A uterine choriocarcinoma in a virgin Donryu rat

A uterine choriocarcinoma was found in a 49-wk-old virgin Donryu rat given intrauterine administration of N-ethyl-N'-nitro-N-nitrosoguanidine (ENNG). The tumor was macroscopically present as a bloody cystic mass and microscopically composed of 2 kinds of cells: small basophilic cells similar to cytotrophoblasts in the rat placenta and large cells with big nuclei resembling giant trophoblasts. The giant cells were positive for 3 beta-hydroxysteroid dehydrogenase (3 beta-HSD), although immunohistochemical examination was negative or nonspecific for chorionic gonadotrophins, including beta human chorionic gonadotrophin (beta hCG), human placental lactogen (hPL), and placental glycoprotein (SP-1), or for placental alkaline phosphatase (ALP). However, the animal exhibited a slight mammotropic status. The results thus suggest a choriocarcinoma nature for this uterine tumor and that the tumor cells secrete a weakly mammotrophic hormone.

Changes in susceptibility of tissues to lipid peroxidation after ingestion of various levels of docosahexaenoic acid and vitamin E

To examine the effects of dietary docosahexaenoic acid (DHA) on the potential changes in endogenous lipid peroxidation in the liver and kidney, diets containing a fixed amount of vitamin E (VE; RRR-alpha-tocopherol equivalent; 134 mg/kg diet) and a graded amount of DHA at the levels of 0, 1.0, 3.4 and 8.7% of total dietary energy were fed to rats for 14 d (Expt 1). In Expt 2, diets containing a fixed amount of DHA (8.7% of total dietary energy) and a graded amount of VE at the levels of 54, 134 and 402 mg/kg were fed to rats for 15 d. In Expt 1 it was found that endogenous lipid peroxide contents of the liver and kidney, as measured by thiobarbituric acid value and chemiluminescence intensity, were higher, and their alpha-tocopherol contents lower than those of the controls, with a gradual increase and decrease in values respectively as the dietary DHA level increased (Expt 1). However, the contents of water-soluble antioxidants, i.e. ascorbic acid and non-protein-SH (glutathione), increased with increases in the dietary DHA level, while the Se-dependent glutathione peroxidase (EC 1.11.1.9) activities did not change or tended to be lower. When the graded level of VE was given to rats in Expt 2, lipid peroxide contents in the liver and kidney did not change significantly in response to the increasing levels of dietary VE, although their alpha-tocopherol contents were higher than control values, increasing with increases in the dietary VE levels. The lipid peroxide scavengers other than alpha-tocopherol changed similarly to those in Expt 1. The results obtained in Expts 1 and 2 indicate that DHA enhances the susceptibility of the liver and kidney to lipid peroxidation concomitant with higher levels of DHA in these tissues, as shown by the fatty acid composition. In addition, VE is unable to protect membranes of the liver and kidney rich in DHA from lipid peroxidation, even after ingestion of the highest level of VE. However, the liver lipid peroxide content of the group given the highest level of DHA was not as high as expected, based on the peroxidizability index which was calculated from the fatty acid composition of the liver lipid.

Lack of carcinogenicity of thiamphenicol in F344 rats

The carcinogenicity of thiamphenicol (TAP), an antibiotic drug, was examined in Fischer 344 rats of both sexes. TAP was given ad lib. in drinking water at levels of 0 (control), 125 or 250 ppm to groups of 50 male and 50 female rats for 2 yr. The treatment did not affect mortality and no toxic lesions were specifically induced. Furthermore, the incidence of tumours in the treated groups did not show any significant dose-related increase as compared with the control group. The results thus indicate that TAP is neither toxic nor carcinogenic, for any organs or tissues of F344 rats when given continuously at levels of 125 or 250 ppm in drinking water for 2 yr.

