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Effetti embriotossici del pesticida carbaryl mediante il Frog Embryo Teratogenesis Assay-Xenopus (FETAX)
No full textSexual maturity in young Dreissena polymorpha from Lake Como (N. Italy)
No full textThe reproductive biology of the zebra mussel Dreissena polymorpha was studied during 1999 in a natural population living in Lake Como (N. Italy), with particular reference to the differences in behavior between young and adult mussels. Histological analysis of gonads was used to study the gametogenic cycles and to evaluate when the young reached sexual maturity. Signs of active gametogenesis were detected in greater than or equal to4 mm shell length mussels. Mature gametes and the first spawning events were observed in greater than or equal to5 mm males and in greater than or equal to6 females. The gonad feature of greater than or equal to7 mm mussels was similar to that of the adults. Size frequency distributions revealed that the new generation (0(+)) first spawned in the year following birth, but only after winter. The length of larval time seemed to vary greatly depending on the spawning period, in addition to the environmental conditions. The first settled mussels greater than or equal to500 mum in shell length were observed 3-4 months after the first depositions. Water temperature seemed to be the most important factor which regulated sexual phenomena of both young and adult mussels. Its role in the onset of the spawning events was confirmed, but it is important to point out that temperature is not enough to trigger reproduction since gamete release is impossible without sufficient energy, especially for young mussels
Histological studies on the zebra mussel Dreissena polymorpha reproduction from a DDT contaminated area in Lake Maggiore (N. Italy)
No full textHistological techniques were used to monitor Dreissena polymorpha reproductive biology during 2001 in Lake Maggiore (N. Italy). Considering the DDT pollution which occurred during the mid 1990s in this lake and the high contamination level registered in 2001, we focused on the course of spawning events in zebra mussels and possible modified reproductive behavior induced by this pollution. Specimens were collected from the lake at Baveno as the polluted station, and at Villa Taranto as the control site. At Villa Taranto, morphological analyses of gonadal changes showed a gamete developing and maturing period until April, spawning phases from May to August, the restart of gametogenesis in females and an inactive period in males, immediately after the end of spawnings. This pattern was perturbed at Baveno where the mussels showed a delay in oocyte maturation with a significant percentage of specimens showing oocyte degeneration. Moreover, the onset of gamete release seemed to shift from May to July in the males at Baveno. Our findings agreed with the well recognized endocrine disrupting properties of DDT, even though the physiological mechanisms involved must be studied further
Oocyte degeneration and altered ovipository activity induced by paraquat in the freshwater snail Physa fontinalis (Gastropoda : Pulmonata)
No full textThe freshwater snail Physa fontinalis was used as a bioindicator to study the effects of the herbicide Paraquat (PQ) in laboratory assays. The test solutions used, 0.125, 0.25, and 0.5 mg/l PQ, were in the range of the concentrations recommended for aquatic weed control. The study was carried out in two stages to determine the influence of PQ on the ovipository activity of Physa fontinalis, and the histological effects on these snails. Specimens exposed to PQ continued to be reproductively active, but the number of egg masses and eggs laid decreased significantly. Mortality was almost the same in all the experimental lots, but was significantly related to the production of egg masses only in the controls. The histological analysis showed a clear trend among PQ concentrations and degenerating oocytes, but no visible effects on the male sex-line were observed. By interfering with fertility, PQ has an action that may go well beyond its lethal effect on individuals, suggesting that this herbicide should be strictly regulated in weed control programmes. Moreover, since PQ was observed to interfere with the reproductive process, its endocrine disrupting action must not be excluded
Reproductive behavior of the freshwater mussel Dreissena polymorpha in Italy: a comparison between two populations
