益生菌对消化道胃酸和胆盐胁迫的应激机理

益生菌进入人体消化道后,会遇到高酸及胆盐等不利益生菌存活的胁迫环境。酸和胆盐胁迫可使益生菌的活性下降,影响益生功能的发挥。亚致死剂量的酸或胆盐胁迫可以提高益生菌的耐受力,有助于益生菌在消化道中的存活。因此,研究益生菌酸胁迫及胆盐胁迫应激机理具有非常重要的意义。本文主要综述益生菌酸胁迫和胆盐胁迫可能的机理,并对未来的研究方向进行探讨。     

抗应激功能食品研究概况

应激是机体受到外来刺激产生的非特异性反应，应激反应是当今社会普遍关注的问题。本文概述了应激的有关概念，对抗应激功能食品作了详尽介绍。     

单核细胞增生李斯特菌对食品加工中的胁迫响应及其机制研究进展

单核细胞增生李斯特菌（简称单增李斯特菌）在食品加工过程中经常会遇到环境胁迫,如酸胁迫、热胁迫、冷胁迫、干燥和高渗透压胁迫以及交叉胁迫等,并产生应激反应,而经过环境胁迫的单增李斯特菌可显著增强其抵抗致死性环境胁迫的能力,给食品安全带来极大危害。单增李斯特菌的酸胁迫响应机制主要包括F0F1-ATPase系统、谷氨酸脱羧酶系统以及精氨酸脱亚胺酶系统。热休克蛋白、冷休克蛋白、相容性溶质在单增李斯特菌的热胁迫、冷胁迫和干燥及高渗透压胁迫反应中起重要作用。本文从以上几方面就单增李斯特菌对环境胁迫响应及其机制的研究现状进行了综述,并提出了今后可能的研究方向,为单增李斯特菌在食品加工过程中的胁迫响应研究及防控提供指导。     

Extending the potential of evaporative cooling for heat-stress relief

Factors were analyzed that limit the range of environmental conditions in which stress from heat may be relieved by evaporative cooling in shaded animals. Evaporative cooling reduces air temperature (Ta), but increases humidity. Equations were developed to predict Ta reduction as a function of ambient temperature and humidity and of humidity in cooled air. Predictions indicated that a reduction of Ta becomes marginal at humidities beyond 45%. A reduction of Ta lessens with rising ambient Ta. The impact of increasing humidity on respiratory heat loss (Hre) was estimated from existing data published on Holstein cattle. Respiratory heat loss is reduced by increased humidity up to 45%, but is not affected by higher humidity. Skin evaporative and sensible heat losses are determined not only by the humidity and temperature gradient, but also by air velocity close to the body surface. At higher Ta, the reduction in sensible heat loss is compensated for by an increased demand for Hre. High Hre may become a stressor when panting interferes with resting and rumination. Effects of temperature, humidity, air velocity, and body surface exposure to free air on Hre were estimated by a thermal balance model for lactating Holstein cows yielding 35 kg/d. The predictions of the simulations were supported by respiratory rate observations. The Hre was assumed to act as a stressor when exceeding 50% of the maximal capacity. When the full body surface was exposed to a 1.5 m/s air velocity, humidity (15 to 75%) had no significant predicted effect on Hre. For an air velocity of 0.3 m/s, Hre at 50% of the maximum rate was predicted at 34, 32.5, and 31.5° C for relative humidities of 55, 65, and 75%, respectively. Similar results were predicted for an animal with two-thirds of its body surface exposed to 1.5 m/s air velocity. If air velocity was reduced for such animals to 0.3 m/s, the rise in Hre was expected to occur at approximately 25° C and 50% relative humidity. Maximal rates of Hre were estimated at 27 to 30° C when ambient humidity was 55% relative humidity and higher. High humidity may stress animals in evaporative cooling systems. Humidity stress may be prevented by a higher air velocity on the body surface of the animal, particularly in sheltered areas in which the exposed body surface is reduced, such as mangers and stalls. This may extend the use of evaporative cooling to less dry environments.     

