Reproductive and neurobehavioural effects in three-generation toxicity study of piperonyl butoxide administered to mice

Piperonyl butoxide (PB) was administered continuously to mice from 5 weeks of age in the F₀ generation to weaning of the F₂ generation. PB was administered in the diet at levels of 0 (control), 0.1, 0.2, 0.4 and 0.8%. Selected reproductive, developmental and behavioural parameters were measured. Litter size and litter weight were reduced in higher-dosed groups, and the body weight of the pups in the lactation period was reduced in dosed pups in each generation. The survival index at postnatal day 21 of the group receiving 0.8% PB was reduced in each generation. The developmental and behavioural parameters in the lactation period were little different from those of the controls, apart from olfactory orientation in the F₁ generation. However, in the F₂ generation mice, surface righting, cliff avoidance and olfactory orientation were adversely affected in treatment groups. The results suggest that PB had adverse effects on reproductive, developmental and behavioural parameters of mice, with increasing effects in subsequent generations of offspring.     

Reproductive and neurobehavioural toxicity study of tartrazine administered to mice in the diet.

Tartrazine was given in the diet to provide levels of 0% (control), 0.05%, 0.15%, and 0.45% (approximately 83, 259, 773 mg/kg/day, respectively) from five weeks of age of the F0 generation to nine weeks of age of the F1 generation in mice, and selected reproductive and neurobehavioural parameters were measured. In movement activity of exploratory behaviour in the F0 generation, number of vertical activity was significantly increased in the middle-dose group in males. There were no adverse effects of tartrazine on either litter size, litter weight and sex ratio at birth. The average body weight of male offspring was significantly increased in the high-dose group and that of female offspring was significantly increased in the middle-dose group at birth. In behavioural developmental parameters, surface righting at PND 4 was significantly accelerated in the high-dose group in male offspring, and those effects were significantly dose-related in a trend test (P<0.01). Cliff avoidance at PND 7 was significantly accelerated in the middle-dose group in male offspring. Negative geotaxis at PND 4 was significantly delayed in the high-dose group in female offspring. Other variables measured showed no significant adverse effects in either sex in the lactation period. In movement activity of exploratory behaviour in the F1 generation, number of movement showed a significant tendency to be affected in the treatment groups in male offspring in a trend test (P<0.05). The dose level of tartrazine in the present study produced a few adverse effects in neurobehavioural parameters during the lactation period in mice. Nevertheless, the high-dose level were in excess of the ADI of tartrazine (0-7.5 mg/kgbw), and the actual dietary intake of tartrazine is presumed to be much lower. It would therefore appear that the levels of actual dietary intake of tartrazine is unlikely to produce any adverse effects in humans.     

Reproductive and neurobehavioural toxicity study of erythrosine administered to mice in the diet.

Erythrosine was given in the diet to provide levels of 0 (control), 0.005, 0.015 and 0.045% from 5 weeks of age of the F(0) generation to 9 weeks of age of the F(1) generation in mice, and selected reproductive and neurobehavioural parameters were measured. There were no adverse effects of erythrosine on either litter size, litter weight or sex ratio at birth. The average body weight of the offspring was significantly increased in the middle-dose group in both sexes during the lactation period. In behavioural developmental parameters, any variables showed no significant adverse effects in either sex in the lactation period. In movement activity of exploratory behaviour, several parameters were significantly changed in the high-dose group, and those effects were dose related in adult females in the F(0) and F(1) generations and in male offspring in the F(1) generation. The dose level of erythrosine in the present study produced few adverse effects in reproductive and neurobehavioural parameters in mice.     

Reproductive and neurobehavioural toxicity study of Ponceau 4R administered to mice in the diet.

