RESUMEN
The vanadium is a metal that presents great interest from the toxicological point of view, because of the numerous alterations that can take place in different biological systems. This work evaluated the capacity of vanadium accumulation and its correlation with genotoxic effects in root cells of Allium cepa L. The bulbs were cultivated in renovated filtered water each 24 h, at a temperature of 25 +/- 0.5 degrees C, in darkness and constant aeration. Treatments were carried out under the same experimental conditions, using water solutions of vanadium of 25, 50, 75 and 100 microg/g for 0, 12, 24, 48 and 72 h. A control was carried out where metal solution was substituted by distilled water. After the treatment, the meristems were fixed with alcohol--acetic acid (3:1) and stained according to the technique of Feulge n. The capacity of accumulation was determined by GFAAS. The analysis of the results revealed an accumulation of the metal for all times and concentrations. No correlation was presented among vanadium accumulation, growth and mitotic index; however, positive correlation was given with the induction of chromosomic aberrations. In conclusion, vanadium is able to induce cytotoxic effect in the exposed roots, but only genotoxic effect was correlated with metal accumulation.(AU)
Asunto(s)
Cebollas/citología , Cebollas/efectos de los fármacos , Cebollas/genética , Vanadio/metabolismo , Vanadio/toxicidad , Aberraciones Cromosómicas/efectos de los fármacos , Cromosomas de las Plantas/efectos de los fármacos , Análisis de Varianza , Daño del ADN/efectos de los fármacos , Meristema/citología , Meristema/efectos de los fármacos , Mitosis/efectos de los fármacos , Factores de TiempoRESUMEN
The vanadium is a metal that presents great interest from the toxicological point of view, because of the numerous alterations that can take place in different biological systems. This work evaluated the capacity of vanadium accumulation and its correlation with genotoxic effects in root cells of Allium cepa L. The bulbs were cultivated in renovated filtered water each 24 h, at a temperature of 25 +/- 0.5 degrees C, in darkness and constant aeration. Treatments were carried out under the same experimental conditions, using water solutions of vanadium of 25, 50, 75 and 100 microg/g for 0, 12, 24, 48 and 72 h. A control was carried out where metal solution was substituted by distilled water. After the treatment, the meristems were fixed with alcohol--acetic acid (3:1) and stained according to the technique of Feulge n. The capacity of accumulation was determined by GFAAS. The analysis of the results revealed an accumulation of the metal for all times and concentrations. No correlation was presented among vanadium accumulation, growth and mitotic index; however, positive correlation was given with the induction of chromosomic aberrations. In conclusion, vanadium is able to induce cytotoxic effect in the exposed roots, but only genotoxic effect was correlated with metal accumulation.
Asunto(s)
Aberraciones Cromosómicas , Cebollas/citología , Cebollas , Cebollas/genética , Cromosomas de las Plantas , Vanadio/metabolismo , Vanadio/toxicidad , Análisis de Varianza , Daño del ADN , Meristema/citología , Meristema , Mitosis , Factores de TiempoRESUMEN
Maleic hydrazide (MH) is an herbicide and is a regulator of the growth of buds in vegetables during storage. It is used in agriculture-in despite its known effect as a mutagenic and clastogenic agent. In this research the effect of MH on the root tips of Allium cepa L. was determined; correlations between the effects of different concentrations and exposure times on the mitotic index (MI) and induction of chromosomal aberrations (ChA) were also examined. Experiments were carried out in triplicate, using aqueous solutions of MH to concentrations of 10(-6), 10(-5), 10(-4) and 10(-3)M, at intervals of 0, 4, 8, 12, 24, and 48 h, with a control for each combination (with the MH substituted by distilled water). The results revealed an inhibition of the MI linked to the concentration and time of treatment (F=845.51, P<0.01 and F=427.58, P<0.01, respectively). For all the concentrations used and exposure periods longer than 12 h, different types of ChA were present, with significantly increased frequencies with increases in the concentration and time of exposure (P<0.01). To determine the mechanism through which the herbicide exerts its toxicity, ultrastructural electron microscopy was conducted. The results reveal nucleolar alterations, suggesting an inhibitory effect of biosynthetic activity.
Asunto(s)
Allium/genética , Aberraciones Cromosómicas/efectos de los fármacos , Exposición a Riesgos Ambientales , Herbicidas/toxicidad , Hidrazida Maleica/toxicidad , Daño del ADN , Herbicidas/farmacología , Hidrazida Maleica/farmacología , Microscopía Electrónica , Pruebas de Mutagenicidad , Raíces de PlantasRESUMEN
This study of the effect of cadmium on nucleolar ultrastructure was carried out with meristematic cell populations of Allium cepa L. Meristems, grown at 25 degrees C, were treated with 10 ppm cadmium chloride. Conventional and silver staining techniques were carried out, and the ultrastructure was analyzed using electron microscopy. Observation showed alterations in the nucleoli of the cells that had been treated with cadmium and this effect varied according to the time of exposure to the metal. After 4h of treatment, nucleolar segregation was observed in interphase, probably because of the effect of cadmium on the synthesis of ribosomal RNA precursors. A decrease in the fibrillar to granular component ratio also occurred in the cells exposed to Cd2+ for 8 h. Some changes were observed in the G1 cells; their chromatin still remained very condensed, and prenucleolus bodies remained scattered within the nucleus. At the same time, there was a large amount of interchromatin granules. These changes produced by cadmium resembled those produced during inhibition of RNA synthesis. The fibrillar bodies, another morphologic feature, resulting from a blocked transcription, were also evidenced. All these observations suggest that one of the ways that cadmium exercises its toxicity is by altering the biosynthesis of the preribosomal RNA precursor.