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Toshio Ichikawa - One of the best experts on this subject based on the ideXlab platform.
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Defensive gin-trap closure response of tenebrionid beetle, Zophobas atratus, pupae.
Journal of insect science (Online), 2012Co-Authors: Toshio Ichikawa, Toshiaki Kurauchi, Yoshifumi YamawakiAbstract:Pupae of the beetle Zophobas atratus Fab. (Coleoptera: Tenebrionidae) have jaws called gin traps on the lateral margin of their jointed abdominal segments. When a weak tactile stimulation was applied to the intersegmental region between the two jaws of a gin trap in a resting pupa, the pupa rapidly closed and reopened single or multiple gin traps adjacent to the stimulated trap for 100200 ms. In response to a strong stimulation, a small or large rotation of the abdominal segments occurred after the rapid closure of the traps. Analyses of trajectory patterns of the last abdominal segment during the rotations revealed that the rotational responses were graded and highly variable with respect to the amplitudes of their horizontal and vertical components. The high variability of these rotational responses is in contrast with the low variability (or constancy) of abdominal rotations induced by the tactile stimulation of cephalic and thoracic appendages. Since the closed state of the gin traps lasts only for a fraction of a second, the response may mainly function to deliver a “painful” stimulus to an attacker rather than to cause serious damage.
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Defensive Abdominal Rotation Patterns of Tenebrionid Beetle, Zophobas atratus, Pupae
Journal of insect science (Online), 2012Co-Authors: Toshio Ichikawa, Tatsuya Nakamura, Yoshifumi YamawakiAbstract:Exarate pupae of the beetle Zophobas atratus Fab. (Coleoptera: Tenebrionidae) have free appendages (antenna, palp, leg, and elytron) that are highly sensitive to mechanical stimulation. A weak tactile stimulus applied to any appendage initiated a rapid rotation of abdominal segments. High-speed photography revealed that one cycle of defensive abdominal rotation was induced in an all-or-none fashion by bending single or multiple mechanosensory hairs on a leg or prodding the cuticular surface of appendages containing campaniform sensilla. The direction of the abdominal rotation completely depended on the side of stimulation; stimulation of a right appendage induced a right-handed rotation about the anterior-posterior axis of the pupal body and vice versa. The trajectories of the abdominal rotations had an ellipsoidal or pear-shaped pattern. Among the trajectory patterns of the rotations induced by stimulating different appendages, there were occasional significant differences in the horizontal (right-left) component of abdominal rotational movements. Simultaneous stimulation of right and left appendages often induced variable and complex patterns of abdominal movements, suggesting an interaction between sensory signals from different sides. When an abdominal rotation was induced in a freely lying pupa, the rotation usually made the pupa move away from or turn its dorsum toward the source of stimulation with the aid of the caudal processes (urogomphi), which served as a fulcrum for transmitting the power of the abdominal rotation to the movement or turning of the whole body. Pattern generation mechanisms for the abdominal rotation were discussed.
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Mechanism of hemolymph circulation in the pupal leg of tenebrionid beetle Zophobas atratus.
Comparative biochemistry and physiology. Part A Molecular & integrative physiology, 2009Co-Authors: Toshio IchikawaAbstract:The long legs of insects require adequate hemolymph flow for maintaining their metabolism and functions. The visualization of hemolymph flow in a pupal leg of the tenebrionid beetle Zophobas atratus revealed that, in addition to a general circuit across all segments (podomeres) of the leg, there were two shortcut channels running within the femur, which is the largest podomere. A unidirectional hemolymph flow was forced by periodic pumping movements of the abdomen and regulated by a valve that exhibited a metamorphic change from a tongue-shaped to a flap-shaped structure. The results suggest that insects with a simple (open) circulatory system have evolved a sophisticated circulatory mechanism that distribute hemolymph adequately to the individual podomeres, which have diverse morphologies and functions.
