bluuebunny/crossref_metadata_2025 huggingface dataset:
Interference of prenatal and postnatal exposure to Ca2+‐antagonist agents on rat functional development of vascular system
Authors: Angrisani M. , Loffreda A. , De Santis D. , Filippelli A. , De Paola C. , Maione S. , Berrino L. , Matera C. , De Pasquale M. , Mauro C. , Guarino V. , Vitagliano S. , Molinario L. , Camarri F. , Marmo E.
Published: February 2006

Exposure to drugs during pregnancy can alter functional development of the vascular system. The present investigation was carried out in order to evaluate the effects of prenatal and postnatal exposure to Ca2+‐antagonist (diltiazem, verapamil, and nimodipine) drugs on the development of rat vasomotor reactivity. Studies were carried out on pregnant female albino rats exposed from the first day of pregnancy until weaning to diltiazem and verapamil (6 and 24 mg/kg in their drinking water ad libitum) and nimodipine (3 and 12 mg/kg in their food ad libitum). After weaning, pups were exposed until the 60th day of age to the same treatment as their mothers were. Afterwards, pups from the 60th to 90th day of age were fed with a normal diet.

In 30‐, 60‐, and 90‐day‐old conscious and anaesthetized pups, we evaluated the following: 1) systolic arterial blood pressure; 2) vasomotor responses elicited by various agents: L‐noradrenaline (0.1, 1, and 5 μ/kg IV), L‐isoprenaline (0.01, 0.1, and 1 μ/kg IV), and acetylcholine (0.01, 0.1, and 1 μ/kg IV) and by sinus‐carotid baroreceptor stimulation; and 3) catecholamine, acetycholinesterase, and adenosinase plasma levels.

Prenatal and postnatal exposure to Ca2+‐antagonist drugs significantly (P < .05) decreased the pressor response to sinus‐carotid baroreceptor stimulation and to L‐noradrenaline and increased the hypotensive responses to L‐isoprenaline and acetylcholine.

Moreover, this type of treatment, although it induced a significant (P < .05) decrease of catecholamine plasma levels, did not modify the acetylcholinesterase and adenosinase plasma levels in 30‐ and 60‐day‐old rats. On the 90th day of age, the evaluated parameters were not different from those of control rats.

Our results showed that exposure to Ca2+ antagonists during pregnancy and the postnatal period may alter the functional development of rat vasomotor reactivity.
Biochemical effects of three carcinogenic chlorinated methanes in rat liver
Authors: Kitchin Kirk T. , Brown Janice L.
Published: February 2006

Three chlorinated methanes, carbon tetrachloride, chloroform, and methylene chloride, known to cause liver tumors in rodents, were given by oral gavage to adult female rats both 21 h and 4 h before sacrifice. Then hepatic DNA damage, ornithine decarboxylase (ODC), cytochrome P‐450, glutathione content, and serum alanine aminotransferase (SGPT) activity assays were performed. Carbon tetrachloride increased rat hepatic ODC activity and decreased cytochrome P‐450 content at doses both below and above cytotoxicity (as measured by increased SGPT activity). At 54 and 160 mg/kg, chloroform increased hepatic ODC activity with minimal or no elevation in SGPT activity. At 480 mg/kg chloroform increased hepatic ODC and SGPT activity. A dose of 1,275 mg/kg methylene chloride caused a small, but significant amount of hepatic DNA damage. When these three compounds are compared on either an equimolar or equitoxic (1/5 LD50) basis, their ability to induce hepatic ODC or increase SGPT activity was carbon tetrachloride > chloroform > methylene chloride. The results of this biochemical study are interpreted with respect to the ability of chemicals to cause hepatic cancer by either genetic or epigenetic mechanisms.
Ozone and ultraviolet light act as additive cocarcinogens to induce in vitro neoplastic transformation
Authors: Borek Carmia , Ong Augustinus , Mason Herbert
Published: February 2006

Ozone, a major chemical oxidant in our environment, is an environmental air pollutant with putative carcinogenic action. Using in vitro transformation, we report for the first time that ozone (6 ppm for 10 min) acts in additive fashion with ultraviolet light (4 J/m2) to produce enhanced levels of transformation in hamster embryo cells and mouse C3H/10T‐1/2 cells as compared to rats induced by each of the agents alone.

The results underscore the hazard of ozone as a toxic pollutant which may have putative carcinogenic effects and interact with other environmental carcinogens.
Toxic and DNA‐damaging activities of the fungicides mancozeb and thiram (TMTD) on human lymphocytes in vitro
Authors: Perocco Paolo , Alessandra Santucci M. , Campani Anna Gasperi , Forti Giorgio Cantelli
Published: February 2006

The cytotoxic and mutagenic effects of the fungicides mancozeb and thiram were studied using human peripheral blood lymphocytes cultured in vitro with or without an S‐9 mix microsomal metabolizing system. The results obtained suggested that the chemicals caused dose‐dependent inhibition of thymidine uptake and unscheduled DNA synthesis on both resting and proliferating lymphocytes in the absence of the S‐9 mix. In the presence of the S‐9 mix, only thiram showed mutagenic activity by eliciting unscheduled DNA synthesis and a significantly higher frequency of sister chromatid exchanges than did controls.
Effects of quinoline and 8‐hydroxyquinoline on mouse bone marrow erythrocytes as measured by the micronucleus assay
Authors: Hamoud M. A. , Ong T. , Petersen M. , Nath J.
Published: February 2006

