Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “INSECTS”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,117 records · Page 62Linked to original sources
PubMed2005

Site-specific antiphagocytic function of the Photorhabdus luminescens type III secretion system during insect colonization.

Photorhabdus is an entomopathogenic bacterium belonging to the Enterobacteriaceae. The genome of the TT01 strain of Photorhabdus luminescens was recently sequenced and a large number of toxin-encoding genes were found. Genomic analysis predicted the presence on the chromosome of genes encoding a type three secretion system (TTSS), the main role of which is the delivery of effector proteins directly into eukaryotic host cells. We report here the functional characterization of the TTSS. The locus identified encodes the secretion/translocation apparatus, gene expression regulators and an effector protein - LopT - homologous to the Yersinia cysteine protease cytotoxin YopT. Heterologous expression in Yersinia demonstrated that LopT was translocated into mammal cells in an active form, as shown by the appearance of a form of the RhoA GTPase with modified electrophoretic mobility. In vitro study showed that recombinant LopT was able to release RhoA and Rac from human and insect cell membrane. In vivo assays of infection of the cutworm Spodoptera littoralis and the locust Locusta migratoria with a TT01 strain carrying a translational fusion of the lopT gene with the gfp reporter gene revealed that the lopT gene was switched on only at sites of cellular defence reactions, such as nodulation, in insects. TTSS-mutant did not induce nodule formation and underwent phagocytosis by insect macrophage cells, suggesting that the LopT effector plays an essential role in preventing phagocytosis and indicating an unexpected link between TTSS expression and the nodule reaction in insects.

Amino Acid Sequence↗
PubMed1999

Comparison of active conformations of the insectatachykinin/tachykinin and insect kinin/Tyr-W-MIF-1 neuropeptide family pairs.

A comparison of solution conformations of active, restricted-conformation analogues of two sequence-similar insect/vertebrate neuropeptide family pairs shed light on the potential existence of molecular evolutionary relationships. Analogues of the locustatachykinins and the mammalian tachykinin substance P, containing a sterically hindered Aib-NMePhe/Tyr residue block, share similar low-energy turn conformations incorporating a cis peptide bond. Conversely, restricted conformation analogues of the insect kinins and the mammalian opiate peptide Tyr-W-MIF-1, with near identical C-terminal tetrapeptide sequences, adopt different conformations. The insect kinins adopt a cisPro 1-4 beta-turn, in which the Phe1 is critical for bioactivity. Tyr-W-MIF-1 prefers a transPro 2-5 turn, and an additional N-terminal Phe severely inhibits mu-opiate receptor binding. Comparisons of the chemical/conformational requirements for receptor interaction are consistent with a distant evolutionary relationship between the insectatachykinins and tachykinins, but not between the insect kinins and Tyr-W-MIF-1. Therefore, analogues of the insect kinins with pest control potential can be readily designed to avoid mammalian interactions.

Amino Acid Sequence↗
PubMed2003

Tracheal respiration in insects visualized with synchrotron x-ray imaging.

Insects are known to exchange respiratory gases in their system of tracheal tubes by using either diffusion or changes in internal pressure that are produced through body motion or hemolymph circulation. However, the inability to see inside living insects has limited our understanding of their respiration mechanisms. We used a synchrotron beam to obtain x-ray videos of living, breathing insects. Beetles, crickets, and ants exhibited rapid cycles of tracheal compression and expansion in the head and thorax. Body movements and hemolymph circulation cannot account for these cycles; therefore, our observations demonstrate a previously unknown mechanism of respiration in insects analogous to the inflation and deflation of vertebrate lungs.

Animals↗
PubMed1999

Chunk versus point sampling: visual imaging in a small insect.

The eyes of strepsipteran insects are very unusual among living insects. In their anatomical organization they may form a modern counterpart to the structural plan proposed for the eyes of some trilobites. Externally they differ from the usual "insect plan" by presenting far fewer but much larger lenses. Beneath each lens is its own independent retina. Anatomical and optical measurements indicate that each of these units is image-forming, so that the visual field is subdivided into and represented by "chunks," unlike the conventional insect compound eye that decomposes the visual image in a pointwise manner. This results in profound changes in the neural centers for vision and implies major evolutionary changes.

Animals↗
PubMed1988

Nonspecific factors involved in attachment of entomopathogenic deuteromycetes to host insect cuticle.