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Larval Cannibalism and Pupal Defense Against Cannibalism in Two Species of Tenebrionid Beetles
Zoological science, 2009Co-Authors: Toshio Ichikawa, Toshiaki KurauchiAbstract:Cannibalism of pupae by larvae has been documented in many species of insects, but the features of larval cannibalism and pupal defensive mechanisms against larval cannibalism have been largely ignored. Pupae of tenebrionid beetles rotate their abdominal segments in a circular motion in response to the tactile stimulation of appendages, including legs, antennae, maxillary pulps, and wings. When the pupal abdominal rotation responses of Tenebrio molitor and Zophobas atratus were completely blocked by transecting the ventral nerve cord (VNC) of the pupae, the appendages of the paralytic pupae became initial, major targets for attack by larval cannibals. The majority of 20 paralytic pupae was cannibalized by 100 larvae within 6 h, and almost all the pupae were killed within 2–3 days. In contrast, only a few pupae of Z. atratus and several pupae of T. molitor were cannibalized when the VNC was intact. The abdominal rotation response of the pupae thus functions as an effective defense against larval cannibalism.
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Periodic abdominal pumping supports leg development during metamorphosis in tenebrionid beetle Zophobas atratus.
Comparative biochemistry and physiology. Part A Molecular & integrative physiology, 2008Co-Authors: Toshio IchikawaAbstract:Rhythmic abdominal pumping movements in a pupa of giant mealworm beetle Zophobas atratus caused large hemolymph pressure pulses of approximately 20 mmHg. The abdominal pumping movements were completely blocked by transecting the ventral nerve cord (VNC) between the first and second abdominal ganglia. Transection of the VNC until 2 days after pupation caused a developmental defect of adult legs: morphogenesis of the tibial and tarsal segments was severely retarded, and the segments remained covered with a thick pupal cuticle. The developmental defect was rescued by artificially inducing rhythmic abdominal bending for 3 days after transection of VNC. Blocking of the abdominal pump did not increase the amount of water loss during the pupal period. The transplanted tibial segments lacking active tracheal ventilation could form a thick adult cuticle. The results suggest that abdominal pumping movements during the pupal period support the development of adult legs by facilitating hemolymph circulation.
Vadim R Viviani - One of the best experts on this subject based on the ideXlab platform.
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bioluminescence of beetle luciferases with 6 amino d luciferin analogues reveals excited keto oxyluciferin as the emitter and phenolate luciferin binding site interactions modulate bioluminescence colors
Biochemistry, 2014Co-Authors: Vadim R Viviani, Rogilene A. Prado, Deimison Rodrigues Neves, Danilo T Amaral, Takuto Matsuhashi, Takashi HiranoAbstract:Beetle luciferases produce different bioluminescence colors from green to red using the same d-luciferin substrate. Despite many studies of the mechanisms and structural determinants of bioluminescence colors with firefly luciferases, the identity of the emitters and the specific active site interactions responsible for bioluminescence color modulation remain elusive. To address these questions, we analyzed the bioluminescence spectra with 6′-amino-d-luciferin (aminoluciferin) and its 5,5-dimethyl analogue using a set of recombinant beetle luciferases that naturally elicit different colors and different pH sensitivities (pH-sensitive, Amydetes vivianii λmax = 538 nm, Macrolampis sp2 λmax = 564 nm; pH-insensitive, Phrixotrix hirtus λmax = 623 nm, Phrixotrix vivianii λmax = 546 nm, and Pyrearinus termitilluminans λmax = 534 nm), a luciferase-like enzyme (Tenebrionidae, Zophobas morio λmax = 613 nm), and mutants of C311 (S314). The green-yellow-emitting luciferases display red-shifted bioluminescence spectra...
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a route from darkness to light emergence and evolution of luciferase activity in amp coa ligases inferred from a mealworm luciferase like enzyme
Biochemistry, 2013Co-Authors: Vadim R Viviani, R. A. Prado, D R Neves, Daiichiro Kato, J A BarbosaAbstract:The origin of luciferases and of bioluminescence is enigmatic. In beetles, luciferases seem to have evolved from AMP-CoA-ligases. How the new oxygenase luminogenic function originated from AMP-ligases leading to luciferases is one of the most challenging mysteries of bioluminescence. Comparison of the cloned luciferase-like enzyme from the nonluminescent Zophobas morio mealworm and beetle luciferases showed that the oxygenase activity may have emerged as a stereoselective oxidative drift with d-luciferin, a substrate that cannot be easily thioesterified to CoA as in the case of the l-isomer. While the overall kcat displayed by beetle luciferases is orders of magnitude greater than that of the luciferase-like enzyme, the respective oxidation rates and quantum yields of bioluminescence are roughly similar, suggesting that the rate constant of the AMP-ligase activity exerted on the new d-luciferin substrate in beetle protoluciferases was the main enzymatic property that suffered optimization during the evolu...
