Prostaglandin biosynthesis by salivary glands isolated from the lone star tick, Amblyomma americanum.

Salivary glands separated from internal tissues of the lone star tick, Amblyomma americanum, are competent to synthesize prostaglandins (PGs). Using an in vitro PG biosynthesis assay four major PGs, namely, PGA2/PGB2, PGD2, PGE2, and PGF2 alpha were synthesized. Under standard assay conditions PGA2/PGB2 was the predominant product.

Eicosanoids mediate microaggregation and nodulation responses to bacterial infections in black cutworms, Agrotis ipsilon, and true armyworms, Pseudaletia unipuncta.

Nodulation is the first, and quantitatively predominant, cellular defense reaction to bacterial infection in insects and other invertebrates. Inhibition of eicosanoid biosynthesis in true armyworms, Pseudaletia unipuncta, and black cutworms, Agrotis ipsilon, immediately prior to intrahemocoelic injections with heat-killed preparations of the bacterium, Serratia marcescens, severely impaired the nodulation response. Five eicosanoid biosynthesis inhibitors, including dexamethasone (a phospholipase A(2) inhibitor), indomethacin, ibuprofen (cyclooxygenase inhibitors), phenidone (dual lipoxygenase/cyclooxygenase inhibitor) and eicosatetraynoic acid (an arachidonic acid analog that inhibits all arachidonic acid metabolism) severely reduced nodulation in infected insects.

What can we learn from prostaglandins and related eicosanoids in insects?

Eicosanoids are oxygenated metabolites of three C20 polyunsaturated fatty acids (20:3n-6, 20:4n-6, and 20:5n-3). While eicosanoids are very well known in mammalian systems, mostly due to their pharmaceutical interest, there is increasing recognition of the significance of these compounds in insects and other invertebrates. In this paper we consider four major concepts emerging from work on eicosanoids in invertebrates.

Enhanced hypo-osmoregulation induced by warm-acclimation in antarctic fish is mediated by increased gill and kidney Na+/K(+)-ATPase activities.

Serum osmolality and serum inorganic ion concentrations were studied in two antarctic fish species, Trematomus bernacchii and T. newnesi, during 5 weeks of acclimation to 4 degrees C and compared with control values for groups acclimated to -1.5 degrees C.

Prostaglandin biosynthesis and subcellular localization of prostaglandin H synthase activity in the lone star tick, Amblyomma americanum.

We report on prostaglandin (PG) biosynthesis in the lone star tick, Amblyomma americanum. In vitro preparations of whole female ticks and internal tissues were competent to biosynthesize four PGs: PGA2/PGB2, PGD2, PGE2, PGF2 alpha. PGA2/PGB2 was the major product under optimal conditions.

Lipid provisioning of turtle eggs and hatchlings: total lipid, phospholipid, triacylglycerol and triacylglycerol fatty acids.

Lipid composition of eggs and hatchlings was studied in painted, snapping and Blanding's turtles from western Nebraska. The average total lipid proportions of the egg yolk, post-embryonic yolk and hatchling soma dry masses were high in painted turtles (29.80%, 42.

Eicosanoid biosynthesis by hemocytes from the tobacco hornworm, Manduca sexta.

We describe eicosanoid biosynthesis by microsomal-enriched preparations of hemocytes from larvae of the tobacco hornworm Manduca sexta. Four major prostaglandins, PGA2, PGE2, PGD2, and PGF2 alpha, and a lipoxygenase product that co-chromatographed with 15-hydroxyeicosatetraenoic acid (HETE) were synthesized under most conditions. The HETE's fraction was the predominant product.

Eicosanoids mediate insect nodulation responses to bacterial infections.

We propose that nodule formation is mediated by eicosanoids in insects. Nodulation is the temporally and quantitatively predominant cellular defense response to bacterial infection in insects and other invertebrates. Inhibition of eicosanoid biosynthesis in larvae of the tobacco hornworm Manduca sexta immediately prior to intrahemocoelic infections with the bacterium Serratia marcescens strongly reduced the nodulation response.

Incorporation of polyunsaturated fatty acids into phospholipids of hemocytes from the tobacco hornworm, Manduca sexta.

We examined the incorporation of four radioactive fatty acids, 18:1n-9, 18:2n-6, 20:4n-6 and 20:5n-3, into cellular lipids of hemocytes from tobacco hornworms, Manduca sexta. Most of the radioactivity associated with 18:1n-9 was recovered from triacylglycerols (TGs), and the radioactivity associated with 18:2n-6 was heavily incorporated into phospholipids (PLs) and TGs. Most of the radioactivity associated with the two eicosanoid-precursor polyunsaturated fatty acids (PUFAs), 20:4n-6 and 20:5n-3, was incorporated into PLs.

Prostaglandin biosynthesis by fat body from the tobacco hornworm, Manduca sexta.

We describe prostaglandin (PG) biosynthesis by microsomal-enriched preparations of fat body from larvae of the tobacco hornworm Manduca sexta. Four major PGs were synthesized under most experimental conditions, PGA2, PGE2, PGD2 and PGF2 alpha. PGA2, was the predominant product under most conditions.

Fatty acid compositions of phospholipids and triacylglycerols from selected terrestrial arthropods.

The fatty acid compositions of phospholipids and triacylglycerols from selected orthognath spider tissues, scorpion body segments, whole millipedes, and whole labidognath spiders were determined. The major components were C16 and C18 saturated and unsaturated fatty acids as well as C20 polyunsaturated fatty acids. The eicosanoid precursor polyunsaturated fatty acids 20:4n-6 and 20:5n-3 were present in substantial proportions of phospholipids in all tissues examined.

