酸乳发酵凝乳过程中的理化性质和生物活性

全脂牛奶在室温发酵制作酸乳过程中 ,其酸度随着发酵时间的延续和微生物添加量的增加而上升 ,pH值则逐渐降低 ;而酸乳粘度则随着发酵时间的延续上升达到最高点开始下降 .当微生物添加量为 4 %～ 5% ,发酵 1 2h时 ,酸乳凝乳良好 ,口感适宜 ,活性乳酸菌总数达到 1 0 7数量级 .     

离子对啤酒酵母代谢产酸的影响

在离子型培养基中分别添加6.804,13.610,27.216 g/L 的KH2PO4以及66.39,138.75, 277.4 mg /L 的CaCl2,对通风发酵过程中的不同K^＋、Ca^2＋浓度影响啤酒酵母代谢产6种有机酸含量的动态变化进行了跟踪检测.研究结果表明,K^＋、Ca^2＋可能通过作用于酵母细胞膜上的膜蛋白或调控生理代谢网络中代谢流相关的酶,从而使不同的K^＋、Ca^2＋浓度影响啤酒酵母响应产酸的峰值和峰值响应时间;在通风发酵过程中,啤酒酵母代谢产乳酸较多（多达8.3 mg/mL）,产琥珀酸较少（不超过250 μg/mL）;发酵终点时,随K^＋、Ca^2＋浓度增大,啤酒酵母代谢产酒石酸和琥珀酸等含量减少.     

接种方式对阿维菌素发酵过程的影响

在摇瓶发酵中对除虫链霉菌的孢子接种工艺进行了初步研究,同时比较了孢子接种、常规的挖块接种和菌丝接种3种不同接种方式对除虫链霉菌菌体生长和细胞代谢参数的影响.实验结果表明:孢子接种的最适孢子接种量在4～6×106个/mL范围内,而不同接种方式导致了发酵过程除虫链霉菌营养物质消耗、pH值变化、菌丝形态以及效价等方面差异.孢子接种方式在摇瓶发酵中表现出明显优势,采用孢子接种方式获得最终阿维菌素的效价比常规的挖块接种方式提高10%以上,比菌丝接种方式提高了20%以上.     

利用Biolog系统进行乳酸生产菌代谢能力的快速分析

利用Biolog系统考察目标菌株对产乳酸途径相关碳源的代谢能力,表明在厌氧条件下两自行筛选的候选菌株中S-18比菌株S-44具有更高的己糖激酶和乳酸脱氢酶等产乳酸代谢关键酶活力;通过好氧条件下产乳酸途径及旁路相关碳源利用能力的考察,显示在好氧条件下丙酮酸更易转向旁路代谢且L-乳酸脱氢酶受到强烈抑制,为乳酸发酵条件的优化与调控奠定了理论基础.利用Biolog系统对特定代谢途径代谢能力进行分析的方法具有快速、简便、重现性高的特点,并适合高通量分析的目的,可促进工业微生物代谢能力及代谢调控研究的普遍开展.     

直接发酵木糖为酒精的新酵母基因工程菌的选育

裂殖酵母,Schizosacchatomyces porebe不能发酵木糖,也不能用它来增殖细胞。但是,这种酵母能发酵木酮糖为酒精,产率和转化率都很高。这表明,它缺少异构酶基因,如果将其它微生物的这种基因克隆到酵母中去,它就能直接发酵木糖。本文介绍了Schizosaceh.porebe的五碳糖磷酸代谢途径,这种代谢途径使得它成为用于这一目的的理想菌株。含有异构酶基因的DNA片段来自Clark和Carbon的大肠杆菌基因库,它的大小为2.4kb,PstⅠ-抗性。将这个基因克隆到上述酵母中去,得到的酵母基因工程菌株不仅能利用木糖作为唯一碳源和能源,还能发酵木糖为酒精,它具有在工业上应用的潜力     