The attachment of the conidia of the insect-pathogenic fungi Nomuraea rileyi, Beauveria bassiana, and Metarrhizium anisopliae to insect cuticle was mediated by strong binding forces. The attachment was passive and nonspecific in that the conidia adhered readily to both host and nonhost cuticle preparations. The hydrophobicity of the conidial wall and the insect epicuticle appeared to mediate the adhesion process. Detergents, solvents, and high-molecular-weight proteins known to neutralize hydrophobicity reduced conidial binding when added to conidium-cuticle preparations. However, these chemicals did not remove the hydrophobic components from the epicuticle or from conidial preparations. The outer surface of the conidium consists of a resilient layer of well-organized fascicles of rodlets. Intact rodlets extracted from B. bassiana conidia bound to insect cuticle and exhibited the hydrophobicity expressed by intact conidia. Both electrostatic charges and various hemagglutinin activities were also present on the conidial surface. However, competitive-inhibition studies indicated that these forces played little, if any, role in the adhesion process.

Journal Article↗
PubMed1992

Insecticidal properties of genetically engineered baculoviruses expressing an insect juvenile hormone esterase gene.

Exploring the possibility of enhancing the properties of baculoviruses as biological control agents of insect pests, we tested the effect of expressing an insect gene (jhe) encoding juvenile hormone esterase. Juvenile hormone esterase inactivates juvenile hormone, which regulates the outcome of an insect molt. A cDNA encoding the juvenile hormone esterase of Heliothis virescens was inserted into the genome of Autographa californica nuclear polyhedrosis virus such that the gene was expressed under the control of a strong, modified viral promoter. This virus, however, naturally encodes an ecdysteroid UDP-glucosyltransferase which inactivates ecdysone, the hormone which initiates molting. Since ecdysteroid UDP-glucosyltransferase could mask the effects of jhe expression by blocking molting entirely, jhe-expressing viruses in which the ecdysteroid UDP-glucosyltransferase gene was deleted or disrupted were constructed. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis of proteins from infected cells revealed several intracellular proteins and two major secreted proteins which reacted with antibodies to authentic juvenile hormone esterase. Western blot analysis coupled with tunicamycin treatment indicated that differential glycosylation was responsible for the multiple products. Hemolymph of recombinant virus-infected fourth-instar Trichoplusia ni larvae contained levels of juvenile hormone esterase activity 40-fold higher than maximal levels found in uninfected larvae. However, little or no difference in developmental characteristics, weight gain, or time of mortality was observed between insects infected with the jhe-expressing viruses and control viruses.

Animals↗
PubMed1992

Topical application of ice-nucleating-active bacteria decreases insect cold tolerance.

The majority of overwintering insects avoid lethal freezing by lowering the temperature at which ice spontaneously nucleates within their body fluids. We examined the effect of ice-nucleating-active bacteria on the cold-hardiness of the lady beetle, Hippodamia convergens, a freeze-intolerant species that overwinters by supercooling to ca. -16 degrees C. Topical application of the ice-nucleating-active bacteria Pseudomonas syringae increased the supercooling point to temperatures as high as -3 degrees C. This decrease in cold tolerance was maintained for at least 3 days after treatment. Various treatment doses (10, 10, and 10 bacteria per ml) and modes of action (bacterial ingestion and topical application) were also compared. At the highest concentration of topically applied P. syringae, 50% of the beetles froze between -2 and -4 degrees C. After topical application at the lowest concentration, 50% of the individuals froze by -11 degrees C. In contrast, beetles fed bacteria at this concentration did not begin to freeze until -10 degrees C, and 50% were frozen only at temperatures of -13 degrees C or less. In addition to reducing the supercooling capacity in H. convergens, ice-nucleating-active bacteria also significantly reduced the cold-hardiness of four additional insects. These data demonstrate that ice-nucleating-active bacteria can be used to elevate the supercooling point and thereby decrease insect cold tolerance. The results of this study support the proposition that ice-nucleating-active bacteria may be used as a biological insecticide for the control of insect pests during the winter.

Journal Article↗
PubMed2005

Aphid-symbiotic bacteria cultured in insect cell lines.

The cells and tissues of many aphids contain bacteria known as "secondary symbionts," which under specific environmental circumstances may be beneficial to the host insect. Such symbiotic bacteria are traditionally described as intractable to cultivation in vitro. Here we show that two types of aphid secondary symbionts, known informally as T type and U type, can be cultured and maintained in three insect cell lines. The identities of the cultured bacteria were confirmed by PCR with sequencing of 16S rRNA gene fragments and fluorescence in situ hybridization. In cell lines infected with bacteria derived from aphids harboring both T type and U type, the U type persisted, while the T type was lost. We suggest that the two bacteria persist in aphids because competition between them is limited by differences in tropism for insect tissues or cell types. The culture of these bacteria in insect cell lines provides a new and unique research opportunity, offering a source of unibacterial material for genomic studies and a model system to investigate the interactions between animal cells and bacteria. We propose the provisional taxon names "Candidatus Consessoris aphidicola" for T type and "Candidatus Adiaceo aphidicola" for U type.

