低温贮藏对鲜切杏鲍菇商品性状的影响

[目的]明晰在低温贮藏条件下鲜切杏鲍菇的形态、感官、生理生化等指标的改变,以为鲜切杏鲍菇加工技术的开发提供科学支撑。[方法]以市售杏鲍菇子实体为材料,经过清洗、切割等工序制备成新鲜切片,包装后分别贮藏于4℃和25℃的条件下,测定其表面的微生物增殖、抗氧化能力、挥发性气味物质等生理生化指标的变化。[结果]通过分析显示贮藏在常温条件下,鲜切杏鲍菇第2 d失去商品价值,出现萎蔫、浸渗现象,表面细菌总数达到2. 7×103CFU/g,过氧化物酶(CAT)下降51. 12%;贮藏在低温条件下的鲜切杏鲍菇在第5 d失去商品价值,此时总抗氧化能力(AOC)与新鲜切片相近,超氧化物歧化酶(SOD)下降15%,切片发生黄变。在挥发性气味物质检测中发现在贮藏期杏鲍菇不会产生明显恶臭气味物质,但在代谢过程中会产生过多的酯类物质,可以使气味发生明显改变,降低蘑菇自身新鲜味道。[结论]低温贮藏条件有利于控制鲜切杏鲍菇表面腐败菌的增殖,在第2 d时仅为60 CFU/g,保持蘑菇醇含量在39. 01%,与常温贮藏处理组相比较,能够减缓组织中的总抗氧化能力和过氧化氢酶的下降分别为2. 53%和19. 64%,商品价值延长至5 d。     

急进高原大鼠肠黏膜机械屏障损伤后细胞自噬变化的初步研究

目的探讨急进高原大鼠肠黏膜机械屏障损伤后细胞自噬的变化情况。方法50只Wistar大鼠随机分为5组：平原组,急进高原6h组、12h组、24h组、48h组,每组各10只。通过低压低氧动物实验舱模拟急进海拔4767m建立急进高原大鼠模型。观察各组大鼠肠黏膜机械屏障损伤情况,用透射电镜观察肠上皮细胞中自噬体;用免疫组织化学法检测肠上皮细胞中自噬相关蛋白Beclinl及LC3B表达。结果与平原组比较,急进高原组可使其肠黏膜机械屏障发生损伤,并且在急进高原肠黏膜损伤6h后可观测到自噬体,24h后检测到自噬相关蛋白Beclinl及LC3B表达显著增高（P〈0．01）。结论急进高原组大鼠肠黏膜机械屏障损伤后自噬相关蛋白Beclinl及LC3B表达明显增加,表明急进高原大鼠肠黏膜机械屏障损伤后细胞自噬活性上调。     

1-MCP、壳聚糖和臭氧在鲜切果蔬保鲜技术中的研究进展

鲜切果蔬因其新鲜、营养和方便的优点而日益受到消费者喜爱,但鲜切果蔬在经过清洗、去皮、切分等工序后,其产品组织结构受到损伤,从而导致组织褐变、微生物侵染及营养损失等问题的出现,严重缩短了鲜切产品的货架期。因此,对鲜切果蔬贮藏保鲜技术的研究已经成为近年来农产品贮藏与加工领域的热点。本综述简述了1-甲基环丙烯、壳聚糖和臭氧,这3种化学保鲜方法在鲜切果蔬中的研究现状,期待能为鲜切果蔬保鲜技术的深入研究提供参考依据。     

细胞自噬进程的分子信号通路研究进展

细胞自噬是广泛存在于真核细胞内的一种胞内物质降解途径。细胞内的待降解蛋白复合物、受损伤细胞器以及入侵的病原体等被自噬泡包裹后运送至溶酶体,然后被溶酶体酸性水解酶消化,并释放到胞浆中以维持细胞的自我稳态。随着2016年诺贝尔生理医学奖授予自噬研究领域的学者,自噬研究越来越受到科研人员的重视。本文整理总结了自噬进程中的自噬信号调节、自噬体以及自噬溶酶体形成过程,同时也讨论了自噬过程中相关的分子信号通路。     

