bluuebunny/crossref_metadata_2025 huggingface dataset:
Grafting of commercially available amines bearing aromatic rings onto poly(vinylidene‐co‐hexafluoropropene) copolymers
Authors: Taguet A. , Ameduri B. , Boutevin B.
Published: February 2006

The grafting of poly(VDF‐co‐HFP) copolymers with different amines containing aromatic rings, such as aniline, benzylamine, and phenylpropylamine, is presented. 19F NMR characterization enabled us to show that the sites of grafting of aromatic‐containing amines were first difluoromethylene of vinylidene fluoride (VDF) in the hexafluoropropene (HFP)/VDF/HFP triad and then that of VDF adjacent to HFP. The kinetics of grafting of benzylamine, monitored by 1H NMR spectroscopy, confirmed those sites of grafting and showed that all VDF units located between two HFPs were grafted in the first 150 min, whereas those adjacent to one HFP unit were grafted in the remaining 3000 min. Parameters such as the temperature or the molar percentage of HFP in the copolymer had an influence on the maximum rate of grafted benzylamine. The higher the temperature, the higher the molar percentage of grafted benzylamine. Furthermore, the higher the molar percentage of HFP in the copolymer, the higher the molar percentage of VDF in the HFP/VDF/HFP triad, and the higher the molar percentage of grafted benzylamine. The spacer length between the aromatic ring and the amino group had an influence on the kinetics of grafting: aniline (pKa = 4.5) could not add onto the polymeric backbone, whereas phenylpropylamine was grafted in the first 150 min, and benzylamine required 3000 min to reach the maximum amount of grafting. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 1855–1868, 2006
Structural changes in poly(ethylene terephthalate) induced by cryomilling and ambimilling
Authors: Zhu Yan‐guo , Li Zhi‐Qiang , Zhang Di , Tanimoto Toshio
Published: February 2006

Poly(ethylene terephthalate) (PET) has been subjected to high energy ball milling at two different temperatures (cryogenic temperature and ambient temperature). The morphological and crystal structural evolutions of milled powders are characterized by means of scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X‐ray diffraction measurement. The particle size and distribution of milled powders are measured by laser diffraction particle size analyzer (LDPSA). The results indicate that the mechanisms of refining and amorphization are remarkably different between cryomilling (mechanical milling under cryogenic temperature) and ambimilling (mechanical milling under ambient temperature). The cryomilled particles are agglomerated morphology, while the ambimilled particles are cold‐welded morphology. Cryomilling induced crystalline PET translates to general amorphous, however, ambimilling induced crystalline PET transforms to oriented amorphous. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 986–993, 2006
Functional evolution within a protein superfamily
Authors: Yi Zhengping , Vitek Olga , Qasim M.A. , Lu Stephen M. , Lu Wuyuan , Ranjbar Michael , Li Jiangtian , Laskowski Michael C. , Bailey‐Kellogg Chris , Laskowski Michael
Published: February 2006

The ability to predict and characterize distributions of reactivities over families and even superfamilies of proteins opens the door to an array of analyses regarding functional evolution. In this article, insights into functional evolution in the Kazal inhibitor superfamily are gained by analyzing and comparing predicted association free energy distributions against six serine proteinases, over a number of groups of inhibitors: all possible Kazal inhibitors, natural avian ovomucoid first and third domains, and sets of Kazal inhibitors with statistically weighted combinations of residues. The results indicate that, despite the great hypervariability of residues in the 10 proteinase‐binding positions, avian ovomucoid third domains evolved to inhibit enzymes similar to the six enzymes selected, whereas the orthologous first domains are not inhibitors of these enzymes on purpose. Hypervariability arises because of similarity in energetic contribution from multiple residue types; conservation is in terms of functionality, with “good” residues, which make positive or less deleterious contributions to the binding, selected more frequently, and yielding overall the same distributional characteristics. Further analysis of the distributions indicates that while nature did optimize inhibitor strength, the objective may not have been the strongest possible inhibitor against one enzyme but rather an inhibitor that is relatively strong against a number of enzymes. Proteins 2006. © 2006 Wiley‐Liss, Inc.
Metabolism of aflatoxin B1, benzo[a]pyrene, and 1,2‐dimethylhydrazine by cultured rat and human colon
Authors: Autrup Herman , Schwartz Rochelle D. , Essigmann John M. , Smith Lee , Harris Curtis C. , Trump Benjamin F.
Published: February 2006

A model system for comparing carcinogen metabolism between human and rat colon has been developed. Tissue explants maintained under chemically defined conditions were treated with radioactively labeled carcinogens. After incubation for 24 hours, the binding of radioactive carcinogen to DNA was quantitated. Further, the carcinogen‐DNA adducts and carcinogen metabolites released into the culture media were identified. Both human and rat colon activate benzo[a]pyrene (BP), aflatoxin B1 (AFB), and 1,2‐dimethylhydrazine (DMH) into chemical species that reacted with cellular macromolecules. When human and rat colons were compared, the metabolism of AFB and DMH was qualitatively similar – the same major carcinogen‐DNA adducts and metabolic profile. However, the mean binding levels of DMH and AFB to colonic DNA were higher in rats than in humans. BP‐guanine adducts were the major adducts formed by both rat and human colonic DNA. However, BP‐adenine adducts were observed in rat colonic DNA but not in human colonic DNA. A positive correlation for the binding of BP and DMH to human DNA of different individuals was observed, but no correlation was found between BP and AFB. The data suggest that similar enzyme systems may be involved in the metabolism of BP and DMH, whereas different enzymes might be involved in the metabolic activation of AFB.
Cortisone‐induced cleft palate in the brachymorphic mouse
Authors: Pratt R. M. , Salomon D. S. , Diewert V. M. , Erickson R. P. , Burns R. , Brown K. S.
Published: February 2006

