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C C Irving

Publications and source records attributed to C C Irving.

At least 19 recordsLinked to original sources
PubMed1989

Changes in aldehyde dehydrogenase during rat urinary bladder carcinogenesis.

We have reported that normal rat urinary bladder possesses significant amounts of an aldehyde dehydrogenase (class 3 ALDH) expressed during hepatocarcinogenesis, but not detectable in normal liver. Changes in expression of both liver and bladder ALDH during N-butyl-N-(4-hydroxybutyl) nitrosamine (BBN)-induced bladder carcinogenesis were studied. The ALDH phenotype was determined at intervals over 42 weeks by histochemical analysis, total ALDH activity assays and gel electrophoresis using propionaldehyde and NAD (P-NAD) which characterizes class 1 and 2 ALDH, or benzaldehyde and NADP (B-NADP) to determine class 3 ALDH. By total activity assays and gel electrophoresis, there was a significant decrease in bladder class 3 ALDH activity during weeks 5-15. Histochemical analysis clearly demonstrates changes in ALDH early in neoplastic development. Intense staining with B-NADP in regions of hyperplasia was first detectable at week 10. Staining in hyperplastic regions was accompanied by a significant decrease in ADLH in neighboring, apparently normal urothelium. As the urothelium became more abnormal, class 3 ALDH activity increased. By week 25, the bladder class 3 ALDH activity of BBN-treated animals was 2 times greater than the control group class 3 ALDH activity. Histochemically, all papillomas and carcinomas examined possessed class 3 ALDH. However, staining was heterogeneous within the lesions. Bladder neoplasm class 3 ALDH specific activity was greater than control group class 3 ALDH activity in 70% of papillomas and carcinomas. These results suggest events may be occurring in bladder similar to those in liver which alter expression of aldehyde dehydrogenase during carcinogenesis.

Aldehyde Dehydrogenase↗
PubMed1988

Oxidation of N-butyl-N-(3-formylpropyl)nitrosamine to N-butyl-N-(3-carboxypropyl)nitrosamine in rat liver and inhibition by disulfiram.

The metabolism of N-butyl-N-(3-formylpropyl)nitrosamine, a presumptive intermediate metabolite of the urinary bladder carcinogen N-butyl-N-(4-hydroxybutyl)nitrosamine, by rat liver has been examined. N-Butyl-N-(3-formylpropyl)nitrosamine was metabolized by an NADH-dependent reduction to N-butyl-N-(4-hydroxybutyl)nitrosamine and by an NAD+-dependent oxidation to N-butyl-N-(3-carboxypropyl)nitrosamine. The reduction of N-butyl-N-(3-formylpropyl)nitrosamine was inhibited by pyrazole. The oxidation of N-butyl-N-(3-formylpropyl)nitrosamine was studied further. The rate of oxidation in total rat liver was 3 mumol/min/g liver or 21 nmol/min/mg protein and was similar to that found for the oxidation of propionaldehyde, a model substrate for isozymes of rat liver aldehyde dehydrogenase. The rate of oxidation of N-butyl-N-(3-formylpropyl)nitrosamine by isozymes in rat liver cytosol was 2-2.5 times that found for propionaldehyde. The apparent Km for the NAD+-dependent oxidation of N-butyl-N-(3-formylpropyl)nitrosamine was 20-30 microM, which is considerably lower than values reported for known substrates of aldehyde dehydrogenase. The NAD+-dependent oxidation of N-butyl-N-(3-formylpropyl)nitrosamine was inhibited 40-50% by 50 microM disulfiram, 60-70% by 100 microM disulfiram, and 50% by 0.4 mM sodium arsenite. These studies show that N-butyl-N-(3-formylpropyl)nitrosamine is very rapidly oxidized to N-butyl-N-(3-carboxypropyl)nitrosamine in rat liver by aldehyde dehydrogenase and the results may help to explain why the 3-formylpropyl intermediate has not been directly identified as a metabolite of N-butyl-N-(4-hydroxybutyl)nitrosamine in urine or in isolated hepatocytes.

Aldehyde Dehydrogenase↗
PubMed1988

Inhibition of DNA methylase activity by acrolein.