Prospects of Breeding Quinoa for Tolerance to Abiotic Stress

Aspects related to the breeding of quinoa for increased tolerance against frost, drought, and salinity are presented with special emphasis on the conditions existing in the Peruvian Andes. Evidence from the literature indicates that plants' responses to these stresses are essentially similar, and the physiological processes involved are interrelated. The evidence suggests that tolerance to abiotic stress is polygenicallyinherited, justifying the application of appropriate plant breeding methods. A compilation of meteorological studies is presented that can be used to define the specific climatic phenomena of night frosts occurring in the quinoa-growing region of the Andes and to specify the conditions for selection of tolerant varieties. A composite-bulk breeding scheme is proposed that could be useful for highly efficient breeding of quinoa varieties. Possible future application of molecular-marker-assisted selection is discussed.     

应力分等设备在胶合木生产中的应用

近年来,胶合木的优势日渐凸显,其制备工艺与应用愈来愈成熟。本文主要介绍了胶合木制备中木材分等工艺的设备应用。胶合木制备中前期的分级工艺是影响胶合木质量的主要因素。因此,使用应力分等设备对木材进行强度分等要做到快速、准确,使生产连续化。     

Prospects of Breeding Quinoa for Tolerance to Abiotic Stress

Aspects related to the breeding of quinoa for increased tolerance against frost, drought, and salinity are presented with special emphasis on the conditions existing in the Peruvian Andes. Evidence from the literature indicates that plants' responses to these stresses are essentially similar, and the physiological processes involved are interrelated. The evidence suggests that tolerance to abiotic stress is polygenicallyinherited, justifying the application of appropriate plant breeding methods. A compilation of meteorological studies is presented that can be used to define the specific climatic phenomena of night frosts occurring in the quinoa-growing region of the Andes and to specify the conditions for selection of tolerant varieties. A composite-bulk breeding scheme is proposed that could be useful for highly efficient breeding of quinoa varieties. Possible future application of molecular-marker-assisted selection is discussed.     

The impact of the postharvest environment on the viability and virulence of decay fungi

Postharvest decay of fruits, vegetables, and grains by fungal pathogens causes significant economic losses. Infected produce presents a potential health risk since some decay fungi produce mycotoxins that are hazardous to human health. Infections are the result of the interplay between host resistance and pathogen virulence. Both of these processes, however, are significantly impacted by environmental factors, such as temperature, UV, oxidative stress, and water activity. In the present review, the impact of various physical postharvest treatments (e.g., heat and UV) on the viability and virulence of postharvest pathogens is reviewed and discussed. Oxidative injury, protein impairment, and cell wall degradation have all been proposed as the mechanisms by which these abiotic stresses reduce fungal viability and pathogenicity. The response of decay fungi to pH and the ability of pathogens to modulate the pH of the host environment also affect pathogenicity. The effects of the manipulation of the postharvest environment by ethylene, natural edible coatings, and controlled atmosphere storage on fungal viability are also discussed. Lastly, avenues of future research are proposed.     

Differential importance of trehalose accumulation in Saccharomyces cerevisiae in response to various environmental stresses

Trehalose is believed to play an important role in stress tolerance in the yeast Saccharomyces cerevisiae. In this research, the responses to various environmental stresses, such as high ethanol concentration, heat, oxidative, and freezing stresses, were investigated in a strain with deletion of the NTH1, NTH2, and ATH1 genes encoding trehalases that are involved in trehalose degradation and the triple deletion strains overexpressing TPS1 or TPS2, both of which encode trehalose biosynthesis enzymes in S. cerevisiae. The contents of trehalose constitutively accumulated in the TPS1- and TPS2-overexpressing triple deletion strains were higher than that in the original triple deletion strain. High trehalose accumulation and growth activity were observed in the TPS2-overexpressing triple deletion strain after ethanol stress induction. The same was also observed in the triple deletion and the TPS1- and TPS2-overexpressing triple deletion strains after heat stress induction. In case of freezing stress, all the recombinant strains with high constitutive trehalose content showed high tolerance. However, in case of oxidative stress, trehalose accumulation could not make the yeast cells tolerant. Our results indicated that high trehalose accumulation can make yeast cells resistant to multiple stresses, but the importance of this accumulation before or after stress induction is varied depending on the type of stress.     