Both quinoline and 8‐hydroxyquinoline (HOQ) were tested for their genotoxicity in CD1 male mice by using a bone marrow micronucleus assay. Mice were intraperitoneally treated in single injections with three dose levels (25, 50, and 100 mg/kg) of each chemical with corn oil as solvent vehicle. Bone marrow was sampled at 24, 48, and 72 h postinjection. Quinoline resulted in a significant dose‐related increase in the number of micronucleated polychromatic erythrocytes (MPCE) at the 24 h sampling time for all doses tested. The high dose (100 mg/kg) and the medium dose (50 mg/kg) also induced statistically significant increases (P < .05) in the number of MPCEs at 48 h interval. The ratios of polychromatic to normochromatic erythrocytes at the 24 h sampling time were lower for the treated than the control animals. Although HOQ resulted in some increases in the number of MPCEs over the control, this compound induced a statistically significant increase in the number of micronucleated normochromatic erythrocytes (MNCEs) at all three doses following 24 h treatment. Both low and medium doses also induced a higher incidence of MNCEs at the 48 and 72 h sampling times. No data were available for the high dose at these times. The cytotoxic effect of this compound was expressed as low PCE/NCE ratios with all doses at 24 h after injection and as a high mortality rate in animals treated with the high dose (100 mg/kg).
Developmental toxicity screen: Results of rat studies with diethylhexyl phthalate and ethylene glycol monomethyl ether
Authors: Morrissey Richard E. , Harris Martha W. , Schwetz Bernard A.
Published: February 2006

The purpose of these investigations was to develop a protocol for an in vivo developmental toxicity screen (DETS) that would provide sufficient data to determine whether to 1) do a full developmental toxicity evaluation without additional range‐finding studies, or, depending on the results, to 2) do no further testing of a chemical. In order to evaluate this screen, we compared results obtained by using the DETS protocol with results of previously conducted developmental toxicity evaluations of diethylhexyl phthalate (DEHP) and ethylene glycol monomethylether (EGME). Five groups (n ± 17) of F344 rats were treated on days 6–15 of gestation by dosed feed (DEHP levels = 0, 0.5, 1.0, 1.5, 2.0%) or gavage (EGME doses = 0, 12.5, 25, 50, 100 mg/kg/day). One half of the rats in these studies were killed on day 16 of gestation, and the remaining animals were allowed to deliver litters which were killed on day 4. EGME caused only a small decrease in maternal weight gain during treatment (100 mg/kg group) that was accompanied by a decrease in gravid uterine weight. The percentage of resorptions was increased in the 50 and 100 mg/kg groups. The number of live pups was decreased in the 25, 50, and 100 mg/kg groups, and litter weight and postnatal survival were decreased in the 100 mg/kg group. These results are consistent with those reported in developmental toxicity studies on EGME conducted by the inhalation and dermal routes. With DEHP, there were treatment‐related reductions in maternal body weight and weight gain. There was also a nonstatistical increase in percentage of resorptions per litter that was also observed, but at relatively high levels, in a definitive study in which F344 dams were treated on days 0–20 of gestation. The results of studies on these two chemicals compare well with published results and would have led to the selection of proper dose levels for subsequent FDA segment 2 studies.
Caffeine toxicity is inversely related to DNA repair in simian virus 40‐transformed xeroderma pigmentosum cells irradiated with ultraviolet light
Authors: Cleaver J. E.
Published: February 2006

Human cells transformed by simian virus 40 (SV40) are more sensitive to killing by ultraviolet light when grown in caffeine after irradiation. The degree of sensitization at 2 mM caffeine (expressed as the ratio of the 37% survival dose for control cells divided by the 37% survival dose for cells grown in caffeine, i.e., the dose modification factor) was approximately 1.9 in transformed normal cells and 3.8–5.8 in excision‐defective xeroderma pigmentosum (XP) groups A, C, and D cells. A large dose modification factor of 12 was observed in a transformed XP variant cell line. Chinese hamster ovary cells were not significantly different from transformed normal human cells, with a maximum dose modification factor of 1.5. Two radioresistant XP revertants that do not excise cyclobutane dimers gave different responses; one resembled its group A parent in being sensitized by caffeine, and one did not. These results can be interpreted on the basis of a single hypothesis that cells are killed as a result of attempts to replicate damaged DNA. Increased replication rates caused by transformation, increased numbers of replication forks in DNA caused by caffeine, and increased numbers of damaged sites ahead of replication forks in excision‐defective cells are all processes that will consequently increase killing according to this hypothesis. A corollary is that the XP variant may be highly sensitized to caffeine because of excision defects at the DNA replication forks, an idea that may be important in designing cloning strategies for the XP variant gene.
Benzamide prevention of ultraviolet radiation‐induced transformation as measured by anchorage‐independent growth and the absence of correlation with thymidine dimer formation and DNA repair
Authors: Milo George E. , D'Ambrosio Steven , Kun Ernest
Published: February 2006

Synchronized human fibroblasts were exposed in early S phase to increasing doses of ultraviolet (UV) irradiation in the presence and absence of an antitrans‐forming drug, benzamide. Cellular survival, initial thymidine dimer formation and its repair, and cellular phenotypic transformation were simultaneously monitored in the presence and absence of 1 mM externally added benzamide that reaches 8 to 15 μM intracellular levels. Cellular transformation as measured by an expression of anchorage‐independent growth was inhibited by nontoxic doses of benzamide. Antitransforming action of benzamide is confined to low intracellular drug concentrations, which in the case of benzamide is in the 4–9 μM range. Because of the lack of effect of benzamide on the formation of UV‐induced thymidine dimers and the specific repair of these dimers, these results suggest that the processes of thymidine dimer formation and its repair are not involved in the mode of action of benzamide that influences the expression of a transformed phenotype with low malignant vigor.
Deletion screening at the hypoxanthine‐guanine phosphoribosyltransferase locus in chinese hamster cells using the polymerase chain reaction
Authors: Xu Zhidong , Yu Yongjia , Hsie Abraham W. , Thomas Caskey C. , Rossiter Belinda , Gibbs Richard A.
Published: February 2006

