bluuebunny/crossref_metadata_2025 huggingface dataset:
Mutagenicity of dimethylsulfoxide (DMSO): In vivo cytogenetics study in the rat
Authors: Kapp R. W. , Eventoff B. E.
Published: February 2006

Various concentrations (1%, 10%, 50%, and 100%) of laboratory grade dimethylsulfoxide (DMSO) were administered by intraperitoneal injection to male Sprague‐Dawley rats for five consecutive days. Femoral bone marrow cells were harvested 24 hours after the last injection and were analyzed for cytogenetic aberration frequencies including chromosome breaks, chromatid breaks, markers, and severely damaged cells. Chromosome breaks revealed no differences between treated and control groups. Chromatid breaks were significantly elevated over the controls in all treated groups except at the 10% level. The incidence of markers was significantly elevated when compared to the controls in all treated groups. Only the high‐level (100%) group showed a significant increase in the incidence of severely damaged cells. When the above data were combined, the resultant percent of aberrant cells per animal was found to increase from 10% aberrant cells at the 1% DMSO level to 68.67% aberrant cells at the 100% DMSO level. The incidences of aberrant cells in all treated groups were significantly elevated when compared to the control (4% aberrant cells) group. These observations suggest that DMSO effectively disrupts the integrity of rat chromsome structure, and further investigation of the genetic activity of DMSO is warranted.
DNA repair and chromosome aberrations: The effect of cytosine arabinoside on the frequency of chromosome aberrations induced by radiation and chemicals
Authors: Preston R. J.
Published: February 2006

The frequency of x‐ray‐induced chromosome aberrations in G0 human lymphocytes was greatly increased when cells were incubated with cytosine arabinoside (ara‐C) after irradiation. The frequency of dicentrics increased with increasing ara‐C incubation times (one, two, and three hours). Lymphocytes from Down syndrome individuals were more sensitive to aberration induction by x‐rays in G0, and the increase in dicentric frequency with ara‐C incubation was much more rapid than with normal cells. When G2 normal lymphocytes were x‐irradiated and incubated for two or three hours with ara‐C until fixation, there was a large increase in deletion frequency compared to cells x‐irradiated and incubated in the absence of ara‐C. However, no exchanges were observed in the presence of ara‐C, compared to 0.29 per cell as when x‐rays alone were given. These results form the basis for a discussion of the mechanism of aberration induction by x‐rays.

Experiments with two chemicals, 4‐nitroquinoline‐N‐oxide and methyl methanesulfonate, show that chromosome‐type aberrations can be induced in G1 treated lymphocytes incubated with ara‐C. However, these chemicals, in the absence of ara‐C incubation, induced no aberrations in G1 at the concentrations used. The mechanism of aberration induction is discussed, particularly in terms of whether or not chemicals can be defined as S‐phase dependent.
Correlation of the chemical structure of 4‐nitroquinolines inactivating human cytomegalovirus and established in vivo carcinogenicity tests
Authors: Albrecht Thomas , Speelman Dan J. , Ramanujam V. M. Sadagopa , Lund Howard W. , Legator Marvin S. , Trieff Norman M.
Published: February 2006

Inactivation of the infectivity of human cytomegalovirus (CMV) and herpes simplex virus type 1 (HSV‐1) and type 2 (HSV‐2) has been observed following exposure to 4‐nitroquinoline 1‐oxide (NQO) or its metabolite, 4‐hydroxyaminoquinoline 1‐oxide (HAQO). The present study of the specificity of the chemical structure of 4‐nitroquinolines demonstrated that both the 4‐nitro and 1‐oxide groups were required for inactivation of virus infectivity. Reduction of the 4‐nitro group to a 4‐hydroxyamino group enhanced activity, while further reduction to an amino group resulted in loss of activity against virus infectivity. The capacity to inactivate virus was also lost by substitution of the pyridine ring for the quinoline nucleus of NQO. The relationship between the chemical structure and the ability to inactivate viruses studied here correlates well with earlier in vivo carcinogenicity studies of the same group of chemicals.
An in vitro investigation of genetic susceptibility to cancer in diploid fibroblasts from retinoblastoma patients
Authors: Weichselbaum Ralph R. , Nove John , Albert Daniel , Little John B.
Published: February 2006

Thirty‐two diploid fibroblast strains from individuals with the three forms of retinoblastoma were examined with an in vitro clonogenic survival assay to determine their sensitivity to killing by X rays. Strains from sporadic unilateral retinoblastoma patients and normal controls were indistinguishable from one another (group D0's = 147 ± 15 rads and 146 ± 5 rads, respectively) while the strains from patients with the hereditary form of the disease were significantly more X‐ray sensitive (D0 = 111 ± 12). Strains derived from individuals with the D‐deletion form of the disease resembled the hereditary strains with respect to sensitivity and heterogeneity, suggesting a possible, common etiology for these two forms of the disease.