Effect of dietary n-3/n-6 fatty acid ratio on the total count, fatty acid composition, and histamine and leukotriene concentrations of mast cells in tunica mucosa bronchiorum of type I allergic guinea pig

To search for the most effective dietary n-3/n-6 ratio to suppress the type I allergic response, we performed basic experiments that applied parameters, associated with the type I allergy. Guinea pigs fed on diets containing lipids with the n-3/n-6 ratio at different levels and the polyunsaturated fatty acid/saturated fatty acid ratio of a fixed level were sensitized with ovalbumin and reared for two weeks. The lowest or critical level of the n-3/n-6 ratio which produced a significant difference in the parameters was as follows: about 2.0 for the response of mast cells and eosinophils; 0.5 and 1.0, respectively, for the uptake of n-3 and n-6 polyunsaturated fatty acids and decreased histamine production; and 0.2 for decreased leukotriene B4 and total leukotrienes 4, and increased leukotrienes 5/leukotrienes 4. The critical level of the n-3/n-6 ratio thus differed widely according to the parameter. Overall, the upper limit for the dietary n-3/n-6 ratio to suppress antigen-induced type I allergic responses is suggested to be around 1.0.

Appearance of eosinophilic granule cells as pathological changes in the uteri of two aged virgin Donryu rats

The morphological features of cells containing eosinophilic granules (EG cells) present as pathological changes in the uteri of 2 aged virgin Donryu rats were described and compared with granulated metrial gland (GMG) cells of a pregnant rat. Microscopically, EG cells distributed diffusely from the mesometrial triangle to the subendometrium with partly focal accumulation in Case 1 and infiltrated diffusely from the endometrium to the serosa without any clumping in Case 2. They were large cells with eosinophilic and hyaline intracytoplasmic granules, positive for the periodic acid-Schiff reaction. Both EG and GMG cells reacted positively to concanavalin A, wheat germ agglutinin, and phytohemagglutinin on lectin histochemical investigation, although common results were not always obtained for immunohistochemistry. These results show that EG cells are morphologically similar to GMG cells, suggesting a possibility that EG cells are GMG cells. EG cells were without neoplastic properties or pronounced cell-proliferative activity. In Case 1, histological changes of the ovaries and vagina were indicative of a pseudopregnant status. In Case 2, the rat had been maintained under abnormal hormonal conditions, and no evidence of any pseudopregnant-like status was found. These results suggest, thus, that the appearance of EG cells is evidence of a reactive pathological condition in the uteri of aged virgin rats, although the precise pathogenesis and biological significance of EG cells remain to be determined.

Thirteen-week subchronic toxicity study of thiamphenicol in F344 rats

A 13-week subchronic toxicity study of thiamphenicol (TAP) was performed in F344 rats. The minimum lethal dose was estimated to be greater than 10 g/kg body weight, when a single dose of 4-10 g/kg of TAP was given orally. In the subchronic toxicity study, groups of 12 F344 rats of each sex were given solutions containing 0 (control), 125, 250 and 500 ppm of TAP as their drinking water ad libitum for 13 weeks. Body weight gain was significantly suppressed in both sexes of the 250 and 500 ppm groups. Slight suppression of erythropoiesis was observed in the highest-dose group along with slightly reduced spermatogenesis in the testes of the males. In addition, spermatogranulomas were found in the epididymis of both middle- and highest-dose groups. The no observed adverse effect level (NOAEL) was concluded to be 125 ppm (daily doses of 9.0 mg/kg in males and 11.6 mg/kg in females). From the above described results, doses of 250 and 125 ppm were selected as appropriate for a 2-year carcinogenicity study.

Purification and some properties of cobalamin-dependent methionine synthase from rat liver

Cobalamin-dependent methionine synthase was purified from rat liver. The enzyme activity was separated into two peaks upon Mono-Q column chromatography. Peaks I and II of the enzyme, eluted in this order, were purified 18,000- and 44,000-fold in overall yields of 0.7 and 1.8%, respectively. Peak II methionine synthase, the major fraction, was homogeneous as judged by SDS-polyacrylamide gel electrophoresis. The enzyme was a large monomeric protein with an apparent molecular weight of 143,000 Da. Interconversion of the enzyme between the two peaks was not observed during purification procedures. The enzyme required S-adenosylmethionine and a reducing system for activity. Apparent K(m) values of the peak II enzyme for 5-methyltetrahydrofolate and homocysteine were 75 and 1.7 microM, respectively.