We have developed a rapid screening method using the polymerase chain reaction (PCR) for detecting deletion mutations at the hypoxanthine‐guanine phosphoribosyltransferase (hprt) locus in Chinese hamster cells. DNA was extracted from spontaneous and ultraviolet (UV) light‐ and X‐ray‐induced hprt‐deficient mutants. Two primer sets were used to amplify 276 bp and 344 bp fragments containing the entire exon 3 and exon 9 coding sequence, respectively. The PCR was performed using Taq DNA polymerase for 40 cycles, and the PCR product was directly analyzed for the presence of the respective amplified DNA using electrophoresis on agarose gels stained with ethidium bromide. With this assay, we have analyzed 39 independently derived hprt‐deficient mutants. Four of ten spontaneous mutants were found to have deletions in exon 9. UV light produced mutants with predominantly wild‐type amplification patterns (10/14). X‐ray induced mostly deletion patterns (11/15); six of these occurred only in exon 9, and five occurred in both exons 3 and 9. These observations are consistent with the classical notion that UV light induces predominantly missense mutations and X‐ray produces a high proportion of deletion mutations. Deletion mutations occurred most frequently at the 3° end of the hprt gene, suggesting the possible existence of hot spots for deletions in this region. The PCR assay for deletion detection has the advantage that it can be completed in less than 4 hr without using radioisotopes. This assay should be useful for routine deletion screening.
Induction of sister chromatid exchange in multiple murine tissues in vivo by various methylating agents
Authors: Neft Robin E. , Conner Mary K.
Published: February 2006

In order to study the reliability of in vivo sister chromatid exchange (SCE) assays for predicting carcinogenicity, several known animal carcinogens were tested in a multicellular in vivo SCE assay and an in vivo/in vitro murine lymphocyte assay. The methylating agents 1,2‐dimethylhydrazine · 2 HCl (DMH), dimethylnitrosamine (DMN), methylnitrosourea (MNU), methyl methane‐sulphonate (MMS), and methylazoxymethanol acetate (MAM) were tested for SCE induction in several murine tissues in vivo, including bone marrow, alveolar macrophages, regenerating and intact liver, and kidney from B6D2F1 mice. In all cell types, clear dose‐responses were observed following exposure of mice to subcytotoxic fractions of the LD50 dose of DMH, MNU, or MMS. DMN (0.03–0.27 mmol/kg) produced small, although not dose‐related, increases in SCE in all cell types. At the doses tested (0.06 and 0.08 mmol/kg), MAM did not induce elevated SCE in the various cell types.

Following a series of multiple i.p. injections of low, non‐toxic doses of DMH (0.15 mmol/kg, once a week, for 10 weeks), significant differences were observed in intact vs. regenerating liver and in single vs. multiple injections in regenerating liver.

Following exposure of B6D2F1 mice to a single i.p. injection of 0.25 mmol/kg DMN, DMH, or MMS or 0.19 mmol/kg MNU, SCE responses were evaluated in Concanavalin A (Con A)‐ and LPS‐stimulated blood and spleen lymphocytes. Considerable cytotoxicity was observed in blood lymphocytes. In Con A‐ and LPS‐stimulated spleen lymphocytes, DMH‐, and DMN‐ and MMS‐induced SCE frequencies were approximately 1.5–2 × baseline levels and MNU‐induced SCE were approximately three‐ to fourfold higher than baseline values in cultures initiated at 1 and 24 h postexposure.

At 48 and 72 h after an i.p. injection of 0.131 mmol/kg MNU, SCE responses in lymphocytes were approximately 2 × baseline levels. At 24 h following one, two, or four injections (one/week) of 0.075 mmol/kg MNU dose‐related increases in SCE were observed in spleen lymphocytes. These studies illustrate that carefully designed in vivo SCE assays may have the capacity to predict the tumorigenic potential of chemical agents.
Embryotoxic and teratogenic studies of phosphamidon in Swiss albino mice
Authors: Soni I. , Bhatnagar P.
Published: February 2006

Phosphamidon, an organophosphate pesticide, is little known for its possible effects on mammalian conceptus. The present investigation was carried out to evaluate its embryotoxic and teratogenic effects on Swiss albino mice. Female mice of similar age and weight were divided into four experimental groups. The animals of groups I and II received 15 and 35 ppm phosphamidon ad libitum, respectively, during the entire gestational period, that is, from days 1 to 18. Groups III and IV were treated before mating with 35 ppm phosphamidon for 30 and 60 days, respectively, and the treatment was continued during pregnancy up to the 18th day. The autopsies were performed on the 18th day of gestation, and routine teratological observations were made. The lower dose did not produce significant effects. The higher dose reduced the number of implants, litter size, and foetal weight and increased the resorption of embryos when administered for 30 days prior to mating. Exposure to the pesticide for 60 days prior to mating and during gestation, however, did not produce significant effects. It appears that the mice probably developed some resistance to the pesticide, when exposed for such a long duration.
Absence of DNA damage‐mediated induction of human methyltransferase specific for precarcinogenic O6‐methylguanine
Authors: Wani Gulzar , Wani Altaf A. , Gibson‐D'Ambrosio Ruth , Samuel Mervyn , Lowder Elizabeth , D'Ambrosio Steven M.
Published: February 2006

