Is meltwater from Alpine glaciers a secondary DDT source for lakes?

A sharp increase in 2005 of pp'DDT and its metabolites was observed in mussels and fish from lakes Como and Iseo, the main glacier-fed southern Alpine lakes. DDTs in zebra mussels (Dreissena polymorpha) were more than 150 times higher than levels in 2003, and concentrations in pelagic fish (0.12 mgkg(-1) w.w.) exceeded the Italian safety threshold for human consumption (0.05 mgkg(-1) w.w.). The histological examination of the ovaries revealed many mussels with oocyte degeneration throughout the studied period. Prior to being banned in Italy in 1978, DDT was used in large amounts for fruit-tree treatment from the 1950s to 1970s in valleys just below the glaciers. Since glacier volume was increasing at that time and then continuously retreated, meltwater should be the main cause of the pollution peak recently observed in biota of downstream lakes. PCBs did not peak in biota tissues to a comparable extent probably because local sources were not as important as for DDTs.

Axial-skeletal defects caused by Carbaryl in Xenopus laevis embryos.

Embryotoxic effects of Carbaryl (CB), a widely used carbamate insecticide, was evaluated by modified Frog Embryo Teratogenesis Assay-Xenopus (FETAX), coupled with a histopathological screening of the survived larvae. X. laevis embryos were exposed to 1, 2, 4, 8, 16 and 24 mg/L CB from stage 8 to stage 47. From an estimated LC50 of 20.28 mg/L and TC50 of 8.43 mg/L a TI of 2.41 was derived, indicating that CB is to be considered teratogenic for X. laevis embryos. The most characteristic terata, classified as abnormal tail flexure, involved a significant percentage of larvae from 1 mg/L CB onward, reaching 100% at 24 mg/L CB. Histopathological screening revealed tail musculature and notochord as the main targets for CB. Skeletal muscle lesions consisted of myotomes reduced in size, showing myocytes with disorganized contractile systems and irregular myosepta, coupled with disarranged myocyte apexes. Notochords from CB exposed larvae appeared wavy or bent, with irregular connective sheaths and histologically characterized by protrusions of fibrous matrix and inclusions of ectopic cell masses. This axial-skeletal damage was hypothesized to be related both to the inhibition of acetylcholinesterase, with consequent muscular tetanic spasms, and to disorders in the organization of the connective tissue matrix surrounding the notochord.

Tire debris organic extract affects Xenopus development.

Tire debris (TD) and its organic components were identified as a main source of PM10 atmospheric and water pollution. Because few data are available on the embryotoxic effects of TD organic components, the lethal and teratogenic potential of tire debris organic extract (TDOE) was evaluated using the frog embryo teratogenesis assay-Xenopus (FETAX), coupled with a histopathological screening of the survived larvae. From stage 8 to stage 47, Xenopus laevis embryos were exposed to TDOE at concentrations of 50, 80, 100, 120 and 140 mg/L. The results showed 50 mg/L TDOE to be the non-observable effect concentration (NOEC). TDOE mortality at 80 mg/L was significantly higher than the control, but did not increase further with higher concentrations. A good concentration-response was observed for percentages of malformed larva and from 80 mg/L on these percentages were significantly higher than the control. Therefore, probit analysis gave a 144.6 mg/L TC50. At 120 and 140 mg/L, many larvae were plurimalformed. The most frequent alterations observed were abnormal gut coiling, microphthalmia, monolateral anophthalmia, and narrowing eyes. The histological screening mainly revealed ocular malformations such as double retina, retina nervous cell layer coiling, and altered lens. Moreover severe vacuolisation and necrosis were scored in liver and axial musculature. These results strongly support the assumption that TDOE is a powerful teratogen for X. laevis.

Determination of myoseverin embryotoxic potential by using FETAX.

BACKGROUND: Since MYS is a microtubular poison with a reversible activity, Xenopus blastulae were exposed to MYS to verify the eventual drug-related developmental suspension and the reversibility of this effect. METHODS: Lethal and teratogenic effects of myoseverin (MYS) were evaluated using the FETAX. Embryos were exposed to different MYS concentrations from stage 8 to stage 47. RESULTS: Probit analysis gave 12.14 microM LC50 and 7.67 microM TC50 from which 1.58 T.I. is derived. Several malformations were observed such as facial abnormalities, abnormal tail flexure, heart ventricle chamber enlargement and external appendix. MYS led to an arrest of living embryo development. Before MYS removing, exposed blastulae showed the lack of mitotic spindles along with different nuclei alterations. Living embryos, moved in control solution, mainly died around the hatching showing severe malformations likely ascribable to the altered planes of newly occurring mitosis. CONCLUSION: In spite of the low T.I, MYS has to be considered a highly teratogenic compound.