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the origin of luciferase activity in Zophobas mealworm amp coa ligase protoluciferase luciferin stereoselectivity as a switch for the oxygenase activity
Photochemical and Photobiological Sciences, 2010Co-Authors: Vadim R Viviani, Valeria Scorsato, Rogilene A. Prado, Jose G. C. Pereira, Kazuki Niwa, Yoshihiro Ohmiya, J A BarbosaAbstract:Beetle luciferases evolved from AMP/CoA-ligases. However, it is unclear how the new luciferase activity evolved. In order to clarify this question, we compared the luminescence and catalytic properties of a recently cloned luciferase-like enzyme from Zophobas mealworm, an AMP/CoA-ligase displaying weak luminescence activity, with those of cloned luciferases from the three main families of luminescent beetles: Phrixthrix hirtus railroad worm; Pyrearinus termitilluminans click beetle and Photinus pyralis firefly. The catalytic constant of the mealworm enzyme was 2–4 orders of magnitude lower than that of beetle luciferases, but 3 orders of magnitude above the non-catalyzed chemiluminescence of luciferyl-adenylate in buffer. Studies with D- and L-luciferin and their adenylates show that the luminescence reaction of the luciferase-like enzyme and beetle luciferases are stereoselective for D-luciferin and its adenylate, and that the selectivity is determined mainly at the adenylation step. Modelling studies showed that the luciferin binding site cavity of this enzyme is smaller and more hydrophobic than that of beetle luciferases. Therefore Zophobas mealworm enzyme displays true luciferase activity, keeping the attributes of an ancient protoluciferase. These results suggest that stereoselectivity for D-luciferin may have been a key event for the origin of oxygenase/luciferase activity in AMP/CoA-ligases, and that efficient luciferase activity may have further evolved mainly by increasing the catalytic constant of the oxidative reaction and the quantum yield of bioluminescence.
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The origin of luciferase activity in Zophobas mealworm AMP/CoA-ligase (protoluciferase): luciferin stereoselectivity as a switch for the oxygenase activity
Photochemical & photobiological sciences : Official journal of the European Photochemistry Association and the European Society for Photobiology, 2010Co-Authors: Vadim R Viviani, Valeria Scorsato, Rogilene A. Prado, Jose G. C. Pereira, Kazuki Niwa, Yoshihiro Ohmiya, J A BarbosaAbstract:Beetle luciferases evolved from AMP/CoA-ligases. However, it is unclear how the new luciferase activity evolved. In order to clarify this question, we compared the luminescence and catalytic properties of a recently cloned luciferase-like enzyme from Zophobas mealworm, an AMP/CoA-ligase displaying weak luminescence activity, with those of cloned luciferases from the three main families of luminescent beetles: Phrixthrix hirtus railroad worm; Pyrearinus termitilluminans click beetle and Photinus pyralis firefly. The catalytic constant of the mealworm enzyme was 2–4 orders of magnitude lower than that of beetle luciferases, but 3 orders of magnitude above the non-catalyzed chemiluminescence of luciferyl-adenylate in buffer. Studies with D- and L-luciferin and their adenylates show that the luminescence reaction of the luciferase-like enzyme and beetle luciferases are stereoselective for D-luciferin and its adenylate, and that the selectivity is determined mainly at the adenylation step. Modelling studies showed that the luciferin binding site cavity of this enzyme is smaller and more hydrophobic than that of beetle luciferases. Therefore Zophobas mealworm enzyme displays true luciferase activity, keeping the attributes of an ancient protoluciferase. These results suggest that stereoselectivity for D-luciferin may have been a key event for the origin of oxygenase/luciferase activity in AMP/CoA-ligases, and that efficient luciferase activity may have further evolved mainly by increasing the catalytic constant of the oxidative reaction and the quantum yield of bioluminescence.
