Piotr Lutz

NEUROBEHAVIOURAL FUNCTIONS IN ADULT PROGENY OF RAT MOTHERS EXPOSED TO METHYLMERCURY OR 2,2',4,4',5,5'-HEXACHLOROBIPHENYL (PCB 153) ALONE OR THEIR COMBINATION DURING GESTATION AND LACTATION

OBJECTIVES Methylmercury (MeHg) and polychlorinated biphenyls (PCBs) are ubiquitous environmental pollutants. Both are neurotoxic, especially for the developing brain. The main source of human exposure to MeHg and PCBs is seafood. The aim of the present work was to find out whether and how separate or combined perinatal exposure to these neurotoxicants affects neurobehavioural functions in maturity. MATERIALS AND METHODS The study was performed on adult Wistar rats, the progeny of rat mothers exposed to MeHg (0.5 mg/kg/day or 2.0 mg/kg/day), PCB 153 (1.0 mg/kg/day or 5.0 mg/kg/day), or to MeHg 0.5 mg/kg/day + PCB 153 5.0 mg/kg/day, from day 7 of pregnancy to day 21 post partum. The following functions were assessed: spontaneous locomotor activity (open field test), spatial short-term memory (radial maze test), long-term memory (passive avoidance test), sensitivity to pain and vulnerability to stress (hot plate test), efficiency of the sensorimotor gating (startle response test), and sensorimotor coordination (the rotarod test). RESULTS The results obtained in the MeHg part of the study showed a reduced locomotor activity in the female progeny of both exposed groups, an impaired passive avoidance in the male progeny of the high and low exposure group and a faster recovery from the effects of the stressful experience (hot plate test) in the male progeny of the high dose group. Results obtained in the PCB part showed an increased locomotor activity in the female progeny of both exposure groups and impairment in rotarod performance in males of the high dose group. Neurobehavioural alterations were not found in either the females or males exposed jointly to MeHg and PCB 153. CONCLUSIONS The results suggest that in condition of the combined exposure, MeHg may protect against the effects of PCB 153 and vice versa.

Behavioral effects following repeated exposure to hexachloronaphthalene in rats.

Polychlorinated naphthalenes (PCNs), including hexachloronaphthalene (HxCN), are widespread global environmental contaminants. Our experiments were aimed at assessing HxCN effects on motor behavior, long-term memory, pain sensitivity, magnitude of stress-induced analgesia, auditory function and sensorimotor gating, following repeated intragastric administration (28 days) of HxCN at 0.3 and 1.0 mg/kg body weight. Three weeks after the exposure termination, male Wistar rats were subjected to the neurobehavioral tests battery performed in the following order: open-field test, passive avoidance test, hot-plate test and acoustic startle response test. Repeated administration of HxCN induced disorders of motivational processes manifested by: anorectic effect caused by aphagia and adipsia; significantly reduced motor activity (hypokinesia); impaired long-term memory and acquired passive avoidance reaction; reduced pain threshold and shortened duration of anxiety reaction after pain stimulus (sensory neglect). Some of these neurobehavioral effects (impaired long-term memory, reduced pain threshold and stress-induced analgesia) were observed at 0.3 mgHxCN/kg body weight without any signs of overt toxicity. The outcome of our study shows that HxCN, like other compounds of the persistent organic pollutants (POPs) group, creates a potential risk of behavioral changes in the central nervous system in the general population as a result of environmental exposure.

Alteration in behavioral sensitivity to amphetamine after treatment with oxotremorine. Effect of dose and test environment.

Our earlier experiment revealed that rats pretreated once with an anticholinesterase develop hyposensitivity to amphetamine (AMPH). One of the likely causes of this effect might be a transient hyperexcitation of the central muscarinic receptors. It has appeared, however, that rats pretreated with oxotremorine (OX), a muscarinic agonist, show an augmented behavioral response to AMPH weeks later. The present experiments were performed in order to obtain more information on the relationship between the OX-induced sensitization to AMPH and the OX dose and dosing regime (single or repeated), and to find out whether the environment associated with the acute effects of OX could affect the response to AMPH. In experiment 1, adult male rats were given a single i.p. injection of OX in home cages at a moderate (0.5 mg/kg) or high (1.0 mg/kg) dose. In experiment 2, the rats received eight 1.0 mg/kg doses of OX in the course of three days. After each injection, some animals returned to their home cages, and some were placed in the test cages for 30 min. In both experiments, the response to AMPH was assessed on day 21 after the treatment. The obtained results indicate that: (i) a single i.p. exposure to OX results in an increase of the rats behavioral sensitivity to AMPH but the moderate dose is more effective in inducing this effect; (ii) repeated exposure to OX at high doses, in a regime enabling development of tolerance to the acute OX effects, does not alter the rat sensitivity to AMPH, and (iii) expression of the AMPH response is suppressed in environment which has been associated with acute effects of OX.

