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PubMed2025

Abiotic conditions can modify the penetrance of transgene-based lethality systems for insect population control.

Modern genetic biocontrol techniques for insect pest management, when compared to chemical insecticide spraying, offer high species specificity and reduced environmental impact, and some of these methods require the environmental release of genetically modified (GM) insects. Because organisms exposed to different environments often show variability in phenotype and gene expression, it is likely that GM insects will also experience environmentally mediated variation, potentially compromising pest control efficiency. This study examines the impact of temperature and nutrition on the early embryonic Tet-off conditional lethality system in Drosophila melanogaster. By independently manipulating parental and offspring environments, we assessed how exposure to variable environments influenced the probability of larval hatching and the transcript abundance of the transgenic system. Our findings revealed that: (i) transgene performance distinctly responds to temperature and nutrition; (ii) thermal stress has a greater impact when embryos, rather than parents, are exposed; and (iii) extreme nutritional conditions can markedly reduce the penetrance of transgenic lethality. Although changes in transgene transcript abundance were observed across environments, these changes did not fully explain the phenotypic variation, suggesting that factors downstream of transcription probably drive variation in transgenic lethality.

Animals↗

PubMedDate not supplied

[Analogs of juvenile hormones in the control of insects of medical or sanitary importance].

The growth and moulting or immature insects is related to three main groups of hormones : cerebral, ecdysonal and juvenile. Juvenile hormone analogues mark a new stage in the control of detrimental insects, and have significant advantages over the conventional insecticides. In order to establish the effectiveness of juvenile hormone analogues a series of biotests were performed : the wax pupal test, injections, systemic and topical applications, the treatment of food, pulverizations and exposure to vapors. In the laboratory, the efficiency of the analogues was tested against the following genera : Anopheles, Aedes, Culex, Culiseta, Musca, Stomoxys and Blattella, obtaining several effects, such as : lengthening of the larval stages, blocking of metamorphosis and ecdysis, blocking of the emergence of adults, morphogenetic ovicide, sterilizing and lethal effects, etc. Exploratory trials were performed in the field with compounds whose effectiveness had been demonstrated, against some Aedes, Musca, Stomoxys, Pediculus and Bovicola species. Laboratory experiments showed, however, that the insects might become resistant to juvenile hormone analogues.

Aedes↗

PubMed1978

Allergy to insect stings. IV. Diagnosis by radioallergosorbent test (R.A.S.T.).

Radioallergosorbent tests (RAST(s)) have been developed and assessed for the diagnosis of insect hypersensitivity by using a purified allergen from honeybee venom, phospholipase A, and crude yellow jacket venom. Sera from 193 patients positive both by history and skin test to one of these insects were compared with various groups of control sera. Eighty percent of sera from skin test-positive patients were RAST positive; positive RAST were found in 16% of sera tested from skin test-negative patients. A highly positive RAST correlates well with a positive skin test and clinical sensitivity, but serum IgE is not measurable in many patients with mast cell or basophil bound antibody. Since biologically important reactions of antigen with IgE require that the antibody be cell bound, skin testing would be preferred to RAST if one were limited to a single test for the diagnosis of insect allergy.

Animals↗

PubMed1978

A comparative ultrastructural study of blood cells from nine insect orders.

An ultrastructural study of hemocytes from 9 different insect orders has led to the identification of 8 cell types: (1) Plasmatocytes, whose cytoplasm is filled with small dense lysosomes and large heterogeneous structures, are phagocytic cells. (2) Granulocytes, filled with uniformly electron dense granules, are involved in capsule formation. (3) Coagulocytes, which contain granules and structured globules and which possess a well developed RER, are involved in phagocytosis. (4) Spherule cells are filled with large spherical inclusions. (5) Oenocytoids are large cells with few cytoplasmic organelles. These 5 hemocyte types represent the majority of insect blood cells. (6) Prohemocytes, blastic cells which are one of the stem cells a hemocytes, are very few in number in each species investigated. (7) Thrombocytoids and (8) Prodocytes are restricted to a small number of insect species. The ultrastructural characteristics of these hemocyte types are discussed.

Animals↗

PubMed1977

Fatty acid synthetase complex from the insect Ceratitis capitata.

