Hormones and pheromones

Currently, much interest is being taken in selective possibilities of the prostaglandins, a family of secondary messengers discovered by von Euler in 1934. They have since been found to be widespread in Nature, and in mammals their task is usually to translate a flux of a hormone or neuro-transmitter into the appropriate physiological result. Their action, which can be violent, is usually short-lived specific dehydrogenases exist to degrade them rapidly after release. Some are stimulant, even irritant, whereas others have healing properties. 

Prostaglandins Ep Eg, and apparently F, cause erythrema, oedema, and pain and, in addition, they sensitize pain receptors to other hyperalgesic substances such as histamine, bradykinin, and SRS (slowly reacting substance) (Collier, 1971, Ferreira and Vane, 1974). The anti-inflammatory action of aspirin, which is still the most used drug for the treatment of arthritis and rheumatism, is due to its inhibition of the biosynthesis of 

The corticosteroids inhibit the synthesis of prostaglandins by a different, though unknown, mechanism (Tashjian et aL I975). 

The main types of insect-specific hormone are a-ecdysone, from the prothoracic glands, which causes moulting the brain hormone that stimulates the prothoracic glands and the juvenile hormone, in the corpora allata, which causes metamorphosis. Further, the corpus cardiacum releases a hormone that increases the amplitude of the muscles of heart and gut (Davey, 1964), and also an adipokinetic hormone which regulates the use of lipids as a source of energy in flight (Stone et al. 1976). 

Juvenile hormone (4.50) is a simple aliphatic substance methyl lo-epoxy-7-ethyl-3, ii-dimethyl-2, 6-tridecadienoate in which both double bonds are trans (Roller et al, 1967). Activity is largely determined by the configuration at the C-i end of the molecule. 

The starting point of their biosynthesis is linoleic acid, an essential dietary constituent for Man. This is converted to arachidonic acid (4.68) (a 20-carbon aliphatic acid with four double bonds) which is stored as a phospholipid in cell membranes. From these it is liberated, on demand, by phospholipase A2. Arachidonic acid is further metabolized by two pathways. In the first of these, it 

The E series of prostaglandins is distinguished by a hydroxyl-group in the 11 position and an oxo-substituent at C-9. The F series has two hydroxyl-groups (at C-9 and C-11) and both series have a hydroxyl-group at C-15. Prostaglandins with the subscript 2 have the extra double bond between C-5 and C-6. 

The cyclic endoperoxide 4.69) gives, by the action of another enzyme (thromboxane synthetase), thromboxane A2 which is responsible for the formation of thrombi (clots) in blood-vessels. Yet another enzyme (prostacyclin synthetase), acting on the same endoperoxide, gives epoprostenol (prostacyclin) 4.71), a substance which protects blood-platelets and prevents clotting. Epoprostenol has a half-life of only 3 minutes in water at 37°C. Chemically it is (5Z,13 )-(8/ ,95,ll/ ,12/ ,155)-6,9-epoxy-ll,15-dihydroxyprosta-5,13-di enoic acid. 

In the second pathway by which arachidonic acid is metabolized, a battery of lipoxygenases converts it to a family of about four leukotrienes of which 4.72) is typical (Murphy, Hammarstrom and Samuelsson, 1979). These cause a much more long-lasting inflammation than that brought about by histamine and are held responsible for most of the distressing symptoms of asthma. Before the chemical constitution of leukotriene C was known, it was referred to as SRS (Slowly Reacting Substance). 

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Morgan ED (1990) Insect trail pheromones a perspective in progress. In McCaffery AR, Wilson ID (eds) Chromatography and isolation of insect hormones and pheromones. Plenum, New York, p 259... 

Kaissling KE, Thorson J (1980) In Sattelle DB, Hall LM, Hildebrand JG (eds) Receptors for transmitters, hormones and pheromones in insects. Elsevier/North-Holland, Amsterdam, p 261... 

A number of compounds important to animal physiology have been identified as isoprenoid compounds. Notable examples are vitamin A, retinal (Section 28-7), and squalene (Table 30-1). Also, terpene hydrocarbons and oxygenated terpenes have been isolated from insects and, like famesol, show hormonal and pheromonal activity. As one example, the juvenile hormone isolated from Cecropia silk moths has the structure shown in 3 ... 

A great deal of biochemical signalling and semiochemistry involves the specific molecular recognition of tiny amounts of molecular messengers such as neurotransmitters, hormones and pheromones. 