Previous studies have shown that the autosomal recessive gene brachymorphic (bm/bm), which is maintained on a C57BL/6J (C57) background, reduces limb growth and sulfation of cartilage proteoglycans. Hydrocortisone administered on gestational days 11–14 resulted in 20% CP in the C57 mouse, but 95% CP in the bm/bm mouse. The bm/bm mouse had a median effective dose for CP of 45 mg/kg, compared to 325 mg/kg for C57 and 40 mg/kg for A/J. Morphometric analysis indicated that the time of palatal elevation was delayed in the bm/bm relative to the C57 mouse both with and without hydrocortisone treatment. The amount of cytoplasmic glucocorticoid receptor protein present in the bm/bm palate on day 14 was the same as the amount found in the C57 palate, and was not elevated as it is in the A/J palate. The levels of cyclic AMP in the bm/bm palate on day 14 were 30–70% higher than that found in the C57 palate with or without hydrocortisone. These results suggest that both bm/bm and A/J exhibit a delay in palatal shelf rotation and elevated levels of cyclic AMP, which appear to be predisposing factors for cortisone‐induced cleft palate. These strains differ in that elevated levels of steroid receptors are present in A/J palate, whereas lower levels are found in the C57 and bm/bm mice.
Comitogenic activity of n‐alkane and related tumor promoters in murine lymphocytes
Authors: Baxter C. Stuart , Fish Larry A. , Bash Jerry A.
Published: February 2006

Linear alkanes of specific chain length were found to enhance differentially the mitogenic response of murine spleen lymphocytes to the lectin phytohemagglutinin. Within the homologous series of compounds having between six and eighteen carbon atoms, a biphasic structure–function relationship was found, with maximum comitogenic activity occurring for tetradecane, and none or little for octane and octadecane. No alkane was mitogenic per se, and no alkane displaced the optimum mitogenic concentration of the lectin. The concentration of tetradecane having equivalent comitogenic activity was similar to that of methyl myristate, a simple alkyl ester of equal alkyl chain length, but approximately four orders of magnitude less that of the potent promoter 12‐0‐tetradecanoylphorbol‐13‐acetate (TPA). A similar ratio of potencies of TPA and the alkane dodecane, also a lymphocyte comitogen, has previously been found for promotion of mouse epidermal tumorigenesis. Maximum comitogenic activity was found when alkane and lectin were added to cultures simultaneously, the effect decreasing sharply when alkane addition was delayed relative to lectin. These findings suggest the existence of a cellular receptor with specificity for hydrophobic functions with chain lengths lying within a restricted range. Binding to this receptor also appears to be a common early event in tumor promotion, comitogenicity, and comutagenicity by agents of several chemical types.
Parametric statistical methods and sample size considerations for dominant lethal experiments: The use of clustering to achieve approximate normality
Authors: Whorton Elbert B.
Published: February 2006

While the dominant lethal (DL) assay is often used to assess the mutagenic potential of suspect agents, questions remain concerning its sensitivity, the appropriate way to analyze resultant data, and the necessary study size. Many questions surrounding the statistical analysis methods relate to a specification of the basic independent unit of experimentation and analysis, the particular type of study design used, and the distributional properties of the study variables. These statistical analysis issues must be resolved before adequate attention can be given to the related questions of experimental sensitivity and sample size. This report deals with the development of a statistical analysis methodology which incorporates a particular type of data clustering scheme to achieve desirable distributional properties of the measured variables so that analysis of variance (AOV) and related parametric testing procedures can be used. Further, the differences between dose groups which can be detected using 20, 10, and 5 cluster units of 6 males and 18 females each are estimated for each variable according to the size of selected Type I and II errors. While these procedures were developed in part using data from two replicate studies on the DL effects of differing doses of n‐butyl glycidyl ether in mice, the clustering scheme suggested can be used with other AOV and regression procedures corresponding to the specific study design employed.
Influence of microinjected alkylating agents on the development of amphibian eggs
Authors: Ellinger Mark S. , Garone Louise M.
Published: February 2006

A direct‐acting alkylating agent, beta‐propiolactone (BPL), was microinjected into eggs of the frog, Bombina orientalis (Anura: Discoglossidae). Response to injected BPL was dose‐dependent. Seventeen or more nmoles of BPL disrupted cortical pigment in the animal hemisphere and completely inhibited cleavage. Ten nmoles of BPL allowed normal cleavage but caused a variety of teratogenic patterns and decreased survivorship at every developmental stage. Small neoplasms were found in several prehatching tadpoles derived from BPL‐microinjected eggs. Responses of diploid and laser‐irradiation‐induced haploid eggs to BPL and ethyl‐methanesulfonate (EMS) were then compared to determine whether or not the induced anomalies could be attributed to genetic (mutational) events; development of the haploid and diploid embryos did not differ. Egg microinjection is not suitable as a mutagenesis assay. However, the technique has potential to reveal insights into nucleocytoplasmic interactions in development, and further analysis of the mode of action of injected alkylating agents, for example, by nuclear transplantation, may provide insights into mechanisms of teratogenesis and neoplasia.
Sister chromatid exchanges and chromosome aberrations in rubber workers
Authors: Mäki‐Paakkanen Jorma , Sorsa Marja , Vainio Harri
Published: February 2006

Sister chromatid exchanges and chromosomal aberrations were studied in peripheral blood lymphocytes of 55 rubber workers (from two different plants) and 35 controls mainly employed in office jobs. In both plants an increased frequency of SCEs (P < 0.05 for plant A and P < 0.01 for plant B) was detected in nonsmoking rubber workers as compared with nonsmoking referents.

