bluuebunny/crossref_metadata_2025 huggingface dataset:
Biochemical epidemiology: Uses in the study of human carcinogenesis
Authors: Vineis Paolo , Faggiano Fabrizio , Terracini Benedetto
Published: February 2006

The use of biochemical markers may improve the potentialities of etiologic epidemiology. Exposure markers or markers of biologically effective dose allow better exposure assessment, therefore decreasing misclassification in epidemiological studies. Markers of individual susceptibility (such as metabolic polymorphism) permit the identification of subgroups of subjects at higher risk of cancer. In general, the integration of biochemical methods and an epidemiological design is helpful in the study of the sources of interindividual variability in response to carcinogenic stimuli. We review several investigations making use of biochemical measurements in the field of cigarette‐induced bladder cancer.
Micronuclei assay in cytokinesis‐blocked binucleated and conventional mononucleated methods in human peripheral lymphocytes
Authors: Channarayappa  , Nath J. , Ong T.
Published: February 2006

Studies were performed to determine the genotoxic effect of cytochalasin‐B (CYB) and to compare the efficacy of the cytokinesis‐blocked binucleated cells (CB) for scoring micronuclei (MN) with the conventional mononuclear method, following treatment with mitomycin C and cyclophosphamide. The results show that 3–4 μg/ml of CYB induced maximum number of binucleated cells without any genotoxic effect and the frequency of MN in binucleated cells was higher than that in the mononucleated cells (P <0.05) but less than twofold. However, MN frequencies in binucleated cells were not equivalent to the frequencies of mononucleated cells, since MN in binucleated cells represent two nuclei. These results suggest that further study is required to consider CB method as a more reliable approach for scoring MN.
Induction of sister chromatid exchanges with hypotonic treatment
Authors: Kröger I. , Nowak C.
Published: February 2006

Hypotonic NaCl solutions and diluted culture medium were tested for induction of sister chromatid exchanges (SCEs) and chromosomal aberrations (CA). Hypotonic treatment conditions were found to induce high frequencies of CA and SCEs. However, an increase in SCEs was observed only in cells that also had CA. Possible lesions and mechanisms leading to SCEs and CA are discussed.
Effects of quercetin, a plant flavonol, on the two‐stage transformation in vitro
Authors: Sakai A. , Sasaki K. , Mizusawa H. , Ishidate M.
Published: February 2006

Quercetin was examined for the effects on the two‐stage chemical transformation of BALB/3T3 cells. Quercetin showed initiating action to induce transformation in the cells which were treated with quercetin and subsequently with 0.49 μM 12‐O‐tetradecanoyl‐phorbol‐13‐acetate (TPA). Both the proportion of dishes with transformed foci and the average number of foci per dish increased with the concentration of quercetin (15–45 μM). However, initiating treatment with quercetin did not induce transformation without subsequent TPA treatment. Quercetin inhibited the promotion caused by 0.49 μM TPA in the transformation initiated by 1.9 μM 3‐methylcholanthrene (MCA). The inhibitory effect of 30 μM quercetin was 56% in the number of foci per dish. Thus quercetin was found to have initiating effect on the transformation of BALB/3T3 cells, but to restrain the promotion by TPA.
32P‐assay of DNA adducts in white blood cells and placentas of pregnant women: Lack of residential wood combustion‐related adducts but presence of tissue‐specific endogenous adducts
Authors: Reddy M. Vijayaraj , Kenny Peter C. , Randerath Kurt
Published: February 2006

Residential wood combustion (RWC), which has been increasingly used as a heating source, is of health concern because emissions from RWC contain carcinogenic polycyclic aromatic hydrocarbons (PAH). To assess health risk, the possible formation of PAH‐DNA adducts in white blood cells (WBC) and placentas of nonsmoking women exposed to RWC smoke during pregnancy was measured by a nuclease P1‐enhanced 32P‐postlabeling assay having a sensitivity limit of one lesion per 109–10 DNA nucleotides. DNA samples isolated from 12 exposed specimens (8 WBC, 4 placentas) and 13 unexposed control specimens (8 WBC, 5 placentas) were hydrolyzed to mononucleotides, which were then 32P‐labeled and separated by high‐resolution thin‐layer chromatography. Comparison of autoradiograms of exposed DNA samples with those of controls failed to show exposure‐related adducts. All placental DNA maps exhibited one major (47 ± 10%) and 12 minor extra spots, however, that were not seen on WBC‐DNA maps. These derivatives corresponded to an average of 12 (± 6) modifications in 109 nucleotides. Similarly, WBC DNA showed four spots that were absent in placental DNA and were not quantified because of their low levels. Neither placental nor WBC DNA adducts coincided chromatographically with the product formed by the reaction of benzo(a)pyrene diol epoxide I with N2 of guanine in DNA. Although these results suggest that RWC smoke does not elicit detectable levels of aromatic DNA adducts in humans, lack of evaluation of RWC exposure levels leaves some uncertainty in this conclusion. The results, however, clearly show that placental and WBC DNA contain covalent modifications that are unrelated to RWC exposure. These DNA derivatives may be caused by ingestion and/or inhalation of, or skin contact with, low levels of environmental genotoxicants or may arise from endogenous electrophiles of as yet unknown origin.
Metabolic activation in the fetal mouse salivary gland culture system with rat hepatocytes, rat S‐9, and human S‐9
Authors: Lyng R. Douglas , Scalf Robert , Monteith David
Published: February 2006

