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PubMed1987

Characterization of some new insect-derived acholeplasmas.

Further analysis of three sterol-nonrequiring Mollicutes (strains PS-1, TAC, and YJS) isolated from gut fluids of insects confirms their similarity to Acholeplasma. They are serologically distinct from acholeplasmas of vertebrates and several other sterol nonrequiring Mollicutes isolated from plant surfaces. The PS-1 strain had a DNA G + C content of 31 mol % and a genome size of 1,030 megadaltons (MDa). Optimum temperature is in the range of 23 to 30 C. Thirty-two new nonhelical Mollicutes isolated from a much wider range of insect hosts were examined for acholeplasmas. Twenty-five of the insect isolates were grown consistently in serum-free broth, with or without Tween 80 supplements. Two of the acholeplasmas were serologically related to Acholeplasma florum, 13 strains were serologically identical to the TAC isolate reported earlier, and 10 of the putative acholeplasmas could not be identified with current reference antisera. Seven of the new nonhelical insect isolates appeared to be sterol-requiring Mollicutes. One sterol-requiring isolate (ELCN-1) was recovered from the hemolymph of a firefly, and is the first report of nonhelical Mollicutes in the insect hemocoel. Two of the seven sterol-requiring Mollicutes, which were nonhelical in earlier passages in broth, later reverted to typically helical spiroplasmas. Confirmation of sterol-requiring, nonhelical Mollicutes in insects would provide an important ecological finding that insects constitute an important reservoir for both acholeplasmas and mycoplasmas.

Acholeplasma↗
PubMed1974

Transport of lipids in insects.

Many insect species are almost completely dependent on lipids for their metabolic needs, although this is usually a function of developmental stage. The primary storage organ is the fat body, which can constitute 50% of the fresh weight of the insect and also acts as the major metabolic center (analogous to the vertebrate adipose tissue and liver). Bathing the fat body (and all other tissues and organs) is the hemolymph, the main functions of which are to transport nutrient substrates to utilization sites and to deliver metabolic wastes to the excretory system. Although neutral lipids are stored as triglycerides, in times of need they appear to be endergonically released into the hemolymph as diglycerides in the majority of insects thus far studied (particularly silkmoths and locusts). Indeed, diglycerides constitute the largest neutral lipid fraction in the hemolymph of silkmoths, locusts, cockroaches, bugs, etc. In the hemolymph the diglyceride is found as a constituent of specific lipoproteins, and one specific lipoprotein class (lipoprotein I; high density lipoprotein) appears to be necessary for the transport of diglyceride from the fat body cell into the hemolymph. This particular lipoprotein is also involved in the transport of cholesterol from the gut into the hemolymph. Thus, lipoprotein I appears to be the major neutral lipid and sterol transport agent in the insects studied and, in addition, plays a regulatory role in the release of both diglycerides and sterols. Hemolymph lipoprotein II (very high density lipoprotein) may be important in providing protein and lipid to the insect ovary during oogenesis. Ecdysone, the polyhydroxy steroidal insect molting hormone, is probably carried "free" in the hemolymph, although reports exist of specific hemolymph-binding proteins in some species. The other major insect growth hormone, juvenile hormone, is transported by hemolymph lipoproteins in silkmoths and locusts and by a lower molecular weight hemolymph protein in the tobacco hornworm.

Adipose Tissue↗
PubMed1968

Insect pheromones.

The evidence for intraspecies chemical communication in insects is reviewed, with emphasis on those studies where known organic compounds have been implicated. These signal-carrying chemicals are known as pheromones. There are two distinct types of pheromones, releasers and primers. Releaser pheromones initiate immediate behavioral responses in insects upon reception, while primer pheromones cause physiological changes in an animal that ultimately result in a behavior response. Chemically identified releaser pheromones are of three basic types: those which cause sexual attraction, alarm behavior, and recruitment. Sex pheromones release the entire repertoire of sexual behavior. Thus a male insect may be attracted to and attempt to copulate with an inanimate object that has sex pheromone on it. It appears that most insects are rather sensitive and selective for the sex pheromone of their species. Insects show far less sensitivity and chemospecificity for alarm pheromones. Alarm selectivity is based more on volatility than on unique structural features. Recruiting pheromones are used primarily in marking trails to food sources. Terrestrial insects lay continuous odor trails, whereas bees and other airborne insects apply the substances at discrete intervals. It appears that a complex pheromone system is used by the queen bee in the control of worker behavior. One well-established component of this system is a fatty acid, 9-ketodecenoic acid, produced by the queen and distributed among the workers. This compound prevents the development of ovaries in the workers and inhibits their queen-rearing activities. In addition, the same compound is used by virgin queen bees as a sex attractant.

