Functional repair of motor endplates after botulinum neurotoxin type A poisoning: biphasic switch of synaptic activity between nerve sprouts and their parent terminals.
Blockade of acetylcholine release by botulinum neurotoxin type A at the neuromuscular junction induces the formation of an extensive network of nerve-terminal sprouts. By repeated in vivo imaging of N-(3-triethyl ammonium propyl)-4-(4-(dibutylamino)styryl) pyridinium dibromide uptake into identified nerve endings of the mouse sternomastoid muscle after a single intramuscular injection of the toxin, inhibition of stimulated uptake of the dye at the terminals was detected within a few days, together with an increase in staining of the newly formed sprouts. After 28 days, when nerve stimulation again elicited muscle contraction, regulated vesicle recycling occurred only in the sprouts [shown to contain certain soluble N-ethylmaleimide-sensitive factor attachment proteins (SNAREs) and to abut acetylcholine receptors] and not at the parent terminals. Therefore, only these sprouts could be responsible for nerve-muscle transmission at this time. However, a second, distinct phase of the rehabilitation process followed with a return of vesicle turnover to the original terminals, accompanied by an elimination of the by then superfluous sprouts. This extension and later removal of "functional" sprouts indicate their fundamental importance in the repair of paralyzed endplates, a finding with ramifications for the vital process of nerve regeneration. (+info)
Comparison of mouse bioassay and immunoprecipitation assay for botulinum toxin antibodies.
OBJECTIVE: To compare a recently developed immunoprecipitation assay (IPA) to the mouse protection bioassay (MPB), currently considered the "gold standard", for detecting antibodies against botulinum toxin A (BTX-A) and to correlate these assay results with clinical responses to BTX-A injections. METHODS: MPB and IPA assays were performed on serum samples from 83 patients (38 non-responders, 45 responders) who received BTX-A injections. Six non-responders had serum tested on two separate occasions. Some patients also received a "test" injection into either the right eyebrow (n=29) or right frontalis (n=19). RESULTS: All patients antibody positive (Ab+) by MPB were also Ab+ by IPA, whereas an additional 19 patients (17 with reduced or no clinical response) who were MPB Ab- were Ab+, with low titres, by IPA. Two of these 19 patients (non-responders) were initially MPB Ab- but later became MPB Ab+. Similar to previous studies, the sensitivity for the MPB was low; 50% for clinical, 38% for eyebrow, and 30% for frontalis responses whereas the IPA sensitivity was much higher at 84% for clinical (p<0.001), 77% for eyebrow (p=0.111, NS) and 90% for frontalis responses (p<0.02). The IPA specificity was 89% for clinical, 81% for eyebrow, and 89% for frontalis responses, whereas the MPB specificity was 100% for all three response types, which were all non-significant differences. CONCLUSIONS: Both assays had high specificity although the sensitivity of the IPA was higher than the MPB. In addition, the IPA seems to display positivity earlier than the MPB, and as such, it may prognosticate future non-responsiveness. Eyebrow and frontalis "test" injections correlated well with clinical and immunological results and are useful in the assessment of BTX non-responders. (+info)
Characterization of a vertebrate neuromuscular junction that demonstrates selective resistance to botulinum toxin.
Botulinum toxin blocks transmitter release by proceeding through a series of four steps: binding to cell surface receptors, penetration of the cell membrane by receptor-mediated endocytosis, penetration of the endosome membrane by pH-induced translocation, and intracellular proteolysis of substrates that govern exocytosis. Each of these steps is essential for toxin action on intact cells. Therefore, alterations in cell structure or cell function that impede any of these steps should confer resistance to toxin. In the present study, screening for susceptibility to four serotypes of botulinum toxin revealed that the cutaneous-pectoris nerve-muscle preparation of Rana pipiens is resistant to type B botulinum toxin. Resistance was demonstrated both by electrophysiologic techniques and by dye-staining techniques. In addition, resistance to serotype B was demonstrated at toxin concentrations that were 2 orders of magnitude higher than those associated with blockade produced by other serotypes. In experiments on broken cell preparations, type B toxin cleaved synaptobrevin from frog brain synaptosomes. However, the toxin did not bind to frog nerve membranes. These findings suggest that resistance is due to an absence of cell surface receptors for botulinum toxin type B. The fact that cutaneous-pectoris preparations were sensitive to other botulinum toxin serotypes (A, C, and D), as well as other neuromuscular blocking agents (alpha-latrotoxin, beta-bungarotoxin), indicates that botulinum toxin type B receptors are distinct. (+info)
A comparison of injections of botulinum toxin and topical nitroglycerin ointment for the treatment of chronic anal fissure.
BACKGROUND AND METHODS: Lateral internal sphincterotomy, the most common treatment for chronic anal fissure, may cause permanent injury to the anal sphincter, which can lead to fecal incontinence. We compared two nonsurgical treatments that avert the risk of fecal incontinence. We randomly assigned 50 adults with symptomatic chronic posterior anal fissures to receive treatment with either a total of 20 U of botulinum toxin injected into the internal anal sphincter on each side of the anterior midline or 0.2 percent nitroglycerin ointment applied twice daily for six weeks. RESULTS: After two months, the fissures were healed in 24 of the 25 patients (96 percent) in the botulinum-toxin group and in 15 of the 25 (60 percent) in the nitroglycerin group (P=0.005). No patient in either group had fecal incontinence. At some time during treatment, five patients in the nitroglycerin group had transient, moderate-to-severe headaches that were related to treatment. None of the patients in the botulinum-toxin group reported adverse effects. Ten patients who did not have a response to the assigned treatment - 1 in the botulinum-toxin group and 9 in the nitroglycerin group - crossed over to the other treatment; the fissures subsequently healed in all 10 patients. There were no relapses during an average of about 15 months of follow-up. CONCLUSIONS: Although treatment with either topical nitroglycerin or botulinum toxin is effective as an alternative to surgery for patients with chronic anal fissure, botulinum toxin is the more effective nonsurgical treatment. (+info)
Persistence of botulinum neurotoxin action in cultured spinal cord cells.
