Developmental toxicity evaluation of orthovanadate in the mouse

Sodium orthovanadate in deionized water was administered once daily by gavage on gestational days 6-15 to mice at doses of 0, 7.5, 15, 30, and 60 mg/kg. Dams were killed on day 18 of pregnancy, and fetuses were examined for external, visceral, and skeletal defects. Maternal toxicity was observed at the highest doses of sodium orthovanadate, as evidenced by a significant number of deaths (60 and 30 mg/kg/d) and reduced weight gain and food consumption (30 and 15 mg/kg/d). Embryolethality and teratogenicity were not observed at maternally toxic doses and below, but fetal toxicity was evidenced by a significant delay in the ossification process of some skeletal districts at 30 mg/kg/d. The no-observed-adverse-effect level (NOAEL) for maternal toxicity was 7.5 mg/kg/d, and 15 mg/kg/d represented a NOAEL for developmental toxicity in mice under the conditions of this study.     

Genotoxicity of stannous chloride in yeast and bacteria

Stannous chloride was found genotoxic in microbial test systems of the yeast Saccharomyces cerevisiae, in one strain of Salmonella typhimurium and in the Mutoxitest of Escherichia coli. Five isogenic haploid yeast strains differing only in a particular repair-deficiency had the following ranking in Sn2+ -sensitivity: rad52delta>rad6delta>rad2delta>rad4delta>RAD, indicating a higher relevance of recombinogenic repair mechanisms than nucleotide excision in repair of Sn2+ -induced DNA damage. Sn2+ -treated cells formed aggregates that lead to gross overestimation of toxicity when not undone before diluting and plating. Reliable inactivation assays at exposure doses of 25-75 mM SnCl2 were achieved by de-clumping with either EDTA- or phosphate buffer. Sn2+ -induced reversion of the yeast his1-798, his1-208 and lys1-1 mutant alleles, in diploid and haploid cells, respectively, and putative frameshift mutagenesis (reversion of the hom3-10 allele) was observed. In diploid yeast, SnCl2 induced intra-genic mitotic recombination while inter-genic (reciprocal) recombination was very weak and not significant. Yeast cells of exponentially growing cultures were killed to about the same extend at 0.1% of SnCl2 than respective cells in stationary phase, suggesting a major involvement of physiological parameters of post-diauxic shift oxidative stress resistance in enhanced Sn2+ -tolerance. Superoxide dismutases, but not catalase, protected against SnCl2-induced reactive oxygen species as sod1delta had a three-fold higher sensitivity than the WT while the sod2delta mutant was only slightly more sensitive but conferred significant sensitivity increase in a sod1delta sod2delta double mutant. In the Salmonella reversion assay, SnCl2 did not induce mutations in strains TA97, TA98 or TA100, while a positive response was seen in strain TA102. SnCl2 induced a two-fold increase in mutation in the Mutoxitest strain IC203 (uvrA oxyR), but was less mutagenic in strain IC188 (uvrA). We propose that the mutagenicity of SnCl2 in yeast and bacteria occurs via error-prone repair of DNA damage that is produced by reactive oxygen species.     

Benzene and the genotoxicity of its metabolites. I. Transplacental activity in mouse fetuses and in their dams

Benzene and some of its metabolites (hydroquinone, phenol, catechol, 1,2,4-benzenetriol, p-benzoquinone, o,o'-biphenol, p,p'-biphenol) have been tested for their capability to induce micronuclei in bone marrow cells of pregnant mice and, transplacentally, in fetal liver cells. Dams are scarcely sensitive to the genotoxic activity of benzene and its metabolites while the latter are able to produce only evident toxic effects. Benzene and hydroquinone transplacentally induce micronuclei in fetal liver cells while all other metabolites show weak or negative genotoxicity, although they produce severe cellular toxicity.     

