; sebaceous adenoma and basal cell carcinoma of the skin/appendage; adenocarcinoma of the small/large intestine; follicular cell adenoma of the thyroid; fibroma of the subcutis, and malignant lymphoma of the lymph node. In addition, an increased trend in tumor incidence was found in the preputial gland, lung, forestomach, pancreas islet, brain, and spleen. In females, significantly increased tumors were adenocarcinoma and fibroadenoma of the mammary gland, squamous cell papilloma of the vagina, and large granular lymphocytic leukemia of the spleen. In addition, an increased trend in tumor incidence was found in Zymbal's gland, the clitoral gland, skin, large intestine, pancreas islet, uterus, and subcutis. Particularly, malignant Zymbal's gland tumors were induced even in males exposed to the lowest concentration, 67 ppm.

CONCLUSION

Two-year inhalation exposure to 2-BP resulted in multi-organ carcinogenicity in rats. Based on sufficient evidence of carcinogenicity in this study, 2-BP has the potential to be a human carcinogen.

Mechanisms of pulmonary disease in F344 rats after workplace-relevant inhalation exposure to cross-linked water-soluble acrylic acid polymers

BACKGROUND

Recently in Japan, six workers at a chemical plant that manufactures resins developed interstitial lung diseases after being involved in loading and packing cross-linked water-soluble acrylic acid polymers (CWAAPs). The present study focused on assessing lung damage in rats caused by workplace-relevant inhalation exposure to CWAAP and investigated the molecular and cellular mechanisms involved in lung lesion development.

METHODS

Using a whole-body inhalation exposure system, male F344 rats were exposed once to 40 or 100 mg/m³ of CWAAP-A for 4 h or to 15 or 40 mg/m³ of CWAAP-A for 4 h per day once per week for 2 months (9 exposures). In a separate set of experiments, male F344 rats were administered 1 mg/kg CWAAP-A or CWAAP-B by intratracheal instillation once every 2 weeks for 2 months (5 doses). Lung tissues, mediastinal lymph nodes, and bronchoalveolar lavage fluid were collected and subjected to biological and histopathological analyses.

RESULTS

A single 4-h exposure to CWAAP-A caused alveolar injury, and repeated exposures resulted in regenerative changes in the alveolar epithelium with activation of TGFβ signaling. During the recovery period after the last exposure, some alveolar lesions were partially healed, but other lesions developed into alveolitis with fibrous thickening of the alveolar septum. Rats administered CWAAP-A by intratracheal instillation developed qualitatively similar pulmonary pathology as rats exposed to CWAAP-A by inhalation. At 2 weeks after intratracheal instillation, rats administered CWAAP-B appeared to have a slightly higher degree of lung lesions compared to rats administered CWAAP-A, however, there was no difference in pulmonary lesions in the CWAAP-A and CWAAP-B exposed rats examined 18 weeks after administration of these materials.

CONCLUSIONS

The present study reports our findings on the cellular and molecular mechanisms of pulmonary disease in rats after workplace-relevant inhalation exposure to CWAAP-A. This study also demonstrates that the lung pathogenesis of rats exposed to CWAAP-A by systemic inhalation was qualitatively similar to that of rats administered CWAAP-A by intratracheal instillation.

Carcinogenicity and chronic toxicity of butyl methacrylate in rats and mice by a two-year inhalation study

We conducted a two-year inhalation study of butyl methacrylate using F344/DuCrlCrlj rats and B6D2F₁/Crl mice. Rats were exposed to 0, 30, 125 and 500 ppm (v/v) and mice were exposed to 0, 8, 30 and 125 ppm (v/v) using whole-body inhalation chambers. Non-neoplastic lesions developed in the nasal cavities of both rats and mice, but neoplastic lesions were not found. There was also a positive trend in the incidence of large granular lymphocytic (LGL) leukemia in the spleen of male rats. No changes were observed in female rats. Overall, there is some evidence of carcinogenicity in male rats, but there is no evidence of carcinogenicity in female rats. In male mice, there was a positive trend by Peto's test in the incidence of hepatocellular adenomas, and the incidence of hepatocellular adenomas and hepatocellular carcinomas combined was significantly increased compared to the controls by Fisher's exact test in the 30 ppm exposed male group. In female mice, the incidence of hemangiosarcoma in all organs combined showed a positive trend by Peto's test. Therefore, there is some evidence of carcinogenicity in male mice, and there is equivocal evidence of carcinogenicity in female mice.

Pulmonary dust foci as rat pneumoconiosis lesion induced by titanium dioxide nanoparticles in 13-week inhalation study

Background

Most toxicological studies on titanium dioxide (TiO₂) particles to date have concentrated on carcinogenicity and acute toxicity, with few studies focusing of pneumoconiosis, which is a variety of airspace and interstitial lung diseases caused by particle-laden macrophages. The present study examined rat pulmonary lesions associated with pneumoconiosis after inhalation exposure to TiO₂ nanoparticles (NPs).

Methods

Male and female F344 rats were exposed to 6.3, 12.5, 25, or 50 mg/m³ anatase type TiO₂ NPs for 6 h/day, 5 days/week for 13 weeks using a whole-body inhalation exposure system. After the last exposure the rats were euthanized and blood, bronchoalveolar lavage fluid, and all tissues including lungs and mediastinal lymph nodes were collected and subjected to biological and histopathological analyses.

Results

Numerous milky white spots were present in the lungs after exposure to 25 and 50 mg/m³ TiO₂ NPs. Histopathological analysis revealed that the spots were alveolar lesions, characterized predominantly by the agglomeration of particle-laden macrophages and the presence of reactive alveolar epithelial type 2 cell (AEC2) hyperplasia. We defined this characteristic lesion as pulmonary dust foci (PDF). The PDF is an inflammatory niche, with decreased vascular endothelial cells in the interstitium, and proliferating AEC2 transformed into alveolar epithelial progenitor cells. In the present study, the AEC2 in the PDF had acquired DNA damage. Based on PDF induction, the lowest observed adverse effect concentration for pulmonary disorders in male and female rats was 12.5 mg/m³ and 6.3 mg/m³, respectively. The no observed adverse effect concentration for male rats was 6.3 mg/m³. There was a sex difference in lung lesion development, with females showing more pronounced lesion parameters than males.

Conclusions

Inhalation exposure to TiO₂ NPs caused PDF, an air-space lesion which is an alveolar inflammatory niche containing particle-laden macrophages and proliferating AEC2. These PDFs histopathologically resemble some pneumoconiosis lesions (pulmonary siderosis and hard metal pneumoconiosis) in workers and lung disease in smokers, suggesting that PDFs caused by exposure to TiO₂ NPs in rats are an early pneumoconiosis lesion and may be a common alveolar reaction in mammals.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s12989-022-00498-3.

No evidence for carcinogenicity of titanium dioxide nanoparticles in 26-week inhalation study in rasH2 mouse model

With the rapid development of alternative methods based on the spirit of animal welfare, the publications of animal studies evaluating endpoints such as cancer have been extremely reduced. We performed a 26-week inhalation exposure studies of titanium dioxide nanoparticles (TiO2 NPs) using CByB6F1-Tg(HRAS)2Jic (rasH2) mice model for detecting carcinogenicity. Male and female rasH2 mice were exposed to 2, 8 or 32 mg/m3 of TiO2 NPs for 6 h/day, 5 days/week for 26 weeks. All tissues and blood were collected and subjected to biological and histopathological analyses. TiO2 NPs exposure induced deposition of particles in lungs in a dose-dependent manner in each exposure group. Exposure to TiO2 NPs, as well as other organs, did not increase the incidence of lung tumors in any group, and pulmonary fibrosis and pre-neoplastic lesions were not observed in all groups. Finally, the cell proliferative activity of alveolar epithelial type 2 cells was examined, and it was not increased by exposure to TiO2 NPs. This is the first report showing the lack of pulmonary fibrogenicity and carcinogenicity (no evidence of carcinogenic activity) of TiO2 NPs in 26-week inhalation study in rasH2 mice exposed up to 32 mg/m3, which is considered to be a high concentration.

