Possible recombinogenic effect of caprolactam in the mammalian spot test

Tests of caprolactam in the mouse spot test showed that treatment with this compound increased the frequency of color spots among animals treated in utero. The nature of these spots suggests that caprolactam may induce spots through the induction of mitotic recombination.     

Transformation of low-molecular linear caprolactam oligomers by the caprolactam-degrading bacterium <Emphasis Type="Italic">Pseudomonas putida</Emphasis> BS394(pBS268)

A biosensor based on the most active caprolactam-degrading strain Pseudomonas putida BS394(pBS268) was used in the study of aerobic degradation of linear caprolactam oligomers by bacterial cells. The changes in the respiratory activity of the strain depend quantitatively on caprolactam dimer concentration, making it possible to develop biosensors for detection of caprolactam oligomers in aqueous media. Based on mass spectrometry data, the scheme of transformation of linear caprolactam oligomers by the degrader strain P. putida BS394(pBS268) was proposed for the first time. It was found that oxidative transamination to respective dicarbonic acids may be one of the mechanisms of transformation of linear caprolactam oligomers. According to the scheme proposed, the ability of the caprolactam-degrading strain to transform linear oligomers results from the broad substrate specificities of two enzymes of the caprolactam degradation pathway: 2-oxoglutarate-6-aminohexanoate transaminase and 6-oxohexanoate dehydrogenase. Transformation of linear oligomers is genetically controlled by the CAP biodegradation plasmid pBS268.     

Influence of ε-caprolactam on growth and physiology of environmental bacteria

ε-Caprolactam was found to have an effect on ecologically important soil bacteria. It inhibited the growth of several Bacillus sp. and Rhizobium sp. but cells of Arthrobacter sp. were able to grow in the presence of caprolactam. Sphingomonas sp. lost its inherent capacity to produce extracellular polymer (EPS) if grown in medium containing caprolactam. In the case of raw domestic sewage, the diversity of native bacteria was diminished in presence of caprolactam. Polluted sea water yielded predominantly one type of caprolactam-degrading bacteria of the genus Achromobacter. These cells efficiently utilized up to 10 g caprolactam/L as the sole source of carbon and nitrogen in synthetic medium even in the presence of 20 g NaCl/L. Compared to cells of Arthrobacter sp., cells of Achromobacter sp. accumulated high amount of 6-aminocaproic acid due to degradation of caprolactam. When using caprolactam as sole source of carbon and nitrogen, Achromobacter cells showed unique physiological ability to produce EPS upon prolonged incubation in solid medium and in broth with low phosphate (C:N:P ratio 100:20:0.05). Hydrolyzed cell-free EPS had glucose as its major component though the only substrate provided in the medium for growth was caprolactam.     

Isolation and characterization of a novel ε-caprolactam-degrading microbe, Acinetobacter calcoaceticus, from industrial wastewater by chemostat-enrichment

For the isolation of a ε-caprolactam-degrading microbe from wastewaters of a factory producing caprolactam, we applied a chemostat-enrichment technique with a selective medium containing caprolactam as sole source of carbon and nitrogen. This allowed for the isolation of a novel caprolactam-degrading microbe, identified as Acinetobacter calcoaceticus. The strain had a critical tolerance of 19 g caprolactam l^?1 in minimal medium, which is higher than any previously reported caprolactam-degrading microbe. A. calcoaceticus also decreased the caprolactam content in medium by 65 % within 72 h despite the high caprolactam content (10 g l^?1). This study highlights the potential use of A. calcoaceticus strain for the bioremediation of recalcitrant synthetic polymers, such as caprolactam.     

Abnormal sperm assay tests on benzoin and caprolactam

Benzoin and caprolactam, two noncarcinogenic chemicals found in association with consumer products, were tested in the mammalian in vivo abnormal spermhead assay. Each chemical was dissolved in a pharmaceutical grade corn oil and administered by gavage. Toxic effects were observed only with caprolactam-treated mice. Neither benzoin nor caprolactam induced a significant increase in the frequency of abnormal sperm as compared to that for animals treated only with the corn oil.     

Biological treatment of the components of solid oligomeric waste from a nylon-6 production plant

On partial analysis of the solid oligomeric waste of a nylon-6 production plant, it was found to contain ε-caprolactam, 6-aminocaproic acid (6-ACA) and its linear and cyclic oligomers. Out of four bacterial isolates capable of utilizing caprolactam as the sole growth substrate, Alcaligenes faecalis was found to be the most potent and utilized 90% of caprolactam in 24 h. In shake flask experiments, when the solid waste after solubilization was treated with a consortium of bacteria of four different genera, except the cyclic oligomers, all the other constituents were found to be degraded. A reduction of the chemical oxygen demand (COD) of the solid waste to the level of 63–66% was obtained when it was treated with either a consortium of the bacterial isolates or only a single isolate, A. faecalis. Alcaligenes faecalis could bring about a decrease of 95% in the caprolactam content of the solid waste, while 6-ACA and its linear oligomers were almost completely degraded. Alcaligenes faecalis cells adapted on solid waste could degrade the linear oligomers at a faster rate as compared to cells adapted on caprolactam. However, cyclic oligomers could not be degraded in either case. When solid waste, partially hydrolysed with acid to yield 6-ACA as the major constituent, was treated with the consortium of bacterial isolates, a 95% reduction in the COD was achieved. This revised version was published online in November 2006 with corrections to the Cover Date.     