Fatty acid synthesis capacity of the insect Ceratitis capitata has been investigated in vitro from [1-14C]acetyl-CoA using homogenates at different stages of development. A maximum activity was observed after 5--6 days of larval development. But homogenates of the pharate adult insect did not show synthetic capacity of fatty acids. Fatty acid synthetase complex has been isolated from the particle-free supernatant fraction of homogenates from the 6-day C. capitata larvae. The enzyme complex was purified 182-fold with respect to the protein contained in the crude extract. The complex was homogeneous when analysed by gel filtration and by polyacrylamide-gel electrophoresis. The molecular weight was 5.2X10(5). The enzyme was dissociated into half-molecular subunits. Amino acid analysis, general properties, stability and kinetic constants (V and Km) for the substrates are reported. The fatty acid synthetase complex from the insect contains 42+/-1-SH residues and one phosphopatetheine moiety per 5.2X10(5). Activity was dependent on the presence of NADPH; FMN strongly inhibited the enzyme activity promoted by NADPH. The enzyme complex synthesized a range of fatty acid (10:0--18:0), palmitate being the predominant end product. The proportions of fatty acids synthesized varied with substrate concentrations. Fatty acids released from the complex were almost completely in the free form.

Amino Acids↗

PubMed1979

Immunologic and biochemical evaluation of the potency of whole insect body extracts.

Recent studies have indicated that currently available whole body extracts have little potency and are ineffective for diagnosis and treatment of stinging insect allergy. Pure venom is a potent effective allergen but is difficult to obtain in sufficient quantities from all Hymenoptera species. In these studies, an attempt was made to prepare a potent whole body extract. Whole bee body extracts were prepared with different extraction periods and at cold and room temperatures. Potency was examined biochemically by measurements of phospholipase A (PLA) activity and immunologically by PLA and bee venom radioallergosorbent test (RAST) inhibition experiments and gel diffusion studies with the use of rabbit antisera. All extracts prepared in the laboratory had some potency, indicating that it is possible to make a whole body extract containing small quantities of PLA or bee venom. However, the potency of these extracts was minimal as compared with bee venom. Three commercial extracts were almost devoid of detectable immunologic activity. While further attempts may be made to prepare a potent whole body insect extract, these results suggest that it is necessary to obtain venom in relatively pure form for the diagnosis and treatment of stinging insect allergy.

Animals↗

PubMed2026

Yorkie/Scalloped-OVOL-Rac1 axis controls insect wing development by promoting cell proliferation.

The regulation of organ size is a fundamental question in developmental biology, and insect wings provide a powerful model for elucidating the genetic mechanisms underlying morphogenesis. Although the conserved Hippo signaling pathway plays a central role in controlling tissue growth, its precise regulatory network during wing development remains incompletely understood. Here, we identify the zinc finger transcription factor OVOL as a critical mediator of Hippo signaling in insect wing development. We indicate that OVOL is essential for normal wing formation in both Locusta migratoria and Drosophila melanogaster, regulating cell proliferation and trichome patterning. Through transcriptomic analysis and functional validation, we further identify the small GTPase Rac1 as a key downstream effector of OVOL that promotes proliferative growth. Moreover, we find that OVOL expression is directly activated by the Yorkie/Scalloped (Yki/Sd) complex, the core transcriptional effector of the Hippo pathway, without forming a feedback loop. This regulation is mediated through a specific Sd-binding motif (GATAA) within the OVOL promoter. Importantly, Yki/Sd-induced Rac1 expression is dependent on OVOL. Collectively, our findings establish the Yorkie/Sd-OVOL-Rac1 pathway that governs insect wing development by promoting cell proliferation, providing mechanistic insights into organ size regulation in animals.

Cell proliferation↗

PubMed1976

Effects of calcium ions and adenosine diphosphate on the activities of NAD+-linked isocitrate dehydrogenase from the radular muscles of the whelk and flight muscles of insects.