红酵母类胡萝卜素发酵助剂的筛选及应用

研究了几种促进剂和前体对红酵母RY－98类胡萝卜素发酵的影响，从中选出了番茄汁、花生油和核黄素3种对红酵母生长及类胡萝卜素合成具有显著促进作用的发酵助剂，并确定了适宜的用量。应用试验和发酵过程动态分析表明，这3种发酵助剂增产效果明显。当同时添加番茄汁3mL/L、花生油1.2mL/L和核黄素3.5mg/L时，菌体量、类胡萝卜素质量分数和产量可分别比对照组提高39.4%、32.8%和85.1%，且对发酵过程菌体生长及生理代谢规律无不良影响。     

米曲霉固体发酵过程中的动力学

对米曲霉固体发酵生产酱油过程中各阶段的微生物动力学行为进行了研究,应用动力学的概念对所建立的菌种筛选模型进行了解释.种子生长和发酵阶段的研究结果表明碳源是米曲霉产孢子的速率限制性底物,种子阶段孢子对残总糖的产率系数为YX/S=2.428×1010 个/g,最大比生长速率μmax=5.28 d-1,产孢子的最大比生长速率与温度之间的关系呈钟罩形.同时建立了产孢子速率与水分含量的关系以及产酶速率与水分之间的关系.在发酵过程中发现了米曲霉的二次生长现象,该现象出现的时间随不同的底物比例发生迁移.     

在模型化基础上对青霉素补料分批发酵过程中经济效益的预测

在研究发酵动力学、生物过程反应计量学、代谢流分布和代谢流控制的基础上 ,结合专家知识、实验及生产数据 ,对生产规模的青霉素反复补料分批发酵 (即半连续发酵 )的全过程进行了数学模拟 ,建立了一套包含 2 5个过程变量和一系列经济学变量的改良机理模型 .根据这一模型 ,预测了一些工艺参数和经济学参数的改变对发酵过程经济效益的影响 ,发现在保持最大生物质浓度、稀释速率 ,及其它工艺条件不变的情况下 ,中间放料间隔时间、初始发酵液体积以及葡萄糖和电力的价格对经济效益产生较大的影响 .模拟运算结果表明 ,葡萄糖和电力的价格降低 5 % ,全年利润可分别提高 6 .35 %和 3.75 % ;中间放料间隔时间由 2 4h缩短为 12h和 1h(接近于连续发酵 ) ,全年利润可分别提高 7.2 2 %和 14 .11% ;初始发酵液装罐体积分数由 75 %提高到 85 % ,全年发酵利润可提高 5 .4 8% .     

生物过程模型化与控制中空气湿度的测量

在好氧发酵等生物过程中通入的空气 ,其水分含量即湿度对氧的传递速率、微生物细胞的呼吸和生长、发酵液体积以及补料稀释率都将产生很大的影响 ,并进而影响发酵过程产率 .对发酵过程进行模拟和对不可测变量进行间接计算 (即所谓软测量 )时 ,如果忽视空气的湿度 ,计算和模拟结果将产生很大的偏差 .因此 ,对好氧发酵过程来说 ,必须高度重视空气湿度的测量和控制 .     

骨血管内皮细胞：治疗骨质疏松症的新靶点

近期的许多研究结果显示, 骨组织血管内皮细胞对骨代谢发挥重要调节作用。骨质疏松症作为最常见的骨代谢疾病, 其发生发展过程中伴随着骨组织血管的功能异常和结构紊乱;而恢复骨血管及血管内皮细胞的正常结构和功能后, 骨质疏松症也在一定程度上得到缓解。因此, 骨血管内皮细胞有望成为防治骨质疏松症的重要靶点, 本文将介绍正常骨组织的血管内皮细胞类型、骨血管对骨代谢的调节作用以及骨质疏松病理状态下的血管结构功能异常, 重点评述近年来基于骨血管内皮细胞治疗骨质疏松症的研究进展, 以求为骨质疏松症和其他骨代谢疾病的治疗提供新思路。     

Surgical decision making

Decision making is an integral part of surgical practice and is a skill that is as important as the ability to operate. Sound decision making is the result of acquiring ‘surgical wisdom’, which is achieved through learning, experience and reflection. This paper reviews the processes of surgical decision making with respect to choosing the correct procedure and deciding when to operate, and how operative decisions are made, together with the factors that influence our surgical decisions.     

