Carbon sequestration in a limestone quarry mine soil amended with sewage sludge

To reclaim a limestone quarry, 200 and 400 Mg/ha of municipal sewage sludge were mixed with an infertile calcareous substrate and spread as mine soil in 1992. Soil samples were taken 1 week later and again after 17 yr of mine soil rehabilitation so as to assess changes in the amount and persistence of soil organic carbon (SOC). Sludge application increased SOC as a function of the sludge rate at both sampling times. Seventeen years after the sludge amendments, the nonhydrolysable carbon was increased in the 400 Mg/ha of sludge treatment. The recalcitrance of SOC was less in sludge‐amended soils than in the control treatment at the initial sampling, but 17 yr later this trend had reversed, showing qualitative changes in soil organic carbon. The CO₂‐C production had not differed between treatments, yet the percentage of mineralized SOC was less in the high sludge dose. When the size of active (C_active) and slow (C_slow) potentially mineralizable C pools was calculated by curve fitting of a double‐exponential equation, the proportion of C_active was observed to be smaller in the 400 Mg/ha sludge treatment. Soil aggregate stability, represented by the mean weight diameter of water‐stable soil aggregates, was significantly greater in mine soil treated with the high dose of sludge (18.5%) and SOC tended to be concentrated in macro‐aggregates (5–2 mm). Results suggest that SOC content in sludge‐amended plots was preserved due by (i) replacement of the labile organic carbon of sludge by more stable compounds and (ii) protection of SOC in aggregates.     

Development of a fluorescent latex immunoassay for detection of a spectinomycin antibiotic

There is a need to develop a rapid and sensitive method to detect spectinomycin residues in animal tissues. A latex fluorescent immunoassay was designed using reagents developed for this assay. The spectinomycin antibody was produced in sheep, and the immunoglobulin (IgG) was purified through a Protein G affinity column and was immobilized onto latex particles. Spectinomycin was labeled with 5-([4,6-dichlorotriazin-2-yl]amino)fluorescein (DTAF). The optimum assay conditions consisted of preincubating the latex-IgG with spectinomycin in buffer solutions or in bovine kidney extracts. DTAF-spectinomycin was added and was further incubated. The bound spectinomycin-DTAF/IgG-latex complex was separated by centrifugation at 4000 g for 10 min. The fluorescence signals of the unbound spectinomycin-DTAF in the supernatant were measured at 485/535 nm excitation/emission. The measured signals were directly proportional to the concentration of spectinomycin in the samples, and spectinomycin was detected at 0-100 ppb with minimum detectability of 5 ppb. The mean regression correlation of four trials in buffer was 0.936 when the % bound complex vs spectinomycin concentration was plotted. Analysis of the kidney extract spiked with 0-100 ppb spectinomycin had a regression correlation of 0.959. This assay provides a rapid screening method for low ppb detection of spectinomycin.     

Immunomodulatory Properties of the Protein Fraction from Phorphyra columbina

The phycobiliproteins from Rhodophyta , R-phycoerythrin (R-PE) and C-phycocyanin (C-PC), have been shown to exert immunomodulatory effects. This study evaluated the effects of a Phorphyra columbina protein fraction (PF) and R-PE and C-PC on rat primary splenocytes, macrophages, and T-lymphocytes in vitro. PF featured various protein species, including R-PE and C-PC. PF showed mitogenic effects on rat splenocytes and was nontoxic to cells except at 1 g L(-1) protein. IL-10 secretion was enhanced by PF in rat splenocytes, macrophages, and especially T-lymphocytes, whereas it was markedly diminished by R-PE and C-PC. The production of pro-inflammatory cytokines by macrophages was inhibited. The effect of PF on IL-10 was evoked by JNK/p38 MAPK and NF-κB-dependent pathways in macrophages and T-lymphocytes. It was concluded that PF has immunomodulatory effects on macrophages and lymphocytes that appear to be predominantly anti-inflammatory via up-regulated IL-10 production and cannot be accounted for by R-PE and C-PC.     

