The late-stage "ferruginization" of the Ediacara Member (Rawnsley Quartzite, South Australia): Insights from uranium isotopes.

The paleoenvironmental setting in which the Ediacara Biota lived, died, and was preserved in the eponymous Ediacara Member of the Rawnsley Quartzite of South Australia is an issue of long-standing interest and recent debate. Over the past few decades, interpretations have ranged from deep marine to shallow marine to terrestrial. One of the key features invoked by adherents of the terrestrial paleoenvironment hypothesis is the presence of iron oxide coatings, inferred to represent the upper horizons of paleosols, along fossiliferous sandstone beds of the Ediacara Member. We find that these surficial oxides are characterized by (234 U/238 U) values which are not in secular equilibrium, indicating extensive fluid-rich alteration of these surfaces within the past approximately 2 million years. Specifically, the oxide coatings are characterized by (234 U/238 U) values >1, indicating interaction with high-(234 U/238 U) fluids derived from alpha-recoil discharge. These oxides are also characterized by light "stable" δ238/235 U values, consistent with a groundwater U source. These U isotope data thus corroborate sedimentological observations that ferric oxides along fossiliferous surfaces of the Ediacara Member consist of surficial, non-bedform-parallel staining, and sharply irregular patches, strongly reflecting post-depositional, late-stage processes. Therefore, both sedimentological and geochemical evidence indicate that Ediacara iron oxides do not reflect synsedimentary ferruginization and that the presence of iron oxides cannot be used to either invoke a terrestrial paleoenvironmental setting for or reconstruct the taphonomic pathways responsible for preservation of the Ediacara Biota. These findings demonstrate that careful assessment of paleoenvironmental parameters is essential to the reconstruction of the habitat of the Ediacara Biota and the factors that led to the fossilization of these early complex ecosystems.

Microbial mat controls on infaunal abundance and diversity in modern marine microbialites.

Microbialites are the most abundant macrofossils of the Precambrian. Decline in microbialite abundance and diversity during the terminal Proterozoic and early Phanerozoic has historically been attributed to the concurrent radiation of complex metazoans. Similarly, the apparent resurgence of microbialites in the wake of Paleozoic and Mesozoic mass extinctions is frequently linked to drastic declines in metazoan diversity and abundance. However, it has become increasing clear that microbialites are relatively common in certain modern shallow, normal marine carbonate environments-foremost the Bahamas. For the first time, we present data, collected from the Exuma Cays, the Bahamas, systematically characterizing the relationship between framework-building cyanobacteria, microbialite fabrics, and microbialite-associated metazoan abundance and diversity. We document the coexistence of diverse microbialite and infaunal metazoan communities and demonstrate that the predominant control upon both microbialite fabric and metazoan community structure is microbial mat type. These findings necessitate that we rethink prevalent interpretations of microbialite-metazoan interactions and imply that microbialites are not passive recipients of metazoan-mediated alteration. Additionally, this work provides support for the theory that certain Precambrian microbialites may have been havens of early complex metazoan life, rather than bereft of metazoans, as has been traditionally envisaged.

Intra- and extra-cellular flux distributions of TCA and glyoxalate cycle and vancomycin production of Amycolatopsis orieantalis grown in different glycerol concentration.

The relationship between tricarboxylic acid (TCA) and glyoxalate cycle and the effect of their metabolites levels on the vancomycin production of Amycolatopsis orientalis were investigated in different concentration of glycerol (2.5-20 g/l). Intracellular glycerol levels increased with respect to increases in glycerol concentrations of the growth medium. Extracellular glycerol levels decreased slowly up to 24 h while uptake rates were increased during 36-48 h for 10 and 15 g/l and during 36-60 h at 20 g/l of glycerol. Intracellular citrate, alpha-ketoglutarate, fumarate levels increased up to 10 g/l glycerol concentration. However, intracellular succinate and malate levels were increased up to 15 g/l glycerol. Extracellular citrate, alpha-ketoglutarate, succinate and malate levels increased with respect to increases in glycerol concentration. The highest alpha-ketoglutarate dehydrogenase activity was determined at 15 g/l glycerol. Isocitrate lyase activity showed a positive correlation with the increases in glycerol concentration of the growth medium. Vancomycin production increased with the increases in glycerol concentration from 5 to 10 g/l. These results showed that A. orientalis grown in glycerol containing medium used glyoxalate shunt actively instead of TCA cycle which supports precursors of many amino acid which are effective on the antibiotic production.

