A case study: evaluation of results and selection of additional studies.
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Animals↗
Biomedical subjects
C Furihata
Publications and source records attributed to C Furihata.
Cytotoxicity of NaCl, a stomach tumor promoter, and prevention by rice extract in stomach mucosa of F344 rats.
Cytotoxicity of NaCl and its prevention by rice extract were studied in the pyloric mucosa of male F344 rat stomach after oral administration of rice extract and 2.6 M NaCl. Effect were observed histologically by hematoxylin and eosin staining and the bromodeoxyuridine method. Replicative DNA synthesis (RDS) was assayed by liquid scintillation counter with [3H]thymidine. NaCl (2.6 M) induced destruction of the surface mucous cells within 1 min. RDS and S-phase cells increased significantly (p < 0.01) and to a maximum at 17 h, and returned to control levels 48 h after exposure. Administration of aqueous rice extract 3 h before NaCl exposure reduced the morphological damage to the mucosa and prevented the increase in RDS dose dependently by up to 65% (p < 0.01). These results showed that NaCl induced rapid mucosal damage and cell proliferation in rat stomach mucosa and that rice extract prevented the damage and reduced the increase in RDS.
Animals↗
Association of minisatellite instability with c-myc amplification and K-ras mutation in methylcholanthrene-induced mouse sarcomas.
Instability of microsatellite sequences are frequently found in human tumors. In addition, minisatellite sequences, another group of highly unstable sequences, serve as sensitive markers of genetic instability. We have studied minisatellite instability in methylcholanthrene-induced mouse sarcomas. These sarcomas frequently carry the amplified c-myc gene. Seven sarcomas without the amplification and seven others with the amplification were selected randomly. Regardless of the state of the c-myc gene amplification, these sarcomas exhibited a varying degree of transplantability in syngeneic mice. The hypervariable mouse minisatellite locus Ms6hm was found to be highly unstable, specifically among sarcomas with the amplified c-myc gene. However, chromosome instability, as analyzed by micronucleus assay, was observed similarly for two groups of sarcomas. In addition, transversion of G to C and A to T was detected at the K-ras gene in four of the seven sarcomas with the amplified c-myc gene, and these mutations are thought to be induced directly by methylcholanthrene. Thus, concomitant occurrence was observed for three seemingly unrelated mutations, amplification of the c-myc locus, point mutation of the K-ras gene, and instability at the hypervariable mouse minisatellite locus. The present study indicates a possible involvement of K-ras mutation and c-myc amplification in induction of genetic instability in methylcholanthrene-induced mouse sarcomas.
Animals↗
Effects of long-term omeprazole treatment on adult rat gastric mucosa--enhancement of the epithelial cell proliferation and suppression of its differentiation.
Effects of long-term omeprazole treatment on the process of epithelial cell proliferation and differentiation in the adult rat gastric mucosa were investigated. Animals were treated with omeprazole (25 mg/kg body weight/day) for 28 days to induce anacidity in the stomach. The treatment induced a marked decrease in the number of chief cells in the gastric mucosa and at the same time an increase in that of immature pepsinogen-producing cells expressing class III mucin. This was accompanied by a decrease to 60% and 10% of the control values in the mucosal levels of pepsinogen and its mRNA, respectively. Moreover, the expression of cathepsin E in surface mucous cells was reduced. Cell proliferation studies revealed that the rate of bromodeoxyuridine-labeled cells was increased by omeprazole. The above-described changes were reversed by cessation of the treatment and they were not caused by the omeprazole-treatment at a dose which does not induce anacidity in the stomach. These results suggest that long-term omeprazole treatment reversibly increases the epithelial cell proliferation and suppresses its differentiation in the adult rate gastric mucosa probably by altering the acidic environment specific for the stomach.
Animals↗
Increasing development of pepsinogen-altered pyloric glands and adenocarcinoma in glandular stomach of analbuminemic rats.