The ability of cultured normal human fetal liver and kidney epithelial cells to repair the premutagenic and precarcinogenic O6‐methylguanine (O6‐MeGua) DNA adduct was determined by directly monitoring its loss in cellular DNA and quantitating the number of O6‐MeGua‐DNA‐methyltransferase (O6‐MT) molecules per cell. Following treatment of the epithelial cells with the direct acting carcinogen N‐methyl‐N‐nitrosourea (MNU), the loss of the O6‐MeGua adduct was biphasic, exhibiting a half‐life of 2.0 and 1.5 h in the liver and kidney cells, respectively. The activity of O6‐MT in the liver and kidney epithelial cells in culture was 0.19 pmol/mg protein or 18,500 molecules/cell. The activity of O6‐MT was maintained throughout the life of the cultures, i.e., 20 subpassages or 50 cumulative population doublings for the liver and kidney. In order to ascertain whether human fetal epithelial cells exhibit an induction of O6‐MT, the cell cultures were treated with single and multiple conditioning doses of N‐methyl‐N‐nitro‐N‐nitroso‐guanidine (MNNG) or γ‐irradiated and assayed for the amount of O6‐MT. A 1 h exposure of cells to 2, 4, and 8 μM MNNG resulted in an 80–100% decrease of the initial O6‐MT activity which was restored to the constitutive levels within 48 and 72 h post‐treatment. Rat hepatoma cells, used as a positive control, increased their levels of O6‐MT to 2.8‐fold the constitutive levels following treatment with MNNG. Treatment of the human liver and kidney epithelial cells with chronic low doses of MNNG exhibited O6‐MT levels identical to untreated cells. The O6‐MT activity in epithelial cells remained unaffected upon pre‐irradiation with 1.2 or 2.5 Gy of γ‐irradiation. These result indicate that (i) the normal human fetal liver and kideny epithelial cells in culture actively repair O6 MeGua; (ii) resynthesis of O6 ‐MT in cultured cell and recovery to the basal constitutive levels occurs followinggonotoxin exposure; and (iii) O6‐MT is not induced following the chllenge does of physical and chemical agents.
Cytotoxicity and effect on mutagenicity of buffers in a microsuspension assay
Authors: Demarini David M. , Dallas Mary M. , Lewtas Joellen
Published: February 2006

We have examined the effects of three buffers–‐Vogel‐Bonner minimal E (VBM) and 0.15 and 0.015 M sodium phosphate, pH 7.4–‐and two concentrations of overnight cells (5× and 10×) on the mutagenicity of two pure compounds and two complex mixtures in strain TA98 using a modification of a microsuspension assay developed by Kado et al. (Mutation Research 121:25–32, 1983). The assay was performed by adding 50 μ1 of cell concentrate of an overnight culture of TA98 resuspended in the appropriate buffer; 50 μ1 of the same buffer or S9 mix; and 2 μ1 of mutagen or dimethyl sulfoxide to a 1‐dram vial or 13 × 150‐mm test tube. The suspension was incubated for 90 min at 37°C, top agar was added, and the contents poured onto a bottom agar of minimal medium. Cell concentration (5× vs. 10×) had little effect on the mutagenic potencies of the agents tested. The mutagenic potencies of the direct‐acting agents (1‐nitropyrene and diesel exhaust) were consistently lower with 0.15 M buffer compared to the mutagenic potencies of these agents with the other two buffers. The three buffers gave similar results for the indirect‐acting agents (2‐aminoanthracene and environmental tobacco smoke). The 0.15 M buffer was considerably cytotoxic in the absence of S9, which may explain why the direct‐acting agents were less potent with this buffer compared to the other buffers. VBM was also somewhat cytotoxic, but this did not appear to affect the mutagenic potencies of the agents studied. Thus, other factors in addition to cytotoxicity may account for the effects of the different buffers on the mutagenic potencies of the direct‐acting mutagens. Based on these results, we recommend the use of 0.015 M sodium phosphate buffer or VBM and either 5× or 10× cells for use with the microsuspension assay described here.
Thioethers, mutagens, and D‐glucaric acid in urine of operating room personnel exposed to anesthetics
Authors: Pasquini R. , Monarca S. , Sforzolini G. Scassellati , Bauleo F. A. , Angeli G. , Cerami F.
Published: February 2006

Mutagenic hazards related to occupational exposure to nitrous oxide and enflurane was studied in the personnel of five operating rooms using a coupled environmental and biological monitoring approach. The environmental monitoring revealed air concentrations of the two anesthetics exceedings the TLVs by 10–15‐fold. These values were correlated individually with the concentrations of the two anesthetics in the expired air of the exposed subjects. The biological monitoring was carried out by determining two parameters associated with mutagen exposure (urinary mutagenicity and thioethers) and a parameter associated with the enzymatic induction (D‐glucaric acid) in the urine of exposed and unexposed subjects (N = 64 and N = 37, respectively). The results showed no difference in the two groups for urine mutagenicity and D‐glucaric acid, but urine thioethers were significantly increased among highly exposed subjects.
Methotrexate resistance in NIH3T3 cells expressing polyoma virus oncogenes
Authors: Wani Maqsood , Snapka Robert M.
Published: February 2006

