The fate of 7[14C]-methylguanine after administration to the rat.
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ABSTRACT:
SUBMITTER: Craddock VM
PROVIDER: S-EPMC1186754 | biostudies-other | 1968 Aug
REPOSITORIES: biostudies-other
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Project description:2,4-Dinitrosanisole (DNAN) is an insensitive munitions component replacing conventional explosives. While DNAN is known to biotransform in soils to aromatic amines and azo-dimers, it is seldom mineralized by indigenous soil bacteria. Incorporation of DNAN biotransformation products into soil as humus-bound material could serve as a plausible remediation strategy. The present work studied biotransformation of DNAN in soil and sludge microcosms supplemented with uniformly ring-labeled 14C-DNAN to quantify the distribution of label in soil, aqueous, and gaseous phases. Electron donor amendments, different redox conditions (anaerobic, aerobic, sequential anaerobic-aerobic), and the extracellular oxidoreductase enzyme horseradish peroxidase (HRP) were evaluated to maximize incorporation of DNAN biotransformation products into the nonextractable soil humus fraction, humin. Irreversible humin incorporation of 14C-DNAN occurred at higher rates in anaerobic conditions, with a moderate increase when pyruvate was added. Additionally, a single dose of HRP resulted in an instantaneous increased incorporation of 14C-DNAN into the humin fraction. 14C-DNAN incorporation to the humin fraction was strongly correlated (R2 = 0.93) by the soil organic carbon (OC) amount present (either intrinsic or amended). Globally, our results suggest that DNAN biotransformation products can be irreversibly bound to humin in soils as a remediation strategy, which can be enhanced by adding soil OC.
| S-EPMC5772931 | biostudies-literature
Project description:1. Glucose 5-phosphate was synthesized from ribose 5-phosphate by an enzyme extract prepared from an acetone-dried powder of rat liver. Three rates of ribose 5-phosphate utilization were observed during incubation for 17 h. An analysis of intermediates and products formed throughout the incubation revealed that as much as 20% of the substrate carbon could not be accounted for. 2. With [1-14C]ribose 5-phosphate as substrate, the specific radioactivity of [14C]glucose 6-phosphate formed was determined at 1, 2, 5 and 30 min and 3, 8 and 17 h. It increased rapidly to 1.9-fold the initial specific radioactivity of [1-14C]ribose 5-phosphate at 3 h and then decreased to a value approximately equal to that of the substrate at 6 h, and finally at 17 h reached a value 0.8-fold that of the initial substrate [1-14C]ribose 5-phosphate. 3. The specific radioactivity of [14C]ribose 5-phosphate decreased to approx. 50% of its inital value during the first 3 h of the incubation and thereafter remained unchanged. 4. The distribution of 14C in the six carbon atoms of [14C]glucose 6-phosphate formed from [1-14C]ribose 5-phosphate at 1, 2, 5 and 30 min and 3, 8 and 17 h was determined. The early time intervals (1--30 min) were characterized by large amounts of 14C in C-2 and in C-6 and with C-1 and C-3 being unlabelled. In contrast, the later time intervals (3--17 h) were characterized by the appearance of 14C in C-1 and C-3 and decreasing amounts of 14C in C-2 and C-6. 5. It is concluded that neither the currently accepted reaction sequence for the non-oxidative pentose phosphate pathway nor the 'defined' pentose phosphate-cycle mechanism can be reconciled with the labelling patterns observed in glucose 6-phosphate formed during the inital 3 h of the incubation.
| S-EPMC1186225 | biostudies-other
Project description:Brain uptake of [(14)C]acetate has been reported to be a useful marker of astrocytic energy metabolism. In addition to uptake values, the rate of radiolabeled acetate washout from the brain appears to reflect CO2 exhaustion and oxygen consumption in astrocytes. We measured the time-radioactivity curves of benzyl [1-(14)C]acetate ([1-(14)C]BA), a lipophilic probe of [1-(14)C]acetate, and compared it with that of benzyl [2-(14)C]acetate ([2-(14)C]BA) in rat brains. The highest brain uptake was observed immediately after injecting either [1-(14)C]BA or [2-(14)C]BA, and both subsequently disappeared from the brain in a single-exponential manner. Estimated [1-(14)C]BA washout rates in the cerebral cortex and cerebellum were higher than those of [2-(14)C]BA. These results suggested that [1-(14)C]BA could be a useful probe for estimating the astrocytic oxidative metabolism. The [1-(14)C]BA washout rate in the cerebral cortex of immature rats was lower than that of mature rats. An autoradiographic study showed that the washout rates of [1-(14)C]BA from the rat brains of a lithium-pilocarpine-induced status epilepticus model were not significantly different from the values in control rat brains except for the medial septal nucleus. These results implied that the enhancement of amino acid turnover rate rather than astrocytic oxidative metabolism was increased in status epilepticus.