Overexpression of PU.1 induces growth and differentiation inhibition and apoptotic cell death in murine erythroleukemia cells

PU.1 is a member of the ets family of transcription factors and is expressed in Friend virus-induced murine erythroleukemia (MEL) cells as a consequence of proviral integration into the PU.1/Spi-1 locus. After induction of MEL cell differentiation by treatment with dimethylsulfoxide (DMSO), expression of the PU.1/Spi-1 gene decreased before induction of beta-globin gene expression. Overexpression of PU.1 by using a zinc-inducible expression plasmid in MEL cells resulted in unexpected growth inhibition of the transfectants. When PU.1-overexpressing transfectants were treated with DMSO, growth inhibition became much pronounced and apoptosis was induced. Expression of the beta-globin gene was not induced under this condition. Neither growth inhibition nor apoptosis was induced in MEL cells after expression of mutant PU.1 proteins with a deletion of the activation domain or the DNA-binding Ets domain irrespective of the presence of DMSO. Interestingly, beta-globin gene expression was not induced in the transfectants expressing the former mutant, whereas it was induced in those expressing the latter one in the presence of DMSO. These results indicate that overexpression of PU.1 in MEL cells results in growth and differentiation inhibition and, in conjunction with DMSO treatment, apoptotic cell death. These results also suggest that the activation domain and the Ets domain of PU.1 contribute differently to induction of these effects.

Effect of vitamin B12-deficiency on testicular tissue in rats fed by pair-feeding

The effect of vitamin B12 (B12)-deficiency on testicular tissue was investigated through morphological observations of the rats which had been fed on a B12-deficient soybean protein diet by pair-feeding for 100 days. Testicular B12 content was depressed distinctly by the deficiency. Testes weight and their relative weight (weight per 100 g body weight) as well, decreased significantly as compared with those of pair-feeding control rats. Although the decrease in the testicular B12 content due to B12-deficiency was compensated by the administration of cyanocobalamin (CN-B12), alleviation of the decrease in testes weight and relative testes weight was not observed under the condition of the short-term CN-B12 administration. Morphological observations of the testicular tissue in B12-deficient rats revealed atrophy of the seminiferous tubules and aplasia of sperms and spermatids, while testicular findings in both ad libitum-feeding control rats and pair-feeding control rats were normal. There was a tendency for the decrease in seminiferous tubules showing spermatogenesis to be alleviated by administration of CN-B12. The above results indicate that the morphological changes in the testicular tissue are ascribable to B12-deficiency.

A case report of superficial necrolytic dermatitis in a beagle dog with diabetes mellitus

A case of superficial necrolytic dermatitis in a young laboratory beagle dog with diabetes mellitus was investigated. Macroscopically, the skin lesion was restricted to paws showing erosion and swelling of the interdigital areas. The most predominant histopathological feature was upper-epidermal vacuolation of keratinocytes. In the pancreas, the number and size of islets were found to be markedly reduced, and only glucagon-positive cells were detected. In the liver, severe and widespread vacuolation of hepatocytes was observed. Blood biochemical assays showed that the serum glucose and plasma glucagon levels were increased. In addition, levels of individual amino acids varied markedly, although the total amino acid concentration was within the normal range. From these results, it was suggested that the skin lesion in this case was primarily caused by hyperglucagonemia in diabetes mellitus.

