bluuebunny/crossref_metadata_2025_split huggingface dataset:
Use of the adult developmental relationship in prescreening for developmental hazards
Authors: Johnson E. Marshall , Christian Mildred S. , Dansky Linda , Gabel B. E. G. 
Published: February 2006

AbstractThe overwhelming majority of chemicals already in commerce or brought into use each year have not been evaluated for their potential to adversely affect in utero development. Data from those that have been evaluated thus far in pregnant laboratory animals establish that most, but not all, were no more hazardous to the conceptus than they were to adult homeostasis. Most did not need standard developmental toxicity testing because avoidance of adult toxic exposure levels would have precluded abnormal in utero development. The six general principles of teratology when modified, expanded, and placed into this type of context of contemporary developmental toxicology allow an updating of the present testing sequence which was devised prior to 1966.The developmental hazard index (A/D ratio) calculated from the adult and developmental NOELs of standard Segment II evaluations is predicted by in vitro means. This determination, when coupled with adequate considerations of exposure can be used to prioritize chemicals for more elaborate developmental toxicity tests. Those chemicals with large ratios, i.e., disruptive of embryogenesis at treatment levels too low to produce overt effects in the mother and/or with significant concern regarding exposure, can be identified and tested in pregnant laboratory animals as high priority items. Those with low ratios and those for which there is a low level of concern regarding exposure potential also can be identified and are not high priority items for testing in pregnant animals. The proposed tier system establishes priorities of testing based on exposure and the concept of target organ toxicity applied to the embryo. It provides intensive in vivo evaluations of those chemicals for which developmental effects testing is most needed and avoids use of resources and animals for unnecessary testing of agents that do not pose threats to the conceptus.
Benomyl‐induced craniocerebral anomalies in fetuses of adequately nourished and protein‐deprived rats
Authors: Ellis William G. , Semple Janet L. , Hoogenboom Elizabeth R. , Kavlock Robert J. , Zeman Frances J. 
Published: February 2006

AbstractBenomyl, a benzimidazole fungicide, produced craniocerebral and systemic malformations in fetal rats when administered by gavage in doses of 31.2, 62.5, and 125 mg/kg of maternal body weight on days 7–21 of gestation. Malformations increased in incidence and severity with increasing benomyl dosage and nearly doubled when coupled with a protein‐deficient diet. Protein deficiency alone produced only decreased fetal weight. High benomyl doses produced higher percentages of fetal resorptions and late fetal deaths, and these percentages also increased with protein deficiency. A benomyl dose of 62.5 mg/kg in proteindeficiency dams, the optimal combination for a high incidence of anomalies and low fetal wastage, produced hydrocephalus in 69.4% of fetuses, meningocele in 8.2%, encephalocele in 14.3%, exencephaly in 44.9%, anencephaly in 14.3%, corpus callosum agenesis in 26.5%, periventricular necrosis in 26.5%, and periventricular cellular “overgrowth” in 55.1%. The most common combination of anomalies was hydrocephalus, exencephaly, and periventricular “overgrowth.” Common systemic malformations included cleft palate, micromelia, hydroureter, and misshapen tails. No fetus was entirely normal at the highest benomyl dose.Benomyl has been shown by others to bind tubulin and inhibit the formation of microtubules that are important in neurulation, mitosis, and cell migration during early brain development. Thus, it is suggested that benomyl, coupled with a protein‐deficient diet, offers a teratogenic model with a spectrum of abnormalities similar to hypervitaminosis A but with a higher yield of specific craniocerebral anomalies.
Dissociation of estrogen‐induced uterine growth and ornithine decarboxylase activity in the postnatal rat
Authors: Sheehan Daniel M. , Branham William S. 
Published: February 2006