The susceptibility of pepsinogen-altered pyloric glands (PAPG) and neoplastic glandular stomach lesions induced by N-methyl-N-nitro-N-nitrosoguanidine (MNNG) and catechol or sodium cholate in Nagase analbuminemic rats (NAR) was compared to Sprague-Dawley rats (SD). Male NAR and SD rats were given a single dose of 80 mg/kg body weight of MNNG by gastric intubation and, 2 weeks later, fed basal diet containing 0.8% catechol or 0.3% sodium cholate for 18 weeks. The animals were killed at the end of week 20 or after maintenance on basal diet at week 60. The number of pepsinogen-altered pyloric glands at week 20 was significantly (P < 0.001) higher in NAR fed either catechol or sodium cholate compared with SD rats. At week 60, adenomatous hyperplasias and adenocarcinomas were observed in 7 (88%; P < 0.01) and 3 (38%; P < 0.01) of 8 NAR fed catechol and in 4 (22%) and 0 of 18 SD rats, respectively. The results show that the frequency of PAPG in NAR and SD rats is related to the susceptibility to glandular stomach carcinoma. PAPG is a useful endpoint lesion for evaluation of gastric carcinogenicity in a 20-week carcinogenicity test, and NAR are sensitive for glandular stomach carcinogenesis.
Adenocarcinoma↗
Cathepsin E is expressed in fetal rat glandular stomach epithelial cells in primary culture in the absence of mesenchymes.
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Animals↗
In vivo short-term assays for tumor initiation and promotion in the glandular stomach of Fischer rats.
Here we summarize the data on 55 compounds tested in in vivo short-term assays for tumor-initiating and tumor-promoting activity in the glandular stomach of male Fischer (F344) rats. Most of the data has been previously published. Tumor-initiating activity was assayed by measuring the induction of unscheduled DNA synthesis (UDS) and DNA single strand scission; tumor-promoting activity was assayed by measuring the induction of ornithine decarboxylase (ODC) activity, increased replicative DNA synthesis (RDS), and of c-fos and c-myc oncogene expression. The compounds were orally administered. Twenty-nine compounds were tested for UDS. Eight were positive, including 5 glandular stomach carcinogens; 16 were negative, including 5 liver carcinogens; and 5 were equivocal. Twenty compounds were tested for DNA single strand scission. Twelve were positive, including 6 glandular stomach carcinogens; 7 negative, including 2 liver carcinogens; and 1 was equivocal. Thirty-two compounds were tested for RDS. Twenty-six were positive, including 8 glandular stomach carcinogens and 6 glandular stomach tumor-promoters; 4 were negative, including 3 liver carcinogens and a stomach irritant; and 2 were equivocal. Forty-five compounds were tested for ODC. Thirty-seven were positive, including 8 glandular stomach carcinogens and 6 glandular stomach tumor promoters; 7 were negative, including 3 liver carcinogens; and one was equivocal. All glandular stomach carcinogens and tumor-promoters examined were positive in both RDS and ODC. Two compounds were tested for c-fos and c-myc expression; one was a glandular stomach carcinogen and one was a glandular stomach tumor promoter, and both were positive. In addition, 2 compounds inhibited the increase in RDS induced by the tumor promoter NaCl, suggesting anti-tumor-promoter activity. Thus these assays are useful for assessing potential tumor-initiating and tumor-promoting activity in the rat glandular stomach.
Animals↗
Comparison of autoradiography, liquid scintillation counting and immunoenzymatic staining of 5-bromo-2'-deoxyuridine for measurement of unscheduled DNA synthesis and replicative DNA synthesis in rat liver.
