In classical neuroscience, Dale´s principle postulates that neuronal identity is conferred by the... more In classical neuroscience, Dale´s principle postulates that neuronal identity is conferred by the specific neurotransmitter that it releases. However, the brain might be more tractable to specific situations regardless of specific specialisation which may contradict this principle. Hence, this constrained approach of how we perceive and study the nervous system must be revisited and revised, specifically by studying the dopaminergic system. We presume a relatively flexible change in the dopaminergic system due to neuronal activity or environmental changes. While the parallel between the reward system of mammals and insects is generally well accepted, herein, we extend the idea that the insect nervous system might also possess incredible plasticity, similar to the mammalian system. In this review, we critically evaluate the available information about the reward system in vertebrates and invertebrates, emphasising the dopaminergic neuronal plasticity, a challenge to the classical Dale's principle. Thus, neurotransmitter switching significantly disrupts the static idea of neural network organisation and suggests greater possibilities for a dynamic response to the current life context of organisms.
The toxicity of the Bacillus thuringiensis (Bt) toxin Cry3Aa—originally used against the main pot... more The toxicity of the Bacillus thuringiensis (Bt) toxin Cry3Aa—originally used against the main potato pest, the Colorado potato beetle, Leptinotarsa decemlineata—was verified on this species and then evaluated against the Egyptian armyworm, Spodoptera littoralis, which is a pest of several economically important plants. Larvae of S. littoralis were fed a semi-artificial diet supplemented either with a recombinant or with a natural Bt toxin Cry3Aa and with the genetically engineered (GE) potato of variety Superior NewLeaf (SNL) expressing Cry3Aa. Cry3Aa concentration in the diet and the content in the leaves were verified via ELISA (enzyme-linked immunosorbent assay) and HPLC (high-performance liquid chromatography) during and at the end of the experiments. The biological effectiveness of the coleopteran-specific Cry3Aa with previous reports of activity against S. littoralis was tested on five different populations of S. littoralis larvae by monitoring 13 parameters involving developm...
Insect exposure to their predators can affect individuals and community processes, through direct... more Insect exposure to their predators can affect individuals and community processes, through direct consumption or nonlethal (i.e., nonconsumptive) effects. However, the links between behavioural and physiological responses and stimuli needed for development of the fear are not clear. We therefore subjected the desert locusts (Schistocerca gregaria) to three nonlethal treatments, using the great tits (Parus major) as a potential predator. The treatments involved: (1) bird - presence of a live great tit and its calls, (2) call - great tit calls only, (3) control - without any treatment. In the first behavioural laboratory experiment, hungry locusts were kept in an experimental cage with a shelter and food on opposite sides of the cage. The duration of hiding and feeding were considered as an indicator of fear responses. In the second laboratory experiment with the same three treatments, levels of the adipokinetic hormone (AKH) were evaluated in the central nervous system (CNS) and haem...
Bees originally developed their stinging apparatus and venom against members of their own species... more Bees originally developed their stinging apparatus and venom against members of their own species from other hives or against predatory insects. Nevertheless, the biological and biochemical response of arthropods to bee venom is not well studied. Thus, in this study, the physiological responses of a model insect species (American cockroach, Periplaneta americana) to honeybee venom were investigated. Bee venom toxins elicited severe stress (LD50 = 1.063 uL venom) resulting in a significant increase in adipokinetic hormones (AKHs) in the cockroach central nervous system and haemolymph. Venom treatment induced a large destruction of muscle cell ultrastructure, especially myofibrils and sarcomeres. Interestingly, co-application of venom with cockroach Peram-CAH-II AKH eliminated this effect. Envenomation modulated the levels of carbohydrates, lipids, and proteins in the haemolymph and the activity of digestive amylases, lipases, and proteases in the midgut. Bee venom significantly reduc...
The fruit fly Drosophila melanogaster brain is the most extensively investigated model of a rewar... more The fruit fly Drosophila melanogaster brain is the most extensively investigated model of a reward system in insects. Drosophila can discriminate between rewarding and punishing environmental stimuli and consequently undergo associative learning. Functional models, especially those modelling mushroom bodies, are constantly being developed using newly discovered information, adding to the complexity of creating a simple model of the reward system. This review aims to clarify whether its reward system also includes a hedonic component. Neurochemical systems that mediate the ´wanting´ component of reward in the Drosophila brain are well documented, however, the systems that mediate the pleasure component of reward in mammals, including those involving the endogenous opioid and endocannabinoid systems, are unlikely to be present in insects. The mushroom body components exhibit differential developmental age and different functional processes. We propose a hypothetical hierarchy of the levels of reinforcement processing in response to particular stimuli, and the parallel processes that take place concurrently. The possible presence of activity-silencing and meta-satiety inducing levels in Drosophila should be further investigated.
