bluuebunny/crossref_metadata_2025 huggingface dataset:
Time to an undetectable prostate‐specific antigen (PSA) after androgen suppression therapy for postoperative or postradiation PSA recurrence and prostate cancer‐specific mortality
Authors: D'Amico Anthony V. , McLeod David G. , Carroll Peter R. , Cullen Jennifer , Chen Ming‐Hui
Published: February 2007

BACKGROUND

For men receiving androgen‐suppression therapy (AST) for a rising postoperative or postradiation prostate‐specific antigen (PSA) recurrence, whether the time to an undetectable (u) PSA was significantly associated with prostate cancer‐specific mortality (PCSM) was evaluated.

METHODS

The study cohort comprised 585 men with a rising PSA and negative bone scan after surgery (n = 415) or radiation therapy (n = 170) that were treated with AST and achieved a uPSA. Gray's regression was used to evaluate whether the time to a uPSA after AST was significantly associated with the time to PCSM after the uPSA adjusting for known prognostic factors.

RESULTS

The median time (interquartile range) to achieve a uPSA was 4.6 (range, 2.8–7.8) months. There were 23 deaths, 4 of which were from prostate cancer. An increasing time to a uPSA (adjusted hazard ratio [HR]: 9.2, 95% confidence interval [CI]: 3.8, 22.1; P < .0001), a decreasing PSA doubling time (DT) (HR: 0.58, 95% CI: 0.43, 0.80; P = .0007), and Gleason score 8 to 10 cancers (HR: 8.6, 95% CI: 1.04, 77; P = .05) were significantly associated with a shorter time to PCSM.

CONCLUSIONS

Despite achieving a uPSA after AST, the risk of PCSM increased significantly as the time to the uPSA lengthens, especially in men with a short pre‐AST PSA DT and high‐grade prostate cancer. These men should be considered for randomized studies evaluating immediate vs delayed chemotherapy after the achievement of the uPSA. Cancer 2007. © 2007 American Cancer Society.
Primary urinary cytodiagnosis of a bladder small‐cell carcinoma
Authors: Rollins Susan , Schumann G. Berry
Published: February 2007

A small‐cell undifferentiated tumor of the bladder in a 69‐yr‐old man with asymptomatic hematuria is described. Urine cytology showed abundant, small, round‐to‐oval hyperchromatic cells with coarse chromatin, nuclear molding, and high nuclear/cytoplasmic ratios. A primary cytodiagnosis of small‐cell undifferentiated cancer with associated severe urothelial atypia was made. Immunohistochemical stains were negative for neuron‐specific enolase, leukocyte common antigen, chromogranin, epithelial membrane antigen, prostatic acid phosphatase, and prostate‐specific phosphatase. The diagnosis was confirmed histologically by studies performed on cystoscopic bladder biopsy material.
Regenerative failure of diabetic nerves bridging transection injuries
Authors: Zochodne Douglas W. , Guo Gui Fang , Magnowski Brooks , Bangash Mohammed
Published: February 2007

Background

Failed regeneration compounds the deficits imposed by diabetes from peripheral neuropathy. In this work, we addressed how diabetes or local glucose toxicity might impact peripheral nerve trunk regeneration and reconstitution across major sciatic nerve transection injuries of rats.

Methods

Specific conduits, amendable to manipulation of infused glucose concentrations through a T connection, were perfused with 5 or 30 mmol/L glucose in nondiabetics or 5 mmol/L glucose in rats with experimental diabetes. Quantitative early and later regenerative outgrowth was measured.

Results

Local glucose exposure had no impact on early axon or Schwann cell outgrowth or partnering nor later myelinated axon regeneration. Despite only mildly attenuated early sprouting of axons with Schwann cells, diabetic bridges exhibited massive later failure of reconstitution by 3 weeks after injury.

Conclusion

Diabetes is associated with severe limitations in regenerative success, despite appropriate early axon outgrowth. Copyright © 2007 John Wiley & Sons, Ltd.
Calculating the insulin to carbohydrate ratio using the hyperinsulinaemic‐euglycaemic clamp—a novel use for a proven technique
Authors: Bevier Wendy C. , Zisser Howard , Palerm Cesar C. , Finan Daniel A. , Seborg Dale E. , Doyle Francis J. , Wollitzer Alison Okada , Jovanovič Lois
Published: February 2007

Background

In patients with type 1 diabetes, three main variables need to be assessed to optimize meal‐related insulin boluses: pre‐meal blood glucose (BG), insulin to carbohydrate ratio (I : C), and basal insulin. We are presenting data for a novel use of the hyperinsulinaemic‐euglycaemic clamp (HEC) in patients with type 1 diabetes that minimizes the impact of these variables and can be used to determine the I : C.

Methods

Ten subjects (six men and four women) using continuous subcutaneous insulin infusion (CSII) pumps were recruited for this study [24–65 years; BMI 27.1 ± 4.9 kg/m2; A1C 7.2 ± 1.4% (mean ± SD)]. The HEC used a primed continuous intravenous insulin infusion of 40 mU/m2/min and a variable infusion of 20% glucose to maintain BG at 90 mg/dL. After subjects were in steady state (SS) for 50 min, a standardized meal (40% of total calories/day − 30% carbohydrate, 30% protein, 40% fat) was consumed. Subjects gave the insulin bolus with their CSII pump. No changes were made in the glucose infusion rate.

Results

Mean BG at SS was 85.7 ± 10.4 mg/dL. Peak BG was 115.0 ± 12.7 mg/dL at 68.5 ± 8.8 min after the meal. Mean I : C was 1 : 9.3 ± 1.7 (range 1 : 7–1 : 12). Insulin sensitivity varied from 1.9 to 9.1 mg/kg/min.