The role of potential splicing factors including RBMY, RBMX, hnRNPG-T and STAR proteins in spermatogenesis

Investigations into the RBM gene family are uncovering networks of protein interactions which regulate RNA processing, and which might operate downstream of signal transduction pathways. Similar pathways likely operate in germ cells and somatic cells, with RBMY, hnRNPGT and T-STAR proteins providing germ cell-specific components. These pathways may be important for normal germ cell development, and might be compromised in men with Y chromosome deletions affecting RBMY gene expression. The STAR proteins have multiple functions in pre-mRNA splicing, signalling and cell cycle control. These processes might have to be very finely regulated during germ cell development, which involves both two sequential meiotic divisions (meiosis I and II) as well as mitotic (spermatogonial) cell divisions, and which is controlled by paracrine signalling within the testis from Sertoli cells.     

The Engström Elsa anaesthetic machine An electronic system for anaesthesia

Six Engstr?m Elsa anaesthetic machines have been in regular use for 18-24 months. The machine incorporates a number of new concepts for anaesthetic delivery and monitoring. At flows below 1000 ml/minute, each machine delivered 20% more than the indicated value; at higher flows, the indicated value was within 10% of the flow delivered. Minute volume, tidal volumes and oxygen concentrations were within the manufacturer's specifications. However, vaporizer and vapour monitor performance was outside the (SD) 5% accuracy claimed by the manufacturers. It was noted that the bistable valve requires user familiarity for the change from controlled to spontaneous ventilation to be accomplished with ease. It was also possible to misconnect the breathing system and so isolate the excess pressure escape valve and high-pressure alarm. Nevertheless, once familiarisation was achieved, the machines have proved easy to operate and are particularly satisfactory when used with low fresh gas flows.     

骨质疏松进程中破骨细胞能量代谢重编程研究进展

骨质疏松症是一种成骨细胞和破骨细胞之间失衡造成的代谢性骨病。破骨细胞通过吸收葡萄糖、脂肪酸、氨基酸等产生的能量,并分化激活代谢程序。代谢重编程产生能量以支持单核前体细胞向多核破骨细胞的表型改变,并促进骨吸收,这是终末分化成熟破骨细胞主要的功能,所有代谢途径紧密联系。因此研究不同能量、不同环境下,破骨细胞代谢重编程具有重要的意义。     

Hemodynamic exercise response in calves with an implantable biventricular centrifugal blood pump

An implantable biventricular assist device (BVAD) has been developed at Baylor College of Medicine using 2 centrifugal blood pumps. The aim of this study was to investigate the exercise-reflex response during nonpulsatile biventricular assistance and to evaluate to which degree the autoregulation of the system would accommodate the changed hemodynamic situation during physical exercise. The Baylor Gyro PI 710 BVAD has been implanted into 2 calves (strain half-Dexter) in a biventricular bypass fashion with native heart remaining. Allowing a 10 day convalescence, 2 animals were subjected to incremental exercise tests. The speed of the treadmill was increased at zero slope from 0.7 mph to 1.5 mph with increments of 0.2 mph every 3 min. During the exercise the pump flows were maintained at a fixed rate (6.93 +/- 0.01 L/min for the left ventricular assist device and 5.36 +/- 1.44 L/min for the right ventricular assist device). Hemodynamic parameters and pump performance were recorded continuously. The cardiac output (CO) and heart rate (HR) increased significantly during the exercise. CO increased from 11.1 +/- 0.3 to 13.1 +/- 0.4 L/min, and HR increased from 99 +/- 7.1 to 114 +/- 2.8 bpm, respectively. Mean aortic pressure, central venous pressure, and left arterial pressure did not change significantly. Also, no change was observed for the left and right pump flows. This totally implantable BVAD showed excellent long-term performance without any mechanical problems. It is feasible to operate without impairment under physical activity. However, the natural heart dominated the hemodynamic response during exercise under BVAD support. The left and the right pump flows did not increase spontaneously with exercise. We therefore conclude that a servo CO control system is necessary to regulate pump flows even during moderate exercise.     

