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PubMed1983

Biological control of insect pests.

Isozyme techniques have proven particularly useful in the past in the field of biological insect control. In this brief review I have tried to give a small selection of the varied approaches that have been used. In the future, isozyme analysis will undoubtedly play a major role. But genetic analyses, as exemplified by the use of isozymes, form but a small part of the knowledge we must have if biological control programs are to be successful. In a pest management program where one is using both chemical and biological methods it is necessary to know a great deal about the biology of the pests, their parasites, predators, and host plants or animals, together with a knowledge of the general ecology of the area where the problem exists. Too often, major control programs have been started with pitifully inadequate basic knowledge of the insect pest concerned, dooming such projects to a series of frantic and generally makeshift attempts to redeem these inadequacies. We are starting to see a much greater emphasis on interrelationships between scientific disciplines, more basic research being conducted, and a resurgence of interaction between those people who are in the applied field and those in the basic sciences. This dialog must be continued. In closing, I want to emphasize again that in pest control we are involved in the management of a coexistence with insects and I think it appropriate to end with the thoughts of W.J. Holland [1949]: when all cities shall have been long dead and crumbled into dust, and all life shall be on the very last verge of extinction on this globe; then on a bit of lichen, growing on the bald rocks beside the eternal snows of Panama, shall be seated a tiny insect, preening its antenna in the glow of the worn-out sun, representing the sole survival of animal life on this our earth--a melancholy 'bug'.

Alleles↗
PubMed1995

Current excitement from insect muscarinic receptors.

Recent electrophysiological, pharmacological and molecular studies suggest that muscarinic ACh receptors (mAChRs) in insects are related to, but distinct from, their mammalian counterparts. Insect mAChRs perform two primary roles that are distinguished by their locations. Presynaptic mAChRs, present on sensory terminals, inhibit transmitter release, thereby reducing the effectiveness of specific afferent inputs. In contrast, postsynaptic mAChRs depolarize and increase the excitability of motoneurons and interneurons, thereby acting as dynamic-gain controls. This postsynaptic modulation is achieved in different ways in specific neurons but generally results from the activation of persistent inward and outward currents. At the level of neural processing, these distinct roles enable insect mAChRs to regulate the transfer of sensory information, and modulate the contributions of central neurons to central pattern generators and reflexes. Because these phenomena can be studied in identified neurons, a combination of physiological and molecular studies of mAChRs in insects should help to elucidate some of their behavioral roles. Furthermore, such studies could lead to the identification of general mechanisms of functional plasticity in neuronal networks.

Amino Acid Sequence↗
PubMed1994

Exchangeable apolipoproteins of insects share a common structural motif.

Elucidation of the secondary structure of the exchangeable apolipoproteins has been hindered by the difficulty in producing crystals suitable for X-ray spectrographic analyses. Consequently, in order to analyze potential structure-function relationships in the family of insect exchangeable apolipoproteins, apolipophorins-III (apoLps-III), two apoLps-III cDNA clones, one from the palo verde beetle (Derobrachus geminatus) and one from the house cricket (Acheta domesticus), have been isolated and sequenced. Multiple sequence alignments of the deduced protein sequences with two previously reported apolipophorins-III from Manduca sexta and Locusta migratoria reveal low sequence identity, suggesting that these proteins are very old and are highly divergent. Computer-assisted predictions of protein structure and subsequent analyses, using the known secondary structure of Locusta migratoria apolipophorin-III as a control, indicate that these insect proteins are composed of five amphipathic helices with characteristics similar to those of the helical domains of the mammalian exchangeable apolipoproteins. Thus, although insect and vertebrate exchangeable apolipoproteins share a common function in assisting lipid transport, precise amino acid identity is less important than the common structural feature of multiple amphipathic helices. Moreover, because these proteins occur widely among insect species, even in those where flight is limited or absent, we hypothesize that apolipophorin-III has a more generalized function in lipid metabolism than had been previously proposed.