| S-EPMC4759666 | biostudies-literature
Project description:1. Evidence is presented for the excretion of 7-methylguanine in normal rat urine at a rate of approx. 65mug./day. Experiments with animals in which the nucleic acids had been prelabelled by treatment of the neonatal rats with [(14)C]-formate gave evidence that the methylated base originated in the nucleic acids of the rat. 2. Injection of [(14)C]dimethylnitrosamine leads to an increased excretion of 7-methylguanine, and the base becomes labelled in the methyl group. The disappearance of labelled 7-methylguanine formed in nucleic acids of rats treated with the carcinogen therefore does not take place by an N-demethylation reaction, but by liberation of the intact methylated base.
| S-EPMC1270604 | biostudies-other
Project description:1. The fate of [(14)C]thalidomide orally administered to pregnant rabbits at the beginning of the sensitive phase of pregnancy has been studied. 2. After the oral administration of [(14)C]thalidomide on the 192nd hour of pregnancy about 68% of the radioactivity appears in the urine and 22% in the faeces. 3. The urinary (14)C is made up as follows (% of dose): thalidomide (2); alpha-(o-carboxybenzamido)glutarimide (16); 2- and 4-phthalimidoglutaramic acids (11); 2-phthalimidoglutaric acid (0.2); 2- and 4-(o-carboxybenzamido)glutaramic acids and 2-(o-carboxybenzamido)-glutaric acid (29). 4. The plasma (14)C concentration is maximal at 12hr. after dosing and the radioactivity persists for more than 58hr. At 4hr. the main compound in the plasma is thalidomide, but its concentration steadily declines while the concentration of its hydrolysis products increases. 5. At 12, 24 and 58hr. after dosing radioactivity is present in the embryo and the maternal tissues examined. The (14)C concentration in the embryo is at nearly all times higher than that in the plasma, brain, skeletal muscle and fat but lower than that in the liver and kidney. 6. At 4hr. after dosing the mother on the tenth day of pregnancy the specific activities of the embryo and the yolk-sac fluid are similar. 7. Thalidomide is found in the embryo together with seven of its hydrolysis products for more than 24hr. after dosing. The accumulation of radioactivity in the embryo is due to retention of the polar hydrolysis products.
| S-EPMC1270621 | biostudies-other
Project description:The metabolism of [2-14C]folic acid over 13 days and a mixture of [2-14C]- and [3',5',9-3h]-folic acid in rats over a 6-day period is described. Both 14C and 3H are excreted in urine over the 6-day period, but 3H and 14C are only detectable in faeces for 2 days. A breakdown product of folic acid labelled with 3H only was found in some urine samples, but no metabolite corresponding to the part of the molecule containing 14C was detected. These experiments show that in the whole animal a substantial portion of orally administered folic acid undergoes scission shortly after administration [Blair Biochem. J. (1957) 68, 385-387] and that the retained folates are a shortage form for folate monoglutamates.
| S-EPMC1185950 | biostudies-other
Project description:1. BD-IV rats were given labelled dimethylnitrosamine (2 mg/kg) by stomach tube on weekdays (Monday to Friday) for up to 24 weeks. The rats killed after 2, 4, 8, 16 and 24 weeks of treatment (72 h after the final dimethylnitrosamine gavage) and DNA was isolated from the pooled livers, kidneys and lungs. Purine bases were released from the DNA by mild acid hydrolysis and separated by Sephadex G-10 chromatography. 2. Throughout the experiment, the content of 7-methylguanine in liver DNA was approx. 16 times that in kidney and lung. The amount of this product increased in the DNA of all three tissues up to 16 weeks, but by 24 weeks had decreased by 20% in the liver and 46% in the other tissues. 3. O6-Methylguanine was not detected in liver DNA, but was easily measured in kidney and lung DNA after 4 weeks of dimethylnitrosamine administration. The amount of O6-methylguanine in kidney and lung DNA increased relative to that of 7-methylguanine, and by 24 weeks was 60% of the 7-methylguanine content in both tissues. 4. Incorporation of radioactive C1 breakdown products of dimethylnitrosamine into normal purines in DNA increased continuously in all three tissues. 5. The results are discussed with respect to the specific hepatocarcinogenic effect of chronic administration of dimethylnitrosamine and the possible contribution of increased DNA repair and DNA synthesis.