Several studies showed that insect endocrine system, especially anti-stress neuropeptides, could ... more Several studies showed that insect endocrine system, especially anti-stress neuropeptides, could be used as a potential target for the pest control. The main role of those neuropeptides is to eliminate or at least to reduce the impact of various stressors on insect organism. This defense response is primarily operated by neurohormones from adipokinetic hormone (AKH) family that control mainly stress energy metabolism. Several neurotoxic insecticides with oxidative-stress activity were tested in several model insect species and their anti-stress response was monitored by suitable markers. The results revealed increased level of AKH in corpora cardiaca, the endocrine glands near the insect brain where the AKHs are synthesized, and in hemolymph after the insecticide treatment. Further, the insecticide treatment affected some basic markers of oxidative stress: it modulated total antioxidative capacity as well as the activity of superoxide dismutase, catalase and glutathione-S-transferas...
In honeybees (Apis mellifera), the rate of aging is modulated through social interactions and acc... more In honeybees (Apis mellifera), the rate of aging is modulated through social interactions and according to caste differentiation and the seasonal (winter/summer) generation of workers. Winter generation workers, which hatch at the end of summer, have remarkably extended lifespans as an adaptation to the cold season when the resources required for the growth and reproduction of colonies are limited and the bees need to maintain the colony until the next spring. In contrast, the summer bees only live for several weeks. To better understand the lifespan differences between summer and winter bees, we studied the fat bodies of honeybee workers and identified several parameters that fluctuate in a season-dependent manner. In agreement with the assumption that winter workers possess greater fat body mass, our data showed gradual increases in fat body mass, the size of the fat body cells, and Vg production as the winter season proceeded, as well as contrasting gradual decreases in these par...
Insect adipokinetic hormones (AKHs) are neuropeptides with a wide range of actions, including the... more Insect adipokinetic hormones (AKHs) are neuropeptides with a wide range of actions, including the control of insect energy metabolism. These hormones are also known to be involved in the insect defence system against toxins and pathogens. In this study, our aim was to demonstrate whether the application of external AKHs significantly enhances the efficacy of the entomopathogenic fungus Isaria fumosorosea in a model species (firebug Pyrrhocoris apterus) and pest species (Egyptian cotton leafworm Spodoptera littoralis and pea aphid Acyrthosiphon pisum). It was found that the co-application of Isaria with AKHs significantly enhanced insect mortality in comparison to the application of Isaria alone. The mode of action probably involves an increase in metabolism that is caused by AKHs (evidenced by the production of carbon dioxide), which accelerates the turnover of Isaria toxins produced into the infected insects. However, several species-specific differences probably exist. Intoxicatio...
Titanus giganteus is one of the largest insects in the world, but unfortunately, there is a lack ... more Titanus giganteus is one of the largest insects in the world, but unfortunately, there is a lack of basic information about its biology. Previous papers have mostly described Titanus morphology or taxonomy, but studies concerning its anatomy and physiology are largely absent. Thus, we employed microscopic, physiological, and analytical methods to partially fill this gap. Our study focused on a detailed analysis of the antennal sensilla, where coeloconic sensilla, grouped into irregularly oval fields, and sensilla trichoidea were found. Further, the inspection of the internal organs showed apparent degeneration of the gut and almost total absence of fat body. The gut was already empty; however, certain activity of digestive enzymes was recorded. The brain was relatively small, and the ventral nerve cord consisted of three ganglia in the thorax and four ganglia in the abdomen. Each testis was composed of approximately 30 testicular follicles filled with a clearly visible sperm. Chroma...
The role of the adipokinetic hormone (AKH) in the control of protease, amylase and lipase activit... more The role of the adipokinetic hormone (AKH) in the control of protease, amylase and lipase activities is examined using the cockroach Periplaneta americana and the fruit fly Drosophila melanogaster as model species. The effects of Peram-CAH-I and-II on the activity of cockroach digestive enzymes in the gastric caeca and midgut are measured both in vivo and in vitro. The results show the activity of proteases, amylases and lipases in both parts of the gut: amylase activity is higher in the gastric caeca than in the midgut; lipase activity presents the opposite trend; and protease activity is similar in both organs. The applied hormones stimulate the activity of all digestive enzymes, although this stimulation is not uniform; AKHs affect enzymes selectively, and in some cases unequally, in the gastric caeca and midgut. No substantial differences between Peram-CAH-I and-II stimulation are recorded. The in vitro results demonstrate that AKH stimulates digestive enzyme activity directly. In agreement with the cockroach results, enzymatic activity in D. melanogaster larvae producing nonfunctional AKH is lower than that in the larvae with ectopically expressed Akh gene, where enzyme activity reaches or even exceeds that of the controls. Overall, the results demonstrate the active role of AKHs in the stimulation of digestive enzyme activity in insects.
Archives of Insect Biochemistry and Physiology, 2019
This study examined the effect of two natural toxins (a venom from the parasitic wasp Habrobracon... more This study examined the effect of two natural toxins (a venom from the parasitic wasp Habrobracon hebetor and destruxin A from the entomopathogenic fungus Metarhizium anisopliae), and one pathogen (the entomopathogenic fungus
This study examined how adipokinetic hormone (AKH) and adenosine affect defense responses in Dros... more This study examined how adipokinetic hormone (AKH) and adenosine affect defense responses in Drosophila melanogaster larvae infected with entomopathogenic nematodes (EPN, Steinernema carpocapsae and Heterorhabditis bacteriophora). Three loss-of-function mutant larvae were tested: Akh, AdoR (adenosine receptor), and Akh AdoR. Mortality decreased in all mutants post-EPN infection compared with the control (w). Additionally, co-application of external AKH with EPN significantly increased mortality beyond rates observed in EPN-only treatment, while also elevating carbon dioxide production, a measure of metabolism. Furthermore trehalose levels increased in both w and Akh larvae post-EPN infection, but the latter group exhibited a lower increase and total trehalose levels. Interestingly, baseline trehalose was relatively high in untreated AdoR and Akh AdoR mutants, with levels remaining unaffected by infection. Infection also elevated haemolymph lipid content overall, but the different mu...
The role of adipokinetic hormone (AKH) in counteracting oxidative stress elicited in the insect b... more The role of adipokinetic hormone (AKH) in counteracting oxidative stress elicited in the insect body is studied in response to exogenously applied hydrogen peroxide, an important metabolite of oxidative processes. In vivo experiments reveal that the injection of hydrogen peroxide (8 μmol) into the haemocoel of the firebug, Pyrrhocoris apterus L. (Heteroptera: Pyrrhocoridae) increases the level of AKH by 2.8-fold in the central nervous system (CNS) and by 3.8-fold in the haemolymph. The injection of hydrogen peroxide also increases the mortality of experimental insects, whereas co-injection of hydrogen peroxide with Pyrap-AKH (40 pmol) reduces mortality to almost control levels. Importantly, an increase in haemolymph protein carbonyl levels (i.e. an oxidative stress biomarker) elicited by hydrogen peroxide is decreased by 3.6-fold to control levels when hydrogen peroxide is co-injected with Pyrap-AKH. Similar results are obtained using in vitro experiments. Oxidative stress biomarkers such as malondialdehyde and protein carbonyls are significantly enhanced upon exposure of the isolated CNS to hydrogen peroxide in vitro, whereas co-treatment of the CNS with hydrogen peroxide and Pyrap-AKH reduces levels significantly. Moreover, a marked decrease in catalase activity compared with controls is recorded when the CNS is incubated with hydrogen peroxide. Incubation of the CNS with hydrogen peroxide and Pyrap-AKH together curbs the negative effect on catalase activity. Taken together, the results of the present study provide strong support for the recently published data on the feedback regulation between oxidative stressors and AKH action, and implicate AKH in counteracting oxidative stress. The in vitro experiments should facilitate research on the mode of action of AKH in relation to oxidative stress, and could help clarify the key pathways involved in this process.
