Safety of Onabotulinumtoxin A in Chronic Migraine: A Systematic Review and Meta-Analysis of Randomized Clinical Trials

Some 14% of global prevalence, based on high-income country populations, suffers from migraine. Chronic migraine is very disabling, being characterized by at least 15 headache days per month of which at least 8 days present the features of migraine. Onabotulinumtoxin A, targeting the machinery for exocytosis of neurotransmitters and neuropeptides, has been approved for use in chronic migraine since 2010. This systematic review and meta-analysis appraises the safety of onabotulinumtoxin A treatment for chronic migraine and the occurrence of treatment-related adverse events (TRAEs) in randomized, clinical studies in comparison with placebo or other comparators and preventative treatments according to the most updated Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA) 2020 recommendations. The search retrieved 888 total records. Nine studies are included and seven were eligible for meta-analysis. The present study demonstrates that toxin produces more TRAEs than placebo, but less than oral topiramate, supporting the safety of onabotulinumtoxin A, and highlights the heterogeneity of the studies present in the literature (I² = 96%; p < 0.00001). This points to the need for further, adequately powered, randomized clinical trials assessing the safety of onabotulinumtoxin A in combination with the newest treatment options.

Bipartite Activation of Sensory Neurons by a TRPA1 Agonist Allyl Isothiocyanate Is Reflected by Complex Ca2+ Influx and CGRP Release Patterns: Enhancement by NGF and Inhibition with VAMP and SNAP-25 Cleaving Botulinum Neurotoxins

The trafficking of transient receptor potential (TRP) channels to the plasma membrane and the release of calcitonin gene-related peptide (CGRP) from trigeminal ganglion neurons (TGNs) are implicated in some aspects of chronic migraines. These exocytotic processes are inhibited by cleavage of SNAREs with botulinum neurotoxins (BoNTs); moreover, type A toxin (/A) clinically reduces the frequency and severity of migraine attacks but not in all patients for unknown reasons. Herein, neonatal rat TGNs were stimulated with allyl isothiocyanate (AITC), a TRPA1 agonist, and dose relationships were established to link the resultant exocytosis of CGRP with Ca2+ influx. The CGRP release, quantified by ELISA, was best fit by a two-site model (EC50 of 6 and 93 µM) that correlates with elevations in intracellular Ca2+ [Ca2+]i revealed by time-lapse confocal microscopy of fluo-4-acetoxymethyl ester (Fluo-4 AM) loaded cells. These signals were all blocked by two TRPA1 antagonists, HC-030031 and A967079. At low [AITC], [Ca2+]i was limited because of desensitisation to the agonist but rose for concentrations > 0.1 mM due to a deduced non-desensitising second phase of Ca2+ influx. A recombinant BoNT chimera (/DA), which cleaves VAMP1/2/3, inhibited AITC-elicited CGRP release to a greater extent than SNAP-25-cleaving BoNT/A. /DA also proved more efficacious against CGRP efflux evoked by a TRPV1 agonist, capsaicin. Nerve growth factor (NGF), a pain-inducing sensitiser of TGNs, enhanced the CGRP exocytosis induced by low [AITC] only. Both toxins blocked NGF-induced neuropeptide secretion and its enhancement of the response to AITC. In conclusion, NGF sensitisation of sensory neurons involves TRPA1, elevated Ca2+ influx, and CGRP exocytosis, mediated by VAMP1/2/3 and SNAP-25 which can be attenuated by the BoNTs.

Meta-Analysis of the Field Efficacy of Seed- and Soil-Applied Nematicides on Meloidogyne incognita and Rotylenchulus reniformis Across the U.S. Cotton Belt

Meta-analysis was used to compare yield protection and nematode suppression provided by two seed-applied and two soil-applied nematicides against Meloidogyne incognita and Rotylenchulus reniformis on cotton across 3 years and several trial locations in the U.S. Cotton Belt. Nematicides consisted of thiodicarb- and fluopyram-treated seed, aldicarb and fluopyram applied in furrow, and combinations of the seed treatments and soil-applied fluopyram. The nematicides had no effect on nematode reproduction or root infection but had a significant impact on seed cotton yield response ([Formula: see text]), with an average increase of 176 and 197 kg/ha relative to the nontreated control in M. incognita and R. reniformis infested fields, respectively. However, because of significant variation in yield protection and nematode suppression by nematicides, five or six moderator variables (cultivar resistance [M. incognita only], nematode infestation level, nematicide treatment, application method, trial location, and growing season) were used depending on nematode species. In M. incognita-infested fields, greater yield protection was observed with nematicides applied in furrow and with seed-applied + in-furrow than with solo seed-applied nematicide applications. Most notable of these in-furrow nematicides were aldicarb and fluopyram (>131 g/ha) with or without a seed-applied nematicide compared with thiodicarb. In R. reniformis-infested fields, moderator variables provided no further explanation of the variation in yield response produced by nematicides. Furthermore, moderator variables provided little explanation of the variation in nematode suppression by nematicides in M. incognita- and R. reniformis-infested fields. The limited explanation by the moderator variables on the field efficacy of nematicides in M. incognita- and R. reniformis-infested fields demonstrates the difficulty of managing these pathogens with nonfumigant nematicides across the U.S. Cotton Belt.

Botulinum Neurotoxin Chimeras Suppress Stimulation by Capsaicin of Rat Trigeminal Sensory Neurons In Vivo and In Vitro

Chimeras of botulinum neurotoxin (BoNT) serotype A (/A) combined with /E protease might possess improved analgesic properties relative to either parent, due to inheriting the sensory neurotropism of the former with more extensive disabling of SNAP-25 from the latter. Hence, fusions of /E protease light chain (LC) to whole BoNT/A (LC/E-BoNT/A), and of the LC plus translocation domain (HN) of /E with the neuronal acceptor binding moiety (HC) of /A (BoNT/EA), created previously by gene recombination and expression in E. coli., were used. LC/E-BoNT/A (75 units/kg) injected into the whisker pad of rats seemed devoid of systemic toxicity, as reflected by an absence of weight loss, but inhibited the nocifensive behavior (grooming, freezing, and reduced mobility) induced by activating TRPV1 with capsaicin, injected at various days thereafter. No sex-related differences were observed. c-Fos expression was increased five-fold in the trigeminal nucleus caudalis ipsi-lateral to capsaicin injection, relative to the contra-lateral side and vehicle-treated controls, and this increase was virtually prevented by LC/E-BoNT/A. In vitro, LC/E-BoNT/A or /EA diminished CGRP exocytosis from rat neonate trigeminal ganglionic neurons stimulated with up to 1 µM capsaicin, whereas BoNT/A only substantially reduced the release in response to 0.1 µM or less of the stimulant, in accordance with the /E protease being known to prevent fusion of exocytotic vesicles.

NGF Enhances CGRP Release Evoked by Capsaicin from Rat Trigeminal Neurons: Differential Inhibition by SNAP-25-Cleaving Proteases

Nerve growth factor (NGF) is known to intensify pain in various ways, so perturbing pertinent effects without negating its essential influences on neuronal functions could help the search for much-needed analgesics. Towards this goal, cultured neurons from neonatal rat trigeminal ganglia—a locus for craniofacial sensory nerves—were used to examine how NGF affects the Ca²⁺-dependent release of a pain mediator, calcitonin gene-related peptide (CGRP), that is triggered by activating a key signal transducer, transient receptor potential vanilloid 1 (TRPV1) with capsaicin (CAP). Measurements utilised neurons fed with or deprived of NGF for 2 days. Acute re-introduction of NGF induced Ca²⁺-dependent CGRP exocytosis that was inhibited by botulinum neurotoxin type A (BoNT/A) or a chimera of/E and/A (/EA), which truncated SNAP-25 (synaptosomal-associated protein with Mr = 25 k) at distinct sites. NGF additionally caused a Ca²⁺-independent enhancement of the neuropeptide release evoked by low concentrations (<100 nM) of CAP, but only marginally increased the peak response to ≥100 nM. Notably, BoNT/A inhibited CGRP exocytosis evoked by low but not high CAP concentrations, whereas/EA effectively reduced responses up to 1 µM CAP and inhibited to a greater extent its enhancement by NGF. In addition to establishing that sensitisation of sensory neurons to CAP by NGF is dependent on SNARE-mediated membrane fusion, insights were gleaned into the differential ability of two regions in the C-terminus of SNAP-25 (181–197 and 198–206) to support CAP-evoked Ca²⁺-dependent exocytosis at different intensities of stimulation.

Population Coding of Capsaicin Concentration by Sensory Neurons Revealed Using Ca2+ Imaging of Dorsal Root Ganglia Explants from Adult pirt-GCaMP3 Mouse

BACKGROUND/AIMS

Nociceptors detect noxious capsaicin (CAPS) via the transient receptor potential vanilloid 1 (TRPV1) ion channel, but coding mechanisms for relaying CAPS concentration [CAPS] remain obscure. Prolonged (up to 1h.) exposure to CAPS is used clinically to desensitise sensory fibres for treatment of neuropathic pain, but its signalling has typically been studied in cultures of dissociated sensory neurons employing low cell numbers and very short exposure times. Thus, it was pertinent to examine responses to longer CAPS exposures in large populations of adult neurons.

METHODS

Confocal fluorescence microscopy was used to monitor the simultaneous excitation by CAPS of neuronal populations in intact L3/4 dorsal root ganglia (DRG) explants from adult pirt-GCaMP3 mice that express a cytoplasmic, genetically-encoded Ca²⁺ sensor in almost all primary sensory neurons. Peak analysis was performed using GraphPad Prism 9 to deconstruct the heterogenous and complex fluorescence signals observed into informative, readily-comparable measurements: number of signals, their lag time, maximum intensity relative to baseline (Max.) and duration.

RESULTS

Exposure for 5 min. to CAPS activated plasmalemmal TRPV1 and led to increased fluorescence due to Ca²⁺ entry into DRG neurons (DRGNs), as it was prevented by capsazepine or removal of extracellular Ca²⁺. Increasing [CAPS] (0.3, 1 and 10 μM, respectively) evoked signals from more neurons (123, 275 and 390 from 5 DRG) with shorter average lag (6.4 ± 0.4, 3.3 ± 0.2 and 1.9 ± 0.1 min.) and longer duration (1.4 ± 0.2, 2.9 ± 0.2 and 4.8 ± 0.3 min.). Whilst raising [CAPS] produced a modest augmentation of Max. for individual neurons, those with large increases were selectively expedited; this contributed to a faster onset and higher peak of cumulative fluorescence for an enlarged responding neuronal population. CAPS caused many cells to fluctuate between high and low levels of fluorescence, with consecutive pulses increasing Max. and duration especially when exposure was extended from 5 to 20 min. Such signal facilitation counteracted tachyphylaxis, observed upon repeated exposure to 1 μM CAPS, preserving the cumulative fluorescence over time (signal density) in the population.

CONCLUSION

Individual neurons within DRG differed extensively in the dynamics of response to CAPS, but systematic changes elicited by elevating [CAPS] increased signal density in a graded manner, unveiling a possible mechanism for population coding of responses to noxious chemicals. Signal density is sustained during prolonged and repeated exposure to CAPS, despite profound tachyphylaxis in some neurons, by signal facilitation in others. This may explain the burning sensation that persists for several hours when CAPS is used clinically.

Ca2+ Signalling Induced by NGF Identifies a Subset of Capsaicin-Excitable Neurons Displaying Enhanced Chemo-Nociception in Dorsal Root Ganglion Explants from Adult pirt-GCaMP3 Mouse

Nociceptors sense hazards via plasmalemmal cation channels, including transient receptor potential vanilloid 1 (TRPV1). Nerve growth factor (NGF) sensitises TRPV1 to capsaicin (CAPS), modulates nociceptor excitability and induces thermal hyperalgesia, but cellular mechanisms remain unclear. Confocal microscopy was used to image changes in intracellular Ca²⁺ concentration ([Ca²⁺]_i) across neuronal populations in dorsal root ganglia (DRG) explants from pirt-GCaMP3 adult mice, which express a fluorescent reporter in their sensory neurons. Raised [Ca²⁺]_i was detected in 84 neurons of three DRG explants exposed to NGF (100 ng/mL) and most (96%) of these were also excited by 1 μM CAPS. NGF elevated [Ca²⁺]_i in about one-third of the neurons stimulated by 1 μM CAPS, whether applied before or after the latter. In neurons excitable by NGF, CAPS-evoked [Ca²⁺]_i signals appeared significantly sooner (e.g., respective lags of 1.0 ± 0.1 and 1.9 ± 0.1 min), were much (>30%) brighter and lasted longer (6.6 ± 0.4 vs. 3.9 ± 0.2 min) relative to those non-responsive to the neurotrophin. CAPS tachyphylaxis lowered signal intensity by ~60% but was largely prevented by NGF. Increasing CAPS from 1 to 10 μM nearly doubled the number of cells activated but only modestly increased the amount co-activated by NGF. In conclusion, a sub-population of the CAPS-sensitive neurons in adult mouse DRG that can be excited by NGF is more sensitive to CAPS, responds with stronger signals and is further sensitised by transient exposure to the neurotrophin.

The Glycine max Conserved Oligomeric Golgi (COG) Complex Functions During a Defense Response to Heterodera glycines

The conserved oligomeric Golgi (COG) complex, functioning in retrograde trafficking, is a universal structure present among eukaryotes that maintains the correct Golgi structure and function. The COG complex is composed of eight subunits coalescing into two sub-complexes. COGs1-4 compose Sub-complex A. COGs5-8 compose Sub-complex B. The observation that COG interacts with the syntaxins, suppressors of the erd2-deletion 5 (Sed5p), is noteworthy because Sed5p also interacts with Sec17p [alpha soluble NSF attachment protein (α-SNAP)]. The α-SNAP gene is located within the major Heterodera glycines [soybean cyst nematode (SCN)] resistance locus (rhg1) and functions in resistance. The study presented here provides a functional analysis of the Glycine max COG complex. The analysis has identified two paralogs of each COG gene. Functional transgenic studies demonstrate at least one paralog of each COG gene family functions in G. max during H. glycines resistance. Furthermore, treatment of G. max with the bacterial effector harpin, known to function in effector triggered immunity (ETI), leads to the induced transcription of at least one member of each COG gene family that has a role in H. glycines resistance. In some instances, altered COG gene expression changes the relative transcript abundance of syntaxin 31. These results indicate that the G. max COG complex functions through processes involving ETI leading to H. glycines resistance.

The mitogen activated protein kinase (MAPK) gene family functions as a cohort during the Glycine max defense response to Heterodera glycines

Mitogen activated protein kinases (MAPKs) play important signal transduction roles. However, little is known regarding how they influence the gene expression of other family members and the relationship to a biological process, including the Glycine max defense response to Heterodera glycines. Transcriptomics have identified MAPK gene expression occurring within root cells undergoing a defense response to a pathogenic event initiated by H. glycines in the allotetraploid Glycine max. Functional analyses are presented for its 32 MAPKs revealing 9 have a defense role, including homologs of Arabidopsis thaliana MAPK (MPK) MPK2, MPK3, MPK4, MPK5, MPK6, MPK13, MPK16 and MPK20. Defense signaling occurring through pathogen activated molecular pattern (PAMP) triggered immunity (PTI) and effector triggered immunity (ETI) have been determined in relation to these MAPKs. Five different types of gene expression relate to MAPK expression, influencing PTI and ETI gene expression and proven defense genes including an ABC-G transporter, 20S membrane fusion particle components, glycoside biosynthesis, carbon metabolism, hemicellulose modification, transcription and secretion. The experiments show MAPKs broadly influence defense MAPK gene expression, including the co-regulation of parologous MAPKs and reveal its relationship to proven defense genes. The experiments reveal each defense MAPK induces the expression of a G. max homolog of a PATHOGENESIS RELATED1 (PR1), itself shown to function in defense in the studied pathosystem.

Harpin-inducible defense signaling components impair infection by the ascomycete Macrophomina phaseolina

Soybean (Glycine max) infection by the charcoal rot (CR) ascomycete Macrophomina phaseolina is enhanced by the soybean cyst nematode (SCN) Heterodera glycines. We hypothesized that G. max genetic lines impairing infection by M. phaseolina would also limit H. glycines parasitism, leading to resistance. As a part of this M. phaseolina resistance process, the genetic line would express defense genes already proven to impair nematode parasitism. Using G. max[DT97-4290/PI 642055], exhibiting partial resistance to M. phaseolina, experiments show the genetic line also impairs H. glycines parasitism. Furthermore, comparative studies show G. max[DT97-4290/PI 642055] exhibits induced expression of the effector triggered immunity (ETI) gene NON-RACE SPECIFIC DISEASE RESISTANCE 1/HARPIN INDUCED1 (NDR1/HIN1) that functions in defense to H. glycines as compared to the H. glycines and M. phaseolina susceptible line G. max[Williams 82/PI 518671]. Other defense genes that are induced in G. max[DT97-4290/PI 642055] include the pathogen associated molecular pattern (PAMP) triggered immunity (PTI) genes ENHANCED DISEASE SUSCEPTIBILITY1 (EDS1), NONEXPRESSOR OF PR1 (NPR1) and TGA2. These observations link G. max defense processes that impede H. glycines parasitism to also potentially function toward impairing M. phaseolina pathogenicity. Testing this hypothesis, G. max[Williams 82/PI 518671] genetically engineered to experimentally induce GmNDR1-1, EDS1-2, NPR1-2 and TGA2-1 expression leads to impaired M. phaseolina pathogenicity. In contrast, G. max[DT97-4290/PI 642055] engineered to experimentally suppress the expression of GmNDR1-1, EDS1-2, NPR1-2 and TGA2-1 by RNA interference (RNAi) enhances M. phaseolina pathogenicity. The results show components of PTI and ETI impair both nematode and M. phaseolina pathogenicity.

A harpin elicitor induces the expression of a coiled-coil nucleotide binding leucine rich repeat (CC-NB-LRR) defense signaling gene and others functioning during defense to parasitic nematodes

The bacterial effector harpin induces the transcription of the Arabidopsis thaliana NON-RACE SPECIFIC DISEASE RESISTANCE 1/HARPIN INDUCED1 (NDR1/HIN1) coiled-coil nucleotide binding leucine rich repeat (CC-NB-LRR) defense signaling gene. In Glycine max, Gm-NDR1-1 transcripts have been detected within root cells undergoing a natural resistant reaction to parasitism by the syncytium-forming nematode Heterodera glycines, functioning in the defense response. Expressing Gm-NDR1-1 in Gossypium hirsutum leads to resistance to Meloidogyne incognita parasitism. In experiments presented here, the heterologous expression of Gm-NDR1-1 in G. hirsutum impairs Rotylenchulus reniformis parasitism. These results are consistent with the hypothesis that Gm-NDR1-1 expression functions broadly in generating a defense response. To examine a possible relationship with harpin, G. max plants topically treated with harpin result in induction of the transcription of Gm-NDR1-1. The result indicates the topical treatment of plants with harpin, itself, may lead to impaired nematode parasitism. Topical harpin treatments are shown to impair G. max parasitism by H. glycines, M. incognita and R. reniformis and G. hirsutum parasitism by M. incognita and R. reniformis. How harpin could function in defense has been examined in experiments showing it also induces transcription of G. max homologs of the proven defense genes ENHANCED DISEASE SUSCEPTIBILITY1 (EDS1), TGA2, galactinol synthase, reticuline oxidase, xyloglucan endotransglycosylase/hydrolase, alpha soluble N-ethylmaleimide-sensitive fusion protein (α-SNAP) and serine hydroxymethyltransferase (SHMT). In contrast, other defense genes are not directly transcriptionally activated by harpin. The results indicate harpin induces pathogen associated molecular pattern (PAMP) triggered immunity (PTI) and effector-triggered immunity (ETI) defense processes in the root, activating defense to parasitic nematodes.

Biological Control of Meloidogyne incognita by Spore-forming Plant Growth-promoting Rhizobacteria on Cotton

In the past decade, increased attention has been placed on biological control of plant-parasitic nematodes using various fungi and bacteria. The objectives of this study were to evaluate the potential of 662 plant growth-promoting rhizobacteria (PGPR) strains for mortality to Meloidogyne incognita J2 in vitro and for nematode management in greenhouse, microplot, and field trials. Results indicated that the mortality of M. incognita J2 by the PGPR strains ranged from 0 to 100% with an average of 39%. Among the PGPR strains examined, 212 of 662 strains (or 33%) caused significantly greater mortality percent of M. incognita J2 than the untreated control. Bacillus was the major genus initiating a greater mortality percentage when compared with the other genera. In subsequent trials, B. velezensis strain Bve2 reduced M. incognita eggs per gram of cotton root in the greenhouse trials at 45 days after planting (DAP) similarly to the commercial standards Abamectin and Clothianidin plus B. firmus I-1582. Bacillus mojavensis strain Bmo3, B. velezensis strain Bve2, B. subtilis subsp. subtilis strain Bsssu3, and the Mixture 2 (Abamectin + Bve2 + B. altitudinis strain Bal13) suppressed M. incognita eggs per gram of root in the microplot at 45 DAP. Bacillus velezensis strains Bve2 and Bve12 also increased seed-cotton yield in the microplot and field trials. Overall, results indicate that B. velezensis strains Bve2 and Bve12, B. mojavensis strain Bmo3, and Mixture 2 have potential to reduce M. incognita population density and to enhance growth of cotton when applied as in-furrow sprays at planting.

A Glycine max homolog of NON-RACE SPECIFIC DISEASE RESISTANCE 1 (NDR1) alters defense gene expression while functioning during a resistance response to different root pathogens in different genetic backgrounds

A Glycine max homolog of the Arabidopsis thaliana NON-RACE SPECIFIC DISEASE RESISTANCE 1 (NDR1) coiled-coil nucleotide binding leucine rich repeat (CC-NB-LRR) defense signaling gene (Gm-NDR1-1) is expressed in root cells undergoing a defense response to the root pathogenic nematode, Heterodera glycines. Gm-NDR1-1 overexpression in the H. glycines-susceptible genotype G. max[Williams 82/PI 518671] impairs parasitism. In contrast, Gm-NDR1-1 RNA interference (RNAi) in the H. glycines-resistant genotype G. max[Peking/PI 548402] facilitates parasitism. The broad effectiveness of Gm-NDR1-1 in impairing parasitism has then been examined by engineering its heterologous expression in Gossypium hirsutum which is susceptible to the root pathogenic nematode Meloidogyne incognita. The heterologous expression of Gm-NDR1-1 in G. hirsutum effectively impairs M. incognita parasitism, reducing gall, egg mass, egg and juvenile numbers. In contrast to our prior experiments examining the effectiveness of the heterologous expression of a G. max homolog of the A. thaliana salicyclic acid signaling (SA) gene NONEXPRESSOR OF PR1 (Gm-NPR1-2), no cumulative negative effect on M. incognita parasitism has been observed in G. hirsutum expressing Gm-NDR1-1. The results indicate a common genetic basis exists for plant resistance to parasitic nematodes that involves Gm-NDR1. However, the Gm-NDR1-1 functions in ways that are measurably dissimilar to Gm-NPR1-2. Notably, Gm-NDR1-1 overexpression leads to increased relative transcript levels of its homologs of A. thaliana genes functioning in SA signaling, including NPR1-2, TGA2-1 and LESION SIMULATING DISEASE1 (LSD1-2) that is lost in Gm-NDR1-1 RNAi lines. Similar observations have been made regarding the expression of other defense genes.

Components of the SNARE-containing regulon are co-regulated in root cells undergoing defense

The term regulon has been coined in the genetic model plant Arabidopsis thaliana, denoting a structural and physiological defense apparatus defined genetically through the identification of the penetration (pen) mutants. The regulon is composed partially by the soluble N-ethylmaleimide-sensitive fusion protein attachment protein receptor (SNARE) syntaxin PEN1. PEN1 has homology to a Saccharomyces cerevisae gene that regulates a Secretion (Sec) protein, Suppressor of Sec 1 (Sso1p). The regulon is also composed of the β-glucosidase (PEN2) and an ATP binding cassette (ABC) transporter (PEN3). While important in inhibiting pathogen infection, limited observations have been made regarding the transcriptional regulation of regulon genes until now. Experiments made using the model agricultural Glycine max (soybean) have identified co-regulated gene expression of regulon components. The results explain the observation of hundreds of genes expressed specifically in the root cells undergoing the natural process of defense. Data regarding additional G. max genes functioning within the context of the regulon are presented here, including Sec 14, Sec 4 and Sec 23. Other examined G. max homologs of membrane fusion genes include an endosomal bromo domain-containing protein1 (Bro1), syntaxin6 (SYP6), SYP131, SYP71, SYP8, Bet1, coatomer epsilon (ϵ-COP), a coatomer zeta (ζ-COP) paralog and an ER to Golgi component (ERGIC) protein. Furthermore, the effectiveness of biochemical pathways that would function within the context of the regulon ave been examined, including xyloglucan xylosyltransferase (XXT), reticuline oxidase (RO) and galactinol synthase (GS). The experiments have unveiled the importance of the regulon during defense in the root and show how the deposition of callose relates to the process.

Chapter 3: Molecular basis for the therapeutic effectiveness of botulinum neurotoxin type A

The utility of botulinum neurotoxin type A (BoNT/A) for treating overactive muscles and endocrine glands is attributable to a unique conflation of properties honed to exploit and inactivate synaptic transmission. Specific, high-affinity coincident binding to gangliosides plus an intraluminal loop of synaptic vesicle protein 2 (SV2) by the heavy chain (HC) of BoNT/A confers selectivity for presynaptic nerve terminals and subsequent uptake by endocytosis. Upon vesicle acidification, the HC forms a channel for transmembrane transfer of the light chain to the cytosol, as observed by single channel recordings. The light chain is a Zn(2+) -dependent endoprotease that cleaves and inactivates SNAP-25, thereby blocking exocytotic release of transmitters, a discovery that revealed the pivotal role of the latter in synaptic vesicle fusion. A di-leucine motif in BoNT/A light chain stabilizes this protease, contributing to its longevity inside nerves. The ubiquity of SV2 and SNAP-25 has prompted re-evaluation of the nerve types susceptible to BoNT/A. In urology, there is emerging evidence that BoNT/A blocks neuropeptide release from afferent nerves, exocytosis of acetylcholine and purines from efferent nerves, and possibly ATP release from the urothelium. Suppression by BoNT/A of the surface expression of nociceptor channels on bladder afferents might also contribute to its improvement of urological sensory symptoms.

Internalization and retrograde axonal trafficking of tetanus toxin in motor neurons and trans-synaptic propagation at central synapses exceed those of its C-terminal-binding fragments

The prominent tropism of tetanus toxin (TeTx) towards peripheral nerves with retrograde transport and transfer to central neurons render it an invaluable probe for exploring fundamental neuronal processes such as endocytosis, retrograde trafficking and trans-synaptic transport to central neurons. While the specificity of TeTx to nerve cells has been attributed to its binding domains (HC and HCC), molecular determinants of the long-range trafficking that ensure its central delivery and induction of spastic paralysis remain elusive. Here, we report that a protease-inactive TeTx mutant (TeTIM) fused to core streptavidin (CS) proved superior to CS-HC and CS-HCC fragments in antagonizing the internalization of the active toxin in cultured spinal cord neurons. Also, in comparison to CS-HC and CS-HCC, CS-TeTIM undergoes faster clearance from motor nerve terminals after peripheral injection, and is detected in a greater number of neurons in the spinal cord and brain stem ipsi-lateral to the administration site. Consistent with trans-synaptic transfer from motor neurons to inter-neurons, CS-TeTIM infiltrated non-cholinergic cells in the spinal cord; in contrast, the retrograde spread of CS-HC was largely restricted to neurons stained for choline acetyltransferase. Peripheral injection of CS-TeTIM conjugated to a lentivirus encoding mutated SNAP-25, resistant to cleavage by botulinum neurotoxin A, E and C1, rendered spontaneous excitatory postsynaptic currents in motor neurons resilient to challenge by type A toxin in vitro, whereas the same virus conjugated to CS-HC proved ineffective. These findings indicate that full-length inactive TeTx greatly exceeds HC and HCC in targeting and invading motor nerve terminals at the periphery and exploits more efficiently the retrograde transport and trans-synaptic transfer mechanisms of motor neurons to arrive at central neurons. Such qualities render TeTIM a more suitable research probe and neuron-targeting vehicle for retro-axonal delivery of viral vectors to the CNS.

The syntaxin 31-induced gene, LESION SIMULATING DISEASE1 (LSD1), functions in Glycine max defense to the root parasite Heterodera glycines

Experiments show the membrane fusion genes α soluble NSF attachment protein (α-SNAP) and syntaxin 31 (Gm-SYP38) contribute to the ability of Glycine max to defend itself from infection by the plant parasitic nematode Heterodera glycines. Accompanying their expression is the transcriptional activation of the defense genes ENHANCED DISEASE SUSCEPTIBILITY1 (EDS1) and NONEXPRESSOR OF PR1 (NPR1) that function in salicylic acid (SA) signaling. These results implicate the added involvement of the antiapoptotic, environmental response gene LESION SIMULATING DISEASE1 (LSD1) in defense. Roots engineered to overexpress the G. max defense genes Gm-α-SNAP, SYP38, EDS1, NPR1, BOTRYTIS INDUCED KINASE1 (BIK1) and xyloglucan endotransglycosylase/hydrolase (XTH) in the susceptible genotype G. max[Williams 82/PI 518671] have induced Gm-LSD1 (Gm-LSD1-2) transcriptional activity. In reciprocal experiments, roots engineered to overexpress Gm-LSD1-2 in the susceptible genotype G. max[Williams 82/PI 518671] have induced levels of SYP38, EDS1, NPR1, BIK1 and XTH, but not α-SNAP prior to infection. In tests examining the role of Gm-LSD1-2 in defense, its overexpression results in ∼52 to 68% reduction in nematode parasitism. In contrast, RNA interference (RNAi) of Gm-LSD1-2 in the resistant genotype G. max[Peking/PI 548402] results in an 3.24-10.42 fold increased ability of H. glycines to parasitize. The results identify that Gm-LSD1-2 functions in the defense response of G. max to H. glycines parasitism. It is proposed that LSD1, as an antiapoptotic protein, may establish an environment whereby the protected, living plant cell could secrete materials in the vicinity of the parasitizing nematode to disarm it. After the targeted incapacitation of the nematode the parasitized cell succumbs to its targeted demise as the infected root region is becoming fortified.

Fusion of Golgi-derived vesicles mediated by SNAP-25 is essential for sympathetic neuron outgrowth but relatively insensitive to botulinum neurotoxins in vitro

Sympathetic neurons ramify to innervate multiple cells in target tissues. In compartmentalized cultures of rat superior cervical ganglion neurons, cleavage of synaptosomal-associated protein of Mr  = 25 000 (SNAP-25) in neurites exposed to botulinum neurotoxin type A (BoNT/A) arrested their growth and collapsed interstitial branches, but this required large, nonclinical doses. A protease-inactive mutant proved ineffective, confirming involvement of SNAP-25 in neurite extension and arborization. BoNT/C1 acted like BoNT/A, but BoNT/E caused only mild inhibition, likely due to transient SNAP-25 proteolysis. Near-total lack of susceptibility to BoNT/B or BoNT/D revealed that vesicle-associated membrane protein (VAMPs) isoforms 1-3 are not essential. Neurite length was not reduced when either BoNT/A or BoNT/C1 was applied to the somata, with no detrimental effect on neuron viability being observed. Treatments that protect cells from deprivation of nerve growth factor failed to prevent the toxin-induced loss of neurites. Inactivation of SNAP-25 caused the accumulation at neurite branch sites of Golgi-derived organelles labelled with N-(4,4-difluoro-5,7-dimethyl-4-bora-3a,4a-diaza-s-indacene-3-pentanoyl)-sphingosine conjugated to bovine serum albumin, prior to the collapse of arbors. Notably, neurite growth was ~ 1000-fold less susceptible to BoNT/A than cholinergic transmission in these neurons. Accordingly, a BoNT/A acceptor synaptic vesicle protein 2 (SV2) was found to be colocalized with VAMP 1-3, but not with VAMP 7, which is implicated in the growth of neurites. In conclusion, neurites depend on SNAP-25 for extension but this is quite resistant to BoNT/A, possibly, because of a low density of SV2 at growth sites that are distant from the highly susceptible regions of neurotransmitter release.

Syntaxin 31 functions in Glycine max resistance to the plant parasitic nematode Heterodera glycines

A Glycine max syntaxin 31 homolog (Gm-SYP38) was identified as being expressed in nematode-induced feeding structures known as syncytia undergoing an incompatible interaction with the plant parasitic nematode Heterodera glycines. The observed Gm-SYP38 expression was consistent with prior gene expression analyses that identified the alpha soluble NSF attachment protein (Gm-α-SNAP) resistance gene because homologs of these genes physically interact and function together in other genetic systems. Syntaxin 31 is a protein that resides on the cis face of the Golgi apparatus and binds α-SNAP-like proteins, but has no known role in resistance. Experiments presented here show Gm-α-SNAP overexpression induces Gm-SYP38 transcription. Overexpression of Gm-SYP38 rescues G. max [Williams 82/PI 518671], genetically rhg1 (-/-), by suppressing H. glycines parasitism. In contrast, Gm-SYP38 RNAi in the rhg1 (+/+) genotype G. max [Peking/PI 548402] increases susceptibility. Gm-α-SNAP and Gm-SYP38 overexpression induce the transcriptional activity of the cytoplasmic receptor-like kinase BOTRYTIS INDUCED KINASE 1 (Gm-BIK1-6) which is a family of defense proteins known to anchor to membranes through a 5' MGXXXS/T(R) N-myristoylation sequence. Gm-BIK1-6 had been identified previously by RNA-seq experiments as expressed in syncytia undergoing an incompatible reaction. Gm-BIK1-6 overexpression rescues the resistant phenotype. In contrast, Gm-BIK1-6 RNAi increases parasitism. The analysis demonstrates a role for syntaxin 31-like genes in resistance that until now was not known.

Quantitative field testing Heterodera glycines from metagenomic DNA samples isolated directly from soil under agronomic production

A quantitative PCR procedure targeting the Heterodera glycines ortholog of the Caenorhabditis elegans uncoordinated-78 gene was developed. The procedure estimated the quantity of H. glycines from metagenomic DNA samples isolated directly from field soil under agronomic production. The estimation of H. glycines quantity was determined in soil samples having other soil dwelling plant parasitic nematodes including Hoplolaimus, predatory nematodes including Mononchus, free-living nematodes and biomass. The methodology provides a framework for molecular diagnostics of nematodes from metagenomic DNA isolated directly from field soil.

Molecular components required for resting and stimulated endocytosis of botulinum neurotoxins by glutamatergic and peptidergic neurons

Proteins responsible for basal and stimulated endocytosis in nerves containing small clear synaptic vesicles (SCSVs) or large dense-core vesicles (LDCVs) are revealed herein, using probes that exploit surface-exposed vesicle proteins as acceptors for internalization. Basal uptake of botulinum neurotoxins (BoNTs) by both SCSV-releasing cerebellar granule neurons (CGNs) and LDCV-enriched trigeminal ganglionic neurons (TGNs) was found to require protein acceptors and acidic compartments. In addition, dynamin, clathrin, adaptor protein complex-2 (AP2), and amphiphysin contribute to the depolarization-evoked entry. For fast recycling of SCSVs, knockdown and knockout strategies demonstrated that CGNs use predominantly dynamin 1, whereas isoform 2 and, to a smaller extent, isoform 3 support a less rapid mode of stimulated endocytosis. Accordingly, proximity ligation assay confirmed that dynamin 1 and 2 colocalize with amphiphysin 1 in CGNs, and the latter copurified with both dynamins from cell extracts. In contrast, LDCV-releasing TGNs preferentially employ dynamins 2 and 3 and amphiphysin 1 for evoked endocytosis and lack the fast phase. Hence, stimulation recruits dynamin, clathrin, AP2, and amphiphysin to augment BoNT internalization, and neurons match endocytosis mediators to the different demands for locally recycling SCSVs or replenishing distally synthesized LDCVs.

Botulinum toxin A detrusor injections reduce postsynaptic muscular M2, M3, P2X2, and P2X3 receptors in children and adolescents who have neurogenic detrusor overactivity: a single-blind study

OBJECTIVE

To analyze the effect of OnabotulinumtoxinA detrusor injections on postsynaptic muscular receptors in children and adolescents with neurogenic detrusor overactivity.

MATERIALS AND METHODS

A bladder augmentation became necessary in 10 children and adolescents (7 males, 3 females; median age, 12 years) who had neurogenic detrusor overactivity. Seven had previously received 1 to 8 (average 3.86) OnabotulinumtoxinA detrusor injections, but their detrusor pressure could not be maintained at tolerable levels because of low-compliance bladder. The last injection session had been completed an average of 3 months (range, 1.5-3.5 months) previously. Three patients had never received that therapy and were considered controls. On the bladder dome resections, a specific receptor analysis (muscarinic M2 and M3 and purinergic P2X1, P2X2, and P2X3) was performed with confocal immunofluorescence, and nerve fiber density was analyzed with light-microscopic 3,3'-diaminobenzidine-immunohistochemical staining.

RESULTS

Receptor analysis showed a downregulation of all examined receptors after OnabotulinumtoxinA injections; the reductions in M2, M3, P2X2, and P2X3 receptors reached a significance level of P <.05 (Mann-Whitney test). The ratios of means (OnabotulinumtoxinA-to-control) were 0.26 for M2, 0.33 for M3, 0.35 for P2X1, 0.19 for P2X2, and 0.37 for P2X3.

CONCLUSION

OnabotulinumtoxinA detrusor injections led to significant reductions in muscular M2, M3, P2X2, and P2X3 receptors. The reductions probably affect the generated force in the urinary bladder and could contribute to the clinically observed increase in residual urine.

