种群矩阵模型在昆虫生态学研究上的应用问题

里斯来矩阵模型和莫里斯—瓦特数学模型是近年来广泛应用于研究有害动物综合治理的数学模型。里斯来矩阵模型是以相等时间间隔划分的年龄组为基础的,用于研究生物种群数量动态,可以推算各年龄组的组成及其变化趋势特征。莫里斯—瓦特数学模型是以昆虫生命表为基础发展的数学模型,适应于推算以一个世代为单位的数量发展趋势。两者各有一定的优点。然而,里斯来矩阵模型仅适用于可以相等时间间隔划分年龄组的生物种群,对大多数昆虫来说,发育阶段及龄期有明显的区别,但各发育阶段及龄期的历期往往是不相同的,因此,为了适应于研究昆虫种群,有必要解决不等期年龄组的种群矩阵模型问题。 本文讨论建立不等期年龄组的矩阵模型的方案,通过适当的数据处理,使里斯来矩阵模型适应于研究昆虫种群问题;同时,并使里斯来矩阵模型与莫里斯—瓦特数学模型结合起来。这将更便于进行昆虫生命表的数据分析,可能有助于昆虫种群动态的研究。     

用昆虫细胞制备生物制品

昆虫细胞作为生产治疗性蛋白〔如单克隆抗体(McAb)〕的一种潜在有效的方法正日益受到重视。目前开发昆虫细胞系的公司有SmithKline(SB)公司和Cystar公司,他们认为昆虫细胞可能是生产廉价蛋白的有用技术。 据SB公司称,他们的昆虫细胞优于哺乳动物和细菌细胞培养物,因为不到三周时间即可在单个果蝇血细胞中插入某种基因的1000多个拷贝;而将同样数量的基因拷贝克隆进哺乳动物细胞则需时6个多月。 由昆虫细胞产生的蛋白还可通过基因工程方法适当折叠,并具有必需的糖基尾,因此能用于动物研究。SB公司的昆虫细胞还能经改变后在无血清培养基上生长,故     

昆虫的药理作用及研究概况

昆虫是自然界中种类和数量最多、生长繁殖最快的动物,在长达4亿年之久的进化过程中,在适应环境、抵御各种生物侵害方面,产生了诸多特殊物质或建立了特定的防御功能。如存于昆虫血淋巴中的抗菌物质能抵御细菌或其它微生物;药用昆虫体内的多     

注射大肠杆菌诱导柞蚕蛹血淋巴产生抗菌物质(简报)

昆虫是地球上数量多分布广的动物,它们能适应环境而得以生存和发展,是具有其独特的内在因素的。近年来对昆虫防御机构的研究已引起重视,特别昆虫免疫问题已取得一定的的进展。1974、1980年Boman等已作了评述。昆虫虽然不象高动物那样具有完善的免疫体系,但它们先天免疫及获得性兔疫能力却是惊人的。1974年Boman等用大肠杆菌Escherichia coli注射于樗蚕Samia cynthia滞育蛹,诱导血淋巴产生抗菌物     

应用杀虫剂防治白背飞虱对褐稻虱种群数量的影响

本文应用昆虫生命表方法和干扰作用控制指数探讨噻嗪酮（扑虱灵）、叶蝉散、喹硫磷三种杀虫剂对白背飞虱种群的控制作用以及及防治白背飞虱对随后发生的褐稻虱种群数量发展趋势的影响。试验结果表明，主要作用于同翅目昆虫而不杀伤在敌的噻嗪酮，对两种飞虱的效果明显， 对害虫及天敌同样起作用的喹硫磷，反而引起这两种害虫种群数量上升，广谱性的杀虫剂不宜在稻地早期大面积应用。     

几种药剂对褐稻虱种群数量控制的研究

本研究应用昆虫生命表及种群趋势控制指数方法,探讨几种药剂对揭稻虱种群数量的控制作。同时研究这几种药剂对稻田天敌密度的作用,并通过杀虫剂的毒力测定,验证主要的两种天敌对几种杀虫剂的反应。 试验结果表明:喹硫磷由于严重杀伤稻田天敌,因而增大了下代的种群趋势,控制指数(14.36)甚低于对照区(28.43)。叶蝉散区的控制指数(29.40)仅略高于对照区,在天敌作用比较明显的环境下(对照区的种群趋势指数为1.8793),防治效果不明显。优乐得(App-laud)区的控制指数最高(65.96),种群趋势指数最低(0.7523),这种药剂属于主要对同翅目昆虫起作用的生长调节剂,不但抑制褐稻虱的种群数量,同时也相对地助长其天敌的作用,因而防治效果较好。 在昆虫生命表的基础上,通过种群趋势控制指数的分析,有助于杀虫剂和天敌协调作用的综合评价。     