A new member of the AKH/RPCH family was isolated from the corpora cardiaca of the firebug Pyrrhoc... more A new member of the AKH/RPCH family was isolated from the corpora cardiaca of the firebug Pyrrhocoris apterus. It is the second adipokinetic peptide identified in this species. The peptide was characterized and its structure was deduced from the multiple MS N electrospray mass spectra as that of an octapeptide with the sequence pGlu-Leu-Thr-Phe-Thr-Pro-Asn-Trp-NH 2. The peptide differs from the original P. apterus AKH (Pya-AKH) by one amino acid in position 3. Topical application and/or injection of the peptide induced lipid mobilization, but was inactive in mobilization of carbohydrates.
Insect fauna of coniferous seed cones: diversity, host plant interactions, and management. Ann Re... more Insect fauna of coniferous seed cones: diversity, host plant interactions, and management. Ann Rev Entomol 39 : 179-212 Wilson IM, Borden JH, Gries R, Gries G (1996) Green leaf volatiles as antiaggregants for the mountain pine beetle, Dendroctonus ponderosae Hopkins (Coleoptera: Scolytidae).
The Egyptian armyworm Spodoptera littoralis is a polyphagous insect attacking a number of plant s... more The Egyptian armyworm Spodoptera littoralis is a polyphagous insect attacking a number of plant species including those belonging to the Solanaceae and Cruciferaceae families. Its digestive physiology must therefore adapt to the food plant to ensure maximum extraction of nutrients with minimum trade-off in terms of growth retardation by pro-oxidant allelochemicals. To investigate this, the caterpillars of S. littoralis were fed on a semi-artificial diet (Manduca Premix-Heliothis Premix) and for 24 h on potato plants (Solanum tuberosum), respectively, at the mature 6th instar, and the levels of oxidative radicals and antioxidant enzymes in their guts were compared. The gut pH, standard redox potential (Eh) and electron availability (pe) revealed that oxidizing conditions prevail which promote oxidation of pro-oxidant allelochemicals in foliage. Oxidative stress in the foregut and midgut tissue and the gut contents was assessed from the generation of superoxide radical, total peroxide content and protein carbonyl content. Antioxidant defense was measured by the activities of superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APOX) and glutathione S-transferase peroxidase (GSTpx). A significant (p < 0.001) increase in the superoxide radical production (in foregut tissue, foregut and midgut contents), concomitant with an increase in total peroxide (in foregut contents) and protein carbonyl levels (in foregut and midgut tissue) were noted in larvae fed on the plants in contrast to those fed the semi-artificial diet. Similarly, a significant up-regulation of antioxidant enzymes SOD (in midgut tissues), CAT (in foregut, midgut tissue and contents), APOX (in foregut contents, midgut tissue and contents) and GSTpx (in foregut tissues) was recorded on the plant diet in comparison to the semi-artificial diet. The pro-oxidant allelochemicals in the plant diet are thus eliminated by the insect at the expense of up-regulation of antioxidative enzymes in response to increased oxidative stress from oxidizable allelochemicals. The results are consistent with the hypothesis that increased concentrations of antioxidants form an important component of the defense of herbivorous insects against both exogenous and endogenous oxidative radicals.
Abstract A vitellogenic female-specific protein was demonstrated in the haemolymph of Pyrrhocoris... more Abstract A vitellogenic female-specific protein was demonstrated in the haemolymph of Pyrrhocoris apterus females by electrophoresis under native conditions. One day before oviposition, eggs contained a major protein with electrophoretic mobility corresponding to that of haemolymph vitellogenin. SDS-PAGE revealed two subunits of the female-specific protein with M , 186 and 150 kDa. The latter was found together with several other polypeptides in the yolk. The identification of the 150 kDa polypeptide as vitellogenin was accomplished by means of ovariectomy and immunoblotting. In control bugs, temporal changes in the vitellogenin titre were recorded; traces of vitellogenin were found in the haemolymph and fat body on day 2 after adult ecdysis, its titre reached a maximum on day 4 and then decreased. Allatectomy of the females resulted in vitellogenin disappearance and a rise in 78 and 82 kDa polypeptides in the haemolymph. Application of a juvenile hormone analogue restored the ability of allatectomized females to produce female-specific polypeptides and to sequester them into the ovaries. The results showed that the synthesis of the 186 and 150 kDa polypeptides depended on juvenile hormone action.
