Variation of the amino acid scores and of the nitrogen-to-protein conversion factors in barley grain as a function of nitrogen content as compared with wheat and rye

Barley grains (9 samples from 7 cultivars) with nitrogen contents (N) ranging from 1.45 to 4.01% of dry matter were analysed for their amino acid (AA) composition with high accuracy from six different hydrolysates per sample. AA levels in grain increased as linear functions ofN with correlation coefficients close to unity. A comparison with literature data confirmed that the AA composition of any grain sample of normal barley can be predicted from itsN for all phenotypes and genotypes. AAs in grain protein changed as hyperbolic functions ofN which increased for Phe, Pro and Glx but more or less strongly decreased for the other AAs. By plotting AA scores againstN, barley proteins were shown to be always richer than wheat and rye in Val and Phe + Tyr; sometimes richer than both other species forN<2 (Lys); 2.2 (Leu and Ile); 3.4 (Thr); sometimes intermediate to wheat and rye above the latterN values. They were also intermediate in sulphur AAs forN<1.9 and drastically poorer forN>1.9. However, they were richer than both other species in Trp forN>1.6. The hyperbolic variations of non-protein nitrogen and nitrogen-to-protein conversion factors were determined as a function ofN and also compared with those of wheat and rye.     

Biochemical and catalytic properties of three recombinant alcohol acyltransferases of melon. sulfur-containing ester formation, regulatory role of CoA-SH in activity, and sequence elements conferring substrate preference

Alcohol acyltransferases (AAT) play a key role in the biosynthesis of ester aroma volatiles in fruit. Three ripening-specific recombinant AATs of cantaloupe Charentais melon fruit (Cm-AAT1, Cm-AAT3, and Cm-AAT4) are capable of synthesizing thioether esters with Cm-AAT1 being by far the most active. All proteins, as well as AAT(s) extracted from melon fruit, are active as tetramers of around 200 kDa. Kinetic analysis demonstrated that CoA-SH, a product of the reaction, is an activator at low concentrations and an inhibitor at higher concentrations. This was confirmed by the addition of phosphotransacetylase at various concentrations, capable of modulating the level of CoA-SH in the reaction medium. Site-directed mutagenesis of some amino acids that were specific to the Cm-AAT sequences into amino acids that were consensus to other characterized AATs greatly affected the selectivity of the original protein and the number of esters produced.     

Protective effects of garlic (Allium sativum) extract upon lindane-induced oxidative stress and related damages in testes and brain of male rats

The purpose of this study, carried out on male Wistar rats, was to evaluate the beneficial effects of garlic (Allium sativum) extract injections upon lindane-induced damages in testes, brain and thyroid function. Under our experimental conditions, lindane poisoning (in drinking water for 30 days, supplying about 50 mg/kg body weight per day) resulted in a decreased weight of testes, epididymides, prostate gland and seminal vesicles (−52%, −42%, −50% and −5%, respectively), a decrease of spermatozoa count and motility (−56%, −37%, respectively), an increased level of free thyroxin (+84%) and decreased levels of TSH and FSH in serum (−74%, −77%, respectively). In addition, lindane treatment triggered an oxidative stress in testes and brain as revealed by an increased level of lipids peroxidation (TBARS) (+96%,+92%), an increase of superoxide-dismutase activity in testes (+69%) and a decrease of glutathione-peroxidase and catalase activities in testes and brain (−52%, −34% and −49%, −45%, respectively). These lindane-induced changes were almost reversed to normal in animals injected with a garlic extract (an amount corresponding to 300 mg fresh garlic/kg/day), what confirms a beneficial effect of this vegetal source of anti-oxidants.     

Surface mobility of postsynaptic AMPARs tunes synaptic transmission

AMPA glutamate receptors (AMPARs) mediate fast excitatory synaptic transmission. Upon fast consecutive synaptic stimulation, transmission can be depressed. Recuperation from fast synaptic depression has been attributed solely to recovery of transmitter release and/or AMPAR desensitization. We show that AMPAR lateral diffusion, observed in both intact hippocampi and cultured neurons, allows fast exchange of desensitized receptors with na?ve functional ones within or near the postsynaptic density. Recovery from depression in the tens of millisecond time range can be explained in part by this fast receptor exchange. Preventing AMPAR surface movements through cross-linking, endogenous clustering, or calcium rise all slow recovery from depression. Physiological regulation of postsynaptic receptor mobility affects the fidelity of synaptic transmission by shaping the frequency dependence of synaptic responses.     

Effects of stocking density on growth, yield and profitability of farming Nile tilapia, Oreochromis niloticus L., fed Azolla diet, in earthen ponds

Two consecutive experiments were conducted to study the effects of stocking density on growth, food utilization, production and farming profitability of Nile tilapia (Oreochromis niloticus) fingerlings (initial mean weight: 16.2 ± 0.2 g) fed Azolla, as a main component in diet. In experiment 1, fish were hand‐fed twice daily with three isonitrogenous (28.5% crude protein) and isocaloric (14.5 kJ g⁻¹) diets A30, A35 and A40 containing 30%, 35% and 40%Azolla, respectively, for 90 days. Diets were formulated by mixing Azolla with locally available by‐products. No significant differences were found in growth parameters and production (P>0.05). Total investment cost was significantly higher with A30 (P<0.05), but same profitability values were obtained with all diets (P>0.05). In experiment 2, three stocking densities, 1, 3 and 5 m⁻², were assigned to three treatments T₁, T₂ and T₃ respectively. Fish were hand‐fed twice daily with diet A40. The final mean weight (89.53–115.12 g), the mean weight gain (0.81–1.10 g day⁻¹), the specific growth rate (1.90–2.20% day⁻¹) and the apparent food conversion ratio (1.29–1.58) were affected by stocking density, with significant difference (P<0.05) at 5 m⁻², compared with the other densities. Stocking density did not affect survival rate (P>0.05). Yield and annual production increased with increasing stocking density, ranging from 7.10 ± 0.90 to 25.01 ± 1.84 kg are⁻¹ and 28.79 ± 3.66 to 101.42 ± 7.48 kg are⁻¹ year⁻¹, respectively, with significant differences between all densities (P<0.05). Higher stocking density resulted in higher gross return and lower cost of fish production, with significant variations (P<0.05). The net return increased with increasing stocking density (P<0.05). However, both densities of 3 and 5 m⁻² produced the same profitability values. On the basis of growth values and economic return, it was concluded that Nile tilapia could be raised at a density of 3 fish m⁻² with A40 to improve production and generate profit for nutritional security and poverty alleviation in rural areas.     

