bluuebunny/crossref_metadata_2025 huggingface dataset:
Carcinogenicity bioassays of bromoacetaldehyde and bromoethanol—potential metabolites of dibromoethane
Authors: Van Duuren Benjamin L. , Melchionne Susan , Kline Stanley A. , Seidman Irving
Published: February 2006

1,2‐Dibromoethane (DBE) and two of its potential metabolites, bromoethanol (BE) and bromoacetaldehyde (BA), were tested for carcinogenicity in male and female B6C3F1 mice using 30 animals of each sex per group. The carcinogen DBE was included in this assay as a positive control. The compounds were administered in distilled drinking water using equimolar concentrations, 4 mmol, of the chemicals. The dose chosen was based on subchronic bioassays of three months' duration. The chronic tests were continued for ∼450 days in the case of DBE and ∼560 days for both BE and BA. DBE induced squamous carcinomas of the forestomach in 22 females and 26 males and squamous papillomas of the esophagus in 3 females. BE induced squamous papillomas of the forestomach only in 10 females and 9 males. BA did not induce a significant incidence of tumors of the forestomach. Significant tumor incidences at other sites were not observed in any groups including the distilled water control group. Based on these findings, it is unlikely that BE or BA are activated carcinogenic intermediates of DBE.
Potentiation of chemically induced cleft palate by ethanol ingestion during gestation in the mouse
Authors: Lee Melvin
Published: February 2006

The influence of ethanol consumption on cleft palate induction by methylmercury, cortisone, and retinyl acetate was investigated in Swiss white mice. Consumption of 20% ethanol throughout gestation significantly increased the incidence of cleft palate compared to water‐fed mice, when methylmercury was given on four consecutive days (days 9–12, 5 mg/kg of body weight). Ethanol also increased the incidence of cleft palate in mice given retinyl acetate (3,400 or 5,100 IU) on day 12, compared to retinol acetate‐treated mice given water, but did not affect cleft palate induction by cortisone (2.5 mg/d, days 8–11). Ethanol significantly reduced fetal weight in the presence or absence of the three teratogens, but the results do not support a hypothesis that growth retardation is directly responsible for the potentiating action of ethanol. It may be that ethanol acts to increase cleft palate induction by some teratogens by retarding fetal developmental processes.
Progressive proliferative changes in the oviduct of mice following developmental exposure to diethylstilbestrol
Authors: Newbold Retha R. , McLachlan John A. , Bullock Bill C.
Published: February 2006

Structural malformation of the oviduct has been reported in experimental animal models and women following prenatal exposure to diethylstilbestrol (DES). To study histological changes in the oviduct in the absence of gross structural malformation, neonatal CD‐1 mice were treated with DES (2 μg/pup/day) on days 1–5 of age. Focal epithelial hyperplasia was present at 1 month of age in 16 out of 18 (89%) of the DES‐treated mice. At 4 months of age, general epithelial hyperplasia with multiple gland‐like structures into and through the muscle wall of the oviduct was observed in 90% of the treated mice; by 12 months of age, epithelial hyperplasia and pseudogland formation were seen in 100% of the DES‐exposed animals. Epithelial hyperplasia and gland formation were not observed in control mice. The alteration induced by DES in the differentiation and proliferation of mouse oviductal epithelium suggests that the oviduct is a target for DES toxic effects. In addition, there was a progression of the epithelial changes with age. The histological changes described in this study may be partially responsible for the decreased fertility previously reported in this mouse model. Similar changes in the oviduct of DES‐exposed women remain to be determined.
An assessment of the effects of cyclophosphamide and sodium valproate on the viability of preimplantation mouse embryos using the fluorescein diacetate test
Authors: Kola Ismail , Folb Peter I.
Published: February 2006

The fluorescein diacetate test is a measure of both esterase enzyme activity and membrane integrity and it has been shown to be useful in assessing the viability of a variety of cells cultured in vitro, mouse embryos after freezing and thawing, and mouse embryos grown under inadequate culture conditions. In this study, the effects were examined of cyclophosphamide and sodium valproate administered respectively to pregnant inbred CBA mice 60 h after fertilization, on the viability of 84‐h blastocysts. Cyclophosphamide 20 and 40 mg/kg bodyweight and sodium valproate 90 mg/kg significantly increased the number of nonviable blastocysts. Cyclophosphamide 4 mg/kg and sodium valproate 23 and 45 mg/kg did not adversely affect blastocyst viability. The intensity of embryo fluorescence correlated well with the subsequent development of the embryos in culture (r = 0.863; p < 0.001). The test had a sensitivity of 83% and a specificity of 100%. Exposure of embryos to fluorescein diacetate under the conditions of this experiment did not adversely influence the subsequent postimplantation development of 84‐h blastocysts cultured in vitro for a further 120 h. These findings suggest that the fluorescein diacetate test is a simple, rapid, and nontoxic procedure that may be useful in assessing the viability of preimplantation embryos after exposure to embryotoxic drugs and chemicals.
Effects on the fetal rat intestine of maternal malnutrition and exposure to nitrofen (2,4‐dichlorophenyl‐p‐nitrophenyl ether)
Authors: Mahboob Soltanali , Hoogenboom Elizabeth R. , Kavlock Robert J. , Zeman Frances J.
Published: February 2006