In classical neuroscience, Dale´s principle postulates that neuronal identity is conferred by the... more In classical neuroscience, Dale´s principle postulates that neuronal identity is conferred by the specific neurotransmitter that it releases. However, the brain might be more tractable to specific situations regardless of specific specialisation which may contradict this principle. Hence, this constrained approach of how we perceive and study the nervous system must be revisited and revised, specifically by studying the dopaminergic system. We presume a relatively flexible change in the dopaminergic system due to neuronal activity or environmental changes. While the parallel between the reward system of mammals and insects is generally well accepted, herein, we extend the idea that the insect nervous system might also possess incredible plasticity, similar to the mammalian system. In this review, we critically evaluate the available information about the reward system in vertebrates and invertebrates, emphasising the dopaminergic neuronal plasticity, a challenge to the classical Dale's principle. Thus, neurotransmitter switching significantly disrupts the static idea of neural network organisation and suggests greater possibilities for a dynamic response to the current life context of organisms.
The toxicity of the Bacillus thuringiensis (Bt) toxin Cry3Aa—originally used against the main pot... more The toxicity of the Bacillus thuringiensis (Bt) toxin Cry3Aa—originally used against the main potato pest, the Colorado potato beetle, Leptinotarsa decemlineata—was verified on this species and then evaluated against the Egyptian armyworm, Spodoptera littoralis, which is a pest of several economically important plants. Larvae of S. littoralis were fed a semi-artificial diet supplemented either with a recombinant or with a natural Bt toxin Cry3Aa and with the genetically engineered (GE) potato of variety Superior NewLeaf (SNL) expressing Cry3Aa. Cry3Aa concentration in the diet and the content in the leaves were verified via ELISA (enzyme-linked immunosorbent assay) and HPLC (high-performance liquid chromatography) during and at the end of the experiments. The biological effectiveness of the coleopteran-specific Cry3Aa with previous reports of activity against S. littoralis was tested on five different populations of S. littoralis larvae by monitoring 13 parameters involving developm...
Insect exposure to their predators can affect individuals and community processes, through direct... more Insect exposure to their predators can affect individuals and community processes, through direct consumption or nonlethal (i.e., nonconsumptive) effects. However, the links between behavioural and physiological responses and stimuli needed for development of the fear are not clear. We therefore subjected the desert locusts (Schistocerca gregaria) to three nonlethal treatments, using the great tits (Parus major) as a potential predator. The treatments involved: (1) bird - presence of a live great tit and its calls, (2) call - great tit calls only, (3) control - without any treatment. In the first behavioural laboratory experiment, hungry locusts were kept in an experimental cage with a shelter and food on opposite sides of the cage. The duration of hiding and feeding were considered as an indicator of fear responses. In the second laboratory experiment with the same three treatments, levels of the adipokinetic hormone (AKH) were evaluated in the central nervous system (CNS) and haem...
Bees originally developed their stinging apparatus and venom against members of their own species... more Bees originally developed their stinging apparatus and venom against members of their own species from other hives or against predatory insects. Nevertheless, the biological and biochemical response of arthropods to bee venom is not well studied. Thus, in this study, the physiological responses of a model insect species (American cockroach, Periplaneta americana) to honeybee venom were investigated. Bee venom toxins elicited severe stress (LD50 = 1.063 uL venom) resulting in a significant increase in adipokinetic hormones (AKHs) in the cockroach central nervous system and haemolymph. Venom treatment induced a large destruction of muscle cell ultrastructure, especially myofibrils and sarcomeres. Interestingly, co-application of venom with cockroach Peram-CAH-II AKH eliminated this effect. Envenomation modulated the levels of carbohydrates, lipids, and proteins in the haemolymph and the activity of digestive amylases, lipases, and proteases in the midgut. Bee venom significantly reduc...
The fruit fly Drosophila melanogaster brain is the most extensively investigated model of a rewar... more The fruit fly Drosophila melanogaster brain is the most extensively investigated model of a reward system in insects. Drosophila can discriminate between rewarding and punishing environmental stimuli and consequently undergo associative learning. Functional models, especially those modelling mushroom bodies, are constantly being developed using newly discovered information, adding to the complexity of creating a simple model of the reward system. This review aims to clarify whether its reward system also includes a hedonic component. Neurochemical systems that mediate the ´wanting´ component of reward in the Drosophila brain are well documented, however, the systems that mediate the pleasure component of reward in mammals, including those involving the endogenous opioid and endocannabinoid systems, are unlikely to be present in insects. The mushroom body components exhibit differential developmental age and different functional processes. We propose a hypothetical hierarchy of the levels of reinforcement processing in response to particular stimuli, and the parallel processes that take place concurrently. The possible presence of activity-silencing and meta-satiety inducing levels in Drosophila should be further investigated.