The expression of a naturally occurring, truncated allele of an α-SNAP gene suppresses plant parasitic nematode infection

Transcriptional mapping experiments of the major soybean cyst nematode resistance locus, rhg1, identified expression of the vesicular transport machinery component, α soluble NSF attachment protein (α-SNAP), occurring during defense. Sequencing the α-SNAP coding regions from the resistant genotypes G. max ([Peking/PI 548402]) and G. max ([PI 437654]) revealed they are identical, but differ from the susceptible G. max ([Williams 82/PI 518671]) by the presence of several single nucleotide polymorphisms. Using G. max ([Williams 82/PI 518671]) as a reference, a G → T(2,822) transversion in the genomic DNA sequence at a functional splice site of the α-SNAP([Peking/PI 548402]) allele produced an additional 17 nucleotides of mRNA sequence that contains an in-frame stop codon caused by a downstream G → A(2,832) transition. The G. max ([Peking/PI 548402]) genotype has cell wall appositions (CWAs), structures identified as forming as part of a defense response by the activity of the vesicular transport machinery. In contrast, the 17 nt α-SNAP([Peking/PI 548402]) mRNA motif is not found in G. max ([PI 88788]) that exhibits defense to H. glycines, but lack CWAs. The α-SNAP([PI 88788]) promoter contains sequence elements that are nearly identical to the α-SNAP([Peking/PI 548402]) allele, but differs from the G. max ([Williams 82/PI 518671]) ortholog. Overexpressing the α-SNAP([Peking/PI 548402]) allele in the susceptible G. max ([Williams 82/PI 518671]) genotype suppressed H. glycines infection. The experiments indicate a role for the vesicular transport machinery during infection of soybean by the soybean cyst nematode. However, increased GmEREBP1, PR1, PR2, PR5 gene activity but suppressed PR3 expression accompanied the overexpression of the α-SNAP([Peking/PI 548402]) allele prior to infection.

Novel chimeras of botulinum and tetanus neurotoxins yield insights into their distinct sites of neuroparalysis

Botulinum neurotoxin (BoNT) A or E and tetanus toxin (TeTx) bind to motor-nerve endings and undergo distinct trafficking; their light-chain (LC) proteases cleave soluble N-ethylmaleimide-sensitive factor attachment protein receptors (SNAREs) peripherally or centrally and cause flaccid or spastic paralysis, respectively. To seek protein domains responsible for local blockade of transmitter release (BoNTs) rather than retroaxonal transport to spinal neurons (TeTx), their acceptor-binding moieties (H(C))--or in one case, heavy chain (HC)--were exchanged by gene recombination. Each chimera, expressed and purified from Escherichia coli, entered rat cerebellar neurons to cleave their substrates, blocked in vitro nerve-induced muscle contractions, and produced only flaccid paralysis in mice. Thus, the local cytosolic delivery of BoNT/A or BoNT/E proteases and the contrasting retrograde transport of TeTx are not specified solely by their HC or H(C); BoNT/A LC translocated locally irrespective of being targeted by either of the latter TeTx domains. In contrast, BoNT/E protease fused to a TeTx enzymatically inactive mutant (TeTIM) caused spastic paralysis and cleaved SNAP-25 in spinal cord but not the injected muscle. Apparently, TeTIM precludes cytosolic release of BoNT/E protease at motor nerve endings. It is deduced that the LCs of the toxins, acting in conjunction with HC domains, dictate their local or distant destinations.

Targeted delivery into motor nerve terminals of inhibitors for SNARE-cleaving proteases via liposomes coupled to an atoxic botulinum neurotoxin

A targeted drug carrier (TDC) is described for transferring functional proteins or peptides into motor nerve terminals, a pivotal locus for therapeutics to treat neuromuscular disorders. It exploits the pronounced selectivity of botulinum neurotoxin type B (BoNT/B) for interacting with acceptors on these cholinergic nerve endings and becoming internalized. The gene encoding an innocuous BoNT/B protease-inactive mutant (BoTIM) was fused to that for core streptavidin, expressed in Escherichia coli and the purified protein was conjugated to surface-biotinylated liposomes. Such decorated liposomes, loaded with fluorescein as traceable cargo, acquired pronounced specificity for motor nerve terminals in isolated mouse hemidiaphragms and facilitated the intraneuronal transfer of the fluor, as revealed by confocal microscopy. Delivery of the protease light chain of botulinum neurotoxin type A (BoNT/A) via this TDC accelerated the onset of neuromuscular paralysis, indicative of improved translocation of this enzyme into the presynaptic cytosol with subsequent proteolytic inactivation of synaptosomal-associated protein of molecular mass 25 kDa (SNAP-25), an exocytotic soluble N-ethyl-maleimide-sensitive factor attachment protein receptor (SNARE) essential for neurotransmitter release. BoTIM-coupled liposomes, loaded with peptide inhibitors of proteases, yielded considerable attenuation of the neuroparalytic effects of BoNT/A or BoNT/F as a result of their cytosolic transfer, the first in situ demonstration of the ability of designer antiproteases to suppress the symptoms of botulism ex vivo. Delivery of the BoNT/A inhibitor by liposomes targeted with the full-length BoTIM proved more effective than that mediated by its C-terminal neuroacceptor-binding domain. This demonstrated versatility of TDC for nonviral cargo transfer into cholinergic nerve endings has unveiled its potential for direct delivery of functional targets into motor nerve endings.

Quantitative field testing Rotylenchulus reniformis DNA from metagenomic samples isolated directly from soil

A quantitative PCR procedure targeting the β-tubulin gene determined the number of Rotylenchulus reniformis Linford & Oliveira 1940 in metagenomic DNA samples isolated from soil. Of note, this outcome was in the presence of other soil-dwelling plant parasitic nematodes including its sister genus Helicotylenchus Steiner, 1945. The methodology provides a framework for molecular diagnostics of nematodes from metagenomic DNA isolated directly from soil.

Classification of Rotylenchulus reniformis Numbers in Cotton Using Remotely Sensed Hyperspectral Data on Self-Organizing Maps

Rotylenchulus reniformis is one of the major nematode pests capable of reducing cotton yields by more than 60%, causing estimated losses that may exceed millions of dollars U.S. Therefore, early detection of nematode numbers is necessary to reduce these losses. This study investigates the feasibility of using remotely sensed hyperspectral data (reflectances) of cotton plants affected with different nematode population numbers with self-organizing maps (SOM) in correlating and classifying nematode population numbers extant in a plant's rhizosphere. The hyperspectral reflectances were classified into three classes based on R. renifomis population numbers present in plant's rhizosphere. Hyperspectral data (350-2500 nm) were also sub-divided into Visible, Red Edge + Near Infrared (NIR) and Mid-IR region to determine the sub-region most effective in spectrally classifying the nematode population numbers. Various combinations of different feature extraction and dimensionality reduction methods were applied in different regions to extract reduced sets of features. These features were then classified using a supervised-SOM classification method. Our results suggest that the overall classification accuracies, in general, for most methods in most regions (except visible region) varied from 60% to 80%, thereby, indicating a positive correlation between the nematode numbers present in plant's rhizosphere and the corresponding plant's hyperspectral signatures. Results showed that classification accuracies in the Mid-IR region were comparable to the accuracies obtained in other sub-regions. Finally, based on our findings, the use of remotely-sensed hyperspectral data with SOM could prove to be extremely time efficient in detecting nematode numbers present in the soil.

Excitatory cholinergic and purinergic signaling in bladder are equally susceptible to botulinum neurotoxin a consistent with co-release of transmitters from efferent fibers

Mediators of neuromuscular transmission in rat bladder strips were dissected pharmacologically to examine their susceptibilities to inhibition by botulinum neurotoxins (BoNTs) and elucidate a basis for the clinical effectiveness of BoNT/A in alleviating smooth muscle spasms associated with overactive bladder. BoNT/A, BoNT/C1, or BoNT/E reduced peak and average force of muscle contractions induced by electric field stimulation (EFS) in dose-dependent manners by acting only on neurogenic, tetrodotoxin-sensitive responses. BoNTs that cleaved vesicle-associated membrane protein proved to be much less effective. Acetylcholine (ACh) and ATP were found to provide virtually all excitatory input, because EFS-evoked contractions were abolished by the muscarinic receptor antagonist, atropine, combined with either a desensitizing agonist of P2X(1) and P2X(3) or a nonselective ATP receptor antagonist. Both transmitters were released in the innervated muscle layer and, thus, persisted after removal of urothelium. Atropine or a desensitizer of the P2X(1) or P2X(3) receptors did not alter the rate at which muscle contractions were weakened by BoNT/A. Moreover, although cholinergic and purinergic signaling could be partially delineated by using high-frequency EFS (which intensified a transient, largely atropine-resistant spike in muscle contractions that was reduced after P2X receptor desensitization), they proved equally susceptible to BoNT/A. Thus, equi-potent blockade of ATP co-released with ACh from muscle efferents probably contributes to the effectiveness of BoNT/A in treating bladder overactivity, including nonresponders to anticholinergic drugs. Because purinergic receptors are known mediators of sensory afferent excitation, inhibition of efferent ATP release by BoNT/A could also help to ameliorate acute pain and urgency sensation reported by some recipients.

Neuro-exocytosis: botulinum toxins as inhibitory probes and versatile therapeutics

For the fundamental process of quantal neurotransmitter release, a consensus is being reached on the recycling pathways for transmitter-containing, small synaptic vesicles (SSVs), and major inroads have been made into deciphering the multiple steps of regulated exocytosis. These advances arose from the identification of approximately 80 proteins in SSVs, elucidation of the structures of pertinent macromolecular complexes, utilisation of different serotypes (A-G) of botulinum neurotoxin (BoNT) together with transgenic mice lacking key genes. Hence, converging evidence continues to emerge for the sequential formation of complexes between the three SNAREs (SNAP-25, syntaxin and VAMP) and their regulatory proteins (complexins, Munc18), as well as for the Ca2+ triggering of membrane fusion/exocytosis via its sensor, synaptotagmin. Moreover, molecular data gained on BoNTs have been translated into Clinical Medicine with type A now being applied worldwide for effectively treating >100 human conditions due to overactivity of nerves supplying various muscles or glands. A recent advance is the successful engineering of a chimera from two BoNTs to acquire the capability of re-targeting a more active moiety to sensory neurons, with resultant inhibition of the release of a pain mediator. Encouragingly, this novel recombinant protein blocks the exocytotic response triggered by a stimulant (capsaicin) of nociceptive C fibres that activates their vanilloid receptors, a feat not possible for either parental toxin. Reaching this landmark has generated optimism for designing further variants of such a versatile therapeutic for normalising the hyper-activity of particular cell types, especially those underlying the many cases of chronic pain that do not respond to existing drugs.