NIH3T3 cell lines expressing different polyoma virus oncogenes were found to differ by almost three orders of magnitude in frequencies of methotrexate‐resistant (MTXr) cells in single‐step selections. Cells expressing the polyoma small T antigen showed the highest frequencies of MTX resistance, whereas cells expressing the polyoma middle T antigen showed the lowest frequencies of MTX resistance. Amplification of the dihydrofolate reductase (dhfr) gene was not a mechanism of MTX resistance in these cell lines. Cells expressing large T antigen also showed a high frequency of MTXr colonies with only two of 20 such colonies showing evidence of marginal (less than threefold) dhfr gene amplification. Cells carrying the cloning vector without an oncogene showed intermediate frequencies of MTX resistance, and in contrast to the oncogene expressing lines, two‐thirds of these MTXr colonies showed marked dhfr gene amplification. The results suggest that the plasticity of the genome as measured by frequency or extent of dhfr gene amplification is not increased by expression of either immortalizing or transforming polyoma oncogenes. These oncogenes may, however, influence MTX resistance through epigenetic mechanisms. In addition, there appears to be no relationship between frequency of methotrexate resistance and frequency of dhfr gene amplification. It is clear that mechanisms of resistance other than dhfr gene amplification can be exclusively associated with either very high or very low frequencies of resistance.
Clastogenic effects of benzo[a]pyrene in postimplantation embryos with different genetic background
Authors: Adler I.‐D. , Kliesch U. , Kiefer F.
Published: February 2006

Certain strains of mice vary in their enzyme inducibility by polycyclic hydrocarbons, i.e., the strain C57 shows high and the strain DBA shows low inducibility of aryl hydrocarbon hydroxylase (AHH) by benzo[a]pyrene (BaP). The effect of this genetically determined difference on the clastogenic response to BaP was studied in 11 day old embryos after transplacental treatment. The four possible crosses, C57 and DBA inter se, C57 × DBA and DBA × C57, were used to determine the influence of the genetic background on the aberration yields in the embryos. Constitutive and induced AHH levels were measured in liver, bone marrow, and placenta of the pregnant females and in their embryos.

Enzyme inducibility was high in tissues of C57 dams and in their homozygous or heterozygous embryos. In contrast, induction of AHH activity was low in tissues of DBA females and their homozygous embryos. The high BaP‐induced AHH activity found in heterozygous embryos of DBA dams is in agreement with the dominant mode of inheritance for high AHH inducibility. The cytogenetic results showed that the clastogenic response was lowest in homozygous C57 embryos and highest in hybrid embryos independent of the genetic constitution of the dams. Homozygous DBA embryos showed an intermediate abberation yield.

The AHH inducibility by BaP did not correlate quantitatively with the induced aberration rates. However, the data suggest that BaP activation in embryonic tissue on day 11 of pregnancy is sufficient to account for the clastogenicity in the fetuses. It is concluded that the genetic endpoint chromosomal breakage is not only determined by the formation of active BaP metabolites but also by genetically controlled detoxification of BaP, repair process, and the rate of transformation of primary DNA lesions into true DNA discontinuities.
Comparative in vivo sister chromatid exchange induction by ethyl carbamate in maternal and fetal tissues of tumor‐susceptible and ‐resistant murine strains
Authors: Neeper‐Bradley T. L. , Conner Mary K.
Published: February 2006

Murine susceptibility to ethyl carbamate‐induced carcinogenesis is strain dependent. In vivo sister chromatid exchange (SCE) responses to ethyl carbamate were evaluated in bone marrow cells of gravid adenoma‐susceptible (ICR/Jcl), and resistant (C57Bl/6J) and (DBA/2J) murine dams, as well as in liver cells of their respective ICR/Jcl, C57Bl/6J × DBA/2J (BDF1), and DBA/2J × C57Bl/6J (BDF), fetuses following a single intravenous injection of 1.1, 2.2, or 3.3 mmol/kg of ethyl carbamate on gestation day 13/14. Bone marrow tissues of C57Bl/6J and DBA/2J, but not ICR/Jcl dams, demonstrated greater sensitivity to SCE induction than liver cells of their respective fetuses. Furthermore, relative SCE responses in bone marrow among dams indicated greater sensitivity of the more tumor‐susceptible ICR/Jcl and C57Bl/6J strains to SCE induction by ethyl carbamate relative to the more tumor‐resistant DBA/2J strain. In addition, concurrent alterations (stimulation or inhibition) of bone marrow cell cycle kinetics by ethyl carbamate were consistent with hormone‐related, strain‐dependent hematopoietic stress during pregnancy.
Effect of Ambient Temperature and Running Wheel Activity on the Outcome of Pregnancy in CD‐1 Mice
Authors: Berman Ezra , House Dennis , Carter Hershell B.
Published: February 2006

The effect of ambient temperature and running activity on fetal outcome was studied in CD‐1 mice. Pregnant mice were allowed to be active in a running wheel at various ambient temperatures (26, 30, 32, 34, or 36°C) for 100 min a day. The dams were killed near term, and various maternal and fetal measures made. Mean deep body temperature (measured using radio‐telethermometers implanted in the abdomen) of pregnant dams was raised to 39.5°C while running at an ambient temperature of 36°C. Bred mice, pregnant or not, continued to increase their running activity, but pregnant mice exercised less from mid‐pregnancy on. Running up to 1 km/hr had no effect on maternal weight gain, number of implantations, number of live fetuses, fetal body weight, and fetal relative brain weight. However, increasing ambient temperature was effective in decreasing maternal weight gain and fetal body weight and increasing fetal relative brain weight. Even though body temperature can be increased significantly by increasing either running rate or ambient temperature, the body temperature increase caused by running appears to have no significant influence on the outcome of pregnancy. At levels in this study, body temperature per se does not appear to be the variable on which to predict fetal effects. This is because only body temperature raised by higher ambient temperature, and not body temperature raised by increased running, was shown to effect a fetal change.
Preparation for Human Study of Pesticide Applicators: Sister Chromatid Exchanges and Chromosome Aberrations in Cultured Human Lymphocytes Exposed to Selected Fumigants
Authors: Garry V. F. , Nelson R. L. , Griffith J. , Harkins M.
Published: February 2006