Several studies showed that insect endocrine system, especially anti-stress neuropeptides, could ... more Several studies showed that insect endocrine system, especially anti-stress neuropeptides, could be used as a potential target for the pest control. The main role of those neuropeptides is to eliminate or at least to reduce the impact of various stressors on insect organism. This defense response is primarily operated by neurohormones from adipokinetic hormone (AKH) family that control mainly stress energy metabolism. Several neurotoxic insecticides with oxidative-stress activity were tested in several model insect species and their anti-stress response was monitored by suitable markers. The results revealed increased level of AKH in corpora cardiaca, the endocrine glands near the insect brain where the AKHs are synthesized, and in hemolymph after the insecticide treatment. Further, the insecticide treatment affected some basic markers of oxidative stress: it modulated total antioxidative capacity as well as the activity of superoxide dismutase, catalase and glutathione-S-transferas...
In honeybees (Apis mellifera), the rate of aging is modulated through social interactions and acc... more In honeybees (Apis mellifera), the rate of aging is modulated through social interactions and according to caste differentiation and the seasonal (winter/summer) generation of workers. Winter generation workers, which hatch at the end of summer, have remarkably extended lifespans as an adaptation to the cold season when the resources required for the growth and reproduction of colonies are limited and the bees need to maintain the colony until the next spring. In contrast, the summer bees only live for several weeks. To better understand the lifespan differences between summer and winter bees, we studied the fat bodies of honeybee workers and identified several parameters that fluctuate in a season-dependent manner. In agreement with the assumption that winter workers possess greater fat body mass, our data showed gradual increases in fat body mass, the size of the fat body cells, and Vg production as the winter season proceeded, as well as contrasting gradual decreases in these par...
Insect adipokinetic hormones (AKHs) are neuropeptides with a wide range of actions, including the... more Insect adipokinetic hormones (AKHs) are neuropeptides with a wide range of actions, including the control of insect energy metabolism. These hormones are also known to be involved in the insect defence system against toxins and pathogens. In this study, our aim was to demonstrate whether the application of external AKHs significantly enhances the efficacy of the entomopathogenic fungus Isaria fumosorosea in a model species (firebug Pyrrhocoris apterus) and pest species (Egyptian cotton leafworm Spodoptera littoralis and pea aphid Acyrthosiphon pisum). It was found that the co-application of Isaria with AKHs significantly enhanced insect mortality in comparison to the application of Isaria alone. The mode of action probably involves an increase in metabolism that is caused by AKHs (evidenced by the production of carbon dioxide), which accelerates the turnover of Isaria toxins produced into the infected insects. However, several species-specific differences probably exist. Intoxicatio...
Titanus giganteus is one of the largest insects in the world, but unfortunately, there is a lack ... more Titanus giganteus is one of the largest insects in the world, but unfortunately, there is a lack of basic information about its biology. Previous papers have mostly described Titanus morphology or taxonomy, but studies concerning its anatomy and physiology are largely absent. Thus, we employed microscopic, physiological, and analytical methods to partially fill this gap. Our study focused on a detailed analysis of the antennal sensilla, where coeloconic sensilla, grouped into irregularly oval fields, and sensilla trichoidea were found. Further, the inspection of the internal organs showed apparent degeneration of the gut and almost total absence of fat body. The gut was already empty; however, certain activity of digestive enzymes was recorded. The brain was relatively small, and the ventral nerve cord consisted of three ganglia in the thorax and four ganglia in the abdomen. Each testis was composed of approximately 30 testicular follicles filled with a clearly visible sperm. Chroma...