No full textThe gametogenic cycle of Dreissena polymorpha is described for two populations living in Lake Come and the Adda River in Northern Italy. Reproduction was monitored by histological examinations of gonads and by morphometric changes in oocyte nuclei from February 1998 to January 1999. Gonadal development commenced overwinter. Gamete deposition started in spring when the water temperature reached 13 degreesC. By May, the reproductive season had commenced but while in Lake Come it finished in August, in the Adda River depositions were observed until the end of October. The course of the Maturity Index and mainly the oocyte nuclei diameter analysis suggested the possibility of two main reproductive events in the lake zebra mussel population. In contrast, more continuous spawning was observed in the river mussels. In both sites, frequency distributions of nucleus size showed maturation of at least two gamete cohorts which supported successive depositions. The gonadal resting stage was longer in males than females. Oogenesis started soon after the end of the reproductive period while spermatogenesis commenced only 3 or 4 months later. This is the first study dealing with the Dreissena polymorpha reproductive cycle in the South Alps. Results are discussed and compared with regard to other populations living in the rest of Europe and North America
Paraquat induces actin assembly in depolymerizing conditions
No full textThe molecular mechanism (or mechanisms) at the basis of paraquat (PQ) (a widely used herbicide) toxicity is far from being fully understood, Until now, two main points of view have emerged: 1) PQ-related cell injuries could be mediated by toxic oxygen free radicals coming from the metabolism of the herbicide by the microsomal enzyme system, and/or 2) PQ, by inducing mitochondrial swelling and breakage, could cause troubles in cell energy charge, then driving the cell to death, Recently, some of cytoskeletal structures (microtubules and microfilaments) have been proposed as further PQ cell targets, The microfilament system in particular seems to be markedly affected by the herbicide, but so far no direct evidence associates PQ to actin damage, In this study, experimental data are presented concerning the direct effect of PQ on actin dynamics in solution, We demonstrate that actin selectively binds PQ; moreover, PQ induces the formation of actin sopramolecular structures in depolymerizing medium (G-buffer), Furthermore, by the interactions with F-actin crosslinking proteins (alpha-actinin and filamin), FITC-phalloidin, and myosin subfragment 1 (S1), it is demonstrated that PQ-induced actin aggregates are undoubtedly built up by F-actin, Electron micrographs showed that PQ-induced actin polymers are very short and tend to aggregate one to another, This mutual cohesion leads to the steric blockage of polymer growing ends as suggested by nucleated actin polymerization assays, Sonication, by releasing F-actin fragments from short polymer aggregates, allows actin polymer ends to regain their growing ability.-Milzani, A., DalleDonne, I., Vailati, G., Colombo, R. Paraquat induces actin assembly in depolymerizing conditions
Paraquat embryotoxicity in the Xenopus laevis cleavage phase
No full textThe high Paraquat (PQ, 1-1'-dimethyl-4,4',bipyridylium dichloride) embryotoxicity in Xenopus laevis has been shown to be due to its rapid reduction and instantaneous re-oxidation which produces a reactive oxygen species, ROS. Nevertheless, PQ did not show any effects before hatching, stage 32, which showed a resistance, in early X. laevis development, to oxidative damage. Moreover, in view of its genotoxic properties in several experimental models, we studied PQ in the X. laevis cleavage phase that, characterized by a series of rapid mitotic divisions, might be damaged by genotoxic compounds. Embryos were exposed to 20, 40, 60, and 80 mg/l PQ concentrations from stage 2 to stage 9, and then left to develop in control FETAX solution until stage 47. The 80 mg/l PQ concentration gave 19% embryo mortality at the end of the exposure time, and 16.7% larvae mortality at the end of the test; both values were statistically different from the control, 5 and 6.8% respectively. These results confirmed the high resistance in early X. laevis development to PQ oxidative damage. The malformed larva percentages in the PQ exposed groups were higher as regards the control value but did not show any concentration-response; the most frequent malformed larvae found were affected by abnormal tail flexure coupled with abnormal gut coiling. A further experiment was carried out using the same methodology, but exposing embryos only to the 80 mg/l PQ concentration. The surviving blastulae were embedded in Paraplast, then the slides were stained with 4',6-diarnidino-2-phenylindole (DA-PI) and the nuclei were examined with a confocal microscope. This new preliminary procedure did not reveal any significant presence of micronucleated micromeres in PQ exposed blastulae with respect to the control. Nevertheless, the mechanism by which PQ induced abnormal tail flexure after cleavage exposure remained unknown. PQ seemed to pass through the jelly coats and vitelline membrane, but it expressed teratogenicity between the 2nd and 3rd day. PQ might be accumulated in the embryos during the exposure, and might express teratogenicity later, but it did not seem to induce genotoxicity during the cleavage phase of X. laevis even at very high concentrations
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