In preparation for a human study of worker exposure to grain fumigants and pesticides, we decided to screen commonly used fumigants for genotoxic effects in vitro. This research strategy was employed to test the possibility that structurally simple chemicals might have similar genotoxic properties in vivo and in vitro. As a first step, we designed our in vitro protocol to mimic to the extent possible, a single in vivo exposure of lymphocytes to fumigants. Go lymphocytes were treated with different doses of carbon tetrachloride, carbon disulfide, methyl bromide, chloropicrin, and melathion with and without addition of rat liver homogenate for 1/2 hour, washed free of toxicant, and stimulated with PHA. After culture, the prepared slides were studied for chromosome aberrations and SCEs. Malathion, methyl bromide, and chloropicrin significantly induced SCEs without S‐9. Carbon disulfide alone required S‐9 for significant SCE induction. Chromosome aberrations were significantly increased by malathion and methyl bromide. Carbon tetrachloride failed to induce SCEs or chromosome aberrations with or without S‐9. We concluded from these preliminary studies and other comparable work that the fumigants studied here may be less likely to express genotoxicity in terms of SCEs or chromosome aberrations than ethylene oxide or phosphine given a single short‐term in vivo exposure. The final design of our human study was altered to focus on seasonal worker exposure rather than on a single exposure event.
Cytogenetic assays in genotoxic studies: Somatic cell effects of benzene and germinal cell effects of dibromochloropropane
Authors: Au William W. , Cantelli ‐Forti Giorgio , Hrelia Patrizia , Legator Marvin S.
Published: February 2006

We have reviewed the results of our cytogenetic studies to evaluate the usefulness of these assays in genotoxic studies. In one study, we observed unusual dose‐response in lymphocyte chromosome aberration frequencies after exposure of mice to low doses of a chemical mixture (benzene, chloroprene, epichlorohydrin, and xylene). The frequency in the high dose group is lower than those of the medium and low dose groups. This reduction of genotoxicity is correlated with a significant induction of a detoxifying enzyme, glutathione‐S‐transferase. The data also suggest that extrapolation of effects from high to low doses for risk assessment may be erroneous. Using benzene as a model clastogen, we found that the clastogenic effect persists for a long time after termination of exposure in mice. This phenomenon is probably due to a gradual release of benzene from absorption of the chemical in body fat. In an inhalation study, we observed that chromosome aberrations are induced in mice after exposure to benzene at below the occupational exposure limit of 1 ppm. Since benzene is a ubiquitous environmental contaminant, it may interact with other environmental agents to modify its genotoxic effects. We found that a nongenotoxic drug, praziquantel, and a free radical scavenger, DMSO, can enhance or reduce respectively the clastogenic activities of benzene in mice. Both modifying agents acted by altering the metabolic pathways of benzene. In a study with rats, we showed that carcinogenic doses of benzene can induce chromosome aberrations in lymphocytes of rats long before the expression of cancer. With dibromochloropropane, we observed that this chemical can induce dominant lethality in rats. In addition, neurobehavioral abnormalities were observed in survived offspring. These studies demonstrate the importance of conducting integrated studies which can provide validated genotoxic information that cannot be provided by using single assays. Our studies also confirm the usefulness of cytogenetic assays for genotoxic studies and suggest that the chromosome aberration endpoint can be used as an early warning signal for development of cancer.
Long‐term assays for carcinogenicity
Authors: Porta Giuseppe Della , Dragani Tommaso A.
Published: February 2006

During the past two decades, the rodent bioassay for detection of chemical carcinogens has reached a high standard of performance with both an increased number of animals and dose levels and a more detailed assessment of findings. However, the basic principles of testing and evaluation of results have remained essentially unchanged. Problems such as the length of the testing, use of maximum tolerated dose (MTD), selection of strains, variability of spontaneous tumors, discordant results between mouse and rat, and the classification of chemical carcinogens according to their mechanism of action have all remained unsolved. By contrast, the results of short‐term tests and of other biological analyses do not always show a direct correlation with those of the long‐term bioassays; this can be interpreted as an indication of different mechanisms of carcinogenicity. Currently available medium‐term tests may detect carcinogenic activity of chemicals at particular organs in a period of time (weeks to months) relatively shorter than that of the 2‐year carcinogenesis bioassay, and they may also provide additional information on mechanisms of carcinogenicity.
Prediction of toxicological interactions in a binary mixture by using pattern recognition techniques: Proposed approach with a developed model
Authors: Trieff Norman M. , Weller Susan C. , Ramanujam V. M. Sadagopa , Legator Marvin S.
Published: February 2006

A model has been suggested to predict the nature of toxicological interaction in binary mixtures. The approach uses the NLM‐HSDB computerized data bases, the ATSDR toxicologic profiles, and other literature for categorizing the nature (synergistic, antagonistic or no interaction) and degree of interaction.
Multivariate modeling (pattern recognition techniques) is the statistical approach utilized to separate groups of compounds into those that interact synergistically or antagonistically with a given toxic compound. Preliminary results indicate (1) that there are sufficient data in the literature on interactions to permit such modeling and (2) that in the case of carbon tetrachloride those compounds that interact synergistically with it are more similar to each other than those that interact antagonistically with respect to a number of structural and toxicologic parameters. This suggested approach of utilizing pattern recognition tools will be quite useful for regulatory agencies in predicting toxicological interactions occurring in complex chemical mixtures in the environment.
Mutagenic and carcinogenic potency indices and their correlation
Authors: Parodi S. , Taningher M. , Romano P. , Grilli S. , Santi L.
Published: February 2006

