Hemoglobin-mediated oxidation of washed minced cod muscle phospholipids: effect of pH and hemoglobin source

Lipid pro-oxidative properties and deoxygenation/autoxidation patterns of hemoglobins from nonmigratory white-fleshed fish (winter flounder and Atlantic pollock) and migratory dark-fleshed fish (Atlantic mackerel and menhaden) were compared during ice storage at pH 7.2 and 6. A washed cod mince model system and a buffer model system were used for studying lipid changes and hemoglobin changes, respectively. TBARS and painty odor were followed as markers for lipid oxidation. At pH 6, all four hemoglobins were highly and equally active as pro-oxidants. At pH 7.2, pro-oxidation by all hemoglobins except that from pollock was slowed down, and activity ranked as pollock > mackerel > menhaden > flounder. The higher catalytic activities of the hemoglobins at pH 6 than at pH 7.2 corresponded with higher formation of deoxyhemoglobin and methemoglobin. Pollock had the most extensive formation of deoxy- and methemoglobin at both pH values, which could explain its high catalytic activity. The pro-oxidative differences among the other hemoglobins at pH 7.2 did not correlate with deoxygenation and autoxidation reactions. This indicates involvement of other structural differences between the hemoglobins such as differences in the heme-crevice volume. It is suggested that a biological reason for the species differences was their adaptations to different depths/water temperatures.     

Lignin signature of subalpine Rendzinas (Tangel- and Moderrendzina) in the Bavarian Alps

Simple phenolic lignin degradation products released from alkaline CuO oxidation are used to characterize the lignin component of a Tangelrendzina and a Moderrendzina. The sum of CuO oxidation products describes the overall lignin decomposition pattern. The ratio of acid/aldehyde of the vanillyl unit and the ratio of syringyl/vanillyl units give an indication of the alteration of the remnant lignin molecule. In both soils the sum of lignin oxidation products shows a pronounced decrease with depth. In the Oh, Ca horizon of the Tangelrendzina and the Ah of the Moderrendzina an accumulation of lignin-derived phenolic compounds is observed. The strong increase of the acid/aldehyde ratio at the transition from the humus to the mineral horizons in both soils and the decrease of the syringyl/vanillyl ratio in the Moderrendzina demonstrate a considerable chemical alteration of the remnant lignin molecule (oxidation of side-chain, enrichment with vanillyl units) with progressive decomposition and humification of litter material. The depth functions of the lignin parameters are influenced by decomposition of lignin, accumulation of water-soluble lignin fragments and the input of root litter.     

Landscape analysis: A design tool for sustainable irrigation development

By taking the proposed smallholder South-West Kano irrigation scheme as a case study, this article illustrates that designing sustainable irrigation schemes requires knowledge of the present landscape and insight into the demands of the society on the environment at present and in the future. First, the effects of irrigated rice production on farming households in four existing irrigation schemes in the Kano Plains in Kenya are evaluated. Second, a landscape analysis is applied to the South-West Kano project area to evaluate the uses and functions of the current landscape. The design criteria formulated from the perspective of these two evaluations form the basis of an assessment of four options of irrigation development in the South-West Kano project area. As socio-economic processes are reflected in the landscape, landscape analysis can be instrumental in visualizing and quantifying data not easily grasped otherwise. It may thus help to make discussions between farmers and engineers more concrete and to the point.     

Chemical form of selenium in naturally selenium-rich lentils (Lens culinaris L.) from Saskatchewan

Lentils (Lens culinaris L.) are a source of many essential dietary components and trace elements for human health. In this study we show that lentils grown in the Canadian prairies are additionally enriched in selenium, an essential micronutrient needed for general well-being, including a healthy immune system and protection against cancer. Selenium K near-edge X-ray absorption spectroscopy (XAS) has been used to examine the selenium biochemistry of two lentil cultivars grown in various locations in Saskatchewan, Canada. We observe significant variations in total selenium concentration with geographic location and cultivar; however, almost all the selenium (86-95%) in these field-grown lentils is present as organic selenium modeled as selenomethionine with a small component (5-14%) as selenate. As the toxicities of certain forms of arsenic and selenium are antagonistic, selenium-rich lentils may have a pivotal role to play in alleviating the chronic arsenic poisoning in Bangladesh.     

Hemoglobin-mediated lipid oxidation and compositional characteristics of washed fish mince model systems made from cod (Gadus morhua), herring (Clupea harengus), and salmon (Salmo salar) muscle