1. The activity of NAD+-linked isocitrate dehydrogenase from the radular muscle of the whelk is higher than those in many vertebrate muscles and only slightly lower than in the flight muscles of insects. The enzyme activity from the whelk (Buccinum undatum) is stable for several hours after homogenization of the radular muscle, whereas that from insect flight muscle is very unstable. Consequently, the enzyme from the whelk muscle is suitable for a systematic investigation of the effects of Ca2+ and ADP. 2. The sigmoid response of the enzyme activity to isocitrate concentration is markedly increased by raising the Ca2+ concentration from 0.001 to 10 muM, but it is decreased by ADP. The inhibitory effect of Ca2+ is most pronounced at pH7.1; it is not observed at pH 6.5. Similar effects are observed for the enzyme from the flight muscle of the locust (Schistocerca gregaria) and the water bug (Lethocerus cordofanus). The percentage activation by ADP of the enzyme from either the whelk or the insects is greater at 10 muM-Ca2+, and 50% of the maximum activation is obtained at 0.10 and 0.16 mM-ADP for the enzyme from whelk and locust respectively at this Ca2+ concentration. At 10 muM-Ca2+ in the absence of added ADP, the apparent Km for isocitrate is markedly higher than in other conditions. Ca2+ concentrations of 0.01, 0.1 and 0.2 muM cause 50% inhibition of maximum activity of the enzyme from the muscles of the whelk, locust and water bug respectively. 3. Recent work has indicated that mitochondria may play a complementary role to the sarcoplasmic reticulum in the control of the distribution of Ca2+ in muscle. The opposite effects of Ca2+ on the activities of isocitrate dehydrogenase and mitochondrial glycerol phosphate dehydrogenase from muscle tissue are consistent with the hypothesis that changes in the intracellular distribution of Ca2+ control the activities of these two enzymes in order to stimulate energy production for the contraction process in the muscle. Although both enzymes are mitochondrial, glycerol phosphate dehydrogenase resides on the outer surface of the inner membrane and responds to sarcoplasmic changes in Ca2+ concentration (i.e. an increase during contraction), whereas the isocitrate dehydrogenase resides in the matrix of the mitochondria and responds to intramitochondrial concentrations of Ca2+ (i.e. a decrease during contraction). It is suggested that changes in intramitochondrial Ca2+ concentrations are primarily responsible for regulation of the activity of NAD+-isocitrate dehydrogenase in order to control energy formation for the contractile process. However, when the muscle is at rest, changes in intramitochondrial concentrations of ADP may regulate energy formation for non-contractile processes.

Adenosine Diphosphate↗

PubMed1976

Microtubules and control of insect egg shape.

This study evidence for tension transmission by microtubules and desmosomes in the follicular epithelium during anisometric growth of certain insect eggs. Most insect oocytes, and the follicles which surround them, grow anisometrically as they assume shapes which approximate to those of long prolate spheroids. Surface growth is most rapid in directions which parallel the polar axis of an oocyte and slowest in circumferential directions at right angles to this axis. The longitudinal axes of microtubule bundles in follicle cells of the gall midge Heteropeza and the cockroach Periplaneta are oriented circumferentially with respect to the surfaces of developing eggs and at right angles to the polar axes of eggs. At cell boundaries, the tubules appear to be attached to spot desmosomes. It is suggested that microtubules and desmosomes form a mechanical continuum throughout a follicular epithelium which transmits tensile forces around the circumference of a growing egg. Follicular resistance to circumferential expansion may be largely responsible for defining the elongate form of insect eggs.

Animals↗

PubMed1977

Correlation between organophosphate poisoning, acetylcholinesterase inhibition, and increased cyclic GMP levels in malathion-treated insects.

Organophosphate poisoning with malathion caused large increases (up to 125 and 440%, respectively) in the level of cyclic GMP in larvae of Mamestra configurata Wlk. and in the fly Sarcophaga bullata Parker. Cyclic AMP was little affected. The malathion-induced increase in cyclic GMP was time and dose dependent. Time-course studies with the head and thorax of S. bullata demonstrated that the increase in cyclic GMP level occurred precipitously after a lag period of about 1 h, during which time the activity of acetylcholinesterase (EC 3.1.1.7) was progressively inhibited. The abrupt increase in cyclic GMP began when acetylcholinesterase activity had been inhibited to a sufficient extent to permit accumulation of acetylcholine. It is suggested that the accumulation of acetylcholine in the malathion-poisoned insects caused cyclic GMP levels to rise. Cyclic GMP may have a role in cholinergic transmission in normally functioning insect neural tissue. Increased levels of cyclic GMP induced by organophosphate and organocholorine (Bodnaryk, R. P. (1976) Can. J. Biochem. 54, 957-962) insecticides appear to be a vital and previously unrecognized biochemical lesion in insects poisoned by these compounds.

