Claudio Vismara

University of Milan, Milano, Lombardy, Italy

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Publications (24)70.34 Total impact

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    ABSTRACT: The embryotoxicity of 4-chloro-2-methylphenoxyacetic acid (MCPA), an extensively used herbicide, has been evaluated and compared to that of phenol and chlorocresol (two common contaminants) with a bioassay that makes use of embryos of the amphibian Xenopus. The MCPA—Na salt used in the bioassay was purified by crystallization and acid-base purification methods, and the concentrations of phenol and chlorocresol were checked by high-performance liquid chromotography. The relationship between the concentration of the tested molecule and the outcomes (i.e., mortality and malformations) was investigated using different models (probit, logit, and complementary log-log). The resulting LC50s for MCPA, chlorocresol, and phenol are 3,607, 13, and 178 mg/L, respectively; the resulting LC10s are 1,526, 6, and 32 mg/L. It is evident that the real MCPA toxicity can be masked by the presence of contaminants much more toxic than the molecule studied. Moreover, our results show that the three chemicals do not present a high teratogenic risk. Growth retardation shows that MCPA, chlorocresol, and phenol are effective at concentrations as low as 2,000, 2.5, and 25 mg/L, respectively.
    Environmental Toxicology and Chemistry 10/2009; 15(5):754 - 760. · 2.62 Impact Factor
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    ABSTRACT: 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.
    Science of The Total Environment 04/2008; 392(1):110-8. · 3.16 Impact Factor
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    ABSTRACT: 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.
    Environment International 08/2007; 33(5):642-8. · 6.25 Impact Factor
  • Claudio Vismara, Francesca Caloni
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    ABSTRACT: Aflatoxins are a group of mycotoxins produced by Aspergillus, A. flavus, and A. parasiticus. Aflatoxin B1 (AFB1) should be a strong teratogen in hamsters, but its effect in rats is equivocal and extremely limited in mice. Therefore, the AFB1 embryotoxic potential in mammals remains unclear. Little is known about the AFB1 effects on amphibians, therefore its embryotoxic potential was evaluated using the frog embryo teratogenesis assay-Xenopus (FETAX). X. laevis blastulae were exposed to: 1) positive controls for bio-activation (4 g/L cyclophosphamide monohydrate, Cy, and 4 g/L Cy+30 mg/L MAS-rat; 4 g/L Cy+30 mg/L MAS-human); 2) positive controls for MAS (30 mg/L MAS-rat and 30 mg/L MAS-human); 3) exposed groups to AFB1 (1 mg/L AFB1); and 4) AFB1 bio-activation (1 mg/L AFB1+30 mg/L MAS-rat and 1 mg/L AFB1 +30 mg/L MAS-human). In MAS-rat and human, Cy did not induce a statistically significant increase of mortality and malformed larvae percentage, but when bio-activated Cy increased the percentage of mortality. Instead, MAS-rat and human alone did not show any increase of mortality and malformed larvae percentages. When bio-activated by MAS-rat and human, AFB1 increased significantly both the mortality and malformed larvae percentages. The malformed larvae were mainly plurimalformed, i.e., affected by generalized edema, abnormal gut coiling, and microphthalmia. This research shows that AFB1 alone is not embryotoxic but, when bio-activated with MAS-rat or MAS-human the percentage of mortality and malformed larvae increased significantly. These results also show that AFB1 must be bio-activated to exert its embryotoxic effects.
    Birth Defects Research Part B Developmental and Reproductive Toxicology 07/2007; 80(3):183-7. · 1.97 Impact Factor
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    ABSTRACT: 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. 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. 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. In spite of the low T.I, MYS has to be considered a highly teratogenic compound.
    Birth Defects Research Part B Developmental and Reproductive Toxicology 09/2006; 77(4):257-67. · 1.97 Impact Factor