Rapid and high yield induction of endometrial adenocarcinomas in CD-1 mice by a single intrauterine administration of N-ethyl-N-nitrosourea combined with chronic 17 beta-estradiol treatment

Induction of uterine endometrial adenocarcinomas in mice by N-ethyl-N-nitrosourea (ENU) and 17 beta-estradiol (E2) was examined. Illumination-induced persistent estrous CD-1 mice were divided into three groups at 10 weeks of age. Group 1 was given a single intra-uterine administration of polyethylene glycol (PEG) 1 week later, while Groups 2 and 3 received ENU (12.5 mg/kg), dissolved in PEG, in the same manner. Group 3 mice were also implanted with E2 pellets s.c. 1 week previously, and thereafter the pellets were renewed every 8 weeks throughout the experiment. At the termination (week 15 after the ENU treatment), all surviving mice were killed and the development of uterine proliferative lesions was assessed. All groups demonstrated endometrial hyperplasias, the severity being greatest in the ENU plus E2-treated animals (Group 3). The incidence of adenocarcinomas in Group 3 (20/29, 69%) was significantly higher than in Group 1 (0/25, 0%) or 2 (0/29, 0%). At 10 weeks after the ENU-treatment, serum E2 and progesterone concentrations in Group 3 were significantly higher and lower, respectively, than those in Groups 1 and 2. Consequently, the E2/progesterone (E2:P) ratio in Group 3 was significantly increased. These results indicate that a continuing high level of serum E2 and low level of progesterone are important for endometrial adenocarcinoma development in mice, with an increased E2:P ratio acting as a promoter for development of the endometrial lesions initiated by ENU treatment.

Effect of age on the induction of endometrial lesions by a single intra-uterine administration of N-ethyl-N'-nitro-N-nitrosoguanidine in F344 rats

A total of 54 10-week-old or 49 10-month-old female F344 rats were given a single intrauterine administration of 20 mg/kg N-ethyl-N'-nitro-N-nitrosoguanidine (ENNG) dissolved in polyethylene glycol (PEG) via the vagina using a non-laparotomy approach. Control animals (32 10-week-old or 29 10-month-old rats) were given PEG alone in the same manner. The animals were killed at 15 and 18 months of age, respectively. One animal in the young treated group presented an endometrial adenocarcinoma (incidence: 2.1%), although the incidence and degree of endometrial hyperplasias were significantly increased in both groups of treated animals, as compared to corresponding controls. Histologically, many of these lesions were polypous glandular hyperplasias (adenomatous polyps) with stromal proliferation. The incidence and grade of proliferative lesions in the young treated group were slightly higher than those in the old treated group. ENNG administration did not appear to affect the hormonal situation in treated animals. These results indicate that young animals may be more sensitive to ENNG than aged ones for induction of endometrial lesions, although ENNG-treatment alone is not sufficient for early and high induction of carcinomas even in young rats of this strain.

Defatting and desalting treatment of indonesian dried-salted fish: dietary effects on alpha-tocopherol and peroxide levels in the serum and liver of rats

The main problem with dried-salted fish (DSF) products is lipid oxidation. PUFA of fish oil is very easily oxidized, and sodium chloride is known to be a pro-oxidant. Many researchers have found that the products of lipid oxidation had negative effects on a variety of species, so we evaluated the effect of a desalting and defatting treatment on the lipid oxidation of Indonesian DSF. The dietary effect of untreated DSF, defatted DSF and desalted DSF on diarrhea, on the internal organs, on hepatic, serum, and urinary lipid peroxidation, and on hepatic and serum alpha-tocopherol were evaluated by using rats. The defatting treatment had a significant effect (p < 0.01) on reducing the lipid oxidation variables of the DSF sample and on protecting the rats from diarrhea. Compared with the rats in the casein group, these in the untreated DSF group had significantly higher values (p < 0.05) for hepatic, serum and urinary lipid peroxidation, but significantly lower values for hepatic and serum alpha-tocopherol. No significant differences were observed between the rats fed with casein and defatted DSF.