The usefulness of an in vitro assay for embryotoxicity may depend on the availability of metabolic activation systems that will function in the culture system. The fetal mouse salivary gland has been investigated as an in vitro assay system. To see if the glands would grow in the presence of metabolic activators and if the glands would react to metabolites known to be embryotoxic, the glands were grown in the presence of cyclophosphamide (CP) and several activation systems. These included isolated rat hepatocytes, uninduced rat S‐9, rat S‐9 induced with 3‐methylcholanthrene (3‐MC), rat S‐9 induced with Aroclor 1254, and human S‐9. Twenty salivary glands were isolated from 13 day embryos (plug day = 0) and were grown in each treatment for 48 h. One control had no activation system or CP, one had an activation system but no CP, and three treatments had the activation system and 25, 75, or 150 μg/ml CP. The S‐9 with cofactors and the appropriate amount of CP was contained in dialysis bags. The greatest suppression of salivary gland growth occurred in co‐culture with hepatocytes activating CP. The S‐9 induced by Aroclor 1254 was nearly as effective as the hepatocytes. The next most effective was a group with similar activity consisting of the uninduced rat S‐9 and the three samples of human S‐9. The 3‐MC‐induced S‐9 was the least effective in suppressing growth of salivary glands. All the activation systems tested can be used with the salivary gland culture system.
Teratogenicity of cobalt chloride in Xenopus laevis, assayed by the FETAX procedure
Authors: Plowman Marilyn C. , Peracha Hameed , Hopfer Sidney M. , Sunderman F. William
Published: February 2006

The teratogenicity of cobalt chloride (CoCl2) was tested by the FETAX (Frog Embryo Teratogenesis Assay: Xenopus) procedure in the South African frog, Xenopus laevis. In five assays, beginning at 5 h post‐fertilization, groups of Xenopus embryos were incubated for 96 h in media that contained CoCl2 at concentrations ranging from 1.8 × 10−6 to 1.8 × 10−2 mol/L; control groups were incubated in the same medium without added CoCl2. At 101 h post‐fertilization, surviving embryos were counted, fixed in formalin, and examined by microscopy to score malformations and measure head‐to‐tail lengths. In control embryos, survival was ≥95% and malformations were ≥5%. Malformations were found in >99% of embryos exposed to Co2 + levels ≥56 μmol/L. Co2 +‐exposed embryos showed a concentration‐related pattern of malformations, comprising gut malrotation, ocular anomalies, kinked tail, craniofacial dysplasia, cardiac deformities, and dermal blisters. Other concentration‐dependent abnormalities, not categorized as malformations, included stunted growth, edema, ventral distention, and hypopigmentation. The median embryolethal concentration (LC50) of CoCl2 was 10.4 (SE ± 0.4) mmol/L; the median teratogenic concentration (EC50) was 25 (SE ± 2) μmol/L; the teratogenic index (Tl = LC50/EC50) was 416 (SE ± 13), indicating that CoCl2 is a potent teratogen for Xenopus laevis.
Statistical methods for analyzing developmental toxicity data
Authors: Piegorsch Walter W. , Haseman Joseph K.
Published: February 2006

A description and review of methods for performing per‐litter analyses involving extrabinomial proportion response is provided. It is stressed that the litter should be regarded as the appropriate experimental unit for quantitative analysis in studies for teratogenic or heritable mutagenic effects. Attention is directed at statistical identification of possible treatment effects, such as a positive dose response to a chemical stimulus. The methods range from distribution‐free, nonparametric analyses to models involving parametric distributions such as the beta‐binomial density. It is seen that most current methods require computer implementation. When concern is raised over misspecification of assumptions critical to the statistical analysis, it is argued that relatively parameter‐free methods are appropriate for use. These include statistical bootstrapping and rank‐based analyses.
Genotoxicity of vanadium compounds in yeast and cultured mammalian cells
Authors: Galli A. , Vellosi R. , Fiorio R. , Croce C. Della , Carratore R. Del , Morichetti E. , Giromini L. , Rosellini D. , Bronzetti G.
Published: February 2006

The ability of vanadium compounds to induce genetic activity was investigated in D7 and D61M strains of Saccharomyces cerevisiae and in Chinese hamster V79 cell line.

In our previous work, ammonium metavanadate (pentavalent form, V5) induced mitotic gene conversion and point reverse mutation in the D7 strain of yeast. The genotoxicity was reduced by the presence of S9 fraction, which probably reduced pentavalent vanadium to the tetravalent form.

In the present study, vanadyl sulfate (tetravalent form, V4) induced no convertants and revertants in yeast cells harvested from stationary growth phase. With yeast cells from logarithmic growth phase, which contain high levels of cytochrome P‐450, a significant increase in genetic effects was observed. Further experiments, performed by treating cells harvested from logarithmic growth phase in the presence of cytochrome P‐450 inhibitors, indicated that the monooxygenase system influenced the genotoxicity of metavanadate while the genetic activity of vanadyl remained unaffected. Aneuploidy effect in the D61M strain of Saccharomyces cerevisiae was induced by either V5 or V4, confirming that vanadium compounds are potentially antitubuline agents in eukaryotic cells.

Although these compounds are very toxic in V79 cells, no mutagenic effect was observed in the presence or in the absence of S9 fraction.
Relationship of cell death to cyclophosphamide‐induced ocular malformations
Authors: Peiffer Robert L. , McCullen Robert , Alles Ajit J. , Sulik Kathleen K.
Published: February 2006

C57BL/6J mice were used to study the ocular teratogenic effects of cyclophosphamide administered to pregnant females on d 9 of pregnancy at a dose of 5 mg/kg body weight. Nile blue staining demonstrated increased cell death at the base of the optic stalk, in the optic vesicle, and in the perivesicular mesenchyme in treated embryos. Malformations studied at gestational d 11 and 16 by light and scanning electron microscopy included microphthalmos, microphakia, and aphakia and were predictable based upon patterns of increased cell death. These anomalies are similar to those reported with exposure to ethanol or isotretinoin on gestational d 7.
Comparative study of micronucleus assay and chromosomal aberration analysis in V79 cells exposed to ethylene oxide
Authors: Zhong Bao‐Zhen , Gu Zu‐Wei , Whong Wen‐Zong , Wallace William E. , Ong Tong‐Man
Published: February 2006