Acrolein, a reactive metabolite of cyclophosphamide, may be responsible for bladder cancer induced by cyclophosphamide. DNA methylase was isolated from the liver and urothelium of rats by high salt extraction of purified nuclei. Acrolein at 10 microM inhibited liver and bladder DNA methylase activity by 30-50%. Kinetic studies with the liver enzyme showed a competitive type of inhibition with a Ki of 6.7 microM. Both dithiothreitol and glutathione afforded protection to the enzyme when added to the assay. At near equimolar concentrations of glutathione to acrolein, the methylase retained 80-90% activity. An increase in DNA had no effect on the inhibition by acrolein, whereas increased amounts of protein protected against acrolein inhibition, suggesting that acrolein reacted with the DNA methylase protein. On the other hand, DNA that had been reacted with acrolein was unable to serve as a substrate for DNA methylase. As the DNA adducts increased the methylation of the DNA decreased. Thus, acrolein has the ability to react with DNA and the DNA methylase protein, either of which results in inhibition of DNA methylation.

Acrolein↗
PubMed1987

Influence of disulfiram on the metabolism of the urinary bladder carcinogen N-butyl-N-(4-hydroxybutyl)nitrosamine in the rat.

The effect of feeding disulfiram (DSF) to rats on the metabolism of N-butyl-N-(4-hydroxybutyl)nitrosamine (BHBN) was examined in order to study the mechanism by which DSF inhibits bladder cancer induction by BHBN. After 2 weeks of feeding 0.5% DSF in the diet, animals were given [14C]BHBN (25 mg/kg) and the urine and expired CO2 were collected for 8 h. Radioactivity in expired air was very low, but DSF caused a significant reduction in expired 14CO2 (control 1.0% of dose; DSF 0.6%), presumably by inhibition of alpha-hydroxylation pathways. There was no difference in the excretion of total urinary radioactivity (control 84%; DSF 85%). Urine was analyzed by h.p.l.c. for BHBN, N-butyl-N-(3-carboxypropyl)nitrosamine (BCPN), N-butyl-N-2-hydroxy-3-carboxypropyl)nitrosamine (BHCPN) and N-butyl-N-carboxymethylnitrosamine (BCMN). DSF did not alter the urinary excretion of BCPN (control 64% of dose; DSF 61%), whereas BHCPN excretion was increased (control 11% of dose; DSF 22%) and urinary levels of BCMN were decreased (control 10% of dose; DSF 4%). The metabolism of BHBN was also studied in isolated hepatocytes from control and DSF-fed rats. Hepatocytes were incubated in Liebovitz's L-15 medium containing 0.5 mM [14C]BHBN and aliquots of the medium were removed for h.p.l.c. analysis at 0.5, 1, 2 and 4 h. Metabolic rates are expressed as mumol/h/5 million cells. There was no difference in the overall rate of metabolism of BHBN in control and DSF-fed rats. BHBN was very rapidly oxidized to BCPN and the rate was not affected by DSF treatment (control 1.82; DSF 1.76). The rate of accumulation of BHCPN was increased 3.5-fold in the DSF-fed rats (control 0.06; DSF 0.21) and BCMN could not be detected. Taken together, these data show that (i) DSF may inhibit the low extent of alpha-hydroxylation of BHBN or BCPN; (ii) DSF does not inhibit the rapid oxidation of BHBN to BCPN and (iii) DSF appears to inhibit the metabolism of BHCPN.

Animals↗
PubMed1984

Characterization of the purine ring-opened 7-methylguanine and its persistence in rat bladder epithelial DNA after treatment with the carcinogen N-methylnitrosourea.