Dose-response relationship of pulmonary disorders by inhalation exposure to cross-linked water-soluble acrylic acid polymers in F344 rats

Background

In Japan, six workers handling cross-linked water-soluble acrylic acid polymer (CWAAP) at a chemical plant suffered from lung diseases, including fibrosis, interstitial pneumonia, emphysema, and pneumothorax. We recently demonstrated that inhalation of CWAAP-A, one type of CWAAP, causes pulmonary disorders in rats. It is important to investigate dose–response relationships and recoverability from exposure to CWAAPs for establishing occupational health guidelines, such as setting threshold limit value for CWAAPs in the workplace.

Methods

Male and female F344 rats were exposed to 0.3, 1, 3, or 10 mg/m³ CWAAP-A for 6 h/day, 5 days/week for 13 weeks using a whole-body inhalation exposure system. At 1 h, 4 weeks, and 13 weeks after the last exposure the rats were euthanized and blood, bronchoalveolar lavage fluid, and all tissues including lungs and mediastinal lymph nodes were collected and subjected to biological and histopathological analyses. In a second experiment, male rats were pre-treated with clodronate liposome or polymorphonuclear leukocyte-neutralizing antibody to deplete macrophages or neutrophils, respectively, and exposed to CWAAP-A for 6 h/day for 2 days.

Results

CWAAP-A exposure damaged only the alveoli. The lowest observed adverse effect concentration (LOAEC) was 1 mg/m³ and the no observed adverse effect concentration (NOAEC) was 0.3 mg/m³. Rats of both sexes were able to recover from the tissue damage caused by 13 weeks exposure to 1 mg/m³ CWAAP-A. In contrast, tissue damage caused by exposure to 3 and 10 mg/m³ was irreversible due to the development of interstitial lung lesions. There was a gender difference in the recovery from CWAAP-A induced pulmonary disorders, with females recovering less than males. Finally, acute lung effects caused by CWAAP-A were significantly reduced by depletion of alveolar macrophages.

Conclusions

Pulmonary damage caused by inhalation exposure to CWAAP-A was dose-dependent, specific to the lung and lymph nodes, and acute lung damage was ameliorated by depleting macrophages in the lungs. CWAAP-A had both a LOAEC and a NOAEC, and tissue damage caused by exposure to 1 mg/m³ CWAAP-A was reversible: recovery in female rats was less than for males. These findings indicate that concentration limits for CWAAPs in the workplace can be determined.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s12989-022-00468-9.

Carcinogenicity and chronic toxicity of acrolein in rats and mice by two-year inhalation study

The carcinogenicity and chronic toxicity of acrolein was examined by whole body inhalation to groups of 50 F344/DuCrlCrlj rats and 50 B6D2F1/Crlj mice of both sexes for two years. The concentration of acrolein was 0, 0.1, 0.5 or 2 ppm (v/v) for male and female rats; and 0, 0.1, 0.4 or 1.6 ppm for male and female mice. Two-year administration of acrolein induced the squamous cell carcinomas in nasal cavity which is rare tumor in one male and two female rats. In females, rhabdomyoma in nasal cavity was observed in four rats exposed to 2 ppm. In mice, since the survival rate of male and female of mice control group were lowered than 25% in late of the administration periods due to renal lesion and/or amyloid deposition, the mice study was terminated at 93rd week in males, and was terminated at 99th week in females. The incidences of adenomas in nasal cavity were observed in 16 females and significantly increased only in female mice. Thus, acrolein is carcinogenic in two species, i.e. rats and mice. Additionally, non-neoplastic nasal cavity lesions in rats and mice were observed.

Inter-laboratory comparison of pulmonary lesions induced by intratracheal instillation of NiO nanoparticle in rats: Histopathological examination results

OBJECTIVE

In this study, in order to investigate the usefulness of intratracheal instillation in assessing the pulmonary toxicity of nanomaterials, intratracheal instillation of nickel oxide-nanoparticles (NiO-NP) was performed.

METHODS

In this study, rats were administered test materials by intratracheal instillation at five different research institutions in order to assess the validity of using intratracheal instillation for hazard identification of nanomaterials. Eight-week-old male SD rats were administered NiO-NP dispersed in deionized water by a single intratracheal instillation at doses of 0 (vehicle control), 0.2, 0.67, and 2 mg/kg BW. Three days after instillation, histopathological examination of the lungs was performed.

RESULTS

NiO-NP was distributed in the vicinity of hilus of the lung and in the alveoli around the bronchioles. Histopathological changes such as degeneration/necrosis of macrophages, inflammation, and proliferation of type II pneumocyte in the lung were observed, and their severity corresponded with increasing dose. The histopathological observations of pulmonary toxicity were almost similar at each institution.

CONCLUSION

The similarity of the histopathological changes observed by five independent groups indicates that intratracheal instillation can be a useful screening method to detect the pulmonary toxicity of nanomaterials.

Carcinogenicity of butyl 2,3-epoxypropyl ether in rats and mice by whole body inhalation for two years

Butyl 2,3-epoxypropyl ether (CAS No. 2426-08-6, synonym: n-butylglycidyl ether, BGE) was exposed by whole body inhalation to F344 rats and BDF1 mice of both sexes (50 animals per group) 6 hours per day, 5 days per week for 104 weeks at targeted concentrations of 0, 10, 30 or 90 ppm (v/v) for rats and 0, 5, 15 or 45 ppm for mice. In rats, 90 ppm of BGE increased the incidences of nasal squamous cell carcinomas in both sexes. Nasal adenomas and splenic mononuclear cell leukemia were increased in male rats exposed to 30 ppm. Splenic mononuclear cell leukemia was increased in female rats by trend test. Non-neoplastic nasal lesions, such as squamous cell hyperplasia with atypia, squamous cell metaplasia and the inflammation of the respiratory region and atrophy of the olfactory epithelium were increased in both sexes in a dose-dependent manner. In mice, the incidences of histiocytic sarcomas of the uterus in female mice were increased in a dose-dependent manner and the incidences of nasal hemangiomas in both sexes were increased in a dose-dependent manner. Nasal squamous cell carcinoma, a rare tumor, was observed, although not statistically significant, in both sexes. Non-neoplastic lesions such as nodular hyperplasia of the transitional epithelium and cuboidal changes of the respiratory epithelium in the nasal cavity, were increased both in males and females in a dose-dependent manner. The present study demonstrated clear evidence of carcinogenicity of BGE in both rats and mice by the 2-year whole body inhalation exposure.

Comparison of single or multiple intratracheal administration for pulmonary toxic responses of nickel oxide nanoparticles in rats

OBJECTIVES

In this study, we focused on the qualitative and quantitative differences of the lung lesions induced by single or multiple intratracheal administration of nickel oxide nanoparticles (NiO).

METHODS

Male rats were randomized into groups receiving intratracheal administrations in a single dose or two to four divided doses of 2 mg/kg/bw. Bronchoalveolar lavage fluid (BALF) analyses were performed at 3 and 28 d post-dose. Histopathological analyses were performed at 28 and 91 d post-dose.

