Lack of selective developmental neurotoxicity in rat pups from dams treated by gavage with chlorpyrifos.

Pregnant Sprague-Dawley rats were given chlorpyrifos (O:, O-diethyl-O:-[3,5,6-trichloro-2-pyridinyl] phosphorothioate; CPF) in corn oil by gavage from gestation day 6 (GD 6) through lactation day 10 (LD 10) at dosages of 0, 0.3, 1, or 5 mg/kg/day in a developmental neurotoxicity study that conformed to U.S. Environmental Protection Agency 1991 guidelines. GD 0 was the day when evidence of mating was observed and postnatal day 0 (PND 0) was the day of birth. Toxicity was limited to the highest dosage level (5 mg/kg/day) and, in the dams, consisted of muscle fasciculation, hyperpnea, and hyperreactivity. A nonsignificant overall trend toward weight gain and feed consumption was also observed in the high-dosage dams, with a statistically significant Group x Time interaction for reduced weight gain in the 5-mg/kg/day group near the end of gestation. Although many developmental indices were normal, pups from high-dosage dams had increased mortality soon after birth, gained weight more slowly than controls, and had several indications of slightly delayed maturation. The early deaths and delayed maturation were attributed to maternal toxicity, though a possible contributing role of direct pup toxicity in delayed development cannot be eliminated. In spite of the apparent delay in physical development, high-dosage pups tested just after weaning had normal learning and memory as tested on a T-maze spatial delayed-alternation task. Habituation, a primitive form of learning, was tested in 2 tasks (motor activity and auditory startle) and was not affected. No overt effects were noted in either dams or pups at 1 or 0.3 mg/kg/day. Based on these data, chlorpyrifos produced maternal and developmental toxicity in the 5-mg/kg/day-dosage group. There was no evidence of selective developmental neurotoxicity following exposure to chlorpyrifos.     

Growth and development in rats given recombinant human epidermal growth factor(1-48) as neonates.

To assess effects of supraphysiologic doses of human recombinant epidermal growth factor(1-48) (rhEGF(1-48)) on neonatal rats, 10 litters of Wistar rats/treatment group were given 0 (formulated vehicle), 10, 100, or 1000 microg/kg daily by subcutaneous injection on postnatal days (PND) 1 through 6. Clinical signs, body weight, acquisition of developmental landmarks and reflexes, and behavior were monitored during treatment and for 5 weeks thereafter (to PND 42). A subset of animals was euthanized weekly from PND 7-28 and necropsied. Selected tissues were examined microscopically. Body weight gain at 1000 microg/kg during treatment was significantly less than control. Precocious incisor eruption, eye opening, vaginal opening, and preputial separation occurred at 100 and/or 1000 microg/kg. Acquisition of reflexes (negative geotaxis, wire maneuver, acoustic startle reflex, and visual placing) was delayed at 1000 microg/kg. Acquisition of adult locomotion was also delayed at 1000 microg/kg. These effects were transient, as locomotor activity at PND 28 and 42 did not differ from control. Effects on acoustic-startle responding persisted in females to final assessment on PND 42. Habituation to repeated acoustic stimuli was impaired, as well as response inhibition following a prepulse acoustic stimulus. rhEGF(1-48) induced structural changes in the skin, retina, kidney, oral and nasal mucosa, lung, and liver. Many of these changes were consistent with the expected mitogenic activity of rhEGF(1-48) and were transient in nature, as severity and incidence diminished with time. An exception was changes observed in the retina at 1000 microg/kg (rosettes/folds and focal defects in the outer nuclear/photoreceptor layers) that were still present 3 weeks after termination of treatment. Acceleration of developmental landmarks; suppression of reflexes, behavior, and somatic growth; and mitogenic responses in epidermal tissues have been reported in rodents treated with epidermal growth factor (EGF) derived from various mammalian species. These results demonstrate that a 48-amino acid fragment of human EGF produced by recombinant technology also induces such effects.     

