Bovine-derived hemoglobin-based oxygen carriers (HBOCs) have been investigated for use in humans (HBOC-201) and approved for veterinary medicine (HBOC-301). We infused pregnant beagles with HBOC-201 to test whether HBOC-induced developmental toxicity previously observed in rats would occur in a species devoid of an inverted visceral yolk sac (invVYS). Phase 1 assessed developmental toxicity of 6g/kg HBOC-201 on gestational day (GD) 21. Phase 2 investigated single infusions of 6g/kg HBOC-201 on one of GDs 21, 25, 29 or 33. Phase 3 studied multiple sequential infusions on GDs 21, 23,25,27,29, 31, and 33 at 0.52g/kg/day (3.6g/kg total dose). Mild to moderate maternal toxicity occurred in all phases. There was an unequivocal absence of developmental toxicity in all phases. Overall, our hypothesis that HBOC, which interferes with the function of the invVYS, would not affect the offspring in dogs was supported. The implications relative to human risk are discussed.

HBOC-201 is a bovine-derived, cross-linked, and stabilized hemoglobin (250 kDa) in physiological saline. Daily intravenous infusions of HBOC (1.95, 3.90, or 5.85 g/kg/day) during gestational days (GDs) 6-18 in Sprague-Dawley rats caused fetal mortality, reduced birth weight, and malformations. Subsequent single-day infusions (5.85 g/kg/day) showed that developmental toxicity was limited to GDs 7-9 when histiotrophic nutrition via the inverted visceral yolk sac (invVYS) is essential. Histiotrophic nutrition is receptor-mediated endocytosis of bulk maternal proteins and subsequent lysosomal degradation providing amino acids and other nutrients for embryonic growth. Controls for protein content, oncotic properties, and hemoglobin content indicated that toxicity was due to hemoglobin. Rat whole embryo cultures verified HBOC interference with invVYS transport capacity and resultant deficient embryonic nutrition. These mechanisms of action are not expected to impact human development based on differences in VYS morphology and function, although a complete understanding of early human embryonic nutrition is lacking. (C) 2015 Published by Elsevier Inc.

Spontaneous ejaculation has been reported in a variety of mammalian species and may occur either as a result of pharmacological treatment or as a component of the daily behavior of normal, untreated animals. Infrequently, increased numbers of spontaneous ejaculatory plugs have been reported among the clinical signs in rat toxicology studies. This mini-review presents an overview on the presence of ejaculatory plugs in rodents and provides recommendations to consider when attempting to understand the toxicological significance of increased numbers of ejaculatory plugs in rat toxicology studies.

Methyl iodide (MeI) induces fetotoxicity in New Zealand White (NZW) rabbits when maternal exposure occurs during a susceptible window late in gestation (gestation days [GD] 23–26). To identify the possible mode of action, comprehensive maternal and fetal bioanalysis and thyroid structure/function assessments were conducted in MeI-exposed (25 ppm by whole-body inhalation) and unexposed time-mated NZW rabbits (10/group) during GD 21–27. Key developmental events were observed within this window in unexposed fetuses, including the appearance of colloid in the thyroid follicular lumen and the detection of serum T3 beginning on GD 22. Fetal T4 and T3 levels were diminished following maternal MeI exposure compared to baseline values. Fetal TSH was significantly increased following 4 days of maternal MeI exposure. MeI-induced changes in the fetal thyroid included reduced colloid formation, epithelial follicular hypertrophy, and epithelial cytoplasmic vacuolation. Time-course investigations using 20 ppm MeI revealed highly concentrated levels of iodide in fetal versus maternal serum. Direct maternal administration of sodium iodide by intravenous infusion during GD 23–26 induced similar effects on fetal thyroid structure and function as MeI, identifying iodide as the putative agent. Elevated S-methylcysteine adduct concentrations were noted in fetal hemoglobin, indicating that some unreacted MeI may be delivered directly to the fetus. However, the weight of evidence from these studies suggests that late-stage fetal death following maternal exposure to MeI during GD 23–26 is the result of preferential accumulation of iodide in the fetal compartment causing disruption of the fetal hypothalamic–pituitary–thyroid axis at a critical time in the development of the rabbit fetal thyroid.

Methyl iodide (Mel), an intermediate used in the manufacture of some insecticides and pharmaceuticals, is under review for U.S. registration as a non-ozone-depleting alternative to methyl bromide in the pre-plant soil fumigation market. Guideline (OPPTS 870.3700) developmental toxicity studies in New Zealand White (NZW) rabbits showed dose-dependent increases in the litter proportions of late fetal deaths and postimplantation loss and/or decreased fetal body weight following inhalation exposure of pregnant rabbits to Mel during gestation days (GD) 6-28. A subsequent phased-exposure study was performed to pinpoint the critical window of gestational exposure that produced the rabbit fetotoxicity. Artificially inseminated NZW female rabbits were exposed to 20 ppm Mel vapors by whole-body inhalation (6 h/day) throughout major organogenesis and fetal development (GD 6-28), during early gestation (GD 6-14) or mid-gestation (GD 15-22) only, or during 2-day intervals late in gestation (GD 23-24, 25-26, or 27-28). No maternal or developmental toxicity was elicited from maternal exposure during GD 6-14,15-22, or 27-28. However, Mel-related fetotoxicity, including increased litter proportions of late fetal deaths with or without corresponding decreases in fetal body weight, were observed for females exposed during GD 6-28 (p<.01), 23-24 and 25-26. Although the increase in late-stage fetal death for each of the 2-day exposures on GD 23-24 and GD 25-26 was not statistically significant, as noted for the combined total of fetal deaths during the GD 6-28 exposure, it can be deduced that the gestational window of GD 23-26 was the most susceptible window of exposure for eliciting developmental toxicity in rabbits exposed to Mel vapors.