基于自噬溶酶体形成机制调控缺血性脑卒中后神经元自噬流

脑卒中是由脑血管阻塞或出血引发的急性脑血管病，约84%的临床脑卒中患者由脑缺血引起。研究表明，自噬广泛参与并显著影响脑卒中病理生理进程。自噬是一个将陈旧蛋白质、损伤细胞器及多余胞质组分等呈递给溶酶体进行降解的代谢过程，其包括自噬的激活、自噬体的形成和成熟、自噬体与溶酶体融合、自噬产物在自噬溶酶体内消化和降解等过程。自噬流通常被定义为自噬/溶酶体信号机制。最近发现，自噬流障碍是导致缺血性脑卒中后神经元损伤的重要原因，而在自噬过程中任一步骤发生障碍均可导致自噬流损伤。本文重点对自噬体-溶酶体融合的机制，以及该机制在缺血性脑卒中后发生障碍的致病机理进行详细阐述，以期基于自噬体-溶酶体融合机制对神经元自噬流进行调节，进而诱导缺血性脑卒中后的神经保护。本文可为脑卒中病理机制研究指明方向，为脑卒中治疗探寻新的线索。     

细胞衰老与细胞自噬的生物学关联及其意义

细胞衰老是指细胞生理功能的衰减,包括增殖能力下降、细胞周期停滞、对促凋亡应激不敏感、衰老相关基因和蛋白表达增加,伴有形态学衰老改变,渐趋死亡的现象,其至少可分为复制性衰老和应激诱导的衰老。细胞自噬属于细胞＂自食＂现象,是细胞依赖溶酶体的分解代谢过程,能降解受损蛋白、衰老或损伤的细胞器等细胞结构,可被多种应激所触发。细胞自噬的典型特征是形成自噬体并呈递给溶酶体,该过程在蛋白质和细胞器质量控制中起基础作用并维持了细胞能量的稳态。最新研究表明,自噬与细胞衰老密切相关,参与蛋白酶和自噬相关调节的BAG蛋白家族中BAG3/BAG1比值在复制性衰老时增高,且BAG3在细胞衰老时能介导自噬的激活。在Ras诱导的细胞衰老进程中亦可观察到较高的自噬活性。再者,自噬作为生物机体抗衰老的效应因子的遗传学证据已在低等真核生物中发现。还有研究证实,作为人类精液主要组分的亚精胺能够触发组蛋白H3脱乙酰基作用,此改变上调了自噬相关转录物的表达,继而引发自噬活性增强,从而延缓了多种细胞的衰老进程。另有研究显示,在P53/Arf的正常调节下,小鼠的衰老进程得以延缓,而Arf在细胞自噬过程的调节中亦是不可或缺的。总之,自噬活性的改变影响细胞衰老进程并可作为细胞衰老新的效应机理。     

自噬对再生中肌肉干细胞的作用

各种遗传缺陷、实质性组织损伤或外源性信号的改变均可引起骨骼肌肌肉组织的损伤,并导致各种原发性或继发性肌病.因此,了解肌肉再生中的生理过程和相关分子机制将有助于更有效的组合治疗策略.自噬最初被认为是营养物质分解的机制,随后的研究进一步发现自噬也是一种降解细胞质成分、蛋白质聚集体和细胞器的生理过程,是细胞结构的调节器,广泛...     

Bel-7402细胞通过自噬逃避FAS/ActD诱导的凋亡

为了探究FAS抗体与放线菌素D（actinomycin D,ActD）诱导肝癌细胞Bel-7402凋亡的作用机制,通过自噬阻断剂3-MA的作用,来探讨自噬与凋亡的关系.利用电子显微镜和流式细胞仪观察细胞自噬及凋亡.结果表明,FAS/ActD在诱导细胞凋亡的同时伴有细胞自噬现象,在3-MA作用下,FAS/ActD所诱导的细胞自噬体减少,而凋亡现象严重.并且通过流式细胞仪分析表明,3-MA明显增高FAS/ActD所诱导的细胞凋亡率. Western印迹分析进一步显示,FAS/ActD能引起caspase-3激活产生断裂,同时刺激LC3和BECN1表达,而3-MA作用后自噬体减少,同时LC3和BECN1表达降低,但是caspase-3断裂带表达明显增加.以上结果提示,FAS/ActD诱导的Bel-7402细胞凋亡的同时伴有细胞自噬,Bel-7402细胞通过自噬逃避FAS/ActD诱导的凋亡.     