Conclusions

The HEC can be used to reduce confounding factors and to determine the I : C. As a first estimate of the I : C in patients with type 1 diabetes, it is recommended to start with a ratio of 1 : 9.3 and to measure post‐prandial BG at 70 min. Copyright © 2007 John Wiley & Sons, Ltd.
Predicting the 20‐year diabetes incidence rate
Authors: Dankner Rachel , Abdul‐Ghani Muhammad A. , Gerber Yariv , Chetrit Angela , Wainstein Julio , Raz Itamar
Published: February 2007

Background

The long‐range prediction from clinical variables of the onset of diabetes is important to patients and clinicians. Our objective was to evaluate the efficacy of various glucose‐related clinical measurements in predicting the 20‐year risk of developing type 2 diabetes (T2DM) in an elderly population.

Methods

In a prospective study, 672 men and women aged 59–92 years, who were not diabetic in 1980 and were part of a nationwide longitudinal randomized study, were followed‐up in 2000–2003. Fasting glucose, 1‐ and 2‐h post‐oral glucose tolerance and insulin were measured in 1980 and 2000–2003.

Results

A group of 174 (25.9%) survivors had progressed to diabetes during the 20‐year follow‐up. Fasting glucose values were a good predictor for diabetes. With the 100 mg/dL cut‐off of impaired fasting glucose (IFG), a 2–4‐times higher predictive sensitivity followed the dramatic increase in IFG prevalence compared to the 110 mg/dL cut‐off, but at a cost of reduced specificity and positive predictive value (PPV). By receiver operating curve (ROC) analysis, a 1‐h post‐load glucose was similar to 2 h and fasting glucose in prediction of the 20‐year incidence of diabetes, and classifying correctly the 77, 74 and 73% of the group, respectively. In adjusted logistic regressions, 2.28, 1.78 and 1.69‐folds increased the 20‐year risk, and were associated with each SD increment of the respective glucose values (p < 0.001).

Conclusions

Although the best population‐based strategy for the diagnosis of T2DM would be the combination of fasting glucose followed by post‐load glucose, for the purposes of long‐term prediction of T2DM risk, fasting glucose is sufficient. Copyright © 2007 John Wiley & Sons, Ltd.
Learning with half a brain
Authors: Lent David D. , Pintér Marianna , Strausfeld Nicholas J.
Published: February 2007

Since the 1970s, human subjects that have undergone corpus callosotomy have provided important insights into neural mechanisms of perception, memory, and cognition. The ability to test the function of each hemisphere independently of the other offers unique advantages for investigating systems that are thought to underlie cognition. However, such approaches have been limited to mammals. Here we describe comparable experiments on an insect brain to demonstrate learning‐associated changes within one brain hemisphere. After training one half of their bisected brains, cockroaches learn to extend the antenna supplying that brain hemisphere towards an illuminated diode after this has been paired with an odor stimulus. The antenna supplying the naïve hemisphere shows no response. Cockroaches retain this ability for up to 24 h, during which, shortly after training, the mushroom body of the trained hemisphere alone undergoes specific post‐translational alterations of microglomerular synaptic complexes in its calyces. © 2007 Wiley Periodicals, Inc. Develop Neurobiol, 2007.
Gas‐Phase Structure and Vibrational Properties of Trifluoromethyl Trifluoromethanesulfonate, CF3SO2OCF3
Authors: Tuttolomondo María E. , Argañaraz Pablo E. , Varetti Eduardo L. , Hayes Stuart A. , Wann Derek A. , Robertson Heather E. , Rankin David W. H. , Ben Altabef Aida
Published: February 2007

Trifluoromethyl trifluoromethanesulfonate, CF3SO2OCF3, has been synthesised and its gas‐phase structure determined from electron‐diffraction data. This structural study was supported by HF, MP2 and DFT (B3LYP and B1B95) calculations, which revealed a strong dependence of the theoretical structure on the polarisation of the basis set. Infrared spectra for the gas and solid and a Raman spectrum for the liquid were obtained, and the observed bands were assigned. The experimental vibrational data, along with theoretical (B3LYP) force constants, were used to define a scaled quantum mechanical force field, which enabled reproduction of the measured frequencies with a final root‐mean‐square deviation of 6 cm–1. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)
Low‐Valent Nickel and Palladium Complexes with 1,1′‐Bis(phosphanyl)ferrocenes: Syntheses and Structures of Acrylic Acid and Ethylene Complexes
Authors: Langer Jens , Fischer Reinald , Görls Helmar , Walther Dirk
Published: February 2007

Thermally stable acrylic acid complexes with low‐valent nickel or palladium of the type [(L)M(η2‐CH2=CH‐COOH)] [1a: M = Ni, L = 1,1′‐bis(diphenylphosphanyl)ferrocene (dppf), 1b: M = Ni, L = 1,1′‐bis(diisopropylphosphanyl)ferrocene (dippf), 1c: M = Pd, L = dippf] were obtained by reaction of [Ni(cod)2] or [(L)Pd(nb)] with acrylic acid in the presence of the phosphane ligands. X‐ray diffraction analysis of 1a and 1c, respectively display that only the olefin part is coordinated. Hydrogen bonds between two carboxyl groups result in dimers in the solid state. The isomeric nickela‐cyclic carboxylates of the type [(L)Ni(CH2CH2COO)] are stable complexes in case of 2a (L = dppf) and 2b (L = dippf) whereas the unstable compound 2c [L = 1,1′‐bis(di‐tert‐butylphosphanyl)ferrocene (dtbpf)] undergoes fast reductive decoupling to form CO2 and the ethylene complex [(dtbpf)Ni(ethylene)] (3c). The related complex [(dippf)Ni(ethylene)] (3b) was prepared from nickel(0) complexes by ligand exchange reaction. 3b and 3c were characterized by elemental analyses, NMR spectroscopy and X‐ray structure analysis of single crystals.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)
Analysis of human lymphoblast mutation assays by using historical negative control data bases
Authors: Penman Bruce W. , Crespi Charles L.
Published: February 2007