Purine ring-opened 7-methylguanine, prepared in vitro by alkaline treatment of 7-methylguanosine or of methylated calf thymus DNA, was extensively characterized by chromatographic and spectral techniques as N5-methyl-N5-formyl-2,5,6-triamino-4-hydroxypyrimidine. This modified base chromatographed as an early-eluting peak on an ion-exchange column but separated into two interconvertible components after reversed-phase or porous-resin h.p.l.c. The two components were analyzed by thermal desorption mass spectrometry and 500 MHz 1H-n.m.r. spectroscopy. Their mass spectra were identical (M+ at m/z 183) and their n.m.r. spectra each exhibited the same two sets of resonances whose relative intensities were solvent-dependent. Analysis by h.p.l.c. showed interconversion of the two components and kinetic studies demonstrated that this reaction was a reversible first-order process. At equilibrium, k1 = k2 = 0.334 h-1 and delta G = 22.9 kcal/mol. These data indicated that the ring-opened 7-methylguanine exists as cis/trans isomers with restricted rotation about the amide bond. Treatment of rats with an intraurethral initiating dose of the carcinogen N-methylnitrosourea resulted in a high level of bladder epithelial DNA modification with 7-methylguanine, O6-methylguanine, and methyl phosphotriesters as major adducts at 2 h after instillation. Purine ring-opened 7-methylguanine, chromatographically identical to the in vitro products, was initially a minor adduct. However, it was the only persistent modification in the bladder epithelial DNA and eventually accounted for 72% of the total carcinogen binding after 21 days. A tumor-promoting regimen, involving dietary sodium saccharin, did not alter the repair or persistence of any of the methylated adducts. These data demonstrate that purine ring-opened 7-methylguanine, previously reported to exist in liver DNA after N,N-dimethylnitrosamine or 1,2-dimethylhydrazine treatment, is present in a carcinogen-target tissue and is considerably more persistent than O6-methylguanine or other DNA methylation products. The possible role of this adduct as a promutagenic lesion initiating urinary bladder carcinogenesis is discussed.

Animals↗
PubMed1984

Comparative carcinogenicity of N-butyl-N-(3-carboxypropyl)-nitrosamine and N-butyl-N-(4-hydroxybutyl)nitrosamine for the urinary bladder of (C57BL/6 X DBA/2)F1 mice.

The carcinogenicity of N-butyl-N-(3-carboxypropyl)-nitrosamine [CAS: 38252-74-3; 4-(N-butyl-N-nitrosamino)butyric acid] in male and female (C57BL/6 X DBA/2)F1 mice was determined. N-Butyl-N-(3-carboxypropyl)nitrosamine given in the drinking water at a concentration of 3 mM (0.056%) for 13 weeks induced only carcinoma of the urinary bladder in both sexes. At 22-28 weeks, the incidences of bladder cancer in the male and female mice were 100 and 88%, respectively. These bladder tumors were classified histologically according to the frequency (%) of tumor type: pure transitional cell carcinoma, 42%; mixed (transitional cell carcinoma with squamous or glandular differentiation, or both), 28%; squamous cell carcinoma, 27%; and carcinoma in situ, 3%. No significant sex differences were observed. In comparative studies, the incidence of bladder cancer was 100% for both sexes after administration of 3 mM (0.052%) N-butyl-N-(4-hydroxybutyl)nitrosamine [CAS: 3817-11-6; 4-(butylnitrosoamino)-1-butanol] in the drinking water. The frequency of pure transitional cell carcinoma was 47%, which was not significantly different from that observed for the carboxypropyl compound. The frequencies of other types of bladder carcinoma induced by N-butyl-N-(4-hydroxybutyl)nitrosamine were the following: mixed, 8%; squamous cell carcinoma, 42%; and carcinoma in situ, 3%.

Animals↗
PubMed1983

The effect of disulfiram on the carcinogenicity of N-butyl-N-(3-carboxypropyl)nitrosamine in the rat.

N-Butyl-N-(3-carboxypropyl)nitrosamine (BCPN) is a proximate carcinogenic metabolite of the bladder specific carcinogen N-butyl-N-(4-hydroxybutyl)nitrosamine (BHBN). The objective of this study was to determine if disulfiram would inhibit the induction of bladder cancer in rats given BCPN, as reported for BHBN (Cancer Res., 39, 3040, 1979). Two groups of 30 male Wistar rats were given 1.5 mM BCPN (0.028%) in the drinking water for 12 weeks. The total dose of BCPN/rat was 5 mmol (0.95 g). During administration of the BCPN, one group of rats was fed a diet containing 0.5% disulfiram, while the other group was maintained on control diet. At the end of 12 weeks, the animals were maintained on control diet without BCPN for an additional 18 weeks, at which time the animals were sacrificed. It was found that 0.5% disulfiram significantly reduced the incidence of bladder cancer, decreasing from 30/30 (100%) in the group receiving BCPN alone to 3/30 (10%) in the group fed the disulfiram diet. The inhibition of BHBN-induced bladder cancer by disulfiram, previously reported, was also confirmed in these experiments.