Effects of angiotensin I-converting enzyme inhibitory substances derived from Indonesian dried-salted fish on blood pressure of rats

Indonesian dried-salted fish (DSF) was produced from skipjack tuna by soaking the flesh in 15% NaCl (DSF I) or 25% NaCl (DSF II). The DSFs were then hydrolyzed by trypsin, chymotrypsin, Pronase E, and pepsin. Angiotensin I-converting enzyme (ACE) inhibitory activity was measured. The pepsin digest showed the highest inhibitory activity (IC50; 0.63 mg protein/ml). DSF II hydrolysate had higher inhibitory activity than that in DSF I. A three-month storage period of DSF gave higher ACE-inhibitory activity than that of 6 months. An oral administration of pepsin hydrolysate significantly decreased the blood pressure of rats. From the purification steps, at least 4 inhibitor peptides were found. The amino acid sequences of the peptides were Val-Ala-Trp-Lys-Leu, Trp-Ser-Lys-Val-Val-Leu, Ser-Lys-Val-Pro-Pro, and Cys-Trp-Leu-Pro-Val-Tyr, with an IC50 value of 31.97, 156.28, 74.22, and 22.20 microM, respectively.

Effects of barbital on neuro-oncogenesis in a transplacental carcinogenicity model using F344 rats

Effects of barbital (BB) on neuro-oncogenesis were examined in a rat transplacental carcinogenesis model. Pregnant F344 rats were divided into 7 groups. Dams in group I received subcutaneous injections of 10 mg/rat 1-butyl-1-nitrosourea (BNU) on the days 15, 18 and 21 of pregnancy and dams in groups II-IV, 1mg/rat BNU on the same time schedule. In addition to the treatment with BNU, dams in group IV were given 0.125% BB solution as their drinking water from the day 12 of pregnancy to parturition. Offspring in groups III and IV received 0.125% BB solution as drinking water from 4 weeks of age until the termination of the study. Animals in groups V and VI were given 0.25% and 0.125% BB solutions, respectively, in the peri- and postnatal period without BNU treatment. Dams in group VII received 250 mg/kg BB subcutaneously on the days 15, 18 and 21 of pregnancy. Offspring in all groups were observed until 105-116 weeks of age. High yields of neurogenic tumors, such as gliomas and neurinomas, were observed in group I. In groups II, III and IV, single cases of a chordoma, a granular cell tumor, and a neurinoma and a malignant reticulosis, which are known to occur spontaneously, were noted, although no gliomas were found. No neurogenic tumors were observed in groups V-VII. With regard to lesions other than those in neurogenic organs, a significant increase in liver tumors was observed in group III compared to group II. In contrast, lung tumors were not found in group III, while they were observed in groups II and IV. These results suggest that BB has no neuro-carcinogenic activity in the rat transplacental carcinogenesis model.

Influence of high-fat diets on the occurrence of spontaneous uterine endometrial adenocarcinomas in rats

The effects of high-fat diets on the spontaneous occurrence of uterine endometrial adenocarcinomas were examined in the Donryu rat. Ninety females at 6 weeks of age were equally divided into 3 groups. Animals in group 1 were fed a basal diet, while those in groups 2 and 3 received powdered basal diets containing 10% and 20% corn oil until 15 months of age, when all survivors were sacrificed. For sequential serum steroid assay and histological examination of sex organs, additional rats were fed diets containing 20% corn oil or without supplement. Body weight gain in group 3 was significantly increased, while in group 2 it was similar to that in the control. In both high-fat groups, calorie intake and weight of fat deposits in the abdominal cavity were significantly increased. The incidences of uterine adenocarcinomas in groups 2 and 3 were 18% (P < 0.05) and 7%, respectively, as compared to 0% in group 1. Severe hyperplasia (hyperplasia+++) also showed a non-significant tendency for increase in incidence. In both high-fat groups, an elevated incidence of persistent estrus was generally observed until 8 months of age. Sequential assays of steroid hormones in rats fed a 20% fat diet showed a tendency for early elevation and continued high values for the serum estrogen: progesterone (E2:P) ratio. In these rats, histological changes in the ovary, uterus, and vagina also appeared at an early stage, as compared to rats fed the basal diet. These results suggest that a high-fat diet may exert a slight promoting effect on the spontaneous occurrence of uterine adenocarcinomas in Donryu rats, and this might be mechanistically related to hormonal imbalance and a high E2:P ratio in particular.

