爬山虎的春天

温暖的午后,院子里安静极了。晓雅望着天空发呆,频频传来的蟋蟀叫声,也没能引起她的注意。晓雅坐在轮椅上,看着墙上的爬山虎出神。她常常在父母上班的日子里,和绿意盎然的爬山虎对视。她万分羡慕爬山虎,觉得它们比自己幸运多了,它们有自己的脚,可以爬上光     

大肠杆菌肽脱甲酰基酶的表达、纯化及活性检测

肽脱甲酰基酶(peptide deformylase,PDF)是原核生物生长、代谢、繁殖必不可少的关键酶,而在人类和其他哺乳动物中不发挥明显作用,因而被视为新一代广谱抗生素药物筛选的理想靶点.最早被发现并进行研究的是大肠杆菌的PDF,但其体外活性非常低且不稳定,20世纪90年代以来人们一直在对不同金属离子形式的PDF进行研究,以获得既稳定活性又高的PDF.     

时间对水螨捕食周期的影响及其在控制蚊繁殖螨的作用

通过对水螨的生态生理学以及生物控制潜力的研究表明,水螨在控制蚊繁殖的应用方面有着广阔的前景。在开始实施生物控制计划之前,我们先在田里养殖了一些水生异翅亚目昆虫,以便于研究不同时间的水螨和被捕幼蚊在淡水生     

干细胞研究的意义和存在的问题

本文以干细胞的定义、造血和神经干细胞的研究和应用为基础，就干细胞研究的意义和存在的问题进行评述。重点就干细胞的扩增和鉴定、干细胞的可塑性和多能干细胞、干细胞在组织修复和个体发育中的意义进行讨论。介绍当前研究动向，从分子生物学水平充分认识干细胞的本质，认识主导干细胞繁殖、定向和跨系分化的内在机制，以更有效地发挥干细胞的潜能，更好地为临床实践服务。     

RNA干扰在吸血媒介研究中的应用

吸血媒介不仅危害动物健康,而且还能传播各种虫媒疾病,从而严重危害人类健康。因此,研究吸血媒介在公共卫生方面具有十分重要的意义,如研究如何控制吸血媒介以及其对病原体的传播具有极其重要的意义。本文概要介绍RNA干扰（RNAi）的基本原理,并对其在吸血媒介基因功能研究、保护性抗原筛选及鉴定、抑制病原体感染吸血媒介及其在吸血媒介中的繁殖等方面的研究进展进行综述。     

糖基因GLT25D2敲除小鼠的制备与基因型鉴定

目的建立GLT25D2基因敲除小鼠模型,为胶原糖基化修饰分子机制研究奠定工作基础。方法采用胚胎干细胞线性打靶技术,获得同源重组的干细胞,繁殖嵌合体,GLT25D2^＋/-小鼠杂交获得GLT25D2^-/-纯合子小鼠。采用PCR技术对小鼠进行基因型鉴定。结果共获得Founder小鼠4只,其中雄性和雌性各2只。经过8个月的配笼繁殖,共获得GLT25D2一小鼠40只;GLT25D2^＋/-小鼠89只;GLT25D2^-/-小鼠34只。不同基因型比例符合孟德尔遗传规律。对不同基因型小鼠合笼配对观察发现,GLT25D2^-/-小鼠生育功能下降,每胎数量平均3～4只,显著少于GLT25D2^＋/-小鼠之间的每胎小鼠数（平均6～8只）。对20,40,以及60d小鼠的体重观察显示,GLT25D2^-/-小鼠体重显著高于GLT25D2^＋/-和GLT25D2^＋/＋型小鼠,但这种体重差异的趋势随小鼠年龄的增加而逐渐减少。结论GLT25D2基因敲除小鼠发育异常,与野生型小鼠相比,体重增加,繁殖功能降低。     