The effects of maternal protein‐energy malnutrition and exposure to nitrofen on selected aspects of intestinal morphology and function were studied in the fetal rat. Pregnant rats were fed, throughout gestation, diets containing 24% or 6% casein as the sole source of protein. Reduced total food intake produced protein‐energy malnutrition (PEM). Each diet group was divided in half and gavaged with either 12.5 mg nitrofen in corn oil/kg/day or corn oil carrier only from days 7 to 21 of gestation. Body weight, intestinal weight, length, and diameter were measured as were villus length (VL), villus width (VW), and number of villi per length of intestine (VMM). Protein (horseradish peroxidase) and lipid absorption were studied histochemically. Lactase and dipeptidase activities were determined in proximal, medial, and distal thirds of the intestine. Results showed that the restricted maternal diet resulted in reduced fetal body weight (BW), intestinal weight (IW) and length (IL), reduced IW/BW and IW/IL ratios, VH, and VMM. The VW was reduced only in the distal third. Protein and lipid absorption were unaffected. Lactase and dipeptidase activities were reduced. Maternal nitrofen exposure resulted in reduced body weight, intestinal size, and lipid absorption, with some evidence of interaction with the diet effects on enzyme activities. It is concluded that effects of maternal malnutrition were extensive, but that nitrofen exposure, at this dosage level, is not likely to contribute to the postnatal fetal mortality rate in either adequately nourished or malnourished rats.
An improved procedure for the efficient injection of radioactive steroids into mouse embryos
Authors: Hochner‐Celnikier Drorith , Monder Carl
Published: February 2006

Retention of 3H‐moxestrol in mouse fetuses after transmaternal, intrafetal, and intraplacental injection were compared. Direct injection into the allantoic placenta resulted in greater retention of radioactivity by the fetus than the other modes of administration between 12 and 16 days of gestation. By this same criterion, intrafetal injection was best for older fetuses. Maternal injection was the least efficient way to transfer 3H‐moxestrol to the fetus.
Induction of sister chromatid exchanges and chromosome damage by gossypol in bone marrow cells of mice
Authors: Nayak B. N. , Buttar H. S.
Published: February 2006

The chromosome‐damaging potential of gossypol was evaluated by scoring sister chromatid exchanges (SCEs), determining the percentage of pulverized metaphases and the mitotic index in bone marrow cells of mice. Bone marrow cells were collected approximately 21 hours after the intraperitoneal (0,20,40,80, or 160 μg/g) and oral (0,40,80, or 160 μg/g) administration of gossypol acetic acid. Irrespective of the dosing schedule (single or multiple doses), the vehicle used (physiological saline, corn oil, or 10% aqueous ethanol), and the route of administration, the mean SCE count per cell was significantly higher (P < 0.05) in gossypol‐treated groups than their control counterparts. At 80 and 160 μg/g dose levels, the occurrence of metaphase chromosome pulverization was significantly greater, while mitotic index values were markedly lower than those of the corresponding control values. The results suggest that gossypol is a potentially mutagenic and clastogenic agent in murine bone marrow cells.
Maternal administration of cyclophosphamide induces chromosomal aberrations and inhibits cell number, histone synthesis, and DNA synthesis in preimplantation mouse embryos
Authors: Kola Ismail , Folb Peter I. , Parker M. Iqbal
Published: February 2006

The effects of cyclophosphamide (CPA), administered to pregnant inbred CBA/Ca mice 60 h after copulation, on cell number, mitotic index, chromosome structure, histone synthesis, and DNA synthesis of 84‐h blastocysts, and the subsequent development of these blastocysts cultured for a further 120 h in vitro are described. Cyclophosphamide 4, 20, and 40 mg/kg significantly increased the number of chromosomally aberrant cells, chromosomal aberrations, and chromosome breaks in the blastocysts. Chromosomal rearrangements were significantly increased in the CPA 20 and 40‐mg/kg treated groups, and in the 40‐mg/kg group the number of cells with ring chromosomes was significantly increased. Histone synthesis and DNA synthesis were significantly inhibited in the CPA 20 and 40‐mg/kg treated groups. Blastocyst cell number in each of the treated groups was less than the controls. On subsequent culture in vitro, significantly fewer embryos in the CPA 20 and 40‐mg/kg groups hatched, attached, developed trophoblast outgrowths, and expanded their inner cell masses. However, the differentiation of inner cell mass into ectoderm and endoderm was impaired by all three doses of the drug. These results demonstrate that CPA administered to pregnant mice 60 h after copulation has a clastogenic effect and interferes with synthesis of DNA and histones in the preimplantation embryo, and that the drug inhibits the subsequent development and differentiation of these embryos. Cytogenetic analysis of preimplantation embryos might be a useful adjunct to the existing methods in the evaluation of the embryotoxicity of drugs and chemicals.
Effect of prenatal propranolol exposure on development of the postnatal rat heart
Authors: Harmon James R. , Delongchamp Robert R. , Kimmel Gary L. , Webb Peggy J.
Published: February 2006

