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At least 865 records · Page 48Linked to original sources
PubMed2006

Comparison of basophil activation tests using CD63 or CD203c expression in patients with insect venom allergy.

BACKGROUND: Flow cytometric basophil activation tests have been developed as cellular tests for in vitro diagnosis of IgE-mediated reactions. Different activation markers (CD63 or CD203c) with distinct ways of regulation have been used after stimulation with various allergens. OBJECTIVE: It was the aim of the present study to compare basophil activation tests by measuring both CD63 and CD203c upregulation in patients with insect venom allergy. MATERIALS AND METHODS: 43 patients with a history of insect venom anaphylaxis were examined. A careful allergy history was taken, and skin tests and determination of specific IgE-antibodies were performed. Basophil activation tests (BAT) using CD63 or CD203c expression were done after stimulation with different concentrations of bee and wasp venom extracts. 25 healthy subjects with negative history of insect venom allergy were studied as controls. RESULTS: The CD203c protocol showed a slightly higher sensitivity than the CD63 protocol (97% vs. 89%) with regard to patients' history. The magnitude of basophil response was higher with CD203c in comparison to CD63 for both insect venoms. Specificity was 100% for the CD63 protocol and 89% for the CD203c protocol with regard to controls with negative history and negative RAST. CONCLUSION: These results support the reliability of basophil activation tests using either CD63 or CD203c as cellular tests in the in vitro diagnosis of patients with bee or wasp venom allergy with a slightly higher sensitivity for the CD203c protocol.

Allergens↗
PubMed1997

Molecular cloning and functional expression of an insect high-affinity Na+-dependent glutamate transporter.

Excitatory amino acid transporters in the central and peripheral nervous systems of insects are thought to assist in maintaining glutamate concentrations in the resting synapse below the activation threshold of glutamate receptors. We have isolated a cDNA from the caterpillar Trichoplusia ni which encodes a high-affinity Na+-dependent glutamate transporter, designated TrnEAAT1. The deduced amino acid sequence shows strong identity with known members of the vertebrate Na+- and K+-dependent amino acid transporter family. Expression of the insect transporter mRNA was predominantly localized in the caterpillar brain. The function of the TrnEAAT1 protein was analyzed in cultured insect cells using a baculovirus expression system. Cells infected with the recombinant virus were found to exhibit a 50-fold increase in ability to accumulate labeled L-glutamate compared to mock-infected cultures, and this activity was shown to be Na+-dependent. Transport activity was further demonstrated by chromatographic identification of various glutamate analogues accumulated by infected cells. Various glutamate uptake inhibitors were used to outline the pharmacological properties of the cloned transporter and to compare it with known mammalian transporters. Despite the significant differences between insect and vertebrate physiology, the characteristics of the respective transporters were found to be remarkably similar.

ATP-Binding Cassette Transporters↗
PubMed2006

Spillover edge effects: the dispersal of agriculturally subsidized insect natural enemies into adjacent natural habitats.

The cross-edge spillover of subsidized predators from anthropogenic to natural habitats is an important process affecting wildlife, especially bird, populations in fragmented landscapes. However, the importance of the spillover of insect natural enemies from agricultural to natural habitats is unknown, despite the abundance of studies examining movement in the opposite direction. Here, we synthesize studies from various ecological sub-disciplines to suggest that spillover of agriculturally subsidized insect natural enemies may be an important process affecting prey populations in natural habitat fragments. This contention is based on (1) the ubiquity of agricultural-natural edges in human dominated landscapes; (2) the substantial literature illustrating that crop and natural habitats share important insect predators; and (3) the clear importance of the landscape matrix, specifically distance to ecological edges, in influencing predator impacts in agroecosystems. Further support emerges from theory on the importance of cross-boundary subsidies for within site consumer-resource dynamics. In particular, high productivity and temporally variable resource abundance in agricultural systems are predicted to result in strong spillover effects. More empirical work examining the prevalence and significance of such natural enemy spillover will be critical to a broader understanding of fragmentation impacts on insect predator-prey interactions.

Agriculture↗
PubMed1974

Insect control of the future: operational and policy aspects.

uman and insect population control have several features in common, all of them indicating that the lag times in converting laboratory discoveries into practical agents are increasing greatly and that ROI calculations are becoming more and more significant in decisions related to the development of new agents. ROI calculations are particularly important in the field of insect control because, by being more specific, the agents of the future are likely to cover smaller markets. Several recommendations for stimulating the development of new methods of insect control are proposed which are addressed primarily to policy-makers. If they are not implemented, then our suggestions should at least stimulate others to make alternative proposals. If neither event occurs, then it is unlikely that there will be any fundamentally new approaches to practical insect control in this decade; a similar prediction (6) that was made 4 years ago in the field of human birth control is rapidly proving to be correct.