Animals↗
PubMed1981

The cellular features of developing carcinoma in murine urinary bladder.

Bladder cancer often results from a widespread reaction of urothelial cells to carcinogenic stimuli. Although developing carcinoma is widely considered to progress through various grades of epithelial atypia, well-controlled prospective studies detailing the morphologic features of these lesions at the cellular level have not appeared in the literature. This study was designed to document the cellular features of developing urothelial carcinoma in experimental animals using the BHBN model system. Developing lesions were monitored by periodic collection of urine and tissue. The specimens were coded and examined by cytology and histology using multiple discriminators. The morphologic changes in the treated bladders were statistically different from those in control tissue. They could be divided into three stages: 1) The earliest abnormalities were an increase in the number of cell layers, loss of polarity, and slight crowding of nuclei in the tissue sections. Among the cellular features, there were increased nuclear size and sharply angulated indentations (notches) in the nuclear borders. A few nuclei exhibited a finely granular pattern, but dusty chromatin predominated. 2) In the intermediate stage, nuclear crowding became more prominent, and there were numerous areas with finely granular, regularly distributed chromatin. A few nucleoli were identified. Mitoses were prominent in the tissue sections. 3) In the late stage, as papillary tumors developed elsewhere, the urothelium of the flat areas changed significantly. Nuclear crowding and notching remained constant but were overshadowed by the appearance of nucleoli and irregularly distributed chromatin. The pattern was finely granular in some cases but coarsely granular in most. Nuclear size decreased markedly as the cells became smaller and more numerous. Cytologically, it was not possible to distinguish these cells from neoplastic cells emanating from the papillary areas. This experimental study tends to confirm deductions made from clinical material that urothelial carcinoma develops through an orderly sequence of morphologic severity. It further indicates that invasive carcinoma can arise from neoplastic cells that neither occupy the full thickness of the epithelium nor represent lateral migration from an adjacent full thickness lesion. The detailed cellular features documented can be used to identify atypical cells in correlative cytologic preparations. Studies such as this could provide an experimental basis for future evaluations of the cytologic characteristics of human urothelial atypia.

Animals↗
PubMed1981

Glucuronide formation in the metabolism of N-substituted aryl compounds.

N-Glucuronide conjugates of N-arylhydroxylamines and O-glucuronides of N-acetyl-N-arylhydroxylamines may play significant roles in the extrahepatic carcinogenicity of arylamines by serving as stable transport forms of metabolically activated precursors. In extrahepatic target organs, these glucuronides can undergo pH-dependent hydrolytic reactions to liberate an activated metabolite or one capable of being further activated.

Animals↗
PubMed1980

Synthesis and mutagenicity of 4-(N-butylnitrosamino)-4-hydroxybutyric acid lactone, a possible activated metabolite of the proximate bladder carcinogen N-butyl-N-(3-carboxypropyl)nitrosamine.

4-(N-Butylnitrosamino)-4-hydroxybutyric acid lactone (BBAL) was synthesized as a possible intermediate produced by metabolic activation of a selective bladder carcinogen, N-butyl-N-(3-carboxypropyl)nitrosamine. BBAL was stable in neutral sodium phosphate buffer (ionic strength, 0.2), having a half-life of more than 30 hr at 25 degrees. The mutagenic effects of BBAL were tested with the use of Salmonella typhimurium TA1535 and Escherichia coli B/rWP2-try-, WP2-try-hcr-, and Sd4. The gene-damaging effects were assayed by repair tests with Bacillus subtilis H17 (rec+) and M45 (rec-). BBAL showed potent effects in the mutation and repair tests on all the strains tested without activation. A possibility is suggested for the metabolic activation of N-butyl-N-(3-carboxypropyl)nitrosamine to BBAL by alpha-hydroxylation at the site of the 3-carboxypropyl chain followed by lactonization in target tissues prior to interaction with macromolecules to lead to carcinogenesis.