肠道腺病毒检测技术

肠道腺病毒（ＥＡｄｓ）是仅次于轮状病毒引起儿童腹泻的病毒。由于其不能在通常培养腺病毒的细胞系中繁殖，简便快速地检测其存在，一直是人们研究的课题。本文总结了几种常用的检测技术，以利于不同实验室根据自身情况选择适合的方法。     

用电阻抗法进行细菌种类鉴别试验

将电阻抗法应用于细菌种类鉴别试验。笔者用自制的微生物传感器和电阻抗测量装置等,在一定条件下,利用微生物在生长繁殖过程可使培养基的电阻抗值减低的现象,通过测量接种细菌的培养基电阻抗值,并将细菌在培养期间内取得的所有电阻抗值数据描记成“阻抗曲线图谱”。试验证实,不同种类细菌所形成的阻抗曲线图谱是不相同的,是该种细菌所特有的。我们可以根据这些 “阻抗曲线图谱”的形态差异进行细菌种类鉴别,试验研究取得了预期的结果。     

基因药物药理学进展刍议

基因工程(gene engineering),又称DNA重组技术,他是把不同生物的基因或DNA分子进行人工剪切、组合及拼接,通过病毒、质粒或嗜菌体等载体转入到宿主细胞内繁殖扩增,使目的基因在宿主细胞内表达,产生所需的基因片断及蛋白质产物。基因工程技术的迅猛发展,推动了整个生物医药领域的巨大进     

缺氧敏感性不同的两种大鼠心、肺组织肾上腺素类受体的比较

蔡氏等的研究表明,平原条件下国外引进繁殖“缺氧敏感大鼠”(Hilltop SD,简作HT)的肺动脉压比国内常用的实验大鼠(Wistar简作W)高,低压舱内模拟5,000米高原缺氧,HT大鼠肺动脉压升高的程度较W大鼠明显。为探讨HT大鼠对缺氧敏感的生物学基础,我们应用放射性配基结合试验检测了平原对照及模拟5,000米高原缺氧15天的HT及W两种不同大鼠心,肺组织膜制备肾上腺素类受体反应性(Kd及Bmax)的变化,并进行     

野生绞股蓝组方预防高粘滞综合征的实验研究

目的了解野生绞股蓝组方预防高粘滞综合征的作用。方法将实验兔分为三组,普通饲料(A组),高脂 组方药(B组)和高脂饲料(C组)分别饲养。在饲养前后各作血液流变学、血脂测定,观察三组间的差别。结果A组饲养前后全血粘度、血浆粘度、血脂无明显变化;B组饲养后全血粘度、血浆粘度、血脂上升,与饲养前比较有差别(P<0.05);C组饲养后全血粘度、血脂明显上升,与饲养前比较有非常显著差别(P<0.001),血浆粘度上升,与饲养前比较有差别(P<0.05),饲养后B组全血粘度、血浆粘度低于C组,与C组比较有差别(P<0.05),血脂明显低于C组,有显著差别(P<0.01)。结论野生绞蓝组方有预防高粘滞综合征的作用。     

Endpoint-attached heparin blocks neutrophil sticking and spreading

Neutrophils adhere to polymer surfaces by partly unknown mechanisms. Heparin-coating of such surfaces is employed to improve biocompatibility of extracorporeal circulation. The aim of the study was to investigate mechanisms for interactions between neutrophils and uncoated versus heparin-coated surfaces. Isolated human neutrophils were incubated in tissue culture plates. Uncoated plates induced sticking and spreading of unstimulated neutrophils. Heparin-coating reduced sticking by approximately 75%, and adherent cells were less spread (p<0.001). Experiments in plates coated with modified heparins showed that sticking and spreading were not related to anticoagulatory ability or surface charge. Unstimulated neutrophil sticking was unchanged whether the media contained divalent cations or 1mM ethylenediaminetetraacetic acid (EDTA). Spreading on uncoated plates was greater in the presence of Ca(2+) and/or Mg(2+) than with EDTA. Spreading of unstimulated neutrophils on heparin-coated plates varied little with different media. Pre-incubation with anti-CD11b/CD18 antibodies did not significantly influence adhesion to heparin-coated plates. There were no differences in expression of the antiadhesive receptor CD43 (leukosialin) on adherent neutrophils on uncoated and heparin-coated plates, and pre-incubation with anti-CD43 antibody had little effect on neutrophil sticking. These data indicate an adhesive mechanism independent of selectins, integrins, and leukosialin, and inhibition of sticking and spreading by heparin-coating.     