细胞自噬在肾小管损伤机制中的研究进展

细胞自噬是由溶酶体介导的清除细胞内受损大分子物质和衰老细胞器的过程,在维持细胞的稳态中有着重要作用。自噬现象普遍存在于所有真核生物细胞中,参与细胞增殖、生长、功能及表型改变等多种重要细胞生理过程的调节。肾小管是多种病因致肾脏损伤的重要靶点,现已在多种肾脏疾病中观察到肾小管上皮细胞自噬的异常。本文就细胞自噬在肾小管损伤中的作用及分子机制的研究进展进行综述。     

自噬在细胞冷应激中的作用研究

有研究证明,自噬在生物应对多种不良环境过程中发挥着重要作用,但是自噬在细胞应对低温环境过程中的功能研究却甚少。该研究给予He La细胞(人子宫颈癌细胞)不同程度的急性冷刺激,探讨此过程中自噬的发生和功能。将He La细胞培养于37°C(对照组)或经不同程度的低温(10、18、28°C)处理,观察对照组与低温处理组细胞表达自噬标志物EGFP-LC3(enhanced green fluorescent protein-microtubule-associated protein 1A/1B-light chain 3)的变化,以监测自噬小体形成。结果显示,低温处理诱导He La细胞发生不同程度的自噬现象:10°C处理3~6 h的细胞内的自噬小体增多且体积增大,18°C处理的细胞内的自噬小体在3 d时最明显,28°C处理的细胞始终维持在较低水平。研究还发现,He La细胞在自噬减弱消失的同时发生细胞死亡,自噬特异性的化学抑制剂Bafilomycin A1处理可以进一步降低不同程度的低温胁迫下He La细胞的存活率,表明自噬在细胞低温应激过程中发挥着保护作用。Bafilomycin A1处理伴随有细胞内活性氧(reactive oxygen species,ROS)水平增高,提示低温胁迫下自噬可能通过调控细胞内ROS水平来保护细胞。该研究结果表明,自噬在真核细胞冷应激中具有重要作用。     

Discovery of a novel gene involved in autolysis of Clostridium cells

Cell a utolysis plays important physiological roles in the life cycle of clostridial cells. Unders tanding the genetic basis of the autolysis phenomenon of pathogenic Clostridium or solvent producing Clostridium cells might provide new insights into this important species. Genes that might be involved in autolysis of Clostridium acetobutylicum, a model clostridial species, were investigated in this study. Twelve putative autolysin genes were predicted in C. acetobutylicum DSM 1731 genome through bioinformatics analysis. Of these 12 genes, gene SMB_G3117 was selected for testing the in tracellular autolysin activity, growth profi le, viable cell numbers, and cellular morphology. We found that overexpression of SMB_G3117 gene led to earlier ceased growth, signifi cantly increased number of dead cells, and clear electrolucent cavities, while disruption of SMB_G3117 gene exhibited remarkably reduced intracellular autolysin activity. These results indicate that SMB_G3117 is a novel gene involved in cellular autolysis of C. acetobutylicum.     

Ultrastructural and functional changes in pancreatic acinar cells during autolysis.

Effects of anoxemic cell injury on rat pancreatic acinar cells were studied in a preparation where tissue samples were incubated at temperature between 18-20 degrees C in a moist atmosphere for 0, 0.5, 1, 3, 6, 12, and 24 h in vitro. Electron microscopy revealed that disintegration of acinar cells began by swelling of various cell compartments and gradual breakdown of cell membranes. Zymogen granules remained morphologically intact for at least 3 h. There were no signs of increased autophagic activity during the period of observation. Myelin figures and other membranous remnants of disintegrated cells, together with individual cells and cell organelles whose morphology was relatively well preserved were seen even after w4 h incubation. The secretory response of acinar cells to pancreozymin stimulation, as measured by amylase release into the incubation medium in vitro, decreased progressively closer to zero during 12 h autolysis. No active trypsin could be detected in the tissue samples during the 24 h observation time. It was concluded that during hypoxic autolysis at room temperature between 18-20 degrees C in vitro: 1. Acinar cell disintegration results from breakdown of cellular membranes, 2. autophagocytosis is not involved, 3. most of zymogen granules remain morphologically intact even at the time when cell membranes show evidence of damage, 4. there is no trypsin activation taking place in the tissue, and 5. the acinar cells are capable of responding to secretory stimulation for 3 to 6 h after removal of the tissue from the experimental animal.     