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An ancestral luciferase in the Malpighi tubules of a non-bioluminescent beetle!
Photochemical and Photobiological Sciences, 2008Co-Authors: Vadim R Viviani, R. A. Prado, F. C. G. Arnoldi, Fábio Camargo AbdallaAbstract:The evolutionary origin of beetle bioluminescence is enigmatic. Previously, weak luciferase activity was found in the non-bioluminescent larvae of Tenebrio molitor (Coleoptera: Tenebrionidae), but the detailed tissular origin and identity of the luciferase-like enzyme remained unknown. Using a closely related giant mealworm, Zophobas morio, here we show that the luciferase-like enzyme is located in the Malpighi tubules. cDNA cloning of this luciferase like enzyme, showed that it is a short AMP-ligase with weak luciferase activity which diverged long ago from beetle luciferases. The results indicate that the potential for bioluminescence in AMP-ligases is very ancient and provide a first reasonable protoluciferase model to investigate the origin and evolution of beetle luciferases.
J A Barbosa - One of the best experts on this subject based on the ideXlab platform.
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a route from darkness to light emergence and evolution of luciferase activity in amp coa ligases inferred from a mealworm luciferase like enzyme
Biochemistry, 2013Co-Authors: Vadim R Viviani, R. A. Prado, D R Neves, Daiichiro Kato, J A BarbosaAbstract:The origin of luciferases and of bioluminescence is enigmatic. In beetles, luciferases seem to have evolved from AMP-CoA-ligases. How the new oxygenase luminogenic function originated from AMP-ligases leading to luciferases is one of the most challenging mysteries of bioluminescence. Comparison of the cloned luciferase-like enzyme from the nonluminescent Zophobas morio mealworm and beetle luciferases showed that the oxygenase activity may have emerged as a stereoselective oxidative drift with d-luciferin, a substrate that cannot be easily thioesterified to CoA as in the case of the l-isomer. While the overall kcat displayed by beetle luciferases is orders of magnitude greater than that of the luciferase-like enzyme, the respective oxidation rates and quantum yields of bioluminescence are roughly similar, suggesting that the rate constant of the AMP-ligase activity exerted on the new d-luciferin substrate in beetle protoluciferases was the main enzymatic property that suffered optimization during the evolu...
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the origin of luciferase activity in Zophobas mealworm amp coa ligase protoluciferase luciferin stereoselectivity as a switch for the oxygenase activity
Photochemical and Photobiological Sciences, 2010Co-Authors: Vadim R Viviani, Valeria Scorsato, Rogilene A. Prado, Jose G. C. Pereira, Kazuki Niwa, Yoshihiro Ohmiya, J A BarbosaAbstract:Beetle luciferases evolved from AMP/CoA-ligases. However, it is unclear how the new luciferase activity evolved. In order to clarify this question, we compared the luminescence and catalytic properties of a recently cloned luciferase-like enzyme from Zophobas mealworm, an AMP/CoA-ligase displaying weak luminescence activity, with those of cloned luciferases from the three main families of luminescent beetles: Phrixthrix hirtus railroad worm; Pyrearinus termitilluminans click beetle and Photinus pyralis firefly. The catalytic constant of the mealworm enzyme was 2–4 orders of magnitude lower than that of beetle luciferases, but 3 orders of magnitude above the non-catalyzed chemiluminescence of luciferyl-adenylate in buffer. Studies with D- and L-luciferin and their adenylates show that the luminescence reaction of the luciferase-like enzyme and beetle luciferases are stereoselective for D-luciferin and its adenylate, and that the selectivity is determined mainly at the adenylation step. Modelling studies showed that the luciferin binding site cavity of this enzyme is smaller and more hydrophobic than that of beetle luciferases. Therefore Zophobas mealworm enzyme displays true luciferase activity, keeping the attributes of an ancient protoluciferase. These results suggest that stereoselectivity for D-luciferin may have been a key event for the origin of oxygenase/luciferase activity in AMP/CoA-ligases, and that efficient luciferase activity may have further evolved mainly by increasing the catalytic constant of the oxidative reaction and the quantum yield of bioluminescence.