Micronucleus formation and chromosomal aberration (CA) in V79 cells were compared for their sensitivity in response to ethylene oxide (EtO) treatment. The results indicate that EtO exposure for 30 min induced CAs in V79 cells at the concentration of 3,500 ppm or higher. A statistically significant difference (P<0.01) was found between treated and control groups at all concentrations tested based on percent aberrant cells. The increase was dose‐dependent with a correlation coefficient of 0.88. The aberrations found include chromatid and isochromatid breaks, fragments, minutes, and exchanges. Results of the micronucleus assay both in mononucleated and binucleated cells showed a slight but not statistically significant increase in micronuclei with doses between 457 to 4115 ppm. At the highest concentration tested (12344 ppm) EtO caused a significant increase in the micronucleus frequency (P<0.05). © 1992 Wiley‐Liss, Inc.
Influence of retinoids on sister chromatid exchanges and chromosomes in cultured human embryonic palatal mesenchymal cells
Authors: Watanabe Toshiaki , Pratt Robert M.
Published: February 2006

The cytogenetic effects of retinoids and their metabolites on human embryonic palatal mesenchymal (HEPM) cells were investigated in cell culture. Treatment with 13‐cis, 4‐oxo‐13‐cis‐, and all‐trans‐retinoic acids did not induce chromosomal structural aberrations even at high concentrations in the presence or absence of metabolic activation system. The frequencies of sister chromatid exchanges (SCE) tended to decrease in HEPM cells treated with retinoids in the absence of S‐9. 4‐Oxo‐13‐cis‐retinoic acid, which is one metabolite of 13‐cis‐retinoic acid, significantly decreased the SCE frequencies. The mitotic index decreased with increasing concentration of retinoic acids, indicating that retinoids inhibit cell proliferation in HEPM cells. We concluded that retinoids inhibit cell proliferation in HEPM cells in culture without causing DNA or chromosome damage. © 1992 Wiley‐Liss, Inc.
Comparative promoting activities of phosphate salts on rat two‐stage bladder carcinogenesis under conditions of equivalent urinary Na+ or K+ Levels
Authors: Shibata Masa‐Aki , Kagawa Masataka , Kawabe Mayumi , Hagiwara Akihiro , Fukushima Shoji
Published: February 2006

Promoting effects of Na or K phosphate salts on rat two‐stage bladder carcinogenesis were compared. Animals were treated with 0.05% N‐butyl‐N‐(4‐hydroxybutyl)nitrosamine (BBN) in their drinking water for 4 weeks and thereafter received 1.4% Na3PO4, 2.0% NaH2PO4, 1.0% K3PO4, or 2.5% KH2PO4, these dietary concentrations being selected because they result in approximately equal levels of Na+ and K+ in the urine, equivalent to moderate natriuresis or kaluresis in comparison with our previous data. Treatment with Na3PO4 or K3PO4 induced significant increase in urinary pH compared with control values, whereas urinary pH in the NaH2PO4 and KH2PO4 groups was comparable to control values. With regard to preneoplastic lesion development, both incidences and multiplicity were significantly increased in the groups given Na3PO4 or K3PO4 compared with both controls and NaH2PO4 or KH2PO4 groups, respectively. Furthermore, treatment with Na3PO4 significantly increased multiplicity of papillomas, accompanied by a tendency to increased incidence. No statistically significant difference in promoting potential between Na3PO4 and K3PO4 groups was evident. The present results thus suggest that tumor promotion under conditions of moderate natriuresis or kaluresis depends primarily on high urinary pH. © 1992 Wiley‐Liss, Inc.
Joint action oft‐retinoic and valproic acids onXenopusembryo development
Authors: Dawson Douglas A.
Published: February 2006

The joint action of all‐transretinoic acid (RA) with valproic acid (VPA) was examined at malformation‐inducing concentrations forXenopusembryos. The compounds were selected for testing to evaluate malformation as an endpoint for the developmental toxicity of chemical mixtures and to help assess whether joint action types can be related to modes or mechanisms of chemical toxicity forXenopus.Three mixtures (3:1, 1:1, and 1:3 RA:VPA) were tested in 96 hr static‐renewal exposures. Three separate tests were conducted on each mixture. Positive controls were also tested (i.e., 1:0 and 0:1 solutions). Using toxic unit analysis, the joint action for induction of malformations of all types, craniofacial malformations, and microcephaly was response addition, indicating the chemicals are dissimilar and non‐interactive. The results support recent joint action studies in providing evidence that similar acting chemicals might be defined as chemicals with the same biochemical/molecular mechanism of action in inducing malformations inXenopusembryos. © 1992 Wiley‐Liss, Inc.
Neural tube and other developmental anomalies in the guinea pig following maternal hyperthermia during early neural tube development
Authors: Cawdell‐Smith Judith , Upfold Jeffrey , Edwards Marshall , Smith Murray
Published: February 2006

Guinea pigs were exposed to hyperthermia for 1 hr once or twice on day 11, 12, 13, or 14 (E11–E14) of pregnancy. The mean rectal temperatures were elevated by 3.4°C–4.0°C. This treatment resulted in a marked elevation of rates of resorption and developmental defects in embryos examined at day E23. The defects observed were those affecting the neural tube (NTD) (exencephaly, encephaloceles, and microphthalmia), kyphosis/scoliosis, branchial arch defects, and pericardial edema. Embryos with NTD and kyphosis/scoliosis have not been found among newborn guinea pigs to date following maternal heat exposure on days E12–E14. It appears that embryos with these defects are filtered out by resorption or abortion by days E30–E35. © 1992 Wiley‐Liss, Inc.
Modulation of cyclophosphamide mutagenicity by vitamin C in the in vivo rodent micronucleus assay
Authors: Ghaskadbi Surendra , Rajmachikar Savita , Agate Chandana , Kapadi A. H. , Vaidya V. G.
Published: February 2006