RESULTS

BALF analyses revealed pulmonary injury, inflammation, and increases in the parameters indicating processing the foreign material in all the NiO-treated groups. Histopathological analyses showed the phagocytosis of NiO by alveolar macrophages, degeneration and necrosis of alveolar macrophages, and inflammatory responses. In the comparison between single and multiple administrations, the trend for stronger toxicity effects was observed after multiple application at 3 d post-dose, while the obvious toxicity effects were also seen in case of single administration. No particular differences of lung lesions depending on the frequency of administration at 28 and 91 d post-dose were evident.

CONCLUSION

Intratracheal NiO administration induced strong toxic response thoroughly even by single administration. Therefore, single administration was concluded to be applicable to assess the inhalation toxicity of nanomaterials and can be used in the screening test.

Improved method for measurement of multi-walled carbon nanotubes in rat lung

Background

Previously, we have developed and reported the method of measuring multi-walled carbon nanotube (MWCNT) in the lung from rats exposed to MWCNT intratracheally. The present research was performed to improve the analytical method of MWCNT to measure multiple samples in a short period of time. For the xanalysis of MWCNTs from tissues, the existence of carbon black may interfere. Therefore, it was examined whether or not carbon black interfere the determination of MWCNT in the standard solutions. Then, MWCNTs were administered to rats and the MWCNTs were determined in the rats by the new method and the recovery rates and time for determination were calculated. The standard solutions for MWCNTs and carbon black were prepared, and the concentrations in the solutions were determined by HPLC with checking their linearity between the concentrations and signal intensities. The reproducibility of the determination was also checked.

Methods

The concentrations of MWCMTs in the standard solutions were determined by HPLC with a fluorescent detector. Those of carbon black were also determined using the same method. The MWCNTs were administered to rats intratracheally. The MWCNTs in the lung were determined in a newly modified method including digestion of lung tissues by strong alkali solution and marking MWCNTs by benzo[ghi]perylene. The time for the determinations was recorded and the recovery rate of MWVNTs was calculated.

Results

MWCNT showed linearity in a range of 0.2 to 1.0 μg/mL. In contrast, carbon black demonstrated a very low slope, showing flat pattern. Regarding the reproducibility of the analysis, the coefficient of variation was lower than 10 %. The analysis of 20 samples were completed in 1.5 h. The recovery rates of MWCNT from the lung of rats receiving intratracheal MWCNT administration were 101 to 102 %.

Conclusions

The improved method for measuring MWCNT allows an efficient MWCNT quantitation in a short period of time. Also, a small amount of MWCNTs can be measured without influence of carbon black.

Quantitative evaluation of local pulmonary distribution of TiO2 in rats following single or multiple intratracheal administrations of TiO2 nanoparticles using X-ray fluorescence microscopy

Uneven pulmonary nanoparticle (NP) distribution has been described when using single-dose intratracheal administration tests. Multiple-dose intratracheal administrations with small quantities of NPs are expected to improve the unevenness of each dose. The differences in local pulmonary NP distribution (called microdistribution) between single- and multiple-dose administrations may cause differential pulmonary responses; however, this has not been evaluated. Here, we quantitatively evaluated the pulmonary microdistribution (per mesh: 100 μm × 100 μm) of TiO2 in lung sections from rats following one, two, three, or four doses of TiO2 NPs at a same total dosage of 10 mg kg(-1) using X-ray fluorescence microscopy. The results indicate that: (i) multiple-dose administrations show lower variations in TiO2 content (ng mesh(-1) ) for sections of each lobe; (ii) TiO2 appears to be deposited more in the right caudal and accessory lobes located downstream of the administration direction of NP suspensions, and less so in the right middle lobes, irrespective of the number of doses; (iii) there are not prominent differences in the pattern of pulmonary TiO2 microdistribution between rats following single and multiple doses of TiO2 NPs. Additionally, the estimation of pulmonary TiO2 deposition for multiple-dose administrations imply that every dose of TiO2 would be randomly deposited only in part of the fixed 30-50% of lung areas. The evidence suggests that multiple-dose administrations do not offer remarkable advantages over single-dose administration on the pulmonary NP microdistribution, although multiple-dose administrations may reduce variations in the TiO2 content for each lung lobe. Copyright © 2016 John Wiley & Sons, Ltd.

The increases in relative mRNA expressions of inflammatory cytokines and chemokines in splenic macrophages from rats exposed to multi-walled carbon nanotubes by whole-body inhalation for 13 weeks

BACKGROUND

The toxicity of multi-walled carbon nanotubes (MWCNT) may be related to the immune system. The objective of this study was to obtain information for immunotoxic mechanisms of MWCNT in situ.

METHODS

Using whole-body inhalation, male and female rats were exposed to 0, 0.2, 1 or 5 mg MWCNT/m³ for 13 weeks. Thereafter, spleens were recovered from the rats. Real-time PCR was done to assess expression of TNFα, IL-1β, IL-6, IL-10, MCP-1 and MIP-1α mRNA in the splenic macrophages; splenic T-lymphocytes were examined for IL-2 and TGF-β1 mRNA expression.

RESULTS

The relative expression of IL-1β mRNA in the cells from female rats exposed to 5 mg MWCNT/m³ was significantly higher than that in control cells. For IL-6 and IL-10, cells from rats in the 0.2 and 5 mg MWCNT/m³ had significantly higher mRNA expressions than did cells from controls. Expression of IL-1β, IL-6 and TNFα genes in cells from males in all exposure groups were higher than in control cells. Expression of MIP-1α in the cells from female 5-mg group was significantly higher than that in cells in the control. Only IL-2 was expression reduced, i.e. cells from male and female rats in all MWCNT groups had significantly lower mRNA expressions than control cells.

CONCLUSIONS

Systemic inflammation would likely occur in rats (or other hosts) exposed to MWCNT via inhalation due to increases in the expression of inflammatory cytokines in splenic macrophages. Moreover, decreases in IL-2 expression in T-lymphocytes may be critical to the potential reductions in anti-tumor responses in MWCNT-exposed hosts.

[Background data of spontaneous tumors in F344/DuCrlCrlj rats]

INTRODUCTION

We investigated the 2-year survival rate and incidence of spontaneous tumors in F344/DuCrlCrlj rats used in carcinogenicity studies of chemical substances. Records for animals used in the control groups of carcinogenicity studies which were conducted during the last 10 years were obtained from the database of the Japan Bioassay Research Center (JBRC). Six hundred ninety-nine males and 550 females were used in 14 and 11 inhalation studies, respectively, and 500 animals of each sex were used in 10 male and 10 female oral studies.

METHODS

In each study, SPF (specific pathogen free) animals were housed for 2 years (104 weeks) as control groups in the carcinogenicity studies. All animals underwent necropsy and histopathological examination. Each study was conducted in accordance with the Good Laboratory Practice.