When the SCEs of worker groups belonging to the different job categories were compared with referents, the only groups showing statistically significant increases in SCEs were the smoking workers from the weighing and mixing departments of factory A and the nonsmoking weighers of factory B. A slight increase in the SCE frequencies was seen especially among smoking workers employed in the chemical mixing departments.

The frequency of structural chromosome aberrations was not significantly increased in the occupational groups studied, the only exception being the small group of nonsmoking weighers in plant B.

Among both the exposed workers and the controls, smokers had a higher mean SCE frequency than nonsmoking referents. This difference was significant between the exposed smokers and nonsmokers of plant A (P < 0.01) and between smoking and nonsmoking controls for plant B (P < 0.001). In addition, the chromosome aberration frequency of smoking controls of plant A was significantly higher (P < 0.01 when gaps excluded and P < 0.05 when gaps included) than that of nonsmoking referents. Also, smokers among controls for plant B had an increased frequency of aberrations in their cultured blood lymphocytes when compared with nonsmokers. This difference was significant (P < 0.05) when gaps were excluded.
Comparative genetic activity of cis‐ and trans‐1,2‐dichloroethylene in yeast
Authors: Bronzetti Giorgio , Bauer Carlo , Corsi Claudio , Del Carratore Renata , Galli Alvaro , Nieri Riccardo , Paolini Moreno , Cundari Enrico , Forti Giorgio Cantelli , Crenshaw John
Published: February 2006

The cis and trans isomers of 1,2‐dichloroethylene were tested for mutagenic effects in a diploid strain (D7) of the yeast Saccharomyces cerevisiae in suspension tests with and without a mammalian microsomal activation system, an S9 mouse liver fraction, and by an in vivo intrasanguineous host mediated assay. The effects of the same agents on aminopyrine N‐demethylase activity and cytochrome P‐450 level in liver were studied in nonpretreated and in phenobarbital + β‐naphtoflavone‐pretreated mice. In the suspension test, both isomers exhibited dose dependent toxicity, and survival was lower with metabolic activation than without. In this test also, both isomers exhibited genetic activity as measured by increases in recombinants at the ade 2 locus in experiments with metabolic activation. In the host‐mediated assay, only the cis isomer showed evidence of mutagenic activity with significant increases in convertants at the trp locus and revertants at the ilv locus. Such mutagenic activity was found both after acute and chronic doses and in liver, kidney, and lung tissue. The two isomers exhibited different effects with respect to aminopyrine N‐demethylase activity and cytochrome P‐450 level. In general, the trans isomer appeared to emphasize induction of enzyme activity or level while the cis isomer more frequently tended to inhibit activity or destroy the enzyme.
Glucuronide conjugation reduces the cytotoxicity but not the mutagenicity of benzo(a)pyrene in the CHO/HGPRT assay
Authors: Recio Leslie , Hsie Abraham W.
Published: February 2006

Benzo(a)pyrene (B[a]P) is biotransformed by the mixed‐function oxidase (MFO) system to numerous metabolites some of which are cytotoxic and/or mutagenic to mammalian cells. However, conjugation of B(a)P metabolites with glucuronic acid in vivo is a major pathway of detoxication and elimination. The effects of glucuronide conjugation on B(a)P‐induced cytotoxicity and mutagenicity were studied using the CHO/HGPRT assay with a rat liver homogenate preparation containing MFO system cofactors (S9 mix) and uridine diphosphate α‐D‐glucuronic acid (UDPGA). B(a)P metabolites proximate to the biologically active B(a)P quinones (B[a]P 6‐OH) and to the B(a)P 7,8‐diol‐9,10 epoxide isomers (B[a]P 7,8‐diol), were also assayed with S9 mix in the absence and presence of UDPGA. The addition of UDPGA to S9 mix reduced B(a)P‐induced cytotoxicity but did not affect mutagenicity. B(a)P 6‐OH‐mediated cytotoxicity was also reduced in the presence of UDPGA. UDPGA had no effect on B(a)P 7,8‐diol‐induced cytotoxicity or mutagenicity. B(a)P phenols have been shown to be the preferred B(a)P‐ metabolite substrates for UDP‐glucuronyltransferase enzymes. Thus, the reduction of B(a)P and B(a)P 6‐OH‐induced cytotoxicity by glucuronide conjugation is likely due to the elimination of cytotoxic phenols and quinones. Since B(a)P 7,8‐ diol is a poor substrate for UDP‐glucuronyltransferase enzymes, no effects on B(a)P‐induced mutagenicity or B(a)P 7,8‐diol‐induced cytotoxicity and mutagenicity were observed.
2,3,7,8‐Tetrachlorodibenzo‐p‐dioxin‐ induced cleft palate in the mouse: Evidence for alterations in palatal shelf fusion
Authors: Pratt Robert M. , Dencker Lennart , Diewert Virginia M.
Published: February 2006