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    ABSTRACT: The principal Aflatoxin B(1) (AFB(1)) hydroxylated metabolite excreted in milk is Aflatoxin M(1) (AFM(1)) classified in group 2B by the International Agency for Research on Cancer (IARC). Human exposure to AFM(1) is due to the consumption of contaminated dairy products and partly to endogenous production through AFB(1) liver metabolism. Since no data are available on AFM(1) embryotoxicity, its lethal and teratogenic potential was investigated using the Frog Embryo Teratogenesis Assay-Xenopus (FETAX). Stage-8 blastulae were exposed to AFM(1) at 1, 4, 16, 64, and 256 microg/L concentrations until stage 47, free-swimming larva. A slight increase of mortality and malformed larva percents was found in AFM(1)-exposed groups but these differences were not statistically significant in comparison with the controls. Therefore, AFM(1) is a non-embryotoxic compound when evaluated with a FETAX model at concentrations under the conditions tested. However, AFM(1) merits further studies using mammals as experimental models to identify a possible risk during human pregnancy.
    Birth Defects Research Part B Developmental and Reproductive Toxicology 07/2006; 77(3):234-7. · 1.97 Impact Factor
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    ABSTRACT: 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. 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. 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. 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."
    Birth Defects Research Part B Developmental and Reproductive Toxicology 07/2006; 77(3):238-43. · 1.97 Impact Factor
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    ABSTRACT: The oxidative agent paraquat induced tail abnormalities during Xenopus laevis development. Specimens exposed from blastula to the tadpole stage revealed pear-shaped myocytes and irregular intersomitic boundaries. The histological feature of the axial musculature was evaluated in embryos sampled at significant stages of the primary myogenesis. During the somitogenesis PQ-treated embryos showed normal appearing myotomes, but reduced PAS activity in the post-rotating myotomal cells, and myoblasts with slight vacuolations. Once etched from the vitelline envelope, embryos showed severely altered myoblasts with irregular cellular apexes, heavy sarcoplasmic vacuolations, pyknotic nuclei and disorganizing intersomitic boundaries. Myotomes with many necrotic myocytes containing disorganized contractile material and heavily malformed intersomitic boundaries characterized the late myogenic stages. Our results evidence the heaviest PQ histopathological effects to affect myogenesis of post-etched embryos, suggesting a possible linkage between the swimming activity and the oxidative damage to muscle tissue.
    Tissue and Cell 07/2006; 38(3):209-17. · 1.04 Impact Factor
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    ABSTRACT: Data on the indicators of environmental impact of tire debris, originated from the tire abrasion on roads, are extremely scarce, while it is well known that tires may produce deleterious effects. Tire debris contains significant quantities of zinc (Zn) which may be released by tire rubber. We have used tire particles (TD) produced in laboratory from new rubber. Two sets of experiments were set up to obtain eluates. One set used 50 and 100 g/L TD to produce eluates at pH 3-7. The Zn quantity was measured with a Inductively Coupled Plasma-Atomic Emission Spectrometry. The eluates at 1%,10%,50%,100% concentrations in culture media were tested on Raphidocelis subcapitata, Daphnia magna and Xenopus laevis embryos (FETAX test). The other set of experiments was performed putting 250 mg/L TD in a column with glass beads to control particle dispersion during the elution process. We demonstrate that factors such as pH, size and particles aggregation deeply influence the elution process, that the amount of Zn leached from particles is related to their aggregation rather than their quantity. These results, even though do not reflect the real environmental toxicity of the leachates, can be successfully used for comparative purposes allowing an initial assessment of the potential effect of tire derived particles.
    Environment International 08/2005; 31(5):723-30. · 6.25 Impact Factor
