A membrane-based cattle insecticide eartag

Insecticide-releasing eartags for cattle have proved valuable for controlling ectoparasites, such as horn flies and face flies, resulting in increased meat or milk production. Most currently available eartags, however, have a monolithic structure, which results in continuously decreasing insecticide release rates, a limited duration of efficacy, and possibly greater insect resistance. To solve these problems, a membrane-based eartag was developed that releases insecticide at a constant rate for nearly the entire duration of release. The insecticide release is determined by the permeability and geometry of the membrane and can be adjusted by changing these parameters. Membrane-based tags containing permethrin and piperonyl butoxide released each component at a constant rate in both laboratory and field tests. The constant release rate resulted in a much longer duration of efficacy against horn flies than monolithic tags exhibit. In field tests, these membrane-based tags released at least 95% of the insecticide at a constant rate, which may prove valuable in reducing insect resistance and increasing duration of efficacy.     

β-BLOCKERS and BLOOD SUGARS

Catecholamines mediate sympathetic activity throughout the body and, since carbohydrate metabolism is under sympathetic control they influence the availability of glucose for utilization as energy. They achieve this by modifying the response to a raised blood sugar by either suppressing insulin release, an a-receptor stimulant effect, or by promoting insulin release, probably a β₂ stimulant effect. When the blood sugar falls, catecholamines initiate metabolic processes which increase blood glucose and restore it to normal. This is also thought to be a β₂-receptor stimulant effect. It would therefore be expected that drugs which blocked β-adrenoreceptors would interfere with both the insulin release which occurs during hyperglycaemia and the glycogenosis and gluconeogenesis which occur in response to a fall in blood sugar. Both of these actions have been demonstrated in acute studies usually in volunteers. The clinical relevance of these effects remains to be determined though some guidelines can be suggested on the basis of data currently available, and are given at the end of the paper.     

Predicting outcome using butyrylcholinesterase activity in organophosphorus pesticide self-poisoning

BACKGROUND: The usefulness of a low butyrylcholinesterase (BuChE) activity on admission for predicting severity in acute organophosphorus (OP) insecticide poisoning has long been debated. Previous studies have been confounded by the inclusion of multiple insecticides with differing inhibitory kinetics. AIM: We aimed to assess the usefulness of admission BuChE activity, together with plasma OP concentration, for predicting death with two specific organophosphorus insecticides. DESIGN: A prospective cohort of self-poisoned patients. METHODS: We prospectively studied 91 and 208 patients with proven dimethoate or chlorpyrifos self-poisoning treated using a standard protocol. Plasma butyrylcholinesterase activity and OP concentration were measured on admission and clinical outcomes recorded. RESULTS: The usefulness of a plasma BuChE activity <600 mU/ml on admission varied markedly--while highly sensitive in chlorpyrifos poisoning (sensitivity 11/11 deaths; 100%, 95% CI 71.5-100), its specificity was only 17.7% (12.6-23.7). In contrast, while poorly sensitive for deaths in dimethoate poisoning [12/25 patients; 48%, (27.9-68.7)] it was reasonably specific [86.4% (75.7-93.6)]. A high OP concentration on admission was associated with worse outcome; however, a clear threshold concentration was only present for dimethoate poisoning. CONCLUSION: Plasma BuChE activity on admission can provide useful information; however, it must be interpreted carefully. It can only be used to predict death when the insecticide ingested is known and its sensitivity and specificity for that insecticide has been studied. Plasma concentration of some OP insecticides predicts outcome. The development of rapid bedside tests for OP detection may aid early assessment of severity.     

BACTERIOPHAGE ISOLATED FROM THE COMMON HOUSE FLY (MUSCA DOMESTICA)

1. Bacteriophage active against four species of bacteria was found in a salt solution extract of house flies. 2. A growth-inhibiting principle, not bacteriophage, active against four other species of bacteria was found to be present in the same extract. 3. An attempt to secure streptococcus bacteriophage by feeding to flies a streptococcus susceptible to the inhibitor but not to the bacteriophage of this filtrate was unsuccessful, indicating that the two activities are quite unrelated.     