2,3,7,8‐Tetrachlorodibenzo‐p‐dioxin (TCDD) causes a high percentage of cleft palate in fetuses when administered during organogenesis in certain strains of mice including the C57BL/6J, but not in certain other strains (AKR/J). The purpose of the present study was to examine various biochemical and morphological aspects of TCDD‐induced changes in the developing palatal shelves. Our results indicate that when TCDD (100 μg/kg) was given on individual days between days 8 and 10 of gestation, a high percentage of cleft palate was observed. Receptors specific for TCDD were detected in the C57BL/6J but not AKR/J palatal shelves. The amount of TCDD receptors is highest in the palatal shelves on day 13 as compared to other embryonic tissues including the liver. Examination of cryostat sections taken from embryos during the time of palatal elevation and fusion demonstrated that TCDD does not interfere with growth, elevation, or initial contact of the palatal shelves, but does interfere with firm adhesion and/or degeneration of the medial epithelial cells. Our results suggest that TCDD exerts a direct effect on the embryonic palatal shelves which results in formation of cleft palate.
The effect of acute maternal toxicity on fetal development in the mouse
Authors: Kavlock Robert J. , Chernoff Neil , Rogers Ellen H.
Published: February 2006

The effects of acute alterations in maternal health status upon fetal development were assessed following exposure of pregnant CD‐1 mice on day 8 of gestation to one of ten chemicals at doses calculated to exert either a low or a moderate degree of maternal lethality. The dams were killed on day 18 of gestation, and the fetuses were examined by routine teratological techniques. The chemicals were cacodylic acid, caffeine, deltamethrin, dinoseb, ethylene bisisothiocyanate sulfide (EBIS), endrin, guthion, kepone, sodium salicylate, and toxaphene. Three (cacodylic acid, EBIS, and kepone) produced dose‐related increases in the incidence of dams with completely resorbed litters. Prenatal mortality in litters that contained live fetuses at term was elevated only for one chemical (cacodylic acid). Fetal weight was reduced in three instances (cacodylic acid, endrin, and guthion), while the incidence of terata was markedly elevated for two (cacodylic acid and kepone). For two other chemicals (endrin and sodium salicylate), a low incidence was found of defects that were similar to defects induced by those chemicals in other species. These effects appear to be chemospecific in nature and not the result of some indirect maternal action. Thus, maternal health status, as measured by the incidence of lethality in the treated groups and by the magnitude of maternal weight gain in surviving females, presents no simple explanation for many manifestations of fetal toxicity. However, for seven chemicals (excluding deltamethrin, EBIS, and kepone) an increased incidence of supernumerary ribs was observed. For three of these seven chemicals (caffeine, dinoseb, and toxaphene). supernumerary ribs was the only observed fetal effect. There was a significant linear inverse‐relationship between maternal weight gain during gestation and the incidence of extra ribs in the treated groups compared to their respective controls. Under the experimental conditions of this study, it appears that the incidence of supernumerary ribs increased in response to a nonspecific maternal toxicity.
Mutagenic activation of 2‐aminofluorene by fluorescent light
Authors: White G. L. , Heflich R. H.
Published: February 2006

To determine the effect of artificially produced light on the direct mutagenicity of 2‐aminofluorene, that arylamine was irradiated with either sun, cool‐white, black, blue, or yellow fluorescent light or held in the dark prior to assaying for mutagenicity using Salmonella typhimurium strain TA98. The effectiveness of these exposures in potentiating the mutagenicity of 2‐aminofluorene was sun > black > cool‐white 〉 blue 〉 yellow ≃ dark. By varying the radiant flux densities produced by the lamps and using optical filters, wavelengths of light up to approximately 450 nm were found to be effective in the mutagenic potentiation. Studies using radical scavengers and oxygen modifiers indicated that the light‐induced mutagenicity was dependent on oxygen and that singlet oxygen may be an effective activator of 2‐aminofluorene. The mutagenicity of fluorene was not increased by exposure to light, while only sunlight potentiated the mutagenicity of 2‐acetylaminofluorene. This result suggested the importance of the primary amine in the mutagenic activation of 2‐aminofluorene by light. Light‐activated 2‐aminofluorene was less mutagenic in strains TA98NR and TA98/1,8‐DNP6 than in TA98. This observation, combined with the dependence of the photoactivation on oxygen and amino‐substitution, indicated that the light‐enhanced mutagenicity was at least partially due to N‐oxidized photoproducts. These studies indicate that the effect of light on environmental contaminants must be considered in assessing their genotoxic potential.
The embryotoxicity of cyclophosphamide in rabbits during the histiotrophic phase of nutrition
Authors: Claussen Uwe , Krengel Hans Georg , Hettwer Horst , Servos Gisela , Voelcker Georg
Published: February 2006