Animals↗
PubMed1988

Expression and complex formation of simian virus 40 large T antigen and mouse p53 in insect cells.

Recombinant baculoviruses were constructed which express simian virus 40 large T antigen (SVT-Ag) or murine p53 to high levels in infected insect cells. Characterization of the expressed proteins revealed that they display many properties of the corresponding mammalian-derived proteins. Both proteins are of wild-type size, localize to the nucleus, are recognized by several SVT-Ag- or p53-specific monoclonal antibodies, and are phosphorylated in this system. Complexes are formed between baculovirus-derived SVT-Ag and p53 after coinfection of insect cells with both recombinant viruses. After infection of insect cells with either virus individually, each protein can self-associate to form a variety of oligomeric species. Pulse-chase experiments indicated that both SVT-Ag and p53 are highly stable in insect cells, even in the absence of complex formation.

Animals↗
PubMed1990

Regulation of pp60c-src and its interaction with polyomavirus middle T antigen in insect cells.

High yields of soluble, biologically active pp60c-src and middle t antigen (MTAg) of polyomavirus were produced in insect cells, using a baculovirus expression system. In mammalian cells, pp60c-src undergoes a regulatory phosphorylation on Tyr-527 in vivo and is autophosphorylated on Tyr-416 in vitro. In insect cells, pp60c-src was phosphorylated primarily on Tyr-416, although Tyr-527 was detectable at a low level. A kinase-negative mutant of pp60c-src was not phosphorylated on either Tyr-527 or Tyr-416 in insect cells and thus is an excellent biochemical reagent to search for the regulatory kinase that usually phosphorylates Tyr-527 in mammalian cells. MTAg synthesized in insect cells was not phosphorylated on tyrosine residues in vivo or in vitro, suggesting that it did not associate with any endogenous tyrosine kinases. However, MTAg isolated from cells coinfected with viruses encoding both MTAg and pp60c-src was phosphorylated on tyrosine residues both in vivo and in vitro.

Animals↗
PubMed1990

Neutralization of poliovirus by cell receptors expressed in insect cells.

To examine the interaction of the poliovirus receptor (PVR) with virus and the role of the PVR in virus entry, the PVR was expressed in insect cells. Poliovirus bound to insect cells infected with a recombinant baculovirus (AcPVR) carrying cDNA encoding the PVR. Antibodies raised against PVR expressed in bacteria immunoprecipitated a 67-kilodalton polypeptide from cytoplasmic extracts of AcPVR-infected cells. Treatment of AcPVR-infected cells with tunicamycin revealed that the PVR is a glycoprotein containing N-glycosidic linkages and that carbohydrate accounts for nearly 50% of its molecular weight as estimated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. When PVR was solubilized from AcPVR-infected insect cells and incubated with poliovirus, viral infectivity was neutralized. Sedimentation analysis revealed that irreversibly altered 135S particles were formed after incubation of poliovirus at 37 degrees C with solubilized extracts of AcPVR-infected insect cells. These results demonstrate that poliovirus eclipse may result from interaction with the cell receptor at neutral pH in the absence of membranes and suggest that soluble receptors may be effective antiviral agents against picornaviruses.

Animals↗
PubMed1990

Characterization and purification of human fos protein generated in insect cells with a baculoviral expression vector.

We generated recombinant baculoviruses that contained the human fos gene and that, upon infection of insect cells, synthesized fos protein. The quantity of fos protein produced was at least 10 to 20 times higher than that observed in any mammalian cells reported so far. The fos protein made in insect cells manifested most of the characteristics of mammalian fos protein, which include (i) 55-kilodalton size, (ii) nuclear localization, (iii) phosphoesterification at serine residues, (iv) identical 35S tryptic peptide maps, (v) ability to make heterodimers with the nuclear jun oncoprotein, and (vi) cooperation with the jun protein to bind to a 12-O-tetradecanoyl-phorbol-13-acetate-responsive element. A 100- to 150-fold purification of the fos protein from infected insect cells was achieved in a single step by immunoaffinity chromatography. Availability of authentic fos protein made by baculoviral vectors in insect cells should allow a more rigorous analysis of its biochemical and biological properties.