A DNA‐repair defect is hypothesized as reflected by the observed hypersensitivity to X‐irradiation in these cells. We suggest that this defect may be associated with the enhanced frequency of spontaneous and radiationinduced second tumors seen in some retinoblastoma patients.
Interactions between initiating chemical carcinogens, tumor promoters, and adenovirus in cell transformation
Authors: Fisher Paul B. , Dorsch‐Häsler Karoline , Weinstein I. Bernard , Ginsberg Harold S.
Published: February 2006

Cell culture systems that respond to the combined action of initiating chemical carcinogens, tumor promoters, and transforming viruses represent useful model systems for studying the complex multifactor nature of the carcinogenic process. We have utilized both secondary rat embryo (2° RE) and a clonal population of established Fischer rat embryo (CREF) cells to study the effect of multiple agents on the process of adenovirus transformation. In the present review we summarize our investigations on the effects of polycyclic aromatic hydrocarbons, tumor promoters, a bee venom polypeptide‐melittin (MEL), and the polypeptide hormone epidermal growth factor (EGF) on transformation of rat embryo cells by a temperature‐sensitive mutant of human adenovirus type 5 (H5ts125). We also describe the effect of tumor promoters on the progression of the transformed phenotype, ie the temporal acquisition of anchorage‐independent growth in adenovirus‐transformed clones and the ability of MEL and EGF to elicit effects similar to those of tumor promoters in adenovirus‐transformed cells.
Association between the presence of the Ah receptor in embryonic murine tissues and sensitivity to TCDD‐induced cleft palate
Authors: Dencker Lennart , Pratt Robert M.
Published: February 2006

TCDD (2,3,7,8‐tetrachlorodibenzo‐p‐dioxin) causes a high percentage of isolated cleft palate in the fetus when administered to the pregnant dam at day 10 of gestation but only in certain strains of mice (ie, C56BL/6J (C57BL)). These strains are also known to have a specific cytosolic receptor protein (Ah‐receptor) in the liver for polycyclic hydrocarbons and TCDD, and respond to these compounds by increased levels of cytochrome P‐450 mediated monooxygenase activities and probably several other enzyme systems. We have shown that midgestational embryos of sensitive strains exhibit high levels of the TCDD cytosolic receptor in the maxillary processes and secondary palatal shelves prior to palate closure. Binding studies and Scatchard plot analysis revealed an apparent Kd of 1.1 nM and a Bmax of 32 fmole bound TCDD/mg cytosolic protein from C57BL maxillary processes on day 13 of gestation. The TCDD resistant strain, AKR/J, did not show any specific binding of TCDD. Mesenchymal cells from C57BL secondary palatal shelves retained the cytosolic receptor for TCDD when grown in culture. These results suggest that the teratogenic effects of TCDD in sensitive murine strains are dependent upon the binding of TCDD to the cytoplasmic receptor in the fetus.
Teratology study with the synthetic prostaglandin ONO‐802 given intravaginally to rabbits
Authors: Petrere Judith A. , Humphrey Ronald R. , Sakowski Raymond , Fitzgerald James E. , de la Iglesia Felix A.
Published: February 2006

ONO‐802, a synthetic E1 prostaglandin, was administered intravaginally via pessaries to Dutch belted rabbits at doses of 250, 62.5, and 12.5 μg/kg on days 6 through 18 of gestation. Rabbits in a vehicle control group were treated with pessaries that did not contain ONO‐802 during the same period. Another group of animals remained untreated throughout gestation. Necropsies were performed on rabbits found dead and on those killed on gestation day 30. Body weight, food and water consumption, and clinical signs were monitored during the experiment. Major organs were weighed when the dams were necropsied on gestation day 30, and litter and fetal data were collected.

Abortion and maternal deaths occurred in drug‐treated groups. Body weight gains and food and water consumption were adversely affected by treatment particularly at the 250 and 12.5 μg/kg dose levels. Wastage (postimplantation loss) was significantly increased among treated groups (all dose levels), while other litter and fetal parameters were unaffected. ONO‐802 was not teratogenic at maternal and embryotoxic dose levels.
Metabolic activation of cyclophosphamide by yolk sac endodermal cells of the early chick embryo
Authors: Gamett Daniel C. , Klein Norman W.
Published: February 2006

Endodermal cells isolated from the yolk sacs of day 3 chick embryos were able to activate metabolically cyclophosphamide. This was demonstrated by the cytotoxicity of cyclophosphamide to the endodermal cells themselves as well as by the ability of endodermal tissue to mediate a cytotoxic response in coculture with KB cells, a human tumor cell line unable to activate cyclophosphamide. Yolk sac endodermal cells from day 3 embryos were sensitive to cyclophosphamide when the drug was added immediately after the start of culture, but not when the drug was added after 24 hr of culture. The ability to metabolize cyclophosphamide by the day 3 embryo appeared limited to the endodermal cells of the yolk sac as cells derived from neither the embryo proper nor yolk sac mesoderm‐ectoderm tissue were positive in these tests. Using whole blastoderms, cyclophosphamide activation was detected as early as 12 hr of egg incubation.
Inhibition of metabolic cooperation between Chinese hamster V79 cells by structurally diverse teratogens
Authors: Welsch Frank , Stedman Donald B.
Published: February 2006