The modulatory effect of vitamin C (Vit C) on the mutagenic effect of the antineoplastic drug cyclophosphamide (CP) was assessed in the in vivo micronucleus test in Swiss mice. Simultaneous oral administration of Vit C with i.p. administration of CP was found to decrease the frequency of micronucleated polychromatic erythrocytes elevated by CP. Vit C exhibited a significant antimutagenic effect over a wide dose range (1.56–200 mg/kg). The dose‐response relationship was highly significant. These results demonstrated the ability of the in vivo micronucleus test to detect in vivo modulation of CP mutagenicity by Vit C. Our earlier results and those from other laboratories also indicate that this model system is suitable for primary in vivo screening of modulation of mutagenesis. © 1992 Wiley‐Liss, Inc.
Tobramycin‐induced changes in renal histology of fetal and newborn Sprague‐Dawley rats
Authors: Mantovani A. , Macrì C. , Stazi A. V. , Ricciardi C. , Guastadisegni C. , Maranghi F.
Published: February 2006

Effects on renal development were studied using tobramycin (TBM) as a model compound. Pregnant Sprague‐Dawley rats were injected i.p. with TBM at 30 or 60 mg/kg body weight/day on gestational days (GD) 10–19. Kidneys from dams and conceptuses were examined on GD 20 and on postnatal day (PD) 9. The dosing regimen caused in dams moderate proximal tubular alterations and increased concentrations in serum creatinine. Fetal kidneys showed granularity and swelling of proximal tubule cells at the 30 mg/kg dose, poor glomerular differentiation at the 60 mg/kg dose, increased glomerular density at both doses, and no changes on macroscopic examination at either dose. In newborns were observed a moderate developmental delay and tubular lesions at the higher dose, and dose‐related increases of glomerular density and relative medullary area at both doses. All findings were more pronounced in males. A maturational disruption of the tubular structures possibly leading to increased glomerular density was attributed to TBM exposure during renal organogenesis in the rat. © 1992 Wiley‐Liss, Inc.
Teratogenic effects of N‐nitrosodiethylamine in embryos of the hermaphroditic fish Rivulus marmoratus
Authors: Park Eun‐H. , Kim Dong S. , Chang Hwa‐H.
Published: February 2006

Exposure of N‐nitrosodiethylamine (NDEA) to hermaphroditic fish (Rivulus marmoratus) embryos induced specific congenital malformations when the chemical was applied to embryos on days 0–6 post morula stage. This sensitive period generally coincided with the known period of organogenesis in this species, and the incidence of anomalies was clearly dose related. These results indicate that NDEA is teratogenic to fish embryos. © 1992 Wiley‐Liss, Inc.
A morphologic basis postulated for valproic acid's embryotoxic action in rats
Authors: Khera K. S.
Published: February 2006

A tentative 3 phase sequence of pathogenesis is proposed for the embryotoxic action of valproic acid (800 mg/kg) administered orally to rats on day 13 of pregnancy. This is based on histopathological changes in the extraembryonic and embryonic tissues which occurred in the absence of any biologically significant effect on maternal homeostasis. Major events in the first, decidual (or maternal) phase are cells lining the maternal sinusoids in the decidua basalis are necrosed, desquamated, and washed away by the arterial circulation through the afferent channels. The necrosed cells, with their walls still intact, occlude the lumen of these arterial channels at the point of their entry into the giant cell‐trophospongial zone. The channel occlusions cause ischemia and homeostasis of the maternal circulation in the labyrinth by reducing the rate of inflow of maternal blood. The embolic occlusion of maternal arterial channels apparently results in a long‐term reduction in the number and size of maternal channels that supply arterial blood to the labyrinth. In the second or placental phase, the parenchyma of the labyrinth and connective tissue in the chorionic plate and umbilical cord, which have been deprived of nutrition and oxygen by the ischemia and stasis of maternal blood in the labyrinth, undergo degenerative changes. In the third or embryonic phase, a pleiotropic karyorrhexis in the embryo, initiated as early as 4 h postdosing, appeared aggravated, presumably by the preceding labyrinthine degeneration of the placental phase. The valproic acid‐induced embryotoxicity thus seemed to result from a combination of maternal, placental, and embryonic changes. © 1992 Wiley‐Liss, Inc.
Evaluation of the developmental toxicity of trichloroethylene and detoxification metabolites using Xenopus
Authors: Fort Douglas J. , Stover Enos L. , Rayburn James R. , Hull Mendi , Bantle John A.
Published: February 2006

Potential mechanisms of trichloroethylene‐induced developmental toxicity were evaluated using FETAX (Frog Embryo Teratogenesis Assay—Xenopus). Early Xenopus laevis embryos were exposed to trichloroethylene for 96 h in two separate definitive concentration‐response assays with and without an exogenous metabolic activation system (MAS) and inhibited MAS. The MAS was treated with either carbon monoxide or cyclohexene oxide to modulate mixed‐function oxidase (MFO) or epoxide hydrolase activity, respectively. Trichloroethylene metabolites: dichloroacetic acid, trichloroacetic acid, trichloroethanol, and oxalic acid were also evaluated in two separate definitive, static renewal tests. Addition of the MAS decreased the 96 h LC50 and EC50 (malformation) of trichloroethylene 1.8‐fold and 3.8‐fold, respectively. Addition of the carbon monoxide inhibited MAS decreased the developmental toxicity of activated trichloroethylene to levels approximating that of the parent compound. Cyclohexene oxide‐inhibited MAS substantially increased the developmental toxicity of trichloroethylene. In addition, each of the metabolites tested were significantly less developmental toxic than the parent compound, trichloroethylene. Results indicate that a highly embryotoxic epoxide intermediate, trichloroethylene oxide, formed as the results of MFO mediated metabolism may play a significant role in the developmental toxicity of trichloroethylene in vitro. ©1993 Wiley‐Liss, Inc.
Embryotoxicity induced by alkylating agents: 7. Low dose prenatal‐toxic risk estimation based on NOAEL risk factor approach, dose‐response relationships, and DNA adducts using methylnitrosourea as a model compound
Authors: Platzek Thomas , Bochert Gerd , Meister Reinhard , Neubert Diether
Published: February 2006

