ISSN:0739-4462    

DOI:10.1002/arch.940220102

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

ISSN:0739-4462    

DOI:10.1002/arch.940220103

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

摘要:

AbstractThree billion (3 × 109) pounds of hexachlorocyclohexanes, polychlorobornanes, and chlorinated cyclodienes (such as lindane, toxaphene, and endosulfan, respectively) were used to control pest insects before their mode of action was established as blocking the GABA‐gated chloride channel. With the restricted use or demise of these polychlorocycloalkanes (each ∼ 50 to ∼ 75% by weight of chlorine), the GABAergic system is for now an underutilized target of insecticide action. Newer compounds with outstanding potency at this receptor and as toxicants to houseflies are suitably‐substituted 2,6,7‐trioxabicyclo[2.2.2]‐octanes, particularly the bicycloorthobenzoates, and 1,3‐dithianes, including those with no halogenated substitutents. Picrotoxinin analogs and alkynylphenylsilatranes also act at this target but are of lower insecticidal activity. [3H]n‐Propyl‐ethynylbicycloorthobenzoate ([3H]EBOB) is for now the best radioligand for this insecticidally‐relevant binding site in insects. Macrocyclic lactones such as the avermectins and moxidectin act at a different binding site to disrupt chloride flux and they have a different spectrum of insecticidal activity and no cross resistance with cyclodienes in houseflies. The search for new insecticides has provided the incentive and probes for a better understanding of the insect GABAergic system. ©

ISSN:0739-4462    

DOI:10.1002/arch.940220104

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

摘要:

AbstractPhilanthotoxin (PhTX) is a neurotoxic constituent of the paralytic venom of the digger wasp,Philanthus triangulum. PhTX inhibits glutamate receptors of insect muscles mostly as a channel blocker, thereby producing muscle paralysis. Since glutamate receptor blockers may be of value as selective insect control agents, numerous derivatives of Ph TX were synthesized and tested for their potencies as inhibitors of insect skeletal muscle glutamate receptors. Structure‐activity relationship studies revealed that shortening the polyamine chain length reduced potency, and quaternarization of the nitrogen destroyed it. The potency was increased by a bulky anchoring group with moderate hydrophobicity at the end of the polyamine chain. The conversion of the tryosyl moiety to 3,5‐diiodo‐tyrosyl also increased potency and so did lengthening the butyryl chain from 4 to 10 carbons. Not only did Ph TXs inhibit different subtypes of glutamate receptors, including the mammalian N‐methyl‐D‐aspartate receptor, but also nicotinic receptors of insects and vertebrates. Because of this low selectively, and the hydrophilicity of the derivatives tested, which interferes with their penetration to the target receptor, these compounds cannot be used as insecticides. Nevertheless, the insect skeletal muscle glutamate receptor is a viable target for selective insecticides and major changes in Ph TX structure may possibly produce derivatives that can be potential insecticides. © 1993 Wil

ISSN:0739-4462    

DOI:10.1002/arch.940220105

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

摘要:

AbstractThe pharmacological uniqueness of the insect sodium channels is indicated by their ability to bind the excitatory and depressant insect selective neurotoxins derived from scorpion venom. The latter were shown to bind and modify sodium conductance exclusively in insect neuronal membranes. The insect sodium channel polypeptides were identified by immunoprecipitation using site‐directed antibody, anti SP19 (corresponding to a highly conserved segment in the sodium channel α subunits), followed by radiophosphorylation and SDS‐PAGE autoradiography. Sodium channel polypeptide in the central nervous system (CNS) of insects belonging to four distinct orders (Orthoptera, Dyctioptera, Diptera, and Lepidoptera) were shown to (1) serve as substrates for phosphorylation by cAMP‐dependent protein kinase; (2) be devoid of disulfide linkage to smaller subunits unlike sodium channels in vertebrate CNS; (3) be glycoproteins as demonstrated by endoglycosidase F treatment and binding to lectins; and (4) reveal a diversity with regard to their apparent molecular mass (Mr240,000–280,000) and partial peptide maps. The locust sodium channels were functionally solubilized (monitored by [3H]saxitoxin (STX) binding) by 1% cholate, 0.2% Triton X‐100, and 0.22% phosphatidylcholine. About 40% of STX binding activity was recovered in the solubilized fraction without affecting affinity (Kd = 0.5 nM). The time and temperature dependent lability of STX binding activity, in the solubilized fraction, was prevented by 20 nM STX. Partial purification of the insect sodium channel by an anion exchanger yielded 20% recovery and a 3.5 times increase in specific STX binding activity. The presence of a radiophosphorylated 245,000 α‐subunit band coincided with the STX binding activity during purification. In sum, the above information concerning the solubilization and characterization of the insect sodium channel will pave the way to the molecular identification of the receptor sites of the insect selective neurotoxins. © 1993 W

ISSN:0739-4462    

DOI:10.1002/arch.940220106

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

摘要:

AbstractThe present study examines the similarity in the symptoms and binding properties between the depressant and excitatory insect‐selective neurotoxins, derived from scorpion venom. A comparison of their primary structures and neuromuscular effects is presented. A new depressant toxin (LqhlT2) was purified from the venom of the scorpionLeiurus quinquestriatus hebraeus. The effects of this toxin on a prepupal housefly neuromuscular preparation mimic its effects on the intact insect, i.e, a brief period of repetitive bursts of regular junction potentials (JPs) is followed by reduced amplitude JPs ending with a block of the neuromuscular transmission. “Loose” patch clamp recordings indicate that the repetitive activity has a presynaptic origin (the motor nerve) and resembles the effect of the excitatory toxin AalT. The final synaptic block is supposed to be the end result of neuronal membrane depolarization. Such an effect is not caused by an excitatory toxin, which induces long ‘trains’ of repetitive firing. The amino acid sequences of three depressant toxins were determined by automatic Edman degradation indicating a high degree of sequence homology. This conservation differs from those of other groups of scorpion toxins. The opposing pharmacological effects of depressant toxins are discussed in light of the above neuromuscular effects and sequence analysis. A genetic approach in the study of the structure‐function relationships of the depressant toxins was initiated by isolating cDNA clones encoding the LqhiT2 and BjlT2 toxins. Their sequence analysis revealed the precursor form of these toxins: A 21 amino acid residue signal peptide followed by a 61 amino acid region of the mature toxin, and three additional amino acids at the carboxy terminus. © 1993 Wil

ISSN:0739-4462    

DOI:10.1002/arch.940220107

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

摘要:

AbstractIn the current molecular model for insect olfaction, pheromones are recognized in a minimum‐energy conformation by specific receptor proteins in a dendritic membrane following their binding‐protein‐mediated transit through the extracellula sensory lymph. Binding to the receptor protein then triggers a G‐protein‐linked phospholipase C, which releases a short pulse of the second messenger inositol 1,4,5‐trisphate (IP3). IP3may act via its receptor to mobilize Ca+ +ions, eventually leading to a transmembrane ion current; alternatively, IP3may directly gate the ion channel. To understand this process, we have synthesized photoaffinity labels for the pheromone receptor sites and for the IP3receptor sites. The latter probe, [125I]‐ASA‐IP3, is now being employed in joint projects to identify membrane IP3receptors in the rat brain, locust brain, rat olfactory cilia, catfish olfactory cilia, and in cockroach and moth sensilla. Fluorine‐substituted pheromone analogs have also been synthesized as probes of receptor site hydrophobicity. The rationale for this approach is presented, and biological studies with selectively‐fluorinated analogs of (Z)‐5‐decenyl acetate (Z5‐10:Ac), (Z)‐7‐dodecenyl acetate (Z7‐12:Ac), (Z)‐9‐dodecenyl acetate (Z9‐12:Ac), (Z)‐9‐tetradecenyl acetate (Z9‐14:Ac), (Z)‐11‐hexadecenal (Z11‐16:Al), and several functional group derivatives for a number of economically important m

ISSN:0739-4462    

DOI:10.1002/arch.940220108

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

摘要:

AbstractNew approaches to the development of insect control agents have been revealed through the molecular description of neuropeptides, their biogenesis, action, and degradation. Prerequisite to the exploitation of a neuropeptide as a lead to control agent development is a thorough understanding of the biochemistry of the neuropeptide and appreciation of its physiological impact. Reliable bioassays must be coupled with advanced biochemical and molecular genetic technologies to overcome limitations imposed by the typically low endogenous levels of individual neuropeptides. Purification, amino acid sequencing, and gene cloning provide the molecular tools necessary for studies on neuropeptide synthesis, processing, secretion, receptor binding, and inactivation. Each of these areas consists of a number of amino acid sequence‐, and enzyme‐dependent steps which may be considered as targets for the development of highly specific control agents. These agents will include antagonists and superagonists, peptidomimetics, recombinant peptides delivered through the baculovirus technology, receptor blockers, and enzyme inhibitors. © 1993 Wiley‐Lis

ISSN:0739-4462    

DOI:10.1002/arch.940220109

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

摘要:

AbstractAntibody against FMRFamide reacts with the stomatogastric innervation and with the midgut endocrine cells in the representatives of most insect orders. The innervation was not revealed in Homoptera, Heteroptera, and Hymenoptera, and the endocrine cells were not recognized in aphids. Other insects exhibited FMRF‐amide positive endocrine cells of both open and closed types. The cells are mostly single, rarely grouped, and are distributed unequally in different midgut regions; some of the cells project cytoplasmic extensions indicative of a paracrine function. Investigations onGalleriarevealed that the gut innervation persists during midgut reconstruction in the course of metamorphosis. The endocrine cells are sloughed off into the new gut lumen, but there they maintain their antigenic properties until a new population of endocrine cells becomes detectable.Antisera to most mammalian gastroenteropancreatic peptides react specifically with the innervation and/or the endocrine cells of insect midgut; only antisera to bombesin, neurotensin, secretin, motilin, and insulin failed to react. All insects seem to contain antigens that can be detected with antisera to pancreatic polypeptide, FMRFamide, enkephalins, and vasopressins. Stomatogastric innervation and the endocrine cells of some lepidopterans also possess allatotropinand diuretic hormone‐like antigens; stomatogastric ganglia, in particular, a prothoracicotropic hormone‐like antigen. © 1993 Wiley‐L

ISSN:0739-4462    

DOI:10.1002/arch.940220110

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

摘要:

AbstractLocusta migratoriadiuretic hormone (Lom‐DH) is a linear 46 amino acid peptide, amidated at the C‐terminus. The purified native hormone and synthetic peptide similarly stimulate the secretion of cAMP by isolated Malpighian tubules in vitro in a dose‐dependent manner. The degree of stimulated fluid secretion in the isolated Malpighian tubule assay is similar for the native and synthetic hormone. Based on ELISA assay, Lom‐DH is mainly found in the storage lobes of the corpora cardiaca (∼ 12 pmol per gland pair) and to a small extent in the brain. Marginal amounts can be detected in the hemolymph. No detectable amounts were found in the glandular lobes of the corpora cardiaca or in the corpora allata or subesophageal ganglion. © 1993 Wiley

ISSN:0739-4462    

DOI:10.1002/arch.940220111

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY