Effects of Environmental Enrichment on Exposure to Human-Relevant Mixtures of Endocrine Disrupting Chemicals in Zebrafish

Fish models used for chemical exposure in toxicological studies are normally kept in barren tanks without any structural environmental enrichment. Here, we tested the combined effects of environmental enrichment and exposure to two mixtures of endocrine disrupting chemicals (EDCs) in zebrafish. Firstly, we assessed whether developmental exposure to an EDC mixture (MIX G1) combined with rearing the fish in an enriched environment influenced behaviour later in life. This was evaluated using locomotion tracking one month after exposure, showing a significant interaction effect between enrichment and the MIX G1 exposure on the measured locomotion parameters. After three months, we assessed behaviour using custom-made behaviour tanks, and found that enrichment influenced swimming activity. Control fish from the enriched environment were more active than control fish from the barren environment. Secondly, we exposed adult zebrafish to a separate EDC mixture (MIX G0) after rearing them in a barren or enriched environment. Behaviour and hepatic mRNA expression for thyroid-related genes were assessed. There was a significant interaction effect between exposure and enrichment on swimming activity and an effect of environment on latency to approach the group of conspecifics, where enriched fish took more time to approach the group, possibly indicating that they were less anxious. Hepatic gene expression of a thyroid-related gene (thrb) was significantly affected by EDC exposure, while enrichment had no discernible impact on the expression of the measured genes. In conclusion, environmental enrichment is important to consider when studying the effects of EDCs in fish.

From cohorts to molecules: Adverse impacts of endocrine disrupting mixtures

Convergent evidence associates exposure to endocrine disrupting chemicals (EDCs) with major human diseases, even at regulation-compliant concentrations. This might be because humans are exposed to EDC mixtures, whereas chemical regulation is based on a risk assessment of individual compounds. Here, we developed a mixture-centered risk assessment strategy that integrates epidemiological and experimental evidence. We identified that exposure to an EDC mixture in early pregnancy is associated with language delay in offspring. At human-relevant concentrations, this mixture disrupted hormone-regulated and disease-relevant regulatory networks in human brain organoids and in the model organisms Xenopus leavis and Danio rerio, as well as behavioral responses. Reinterrogating epidemiological data, we found that up to 54% of the children had prenatal exposures above experimentally derived levels of concern, reaching, for the upper decile compared with the lowest decile of exposure, a 3.3 times higher risk of language delay.

Thyroid function and immune status in perch (Perca fluviatilis) from lakes contaminated with PFASs or PCBs

The environment contains a multitude of man-made chemicals, some of which can act as endocrine disruptors (EDCs), while others can be immunotoxic. We evaluated thyroid disruption and immunotoxic effects in wild female perch (Perca fluviatilis) collected from two contaminated areas in Sweden; one site contaminated with per- and polyfluoroalkyl substances (PFASs) and two sites contaminated with polychlorinated biphenyls (PCBs), with one reference site included for each area. The hepatic mRNA expression of thyroid receptors α and β, and the thyroid hormone metabolising iodothyronine deiodinases (dio1, dio2 and dio3) were measured using real-time PCR, while the levels of thyroid hormone T3 in plasma was analysed using a radioimmunoassay. In addition, lymphocytes, granulocytes, and thrombocytes were counted microscopically. Our results showed lower levels of T3 as well as lower amounts of lymphocytes and granulocytes in perch collected from the PFAS-contaminated site compared to reference sites. In addition, expressions of mRNA coding for thyroid hormone metabolising enzymes (dio2 and dio3) and thyroid receptor α (thra) were significantly different in these fish compared to their reference site. For perch collected at the two PCB-contaminated sites, there were no significant differences in T3 levels or in expression levels of the thyroid-related genes, compared to the reference fish. Fish from one of the PCB-contaminated sites had higher levels of thrombocytes compared with both the second PCB lake and their reference lake; hence PCBs are unlikely to be the cause of this effect. The current study suggests that lifelong exposure to PFASs could affect both the thyroid hormone status and immune defence of perch in the wild.

Assessing the effects of textile leachates in fish using multiple testing methods: From gene expression to behavior

The textile industry, while of major importance in the world economy, is a toxic industry utilizing and emitting thousands of chemical substances into the aquatic environment. The aim of this project was to study the potentially harmful effects associated with the leaching of chemical residues from three different types of textiles: sportswear, children's bath towels, and denim using different fish models (cell lines, fish larvae and juvenile fish). A combination of in vitro and in vivo test systems was used. Numerous biomarkers, ranging from gene expression, cytotoxicity and biochemical analysis to behavior, were measured to detect effects of leached chemicals. Principle findings indicate that leachates from all three types of textiles induced cytotoxicity on fish cell lines (RTgill-W1). Leachates from sportswear and towels induced mortality in zebrafish embryos, and chemical residues from sportswear reduced locomotion responses in developing larval fish. Sportswear leachate increased Cyp1a mRNA expression and EROD activity in liver of exposed brown trout. Leachates from towels induced EROD activity and VTG in rainbow trout, and these effects were mitigated by the temperature of the extraction process. All indicators of toxicity tested showed that exposure to textile leachate can cause adverse reactions in fish. These findings suggested that chemical leaching from textiles from domestic households could pose an ecotoxicological threat to the health of the aquatic environment.