Developmental toxicity of soman in rats and rabbits

Soman (GD; phosphonofluoridic acid, methyl-,1,2,2-trimethylpropyl ester) is an organophosphate compound with potent anticholinesterase activity. To determine developmental toxicity, soman was administered orally to CD rats on days 6 through 15 of gestation at dose levels of 0, 37.5, 75, 150, or 165 micrograms/kg/day and to New Zealand White (NZW) rabbits on days 6 through 19 of gestation at dose levels of 0, 2.5, 5, 10, or 15 micrograms/kg/day. At sacrifice, gravid uteri were weighed and examined for number and status of implants. Individual fetal body weights and external, visceral, and skeletal malformations were recorded. Mean maternal weight changes, fetal implantation status/litter, fetal weight, and fetal malformations/litter were compared between dose groups. Monitors for maternal toxicity were net body weight change, treatment weight change, mortality, and clinical signs of toxicity such as lethargy, ataxia, and tremors. Maternal rats and rabbits in the high-dose groups exhibited statistically significant increases in toxicity and mortality when compared to controls. There were no significant dose-related effects among dose groups in the prevalence of postimplantation loss, malformations, or in average body weight of live fetuses per litter. There was no evidence of increased prenatal mortality or fetal toxicity in the CD rat or NZW rabbit following exposure to soman, even at a dose that produced significant maternal toxicity.     

Developmental toxicity of valproic acid

Valproic acid is a very effective anticonvulsant agent widely used in the management of various forms of epilepsy. Administration of the drug during pregnancy results in increased incidence of congenital abnormalities in both humans and experimental animals. In recent years, a significant number of research efforts have attempted to define the contributory role of valproic acid to the impairment of normal prenatal growth and development. The present report summarizes current knowledge that has emerged from clinical and research studies. The specific topics include: the placental transfer of valproic acid; the teratogenic potential; structure-teratogenicity and dose-response relationships; species and strain differences; biochemical changes evoked by the drug in the fetus.     

Low productivity of ribonucleotide reductase in Saccharomyces cerevisiae increases sensitivity to stannous chloride

Ribonucleotide reductase (RNR) of the yeast Saccharomyces cerevisiae is a tetrameric protein complex, consisting of two large and two small subunits. The small subunits Y2 and Y4 form a heterodimer and are encoded by yeast genes RNR2 and RNR4, respectively. Loss of Y4 in yeast mutant rnr4Delta can be compensated for by up-regulated expression of Y2, and the formation of a small subunit Y2Y2 homodimer that allows for a partially functional RNR. However, rnr4Delta mutants exhibit slower growth than wild-type (WT) cells and are sensitive to many mutagens, amongst them UVC and photo-activated mono- and bi-functional psoralens. Cells of the haploid rnr4Delta mutant also show a 3- to 4-fold higher sensitivity to the oxidative stress-inducing chemical stannous chloride than those of the isogenic WT. Both strains acquired increased resistance to SnCl2 with age of culture, i.e., 24-h cultures were more sensitive than cells grown for 2, 3, 4, and 5 days in liquid culture. However, the sensitivity factor of three to four (WT/mutant) did not change significantly. Cultures of the rnr4Delta mutant in stationary phase of growth always showed higher frequency of budding cells (budding index around 0.5) than those of the corresponding WT (budding index <0.1), pointing to a delay of mitosis/cytokinesis.     

Accumulation and toxicity of chloride in bean plants

Summary Chloride tends to accumulate in tissues, particularly leaves, of some plants to toxic levels. Chloride accumulation in plants is closely related to Cl concentration in the external solution and the genotype.An experiment was conducted to study the rate of Cl accumulation in bean plants under greenhouse conditions and to determine the toxic levels of this anion in the leaves of red kidney beans. Plants were grown in large tanks containing a basal nutrient solution, salinized with either NaCl or Na₂SO₄ to produce 80 meq/l solutions of these two salts. Control plants were grown in nonsalinized nutrient solutiosn. Salt-treated plants were harvested at different time intervals and analyzed. Chemical analysis of leaves showed that accumulation of chloride was different from that of other ions derived from salines. The leaf-Cl accumulation was shown to be dependent on Cl concentration of the culture solution as well as the duration of the experiment. The data also revealed two processes of rapid Cl accumulation in the leaves of bean plants when a relatively high concentration of this ion is present in the external solution. These are: (a) a rapid Cl accumulation occurring between transplanting and the first harvest; (b) a second rapid Cl accumulation occurring after the fourth harvest to the end of the experiment leading to a toxic concentration of Cl in the leaves. The second rapid absorption period was absent for the other ions derived from salines.     

