Antitumour activities of levans produced by Zymomonas mobilis strains

Levans produced by four Zymomonas mobilis strains showed antitumour activity against sarcoma 180 and Ehrlich carcinoma in Swiss albino mice. Levans from two strains (ZAP and CP4) had the highest effects. NMR analysis showed that the polymers were composed only of fructose units. The results suggested that the antineoplasic effect is associated to the polysaccharide molecular weight and that a particular molecular weight range may be responsible for this effect.     

Endoplasmic reticulum distribution during bovine oocyte activation is regulated by protein kinase C via actin filaments

Fertilization-induced [Ca²⁺]_i oscillations generally depend on the release of calcium ions from the endoplasmic reticulum (ER). Since ER is the main store of calcium ions, it plays an important role in oocyte fertilization. However, the mechanism of ER organization at oocyte activation is unknown. Here, we show that protein kinase C (PKC) is involved in ER distribution during bovine oocyte activation, but not involved in cell cycle resumption and spindle organization. Actin filaments were affected by PKC pharmacological inhibition. In addition, similar to PKC results, the actin-depolymerizing drug cytochalasin B affected the ER distribution during oocyte activation. Specifically, we have demonstrated that ER organization during bovine oocyte activation is regulated by PKC possibly through its action on actin filaments regulation. Taken together, the results presented here provide further information on the pathway involved in the regulation of ER organization during oocyte activation and new insight into the functional role of PKC and actin filaments during this process.     

Euclein: A new binaphthaquinone from Euclea pseudebenus

7-MethyljugIone, 8,8′-dihydroxy-4,4′-dimethoxy-6,6′-dimethyl-2,2′-binaphthyl-1,1′-quinone, 2-methylnaphthazarin, mamegakinone and euclein have been isolated from Euclea pseudebenus. Euclein is the 3,6′-dimer of 7-methyljuglone.     

Subcellular Distribution of Two Spin Trapping Agents in Rat Heart: Possible Explanation for Their Different Protective Effects Against Doxorubicin-Induced Cardiotoxicity

Previous investigations, performed on isolated rat atria, showed that the lipophylic spin-trapping agent N-tert-butyl-alpha-phenylnitrone (PBN) is able to prevent the acute cardiotoxic effects produced by doxorubicin (DXR), whereas the hydrophylic compound 5,5-dimethyl-pyrroline-N-oxide (DMPO) is inactive. The present study was designed to ascertain whether differences in the pharmacological effects of the two spin traps are related to their different subcellular distribution. Langendorff rat hearts were perfused for 60 minutes with [^I4C]-DXR and either PBN or DMPO. The subcellular mapping of the three compounds was performed by measuring DXR by liquid scintillation counting, PBN by GC/MS, and DMPO by HPLC in the following isolated fractions: nuclei, mitochondria, sarcoplasmic reticulum, sarcolemma, cytosol. DMPO was shown to accumulate in the cytosolic compartment; both PBM and DXR are taken up by nuclei and mitochondria, while only trace amounts of DXR were detected in the sarcoplasmic reticulum. These results suggest that mitochondrial (and not sarcoplasmic) enzymes are mainly involved in DXR-induced free radical production, which is thought to cause the acute cardiotoxic effects of DXR. An involvement of DXR-induced free radical generation in the nuclear compartment seems unlikely in the short-term “in vitro” effects observed with the experimental model adopted for these studies, although it may play a role in the delayed pathology.     

Skipper impoverishment on large West Mediterranean islands (Lepidoptera Hesperioidea): deterministic,historical and stochastic factors

Biogeographical analyses are applied to skipper (Hesperioidea) presence/absence data from the Western Mediterranean mainland and the three largest islands (Sardinia, Corsica and Sicily) in order to identify potential conservation issues. The analyses performed on species, both collectively and individually, indicate that regional species richness and occurrence in the Mediterranean zone are largely predicted by latitude and area but that islands have impoverished faunas. Several species, predicted to be present on these islands from logistic regression of their continental distributions, are actually absent. The number of species predicted to be present from logistic regression analyses for each island, closely matched the number of species predicted to occur in regional-focused multiple regression analysis. This suggests that missing species have been identified. When compared with species that occur in Sicily and Corsica, the missing species are shown to differ for ecological traits, mainly those linked to altitudinal tolerance. No ecological distinctions were disclosed for Sardinian skippers suggesting a mainly stochastic colonisation. These results, and those from an analogous study carried out on Papilionoidea, point to Hesperioidea having (i) overall more impoverished faunas on islands and (ii) being subject to stochastic or historical colonisation events more than Papilionoidea. Species not predicted to occur on islands based on their mainland distributions and ecological traits, are foci for conservation attention. However, as many species becoming extinct on the islands may be irreplaceable, all species, in particular the Sardinian ones, deserve to be conserved.     