Alcohols↗
PubMed1982

Insect toxic component from the venom of a chactoid scorpion, Scorpio maurus palmatus (Scorpionidae).

Several insect toxic components were isolated from the venom of the chactoid scorpion, Scorpio maurus palmatus (Scorpionidae), by column chromatography, with the following findings. 1) The toxicity of the crude venom to insects is due to three separate groups of substances, the so-called cytotoxins, phospholipases, and neurotoxins, which play a dominant role. 2) The neurotoxic fraction contains two factors: the fast reversibly paralytic and the slow lethal. 3) The slow lethal factor is composed of two toxins (IT1 and IT2), the purity of which was assessed by column chromatography, disc electrophoresis, isoelectrofocusing, analytical ultracentrifugation, and amino acid analyses. 4) IT1 and IT2 are two polypeptides possessing unique amino acid compositions with molecular weights of 3232 and 3963, pHi 8.8 and 9.2, and supposed to contain two and three disulfide bridges, respectively. 5) A clear cooperative interaction was demonstrated between the fast paralytic and lethal fractions as well as between the two insect toxins, resulting in an evident recovery of the original toxicity to insects of the crude venom. 6) When assayed on an isolated insect axonal preparation under current and voltage clamp conditions, the combination of IT1 and IT2 caused a reversible blockage of both the sodium and potassium currents. This may explain the specific symptomatology and the mechanism of the paralysis induced by these toxins to an insect. The above data were compared with information concerning buthoid scorpion venom insect toxins.

Amino Acids↗
PubMed2001

Recombinant baculoviruses for insect control.

Baculoviruses are double-stranded DNA viruses which are highly selective for several insect groups. They are valuable natural control agents, but their utility in many agricultural applications has been limited by their slow speed of kill and narrow host specificity. Baculoviruses have been genetically modified to express foreign genes under powerful promoters in order to accelerate their speed of kill. In our and other laboratories, the expression of genes coding for insect juvenile hormone esterases and various peptide neurotoxins has resulted in recombinant baculoviruses with promise as biological insecticides. These viruses are efficacious in the laboratory, greenhouse and field and dramatically reduce damage caused by insect feeding. The recombinant viruses synergize and are synergized by classical pesticides such as pyrethroids. Since they are highly selective for pest insects, they can be used without disrupting biological control. Because the recombinant virus produces fewer progeny in infected larvae than the wild-type virus, they are rapidly out-competed in the ecosystem. The viruses can be used effectively with crops expressing endotoxins of Bacillus thuringiensis. They can be produced industrially but also by village industries, indicating that they have the potential to deliver sustainable pest control in developing countries. It remains to be seen, however, whether the current generation of recombinant baculoviruses will be competitive with the new generation of synthetic chemical pesticides. Current research clearly indicates, though, that the use of biological vectors of genes for insect control will find a place in agriculture. Baculoviruses will also prove valuable in testing the potential utility of proteins and peptides for insect control.

Animals↗
PubMed1994

Restricted occurrence of Locusta migratoria ovary maturing parsin in the brain-corpora cardiaca complex of various insect species.

Ovary maturing parsin (OMP) is a gonadotrophic molecule previously isolated from the neurosecretory lobes of the corpora cardiaca of Locusta migratoria (acridian Orthoptera). A polyclonal antiserum directed against the two biologically active domains of the L. migratoria (Lom) OMP was used to investigate the occurrence of Lom OMP-like substances in brain-corpora cardiaca complexes of other insect species. Using immunohistochemistry, specimens of 40 different insect species belonging to 13 insect orders were tested. The Lom OMP-like substance was strictly limited to specimens of insect species belonging to the Acridae. It occurred in non-basophilic cells of the pars intercerebralis that project to the corpora cardiaca, as in Locusta. Although the antiserum only detected Lom OMP-like material in the Acridae, it is possible that related molecules exist in other insects. The antiserum may be very specific for domains of the Lom OMP molecule that have not been highly conserved during evolution or possibly these domains are not accessible to the antiserum in other insects.