Cell‐cell communication through chemical messengers is a fundamental event required for the differentiation of embryonal cells. Interference with this process by xenobiotics may disrupt embryogenesis. Chinese hamster cells (V79) which display a specific form of cell‐cell communication called metabolic cooperation were cultured in the presence of structurally diverse chemical teratogens. Among them were 12‐0‐tetradecanoyl‐phorbol‐13‐acetate (TPA), diphenylhydantoin (DPH), warfarin, and a series of monoalkyl ethers of ethylene glycol with alcohol chain lengths from methyl to butyl. Sodium saccharin and ascorbic acid were examined to represent two chemicals which have been thoroughly tested for teratogenic effects in laboratory animals and cause no birth defects. Recovery of 100 6‐thioguanine‐resistant V79 (6‐TGr) cells in coculture with 400,000 6‐thioguanine‐sensitive V79 (6‐TGs) cells in the presence of 6‐thioguanine (6‐TG) and the chemical agent was measured. In amounts that neither interfered with colony forming ability nor caused cytostasis when 100 6‐TGr cells were plated alone, all of the substances except for saccharin and vitamin C increased the number of surviving 6‐TGr cells in a concentration‐related manner. The recovery was increased by the presence of TPA (to 100% by 4 ng/ml), DPH (from 26% at 91 μM to 43% at 274 μM), warfarin (from 15.5% at 162 μM to 44.5% at 487 μM) and to variable extents by all five glycol ethers. The most efficacious in the latter group of compounds was the isopropyl ether which raised 6‐TGr recovery from 8% at 0.017 M to 66% at 0.087 M. Based on the evidence accumulated by previous studies involving TPA, we postulate that the teratogens employed inhibited metabolic cooperation. These observations suggest that V79 cells may be suitable to study inhibition of cell‐cell communication as a mechanism of teratogenesis.
Effects of endotoxin on placental labyrinth formation in the golden hamster: A light and electron microscopic study
Authors: Lanning John C. , Hilbelink Don R.
Published: February 2006

Animal studies of endotoxemia during pregnancy have suggested that the placenta is the primary site of action. This study was designed to evaluate the effects of endotoxin at previously established resorptive and teratogenic dose levels during the development of the placenta in the hamster. At the higher dose levels, total necrosis of the placenta was observed within 24 hr after treatment. Formation of fibrin thrombi was only apparent well after the initiation of necrotic events. At the teratogenic dose, a marked decrease in the formation of the placental labyrinth was evident, but invading fetal capillaries and fetal blood cells appeared normal. However, scattered necrotic foci of trophoblastic cells were observed.
Comparative teratogenic activities of two retinoids: Effects on palate and limb development
Authors: Kochhar D. M. , Penner John D. , Tellone Carmella I.
Published: February 2006

Two closely related retinoids, all‐trans and 13‐cis retinoic acids, were assessed for their relative activities as teratogens in ICR mice by monitoring the frequency with which either isomer produced discrete dysmorphogenesis of the embryonic limb and the secondary palate. A single oral dose of all‐trans retinoic acid at 100 mg/kg on either day 11.5 or 12.0 of gestation (plug day = day one) was maximally effective; more than 90% of the treated embryos developed reduction defects of the limb bones and an equally high percentage also had cleft palate. The limb development was most sensitive on day 11.5 of gestation while the peak susceptibility for palatal clefts began on day 12.0. Under identical experimental conditions, treatment with 100 mg/kg 13‐cis retinoic acid produced no apparent teratogenic effects. By assessing the relative incidence of readily identifiable malformations of the limb and palate associated with various doses of the two isomers, we found that 13‐cis retinoic acid was four to eight times less embry‐opathic than all‐trans retinoic acid. Since the mechanism of teratogenic action of retinoids is still far from clear, it is suggested that further studies on causative factors will be greatly assisted by the use of these two closely related retinoids, which substantially differ from each other in their teratogenic potency.
Genetic activity of the carcinogen N‐ nitrosodiethanolamine (NDELA) on unstable mutant alleles of the white locus in Drosophila melanogaster
Authors: Fahmy Myrtle J. , Fahmy O. G.
Published: February 2006

The genetic activities of the carcinogen N‐nitrosodiethanolamine (NDELA) were assayed somatically and germinally on two stocks carrying unstable alleles of the white (w+) eye colour gene: one incorporating a TE (z TE w+; coded UZ), the other with a tandem duplication of part of the encoding w+ sequence (wi16). Treatment was applied topically on late embryonic and early larval stages over a wide dose range (0.01–2.0 M) and the general mutagenic levels actually achieved were measured in terms of the X‐recessive mutations (lethals and visibles) recovered in Muller‐5 tests on samples of the males scored for somatic sectoring. The carcinogen was germinally ineffective on the z TE w+ and wi16 loci even at the maximal tested dose (2.0 M), and was only weakly mutagenic with respect tothe X‐recessives (lethals + visibles) at massive doses (1.0–2.0 M). In contrast, it proved to be genetically effective somatically, inducing red eye sectors through regulatory effects involving the TE in the UZ stock and complete reversion to w+ in the case of wi16 at comparatively moderate doses (≤0.26 M). The possible implications of the demonstration of the genetic activity of NDELA in the soma to the carcinogenic process, and to the wider problem of screening for environmental genotoxic compounds, are discussed.
Transplacental genetic and cytogenetic effects of alkylating agents in the mouse. I: Induction of somatic coat color mutations
Authors: Braun Rolf , Hüttner Edith , Schöneich Jörg
Published: February 2006

Induction of somatic coat color mutations by the alkylating agents ENU, MNU, EMS, MMS, DES, DMS, and trenimon and by the tuberculostatic drug INH was investigated in the mammalian spot test. Positive results were obtained with EMS (100 mg/kg), ENU (20–60 mg/kg), and INH (100 mg/kg), while trenimon (100 μg/kg), DES (225 mg/kg), and MNU (2 mg/kg) yielded inconclusive data. No mutagenic activity was found for MMS (125 mg/kg) and DMS (50 mg/kg). The mutagenic potency of monofunctional alkylating agents at subtoxic doses decreases as follows ENU > EMS > DES > MMS = DMS. The hypothesis that somatic coat color mutations in the mouse are predominantly due to intragenic changes is discussed. Differences in the RS frequency between offspring of the crosses NMRI × DBA and C57 × T are due to differences in loci available for mutation induction. Mutations that uncover the recessive allele p contribute to a significant extent to the total RS frequency observed in the mammalian spot test.
Effect of repeated ether anesthesias on the mono‐oxygenase system of rat liver S‐9 fraction
Authors: Paolini M. , Bauer C. , Corsi C. , Tonelli F. , Hrelia P. , Bronzetti G. , Forti G. Cantelli
Published: February 2006