We describe here historical negative control data bases for gene locus mutation assays at the thymidine kinase locus and hypoxanthine‐guanine phosphoribosyl transferase locus in TK6 and AHH‐1 human lymphoblasts, respectively. Protocols have been designed which minimize the variability among independent experiments and thus facilitate the use of historical negative control data bases for assay analysis. The historical negative control data bases for both cell lines can be accurately modeled as gamma or Poisson distributions; confidence limits can be calculated from these distributions. We describe and justify a mutagenicity assay analysis procedure which uses a comparison to the concurrent negative control cultures via a t‐test in conjunction with a comparison to the historical negative control data base. The incorporation of a comparison to the historical negative control data base allows the use of a higher confidence level without substantially sacrificing the sensitivity of the mutation assays. The analysis of the mutagenicity of saccharin in TK6 cells is presented as an example; saccharin was found to be nonmutagenic under the conditions tested.
Plant activation of m‐phenylenediamine by tobacco, cotton, and carrot cell suspension cultures
Authors: Lhotka Monica A. , Plewa Michael J. , Gentile James M.
Published: February 2007

Tobacco, cotton, and carrot plant cell suspension cultures activated the promutagen m‐phenylenediamine into a mutagen as detected by Salmonella typhimurium strain TA98 with the use of the plant cell/microbe coincubation assay. For each cell line, mid‐log phase plant cells at a density of 100–150 mg/ml were coincubated for 1 hr with concentrations of m‐phenylenediamine that ranged from 0.1 to 10 μmol per reaction tube in the preincubation test of the plant cell/microbe coincubation assay. Further experiments were conducted to optimize the activation response for each plant cell line. The density of plant cells in the reaction mixture, the time of coincubation of the reaction mixture, and the stage of the growth curve at which the plant cells were harvested for use in the reaction mixture all affected the response. Experiments that used the conditions determined as optimum for each plant cell line were then conducted. With each cell line, the optimized conditions enhanced the activation response that had been observed with the preliminary conditions. A ranking order based on the concentration‐response curves indicated a relationship of tobacco cells >> carrot cells > cotton cells. Tobacco cells were able to activate m‐phenylenediamine into a mutagen at concentrations of less than 10 nmol per plate when using TA98 as the genetic indicator organism. Finally, experiments to determine the type of genetic lesion induced by plant‐activated m‐phenylenediamine were conducted. By using five of the Ames strains, m‐phenylenediamine was shown to be active in inducing revertants in strains TA1538 and TA98 following activation by tobacco cells under the optimized conditions. We conclude that m‐phenylenediamine is activated by plant cells into a mutagen that primarily induces frameshift mutations.
Predicting the carcinogenic potential of environmental nitropyrenes
Authors: Rosenkranz Herbert S.
Published: February 2007

Nitrated polycyclic aromatic hydrocarbons (nitroarenes) constitute a large group of anthrapogenic environmental contaminants. Some members of the group are mutagenic and genotoxic in a wide spectrum of systems while others are either mutagenic only in Salmonella typhimurium or devoid of activity altogether. Additionally, some nitroarenes are uniformly carcinogenic in rodents while others are not. In view of the logistic and economic problems involved in preparing large quantities of individual nitroarenes in pure (>99.5%) form and assaying them for carcinogenicity in animals, we have analyzed the results that nitropyrenes and related chemicals yield in short‐term tests by CPBS, the Carcinogen Prediction, and Battery Selection method, and demonstrate that CPBS classifies them correctly with respect to carcinogenicity.
The simultest: A new approach to screening chemicals with the Salmonella reversion assay
Authors: Nestmann Earle R. , Brillinger Renata L. , McPherson Marcia F. , Maus K. Laurie
Published: February 2007

A new Salmonella mutagenicity test method is under development to test a chemical with more than one strain simultaneously (the “SIMULTEST”), that is, different Salmonella typhimurium tester strains are used in combination on the same plate. Strains are combined in two sets: strains with plasmid pKM101 (TA97, TA98, TA100, and TA102) and strains without the plasmid (TA1535, TA1537, and TA1538). The SIMULTEST combinations successfully detect the mutagenic activity of five mutagens in different chemical classes. This approach may be useful in reducing the workload associated with mutagenicity testing with Salmonella.
Lack of uds activity in the livers of mice and rats exposed to dichloromethane
Authors: Trueman R. W. , Ashby J.
Published: February 2007

Dichloromethane (DCM) has been evaluated for its ability to initiate unscheduled DNA synthesis (UDS) in the livers of male mice and rats in vivo. Two types of experiment were conducted. In the first, Alpk:AP rats were exposed by oral gavage to 100, 500, or 1,000 mg/kg DCM and hepatocytes assessed for UDS via autoradiography 4 and 12 hours later. In the second, Fischer F344 rats or B6C3F1 mice were exposed by inhalation to either 2,000 or 4,000 ppm of DCM for either 2 or 6 hours, and hepatocytes assessed for UDS immediately after exposure. The dose levels and strains of rodent employed in the latter protocol correspond to those employed in a recent cancer bioassay of DCM conducted by the U.S. National Toxicology Program. DCM failed to induce UDS in any of the experiments. These data are discussed within the context of other evidence indicating DCM to be nongenotoxic in vivo, despite its reported carcinogenicity in the mouse.
A review of the mutagenicity of chloroform
Authors: Rosenthal Sheila L.
Published: February 2007