Amino Acids↗
PubMed1994

Apparent functional role for a cysteine-rich polydnavirus protein in suppression of the insect cellular immune response.

Polydnaviruses suppress the cellular immune response and inhibit growth and development in their lepidopteran host, allowing survival of their endoparasitic hymenopteran host. Characterization of genes disrupting insect physiological systems is a major objective in the study of polydnaviruses. Recently, a cysteine-rich gene family encoding a motif composed of invariable cysteine residues flanking hypervariable intercysteine amino acids was described (S.D. Dib-Hajj, B.A. Webb, and M.D. Summers, Proc. Natl. Acad. Sci. USA 90:3765-3769, 1993). They noted similarities to the positive selection pressure for mutations within the vertebrate major histocompatibility complex (MHC) class II genes and speculated that this class of polydnavirus genes may target and disrupt the insect immune system. To study the functional activity of this family of predicted cysteine-rich proteins, the VHv1.1 gene product was produced from bacterial and baculovirus expression systems. Polyclonal antiserum produced from the bacterial fusion protein reacted with a 30-kDa protein from hemocytes, cell-free plasma, and fat body of parasitized larvae. Immunofluorescence analysis of hemocytes from parasitized insects detected the 30-kDa protein bound to granulocytes and plasmacytes. To assay the functional activity of the 30-kDa VHv1.1 protein, a recombinant baculovirus was constructed allowing in vivo expression of the 30-kDa polydnavirus protein from infected insects. Expression of the VHv1.1 protein from the baculovirus system reduced the encapsulation response to washed wasp eggs relative to controls. The experimental evidence demonstrates that Campoletis sonorensis polydnavirus-infected cells secrete VHv1.1 into the hemolymph, where it binds to hemocytes and is associated with the inhibition of the cellular immune response.

Animals↗
PubMed1999

Insect P450 enzymes.

The P450 enzymes (mixed function oxidases, cytochrome P450 monooxygenases), a diverse class of enzymes found in virtually all insect tissues, fulfill many important tasks, from the synthesis and degradation of ecdysteroids and juvenile hormones to the metabolism of foreign chemicals of natural or synthetic origin. This diversity in function is achieved by a diversity in structure, as insect genomes probably carry about 100 P450 genes, sometimes arranged in clusters, and each coding for a different P450 enzyme. Both microsomal and mitochondrial P450s are present in insects and are best studied by heterologous expression of their cDNA and reconstitution of purified enzymes. P450 genes are under complex regulation, with induction playing a central role in the adaptation to plant chemicals and regulatory mutations playing a central role in insecticide resistance. Polymorphisms in induction or constitutive expression allow insects to scan their P450 gene repertoire for the appropriate response to chemical insults, and these evolutionary pressures in turn maintain P450 diversity.

Animals↗
PubMed2004

Wasp parasitoid disruption of host development: implications for new biologically based strategies for insect control.

Wasp parasitoids use a variety of methods to commandeer their insect hosts in order to create an environment that will support and promote their own development, usually to the detriment of the host insect. Parasitized insects typically undergo developmental arrest and die sometime after the parasitoid has become independent of its host. Parasitoids can deactivate their host's immune system and effect changes in host hormone titers and behavior. Often, host tissues or organs become refractory to stimulation by tropic hormones. Here we present an overview of the manipulative capabilities of wasp-injected calyx fluid containing polydnaviruses and venom, as well as the parasitoid larva and the teratocytes that originate from the serosal membrane that surrounds the developing embryo of the parasitoid. Possibilities for using regulatory molecules produced by the parasitoid or its products that would be potentially useful in developing new, environmentally safe insect control agents are discussed.

Animals↗
PubMed2001

Fat metabolism in insects.

The study of fat metabolism in insects has received considerable attention over the years. Although by no means complete, there is a growing body of information about dietary lipid requirements, and the absolute requirement for sterol is of particular note. In this review we (a) summarize the state of understanding of the dietary requirements for the major lipids and (b) describe in detail the insect lipid transport system. Insects digest and absorb lipids similarly to vertebrates, but with some important differences. The hallmark of fat metabolism in insects centers on the lipid transport system. The major lipid transported is diacylglycerol, and it is carried by a high-density lipoprotein called lipophorin. Lipophorin is a reusable shuttle that picks up lipid from the gut and delivers it to tissues for storage or utilization without using the endocytic processes common to vertebrate cells. The mechanisms by which this occurs are not completely understood and offer fruitful areas for future research.

Animals↗
PubMed1997

Hormonal regulation in insects: facts, gaps, and future directions.