Amino Acid Sequence↗
PubMed1976

Biochemical adaptations for flight in the insect.

1. Flight by insects is characterized by the most intense respiration known in biology and also the most controlled. Thus insect flight muscle may be the tissue of choice for the study of biochemical adaptation in the control of catabolism and biological oxidations, and many of the results obtained with insects have a significance and a relevance that transcend the boundaries between classes. In insects, such as the blowfly, flight is distinguished additionally by high wingbeat frequencies and an asynchronous type of excitation-contraction coupling. In spite of this intense muscular work, metabolic processes are not limited by the availability of oxygen. Also of importance is the morphological organization of the flight muscle and mitochondria, which have evolved ultrastructurally and biochemically into an effective catabolic machine. 2. In the fly, carbohydrate, principally glycogen, is the sole metabolic fuel; fats are not used in flight and enzymes concerned with fatty acid utilization are virtually lacking. Glycogenolysis does not lead to lactic acid; instead, the end products of glycolysis are pyruvate and alpha-glycerophosphate. The alpha-glycerophosphate cycle provides a mechanism not only for the reoxidation of glycolytically produced NADH but also for the stoicheiometric formation from each molecule of hexose equivalent of two molecules of pyruvate, which are then available for oxidation via the tricarboxylate cycle. The absence of dicarboxylate and tricarboxylate carriers from the mitochondria ensures that tricarboxylate-cycle intermediates do not exit from the mitochondrion but that pyruvate is oxidized to completion. On initiation of flight, mitochondrial oxidation of pyruvate is impeded by the lack of tricarboxylate-cycle intermediates for the generation of oxaloacetate. This is circumvented by the oxidation of proline. 3. The controls on metabolism in flight muscle, i.e. (1) glycogenolysis at phosphorylase and phosphorylase kinase, (2) glycolysis at phosphofructokinase, (3) alpha-glycerophosphate dehydrogenase, (4) proline dehydrogenase and (5) tricarboxylate cycle at isocitrate dehydrogenase, are effected by the phosphate potential and/or Ca2+. It is suggested that the metabolic changes, such as those seen in the rest-to-flight transition, are achieved by the concerted actions of these effectors at the different loci.

Adaptation, Physiological↗
PubMed1994

A DNA-based approach to the identification of insect species used for postmortem interval estimation.

Insect larvae found on a corpse can be used for estimating postmortem intervals. Here, we describe a molecular method for rapid identification of these insects. Specific insect DNA fragments were amplified using the polymerase chain reaction (PCR), followed by direct DNA sequencing of the amplification products. We sequenced 2300 base pairs of mitochondrial DNA from each of three blowfly species: Phormia regina, Phaenicia sericata and Lucilia illustris. All three species are important in forensic entomology. We found 118 nucleotide differences between the L. illustris and P. sericata sequences, 186 between L. illustris and P. regina, and 192 between P. sericata and P. regina. Based on these abundant DNA sequence differences, we can unambiguously identify the immature larval stages of these insects. These DNA sequence differences were also used to predict species-specific, diagnostic restriction sites in the amplified DNA, and these predictions were verified by digestion with nine restriction enzymes. The DNA sequences reported here encode the mitochondrial COI, COII and tRNA-leucine genes.

Animals↗
PubMed1993

Expression, targeting, and assembly of functional Na,K-ATPase polypeptides in baculovirus-infected insect cells.