Roles of stress response-related signaling and its contribution to the toxicity of zearalenone in mammals

Zearalenone (ZEA) is a mycotoxin frequently found in cereal crops and cereal-derived foodstuffs worldwide. It affects plant productivity, and is also a serious hazard to humans and animals if being exposed to food/feed contaminated by ZEA. Studies over the last decade have shown that the toxicity of ZEA in animals is mainly mediated by the various stress responses, such as endoplasmic reticulum (ER) stress, oxidative stress, and others. Accumulating evidence shows that oxidative stress and ER stress signaling are actively implicated in and contributes to the pathophysiology of various diseases. Biochemically, the deleterious effects of ZEA are associated with apoptosis, DNA damage, and lipid peroxidation by regulating the expression of genes implicated in these biological processes. Despite these findings, the underlying mechanisms responsible for these alterations remain unclear. This review summarized the characteristics, metabolism, toxicity and the deleterious effects of ZEA exposure in various tissues of animals. Stress response signaling implicated in the toxicity as well as potential therapeutic options with the ability to reduce the deleterious effects of ZEA in animals were highlighted and discussed.     

真菌中氧胁迫调控因子AP-1研究进展

氧化应激是细胞应激反应的一种,在所有生物中都是保守进化的。应激反应的调控包括转录、翻译和翻译后修饰,决定生物体是否适应、存活、或者死亡。酵母中b-ZIP型激活蛋白(Yap)家族包括8个成员,Yap1是酵母Yap家族中首先发现的成员,具有DNA结合结构域和转录激活活性,在细胞的氧化应激中发挥着必不可少的作用。在氧化压力下,Yap1的活性增加。本文对近年来AP-1转录因子在真菌中的主要研究进展进行了综述,重点介绍了AP-1作为主要的氧化应激调节器参与的生物学应激反应、致病性及产生真菌毒素等,并介绍了AP-1在铁代谢、钴毒性、DNA损伤、耐药性中的功能。     

Heat-enhanced production of chitosanase from Streptomyces griseus in the presence of liposome

The effects of heat stress and liposome treatment on the growth of Streptomyces griseus cells and chitosanase production were investigated on the basis of using the designed strategy of a stress-mediated bioprocess. The effective conditions for increasing the interaction between chitosanase and the 1-palmitoyl-2-oleoyl-3-phosphocholine (POPC) liposome under heat stress condition were determined on the basis of the results of circular dichroism (CD) and dielectric dispersion analysis (DDA). Under these effective conditions, S. griseus cells were cultivated for the effective production of chitosanase. The results obtained from both CD spectra and DDA showed that heat stress enhances the interaction of the POPC liposomes and chitosanase. The strongest interaction between them could be obtained in the specific temperature range of 40-45 degrees C. The enhancement of the target chitosanase production was conducted under heat stress at 41 degrees C in the presence and absence of the POPC liposomes. The growth rates of S. griseus cells in the cases of heat (41 degrees C) and heat (41 degrees C)/POPC treatments were respectively 1.2 and 1.4 times higher than that obtained under the control condition. In the heat (41 degrees C) and heat (41 degrees C)/POPC treatments, chitosanase activity increased to 1.8 and 2 times, respectively, higher than that obtained under the control condition. Heat stress and the addition of the POPC liposomes could therefore be utilized to induce the potential functions of bacterial cells for the enhancement of the final target production.     