This study was designed to investigate the effect of ether anesthesia in rats, before i.p. injections to induce the mono‐oxygenase enzyme system, on biochemical properties of liver S9 fractions. Aminopyrine N‐demethylase and ρ‐nitroanisole O‐demethylase activity levels, their stability, and lipid peroxidation were determined in S9 fractions after etherization (about 1 min in ether vapor chamber daily for 3 consecutive days, before i.p. injections of Na‐phenobarbital and β‐naphthoflavone) and compared with controls receiving the same injections without etherization. The activities were slightly (but not significatively) enhanced after this treatment, but stability was markedly and significatively greater after 1 h of incubation in the conditions of the liver microsomal assay (+ 14.8% and +74.7%, respectively); lipid peroxidation was strongly and significatively depressed (−76.0%). Etherization sufficient to kill the animals on the 4th day resulted in equally active but less stable S9 fraction enzymes. Dimethylnitrosamine (as a standard premutagen) was assayed with the D7 strain of Saccharomyces cerevisiae using S9 fractions obtained from both anesthetized and nonanesthetized rats. According to biochemical data, results obtained with S9 from partially anesthetized rats were comparable with the conventional ones (S9 from nonanesthetized rats). On the contrary, the use of more prolonged ether anesthesia, including one on the day the animals are killed, gives S9 fraction significantly less effective.

We conclude that if brief etherizations are used, for i.p. injections only, the S9 fractions obtained are entirely satisfactory and the procedures involved in production are simplified; the additional animal treatment (etherization) must be specified.
Implications of multiple mechanisms of carcinogenesis for short‐term testing
Authors: Harper Barbara L. , Morris Debra L.
Published: February 2006

The attempt has been made recently to categorize carcinogens into two mechanistic types based on their mechanism of action: genotoxic (capable of reacting with and damaging DNA) and epigenetic (unable to damage DNA to any detectable extent). By requiring that a given chemical fit into one or the other of these narrowly defined categories for regulatory purposes, we are probably oversimplifying potential biological effects. In fact, based on our limited understanding of carcinogenic mechanisms, this artificial distinction should probably be abandoned in favor of a more precise statement of each chemical's mechanism or relative potency of initiating and promoting effects.

Since the standard short‐term tests by which carcinogenicity of chemicals is screened were designed to detect certain chemical classes with active electrophilic intermediates, weak or specialized carcinogens may be missed and may be assumed erroneously to be nongenotoxic. The mechanisms of carcinogenicity for such carcinogens may include particulate deposition, active radical formation, liver toxicity, and hormonal interactions. Not all of these secondary mechanisms depend upon a detectable level of binding to DNA, damage to DNA, or modification of the DNA sequence, even though they may demonstrate other characteristics of a complete carcinogen (that is, irreversibility and lack of a threshold).

Certain agents have been labeled as epigenetic. However, a consideration of the literature on sample agents (diethylstilbestrol, asbestos, and urethane) reveals that these are not epigenetic carcinogens despite their being labeled as such.

Agents with irreversibility and no threshold have initiating potential and, as such, are genotoxic, whereas carcinogens that are classified as nongenotoxic are largely agents that promote the growth of liver tumors. Even promotion can be a mechanistically specialized phenomenon. For example, some promoters are cytotoxic to the liver, but not all liver toxins are liver tumor promoters or liver carcinogens. Further, the carcinogens commonly labeled as epigenetic might cause a unique specialized genotoxicity not detected by common screening tests routinely used for detecting genotoxicity.

If we assume that this unrecognized but necessary initiating potential is mediated by some specialized genotoxicity, extra care must be taken to establish a genuine lack of genotoxicity before an agent can be classified (and regulated) as a promoter (lacking the ability to initiate tumor growth but still enhancing tumor development). There is no question that reversible effects with definite thresholds should be evaluated differently from thos that are irreversible and lack a threshold, but the distinction should be based on their effect and potncy, not on their (often unknown) mechanism of genotoxicity.
Cyclophosphamide teratogenesis: A review
Authors: Mirkes Philip E.
Published: February 2006

