Correction to: Histological liver chances in Swiss mice caused by tannery effluent.

There is a problem in the original publication of this paper (Figure 2 Graphs are in Portuguese). Shown in this paper is the correct version.

The intake of water containing a mix of pollutants at environmentally relevant concentrations leads to defensive response deficit in male C57Bl/6J mice.

Previous studies have individually confirmed the toxic effects from different pollutants on mammals. However, effects resulting from the exposure of these animals to multi-pollutant mixes have not been studied so far. Thus, the aim of the current study is to assess the effect from the chronic exposure (105days) of C57Bl/6J mice to a mix of pollutants on their response to potential predators. In order to do so, the following groups were formed: "control", "Mix 1× [compounds from 15 pollutants identified in surface waters at environmentally relevant concentration (ERC)]", "Mix 10×" and "Mix 25×" (concentrations 10 and 25 times higher than the ERC). From the 100th experimental day on, the animals were subjected to tests in order to investigate whether they showed locomotor, visual, olfactory and auditory changes, since these abilities are essential to their anti-predatory behavior. Next, the animals' behavior towards potential predators (Felis catus and Pantherophis guttatus) was assessed. The herein collected data did not show defensive response from any of the experimental groups to the predatory stimulus provided by P. guttatus. However, the control animals, only, presented anti-predatory behavior when F. catus was introduced in the apparatus, fact that suggests defensive response deficit resulting from the treatments. Thus, the current study is pioneer in showing that the chronic intake of water containing a mix of pollutants (even at low concentrations) leads to behavioral disorders able to affect the survival and population dynamics of mammalian species at ecological level.

Precopulatory sexual behavior of male mice is changed by the exposure to tannery effluent.

Although the toxic potential of tannery effluents (TE) is acknowledged, the impacts these residues have on mammals who intake water contaminated with this pollutant are not completely known. Thus, in order to broaden the knowledge about how these contaminants affect the biota, the aim of the current study is to assess different behavioral categories (e.g.: sexual odor preference, opposite-sex attraction, and sexual discrimination) related to the sexual motivation and pre-copulation of male Swiss mice subjected to TE intake for 30 days, at concentrations 0.8% and 22%. The animals were subjected to locomotor performance evaluation through the Basso Mouse Scale (BMS), as well as to the open field (OF), odor preference (OPT), sexual orientation (SOT) and to scent marking tests (SMT) one week before the experiment ended. Our results evidenced that the treatments did not affect the animals' locomotor activity (in OF and BMS) or caused changes compatible to anxiogenic or anxiolytic behavior (in OF). However, mice exposed to TE (at both concentrations) presented discriminatory capacity deficit in the OPT test at the time to distinguish conspecific odors from the same sex, and from the opposite sex. They randomly explored (without preference) males and females, did not responded to stimuli in the SOT test, as well as did not appear capable of detecting female odor (in estrus phase) during the SMT. Thus, the current study was pioneer in evidencing that TE can influence the reproduction and the population dynamics of small rodents who intake water contaminated with the pollutant.

Histological liver chances in Swiss mice caused by tannery effluent.

Although tannery effluents are known for being highly toxic to organisms, reports about the effects of the intake of these xenobiotics on experimental mammal models are recent. Studies about the damages the chronic intake of these effluents can cause in the liver of outbred mice remain an unexplored field. Thus, the aim of the present study is to assess (histological) the hepatic condition of Swiss mice (outbred strain) chronically exposed to the intake of different raw tannery effluent concentrations diluted in water for 150 days. Accordingly, the mice (males and females) were divided in the following groups: control group-animals treated with drinking water, only; and groups 5 and 10%-treated with raw tannery effluent diluted in water. After exposure, the animals were subjected to euthanasia for liver fragment sample collection and histological analysis, respectively. Moderate hydropic degeneration was observed in the centrilobular regions of the liver of mice exposed to 5 and 10% tannery effluent, as well as greater amounts of hepatocytes presenting karyomegaly and necrotic hepatocytes, and a smaller amount of Kuffer cells in the liver of mice exposed to the xenobiotic. Finally, animals exposed to 10% tannery effluent showed mild hyperplasia of the bile ducts in the portal areas and fibroblast proliferation around the bile ducts, thus suggesting a fibrous process. Except for the frequency of hepatocytes presenting karyomegaly (lower in females), the herein observed hepatic changes were similar in male and female Swiss mice. Accordingly, the present data support the hypothesis that the chronic intake of tannery effluent by outbred mice (Swiss) causes damages in the liver, a fact that broadens the knowledge about the toxic potential of this pollutant, which goes beyond that of C57Bl/6J male mice (inbred strain).