Maternal propranolol (PRO) treatment has previously been associated with adverse effects on the fetus and neonate. In the present study, pregnant rats were treated with PRO (25 or 50 mg/kg/day s.c.) on gestation days 8–20 to assess its possible effects on the developing heart. Maternal weight gain and pup weight on postnatal day (PND) 1 were reduced in a dose‐dependent manner; litter size was unaffected. Pup body weight and heart weight both showed a dose‐related decrease at all ages tested (PNDs 5/6, 8/9, 15/16, and 22/23). Since heart protein, but not DNA, was similarly reduced, the decrease seen in heart weight most likely reflects a decrease in cell size instead of cell number. Basal ornithine decarboxylase (ODC), an enzyme associated with growth and development, was unaffected by maternal PRO treatment. Insulin and isoproterenol stimulation of ODC, suggested markers for testing the function of the sympathetic pathway to the heart and of the heart's ODC response system, respectively, also showed no PRO‐related response. In conclusion, prenatal PRO exposure resulted in reduced body weight, heart weight, and heart protein, but had little effect on heart DNA or ODC activity. Since PRO treatment also reduced maternal weight gain, the adverse effects seen in the pups may be due to generalized PRO toxicity. The results suggest that when high PRO doses were used clinically, the careful monitoring of maternal weight gain during pregnancy might be useful in predicting adverse fetal effects.
Influence of the nature and the dose of the initiator on the development of premalignant and malignant lesions in rat hepatocarcinogenesis
Authors: Préat V. , de Gerlache J. , Lans M. , Taper H. , Roberfroid M.
Published: February 2006

Using a triphasic protocol recently described to induce malignant tumors in rat liver, the question has been asked whether both the nature and the dose of the initiator influence the carcinogenic process. Two nitrosamines (diethylnitrosamine DEN and N‐nitrosomorpholine NNM) have been used to initiate that process.

With regard to the premalignant stages appearing in the liver up to 19 weeks after initiation, there is a dose‐dependent relationship between the dose of initiator and both the percentage of the parenchyma occupied by and the number of GGT+ lesions. DEN is always more potent than equivalent doses of NNM.

With regard to malignant tumors appearing within the period of observation (up to 44 weeks), the two highest doses (100 and 200 mg/kg) of DEN appear to be the only carcinogenic treatments. Cancer incidence (percentage of rats bearing histologically characterized malignant tumor) is the same after both treatments, but the tumor yield (number of tumors per rat bearing macroscopic tumors) is higher (± 2 ×) after 200 mg/kg than after 100 mg/kg.
Deoxycytidine reverses inhibition of morphogenesis by thymidine in young chick blastoderm
Authors: Zagris Nikolas
Published: February 2006

Exogenous thymidine affects morphogenesis of the early chick blastoderm possibly by depleting the deoxycytidine triphosphate pool. The aim of this study is to determine whether the inhibitory action of thymidine on early chick blastoderm morphogenesis is alleviated by the removal of thymidine and/or treatment with deoxycytidine.

Chick blastoderms at the full hypoblast stage develop abnormally in egg albumen containing 1.23 × 10−3 M thymidine. Development is normal when deoxycytidine is included simultaneously in the culture medium with thymidine at equimolar concentrations. Blastoderms were cultured in egg albumen containing 15 μCi/ml thymidine [methyl‐3H] or 10 μCi/ml deoxycytidine [5‐3H], and 1.2 × 10−3 M 2′ ‐deoxycytidine or 1.23 × 10−3 M thymidine, respectively. The culture was interrupted at timed intervals, and the amount of radioactivity associated with DNA was determined. Exogenous deoxycytidine in the culture medium caused a noticeable increase in the incorporation of 3H‐thymidine, while exogenous thymidine markedly inhibited the uptake and incorporation of 3H‐deoxycytidine into DNA of blastoderms.

Thymidine does not inhibit the expansion of blastoderm, the migration of cells for formation of the primitive streak (PS), and the induction of axial tissues, but it interferes with the organization of these tissues to form the embryonic axis. Blastoderms show slight signs of recovery when thymidine is removed. Deoxycytidine counteracts the action of thymidine and seems to be a rate‐limiting factor in normal differentiation of the early chick blastoderm.
Mutagenic and cytotoxic potencies of a series of anthracycline derivatives as measured by HIS+ reversion, 8‐azaguanine resistance and direct plating cytotoxicity tests in Salmonella typhimurium
Authors: Thomas Harvey F.
Published: February 2006

His+ reversion at multiple his− loci, 8‐azaguanine resistance, and a previously reported direct plating cytotoxicity test were used to measure the genotoxic potencies of a series of anthracycline derivatives in Salmonella typhimurium. N‐demethylated amino sugar monosaccharide anthracyclines reverted most his−tester strains and were positive with 8‐azaguanine selection. Reversion of strain TA98 was the most sensitive end point for measuring the mutagenic activity of the N‐demethylated anthracyclines. N,N‐dimethyl amino sugar derivatives of Adriamycin and daunomycin were negative as measured by His+ reversion in tester strain TA98, but generated positive responses in tester strain TA102 that were equal to or greater than those of the demethylated parent coumpounds. Similarly, N,N‐dimethyl amino sugar derivatives of pyrromycinone and 1‐deoxypyrromycinone had no mutagenic activity as measured by His+ reversion except in tester strains TA102 and TA104. These later compounds also gave positive responses with 8‐azaguanine selection. In view of these results, the importance of amino sugar dialkylation and anthracycline mechanisms of mutagenesis are discussed.
Uptake by cells of nucleic acids promoted by compounds sharing the pleiotropic effects of poly(ethylene glycol)
Authors: Klebe Robert J. , Hanson Danelle P. , Harris June V. , Bentley Kevin L.
Published: February 2006