Cyclophosphamide (CP) is one of the best studied teratogens; it produces primarily central nervous system and skeletal anomalies in rats, mice, rabbits, monkeys, and humans. Furthermore, CP is one of the most extensively studied antienoplastic agents. Recent work using in vitro rodent embryo culture has demonstrated that CP must be bioactivated to be teratogenic. This finding extends earlier work showing that CP must be activated to achieve its antineoplastic and mutagenic effects. Activation of CP to its teratogenic, mutagenic, and antineoplastic form is mediated by microsomal cytochrome P‐450 monooxygenases, which convert CP to 4‐hydroxycyclophosphamide (4OHCP). In the absence of detoxification, 40HCP spontaneously breaks down to phosphoramide mustard (PM) and acrolein (AC). PM is the CP metabolite believed to be responsible for the antineoplastic and mutagenic effects of CP, whereas AC is thought to cause the side effects associated with CP chemotherapy. Recent work has shown that the teratogenic effects of CP are mediated by both PM and AC. Although it is far from proven, available evidence supports the hypothesis that DNA is the primary target in terms of the teratogenic, mutagenic, and antineoplastic effects of CP. Although the nature of the DNA lesions produced by CP, which are responsible for its teratogenic, mutagenic, and antineoplastic effects, is not completely understood, cross‐linking of DNA seems to play a critical role in the antineoplastic properties of CP. Preliminary information obtained from embryos exposed to CP metabolites suggests that, although DNA cross‐linking might play a role in CP teratogenesis, metabolite‐induced DNA strand breakage and/or induction of mutations might also play a role. Although insights into the molecular mechanisms underlying CP teratogenesis are just beginning to accumulate, the availability of in vitro embryo culture combined with the modern armamentarium of molecular biology will allow teratologists to probe further the molecular aspects of teratogenesis.
pH‐Induced changes in mitotic and developmental patterns in sea urchin embryogenesis. I. Exposure of embryos
Authors: Pagano Giovanni , Cipollaro Maria , Corsale Giuliana , Esposito Agostino , Ragucci Enrica , Giordano Giovan Giacomo
Published: February 2006

The effects of different pH conditions have been investigated on sea urchin larval development following exposure of embryos to controlled, though changing, decreases or increases of seawater pH. The pH of filtered natural seawater was initially adjusted with 1 N HCl of 1 N KOH and then was altered back to its normal values (8.0–8.2) by the exchange with atmospheric CO2 and subsequent carbonic acid equilibrium. During cultures, pH was regularly monitored.

When developing embryos were reared in different pH conditions, larval differentiation was sharply affected by an apparently moderate pH decrease, such as 0.5 pH units. However, even pH decreases as small as 0.2 pH units from the normal value showed reproducible damage to embryogenesis. This damage appeared to be early and irreversible, since the exposure of cleaving embryos resulted in more severe developmental defects than exposure of posthatching blastulae. Moreover, mitotic abnormalities were observed following early exposure of embryos to decreased pH.

Increased pH, up to 8.6 (∼ 0.5 pH units above normal value), failed to exert any adverse effect on subsequent development. Moreover, an initial pH increase (8.5–8.7) resulted in the final adjustment of culture pH to 8.1–8.2, thus providing optimal conditions for rearing embryos. Two attempts to stabilize culture pH were performed by decreasing gaseous exchanges or by using Tris as a buffering agent. Both approaches appeared to be impractical, thus ruling out any further attempts.

The results point out the hazards of acid contamination in restricted bodies of seawater, leading to apparently “moderate” decreases in pH, which can result in severe damage to some marine organisms, both adult and larval forms.
Teratogen metabolism: Spontaneous decay products of thalidomide and thalidomide analogues are not bioactivated by liver microsomes
Authors: Braun Andrew G. , Weinreb Steven L.
Published: February 2006

Thalidomide and two analogues, EM87 and EM12, inhibited the attachment of tumor cells to concanavalin A‐coated surfaces only if the drugs were first incubated with hepatic microsomes and cofactors. Most agents that inhibit attachment are demonstrated teratogens. Thalidomide undergoes spontaneous hydrolysis to at least 12 products in saline buffered to a pH of greater than 7. These hydrolysis products did not inhibit attachment nor could they be activated to inhibitory products with hepatic microsomes. Similarly EM12 and EM 87 hydrolysis products were neither inhibitory nor substrates for activation. If the three drugs were incubated in buffered saline, there was a progressive decline in their ability to act as substrates for activation to an inhibitory product. It was possible to remove microsomes from the incubation mixture following drug activation by centrifugation. This microsome‐free mixture inhibited cell attachment. When mouse ovarian tumor (MOT) cells were added to the microsome‐free mixture, attachment was inhibited. However, if the activated drugs were incubated in saline, there was a progressive decline in their ability to inhibit attachment. Decay rates differed for the three compounds. At a pH of 7.4, thalidomide, EM87, and EM12 required 3 h, 1 h and 6 h, respectively, to decay to control levels. These relative rates of decay are consistent with the relative teratogenicity of the three drugs.
Correlations between the degree and type of forebrain malformations and the simultaneous neuro‐oncogenic properties of ethylnitrosourea after diaplacental exposure in rats, alone and in combination with X‐irradiation
Authors: Schmahl W. , Kriegel H.
Published: February 2006

Single and combined treatments were performed in rats on day 13 of gestation with either ENU or ENU subsequent to various X‐irradiation doses between 0.5 and 1.5 Gy. At this time of gestation, developmental anomalies of the brain are still inducible by any of these treatments, in addition to neurocarcinogenic effects after ENU alone or in combination with X‐irradiation. We looked for correlations between the degree of brain malformations still detectable in the adult animals and the simultaneous occurrence of brain tumors. These evaluations were based on a histopathological analysis regarding the type and degree of malformation residues, as well as the type and distribution pattern of the tumors (especially regarding gliomas) within the forebrain.

Both after ENU and X‐irradiation plus ENU‐treatment, the occurrence of glioma in the offspring was positively correlated with the degree of brain dysplasia. This effect was not only restricted to the total glioma incidence but also confirmed by the higher glioma multiplicity in major dysplastic brains. Additionally, gliomas were preferentially located within the subependymal layer, which simultaneously was most severely affected by the teratogenic effects after prenatal treatment.

