Mysid crustaceans as standard models for the screening and testing of endocrine-disrupting chemicals

Author Posting. © Springer, 2007. This is the author's version of the work. It is posted here by permission of Springer for personal use, not for redistribution. The definitive version was published in Ecotoxicology 16 (2007): 205-219, doi:10.1007/s10646-006-0122-0.Investigative efforts into the potential endocrine-disrupting effects of chemicals have mainly concentrated on vertebrates, with significantly less attention paid to understanding potential endocrine disruption in the invertebrates. Given that invertebrates account for at least 95% of all known animal species and are critical to ecosystem structure and function, it remains essential to close this gap in knowledge and research. The lack of progress regarding endocrine disruption in invertebrates is still largely due to: (1) our ignorance of mode-of-action, physiological control, and hormone structure and function in invertebrates; (2) lack of a standardized invertebrate assay; (3) the irrelevance to most invertebrates of the proposed activity-based biological indicators for endocrine disruptor exposure (androgen, estrogen and thyroid); (4) limited field studies. Past and ongoing research efforts using the standard invertebrate toxicity test model, the mysid shrimp, have aimed at addressing some of these issues. The present review serves as an update to a previous publication on the use of mysid shrimp for the evaluation of endocrine disruptors (Verslycke et al., 2004a). It summarizes recent investigative efforts that have significantly advanced our understanding of invertebrate-specific endocrine toxicity, population modeling, field studies, and transgeneration standard test development using the mysid model.Supported by a Fellowship of the Belgian American Educational Foundation

Malignant hyperthermia

Malignant hyperthermia (MH) is a pharmacogenetic disorder of skeletal muscle that presents as a hypermetabolic response to potent volatile anesthetic gases such as halothane, sevoflurane, desflurane and the depolarizing muscle relaxant succinylcholine, and rarely, in humans, to stresses such as vigorous exercise and heat. The incidence of MH reactions ranges from 1:5,000 to 1:50,000–100,000 anesthesias. However, the prevalence of the genetic abnormalities may be as great as one in 3,000 individuals. MH affects humans, certain pig breeds, dogs, horses, and probably other animals. The classic signs of MH include hyperthermia to marked degree, tachycardia, tachypnea, increased carbon dioxide production, increased oxygen consumption, acidosis, muscle rigidity, and rhabdomyolysis, all related to a hypermetabolic response. The syndrome is likely to be fatal if untreated. Early recognition of the signs of MH, specifically elevation of end-expired carbon dioxide, provides the clinical diagnostic clues. In humans the syndrome is inherited in autosomal dominant pattern, while in pigs in autosomal recessive. The pathophysiologic changes of MH are due to uncontrolled rise of myoplasmic calcium, which activates biochemical processes related to muscle activation. Due to ATP depletion, the muscle membrane integrity is compromised leading to hyperkalemia and rhabdomyolysis. In most cases, the syndrome is caused by a defect in the ryanodine receptor. Over 90 mutations have been identified in the RYR-1 gene located on chromosome 19q13.1, and at least 25 are causal for MH. Diagnostic testing relies on assessing the in vitro contracture response of biopsied muscle to halothane, caffeine, and other drugs. Elucidation of the genetic changes has led to the introduction, on a limited basis so far, of genetic testing for susceptibility to MH. As the sensitivity of genetic testing increases, molecular genetics will be used for identifying those at risk with greater frequency. Dantrolene sodium is a specific antagonist of the pathophysiologic changes of MH and should be available wherever general anesthesia is administered. Thanks to the dramatic progress in understanding the clinical manifestation and pathophysiology of the syndrome, the mortality from MH has dropped from over 80% thirty years ago to less than 5%

Effects of cadmium and zinc on Procambarus clarkii: Simulation of the Aznalcóllar mining spill

Female red swamp crayfish, Procambarus clarkii, were exposed for 21 days in the laboratory to different dissolved concentrations of zinc (1000 µg L–1 and 3000 µg L–1) and cadmium (10 µg L–1 and 30 µg L–1), determined in the Guadiamar River after the Aznalcóllar mining spill (SW Spain). Female gonadosomatic and hepatosomatic indexes were analyzed at the end of the bioassay, and a general decrease in the gonadosomatic index and increase in the hepatosomatic index were observed in individuals at the same maturation stage, exposed to increasing heavy metal concentrations. Only the decrease in the gonadosomatic index values was significant at the highest zinc concentration. Decreases in gonadosomatic indexes were associated with reduced fecundity

Effects of elevated ambient histamine level on survival, growth, sexual maturity and tissue histamine accumulation of the mysis Neomysis awatschensis and Neomysis japonica Nakazawa

In Asia, trash fish have been routinely used in aquaculture often due to their local availability and lower costs compared to formulated feed. However, stale trash fish contain high levels of biogenic amines, which have been reported to be harmful to poultry and some aquatic animals. The present study elevated the effects of histamine levels in the water on survival, growth, sexual maturity and tissue histamine accumulation of two estuarine mysis, Neomysis awatschensis and Neomysis japonica Nakazawa. Newly hatched neonates of each mysis species were cultured in brackish water containing 0 (control), 5, 10 and 15 mg/L histamine until they reached sexual maturity. The results showed that compared to the control, survival of N. awatschensis was significantly lower in both 10 and 15 mg/L histamine treatments (69.5 and 62.5% vs. 86.5%). In the case of N. japonica Nakazawa, significantly lower survival was found for the 15 mg/L treatment (53.9% vs. 72.4%) (P < 0.05). In a separate experiment, neonates of each mysis species were cultured individually (15 neonates/treatment) to assess the sub-lethal effects of histamine. It was shown that at the level of 15 mg/L, histamine had a significant impact on body weight and length of sexual matured N. japonica Nakazawa, which were only 87.7 and 78.7% of that of the control. However, no significant difference in intermolt period was detected. In the case of N. awatschensis, no significant differences in both body weight and length among treatments were detected (P > 0.05) but the intermolt period was substantially prolonged at all histamine levels tested when compared to that of the control. Meanwhile, the timings required to reach sexual maturity for both male and female of the two mysis were generally increased with increasing histamine level, and such differences were often statistically significant (P < 0.05). Compared to the control, the tissue histamine concentration of the mysis increased significantly at histamine concentrations of 10 and 15 mg/L for N. japonica Nakazawa (P < 0.05). In the case of N. awatschensis, however, no significant differences were found among all treatments. Our findings indicate that histamine had clear negative effects on both mysis species although their responses and sensitivity appeared somewhat different. Our results suggest that further research is needed to assess the effects of water borne histamine on various aquatic animals