The mouse spot test. Evaluation of its performance in identifying chemical mutagens and carcinogens

The published results on 60 chemicals and X-rays investigated in the mouse spot test were compared with data on the same chemicals tested in the bacterial mutation assay (Ames test) and lifetime rodent bioassays. The performance of the spot test as an in vivo complementary assay to the in vitro bacterial mutagenesis test reveals that of 60 agents, 38 were positive in both systems, 6 were positive only in the spot test, 10 were positive only in the bacterial test and 6 were negative in both assays. The spot test was also considered as a predictor of carcinogenesis; 45 chemicals were carcinogenic of which 35 were detected as positive by the spot test and 3 out of 6 non-carcinogens were correctly identified as negative. If the results are regarded in sequence, i.e. that a positive result in a bacterial mutagenicity test reveals potential that may or may not be realized in vivo, then 48 chemicals were mutagenic in the bacterial mutation assay of which 38 were active in the spot test and 31 were confirmed as carcinogens in bioassays. 12 chemicals were non-mutagenic to bacteria of which 6 gave positive responses in the spot test and 5 were confirmed as carcinogens. These results provide strong evidence that the mouse coat spot test is an effective complementary test to the bacterial mutagenesis assay for the detection of genotoxic chemicals and as a confirmatory test for the identification of carcinogens. The main deficiency at present is the paucity of data from the testing of non-carcinogens. With further development and improvement of the test it is probable that the predictive performance of the assay in identifying carcinogens should improve, since many of the false negative responses may be due to inadequate testing.     

Apparent motion effect under undetermined trajectory of presentation of test dot stimuli

The influence of such factor as determinacy of trajectory of stroboscopically presented test spot on apparent movement illusion appearance, was studied. Six subjects took part in psycho-physiological experiments during which a test spot was presented successively along the straight line to observer on a display, randomly deviating from this line up or down by 0.39, 0.78, 1.17 or 1.56 angular minutes. It was computed that with the test spot deviating by 0.92 angular minutes from the straight trajectory prognosticated by the observer, the probability of disappearance of apparent straight uniform motion of the spot was equal to 0.75. The findings suggest than one of the conditions under which apparent movement illusion appears involves an agreement between the shape of trajectory of test object presentation as expected by the observer, and its real shape in the experiment.     

DNA damage in mouse and rat liver by caprolactam and benzoin, evaluated with three different methods

Benzoin and caprolactam were examined for their capability of inducing alkaline DNA fragmentation in mouse and rat liver DNA after treatment in vivo. Three different methods were used. With the alkaline elution technique we measured an effect presumably related to the conformation of the DNA coil. With a viscometric and a fluorometric unwinding method we measured an effect presumably related to the number of unwinding points in DNA. For both compounds only the alkaline elution technique was clearly positive. The results suggest that both caprolactam and benzoin can induce an important change in the conformation of the DNA coil without inducing true breaks in DNA.     

Mutagenicity testing with transgenic mice. Part II: Comparison with the mouse spot test

The mouse spot test, an in vivo mutation assay, has been used to assess a number of chemicals. It is at present the only in vivo mammalian test system capable of detecting somatic gene mutations according to OECD guidelines (OECD guideline 484). It is however rather insensitive, animal consuming and expensive type of test. More recently several assays using transgenic animals have been developed. From data in the literature, the present study compares the results of in vivo testing of over twenty chemicals using the mouse spot test and compares them with results from the two transgenic mouse models with the best data base available, the lacI model (commercially available as the Big Blue(R) mouse), and the lacZ model (commercially available as the Mutatrade mark Mouse). There was agreement in the results from the majority of substances. No differences were found in the predictability of the transgenic animal assays and the mouse spot test for carcinogenicity. However, from the limited data available, it seems that the transgenic mouse assay has several advantages over the mouse spot test and may be a suitable test system replacing the mouse spot test for detection of gene but not chromosome mutations in vivo.     