Although chloroform (CHCI3) is metabolized in vivo and in vitro to a substance that covalently interacts with protein and lipid, its potential for binding to DNA is low. In addition, most of the assays for genotoxicity are negative. However, many of the genotoxicity results are inconclusive because of inadequacies in the experimental protocols. The types of genotoxicity tests this report is based on include bacterial, yeast, host‐mediated, Drosophila sex‐linked recessive lethal, mammalian cell mutagenicity, sperm head abnormality, cytogenetic, and DNA damage. On the basis of presently available information, no definitive conclusion on the mutagenic potential of CHCI3 can be reached.
Radiation‐induced micronuclei in peripheral erythrocytes of Rana catesbeiana: An aquatic animal model for in vivo genotoxicity studies
Authors: Krauter P. W. , Anderson S. L. , Harrison F. L.
Published: February 2007

An in vivo micronucleus assay for peripheral erythrocytes of Rana catesbeiana tadpoles was developed and evaluated. The assay was used to determine the spontaneous frequency of micronuclei in circulating erythrocytes in tadpoles from two different populations, to define the time from administering the clastogen to the maximum micronucleus frequency in peripheral erythrocytes, and to determine the response to radiation.

The spontaneous frequency of micronuclei in circulating erythrocytes of early‐stage tadpoles was low (3.6 ± 2.8 micronuclei per 1,000 erythrocytes, MN o/oo), but higher than that of late‐stage tadpoles (1.7 ± 0.7 MN o/oo). The time from the exposure of early‐stage tadpoles to radiation (2.1 Gy) to the maximum micronucleus frequency was about 2 wk.

The increase in frequency of micronuclei in peripheral erythrocytes of late‐stage tadpoles receiving doses ranging from 0.5 to 3.0 Gy was linear with dose; a 3‐fold increase was obtained with a dose of 3.0 Gy. The spontaneous frequency of micronuclei in erythrocytes and the increase in frequency induced by radiation appeared to differ in tadpoles from different populations. Quantification of micronuclei in the peripheral erythrocytes of R catesbeiana tadpoles provides a promising whole‐animal system for studies of genotoxicity in aquatic environments.
Re‐evaluation of the need for multiple sampling times in the mouse bone marrow micronucleus assay: Results for DMBA
Authors: Ashby J. , Mirkova E.
Published: February 2007

7,12‐dimethylbenzanthracene (DMBA) is confirmed as active in the mouse bone marrow micronucleus assay 24 hr after dosing as a corn‐oil homogenate via either oral gavage or intraperitoneal (ip) injection. These data are consistent with recent observations made by several investigators. However, when dosed via ip injection as a solution in DMSO, peak activity was evident 48 hr after dosing and a dramatic reduction in erythropoiesis was observed. The latter results are consistent with early observations made by Salamone and Heddle. The early observations of Salamone and Heddle were highlighted in the Gene‐Tox review of this assay and led the OECD to recommend the use of 3 sampling times for this assay (between 12 and 72 hr). The present data indicate that this advice should be reviewed. In particular, it suggested that a maximum of two sampling times is adequate and that, as a consequence, the number of animals employed in the conduct of the test could be reduced with no loss of sensitivity. The present data also suggest that the use of a corn‐oil homogenate of insoluble test agents may provide an efficient replacement for the use of ground suspensions or solutions in DMSO.
Mutagenic and clastogenic properties of 3‐chloro‐4‐(dichloromethyl)‐5‐hydroxy‐2 (5H)‐furanone: A potent bacterial mutagen in drinking water
Authors: Meier John R. , Blazak William F. , Knohl Richard B.
Published: February 2007

3‐Chloro‐4‐(dichloromethyl)‐5‐hydroxy‐2(5H)‐furanone (MX) was found to be a direct‐acting mutagen in the Ames test for strains TA1535, TA1538, TA92, TA97, TA98, TA100 and TA102. The highest mutagenic response (∼13,000 revertants/nmol) was seen in strain TA100. The TA100 response was six‐ to tenfold higher than in TA98, TA97, and TA102, and 100‐ to 500‐fold higher than in TA1535, TA92, and TA1538. The addition of a 9,000 × g supernatant fraction (S‐9) from livers of polychlorinated biphenyl‐treated rats, along with cofactors for NADPH generation, resulted in a 90% reduction in the TA100 mutagenicity. MX induced chromosomal aberrations in Chinese hamster ovary cells after 6–8 hr exposure without S‐9 at a dose as low as 4 μg/ml, and after 2 hr exposure with S‐9 at a dose of 75 μg/ml. The oral dose of MX lethal to 50% (LD50) in Swiss‐Webster mice was determined to be 128 mg/kg. MX did not induce micronuclei in mouse bone marrow when administered by oral gavage at doses up to 70% of the LD50.
Detection of TEM‐induced reciprocal translocations in F1 sons of CD‐1 male mice: Comparison of sequential fertility evaluation and cytogenetic analysis
Authors: Morris S. M. , Kodell R. L. , Domon O. E. , Bishop J. B.
Published: February 2007

