Schistocerca Americana Gregaria Research Articles

Biosynthesis of taurine in tissues of the locust ( Schistocerca americana gregaria) and the effect of physiological and toxicological stresses on biosynthetic rate of this amino acid

The biosynthesis of the amino acid taurine has been studied in the locust Schistocerca americana gregaria. Tissue concentrations of putative precursors of taurine, and taurine itself were estimated in haemolymph, nervous tissue and muscle. Following this locusts were injected with 20 μCi of [ 35S]cysteine and tissue samples were taken at times thereafter, and taurine and its precursors were extracted and separated by thin-layer chromatography (TLC). Taurine, cysteine sulphinic acid (CSA) were quantified by scintillation counting. Cysteic acid and hypotaurine were qualitatively detected by autoradiography of TLC plates. Results indicate that in haemolymph and muscle the biosynthetic pathway for taurine is cysteine then CSA, cysteic acid and thereafter taurine. In nervous tissue both cysteic acid and hypotaurine were detected suggesting two possible pathways for taurine since both are immediate precursors of this amino acid. Taurine biosynthesis was markedly greater in juvenile compared with mature adult locusts. It was also observed that picrotoxin treatment and prolonged flying, which have both previously been found to cause a redistribution of taurine in the locust, increased the biosynthesis of this amino acid.

Uptake of [ 14C]taurine into tissues of schistocerca gregaria in vivo

Locusts ( Schistocerca americana gregaria) were injected with a tracer dose of 0.25 μCi of [ 14C]taurine into the haemolymph and its clearance from haemolymph and uptake into flight muscle, thoracic ganglia and eye were studied at times thereafter. Clearance of labelled taurine from haemolymph suggested that the amino acid was rapidly taken up by some tissues and more slowly by others. Thus uptake of [ 14C]taurine was rapid into nervous tissues and eye, but was much more gradual into flight muscle. Uptake was inhibited by cold and the structural analogues of taurine, ß-alanine, γ-aminobutyric acid and hypotaurine. Taurine was retained in all tissues over a long period, indicating a very slow rate of catabolism for this amino acid in the locust.

Effect of Taurine on Calcium Accumulation in Resting and Depolarised Insect Synaptosomes

The effect of taurine (2-aminoethanesulphonic acid) on 45Ca2+ accumulation in resting and depolarised synaptosomes obtained from the locust Schistocerca americana gregaria was studied. Taurine reduced 45Ca2+ accumulation in resting synaptosomes, and this effect was more pronounced when synaptosomes were depolarised with either high [K+] or veratridine. Veratridine-induced 45Ca2+ accumulation was not affected by either gamma-aminobutyric acid or leucine, but was reduced by both verapamil and tetrodotoxin.

The inhibition of lipid synthesis in vitro in the locust, Schistocerca gregaria, by factors from the corpora cardiaca

ABSTRACT. The rate of lipid synthesis from [14C]acetate in fat body from Schistocerca americana gregaria has been studied in vitro. Maximum incorporation is found on days 6–10 in adults and day 4 of the fifth stadium. The label appeared in the fatty acid components of triacyl‐glycerol, diacylglycerol and phospholipid.Lipid synthesis in vitro was inhibited by extracts of corpora cardiaca, and such inhibition was most marked (up to 85%) in fat bodies from insects at stages where fatty acid synthesis was greatest. HPLC separation of corpora cardiaca extracts gave several active fractions of which the most active was adipokinetic hormone 1 (AKH‐1).

The effects of octopamine on contraction kinetics and power output of a locust flight muscle

1. Perfusion with saline containing octopamine resulted in an increase in mechanical power output, and an increase in twitch and tetanic tension, from a flight muscle (metathoracic, second tergocoxal muscle) of the desert locust,Schistocerca americana gregaria. 2. Mechanical power output was measured under conditions approximating those of flight. Power output increased upon exposure to 10−6M DL-octopamine by about 20% when the muscle was activated by 1 stimulus per cycle and by about 8% when the muscle was activated by paired stimuli. 3. The increase in twitch tension was approximately proportional to the log of the octopamine concentration from 10−8M to 10−5M. At 10−6M, the twitch tension was about 19% greater than control values and the tetanic tension was about 8% above control values. The average twitch tension in control muscles was 17.0 N/cm2, and the average control tetanic tension was 27.9 N/cm2. 4. The maximum shortening velocity was little affected by octopamine. In control muscles, the maximum shortening velocity was 8.3 muscle lengths/s (L/s) for slack-test measurements and 5.7 L/s by extrapolation of force-velocity curves. In octopamine, the corresponding maximum shortening velocities were 8.0 and 5.9 L/s, respectively. 5. Octopamine perfusion resulted in a small increase in twitch duration (control mean = 40.5 ms at 30 °C). Both contraction and relaxation times increased by about 4%.