Conservation of cyclodiene insecticide resistance-associated mutations in insects

Cyclodiene insecticide resistance has accounted for over 60% of reported cases of insecticide resistance. in Drosophila melanogaster resistance is associated with a single base pair substitution in the GABA receptor/chloride ion channel gene Rdl. This substitution predicts the replacement of an alanine with a serine in the second membrane spanning domain, the region thought to line the chloride ion channel pore. Here we report, via the use of degenerate primers in the polymerase chain reaction, that precisely the same substitution is present in three pests from three different insect orders: the house fiy (Diptera), red flour beetle (Coleoptera) and American cockroach (Dicty-optera). This finding suggests that there are a limited number of mutations that can confer resistance to cyclodienes, putative channel blockers, while still maintaining adequate chloride ion channel function. The conservation of the resistance-associated mutation between Drosophila and pest insects directly validates the approach of using this insect as a model system for isolating and studying resistance genes. The importance of single base pair substitutions in the evolution of pesticide resistance and in the design of molecular monitoring techniques is discussed.     

Release of testosterone from an osmotic pump tablet utilizing (SBE)7m-beta-cyclodextrin as both a solubilizing and an osmotic pump agent.

A controlled porosity osmotic pump system for poorly water soluble drugs has been developed using sulfobutyl ether-beta-cyclodextrin sodium salt, (SBE)7m-beta-CD, which can act as both a solubilizing and an osmotic agent. The release of testosterone, a poorly water soluble drug (0.039 mg/ml at 37 degrees C), was evaluated using a new model device. The effect of (SBE)7m-beta-CD as the solubilizing and osmotic pump agent was compared with hydroxypropyl-beta-cyclodextrin (HP-beta-CD), a neutral cyclodextrin, and a sugar mixture (osmotic agent only). Testosterone release from the device was significantly faster with (SBE)7m-beta-CD than with HP-beta-CD or the sugar mixture. The solubility of testosterone in the device increased to 76.7 mg/ml through complexation with (SBE)7m-beta-CD in the imbibed water. It appears that testosterone release from the device in the presence of (SBE)7m-beta-CD was mainly due to osmotic pumping while for HP-beta-CD the major contribution appears to be due to diffusion. In the case of the sugar mixture, testosterone was poorly released, presumably due to the absence of a solubilizer. Therefore, it was concluded that (SBE)7m-beta-CD provides novel properties for the development of controlled- porosity osmotic pump tablets for poor solubility drugs.     

Insect glutathione transferases and insecticide resistance

Glutathione transferases (GSTs) are a diverse family of enzymes found ubiquitously in aerobic organisms. They play a central role in the detoxification of both endogenous and xenobiotic compounds and are also involved in intracellular transport, biosynthesis of hormones and protection against oxidative stress. Interest in insect GSTs has primarily focused on their role in insecticide resistance. GSTs can metabolize insecticides by facilitating their reductive dehydrochlorination or by conjugation reactions with reduced glutathione, to produce water-soluble metabolites that are more readily excreted. In addition, they contribute to the removal of toxic oxygen free radical species produced through the action of pesticides. Annotation of the Anopheles gambiae and Drosophila melanogaster genomes has revealed the full extent of this enzyme family in insects. This mini review describes the insect GST enzyme family, focusing specifically on their role in conferring insecticide resistance.     

Fipronil is a potent open channel blocker of glutamate-activated chloride channels in cockroach neurons

Fipronil, a phenylpyrazole insecticide, displays high insecticidal activity and reduced mammalian toxicity. To better elucidate the mechanism of its selective toxicity between insects and mammals and activity against dieldrin-resistant insects, we studied fipronil action on glutamate-gated chloride channels (GluCls), unique invertebrate ligand-gated chloride channels, in cockroach thoracic ganglion neurons, using the whole-cell patch clamp technique. Glutamate evoked two types of chloride currents, a desensitizing current and a nondesensitizing current. Fipronil differentially inhibited these two types of currents with different potencies and with different rates of reversibility. Fipronil inhibited the desensitizing and nondesensitizing GluCls with IC50 values of 801 and 10 nM, respectively. Kinetic analysis revealed that fipronil blocks required channel opening. Recovery of the desensitizing current from fipronil block required channel opening, whereas recovery of nondesensitizing current from block was independent of channel opening. The high potency of fipronil against the nondesensitizing current was due to a slow unblocking rate constant. In addition, when the nondesensitizing GluCls were occupied by picrotoxinin, the receptors became less sensitive to fipronil block. It is concluded that GluCls are a critical target for fipronil, especially for the selective toxicity between mammals and insects, and that fipronil block of GluCls may play a role in the lack of the cross-resistance with dieldrin.     