Influence of sediment characteristics on shrimp physiology: pH as principal effect

Penaeid shrimp reared in earthen ponds are exposed to sediment, which can, in some instances, induce a stress. In seawater, the osmoregulatory capacity (hyporegulation) is a useful tool to compare the physiological condition of shrimp exposed to various stressors. By keeping some shrimp in cages at different locations of a single pond heterogeneous in terms of sediment quality, it was possible, using osmotic pressure (OP), to identify some locations where the stress was maximum and some others where it was minimum. Simultaneously, sediment samples were taken and analysed in order to evaluate some physico-chemical parameters that could be related to the stress observed in the shrimps kept in the cages. This approach allowed to show a significant positive correlation between the pH of the sediment surface and the shrimp osmotic pressure. This result was confirmed in a study carried out in experimental 70-l tanks, where osmotic pressure decreased significantly as water pH decreased from 7.0 to 6.5. The methodology developed in this study may be useful to evaluate the stress caused by sediment in shrimp farms.     

Abundance response of western European forest species along canopy openness and soil pH gradients

In order to better understand the structure and composition of forest plant communities, we aimed to predict the abundance of understory herbaceous species locally at the stand level and according to different environments. For this, we seeked to model species distributions of abundance at a regional scale in relationship with the local stand structure (canopy openness) and regional soil resources (soil pH).Floristic inventories, performed in different light and soil conditions located in 1202 records of north eastern France, were used to analyze the combined effect of canopy openness and soil pH on the abundance of 12 common western European forest species: Anemone nemorosa, Deschampsia flexuosa, Festuca altissima, Hedera helix, Lamium galeobdolon, Lonicera periclymenum, Molinia caerulea, Oxalis acetosella, Pteridium aquilinum, Rubus fruticosus, Rubus idaeus, and Vaccinium myrtillus. Ordinal regression models relating species abundance responses to their environment were developed.For most species (eight out of 12), distribution was significantly affected by canopy openness and soil pH. Differences among low-abundance (i.e. cover <25%) and high-abundance (i.e. cover >25%) responses were noted for 11 species along the canopy openness gradient and four species along the pH gradient. The present study quantifies optimal light and soil nutrient requirements for high-abundance responses and quantifies light and soil nutrients tolerance conditions for low-abundance responses. The combination of both factors highlights the pre-eminence of pH conditions occurrence and canopy openness for species abundance.The models developed by this study may be used to define canopy openness thresholds in function of soil characteristics to control the development of species during forest regeneration. The species-specific reactions on local canopy openness along a regional soil gradient illustrate the need for a species-specific management approach.     

漆酶-介体系统处理麦草化学浆全无氯漂白性能的研究

采用漆酶－介体系统对麦草化学浆进行预处理，研究了几种全无氯漂白（TCF漂白）[氧碱脱木质素配合两段过氧化氢漂白（OEPP），两段过氧化氢漂白（QPP）和过乙酸配合一段过氧化氢漂白(PaP)]对漆酶处理后纸浆漂白性能的作用，结果表明，麦草浆经过漆酶预处理后，白度上升了12．9个白度单位（%,ISO)，漆酶处理浆氧碱脱木质素配合过氧化氢漂白后比原浆在相同条件下漂白后白度高14个白度单位以上，经两段过氧化氢漂白后白度比原浆在相同条件下（过氧化氢用量4％）漂白后白度高18．3个白度单位，经过乙酸过氧化氢漂白后比原浆在相同条件下漂白后白度高8．1个白度单位。漆酶处理浆漂白后强度比原浆漂白后的低，但是其白度高，如漂至相同的白度可以节约大量漂剂，有利于改善浆的质量，降低漂白废水的污染负荷。     

Dietary toxicity of decomposed arborescent leaf litter against larval mosquito: involvement of a lignin-polypeptidic complex

To characterize the toxic compounds involved in the dietary toxicity of decomposed arborescent leaf litter against larval mosquito, a toxic fraction was extracted from crude leaf litter by using hot water. Preliminary characterization of this fraction, called the insoluble fraction (IF) because it progressively precipitates after extraction, has suggested the involvement of lignin-like compounds in the toxicity. Further analyzes are currently being performed by using additional phytotoxicity-based methods. The involvement of lignin-like compounds in the toxicity was indicated by both the comparative effects of different enzymatic oxidative treatments and reversed-phase high-performance liquid chromatography analysis of the phenolic aldehydes and acids obtained after alkaline nitrobenzene oxidation. However, these lignin-like compounds may not be involved alone in the toxicity, as no specific feature of those components was associated with the toxicity. Among the possible compounds associated with lignin-like compounds in the toxicity, peptidic compounds were suggested by comparative determination of the C/N ratio and then revealed by denaturation experiments, use of specific binding protein molecules, and thin-layer chromatography analysis. A possible role of these peptidic compounds associated with lignin-like compounds in the dietary toxicity of the leaf litter against the larval mosquito midgut is discussed.