Učinak bakra na toksičnost i genotoksičnost kadmija u vodenoj leći (Lemna minor L.)

We investigated interactions between copper (in the concentrations of 2.5 μmol L-1 and 5 μmol L-1) and cadmium (5 μmol L-1) in common duckweed (Lemna minor L.) by exposing it to either metal or to their combinations for four or seven days. Their uptake increased with time, but it was lower in plants treated with combinations of metals than in plants treated with either metal given alone. In separate treatments, either metal increased malondialdehyde (MDA) level and catalase and peroxidase activity. Both induced DNA damage, but copper did it only after 7 days of treatment. On day 4, the combination of cadmium and 5 μmol L-1 copper additionally increased MDA as well as catalase and peroxidase activity. In contrast, on day 7, MDA dropped in plants treated with combinations of metals, and especially with 2.5 μmol L-1 copper plus cadmium. In these plants, catalase activity was higher than in copper treated plants. Peroxidase activity increased after treatment with cadmium and 2.5 μmol L-1 copper but decreased in plants treated with cadmium and 5 μmol L-1 copper. Compared to copper alone, combinations of metals enhanced DNA damage after 4 days of treatment but it dropped on day 7. In conclusion, either metal given alone was toxic/genotoxic and caused oxidative stress. On day 4 of combined treatment, the higher copper concentration was more toxic than either metal alone. In contrast, on day 7 of combined treatment, the lower copper concentration showed lower oxidative and DNA damage. These complex interactions can not be explained by simple antagonism and/or synergism. Further studies should go in that direction.U svrhu istraživanja interakcija između bakra kao esencijalnog elementa te kadmija kao neesencijalnog i toksičnog metala, vodenu leću Lemna minor L. uzgajali smo na podlogama s kadmijem (5 μmol L-1) odnosno s bakrom (2,5 μmol L-1 i 5 μmol L-1) te s njihovim kombinacijama. Unos metala u biljke povećavao se s trajanjem pokusa, a kod kombinacije metala u biljkama je izmjerena niža količina kadmija nego u onima uzgajanima samo na kadmiju. U biljkama tretiranim pojedinačnim metalom došlo je do povećanja sadržaja malondialdehida (MDA) te aktivnosti katalaze i peroksidaze u odnosu na kontrolne biljke. Također, primijećeno je oštećenje DNA iako kod bakra tek sedmog dana tretmana. Količina MDA i aktivnost obaju enzima dodatno se povećala na tretmanu kombinacijom kadmija i bakra (5 μmol L-1) nakon četvrtog dana pokusa, dok se količina MDA smanjila nakon sedmog dana kod kombinacije kadmija i 2,5 μmol L-1 bakra. U tim biljkama primijećena je i veća aktivnost katalaze, dok je aktivnost peroksidaze porasla na tretmanu kadmijem i 2,5 μmol L-1 bakrom, ali se smanjila na tretmanu kadmijem i 5 μmol L-1 bakrom. Oštećenje DNA koje je bilo veće kod kombinacije metala nakon četvrtog dana, osobito u usporedbi sa samim bakrom, smanjilo se nakon sedmog dana pokusa. Iz ovih rezultata može se zaključiti da su oba metala u istraživanim koncentracijama toksična i genotoksična za vodenu leću i da uzrokuju oksidacijski stres. Kadmij u kombinaciji s bakrom više koncentracije bio je toksičniji od pojedinačnih metala nakon četvrtog dana pokusa, dok su u biljaka tretiranih kombinacijom kadmija i bakra niže koncentracije toksični učinci bili manji. Budući da su primijećene interakcije vrlo kompleksne i ne uključuju samo antagonizam odnosno sinergizam potrebna su daljnja istraživanja

Impact of bleaching conditions on the components of non-photochemical quenching in the zooxanthellae of a coral

Mass coral bleaching events are a worldwide phenomenon, which generally occur during periods of elevated sea surface temperature and intense sunlight. These conditions result in a decline in photochemical efficiency of symbiotic microalgae (zooxanthellae) which ultimately leads to the expulsion of these symbionts. The physiological mechanism which triggers the release of the zooxanthellae has yet to be adequately determined. Under bleaching conditions, non-photochemical quenching (NPQ) is used to dissipate excess energy from photosystem II (PSII). NPQ was partitioned into three components, (energy dependent quenching [qE], state transition quenching [qT] and photoinhibitory quenching [qI]), based on relaxation kinetics upon addition of 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU) and darkening. This investigation revealed that for corals not exposed to bleaching stress, qE was the principle means of energy dissipation (∼60% of the total NPQ). In corals exposed to either high-light (475 μmol photons m-2 s-1 and 25°C) or elevated temperature (225 μmol photons m-2 s -1 and 32°C) treatments, the dominant component of NPQ was qE and the relative proportions did not change during the exposure period (1-8 h). When exposed to bleaching conditions (475 μmol photons m-2 s -1 and 32°C) the contribution of the different components changed after 4 h and the total NPQ increased. At this time, the contribution of qT to the total NPQ significantly increased to equal that of qE (40%), suggesting state transitions become more important under such conditions. Throughout the exposure period in all treatments, no change in the proportion of qI was observed. © 2005 Elsevier B.V. All rights reserved

Evidence for the presence of ion pumps in the photophores of 2 mesopelagic fishes <i>Argyropelecus</i> and <i>Maurolicus</i>

1. Adenosine triphosphatase (ATPase) activity has been measured on homogenates of photophores from two mesopelagic fishes Argyropelecus and Maurolicus. This activity is equivalent for both fishes when reported to the protein content as is their O2 consumption.2. The activity is optimal at pH 6.8-7.5. It is not specific for ATP since GTP, ITP, UTP and CTP are also hydrolyzed to a significant extent. It is also not specific for Mg2+, the activity being equivalent (Argyropelecus) or higher (Maurolicus) with Ca2+ and high also with Co2+ and Mn2+.3. Twenty to 30 per cent of the activity measured at pH 7.4 is probably due to the mitochondrial ATPase as it is shown by oligomycin and venturicidin inhibition.4. Activities of both fishes photophores are partly inhibited by N-N’-dicyclohexylcarbodiimide (DCCD), azide, LaCl3, vanadate, diethylstilbestrol (DES) and N-ethylmaleimide (NEM) which are all inhibitors of ionic pumps.5. Argyropelecus activity is sensitive to ouabaïn.6. Our results show the presence of ionic pumps in Argyropelecus and Maurolicus photophores. If there is evidence for the absence or very low activity of a H+ pump, it is sure that Argyropelecus at least possess a Na+K+-ATPase.7. The significance of a high protein content in Maurolicus photophores and of a large inorganic phosphate concentration in Argyropelecus is discussed