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    ABSTRACT: BACKGROUND: It is estimated that over 80% of respirable particulate matter (PM10) in cities comes from road transport and that tire and brake wear are responsible for the 3-7% emission of it. Data on the indicators of environmental impact of tire debris (TD), originated from the tire abrasion on roads, are extremely scarce, even though TD contains chemicals (zinc and organic compounds) which can be released in the environment. METHODS: TD particle morphology was analysed with SEM, TEM and FIB instruments. TD eluates and TD organic extracts were tested at dilution series on human cell lines and Xenopus laevis embryos. 50 and 100 g/L TD were used for the eluates obtained after 24 h at pH 3 and the quantity of zinc present was measured with a ICP-AES. Eluates diluted to 1%, 10%, 50% in culture media and undiluted were used on X. laevis embryos in the FETAX test. HepG2 cells were exposed for 24 h to 0.05 - 50 mug/ml of zinc salt while A549 cells were exposed for 24, 48 and 72 h to 10, 50, 60, or 75 mug/ml of TD extract. X. laevis embryos were exposed to 50, 80, 100, or 120 mug/ml TD extract. RESULTS: The solution of undiluted 50 g/L TD produced 80.2% mortality (p < 0.01) in X. laevis embryos and this toxic effect was three times greater than that produced by 100 g/L TD. Zn accumulation in HepG2 cells was evident after 4 h exposure. A549 cells exposed to TD organic extract for 72 h presented a modified morphology, a decrease in cell proliferation and an increase in DNA damage as shown by comet assay. The dose 80 mug/ml of TD extract produced 14.6% mortality in X. laevis embryos and 15.9% mortality at 120 mug/ml. Treatment with 80, 100, or 120 mug/ml TD organic extract increased from 14.8% to 37.8% malformed larvae percentages compared to 5.6% in the control. CONCLUSION: Since the amount of Zn leached from TD is related to pH, aggregation of particles and elution process, the quantity of TD present in the environment has to be taken into account. Moreover the atmospheric conditions, which may deeply influence the particle properties, have to be considered. The TD organic fraction was toxic for cells and organisms. Thus, because of its chemical components, TD may have a potential environmental impact and has to be further investigated.
    Particle and Fibre Toxicology 03/2005; 2(1):1. · 9.18 Impact Factor
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    ABSTRACT: 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.
    Aquatic Toxicology 01/2005; 70(3):189-200. · 3.51 Impact Factor
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    ABSTRACT: The 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-diamidino-2-phenylindole (DAPI) 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.
    Aquatic Toxicology 12/2001; 55(1-2):85-93. · 3.51 Impact Factor
  • C Vismara, G Vailati, R Bacchetta
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    ABSTRACT: The toxicity of herbicide Paraquat (PQ, 1-1'-dimethyl-4,4'bipyridylium dichloride) in animal cells is related to its rapid reduction and instantaneous reoxidation to produce the reactive oxygen species. Recently, the PQ evaluation with the Frog Embryo Teratogenesis Assay-Xenopus (FETAX) showed its high embryotoxicity. Supposing that the embryos' death was due to PQ-related oxidative damage, we used ascorbic acid (AA), a well known antioxidant, to reduce the PQ embryotoxicity in Xenopus laevis. Embryos were exposed from stage 8 to 47 to 0.1 mg/l PQ alone, and to PQ with AA concentrations ranging from 20 to 200 mg/l, using the FETAX procedure. PQ caused 72.2% mortality, while 17.1% of surviving larvae were affected by abnormal tail flexure. The PQ mortality percentages were reduced in a clear concentration-response by up to 15.2% in the group exposed to PQ with 200 mg/l AA. The histopathologic diagnoses revealed abnormal notochord flexure coupled with vesiculated, pear-shaped myocytes only in the PQ group. After embryo exposure to PQ with 200 mg/l AA, restoration of normal axial tail structures was evident. In conclusion, PQ embryotoxicity in X. laevis was most likely due to oxidative damage that was drastically reduced by AA.
    Aquatic Toxicology 02/2001; 51(3):293-303. · 3.51 Impact Factor