To determine the positive and negative classification error rates associated with the HTA in our laboratory, F1 sons of TEM‐exposed CD‐1 male mice were evaluated by the sequential fertility method with subsequent cytogenetic analysis. Males who sired three litters of size 10 or less when mated to primiparous females from either the B6C3F1 or the BCF1 strain were classified as partial steriles. When meiotic chromosome analyses revealed the presence of at least two cells containing multivalent figures, males were classified as translocation heterozygotes. When the fertility evaluation and the cytogenetic analysis were compared, normal fertility was observed on 5 of 83 (6.02 %) translocation‐bearing F1 males mated to B6C3F1 tester females and on 3 of 83 (3.61 %) F1 males mated to BCF1 tester females. Thus, the false‐negative error rates were 6.02% and 3.61% with these two tester strains. Multivalent figures were not observed in the meiotic chromosomes of 410 F1 males. Of these, 12 (2.93%) had reduced fertility when mated to the B6C3F1 tester strain as did 7 (1.71%) mated to the BCF1 strain. Thus, the false‐positive error rates with these two tester strains were 2.93% for the B6C3F1 strain and 1.71 % for the BCF1 strain. Our results indicate that nonzero error rates, both false‐positive and false‐negative, are associated with the sequential mating method HTA. In addition, the magnitude of these error rates was influenced not only by the tester female strain but also by the genotype of the F1 male.
Clastogenicity of tritiated thymidine to the mouse bone marrow
Authors: Ratpan Flora , Ashby J.
Published: February 2007

Tritiated thymidine (3HTdR; 120 μCi/mouse) increases the incidence of micronucleated polychromatic erythrocytes (MPE) in bone marrow PE of both B6CF1 and CBA male mice. This effect observed in vivo reflects the clastogenicity reported by other investigators for 3HTdR in vitro. Thymidine itself was concluded to be inactive in the assay at a dose‐level 100 times greater than that required to show activity for 3HTdR. These observations are of relevance to those employing 3HTdR to monitor the mitogenic activity and the genotoxicity of chemicals.
Mutagenesis of bleomycin‐damaged lambda phage in SOS‐deficient and repair endonuclease‐deficient escherichia coli
Authors: Povirk Lawrence F. , Houlgrave C. Webster
Published: February 2007

Previous DNA sequence analysis of bleomycin‐induced forward mutations in repackaged lambda phage has suggested SOS‐dependent replicative bypass of oxidized apyrimidinic sites as a possible mechanism of mutagenesis. In order to evaluate this hypothesis further, frequencies of mutation to a clear‐plaque phenotype were compared for bleomycin‐damaged phage grown in various repair‐deficient strains of Escherichia coli. Survival of bleomycin‐damaged phage was virtually identical in all host strains. Studies in SOS‐deficient strains indicated specific requirements for functional recA+ and umuC+ alleles in the generation of the majority of bleomycininduced mutations, as well as a less stringent requirement for induction of the SOS response by ultraviolet irradiation of the host cells. These results are expected for mutagenesis resulting from apyrimidinic sites. However, the mutation frequency for bleomycin‐damaged phage was the same whether the phage were grown in a wild‐type strain or in strains deficient in apurinic/apyrimidinic repair endonucleases; this was true even for an nth∼nfo∼xth∼ strain lacking all three major apurinic/apyrimidinic endonucleases (endonuclease III, endonuclease IV, and exonuclease III). Likewise, phage grown in an endonuclease IV‐overproducing strain showed the same mutation frequency as those grown in wild‐type cells. These data suggest that either i) bleomycin‐induced mutagenesis results from SOS‐dependent bypass of lesions other than apyrimidinic sites or ii) the number of apyrimidinic sites available for SOS processing is virtually independent of the level of apurinic/apyrimidinic endonuclease activity in the cell. It is possible that a fraction of the apyrimidinic sites induced by bleomycin either are intrinsically resistant to repair or undergo secondary reactions that render them resistant.
Induction of mitotic chromosome loss in the diploid yeast saccharomyces cerevisiae D61 M by genotoxic carcinogens and tumor promoters
Authors: Albertini S. , Friederich U. , Würgler F. E.
Published: February 2007

Three genotoxic carcinogens and eight tumor promoters were tested for induction of aneuploidy, specifically chromosome loss, in Saccharomyces cerevisiae D61.M. This is a heterozygous diploid yeast strain that permits the scoring of segregants expressing three linked recessive markers (cyhR2, ade6, and leul), two of which (ade6 and leul) are located close to the centromere on opposite arms of chromosome VII. The centromere marker leu was routinely checked, and a positive control (bavistan) was run with every experiment. The three genotoxic carcinogens aflatoxin B1, benzo(a)pyrene, and 7,12‐dimethylbenz(a)anthracene did not induce aneuploidy, independent of the presence or absence of an exogenous metabolic activation system (rat liver homogenate; S9). Four of the eight tumor promoters tested induced chromosome loss but no mitotic recombination or mutation: cholic acid, lithocholic acid, phenobarbital, and saccharin. Diethylstilbestrol (DES) led to positive as well as to negative results in several independent experiments. In the case of the positive experiment, DES also induced putative recombinants. Three tumor promoters induced neither chromosome loss nor mitotic recombination: anthralin, 4,4′‐dichloro‐diphenyl‐ethane (DDT) and γ‐hexachlorcyclohexane (lindane). From our experiments it can be concluded that the hypothesis put forward by Parry et al. [Nature; 294:263–265], according to which tumor promoters induce chromosome loss in yeast, is not correct in a general sense. In our set of eight tumor promoters, only one half distinctly induced chromosome loss.
Molecular analyses of in vivo hprt mutant T cells from atomic bomb survivors
Authors: Hakoda Masayuki , Hirai Yuko , Kyoizumi Seishi , Akiyama Mitoshi
Published: February 2007