Deciphering the roles of the individual subunits of the heteromeric Na,K-ATPase in the structure, function, and assembly of this enzyme has been complicated because most expression systems have endogenous levels of Na,K-ATPase activity. This problem has become even more significant in light of the recent identification of multiple isoforms for both the alpha and beta subunits. The baculovirus expression system, which uses the baculovirus Autographica californica to infect insect cells, affords two distinct advantages for the expression of the Na,K-ATPase; some insect cells have little or no levels of Na,K-ATPase, and baculovirus-infected cells produce extremely high levels of foreign protein. We have made two separate recombinant baculoviruses containing the rodent alpha 1 or beta 1 cDNAs and used them to infect the insect cell line Sf-9. The infected Sf-9 cells produce Na,K-ATPase subunit protein on the order of 5-10 micrograms of protein/ml of cultured cells. The rodent alpha 1 polypeptide produced in the Sf-9 cells is indistinguishable electrophoretically and antigenically from the native subunit. The expressed beta 1 subunit is also antigenically identical but has a higher electrophoretic mobility due to differential glycosylation by the infected Sf-9 cell. In contrast to other systems, when expressed alone, each individual Na,K-ATPase subunit is targeted to the infected Sf-9 plasma membrane. In contrast, when infected with a virus that induces the heavy chain of murine IgG, the infected Sf-9 cell retains the polypeptide in the endoplasmic reticulum. However, when both IgG light and heavy chains are expressed, the polypeptides are properly processed and secreted. When the Na,K-ATPase alpha 1 and beta 1 polypeptides are simultaneously expressed, they form detergent-resistant complexes that are functional. Ouabain-sensitive ATPase activity on the order of 5 mumol Pi/mg/h in infected Sf-9 membranes was dependent on the expression of both the alpha 1 and beta 1 subunits. Sodium-dependent phosphorylated intermediates were detected that were potassium- and ouabain-sensitive. No increase in ouabain-sensitive activity or phosphorylated intermediates was detected when either subunit was expressed alone. The alpha 1 beta 1-coinfected cells were also able to transport ions, as detected in 86Rb uptake experiments. Thus, the recombinant Na,K-ATPase expressed in insect cells is biologically active and is suitable for structural and functional analysis.

Animals↗
PubMed1995

Insect sound production: transduction mechanisms and impedance matching.

The chain of sound production in insects can be summarised as: (1) muscle power-->(2) mechanical vibration of the sound-producing structure-->(3) acoustic loading of this source-->(4) sound radiation. At each link (-->) optimal impedance matching is desirable but, to meet other acoustic requirements, each stage has special properties. The properties of sound waves are discussed in the context of impedance matching between sources of different sizes or configurations and the surrounding fluid medium. Muscles produce high pressures over small areas, but sound sources produce low pressures over large areas. Link 1-->2 requires a change in the force: area ratio between the muscle and the sound source. Because the source size is necessarily small, sounds tend to be produced at a higher frequency than that of the driving muscle contraction, so link 1-->2 may involve a frequency multiplication mechanism. This can also be regarded as a mechanism of impedance matching between the aqueous muscle and the structure from which the insect produces sound. Stage 2 typically involves a resonant structure that determines the song frequency and is excited by link 1-->2. If link 2-->3 provides good impedance matching, the mechanical resonance is likely to be damped, with loss of song purity. So it is desirable for the stage 2 resonance to be sustained by coherent excitation and for the acoustic loading (link 2-->3) to maintain the dominant frequency between stages 2 and 4. Examples where this occurs are cricket wings and cicadas. At stage 3, the source size or configuration should allow impedance matching between the sound source (3) and its load (4). A variety of acoustic devices are exploited, leading to loud, efficient sound production. Examples that use resonant loads, tuned to the insects' song frequency, are the burrows of mole crickets and the abdomens of cicadas. Overall, the mechanisms of sound production of many insects are capable of producing songs of high species-specificity that act as long-range signals.

Animals↗
PubMed1996

Intradermal reactivity to various insect and arachnid allergens among dogs from the southeastern United States.