Induction of endometrial adenocarcinomas in persistent estrous Donryu rats by a single intra-uterine administration of N-ethyl-N'-nitro-N-nitrosoguanidine

Induction of endometrial adenocarcinomas in persistent estrous Donryu rats by a single intra-uterine administration of N-ethyl-N'-nitro-N-nitrosoguanidine (ENNG) was examined. Female Donryu rats were divided into four groups at 7 weeks of age. Rats in Croup 1 were controls under a 12-h light/12-h dark regimen while Groups 2-4 were persistent estrous animals maintained under 24-h light conditions. At 10 weeks of age, rats in Group 1 and 2 were given a single intra-uterine administration of polyethylene glycol(PEG), and those in Groups 3 and 4 received ENNG(20 mg/kg body weight), dissolved in PEG, in the same manner. Group 4 rats also received an s.c. 17 beta-estradiol(E2) implant one week thereafter. At the termination of the experiment (week 42 after the ENNG-treatment), all surviving rats were killed and the development of uterine proliferative lesions assessed. All groups demonstrated hyperplasias, the incidence and severity being higher in ENNG-treated animals. The incidence of uterine adenocarcinomas in Group 2(2/20, 10%) was slightly higher than that in Group 1(0/16, 0%), although this difference was not significant. In Groups 3(7/19, 37%) and 4(6/20, 30%) statistically significant induction of adenocarcinomas was noted, two lesions in the latter case being very large with prominent invasion of tumor cells into the perimetrium. At 10 and 25 weeks after ENNG-treatment, the E2-progesterone(E2:P) ratios in Groups 2, 3 and 4 were significantly higher than in Group 1.(ABSTRACT TRUNCATED AT 250 WORDS)

High-yield induction of uterine endometrial adenocarcinomas in Donryu rats by a single intra-uterine administration of N-ethyl-N'-nitro-N-nitrosoguanidine via the vagina

A total of 130 female Donryu rats (10-week-old) were divided into two groups; 80 animals in the experimental group were given a single intra-uterine administration of 20 mg/kg N-ethyl-N'-nitro-N-nitrosoguanidine (ENNG) dissolved in polyethylene glycol (PEG) via the vagina without laparotomy, and 50 animals in the control group received PEG alone in the same manner. Small numbers of animals in both groups were killed at 3, 6, 9 and 12 months after ENNG treatment for sequential histological and endocrinological examination, and at 12.5 experimental months (15 months of age) all survivors were killed. At the termination, endometrial adenocarcinomas were present in 49% of the experimental group, compared to 0% in the control group. Severe endometrial hyperplasias were also found only in the experimental group and sequential histological examination showed first appearance of hyperplasia at 6 months and adenocarcinoma at 9 months. No tumors other than uterine carcinomas were induced by ENNG and the carcinogen treatment did not affect the endocrine environment of rats, persistent estrus appearing at 6 months after the start and increasing with age in both groups. The estradiol-17 beta:progesterone (E:P) ratio was also increased after 6 months, with further elevation at 12 months to about 8 times higher than the level at 6 months. These results indicate that an increased E:P ratio might act as a promoter of development of endometrial proliferative lesions initiated by ENNG in this rat strain. The study indicates that the present simple method using Donryu rats provides a good animal model for endometrial adenocarcinoma development in women.

Sequential observation of spontaneous endometrial adenocarcinoma development in Donryu rats

Sequential observation of spontaneous endometrial adenocarcinoma development revealed a clear, hormone-dependent, histogenetic pathway in Donryu rats. The first histological changes of the uterine endometrium appeared in both the lining epithelium and uterine gland of the endometrium at 6 mo of age, along with the beginning of persistent estrus. These changes included areas of tall columnar epithelium and gland formation in the lining epithelium as well as metaplastic change in the uterine gland. At 8 mo of age, endometrial hyperplasias were found, with subsequent increase in both incidence and degree. At 8-10 mo of age, hyperplasias were all within the limit of grade ++. After 12 mo of age, however, severe hyperplasias (grade ) began to increase markedly, and adenocarcinomas developed at 15 mo of age. The findings thus suggest that uterine endometrial adenocarcinomas arise from hyperplastic lesions, which should therefore be regarded as preneoplastic, as in the human case. Sequential analysis of plasma gonad steroids also ascertained a link between the appearance of these lesions and an increased estrogen:progesterone ratio, suggesting that estrogen may play an important role in development of both hyperplastic and neoplastic lesions. In Fischer-344 rats used for comparative assessment of strain differences, neither advanced histological changes nor hormonal changes were evident.