We have analyzed a significant number of studies existing in the literature, in which the ability of different short‐term tests for predicting carcinogenicity in rodents was investigated. We have separated these studies into two groups. In the better known group of studies, qualitative predictivity was investigated (sensitivity and specificity). In the second group of studies (analyzed in greater detail), positive results were examined for the correlation between carcinogenic potency and potency of response in a given short‐term test. There is substantial agreement between qualitative and quantitative predictivity; both appear to be situated between a low and moderate level. We have analyzed the interesting possibility of using the quantitative approach not only for positive data but for combined positive and negative data as well. We have stressed that short‐term tests of genotoxicity should be asked to predict only initiation and irreversible alterations in the genome and not to predict a combination of these events, including promotion and modulation of differentiation. Even with regard to only initiation, genotoxicity data should be related to comparative metabolism, as well as to considerations of the significance of different end points and structure‐‐activity relationship data. In conclusion, the information coming from short‐term tests of genotoxicity is probably useful but should be used in conjunction with other types of information and only for predicting one particular class of events in the entire process of carcinogenesis.
Strategies and governmental regulations
Authors: Carere A. , Benigni R.
Published: February 2006

An overview of testing strategies for the detection of genotoxins under OECD Guidelines and the EEC Directive 79/831 (VI Amendment) is outlined. The viewpoint of the Italian National Advisory Committee on Toxicology is also presented. In this context, the main issues of Genetic Toxicology (e.g., role of tests, tests recommended, classification of mutagens) are discussed.
Development and application of biomarkers exploitable for human exposure monitoring
Authors: De Flora Silvio
Published: February 2006

The objectives, applications and limitations of laboratory methods for assessing human exposure to carcinogens are concisely discussed. The available technologies include cytological, cytogenetic and molecular analyses, somatic cell mutation, carcinogen‐DNA or carcinogen‐protein adducts, metabolic markers, and chemical or biological analyses of expired air, body fluids, and excreta.
32P‐postlabeling of 7‐methylguanine adducts in DNA
Authors: Hemminki Kari , Mustonen Riitta
Published: February 2006

The 32P‐postlabeling technique introduced by Randerath and co‐workers has been particularly successful with stable and nonpolar DNA adducts, but the assay has not been used to any large extent to detect 7‐alkylguanine derivatives. In the present communication, we have investigated the phosphorylation reaction by T4 polynucleotide kinase using 7‐methyl‐3′‐dGMP, ring‐opened 7‐methyl‐3′‐dGMP and enzyme‐digested methylated DNA as substrates.

The methylated substrates were detected at femtomol (fmol) sensitivities. 7‐methyl‐3′‐dGMP was quantitatively phosphorylated at these low concentrations. The efficiency of phosphorylation of the ring‐opened product was less. It was shown that ring‐opened 7‐methyl‐3′‐dGMP was resistant to digestion with nuclease P1, making alkali‐treatment and enzyme digestion of DNA possible approaches to the determination of 7‐methyl‐guanine in DNA.
International symposium on strategies for the control of mutagenic and carcinogenic risk: Current status and perspectives, Friday, May 5, 1989, Bologna
Authors: Sobels F. H.
Published: February 2006

The 18 posters, grouped under mutagenicity testing, metabolic activation, mechanisms of mutation and chromosome damage, human monitoring and safety are critically discussed. It is pointed out that rather than applying a single test, a battery of well‐validated in vitro and in vivo tests is required. As a testing strategy, the one developed by Ashby (2) is briefly mentioned. The value of the Salmonella assay and of in vitro cytogenetics as short term tests for detecting carcinogens, and of the bone marrow micronucleus test as one for assessing germ cell mutagenesis is pointed out. Various assays now available for measuring gene mutations in human lymphocytes and erythrocytes are briefly described. Since we have a considerable data‐base for germ cell mutations in the mouse and data are now being collected for mutations in human somatic cells, the importance of studies on mutation induction in somatic cells of the mouse is emphasized. Such data on mouse somatic cells will help to define with greater precision mutation induction to be expected in human germ cells; that is genetic risks in humans on the basis of a “parallelogram‐like” extrapolation using somatic mutations in man and germ cell mutations in the mouse can now be calculated.
Dimethylsulfoxide as modifier of the organospecific mutagenicity of metronidazole in mice
Authors: Hrelia Patrizia , Scotti Miriam , Morotti Marta , Vigagni Fernanda , Paolini Moreno , Sapigni Ester , Cantelli‐Forti Giorgio
Published: February 2006

Mutagenicity and carcinogenicity of metronidazole (MT) are imputable to the formation of toxic intermediates, which include radical forms derived from the nitroreductive process. Since dimethylsulfoxide (DMSO) the “universal” solvent, can quench free radicals in vitro, it was suggested that DMSO might protect by scavenging free radical generation in vivo. This study wanted to evaluate if DMSO (given concomitantly or prophylactically) protects against the organospecific mutagenicity of MT in vivo by means of the intrasanguineous host‐mediated assay. DMSO used as solvent showed a 20%–30% reduction in the mutation frequencies by MT. Prophylactic administration of DMSO for 3 d caused a suppression of the organospecific mutagenicity. However, some increases in the spontaneous mutation frequency and enhancement of MT mutagenicity in kidney were observed. The protective effect was paralleled by a decrease in NADPH cytochrome c (P450) reductase in liver, kidney, and to a lesser extent in lung microsomes from pretreated mice. Inhibition of mutagenic activity might be related to scavenging of radical species as supported by the lack of tissue specificity and no appreciable changes in specific enzyme activity. However, changes in reductase content in prophylactically pretreated mice can affect the quantitative biotransformation of MT to the proximal mutagen contributing to the observed suppression in mutation frequencies.
Effects of alkylating antineoplastics alone or in combination with 3‐aminobenzamide on genotoxicity, antitumor activity, and NAD levels in human lymphocytes in vitro and on ehrlich ascites tumor cells in vivo
Authors: Petrou C. , Mourelatos D. , Mioglou E. , Dozi‐Vassiliades J. , Catsoulacos P.
Published: February 2006