Effects of hydrogen peroxide on the content of major volatile halogenated compounds in the red alga <Emphasis Type="Italic">Asparagopsis taxiformis</Emphasis> (Bonnemaisoniaceae)

The genus Asparagopsis is a prolific source of halogenated metabolites. Due to its commercial applications, it has been intensively cultivated in southern Portugal. In the present study, we assess if the internal levels of the major halogenated metabolites (bromoform and dibromoacetic acid) in Asparagopsis taxiformis can be increased with hydrogen peroxide (H₂O₂) addition. Previous studies with red algae showed that the production/release of bromoform can be enhanced by exogenously supplying H₂O₂. However, no study has assessed if H₂O₂ supply enhances the content of secondary metabolites within the biomass. This detail is important as the objective of the proposed research is to enhance the content of these valuable metabolites in the produced biomass. Both the activity of the haloperoxidase enzyme and the metabolite content were assessed on short-term and long-term incubation periods to H₂O₂. To determine the susceptibility of A. taxiformis photosynthetic performance to the imposed oxidative stress, the in vivo fluorescence of photosystem II was monitored. A. taxiformis was shown to be physiologically vulnerable to H₂O₂, given the observed decrease of the maximum quantum yield of photosynthesis (F _v/F _m). Contrary to what was expected, the presence of H₂O₂ inhibited the activity of the iodoperoxidase enzyme. Nevertheless, the extracted halogenated metabolites were higher over the first hours of exposure to H₂O₂, decreasing after 48 h. These results are probably related to the prosthetic group of the halogenated enzyme in A. taxiformis and the long-term oxidative stress damage of H₂O₂ exposure. Considering the objective of the proposed research, addition of H₂O₂ to the cultures, prior (3 h) to biomass harvesting, increases the metabolite content.     

Effects of disturbance on phosphorus turnover and plankton dynamics

In coastal lagoons, one common type of anthropogenic disturbanceis opening of the sand barriers that isolate these lagoons fromthe sea. We investigated how a disturbance caused by an artificialopening of the sand barrier affects phytoplankton and bacterioplanktondynamics and alkaline phosphatase activities (APA) in a Braziliancoastal lagoon. We propose an index of potential phosphorusturnover time (PPTT) calculated as the ratio of total phosphorus(TP) and APA in an attempt to quantify the effect of disturbanceson phosphorus recycling within the plankton community. Openingthe barrier caused increased phytoplankton biomass, TP concentrations,APA and PPTT, and decreased bacteria to phytoplankton biomassratio. PPTT is easily calculated and may be used to detect planktonresponses to anthropogenic disturbances.     

Suitability of Macrolampis firefly and Pyrearinus click beetle luciferases for bacterial light off toxicity biosensor

Bioluminescence is widely used in biosensors. For water toxicity analysis, the naturally bioluminescent bacteria Vibrio fischeri have been used extensively. We investigated the suitability of two new beetle luciferases for Escherichia coli light off biosensors: Macrolampis firefly and Pyrearinus termitilluminans click beetle luciferases. The bioluminescence detection assay using this system is very sensitive, being comparable or superior to V. fischeri. The luciferase of P. termitilluminans produces a strong and sustained bioluminescence that is useful for less sensitive and inexpensive assays that require integration of the emission, whereas Macrolampis luciferase displays a flash-like luminescence that is useful for fast and more sensitive assays. The effect of heavy metals and sanitizing agents was analyzed. Zinc, copper, 1-propanol, and iodide had inhibitory effects on bioluminescence and growth assays; however, in these cases the bioluminescence was not a very reliable indicator of cell growth and metabolic activity because these agents also inhibited the luciferase. On the other hand, mercury and silver strongly affected cell bioluminescence and growth but not the luciferase activity, indicating that bioluminescence was a reliable indicator of cell growth and metabolic activity in this case. Finally, bioluminescent E. coli immobilized in agarose matrix gave a more stable format for environmental assays.