Hormonal Effects on the in vitro Larval Growth of the Swine Intestinal Roundworm,Ascaris suum

Summary

Several biogenic amines and insect juvenile hormone III were tested in a growth bioassay of the parasitic nematode, Ascaris suum. Compounds (1 to 1000μzmol) were placed in culture with third-stage larvae for 24 hr, larvae were then rinsed several times, and larval cultures were returned to incubators for 6 more days. By this time, larvae had developed to the fourth-stage. The larvae were fixed in hot formalin, and their lengths were measured. Epinephrine and norepinephrine oxidized and were nematocidal under these culture conditions. Histamine and serotonin had no effect on length of the larvae. Octopamine (10–50μmol) exposure resulted in a significant dose-dependent increase in length. When incubated with octopamine (10μzmol) for 7 days, larvae grew more slowly than controls without octopamine (P< 0.05). Juvenile hormone III stimulated a dose-dependent (0 to 10μmol) increase in length after a 24 hr exposure. No synergism was detected between juvenile hormone III and ecdysone when co-incubated with larvae. These results indicate that Ascaris larvae are growth-insensitive to low concentrations of biogenic amines of host origin. Conversely, biological transmitters of invertebrate origin are potent stimulators of larval growth.     

effect of stress on levels of octopamine,dopamine and serotonin in the American cockroach (Periplaneta americana L.)

1. Various biogenic amines including octopamine, dopamine and serotonin, and their precursors and metabolites in haemolymph and the central nervous system from American cockroaches (Periplaneta americana L.) were measured using electrochemical detection.2. Octopamine was found in similar high relative abundances in haemolymph and the central nervous system.3. The amount of octopamine was much higher than that of tyramine and synephrine in haemolymph and thoracic nerve cord, whereas tyramine was at the highest level followed by octopamine and synephrine in the brain.4. Insects were stressed by vibrating at 100 or 1000 Hz, visually by flashing light at 4 Hz for 15 min or by immersing the insect in water at 60°C for 30 sec, which resulted in the elevation of octopamine, tyramine, synephrine and tyrosine levels in thoracic nerve cord.     

Effect of various insecticides on the larval growth and biogenic amine levels of Tribolium castaneum Herbst

Various insecticides reduced larval growth of the red flour beetle (tribolium castaneum Herbst) and various biogenic amines, including octopamine (OA), dopamine (DA), serotonin (5-HT), epinephrine (E), norepinephrine (NE), their precursors and metabolites in the insects were measured by high-performance liquid chromatography coupled with electrochemical detection. Tyrosine occurred in the highest concentration followed by OA, tryptophan and 3,4-dihydroxymandelic acid (DOMA). Tyramine (a precursor of OA in the biosynthetic pathway), synephrine (N-methyl OA), DA, 5-HT, E, NE and their related substances occurred in extremely low quantities compared with OA. The insects were stressed by various insecticides, which resulted in a dramatic change of biogenic amine levels: the OA levels increased, whereas the levels of other biogenic amines and related substances decreased.     

Agonist-induced desensitization of an octopamine receptor

The octopamine-sensitive adenylate cyclase associated with haemocytes of the American cockroach, Periplaneta americana, has been used as a model system with which to study desensitization of the octopamine receptor. Preincubation of the haemocytes with octopamine results in a large decrease in subsequent maximal stimulation of cyclic AMP production by octopamine with little change in affinity of the receptor for the agonist. This effect of preincubation is dependent upon the concentration of octopamine in the preincubation media and on the duration of exposure. The attenuation appears to be a receptor-mediated event rather than an artifact of the preincubation. Octopamine receptor agonists (octopamine, synephrine, N-demethylchlordimeform) induce desensitization while biogenic amines with poor octopamine receptor affinity (dopamine, serotonin, norepinephrine) are without affect. In contrast, the octopamine receptor antagonist, phentolamine, appears to enhance subsequent stimulation by octopamine. The attenuation of octopamine stimulation of adenylate cyclase is conserved in broken-cell preparations with no alteration of responses to NaF or forskolin. Incubation of the cells with dibutyryl cyclic AMP or forskolin does not induce desensitization. The data indicate that the OA receptors coupled to AC in cockroach haemocytes undergo an homologous desensitization in response to exposure to agonists.     