AbstractEstrogens are teratogens and developmental carcinogens in several species. We have used uterine growth to quantitate the potency of three estrogens [estradiol (E2), diethylstilbestrol (DES), ethynylestradiol (EE2)] during four postnatal periods (days 1–5, 10–14, 20–24, and 60–64) in the rat. Alphafetoprotein (AFP), present at high levels in neonatal serum, is thought to regulate estrogen bioavailability. Association constants for DES and EE2 were 2.7% and 4.9% of that for E2 binding to AFP, determined in a batch Sephadex equilibrium binding assay. On days 1–5, DES and EE2 were about 80‐fold more potent than E2 in increasing uterine weight. As AFP levels fell, potency differences between E2 and the synthetic estrogens decreased. In the adult, which essentially lacks AFP, the three estrogens were nearly equipotent. These data are consistent with AFP regulation of estrogen potency. On days 10–14, uterine growth was less sensitive than at other ages to all three estrogens, perhaps related to uterine differentiation and/or the high endogenous serum E2 levels reported at this age.However, when we examined another uterine estrogen response, ornithine decarboxylase (ODC) induction at 6 h following estrogen injection, all three hormones were about equipotent in both neonatal and adult animals. This apparently AFP‐independent event shows dissociation of ODC induction and uterine growth, which could be due to separate mechanisms for hormone entry to target tissue or subsequent intracellular events.
The covalent binding of 1, 1,2,2‐tetrachloroethane to macromolecules of rat and mouse organs
Authors: Colacci Annamaria , Grilli Sandro , Lattanzi Giovanna , Prodi Giorgio , Turina M. Paola , Forti Giorgio Cantelli , Mazzullo Mario 
Published: February 2006

AbstractThe in vivo interaction of the hepatocarcinogen 1,1,2,2‐tetrachloroethane (1,1,2,2‐TTCE) with DNA, RNA, and proteins of male Wistar rats and BALB/c mice was measured 22 hr after i.p. injection. Covalent binding index (CBI) to liver DNA was about 500 and was comparable to those of carcinogens classified as moderate initiators. It was higher than those of other chloroethanes, even than that of 1,2‐ dichloroethane (1,2‐DCE), a symmetrically substituted haloethane whose genotoxicity has been widely demonstrated.In in vitro cell‐free systems, 1,1,2,2‐tetrachloroethane was bioactivated by mixed‐function oxidase(s) and glutathione‐S‐transferase(s) (GSH‐T) from microsomal and cytosolic fractions of rat and mouse liver and, to a lesser extent, of mouse lung. The in vitro activation led to formation of reactive species capable of binding to exogenous DNA and to the subcellular constituents of enzymatic fractions.These data, along with previous literature reports, provide sufficient evidence of 1,1,2,2‐TTCE genotoxicity.
Depression of glutathione in male reproductive tissues and potentiation of EMS‐induced germ cell mutagenesis by L‐buthionine sulfoximine
Authors: Teaf Christopher M. , Bishop Jack B. , Harbison Raymond D. 
Published: February 2006

AbstractButhionine sulfoximine (BSO) treatment significantly reduced testicular epididymal and vas deferens glutathione (GSH) levels in rats. Testicular levels of GSH were reduced by 20%, while epididymal GSH levels were reduced by more than 50%. BSO treatment correspondingly enhanced ethyl methanesulfonate (EMS)‐induced dominant lethal mutations. EMS‐induced resorption rates were doubled following BSO treatment. This effect was observed in mating wk 2 and 3 (d 8–19 following treatment), indicating effects on those germ cells which were in late testicular stages or were caput epididymal spermatozoa at the time of EMS treatment. The enhancement of the mutagenic action of EMS by BSO is restricted to the same time period (spermatid‐spermatozoa transition, early epididymal maturation) as maximum sensitivity to the clastogenic action of EMS on male germ cells. The temporal pattern of EMS alkylation of rat spermatozoa correlated with the incidence of EMS‐induced dominant lethal mutations. BSO depresses GSH in the male reproductive tract in a dose‐ and time‐dependent manner. Perturbation of GSH in the male reproductive tract appears to influence chemical‐induced germ cell mutations.
Factors influencing the initiation by gamma rays of hepatocarcinogenesis in the rat
Authors: Kaufmann William K. , MacKenzie Susan A. , Kaufman David G. 
Published: February 2006

AbstractF344 male rats were irradiated once with 6 G of cesium 137 gamma rays at various times after a two‐thirds partial hepatectomy (PH) and then fed a diet containing the liver tumor promoter phenobarbital to evoke the expression of initiated hepatocytes. Yields of hepatocellular neoplasms were enumerated at 45 weeks after irradiation. Although proliferating hepatocytes in regenerating livers appeared to have increased risk of initiation by gamma rays, there was no apparent variation in risk among groups that were treated at times when hepatocytes were in different portions of the cell cycle (G1, S, G2/M). Gamma irradiation delayed the onsets of DNA synthesis and mitosis by proliferating hepatocytes by 18–20 h. The rate of rejoining of radiation‐induced DNA strand breaks was analyzed in primary cultures of hepatocytes; 98% of the strand breaks were rejoined within 30 min after irradiation. Efficient repair of certain types of radiation‐induced damage to DNA before the damaged DNA is replicated should cause a substantial reduction in the probability of induction of base‐substitution mutations. Hepatocellular islands and neoplasms that were initiated by gamma rays may be derived from proliferating hepatocytes which incurred other radiation‐induced DNA damages such as chromosomal aberrations.
Effect of duration of exposure to benzo(a)pyrene diol‐epoxide on neoplastic transformation, mutagenesis, cytotoxicity, and total covalent binding to DNA of rodent cells
Authors: Krolewski Bozena , Little John B. , Reynolds Richard J. 
Published: February 2006

