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It is known that production in a host of antibodies against a protein is associated with various molecular events. These include the stimulation of specific T-lymphocytes, a step that implies the processing of the protein into peptides by various endosomal/lysosomal enzymes, such as cathepsins. Strikingly, however, we observed in vitro that cathepsins B and D have no degrading effect on toxin α from...
A novel combination of theoretical approaches was exploited to predict which amino acid residues of various botulinum neurotoxin serotypes participate in forming ion channels. Estimates of sequence hydrophobic moments were used initially to identify residues within amphipathic regions in the N-terminal half of the heavy chain. A neural network algorithm was then used to make additional secondary...
Neurotoxins of natural origin have proved to be of considerable value in the isolation and characterization of vertebrate muscle and neuronal nicotinic acetylcholine receptors (nAChRs). To date, they have been used less extensively in studies of invertebrate nAChRs. Here we examine how a variety of neurotoxins (the snake toxins α-bungarotoxin, α-BGT, and κ-bungarotoxin, κ-BGT, the molluscan toxin,...
The neural cell adhesion molecule (N-CAM) is a convenient neurospecific marker for investigating the effects of neurotoxins on cell migration, cell recognition and differentiation of neurons during development. In this report, we discuss the developmental toxicity of valproic acid studied by two different approaches (the immunochemical detection of N-CAM content and polypeptide composition, and immunohistochemical...
The enterotoxin of Clostridium perfringens type A, a channelpore forming protein toxin, inhibited neuromuscular transmission in isolated mouse phrenic nerve-diaphragm preparation at low concentrations of calcium. We investigated immunohistochemically the localization of the binding sites of the enterotoxin in the preparation under the conditions in which the enterotoxin reduced maximally the amplitudes...
Exposure of isolated mouse hemidiaphragms to botulinum neurotoxins, 0.1 nM BoNT-A or BoNT-B, at 36°C reduced nerve-elicited peak isometric twitch tension to 50% of control values at 55 min (BoNT-A) to 68 min (BoNT-B) after application. Either coincubation of BoNT with the heavy metal chelator TPEN, preincubation with TPEN followed by BoNT, or application of TPEN after BoNT but before neuromuscular...
Incubation of coronal slices of rat brain with neurotoxic concentrations of kainate (300 μM) and N-methyl-d-aspartate (NMDA; 500 μM) for 40 min reduced the activity of the glial enzyme, glutamine synthetase, by 33% and 21%, respectively. The immunoreactivity of the neuronal enzyme, γγ-enolase (neuron-specific enolase), was also decreased, but to a lesser extent than glutamine synthetase. Pre-incubation...
The venom of some Dendroaspis snakes contains small proteins (7500 mol. wt) that inhibit the binding of radiolabelled muscarinic antagonist to brain synaptomal membranes. There were no peptides described among muscarinic ligands until Adem et al. (Biochim. biophys. Acta968 , 340-345, 1988) reported that muscarinic toxins (MTxs), MTx1 and 2 were able to inhibit 3 H-QNB binding to rat brain...
Crotoxin and taipoxin are both neurotoxic phospholipases A 2 capable of affecting the presynaptic activity to bring about ultimate blockade of synaptic transmission. The enzymatic activity has generally been considered to be necessary but not sufficient for the blockade. Since many phospholipases A 2 with comparable or even higher enzymatic activity are not toxic, it has been postulated...
Scorpion venoms contain toxins that block different types of potassium channels. Some of these toxins have affinity for high conductance Ca 2+ -activated K + channels and for dendrotoxin-sensitive voltage-dependent K + channels. The structural features that determine the specificity of binding to different channel types are not known. We investigated this using natural...
Mamba venoms contain pharmacologically active proteins that interfere with neuromuscular transmission by binding to and altering the normal functioning of neuronal proteins involved, directly or indirectly, with regulating nerve transmission. Of the mamba toxins studied to date, many act on voltage-sensitive K + channels, nicotinic or muscarinic acetylcholine receptors, or acetylcholinesterase...
Ammodytoxin A, the presynaptic neurotoxin from Vipera ammodytes ammodytes venom, was found to bind specifically and with high affinity to bovine cortex synaptic membrane preparation. The detected ammodytoxin A high-affinity binding was characterized by equilibrium binding analysis which revealed a single high-affinity binding site with K d 4.13 nM and B max 6.67 pmoles/mg...
The botulinal neurotoxins (BoNT) associate with non-toxic proteins (ANTP) by non-covalent bonds to form large complexes. In C. botulinum C, the BoNT/C1 locus consists of six genes which are organized in three clusters. Cluster 1 encompasses the genes of BoNT/C1 and ANTP/139 which could be involved in the resistance of the BoNT/C1 to the acidic pH and protease degradation. The second cluster consists...
Highly purified α-latrotoxin from the black widow spider venom (α-LTX) consists of two polypeptides with mol. wts of 130,000 and 8000 (LMWP). We have isolated two low mol. wt proteins LMWP and LMWP2 from the low mol. wt fraction of this venom. The chemical properties of these proteins and partial amino acid sequence of novel protein LMWP2 were studied. By means of i.v. or intracerebroventricular...
Botulinum neurotoxin type A blocks acetylcholine release from the peripheral nervous system. We have previously described a putative botulinum neurotoxin type A receptor of presynaptic plasma membranes from Torpedo. The electric organ of Torpedo, which is largely enriched in cholinergic nerve endings, is homologous to the neuromuscular junction, allowing us to isolate large scale of presynaptic...
The sequence of muscarinic toxin 1 (MT1) from Dendroaspis angusticeps (green mamba) was determined (66 amino acids, M r 7509). The central part, peptide 25-40, is rich in hydrophobic amino acids, which is a characteristic of muscarinic toxins. MT1 started to inhibit [ 3 H]-NMS (N-methylscopolamine) binding to synaptosomal membranes of porcine brain (contains all five receptor subtypes)...
Zinc-dependent metalloprotease inhibitors phosphoramidon, captopril and a peptide hydroxamate were studied as potential pretreatment compounds by examining their ability to delay the onset or to prolong the time to 50% block of nerve-elicited muscle twitch tension in the mouse phrenic-nerve diaphragm (in vitro at 36°C) after botulinum neurotoxin serotypes A and B (BoNT-A, BoNT-B). Addition of BoNT-A...
Dibromosceptrin and clathrodin are alkaloid compounds purified from tropical marine sponges of the genus Agelas. Experiments done using the whole cell configuration of the patch clamp technique revealed that these compounds have neurotoxic activity. Both compounds decreased by 27-40% the average maximum amplitudes of pharmacologically isolated inward sodium currents in cells isolated from chick...
The effects of the potassium channel inhibitor and putative botulinum toxin antagonist 3,4-diaminopyridine (3,4-DAP) were investigatedin vitro on the contractile properties of rat diaphragm muscle. In the presence of 100 pM botulinum neurotoxin A (BoNT/A), twitches elicited by supramaximal nerve stimulation (0.1 Hz) were reduced to approximately 10% of control in 3 hr at 37°C. Addition of 3,4-DAP...
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