The genotoxicities of N-nitrosamines in Drosophila melanogaster in vivo: the correlation of mutagenicity in the wing spot test with the DNA damages detected by the DNA-repair test

The genotoxicities of a series of N-nitrosamines were assayed in the wing spot test and a new short-term test of Drosophila melanogaster. In the spot test, larval flies trans-heterozygous for the somatic cell markers mwh and flr3 were fed the test reagents and the wing hairs in adults were inspected for clones expressing the phenotypes of the markers. In the other test, larval stock consisting of meiotic recombination-deficient (Rec-) double mutant mei-9a and mei-41D5 males and repair-proficient Rec+ females were grown on feed containing the reagents and the DNA damages were detected with the preferential killing of the Rec- larvae as an endpoint. The carcinogenic nitrosamines tested, N-nitrosodimethylamine (NDMA), N-nitrosodiethylamine (NDEA), N-nitrosodi-n-butylamine (NDBA), N-nitrosomorpholine (NMOR), N-nitro-sopiperidine (NPIP) and N-nitrosopyrrolidine (NPYR), all showed clearly positive activities in both tests. The activities in the wing spot test were ranked in a sequence of NDMA much greater than NMOR greater than NPIP greater than NDEA greater than NPYR greater than NDBA. A similar ranking was obtained in the repair assay. The genotoxicity of N-nitrosodiphenylamine (NDPhA), carcinogenicity studies of which are inconclusive, was marginal in the spot test. The non-carcinogenic N-nitrosoproline (NPRO) and the non-mutagenic N-nitrosothioproline (NTPRO) were negative in the spot test. NDPhA and NPRO were negative in the repair test as well. The DNA-repair test is thus a convenient technique for estimating the mutagenicity of compounds because of its simplicity compared with the wing spot test. These Drosophila tests may be useful in predicting carcinogenic potentials of compounds.     

Regulation of the expression of plasmid determination responsible for caprolactam degradation by bacteria of the genus Pseudomonas]

On the basis of the study of some Tn5 induced mutants in Pseudomonas putida strain BS836 containing the plasmid pBS268 coding caprolactam degradation, growth on caprolactam and its intermediates, and the data on the induction of oxidative activities in plasmid containing P. putida strain BS831 it was shown that plasmid and chromosome genes regulated the expression of CAP-determinants. The regulation has some elements of the negative control mechanism. Caprolactam is the inducer of the synthesis of key enzymes cleaving it and its intermediates (aminocaproic and adipic acids). At the same time each of its intermediates induced the synthesis of enzymes responsible for its cleavage.     

Caprolactam,a light-promoted growth inhibitor in sunflower seedlings

A neutral growth inhibitor, isolated from methanolic extracts of sunflower seedlings, was characterized by spectral data as caprolactam. Light-grown se     

ε-Caprolactam-degradation by Alcaligenes faecalis for bioremediation of wastewater of a nylon-6 production plant

Alcaligenes faecalis G utilized 95–97% of 5–15 g -caprolactam l^–1 in 24–48 h over a pH range of 6–8.5 and at 23–40 °C, without complex nutrient requirement. In the absence of KH₂PO₄ and K₂HPO₄/MgSO₄ in the medium, only 7.6% and 0.2% of 10 g caprolactam l^–1 was utilized, respectively. The chemical oxygen demand (COD) of the wastewater of nylon-6 plant was mainly due to its caprolactam content. A. faecalis G decreased the caprolactam content and COD of the wastewater by 80–90% of the original in spite of the wastewater having higher caprolactam content (3600 mg l^–1) and COD (7700 mg l^–1) than those of any of the previous reports.     

Synthesis and evaluation of unsaturated caprolactams as interleukin-1beta converting enzyme (ICE) inhibitors

Peptidomimetic compounds possessing a caprolactam ring constraint were prepared and evaluated as interleukin-1beta converting enzyme (ICE) inhibitors. The caprolactam ring was used to constrain the P3 region of our inhibitors. This strategy proved to be effective for the synthesis of ICE inhibitors, maintaining key hydrogen bond interactions with the enzyme and invoking a preferred conformation for binding. Several compounds exhibited IC(50) values less than 10nM in a caspase-1 enzyme assay and less than 100nM in a THP-1 whole cell assay measuring IL-1beta production. Two compounds, 13c and 13j, were found to have good oral bioavailability (>50%) in rats when administered as prodrugs.     

Role of competition for inorganic nutrients in the biodegradation of mixtures of substrates.

A study was conducted to determine whether competition for inorganic nutrients affects the biodegradation of mixtures of substrates. Little benzylamine was mineralized by Pseudomonas putida in solutions with no added P, but the substrate was degraded if the medium contained 100 nM P. The enhancement by P addition did not occur if the medium also contained caprolactam and a caprolactam-utilizing strain of Pseudomonas aeruginosa. The suppression by the second bacterium was overcome by a higher P concentration. The rate of caprolactam utilization by P. aeruginosa was reduced if benzylamine and P. putida were also present in media with 100 nM P, but the suppression was absent if the solution contained a higher P concentration. Glutamate increased and inorganic N plus P decreased the length of the acclimation phase prior to benzylamine mineralization in lake water. We suggest that the effect of one biodegradable substrate on the metabolism of a second often results from a competition for inorganic nutrients.     