Estimation of placental and lactational transfer and tissue distribution of atrazine and its main metabolites in rodent dams,fetuses, and neonates with physiologically based pharmacokinetic modeling

Atrazine (ATR) is a widely used chlorotriazine herbicide, a ubiquitous environmental contaminant, and a potential developmental toxicant. To quantitatively evaluate placental/lactational transfer and fetal/neonatal tissue dosimetry of ATR and its major metabolites, physiologically based pharmacokinetic models were developed for rat dams, fetuses and neonates. These models were calibrated using pharmacokinetic data from rat dams repeatedly exposed (oral gavage; 5 mg/kg) to ATR followed by model evaluation against other available rat data. Model simulations corresponded well to the majority of available experimental data and suggest that: (1) the fetus is exposed to both ATR and its major metabolite didealkylatrazine (DACT) at levels similar to maternal plasma levels, (2) the neonate is exposed mostly to DACT at levels two-thirds lower than maternal plasma or fetal levels, while lactational exposure to ATR is minimal, and (3) gestational carryover of DACT greatly affects its neonatal dosimetry up until mid-lactation. To test the model's cross-species extrapolation capability, a pharmacokinetic study was conducted with pregnant C57BL/6 mice exposed (oral gavage; 5 mg/kg) to ATR from gestational day 12 to 18. By using mouse-specific parameters, the model predictions fitted well with the measured data, including placental ATR/DACT levels. However, fetal concentrations of DACT were overestimated by the model (10-fold). This overestimation suggests that only around 10% of the DACT that reaches the fetus is tissue-bound. These rodent models could be used in fetal/neonatal tissue dosimetry predictions to help design/interpret early life toxicity/pharmacokinetic studies with ATR and as a foundation for scaling to humans.     

Buprenorphine and midazolam act in combination to depress respiration in rats.

High dose buprenorphine is used as substitution treatment in human heroin addiction. Deaths have been reported in addicts using buprenorphine, frequently in association with benzodiazepines. In the current study, we observed the effects of buprenorphine and midazolam alone and in combination on arterial blood gases. Four groups of 10 male Sprague-Dawley rats received a parenteral injection of aqueous solvent, buprenorphine (30 mg/kg, iv), midazolam (160 mg/kg, ip), or buprenorphine (30 mg/kg, iv) plus midazolam (160 mg/kg, ip). Serial blood gases were obtained over 3 hours. There was a mild but significant effect of buprenorphine alone in comparison with the aqueous solvent on PaCO2 at 60 min (6.24 vs. 5.65 kPa, p< 0.01). There was also a mild but significant effect of midazolam alone in comparison with aqueous solvent on arterial pH at 90 min (7.33 vs. 7.41,p< 0.001) and PaCO2 at 60 min (6.52 vs. 5.65 kPa,p< 0.01). The combination of midazolam and buprenorphine produces a rapid, profound, and prolonged respiratory depression, as demonstrated by an increase in PaCO2 at 7.65 +/- 0.12 kPa at 20 min and a decrease in arterial pH at 7.25 +/- 0.02 at 20 min, with appearance of delayed hypoxia with a decrease in PaO2 at 8.74 +/- 0.20 kPa at 120 min. These data show that high doses of midazolam and buprenorphine alone have limited effects on arterial blood gases in rats while midazolam and buprenorphine appear to act in an additive or synergistic fashion to depress ventilation in rats.     

Effects of intermittent exposure to aflatoxin B1 on DNA and RNA adduct formation in rat liver: dose-response and temporal patterns.