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The origin of luciferase activity in Zophobas mealworm AMP/CoA-ligase (protoluciferase): luciferin stereoselectivity as a switch for the oxygenase activity
Photochemical & photobiological sciences : Official journal of the European Photochemistry Association and the European Society for Photobiology, 2010Co-Authors: Vadim R Viviani, Valeria Scorsato, Rogilene A. Prado, Jose G. C. Pereira, Kazuki Niwa, Yoshihiro Ohmiya, J A BarbosaAbstract:Beetle luciferases evolved from AMP/CoA-ligases. However, it is unclear how the new luciferase activity evolved. In order to clarify this question, we compared the luminescence and catalytic properties of a recently cloned luciferase-like enzyme from Zophobas mealworm, an AMP/CoA-ligase displaying weak luminescence activity, with those of cloned luciferases from the three main families of luminescent beetles: Phrixthrix hirtus railroad worm; Pyrearinus termitilluminans click beetle and Photinus pyralis firefly. The catalytic constant of the mealworm enzyme was 2–4 orders of magnitude lower than that of beetle luciferases, but 3 orders of magnitude above the non-catalyzed chemiluminescence of luciferyl-adenylate in buffer. Studies with D- and L-luciferin and their adenylates show that the luminescence reaction of the luciferase-like enzyme and beetle luciferases are stereoselective for D-luciferin and its adenylate, and that the selectivity is determined mainly at the adenylation step. Modelling studies showed that the luciferin binding site cavity of this enzyme is smaller and more hydrophobic than that of beetle luciferases. Therefore Zophobas mealworm enzyme displays true luciferase activity, keeping the attributes of an ancient protoluciferase. These results suggest that stereoselectivity for D-luciferin may have been a key event for the origin of oxygenase/luciferase activity in AMP/CoA-ligases, and that efficient luciferase activity may have further evolved mainly by increasing the catalytic constant of the oxidative reaction and the quantum yield of bioluminescence.
Grzegorz Rosinski - One of the best experts on this subject based on the ideXlab platform.
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The influence of hormones on the lipid profile in the fat body of insects
ISJ-Invertebrate Survival Journal, 2015Co-Authors: Magdalena Cerkowniak, Grzegorz Rosinski, Malgorzata Slocinska, Piotr Stepnowski, Aleksandra Ostachowska, Marek GołębiowskiAbstract:Peptide hormones play a special role in the neuroendocrine systems of insects and affect a number of physiological processes related to their development, reproduction and behavior. The lipid content in the fat body of insects is closely correlated with the work of the endocrine glands. The lipid profile of the fat body of the Zophobas atratus beetle reveals a predominant proportion of triacylglycerols when compared to free fatty acids and other lipid compounds, such as fatty acid esters, fatty alcohols and sterols. Although it may depend on the stage of the insects’ development, the disparate impacts of the adipokinetic hormone (AKH) on the lipid content in the fat bodies of the feeding larvae and the non-feeding pupae of Z. atratus, may signify the different roles this hormone plays in the indirect control of the insects’ metabolism.
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cardioactive properties of solanaceae plant extracts and pure glycoalkaloids on Zophobas atratus
Insect Science, 2015Co-Authors: Emanuela Ventrella, Pawel Marciniak, Grzegorz Rosinski, Zbigniew Adamski, Szymon Chowanski, Patrizia Falabella, Laura Scrano, Sabino Aurelio BufoAbstract:Glycoalkaloids, the biologically active secondary metabolites produced by Solanaceae plants, are natural defenses against animals, insects and fungi. In this paper, the effects of glycoalkaloids present in extracts of Solanaceae plants (potato, tomato and black nightshade) or pure commercial glycoalkaloids on the coleopteran Zophobas atratus F. were evaluated by in vitro and in vivo bioassays using heart experimental models. Each tested extract induced a dose-dependent cardioinhibitory effect. The perfusion of Zophobas atratus semi-isolated heart using the highest potato and tomato extract concentration (1 mmol/L) caused irreversible cardiac arrests, while extract from black nightshade produced fast but reversible arrests. Pure commercial glycoalkaloids caused similar but less evident effects compared with extracts. Our results showed that the bioactivity of tested compounds depended on their structure and suggested the existence of synergistic interactions when combinations of the main glycoalkaloids of potato and black nightshade were used for trials. Surprisingly, injection of tomato and potato extracts in 1-day-old pupae of Zophobas atratus induced reversible positive chronotropic effects and decreased the duration of the both phases (anterograde and retrograde) of the heart contractile activity. Furthermore, these extracts affected the amplitude of the heart contractions.