Rats were rapidly trained to discriminate between 0.8 mg/kd d-amphetamine and 6 mg/kg pentobarbital in a two-lever food-motivated operant task by imposing the drug states from the earliest stage of training, i.e., at the initiation of shaping to lever-press. Once trained, rats were administered each of the training drugs and were allowed to lever press without reinforcement until 10 responses were made on the lever that was not their first choice lever selection. By employing this extended schedule of responding in extinction, the amphetamine-induced interoceptive cue was observed to produce equivalent perseverance as that produced by pentobarbital. However, the administration of saline, the non-drugged state, produced significantly more pentobarbital-appropriate responding than amphetamine-appropriate responding when tested during the daytime, whereas it produced random responding when tested during the night. The results suggest that the arousal state of the rat, a nocturnal species, may differentially influence saline tests in the daytime and in the night time.

Octamethylcyclotetrasiloxane (D4) has been shown to have effects on the female rat reproductive cycle. This study evaluated the phase of the female rat reproductive cycle affected by D4 using a study design that allowed the complete female reproductive cycle, as well as phases of the cycle, from pre-mating through gestation, to be evaluated. Rats were exposed via whole body vapor inhalation up to 700ppm D4 during the overall phase (28 days prior to mating through gestation day (GD) 19), the ovarian phase (31–3 days prior to mating), the fertilization phase (3 days prior to the start of mating through gestation day 3), and the implantation phase (GD 2–GD 5) of the reproductive cycle. D4 was associated with decreases in implantation sites and litter size in the overall and fertilization phases, but not in the ovarian or implantation phases. In order to further define the sensitive period for D4 exposure, additional groups of rats were exposed on single days. A single 6h exposure to D4 on the day prior to mating resulted in a significant reduction in fertility. These data indicate that there is a very narrow window, around the time of ovulation and fertilization, for D4 to exert effects on the reproductive cycle of the female rat. Subsequent research, reported elsewhere, has elucidated the mode of action and assessed its potential relevance to humans.

S-111-S-WB (CAS No. 72968-38-8), a mixture of perfluoro fatty acid ammonium salts, was administered daily via oral gavage to 30 Crl:CD(SD) rats/sex/group at 0.025, 0.125 and 0.6mg/(kgday) over two generations to assess potential reproductive toxicity. Reproductive performance, mean litter size, pup survival and pup weights were unaffected. Lower mean body weights were observed in 0.6mg/(kgday) group F(0) and F(1) males. Higher liver weights, correlating to hepatocellular hypertrophy in the 0.6mg/kg group, were noted for parental males in the 0.125 and 0.6mg/(kgday) groups, parental females in the 0.6mg/(kgday) group and F(1) pups in the 0.125 and 0.6mg/(kgday) groups. Higher kidney weights, correlating to renal tubule hypertrophy in the 0.6mg/kg group, were observed for parental males and females in the 0.125 and 0.6mg/(kgday) groups. Systemic exposure (measured only in females) to total S-111-S-WB was proportional to dose following 9 weeks of daily administration on the gestation day 19. Total S-111-S-WB concentration in the serum of male and female pups was 1.2-1.4-fold higher than in the dams 2h following administration to the dams on lactation day 13. A dosage level of 0.6mg/(kgday) was considered to be the no-observed-adverse-effect level (NOAEL) for reproductive function. A dosage level of less than 0.025mg/(kgday) was considered to be the NOAEL for F(0) and F(1) parental systemic toxicity based on microscopic hepatic findings in the males of all test article groups, and a dosage level of 0.025mg/(kgday) was considered to be the NOAEL for neonatal toxicity based on higher liver weights in the F(1) and F(2) pups at 0.125mg/(kgday) and higher.