RESULTS

The incidence of interstitial cell tumors was highest in both inhalation studies and oral studies (inhalation studies 86.1%, oral studies 68.6%). Tumors which had an incidence of 6% or higher were adenoma of the pituitary, C-cell adenoma of the thyroid, and mononuclear cell leukemia (LGL leukemia) of the spleen in male and female rats; fibroma of the subcutaneous tissue, adrenal pheochromocytoma, and islet cell adenoma of the pancreas in male rats; and endometrial stromal polyps and fibroadenoma of the mammary gland in female rats. Tumors other than the above had rare incidence rates. A clear difference in the incidence of spontaneous tumors was not observed between the inhalation and oral studies. The incidences of spontaneous tumors in control groups of previous oral studies are similar to our findings. There are no other reports of the spontaneous tumor incidence in the control groups of inhalation studies using F344/DuCrlCrlj rats. The 2-year survival rate was about 77% in both the inhalation and oral studies, and a gender difference was not observed. The F344/DuCrlCrlj rats used at JBRC had a higher 2-year survival rate than F344/N rats. This difference is possibly due to the low incidence of LGL leukemia in the F344/DuCrlCrlj rat.

CONCLUSIONS

The incidences of spontaneous tumors in F344/DuCrlCrlj rats used in control groups of both inhalation and oral studies during the last 10 years at JBRC are similar to each other and similar to those reported in other studies. This is the first report on the incidence of spontaneous tumors in inhalation studies and contributes to the toxicological evaluation of studies using F344/DuCrlCrlj rats.

Spontaneous harderian gland adenocarcinoma in a female f344 rat: a case report

Harderian gland tumors are extremely rare in female F344 rats. An expansive enlarging lesion of the Harderian gland with compression, distortion and invasion of the surrounding muscle was found in a 110-week-old female F344/DuCrj rat, which was diagnosed as a Harderian gland adenocarcinoma. Epithelial growth patterns such as glandular, lobular, papillary and duct forming patterns were exhibited in most areas of the tumor. The tumor cells were pleomorphic and atypical. In one part of the tumor, poorly differentiated areas were found. This case was observed in the middle dose group of a carcinogenicity study of diphenylamine, which was not carcinogenic, we determine to be this case was a spontaneous tumor.

Inhalation exposure to 1,2-dichloropropane: Distribution of blood and tissue concentrations of 1,2-dichloropropane in rats during and after exposure

The present investigation was undertaken to determine the distribution and accumulation of 1,2-dichloropropane (DCP) in the blood, lung, liver, kidney, and abdominal fat of rats during and after inhalation exposure. Male rats were exposed to 80 or 500 ppm (v/v) DCP vapor for 360 min and the concentrations of DCP in the blood and tissues during the inhalation exposure period and after the end of the exposure period were measured. DCP accumulation in the abdominal fat was much greater than that in the blood and other tissues. Eighteen hours after the end of inhalation exposure, DCP could still be detected in the abdominal fat in the 80-ppm group, and in the blood, liver, kidney, and abdominal fat in the 500-ppm group. Our results are valuable data pertaining to the pharmacokinetics of DCP and to human health risk assessment of exposure to DCP vapor by inhalation.

Systemic and myelotoxic effects of single administration of 2,3,7,8-tetrabromodibenzo-p-dioxin in rats

OBJECTIVE

Systemic and myelotoxic effects of 2,3,7,8-tetrabromodibenzo-p-dioxin (TBDD) were examined by the single administration of TBDD by gavage to rats.

METHODS

Fifteen Wistar rats of both sexes per group received 0, 10, 30, 100 or 300 μg TBDD/kg body weight. Rats surviving to the scheduled necropsy on Days 2, 7 and 36 after TBDD administration were examined for growth rate, organ weight, hematology, histopathology and adipose tissue levels of TBDD.

RESULTS

Three 300 μg/kg-dosed females died on Days 21, 23 and 27, and exhibited a marked decrease in body weight, severe thymic atrophy, decreased bone marrow hematopoiesis and hemorrhage in the subarachnoid space of brain and spinal cord. TBDD-dosed surviving rats exhibited growth retardation, decreased bone marrow hematopoiesis, decreases in red blood cell counts, hemoglobin concentrations, and hematocrit values, an increase in reticulocytes and decreases in platelet counts, white blood cell counts and eosinophils. These signs suggested TBDD myelotoxicity. Splenic extramedullary hematopoiesis was increased in both sexes given TBDD, whereas atrophy of the splenic white pulp occurred only in TBDD-dosed females. Marked decreases in body weights and the size and weight of the thymus, severe thymic atrophy and death in TBDD-dosed females suggested a wasting syndrome. The adipose tissue level of TBDD culminated on Day 7 and decreased to 20-30% of the Day 7 level on Day 36.

CONCLUSIONS

The TBDD-induced effects were characterized by a wasting syndrome and myelotoxicity that appeared at the dose levels of 30 μg/kg and higher and caused death in 300 μg/kg-dosed females.

Thirteen-week inhalation toxicity of 1,4-dioxane in rats

Thirteen-week inhalation toxicity of 1,4-dioxane was examined by repeated inhalation exposure of male and female F344 rats to 0 (control), 100, 200, 400, 800, 1600, 3200, or 6400 ppm (v/v) 1,4-dioxane vapor for 6 h/day and 5 days/wk. All the 6400-ppm-exposed males and females died during the first week. Terminal body weight decreased, and relative weights of liver, kidney, and lung increased. AST increased in the 200 ppm-and 3200-ppm-exposed females, and ALT increased in the 3200-ppm-exposed males and females. Nuclear enlargement of nasal respiratory epithelial cells occurring in the 100-ppm-exposed males and females was the most sensitive, followed by the enlarged nuclei in the olfactory, tracheal, and bronchial epithelia. 1,4-Dioxane-induced liver lesions occurred at higher exposure concentrations than the nasal lesions did, and were characterized by single-cell necrosis and centrilobular swelling of hepatocytes in males and females. Glutathione S-transferase placental form (GST-P) positive liver foci were observed in the 1600-ppm-exposed females and 3200-ppm-exposed males and females, which are known as a preneoplastic lesion in rat hepatocarcinogenesis. Plasma levels of 1,4-dioxane increased linearly with an increase in the concentrations of exposure to 400 ppm and above. The enlarged nuclei in the nasal epithelia and the GST-P-positive liver foci were discussed in light of the possible development of nasal and hepatic tumors by long-term inhalation exposure to 1,4-dioxane. A lowest-observed-adverse-effect level (LOAEL) was determined at 100 ppm for the nasal endpoint in both male and female rats.

Occurrence of two different types of glutathione S-transferase placental form-positive hepatocytes after a single administration of 2,3,7,8-tetrabromodibenzo-p-dioxin in rats

Occurrence of glutathione S-transferase placental form (GST-P)-positive hepatocytes was examined, using 15 Wistar rats of both sexes each orally administered 2,3,7,8-tetrabromo-dibenzo-p-dioxin (TBDD) by gavage at a single dose of 0, 10, 30, 100 or 300 microg/kg body weight. Liver tissues were stained with anti-GST-P antibody. Two different types of GST-P-positive hepatocytes were found in the TBDD-dosed rat. One type was of the hepatocytes stained homogeneously with anti-GST-P antibody and clearly distinguishable from the surrounding normal tissue. The foci were composed of 2 to 60 hepatocytes exhibiting morphologically focal and clonal proliferation. The GST-P-positive hepatocellular foci occurred at two higher dose levels and only on Day 36 after the single administration. Another type was of the area occupied by the positively but heterogeneously stained hepatocytes appearing predominantly in the centrilobular region, at lower dose levels and persistently on Day 2 through 36. The stained hepatocytes appeared to be neither focally nor clonally proliferating. Females were more susceptible to formation of the two differently stained hepatocytes than males. It is suggested that the GST-P-positive foci represent an early stage of hepatocarcinogenesis, while the GST-P-positive area is associated with the induction of detoxifying Phase II GSTs.