AbstractWe examined the effect of different durations of exposure (20 sec to 24 hr) to (±) 7‐β,8α‐dihydroxy‐9α, 10α ‐epoxy‐7,8,9,10‐tetrahydrobenzo(a)pyrene (BPDE I) on the induction of transformation in C3H/10T1/2 cells and of mutations to 6‐thioguanine resistance in Chinese hamster ovary cells (CHO), as well as on BPDE I‐DNA binding in these two cell lines. A 20‐sec exposure of the cells to BPDE I was sufficient to induce mutations and morphological transformation in vitro. However, the transformation frequency in CH3 mouse‐embryo‐derived 10T1/2 cells increased twofold and the frequency of mutations in CHO cells sixfold when the exposure time to BPDE I was increased from 20 sec to 8 h. Cytotoxicity increased under similar conditions. A large number of BPDE I‐DNA adducts were formed in both cell lines within the first 15‐min of exposure of the cells to this ultimate carcinogen. The total covalent binding did not increase with longer than 15‐min incubation times. These results suggest that in addition to its covalent binding to DNA, BPDE I may influence other cellular mechanism(s) that are responsible for the initiation of transformation and mutagenesis.
Induction of sister chromatid exchanges by ergot compounds in chinese hamster ovary cells in vitro
Authors: Dighe Rajani , Vaidya V. G. 
Published: February 2006

AbstractFive ergot alkaloids, d‐lysergic acid derivatives, were tested for the induction of sister chromatid exchange (SCE) frequencies in cultured Chinese hamster ovary cells. The concentrations of the test substances ranged between 10−5 and 10−8 M. Ergotamine, ergonovine, and methylergonovine induced a significantly high number of SCEs at all the concentrations used, while with ergocristine this occurred only at the highest concentration. α‐Ergocryptine failed to induce SCEs at any concentration. It is therefore surmised that ergotamine, ergonovine, and methylergonovine are effective inducers, ergocristine is a weak inducer, and α‐ergocryptine is a noninducer in Chinese hamster ovary cells in vitro.
Development of a metabolic activation system for the frog embryo teratogenesis assay: Xenopus (FETAX)
Authors: Fort Douglas J. , Dawson Douglas A. , Bantle John A. 
Published: February 2006

AbstractFETAX (frog embryo teratogenesis assay: Xenopus) is a 96‐hr teratogenesis screening assay using embryos of the South African clawed frog, Xenopus laevis. Since Xenopus embryos have limited xenobiotic metabolism through 96 hr of development, we have developed an in vitro metabolic activation system employing Aroclor 1254‐induced rat liver microsomes. By adding an exogenous source of mixed functional oxidase (MFO) activity, we may more accurately assess the teratogenic risk of proteratogenic compounds. Xenopus embryos were cocultured with varying concentrations of cyclophosphamide (CP), Aroclor 1254‐induced microsomal protein, an NADPH‐generating system, and antibiotics in a static renewal fashion for 96 hr. Residual Aroclor 1254 remaining in the microsomes was successfully reduced during purification to levels that had no significant effect on embryo survival and development. The results of three definitive dose‐response tests performed with CP revealed that activation reduced the 96 hr LC50 from 8.0 to 1.4 mg/ml (5.7‐fold). The 96‐hr EC50 (malformation) was reduced from 6.2 to 0.4 mg/ml (15.5‐fold). Activation also increased the types and severity of malformation and reduced embryonic growth. Aroclor 1254‐induced rat liver microsomes may be used as an acceptable in vitro metabolic activation system for FETAX.
Effects of sodium azide on sea urchin embryos and gametes
Authors: Pagano G. , Cipollaro M. , Corsale G. , Esposito A. , Mineo A. , Ragucci E. , Giordano G. G. , Kobayashi N. , Trieff N. M. 
Published: February 2006

