bluuebunny/crossref_metadata_2025_split huggingface dataset:
Homogeneous populations of Artemia nauplii and their potential use for in vitro testing in developmental toxicology
Authors: Sleet R. B. , Brendel K. 
Published: February 2006

AbstractEfforts have begun to establish test subjects other than the intact pregnant mammal to serve as models for rapid teratology screens. Artemia nauplii transcending instar I to later instars were examined to determine their potential for indicating chemicals as potential developmental hazards and thus prioritizing them for more extensive in vivo testing. Several criteria selected for assessing the system's potential for screening were the ability to: 1) collect homogeneous populations of instar I nauplii; 2) characterize intermediate development by technically simple measurements; and 3) demonstrate development‐related differentials in naupliar vulnerability.Homogeneous populations of nauplii were harvested from a flow‐through hatching and cold storage system. Nauplii accumulated in the system are stored at 4°C in a quiescent state with little physical (body length, body water volume) and biochemical (DNA and protein levels) change and thus are maintained at instar I. Intermediate development of nauplii transcending instar I to IV was characterized after the onset of 25°C incubation by measuring changes in drinking activity, body length, body water volume, and DNA and protein levels. During the first day of incubation, development was greatest between 6 and 24 hours of incubation.Development‐related differentials in naupliar vulnerability were shown by comparing median lethal concentrations (LC50) estimated for cadmium sulfate (CdSO4), mercuric chloride (HgCl2), and sodium azide (NaN3) at various times during incubation. With cadmium and mercury, LC50s decreased as nauplii aged and developed; whereas, with azide, LC50s did not vary. Developing nauplii were differentially vulnerable to cadmium and inorganic mercury. Artemia nauplii transcending instar I to IV appear useful for indicating chemicals that preferentially interact with developmental events.
Teratogenic effects of carcinogenic agents on limb regeneration in the japanese newt Cynops pyrrhogaster
Authors: Pfeiffer Carl J. , Nagai Toshihiro , Fujimura Masaki , Tobe Takayoshi 
Published: February 2006

AbstractNormal regeneration of the amputated forelimb of the Japanese newt Cynops pyrrhogaster and regeneration after a single intraperitoneal injection of three potent mutagenic/carcinogenic agents was investigated. Three dose levels of each agent and controls were tested for teratogenicity in this newt model with the following chemicals: N‐methyl‐N′‐nitro‐N‐nitrosoguanidine (MNNG), 4‐nitro‐quinoline‐1‐oxide, and 2‐(2‐furyl)‐3‐(5‐nitrofuryl)acrylamide. These chemicals were administered at 10 days (late dedifferentiation stage), 20 days (late bud stage), and 30 days (early digits stage) after amputation at the midforelimb. A total of 628 newts, with 16–20 animals per group, were used. Normal forelimb regeneration in Cynops pyrrhogaster closely paralleled that reported for other species. A variety of deformities, including syndactyly, polydactyly, oligodactyly, brachydactyly, and digital branching, were occasionally observed in control regenerating forelimbs, with syndactyly occurring at highest incidence (17.5%).All three mutagens at all tested dose levels enhanced the incidence of teratogenic changes, though increases were not always statistically significant. MNNG, particularly when administered at the time of initial chondrogenesis (20 days, late bud stage), was especially teratogenic. The type of forelimb deformity was not mutagen‐specific in this experiment. As Cynops pyrrhogaster is easily and inexpensively maintained and tolerates surgery well, this model with the regenerating forelimb should prove useful for further studies on teratogen screening. Also, studies directed toward mutagenic and epigenetic effects of exogenous agents on rapidly proliferating and differentiating tissues can be investigated with this model, which obviates transplacental excursion and metabolism of test compounds.
Suppression by cyclohexanetriones of retinoic acid‐induced cartilage degradation in vitro and teratogenicity in vivo
Authors: Kistler Andreas 
Published: February 2006

AbstractIn cultured fetal rat bones, cyclohexanetriones that stimulate prostaglandin synthesis inhibited retinoic acid‐induced cartilage degradation in a dose‐dependent manner. The inhibition by the cyclohexanetrione Ro 31‐0521 was reversible, indicating that the effect was not due to cytotoxicity. Excess retinoic acid is teratogenic in rats and adversely affects the normal differentiation of various morphogenetic systems, depending on the time of administration. The following retinoic acid‐induced malformations were suppressed by Ro 31‐0521: malformations of long bones and of apical phalanges induced on days 13 and 15 of gestation, respectively; spina bifida and tail malformations induced on day 11 of gestation and cleft palate induced on day 15 of gestation. However, cleft palate and other head malformations including exencephaly induced by retinoic acid on day 11 of gestation were not suppressed but even increased by Ro 31‐0521. At a high dose, Ro 31‐0521 given alone on day 11 of gestation was embryolethal and teratogenic but was not on the tested other days, indicating that the cyclohexanetrione at specific stages and doses also interfered with normal morphogenesis like retinoic acid. Assuming that stimulation of prostaglandin synthesis is the main biological effect of the cyclohexanetriones, our findings suggest that prostaglandins may be involved in mediating retinoid action.
Co‐culture of rat embryos and hepatocytes: In vitro detection of a proteratogen
Authors: Oglesby Linda A. , Ebron Marian T. , Beyer Patricia E. , Carver Brenda D. , Kavlock Robert J. 
Published: February 2006

AbstractThe technique of whole embryo culture developed by New [Environ Health Perspect 18:105–110, 1976] provides a sensitive assay to evaluate the effects of a test chemical on embryo development independent of maternal influences. To detect proteratogens, this assay must be coupled with an exogenous metabolic activation system. We have developed methods for the co‐cultivation of rat embryos with primary hepatocytes, which offers several advantages over subcellular fractions when providing metabolic activation for in vitro assays. In the present study, rat embryos removed from the dam on day 10 of pregnancy were cocultivated in vitro with primary cultures of rat, rabbit, or hamster hepatocytes. Embryos co‐cultivated with hepatocytes developed normally, as did embryos exposed to a test chemical, cyclophosphamide (CP) in the absence of hepatocytes. When embryos were co‐cultivated with hepatocytes and exposed to CP, a doserelated embryotoxicity was observed, indicating metabolic activation of the proteratogen. Using hepatocytes isolated from rats pretreated in vivo with phenobarbital, we observed an increase in CP‐induced malformations and embryotoxicity compared to those of embryos exposed to CP in the presence of uninduced hepatocytes. The teratogenic bioactivation of CP was inhibited in vitro by the addition of metyrapone. When similar numbers of hepatocytes were used for metabolic activation of CP the induced embryotoxicity was greater in the presence of rabbit and hamster hepatocytes than with rat hepatocytes. Development of procedures for the culture of rat embryos with hepatocytes from other species suggests the utility of this in vitro system for the investigation of species differences in sensitivity to chemical teratogens.
Microsomal mediated embryo toxicity due to superoxide radicals
Authors: Iannaccone P. M. 
Published: February 2006

AbstractThe transfer of toxic substances to the developing fetus with deleterious results on pregnancy outcome is well known. It is now clear that the preimplantation period of development is susceptible to such exposure. This early developmental period is a time of critical genetic determination and a period during which much membrane synthesis is occurring. Since disruption of membrane formation might be important in the disorganization of embryos, microsomal protein‐mediated toxicity in mouse blastocysts was explored. The embryos were shown to be completely disorganized by exposure to induced microsomal proteins in the presence of NADPH. All of the embryos exposed died within 18 hr. The effect was completely eliminated by boiling the microsomes or by removal of NADPH. Decreasing toxicity of the exposure could be achieved by adding butyl hydroxy toluene, an antioxidant. An amount of 0.001 mg/ml resulted in 100% viability in the presence of microsomes and cofactors after 2 hr (33% viability after 18 hr); however BHT resulted in its own toxicity at 0.025 mg/ml. Superoxide dismutase, an enzyme that removes superoxide radicals by dismutation, was completely protective with as little as 0.6 IU of enzyme added to the incubation mixture.
Quantitative analysis of the metabolism of benzo(a)pyrene by transformable C3H10T1/2CL8 mouse embryo fibroblasts
Authors: Rudo Kenneth , Ellis Scott , Bryant B. J. , Lawrence Kay , Curtis Gaynelle , Garland Helen , Nesnow Stephen 
Published: February 2006

AbstractThe metabolism of benzo(a)pyrene [B(a)P] to organic soluble and water soluble metabolites by transformable C3H10T1/2CL8 mouse embryo fibroblasts was studied as a function of time, B(a)P concentration, and cell density. The total formation of organic‐soluble and water‐soluble metabolites increased with incubation time from 4 to 48 h and with B(a)P concentration from 4 to 40 μM. As cell density increased, the metabolic rate decreased for organic‐soluble and water‐soluble products between 6,300 and 54,000 cells/cm2 probably due to decreases in B(a)P concentrations to values below saturation. Specific organic‐soluble metabolites identified were B(a)P‐pre‐9, 10‐diols, B(a)P‐9,10‐diol, B(a)P‐7,8‐diol, B(a)P‐3,6‐quinone, B(a)P‐3‐phenol, and B(a)P‐9‐phenol. Water‐soluble metabolites were subjected to enzymatic hydrolysis with β‐glucuronidase and aryl sulfatase to identify specific conjugated products. The sulfate conjugated metabolites identifed were B(a)P‐7,8‐diol, B(a)P‐pre‐9, 10‐diols, B(a)P‐9, 10‐diol, and B(a)P‐3, 6‐quinone. The β‐glucuronic acid metabolites identified were B(a)P‐pre‐9, 10‐diols, B(a)P‐3, 6‐quinone, and B(a)P‐3‐phenol. Patterns of metabolite formation rates are discussed as to their possible effect on morphological transformation rates in C3H10T1/2 cells with respect to incubation time and cell density.
Teratogenic effects of the fungicide dinocap in the mouse
Authors: Rogers John M. , Carver Brenda , Gray L. Earl , Gray Jacqueline A. , Kavlock Robert J. 
Published: February 2006

AbstractThe teratogenic potential of the fungicide dinocap was evaluated in CD‐1 mice. Pregnant mice were dosed by intubation with dinocap in corn oil on gestation days 7‐16. Doses used were 0, 5, 10, 20, 40, 80, and 120 mg/kg/day, based on day 6 weight. Dams were killed on day 18, at which time fetuses were counted, weighed, and preserved for necropsy or skeletal examination. The highest dose killed 80% of the dams dosed, while 29% of the dams in the 80 mg/kg group died during dosing. There was no dose‐related maternal mortality at lower doses. Net maternal weight gain was affected only at 80 mg/kg/day. There were no live fetuses at 120 mg/kg/day. The number of live fetuses per litter was decreased and resorptions increased at 80 mg/kg. Dose‐related decreases in gravid uterus weight and fetal weight were significant at all doses of dinocap. Cleft palate was found in fetuses at 5(1/234; 0.4%), 20(46/195; 23.6%), 40(140/185; 75.5%), and 80(63/85; 74.1%) mg/kg/day. There was a dose‐related increase in supernumerary ribs and a low frequency of exencephaly and umbilical hernia at high doses. This study shows that dinocap is teratogenic in the CD‐1 mouse at doses well below those causing maternal toxicity.
Expression of the major heat shock protein (hsp 70) family during early mouse embryo development
Authors: Hahnel Ann C. , Gifford David J. , Heikkila John J. , Schultz Gilbert A. 
Published: February 2006

AbstractStress or heat shock proteins (hsp) are synthesized by most cells in response to adverse environmental conditions. In mammalian cells, the major proteins synthesized in response to stress have relative molecular weights (Mr) in the range of 68 to 74 kilodaltons (kD) and are encoded by a small multi‐gene family collectively referred to as hsp 70 genes. In unfertilized mouse eggs, no members of the hsp 70 family appear to be synthesized under normal or stressful (heat shock) conditions. At the two‐cell stage, two proteins with Mr = 74 kD and Mr = 70 kD are expressed as a consequence of developmentally activated transcription of these hsp 70 genes. No stressinduced synthesis in response to heat shock is observed at this stage. At the eight‐cell stage, constitutive synthesis of the 70‐kD protein continues, but, as in the two‐cell embryo, no heat shock induced synthesis of a novel heat shock protein is observed. By the blastocyst stage, however, an inducible protein with Mr = 68 kD is synthesized in response to heat shock in addition to constitutive synthesis of the 70‐kD protein. The constitutively synthesized cognate proteins are coded for by a set of mRNAs about 2,000 nucleotides in length. The induced hsp 68 proteins are coded for by mRNAs of larger size (about 2,600 nucleotides). Only the smaller mRNA class is detectable on Northern blots of RNA extracted from control or heat shock cleavage stage embryos and control blastocysts. As predicted from protein synthetic studies, both classes are resolved in RNA preparations derived from heat‐shocked blastocysts.
A comparison of developmental toxicity evident at term to postnatal growth and survival using ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, and ethanol
Authors: Wier Patrick J. , Lewis Steven C. , Traul Karl A. 
Published: February 2006