We studied the effects of intermittent exposure to aflatoxin B1 (AFB1) on hepatic DNA and RNA adduct formation. Fisher-344 male rats were fed 0.01, 0.04, 0.4, or 1.6 ppm of AFB1 intermittently for 8, 12, 16, and 20 weeks, alternating with 4 weeks of dosing and 4 weeks of rest. Other groups of rats were fed 1.6 ppm of AFB1 continuously for 4, 8, 12, and 16 weeks. Control rats received AFB1-free NIH-31 meal diet. AFB1-DNA and -RNA adducts were measured by HPLC with fluorescence detection. The data are presented as total DNA or RNA adducts. The DNA and RNA adduct levels increased or decreased depending on the cycles of dosing and rest. Rats removed from treatment 1 month after 1 or 2 dosing cycles (8 and 16 weeks of intermittent exposure) showed approximately a twofold decrease in DNA adduct levels and a two- to elevenfold decrease in RNA adduct levels compared with rats euthanized immediately after the last dosing cycle (12 and 20 weeks of intermittent exposure). Our data indicate that DNA and RNA adducts increased linearly, from 0.01 ppm to 1.6 ppm of AFB1 after 12 and 20 weeks of intermittent treatment. A linear dose response was also apparent for DNA but not for RNA adducts after 8 and 16 weeks of treatment. As biomarkers of exposure, AFB1-RNA adducts were three to nine times more sensitive than AFB1-DNA adducts but showed greater variability. These results suggest that binding of AFB1 to hepatic DNA is a linear function of the dose, regardless of the way this is administered. The dose-response relationship for RNA adducts depends on the length of the no-dosing cycles and on the turnover rate of RNA.     

Hematological cell findings in bone marrow and peripheral blood of rabbits after experimental acute exposure to Loxosceles intermedia (brown spider) venom.

The purpose of this work was to find out the cellular changes occurring in bone marrow and peripheral blood after acute exposure to the venom of Loxosceles intermedia. Doses of 40 microg of venom were injected intradermally into five rabbits, and five rabbits receiving only phosphate-buffered saline (PBS) were used as controls. Bone marrow and peripheral blood samples were obtained before the envenomation and 4, 8, 12, 24 and 48 h, and 5, 10, 15, 20 and 30 days after envenomation. In bone marrow samples we assessed cellularity, nucleated red cells, megakaryocytes and neutrophils, and in peripheral blood we assessed red cells (red cell concentration, hemoglobin and hematocrit), leukocytes, neutrophils and platelets. Our objective was to find out if the venom has a direct effect on bone marrow and peripheral blood or if changes in both of them are secondary to the needs of tissues, and if there is a good correlation between histopathological and hematological findings. We found that the red cell parameters were not affected by the venom, except for nucleated red cells which decreased after venom exposure. The depression of megakaryocyte numbers and thrombocytopenia showed a strong correlation with the histopathologic changes observed in skin biopsies obtained from the rabbits. The changes in cellularity and neutrophils of bone marrow were strongly correlated with those in peripheral blood and skin. The thrombocytopenia and neutropenia in peripheral blood are due to marrow depression, which may be a consequence of an extensive migration of platelets and neutrophils to the necrotic lesion or the marrow depression may be a transitory effect of evenoming by L. intermedia.     

Confirmation of brevetoxin metabolism in cockle, Austrovenus stutchburyi, and greenshell mussel, Perna canaliculus, associated with New Zealand neurotoxic shellfish poisoning, by controlled exposure to Karenia brevis culture.

We examined metabolism of PbTxs in New Zealand cockle, Austrovenus (A.) stutchburyi, and greenshell mussel, Perna (P.) canaliculus, by means of liquid chromatography coupled with tandem mass spectrometry. PbTx-2, PbTx-3 and BTX-B5 were detected in Karenia (K.) brevis culture medium in the ratio of ca. 50:2:5. The amounts of PbTx-3 and BTX-B5 were greatly increased in both seawater and shellfish exposed to K. brevis cultures or supernatant prepared by disruption of K. brevis under appropriate condition, while those of PbTx-2 were decreased. Some PbTx-2 was present in P. canaliculus, but not in A. stutchburyi. Low levels of BTX-B1 were detected in A. stutchburyi, but not P. canaliculus. Levels of PbTx-3 and BTX-B5 were highest immediately after exposure and then declined rapidly in both shellfish. BTX-B1 increased in concentration after exposure, and was then gradually eliminated from A. stutchburyi. Three successive exposures of A. stutchburyi to K. brevis cultures resulted in similar initial levels of PbTx-3 and BTX-B5, while BTX-B1 accumulated after each dose. In P. canaliculus, initial levels of PbTx-3 were similar, while PbTx-2 and BTX-B5 accumulated after each dose. PbTx-3 and BTX-B5 are proposed to be suitable markers for monitoring shellfish toxicity after a red tide event.     