There are two main classes of hormones in insects: 1) the true hormones produced by epithelial glands and belonging to the ecdysteroids or juvenile hormones and 2) the neuropeptide hormones produced by neurosecretory cells. Members of these classes regulate physiological, developmental, and behavioral events in insects. Detailed accounts are given on isolation, identification, structure-activity relationships, mode of action, biological function, biosynthesis, inactivation, metabolism, and feedback for hormones involved in 1) metabolic regulation such as the adipokinetic/hypertrehalosemic peptides and the diuretic and antidiuretic peptides; 2) stimulation or inhibition of muscle activity such as the myotropic peptides; 3) control of reproduction, growth, and development such as allatotropins, allatostatins, juvenile hormones, ecdysteroids, folliculostimulins and folliculostatins, ecdysis-triggering and eclosion hormones, pheromone biosynthesis activating neuropeptides, and diapause hormones; and 4) regulation of tanning and of color change. Because of the improvements in techniques for isolation and structure elucidation, there has been rapid progress in our knowledge of the chemistry of certain neuropeptide families. With the employment of molecular biological techniques, the genes of some neuropeptides have been successfully characterized. There are, however, areas that are still quite underdeveloped. These are, for example, 1) receptor studies, which are still in their infancy; 2) the hormonal status of certain sequenced peptides is not clarified; and 3) functional studies are lacking even for established hormones. The authors plead for a concerted effort to continue research in this field, which will also advance our knowledge into the use of insect hormones as safer and species-specific molecules for insect pest management.

Amino Acid Sequence↗
PubMed1989

Expression of hemolytically active human complement component C1r proenzyme in insect cells using a baculovirus vector.

The gene of human C1r has been expressed in a baculovirus-insect-cell system via the pAc373 transplacement vector. The full-length cDNA copy was inserted into the pAc373 vector downstream from the strong polyhedrin promoter of the baculovirus, Autographa californica nuclear polyhedrosis virus (AcNPV). Spodoptera frugiperda cells were cotransfected with the resultant plasmid, pAcC1r, and the wild-type AcNPV DNA. Recombinant viruses, which drove the expression of C1r protein, were selected by plaque morphology and ELISA. Insect cells infected with the recombinant virus produced and secreted human C1r protein, at a level of 1-2 mg/l of medium. The expressed C1r was isolated from the medium by chromatofocusing. On reducing gels only a single Coomassie-staining band was observed, and this band migrated at 80-83 kD characteristic of the unactivated C1r proenzyme. Its identification as C1r was immunologically confirmed on Western blots. C1 reconstituted from purified C1r expressed in insect cells together with human C1q and C1s proved biologically active in a hemolytic assay. Thus, the baculovirus-insect-cell system is capable of expressing and secreting a sophisticated, multifunctional human complement subcomponent in its biologically activatable form.

Animals↗
PubMed2006

Comparative psychoneuroimmunology: evidence from the insects.

Interactions between immune systems, nervous systems, and behavior are well established in vertebrates. A comparative examination of these interactions in other animals will help us understand their evolution and present adaptive functions. Insects show immune-behavioral interactions similar to those seen in vertebrates, suggesting that many of them may have a highly conserved function. Activation of an immune response in insects results in illness-induced anorexia, behavioral fever, changes in reproductive behavior, and decreased learning ability in a broad range of species. Flight-or-fight behaviors result in a decline in disease resistance. In insects, illness-induced anorexia may enhance immunity. Stress-induced immunosuppression is probably due to physiological conflicts between the immune response and those of other physiological processes. Because insects occupy a wide range of ecological niches, they will be useful in examining how some immune-behavioral interactions are sculpted by an animal's behavioral ecology.

Animals↗
PubMed2001

Evolution and phylogeny of insect endogenous retroviruses.

BACKGROUND: The genome of invertebrates is rich in retroelements which are structurally reminiscent of the retroviruses of vertebrates. Those containing three open reading frames (ORFs), including an env-like gene, may well be considered as endogenous retroviruses. Further support to this similarity has been provided by the ability of the env-like gene of DmeGypV (the Gypsy endogenous retrovirus of Drosophila melanogaster) to promote infection of Drosophila cells by a pseudotyped vertebrate retrovirus vector. RESULTS: To gain insights into their evolutionary story, a sample of thirteen insect endogenous retroviruses, which represents the largest sample analysed until now, was studied by computer-assisted comparison of the translated products of their gag, pol and env genes, as well as their LTR structural features. We found that the three phylogenetic trees based respectively on Gag, Pol and Env common motifs are congruent, which suggest a monophyletic origin for these elements. CONCLUSIONS: We showed that most of the insect endogenous retroviruses belong to a major clade group which can be further divided into two main subgroups which also differ by the sequence of their primer binding sites (PBS). We propose to name IERV-K and IERV-S these two major subgroups of Insect Endogenous Retro Viruses (or Insect ERrantiVirus, according to the ICTV nomenclature) which respectively use Lys and Ser tRNAs to prime reverse transcription.