The role of the adipokinetic hormone (AKH) in the control of protease, amylase and lipase activit... more The role of the adipokinetic hormone (AKH) in the control of protease, amylase and lipase activities is examined using the cockroach Periplaneta americana and the fruit fly Drosophila melanogaster as model species. The effects of Peram-CAH-I and-II on the activity of cockroach digestive enzymes in the gastric caeca and midgut are measured both in vivo and in vitro. The results show the activity of proteases, amylases and lipases in both parts of the gut: amylase activity is higher in the gastric caeca than in the midgut; lipase activity presents the opposite trend; and protease activity is similar in both organs. The applied hormones stimulate the activity of all digestive enzymes, although this stimulation is not uniform; AKHs affect enzymes selectively, and in some cases unequally, in the gastric caeca and midgut. No substantial differences between Peram-CAH-I and-II stimulation are recorded. The in vitro results demonstrate that AKH stimulates digestive enzyme activity directly. In agreement with the cockroach results, enzymatic activity in D. melanogaster larvae producing nonfunctional AKH is lower than that in the larvae with ectopically expressed Akh gene, where enzyme activity reaches or even exceeds that of the controls. Overall, the results demonstrate the active role of AKHs in the stimulation of digestive enzyme activity in insects.
Archives of Insect Biochemistry and Physiology, 2019
This study examined the effect of two natural toxins (a venom from the parasitic wasp Habrobracon... more This study examined the effect of two natural toxins (a venom from the parasitic wasp Habrobracon hebetor and destruxin A from the entomopathogenic fungus Metarhizium anisopliae), and one pathogen (the entomopathogenic fungus
This study examined how adipokinetic hormone (AKH) and adenosine affect defense responses in Dros... more This study examined how adipokinetic hormone (AKH) and adenosine affect defense responses in Drosophila melanogaster larvae infected with entomopathogenic nematodes (EPN, Steinernema carpocapsae and Heterorhabditis bacteriophora). Three loss-of-function mutant larvae were tested: Akh, AdoR (adenosine receptor), and Akh AdoR. Mortality decreased in all mutants post-EPN infection compared with the control (w). Additionally, co-application of external AKH with EPN significantly increased mortality beyond rates observed in EPN-only treatment, while also elevating carbon dioxide production, a measure of metabolism. Furthermore trehalose levels increased in both w and Akh larvae post-EPN infection, but the latter group exhibited a lower increase and total trehalose levels. Interestingly, baseline trehalose was relatively high in untreated AdoR and Akh AdoR mutants, with levels remaining unaffected by infection. Infection also elevated haemolymph lipid content overall, but the different mu...
The role of adipokinetic hormone (AKH) in counteracting oxidative stress elicited in the insect b... more The role of adipokinetic hormone (AKH) in counteracting oxidative stress elicited in the insect body is studied in response to exogenously applied hydrogen peroxide, an important metabolite of oxidative processes. In vivo experiments reveal that the injection of hydrogen peroxide (8 μmol) into the haemocoel of the firebug, Pyrrhocoris apterus L. (Heteroptera: Pyrrhocoridae) increases the level of AKH by 2.8-fold in the central nervous system (CNS) and by 3.8-fold in the haemolymph. The injection of hydrogen peroxide also increases the mortality of experimental insects, whereas co-injection of hydrogen peroxide with Pyrap-AKH (40 pmol) reduces mortality to almost control levels. Importantly, an increase in haemolymph protein carbonyl levels (i.e. an oxidative stress biomarker) elicited by hydrogen peroxide is decreased by 3.6-fold to control levels when hydrogen peroxide is co-injected with Pyrap-AKH. Similar results are obtained using in vitro experiments. Oxidative stress biomarkers such as malondialdehyde and protein carbonyls are significantly enhanced upon exposure of the isolated CNS to hydrogen peroxide in vitro, whereas co-treatment of the CNS with hydrogen peroxide and Pyrap-AKH reduces levels significantly. Moreover, a marked decrease in catalase activity compared with controls is recorded when the CNS is incubated with hydrogen peroxide. Incubation of the CNS with hydrogen peroxide and Pyrap-AKH together curbs the negative effect on catalase activity. Taken together, the results of the present study provide strong support for the recently published data on the feedback regulation between oxidative stressors and AKH action, and implicate AKH in counteracting oxidative stress. The in vitro experiments should facilitate research on the mode of action of AKH in relation to oxidative stress, and could help clarify the key pathways involved in this process.