Mice exposure to tannery effluents changes their olfactory capacity, and their response to predators and to the inhibitory avoidance test.

The current study has assessed whether the oral and/or dermal exposure of C57Bl/6 J mice to tannery effluent (a complex pollutant consisting of xenobiotic mixtures) could damage their olfactory functions, as well as whether it changes their aversive behavior in the inhibitory avoidance test. Accordingly, the animals were distributed in groups which were exposed or not to this xenobiotic through two different routes (oral and dermal), for 15 days. The effluent group subjected to oral exposure received drinking water containing 5% tannery effluent, whereas the animals in the dermal group were exposed to raw tannery effluent for 1 h/day. The animals dermally exposed to the tannery effluent (males and females) have shown the highest latency to find palatable food in the buried food test. The shortest time spent by the animals (orally or dermally) exposed to tannery effluent in the safety zone of the apparatus used in the predator exposure test, as well as the longest time spent by them in the aversive zone, have shown failures in their perception to the risk represented by the presence of the predator (cat). The passive avoidance test results have shown that the dermal exposure to tannery effluent led to partial memory deficit in male and female mice; therefore, the present study has confirmed the tannery effluent toxicity to mammals. Moreover, the present study was pioneer in demonstrating that the dermal exposure to this xenobiotic, even for a short period-of-time, can change the olfactory and cognitive functions of animals, as well as lead to harmful consequences to their health.

Short-term social memory deficits in adult female mice exposed to tannery effluent and possible mechanism of action.

The accumulated organic residues in tannery-plant courtyards are an eating attraction to small rodents; however, the contact of these animals with these residues may change their social behavior. Thus, the aim of the present study is to investigate whether the exposure to tannery effluent (TE) can damage the social recognition memory of female Swiss mice, as well as to assess whether vitamin C supplementation could provide information about how TE constituents can damage these animals' memory. We have observed that resident females exposed to TE (without vitamin supplementation) did not explore the anogenital region, their body or chased intruding females for shorter time or with lower frequency during the retest session of the social recognition test, fact that indicates social recognition memory deficit in these animals. Such finding is reinforced by the confirmation that there was no change in the animals' olfactory function during the buried food test, or locomotor changes in females exposed to the pollutant. Since no behavioral change was observed in the females exposed to TE and treated with vitamin C (before or after the exposure), it is possible saying that these social cognitive impairments seem to be directly related to the imbalance between the cellular production of reactive oxygen species and the counteracting antioxidant mechanisms (oxidative stress) in female mice exposed to the pollutant (without vitamin supplementation). Therefore, the present study evidences that the direct contact with tannery effluent, even for a short period-of-time, may cause short-term social memory deficits in adult female Swiss mice.

Protective effect of vitamin C in female Swiss mice dermally-exposed to the tannery effluent.

Previous studies involving the oral exposure of mice to tannery effluents have found neurotoxic effects. However, studies about the effects the dermal exposure to pollutant have on the cognitive function of females have not been found in the literature. Thus, the aim of the current study is to investigate whether the dermal exposure of female Swiss mice to tannery effluents (2 h/day for 20 days) can cause cognitive impairment, as it was already evidenced in male Swiss mice. Furthermore, based on the administration of vitamin C (before or after the exposure to the xenobiotic), the current study also aims to assess the protective effect of vitamin C in female Swiss mice dermally-exposed to the tannery effluent. Female Swiss mice exposed to the tannery effluent (without vitamin supplementation) have shown lower novel object recognition index during the test session of the novel object recognition task, and they have descended significantly faster from the inhibitory avoidance platform when they were compared to mice belonging to the other groups, therefore evidencing memory deficit. However, the test performance of females receiving vitamin C was similar to that of control animals. Thus, the current study confirms the initial hypothesis that the dermal exposure to the pollutant, even for a short period, causes cognitive deficit in female Swiss mice. The herein presented findings also provide evidence that the mechanisms of action of the tannery effluent in these animals are related to oxidative damages in specific brain regions directed to the formation of short memory to perform aversive and object recognition tasks.