Effects of inhalation exposure to propylene oxide on respiratory tract, reproduction and development in rats

Nasal, respiratory, reproductive and developmental toxicities of propylene oxide (PO) were examined by exposing male and female Sprague-Dawley rats to PO vapor by inhalation at a concentration of 0 (control), 125, 250, 500 or 1,000 ppm for 6 h/d, 7 d/wk, during a 5- to 6-wk period, including premating, mating and postmating or gestation. The inhalation exposure to 1,000 ppm PO seriously affected parental survival, the upper and lower respiratory tract, male and female reproductive systems, motor function, and fetal survival and development, whereas the exposure to 500 ppm or less primarily caused nasal lesions without any sign of reproductive or developmental toxicity. Because atrophy of the olfactory epithelium in the male rats exposed to 250 ppm was the most sensitive endpoint for PO toxicity, the NOAEL was determined to be 125 ppm for the nasal endpoint. An additional inhalation experiment was carried out to further examine developmental toxicity by exposing pregnant rats to 0, 125, 250, 500, 750 or 1,000 ppm PO during a 2-wk period of gestation, Day 6 through Day 19. The 2-wk inhalation experiment revealed that reduced fetal body weights and delayed ossification occurred in association with significantly reduced body weights of the dams exposed to 750 and 1,000 ppm, whereas neither fetal death nor teratogenicity occurred at those two exposure levels. It was concluded that the developmental toxicity of fetal death was manifested at parentally toxic exposure levels above 500 ppm, a level which seriously affected parental survival, the upper and lower respiratory tracts and reproductive system.

Carcinogenicity and Chronic Toxicity in Rats and Mice Exposed by Inhalation to 1,2‐Dichloroethane for Two Years

Carcinogenicity and chronic toxicity of 1,2-dichloroethane (DCE) were examined by inhalation exposure of groups of 50 F344 rats and 50 BDF1 mice of both sexes to DCE vapor or clean air as control for 6 h/d, 5 d/wk and 104 wk. The rats were exposed to 10, 40 or 160 ppm (v/v) DCE, while the mice were exposed to 10, 30 or 90 ppm. The 2-yr exposure to DCE produced a dose-dependent increase in incidences of benign and malignant tumors, including subcutaneous fibroma, mammary gland fibroadenoma and peritoneal mesothelioma in male rats; subcutaneous fibroma and mammary gland adenoma, fibroadenoma and adenocarcinoma in female rats; and bronchiolo-alveolar adenoma and carcinoma, endometrial stromal polyp, mammary gland adenocarcinoma and hepatocellular adenoma in female mice. No exposure-related change in the incidence of non-neoplastic lesions or in any hematological, blood biochemical or urinary parameter occurred in any DCE-exposed rat or mouse group. The types of tumors and their target organs found in this study were consistent with those observed in rats and mice administered DCE by gavage in a NCI study. Selection of the exposure concentrations was considered appropriate with reference to the maximum tolerated dose for the highest doses and an occupational exposure limit of DCE for the lowest dose. The present findings suggest that those carcinogenic responses be primarily considered for standard setting of occupational and environmental exposure to DCE.

Developmental Toxicity Induced by Inhalation Exposure of Pregnant Rats to N,N ‐Dimethylacetamide

Developmental toxicity of N,N-dimethylacetamide (DMAC) was examined by exposing pregnant rats by inhalation to DMAC vapor at 0 (control), 100, 300, 450 or 600 ppm (v/v) for 6 h/d during Gestation Days 6 through 19. Fetal body weight and the number of male live fetuses were significantly decreased, along with a tendency of the number of intrauterine deaths to increase. The number of fetuses with visceral and skeletal malformations was significantly increased in the 450 and 600 ppm groups, while the number of fetuses with anasarca as an external malformation was increased at 600 ppm. Observed cardiovascular malformations included ventricular septum defect, persistent truncus arteriosus, malpositioned subclavian branch and retroesophageal subclavian artery. Persistent truncus arteriosus was accompanied by ventricular septal defect (VSD). Incidences of the persistent truncus arteriosus, which was classified as a serious congenital heart disease affecting postnatal survival, were increased at 450 and 600 ppm. Increased liver weights and hepatocellular swelling occurred in the dams exposed to 300 ppm and above, whereas neither hepatocellular necrosis nor increased serum activity of liver transaminases was observed in any of the exposed groups. Maternal body weights were decreased at 450 and 600 ppm. The most sensitive signs of developmental toxicity appeared at the exposure level of 300 ppm which was also the level of slight maternal toxicity. The No-Observed-Adverse-Effect-Level (NOAEL) was determined as 100 ppm for the endpoints of fetal and maternal toxicities. The NOAEL of 100 ppm and the induction of serious cardiovascular malformations occurring at 450 ppm and above were discussed with reference to the existing occupational exposure limit for DMAC.

Carcinogenicity and Chronic Toxicity of Para-Chloronitrobenzene in Rats and Mice by Two-Year Feeding

Carcinogenicity and chronic toxicity of para-chloronitrobenzene (p-CNB) were examined by feeding diets containing p-CNB to rats and mice of both sexes for two years. The dietary concentration of p-CNB was 0 (control), 40, 200, or 1000 ppm (w/w) for rats and 0, 125, 500, or 2000 ppm for mice. Survival rates of the high-dosed male rats and male mice were significantly decreased compared with those of the respective controls, and this was attributed to the increased number of cancer deaths. Therefore, the high-dose levels were considered not to exceed the maximum tolerated dose. Significant decreases in red blood cell counts and hematocrit value and an increase in mean corpuscular volume were noted in the p-CNB-fed rats and mice. Nonneoplastic splenic lesions were characterized by capsule hyperplasia, fibrosis, fatty metamorphosis, and increased extramedullary hematopoiesis in rats, and congestion, increased extramedullary hematopoiesis, hemosiderin deposition, and ossification in mice. Incidences of fibromas, fibrosarcomas, osteosarcomas, sarcomas (NOS), and hemangiosarcomas in males and fibrosarcomas in females were significantly increased in the spleen of high-dosed rats. The most frequently observed splenic tumor was fibrosarcomas, followed by fibromas. The tumor incidences were increased in a dose-related manner and were more prevalent in males than in females. The malignant tumors metastasized mainly to the liver, peritoneum, and pancreas. Adrena/medullary hyperplasia and pheochromocytomas were significantly increased in the p-CNB-fed females. No tumor was induced in any of the p-CNB-fed mice of either sex except hepatic hemangiosarcomas in the 2000 ppm-fed females. Causative factors of p-CNB-induced carcinogenicity and chronic toxicity are discussed in light of the subchronic and chronic hematotoxicity reported in our present and previous studies and in the literature.

