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Biomedical subjects

F Navari-Izzo

Publications and source records attributed to F Navari-Izzo.

10 recordsLinked to original sources
PubMed2006

Enzymatic and non-enzymatic protective mechanisms in recalcitrant seeds of Araucaria bidwillii subjected to desiccation.

The changes in several antioxidants as well as in the level of C-centered free radicals and thiobarbituric acid reactive substances (TBARS) were studied in seeds of Araucaria bidwillii Hook desiccated to 37%, 28% and 21% moisture content. The lowest-safe moisture content for the seedling establishment was 37%. The embryo, besides double amounts of free radicals, showed higher levels of both enzymatic and non-enzymatic antioxidants than endosperm. Lutein decreased in both organs whereas alpha-tocopherol values were not affected by desiccation. In the embryo at 37% seed moisture content the antioxidant defense system increased giving rise to a decrease in free radicals. Beyond this point, free radicals and TBARS increased in agreement with the umpiring of the ascorbate/glutathione cycle by the decrease in reduced glutathione and glutathione reductase activity (GR, EC 1.6.4.2). At 21% moisture GR decreased. In the endosperm during desiccation, the consumption of ascorbate, total glutathione and lutein prevented the rise in free radicals and TBARS till 28% moisture, at which an increase in oxidized glutathione was also observed.

Antioxidants↗
PubMed2005

Phytoextraction of metals from a multiply contaminated soil by Indian mustard.

The effects of nitrilotriacetate (NTA) and citric acid applications on metal extractability from a multiply metal-contaminated soil, as well as on their uptake and accumulation by Indian mustard (Brassica juncea) were investigated. Desorption of metals from the soil increased with chelate concentration, NTA being more effective than citric acid in solubilising the metals. Plants were grown in a sandy soil collected from a contaminated field site and polluted by Cd, Cr, Cu, Pb and Zn. After 43 days of plant growth, pots were amended with NTA or citric acid at 5 mmol kg-1 soil. Control pots were not treated with any chelate. Harvest of plants was performed 1 week after chelate addition. Soil water-, NH4NO3- and DTPA-extractable Cd, Cu, Pb and Zn fractions were enhanced only in the presence of NTA. In comparison to unamended plants, Indian mustard shoot dry weights suffered significant reductions following NTA application. NTA treatment increased shoot metal concentrations by a factor of 2-3, whereas citric acid did not induce any difference compared to the control. Chromium was detected in the above-ground tissues only after NTA amendment. Due to differences in dry matter yield, a significant enhancement of metal uptake was observed in NTA-treated plants for Cu and Zn.

Biodegradation, Environmental↗
PubMed2005

Nitrilotriacetate- and citric acid-assisted phytoextraction of cadmium by Indian mustard (Brassica juncea (L.) Czernj, Brassicaceae).

In a pot experiment the effects of nitrilotriacetate (NTA) and citric acid applications on Cd extractibility from soil as well as on its uptake and accumulation by Indian mustard (Brassica juncea) were investigated. Plants were grown in a sandy soil with added CdS at four levels ranging from 50 to 200 mg Cd kg(-1) soil. After 30 days of growth, pots were amended with NTA or citric acid at 10 and 20 mmol kg(-1). Control pots were not treated with chelates. Harvest of plants was performed immediately before and one week after chelate addition. Soil water-, NH(4)NO(3)- and EDTA-extractable Cd fractions increased constantly with both increasing soil metal application and chelate concentration. Shoot dry weights did not suffer significant reductions with increasing Cd addition to the soil except for both NTA treatments in which at 200 mg Cd kg(-1) a 30% decrease in dry matter was observed. Generally, following NTA and citric acid amendments, Cd concentration in shoots increased with soil Cd level. However, due to Cd toxicity, at the highest metal application rate both NTA treatments lowered Cd concentration in the above-ground parts. Compared to the control, at 10 mmol kg(-1) citric acid did not change Cd concentration in shoots, whereas NTA-treated plants showed an about 2-fold increase. The addition of chelates at 20 mmol kg(-1) further enhanced Cd concentration in shoots up to 718 and 560 microg g(-1) dry weight in the NTA and citrate treatments, respectively.

Cadmium↗
PubMed2001

Photosystem II photochemical efficiency, zeaxanthin and antioxidant contents in the poikilohydric Ramonda serbica during dehydration and rehydration.