AbstractSodium azide (SA) was tested on sea urchin embryos and gametes (Paracentrotus lividus). Developing embryos were exposed to SA (10−6 to 10−3 M) up to pluteus larval stage, or for shorter intervals before or after hatching. Developmental defects in SA‐exposed embryos consisted mainly of gut abnormalities, without any detectable differences between pre‐ or post‐hatch‐exposed embryos. SA‐induced damage to gut was exerted during gastrulation, as evident by lectin binding of extracellular matrix. No mitotic damage was observed in SA‐exposed embryos, nor could pH‐related variations be detected in SA‐induced embryotoxicity at pH's ranging from 8 to 6. Concurrently, no effect ensued in the exposure of unfertilized eggs to SA (10−5 to 10−2 M) both in terms of fertilization success and of offspring quality. When sperm were suspended in filtered seawater at pH's ranging from 8 to 6, and SA levels ranging from 10−5 to 10−2 M, fertilization success of SA‐exposed sperm appeared to be modulated by pH, by displaying three distinct dose‐response trends at pH 8, 7, or 6. The consequences of sperm pretreatment on offspring quality failed to show any significant SA‐induced changes on larval malformations or mortality, while confirming the previously reported pH‐induced increase of developmental defects in the offspring of acid‐exposed sperm (Pagano et al.: Teratogenesis Carcinogen Mutagen 5:113–121, 1985).
Effects of in vivo and in vitro exposure to rhodamine dyes on mitochondrial function of mouse embryos
Authors: Ranganathan Sulabha , Hood Ronald D. 
Published: February 2006

AbstractCationic rhodamines (Rh 123 and Rh 6G) can cause developmental toxicity in mice and inhibit embryonic mitochondrial respiration following in vivo or in vitro dye exposure. Rh B, a neutral rhodamine, fails to show such effects at comparable doses. To assess effects of rhodamines on development, F0F1ATPase activity and ADP translocation were measured on gestation day (GD) 12 in embryonic and adult mitochondria. ATP synthesis in embryonic mitochondria transplacentally exposed to Rh 123 (15 mg/kg/day) or Rh 6G (0.5 mg/kg/day) given to dams by i.p. injection from GD 7 to 10 were inhibited 39% and 49%, respectively. When isolated mitochondria were treated, dose‐dependent inhibition was seen; at 5 μg of dye/mg mitochondrial protein, ATP synthesis was inhibited 65% and 81% by Rh 123 and Rh 6G, respectively. When F0F1ATPase activity was assessed, in vitro Rh 123 and Rh 6G exposures at levels up to 8 μg/mg mitochondrial protein resulted in enzyme inhibition, but at 10 μg/mg, ATPase activity was stimulated. Uncoupler‐stimulated ATPase activity was also inhibited. ADP translocation was decreased by 19.1% and 37.7% by Rh 123 and Rh 6G, respectively, at dye concentrations of 20 μg/mg. Results of in vitro exposure of maternal liver mitochondria were similar to those for embryonic mitochondria, whereas liver from dams exposed in vivo on GD 7–10 was unaffected on GD 12. In vivo or in vitro treatment with Rh B did not affect any embryonic or maternal parameters. Such results support the hypothesis that inhibition of mitochondrial energy metabolism is a mechanism for the developmental toxicity of cationic rhodamines.
Limb bud cell culture for in vitro teratogen screening: Validation of an improved assessment method using 51 compounds
Authors: Renault J.‐Y. , Melcion C. , Cordier A. 
Published: February 2006

AbstractRat embryo limb bud cells multiply and undergo chondrogenesis in micromass culture. Teratogenic agents are identified from their inhibition of chondrogenesis, which is quantified by determination of cartilaginous foci number or proteoglycan production. In other in vitro systems, the detection is based on their ability to affect cell proliferation. So far, these methods have failed to distinguish among true inhibition of differentiation, inhibition of cell proliferation, and nonspecific cytotoxicity. The improved technique involves simultaneous measurement of cartilage synthesis and cell multiplication. Differentiation was evaluated by measurement, using an Artek Counter, of nodule areas after Alcian blue staining and proliferation by spectrophotometric quantification of Crystal‐Violet bound to micromass cells. Using this method, retinoic acid was shown to inhibit chondrogenesis without affecting cell multiplication, whereas 6‐aminonicotinamide preferentially inhibited cell multiplication without affecting nodule size. Doxylamine (succinate), a known nonteratogen, induced inhibition of chondrogenesis, but with a parallel inhibition of cell multiplication, reflecting a nonspecific toxic effect. This improvement increases the specificity of the micromass culture test. Validation was performed using 51 compounds. Compounds were classified according to their inhibitory activity and their active concentration. The sensitivity of the test was 61%; the specificity, 100%; and the final accuracy, 75%. The method is fully miniaturised, automated, and computerised, allowing numerous compounds to be rapidly tested at very low cost.
Mutagenic lipid peroxides from edible oils
Authors: Kensese Sontin Mossanda , Teng Jon I. , Smith Leland L. 
Published: February 2006