Ponceau 4R was given to mice in the diet at levels of 0 (control), 0.12%, 0.24%, and 0.48% from 5 weeks of age of the F(0) generation to 9 weeks of age of the F(1) generation, and selected reproductive and neurobehavioural parameters were measured. There was no adverse effect of Ponceau 4R on litter size, litter weight or sex ratio at birth. The average body weight of male and female offspring was increased significantly in the high-dose group at postnatal days (PNDs) 0, 4 and 21. In behavioural developmental parameters, surface righting at PND 4 was affected significantly in the high-dose group in male offspring. Other variables measured showed no consistently significant adverse effect on either sex in the lactation period. In multiple water T-maze performance in the F(1) generation, the time taken was significantly longer than the control in the middle-dose and high-dose groups in males, and those effects were significantly dose-related (P<0.01). The dose level of Ponceau 4R in the present study produced no adverse effect on reproduction, and a few adverse effects on neurobehavioural parameters in mice. The non-observed adverse effect level (NOAEL) was presumed to be 0.12% in the diet (approximately 205mg/kg per day) for maze learning by males in the F(1) generation. Nevertheless, the middle-dose and high-dose levels were in excess of the acceptable daily intake (ADI) of Ponceau 4R (0-4.0mg/kg body weight), and the actual dietary intake of Ponceau 4R in humans is presumed to be much lower. It would appear, therefore, that the level of dietary intake of Ponceau 4R is unlikely to produce any adverse reproductive or neurobehavioural effect in humans.     

Reproductive and neurobehavioural toxicity study of bis(2-ethylhexyl) phthalate (DEHP) administered to mice in the diet.

Bis(2-ethylhexyl) phthalate (DEHP) was given in the diet to provide levels of 0 (control), 0.01, 0.03, and 0.09% from 5 weeks of age of the F0 generation to 9 weeks of age of the F1 generation in mice, and selected reproductive and neurobehavioural parameters were measured. There were no adverse effects of DEHP on either litter size, litter weight or sex ratio at birth. The average body weight of male offspring was significantly decreased in the low-dose group at birth. In behavioural developmental parameters, surface righting at PND 4 was significantly delayed in the low- and middle-dose group in female offspring, and those effects were slightly dose related (P < 0.05). Surface righting at PND 7 was significantly depressed in the high-dose group of male offspring, and those effects were significantly dose related (P < 0.001). That of female offspring was significantly depressed in the low-dose group. The dose level of DEHP in the present study produced few adverse effects in reproductive and neurobehavioural parameters in mice.     

Reproductive and neurobehavioural effects of bis(2-ethylhexyl) phthalate (DEHP) in a cross-mating toxicity study of mice.

Bis(2-ethylhexyl) phthalate (DEHP) was given in the diet to provide levels of 0% (C) or 0.03% (T) from 5 weeks of age of the F0 generation to 9 weeks of age of the F1 generation in mice. At 9 weeks of age, each female was paired with one male from the same or another treatment groups (cross-mating: C/C, T/C, C/T, T/T), for a period of 5 days. The selected reproductive and neurobehavioural parameters were measured. There were no adverse effects of DEHP on either litter size, litter weight and sex ratio at birth. The average body weight of female offspring was significantly affected in group IV (T/T) at PND 14. In behavioural developmental parameters, swimming direction at PND 4 was significantly accelerated in group III (C/T) in female offspring. In movement activity of exploratory behaviour at 3 weeks of age, number of movement of male offspring was significantly affected in group IV (T/T). The dose level of DEHP in the present cross-mating study produced few adverse effects in reproductive and neurobehavioural parameters in mice.     

Short-, medium-, and long-term effects of prenatal oxazepam on neurobehavioural development of mice

A benzodiazepine (oxazepam) was given to nulliparous mice on days 12–16 of pregnancy, and the development and young adult behaviour of the offspring were studied. Experiment 1, using 5, 15, and 50 mg/kg doses given PO twice daily, showed a dose-dependent retardation of postnatal development of several responses such as righting, bar holding, limb placing, and auditory startle. These changes were maximal in the first 2 postnatal weeks and then were markedly attenuated, or disappeared, being apparently related to a temporary retardation of body growth. A reduction of locomotor activity at 60 days was found only in the 50 mg/kg group. The effects of the 15 mg/kg dose on postnatal body growth and neurobehavioural development were replicated in Experiments 2 and 3. Moreover, in these experiments prenatal oxazepam reduced open field activity at 14–16 days and attenuated the hyperactivity induced by dl-amphetamine sulphate (2 mg/kg IP). On the other hand activity, habituation, and response to a scopolamine challenge (2 mg/kg IP) at 21–23 days were not significantly different from those of appropriate controls. Experiment 3, using a cross-fostering procedure, showed that postnatal maternal effects were not responsible for the changes so far mentioned. Experiment 2 also investigated the acquisition of several go-no go avoidance discriminations in a shuttle-box, using either light (L) or buzzer noise (N) as the go signal, a compound no go signal (NL in the L-go groups and LN in the N-go groups), and either an extinction or a passive avoidance contingency during the no go signal (4 weeks of training, starting at 60 days). The main effect of prenatal oxazepam was an impairment of active avoidance responding, while the treatment effects on overall discrimination performance were less marked and limited to the later stages of training.     