Bacillus subtilis↗
PubMed1979

Influence of dose of N-methyl-N-nitrosourea on the induction of urinary bladder cancer in rats.

N-methyl-N-nitrosourea (MNU) was instilled by a urethral catheter into the urinary bladders of female Wistar rats in weekly doses of 0.5 mg for 1, 2, 3 and 4 weeks. At 75 weeks after the initial dose of MNU, the incidences of bladder cancer were 0, 7, 50 and 64% for the total doses of MNU of 0.5, 1.0, 1.5 and 2.0 mg, respectively. Control rats instilled with 0.9% NaCl only for 1--4 weeks did not develop bladder cancer by 75 weeks. Higher doses of MNU of 4.0 and 6.0 mg, given weekly in 0.5 mg amounts for 8 and 12 weeks, respectively, induced a higher incidence (nearly 90%) of urinary bladder cancer in rats at 22--28 weeks. However, it was shown that control rats given 12 weekly installations of solvent only developed a significant number (33%) of bladder cancers by 22--28 weeks.

Animals↗
PubMed1979

O6-methylguanine accumulates in DNA of mammary glands after administration of N-methyl-N-nitrosourea to rats.

N-Methyl-N-nitrosourea (MNU) induces mammary carcinoma in female rats when given intravenously. After a single intravenous dose of N-methyl-N-nitrosourea (5 mg/100 g body wt.), we were unable to detect a shift of rat mammary gland DNA on an alkaline sucrose gradient. However, the alkylated products in DNA, 7-methylguanine and O6-methylguanine, were determined at various times following treatment with N-methyl-N-nitrosourea. O6-Methylguanine was removed from the DNA at a slower rate than 7-methylguanine and increased in the DNA with a second injection of N-methyl-N-nitrosourea. 3-Methyladenine was not detected in DNA from the mammary gland of the rat. These data support previous work with brain and bladder that suggest the persistence of O6-methylguanine in DNA might be involved in the induction of cancer by N-methyl-N-nitrosourea.

Animals↗
PubMed1979

Inhibition of N-n-butyl-N-(4-hydroxybutyl)nitrosamine-induced urinary bladder cancer in rats by administration of disulfiram in the diet.

The objective of this study was to determine if disulfiram would influence the induction of urinary bladder cancer in rats given N-n-butyl-N(4-hydroxybuty)nitrosamine (BHBN). Adult male Wistar rats were divided into: Group 1, control diet, 30 rats; Group 2, control diet plus 0.025% BHBN in the drinking water, 60 rats; Group 3, control diet containing 0.5% disulfiram, 30 rats; and Group 4, control diet containing 0.5% disulfiram plus 0.025% BHBN in the drinking water, 60 rats. The animals were kept on these regimens for 15 weeks and then were transferred to and maintained on control diet. The average total intake of BHBN was 1.21 g/rat for Group 2 and 1.23 g/rat for Group 4. The cumulative incidences of bladder cancer at 25 weeks after initial exposure to BHBN were: Group 1, 0 of 9; Group 2, 27 of 27; Group 3, 0 of 9; and Group 4, 0 of 27. At termination of the experiment (32 to 42 weeks), the final bladder cancer incidences were: Group 1, 0 of 30 (0%); Group 2, 57 of 57 ()00%); Group 3, 0 of 24 (0%); and Group 4, 7 of 55 (13%). Except for a carcinoma of the renal pelvis in one rat in Group 2 and the bladder tumors in Groups 2 and 4, tumors were not detected in other organs of any of these rats. It was concluded that disulfiram significantly inhibited the induction of bladder cancer in rats exposed to BHBN. The mechanism of action of disulfiram in this process is under investigation.

Animals↗
PubMed1978

The development of polyploidy in two classes of rat liver nuclei.