TWO-YEAR FEED STUDY OF CARCINOGENICITY AND CHRONIC TOXICITY OF ORTHO-CHLORONITROBENZENE IN RATS AND MICE

Carcinogenicity and chronic toxicity of ortho-chloronitrobenzene (o-CNB) were examined by feeding groups of 50 F344 rats and 50 BDF(1) mice of both sexes o-CNB-containing diets for 2 years. The dietary concentration of o-CNB was 0, 80, 400 or 2000 ppm (w/w) for rats and 0, 100, 500 or 2500 ppm for mice. The 2-year administration of o-CNB produced a dose-dependent increase in incidences of hepatocellular adenomas and carcinomas in rats and mice of both sexes and hepatoblastomas in mice of both sexes. Incidences of altered cell foci in the liver were increased in the o-CNB-fed rats of both sexes. Metastasis from mouse malignant liver tumors occurred predominantly in the lung. The hepatocarcinogenic response to o-CNB was found to be more potent in mice than in rats. Marginally increased incidences of renal cell adenomas in the 2000 ppm-fed female rats and renal cell carcinomas in the 2000 ppm-fed male rats were noted, together with a significantly increased incidence of atypical tubule hyperplasias. Spontaneous, age-related chronic progressive nephropathy was exacerbated in a dose-related manner, and caused the death of 47 male rats fed 2000 ppm before the end of the 2-year administration period. The highest dose levels of o-CNB except for the administration of 2000 ppm to male rats were thought to meet the criteria of the maximum tolerated dose set by both NCI and IARC guidelines. Causative factors of o-CNB-induced carcinogenicity were discussed with reference to our previous rodent studies of subchronic toxicity of o-CNB and carcinogenicity and chronic toxicity of para-chloronitrobenzene.

Carcinogenicity and Chronic Toxicity after Inhalation Exposure of Rats and Mice to N,N ‐Dimethylformamide

Carcinogenicity and chronic toxicity of N,N-Dimethylformamide (DMF) were examined by inhalation exposure of groups of 50 rats and 50 mice of both sexes to DMF vapor at a concentration of 0, 200, 400 or 800 ppm (v/v) for 6 h/d, 5 d/wk, for 104 wk. In rats, incidences of hepatocellular adenomas and carcinomas significantly increased in the 400 and 800 ppm-exposed groups and in the 800 ppm-exposed group, respectively. The hepatocellular adenoma did not increase significantly in the 400 ppm-exposed female rats, but its incidence exceeded a range of historical control data in the Japan Bioassay Research Center (JBRC). In mice, incidences of hepatocellular adenomas and carcinomas significantly increased in all the DMF-exposed groups. Incidence of hepatoblastomas significantly increased in the 200 and 400 ppm-exposed male mice, and 4 cases of hepatoblastomas in the 400 ppm-exposed female mice and the 800 ppm-exposed male mice exceeded the range of historical control data of the JBRC. Incidences of altered cell foci increased in the liver of exposed rats and mice in an exposure concentration-related manner, and those foci were causally related to the hepatocellular tumors. Liver weights increased in both rats and mice exposed to DMF at 200 ppm and above. Increased levels of gamma-GTP, ALT, AST and total bilirubin in exposed rats of both sexes and AST and ALT in exposed mice of both sexes were noted. It was concluded that 2-yr inhalation exposure to DMF increased incidences of hepatocellular adenomas and carcinomas in rats and incidences of hepatocellular adenomas, carcinomas and hepatoblastomas in mice, and that hepatocarcinogenicity of DMF was more potent in mice than in rats.

Toxicity due to 2‐ and 13‐wk Inhalation Exposures of Rats and Mice to N , N ‐Dimethylformamide

In order to better characterize the toxicity of N,N-dimethylformamide (DMF) and to provide its basic toxicity data for risk assessment of workers exposed to DMF, F344 rats and BDF1 mice of both sexes were exposed by inhalation (6 h/d x 5 d/wk) to 100, 200, 400, 800 or 1,600 ppm DMF for 2 wk, and 50, 100, 200, 400 or 800 ppm DMF for 13 wk. Three male and 7 female rats died during the 2-wk exposure to 1,600 ppm DMF, but no death of the exposed rats or mice occurred under any other exposure conditions. Massive, focal and single cell necroses were observed in the liver of DMF-exposed rats and mice. The massive necrosis associated with the centrilobular fibrosis occurred at the highest exposure concentration. The single cell necrosis was associated with fragmentation of the nucleoli as well as an increased mitotic figure. The 13-wk exposures of rats and mice to DMF were characterized by increases in the relative liver weight and the incidence of the centrilobular hepatocellular hypertrophy as well as increased serum levels of AST, ALT, LDH, total cholesterol and phospholipid. Lower confidence limits of the benchmark dose yielding the response with a 10% extra risk (BMDL10) were determined for the relative liver weight and the incidence of hepatocellular hypertrophy of the 13-wk exposed animals. The BMDL10 resulted in 1 ppm for the increased relative liver weight of male rats and mice and 17 ppm for the hepatocellular hypertrophy of male mice.

Clinical benefits and tolerability of increased fill volumes in Japanese peritoneal dialysis patients

BACKGROUND

Increasing fill volume is an effective means of improving clearances in patients on peritoneal dialysis (PD). Since Japanese PD patients are physically smaller than their Western counterparts, there is some concern that PD patients in Japan may be unable to tolerate larger fill volumes.

OBJECTIVE

To determine patient tolerance and changes in solute clearance and net ultrafiltration resulting from increased fill volumes in Japanese patients on PD.

DESIGN

Prospective double-blind study, randomizing patients to three different fill volumes (2.5% dextrose solution: 1.5 L, 2.0 L, or 2.5 L) administered in random order on three different occasions separated by 1 week.

RESULTS

Twenty-one patients with a mean age of 55.4 +/- 2.1 years and a mean body surface area of 1.66 +/- 0.03 m2 were studied. On a scale of 0 to 10, patients' mean discomfort scores were 2.14 +/- 0.59, 3.48 +/- 0.54, and 3.81 +/- 0.63 (p = 0.047) at the end of the 1.5-L, 2.0-L, and 2.5-L dwells, respectively. There were no reports of cramps or shortness of breath with any fill volume. Patients were able to correctly guess the actual fill volume for only 34 of the 63 total exchanges (54.0%). Increasing fill volume resulted in an incremental improvement in peritoneal creatinine clearance, from 3.74 +/- 0.16 to 4.49 +/- 0.21 (p < 0.001, 2.0 L vs 1.5 L) to 5.12 +/- 0.20 mL/minute (p< 0.001, 2.5 L vs 2.0 L) for 1.5-L, 2.0-L, and 2.5-L dwells, respectively. Peritoneal urea clearance also increased significantly, from 5.65 +/- 0.13 to 7.04 +/- 0.17 (p < 0.001, 2.0 L vs 1.5 L) and 8.16 +/- 0.29 mL/minute (p < 0.001, 2.5 L vs 2.0 L), with incremental increases in fill volume. Similarly, net ultrafiltration in a 4-hour dwell increased significantly with fill volume, from 255.24 +/- 24 mL with 1.5 L, to 356 +/- 24 (p < 0.004, 2.0 L vs 1.5 L) and 392 +/- 29 mL (p < 0.086, 2.5 L vs 2.0 L) in patients receiving 2.0 L and 2.5 L, respectively.

CONCLUSION

Increasing the fill volume results in improvement in solute clearance and net ultrafiltration in Japanese PD patients, with minimal increase in patient discomfort. A large percentage of patients were unable to identify the actual fill volume.

[Primary carcinoma in situ of the ureter: a case report]

A 55-year-old male visited our hospital with a complaint of gross hematuria and right lower abdominal pain. Cytological findings of voided urine suggested the presence of malignant cells. Cystoscopic examination revealed bloody urine discharge from the right ureteral orifice and no abnormality in the bladder wall. The retrograde pyelogram showed no tumor masses. However, malignant cells were detected cytologically in the right ureteral catheteral urine twice. Under the preoperative diagnosis of primary urothelial tumor of the right upper urinary tract, right total nephroureterectomy was performed. A histological study revealed transitional cell carcinoma in situ in the lower portion of the ureter. We reviewed 46 cases of primary carcinoma in situ of the upper urinary tract previously reported in Japan.