The survival of poliomyelitis and Coxsackie viruses following their ingestion by flies

Poliomyelitis virus and Coxsackie (or C) virus were quantitatively fed to blowflies, Phormia regina and Phaenicia sericata, and to houseflies, Musca domestica. Naturally infectious human stools were the source of virus. Poliomyelitis virus can be almost quantitatively recovered from flies and from their excreta collected over a period of several days following the feeding. C virus can also be recovered but in lesser yields. No conclusive evidence for virus multiplication in these laboratory-bred insects was obtained. Poliomyelitis virus from human sources could be detected in flies between the 5th and 17th day and in the excreta between the 4th and 10th day. Murine-adapted strains of poliomyelitis virus and murine encephalomyelitis virus could not be detected beyond the 5th day, even though comparable amounts of virus were fed. The persistence of C virus excretion (2 to 12 days) varied directly with the amount of virus fed. Poliomyelitis virus, as present in human stools, survived drying and storage at room temperature for at least 3 days and at 4° for 3 weeks. C virus from human stools under the same circumstances was detected for 15 days at room temperature (with marked drop in titer after the 3rd day) and for 21 days at 4° with little loss in titer. When stool samples were fed to flies and the dried excreta of the insects examined, it was found that (a) poliomyelitis virus persisted for at least 1 to 2 days at room temperature and for 3 to 4 days at 4°, and (b) C virus persisted for 1 day at room temperature and for 5 days at 4°. Poliomyelitis virus could be carried through only two serial passages in adult flies. Flies emerging from maggots fed virus were free from the agent.     

Mycetome endosymbionts of tsetse flies constitute a distinct lineage related to Enterobacteriaceae

Tsetse flies (Diptera: Glossinidae) harbour two morphologically different endosymbionts intracellularly associated with gut tissue: a primary (P) and a secondary (S) organism. The P-endosymbiont is a gram-negative rod, 8–10 μm in size, and resides intracellularly within specialized cells, mycetocytes which are organized into an organelle (mycetome), in the anterior portion of the gut. The S-endosymbiont is a smaller (1–2 μm) gram-negative rod and is harboured in the epithelial sheath cells in midgut. Phylogenetic characterization of S-endosymbionts from taxonomically distant insects including tsetse flies has shown that they are related to the free-living bacterium, Escherichia coli , and are members of the family Enterobacteriaceae within the γ-3 subdivision of Proteobacteria. In this study, a polymerase chain reaction (PCR) based assay was designed utilizing the conserved sequences of 16S rDNA in order to phylogenetically characterize the mycetome-associated P-endosymbionts directly from tsetse mycetome tissue. Analysis from five species of flies representing the three major subgenera of genus Glossina indicates that P-endosymbionts constitute a distinct lineage within the γ-3 subdivision of Proteobacteria. Mycetome endosymbiont phylogeny appears to parallel the classic taxonomic assignments independently developed for their insect host species. This suggests an ancient association for this symbiosis, which may have subsequently radiated with time, giving rise to the current species of tsetse flies and their modern-day endosymbionts. Based on endosymbiont phylogeny, the fusca flies constitute the most ancient subgenus, followed by the morsitans and palpalis groups.     

