Evaluation of hydroxyl radical-scavenging property of garlic

While antibiotics are broadly used in dental and medical therapy, little attention has been directed towards the potential toxic side effects of antibiotics on tissue regeneration. Here we examined the effect of a quinolone antibiotic, pefloxacin (Rhone Poulenc) on rat parotid gland responses to chronic isoproterenol treatment. Groups of rats received injections of isoproterenol to induce glandular growth, saline (controls), pefloxacin, or isoproterenol and pefloxacin in combination. Parotid gland weight decreased significantly after pefloxacin treatment for 7 days as well as inhibiting glandular enlargement provoked by isoproterenol. The same trend was observed for the rates of DNA synthesis, with the incorporation of [³H]-thymidine in isoproterenol/pefloxacin-treated rats reduced to 49% of isoproterenol treatment alone levels. Saline-treated animals were 42% of the rate of [³H]-thymidine incorporation into DNA observed in isoproterenol treated rats. While isoproterenol treatment increased steady-state mRNA levels for fos, jun, myc, src, c-erbB-2, ras and topo II, inclusion of pefloxacin with the isoproterenol regimen blocked these increases. Pefloxacin treatment by itself did not alter proto-oncogene mRNA levels in the parotid gland. Glandular amylase activity was decreased in the pefloxacin treated group, while the combination of isoproterenol with pefloxacin did not decrease glandular amylase levels to the extent of that observed with -agonist treatment alone. In acute experiments, pefloxacin significantly decreased the volume of saliva secreted by the parotid gland. These results suggest that quinolone-based antibiotics disturb the secretory function of the parotid gland and can inhibit cell proliferation and regeneration. (Mol Cell Biochem 165: 55–63, 1996)     

A stochastic model for the sigmoidal behaviour of cooperative biological systems

A stochastic model for cooperative transitions in biological systems based on a Markov chain is proposed. This model requires only two parameters, the mean probability, p, and the coupling capacity, Deltap, which measure the probability of forming a new weak bond depending on the number of similar bonds already formed and it is also responsible for the transition. In this paper we show how the model works for a large number of identical molecules and how it can be useful for studying the noise around the centre of the transition where, increasing the degree of cooperativity, i.e. the number n in the well-known Hill equation, the width of the noise increases along with its fractal dimension. A simple relationship between the degree of cooperativity and the parameter Deltap is proposed, suggesting that the cooperativity of real biological transitions is related to the coupling capacity Deltap of the present model.     

苏云金芽孢杆菌δ-内毒素基因穿梭质粒的构建

在农业生产中长期使用化学农药已对环境和生态平衡造成一定破坏作用,同时有不少害虫也逐渐产生抗药性从而引起某些害虫的大流行,给农业生产带来巨大损失。应用苏云金杆菌杀虫蛋白基因(Bt基因)可构建具有抗虫作用的抗虫工程菌,这样通过拌种或植物叶面喷雾可达到快速、经济、有效的防治虫害的目的。国际上抗虫工程菌研究应用很快,如美国将BI基因转入到一种正常情况下定居在植物组织中的棒杆菌,将这种工程菌拌玉米种子,这样随植物生长该菌在植物体内大量繁殖,当玉米螟在茎和叶取食时,即因食用表达苏云金杆菌毒蛋白的工程菌而死亡。 田颖川等已克隆了苏云金芽孢杆菌内毒素基因CryIA(b)和CryIA(c)。本文将Bt基因CryIA(c)插入到大肠-枯草穿梭载体pBE-2中构建成Bt毒蛋白基因穿梭质粒pAMY,利用电穿孔法转人大肠杆菌DH5a,枯草芽孢杆菌B.subtilis BR151,IA511,野生型蜡状芽孢杆菌B.cereusa-47,短芽孢杆菌B.brevis A-5和枯草芽孢杆菌90-8,获得了具有较高杀虫活性的工程菌克隆。     

部分酶解酵母高效电击转化研究

以酵母质粒YCp50为外源DNA,电击转化部分酶解酵母宿主菌AB1380,转化效率稳定在10~6转化子/μg质粒DNA左右,比不酶解酵母或酵母原生质球作受体的电击转化效率高一个数量级以上,也比PEG介导的酵母原生质球转化高3～5倍,而且适合于大片段DNA如水稻YAC分子的转化。达最佳转化时的有关技术参数为:新接菌种通气培养至细胞密度1×10~8～1.5×10~8个/ml;转化时细胞密度控制在1×10~9～1.5×10~9个/ml;每毫升酶解缓冲液加15u溶菌酶(lyticase),30℃下处理酵母5min进行部分酶解;电击时,电场设置在6.25kV/cm、电容25μF,电击后直接铺板。     

猪精子凝集素的纯化,性质及其作用

用胎球蛋白－Ｓｅｐｈａｒｏｓｅ亲和层析和凝胶过滤层析从精子和精浆中分离纯化了猪精子凝集素（简称ＢＳＬ）。ＢＳＬ的血凝活性只被若干糖蛋白和聚糖所抑制。ＢＳＬ的分子量为５６ｋｄ,由分子量分别为１３．６ｋｄ（β）和１６．０ｋｄ（α）的两个不同的亚基以α１β３所组成。ＢＳＬ为糖蛋白,含中性糖３．２％,不含唾液酸。用ＥＬＩＳＡ法测定猪精子中ＢＳＬ的含量及分布,表明７０％嵌入在精子膜中,２５％结合在精子表面,     