Amino Acid Motifs↗
PubMed1997

Molecular characteristics of mammalian and insect amino acid transporters: implications for amino acid homeostasis.

In mammalian cells, the uptake of amino acids is mediated by specialized, energy-dependent and passive transporters with overlapping substrate specificities. Most energy-dependent transporters are coupled either to the cotransport of Na+ or Cl- or to the countertransport of K+. Passive transporters are either facilitated transporters or channels. As a prelude to the molecular characterization of the different classes of transporters, we have isolated transporter cDNAs by expression-cloning with Xenopus laevis oocytes and we have characterized the cloned transporters functionally by uptake studies into oocytes using radiolabelled substrates and by electrophysiology to determine substrate-evoked currents. Mammalian transporters investigated include the dibasic and neutral amino acid transport protein D2/NBAT (system b0+) and the Na(+)- and K(+)-dependent neuronal and epithelial high-affinity glutamate transporter EAAC1 (system XAG-). A detailed characterization of these proteins has provided new information on transport characteristics and mechanisms for coupling to different inorganic ions. This work has furthermore advanced our understanding of the roles these transporters play in amino acid homeostasis and in various pathologies. For example, in the central nervous system, glutamate transporters are critically important in maintaining the extracellular glutamate concentration below neurotoxic levels, and defects of the human D2 gene have been shown to account for the formation of kidney stones in patients with cystinuria. Using similar approaches, we are investigating the molecular characteristics of K(+)-coupled amino acid transporters in the larval lepidopteran insect midgut. In the larval midgut, K+ is actively secreted into the lumen through the concerted action of an apical H+ V-ATPase and an apical K+/2H+ antiporter, thereby providing the driving force for absorption of amino acids. In vivo, the uptake occurs at extremely high pH (pH 10) and is driven by a large potential difference (approximately -200 mV). Studies with brush-border membrane vesicles have shown that there are several transport systems in the larval intestine with distinct amino acid and cation specificities. In addition to K+, Na+ can also be coupled to amino acid uptake at lower pH, but the Na+/K+ ratio of the hemolymph is so low that K+ is probably the major coupling ion in vivo. The neutral amino acid transport system of larval midgut has been studied most extensively. Apart from its cation selectivity, it appears to be related to the amino acid transport system B previously characterized in vertebrate epithelial cells. Both systems have a broad substrate range which excludes 2-(methylamino)-isobutyric acid, an amino acid analog accepted by the mammalian Na(+)-coupled system A. In order to gain insights into the K(+)-coupling mechanism and into amino acid and K+ homeostasis in insects, current studies are designed to delineate the molecular characteristics of these insect transporters. Recent data showed that injection of mRNA prepared from the midgut of Manduca sexta into Xenopus laevis oocytes induced a 1.5- to 2.5-fold stimulation of the Na(+)-dependent uptake of both leucine and phenylalanine (0.2 mmoll-1, pH 8). The molecular cloning of these transporters is now in progress. Knowledge of their unique molecular properties could be exploited in the future to control disease vectors and insect pests.

Amino Acid Transport Systems↗
PubMed1976

Control and management of insect populations by chemosterilants.

Chemosterilants, i.e., chemical compounds that interfere with the reproduction potential of sexually reproducing organisms, can be used in three new approaches to insect control. In the sterile-insect release technique, the principal problem is to develop compounds and methods for their application that would not result in introducing harmful residues into the environment. Because of the unusual and often unique circumstances connected with releasing large numbers of sterilized insects, the residue problem and its cost-benefit aspects must be examined individually for each intended control or eradication program. In the direct application technique, chemosterilants must meet the same efficiency and safety standards required from approved insecticides. Combined insecticidal and sterilizing activity is characteristic for some compounds now being investigated. In the genetic technique, chemosterilants may be used for inducing heritable changes in the insect's genome under laboratory conditions, and such procedures would not present any residue problems. Only the first two chemosterilant techniques are approaching practical application, and their safety aspects require detailed evaluation and assessment.

Chemosterilants↗