A morphine-triggered delivery system useful in the treatment of heroin addiction

The ultimate objective of this work is to develop a device that can be triggered by morphine to release naltrexone. Two device configurations are described. In one configuration, naltrexone is dispersed in cellulose acetate phthalate microspheres which are then spray-coated with trilaurin. In the other configuration, naltrexone is dispersed in an n-octyl half ester of methyl vinyl ether and maleic anhydride copolymer and the mixture fabricated into a disk which is then coated with trilaurin. The microspheres are designed to release naltrexone abruptly while the disks are designed to release naltrexone at a constant rate over a two week period. The microspheres, or the disk along with a reversibly inactivated lipase are placed inside a semipermeable membrane that allows free passage of morphine and naltrexone but excludes the higher molecular weight components of the device. Reversible inactivation of lipase is achieved by covalent attachment of morphine and complexing with morphine antibody. Activation of the device occurs by diffusion of morphine into the device and displacing the lipase-morphine conjugate from the antibody. The activated lipase then removes the trilaurin protective coating, thus triggering naltrexone release.     

Modeling and analysis of dispersed-drug release into a finite medium from sphere ensembles with a boundary layer.

Mathematical models were developed and analytical solutions were derived for describing kinetics of dispersed-drug release into a finite external medium from multi-particulate systems, such as ensembles of matrix spheres and microcapsules with a diffusion boundary layer. The solutions can be used to compute profiles of the moving boundary of a dispersed drug and the amount of drug released for multiparticulate ensembles with various ratios of initial drug loading (C(0)) to drug solubility (C(s)) in a finite to infinite medium. They are also applicable to a single sphere without a boundary layer in a perfect sink. The determinants of release kinetics, such as the liquid volume, the initial drug loading, the boundary layer thickness, and the number of spheres in a population, were analyzed using the derived solutions. The effect of coating thickness and material on the release profiles of microcapsules was studied as well. Criteria were established for finding the conditions when drug release would stall due to saturation of the medium, which can be used to determine suitable liquid volume and time for refreshing the medium.     

Discovery of genes related to formothion resistance in oriental fruit fly (Bactrocera dorsalis) by a constrained functional genomics analysis

Artificial selection can provide insights into how insecticide resistance mechanisms evolve in populations. The underlying basis of such phenomena can involve complex interactions of multiple genes, and the resolution of this complexity first necessitates confirmation that specific genes are involved in resistance mechanisms. Here, we used a novel approach invoking a constrained RNA sequencing analysis to refine the discovery of specific genes involved in insecticide resistance. Specifically, for gene discovery, an additional constraint was added to the traditional comparisons of susceptible vs. resistant flies by the incorporation of a line in which insecticide susceptibility was ‘recovered’ within a resistant line by the removal of insecticide stress. In our analysis, the criterion for the classification of any gene as related to insecticide resistance was based on evidence for differential expression in the resistant line as compared with both the susceptible and recovered lines. The incorporation of this additional constraint reduced the number of differentially expressed genes putatively involved in resistance to 464, compared with more than 1000 that had been identified previously using this same species. In addition, our analysis identified several key genes involved in metabolic detoxification processes that showed up‐regulated expression. Furthermore, the involvement of acetylcholinesterase, a known target for modification in insecticide resistance, was associated with three key nonsynonymous amino acid substitutions within our data. In conclusion, the incorporation of an additional constraint using a ‘recovered’ line for gene discovery provides a higher degree of confidence in genes identified to be involved in insecticide resistance phenomena.     

Glycosyltransferases: the multifaceted enzymatic regulator in insects

Glycosyltransferases (GTs) catalyse the reaction of glyco-conjugation of various biomolecules by transferring the saccharide moieties from an activated nucleotide sugar to nucleophilic glycosyl acceptor. In insects, GTs show diverse temporal and site-specific expression patterns and thus play significant roles in forming the complex biomolecular structures that are necessary for insect survival, growth and development. Several insects exhibit GT-mediated detoxification as a key defence strategy against plant allelochemicals and xenobiotic compounds, as well as a mechanism for pesticide cross-resistance. Also, these enzymes act as crucial effectors and modulators in various developmental processes of insects such as eye development, UV shielding, cuticle formation, epithelial development and other specialized functions. Furthermore, many of the known insect GTs have been shown to play a fundamental role in other physiological processes like body pigmentation, cuticular tanning, chemosensation and stress response. This review provides a detailed overview of the multifaceted functionality of insect GTs and summarizes numerous case studies associated with it.     