Dynamics of the Antimicrobial Peptide PGLa Action on Escherichia coli Monitored by Atomic Force Microscopy

Summary Atomic force microscopy (AFM) images of living cells in physiological solution were used to monitor the different stages involved in the interaction between Escherichia coli and the antimicrobial peptide PGLa. Damage on bacterial membranes was observed in the past using standard electron microscopy; stiffness measurements and images scanned in physiological solution demonstrate the advantage of AFM for such studies. From force versus separation curve measurements it is possible to determine the variation of the cellular stiffness. PGLa action on components of the cell structure like the outer membrane, the bacterial pili, the peptidoglycan wall and the inner membrane was determined by the comparison of AFM images of bacteria before and after PGLa addition. The interaction of Escherichia coli with PGLa in the culture medium has two stages. The first is characterized by the loss of surface stiffness and the formation of micelles probably originating from the disruption of the outer membrane and the loss of the bacteria’s ability to adhere to the substrates. In the second stage there is further damage, which resulted in total cell rupture. AFM images of bacteria in air and surface roughness measurements were also used to estimate peptide damage.     

Bone marrow cryopreservation: biological aspects

Ten bone marrow suspensions have been cryopreserved by a Programmed Freezer Planer R 201. Total cellularity, viability, differential myelograms, cytochemical pattern and CFU-GM growth "in vitro", have been evaluated on the cellular suspensions both before and after 1 and 18 months of storage in liquid nitrogen. Total cellular recovery and viable cell recovery were satisfactory, cellular loss being due, almost entirely to death of the more mature cells. NASDA reaction did not vary after freezing, on the contrary peroxidase reaction and overall PAS reaction showed respectively a slight and an almost complete disappearance. LAP reaction was not valuable, after freezing, because of the more mature myeloid cell loss. CFU-GM recovery was satisfactory and clusters and colonies growth in methylcellulose appeared quite similar before and after 1 and 18 months of storage at very low temperature. Our cryopreservation technique cannot prevent some cellular loss or some qualitative cellular damage, but colonizing ability is almost completely preserved.     

Autolysis of Blakeslea trispora during carotene production from cheese whey in an airlift reactor

The phenomenon of autolysis in Blakeslea trispora during carotene production from deproteinized hydrolyzed whey in an airlift reactor was investigated. The process of cellular autolysis was studied by measuring the changes in carotene concentration, dry biomass, residual sugars, pH, intracellular protein, specific activity of the hydrolytic enzymes (proteases, chitinase), and micromorphology of the fungus using a computerized image analysis system. All these parameters were useful indicators of autolysis, but image analysis was found to be the most useful indicator of the onset and progress of autolysis in the culture. Autolysis of B. trispora began early in the growth phase, continued during the stationary phase, and increased significantly in the decline phase. The morphological differentiation of the fungus was a result of the degradation of the cell membrane by hydrolytic enzymes. The biosynthesis of carotenes was carried out in the exponential phase, where the phenomenon of autolysis was not intense.     

Autolysis-mediated membrane vesicle formation in Bacillus subtilis

It is known that Bacillus subtilis releases membrane vesicles (MVs) during the SOS response, which is associated with cell lysis triggered by the PBSX prophage-encoded cell-lytic enzymes XhlAB and XlyA. In this study, we demonstrate that MVs are released under various stress conditions: sucrose fatty acid ester (SFE; surfactant) treatment, cold shock, starvation, and oxygen deficiency. B. subtilis possesses four major host-encoded cell wall-lytic enzymes (autolysins; LytC, LytD, LytE, and LytF). Deletions of the autolysin genes abolished autolysis and the consequent MV production under these stress conditions. In contrast, deletions of xhlAB and xlyA had no effect on autolysis-triggered MV biogenesis, indicating that autolysis is a novel and prophage-independent pathway for MV production in B. subtilis. Moreover, we found that the cell lysis induced by the surfactant treatment was effectively neutralized by the addition of exogenous purified MVs. This result suggests that the MVs can serve as a decoy for the cellular membrane to protect the living cells in the culture from membrane damage by the surfactant. Our results indicate a positive effect of B. subtilis MVs on cell viability and provide new insight into the biological importance of the autolysis phenomenon in B. subtilis.     

Enchancement of streptococcal transformation yield by proteolytic enzymes.