Poly(ethylene glycol) (PEG) is a member of a group of membrane active compounds that have pleiotropic effects on cells, eg, promotion of cell fusion, induction of erythroleukemia cell differentiation, and protection of cells from freezing damage. Since PEG has recently been shown to be an efficient promoter of genetic transformation in bacteria, yeast, and mammalian cells, studies were carried out to determine whether other PEG‐related compounds could also promote genetic transformation. In this study, 24 compounds, which behave like PEG in other biological systems, are shown to promote transfection of human cells with isolated poliovirus RNA. That PEG and other commercially important compounds promote transfection indicates that such compounds may represent a biohazard to man.
Antimutagenic effects of natural and synthetic hormonal steroids
Authors: Wilpart Myriam , Speder Anne , Ninane Pascale , Roberfroid Marcel
Published: February 2006

Among the steroid molecules, bile acids have been shown to have either a co‐ or an antimutagenic activity toward various direct and indirect acting mutagens in the Ames test. The present report extends such observations to other steroids having hormonal activity. The main effect of the active hormones is an inhibition of the genotoxicity of both direct and indirect acting mutagens. This effect is strictly structure‐related. Moreover, both ethinyl oestradiol and mestranol, which are synthetic derivatives of β‐oestradiol largely used in contraceptive pills, are strong inhibitors of the mutagenicity, acting at nanomolar concentrations.

The present article emphasizes the possible role of compounds with steroid structure as modulators of genotoxicity.
The effects of maternal murine cytomegalovirus infection on the mouse conceptus at different gestational stages
Authors: Huang Yuan‐Shen , Chernoff Neil , Kavlock Robert J. , Kawanishi Clinton Y.
Published: February 2006

The effects of murine cytomegalovirus (MCMV) on the prenatal development of the CD‐1 mouse were investigated. Two sets of experiments were performed. In the first, mice were inoculated with different doses of MCMV on gestational day 7, and in the second, pregnant animals were inoculated with a subacute injection dose at different gestational stages. The effects of maternal infection on pregnancy in terms of maternal sickness, embryo lethality, date of parturition, litter size, postnatal death, and pups' body weight on d 1 and d 3 postpartum were investigated. High‐dose MCMV infection on d 7 of pregnancy resulted in a significant increase in early embryo resorption and also in a reduction of the neonatal body weight of surviving pups. Two gestational stages were identified as being especially susceptible to MCMV infection. Most embryonic death as indicated by resorption rates was found after treatment on d 9, whereas perinatal death was most frequent when treatment was done on d 13 of gestation. Still births and neonatal death within 24 h of birth were found commonly in this latter group, which also showed the most pronounced growth retardation. The phenomenon of delay in time of parturition was noted and found to be most significant in groups of animals that were inoculated on d 3 or d 13. This investigation suggests that the effects of MCMV on the CD‐1 mouse vary greatly with the age of the embryo and the course of the infection.
Cell number and size in selected organs of fetuses of rats malnourished and exposed to nitrofen
Authors: Zeman Frances J. , Heng Helen , Hoogenboom Elizabeth R. , Kavlock Robert J. , Mahboob Soltanali
Published: February 2006

The effects of maternal exposure to nitrofen or protein‐energy malnutrition on the number and sizes of cells in selected organs of the fetal rat have been studied. Pregnant rats were fed either an adequate (CON) or protein‐energy deficient diet (PEM) throughout gestation. Each diet group was divided into two subgroups. One subgroup was gavaged with 25 mg nitrofen/kg body weight on gestational days 7–21 and the other, with corn oil carrier only. Fetal liver, kidneys, intestine, heart, lung, and brain were weighed and assayed for DNA, RNA, and protein. Maternal protein deficiency resulted in a reduction in organ weight and total DNA, RNA, and protein in all six organs. Maternal nitrofen exposure resulted in reduced weight and reduced protein in all organs except the brain. Total DNA and RNA were reduced in intestine, heart, and lung, and total RNA was also reduced in the liver following maternal nitrofen exposure. An interaction between diet and toxin affected lung weight, DNA, RNA, and protein, intestinal total protein, and heart DNA. Protein/DNA ratios were reduced in liver, intestine, and brain in the group fed the inadequate diet and in intestine only following nitrofen exposure. The deficient diet resulted in increased RNA/DNA ratio in the fetal liver and heart and a decreased ratio in the kidney and brain. Nitrofen exposure resulted in a lower RNA/DNA ratio in the liver. The data indicate that maternal protein‐energy malnutrition results in smaller organs in the fetuses with fewer cells and containing less protein and RNA. The greater reduction in protein than that expected from the decrease in numbers of cells in the liver, intestine, and brain in fetuses of malnourished dams suggests that cells were also smaller. Effects on RNA/DNA were essentially in the same direction as seen for protein/DNA. In general, the diet deficiency appeared to have a general metabolic effect reducing cell replication that, however, spared the brain. Nitrofen exposure results in an organ‐specific reduction in cell replication in the intestine, heart, and lung. An interaction between restricted diet and nitrofen exposure involves the lung primarily.
Heavy metal inhibition of carnitine acetyltransferase activity in human placental syncytiotrophoblast: Possible site of action of HgCl2, CH3HgCl, and CdCl2
Authors: Shoaf Antony R. , Jarmer Scott , Harbison Raymond D.
Published: February 2006