Strain difference in the induction of T-cell activation-associated, interferon gamma-dependent hepatic injury in mice

A single intravenous injection of concanavalin A (Con A) induces T-cell activation-associated inflammatory injury selectively in the liver. This study investigated the strain difference in the development of Con A-induced hepatic injury. Normal C57BL/6 and BALB/c spleen cells produced comparable levels of T-cell-derived lymphokines (interferon gamma [IFN-gamma], tumor necrosis factor alpha [TNF-alpha], and interleukin-2 [IL-2]) following in vitro stimulation with Con A. A single intravenous injection of Con A to C57BL/6 mice induced the plasma levels of TNF-alpha and IL-2 comparable with or slightly higher than those observed in BALB/c mice, whereas the same treatment resulted in an apparently lower level of IFN-gamma production in C57BL/6 mice. RNA from livers of Con A-treated C57BL/6 mice exhibited lower levels of IFN-gamma mRNA than RNA of BALB/c livers. Unexpectedly, a dramatic difference in the severity of hepatic injury was observed between C57BL/6 and BALB/c. Namely, the peak alanine transaminase (ALT) level was more than 15,000 U/L and inducible as early as 8 hours after injection of 0.2 mg Con A per mouse in the C57BL/6 strain, whereas the peak was approximately 3,000 U/L and induced as late as 24 hours after Con A injection in the BALB/c strain. The increase in plasma ALT levels was limited to less than 10% by injection of anti-IFN-gamma monoclonal antibody (mAb) in both strains. The C57BL/6 strain inducing lower levels of IFN-gamma exhibited higher IFN-gamma responsiveness as exemplified by the intrahepatic expression of an IFN-gamma-inducible gene, an inducible type of nitric oxide (NO) synthase (iNOS). These results indicate that, while IFN-gamma produced in vivo by activated T cells induces hepatic injury, there exists a striking strain difference in the induction of IFN-gamma-dependent hepatic injury.

[Leydig cell tumor of the testis: a case report]

A 63-year-old male visited our hospital with a complaint of painless swelling of the left scrotum. Left high orchiectomy was performed since ultrasonography suggested a testicular tumor. Histologically, this testicular mass was a Leydig cell tumor. We reviewed 47 cases of this tumor previously reported in Japan.

Studies on anti-inflammatory agents. V. Synthesis and pharmacological properties of 3-(difluoromethyl)-1-(4-methoxyphenyl)-5- [4-(methylsulfinyl)phenyl]pyrazole and related compounds

A series of novel 1,5-diphenylpyrazole derivatives bearing hydrophilic substituents was prepared. The anti-inflammatory and analgesic activities of these compounds were evaluated by using the adjuvant arthritis and Randall-Selitto assays in rats, and the structure-activity relationships were studied. The optimal compound was 3-(difluoromethyl)-1-(4-methoxyphenyl)-5-[4-(methylsulfinyl)phenyl]pyraz ole (10) with oral ED50 values of 0.31 and 2.6 mg/kg on adjuvant-induced arthritis and carrageenin-induced foot edema, respectively. Compound 10 showed analgesic activities not only toward inflamed paw but also toward normal paw (ED30 = 0.55 and 1.8 mg/kg, respectively) in the Randall-Selitto assay, and moreover, 10 was effective in the tail-pinch assay (ED50 = 21 mg/kg) similarly to morphine. The asymmetric synthesis and pharmacological properties of the enantiomers of 10 are also reported.

Studies on anti-inflammatory agents. IV. Synthesis and pharmacological properties of 1,5-diarylpyrazoles and related derivatives

A series of novel 1,5-diarylpyrazole derivatives was synthesized and tested for anti-inflammatory and analgesic activities to develop anti-inflammatory agents with fewer side effects than existing nonsteroidal anti-inflammatory drugs. The structure-activity relationships in this series were extensively studied. Electron-withdrawing substituents such as CN and CF3 were optimal at the 3-position of the pyrazole ring. Replacement of these substituents with bulky ones gave less active compounds. The 4-(methylsulfonyl)phenyl group seemed to be the optimal group at the 5-position of the pyrazole ring. The most potent compound was 1-(4-fluorophenyl)-5-[4-(methylsulfonyl)phenyl]-pyrazole-3-carbonitrile (19a), with oral ED50 value of 0.030 and 0.47 mg/kg on adjuvant-induced arthritis and collagen-induced arthritis, respectively, and an ED30 value of 7.4 mg/kg in the yeast-induced hyperalgesia (Randall-Selitto) assay. Compound 19a also showed potent inducible cyclooxygenase (COX-2)-inhibitory activity (IC50 = 0.24 microM) with no COX-1 inhibition even at 100 microM.

Spontaneous lesions of nasal cavity in aging F344 rats and BDF1 mice

The outline of spontaneous lesions of the nasal cavity that were commonly observed in F344 rats and BDF1 mice used as untreated control groups in ten 2-year carcinogenicity studies were presented. In rats, the common spontaneous lesions were eosinophilic change of the respiratory epithelium and the olfactory epithelium, respiratory metaplasia of glands and the olfactory epithelium, foreign body inflammation, deposit of calcium, and thrombus. In mice, the common spontaneous lesions were eosinophilic change of the respiratory epithelium and olfactory epithelium, and respiratory metaplasia of glands and the olfactory epithelium. Some of these lesions revealed either species or sex-related differences of incidence.

Critical involvement of interferon gamma in the pathogenesis of T-cell activation-associated hepatitis and regulatory mechanisms of interleukin-6 for the manifestations of hepatitis

A single intravenous injection of concanavalin A (Con A) induces T-cell activation and an acute hepatitis in mice. This study investigated the role of interferon gamma (IFN-gamma) in the pathogenesis of this hepatitis model. Striking increases in the plasma levels of various cytokines, including tumor necrosis factor (TNF), interleukin-2 (IL-2), and IFN-gamma, were detected before the increase in plasma aminotransferase levels induced by Con A injection. TNF levels peaked within 2 hours, whereas IFN-gamma levels peaked at 6 hours after Con A injection. In contrast to a sharp peak of TNF levels, high IFN-gamma levels were detected for a more prolonged period. Passive immunization with anti-IFN-gamma monoclonal antibody (MAb) conferred a dose-dependent protection against liver injury in this model. This protection was observed when anti-IFN-gamma MAb was administered at least 30 minutes before Con A injection but not when given 1 hour after Con A injection. The protection from Con A-induced hepatitis was also induced by administration of rIL-6 before Con A injection. rIL-6 treatment induced significant albeit incomplete inhibition of IFN-gamma and TNF production, whereas this regimen did not affect IL-2 production. Despite striking protective effects of rIL-6 or anti-IFN-gamma MAb, comparable levels of cellular (both T cell and polymorphonuclear cell) infiltration were detected in liver sections from animals untreated, or treated with either rIL-6 or anti-IFN-gamma MAb. Moreover, electron microscopic examination showed that infiltrating T cells exhibited a blastoid appearance in all groups. These results indicate that IFN-gamma plays a critical role in the development of Con A-induced acute hepatitis and suggest that IL-6 administration can regulate the manifestation of hepatitis through mechanisms including the reduced production of inflammatory cytokines such as IFN-gamma.