In vivo‐derived hprt‐deficient mutant T cells isolated from three nonirradiated controls and two atomic bomb survivors were studied by Southern blot analysis to investigate the molecular spectra of the mutations. Mutant frequencies for the three controls were 1.8, 2.3, and 7.3 × 10−6, and those for the two survivors (who had received radiation doses of 2.46 and 2.15 Gy, based upon the revised atomic bomb shielded kerma estimates) were 9.3 and 14.4 × 10−6, respectively. Fourteen (13%) of 105 mutant T‐cell colonies from the controls showed various structural changes in the hprt gene. The frequency of mutants with hprt gene structural changes in one atomic bomb survivor, who exhibited a mutant frequency of 9.3 × 10−6, was 26% (16/61), which was significantly higher than that of the controls. However, the frequency of structural changes in the other survivor (14%, 8/59) was not higher than that of the controls. Two sets of mutants (in total, eight mutants) from the survivor, who showed a significantly higher frequency of mutants with hprt gross alterations than did the controls, had the same hprt changes and the same rearrangements of T‐cell receptor (TcR) β‐ and γ‐chain genes, indicating a clonal expansion from one progenitor mutant. This phenomenon may reflect an in vivo recovery process of T cells in the periphery after exposure to atomic bomb radiation. However, when comparing the frequency of mutations, these two sets of mutants should be reduced. After reducing the total number of mutants from the number of gross hprt changes, the frequency was not significantly higher than that of the controls.
Induction of chromosomal aberrations by hypotonic culture conditions is independent of the S‐phase in V79 hamster cells
Authors: Nowak C.
Published: February 2007

A deviation from physiological osmolality (300 mOsm/kg H2O) can lead to genotoxic effects. A 30‐min treatment of V79 hamster cells with hy‐potonic sodium chloride of 60 mOsm/kg H2O or with diluted culture medium of the same osmolality induces extraordinarily high frequencies of chromosomal aberrations. In this study, multiple fixation times over a 24‐hr period were used to identify cells in various stages of the cell cycle at the time of treatment and to find out whether or not hypotonic conditions are able to induce aberrations in all cell cycle stages. Because of the aberration pattern observed, it is suggested that hypotonic treatment acts as an S‐independent agent, like X‐rays or restriction endonucleases. Whether the aberrations originate from directly induced DNA damage or from a release of DNase after lysosomal breakdown is discussed.
DNA strand breakage in normal and solar ultraviolet‐sensitive ICR 2A frog cell lines exposed to solar ultraviolet wavelengths
Authors: Rosenstein Barry S.
Published: February 2007

ICR 2A frog cells and two solar ultraviolet (UV)‐sensitive cell lines, DRP 36 and DRP 153, were irradiated with 150 kj/m2 of the UV radiation produced by a fluorescent sun lamp, the radiation from which was passed through a sheet of 48A Mylar (DuPont, Wilmington, DE) to eliminate wavelengths shorter than approximately 315 nm. The irradiated cultures were also exposed to photoreactivating light (PRL), resulting in the removal of most of the pyrimidine dimers induced by the sun lamp UV irradiation, and then incubated 0–4 hr. At the end of the incubations, the cells were subjected to the alkaline elution assay. In these elutions, the cell lysates were either treated with proteinase K (proK) to eliminate any DNA‐protein crosslinks (DPC) that may be present in the cells, or left untreated with proK. For the ICR 2A cells, the level of apparent DNA single‐strand breaks (ssb) detected in elutions using proK increased with the incubation time after irradiation and remained high. However, when the DNA was eluted without proK pretreat‐ment, the number of ssb fell rapidly. In contrast, the levels of ssb decreased in the DRP 36 and DRP 153 cells regardless of the use of proK in the elutions. Hence, this differential response in ssb induction may be indicative of a system involved with recovery following irradiation with solar UV wavelengths.
Sodium thiosulfate inhibits cisplatin induced mutagenesis in somatic tissue of Drosophila
Authors: Katz Alan J.
Published: February 2007

The antitumor agent cisplatin was evaluated for genotoxicity in the somatic tissue of Drosophila melanogaster in combination with the nucleo‐philic compound sodium thiosulfate (STS). Third instar larvae transheterozygous for mwh and flr3 were grown on media containing (1) water, (2) 200 mM STS, (3) 0.05 mM cisplatin in 200 mM STS, or (4) 0.05 mM cisplatin. Wings of surviving adults were scored for the presence of twin spots and both small and large single spots; 200 mM STS was nongenotoxic in the assay. Whereas 0.05 mM cisplatin significantly induced all three endpoints, 0.05 mM cisplatin in combination with 200 mM STS was found to have no genotoxic activity. Hence, STS possessed antimutagenic activity in the wing‐spot assay and completely inhibited cisplatin‐induced mutagenesis and mitotic recombination.
Micronuclei formation in somatic cells of mice exposed to 50‐Hz electric fields
Authors: El Nahas Soheir M. , Oraby Hanaa A.
Published: February 2007

Male Swiss mice are tested under uniform 50‐Hz electric field intensities of 100, 170, 220, and 290 kV/m. These values on the basis of equal induced current density are equivalent to the case of a human exposed to field intensities of nearly 8, 14, 18, and 24 kV/m, respectively. The latter values may be found beneath or in vicinity of extra‐high‐voltage power lines whose voltages range from 220 to 765 kV. The cytogenetic effect of extremely low‐frequency (ELF) electric fields, as expressed by micronuclei formation, is assessed. Mice are exposed for 24 hr, and samples are taken 48, 72, and 96 hr from the beginning of exposure. Sham‐exposed mice served as controls. The number of micronucleated polychromatic erythrocytes (PCE) in exposed animals are significantly higher than those of the control. The increase in micronucleated PCE was significantly dose dependent at all times. Samples taken 96 hr after exposure show a decrease in percentages of micronucleated PCE, which may be taken as an indication of recovery.
Role of nitroreduction in the synergistic mutational response induced by mixtures of 1‐ and 3‐ nitrobenzo[a]pyrene in Salmonella typhimurium
Authors: Thornton‐Manning Janice R. , Campbell Warren L. , Hass Bruce S. , Chen James J. , Fu Peter P. , Cerniglia Carl E. , Heflich Robert H.
Published: February 2007