The effect of the heavy metal toxicants HgCl2, CH3HgCl, and CdCl2 on the acetylating activity of membranous carnitine acetyltransferase (CarAc) in membrane vesicles from the maternal surface of human placental syncytiotrophoblast has been investigated. CarAc was inhibited by inorganic and organic mercury and cadmium. Carnitine acetylation was inhibited by as little as 5 μM mercury, with complete inhibition at 50 μM inorganic and organic mercury. Inhibition by cadmium was incomplete (< 60%) at 500 μM CdCl2. Kinetic studies using Hanes plots revealed a mixed type of inhibition of CarAc by the metals. Cysteine preincubation decreased the amount of inhibition of CarAc by the metals. These results indicate that the inhibition of CarAc by heavy metals occurs by binding of the sulfhydryl on the enzyme by the metals. This interaction may be a mechanism of the heavy metal‐induced fetotoxicity.
Validation of an in vivo developmental toxicity screen in the mouse
Authors: Seidenberg Janice M. , Anderson David G. , Becker Richard A.
Published: February 2006

A test system for identifying toxicity, including potential teratogenicity has been developed that is based on growth and viability of embryonic, fetal, and postnatal mice (J. Toxicol Environ Health 10:541–550, 1982). To test the utility of this assay, a series of 55 compounds was administered to timed‐pregnant ICR/SIM mice during organogenesis. The test compounds included known teratogens, known nonteratogens, and equivocal teratogens. They represented a wide variety of classes including pesticides, organic solvents, metals, steroids, nutrients, food additives, antimetabolites, alkylating agents, and pharmaceutical agents. A single dose level, at or near the level producing overt maternal toxicity in preliminary range‐finding studies, was administered by gavage on gestation days 8 through 12. Females were allowed to deliver; litter size and weight on the day of birth and 2 days postpartum were recorded, and stillborns were examined. Dams that had not given birth by gestation days 21 or 22 were killed and their uteri were examined. The results confirmed a strong correlation between reported teratogenic activity and embryo/fetal viability, and/or postnatal growth and viability. The results indicate that this test system is an effective, cost‐efficient means of prioritizing compounds for more detailed teratogenicity testing.
Sirenomelia: Analysis in the cadmium‐ and lead‐treated golden hamster
Authors: Hilbelink Don R. , Kaplan Stanley
Published: February 2006

Sirenomelia, a fusion of the lower extremities, is believed to result from a median, bilateral symmetric defect of the caudal portion of the embryo at a very early stage in development. Anomalies of the gastrointestinal and urogenital systems are commonly associated with this malformation. Sirenomelia is not an embryolethal condition but typically is incompatible with postnatal life when combined with the associated malformations. In this study, intravenous treatment of hamsters with a combination of cadmium and lead on the morning of the eighth day of gestation resulted in 1.4, 22.2, and 35.6% of the viable fetuses displaying sirenomelia in litters recovered on days 15, 12, and 10 of gestation, respectively. With the exception of several fetuses with exencephaly, most structures cranial to the level of the umbilicus were normal. Caudal abdominal and pelvic structures were severely affected, with agenesis or dysgenesis of the kidneys, bladder, umbilical arteries, and external genitalia frequently noted. The administration of a combination of cadmium and lead has proven to be an effective and consistent means of inducing sirenomelia in the golden hamster.
Enhancement of cytogenetic damage by inhibitors of poly(ADP‐ribose)polymerase in human lymphocytes exposed to antineoplastics in vivo and in vitro
Authors: Mourelatos D. , Kourakis A. , Koliouskas D. E. , Hatzitheodoridou P. , Dozi‐Vassiliades J.
Published: February 2006

The effect of benzamide (B) and 3‐aminobenzamide (3‐AB) on sister chromatid exchanges (SCEs) and cell kinetics induced in vitro by melphalan (MELPH) or thiotepa (THIO) was studied in normal human lymphocytes. The combined treatments with either MELPH or THIO plus B or 3‐AB showed the potentiating ability on SCE rates and the ability to induce cell division delays of the latter chemicals.

In a combined in vivo and in vitro study, lymphocytes taken from six cancer patients who had been given cytoxan by injection 2 hr before and then treated with theophylline (THEOPH) or B or 3‐AB in vitro were found to have synergistically increased exchange rates and cell division delays. The frequency of SCEs in the patients own lymphocytes with and without exposure to inhibitor of Poly(ADP‐ribose) polymerase (P(ADPR)polymerase) was determined before the cytostatic therapy and was used as a control for later comparison in each individual case. These results further substantiate the use of this approach for detecting the induction of cytogenetic damage concerning controlled mutagen human exposure in combined in vivo and in vitro studies.

