Fractional contribution of major ions to the membrane potential of Drosophila melanogaster oocytes.

In ovarian follicles of Drosophila melanogaster, ion substitution experiments revealed that K(+) is the greatest contributor (68%) in setting oocyte steady-state potential (E(m)), while Mg(2+) and a metabolic component account for the rest. Because of the intense use made of Drosophila ovarian follicles in many lines of research, it is important to know how changes in the surrounding medium, particularly in major diffusible ions, may affect the physiology of the cells. The contributions made to the Drosophila oocyte membrane potential (E(m)) by [Na(+)](o), [K(+)](o), [Mg(2+)](o), [Ca(2+)](o), [Cl(-)](o), and pH (protons) were determined by substitutions made to the composition of the incubation medium. Only K(+) and Mg(2+) were found to participate in setting the level of E(m). In follicles subjected to changes in external pH from the normal 7.3 to either pH 6 or pH 8, E(m) changed rapidly by about 6 mV, but within 8 min had returned to the original E(m). Approximately half of all follicles exposed to reduced [Cl(-)](o) showed no change in E(m), and these all had input resistances of 330 kOmega or greater. The remaining follicles had smaller input resistances, and these first depolarized by about 5 mV. Over several minutes, their input resistances increased and they repolarized to a value more electronegative than their value prior to reduction in [Cl(-)](o). Together, K(+) and Mg(2+) accounted for up to 87% of measured steady-state potential. Treatment with sodium azide, ammonium vanadate, or chilling revealed a metabolically driven component that could account for the remaining 13%.

Subchronic feeding study of herbicide-tolerant soybean DP-356Ø43-5 in Sprague-Dawley rats.

Optimum GAT1 soybean is a genetically modified (GM) soybean containing event DP-356Ø43-5 (356043) that was produced by integration of the coding sequences of the GAT4601 and GM-HRA proteins. In planta expression of these proteins confers tolerance to glyphosate and sulfonylurea/imidazolinone herbicides, respectively. This paper reports the results from a subchronic rat feeding study conducted with 356043 soybeans. Dehulled/defatted toasted meal and toasted ground hulls were prepared from soybeans from untreated plants (356043), herbicide-treated plants (356043+Gly/SU), non-transgenic isoline control (091), and three commercial non-transgenic reference varieties (93B86, 93B15, and 93M40). Individual diets conforming to standard certified rodent chow formulation (Purina Rodent LabDiet) 5002) were prepared with 20% meal (w/w) and 1.5% hulls (w/w). Diets were fed to young adult Sprague-Dawley rats (12/sex/group) for at least 93 days. Compared with rats fed the isoline control or conventional reference diets, no biologically-relevant, adverse effects were observed in rats fed diets containing 356043 or 356043+Gly/SU soybean with respect to body weight/gain, food consumption/efficiency, clinical signs, mortality, ophthalmology, neurobehavioral assessments (sensory response, grip strength, motor activity), clinical pathology (hematology, coagulation, serum chemistry, urinalysis), organ weights, and gross and microscopic pathology. The results from this study indicate that 356043 soybeans are as safe and nutritious as conventional non-GM soybeans.

Subchronic feeding study of high oleic acid soybeans (Event DP-3Ø5423-1) in Sprague-Dawley rats.

DP-3Ø5423-1 (305423) is a genetically-modified (GM) soybean that was produced by biolistic insertion of a gm-fad2-1 gene fragment and the gm-hra gene into the germline of soybean seeds. The gm-fad2-1 gene fragment cosuppresses expression of the endogenous FAD2-1 gene encoding the seed-specific omega-6 fatty acid desaturase resulting in higher concentrations of oleic acid (18:1) relative to linoleic acid (18:2). The gm-hra gene encoding a modified acetolactate synthase (ALS) enzyme was used as a selectable marker. In the current study, processed fractions (meal, hulls, and oil) from 305423 soybeans, non-GM soybeans with a similar genetic background (near isoline control) and three commercially-available non-GM varieties were used to formulate diets that were nutritionally comparable to PMI Certified Rodent LabDiet 5002. Diets were fed to young adult Crl:CD(SD) rats (12/sex/group) for approximately 90 days. Compared with rats fed the non-GM control diet, no biologically relevant differences were observed in rats fed the 305423 diet with respect to body weight/gain, food consumption/efficiency, mortality, clinical signs of toxicity, or ophthalmological observations. No test diet-related effects were observed on neurobehavioral assessments, organ weights, or clinical or anatomic pathology. These results demonstrated that 305423 soybeans are as safe and wholesome as non-GM soybeans.

Subchronic, reproductive, and developmental toxicity of a fluorotelomer-based urethane polymeric product.