Competitive interactions between parasitoid larvae and the evolution of gregarious development

We report experiments using two closely related species of alysiine braconids directed at understanding how gregarious development evolved in one subfamily of parasitoid wasps. Theoretical models predict that once siblicide between parasitoid wasps has evolved, it can only be lost under stringent conditions, making the transition from solitary to gregarious development exiguous. Phylogenetic studies indicate, however, that gregariousness has independently arisen on numerous occasions. New theoretical models have demonstrated that if gregarious development involves reductions in larval mobility, rather than a lack of fighting ability (as in the older models), the evolution of gregariousness is much more likely. We tested the predictions of the older tolerance models (gregariousness based on non-fighting larval phenotypes) and the reduced mobility models (gregariousness based on non-searching larval phenotypes) by observing larval movement and the outcome of interspecific competition between Aphaereta genevensis (solitary) and A. pallipes (gregarious) under multiparasitism. Differences in larval mobility matched the prediction of the reduced mobility model of gregarious development, with the solitary A. genevensis having larvae that are much more mobile. The proportion of hosts producing the solitary species significantly declined after subsequent exposure to females of the gregarious species. This contradicts the prediction of the older models (fighting vs non-fighting phenotypes), under which any competitive interactions between solitary and gregarious larvae will result in a highly asymmetrical outcome, as the solitary species should be competitively superior. The observed outcome of interspecific competition offers evidence, with respect to this subfamily, in favour of the new models (searching vs non-searching phenotypes).     

Biogenic amines modulate olfactory receptor neurons firing activity in Mamestra brassicae

The modulatory effects of the biogenic amines octopamine and serotonin on pheromonal receptor neurons of Mamestra brassicae were investigated. The responses to sex pheromone components of two cells types (A and B) in single male long sensilla trichodea were monitored. Cell types A and B do not respond to the same compound. The response of type A to a pulse of the major sex pheromone component increased 5 min after octopamine injection. Responses of type B to other odorants increased after 30 min. In the absence of any pheromone stimulation the background firing activity of type A increased following octopamine injection. This background activity was used to evaluate the kinetics of octopamine and other biogenic amine effects on olfactory receptor neurons. Octopamine increased this background activity in a concentration- and time-dependent manner. Clonidine, an octopamine agonist, was shown to be more powerful in increasing the background activity of olfactory receptor neurons. The effects of octopamine and clonidine were hypothesized to arise from specific receptor activation as chlorpromazine (an octopamine antagonist) was shown to block the effect of octopamine. Serotonin, a known neuromodulator in most animal species, induced a reversible inhibition of spike firing. Altogether, these results indicate that biogenic amines can modulate the sensitivity of olfactory receptor neurons of moths either directly or by an action on adaptation.     

Tyramine and octopamine have opposite effects on the locomotion of Drosophila larvae

Biogenic amines are believed to play important roles in producing behaviors. Although some biogenic amines have been extensively studied in both vertebrates and invertebrates, little is known about the effects of trace amines like tyramine and octopamine. We investigated how trace amines affect behaviors using quantitative morphometric methods on Drosophila Tbetah(nM18) and iav(N) mutants that have altered levels of tyramine and octopamine. Locomotion of wild-type and mutant third instar larvae was analyzed using Dynamic Image Analysis System (DIAS) software. We found that Tbetah(nM18) mutants, with elevated tyramine levels and reduced octopamine levels, had a severe locomotion phenotype. Mutant larvae spent much more time in pausing episodes than wild-type larvae and displayed a reduction in speed and linear translocation. The locomotion phenotype was partially rescued by feeding Tbetah(nM18) larvae octopamine, an effect that could be nullified with simultaneous feeding of tyramine. Feeding Tbetah(nM18) larvae yohimbine, an agent that inhibits the activity of Drosophila tyramine receptors, also improved some locomotion parameters. Feeding both octopamine and yohimbine further improved rescue efficiency. Simultaneously reducing the octopamine and tyramine levels as in iav(N) larvae, in contrast, led to a less severe behavioral phenotype than that of Tbetah(nM18) mutants. Feeding iav(N) larvae either tyramine or octopamine exerted only a minor improvement in locomotion. These results suggest that tyramine and octopamine have opposite effects on Drosophila larval locomotion regulation and that a balance between the two is important in producing normal behavior.     