Enhanced cytogenetic damage by the homo‐aza‐steroidal ester of p‐bis (2‐chloroethyl)‐aminophenylacetic acid (ASE) was observed when human lymphocytes in vitro or Ehrlich ascites tumor (EAT) cells in vivo were exposed to nontoxic concentrations of 3‐aminobenzamide (3‐AB). 3‐AB at these concentrations was found to enhance synergistically the cytogenetic damage induced in vivo by cyclophosphamide (CP), a metabolically activated chemotherapeutic, or chlorambucil (CBC) in EAT cells. One hour before i.p. injection of 5‐bromodeoxyuridine (BrdUrd) adsorbed to activated charcoal, EAT‐bearing mice treated i.p. with ASE or CP showed a dose‐dependent increase in sister chromatid exchange (SCE) rates and cell division delays. The treatment of human lymphocytes in vitro with ASE led to the depletion of cellular NAD, and addition of 3‐AB, a potent inhibitor of poly(ADP‐ribose)polymerase [P(ADPR)polymerase], to ASE‐treated human lymphocytes prevented the drop of NAD, which remained at approximately control levels. Also, the in vivo treatment of EAT cells with CBC, ASE, or CP led to the depletion of NAD, whereas addition of 3‐AB to CBC‐, ASE‐, or CP‐treated cells prevented the drop of NAD, which remained at nearly control levels. 3‐AB in conjunction with CBC, ASE, or CP increased the survival time of the EAT‐bearing mice and markedly reduced the ascitic volume. Thus cytogenetic damage induced by ASE plus 3‐AB in vitro and by CBC, ASE, or CP plus 3‐AB in vivo correlates well with (1) the prevention of NAD depletion in the presence of 3‐AB in cells treated with the same alkylating agents in vitro or in vivo and (2) the in vivo antitumor effect by ASE, CBC, or CP in combination with 3‐AB.
Image analysis and mathematical correlation between cell number and diameter of colonies in soft agar as a measurement of growth in soft agar
Authors: Lewis John C. , Milo George E.
Published: February 2006

Automated image analysis was used to measure the colony diameter and estimate the cell number in colonies under conditions for anchorage‐independent growth (AIG). The calculated values for the number of AIG cells in a colony of a diameter ⩾ 60 μm were decidedly different from the actual values obtained by either automated or manual cell counting. Like animal cells that exhibit AIG, these colonies demonstrating anchorage independence can be enumerated reproducibly. However, the assumption is incorrect that the number of cells (N) in a colony expressing AIG varies directly with a change in the diameter of a colony (d). Whether one counts the number of cells manually in a colony of a definite diameter or arbitrarily uses a diameter function of ⩾ 60 μm as a linear distance that indicates the presence of 50 or more cells in a colony, each procedure has its own built‐in bias. In procedures that require quantitative data, the most reliable procedure is to standardize the values for diameter of colonies with cell numbers in colonies.
Acetaminophen toxicity to cultured rat embryos
Authors: Weeks Benjamin S. , Gamache Paul , Klein Norman W. , Hinson Jack A. , Bruno Mary , Khairallah Edward
Published: February 2006

We tested the effects of acetaminophen on cultured rat embryo development. When added directly to culture media at 300 μM, a concentration approximately twice the human therapeutic blood level, acetaminophen caused abnormalities in the cultured embryos. Sera from both rats and monkeys following gavage with acetaminophen were also toxic to cultured embryos. The sera toxicities were related to acetaminophen concentrations, and the toxicity could be removed by serum dialysis. With regard to the metabolism of acetaminophen, glutathione levels in the yolk sac decreased in a concentration related fashion with addition of the drug. Also, buthionine sulfoximine, an inhibitor of glutathione synthesis, appeared to enhance acetaminophen embryo toxicity, and N‐acetylcysteine, a glutathione precursor, appeared to protect embryos from acetaminophen toxicity. These results suggested that acetaminophen embryo toxicity resulted from direct exposure of embryos to acetaminophen and not a maternal metabolite.
Analysis of the syndrome of congenital malformations induced in genetically defined mice by acute riboflavin deficiency
Authors: Kalter H.
Published: February 2006

The role of genetics in the expression of a complex syndrome of teratologically induced congenital malformations was examined by the use of three inbred strains and 15 related crosses of mice. The syndrome, which included various limb, brain, orofacial, gastrointestinal, and miscellaneous malformations, was induced by an intense riboflavin deficiency produced by feeding the antagonist galactoflavin during midgestation. Analyses of the data showed that, although all three strains shared the major and most other features of the syndrome, there occurred in its manifestation vast quantitative and qualitative differences among them, in which they were resembled by their related crosses, such as to constitute strain‐specific malformation patterns. The results can be regarded as typifying an animal counterpart of human situations, the three strains representing in toto the mouse family, each strain individually exhibiting the variety that occurs between siblings in expressing a single syndrome.