Although forebrain dysplasia generally presents a significant predisposition for glioma inducibility, this oncogenic event is apparently strictly inversely related to a certain type of forebrain malformation, namely the occurrence of heterotopic neuronal nodules within the telencephalic roof. They emerge from “rosettes,” which are typical radiation lesions occurring only after doses above 1.0 Gy. In none of the forebrains which still revealed rosette‐residues in later life could a simultaneous occurrence of gliomas be observed. This explains not only the substantial decrease of glioma incidence after combined treatment with 1.0 and 1.5 Gy X‐irradiation doses, but also the consistent glioma multiplicity despite the decrease of frequency.
Effects of anticonvulsant drugs on brain cultures from chick embryos: A comparison with cultures from embryos treated in ovo
Authors: Sedowofia S. K. A. , Clayton R. M.
Published: February 2006

The effects of anticonvulsant drugs phenytoin, phenobarbitone, and sodium valproate on neurons and glia from embryonic chicken brain have been tested. These effects have been compared with those produced in neuronal and glial cultures established from embryos that were injected with the drugs in ovo. Choline acetyl transferase activity and accumulation of γ‐aminobutyric acid were measured in neuronal cultures, and carbonic anhydrase and 2,′3′‐cyclic nucleotide 3′ phosphohydrolase activities were measured in glial cultures. Similarities have been observed in the morphological and biochemical changes brought about by the in vitro and in vivo treatment with the drugs. The use of in vitro cell culture systems for screening drugs for potential behavioural teratogenic effects is discussed.
Erythrocytes‐mediated metabolic activation of cyclophosphamide in yeast mutagenicity test
Authors: Paolini Moreno , Forti Giorgio Cantelli , Corsi Claudio , Galli Alvaro , Bronzetti Giorgio
Published: February 2006

The degree of conversion of cyclophosphamide (CP) into mutagenic intermediates was studied using mouse erythrocytes as the metabolic activation system. The amount of mutagenic intermediates produced was measured indirectly in terms of induced frequencies of mitotic recombination, mitotic gene conversion, and reverse mutation in the diploid D7 strain of Saccharomyces cerevisiae. In the absence of S9 microsomal fraction or erythrocytes, CP did not induce any genetic response. In the presence of erythrocytes, on the other hand, CP clearly induced increases in the three genetic endpoints. The responses, however, were lower than those observed with the S9 activation system. The activating principle seems to be the oxyhemoglobin. In fact, neither p‐nitroanisole O‐demethylase activity nor genotoxic responses performed with red‐blood cells from uninduced and PB‐induced mice indicate that (possible) water‐soluble forms of cytochrome P‐450 were responsible for the activation of CP by erythrocytes.
Genotoxic classification of anticancer drugs
Authors: Matney Thomas S. , Nguyen Tot V. , Connor Thomas H. , Theiss Jeffrey C. , Dana William J.
Published: February 2006

The effects of bacterial DNA excision repair on the mutagenic and lethal actions of 17 injectable anticancer drugs have been used to classify them into three levels of potential risk to medical personnel who are involved in their preparation and administration.
Hyperthermia and other factors increasing sensitivity of Euglena to mutagens and carcinogens
Authors: Mačor Marian , Ebringer Libor , Siekel Peter
Published: February 2006

The effects of different factors (temperature, light, enzymic activation) on the ability of selected mutagens and carcinogens to induce hereditary bleaching of Euglena gracilis were investigated. In the resting medium, the elevation of incubation temperature from 25°C to 37°C increased significantly the effect of all compounds tested on the frequency of bleached mutants of E. gracilis. The effect of light is not so unambiguous. While nitrosoguanidine (NG) exhibited practically the same bleaching activity both in the light and dark, the mutagenic effect of sodium azide (SA), nitrovin (NV), nitrosoethylurea (NEU), and benzo(a)pyrene (BP) was decreased in light. On the other hand, the light increased the bleaching activity of 5‐nitro‐2‐furylacrylic acid (NFAA) significantly. The activation mixture S9 increased bleaching effect of NFAA and BP, whereas other mutagens were partially (NG and SA) or completely (NV and NEU) inactivated.
Comparative enzymatic acetylation of carnitine and choline by human placenta syncytiotrophoblast membrane vesicles
Authors: Jarmer Scott , Shoaf Antony R. , Harbison Raymond D.
Published: February 2006

Microvillous membrane vesicle preparations from the maternal surface of human placental syncytiotrophoblast were examined for the presence of carnitine and choline acetyltransferase activity. Radiometric assay for acetylcholine employed butyronitrile‐tetraphenylboron extraction of the quaternary ions. Acetylcarnitine was assayed by anion exchange chromatography. The data reveal that carnitine is the primary substrate for the vesicle acetyltransferase enzyme(s), whereas choline appears to be a minor substrate. For acetylcarnitine synthesis, the Km is 0.749 mM carnitine and Vmax is 641 pmol·mg protein−1 ·minute−1, respectively; for acetylcholine synthesis, the Km is 0.5 mM choline and Vmax is 53 pmol·mg protein−1·minute−1, respectively. Approximately ten times more acetylated product was formed with carnitine than with choline. The carnitine‐mediated reaction obeyed Michaelis‐Menten kinetics, whereas the choline reaction exhibited anomalous behavior. Vesicle preparations were stable for 21 days at —80°C. Preliminary studies on hypotonically lysed vesicles demonstrate that the acetyltransferase is particulate and is bound to the membrane of the vesicle. These findings demonstrate that carnitine acetyltransferase activity is in the plasmalemma membrane of the syncytiotrophoblast and suggest a role for this enzyme, analogous to the mitochondrial fatty acid shuttle system, in the maternofetal translocation of fatty acyl residues.
Species differences in mutagenicity testing: I. Micronucleus and SCE tests in rats, mice, and Chinese hamsters with aflatoxin B1
Authors: Madle Elisabeth , Korte Anke , Beek Bernd
Published: February 2006