Prenatal‐toxic risk estimation for the alkylating model compound methylnitrosourea (MNU) was performed using different procedures. Risk of low doses was estimated using linear extrapolation to zero (estimated ED0.1%: 0.1 mg/kg body wt MNU) as well as extrapolation by probit analysis based on a dose‐response study (estimated ED0.1%: 1.6 mg/kg body wt). Furthermore, a “virtually safe dose” was established by means of the NOAEL risk factor approach (e.g., factor 30: 0.03 mg MNU per kg body wt). In previous studies in murine embryos using MNU, we combined dose‐response data and DNA adduct rate measurements and deduced that O6‐methylguanine is a suitable variable for molecular dosimetry. In a tentative approach, we estimated the teratogenic risk of low doses based on the adduct rates of O6‐methylguanine in the DNA of the embryos. It is concluded that in the case of steep dose‐response relationships, which are typical for the majority of teratogenic effects, the NOAEL risk factor approach is more conservative than extrapolation based on probit analysis. Risk estimation using dosimetry with this model compound yields estimated incidences similar to linear extrapolation. ©1993 Wiley‐Liss, Inc.
Embryotoxicity induced by alkylating agents: 8. DNA adduct formation induced by ethylmethanesulfonate in mouse embryos
Authors: Platzek Thomas , Bochert Gerd , Rahm Ute
Published: February 2006

In previous studies using methylating agents a correlation was found between the initial DNA adduct rate (O6‐methylguanine) in the embryo and the teratogenic efficiency. This was shown by measuring DNA adduct rates in the teratogenic dose range which exhibited similar adduct rates at the equivalent teratogenic dose levels.

A similar approach was performed using the ethylating agent ethylmethanesulfonate (EMS). In the teratogenic dose range (150–250 mg/kg bw) the adduct rates of O6‐ethylguanine were similar compared to those of O6‐methylguanine which were obtained with methylating agents. We conclude that a correlation between teratogenicity and adduct rate (O6‐alkylguanine) exists for both methylating and ethylating agents.

Furthermore, DNA adduct formation following doses at and below the no‐observed‐adverse‐effect‐level (NOAEL) of teratogenicity was determined. The lowest experimental dose was 45 mg/kg EMS. Substantial DNA adduct rates in the embryos were found. These data will be used for molecular dosimetry in a risk assessment of low doses. © 1994 Wiley‐Liss, Inc.
Antitransforming activity of chlorophyllin against selected carcinogens and complex mixtures
Authors: Wu Z. L. , Chen J. K. , Ong T. , Brockman H. E. , Whong W.‐Z.
Published: February 2006

Chlorophyllin, a derivative of chlorophyll, is known to be an antimutagenic agent. Studies were performed to determine whether chlorophyllin can also inhibit morphological transformation of BALB/3T3 cells induced by carcinogens and complex mixtures. Chlorophyllin was added to the cultures simultaneously with carcinogens or complex mixtures while the transformation assay was conducted. At concentrations that did not significantly affect cell growth, chlorophyllin was found to inhibit morphological transformation induced by N‐methyl‐N′‐nitro‐N‐nitrosoguanidine, 3‐methylcholanthrene, 7,12‐dimethylbenz(a)anthracene, benzo(a)pyrene, aflatoxin B1, and extracts of coal dust, tobacco snuff, and chewing tobacco. In all cases, the mean number of transformed foci per flask treated with chlorophyllin was significantly lower than that of untreated cultures. The reduction in the number of transformed foci was dependent on the concentration of chlorophyllin tested. These results indicate that chlorophyllin is an antitransforming agent. © 1994 Wiley‐Liss, Inc.
Structural basis for the induction of preneoplastic glutathione S‐transferase positive foci by hepatocarcinogens
Authors: Sakai Toshihisa , Klopman Gilles , Rosenkranz Herbert S.
Published: February 2006

A data base consisting of 100 chemicals tested for the ability to enhance the formation of glutathione‐S‐transferase (GST) positive preneoplastic lesions were analyzed by the CASE structure‐activity relational system. A number of structural determinants associated with the induction of GST‐positive foci were recognized. The majority of these describe non‐electrophilic moieties. It is concluded that there is a structural basis for the induction of these neoplastic lesions; interestingly, it was found that this activity is associated with structures that are non‐electrophilic. Reconstruction experiments have indicated that the identified structures are meaningful and that their significance could be better understood with the availability of test results on additional chemicals. © 1994 Wiley‐Liss, Inc.
Morphological transformation induced by glass fibers in BALB/c‐3T3 cells
Authors: Gao H.‐G. , Whong W.‐Z. , Jones W. G. , Wallace W. E. , Ong T.
Published: February 2006

Studies were conducted to determine whether (1) glass fibers can induce morphological transformation in BALB/c‐3T3 cells, (2) the transforming activity of glass fibers is related to fiber size, and (3) transformed cells induced by glass fibers possess neoplastic properties. In the transformation assay, BALB/c‐3T3 cells were treated with three different types of glass fibers: Manville code 100 (JM‐100, Manville Corp., Denver, CO), Owens‐Corning AAA‐10 (AAA‐10, Owens‐Corning Corp., Toledo, OH), and Owens‐Corning general building insulation (ISL, Owens‐Corning Corp.) fibers. The neoplastic properties were investigated using the soft agar cloning and gene transfection methods. All three different glass fibers were cytotoxic at high concentrations and induced dose‐related increases in morphological transformation. The transforming activity was inversely related to fiber size, with AAA‐10 showing higher activity than JM‐100 and JM‐100 showing higher activity than ISL fiber. Transformed cells induced by glass fibers exerted anchorage‐independent growth (90%) and DNA transfection‐mediated transformation (100%). These results indicate that glass fibers are capable of transforming mammalian (BALB/c‐3T3) cells in vitro as a function of their physical properties and that glass fiber‐induced transformed cells possess preneoplastic characteristics © 1995 Wiley‐Liss, Inc.