Different methods for evaluating unscheduled DNA synthesis (UDS) and replicative DNA synthesis (RDS) were studied in hepatocytes of F344 rats exposed in vivo to dimethylnitrosamine (DMN) or CCl4. Hepatocytes were isolated and incubated in Williams' medium E supplemented with either [3H]thymidine for autoradiography or 5-bromo-2'-deoxyuridine for immunoenzymatic staining. In the method of liquid scintillation counting, the cells were incubated with [3H]thymidine with or without hydroxyurea. The nuclear fraction was isolated and the incorporation of [3H]thymidine into nuclear DNA was determined by a liquid scintillation counter. DMN at doses of 0.625-5 mg/kg body weight induced UDS of 1.6-37.9 (0 dose; -6.9) net grains/nucleus measured by autoradiography and 337-1377 (0 dose; 177) dpm/microgram DNA in the presence of hydroxyurea measured by a liquid scintillation counter. CCl4 at doses of 50-400 mg/kg body weight induced RDS in 1.5-12.1% (0 dose; 0.12%) and 1.8-14.6% (0 dose; 0.16%) of cells with the methods of autoradiography and immunoenzymatic staining, respectively, and of 2991-24256 (0 dose; 324) dpm/microgram DNA in the absence of hydroxyurea with the method of liquid scintillation counting. Similar dose-dependent induction of UDS and RDS was observed with these methods. These results suggest that the methods of liquid scintillation counting and immunoenzymatic staining have almost the same sensitivity for measuring UDS and RDS as that of autoradiography.
Animals↗
DNA damaging and cell proliferative activity of 1-methyl-1-nitrosourea in rat glandular stomach mucosa.
The DNA damaging and cell proliferative activity of 1-methyl-1-nitrosourea (MNU), a glandular stomach carcinogen, was studied in the pyloric mucosa of male F344 rats after administration by gastric tube. DNA damage was measured with unscheduled DNA synthesis (UDS) and DNA single strand scission as markers, while cell proliferation was measured with replicative DNA synthesis (RDS) and ornithine decarboxylase (ODC) as markers. MNU at doses of 30 and 60 mg/kg body wt and 80 min after administration dose-dependently induced UDS (49 and 79 (0 dose, 19) dpm/micrograms DNA) measured by liquid scintillation counting in the presence of hydroxyurea (an inhibitor of RDS). RDS (DNA synthesis in the absence of hydroxyurea; 239 dpm/micrograms DNA at 0 dose) did not increase at that time. MNU at doses of 10 and 60 mg/kg body wt and 2 h after administration dose-dependently induced DNA single strand scission of 8.2 and 43.5 (0 dose, 1.4) elution rate constant (x 10(-3)/ml). MNU at doses of 30 and 60 mg/kg body wt and 24 h after administration dose-dependently induced an increase in RDS (1362 and 2393 (0 dose, 682) dpm/micrograms DNA). MNU at doses of 60, 90 and 120 mg/kg body wt and 24 h after administration dose-dependently induced an increase in ODC activity (22.0, 29.4 and 38.4 (0 dose, 6.3) p mol CO2/30 min/mg protein). These results suggest that MNU has possible tumor initiating activity (UDS and DNA single stand scission) and tumor promoting activity (RDS and ODC) in rat stomach mucosa.
Animals↗
Induction of c-fos and c-myc oncogene expression in the pyloric mucosa of rat stomach by N-methyl-N'-nitro-N-nitrosoguanidine and taurocholate.
The induction of c-fos and c-myc expression in the pyloric mucosa of 8-week-old F344 male rats after oral administration of the glandular stomach carcinogen, N-methyl-N'-nitro-N-nitrosoguanidine (MNNG), or the tumor-promoter, taurocholate, was examined by Northern blotting. MNNG at doses of 5-50 mg/kg body weight dose-dependently induced transient increase of up to 30-fold c-fos expression with a maximum after 30 min, and of 8-fold c-myc expression with a maximum after 3 h. It also induced up to 3-fold increase in S-phase cells in the proliferation zone of the pyloric mucosa after 16 h. Similar effects were observed with sodium taurocholate at doses of 200-800 mg/kg body weight. These results suggest that c-fos and c-myc oncogenes play a role in stomach carcinogenesis.
Animals↗
Recommendations for the performance of UDS tests in vitro and in vivo.