This study evaluated the potential toxicity of whole-body vapor inhalation of octamethylcyclotetrasiloxane (D4) on reproductive capabilities in exposed F0 and F1 parental animals and the potential effects on neonatal survival, growth, and development of the F1 and F2 offspring. F0 male and female Sprague–Dawley rats (30/sex/group) were exposed to D4 vapor at concentrations of 0, 70, 300, 500 or 700 ppm 6 h per day for at least 70 consecutive days prior to mating and lasted through weaning of the pups on postnatal day (PND) 21. Female exposures were suspended from gestation day (GD) 21 through PND 4 to allow for parturition and permit continuous maternal care for the early neonates. Starting on PND 22, F1 weanlings were exposed to D4 as described for the F0 generation. The F2 pups were not directly exposed to D4. F0 animals were mated once to produce the F1 generation; F1 parental animals were mated twice to produce two F2 litters. In addition, the F1 males were mated with unexposed females. Prolonged estrous cycles, decreased mating and fertility indices were observed in the F1 generation exposed to D4 for the first and second matings. Significant reductions in the mean number of pups born and mean live litter size were observed in the 500 and 700 ppm groups for both the F0 and F1 generations. Implantation sites were also reduced at 700 ppm for both F0 and F1 generations. No adverse effects were observed at any exposure level on anogenital distance, vaginal patency and preputial separation. No adverse effects were seen on male functional reproductive parameters, spermatogenic endpoints, microscopic evaluation of male reproductive tissue, or when the D4-exposed F1 males were mated with the unexposed females, demonstrating that the reproductive toxicity observed was due to D4 exposure to the females. Based on the lack of effect on reproduction when the D4-exposed males were mated to näive females, the NOAEL for male reproductive toxicity was considered to be 700 ppm. Based on the statistically significant effects on fertility and litter size, NOAEL for female reproductive toxicity was considered to be 300 ppm. The findings observed in this study are consistent with suppression or delaying of LH surge as well as acceleration of the onset of female reproductive senescence in the rat. While analogous pathways control ovulation in both rats and humans, there are significant differences in the mechanism for timing and release of LH and resulting changes in the control of ovulation and mating behavior between the two species. If D4 delays rather than causes a prolonged suppression or ablation of the LH surge, the reproductive mode of action of D4 would not likely be relevant for humans.

This two-generation reproduction study assessed the reproductive hazard potential of decamethylcyclopentasiloxane (D5). Sprague–Dawley rats (30/sex/group) were exposed by whole-body vapor inhalation to a target concentration of 30, 70, or 160 ppm D5 or filtered air for 6 h/day. Exposures for the F0 and F1 generations started at least 70 days prior to mating and lasted through weaning of the respective pups on postnatal day (PND) 21. Female exposures were interrupted from gestation day (GD) 21 through PND 4 to allow for parturition and to permit continuous maternal care for the early neonates. F2 pups were not directly exposed to D5. There were no exposure-related mortalities, clinical signs of toxicity, or effects on body weight or food consumption. There were no treatment-related gross findings or organ weight effects at the F0 and F1 necropsies. Other than minimal alveolar histiocytosis in all exposed groups, there were no noteworthy microscopic findings. Reproductive parameters (number of days between pairing and mating, mating and fertility indices, gestation length, and parturition), spermatogenic parameters and ovarian primordial follicle counts and numbers of corpora lutea in the F0 and F1 parental animals were not significantly changed between treated and control groups. Mean live litter sizes, number of pups born, sex ratios, pup body weights, postnatal pup survival and general physical condition of offspring in each generation were not affected. The slight, but statistically significant, increase in the mean F1 male pup AGD in the 160 ppm group was not considered to be related to treatment. Vaginal patency and balanopreputial separation were unchanged compared to controls. Thus, the No-Observed-Adverse-Effect-Level (NOAEL) for parental and reproductive toxicity was determined to be 160 ppm D5.

One of the principal applications of toxicology data is to inform risk assessments and support risk management decisions that are protective of human health. Ideally, a risk assessor would have available all of the relevant information on (a) the toxicity profile of the agent of interest; (b) its interactions with living systems; and (c) the known or projected exposure scenarios: to whom, how much, by which route(s), and how often. In practice, however, complete information is seldom available. Nonetheless, decisions still must be made. Screening-level assays and tools can provide support for many aspects of the risk assessment process, as long as the limitations of the tools are understood and to the extent that the added uncertainty the tools introduce into the process can be characterized and managed. Use of these tools for decision-making may be an end in itself for risk assessment and decision-making or a preliminary step to more extensive data collection and evaluation before assessments are undertaken or completed and risk management decisions made. This paper describes a framework for the application of screening tools for human health decision-making, although with some modest modification, it could be made applicable to environmental settings as well. The framework consists of problem formulation, development of a screening strategy based on an assessment of critical data needs, and a data analysis phase that employs weight-of-evidence criteria and uncertainty analyses, and leads to context-based decisions. Criteria for determining the appropriate screening tool(s) have been identified. The choice and use of the tool(s) will depend on the question and the level of uncertainty that may be appropriate for the context in which the decision is being made. The framework is iterative, in that users may refine the question(s) as they proceed. Several case studies illustrate how the framework may be used effectively to address specific questions for any endpoint of toxicity.

Birth Defects Research Part A: Clinical and Molecular TeratologyVolume 76, Issue 5 p. 313-340 Platform Session Abstracts Teratology Society Platform Session Abstracts First published: 17 May 2006 https://doi.org/10.1002/bdra.20261Citations: 1AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat Citing Literature Volume76, Issue5May 2006Pages 313-340 RelatedInformation