Chemically induced cytotoxicity manifested as an alteration (division delay) in cell kinetics and as synergistic DNA damage by cytostatics and inhibitors of P(ADPR)polymerase may be of use in the treatment of human cancer.
The direct‐acting mutagenicity of nitroimidazo[2,1‐b]thiazoles in Salmonella typhimurium
Authors: Hrelia P. , Paolini M. , Biagi G. L. , Cantelli‐Forti G.
Published: February 2006

A series of nitroimidazo[2,1‐b]thiazole derivatives was investigated for directacting mutagenic potency with the Salmonella assay. All of the nine derivatives tested were mutagenic. The compounds induced predominantly base displacements resulting in frame‐shift mutations. The mutagenic activity did not require the S9 fraction but was largely dependent on “classical” bacterial nitroreductase. The primary basis of the mutagenic activity of nitroimidazo[2,1‐b]thiazoles appears to be a reduction of the nitro‐function to the corresponding hydroxylamine. Mutagenicity seems to be paralleled by an increase of the nitro groups: dinitroderivatives were more active than nitroderivatives. Other electrophiles and sterically constrained nitro groups could account for differences in genotoxicity.
Malformations induced in cultured rat embryos by enzymically generated active oxygen species
Authors: Jenkinson P. C. , Anderson Diana , Gangolli S. D.
Published: February 2006

Day 9.5 rat embryos were exposed in culture to xanthine/xanthine oxidase generated active oxygen species. Growth and development were assessed after 46 hr of culture. The treatment induced abnormalities of the neural suture, the severity of which increased in a dose‐related manner with the concentration of substrate or enzyme. Glutathione (10 mM) or catalase (50 μg/ml) either partially or completely abolished the effects of xanthine/xanthine oxidase, whereas the addition of superoxide dismutase (50 μg/ml) or desferrioxamine (1mM) did not reduce the number of malformed embryos. These findings suggest that hydrogen peroxide and/or hydroxyl radicals are responsible for the effects of xanthine and xanthine oxidase.
The heat‐shock response in vivo: Experimental induction during mammalian organogenesis
Authors: German James , Louie Elaine , Banerjee Debendranath
Published: February 2006

According to the embryonic stress hypothesis of teratogenesis, anatomical malformation can be the consequence of the induction of a heat‐shock response (HSR) in the embryo at some critical stage during the determination or differentiation of organs. This hypothesis states that a teratogen is any agent (i) that is capable of inducing a HSR and (ii) that can reach the developing embryo. As a first step in determining whether the hypothesis is tenable, it was necessary to determine whether the embryo in fact is capable of making the HSR during the period of organogenesis. Pregnant mice were treated with two classical inducers of the HSR, one a physical and the other a chemical agent—namely, hyperthermia and sodium arsenite. The embryos, while still in the living mouse, responded with heat‐shock protein induction, as did control bone marrow.
Hyperthermia as a teratogen: A review of experimental studies and their clinical significance
Authors: Edwards M. J.
Published: February 2006

Although hyperthermia is teratogenic in birds, all the common laboratory animals, farm animals, and primates and satisfies defined criteria as a teratogen, its study as a human teratogen has been neglected. Homeothermic animals, including humans, can experience body temperature elevations induced by febrile infections, heavy exercise and hot environments which exceed the thresholds (1.5–2.5°C elevation) which are known to cause a syndrome of embryonic resorptions, abortions, and malformations in experimental animals. Hyperthermia is particularly damaging to the central nervous system, and if a threshold exposure occurs at the appropriate stages of embryonic development, exencephaly, anencephaly, encephalocoele, micrencephaly, microphthalmia, neurogenic talipes, and arthrogryposis can be produced in a high proportion of exposed embryos, the incidence and type of defect depending on the species and strain within species, the stage of development, and the severity of hyperthermic exposure. Other defects which can be induced experimentally include exomphalos, hypoplasia of toes and teeth, renal agenesis, vertebral anomalies, maxillary hypoplasia, facial clefting, cataract, coloboma, and heart and vascular defects. Proliferating cells are particularly sensitive to temperature elevations, resulting in arrest of mitotic activity and immediate death of cells in mitosis with threshold elevations (1.5–2.5°C) and delayed death of cells probably in S phase with higher elevations (3.5°C). In general, lower temperature elevations (2.5°C) require longer durations of elevation to cause defects than a simple spike at a higher elevation (4.5°C). The death of cells is largely confined to the brain and in the day 21 guinea pig embryo to the alar regions of the brain. Cell death probably accounts for most of the defects in the central nervous system, but microvascular disturbances leading to leakage, oedema and haemorrhage, placental necrosis, and infarction are other known effects of hyperthermia; and these are probably involved in the pathogenesis of many defects of the heart, limbs, kidneys, and body wall. Recent experiments have demonstrated protection of rat embryos in culture against a known teratogenic exposure by a brief nonteratogenic exposure given at least 15 min earlier. This protection is associated with the synthesis of heat‐shock proteins, and temporary arrest of the cell proliferative cycle. Hyperthermia appears to be capable of causing congenital defects in all species and may act alone or synergistically with other agents. With minimally teratogenic doses of heat plus arsenic, lead, or vitamin A, the combined responses with heat have been clearly augmented compared with the additive responses of single treatments. The contribution of hyperthermia to abortions is well documented, and its effect on human birth defects needs careful evaluation.
A summary of the results of 55 chemicals screened for developmental toxicity in mice
Authors: Seidenberg Janice M. , Becker Richard A.
Published: February 2006