The Working Group (WG) dealt with the harmonization of routine methodologies of tests for unscheduled DNA synthesis (UDS) both in vitro and in vivo. In contrast to the existing guidelines from OECD, EPA and EC on in vitro UDS tests (there is no Japanese UDS guideline), the Working Group recommends that in general in vitro UDS tests should be performed with primary hepatocytes. For routine applications any other cell types would need special justification. Hepatocytes from male rats are preferable, unless there are contra-indications on the basis of e.g. toxicokinetic data. According to the OECD, EPA and EC guidelines, UDS may be analysed by means of autoradiography (AR) or liquid scintillation counting (LSC). The WG recommends use of AR. LSC is less suitable due to the problem of differentiation between UDS activity and replicative DNA synthesis, and the disadvantage that cells cannot be analysed individually. Since a specific cell type was recommended by the WG, methodological aspects could be described in more detail than in the present guidelines. For in vitro tests, it was agreed that the initial viability of freshly isolated hepatocytes should be at least 70%. With regard to the need for confirmatory experiments in the event of a clear-cut negative result, the majority view was that confirmation by a second (normally not identical) experiment is still needed; this is in line with the present OECD and EC guidelines. Evaluation of results from UDS tests should be based primarily on net nuclear grain (NNG) values, although it is recognised that nuclear and cytoplasmic grains result from different biological processes. Since grain counts are influenced by a number of methodological parameters, no global threshold NNG value can be recommended for discrimination of positive and negative UDS results. For in vitro assays, the criteria for positive findings go beyond those of the present guidelines and two alternative approaches are given which are based on (1) dose-dependent increases in NNG values and (2) reproducibility, dose-effect relationship and cytotoxicity. At present there is no official guideline on the performance of in vivo UDS tests. Some fundamental recommendations given for in vitro methodology also apply to the in vivo assay. For routine testing with the in vivo UDS test, again the general use of hepatocytes from male rats is recommended. However, concerning the requirement to use one or two sexes, consistency with other in vivo genotoxicity assays (e.g. the micronucleus assay) would be preferable. As for the in vitro methodology, AR is preferred rather than LSC.(ABSTRACT TRUNCATED AT 400 WORDS)
Animals↗
Effects of dietary restriction on induction of unscheduled DNA synthesis (UDS) and replicative DNA synthesis (RDS) in rat liver.
The effects of dietary restriction on the induction of unscheduled DNA synthesis (UDS) and replicative DNA synthesis (RDS) were studied in the hepatocytes of F344 rats exposed in vivo to dimethylnitrosamine (DMN) or CCl4. The animals were given food ad libitum, a restricted amount of food (4 g/rat/overnight) or no food. Hepatocytes were isolated 2 h after oral administration of DMN at a dose of 5 mg/kg body weight and 48 h after oral administration of CCl4 at a dose of 400 mg/kg body weight, and incubated for 4 h in Williams' medium E supplemented with either [3H]thymidine for UDS or 5-bromodeoxyuridine for RDS. UDS was determined by autoradiography and RDS was determined by the immunoenzymatic staining method. The background levels of UDS (net grains/nucleus) and RDS (cells in S phase) in control were -12.4 and 0.64% for ad libitum feeding, -6.8 and 0.04% for restricted feeding, and -8.1 and 0% for fasting. UDS induced by DMN and RDS induced by CCl4 were 19.4 and 3.3% for ad libitum feeding, 34.5 and 10.4% for restricted feeding, and 47.8 and 15.1% for fasting. DMN demethylase activity in rat liver was also found to increase with dietary restriction. These results indicate that dietary restriction modulates the responses of UDS and RDS in the liver of rats.
Animals↗
Fetal rat glandular stomach epithelial cells differentiate into surface mucous cells which express cathepsin E in the absence of mesenchymal cells in primary culture.
It is well established that the differentiation of glandular stomach epithelial cells is affected by many factors including epithelial-mesenchymal interactions. To clarify the control mechanism of their differentiation, we developed a primary culture system for fetal rat glandular stomach epithelial cells, and examined their differentiation in the absence of mesenchyme. Pure glandular stomach epithelial tissues obtained from 16.5-day fetal rats proliferated rapidly, increasing their number about 20 times in the first 7 days. The epithelial nature of the cells was confirmed by the presence of cytokeratin in the cells. Glandular stomach epithelial cells formed simple cuboidal/squamous epithelia with many mucous granules in their cytoplasm, and exhibited epithelial polarity with microvilli on the luminal surface, basal lamina-like material on the basal surface, and junctional complexes in the apical region. Biochemical analysis showed that the cells expressed acid protease activity in culture. Previous studies showed that glandular stomach epithelial cells specifically expressed two types of acid proteases: pepsinogens in chief and mucous neck cells, and cathepsin E in surface mucous cells. Immunohistochemical studies using specific antibodies showed that the cultured cells expressed cathepsin E but not pepsinogens, and the result was confirmed by zymogram and Western blotting analysis. We thus concluded that fetal rat glandular stomach epithelial cells differentiated into surface mucous cells that expressed cathepsin E in primary culture in the absence of mesenchyme.