Nitrogen Mobility at the Sediment-Water Interface of Lake Maracaibo,Venezuela

Nitrogen is one of the two most important elements in the metabolism of aquatic ecosystems. At low concentrations it can limit primary productivity and when present at very high concentrations it can participate in the eutrophication process of these environments. The mechanism of nitrogen transport in sediments is almost unknown, nevertheless it is of vital importance for establishing mass balances in aquatic systems. In the study presented here, we assessed the nitrogen flux in sediments of the central part of tropical Lake Maracaibo, Venezuela, in particular with regard to dissolved oxygen concentrations. Experiments were performed under laboratoryconditions in a batch system, and at varying dissolved oxygenregimes (aerobic and anaerobic). Every two days, during 3 months,overlying water samples were taken to analyze nitrite, nitrate,ammonium and Kjeldahl total nitrogen. Average release rates oftotal nitrogen were 0.86 in aerobic, and 1.06 mmol N m^-2 d^-1 in anaerobic systems corresponding to 41.7% of total N input to the lake. The behavior of nitrogen was strongly influenced by nitrate concentrations under aerobic conditions, and by organic nitrogen under anaerobic conditions during the course of the experiment. A major trend for the release of organic nitrogen during anaerobic conditions, and of nitrate, during aerobic conditions, was observed. Also fluxes of NO₃ ^-, NH₄ ⁺, organic N and Total N across the sediment-water interface were measured. In anaerobic conditions, which are predominant in the hypolimnetic cone of LakeMaracaibo, denitrification was estimated to be 0.02 mmol N m^-2 d^-1, which corresponds to 1.89% of the total N released from sediments.This is to our knowledge the first study of nitrogen fluxes insediments from Lake Maracaibo. The laboratory data presented herereflects conditions in the lake when major nutrients accumulation occurs.     

Effect of pH on hemoglobin-catalyzed lipid oxidation in cod muscle membranes in vitro and in situ

The effect of pH and hemoglobin on oxidation of the microsomal lipids of cod was determined in isolated microsomes and in washed cod muscle. An increase of hemoglobin concentration from 0.5 to 15 microM accelerated lipid oxidation in both systems. In cod microsomes the rate of lipid oxidation increased in the order pH 6.8 > pH 7.6 > pH 8.4 > pH 6.0 > pH 3.5. However, in washed cod muscle a decrease of pH from 7.8 to 6.8 greatly increased the lag phase and decreased the rate of lipid oxidation. A further decrease in pH to 3.5 decreased the lag phase and increased the rate of lipid oxidation further. A decrease of pH from 7.6 to 6.4 greatly reduced the affinity of hemoglobin for oxygen. Formation of methemoglobin due to autoxidation occurred more rapidly at pH 6.0 than at pH 7.5. Structural changes of the isolated microsomal membranes could be the reason for the unexpected slow lipid oxidation in microsomes at pH 6.0 and below.     

Yeast-induced inhibition of (+)-catechin and (-)-epicatechin degradation in model solutions

(+)-catechin and (-)-epicatechin degradation in water-alcohol solutions containing Fe2+ and tartaric acid was studied in the presence and absence of yeasts. On the basis of the results, yeast partially inhibited the degradation of both flavans, with much slower formation of browning products absorbing at 420 and 520 nm. In comparative terms, yeast was found to be more efficient toward the degradation products of (+)-catechin absorbing at the latter wavelength. Likewise, the presence of yeast decreased the yield of a group of colored compounds eluting at high retention times in HPLC and indicated these as important contributors to color darkening in white wines. This inhibitory effect may in part account for the resistance to browning observed over periods of several years in sherry wines subjected to biological aging under flor yeast.     

The interactive effect of an AM fungus and an organic amendment with regard to improving inoculum potential and the growth and nutrition of Trifolium repens in Cd-contaminated soils

Aspergillus niger-treated dry olive cake (DryOC) can be used as a soil organic amendment and the aim of this work was to study the effectiveness of this amendment and a Cd-adapted arbuscular mycorrhizal (AM) fungus in improving Trifolium repens growth and nutrition in Cd-contaminated soil. In a compartmentalized growth system, consisting of a root compartment (RC) and two hyphal compartments (HCs), we investigated the influence of the amendment on intraradical and extraradical AM fungi development. In addition, we studied the viability and infectivity of the detached extraradical mycelium in plants, designated as receptor plants, grown in the HC after removal of the RC. Both the amendment and the AM fungus increased shoot and root biomass and nodulation in both the non-contaminated and Cd-contaminated soils. The positive interaction between the microbiologically treated DryOC and the AM fungus resulted in the highest plant yield, which can be explained by enhanced nutrient acquisition and arbuscular richness as well as by the immobilisation of Cd in amended soils. However, A. niger-treated DryOC had no effect on the extraradical mycorrhizal mycelium development. Although Cd decreased AM hyphal length density, symbiotic infectivity was similar in receptor plants grown in non-contaminated and contaminated soil, thus confirming the AM fungal inoculum potential.The combination of the AM fungus and A. niger-treated DryOC increased plant tolerance to Cd in terms of plant growth and nutrition and can be regarded as an important strategy for reclaiming Cd-contaminated soils.     

