玉米种子脱水耐性与其线粒体完整性及抗氧化系统的关系

本文以正常性玉米种子‘农大108’(Zea Mays L. ‘Nongda 108’) 种胚为实验材料，研究了玉米种子发育过程中脱水耐性的变化规律，细胞匀浆以及线粒体水平上活性氧清除酶活性与种子脱水耐性/敏感性的关系，以及线粒体结构和功能完整性在发育过程中不同阶段对脱水的应答，以期在亚细胞分区水平上，针对活性氧产生的源头位点 (线粒体) 探明种子细胞脱水耐性/敏感性与抗氧化系统运转的关系。结果表明： 玉米种子在发育过程中先获得萌发能力后获得脱水耐性，并且脱水耐性的获得是一个渐进的过程。人工授粉后26天 (Days after pollination, DAP) 之前的种胚不具有脱水耐性，26 DAP时开始获得脱水耐性，到34 DAP后种胚完全获得脱水耐性。 在发育过程中，种胚线粒体的呼吸速率逐渐降低，并且对脱水的敏感性也逐渐下降。脱水会降低脱水敏感性种胚线粒体的结构完整性；脱水同时会降低线粒体功能的完整性，包括线粒体能量产生的速率和效率，以及三羧酸循环关键酶的活性。但当种胚获得脱水耐性后，脱水将不再影响种胚线粒体结构和功能的完整性。 玉米种胚发育过程中脱水耐性的变化与细胞中的抗氧化系统有关。在细胞匀浆水平上，脱水过程中脂质过氧化产物的积累与细胞脱水耐性的关系不明显；但是在线粒体水平上脱水会明显导致脱水敏感性种胚线粒体膜质过氧化程度的升高。脱水导致脱水敏感种胚细胞中几个重要的抗氧化酶活性的下降，但是与细胞匀浆水平相比，在线粒体水平上抗氧化酶系统对脱水更加敏感。 总之，发育早期玉米胚对脱水之所以敏感有两方面的原因，一方面是发育早期线粒体具有较高的代谢速率因而产生过多的活性氧，另一方面是由于脱水导致各抗氧化酶活性的显著降低，失去了抗氧化保护功能。而在发育晚期，早期本来很活跃的许多代谢随之关闭，呼吸速率降到很低，因而产生的活性氧减少，同时由于抗氧化系统对脱水的耐受性，所以脱水不会对线粒体的结构和功能造成伤害。与细胞匀浆水平相比，线粒体水平上抗氧化系统的运转与种胚在发育过程中脱水耐性的获得的关系更加密切。

Nanoindentation measurements of bone viscoelasticity as a function of hydration state

Bone is an anisotropic material, and its mechanical properties are determined by its microstructure as well as its composition. Mechanical properties of bone are a consequence of the proportions of, and the interactions between, mineral, collagen and water. Water plays an important role in maintaining the mechanical integrity of the composite, but the manner in which water interacts within the ultrastructure is unclear. Dentine being an isotropic two-dimensional structure presents a homogenous composite to examine the dehydration effects. Nanoindentation methods for determining the viscoelastic properties have recently been developed and are a subject of great interest. Here, one method based on elastic-viscoelastic correspondence for 'ramp and hold' creep testing (Oyen, J. Mater. Res., 2005) has been used to analyze viscoelastic behavior of polymeric and biological materials. The method of 'ramp and hold' allows the shear modulus at time zero to be determined from fitting of the displacement during the maximum load hold. Changes in the viscoelastic properties of bone and dentine were examined as the material was systematically dehydrated in a series of water:solvent mixes. Samples of equine dentine were sectioned and cryo-polished. Shear modulus was obtained by nanoindentation using spherical indenters with a maximum load hold of 120s. Samples were tested in different solvent concentrations sequentially, 70% ethanol to 50% ethanol, 70 % ethanol to 100% ethanol, 70% ethanol to 70% methanol to 100% methanol, and 70% ethanol to 100% acetone, after storage in each condition for 24h. By selectively removing and then replacing water from the composite, insights in to the ultrastructure of the tissue can be gained from the corresponding changes in the experimentally determined moduli, as well as an understanding of the complete reversibility of the dehydration process. © 2006 Materials Research Society.

Physics in fish processing technology

To design, develop and put into operation an equipment either to increase the productivity or to improve the existing technique to obtain a better quality of the product, the fishery engineer/scientist should have a comprehensive knowledge of fundamental principles involved in the process. Many a technique in fish processing technology, whether it applies to freezing, dehydration or canning, involves always a type of heat transfer, which is dependent to a certain extent on the external physical parameters like temperature. humidity, pressure, air flow etc. and also on the thermodynamic properties of fish muscle in the temperature ranges encountered. Similarly informations on other physical values like dielectric constant and dielectric loss in the design of quick trawlers and in quality assessment of frozen/iced fish, refractive index and viscosity in the measurement of the saturation and polymerisation of fish oils and shear strength in the judgement of textural qualities of cooked fish are also equally important.