OBJECTIVE: To compare cutaneous reactivity to insect and arachnid allergens in clinically normal (control) and allergic dogs in the southeastern United States. DESIGN: Prospective, controlled study. ANIMALS: 26 clinically normal dogs and 82 allergic dogs from the southeastern United States. PROCEDURE: Intradermal skin testing with various dilutions of 13 insect and arachnid allergens was performed on control dogs to establish skin threshold concentrations (ie, concentrations to which < 25% of the dogs had positive reactions). These established threshold concentrations were then used to test allergic dogs for reactivity. Prevalence of single and multiple insect and arachnid reactions were determined. RESULTS: Flea allergen was the only allergen that caused a significantly higher prevalence of positive reactions in allergic dogs than in control dogs. CLINICAL IMPLICATIONS: Flea hypersensitivity is the most important arthropod hypersensitivity in dogs. The importance of reactivity to insect and arachnid allergens other than flea allergen can be determined only when prevalence of positive reactivity has been determined in an appropriate regional control group of dogs.

Allergens↗
PubMed1997

Overexpression of delta-opioid receptors in recombinant baculovirus-infected Trichoplusia ni "High 5" insect cells.

"High 5" cells derived from Trichoplusia ni ovaries were infected with baculovirus bearing the cDNA of the mouse delta-opioid receptor. The maximal binding capacity for the narcotic antagonist [3H] naltrindole was 1.4 pmol/mg of membrane protein, and that for the agonist [3H][D-penicillamine2,D-penicillamine5]enkephalin (DPDPE) was 0.3 pmol/mg. DPDPE proved highly potent in competing with its tritiated analogue at delta-receptors of NG108-15 hybrid cells and of High 5 and Sf9 insect cells. However, in insect cells the opioid was more than 100-fold less effective in competing with [3H]naltrindole as compared with the mammalian cells. This decline in potency was counteracted in a dose-dependent manner by exposure of High 5 membranes to the exogenous G protein G(o), which increased the binding capacity for DPDPE. Functional studies revealed a dose-dependent inhibition (up to 30%) by opioids on forskolin-stimulated cyclic AMP synthesis, and this effect was potentiated by G(o). Quantification of G alpha o and G alpha i disclosed striking differences between Sf9 and High 5 insect cells, both of which overexpressed the cloned delta-opioid receptor. Although no inhibitory G proteins were detected in membranes of Sf9 cells, High 5 cells contained 0.5 pmol of G alpha o/mg of membrane protein, and a 20-fold higher concentration for G alpha i. The distinct G-protein expression in insect cells may be considered an advantage for studying functions of G protein-coupled receptors.

Adenylyl Cyclases↗
PubMed1999

An 86 kDa diapause protein 1-like protein is a component of early-staged encapsulation-relating proteins in coleopteran insect, Tenebrio molitor larvae.

Recently, we reported two novel early-staged encapsulation-relating proteins (56 kDa and 48 kDa ERPs) isolated from the hemolymph of coleopteran insect, Tenebrio molitor larvae [Cho et al. (1999) Eur. J. Biochem. (in press)]. Here, a cDNA clone for another early-staged encapsulation-relating protein (86 kDa) was isolated. We found that the 86 kDa protein shows high homology with insect diapause protein 1. The 86 kDa protein was localized in the fat body and hemolymph, but not hemocyte lysate. A significant level of 86 kDa protein was detected in pre-pupae stage, but it decreased rapidly at late larvae and pupae, and no protein was found in embryo, early larvae and adult stages. This diapause protein 1-like protein is likely to be a component of early-staged encapsulation-relating proteins in the insect cellular defense reaction.

Amino Acid Sequence↗
PubMed2002

Dominant lethality and insect population control.

Recent advances in insect genetic engineering have opened up new possibilities in the genetic control of insect vectors of human diseases. We outline the current state of the sterile insect technique and show how the use of engineered dominant lethals can greatly increase the effectiveness of this approach. We consider alternative strategies based on the use of conditional dominant lethals that are not always active in the environment.

Animals↗
PubMed1996

Immunity to eukaryotic parasites in vector insects.