Novel chimeras of botulinum neurotoxins A and E unveil contributions from the binding, translocation, and protease domains to their functional characteristics

Hyperexcitability disorders of cholinergically innervated muscles are treatable with botulinum neurotoxin (BoNT) A. The seven serotypes (A-G) potently block neurotransmission by binding to presynaptic receptors, undergoing endocytosis, transferring to the cytosol, and inactivating proteins essential for vesicle fusion. Although BoNT/A and BoNT/E cleave SNAP-25, albeit at distinct sites, BoNT/E blocks neurotransmission faster and more potently. To identify the domains responsible for these characteristics, the C-terminal heavy chain portions of BoNT/A and BoNT/E were exchanged to create chimeras AE and EA. After high yield expression in Escherichia coli, these single chain chimeras were purified by two-step chromatography and activated by conversion to disulfide-linked dichains. In vitro, each entered neurons, cleaved SNAP-25, and blocked neuromuscular transmission while causing flaccid paralysis in vivo. Acidification-dependent translocation of the light chain to the cytosol occurred more rapidly for BoNT/E and EA than for BoNT/A and AE because the latter pair remained susceptible for longer to inhibitors of the vesicular proton pump, and BoNT/A proved less sensitive. The receptor-binding and protease domains do not seem to be responsible for the speeds of intoxication; rather the N-terminal halves of their heavy chains are implicated, with dissimilar rates of cytosolic transfer of the light chains being due to differences in pH sensitivity. AE produced the most persistent muscle weakening and therefore has therapeutic potential. Thus, proof of principle is provided for tailoring the pharmacological properties of these toxins by protein engineering.

Vertical Distribution of Rotylenchulus reniformis in Cotton Fields

The possible impact of Rotylenchulus reniformis below plow depth was evaluated by measuring the vertical distribution of R. reniformis and soil texture in 20 symptomatic fields on 17 farms across six states. The mean nematode population density per field, 0 to 122 cm deep, ranged from 0.4 to 63 nematodes/g soil, and in 15 fields more than half of the R. reniformis present were below 30.5 cm, which is the greatest depth usually plowed by farmers or sampled by consultants. In 11 fields measured, root density was greatest in the top 15 cm of soil; however, roots consistently penetrated 92 to 122 cm deep by midseason, and in five fields in Texas and Louisiana the ratio of nematodes to root-length density within soil increased with depth. Repeated sampling during the year in Texas indicated that up to 20% of the nematodes in soil below 60 cm in the fall survived the winter. Differences between Baermann funnel and sugar flotation extraction methods were not important when compared with field-to-field differences in nematode populations and field-specific vertical distribution patterns. The results support the interpretation that R. reniformis below plow depth can significantly impact diagnosis and treatment of cotton fields infested with R. reniformis.

Effect of Controlled Cold Storage on Recovery of Rotylenchulus reniformis from Naturally Infested Soil

Rotylenchulus reniformis is rapidly becoming the most economically important pest associated with cotton in the southeastern United States. Incentive programs have been implemented to support sampling of production fields to determine the presence and abundance of R. reniformis. These sampling programs have dramatically increased the number of soils samples submitted to nematology laboratories during autumn. The large numbers of samples overwhelm most labs and require placement in cold storage until extraction. Therefore, the objective of this study was to examine the length of time soils infested with R. reniformis can be stored before nematode extraction without compromising the accuracy of estimates of population densities. A sandy loam and a silty loam were the two cotton production soils used in this study. Rotylenchulus reniformis numbers decreased 61%during the first 180 days of storage in both soils. Rotylenchulus reniformis numbers from the initial sampling through 180 days decreased as a linear function. The decline of R. reniformis numbers during storage was estimated as 0.28% of the population lost daily from the maximum population through 180 days. The diminution of nematode numbers from 180 through 1,080 days in storage continued, but at a slower rate. Numbers of R. reniformis declined to less than 89%, 93%, and 99% of the initial population within 360, 720, and 1,080 days, respectively, of storage. The reduction of R. reniformis numbers over 180 days can be adjusted, allowing a more accurate estimation of R. reniformis levels in soil samples stored at 4 degrees C.

Accelerated degradation of aldicarb and its metabolites in cotton field soils

The degradation of aldicarb, and the metabolites aldicarb sulfoxide and aldicarb sulfone, was evaluated in cotton field soils previously exposed to aldicarb. A loss of efficacy had been observed in two (LM and MS) of the three (CL) field soils as measured by R. reniformis population development and a lack of cotton yield response. Two soils were compared for the first test-one where aldicarb had been effective (CL) and the second where aldicarb had lost its efficacy (LM). The second test included all three soils: autoclaved, non-autoclaved and treated with aldicarb at 0.59 kg a.i./ha, or not treated with aldicarb. The degradation of aldicarb to aldicarb sulfoxide and then to aldicarb sulfone was measured using high-performance liquid chromatography (HPLC) in both tests. In test one, total degradation of aldicarb and its metabolites occurred within 12 days in the LM soil. Aldicarb sulfoxide and aldicarb sulfone were both present in the CL soil at the conclusion of the test at 42 days after aldicarb application. Autoclaving the LM and MS soils extended the persistence of the aldicarb metabolites as compared to the same soils not autoclaved. The rate of degradation was not changed when the CL natural soil was autoclaved. The accelerated degradation was due to more rapid degradation of aldicarb sulfoxide and appears to be biologically mediated.

Competition of Meloidogyne incognita and Rotylenchulus reniformis on Cotton Following Separate and Concomitant Inoculations

It has been hypothesized Rotylenchulus reniformis (Rr) has a competitive advantage over Meloidogyne incognita (Mi) in the southeastern cotton production region of the United States. This study examines the reproduction and development of Meloidogyne incognita (Mi) and Rotylenchulus reniformis (Rr) in separate and concomitant infections on cotton. Under greenhouse conditions, cotton seedlings were inoculated simultaneously with juveniles (J2) of M. incognita and vermiform adults of R. reniformis in the following ratios (Mi:Rr): 0:0, 100:0, 75:25, 50:50, 25:75, and 0:100. Soil populations of M. incognita and R. reniformis were recorded at 3, 6, 9, 14, 19, 25, 35, 45, and 60 days after inoculations. At each date, samples were taken to determine the life stage of development, number of egg masses, eggs per egg mass, galls, and giant cells or syncytia produced by the nematodes. Meloidogyne incognita and R. reniformis were capable of initially inhibiting each other when the inoculum ratio of one species was higher than the other. In concomitant infections, M. incognita was susceptible to the antagonistic effect of R. reniformis. Rotylenchulus reniformis affected hatching of M. incognita eggs, delayed secondary infection of M. incognita J2, reduced the number of egg masses produced by M. incognita, and reduced J2 of M. incognita 60 days after inoculations. In contrast, M. incognita reduced R. reniformis soil populations only when its proportion in the inoculum ratio was higher than that of R. reniformis. Meloidogyne incognita reduced egg masses produced by R. reniformis, but not production of eggs and secondary infection.

Efficacy of Aldicarb to Rotylenchulus reniformis and Biodegradation in Cotton Field Soils

The microbial degradation of aldicarb was examined in the greenhouse using soil from four cotton fields with a history of aldicarb use. The addition of aldicarb at 0.59 kg a.i./ha to natural soil increased Rotylenchulus reniformis numbers 6.6% in one soil and decreased R. reniformis numbers only 25.8% in another soil as compared to the corresponding natural soil without aldicarb. The use of increasing rates of aldicarb did not increase the efficacy of aldicarb in these soils. Rotylenchulus reniformis numbers were reduced 39.8, 22.6, and 6.8%, and increased 5.7% for aldicarb applied at 0.29, 0.59, 0.85, and 1.19 kg a.i./ha, respectively, in one natural soil. In another natural soil, R. reniformis numbers were reduced 42.5 and 21.9% for aldicarb applied at 0.29 and 1.19 kg a.i./ha, respectively, but increased 19.1 and 10.6% for aldicarb applied at 0.59 and 0.85 kg a.i./ha, respectively. Autoclaving the soils restored aldicarb toxicity in both soils, and R. reniformis numbers were reduced 96 and 99%, respectively, as compared to autoclaved soil without aldicarb. Bacterial populations were greater in the natural soils where aldicarb did not reduce R. reniformis numbers relative to the same soils that were autoclaved. However, no bacterial species was consistently associated with aldicarb degradation.

Evaluation of the therapeutic usefulness of botulinum neurotoxin B, C1, E, and F compared with the long lasting type A. Basis for distinct durations of inhibition of exocytosis in central neurons

Seven types (A-G) of botulinum neurotoxin (BoNT) target peripheral cholinergic neurons where they selectively proteolyze SNAP-25 (BoNT/A, BoNT/C1, and BoNT/E), syntaxin1 (BoNT/C1), and synaptobrevin (BoNT/B, BoNT/D, BoNT/F, and BoNT/G), SNARE proteins responsible for transmitter release, to cause neuromuscular paralysis but of different durations. BoNT/A paralysis lasts longest (4-6 months) in humans, hence its widespread clinical use for the treatment of dystonias. Molecular mechanisms underlying these distinct inhibitory patterns were deciphered in rat cerebellar neurons by quantifying the half-life of the effect of each toxin, the speed of replenishment of their substrates, and the degradation of the cleaved products, experiments not readily feasible at motor nerve endings. Correlation of target cleavage with blockade of transmitter release yielded half-lives of inhibition for BoNT/A, BoNT/C1, BoNT/B, BoNT/F, and BoNT/E (31, 25, approximately 10, approximately 2, and approximately 0.8 days, respectively), equivalent to the neuromuscular paralysis times found in mice, with recovery of release coinciding with reappearance of the intact SNAREs. A limiting factor for the short neuroparalytic durations of BoNT/F and BoNT/E is the replenishment of synaptobrevin or SNAP-25, whereas pulse labeling revealed that extended inhibition by BoNT/A, BoNT/B, or BoNT/C1 results from longevity of each protease. These novel findings could aid development of new toxin therapies for patients resistant to BoNT/A and effective treatments for human botulism.