The use of washed cod light muscle minces in mechanistic studies of hemoglobin (Hb)-mediated fish lipid oxidation has largely increased in the past 5 years. Although cod light muscle has a low level of intrinsic lipid oxidation catalysts, a prerequisite for a good oxidation model system, we believe it cannot fully mimic the oxidation kinetics taking place in other fish species being more susceptible to lipid oxidation. The aim of this study was to systematically investigate whether washed mince model systems useful in Hb-mediated oxidation studies could be prepared also from herring (Clupea harengus) and salmon (Salmo salar) light muscles. The kinetics of oxidation in the washed models was measured during ice storage (+/-Hb), and the results were related to compositional differences. Minces from cod, herring, and salmon light muscles were washed 3 times with 3 volumes of water and buffer. A 20 microM portion of Hb and 200 ppm streptomycin was then added, followed by adjustment of pH and moisture to 6.3 and 86%, respectively. Samples with or without Hb were then stored on ice, and oxidation was followed as peroxide value (PV), rancid odor, redness (a*) loss and yellowness (b*). Prior to storage, all minces and models were also analyzed for total lipids, fatty acids, alpha-tocopherol, proteins, Hb, Fe, Cu, and Zn. Hb-mediated lipid oxidation appeared within 2 days on ice in all models. Small differences in the oxidation rates ranked the models as herring > cod > salmon. These differences were ascribed to more preformed peroxides and trace elements in the herring model, and more antioxidants in the salmon model. Controls, without Hb, stayed stable in all cases except herring, where a very slight oxidation appeared, especially if the herring raw material had been prefrozen. In conclusion, fattier fish like dark muscle species and salmonoids are useful for making washed mince model systems and would be a better choice than cod if there is an interest in the oxidation kinetics of such species.     

Multienzyme inhibition assay for residue analysis of insecticidal organophosphates and carbamates

A recently developed spectrophotometric assay for the detection of organophosphorus and carbamate insecticides by means of cutinase inhibition has been successfully extended to two esterases derived from Bacillus subtilis (BS2) and rabbit liver. These esterases were selected because of their high sensitivity to the examined insecticide classes and their pronounced inhibition profile. With inhibition constants (ki) of 2.0x10(7) and 2.6x10(6) L/(mol.min) for rabbit liver esterase and BS2, respectively, chlorpyrifos oxon proved to be the strongest inhibitor directly followed by paraoxon. As compared to choline esterases and the recently studied cutinase, both esterases are surprisingly strongly inhibited by organophosphorus thions, showing k i in the range of 5.3x10(2) to 2.3x10(4) L/(mol.min). All tested insecticidal carbamates were also inhibitors of BS2 and rabbit liver esterase, albeit in a rather uniform manner. Generally, both enzymes were found to be about 2 orders of magnitude more sensitive on the studied insecticides than cutinase even with an enhanced sensitivity against plant matrix effects. Plant extracts, obtained according to the QuEChERS method, were subjected to solid-phase extraction (SPE) using a mixed mode strong anion exchanger/primary secondary amine sorbent and C18endcapped cartridges for superior cleanup. With spiked samples of apple juice, best recoveries of 73% (+/-61%), 94% (+/-25%), and 134% (+/-17%) were obtained for chlorpyrifos, parathion-methyl, and paraoxon, respectively. Results of exemplarily performed liquid chromatography-mass spectrometry control measurements were well in accordance with measurements obtained by enzyme inhibition.     

Melatonin synthesis: adenosine 3',5'-monophosphate and norepinephrine stimulate N-acetyltransferase

Treatment of cultured rat pineal glands with norepinephrine or dibutyryl adenosine 3',5'-monophosphate causes a six- to tenfold stimulation of N-acetyltransferase. This enzyme converts serotonin to N-acetylserotonin, the immediate precursor of melatonin. The increased synthesis of melatonin caused by norepinephrine treatment appears to be the result of stimulation of N-acetyltransferase by an adenosine 3',5'-monophosphate mechanism.     

Acid‐extractable potassium in agricultural soils: Source minerals assessed by differential and quantitative X‐ray diffraction

Different extraction methods are used world‐wide in routine soil analysis to estimate long‐term potassium (K) reserves for plants. In Sweden, K extracted with 2 M HCl at 100°C (K_HCl) is frequently used, although with limited understanding of the phases extracted. In the present study, we quantified the effects of this extraction on soil minerals in particle size fractions ranging from clay to sand, and estimated their relative contribution to K_HCl. The study included three Swedish long‐term agricultural field experiments with texture ranging from loamy sand to silty clay, as well as mineral specimens of K feldspar. Total weight loss of particle size fractions was determined, and quantitative and differential X‐ray powder diffraction (QXRD, DXRD), applied on solids before and after extraction, was used to quantify the dissolution of individual mineral phases. QXRD and DXRD included spray‐drying of samples, addition of an internal standard and full pattern fitting, where a combination of mineral‐standard XRD traces was matched with the experimental one. Our results show that K_HCl was primarily associated with clay minerals concentrated in the two finest fractions (2–20 and < 2 μm). Highly expandable and mixed‐layer phyllosilicates were quantitatively the most important minerals dissolved. The K was released from micaceous layers in mixed‐layer phyllosilicates with a vermiculitic character. Whether di‐ or trioctahedral, a shared property of the dissolved phases was that they were rich in Fe. In the loamy sand, the coarser fractions (20–2000 μm), where feldspars were prominent, accounted for 35% of K_HCl. According to DXRD, there was no significant decrease in K feldspars in any of the samples, and K_HCl data for the feldspar specimens suggest that clay minerals contributed at least 70% of K_HCl also in the loamy sand. Our study provides insights about the soil minerals that contribute to the long‐term K delivery capacity of soils and an explanation for the prior observation that K_HCl is a dynamic fraction that can be affected by management.