Arachidonic acid and prostaglandin E2 in Malpighian tubules of female yellow fever mosquitoes.

The fatty acid compositions of Malpighian tubules from adult females of the mosquito Aedes aegypti were determined for total lipids, phospholipids, triacylglycerols and three phospholipid fractions, namely phosphatidylcholine (PC), phosphatidylethanolamine (PE) and phosphatidylinositol/phosphatidylserine (PI/PS). The prostaglandin precursor arachidonic acid (20:4n-6) occurred in total lipids and phospholipids, but not triacylglycerols. Within phospholipids, nearly all of the 20:4n-6 was detected in PC, with only traces in PE, and none was detected in PI/PS.

Phospholipase A2 activity in the fat body of the tobacco hornworm Manduca sexta.

We report on phospholipase A2 (PLA2) activity in homogenates prepared from fat bodies of the tobacco hornworm Manduca sexta. PLA2 activity is responsible for hydrolyzing fatty acids from the sn-2 position of phospholipids. The rate of hydrolysis increased with increasing homogenate protein concentration up to approximately 320 micrograms protein/ml reaction volume.

Comparative eicosanoid physiology in invertebrate animals.

A comparative survey of eicosanoid physiology in invertebrate animals is presented. Topics include host skin penetration behavior in blood flukes, oocyte maturation in starfishes, prevention of polyspermic fertilizations in sea urchins, ion regulation in bivalves, egg production in snails, egg release in scallops, neurobiology of Aplysia, hatching in barnacles, and release of egg-laying behavior in some insects. Some eicosanoid actions, such as ion regulation, may be common to most vertebrate and invertebrate animals, whereas other actions, such as mediation of whole organism behavior, are not shared.

Insect immune response to bacterial infection is mediated by eicosanoids.

Inhibition of eicosanoid formation in larvae of the tobacco hornworm Manduca sexta, using specific inhibitors of phospholipase A2, cyclooxygenase, and lipoxygenase, severely weakened the ability of larvae to clear the bacterium Serratia marscescens from their hemolymph. The reduced capability to remove bacteria is associated with increased mortality due to these bacteria. There is a dose-dependent relationship between the phospholipase A2 inhibitor dexamethasone and both the reduced bacterial clearance and increased larval mortality.

De novo biosynthesis of arachidonic acid and 5,11,14-eicosatrienoic acid in the cricket Teleogryllus commodus.

The de novo biosynthesis of 5,11,14-eicosatrienoic acid (5,11,14-20:3), arachidonic acid (20:4(n - 6] and eicosadienoic acid (20:2(n - 6] and the elongation/desaturation of linoleic acid (18:2(n - 6] to 20:4(n - 6) and alpha-linolenic acid (18:3(n - 3] to eicosapentaenoic acid (20:5(n - 3] were demonstrated in adult males of the field cricket Teleogryllus commodus. Sodium [1-14C]acetate, [1-14C]18:2(n - 6) and [1-14C]18:3(n - 3) were injected into adult male crickets and after an incubation period, the testes and remaining tissues were extracted and the methyl esters obtained from the phospholipid and triacylglycerol fractions were analyzed. After 5 days of daily injections of [1-14C]acetate, the methyl esters of the triene and tetraene fatty acids from the testicular phospholipid fraction were purified by AgNO3-TLC and HPLC and analyzed by GLC, radio-HPLC, and radio-GLC of ozonolysis products.

PHYSIOLOGICAL ROLES OF PROSTAGLANDINS AND OTHER EICOSANOIDS IN INVERTEBRATES.

Prostaglandins and other biologically active derivatives of polyunsaturated fatty acids have been detected in a large number of invertebrate species. A brief summary of the mammalian background of arachidonic acid metabolism is provided, and the physiological significance of these compounds in invertebrates is reviewed. Topics include regulation of ion flux, temperature regulation, reproductive biology, cell aggregation, and host-parasite interactions.

Fatty acid composition of whole bodies, specific tissues and cell lines of two lepidopteran insects.

We detail the fatty acid compositions of last larval instars of two lepidopterans, Spodoptera frugiperda and Trichoplusia ni, two tissues from T. ni, a cell line derived from each species and the respective larval and cell culture media. Larval whole-body and specific tissue fatty acid profiles exhibited the major features commonly found in previous lepidopteran analyses, whereas the cell-line fatty acid compositions were substantially different from the compositions of both their growth media and larvae of their respective species.

De novo biosynthesis of prostaglandins by the Australian field cricket, Teleogryllus commodus.

The accumulation and metabolism of certain polyunsaturated fatty acids by testes from the Australian field cricket, Teleogryllus commodus, are described. Testes accumulated a substantial proportion (about 16%) of label from radioactive C20:3n6 that was injected into the haemocoel. Fifty percent of the label accumulated by testes was associated with the phospholipid fraction, whereas in the remainder of the body 30% was incorporated into the phospholipid fraction.

Prostaglandins: Their role in egg-laying of the cricket Teleogryllus commodus.

Mating of the Teleogryllus commodus female causes increased oviposition mediated by PGE(2), which is synthesized in the female's spermatheca from the precursor, arachidonic acid, in the presence of a PG-synthesizing complex. The latter, together with sperm, is transferred from the male to the female via a spermatophore. Only nanogram quantities of PGE(2) injected into oviduct are necessary to simulate mating-induced egg release.