Animals↗
PubMed1990

Identification of Epstein-Barr virus terminal protein 1 (TP1) in extracts of four lymphoid cell lines, expression in insect cells, and detection of antibodies in human sera.

The terminal proteins TP1 and TP2 are putative products of Epstein-Barr virus (EBV) genes expressed during the latent cycle of the virus. They are predicted to code for 53- and 40-kilodalton integral membrane proteins. We used the baculovirus Autographa californica nuclear polyhedrosis virus as an expression vector to produce TP1 in large amounts in insect cells. The DNA sequences used to express TP1 originated from a TP1 cDNA derived from an M-ABA/CBL1 cDNA library. Rabbit antisera raised against procaryotic TP1 fusion proteins recognized a monomer and a dimer of the recombinant TP1 protein in the infected insect cells. Immunofluorescence studies of living insect cells showed that the recombinant protein is located in the plasma membrane. The insect cells infected with the recombinant baculovirus producing TP1 provided a test system to screen human antisera for TP1 antibodies. A total of 168 human EBV-positive and EBV-negative antisera were studied. TP1 antibodies were detected only in sera from nasopharyngeal carcinoma patients (16 out of 42). Rabbit antiserum raised against the recombinant TP1 protein expressed in the baculovirus system specifically recognized a protein of about 54 kilodaltons in the lymphoblastoid cell lines M-ABA and M-ABA/CBL1 and in the Burkitt's lymphoma cell lines BL18 and BL72. This protein could be located in the total membrane fraction of M-ABA cells and is upregulated by treating the cells with 12-O-tetradecanoylphorbol-13-acetate.

Animals↗
PubMed1996

DNA encapsidation by viruslike particles assembled in insect cells from the major capsid protein VP1 of B-lymphotropic papovavirus.

Capsids of polyomaviruses--small, nonenveloped DNA viruses--consist of the major structural protein VP1 and the minor structural proteins VP2 and VP3. The contributions of the individual capsid proteins to functions of the viral particle, such as DNA encapsidation, cell receptor attachment, entry, and uncoating, are still not clear. Here we show that viruslike particles assembled in nuclei of insect cells from VP1 of the monkey B-lymphotropic papovavirus (LPV) are sufficient to unspecifically encapsidate DNA. LPV VP1 expressed in large amounts in insect cells by a baculovirus vector assembled spontaneously in the nuclei to form viruslike particles. After metrizamide equilibrium density gradient purification and nuclease digestion, a fraction of these particles was shown to contain VP1-associated linear, double-stranded DNA with a predominant size of 4.5 kb. The fraction of DNA-containing VP1 particles increased with time and dose of baculovirus vector infection. The DNA-containing particles, further purified by sucrose gradient centrifugation, appeared as "full" particles in negative-staining electron microscopy. As shown by DNA hybridization, the encapsidated DNA consisted of insect cell and baculoviral sequences with no apparent strong homology to LPV sequences. Three non-LPV VP1-derived host proteins with apparent molecular masses of approximately 14, 15, and 16 kDa copurified with the DNA-containing particles and may represent insect cell histones encapsidated together with the DNA. A similar species of host DNA was also found in purified LPV wild-type virions. These data suggest that LPV VP1 alone can be sufficient to encapsidate linear DNA in a sequence-independent manner.

Animals↗
PubMed1997

Expression of human endogenous retrovirus type K envelope glycoprotein in insect and mammalian cells.