Changes in photochemical efficiency, non-radiative energy dissipation (NRD), de-epoxidation state of xanthophyll cycle components (DPS) and contents of the antioxidants ascorbic acid and glutathione were studied in leaves of the poikilohydric Ramonda serbica Panc. (Gesneriaceae) during cycles of dehydration and subsequent rehydration. In drying leaves, the intrinsic efficiency of PS II photochemistry and the photon yield of PS II electron transport showed strong progressive decreases. Simultaneously, the fraction of excitation energy dissipated as heat in the PS II antenna increased markedly. The energy-dependent component of non-photochemical quenching (NPQ) showed an increase in dehydrating leaves down to relative water contents (RWC) values near 30%. Further decreases in RWC below these values caused a decrease in NPQ. Accordingly, DPS showed a similar behaviour, with a sharp increase and a subsequent decrease at very low RWC, although the maximum DPS was reached at slightly lower RWC than that for the maximum NPQ. The pools of reduced ascorbate and glutathione increased strongly when the RWC values fell below 40% and remained high in fully dehydrated leaves. When plants were re-watered photosynthetic efficiency, NRD, DPS and antioxidant contents recovered their initial control values. However, during rehydration, the zeaxanthin content showed a transient increase, as did NPQ, indicating an increasing demand for non-radiative dissipation. On the other hand, the contents of reduced ascorbate and reduced glutathione decreased but were still relatively high in the initial phase of rehydration, when the rate of photosynthetic electron transport, proton pumping and NRD were still relatively low. These results indicate that several photoprotective mechanisms are operating in R. serbica. Protection from photo-oxidation and photoinhibition appears to be achieved by co-ordinated contributions by ascorbate, glutathione and zeaxanthin-mediated NPQ. This variety of photoprotective mechanisms may be essential for conferring desiccation-tolerance.

Journal Article↗
PubMed2001

Lipids and NADPH-dependent superoxide production in plasma membrane vesicles from roots of wheat grown under copper deficiency or excess.

The effects of in vivo copper on the lipid composition of root plasma membrane and the activities of membrane-bound enzymes, such as NADPH-dependent oxidases and lipoxygenase, were studied. Plants were grown in hydroponic culture for 11 d without Cu supply or in the presence of 50 microM Cu. Control plants were supplied with 0.3 microM Cu. Growth of roots was severely affected in the 50 microM Cu-grown plants, whereas roots grown in Cu-deficient solution did not show any difference in comparison with the control. The 50 microM Cu concentration caused an increase in the leakage of K(+) ions as well. Excess metal supply resulted in a decrease in the total lipid content of plasma membrane, a higher phospholipid amount and a reduction of steryl lipids (free sterols, steryl glycosides and acylated steryl glycosides). Cu depletion in the growth solution had only a slight effect on the plasma membrane lipid composition. In comparison with the control, only the excess of Cu caused a decrease in the lipid to protein ratio as well as a change in the phospholipid composition, with a lower phosphatidylcholine to phosphatidylethanolamine ratio. The degree of unsaturation of root plasma membranes decreased following the 0 Cu treatment and even more after the 50 microM Cu supply. Plasma membranes of wheat grown under metal deficiency and excess showed increased NADPH-dependent superoxide-producing oxidase activities, whereas membrane-bound lipoxygenase was not increased or activated due to Cu treatments. The consequences of changes in plasma membrane lipid composition and activated oxygen production as a result of Cu treatments are discussed.

Cell Membrane↗
PubMed2000

Protein dynamics in thylakoids of the desiccation-tolerant plant Boea hygroscopica during dehydration and rehydration.

Plants of Boea hygroscopica F. Muell were dehydrated to 9% relative water content (RWC) by withholding water for 26 d, and afterward the plants were rehydrated. Leaves were taken from control plants after 7, 12, and 26 d from the beginning of dehydration, and after 6 and 48 h from rehydration. The RWC decreased by 80% during dehydration, but the leaves regained RWC with rehydration. Dehydrated plants showed lesser amounts of proteins, lipids, and chlorophyll, all of which increased following rewatering. The lipid-to-protein ratio, which decreased during dehydration, returned to control level after 48 h of rehydration. Thylakoid lipids were more unsaturated when RWC reached the value of 9%. EPR measurements of spin-labeled proteins showed the presence of three different groups of proteins with different mobility in thylakoid membranes. The rotational correlation time of groups 1 and 2 increased with dehydration and decreased upon rehydration, whereas group 3 showed little changes. Desiccation did not cause thylakoid swelling or breakage, but the membrane system assemblage showed changes in thylakoid stacking. After 48 h of rehydration the membrane system recovered completely the organization of the fully hydrated state, showing several well-defined and regularly distributed grana.