The distribution of taurine in the tissues of some species of insects

Taurine concentration was measured in the tissues of Schistocerca americana gregaria, Blatella orientalis and Tenebrio molitor and was found to be present in all those examined. In the locust Schistocerca gregaria it was found in particularly high concentration in active flight muscle (26 μmol/g) to a lesser extent in the eye (7 μmol/g). The thoracic concentration of taurine in developing locusts showed a strong correlation with the development of flight muscle, increasing from 4.4 to 11.3 μmol/g in the thorax during the first 24 days of adult life. Analysis of the thoracic content of taurine in adults of the three species examined confirmed that high taurine concentrations are associated with fully functional flight muscle. The concentration in the thorax of the flightless flour beetle T. molitor was only 1.79 μmol/g compared to 11.33 μmol/g for the locust. Stress due to flying and picrotoxin poisoning caused the release of taurine from the muscles into the haemolymph, causing the concentration to rise from 1.1 to 2.2 and 5.76 μmol/g respectively. Analysis of the distribution of arginine kinase showed that this release was not due to breakdown of the muscle tissue.

Adipokinetic hormone-immunoreactive peptide in the endocrine and central nervous system of several insect species: A comparative immunocytochemical approach

The distribution of intrinsic glandular cells containing adipokinetic hormone (AKH)-like material in the corpora cardiaca (CC) and the occurrence of immunoreactive neurons in the nervous system in 19 species belonging to nine insect orders was studied by means of an immunocytochemical method (peroxidase-antiperoxidase), with antisera raised against an AKH analogue ([Tyr 1]-AKH). The CC gland cells in Locusta migratoria migratorioides and Schistocerca americana gregaria were strongly immunoreactive. Those in other orders showed less or no immunoreactivity indicating that AKH has a very restricted distribution. Neurons containing immunoreactive material were found in the brain and ventral ganglia in all species investigated. As the specificity of the antiserum has not been determined, it is not known whether this peptide is identical to AKH. Considering the distribution of their axons, these neurons may be involved with one or more of the following functions: (1) nervous communication within the central nervous system; (2) communication with the stomatogastric nervous system; (3) possible release of peptide from the CC; (4) release of neuropeptide in or from the corpus allatum. A combination of these features has been found in only a few of the species investigated. The immunocytochemical study demonstrated significant differences among species belonging to Apterygota, Hemi-, and Holometabola in the number of neurons, the length and degree of branching of their axon, and the amount of immunoreactive peptide stored therein.

Autoradiographic localization of 3H-histamine accumulation by the visual system of the locust

The uptake of [3H]-histamine into the retina and optic lobe of the locust, Schistocerca americana gregaria was studied by means of autoradiography at the light- and electron-microscopic levels. Light-microscopic autoradiography showed a significant accumulation of [3H]-histamine in several regions of the optic lobe. Dense accumulations of silver grains were concentrated along the medial border of the medullary neuropil and around the entire periphery of the lobula. No significant accumulations of grains were present within the retina or the neuropil zones of the lamina, medulla or lobula.

Studies on the Mode of Action of Octopamine, 5-Hydroxytryptamine And Proctolin on A Myogenic Rhythm in the Locust

The modes of action of the modulatory compounds octopamine, 5-hydroxytryptamine (5-HT) and proctolin on the frequency of the myogenic rhythm of the extensor-tibiae muscle of the hindleg of the locust, Schistocerca americana gregaria, have been investigated. 5-HT and proctolin increase the frequency of the myogenic rhythm and the results of the present study suggest that they may mediate their effects by increasing the levels of cyclic AMP in the pacemaker of the myogenic bundle. In contrast, octopamine reduces the frequency of the myogenic rhythm and appears to mediate its effects by a mechanism that does not involve an elevation of cyclic AMP. A number of other possible mechanisms for the action of octopamine are discussed.

