Sensitivity, pheromones

The oceurrence of a large number of pyrazines as flavouring or aroma eonstituents and as pheromones in extremely low coneentrations has led to mass spectrometry being the method of ehoiee for determining the gross struetural details of a pyrazine nueleus. The method appears to be generally applieable and relatively specifie and sensitive. 

This is the first example of a reaction for which the presence of a chelating ligand was observed to facilitate rather than retard metal-catalysed epoxidation (Gao et al., 1987). It was found that the use of molecular sieves greatly improves this process by removing minute amounts of water present in the reaction medium. Water was found to deactivate the catalyst. All these developments led to an improved catalytic version that allows a five-fold increased substrate concentration relative to the stoichiometric method. Sensitive water-soluble, optically active glycidols can be prepared in an efficient manner by an in situ derivatisation. This epoxidation method appears to be competitive with enzyme-catalysed processes and was applied in 1981 for the commercial production of the gypsy moth pheromone, (-1-) disparlure, used for insect control (Eqn. (25)). 

The production of a female-influencing secretion from the chin gland of male Plethodontid salamander (P. jordani) points to a similar extension of function by the acquisition of female olfactory sensitivity to an intercellular signal protein. Female receptivity is enhanced by a male cytokine-like compound of the interleukin-6 family, in its released form. Rollman et al. (1999) note that pheromonal activity is a previously unrecognised function for cytokines. 

AOS responsiveness to hormonal influences is shown in the action of sodefrin on the lateral nasal sinus of newts (Cynops). The receptors in the accessory pocket are differentially affected by pituitary and ovarian hormones (Toyoda et al., 2000). The local EOG response to the pheromone (Fig. 5.1) was enhanced by the presence of prolactin or of estrogen alone. Receptor sensitivity increase is perhaps an alternate strategy to AOS receptor density increase several alternate routes of signal receptor adaptation (Fig. 7.1) have been hypothesised (Sorenson and Stacey, 1998). 

Dorries K.M., Adkins-Regan E. and Halpem B.P. (1995). Olfactory sensitivity to the pheromone, androstenone, is sexually dimorphic in the pig. Physiol Behav 57, 255-259. 

Tsujikawa K. and Kashiwayanagi M. (1999). Protease-sensitive urinary pheromones induce region-specific fos-expression in rat accessory olfactory bulb. Biochem Biophys Res Comm 260, 222-224. 

Currently, LC-MS is widely used for the analysis of polar compounds, such as medicinal metabolites and bioactive peptides, since the interface has been improved and several new ionization methods have been developed. The sensitivity and reproducibility are sufficient for a daily quantitative analysis. The usefulness of the LC-MS has been demonstrated for studies on Type II pheromones using a time-of-flight MS with electrospray ionization (ESI) [180]. Each epoxydiene derived from the (Z3,Z6,Z9)-triene shows three ion series of [M+NHJ+, [M+H]+, and [M-OH]+ with high resolution and good sensitivity, indicating its molecular formula. In addition to these, characteristic fragment... 

Domes, K. M., Adkins Regan, E. and Halpem, B. P. (1997) Sensitivity and behavioural responses to the pheromone androstenone are not mediated by the vomeronasal organ in domestic pigs. Brain Behav. Evolut. 49, 53-62. 

Coureaud, G., Montigny, D., Dewas, M., Moncomble, A.S., Patris, P. and Schaal, S. (2005) A sensitive period for pheromone-induced odour learning in newborn rabbits. 29th International Ethological Conference, Budapest, Hungary, 20-27 August. 

Hudson, R. and Distel, H. (1990) Sensitivity of female rabbits to changes in photoperiod as measured by pheromone emission. J. Comp. Physiol. A 167, 225-230. 

Acetalization of oxo aldehydes is used to protect sensitive aldehyde products, especially in asymmetric hydroformylation preventing racemization of an a-chiral aldehyde product [18-22,27]. Acetal formation can also be applied to the synthesis of monocyclic or spirocyclic pyranes as potential precursors and building blocks for natural products such as pheromones or antibiotics. A representative example is the synthesis of the pyranone subunit of the Prelog-Djerassi lactone. For this purpose, various 1,2-disubstituted homoal-lylic alcohols were used (Scheme 3) [32],... 

Because the chemical signals (semiochemicals) are normally produced in minute amounts and diluted in the environment with a complex mixture of chemical compounds derived from a myriad of sources, the olfactory system in insects evolved as a remarkably selective and sensitive system, which approaches the theoretical limit for a detector. For example, it has been estimated that the male silkworm moth is able to distinguish within 1 s 170 nerve impulses generated by the female silkworm moth s sex pheromone from 1700 spontaneous nervous impulses [ 1 ], thus, operating on a remarkably low S/N ratio ... 

Earlier experiments based on EAG and SSR highlighted the inordinate specificity and sensitivity of the insect olfactory system. While minimal structural modifications to pheromone molecules render them inactive [12], a single molecule of the native ligand is estimated to be sufficient to activate an olfactory neuron in male antennae [14]. The large number of detectors certainly contributes to the sensitivity of the olfactory system, but selectivity is a matter of... 

From the examples discussed above, it is clear that heteropteran species have unique and interesting chemistry. Given that much less than 1% of the number of known species have been examined, a wealth of novel compounds must remain to be discovered. The discovery process should become easier, for several reasons. First, as the sensitivity of analytical methods increases, it will be possible to identify ever-smaller quantities of novel compounds. This may provide the key to identifying the pheromones of some of the problem species. In par-... 

Females of several species use (R)-5-[(lZ)-l-octenyl]oxacyclopentan-2-one, buibuilactone 69 [ 140-144]. The first y-lactone identified from a scarab beetle was (R)-5-[(Z)-l-decenyl]oxacyclopentan-2-one, japonilure 70, the female produced sex pheromone of the Japanese beetle Popillia japonica [145]. Both 69 and 70 are components of specific blends of several species [140-143]. The Japanese beetle is extremely sensitive to the non-natural enantiomer of his pheromone as little as 1% of the (S)-enantiomer inhibits the attractiveness of the pheromone [ 145]. With respect to species discrimination, this is particularly... 

Attractive Compounds. Pheromones of dermestid beetles were among the first ones identified from insects. Almost all have been described as one-component-systems , and re-investigations employing refined techniques, especially GC-EAD and sensitive GC-MS, may reveal the presence of additional and important compounds, which may lead to improved activity of synthetic lures, and under natural conditions may account for species specificity etc. 

The male-produced aggregation pheromone of the square-necked grain beetle, Cathartus quadricollis has been identified to be (3R,6 )-3-acetoxy-7-methylnon-6-ene 157 [297]. The compound, termed quadrilure, is attractive to both sexes, however, females are more sensitive at low concentrations. The (S)-enantiomer is biologically inactive. 

---