Animals↗
Cumulative effects of chromosome aberrations and sister chromatid exchanges in rat liver induced in vivo by heterocyclic amines.
Cumulative effects of chromosome aberrations and sister chromatid exchanges (SCEs) were studied in hepatocytes of F344 rats exposed in vivo to 2-amino-3-methylimidazo[4,5-f]quinoline (IQ) at doses of 12.5, 25 or 50 mg/kg body wt/day or 2-nitro-3-methylimidazo[4,5-f]quinoline (nitro-IQ) at doses of 12.5, 25 or 50 mg/kg body wt/day. Hepatocytes were isolated 24 h after 1, 7, 14 or 28 repeated doses (once a day) by gastric intubation and allowed to proliferate in Williams' medium E supplemented with epidermal growth factor. Cells were fixed after a culture period of 48 h. Multiple treatment with IQ or nitro-IQ induced significant chromosome aberrations time- and dose-dependently, the maximum frequency of chromosome aberrations in metaphase cells being 39 and 33% respectively, while that in controls was 1.1%. Single treatment with IQ or nitro-IQ induced significant SCEs dose-dependently, the maximum frequency being 0.83 and 0.79 per chromosome respectively, while the control value was 0.51. Multiple treatment with nitro-IQ induced significant SCEs to a plateau level of 0.90 per chromosome. Cytogenetic damage in the liver by IQ was greater than that by nitro-IQ. These results show that this assay of chromosome aberrations and SCEs in rat liver in vivo without partial hepatectomy or mitogen treatment in vivo is a sensitive method for evaluating the cumulative tumor-initiating activities of carcinogenic heterocyclic amines at low doses and should be useful for the detection of unknown hepatocarcinogens.
Amines↗
Effects of omeprazole on gastric mucosal growth and differentiation in developing rat.
The effects of omeprazole on developing rat stomach mucosa were investigated. Infant rats were given subcutaneous injections of either omeprazole (25 mg/kg body weight/day) or vehicle once a day from the day after birth. As a result, omeprazole caused an elevation of mucosal pH and suppressed an increase in mucosal pepsinogen and its mRNA levels during stomach development. Histologically, these changes were associated with a reduction in mature pepsinogen-producing cells throughout stomach mucosa. Omeprazole also caused a delay in the expression of cathepsin E in surface mucous cells and an increase in labeled cells with bromodeoxyuridine. Thus, the present results indicate that omeprazole induces an increase in mucosal cell proliferation and delays the differentiation of developing rat stomach mucosa. Since the observed changes were remarkable especially from days 15 to 21 after birth when significant development of acid secretion occurs, the effects of omeprazole appear to be related with the potent acid inhibitory effect of the reagent.
Aging↗
Ability of N-methyl-N'-nitro-N-nitrosoguanidine, 4-nitroquinoline 1-oxide, dimethylnitrosamine, and NaCl to induce unscheduled DNA synthesis, stimulate replicative DNA synthesis, and produce DNA single-strand breaks in pyloric mucosa of rat stomach.