After iv injection of cyclophosphamide (CP; 80 mg/kg) and dechlor‐CP (60 mg/kg) on the 9th day of gestation (histiotrophic phase of nutrition) in rabbits, the concentrations of activated CP and activated dechlor‐CP were determined fluorometrically in the maternal blood and in the yolk sac fluid. Activated CP and dechlor‐CP could be measured in the maternal blood but not in the yolk sac fluid. This holds true for both the free as well as the protein bound form. During the histiotrophic phase of nutrition on the 9th day of gestation, the yolk sac wall seems to be a barrier for activated CP and dechlor‐CP. This phenomenon has to be traced back on the oxazaphosphorinring activated in position C4 and not on the alkylating activity. Therefore, a direct effect of activated CP can be excluded as the main reason for the embryotoxicity of CP. Consequently, the effects of iv‐injected CP on the entoderm of the visceral layer of the yolk sac placenta were investigated. Three, 6, 12, and 24 hours after CP injection, the maternal animals were laparotomized and the entoderm of the visceral layer of the yolk sac placenta in the mesometral parts of the blastoderms were prepared for electron microscopy. Like in the control group, 3 hours after CP injection no differences are found. Six hours after CP injection, a relatively flat cell‐type can be observed, which is probably based on the reduced absorptive capability of the entoderm. Twelve hours after CP injection the entoderm cells are nearly uniformly of the columnar type; this is interpreted as a restored absorptive activity. Twenty‐four hours after CP injection the columnar form of the entoderm cells and the reduced pinocytotic activity are interpreted as a state of secretion. During the histiotrophic phase of nutrition (9th day of gestation in rabbits), CP‐induced inhibition of the absorptive activity of the entoderm cells might lead to a quantitatively and/or qualitatively changed nutrition of the developing embryo. This changed nutrition may be the source of the embryotoxic effects of CP.
pH‐Induced changes in mitotic and developmental patterns in sea urchin embryogenesis. II. Exposure of sperm
Authors: Pagano Giovanni , Cipollaro Maria , Corsale Giuliana , Esposito Agostino , Ragucci Enrica , Giordano Giovan Giacomo
Published: February 2006

pH decrease and increase were tested for their ability to affect the fertilizing capacity of sea urchin sperm, as well as to induce developmental defects and mitotic abnormalities in the embryos generated by pretreated sperm.

Seawater (sw) at different pH values was obtained by mixing acidified (HCl) sw and alkalinized (KOH) sw. Thereafter sperm were exposed to different pHs for a defined time interval, or subjected to inactivation, while suspended in sw at defined pHs, as long as their fertilizing capacity was maintained.

The study was carried out over the pH range 5–9; sperm showed optimal fertilizing capacity between pH 6 and 7. Below pH 6 and above pH 8 a drop in the fertilizing capacity was observed, whereas at normal sw pH (8.0–8.2) sperm showed intermediate values.

pH decrease in sperm suspension induced a reproducible increase in developmental defects and mitotic abnormalities in the offspring of pretreated sperm. This effect displayed a dose‐response relationship, which was most evident for pH ranging from 7 to 8. The effects of decreased pH were detected as well in terms of quantitative changes in mitotic activity, which decreased in embryos generated by sperm exposed to low pH (5–6).

The results are consistent with the induction of genetic damage following exposure of sperm to low pHs. This observation suggests a genotoxic action of hydronium ions per se. Another possible explanation for the observed genotoxicity of decreased pH might be based on the pH‐dependent activity of several genotoxins present in sw at trace levels.
The mutagenicity of sodium bisulfite on base‐substitution strains of Salmonella typhimurium
Authors: De Giovanni‐Donnelly Rosalie
Published: February 2006

The mutagenic effects of sodium bisulfite on Salmonella typhimurium LT2 strains carrying the hisG46 allele were investigated. Treating the cells with 1 M sodium bisulfite in 0.2 M acetate buffer (pH 5.2) for various time intervals at 37°C resulted in an increase in the yield of mutants above the spontaneous level. The fold enhancement of the mutant yield and the fold enhancement of the mutant frequency were greatest for the parent strain hisG46 with wild type DNA repair; the derived strains with reduced repair capacity responded to a lesser degree. While sodium bisulfite was mutagenic when tested in liquid suspension assays, strain hisG46 did not respond when the standard Ames plate incorporation assay was used. The greater mutagenic response in repair‐proficient strains suggests that normal repair capacities may favor the mutagenic activity of sodium bisulfite. Transduction studies demonstrated that mutations of his+ were closely linked to the hisD gene, and probably were in the structural hisG gene itself.
Extrapolation of the evidence on teratogenicity of chemicals between humans and experimental animals: Chemicals other than drugs
Authors: Hemminki K. , Vineis P.
Published: February 2006

Epidemiologic literature regarding the possible association between malformations and 23 exposures or occupations other than pharmaceutical products, was analysed. The qualitative level of scientific evidence was classified into four categories: high (ethanol, methylmercury, PCBs, laboratory work), limited (anesthetic gases, carbon monoxide), low (hexachlorophene, LSD, nitrous oxide, smelter work, tobacco), and inadequate (all other exposures). Human data for exposures belonging to categories “high” and “limited” were quantitatively compared to results of animal teratogenicity tests of the relevant chemicals. Ethanol, methyl‐mercury, and PCBs have caused malformations in experimental animals, and the effective doses have ranged from 0.2 to 8.0 times the effective human doses. Ethanol and PCBs caused similar types of lesions in some animal species as have been observed in humans.
Inhibition of metabolic cooperation by the anticonvulsants, diphenylhydantoin and phenobarbital
Authors: Jone Cyrenius M. , Erickson Laurie M. , Trosko James E. , Netzloff Michael L. , Chang Chia‐Cheng
Published: February 2006

High densities of 6‐thioguanine‐sensitive Chinese hamster V79 cells reduce the recovery of co‐cultured 6‐thioguanine‐resistant cells through a form of intercellular communication (metabolic cooperation). Diphenylhydantoin and phenobarbital, suspected human and animal teratogens and tumor promoters, were able to inhibit intercellular communication at noncytotoxic doses. A potentiation was observed when a mixture of the two chemicals was used.
Increased carcinogen metabolism and survival of retrovirus‐infected fischer rat embryo cells following repetitive carcinogen treatment
Authors: Raineri R. , Poiley J. A. , Hillesund T. , Ernst M. K. , Tennant R. W.
Published: February 2006