昆虫体内章鱼胺的分布、功能及其研究进展

章鱼胺是无脊椎动物神经系统中普遍存在的多种微量生物胺之一。章鱼胺的分布及含量变化对于昆虫的生长、取食、代谢等多种生理、生物效应具有重要的作用。文章对昆虫体内章鱼胺的功能性、昆虫体内章鱼胺的分布及其主要功能、章鱼胺痕量测定方法、生存环境的改变及化学药剂的作用对章鱼胺含量的影响以及外界刺激对章鱼胺含量影响的生理及生物化学机理研究进行了综述。     

An Inhibitor of Acetolactate Synthase from a Microbe

Such stress factors as mechanical (vibration), thermal (unfavorable temperature), optical (light), and starvation reduced the larval growth of the red flour beetle (Triholium castaneum Herbst). Various biogenic amines, including octopamine (OA), dopamine (DA), serotonin (5-HT), epinephrine (E), norepinephrine (NE), their precursors, and metabolites, in whole-body T. castaneum were measured by high-performance liquid chromatography coupled with electrochemical detection (ECD). Tyrosine occurred in the highest concentration, followed by OA, tryptophan, and 3,4-dihydroxymandelic acid. The amount of OA was much higher than that of tyramine (a precursor of OA in the biosynthetic pathway) and of synephrine (N-methyl OA). DA, 5-HT, E, NE, and their related substances occurred in extremely low quantities compared with OA. Insects were stressed by vibrating at 1, 10, 100, or 1000Hz, optically under a 24-h light (15W, 50Hz) photoperiod, thermally by changing the incubation temperature from an initial value of 30°C, or by starvation, which resulted in dramatic changes of levels of biogenic amines, including OA.     

Cloning, expression and functional analysis of an octopamine receptor from Periplaneta americana

Octopamine regulates multiple physiological functions in invertebrates. The biological effects of octopamine and the pharmacology of octopamine receptors have been extensively studied in the American cockroach, Periplaneta americana. This paper reports the cloning of the first octopamine receptor from Periplaneta americana. A cDNA encoding a putative 7 transmembrane receptor was isolated from the head of Periplaneta americana. The encoded protein contains 628 amino acids and has sequence similarity to other biogenic amine receptors. This protein was expressed in COS-7 cells for radioligand binding studies using the antagonist 3H-yohimbine. Competitive binding comparing biogenic amines that could potentially function as endogenous ligands demonstrated this receptor had the highest affinity for octopamine (Ki = 13.3 microM) followed by tyramine, dopamine, serotonin and histamine. Octopamine increased both cAMP levels (EC50 = 1.62 microM) and intracellular concentrations of calcium through the receptor expressed in HEK-293 cells. Tyramine increased levels of both of these second messengers but only at significantly higher concentrations than octopamine. The cAMP increase by octopamine was independent of the increase in calcium. Competitive binding with antagonists revealed this receptor is similar to Lym oa1 from Lymnaea stagnalis. The data indicate that this cDNA is the first octopamine receptor cloned from Periplaneta americana and therefore has been named Pa oa1.     

PRODUCTS OF BIOGENIC AMINE METABOLISM IN THE LOBSTER: SULFATE CONJUGATES

Octopamine, dopamine and serotonin, the three biogenic amines found in the lobster nervous system, are each converted by lobster tissues into two principal classes of products, A and B metabolites. In this paper, evidence is presented that the B metabolites are sulfate conjugates of the amines and their A metabolites. Two double-labelled conjugates were formed from each of the three amines during incubations of lobster nerves with tritiated amine and ³⁵SO₄. When the two octopamine conjugates were hydrolyzed by mild acid, one of the conjugates was converted to a mixture of ³⁵SO₄ and [³H]-octopamine, and the other to a mixture of ³⁵SO₄, [³H]octopamine, and [³H]metabolite A. [³H]Metabolite A was also converted to octopamine by acid hydrolysis. The results indicated that one of the double-labelled conjugates was octopamine-sulfate, and the other metabolite-A-sulfate. An enzyme fraction prepared from nerve homogenates catalyzed the synthesis of double-labelled sulfate conjugates from the tritiated amines and [³⁵S]3′-phosphoadenosine-5′-phospho-sulfate. Double-labelled conjugates formed in this way contained 1 mol of sulfate per mol of amine. Indirect evidence suggested that the sulfate was in ester linkage with the ring hydroxyls of the amines. Neither monoamine oxidase, nor catechol-O-methyl transferase is found in lobster tissues; therefore, in these animals, sulfation may be a major means of inactivation of the biogenic amines following their release from nerve endings.     