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    ABSTRACT: Paraquat (PQ, 1-1′-dimethyl-4,4′-bipyridylium dichloride) is an effective herbicide widely used in agriculture with a rate of application for aquatic weed control ranging from 0.1 to 2 parts per million. Considering its wide-spread presence in Italian wetlands, we studied its embryotoxic effects with the Frog Embryo Teratogenesis Assay-Xenopus (FETAX). The percentage of mortality as well as the percentage of malformed larvae was investigated by probit analysis. The results showed that PQ was highly embryolethal. From a LC50 of 0.138 mg/l and TC50 of 0.267 mg/l, a TI50 of 0.52 was derived; indicating that PQ is to be considered a non-teratogenic compound. Remarkable was the presence of a specific malformation, classified as ventral tail flexure, in the 29% of living larvae exposed to 0.125 mg/l PQ concentration. Their histological examination showed several zones of abnormal somites containing severely affected myocytes. This confirmed the molecular mechanism of PQ toxicity in cell microfilaments. Even at the lowest concentration of 0.0625 mg/l, the difference between the mean head–tail length of control and exposed larvae was statistically significant, a sign of growth retardation. All our data emphasize that PQ must be consider highly embryotoxic on amphibian development, and suggest that this herbicide should be strictly regulated in weed control programs.
    Aquatic toxicology (Amsterdam, Netherlands) 07/2000; · 3.12 Impact Factor
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    ABSTRACT: 1. Several immunological abnormalities have been found in schizophrenia but their significance still remains largely unknown. In this study the authors analyzed mitogen-stimulated interleukin (IL)-2, Interferon gamma (IFN)-gamma and IL-10 (type 2 cytokine) production in a sample of 37 chronic schizophrenic patients as compared with a sample of 40 age and sex-matched controls with the aim to evaluate whether patients belonging to different diagnostic subtypes (i.e. paranoid patients vs non paranoid patients) could be immunologically different from each other. 2. The findings indicate that paranoid patients produce less IL-10 than the others and thus, from an immunological viewpoint, they are more similar to healthy controls. 3. Furthermore, neuroleptic medications were observed to differently affect IL-2 production; this preliminary finding might stimulate further studies aiming to get a link between different drug profile of action both in terms of clinical and receptorial profile and different immunological effects.
    Progress in Neuro-Psychopharmacology and Biological Psychiatry 09/1998; 22(6):947-57. · 3.55 Impact Factor
  • Claudio Vismara
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    ABSTRACT: The current study proposes an ecotoxicological test that makes use of Artemia salina cyst; the results obtained made it possible to calculate the percentage of cyst mortality (no sign of development), and growth inhibition (a delay in normal development), as well as the percentage of larva malformation, and mortality. The dehydrated cysts were directly exposed for forty-eight hours to the action of three alcohols, methanol, ethanol, and n-propanol. No teratogenic or lethal effects on larvae were found at any methanol or ethanol concentrations. Predicted values of effect concentration, EC1, EC10 and EC50 were calculated from the estimated probit models for larva growth inhibition, GI, and for cyst lethal concentration, LC. At concentrations of 0.21 M methanol and 0.13 M ethanol, there were no signs of alterations in Artemia salina cyst development; these concentrations show a NOEC (No Observed Effect Concentration) value, and properly employed do not interfere with effects due to a given chemical. The n-propanol was only used to verify the extreme resistance of the dried cysts to various environmental factors.
    Chemosphere 01/1998; 37(14):3027-3034. · 3.14 Impact Factor
  • C Vismara, A Garavaglia
    Bulletin of Environmental Contamination and Toxicology 05/1997; 58(4):582-8. · 1.11 Impact Factor
  • Bulletin of Environmental Contamination and Toxicology 02/1996; 56(1):85-9. · 1.11 Impact Factor
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    ABSTRACT: Keywords:immunology;HIV infection;tumor immunology;pregnancy
    Infectious Diseases in Obstetrics and Gynecology 02/1996; 4(3):117-21.
  • Bulletin of Environmental Contamination and Toxicology 09/1995; 55(2):195-200. · 1.11 Impact Factor

Publication Stats

325 Citations
70.34 Total Impact Points

Institutions

  • 1993–2009
    • University of Milan
      • Department of Anesthesia, Intensive Care and Dermatologic Sciences
      Milano, Lombardy, Italy
  • 2005–2007
    • Università degli Studi di Milano-Bicocca
      • Department of Earth and Environmental Sciences
      Milano, Lombardy, Italy
  • 1996
    • Istituto Nazionale Tumori "Fondazione Pascale"
      Napoli, Campania, Italy