A comparative study of various extenders of milkfish, Chanos chanos (Forsskal) sperm preservation

Four chemical extenders in 7 different concentrations (potassium chloride, sodium chloride, glucose, sodium citrate, Ringer s solution, cow serum and milkfish (Chanos chanos) serum) were compared in the preservation of milkfish sperm. Results showed milkfish serum to be the most suitable of the various extenders tested. This may be attributed to suitable osmotic potential and/or presence of proteins which may have directly or indirectly influenced sperm viability. The effects of milkfish serum on the motility and fertilizing capacity of sperm at different durations of storage however need to be investigated.

Effect of cooking and drying on carbonyls of oil sardine

Changes in the total as well as major individual carbonyls of oil sardine during steam cooking, oven drying, sun drying and freeze drying are presented. Carbonyls extracted with hexane were converted to their 2:4 dinitro phenyl hydrazone (DNPH) derivatives and were separated into major classes by column chromatography on celite/magnesia. Individual carbonyls were then identified by capillary gas chromatography of the DNPH derivatives. Dehydration and heating increase the carbonyl production from highly unsaturated fish lipids. The carbonyls produced react with other muscle constituents leading to complex changes. The influence of the mode of dehydration on these different aspects and their net effect on flavour are discussed.

Effect of salinity and food ration level on the growth of Nile tilapia (Oreochromis niloticus L.)

The effect of salinity (0, 10 & 20‰, water temperature 28 ± 1°C) and food ration (3 and 4.5% bw/day) on food consumption and growth of Nile tilapia, Oreochromis niloticus (10.77 ± 0.21g) were investigated. Individual food consumption was measured using X-radiography technique. Salinities (0, 10 & 20‰) did not have significant effect on the growth rate of groups of Nile tilapia fed at different ration levels (3 & 4.5% bw/day). This study showed that the growth of all-male fish was significantly better than all-female fish for all three salinities and two rations. Salinities from 0 to 20‰ had no effect on growth performance of males or female fish. In the present study, it was evident that fish fed at 3% bw/day ration ate all the food offered and fish fed at 4.5% bw/day did not consumed all amounts. Also, growth performance did not significantly differ among fish fed at 3% bw/day ration level and reared at different salinities. Fish reared under higher salinities (20‰) and fed at higher ration (4.5% bw/day) level had skin lesions and injuries on their body. It was assumed that fish fed at higher ration under higher salinities (20‰) and maintained higher osmoregulatory costs together with osmotic stress may have a negative influence on the appetite of fish. Another possibility that may have affected the appetite could be the unionized ammonia levels that were high. The high-unionized ammonia levels combined with the osmotic stress may have been the cause, or have aided, development of skin lesions and injuries on the fish at higher salinities.

Biogeochemical study of poly aromatic hydrocarbons (PAHs) and its physiological affection response in mudskipper (Boleophthalmus dussumieri) at coast of Khuzestan

Study on the biomarkers types to assess health status of marine ecosystems in environmental biomonitoring has an important value. Accordingly, accumulation of polycyclic aromatic hydrocarbons(PAHs) in sediment, water and tissues (liver and gill) of mudskipper(i.e. Boleophthalmus dussumieri) and some physiological responses like lysosomal membrane change performed on haemocytes, stability of red blood cell membrane and the Glutathione-S Transferase (GST) activity in the liver were measured in mudskipper. Samples were obtained from five sites along north western coast of the Persian Gulf (Khuzestan coast). Red blood cell membrane changes after different concentration of PAHs at different time was also studied to evaluate impact of PAHs compound on cell membrane. PAHs concentration was measured by HPLC method. The activity of GST enzyme was analysed by spectrophotometric method. Lysosomal membrane change was measured by NRR time method and stability of red blood cell membrane was evaluated by EOF test. Total PAH concentrations in the coastal sea water, the sediments, the liver and the gill tissues ranged between 0.80-18.34 μg/l, 113.50-3384.34 ng g-1 (dry weight), 3.99-46.64 ng g-1 dw and 3.11-17.76 ng g-1 dw, respectively. Highest PAHs pollution was found at Jafari while the lowest was detected at Bahrakan sampling sites. The lowest enzymatic activity was identified at Bahrakan (7.19 ± 1.541 nmol/mg protein/min), while the highest was recorded at Jafari (46.96 ± 7.877 nmol/mg protein/min). Comparative analysis of GST activity in the liver of mudskippers showed significant difference (p < 0.05) between the locations of Jafari and Bahrakan, and with other sites. Moreover, no significant difference was detected between the locations of Arvand, Zangi and Samayeli (p < 0.05). The mean RT was below 90 minutes in all sampling sites. Values of mean RT of the dye ranged from 34 (for the blood samples of mudskipper collected from Jafari site) to 78 minutes (for the blood samples of mudskipper collected from Bahrakan site). Spatial evaluation revealed the longest RT in fish from Bahrakan as compared with those from other sites. Preliminary results showed a significant difference (p < 0.05) among sampling sites except between Arvand and Zangi (p > 0.05). Osmotic fragility curves indicated that erythrocytes collected from mudskippers at Jafari were the most 009 fragile followed by Zangi> Arvand> Samayeli> and Bahrakan. The mean erythrocyte fragility was significantly higher at Jafari site (p < 0.05) when compared to other sites. Significant differences were found between the various sites (p < 0.05).The result indicated no significant differences between the control and treatments of mudskipper RBC exposed to field concentrations of PAHs (P>0.05). The results further indicated significant differences (P<0.05) between the control and treatments of mudskipper RBC exposed to acute. Potency Divisor concentrations. It is clear from the present result that chronic. Potency Divisor concentrations protect red cells against osmotic hemolysis. This study, however, showed that PAH concentrations in this region are not higher than the available standards. The findings showed that Lysosomal membrane destabilization, liver GST activities and fragility of red cell membrane are highly sensitive in the mudskipper, B. dussumieri. Thus, mudskipper perceived to be good sentinel organisms for PAH pollution monitoring. Sediment PAH concentrations were strongly correlated with biomarkers, indicating that PAH type pollutants were biologically available to fish. One of the possible risk assessment implications of this study is that biomarkers can be applied not only to characterize biological effects of pollution exposures, but also to determine the bioavailability of pollution in aquatic systems. The results also indicated that PAHs compound possess anti haemolytic property.

The effect of cationic, non-ionic and amphiphilic surfactants on the intercalation of bentonite

Surfactant-clay interactions are key for the development of new clay applications and inorganic-organic nanocomposites. Bentonite, with montmorillonite as the principal clay mineral constituent, was modified with varying concentrations of hexadecethyltrimethylammonium chloride (HDTMA), as a reference cationic surfactant, polypropylene glycol (PPG) 1200 and 2000, as non-ionic surfactants, and lecithin and Topcithin®, as amphiphilic phospholipid surfactants, according to the cation exchange capacity (CEC). The modified bentonites were characterised by X-ray diffraction, thermogravimetric analysis (TGA), Fourier transform infrared (FTIR) spectrometry, specific surface area and pore volume. Three intercalation regions have been identified depending on the surfactant. The non-ionic surfactant caused only a crystalline expansion of bentonite interlayers, while the cationic surfactant induced an osmotic intercalation. The amphiphilic lecithin derivatives intercalated more extensively with the bentonite matrix. The TGA and the FTIR spectra showed that, at lower concentrations, the PPGs and HDTMA adopted a disordered conformation that required more energy to degrade, while at higher concentrations, the surfactants were ordered in the interlayer space of the bentonite. The lecithin derivative surfactant had a greater thermal and conformation stability. The specific surface area reduced with increasing surfactant concentrations. This study highlights the effect of surfactant type on the interlayer space of montmorillonite in the perspective of developing novel clay functions. © 2013.

Effects of salt stress on carbohydrate metabolism in desert soil alga Microcoleus vaginatus Gom.

The effects of salt stress on carbohydrate metabolism in Microcoleus vaginatus Gom., a cyanobacterium isolated from desert algal crusts, were investigated in the present study. Extracellular total carbohydrates and exopolysaccharides (EPS) in the culture medium produced by M. vaginatus increased significantly during the growth phase and reached a maximum during the stationary phase. The production of extracellular carbohydrates also significantly increased under higher salt concentrations, which was attributed to an increase in low molecular weight carbohydrates. In the presence of NaCl, the production of cellular total carbohydrates decreased and photosynthetic activity was impaired, whereas cellular reducing sugars, water-soluble sugars and sucrose content and sucrose phosphate synthase activity increased, reaching a maximum in the presence of 200 mmol/L NaCl. These parameters were restored to original levels when the algae were transferred to a non-saline medium. Sodium and K+ concentrations of stressed cells decreased significantly and H+-ATPase activity increased after the addition of exogenous sucrose or EPS. The results suggest that EPS and sucrose are synthesized to maintain the cellular osmotic equilibrium between the intra- and extracellular environment, thus protecting algal cells from osmotic damage, which was attributed to the selective exclusion of cellular Na+ and K+ by H+-ATPase.

Salt tolerance of Microcoleus vaginatus Gom., a cyanobacterium isolated from desert algal crust, was enhanced by exogenous carbohydrates

Microcoleus vaginatus isolated from a desert algal crust of Shapotou was cultured in BG-11 medium containing 0.2mol l(-1) NaCl or 0.2mol l(-1) NaCl plus 100mg l(-1) sucrose, extracellular polymeric substances (EPS) or hot water-soluble polysaccharides (HWP), respectively. Photosynthetic oxygen evolution rates, photosystem 11 activity (Fv/Fm) and dark respiration of NaCl-stressed cells were enhanced significantly by the added sucrose or EPS under salt stress conditions (0.2mol l(-1) NaCl). Compared with cells treated with salt alone, sodium contents in cells reduced significantly; the content of cellular total carbohydrate did not change, and intracellular sucrose, water-soluble sugar increased significantly following the addition of exogenous carbohydrates. Sucrose synthase (SS) activity of NaCl-stressed cells increased following the addition of sucrose, and sucrose phosphate synthase (SPS) activity of NaCl-stressed cells increased following the addition of exogenous sucrose, EPS or HWP compared with cells stressed with NaCl only. The results suggested that the extruded EPS might be re-absorbed by cells of M. vaginatus as carbon source, they could increase salt tolerance of M. vaginatus through the changes of carbohydrate metabolism and the selective uptake of sodium ions. (C) 2003 Elsevier Science Ltd. All rights reserved.

Photosynthetic bicarbonate utilization in Porphyra haitanensis (Bangiales, Rhodophyta)

The activities of carbonic anhydrase (CA) and photosynthesis of Porphyra haitanensis were investigated in order to see its photosynthetic utilization of inorganic carbon source. Both intra- and extra-cellular CA activities existed in the thallus. CA inhibitors, acetazolamide (AZ) and ethoxyzolamide (EZ), remarkably depressed the photosynthetic oxygen evolution in seawater of pH 8.2 and 10.0, and EZ showed stronger inhibition than AZ. The observed net photosynthetic rate In seawater of pH 8.2 was much higher than that of CO2 supply theoretically derived from spontaneous dehydration of HCO3-. P. haitanensis also showed a rather high pH compensation point (9.9). The results demonstrated that P. haitanensis could utilize bicarbonate as the external inorganic carbon source for photosynthesis. The bicarbonate utilization was closely associated with HCO3- dehydration catalyzed by extracellular CA activity. The inorganic carbon composition in seawater could well saturate the photosynthesis of P. haitanensis. The low K-m value and compensation points for inorganic carbon reflected the existence of CO2-concentrating mechanism in this alga.

Upgrading bio-oil over different solid catalysts

Solid acid 40SiO(2)/TiO2-SO42- and solid base 30K(2)CO(3)/Al2O3-NaOH were prepared and compared with catalytic esterification activity according to the model reaction. Upgrading bio-oil by solid acid and solid base catalysts in the conditioned experiment was investigated, in which dynamic viscosities of bio-oil was lowered markedly, although 8 months of aging did not show much viscosity to improve its fluidity and enhance its stability positively. Even the dehydration by 3A molecular sieve still kept the fluidity well. The density of upgraded bio-oil was reduced from 1.24 to 0.96 kg/m(3), and the gross calorific value increased by 50.7 and 51.8%, respectively. The acidity of upgraded bio-oil was alleviated by the solid base catalyst but intensified by the solid acid catalyst for its strong acidification. The results of gas chromatography-mass spectrometry analysis showed that the ester reaction in the bio-oil was promoted by both solid acid and solid base catalysts and that the solid acid catalyst converted volatile and nonvolatile organic acids into esters and raised their amount by 20-fold. Besides the catalytic esterification, the solid acid catalyst carried out the carbonyl addition of alcohol to acetals. Some components of bio-oil undertook the isomerization over the solid base catalyst.

Solid-core tellurite glass fiber for infrared and nonlinear applications

By optimizing glass composition and using a multistage dehydration process, a ternary 80TeO(2)-10ZnO-10Na(2)O glass is obtained that shows excellent transparency in the wavelength range from 0.38 mu m up to 6.10 mu m. Based on this optimized composition, we report on the fabrication of a single-mode solid-core tellurite glass fiber with large mode area of 103 mu m(2) and low loss of 0.24 similar to 0.7 dB/m at 1550 nm. By using the continuous-wave self-phase modulation method, the non-resonant nonlinear refractive index n(2) and the effective nonlinear parameter gamma of this made tellurite glass fiber were estimated to be 3.8x10(-1)9 m(2)/W and 10.6 W-1.m(-1) at 1550 nm, respectively. (C) 2009 Optical Society of America