A commercial fluorotelomer-based urethane polymeric dispersion, consisting of polymer, surfactant, and water, was evaluated in subchronic, reproduction, and developmental toxicity studies. The dispersion was administered daily by gavage to rats at dosages of 0, 50, 250, or 1000 mg polymer/kg/day or with 70 mg/kg/day of the sulfonate surfactant. Dose levels of 0, 50, 250, or 1000 mg polymer/kg/day were also used for the reproductive and developmental studies. Nasal olfactory epithelial degeneration and necrosis occurred in all dose groups in the 90-day study. Nasal adhesions were observed only in rats administered surfactant alone. Liver-enzyme alterations at 250 and 1000 mg/kg were considered to be potentially adverse effects. The subchronic no-observed-adverse-effects level (NOAEL) was 50 mg/kg. For the reproduction study, rats were dosed for 10 weeks prior to cohabitation and throughout mating, gestation, and lactation. There were no effects on reproductive function in males or females at any dosage. Thyroid weight was decreased in the 250 and 1000 mg/kg day F(1) groups unaccompanied by microscopic effects. In the developmental toxicity study, female rats were dosed from gestation days 6-20; there was no test-substance-related embryolethality, nor was there any dose-related increase in either fetal malformations. Fetal weight was minimally decreased at 1000 mg/kg/day in the presence of slight maternal toxicity; the NOAEL for developmental parameters was 250 mg/kg/day. The polymeric product was not a specific developmental or reproductive toxin.

Evaluation of the reproductive and developmental toxicity of 6:2 fluorotelomer alcohol in rats.

6:2 Fluorotelomer alcohol (6:2 FTOH) was evaluated for potential developmental and reproductive toxicity. 6:2 FTOH was administered by oral gavage to Sprague-Dawley rats as a suspension in 0.5% aqueous methylcellulose at dosages of 5, 25, 125, or 250 mg/kg/day. The developmental toxicity study was performed in accordance with the Organization for Economic Development (OECD) Test Guideline 414, and the one-generation reproductive toxicity study was performed in accordance with the OECD Test Guideline 415. For the developmental toxicity study, adverse maternal toxicity observed at 250 mg/kg/day included reductions in body weight parameters and food consumption. Evidence of developmental toxicity was limited to increases in skeletal variations (ossification delays in the skull and rib alterations) at 250 mg/kg/day. There were no adverse maternal or developmental effects observed at 5, 25, or 125 mg/kg/day and there were no effects on reproductive outcome or quantitative litter data at any dose level. For the one-generation reproduction toxicity study, systemic parental and developmental toxicity were observed at 125 and 250 mg/kg/day. At 250 mg/kg/day, there was increased mortality among male and female parental rats, effects on body weight parameters, food consumption, and clinical signs, and there were effects on offspring survival indices and body weights. At 125 mg/kg/day, there was an increase in mortality in parental males only, and parental toxicity was limited to effects on body weight gain, food consumption (lactation), and clinical signs. Uterine weights were decreased at 125 and 250 mg/kg/day, although there were no corroborative histopathological changes. At 125 mg/kg/day, pup mortality was increased on lactation day 1, and body weights of the offspring were decreased during the second half of lactation. There was no evidence of either parental or developmental toxicity at 5 or 25mg/kg/day, and there were no effects on reproductive outcome at any dose level. Based on these data, 6:2 FTOH is not a selective reproductive or developmental toxicant at dosages that induce clear maternal/parental toxicity. Therefore, 6:2 FTOH would not be classified for reproductive/developmental toxicity under the United Nations' Globally Harmonized System of Classification and Labeling of Chemicals.

Mutagenicity studies with N-acetyl-L-aspartic acid.

Analytical studies have reported that N-acetyl-L-aspartic acid (NAA) is present at low concentrations in many foods. The current studies were conducted to assess the mutagenicity of NAA using standard OECD guideline in vitro bacterial and in vivo mammalian mutagenicity studies. For comparison and control data, mutagenicity studies were also conducted with its constituent amino acid L-aspartate (ASP) because NAA is metabolized to ASP. The combination of an in vitro method for assessing point mutations in bacteria and an in vivo method to assess clastogenicity in an animal model provided adequate evidence for mutagenicity hazard assessment of NAA. No evidence of mutagenicity was observed in either test system with either NAA or ASP. The results from the current studies demonstrate that the presence of NAA in foods is not likely to represent a risk for mutagenicity.

Subchronic feeding study of grain from herbicide-tolerant maize DP-Ø9814Ø-6 in Sprague-Dawley rats.