This Article is a US Government work and, as such, is in the public domain in the United States of America.
Evaluation of the OECD 421 reproductive toxicity screening test protocol using 1‐(butylcarbamoyl)‐2‐benzimidazolecarbamate (benomyl)
Authors: Piersma A. H. , Verhoef A. , Dortant P. M.
Published: February 2006

The OECD 421 reproductive toxicity screening test protocol was evaluated using the fungicide benomyl as a test compound at 10, 30, or 90 mg/kg per day. Male rats showed dose‐dependent testicular degeneration after 28 days exposure, as expected on the basis of literature data. Dams in the high dose group, exposed from 14 days premating to postnatal day 6, had pups with decreased weights at postnatal days 1 and 6. Prenatal deaths were increased, but no malformations were found. In contrast, in a developmental toxicity test with exposure between gestation days 6 and 15,90 mg/kg induced a high level of postimplantation loss, with ophthalmic malformations in the surviving offspring, in agreement with literature data. It is suggested that premating exposure in the OECD 421 protocol may have induced tolerance to the compound, e.g., by modulation of biotransformation in the dam. These findings indicate that the teratogenic potential of a compound need not necessarily be revealed using this screening test. The OECD 421 protocol appeared sufficiently sensitive to reveal the reproductive hazard of benomyl on the basis of prenatal deaths and testicular and pup weight effects. However, the absence of congenital anomalies in the offspring after benomyl treatment according to the OECD 421 protocol underscores the notion that lack of biological activity in the test should not be regarded as evidence of lack of activity of a compound on reproductive parameters. © 1995 Wiley‐Liss, Inc.
Evaluation of the modifying influence of arecanut on the garlic‐modulated hepatic detoxication system enzymes, sulfhydryl content, and lipid peroxidation in mice
Authors: Singh Anjali , Rao A. R.
Published: February 2006

This paper evaluates the potential effects of arecanut (Areca catechu, L.), an important ingredient of betel quid, on the garlic (Allium sativum, L.)‐modulated activities of hepatic detoxication system enzymes, acid soluble sulfhydryl content, and lipid peroxidation in mice. Mice were fed on either a normal diet or a diet containing 0.25%, 0.5%, or 1% (w/w) arecanut for 45 days. During the last 10 days of treatment oral administration of garlic at the dose level of 20 or 100 mg/kg body weight/day was supplemented. Significant modulation in the activities of phase I and phase II enzymes, –SH content, and malondialdehyde (MDA) level by garlic was observed. Garlic‐modulated alterations in glutathione S‐transferase (GST) activity and –SH content were decreased, while cytochrome b5, cytochrome P‐450, and MDA levels were further augmented by the arecanut plus garlic treatments. © 1995 Wiley‐Liss, Inc.
Influence of high‐fat diets on the occurrence of spontaneous uterine endometrial adenocarcinomas in rats
Authors: Nagaoka Takaharu , Onodera Hiroshi , Hayashi Yuzo , Maekawa Akihiko
Published: February 2006

The effects of high‐fat diets on the spontaneous occurrence of uterine endometrial adenocarcinomas were examined in the Donryu rat. Ninety females at 6 weeks of age were equally divided into 3 groups. Animals in group 1 were fed a basal diet, while those in groups 2 and 3 received powdered basal diets containing 10% and 20% corn oil until 15 months of age, when all survivors were sacrificed. For sequential serum steroid assay and histological examination of sex organs, additional rats were fed diets containing 20% corn oil or without supplement.

Body weight gain in group 3 was significantly increased, while in group 2 it was similar to that in the control. In both high‐fat groups, calorie intake and weight of fat deposits in the abdominal cavity were significantly increased. The incidences of uterine adenocarcinomas in groups 2 and 3 were 18% (P < 0.05) and 7%, respectively, as compared to 0% in group 1. Severe hyperplasia (hyperplasia+++) also showed a non‐significant tendency for increase in incidence. In both high‐fat groups, an elevated incidence of persistent estrus was generally observed until 8 months of age. Sequential assays of steroid hormones in rats fed a 20% fat diet showed a tendency for early elevation and continued high values for the serum estrogen: progesterone (E2:P) ratio. In these rats, histological changes in the ovary, uterus, and vagina also appeared at an early stage, as compared to rats fed the basal diet. These results suggest that a high‐fat diet may exert a slight promoting effect on the spontaneous occurrence of uterine adenocarcinomas in Donryu rats, and this might be mechanistically related to hormonal imbalance and a high E2:P ratio in particular. © 1995 Wiley‐Liss, Inc.
Absence of promoting potential of bracken fern (Pteridium aquilinum) in rat urinary bladder carcinogenesis induced by N‐butyl‐N‐(4‐hydroxybutyl)‐nitrosamine and uracil
Authors: de Oliveira Maria Luiza , Rocha Noeme Souza , Fukushima Shoji , de Camargo João Lauro
Published: February 2006