The amino acids of the locust nervous system: Their concentrations and release in vitro

1. 1. Amino acid concentrations were measured in the ganglia and haemolymph of the locust ( Schistocerca americana gregaria) immediately after dissection and in the nervous tissue after incubation in various artificial media. 2. 2. Alanine, aspartate, Gaba and glutamate were found to be present in greater concentration in the nervous tissue of the living insect than in the haemolymph, while the opposite was true of glycine, isoleucine, leucine, proline, phenylalanine, tyrosine and valine. 3. 3. Efflux of the amino acids varied with the nature of the medium in such a way as to suggest that there was active uptake of aspartate, Gaba, glutamate and possibly alanine, while all the other amino acids except glycine were maintained in equilibrium due to processes of facilitated diffusion. 4. 4. Electrical stimulation altered the proportions of the amino acids in the free pool, increasing the concentrations of glutamate and aspartate, while generally decreasing the efflux of the amino acids to the media.

Stress-induced changes in the octopamine levels of insect haemolymph

The relationship between stress and haemolymph octopamine levels has been examined in the locust Schistocerca americana gregaria and the cockroach Periplaneta americana. The resting level of octopamine ( ± SE, n = 24 ) in haemolymph sampled in the first quarter of the light cycle from the metathoracic leg of locusts was 7.5 ± 0.7 pg/μl and 4.4 ± 0.8 pg/μl from the cockroach thorax. In P. americana, 74% of the octopamine in the haemolymph was present in the plasma. Significant variation in resting levels was found when haemolymph was taken from different sampling sites in locusts and when haemolymph was removed at various times during a 24 hr period from cockroaches, with the highest concentration coinciding with the peak of locomotor activity. This pattern was reversed in cockroach nervous tissue with octopamine accumulating in the photophase and being reduced in the scotophase. An increase in haemolymph octopamine was a common response to a variety of stressful stimuli in insects, with rises of up to 10-fold in locusts and 3-fold in cockroaches. The results are discussed in relation to insect activity levels and the proposed neurohormonal role of octopamine in mediating the fight or flight response in insects.

Pharmacology of the octopamine-stimulated adenylate cyclase of the locust and tick CNS

1. The presence of an octopamine-stimulated adenylate cyclase is shown in homogenates of the cerebral ganglion of the locust Schistocerca americana gregaria and the synganglion of the tick Boophilus microplus. 2. A detailed study of the pharmacology of the activation of the enzyme of the two species is reported and compared with the pharmacology of octopamine receptors in other invertebrate preparations.

Octopamine distribution in solitarious and gregarious forms of the locust, Schistocerca Americana gregaria

The distribution of octopamine has been examined in the solitarious and gregarious forms of the locust, Schistocerca americana gregaria. No evidence was obtained of any phase-related differences in octopamine levels in nervous tissue or muscle. Octopamine values measured for whole heads agreed well with the sums of their component parts. The results are discussed in relation to previous claims of phase-related changes in octopamine levels.

The release and removal of octopamine by tissues of the locust Schistocerca americana gregaria

The octopamine content of dorsal longitudinal nerves and of dorso-ventral nerve-muscle tissues was lower in locusts flown for 10 min than in unflown controls. No such change was found for the octopamine content of brain or thoracic ganglia. Endogenous octopamine was released from isolated working thoracic muscle preparations perfused in the presence of yohimbine. It is proposed that release of octopamine from thoracic nerves can account for much of the increase in octopamine that occurs in haemolymph during the first few minutes of flight. Octopamine injected into locusts in vivo was rapidly removed from the haemolymph. In vitro experiments showed that Malpighian tubules were effective at removing octopamine added to the incubation medium. When the octopamine content of crude tissue preparations such as whole tagmata is estimated by radioenzymatic procedures, erroeneously high results are obtained unless precautions are taken to purify the labelled product.

Incorporation in vivo of [4- 14C]-cholesterol into the conjugated ecdysteroids in ovaries and eggs of Schistocerca americana gregaria

The incorporation in vivo of [4- 14C]-cholesterol into ecdysteroids at levels significantly higher than those obtained with any other in vivo insect system is reported. This has been made possible by taking advantage of the large endogenous biosynthesis of conjugated ecdysteroids, which takes place in the ovaries of Schistocerca americana gregaria towards the end of öogenesis. Incorporations of 0.5–1.0% of the injected label into conjugated ecdysteroids (mainly ecdysone and 2-deoxyecdysone with lesser amounts of 20-hydroxyecdysone) of newly laid eggs were usually obtained. This method of producing radioactive conjugated ecdysteroids within eggs of S. americana gregaria has been used to study the fate of these ecdysteroids during embryogenesis. During the first twelve days of embryogenesis, the relative proportions of radioactive conjugated ecdysteroids does not alter appreciably, but thereafter production of an apolar ecdysteroid and a 26-hydroxyecdysteroid is indicated. In addition, the presence of highly polar ecdysteroid metabolites which are refractory to enzymic hydrolysis, is also indicated during late embryogenesis.