Animals↗

PubMed1977

Intercellular junctions in the central nervous system of insects.

The intercellular junctional complexes in the central nervous system (CNS) from a variety of insect species have been examined by thin-sectioning and freeze-fracturing techniques. Of particular concern has been the fine-structural basis of the blood-brain barrier observed to be present in the outer perineurial layer around the avascular insect CNS. The basis of this has been found in the form of tight junctions (zonulae occludentes) present both in sections and in replicas of the perineurium. In the latter, they appear as one or two simple linear ridges, lying parallel to the outer surface, which occasionally display overlapping. The complex geometry of the interdigitating perineurial cells apparently permits such a relatively simple series of ridges to function as a barrier, since tracers are found not to penetrate beyond this level into the underlying nervous tissue. Such evidence is supported by microprobe X-ray analysis of lanthanum-incubated tissues, the perineurium compared with the glia-ensheathed axons showing the presence and absence of lanthanum, respectively. Possible physiological mechanisms that could operate 'in vitro' to maintain the blood-brain barrier are also considered. Other intercellular junctions such as desmosomes, septate junctions and gap junctions are found in the perineurial layer too, the last exhibiting EF particle plaques and PF pits. Glia-glia junctions also occur in some insect species; they include desmosomes, inverted gap junctions and occasional tight junctions. Septate, gap and tight junctions are also found on the membranes of tracheoles penetrating the CNS. Short, ridge-like elaborations and other particle arrays are found on the PF on the axon surfaces and the significance of these structures is discussed.

Animals↗

PubMed1976

Environmental and toxicological aspects of insect growth regulators.

Insect growth regulators (IGRs) are a class of new chemicals that interfere with maturation and reproduction in insects. Proposed hypotheses on the biochemical mechanism of action are presented herein. The environmental aspects as metabolism in soils, plants, insects, and animals suggest strongly that these chemicals undergo rapid degradation and metabolism to innocuous metabolites. The toxicological properties determined for registration of the IGR methoprene, isopropyl (E,E)-11-methoxy-3,7,11-trimethyl-2,4-dodecadienoate, reflected no significant effects against any of the species tested. Toxicological evaluations in swine, sheep, hamsters, rats, dogs, rabbits, guinea pigs, and cattle revealed no clinical signs of toxicosis. Additionally, teratological studies in swine, sheep, hamsters, rats, and rabbits also resulted in no observable effects in the animals at the levels administered.

Animals↗

PubMed1979

Cellular recognition of foreign-ness in two insect species, the American cockroach and the desert locust.

Encapsulation of tissue implants by haemocytes was used as the assay for immune recognition in the insects studied. If haemocytes attach to and encapsulate an object implanted within the haemocoele, it may be assumed the implant is recognized as 'not-self'; lack of encapsulation of tissue implants may be assumed to indicate lack of recognition. The American cockroach, Periplaneta americana, and the desert locust, Schistocerca gregaria, were used both as donors of tissue, and as recipients of tissue implants from various insect species. Allografts were not recognized as foreign and encapsulated by haemocytes of either S. gregaria or P. americana, a phenomenon which has been reported frequently for other insect species. Haemocytes of S. gregaria recognized and encapsulated a smaller range of xenografts compared with haemocytes of P. americana, and it appears that the acuity of immune recognition by haemocytes differs between S. gregaria and the other species tested. Reasons for the different recognition responses of P. americana and S. gregaria are suggested and discussed with particular reference to the results for Nauphoeta cinerea tissue in P. americana, and Gryllus domesticus tissue in S. gregaria, where at least half the number of implants are totally but weakly encapsulated, and it is suggested that haemocytes do not react to 'difference' unless it surpasses a certain threshold.

Animals↗

PubMedDate not supplied

Insects as inhalant allergens.