A comparison of the signalling properties of two tyramine receptors from Drosophila

In invertebrates, the phenolamines, tyramine and octopamine, mediate many functional roles usually associated with the catecholamines, noradrenaline and adrenaline, in vertebrates. The α‐ and β‐adrenergic classes of insect octopamine receptor are better activated by octopamine than tyramine. Similarly, the Tyramine 1 subgroup of receptors (or Octopamine/Tyramine receptors) are better activated by tyramine than octopamine. However, recently, a new Tyramine 2 subgroup of receptors was identified, which appears to be activated highly preferentially by tyramine. We examined immunocytochemically the ability of CG7431, the founding member of this subgroup from Drosophila melanogaster, to be internalized in transfected Chinese hamster ovary (CHO) cells by different agonists. It was only internalized after activation by tyramine. Conversely, the structurally related receptor, CG16766, was internalized by a number of biogenic amines, including octopamine, dopamine, noradrenaline, adrenaline, which also were able to elevate cyclic AMP levels. Studies with synthetic agonists and antagonists confirm that CG16766 has a different pharmacological profile to that of CG7431. Species orthologues of CG16766 were only found in Drosophila species, whereas orthologues of CG7431 could be identified in the genomes of a number of insect species. We propose that CG16766 represents a new group of tyramine receptors, which we have designated the Tyramine 3 receptors.     

Biogenic amines modulate pulse rate in the dorsal blood vessel of Lumbriculus variegatus

The biogenic amines are widespread regulators of physiological processes, and play an important role in regulating heart rate in diverse organisms. Here, we present the first pharmacological evidence for a role of the biogenic amines in the regulation of dorsal blood vessel pulse rate in an aquatic oligochaete, Lumbriculus variegatus (Müller, 1774). Bath application of octopamine to intact worms resulted in an acceleration of pulse rate, but not when co-applied with the adenylyl cyclase inhibitor MDL-12,330a. The phosphodiesterase inhibitor theophylline mimicked the effects of OA, but the polar adenosine receptor antagonist 8(p-sulphophenyl)theophylline was significantly less potent than theophylline. Pharmacologically blocking synaptic reuptake of the biogenic amines using the selective 5-HT reuptake blocker fluoxetine or various tricyclic antidepressants also accelerated heart rate. Depletion of the biogenic amines by treatment with the monoamine vesicular transporter blocker reserpine dramatically depressed pulse rate. Pulse rate was partially restored in amine-depleted worms after treatment with octopamine or dopamine, but fully restored following treatment with serotonin. This effect of 5-HT was weakly mimicked by 5-methoxytryptamine, but not by α-methylserotonin; it was completely blocked by clozapine and partially blocked by cyproheptadine. Because they are known to orchestrate a variety of adaptive behaviors in invertebrates, the biogenic amines may coordinate blood flow with behavioral state in L. variegatus.     

Insulin‐like receptor substrate gene chico regulates octopamine metabolism in Drosophila melanogaster

Octopamine, one of the main insect biogenic amines, plays an important role in the control of fitness in Drosophila melanogaster Meigen. The present study examines the effects of a null mutation of the gene of the insulin‐like receptor substrate (chico), in the heterozygous state, on octopamine metabolism, heat stress resistance and fecundity of D. melanogaster. A rise in the activity of one of the key enzymes of octopamine synthesis, tyrosine decarboxylase, as well as that of an enzyme of its degradation, octopamine‐dependent N‐acetyl transferase, is observed in chico^1/+ females. It is also found that the resistance to heat stress is decreased and fecundity is reduced dramatically in chico^1/+ flies. Such changes in these parameters in D. melanogaster females result from a rise in octopamine titre, which suggests that chico affects the octopamine level by regulating the activity of tyrosine decarboxylase.     