Evidence for an origin of ethyl-nitrosourea-induced rat central nervous system tumors from pluripotent germinal neuroepithelium

Brain tumors induced by transplacental application of ethyl-nitrosourea (ENU) in F344 rats were immunohistochemically demonstrated to consist of undifferentiated cells, astriocyte-like cells, oligodendroglia-like cells, and two distinct types of vimentin-expressing cell groupings termed as perivascular small cell nests (PSCNs) and large cell nests (LCNs). Co-distribution of vimentin and glial fibrillary acidic protein (GFAP) was sparsely observed in the astrocyte-like cells, which suggested an immature glial phenotype. PCSNs contained cells expressing GFAP, neuron-specific enolase (NSE), beta-tubulin isotype III, and low-affinity nerve growth factor receptors (LNGFRs). LCNs contained cells showing a neuronal phenotype with expression of low- and middle-molecular mass neurofilament proteins (NF-L and -M) as well as NSE, beta-tubulin isotype III and LNGFR. Double-labelling immunohistochemistry revealed the NF-L-expression in LNGFR-positive LCN-forming cells. Oligodendroglia-like cells and their intercellular neuropil-like structures expressed beta-tubulin isotype III, synaptophysin and NSE, in addition to the expressions of vimentin and GFAP. Electron microscopically, synapse-like structures were formed between these oligodendroglia-like cells and their dendritic processes. Topographically, bidirectional cell transitions from PSCNs to astrocytes and LCNs were indicated. The present study strongly suggests that so-called ENU-induced "gliomas" originate from pluripotent germinal neuroepithelium. Furthermore, LNGFR expression may be responsible for acquisition of neuronal phenotype in these tumors.

Subchronic (12-week) inhalation toxicity study of methanol-fueled engine exhaust in rats

To evaluate the inhalation toxicity to rats of exhaust at low concentration for longer periods, Fischer 344 rats were exposed to 3 concentrations of exhaust generated by an M85 methanol-fueled engine (methanol with 15% gasoline) without catalyst for 8 h/d, 6 d/wk for 4, 8, or 12 wk. Concentration- and time-dependent increase carboxyhemoglobin in the erythrocytes and decrease in cytochrome P-450 in the lungs were observed in all treated groups. Furthermore, significant increases in plasma formaldehyde were observed in all treated groups. Furthermore, significant increases in plasma formaldehyde were observed in the group exposed to the highest concentration of exhaust (carbon monoxide, 89.8 ppm; formaldehyde, 2.3 ppm; methanol, 8.1 ppm; nitrogen oxides, 22.9 ppm; nitrogen dioxide, 1.1 ppm) for 8 or 12 wk. No change of plasma folic acid was observed in any group, and no methanol or formic acid was detected in the plasma in any animals. Histopathologically, exposure-related changes were found only in the nasal cavity of the high-concentration group. Slight hyperplasia/squamous metaplasias of the respiratory epithelium lining the nasoturbinate and maxilloturbinate were observed after 4 wk of exposure, and the incidences and degrees of these lesions increased slightly with the exposure time. No changes were found in the olfactory epithelium of the nasal cavity. As judged by optical microscopy, the exhaust concentration with no effect on the nasal cavity under the experimental conditions was concluded to be the medium concentration level containing 0.55 ppm formaldehyde. In the present study, however, concentration- and time-dependent increase of carboxyhemoglobin in the erythrocytes and decrease of the lung P-450 level were observed. Therefore, further study on more long-term inhalation of lower concentrations of exhaust might be needed.