Conventional studies on bracken fern (Pteridium aquilinum; PA) carcinogenicity have used high dietary concentrations (around 30%) and long‐term exposure (up to 52–70 weeks) without consideration of the multistep character of the chemical carcinogenesis process. The present study evaluated specifically the promoting potential of 3–5% dietary crude PA in the rat urinary bladder mucosa in a 32‐week‐long initiation‐promotion assay for chemical carcinogenesis. Initiation of urothelial carcinogenesis was accomplished with N‐butyl‐N‐(4‐hydroxybutyl)‐nitrosamine (BBN). Uracil (U) was provided through the diet in order to expand the population of initiated cells. Seven groups (G) of male Wistar rats were submitted to the following treatments: G1 = BBN (n = 8); G2 = U (n = 10); G3 = BBN‐U (n = 9); G4 = BBN‐PA‐U‐PA (n = 16); G5 = PA (n = 8); G6 = BBN‐PA (n = 10); G7 = PA‐U‐PA (n = 12). At the end of the experiment rats presenting epithelial papillary or nodular hyperplasia (PNH), papillomas (PAP), or simultaneous PNH plus PAP numbered, respectively G1: 2‐0‐1; G2: 0‐0‐0; G3: 3‐0‐2; G4: 4‐3‐2; G5: 1‐0‐1; G6: 8‐0‐0; and G7: 0‐0‐0, with no significant differences in the incidence of lesions among the groups. More frequent and more severe lesions occurred in BBN‐initiated animals, predominantly in those also exposed to uracil (G3 and G4). Low‐dose crude bracken fern in the diet does not promote rat urinary bladder carcinogenesis after a 32‐week period of exposure, even when the initiated urothelial cell population has been expanded through a mechanical stimulus. © 1995 Wiley‐Liss, Inc.
International safety assessment of pesticides: Dithiocarbamate pesticides, ETU, and PTU—A review and update
Authors: Vettorazzi Gaston , Almeida Waldemar F. , Burin Gerry J. , Jaeger Robert B. , Puga Flavio R. , Rahde Alberto F. , Reyes Felix G. , Schvartsman S.
Published: February 2006

For the last 30 years the Joint FAO/WHO Meeting on Pesticide Residues (JMPR) has carried out toxicological evaluations and safety assessments of dithiocarbamate pesticides, continuously adjusting previous appraisals in the light of new data and advances in the understanding of the principles and mechanisms of toxic action of these compounds. The historical narrative of the evaluative process is followed by an account of the present international safety assessment status of the dithiocarbamate pesticides so far examined by the JMPR. They are ferbam, mancozeb, maneb, metiram, nabam, propineb, thiram, zineb, ziram, and the associated substances, ethylenethiourea (ETU) and propylenethiourea (PTU). © 1996 Wiley‐Liss, Inc.
Molecular taxonomy of the yeasts
Authors: Kurtzman Cletus P.
Published: February 2006

The term ‘yeast’ is often taken as a synonym for Saccharomyces cerevisiae, but the phylogenetic diversity of yeasts is illustrated by their assignment to two taxonomic classes of fungi, the ascomycetes and the basidiomycetes. Subdivision of taxa within their respective classes is usually made from comparisons of morphological and physiological features whose genetic basis is often unknown. Application of molecular comparisons to questions in yeast classification offers an unprecedented opportunity to re‐evaluate current taxonomic schemes from the perspective of quantitative genetic differences. This review examines the impact of molecular comparisons, notably rRNA/rDNA sequence divergence, on the current phenotypically defined classification of yeasts. Principal findings include: 1) budding ascomycetous yeasts are monophyletic and represent a sister group to the filamentous ascomycetes, 2) fission yeasts are ancestral to budding and filamentous ascomycetes, 3) the molecular phylogeny of basidiomycetous yeasts is generally congruent with type of hyphal septum, presence or absence of teliospores in the sexual state, and occurrence of cellular xylose.
A new definition of viscosity solutions for a class of second-order degenerate elliptic integro-differential equations
Authors: Arisawa Mariko
Published: February 2006

We present a new definition of the viscosity solution for a class of integro-differential equations in a bounded open domain

Ω

in

\mathbf{R}^{N}

. We consider either the Dirichlet boundary condition or the Neumann boundary condition on the boundary. These equations correspond to the process which is a combination of the jumps and the Brownian motion. We give the comparison and the existence results for the viscosity solution in our new framework.

Nous présentons une nouvelle définition de la solution de viscosité pour certaine classe des équations intégro-différentielles sur un ouvert borné dans

\mathbf{R}^{N}

. Sur le bord, on considère soit la condition de Dirichlet ou soit la condition de Neumann. Ces équations correspondent au processus de la combinaison des sauts et du mouvement brownien. Nous donnons des résultats de la comparaison et de l'existence de la solution de viscosité dans notre cadre.
Planar binary trees and perturbative calculus of observables in classical field theory
Authors: Harrivel Dikanaina
Published: February 2006

We study the Klein–Gordon equation coupled with an interaction term

(□ + m^{2})\phi + \lambda \phi ^{p} = 0

. In the linear case (

\lambda = 0

) a kind of generalized Noether's theorem gives us a conserved quantity. The purpose of this paper is to find an analogue of this conserved quantity in the interacting case. We will see that we can do this perturbatively, and we define explicitly a conserved quantity, using a perturbative expansion based on Planar Trees and a kind of Feynman rule. Only the case

p = 2

is treated but our approach can be generalized to any

\phi ^{p}

-theory.