Fifty‐five chemicals, including known teratogens, known embryotoxins, equivocal teratogens, nonembryotoxins, and nonteratogens, as well as compounds of unknown teratogenic or embryotoxic potential, were evaluated in the Chernoff/Kavlock developmental toxicity screen. All chemicals were administered by gavage to pregnant ICR/SIM mice on gestation days 8 through 12. The mice were allowed to deliver, and several neonatal growth and viability parameters were measured in the offspring. Comparative statistical analysis of these parameters between treated animals and concurrent (vehicle‐treated) controls provided a data base to evaluate the validity of the developmental toxicity screen as an assay to detect teratogens and embryotoxins. Of the 26 compounds reported in the literature to be teratogenic or embryotoxic in mice following oral administration, 24 were positive in the developmental toxicity screen. Of the compounds previously tested in conventional assays and found to be devoid of teratogenic or embryotoxic activity in mice, 93% were negative in the developmental toxicity screen. The importance of experimental design, dose selection, and neonatal growth and viability measurements as they relate to interpretation and evaluation of the results of the developmental toxicity assay are discussed.
The Chernoff‐Kavlock assay: Its validation and application in rats
Authors: de S. Wickramaratne G. A.
Published: February 2006

As the rat is the preferred species for teratogenicity studies in our laboratories, the Chernoff‐Kavlock assay was modified and validated for use in this species. The Alpk:AP (Wistar‐derived) strain, which is also used routinely for toxicology studies, was used, under standard SPF conditions. Twenty‐six chemicals have been assayed to demonstrate the utility of the system as a predictor of rat teratogens and to develop a set of rules for interpretation of the results. Routes of chemical administration were largely gavage, with some dermal, subcutaneous, inhalation, and intraperitoneal applications. The use of the assay in five modes to assist the toxicological evaluation or understanding of chemicals is displayed. These modes are (1) as a pre‐screen, (2) to compare analogues/homologues, (3) to provide a rapid hazard estimate, (4) to generate a dose‐response, and (5) to test a hypothesis.
Overview and summary: Workshop on the Chernoff/Kavlock preliminary developmental toxicity test
Authors: Hardin Bryan D. , Becker Richard A. , Kavlock Robert J. , Seidenberg Janice M. , Chernoff Neil
Published: February 2006

The Chernoff/Kavlock assay, proposed as a preliminary screen for teratogenic potential, was the subject of a 2‐day workshop sponsored by the National Institute for Occupational Safety and Health. Data from three large testing programs were presented, representing tests of 165 chemicals, of which 33 were tested at least twice. Applications of the test in industrial laboratories and product development, hazard identification, and risk assessment were discussed. Workshop participants recognized the assay as one of several valid ways to preliminarily evaluate chemicals with unknown developmental toxicity. Other preliminary tests were also discussed in terms of their relationship to this test, which was seen as having the advantage of providing information on neonatal viability. Other techniques, particularly an abbreviated conventional teratology study, were also recognized as appropriate screens. The preferred test in a particular laboratory will be dependent upon the particular skills and objectives of that laboratory. Standardized protocols were suggested, but flexibility in experimental design was considered necessary, and many variations on the basic test could be appropriate. This preliminary test has been used most often as a single‐dose test in mice, but might provide more generally useful data if conducted in rats using two dose levels. Workshop participants viewed the test as highly reliable in correctly identifying developmentally toxic chemicals and suggested that a negative finding in a properly conducted Chernoff/Kavlock test could be a sufficient basis for regulatory agencies to determine that conventional teratology tests in the same species are not warranted.
An evaluation system for ranking chemicals with teratogenic potential
Authors: Wang G. M. , Schwetz B. A.
Published: February 2006

An evaluation system has been developed which permits comparison of the relative toxicity of chemicals based on their potential to alter embryonal and early‐stage fetal development. It was considered necessary, from a regulatory standpoint, to develop a system for ranking chemicals which possess teratogenic potential. A detailed discussion of the various parameters selected and their relative importance is provided.
Effect of ethylene glycol monomethyl ether on spermatogenesis, dominant lethality, and F1 abnormalities in the rat and the mouse after treatment of F0 males
Authors: Anderson Diana , Brinkworth M. H. , Jenkinson P. C. , Clode S. A. , Creasy D. M. , Gangolli S. D.
Published: February 2006

Adult male CD rats and CD‐1 mice were given a single oral dose of ethylene glycol monomethyl ether (EGM) at 0, 500, 750, 1,000, or 1500 mg/kg. Groups of 10 were killed at weekly intervals after dosing for analysis of sperm counts and morphology or testicular histology; further groups of 10 were sequentially mated to pairs of virgin females to test for dominant lethality or gross foetal malformations in the F1 generation (F1 abnormalities).

EGM was found to deplete the spermatocytes of both species severely, principally pachytene cells, but with other stages affected with increasing dose. A delay in the progression of spermatogenesis may account for a discrepancy between the apparent stage‐specificity of damage deduced from lowered sperm counts and that observed histologically. In the rat, morphological abnormalities were observed in sperm that had been exposed as spermatocytes; in the mouse, however, the sensitive cells were the late spermatocytes and early spermatids. In all these parameters there was an indication of a dose‐response relationship in both rats and mice. In the mating studies EGM induced a dose‐related decrease in fertility 5 weeks after dosing in the rat, but complete sterility in all but the lowest dose after 6 weeks. In contrast, EGM had no effect on the reproductive capacity of the mouse. There was no statistically significant evidence for the induction of dominant lethal mutations or F1 abnormalities in either species.