Intracellular superoxide dismutase, catalase, and glutathione peroxidase activities and membrane lipid peroxide levels in Fusarium acuminatum upon environmental changes in a defined medium.

The variations of superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GSH-Px) activities and lipid peroxide (LPO) levels in Fusarium acuminatum, an aerobic filamentous fungus, were investigated depending on the carbon and nitrogen sources during the incubation period. Fungus was cultivated in growing medium containing either maltose or saccharose in 5-25 g/L concentration range as a carbon source and either glycine or peptone in 5-35 g/L concentration range as a nitrogen source at 28 degrees C and 100 rpm. The observed highest SOD, CAT, and GSH-Px activities were 31.2+/-0.655, 62.5+/-5.23, and 1.52+/-0.0122 IU/mg in the presence of 20 g/L maltose and 73.96+/-1.48, 74.46+/-2.94, 3.48+/-0.083 IU/mg in the 15 g/L glycine-containing medium at 16 days, respectively. At the same time, the minimum LPO level was observed at 20 g/L maltose and 15 g/L glycine compared with the other carbon and nitrogen sources. The results showed a negative correlation between antioxidant enzyme activities and membrane LPO levels in F. acuminatum cells.

Effects of Se, Cu and Se + vitamin E deficiency on the activities of CuZnSOD, GSH-Px, CAT and LPO levels in chicken erythrocytes.

Antioxidant enzymes and vitamins provide a defence against the damage of cells by reactive oxygen species in living systems. The effect of Cu, Se and vitamin E deficiencies on the antioxidant enzyme activities and lipid peroxide levels of chicken erythrocytes were investigated during 6 weeks of a depletion diet. CuZnSOD activity and the plasma Cu level of the Cu-deficient group which was fed a diet containing 0.2 mg Cu x kg(-1) were reduced to 62 and 71% respectively. GSH-Px activity of the Se-deficient group was decreased by 46% but by 21% in the Cu-deficient group. CAT activity values of Se- and Cu-deficient groups were increased by 28 and 10% respectively. The maximum increase of LPO levels in erythrocyte membranes was observed as 32% for the Se+E-deficient group. The LPO level of the Cu-deficient group which had decreased CuZnSOD and GSH-Px activity, was also observed to be significantly increased when compared with the controls (p < 0.05).

The effects of some antioxidant vitamin- and trace element-supplemented diets on activities of SOD, CAT, GSH-Px and LPO levels in chicken tissues.

The effect of diets containing antioxidant vitamins and trace elements on chicken tissue activities of SOD, CAT, GSH-Px and of LPO levels was investigated. Chickens, 45 weeks of age were divided into six groups: control group, Cu group (13.2 mg Cu kg(-1) diet); Se group (0.07 mg Se kg(-l) diet); vitamin E group (70 mg DL-alpha-tocopherol acetate kg(-1) diet) and a constant level vitamin C, 200 mg kg(-1) diet); vitamin A group (240 mg retinol acetate kg(-1) diet) and vitamin C group (500 mg ascorbic acid kg(-1) diet). Significant variation of these antioxidant enzyme activities and LPO levels according to gender was demonstrated statistically. In the Cu group, CuZnSOD activity in the liver, erythrocyte, kidney and heart significantly increased by 75, 40, 12, 12% respectively (P<0.05). MnSOD activity in the heart, liver, kidney and brain of the vitamin C and in the heart of Cu group were found to be increased by approximately 15%, while in liver tissue of the Cu group it was reduced by 19% (P<0.05). GSH-Px activities in the Se, vitamin E and C groups were significantly increased, conversely LPO levels decreased (P<0.001). CAT activities in the liver and heart of the vitamin C group were significantly decreased (by 32%), but in kidney tissue only that of the Cu group was increased from 30.2 +/- 4.767 to 144.49 +/- 6.93 U mg(-1) P<0.001. The resistance to stress of the vitamin E and C groups, which had significantly increased activities of antioxidant enzymes and decreased lipid peroxide levels, were determined in 60% moisture medium at 45 degrees C.