Assessment of neurobehavioral and biochemical effects in rats exposed to copper smelter dusts

Female Wistar rats were instilled per os by gavage with different copper dust samples: P-25 obtained by passing the test material through a 25 μmsieve, and P-0.1 containing soluble matter and ultra-fine, non-soluble<100 nm particulate matter (PM) fraction. The control group received sterile saline. The effects were studied at day 1, 7, and 30 post-exposure, focusing on bronchoalveolar lavage fluid (BALF) analysis (including biochemistry, cell morphology, cell viability, and Clara cell 16 protein concentration) and pathomorphology of lung. Results of biochemical tests showed a strong pro-inflammatory effect of both particulate fractions. The morphological studies after exposure to P-25 and P-0.1 fractions showed multi-focal infiltrations in the alveoli. Changes in behavioral (radial maze and passive avoidance tests) have shown that memory in groups exposed to dust was impaired. Our findings indicate that both samples of dust from Copper Smelter cause greater and lesser intensity (P-25 > P-0.1) of the symptoms of acute inflammatory reaction immediately 24 h after instillation to rats. Exposure results in dropping CC16 protein level in serum of rats. After one month, previous acute inflammation was resolved and transformed in persistent low-grade inflammation. The low-grade inflammation resulted in induction of neurobehavioral effects probably by changes in “cholinergic anti-inflammatory pathway” in which acetylcholine modulates neurotransmission.

Fertility and developmental toxicity studies of diethylene glycol monobutyl ether (DGBE) in rats

ObjectivesThe solvent, dimethylene glycol monobutyl ether (DGBE), is a component of latex paints, inks; it is used as a degreasing agent, industrial detergent. The aim of the study was evaluating the effects of DGBE administered by gavage on the estrous cycle and given with drinking water on fertility in rats and early development of their progeny.Materials and MethodsFemale rats were exposed to DGBE by gavage during 8 weeks at 250, 500 or 1000 mg/kg/day. Vaginal smears were collected during the exposure and 4 weeks after its cessation. Fertility studies were performed in male and female animals exposed to in drinking water. Males were exposed for 10 weeks and then mated with females exposed before mating, during pregnancy and lactation. Young animals were observed during 3 weeks after birth.ResultsDGBE does not cause disturbances of the menstrual cycle in females. Parameters used to assess the general toxicity indicate that males receiving DGBE in drinking water are more sensitive to this compound than females: significantly greater, dose-dependent relative spleen weight, significant decrease in hematological parameters from 8% to 15% depending on the dose, were observed. Clinical chemistry parameters (HDL-cholesterol, BUN) and some markers of oxidative stress differ between the exposed groups and the control one, but without adverse health effect. The microscopic examination of internal organs did not reveal morphological changes in male and female rats.ConclusionThe results of our study on the impact of exposure to DGBE on fertility in rats indicate that the substance administered for 9–10 weeks to females and males at a limit dose of 1000 mg/kg did not impair fertility or viability of their offspring during the first three weeks of life.

Comparison of neurobehavioral and biochemical effects in rats exposed to dusts from copper smelter plant at different locations

Mixed exposure to metals (including arsenic and lead) associated with the neurological and respiratory effects constitute one of the major health problems of copper smelting. Chemical composition of the dust, and the expected health effect of inhalation can be very diverse at different parts of the smelter plant. The aims of this study were to compare lung responses and behavioral effects in female Wistar rats after instillation of dust collected from different production processes at the same smelter department. Dusts collected at two different locations of furnace hall were sifted through 25-μm-mesh sieve. Obtained dust fractions, P-25(I) collected near stove, rich in heavy metals and arsenic, and P-25(II) collected near anode residue storage site, rich in aluminium, were instilled to rats. At 1, 7 and 30 days after dusts instillation, lung injury and inflammation were measured by analyzing sings of lung permeability in the bronchoalveolar lavage fluid (BALF), cell differentiation in BALF sediment and lung morphology. The behavioral studies were done 30 days after exposure. Results of biochemical tests showed a strong pro-inflammatory effect of P-25(I) fractions. Mostly characteristic effects after instillation of P-25(I) samples were 10× increased protein leakages in BALF. Both P-25(I) and P-25(II) fractions caused a reduction of Clara-cell 16 protein concentration (CC16) in BALF and activation of serum butyrylcholinesterase (BChE) at all time points. The morphological studies after exposure to P-25(I) fractions showed multi-focal infiltrations in the alveoli. The behavioral results, especially P-25(II) group rats (in open filed, passive avoidance and hot plate tests), indicated adverse effects in the nervous system, which may be related to changes in the dopaminergic and cholinergic pathway. The symptoms were noted in the form of persistent neurobehavioral changes which might be associated with the content of neurotoxic metals. e.g. Al, Mn and/or As. Decrease of CC16 concentration that occurred immediately after instillation of both dust samples, point out impaired anti-inflammatory potential, resulted in early harmful effect not only to the respiratory tract but also to the whole body, including the nervous system.