Behavioral effects of urotensin-II centrally administered in mice

Urotensin-II (U-II) receptors are widely distributed in the central nervous system. Intracerebroventricular (i.c.v.) injection of U-II causes hypertension and bradycardia and stimulates prolactin and thyrotropin secretion. However, the behavioral effects of centrally administered U-II have received little attention. In the present study, we tested the effects of i.c.v. injections of U-II on behavioral, metabolic, and endocrine responses in mice. Administration of graded doses of U-II (1–10,000 ng/mouse) provoked: (1) a dose-dependent reduction in the number of head dips in the hole-board test; (2) a dose-dependent reduction in the number of entries in the white chamber in the black-and-white compartment test, and in the number of entries in the central platform and open arms in the plus-maze test; and (3) a dose-dependent increase in the duration of immobility in the forced-swimming test and tail suspension test. Intracerebroventricular injection of U-II also caused an increase in: food intake at doses of 100 and 1,000 ng/mouse, water intake at doses of 100–10,000 ng/mouse, and horizontal locomotion activity at a dose of 10,000 ng/mouse. Whatever was the dose, the central administration of U-II had no effect on body temperature, nociception, apomorphine-induced penile erection and climbing behavior, and stress-induced plasma corticosterone level. Taken together, the present study demonstrates that the central injection of U-II at doses of 1–10,000 ng/mouse induces anxiogenic- and depressant-like effects in mouse. These data suggest that U-II may be involved in some aspects of psychiatric disorders.     

A meta-analytical approach to neurobehavioural effects of occupational toluene exposure

Twenty-two studies investigating neurobehavioural effects of toluene were reviewed. Repeatedly applied neuropsychological performance tests and appropriately documented results allowed to include 10 of the studies into a meta-analysis based on effect sizes. Mean exposure level of the studies was 57 ppm (range 20–117 ppm) toluene.

Five of the six analyses of neuropsychological tests obtained effect sizes suggesting a negative impact of toluene, but for none of the analyses a significant effect size was estimated at averaged exposure levels between 33 and 89 ppm. The tests represented the psychological domains of attention and constructional performance. Additionally, the relation between exposure conditions (level of exposure, length of exposure), potential confounders (age, verbal intelligence), and effect sizes was analysed. Only pre-exposure intellectual capacity showed a consistent relation to effect sizes.

The study suggests that homogenisation of study groups with respect to intelligence, cultural background and practice trials is important when investigating low-level exposure. Efforts to homogenize studies should be completed by a thorough documentation of feasible influences.     

The behavioural effects of intravenously administered tryptamine in mice

The behavioural effects of intravenously administered tryptamine were examined in mice. Tryptamine in a dose greater than 15 mg/kg induced distinct head-weaving and hindlimb abduction. These behavioural syndromes appeared immediately after the injection and disappeared within 3 min. The changes in time course of the behaviour induced by tryptamine were consistent with those of the levels of tryptamine in the brain. Pretreatment with p-chlorophenylalanine, a depleter of 5-hydroxytryptamine (5-HT), failed to alter the effects of tryptamine on head-weaving or hindlimb abduction but did result in head-twitches which were never seen after tryptamine alone. Metergoline strongly antagonized the behavior induced by tryptamine. Pirenperone and haloperidol inhibited the behavioural syndrome, antagonizing the head-weaving in particular. alpha-Methyl-p-tyrosine, a depleter of dopamine, reduced the head-weaving without affecting the hindlimb abduction. These results indicate that the 5-HT syndrome induced by intravenous administration of tryptamine is due to the direct effect of tryptamine on the 5-HT receptor. Tryptamine-induced behaviour, especially head-weaving, seems to be linked with dopaminergic neurones.     