Purification and characterization of superoxide dismutase from chicken liver.

Superoxide dismutase (SOD; EC 1.15.1.1) is an enzyme that protects against oxidative stress from superoxide radicals in living cells. This enzyme has been isolated, purified and partially characterized from chicken liver. The following steps were carried out in order to purify chicken liver SOD. Initially, the liver was homogenized and hemoglobin was removed. Subsequently protein precipitation was effected with (NH(4))(2)SO(4), methanol, (NH(4))(2)SO(4)-methanol and polyethylene glycol methods. The product from polyethylene glycol-3350 precipitation was found to have the highest SOD activity. Polyethylene glycol was removed by chromatography using a PD-10 column. After passing through an ultrafilter, the superoxide dismutase was fractionated by DEAE-ion chromatography and then Sephadex G-75 gel filtration chromatography. During this purification procedure, a specific activity of 4818.2 IU/mg was reached, corresponding to 285.8-fold purification. The purified enzyme, which was characterized as cyanide-sensitive SOD, contained two subunits having Cu and Zn elements with a molecular weight of 16000+/-500 for each. The optimum pH of purified CuZnSOD was determined to be 8.9. The enzyme was found to have good pH stability in the pH range 6.0-7.5 at 25 degrees C over a 2-h incubation period and displayed good thermal stability up to 45 degrees C at pH 7.4 over a 1-h incubation period. The SOD enzyme was not inhibited by DTT and beta-mercaptoethanol, but inhibited by CN(-) and H(2)O(2). In the presence of 2 mM iodoacetamide, the enzyme showed an approximately 40% activity loss. Finally, the inhibitory effect of ionic strength on SOD was also investigated.

Effects of antioxidant vitamins A, C, E and trace elements Cu, Se on CuZn SOD, GSH-Px, CAT and LPO levels in chicken erythrocytes.

The biologically damaging effects of reactive oxygen species are controlled in vivo by a wide spectrum of antioxidant defence mechanisms. Dietary constituents of antioxidant vitamins and trace elements may play an important role in protecting against oxidant damage. The effects of supplementation of vitamins A, C, E and trace elements Cu and Se on the activities of antioxidant enzymes and lipid peroxide levels in chicken erythrocytes were investigated depend on the time. CuZnSOD activity and plasma Cu levels in the Cu group were increased by 39 and 37 per cent respectively. CuZnSOD activity in vitamin C groups was also increased by 20 per cent. The GSH-Px activity in Se, Se+E and Se+Cu groups was raised by 35, 46 and 69 per cent respectively. Also, the GSH-Px activity in the vitamin C group was increased by 33 per cent. Catalase activity in all of these groups was not significantly different when compared with controls (p<0.01). The maximum decrease in LPO levels of 42 per cent was obtained for the Se+E group.

Enzymatic properties of immobilized catalase on protein coated supports.

Sephadex-100, DEAE-Sephadex and polyvinyl alcohol supports used for immobilization of catalase were prepared by modifications initially with 2-amino-4,6-dichloro-s-triazine and then with diaminohexane and glutaraldehyde prior to coating with gelatine, whereas the Fe2O3 support was coated directly. Optimum support/enzyme ratios were determined for these protein coated supports in a series of immobilization reactions with varying amounts of catalase in the presence of the crosslinking agent glutaraldehyde. Activity variations with respect to pH, temperature, stability behaviour and the inhibition effect of hydroxylamine were investigated for the immobilized catalase preparations. The time-dependent decomposition rate of H2O2 and the deactivation rate constants for catalase were investigated in a discontinuous batch-type reactor system.