H2O2 induces abnormal tail flexure in Xenopus embryos: similarities with Paraquat teratogenic effects.

BACKGROUND: As previously shown, Paraquat (PQ) treatments of Xenopus developing embryos mainly induce a characteristic developmental alteration we named "abnormal tail flexure." PQ oxidative activity has been indicated as the cause of this malformation. Since PQ evokes reactive oxygen species (ROS), among which hydroxyl radicals (OH(*)), and H(2)O(2) can be converted to (OH(*)) via Fenton reaction, we compared here the lethal and teratogenic potentials of both oxidants by using the Frog Embryo Teratogenesis Assay-Xenopus (FETAX), in order to grasp eventual similarities in their teratogenic activity. METHODS: Xenopus embryos were exposed, from stage 8 to stage 47, at 368, 491, 612, and 735 microM H(2)O(2) and 0.388 microM PQ. The probit analysis of H(2)O(2) mortality and malformed larva percents gave a 598.82 microM Lethal Concentration 50% (LC(50)) and 536.04 microM Teratogenic Concentration 50% (TC(50)) from which a 1.11 Teratogenic Index (T.I.) has been calculated. This T.I. value should allow the classification of H(2)O(2) as a non-teratogenic compound. RESULTS: A comparison of H(2)O(2) mortality and malformed larva percents with those obtained from PQ exposure showed the higher embryotoxicity of PQ, but, markedly, both compounds mainly induced the "abnormal tail flexure." Histological analysis of both H(2)O(2) and PQ malformed embryo tails showed a similar distorted morphology of both somites and myocytes. Some of muscle cells were necrotic and affected by an apical enlargement as well as a detachment from the connective tissue of intersomitic boundaries. CONCLUSIONS: In our opinion, both of the tested chemicals likely weaken the mechanical bridge connecting the myocyte contractile apparatus to the extracellular matrix, therefore causing the detachment of some of tail myocytes from their connectival septum as well as their apical enlargement. This could lead to the unbalance of tail tensional forces and, in turn, to the appearance of the "abnormal tail flexure."

Comparative teratogenicity of chlorpyrifos and malathion on Xenopus laevis development.

The embryotoxic potential of chlorpyrifos (CPF) and malathion (MTN), two organophosphorus insecticides (OPs), was evaluated by modified Frog Embryo Teratogenesis Assay-Xenopus (FETAX). CPF and MTN were not embryolethal even at the highest concentration tested (6000 microg/l), but both exhibited a powerful teratogenicity. The probit analysis of malformed larva percentages showed a TC(50) of 161.54mug/l for CPF, and a TC(50) of 2394.01 microg/l for MTN. Therefore, CPF teratogenicity was about 15 times higher than MTN. Larvae of both exposed groups were mainly affected by ventral and/or lateral tail flexure coupled with abnormal gut coiling. Histopathological diagnosis displayed abnormal myotomes and myocytes with marked hypertrophies localized at the cell extremity, probably due to a break away of myofibril extremities at the intersomitic junction level. We speculate that this muscular damage was related to inhibition of acetylcholinesterase that showed a clear concentration-response in CPF and MTN exposed larvae. The teratogenic effects of these anti-cholinesterase compounds on Xenopus laevis myogenesis suggest a possible role played by OPs on induction of congenital muscular dystrophy.

DDT in zebra mussels from Lake Maggiore (N. Italy): level of contamination and endocrine disruptions.

The DDT contamination of Lake Maggiore (Northern Italy) has been monitored since a serious pollution event occurred in 1996. To assess the environmental risk associated with this contamination, bioaccumulation data coupled with histopathological markers were evaluated on zebra mussel populations from two different contaminated sites from April 2001 to April 2002. Biomonitoring results showed high DDT pollution in 2001 because of a flood which transported DDTs still contained in the sediments of a polluted river to the lake. DDT concentrations reached values of 4-5 microg/g lipids, higher than those recorded in other industrialized countries but comparable to levels measured in developing ones. In the ovaries of the most highly polluted mussels, histological analyses showed a delay in oocyte maturation and a high incidence of pathological pictures mainly referable to oocyte degeneration and haemocytic infiltration. Moreover, despite the presence of mature sperms, in 2001 first male gamete release occurred about 2 months later than in females. These results indicated a neuroendocrine interference of DDT on Dreissena polymorpha reproduction and also showed that these invertebrates can be successfully used to evaluate ecological implications due to exposure to endocrine disruptors in freshwater environments.