Trypsin and other proteolytic enzymes, added together with transforming DNA or during cell-DNA contact to competent cultures of several streptococcal strains, enchanced (10 to 600%) the yield of genetic transformation (stimulation). With few exceptions, the level of stimulation was high (over 100%) when competence was low (below 2%). Stimulation was caused by the action of an enzyme on competent cells and not on any other component of transformation mixture. The phenomenon occurred when the enzyme was added to the culture not earlier than 7 min before and not later than 5 min after the period of cell-DNA contact. The presence of trypsin during cell-DNA contact caused: (i) the alterations at cell surface, demonstrated by electron microscopy, increased release of 3H-amino acid-labeled material, and higher cell susceptibility to autolysis; (ii) the increase of both total and irreversible binding of DNA by the cells; and (iii) the decrease of early nucleolytic degradation of DNA by cells. These and other data point to the importance of a delicate balance of recipient cell's surface nuclease activities in the effectiveness of transformation process. It is also possible that trypsin eliminates an unknown cellular factor which obstructs DNA-cell receptors interaction.     

Effect of temperature and ripening stages on membrane integrity of fresh-cut tomatoes

The shelf-life of fresh-cut tomatoes mainly depends on loss of tissue integrity and firmness that occurs also in intact fruits after long-term cold storage due to chilling injury. Round-fruit tomatoes (Solanum lycopersicum L.) cv. Jama were stored in 1.1-L plastic (polyethylene) fresh-cut produce containers as 10.0-mm-thick tomato slices and as intact tomatoes at 4 ± 0.5 °C. The aim of this work was to study the loss of membrane integrity and biochemical processes involved in membrane disruption. Electrolyte leakage and lipid peroxidation were studied at different stages of maturity: mature green, pink (PK), fully ripe and two different storage temperatures: 4 and 15 °C. The tomato slices of PK stage stored at 4 °C did not show changes for both parameters, while significant increase in membrane leakage and lipid peroxidation was observed at 15 °C, especially after 24 h of storage. The enzymes showed a simultaneous increase in their activities with a rise in electrolyte leakage and lipid peroxidation after 7 days of storage. Finally, phospholipase C (PLC) and phospholipase D (PLD) were investigated for intact fruit and tomato slices stored at 4 °C. The PLC had higher activity compared with PLD. In conclusion, the loss of membrane integrity in fresh-cut tomatoes is mainly affected by ripening stages, storage temperature and duration. The wounds enhance the PLC and PLD activities and they play a role late during storage.     

Studies on the Autolysis of Aspergillus oryzae

The conditions of autolysis of washed mycelia of Aspergillus oryzae were systematically examined as for temperature, pH, aeration, energy supply, and chemicals which stimulate autolysis. Below 45°C, the higher the temperature the faster was the rate of autolysis. Optimum pH of autolysis with special reference to the excretion of nucleic acid components and amino acids was 5. With the optimum conditions of autolysis settled by us, 90 to 100% of nucleic acids, 75% of protein, and 20% of sugars in the mycelia were excreted into the medium within three days.

In the presence of lipophilic compounds such as toluene and sodium salts of fatty acids, autolysis occurred much faster than in distilled water. Autolysis was inhibited by the addition of glucose and aeration.

Mycelia of Aspergillus oryzae were autolyzed in distilled water, in toluene-saturated water, or in acetate buffer, pH 5.4, at 30°C. The cytoplasmic materials disappeared from cells during autolysis, but the cell wall retained its shape even after autolysis. The disappearance of the cytoplasmic materials started from the inner part under an aerobic condition and from the outer part under an anaerobic condition. During the autolysis, 15% of the cellular proteins was excreted as free amino acids (60%) and peptides (15%). Glucose, ribose, glucosamine, and three unidentified sugars were found in autolyzate. After eighteen hours of autolysis stimulated by toluene, 81% of the cellular nucleic acids was excreted as uridine (28%), xanthine (24%), hypoxanthine (17%), and two other nucleosides or bases.     

Suitability of cryopreservation for the long-term storage of rare and endangered plant species: a case history for Cosmos atrosanguineus

The suitability of cryopreservation for the secure, long-term storage of the rare and endangered species Cosmos atrosanguineus was investigated. Using encapsulation/dehydration of shoot tips in alginate strips, survival rates of up to 100 % and shoot regeneration of up to 35 % were achieved. Light and electron microscopy studies indicated that cellular damage to some regions of the shoot tip during the freeze/thaw procedure was high, although cell survival in and around the meristematic region allowed shoot tip regeneration. The genetic fingerprinting technique, amplified fragment length polymorphisms (AFLPs), showed that no detectable genetic variation was present between material of C. atrosanguineus at the time of initiation into tissue culture and that which had been cryopreserved, stored in liquid nitrogen for 12 months and regenerated. Weaned plantlets that were grown under glasshouse conditions exhibited no morphological variation from non-frozen controls.