Animals↗
PubMed1999

The embryonic expression pattern of labial, posterior homeotic complex genes and the teashirt homologue in an apterygote insect.

During embryogenesis of the fruit fly, Drosophila melanogaster, the homeotic genes are required to specify proper cell fates along the anterior-posterior axis of the embryo. We cloned partial cDNAs of homologues of the Drosophila homeotic gene teashirt and five of the homeotic-complex (HOM-C) genes from the thysanuran insect, Thermobia domestica, and assayed their embryonic expression patterns. The HOM-C genes we examined were labial, Antennapedia, Ultrabithorax, abdominal-A and Abdominal-B. As the expression pattern of these HOM-C genes is largely conserved among insects and as Thermobia is a member of a phylogenetically basal order of insects, we were able to infer their ancestral expression patterns in insects. We compare the expression patterns of the Thermobia HOM-C genes with their expression in Drosophila and other insects and discuss the potential roles these genes may have played in insect evolution. Interestingly, the teashirt homologue shows greater variability between Thermobia and Drosophila than any of the HOM-C genes. In particular, teashirt is not expressed strongly in the Thermobia abdomen, unlike Drosophila teashirt. We propose that teashirt expression has expanded posteriorly in Drosophila and contributed to a homogenization of the Drosophila larval thorax and abdomen.

Amino Acid Sequence↗
PubMed2003

Isolation and characterization of a novel insect defensin from Rhodnius prolixus, a vector of Chagas disease.

An antimicrobial peptide belonging to the defensin family of small cationic peptides associated with innate immunity in insects was isolated from the hemolymph of Rhodnius prolixus, a vector of Chagas disease. This peptide, designated R. prolixus defensin A, was purified and sequenced. The active peptide contains 43 residues and aligns well with other insect defensins. However the pre-pro region of the sequence has little shared identity with other insect defensins. We have identified 3 isoforms of R. prolixus defensin from cDNA clones obtained from RNA isolated from the whole bodies of immune activated insects. Northern analysis and Real-Time Quantitative PCR indicate that there is a very low baseline transcription of this peptide in naïve insects, and that transcription increases significantly in the fat body of immune activated insects. In addition there is a delayed induction of transcription of this peptide in the intestine 24 h post activation suggesting that the midgut/intestine of this species is active in the immune response against pathogens.

Amino Acid Sequence↗
PubMed2002

Molecular identification of the insect adipokinetic hormone receptors.

The insect adipokinetic hormones (AKHs) are a large family of peptide hormones that are involved in the mobilization of sugar and lipids from the insect fat body during energy-requiring activities such as flight and locomotion, but that also contribute to hemolymph sugar homeostasis. Here, we have identified the first insect AKH receptors, namely those from the fruitfly Drosophila melanogaster and the silkworm Bombyx mori. These results represent a breakthrough for insect molecular endocrinology, because it will lead to the cloning of all AKH receptors from all model insects used in AKH research, and, therefore, to a better understanding of AKH heterogeneity and actions. Interestingly, the insect AKH receptors are structurally and evolutionarily related to the gonadotropin-releasing hormone receptors from vertebrates.

Amino Acid Sequence↗
PubMed1985

The promoter of the late p10 gene in the insect nuclear polyhedrosis virus Autographa californica: activation by viral gene products and sensitivity to DNA methylation.