Male F344 rats were given test chemicals orally, and samples of their pyloric mucosa were incubated in vitro. Induction of unscheduled DNA synthesis (UDS) and stimulation of replicative DNA synthesis in the pyloric mucosa were then examined by addition of [3H]thymidine and simultaneous determinations of DNA synthesis in the presence and absence of hydroxyurea, an inhibitor of replicative DNA synthesis. DNA damage was also examined by the alkaline elution method with DNA single-strand scission as a marker. The results showed four types of abilities of the chemicals to affect UDS and replicative DNA synthesis in the pyloric mucosa of rat stomach 1-2 h after their administration: (1) induction of UDS and stimulation of replicative DNA synthesis by N-methyl-N'-nitro-N-nitrosoguanidine (MNNG), a glandular stomach carcinogen, (2) induction of only UDS by 4-nitroquinoline 1-oxide (4NQO), a glandular stomach carcinogen, (3) stimulation of only replicative DNA synthesis by NaCl, a glandular stomach tumor promoter, and (4) neither induction of UDS nor stimulation of replicative DNA synthesis by dimethylnitrosamine (DMN), a liver carcinogen. DNA single-strand scission was induced by MNNG and 4NQO, being maximal 2 h after their administration, but was not induced by NaCl or DMN. Thus it correlated well with the induction of UDS. The present results indicate four types of inductive abilities of chemicals on UDS and replicative DNA synthesis in rat stomach pyloric mucosa and show that this method can detect differences in the action mechanisms and organ specificities of glandular stomach carcinogens.
4-Nitroquinoline-1-oxide↗
DNA methylation of the pepsinogen 1 gene during rat glandular stomach carcinogenesis induced by N-methyl-N'-nitro-N-nitrosoguanidine or catechol.
The methylation patterns of the rat pepsinogen 1 (Pg1) gene in preneoplastic and neoplastic stomach lesions induced by genotoxic N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) or the non-genotoxic carcinogen catechol were investigated. Male WKY/Ncrj rats were given MNNG in their drinking water (50 mg/l) for 30 weeks or 0.8% catechol throughout the experiment (60 weeks). MNNG induced Pg1 altered pyloric glands (PAPG), adenomatous hyperplasias and well-differentiated adenocarcinomas. Catechol also induced PAPG and adenomatous hyperplasias although cancers did not develop. Adenomatous hyperplasias and adenocarcinomas all consisted of gastric type cells resembling surface mucous cells or pyloric gland cells with little or no Pg1 expression. In MNNG-induced stomach cancers generally lacking Pg1, altered Pg1 gene methylation was observed with both CCGG and GCGC sites being methylated more than normal pyloric mucosa. MNNG or catechol-induced adenomatous hyperplasias also demonstrated essentially the same methylation changes in the CCGG, but not in the GCGC sites. In the mucosa containing PAPG in groups treated with MNNG or catechol the methylation patterns of the Pg1 gene were quite similar to those of normal pyloric mucosa, although the CCGG sites tended to demonstrate slightly increased methylation. The results suggest that the altered methylation of the Pg1 gene observed in stomach cancers is acquired early in the carcinogenic process and progressive methylation changes occur with tumor development.
Adenocarcinoma↗
Possible tumor-initiating and -promoting activity of p-methylcatechol and methylhydroquinone in the pyloric mucosa of rat stomach.
The possible tumor-promoting and tumor-initiating activities of p-methylcatechol and methylhydroquinone in the pyloric mucosa of male F344 rats were studied. Ornithine decarboxylase (ODC) and replicative DNA synthesis (RDS) were used as markers of tumor promotion and DNA single strand scission and unscheduled DNA synthesis (UDS) as markers of tumor initiation. The compounds were administered by gastric intubation and results were compared with those after administration of catechol. p-Methylcatechol at doses of 60 to 180 mg/kg body weight dose-dependently induced up to 20-fold increase in ODC activity and 9-fold increase in RDS with maxima 24 h after its administration, but it did not induce significant DNA single strand scission or UDS. Methylhydroquinone at a dose of 200 mg/kg body weight induced up to 6-fold increase in ODC activity 24 h, and 5-fold increase in RDS 16 h after its administration, but the induction was not dose-dependent. At a dose of 200 mg/kg body weight it induced DNA single strand scission, but not UDS. These results and previous findings show that the possible tumor-promoting activities of catechol are several times higher than those of p-methylcatechol and 10 times higher than those of methylhydroquinone.
Adenocarcinoma↗