Insights into a basis for incomplete inhibition by botulinum toxin A of Ca2+-evoked exocytosis from permeabilised chromaffin cells

Inhibition of regulated exocytosis by botulinum toxins type A and B was studied in chromaffin cells. Both virtually abolished catecholamine release triggered from intact cells by depolarising stimuli, whereas the blockade by type A, but not B, was only partial after cell permeabilisation and direct stimulation of exocytosis by Ca(2+). Botulinum toxin A did not alter the [Ca(2+)]-dependency of exocytosis in permeabilised cells but, rather, proportionally reduced the amount of release at each concentration tested. Likewise, this toxin decreased the extents of Ca(2+)-induced structural changes in SNAP-25, synaptobrevin and syntaxin (known collectively as SNAREs), whilst leaving their [Ca(2+)]-sensitivity unaltered. Thus, botulinum toxin A does not reduce the Ca(2+)-sensitivity of the exocytosis sensor, but hinders transmission of the signal to the SNAREs which mediate fusion.

Ca2+-induced changes in SNAREs and synaptotagmin I correlate with triggered exocytosis from chromaffin cells: insights gleaned into the signal transduction using trypsin and botulinum toxins

Ca2+-triggered catecholamine exocytosis from chromaffin cells involves SNAP-25, synaptobrevin and syntaxin (known as SNAREs). Synaptotagmin I has been implicated as the Ca2+-sensor because it binds Ca2+, and this enhances its binding to syntaxin, SNAP-25 and phospholipids in vitro. However, most of these interactions are only mediated by [Ca2+]i two orders of magnitude higher than that needed to elicit secretion. Thus, the Ca2+ sensitivities of synaptotagmin I and the other SNAREs were quantified in situ. Secretion elicited from permeabilised cells by μM Ca2+ was accompanied,with almost identical Ca2+ dependencies, by changes in synaptotagmin I, SNAP-25, syntaxin and synaptobrevin that rendered them less susceptible to trypsin. The majority of the trypsin-resistant SNAREs were not associated with SDS-resistant complexes. None of these proteins acquired trypsin resistance in cells rendered incompetent for exocytosis by run-down. Removal of nine C-terminal residues from SNAP-25 by botulinum toxin A reduced both exocytosis and the SNAREs' acquisition of trypsin resistance but did not alter the Ca2+ sensitivity, except for synaptotagmin I. Even after synaptobrevin had been cleaved by botulinum toxin B, all the other proteins still responded to Ca2+. These data support a model whereby Ca2+ is sensed, probably by synaptotagmin I, and the signal passed to syntaxin and SNAP-25 before they interact with synaptobrevin.

Multiple forms of SNARE complexes in exocytosis from chromaffin cells: effects of Ca2+, MgATP and botulinum toxin type A

The changes that SNAREs undergo during exocytosis were studied in permeabilised chromaffin cells treated with Ca2+, MgATP or botulinum neurotoxin A. High-resolution 2D SDS-PAGE revealed multiple SDS-resistant SNARE complexes having a wide range of sizes and in which SNAP-25 and syntaxin predominate over synaptobrevin. Their formation increased upon Ca2+-stimulated exocytosis; notably, the 2D protocol proved much superior to 1D SDS-PAGE for the detection of large complexes and revealed that for forms with relative molecular mass greater than 100,000 stimulated induction was more significant than for smaller species. MgATP enhanced Ca2+-triggered catecholamine release but reduced the content of complexes. By contrast, botulinum neurotoxin type A inhibited exocytosis and altered the stoichiometry of the SNAP-25:syntaxin binary association, without lowering its abundance. The individual SNAREs were protected against trypsin proteolysis to varying extents in binary and ternary complexes of different sizes, suggestive of distinct folding intermediates. Our data suggest that Ca2+ triggers an early stage of SNARE complex formation causing an accumulation of partially folded intermediates, especially of binary forms, as well as their maturation into smaller, more protease resistant states. In addition, botulinum neurotoxin A inhibits exocytosis by perturbing the syntaxin:SNAP-25 ratio in binary intermediates.

First Report of Pythium Root Rot on Grain Sorghum in Mississippi

In May 2000, seedling death in grain sorghum (Sorghum bicolor L.) was reported in fields located in the delta region of Mississippi, following a wet planting season when precipitation and relative humidity were 50 and 10.5% greater, respectively, than the 5-year average. Seedlings exhibited various symptoms, including necrosis of the leaf tip and blade, collar rot, root rot, and streaking of the vascular system at the soil line that resulted in plant death. Tissue sections from plants with collar and root rot were plated aseptically on potato dextrose, V8, and cornmeal agars. Pythium ultimum was the only pathogenic fungus isolated and appeared on 63% of tissue sections. Recovered isolates exhibited similar growth and morphology in vitro and were stimulated to produce fruiting structures by the grass leaf-baiting method. Isolates produced primary terminal globose oogonia, 19 μm in diameter. Oospores were aplerotic and approximately 16.4 µm in diameter, with a 2.1-μm-thick wall. Antheridia were monoclinous or diclinous and short-stalked, with 1 to 2 antheridia per oogonium. Zoospores were produced only in sterile water grass blade cultures and were reniform and biciliate, erupting from spherical vesicles in groups of 15 to 30. Pathogenicity tests were conducted in a controlled growth chamber. P. ultimum was increased on sterile common millet seed and incorporated into sterile field soil at an 0.5% (vol/vol) ratio. Noninfested millet seed was incorporated into field soil as a control. Soil was placed in pots, planted with five-grain sorghum seed, and placed in a growth chamber at 5°C, with a 12-h photoperiod. Treatments were replicated five times, and the experiment conducted twice. At 21 days after planting, the inoculated grain sorghum plants developed collar and root rot, with some leaf necrosis, similar to symptoms observed in the field. Symptoms did not develop on the control plants. Reisolations of P. ultimum on corn meal agar and by the grass-baiting method were successful. P. ultimum commonly is in Mississippi soils and is pathogenic to a number of agronomic crops, although it has not been reported previously as a pathogen on grain sorghum in Mississippi.

A survey of plant-parasitic nematodes associated with cotton in northeastern louisiana

A survey was conducted in northeastern Louisiana to determine the frequency and abundance of plant-parasitic nematodes associated with cotton. In fall 1997 and 1998, more than 600 soil samples were collected from cotton fields representing 6,200 ha, which is 5.3% of the cotton production hectarage in this region. Composite soil samples were collected from 10 ha in each field. Nematodes were extracted by gravity screening and sucrose centrifugation, identified to genus, and quantified. Nine genera of plant-parasitic nematodes were identified. Rotylenchulus reniformis was found in 67% of the fields sampled, with an average population of 12,959 juveniles and vermiform adult stages per 500 cm(3) of soil. Meloidogyne incognita was identified in 25% of the fields sampled, with an average population of 998 juveniles per 500 cm(3) of soil. Hoplolaimus spp. were identified in 3%, or 155 ha, with an average population of 282 juveniles and adult stages per 500 cm[sup3] of soil. Rotylenchulus reniformis and M. incognita occurred at population levels above reported economic thresholds in 49% and 21% of the fields, respectively.

Effect of Foliar Applications of Oxamyl with Aldicarb for the Management of Rotylenchulus reniformison Cotton

The efficacy of foliar applications of oxamyl were evaluated for the management of Rotylenchulus reniformis on cotton in Mississippi. Two tests were established in Tallahatchie County on a fine sandy loam soil (56.8% sand, 37.8% silt, 5.3% clay, pH 5.4, and 0.3% OM) naturally infested with R. reniformis. Oxamyl was applied as a foliar spray at 0.14, 0.27, or 0.53 kg a.i./ha to cotton plants that had reached the sixth true leaf growth stage. A second oxamyl application was applied 14 days after the first treatment at the same rates. All oxamyl treatments also received aldicarb at 0.59 kg a.i./ha at planting. Controls consisted of aldicarb alone, disulfoton (which is not a nematicide), and an untreated control. Oxamyl reduced R. reniformis numbers at 79 and 107 days after planting in Test 1 and at 62 and 82 days after planting in Test 2 compared to aldicarb at 0.59 kg a.i./ha alone and the controls that received neither material. Average reniform population densities in oxamyl-treated plots were 24.5% and 30% lower than with aldicarb alone and the controls. Cotton plant height was greater in plots that received oxamyl at all rates than in the controls. Cotton in oxamyl plus aldicarb and aldicarb alone treatments produced more bolls per plant and had a greater total boll weight than disulfoton and the untreated control. Seed cotton yields were greater in oxamyl-treated plots than for disulfoton-treated and the untreated control.

The potential of ivermectin to control the malaria vector Anopheles farauti

We investigated mortality in Anopheles farauti mosquitoes, a major coastal malaria vector in the south-west Pacific, fed on a volunteer who had taken a 250 micrograms/kg dose of ivermectin. High mortality was recorded in mosquitoes feeding during the first week after treatment of the volunteer, for instance 100-80% failed to survive 3 days. A long-term residual effect of ivermectin in the blood was indicated by a small but significantly higher mortality in mosquitoes fed 6 weeks after ivermectin was taken. These effects were included in malaria transmission models that incorporated host choice and host-induced mortality parameters. For the zoophilic An. farauti, ivermectin treatment of animals resulted in a greater reduction in malaria than ivermectin treatment of humans alone, whereas for an anthropophilic vector, treatment of humans was more important. This suggests that ivermectin treatment of animals could have an important role in malaria control where An. farauti is the vector. Improvement in the health of humans and domestic animals through control of parasitic worms and mites might encourage community participation in strategies involving ivermectin.