Previous studies showed that binary mixtures of the environmental pollutants 1‐ and 3‐nitrobenzo[a]pyrene produced a synergistic mutational response in the Salmonella reversion assay. Since nitroreduction is believed to mediate the direct‐acting mutagenicity of the individual compounds, we have examined the role of nitroreduction in the mutagenicity of mixtures of 1 ‐ and 3‐nitrobenzo[a]pyrene in the Salmonella plate incorporation assay. While mixtures of 1 ‐ and 3‐nitrobenzo[a]pyrene induced up to 183% more revertants in strain TA98 than produced by equivalent amounts of the individual compounds, in the nitroreductase‐deficient strain TA98NR the same mixtures only induced up to 57% more revertants than the individual compounds. Analysis of mixtures of 1 ‐ and 3‐nitrosobenzo[a]pyrene (the two‐electron reduction products of 1 ‐ and 3‐nitrobenzo[a]pyrene) for mutation induction in TA98 yielded no evidence of a synergistic effect between the compounds. The mutagenicity of the mixtures was dependent upon the amount of the more mutagenic component.

Salmonella cultures were also incubated with mixtures of 1 ‐ and 3‐nitrobenzo[a]pyrene, as well as with equivalent amounts of the individual compounds. In two experiments, nitroreductive ability, as measured by the amount of 1 ‐nitropyrene metabolized to 1 ‐aminopyrene in 1 hr, was increased 9 to 105% in cultures pretreated with the mixtures as compared with cultures pretreated with the individual compounds. The results of this study support the hypothesis that nitroreduction is a major factor in the synergistic mutational response induced by 1 ‐ and 3‐nitrobenzo[a]pyrene in Salmonella typhimurium.
Rapid detection of DNA‐interstrand and DNA‐protein cross‐links in mammalian cells by gravity‐flow alkaline elution
Authors: Hincks Jeffrey R. , Coulombe Roger A.
Published: February 2007

Alkaline elution is a sensitive and commonly used technique to detect cellular DNA damage in the form of DNA strand breaks and DNA cross‐links. Conventional alkaline elution procedures have extensive equipment requirements and are tedious to perform. Our laboratory recently presented a rapid, simplified, and sensitive modification of the alkaline elution technique to detect carcinogen‐induced DNA strand breaks. In the present study, we have further modified this technique to enable the rapid characterization of chemically induced DNA‐interstrand and DNA‐protein associated cross‐links in cultured epithelial cells. Cells were exposed to three known DNA cross‐linking agents, nitrogen mustard (HN2), mitomycin C (MMC), or ultraviolet irradiation (UV). One hour exposures of HN2 at 0.25, 1.0, and 4.0 μM or of MMC at 20, 40, and 60 μM produced a dose‐dependent induction of total DNA cross‐links by these agents. Digestion with proteinase K revealed that HN2 and MMC induced both DNA‐protein cross‐links and DNA‐interstrand cross‐links. Ultraviolet irradiation induced both DNA cross‐links and DNA strand breaks, the latter of which were either protein and nonprotein associated. The results demonstrate that gravity‐flow alkaline elution is a sensitive and accurate method to characterize the molecular events of DNA cross‐linking. Using this procedure, elution of DNA from treated cells is completed in 1 hr, and only three fractions per sample are analyzed. This method may be useful as a rapid screening assay for genotoxicity and/or as an adjunct to other predictive assays for potential mutagenic or carcinogenic agents.
Genetic profile of a nalidixic acid analog: A model for the mechanism of sister chromatid exchange induction
Authors: Holden Henry E. , Barett John F. , Huntington Channing M. , Muehlbauer Paula A. , Wahrenburg Margitta G.
Published: February 2007

In recent years, evidence has accumulated that suggests that mammalian topoisomerase may play a role in the formation of spontaneous or chemically induced sister chromatid exchange (SCE). In microbial systems, nalidixic acid is known to disrupt the function of a topoisom‐erase‐like enzyme, DNA gyrase. To explore the possible relationship to topoisomerase function and SCE formation in mammalian cells, an analog of nalidixic acid with potent topoisomerase II inhibitory activity was selected for examination in a variety of genetic toxicology assays. This analog, CP‐67, 015, proved to be a positive direct‐acting mutagen in the L5178Y/TK+/‐, CHO/ HGPRT, and V79/HGPRT systems. However, no gene mutational activity was observed using the Ames test in direct plate, mouse and rat metabolic activation, and mouse urine tests. In vitro cytogenetic studies showed strong clastogenic activity in human lymphocytes and in CHO cells. Compound‐induced chromosome damage was also observed in vivo in mouse bone marrow cells. Surprisingly, SCE studies in vitro in human lymphocytes or CHO cells showed only slight increases, even at levels producing severe chromosome breakage. Mouse bone marrow showed no significant elevation of SCE following parenteral treatment with CP‐67, 015.