昆虫的药用价值及研究进展

近年来有关药用昆虫的各项研究及临床应用均有很大的进展 ,现综述如下 :１药用资源药用昆虫是指昆虫虫体或其产物可直接用来治疗疾病的昆虫 ,是中医中药中不可缺少的组成部分。在我国的传统中药中主要通过使用昆虫作为一种配方 ,与其它动植物药材配伍 ,形成了很多疗效显著的处方。如大黄虫丸出自汉张仲景著《金匮要略》 ,由３种昆虫和其他９味中药组成 ,有活血通络、祛瘀生新、缓中补虚的功效。又如苍耳蠹虫 ,其药用在《圣济总录》和《本草纲目》中均有记载 ,具有“治一切疥肿及无名肿毒恶疮”之功效。药用昆虫及其产物的作用表现在 :散风解…     

镉胁迫对昆虫的毒性效应及昆虫防御机制的研究进展

镉是重要的重金属污染物之一,其毒性大,蓄积性强,易对人类健康造成严重危害,这种危害也涉及到无脊椎动物,尤其是镉胁迫对昆虫的影响已引起人们关注。环境中的镉可通过摄食和呼吸等途径进入昆虫体内,影响昆虫的生长发育,并通过氧化损伤等途径诱导细胞凋亡。昆虫对镉胁迫有一定的防御能力,可在一定程度上依靠金属结合蛋白、抗氧化酶、热休克蛋白的保护作用及排泄行为的解毒作用减少镉对机体的损害。镉的毒性效应可能随昆虫种类不同而不同。本文就镉胁迫对昆虫生长和发育的影响、诱导细胞凋亡的分子机制以及昆虫对镉胁迫的防御机制等研究进展进行回顾综述。     

动物习性造就药性

李时珍《本草纲目》记载了400余种动物、昆虫可以入药，并有特殊疗效，而且其中一些药性疗效正是这些动物、昆虫长期生活习性和生理特征造就的，两者有密切的内在联系。     

稻纵卷叶螟防治策略的探讨(一)——稻纵卷叶螟生命表及其主要死亡因子分析

本文应用昆虫生命表方法在阳江县海陵岛研究稻纵卷叶螟种群数量动态问题。试验自1976年开始,至1981年积累了6年第二世代稻纵卷叶螟生命表的数据。通过生命表的组份分析,说明了海陵岛于1976—1981年间贯彻执行的综合防治措施是合理的,是6年来第三世代以后不致达到为害水平的重要原因;说明了天敌对第二世代稻纵卷叶螟种群数量起着重要的抑制作用;通过分析,找出了对稻纵卷叶螟第二世代种群数量起主要作用的因素和对种群数量起关键作用的因素。该项研究为进一步建立海陵岛第二世代稻纵卷叶螟为害期的数量预测和第三世代卵期的数量预测模型提供基础。关于数量预测模型将在下文介绍。     

Fusion of fungicidal peptide dhvar4 to enterococcal peptide pheromone increases its bactericidal activity against Enterococcus faecalis

Bacterial peptide pheromone has a high affinity to its membrane receptor. Fusion of these peptides to pore-forming antimicrobial peptide might enhance its bactericidal activity against pheromone-sensing bacteria. We constructed two chimeric peptides by fusing the pore-forming fungicidal peptide dhvar4 to the C-terminus of enterococcal peptide pheromones cCF10 and cOB1 individually. Comparison on the bactericidal activities against pheromone-sensing bacteria Enterococcus faecalis demonstrates that the chimeric peptides cCF10-dhvar4 and cOB1-dhvar4 are more potent than the parent peptide dhvar4. The LD(50)s of both chimeric peptides (1.0 microm) are 10 times lower than that of dhvar4 (10.8 microm). Free peptide pheromone could inhibit E. faecalis killing mediated by both chimeric peptides. As same as that of the parent peptide, both chimeric peptides kill bacteria by disrupting its cell membrane. These results indicate that fused enterococcal peptide pheromone increases the bactericidal activity of fungicidal peptide against E. faecalis by improving its ability to reach the cell membrane.     

Novel approaches to the design of bioavailable melanotropins

Introduction: The melanocortin system is a primordial and critical system for survival, involved in a wide variety of physiological functions. It includes melanocortin receptors (MCRs) and melanotropin ligands (MCLs). MCRs are important drug targets that can regulate several key physiological processes. Extensive efforts have been made to develop peptide and peptidomimetics targeting melanocortin receptors including MC1R, MC3R, MC4R and MC5R. Most research is focused on developing potent and selective melanotropins. However, developing bioavailable melanotropins remains challenging.