AbstractThis study was designed to compare an abbreviated evaluation of uterine contents at term (teratology probe) with a modified Chernoff‐Kavlock assay (postnatal study), [Chernoff N, Kavlock RJ: J Toxicol Environ Health 10:541–550, 1982]. Mice were intubated during gestation and were evaluated for signs of toxicity. In the teratology probe, uterine contents were examined at term. In the postnatal study, offspring were examined and weighed through day 22 postpartum.Ethylene glycol monoethyl ether (EGEE) produced embryo lethality and malformations, and decreased fetal weight at a dose level which was not maternally toxic in the teratology probe. In the postnatal study, EGEE decreased litter size and neonatal body weight; while litter size continued to decrease beyond the neonatal period, body weights of surviving pups were not significantly different from control. Pups exposed prenatally to EGEE developed kinked tail which was not apparent in fetuses or neonates.Maternally toxic dose levels of ethylene glycol monobutyl ether and ethanol were associated with increased embryo lethality in teratology probe studies. In postnatal studies, there were no significant effects on pup growth or survival at maternally toxic dose levels.Preliminary conclusions regarding maternal and developmental toxicity were comparable based on the teratology probe or postnatal study. Both assays measure litter size and offspring weight, but the teratology probe measures resorption incidence which may be a more sensitive index of prenatal death than number of live born. Neither fetal weight nor neonatal weight reliably predict permanent alteration of growth. A postnatal study permits detection of internal malformations or functional defects which reduce postnatal survival and gross abnormalities which appear postnatally.
An indirect assessment of the Chernoff/Kavlock assay
Authors: Palmer A. K. 
Published: February 2006

AbstractThe underlying principle of the Chernoff/Kavlock assay—namely that prenatal toxicity can be detected by means of simple postnatal endpoints—is strongly supported by experience gained in performing reproductive and developmental toxicity studies to international requirements.Compared with the supposedly more sophisticated procedures of regulatory tests, the simpler endpoints of the assay offer greater speed, economy, consistency and reliability. At the most, there is only a marginal loss of sensitivity in respect of detecting the lowest dosage at which effects may occur.The assay is best used as a concept rather than as a protocol with, “tailored” variations providing effective means of priority selection from a series of chemicals, especially analogue series. The underlying principle is applicable at levels through and beyond formal regulatory testing.
DNA damage in the central nervous system of rats after in vivo exposure to chemical carcinogens: Correlation with the induction of brain tumors
Authors: Robbiano Luigi , Brambilla Marco 
Published: February 2006

AbstractThe alkaline elution technique has been used to evaluate DNA damage in brain of rats treated with a single equimolar dose of 14 carcinogens of different chemical structure. A clear‐cut increase of DNA elution rate, which is considered indicative of DNA fragmentation, was produced by 10 compounds known to induce the development of tumors in the rat central nervous system: N‐nitroso‐N‐methylurea, N‐nitroso‐N‐ethylurea, N‐nitroso‐N‐butylurea, N‐nitroso‐N‐methylurethane, methyl methanesulfonate, ethyl methanesulfonate, dimethyl sulfate, diethyl sulfate, 1,3‐propansultone, and procarbazine. Similar amounts of DNA fragmentation were produced by both potent and weak brain carcinogens. In contrast, any significant increase of DNA elution rate was absent in rats treated with N‐methyl‐N′‐nitro‐N‐nitrosoguanidine, N‐nitrosodimethylamine, N‐nitrosodiethylamine, and β‐propiolactone, all of which are devoid of carcinogenic activity for the rat central nervous system. These results suggest that the described in vivo brain DNA damage/alkaline elution assay deserves further studies on a wide number of carcinogens and noncarcinogens aimed to establish its possible usefulness for a qualitative preliminary assessment of the ability of a compound to induce neurogenic tumors.
Multiple abnormalities in the ultraviolet light response of cultured fibroblasts derived from patients with the basal cell nevus syndrome
Authors: Nagasawa H. , Burke M. J. , Little F. F. , McCone E. F. , Chan G. L. , Little J. B. 
Published: February 2006