Two classes of nuclei from livers of Sprague-Dawley rats were isolated, one pelleting in 2.3 M sucrose (H nuclei) and the second class sedimenting through 1.6 and 1.8 M sucrose and banding at the 1.8/2.3 M sucrose interface (L nuclei) of a three-step discontinuous gradient. In younger animals, the L nuclear fraction was the major fraction, but the percentage of nuclei found in the L fraction decreased as the animals grew. Nuclear ploidy was determined by flow microfluorometry using propidium iodide as a DNA stain. Both the H and L nuclear fractions contained diploid, tetraploid and octaploid nuclei; but the degree of polyploidy was greater in the H fraction. Concomitant with the change in distribution of nuclei between the H and L fractions with increasing age was a progressive increase in the degree of polyploidy in the H fraction. Polyploidy did not increase linearly with age in the H nuclear fraction but increased in cycles marked by large changes in the numbers of nuclei found in H and L nuclear fractions. By 12 weeks of age, 4n-H nuclei were the largest single population of nuclei in rat liver. These observations suggested that the shift of liver nuclei from the L fraction to the H fraction was associated with the development of polyploidy and with the differentiation of hepatocytes.

Aging↗
PubMed1977

The effect of S-adenosylhomocysteine on DNA methylation in isolated rat liver nuclei.

DNA methylation was studied in vitro using whole nuclei from regenerating rat liver. Methyl incorporation from S-adenosyl-[Me-3H]methionine in nuclei from regenerating liver was four times higher than that of normal liver. The effect of S-adenosylhomocysteine on DNA methylation was examined, and it was found at equal molar concentrations of S-adenosylhomocysteine to to S-adenosylmethionine that DNA methylation was competitively inhibited 50%.

Animals↗
PubMed1977

Methylation of DNA in rat liver and intestine by dimethylnitrosamine and N-methylnitrosourea.

A chromatographic procedure for improved separation of deoxyribonucleosides and methylated deoxyribonucleosides is described. DNA was isolated from liver and small intestine of rats treated with [14C]dimethylnitrosamine ([14C]DMN) or N-[3H]methyl-N-nitrosourea ([3H]MNU), and the purified DNA was hydrolyzed enzymatically. The deoxyribonucleosides were chromatographed on an Aminex A-6 cation exchange column at 37 degrees C with 0.4 M ammonium formate, pH 4.5, as eluant. In addition to showing the presence of the expected alkylated products, N7-methyldeoxyguanosine (determined as N7-methylguanine) and O6-methyldeoxyguanosine, several other minor methylated products were found in liver and intestinal DNA of rats treated with DMN or MNU. Two of these products are believed to be N3-methylthymidine and O4-methylthymidine.

Animals↗
PubMed1977

Inhibition of DNA methylation by S-adenosylethionine with the production of methyl-deficient DNA in regenerating rat liver.

Ethionine, a liver carcinogen, was administered p.o. (300 mg/kg) to rats 17 hr after partial hepatectomy. At 6 hr after administration of the ethionine, hepatic S-adenosylethionine levels were 30- to 40-fold greater than the hepatic level of S-adenosylmethionine. A 10-fold ratio of S-adenosylethionine to S-adenosylmethionine still persited at 24 hr after ethionine administration. When given at 17 hr after partial hepatectomy, ethionine produced a 30% inhibition of DNA synthesis, measured by the incorporation of [methyl-3H]thymidine at 23 to 24 hr after partial hepatectomy (6 to 7 hr after ethionine administration). DNA synthesized during this interval was methyl deficient as judged by the reduced incorporation of radioactivity from L-[methyl-3H]methionine into 5-methylcytosine residues of DNA. In an assay for DNA methylation in vitro using whole nuclei, the methyl-deficient DNA was methylated by S-adenosylmethionine 8 times more than was control DNA; the DNA methylation was competitively inhibited by S-adenosylethionine. These data suggest that S-adenosylethionine, formed in vivo from ethionine, competitively inhibits the methylation of DNA in vivo by S-adenosylmethionine, resulting in the production of methyl-deficient DNA.

Animals↗