A machine learning-based framework for delivery error prediction in proton pencil beam scanning using irradiation log-files

PurposeThis study aims to investigate the use of machine learning models for delivery error prediction in proton pencil beam scanning (PBS) delivery.MethodsA dataset of planned and delivered PBS spot parameters was generated from a set of 20 prostate patient treatments. Planned spot parameters (spot position, MU and energy) were extracted from the treatment planning system (TPS) for each beam. Delivered spot parameters were extracted from irradiation log-files for each beam delivery following treatment. The dataset was used as a training dataset for three machine learning models which were trained to predict delivered spot parameters based on planned parameters. K-fold cross validation was employed for hyper-parameter tuning and model selection where the mean absolute error (MAE) was used as the model evaluation metric. The model with lowest MAE was then selected to generate a predicted dose distribution for a test prostate patient within a commercial TPS.ResultsAnalysis of the spot position delivery error between planned and delivered values resulted in standard deviations of 0.39 mm and 0.44 mm for x and y spot positions respectively. Prediction error standard deviation values of spot positions using the selected model were 0.22 mm and 0.11 mm for x and y spot positions respectively. Finally, a three-way comparison of dose distributions and DVH values for select OARs indicates that the random-forest-predicted dose distribution within the test prostate patient was in closer agreement to the delivered dose distribution than the planned distribution.ConclusionsPBS delivery error can be accurately predicted using machine learning techniques.     

Evaluation in Drosophila melanogaster of the mutagenic potential of furfural in the mei-9a test for chromosome loss in germ-line cells and the wing spot test for mutational activity in somatic cells.

The mutagenic potential of furfural was evaluated by means of the chromosome loss test in germ cells and the wing spot test in somatic cells of Drosophila melanogaster. The chromosome loss test was carried out employing repair-proficient as well as repair-deficient females. Males carried the compound Y chromosome, BSYy+. Two routes of administration were used: injection and feeding of adult males. Genetic damage was demonstrable after matings of treated males with females carrying the excision repair-deficient mutant mei-9a. The somatic mutation and recombination test was carried out treating 72-h transheterozygous mwh+/+flr3 larvae. Acute treatment of larvae was chosen as the method of exposure. Evidence indicates that furfural induces somatic damage as measured in the wing spot test.     

White Flank Spots Signal Feeding Dominance in Female Diamond Firetails,Stagonopleura guttata

Plumage colour can be used as an honest signal to convey health and status, which has traditionally been examined in the sexual selection context of choosy females and elaborate males. We use a model avian system to study the role of plumage coloration in a social context such as inter‐ and intrasexual competition over food resources. The diamond firetail (Stagonopleura guttata) is an endemic Australian finch: females have more white flank spots than males, and white spot number was correlated with cell‐mediated immune response in females. We use two experimental designs to test the role of white flank spots for feeding dominance and dominance discrimination in a group‐living bird. The results from two‐choice trials and from single‐arena trials showed that female ornamentation was consistently important in social food contests, and males consistently responded to female spot number. Females with higher spot number fed first, in trials with males and/or females. Also, females preferred to feed next to test birds with low spot number, but males showed no preference for feeding next to birds with few or many spots. Finally, latency to feed was predicted by spot number: both males and females had longer latency to feed if test birds had more spots than the focal birds. We conclude that female, but not male, ornamentation was important for inter‐ and intrasexual food competition. This is one of the very few studies to show that the same plumage ornament can have a different function between the sexes as a signal of social status. Moreover, this study shows that white plumage can be a signal of dominance.     

Microbiological mutagenicity studies of pesticides in vitro.

14 pesticides were tested as pure compounds for the induction of point mutations in four strains of Salmonella typhimurium--TA1535, TA1536, TA1537 and TA1538--in the presence and in the absence of rat-liver microsomal fractions and for the induction of resistance to low concentrations of streptomycin in the filamentous bacterium, Streptomyces coelicolor. The technique used was essentially the so-called "spot test". The pesticides investigated were: aminotriazole, Benomyl, Captafol, Captan, Dichlorvos, Dalapon-Na, Dinobuton, Dodine, Ioxynil, Mecoprop, Neburon, Picloram, Triallate and Trichlorphon. In Salmonella, Captan and Triallate were mutagenic on the TA1535 strain; Dichlorvos and Trichlorphon were negative in the spot test but mutagenic after incubation in liquid cultures of strain TA1535. By using the S. coelicolor forward-mutation test, aminotriazole, Dichlorvos, Picloram, Trichlorphon and Triallate were mutagenic with the "spot test" technique; Captan showed a weak mutagenic activity with a "plate-incorporated" technique.