Efficiency of natural phenolic compounds regenerating alpha-tocopherol from alpha-tocopheroxyl radical

Benzoic acid-derived phenolics (p-hydroxybenzoic acid, 3,4-dihydroxybenzoic acid, vanillic acid, syringic acid, and gallic acid) and the polyphenols epicatechin and epigallocatechin gallate (EGCG) were evaluated for their efficiency in regenerating alpha-tocopherol from alpha-tocopheroxyl radical in comparison with ascorbyl palmitate, which is known to regenerate alpha-tocopherol. Ethanolic solutions of phenolic compounds were added to a homogeneous hexane medium containing alpha-tocopheroxyl radical generated by reaction of alpha-tocopherol in molar excess with 1,1-diphenyl-2-picrylhydrazyl radical, and the alpha-tocopheroxyl radical was monitored by electron spin resonance spectroscopy. p-Hydroxybenzoic acid, vanillic acid, and syringic acid (400 microM) did not exhibit a significant effect on alpha-tocopheroxyl radical concentration (0.6-0.7 microM). In contrast, 3,4-dihydroxybenzoic acid and gallic acid were able to reduce the concentration of alpha-tocopheroxyl radical by 16 and 64%, respectively. Epicatechin showed a reduction of alpha-tocopheroxyl radical similar to gallic acid, and EGCG and ascorbyl palmitate were the most effective, reducing alpha-tocopheroxyl radical completely at a much lower phenolic concentration (66.7 microM). The moles of alpha-tocopheroxyl radical reduced per mole of ascorbyl palmitate (0.93), EGCG (0.066), gallic acid (4.3 x 10(-4)), and epicatechin (4.5 x 10(-4)) were determined, and the logarithm of these stoichoimetric ratios showed a negative linear relationship with the bond dissociation enthalpies of the O-H bond of the phenolics. The relative capacity to reduce alpha-tocopheroxyl radical was found to be ascorbyl palmitate (2142) > EGCG (151) > gallic acid (1) approximately epicatechin (1).     

Probiotic effect of Streptomyces spp. on shrimp (Litopenaeus vannamei) postlarvae challenged with Vibrio parahaemolyticus

The effect of Streptomyces strains RL8 and N7 on the growth, survival and histological structure of the hepatopancreas of Litopenaeus vannamei was determined. Shrimp post‐larvae of 0.02 ± 0.01 g were fed with diets supplemented with Streptomyces spp. RL8 and N7 at 10⁸ CFU g^?1 of feed for 30 days, followed by challenge with Vibrio parahaemolyticus. Toxicity was also assessed by recording the mortality associated with the use of 1‐100 g/L of cell mass and 10⁸‐10¹⁰ CFU/g of feed of these strains in Artemia salina and L. vannamei, respectively. The group treated with Streptomyces sp. RL8 had significantly better weight gain (0.62 ± 0.18 g) and survival rates (84.44 ± 5.7%) after challenge, whereas the one fed with Streptomyces sp. N7 showed significantly higher survival rate (57.77 ± 6.8%) than the control group (0.55 ± 0.20 g and 11.11 ± 9.0%, respectively). The hepatopancreas of Streptomyces‐fed shrimps showed better histological integrity with significantly lower degree of atrophy and necrotic tubules than their unfed counterpart. No toxicity associated with these strains was found. Consequently, they can be excellent probiotic candidates to improve the physiological status and prevent infectious diseases of cultured L. vannamei.     

Impact of seed potatoes infected withPhytophthora infestans (US-1 or US-8 genotypes) on crop growth and disease risk

As the surface area with late blight symptoms of seed tubers increased, the incidence of plant emergence decreased. This relationship was more dramatic with the US-8 genotype than the US-1 genotype ofhytophthora infestans, causal agent of late blight. However, when seed tubers were inoculated with both US-1 and US-8 isolates, the plant growth responses were generally intermediate to those obtained with the two genotypes alone. More resistant cultivars (eg. Dorita, Island Sunshine, and Sebago) had greater plant emergence and less seed rot than more susceptible cultivars (eg. Green Mountain and Shepody) but the response differences between resistant and susceptible cultivars was less clear with US-8 as most cultivars had 100% seed rot. Seed handling treatments affected crop growth and disease risk; as the inoculum levels and in some cases, the pre-planting storage period increased, plant emergence decreased generally due to greater seed rot incidences. Of the one registered seed treatment fungicide and several non-registered and/or experimental fungicides tested, only two significantly improved plant emergence. During three years of study, “diseased” seed treatments generally led to seed rot except in 1996 when one plant in one experimental plot of infected seed had subsequent spread of the disease to the foliage. Furthermore, within one week, a field epidemic developed outwardly from the single infected plant due to the occurrence of favourable weather conditions. Further research opportunities are discussed relative to the impact of infected seed on crop growth and disease risk