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Cardioactive properties of Solanaceae plant extracts and pure glycoalkaloids on Zophobas atratus F.
'Wiley', 2015Co-Authors: Ventrella E., Pawel Marciniak, Grzegorz Rosinski, Zbigniew Adamski, Szymon Chowanski, Falabella Patrizia, Scrano Laura, Bufo, Sabino AurelioAbstract:Glycoalkaloids, the biologically active secondary metabolites produced by Solanaceae plants, are natural defenses against animals, insects and fungi. In this paper, the effects of glycoalkaloids present in extracts of Solanaceae plants (potato, tomato and black nightshade) or pure commercial glycoalkaloids on the coleopteran Zophobas atratus F. were evaluated by in vitro and in vivo bioassays using heart experimental models. Each tested extract induced a dose-dependent cardioinhibitory effect. The perfusion of Zophobas atratus semi-isolated heart using the highest potato and tomato extract concentration (1 mmol/L) caused irreversible cardiac arrests, while extract from black nightshade produced fast but reversible arrests. Pure commercial glycoalkaloids caused similar but less evident effects compared with extracts. Our results showed that the bioactivity of tested compounds depended on their structure and suggested the existence of synergistic interactions when combinations of the main glycoalkaloids of potato and black nightshade were used for trials. Surprisingly, injection of tomato and potato extracts in 1-day old pupae of Zophobas atratus induced reversible positive chronotropic effects and decreased the duration of the both phases (anterograde and retrograde) of the heart contractile activity. Furthermore, these extracts affected the amplitude of the heart contractions
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adipokinetic hormone induces changes in the fat body lipid composition of the beetle Zophobas atratus
Peptides, 2014Co-Authors: Marek Golebiowski, Aleksandra Urbanek, Magdalena Cerkowniak, Grzegorz Rosinski, Malgorzata Slocinska, Piotr StepnowskiAbstract:Abstract In insects, neuropeptide adipokinetic hormone (AKH) released from the corpora cardiaca mobilizes lipids and carbohydrates in the fat body. We examined the developmental differences in the action of Tenmo-AKH, a bioanalogue belonging to the adipokinetic/hypertrahelosemic family (AKH/HrTH), on the lipid composition of larval and pupal fat bodies in the beetle Zophobas atratus . Tenmo-AKH was administered to the beetle larvae and pupae either as a single dose or as two doses of 20 pmol during a 24 h interval. Extracts of fat bodies were used to analyse the lipid composition by gas chromatography (GC) combined with mass spectrometry (GC–MS). Control extracts were analyzed using the same method. Fatty acids (FA) and fatty acid methyl esters (FAME) were the most abundant compounds in the fat bodies from both developmental stages. We observed significant differences in their concentrations following hormonal treatment. Tenmo-AKH also induced a distinct increase in larval sterols, fatty alcohols and benzoic acid.
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Identification and localisation of selected myotropic neuropeptides in the ventral nerve cord of tenebrionid beetles.
Comparative biochemistry and physiology. Part A Molecular & integrative physiology, 2013Co-Authors: Paweł Marciniak, Neil Audsley, Monika Szymczak, Joanna Pacholska-bogalska, Grzegorz RosinskiAbstract:MALDI-TOF MS and MS/MS techniques were used for the isolation and identification of neuropeptides from the ventral nerve cord (VNC) of two beetle species Tenebrio molitor and Zophobas atratus. Two peptides, proctolin and myosuppressin (Zopat-MS), with well-established myotropic properties were identified as well as Trica-NVPL-4trunc. The presence of proctolin and myosuppressin was confirmed by immunocytochemical studies in adults and larvae of both beetles. In addition, the myosuppressin gene in Z. atratus was sequenced and expression analyses showed that it is present in all parts of the beetle central nervous system. Results suggest that the identified peptides act as neurotransmitters/neuromodulators in beetles, regulate visceral muscle contractions and indirectly influence important physiological processes such as feeding and reproduction.