Developmental shift in bidirectional functions of taurine-sensitive chloride channels during cortical circuit formation in postnatal mouse brain

Taurine (2-aminoethanesulfonic acid) is the most abundant free amino acid in the developing mammalian cerebral cortex, however, few studies have reported its neurobiological functions during development. In this study, by means of whole-cell patch-clamp recordings, we examined the effects of taurine on chloride channel receptors in neocortical neurons from early to late postnatal stages, which cover a critical period in cortical circuit formation. We show here that taurine activates chloride channels in cortical neurons throughout the postnatal stages examined (from postnatal day 2 to day 36). The physiological effects of taurine changed from excitatory to inhibitory due to variations in the intracellular Cl- concentration during development. An antagonist blocking analysis also demonstrated a developmental shift in the receptor target of taurine, from glycine receptors to GABAA receptors. Taken together, these results may reflect genetically programmed, bidirectional functions of taurine. At the early developmental stage, taurine acting on glycine receptors would serve to promote cortical circuit formation. As cortical circuit has to be regulated in the later stages, taurine would serve as a safeguard against hyperexcitable circuit.     

Developmental toxicity of fumonisin in Syrian hamsters

The effects of fumonisin on development of Syrian hamster fetuses were studied using fumonisin B₁ and B₂ extracted fromFusarium moniliforme corn-culture and purified fumonisin B₁. A significant increase in litters with fetal deaths occurred with the high doses of purified (18 mg FB₁/kg) and culture-extracted (18 mg FB₁ plus 4.5 mg FB₂) fumonisin. It is concluded that prenatal exposure to fumonisin on days 8 and 9 of gestation is detrimental to fetal hamster survivability but does not induce clinical maternal intoxication at these doses. Equivalent doses of fumonisin B₁, whether from culture-extract or pure solution produced similar results.     

Interaction of stannous chloride leads to alteration in DNA, triphosphate nucleotides and isolated bases

Stannous chloride (SnCl₂) is a reducing chemical agent used in several man-made products. SnCl₂ can generate reactive oxygen species (ROS); therefore, studies have been carried out in order to better understand its damaging action in biological systems. In this work, calf thymus DNA, triphosphate nucleotides and isolated bases were incubated with SnCl₂ and the results were analyzed through UV spectrophotometry. The presence of stannous ions altered the absorption spectra of all three isolates. The amount of stannous ions associated to DNA was measured by atomic absorption spectrophotometry. Data showed that more than 40% of the initial SnCl₂ concentration was present in the samples. Our results are in accordance with the damaging potential of this salt and present evidence that stannous ions can complex with DNA, inducing ROS in its vicinity, which may be responsible for the observed lesions. (Mol Cell Biochem xxx: 173–179, 2005)     

Developmental toxicity of ethanol in Drosophila melanogaster

Ethanol was tested for teratogenicity in Drosophila melanogaster. Treatment consisted of rearing the fly larvae in media containing initial ethanol concentrations of 0%, 4%, 8%, or 14% by weight. Emerging flies were inspected for gross malformations. A low frequency of malformations was seen among controls (0.82%), increasing to 10.36% of emerging adults at the highest ethanol dose. The most common malformation involved the legs (segments missing or distorted or complete absence) and wings (uninflated, distorted, or absent). Less frequent defects included fused or missing mouth parts and missing halteres. Also, by exposing staged larvae to ethanol and examining the emerging flies, developmental stage sensitivity of Drosophila was investigated in terms of timing of treatment initiation. The results suggested that the incidence of defects increased with length of exposure. These results support the assumption that ethanol itself is the causative agent in ethanol-induced developmental toxicity and further support the use of Drosophila for developmental toxicity screening.     

Immunohistochemical localization of entactin and laminin in mouse embryos and fetuses

The temporal appearance and the anatomic distribution of entactin in the developing mouse embryo was studied by light and electron microscopic immunohistochemistry and compared with the appearance and the distribution of laminin. Immunohistochemically detectable entactin first appeared in the hatched blastocysts, in contrast to laminin which became apparent as early as the 8-cell stage of development. However, beginning with the appearance of entactin in the hatched blastocyst, antibodies to these two basement membrane glycoproteins co-localized in all extraembryonic matrices. These findings indicate that the synthesis of entactin and laminin is asynchronous in the early stages of mouse embryonic development but becomes synchronized in the postimplantational stages of development.     