用人工合成的丁型肝炎病毒抗原多肽检测丁肝病毒IgM抗体及其初步应用

用人工合成的丁型肝炎病毒抗原（ＨＤＶ－Ａｇ）肽建立了检测抗ＨＤＶ－ＩｇＭ抗体的ＥＬＩＳＡ方法,本法操作简便、快速,重复性好,特异性强,与抗ＨＡＶ－ＩｇＭ、抗Ｈｋ－ＩｇＭ、抗ＨＢｓ－ＩｇＭ、抗ＨＣＶ－ＩｇＩ、抗ＣＭＶ－ＩｇＭ、抗ＲＶ－ＩｇＭ、类风湿因子（ＲＦ）及抗核抗体（ＡＮＡ）阳性血清均不起反应,且可被２－巯基乙醇阻断而不起反应。经初步临床应用,３１例正常人血清抗ＨＤＶ－ＩｇＭ全部阴性,２８例慢活肝患者检出率为３２．１％（９／２８）,１７例慢迁肝患者血清阳性率为１１．８％（２／１７）１８例肝癌和肝硬化病人血清阳性率为２２．２％（４／１８）这三组病人与正常对照者相比较均有显著性差异（Ｐ＜０．００１）。此外,抗ＨＤＶ－ＩｇＭ阳性血清的ＡＬＴ值均明显高于正常参考范围,提示在ＨＤＶ感染过程中,患者肝细胞进一步受损。实验结果证明,抗ＨＤＶ－ＩｇＭ是诊断ＨＤＶ感染的重要指标,对ＨＤＶ感染早期诊断具有重要价值。     

武汉东湖水生植被及其恢复途径探讨

１９９２～１９９３年对武汉东湖三个主要湖区（郭郑湖、汤林湖和牛巢湖）水生植被的调查表明,该湖区共有水生植物３２种,优势种为大茨藻、狐尾藻、苦草和菱。金鱼藻呈不断扩大的趋势。植被类型可分为１１个群丛,植被面积约为０．６５ｋｍ￣２,总生物量为１２３６．３９ｔ（湿重）,植被带状分布仅见于汤林湖北部和其他部分湖汊。汤林湖和牛巢湖水生植被正处于自然恢复演替阶段。     

Atomic composition of the hydrophobic and hydrophilic membrane sides of self-assembled SC3p hydrophobin.

The hydrophobin SC3p of Schizophyllum commune self-assembles into a 10-nm-thick amphipathic membrane at hydrophilic-hydrophobic interfaces. X-ray photoelectron spectroscopy of the hydrophobic membrane side of SC3p, assembled in vitro, showed an atomic composition similar to the calculated composition of SC3p when glycosylation was taken into account. The atomic composition measured at the hydrophilic membrane side deviated from that at the hydrophobic side and indicated the presence of a lower number of peptide bonds. High levels of S and N were detected only on mycelia carrying hydrophobic aerial hyphae, as expected with assembled SC3p present at the surface of these hyphae.     

Reaction mechanism of isomaltooligosaccharides synthesis by α-glucosidase fromAspergillus carbonarious

Summary An -glucosidase fromAspergillus carbonarious CCRC 30414 was employed for investigating the enzymatic synthesis of isomaltooligosaccharides from maltose. The enzyme transferred a glucose unit from the nonreducing end of maltose and other -linked glucosyl oligosaccharides to glucose and other glucosyl oligosaccharides which function as accepting co-substrates. The transfer of a glucose unit occurs most frequently to the 6-OH position of the nonreducing end of acceptor, but transfer to 4-OH position also occurs. Treatment of 30 % (w/v) maltose with the enzyme under optimum conditions afforded more than 50% isomaltooligosaccharides.     

Abscisic Acid-Induced Membrane Potential Changes in Barley Aleurone Protoplasts: a Possible Relevance for the Regulation of rab Gene Expression

The effect of ABA on the membrane potential of barley (Hordeumvulgare cv. Himalaya) aleurone protoplasts was studied by measuringthe distribution of the lipophilic cation tetraphenylphosphonium(TPP⁺). The resting membrane potential (E_m) according to ourmeasurements with TPP⁺ is about –53 mV and is in agreementwith membrane potential values as measured with intracellularmicroelectrodes (about –55 mV). The TPP⁺-measurementscould demonstrate a clear dependence of the resting E_m on theexternal pH (pH_e). Stimulation of the protoplasts with ABA induced a transienthyperpolarization of the membrane to –62 mV as measuredwith TPP⁺. The hyperpolarization was ABA-concentration dependent. Inhibition of the H⁺-ATPases with the specific proton pump inhibitorsdiethylstilbestrol (DES) or Micanozole effectively preventedhyperpolarization. This indicates that the hyperpolarizationis consistent with the activation of plasma membrane H⁺-ATPases.The K⁺-inward rectifier inhibitor BaCl₂ was able to prolongthe hyperpolarization. This result suggests that the hyperpolarizationcauses the opening of K⁺-channels. The ABA-induced proton-pump activation may be involved in ABA-inducedgene-expression, as DES was able to inhibit this gene expression.BaCl₂ did only show a slight inhibitory effect on ABA-inducedgene-expression. (Received January 4, 1994; Accepted April 12, 1994)