Potent inhibition of both the acute and delayed emetic responses to cisplatin in piglets treated with GR205171, a novel highly selective tachykinin NK1 receptor antagonist

1. The effects of {"type":"entrez-nucleotide","attrs":{"text":"GR205171","term_id":"238470896","term_text":"GR205171"}}GR205171, a selective tachykinin NK₁ receptor antagonist, were investigated on both the acute and delayed phases of cisplatin-induced nausea-like behaviour and vomiting in the conscious piglet.
2. Animals receiving cisplatin (5.5 mg kg⁻¹, i.v.) were observed for 60 h. Fifteen min prior to cisplatin infusion (T0_−15 min), eight piglets acting as controls received an intravenous injection of saline solution (1 ml kg⁻¹), whereas experimental animals received a single i.v. administration of {"type":"entrez-nucleotide","attrs":{"text":"GR205171","term_id":"238470896","term_text":"GR205171"}}GR205171 (1 ml kg⁻¹) at a dose of 0.01 (n=8), 0.03 (n=8), 0.1 (n=8), 0.3 (n=16) or 1.0 (n=13) mg kg⁻¹. In eight additional piglets, {"type":"entrez-nucleotide","attrs":{"text":"GR205171","term_id":"238470896","term_text":"GR205171"}}GR205171 (1 mg kg⁻¹) was administered 15 min before the onset of the delayed phase (T16_−15 min). A further five piglets received {"type":"entrez-nucleotide","attrs":{"text":"GR205171","term_id":"238470896","term_text":"GR205171"}}GR205171 (1 mg kg⁻¹) every 6 h throughout the experiment.
3. The latencies of the first emetic episode (EE) and nausea-like behavioural episode (NE) increased in all experimental groups treated at T0_−15 min, and the total number of both EE and NE during the 60 h was reduced in a dose-dependent manner. In piglets treated at T0_−15 min with {"type":"entrez-nucleotide","attrs":{"text":"GR205171","term_id":"238470896","term_text":"GR205171"}}GR205171 1 mg kg⁻¹, eight out of 13 (62%) did not vomit throughout the experiment. Animals treated with {"type":"entrez-nucleotide","attrs":{"text":"GR205171","term_id":"238470896","term_text":"GR205171"}}GR205171 (1 mg kg⁻¹) at T16_−15 min exhibited an acute response to cisplatin but did not vomit during the delayed phase. The greatest inhibition of both nausea-like behaviour and vomiting was observed in piglets receiving multiple injections of {"type":"entrez-nucleotide","attrs":{"text":"GR205171","term_id":"238470896","term_text":"GR205171"}}GR205171.
4. These results demonstrate the long-lasting anti-emetic effects of {"type":"entrez-nucleotide","attrs":{"text":"GR205171","term_id":"238470896","term_text":"GR205171"}}GR205171, and confirm the key role of substance P within the emetic reflex.

     

In vitro and in vivo evaluation of the estrogenic, androgenic, and progestagenic potential of two cyclic siloxanes.