Three animal species used in in vivo mutagenicity testing—rats, mice and Chinese hamsters—were compared with respect to their mutagenic response to the mycotoxin aflatoxin B1 (AFB1). The micronucleus test and the SCE test with bone marrow cells were chosen as test methods, employing similar protocols for all species. The mutagenic potential of AFB1 was detected with rats and mice but not with Chinese hamsters. Rats were more susceptible to the mutagenic action of AFB1 than mice with regard to the effective dose. A difference in sensitivity between males and females was evident in rats and mice: male animals exhibited higher induced micronucleus frequencies than females, and a clear SCE‐inducing effect was only detectable in male animals. These results are in agreement with those of in vitro and carcinogenicity studies. They may be due to metabolic differences between the species and sexes, predominantly differences in glutathion conjugation of the reactive AFB1 epoxide and in the formation of the metabolite aflatoxicol. Furthermore, it could be demonstrated that AFB1 seems to be a more potent inducer of micronuclei than of SCE. Since our results obtained with rats and mice were clearly positive, but with the Chinese hamster the mutagenic potential of AFB1 was not detectable with the test systems used, it can be concluded that the choice of an “inappropriate” test species may lead to a false negative judgment on the genotoxic potential of a test compound.
Prenatal exposure to the fungicide dinocap causes behavioral torticollis, ballooning and cleft palate in mice, but not rats or hamsters
Authors: Gray L. Earl , Rogers John M. , Kavlock Robert J. , Ostby Joseph S. , Ferrell Janet M. , Gray Katrina L.
Published: February 2006

The present study is an evaluation of the developmental toxicity of dinocap in three rodent species using an in vivo teratology screen. Our protocol uses postnatal viability, weight gain, and morphological and behavioral development through weaning to assess the developmental toxicity of compounds.

Dinocap administered orally on days 7 to 16 of gestation to the CD‐1 mouse resulted in increased postnatal mortality at 25 mg/kg/d (80% in block 1 and 40% in block 2). Many of the treated pups that died during the neonatal period were “ballooned” and had cleft palates. Although there was no treatment related mortality in the 12 mg/kg/d dosage group, 6% (14/226) of these mice and 24% (23/96) of the survivors from the 25 mg/kg/d dosage group displayed torticollis (a twisting of the neck resulting in an abnormal tilting of the head). These tilted‐head mice held the head and forepart of the body tilted constantly to one side, both when resting and walking. The tilt was in either direction but was always constant for a given animal; in different mice, the angle varied considerably from almost 0 to 30°. Some mice circled repeatedly in one direction in the home cage, others bobbed their heads and did back‐flips, while others rolled over, always rolling in the same direction.

In the hamster, developmental toxicity was seen at (100 and 200 mg/kg/d) or near (50 mg/kg/d) maternally toxic doses but no behavioral alterations were noted and none of the pups were ballooned.

The highest dose of dinocap (100 mglkgld during days 7–20) used in the rat study produced mild maternal toxicity (reduced maternal weight gain from day 3 to 10 of gestation), but did not alter the postnatal development of this species.
Induction of sister chromatid exchange in preimplantation mouse embryos in vitro by 3H‐thymidine or ultraviolet light in combination with caffeine
Authors: Müller W.‐U. , Spindle Akiko
Published: February 2006

Preimplantation mouse embryos were exposed in vitro to 3H‐thymidine (25, 100, or 250 Bq/ml) or ultraviolet (UV) light (1.35 or 4.05 J/m2), either alone or in combination with caffeine (1 mM with 3H‐thymidine and 0.5 mM with UV light). Exposure to 3H‐thymidine lasted for 2 days, from the two‐cell stage to the late morula/early blastocyst stage, and UV radiation was applied acutely at the late morula/early blastocyst stage. The effects were quantified by the sister chromatid exchange (SCE) assay. All three agents induced SCEs when used singly. 3H‐thymidine was effective in inducing SCEs only at 250 Bq/ml, whereas UV light was effective at both fluences. Although caffeine did not induce SCEs when it was added before exposure to bromodeoxyuridine (BrdUrd), which is used to visualize SCEs, it did induce SCEs when present during the entire culture period (3H‐thymidine experiments) or during incubation in BrdUrd (UV experiments). Caffeine markedly enhanced the SCE‐inducing effect of UV light but did not influence the effect of 3H‐thymidine.
Cardiovascular defects in rat embryos cultured on serum from rats chronically exposed to phenytoin
Authors: Clapper Margie L. , Clark Michael E. , Klein Norman W. , Kurtz Perry J. , Carlton Betsy D. , Chhabra Rajendra S.
Published: February 2006

Headfold‐stage rat embyros were cultured for 48 hours on serum from rats chronically exposed to phenytoin for periods as long as from conception until 11 months of age. Serum from phenytoin‐exposed rats caused approximately 50% of the cultured rat embryos to develop cardiovascular defects as compared to 12% for controls. These morphological abnormalities included hemorrhaging of blood vessels within the embryo, pericardial edema, and absence of yolk sac circulation. Neither serum glucose nor phosphate levels nor serum osmolality were appreciably affected by phenytoin treatment. However, serum protein concentration was reduced in rats exposed to phenytoin as compared to controls. An absence of the serum protein hemopexin was associated with the reduction in serum protein levels but did not appear to be responsible for the observed cardiovascular defects.
Effect of prenatal imipramine exposure on development of the postnatal rat heart and brain
Authors: Harmon James R. , Webb Peggy J. , Kimmel Gary L. , Delongchamp Robert R.
Published: February 2006