The Function of Hair Sensilla on the Locust’s Leg: the Role Of tibial hairs

ABSTRACT In Schistocerca americana gregaria hairs of the simple trichoid sensillum type on the hind tibia near the tibia-tarsus joint can mediate an avoidance response during which the hind leg is lifted by flexion of several joints. The responsiveness of this reflex can be improved by partially isolating the metathoracic ganglion. In these operated animals, the response can even be elicited after stimulation of one hair. Myograms from various muscles in the tibia, femur, coxa and thorax revealed which muscles were active during the avoidance response. The delay times between the stimulus (bending several hairs with an eyelash) and the first muscle activity are variable (median values 150–200 msec). It is concluded that the pathway is polysynaptic and situated within the metathoracic ganglion.

Connexions Between A Movement-Detecting Visual Interneurone and Flight Motoneurones of A Locust

ABSTRACT Both of the descending contralateral movement detector (DCMD) neurones of Schistocerca americana gregaria, which respond to stimulation of the contralateral eye or to loud noises, mediate excitatory postsynaptic potentials in most ipsilateral flight motoneurones.

Kinetic properties of purified aldolase from flight muscle of Schistocerca americana gregaria. Role of the enzyme in the transition from carbohydrate to lipid-fueled flight

Aldolase (E.C.4.1.2.13) from the flight muscle of the locust, Schistocerca americana gregaria, was purified to homogeneity using phosphocellulose affinity chromatography. The activity of the enzyme (13 units/g wet wt.) was one of the lowest of the glycolytic enzymes in flight muscle. The enzyme has a molecular weight of 155,000 ± 5000, a pI of 4.9 ± 0.5, a pH optimum of 7.3 in Tris buffer, and a K m for fructose-1.6-P 2 of 4.0 ± 0.5 μM. The enzyme resembles muscle aldolases from other sources in displaying a V max activity ratio ( V fructose-1,6-P 2 V fructose-1-P ) of 37. The enzyme was inhibited by the adenylates (ATP, ADP, AMP), NAD +, NADH, excess Mg 2+ and Mn 2+, citrate, and palmitoyl-carnitine. Only citrate (K i = 1.88 ± 0.20 mM) and palmitoyl-carnitine (K i = 18 ± 4 μM) appear to be significant effectors of the enzyme in vivo. Inhibition by these two compounds was mixed competitive with respect to fructose-1,6-P 2. Citrate and palmitoyl-carnitine inhibitions of aldolase may be the signals used to inhibit flight muscle glycolysis during lipid oxidation. The central role of aldolase in the transition from short-term, carbohydrate based flight to long-term, lipid-based flight in the locust is discussed.

The d-octopamine content of the haemolymph of the locust, Schistocerca Americana gregaria and its elevation during flight

Octopamine is present in the haemolymph of adult locusts at a concentration of 33 ± 3 nM. When locusts fly there is a rapid increase in the concentration of octopamine in the haemolymph until it reaches a maximum value of 173 ± 8 nM after 10 min. Thereafter the concentration decreases until, after 60 min flight, it is close to the resting value. It is suggested that octopamine could have a physiological role in stimulating oxidation of substrates in the flight muscle during the early period of flight. Evidence is presented that it is the d-isomer of octopamine which is present in haemolymph. A modified assay procedure for octopamine is described in which the octopamine is first enzymically methylated using labelled S-adenosyl methionine and the radioactive synephrine produced is selectively isolated by co-crystallization with carrier synephrine.

The relative importance of glucose and trehalose in the nutrition of the nervous system of the locust Schistocerca americana gregaria

(1) The work presented, attempts by a combination of results obtained in vivo and in vitro, to determine the importance of trehalose as an energy substrate for the central nervous system when the locust is at rest or flying. (2) In agreement with many previous authors, a substantial fall (>70%) was found in the concentration of trehalose in the haemolymph in the course of a two hr tethered flight. The much lower concentration of glucose was more stable. (3) Oxygen uptake studies showed that trehalose was not an efficient substrate for the nervous system in vitro. Possible reasons for this were, (a) the high K m (10 mM) of the trehalase of the nervous system for its substrate, and (b) the low concentration of the sugar in the nervous tissue, both in vivo and in vitro. (4) When the concentrations of glucose and trehalose found in the haemolymph were reproduced in vitro, the proportional utilization of the trehalose by the thoracic ganglia was much less than might have been expected on the basis of its high concentration.