Embryotoxic and teratogenic effects of intraperitoneally administered metavanadate in mice.

Metavanadate was evaluated for developmental toxicity in pregnant Swiss mice. Sodium metavanadate (NaVO3) was administered intraperitoneally on d 6-15 of gestation at doses of 0, 2, 4, or 8 mg/kg/d. On gestation d 18, all live fetuses were examined for external, visceral, and skeletal malformations and variations. Maternal toxicity was observed at 2, 4, and 8 mg/kg/d as evidenced by decreased weight gain during treatment. Increased resorptions and dead fetuses, increased percentage postimplantation loss, and reduced fetal body weight per litter were observed at 4 and 8 mg/kg/d. There were no significant increases in the type or incidence of external and skeletal anomalies, but a significant increase in the incidence of cleft palate was detected at 8 mg/kg/d. The lowest-observed-adverse-effect level (LOAEL) for maternal toxicity was 2 mg NaVO3/kg/d, while 2 mg/kg/d was also the no-observed-adverse-effect level (NOAEL) for significant developmental toxicity.     

Behavioral effects of intracerebroventricularly administered neurohypophyseal hormone analogs in mice

The neurohypophyseal hormones oxyutocin and vasopressin evoke characteristic behavioral changes after intracerebroventricular injection in mice. These include the induction of excessive grooming and scratching in aronment and of escape behavior in stressful situations. The structure-activity relations of 33 neurohypophyseal hormones and hormone analogs in the induction of these behavioral changes were examined. The results demonstrate that these effects generally parallel the vasoconstrictory effects of the peptides. It is suggested that the behavioral effects are mediated by a receptor that is closely related biochemically to the vasopressin receptors in blood vessels. They are not related to the long-term effects of neurohypophyseal hormones on learned behavior. A competitive antagonist of the short-term behavioral effects of these peptides is described. This analog also antagonizes some of the hormonal effect of vasopressin and related peptides.     

A summary of two meta-analyses on neurobehavioural effects due to occupational lead exposure

The conclusions from published results about neurotoxic effects of inorganic lead exposures <700 microg lead/l blood are contradictory at present. Effects measured by neurobehavioural methods are evaluated differently as far as recommendations for a Biological Exposure Index (BEI) of occupational lead exposure are concerned. Arguments against the German BEI of 400 microg/l were put forward in new publications, and discussion of the issues is the aim of this article. It summarizes two different meta-analytical reviews on neurobehavioural effects in order to show the main tendencies of 24 selected publications on the matter. Calculations on effect sizes are compiled for 12 tests analysed in two meta-analyses and of ten tests analysed in one of the meta-analyses. The survey of six tests of learning and memory gives hints on impairments measured with two tests, covering Logical Memory and Visual Reproduction. The survey of seven tests of attention and visuospatial information processing describes impairments in four tests, namely Simple Reaction, Attention Test d2, Block Design, and Picture Completion. The survey of four tests for psychomotor functions shows impairments for three tests, namely Santa Ana, Grooved Pegboard, and Eye-hand Coordination. These test results provide evidence for subtle deficits being associated with average blood lead levels between 370 and 520 microg/l. In evaluating the adversity of such effects it is concluded that the results of both meta-analytical reviews support the recommendation for the German BEI.     

Exposure to metal oxide nanoparticles administered at occupationally relevant doses induces pulmonary effects in mice

In spite of the great promises that the development of nanotechnologies can offer, concerns regarding potential adverse health effects of occupational exposure to nanoparticle (NP) is raised. We recently identified metal oxide NP in lung tissue sections of welders, located inside macrophages infiltrated in fibrous regions. This suggests a role of these NP in the lung alterations observed in welders. We therefore designed a study aimed to investigate the pulmonary effects, in mice, of repeated exposure to NP administered at occupationally relevant doses. We therefore chose four metal oxide NPs representative of those found in the welder’s lungs: Fe₂O₃, Fe₃O₄, MnFe₂O₄ and CrOOH. These NPs were administered weekly for up to 3 months at two different doses: 5?μg, chosen as occupationally relevant to welding activity, and 50?μg, chosen as occupationally relevant to the context of an NP-manufacturing facility. Our results show that 3 month-repeated exposures to 5?μg NP induced limited pulmonary effects, characterized by the development of a mild peribronchiolar fibrosis observed for MnFe₂O₄ and CrOOH NP only. This fibrotic event was further extended in terms of intensity and localization after the repeated administration of 50?μg NP: all but Fe₂O₃ NP induced the development of peribronchiolar, perivascular and alveolar fibrosis, together with an interstitial inflammation. Our data demonstrate for the first time a potential risk for respiratory health posed by repeated exposure to NP at occupationally relevant doses. Given these results, the development of occupational exposure limits (OELs) specifically dedicated to NP exposure might therefore be an important issue to address.     