In lepidopteran insect cells infected with the baculovirus Autographa californica nuclear polyhedrosis virus (AcNPV), two major late viral gene products are expressed: the polyhedrin, a 28 000 mol. wt. protein which makes up the mass of the nuclear inclusion bodies, and a 10 000 mol. wt. protein (p10) whose function is unknown. The nucleotide sequences of these strong promoters conform to those of other eukaryotic promoters and are rich in AT base pairs. We used the pSVO-CAT construct containing the prokaryotic gene chloramphenicol acetyl transferase (CAT) to study the function of the p10 gene promoter in insect and mammalian cells. Upon transfection of the pAcp10-CAT construct, which contained 402 bp of the p10 gene of AcNPV DNA in the HindIII site of pSVO-CAT, CAT activity was determined. The p10 gene promoter was inactive in human HeLa cells and in uninfected Spodoptera frugiperda insect cells. The same promoter was active, however, in AcNPV-infected S. frugiperda cells and exhibited optimal activity when cells were transfected 18 h after infection with the insect virus. This finding demonstrated directly that the p10 gene promoter required other viral gene products for its activity in insect cells. The nature of these products was unknown. The p10 gene promoter sequence contained one 5'-CCGG-3' site 40 bp upstream from the cap site of the gene and two such sites 178 and 192 bp downstream from the ATG initiation codon of the gene. Since Drosophila DNA or S. frugiperda DNA contained no 5-methylcytosine or extremely small amounts of it, we were interested in determining the effect of site-specific methylations on the p10 gene insect virus promoter. Methylation at the 5'-CCGG-3' sites led to a block of this promoter.(ABSTRACT TRUNCATED AT 250 WORDS)

Acetyltransferases↗
PubMed1989

Role of virus-like particles in parasitoid-host interaction of insects.

Insect endoparasitoids are capable of suppressing the immune reaction of their habitual hosts in a specific way. Salt (1968) characterized some of the implications: This seeming contradiction--that defence reactions against all kinds of foreign bodies are available to insects and that endophagous parasitoids are nevertheless able to develop in insect hosts--is resolved by recourse to one of the principles of host specificity. Although insects as a group react to every foreign body in the sense that any organism or substance evokes a reaction in most insects, each species of insect fails to make a reaction (or makes an ineffective reaction) to a small group of organisms, its habitual parasites. It is the common paradox of parasitology that defence reactions are least effective against the most noxious parasites, involving the tautology that the most noxious parasites are those against which defence reactions are least effective. Recently, VLP of hymenopteran wasps have been shown to play a crucial part in suppressing the cellular encapsulation reaction (Stoltz and Vinson, 1979a). In some parasitoid wasps, polydnavirus particles are involved in the phenotypic transformation of hemocytes, reducing the capability of the host to mount an immune reaction towards the parasitoid egg (Stoltz and Guzo, 1986; Davies et al., 1987). However, at least in Venturia, the eggs are effectively protected by VLP that lack significant amounts of nucleic acids, precluding any virus expression in the host. The question was raised whether VLP could have acquired properties of the host immune system, which allows specific suppression of the immune response. The finding of structural similarities between VLP proteins and a host component indicated that a host function is expressed in VLP (Feddersen et al., 1986) and this observation has subsequently permitted the identification and characterization of a protein in caterpillars, which appears to inhibit cellular defense reactions (Berg et al., 1987). On the basis of these results we continue to approach this parasitoid-host interaction, assuming that VLP have evolved in the host organism and eventually acquired the coding sequences of a host protein with properties of an inhibitor of encapsulation. Although there are several ways to explain the emergence of VLP in endophagous parasitoid wasps, a simple proposal would be that such hypothetical viruses, which were able to suppress immune reaction in lepidopteran hosts, were incorporated into a parasitoid wasp to become part of the life cycle of the parasitoid.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1995

Insect nuclear receptors: a developmental and comparative perspective.