The carcinogens N‐2‐acetylaminofluorene (AAF) and diethylnitrosamine (DEN) often give negative results when tested in the Fischer rat embryo cell survival assay with the standard single 72‐hour regimen, whereas another carcinogen, benzo(a)pyrene [B(a)P], may yield varied results between different laboratories and may require relatively high concentrations (compared with other polycyclic aromatic hydrocarbons) for a positive result to occur. Enhanced survivals (compared with controls) were 56% or less with these carcinogens. In place of the standard single 72‐hour treatment with test chemical, the cells were exposed to three consecutive 24‐hour treatments. The amount of B(a)P metabolized during the last of the three 24‐hour treatment periods was 3.2 times greater than that during the first 24‐hour period, indicating that an induction effect occurred. Furthermore, the total amount of metabolites of B(a)P formed with repetitive treatments was 2.1 times greater than with a single 72‐hour treatment. The total amount of AAF metabolites formed with repeated treatments was 1.6 times greater than with the single treatment regimen, although no induction effect was observed between treatment periods. Survival enhancement with the repetitive regimen increased to 181% with B(a)P, 172% with AAF, and 188% with DEN. With benzo(e)pyrene, anthracene, and pyrene, enhanced survival was 14% or less following the single treatment regimen and did not increase following repetitive treatments. When the carcinogen cinnamyl anthranilate was tested using repetitive treatments, survival enhancement was more than 100% at three of six doses, versus less than 0% when the standard single treatment regimen was used.
Teratogenicity of arotinoid ethyl ester (RO 13‐6298) in mice
Authors: Zimmermann Bernd , Stürje Helga , Tsambaos Dionysios
Published: February 2006

Arotinoid ethyl ester (RO 13‐6298) is a new and very potent retinoid that exerts a profound influence on epithelial and mesenchymal differentiation in doses 500 times lower than those of compounds of the first and second retinoid generation. In the present study the teratogenicity of arotinoid ethyl ester was investigated in NMRI mice employing different treatment schedules. Recording of abnormalities was performed on day 18 (day 0 = day of conception) according to Wilson and with cleared skeletal preparations.

Intraperitoneal application of the drug at a dosage of 10 μg/kg/day for three consecutive days (days 9–11 or 12–14) caused severe malformations, particularly in the skeletal system and the cavernous organs. Skeletal elements were reduced in number, shortened, or abnormally shaped. Ossification was diminished. Atresiae of anus and urethra were frequent. Single application of 200 μg/kg between days 8 and 14 also caused multiple and severe malformations. However, no stagespecific pattern of abnormalities was detectable. Some skeletal malformations indicated more or less vulnerable stages that were in concordance with special developmental steps. Others, however, seemed to be equally susceptible over a longer period, eg, rays 1 and 5 of the hand or foot and the development of the mandibular joints. The pattern of abnormalities caused by these very low doses of RO 13‐6298 is comparable to that obtained with other retinoids and is achieved within the same relative dose‐response range. Preconceptional treatment of the animals did not induce any malformations.
Murine oocyte destruction following intraovarian treatment with 3‐methylcholanthrene or 7,12‐dimethylbenz(a)anthracene: Protection by alpha‐naphthoflavone
Authors: Shiromizu Kenji , Mattison Donald R.
Published: February 2006

Bilateral or unilateral intraovarian injection with the polycyclic aromatic hydrocarbons 3‐methylcholanthrene (3‐MC), or 7,12‐dimethylbenz(a)anthracene (DMBA) destroys oocytes in C57BL/6N and DBA/2N mice. The threshold for small oocyte destruction following bilateral intraovarian treatment with 3‐MC was between 0.1 and 1 μg/ovary in both DBA/2N and C57BL/6N mice. After intraovarian treatment with DMBA, a more potent ovotoxin, the thresholds for small oocyte destruction were between 0.01 and 0.1 μg/ovary. Calculated ED50's for small oocyte destruction following bilateral intraovarian treatment with 3‐MC were C57BL/6N, 0.33 μg/ovary; DBA/2N, 1.02 μg/ovary—for DMBA the ED50's were C57BL/6N, 0.11 μg/ovary; DBA/2N, 0.03 μg/ovary. Unilateral intraovarian treatment also destroyed oocytes in the treated ovary. Treatment with intraperitoneal alpha‐naphthoflavone (ANF), a competitive inhibitor of polycyclic aromatic hydrocarbon metabolism by microsomal monooxygenases, inhibited oocyte destruction. Intraovarian treatment with ANF decreased oocyte destruction produced by intraovarian DMBA. These data suggest that both 3‐MC and DMBA are indirect acting ovotoxins requiring metabolic activation before oocyte destruction occurs. In addition, these data also suggest that the ovary contains the enzymes necessary to biotransform xenobiotics like 3‐MC and DMBA to ovotoxic metabolites. Metabolic activation of xenobiotics to reactive products within the ovary may represent a special threat to the integrity of oocyte DNA.
Detection of sister chromatid exchanges induced by volatile genotoxicants
Authors: Tucker James D. , Xu Jing , Stewart John , Baciu Peter C. , Ong Tong‐Man
Published: February 2006