| S-EPMC1164928 | biostudies-other
Project description:The alkylation of purine bases in DNA of several rat tissues was determined during weekly injections (10 mg/kg) of N-[3H]methyl-N-nitrosourea, a dose schedule known to selectively induce tumours of the nervous system. Each group of animals was killed 1 week after the final injection, and the DNA hydrolysates were analysed by chromatography on Sephadex G-10. After five weekly applications, O6-methylguanine had accumulated in brain DNA to an extent which greatly exceeded that in kidney, spleen and intestine. In the liver, the final O6-methylguanine concentration was less than 1% of that in brain. Between the first and the fifth injection, the O6-methylguanine/7-methylguanine ratio in cerebral DNA increased from 0.28 to 0.68. In addition, 3-methylguanine was found to accumulate in brain DNA whereas in the other organs no significant quantities of this base were detectable. The results are compatible with the hypothesis that O6-alkylation of guanine in DNA plays a major role in the induction of tumours by N-methyl-N-nitrosourea and related carcinogens. The kinetics of the increase of O6-methylguanine in cerebral DNA suggest that there is no major cell fraction in the brain which is capable of excising chemically methylated bases from DNA. This repair deficiency could be a determining factor in the selective induction of nervous-system tumours by N-methyl-N-nitrosourea and other neuro-oncogenic compounds.
| S-EPMC1165571 | biostudies-other
Project description:Zinc oxide (ZnO) particles have been used as dietary supplements because zinc is an essential trace element for humans. Along with the rapid development of nanotechnology, the use of ZnO nanoparticles (NPs) is increasing in the food industry, but their oral toxicity potential still remains to be answered. In this study, the effects of particle size and biological fate of ZnO on acute toxicity, toxicokinetics, and gene expression profiles in the livers were investigated after oral administration of ZnO NPs (N-ZnO), bulk-sized ZnO (B-ZnO) or Zn ions in rats. The plasma concentration-time profiles after a single-dose oral administration of ZnOs differed depending on particle/ionic forms and particle size, showing high absorption of Zn ions, followed by N-ZnO and B-ZnO, although in vivo solubility did not differ from particle size. No significant acute toxicity was found after oral administration of ZnOs for 14 days in rats. However, transcriptomic responses in the livers were differently affected, showing that metabolic process and metal biding were up-regulated by Zn ions and N-ZnO, respectively, which were not pronounced in the liver treated with B-ZnO. These findings will be useful to predict the potential oral toxicity of ZnO NPs and further mechanistic and long-term exposure studies are required to assume their safety.
| S-EPMC7915389 | biostudies-literature
Project description:PURPOSE:Anlotinib is a novel oral multi-targeted receptor tyrosine kinase inhibitor, which selectively inhibits VEGFR2/3, FGFR1-4, PDGFR ?/?, c-kit, and Ret. It shows antitumor effect in patients with advanced refractory solid tumors. The detailed absorption, metabolism, and excretion pathways of anlotinib have not yet been fully investigated. METHODS:Six male patients were enrolled and divided into two groups. Group A (containing two patients) received 14.15 mg/80 µCi/subject [14C]-anlotinib hydrochloride. Group B (containing four patients) received 14.15 mg/120 µCi/subject [14C]-anlotinib hydrochloride. The blood, urine, and feces of all the six patients after orally administration of [14C]-anlotinib were collected. The absorption, metabolism, and excretion of [14C]-anlotinib were investigated, and the efficacy and safety of anlotinib were evaluated. RESULTS:In plasma, the average time to peak concentration (Tmax) of total radioactivity was 4.42 h and the average peak concentration (Cmax) of total radioactivity was 18.80 ng Eq./g. The average values of AUC0-last, AUC0-?, and MRT0-t were 4071 h.ng Eq./g, 13,555 h.ng Eq./g, and 125 h, respectively. The average recovery of total radioactivity (TRA) in urine and feces was 62.03%, accounting for 48.52% and 13.51% in feces and urine of the total dosage, respectively. The parent drug, a carboxylic metabolite (M30), and mono-oxidation products (M46/M66) were major drug-related components in human plasma. Oxidative metabolism played the major role in drug clearance in human. The major metabolic pathways include oxidative deamination to M2, mono-oxidation to M1, and the formation of M30. Adverse events occurred in five patients and severe adverse events (SAE) occurred in one. Tumor response were evaluated as stable disease (SD) in three, partial response (PR) in one, and progressive disease (PD) in one of the patients, respectively. CONCLUSIONS:Anlotinib had a good pharmacokinetic profile with rapid absorption, long half-life, and extensive hepatic metabolism. The adverse events and efficacy were as expected.
| S-EPMC7188728 | biostudies-literature