Imipramine (IMI) was administered s.c. at 0, 5, or 10 mg/kg/day to pregnant rats on gestation days 8–20 to assess possible alterations in postnatal heart and brain development. Maternal weight gain was significantly reduced in a dose‐response manner, but litter size and pup weight on postnatal day (PND) 1 were unaffected. On PND 1, litters were culled to 10 pups for analysis on PNDs 4/5, 7/8, 14/15, and 21/22. Pup body weight was not affected at any age measured, but heart weight was significantly reduced at 10 mg/kg IMI on PNDs 4/5 and 7/8. Brain weight was increased in a dose‐related pattern on PNDs 4/5 and 7/8 and was significantly higher at 5 mg/kg IMI on PND 14/15. No significant effect was observed in heart or brain protein and DNA content or in cardiac beta‐adrenergic receptor concentration. Prenatal IMI exposure had no effect on basal cardiac ornithine decarboxylase (ODC), an enzyme associated with growth and development, but basal brain ODC was lower at 5 mg/kg IMI at all ages measured. Cardiac ODC stimulation by insulin was unaffected by prenatal exposure to IMI, but isoproterenol‐stimulated ODC was increased on PND 21/22 at 5 mg/kg IMI. In conclusion, the IMI‐related changes in several parameters suggest that when maternal IMI treatment is used, alterations in postnatal heart and brain development must be considered as possible outcomes.
Studies on the embryopathic effects of ethanolamine in Long‐Evans rats: Preferential embryopathy in pups contiguous with male siblings in utero
Authors: Mankes R. F.
Published: February 2006

The embryopathic effects of high doses of ethanolamine were evaluated in pregnant Long‐Evans rats during the “critical period” or organogenesis. Ethanolamine was given by gavage at levels of 0, 500, 300, or 50 mg/kg/day (24%, 14.4%, or 2.4% of the LD50 value). Ethanolamine caused dose‐dependent increases in intrauterine deaths, malformations, and intrauterine growth retardation. Embryolethality caused by 500 mg/kg of ethanolamine was not random: male pups contiguous to two male siblings (designated mMm) were almost quantitatively replaced by resorptions that were contiguous to two live male pups (designated mRm) (mMm pups constituted 6.7% of control implants and decreased to only 0.9% of group II implants while mRm resorptions increased from 0.3% in controls to 5.6% in group II dams). Intrauterine growth retardation and increases in gross structural anomalies (considered indicative of depressed fetal growth) more severely affected male than female offspring at all dose levels. Pups of either sex who were contiguous to male siblings were more adversely affected than those offspring contiguous to one or more female siblings. As ethanolamine was given prior to the period of greatest fetal growth and fetal sex steroidogenesis, it is suggested that intrauterine levels of female sex steroids (estradiol) enhance fetal repair of cellular damage while testosterone inhibits fetal repair or exacerbates previous embryonic damage by some unknown mechanism. Such interaction furthers the concept that intrauterine position affects the endpoints of developmental toxicity, as expressed at parturition.
Developmental effects of chemicals and the heat shock response in Drosophila cells
Authors: Bournias‐Vardiabasis Nicole , Buzin Carolyn H.
Published: February 2006

Exposure of prokaryotic and eukaryotic cells to heat shock (hyperthermia) or to a number of diverse environmental stresses such as teratogens, anoxia, and inhibitors of oxidative phosphorylation results in the enhanced synthesis of a number of proteins which have been previously referred to as heat shock proteins (hsps). More recently, in view of the diverse types of agents that can induce these proteins, they have also been referred to as stress proteins. This phenomenon is one of the most basic regulatory mechanisms in living organisms. Exposure of Drosophila embryos, larvae, or pupae to these types of stresses also results in a variety of developmental abnormalities in the ensuing adult. Although the function(s) of these heat shock proteins has yet to be determined, they are widely thought to play an important role in cell survival and protection following some types of environmental stress. In our laboratory, we have developed an in vitro assay for detecting agents that act as teratogens, utilizing Drosophila embryonic cultures. Drosophila embryonic cells differentiate in vitro to a number of functional cell types including myotubes and ganglia. A number of drugs that have been shown to act as teratogens in mammals have also been found to inhibit muscle and/or neuron differentiation in Drosophila embryonic cultures. We have examined, by twodimensional gel electrophoresis, the effects of such teratogens on protein synthesis in Drosophila embryonic cells. Inhibition of muscle and/or neuron differentiation correlates well with the induction of two proteins of about 20 kilodaltons. These are identical to two of the heat shock proteins (hsp 23, 22) as shown by electrophoretic mobilities and peptide mapping by partial proteolysis. Heat shock and other treatments such as exposure to some of the metal ions and ether induces the entire set of seven major heat shock proteins in the Drosophila embryonic cells. Dose‐response studies of several teratogens show a correlation between the degree of inhibition of differentiation and the level of induction of hsps. Since heat shock proteins have been suggested as possibly serving a protecting role, our present studies are aimed at identifying the role of hsps in teratogenesis and investigating the differential regulation of heat shock genes in response to different external stimuli.