To test the recently developed method of exposing cells to volatile compounds, phytohemagglutinin‐stimulated human peripheral lymphocyte cultures were exposed to gaseous methyl bromide, ethylene oxide, and proplyene oxide, as well as diesel exhaust. The cultures were placed in sterile dialysis tubing and inserted into enclosed flasks containing additional culture medium. The test compounds (in gaseous state) were diluted with air and bubbled through the flasks for various lengths of time. The cells were then washed and incubated for a total of 75 h. The harvest was performed according to established procedures, and second‐division cells were scored for induction of sister chromatid exchanges (SCEs). The SCE frequency was more than doubled in the cultures treated with ethylene oxide and propylene oxide; methyl bromide also induced SCEs. Cultures treated with diesel exhaust showed an increase in the SCE frequency in cells from two of four donors tested. These results further substantiate the use of this method for detecting the induction of SCEs by airborne genotoxins.
Transplacental genetic and cytogenetic effects of alkylating agents in the mouse. II. Induction of chromosomal aberrations
Authors: Braun Rolf , Hüttner Edith , Schöneich Jörg
Published: February 2006

Six monofunctional alkylating agents, trenimon, cyclophosphamide, and isoniazid were proven for transplacental cytogenetic activity in mouse embryos at day 10 of gestational age under the same conditions as used in the mammalian spot test. With the exception of isoniazid, all compounds led to an increase in the aberration frequencies in embryonal cells. The results were statistically not significant in the case of EMS, while all other chemicals showed a dose‐dependent clastogenic activity. After treatment with monofunctional alkylants, chromatid breaks were dominating, while polyfunctional compounds also produced chromatid exchanges, especially in the case of trenimon. ENU and DMS showed a very early aberration maximum 6 hr after injection. For both compounds, very similar dose‐response curves were found for induction of chromatid breaks in the dose range 10‐75 mg/kg. There is no correlation between the Swain‐Scott factors of monofunctional alkylants and their ability to induce chromosomal damage when compared in terms of pharmacological doses.

A quantitative comparison of data found in the cytogenetic test in embryonal cells with those obtained in the mammalian spot test led to the conclusion that chromosomal mutations are of minor relevancy for the expression of recessive alleles in heterozygous mouse embryos. With this respect, the mammalian spot test must be considered as an in vivo test for the detection of gene mutations in somatic cells of the mouse.
Endotoxin‐induced hyperthermia in pregnant golden hamsters
Authors: Hilbelink D. R. , Chen L. T. , Bryant M.
Published: February 2006

The degree of elevation and the duration of induced fever following endotoxin treatment of pregnant golden hamsters were examined. A radiothermistor was surgically implanted in the abdomen of each animal on day 6 of pregnancy. The animals were intravenously treated with a bolus injection of saline or endotoxin (1, 10, 20, or 200 μg/kg) on the morning of day 8 of gestation. Abdominal temperatures were monitored at 15‐minute intervals on days 8 and 9 and at 1‐hour intervals on days 10 through 14 of gestation. The mean temperature of the salinetreated control animals was 37.2°C with a range from 36.5 to 38.2°C. The total number of viable fetuses, and the mean fetal weight of the 1‐μg/kg group were not significantly different from those of the saline controls, although a statistically significant monophasic temperature elevation did occur between 3 and 9 hr post‐treatment. Three of seven females that received 10 μg/kg had viable litters and exhibited a monophasic fever. The remaining four animals exhibited a biphasic fever and total resorption of all implanted fetuses. The first phase began 2.5 hr post‐treatment and lasted for 3–6 hr. The second phase began 12–15 hr post‐treatment and lasted for 15 to 25 hr. All animals receiving 20 or 200 μg/kg demonstrated similar multiple temperature elevations. Treatment of animals with >20 μg/kg resulted in total resorption of all implanted fetuses and maternal weight loss. Nonpregnant females treated with 20 μg/kg of endotoxin exhibited a biphasic temperature elevation; thus the second phase of the fever response can not be attributed to embryo death and resorption.
Twin study methodology and variability in xenobiotic placental metabolism
Authors: Gottlieb Karen , Manchester David K.
Published: February 2006

The present study assesses the contribution of genetic and environmental factors to variability in placental aryl hydrocarbon hydroxylase and glutathione transferase activities using twin study methodology. Twin placentas were collected at the time of delivery. The placenta, except for a single layer of maternal decidua, consists of fetal tissue exhibiting fetal genotype. Microsomal and cytosolic fractions were prepared under stringent protocols to prevent enzyme activity loss. There were two monozygotic‐monochorionic pairs, five monozygotic‐dichorionic pairs, and 21 dizygotic‐dichorionic pairs that showed measurable aryl hydrocarbon hydroxylase activity using the direct fluorometric assay. Most of the mothers were smokers. Aryl hydrocarbon hydroxylase activity was measured with two different substrates, benzo(a)pyrene and 7‐ethoxyresorufin. Glutathione transferase activity was measured using glutathione and 1‐chloro‐2,4‐dinitrobenzene as substrates for a spectrophotometric assay that follows the conversion of the aromatic substrate. Twin pair similarity was calculated with intraclass correlation coefficients. There is a high correlation between the activities of the two aryl hydrocarbon hydroxylase substrates (r = .814), but no correlation between aryl hydrocarbon hydroxylase and glutathione transferase activity levels. There is little evidence of genetic variability underlying the variation in the enzyme activities because monozygotic‐dichorionic twins are no more similar to each other for the three substrate activities than are the dizygotic twins. To delineate the prenatal environmental influences on placental enzyme variability, dichorionic placentation was subdivided further into contiguous and noncontiguous placental position. Lower intraclass correlation coefficients are obtained for the dizygotic twins whose placentas were noncontiguous compared with dizygotic twins with contiguous placentas. The results suggest that most of the variability seen in these placental enzyme systems is due to environmental differences within uteri, rather than genetic variability in the population. This does not negate the possibility that between‐pair, or population, variability may have a genetic component, because even dizygotic twins share a large proportion of their genes. This study points out that a significantly variable environment exists within the human uterus.
Sublethal pH decrease may cause genetic damage to eukaryotic cell: A study on sea urchins andSalmonella typhimurium
Authors: Cipollaro Maria , Corsale Giuliana , Esposito Agostino , Ragucci Enrica , Staiano Norma , Giordano Giovan Giacomo , Pagano Giovanni
Published: February 2006