These results, taken together, demonstrate that CP‐67, 015 is a direct‐acting mutagen in mammalian cells with both gene and chromosomal level effects. The relative ineffectiveness in producing SCEs suggests that CP‐67, 015 may interfere with a DNA replicative/repair process, perhaps by alteration of one or more DNA polymerase activities. This suggestion is based in part on the known effect of the analog nalidixic acid on DNA gyrase in microbial cells and on topoisomerase in mammalian cells. The profile of genetic activity of CP‐67, 015, coupled with its inhibitory effect on topoisomerase function, gives rise to a model for SCE formation that is based on anomalies of topoisomerase activity during DNA synthesis.
Toxic effects of methyl methanesulfonate (MMS) on activated macrophages from chickens
Authors: Qureshi Muquarrab A. , Bloom Stephen E. , Hamilton Joshua W. , Dietert Rodney R.
Published: February 2007

Adherent peritoneal exudate cells rich in macro‐phages were harvested from Cornell K‐strain chickens 42 hr after i.p. stimulation with Sephadex G‐50. Glass‐adherent monolayers were obtained on coverslips and subjected to in vitro exposure to methyl methanesulfonate (MMS) at various doses for 1 hr. Solvent (0.17% ethanol final concentration) and sham (RPMI 1640 growth media) exposures were also performed. At selected times after exposure, the macrophages were analyzed for cell viability, adherence, DMA damage, and functional activity. Although MMS doses of 5 × 10−3 M and 1 × 10−3 M concentrations resulted in significant cytoxicity, 2 × 10−4 M had no significant cytotoxic effect. However, this exposure resulted in DNA damage as measured by alkaline elution. Concomitant with the DNA damage was a significant decrease in the phagocytic activity of macrophages. Repair of MMS‐induced DMA lesions in macrophages was indicated by a normal DNA alkaline elution profile 10 hr postrecovery. Functional activity of cells also returned to normal levels. In contrast, the incidence of Fc receptor‐positive cells detected by rosetting increased immediately after MMS exposure, and phagocytosis of opsonized SRBCs was not affected by 2 × 10−4 M MMS treatment. Similarly, MMS treatment did not alter the acid phosphatase activity of macrophages. However, bactericidal ability of MMS‐treated macrophages for unopsonized Escherichia coli was significantly depressed. These results suggest that the avion macrophage is a useful target cell for examining possible relationships between genotoxic and immunotoxic effects of environmental mutagens.
Genotoxicity of azidoalanine in mammalian cells
Authors: Arenaz P. , Hallberg L.
Published: February 2007

Sodium azide mutagenesis is mediated through a metabolic intermediate in bacteria and plant species. However, very little is known about the interaction of this intermediate with nucleic acids, its genotoxic potential, or its mechanism of action, especially in mammalian cells. Chinese hamster cells and normal human skin fibroblasts were treated with extracts from Salmonella typhimurium or Hordeum vulgare (barley) containing a crude mutagenic metabolite, as well as with synthetically produced azidoalanine. The cells were evaluated for the induction of sister chromatid exchanges and the ability to perform unscheduled DNA synthesis. With the purified azidoalanine and the azide‐treated extracts from Hordeum vulgare, there was a statistically significant increase in the frequency of sister chromatid exchanges observed in both Chinese hamster cells and human fibroblasts. This increase was about twofold, as compared with the control. On the other hand, there was no detectable genotoxic response when cells were exposed to azide‐treated extract from Salmonella typhimurium. The results imply that azidoalanine and the crude mutagenic metabolite from Hordeum vulgare are weakly genotoxic in mammalian cells.
Flow cytometric analysis of bromodeoxyuridine‐induced inhibition of cell proliferation in the human teratocarcinoma‐derived cell line, p3
Authors: Morris Suzanne M. , McGarrity Lynda J. , Domon Olen E. , Hinson William G. , Kodell Ralph L.
Published: February 2007

We have developed methods in our laboratory whereby the effects of toxicant exposure on cell proliferation can be evaluated flow cytometrically. We sought to relate the flow cytometric analyses to other biological response measurements. Thus, we exposed P3 cells to increasing concentrations of bromodeoxyuridine (BRdU) and measured sister‐chromatid exchange (SCE) frequency, average generation time (AGT), and relative cloning ability. Each of these is well documented (see introduction) to respond to BRdU exposure in a concentration‐dependent manner. In this study, SCE frequency remained constant between the concentrations of 2.5 and 10 μM of BRdU. However, a small, but significant, increase in SCE frequency was observed between the concentrations of 10 μM and 50 μM BRdU. A significant increase in AGT was noted in 50 μM BRdU‐exposed cells. Relative cloning efficiency decreased in a concentration‐dependent manner when cells were cultured for 24, 48, or 72 hours with BRdU. When cell proliferation was assessed by flow cytometric analysis in cells exposed to 0, 10, or 50 μM BRdU, a statistically significant delay in the cell‐cycle was observed in BRdU‐exposed cells. These results may be interpreted to mean that inhibition of cell proliferation is detected by this type of analysis at toxicant concentrations that induce other biological endpoints. The inclusion of flow cytometric analysis in a test battery to evaluate toxicant effects is warranted.
Molecular analyses of in vivo hprt mutations in human t‐lymphocytes: IV. Studies in Newborns
Authors: McGinniss Matthew J. , Nicklas Janice A. , Albertini Richard J.
Published: February 2007

In order to characterize in vivo gene mutations that occur during fetal development, molecular analyses were undertaken of mutant 6‐thiogua‐nine resistant T‐lymphocytes isolated from placental cord blood samples of 13 normal male newborns. These mutant T‐cells were studied to define hypoxanthine‐guanine phosphoribosyl‐transferase (hprt) gene structural alterations and to determine T‐cell receptor (TCR) gene rearrangement patterns. Structural hprt alterations, as shown by Southern blot analyses, occurred in 85% of these mutant clones. These alterations consisted mostly of deletion of exons 2 and 3. These findings contrast with the 10–20% of gross structural alterations (i.e., those visible on Southern blots) occurring randomly across the entire gene previously reported for T‐cell mutants isolated from normal young adults. Iterative analyses of hprt structural alterations and TCR gene rearrangement patterns show that approximately one‐third of the newborn derived mutants may have originated as pre‐ or intrathymic hprt mutations. This too contrasts with previous findings in adults where the background in vivo hprt mutations appeared to originate in post‐thymic T‐lymphocytes.