Antianginal effects of FK409, a new spontaneous NO releaser

1. The aim of this study was to compare antianginal effects of (+/-)-(E)-ethyl-2-[(E)-hydroxyimino]-5-nitro-3-hexeneamide (FK409), a new spontaneous nitric oxide releaser, with those of isosorbide dinitrate (ISDN). We used two types of rat angina model; methacholine- and arginine vasopressin (AVP)-induced coronary vasospasm models. 2. In the in vitro study, FK409 showed 80 times more potent vasorelaxant effect in dog isolated coronary artery than ISDN (EC50 = 16.7 +/- 4.8 and 1340 +/- 320 nM, respectively). 3. In the rat methacholine-induced coronary vasospasm model, FK409 suppressed the elevation of ST segment dose-dependently and significantly at 0.1 mg kg-1, i.d. On the other hand, ISDN suppressed it significantly at 3.2 mg kg-1, i.d. In addition, the efficacy of 3.2 mg kg-1 ISDN in the model was almost the same as that of 0.1 mg kg-1 FK409. 4. In the above experiments, FK409 and ISDN decreased mean blood pressure significantly at the maximum dose tested (1.0 mg kg-1, i.d. and 3.2 mg kg-1, i.d., respectively) but did not change heart rate at these doses. Therefore, the hypotensive effect of FK409 was 10 times weaker than the antianginal effect of the compound, while those of ISDN were almost the same. 5. In the rat AVP-induced coronary vasospasm model, 32 mg kg-1 FK409 significantly inhibited the depression of ST segment 60 min after oral administration. On the other hand, 32 mg kg-1 ISDN did not inhibit it at 60 and 120 min after oral administration. 6. In conclusion, FK409 inhibits coronary vasospasm more potently in two types of rat angina models than ISDN. In addition, FK409 shows an antianginal effect more selectively that a hypotensive effect,compared with ISDN.

A case of nodular fasciitis of the bladder

A case of nodular fasciitis occurring at the bladder vertex in a 34-year-old male is reported. The tumor was about 1 cm in diameter. A urachal tumor was diagnosed, and excised en bloc from the umbilicus to the bladder vertex. This tumor was diagnosed as nodular fasciitis from the histopathological findings. No recurrence has been seen for 3 years. Nodular fasciitis occurs mainly in the limbs or trunk. Occurrence in the bladder is very rare. Only 14 cases (including our case) of nodular fasciitis occurring in the bladder are known.

T cell activation-associated hepatic injury: mediation by tumor necrosis factors and protection by interleukin 6

This study investigates the molecular mechanisms underlying the induction of and protection from T cell activation-associated hepatic injury. When BALB/c mice were given a single intravenous injection of concanavalin A (Con A) (> or = 0.3 mg/mouse), they developed acute hepatic injury as assessed by a striking increase in plasma transaminase levels within 24 h. Histopathologically, only the liver was injured while moderate infiltration of T cells and polymorphonuclear cells occurred in the portal areas and around the central veins. The induction of hepatic injury was dependent on the existence as well as the activation of T cells, as untreated BALB/c nu/nu mice or BALB/c mice pretreated with a T cell-specific immunosuppressive drug, FK506, failed to develop disease. Significant increases in the levels of various cytokines in the plasma were detected before an increase in plasma transaminase levels. Within 1 h after Con A injection, tumor necrosis factor (TNF) levels peaked, this being followed by production of two other inflammatory cytokines, interleukin 6 (IL-6) and IL-1. Passive immunization with anti-TNF but not with anti-IL-1 or anti-IL-6 antibody, conferred significant levels of protection. Moreover, administration of rIL-6 before Con A injection resulted in an IL-6 dose-dependent protection. A single administration of a given dose of rIL-6 completely inhibited the release of transaminases, whereas the same regimen induced only 40-50% inhibition of TNF production. More than 80% inhibition of TNF production required four consecutive rIL-6 injections. These results indicate that: (a) TNFs are critical cytokines for inducing T cell activation-associated (Con A-induced) hepatitis; (b) the induction of hepatitis is almost completely controlled by rIL-6; and (c) rIL-6 exerts its protective effect through multiple mechanisms including the reduction of TNF production.

Effects of adenosine A2 receptor agonists on the excitation of capsaicin-sensitive afferent sensory nerves in airway tissues

We examined the effects of adenosine analogues on the asthmatic reactions induced by the stimulation of capsaicin-sensitive afferent sensory nerves. Intravenous (i.v.) injection of adenosine A2 receptor agonists, 5'-(N-ethylcarboxamido)-adenosine (NECA) and 2-[p-(carboxyethyl)-phenylethylamino]-5'-N-ethylcarboxamido-adenos ine (CGS 21,680), dose dependently inhibited capsaicin-induced guinea-pig bronchoconstriction (1-1000 nmol kg-1), whereas i.v. administration of the adenosine A1 receptor agonist, N6-cyclo-hexyladenosine (CHA), did not affect it (1000 nmol kg-1). Intratracheal injection of NECA (0.05-5 nmol site-1) and CGS 21,680 (0.05-5 nmol site-1) also reduced capsaicin-induced constriction in a dose-dependent manner. However, NECA (1000 nmol kg-1) failed to inhibit substance P-induced guinea-pig bronchoconstriction. NECA (1-1000 nmol kg-1) dose-dependently inhibited cigarette smoke-induced rat tracheal plasma extravasation, but not substance P-induced reaction. NECA (0.1-10 microM) and CGS 21,680 (10 microM) significantly blocked the capsaicin-induced release of substance P-like immunoreactivity from guinea-pig lung, whereas CHA (10 microM) had no effect. This evidence suggests that adenosine A2 receptors modulate negatively the excitation of capsaicin-sensitive afferent sensory nerves and substance P release from their endings in airway tissues.

A case of multilocular cystic nephroma

The patient was a 23-year-old female. Excretory urography, abdominal CT scanning, and renal angiography revealed a large multilocular cystic nephroma on the right kidney.

Type II collagen-induced murine arthritis: induction of arthritis depends on antigen-presenting cell function as well as susceptibility of host to an anticollagen immune response

Two sets of ((resistant x susceptible) F1----parent) and (parent----F1) chimeric mice were prepared. In the chimeric combinations involving BALB/c and DBA/1 mice, all (F1----F1) chimeras developed arthritis as well as potent anticollagen responses after immunization with collagen, whereas all (F1----BALB/c) and (BALB/c----F1) chimeras induced neither arthritis nor immune responses. This type of F1 T cells could be activated with APC from DBA/1 but not from BALB/c mice. Thus, the failure of the [F1 in equilibrium with BALB/c] chimeras to mount anticollagen responses was due to a defect at the APC level. Another arthritis-resistant strain, C57BL/6, exhibited adequate APC function, but reduced T cell responsiveness, representing an intermediate responder. In the chimeric combinations involving C57BL/6 and DBA/1 mice, (F1----F1) and (C57BL/6----C57BL/6) chimeras developed very high and very low incidence of arthritis, respectively. (C57BL/6----F1) chimeras developed an appreciable incidence of arthritis under conditions in which this group of chimeras generated intermediate levels of anticollagen responses. In contrast, (F1----C57BL/6) chimeras developed low incidence of disease despite induction of strong responses. Moreover, cells from collagen-immunized (F1----C57BL/6) chimeras, when transferred into T cell-depleted B cell mice of F1 or C57BL/6 strain, produced comparable immune responses in both groups but induced much more severe arthritis in F1 than in C57BL/6 recipients. These results indicate that: i) two types of arthritis-resistant strains can be identified, each of which has anticollagen APC defect as a low responder and reduced T cell responsiveness as an intermediate responder and ii) a discrepancy between the degree of anticollagen responses and clinical arthritis is attributed to the differential susceptibility to anticollagen immune responses.