This 13-week feeding study conducted in Sprague-Dawley rats evaluated the potential health effects from long-term consumption of a rodent diet formulated with grain from genetically modified (GM), herbicide-tolerant maize DP-Ø9814Ø-6 (98140; trade name Optimum GAT (Optimum GAT is a registered trademark of Pioneer Hi-Bred)). Metabolic inactivation of the herbicidal active ingredient glyphosate was conferred by genomic integration and expression of a gene-shuffled acetylase coding sequence, gat4621, from Bacillus licheniformis; tolerance to acetolactate synthase (ALS) inhibiting herbicides was conferred by overexpression of a modified allele (zm-hra) of the endogenous maize ALS enzyme that is resilient to inactivation. Milled maize grain from untreated (98140) and herbicide-treated (98140+Gly/SU) plants, the conventional non-transgenic, near-isogenic control (091), and three commercial non-transgenic reference hybrids (33J56, 33P66, and 33R77) was substituted at concentrations of 35-38% w/w into a common rodent chow formula (PMI) Nutrition International, LLC Certified Rodent LabDiet 5002) and fed to rats (12/sex/group) for at least 91 consecutive days. Compared with rats fed diets containing grain from the conventional near-isogenic control maize, no adverse effects were observed in rats fed diets containing grain from 98140 or 98140+Gly/SU maize with respect to standard nutritional performance metrics and OECD 408-compliant toxicological response variables [OECD, 1998. Section 4 (Part 408), Health Effects: Repeated Dose 90-Day Oral Toxicity Study in Rodents, Guideline for the Testing of Chemicals. Organisation of Economic Co-operation and Development, Paris, France]. These results support the comparative safety and nutritional value of maize grain from genetically modified Optimum GAT and conventional, non-transgenic hybrid field corn.

Evaluation of the reproductive and developmental toxicity of a fluoroalkylethanol mixture.

The objective of these studies was to evaluate the reproductive and developmental toxicity of a commercial fluoroalkylethanol mixture, which is an intermediate in the production of fluorotelomers. The test substance was administered daily by gavage to Sprague-Dawley rats as a suspension in 0.5% aqueous methylcellulose. In a one-generation reproductive toxicity study, rats (20 per sex per group) were given dosages of 0, 25, 100, or 250 mg kg(-1) day(-1) for a period of 74 days prior to cohabitation, and during mating, gestation, and lactation. Body weights, feed consumption, clinical signs, gross pathology, sperm parameters, estrous cyclicity, and reproductive performance were evaluated for the P1 generation. The F1 offspring were.evaluated during the lactation period for growth and survival and given a gross pathology examination at weaning. A subset of the offspring were retained; body weights, feed consumption, clinical signs, and age at onset of vaginal opening and preputial separation were evaluated, and gross pathology was performed on postnatal day 60. In the developmental toxicity study, groups of time-mated Sprague-Dawley female rats were given the test substance as a suspension in 0.5% aqueous methylcellulose at daily dosages of 0, 50, 200, or 500 mg kg(-1) day(-1) by gavage on gestation days 6-20. During the in-life portion of the study, growth parameters and clinical observations were made. On gestation day 21, dams were euthanized, and the thoracic and abdominal viscera were examined. The uterine contents were removed and examined, and fetuses were evaluated for any alterations. In the reproduction study, litter size at birth, number of live pups per litter on day 0 and 4 of lactation, and pup weights during lactation were reduced in groups administered > or =100 mg kg(-1) day(-1). No other reproductive parameters were affected. There were no adverse reproductive effects observed at 25 mg kg(-1) day(-1). In the developmental toxicity study, reduced maternal body weight parameters, increased perineal fur staining, and increased fetal skeletal alterations were observed at 500 mg kg(-1) day(-1). There was no maternal or developmental toxicity at 50 or 200 mg kg(-1) day(-1). Under the conditions of the studies, the no-observed adverse effect levels for this mixture were 25 mg kg(-1) day(-1) for subchronic toxicity and reproductive parameters and 200 mg kg(-1) day(-1) for developmental toxicity end points. No functional reproductive or developmental effects were observed at dose levels that did not adversely affect adult animals.

Developmental toxicity study of dimethylpiperidone.

The potential maternal and developmental toxicity of dimethylpiperidone (DMPD) was assessed in rats. Groups of 25 mated female Crl:CD (SD)IGS BR rats were exposed by inhalation (whole-body exposures) for approximately six hours per day over days 7-21 of gestation (G); day 1G was the day of copulation plug detection. The exposure levels were 0, 52, 260, or 340 (vapor plus aerosol) mg/m3 DMPD. During the in-life portion, body weights, food consumption, and clinical observation data were collected. On day 22G, the dams were euthanized and examined for gross external and internal alterations. The uterine contents were described and the fetuses were weighed and examined for external, visceral, and skeletal alterations. Maternal toxicity was seen at both 260 and 340 mg/m3. At 340 mg/m3, evidence of maternal toxicity included mortality, increased clinical observations, and decreased body weight and food consumption. At 260 mg/m3, maternal toxicity was limited to increased clinical observations and decreased food consumption. Developmental toxicity was also produced at 260 and 340 mg/m3. At 340 mg/m3, evidence of developmental toxicity included decreased fetal weight, increased embryofetal lethality with concomitant reductions in litter size, and increased fetal malformations and variations. At 260 mg/m3, effects in fetuses were limited to slightly decreased fetal weight and increased fetal variations; additionally, one litter from this level consisted entirely of resorptions. There were no compound-related effects in either dams or fetuses at 52 mg/m3. It was, therefore, concluded that DMPD was not selectively toxic to the rat conceptus.