Reproductive and genomic effects in testes from mice exposed to the water disinfectant byproduct bromochloroacetic acid

A byproduct of drinking water disinfection, bromochloroacetic acid (BCA), acts as a reproductive toxicant in rats. To determine if BCA produces similar reproductive toxicity in mice, juvenile and adult C57BL/6 males were exposed to 0, 8, 24, 72 or 216 mg/kg of BCA once daily for 14 days. Five of 12 animals from each dose-group were sacrificed at the end of dosing, and testes, epididymes, and seminal vesicles harvested and weighed. Seven mice from each dose-group (including juvenile-exposed mice, following a 14-week maturation period) were used in a 40-day sequential breeding assay to determine if BCA targets a particular phase of spermatogenesis. No significant effects were observed in mice exposed to BCA as juveniles, and there were no effects on fertility by 14 weeks after dosing. However, effects were observed in adult-exposed mice over the first 10 days after BCA exposure: mean number of litters/male, percentage of litters/female bred, and total number of fetuses/male were all reduced by 72 and 216 mg/kg BCA. These results in adult mice indicate BCA disrupted differentiation of spermatids during dosing and the first 10 days of mating, and are consistent with the spermatid retention and atypical residual bodies observed in animals exposed to 72 and 216 mg/kg BCA. To investigate mechanisms involved, we utilized cDNA microarrays containing 950 testis-expressed genes to profile gene expression from Control and BCA-treated mice. Statistical analyses of microarray results identified 40 well-characterized genes differentially expressed in a dose responsive manner as a result of BCA exposure. Microarray results were supplemented with quantitative real-time PCR and Westerns for several genes and proteins. The 40 genes whose expression was altered by BCA are involved in numerous biological processes including: cell communication and adhesion, cell cycle and cell proliferation, metabolism, signal transduction, stress response, and spermatogenesis and male fertility. Modulated expression of these genes, particularly the 15 expressed in Sertoli cells and spermatids, offers new insights into potential mechanisms of BCA toxicity in the mouse testis.     

Neonatal iron exposure induces neurobehavioural dysfunctions in adult mice.

Excess iron in the brain has been implicated in the pathogenesis of several human neurodegenerative disorders, i.e., Parkinson's and Alzheimer's disease. The neonatal period is critical for the establishment of normal iron content in the adult brain. In the present study, the long-term neurobehavioral effects of iron exposure during this period were assessed by treating NMRI mice orally with 0.0, 3.7, or 37.0 mg Fe(2+)/kg body wt on postnatal days 10-12. Spontaneous motor behavior and radial arm maze learning were tested at the age of 3 months. It was found that the mice treated with the higher dose of Fe(2+), 37.0 mg/kg body wt, were hypoactive during the first 20 min of testing but hyperactive during the final 20 min, showing an almost complete lack of habituation of spontaneous activity in the test chambers. These changes were also seen in animals treated with the lower dose of Fe(2+), 3.7 mg/kg body wt, but the effects were less pronounced, indicating a dose-response relationship. In the radial arm maze, the Fe(2+) 37.0 mg/kg group evidenced significantly both more errors in arm choices and longer latencies to acquire all eight pellets. Both dose groups showed attenuated performance increments on successive trials. Analysis of brain iron content indicated significantly more total iron (microgram/g) in the basal ganglia, but not frontal cortex, of the higher, 37 mg/kg, dose group. The knowledge of the long-term effects of iron entering the brain during this critical period of rapid brain growth is limited. Increased amounts of iron in the brain, especially in the basal ganglia, may contribute to neurodegenerative processes.