Quantifying the attachment strength of climbing plants: A new approach

In order to grow vertically, it is essential for climbing plants to firmly attach to their supporting structures. In climbing plants, different strategies for permanent attachment can be distinguished. Besides twining stems and tendrils, many plants use attachment pads or attachment roots for this purpose. Using a novel custom-built tensile testing setup, the mechanical properties of different permanent attachment structures of self-clinging plant species were investigated, namely the attachment pads of Boston ivy (Parthenocissus tricuspidata), the attachment roots of ivy (Hedera helix) and the clustered attachment roots of trumpet creeper (Campsis radicans). Force–displacement measurements of individual attachment pads as well as of complete structures consisting of several pads or roots were conducted for both natural and laboratory growth conditions. The shapes of the curves and the maximum forces determined indicate clear differences in the detachment process for the different plants and structures tested. Based on these findings, it is argued that the attachment structures are displacement-optimized rather than force-optimized.     

Optimal effort investment for overcoming the weakest point: new insights from a computational model of neuromuscular adaptation

The occurrence of so-called sticking points in a lift is pervasive in weight training practice. Biomechanically complex exercises often exhibit multi-modal variation of effective force exerted against the load as a function of the elevation and velocity of the load. This results in a variety of possible loci for the occurrence of sticking points and makes the problem of designing the optimal training strategy to overcome them challenging. In this article a case founded on theoretical grounds is made against a purely empirical method. It is argued that the nature of the problem considered and the wide range of variables involved limit the generality of conclusions which can be drawn from experimental studies alone. Instead an alternative is described, whereby a recently proposed mathematical model of neuromuscular adaptation is employed in a series of computer simulations. These are used to examine quantitatively the effects of differently targeted partial range of motion (ROM) training approaches. Counter-intuitively and in contrast to common training practices, the key novel insight inferred from the obtained results is that in some cases the most effective approach for improving performance in an exercise with a sticking point at a particular point in the ROM is to improve force production capability at a different and possibly remote position in the lift. In the context of the employed model, this result is explained by changes in the neuromuscular and biomechanical environment for force production.     

Effect of aggregating agents and their inhibitors on the mean platelet shape

The `swirling' seen when platelet-rich plasma is stirred is caused by the average asymmetry of the platelets and a technique for recording the swirling is reported. After the addition of adenosine diphosphate, 5-hydroxytryptamine, thrombin, and collagen, platelets become rounded and more symmetrical immediately before they become sticky. Monoiodo-acetate and adenosine prevent both the change in shape and sticking whereas E.D.T.A. and p-tosyl arginine methylester prevent sticking but the shape still changes. Adrenaline produces sticking but no change in shape. The effects of temperature and E.D.T.A. are also reported. All these findings are discussed and diagrammatic representations of some reactions are tentatively proposed.     

The electrocardiogram of sheep,monitored by radiotelemetry,during electrical or carbon-dioxide stunning and subsequent slaughter