The human endogenous retrovirus type K (HERV-K) family codes for the human teratocarcinoma-derived retrovirus (HTDV) particles. The existence of the envelope protein (ENV) of HERV-K encoded by the subgenomic env mRNA has not yet been demonstrated. To study the genetic requirements for successful expression of ENV, we have constructed a series of recombinant HERV-K env expression vectors for infection and transfection experiments in insect cells and mammalian cells, respectively. Six baculovirus constructs bearing full-length or truncated HERV-K env with or without homologous or heterologous signal peptides were used for infections of insect cells. All recombinant baculoviruses yielded ENV proteins with the expected molecular masses. The full-length 80- to 90-kDa HERV-K ENV protein including the cORF leader sequence was glycosylated in insect cells. In addition, the 14-kDa cORF protein was expressed due to splicing of the full-length env mRNA. The ENV precursor protein is not cleaved to the surface (SU) and transmembrane (TM) glycoproteins; it does not appear on the surface of infected insect cells and is not secreted into the medium. For ENV expression in COS cells, plasmid vectors harboring the cytomegalovirus immediate-early promoter/intron A element and the tissue plasminogen activator (t-PA) signal peptide or the homologous HERV-K signal peptide upstream of the env gene were employed. Glycosylated and uncleaved ENV was expressed as in GH teratocarcinoma cells but at higher levels. The heterologous t-PA signal sequence was instrumental for expression of HERV-K ENV on the cell surface. Hence, we have shown for the first time that the HERV-K env gene has the potential to be expressed as a full-length envelope protein with appropriate glycosylation. In addition, our data provide explanations for the lack of infectivity of HERV-K/HTDV particles.

Animals↗
PubMed1998

Functionality and cell anchorage dependence of the African swine fever virus gene A179L, a viral bcl-2 homolog, in insect cells.

The African swine fever virus gene A179L has been shown to be a functional member of the ced9/bcl-2 family of apoptosis inhibitors in mammalian cell lines. In this work we have expressed the A179L gene product (p21) under the control of the baculovirus polyhedrin promoter using a baculovirus system. Expression of the A179L gene neither altered the baculovirus replication phenotype nor delayed the shutoff of cellular protein synthesis, but it extended the survival of the infected insect cells to very late times postinfection. The increase in cell survival rates correlated with a marked apoptosis reduction after baculovirus infection. Interestingly, prevention of apoptosis was observed when recombinant baculovirus infections were carried out in monolayer cell cultures but not when cells were infected in suspension, suggesting a cell anchorage dependence for p21 function in insect cells. Cell survival was enhanced under optimal conditions of cell attachment and cell-to-cell contact as provided by extracellular matrix components or poly-D-lysine. Since it was observed that cytoskeleton organization varied depending on culture conditions of insect cells (grown in monolayer versus grown in suspension), these results suggested that A179L might regulate apoptosis in insect cells only when the cytoskeletal support of intracellular signaling is maintained upon cell adhesion. Thus, cell shape and cytoskeleton status might allow variations in intracellular transduction of signals related to cell survival in virus-infected cells.

African Swine Fever Virus↗
PubMed1999

Persistent Hz-1 virus infection in insect cells: evidence for insertion of viral DNA into host chromosomes and viral infection in a latent status.

Persistent/latent viral infections of insect cells are a prominent though poorly understood phenomenon. In this study, the long-term association between the Hz-1 virus and insect host cells, conventionally referred to as persistent viral infection, is described. With the aid of a newly developed fluorescent cell-labeling system, we found that productive viral replication occurs by spontaneous viral reactivation in fewer than 0.2% of persistently infected cell lines over a 5-day period. Once viral reactivation takes place, the host cell dies. The persistently infected cells contain various amounts of viral DNA, and, in an extreme case, up to 16% of the total DNA isolated from infected cells could be of viral origin. Both pulsed-field gel electrophoresis and in situ hybridization experiments showed that some of these viral DNA molecules are inserted into the host chromosomes but that the rest of viral DNA copies are free from host chromosomes. Thus, Hz-1 virus is the first nonretroviral insect virus known to insert its genome into the host chromosome during the infection process. These data also suggest that the previously described persistent infection of Hz-1 virus in insect cells should be more accurately referred to as latent viral infection.

Animals↗
PubMed1992

Antibody to a 63 kilodalton insect protein in ankylosing spondylitis.

Ankylosing spondylitis (AS) is associated with antibodies to a heat shock puff on drosophila chromosomes. This observation was investigated by immunoblotting using extracts of the Schneider insect cell line and HeLa cells, before and after heat shock. An insect protein of 63 kilodaltons (but no equivalent human protein) was recognised by 21 (46%) of 46 serum samples from patients with AS, one of two patients with Reiter's syndrome, four (7%) of 60 patients with systemic lupus erythematosus, and two (4%) of 50 control subjects, but not by serum samples from patients with rheumatoid arthritis (RA). Previous heat shock did not appear to affect the strength of reaction, but ML-30, a monoclonal antibody to the mycobacterial 65 kilodalton heat shock protein (hsp65), also recognised an insect protein of 63 kilodaltons by immunoblotting. Antibodies to recombinant mycobacterial hsp65 were measured by enzyme linked immunosorbent assay (ELISA) in serum samples from patients with AS and RA. IgA binding to hsp65 was increased in 41% of AS and 19% of RA serum samples, but there was no correlation with detection of antibody to the insect 63 kilodalton protein.

