超高压处理对凡纳滨对虾虾仁蛋白质和微观结构的影响

为丰富超高压技术在虾类保鲜与加工中的应用基础理论并实现工业化生产,实验以未处理的凡纳滨对虾虾仁为对照,用超高压(100、300、500 MPa)分别处理虾仁5、10、20、30 min,分析蛋白质含量、组成和热稳定性的变化,观察虾仁肌肉组织的微观结构。结果显示,100 MPa处理使虾仁的肌浆蛋白含量增加,300和500 MPa处理使肌浆蛋白含量显著下降。超高压处理使肌原纤维蛋白含量显著下降,使虾仁蛋白质发生了变性、肌球蛋白和肌动蛋白的热稳定性降低;随着压强的升高和处理时间的延长,虾仁肌原纤维排列变得紧实致密,肌节严重收缩,肌纤维之间空隙变模糊而呈现出絮状结构。研究表明,超高压处理能使对虾蛋白质变性而产生凝胶化,从而有利于人体的消化和吸收,说明超高压可以用于加工即食虾类产品。     

Thermostability variation in alleles of barley beta-amylase

Thermostability assays in conjunction with IEF and molecular mapping were used to identify three beta-amylase alleles (Bmyl-Sd1, -Sd2L, -Sd2H) in cultivated barley and an additional allele (Bmy1-Sd3) in an accession of wild barley Hordeum vulgare ssp. spontaneum. The four forms of beta-amylase exhibit different rates of thermal inactivation in barley extracts. This variation was shown to persist after the proteolytic processing of the enzyme that occurs during germination. Three forms of beta-amylase representing the range of thermostabilities were purified and shown to have T₅₀ temperatures of 56·8°C for the Sd2L enzyme, 58·5°C for the Sd1 enzyme, and 60·8°C for the Sd3 beta-amylase from wild barley. Analysis of the relationship between beta-amylase thermostability and fermentability, i.e. the yield of fermentable sugars obtained from starch hydrolysis during brewing in 42 commercial malt samples suggests that increased thermostability results in more efficient starch degradation. Screening for specific beta-amylase alleles is proposed as a method for increasing fermentability in malting barley.     

耐高温酶制剂对奥尼罗非鱼免疫和肠道结构的影响

为了验证耐高温酶制剂的使用效果,试验在基础饲料中添加0.1%的耐高温饲用酶,饲养奥尼罗非鱼60d,测定罗非鱼血清中非特异免疫指标,并电镜观察小肠细胞微绒毛排列情况;同时测定饲料厂制粒前后蛋白酶活力的变化情况。结果表明,添加耐高温酶制剂组超氧化物歧化酶(SOD)和溶菌酶水平比对照组有显著提高(P<0.05);同时,试验组罗非鱼小肠细胞微绒毛排列整齐、细而长,吸收面积增大;对照组的小肠细胞的微绒毛稀疏、短,排列不均匀。结果证实,在罗非鱼饲料中添加耐高温酶可以显著增强其免疫力,增加其对饲料的吸收率。制粒冷却包装后酶活力仍可保持90%以上,而普通酶只有25%左右。     

Hydrogen peroxide reduces heat‐induced yield losses in cotton (Gossypium hirsutum L.) by protecting cellular membrane damage

We investigated the effect of various growth substances such as hydrogen peroxide, salicylic acid (SA), moringa leaf‐extract (MLE) and ascorbic acid (ASA) on leaf physiology and seed cotton yield (SCY) of heat‐stressed cotton. Cotton plants were exposed to elevated temperatures at three reproductive stages, either by staggering planting time in the field or by increasing growth cabinet temperatures (38/24°C and 45/30°C) in glasshouse. Elevated temperature at any reproductive phase significantly damaged cellular membrane and reduced SCY. Plants exposed to 38/24°C and 45/30°C in glasshouse produced 63% and 22% lower SCY, respectively, compared with plants under optimal temperature ((32/20°C). In response to high temperature, cotton plants up‐regulated activities of anti‐oxidative enzymes e.g. peroxidase and ascorbic acid. However, this defensive system could not protect cellular membrane of stressed plants from extreme temperature (38 and 45°C). In contrast, growth substances such as H2O2, ASA and MLE significantly increased anti‐oxidative enzymes activity to an extent, which reduced heat‐induced damage to cellular membrane. No significant effect of any regulator was observed on SCY under optimum temperatures; although H2O2, MLE and ASA significantly increased SCY of heat‐stressed cotton. Hydrogen peroxide increased SCY of April and May thermal regimes crops by 16% (averaged across both sowing dates) under field, while it caused 14% and 20% increase in SCY of plants exposed to sub (38/24°C) and supra optimal (45/30°C) thermal regimes under glasshouse. We concluded that growth regulators, specifically, H2O2 can protect cotton crops from heat‐induced cellular membrane damage by up‐regulating antioxidant defense system.     