AbstractBasal Cell Nevus Syndrome (BCNS) is a rare autosomal‐dominant inherited disorder associated with a marked hypersusceptibility to spontaneous and radiation‐induced skin cancer. We examined the changes in cell survival, unscheduled DNA synthesis (UDS) and the frequency of sister chromatid exchanges (SCE) induced by ultraviolet light (UVL) in confluent normal and BCNS fibroblasts. BCNS cells appeared slightly hypersensitive to the cytotoxic effects of UVL. The rate of UDS induced by UVL exposure in normal cell strains increased linearly following doses up to 30 J/m2, whereas in BCNS cells UDS became saturated at doses of 10 J/m2 showing no further increase with doses up to 30 J/m2. UDS activity persisted for longer periods after UVL exposure in BCNS as compared with normal cells. The dose‐response relationship for UVL‐induced SCE was similar in normal and BCNS fibroblasts. However, the frequencies of UVL‐induced SCE declined to near background levels in normal cells following 12–24 hr of confluent holding prior to subculture whereas they remained elevated in BCNS cells with holding times up to 24 hr after UVL exposure. Overall, these results suggest that BCNS fibroblasts may have a diminished capacity for the repair of some type of DNA damage as compared with normal fibroblasts.
Transplacental teratogenesis and mutagenesis in mouse fetuses treated with cyclophosphamide
Authors: Porter A. J. , Singh S. M. 
Published: February 2006

AbstractWe studied transplacental fetotoxicity, teratogenicity, and mutagenicity in Swiss Webster mice following different doses of cyclophosphamide (CP; 0, 5, 10, 15, or 20 mg/kg), a well‐known mutagen/teratogen, on day 12 of gestation. The fetal survival and weight on day 18 of gestation decreased significantly with increasing CP dose (P < 0.01). The CP‐treated fetuses were also dysmorphic (e.g., shortened limbs, digital defects, cleft palate, open eyes, and hydrocephaly) and the percentage of dysmorphology increased with increasing CP doses (P < 0.01). To evaluate mutagenesis, a separate group of females received 5‐bromodeoxyuridine tablet (50‐mg) implants on day 12 of gestation and a CP treatment 8 h later. Fetal liver cells were harvested 24 h post‐BrdU implant to analyze sister chromatid exchange (SCE) frequency and micronuclei. CP caused a significant increase in the SCEs per fetal liver cell from 3.4 ± 0.02 (control) to 90.0 ± 0.04 (20 mg/kg CP) (P < 0.01). The increasing CP dose was also related to an increase in micronuclei. The data suggest that CP is transplacentally toxic, teratogenic, and mutagenic. Further analyses of the data suggest that the mutagenic effects of CP may in fact contribute indirectly to the CP‐related teratogenic effects. Such conclusions are based on path analysis with directional causations associated with SCEs per cell and the dysmorphic features studied.
Effects of exposing rat embryos in utero to physical or chemical teratogens are expressed later as enhanced induction of heat‐shock proteins when embryonic hearts are cultured in vitro
Authors: Higo Hiromi , Higo Ken‐Ichi , Lee Juing Yi , Hori Hiroshi , Satow Yukio 
Published: February 2006

AbstractIn order to get more insight into the effects of teratogens on developing embryos, we investigated the protein synthesis patterns of the target organs isolated from teratogen‐treated embryos. Rat embryos were either irradiated in utero with either 252Cf fission neutrons or 60Co gamma rays on day 8 of gestation or treated in utero with a bis(dichloroacetyl)diamine (a chemical teratogen) on days 9 and 10. Hearts were removed from the embryos on day 12 and were incubated in vitro at 37°C in the presence of [35S]methionine for up to 8 hr. The newly synthesized labeled proteins were then analyzed qualitatively by two‐dimensional polyacryl‐amide gel electrophoresis. Enhanced and prolonged induction of a family of heat‐shock (stress) proteins with a molecular weight of about 70,000 (SP70s) was observed as compared with those of controls. Among the teratogen‐treated hearts, those with gross malformations already detectable at this early stage showed especially higher inductions of SP70s than did the others. The abnormal expression of SP70s observed in the present study appears to be a reflection of persisting cellular (tissue) damage inflicted by the teratogens, and the extent of the induction may be indicative of the degree and/or type of the damage. Such persisting defects in surviving cells, manifested by abnormal induction of SP70s in the present study, might be related to malformation of embryonic hearts.