Mosquitoes and blackflies have been the focus of recent efforts to elucidate factors influencing the susceptibility of vector insects to metazoan and protozoan parasites of medical significance. Vector species exhibit variation in cellular and humoral immune responses, as highlighted by studies of melanotic encapsulation and components of the phenoloxidase system. Significant progress has been made in the development of genetic maps based upon molecular markers, leading to the genetic analysis of loci influencing susceptibility. The identification of specific inducible antibacterial peptides, and the cloning of genes encoding immune effector proteins as well as potential regulatory factors, open the path to fruitful studies of vector insect innate immunity and its relationship to insect-parasite interactions.

Animals↗
PubMed2003

Innovations: applications of insect transgenesis.

The recent establishment of broadly applicable genetic transformation systems will allow the analysis of gene function in diverse insect species. This will increase our understanding of developmental and evolutionary biology. Furthermore, insect transgenesis will provide new strategies for insect pest management and methods to impair the transmission of pathogens by human disease vectors. However, these powerful techniques must be applied with great care to avoid harm to our environment.

Animals↗
PubMed1996

Sequencing analysis of cDNA clones encoding the American cockroach Cr-PI allergens. Homology with insect hemolymph proteins.

A previous article described the isolation of several lambdagt22A cDNA clones expressing the American cockroach (Periplaneta americana) Cr-PI allergens recognized by both human atopic IgE antibodies and anti-Cr-PI monoclonal antibodies (Wu, C. H., Lee, M. F., and Liao, S. C.(1995) J. Allergy Clin. Immunol. 96, 352-359). This article presents the nucleotide and deduced amino acid sequences of two cDNA clones encoding major allergens of P. americana. Clones C12 and C20 encode proteins of 685 and 631 amino acids with two potential N-glycosylation sites each. The predicted molecular weights for C12 and C20 cloned proteins are 79,300 and 75, 500 with isoelectric point values of 6.26 and 6.63, which are compatible with the determined sizes (Mr 78,000 and 72,000) and isoelectric point value (6.2) of the Cr-PI allergens of P. americana. A high degree of identity (69.1%), including several overlapped predicted central antigenic determinant residues, was found between two allergens. The anti-fusion protein antibody-based enzyme-linked immunosorbent assay was able to detect crude American cockroach extract, Cr-PI, recombinant proteins, and commercial cockroach extracts, which provides further evidence that two allergens share common antigen determinants. Recombinant allergens of clones C12 and C20 both showed 47.4% skin reactivities on 19 cockroach-sensitive asthmatic patients. Unexpectedly, although no sequence similarity was found to other known allergens, two aromatic amino acid-rich allergens were found to have a striking sequence identity to insect storage proteins (20.1-33.9%), insect juvenile hormone-suppressible proteins (30.9-36.4%), and arthropod hemocyanins (29.7-34.6%). Results suggested that two prominent allergens of P. americana are ancestrally related to these insect hemolymph proteins and represent a new group of proteins in the hemocyanin superfamily. These data will now facilitate epitope-mapping studies, and the recombinant allergens may be valuable for diagnostic and therapeutic purposes.

Adolescent↗
PubMed2005

Activation of the lipid droplet controls the rate of lipolysis of triglycerides in the insect fat body.