The purpose of these experiments was to determine the potential estrogenic, androgenic, and progestagenic activity of two cyclic siloxanes, octamethylcyclotetrasiloxane (D4) and decamethylcyclopentasiloxane (D5). Receptor-binding experiments and a luciferase reporter gene assay were used to determine if the materials were able to bind and activate either the estrogen receptors (ERs) or progesterone receptors (PRs)-alpha or beta. The rat uterotrophic assay (RUA) for estrogenic activity and the Hershberger assay for androgenic activity were utilized as the in vivo assays. For the ER-binding studies, D4 was shown to bind to ERalpha but not to ERbeta. D5 did not bind to either of the two receptors. D4 activated the reporter gene at 10 microM, while D5 was considered negative in the estrogen reporter gene assay. Neither material was a ligand for the PRs. Both the RUA and Hershberger assays were conducted using whole-body inhalation of the two materials for 16 h/day. D4 resulted in a small but significant increase in both wet and blotted uterine weight as well as increases in both luminal and glandular epithelial cell height in both Sprague Dawley and Fischer 344 rats. D5 was negative in both rat strains, indicating that D5 does not possess estrogenic activity. Neither material possessed any significant antiestrogenic activity. Both materials were negative in the Hershberger assay indicating that neither material possesses any significant androgenic activity. Our studies have shown that D4 exhibits a low affinity for ERalpha in vitro and a weakly estrogenic response in vivo.     

Acute pulmonary and systemic effects of inhaled coal fly ash in rats: comparison to ambient environmental particles.

Although primary particle emissions of ash from coal-fired power plants are well controlled, coal fly ash (CFA) can still remain a significant fraction of the overall particle exposure for some plant workers and highly impacted communities. The effect of CFA on pulmonary and systemic inflammation and injury was measured in male Sprague-Dawley rats exposed to filtered air or CFA for 4 h/day for 3 days. The average concentration of CFA particulate matter less than 2.5 microm (PM(2.5)) was 1400 microg/m(3), of which 600 microg/m(3) was PM(1). Animals were examined 18 and 36 h postexposure. Chemical analysis of CFA detected silicon, calcium, aluminum, and iron as major components. Total number of neutrophils in bronchoalveolar lavage fluid (BALF) following exposure to CFA was significantly increased along with significantly elevated blood neutrophils. Exposure to CFA caused slight increases in macrophage inflammatory protein-2, and marked increases in transferrin in BALF. Interleukin-1beta and total antioxidant potential in lung tissues were also increased in rats exposed to CFA. Histological examination of lung tissue demonstrated focal alveolar septal thickening and increased cellularity in select alveoli immediately beyond terminal bronchioles. These responses are consistent with the ability of CFA to induce mild neutrophilic inflammation in the lung and blood following short-term exposure at levels that could be occupationally relevant. However, when comparing the effects of CFA with those of concentrated ambient particles, CFA does not appear to have greater potency to cause pulmonary alterations. This study furthers our understanding of possible mechanisms by which specific sources of particulate air pollution affect human health.     

Genotoxicity studies of organically grown broccoli (Brassica oleracea var. italica) and its interactions with urethane,methyl methanesulfonate and 4-nitroquinoline-1-oxide genotoxicity in the wing spot test of Drosophila melanogaster

Broccoli (Brassica oleracea var. italica) has been defined as a cancer preventive food. Nevertheless, broccoli contains potentially genotoxic compounds as well. We performed the wing spot test of Drosophila melanogaster in treatments with organically grown broccoli (OGB) and co-treatments with the promutagen urethane (URE), the direct alkylating agent methyl methanesulfonate (MMS) and the carcinogen 4-nitroquinoline-1-oxide (4-NQO) in the standard (ST) and high bioactivation (HB) crosses with inducible and high levels of cytochrome P450s (CYPs), respectively. Larvae of both crosses were chronically fed with OGB or fresh market broccoli (FMB) as a non-organically grown control, added with solvents or mutagens solutions. In both crosses, the OGB added with Tween–ethanol yielded the expected reduction in the genotoxicity spontaneous rate. OGB co-treatments did not affect the URE effect, MMS showed synergy and 4-NQO damage was modulated in both crosses. In contrast, FMB controls produced damage increase; co-treatments modulated URE genotoxicity, diminished MMS damage, and did not change the 4-NQO damage. The high dietary consumption of both types of broccoli and its protective effects in D. melanogaster are discussed.