The role of octopamine in locusts and other arthropods

The biogenic amine octopamine and its biological precursor tyramine are thought to be the invertebrate functional homologues of the vertebrate adrenergic transmitters. Octopamine functions as a neuromodulator, neurotransmitter and neurohormone in insect nervous systems and prompts the whole organism to “dynamic action”. A growing number of studies suggest a prominent role for octopamine in modulating multiple physiological and behavioural processes in invertebrates, as for example the phase transition in Schistocerca gregaria. Both octopamine and tyramine exert their effects by binding to specific receptor proteins that belong to the superfamily of G protein-coupled receptors. Since these receptors do not appear to be present in vertebrates, they may present very suitable and specific insecticide and acaricide targets.     

Cloning and expression pattern of a putative octopamine/tyramine receptor in antennae of the noctuid moth <Emphasis Type="Italic">Mamestra brassicae</Emphasis>

In insects, biogenic amines have been shown to play an important role in olfactory plasticity. In a first attempt to decipher the underlying molecular mechanisms, we report the molecular cloning and precise expression pattern of a newly identified octopamine/tyramine-receptor-encoding gene in the antennae of the noctuid moth Mamestra brassicae (MbraOAR/TAR). A full-length cDNA has been obtained through homology cloning in combination with rapid amplification of cDNA ends/polymerase chain reaction; the deduced protein exhibits high identities with previously identified octopamine/tyramine receptors in other moths. In situ hybridization within the antennae has revealed that MbraOAR/TAR is expressed at the bases of both pheromone-sensitive and non-sensitive olfactory sensilla and in cells with a neurone-like shape. In accordance with previous physiological studies that have revealed a role of biogenic amines in the electrical activity of the receptor neurones, our results suggest that biogenic amines (either octopamine or tyramine) target olfactory receptor neurones to modulate olfactory coding as early as the antennal level.     

Developmental Changes in Biogenic Amine Levels in the Central Nervous System and the Haemolymph of the Eastern Death's Head Hawk Moth,Acherontia styx (Lepidoptera: Sphingidae)

In an effort to understand the role of biogenic amines in insect development, changes in the levels of octopamine (OA), dopamine (DA), epinephrine (E), norepinephrine (NE), and serotonin (5-HT) in the brain, the optic lobes and the haemolymph of different developmental stages of Acherontia styx were analyzed using HPLC with electrochemical detector. In the brain, OA was the most abundant monoamine. DA, OA, and E levels in larvae peaked around the wandering stage (W). A dramatic increase in DA, 5-HT, and E levels was observed in the brain of the adult as compared to the pupal stage. NE, however, was not detected in the brain of most stages of the insect, except in the brain of 20-day-old pupae and adults. A 3-fold increase in OA levels was observed in the optic lobes of the adult as compared to late pupal stage. No changes were observed for E, DA, and 5-HT. NE was not detected in the optic lobes. In the haemolymph of 5^th instar larvae, OA was also the most abundant amine. Both DA and OA peaked prior to the onset of the W stage. In contrast, E and NE concentrations decreased with development of the 5^th instar larvae. 5-HT was not detected in the haemolymph. Finally, different profiles for amine levels were observed for the two forms of the 5^th instar larvae (green vs brown). These results are interpreted in the light of the role of biogenic amines and their relation to development in the nervous system of lepidopteran insects.     

Cockroach oviducts: The presence and release of octopamine and proctolin

The oviducts of the cockroach, Periplaneta americana, contain octopamine (determined by radioenzymatic assay) and proctolin (determined from proctolin-like bioactivity following separation on reversed-phase high performance liquid chromatography). Octopamine content is 5–10-fold greater than proctolin content. Both substances are released in a calcium-dependent manner following depolarisation with high potassium saline. This method resulted in the release of 14% of the total store of octopamine, but only 0.3% of the total store of proctolin. The results are discussed in relation to the recent demonstration of octopamine-containing and proctolin-containing neurones associated with locust oviducts.