Further evidence is reported here of genetic and developmental damage that can be induced by a sublethal pH decrease. The effects of three inorganic acids (HCl, H2SO4, and H3PO4) on embryos and sperm from the sea urchinsSphaerechinus granularisandParacentrotus lividuswere evaluated. In addition, acidification of the medium was tested for spontaneous reversion to His+prototrophy inSalmonella typhimurium(strains TA97, TA98, TA100, TA102, TA1535) up to toxic levels, by both liquid incubation and agar plate incorporation.

The induction of developmental and mitotic abnormalities inS. granularisconfirmed our previous observations onP. lividus. Embryotoxicity was exerted inS. granularismore severely by H3PO4than by HCl or H2SO4(pH 7 to 6), while the induction of mitotic abnormalities appeared at a pH of ≤ 6.5 irrespective of the acids used. By suspendingS. granularisorP. lividussperm in acidified filtered seawater (fsw) and then inseminating the eggs in natural fsw (pH = 8.0), the offspring showed developmental and mitotic abnormalities. Low‐pH‐induced spermiotoxicity was ruled out in our experiments, since fertilization success of acid‐exposed sperm was actually enhanced, as compared to sperm suspended in untreated fsw.

The exposure ofS. typhimuriumto different pH's (ranging from 4 to 9) invariably failed to induce any changes in reversion rates, regardless of the acids (or alkali) being used.

These results suggest that extracellular acidification may cause sublethal damage that in turn leads to an impairment of mitotic activity and cell differentiation.
Genetic variation in the susceptibility to mercury and other metal compounds in Drosophila melanogaster
Authors: Magnusson Jan , Ramel Claes
Published: February 2006

The tolerance of Drosophila melanogaster to heavy metal compounds was investigated with special emphasis on methylmercury. A pronounced variation in tolerance to CH3HgOH, HgCl2, (C2H5)3PbCl, (CH3)3SnCl, and CdCl2 was recorded between 12 wild‐type strains. After ranking the tolerance of the strains with respect to the five compounds rank correlations for experiments within and between compounds were calculated. The results showed a high degree of correlation within compounds but no unequivocal indication of a correlation between compounds, indicating that different mechanisms of genetic control for tolerance were operating for the five compounds. Rank correlations for experiments with 12 different mercury, lead, tin, and cadmium compounds and the same 12 wild‐type strains only indicated one significant correlated response, between tripropyltin and tributyltin.

A selection experiment for tolerance to methylmercury was performed with a foundation population, synthesized from four wild‐type strains, showing a high initial tolerance. One control and two levels of treatment doses were used. A distinct selection response was obtained and a high tolerance was reached particularly for the high‐dose selection line after 12 generations, when the experiment ended. Genetic analysis of the tolerance indicated a dominant and polygenic inheritance. Investigation of the uptake and excretion of CH3Hg203OH showed that the level of tolerance to methylmercury was correlated with the uptake of the mercury but apparently not with the rate of excretion.

Cystein increased the susceptibility to methylmercury. Inorganic mercury and trimethyl lead exhibited a synergistic toxic effect, evidently as the result of an in vitro transmethylation of mercury.

A high somatic susceptibility to methylmercury also applied to the induction of nondisjunction and sex‐linked recessive lethals.
Comparative in vivo and in vitro sister chromatid exchange studies in chinese hamster bone marrow and spleen cells
Authors: Krishna G. , Nath J. , Ong T.
Published: February 2006

The sister chromatid exchange (SCE) assay in bone marrow and spleen cells of Chinese hamsters was used to evaluate the differences between in vivo and in vivo/in vitro (exposure of animals to chemical followed by culturing of cells) conditions. Cyclophosphamide, a mutagenic carcinogen, caused dose‐related SCEs both in vivo and in vivo/in vitro. In the in vivo group, both bone marrow and spleen cells showed approximately a five‐fold increase in SCEs over controls following 40 mg cyclophosphamide/kg treatment. The same dose, under in vivo/in vitro conditions, caused about three‐ and six‐fold increases in SCEs over controls in bone marrow and spleen cells, respectively. While the extent of cyclophosphamide‐induced SCEs (after subtraction of baseline level) in bone marrow is approximately the same under both conditions, the response was significantly higher in spleen cells in vivo/in vitro than in vivo. Under in vitro conditions, treatment of bone marrow and spleen primary cell cultures with a direct acting mutagen, trinitrofluorenone, caused significant dose‐related increases in SCEs in both cell types in an equivalent manner. The replicative indices under these experimental conditions remained almost the same. Thus, this study indicates the potential usefulness of Chinese hamster bone marrow and spleen cells for in vivo and in vitro comparative studies with the same tissue to better assess the genotoxic hazard of chemicals.