AbstractWeak mutagenic activity was detected in several commercially available edible palm and corn oils using liquid incubation bioassays with Salmonella typhimurium TA1537. Chromatographic fractionation of unrefined palm oil established that mutagenic activity was present in three fractions that also contained fatty acyl hydroperoxides. Similar weak mutagenic activity was also demonstrated for linoleic and linolenic acid hydroperoxides. In all cases, the mutagenicity was abolished by exogenous catalase, implying that the observed activity was moderated by hydrogen peroxide.
Cell cycle alterations and cell death in cyclophosphamide teratogenesis
Authors: Chernoff Neil , Rogers John M. , Alles Ajit J. , Zucker Robert M. , Elstein Kenneth H. , Massaro Edward J. , Sulik Kathleen K. 
Published: February 2006

AbstractLitters of pregnant mice treated with cyclophosphamide (CP) exhibit malformations of the limbs ranging from oligodactyly to amelia. Previous studies have indicated that cell death occurs in limb buds shortly after maternal exposure. We have investigated the relationship of cell death, cell cycle perturbation, and embryo/fetal toxicity in the mouse using vital staining and flow cytometry (FCM). CP (20, 30, and 40 mg/kg) was investigated via intraperitoneal administration to Swiss‐Webster mice on day 10 of gestation. At 4, 8, or 28 hours later, embryos were removed. Cell death was identified with Nile blue sulphate (NBS). Two embryos per litter were stained with NBS, and the remaining embryos were frozen at – 70°C prior to FCM analysis. After thawing, the forelimb buds were removed for the isolation of nuclei. Tissues were dissociated through a wire mesh followed by cytolysis with 0.1% nonidet P‐40 in PBS with 0.5 mg/ml RNase. Nuclei were stained with the fluorescent nucleic acid probe propidium iodide and analyzed (10,000 nuclei per sample) for propidium iodide fluorescence by FCM. NBS revealed a dose‐related increase in cell death by 8 hours after dosing. CP‐induced cell death was greatest in areas of rapid cell proliferation (DNA synthesis). FCM analysis revealed retardation of progression through the S‐phase of the cell cycle by 4 hours post‐exposure at all doses. This retardation occurred earlier in S‐phase with increasing dose and persisted through 8 hours. At 28 hours, cell cycle histograms were normal in the low‐dose embryos, but remained perturbed in the intermediate‐ and high‐dose embryos. On day 17 of gestation, the last group of dams was killed. A high incidence of fetal malformations, including limb defects, occurred at the 20 mg/kg dose, and fetal mortality was observed at 30 and 40 mg/kg. The pattern and magnitude of cell deth corelated with cell cycle perturbation and fetal toxicity at term, suggesting a relationship between cell cycle perturbation, cell death, and malformations produced by CP.
Biochemical studies of promoters of carcinogenesis in rat liver
Authors: Kitchin Kirk T. , Brown Janice L. 
Published: February 2006

AbstractAdult female rats were orally dosed with 1/5 to 3/5 the published LD50 of either promoters or putative promoters of carcinogenesis [hexachlorobenzene (HCB), α‐hexachlorocyclohexane (α‐HCH), kepone and toxaphene] or noncarcinogens [coumaphos, EDTA, caprolactam, 8‐hydroxyquinoline, titanium (IV) oxide, sodium diethyldithiocarbamate (DEDTC), and sucrose] at 21 and 4 h before sacrifice. The promoters selected in this study were all of the halogenated hydrocarbon class. At doses of 1/5 to 3/5 the LD50, all four promoters or putative promoters induced rat hepatic ODC activity. The seven noncarcinogens produced several biochemical effects at doses of 1/5 the LD50: increased serum alanine aminotransferase activity (SGPT) (caprolactam and DEDTC), decreased hepatic cytochrome P‐450 content (DEDTC), and increased hepatic ODC activity (8‐hydroxyquinoline and DEDTC). None of the seven noncarcinogens caused hepatic DNA damage or coordinate induction of hepatic ODC and cytochrome P‐450. The results support the interpretation that several of these biochemical parameters are useful in distinguishing potential tumor promoters and noncarcinogens.