Pharmacological and pathological modulation of cerebral physiology

Homeostatic mechanisms exist to enable the supply of oxygen and glucose for cerebral metabolism and neuronal function. In health, cerebral autoregulation, neurogenic and metabolic processes ensure that the supply of these nutrients is adequate to meet the metabolic requirements, hence preventing neuronal cell damage. The goals of neuroanaesthesia are to provide optimal operating conditions and provide adequate cerebral blood flow, often in the context of a vulnerable brain which is exposed to the physiological stress of surgical trauma. This article outlines how delivery of anaesthesia and disease processes affecting the brain modulate the mechanisms that regulate cerebral blood flow and metabolism.     

Pharmacological and pathological modulation of cerebral physiology

Homeostatic mechanisms exist to enable the supply of oxygen and glucose for cerebral metabolism and neuronal function. In health, cerebral autoregulation, neurogenic and metabolic processes ensure that the supply of these nutrients is adequate to meet metabolic requirements, thus preventing neuronal cell damage. The goals of neuroanaesthesia are to provide optimal operating conditions and provide adequate cerebral blood flow, often in the context of a vulnerable brain which is exposed to the physiological stress of surgical trauma. This article outlines how delivery of anaesthesia and disease processes affecting the brain modulate the mechanisms that regulate cerebral blood flow and metabolism.     

The neural bases of sentence comprehension: a fMRI examination of syntactic and lexical processing

One of the challenges to functional neuroimaging is to understand how the component processes of reading comprehension emerge from the neural activity in a network of brain regions. In this study, functional magnetic resonance imaging (fMRI) was used to examine lexical and syntactic processing in reading comprehension by independently manipulating the cognitive demand on each of the two processes of interest. After establishing a consistency with earlier research showing the involvement of the left perisylvian language areas in both lexical access and syntactic processing, the study produced new findings that are surprising in two ways: (i) the lexical and syntactic factors each impact not just individual areas, but they affect the activation in a network of left-hemisphere areas, suggesting that changing the computational load imposed by a given process produces a cascade of effects in a number of collaborating areas; and (ii) the lexical and syntactic factors usually interact in determining the amount of activation in each affected area, suggesting that comprehension processes that operate on different levels of language may nevertheless draw on a shared infrastructure of cortical resources. The results suggest that many processes in sentence comprehension involve multiple brain regions, and that many brain regions contribute to more than one comprehension process. The implication is that the language network consists of brain areas which each have multiple relative specializations and which engage in extensive interarea collaborations.     

Pusher-Plate Type TAH System Operated in the Left and Right Free-Running Variable Rate Mode

A TAH system utilizing two pusher-plate type pumps was developed and tested in two calves for 45 and 108 days with excellent results. A Hall effect sensor was utilized to operate each pump with a full stroke at variable rates (VR); each pump was then allowed to run independently at different rates depending on its own preload and afterload. With this system, the animals' atrial pressures were kept to near-normal levels (less than 10 mmHg). However, significant differences in the left and right pump flows were observed (left higher than right) and they ranged from 5 to 30% of the left flow with a mean of 15%. These flow differences may be due to the bronchial circulation and related shunts. Right pump flows averaged 70 to 95 ml/min-kg and circulating blood volume ranged from 67 to 95 ml/kg. When various control modes including fixed rate and master-slave type simultaneously or alternately ejecting VR modes were applied in the same animals and both pump flows were forced to be equal, unphysiological atrial pressures resulted. This result indicates that perhaps left and right flow differences are necessary physiological conditions to regulate the atrial pressures within normal ranges. Metabolic data also indicated that under simultaneously and alternately ejecting modes, A-V O₂ content differences were increased due to decreased right pump flow as compared with those of the free-running VR mode. The left and right free-running VR mode of operation imposed minimal constraints on the animals' cardiovascular system and therefore yielded excellent hemodynamic and metabolic results.     

Cell polarity and cystic kidney disease

Epithelial cell polarity is essential for organ development; aberrations in this process have been implicated in various diseases, including polycystic kidney disease. Establishment and maintenance of cell polarity is governed by a number of molecular processes and how these processes operate remains an interesting question. Conserved protein complexes guide both apical–basolateral polarity and planar cell polarity. In this review we discuss the recent findings that provide insights into polarity mechanisms and the intriguing crosstalk between apical–basolateral polarity and planar cell polarity, and their relationship to cystic kidney disease.