Areas covered: Herein, the authors summarize promising strategies for developing bioavailable MCLs by using cyclized N-methylated melanotropins, and using cyclotide and tetrapeptide as templates. They discuss their unique advantages in oral availability and targeting MCRs in the central nervous system or in peripheral tissues. Finally, they discuss the observed differences in thepharmacology of MCRs between in vitro and in vivo tests.

Expert opinion: N-methylated cyclized melanotropins have great potential to become bio- available drugs targeting MCRs in the brain, while MCR-grafted cyclotides tend to target MCRs in peripheral tissue. A better understanding of the biased signaling process is a new challenge and opportunity for the future discovery of bioavailable MCLs.     

Conformational modification of the PRP-hexapeptide by a direct covalent attachment of aromatic side chain groups

PRP-hexapeptide possessing the azo-bridge between Tyr¹ and Phe⁵ residues, called azo-PRP-hexapeptide: Tyr-Val-Pro-Leu-Phe-Pro, was synthesized and tested for immunoregulatory activity. High biological activity of the synthesized azo-PRP-hexapeptide suggests that the biologically active conformation of PRP-hexapeptide must be such that both aromatic rings (Tyr and Phe) are apparently close to each other.     

Peptide aggregates: a novel model system to study self-assembly of peptides

Ordered aggregates of Val-Leu-Pro-Phe, tetrapeptide 1 , have been found in aqueous solutions. Evidence for the formation of aggregates for the above peptide was obtained by conductometric, pH metric, UV and fluorescence spectroscopic techniques. Values of critical micelle concentration (CMC) for the above peptide obtained by these methods are in good agreement with each other. The formation of organized aggregates of the peptide is favoured upon increasing the temperature (viz. the process of aggregation is endothermic). The aggregation number has been determined at different temperatures. Values of ΔG°_mΔH°_mΔS°_m and ΔC°_p have also been estimated. Binding studies with the 8-anilinonaphthyl sulfonic acid (ANS) and pyrene indicate that the interior of the aggregate is nonpolar. There are two processes with regard to the change of thermodynamical parameters like ΔG°_mΔH°_mΔS°_mΔC°_p aggregation number (N). In the first process (from 5°C to 40°C) the driving force for aggregation seems to be the positive entropy because of water release due to intermolecular association of ionic moieties. The second process (from 40°C and above) is due to intramolecular ionic interaction. The chemical shifts of the amide protons of the peptide have been presented in the light of inter- and intramolecular hydrogen-bond formation, and forces implicated in aggregation for both the first and second processes. © Munksgaard 1995.     

Biological versatility of crotamine – a cationic peptide from the venom of a South American rattlesnake

Importance of the field: Molecules isolated from animals, insects, plants or microorganisms can provide prototypes for design of biopharmaceutical products. Some venom toxins and their derivatives are used in medicine, while others provide templates for development of new drugs.

Areas covered in this review: The mild toxin, crotamine, a small basic low-molecular-weight polypeptide purified from the venom of a South American rattlesnake, Crotalus durissus terrificus. Crotamine was discovered more than 50 years ago and only in the past six years has its exceptional biological versatility been demonstrated. Particularly, its cell-penetrating ability, which allows crotamine to cross cell membranes and to accumulate in the nucleus; its use for intracellular vesicle tracking and as a cell cycle marker and its capability for delivering DNA into replicating mammalian cells. Both antimicrobial action and potential selective antitumor activity of crotamine have also been found.

What the reader will gain: Multidisciplinary approaches and pathways of discovery placed crotamine in a rare category of versatile biomolecules, in which concentration, molecular target preference, structural ancestry and specificity toward biological membranes play an integral role.

Take home message: Crotamine is a druggable peptide with high potential for use as an imaging agent for detecting dividing cells, for intracellular delivery of hydrophilic biomolecules, and as an alternative chemotherapeutic compound against aggressive types of cancer.     