The hydrolysis of triglyceride (TG) stored in the lipid droplets of the insect fat body is under hormonal regulation by the adipokinetic hormone (AKH), which triggers a rapid activation cAMP-dependent kinase cascade (protein kinase A (PKA)). The role of phosphorylation on two components of the lipolytic process, the TG-lipase and the lipid droplet, was investigated in fat body adipocytes. The activity of purified TG-lipase determined using in vivo TG-radiolabeled lipid droplets was unaffected by the phosphorylation of the lipase. However, the activity of purified lipase was 2.4-fold higher against lipid droplets isolated from hormone-stimulated fat bodies than against lipid droplets isolated from unstimulated tissue. In vivo stimulation of lipolysis promotes a rapid phosphorylation of a lipid droplet protein with an apparent mass of 42-44 kDa. This protein was identified as "Lipid Storage Droplet Protein 1" (Lsdp1). In vivo phosphorylation of this protein reached a peak approximately 10 min after the injection of AKH. Supporting a role of Lsdp1 in lipolysis, maximum TG-lipase activity was also observed with lipid droplets isolated 10 min after hormonal stimulation. The activation of lipolysis was reconstituted in vitro using purified insect PKA and TG-lipase and lipid droplets. In vitro phosphorylation of lipid droplets catalyzed by PKA enhanced the phosphorylation of Lsdp1 and the lipolytic rate of the lipase, demonstrating a prominent role PKA and protein phosphorylation on the activation of the lipid droplets. AKH-induced changes in the properties of the substrate do not promote a tight association of the lipase with the lipid droplets. It is concluded that the lipolysis in fat body adipocytes is controlled by the activation of the lipid droplet. This activation is achieved by PKA-mediated phosphorylation of the lipid droplet. Lsdp1 is the main target of PKA, suggesting that this protein is a major player in the activation of lipolysis in insects.

Adipocytes↗
PubMed1975

Development of morphogenetic agents in insect control.

Chemicals which interfere with the growth and development of insects (morphogenetic agents) have been receiving major attention as potential means of selective insect control. Major advances in this field resulted from the identification of Juvenile Hormones -1, -2, and -3, and the discovery that various terpenoid and sesquiterpenoid derivatives were more potent morphogenetic agents than the three known Juvenile Hormones. Several highly active compounds have emerged from these research programs. Their field performance, problems, and prospects in selective insect control are considered here.

Animals↗
PubMed2005

Clinical reactivity to insect stings.

PURPOSE OF REVIEW: Allergy to insect stings remains a hazard worldwide and is the object of updated guidelines on management. This paper reviews the various clinical responses that may occur following an insect sting. RECENT FINDINGS: Although the general population is at slight risk, certain groups are more susceptible, including occasionally stung adult male agricultural workers, hobby honey beekeepers and family members of beekeepers. Individuals with systemic mastocytosis are especially reactive to stings. The body of evidence attesting to the marked beneficial effect that 3-5 years of venom immunotherapy has on the natural history of hymenoptera hypersensitivity is especially evident in children. Case reports indicate other consequences of hymenoptera sting, and these are discussed. SUMMARY: Hypersensitivity to insect stings is common and may be life threatening. Although most occur away from medical facilities, their diagnosis and management are important to a wide spectrum of health care professionals. Most reactions to stings are nonallergic manifestations of the venom's toxic effects, and present as erythema, pain and swelling about the sting site. Fire ants bite with their mandibles and pivot their head, inflicting multiple stings that usually result in a sterile pseudopustule at the site. Hypersensitivity responses to venom range from large local reactions (a late-phase response) to life-threatening anaphylaxis. Venom-specific immunotherapy is highly effective in the modification of subsequent reactions to hymenoptera stings, as is whole body extract for fire ant stings.

Adolescent↗
PubMed2006

Phylogenomic analysis reveals bees and wasps (Hymenoptera) at the base of the radiation of Holometabolous insects.

Comparative studies require knowledge of the evolutionary relationships between taxa. However, neither morphological nor paleontological data have been able to unequivocally resolve the major groups of holometabolous insects so far. Here, we utilize emerging genome projects to assemble and analyze a data set of 185 nuclear genes, resulting in a fully resolved phylogeny of the major insect model species. Contrary to the most widely accepted phylogenetic hypothesis, bees and wasps (Hymenoptera) are basal to the other major holometabolous orders, beetles (Coleoptera), moths (Lepidoptera), and flies (Diptera). We validate our results by meticulous examination of potential confounding factors. Phylogenomic approaches are thus able to resolve long-standing questions about the phylogeny of insects.

Animals↗