Primary dissociated fetal mouse spinal cord cultures were used to study the mechanisms underlying the differences in persistence of botulinum neurotoxin A (BoNT/A) and botulinum neurotoxin/E (BoNT/E) activities. Spinal cord cultures were exposed to BoNT/A (0.4 pM) for 2-3 days, which converted approximately half of the SNAP-25 to an altered form lacking the final nine C-terminal residues. The distribution of toxin-damaged to control SNAP-25 remained relatively unchanged for up to 80 days thereafter. Application of a high concentration of BoNT/E (250 pM) either 25 or 60 days following initial intoxication with BoNT/A converted both normal and BoNT/A-truncated SNAP-25 into a single population lacking the final 26 C-terminal residues. Excess BoNT/E was removed by washout, and recovery of intact SNAP-25 was monitored by Western blot analysis. The BoNT/E-truncated species gradually diminished during the ensuing 18 days, accompanied by the reappearance of both normal and BoNT/A-truncated SNAP-25. Return of BoNT/A-truncated SNAP-25 was observed in spite of the absence of BoNT/A in the culture medium during all but the first 3 days of exposure. These results indicate that proteolytic activity associated with the BoNT/A light chain persists inside cells for > 11 weeks, while recovery from BoNT/E is complete in < 3 weeks. This longer duration of enzymatic activity appears to account for the persistence of serotype A action. (+info)
Pure botulinum neurotoxin is absorbed from the stomach and small intestine and produces peripheral neuromuscular blockade.
Clostridium botulinum serotype A produces a neurotoxin composed of a 100-kDa heavy chain and a 50-kDa light chain linked by a disulfide bond. This neurotoxin is part of a ca. 900-kDa complex, formed by noncovalent association with a single nontoxin, nonhemagglutinin subunit and a family of hemagglutinating proteins. Previous work has suggested, although never conclusively demonstrated, that neurotoxin alone cannot survive passage through the stomach and/or cannot be absorbed from the gut without the involvement of auxiliary proteins in the complex. Therefore, this study compared the relative absorption and toxicity of three preparations of neurotoxin in an in vivo mouse model. Equimolar amounts of serotype A complex with hemagglutinins, complex without hemagglutinins, and purified neurotoxin were surgically introduced into the stomach or into the small intestine. In some experiments, movement of neurotoxin from the site of administration was restricted by ligation of the pylorus. Comparison of relative toxicities demonstrated that at adequate doses, complex with hemagglutinins, complex without hemagglutinins, and pure neurotoxin can be absorbed from the stomach. The potency of neurotoxin in complex was greater than that of pure neurotoxin, but the magnitude of this difference diminished as the dosage of neurotoxin increased. Qualitatively similar results were obtained when complex with hemagglutinins, complex without hemagglutinins, and pure neurotoxin were placed directly into the intestine. This work establishes that pure botulinum neurotoxin serotype A is toxic when administered orally. This means that pure neurotoxin does not require hemagglutinins or other auxiliary proteins for absorption from the gastrointestinal system into the general circulation. (+info)
Activation of store-operated Ca2+ current in Xenopus oocytes requires SNAP-25 but not a diffusible messenger.
Depletion of Ca2+ stores in Xenopus oocytes activated entry of Ca2+ across the plasma membrane, which was measured as a current I(soc) in subsequently formed cell-attached patches. I(soc) survived excision into inside-out configuration. If cell-attached patches were formed before store depletion, I(soc) was activated outside but not inside the patches. I(soc) was potentiated by microinjection of Clostridium C3 transferase, which inhibits Rho GTPase, whereas I(soc) was inhibited by expression of wild-type or constitutively active Rho. Activation of I(soc) was also inhibited by botulinum neurotoxin A and dominant-negative mutants of SNAP-25 but was unaffected by brefeldin A. These results suggest that oocyte I(soc) is dependent not on aqueous diffusible messengers but on SNAP-25, probably via exocytosis of membrane channels or regulatory molecules. (+info)
Botulinum toxin treatment of hemifacial spasm and blepharospasm: objective response evaluation.
Twenty seven patients with hemifacial spasm (HFS) and sixteen patients with blepharospasm (BS) having mean Jankovic disability rating scale score of 2.56+0.58 SD and 2.81+0.54 SD, respectively, were treated with botulinum toxin A (BTX-A) injections. The total number of injection sessions were ninety one with relief response in 98.91%. The mean improvement in function scale score was 3.78+0.64 SD and 3.29+1.07 SD respectively, in HFS and BS groups. The clinical benefit induced by botulinum toxin lasted for a mean of 4.46+3.11 SD (range 2 to 13) months in HFS group and 2.66+1.37 SD (range 1 to 6) months, in BS groups. Transient ptosis was seen in 4.39% of total ninety one injection sessions. These findings show that local botulinum toxin treatment provides effective, safe and long lasting relief of spasms. (+info)