亚热带丘陵茶园间作白三叶草的生态效应

在亚热带丘陵区1a生幼龄茶园通过连续4a的大田对比试验,研究了茶园间作白三叶草的生态效应,结果发现：茶园间作白三叶草降低了土壤容重,提高了土壤孔隙度、有机质、全N、水解N的含量、K的活性、蚯蚓的数量和生物量,消耗了部分有效P;增加了土壤关键层次（0—20cm）和关键时期（4～6月）的水分含量,延缓和缩短了夏季高温干旱与秋季持续干旱时间;获得了土壤降温时增温、保温与升温时降温的双向动态调控效果,增加了同一层次土壤温度的稳定性,延缓了高温和低温的出现时间,缩短了过度高温时间,减少了高温对茶树生长产生的影响;抑制了杂草生长,增加了天敌的种类和种群数量,减少了虫害发生率。从而形成了立地环境．茶树．伴生生物群落系统自我调节的动态平衡,促进了茶树生长,改善了茶叶品质,显著增加了茶叶产量。与清耕茶园相比,茶园间作白三叶草后,春秋茶的酚氨比分别下降了17．10％和30．90％,产量提高了32．65％。     

Biotransformation of linear alkylbenzene sulfonate (LAS) by Phanerochaete chrysosporium: oxidation of alkyl side-chain

The white rot fungus Phanerochaete chrysosporium, which generally mineralizes substituted aromatics to CO₂, transformed linear alkylbenzene sulfonate (LAS) surfactants mainly at their alkyl side chain. Degradation of LAS was evidenced by a zone of clearing on LAS-containing agar plates and colorimetric analysis of liquid cultures. Disappearance of LAS was virtually complete within 10 days in low nitrogen (2.4 mM N), high nitrogen (24 mM N) and malt extract (ME) liquid media. After 5 days of incubation in ME medium, transformation of LAS was complete at concentrations4 mg l^-1, but decreased at higher concentrations. The LAS degradation was not dependent on lignin peroxidases (LiPs) and manganese-dependent peroxidases (MnPs). Mineralization of¹⁴C-ring-LAS to ¹⁴CO₂ by P. chrysosporium was <1% regardless of the culture conditions used. Thin layer chromatography and mass spectral analyses indicated that P. chrysosporium transformed LAS to sulfophenyl carboxylates (SPCs) through oxidative shortening of the alkyl side-chains. While LAS disappearance in the cultures was not dependent on LiPs and MnPs, transformation of the parent LAS moieties to SPCs was more extensive in low N medium that favors expression of these enzymes. The SPCs produced in LN cultures were shorter in chain-length than those produced in ME cultures. Also there was a notable shift in the relative abundance of odd and even chain length metabolites compared to the starting LAS particularly in the low N cultures suggesting the possible involvement of processes other than or in addition to-oxidation in the chain-shortening process.     

The Amino Acid Sequence of Wood Duck Lysozyme

The amino acid sequence of wood duck (Aix sponsa) lysozyme was analyzed. Carboxymethylated lysozyme was digested with trypsin and the resulting peptides were sequenced. The established amino acid sequence had the highest similarity to duck III lysozyme with four amino acid substitutions, and had eighteen amino acid substitutions from chicken lysozyme. The valine at position 75 was newly detected in chicken-type lysozymes. In the active site, Tyr34 and Glu57 were found at subsites F and D, respectively, when compared with chicken lysozyme.     

Doxorubicin-induced alterations in kidney functioning,oxidative stress,DNA damage,and renal tissue morphology; Improvement by Acacia hydaspica tannin-rich ethyl acetate fraction

Doxorubicin (DOX) is an anthracycline drug used for cancer treatment. However, its treatment is contiguous with toxic effects. We examined the nephroprotective potential of A. hydaspica polyphenol-rich ethyl acetate extract (AHE) against DOX persuaded nephrotoxicity. 36 male Sprague Dawley rats were randomly assorted into 6 groups. Control group received saline; DOX group: 3 mg/kg b.w. dosage of DOX intraperitoneally for 6 weeks (single dose/week). In co-treatment groups, 200 and 400 mg/kg b.w AHE was given orally for 6 weeks in concomitant with DOX (3 mg/kg b.w, i.p. injection per week) respectively. Standard group received silymarin 400 mg/kg b.w daily + DOX (single dose/week). Biochemical kidney function tests, oxidative stress markers, genotoxicity, antioxidant enzyme status, and histopathological changes were examined. DOX caused significant body weight loss and decrease kidney weight. DOX-induced marked deterioration in renal function indicators in both urine and serum, i.e., PH, specific gravity, total protein, albumin, urea, creatinine, uric acid, globulin, blood urea nitrogen, etc. Also, DOX treatment increases renal tissue oxidative stress markers, while lower antioxidant enzymes in tissue along with degenerative alterations in the renal tissue compared to control rats. AHE co-treatment ameliorates DOX-prompted changes in serum and urine chemistry. Likewise, AHE treatment decreases sensitive markers of oxidative stress and prevented DNA damages by enhancing antioxidant enzyme levels. DOX induction in rats also caused DNA fragmentation which was restored by AHE co-treatment. Moreover, the histological observations evidenced that AHE effectively rescued the kidney tissue from DOX interceded oxidative damage. Our results suggest that co-treatment of AHE markedly improve DOX-induced deleterious effects in a dose-dependent manner. The potency of AHE co-treatment at 400 mg/kg dose is similar to silymarin. These outcomes revealed that A. hydaspica AHE extract might serve as a potential adjuvant that avoids DOX-induced nephrotoxicity.     

