Toxins

The past year has been a notable one for the structural study of toxins. Several new toxin structures have been determined, including the first example of a superantigen. Another first is the visualization of binding interactions with a cell-surface receptor. Unexpected structural homologies hint at unsuspected evolutionary relationships among toxin families.     

凝集素和毒素

总的说来,凝集素并不很毒,但是在凝集素和毒素之间却存在一些关系。ＥＢＡ类毒素可以分为两个主要部分。其中一个部分呈现糖结合活性,负责靶向。另一部分则具有不同的酶活性,决定了其毒性。从天花粉中分离得到凝集素分享了ＤＥＡ类毒素（例如蓖麻毒素）的一些特性。还有一些毒素可以在细胞膜上造成孔,形成离子通道。半夏凝集素似乎可归属于这类毒素。从蛇毒中分离得到了一此凝集素,它们和蛇毒中的其它一些成员在氨基酸序列上有     

Food-Borne Bacterial Toxins

Food poisoning caused by the ingestion of preformed bacterial toxins is considered in relation to comparative symptoms, procedures for extraction and purification of the causal toxins, their chemistry, serology, assay procedures and pharmacology, in so far as these are known.The bacteria discussed in this context are Clostridium botulinum, C. perfringens, Staphylococcus aureus, Bacillus cereus, and Vibrio parahemolyticus. The possible roles of the enterococci, Proteus, E. coli and of unknown species, in relation to production of non-antigenic toxic substances, are discussed briefly.Requirements for prevention of the various forms of bacterial food poisoning are outlined.     

Sodium Channel Toxins and Neurotransmitter Release

Voltage-dependent sodium channels (VDSC) are an important class of ion channels in excitable cells, where they are responsible for the generation and conduction of action potential. In addition, the release of neurotransmitters from nerve terminals is influenced by sodium channel activity. The function of VDSC is subject to modulation by various neurotoxins, such as scorpion toxins, which have long been used as tools in the investigation of neurotransmitter release. This opens an interesting perspective concerning modulation of neurotransmission via pharmacological manipulation of sodium channel properties, which can lead to a better understanding of their physiological and pathological roles. Here we briefly review the studies of neurotoxins acting on sodium channels, focusing primarily on the view of the mechanisms of neurotransmitter release.     

Toxins of Vibrio cholerae

Surveyed in the paper are published data on properties, biological activity, genetic determinants and action mechanisms of recently known toxins produced by different strains of Vibrio cholerae irrespectively of their capacity for the synthesis of choleric toxin--the main virulence factor. Their possible importance both for the general clinical pattern of cholera provoked by cholerogenic agents and as independent virulence factors causing diarrhea without cholera is elucidated. The sets and levels of expression of additional toxins can differ for different pathogenic clones and they can correspondingly condition degrees of their epidemic and etiological safety.     

海洋毒素研究进展

从海洋生物中分离出大量结构新颖、生物活性独特的海洋毒素。本文对目前分离得到的海洋毒素进行了总结,包括:河豚毒素、麻痹性贝毒素、腹泻性贝毒素、肝脏毒贝毒素、神经性贝毒素、记忆丧失性贝毒素、西加毒素和其它类型的海洋毒素。海洋毒素不仅可以作为寻找新型防治心血管疾病药物和抗肿瘤药物的先导化合物,还是研究生命科学有用的工具。本文列出了67个重要的海洋毒素的结构并提供70篇参考文献。     

Structure and Action of Nemertine Toxins

Bacq (1936, 1937) discovered two substances by pharmacologicalexperiments using whole body extracts of various nemertine species."Amphiporine," found only in hoplonemertines, stimulated nicotinicacetylcholine receptor-mediated events. "Nemertine" evoked spontaneousaction potentials in isolated crab nerves. Both substances causedconvulsions when injected into crabs. Anabaseine, a pyridinealkaloid isolated from the hoplonemertine Paranemertes peregrina,has chemical and pharmacological properties equivalent to "amphiporine."Hoplonemertines produce a wide variety of pyridine toxins dependingon the species. The heteronemertine Cerebratulus lacteus contains cytolytic(10,000 dalton) and neurotoxic (6,000 dalton) proteins. Theneurotoxic polypeptides most closely resemble "nemertine": theycause repetitive spiking in isolated crustacean axons. Severalcytolytic and neurotoxic "isotoxins" occur within Cerebratulus. Both the hoplonemertine and heteronemertine toxins are localizedin the integumentary tissues of the body wall and proboscis.So far, the pyridine alkaloid toxins are only found in the Enoplanspecies, where they probably function as both offensive anddefensive toxins. Protein toxins have only been found in Anoplanspecies; they probably serve as a chemical defense against somepredators.     

Enzymes of snake venoms

Snakes' venom is a mixture of biologically active substances, containing proteins and peptides. A number of these proteins interact with haemostasis system components. Activators and inhibitors affecting blood coagulation and fibrinolysis systems are of special interest. Venom components can be classified into three main groups, such as procoagulants, anticoagulants and fibrinolytic enzymes according to their action. This review is focused on enzymes from Agkistrodon halys halys venom. They are thrombine-like enzyme, named Ancystron-H, flbrinogenolytic enzyme, protein C activator and platelet aggregation inhibitor. Ancystron-H is used for determination of fibrinogen level in blood plasma of patients undergoing heparin treatment and blood coagulation inhibitors accumulation. The fibrinogenolytic enzyme can be used as the instrument for protein-protein interactions in fibrinogen-fibrin system. The protein C activator is used for protein C level determination in blood plasma with different pathologies. Functions of the platelet aggregation inhibitor, belonging to disintegrins group, can be used for development of antithrombotic preparations. Information about the use of snake venoms in science and medicine is presented.