Plasma concentrations of delta-9-tetrahydrocannabinol in dams and fetuses following acute or multiple prenatal dosing in rats

Delta-9-tetrahydrocannabinol (THC) was administered by gastric intubation to pregnant rats to study the effects of dose-level and dosing regimen on plasma concentration in dams and fetuses. Two multiple-dose groups were administered either 15 or 50 mg/kg of delta-9-THC once daily during the last two weeks of gestation. Two acute groups were administered the same dose as above but only once on the last day of gestation. Sixty min after receiving the last dose all dams and their fetuses were sacrificed by decapitation, blood collected, centrifuged and plasma removed. Quantitative measurement of delta-9-THC in plasma was carried out using GS/MS. Among the dams, plasma concentrations covaried with dose and multiple dosing produced higher concentrations than acute, especially at the high dose. Among the fetuses, plasma concentrations were approximately 10% of those found in the dams. The fetuses from the high, multiple-dose dams similarly yielded significantly higher concentrations. These findings are discussed with respect to other studies of the placental transfer of delta-9-THC and effects of postnatal developmental.     

Developmental toxicity of dichloroacetate in the rat.

Dichloroacetic acid (DCA) is a principal by-product of the chlorine disinfection of water containing humic and fulvic acids, and is also a drug of interest in the therapeutic management of metabolic disorders. The developmental effects of DCA were evaluated in the pregnant Long-Evans rat. In two separate studies, animals were dosed by oral intubation on gestation days 6-15 (plug = 0) with 0, 900, 1,400, 1,900 or 2,400 mg/kg/day and 0, 14, 140, or 400 mg/kg/day. The vehicle control was distilled water. Maternal observations included clinical signs, weight change, and gross evaluation of organ weights and uterine contents at necropsy (day 20). Corpora lutea were counted and uteri stained for implantation sites. Live fetuses were examined for external, skeletal, and soft tissue malformations. Seven dams died during treatment (1,400 mg 1/19, 1,900 mg 2/19, 2,400 mg 4/21), and maternal weight gain was reduced at all except the lowest treatment levels. Liver, spleen, and kidney weights increased in a dose-related manner. The mean percentage of resorbed implants per litter was significantly elevated at greater than or equal to 900 mg/kg/day. Live fetuses showed dose-dependent reductions in weight and length at doses above 140 mg/kg. Statistically significant frequencies of soft tissue malformations ranged from 2.6% (140 mg/kg) to 73% (2,400 mg/kg). These were principally in the cardiovascular system and predominantly comprised defects between the ascending aorta and the right ventricle. Skeletal malformations were not observed in significant numbers in any dose group.(ABSTRACT TRUNCATED AT 250 WORDS)     

Developmental toxicity of carbon black oil in mice

BACKGROUND: Carbon black oil (CBO) is a refinery side-stream product used to produce asphalt and other commercial products. CBO contains several classes of hydrocarbons, several of which are known to exhibit systemic and gestational toxicities, making this mixture a candidate for causing reproductive toxicity. METHODS: Swiss-Webster mice were administered CBO (300, 350, 400 mg/kg/day) via oral gavage in a dosage volume of 10 microl/g body weight on gestation days (GD) 6-15. Uterine contents were evaluated on GD 18. RESULTS: Treatment with CBO at all dosage levels resulted in a high frequency of maternal clinical symptoms and a decrease in maternal weight gain. Decreased fetal viability was observed, manifested as a decrease in viable implants and, in a high percentage of treated dams, as early resorption of the entire litter. A significant reduction in fetal weight was also observed. However, neither structural malformations nor developmental delays in ossification were observed in any of the living offspring. To minimize maternal toxicity, the dosage range was lowered (100, 200, 300 mg/kg/day), and the concentration was adjusted such that the volume administered to each dam was decreased by 20%. In this trial, the only maternal effect observed was an increase in maternal liver weight at 200 and 300 mg/kg. The fetal lethality effects observed previously were reduced substantially. Nevertheless, the frequency of resorption among all treatment groups was higher statistically than in controls. CONCLUSIONS: These data support the hypothesis that CBO is reproductively toxic in Swiss-Webster mice at oral doses of >/=100 mg/kg/day.