Animals↗
PubMed2005

Serial passage of the opportunistic pathogen Aspergillus flavus through an insect host yields decreased saprobic capacity.

To study the early stages of the effect of host restriction on pathogen evolution, we subjected the opportunistic fungus Aspergillus flavus to a serial propagation scheme, whereby insect-virulent conidia were selected for repeated passage through an insect host (Galleria mellonella larvae) for 5 generations. Of the 35 lineages promulgated through this scheme, there were no consistent changes in virulence, which was measured by percent mortality of the larvae. There were, however, increases in the number of conidia on the insect cadavers (9 of 35 lineages) and decreases in the number of days between death and the appearance of fungal growth on the cadavers (4 of 35 lineages). Notably, most of the lineages (28 of 35 lineages) demonstrated a statistically significant decrease in the diameter of the colonies subcultured onto artificial media, indicating a decreased ability to grow saprobically. Conversely, most of the A. flavus cultures successively grown on agar media (9 of 10 lineages) exhibited no change in colony diameter after 15 rounds of subculturing. Propagation of the opportunist A. flavus through the insect host G. mellonella resulted in a diminished capacity to grow on an alternate substrate, while maintaining or increasing its ability to use the host as a nutrient supply.

Animals↗
PubMed1996

Tympanal hearing in insects.

Specialized hearing organs, known as tympanal organs, have evolved in at least seven different orders of insects. Tympanal organs are usually defined by the presence of a tympanal membrane (or eardrum). They are backed by an air-filled space or cavity and are innervated by a chordotonal sensory organ. In some insects, however, a recognizable tympanal membrane may not be easily identified by visual inspection, yet may possess tympanal hearing organs. In insects that possess them, tympanal hearing organs may mediate the detection of predators, prey, and potential mates and rivals. Unlike the ears of vertebrates, which are localized to cranial segments, the ears of insects may be found in a bewildering variety of locations on their bodies, depending on the species. The embryological and evolutionary origins of tympanal organs are related to ancestral states as proprioceptive chordotonal organs.

Journal Article↗
PubMed1997

Adaptations in scale insects.

Many unusual features of scale insects (Hemiptera: Coccoidea) can be explained as historical legacy. Developmental specializations in ancestral coccoids resulted in a neotenous adult female and a drastic metamorphosis of the male. Subsequent evolution led to numerous, often convergently derived, adaptations to parasitic life on higher plants. The sedentary lifestyle of female scale insects has favored the evolution of appendage reduction or loss, gross changes in body shape, and protective wax secretions, tests, and other scale covers. Morphological peculiarities of adult males relate to flight or to mating with concealed females. Scale insects have diverse egg-protecting methods, a range of chromosome behaviors (including several methods of sex determination), marked sexual dimorphism [even sometimes in first-instar nymphs (crawlers)], and more rarely sexual dichronism. Crawlers have evolved as the main agents of dispersal. The biotic interactions of scale insects include diverse endosymbioses with microorganisms, sometimes morphological and behavioral adaptations for obligate association with ants, and often highly specific host-plant associations that may lead to demic adaptation or the evolution of complex galls.

Journal Article↗
PubMed1997

Photoperiodic time measurement and related physiological mechanisms in insects and mites.

For over 60 years, many species of insects and mites have been known to respond in an adaptive way to seasonal changes in daylength. Responses to photoperiod allow them to survive periods of unfavorable environmental conditions. Since the early 1950s, light-sensitive and temperature-compensated circadian clocks have also been known to regulate the timing of many events (behavioral, physiological, biochemical) in all eukaryotic organisms, including insects and mites. Over the past 30 years, considerable effort has been directed at elucidation of the nature of the clock mechanism that underlies photoperiodism. Mathematical models using a number of insect systems have been developed that attempt to causally relate the circadian clock to photoperiodic time measurement. Although some experimental evidence supports these circadian-based models, some insects and mites appear to utilize a non-periodic hourglass timer as the photoperiodic clock. Future work in this field would benefit by following the approach that has proven to be very successful in identifying genes and gene products that regulate circadian rhythmicity in Drosophila melanogaster.

Journal Article↗