Journal of natural toxins最新文献

Attempts were made to isolate the bacteria from toxic dinoflagellate Alexandrium minutum T1 and to study the effect of these bacteria on the growth and toxicity of A. minutum T1. It was found that intracellular bacterial species including Pasteurella haemolytica, Pseudomonas vesicularis, and Sphingomonas sp., and extracellular bacterial species including Pasteurolla pneumotropica, Morganella wisconsensis, Flavobacterium oryzihabitans, Pseudomonas pseudomallei, and Sphingomonas sp. All of them were cultured and determined to have non-PSP-producing ability. The maximum cell number of A. minutum cultured without isolated bacteria was higher than that cultured with isolated bacteria. The total toxicity of A. minutum cultured with bacteria was similar to that of A. minutum T1 cultured without bacteria from lag phase to stationary phase, but it was lower after stationary phase. The growth of A. minutum T1 cultured without antibiotics was also better than that cultured with antibiotics. The total toxicity of A. minutum cultured without antibiotics was higher than that of A. minutum cultured with antibiotics. However, the cell toxicity of A. minutum did not decrease even if the culture medium was added with antibiotics.

Type A botulinum neurotoxin is produced along with 6-7 neurotoxin associated proteins to form a complex in addition to the neurotoxin. Immunological reactivity of type A botulinum complex and purified hemagglutinin (Fu et al., 1998) to polyclonal antibody raised against the complex have been investigated using ELISA. In competitive ELISA, 50% inhibition of the binding of IgG antibody against complex A is observed at 78 ng/ml of complex and hemagglutinin-33, suggesting that the hemagglutinin-33 accounts for most of the immunogenic response of the complex. Considering the fact that the complex consists of a group of proteins with a cumulative molecular weight of 900 kDa, hemagglutinin-33 may be one of the major immunoreactive proteins present in the type A neurotoxin complex.

Several investigators have isolated nerve growth factor (NGF) from various tissues and organs of different animals. There is no published documentation about NGF from body fluids, such as blood serum, saliva, and urine. Contrary to the unsuccessful attempts to detect or isolate NGF in serum in the past, this investigation reports the isolation of NGF from human serum, saliva, and urine. It further reports the comparison of properties between NGFs derived from cobra venom and cobra serum. NGF from serum, saliva, and urine was isolated by high pressure liquid chromatography (HPLC) and was identified as described by Lipps (1998). The identified fractions of NGF were further purified to study the biological and immunological properties. The biological activities of NGFs from human body fluids and cobra serum on PC12 cells were miniscule in comparison to the cobra venom derived NGF. The molecular weights of NGFs from human serum, saliva, and urine were identical, 36.0 kDa. However, the molecular weights of cobra serum and cobra venom NGFs were different, 55.0 kDa and 13.5 kDa, respectively. NGF level is age dependent and varies under different conditions. Using anti-human NGF, diagnostic tests can be developed for neurological disorders. This investigation also emphasizes the replacement of invasive blood collection for serum by use of saliva and urine for clinical diagnostic use in general.

Fibrinopeptide A and B releasing enzyme, flavoviridiobin, was isolated from the venom of Trimeresurus flavoviridis using Q-Sepharose, CM-Cellulose, and Sephadex G-75 column chromatographies. Homogeneity was established by the formation of a single band in polyacrylamide gel electrophoresis, isoelectric focusing, and Ouchterlony immunodiffusion. The enzyme has a molecular weight of 48,000, isoelectric point of 8.1, consists of 237 total amino acid residues, and demonstrates clotting activity. However, no tosyl-L-arginine methyl ester (TAME) hydrolytic and kinin-releasing activities were observed. This clotting enzyme was inhibited by p-amidinophenylmethanesulfonyl fluoride hydrochloride (p-APMSF), benzamidine, and beta-mercaptoethanol, suggesting that serine, acidic amino acids, and disulfide bonds are involved in the expression of the enzyme's clotting activity. This thrombin-like enzyme hydrolyzes B beta-chain of human fibrinogen at first, followed by hydrolysis A alpha-chain. The enzyme was stable over the pH range of 7-10 and was shown to be heat resistant.

The purpose of this study is to examine the toxicity of Alexandrium tamarense strains using a channel biosensor. With this biosensor, we were able to measure very small quantities of PSP toxin contained within an individual plankton cell. However, measurement of at least 100 cells is more desirable for increasing the sensitivity of the assay. Therefore, in the near future, the proposed biosensor system may be used for monitoring the STX (saxitoxin) produced by a few naturally toxic phytoplankton, and also measuring small amounts of toxin in shellfish.

The heat-stable enterotoxins (STs) produced by enterotoxigenic Escherichia coli are classified into two groups, methanol-soluble (STI) and methanol-insoluble (STII) enterotoxins. These are distinct toxins with unique properties. Their features in common include heat-stability, low molecular weight, secretion from the bacteria, and ability to induce fluid secretion from the intestine. STI is an 18- or 19-amino acid extracellular peptide with three intramolecular disulfide bonds, which is produced by proteolytic cleavage of 72 amino acid precursor. The STI in the lumen of the intestine binds to specific protein receptors (guanylate cyclase C) located in the brush border membrane and leads to elevation of intracellular cyclic GMP level. Several factors involved in the activation of guanylate cyclase by STI have been identified. Elevation of cyclic GMP level induces intestinal fluid secretion by stimulation of chloride secretion. Cystic fibrosis transmembrane conductance regulator, which is a chloride channel, might be involved in chloride secretion. In contrast, STII is a 48-amino acid peptide with two intramolecular disulfide bonds, which results from 71 amino acid precursor. Compared with STI, the steps that lead to intestinal fluid secretion by STII are not well established. It has been proposed that sulfatide in the brush border is a receptor for STII and that the STII bound to the receptor opens GTP-binding regulatory protein-linked calcium channels. These actions of STII induce not only stimulation of the production of secretagogues such as prostaglandin E2 and serotonin, but also activation of the calcium-calmodulin-dependent protein kinase II in the cells.

Cholera toxin (Ctx) from Vibrio cholerae and the closely related Escherichia coli heat-labile enterotoxin (Etx) are the primary virulence factors responsible for causing cholera and traveller's diarrhea, respectively. Studies on the mode of action of these toxins on gut epithelial cells have revealed important insights into the mechanisms of toxin uptake and trafficking in eukaryotic cells. However, of perhaps even greater fascination have been the discoveries that Ctx and Etx exhibit remarkable immunological properties. When either of these toxins is administered via mucosal routes, it triggers a potent mucosal and systemic anti-toxin immune response. By contrast, local or systemic immunization with other soluble protein antigens usually stimulates only a meagre immune response, or results in a state of immunological tolerance. Even more striking are the findings that when Ctx or Etx are mixed with heterologous antigens, they function as adjuvants, leading to stimulation of mucosal responses to the admixed antigen, and the abrogation of oral tolerance. In addition, recent observations have shown that the receptor-binding component of these toxins can down-regulate inflammatory diseases associated with the induction of autoimmune disorders such as rheumatoid arthritis, diabetes, and multiple sclerosis. While the underlying mechanisms responsible for these remarkable properties have yet to be resolved, it is clear that the toxins' ability to bind to cell surface receptors plays an important role in their potent immunogenicity, adjuvanticity, and immunotherapeutic properties. This review provides an overview of the latest developments within the Ctx/Etx field, with a special emphasis on the cell entry mechanisms and immunomodulatory action of Ctx/Etx and their component subunits.