Understanding the gastrointestinal physiology and responses to feeding in air-breathing Anabantiform fishes

The Mekong Delta is host to a large number of freshwater species, including a unique group of facultative air-breathing Anabantiforms. Of these, the striped snakehead (Channa striata), the climbing perch (Anabas testudineus), the giant gourami (Osphronemus goramy) and the snakeskin gourami (Trichogaster pectoralis) are major contributors to aquaculture production in Vietnam. The gastrointestinal responses to feeding in these four species are detailed here. Relative intestinal length was lowest in the snakehead, indicating carnivory, and 5.5-fold greater in the snakeskin, indicating herbivory; climbing perch and giant gourami were intermediate, indicating omnivory. N-waste excretion (ammonia-N + urea-N) was greatest in the carnivorous snakehead and least in the herbivorous snakeskin, whereas the opposite trend was observed for net K⁺ excretion. Similarly, the more carnivorous species had a greater stomach acidity than the more herbivorous species. Measurements of acid-base flux to water indicated that the greatest postprandial alkaline tide occurred in the snakehead and a potential acidic tide in the snakeskin. Additional findings of interest were high levels of both PCO₂ (up to 40 mmHg) and HCO₃ ^- (up to 33 mM) in the intestinal chyme of all four of these air-breathing species. Using in vitro gut sac preparations of the climbing perch, it was shown that the intestinal net absorption of fluid, Na⁺ and HCO₃ ^- was upregulated by feeding but not net Cl^- uptake, glucose uptake or K⁺ secretion. Upregulated net absorption of HCO₃ ^- suggests that the high chyme (HCO₃ ^- ) does not result from secretion by the intestinal epithelium. The possibility of ventilatory control of PCO₂ to regulate postprandial acid-base balance in these air-breathing fish is discussed.

Flow and Tracer Experiments in Crystalline Rocks: Results from Several Swedish in Situ Experiments

In a final repository for radioactive waste in crystalline rock, water flowing in the fractures may transport the radionuclides eventually leached from the waste. To be able to predict the migration of the radionuclides the processes involved must be understood. To quantify the processes, data from flow and transport in real fractures under realistic conditions are needed. Models used for prediction must include descriptions of the important processes and mechanisms.

Origin of sympathetic and sensory innervation of the endolymphatic sac. A retrograde axonal tracing study in the guinea pig

Lectin-conjugated horseradish peroxidase (WGA-HRP) was used as a retrograde axonal tracer to determine endolymphatic sac (ES) innervation and the nature of such a nervous supply. WGA-HRP placed into the ES of the guinea pig resulted in labelling of neurons in the ipsilateral sympathetic superior cervical ganglion and the sensory trigeminal ganglion. The number of labelled neurons in the cervical superior ganglion varied according to the survival time with peak labelling occurring after 48 h. Sparse labelling of the sensory trigeminal ganglion was also present after 48 h. The results indicate that sympathetic neurons from the superior cervical ganglion and to a certain extent trigeminal somatosensory neurons innervate the ES or perisaccular tissue. If these findings reflect the existence of a sympathetic functional reflex unit remains to be elucidated.

Modern oral contraceptives and dysmenorrhoea

Women with primary dysmenorrhoea not sufficiently helped by triphasic oral contraceptives (OCs) were offered a modern, low-dose monophasic OC containing 30 micrograms of ethinylestradiol and 150 micrograms of desogestrel. The study shows that for these women, the monophasic pill was the better alternative. The fact that 19 of 23 women who continue treatment on the monophasic OC indicates that this type of pill may be chosen as the first alternative for women with primary dysmenorrhoea.

Effect of Tranylcypromine on Platelet Aggregation Induced by Thrombin, ADP, Adrenaline, Collagen and Arachidonic ACID

The monoaminooxidase inhibitor tranylcypromine has been suggested to be a selective inhibitor of prostacyclin synthetase with no inhibitory effect on thromboxane A2 formation in platelets. The substance would then be a suitable tool for discrimination between prostacyclin synthesis and release on one hand and other possible thrombocytophobic properties of the endothelial cell particularly its surface on the other. This study, however, shows that tranylcypromine interferes with platelet aggregation induced by thrombin, ADP, adrenaline and collagen whereas that of arachidonic acid is not affected. The results indicate an inhibition at an earlier common pathway of platelet aggregation than the metabolism of arachidonic acid. It is also suggested that the search for a selective inhibitor of prostacyclin synthesis which does not interfere with platelet functions should continue.