Rescue of exocytosis in botulinum toxin A-poisoned chromaffin cells by expression of cleavage-resistant SNAP-25. Identification of the minimal essential C-terminal residues

Botulinum neurotoxin (BoNT) types A and B selectively block exocytosis by cleavage of SNAP-25 and synaptobrevin, respectively; in humans, many months are required for full recovery from the resultant neuromuscular paralysis. To decipher the molecular basis for such prolonged poisoning, intoxication in adreno-chromaffin cells was monitored over 2 months. Exocytosis from BoNT/B-treated cells resumed after 56 days because of the appearance of intact synaptobrevin. However, inhibition continued in BoNT/A-treated cells, throughout the same interval, with a continued predominance of cleaved SNAP-25-(1-197) over the intact protein. When recovery from poisoning was attempted by transfection of the latter cells with the gene encoding full-length SNAP-25-(1-206), no restoration of exocytosis ensued even after 3 weeks. To ascertain if this failure was because of the persistence of the toxin's protease activity, the cells were transfected with BoNT/A-resistant SNAP-25 constructs; importantly, exocytosis was rescued. C-terminal truncation of the toxin-insensitive SNAP-25 revealed that residues 1-201, 1-202, 1-203 afforded a significant return of exocytosis, unlike shorter forms 1-197, -198, -199, or -200; accordingly, mutants M202A or L203A of full-length SNAP-25 rescued secretion. These findings give insights into the C-terminal functional domain of SNAP-25, demonstrate the longevity of BoNT/A protease, and provide the prospect of a therapy for botulism.

First Report of Premature Boll Rot Associated with Cotton in Louisiana

A premature boll rot has been observed with increasing frequency in association with cotton (Gossypium hirsutum) in the Delta region of Louisiana-Mississippi. The initial developing cotton boll, sepals, and peduncle rapidly become necrotic and mummified. A dark brown to black lesion approximately 1 cm in length develops at the base of the peduncle, extending down the petiole below the diseased cotton boll. The diseased boll and peduncle remain attached to the petiole, hanging by a small portion of peduncle tissue. In an initial survey, the symptomatic boll rot was observed in 95% of the cotton fields in the Delta in 1996. A Phomopsis sp. was isolated from 58% of the diseased bolls, 42% of the cotton boll peduncles, and 52% of the leaf petioles collected from three cotton varieties. Fusarium spp. and Alternaria alternata were isolated from the diseased bolls with a frequency of 18 and 11%, respectively. Phomopsis sp. mycelium is dense, immersed, septate, and hyaline to pale brown in color. Stromata are pulvinate, less than 5 mm in diameter and form in a ring pattern. Pycinidia are erumpet, dark brown to black, separate or aggregated, and globose with ostiolate necks. Conidia are unicellular and hyaline, with alpha conidia oblong-elliptical and biguttulate while beta conidia are filiform and hamate in shape. The ratio of alpha to beta spores varies depending on the age of the culture. Pathogenicity tests with the sterile toothpick inoculation technique were conducted in a field planted with cotton cv. DPL 50. Developing cotton bolls approximately 5 to 8 mm in diameter were inoculated with either sterile toothpicks or toothpicks infested with a Phomopsis sp. Characteristic symptoms identical to the original boll rot were observed on 80% of the inoculated bolls 7 days after inoculation. A Phomopsis sp. was reisolated from the diseased bolls, completing Koch's postulates. No symptoms developed nor was the pathogen reisolated from the controls.

Importance of two adjacent C-terminal sequences of SNAP-25 in exocytosis from intact and permeabilized chromaffin cells revealed by inhibition with botulinum neurotoxins A and E

Types A and E botulinum neurotoxin (BoNT) are Zn2+-requiring endoproteases which cleave nine and twenty-six residues, respectively, from the C-terminus of synaptosomal-associated protein of Mr = 25 kDa (SNAP-25). Involvement of SNAP-25 in the exocytosis of large dense-core vesicles in bovine adrenochromaffin cells was examined by measuring cleavage of SNAP-25 in relation to the levels of Ca2+-evoked catecholamine release from cells exposed to BoNT/A or /E, either before or after permeabilization. The dose-dependency of inhibition of exocytosis correlated closely with the extents of SNAP-25 cleavage in cells permeabilized and then treated with BoNT/E. In intact cells exposed to 66 nM BoNT/A, virtually all of the SNAP-25 was truncated, accompanied by a near-complete inhibition of exocytosis; however, after their permeabilization a significant level of secretion was recorded upon Ca2+-stimulation. Importantly, this BoNT/A-resistant release from the permeabilized cells was dramatically lowered by subsequently adding BoNT/E, which further truncated the SNAP-25 fragment (lacking the C-terminal nine residues) that had been produced earlier by BoNT/A. Moreover, anti-SNAP-25 IgG decreased the BoNT/A-insensitive exocytosis. When permeabilized cells were exposed to either neurotoxin, both blocked MgATP-dependent secretion but only BoNT/E attenuated the energy-independent phase. These distinct inhibitory effects of the two neurotoxins demonstrate that residues 197-205 at the C-terminus of SNAP-25 are absolutely essential for exocytosis from intact cells whereas even after their removal a significant proportion of the exocytotic response can be elicited from permeabilized cells, but this is reliant on amino acids 180-196. Moreover, the latter but not residues 197-205 are implicated in a late, MgATP-independent step of exocytosis, which is blocked by BoNT/E but nonsusceptible to BoNT/A.

Phase I trial in humans of an oil-based adjuvant SEPPIC MONTANIDE ISA 720

Seppic MONTANIDE ISA 720 is a metabolizable oil adjuvant that has given good results in animals with recombinant malarial antigens. Twelve human volunteers were given increasing intramuscular doses of MONTANIDE ISA 720, ranging from 0.6 to 1.8 ml. The adjuvant was well tolerated with only minor local effects, including tenderness, local swelling and discomfort on use. MONTANIDE ISA 720 may prove to be an acceptable and effective adjuvant for use in people.

Distinct exocytotic responses of intact and permeabilised chromaffin cells after cleavage of the 25-kDa synaptosomal-associated protein (SNAP-25) or synaptobrevin by botulinum toxin A or B

Botulinum neurotoxin (BoNT) types A and B are Zn2+-requiring endoproteases which potently block neurotransmitter release by cleavage of a 25-kDa synaptosomal-associated protein (SNAP-25) and synaptobrevin, respectively. Synaptobrevin is important for the exocystosis of catecholamines from dense-core granules and evidence is presented here for the involvement of SNAP-25 in this process in neuroendocrine cells. The effects of BoNT/A and BoNT/B on regulated secretion were compared in intact bovine chromaffin cells to investigate the consequences of cleavage of the different targets. Catecholamine secretion elicited by Ba2+, by elevated K+ concentrations or by nicotine was prevented by each toxin. A very good correlation was observed between the extents of SNAP-25 cleavage or synaptobrevin cleavage and inhibition of secretion by BoNT/A or BoNT/B, respectively, which indicates the importance of SNAP-25 and synaptobrevin in regulated exocytosis. Despite truncation of almost the entire SNAP-25 pool by exposure of the cells to BoNT/A, a residual fraction of secretion persisted that was induced by 20microM Ca2+ (and to a lesser extent by 1 mM Ba2+) following permeabilisation. Addition of more BoNT/A failed to reduce this level of secretion. Inclusion of Mg.ATP, which greatly enhanced secretion from permeabilised cells, was required for Ca2+-stimulated or Ba2+-stimulated BoNT/A-resistant secretion. Furthermore, synaptobrevin is essential for this response because the response was not observed in BoNT/B treated cells. In view of the ability of BoNT/E to abolish secretion from permeabilised cells and to delete 26 amino acids from the C-terminus of SNAP-25, it can be deduced that cleavage of only nine residues by BoNT/A does not prevent the resultant truncated form exhibiting attenuated activity under the conditions created by permeabilisation. This identification of a novel component of secretion from permeabilised cells should facilitate investigation of the functional interaction of SNAP-25 with other proteins involved in regulated exocytosis.

Activity and Persistence of Steinernema carpocapsae and Spodoptera exigua Nuclear Polyhedrosis Virus against S. exigua Larvae on Soybean

Experiments were conducted to assess the effects of the entomopathogenic nematode Steinernema carpocapsae and Spodoptera exigua multinucleocapsid nuclear polyhedrosis virus (SeMNPV), alone and in combinations, on mortality of the beet armyworm, S. exigua, larvae on soybean. In 1991 tests, field-grown soybean plants were treated with S. carpocapsae at 0.3 and 0.6 nematodes/cm(2) of leaflet, SeMNPV at 20 and 40 polyhedral inclusion bodies (PIB)/cm(2), and all possible combinations. Treated leaflets were collected from plants and bioassayed with 5-day-old larvae. The combination of S. carpocapsae at 0.6 nematodes/cm(2) + SeMNPV at 40 PIB/cm(2) produced significantly higher larval mortality (61.7%) compared with either S. carpocapsae (24.8-35.1%) or SeMNPV (26.5-33.7%) alone. In 1992, similar tests were repeated using S. carpocapsae at 0.2 and 0.5 nematodes/cm(2), and SeMNPV at 14 and 35 PIB/cm(2). The combination of 0.5 nematodes/cm(2) + 35 PIB/cm(2) resulted in significantly higher larval mortality (64.0%) than either pathogen alone (41.5-49.0%). Steinernema carpocapsae and SeMNPV produced additive effects on beet arlnyworm mortality. Persistence of S. carpocapsae was 12-24 hours and SeMNPV was 96-120 hours on soybean.