Ichikawa T., Hasegawa K., Shimizu I., Katsuno K., Kataoka H. and Suzuki A. (1995) Structure of neurosecretory cells with immunoreactive diapause hormone and pheromone biosynthesis activating neuropeptide in the silkworm, Bombyx mori. Zool. Sci. 12, 703-712. 

Sato Y., Ikeda M., Yamashita O. (1994) Neurosecretory cells expressing the gene for common precursor for diapause hormone and pheromone biosynthesis activating neuropeptide in the subesophageal ganglion of the silkworm, Bombyx mori. Gen. Comp. Endocrin. 96, 27-36. 

Kaissling K.-E. and Thorson J. (1980) Insect olfactory sensilla structural, chemical and electrical aspects of the functional organisation. In Receptors for Neurotransmitters, Hormones and Pheromones in Insects, eds D. B. Sattelle, L. M. Hall and J. G. Hildebrand, pp. 261-282. Elsevier/North-Holland Biomedical Press. 

Insects are so successful because of their mobility, high reproductive potential, ability to exploit plants as a food resource, and to occupy so many ecological niches. Plants are essentially sessile and can be seen to produce flowers, nector, pollen, and a variety of chemical attractants to induce insect cooperation in cross-pollination. However, in order to reduce the efficiency of insect predation upon them, plants also produce a host of structural, mechanical, and chemical defensive artifices. The most visible chemical defenses are poisons, but certain chemicals, not intrinsically toxic, are targeted to disrupt specific control systems in insects that regulate discrete aspects of insect physiology, biochemistry, and behavior. Hormones and pheromones are unique regulators of insect growth, development, reproduction, diapause, and behavior. Plant secondary chemicals focused on the disruption of insect endocrine and pheromone mediated processes can be visualized as important components of plant defensive mechanisms. 

Structures of DSK I and II were determined by molecular biological techniques. Expression of these peptides has not been demonstrated, t Schoofs, L., in Chromatography and Isolation of Insect Hormones and Pheromones, in press. 

In addition to the L. maderae myotropic peptides, a series of five myotropic peptides were isolated and structurally characterized from head extracts of the cricket, Acheta domesticus. with the same purification system and bioassay (Holman, G. M., et al. Chromatography and Isolation of Insect Hormones and Pheromones, in press.). The structures of these five myotropic peptides, the achetakinins, are shown in Table 1. Like the leucokinins, the achetakinins (Ak s) contain a C-terminal pentapeptide core which is responsible for the myotropic activity (12). In Ak s III and V, the C-terminal pentamer is the same as the leucokinin pentamer (Phe-X-Ser-Trp-Gly-NH2, where X = Asn, His, Ser, or Tyr) but in Ak s I, II, and IV a slightly different pentamer (Phe-X-Pro-Trp-Glv-NH is present. 

The final peptide structure shown in Table 2 represents an insect sulfakinin recently isolated from br-cc/ca extracts of the locust, Locusta migratoria. and structurally characterized. A modification of the four-step HPLC purification system (10) in which all gradients were extended to a higher final acetonitrile concentration was utilized. In addition, a C-8 reverse-phase column was substituted for the C-18 column (Schoofs, L., et al. Chromatography and Isolation of Insect Hormones and Pheromones, in press.). The isolated hindgut of L. maderae was used as the bioassay. Lom-SK contains residues of Leu and Ala at the 2- and 3-positions, respectively. The remainder of the sequence is identical with the 2-10 sequence of LSK-II. 

L - leucokinin A - achetakinin. Average of five replicates. Threshold concentration determination procedure has been previously described (16). Holman, M., Nachman, R., and Wright, M. in Chromatogr. 6e Isolation of Insect Hormones and Pheromones. in press. 

Goodman, C.S. Spitzer, N.S. In "Receptors for Neurotransmitters, Hormones and Pheromones in Insects" Sattelle, D.B. Hall, L.M. Hildebrand, J.G., Eds. Elsevier/North-Holland Biomedical Press Amsterdam, 1980 pp. 195-207. 

Micro-organisms produce hormones and pheromones so as to regulate their own lives. They also generate diverse secondary metabolites such as toxins and antibiotics to control the lives of the organisms. Some of the secondary metabolites possess rather complicated structures, and have attracted the attention of chemists. Medicinally important antibiotics were especially well studied. This chapter describes our synthetic works on biofunctional molecules of microbial origin. 

I presented an overview of the crustacean endocrine system, which historically has focused on decapods. Of course, there are other important crustacean groups. Very little is known about the structures of their endocrines, not to mention their methods of chemical mediation. For both practical and basic interests, future comparative research will need to encompass these other crustacean groups and examine their individual variations of hormonal and pheromonal mechanisms. 

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