A single oral dose of cyclophosphamide (CTX) at 100 mg/kg induced a significant increase in dominant lethality in both species. CTX reduced the number of total implants in the rat and induced a nonsignificant increase in the number of abnormal offspring sired by treated male mice.
Potentiating effect of caffeine on embryotoxicity of cyclophosphamide treatment in vivo during the preimplanation period
Authors: Vogel Richard , Spielmann Horst
Published: February 2006

Since it is unknown if chemicals which are generally safe in pregnancy can potentiate the embryotoxicity of cytotoxic drugs before implantation, the combined effects of cyclophosphamide (CPA) and caffeine (CF) were studied in the mouse (day 2) with CPA at 20 mg/kg, which induces a 18% resorption rate, and CF at 100 mg/kg, which does not increase embryolethality. The embryotoxicity of CPA did not increase when CF was either given 6 h before or simultaneously with CPA on day 2. However, when CF was given 6 h after CPA, a potentiated increase of embryolethality was observed at term and of structural chromosomal aberrations in embryos even before implantation, while sister chromatid exchange (SCE) frequency was less increased than after single CPA treatment. The results demonstrate the importance of pharmacokinetics in pregnancy even before implantation. Furthermore, since SCE may not only indicate DNA damage but also repair, the reduced SCE rate and the increase in structural chromosome aberrations suggest that CF can inhibit the repair of CPA‐induced DNA damage in preimplantation embryos. Finally, for the first time the data are providing evidence that CF at subthreshold doses can potentiate the embryotoxicity of an alkylating agent in vivo even before implantation.
Cyclophosphamide‐induced cytogenetic effects in mouse bone marrow and spleen cells in in vivo and in vivo/in vitro assays
Authors: Krishna G. , Nath J. , Petersen M. , Ong T.
Published: February 2006

Sister chromatid exchange (SCE) and chromosomal aberration studies have been used to monitor human populations for genotoxic exposure to chemical substances. These monitoring techniques involve collection of blood and/or bone marrow from the exposed subjects and culturing cells for one or two cell cycles with various treatments in culture. The results obtained from such in vivo/in vitro studies may lead to an over‐or underestimation of the damage that could occur in vivo. In the present study, which uses a mouse model, the in vivo/in vitro cytogenetic assays (SCEs and chromosomal aberrations) have been compared with similar in vivo systems in bone marrow and spleen cells treated with various doses of cyclophosphamide (CPA). The results indicate a significant difference in CPA‐induced cytogenetic endpoints between in vivo and in vivo/in vitro conditions in both organs. However, linear relationships were found between CPA dose and cytogenetic end point analyzed under both conditions. Based on these results it appears that the in vivo/in vitro assay is a useful technique for indicating potential in vivo damage of chemicals.
Problems facing the decision‐maker in the risk assessment process
Authors: Moore John A.
Published: February 2006

This paper presents an overview of the U.S. Environmental Protection Agency's risk assessment process, describes problems that the Agency faces in conducting risk assessment, in general, and identifies some specific problems that the Agency confronts when conducting risk assessments on suspected developmental toxicants. As noted by the NAS (National Research Council: “Risk Assessment in the Federal Government: Managing the Process.” Washington, DC: National Academy Press, 1983, pp 17–83), improving the quality and comprehensiveness of knowledge is the most effective way to improve risk assessment, but some limitations are inherent and may remain unresolvable. Therefore, inferences will always be required. The Agency's challenge is to ensure that these inferences are as soundly based as possible.
Maternal factors in developmental toxicity
Authors: DeSesso John M.
Published: February 2006

The maternal organism provides the developing embryo with its physical environment, nutrients, and a mechanism for eliminating metabolic wastes. Since the physiological state of the pregnant female affects her ability to provide those requirements for the developing embryo, it is not surprising that there are maternal factors that can affect the wellbeing of the embryo. Extremes of maternal age in both humans and animals have been implicated in growth retardation, as well as autosomal trisomies. The influence of maternal size on fetal size is more pronounced among larger species with longer gestation periods such as humans and domestic animals. A clear relationship between the parity of the mother and potential developmental toxicity in humans has not been established due to the confounding influences of maternal age. Among laboratory rodents, however, it appears that offspring of multiparous animals are at increased risk of developmental toxicity. A variety of infectious agents, particularly viruses, have either been demonstrated or implicated as causes of developmental toxicity. In addition, hyperthermia is a possible confounding factor inherent with maternal infection. Although under experimental conditions hyperthermia is teratogenic in laboratory animals, a causative role for transient hyperthermia, which occurs during febrile states concomitant with infections, cannot be clearly established. Chronic maternal vascular disease states including essential hypertension, heart disease, or diabetes mellitus are likely to contribute to uteroplacental insufficiency and developmental toxicity. Poor maternal nutrition among humans contributes to growth retardation, but not to malformations. The production of “abnormal” maternal antibodies, such as are present in Rh incompatibility, can cause fetal wastage. An important maternal factor in humans is uteroplacental insufficiency, which can occur in normal states like twinning, as well as in abnormal conditions including reduced placental size, chronic maternal hypoxia, or uterine ischemia. Although all these maternal factors can contribute to developmental toxicity, they do not necessarily occur as isolated events. Some developmental toxicants exert deleterious effects within both the embryo and the maternal system.