In vitro and in vivo release of levonorgestrel from poly(ortho esters): I. Linear polymers

The in vitro and in vivo release of levonorgestrel from linear poly(ortho ester) cylindrical devices containing 30 wt.% drug and 2 wt.% calcium lactate was studied. The in vitro release rate was a relatively constant 20 μg/day for about one year at which time the experiment was discontinued. The in vivo release rate in rabbits was about 33 μg/day. In both studies rate of polymer erosion is about the same and significantly leads rate of drug release. Therefore, factors other than polymer erosion determine rate of drug release. SEM studies of devices explanted from rabbits show the formation of a foamed drug layer surrounding the device. The formation of this layer is caused by polymer erosion around undissolved drug. Rate of drug delivery from the device is controlled by dissolution of levonorgestrel from the outside of the foamed drug layer. The higher in vivo release is attributed to the presence of lipophilic species that facilitate dissolution of levonorgestrel.     

IgG antibodies against polyisocyanates in car painters

A group of thirty car painters exposed to vapours and aerosols of paint containing prepolymer andmonomer of hexametylene diisocyanate (HDI) was investigated. Specific antibodies against monomer HDI and prepolymerized HDI were analysed with RAST (IgE) and ELISA (IgG) assays after conjugation of the haptens with human serum albumin. There was no significant increase of serum IgG antibodies against HDI monomer, nor of specific IgE antibodies against HDI monomer or prepolymer. Specific IgG antibodies against prepolymerized HDI were significantly increased, as compared with non-exposed referents (medians 0.11 vs 0.03 absorbance (A]. Six car painters were found to have specific IgG antibodies of subclass 4 against HDI prepolymer, four also against HDI monomer. This shows an association between exposure and specific IgG antibodies. Thirteen subjects had suffered symptoms of rhinitis and/or conjunctivitis, and ten had symptoms from the bronchi (two asthma). There was no significant association between symptoms and levels of specific antibodies. Most of the symptoms were slight and unspecific, probably due to irritative effects of the exposure.     

Superfamily of genes encoding G protein‐coupled receptors in the diamondback moth Plutella xylostella (Lepidoptera: Plutellidae)

G protein‐coupled receptors (GPCRs) are the largest and most versatile superfamily of cell membrane proteins, which mediate various physiological processes including reproduction, development and behaviour. The diamondback moth, Plutella xylostella (Lepidoptera: Plutellidae), is one of the most notorious insect pests, preferentially feeding on cruciferous plants. P. xylostella is not only one of the world's most widespread lepidopteran insects, but has also developed resistance to nearly all classes of insecticides. Although the mechanisms of insecticide resistance have been studied extensively in many insect species, few investigations have been carried out on GPCRs in P. xylostella. In the present study, we identified 95 putative GPCRs in the P. xylostella genome. The identified GPCRs were compared with their homologues in Bombyx mori and Drosophila melanogaster. Our results suggest that GPCRs in different insect species may have evolved by a birth‐and‐death process. One of the differences among compared insects is the duplication of short neuropeptide F receptor and adipokinetic hormone receptors in P. xylostella and B. mori. Another divergence is the decrease in quantity and diversity of the stress‐tolerance gene, Mth, in P. xylostella. The evolution by the birth‐and‐death process is probably involved in adaptation to the feeding behaviour, reproduction and stress responses of P. xylostella. Some of the genes identified in the present study could be potential targets for the development of novel pesticides.     

苹果泥预防和改善管饲患者腹泻的临床观察

目的探讨苹果泥预防管饲患者腹泻及改善腹泻症状的效果。方法将52例管饲患者按入院顺序随机分为观察组和对照组各26例,观察组行常规管饲喂养加苹果泥管饲喂入,对照组行常规管饲喂养加米汤。结果观察组发生腹泻4例(15.3%),对照组11例(42.3%),两组比较,差异有统计学意义(P<0.05)。且观察组腹泻持续时间和每日腹泻次数均低于对照组(P<0.01,P<0.05)。结论苹果泥可预防和减少管饲患者腹泻的发生率并改善其腹泻症状。