Purification and characterization of high antioxidant peptides from duck egg white protein hydrolysates

The hydrolysate from duck egg white protein (DEWP) prepared by “SEEP–Alcalase” at degree of hydrolysis (DH) value of 21% (namely HSA₂₁) exhibited high antioxidant capacity in different oxidation systems. A consecutive chromatographic method was then developed for separation and purification of HSA₂₁, including ion-exchange chromatography, macroporous adsorption resin (MAR) and gel filter chromatography. The final peptides “P_21-3–75-B” were obtained with significantly enhanced antioxidant activity (p < 0.05). It was further confirmed that the product mainly consisted of five oligopeptides (Mr: 202.1, 294.1, 382.1, 426.3, and 514.4 Da). Furthermore, the antioxidant activity of P_21-3–75-B kept stable after in vitro digestive simulation. Antioxidant capacity of the purified peptides was closely related to the molecular mass, hydrophobic amino acid residues, acidic amino acid and some antioxidant amino acids. This research provided a valuable route for producing new natural-source peptides with strong antioxidant capacity and high nutritious value for our daily intake.     

Isolation and characterization of microsatellite markers from Pacific white shrimp (Litopenaeus vannamei)

We report the development of 11 polymorphic microsatellite loci in pacific white shrimp (Litopenaeus vannamei) using an unenriched genomic library. The number of the alleles ranged from two to 18 and observed hererozygosity ranged from 0.0286 to 0.9429, indicating that these markers will be useful for population studies and mapping in pacific white shrimp. Seven loci were detected deviated from Hardy–Weinberg, caused by deficiency of heterozygote, suggesting population genetic structure across the sampled population. No evidence for linkage disequilibrium was found.     

The effect of soil nutrient availability on retranslocation of Ca,Mg and K from senescing sapwood in Atlantic white cedar

Nutrient resorption from senescing tissues increases plant nutrient-use efficiency, and may be an adaptation to nutrient limitation. In some tree species, retranslocation of nutrients from sapwood during heartwood formation is a comparable process. We measured Ca, Mg and K concentrations in Atlantic white cedar (Chamaecyparis thyoides) stemwood samples taken from two swamps in the northeastern United States and compared them to soil mineral nutrient availability at each site. We found that Ca, Mg and K concentrations were 60–700% higher in sapwood than in the immediately adjacent heartwood, indicating retranslocation of these nutrients from senescing sapwood. Sapwood nutrient concentrations were similar between the two sites. However, nutrient concentrations in the heartwood differed significantly between the sites, as did the relative degree of Ca and Mg retranslocation from senescing sapwood. We found these differences between sites to be inversely related to significant differences in exchangeable Ca, Mg and K as well as Al concentrations in the soil. These findings suggest that the degree of nutrient retranslocation from senescing sapwood may be influenced by soil nutrient availability. This revised version was published online in July 2006 with corrections to the Cover Date.     

Senescence and decomposition of white clover stolons in grazed upland grass/clover swards

The fate of marked sections of stolons of white clover (Trifolium repens) over a 50-week period from May 1987 was followed in grazed grass/clover swards maintained at 5-cm sward surface height with and without N fertiliser. There was little effect of N treatment on the pattern of survival of stolon sections. The proportion of live stolons recovered decreased during the experiment, and in May 1988 on average only 29% of the marked sections remained alive. At all harvests only a small percentage of stolon sections showed signs of senescence; the maximum percentage, on average 20% of those marked, occurred in autumn, 15–20 weeks after marking. Following this period, i.e. in late autumn/winter, the most rapid increase in percentage of decomposed stolons was measured. Over 50% of stolon sections were buried within the 5-week period following marking and nearly all were buried after 20 weeks; generally a much smaller proportion of stolon tips was buried. Nutrient concentrations of N, P and K fell to their lowest levels in autumn, before increasing in the following spring. Results are discussed in relation to the cycling of nutrients via stolon senescence.