The e.c.g., monitored by telemetry, was used to study changes in the heart activity of sheep bled out after electrical stunning or carbon-dioxide anaesthesia. The decrease in ventricular rate which occurs as sheep are bled out after electrical stunning is apparently attributable to increasingly severe anoxia, rather than to changes in blood pressure. The heart rate at sticking is directly related to the heart rate before electrical stunning, but no relationship was found between the wattseconds used and the heart rate at sticking. However, the greater the number of wattseconds applied, the lower the minimum heart rate recorded after sticking. Exposure to carbon dioxide caused an initial tachycardia, followed by a decreased heart rate and then a secondary increase. The rate rose further when the sheep were removed from the gas. As the percentage of carbon dioxide used increased, the duration of heart activity after sticking decreased. Since high stunning currents cause early atrioventricular block, they might adversely affect bleeding out, if this is dependent on heart activity. High concentrations of carbon dioxide results in earlier termination of heart activity and might affect bleeding out similarly. The lower heart rate of sheep before electrical stunning may indicate that it is inherently less stressful than carbon-dioxide anaesthesia and so less likely to affect meat quality.     

Fibronectin adsorpton kinetics on phase segregated polyurethaneureas

The kinetics of fibronectin (FN) adsorption upon three polyurethaneureas (PUU) were measured by Fourier transform infrared spectroscopy. The three polymers had soft blocks composed of polydimethylsiloxane (PDMS), polytetramethyleneoxide (PTMO), and polyethyleneoxide (PEO). On each polymer, the amount of adsorbate increased proportional to the square root of time, but the rates were less than that predicted for purely diffusion controlled adsorption. Adsorption rate constants and sticking coefficients (the fraction of encounters with the surface which result in adsorption) were calculated from the data. The adsorption rate constants are 4.8 x 10^-4, 1.3 × 10^-4, and 2.5 x 10^-5 cm/s on PDMS-PUU, PTMO-PUU and PEO-PUU respectively. The rate constants and sticking coefficients fall within the range of previously reported values for other protein/polymer systems. The sticking coefficients correlate in general with the amount of FN adsorbed at 120 min, and with the extent of conformational change of the adsorbed protein.     

Cinematics and sticking of heart valves in pulsatile flow test

The aim of the project was to develop laboratory test devices for studies of the cinematics and sticking behaviour of technical valve protheses. The second step includes testing technical valves of different types and sizes under static and dynamic conditions. A force-deflection balance was developed in order to load valve rims by static radial forces until sticking or loss of a disc (sticking- and clamping-mould point) with computer-controlled force deflection curves. A second deflection device was developed and used for prosthetic valves in the aortic position of a pulsatile mock circulation loop with simultaneous video-cinematography. The stiffness of technical valve rims varied between 0.20 (St. Jude) and about 1.0 N/micron (metal rim valves). The stiffness decreased significantly with increasing valve size. Sticking under pulsatile flow conditions was in good agreement with the static deflection measurements. Hence, valve sticking with increasing danger of thrombus formation is more likely with a less stiff valve rim. In the case of forces acting perpendicularly to the pendulum axis, the clamping mould-point of the valve can be reached, followed by disc dislodgement.     

犬膝半月板前后角附着部拉伸参数的测定及断裂方式

对１８只犬膝半月板前后角附着部作拉伸试验，加载方向与胫骨平台平行，准静态和动态两种加载速率。对每一标本确定其极限载荷、应力、应变、弹性模量和断裂方式。结果表明，前后角附着部可承受的拉伸载荷平均为５５２Ｎ。平均极限应力和应变分别为５１ＭＰａ和４１％。因为这两个参数高于半月板本身的断裂参数，因此，正常活体不会发生附着部断裂。将来，半月板假体固定时要求达到类似的强度。与动态加载时的结果相比，准静态加载时极限应力显著降低并有撕脱断裂的倾向。这表明离体测试时模拟生理条件有着重要意义。     

医用丝素蛋白皮肤再生膜的细胞相容性评价

评价医用丝素蛋白皮肤再生膜的细胞相容性。其方法是采用细胞增殖度试验和溶血试验,对医用丝素蛋白皮肤再生膜进行细胞毒性和溶血反应的实验研究。结果表明：该再生膜无明显细胞毒性存在,溶血率为1.15%。医用丝素蛋白皮肤再生膜具有良好的细胞相容性。