Neuroendocrine and behavioral response to amphetamine challenge after exposure to an organophosphorus pesticide

ObjectivesExposure to various stressors is known to result in sensitization to psychostimulants, a state related to the psychostimulant dependence and addiction. It has been shown in some studies that the rise in corticosterone (CORT) concentration is indispensable for both the induction and the expression of behavioral sensitization. Therefore, it might be suspected that behavioral hyposensitivity to amphetamine (AMPH) is somehow related to a reduced CORT response to the psychostimulant subsequent to the chlorphenvinphos (CVP) intoxication.Materials and MethodsThe male adult Wistar rats received single i.p. injections of CVP at the doses 0.5, 1.0 or 3.0 mg/kg b.w., or pure corn oil. CORT concentration was determined in samples of blood drawn from the tail vein before and then 30, 60, 180 min and 24 h after injection. The other rats were divided into two groups and tested, three weeks after the CVP injection for the effect of AMPH (0.5 mg/kg b.w. i.p.) on the serum CORT concentration. In addition, behavioral sensitivity to AMPH was assessed by measuring locomotor activity of the animals in an open-field.Results1) The stressor property of CVP was confirmed. The injection resulted in up to tenfold increase in the serum CORT concentration. The magnitude and duration of this response were dose-related. 2) Three weeks after the CVP exposure, the CORT response to AMPH was significantly increased. 3) The behavioral response to the psychostimulant, i.e. augmented locomotion, was significantly reduced compared to the control.ConclusionsThe results confirm that CVP exposure causes behavioral hyposensitivity to AMPH. This effect, however, could not be ascribed to a diminished CORT response.

Developmental toxicity of N-methylaniline following prenatal oral administration in rats.

OBJECTIVES The objective of the study was to assess prenatal toxicity of N-methylaniline (NMA) administered by gavage to pregnant female rats. MATERIAL AND METHODS Pregnant female rats were administered N-methylaniline in corn oil by gavage at daily doses of 0.8 mg/kg of body weight (b.w.), 4 mg/kg b.w., 20 mg/kg b.w. and 100 mg/kg b.w. from implantation (the 5th day post mating) to the day prior to the scheduled caesarean section (the 20th day of pregnancy). General behavior, body weight, food and water consumption, hematological, biochemical analyses and pathomorphological changes of the dams were recorded. RESULTS All the females survived until the end of the study. The test substance was toxic to pregnant females, even at the lowest of the used doses, i.e., 0.8 mg/kg b.w./day. Lower weight gain during pregnancy and significantly higher NMA-dose-dependent absolute weight of the organs were noted in the exposed females. The females from the groups exposed at doses of 20 mg/kg b.w./day and 100 mg/kg b.w./day developed anemia and showed higher concentrations of free thyroxine (FT3) and free triiodothyronine (FT4) thyroid hormones. Total protein concentration exhibited an increase in all the exposed groups of females. In the prenatal toxicity study, administration of N-methylaniline throughout the embryonic and fetal periods produced embryotoxic effects at doses ranging 4-100 mg/kg b.w./day. CONCLUSIONS Considering the data obtained in this study, it is reasonable to assume that N-methylaniline administered orally to pregnant rats is toxic for mothers even at a low dose of 0.8 mg/kg b.w./day. However, this dose was not associated with any significant effects to their offspring. This prenatal exposure level may be considered as no-observed-adverse-effect level (NOAEL) for the progeny and a dose of 4 mg/kg b.w./day as the lowest-observed-adverse-effect level (LOAEL) for the progeny.

Partial protection from organophosphate-induced cholinesterase inhibition by metyrapone treatment

BackgroundOrganophosphates are cholinesterase (ChE) inhibitors with worldwide use as insecticides. Stress response, evidenced by a dramatic and relatively long-lasting (several hours) rise in the plasma glucocorticoid concentration is an integral element of the organophosphate (OP) poisoning symptomatology. In rodents, corticosterone (CORT) is the main glucocorticoid. There are several reports suggesting a relationship between the stressor-induced rise in CORT concentration (the CORT response) and the activity of the cerebral and peripheral ChE. Thus, it seems reasonable to presume that, in OP intoxication, the rise in plasma CORT concentration may somehow affect the magnitude of the OP-induced ChE inhibition. Metyrapone (MET) [2-methyl-1,2-di(pyridin-3-yl)propan-1-one] blocks CORT synthesis by inhibiting steroid 11β-hydroxylase, thereby preventing the CORT response. Chlorfenvinphos (CVP) [2-chloro-1-(2,4-dichlorophenyl) ethenyl diethyl phosphate] is an organophosphate insecticide still in use in some countries.Material and MethodsThe purpose of the present work was to compare the CVP-induced effects — the rise of the plasma CORT concentration and the reduction in ChE activity — in MET-treated and MET-untreated rats. Chlorfenvinphos was administered once at 0.0, 0.5, 1.0 and 3.0 mg/kg i.p. Metyrapone, at 100 mg/kg i.p., was administered five times, at 24-h intervals. The first MET dose was given two hours before CVP.ConclusionThe following was observed in the MET-treated rats: i) no rise in plasma CORT concentration after the CVP administration, ii) a reduced inhibition and a faster restitution of blood and brain ChE activities. The results suggest that MET treatment may confer significant protection against at least some effects of OP poisoning. The likely mechanism of the protective MET action has been discussed.