Nous étudions l'équation de Klein–Gordon couplée avec un terme d'interaction

(□ + m^{2})\phi + \lambda \phi ^{p} = 0

. Dans le cas où l'équation est linéaire (

\lambda = 0

), une généralisation du théorème de Noether nous donne une quantité conservée. Le but de cet article est de trouver un analogue de cette quantité dans le cas non-linéaire (

\lambda \neq 0

). Nous verrons que pour

λ

petit, on peut définir explicitement une quantité conservée en utilisant un développement perturbatif basé sur les Arbres Plans et des règles de Feynman particulières. Seul le cas

p = 2

est traité mais notre approche peut être appliquée pour tout

p \geq 2

.
hPTH‐fragments (53–84) and (28–48) antagonize the stimulation of calcium release and repression of alkaline phosphatase activity by hPTH‐(1–34) in vitro
Authors: Duvos Christian , Scutt Andrew , Mayer Hubert
Published: February 2006

Different C‐terminal fragments of parathyroid hormone (PTH)‐(1–84) in blood participate in the regulation of calcium homeostasis by PTH‐(1–84), and an antagonizing effect for the large carboxyl‐terminal parathyroid hormone (C‐PTH)‐fragment (7–84) on calcium release has been described in vivo and in vitro. In this study the smaller C‐PTH‐fragment (53–84) and mid‐regional PTH fragment (28–48), which represent discrete areas of activity in the PTH‐(7–84) molecule, were assayed for their effects on calcium release and alkaline phosphatase (ALP) activity in a chick bone organ culture system. Neither PTH‐(28–48) nor PTH‐(53–84) had any effect on calcium release into the medium and both fragments stimulated ALP activity in the bone tissue, suggesting that the cAMP/PKA signalling pathway was not affected by these fragments. However they suppressed the calcium release induced by PTH‐(1–34) and attenuated the down regulation of ALP activity caused by PTH‐(1–34), suggesting that the effect on the cAMP/PKA signalling pathway may be indirectly. In conclusion, the study shows that the PTH‐fragments (53–84) and (28–48) antagonize the PTH‐(1–34) induced effects on calcium release and inhibition of ALP activity in a chick bone organ culture system.
Roles of cAMP in regulating microtubule sliding and flagellar bending in demembranated hamster spermatozoa
Authors: Kinukawa Masashi , Oda Shoji , Shirakura Yoshiyuki , Okabe Masaki , Ohmuro Junko , Baba Shoji A. , Nagata Masao , Aoki Fugaku
Published: February 2006

To understand the mechanism regulating spermatozoa motility, it is important to investigate the mechanism regulating the conversion of microtubule sliding into flagellar bending. Therefore, we analyzed microtubule sliding and its conversion into flagellar bending using a demembranated spermatozoa model in which microtubule sliding and flagellar bending could be analyzed separately by treating the demembranated spermatozoa with and without dithiothreitol, respectively. Using this model, we examined the roles of cAMP and its target molecules in regulating flagellar bending and microtubule sliding. Although flagellar bending did not occur in the absence of cAMP, microtubule extrusion occurred without it, suggesting that cAMP is necessary for the conversion of microtubule sliding into flagellar bending, but not for microtubule sliding itself. The target of cAMP for regulating flagellar bending was not cAMP‐dependent protein kinase (PKA), since flagellar bending was still observed in the spermatozoa treated with a PKA‐specific inhibitor. Alternatively, the Epac/Rap pathway may be the target. Epac2 and Rap2 were detected in hamster spermatozoa using immunoblotting. Since Rap2 is a GTPase, we investigated the flagellar bending of demembranated spermatozoa treated with GTPγS. The treatment markedly increased the beat frequency and bending rate. These results suggest that cAMP activates the Epac/Rap pathway to regulate the conversion of microtubule sliding into flagellar bending.
Mammalian l‐to‐d‐amino‐acid‐residue isomerase from platypus venom
Authors: Torres Allan M. , Tsampazi Maria , Tsampazi Chryssanthi , Kennett Eleanor C. , Belov Katherine , Geraghty Dominic P. , Bansal Paramjit S. , Alewood Paul F. , Kuchel Philip W.
Published: February 2006

The presence of d‐amino‐acid‐containing polypeptides, defensin‐like peptide (DLP)‐2 and Ornithorhyncus venom C‐type natriuretic peptide (OvCNP)b, in platypus venom suggested the existence of a mammalian d‐amino‐acid‐residue isomerase(s) responsible for the modification of the all‐l‐amino acid precursors. We show here that this enzyme(s) is present in the venom gland extract and is responsible for the creation of DLP‐2 from DLP‐4 and OvCNPb from OvCNPa. The isomerisation reaction is freely reversible and under well defined laboratory conditions catalyses the interconversion of the DLPs to full equilibration. The isomerase is ∼50–60 kDa and is inhibited by methanol and the peptidase inhibitor amastatin. This is the first known l‐to‐d‐amino‐acid‐residue isomerase in a mammal.
Holocene variations in the Asian monsoon inferred from the geochemistry of lake sediments in central Tibet
Authors: Morrill Carrie , Overpeck Jonathan T. , Cole Julia E. , Liu Kam-biu , Shen Caiming , Tang Lingyu
Published: February 2006

We present a record of monsoon variations for the early and middle Holocene that is inferred from the geochemistry of sediment cores from Ahung Co, a lake in central Tibet. The resolution of this record is better than 50 yr and the age model is derived from radiocarbon ages of terrestrial charcoal, which eliminates errors associated with the lake hard-water effect. We made down-core geochemical measurements of % carbonate, % organic carbon, C/N and δ13C of bulk organic matter, δ13C and δ18O of carbonate, and % dolomite. Proxy calibration and modern water-balance reconstruction show that these are proxies for lake depth and the amount of monsoon precipitation. We find that lake level and monsoon precipitation have been decreasing at Ahung Co since the early Holocene (∼7500 cal yr B.P.). Superimposed on this trend are rapid declines in monsoon rainfall at 7000–7500 and 4700 cal yr B.P. and seven century-scale wet–dry oscillations. The cores do not contain sediment from the last ∼4000 yr. Surface sediments from the lake accumulated during the 20th century, however. From this, we argue that lake levels have risen again recently following a late Holocene dry period.