Antioxidants↗
PubMed1999

Superoxide and hydroxyl radical generation, and superoxide dismutase in PSII membrane fragments from wheat.

Illumination of photosystem II (PSII) membrane fragments of wheat (Triticum durum Desf. cv. Adamello) gave rise to both O2*- and *OH radicals adducts of the novel spin trap 5-(diethoxyphosphoryl)-5-methyl-1-pyrroline-N-oxide (DEPMPO). With time, *OH became predominant displaying the conversion of O2*- into *OH. An intrinsic activity of superoxide dismutase (SOD) was found in PSII. Photoreduction of nitroblue tetrazolium (NBT) by PSII membrane fragments was induced by the addition of sodium azide and hydrogen peroxide. Western blotting of PSII proteins showed that a 29 kDa protein was recognised by an antibody against chloroplastic Fe-SOD from water lily. An increased formation rate of O2*- was observed in damaged PSII where the SOD activity decreased following a treatment with a free radical-generating system. Damage in PSII consisted also in a decrease in chlorophyll and in carotenoids as well as in a change in the lipid : chlorophyll : protein ratio. Upon treatment a decrease in the unsaturation of PSII membrane fragments was also monitored together with a degradation towards more saturated molecular species of monogalactosyldiacylglycerol.

Electron Spin Resonance Spectroscopy↗
PubMed1999

Activated oxygen generation from thylakoids: a novel spin trap.

Using a novel phosphorylated spin trap, 5-(diethoxyphosphoryl)-5-methyl-1-pyrroline-N-oxide (DEPMPO), an analogue of the commonly used spin trap 5,5'-dimethyl-1-pyrroline N-oxide (DMPO), we have investigated the production of oxygen radical species under illumination of thylakoids from wheat (Triticum durum Desf cv. Ofanto). DEPMPO reacted with superoxide (O2*-) and hydroxyl radical (HO*) forming distinctive spin trap adducts. Spectra of (O2*-) and HO* adducts of DEPMPO were recorded in the presence of xanthine/xanthine oxidase and FeSO4/H2O2, respectively, and computer simulation of spectra was performed. During illumination of thylakoids both O2*- and HO* were detected as well. Transition metals catalysed transformation of O2*- into HO*. The conversion was enhanced by H2O2 and prevented by exogenous superoxide dismutase and catalase. The presence of a thylakoid-bound superoxide dismutase, whose activity was inhibited by H2O2 and diethyldithiocarbamic acid, was responsible for H2O2 production from O2*- and thus for HO* generation.

Cyclic N-Oxides↗
PubMed1999

Antioxidative defense system, pigment composition, and photosynthetic efficiency in two wheat cultivars subjected to drought

We analyzed antioxidative defenses, photosynthesis, and pigments (especially xanthophyll-cycle components) in two wheat (Triticum durum Desf.) cultivars, Adamello and Ofanto, during dehydration and rehydration to determine the difference in their sensitivities to drought and to elucidate the role of different protective mechanisms against oxidative stress. Drought caused a more pronounced inhibition in growth and photosynthetic rates in the more sensitive cv Adamello compared with the relatively tolerant cv Ofanto. During dehydration the glutathione content decreased in both wheat cultivars, but only cv Adamello showed a significant increase in glutathione reductase and hydrogen peroxide-glutathione peroxidase activities. The activation states of two sulfhydryl-containing chloroplast enzymes, NADP+-dependent glyceraldehyde-3-phosphate dehydrogenase and fructose-1,6-bisphosphatase, were maintained at control levels during dehydration and rehydration in both cultivars. This indicates that the defense systems involved are efficient in the protection of sulfhydryl groups against oxidation. Drought did not cause significant effects on lipid peroxidation. Upon dehydration, a decline in chlorophyll a, lutein, neoxanthin, and beta-carotene contents, and an increase in the pool of de-epoxidized xanthophyll-cycle components (i.e. zeaxanthin and antheraxanthin), were evident only in cv Adamello. Accordingly, after exposure to drought, cv Adamello showed a larger reduction in the actual photosystem II photochemical efficiency and a higher increase in nonradiative energy dissipation than cv Ofanto. Although differences in zeaxanthin content were not sufficient to explain the difference in drought tolerance between the two cultivars, zeaxanthin formation may be relevant in avoiding irreversible damage to photosystem II in the more sensitive cultivar.

Journal Article↗