热锻炼对小麦叶片细胞膜及有关酶活性的影响

３４℃１－５天的热锻炼提高了小麦叶片的膜稳定性、超氧物歧化酶（ＳＯＤ）和过氧化氢酶（ＣＡＴ）的活性，耐热品种提高程度大大高于热敏感品种。同时热锻炼降低了小麦叶片的可溶性蛋白含量但提高了蛋白质的稳定性。３４℃热锻炼后小麦叶片在５０℃高温伤害处理过程中，耐热品种比热敏感品种保持有较高的ＳＯＤ酶活性和较低的膜伤害（即高的膜稳定性）。可以认为，高温引起膜伤害是一个自由基伤害的过程，而ＳＯＤ酶、ＣＡＴ酶活性     

Breeding for adaptation to drought and heat in cowpea

Accomplishments in breeding for adaptation to drought and heat are reviewed based upon work with the indeterminate grain legume species cowpea. Plant traits and some crop management methods are examined that influence adaptation to rainfed production in the drought-prone, semiarid tropical Sahelian zone of Africa. Drought escape, drought resistance, delayed-leaf-senescence, and varietal intercrops are examined. In addition, adaptation to the heat that can detrimentally impact irrigated production in the hot, subtropical arid zone of California is evaluated. Heat tolerance during reproductive development, electrolyte leakage, membrane thermostability, some aspects of crop management including date of sowing, and chilling tolerance during emergence including the beneficial effects of a dehydrin protein are considered. Methods for breeding cowpeas with adaptation to drought and heat are described that have been effective.     

白色链霉菌产木聚糖酶规律及其耐热耐碱性的初步研究

该文采用白色链霉菌为实验菌种,在不同诱导产酶培养基上经过240 h的振荡培养,探索其产酶时程规律. 结果表明,不同的诱导底物诱导产生的最大木聚糖酶活不等,其中木粉的诱导效果好于纯木聚糖,复合底物的诱导效果好于单一底物. 该菌在筛选出的最佳诱导产酶培养基上培养144 h后达到产酶高峰,粗酶液酶活可达到45.66 U/mL. 对该酶进行高温及碱性处理的结果表明,它具有较好的耐热耐碱性,在pH 7.0下反应表现最高活性,同时在90℃下保温30 min后酶活残留达83.46％.      

柑橘叶片细胞膜热稳定性的研究

应用电导法研究了不同抗热性的柑橘品种在高温条件下其细胞膜的稳定性。结果表明,高温处理时间相同时,随着处理温度的增高,柑橘叶片细胞膜的热稳定性降低,其伤害率的变化符合Ｌｏｇｉｓｔｉｃ方程所描述的曲线,该曲线的拐点温度与柑橘的抗热性相一致,在相同的温度条件下,叶片细胞膜的伤害率随热处理时间的延长逐渐增大,其热稳定性逐渐降低。从而证明柑橘叶片细胞膜的热稳定性与其抗热性密切相关,可以用电导法来鉴定柑橘的抗     

细胞膜热稳定性及保护酶和大白菜耐热性的关系

耐热性强弱不同的大白菜品种在细胞膜热稳定性上存在明显差异。经２８～３８℃的短期（１天）高温锻炼能提高细胞膜热稳定性，而常温的脱锻炼又能使细胞膜热稳定性发生可逆变化。持续１０天３２和３６℃的高温处理在提高细胞膜热稳定性的同时，也使植株产生明显的热害症状，耐热性弱的品种比耐热性强的品种更为严重、对保护酶系统酶活性的研究表明：高温导致过氧化物酶（ＰＯＤ）活性降低、过氧化氢酶（ＣＡＴ）活性升高，耐热性强的品种ＰＯＤ活性高于耐热性弱的品种，且超氧化物歧化酶（ＳＯＤ）活性在高温下也较为稳定。     

奶牛血液抗氧化酶活性的季节变化

为了研究奶牛耐热性与体内抗氧化酶活性的相关性,本试验选择胎次相近的35头荷斯坦奶牛,按夏季产奶量下降率分为耐热组(下降率10%以下)和热应激组(下降率40%以上),分别测定春季、夏季试验牛血浆中超氧化物歧化酶(superoxide dismutase,SOD)、谷胱甘肽过氧化物酶(glutathione peroxidase,GSH-Px)活力,以及丙二醛(malondialdehyde,MDA)含量。结果表明:(1)奶牛血液抗氧化指标受季节性影响较大,夏季血浆中SOD活力、GSH-Px活力极显著低于春季(P<0.01),夏季MDA含量极显著高于春季(P<0.01);(2)血液中抗氧化指标在同一季节、不同组别之间差异较大,春季耐热组SOD活力极显著高于热应激组(P<0.01),耐热组MDA含量显著低于热应激组(P<0.05),夏季耐热组SOD活力、GSH-Px活力显著高于热应激组(P<0.05),耐热组MDA含量显著低于热应激组(P<0.05);(3)夏季奶牛血液中GSH-Px活力及MDA含量分别与夏季奶牛产奶量下降率极显著强负相关(r=?0.710,P<0.01)和极显著强正相关(r=0.733,P<0.01),夏季血液中SOD活力与夏季奶牛产奶量下降率之间没有显著的相关性,夏季GSH-Px活力下降率与产奶量下降率间呈显著正相关(r=0.493,P<0.05),但夏季血液中SOD活力下降率和MDA上升率与夏季奶产量下降率之间无显著的相关性。以上结果提示:(1)奶牛血液抗氧化酶受季节影响较大;(2)奶牛的耐热性可能与血液的抗氧化性相关。