The importance of insect dust as inhalant allergen (e.g. locust, cockroach, mite, butterfly, bee, fly, etc.) is frequently underestimated as a cause of allergic conjunctivitis, rhinitis and bronchial asthma. The high allergenic potency of insect dust is demonstrated in cases of occupational allergy against locust. This dust is an obligatory sensitizing agent depending upon the degree of exposure and the potency of the allergen irrespective of constitutional factors. No doubts exist any more about the importance of house-dust mite (Dermatophagoides pteronyssinus) as an inhalative allergen. Allergy analysis should be extended also to these insect allergens especially in unclarified cases of perennial and particularly seasonal bronchial asthma or its "equivalents" (atopic rhinitis and conjunctivitis).

Allergens↗

PubMedDate not supplied

[Biosynthesis of group B vitamins by yeasts--symbionts of xylophagous insects].

The biosynthesis of vitamins of the B group was studied in the yeasts Debaryomyces and Zygowillia--the symbionts of insects--xylophages. These yeasts provide the vitamins of the B group (biotin, thiamine, inositol, pyridoxine, nicotinic and pantothenic acids) for the preimaginal phases of insects--xylophages. The presence of these vitamins under the bark of trees and in other places of insect habitation is related to the viability of the yeasts. The content of the vitamins in the phloem depends on the quantity of the yeast organisms in it.

Animals↗

PubMed2024

A PLA2 deletion mutant using CRISPR/Cas9 coupled to RNASeq reveals insect immune genes associated with eicosanoid signaling.

Eicosanoids mediate insect immune responses and synthesized by the catalytic activity of phospholipase A2 (PLA2). A uniquely encoded secretory PLA2 (sPLA2) is associated with immune responses of a lepidopteran insect, Spodoptera exigua. Its deletion mutant was generated using a CRISPR/Cas9 genome editing technology. Both wild and mutant lines were then immune-challenged, and the resulting transcripts were compared with their naïve transcripts by RNASeq using the Illumina-HiSeq platform. In total, 12,878 unigenes were further analyzed by differentially expressed gene tools. Over 69% of the expressed genes in S. exigua larvae are modulated in their expression levels by eicosanoids, recorded from CRISPR/Cas9 mutagenesis against an eicosanoid-synthetic gene, Se-sPLA2. Further, about 36% of the immune-associated genes are controlled by the eicosanoids in S. exigua. Indeed, the deletion mutant suffered significant immunosuppression in both cellular and humoral responses in response to bacterial challenge as well as severely reduced developmental and reproductive potentials.

Animals↗

PubMed1976

Hormonal studies of uridine utilization in an insect cell line CP-1268 derived from the codling moth Laspeyresia pomonella.

Ecdysterone decreased cellular growth and the incorporation of uridine into RNA following 4 days of hormone exposure. This hormone did not affect uridine incorporation following short-term exposure up to 25 hours. Juvenile hormone and farnesol both significantly decreased uridine uptake and incorporation into RNA; however, uridine uptake was inhibited to a greater extent than uridine incorporation. Cyclic AMP increased the incorporation of uridine into RNA but had no demonstrable effect on the uptake process. This stimulation was not the result of cAMP degradation products. Cyclic AMP and ecdysterone together produced a significant increase in uridine incorporation into RNA. These studies demonstrate the potential utilization of insect cell lines for studying the mode of action of insect developmental hormones.

Cell Line↗

PubMed1978

A controlled trial of immunotherapy in insect hypersensitivity.

Insect hypersensitivity is currently treated by immunization using whole-body extracts. We compared this regimen with immunotherapy using insect venoms or placebo in groups of 20 patients matched for history and sensitivity, as judged by venom skin test, histamine release and IgE antibody to venom. After six to 10 weeks of immunization, systemic reactions to stings occurred in seven of 12, seven of 11, and one of 18 patients treated with placebo, whole-body extract, and venom, respectively. Placebo and whole-body extract gave similar results and were significantly less effective than venom immunotherapy (P less than 0.01). The 14 patients with failure of treatment with whole-body extract and placebo were subsequently provided with venom immunotherapy; one reacted to a subsequent sting. We conclude that venom immunotherapy is clinically superior to therapy on whole-body extract or placebo.

Anaphylaxis↗