The appearance of puffs on the polytene chromosomes of insect salivary glands incubated with 20-hydroxyecdysone provided the first demonstration that steroids act directly at the gene transcriptional level to bring about subsequent cellular changes (Becker, 1959; Clever and Karlson, 1960). Despite that auspicious beginning, learning about the molecular mechanisms that underlie the hormonal regulation of insect development was impeded for many years by the difficulty associated with isolating and identifying rare regulatory factors from limited tissue sources. The advent of recombinant DNA methodology and powerful techniques such as the polymerase chain reaction (PCR) along with the recognition that many important endocrine factors are structurally conserved across a wide range of species has, however, all but eliminated the technical obstacles once facing the insect endocrinologist trying to isolate and study these regulatory molecules. This review will discuss recent progress and recall some earlier experiments concerning the molecular basis of hormonal action in insects focusing primarily on the members of the nuclear hormone receptor superfamily in Drosophila melanogaster. Two members of this family comprise the functional ecdysteroid receptor and at least a dozen other "orphans" have been identified in Drosophila for which no cognate ligand has yet been found. Many of these orphans are regulated by ecdysteroids. A discussion of juvenile hormone binding proteins that are not family members has been included because of their potential impact on nuclear receptor function. As receptor homologues have been identified in other insects, several general ideas concerning insect hormonal regulation have begun to emerge and these will be examined from a comparative point of view.

Amino Acid Sequence↗
PubMed2006

ICD-9-CM coding of emergency department visits for food and insect sting allergy.

PURPOSE: Little is known about the role of International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9-CM) codes for identification of specific allergic reactions in the emergency department (ED). METHODS: Investigators in 10 EDs reviewed 1395 charts of consecutive patients presenting with food allergy (ICD-9-CM codes 693.1 and 995.60 to 995.69) and insect sting allergy (code 989.5). They also reviewed charts of patients with "unspecified" allergic reactions (codes 995.0 [other anaphylactic shock] and 995.3 [allergy, unspecified]) to identify additional patients with food or insect sting allergy. RESULTS: Of 406 patients with food allergy, 216 patients (53%) were coded as food allergy, whereas the remaining 190 patients (47%) were not. Of 394 patients with insect sting allergy, 341 (87%) were coded as insect sting allergy, whereas 53 patients (13%) were not. Characteristics of ICD-9-CM-identified compared with chart-review-identified patients differed for both food and insect sting allergy. ICD-9-CM-identified patients with food allergy were less likely to experience anaphylaxis. CONCLUSIONS: Almost half the patients with food allergy would have been missed by using food-specific ICD-9-CM codes alone, whereas only 13% of patients with insect sting allergy would have been missed. Furthermore, characteristics of these allergy patients would have been biased by studying only patients identified by using the allergen-specific ICD-9-CM codes.

Adult↗
PubMed2005

"Neuroethoendocrinology": integration of field and laboratory studies in insect neuroendocrinology.

Progress in the field of insect neuroendocrinology has been rapid despite the relatively small number of investigators working on insect systems. This progress, in part, reflects the ease of studying insect behavior in the laboratory, and a historical perspective reveals that insect neuroendocrinology has been dominated since its inception by laboratory studies. Recent advances in methodology and a renewed interest in the concept of behavioral state in insects suggest that it might be useful for insect neuroendocrinologists to spend a little more time in the field.

Animals↗
PubMed2001

Adipokinetic hormones of insect: release, signal transduction, and responses.

Flight activity of insects provides an attractive yet relatively simple model system for regulation of processes involved in energy metabolism. This is particularly highlighted during long-distance flight, for which the locust constitutes a well-accepted model insect. Peptide adipokinetic hormones (AKHs) are synthesized and stored by neurosecretory cells of the corpus cardiacum, a neuroendocrine gland connected with the insect brain. The actions of these hormones on their fat body target cells trigger a number of coordinated signal transduction processes which culminate in the mobilization of both carbohydrate (trehalose) and lipid (diacylglycerol). These substrates fulfill differential roles in energy metabolism of the contracting flight muscles. The molecular mechanism of diacylglycerol transport in insect blood involving a reversible conversion of lipoproteins (lipophorins) has revealed a novel concept for lipid transport in the circulatory system. In an integrative approach, recent advances are reviewed on the consecutive topics of biosynthesis, storage, and release of insect AKHs, AKH signal transduction mechanisms and metabolic responses in fat body cells, and the dynamics of reversible lipophorin conversions in the insect blood.

Animals↗
PubMed2002

Enhanced in vivo activity of peptidase-resistant analogs of the insect kinin neuropeptide family.