采后水分和营养胁迫对西兰花未成熟衰老中相关酶活性的影响

本研究以西兰花(Brassica oleracea)花蕾为试材,研究了采后水分胁迫和营养胁迫对西兰花贮藏过程中色值变化、叶绿素含量、抗坏血酸(Vitamin C,Vc)含量、呼吸强度、超氧化物歧化酶(Superoxide Dismutase,SOD)、过氧化物酶(Peroxidase,POD)、过氧化氢酶(Catalase,CAT)活性和丙二醛(Malondialdehyde,MDA)含量以及总抗氧化能力的影响。结果表明,西兰花在采后贮藏过程中花蕾出现黄化现象,采后水分和营养胁迫加速了西兰花叶绿素、Vc的降解。采后12 h,对照、水处理、聚乙二醇(polyethylene glycol,PEG)处理、PEG加营养液处理和营养液处理的花球Vc含量为8.84 mg/100g,12.16 mg/100g,PEG 24.44 mg/100g,PEG 30.68 mg/100g,27.56 mg/100g。采后水分和营养胁迫均可导致西兰花花蕾POD活性下降,CAT活性峰值升高,两者同时发生时,延缓了西兰花花蕾总抗氧化性的上升。SOD、POD、CAT活性和总抗氧化性相比较可以看出,总抗氧化能力比单纯的某一种抗氧化酶更能反映西兰花的抗衰老能力。     

梳棉机盖板传动用蜗轮强度的校核分析

结合实例对梳棉机盖板传动用的特殊蜗轮进行表面接触疲劳强度及弯曲疲劳强度进行校分析，为设计人员在强度校和尺寸设计时提供参考依据。     

Stress relaxation behaviour of high acyl gellan gels

Stress relaxation behaviour of high acyl gellan gels has been investigated, and data were fitted successfully by a seven elements empirical model and a four term modified Maxwell model with three fixed relaxation times (20, 200 and 2000 s). In addition, the effect of testing parameters on stress relaxation characteristics and the relationship between those characteristics and intrinsic gel properties were studied. High acyl gellan gels were tested in stress relaxation with different cross‐head speeds (0.1–10 mm s^?1) to applied strains (3–30%). The results showed that the cross‐head speed had little effect on stress relaxation behaviour of gels. With increasing the applied strain, the initial stress and the equilibrium stress increased. The equilibrium stresses from relaxation measurement were positively related to the hardness from TPA tests (R² = 0.991). Relaxation appeared to be associated with the shifting of cross‐links in the gel matrix.     

钢丝拉拔过程中的残余应力

介绍钢丝拉拔过程中残余应力的研究现状及影响残余应力的各种因素。通过研究存在的各类问题,对残余应力影响因素进行了讨论,指出有限元技术、数值模拟与实验的对比性研究成为测量残余应力的有效方法,对今后的研究方向提出建议。     

Factors affecting quality and postharvest properties of vegetables: integration of water relations and metabolism

Growing of vegetables in the field, harvesting, handling in the packing house and storage are events in the lifetime of vegetables that are analysed from the point of view of the complex series of physiological transitions taking place in each of these events. Water is the major factor limiting plant metabolism and plants have developed fascinating mechanisms to cope with this limiting factor. Therefore, water relations (water, pressure and osmotic potential) are used as criteria for discussing plant stress physiology aspects such as osmotic, elastic adjustment and cold acclimation, as well as mechanical stress when the vegetable is harvested and during handling in the packing house. Consequences for the storage potential and quality of the vegetable are discussed. After harvesting, the postharvest cell has the ability to complete a complex series of physiological transitions that will influence vegetable quality andfurther processing operations. Metabolic changes in the cytosol, cell membrane and cell wall are described.     

烟草过氧化氢酶基因CAT2克隆与表达特征分析

基于已有的植物Catalase 2基因（CAT2）序列设计烟草Nicotiana tabacum CAT2的特异性引物,通过RT-PCR扩增克隆获得Nicotiana tabacum var.NC89 CAT2全长mRNA序列,包含1479 bp完整的读码框（ORF）,可编码492个氨基酸残基。遗传进化分析显示,烟草NC89 CAT2与N.benthamiana CAT2基因亲缘关系最近。利用Quantitative Real-time PCR技术分析了CAT2基因在NC89烟草中的组织特异性表达和其应对生物和非生物胁迫的表达差异。结果表明,CAT2基因在烟草NC89的根、茎、叶、花瓣、花萼、种子中均有表达,其中在花中相对表达量最高,其次为叶、茎、种子和根。生物和非生物胁迫处理烟株,其CAT2诱导表达分析显示,机械损伤、渗透压、低温和高温、干旱和感染PVY时CAT2表达量均上调。上述研究表明烟草CAT2基因可能参与了应对非生物和生物胁迫的过程。