Jean-paul Delbecque - One of the best experts on this subject based on the ideXlab platform.
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l initiation de la metamorphose chez Zophobas atratus fab effets des ligatures et des regulateurs de croissance coleoptera tenebrionidae
Annales De La Societe Entomologique De France, 1999Co-Authors: Nadia Aribi, André Quennedey, Noureddine Soltani, Jean-paul DelbecqueAbstract:La metamorphose chez Zophobas atratus depend des strictes conditions de l'isolement des larves. Les regulateurs de croissance testes (ZR-515, KK-42 et Precocene 2) ainsi que les ligatures perturbent la metamorphose quand le traitement est effectue durant les quatre premiers jours de l'isolement des larves en periode A (jour 0 a 4). L'analyse des concentrations d'ecdysteroides hemolymphatiques, par un dosage immuno-enzymologique (EIA) revele que le profil hormonal est modifie par les analogues ou inhibiteurs de l'hormone juvenile. Les resultats obtenus montrent que l'initiation de la metamorphose chez Z. atratus se produit entre les jours 4 et 6 de l'isolement des larves en periode A.
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2-Deoxyecdysone is a circulating ecdysteroid in the beetle Zophobas atratus
Biochimica et biophysica acta, 1997Co-Authors: Nadia Aribi, Nicole Pitoizet, André Quennedey, Jean-paul DelbecqueAbstract:A qualitative analysis of ecdysteroids has been performed during the post-embryonic development of the tenebrionid beetle, Zophobas atratus, by high performance liquid chromatography (HPLC) combined with enzyme immunoassay (EIA) using two different antibodies. Three HPLC peaks were found to be immunoreactive, in hemolymph extracts of both sexes. Moreover, these peaks had ecdysteroid-like UV spectra, determined using a photodiode array detector. The use of two different HPLC systems (reverse and normal phases), in combination with two different EIA antibodies, allowed us to identify 20-hydroxyecdysone (20E) and ecdysone (E), as the two main ecdysteroids, but also suggested the presence of 2-deoxyecdysone (2dE) as the third hemolymph component. Secretion of putative 2dE, together with E (but not 20E) was also demonstrated in vitro from incubations of prothoracic glands and of tegumental explants. In these experiments, either in vivo or in vitro, 3-dehydroecdysone was never observed. Our observations thus strongly suggest that 2dE is a circulating ecdysteroid in Z. atratus and may function as a prohormone during the development of some insects.
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Postembryonic Development of Zophobas atratus Fab. (Coleoptera: Tenebrionidae) under Crowded or Isolated Conditions and Effects of Juvenile Hormone Analogue Applications
Journal of Insect Physiology, 1995Co-Authors: André Quennedey, Nadia Aribi, Claude Everaerts, Jean-paul DelbecqueAbstract:Abstract Pupation in Zophobas atratus is dependent on isolation and this provides a model for study of the onset of metamorphosis in beetles. We have analyzed the effects of isolation vs grouping on certain developmental parameters; the number of larval instars; their duration and weight. Sex differences were detected, such as the occurrence of regressive moults in females. Moreover, the development of Z. atratus is discussed in relation to Tenebrio molitor , the physiological timing of which appeared in part extendable to Z. atratus . Experiments show that 4–6 days of isolation are required for commencement of metamorphosis, as indicated by an immobile crooked posture observed at the end of this period, characterizing the beginning of prepupal development. During this period, return to grouped conditions, as well as applications of a juvenile hormone analogue (ZR 515) prevented metamorphosis and precipitated another larval moult. This suggests that grouped conditions may delay the onset of metamorphosis through the modulation of juvenile hormone titres.