A new member of the AKH/RPCH family was isolated from the corpora cardiaca of the firebug Pyrrhoc... more A new member of the AKH/RPCH family was isolated from the corpora cardiaca of the firebug Pyrrhocoris apterus. It is the second adipokinetic peptide identified in this species. The peptide was characterized and its structure was deduced from the multiple MS N electrospray mass spectra as that of an octapeptide with the sequence pGlu-Leu-Thr-Phe-Thr-Pro-Asn-Trp-NH 2. The peptide differs from the original P. apterus AKH (Pya-AKH) by one amino acid in position 3. Topical application and/or injection of the peptide induced lipid mobilization, but was inactive in mobilization of carbohydrates.
Insect fauna of coniferous seed cones: diversity, host plant interactions, and management. Ann Re... more Insect fauna of coniferous seed cones: diversity, host plant interactions, and management. Ann Rev Entomol 39 : 179-212 Wilson IM, Borden JH, Gries R, Gries G (1996) Green leaf volatiles as antiaggregants for the mountain pine beetle, Dendroctonus ponderosae Hopkins (Coleoptera: Scolytidae).
The Egyptian armyworm Spodoptera littoralis is a polyphagous insect attacking a number of plant s... more The Egyptian armyworm Spodoptera littoralis is a polyphagous insect attacking a number of plant species including those belonging to the Solanaceae and Cruciferaceae families. Its digestive physiology must therefore adapt to the food plant to ensure maximum extraction of nutrients with minimum trade-off in terms of growth retardation by pro-oxidant allelochemicals. To investigate this, the caterpillars of S. littoralis were fed on a semi-artificial diet (Manduca Premix-Heliothis Premix) and for 24 h on potato plants (Solanum tuberosum), respectively, at the mature 6th instar, and the levels of oxidative radicals and antioxidant enzymes in their guts were compared. The gut pH, standard redox potential (Eh) and electron availability (pe) revealed that oxidizing conditions prevail which promote oxidation of pro-oxidant allelochemicals in foliage. Oxidative stress in the foregut and midgut tissue and the gut contents was assessed from the generation of superoxide radical, total peroxide content and protein carbonyl content. Antioxidant defense was measured by the activities of superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APOX) and glutathione S-transferase peroxidase (GSTpx). A significant (p < 0.001) increase in the superoxide radical production (in foregut tissue, foregut and midgut contents), concomitant with an increase in total peroxide (in foregut contents) and protein carbonyl levels (in foregut and midgut tissue) were noted in larvae fed on the plants in contrast to those fed the semi-artificial diet. Similarly, a significant up-regulation of antioxidant enzymes SOD (in midgut tissues), CAT (in foregut, midgut tissue and contents), APOX (in foregut contents, midgut tissue and contents) and GSTpx (in foregut tissues) was recorded on the plant diet in comparison to the semi-artificial diet. The pro-oxidant allelochemicals in the plant diet are thus eliminated by the insect at the expense of up-regulation of antioxidative enzymes in response to increased oxidative stress from oxidizable allelochemicals. The results are consistent with the hypothesis that increased concentrations of antioxidants form an important component of the defense of herbivorous insects against both exogenous and endogenous oxidative radicals.
Abstract A vitellogenic female-specific protein was demonstrated in the haemolymph of Pyrrhocoris... more Abstract A vitellogenic female-specific protein was demonstrated in the haemolymph of Pyrrhocoris apterus females by electrophoresis under native conditions. One day before oviposition, eggs contained a major protein with electrophoretic mobility corresponding to that of haemolymph vitellogenin. SDS-PAGE revealed two subunits of the female-specific protein with M , 186 and 150 kDa. The latter was found together with several other polypeptides in the yolk. The identification of the 150 kDa polypeptide as vitellogenin was accomplished by means of ovariectomy and immunoblotting. In control bugs, temporal changes in the vitellogenin titre were recorded; traces of vitellogenin were found in the haemolymph and fat body on day 2 after adult ecdysis, its titre reached a maximum on day 4 and then decreased. Allatectomy of the females resulted in vitellogenin disappearance and a rise in 78 and 82 kDa polypeptides in the haemolymph. Application of a juvenile hormone analogue restored the ability of allatectomized females to produce female-specific polypeptides and to sequester them into the ovaries. The results showed that the synthesis of the 186 and 150 kDa polypeptides depended on juvenile hormone action.
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