The diuretic/myotropic insect kinin neuropeptides, which share the common C-terminal pentapeptide core FX(1)X(2)WG-NH(2), reveal primary (X(2)-W) and secondary (N-terminal to F) sites of susceptibility to peptidases bound to corn earworm (H. zea) Malpighian tubule tissue. Analogs designed to enhance resistance to tissue-bound peptidases, and pure insect neprilysin and ACE, demonstrate markedly enhanced in vivo activity in a weight gain inhibition assay in H. zea, and strong in vivo diuretic activity in the housefly (M. domestica). The peptidase-resistant insect kinin analog pQK(pQ)FF[Aib]WG-NH(2) demonstrates a longer internal residence time in the housefly than the native muscakinin (MK), and despite a difference of over 4 orders of magnitude in an in vitro Malpighian tubule fluid secretion assay, is equipotent with MK in an in vivo housefly diuretic assay. Aminohexanoic acid (Ahx) is shown to function as a surrogate for N-terminal Lys, while at the same time providing enhanced resistance to aminopeptidase attack. Peptidaese-resistant insect kinin analogs demonstrate enhanced inhibition of weight gain in larvae of the agriculturally destructive corn earworm moth. Potent peptidase resistant analogs of the insect kinins, coupled with an increased understanding of related regulatory factors, offer promise in the development of new, environmentally friendly pest insect control measures.

Animals↗
PubMed1997

Hydrolysis of insect neuropeptides by an angiotensin-converting enzyme from the housefly, Musca domestica.

The presence in insect tissues of peptides with structural similarities to angiotensin I and to bradykinin, the two best known substrates of mammalian angiotensin-converting enzyme, has not been reported. As part of our study to identify potential substrates for insect angiotensin-converting enzyme, we have investigated the susceptibility of a number of known insect peptide hormones and neurotransmitters to hydrolysis by Musca domestica angiotensin-converting enzyme. Insect peptides belonging to the red pigment-concentrating hormone, leucokinin, locust tachykinin, and depolarizing peptide families were hydrolyzed by housefly angiotensin-converting enzyme, whereas proctolin and crustacean cardioactive peptide were not substrates. Cus-DP II, LK I, LK II, and Lom-TK I were all cleaved at the penultimate C-terminal peptide bond to release a dipeptide amide as a major fragment with Km values of 94 +/- 11, 634 +/- 8, and 296 +/- 35 microM for Cus-DP II, LK I, and Lom-TK I, respectively. The ability of insect angiotensin-converting enzyme to hydrolyze C-terminally amidated peptides in vitro might be of functional significance because the enzyme has been localized to neuropile regions of the insect brain and is present in the hemolymph of houseflies.

Animals↗
PubMed2004

Sexually transmitted diseases of insects: distribution, evolution, ecology and host behaviour.

Sexually transmitted diseases (STDs) of insects are known from the mites, nematodes, fungi, protists and viruses. In total 73 species of parasite and pathogen from approximately 182 species of host have been reported. Whereas nearly all vertebrate STDs are viruses or bacteria, the majority of insect STDs are multicellular ectoparasites, protistans or fungi. Insect STDs display a range of transmission modes, with 'pure' sexual transmission only described from ectoparasites, all of which are mites, fungi or nematodes, whereas the microparasitic endo-parasites tend to show vertical as well as sexual transmission. The distribution of STDs within taxa of insect hosts appears to be related to the life histories of the hosts. In particular, STDs will not be able to persist if host adult generations do not overlap unless they are also transmitted by some alternative route. This explains the observation that the Coleoptera seem to suffer from more STDs than other insect orders, since they tend to diapause as adults and are therefore more likely to have overlapping generations of adults in temperate regions. STDs of insects are often highly pathogenic, and are frequently responsible for sterilizing their hosts, a feature which is also found in mammalian STDs. This, combined with high prevalences indicates that STDs can be important in the evolution and ecology of their hosts. Although attempts to demonstrate mate choice for uninfected partners have so far failed it is likely that STDs have other effects on host mating behaviour, and there is evidence from a few systems that they might manipulate their hosts to cause them to mate more frequently. STDs may also play a part in sexual conflict, with males in some systems possibly gaining a selective advantage from transmitting certain STDs to females. STDs may well be important factors in host population dynamics, and some have the potential to be useful biological control agents, but empirical studies on these subjects are lacking.

Animals↗