The C57BL/6J mice offspring originated from a parental generation exposed to tannery effluents shows object recognition deficits.

The main aim of the present paper is to assess whether the parental generation exposure to such discharges could cause object recognition deficits in their offspring. Male and female C57Bl/6J mice were put to mate after they were exposed to 7.5% and 15% tannery effluents or water (control group), for 60 days. The male mice were withdrawn from the boxes after 15 days and the female mice remained exposed to the treatment during the gestation and lactation periods. The offspring were subjected to the object recognition test after weaning in order to assess possible cognition losses. The results of the analysis of the novel object recognition index found in the testing session (performed 1 h after the training session) applied to offspring from different experimental groups appeared to be statistically different. The novel object recognition index of the offspring from female mice exposed to tannery effluents (7.5% and 15% groups) was lower than that of the control group, and it demonstrated object recognition deficit in the studied offspring. The present study is the first to report evidences that parental exposure to effluent of tannery (father and mother) can cause object recognition deficit in the offspring, which is related to problems in the central nervous system.

Dermal exposure to tannery effluent causes neurobehavioral changes in C57Bl/6J and Swiss mice.

Tannery effluents constitute highly polluting residues, which can cause negative impacts to people's health and the environment. However, studies that have investigated the effects of the exposure to these xenobiotics on the central nervous system of mammal experimental models are rare, the few that have been published focusing on the exposure via oral intake (ingestion of water containing tannery effluent concentrations). In this sense, and with the objective of expanding the knowledge beyond the neurotoxic effects observed when water contaminated by these xenobiotics is ingested, the neurobehavioral effects of dermal exposure of male C57Bl/6J and Swiss mice were analyzed. The animals were exposed to raw (wet blue-type) tannery effluent for two hours during five days, totalizing 15 days of exposure. Afterwards, the animals underwent the elevated plus-maze (predictive of anxiety) and the object recognition tests (identification of memory deficit). Our data show that the dermal exposure to the tannery effluent caused an anxiogenic behavior in these animals, when compared those that did not have direct contact with these xenobiotics. It was also observed that the animals exposed to the tannery effluent obtained lower novel object recognition indices, thus evidencing memory deficit and indicating a possible influence of the tannery effluent constituents in animal cognition. The present study attests the hypothesis that dermal exposure to tannery effluents containing neurotoxic substances causes behavioral disorders in C57Bl/6J and Swiss mice.

Memory deficit in Swiss mice exposed to tannery effluent.

Although it is known that tannery effluents constitute highly toxic pollutants whose effects in humans represent public health problems in several countries, studies involving experimental mammalian models are rare. In this context, the objective of the present study was to assess the effect of the exposure to tannery effluent on the memory of male and female Swiss mice. Animals of each sex were distributed into two experimental groups: the control group, in which the animals received only drinking water and the effluent group, in which the mice received 1% of gross tannery effluent diluted in water. The animals were exposed to the effluent by gavage, oral dosing, for 15days, ensuring the administration of 0.1mL of liquid (water or effluent)/10g of body weight/day. On the 14th and 15th experimental days the animals were submitted to the object recognition test. It was observed that the new object recognition indices calculated for the animals exposed to the effluent (males and females) were significantly lower than those obtained with the control group. The exposure to tannery effluent caused memory deficit in Swiss mice in a similar way for both sexes, reinforcing previous findings that these pollutants affect the central nervous system. It contributes to the knowledge in the area by attesting harmful effects to the cognition of such animals.