短肽类药物与中枢神经系统疾病

中枢神经系统疾病的治疗一直是医学领域的难题。传统药物无法防治急慢性中枢神经系统损伤、阿尔采末病、帕金森病、癫痫等中枢神经系统疾病。医学界一直在致力于寻找治疗中枢神经系统疾病的新药。短肽类药物是近年来研究的热点。人工合成的联接蛋白43模拟肽、载脂蛋白E模拟肽、神经营养因子模拟肽、神经细胞黏附分子模拟肽、金属硫蛋白模拟肽、促红细胞生成素模拟肽等短肽类药物对中枢神经系统疾病的治疗价值已获得证实。该文对短肽类药物在中枢神经系统疾病治疗中的研究进展进行了全面分析综述。     

Direct synthesis and characterisation of multi-dendritic peptides for use as immunogens

The direct synthesis and subsequent rapid characterisation of multiple antigen peptides (MAPs) for use as immunogens has presented difficulties, partly because of the formation of incomplete or truncated peptide sequences during the synthetic procedure. Therefore, many researchers have resorted to ligation procedures for the synthesis of MAP constructs. This article describes a method to improve the yield of MAP constructs by direct synthesis methods, as well as a general procedure that enables easier characterisation of the synthetic products. In particular, during the synthesis of MAP constructs, a capping procedure was introduced after each amino acid coupling step, thus improving significantly the yield of me desired multi-dendritic peptidic immunogens. Through the use of this capping procedure, problems arising from the incomplete amino acid residue coupling at the point of synthesis were minimised, and any deletion peptides which formed could be eliminated more readily during the subsequent purification procedures. In addition, previous difficulties in purification and characterisation of MAP construct by, e.g. electrospray mass spectroscopy (ES-MS), often led to the multi-dendritic peptidic immunogens being used without full characterisation after dialysis and recovery of the product(s). This article describes an enzymatic (tryptic) digestion method with the MAP construct, followed by characterisation of the enzymatic digest by reversed phase high-performance liquid chromatography-ES-MS. With this method, fragments of the MAP construct cleaved at specific amino acid residue sites (e.g. lysine or arginine) within the sequence of the parent peptide can be readily determined and the kinetics of the digestion easily followed. This enzymatic digestion procedure thus provides a facile approach to confirm that all of the multi-dendritic arms of the purified MAP construct have been equivalently elongated during the peptide synthesis and that consequently the purified construct structure contains the correct peptide sequence.     

Synthesis of HC toxin and related cyclopeptides containing the (L-Ala-D-Ala-L-Ada-D-Pro) sequence

In studies leading to HC toxin synthesis, a phytotoxic cyclic tetrapeptide with the sequence cyclo (L-Ala-D-Ala-L-Aoe-D-Pro), we have determined optimal conditions for the cyclization which constitutes one of the most important steps in the synthesis of the toxin. All four possible sequences containing an optically active precursor, i.e. L-Ada = (2 S)-2-amino-9-decenoic acid instead of Aoe, have been prepared and subjected to cyclization. Owing to the differences in racemization risk during activation of the terminal carboxyl aminoacid different cyclization procedures have been applied. Cyclopeptide yields and selectivity between cyclomonomer and dimer both containing the title sequence are mainly controlled by the linear precursor sequence. The cyclic tetrapeptide is only obtained with D-proline in the C-terminal position, the best yield reached by the -ONSu activation method. Starting from the peptide, the (9S, 9R) HC toxin epimer on the epoxidic carbon atom has been further synthesized in two steps.     

Characterization of the Salts of a Cyclic RGB Peptide

Pharmaceutical Research -     

Addition and omission analogs of the 13-residue antibacterial and hemolytic peptide PKLLKTFLSKWIG: structural preferences,model membrane binding and biological activities

The consequences of selective addition or deletion of polar amino acids in a 13-residue antibacterial peptide PKLLKTFLSKWIG on structure, membrane binding and biological activities have been investigated. The variants generated are (a) S and T residues replaced by K, (b) S and T residues deleted individually and together, (c) introduction of two additional K and (d) deletion of L and L with T. In the aqueous environment all the peptides were unordered. In trifluoroethanol, the spectra of peptides belonging to groups (a-c) suggest distorted helical conformation. Peptides in group (d) appear to adopt β-sheet conformation. The peptides bind to zwitterionic and negatively charged lipid vesicles, although to different extents. With the exception of peptides in group (d), all the other peptides exhibited comparable antibacterial activity against Escherichia coli and Staphylococcus aureus. However, the changes made in the peptides in groups (a-c) resulted in reduction of hemolytic activity compared to the parent peptide. Extent of binding to lipid vesicles composed of phosphatidylcholine and cholesterol appears to correlate with hemolytic activity. It appears that polar and charged residues play a major role in modulating the biological activities of the 13-residue peptide PKLLKTFLSKWIG. The 11-residue peptide-like PKLLKFLKWIG has selective antibacterial activity. Thus, by judicious engineering it should be possible to generate short peptides with selective antibacterial activity.